On the Strength Characteristics of Bolted Joint with Gasket under Thermal Change

本文研究了螺栓连接在热变化条件下的特性。当螺栓的线膨胀系数小于被夹件的线膨胀系数的螺栓连接处于热变化时，螺栓中产生的螺栓轴向力和被夹件之间的压缩随温度的升高而增大。分析了螺栓轴向力和被夹持件之间的压缩量随温度升高的变化规律，提出了计算这些变化量的公式。在实验中，高温应变片被粘到由钢制成的螺栓的柄部和由铝制成的被夹持部分的外圆周上。当螺栓连接被放入炉中时，在温度升高的过程中测量螺栓和被夹持部件的应变。数值计算结果与实验结果吻合较好。此外，还研究了在室温下用螺母和钢螺栓紧固铝合金矩形厚板的螺栓连接接头在热传导作用下的特性。实验中，用热电偶测量了厚板上的温度分布，用应变片测量了厚板一侧锤击、另一侧冷却时，由于线膨胀系数的不同而产生的螺栓轴向力增量和螺栓中的最大应力。利用差分法分析了热传导作用下平板内的温度分布。提出了一种求解螺栓轴力增量和螺栓最大应力的方法。分析结果与实验结果相当一致。

This research deals with the characteristics of bolted Joints under thermal changes. When a bolted joint in which the coefficient of linear expansion of bolts is less than that of clamped parts is put under thermal changes, the bolt axial force produced in the bolt and the compression between the clamped parts are increased with an increase of temperature. The variations of the bolt axial force and the compression between the clamped parts are analyzed during an increase of temperature, and a formula to obtain these variations is proposed. In the experiments strain gauges for high temperature are glued to the shank of the bolt made of steel and the outer circumference of the clamped parts made of aluminum. When a bolted joint is put in a furnace, the strains of the bolt and the clamped parts are measured during an increase of temperature. The numerical results are in fairly good agreement with the experimental results.In addition, the characteristics of a bolted joint, in which a rectangular thick plate made of aluminum was fastened at room temperature by a nut and a bolt made of steel, were examined when the joint was subjected to heat conduction. In the experiments, temperature distributions on the plate were measured with thermocouples, and an increment of bolt axial force and the maximum stress produced in the bolt due to the difference of the coefficients of linear expansion were measured by strain gauges for high temperature when one side of the thick plate was beaten and the opposite side was cooled. Using the difference method, the temperature distributions in the plate subjected to the heat conduction were analyzed. A method to obtain an increment of bolt axial force and the maximum stress produced in the bolt was proposed. The analytical results were fairly consistent with the experimental ones.