Articoli di riviste: "Open Hole Specimens"

1

Fan, Xiang, Rui Chen, Hang Lin, Hongpeng Lai, Chunyang Zhang e Qihua Zhao. "Cracking and Failure in Rock Specimen Containing Combined Flaw and Hole under Uniaxial Compression". Advances in Civil Engineering 2018 (2018): 1–15. http://dx.doi.org/10.1155/2018/9818250.

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Flaw is a key factor influencing failure behavior of a fractured specimen. In the present study, rectangular-flawed specimens were prepared using sandstone to investigate the effect of flaw on failure behavior of rock. Open flaw and cylindrical hole were simultaneously precut within rock specimens using high-pressure water jet cutting technology. Five series of specimens including intact, single-hole-alone, two-hole-alone, single-hole and two-flaw, and two-hole and single-flaw blocks were prepared. Uniaxial compressive tests using a rigid servo control instrument were carried out to investigate the fracture processes of these flawed specimens. It is observed that during loading, internal stress always intensively distributed at both sidewalls of open hole, especially at midpoint of sidewalls, so rock crumb flaking was firstly observed among all sandstone specimens containing single hole or two holes. Cracking around open hole is associated with the flaw inclination angle which was observed in Series III and V. Crack easily initiated at the tips of flaw with inclination angles of 0°, 30°, and 60° but hard for 90° in Series III and V. Rock burst was the major failure mode among most tested specimens, which generally induced new cracks and finally created crater shape. Additionally, due to extrusion between blocks, new shear or tensile cracks were generated and the rock specimen surface spalled. Eventually, four typical failure processes including rock crumb flaking, crack initiation and propagation, rock burst, and second rupture, were summarized.

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Strungar, Elena, Dmitrii Lobanov e Valery Wildemann. "Evaluation of the Sensitivity of Various Reinforcement Patterns for Structural Carbon Fibers to Open Holes during Tensile Tests". Polymers 13, n. 24 (7 dicembre 2021): 4287. http://dx.doi.org/10.3390/polym13244287.

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This paper is devoted to the experimental study of polymeric composite specimens, with various types of reinforcement, in order to evaluate the breaking strength of specimens with open holes when undergoing uniaxial compression and tensile tests. Four types of interlaced 3D woven preforms were considered (orthogonal, orthogonal combined, with pairwise inter-layer reinforcement, and with pairwise inter-layer reinforcement and a longitudinal layer), with a layered preform used for comparison. Tensile tests of solid specimens without a hole, under ASTM D 3039, and of specimens with an open hole, under ASTM D 5766, were carried out using the Instron 5989 universal electromechanical testing system. Movements and strains on the specimen surface were recorded using a Vic-3D contactless optical video system and the digital images correlation method (DIC). For all the series of carbon fiber tension specimens, strain and stress diagrams, mechanical characteristics, and statistical processing for 10 specimens were obtained. The paper evaluated deformation fields for certain points in time; the obtained fields showed an irregular distribution of deformation and dependency on types of reinforcing fibers. A coefficient of strength variation is introduced, which is defined as a ratio of the ultimate stress limits obtained on solid samples with and without open holes. Within the framework of ASTM D 5766, when calculating the ultimate stress, the hole is not taken into account, and the paper shows that for certain structures a hole cannot be excluded. The hole size must not be neglected when calculating the ultimate stress.

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Ivetic, Goran, Ivan Meneghin e Enrico Troiani. "Numerical Analysis of Laser Shock Peening as a Process for Generation of Compressive Residual Stresses in Open Hole Specimens". Materials Science Forum 681 (marzo 2011): 267–72. http://dx.doi.org/10.4028/www.scientific.net/msf.681.267.

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A numerical analysis of Laser Shock Peening (LSP) process is illustrated, applied to an open hole specimen. This specimen is representative of a section of an aircraft fuselage lap joint, typically prone to fatigue crack nucleation at the rivet holes. The effect of the residual stress field induced by LSP on the fatigue life of open hole specimens is investigated. The results show that significant compressive residual stresses can be introduced in fatigue sensitive areas using LSP, postponing fatigue crack nucleation.

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LIANG, SHUANGQIANG, QIHONG ZHOU e GE CHEN. "Open hole size effects on tensile properties of 3D braided composites". Industria Textila 72, n. 05 (30 ottobre 2021): 545–51. http://dx.doi.org/10.35530/it.072.05.202010.

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Owing to the excellent integrated structure, notch-insensitivity, delamination-free characteristics, 3D braided composites have a broad range of engineering applications. In this paper, the notch size effects on two types of 3D braided composites were experimentally examined. Style I incorporated 40% of longitudinal lay-in yarns. Style II was the pure braids. The Point Stress Criterion (PSC) was applied to predict the open-hole strength of 3D braided composites. It is found the 3D braided composites can keep higher proportion residual strength after involving the different circular hole sizes compared to plain woven laminates. The open-hole pure braided specimen shows better performance than that the braids with longitudinal yarns, the lay-in longitudinal yarns improve neither specimens’ un-notched strength, nor the modulus. The predicted open-hole strength were compared with experimental results. The traditional analytical method can predict the open-hole strength of 3D braided composite to some extent. Under uniaxial tensile stress, the failure behaviour of two types of 3D braided specimens are different. For un-notched specimen, clear cracks usually show up on the Style II specimen, while it is not true for Style I coupon. For notched specimen, the crack of both notched specimens will propagate along the notch and finally render the specimen to fail

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Murdani, Anggit, Utsman Syah Amrullah e R. N. Akhsanu Takwim. "Experimental investigation on strain behavior of jute/polyester composite with an open hole under axial loading". Jurnal Polimesin 21, n. 3 (30 giugno 2023): 351–57. http://dx.doi.org/10.30811/jpl.v21i3.3931.

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Mechanical assembly requires joint mechanism involving fasteners and holes. Deformation of the holes will greatly affect the integrity of the mechanical joins. This research objective is to reveal the strain behavior of jute/polyester composite containing open hole under axial loading. It is very important to know the behavior of the strain surrounding the hole under loading. Experiments were carried out by preparing jute/polyester composites. The composites were manufactured by using a vacuum infusion method. There are two configurations of the number of laminations, i.e., 3 and 5 sheets and of hole sizes, i.e., 5 and 10mm holes. An axial load is applied to the specimen through a tensile test. Strain gauges are attached near the holes, axially and laterally. Strain in axial and lateral directions in the vicinity of a hole is recorded and presented. The research result shows that the strain gauges located parallel to the loading axis indicate a positivestrain value. On the other hand, the strain gauges located lateral to the loading axis indicate a negative value. Furthermore, the strain gauges located beside the hole in the direction parallel to the loading axis indicate the highest strain value in all types of specimens.

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Maimí, P., D. Trias, E. V. González e J. Renart. "Nominal strength of quasi-brittle open hole specimens". Composites Science and Technology 72, n. 10 (giugno 2012): 1203–8. http://dx.doi.org/10.1016/j.compscitech.2012.04.004.

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Wang, Hongxiao, Xiaohui Zhang e Yugang Duan. "Investigating the Effect of Low-Temperature Drilling Process on the Mechanical Behavior of CFRP". Polymers 14, n. 5 (4 marzo 2022): 1034. http://dx.doi.org/10.3390/polym14051034.

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Previous research has found that lower temperature drilling is helpful to improve the hole quality of carbon fiber reinforced polymer (CFRP). However, the influence of the lower temperature drilling process on the mechanical behavior of composites is yet not fully understood. To examine the influence of the lower temperature drilling process on the mechanical behavior of CFRP, the open hole CFRP specimens used for mechanical tests were obtained with three cases: drilling with −25 °C/uncoated carbide drills/(1000 rpm, 0.02 mm/r), 23 °C/coated carbide drills/(4000 rpm, 0.03 mm/r), and 23 °C/uncoated carbide drills/(1000 rpm, 0.02 mm/r), respectively; corresponding, three groups of open-hole specimens are obtained: specimens drilling at low-temperature with low damage, specimens drilling at room-temperature with low damage and specimens drilling at room-temperature with low damage; the mechanical behavior of the three groups specimens were obtained by static tensile, tensile–tensile fatigue cyclic tests and residual tensile strength test. The results have shown that the mechanical properties of specimens with a low-temperature drilling process is lower than those of the specimen with a normal drilling process due to the better drilling quality. The damage accumulation in specimens was increased with the damage degree of the original hole, the greater the damage degree, the worse the mechanical properties.

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8

Liang, Shuangqiang, Qihong Zhou, Haiyang Mei, Ge Chen e Frank Ko. "Fatigue Behavior of 3D Braided Composites Containing an Open-Hole". Polymers 12, n. 9 (21 settembre 2020): 2147. http://dx.doi.org/10.3390/polym12092147.

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The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the residual strength of the samples that survived millions of cycles was tested. The cross-section of the 3D braided specimens was observed after fatigue loading. It was found that the static and fatigue properties of low angle 3D braided behaved better than longitudinally reinforced 3D braided composites. For failure behavior, pure braids contain damage better and show less damage area than the braids with longitudinal yarns under fatigue loading. More cracks occurred in the 3D braided specimen with axial yarn cross-section along the longitudinal and transverse direction.

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Dave, Harshit K., Ashish R. Prajapati, Shilpesh R. Rajpurohit, Naushil H. Patadiya e Harit K. Raval. "Open hole tensile testing of 3D printed parts using in-house fabricated PLA filament". Rapid Prototyping Journal 26, n. 1 (6 gennaio 2020): 21–31. http://dx.doi.org/10.1108/rpj-01-2019-0003.

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Purpose Fused deposition modeling (FDM) is being increasingly used in automotive and aerospace industries because of its ability to produce specimens having difficult geometrical shape. However, owing to lack of critical information regarding the reliability and mechanical properties of FDM-printed parts at various designs, the use of 3D printed parts in these industries is limited. Therefore, the purpose of this paper is to investigate the impact of process parameters of FDM on the tensile strength of open-hole specimen printed using in-house-fabricated polylactic acid (PLA). Design/methodology/approach In the present study, three process parameters, namely, raster angle, layer thickness and raster width, are selected for investigation of tensile strength. To produce the tensile specimens in the FDM machine, the PLA filament is used which is fabricated from PLA granules using a single-screw extruder. Further, the experimental values are measured and critically analysed. Failure modes under tests are studied using scanning electron microscopy (SEM). Findings Results indicate that the raster angle has a significant effect on the tensile strength of open-hole tensile specimen. Specimens built with 0° raster angle, 200-µm layer thickness and 500-µm raster width obtained maximum tensile strength. Originality/value In this work, a new concept of testing a plate that has a rectangular shape and a circular hole at the centre is tested. Open-hole tensile test standard ASTM D5766 has been implemented for the first time for the FDM process.

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10

Gaerke, J., X. Zhang e Z. Wang. "Life enhancement of fatigue-aged fastener holes using the cold expansion process". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 214, n. 5 (1 maggio 2000): 281–93. http://dx.doi.org/10.1243/0954410001532060.

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This paper examines the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint. The specimens were pre-cycled to 25, 50 and 75 per cent of the baseline fatigue life of a non-expanded specimen and then cold expanded prior to cycling to final failure. The experimental test was designed to provide a close comparison with standard maintenance practices for aircraft structures and used the FALSTAFF spectrum which was derived from actual flight loading. The test results have indicated that part-life cold expansion can provide substantial improvements in fatigue life, but the actual benefit is dependent upon the degree of precycling and he length of existing cracks when the specimen is cold expanded. Additionally, tests on open hole specimens of the same material and thickness were also carried out, with attempts being made to predict the crack growth lives of these specimes.

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Ghasemi, Ahmad Reza, Ali Tabatabaeian e Mehdi Moradi. "A new insight into impact of thermal cycling on the un-notched and circular hole polymeric composite rings via naval ordnance laboratory-ring test". Journal of Composite Materials 54, n. 23 (24 marzo 2020): 3287–95. http://dx.doi.org/10.1177/0021998320912836.

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In this paper, different mechanical responses of polymer matrix composite rings under thermal cycling are analyzed. The polymer matrix composite rings are classified to un-notched and open-hole specimens and tested based on the naval ordnance laboratory-ring tensile test method. Internal pressure, fracture and surface degradation changes as a function of the hole diameter and number of cycles are investigated. Experimental results suggest that specimens with larger hole radius have more mechanical property variations during thermal cycling. Also, it is revealed that the mechanical properties of laminates degrade as a function of the number of cycles and the hole diameter. The results also demonstrate that long splitting fiber breakage is the main mode for the failure of un-notched specimens, whereas fiber breakage and fiber matrix debonding are the two main modes for the failure of open-hole specimens. Finally, a multiple regression model is proposed to predict the tensile response of un-notched and open-hole polymer matrix composite rings subjected to thermal cycling condition.

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12

Bale, J. "Damage Behaviour and Stress Concentration Factor of Open Hole Tensile (OHT) Glass Fibre Reinforced Polymer (GFRP) Composites". International Journal of Automotive and Mechanical Engineering 16, n. 4 (30 dicembre 2019): 7299–314. http://dx.doi.org/10.15282/ijame.16.4.2019.09.0543.

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In many applications of composites, open-hole frequently includes for various purposes. However, further study on open-hole behaviour is still required, including on its strength and damage properties by combining experimental testing, real-time observations and calculations based on theoretical analysis and simulation model. The objective of this study is to understand the effect of an open-hole glass fibre reinforced polymer (GFRP) composites on tensile (static) properties, damage behaviour through Non-destructive Testing (NDT) Thermography and stress concentration factor (SCF). This study used an open-hole rectangular of GFRP specimens that fabricated by filament winding (FW) method and resin transfer moulding (RTM) method. It is found that the RTM specimens generate ≈ 170 % higher of tensile strength and ≈ 100 % higher of tensile modulus compared to the FW specimens. Infra-red (IR) camera shown the good detection on damage behaviour based on temperature increase at elastic and failure phase. Moreover, theoretical analysis and simulation results shown the good correlation where SCF reaches more than 4 times at the edge of the hole. This study concludes that open-hole on GFRP composites affects the tensile properties and generates damage marked by temperature increase and high SCF at the edge of the hole.

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13

Ivetic, Goran, Ivan Meneghin, Enrico Troiani, Gianluca Molinari, José Ocaña, Miguel Morales, Juan Porro et al. "Fatigue in laser shock peened open-hole thin aluminium specimens". Materials Science and Engineering: A 534 (febbraio 2012): 573–79. http://dx.doi.org/10.1016/j.msea.2011.12.010.

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14

Krajangsawasdi, Narongkorn, Ian Hamerton, Benjamin K. S. Woods, Dmitry S. Ivanov e Marco L. Longana. "Open Hole Tension of 3D Printed Aligned Discontinuous Composites". Materials 15, n. 23 (6 dicembre 2022): 8698. http://dx.doi.org/10.3390/ma15238698.

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This paper explores the use of Discontinuous Aligned Fibre Filament (DcAFF), a novel discontinuous fibre reinforced thermoplastic filament for 3D printing, to produce structural complex parts. Compared to conventional composite manufacturing, 3D printing has great potential in steering fibres around small structural features. In this current study, the initial thin carbon fibre (CF)-poly(L-lactic acid) (PLA) tape, produced with the High Performance Discontinuous Fibre (HiPerDiF) technology, is now reshaped into a circular cross-section filament, the DcAFF, using a bespoke machine designed to be scalable to high production rates rather than using a labour-intensive manual moulding method as in previous work. The filaments are then fed to a general-purpose 3D printer. Tensile and open-hole tensile tests were considered in this paper for mechanical and processability of DcAFF. The 3D printed specimens fabricated with the DcAFF show superior tensile properties compared to other PLA-based 3D printed composites, even those containing continuous fibres. Curvilinear open-hole tensile test samples were fabricated to explore the processability and performances of such material in complex shapes. The mechanical performance of the produced specimens was benchmarked against conventionally laid-up specimens with a cut hole. Although the steered specimens produced have lower strength than the fully consolidated samples, the raster generated by the printing path has turned the failure mechanism of the composite from brittle to ductile.

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Zhang, Jipeng, Yue Wang, Wen Yang e Yuan Zhao. "Effect of Hole Arrangement on Failure Mechanism of Multiple-Hole Fiber Metal Laminate under On-Axis and Off-Axis Loading". Materials 14, n. 19 (2 ottobre 2021): 5771. http://dx.doi.org/10.3390/ma14195771.

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Mechanical joints are commonly required in structures made of fiber metal laminate (FML), which pose a threat due to multi-site stress concentrations at rivet or bolt holes. Thus, for a reasonably designed FML joint, it is essential to characterize the failure mechanism of multiple-hole FML; however, little information about this has been found in open literature. In the present work, influences of hole arrangement and loading strategy (on-axis or off-axis) on the failure mechanism of multiple-hole FML were investigated, by performing finite element analyses and energy dissipation analyses with elastoplastic progressive damage models that took curing stress into account. Six types of specimens with holes arranged in parallel and staggered forms were designed, whose geometrical parameters were in strict accordance with those specified for composites joints. It indicated that the stress distribution, gross/net notched strength, critical fracture path, and damage evaluation process were only slightly influenced by the hole number and hole arrangement. On the other hand, they were strongly influenced by the loading strategy, due to the transition of failure domination. Results presented here can provide evidence for introducing design regulations of composite joints into the more hybrid FML, and for reasonably determining its multiple-hole strength merely based on the sing-hole specimen.

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Swanson, S. R., D. S. Cairns, M. E. Guyll e D. Johnson. "Compression Fatigue Response for Carbon Fiber With Conventional and Toughened Epoxy Matrices With Damage". Journal of Engineering Materials and Technology 115, n. 1 (1 gennaio 1993): 116–21. http://dx.doi.org/10.1115/1.2902143.

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This paper compares the open hole compression, compression after impact, compression fatigue of open hole specimens, and compression fatigue after impact response of quasi-isotropic laminates with IM7 carbon fiber and 3501-6 and 8551-7 epoxy matrices. These matrices can be considered to be a relatively brittle and a high-toughness resin, respectively. The objective was to establish whether the improved compression after impact response associated with high toughness matrices also held after fatigue loading. The results of impact and compression fatigue tests show that residual strengths of the toughened epoxy matrix system were approximately twice that of the brittle matrix system, and that fatigue resistance after impact and of open hole specimens was generally improved.

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Jumahat, Aidah. "Tensile Properties of Open Hole and Unhole Sugar Palm ‘Ijuk’ (SPI) Fibre Composite Treated with Sodium Hydroxide (NaOH)". Journal of Mechanical Engineering 21, n. 3 (15 settembre 2024): 165–81. http://dx.doi.org/10.24191/jmeche.v21i3.27352.

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This study evaluates the effects of sodium hydroxide (NaOH) treatment on tensile properties of sugar palm 'ijuk' (SPI) fibre-reinforced polymer (FRP) composites, with and without an open hole that acts as a stress concentrator. The NaOH treatment is aimed to improve the interfacial adhesion between SPI fibres and polymer matrix. Composite specimens were prepared using the hand lay-up method, incorporating SPI fibres in various orientations, and featuring a 6 mm diameter hole. Tensile tests were conducted to evaluate the mechanical performance of SPI FRP composite, including ultimate tensile strength, Young's modulus, and elongation at break. The research also compared the properties of SPI to those of synthetic glass fibre in fibre-reinforced polymer composites. The results showed that NaOH treatment significantly improves the fibre-matrix adhesion with 26% increase in tensile strength, leading to enhanced tensile properties in both samples, regardless of hole presence. The 0° orientation provides the highest strength and stiffness when the load is applied in the direction of the fibres. While for the 90° orientation, strength reduces by 14%. The impact of the hole on stress concentration and the subsequent mechanical behaviour of the open-hole specimens is substantial. The findings of this study offer insightful perspectives on the potential use ofNaOH-treated SPI fibre in structural and other applications, demonstrating its ability to withstand tensile stresses, even with geometric discontinuities like holes.

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Strungar, Elena, Dmitrii Lobanov, Ekaterina Chebotareva e Yaroslava Kochneva. "Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods". Frattura ed Integrità Strutturale 18, n. 68 (15 febbraio 2024): 63–76. http://dx.doi.org/10.3221/igf-esis.68.04.

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In this paper, tensile tests of specimens with a pattern of holes made of fiber-glass plastic based on combined epoxy and phenol-formaldehyde resins are carried out in order to study the processes of damage accumulation and tension fracture. The Vic-3D video system is used to evaluate damage development and inhomogeneity of strain localization during loading. Continuous recording of acoustic emission signals is carried out during the tests, resulting in obtaining data on fracture mechanisms in the material. Ranges of peak frequencies are identified. Surface analysis of specimens was carried out using a microscope. A significant reduction in strength occurs due to the presence of a circular hole in the material, although additional holes do not exacerbate this effect. Fracture patterns of specimens with a hole pattern have been analyzed, and different "paths" of fracture have been observed. The comparison of strain fields obtained on the basis of application of three-dimensional digital optical system with the configuration of strain fields constructed as a result of numerical modeling by the finite element method has been carried out. It is found that the strain fields for different open hole patterns are quantitatively and qualitatively similar and identical.

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Eleonsky, Sviatoslav, Yury Matvienko, Vladimir Pisarev e Igor Odintsev. "Quantitative description of low-cycle fatigue damage accumulation in contact interaction zone by local strain evolution". Frattura ed Integrità Strutturale 16, n. 62 (22 settembre 2022): 541–60. http://dx.doi.org/10.3221/igf-esis.62.37.

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The novel non-destructive method for quantitative description of low-cycle fatigue damage accumulation is expanded to a case of contact interaction in the stress concentration area. Investigated objects are plane aluminium specimens with the centred hole filled by cylindrical steel inclusion. The specimen is subjected to cyclic pull-push loading. The key point, that defines scientific novelty and powerfulness of the developed approach, consists of involving local deformation parameters as current damage indicators. Required strain values follow from distributions of all three displacement components along the filled hole edge measured by reflection hologram interferometry. The data, which are derived at different stages of low-cycle fatigue for the single specimen, provide normalized dependencies of local strain values from number of loading cycle, which are a source of damage accumulation functions. These functions are constructed for the specimen with the filled hole and geometrically analogous specimen with the open hole. Obtained data quantitatively describe a difference in damage accumulation rates for two cases.

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Marouene, Aymen, Pierre Legay e Rachid Boukhili. "Experimental and numerical investigation on the open-hole compressive strength of AFP composites containing gaps and overlaps". Journal of Composite Materials 51, n. 26 (1 febbraio 2017): 3631–46. http://dx.doi.org/10.1177/0021998317690917.

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Laminated composite structures manufactured via the automated fiber placement process inherently contain process defects know as gaps and overlaps. These defects raise concerns when they are located on or near holes intended for mechanical fastening. This investigation attempts to predict the effect of automated fiber placement-generated defects on the open-hole compression strength by combining both experimental tests and numerical simulation. Tested open-hole compression specimens containing gaps and overlaps oriented at 0° or 90° and centered on or shifted near the hole show that, depending on their location, the gaps and overlaps may have negative, negligible, or positive effects on the open-hole compression strength. The better than expected effects are compatible with microscopic observations that clearly show the rearrangement of the plies during the consolidation process, which prevent the formation of deleterious discontinuities. Incorporating these observations in a numerical model, which simulates gaps and overlaps embedded inside the composite laminates, and applying a progressive failure analysis, confirms that the effects of automated fiber placement defects depend as much on their type as on their location relative to the hole center. Finally, the results obtained from a parametric study provided further explanation on the effects of automated fiber placement defects on the failure strength of perforated composite laminates.

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Wu, Hao, Guoyan Zhao, Weizhang Liang, Enjie Wang e Shaowei Ma. "Experimental Investigation on Fracture Evolution in Sandstone Containing an Intersecting Hole under Compression Using DIC Technique". Advances in Civil Engineering 2019 (7 aprile 2019): 1–12. http://dx.doi.org/10.1155/2019/3561395.

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Failure of underground structures, especially intersections, becomes more severe as the depth increases, which poses a new challenge for the safe construction and operation of deep rock engineering. To investigate the mechanical properties and fracture behavior of rock with an intersecting hole under compressive loads, a series of uniaxial compression tests was carried out on cuboid red sandstone specimens containing an intersecting hole with three types of shapes by digital image correlation (DIC) technique. The results showed that the existing hole inside specimens leads to almost a 50% reduction of mechanical parameters from that of intact ones, and this weakening effect is associated with the shapes of holes. Failure of specimens is a progressive process in which cracks, i.e., primary tensile cracks, secondary tensile cracks, and shear cracks, initiate from stress concentration zones, propagate along certain direction, and coalesce with each other into macrofractures. Both the real-time principal strain fields and horizontal displacement fields of specimens under compression could be visually displayed by DIC system, and they were in good consistency in characterizing the fracture behavior. Moreover, the propagation characteristics of primary tensile cracks were studied further by quantitatively analyzing the strain variation during the loading process, and the propagation mechanism of “open-close-reopen” of primary tensile cracks was explained in detail.

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Xu, Liang, Yi He, Shaohua Ma, Li Hui, Yaoxiong Jia e Yiming Tu. "Effects of aging process and testing temperature on the open-hole compressive properties of a carbon fiber composite". High Performance Polymers 32, n. 6 (8 gennaio 2020): 693–701. http://dx.doi.org/10.1177/0954008319897291.

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The properties of T800 carbon fiber–epoxy composite specimens with a hole were studied in terms of mass change, scanning electron microscopy, glass transition temperature ( T g), heat-resistant temperature, Fourier-transform infrared (FTIR) spectroscopy, open-hole compressive strength at different temperatures, and stereomicroscopic observations after being subjected to hygrothermal aging and thermal-oxidative aging processes. FTIR spectra indicated that after hygrothermal aging at 70°C and 85% relative humidity (RH), chemical aging did not occur, whereas after thermal-oxidative aging at 190°C, the specimens exhibited chemical aging. The unaged specimens had a T g of 229°C and an extreme heat-resistant temperature T gmod of 184°C; after hygrothermal aging, the specimens had a T g and T gmod of 207°C and 143°C, respectively; and after thermal-oxidative aging, the specimens had a T g and T gmod of 252°C and 215°C, respectively. The effects of temperature on open-hole compressive strength were evaluated at room temperature of 23°C, 50°C, 100°C, 150°C, and 200°C. The compressive strengths of the specimens decreased after aging and with the increasing test temperature. At the highest test temperature, the unaged specimens, hygrothermal-aged, and thermal-oxidative-aged specimens retained over 73.7%, 65.5%, and 67.9%, respectively, of their compressive strength. Thus, the T800 carbon fiber–epoxy composite evaluated in this study exhibited good resistance to the effects of aging and high temperature. These results should be beneficial to the understanding of the long-term performance of composites.

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Russo, Angela, Federica Russo, Concetta Palumbo e Aniello Riccio. "Numerical Assessment on the Fatigue Behavior of Composite Open‐Hole Tensile Specimens". Macromolecular Symposia 404, n. 1 (agosto 2022): 2100454. http://dx.doi.org/10.1002/masy.202100454.

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Kabeel, A. M., P. Maimí, N. Gascons e E. V. González. "Nominal strength of quasi-brittle open hole specimens under biaxial loading conditions". Composites Science and Technology 87 (ottobre 2013): 42–49. http://dx.doi.org/10.1016/j.compscitech.2013.07.022.

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Zhang, Xiao Qiong, Wei Guo Guo e De Shuan Kong. "Damage Analysis of 2D Woven Composite Laminates Containing an Open-Hole under Tensile Loadings". Key Engineering Materials 525-526 (novembre 2012): 373–76. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.373.

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In order to understand damage mechanism, the influences of lay-up construction of laminates and environgment on tension behavior of 2D woven composite laminates with an open-hole, which was manufactured by a new technology, uniaxial tension tests are performed in 3 different environments on 4 kinds of lay-up specimens, using a WE-50 electromechanical universal material testing machines. The fracture of specimens are analysed through micrographic observations. The result show that there is a large difference both in tensile strength and damage mechanism due to different kinds of lay-up specimens: 1) the tensile strength of specimens that only with ±45 degree laminated is much lower than other samples with different kinds of layup and its tensile stress-strain curves presents nonlinear; 2)The failure modes and damage mechanism determines the strength of specimens; 3)The change of environment had a certain effect on the mechanical behaviors of materials, in this paper, it will cause the tensile strength of speicmens decreasing.

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Matta, Seshadri, Naresh Reddy Kolanu, Viswanath Chinthapenta, C. M. Manjunatha e M. Ramji. "Progressive damage analysis of adhesively bonded patch repaired carbon fibre–reinforced polymer specimen under compression involving cohesive zone model". International Journal of Damage Mechanics 28, n. 10 (24 febbraio 2019): 1457–89. http://dx.doi.org/10.1177/1056789519832062.

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In this paper, the in-plane compression behaviour of open-hole carbon fibre composite specimens adhesively bonded with the external carbon fibre composite patches on the single- and double side are studied. Uniaxial compression tests are conducted on MTS machine using ASTM anti-buckling fixture. A 3D progressive damage model is developed to predict the damage initiation and failure in both unrepaired open cutout and repaired carbon fibre composite specimens under compressive load. Stress-based 3D-Hashin's failure criteria are used for predicting the fibre and matrix damage in carbon fibre composite. The cohesive zone model element is used for modelling the interlaminar delamination in carbon fibre composite specimen and also the adhesive layer between patch and specimen. Initial stiffness, damage initiation load and ultimate load of the specimen are obtained using progressive damage model based on finite element analysis, and they are compared against the experimental values. The load–deflection curve and the damage progression obtained from finite element analysis using progressive damage model is found to be in good coherence with the experimental predictions. In case of patch bonded carbon fibre composite specimens, failure mechanism starts with partial patch debonding followed by complete specimen failure.

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Zhou, Rui, Weicheng Gao, Wei Liu e Jianxun Xu. "Effects of Open-Hole and Reinforcement on the Bearing Performance of the Plain-Woven Fabric Composite I-Section Beams under Shear Load". Aerospace 9, n. 10 (22 settembre 2022): 537. http://dx.doi.org/10.3390/aerospace9100537.

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In this article, experiments and finite-element (FE) analyses have been conducted in order to study the effects of open-hole and reinforcement on the buckling and failure of the plain-woven fabric (PWF) composite I-section beams under shear load. With the shear experiments, the buckling and failure characteristics of the PWF composite beams have been obtained, and experimental results of the beams in perfect conditions are compared with the results from the specimens with open-hole and reinforcement in the web region. FE analyses for the composite beams are then carried out with the assistance of the multi-scale method proposed for the PWF composites. With the comparison between the experimental and numerical results, the composite beams’ FE models and the utilized calculation methods are proved to be feasible. According to the parametric study based on the validated models and the multi-scale methods, it is found that the existence of the open-hole decreases the flexural rigidity of the beams’ web region and introduces the stress concentration, which further reduces the structural stability and the shear carrying capacity of the composite beams. With the effects of restraining the structural off-plane deformation and relieving the hole-edge stress concentration, the intercalation reinforcement could effectively improve the bearing performance of the PWF composite beams with open-holes.

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Abdellah, Mohammed Y., Mohamed K. Hassan, Ahmed F. Mohamed e Khalil Abdelrazek Khalil. "A Novel and Highly Effective Natural Vibration Modal Analysis to Predict Nominal Strength of Open Hole Glass Fiber Reinforced Polymer Composites Structure". Polymers 13, n. 8 (12 aprile 2021): 1251. http://dx.doi.org/10.3390/polym13081251.

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Glass fiber reinforced polymer (GFRP) composite laminates are considered the key material in many industries such as the infrastructure industries and the aerospace sector, and in building structures due to their superior specific strength and lightweight properties. The prediction of specimens’ nominal strength with open holes is still an attractive and questionable field of study. The specimen size effect is referred to its strength degradation due to the presence of holes when specimen geometry gets scaled. The non-destructive test used to measure the nominal strength of such material is a great tool for fast selection purposes, but not secure enough for several purposes. Furthermore, the destructive tests which are more expensive and time-consuming should be avoided in such structures. The present work aims to predict the nominal strength of open-hole GFRP’s composite using modal analysis of their natural frequency as non-destructive tests. At this end, the natural frequency, which is measured using modal analysis procedures, is combined with both linear elastic fracture mechanics (LEFM) and the theory of elasticity to predict the nominal strength of open-hole composite laminates. This advanced model employs two parameters of surface release energy resulting from a simple tension test and Young’s modulus based on vibration modal analysis. It is well established that these types of materials are also subjected to a size effect in dynamic response. Inversely to the known static loading size effect, the size effect in dynamic response increases with specimen size. The novel model gives excellent and acceptable results when compared with experimental and finite element ones. Size effects curves of a nominal strength of these laminates have a very close relative value with those obtained from finite element and analytical modeling. Moreover, the received design tables and graphs would be highly applicable when selecting suitable materials for similar industrial applications.

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Nixon-Pearson, O. J., S. R. Hallett, P. W. Harper e L. F. Kawashita. "Damage development in open-hole composite specimens in fatigue. Part 2: Numerical modelling". Composite Structures 106 (dicembre 2013): 890–98. http://dx.doi.org/10.1016/j.compstruct.2013.05.019.

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Nixon-Pearson, O. J., S. R. Hallett, P. J. Withers e J. Rouse. "Damage development in open-hole composite specimens in fatigue. Part 1: Experimental investigation". Composite Structures 106 (dicembre 2013): 882–89. http://dx.doi.org/10.1016/j.compstruct.2013.05.033.

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31

Leontiev, A. V., E. V. Rubtsova e A. A. Skulkin. "Lab-scale simulation of hydraulic fracturing: some outcomes". Interexpo GEO-Siberia 2, n. 3 (18 maggio 2022): 202–7. http://dx.doi.org/10.33764/2618-981x-2022-2-3-202-207.

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The paper describes the lab-scale physical simulation of hydraulic fracturing in measurement holes. The tests were carried out using cubical polymethyl methacrylate specimens with faces of 200 mm. The open-end or dead-end holes with diameter of 12 mm were made in the test specimens. In the preset intervals in the holes, the longitudinal or latitudinal (ring-wise) slots with depths up to 3 mm were precut to initiate and orient created fractures. Hydrofracturing was carried out using prototype tools for sealing a test interval in a hole (packer-to-packer spacing) and to feed it with power fluid under pressure. The model specimens were tested under different triaxial loading conditions on a special testing machine. The representative cases of the created fracture growth in the model specimens were analyzed. The physical simulation outcomes can be used in formulation and solution of analytical problems on HF stress measurement, as well as to improve procedures and equipment involved in this method of stress control in underground mines.

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Kötter, Benedikt, Julian Karsten, Johann Körbelin e Bodo Fiedler. "CFRP Thin-Ply Fibre Metal Laminates: Influences of Ply Thickness and Metal Layers on Open Hole Tension and Compression Properties". Materials 13, n. 4 (18 febbraio 2020): 910. http://dx.doi.org/10.3390/ma13040910.

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Thin-ply laminates exhibit a higher degree of freedom in design and altered failure behaviour, and therefore, an increased strength for unnotched laminates in comparison to thick-ply laminates. For notched laminates, the static strength is strongly decreased; this is caused by a lack of stress relaxation through damage, which leads to a higher stress concentration and premature, brittle failure. To overcome this behaviour and to use the advantage of thin-ply laminates in areas with high stress concentrations, we have investigated thin-ply hybrid laminates with different metal volume fractions. Open hole tensile (OHT) and open hole compression (OHC) tests were performed with quasi-isotropic carbon fibre reinforced plastic (CFRP) specimens. In the area of stress concentration, 90° layers were locally substituted by stainless steel layers of differing volume fractions, from 12.5% to 25%. The strain field on the specimen surface was evaluated in-situ using a digital image correlation (DIC) system. The embedding of stainless steel foils in thin-ply samples increases the OHT strength up to 60.44% compared to unmodified thin-ply laminates. The density specific OHT strength is increased by 33%. Thick-ply specimens achieve an OHC strength increase up to 45.7%, which corresponds to an increase in density specific strength of 32.4%.

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Roh, Sung Woo, Daniel H. Kim, Alberto C. Cardoso e Richard G. Fessler. "Endoscopic foraminotomy using a microendoscopic discectomy system in cadaveric specimens". Neurosurgical Focus 4, n. 2 (febbraio 1998): E4. http://dx.doi.org/10.3171/foc.1998.4.2.5.

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Although the anterior approach is more commonly performed for the treatment of cervical disc disease, the posterior approach has distinct advantages in selected cases of foraminal stenosis and posterolateral disc herniation. The authors performed cervical key hole foraminotomies using a microendoscopic discectomy (MED) system in four cadaveric cervical spine specimens to evaluate this minimally invasive surgical approach for cervical disc diseases. The amount of bone decompression achieved by using the MED system was compared with that achieved by using the open foraminotomy procedure in each cadaveric specimen. Three noncontiguous cervical nerve roots were selected between C-3 and C-8 in each specimen and were decompressed using the MED system on one side and using the open foraminotomy procedure on the contralateral side. Postoperative computerized tomography (CT) myelography showed that adequate bone decompression was achieved by using either the MED or open procedure in all specimens. Postoperatively, open dissection was performed to confirm and compare the amount of decompression in both the MED and open procedures. The laminotomy size (vertical and transverse diameter), the length of decompressed nerve root, and the proportion of removed facet joint were measured on every operative level. The average vertical diameter of laminotomy area and the percentage of facet removed were significantly greater in the MED procedure than the open procedure (p < 0.05). The transverse diameter of the laminotomy area and the average decompressed root length were not significantly different between MED and open surgery. The authors conclude that endoscopic cervical foraminotomy using the MED system is a feasible procedure and may be clinically applicable in the treatment of foraminal stenosis and laterally located cervical disc herniation.

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Özaslan, Emre, Ali Yetgin e Bülent Acar. "Stress concentration and strength prediction of 2×2 twill weave fabric composite with a circular hole". Journal of Composite Materials 53, n. 4 (10 luglio 2018): 463–74. http://dx.doi.org/10.1177/0021998318785994.

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Stress concentration and strength prediction of 2 × 2 twill weave carbon fiber reinforced composite specimens with different hole sizes are investigated on numerical and analytical basis. Stress distribution around the hole is obtained using Lekhnitskii’s model together with Tan’s finite width correction factor and also finite element analysis. Validity of Lekhnitskii’s formula together with Tan’s correction is demonstrated for 2 × 2 twill weave composites with different w/d ratios. Tan’s correction factor is compared with finite element analysis results at a characteristic distance away from hole tip where the stresses are important for strength prediction. Applicability of point stress criteria and average stress criteria strength prediction methods for open hole specimens to 2 × 2 twill weave material is demonstrated. The performances of the point stress criteria and average stress criteria methods are compared in the case of eccentric tension loading. All analytical and numerical results are verified by experimental study.

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Bale, Jefri, Kristomus Boimau e Marselinus Nenobesi. "Natural Composite Reinforced by Lontar (Borassus flabellifer) Fiber: An Experimental Study on Open-Hole Tensile Strength". International Journal of Biomaterials 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/7685047.

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A research has been conducted in the present study to investigate the effect of hole configuration on tensile strength of lontar fiber-reinforced composites. The lontar fiber-reinforced composites used in this study were produced by hand lay-up process. The lontar fiber-reinforced composites consist of short random fiber of 5 cm that contains 32% of nominal fiber volume as the reinforcement and unsaturated polyester as the matrix. The results show that the differences of hole configuration have an effect on tensile strength of lontar fiber-reinforced composites. It is found that the specific area of four-hole specimens experiences smaller strain propagation due to the redistributed stress and no stress passes through the hole. The damage of lontar fiber-reinforced composites with different hole configurations in tension is fairly straight and transverse to the loading axis, where the initial damage occurs in the form of matrix cracking, propagates into interfacial failure in form of delamination, and ultimately failed mainly due to the fiber breakage.

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NAKATANI, Hayato, Tatsuro KOSAKA, Katsuhiko OSAKA, Yoshihiro SAWADA e Tomonaga OKABE. "Crack Growth Behaviour of Open-Hole Specimens of Ti/GFRP Laminates under Fatigue Loading". Journal of the Society of Materials Science, Japan 58, n. 5 (2009): 389–95. http://dx.doi.org/10.2472/jsms.58.389.

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Baykan, Buşra M., Ugur Yolum, Emre Özaslan, Mehmet A. Güler e Bora Yıldırım. "Failure Prediction of Composite Open Hole Tensile Test Specimens Using Bond Based Peridynamic Theory". Procedia Structural Integrity 28 (2020): 2055–64. http://dx.doi.org/10.1016/j.prostr.2020.11.029.

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Newman Jr., J. C., e W. Abbott. "Fatigue-life calculations on pristine and corroded open-hole specimens using small-crack theory". International Journal of Fatigue 31, n. 8-9 (agosto 2009): 1246–53. http://dx.doi.org/10.1016/j.ijfatigue.2009.01.007.

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Keleş, Özgür, Caleb Wayne Blevins e Keith J. Bowman. "Effect of build orientation on the mechanical reliability of 3D printed ABS". Rapid Prototyping Journal 23, n. 2 (20 marzo 2017): 320–28. http://dx.doi.org/10.1108/rpj-09-2015-0122.

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Abstract (sommario):

Purpose Increasing use of 3D printing techniques to manufacture consumer products and open-source designs raises the question of “What is the mechanical reliability of 3D printed parts?” Therefore, the purpose of this paper is to investigate the impacts of build orientation on the mechanical reliability of acrylonitrile butadiene styrene (ABS) produced using 3D printing. Design/methodology/approach Tensile tests on ABS specimens were performed with and without a hole in the center, which were produced by fused deposition modeling (FDM). Seven sets of approximately 30 specimens were printed in XY, XZ and C+45 orientations to obtain reliable fracture statistics. Weibull analysis was performed to quantify the variation in the tensile strength. Findings The Weibull analysis showed that the reliability of FDM produced ABS can be as low as advanced ceramics. Weibull moduli of specimens without a hole were between 26 and 69, and specimens with a hole had Weibull moduli between 30 and 41. P-type deviations from the Weibull statistics were observed. The XZ orientation resulted in the highest average fracture strength for specimens with and without a hole, and C+45 orientation resulted in the lowest strength. Practical implications As the Weibull distribution relates the applied stress to probability of failure, the Weibull analysis provides a practical design criterion to achieve specific reliability levels for additively manufactured parts. Originality/value This study, for the first time, provides Weibull statistics for FDM-produced ABS parts, which can be used to predict mechanical reliability.

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Hur, Mi-Sun, Seunggyu Lee, Chang-Seok Oh e Yeon Hyeon Choe. "Newly-found channels in the interatrial septum of the heart by dissection, histologic evaluation, and three-dimensional microcomputed tomography". PLOS ONE 16, n. 2 (8 febbraio 2021): e0246585. http://dx.doi.org/10.1371/journal.pone.0246585.

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A minute thrombus can pass through a small type of interatrial communication, which can result in a stroke or transient ischemic attack and several associated symptoms. This study sought to investigate a new type of interatrial communication. Thirty-one hearts from embalmed adult cadavers were investigated. Each interatrial channels (IACs) was classified as either an open or obstructed channel according to the connection of each hole on the right and left surfaces of the interatrial septum. Open channels were found in two specimens (6.5%). Both open and obstructed IACs followed tortuous courses through the interatrial septum. On the right surface of the interatrial septum, the hole was usually found adjacent to the left border of the interatrial septum between the opening of the superior vena cava into the right atrium and the superior margin of the fossa ovalis. Conversely, holes on the left surface of the interatrial septum were usually found in the upper and middle parts adjacent to the left border of the interatrial septum. This novel finding is expected to support our understanding of the onset of possible symptoms such as stroke in the absence of classical atrial septal defects.

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Ding, Xiaohua, Xiang Lu, Wei Zhou, Xuyang Shi, Boyu Luan e Ming Li. "Blasting Impact Simulation Test and Fragmentation Distribution Characteristics in an Open-Pit Mine". Shock and Vibration 2019 (27 maggio 2019): 1–13. http://dx.doi.org/10.1155/2019/4080274.

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Based on the split Hopkinson pressure bar (SHPB) test system, dynamic impact tests of coal specimens under different impact pressures were carried out to study the relationship between the impact load and the size of crushed lump coal. Based on the theory of stress wave attenuation, the relationship between the blasting impact load in a single-hole blasting area of a coal seam and the load applied in an impact failure test of a coal specimen in the laboratory was established. According to the characteristics of the fragmentation distribution of the coal specimens destroyed under a laboratory impact load and the requirement of the minimum cost control of coal blasting in an open-pit coal mine, the fragmentation size range was divided into three groups: large-diameter, medium-diameter, and powder particles. Based on this range, the variation rule of the mass percentage of coal fragments with impact pressure was obtained. Established on the evaluation principle of the blasting effect in an open-pit coal mine, a good impact fragmentation effect was obtained. The good pressure range is 0.30 MPa≤P<0.90 MPa.

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42

Tong, An Shi, Li Yang Xie, Xin Bai, Ming Li e Wei Ying Meng. "Damage Monitoring and Analysis of Fiber-Metal Laminates with an Open Hole Using Digital Image Correlation". Applied Mechanics and Materials 868 (luglio 2017): 323–27. http://dx.doi.org/10.4028/www.scientific.net/amm.868.323.

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Notched fiber-mental laminates are susceptible to damage. Nowadays, damage detection mainly depends on visual inspection and C scan. But the two methods are limited to the technical skill of the inspectors, causing missed detection or even fault detection. This paper devotes to exploring the DIC monitoring technique to assess of the damage process taking place in notched (open hole) specimens under uniaxial tensile loading. Two-dimensional (2D) Digital Image Correlation (DIC) techniques are employed to obtain full-field surface strain measurements of GLARE3-3/2 and GLARE6-3/2 laminate with an open circular hole under tensile loading. Failure modes,damage initiation and progression of notched fiber-metal laminates are characterized and discussed.

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Qin, Jian Jun, Yan Hua e Zhen Long He. "Design and Development for the Self-Expandable Packer Test-Bed". Applied Mechanics and Materials 427-429 (settembre 2013): 2050–53. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2050.

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A new self-expandable packer test-bed for performance testing is developed against many problems of self-expandable packer test-beds which are in existence during detection process, for instance, imitative open hole cannot be used to detect environments in the downhole, size of a specimen for detection is undersize, pressure in experiments is low and detailed data cannot be gathered in development phrase. The new test-bed makes autoclave a modular design, which can test various performance of a specimen in a high-pressure environment and match relevant replacement parts of autoclave with the purpose of doing a variety of experiments on specimens. In this way, many existing problems of test-bed during the experiments can be solved.

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Zarouchas, Dimitrios, Casper van Dien e Nick Eleftheroglou. "In-situ impact analysis during fatigue tests of open-hole carbon fibre reinforced polymer specimens". Composites Part C: Open Access 6 (ottobre 2021): 100199. http://dx.doi.org/10.1016/j.jcomc.2021.100199.

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Nixon-Pearson, O. J., e S. R. Hallett. "An investigation into the damage development and residual strengths of open-hole specimens in fatigue". Composites Part A: Applied Science and Manufacturing 69 (febbraio 2015): 266–78. http://dx.doi.org/10.1016/j.compositesa.2014.11.013.

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46

Boni, L., D. Fanteria, A. Lanciotti e C. Polese. "Experimental and analytical assessment of fatigue and crack propagation in cold worked open hole specimens". Fatigue & Fracture of Engineering Materials & Structures 36, n. 9 (30 aprile 2013): 930–41. http://dx.doi.org/10.1111/ffe.12050.

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47

Shi, Jian, Mingbo Tong, Chuwei Zhou, Congjie Ye e Xindong Wang. "Progressive Failure Analysis in Open-Hole Tensile Composite Laminates of Airplane Stringers Based on Tests and Simulations". Applied Sciences 11, n. 1 (27 dicembre 2020): 185. http://dx.doi.org/10.3390/app11010185.

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The failure types and ultimate loads for eight carbon-epoxy laminate specimens with a central circular hole subjected to tensile load were tested experimentally and simulated using two different progressive failure analysis (PFA) methodologies. The first model used a lamina level modeling based on the Hashin criterion and the Camanho stiffness degradation theory to predict the damage of the fiber and matrix. The second model implemented a micromechanical analysis technique coined the generalized method of cells (GMC), where the 3D Tsai–Hill failure criterion was used to govern matrix failure, and the fiber failure was dictated by the maximum stress criterion. The progressive failure methodology was implemented using the UMAT subroutine within the ABAQUS/implicit solver. Results of load versus displacement and failure types from the two different models were compared against experimental data for the open hole laminates subjected to tensile displacement load. The results obtained from the numerical simulation and experiments showed good agreement. Failure paths and accurate damage contours for the tested specimens were also predicted.

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Liu, Yang, e Shutian Liu. "Experimental Research on Fatigue Crack Growth Behavior of Diffusion-Bonded Titanium Alloy Laminates with Preset Unbonded Areas". Materials 15, n. 15 (28 luglio 2022): 5224. http://dx.doi.org/10.3390/ma15155224.

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This paper aimed to study the fatigue crack growth behavior of diffusion-bonded titanium alloy laminates (DB-TAL) with preset unbonded areas using an experimental method to understand the toughening mechanisms of presetting unbonded areas in DB-TAL. For two series of specimens of DB-TAL with preset unbonded areas with an open hole, which have a pre-notch at the open hole edge, fatigue experiments under tension–tension cyclic loading were conducted. The fatigue crack growth process, the crack growth rate, and the stress intensity factor on the crack front were analyzed. The results showed that the preset unbonded area leads the crack away from the stress concentration zone and slows down the crack growth rate. Therefore, the preset unbonded area significantly improved the fracture property of DB-TAL.

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George, K., HS Reemsnyder, JK Donald e RJ Bucci. "Development of a DCPD Calibration for Evaluation of Crack Growth in Corner-Notched, Open-Hole Specimens". Journal of ASTM International 1, n. 9 (2004): 19044. http://dx.doi.org/10.1520/jai19044.

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de Matos, P. F. P., P. M. G. P. Moreira, I. Nedbal e P. M. S. T. de Castro. "Reconstitution of fatigue crack growth in Al-alloy 2024-T3 open-hole specimens using microfractographic techniques". Engineering Fracture Mechanics 72, n. 14 (settembre 2005): 2232–46. http://dx.doi.org/10.1016/j.engfracmech.2005.02.005.

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