切削加工残余应力的有限元分析

在切削加工中,为了提高已加工工件的表面质量,需要研究切削速度和进给量对已加工工件残余应力的影响规律。根据弹塑性有限元理论,利用有限元软件建立了切削模型,得到了不同切削速度和进给量下已加工工件的残余应力。结果表明,增大切削速度有利于增大深层压应力,同时也会增大表面拉应力;增大进给量有利于增大深层压应力,但对表面拉应力的影响无明显规律。     

高速切削时摩擦系数对切削加工性能的影响

高速切削加工中,刀屑间的摩擦系数对切削产生重大影响。为此,采用大型仿真软件Deform3D数值模拟了摩擦系数对切削力、残余应力、等效应力、等效应变和切削温度的影响。通过对有限元模拟结果的分析,优选出合理的参数指导生产加工,具有一定的实际意义。     

难加工材料硬态干车削中切削参数对残余应力的影响

本文对切削参数和残余应力之间的关系的进行研究.针对某型号高强高硬钢在硬态干车削过程,研究了各切削参数对已加工表面残余应力及残余应力层深分布的影响.结果发现,不同的切削参数条件下,工件已加工表面残余应力可以为拉应力也可以为压应力,残余应力作用层深度为300μm左右.对残余应力影响较大的切削因素为切削速度和进给量,切深对残余应力影响较小,切削参数选择低速低进给时,容易得到有利于提高工件疲劳寿命的表面残余压应力.     

高速硬态切削工件表层显微硬度与白层研究

高速和硬态切削使得工件已加工表面及其表层中出现特有的现象.研究结果表明,切削速度和材料硬度是决定高速和硬态切削工件已加工表面及其表层结构形成的主要影响因素,切削热使被切削材料产生高温软化,刀具挤压摩擦使被切削材料变形加剧,工件表层材料显微硬度分布发生改变,出现了硬脆的白层组织,白层组织的出现将对零件的使用将造成不利影响.随着切削用量和材料硬度增大,切削变形增大,切削温度升高,白层厚度增大,工件表层材料显微硬度提高.抑制白层组织产生的措施是对工件降温.     

天然金刚石刀具晶面选择对切削变形和加工表面质量的影响

超精切削中刀具和被加工材料间的摩擦直接影响切削变形和加工表面质量。金刚石晶体具有明显的各向异性,我们实测了金刚石的摩擦系数,其值为0.06～0.14,随晶面不同和方向不同而异。通过实际的超精切削验证,金刚石刀具采用摩擦系数小的(100)晶面作前面和后面,较常用的(110)晶面可降低切削变形和提高加工表面质量。     

某复杂零件加工工艺技术研究

某产品零部件结构较为复杂,由下筒体、钢环、套筒组装而成,组装时要经过粘接、预热、压装、焊接等多道工序加工,组装后再进行车削加工。在车削外形时,出现了套筒外圆变形问题,废品率较高,影响了产品加工质量。经技术分析排查确定了套筒加工变形的原因,通过改进加工工艺,消除焊接残余应力,增加切削走刀次数,避免切削应力产生,优化机加切削参数,降低切削力,解决了复杂零件加工变形尺寸超差问题。     

残余应力对切削加工精度的影响及消除

探讨了机械制造过程中残余应力的形成原因及对机械零部件切削加工精度的影响,通过对车削、铣削等常用机加工过程中残余应力的形成以及对加工品质、使用寿命、失效形式的分析,有针对性地采取了有效措施,减小残余应力的产生,消除残余应力,从而改善加工品质,提高工件的切削精度和使用寿命。     

数控车削刀具圆弧半径对切削过程影响的数值分析

数控车削加工中刀具的圆弧半径对切削力,切屑的断屑,切屑的形状,加工表面质量、加工变形以及已切削表面的残余应力的大小,状态,分布有着很大的影响.本文采用有限元分析方法,利用有限元增量理论,建立了二维金属切削仿真模型,分析中采用网格自适应准则,模拟了典型零件车削二维切削过程中切屑的形成,得到了加工后已加工表面的残余应力的大小,状态以及分布状况,对于工程中的实际应用具有重要的意义.     

42CrMo钢精车加工表面残余应力有限元仿真研究

基于ABAQUS软件建立了42CrMo锻钢活塞外圆精车加工的二维切削仿真模型,采用单因素法研究了切削参数对残余应力的影响规律.结果 表明:42CrMo钢精车加工过程中,热应力引起的残余拉应力起主导作用,已加工表面产生残余拉应力并沿深度方向迅速转变为压应力.残余应力层深度随进给量和背吃刀量的增大而增大,切削速度对残余应力层深度影响不显著.表面残余拉应力随切削速度和进给量的增大而增大,背吃刀量对表面残余应力影响不显著.最大残余拉应力出现在工件已加工表面以下,表面残余应力、最大残余拉应力和最大残余压应力随切削参数的变化趋势与切削温度随切削参数的变化趋势基本一致.     

微切削加工Al7050-T7451过程力学性能及表面完整性研究

采用硬质合金刀具,通过单因素试验对铝合金7050-T7451微切削加工过程进行了研究。考虑刃口半径的影响,切削深度参数选择涵盖了大于及小于刃口半径的范围,通过试验得到了切削力、已加工表面残余应力、表面微硬度及表面粗糙度。结果表明,刃口半径的存在是引起尺度效应的重要因素。同时,分析了刃口半径、切削速度、切削深度等切削参数对于切削力、摩擦系数、已加工表面残余应力、表面微硬度及已加工表面粗糙度等的影响规律。     

涂层刀具车削淬硬钢时前刀面摩擦系数的自组织特征

采用四种硬质合金涂层刀片对45和T10A淬硬钢两种材料进行了正交切削试验,通过所测得的三向切削力计算了前刀面平均摩擦系数,详细分析了前刀面摩擦系数随切削过程的变化情况,以及切削参数对摩擦系数的影响。结果表明前刀面摩擦系数随切削过程的进行迅速减小并趋于稳定,表征了涂层刀具切削淬硬钢时的自组织现象。     

微织构(W,Mo)C基刀具和YG8刀具对钛合金干切削性能的影响

刀具切削钛合金时存在切削温度高、单位面积上切削力大等问题,微织构刀具可以有效减小摩擦力,减小切削力。通过正交实验法设计微织构参数,研究微织构参数对Al 2O 3/La 2O 3/(W,Mo)C无黏结相硬质合金刀具以及YG8刀具切削钛合金实验的切削性能影响。实验结果表明,合适参数的沟槽型微织构能有效降低Al 2O 3/La 2O 3/(W,Mo)C无黏结相硬质合金刀具和YG8刀具切削TC4钛合金的切削力,相同沟槽参数下,无黏结相硬质合金刀具的切削力明显低于YG8刀具的切削力;合适参数的沟槽型微织构能有效降低刀具刀屑界面的摩擦系数,相同沟槽参数下,无黏结相硬质合金刀具的摩擦系数大都低于YG8刀具的摩擦系数;沟槽深度10μm、沟槽间距100μm以及沟槽宽度30μm的沟槽参数下,切削钛合金时,无黏结相硬质合金刀具前刀面无明显磨损,后刀面只有边界磨损,YG8刀具发生崩刃,前刀面出现切屑的滞留。     

Performance of the self-lubricating textured tools in dry cutting of Ti-6Al-4V

Surface textures were made using laser on the rake or flank face of the cemented carbide (WC/Co) inserts. Molybdenum disulfide solid lubricants were filled into the textured grooves to form self-lubricating textured tools. Dry cutting tests on Ti-6Al-4V were carried out with these self-lubricating textured tools and conventional tool. The machining performance was assessed in terms of the cutting forces, cutting temperature, chip thickness ratio, friction coefficient at the tool–chip interface, and tool wear. Results show that the cutting forces and cutting temperature of the self-lubricating textured tools were reduced compared with that of the conventional tool. The application of the self-lubricating textured tool with elliptical grooves on its rake face can reduce the tool–chip friction coefficient and the chip thickness ratio. The tool life of the textured tools is improved compared with that of the conventional tool. The effectiveness of the self-lubricating textured tools in improving cutting performance is related to the cutting parameter.     

基于AdvantEdge的斜角车削仿真实验确定刀屑摩擦因数的方法

当使用AdvantEdge软件进行切削仿真实验时,刀屑摩擦因数对仿真结果的影响明显,但现有有限元软件未提供刀屑摩擦因数数据库。为建立一种基于AdvantEdge的斜角车削仿真实验的刀屑摩擦因数确定方法,首先提出基于斜角车削的摩擦力计算方法,然后建立AdvantEdge三维斜角车削仿真模型,设定不同切削速度、切削深度、进给量及摩擦因数,通过AdvantEdge 仿真正交试验,获得刀屑摩擦因数的经验计算公式。为验证刀屑摩擦因数经验计算公式的正确性,设定不同切削速度和切削深度及进给量的斜角车削正交试验,获得切削力数据,并基于摩擦因数经验计算公式求得对应刀屑摩擦因数。利用求得的摩擦因数数据修改AdvantEdge中刀屑摩擦因数参数,进行残余应力切削仿真实验。仿真实验获得的残余应力与实际切削实验获得的残余应力相比,误差在10%以内,证明提出的刀屑摩擦因数确定方法是正确的。     

Experimental assessment of textured tools with nano-lubricants in orthogonal cutting of titanium alloy

In this study, we investigated the effects of composite nano-Cu/WS₂ lubricating oil and single-point diamond indentation-textures on improving the cutting performance of YG8 cemented carbide tools, which is crucial for textures tool applications. The aims of the study were to improve wear resistance and reduce chip adhesion at the tool’s rake face in cutting of titanium alloys. Dot textures with different spacings were fabricated on the surface of YG8 cemented carbide tools through the single-point diamond indentation method, and composite nano-Cu/WS₂ lubricating oil was prepared. Orthogonal cutting tests were carried out under dry cutting and minimal quantity lubricated (MQL) conditions. Investigate the effect of different texture spacing on the cutting performance in the light of cutting forces, friction coefficient, the deformed chip thickness, tool adhesions, and chip morphology. The results show that the dot texture effectively improved the lubrication conditions in machining titanium alloys under the MQL conditions. The dot texture is effective at low speed in the dry cutting conditions. With the increase of cutting speed, the friction coefficient of dot texture tool is affected by texture spacing, and the friction coefficient of DT-200 tool is the smallest. In addition, composite nano Cu/WS₂ lubricating oil forms a lubricating film on the wear path by atomizing the lubricating oil and stores it in the dot texture, which enhances the anti-wear performance in the cutting process and reduces the cutting force and friction coefficient at the tool chip interface. By evaluating cutting force, friction coefficient, chip and tool morphology, it is concluded that DT-100 tool is more effective in improving lubrication conditions.

     

STUDY ON NEAR DRY CUTTING OF ALUMINUM ALLOYS

Series of orthogonal cutting tests of aluminum alloys with different amount of silicon content have been carried out to investigate the chip formation process and adhesion of the work material to the rake face of the cutting tool under near dry cutting conditions. No adhesion is observed when cut with the sintered diamond tool regardless of the amount of the silicon content. On the other hand, the amount of adhesion increases with an increase in the silicon content in the aluminum alloys when cut with the cemented carbide and DLC-coated tools. No adhesion is formed when the nominal coefficient of friction on the rake face is 0.3 or less, and adhesion is formed when the nominal coefficient of friction is 0.4 or more. The amount of adhesion decreases with an increase in the rake angle when cut with the cemented carbide tools and the DLC-coated tool.     

STUDY ON NEAR DRY CUTTING OF ALUMINUM ALLOYS

Series of orthogonal cutting tests of aluminum alloys with different amount of silicon content have been carried out to investigate the chip formation process and adhesion of the work material to the rake face of the cutting tool under near dry cutting conditions. No adhesion is observed when cut with the sintered diamond tool regardless of the amount of the silicon content. On the other hand, the amount of adhesion increases with an increase in the silicon content in the aluminum alloys when cut with the cemented carbide and DLC-coated tools. No adhesion is formed when the nominal coefficient of friction on the rake face is 0.3 or less, and adhesion is formed when the nominal coefficient of friction is 0.4 or more. The amount of adhesion decreases with an increase in the rake angle when cut with the cemented carbide tools and the DLC-coated tool.     

高载荷条件下的材料表面摩擦因数测量

针对材料表面高载荷条件的要求，提出了测量摩擦因数的方法，并进行了相应测试装置的设计，该测试装置由正向加载装置、侧向加载装置和数据处理装置3部分组成。可以用来测量高载荷条件下材料表面的静摩擦因数和滑动摩擦因数，同时得到整个滑动过程中摩擦因数变化情况。利用该装置对某国防减摩涂层进行了测试，结果表明在高载荷条件下该涂层对碳钢表面具有较好的减摩效果。     

Investigation of secondary deformation zone and mean coefficient of friction during the machining of 5083-H34 aluminum alloy

An experimental analysis was performed to evaluate the width of the secondary deformation zone and the mean coefficient of friction during the machining of 5083-H34 aluminum alloy. Dry orthogonal cutting tests using high speed steel and sintered carbide tools of different rake angles were carried out at a wide range of feed rates at constant cutting speed for tubular workpieces.The width of the secondary deformation zone and the mean coefficient of friction were found to be direct functions of the parameters involved in the cutting process. The results were analyzed in terms of the variation in the mean tool-chip contact temperature and its influence on the specific tangential load and specific normal pressure on the tool face.     

Statistical analysis of process parameters in drilling of AL/SICP metal matrix composite

Four micro-holes were made using micro-EDM on rake face of the cemented carbide (WC/TiC/Co) tools. MoS₂, CaF₂, and graphite solid lubricants were respectively embedded into the four micro-holes to form self-lubricated tools (SLT-1, SLT-2, and SLT-3). Dry machining tests on hardened steel were carried out with these self-lubricated tools and conventional tools (SLT-4). The cutting forces, average friction coefficient between tool and chip, and tool wear were measured and compared. It was shown that the cutting forces and tool wear of self-lubricated tools were clearly reduced compared with those of the SLT-4 conventional tool. The SLT-1 self-lubricated tool embedded with MoS₂ just exhibited lower friction coefficient between tool and chip in cutting speed of less than 100?m/min; the SLT-2 self-lubricated tool embedded with CaF₂ possessed lower friction coefficient in cutting speed of more than 100?m/min; and the SLT-3 self-lubricated tool embedded with graphite accomplished good lubricating behaviors steadily under the test conditions. It is indicated that cemented carbide inserts with four micro-holes on rake face embedded with appropriate solid lubricants on rake face is an effective way to reduce cutting forces and rake wear.