Papers by Keyword: Shear Stress

Abstract: Accurate modeling of the real material behavior is fundamental to improve the accuracy of the finite element analysis (FEA) of sheet metal forming processes. Classical material models such as Hill’48 or Barlat Yld2000-2d do not consider the material behavior under plane strain and shear, even though these states are the primary cause of failures observed in sheet metal forming. Moreover, yield criteria are conventionally calibrated at the onset of plastic deformation to determine the initial yield locus. Isotropic hardening is subsequently assumed, based on the flow curve under uniaxial tension. However, some modern sheet metals exhibit a pronounced distortional hardening behavior, which cannot be sufficiently mapped by the conventional modeling strategy. Hence, this contribution aims to improve the mapping of the yield locus distortion by considering the plane strain and shear stress states and by performing the parameter calibration at higher plastic strains. Hereby, the yield locus exponent of the Barlat Yld2000-2d is adapted in order to accurately map the material behavior under plane strain or shear. Moreover, the influence of a strain-dependent calibration of the yield locus on the mapping accuracy is investigated. Two materials, AA5182 and DP600, are being investigated. It is observed that the consideration of the plane strain state leads to a reduction of the yield locus exponent while the consideration of the shear stress state is accompanied with an increase of the yield locus exponent.

Abstract: The thickness of the residual limb’s soft tissue plays a crucial role in determining the mechanical behavior and stress distribution at the stump–prosthesis interface. Using finite element analysis (FEA), this study investigates the biomechanical effects of different soft tissue thicknesses (30 mm, 50 mm, and 70 mm) on stress distribution. A patient-specific finite element model of the residual limb was developed to simulate realistic anatomical and mechanical conditions. To replicate physiological loading, a static vertical load of 350 N was applied, and the interface between the residual limb and the prosthetic liner was modeled using appropriate contact mechanics. The results revealed that reducing the soft tissue thickness to 3 cm produced higher Von Mises stress concentrations (0.115 MPa) and contact pressure (0.0697 MPa), which may increase discomfort and the risk of tissue damage. Conversely, increasing the thickness to 70 mm reduced stress values (0.016 MPa) and contact pressure (0.0312 MPa) but led to excessive deformations (6.277 mm) that could compromise prosthetic stability. An optimal soft tissue thickness of 5 cm was identified, where Von Mises stress and contact pressure remained at moderate levels, offering a balance between stress distribution and mechanical stability. These findings provide valuable guidance for optimizing prosthetic socket design, as maintaining appropriate soft tissue thickness can enhance comfort, reduce pressure-related injuries, and improve the overall functionality of lower-limb prostheses.

Abstract: This work evaluates the shear stress in concrete beams with the addition of reinforcing fibers. Since there is no established standard in Peru, it was proposed to use the "JSCE-SF6" test method recommended by the Japanese Society of Civil Engineers and an analytical model to determine the shear strength of concrete with fibers. For this purpose, steel and polypropylene fibers were used in the proportions of 3kg, 5kg, 7kg and 9kg for each design. The main test was the shear test based on Japanese standards, however, secondary tests such as compression and flexural tests were also performed. The results obtained showed the contribution of the fibers in the three tests performed. In the shear test, the polypropylene fibers obtained a higher shear strength in all their mix designs in the same proportions. Additionally, an analytical model is proposed to determine the shear stress in concrete with fibers, which includes as variables the compressive strength, the mass fraction of fibers and the tensile strength of the fibers, which generates acceptable values close to those obtained experimentally with the Japanese Standard Shear Test.

Abstract: The crankshaft is one of the main components of the combustion engine used for continuous rotation. Therefore, this research aims to analyze the crankshaft failure of a jeep with a four-cylinder diesel engine used to transport 4 tons of logs on rugged terrain and uneven roads for 12 months. This research was carried out using the Scanning Electron Microscope (SEM), microstructure, hardness, chemical composition, and stress analysis testing methods. The chemical composition and microstructure test results showed that the crankshaft was made of AISI 3150 material with a pearlite phase. From the results of the visual observation on the fracture surface, the characteristics of failure due to fatigue are indicated by a beach mark pattern on the fracture surface. SEM test shows a crack initiation at the edge of the balancer due to the dynamic loads experienced by the crankshaft, which causes propagation from the initial beach marks pattern to the final fracture.

Abstract: The purpose of this research is to improve the parameters of shear strength in granular volcanic soil, by adding a percentage of Portland type I cement. The first step for this research was to classify the soil through a Granulometry test, according to the Unified Soil Classification System (USCS), the result was considered as a poorly graded sand with gravel also considered by The American Association of State Highway and Transportation Officials (AASHTO) as “A-1-b”. In addition, the compaction curve of the volcanic soil has a Maximum Dry Density (MDD) of 1.21 kg/cm2 and an optimum moisture content of 17.8%. Also, the friction angle of 33.5° and a cohesion of 0 kg/cm2, and the results of the Direct Shear Test indicate the Residual Stresses of 0.63, 1.34 and 2.65 kg/cm2 according to the Normal Stresses 1, 2 and 4 kg/cm2, respectively. The second step was to apply a Modified Proctor Test as following: one sample for natural soil and four samples adding 3%, 5%, 7% and 9% of cement. Finally, applied the Direct Shear Test: one sample for natural soil and three samples adding 3%, 5%, and 7% of cement after 7 days of curing, then three more samples are taken adding 3, 5% and 7% of cement at 14 days of curing. The results of the Modified Proctor Test of the volcanic soil with the addition of 5% cement has a maximum peak of a Maximum Dry Density of 1.33 kg/cm2 and with an Optimal Moisture Content of 22.7%, improved the MDD by 10% in regard to the natural soil. And the results of the Direct Shear Test shown in each sample an increase from 14.6% to 79.1% in the friction angle in comparison with the natural soil from 25.8% to 161.5% in shear strength. Likewise, the behavior of the volumetric deformation is shown, presenting a greater contraction when a normal stress of 1 kg/cm2 is applied and a greater expansion when a normal stress of 4 kg/cm2 is applied. Also, the volcanic soil at 7 days of curing with 7% cement addition increases its resistance by 67.34% and the volumetric variation decreases by 50% and the volcanic soil at 14 days of curing with 5% addition of cement increases its resistance by 103.40% and the volumetric variation decreases by 25%.

Abstract: The subject of the article is the analysis of the design of concrete members for shear from the point of view of theory and code regulations. These give formulae for verification of shear resistance and recommended limits of individual parameters, respectively. The authors explain the relevant formulae using a Strut and Tie analogy, especially the effect of the inclination of struts and the inclination of stirrups on the shear capacity of beams as well as the effect of a single concentrated force acting at distance up to 2d from the edge of support.

Abstract: The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve implant fixation.

Abstract: The determination of residual stresses is of great importance for many threated metal applications. In this work, the XRD residual stress analysis was used to characterized tempered aluminum-based specimen 6082T with rotation angles (phi) 0°, 45° and 90°, respectively. Highest stress levels were found in the rolling direction (phi = 0°), while negligible along transfers direction (phi = 90°). In addition, a shear stress along rolling and transverse direction, and also the present of texture along (110) can be observed.

Abstract: Titanium and its alloys, especially Ti-6Al-4V have found application as hip implants due to their mechanical properties, excellent biocompatibility, and corrosion resistance. The use of cementless hip implants has increased over the years as it is thought that this type is more durable compared to cemented hip implants. Cementless hip implants have a porous surface that allows the bone to grow into it and form a strong bone–implant connection. The goal of this study is the use of Finite Element Method simulations to obtain information about how different types of surface topography of a TI-6Al-4V hip implant affect the shear stress, which is used to access the bone-implant connection. Finite Element Analysis is used to analyze the stress distribution in three simple surface modifications in a hip implant under different types of loads. The optimal surface modification out of these three is obtained based on the shear stress distribution, as it is known that lower shear stress promotes bone ingrowth. In this study, we have considered the interaction between cortical bone and implant surface. Material properties and boundary conditions used for the simulations have been adapted from literature.

Abstract: The effect of shear stress on the viscosity and crystallization behavior of CaO-SiO₂-Al₂O₃ based mold fluxes were investigated, and the structure evolution of molten slag under shear stress were characterized by magic-angle spinning nuclear magnetic resonance technology (MAS-NMR). The results showed that with an increase of shear stress, the shear-thinning behavior of molten slag was found, and the strongest shear-thinning behavior was formed with an addition of 15% Al₂O₃. Correspondingly, the decrement of Q³(1Al) and Q²(1Al) species in molten slag were the largest from MAS-NMR results. In addition, under agitation, the crystallization fraction of sample increased from 71% to 88%, and the average grain size was reduced 23%. However, the shear stress has no influence on the crystal phase.