자동차용 강판, 구조용 강재 및 비철금속 동적인장물성의 측정불확도평가

Abstract

Lightweight vehicle design is a recent mega-trend in the auto industries for improvement of fuel efficiency to meet consolidated emission-gas regulation. Lightweight design, however, must be accompanied by crashworthiness of auto-body for passenger safety. One of the solutions for the two contradicted problems is to replace conventional steels with lighter and stronger materials such as aluminum alloys in order to achieve both enhanced crashworthiness and lightweight design of auto-body. The auto-body design is usually performed to achieve lightweight design with enhanced crashworthiness by numerical analyses which require reliable material data. In order to evaluate the crashworthiness of auto-body structure, finite element methods has been conducted for crash analysis. Generally, strain rates distribution of auto-body structure in the car crash ranging from 0.001/s to 500/s. Since the material properties of aluminum alloys depend on the strain rates, the dynamic behavior must be examined and applied to the finite element model appropriately. This paper is concerned with the evaluation of measurement uncertainty of modified measurement of dynamic tensile properties of aluminum alloy for hood. Obtaining procedure of the true stress–true strain data at intermediate strain rates is properly designed for the experiment and data acquisition compared with previous procedure. Standard uncertainty of the true stress is evaluated considering sources of uncertainties of input quantities and their associated sensitivity coefficients. A combined standard uncertainty is evaluated from not only the uncertainties of the input quantities but also the influence factor for the true stress. The results show that the standard uncertainty evaluation procedure has been successfully applied to high speed tensile properties