KEYWORDS: Temperature metrology, Foam, Digital image correlation, Speckle, Satellites, CCD cameras, Control systems, Image processing, Time metrology, Image quality
Porous flexible foam material board, represented by polyimide, has the characteristics of lightweight, vibration damping, and heat insulation, which is widely used in the cushioning and heat insulation structure of super-static, super-stable, and super-precision satellites. As the thermal insulation and buffer layer of satellite, the coefficient of thermal expansion is the key performance parameter and the important index of satellite structure design under the space environment with large temperature variation. However, the existing thermal expansion coefficient measurement technology has some problems, such as contact force interference, low measurement accuracy, complex measurement process. To solve the above measurement problems, this paper designs a thermal expansion coefficient measurement method of porous flexible materials based on digital image correlation (DIC) measurement technology. This method uses the temperature loading system with adjustable size to control the temperature of the measured object, and combines multi-target processing method and DIC technology to realize the thermal expansion coefficient measurement of porous flexible materials. Through the uncertainty evaluation and verification experiment of the method, it is shown that the method is accurate and reliable.
The oblique impact damage model of hybrid fiber metal laminates is established, and the process of the bullet impacting aluminum alloy-carbon/glass hybrid fiber laminates with multi-angle and high speed is numerically simulated to explore the influence of impact angle on energy absorption, contact force and interlayer failure area of metal fiber laminates. The results show that the kinetic energy consumption decrease with the increase of the impact angle. The impact angle directly affects the energy absorption characteristics of the hybrid fiber metal laminate. As a whole, the failure area of metal layer and fiber layer decreases with the impact angle. The failure area of the carbon fiber layer is smaller than that of the glass fiber layer, and the failure area of the glass fiber layer from the top to the bottom gradually increases, but the failure area of the carbon fiber layer from the top to the bottom has no obvious change. Because of the impact angle, the kinetic energy dissipation, the maximum fiber stress position and failure area of hybrid fiber metal laminates have significant effects.
The high-order accurate finite-difference method is used to simulate the hypersonic flow field around a blunt wedge under the condition of the wall roughness element. The influence of the position of the independent wall roughness element on the interaction between the free flow and the wall is analyzed, and the influence of the position of the roughness element on the wall pressure, the wall friction resistance and wall heat flow are studied. The results show that two compression waves and one expansion wave are formed in the flow field by rough elements, and the wave intensity increases when the position of rough elements move forward. When the center of the rough element is xp≥1.5, a vortex will form at the leading edge of the rough element. The backward moving of the rough element will increase the length of the vortex, inhibit the change of the flow parameters in the first-half of the rough element, promote the change of the flow parameters in the second-half of the rough element, which will reduce the wall friction resistance and inhibit the heating of the incoming flow to the first-half of the rough element.
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