切削比能模型的建立及参数影响分析

从材料去除机理角度分析了材料去除过程中的能量耗散机理,并对材料去除能耗进行建模量化,推导出切削比能经验公式。根据试验数据拟合出端面车削的切削比能幂率公式,拟合度在95%以上。鉴于切削参数对切削比能影响的差异性,结合试验分析了切削三要素对切削比能的影响机理,研究结果为面向节能的切削工艺参数的制定及低碳制造量化评估清单数据要求提供了基础支持。

高质量绿色环保的精车切削优化

绿色制造中的切削参数优化对于提高加工质量、加工成本、产品利润和节能环保具有非常重要的意义。考虑实际加工约束条件,建立了加工精度与切削能量的双目标精车切削优化模型。通过实例运用NSGA-II算法与MOPSO算法对精车优化切削模型进行仿真,结果表明,NSGA-II算法获得了更优的Pareto最优解集。在给定加工余量条件下,加工精度与切削能量的Pareto最优前沿可由三次曲线方程拟合,且拟合相关指数为0.999 9。在加工精度与切削能量的Pareto最优解集下,加工精度和进给量的关系可由二次曲线方程拟合,且拟合相关指数为0.999 99,为精车切削参数优化选择提供了实践指导。

热源参数对切削性能影响的有限元分析

从工件塑性变形和刀具与工件摩擦的角度出发,分析了切削仿真过程中热量的来源,分别针对不考虑切削热、只考虑塑性热、只考虑摩擦热、同时考虑塑性热及摩擦热四种工况,研究了切削仿真过程中的切削力、切削温度、工件应力和应变以及能量的变化规律,并对不同工况下的仿真效率进行了对比分析。结果表明:在热源参数的软化作用下,切削力和工件应力都会降低,而应变会略有增加;摩擦热源参数对切削力、工件应力的贡献度相对较大,而塑性热源参数对切削温度的贡献较大;考虑切削热的仿真效率要远远低于不考虑切削热的情况,并且摩擦热源参数对仿真效率的影响要大于塑性热源参数。

面向现代绿色制造的精车车削优化

考虑车削加工约束条件,建立切削能量最小与表面粗糙度最小的精车车削优化模型。通过实例运用非支配排序遗传算法(NSGA-II)与多目标粒子群算法(MOPSO)对精车优化切削模型进行仿真优化,结果表明NSGA-II算法与MOPSO算法切削能量和表面粗糙度的Pareto最优解集均可由同一的六次曲线方程拟合,且拟合相关指数为0.999 5、0.998 2。在表面粗糙度和切削能量的Pareto最优解集下,获得了精车优化切削模型相应的进给量、切削速度,为优化选择精车切削参数提供了参考。

钛合金顺铣和逆铣的有限元仿真对比分析

为对比研究顺铣和逆铣方式对加工结果的影响,采用有限元仿真方法建立钛合金铣削三维仿真模型,同时以切削力、摩擦力、工件应力以及动能和塑性能等输出变量为评价标准,研究了不同铣削方式下仿真结果的差异。结果表明,逆铣的平均应力为800MPa,顺铣的平均应力为650MPa,逆铣的应力大于顺铣;在X轴方向上,逆铣切削力大于顺铣切削力,顺铣的摩擦力大于逆铣摩擦力;在Z轴方向上,顺铣的切削力大于逆铣切削力,逆铣的摩擦力大于顺铣摩擦力,逆铣的整体动能和塑性能大于顺铣。

工程陶瓷的机械加工技术研究进展

工程陶瓷具有硬度高、耐磨性好、性能稳定等许多优异的性能,因而在各个行业中都得到了广泛的应用。在国内外学者的相关研究基础上,工程陶瓷加工技术的新方法得到了长足发展。由于工程陶瓷具有的显著硬脆特性,机械加工是最为常用的传统加工技术。结合最近几年相关文献与资料,本文阐述了国内外关于高速/超高速磨削、深切缓进给磨削、高速深磨磨削等工程陶瓷机械加工技术的相继发展情况。此外,还阐述了基于边缘碎裂效应的切割-推挤式加工和能量辅助切削加工两项新型加工技术。

Modeling of Transient Thermal Conditions in Cutting

The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.

注浆岩体强度随钻评价试验研究

复杂条件地下硐室安全控制的难点在于破碎围岩的有效支护,锚注支护是破碎围岩有效控制的主要手段,注浆后的岩体强度是锚注支护参数合理设计优化的重要依据。目前对于注浆岩体强度的定量测试评价方法研究较少,数字钻进测试技术为实现注浆岩体强度的定量获取提供了新思路,其关键在于建立数字钻进参数与注浆岩体强度参数的定量关系。基于此,本文以厚冲积层高应力矿井——万福煤矿为工程背景,利用研发的岩体数字钻进试验系统,开展注浆岩体数字钻进试验,讨论分析不同水灰比及不同岩体粒径因素对钻进参数、切削能量和抗压强度的响应规律。在此基础上,结合回归分析方法,得到数字钻进PDC钻头条件下的钻进能耗系数和钻进能耗常数,以及钻进岩体破碎系数,建立基于能量分析的注浆岩体钻进参数与等效强度定量关系模型(EDP-ECS模型),提出注浆岩体等效强度随钻评价方法。本文研究为基于数字钻进测试实现地下工程注浆围岩强度的定量评价提供了理论与方法基础。