一种改进的纳米压入测试方法

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The accuracy of reduced elastic modulus obtained by Oliver-Pharr method from nanoindentation data was analyzed by dimensional theorem and finite element simulation.The results show that the error depends on the final depth at the maximum depth ratio（hf/hm） and hardening coefficient（n） obviously.The maximum error is near upon 32% at hf/hm0.7 and n=0 because the predicted contact depth is lower than the true contact depth.Thereby,a modified method is brought forward to amend the predicted contact depth.The maximum error of reduced elastic modulus obtained by the modified method can be controlled within ±15%.The results of two indentation tests of aluminum materials agree well with the conclusion.利用过量纲理论和有限元模拟分析了Oliver-Pharr方法识别材料折合弹性模量的精度。结果表明：理论测试误差明显依赖于卸载后的残余深度与最大压入深度的比值（hf/hm）和材料的应变硬化指数n。当hf/hm〉0.7、n=0时,Oliver-Pharr方法计算的折合弹性模量最大测试误差将近32,其原因是由于估算得到的接触深度明显低于真实的接触深度。在此基础上,提出一种改进的计算方法,对接触深度的估算进行修正,应用改进方法确定材料折合弹性模量时,最大误差可控制在±15以内。两种铝合金材料的压入试验也证明了此结论。