共查询到17条相似文献,搜索用时 250 毫秒
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立方氮化硼超硬磨料与45钢钎焊接头残余应力有限元分析 总被引:1,自引:0,他引:1
针对立方氮化硼(CBN)超硬磨料高温钎焊冷却过程中可能产生较大热应力而导致磨粒破碎和接头断裂的问题,利用弹塑性有限元法对Ag-Cu-Ti合金钎焊CBN磨粒与45钢基体时接头的残余应力进行模拟分析.结果表明;磨粒球体内部中心轴线、中心平面半径方向以及磨粒与钎料顶层圆形断面半径方向是磨粒内部残余应力变化最显著的区域,而圆形断面边缘部分为磨粒内部最大残余拉应力的存在区域.试验验证有限元分析结果与测试结果基本一致.基于磨粒内部的最大残余拉应力,为确保焊后磨粒强度和钎焊砂轮容屑空间,CBN磨粒在钎料层中的包埋深度宜控制在30%~40%之间. 相似文献
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刘山梁子 《机械工程与自动化》2013,(1):125-126
采用ANSYS有限元法计算了SiC/Ti55复合材料中的残余应力,分析了不同纤维体积分数下纤维中径向、轴向和环向残余应力的大小和分布。结果表明,径向和轴向残余压应力均随纤维体积分数的增大而减小;环向残余应力在纤维内部为压应力,表面附近为拉应力,且纤维体积分数越高,表面环向拉应力越大。 相似文献
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为了明确激光晶体材料研磨表面残余应力形成机制,以典型的激光晶体材料YAG晶体为研究对象,利用大型有限元软件Ansys,建立了晶体元件研磨加工过程的单颗粒作用模型,研究了 YAG晶体材料的塑性特性,分析了研磨过程中磨粒机械作用对晶体表面残余应力分布的影响.结果表明,YAG晶体受单颗粒作用载荷18 mN时,晶体材料内部的残余应力主要表现为压应力(最大分布深度约3 μm),但在工件表层(深度<150 nm)范围内为拉应力,且拉应力最大值超过材料拉伸极限强度,将诱导晶体表面形成微裂纹;当单颗粒载荷为2.3 mN时,晶体表面残余最大拉应力值小于材料拉伸极限强度,可以实现晶体材料塑性域加工去除. 相似文献
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完成镀膜CBN珩轮激光钎焊需要1套完整的工艺,包括珩轮基体钎焊前清洗、镀膜CBN粗化、黏结剂涂覆、钎料及磨粒固着、激光钎焊等。任意1项出现纰漏,都会对镀膜CBN钎焊连接质量造成一定的影响,降低钎焊后珩轮精度。本文在总结以往试验的基础上,对镀膜CBN珩轮激光钎焊工艺进行了基础性研究,制定出1套激光钎焊镀膜CBN珩轮制作工艺,并对激光钎焊过程中常见的镀膜CBN磨粒缺陷进行了分析,阐述了产生缺陷的原因,提出避免缺陷产生的方法,为珩轮的制备提供了新的方法,对于加快新型珩轮的开发和推动珩齿工艺的发展提供了有益的帮助。 相似文献
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《机械工程材料》2016,(9)
利用自主研发的SWXRD-1000型短波长X射线衍射仪对去应力热处理前后纳米铝块体的内部残余应力进行了测试;为研究残余应力沿试样厚度方向的分布,采用Xstress-3000型X射线应力仪对未热处理的纳米铝块体表面残余应力进行了测试。结果表明:纳米铝块体内部的晶粒取向分布均匀;随着热处理温度升高,块体中心处的残余应力呈下降的趋势,中心处的径向残余应力由未热处理时的113MPa降至4MPa,切向残余应力由未热处理时的91 MPa降至38 MPa;未热处理试样厚度方向上的残余应力分布整体呈为外压内拉,直径方向上的内部残余应力呈现出中间高两侧低的分布趋势,且中心附近为残余拉应力。 相似文献
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《机械制造与自动化》2016,(1):18-21
应用裂纹柔度法测量了7055-T7751铝合金预拉伸板的内部残余应力。结果表明,该板材内部残余应力近似呈外压内拉的"W型曲线"分布,其中,轧制方向最大残余拉应力约为31.3 MPa,最大残余压应力约为-23.7 MPa,宽度方向最大残余拉应力约为7.1 MPa,最大残余压应力约为-12.8 MPa。相比较于其他典型7×××系列铝合金预拉伸板,7055作为目前合金化程度最高、强度也最高的铝合金,在提高性能的同时,内部残余应力也相应提高,导致加工变形较大。 相似文献
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利用超高频感应钎焊在不同钎焊温度条件下制备立方氮化硼(CBN)砂轮,采用扫描电子电镜(SEM)和能量分散谱仪(EDS)对磨粒表面新生化合物进行观察与分析,并通过与电镀CBN砂轮进行比较,对感应钎焊CBN砂轮的磨削性能进行评价。结果表明:CBN磨粒界面新生化合物主要组成元素有N、B、Ti三种,活性元素Ti发生扩散并与N和B发生化合反应;当感应钎焊温度为940℃时,磨粒表面生成物致密覆盖在表面,且所制备的CBN钎焊砂轮的磨削力和磨削比能较小。在相同磨削用量下,对电镀CBN砂轮和感应钎焊CBN砂轮的磨损形式进行对比分析发现,电镀CBN砂轮的磨损形式为黏附磨损,钎焊CBN砂轮的磨损形式为破碎磨损。 相似文献
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以Ni-Cr合金为钎料,分别用真空加热和高频感应加热两种方式进行了金刚石磨粒与0Cr18Ni9不锈钢基体的钎焊,制作了基体外径为3 mm的薄壁小孔钻头。进行了半钢化玻璃钻削试验,用扫描电子显微镜观察钻削试验前后钻头的微观形貌。结果表明:两种钎焊工艺皆实现了金刚石磨粒的高强度连接;加热源不同及金刚石磨料出露高度差异性是影响钻头磨损方式的主要因素;为确保钻头的寿命和高效,磨粒出露高度应控制在其自身高度的50%-60%之间。 相似文献
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Xufeng Zhao Tianbiao Yu Chuang Jia Shuhao Lu Liaoyuan Chen Wanshan Wang 《The International Journal of Advanced Manufacturing Technology》2020,106(3):865-876
In this investigation, in order to improve bonding strength between superabrasive/metal matrix/grinding substrate, life span of grinding wheel, and grinding using small grits in continuous grinding simultaneously to fit for high speed and high precision machining in industry, coaxial powder feeding laser cladding method with CAD/CAM technology is introduced to manufacture textured CBN/CuSnTi–grinding wheels. The morphology of CBN grit on laser-cladding layer under optimized laser-cladding parameters and a pit created by fallen-off CBN on laser-cladding layer with lower laser–cladding energy density are observed by scanning electron microscope (SEM). The element distributions of interfaces of CBN/CuSnTi/AISI 1045 are analyzed by SEM and energy disperse spectroscope (EDS). The morphology and elements distribution of residual resultants on the surface of CBN grits etched by nitric acid are analyzed by SEM and EDS. Comparative-grinding process between laser cladding–grinding wheel (LCGW) and customized electroplated grinding wheel (EGW) is analyzed with grinding forces and temperature aspects respectively. The wear morphology of CBN grits on LCGW after grinding is observed by SEM. The results show that CBN grit with integrate cutting edges can protrude 50% height of its diameter on laser-cladding layer under optimized laser–cladding parameters. Fe, N, Ti, and B segregates attached to the interfaces of CBN/CuSnTi/AISI 1045 with Cu and Sn distributed uniformly in the laser-cladding layer. Residual resultants on CBN can be divided into two parts based on the distances from the surface of CBN grits. The grinding forces (Fz and Fy) and grinding temperature from LCGW are lower than those from EGW. The wear conditions of CBN on laser cladding are three parts: microfracture, cleavage plane, and wear-out. 相似文献
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金属结合层包覆单列磨粒小直径CBN砂轮在端面磨削过程中突出高度不同的CBN磨粒相继发生后面磨损、切削刃破碎和脱落,产生了砂轮自锐效应。砂轮磨削力呈现低频起伏和高频波动变化的特征,这是由于磨削过程中CBN磨粒后面磨损钝化使磨削力增大以及随后磨钝磨粒破碎变得锐利使磨削力减小的综合作用结果。砂轮磨削过程受到CBN磨粒性能及其切削刃状态的支配,多晶强韧CBN磨粒(BORAZON550,GE产品)耐磨性改善、磨粒微细破碎保持了砂轮的锐利性,延长了单个磨粒服务时间,突出高度不同的磨粒加入磨削过程的批次效应显著,磨削力低频起伏明显,单晶CBN磨粒(BORAZON500,GE产品)破碎范围大有效降低了磨粒切削刃突出高度、新磨粒加入磨削的过程具有连续性,磨削力高频波动明显。 相似文献
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Understanding the residual stress distribution in brazed polycrystalline CBN abrasive grains 总被引:1,自引:0,他引:1
Yejun Zhu Wenfeng Ding Xin Huang Honghua Su Guoqin Huang 《The International Journal of Advanced Manufacturing Technology》2017,88(1-4):97-106
This article investigates the brazing-induced residual stresses in the polycrystalline cubic boron nitride (PCBN) abrasive grains based on finite element simulation. The effects of embedding depth and gap thickness on the residual stress distribution in brazed PCBN grains are discussed. Results obtained show that, compared with the Ag-Cu-Ti alloy joining CBN grains and AISI 1045 steel substrate, the AlN binder materials in the polycrystalline CBN grains always have a greater effect on the brazing-induced residual stresses; meanwhile, large residual tensile stresses usually exist at the interface between the microcrystalline CBN particles and AlN binders. In comparison to the embedding depth, the gap thickness has little influence on the brazing-induced residual stresses. Furthermore, compared with the other embedding depth, in the case of the embedding depth of 40 %, the residual stresses in the brazed PCBN grain are generally the lowest in the grain bottom and the largest in the grain top surface. Finally, the finite element model applied in the current simulation work is validated through measurement experiments of the brazing-induced residual stresses in the monocrystalline CBN grain. 相似文献
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钎焊单层金刚石砂轮关键问题的研究 总被引:8,自引:1,他引:8
概述了用活性钎料将金刚石磨料钎焊到钢基体表面制作单层金刚石砂轮,比传统的单层电镀金刚石钞轮具有明显的工艺优势。分析指出了钎焊工艺用现存的关键问题,即如何实现金刚石磨料与合金钎料层高的结合强度,钎料层厚度的均匀性和金刚石磨料的有序排布。给出了可行的解决方案,即利用Ag-Cu-Cr或Ni-Cr等活性钎料与金刚石界面化学反应生成的Cr7C3和Cr23C7,实现钎料层与金刚石间的高强度结合;通过化地貌优化,优化出磨粒排布方式,然后按优化的结果排布磨料。 相似文献
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Wen-Feng Ding Jiu-Hua Xu Zhen-Zhen Chen Hong-Hua Su Yu-Can Fu 《The International Journal of Advanced Manufacturing Technology》2010,51(5-8):541-550
Wear behavior and mechanism of single-layer brazed CBN abrasive wheels during creep-feed grinding nickel-based superalloy K424 was investigated. Grinding force and temperature acting on the abrasive wheels were measured. Optical microscopy and scanning electron microscopy were utilized to detect grain protrusion and wheel wear morphology. The normal distribution of the protrusion height of the brazed CBN grains on the wheel surface was determined. The results show that, though the grinding zone temperature is merely about 180°C during creep-feed grinding nickel-based superalloy, the grinding heat still has an important effect on the grain wear owing to the high temperature of the individual grain up to 500–600°C. Wear patterns of brazed wheels are composed of mild wear (attritious wear and grain micro-fracture) and severe wear (grain macro-fracture, erosion of the bonding layer). Strong joining of brazed CBN grains and Ag–Cu–Ti bonding layer improves significantly the resistance to grain pullout. 相似文献