Abstract
Abstract Shock environment assessment and improvement during stage separation is an important issue of concern in aerospace engineering. This paper focuses on shock response caused by dynamic fracture of aluminum alloy separation plate, which usually undergoes mixed mode loading during separation. Based on Split Hopkinson Tensile Bar (SHTB) apparatus, five groups of U-notched ZL205A specimens with different loading angles (0°, 30°, 45°, 60°, and 90°) are designed to simulate mixed mode loading for shock characteristics testing. There piezoelectric accelerometers are used to measure the acceleration time histories, and the maximum shock response spectrum (SRS) are applied for shock data analysis. Meanwhile, the ANSYS/LS-DYNA finite element software is implemented for numerical analysis. The actual fracture angles measured from the recovered specimens are used to describe the actual fracture modes. The numerical and experimental results are in good agreement, showing that the shock response along the specimen’s length and thickness directions increases with the fracture angle, while there is a slight distinction in the specimen’s width direction with different fracture angles. On average, the shock response is more remarkable in pure tensile fracture mode, which is 2.6 times the pure shear fracture mode. As a result, increasing the study of shear fracture component is meaningful for the shock reduction through the structural design of separation plate.
Highlights
ZL205A is a series of Al-Cu-Mn cast aluminum material, which is intensively used in aerospace industry due to its high strength, low density, corrosion resistance, and high production efficiency (Li et al 2011)
According to the one-dimensional stress wave theory in Split Hopkinson Tensile Bar (SHTB) tests, the force and elongation of the specimen can be expressed as: f Eb Ab t t where Ab is the cross-sectional area of the output bar; Eb and Cb are Young’s modulus and one-dimensional elastic stress wave velocity of the incident/transmitted bar; εi(t) and εr(t) are strain histories of the incident and reflected waves recorded by strain gauges on incident bar; and εt(t) is strain history of the transmitted wave recorded by strain gauges on transmitted bar
There are some differences between numerical simulation and experiments, that maximum force values are basically consistent but the relative error of final elongation e0 between numerical simulation and experiments increases with the increase of loading angle β
Summary
ZL205A is a series of Al-Cu-Mn cast aluminum material, which is intensively used in aerospace industry due to its high strength, low density, corrosion resistance, and high production efficiency (Li et al 2011). An important application of ZL205A is used as separation plate material in expansion tube separation device. The energy of the MDF will drive the flat tube expand rapidly which further fracture the surrounding separation plate from the prefabricated notch to achieve stage separation. The fracture will produce significant shock to the separation structure owing to the sudden release of strain energy when the separation plate cracks no matter what fracture patterns (Chang and Kern 1986; Evans et al 1987; Bement 1988). The influence to shock response of different fracture patterns is focused, which is of great significance to research on reducing the shock applied to equipment and astronauts in space rocket area
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