CHINESE JOURNAL OF APPLIED MECHANICS 130 Microscopic strength model for eutectic composite ceramics with platelet defects Fu Yunwei Liu Xiequan Ni Xinhua Chen Cheng Abstract:According to the distribution feature of inherent defect in eutectic ceramics a relevant micro-mechanic model is established.Defects are assumed to be platelet and matrix around is rans stress field is obtained basedon damage theory,and Griffith strength of anisotropic material is obtained based on equivalent inclusion method.By considering the random tropism of defects,the relationship between defect size, defect fraction and strength is analyzed.Result obtained indicates that strength and reciprocal of defect radius's quadratic root reveals liner relation.The strength reduces as defect size increase and this reduction is sharp especially when the defect is small.Defects fraction has significant itte fraction change may ce compsie rengh reduce rapily as the than property of matrix has great influence on defect extending,and defect always extends from the smaller axis in isotropic matrix while it will extend from the axis of greater elastic modulus for penny shaped defect in anisotropic,and finally the defect shape and elastic modulus keep the specific proportional relation under simple tension condition Keywords:platelet defect,equtvalent inclusion method.microscopic strength model,Griffith strength. Improved threshold de-noising of embedded piezoelectric ultrasonic signal based on lifting wavelet Wang Qin Chen Yu Tan Bin Li Pengcheng Xu Zhilong Abstra:De-noising is akey step to improve the detection of structure and to realize structures to be intelligent.On the basis of traditional wavelet threshold de-noising akin of modified threshold de-noising technique based on lifting wavelets is put forwarded.The measured ultrasonic signal is de-noised on conditions of different SNR(Signal Noise Ratio)by the modified method and traditional method.respectively.Results obtained show that the modified method can be able to reduce signal oscillation Compared with hard and soft threshold de-noising.SNR value increased by58%at most and MSE (Mear Square Error)value is creased by 64.28%at least.Furthermore,the effectiveness of the proposed method is verified by the Wigner-Ville time-frequency distribution of the measured signal. Keywords:lifting wavelet.piezoelectric.embedded.concrete.ultrasonic. Analytical solutions of temperature field in the concrete slab on fire Tang Songhua2 Luo Yingshe Peng Xianghua (1 Key Laboratory .410004.Ch a,Chin Abstract:Analytical solutions are important in the study of effect of fire temperature field on components in it.vi CHINESE JOURNAL OF APPLIED MECHANICS Vol.30 Microscopic strength model for eutectic composite ceramics with platelet defects Fu Yunwei1 Liu Xiequan2 Ni Xinhua1 Chen Cheng1 (1 Department of Vehicle and Electrical Engineering, Ordnance Engineering College, 050003, Shijiazhuang, China; 2 Department of Basic Courses, Ordnance Engineering College, 050003, Shijiazhuang, China) Abstract: According to the distribution feature of inherent defect in eutectic ceramics, a relevant micro-mechanic model is established. Defects are assumed to be platelet, and matrix around is transversely isotropic. Effective stress field is obtained based on damage theory, and Griffith strength of anisotropic material is obtained based on equivalent inclusion method. By considering the random tropism of defects, the relationship between defect size, defect fraction and strength is analyzed. Result obtained indicates that strength and reciprocal of defect radius’s quadratic root reveals liner relation. The strength reduces as defect size increase and this reduction is sharp especially when the defect is small. Defects fraction has significant influence on strength also, a little fraction change may cause composite strength reduce rapidly as the fraction is lower than 3%. Anisotropic property of matrix has great influence on defect extending, and defect always extends from the smaller axis in isotropic matrix while it will extend from the axis of greater elastic modulus for penny shaped defect in anisotropic, and finally the defect shape and elastic modulus keep the specific proportional relation under simple tension condition. Keywords: platelet defect, equivalent inclusion method, microscopic strength model, Griffith strength. Improved threshold de-noising of embedded piezoelectric ultrasonic signal based on lifting wavelet Wang Qin Chen Yu Tan Bin Li Pengcheng Xu Zhilong (College of Electronics and Information Engineering, Sichuan University, 610065, Chengdu, China) Abstract: De-noising is a key step to improve the detection quality of piezoelectric embedded concrete structures, and to realize concrete structures to be intelligent. On the basis of traditional wavelet threshold de-noising, a kind of modified threshold de-noising technique based on lifting wavelets is put forwarded. The measured ultrasonic signal is de-noised on conditions of different SNR (Signal Noise Ratio) by the modified method and traditional method, respectively. Results obtained show that the modified method can be able to reduce signal oscillation. Compared with hard and soft threshold de-noising, SNR value increased by 58.32% at most and MSE (Mean Square Error) value is decreased by 64.28% at least. Furthermore, the effectiveness of the proposed method is verified by the Wigner-Ville time-frequency distribution of the measured signal. Keywords: lifting wavelet, piezoelectric, embedded, concrete, ultrasonic. Analytical solutions of temperature field in the concrete slab on fire Tang Songhua1,2 Luo Yingshe3 Peng Xianghua4 (1 Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, 210096, Nanjing, China; 2 School of Civil and Architectural Engineering, Central South University, 410075, Changsha, China; 3 Institute of Rheological Mechanics and Material Engineering, Central South University of Forestry and Technology, 410004, Changsha, China; 4 Institute of Foreign Affair, Central South University of Forestry and Technology, 410004, Changsha, China) Abstract: Analytical solutions are important in the study of effect of fire temperature field on components in it