工程塑料应变测试误差的研究

Temperature-Induced Apparent Strain of Engineering Plastics

本文采用了五种不同尺寸的应变片,在不同的测试电压下,利用四分之一桥电路和半桥电路,用system 4000应变仪测定了四种常见的工程塑料的静态表观应变。实验发现,这些工程塑料的表观应变具有明显的滞后特性,测试的表观应变值与测试电压成正比,与应变片的面积成反比。它还直接与测试时间、所测材料的传热能力、弹性模量以及它与应变片栅丝的热膨胀系数差值有较大关系。本文也比较了半桥测试法和四分之一桥测试法的结果,结果表明,四分之一桥测试法的测试误差远大于具有热补偿作用的半桥测试法,然而半桥测试法的热补偿作用仍然未令人满意。本文为此作出了一些解释,并提出了减小和消除测试误差的方法和途径。

The temperature-induced apparent strain of four common engineering plastic materials has been evaluated at three bridge excitation voltages in half and quarter-bridge arrangements with five strain gauge sizes. It is found that the temperature-induced apparent strain is related to the dimensions of the strain gauge,bridge supply voltage,measurement duration,elastic modulus and heat transmission capacity of the tested specimen,and the difference in thermal expansion coefficients between substrate and strain gauge grid. Time lag phenomenon of apparent strain is also observed.The half-bridge arrangement with compensation dummy gauge cannot eliminate the apparent strain completely but is far better than the quarter-bridge arrangement. Methods to reduce and eliminate error due to temperature-induced apparent strain are suggested and discussed.