复合环形气瓶爆裂原因分析

Bursting Analysis of Compound Circular Gas Cylinder

复合环形气瓶爆破压力58 MPa,未满足60 MPa设计指标。气瓶水压爆破试验前依次经强度试验、气密性检查和疲劳试验。气瓶外层缠绕芳纶纤维,内衬为TC4钛合金超塑成形后激光焊接。运用多种分析手段开展内衬裂纹及断口的宏微观形貌分析、特征微区化学成分测定、焊缝金相组织检查。结果发现:在内衬内焊缝收弧焊趾部位存在裂纹源,裂纹源由数个微氧化脆性准解理小平面组成,源区与瞬断过渡区有疲劳条带特征。分析表明,裂纹源形成于焊接过程,在疲劳试验中发生疲劳扩展,而后爆破试验因裂纹前端应力强度因子达到临界值而发生失稳爆裂,裂纹性质为氢脆裂纹,属焊接气体保护不充分引起的环境吸氢。

During water pressure testing,the compound circular gas cylinder burst when the water pressure rose to 58 MPa.The designed pressure is 60MPa.Beforethe water pressure testing,strength testing,air tightness testing and fatigue testinghad beencarried out.The lining of the cylinder is TC4 titanium alloy by superplastic forming and laser welding,and the outer wrapping is aramid fiber.In order to find out the failure cause,macro and micro observation,chemical composition analysis and metallographic structure examination were carried out.The results show that the crack originated from the weld toe of the inside weld of the lining,and there are several small brittle quasi cleavage planes slightly oxidized at the source zone.Fatigue striations can be seen at the transition zone between the source zone and fast fracture zone.The analysis shows that the crack initiated during the welding and propagated during the fatigue testing.Then during water pressure testing,the stress intensity factor reached the critical value,resulting in bursting.The crack is hydrogen embrittlement crack.Environment absorbing hydrogen occurred during welding due to poor gas protection.