Research On Plastic Forming Of Aluminum Foam Sandwich Panel And Surface Quality Of Formed Parts

Sandwich composite panel is a kind of lightweight material composed of face sheet and core layer.This special structure has excellent mechanical performance and functional characteristics,with low density,high strength and stiffness,strong impact resistance,as well as shock absorption and thermal insulation properties.Sandwich panels are widely used in automotive,aerospace,and marine fields,and there is also a great demand for curved sandwich composite panels in engineering.The traditional method of preparing curved sandwich panels involves separately forming the face sheet and core layer,and then connecting them to form a composite curved surface,which is inefficient,costly,and difficult to guarantee the accuracy of the connection between the face sheet and core layer.Direct plastic forming of sandwich composite panel can overcome the disadvantages of traditional methods and improve production efficiency.However,the forming of sandwich panels is more complex than that of ordinary metal plates,and is influenced by multiple factors.At present,there is not much related research.This paper takes foam aluminum core sandwich panels as the research object.Through numerical simulation method,we studied the characteristics,forming defects,and surface quality of single curvature and double curvature plastic forming of aluminum foam sandwich panels.The main research contents are as follows:1.Based on the foaming characteristics of aluminum foam itself,two mesoscopic models of aluminum foam core,cubic sphere(CS)and tetrakaidecahedral(TKD),were determined for numerical simulation of plastic forming of sandwich panel considering the calculation efficiency and authenticity.In response to the surface defect characteristics that occur during the plastic forming of foam aluminum sandwich panels,evaluation parameters for the surface quality of the sandwich panels have been defined.2.Using CS and TKD models,the multi-point cylindrical,spherical and saddleshaped forming finite element models of aluminum foam sandwich panels were constructed.The stress and strain distribution characteristics of the upper and lower face sheets and the core during the forming process were analyzed.It was found that the stress and strain in the unsupported areas of the face sheet were larger,and the deformation in the bending direction and the contact area with the face sheet was larger for the core.The equivalent stress and strain values on the spherical hole wall of the CS model and the inclined hole wall of the TKD model were relatively small.Face sheet wrinkling,local straight surface and face dimpling defects during the forming process were the main factors determining surface quality.We analyzed the influence of core material properties and thickness on core fracture defects.3.The study focuses on the sandwich panel with cylindrical,spherical and saddle shapes.The finite element method was used to analyze the effects and laws of the thickness of the upper and lower face sheets,the cell size of the core,the material properties of the face sheets,and the forming curvature radius on the stress,strain,and surface quality of the sandwich panel.The differences in the normal deviation of the formed part under different upper and lower face sheet thicknesses and forming radius of curvature were compared.The evaluation parameters of the surface quality of formed parts and mesoscopic models were compared,and the effectiveness of the two mesoscopic models was verified.4.The multi-point forming experiments of cylindrical,spherical and saddleshaped surface of aluminum foam sandwich panel were carried out,and the core fracture defects of three kinds of sandwich panel surfaces were compared.The threedimensional scanning device ATOS Triple Scan 16 M was used to measure the surface of the formed part.The numerical simulation results are compared with the crosssection profile lines of the formed part to verify the shape accuracy of the numerical simulation results.