爆炸焊接非平衡过程熵能分析与工艺调控

Explosive welding technologies(explosive welding and laser impact welding) have been widely used to prepare structure materials in industry. But academic researches mainly focused on welding achievement. Quantitative analysis and manipulating theory for energy effect and corresponding response of welding interface have not been established till now. Therefore researches for these problems are great significance both theoretical and practical. In this project, welding interface forming and developing will be studied from energy and entropy perspectives. Basic and flyer plates will be regarded as an open system which can exchange energy with environment, and the welding process is nonequilibrium and irreversible which entropy increases because of dissipation energy, and bring out wavy welding interface. Thereby, according to the idea of Carnot cycle in thermodynamic, the welding process will be devided into four stages, then energy and entropy will be analyzed by the thermodynamic characters of stages. Secondly, based on the idea that the fracture toughness of welding interface is equivalent to its interfacial bonding energy, then the energy and entropy of welding interface can be obtained by fracture experimental test. Lastly, we will try to establish the physical relationship of the energy and entropy between the welding process and the welding interface, and to understand the important factors which resolve the effects of energy and entropy, then to draw the manipulation theory for the welding design. Besides, numerical model will be established by Autodyn and Abaqus to testify and improve the manipulation theory.

爆炸焊接技术已在工业上得到广泛应用，但大量的研究所形成的结论主要侧重于复合实现，暂未能对焊接过程中能量作用效果及对应的焊接界面响应形成定量分析并建立调控理论，对该问题的研究具有重要科学意义和工程应用价值。本课题从熵、能角度看待焊接界面形成与发展，将爆炸焊接基、复板系统视为与环境有能量交换的开放系统，认为焊接是非平衡不过逆过程，系统通过能量耗散发生熵增响应，实现焊接并形成波状形貌。研究过程中首先借鉴热机卡诺循环分析思路，通过对焊接过程进行阶段划分并判定热力学特征，开展熵能物理量分析；再基于界面断裂能是其结合能的有效体现之立意，通过断裂实验获得界面结合能及对应熵增；最后建立爆炸焊接循环过程熵、能总量与界面结合熵、能关联表达式，从而揭示炸药爆轰能量有效转化为界面结合能及引起的熵增规律，认识影响界面熵、能作用效果的重要因素，形成工艺调控理论，并建立调控分析数值模型。

本项目系统地探讨爆炸焊接界面形成及服役非平衡过程熵、能状态及物理关系。研究过程中首先观察横截面、纵剖面结构的不均匀性，并基于非平衡运动方程，解释界面结构产生不均匀性的机理。进一步，针对界面波的方向特性，测试其剪切行为随定位角变化特征。利用SEM观察剪切断口形貌，认识界面结构对其断裂模式影响。研究表明，爆炸焊接装药爆轰压力脉动是导致界面结构不均匀性的根本原因，而界面波延展方向决定了断裂失效模式和损伤裂纹扩展行为。. 进一步，针对界面结构与力学行为的各向异性，进行实验测试与观察，获得了定量化的界面损伤、失效载荷、应力及能量数据；并通过三维超景深显微观测，基于图像处理技术，导出了界面断口形貌结构定量表征的分维值，实现了非平衡过程导致的结构与行为定量分析。根据界面断口分维值提取算法之信息熵原理，建立断口结构信息熵与热力学熵逻辑关系，继而由热力学熵与热力学能的关联，结合断裂力学中位移－应力双线性模型，建立界面断口结构与断裂能量的定量表征关系，获得了与实验结果吻合良好的表达式。. 最后，基于爆炸焊接界面结构是物理非平衡过程发生与发展的最终体现，通过爆炸焊接非平衡方程的建立，阐明界面结构的成因及关键影响因素，为爆炸焊接界面调控方案制定提供理论依据。针对界面形貌结构受爆炸焊接动力学过程参数影响规律，旨在建立爆炸焊接界面调控方案制定依据。该部分工作阐明了爆炸焊接非平衡过程是由于炸药爆轰能量的激发，使基、复板状态发生偏离原始平衡态，但由于热力学过程熵增的物理本质，其发展过程受另一平衡状态的约束，也即非平衡过程的解处于两个平衡过程限制域内；从物理本质上阐明了界面形貌结构极限值。