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Numerical simulation and optimization of hot stamping and quenching
processes of automobile anticollision beam
Zezhong Chen1,a,Xi Su2,b and Xueyuan Li3,c
1,2,3School of Materials Science and Engineering, University of Shanghai for Science and
Technology, Shanghai 200093, China
azzhchen@usst.edu.cn, b330984149@qq.com, cqianlansejiyi@qq.com
Keywords: Numerical Simulation; Optimization; Hot Stamping; Quenching; Anticollision Beam
Abstract. LS-DYNA and ANSYS software are adopted to simulate hot stamping and quenching
processes of M-shaped 1038mm*1.85mm B1500HS automobile anticollision beam. Different stress
distribution are obtained among different start temperature as 800 ℃, 850 ℃, 900 ℃, 950 ℃and
different stamping velocity as 25mm/s, 50mm/s, 75mm/s and 100mm/s. The higher the start
temperature, the better the metal formability; the higher the temperature at the end of forming, the
smaller the flow stress. The faster the stamping velocity, the shorter the cooling time, and the lower
the maximum flow stress. After optimization, the difference between the minimum and maximum
temperature of forming part decreases from 74℃to 47℃, indicating that the temperature distribution
after cooling is more uniformed.
Introduction
Hot stamping technology means the sheet metal is heated above the austenite temperature and
insulate for a period of time in order to make materials complete austenitizing, then stamped and
quenched in closed water cooling die which causes materials phase changed from austenitic structure
to martensitic structure [1], the strength of the final parts is up to 1500Mpa. The processes include
two stages: forming and quenching[2].
Numerical simulation
The M-shaped 1038mm*1.85mm B1500HS automobile anticollision beam is studied (Fig. 1). The
hot stamping forming is carried out without blank holder, and cooling water is cycled in cooling
runners among the die during stamping and quenching. Radius of cooling runners is less than 5mm in
order to improve service life of the die.
Fig. 1 M-shaped 1038mm*1.85mm B1500HS automobile anticollision beam
LS-DYNA software is adopted to simulate the hot stamping and quenching processes (Fig. 2). High
temperature characteristics of material should be considered, which means the coefficient of heat
conduction, the specific heat and the thermal expansion coefficient of B1500HS are all variables [3].
The forming time is set as 0.2~1s. The quenching time is set as 2~10s in view of the heat transmission
among punch, die and cooling water, ensuring that the quenching process meets the martensitic
formation temperature.
4th International Conference on Sensors, Mechatronics and Automation (ICSMA 2016)
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This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
Advances in Intelligent Systems Research, volume 136
284
（a）0.06s （b）0. 2s
Fig. 2 Forming process of anticollision beam
Analysis
When the start temperature of the sheet ranges from 800℃to 950℃, and the velocity of the stamping
is set as 100 mm/s, the distribution of the end temperature and stress is shown in Fig. 3 and 4.
(a)800℃(b)850℃(c)900℃(d)950℃
Fig. 3 End temperature distribution of forming parts in different start temperatures
(a)800℃(b)850℃(c)900℃(d)950℃
Fig. 4 Stress distribution of the forming parts in different start temperatures
If the start temperature of the sheet is set uniformly as 950 ℃, the stamping speed ranges from
25mm/s to 100mm/s, the temperature and stress after forming is shown in Fig. 5 and 6.
(a)25mm/s (b)50mm/s (c)75mm/s (d)100mm/s
Fig. 5 End temperature distribution of forming parts in different stamping speeds
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(a)25mm/s (b)50mm/s (c)75mm/s (d)100mm/s
Fig. 6 End stress distribution of forming parts in different stamping speeds
Optimization
Based on ANSYS software, a 2D simulation model of quenching system is established (Fig. 7). The
material parameters are the same as before, and the start temperature of material, die and cooling
water are defined as 950 ℃, 25 ℃and 15 ℃. Heat solid element PLANE55 is set for the mesh
definition [4].
Transient temperature distributions of hot stamping parts and die after 8s cooling and quenching
processes are simulated, as shown in Fig. 7, which shows that the maximum temperature of forming
parts reaches up to 242. 792℃after cooling and quenching, while the minimum temperature value is
168. 706℃, and the difference between the maximum and minimum temperature is about 74℃.
Fig. 7 Temperature distribution of die and forming parts after 8s cooling and quenching
The influence factors of die structure to forming parts’ cooling and quenching include cooling water
runner radius, runners’ spacing and the distance between runner and forming surface. In order to
optimize cooling and quenching, the vertical and horizontal coordinates of runner center, and the
runner radius are selected as variables to be optimized. The objective function is as follows [5]:
2
1
1 1
N
i
i
T
F T
T
(1)
Where,
is the variables to be optimized;
is the weight coefficient,
i
T
is the temperature of every
selected node in cross-section;
T
is the average temperature of selected nodes in cross-section;
N
is
the amount of selected nodes in cross-section.
Five groups of variables values after optimization are simulated and showed respectively in Table 1,
wherein, R is runner radius, a is vertical coordinates of upper die runner center, b is horizontal
coordinates of upper die runner center, c is vertical coordinates of lower die runner center, d is
horizontal coordinates of lower die runner center.
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Table 1 Variables of runner after optimization (mm)
Ordinate of upper
die runner center
a1
a2
a3
a4
a5
a6
a7
a8
144. 23
144.50
136. 55
119. 60
102. 90
119. 97
136.74
142.26
Abscissa of upper
die runner center
b1
b2
b3
b4
b5
b6
b7
90. 59
70. 78
52. 55
42. 43
30. 26
25. 87
20. 31
Ordinate of lower
die runner center
c1
c2
c3
c4
c5
c6
c13
c14
120. 23
120. 6
106. 87
89. 14
78. 79
80. 87
118. 77
99. 23
Abscissa of lower
die runner center
d1
d2
d3
d4
d5
d6
d14
95. 33
76. 27
61. 81
51. 96
34. 42
14. 03
6. 47
Radius of cooling
runner
R
4. 84
The objective function value is 1658 after optimization which reduces by 30% than the value as 2373
before optimization. After optimization, the maximum temperature of the forming part is only
186.872 ℃, which reduces by about 56℃than the value before optimization, and the difference
between the maximum and minimum decreases from 74℃to 47℃.
Conclusions
With the use of LS-DYNA and ANSYS software，the hot stamping and quenching processes of
M-shaped 1038mm*1.85mm B1500HS automobile anticollision beam is simulated and optimized.
Different stress distribution are obtained among different start temperature as 800℃, 850℃, 900℃,
950℃and different stamping velocity as 25mm/s, 50mm/s, 75mm/s and 100mm/s. The higher the
start temperature, the better the metal formability; the higher the temperature at the end of forming,
the smaller the flow stress. The faster the stamping velocity, the shorter the cooling time, and the
lower the maximum flow stress.
After optimization, the difference between the minimum and maximum temperature of forming
part decreases from 74℃to 47℃, indicating that the temperature distribution after cooling is more
uniformed.
References
[1] Abdulhay, B.，Bourouga, B., Dessain, C. Experimental and theoretical study of thermal aspects of
the hot stamping process. Applied Thermal Engineering 31, 674-685. (2010)
[2] Merklein, M., Lechler, J., Stoehr, T. Investigations on the thermal behavior of ultra high strength
boron manganese steels within hot stamping. International Journal of Material Forming 2, 259-262.
(2009)
[3] Bosetti, P., Bruschi, S., Stoehr, T. Interlaboratory comparison for heat transfer cofficient
identification in hot stamping of high strength steels. International Journal of Material Forming 3,
817-820. (2010)
[4] Caron, E., Daun, K.J., Wells, M.A. Experimental characterization of heat transfer coefficients
during hot forming die quenching of boron Steel. Metallurgical and Materials Transactions B 44,
332-343. (2013)
[5] CHOI, H.S., KIM, B.M., NAM, K.J. Development of hot stamped center pillar using form die
with channel type indirect blank holder. International Journal of Automatic Technology 12,
887-894. (2011)
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