热电偶焊接对Gleeble温度测量的影响及修正方法

Influence of thermocouple welding on the Gleeble temperature measurement error and a scheme for its correction

采用有限元方法模拟了柱状钛合金样品的Gleeble热压缩实验过程,重点关注不同的热电偶焊接形式和状态对Gleeble样品温度测量准确性的影响规律.研究表明,热电偶的引入使样品的局域温度场发生畸变,导致温度测量误差,且某些条件下误差较大.通过多种因素改变的模拟及详细分析表明,样品的热传导系数、热电偶焊点间距、焊点位置偏离轴向中点、热电偶焊点面积等的变化以及热电偶缠绕都将导致测量偏差,热电偶自身的塞贝克(Seebeck)效应可进一步放大误差.在有限元模拟的基础上提出了相应的修正方法和修正公式.

Finite element analysis was performed to model the process of thermal compression of titanium alloy rods on Gleeble 3800,concentrating on the effect of thermocouple welding on the accuracy of temperature measurement during the Gleeble test. The study shows that the thermocouple application distorts the local temperature distribution around the welding area, and cause errors in temperature measurement. Analysis of the influence of different factors shows that the change in the thermal conductivity of the thermocouple materials, the separation of the thermocouple wires, the change in the contact area of the thermocouple wires with the sample, the deviation of the welding points from the mid-point of the samples, and even the twining of the thermocouple wires will lead to the deviation of the measured temperature, and may cause error or even failure of the Gleeble test. Based on our finite element method simulations, a correction scheme and equation are proposed.