【作者】 王扬渝；

【导师】 计时鸣； 文东辉；

【作者基本信息】 浙江工业大学 ， 机械电子工程， 2013， 博士

【摘要】 淬硬钢是经热处理后硬度达到50HRC以上的高碳钢或合金钢,具有良好的淬透性和抗磨损性能,适合于制造各类冷作冲压模具的镶块及模体。多硬度拼接淬硬钢是指由材料牌号、硬度各异且经过精密切削的淬硬钢单体,采用特定装配顺序和工艺获得的拼接间隙小于0.3μm的装配体,广‘泛应用于大型模具、拼接模具制造等领域。拼接淬硬钢在动态铣削力的作用下,由于其硬度的差异,加工过程易发生颤振,加工质量难以保证。本文结合结构力学、有限元分析、模态分析与试验研究等方法,对拼接淬硬钢铣削过程中的切削力、铣削振动及稳定性进行了深入探讨,推导了铣削加工颤振稳定性预测模型,进行了稳定性仿真分析,并完成了实验验证。本文相关研究工作,对于揭示多硬度拼接淬硬钢硬态铣削机理,推动硬态切削基础理论的完善,提高淬硬钢铣削技术水平具有重要意义。本文的主要研究内容及结论如下：(1)基于拼接件的力学本构模型与硬度特性,建立了多硬度拼接淬硬钢切削过程数值力学模型,模拟了多硬度拼接淬硬钢的切削力,研究了工件硬度对切削力的影响规律。在此基础上,应用正交试验法进行了球头精铣淬硬钢倾斜表面的切削力试验研究,得到了切削参数对切削力的影响规律。(2)基于多参考最小二乘复指数法(LSCE)与工作模态分析(OMA)方法,提出了一种切削系统工作模态动态分析方法。使用锤击试验时脉冲激励下的主轴响应点间的互谱函数,利用OMA进行模态分析,通过LSCE提取主轴系统模态参数,并与锤击模态试验中通过传统频响函数识别的模态参数进行对比,验证了该方法的有效性。(3)基于再生颤振理论建立了两自由度铣削加工动力学模型,在此基础上建立了拼接淬硬钢铣削稳定性预测模型,仿真分析了工艺参数对铣削稳定性的影响,并通过稳定性试验验证了稳定性叶瓣图的正确性。(4)进行了多硬度拼接条件下的淬硬钢铣削实验,验证了本文相关理论研究成果的正确性,并对铣削振动时频特性、加工参数对铣削振动影响规律等问题进行了进一步研究。以多硬度拼接工件过渡区附近的表面粗糙度最小为优化目标对铣削参数进行了优化,提出了拼接条件下的铣削工艺参数的选用原则。更多还原

【Abstract】 Hardened steel is high carbon steel or alloyed steel with high hardness (more than50HRC) after heat processing. Hardened steel owning excellent hardenability and wear-resistance is suitable for manufacturing of assembled die and body mold for cold-working punching mould. Assembled hardened steel with different hardness consists of a lot hardened steel single bodies with different material trademarks and hardness after accurate cutting. Special assembling and technical process was used to deal with assembled hardened steel with different hardness to own low assembling space (less than0.3μm). So assembled hardened steels with different hardnesses are widely applied in the fields of large-scale mould, manufacturing of assembled mould.Chattering dither always happens in the assembled hardened steel machining process under dynamic milling force for the hardness difference. So the machining quality cannot steadily keep high level. The structural mechanics, finite element (FE) analysis, modal synthesis and experimental investigation are introduced in the present study. The target of present thesis is to investigate the milling force, vibration and stability in the milling process of the assembled hardened steel. The model of milling chattering dither steadily is established. FE emulation analysis about the steadily is conducted, and corresponding experiments are completed. So the works completed in the present thesis is significative for revealing milling mechanism of assembled hardened steel with different hardness, promoting basic theory of hard cutting, enhancing technical level of hardened steel milling.The main contents and conclusions:(1) Numerical mechanical model of cutting process of assembled hardened steel with different hardness is established based on mechanical constitutive model and hardness feature. The cutting force used for machining assembled hardened steel with different hardness is simulated. The influence of workpiece hardness on cutting force is investigated. Based on aforementioned works, the orthogonal design method is introduced to investigate the cutting force when ball end miller is employed to deal with declivity surface of hardened steel. The regular pattern of influence of cutting parameters on cutting force is owned;(2) One kind of method of operational modal dynamic analysis about cutting system is given based on least squares complex exponential (LSCE) multi-reference method (LSCE) operational modal dynamic (OMA) method. Cross-spectral function among response points of basic shaft under impulse excitation in hammering process is calculated. Modal parameter of basic shaft is extracted based on LSCE. OMA is used to conduct dynamic modal analysis, the results is compared to the modal parameter owned from analysis of the traditional frequency response function in hammering process. The availability of this new method is proved;(3) Two-degree milling dynamics model is established based on regenerative chattering dither method. And then, universal milling stability prediction model is established. The influence of technical parameters (milling force coefficient, radial cutting-in) on milling stability is analyzed by emulation method. The experiment of milling stability proves the correctness of Stability lobes;(4) The milling experiments of hardened steels assembled with different hardness under ball end miller are conducted. The correctness of correlative investigation conclusions in this study are proved based on aforementioned experimental results. Some key problems, such as cutting vibration, wear mechanism, cutting morphology, are also discussed. The milling parameters of the transient area of assembled hardened steel with different hardness are optimized. The surface roughness of the machining surface and wear extent of tool are employed to be evaluating indicator. Finally, the select principle of cutting technical parameter under assembled condition is given.更多还原