Experimental assessment of unvalidated assumptions in classical plasticity theory.

Brannon, Rebecca Moss (University of Utah, Salt Lake City, UT) ; Burghardt, Jeffrey A. (University of Utah, Salt Lake City, UT) ; Bauer, Stephen J. ; Bronowski, David R.

关键词: APPROXIMATIONS;    CERAMICS;    DATA ANALYSIS;    INSTABILITY;    PLASTICITY;    STRAINS;    TESTING;    METALS;    ROCKS;    RESPONSE FUNCTIONS Plasticity-Mathematical models.;    Thermal loading-Mathematical models.;   

DOI  :  10.2172/948711
RP-ID  :  SAND2009-0351
PID  :  OSTI ID: 948711
Others  :  TRN: US200908%%10

学科分类：材料科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

This report investigates the validity of several key assumptions in classical plasticity theory regarding material response to changes in the loading direction. Three metals, two rock types, and one ceramic were subjected to non-standard loading directions, and the resulting strain response increments were displayed in Gudehus diagrams to illustrate the approximation error of classical plasticity theories. A rigorous mathematical framework for fitting classical theories to the data, thus quantifying the error, is provided. Further data analysis techniques are presented that allow testing for the effect of changes in loading direction without having to use a new sample and for inferring the yield normal and flow directions without having to measure the yield surface. Though the data are inconclusive, there is indication that classical, incrementally linear, plasticity theory may be inadequate over a certain range of loading directions. This range of loading directions also coincides with loading directions that are known to produce a physically inadmissible instability for any nonassociative plasticity model.