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1. Buckling Solutions of FGM Timoshenko Beams in Terms of Those of the Homogenous Euler-Bernoulli Beams | |||
Shirong Li,Zeqing Wan | |||
Mechanics 27 January 2012 | |||
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Abstract:Analytical relationships between the solutions of buckling of functionally graded material (FGM) Timoshenko beams and those of the homogenous Euler-Bernoulli beams subjected to axial compressive load were investigated for different boundary conditions. Based on the first order shear deformation theory, governing equation of buckling of FGM beams with the material properties changing continuously arbitrarily in the thickness direction were derived only in terms of the deflection, which has the same form as that of the homogenous Euler-Bernoulli beams. By solving the governing equation with specific boundary conditions, an analytical relationship between the critical buckling loads of the FGM Timoshenko beams and those of the corresponding Euler-Bernoulli beams were obtained which is valid for the clamped-clamped(C-C), simply supported-simply supported (S-S) and clamped-free(C-F) end constraints. Unfortunately, the above mentioned relationship is not valid for the beams with clamped-simply supported (C-S) ends. However, a simple eigenvalue equation is presented to find the critical buckling load for a C-S FGM Timoshenko beam. Consequently, buckling loads of FGM Timoshenko beams with C-C, S-S and C-F ends can be simplified as calculations of two coefficients determined by the material gradients and the geometry of the FGM beams when the critical buckling load parameters are known.) | |||
TO cite this article:Shirong Li,Zeqing Wan. Buckling Solutions of FGM Timoshenko Beams in Terms of Those of the Homogenous Euler-Bernoulli Beams[OL].[27 January 2012] http://en.paper.edu.cn/en_releasepaper/content/4463997 |
2. FE analysis of creep deformation of single crystal under temperature gradient | |||
YU Qingmin | |||
Mechanics 17 January 2012 | |||
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Abstract:In this study, thin-walled cylindrical specimen was used to model air-cooled gas turbine blade. The deformation characteristic during creep under temperature gradient was investigated by finite element method. The creep parameters along [001] and elastic constants were taken from the experiment results of nickel-based single crystal superalloy DD3. The results show that the temperature gradient has notable influence on stress and strain distributions during creep. The stress of low temperature zone increases and that of high temperature zone decreases with the development of creep. The lower the temperature is, the higher the stress is. The increase of stress induces the increase of strain rate in low temperature zone. The strain rate in high temperature zone decreases due to the stress drop. The rapid changes of stress value and distribution result in the redistribution of strain in different temperature zone. The crack will appear firstly in low temperature zone for the higher stress and strain. | |||
TO cite this article:YU Qingmin. FE analysis of creep deformation of single crystal under temperature gradient[OL].[17 January 2012] http://en.paper.edu.cn/en_releasepaper/content/4462846 |
3. Experimental study on creep-ratcheting-fatigue interaction of SS304 stainless steel at room and high temperatures | |||
Zhang Juan,Kang Guozheng,Gao Qing,Liu Yujie | |||
Mechanics 17 January 2012 | |||
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Abstract:The creep, ratcheting behaviour and fatigue failure, as well as their interaction were investigated by uniaxial cyclic stressing tests for SS304 stainless steel at room temperature, 100oC and 300oC. The effects of mean stress, stress amplitude, stress rate and the peak stress holds on the ratcheting strain and final failure life were discussed. Simultaneously, the variations of responded strain amplitude with the number of cycles were illustrated to discuss the interaction of creep, ratcheting behaviour and fatigue failure. The experimental results show that the creep and ratcheting behaviour for SS304 stainless steel at different temperatures are different. The fatigue life of the material at room and high temperatures all depend greatly on mean stress, stress amplitude, stress rate and the peak stress holds of uniaxial cyclic stressing. And the material show different kind of failure modes: ratcheting failure due to large ratcheting strain and fatigue failure due to low-cycle fatigue with nearly constant responded strain amplitude. | |||
TO cite this article:Zhang Juan,Kang Guozheng,Gao Qing, et al. Experimental study on creep-ratcheting-fatigue interaction of SS304 stainless steel at room and high temperatures[J]. |
4. Microstructure in the near-tip process zone for an impermeable macrocrack in piezoelectric materials | |||
Liu Q D,Cui Y H,Liu M B | |||
Mechanics 10 January 2012 | |||
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Abstract:The influence of microstructures e.g. microcracks on the near-tip stress-electric field for an impermeable macrocrack in piezoelectric materials was studied using the existing pseudo-traction methods. The macrocrack could be modeled as impermeable one for its surrounding insulation environment whilst the microcracks could be modeled as permeable slit cracks due to poling or other sources without the crack surface opening effect. The conservation of the J-integral holds true for the configuration with a permeable microcrack near the tip of an impermeable macrocrack. Finally, the influence of the permeable microcrack on the macrocrack tip could be modeled as the stress intensity factor (SIF), electric displacement intensity factor (EDIF), and mechanical strain energy release rate (MSERR) in comparison with the previous work. It is found that the divergences between the present permeable microcrack model and the previous study are remarkable under combined electric-mechanical loading. The disturbance of the permeable microcracks on the near-tip stress-electric field due to the positive electric field loading is always much smaller than that given in the previous impermeable model. | |||
TO cite this article:Liu Q D,Cui Y H,Liu M B. Microstructure in the near-tip process zone for an impermeable macrocrack in piezoelectric materials[OL].[10 January 2012] http://en.paper.edu.cn/en_releasepaper/content/4460318 |
5. Finite element analysis on the permeable and impermeable hole in ferroelectrics | |||
Liu Qida,Cui Yuanhu | |||
Mechanics 22 December 2011 | |||
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Abstract:The finite element method is used to study the creeping polarization and strains around a circular hole in the ferroelectric ceramics under various constant levels of electric field. Two kinds of electrical boundary conditions, the permeable and impermeable boundary conditions, are applied on the rim of the hole, while the evolution of strains and polarization distribution is computed around the hole. The strain and polarization distribution around the hole are significantly different for two conditions, which is confirmed by the birefringence measurement on PLZT specimen with an impermeable hole. | |||
TO cite this article:Liu Qida,Cui Yuanhu. Finite element analysis on the permeable and impermeable hole in ferroelectrics[OL].[22 December 2011] http://en.paper.edu.cn/en_releasepaper/content/4457060 |
6. Acoustic emission analysis on tensile failure of air plasma-sprayed thermal barrier coatings | |||
Yao Wangbin,Dai Cuiying,Mao Weiguo,Lu Chunsheng,Zhou Yichun | |||
Mechanics 04 December 2011 | |||
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Abstract:An acoustic emission technique was used to monitor the cracking behavior and fracture process of thermal barrier coatings subjected to tensile loading. Acoustic emission signals were extracted and preformed by fast Fourier transform, and their corresponding characteristic frequency spectrums and dominant bands were obtained to reveal fracture modes. Three different characteristic frequency bands were confirmed, corresponding to substrate deformation, surface vertical crack and interface delamination, with the aid of scanning electronic microscopy observations. A map of the tensile failure mechanism of air plasma-sprayed thermal barrier coatings was established. Using experimental data, the fracture strength and interface shear strength were estimated as 45.73 ± 3.92 MPa and 20.51 ± 1.74 MPa, respectively, which are well agreement with available results.. | |||
TO cite this article:Yao Wangbin,Dai Cuiying,Mao Weiguo, et al. Acoustic emission analysis on tensile failure of air plasma-sprayed thermal barrier coatings[OL].[ 4 December 2011] http://en.paper.edu.cn/en_releasepaper/content/4453646 |
7. Four parallel non-symmetric permeable mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane | |||
ZHOU Zhengong | |||
Mechanics 25 November 2011 | |||
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Abstract:The behavior of four parallel non-symmetric permeable finite length cracks in a functionally graded piezoelectric/piezomagnetic material plane subjected to anti-plane shear stress loading was studied by the Schmidt method. The problem was formulated through Fourier transform into four pairs of dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. To solve the dual integral equations, the displacement jumps across the crack surfaces were directly expanded as a series of Jacobi polynomials. The results show that the stress, the electric displacement and the magnetic flux intensity factors at the crack tips depend on the material parameters, the lengths and spacing of cracks. It is also revealed that the crack shielding effect presents in functionally graded piezoelectric/piezomagnetic materials. | |||
TO cite this article:ZHOU Zhengong. Four parallel non-symmetric permeable mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane[OL].[25 November 2011] http://en.paper.edu.cn/en_releasepaper/content/4451508 |
8. First-passage problem of 5DOF strongly nonlinear oscillators under wide-band stochastic excitation | |||
Wu Yongjun,Gao Yangyan,Zhang Lei | |||
Mechanics 04 November 2011 | |||
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Abstract:First-passage problem of 5DOF strongly nonlinear oscillators under wide-band stochastic excitations is studied theoretically in this paper. By using stochastic averaging method, the equations of motion of the original system are reduced to a set of averaged Itô stochastic differential equations about the amplitudes. The 6-dimensional backward Kolmogorov equation and the 5-dimensional Pontryagin equation are established. These two high-dimensional partial differential equations are solved by using finite difference method to yield the conditional reliability function and mean first-passage time, respectively. The accuracy of the theoretical method is verified by Monte Carlo digital simulation. | |||
TO cite this article:Wu Yongjun,Gao Yangyan,Zhang Lei. First-passage problem of 5DOF strongly nonlinear oscillators under wide-band stochastic excitation[OL].[ 4 November 2011] http://en.paper.edu.cn/en_releasepaper/content/4448523 |
9. Methods on Applying Stream Function Boundary Conditions in DQ Modeling of 2D Lid-driven Cavity Flow | |||
WANG Tong,GE Yaojun,CAO Shuyang | |||
Mechanics 25 September 2011 | |||
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Abstract:The two-dimensional (2D) lid-driven cavity flow is simulated by applying the ordinary differential quadrature (DQ) method to solve the incompressible Navier-Stokes equations in stream function-vorticity form. There are two boundary conditions, one Dirichlet and one Neumann, for the stream function at each boundary though its governing equation is just second-order. Analysis on this over-specified problem is carried out, based on which a new method is proposed to implement these boundary conditions: the Neumann condition is just considered in the vorticity equation while only the Dirichlet condition is applied in the stream function equation. Availability of this method is verified by comparing its numerical results with benchmark data. Two other methods, the One-layer approach and the Two-layer approach, introduced by Shu and Xue (1998) are also shown as a contrast, and detailed formulations are repeated especially for the One-layer approach to reveal its underlying problem: this method is sensitive to the parity of grid numbers in two directions. Comparison between the present method and the Two-layer approach indicates that the former is more convenient to be used in practice for it avoiding the over-specified problem, and also more accurate, while the latter is relatively more efficient. | |||
TO cite this article:WANG Tong,GE Yaojun,CAO Shuyang. Methods on Applying Stream Function Boundary Conditions in DQ Modeling of 2D Lid-driven Cavity Flow[OL].[25 September 2011] http://en.paper.edu.cn/en_releasepaper/content/4442193 |
10. Aerodynamic Effects on Airfoil with Leading and Tailing Edges Protuberances | |||
Zou Lin | |||
Mechanics 31 August 2011 | |||
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Abstract:The effect of the protuberances leading and tailing edges on the aerodynamic characteristics of a modified airfoil is studied using the large eddy simulations. A more gentle lift characteristic is obtained during stall. For angles of attack less than the baseline stall angle of a NACA0012 airfoil, a lift coefficient reduction was observed for the modified airfoil, while the lift coefficient increases up to 37% greater than that of a NACA0012 airfoil when the angle of attack is larger than the baseline stall angle of the NACA0012 airfoil. | |||
TO cite this article:Zou Lin. Aerodynamic Effects on Airfoil with Leading and Tailing Edges Protuberances[OL].[31 August 2011] http://en.paper.edu.cn/en_releasepaper/content/4441659 |
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