Lightweight construction by hydroforming of laser brazed and soldered steel-aluminum Tailored Hybrid Tubes

The joint is the weak point at a hybrid metal semifinished product in tube hydroforming. In real forming processes, a deformation at the joint would be prevented in order to avoid failure. A better knowledge of the forming behavior enables to reduce the effort in process design. Thus, this study investigates in hybrid material combinations and the forming behavior of the joint area regarding their suitability for tube hydroforming.

hydroforming, tube, steel-aluminum, FEA

A main target in automotive engineering research and development is currently to reduce fuel consumption and CO2 emissions. Therefore in this project lightweight design was combined with material design in order to produce more efficient structural components. The joining process for tubes of steel and aluminum by laser brazing was investigated to create a joint area that is highly formable. These steel-aluminum joints were afterwards hydroformed, at which steel and aluminum parts were formed in a single step. This process is called "IHU-THT" and can provide lightweight components with excellent mechanical properties.

FEA, hydro forming, tailored forming

The challenge in developing a hydroforming process for Tailored Hybrid Tubes is to provide feasible forming conditions for both the steel and the aluminum part of the semi-finished hybrid material. The aim of these investigations is to develop one-stage tube hydroforming processes for steel-aluminum-joints. Therefore, the effects on the materials’ forming behavior, especially the flow stress, of the parameters alloy, thickness, forming rate and seam design are being investigated. Forming tests were carried out on sheet metal specimens of joined steel and aluminum to investigate the impact of the varied parameters and to analyze the joint area’s forming behavior. Based on the results of the forming tests an FEA-simulation will be set up in order to design a hydroforming process for Tailored Hybrid Tubes of laser joined steel and aluminum. Eventually the hydroforming process of Tailored Hybrid Tubes shall be executed for a sample part.

hydroforming, automotive, laser brazing, laser soldering, steel-aluminum, car body, engine downsizin

In this study two approaches in automotive lightweight construction have been combined: weight reduction based on material and based on structural design. Steel and aluminum are used for the first approach, and hydroforming is the method for design optimization by shaping. Steel and aluminum show different forming behaviors due to their characteristic yield stresses. The challenge in developing a hydroforming process for THTs is to provide feasible forming conditions for both the steel and the aluminum part. Forming tests were carried out on sheet metal specimens of laser brazed and laser soldered steel and aluminum to investigate the impact of specific parameters and to analyze the joint area’s forming behavior. An FEA simulation was set up in order to design a tube hydroforming process for THTs of laser joined steel and aluminum. Eventually, the hydroforming process for THTs will be designed and executed.

hydroforming, automotive, laser brazing, laser soldering, steel-aluminum, car body, engine downsizin