激光冲击航空发动机钛合金薄壁焊缝抗振动疲劳断裂理论基础研究

Vibration fatigue fracture of titanium alloy thin-walled weld joint components is a serious and difficult problem in “the cartilage disease” of advanced aero-engine in our country. Due to the thermal effect in welding process, the mismatch of residual stress and micro-structure between weld zone and heat-affected zone is the main cause of vibration fatigue failure. Therefore, the project is designed to achieve the coupling of three effects of residual stress optimization design, gradient structure toughening design and vibration reduction design by impacting titanium alloy welded thin-walled parts through LSP (laser shock peening) so as to improve vibration fatigue performance. The key scientific issues of the research is“the propagation law of laser shock wave in titanium alloy thin-walled weld joint and the trans-scale mechanical behavior of gradient micro-structure induced-by LSP”. Ultrahigh strain-rate constitutive model and model parameters identification of laser impact were established in thin-walled weld joints, so dynamic numerical simulation of LSP in titanium alloy thin-blade was conducted, and the influencing mechanism of stress-wave reflection on residual stress distribution was indicated. The stress-wave propagation law with a stress-wave transmission layer was studied. It could optimize residual stress field and control deformation. Furthermore, a mechanical constitutive model based on strain gradient nonlocal elastic theory was constructed to study the trans-scale mechanical behavior and vibration response gradient micro-structure induced-by laser impact of thin-walled weld joint. Advanced micro-mechanical test and higher-order vibration characteristic simulated specimens were used to carry out experimental verification and reveal the strengthening and toughening mechanism of the gradient micro-structures. Finally, it is expected that the vibration fatigue performance of titanium alloy thin-walled weld joint after LSP is improved by 10% technical index. By exploring the establishment of independent and innovative thin-wall weld laser impact enhancement technology theory and method, the project provides a theoretical basis and a large amount of experimental data for the engineering application and design of LSP for titanium alloy thin-walled weld components of advanced aero-engine.

钛合金薄壁焊缝结构振动疲劳断裂是我国先进航空发动机“软骨病”的重难点问题，由于焊接过程存在热影响，焊缝区和热影响区应力和组织不匹配是振动疲劳失效主要诱因。为此，项目拟通过激光冲击钛合金焊缝薄壁件实现应力场优化、梯度结构强韧化设计和减振三种效果耦合，提高振动疲劳性能，其核心科学问题是“焊缝材料激光冲击波传播特性与梯度结构跨尺度力学行为”。主要内容为建立薄壁焊缝超高应率激光冲击本构模型和参数识别，探究非均质材料激光冲击波传播特性规律，优化残余应力场和控制变形；构建基于应变梯度的激光冲击梯度结构力学模型，研究焊缝梯度结构跨尺度力学行为和振动响应规律，并采用先进力学测试和设计高阶振动模拟件进行试验验证，揭示梯度结构强韧化机制与减振机理，最终期望实现钛合金薄壁焊缝振动疲劳强度提高10%技术指标。项目成果将为先进航空发动机钛合金薄壁焊缝结构激光冲击强化技术工程应用和设计提供理论基础和大量试验数据。

面向先进航空发动机机匣钛合金薄壁焊缝振动疲劳裂纹重大需求，本项目创新研究激光冲击在焊缝表面制备梯度结构和优化设计应力场提高其振动疲劳强度，通过建立 TC4 钛合金薄壁焊缝超高应率激光冲击本构模型和参数识别，探究非均质薄壁材料激光冲击波传播特性规律，优化残余应力场和变形控制；在此基础上，构建基于应变梯度的激光冲击梯度结构力学本构模型，研究焊缝梯度结构跨尺度力学行为和振动响应规律，并开展试验验证研究，最终实现钛合金薄壁焊缝振动疲劳强度提高10%的技术指标。为现役、在研和下一代军用航空发动机钛合金薄壁焊接件激光冲击强化技术工程应用和设计提供理论基础和技术支持。研究成果对风扇机匣模拟焊缝件处理，室温强化拉拉疲劳强度提升19.8%，进而对WS-XX发动机风扇/进口机匣焊缝处理，通过600h装机考核验证，已在外场批次装机23台，解决空军“拉条挂账”技术难题。项目形成的机理、工艺成果已在606所、中国人民解放军5718厂、中国人民解放军5719厂、中国人民解放军5720厂、中国人民解放军5721厂的WS-XX、D- XX、WS- X、AL- XX、弹用发动机裂纹修复件及歼XX、歼XX、歼轰X飞机导管部件应用。2019年，空军工管局为进一步推广研究成果，组织召开激光冲击强化技术空军修理应用研讨会，12个修理厂全部参加，在全空军范围推广。负责人在项目支持和培养下，入选国家万人计划青年拔尖人才、陕西省杰出青年基金、陕西省青年拔尖人才计划等。项目共发表SCI论文18篇，授权发明专利4项、获得2021年陕西省创新创业大赛二等奖、2022年教育部科学技术二等奖、2021年国防科技进步一等奖等奖励。