Papers by Keyword: Stress Classification Line

Abstract: In the ASME Code Section III ‘design by analysis’ approach, stresses are determined by numerical method and compared with corresponding stress limits. This approach provides several stress criteria for fatigue life assessment and procedures for categorizing the representative stress components. Since the stress criteria were derived from two-dimensional basis, however, it may inappropriate to delineate structural components with complex geometry. In this paper, detailed transient analyses are performed for modular pressurizer with an asymmetric geometry, which includes perforated parts to mount various piping and equipments. Also, the applicability of an effective elastic modulus to consider the perforation and the appropriateness of stress linearization method using stress classification line are assessed. Then, the cumulative usage factor as well as stress intensities at critical locations of the pressurizer are calculated and compared with corresponding allowable design stress limits. The key findings of this work can be used to make regulatory guides for evaluation and confirmation of structural intensity of components with asymmetric perforated parts.

Abstract: In ASME Sec. III ‘design by analysis’ approach, stresses are generally calculated by finite element method and compared to corresponding stress limits after categorizing those components. However, in order to obtain optimum results, time consuming and expensive manipulations are required owing to its mesh size dependency and complicate stress categorization. In this paper, a new approach based on structural stress is proposed to resolve the issues and applied to a heat exchanger motor operated valve. At first, the technical bases and specific features of structural stress approach are briefly discussed. Secondly a series of finite element analyses are carried out to show the limitations of current ASME approaches and to get basic data for the proposed approach. Finally, a structural stress concentration factor of motor operated valve is determined after comparison of local stresses and structural stresses, and utilized for fatigue life evaluation. Since the results show a promising applicability, it seems that the structural stress based approach can be utilized for fatigue life evaluation of components with complex geometries.