送交者: boxer 于 2005-5-04, 17:07:58:
回答: 得，看来你同意R变化一样大，只是对俺的模型有意见？还是你认为俺说delta R一样错了？ 由 Smashedmouth 于 2005-5-04, 14:58:36:
Thin object and thick object is totally different.
I hope Berkley wolf could be here. From my knowledge of mechanics, which is not a lot, the inner part and the near surface part of the materials have different strain and stress level, as a result of the constraint of the surface. For an extremely large object, it could be idealized to so called "平面应变状态". For relatively thin object, it is called "平面应力状态". The solution is totally different.
The physics you talked about is based on the strain free model, which is not true for most engineering situation.
微观模型 for this kind of issue is more complex. The strength of idealized crytals is at least one scale larger than polycrstallines.