ISO20332 guidance

[__G__]

I'm seeking guidance on ISO20332, Specifically, parts relating to fatigue assessment. The parameter 'm' is related to the relationship between stress and load cycles. Clause 6.2.3 permits using m=3 for a simplified assessment, however, most of the example cases in Table D.1 are for m=5. It seems that m=5 is the more conservative approach, but it's too conservative in my case. What is the intended workflow for selecting and applying the value of 'm'?

EDIT: Furthermore, the formula: Δσ[sub]Rd[/sub] = Δσ[sub]c[/sub]/ (γ[sub]mf[/sub] x (s[sub]m[/sub])^(1/m)) (eq 39) yields a value HIGHER than the material yield stress for many (most?) value combinations (e.g. Δσ[sub]c[/sub]=160, γ[sub]mf[/sub] = 1.25, m=3 or 5, s[sub]m[/sub]=0.032. Which doesn't makes sense in the case of non-reversing loads.

 

[SWComposites]

What is the application?
What is the material?
What are the regulatory requirements?

 

[__G__]

I'm not quite sure how to answer that one. ISO20332 is fairly specific, so it's somewhat self-explanatory. In any case, the application is a crane application (in my case, a static winch), the material is mild carbon steel, and the regulatory requirement is to comply with ISO20332.

I hope that helps clarify my enquiry.

 

[SWComposites]

Ok, thanks. I’m not familiar with that ISO and am not going to purchase it.

Seems like selection of m would depend on the criticality / redundancy of the part and consequences of failure. Also would depend on whether there are other conservatisms in the fatigue loads calculation.

 

[__G__]

Hi, thanks for taking the time to respond, but without a knowledge of the specific standard, any answer is a guess and isn't helpful.