Abstract
Research and/or Engineering Questions/Objective
To overcome some drawbacks of using AHSS (Advanced High Strength Steel) in hard machining and part welding for vehicle weight reduction, such as brittleness, spot weld HAZ (Heat Affected Zone) softening and high cost, a new ridgeline strengthening technology was introduced and applied to the thinwalled structure. The objective of this study was to investigate mechanical properties of thin-walled box structure with higher strength in ridgelines under axial compression, then to fully replace a common box structure with inner enhancement part in BIW (body in white) to reduce weight.
Methodology
Recently the vehicle body structure has being required for a better crashworthiness and light-weighting to reduce the injuries in traffic accidents and the carbon emission. Nowadays, there are usually two ways to strengthen the box structure section resistance. One is to increase the thickness of stamping parts, which will increase the weight and also result in the increase of fuel consumption, such as thin-walled box structure with inner enhancement part. The other is to use high or ultra-high strength steel. However, above ways aren’t best ways to solve the conflict in body design. In this study the ideal folding model presented by Wierzbicki and Abramowicz has been introduced to analysis the effect of ridgeline strengthening in thin-walled box structure. CAE simulations with a rectangular structure will be used to support the analysis in this study.
Results
In the paper the mean crushing force of a rectangular structure with strengthened ridgelines can be presented as function of geometry parameters of cross section and yield stress ratio of ridgeline to plate. The main finding is that the maximum section resistance force of rectangular structure with thickness of 1mm can be promoted significantly by about 30% after four ridgelines were stress-strengthened by laser quenching. Application of the above rectangular structure as the box structure with inner enhancement part would perform well in side crash.
Limitations of this study
An important limitation of the current study is the local ridgeline heat treatment by laser. Furthermore, the strength of adjacent region were also affected by stress strengthening processing. So the expected strength of ridgeline is not easy to acquire every time.
What does the paper offer that is new in the field including in comparison to other work by the authors?
The theoretical analysis and property comparison with ridgeline strengthing for rectangular structure presented in this paper is new as well the engineering application in BIW for reducing the weight.
Conclusions
New prediction formula of mean crushing force for thin-walled rectangular structure with different strength in ridgelines has been developed. The ridgeline strengthing technology is smartly introduced to adjust the mechanical properties of thin-walled box structure.
Key Words : Mechanical properties; rectangular structure; ridgeline strengthening; mean crushing force; simulation