| Abstract: | The sensitivity of the unified constitutive theories, proposed by Bodner, Walker, Krieg, and Miller, to numerical integration techniques and slight changes in material parameters was investigated. Evaluations were based upon numerical simulations of Hastelloy-X at 1800° F in uniaxial form by specifying input strain histories and comparing output stress histories. The integration sensitivity study involved the use of both single and multi-step integration schemes. The various algorithms were compared with regard to accuracy, stability, and computational economy. The material parameter sensitivity was studied by varying the material constants by a specified amount and comparing predicted responses. Numerical comparisons show that, of the numerical integration methods studied, Euler's method is the most accurate, stable, and efficient procedure. The input sensitivity studies indicated that some constitutive models are more sensitive to experimental errors than others and that a 5% error in certain material constraints may lead to 15-30% changes in predicted response. |
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