关键词: 热压缩, Gleeble, 有限元模拟, 温度测量, 误差修正

Abstract: Titanium alloys and Titanium based intermetallic compounds are important materials in aerospace field. High-temperature plastic deformation is one of the main approach for their component fabrication. In order to optimize the forming process, more and more finite element process simulations have been used in recent years to obtain the details of the influence of different factors on the forming process, so as to avoid the occurrence of defects and im-prove product quality, increase the processing efficiency, and reduce the resource and time consumption in the pro-cess of material development and manufacturing. The accurate determination of the mechanical constitutive relation of materials is very important for the design, optimization and even the prediction of the mechanical behavior of mate-rials. Current constitutive relation measurement is usually carried out by Gleeble thermal simulation experiment. The premise of obtaining accurate constitutive relation is to accurately measure the temperature of the material. In this study, finite element simulations were carried out to simulate the Gleeble thermal compression experiment of colum-nar titanium alloy sample, focusing on different thermocouple design parameters, including thermocouple material and thermocouple wire diameter, etc., and in order to obtain their influences on the accuracy of Gleeble sample tempera-ture measurement. The results show that, introduction of thermocouple, due to its heat dissipation, distorts the local temperature field of the contact point between sample and thermocouple, resulting in deviation of the measured tem-perature from the actual sample temperature, and the deviation is large under certain conditions, which will affect sig-nificantly the measurement results for materials with low thermal conductivity, such as titanium alloy. Through FEM simulation and analysis of the changes caused by various factors, and comparison with the metallographic morpholo-gy of titanium alloys samples from relevant heat treatment experiments, it is shown that the material and wire diameter of the thermocouple, the thermal conductivity coefficient of sample and the testing temperature of the sample will all affect the measurement results. The thermal conductivity of sample has the largest influence on the measurement accuracy. Deviations due to these reasons are systematic errors, therefore can be corrected by some means, espe-cially for the materials with low thermal conductivity such as titanium alloy, the temperature measurement error in Gleeble high-temperature test is relatively large, which should be corrected. Based on the finite element simulation and experimental comparison, the corresponding correction method and correction formula are proposed.

Key words: compression, Gleeble, FEM, temperature measurement, error correction