Finite element analysis allowable stress

When a fatigue evaluation is required, it is necessary to determine the peak stresses around the openings. The current methods are the stress index method, experimental tests and measurements, or a theoretical analysis procedure such as a finite element analysis. The stress index method is the easiest method and is allowed by the ASME Code, III-l and VIII-2. The stress index method was developed from reviewing a large amount of experimental and analytical data determined in a program conducted by the Pressure Vessel Research Committee. 

It is known that for a materials with two or more phases the stress field is the superposition of stresses at two levels Macroscopic stresses which exist between the different layers and result from the internal force balance through the whole material. Microscopic stresses which appear between grains or phases in the material. Thus, the micro residual stresses stemming from the two-phase system have to be added to the results from finite element analysis (where only macro residual stresses are determined) allowing direct comparison with the total stresses experimentally measured. Figure 9 shows the macro residual surface stresses from the numerical analysis for the two and three layer specimens. One can see that the results from X-ray measurements agree fairly well with the predicted values. 

Residual stresses are often impossible to avoid as a result of manufacturing operations. The graded concept shows, however, that a desired stress state can be designed allowing the dispersion or even optimization of these stresses. Furthermore, the finite element analysis turns... 

Optimisation of weight reduction in CLS has been carried out(Senthilkumar Vijayarangan,2007). The finite element analysis of composite multi leaf spring with 7 leaves shows that maximum deflection of the leaf spring and the bending stress induced are well within the allowable limit (factor of safety 2.8). So, it is decided to optimize the number of leaves with minimum of 2 leaves and maximum of 7 leaves using ANSYS 7.1 itself, for the... 

Finite element analysis was then performed on the bolted connection, using a calculated preload of 9,740 N. The analysis showed that the highest principal compressive stress under the washer is 269 MPa (39 kpsi). According to the creep curves for Minion, in order for the cover not to creep and allow a loss of preload, the stress level would have to be less than 13.8 MPa (2,(XX) psi) during operation at peak temperatures. The FEA curves show the principal stress distribution in cross-sections for the bolted connection. 

Finite element analysis (FEA) or finite element modelling (FEM) decomposes a solid into a mesh made of discrete elements. For each element, the relevant parameters are supposed to be known (physical, chemical, mechanical properties) or locally determined (stress, temperature). Then after each increment of time the overall behaviour of the object can be determined. A step-by-step procedure is used to determine the behaviour of a glass object with time. Notably, when the shape varies the mesh has to be redefined continuously. This technique has become widely used since it allows complex loading and geometries to be considered that make it very attractive for industry and R D. 

The S -shaped flexible elements were required to keep the stiffness and stresses low, due to the relatively heavy rotor weight as evident by the finite element stress analysis shown in Figure 6-30. The wire EDM teehnology allows the produetion of sueh a damper deviee, whieh ean be easily designed with an offset to eompensate for the defleetion due to rotor weight. 

Some advanced general purpose finite-element codes, well adapted for stress analysis in particular, e.g. ABAQUS or MSC.MARC, have certain capabilities to simulate the stress-assisted diffusion, too. Unfortunately, they still are limited in some rather important aspects. As regards ABAQUS, this allows to perform simulations of the stress-assisted diffusion governed by equation (5) "over" the data of an accomplished solution of a geometrically and physically nonlinear stress-strain analysis, i.e., for the stationary stress field at the end of some preliminary loading trajectory, but not for the case of simultaneous transient loading and hydrogenation. 

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