Wuhan University of Technology Undergraduate Graduation Thesis

Thesis Title : Analysis of impact welding technology for heterogeneous metals in new energy automobile body

School: School of International Education

Specialty amp; Class: Automotive Engineering gj1602

Name: Tao Yifei

Tutor: Meng Zhenghua

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Abstract

In recent years, with the further improvement of vehicle lightweight, the multi material body is favored in the automotive design and manufacturing industry. However, the traditional welding and some mechanical welding processes are difficult to meet the strength requirements of the multi material body welding. As a high-speed impact joining process, foil vaporization impact welding is one of the effective ways to solve the difficulty of dissimilar metal welding.

In this paper, a new impact forming welding process is proposed based on the foil vaporized impact welding. The impact forming welding process is studied with aluminum and steel as the connecting material. A simplified simulation model for aluminum / steel forming is established, and the numerical simulation method formed by the aluminum / steel forming welding interface is used. The effects of the pre-deformation and impact joining process of the target and the material coefficient of the aluminum alloy on the joint performance of the aluminum / steel joint are studied.

After simplifying the impact forming welding process model, combining with the numerical simulation method of Lagrange and smoothed particle dynamics (SPH), the formation law of wavy characteristics of aluminum / steel joint interface is studied. The results of pre-deformation process parameters show that the welding interface is difficult to form in the central area of welding, and the complete welding state should be circular welding in the middle area. With the increase of the height or diameter of the convex hull, the wavelength and amplitude of the interfacial wave will increase. In the edge area, the increase of the height or diameter of the convex hull will reduce the wavelength and amplitude of the interface wave. The results of the impact joining process indicate that the increase of the initial shock velocity in the intermediate area will increase the wavelength of the interface wave first and then decrease, and the wave amplitude will continue to increase. With the increase of initial impact velocity, the wavelength and amplitude will increase and the waveform will be more clear. But when the initial impact velocity exceeds 1000m/s, the joint will easily form cavity and crack, which will affect the welding strength.

The experimental results of different materials show that the process of pre-deformation and impact forming welding can effectively connect aluminum / steel dissimilar metals, and 5083 aluminum alloy can achieve more reliable welding with DP590 steel than the 7039 aluminum alloy and 6061 aluminum alloy at the same initial speed. The waveform parameters formed by these three series aluminum alloys in the central area are closer. But in the edge area, the waveform formed by the 5083 aluminum alloy is obviously stronger than that of the other two kinds of aluminum alloys. We can predict the welding strength by analyzing the proportion of the aluminum alloy welding in each department, of which 5083 aluminum alloy is far more than 7039 aluminum alloy and 6061 aluminum alloy, the larger the effective welding area is, the higher the strength of the joint is. Moreover, the proportion of the 7039 aluminum alloy in the edge area is too low, so we think the 5083 aluminum alloy is more suitable for high-speed impact welding, while the 7 aluminum material is not suitable for this way of welding.

Keywords: impact forming welding, wavy interface, dissimilar metal, lightweight

Catalog

Abstract I

Chapter 1 Introduction. 1

1.1 Research background and research significance 1

1.1.1 Research background 1

1.1.2 Research purpose and significance 2

1.2 Research status of aluminum / steel dissimilar metal welding 3

1.2.1 Explosive welding 3

1.2.2 Magnetic pulse welding 4