Research On Fracture Of Thick Aluminum Alloy Plate During Stretching Process For 10000-ton Tensile Stretching Machine

The project originates fromthe sub-project“10000-ton tensile stretching machinefor the aeronautic aluminum alloy plate” of National Science and Technology Major Project“High-grade CNC machine tool and fundamental manufacturing equipment”(No: 2015ZX04005-011) and specially appointed and funded program of national scienceand technology“Stretching process control and application of 12000-ton tensile stretching machine for aeronautic aluminum alloy plate”(No: 2009GJF10028).10000-ton tensile stretching machine is the key equipment to produce high quality aeronautic aluminum alloy plate. The occurrence of fracture during stretching process is inevitable, the huge impact force on the fracture will destroy the tensile stretching machine. As a consequence,the protection technology for fracture impact cushion of 10000-ton tensile stretching machine during stretching process is becoming worldwide issues. This study takes the 10000-ton tensile stretching machine as research object, and the finite element method and experimental technique are adopted to study the fracture during stretching process for the aluminum alloy plate, which is significant for improvingthe structure of tensile stretching machine and its impact cushion.The main research contents are as follows:(1)Take the 10000-ton tensile stretching machine as research object, the structure and working mechanism of which are introduced, and its impact cushion is also introduced. The strength and rigidity of the 10000-ton tensile stretching machine are analyzed using the finite element method to verify the rationality of the structure for the tensile stretching machine;(2)Based on the relationship of components and parts of 10000-ton tensile stretching machine, the friction contact between aluminum alloy plate and jaw is defined, the contact between jaw and assembly is also be defined. Considering the influence of thickness of aluminum alloy plate, defect of material and the quenching residual stress, the tensile fracture analysis model for 10000-ton tensile stretching machine is established;(3)Considering the coupling relationship of jaw and aluminum alloy plate, the impact for jaw during tensile fracture is simulated, and the impact force of jaw, elasticbolt and frame are calculated. The variations of stress and strain on the key components and parts of tensile stretching machine are analyzed, so that to verify the structure and cushion of 10000-ton tensile stretching machine are favorable;(4)According to the initial void volume fraction under the best tensile ratio got from the tensile fracture model, the sizes of the voids in material based on different thick aluminum alloy plate are calculated, which can be used to nondestructive examination before the stretching process to protect the occurs of fracture; Considering the influence of quenching residual stress imported into the tensile fracture model of aluminum alloy thick plate, the stress intensity factors during fracture are analyzed, and the variations of stress intensity factors with cracks propagation are calculated;(5)Five typical conditions including conventional plate, most width of plate, maximum load factor of jaw, maximum thickness of plate, and tensile fracture are tested in the worksite for the 10000-ton aluminum alloy thick plate tensile stretching machine, the stress and strain got from testing match very wellwith the simulations, which improves that the tensile fracture model for 10000-ton aluminum alloy thick plate tensile stretching machine is well.