【作者】 张凯；

【导师】 赵军；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2009， 硕士

【摘要】 本文在纳米陶瓷刀具材料的基础上引入梯度功能概念,成功制备出新型的Al₂O₃基梯度纳米复合刀具材料。研究了其力学性能、微观结构、压痕裂纹扩展形态。采用有限元法对其抗热震性能和切削过程进行了仿真研究,并通过316L不锈钢切削试验,研究了Al₂O₃基梯度纳米复合刀具的切削性能及失效机理。通过合理选择制备工艺参数,当基体Al₂O₃的体积含量为54%、TiCN含量为45%、MgO和NiO各为5%时,在烧结温度1650℃、烧结压力30MPa、保温时间10min,获得综合性能较好的梯度纳米复合陶瓷材料,抗弯强度为810MPa、硬度19.5GPa、断裂韧性6.6MPa·m^1/2。断口微观结构分析表明,梯度纳米复合陶瓷刀具为主要以穿晶断裂为主;在压痕扩展路径上存在裂纹偏转、桥联和裂纹分叉现象,这些都有利于提高材料的力学性能。采用有限元软件ANSYS仿真了Al₂O₃基梯度纳米复合刀具材料的瞬态温度场及热应力场,分析了层厚比、体积分数组成等结构参数对抗热震性的影响。通过仿真研究优化了梯度结构参数。采用有限元软件DERORM-2D对Al₂O₃基梯度纳米复合刀具切削加工316L不锈钢的过程进行建模和仿真,研究了温度场、应力场、切削力与切削速度的关系。结果表明:Al₂O₃基梯度纳米复合刀具温度随着切削速度的增加而增大,切削温度低于均质陶瓷刀具;刀具应力随着切削速度的增加也增大,在较大速度范围内比均质陶瓷刀具应力小。切削力随着削速度的增加而减小,与均质陶瓷刀具相比,切削力相差不大。通过连续切削316L不锈钢,研究了Al₂O₃基梯度纳米复合刀具的切削力、切削温度及刀具失效机理。加工316L不锈钢时,随着切削速度升高,主切削力减小,切削温度升高。在相同的试验条件下,梯度纳米陶瓷刀具的使用寿命优与其他陶瓷刀具。较低速度下,刀具的失效形式主要以前、后刀面磨损及微剥落为主,磨损机理是磨粒磨损,剥落由机械疲劳造成;较高速度下,刀具的失效形式主要以前、后刀面磨损以及边界磨损为主,磨损机理是磨粒磨损和粘结磨损。更多还原

【Abstract】 By introducing functionally graded composite into Nano-composite ceramic tool material,an Al₂O₃/TiCN graded Nano-composite ceramic tool material was fabricated successfully.The mechanical properties,microstructure and fracture extension pattern of the ceramics were studied.Thermal shock resistance and cutting process were studied by FEM.By cutting AISI316L,cutting performance and fool failure mechanisms were detailed studied.When the volume fractions of Al₂O₃,TiCN,MgO and NiO are 54%,45%,5%and 5%,Al₂O₃/TiCN graded Nano-composite ceramic with strength of 810 MPa,hardness of 19.5GPa and touchness of 6.6 MPa·m^1/2 can be obtained by hot-press sintering under the temperature of 1650℃,pressure of 30MPa and holding time of 10 minutes.The microstructure of the Al₂O₃/TiCN graded Nano-composite ceramic is mainly characterized by transgranular fracture;the crack deflection,crack bridging and crack branching in the crack extension path also contribute to the improvement of mechanical properties.Thermal shock resistance of Al₂O₃/TiCN graded Nano-composite ceramic was simulated using ANSYS.The influence of Layer-thickness ratio and compositional distribution on thermal shock resistance were analyzed,and consequently the graded structure parameters were optimited.The cutting process of Al₂O₃/TiCN graded Nano-composite ceramic tool when machining AISI316L was simulated by DEFORM-2D.The influences of cutting speed on cutting temperature field,thermal stress field and cutting force were studied.With the speed increased,the tool temperature is higher.Compared with homogeneous ceramic tools,it has good thermal shock resistance.With the speed increased,tool stress also increased,the tool stress is lower than homogeneous ceramic tools at high cutting speeds.The cutting force decreased with the speed increased,which is equvilent to that of other ceramic tools.As for the maching of AISI316L steel,cutting force,temperatue,tool failure mechanisms of Al₂O₃/TiCN graded Nano-composite ceramic tool were studied.The cutting force decreased and temperature increased with the speed increased. Al₂O₃/TiCN graded Nano-composite ceramic tool has longer life than other ceramic tools under the same condition.The main failure mode is rake wear,flank wear and spalling when speed is low,because of abrasive and mechanical fatigue.The main failure mode is rake wear,flank wear and notch wear when speed is high,because of abrasive and adhesive.更多还原