20 Multi-Objective Optimization of Automotive Front Rail …
253
Table 20.1 Material property
of mild steel
Density
Young’s
modulus
Poisson’s ratio
Name In
LS-DYNA
7800 kg/m 3
206 GPa
0.3
material #24
Fig. 20.2 Strain hardening
curve of mild steel
mass points.The reduced FE model contains 428,263 elements and 451,820 nodes
while the percent of triangular elements less than 5%. According to the standards
of frontal impact test against deformable barrier with 40% overlapping in C-NCAP,
the speed of impact is set as 64 km/h while the simulation time is set as 100 ms.
LS-DYNA is utilized for collision simulation. The contact force in a collision is
necessary to be considered in modeling [12], therefore the contact force is detailed
construction in FE model.
The structure considered in this study is a front rail that consists of several thinwalled parts, and the material is mild steel, then the properties of material are listed
as Table 20.1. And this material has a piecewise linear elastic-plastic behavior with
strain hardening. Figure 20.2 illustrates the relationship between the plastic stress
and plastic strain of mild steel [13].
The process of optimization design on lightweight and crashworthiness can be
draw as Fig. 20.3.
20.3 Definition of Multi-objective Optimization Problem
20.3.1 Optimization Objectives and Constrains
The target of optimization design is to achieve lightweight and improve crashworthiness. In this paper, the maximum acceleration of B-pillar a max and mass of front
rail m are considered as objectives while the rearward intrusion of A-pillar D 1 ,
253
Table 20.1 Material property
of mild steel
Density
Young’s
modulus
Poisson’s ratio
Name In
LS-DYNA
7800 kg/m 3
206 GPa
0.3
material #24
Fig. 20.2 Strain hardening
curve of mild steel
mass points.The reduced FE model contains 428,263 elements and 451,820 nodes
while the percent of triangular elements less than 5%. According to the standards
of frontal impact test against deformable barrier with 40% overlapping in C-NCAP,
the speed of impact is set as 64 km/h while the simulation time is set as 100 ms.
LS-DYNA is utilized for collision simulation. The contact force in a collision is
necessary to be considered in modeling [12], therefore the contact force is detailed
construction in FE model.
The structure considered in this study is a front rail that consists of several thinwalled parts, and the material is mild steel, then the properties of material are listed
as Table 20.1. And this material has a piecewise linear elastic-plastic behavior with
strain hardening. Figure 20.2 illustrates the relationship between the plastic stress
and plastic strain of mild steel [13].
The process of optimization design on lightweight and crashworthiness can be
draw as Fig. 20.3.
20.3 Definition of Multi-objective Optimization Problem
20.3.1 Optimization Objectives and Constrains
The target of optimization design is to achieve lightweight and improve crashworthiness. In this paper, the maximum acceleration of B-pillar a max and mass of front
rail m are considered as objectives while the rearward intrusion of A-pillar D 1 ,