Journal articles on the topic 'Non-Standard bending test'
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1
Liu, Chao, Ning Ding, Jingsong Duan, Lili Zhou, Shanfu Cui, Shuna Jiang, and Aofei Li. "Precise mathematical model for the ratchet tooth root bending stress." Mechanical Sciences 12, no. 2 (December 20, 2021): 1105–13. http://dx.doi.org/10.5194/ms-12-1105-2021.
Abstract:
Abstract. A ratchet is an essential component of the ratchet pawl mechanism. But the traditional ratchet strength check method has certain limitations in the design process. In this paper, the stress analysis of the ratchet is discussed and a precision mathematical model for the ratchet tooth root bending stress is proposed for the first time. This model was established by the folded section and defined by the incision effect theory. To test the prediction ability of the proposed mathematical model, the maximum stress of three standard ratchets and one non-standard ratchet were analyzed by the FEA (finite element analysis) method. The non-standard ratchet was adapted in the ratchet experiment to analyze its maximum stress. The analysis results presented in this paper show that the proposed mathematical model has a good predictability, regardless of whether it is a standard or non-standard ratchet. It is recommended that this model can be used to predict the ratchet tooth root bending stress in the ratchet design process.
2
Kalia, Ajit, Juhi Joshi, Mohammed Mandsaurwala, Sayali Bobade, and Azmat Azha Khan. "Esthetic nickel titanium wires– Do they deliver the same force?" IP Indian Journal of Orthodontics and Dentofacial Research 8, no. 4 (December 15, 2022): 260–66. http://dx.doi.org/10.18231/j.ijodr.2022.045.
Abstract:
To test the difference in loading and unloading forces delivered by six coated nickel-titanium wires and their non-coated equivalents. Commercially available six coated nickel-titanium wires and their non-coated equivalents of sizes 0.016-inch diameter round and 0.016 X 0.022-inch rectangular cross-section were procured. The wires were evaluated using a three-point bending test based on the method in ISO Standard 15841. No statistically significant differences in force values were found between coated and non-coated wires, listed by deflection in three-point bending, for these specific groups.Statistical analysis was done using SPSS version 11.5 (Chicago, III). Analysis of variance was performed with Sheffe post hoc for the mean comparison among the measurements of each loading and unloading deflection for coated and non-coated wires. Student’s t-tests was performed for the mean comparisons between non coated and coated groups for each deflection. There is no significant difference in load response between coated and non-coated nickel-titanium wires of the same size when subjected to the same deflection using a standard three-point bend test method.
3
Chai, Teck Jung, Tan Cher Siang, Tang Hing Kwong, and Koh Heng Boon. "Bending Strength of Magnesium Oxide Board." Key Engineering Materials 879 (March 2021): 169–78. http://dx.doi.org/10.4028/www.scientific.net/kem.879.169.
Abstract:
Magnesium Oxide (MgO) board has been widely used in prefabricated lightweight steelframe wall systems and as the floor board covering component. It is a non-insulating sheathingboard product which consists of sustainable materials with the characteristics of fire resistance,weather-ability, strength, resistance to mold and mildew. Although MgO board has recentlyworldwide used in façade construction but the research data related to the laboratory work such asthe bending strength is still limited. The previous studies on the bending strength of MgO board arebased on various standards such as ASTM, JC688 and British Standard subjected to the productscharacteristics and patterns. Therefore, the bending strength values obtained were inconsistent andnot convincing. Thus, this paper aims to examine the bending strength of MgO board with threedifference thicknesses (6mm, 9 mm and 12 mm) based on BS EN 310:1993 subjected to threepoints bending test. The failure modes during three points bending test was observed and theexperimental results obtained were compared with the theoretical values and others relevantstandards. A total of thirty six specimens with twelve specimens for each thickness in two groupdirections namely longitudinal (length) and transverse (width) direction were tested. The specimenswere prepared based on BS EN 326-1:1994 and BS EN 325:2012. The maximum flexure load of thespecimens was recorded and arithmetic mean bending strength for each thickness was presented.The experimental results showed the tested MgO board was not achieved minimum bendingstrength for load bearing used. It is recommended to be used in non-load bearing façade claddingconstruction.
4
Kunecký, Jiří, Václav Sebera, Jan Tippner, Hana Hasníková, Michal Kloiber, Anna Arciszewska-Kędzior, and Jaromír Milch. "Mechanical Performance and Contact Zone of Timber Joint With Oblique Faces." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 63, no. 4 (2015): 1153–59. http://dx.doi.org/10.11118/actaun201563041153.
Abstract:
The goal of the work was to evaluate mechanical performance of full-scale timber beams containing scarf joint with a dowel. Work focused on standard testing using modular system to obtain effective stiffness and strength of the beams with and without the joint. The work further researched a contact zone between two timber parts of the joint – at the scarf face. This was carried out using non-destructive optical technique – digital image correlation (DIC) and newly developed algorithm. The joint was made of Norway spruce, dims. 6×0.2×0.24 m and was loaded by two modes: a) 3-point bending and b) 4-point bending. During the loading, a sequence of images was acquired for further investigation of contact zone using the proposed algorithm. The joint with scarf and dowel provided enough effective stiffness, ie. 73–93% for 3-point bending test and 71% for 4-point bending with respect to MOE measured on reference solid beams. Effective strength of the joint was also relatively high and in a range of 55% and 60% with respect to reference solid beams in both 3-point and 4-point bending tests. Contact length differed for loading modes. Mean contact length in symmetrical 4-point bending was about 40%, for asymmetrical 3-point bending test, it was approx. 20% on face closer to support and 44% on a face closer to loads.
5
Kosior-Kazberuk, Marta, and Rafał Wasilczyk. "Influence of static long-term loads and cyclic freezing/thawing on the behaviour of concrete beams reinforced with BFRP and HFRP bars." MATEC Web of Conferences 174 (2018): 04013. http://dx.doi.org/10.1051/matecconf/201817404013.
Abstract:
The purpose of this study was to define the influence of static longterm loads and cyclic freezing/thawing on the deflections and cracking of concrete beams with non-metallic reinforcement. The rods made of basalt fiber reinforced polymer (BFRP) and hybrid fiber reinforced polymer (HFRP) were used as non-metallic reinforcement. Four series of single span beams were loaded with a single static force in a three-point bending test, then specimens were subjected to 150 freezing/thawing cycles in a large-size climatic chamber. The experimental test results were compared to those obtained from prior carried out short-term tests and theoretical calculations based on ACI 440:1R-06 standard concerning concrete element with non-metallic reinforcement.
6
Susanto, Eko, Yulian Maheswara, and Akhmad Basuki Widodo. "Bending Strength of Apus Bamboo Fiber Reinforced Asphalt Composite Materials as Small Ship." BERKALA SAINSTEK 10, no. 4 (December 10, 2022): 195. http://dx.doi.org/10.19184/bst.v10i4.32604.
Abstract:
Bamboo is generally widely used as a material or construction material in homes. However, the use of bamboo as a raw material for shipbuilding is not yet available. To make bamboo as a material in shipbuilding, the bamboo is assembled or made into a composite to meet class standards as a material for shipbuilding. In this study, the composites used were apus bamboo fiber and asphalt. The method of making the composite uses the hand lay-up method with variations of 1 layer of reinforcement, 3 layers of reinforcement, and 5 layers of reinforcement. The dimensions of the test specimen size refer to ASTM D 790-3 which is then carried out by bending tests to determine the strength of the material due to loading and the elasticity of the material. Furthermore, the results of the bending test will be analyzed using the Anova method and compared with the standard material class in ship construction. Results Asphalt composite material with apus bamboo fiber has the highest bending test value of 27,068 Mpa and the lowest bending test value of 25,998 Mpa. Based on these results, it is stated that the Bamboo reinforced asphalt (BRA) material has not been able to match and even exceed the Bamboo reinforced plastic (BRP) material in the woven, non-woven and random fiber variants. It is influenced by the diameter, and the strength of the shape between the fiber and the matrix.
7
Vu, Ngoc-Hung, Xuan-Tan Pham, Vincent François, and Jean-Christophe Cuillière. "Inverse procedure for mechanical characterization of multi-layered non-rigid composite parts with applications to the assembly process." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 17 (July 7, 2019): 6167–76. http://dx.doi.org/10.1177/0954406219861126.
Abstract:
In assembly process, non-rigid parts in free-state may have different forms compared to the designed model caused by gravity load and residual stresses. For non-rigid parts made by multi-layered fiber-reinforced thermoplastic composites, this process becomes much more complex due to the nonlinear behavior of the material. This paper presented an inverse procedure for characterizing large anisotropic deformation behavior of four-layered, carbon fiber-reinforced polyphenylene sulphide, non-rigid composite parts. Mechanical responses were measured from the standard three points bending test and the surface displacements of composite plates under flexural loading test. An orthotropic hyperelastic material model was implemented as a UMAT user routine in the Abaqus/Standard to analyze the behavior of flexible fiber-reinforced thermoplastic composites. Error functions were defined by subtracting the experimental data from the numerical mechanical responses. Minimizing the error functions helps to identify the material parameters. These optimal parameters were validated for the case of an eight-layered composite material.
8
DeTora, M., and K. Kraus. "Mechanical testing of 3.5 mm locking and non-locking bone plates." Veterinary and Comparative Orthopaedics and Traumatology 21, no. 04 (2008): 318–22. http://dx.doi.org/10.3415/vcot-07-04-0034.
Abstract:
SummaryLocking plate technologies are being developed in order to provide the surgeon with advantages over previous bone plate systems (both locking and non-locking). Locking plate systems possess inherent biological advantages in fracture fixation by preserving the periosteal blood supply, serving as internal fixators. It is important to consider the strength of each orthopaedic implant as an important selection criterion while utilizing the reported advantages of locking plate systems to prevent catastrophic fracture failure. Mechanical testing of orthopaedic implants is a common method used to provide a surgeon with insight on mechanical capabilities, as well as to form a standardized method of plate comparison. The purpose of this study was to demonstrate and to quantify observed differences in the bending strength between the LCP (Limited Contact Plate), LC-DCP, 3.5 mm Broad LC-DCP (Limited Contact Dynamic Compression Plate), and SOP (String of Pearls) orthopaedic bone plates. The study design followed the ASTM standard test method for static bending properties of metallic bone plates, which is designed to measure mechanical properties of bone plates subjected to bending, the most common loading encountered in vivo. Single cycle four point bending was performed on each orthopaedic implant. The area moment of inertia, bending stiffness, bending strength, and bending structural stiffness were calculated for each implant. The results of this study demonstrated significant differences (p<0.001) in bending strength and stiffness between the four orthopaedic implants (3.5 Broad LC-DCP>SOP>LCP=LC-DCP). The 3.5 mm LCP should be expected to provide in vivo strength and stiffness similar to a comparable LC-DCP. The SOP should provide strength and stiffness that is greater than a comparable LC-DCP but less than a 3.5 mm Broad LC-DCP.
9
Concli, Franco. "Numerical Study of the Impact of Shot Peening on the Tooth Root Fatigue Performances of Gears Using Critical Plane Fatigue Criteria." Applied Sciences 12, no. 16 (August 18, 2022): 8245. http://dx.doi.org/10.3390/app12168245.
Abstract:
Gears are one of the the most widespread mechanical components and their design is supported by standard calculation methods. Among all the possible failure modes of gears, tooth root bending is the most critical and could lead to catastrophic failures. In this regard, different surface treatments could be exploited to improve the gear strength. Among them, shot peening is the most common. The aim of this study is to evaluate the effectiveness of shot peening on improving the tooth root bending resistance. This is achieved by exploiting the Finite Element Method (FEM) in combination with advanced multiaxial fatigue criterion based on the critical plane concept. A standard Single Tooth Bending Fatigue test was reproduced numerically via FEM. Beside the wrought gears, shot peened ones were also simulated. The state of stress induced by the shot peening was obtained numerically by simulating the surface treatment itself with non-linear dynamic analyses. The results have shown quantitatively how the residual stresses promote an improvement in the resistance and how the local hardening could lead to different early paths of nucleation and propagation of cracks on the tooth fillet.
10
Fuentes-Talavera, F. J., J. A. Silva-Guzmán, R. Rodríguez-Anda, M. G. Lomelí-Ramírez, R. Sanjuán-Dueñas, and H. G. Richter. "Strength properties and natural durability of Avocado (Persea americana Mill.) branch wood." Madera y Bosques 17, no. 1 (August 30, 2016): 37–47. http://dx.doi.org/10.21829/myb.2011.1711153.
Abstract:
This paper reports on mechanical properties and natural durability of avocado branch wood (Persea americana Mill.) with the objectives of providing a reliable property profile and to promote the rational use of this abundant yet largely neglected natural resource. The mechanical properties (static bending, compression, shear, impact bending) and hardness were determined in accordance with European standards (CEN). Natural durability was assessed according to the European standard EN 350-1 (agar block test) using the white rot fungi Trametes versicolor and Phanerochaete chrysosporium, and the brown rot fungus Postia placenta. Avocado trees yield a low to medium density (0,44-0,54-0,64 g/cm3 at 12% mc) branch wood with below average strength under static bending, compression and tension parallel to the grain and average values for longitudinal shear, impact bending and hardness. The wood is rated non-resistant (class 5 according to EN 350-1) and thus is not suitable for exterior applications unless treated. Considering its property profile and the small dimensions available, avocado wood is recommended for general carpentry, furniture, interior paneling, glue-boards for closets and cabinets, and glue-lams for indoor framework.
11
Ma, Yifan, Yazhi Li, and Lu Liu. "Off-Axis Tension Behaviour of Unidirectional PEEK/AS4 Thermoplastic Composites." Applied Sciences 13, no. 6 (March 9, 2023): 3476. http://dx.doi.org/10.3390/app13063476.
Abstract:
An experimental method for non-standard off-axis tension tests of unidirectional composites is developed. A new oblique end-tab is designed to eliminate stress concentration and in-plane bending moment induced by off-axis tension loading. Finite element analysis and experiments on Polyetheretherketone (PEEK)/AS4 unidirectional thermoplastic composites (CFRTP) were conducted to evaluate the effectiveness of the proposed testing method. Simulation and test results demonstrate that the use of oblique end-tabs eradicates stress concentration and bending movements. The digital image correlation (DIC) method was used to help investigate the full-field tension/shear coupling deformation response of the off-axis specimen. Test results show significant nonlinear behaviour and inhomogeneous strain distribution under tension/shear combined stresses. A fractographic study was carried out to study the damage mechanisms under a tension/shear combined stress state. Specimens with 30°, 45° and 60° off-axis angles, fail in tension/shear mixed failure mode. Fracture surface morphology indicates that matrix plastic deformation and ductile drawing under tension/shear coupled stress state induced the nonlinear stress-strain response.
12
Trinidad-Fernández, Manuel, David Beckwée, Antonio Cuesta-Vargas, Manuel González-Sánchez, Francisco-Angel Moreno, Javier González-Jiménez, Erika Joos, and Peter Vaes. "Validation, Reliability, and Responsiveness Outcomes of Kinematic Assessment with an RGB-D Camera to Analyze Movement in Subacute and Chronic Low Back Pain." Sensors 20, no. 3 (January 27, 2020): 689. http://dx.doi.org/10.3390/s20030689.
Abstract:
Background: The RGB-D camera is an alternative to asses kinematics in order to obtain objective measurements of functional limitations. The aim of this study is to analyze the validity, reliability, and responsiveness of the motion capture depth camera in sub-acute and chronic low back pain patients. Methods: Thirty subjects (18–65 years) with non-specific lumbar pain were screened 6 weeks following an episode. RGB-D camera measurements were compared with an inertial measurement unit. Functional tests included climbing stairs, bending, reaching sock, lie-to-sit, sit-to-stand, and timed up-and-go. Subjects performed the maximum number of repetitions during 30 s. Validity was analyzed using Spearman’s correlation, reliability of repetitions was calculated by the intraclass correlation coefficient and the standard error of measurement, and receiver operating characteristic curves were calculated to assess the responsiveness. Results: The kinematic analysis obtained variable results according to the test. The time variable had good values in the validity and reliability of all tests (r = 0.93–1.00, (intraclass correlation coefficient (ICC) = 0.62–0.93). Regarding kinematics, the best results were obtained in bending test, sock test, and sit-to-stand test (r = 0.53–0.80, ICC = 0.64–0.83, area under the curve (AUC) = 0.55–84). Conclusion: Functional tasks, such as bending, sit-to-stand, reaching, and putting on sock, assessed with the RGB-D camera, revealed acceptable validity, reliability, and responsiveness in the assessment of patients with low back pain (LBP). Trial registration: ClinicalTrials.gov NCT03293095 “Functional Task Kinematic in Musculoskeletal Pathology” 26 September 2017
13
Teder, Marko, Kalle Pilt, Matis Miljan, Vello Pallav, and Jaan Miljan. "INVESTIGATION OF THE PHYSICAL-MECHANICAL PROPERTIES OF TIMBER USING ULTRASOUND EXAMINATION." Journal of Civil Engineering and Management 18, no. 6 (November 20, 2012): 795–801. http://dx.doi.org/10.3846/13923730.2012.736233.
Abstract:
This research uses a non-destructive method – ultrasound – to examine timber, combining the results of measurement with the properties of strength and stiffness. The purpose of this work is to explore the possibilities of grading wood structure in situ using ultrasound measurements, specifically, the moisture content and density of the timber. The timber used in these experiments was taken from existing buildings of different ages. The potential of replacing direct measurements with indirect measurements by ultrasound was also investigated. The physical-mechanical properties of wood were determined in laboratory conditions according to standard practices, and the method of non-destructive measurements was based on a commercial test device based on 54 kHz compressional wave 50 mm diameter ultrasound transducers. Direct measurements were performed in the longitudinal and radial material directions. Indirect measurements were performed with transducers positioned on the same lateral surface of the sample. A weak correlation was found with-in the different measurements. Longitudinal measurements characterise bending strength with R2 = 0.18 and modulus of elasticity with R2 = 0.37. In multiple regression analysis, stronger correlations were found; prediction equations of bending strength and modulus of elasticity were found with R2 = 0.40 and R2 = 0.81, respectively.
14
Jin, Ai Hua, and Bai Shou Li. "Research on Axial Behavior of Thin-Walled T-Shaped Steel Stub Columns Filled with Recycled Demolished Concrete Lump." Advanced Materials Research 690-693 (May 2013): 881–85. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.881.
Abstract:
An axial compression test has been done on 12 short columns, ribbed and spiral stirrup short column filled with recycled demolished concrete lump to study the axial compression variable characteristics and ultimate bearing capacity of thin-wall T-shaped steel tube column filled with recycled demolished concrete lump. The load displacement curve has been analyzed, ultimate bearing capacity of standard formula has been compared and the reliability of finite element numerical simulation and been discussed. The result shown that the form of steel tube embedded with structural members has more effectively increased the tensility, delayed bending occurrence, enhanced the effect of restraint of core concrete and increased the ultimate bearing capacity than that the form of plain section form. The ultimate bearing capacity of ribbed form has been increased by 16.76% than non-ribbed form，and the ultimate bearing capacity of spiral stirrup form has been increased by 11.98 % than non-spiral stirrup form. The finite element simulation and the test result was identical properly.
15
Casado, Milagros, Luis Acuña, Luis-Alfonso Basterra, Gemma Ramón-Cueto, and Daniel Vecilla. "Grading of structural timber of Populus × euramericana clone I-214." Holzforschung 66, no. 5 (July 1, 2012): 633–38. http://dx.doi.org/10.1515/hf-2011-0153.
Abstract:
Abstract Grading tests were performed on 338 poplar wood samples (Populus × euramericana I-214) with dimensions of 150×50 mm2, 150×80 mm2, and 200×100 mm2 prepared for structural utilization. The non-destructive testing methods included ultrasound (Sylvatest) and induced vibrations (Portable Lumber Grader) combined with visual grading criteria. Additionally, screw withdrawal resistance was tested by the instrument Fakopp. These results were compared with those obtained by a four-point bending test according to the EN 408 (2004) standard. Ultrasound and induced vibrations overestimated the quality of this type of wood. Correlation equations are proposed to determine the true characteristics for each testing method. It can be concluded that poplar timber from clone I-214 has acceptable flexural strength, but a comparatively low elastic modulus, whereby it is not graded within a high strength class according to the EN 338 (2009) standard.
16
Shmulsky, Rubin, Laurice Mara Spinelli Correa, and Franklin Quin. "Strength and stiffness of 3-ply industrial bamboo matting." BioResources 16, no. 3 (August 1, 2021): 6392–400. http://dx.doi.org/10.15376/biores.16.3.6392-6400.
Abstract:
There is a pressing need to develop engineering standards for timber- and other wood-based mats suitable for supporting construction vehicles, etc. In 2018, a group of mat producers and users began discussing a potential grading standard specific to mats. There are large gaps in the literature regarding the performance of the available raw materials as well as bolt-laminated mat systems. This study addresses the issue of determining the strength and stiffness values of a commercially sourced industrial bamboo mat. A total of seven 8 ft × 14 ft (2.44 m × 4.27 m) commercial bamboo mats were cut into 28 billets that were 21.5 in (54.6 cm) in width. The bamboo mat billets were evaluated for bending stiffness (modulus of elasticity [MOE]) and strength (modulus of rupture [MOR]) using a three-point static bending test. The 5th percentile non-parametric tolerance limit (5% NTL) and design value for fiber stress in bending (Fb) were calculated. The mechanical property values measured for the 3-ply bamboo mat were at least 25% less than values reported for mixed hardwood timber mats. This type of structural performance information is helpful and useful in the development of matting standards, as it describes the minimum performance characteristics for this type of composite matting.
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Landowski, Michał, Aleksandra Świerczyńska, Grzegorz Rogalski, and Dariusz Fydrych. "Autogenous Fiber Laser Welding of 316L Austenitic and 2304 Lean Duplex Stainless Steels." Materials 13, no. 13 (June 30, 2020): 2930. http://dx.doi.org/10.3390/ma13132930.
Abstract:
This study presents results of experimental tests on quality of dissimilar welded joints between 316L austenitic and 2304 lean duplex stainless steels, welded without ceramic backing. Fiber laser welded butt joints at a thickness of 8 mm were subjected to non-destructive testing (visual and penetrant), destructive testing (static tensile test, bending test, and microhardness measurements) and structure observations (macro- and microscopic examinations, SEM, element distribution characteristics, and ferrite content measurements). Non-destructive tests and metallographic examinations showed that the welded joints meet the acceptance criteria for B level in accordance with EN ISO 13919–1 standard. Also the results of the destructive tests confirmed the high quality of the joints: specimens were fractured in base material with lower strength—316L austenitic stainless steel and a 180° bending angle was obtained confirming the high plasticity of the joints. Microscopic examination, SEM and EDS analysis showed the distribution of alloying elements in joints. The microhardness of the autogenous weld metal was higher by about 20 HV0.2 than that of the lean duplex steel. Ferrite content in the root was about 37% higher than in the face of the weld. The Schaeffler phase diagram was used to predict the phase composition of the welded joints and sufficient compliance with the magnetic method was found. The presented procedure can be used for welding of 316L–2304 stainless steels dissimilar welded joints of 8 mm thickness without ceramic backing.
18
Živčák, Jozef, Martin Petrík, Radovan Hudák, Teodor Tóth, Dusan Knezo, and Eva Kovalova. "Embedded Tensile Strenght Test Machine FM1000 – An Upgrade of Measurement and Control." Solid State Phenomena 147-149 (January 2009): 657–62. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.657.
Abstract:
In order to compare the strengths of various materials it is necessary to carry out a standard form of test to establish their relative properties. The tensile test, compression test, bending, shearing and torsion tests are used for examining mechanical properties of biological materials. Except for non-destructive methods (optical, electromagnetic, sonic, thermal, infrared), destructive testing is another very important tool for the assessment of biomechanical properties and behavior of biomedical materials. The tensile strength test is one of the most common testing methods, which uses specific testing machines. Many tensile testing machines are equipped to plot a curve which shows the load or stress and the strain or movement that occurs during the test operation. In the testing operation, the load is increased gradually and the specimen will stretch or elongate in proportion to the tensile load. The load cells and extensometers measure the key parameters of force and deformation. The presented paper is a report which describes a specific and unique technical solution and upgrade of FM 1000 machine from the control and output processing point of view. Modern sensoric systems and I/O modules were used and custom software was developed. The fu
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May, Nguyen Huu, Huynh Trong Phuoc, Le Thanh Phieu, Ngo Van Anh, Chau Minh Khai, and Le Nong. "Recycling of waste incineration bottom ash in the production of interlocking concrete bricks." Journal of Science and Technology in Civil Engineering (STCE) - NUCE 15, no. 2 (April 15, 2021): 101–12. http://dx.doi.org/10.31814/stce.nuce2021-15(2)-09.
Abstract:
This study presents an experimental investigation on the recycling of waste incineration bottom ash (IBA) as a fine aggregate in the production of interlocking concrete bricks (ICB). Before being used, the concentration of heavy metal in IBA was determined to confirm it is a non-toxic material. In this study, the IBA was used to replace crushed sand (CSA) in the brick mixtures at different replacement levels of 0%, 25%, 50%, 75%, and 100% (by volume). The ICB samples were checked for dimensions, visible defects, compressive strength, bending strength, water absorption, and surface abrasion in accordance with the related Vietnamese standards. The test results demonstrated that the IBA used in this study was a non-toxic material, which can be widely used for construction activities. All of the ICB samples prepared for this study exhibited a nice shape with consistent dimensions and without any visible defects. The incorporation of IBA in the brick mixtures affected engineering properties of the ICB samples such as a reduction in the compressive strength and bending strength and an increment in water absorption and surface abrasion of the brick samples. As a result, the compressive strength, bending strength, water absorption, and surface abrasion values of ICB samples at 28 days were in the ranges of 20.6 – 34.9 MPa, 3.95 – 6.62 MPa, 3.8 – 7.2%, and 0.132 – 0.187 g/cm2, respectively. Therefore, either partial or full replacement of CSA by IBA, the ICB with grades of M200 – M300 could be produced with satisfying the TCVN 6476:1999 standard in terms of dimensions, visible defects, compressive strength, water absorption, and surface abrasion. These results demonstrated the high applicability of the local IBA in the production of the ICB for various construction application purposes.
Keywords:
interlocking concrete brick; waste incineration bottom ash; visible defect; compressive strength; bending strength; water absorption; surface abrasion.
20
Šmídová, Eliška, and Petr Kabele. "CONSTITUTIVE MODEL FOR TIMBER FRACTURE USED FOR FE SIMULATION OF LVL ARCH." Acta Polytechnica CTU Proceedings 15 (December 31, 2018): 109–13. http://dx.doi.org/10.14311/app.2018.15.0109.
Abstract:
Non-linear finite element simulation of four-point bending test of a small-size arch is described in this paper. The arch of 780mm span is made of Yellow Poplar (<em>Liriodendron tulipifera</em>) laminated veneer lumber (LVL) and it is manufactured with a through crack parallel to fibers in the middle of its crown. 2D homogeneous orthotropic constitutive model of tensile and shear fracture in timber that has been recently developed and implemented into ATENA<sup>®</sup> element software by the authors is used for the numerical calculation. Both standard and compact tension (CT) test results are used for the material model calibration. Results show that the model successfully reproduces the increasing part of the load-displacement response. Furthermore, the model can capture the most distinctive features of the crack pattern.
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Pokorska, Iwona, Mariusz Poński, Wojciech Kubissa, Tomasz Libura, Adam Brodecki, and Zbigniew Kowalewski. "Computational Fracture Evolution Analysis of Steel-Fiber-Reinforced Concrete Using Concrete Continuous Damage and Fiber Progressive Models." Materials 16, no. 16 (August 15, 2023): 5635. http://dx.doi.org/10.3390/ma16165635.
Abstract:
The process of concrete cracking is a common problem because the first micro-cracks due to the loss of moisture may appear even before the concrete is loaded. The application of fracture mechanics allows for a better understanding of this problem. Steel-fiber-reinforced concrete (SFRC) samples with a notch were subjected to a three-point bending test, and the results for crack energy were used to analyze the concrete’s material properties. In this paper, an experimental and numerical analysis of SFRC with rapid changes in the force (F) crack mouth opening displacement (CMOD) curve (F-CMOD) is presented. In order to obtain the relevant F-CMOD diagrams, three-point bending tests were carried out with non-standard samples with a thickness equal to one-third of the width of standard samples. For analysis purposes, crimped steel fibers were adopted. A probabilistic analysis of the most important parameters describing the material in question, such as peak strength, post-cracking strength, crack mouth opening displacement (CMOD), fracture energy, and the post-cracking deformation modulus, was conducted. The tests and the analysis of their results show that the quasi-static numerical method can be applied to obtain suitable results. However, significant dynamic effects during experiments that influence the F-CMOD curves are hard to reflect well in numerical calculations.
22
Skarzynski, Ł., and J. Tejchman. "Numerical Mesoscopic Analysis of Fracture in Fine-Grained Concrete." Archives of Civil Engineering 58, no. 3 (September 1, 2012): 331–61. http://dx.doi.org/10.2478/v.10169-012-0019-7.
Abstract:
Abstract This paper presents numerical two-dimensional results for fine-grained concrete under quasi-static three-point bending at meso-scale. Concrete was modelled as a random heterogeneous three-phase material. The simulations for notched concrete beams were carried out with the standard finite element method using an isotropic damage constitutive model enhanced by a characteristic length of micro-structure by means of a non-local theory. The effect of the volume fraction, shape, size, statistical distribution and stiffness of aggregate was analysed. Moreover, the effect of the bond thickness, notch size and characteristic length of micro-structure on the material behaviour was numerically investigated. The FE results were compared with own laboratory test results and other meso-scale calculations for three-phase concrete elements.
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Carreira, Marcelo Rodrigo, Pedro Gutemberg de Alcântara Segundinho, Fabricio Gomes Gonçalves, Juarez Benigno Paes, Antônio Alves Dias, Pedro Nicó de Medeiros Neto, Leonor da Cunha Mastela, and Yonny Martinez Lopez. "Influence of moisture content on the dynamic modulus of elasticity." Research, Society and Development 11, no. 11 (August 21, 2022): e232111133687. http://dx.doi.org/10.33448/rsd-v11i11.33687.
Abstract:
Pinus forests are the second most planted in Brazil and the wood obtained from them is mainly used as structural elements in the civil construction sector. The Brazilian standard that deals with calculations of wooden structures projects recommends the use of wood in the range of 10% to 20% of moisture content. Thus, this study aimed to present an investigation about the influence of moisture content on the static modulus of elasticity (MOEst) of wooden beams by transverse vibration tests. The MOEst was evaluated by static bending tests and transverse vibration tests for various moisture content. The transverse vibration test was performed in a free condition using an accelerometer and an impulse hammer, and the dynamic modulus of elasticity (MOEd) was determined from the frequency of the first bending vibration mode. A total of 20 wooden beams were obtained from freshly cut Pinus spp. logs with initial high moisture content were used, with nominal dimensions of 5 cm × 10 cm × 200 cm (thickness × width × length). It was observed that the MOEd is also affected by moisture content according to the non-linear regression model. There were significant changes in the dynamic modulus of elasticity (MOEd) for the moisture contents (M) below 25% (near the fiber saturation point - FSP).
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Jamshidi Avanaki, Mohammad, Mohammad Abedi, and Abdollah Hoseini. "Stress-Strain Constitutive Material Models for Hybrid Steel Fiber Reinforced Concrete." Journal of Civil Engineering and Construction 9, no. 2 (May 15, 2020): 74–82. http://dx.doi.org/10.32732/jcec.2020.9.2.74.
Abstract:
Recent advancements in fiber reinforced concrete (FRC) technology has led to the development of fibrous concrete composites, comprised of fibers with different material and/or geometry, commonly known as hybrid FRC. In one type of hybrid FRC composites, advantageous behaviors of fibers of the same material but with different geometries are gathered in a single FRC mix. The aim of this paper is to develop and validate stress-strain relationships for hybrid steel FRC composites. Six different steel FRC mixes are produced and characterization tests are conducted. Cube, cylindrical and beam specimens are produced for each characterization test corresponding to each of the Steel FRC (SFRC) composites. In this regard, an experimental program is performed to determine the basic engineering properties of SFRC composites using standard compressive, splitting tensile and three-point bending tests. The prescribed procedure of the RILEM guideline, originally developed for non-hybrid FRC, is followed using the obtained experimental results to develop stress-strain behavior models for the SFRC mixes. To validate results for the hybrid SFRC composites, numerical simulations of the 3-point bending tests were performed and compared to that of corresponding experimental results. The results indicated that the proposed stress-strain relationships yield acceptable results for characterizing the behavior of hybrid SFRC composites.
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Cho, Seong-Mook, Brian G. Thomas, Jong-Yeon Hwang, Jong-Geun Bang, and Il-Sin Bae. "Modeling of Inclusion Capture in a Steel Slab Caster with Vertical Section and Bending." Metals 11, no. 4 (April 17, 2021): 654. http://dx.doi.org/10.3390/met11040654.
Abstract:
Particles in molten steel, including argon-gas bubbles, slag droplets, and non-metallic inclusions, are removed into the surface-slag layer or captured by the solidifying steel-shell during continuous steel casting. Captured particles often become serious defects in the final steel product, so understanding particle-capture mechanisms is important for steel quality. Slab casters often have a straight mold and upper-strand prior to a curved lower-strand. The present work investigates particle capture in such a caster using computational modeling with a standard k-ε model for molten-steel flow, a discrete phase model for inclusion transport, and an advanced capture criterion for inclusion entrapment and engulfment into the steel shell. A new postprocessing methodology is presented and applied to predict inclusion-capture rates in commercial cast product. The locations and size distributions of particles captured into the shell, and actual capture rates are quantified. The model predictions are validated with ultrasonic-test plant measurements of the locations of large particles captured in a steel slab. The results reveal how large-inclusion capture accumulates in the beginning of the curved strand, leading to a capture band in the slab inside radius. Finally, the capture fractions and locations due to all capture mechanisms are compared for different inclusion sizes, and the implications are discussed.
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Yan, Zhao. "Research New Waterproof Agent of the Particleboard." Advanced Materials Research 960-961 (June 2014): 43–46. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.43.
Abstract:
Modern society,with the rapid development of economy,people living standard increasing, for the plate demand continues to grow. Because the forest resources dwindling, To make full use of waste bagasse, corn straw and non wood fiber materials to produce an artificial plate material instead of wood man-made board has be imperative.Corn straw shavings can realize the recycling of waste materials, bring the economic value, so this topic with corn straw shavings as raw material, in the laboratory preparation of melamine resin adhesive, pressing flake molded sheet.Melamine plastic using M ( melamine ):U ( urea ) :F ( formaldehyde ) =1∶0.6∶2.5, adhesive solid content is 54%, the sizing, hot pressing temperature, hot pressing time as three factors orthogonal experiment, pressed sheet. On the plate thickness swelling, internal bond strength and surface plate bending strength test, on the analysis and summarization of results, the optimum process parameters: sizing quantity20%, temperature 150 °C, hot pressing time25min. The corresponding optimum mechanical properties: the absorbing water thickness expansion rate (2H ) 9.76%, inner strength, bend strength of17.49Mpa,0.45MPa. Key words: Non wood shavings; Molded sheet; Process parameters; Mechanical properties
27
Simegnaw, Abdella Ahmmed, Yetanawork Teyeme, Benny Malengier, Tamrat Tesfaye, Hundessa Daba, Kaledawit Esmelealem, and Lieva Van Langenhove. "Smart Shirt for Measuring Trunk Orientation." Sensors 22, no. 23 (November 23, 2022): 9090. http://dx.doi.org/10.3390/s22239090.
Abstract:
Improper cycling posture is linked to a variety of spinal musculoskeletal diseases, including structural malformation of the spine and back discomfort. This paper presents a novel smart shirt integrated tri-axial gyroscope and accelerometer that can detect postural variation in terms of spinal curvature changes. To provide accurate feedback to the wearer and improve the wearer’s correct movement, the garment is able to recognize trunk body posture. The gyroscope/accelerometer was placed around the upper and mid trunk of the user to record tri-axial angular velocity data. The device can also be used to help determine the trunk bending angle and monitor body postures in order to improve optimal orientation and position. The garment enables continuous measurement in the field at high sample rates (50 Hz), and the sensor has a large measurement range (16 g, 2000°/s). As electronic components are non-washable, instead of encapsulating them, a detachable module was created. In this, magnets are embedded in the jersey, and allow the positioning and removal of the sensor. The test results show that the average trunk-bending angle was 21.5°, and 99 percent of the observed angle fell within the standard (ranging from 8° to 35°). The findings demonstrate the feasibility of employing the smart shirt sensor to estimate trunk motions in the field on a regular basis.
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Sauri, Fauzan, and Mulianti Mulianti. "The Effect of Preheating and Non-Preheating in Cast Iron Welding Toward Mechanical Properties." Teknomekanik 3, no. 2 (December 10, 2020): 70–74. http://dx.doi.org/10.24036/teknomekanik.v3i2.7272.
Abstract:
Cast iron material is a material that has brittle properties and is less able to withstand stress due to the welding cycle caused by flake graphite in cast iron. Because of these problems, in connecting cast iron materials using the SMAW welding method, it is necessary to have heat treatment (preheating) to avoid the welding problems on the properties of cast iron. The purpose of this study is to determine the effect of heating and non-heating on the cast iron before the welding process. Therefore, this research will play a crucial contribution as a reference for cast iron welding researchers and cast iron welding process. The method of the research was experimental research, where the measurement results were obtained directly from the specimens. The welding was using an open V seam. The specimen used was cast iron with a thickness of 8 mm. One cast iron was given heat treatment at a temperature of 260ºC and the others did not receive heat treatment before being welded. The welding process used SMAW with CIN - 2 electrodes with a diameter of 3 mm. The test used the bending test on the face specimens according to the American Welding Society D1.1 standard. The results showed that there was an effect of the preheating treatment on cast iron, which that the non-preheating specimens were easier to fracture than the preheating specimens. Thus, it can be concluded that welding with preheating is better than welding without preheating.
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Bahtiar, Effendi Tri, Erizal Erizal, Dede Hermawan, Naresworo Nugroho, and Rizky Hidayatullah. "Experimental Study of Beam Stability Factor of Sawn Lumber Subjected to Concentrated Bending Loads at Several Points." Forests 13, no. 9 (September 14, 2022): 1480. http://dx.doi.org/10.3390/f13091480.
Abstract:
The beam stability factor (CL) is applied in construction practices to adjust the reference bending design value (Fb) of sawn lumber to consider the lateral-torsional buckling. Bending tests were carried out on 272 specimens of four wood species, namely, red meranti (Shorea sp.), mahogany (Swietenia sp.), pine (Pinus sp.), and agathis (Agathis sp.), to analyze a simply supported beam subjected to concentrated loads at several points. The empirical CL value is a ratio of the modulus of rupture (SR) of a specimen to the average SR of the standard-size specimens. The non-linear regression estimated the Euler buckling coefficient for sawn lumber beam (KbE) in this study as 0.413, with 5% lower and 5% upper values of 0.338 and 0.488. Applying the 2.74 factor, which represents an approximately 5% lower exclusion value on the pure bending modulus of elasticity (Emin) and a factor of safety, the adjusted Euler buckling coefficient (KbE′) value for a timber beam was 1.13 (0.92–1.34), which is within the range approved by the NDS (KbE′ = 1.20). This study harmonizes the NDS design practices of CL computation with the empirical results. Because agathis has the lowest ductility (μ), most natural defects (smallest strength ratio, S), and highest E/SR ratio, the agathis beam did not twist during the bending test; instead, it failed before twisting could occur, indicating inelastic material failure. Meanwhile the other specimens (pinus, mahogany, and red meranti), which have smaller E/SR ratio, higher ductility, and less natural defects, tended to fail because of lesser beam stability. This phenomenon resulted in the CL curve of agathis being the highest among the others. The CL value is mathematically related to the beam slenderness ratio (RB) and the E/SR ratio. Because the strength ratio (S) and ductility ratio (μ) have significant inverse correlations with the E/SR ratio, they are correlated with the CL value. Applying the CL value to adjust the characteristic bending strength is safe and reliable, as less than 5% of the specimens’ SR data points lie below the curve of the adjusted characteristics values.
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Zhang, Qin, Song Mao, Mao Jiang, Xiao Dong Chen, and Wei Cheng. "Experiment on Decarburization of High Carbon Fly Ash and Preparation of Concrete." Advanced Materials Research 881-883 (January 2014): 1250–54. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1250.
Abstract:
The raw fly-ash applied in this study has an ignition loss of 17.30 %. The results of floatation experiment show 4.40 % coal content of tailing ash. The screen analysis results on decarburized fly ash shows that the content of +45 μm is above 12 %, failing to meet the quality of Grade I fly ash determined in the standard of China. Therefore, the decarburized fly ash was processed by grinding to meet the required quality. The analysis of the main constituents of different grinding methods conducted for tail fly ash shows that fly ash obtained by open circuit ball mill are the most suitable one used as admixture of concrete. Comparisons were made on the compressive strength and bending strength of 7d and 28d under the conditions of non-grinding and five ways of grinding. The test results show that grinding can improve the compressive strength of fly ash concrete. By way of closed-circuit grinding rod mill, concrete, can fly ash concrete strength be increased remarkablely.
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Suwanasri, Cattareeya, Thanapong Suwanasri, and Phanupong Fuangpian. "Investigation on Partial Discharge of Power Cable Termination Defects using High Frequency Current Transformer." ECTI Transactions on Electrical Engineering, Electronics, and Communications 12, no. 1 (November 19, 2013): 16–23. http://dx.doi.org/10.37936/ecti-eec.2014121.170810.
Abstract:
This paper presents partial discharge (PD) investigation of different cable termination defects. The medium voltage power cables as rated of 3.6/6(7.2) kV are applied. Finite Element Method Magnetic (FEMM) program is used as a simulation tool for electric field stress investigation. The partial discharges patterns are detected by using a commercial High Frequency Current Transformer (HFCT). The simple cases for internal, surface and corona discharge are firstly observed in order to investigate the performance of the HFCT. Then eight different case studies of cable termination defects are further investigated, which includes non-terminator, voids between XLPE and stress control, 20 mm. overlaps between semiconductor and stress control, particles on XLPE, non-smooth XLPE, needle tip on insulation screen, impropriate cable bending, and proper termination. The results are then compared with the results from a conventional PD diagnosis tool according to IEC 60270 standard. The results of PD detection show that the commercial product can detect the PD waveform and measure the electric charge when it is highly enough. The test can also identify trends toward breakdown and there severity due to improper cable termination defects.
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van Blokland, Joran, Stergios Adamopoulos, and Sheikh Ali Ahmed. "Performance of Thermally Modified Spruce Timber in Outdoor Above-Ground Conditions: Checking, Dynamic Stiffness and Static Bending Properties." Applied Sciences 10, no. 11 (June 8, 2020): 3975. http://dx.doi.org/10.3390/app10113975.
Abstract:
Previous studies have shown that thermally modified wood (TMW) performs well in outdoor, above-ground conditions in terms of resistance to wood-decaying fungi. Yet, little is known about the development of defects such as checks and the corresponding mechanical properties of TMW in this condition. This experiment focused on the effect of 30 months outdoor above-ground exposure (weathering) on the degree of checking, dynamic stiffness and static bending properties of thermally modified timber (TMT) of Norway spruce. Two board pairs per log were cut from 190 logs; one board of each pair was thermally modified and the other used as control. Then, 90 board pairs were exposed to the weather in south Sweden. Surface checking and axial stiffness were monitored at six-month intervals by using digital photography and non-destructive tests (time-of-flight and resonance method) to monitor changes in the material upon weathering. Finally, all boards were tested destructively in a 4-point static bending test following EN 408 standard. Results showed that weathering had no significance influence on static bending properties of TMT even though the degree of checking was considerably higher in TMT than unmodified timber after weathering. In particular, checks along growth rings were deeper, longer and more common in TMT after weathering, especially on the pith side of boards. The maximum depth of these checks did not depend on board orientation (i.e., which side was exposed) and exceeded limits given in strength grading standards for 7% of the modified boards included. Axial dynamic stiffness determined at 6-month intervals was less influenced by fluctuations in moisture content for TMT compared to unmodified timber, but did not confirm the increase in the degree of checking of TMT. The presence of checks from weathering did influence failure modes in TMT; horizontal shear failure became more frequent and some boards failed in compression.
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Krzosek, Sławomir, Marek Grześkiewicz, Izabela Burawska Kupniewska, Piotr Mańkowski, and Marek Wieruszewski. "MECHANICAL PROPERTIES OF POLISH-GROWN PINUS SYLVESTRIS L. STRUCTURAL SAWN TIMBER FROM THE BUTT, MIDDLE AND TOP LOGS." WOOD RESEARCH 66(2): 2021 66, no. 2 (April 30, 2021): 231–42. http://dx.doi.org/10.37763/wr.1336-4561/66.2.231242.
Abstract:
The research consisted in testing Polish sawn timber dedicated for construction applications made of pines (Pinus sylvestris L.) that grew in the Silesian Forestry Region, taking into account three parts of the log: butt, middle and top. The boards had the same cross section, a nominal thickness of 40 mm and width of 138 mm, typical for Polish structural timber. The mean nominal length of the boards under research amounted to 3500 mm. Each set was composed of 70 boards. Before the tests, boards were dried in an industrial drier until reaching the moisture content of 12%, and they were planed on 4 sides. First of all, the sawn timber was graded into strength classes, and their dynamic modulus of elasticity (MOE_dyn) was tested with a non-destructive method, with the use of a portable MTG device. The next step consisted in a bending test with four points of support, according to the EN 408 standard, and with the use of the TiraTest 2300 machine, in order to determine the global modulus of elasticity (MOE_EN-408) and the static bending strength, also referred to as modulus of rupture (MOR). Finally, the average growth ring width was determined for each board (PN-D-94021), as well as wood density according to EN-408. The hereby paper presents the test results for all the tested sawn timber boards, taking into account the part of log that each board came from: butt, middle or top. The hereby paper presents the influence of density on the mechanical properties of wood, taking into account the location on the round timber. The analysis does not include the influence of the width of annual growth rings and the proportion of latewood on the wood properties under research.
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Adamczak-Bugno, Anna, Grzegorz Świt, and Aleksandra Krampikowska. "Fibre-Cement Panel Ventilated Façade Smart Control System." Materials 14, no. 17 (September 5, 2021): 5076. http://dx.doi.org/10.3390/ma14175076.
Abstract:
This paper outlines a design for a fibre-cement panel ventilated façade smart control system based on the acoustic emission method. The paper also provides methodology and test results, as well as statistical analysis of the three-point bending results with AE signal acquisition as a basis for the development of the system in question. The test items were samples cut from a full-size fibre-cement panel for interior and exterior use, according to the standard guidelines. The recorded acoustic emission signals were classified statistically into four classes, which were assigned to the processes occurring in the material structure as a result of the applied load. The system development was based on the differences between the characteristics of the individual signal classes and their number for each test case, as well as on the different distribution of successive classes over time. Given the results of the tests and the resulting conclusions indicating the applicability of the acoustic emission method (based on signal classification using the k-means algorithm for the assessment of variations in the mechanical parameters of cement-fibre composites), a methodology for such assessment was therefore developed. The approach proposed is a reasonable method for assessing the variation in mechanical parameters of fibre-cement panels on the basis of the parameters determined by the non-destructive method indicated.
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Zhang, Hou Jiang, Lei Zhu, Yan Liang Sun, Xi Ping Wang, and Hai Cheng Yan. "Determining Modulus of Elasticity of Ancient Structural Timber." Advanced Materials Research 217-218 (March 2011): 407–12. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.407.
Abstract:
During maintenance of ancient timber architectures, it is important to determine mechanical properties of the wood component materials non-destructively and effectively, so that degraded members may be replaced or repaired to avoid structural failure. Experimental materials are four larch (Larix principis-rupprechtii Mayr.) components, which were taken down from the drum-tower of Zhengjue Temple of Yuanmingyuan (Old Summer Palace), Beijing, China. The larch components were cut into standard specimens first, and then stress wave transmission times, resistograph and densities were tested. Product of resitograph and stress wave speed squared is defined as modulus of stress-resistograph. Comparing with the modulus of elasticity (MOE) of the specimens tested by the traditional bending test method, it is found that there is a linear relationships between the modulus of stress-resistograph and modulus of elasticity (MOE), and the correlation coefficients are 0.7111. In order to better evaluate the modulus of elasticity (MOE) with the modulus of stress-resistograph, 95% confidence regression lines are suggested to be used for the future calculation.
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Gajewski, Tomasz, Tomasz Garbowski, Natalia Staszak, and Małgorzata Kuca. "Crushing of Double-Walled Corrugated Board and Its Influence on the Load Capacity of Various Boxes." Energies 14, no. 14 (July 17, 2021): 4321. http://dx.doi.org/10.3390/en14144321.
Abstract:
As long as non-contact digital printing remains an uncommon standard in the corrugated packaging industry, corrugated board crushing remains a real issue that affects the load capacity of boxes. Crushing mainly occurs during the converting of corrugated board (e.g., analog flexographic printing or laminating) and is a process that cannot be avoided. However, as this study shows, it can be controlled. In this work, extended laboratory tests were carried out on the crushing of double-walled corrugated board. The influence of fully controlled crushing (with a precision of ±10 µm) in the range from 10% to 70% on different laboratory measurements was checked. The typical mechanical tests—i.e., edge crush test, four-point bending test, shear stiffness test, torsional stiffness test, etc.—were performed on reference and crushed specimens. The residual thickness reduction of the crushed samples was also controlled. All empirical observations and performed measurements were the basis for building an analytical model of crushed corrugated board. The proven and verified model was then used to study the crushing effect of the selected corrugated board on the efficiency of simple packages with various dimensions. The proposed measurement technique was successfully used to precisely estimate and thus control the crushing of corrugated board, while the proposed numerical and analytical techniques was used to estimate the load capacity of corrugated board packaging. A good correlation between the measured reduced stiffness of the corrugated cardboard and the proposed analytical predictive models was obtained.
37
Fu, Baofei, Chenzhuo Li, Bo Dong, and Pan Ou. "Enhanced Digital Gradient Sensing Using Backlight Digital Speckle Target." Sensors 20, no. 22 (November 17, 2020): 6557. http://dx.doi.org/10.3390/s20226557.
Abstract:
Digital gradient sensing (DGS) is a non-contact and full-field optical measurement technique, which assesses mechanical behaviors of transparent materials or specular structures by measuring angular deflections of light rays. However, owing to the poor light-gathering capability of its imaging system, the dynamic performance of DGS is heavily restricted. Here, a method of enhancing the dynamic performance of DGS by improving its speckle target is proposed. The method employs the technique of backlight illumination, which significantly increases the utilization efficiency of light, shortens the exposure time, and enhances the dynamic performance of DGS. Additionally, it also uses the optimized digital speckle pattern to improve the measurement precision and accuracy. For validation, a comparison experiment was conducted, proving that the proposed method can improve the utilization efficiency of light by about 80 times and improve the quality of the speckle images by about 40%. Real tests, including a uniaxial tension test using transmission-mode DGS (t-DGS) and a three-point bending test using reflection-mode DGS (r-DGS), were also carried out, showing the efficacy and high compatibility of the proposed backlight digital speckle target. In summary, this simple method greatly improves the performance of DGS, which can be used as a standard method in both t-DGS and r-DGS.
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İşleyen, Ümmü K., Rahim Ghoroubi, Ömer Mercimek, Özgür Anil, and Recep Tuğrul Erdem. "Behavior of glulam timber beam strengthened with carbon fiber reinforced polymer strip for flexural loading." Journal of Reinforced Plastics and Composites 40, no. 17-18 (April 9, 2021): 665–85. http://dx.doi.org/10.1177/0731684421997924.
Abstract:
In the last 20 years, the use of wooden structures and their dimensions have gradually increased. The wood application has increased in different structures such as multistory buildings, sports, industrial facilities, road and railway bridges, power transmission lines, and towers. The widespread use and size of wood structures have increased the research on developing special types of wood products supported by composite materials. Laminated wood elements are the leading composite wood materials. Laminated wooden beams allow making much larger openings than standard solid wood structural elements. The development of the sizes and usage areas of wooden structures has increased the capacity of glulam structural elements and reveals the need to improve their performance. Carbon fiber reinforced polymers (CFRPs) are the most suitable options for increasing the bearing capacity values of glulam beams and improving general load–displacement behaviors. In this study, the use of CFRP strips in different layouts to increase glulam wooden beams and the application of CFRP fan-type anchors in the CFRP strip endpoints are the studied variables. Anchored and non-anchored glulam wooden beams reinforced with CFRP strips with different layouts were tested using a three-point bending test. The ultimate load capacity, initial stiffness, displacement ductility ratio, energy dissipation capacity, failure mechanisms, and general load–displacement behavior of wooden beam test specimens were obtained and interpreted as a result of the experiments.
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Rakhmanov, V. A., V. I. Melikhov, and A. A. Safonov. "Wind loads tests of external walls blocks masonry of noncombustible polystyrene concrete." Concrete and Reinforced Concrete 617, no. 3 (July 31, 2023): 15–23. http://dx.doi.org/10.37538/0005-9889-2023-3(617)-15-23.
Abstract:
Introduction. Blocks of non-combustible polystyrene concrete of D300 density grade, B1 compressive strength class with normalized thermal conductivity λ0 = 0,078 W/(m·°C) and frost resistance grade not lower than F75, developed by LLC “Institute VNIIZhelezobeton”, were used in masonry with a thickness of 375 mm without special fireproof lining. Such masonry successfully passed standard fire tests for fire hazard and fire resistance, which showed the possibility of its use in external non-bearing energysaving walls of multi-storey buildings (up to 25 floors inclusive, about 75 m high).Aim. Evaluation of the strength and deformation characteristics of non-combustible wall masonry made of noncombustible polystyrene concrete blocks with a density of D300 at design wind loads at a height of about 75 m. Materials and methods. Fragments of uncoated wall masonry 375 mm thick, 2,7 m high and 1,2 m wide of noncombustible polystyrene concrete blocks mounted on a mortar with over-all dimensions of 295 × 375 × 595 mm were tested.The test procedure is in accordance with State Standard 8829-2018.Results. The destructive bending load exceeded the calculated one by an average of 4,1 times, while the deflection in the middle of the fragment was 1,9 times less than the permissible one.A methodology has been developed for calculating the strength and deformability of masonry of polystyrene concrete blocks under wind loads, taking into account the influence of horizontal and vertical masonry joints, which is scheduled to be reflected in Amendment No. 1 SP 434.1325800.2018.Conclusions. The results of wind load tests showed that for unlined masonry made of non-combustible polystyrene concrete blocks with a density of D300 and a thickness of 375 mm, the requirements for strength and deformability are met with a significant margin. The results of tests for wind and fire effects of the specified block masonry make it possible to use it in nonbearing external walls of multi-storey residential energyefficient buildings up to 75 m high in virtually all regions of Russia.
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Ahmad, Bilal, and Xiangfan Fang. "Modeling Shear Behavior of Woven Fabric Thermoplastic Composites for Crash Simulations." Applied Composite Materials 27, no. 6 (November 20, 2020): 739–65. http://dx.doi.org/10.1007/s10443-020-09844-0.
Abstract:
AbstractWoven fabric thermoplastic composites possess high specific strength and stiffness along with thermoformability. To utilize the full potential of these materials to achieve better crash-safe designs in automotive structural parts, the measurement of non-linear shear behavior and its material modeling for FEM simulations is required. The standard testing method was used to measure the pure shear behavior of woven fabric composites. These results were compared with the shear behavior of material in the presence of normal stresses along the fiber direction. Tensile and compression cyclic testing of ± 45° laminate were carried out to measure the stiffness degradation and hardening of the material in the presence of tensile normal and compression normal stress. A methodology is proposed for taking into account the differences in shear behavior under different loading directions in an FEM simulation. Based on the experimental evidence, improvements in the mathematical description of plasticity and damage in continuum damage mechanics models are proposed. The model was implemented as a user-defined material subroutine (VUMAT) for Abaqus. The experimental results from coupon tests were used to verify the results of a single element simulation. Finally, a three-point bending test was used to validate the predictions of the user material model.
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Lolli, S., A. Hidalgo, C. Alamprese, V. Ferrante, and M. Rossi. "Layer performances, eggshell characteristics and bone strength in three different housing systems." Biotehnologija u stocarstvu 29, no. 4 (2013): 591–606. http://dx.doi.org/10.2298/bah1304591l.
Abstract:
The aim of this study was to determine the effects of three different housing systems for laying hens (cages, barn and organic) on layer performances, eggshell characteristics and bone strength. In each system, the same strain of laying hens (Hyline Brown?) was housed in agreement with current European regulation and the hens were fed on the same level of nutrition (2800 ME). The study was conducted over one year period in three typical farms in the north of Italy, from the 18th to the 70th weeks of layers age. The number of eggs collected and laid on the floor were recorded weekly, as well as the mortality and the feed consumption. At 27, 30, 35, 43, 53 and 68 weeks of layers age, the weight and the shell characteristics of eggs from the different systems were analysed. Bone breaking strength and stiffness were determined by three point bending test. The percentage of deposition was generally higher in comparison to the standard production of Hyline hens, probably, due to a high management standard and to the production persistence. The results indicated a clear relationship between the percentage of cracked eggs and the strength characteristics of the shells, with organic eggs showing the highest shell thickness, the most resistant shell and consistently the less cracked eggs. Considering the changes that occur during the laying cycle, shell strength and thickness in non-cage eggs were highly affected by hen age, while they were much stable in cage eggs. Organic hens also showed the strongest humerous, while their tibiotarsus were as robust as those of cage hens.
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Subramanya, N., A. R. Satheesh Kumar, D. G. Visakh, and K. Balasubramanya. "Certification of welder for tungsten inert gas welding in unmanned aerial vehicle systems." IOP Conference Series: Materials Science and Engineering 1291, no. 1 (September 1, 2023): 012036. http://dx.doi.org/10.1088/1757-899x/1291/1/012036.
Abstract:
Abstract Aluminum and its alloys is one of the extensively used non-ferrous metal in aerospace engineering applications due to its excellent properties like higher strength to weight ratio, non-magnetic property, high thermal conductivity, good machinability, recyclability, and excellent formability. However, welding of aluminum and its alloys has always been a challenge due to drastic reduction in strength near heat affected zone (HAZ). Due to softness, ductility, lower melting point of aluminum and its alloys impose additional challenges to weld aluminum alloy components. Due to this, the quality and quantum of skill set needed to weld aluminum alloy joints for flight critical components is much more than that of welding of ferrous materials. The qualification and certification of welder is one of the prime requirements in welding applications especially in aerospace industry. This paper mainly discusses the various aspects involved in qualifying and certifying a welder for tungsten inert gas (TIG) welding process of aluminum alloys, which is treated as one of the special processes. The welder certification is a written verification that weld joints produced by welder meets the prescribed standard of welder performance. It is to verify the ability of an individual to execute a qualified welding procedure specification to produce a sound weld. Aluminum alloy 6xxx series is considered for base metal for sample preparation and weld joint assessment studies, as it is one of the prevalently used aluminum alloy material in unmanned aerial vehicle (UAV) applications. Weld samples are prepared as per internationally practiced standards and welding procedure specification (WPS) is recorded. Various mechanical tests carried out on weld samples during certification process are discussed in the paper. Weld joints are subjected to tensile testing, bending test and macro test. The certifying agencies are involved at every stage to ensure consistency of welder performance.
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Bui, Tien Thanh, Guido De Roeck, Jeroen Van Wittenberghe, Patrick De Baets, and Wim De Waele. "Fatigue damage identification in threaded connection of tubular structures through in-situ modal tests." International Journal Sustainable Construction & Design 2, no. 2 (November 6, 2011): 207–2016. http://dx.doi.org/10.21825/scad.v2i2.20518.
Abstract:
The use of threaded connection is a valuable alternative to conventional welding in tubularconstructions, e.g. pipelines, drill pipes and deep water risers. Those applications are normally exposed toenvironmental hazards – wave induced vibrations, temperature changes, etc. – as well as subjected tosevere service conditions. A classical way to determine fatigue strength in many engineering situations is tocalibrate material models by means of ad hoc designed experiments. Unfortunately, it is very difficult in thiscase even under laboratory conditions due to complicated stress and strain states in the contacting taperedhelical thread surfaces of the connection. Therefore, a classical four-point bending fatigue test setup hasbeen built with a real pipe specimen of 3.75 meter long, consisting of two standard API pipes connected bya threaded coupling, under unsymmetric (non-zero average) load control cycles. A complete vibration studyhas been carried out based on input-output modal tests for the entire period of the fatigue experiment. Inputexcitation is due to hammer impact and responses are recorded by accelerometers and by reusabledynamic strain gauges. The measured modal strains from the dynamic strain gauges allow for directcalculation of the modal curvatures, rather than deriving approximately from acceleration information. Bycomparing the measured modal parameters with those of a numerical model of the same structure inundamaged condition, damage detection, localization in the coupling and quantification are possible. Thisstudy leads to the following conclusion of practical use: the recent advancement in modal analysis, i.e. thereference based input-output combined deterministic-stochastic subspace identification, makes it possibleto identify the structural modal properties from in-situ modal tests, which are performed while the fatiguetest is ongoing. In this way the fatigue test is uninterrupted to avoid the problem of stress and straindisturbances happened in un-reversing load cycles test.
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Bhanushali, J. D., and M. Nithyadharan. "Experimental studies on fiber cement boards under compression loading." Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, no. 1 (December 19, 2022): 179–86. http://dx.doi.org/10.38208/acp.v1.492.
Abstract:
Fibre cement boards are widely used as external cladding in cold-formed steel (CFS) building systems, due to their superior durability and weather-resistant characteristics. These boards are made of cement and reinforced with short, randomly oriented, non-hazardous cellulose fibres. Characterizing the observed stress-strain behaviour of the board under compression loading is a challenging task due to: a) loading eccentricity which induces bending, b) global buckling caused by high slenderness of the specimen, and c) stress concentrations at the loading end resulting in bearing failure. The above failures are usually handled at the specimen preparation stage by gluing additional numbers of boards to reduce slenderness, and by the inclusion of end tabs to avoid bearing failure. However, the introduction of glue in the board specimen may alter the strength characteristics and modify the load transfer path. Preliminary studies on the board specimens following the standard testing procedure (ASTM D3501) for wood-based panels fail to simulate the real material behaviour of the boards under compression loading. It is clear that the existing test methods have several shortcomings and hence cannot be adopted for fibre cement boards. In this paper, the fibre cement boards were tested under compression loading using combined loading compression (CLC) test fixture. This paper presents the details of the experimental study and the results for board of thicknesses 8, 10, and 12 mm, respectively. The test matrix includes specimens tested in both longitudinal and transverse directions. Under compression loading, the board exhibited nonlinear behaviour up to failure. The structural parameters like ultimate stress, ultimate strain, Young's modulus, and Poisson ratio in both longitudinal and transverse directions were obtained. This study proposes a nonlinear constitutive model for the board material.
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Kauniste, Maarja, Alar Just, Eero Tuhkanen, and Targo Kalamees. "Assessment on Strength and Stiffness Properties of Aged Structural Timber." Journal of Sustainable Architecture and Civil Engineering 34, no. 1 (February 19, 2024): 62–74. http://dx.doi.org/10.5755/j01.sace.34.1.35534.
Abstract:
Despite the growing popularity of wood and wood-based products in the construction industry, there has been insufficient focus on assessing the condition, preservation, and potential reuse of existing timber. While numerous standards evaluate the quality of freshly sawn timber, there is currently no standardized system for assessing the strength properties of aged and reused timber. The lack of these guidelines is also one of the reasons the results obtained in numerous research are often fluctuating, and we cannot draw clear conclusions. The matter is further complicated by the lack of data on old in-situ wood and its exploitation, which would help to evaluate its condition. Consequently, there is a real practical need to assess the condition of old timber to avoid unnecessary demolition and the loss of valuable and structurally sound building material. What sets this study apart from others is that, in addition to destructive testing, the 4-point non-destructive (ND) bending tests were conducted on all four faces of test specimens. This provided an opportunity to assess the wood visually and then find connections to associate external characteristics with real properties. This methodology aimed to determine whether it is feasible to visually assess the most practical way to use wooden elements in construction. If this question arises, which face of the beam would be better suited for the tension side and which for the compression side? The old timber used in testing originated from an old library building located on Vaksali Street, Tartu, Estonia and is estimated to be about 120 years old. This paper investigates and compares the collected data with a Nordic standard for grading fresh-sawn timber and two established Italian standards for visually assessing aged timber. This comparison contributes to developing a standardized framework for future visual assessments. ND and destructive four-point bending tests were performed to validate and find appropriate visual characteristics to determine the strength and stiffness of the timber elements. The primary goals of this study were first to compare the results obtained from existing ND methods with actual results and secondly to provide guidelines for better visual grading of wood in the future, based on Nordic Standard INSTA 142 (2010) and Italian standards UNI 11119 (2004) and UNI 11035 (2010) Contrary to previous research conclusions, the visual assessment results yielded unexpected outcomes. The results show that the grading standards significantly underestimated the real strength of the wood, and even more, none of the visual assessments overestimated the real strength of the specimens. Therefore, based on prior research and the findings derived from this study, there is evident a substantial potential for extensive development and optimization within this field.
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Carvalho, Ronaldo Lúís Almeida de, Estevão Tomomitsu Kimpara, Eduardo Bresciani, Márcia Carneiro Valera, and Renata Marques Melo. "Effect of thermocycling aging on the flexural strength of feldspathic ceramic." Brazilian Dental Science 21, no. 3 (August 1, 2018): 315. http://dx.doi.org/10.14295/bds.2018.v21i3.1554.
Abstract:
<p><strong>Objective: </strong>The aim of the study was to evaluate the effect of aging through different thermocycling protocols on the flexural strength of a feldspathic ceramic. <strong>Material and Methods:</strong> Fifty ceramic bars, Vitablock Mark II (VITA), with dimensions of 18X4X2mm were prepared. The bars were randomly distributed to the groups (n = 10), which were defined according to the number of thermal cycles (TCy): G0 - no TCy; G500 - 500 cycles of TCy; G6000 - 6000 TCy; G10000 - 10000 TCy; G15000 - 15000 TCy. After aging, the specimens were subjected to the three point bending test in a universal testing machine (EMIC DL 1000), under 0.5mm/min speed and loading of 50kgf, until catastrophic failure. A sample of each group was evaluated for topographic morphology under Scanning Electron Microscopy. <strong>Results:</strong> For mechanical testing, the following mean values and standard deviation (MPa) were obtained: G0 (99.78 ± 5.07); G500 (101.64 ± 5.59); G6000 (98.13 ± 4.95); G10000 (91.77 ± 9.68); G15000 (101.51 ± 4.22). An analysis of variance by regression equation (p = 0.387) was performed, demonstrating a weak and non-significant correlation between flexural strength and number of thermal cycles. <strong>Conclusion: </strong>It can be concluded that aging in water solely by different numbers of temperature cycles did not influence on the flexural strength of a feldspathic ceramic.</p><p> </p><p><strong>Keywords</strong></p><p> Material resistance; Aging; Ceramics.</p>
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Fajrin, Jauhar, Ni Nyoman Kencanawati, Miko Eniarti, and Arismanto Arismanto. "Core Configuration Effect On The Flexural Behaviour Of Sandwich Panel Made Of Aluminium Skin And Sengon Wood Core." Jurnal Rekayasa Sipil (JRS-Unand) 17, no. 3 (February 26, 2022): 186. http://dx.doi.org/10.25077/jrs.17.3.186-193.2021.
Abstract:
Among the many choices of composite sandwich panel cores, Balsa wood is one of the main alternatives of cores made of wood. However, the availability and price of Balsa wood are quite expensive, so it needs alternatives from other types of wood such as Sengon wood. The purpose of this study was to evaluate the feasibility of Sengon wood as a core of composite sandwich panels. Three variations of the Sengon wood layout had been prepared as the core of the sandwich panels with a skin made of aluminum. All specimens, including the control specimens made of whole Sengon wood, were prepared with a size of 550 x 50 x 24 mm for length, width, and depth, respectively. Each variation and also the control specimens were made of 3 pieces. Tests were carried out based on the ASTM C 393-94 standard under the three-point bending test scheme. The results showed that the sandwich panel with plain Sengon wood core has the highest capacity to carry a flexural load, which is approximately 177.391 MPa, followed by a sandwich panel with long and end grain Sengon board that possess flexural strength of 153.913 MPa and 79.101 MPa, respectively. The flexural strength of these sandwich panels is superior to solid Sengon wood. The sandwich panels showed a typical ductile material indicated by a non-linear curve without a distinct yielded point before reach the maximum failure load. Three sandwich panels with various Sengon wood cores collapsed under three types of failure mechanisms; face wrinkling, shearing of the core, and delamination between the interface of skin and core. In conclusion, Sengon wood has a great potential to be used as the core material for a composite sandwich panel.
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Al-Qahtani, Amal S., Huda I. Tulbah, Mashael Binhasan, Maria S. Abbasi, Naseer Ahmed, Sara Shabib, Imran Farooq, et al. "Surface Properties of Polymer Resins Fabricated with Subtractive and Additive Manufacturing Techniques." Polymers 13, no. 23 (November 24, 2021): 4077. http://dx.doi.org/10.3390/polym13234077.
Abstract:
This study aimed to compare the surface roughness, hardness, and flexure strength of interim indirect resin restorations fabricated with CAD-CAM (CC), 3D printing (3D), and conventional techniques (CV). Twenty disk (3 mm × Ø10 mm) and ten bar specimens (25 × 2 × 2 mm) were fabricated for the CC, 3D, and CV groups, to be used for surface roughness, micro-hardness, and flexural strength testing using standardized protocol. Three indentations for Vickers micro-hardness (VHN) were performed on each disk and an average was identified for each specimen. Surface micro-roughness (Ra) was calculated in micrometers (μm) using a 3D optical non-contact surface microscope. A three-point bending test with a universal testing machine was utilized for assessing flexural strength. The load was applied at a crosshead speed of 3 mm/min over a distance of 25 mm until fracture. Means and standard deviations were compared using ANOVA and post hoc Tukey–Kramer tests, and a p-value of ≤0.05 was considered statistically significant. Ra was significantly different among the study groups (p < 0.05). Surface roughness among the CC and CV groups was statistically comparable (p > 0.05). However, 3D showed significantly higher Ra compared to CC and CV samples (p < 0.05). Micro-hardness was significantly higher in 3D samples (p < 0.05) compared to CC and CV specimens. In addition, CC and CV showed comparable micro-hardness (p > 0.05). A significant difference in flexural strength was observed among the study groups (p < 0.05). CC and 3D showed comparable strength outcomes (p > 0.05), although CV specimens showed significantly lower (p < 0.05) strength compared to CC and 3D samples. The 3D-printed provisional restorative resins showed flexural strength and micro-hardness comparable to CAD-CAM fabricated specimens, and surface micro-roughness for printed specimens was considerably higher compared to CAD-CAM and conventional fabrication techniques.
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Moh, Eun Ho, Kyo Shik Park, Jeong Woo Jo, and Myeong Hui Yu. "A Study on the Improvement of Safety Management by Improving the Production Quality of PC(Precast Concrete) : PC Slab Falling Accident in Construction of Logistics Warehouse." Forum of Public Safety and Culture 19 (November 30, 2022): 15–30. http://dx.doi.org/10.52902/kjsc.2022.19.15.
Abstract:
On 16th of November 2021, the PC slab had been fallen out and dropped to approximately 10M downstairs slab during the PC slab concrete pouring work on the rooftop floor of new logistics warehouse construction in Hwaseoung, Gyeonggi-do, and this accident was mainly caused by the bending fracture of concrete since the weaker strength of the upper compressed concrete compared to the tensile strength of central lower parts failed to withstand the high stress of upper topping concrete pouring. For the investigation of root-cause for above mentioned accident, the design compressive strength had been tested by utilizing the core sampling(extracting) method for the PC slab which was fallen out while pouring topping concrete, and as a result, the average compressive strength of three(3) concrete specimens collected from the relevant member through the destructive test was observed as 21.7MPa (No.1 – 20.6MPa, No.2 – 18.1MPa, No.3 – 26.5 MPa) which is only 55% level of the design compressive strength of 40MPa. The main cause that the average compressive strength was observed at about 55% level of the design compressive strength of 40MPa is the failure to comply with the required standard/specification for steam curing during the PC production processing. The required conditions to be complied for the steam curing are 60±10℃(Max. 80℃ or less) of curing temperature, 20℃/h or less of temperature rise rate and shall be managed by the concrete maturity, however, it was reported as a result of investigating the PC manufacturer that the strength had not reached to the standard strength before the mold deformation due to the steam curing with low temperature condition at opened space. The logistics warehouses have been continuously requested to be expanded after COVID-19 Pandemic, and the demand of PC which has merit in logistics warehouse construction work has been rapidly increasing. As a result, the operation rate of PC manufacturers currently reaches the maximum production limit, instead, PCs have been indiscriminately produced at small workplaces which have not able to satisfy the design compressive strength, construction quality and safety requirements. In the current situation, the construction site and workers are exposed to the potential risk of falling accidents since any relevant law or regulation on non-securing quality requirements such as the compressive strength is not stipulated yet. For this reason, the PC products with secured quality requirements shall delivered and construction safety management shall be improved by implementation of PC Factory Certification System at the earliest. For the purpose of this study, the PC factory certification system should be introduced, the research method was selected based on PC drop accidents and domestic and international operational cases of each country's certification system.
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Mikoliūnas, Audrius, and Rimantas Kačianauskas. "STIFFNESS CHARACTERISTICS OF GEOMETRICALLY NON-LINEAR BEAM FINITE ELEMENT/GEOMETRIŠKAI NETIESINIO LENKIAMO STRYPO BAIGTINIO ELEMENTO STANDUMO RODIKLIŲ NUSTATYMAS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 3, no. 10 (June 30, 1997): 52–59. http://dx.doi.org/10.3846/13921525.1997.10531684.
Abstract:
Two-dimensional geometrically non-linear beam element is considered in this paper. The explicit expressions of stiffness characteristics of element with three nodes are derived and tested. Among models of the geometrically non-linear beams, the elements with 2 nodes dominate [1–8]. Such elements produce constant axial force. The idea of more complex elements with tree nodes was suggested in [3]. In this paper geometrically non-linear flat bending beam element with 3 nodes for evaluating of axial force is investigated and nonlinear stiffness characteristics are derived. Basic relations of element e are derived using virtual displacement method. On the level of element e, the principle of virtual displacements is expressed by equalities (1–3). Using displacement approach, displacement functions are prescribed in the bounds of one finite element. Generalised deformations are obtained by introducing displacements approximation (4) and inserting them into non-linear geometric equations (5–6). Variation of deformation energy (3) is expressed in (7). Putting equality (7) into (1), it is possible to write equality of virtual works in terms of non-linear algebraic equations (8). Non-linear stiffness matrix is presented as the sum of 3 matrices (9). The first matrix [K 0e ] (linear matrix) is the matrix of small deflections, which is independent on deformed shape. The second matrix [K Ne ] is the matrix of large deflections. The third matrix [K Ge ] is a geometrical stiffness matrix. It reflects the second member of equality (7). Expressions of geometrically non-linear stiffness matrices are greatly dependent on the introduced assumptions and appropriate elements. Shallow beam finite element is shown in Fig 1. This finite element has 3 nodes. In the initial configuration a beam can be straight (Fig 1a), or curved (Fig 1b). The initial configuration of a beam is described by a vector z = {z1 αx1, Z2, αx2}T of a beam final nodal co-ordinates, where z i means nodes co-ordinates, αxi—initial rotations (Fig lb). However, the initial configuration is a relative statement, and is generally described by vector z. If in initial configuration the element is straight, vector z=0. Physical properties of the element are denoted with capital EA (tensional rigidity) and EI (flexural rigidity). The finite element has 7 degrees of freedom: 3 of them are defined at each end of the element (2 linear and 1 rotation) and 1 in the middle of the element Vector Ue of nodal deflections for this element is split into two parts: Ue= {u, w}T , u = {u1, u2,u3}T, w'=z+w, w={w1,Θx1, w2, Θx2}T. Deflection u3 shows the deflection of the middle beam node, which is not proportional to the final nodal deflections. To be more strict, u3 is straightened by linear law. So the linear element in the direction of longitudinal deformation expression is (11). The deflection of a point which is moved from the centre of plane surface in distance z1, deflection u (in direction x) is expressed in (12). Deformation is expressed by summarised deformations (13). So the deformed element only longitudinal deformation Δ is assigned, which is shown in (16). Evaluating earlier received expressions, it is possible to make equality of virtual work (1), where generalised vectors Θ e (x)={Δx, κ}T and Q e (x)={N, M}T. Generalised deformations Δ and κ expressed by deflections approximating expressions (4). For convenience, vertical and horizontal deflections are separated (17). By analogy with deflections, vector z and its derivatives are approximated by (24–25). Beam's curvature (15) is also expressed by nodal deflections: (26–27). Putting (20, 21, 26) into (16) and (15, 16) into (13) and expression (28) is got. Evaluating that the element work in elastic stage, expression (10) can be rewritten (29). The final stiffness matrix expression (9) is given in the form of block matrices (30). Expressions of block matrices are presented by (31–33). Having completed operations in expressions (31–33), final stiffness matrix is (34–36). After integrating, linear matrix is (37). Analogous operations are performed with matrices (35)–(38). Elements of this matrix are calculated using computer algebra. Matrix (36) consists of three parts. The first integral (39) is stiffness matrix of bending beam. If we assume that axial force in beam's length is invariable, the third integral is equal to (41). Assuming that axial force in the length of element is not constant (the axial force is calculated according to forms (28,29)), the expressions of geometrical stiffness matrix become very complicated. Analysis of geometrically non-linear system of finite elements is described by algebraic equation (42). Usually expression of non-linear deformation is investigated as a process varying in time t, where outer load F and deflections U are functions of time: F≡6F(t) and U≡6U(t). Load in the moment of time t i+1 = t i + Δt is added in portions (43). Deflections are expressed by analogy with (44). Non-linear model (42) is expressed by increments (45). Vector of residuals γ reflects solution of equation (42) inadequacy of state variables. Nowadays there exists many algorithms of different complexity for solution of non-linear problems [2–4,9,10]. The majority of methods that have already become standard uses different Newton-type variety of algorithms. Classical Newton-type algorithms are adapted to non-linear process with so called “softening” curve to model (Fig 2a). In the work there was done and realised a combined algorithm for non-linear process with “hardening” or “softening” curve to model. The illustration of algorithm is given in Fig 3. Using the algorithm in every load step, tangent stiffness matrix is counted twice. The first matrix corresponds to tangent of load step at the beginning (tangent 1), and the second one to the step at the end (tangent 2). Algorithm is implemented in the program created by the authors. A simple cantilever beam (Fig 4) is taken for the test. History of deformation was investigated. The results are given in non-dimensional quantities (Fig 5). Euler's method is realised as a particular case of implemented algorithm. The same example was also solved using program ANSYS, where beam elements are used and described only by two nodes. The results presented show obviously the advantages of three-node element and validity of proposed assumptions.