Crash Response of Laser-Welded Energy Absorbers Made of Docol 1000DP and Docol 1200M Steels.

Paweł Prochenka,Jacek Janiszewski,Michał Kucewicz

doi:10.3390/ma14112808

Abstract

The crushing response of a laser-welded square tube absorber made of two commercial steel grades, Docol 1000DP and Docol 1200M, is presented in the paper. Crush experiments are performed at two different loading conditions, namely, quasi-static loading at 0.5 mm/s deformation speed and impact loading at 25–28 m/s. A new approach has been proposed to study the square tube absorber under impact loading using a direct impact Hopkinson (DIH) method. To characterize the mechanical properties of the tested steels, tensile quasi-static and high strain rate testing are also performed with the use of specimens with a 7 mm gauge length. The applied strain rates are 10−3, 100, and above 103 s−1. The laser-welded joints are also characterized by microhardness test involving the base material, heat-affected zone, and fusion zone. The crashworthiness of model square tube absorbers is estimated based on the following parameters: absorbed energy, mean force, crushing force efficiency factor, and specific energy absorbed. It has been found that the square tube absorbers made of Docol 1200M steel show a higher potential in mechanical energy absorption capacity than Docol 1000DP absorber. Moreover, crushing tests prove that laser-welded joints in 0.6 mm sheets made of Docol 1000DP and Docol 1200M steels reveal high cracking toughness. In turn, strength testing at different strain rates confirms the higher strain rate sensitivity of Docol 1000DP steel than in the case of Docol 1200M steel as well as an increase in the high ductility properties of both steel grades under the high strain rate loading conditions.

Highlights

Due to environmental issues, the automotive industry is focused on the development of fuel-efficient and electric vehicles [1,2,3,4]
All the bars were made of C40 steel, which was was calculated based on the direct measurement of the striker bar displacement d(t)
The specific energy absorbed (SEA) level may be comparable to the results found in other research [38]

Summary

Introduction

Due to environmental issues, the automotive industry is focused on the development of fuel-efficient and electric vehicles [1,2,3,4] In both cases, engineers confront new challenges, of which the most important is to decrease the vehicle mass while increasing safety to prevent passenger injuries and, in electric cars, to protect sensitive components such as batteries. Engineers confront new challenges, of which the most important is to decrease the vehicle mass while increasing safety to prevent passenger injuries and, in electric cars, to protect sensitive components such as batteries This can be achieved in two different ways: application of novel complex energy-absorbing structures with various shapes, composition, and filling [5,6,7] or the use of advanced materials with increased strength [8,9,10,11,12,13]. These materials, due to their mechanical properties, crashworthiness, and recycling potential [18], belong to a group of materials with a high development potential, which is exemplified by the introduction of the third generation of AHSS to the market

Objectives

Results

Conclusion