Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelas...Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.展开更多
A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion devi...A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.展开更多
Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin st...Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.展开更多
板结构的稳定性在船舶设计和强度校核中占据重要地位。为研究船体薄板的剪切稳定性,本文设计画框式夹具对方形薄板进行面内剪切屈曲试验,试验中采用三维数字图像相关法(3 Dimensions Digital Image Correlation,简称3D-DIC),获得了载荷...板结构的稳定性在船舶设计和强度校核中占据重要地位。为研究船体薄板的剪切稳定性,本文设计画框式夹具对方形薄板进行面内剪切屈曲试验,试验中采用三维数字图像相关法(3 Dimensions Digital Image Correlation,简称3D-DIC),获得了载荷-端部伸长率曲线、全场位移/应变等力学响应信息。载荷-端部伸长率关系揭示了薄板在面内剪切工况下的承载特性,确定了屈曲失稳临界载荷;通过分析薄板在典型时刻的位移场、应变场信息,发现薄板的法向变形会随面内剪切载荷增加而增大。薄板失稳后,沿垂直对角线存在对称分布的三个半波,内部波幅大于外部波幅,应变波形和云图在后屈曲过程中会趋于稳定。通过分析薄板关键点的法向位移和米塞斯应变随时间的响应曲线,提出并验证了一种识别面内受剪薄板屈曲失稳的新方法。本文为船用薄板面内剪切稳定性的试验研究和力学行为分析等提供了有益参考。展开更多
运用辛叠加方法求出相邻两边固支其他两边自由(two adjacent edges clamped and the other edges free, CCFF)正交各向异性矩形薄板屈曲问题的级数展开解。首先,将原屈曲问题的控制方程转化为哈密顿系统,通过分析边界条件,将原屈曲问题...运用辛叠加方法求出相邻两边固支其他两边自由(two adjacent edges clamped and the other edges free, CCFF)正交各向异性矩形薄板屈曲问题的级数展开解。首先,将原屈曲问题的控制方程转化为哈密顿系统,通过分析边界条件,将原屈曲问题分解为两个子屈曲问题,再利用辛本征函数展开法分别求得两个子屈曲问题的通解;然后,利用叠加方法得到原屈曲问题的辛叠加解;最后,应用所得辛叠加解分别计算了单/双向载荷作用下的CCFF各向同性和正交各向异性矩形薄板的屈曲问题。计算结果表明,所得辛叠加解是正确的并且其收敛速度较快。展开更多
文摘Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.
基金Project(2007DFR70070) supported by Sino-Russia Intergovernmental Science and Technology Cooperation Program
文摘A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.
基金financially supported by the National Security Major Foundation Research Project(973)of China(6133050102)the National Natural Science Foundation of China(Grant No.51409253)
文摘Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.
文摘板结构的稳定性在船舶设计和强度校核中占据重要地位。为研究船体薄板的剪切稳定性,本文设计画框式夹具对方形薄板进行面内剪切屈曲试验,试验中采用三维数字图像相关法(3 Dimensions Digital Image Correlation,简称3D-DIC),获得了载荷-端部伸长率曲线、全场位移/应变等力学响应信息。载荷-端部伸长率关系揭示了薄板在面内剪切工况下的承载特性,确定了屈曲失稳临界载荷;通过分析薄板在典型时刻的位移场、应变场信息,发现薄板的法向变形会随面内剪切载荷增加而增大。薄板失稳后,沿垂直对角线存在对称分布的三个半波,内部波幅大于外部波幅,应变波形和云图在后屈曲过程中会趋于稳定。通过分析薄板关键点的法向位移和米塞斯应变随时间的响应曲线,提出并验证了一种识别面内受剪薄板屈曲失稳的新方法。本文为船用薄板面内剪切稳定性的试验研究和力学行为分析等提供了有益参考。
文摘运用辛叠加方法求出相邻两边固支其他两边自由(two adjacent edges clamped and the other edges free, CCFF)正交各向异性矩形薄板屈曲问题的级数展开解。首先,将原屈曲问题的控制方程转化为哈密顿系统,通过分析边界条件,将原屈曲问题分解为两个子屈曲问题,再利用辛本征函数展开法分别求得两个子屈曲问题的通解;然后,利用叠加方法得到原屈曲问题的辛叠加解;最后,应用所得辛叠加解分别计算了单/双向载荷作用下的CCFF各向同性和正交各向异性矩形薄板的屈曲问题。计算结果表明,所得辛叠加解是正确的并且其收敛速度较快。
