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一、前言 60年代以来,由于断裂力学的兴起,使工程构件的设计思想发生了很大变化。从传统的无限寿命设计变为有限安全寿命设计。因而对材料的性能测试提出了新的要求。除提供常规力学性能数据外,还要提供材料的断裂韧性K_(IC)及疲劳裂纹扩展速率da/dN。因此如何可靠地测出材料的da/dN数据,已成为材料试验中的一个重要问题。测试da/dN的关键在于如何方便、迅速、准确地测出试样的裂纹长度。在室温空气中,通常采用20～30倍的读数显微镜直接测量试样的表面裂纹长度。然而在高温下,很
I. Introduction Since the 1960s, due to the rise of fracture mechanics, great changes have taken place in the design thinking of engineering components. From the traditional infinite life design into a limited safety life design. Therefore, the performance of the material testing put forward new requirements. In addition to providing general mechanical properties data, but also to provide the material fracture toughness K_ (IC) and fatigue crack growth rate da / dN. Therefore, how to reliably measure the da / dN data of a material has become an important issue in material testing. The key to da / dN testing is how to measure the crack length of the sample conveniently, quickly and accurately. In the air at room temperature, usually 20 to 30 times the reading microscope directly measure the surface crack length of the sample. However, at high temperatures, very