基于实测剪切应力及局部应变的Ti-6Al-4V绝热剪切带的峰值温度估算

An Assessment of the Peak Temperature in the Adiabatic Shear Band of Ti-6Al-4V Based on the Measured Shear Stress and Local Strain

摘要:

认为试样表面的变形场出现不连续性不是绝热剪切带出现的标志，而是形变绝热剪切带进一步发展的结果；在计算绝热剪切带内部的峰值温度时应从局部剪切应变中扣除弹性应变，因为弹性应变不会对塑性功有所贡献。以动态扭转的Ti-6Al-4V试样（TA-50）为例，计算了绝热剪切带内部的峰值温度，其被划分为3部分：环境温度、均匀和非均匀变形引起的温度。在两种条件下（从局部剪切应变中扣除弹性应变与否），计算出的峰值温度分别为669和665 ℃，其在热回复和再结晶的温度范围之内，未达到相变的温度，比Liao及Duffy的理论计算值（630 ℃）要高。如果剪切应力-局部塑性剪切应变的关系不能完全确定，适当的近似是必要的。

Abstract:

The appearance of the discontinuous strain in the outer surface of a specimen does not indicate the just formation of the adiabatic shear band. The phenomenon is believed to be a result of the further development of the deformed adiabatic shear band. For calculating the peak temperature in the adiabatic shear band, the elastic shear strain should be extracted from the local shear strain because the elastic part does not contribute to the plastic work. The peak temperature in the adiabatic shear band in a Ti-6Al-4V specimen (TA-50) in dynamic torsion is calculated. It is divided into 3 parts: ambient temperature and temperatures caused by homogenous and inhomogenous shear strains, respectively. In two cases (the elastic shear strain is extracted from the local shear strain or not), the calculated temperature values are 669 °C and 665 °C, which are in the range of the thermal recovery/recrystallization temperature and do not exceed the phases transformation temperature. The calculated results in the paper are higher than the calculated result of 630 °C by Liao and Duffy (1998). If the relation between the shear stress and the local plastic shear strain is not completely clear, an appropriate approximation is necessary.