Elasto-plastic Stress Analysis Research Articles

Elasto-Plastic Stress Analysis in a Tube Made of Isotropic Material and Subjected to Pressure and Mechanical Load

Elasto-Plastic Stress Analysis in a Tube Made of Isotropic Material and Subjected to Pressure and Mechanical Load

Fatigue behaviour of thin-walled cold roll-formed steel sections

This paper presents experimental research aimed at addressing the fatigue behaviour of thin-walled cold roll-formed steel sections, very commonly used in rack structures. This research is performed under the FASTCOLD-RFCS project, which aims to fill an existing gap on fatigue design rules. A new design S-N curve is derived from an innovative testing methodology, which supports the current revision of the Eurocode 3 (EN 1993-1-9). Additionally, a local fatigue approach, encompassing residual stresses from numerically simulating the manufacturing process and structural elastoplastic stress analysis supported by the Theory of Critical Distances, returned consistent fatigue life predictions for the tested profiles.

Expansion Vessel. Pressurized Equipment Design. PED.

With the publication 2020-21.06 we dealt with the design of an expansion vessel. After identifying the normative references that regulate the pressure equipment, then the PED directive (2014/68 / EU), with reference to the project data that classify the pressure equipment to category IV (Annex II of the PED directive) we chose as a design method, the DBF analytical method envisaged by the EN 13445 standard that the PED directive has adopted. Having identified the mechanical characteristics of the material used for the construction of the vessel (yield point, traction limit and other mechanical properties), we calculated the safety factor based on the analysis of the loads that the pressure equipment will have to support under operating conditions (both normal and exceptional). Since 6 nozzles were connected to the expansion tank, it was necessary to check the reinforcement of the nozzle which confirms the request for reinforcement for the nozzles connected to the casing, with a larger diameter. Assuming three types of (periodic) oscillating loads, we carry out the fatigue test in all the load hypotheses considered. The checks and analyzes carried out on the results and calculations have demonstrated the required design safety even in exceptional cases such as temperature and pressure peaks, confirming the elastic regime (even if at the limit) with a temperature more than double the operating temperature (from 220 ° C at 450 ° C) in combination with a peak pressure equal to twice the operating pressure (from 25 bar to 50 bar). With the intention of achieving certainty of the results obtained, it was appropriate to size the container using an alternative calculation method to compare the results; for this purpose we used the calculation model provided by ASME VIII, which provides for the calculation of the pressure necessary for the complete plasticization of the section according to the Tresca criterion and which having provided, the same results as the model provided for by the EN 13445 DBF standard (model calculation based on the hypothesis of not exceeding the yield point of the material, therefore in the hypothesis of linearity determined by Hooke's law) it allows us to believe that the certainty of the results has been reached, aimed at operating safety of the pressure equipment. The project calculation ends with the Elasto Plastic Stress Analysis: deformation analysis according to the DBA Method (ASME VIII Div. 2) which allows us to calculate the plastic deformation, the collapse limit of the material and to carry out a study of the deformations at the elastic field limit and in the plastic field by Navier's theory (Claude-Louis-Marie Navier) which applies the constitutional laws of materials known as Hooke's law for the elastic field and the constitutional laws of Ramberg-Osgood material for the field plastic.

Elasto-Plastic Contact Stress Analysis of Hardened Elements under Repeated Contact Loading

An elastic-plastic contact stress analysis is presented to study cyclic plastic deformation of surface hardened rolling elements under repeated contacts. The rolling contact is simulated by a Hertz contact loading moving across an elastic-plastic half-space. An exponential model with hardness varying with depth is employed for the surface hardened components, and the Chaboche nonlinear hardening rule is used to model cyclic plastic behavior of contact elements. Numerical results show that the hardened layer can effectively reduce the plastic deformation near contact surface. The contact elements with sufficient surface hardness may reach elastic shakedown state under repeatedly rolling contact. As the hardened layer reaches a certain depth, e.g. two times of half contact length, however, the effects of case depth on plastic strain and residual stress become negligible after hundred contact cycles.

A unified analytical solution for elastic–plastic stress analysis of a cylindrical cavity in Mohr–Coulomb materials under biaxial in situ stresses

This paper presents a unified analytical solution for elastoplastic stress analysis around a cylindrical cavity under biaxial in situ stresses during both loading and unloading. The two-dimensional solution is obtained by assuming that the connected plastic zone is statically determinate and using the complex variable theory in the elastic analysis. It is shown that the biaxial state of initial stresses applies significant influences on the stress distribution around the inner cavity. Under biaxial far-field stresses, the asymptotic conformal mapping function predicts that the outer boundary of the statically determinate plastic zone is in oval shape in Mohr–Coulomb materials. The major axis of the elastic–plastic interface lies in the direction of the greatest far-field compression pressure during loading, whereas it is along the perpendicular direction during unloading. The loading and unloading solutions are validated by comparing with the results of numerical simulation and other analytical solutions. In the assumed states, the new solution provides an accurate analytical method to capture the biaxial in situ stress effect in the prediction of the plastic failure zone and calculations of the static stress field and the elastic displacement field around a cylindrical cavity within an infinite medium.

Repair of an aluminum plate with an elliptical hole using a composite patch

Abstract In this paper, the stress on axially loaded metal sheets with elliptical holes reinforced by a double-sided composite patch was analysed. The metal sheets with elliptical holes were subjected to axial loading, although no load was applied along the edges of the holes. The central elliptical holes on the metal plates had different diameters. The overlap distance of composite patches, which were adhesively bonded on each side, was of varied lengths. Elasto-plastic stress analyses were examined by means of the finite element method (FEM). The experimental results were compared with numerical results and a convergence rate of 92 % was achieved.

Thermal Analysis on Various Design Concepts of ITER Divertor Langmuir Probes

The thermal performance of the divertor Langmuir probe conceptual design developed for the ITER divertor, which consists of a shielded probe bolted to a copper heat sink, has been predicted by the finite element analysis package ANSYS to have a high risk of damage due to poor heat transfer ability. In order to mitigate this risk, three alternative designs focusing on improving heat conduction have been proposed, and the power-handling abilities, damage risk, and interface challenges of the three designs have been compared. First simulation results indicate that a design involving casting a tungsten probe sensor into a copper heat sink could provide adequate heat-handling capacity. Elasto-plastic stress analysis will be needed to evaluate the thermal stresses at W/Cu interface in our future work. Langmuir probe prototypes will be prepared and high heat flux tests will be performed on electron beam facilities at the Southwestern Institute of Physics to verify the probe functionality once analysis has identified a suitable candidate design.

Influence of strength differential effect on material effort of a turbine guide vane based on thermoelastoplastic analysis

ABSTRACTThe strength differential (SD) effect has been observed in many iron-based metals such as 4310, 4330, maraging steel, and HY80 steels as well as titanium, aluminium 2024-T351, magnesium, and nickel-based super alloys such as aged Inconel 718. Moreover, the SD effect increases with temperature. The Huber–Mises–Hencky (HMH) J2 yield condition is insufficient to simulate the response of metals that exhibit the SD effect. Our work demonstrates the importance of taking into account the SD effect during strength analysis of turbine components. Two yield conditions are considered: the HMH condition and the SD-dependent Burzynski condition. The equivalent stresses produced by these conditions in the elastic state are compared. Plastic zone areas and effective strain values predicted by the two conditions are compared. Our investigation was performed based on thermal-fluid-structure interaction (FSI) analysis of a turbine guide vane made of a nickel-based super alloy that exhibits the SD effect. Conjugate heat transfer analysis was performed, and then elastoplastic stress analysis was performed with boundary conditions obtained from the computational fluid dynamics (CFD) analysis. The paraboloid Burzynski yield condition was implemented in an FE code. Implementation was based on the Euler backward method with consistency tangent moduli evaluated in the explicit form.

Elastoplastic stress analysis of tunnel considering different principal stress directions

Based on the unified strength theory, the elastic-plastic stress analysis is carried out under the premise that the first principal stress in two cases of radial stress and circumferential stress, and the formula of the radius of the surrounding rock and the plastic zone is derived. Tunnel surrounding rock has three states which including the elastic state, the elastoplastic state that the maximum principal stress is the radial stress and the elastoplastic state that the maximum principal stress is the circumferential stress. When the elastic-plastic analysis was carried out on the tunnel, the state of the surrounding rock should be judged and the correct formula is chosen to calculate. Analysis results show that the intermediate principal stress is benefit to the rock to give full play to the strength of the potential, so as to improve the stability of surrounding rock of the tunnel and the smaller intermediate principal stress coefficient, the higher sensitivity of the surrounding rock stability to the intermediate stress. When the inside pressure is less than the second critical stress and increasing the hole pressure is beneficial to improving the stability of surrounding rock, while the hole pressure is greater than the second critical stress, the stability of surrounding rock will reduce with the increase of the hole pressure.

Elasto-Plastic Stress Analysis in Rotating Disks and Pressure Vessels Made of Functionally Graded Materials

A new elastio-plastic stress solution in axisymmetric problems (rotating disk, cylindrical and spherical vessel) is presented. The rotating disk (cylindrical and spherical vessel) was made of a ceramic/metal functionally graded material, i.e. a particle-reinforced composite. It was assumed that the material's plastic deformation follows an isotropic strain-hardening rule based on the von-Mises yield criterion. The mechanical properties of the graded material were modeled by the modified rule of mixtures. By assuming small strains, Hencky's stress-strain relation was used to obtain the governing differential equations for the plastic region. A numerical method for solving those differential equations was then proposed that enabled the prediction of stress state within the structure. Selected finite element results were also presented to establish supporting evidence for the validation of the proposed approach.

Elasto-Plastic Stress Analysis in a Ductile Adhesive & Aluminum Adherends

In this study, an elasto-plastic stress analysis is proposed in an aluminum adherend and a ductile adhesive. Elasto-plastic analysis was carried out for the aluminum adherend and DP460 ductile adhesive in a double-lap joint. The analytical solution was compared with the finite element solution. ANSYS 12 was used in the stress analysis. The analytical solution was performed for the one-dimensional case in the adhesive and the adherends. A FEM solution was given for the two-dimensional case. Similar results were obtained for both. In addition, the solution was carried out for brittle and ductile materials. The mechanical properties of the loctite were nearly the same as the ductile DP460 adhesive. It was observed that the ductile adhesive increased the strength of the structure due to the small shear stresses at the free ends of the adhesive.

Elastoplastic Analysis of Novel Parabola-Arc-Shaped Head for Internal Pressure Vessel

In this paper, the elastoplastic stress analysis of a novel parabola-arc-shaped head subjected to internal pressure has been carried out using finite element method. Limit loads and burst pressures are obtained for various geometric parameters and compared with the conventional torispherical and ellipsoidal heads. For the same middle diameter and thickness, the novel parabola-arc-shaped head shows better mechanical performance than the torispherical head. The burst pressure is mainly determined by the size of cylinder and the burst always occurs in cylinder. The head can improve the burst load when the cylinder is relatively short. The improvement of the novel parabola-arc-shaped head is almost the same as the ellipsoidal head, while the torispherical head is slightly inferior. As the novel parabola-arc-shaped head can be more easily formed with less material consumed compared to the conventional ones, it should thus be applicable in engineering practice.

Elastoplastic Analysis and Optimization Design for the Tube Channel End of Screw Lock Closure Type Heat Exchanger

With the usage of the FEM software ANSYS, an axisymmetric model for the tube channel end of a screw lock closure type heat exchanger was built. The elastic and elastoplastic stress analyses were carried out. The variations of the stress distribution at the root of threads and the contact pressure on threads engaged surfaces were invesgated. Furthemore, an optimization design based on the elastic model for this type heat exchanger was also conducted in order to obtain reasonable structure dimensions and make full use of materials.

Elasto-Plastic Stress Analysis of Thick Cylinders

– Pressure vessels often have a combination of high pressure together with high temperature such as gun barrels and high pressure hydraulic rams. For high pressure application, the cylindrical vessels are made to withstand the working pressure. These types of pressure vessels are made by two techniques, one is shrink-fit cylinders and other one is autofrettage cylinders. Autofrettage technique is used to ensure the pressure vessel highly strengthened due to prestressed effect causing the internal portion of the part to yield and resulting in internal compressive residual stresses. The present work is concerned about the elastoplastic stress analysis of thick cylinders. The numerical analysis is carried out on four different materials which are widely used in pressure vessels by using finite element software ANSYS. The elastic breakdown pressure, overstrain pressure, and bursting pressure of the cylinder are found out and the results are compared with experimental results.

Elasto-Plastic Stress Analysis in Laminated Thermoplastic Composite Plates with an Elliptic Hole

In this paper, elasto-plastic stress analysis in laminated thermoplastic composite plates having an elliptic hole in the middle is examined by using finite element method. Composite plates consist of four orthotropic laminations and bonded symmetrically \([\theta^{0}/-\theta^{0}]\). Uniform loadings in vertical direction are applied to the selected composite plates. The loading and reinforcement angle are gradually increased from the yield point of the plate. The load steps increased as 0.0001 MPa at each iteration. Iteration numbers are chosen 25, 50, 75 and 100. A quarter of the plate is taken into consideration due to symmetry. Elasto-plastic stresses are obtained according to load steps and orientation angles.

Elasto-plastic stress distributions in adhesively bonded double lap joints

Elasto-plastic stress analysis is an important solution for a used ductile adhesive in single or double lap solutions. After loading, the joint strength can be increased by residual stresses. In this study, an elasto-plastic stress analyses of the shear and peel stresses are carried out in a double-lap joint. The adhesive material is chosen as a ductile material which is DP460. Elasto-plastic solution of the shear stress is obtained in a simple and accurate form in one dimensional case. Then, the solution of the peel stress is performed by considering the shear stress in the elasto-plastic form. In this solution, the boundary conditions are satisfied by the Newton–Raphson method. A good agreement is obtained between these analytical and numerical (ANSYS 10) solutions. The values are calculated highest at the ends of the adhesive.

Effect of protrusion at the ends of bondline in single lap joints under tension and bending

In this work, elasto-plastic stress analysis of single lap joints with and without protrusion in adhesive bondline subjected to tension and bending was carried out using 2D non-linear finite element analysis and confirmed experimentally. AA 2024-T3 aluminum adherends were bonded with SBT 9244 film adhesive. The protrusion was obtained by extending the adhesive film by 2 mm from the overlap length at both overlap ends. Three different adherend thicknesses and overlap lengths for each loading and bondline type were used. The joints with and without protrusion, for comparison, were loaded with the same load for each adherend thickness and overlap length. Finally, it was observed that the protrusion reduces the strength in the joint under tension, while the protrusion increases the strength in the joint under bending.

Elasto-plastic Stress Analysis at the Bearing Surfaces in Bolted Joints with Plain Washers under External Tensile Loadings

Elasto-plastic Stress Analysis at the Bearing Surfaces in Bolted Joints with Plain Washers under External Tensile Loadings

OS1403 平座金を用いたボルト締結体座面の弾塑性応力解析と変形について

OS1403 平座金を用いたボルト締結体座面の弾塑性応力解析と変形について

Elasto-plastic stress analysis in an adhesively bonded single-lap joint

In this study, an analytical elasto-plastic stress analysis was proposed to determine the shear stress in a ductile adhesively bonded single-lap joint. DP460 adhesive was employed in the present study. The von-Mises criterion was used for checking the yield condition of the adhesive material. In the solution, the shear stress was assumed to be constant across the thickness of the adhesive. Bending moment was neglected in the solution. Analytical results were checked by using the finite element analysis. ANSYS 10 was employed in the numerical solution. Analytical and numerical solutions are found to be in a good agreement.