What type of stress is the stress obtained through finite element analysis per JB4732-2005?
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What should the stress obtained through finite element analysis for modeling be called? JB4732-2005. It is divided into 5 values: 5.3.1–5.3.5: primary overall membrane stress, primary local membrane stress, primary membrane plus bending stress, primary and secondary stresses, peak stress. The problem is that the allowable limits for these five stress intensities are different. Therefore, I’m confused: should the stress values obtained from finite element analysis be less than those limits in order to be considered safe? I hope someone knowledgeable can help me out. Thank you!
According to the current JB4732, the stresses obtained from finite element analysis must be linearized, and categories such as SI, SII, SIII, SIV, and Q are identified; structural safety is determined through progressive evaluation.
This post was last edited by wanlirn on 2021-7-19 at 15:19. You still don’t understand what finite element analysis is; the various forces you mentioned are not the forces that are used for evaluation. You should look for books on finite element analysis specifically for pressure vessels and study them. As mentioned by the person on the second floor, linearization processing, along with many other treatments, requires experience and is quite complicated – this isn’t something to take lightly； If you want to learn finite element analysis, it’s best to have a teacher guide you in the beginning
Thanks, it seems really complicated indeed
Thank you, it sounds really complicated just by hearing about it.
According to the first strength theory in GB150, for the cylinder and head analyzed using finite element analysis, it is sufficient that the maximum principal stress is less than the allowable stress. However, relying solely on the maximum principal stress isn’t sufficient to handle issues related to openings, flanges, etc； Our 4732 applies the third strength theory, namely the stress intensity. However, current finite element analysis software cannot provide this value directly; manual processing is required. One must select points and perform linearization. This post-processing step requires experience; consequently, the conclusions drawn by different people can vary significantly. . The fourth strength theory, namely von Mises, is currently the default theory used in finite element software; however, it is not applicable to pressure vessels.
In my understanding, finite element analysis yields the total stress, and those who work in solid mechanics break this total stress down into various types of stress, such as primary stress, secondary stress, peak stress, etc. The risk levels associated with different stresses vary, and corresponding safety factors are specified; various combinations are required to meet the respective requirements. All of these conditions must be met.
Thank you, I’ve learned something. Stress analysis is generally not required for cylinder heads; conventional methods are sufficient. The values for openings, flanges, etc. aren’t the actual values given, which makes it quite difficult to understand. Thank you for the advice!