【作者】 李林文；

【导师】 李斌； Kornel F.Ehmann；

【作者基本信息】 华中科技大学 ， 机械电子工程， 2013， 博士

【摘要】 硬切削加工过程中，切削温度及分布是影响刀具使用寿命和加工质量的关键因素之一，其中切削区域温度及分布的精确测量与预测一直是切削加工机理研究的热点和难题，主要问题是现有的温度测量方法很难实现对切削区域温度分布的原位（在接近切削作用区域）测量，其温度测量结果的时间和空间分辨率难以满足要求，因此切削区域温度预测模型的有效性和准确性难以得到验证。论文针对上述难题，在深入分析切削加工过程中材料塑性变形区复杂热力耦合效应的基础上，考虑了第二变形区切屑材料滞留区的影响，提出了前刀面上切屑沿刀具与切屑作用面间非线性流动的数学模型，并修正了Komanduri和Hou模型中关于前刀面和后刀面之间的绝热假设，提出了一个正交切削条件下的切削温度分布解析模型，该模型可用于预测切削作用区域的热、力参数。在切削温度测量方法上，论文采用无缝嵌入到PCBN刀具中的微尺度薄膜热电偶传感器阵列(Micro-scale Thin Film Thermocouples, TFTCs)，实现了刀具切削区域温度分布的原位获取与准确测量。在同等切削条件下，通过硬车削实验中获得的切削温度、切削力、以及切屑厚度等数据，验证了所建立的解析模型的预测精度，验证结果表明，解析模型的预测结果与实验数据之间表现出了较高的预测精度。论文根据所提出的解析模型和硬车削条件下所进行的切削实验结果，对切削区域的热力耦合行为及一些尚未澄清的机理问题进行了分析与探讨。基于所提出的解析模型的预测结果，分析了硬车削加工条件下切削区域的切削温度、应力分布、切屑流动速度之间的稳态热力耦合行为，研究结果表明，随着切削速度的变化，切削区域的热源位置与热释放强度分布、热传导过程中的热分配比例关系等是影响刀具切削区域温度分布状态及其变化趋势的重要原因。另外，基于硬切削实验中获得的温度数据、切削力和振动信号，对硬车削加工中切屑形成区域的动态热力耦合行为进行了分析，研究结果发现主剪切区域所发生的绝热剪切过程，导致的工件材料周期性的裂纹萌生与扩展，会引起切屑形成区域的材料流动应力及切削温度的周期性耦合脉动，进而影响到硬车削加工的切屑宏观形貌和切屑的锯齿化形成过程。同时，主剪切区域的绝热剪切带位置，同样会影响刀具前刀面上的切削温度及分布状态。总体而言，研究成果可广泛应用于金属切削理论研究，加工过程的参数优化，以及切削过程监测等，丰富了金属切削加工研究的理论方法和实验手段。更多还原

【Abstract】 As well-known as the cutting temperature and its distribution in the cutting zone are acritical factor that significantly affects tool life and degrades part accuracy during hardcutting processes. However, issues surrounding their modeling and experimentalvalidation in the immediate cutting zone still remain an unresolved issue. A majorimpediment is the unavailability of adequate temperature measurement methods withsufficient temporal and spatial resolution to measure actual temperatures and validatepredictive models.From the standpoint of the common issues with the limitations that existed in thecutting temperature models and experimental measurements. In this paper, a model for thedry orthogonal cutting process with thermo-mechanical coupling effects is proposed topredict cutting temperature distribution as well as the relevance parameters in the cuttingzone. In this model, to model the non-uniform distribution of the chip flow velocity alongthe tool/chip interface, a unique stagnant region within the secondary shear zone wasadded into the slip-line field. Based on Komanduri and Hou’s approach, a modifiedthermal assumption for the temperature rise in the cutting tool that considers the fact heattransfer occurs from both the rake and flank faces was also proposed.Cutting temperature distributions were measured by Micro-scale Thin FilmThermocouples (TFTCs) embedded into PCBN cutting inserts in the immediate vicinity ofthe tool-chip interface. Using these measurements and predictions during hard turning, thefeasibility and prediction accuracy of the model is verified by experimental measurementsthrough TFTC arrays embedded into the PCBN tooling. The experimental verification isperformed under hard turning conditions. It has been shown that the predictions of theproposed model are in very close agreement with the experimentally measured resultsincluding the cutting forces, chip thickness and cutting temperature distributions on the rake and flank faces in the cutting zone.Numerous detailed analysis of the thermo-mechanical coupling mechanisms andsome of the unresolved issues in the hard turning processes have been offered with the twocontents that combined by experiment measurements and modeling predictions. Based onthe predictions of the analytical approach, the modeling results have also provided anessential understanding on steady-state thermo-mechanical effects, i.e., the influencesamong in cutting temperatures in the cutting interfaces, stress distributions at the tool/chipand work/tool interfaces as well as of the nature of the chip flow velocity along the rakeface of the cutting tool. It has been shown that the temperature changes in the cutting zonedepend on the heat resource’s location in the chip and the thermal transfer rate from theheat generation zone to the cutting tool.Moreover, in current work, a combined investigation on dynamic as well as chipmorphology and formation process analyses were performed based on the cuttingtemperature and cutting force variations in the cutting zone. It became evident that thecyclically changes in the material flow stress and the adiabatic shearing bands generatedgreatly affect not only the chip formation morphology but also the cutting temperaturefield distributions in the cutting zone of the cutting insert.Overall，The research achievements can be used to perform more fundamentalinvestigations for metal removal machining mechanism and for widespread applicationssuch as cutting parameters optimization and machining process monitoring etc. Theproposed approach also possesses the abilities that used to advance the metal removalprocessing research evolution forward.更多还原