Papers by Keyword: Stress Distribution

Abstract: Alumina ceramics sintered at 1350, 1450 and 1550 °C with different grain sizes were tested under dynamic load using a small-scale compressed air gun with sharpened tungsten carbide bullets impacting at a sub-ballistic velocity of 360 km/h. The deformation behavior and sub-surface cracks were recorded by visual examination. Cr³⁺ fluorescence was used to measure the residual stress distribution on and beneath the impact site. The results show the alumina sintered at 1350 °C with a fine grain size of 1.7 μm and high hardness of 18.3 GPa is good at bulletproof due to the cone cracks can spread the dynamic stress effectively and consume much impact energy.

Abstract: The roll forming is one of the simplest manufacturing processes for meeting the continued needs of various industries. The roll forming is increasingly used in the automotive industry to form High Strength Steel (HSS) and Advanced High Strength Steel (AHSS) for making structural components. In order to reduce the thinning of the sheet product, traditionally the roll forming has been suggested instead of the stamping process. The increased product performance, higher quality, and the lowest cost with other advantages have made roll forming processes suitable to form any shapes in the sheets. In this numerical study, a Finite Element Method is applied to estimate the stress, strain and the thickness distribution in the metal sheet with quadrilateral shape, ribs formed by the 11 steps roll forming processes using a validated model. The metal sheet of size 1,000 × 662 × 1.6 mm taken from SGHS steel was used to form the quadrilateral shape ribs on it by the roll forming process. The simulation results of the 11 step roll forming show that the stress distribution was almost uniform and the strain distribution was concentrated on the ribs. The maximum thinning strain was observed in the order of 15.5 % in the middle rib region possibly due to the least degree of freedom of the material.

Abstract: Roll forming is a continuous profile production process to form sheet metal progressively into the desired shape with closer tolerances. The process offers several advantages such as complex geometrical shapes, high strength, dimensional accuracy, closer tolerances, better quality and consistency, high production rate, improved conformity, and good surface finish. Several parts of automobile body are produced with this process. Nowadays roll forming technology draws more attentions than before in the automotive industry. In this paper, A Finite Element Method applied to study von mises stress, equivalent plastic strain, thickness, plastic strain, longitudinal strain and spring back of the metal sheet with ribs formed by roll forming process. The thickness variation was almost -6.144%.

Abstract: Roll forming process, due to increased product performance, higher quality, and lower cost with other advantages, has been made suitable process to form any shapes in the sheets. In this paper stress, strain and thickness distribution in the steel galvanized hot coil commercial (SGHC) sheet with Round shape ribs formed by roll forming process was investigated by a Finite Element code, ABAQUS software. The stress and strain distributions are considered during forming. Since in round shape ribs the flow of material is easier than quadrilateral one, the Stress distribution was more uniformand thinning strain was concentrated in the ribs with maximum value of 14.5% while this value in quadrilateral shape rib forming is 15.5%. The results show that this method is applicable in reducing the thickness strain.

Abstract: Fiber-metal laminates (FMLs) are composites materials that are commonly used in areas such as aircraft industry. They are composed of ductile metal layers with high strength fiber reinforced polymer layers. So far, however, only uniaxial tests have been used to characterize the quasistatic mechanical properties, which cannot reflect the real loading situation of the FML applications. In this work biaxial tensile behavior of FMLs with glass and Kevlar fibers based on aluminum alloy is studied with finite element method simulation. The simulation is run to find the stress-strain relationship for FMLs at the off-axis angles of 0˚ and 45˚ for glass and Kevlar fibers. The “composites layups” are constructed for the 3D FML part. Two different elements C3D8R (8-node linear) and C3D20R (20-node quadratic) are used to carry out the simulation. The results show that C3D20R shows major advantages. Analytical solutions based on the classical laminate theory are obtained to compare with the finite element method (FEM) solutions. The results show good consistency.

Abstract: Knee malalignment is considered one of the key biomechanical factors that influence the progression of knee osteoarthritis. In this context, a three-dimensional Finite Element model of the knee joint is developed and used to investigate the effect of the frontal plane femoro-tibial angle as well as the body weight load on the stress distribution in the knee cartilage and menisci. Therefore, the knee joint model is obtained through CAD software. Bones, articular cartilage and menisci are considered linear, elastic and isotropic materials. Ligaments were modelled using connectors. Consequently, contact pressures and equivalent stress (von-Mises) are calculated in Abaqus software. This model was validated using experimental and numerical results obtained by other authors. Results of this work demonstrated that; compressive stress and contact pressure on the medial compartment of the knee joint were found to be larger compared to those in the lateral compartment when the femoro-tibial angle and the body weight load increased from 0° to 12° varus and 500 N to 1250 N, respectively, suggesting that these two parameters might be risk factors for developing medial compartment knee osteoarthritis.

Abstract: The finite element model of diffusion bonding was established based on the analysis software of ANSYS, and the stress distribution characteristics of AZ31B/LY12 vacuum diffusion welded joint using Cu foil as the intermediate layer were analyzed. The effects of three factors, the welding temperature, the thickness of the intermediate layer Cu foil and the welding pressure, on the stress distribution of the AZ31B/Cu/LY12 joint were studied. The simulation results show that, when diffusion bonding of AZ31B and LY12 with intermediate layer Cu, the stress located on the center area of joint distribution is uniform, while the edge stress value is larger; welding parts along the axial stress distribution does not change significantly, while the maximum axial stress increases slightly when the temperature increases from 520 to 540 °C; when the thickness of intermediate layer Cu foil changes from 50 to 100 μm, the maximum shear stress value increases, while the position of that has no significant change; The stress distribution does not change, while the region of high stress increases when the welding pressure changes from 1 to 3 MPa.

Abstract: In this paper, flexible pavement system behavior due to heavy axle load is discussed. The effects of axle load, vehicle speed, and pavement thickness are studied numerically by means of PLAXIS 2D. The simulation results show that both vehicle speed and load significantly induce the deformation. The elastic deformation varies significantly when the speed and load change. However, the plastic deformation mostly depends on the vehicle speed. The effect of load becomes significant when the speed is slowing down. The pavement thickness also play important role to increase the stiffness to reduce the pavement deformation.

Abstract: Basal plane bending and stress distribution in physical vapor transport-grown n-type 4H-SiC crystals were investigated. High resolution X-ray diffraction measurements were performed on commercially available 3-inch-diameter 4H-SiC substrates and along the growth front surface of as-grown 1-inch-diameter 4H-SiC boules. The measurements revealed that structural parameters such as the c-lattice constant, basal plane tilting, and FWHM showed characteristic variations across the substrates and as-gown boules, indicating that the crystals had a non-uniform distribution of dislocations comprising domain structures. Residual stress measured by micro Raman spectroscopy showed a similar behavior, which was an oscillatory spatial variation. On the basis of these results, defect structures in the crystals are elucidated.

Abstract: The paper summarizes the results of numerical analysis conducted with the aim to compare the distribution of stresses in masonry pillars constructed using different bricklaying techniques. The analysis was carried out in reaction to the discussion of members of Czech standardization committee TNK 37 – Masonry structures. Currently, most of masonry load-bearing structures in the Czech Republic are made from clay blocks without mortar in perpend joints. The analysis seeks the answer to the question whether it is possible, in case of the eccentrically loaded masonry pillars with unfilled perpend joints, to consider the value of design compressive strength calculated using the same approach as for pillars with filled perpend joints for the check of vertical load resistance. Supplementary comparison of the behavior of the pillars with filled and unfilled perpend joints loaded by lateral load in the plane of the pillar (corresponding to short shear walls) was also conducted. 2D FEM model created in ATENA Science software was exploited for the analysis. The results confirmed that the approaches contained in ČSN EN 1996-1-1 [1] are basically applicable for pillars with unfilled perpend joints.