The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dy...The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dynamic three-point bending tests of each alloy are carried out at different impact velocities.The initiation fracture toughness and average propagation fracture toughness of 2024-T4 and 7075-T6 are determined at different loading rates.The results show that both the initiation toughness and the propagation toughness increase with the loading rate.Further,the difference between the fracture toughness behaviors of 2024-T4 and 7075-T6 is found to be dependent on the variation of fracture mechanism.The comprehensive fractographic investigations of the fracture surfaces clearly demonstrate that the fracture mode of 2024-T4 is predominantly transgranular fracture with high density small-sized dimples,and the fracture mode of 7075-T6 is mainly intergranular fracture with many intermetallic particles in the bottom of voids located in the fracture surface.展开更多
The cylindrical tungsten alloy fragment is often prefabricated in the directional warhead to improve the killing ability or interception ability of the warhead.To study the influence of the attitude of fragments on th...The cylindrical tungsten alloy fragment is often prefabricated in the directional warhead to improve the killing ability or interception ability of the warhead.To study the influence of the attitude of fragments on the ability to penetrate thin metal target plates,theoretical calculation,and numerical simulation are used to study the ultimate penetration velocity of cylindrical tungsten alloy fragments with different aspect ratios impacting thin metal target plates vertically with a different attitude.The angle between the axis of a cylindrical tungsten alloy fragment and the normal direction of the target plate is defined as the attitude angle of the fragment perpendicular to the target plate.It is found that when the attitude angle changes from 0°to 90°,the ultimate penetration velocity of fragments increases first and then decreases.When the length-to-diameter ratio of fragments is 1.0,1.2,and 1.5,the relative errors between the minimum and maximum values of the ultimate penetration velocity are about 11.99%,15.75%,and 14.35%,respectively.The ultimate penetration velocity of fragments increases with the increase of the projection area of fragments on the target plate.展开更多
基金supported by the NatiS100onal Science Foundation of China under Grant No.11072119the Defense Industrial Technology Development Program under Grant No.B1520110003+2 种基金the K.C.Wong Magna Foundation of Ningbo University,Chinaa grant from the Department of Education of Zhejiang Province through the Impact and Safety of Costal Engineering Initiativea COE Program at Ningbo University
文摘The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dynamic three-point bending tests of each alloy are carried out at different impact velocities.The initiation fracture toughness and average propagation fracture toughness of 2024-T4 and 7075-T6 are determined at different loading rates.The results show that both the initiation toughness and the propagation toughness increase with the loading rate.Further,the difference between the fracture toughness behaviors of 2024-T4 and 7075-T6 is found to be dependent on the variation of fracture mechanism.The comprehensive fractographic investigations of the fracture surfaces clearly demonstrate that the fracture mode of 2024-T4 is predominantly transgranular fracture with high density small-sized dimples,and the fracture mode of 7075-T6 is mainly intergranular fracture with many intermetallic particles in the bottom of voids located in the fracture surface.
基金supported by National Natural Science Foundation of China (Grant No.12102213)。
文摘The cylindrical tungsten alloy fragment is often prefabricated in the directional warhead to improve the killing ability or interception ability of the warhead.To study the influence of the attitude of fragments on the ability to penetrate thin metal target plates,theoretical calculation,and numerical simulation are used to study the ultimate penetration velocity of cylindrical tungsten alloy fragments with different aspect ratios impacting thin metal target plates vertically with a different attitude.The angle between the axis of a cylindrical tungsten alloy fragment and the normal direction of the target plate is defined as the attitude angle of the fragment perpendicular to the target plate.It is found that when the attitude angle changes from 0°to 90°,the ultimate penetration velocity of fragments increases first and then decreases.When the length-to-diameter ratio of fragments is 1.0,1.2,and 1.5,the relative errors between the minimum and maximum values of the ultimate penetration velocity are about 11.99%,15.75%,and 14.35%,respectively.The ultimate penetration velocity of fragments increases with the increase of the projection area of fragments on the target plate.
