【作者】 吴钢；

【导师】 陈炳森；

【作者基本信息】 同济大学 ， 机械制造及自动化， 2006， 博士

【摘要】 激光相变硬化技术在零件结构比较复杂、易变形、或选择性局部处理等常规淬火难以胜任场合下的零件表面硬化处理中具有独特优势。本文重点针对激光相变硬化研究中的激光扫描工艺及参数优化控制问题开展了比较深入的理论与实验研究。 首先，比较全面地论述了激光相变硬化质量指标，根据属性将其划分为三大模块，采用层次模型建立了质量指标体系，提出了质量控制总体决策框架模型； 其次，通过对激光扫描温度场分布特征的理论分析、并结合实际硬化层分布特点，提出了分别采用工件纵、横截面内的温度场模型进行硬化层分布模拟的方法，建立了相关理论模型，并进一步提出了采用辅助热源考虑工件边界条件的影响，通过将两个模型整合，建立了三维硬化层分布快速模拟的有效方法； 第三，通过实验研究和理论分析，对激光功率P和扫描速度v与硬化层深及表面硬度之间的内在关系开展了较为深入、系统的研究，重点探讨了激光扫描工艺参数变化对层深及硬度影响的敏感性，并对实验结果进行了详细的理论分析，给出了合理解释； 第四，对相变硬化层分布形态和激光扫描进出端层深差异问题开展了理论和实验研究，探讨了改善硬化层分布均匀性的途径和方法，提出了通过合理选择P-v组合、采用分段变速扫描工艺以改善硬化层分布整体均匀性的可行方法； 第五，建立了以层深、表面硬度和硬化层分布均匀性为综合目标的激光扫描工艺及参数优化决策框架模型，提出了具体优化方法，并从理论和实验两方面验证了该优化方法的可行性； 最后，研究开发了激光相变硬化模拟与参数优化的可视化程序模块，为深入开展激光相变硬化研究提供了一种可靠、实用的工具。更多还原

【Abstract】 Laser transformation hardening (LTH) has the obvious advantages of the traditional surface quenching techniques in the case of surface hardening for complicated structure parts, easy to distort or selected area of the part. This dissertation mainly studied on the optimum controlling of laser scanning technique and the parameters both with theoretical and experimental methods.The first, the paper gave a comprehensive discussion about the quality index of laser transformation hardening. According to their attributes, the quality indexes were classified to three different performance modules. Then, the paper gave a hierarchical structure for the LTH quality index system. And the decision-making framework model of the quality control was also set up.The second, based on the theoretical analysis of the temperature distribution characteristics and the actual hardened case distribution, the paper put forth that the simulation on the hardened case can be carried out with the temperature models respectively in the longitudinal and the cross section of the part. Furthermore, the paper put forward that by taking accessorial heat source to considering the influences of the boundary conditions and combining with the two temperature models, the simulation on three dimensions distribution of the case could be calculated much faster than pure numerical calculation.The third, with experimental and theoretical methods, the paper researched the relationships between the surface hardness, the case-depth and the laser power, scanning velocity. The researches aimed at the sensitivity of the variation of laser power and scanning velocity to the hardness and the case-depth. The reasonable explanation was put forward on the experimental results.The fourth, the theoretical and experimental researches were executed on the case distribution shape and the case discrepancy between the beginning and the ending boundaries of the part. The methods were also discussed to improve the uniformity for the hardened case distribution. The paper put forward feasible methods to improve the uniformity, which were the laser power and the scanning velocity optimum combination and the techniques of laser scanning with sectionally changing velocity along the scanning path. The fifth, taking the case-depth, surface hardness and the case distribution uniformity更多还原