Abstract
This paper presents a simple method of determining stresses and strains and a severity of loading history under non-proportional loadings with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. Based on the method, non-proportional stress and strain ranges are derived and applicability of the range to the life evaluation for low carbon steel under non-proportional random strain paths are discussed. The strain range taking account of intensity of loading path reducing life can be suitable parameter for multiaxial fatigue life evaluation under multiaxial non-proportional loading. This paper also shows a method of visually presenting the principal stress and strain that assists designers to understand the loading mode whether proportional or non-proportional under 3 dimensional (6 stress/strain components) multiaxial loading.
Highlights
Most design codes use equivalent values to express the intensity of multiaxial stress or strain, like von Mises or Tresca equivalent stress and strain, and fatigue lives are usually estimated using equivalent values under multiaxial stress and strain states
This paper presents a simple method of determining stresses and strains and a severity of loading history under non-proportional loadings with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space
This paper proposed a simple method of determining the principal stress and strain ranges together with the mean stress and strain under proportional and non-proportional loading in 3D stress and strain space
Summary
Most design codes use equivalent values to express the intensity of multiaxial stress or strain, like von Mises or Tresca equivalent stress and strain, and fatigue lives are usually estimated using equivalent values under multiaxial stress and strain states. FNP evaluates comprehensively the severity of non-proportional cyclic loading based on the amplitude of strain and the direction change of principal strain. Integrating the product of amplitude and principal direction change of stress and strain by path length in Eq (15) is more suitable for evaluation of fatigue damage rather than the integration by time. Employed was determined from the degree of additional hardening This result suggests that a suitable strain parameter for multiaxial LCF life evaluation must take account of intensity of non-proportionality of loading and additional hardening due to non-proportional loading. The former is the nonproportional factor, fNP or f NP, and the latter is the material constant, , in NP. S-N curve base data and the IS-method are employed with the rain-flow cycle counting method and cumulative damage rule
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
