The Lightweight Design And Crashworthiness Research Of Thin-walled Double Hat-shaped Tube

As people’s living standards continue to improve, there has been a substantial increase in the number of cars, followed by more frequent traffic accidents. So more and more attention are paying to the safety of cars, in this issue, improve the car’s passive safety is the key to improving vehicle safety and also an important measure of automotive design. Meanwhile, for the purpose of energy conservation and easing the energy crisis, the lightweight of the cars should be taken into account in automotive design process. In view of this, some new lightweight materials such as magnesium alloys, aluminum and carbon fiber etc. show great advantage in improving vehicle safety and achieving weight reduction of cars.Double hat thin-walled tube is commonly used as energy-absorbing component in automotive body. In the process of automobile collision, especially in side impact, energy absorbing structures often experience bending deformation, so the lateral crashworthiness research and lightweight design double hat thin-walled tube has important practical significance.Firstly, to obtain the desired stress-strain curve, the material performance test has been conducted. Then, design the quasi-static three-point bending test and the finite element simulation of steel double hat-shaped tube. Analyze the energy-absorbing characteristics and deformation mode of steel double hat-shaped tube, study the influence of thickness in crashworthiness of steel double hat-shaped tube through finite element simulation. The study show that:with a reasonable arrange the thickness of the top hat and bottom hat, the energy absorption capacity of steel double hat-shaped tube can be significantly improved on the condition of keeping the weight of the structure remain unchanged.In order to reduce the weight of conventional steel double hat-shaped tube, achieve lightweight of structures, the magnesium alloy double hat-shaped tube were introduced. To study the lateral crashworthiness of magnesium alloy double hat-shaped tube, the quasi-static three-point bending test and the finite element simulation were conducted just as steel double hat-shaped tube. The results show that:the deformation mode of magnesium alloy double hat-shaped tube is similar to steel double hat-shaped tube, however, partially cracks appear in the magnesium alloy double hat-shaped tube when it’s under lateral load, this deformation pattern limits its energy absorption capability to a certain extent. In order to study the lightweight effect of magnesium alloy double hat-shaped tube, the multi-objective optimization was applied, results showed that:compare to conventional steel double hat-shaped tube, the magnesium alloy tube reflects the good lightweight advantages, however, in order to reach the same energy absorption of steel double hat-shaped tube, the thickness of magnesium alloy double hat-shaped tube will be too thick.Thus, in order to combine the good carrying capacity of steel double hat-shaped tube and good lightweight advantages of magnesium alloy double hat-shaped tube, the steel-magnesium hybrid double hat-shaped tube was introduced. The quasi-static three bending test and finite element simulation analysis were conducted for two kinds of hybrid tube to investigate its energy absorption characteristics. Then multi-objective optimization was conducted. The results show that:in terms of lightweight or energy absorption, the overall performance of the steel/magnesium hybrid tube (top steel bottom magnesium) is much better than magnesium/steel hybrid tube (top magnesium bottom steel). Compared to traditional single-material double hat-shaped tube, the steel/magnesium hybrid tube combines the respective strengths of steel and magnesium alloy, this hybrid structure can significantly improve energy absorption capacity and has a good lightweight effect. Therefore the steel/magnesium hybrid tube (top steel bottom magnesium) can be used as a good crashworthiness component that can be applied in automobile body.