陈道勇
,
张剑寒
,
张宇民
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2009.06.014
采用CVD工艺在反应烧结碳化硅(RB-SiC)反射镜坯体上沉积了一层致密的碳化硅薄膜作为反射镜镜面.CVD-SiC和RB-SiC热物理性能上的差异引起的热残余应力和热变形,在很大程度上影响反射镜的质量,本文采用有限单元法计算了沉积过程中反射镜的温度场、应力场和热变形,采用X射线衍射方法测试了薄膜表面的残余应力.分析结果表明,薄膜存在较大的残余应力,包括热应力和本征应力,两者量值相当,热变形很小.
关键词:
碳化硅
,
反射镜
,
有限元
,
热应力
,
热变形
K.H.Chang
,
G.C.Jang
,
C.H.Lee
,
S.H.Lee
材料科学技术（英文）
In the squeeze casting process, loaded high pressure (over approximately 100 MPa) and high temperature influence the thermo-mechanical behavior and performance of the used metal mold. Therefore, to safely maintain the metal molds, the thermo-mechanical characteristics (temperature and thermal stress) of metal mold in the squeeze casting must be investigated. In this paper, temperature and thermal stress distribution of steel mold in squeeze casting process were investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis considering temperature-dependent thermophysical and mechanical properties of the steel mold.
关键词:
Squeeze casting
,
null
,
null
,
null
Ziliang LI
,
Junruo CHEN
,
Miao ZHANG
,
Yihong GUAN
材料科学技术（英文）
Based on a transient temperature distribution of a 45 steel cylinder workpiece during magnetic quenching, which was obtained by solving the governing equations with nonlinear boundary on the condition of coupling effects of heat-magnetism. According to the theory of thermal non-elasticity, computational mechanics, ferromagnetism and phase transformation, a new constitutive equation considering effects of phase transformation is proposed and solved by means of finite element method. The transient thermal stress and residual stress are obtained and the influencing factors on the thermal stress of magnetic field are analyzed and discussed.
关键词:
Numerical simulation
,
null
,
null
,
null
王海棠
,
李元东
,
杨贵荣
,
刘生龙
,
郝远
表面技术
doi:10.3969/j.issn.1001-3660.2009.06.012
为了满足工况条件对表面功能材料在高温、摩擦和激冷激热等方面的要求,采用负压铸渗法在铸铁表面制备了Ni/WC复合渗层,观察了渗层与基体结合形貌,研究了渗层的热疲劳性能.结果表明:在热循环过程中,渗层与基体表面出现了不同程度的氧化现象,裂纹开始出现的热循环次数随着渗层中WC含量的增加而增加,表面复合渗层最终剥落破损的热循环次数随着WC含量的增加呈先增加后减少的趋势.
关键词:
渗层
,
热疲劳
,
热应力
Xiancheng ZHANG
,
Binshi XU
,
Haidou WANG
,
Yixiong WU
材料科学技术（英文）
The mechanical integrity and reliability of coated devices are strongly affected by the residual stresses in thin films and coatings. However, due to the metallurgical complexity of materials, it is rather difficult to obtain a closed-form solution of residual stresses within multilayered coatings (e.g. functionally graded coatings, FGCs). In this paper, an analytical model is developed to predict the distribution of residual stresses within multilayered coatings. The advantage of this model is that the solution of residual stresses is independent of the number of layers. Specific results are obtained by calculating elastic thermal stresses in ZrO2/NiCoCrAlY FGCs, which consist of different material layers. Furthermore, the residual stress distribution near the edges and the stress-induced failure modes of coating are also analyzed. The topics discussed provide some insights into the development of a methodology for designing fail-safe coating systems.
关键词:
Multilayered coatings
,
null
,
null
