TB8钛合金紧固件疲劳断裂分析  

Analysis of Fatigue and Fracture of TB8 Titanium Alloy Fasteners

作　　者：商国强[1] 王新南[1] 费跃[1] 刘洲[1] 米保卫[2] 朱知寿[1] 

机构地区：[1]北京航空材料研究院钛合金研究所,北京100095 [2]中航工业第一飞机设计研究院,陕西西安710089

出　　处：《稀有金属》2016年第7期640-646,共7页Chinese Journal of Rare Metals

基　　金：总装预先研究项目(51312030507)资助

摘　　要：采用外观检查、扫描电镜(SEM)断口观察、金相(OM)检验等方法分析了TB8钛合金紧固件疲劳断裂后的断口形貌和显微组织,并对紧固件头部附近的受力情况进行了有限元模拟分析。研究结果表明,疲劳试验后头部完全断裂的TB8钛合金紧固件均为多源疲劳开裂,同时可见三块疲劳区域,主疲劳区扩展相对较充分,但疲劳裂纹扩展距离均较短。不同疲劳试验结果的TB8钛合金紧固件显微组织均由等轴初生α相和β转变组织组成,再结晶后的β晶粒较小,且没有形成明显的晶界;而通过有限元模拟计算可知,当挤头部圆角半径(R)接近于1.0mm,同时紧固件抛物线流线离倒角较远时,紧固件头部的疲劳性能较好,这与疲劳试验结果相一致。因此,通过减小镦制时丝材端面与模具型面的摩擦力,以控制TB8钛合金紧固件挤头部区域的流线形态,同时在满足技术要求的前提下尽量减小R的尺寸,可以获得较高的疲劳强度。The fracture morphology and microstructure of TB8 titanium alloy fasteners after fatigue testing were analyzed by optical microscope （OM） and scanning electron microscope （SEM） techniques. Besides, the stress and strain response around the fastener head was investigated using the finite element method. The results showed that the fatigue specimens with complete rupture head mainly exhibited multi-source fatigue cracking mode. Three characteristic regions could be seen in the fracture, and the crack in the main fatigue zone was more fully propagated compared to that in the other two regions. However, the propagation distances of the crack in the three regions were all small. The mierostructure of TB8 titanium alloy fasteners mainly consisted of globular α particles and β crystalli- zation grains with small size. The simulation results showed that the fastener had better fatigue property when R was near 1.0 mm and the fastener parabola was far away from the R chamfer. The simulation results were in good agreement with the experimental results. According to the experimental and simulation results, high fatigue strength could be obtained by controlling the streamline state of R re- gion of fastener through reducing the friction between the wire end and mold surface and decreasing the size of R in the allowable range.

关 键 词：TB8钛合金 紧固件 疲劳断裂 显微组织 

分 类 号：TG146.2[一般工业技术—材料科学与工程]