超高强度螺栓材料高温力学性能实验设计

Experimental Design of High Temperature Mechanical Behavior of the Super High-tension Bolt Material

为研究高温环境中高强螺栓的变形与断裂过程及力学性能的变化规律,在20~750℃(间隔50或者100℃)环境下对10.9级高强度螺栓(HB)和14.9级超高强度螺栓(SHTB)的力学性能进行了测试:利用振动法测试了2种螺栓的高温弹性模量;用高温拉伸试验机测试了2种螺栓在不同温度下的屈服强度、抗拉强度、峰值应变、断后伸长率、断面收缩率以及断裂应变,并建立了2种螺栓7个高温力学性能的数学模型。结果表明:在相同温度(20≤T≤750℃)下,2种螺栓的破坏形态基本相同,但14.9级SHTB的屈服强度和抗拉强度及相应的折减系数均高于10.9级HB;T>400℃时,二者峰值应变显著减小;T=750℃时,二者的抗拉强度值均不足常温时的10%;T≤600℃时,14.9级SHTB断后伸长率、断面收缩率均低于10.9级HB,但其折减系数相当甚至更高。

To investigate the mechanical properties and failure behavior of grade 10.9 high-strength bolt(HB)and grade 14.9 super high-tension bolt(SHTB)under elevated temperature,the authors conduct the tensile tests and vibration tests at a temperature ranges from 20 to 750,where the vibration test is used to measure the elastic modulus of steel under high temperature.Based on these tests,the yield strength,ultimate tensile strength and corresponding strain,elongation,percentage reduction of area and fracture strain are obtained.Then,the authors proposed numerical model through analysis and fitting of the experimental data.Results indicate that both grade 10.9 HB and grade 14.9 SHTB exhibit significantly necking when failure.Furthermore,when the test temperature lower than 400,the strain corresponding to ultimate strength shows an obvious decreasing trend;and when temperature reaches 750,the value decreases to less than 10%of the value at room temperature.In addition,when temperature is less than 600,grade 14.9 SHTB shows a smaller elongation and percentage reduction of area of grade than 10.9 HB,but the grade 14.9 SHTB has a higher reduction factor.