Friction stir welding provides better retention of ductility and plasticity in comparison to fusion welding and it increases the stability against cracking.This study aims to enhance both the ductility and strength of...Friction stir welding provides better retention of ductility and plasticity in comparison to fusion welding and it increases the stability against cracking.This study aims to enhance both the ductility and strength of the welded joints.Tool profile was found to play an important role in retaining ductility,understanding the metal flow behavior and determining the fracture initiating point.The microstructure of different regions in the onion ring was inferred to correlate the strength with the metal flow pattern.The onion ring pattern strengthened the weld nugget.Shoulder and taper threaded profile tool resulted in superior mechanical properties.Microhardness results confirmed that the fracture runs through low hardness areas such as heat affected zone and thermo-mechanically affected zone.The scanning electron microscopic images revealed elongated grains and dimples,justifying ductile mode of fracture.展开更多
To reduce defects caused by non-homogeneous metal flow in conventional extrusion,a die with guiding angle was designed to improve the metal flow behavior. The characteristic quantities such as the second invariant of ...To reduce defects caused by non-homogeneous metal flow in conventional extrusion,a die with guiding angle was designed to improve the metal flow behavior. The characteristic quantities such as the second invariant of the deviator stress J2 and Lode's coefficient μ were employed for the division of deformation area. The results show that when the metal is extruded with the guiding angle,no metal flow interface forms at the container's bottom,the dead zone completely disappears,the deformation types of the metal in the plastic deformation area change from three types to one type of tension,and the homogeneity of the deformation as well as metal flow are greatly improved. The non-homogeneous metal flow at the final stage of extrusion is improved,reducing the shrinkage hole at the axis end. The radial stress of the furthest point from the axis is transformed from tensile stress to compressive stress and the axial stress,and decreased from 70.8 to 34.8 MPa. Therefore,the surface cracks caused by additional stress are greatly reduced.展开更多
文摘为规范编制生产结构图提供依据,简化链式微分法则[火用]成本建模方法,分离导致单位产品[火用]成本增大的不同影响因素,提出了基于[火用]流属性分类的热力系统成本建模及计算方法.给出基于[火用]流属性分类法生产结构图生成规则,将生产过程中不同类型[火用]流进行归类,按照热力系统[火用]流属性分类构建虚拟组元以及生产组元与虚拟组元连接关系原则,结合生产结构图定义了3类建模准则,根据生产组元的输入输出[火用]流属性分类将生产组元分为4类,构造热力系统单位[火用]成本的迭代算法.算法可有效避免高维模型的推导误差,计算结果分析显示,相同属性的流拥有相同的成本,随着热力系统生产过程的递进,不同属性的[火用]流[火用]成本逐渐增大,相邻的不同属性[火用]流[火用]成本差值为该生产过程本身的热力学损失,可分离不同属性[火用]流[火用]成本的成因,给出不同属性[火用]流[火用]成本之间的交互关系.仿真计算表明,在保持较高仿真精度的基础上,仿真耗时由3 s下降为1 s.
基金Project(ISRO/RES/3/683/15-16 dt 07.08.2015)supported by Indian Space Research Organization
文摘Friction stir welding provides better retention of ductility and plasticity in comparison to fusion welding and it increases the stability against cracking.This study aims to enhance both the ductility and strength of the welded joints.Tool profile was found to play an important role in retaining ductility,understanding the metal flow behavior and determining the fracture initiating point.The microstructure of different regions in the onion ring was inferred to correlate the strength with the metal flow pattern.The onion ring pattern strengthened the weld nugget.Shoulder and taper threaded profile tool resulted in superior mechanical properties.Microhardness results confirmed that the fracture runs through low hardness areas such as heat affected zone and thermo-mechanically affected zone.The scanning electron microscopic images revealed elongated grains and dimples,justifying ductile mode of fracture.
基金Project(RC2010QN017008) supported by the Excellent Young Teachers Program of Harbin City, China
文摘To reduce defects caused by non-homogeneous metal flow in conventional extrusion,a die with guiding angle was designed to improve the metal flow behavior. The characteristic quantities such as the second invariant of the deviator stress J2 and Lode's coefficient μ were employed for the division of deformation area. The results show that when the metal is extruded with the guiding angle,no metal flow interface forms at the container's bottom,the dead zone completely disappears,the deformation types of the metal in the plastic deformation area change from three types to one type of tension,and the homogeneity of the deformation as well as metal flow are greatly improved. The non-homogeneous metal flow at the final stage of extrusion is improved,reducing the shrinkage hole at the axis end. The radial stress of the furthest point from the axis is transformed from tensile stress to compressive stress and the axial stress,and decreased from 70.8 to 34.8 MPa. Therefore,the surface cracks caused by additional stress are greatly reduced.
