Discussion Overview
The discussion revolves around the acceptance criteria for Hertzian static contact stress, particularly in the context of using Grade 5 Structural Steel. Participants explore the validity of using a multiple of the yield strength as a pass criterion and seek references to support their claims.
Discussion Character
- Technical explanation
- Debate/contested
Main Points Raised
- One participant calculated a static contact stress of 670 N/mm2 and noted the absence of acceptance criteria, questioning the validity of using 2.5 times the yield strength as a reference.
- Another participant provided a reference from "Mechanics of Materials" indicating that uncontained plastic flow begins at a contact stress of approximately 2.8 times the yield strength.
- A third participant affirmed that Grade 5 structural steel is sufficiently ductile for the proposed approach, while cautioning that more brittle materials require careful consideration due to service factors.
- Further elaboration was provided regarding the evaluation of Hertz contact stresses based on shear stress below the surface and the implications of surface roughness on stress values.
- A participant offered a freeware program for calculating Hertzian stresses, suggesting it as a resource for further exploration.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the acceptance criteria for Hertzian static contact stress, with multiple competing views and references presented regarding the appropriate multiples of yield strength.
Contextual Notes
Limitations include the dependence on specific material properties and service conditions, as well as the lack of universally accepted criteria in the literature for the proposed multiples of yield strength.