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

研究了热变化条件下螺栓连接的特性。当将螺栓线膨胀系数小于被固件线膨胀系数的螺栓连接置于热变化条件下时，螺栓内产生的螺栓轴向力和被固件之间的压缩力随温度的升高而增大。分析了温度升高时螺栓轴向力和夹紧件间压缩力的变化规律，并给出了计算公式。在实验中，高温应变片粘接在螺栓的钢柄和被夹件的铝外缘上。将螺栓连接放入炉中，在温度升高时测量螺栓和夹紧部件的应变。数值计算结果与实验结果吻合较好。此外，还研究了用螺母和钢螺栓在室温下紧固铝制矩形厚板的螺栓连接在热传导作用下的特性。在实验中，利用热电偶测量了厚板上的温度分布，并利用应变片测量了高温下厚板一侧加热而另一侧冷却时螺栓轴向力的增量和螺栓内由于线膨胀系数的差异而产生的最大应力。采用差值法，分析了热传导作用下板内的温度分布。提出了一种求得锚杆轴向力增量和锚杆产生的最大应力的方法。分析结果与实验结果基本一致。

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.