行波管阴极组件激光焊接残余应力及其对结构强度的影响分析

Influence of Residual Stress on Structural Strength of Laser Welded Cathode Assembly in Traveling Wave Tube:A Simulation and Experimental Study

对行波管阴极钼筒和钽支撑筒的焊接材料及焊接工艺进行了研究,并用数值模拟方法对焊接结构的残余应力进行了分析,获得焊接残余应力值及其分布,并与试验值进行了比对,仿真结果与试验结果一致。同时将残余应力结果作为预应力加载到行波管阴极组件上,分析了其对结构强度的影响。结果表明:焊接残余应力使阴极组件结构在实际工作中的应力值增大且应力分布发生了变化,在残余应力的影响下,钽支撑筒在高温工作时的应力由332变化为412 MPa,增幅达24%,而且最大应力的位置也由钽爪内表面转移到钽爪拐角处。而六个钽支撑爪子的外表面(焊接处)由于残余应力最大,该处应力值也由101增加到250 MPa,增幅高达150%。因此阴极组件中钽支撑筒与阴极钼筒的焊接处很容易因应力值过大而失效,需要对焊接处残余应力进行消除和控制并对结构进行加固设计。

The residual stress distribution of the laser-welded Mo-tube and Ta-support with a ring and 6-claws,of the traveling wave tube（ TWT） cathode assembly,was mathematically modeled,numerically simulated in finite element method and experimentally evaluated with X-ray diffraction. The influence of the residual stress on the structural strength of the TWT cathode assembly in operation was investigated. The simulated results show that the residual stress strongly affects the thermal stress profile of the Ta-supportat high working temperatures. For example,ata highest Mo-Ta contact temperature（ ~ 844℃）,the residual stress increases the thermal stress from 332 to 412 MPa,a 24% increment; the strongest stress moves from the inner to the outer surfaces at the claws＇ elbow-knuckle,accompanied by a change from 101 to 250 MPa,nearly 150% increase,indicating a high risk stress-induced fracture there. The simulated and measured results were in good agreement.