Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stre...Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics(FVDAM). Compared with the results calculated by failure criterion based on macro-stress field(the maximum stress criteria and Hashin criteria) and micro-stress field(Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.展开更多
Experimental research was conducted to study the structural behaviors of a steel roof truss model without fire-proof coating under pool fire conditions. The data of temperature distribution and displacements of typica...Experimental research was conducted to study the structural behaviors of a steel roof truss model without fire-proof coating under pool fire conditions. The data of temperature distribution and displacements of typical members were obtained. It is found that the temperature distribution of environment inside the structure, which is found to be in accordance with the multi-zone model with height, has a decisive effect on the tempera^tre evolution of steel members. Besides, it can also be observed that due to the restriction and coordination among the truss members in the localized fire, the maximum relative deflection, which occurs at the mid-span of the top chord, is relatively slight and has not exceeded 1 mm under experimental conditions. On the other hand, the column experiences a notable thermal expansion during the test. Then, a finite element model is presented and validated by the test results.展开更多
The free surface flow generated by twin-cylinders in forced motion submerged beneath the free surface is studied based on the boundary element method. Two relative locations, namely, horizontal and vertical, are exami...The free surface flow generated by twin-cylinders in forced motion submerged beneath the free surface is studied based on the boundary element method. Two relative locations, namely, horizontal and vertical, are examined for the twin cylinders. In both cases, the twin cylinders are starting from rest and ultimately moving with the same constant speed through an accelerating process. Assuming that the fluid is inviscid and incompressible and the flow to be irrotational, the integral Laplace equation can be discretized based on the boundary element method. Fully-nonlinear boundary conditions are satisfied on the unknown free surface and the moving body surface. The free surface is traced by a Lagrangian technique. Regriding and remeshing are applied, which is crucial to quality of the numerical results. Single circular cylinder and elliptical cylinder are calculated by linear method and fully nonlinear method for accuracy checking and then fully nonlinear method is conducted on the twin cylinder cases, respectively. The generated wave elevation and the resultant force are analysed to discuss the influence of the gap between the two cylinders as well as the water depth. It is found that no matter the kind of distribution, when the moving cylinders are close to each other, they suffer hydrodynamic force with large absolute value in the direction of motion. The trend of force varying with the increase of gap can be clearly seen from numerical analysis. The vertically distributed twin cylinders seem to attract with each other while the horizontally distributed twin cylinders are opposite when they are close to each other.展开更多
A mathematical model and finite element model for analysis of temperature rise of the hoisting machine brake sys- tem was constructed, limit conditions were defined, and the law of temperature rise of brake shoes duri...A mathematical model and finite element model for analysis of temperature rise of the hoisting machine brake sys- tem was constructed, limit conditions were defined, and the law of temperature rise of brake shoes during emergent brake course was analyzed and calculated by using finite element software. By analyzing the calculation results, the law of tempera- ture change of surface of brake disk and shoes during the braking process was found. The law of brake shoes surface tempera- ture distribution and the law of temperature change along with thickness of brake shoes at brake time 0.5 s, 1.0 s and 1.5 s was analyzed. A hoisting machine emergent braking test was carried out. Finally, the author concluded that velocity rebound in the process of hoisting machine emergent brake is due to decreased friction coefficient caused by the temperature rise of the brake shoes surface.展开更多
High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes th...High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes the surface-to-volume ratio.It can be seen as a plate structure stiffened by veins.Compared with a high-speed machine tool working table,leaf veins play a role of supporting part which is similar to that of stiffening ribs,and they can provide some new design ideas for lightweight design of the table.In this paper,distribution rules of leaf veins were investigated,and a structural bionic design for the table was achieved based on regulation of leaf veins.First,statistical analysis on geometric structure of leaf veins was carried out,and four distribution rules were obtained.Then,relevant mechanical models were developed and analyzed in finite element software.Based on the results from mechanical analysis on those relevant models,the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved.Both simulation and experimental verifications were carried out,and results showed that the average displacement of the working table was reduced by about 33.9%.展开更多
基金Project(51075204)supported by the National Natural Science Foundation of ChinaProjects(2012ZB52026,2014ZB52024)supported by the Aeronautical Science Foundation of ChinaProject(NS2014024)supported by the Fundamental Research Funds for the Central Universities,China
文摘Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics(FVDAM). Compared with the results calculated by failure criterion based on macro-stress field(the maximum stress criteria and Hashin criteria) and micro-stress field(Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.
基金Project(50706059) supported by the National Natural Science Foundation of ChinaProject(HZ2009-KF05) supported by Open Fund of State Key Laboratory of Fire Science of University of Science and Technology in ChinaProject supported by the Fundamental Research Funds for the Central Universities of China
文摘Experimental research was conducted to study the structural behaviors of a steel roof truss model without fire-proof coating under pool fire conditions. The data of temperature distribution and displacements of typical members were obtained. It is found that the temperature distribution of environment inside the structure, which is found to be in accordance with the multi-zone model with height, has a decisive effect on the tempera^tre evolution of steel members. Besides, it can also be observed that due to the restriction and coordination among the truss members in the localized fire, the maximum relative deflection, which occurs at the mid-span of the top chord, is relatively slight and has not exceeded 1 mm under experimental conditions. On the other hand, the column experiences a notable thermal expansion during the test. Then, a finite element model is presented and validated by the test results.
基金Foundation item： Supported by the Lloyd＇s Register Foundation, the Fundamental Research Funds for the Central Universities （Gram No. HEUCF140115）, the National Natural Science Foundation of China （11102048, 11302057）, the Research Funds for State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University （Grant No. 1310）, and the Specialized Research Fund for the Doctoral Program of Higher Education of China （20132304120028）.
文摘The free surface flow generated by twin-cylinders in forced motion submerged beneath the free surface is studied based on the boundary element method. Two relative locations, namely, horizontal and vertical, are examined for the twin cylinders. In both cases, the twin cylinders are starting from rest and ultimately moving with the same constant speed through an accelerating process. Assuming that the fluid is inviscid and incompressible and the flow to be irrotational, the integral Laplace equation can be discretized based on the boundary element method. Fully-nonlinear boundary conditions are satisfied on the unknown free surface and the moving body surface. The free surface is traced by a Lagrangian technique. Regriding and remeshing are applied, which is crucial to quality of the numerical results. Single circular cylinder and elliptical cylinder are calculated by linear method and fully nonlinear method for accuracy checking and then fully nonlinear method is conducted on the twin cylinder cases, respectively. The generated wave elevation and the resultant force are analysed to discuss the influence of the gap between the two cylinders as well as the water depth. It is found that no matter the kind of distribution, when the moving cylinders are close to each other, they suffer hydrodynamic force with large absolute value in the direction of motion. The trend of force varying with the increase of gap can be clearly seen from numerical analysis. The vertically distributed twin cylinders seem to attract with each other while the horizontally distributed twin cylinders are opposite when they are close to each other.
基金Supported by the National Natural Science Foundation of China （50875252）
文摘A mathematical model and finite element model for analysis of temperature rise of the hoisting machine brake sys- tem was constructed, limit conditions were defined, and the law of temperature rise of brake shoes during emergent brake course was analyzed and calculated by using finite element software. By analyzing the calculation results, the law of tempera- ture change of surface of brake disk and shoes during the braking process was found. The law of brake shoes surface tempera- ture distribution and the law of temperature change along with thickness of brake shoes at brake time 0.5 s, 1.0 s and 1.5 s was analyzed. A hoisting machine emergent braking test was carried out. Finally, the author concluded that velocity rebound in the process of hoisting machine emergent brake is due to decreased friction coefficient caused by the temperature rise of the brake shoes surface.
基金supported by the National Natural Science Foundation of China (Grant No. 50975012)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091102110022)
文摘High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes the surface-to-volume ratio.It can be seen as a plate structure stiffened by veins.Compared with a high-speed machine tool working table,leaf veins play a role of supporting part which is similar to that of stiffening ribs,and they can provide some new design ideas for lightweight design of the table.In this paper,distribution rules of leaf veins were investigated,and a structural bionic design for the table was achieved based on regulation of leaf veins.First,statistical analysis on geometric structure of leaf veins was carried out,and four distribution rules were obtained.Then,relevant mechanical models were developed and analyzed in finite element software.Based on the results from mechanical analysis on those relevant models,the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved.Both simulation and experimental verifications were carried out,and results showed that the average displacement of the working table was reduced by about 33.9%.
