【作者】 胡旺；

【导师】 童彦刚；

【作者基本信息】 重庆大学 ， 材料加工工程， 2002， 硕士

【摘要】 本文针对传统焊接HAZ热循环测试方法的局限性，采用计算机软、硬件技术和数据处理方法，研究和开发了一种新型焊接热循环测试及分析系统。该系统由热电偶、A／D插口板、微机等组成，集焊接热循环温度数据采集、存储、处理和分析功能于一体，与传统的X-Y函数记录仪测试方法相比，本系统具有精度高、误差小、实时性好、使用方便、界面友好、性价比高等优点。 本文设计了公式法、线算图法、人工神经网络法等仿真计算焊接热循环参数的计算机程序，为设计、制定、评定和优化焊接工艺提供了重要的依据。 本文采用运算量较少的均值滤波方法平滑随机噪声，设计了变长滑动窗口算法进行数据分析。通过采用本系统现场实测试验以及数据分析，首次在HAZ热循环曲线上获得了明显的焊接冷却固态相变温度平台，为进一步分析热影响区的相变提供了强有力的证据，从而提出了利用焊接冷却相变在热循环曲线上表征为温度平台现象来研究HAZ相变机理与组织性能的新思路。 通过观察分析本系统所采集的HAZ热循环曲线，首次发现在焊接冷却相变之前有明显的温度陡降现象。作者根据预马氏体转变理论和贝氏体相变孕育期内的预相变理论，用能量的观点对此现象进行了分析和解释。 本文对实验结果中出现的焊接冷却相变温度平台进行了原理分析，并结合焊接工件的热影响区金相组织进行了对比分析，结果表明本系统获得的焊接冷却相变特征与观察到的金相组织基本吻合。 综上所述，本文研究和设计了新型焊接热循环测试及分析系统，开发了焊接热循环参数的仿真计算程序，获得了HAZ热循环曲线上的固态相变温度平台，发现了焊接固态相变之前的温度陡降的新现象。以上这些对改进测定焊接热循环的方法，研究HAZ的组织和性能，分析焊接冷却过程相变机理，制定新材料的焊接CCT图，建立和验证HAZ热循环参数计算模型均具有较高的理论意义和实际的使用价值。更多还原

【Abstract】 A new type of computer-aided system for testing and analyzing weld thermal cycle is presented in this paper. To overcome the shortcomings of the traditional method for testing thermal cycle in welding heat affected zone (HAZ), the system employs computer technology which can collect and process data conveniently. It consists of thermocouples, an A/D interface board and a microcomputer. The system is the integration of data collecting, data processing and data analyzing, and which has following advantages: high precision, easy usage and high ratio of quality to price.To simulate the parameters of weld thermal cycle, some programs are developed using C++ language, which adopt such methods as formulation, linear calculation and artificial neural networks. By doing so, it can provide significant aids to establish, qualify and optimize welding procedures.A method named mean-value filter is used to smooth the random noise and an algorithm called variable-length-sliding window is designed for data analyzing. For the first time, obvious temperature plateaus are found in thermal cycle curves of HAZs in a low carbon alloyed steel, and a new idea is thereby put forward to study the phase transformation of HAZ.Analyzing the curves of experiments, a new phenomenon of sudden temperature drop is found before the temperature plateaus appear in weld cooling transformation. In terms of the Martansite pre-transformation theory and Bainite phase theory, explanations are given from the view of energy.Finally, metallograph examinations are given for the explanation of the observed transformation temperature plateau. The results show the consistency between the features obtained in weld cooling transformation by this system and metallographic structures.As a whole, a new type system for testing and analyzing weld thermal cycle is designed and simulating programs are developed in this paper. Most important of all, temperature plateaus are obtained in the thermal cycle curves of HAZ and a new phenomenon of sudden temperature drop is found before solid transformation. By using such enhanced methods, the system is applicable to researching the microstructures and mechanical properties of HAZ. It may also be helpful for establishing the welding CCT curves for new materials.更多还原