基于非傅里叶热传导理论的含裂纹弹带热塑性行为研究

Due to the limitation of the manufacturing technique of rotating band, it is inevitable that a significant crack exits at the joint of the band, which affects the mechanical responses of the band remarkably during the motion of projectile within the barrel. Based on the non-Fourier heat conduction theory, the disturbed temperature field of the cracked bands will be studied in this project. And the thermal concentration at the crack tip will be analyzed by introducing the concept of heat flux intensity factor. Referring to the generalized thermoelasticity theory, the generalized thermoplasticity theory is established by incorporating the non-Fourier heat conduction model and the plastic constitutive model of the band. Accordingly, the effect of crack on the thermal stress fields is studied. In the meanwhile, the stress concentration degree and the strain rate around the crack tip will be calculated. With the help of transient temperature and thermal stress fields, the dynamic recrystallization process of the bands is simulated numerically by developing a graph-based model which could describe the evolution of meso-structure topology. Finally, in order to justify the thermoplasticity and dynamic recrystallization models proposed in this project, the meso-structure change of the band during the inner-bore motion is tested using the metallographic analysis technique and scanning electron microscope. This project has a great influence on the further analysis of material property degradation caused by the crack and investigation of rotating band safety as well as projectile flying stability during the external ballistics period.

由于制造工艺的限制，弹带在其两端接缝处不可避免地含有裂纹，这会对弹带在膛内运动中的力学响应产生很大影响。本项目基于非傅里叶热传导定律研究含裂纹弹带在膛内运动过程中的扰动温度场，通过定义热流密度强度因子，分析裂纹尖端的热量聚集效应。参考广义热弹性理论，在非傅里叶模型和弹带塑性本构关系的基础上，构建广义热塑性理论。基于此理论，研究裂纹对热应力场的影响，计算裂尖应力集中程度和应变率大小。在获得瞬态温度场、应力场的基础上，建立描述细观结构演化的可视化模型，数值模拟弹带材料的动态重结晶过程。最后，通过金相分析仪、扫描电子显微镜等设备观测弹带在膛内运动中的细观结构变化，验证广义热塑性模型和动态重结晶模型的正确性。本项目的研究对于今后分析裂纹造成的弹带材料性能退化和研究外弹道中弹带安全性、弹丸飞行稳定性具有重要意义。

弹带是弹丸的重要部件，在火炮射击过程中，起到密闭弹后燃气和导引弹丸旋转的作用。在内膛这种高温高压瞬态环境下，准确描述弹带材料的瞬态大变形行为、热应力场、裂纹对温度场和应力场的影响、裂纹尖端材料微观变形规律对火炮身管寿命和射击精度的提升都具有重要意义。本项目首先基于非傅里叶热传导定律研究了含裂纹弹带结构的瞬态热应力场，克服了傅里叶热传导定律有限大热波速的缺陷，通过定义热流密度强度因子，定量表达了裂纹尖端热量的聚集程度。通过典型拉压实验系统和新研制的内膛环境下弹带材料力学性能模拟实验系统，测试获得了不同温度范围和应变率下的弹带材料力学特性，拟合了材料的塑性本构关系。基于热力学基本定律和非傅里叶热传导定律，将广义热弹性理论推广到塑性阶段，建立了求解弹带大变形热应力场的广义热塑性理论，并通过对有限元二次开发，计算获得了弹带温度场和应力场，发现弹带表面最高温度可达1200K，应力可达470MPa。为了进一步掌握弹带裂纹尖端的微观变形机制，使用分子动力学方法研究了温度对弹带材料中裂纹扩展机制的影响规律，发现不同温度下裂纹都是通过孪生的方式释放应力，但是，不同温度下孪晶带的方向是不同的，温度越高越容易发生交滑移运动。本项目的研究成果将为火炮身管寿命的研究奠定良好基础。