Nondestructive testing method of residual stresses in metallic materials based on Knoop indentation technique

ABSTRACT

In the process of manufacturing and shaping critical mechanical structures, the inevitable result is the creation of non-uniform residual stresses (RS). These residual stresses significantly affect the mechanical properties, fatigue strength, and resistance to stress corrosion cracking in the structures, ultimately posing risks to their safety and operational lifespan. Furthermore, obtaining residual stress for equipment in service continues to be a challenging endeavour. Hence, the development of an in-situ testing method for measuring residual stresses is crucial to ensure the safe operation and extended lifespan of structures. In this study, we used finite element analysis to thoroughly examine the connection between residual stresses, indentation loading curves, and material mechanical properties. We then developed a biaxial residual stress testing method suitable applicable to part of mechanical properties, utilising the Knoop indentation technique. The reliability of method is experimentally validated using nuclear pipe material 316 L and 304 stainless steels. The results indicate that this method enables the transformation of biaxial residual stresses into two orthogonal uniaxial residual stresses. By conducting a pair of orthogonal indentation tests, biaxial residual stresses can be accurately determined, with errors mostly within a 16% margin. This method fulfils the criteria for non-destructive testing in engineering, providing ease of use and in-situ applicability.

KEYWORDS:

• Instrumented indentation technique
• Knoop indenter
• residual stress
• biaxial stress
• finite element method

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions statement

Yubiao Zhang: Conception, Design, Validation, Data analysis and interpretation, Drafting of the paper, Revising of the paper. He Xue: Conception, Final approval, Funding acquisition, Project administration. Yongjie Yang: Design, Validation, Revising of the paper. Shuai Wang: Drafting of the paper, Revising of the paper. Zheng Wang: Data analysis and interpretation, Validation. Jun Wu: Software, Validation, Data curation. Chao Yang: Conception, Investigation, Data analysis and interpretation.

Additional information

Funding

This work was supported by the International Exchanges Programme Scheme project by the Royal Society and National Natural Science Foundation of China [5211101978]; the National Natural Science Foundation of China [52075434]; the Natural Science Basic Research Plan in Shaanxi Province, China [2023-JC-QN-0474]; and the Postdoctoral Research Project in Shaanxi Province, China [2023BSHEDZZ311].