Comparative Evaluation of the Energy Absorption Performance of Magnesium and Aluminum Alloys in Automotive Crash-Absorbing Structures Using Finite Element Analysis

Crash boxes are critical components of passive vehicle safety systems that dissipate impact energy through controlled progressive deformation and thereby reduce the loads transmitted to the vehicle body and passenger compartment. The material selection and structural design of these components must simultaneously consider energy-absorption capacity, structural mass, deformation stability, and peak crushing force. In lightweight automotive applications, magnesium and aluminum alloys are particularly attractive because of their low density and potential for improving mass efficiency. Although steel structures can provide higher absolute energy absorption, lightweight alloys may achieve superior specific energy absorption due to their lower mass.This study presents a comparative investigation of the crashworthiness performance of magnesium and aluminum alloys in automotive crash-absorbing structures using finite element analysis. The main evaluation criteria include total energy absorption (EA), specific energy absorption (SEA), peak crushing force (PCF), mean crushing force (MCF), and crush force efficiency (CFE). These parameters enable a comprehensive assessment of both the overall energy-dissipation capability and mass efficiency of the investigated structures. Particular attention is given to magnesium AZ۳۱, whose crashworthiness performance is strongly affected by structural geometry and deformation-triggering mechanisms. Experimental studies have demonstrated that tapering and triggering strategies can significantly improve the energy-absorption characteristics of AZ۳۱ structures.A common crash-box geometry is therefore considered for both magnesium and aluminum alloys under identical geometric, loading, boundary, and impact conditions. The resulting force–displacement responses, deformation modes, and energy-absorption characteristics are compared. The objective is not to identify a universally superior material, but to determine the conditions under which the lower density of magnesium or the established mechanical performance of aluminum provides a more favorable crashworthiness response for lightweight automotive applications.