Journal articles on the topic 'Dead loads (Mechanics) Testing'
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1
Pinto, Paulo, Michael McVay, Marc Hoit, and Peter Lai. "Centrifuge Testing of Plumb and Battered Pile Groups in Sand." Transportation Research Record: Journal of the Transportation Research Board 1569, no. 1 (January 1997): 8–16. http://dx.doi.org/10.3141/1569-02.
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Pile groups are generally used under structures subject to heavy axial loads or large lateral forces with or without scour. The focus in this paper is only on pile groups subject to large lateral forces. Currently, little, if any, full-scale lateral load data exist on pile groups that vary pile head fixity or batter. Reported here is the summary of a series of centrifuge tests on free- and fixed-head plumb and battered pile groups. Influence of pile head constraint, pile spacing, soil density, and vertical dead load is reported for groups ranging from 3 × 3 to 3 × 7 in size. Results reveal a significant lateral resistance of fixed- over free-head pile groups; fixed-head piles develop significant axial forces; battered piles without vertical dead loads are generally no better than plumb piles; and in the case of plumb piles, the use of multipliers to represent group interaction is valid.
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Morrison, C. J., and D. R. Hayhurst. "Design-development of a variable load tension—compression creep testing machine." Journal of Strain Analysis for Engineering Design 21, no. 1 (January 1, 1986): 25–31. http://dx.doi.org/10.1243/03093247v211025.
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The design and development is described of a variable load tension-compression creep machine (±50 kN) which overcomes the disadvantages of servo-hydraulic and recirculating ball screw testing machines. The use of dead weight levers to apply specimen loads ensures the achievement of low running costs. Screwed end specimens are used with a 25.40 mm parallel sided gauge length and a diameter of 12.70 mm. It is shown that, provided modest rates of loading (0.4 kN/s) are used, high accuracy ‘through zero’ loadings can be achieved. The machine has been shown to operate satisfactorily for long periods under tension-compression high temperature creep.
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Mustapha, Khameel Bayo. "On the Dynamic Model of a Functionally Graded Spinning Structural Element of an Aircraft Appendage." Applied Mechanics and Materials 629 (October 2014): 89–94. http://dx.doi.org/10.4028/www.scientific.net/amm.629.89.
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The use of advanced materials in automotive, aerospace and communication technologies has called for re-assessment of classical models of many structural elements. The primary objective of this study relates to the use of a higher-order continuum model for discerning the contribution of certain geometric and material properties on wave propagation behavior of a spinning appendage of an aircraft appendage. The spinning appendage is characterized by a through-thickness functional material gradation and subjected to an axial dead load. The foundation of the present model rests on the trio of the mechanics of functionally graded solid structures, the extended Hamilton’s principle and the thin beam theory. Numerical results from the wave mechanics analyses reveal the noticeable influence of axial dead load and attendant wave splitting effect caused by the gyroscopic moment of the system. The wave mechanics result paves the way for the non-destructive damage testing of the element.
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Abdou, Samia, Wuzhen Zhang, and John W. Fisher. "Orthotropic Deck Fatigue Investigation at Triborough Bridge, New York." Transportation Research Record: Journal of the Transportation Research Board 1845, no. 1 (January 2003): 153–62. http://dx.doi.org/10.3141/1845-17.
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The Triborough Bridge connects the boroughs of Manhattan, Queens, and the Bronx in New York City. The bridge has suspended spans with a total length of 2,700 ft (823 m). The existing concrete deck is being replaced with an orthotropic steel deck to reduce the overall dead load. Before deck replacement, a prototype steel orthotropic deck was installed on the main span for a length of 120 ft (36.6 m). About 300 strain gauges were installed at critical locations to investigate the fatigue strength under static and dynamic loads of the AASHTO fatigue truck and under normal traffic. The strain gauge testing was done in three phases, and structural refinements were made to the deck system between phases. Traffic monitoring was conducted for the most critical locations over a 30-day period during Phase III. The results from three phases of the strain gauge testing, including influence lines and traffic monitoring data, were used to calculate fatigue stress ranges and the fatigue life for each detail. In addition to strain gauge testing, a finite element analysis of the orthotropic deck was performed with loading criteria set by AASHTO load and resistance factor design. The results from the finite element analysis were compared with the results obtained from the strain gauge testing. It was concluded that the heavy trucks on the bridge cause fatigue stresses higher than what had been anticipated by AASHTO. The investigation assisted in modifying the design to obtain a longer service life for the deck system under heavy-truck traffic.
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Wu, Wen-hua, Yan Zhao, Ying Gou, Bai-cheng Lyu, Qing-zhen Lu, Zhao-kuan Lu, and Jun Yan. "An Overview of Structural Design, Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser." China Ocean Engineering 36, no. 4 (August 2022): 511–31. http://dx.doi.org/10.1007/s13344-022-0044-5.
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AbstractOffshore oil and gas development plays an important part in the global energy sector. Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system. Because of the randomness and uncertainty of wave and current loads in the ocean environment, the structural design and mechanical analysis of the marine equipment can be highly complicated. Therefore, this paper reviews the recent works of the theoretical model, numerical simulation, and experimental test in three research areas: hydrodynamic analysis of offshore platforms, structural mechanics analysis of flexible pipe and cable, and monitoring technology of offshore floating structures under marine loads. By analyzing their main research methods and key technical difficulties, this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines. Also, China is relatively backward in the design of marine floating platform, the design, analysis and testing of flexible pipeline and cable, as well as the marine equipment prototype monitoring technology research. Calling for breakthroughs at the earliest possible stage in the above fields, prime research should be focused on and strategic planning should be made to deal with “key areas and stranglehold problems”. It is of great significance for the development of China’s deep-sea energy and resource development of independent technology and on time to achieve the “carbon peak” national strategic objectives.
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Mohd Noh, Hamidun, Nor Lailatul Izzatil Azwani Mohamad, Rolly Bangau, and Nur’Ain Idris. "Performance of Hollow Reinforced Concrete Beam in Structural Member." journal of Mechanical Engineering 17, no. 2 (July 15, 2020): 1–11. http://dx.doi.org/10.24191/jmeche.v17i2.15296.
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Recently, the problem faced by the construction industry is a significant shortage of raw materials of concrete. Thus, the main idea of this research is to replace the use of concrete at the middle area of neutral axis of beam with voided system by incorporating PVC pipe. This research aims to reduce the concrete usage; structure’s self-weight without neglecting its strength performance. The experimental work consists of casting and testing the 1200 x 160 x 160 mm beams with (Ø40 mm, Ø50 mm, and Ø100 mm) and without void at the neutral axis. The test results indicated that the strength performance of all RC beams with voided section is stronger than the ordinary RC beam where the V50 RC beam is able to withstand loads up to 38.25 kN and has a strength increment of 49.2% compared to the ordinary RC beam. By this material optimization, the reduction of concrete usage and self-weight of the V100 RC beam recorded a reduction of up to 35.14% but in terms of its strength is relatively low compared to the V40 RC beam and V50 RC beam. This findings show a positive result in reducing the dead load without affecting the strength of the structure. Besides aiming to the reduction of concrete usage and structure’s self-weight, the idea of this research could be used and implemented in producing a lightweight structure with easy handling and installing, and at the same time focusing to meet the IBS system.
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Sinha, N. K., G. W. Timco, and R. Frederking. "Recent Advances in Ice Mechanics in Canada." Applied Mechanics Reviews 40, no. 9 (September 1, 1987): 1214–31. http://dx.doi.org/10.1115/1.3149553.
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Work on the mechanics of ice, which has been carried forward on a broad front in Canada, has resulted in a number of significant advances in the last 10 years. The factors influencing the growth of various types of sea ice have been quantified fundamentally and methods for examining the resulting material structure have been developed. Extensive work has been done on strength and deformation characteristics of ice. A significant effort has been the development of analytical expressions to describe the rheological behavior of ice. Elastic modulus, Poisson’s ratio, and creep were also treated. A great deal has been done on measuring the compressive strength of various types of naturally occurring ice and subsequently these data were combined into a suitable description of a failure envelope. Work has also been done on measuring the flexural strength, shear strength, adhesion and fracture toughness. Methods for laboratory testing and in situ measurements of mechanical properties have been developed. The problem of defining ice forces on structures has been the primary motivation for research on ice. Analytical modelling, physical modelling, laboratory studies and very extensive field studies have been used. Work done in this area has included development of methods and their application to actual problems and has benefitted greatly from the integration of all four approaches. Very significant progress has been made. Ice and ice covers have been successfully used to support various offshore activities: drilling off floating ice platforms, stabilizing grounded rubble fields to protect structures and transporting large loads over ice.
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Mirmohammadsadeghi, Mahmoudreza, Hua Zhao, and Akira Ito. "Optical study of gasoline substitution ratio and diesel injection strategy effects on dual-fuel combustion." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 4 (July 16, 2019): 1075–97. http://dx.doi.org/10.1177/0954407019864013.
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Ever growing population and increased vehicles have resulted in higher atmospheric concentration of the greenhouse gases, such as carbon dioxide and methane, thus increasing our planet’s average temperature leading to irreversible climate changes, which has led to increasingly demanding and stricter legislations on pollutant emission and CO2, as well as fuel economy targets for the automotive industry. As a result, a great deal of efforts and resources has been spent on the research and development of high efficiency and low emission engines for automotive applications in the attempt to reduce greenhouse gas emissions and levels of nitrogen oxides and soot emissions, which affect the air quality. This research has developed strategies to investigate the combustion characteristics, engine performance and exhaust emission of diesel–gasoline dual-fuel operation in a Ricardo Hydra single-cylinder optical engine running at 1200 r/min, equipped with a high-pressure common rail injection system for diesel fuel delivery, and a port fuel injection system, designed and manufactured by the author, for gasoline fuel delivery, in order to allow for dual-fuel operations. In-cylinder pressure measurement is used for calculating all engine parameters, heat release rate and efficiency. In addition to the thermodynamic analysis of the combustion parameters, high-speed imaging of spray and combustion chemiluminescence was used for the optical analysis of the effect of the above-mentioned parameters on auto-ignition and combustion processes. Effects of different substitution ratios and diesel injection strategies at low engine loads were studied when the total fuel energy was kept constant. The three main substitution ratios used in this study include 45%, 60% and 75%, which also indicates the amount of fuel energy from port-injected gasoline, where the rest is provided by the direct injection of diesel. Depending on the testing conditions, such as injection strategy and intake conditions, some dual-fuel operations were able to deliver high efficiency and improved emissions compared to that of a pure diesel engine operation, with the diesel–gasoline operation offering more consistency in improved thermal efficiency. The optical analysis of the combustion illustrates the main difference in the flame propagation, distribution and quality for each substitution percentage, as well as the condition under examination. It was observed that combustions with higher concentration of diesel fuel having more diffusion-like combustion, especially with diesel injection timings closer to the top dead centre, where there is less time for the two fuel and air to properly mix before combustion occurs, resulted in higher temperature and levels of NOx due to the pockets of high diesel concentrations within the combustion chamber, whereas higher concentration of gasoline, especially at earlier diesel injection timings, resulted in more homogeneous fuel mixture and thus lower combustion temperatures. In other words, when the gasoline substitution ratio is lower, optimised start of injection is advanced further, so that richer diesel mixture needs longer ignition delay to have proper combustion timing, and combustion is milder and peak heat release rate is slightly lower due to less local diesel rich mixture area by means of earlier injection timing, and in terms of emissions, lower gasoline substitution ratio, decreases NOx with more homogeneous diesel mixture, and same can be said for total hydrocarbon. Performing the thermodynamics testing with an all metal piston alongside the optical testing allowed for the confirmation of these outcomes. This study not only delivers an insight to the benefits of dual-fuel engine operation, it also represents the benefits of optical engines in providing better understanding of engine operation and ways of improving it.
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Takabatake, Hideo. "Effects of Dead Loads in Static Beams." Journal of Structural Engineering 116, no. 4 (April 1990): 1102–20. http://dx.doi.org/10.1061/(asce)0733-9445(1990)116:4(1102).
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Takabatake, Hideo. "Effects of Dead Loads in Dynamic Plates." Journal of Structural Engineering 118, no. 1 (January 1992): 34–51. http://dx.doi.org/10.1061/(asce)0733-9445(1992)118:1(34).
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Fang, Dai Ning, Xu Jun Zhao, Yong Mao Pei, Zhan Wei Liu, Fa Xin Li, and Xue Feng. "Experimental Study on Electro-Magneto-Mechanical Behaviour of Electromagnetic Solids." Key Engineering Materials 326-328 (December 2006): 5–12. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.5.
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New experiment systems that can offer electromechanical and electromagnetic coupling loads were established. Measurement skills and technologies under coupling loads have been developed. The experimental difficulties and technical problems, such as insulation, discharge, compressive testing of brittle ferroelectrics and so on, were well resolved. The constitutive experiments of piezo/ferroelectrics or ferromagnetic materials were carried out. Moiré Interferometry was applied to the measurement of transformation of the crack tip in ferroelectric ceramics under coupling loads. The deformation concentration near the internal electrode tip caused by non-uniform electric field was investigated by means of Digital Speckle Correlation Method (DSCM). With an aim to accomplish both measurements of constitutive response of the magnetostrictive materials and the fracture experiments of general soft ferromagnetic materials, a magnetomechanical-coupling testing setup was established, which is controlled by an industrial PC. The software was programmed to monitor the testing process and to deal with the acquired data. The characteristic curves of ferromagnetic materials, such as TbxDy1-xFe2 alloys, were measured, including the hysteresis loops, the magnetostriction curve and stress-strain curve.
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Choi, Chang‐Koon, Hye‐Kyo Chung, Dong‐Guen Lee, and E. L. Wilson. "Simplified Building Analysis with Sequential Dead Loads—CFM." Journal of Structural Engineering 118, no. 4 (April 1992): 944–54. http://dx.doi.org/10.1061/(asce)0733-9445(1992)118:4(944).
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Verbiţchi, Victor, and Horia Florin Dascau. "Quality Requirements for the Design, Fabrication and Repair of Welded Vessels." Advanced Materials Research 814 (September 2013): 141–46. http://dx.doi.org/10.4028/www.scientific.net/amr.814.141.
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The Eurocode standards provide common structural design rules. The design is based on selecting minimum weight members to satisfy given conditions. The standard applicable to the design of various tanks, vessels, containers and bottles for gas and liquid is: EN 1993-4-2; Eurocode 3; Design of steel structures; Part 4.2: Tanks. For the verification of certain mechanical characteristics of such vessels, the applied standard is EN 1993-1-6; Supplementary rules for the strength and stability of shell structures. Verification of the specific actions on structures, that imply dead and live loads, must be also applied for the tanks and vessels, according to EN 1991 and related standards. Construction of welded vessels must be performed with qualified welding procedures. WPS/PQR and welder approvals (EN 287 and EN ISO 15614) are required. The longitudinal and circumferential joints must be butt-welded, both with full penetration. Tolerances, heat treatment and marking are indicated. Some examples of own realized welded vessels are presented. Manufacturing inspection, by visual examination, must cover most aspects: bending, groove preparation, alignment before and after welding, welding process, penetration, tolerances for circumference, straightness and circularity, double-sided welds, heat treatment, small diameter welds around the nozzles, detecting of undercut, excessive convexity, distortions, etc. Defect acceptance criteria are presented, depending on the weld types and quality level, according to EN ISO 5817. Macrographic examination according to EN 1321 of a transverse section of the welds, tensile test according to EN ISO 4136 and radiography testing of welds in accordance with EN 1435 class B are required. For pressure vessels, according to the ISCIR Technical Prescriptions, active in Romania, C 4-2010 „Static metal pressure vessels”, respective C12-2010 „Technical requirements for metal tank, container and barrel recipients for compressed, liquefied and solved gases, under pressure”, tightness and hydrostatic tests are performed at the maximal design pressure for 60 min. For the stability verification, the ultimate limit state of local shell buckling should be applied, according to EN 1993-1-6, by the conventional method, stress design concept or global second order beam theory. The fatigue strength of the structural shell must be verified by the methods given in EN 1993-1-6. Weld repairs are allowed, with no limit on the number and extent of defects. The repairs by welding are carried out according to ASME Code, Sections IX and VIII. According to the ISCIR Technical Prescriptions, a technology for repair welding must be elaborated by the manufacturer and approved by ISCIR. The design, fabrication and repairs of vessels must be performed according to the mentioned standards, depending on the class of the vessel.
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Takabatake, Hideo. "Effect of Dead Loads on Natural Frequencies of Beams." Journal of Structural Engineering 117, no. 4 (April 1991): 1039–52. http://dx.doi.org/10.1061/(asce)0733-9445(1991)117:4(1039).
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Rothert, Heinrich, and Norbert Gebbeken. "On Numerical Results of Reticulated Shell Buckling." International Journal of Space Structures 7, no. 4 (December 1992): 299–319. http://dx.doi.org/10.1177/026635119200700407.
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This paper is mainly focused on the numerical methods which are used to calculate realistically the load-carrying behaviour of reticulated shell structures. It is generally assumed that for an economical analysis, aimed at the saving of material, the material non-linearity has to be taken into consideration if dead loads prevail. For this in the context of finite element analysis the stiffness matrices of elastic and elastic-plastic rod elements are presented. In order to ensure the stability of structures it is indispensable to detect limit loads such as snap-through loads and bifurcation loads. Assuming that snap-through phenomena are quasi static, path-following algorithms can be implemented to trace the load-deflection curves in the postbuckling domain. The testing of the reliability and stability of the algorithms requires a sufficient number of numerical examples. Few will be presented.
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Bakht, Baidar, and Leslie G. Jaeger. "Behaviour and evaluation of pin-connected steel truss bridges." Canadian Journal of Civil Engineering 14, no. 3 (June 1, 1987): 327–35. http://dx.doi.org/10.1139/l87-052.
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Two posted bridges, with pin-connected steel trusses, were recently proof tested in Ontario. This paper presents some results of the tests and draws conclusions, which are also applicable to other similar structures. It is concluded that, unlike other bridge types, this type of bridge does not possess reserve strengths beyond those ascertained analytically. An experimental procedure is given in the paper using which the ratio of dead loads in the two components of a tension chord can be readily determined. This paper also describes a procedure by which equivalence between the test and design vehicles is established, thereby providing a basis for determination of the posting loads. Key words: bridge evaluation, bridge testing, pin-connected truss, posting load, proof test, through truss, steel truss, tension chord.
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Liu, Xiaoping, and R. D. James. "Stability of Fiber Networks Under Biaxial Stretching." Journal of Applied Mechanics 62, no. 2 (June 1, 1995): 398–406. http://dx.doi.org/10.1115/1.2895944.
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This paper is concerned with the constitutive behavior of a particular orthogonal fiber network under biaxial dead loading. We also describe a new kind of biaxial, dead-loading machine which is applicable to anisotropic materials. The machine does not require that the loads are exerted along symmetry axes of the material. A specimen of the cloth was loaded by different loading paths to the same equibiaxial dead-load, and two different final deformations were observed. A related observation was reported by Treloar for rubber in 1948. In order to understand this instability, we experimentally determined the energy function for the cloth. The energy function is then used in a variational calculation to explain this instability.
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Schmid, Ben L., Richard J. Nielsen, and Robert R. Linderman. "Narrow Plywood Shear Panels." Earthquake Spectra 10, no. 3 (August 1994): 569–88. http://dx.doi.org/10.1193/1.1585789.
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The Uniform Building Code allows plywood sheathed narrow shear panels having a height-to-width ratio of 3.5-to-one (UBC Table 25-I) to be used as lateral force resisting elements. Previous laboratory testing has concentrated on panels having a height-to-width ratio of one-to-one. This paper presents some results from the testing of plywood shear panels with a height-to-width ratio of two-to-one. Three panels were tested; each was configured to model a different construction scenario. The panels were subjected to fully reversed cyclic pseudo-static loads. Comparison of the results from the three panels indicate that the tie-down anchors must be installed with careful attention to bolt tightening sequence and torque in order to better resist lateral displacements in an earthquake. Vertical dead loads were found to reduce uplift of the panel which, in turn, reduces lateral displacements resulting from panel rotation. Decreased shear values for plywood shear walls subjected to cyclic loading and additional decreased shear values for walls with a height-to-width ratio of two-to-one are recommended.
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Li, Lei, Yan Xiao, and Rui Zhen Yang. "Experimental Study on Creep and Mechanical Behavior of Modern Bamboo Bridge Structure." Key Engineering Materials 517 (June 2012): 141–49. http://dx.doi.org/10.4028/www.scientific.net/kem.517.141.
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A full-scale testing model of laminated bamboo truck load bridge was made based on the original structure. The mid-span deflection of CFRP-reinforced bamboo girders, temperature and relative air humidity were obtained through over three years creep test under self-weight, and the analysis based on experimental results was finished. The results indicate that the average creep deflection of the girders after three years is approximately 8-mm. In addition, the increase in temperature and humidity may contribute to creep. On the basis of creep test, a short-term loading test was carried out applied with dead load, and the bridge collapsed under the load of 18.5-t. By the analysis of the experimental results, it is realized that long span CFRP-reinforced bamboo girders have sufficient capacity to meet the strength and durability needs of practical use. Although CFRP layers could improve the performance of bamboo girders effectively, there is a decrease in strength and stiffness when considering the long-term performance. All these studies may contribute to improving the design of bamboo bridge structures, and some construction measures are suggested for the bamboo bridge according to the results of the experimental and analysis results.
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Xie, Wei, Fei Xu, and Hui Ming Yang. "Observations on Mechanics Properties of Stitched Foam-Core Sandwich by Flexural Testing." Advanced Materials Research 487 (March 2012): 337–41. http://dx.doi.org/10.4028/www.scientific.net/amr.487.337.
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Stitched foam-core sandwich structure is a new light weight sandwich structure material. In this paper, flexural testing was performed. For comparison purposes, the stitched foam-core sandwich structure with different stitch density and the unstitched foam-core sandwich structure were tested. The experimental results show the maximum failure loads was decreased owing to stitch for the flexural testing. The bending stiffness increases for stitched foam-core sandwich structure.
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Minaev, Andrey Ja, Hammat H. Valiev, Jury V. Korovkin, and Gennady V. Stepanov. "Testing of Magnetoactive Elastomeric Composite Materials." Key Engineering Materials 910 (February 15, 2022): 1115–20. http://dx.doi.org/10.4028/p-7ulh2t.
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Dynamic tests of new magnetoactive elastomers were carried out in various amplitude-frequency modes on vibrodynamic stands. These materials regular changes in resonance properties under the external constant magnetic fields and loads influence have been established. The relationship between vibrodynamic and damping properties in these composites and atomic force microscopy data on the magnetic fillers restructuring under magnetic field action in a silicone elastomers matrix is discussed.
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Che, Lin, Bo Wang, and Guo Li. "A Novel Testing System for Mechanics Properties of the Thin-Walled Micro Components in Inertial System." Materials Science Forum 861 (July 2016): 229–35. http://dx.doi.org/10.4028/www.scientific.net/msf.861.229.
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In this paper, micro tensile method was combined with micro bridge dynamic test method as a new testing method for mechanics performance to be put forward, and a novel testing system for mechanics properties of the thin-walled micro components was established. The micro testing specimen were designed and manufactured. And related mechanics performance tests were carried on to verify the feasibility and reliability of the test system. The experimental results show that displacements of the testing system are measured with 0.01μm resolution and axial loads are measured with 0.005N resolution.
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MAC SITHIGH, GEAROID P., and YI-CHAO CHEN. "BIFURCATION AND STABILITY OF AN INCOMPRESSIBLE ELASTIC BODY UNDER HOMOGENEOUS DEAD LOADS WITH SYMMETRY." Quarterly Journal of Mechanics and Applied Mathematics 45, no. 2 (1992): 277–91. http://dx.doi.org/10.1093/qjmam/45.2.277.
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MAC SITHIGH, GEAROID P., and YI-CHAO CHEN. "BIFURCATION AND STABILITY OF AN INCOMPRESSIBLE ELASTIC BODY UNDER HOMOGENEOUS DEAD LOADS WITH SYMMETRY." Quarterly Journal of Mechanics and Applied Mathematics 45, no. 2 (1992): 293–313. http://dx.doi.org/10.1093/qjmam/45.2.293.
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Sadeghnejad, Amir, Sheharyar Rehmat, Islam M. Mantawy, and Atorod Azizinamini. "Comparative Study of Cyclic and Shake Table Tests for Simple for Dead Load and Continuous for Live Load Steel Bridge System in Seismic Area." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 7 (June 5, 2020): 233–43. http://dx.doi.org/10.1177/0361198120921853.
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A new superstructure to pier connection for simple for dead load and continuous for live load (SDCL) steel bridge system in seismic areas was developed. As proof of concept, component level and system level tests were carried out on scale models. The component test was conducted under cyclic loading and the results showed satisfactory performance conforming to design standards. The same detail was incorporated in a system level shake table testing which was subjected to bidirectional earthquake excitations. The results showed that the connection behaved well under high levels of drift and acceleration. The capacity protected elements sustained minimal damage and the plastic hinge was limited to a predefined location in the column. In this paper, a summary of results from both tests is presented and compared. The results showed that the SDCL components remained within the elastic range. It was concluded that the dowel bars in the cap beam are the main load-carrying elements under excitations in the longitudinal direction of the bridge and the provisions of current design codes are adequate for the design of these reinforcing bars. Both test protocols showed similar behavior despite the differences in construction methods and material properties.
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Lutes, Loren D., Shahram Sarkani, David P. Kihl, and Jeffrey E. Beach. "Optimal S/N Fatigue Testing for Stochastic Service Loads." Journal of Structural Engineering 131, no. 10 (October 2005): 1611–19. http://dx.doi.org/10.1061/(asce)0733-9445(2005)131:10(1611).
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Paultre, Patrick, Jean Proulx, and Martin Talbot. "Dynamic Testing Procedures for Highway Bridges Using Traffic Loads." Journal of Structural Engineering 121, no. 2 (February 1995): 362–76. http://dx.doi.org/10.1061/(asce)0733-9445(1995)121:2(362).
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Fathoni, Fathoni. "RANCANG BANGUN PERANGKAT PEMBANGKIT PWM BIPOLAR." JURNAL ELTEK 16, no. 1 (August 21, 2018): 14. http://dx.doi.org/10.33795/eltek.v16i1.83.
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Electrical power settings, both AC and DC can be done by linear or switching. Controlled loads may be motors, heating elements or incandescent lamps. Generally the efficiency of load power control by way of switching is better than linear way so the way switching is widely used today. Switching also allows for automatic, remote and wireless control In load power management system with microcontroller, PWM generator circuit output is used for control of power switch. The output pulse can be TTL standard or with lower amplitude and on the control of the H bridge circuit required bipolar PWM with additional dead band on each side of the pulse ride. The bipolar PWM generator designed in this study has an output with TTL standard with a dead band circuit and a short circuit protection for VCC = 5 volts and a ground path, Testing with no load and short circuit in low and high output states is as follows. VOL(min) = 0.4 volts, VOH(max) = 4.2 volts. The short circuit of output to high GND is 100 mA and short circuit current to VCC path at low output is 90 mA, The output frequency of bipolar pulses is, 50, 100, 1k, 10k and 20k Hz with 10μs dead band
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Silva, P. F., and F. Seible. "EXPERIMENTAL PROCEDURE FOR TESTING OF PILES UNDER VARYING AXIAL AND LATERAL LOADS." Experimental Techniques 25, no. 1 (January 2001): 25–29. http://dx.doi.org/10.1111/j.1747-1567.2001.tb00004.x.
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Jenkins, M. G. "Long-Term Testing of Advanced Ceramics: Concerns, Insights, and Recommendations." Journal of Engineering for Gas Turbines and Power 118, no. 4 (October 1, 1996): 704–10. http://dx.doi.org/10.1115/1.2816983.
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Advanced ceramics have reached a level of material development to warrant serious consideration for use in advanced heat engine designs. Typically, design requirements based on service conditions may include 25,000 h lifetimes under stresses and temperatures of up to 250 MPa and 1370°C, respectively, with probabilities of failure of <0.1 percent. To assure that materials meet these stringent requirements requires long-term testing under the service conditions. Tensile tests at 1370°C in ambient air have been conducted on silicon nitride alloys to 5000 h with reports of 10,000 h tests for silicon carbide. To provide useful data, such long-term tests must incorporate such meticulous attention to detail as: strict temperature control (±5°C); accurate temperature measurement (1 percent of the nominal temperature); close control of grip cooling (±0.1°C) and ambient environment (±0.25°C); stable, high-resolution extensometry (±0.5 μm); reliable heating (MTBF > 10,000 h) and load control (gravity-controlled, dead load), and responsive data acquisition systems (12-bit, digital collection). Data thus obtained can be used as input into design codes such as NASA CARES/LIFE to predict and confirm reliability/durability.
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Wahab, Abdul Malek Abdul, Emiliano Rustighi, and Zainudin A. "Actuation and dynamic mechanical characteristics of a core free flat dielectric electro-active polymer soft actuator." Journal of Mechanical Engineering and Sciences 14, no. 4 (December 17, 2020): 7396–404. http://dx.doi.org/10.15282/jmes.14.4.2020.08.0582.
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Various complex shapes of dielectric electro-active polymer (DEAP) actuator have been promoted for several types of applications. In this study, the actuation and mechanical dynamics characteristics of a new core free flat DEAP soft actuator were investigated. This actuator was developed by Danfoss PolyPower. DC voltage of up to 2000 V was supplied for identifying the actuation characteristics of the actuator and compare with the existing formula. The operational frequency of the actuator was determined by dynamic testing. Then, the soft actuator has been modelled as a uniform bar rigidly fixed at one end and attached to mass at another end. Results from the theoretical model were compared with the experimental results. It was found that the deformation of the current actuator was quadratic proportional to the voltage supplied. It was found that experimental results and theory were not in good agreement for low and high voltage with average percentage error are 104% and 20.7%, respectively. The resonance frequency of the actuator was near 14 Hz. Mass of load added, inhomogeneity and initial tension significantly affected the resonance frequency of the soft actuator. The experimental results were consistent with the theoretical model at zero load. However, due to inhomogeneity, the frequency response function’s plot underlines a poor prediction where the theoretical calculation was far from experimental results as values of load increasing with the average percentage error 15.7%. Hence, it shows the proposed analytical procedure not suitable to provide accurate natural frequency for the DEAP soft actuator.
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Wu, T. W. "Microscratch and load relaxation tests for ultra-thin films." Journal of Materials Research 6, no. 2 (February 1991): 407–26. http://dx.doi.org/10.1557/jmr.1991.0407.
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The microindenter has proven to be a powerful device in the characterization of the mechanical properties of thin films. The machine has both high resolution in the applied load and penetration depth measurements, as well as the versatility to perform different types of testing. The former provides the capability to deal with extremely thin films, while the latter allows for other mechanical properties, in addition to hardness, to be acquired. Four types of tests, namely indentation, scratch, load relaxation, and indentation fatigue tests can currently be conducted using the microindenter via different operating procedures. Only the scratch and load relaxation techniques will be covered in this paper. In a microscratch test, the normal load, tangential load, scratch length, and acoustic emission are monitored simultaneously during an entire scratch process for the purposes of measuring the critical load and studying the failure mechanisms of the deposited films. The adhesion strength, scratch hardness, fracture toughness, and friction are the mechanical properties which are possible to obtain by using this technique. Results from aluminum, carbon, and zirconia coatings will be discussed. The load relaxation test provides information on the creep properties of the films and results in an empirical constitutive relation between the applied stress and plastic strain rate. The creep properties of DC sputtered Al films will be used as an illustration of this.
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Hollis, J. M. "A Six-Degree-of-Freedom Test System for the Study of Joint Mechanics and Ligament Forces." Journal of Biomechanical Engineering 117, no. 4 (November 1, 1995): 383–89. http://dx.doi.org/10.1115/1.2794196.
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A joint testing system was designed to transmit a specified motion or force to a joint in all six degrees of freedom (d.o.f.) using a spatial linkage system for position feedback. The precise reproducibility of position provided by this method of position feedback allows determination of in situ ligament forces for external joint loadings. Load on the structure of interest is calculated from six d.o.f. load cell output after the loaded position is reproduced with all other structures removed. In a test of this system, measured loads showed good agreement with applied loads.
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Ogrinec, Primož, Janko Slavič, and Miha Boltežar. "Harmonic Equivalence of the Impulse Loads in Vibration Fatigue." Strojniški vestnik – Journal of Mechanical Engineering 65, no. 11-12 (November 18, 2019): 631–40. http://dx.doi.org/10.5545/sv-jme.2019.6197.
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In vibration fatigue, three unique types of loads are typical: random, harmonic and impulse. In an application any of these loads are possible. A fatigue-life analysis is possible in the time and frequency domains using the frequency-response function of a structure. Recent studies demonstrated that the impulse loads influence the accuracy of a fatigue-life prediction in the frequency domain. The focus of this research is a theoretical study of an equivalent harmonic load to the impulse load on a single-degree-of-freedom system in order to investigate the feasibility of impulse loads in vibration testing. This research shows that there is a relationship between the impulse and harmonic loads that is related to the underlying dynamic properties (e.g., damping, natural frequency). Based on a theoretical analysis an experimental procedure was developed for both cases of excitation, which was able to confirm the theoretical analysis. Using the modal decomposition the single-degree-of-freedom approach can be generalized to multiple-degrees-of-freedom systems.
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Bulsara, V. H., Y. Ahn, S. Chandrasekar, and T. N. Farris. "Mechanics of Polishing." Journal of Applied Mechanics 65, no. 2 (June 1, 1998): 410–16. http://dx.doi.org/10.1115/1.2789069.
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A model has been developed to determine the number and sizes of abrasive particles involved in material removal in polishing, and the forces acting on these particles. The effect of particle size on these parameters has been simulated for a range of particle sizes. It is shown that when polishing with abrasive powders having relatively broad size distributions, only a very small percentage of the particles are involved in material removal. Further, these particles are comprised of the larger particles occurring in the tail end of the particle size distribution. The average force on a particle is found to be in the range of 5–200 mN under typical polishing conditions, which is of the order of loads used in micro-indentation hardness testing. These predictions of the model are consistent with observations pertaining to polished surfaces and the polishing process.
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Hsieh, M. F., D. N. Moreton, J. Mistry, and D. G. Moffat. "Limit loads for knuckle-encroaching nozzles in torispherical heads: Experimental verification of finite element predictions." Journal of Strain Analysis for Engineering Design 37, no. 4 (May 1, 2002): 313–26. http://dx.doi.org/10.1243/030932402760074535.
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The manufacturing and testing procedures for two experimental pressure vessels with large nozzles encroaching into the knuckle region of the vessel head are described. Experimental linear elastic stress levels and plastic loads for pressure and combined axial and in-plane bending nozzle loads are compared with predicted values determined using non-linear finite element analysis. The quality of the results are considered to justify the procedures developed by the authors to conduct a parametric study of the individual limit loads and their interaction for these complex structures.
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Armanini, C., F. Dal Corso, D. Misseroni, and D. Bigoni. "From the elastica compass to the elastica catapult: an essay on the mechanics of soft robot arm." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2198 (February 2017): 20160870. http://dx.doi.org/10.1098/rspa.2016.0870.
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An elastic rod is clamped at one end and has a dead load attached to the other (free) end. The rod is then slowly rotated using the clamp. When the load is smaller than the buckling value, the rod describes a continuous set of quasi-static forms and its end traces a (smooth, convex and simple) closed curve, which would be a circle if the rod were rigid. The closed curve is analytically determined through the integration of the Euler’s elastica, so that for sufficiently small loads the mechanical system behaves as an ‘elastica compass’. For loads higher than that of buckling, the elastica reaches a configuration from which a snap-back instability occurs, realizing a sort of ‘elastica catapult’. The whole quasi-static evolution leading to the critical configuration for snapping is calculated through the elastica and the subsequent dynamic motion simulated using two numerical procedures, one ad hoc developed and another based on a finite-element scheme. The theoretical results are then validated on a specially designed and built apparatus. An obvious application of the present model would be in the development of soft robotic limbs, but the results are also of interest for the optimization analysis in pole vaulting.
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BASINIUK, Vladimir L., Alexander V. BOGDANOVICH, and Oleg M. YELOVOY. "MODERN TRENDS IN THE DEVELOPMENT OF METHODS AND MEANS OF EXPERIMENTAL MECHANICS. PART 2." Mechanics of Machines, Mechanisms and Materials 1, no. 58 (March 2022): 71–82. http://dx.doi.org/10.46864/1995-0470-2022-1-58-71-82.
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The article considers a number of new directions in the development of methods and means of experimental mechanics. They are: the unification of test and calculation methods; the development of equipment and test methods in extreme conditions; the widespread use of acoustic emission methods and video recording during testing; the creation and development of equipment and methods for complex testing (for example, wear-fatigue) of materials and products. The achievements of Belarusian scientists are also noted in the field of experimental mechanics of contact interaction, including: an adhesiometer for measuring the molecular interaction of technical surfaces; a millitribometer for measuring friction forces under loads which are characteristic of a precision contact; an onboard tribometer for testing materials for friction and wear in extreme conditions of the action of space factors.
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Savinov, A. V., V. E. Frolov, Y. N. Brovikov, and M. P. Kozhinskiy. "EXPERIMENTAL TESTS OF A BEARING CAPACITY OF «FUNDEX» PILES AFTER THE LONG “RELAXATION” IN CLAY SOILS THE DEAD PRESSING AND PULLING-OUT LOADS." Construction and Geotechnics 10, no. 2 (December 15, 2019): 13–29. http://dx.doi.org/10.15593/2224-9826/2019.4.02.
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In the article analyzes the results of experimental tests of new “Fundex” piles for The City of Saratov. Сlassification of piles based on their interplay with the pile base has been devised by Doctor of Technical Science, Professor F.K. Lapshin. Changes introduced in 2016 into SP 24.13330.2011 “Pile foundations” concerning calculation of the displacing stuffed concrete piles. The short analysis of history of creation of tables SP 24.13330 by determination of rated resistance on a lateral area and under the lower end of piles is carried out. It is shown that these sizes are not the limit resistances at exhaustion of a carrying capacity of a soil at “failure”, and are accepted with some stock at achievement by a pile of “predetermined” settling. There has been noted the existence of a large number of piles testing methods by means of incrementally increasing load different from methodology GOST 5686-2012 “Soils. Methods of field trials of piles” by various assessment criteria of the ultimate pile bearing capacity. Two identical piles have been manufactured in identical soils and after a long (3 months) “relaxation” without load tests have been conducted under GOST 5686 with static indenting and pull out loads. Engineering-geological conditions of the platform and distance between piles excluded their interference at manufacture and tests. the dead pressing and pulling-out loads. Comparison of results of field tests of “Fundex” piles to design values of a bearing capacity of the displacing piles determined by the recommendations of SP 24.13330 is carried out. The essential divergence of the experimental and estimated values at assessment of a bearing capacity of a heel of a pile is noted. Conclusions are drawn on need of additional experimental research of the basis of “Fundex” piles for the wide range of soil conditions by laboratory and field methods with parallel tests static indenting and pull out loads.
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Smith, L. C., and T. M. Adams. "Comparison and Evaluation of Analytical Structural Solutions With EPRI Safety Valve Test Results." Journal of Pressure Vessel Technology 107, no. 4 (November 1, 1985): 380–86. http://dx.doi.org/10.1115/1.3264471.
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All operating plant licensees and applicants are required to verify the acceptability of plant specific pressurizer safety valve piping systems for valve operation transients by testing per NUREG-0737 (issued November, 1980) and all subsequent U.S. NRC generic follow-up letters. Of particular concern was the operability of the safety valves and the acceptability of the downstream piping when subjected to the dynamic thermal hydraulic loadings associated with these transients. To aid in this verification process the Electric Power Research Institute (EPRI) conducted an extensive program testing different safety valves subjected to varying operating conditions. Downstream piping loads associated with the various loading cases were also measured. This paper presents and compares analytically determined solutions for the structural response of the test configuration to actual test results. A brief description of the methods used to generate the thermal hydraulic loads is presented but the major emphasis is on the piping dynamic response. Discussed are the piping and support modeling techniques, the dynamic solution methods and the load application methods employed. Analytically calculated piping stresses, support loads, displacements, and valve nozzle loads are compared to the test results.
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Juran, C. M., M. F. Dolwick, and P. S. McFetridge. "Shear Mechanics of the TMJ Disc." Journal of Dental Research 92, no. 2 (November 19, 2012): 193–98. http://dx.doi.org/10.1177/0022034512468749.
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The temporomandibular joint (TMJ) is a complex hinge and gliding joint that induces significant shear loads onto the fibrocartilage TMJ disc during jaw motion. The purpose of this study was to assess regional variation in the disc’s shear loading characteristics under physiologically relevant loads and to associate those mechanical findings with common clinical observations of disc fatigue and damage. Porcine TMJ discs were compressed between an axially translating bottom platen and a 2.5-cm-diameter indenter within a hydrated testing chamber. Discs were cyclically sheared at 0.5, 1, or 5 Hz to 1, 3, or 5% shear strain. Within the anterior and intermediate regions of the disc when sheared in the anteroposterior direction, both shear and compressive moduli experienced a significant decrease from instantaneous to steady state, while the posterior region’s compressive modulus decreased approximately 5%, and no significant loss of shear modulus was noted. All regions retained their shear modulus within 0.5% of instantaneous values when shear was applied in the mediolateral direction. The results of the disc’s regional shear mechanics suggest an observable and predictable link with the common clinical observation that the posterior region of the disc is most often the zone in which fatigue occurs, which may lead to disc damage and perforation.
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Wardana, Danindra Pramudya, Gilang Fadhlurrahman Evriantama, and Muhtarom Riyadi. "PEMANFAATAN STYROFOAM SEBAGAI PENGGANTI SEBAGIAN AGREGAT HALUS PADA BETON DENGAN FAS 0.4." Construction and Material Journal 3, no. 1 (March 31, 2021): 65–72. http://dx.doi.org/10.32722/cmj.v3i1.3731.
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Concrete is a material commonly used for structural work. However, concrete has one disadvantage, namely that its specific gravity is high enough so that the dead load on a structure becomes large. One way to deal with high concrete density is to use Styrofoam waste as a substitute for some of the fine aggregate. This research was conducted to examine the physical and mechanical properties as well as the optimum value of compressive strength, split tensile strength and modulus of elasticity of concrete with a 0.4 fas using Styrofoam as a partial substitute for fine aggregate. The research method used is an experimental method by making the test object in the form of a concrete cylinder with a diameter of 15 cm and a height of 30 cm. The composition of the concrete mixture used is a volume ratio of 1 Pc: 2 Ps: 2 Kr with a fas 0.4. The styrofoam variations used are 10%, 20%, and 30% of the ratio to the volume of fine aggregate in normal concrete mixtures. Testing of the mechanical properties of concrete was carried out at the age of 7, 14, 21, and 28 days for the concrete compressive strength test, and 28 days for the split tensile strength of the concrete, and the modulus of elasticity. The results showed that the compressive strength of the concrete increased with the age of the concrete and the addition of the styrofoam variations with the exception of the 10% variation. For the split tensile strength test, there was an increase in line with the increase in the styrofoam variation, while the modulus of elasticity decreased at 10% variation against 0% variation and increased at 20% and 30% variation with 0% variation.
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Bagio, Toni Hartono, Sofia W. Alisjahbana, Helmy Darjanto, and Najid Najid. "Orthotropic plates with dynamic vertical seismic load modeled as multi line." Engineering Solid Mechanics 11, no. 2 (2023): 135–50. http://dx.doi.org/10.5267/j.esm.2023.1.002.
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Calculation plate floor concrete, using a static load which is a gravity load consisting of a live load and a dead load, with various of boundary conditions, floor slabs are orthotropic plate, and rarely account for dynamic loads due to vertical seismic loads, with other boundary conditions, such as Clamped, simply supported, ES (Elastic Support), ER (Elastic Restraint), and ESR (Elastic Support and Restraint). Analytical solution based on the Modified Bolotin Method to analyze floor slab under Vertical Peak Ground Acceleration (PGAv), the natural frequency solution based on auxiliary Levy’s type problems. Dynamic vertical seismic loads using multiline, first line at 0 < t < 0.5 is linear equation, second line at 0.05 < t < 0.15 is quadratic equation, third line 0.15 > t < 0.6 is sextic equation, last line, t > 0.6 is linear equation, vertical seismic load with two conditions far fault and near fault, multi-line equation are depending on (PGAv/g). A numerical example is given, for various boundary conditions, and far fault, translational stiffness (kx, ky) and rotational stiffness (cx ,cy), from the results of plate calculations due to dynamic vertical seismic loads with 5 types of edge support, ES (elastic support) is the best result.
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Kuhlen, Karl Gerhard, Paul Rothe, and Thomas Seifert. "Near-component testing of materials for cylinder heads to determine thermomechanical fatigue under superimposed high-frequency mechanical loads." Materials Testing 63, no. 12 (December 1, 2021): 1081–89. http://dx.doi.org/10.1515/mt-2021-0059.
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Abstract Due to higher combustion chamber temperatures and pressures in efficient combustion engines, both the high-cycle and thermomechanical fatigue loads on service life-critical components, such as the cylinder head, are increasing. Material comparisons and analysis of damage behavior are very expensive and time-consuming using component tests. This study therefore develops a test method for cylinder head materials that takes into account the combined loading conditions from the above-mentioned loads and allows realistic temperature transients and gradients on near-component samples. The near-component cylinder head sample represents the failure-critical exhaust valve crosspiece and is tested in a test rig specially designed with the aid of conjugate heat transfer simulations. In the test rig, the sample is subjected to thermal stress by a hot gas burner and to mechanical stress by a high-frequency pulsator. Optical crack detection allows permanent observation of fatigue crack growth and crack closure during the test. Fractographic and metallo-graphic examinations of the fracture areas as well as analyses of the damage patterns show that loads close to engine operation can be set in this way and their influences on the damage can be monitored.
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Fugger, Rebecca, Sara Fares, Pietro Meriggi, Francesca Nerilli, Sonia Marfia, Elio Sacco, and Gianmarco de Felice. "Testing of Fabric Reinforced Cementitious Matrix in Shear without Substrate." Key Engineering Materials 916 (April 7, 2022): 105–11. http://dx.doi.org/10.4028/p-xch378.
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This paper aims at investigating the matrix-to-textile stress transfer in a fabric reinforced cementitious matrix FRCM system, not bonded to any substrate, under shear loads. To this end, direct shear tests are performed on a basalt FRCM specimen introduced into an innovative properly designed four-hinge frame loaded by a universal testing machine. The role of the single components in the global shear behavior of the FRCM is experimentally analyzed. Digital image correlation (DIC) is adopted for evaluating both the displacement and strain fields as well as for detecting the damage. Furthermore, the shear response of the tested FRCM material is reproduced via an effective numerical approach that considers the nonlinear behavior of the mortar and the possible micro-mechanisms that arise between the textile and the matrix, introducing suitable interfaces joining the FRCM constituent layers, i.e. textile and mortar layers. Experimental outcomes highlighted the non-negligible influence of the matrix in the shear response of the composite, both in strength and stiffness. The proven DIC technique demonstrated to be suitable also for this novel test type, since it allows to obtain shear strains, location and amplitude of cracks with satisfying accuracy, such as to make direct shear tests results a benchmark to be used for numerical simulations. Numerical analyses are performed in order to verify the efficiency of the proposed model in reproducing the mechanical behavior of FRCM composites under shear loads and in describing the damage patterns during the loading process.
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Lautenschläger, Thea, Markus Rüggeberg, Niclas Noack, Katharina Bunk, Monizi Mawunu, Thomas Speck, and Christoph Neinhuis. "Functional principles of baobab fruit pedicels – anatomy and biomechanics." Annals of Botany 126, no. 7 (August 18, 2020): 1215–23. http://dx.doi.org/10.1093/aob/mcaa149.
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Abstract Background and Aims Fruit pedicels have to deal with increasing loads after pollination due to continuous growth of the fruits. Thus, they represent interesting tissues from a mechanical as well as a developmental point of view. However, only a few studies exist on fruit pedicels. In this study, we unravel the anatomy and structural–mechanical relationships of the pedicel of Adansonia digitata, reaching up to 90 cm in length. Methods Morphological and anatomical analyses included examination of stained cross-sections from various positions along the stalk as well as X-ray microtomography and scanning electron microscopy. For mechanical testing, fibre bundles derived from the mature pedicels were examined via tension tests. For establishing the structural–mechanical relationships, the density of the fibre bundles as well as their cellulose microfibril distribution and chemical composition were analysed. Key Results While in the peduncle the vascular tissue and the fibres are arranged in a concentric ring-like way, this organization shifts to the polystelic structure of separate fibre bundles in the pedicel. The polystelic pedicel possesses five vascular strands that consist of strong bast fibre bundles. The fibre bundles have a Young’s modulus of up to 5 GPa, a tensile strength of up to 400 MPa, a high density (>1 g cm−3) and a high microfibril angle of around 20°. Conclusions The structural arrangement as well as the combination of high density and high microfibril angle of the bast fibre bundles are probably optimized for bearing considerable strain in torsion and bending while at the same time allowing for carrying high-tension loads.
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Merrigan, Justin J. "Effects of Maximal Effort Running on Special Agents’ Loaded and Unloaded Drop Jump Performance and Mechanics." International Journal of Environmental Research and Public Health 18, no. 19 (September 25, 2021): 10090. http://dx.doi.org/10.3390/ijerph181910090.
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The purpose was to investigate the effect of load and fatigue on landing forces and mechanics. Thirteen Department of State special agents first completed drop jump testing, a maximal treadmill test, and another round of drop jump testing. During drop jump testing, agents performed 3 maximal effort drop jumps from 30 cm with body mass only (unloaded) or a 15 kg weight-vest (loaded). A force plate was used to collect force–time data, while two laptops were placed 3 m from the force plate from frontal and sagittal planes. Two-way analyses of variance were used to analyze the effect of load and fatigue on landing forces and Landing Error Scoring System (LESS) with alpha of p < 0.05. Dropping from 30 cm with 15 kg resulted in greater landing impulse, which was driven by increases in contact time. The loaded condition also resulted in lower jump height and reactive strength indexes. After the maximal graded treadmill test there were no further changes in drop jump ground reaction forces or performance. However, relative aerobic capacity was related to impulse changes following the treadmill test in unloaded (R2 = 0.41; p = 0.018) and loaded conditions (R2 = 0.32; p = 0.044). External loads of 15 kg increased impulse and contact time and resultantly decreased drop jump height and reactive strength indexes. It is encouraged that training protocols be aimed to concomitantly improve aerobic capacity and lower body power. Plyometric training with progressive overloading using external loads may be helpful, but further research is warranted.
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Shetty, Santosh, and Tommi Reinikainen. "Three- and Four-Point Bend Testing for Electronic Packages." Journal of Electronic Packaging 125, no. 4 (December 1, 2003): 556–61. http://dx.doi.org/10.1115/1.1604158.
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This study demonstrates the application of three-point and four-point bending tests for evaluating the reliability of chip scale packages under curvature loads. A three-point bend test is conducted on 0.5-mm-pitch chip-scale packages (CSPs) mounted on FR4 (Flame Retardant) substrates. This test is simulated by using the finite element method and the results are calibrated experimentally to formulate a reliability model. A three-point bend scheme is an ideal choice for generating reliability models because multiple packages can be tested under multiple loads in a single test. This reliability model can be used to predict the durability of the packages in the real product under any printed wiring board (PWB) curvature loading conditions. A four-point bending simulation is also demonstrated on the test substrate. Four-point bending test is an ideal method for testing a larger sample size of packages under a particular predefined stress level. This paper describes the bending simulation and testing on packages in a generic sense. Due to the confidentiality of the test results, the package constructional details, material properties, and the actual test data have not been presented here.
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Saucedo-Muñoz, Maribel L., Shin-Ichi Komazaki, Toru Takahashi, Toshiyuki Hashida, and Tetsuo Shoji. "Creep property measurement of service-exposed SUS 316 austenitic stainless steel by the small-punch creep-testing technique." Journal of Materials Research 17, no. 8 (August 2002): 1945–53. http://dx.doi.org/10.1557/jmr.2002.0288.
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The creep properties for SUS 316 HTB austenitic stainless steel were evaluated by using the small-punch creep test at 650 °C for loads of 234, 286, 338, 408, and 478 N and at 700 °C for loads of 199 and 234 N. The creep curves, determined by means of the small-punch creep test, were similar to those obtained from a conventional uniaxial creep test. That is, they exhibited clearly the three creep stages. The width of secondary creep stage and rupture time tr decreased with the increase in testing load level. The creep rupture strength for the service-exposed material was lower than that of the as-received material at high testing loads. However, the creep resistance behavior was opposite at relatively low load levels. This difference in creep resistance was explained on the basis of the difference in the creep deformation and microstructural evolution during tests. It was also found that the ratio between the load of small-punch creep test and the stress of uniaxial creep test was about 1 for having the same value of creep rupture life.
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Hou, J. P., J.-Y. Cherruault, G. Jeronimidis, and R. Mayer. "Design, Testing, and Simulation of Fibre Composite Leaf Springs For Heavy Axle Loads." Journal of Strain Analysis for Engineering Design 40, no. 6 (August 1, 2005): 497–504. http://dx.doi.org/10.1243/030932405x30704.
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This paper summarizes the design, manufacturing, testing, and finite element analysis (FEA) of glass-fibre-reinforced polyester leaf springs for rail freight vehicles. FEA predictions of load-deflection curves under static loading are presented, together with comparisons with test results. Bending stress distribution at typical load conditions is plotted for the springs. The springs have been mounted on a real wagon and drop tests at tare and full load have been carried out on a purpose-built shaker rig. The transient response of the springs from tests and FEA is presented and discussed.