Numerical analysis of residual stress relaxation in unsintered pressed specimensстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 4 сентября 2018 г.
Аннотация:The phenomenon of residual stress relaxation (redistribution with the passage of time) in powders pressed in rigid dies has been known for a long time. In [I] this process is 9 linked with changes in volume and shape of compacts, and in [2, 3] it is regarded as being 9 responsible for various pressing defects. Unfortunately, reliable information on the magni- " rude, distribution, and changes with time of residual stresses in pressed parts is virtually nonexistent, which may be attributed to difficulties experienced in their experimental inves- tigation [4]. These difficulties are further, aggravated when the stressed state of a com- pact is very nonuniform along both its radius and height [3]. It may be added that assess- ment of the stressed state of a powder compact becomes even more complicated when the rheo, nomic properties of the powder are taken into account. For all these reasons, study of re- sidual stress relaxation processes by analytical methods is a matter of considerable diffi- culty.
A possibility of "inspecting" the inside of a compact is provided by numerical methods. Of these, the finite elements method (FEM) has been found very successful in solving tech- nological problems, in particular those of densification [5, 6].
In this article an algorithm based on the FEM is proposed for investigating residual stresses in parts produced from powders by cold pressing in rigid cylindrical dies. Use of the FEM has made it possible to allow for initial stresses in a compact and for the charac- ter of boundary conditions and to analyze the process of residual stress relaxation.