In-situ bending and stretching were conducted on hot-rolled and annealed Ti/Al/Mg/Al/Ti laminates,with a focus on crack initiation and propagation of intermetallics and component layers,which helps to clarify their de...In-situ bending and stretching were conducted on hot-rolled and annealed Ti/Al/Mg/Al/Ti laminates,with a focus on crack initiation and propagation of intermetallics and component layers,which helps to clarify their deformation behavior and fracture forms.The results show that delamination is the early fracture form of laminate with or without intermetallics at Al/Mg interface,so Al/Mg interfacial bonding strength determines the mechanical properties of laminate.Various and irregular intermetallics cracks lead to Al/Mg interface delamination in annealed laminate and help to release stress.Necking and fracture of component layers are observed at the late deformation stage,and the sequence is Al,Mg and Ti layers,resulting from their strength.Angle between crack propagation direction and stretching direction of Mg layer both in rolled and annealed laminates is around 45°due to the effect of shear deformation,and crack convergence leads to final complete fracture of Mg layer.展开更多
Fracture in sheet metal forming usually occurs as ductile fracture, rarely as brittle fracture, at the operating temperatures and rates of loading that are typical of real processes in two different modes：（1） tensi...Fracture in sheet metal forming usually occurs as ductile fracture, rarely as brittle fracture, at the operating temperatures and rates of loading that are typical of real processes in two different modes：（1） tensile and（2） in-plane shear（respectively, the same as modes I and II of fracture mechanics）. The circumstances under which each mode will occur are identified in terms of plastic flow and ductile damage by means of an analytical approach to characterize fracture loci under plane stress conditions that takes anisotropy into consideration. Fracture loci was characterized by means of the fracture forming limit line and by the shear fracture forming limit line in the fracture forming limit diagram. Experiments were performed with single point incremental forming and double-notched test specimens loaded in tension, torsion and in-plane shear give support to the presentation and allow determining the fracture loci of AA1050-H111 aluminium sheets with1 mm thickness. The relation between fracture toughness and the fracture forming limits was also investigated by comparing experimental values of the strains at fracture obtained from a truncated conical part produced by single point incremental forming and from double-notched test specimens loaded in tension.展开更多
The final fractural forms and variation status of hard inclusion samples under biaxial compression have been primarily studied in this paper. The lateral fractural forms of samples are mainly compressive shear fractu...The final fractural forms and variation status of hard inclusion samples under biaxial compression have been primarily studied in this paper. The lateral fractural forms of samples are mainly compressive shear fracture, two kinds appear on surface: one is strike slip fault with reversed thrust, and another is thrust. Some hard inclusions rupture and some do not while hard contact serves between hard inclusions and sample; main fracture bypasses hard inclusion while soft contact serves. Finally, process of stress concentration, yield, softening until failure for hard inclusions have been analysed under a certain condition.展开更多
基金financially supported by Shanxi provincial Youth Fund(No.201801D221101)the National Natural Science Foundation of China(Nos.52005362,U1810208,U1710254)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(Nos.2019L0149,2019L0994)。
文摘In-situ bending and stretching were conducted on hot-rolled and annealed Ti/Al/Mg/Al/Ti laminates,with a focus on crack initiation and propagation of intermetallics and component layers,which helps to clarify their deformation behavior and fracture forms.The results show that delamination is the early fracture form of laminate with or without intermetallics at Al/Mg interface,so Al/Mg interfacial bonding strength determines the mechanical properties of laminate.Various and irregular intermetallics cracks lead to Al/Mg interface delamination in annealed laminate and help to release stress.Necking and fracture of component layers are observed at the late deformation stage,and the sequence is Al,Mg and Ti layers,resulting from their strength.Angle between crack propagation direction and stretching direction of Mg layer both in rolled and annealed laminates is around 45°due to the effect of shear deformation,and crack convergence leads to final complete fracture of Mg layer.
基金support provided by Fundacao para a Ciência e a Tecnologia of Portugal within project LAETA-UID/EMS/50022/ 2013 and SFRH/BSAB/105959/2015funding by the German Research Foundation (DFG) within the scope of the Transregional Collaborative Research Centre on sheet-bulk metal forming (SFB/TR 73) in the subproject C4 ‘Analysis of load history dependent evolution of damage and microstructure for the numerical design of sheet-bulk metal forming processes’
文摘Fracture in sheet metal forming usually occurs as ductile fracture, rarely as brittle fracture, at the operating temperatures and rates of loading that are typical of real processes in two different modes：（1） tensile and（2） in-plane shear（respectively, the same as modes I and II of fracture mechanics）. The circumstances under which each mode will occur are identified in terms of plastic flow and ductile damage by means of an analytical approach to characterize fracture loci under plane stress conditions that takes anisotropy into consideration. Fracture loci was characterized by means of the fracture forming limit line and by the shear fracture forming limit line in the fracture forming limit diagram. Experiments were performed with single point incremental forming and double-notched test specimens loaded in tension, torsion and in-plane shear give support to the presentation and allow determining the fracture loci of AA1050-H111 aluminium sheets with1 mm thickness. The relation between fracture toughness and the fracture forming limits was also investigated by comparing experimental values of the strains at fracture obtained from a truncated conical part produced by single point incremental forming and from double-notched test specimens loaded in tension.
文摘The final fractural forms and variation status of hard inclusion samples under biaxial compression have been primarily studied in this paper. The lateral fractural forms of samples are mainly compressive shear fracture, two kinds appear on surface: one is strike slip fault with reversed thrust, and another is thrust. Some hard inclusions rupture and some do not while hard contact serves between hard inclusions and sample; main fracture bypasses hard inclusion while soft contact serves. Finally, process of stress concentration, yield, softening until failure for hard inclusions have been analysed under a certain condition.
