APPDENDIX A
100
High severity
Mid severity
Low severity
2
Acceleration (m/s )
80
60
40
20
0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
Time (s)
Fig. A1. Rear impact crash pulses within the corridors of
Fig. A2. Measurement of height and backset of head restraint
EuroNCAP whiplash test protocol (2010)
(arrow direction is positive )
Statistic counting
Local screening
Fig. A3. Harvest method and robustness inspection of optimal design
10
8
Acceleration (g)
Original seat
Sliding seat
6
4
2
0
-2
0.0
Deformation of EA system
0.1
0.2
Time (s)
0.3
0.4
0.5
Fig. A4. Crash pulses of the two sled tests
Fig. A5. Plastic deformation of EA system
Place of backward sliding
Fig. A6. The positions of the seat pan before (left) and after test (right)
Original seat
Sliding seat
Original seat
Sliding seat
100
Neck tension force (N)
Neck shear force (N)
400
300
200
100
0
Upper neck bending moment (Nm)
150
500
50
0
-50
-100
-100
-200
-150
-300
0.0
0.1
0.2
0.3
0.4
0.5
-200
0.0
0.1
0.2
0.3
0.4
0.5
50
Original seat
Sliding seat
40
30
20
10
0
-10
0.0
0.1
0.2
0.3
0.4
0.5
Time (s)
Time (s)
Time (s)
Fig. A7. Comparison of dummy responses from original and sliding seats: neck shear force, neck tension force and upper neck bending
momentum (from left to right)
Table A1. Design space for optimization of energy-absorption sliding seat
Subject
Recliner
Variable
Range
Step
Baseline
Recliner stiffness (Nm/deg)
20 ~ 200
20
67.5
Yielding torque (Nm)
373 ~ 2000
95
580
Cushion
stiffness
Seatback stiffness
0.1 ~ 5.0
0.17
1.0
Head restraint stiffness
0.1 ~ 5.0
0.17
1.0
Seat pan
EA restraint force level (kN)
1 ~ 10
0.5
10
APPDENDIX B
Design of Metal Strip Winding for Required EA Force Level
The sliding EA mechanism is shown in Figure A8. Pulling a metal strip winding around a cylinder can
provide a desirable EA force level. For designing such an EA mechanism, finite element simulations were
used followed by validation tests. First, a finite element model of the EA mechanism, as shown in Figure
A9, was built in LS-DYNA. The restraint wall, the fixed cylinder and the moving clamp were modelled
with rigid material (MAT 20), and the metal strip was modelled with elastic-plastic material (MAT 24)
with its property listed in Table A2. As the metal strip is pulled by seat’s sliding, it is bent around the
cylinder and re-bent back. The friction coefficient between the metal strip and the fixed cylinder was set to
0.2.
Figure A10 shows the traction force-displacement curves from the simulations under four combinations of
the thickness of the metal strip and the diameter of the cylinder. All of them exhibit plateau force levels,
which is ideal for energy absorption. The initial ramps are within 5 mm, which is small compared to the
entire EA sliding stroke (100 mm maximum). The force levels increase with the increase of the thickness of
the metal strip and the decrease of the diameter of the cylinder.
To validate the simulation results, a prototype of the EA mechanism, as shown in Figure A15, was
fabricated. The structure of the EA prototype consisted of a moving clamp, a fixed cylinder, a metal strip, a
restraint wall and a fixed clamp. The moving clamp represents the traction cylinder and the fixed plate
represents the locking plate, respectively. The metal strip is made of the widely used ductile steel Q235,
with the material property parameters listed in Table A2. The dimension of the metal strip is 10 mm in
width and 120 mm in length. The thickness of the metal strip of 1.0 mm and 1.6 mm and the diameter of
the fixed cylinder of 10 mm and 14 mm, were respectively tested. Quasi-static tests were conducted on a
uniaxial tension machine. The moving clamp was connected to and pulled by the upper grip of the machine
at a constant speed of 10 mm/min. The fixed end was connected to the lower grip. The test results and the
simulation results are compared in Figure A10, showing a good correlation.
Using rigid-perfectly-plastic material model and balance of internal work and external work, the plateau
force level of the metal strip winding around the cylinder can also be predicted by the following equation
(Zhang 2012):
𝜇𝑒 𝜇𝜋 𝜎𝑌 𝑏𝑡 2
𝐹 = (𝜇𝑒 𝜇𝜋
−𝑒 𝜇𝜋 −𝜇𝜋−1)𝑑
(A-1)
where 𝜇 is the friction coefficient between the metal strip and the fixed cylinder, 𝑒 is Euler's number, 𝜎𝑌 is
the yielding stress of the metal strip material, 𝑏 is the width and 𝑡 is the thickness of the metal strip,
respectively, and 𝑑 is the diameter of the fixed cylinder. Based on this equation, the theoretical relationship
between the plateau force, the metal strip thickness and the cylinder diameter is plotted in Figure A11
together with the test results. The friction coefficient 𝜇, 0.2 and 0.22 were set as the lower bound and the
upper bound, respectively. Note that the friction coefficient range was only an estimate and the strain
hardening of the metal strip material was not considered in the theoretical equation. The theoretical
equation only provides the relationship among the design parameters. Its prediction can be used for
examining the trend of the EA plateau force with the design parameters, not for an absolute prediction.
The simulation and the test results suggest that the configuration of the metal strip thickness of 1.6 mm and
the cylinder diameter of 10 mm can provide a plateau force level of 1.6 kN. Two of such metal strip
winding devices can be integrated into the two seat rails under seat pan, one on each side, and would give
an expected plateau force level of about 3 kN, which can provide good protection against whiplash neck
injury in rear crashes of low and medium severities.
Furthermore, it is designable to make the EA force level adjustable for protection under rear crashes of
different severities or even for occupants of different sizes. For example, as shown in Figure A12,
additional cylinders can be used to change the route and amount of the metal strip winding, and the position
of one of the cylinders may be adjustable by some execution devices according to crash severity or other
factors. With this kind of designs, the sliding seat concept can become an adaptive countermeasure against
whiplash neck injury for more complicated crash conditions.
Table A2. Material parameters of Q235 cold rolling steel sheet
Material
Q235
Young’s modulus (GPa)
210
Poisson’s ratio
0.3
Yielding stress(MPa)
205
Tangent modulus (GPa)
79
(a) CAD design
(b) Prototype structure
Fig. A8. Prototype design of EA mechanism
(a) Finite element model of EA configuration
(b) Stress distribution during EA stroke
Fig. A9. Finite element model and its deformation
2500
2500
Test (thickness = 1.0 mm)
Test (thickness = 1.6 mm)
Simulation (thickness = 1.0 mm)
Simulation (thickness = 1.6 mm)
2250
2000
1750
1750
1500
1500
Force (N)
Force (N)
2000
Test (thickness = 1.0 mm)
Test (thickness = 1.6 mm)
Simulation (thickness = 1.0 mm)
Simulation (thickness = 1.6 mm)
2250
1250
1000
750
1250
1000
750
500
500
250
250
Diameter: 14 mm
Diameter: 10 mm
0
0
5
10
15
20
25
Displacement (mm)
30
35
40
0
0
5
10
15
20
25
Displacement (mm)
30
35
40
(a) Diameter of cylinder: 14 mm
(b) Diameter of cylinder: 10 mm
Fig. A10. Force-displacement curves of tests and simulations
2500
2000
μ=0.20， d=10mm
μ=0.22， d=10mm
μ=0.20， d=14mm
μ=0.22， d=14mm
Test (d=10mm)
Test (d=14mm)
Movable cylinder
Force (N)
1500
Fixed cylinder
Fixed cylinder
1000
500
0
0.0
0.5
1.0
1.5
2.0
2.5
Metal strip thickness (mm)
Fig. A11. Predicted and measured plateau forces vs. metal strip
Fig. A12. EA mechanism design for having adjustable force level
thickness
with the metal strip winding mechanism
Appendix C
Design of Sliding Mechanism of Sliding Seat
While designing of a sliding mechanism and an EA mechanism of the sliding seat, three basic requirements
need to be considered. First, the normal adjustment function of seat position should not be affected.
Second, it can slide backward under certain restraint plateau force level under rear impact. Third, occupant
injury risk should not increase in other crash types when using the passive sliding seat rail system.
Figures A13 and A14 show the structure of a non-sliding seat rail system. The latch plate is rigidly attached
to the upper rail (fixed to the seat pan) and also constrained to the lower rail (fixed to the vehicle floor) by
the locking teeth when the seat pan is stationary. The sliding seat prototype was fabricated by modifying
the locking plate, as shown in Figure A15. A trough (Figures A16-A18) was built in the upper rail to allow
seat pan to slide relatively to the locking plate along the trough in backward direction. Figure A16 shows a
detailed layout of the EA mechanism including a fixed cylinder, a metal strip, a restraint wall, a traction
cylinder, a speed-limiting baffle on the locking plate. The fixed cylinder is mounted on the locking plate,
and the metal strip, with one end connected to the upper rail through a traction cylinder and the other end
free, is winded around this fixed cylinder. For normal seat position adjustment, the locking teeth are
released, and the locking plate and the handle (attached to the upper rail) move together with the upper rail
(attached to the seat pan) relative to the lower rail (attached to the floor), as shown in Figure A17. The
speed-limiting baffle is mounted in the sliding direction of the traction cylinder to serve as a threshold and
activated only when a rear impact is sufficiently severe. The restraint wall mounted on the locking plate is
used to restrain the metal strip. Since the rear stopper and the speed-limiting baffle on the locking plate
constrain the forward and rearward motions of the upper rail, the seat pan cannot move forward or rearward
in normal use.
Under a minor rear impact, the threshold from the speed-limiting baffle cannot be reached and therefore the
seat pan rearward motion is not triggered. When a rear impact is sufficiently severe, the traction cylinder
overcomes the resistance from the speed-limiting baffle, and then, the EA mechanism is activated. The seat
pan moves rearward relative to the lower rail, which is similar to the normal seat adjustment motion, under
a certain restraint force generated by pulling the metal strip to bend around the fixed cylinder. The frontal
stopper limits the rearward motion of the seat pan when the sliding distance exceeds 100 mm (Figure A18).
During the seat sliding, part of the occupant’s kinetic energy is absorbed by the EA mechanism. Figure A19
shows the integrated EA mechanism of the sliding seat rail system. For design details of the sliding
mechanism, please refer to Zhang (2012).
Fig. A13. Rail system of a benchmark seat
Fig. A14. The EA Position on one side of upper rail
Fig. A15. Main components of EA configuration
Figure A16. Locking status of EA configuration
Fig. A17. Adjustment status of EA configuration
Fig. A18. Sliding status of EA configuration
Locking plate
EA system
Fig. A19. Seat rail system of the sliding seat concept