Experimental measurement of mode-I fracture toughness of dissimilar material joints with thermal residual stresses
Experimental measurement of mode-I fracture toughness of dissimilar material joints with thermal residual stresses
复制标题
具有热残余应力的异种材料接头I型断裂韧性的实验测量
DOI：
10.1016/j.engfracmech.2020.107249
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发表时间：
2020
影响因子：
5.4
通讯作者：
Kawada Hiroyuki
中科院分区：
文献类型：
--
作者：
Jespersen Kristine M.;Ota Hiroki;Harada Kazuki;Hosoi Atsushi;Kawada Hiroyuki
目前的研究提出了一种新的测试方法，以实验抵消不同材料接头的热应力。对于常用的双悬臂梁试验，热应力的存在会在裂纹尖端产生显著的模式混合，即使粘结体的弹性性质相似，这种混合也会随着施加的载荷而变化。由于热膨胀系数的巨大差异，这对粘结在金属上的纤维增强塑料来说是一个特别大的挑战。第二型加载的存在可能会提供比在纯第一型加载下测试更高的断裂能，这在使用标准测试方法时可能导致非保守的结果。为了克服这一挑战，受混合模式弯曲试验的启发，提出了一种新的试验方法。结果表明，在试验过程中施加初始恒定载荷可消除热应力，并可在特定条件下获得纯I型载荷下的断裂韧性。利用粘结区有限元模型进行了虚拟柔度标定实验，验证了测试方法的有效性。由于该试验方法仅依赖于分析计算，并可与标准试验设备一起使用，因此在实践中应用相对简单。
The current study presents a novel test method to experimentally cancel out the thermal stresses in dissimilar material joints. For the commonly used double cantilever beam test the presence of thermal stresses results in a significant mode mixity at the crack tip, which varies with applied load even if the elastic properties of the adherends are similar. This is particularly a challenge for fibre reinforced plastics bonded to metals due to the large difference in thermal expansion coefficients. The presence of mode-II loading is likely to provide a higher fracture energy from experiments than if tested under pure mode-I loading, which can lead to non-conservative results when using standard test methods. To overcome this challenge a novel test method inspired by the mixed mode bending test is developed. It is shown that the thermal stresses can be cancelled by applying initial constant loads during testing, and that the fracture toughness under pure mode-I loading can be obtained under specific conditions. The test method is validated by carrying out virtual compliance calibration experiments using cohesive zone finite element modelling. As the test method relies solely on analytical calculations and can be used with standard test equipment, it is relatively simple to apply in practice.