True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-tru...True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-true curve,the stress increases with the increase of strain to 0.15,then dramatically decreases with the increase of strain to 0.80,and finally keeps almost a horizontal line.Meanwhile,initial elongated grains are gradually changed into equiaxed grains and the initial strong Brass {0 1 1} <2 1 1> and S {1 2 3} <6 3 4> orientations are turned into nearly random orientation with increasing strain.All these results suggest that dislocation activity is the dominant mechanism during the first stage,then dynamic recrystallization occurs,and grain rotation is expected as an accommodation for grain boundary sliding(GBS).At larger strains,grain boundary migration(GBM) becomes necessary to accommodate GBS.展开更多
Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils ...Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils are generally used for electromagnetic forming of sheet metals. However, with this type of coil the central portion of the workpiece experiences marginal magnetic force. This leads to in-sufficient deformation at this portion and other problems like air entrapment. In this study, a conceptual design of flat coil was proposed for better distribution of magnetic forces over the workpiece. Comparative analysis of distribution of magnetic force, magnetic field and current density using the proposed and the existing coil designs were carried out using FEM. The result indicates that the proposed coil design produces comparatively better magnetic force distribution over the workpiece. Calculation of self-inductance of such coils was also carried out and was compared with FE simulation.展开更多
The electromagnetic forming is a procedure of high-speed processing,which favors the increase of the formability of some plastically deformed metals.In order to evaluate the capacity of some light metals,such as alumi...The electromagnetic forming is a procedure of high-speed processing,which favors the increase of the formability of some plastically deformed metals.In order to evaluate the capacity of some light metals,such as aluminum and its alloys,to be deformed through this procedure,it is useful to know the stress and strain state that occurs in the material during forming.In this work,the modeling of stresses and strains in electromagnetically deformed AlMn0.5Mg0.5 sheet was made.The modeling was achieved using the finite element method and it was verified through experimental tests.To determine the residual stresses,the X-ray diffraction method was used.The strains were established by measuring the displacements of the nodes in the network inscribed on the specimen by means of three coordinates measuring machine.A good agreement between the modeling results and experimental data was found.展开更多
Mechanics effect of laser thermal stress is a new manufacturing technology, which uses thermal stress by high power laser acted on the surface of metal material to produce stress field. The technologies such as sheet ...Mechanics effect of laser thermal stress is a new manufacturing technology, which uses thermal stress by high power laser acted on the surface of metal material to produce stress field. The technologies such as sheet metal formation by laser thermal stress, measurement by laser scratching and measurement by XRD (X-ray diffraction) are formed based on mechanics effects of laser thermal stress. The mechanisms of sheet metal formation by laser thermal stress, measurement by laser scratching and measurement by XRD are analyzed, and the theory of photo-mechanics manufacturing and detecting technologies based on laser thermal stress is originally put forward, whose experiment is primitively researched, and the manufacturing theory by mechanics effects of laser thermal stress is established.展开更多
The study illustrates differences between colors of poplar I-214 veneers dyed by reactive blue KN-R and 4 kinds of chemical reagents, and those of treated veneer exposed to UV-ray for 3 days. The results show there ar...The study illustrates differences between colors of poplar I-214 veneers dyed by reactive blue KN-R and 4 kinds of chemical reagents, and those of treated veneer exposed to UV-ray for 3 days. The results show there are some laws in poplar I-214 dyeing and UV-ray attenuation of each chemically treated veneer color. The chemical reaction carded out between cellulose or lignin on veneer surface and dye molecules when they met with. The capability of dyeing and discoloration of veneer is improved by control of dyeing technology, especially chemical treatments; being treated by acetylation and maleic anhydride protects dyed wood discoloration.展开更多
The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed...The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed that different layers are perfectly bonded to each other with piezoelectric actuator patches embedded. The nonlinear equations of motion for the laminated composite piezoelectric rectangular plate are derived from von Karman-type equation and third-order shear deformation plate theory of Reddy. The two-degree-of-freedom dimensionless equations of motion are obtained by using the Galerkin approach to the partial differential governing equation of motion for the laminated composite piezoelectric rectangular plate. The four-dimensional averaged equation in the case of primary parametric resonance and 1:3 internal resonances is obtained by using the method of multiple scales. From the averaged equation, the theory of normal form is used to find the explicit formulas of normal form. Based on the normal form obtained, the energy phase method is utilized to analyze the multi-pulse global bifurcations and chaotic dynamics for the laminated composite piezoelectric rectangular plate. The analysis of the global dynamics indicates that there exist multi-pulse jumping orbits in the perturbed phase space of the averaged equation. Based on the averaged equation obtained, the chaotic motions and the Shilnikov type multi-pulse orbits of the laminated composite piezoelectric rectangular plate are also found by numerical simulation. The results obtained above mean the existence of the chaos in the Smale horseshoe sense for the simply supported laminated composite piezoelectric rectangular plate.展开更多
基金Project(2006DFA53250) supported by the International Science and Technology Cooperation Program of ChinaProject(2005CB623706) supported by the National Basic Research Program of China
文摘True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-true curve,the stress increases with the increase of strain to 0.15,then dramatically decreases with the increase of strain to 0.80,and finally keeps almost a horizontal line.Meanwhile,initial elongated grains are gradually changed into equiaxed grains and the initial strong Brass {0 1 1} <2 1 1> and S {1 2 3} <6 3 4> orientations are turned into nearly random orientation with increasing strain.All these results suggest that dislocation activity is the dominant mechanism during the first stage,then dynamic recrystallization occurs,and grain rotation is expected as an accommodation for grain boundary sliding(GBS).At larger strains,grain boundary migration(GBM) becomes necessary to accommodate GBS.
文摘Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils are generally used for electromagnetic forming of sheet metals. However, with this type of coil the central portion of the workpiece experiences marginal magnetic force. This leads to in-sufficient deformation at this portion and other problems like air entrapment. In this study, a conceptual design of flat coil was proposed for better distribution of magnetic forces over the workpiece. Comparative analysis of distribution of magnetic force, magnetic field and current density using the proposed and the existing coil designs were carried out using FEM. The result indicates that the proposed coil design produces comparatively better magnetic force distribution over the workpiece. Calculation of self-inductance of such coils was also carried out and was compared with FE simulation.
文摘The electromagnetic forming is a procedure of high-speed processing,which favors the increase of the formability of some plastically deformed metals.In order to evaluate the capacity of some light metals,such as aluminum and its alloys,to be deformed through this procedure,it is useful to know the stress and strain state that occurs in the material during forming.In this work,the modeling of stresses and strains in electromagnetically deformed AlMn0.5Mg0.5 sheet was made.The modeling was achieved using the finite element method and it was verified through experimental tests.To determine the residual stresses,the X-ray diffraction method was used.The strains were established by measuring the displacements of the nodes in the network inscribed on the specimen by means of three coordinates measuring machine.A good agreement between the modeling results and experimental data was found.
基金this research from the Scientific Research Fund of Jiangsu Polytechnic University(GrantNo.ZMF07020042)Fund of Jiangsu ProvincialKey Laboratory for Science and Technology of Photo-manufacroring (Grant No.GZ-1-02)the NaturalScience Foundation of the Jiangsu Higher EducationInstitutions of China( Grant No. 08KJB430002 ) is gratefully acknowledged.
文摘Mechanics effect of laser thermal stress is a new manufacturing technology, which uses thermal stress by high power laser acted on the surface of metal material to produce stress field. The technologies such as sheet metal formation by laser thermal stress, measurement by laser scratching and measurement by XRD (X-ray diffraction) are formed based on mechanics effects of laser thermal stress. The mechanisms of sheet metal formation by laser thermal stress, measurement by laser scratching and measurement by XRD are analyzed, and the theory of photo-mechanics manufacturing and detecting technologies based on laser thermal stress is originally put forward, whose experiment is primitively researched, and the manufacturing theory by mechanics effects of laser thermal stress is established.
基金This research was conducted in Japan under the Research Planning of Japan-China Cooperation Project (the Research Project onTimber from Plantion Forests in China: JICA Project).
文摘The study illustrates differences between colors of poplar I-214 veneers dyed by reactive blue KN-R and 4 kinds of chemical reagents, and those of treated veneer exposed to UV-ray for 3 days. The results show there are some laws in poplar I-214 dyeing and UV-ray attenuation of each chemically treated veneer color. The chemical reaction carded out between cellulose or lignin on veneer surface and dye molecules when they met with. The capability of dyeing and discoloration of veneer is improved by control of dyeing technology, especially chemical treatments; being treated by acetylation and maleic anhydride protects dyed wood discoloration.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10872010, 10732020 and 11072008)the National Science Foundation for Distinguished Young Scholars of China (Grant No. 10425209)+1 种基金the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipalitythe Ph.D. Programs Foundation of Beijing University of Technology (Grant No. 52001015200701)
文摘The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed that different layers are perfectly bonded to each other with piezoelectric actuator patches embedded. The nonlinear equations of motion for the laminated composite piezoelectric rectangular plate are derived from von Karman-type equation and third-order shear deformation plate theory of Reddy. The two-degree-of-freedom dimensionless equations of motion are obtained by using the Galerkin approach to the partial differential governing equation of motion for the laminated composite piezoelectric rectangular plate. The four-dimensional averaged equation in the case of primary parametric resonance and 1:3 internal resonances is obtained by using the method of multiple scales. From the averaged equation, the theory of normal form is used to find the explicit formulas of normal form. Based on the normal form obtained, the energy phase method is utilized to analyze the multi-pulse global bifurcations and chaotic dynamics for the laminated composite piezoelectric rectangular plate. The analysis of the global dynamics indicates that there exist multi-pulse jumping orbits in the perturbed phase space of the averaged equation. Based on the averaged equation obtained, the chaotic motions and the Shilnikov type multi-pulse orbits of the laminated composite piezoelectric rectangular plate are also found by numerical simulation. The results obtained above mean the existence of the chaos in the Smale horseshoe sense for the simply supported laminated composite piezoelectric rectangular plate.
