【作者】 查炎锋；

【导师】 张宇民；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2008， 硕士

【摘要】 磨削是SiC陶瓷主要的机械加工方式,磨削过程在陶瓷表面产生大量的残余应力,对SiC陶瓷的性能产生很大的影响。本文通过有限元模拟计算和X射线衍射测量的方法分析了不同磨削条件下磨削过程引入的残余应力。并且,采用抛光和热处理对磨削后的试样进行处理,比较不同处理方法对磨削残余应力和弯曲强度的影响。采用有限元模拟计算和X射线衍射的方法来分析磨削过程中的残余应力。通过移动加载和移动热源模型来模拟磨削过程,分别计算出磨削过程中产生的机械残余应力和热残余应力。计算结果表明,在湿磨情况下,由于冷却液的冷却作用,热残余应力几乎可以忽略,试样表面主要是机械残余压应力且随磨削深度的增加而减小。计算结果得到X射线衍射测量结果的证实。不同的处理手段对材料的残余应力和特征强度的影响有较大的不同。退火、抛光等处理手段能有效的减小磨削后试样中的残余应力数值,其中800℃退火后残余应力值最小。同时,韦伯模量的计算表明:退火、抛光过程能引起材料内部裂纹的变化,韦伯模量越小,裂纹平均尺寸越大,材料的弯曲强度越小,而磨削后的残余压应力会提高材料的弯曲强度,残余应力和韦伯模量的双重作用使得未作任何处理的磨削试样的特征强度值最大;韦伯模量值较大的800℃退火特征强度次之;抛光过程残余应力对材料的强度没有贡献,但由于其韦伯模量大于1000℃退火,故特征强度第三,1000℃退火特征强度最小。通过分析磨削表面状态发现,在XPS分析中,磨削后试样表面Si-O键峰比例占31.3%,与表面暴露于空气中的SiC材料的Si-O键峰比例相近,说明磨削过程中未发生明显的氧化。退火处理对于试样的表面形貌和粗糙度的影响不大;抛光处理能极大的改善试样的表面质量,降低粗糙度。通过试样的断口形貌分析,试样断面呈现脆性断裂方式包括穿晶断裂及部分沿晶断裂。更多还原

【Abstract】 Grinding is the main mechanical machine method, Homever there will introduce many residual stress in the materials, Which will greatly effect the performance of the materials. Here we will analyze the residual stress introduced by grinding in different feed speeds through finity element calculation and X ray diffraction measurement. The heat treatment and polishing method were adopted to treat the specimens in order to compare and analyze the residual stress and flexural strength with different treatments.The residual stress introduced by grinding process is analysised by finity element and X-ray diffraction methods. Using the locomotive loading and locomotive heat source calculate the mechanical and thermic residual stress separately. The result shows that the thermic residual stress can be ignored in waterish grinding because of the cooling effect of the refrigerant, the main residual stress in the material surface is the compress residual stress, which is reduce with the feed speeds slow down. And that is proved by the X-ray diffraction methods.The different treatments to the material cause the different effect to the material performances. Anneal in different temperature and polishing process can reduce the residual stress effectively, After 800 degree Anneal the residual stress is the lowest. The result of the weibull modulus calculation shows that anneal and polishing process can change the crack size inside the material. the weibull modulus stand for the crack average size, the bigger of the crack average size, the lower of the flexural strength. While the compress residual stress can improve the strength, and residual stress and weibull modulus work together make the specimens which just ground without treatment have the biggest strength; the 800 degree anneal specimens second; the polishing specimens third and the 1000 degree anneal lowest.Analysis the surface situation of the ground specimens and judge the break-out way. The XPS measurement shows that the Si-O chemical bond is 31.3% in grind surface, Which is similar with the SiC material exposed in the air. This means that in the grinding process there is little oxidation occurrence. The anneal treatment have little effect to the specimens surface shape and roughness; while the polishing process can improve the surface greatly and reduce roughness. The main failure way of the specimens in the three point flexural process is brittle fracture including inter-granular and intra-granular fractured patterns.更多还原