Advanced Materials Research Vol. 740 (2013) pp 350-358
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.740.350
The Assessment of Stress Analysis for a Notebook’s Hinge Stopper
Using the FEM Method
Min-Chie Chiu1, a, Long-Jyi Yeh2,b and I - Lang Chiu2,c
1
Department of Mechanical and Automation Engineering, Chung Chou University of Science and
Technology. 6, Lane 2, Sec.3, Shanchiao Rd., Yuanlin, Changhua 51003, Taiwan, R.O.C.
2
Department of Mechanical Engineering, Tatung University, Taipei, Taiwan, R.O.C.
a
b
c
minchie.chiu@msa.hinet.net, ljyeh@ttu.edu.tw, ichiro.chiu@szs.com.tw
Keywords: CAE, hinge, FEM, stress
Abstract. Computer Aided Engineering (CAE) software is a vital analytical tool which is often
adopted for product design. Engineers can obtain related design information for stress, strain,
displacement, fatigue, and longevity of products via a CAE simulation. In order to improve product
reliability, analysis of a product’s structure using CAE is compulsory. The purpose of this research is
to implement CAE analysis on a laptop’s hinge. A 3-D model of the laptop’s hinge was first
established by Pro/Engineer software and then transferred onto ANSYS/Workbench software.
Moreover, all boundary conditions, connections, materials, and mesh property were set into an
ANSYS program. Subsequently, the calculation of kinetic behavior for the hinge structure and
maximum stress and stress allocation were performed by the ANSYS. In order to verify the
correctness of the parameter settings on ANSYS/Workbench software, a product’s breaking test was
conducted. A comparison between the experimental data and the theoretical data of the ANSYS was
also carried out. Consequently, the deviation between the analyzed data and the real testing data is
within 5%. Therefore, the analytical methods established above can provide a quick and efficient
design for the structural strength of a hinge stopper.
Introduction
A hinge connecting the system and the LED monitor to support the system’s weight plays an essential
role in the notebook. It provides a rotating function for the LED monitor. Therefore, sufficient hinge
strength that endures repeated operations is required. In 1965, Paros and Weisbord [1] proposed a
design guideline for a bending hinge. In 1988, Smith et al. [2] presented an efficient rotating
mechanism for a high precision machine. In 1998, Kim and Chen [3] assessed the influence of a
repeatedly strained plastic hinge with respect to various external forces and geometry. In 1991, Shifu
and Qingsing [4] proposed a mechanical design for a precision machine. However, numerical analysis
and experimental verification of the notebook’s hinge was lacking. Therefore, analysis of the
stress/strain of the notebook’s hinge and an assessment of the experimental test are needed. In this
study, three kinds of auto-closed type hinges (type1, type-2, and type-3) are introduced along with an
analysis of the hinge’s stress using the finite element method (FEM). Moreover, an experimental test
for the strength of the hinge stopper via maximizing the opening angle of the hinge is performed.
Subsequently, a comparison of the theoretical data and the experimental value is executed. Here, the
results reveal that the data is at least 95% accurate. Therefore, predicting the hinge stress using the
FEM method is reliable. Design efficiency will be improved and design time shortened by using the
theoretical simulation.
Structure of the Auto-Closed Hinge
For a conventional hinge shown in Fig. 1(A), the principle of the hinge’s function is to produce an
axial pushing force by tightly integrating the disk type leaf spring and locking the screw. Torsion will
be produced by rotating the related components. The torsion can also be adjusted by the screw. The
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351
rotating angle can be extended to 360 degrees. However, because the friction area is small, a large
diameter is required. In addition, the assembly time and error possibility in the assembly will increase
due to numerous parts in the hinge. Also, an anti-loosening design for the screw is required when
using the screw to adjust the torsion. To reduce the diameter and stabilize the torsion, an auto-closed
hinge shown in Figs. 1(B) is adopted. As indicated in Figs. 1(B), the primary components include the
rotating axle, packing, leaf spring, saddle, screw, concave gear, and the convex gear. The auto-closed
hinge is similar to a conventional hinge. The principle of the hinge’s function is to produce an axial
pushing force by tightly integrating the disk type leaf spring and locking the screw. Torsion will be
produced by rotating the related parts. Torsion can also be adjusted by the screw. The difference
between a conventional hinge and the auto-closed hinge is its concave and convex gear. There is an
automatic closing and a force-changing function in the auto-closed hinge using the concave and the
convex gear. Because of this mechanism, its rotating angle can be extended to 360 degrees. The
advantages of the auto-closed hinge include (1)The system and the cover are closed without adding
extra elements; (2) Used extensively in industry;(3) Stable torsion.;(4) Stopper swing longevity;(5)
Components can be shared.
(A) a conventional hinge (B) an auto-closed-type hinge
Figure 1 The assembly drawing of hinges.
Stress Analysis of the Hinge’s Stopper Using the ANSYS
The procedures in the ANSYS program simulation used in assessing the stress situation of a product
include the “pre-processor”, the “solution”, and the “post- processor.” The “pre-processor” is used to
establish the geometric shape within a finite element model, to define the material property, and to
setup the boundary condition. The “solution” is used to find the numerical solution of the metrical
equations using a finite element theory. The “post-processor” is used to deal with the resulting
solution, to plot the results with a profile, and to output the resulting animation [5]. An Ansys
Workbench 11.0 is adopted and used in the stress analysis of the auto-closed hinge stopper. The flow
diagram of the stress analysis is shown in Fig. 2. The analysis of the related module will be initialized
when inputting the hinge model into the ANSYS.The related material property for each related
component is shown in Table 1.
Figure 2 The flow diagram of the stress analysis.
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Table 1 Material property.
component
Lower saddle /upper saddle
packing /stopper
Rotating axle
Long support
Concave/convex wheel
Molding block/screw
Panel/baclboard
screw nut
material
Yielding strength Mpa
Tensile strength Mpa
SK7
1360
1865
AISI1144
SECC
Fe- 8Ni
S50C
Aluminum
SWRM
1034
140
1230
1425
165
285
1378
205
1230
1650
330
330
A connection and contact exists within the objects. With regard to the screw and rivet, neither
friction nor sliding occurs in the contact pair; therefore, as indicated in Fig. 3, “Bonded” is set for the
screw and the rivet. In addition, the hinge is composed of many parts. Because the source of torsion is
the axis force induced by the compressed leaf spring, setting the K value for the leaf spring is
necessary. In the FEM analysis, “Spring“ is selected in the “Connection.” As indicated in Fig. 4, the K
value of 1540 N/mm produced by the integrated leaf spring is inputted into “Longitudinal Stiffness.”
Figure 3 The contact pair for the screw and the rivet.
Figure 4 Setup of the torsion zone for the leaf spring.
Quality of the element will influence the solution’s accuracy and the simulation time. As indicated
in Fig. 5, the mesh will be automatically produced by clicking “Generate Mesh.” However, it does not
easily converge at the position of the hinge stopper joint. Therefore, the mesh dimension of the
stopper joint needs to be reduced to 0.1mm ~ 0.3mm. The mesh dimension for the other regions will
remain the same. A deforming process for the hinge stopper is predicted using static analysis. As
indicated in Fig. 6, for the static analysis setting of the hinge stopper, “Number of Steps” is set as 1,
“Auto Time Stepping” is set as “ON,” “Initial Time Steps” is set as 50, “Minimum Substeps” is set as
50, “Maximum Substeps” is set as 100, and “Large Deflection” is set as “ON.” As indicated in Fig. 7,
the fixed face for the longevity test is selected. As indicated in Fig. 8, the damage force for the stopper
is inputted into the X component. As can be seen the von Mises criterion is often selected as the
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damage criterion in ductile material (i.e., steel and copper) [5]. Therefore, the von Mises criterion is
adopted as an equivalent stress. As indicated in Fig. 9, the setting of the von Mises criterion has been
accomplished.
Figure 5 Mesh generation.
Figure 6 The static analysis setting.
Figure 7 The fixed face definition for the longevity test.
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Figure 8 The damage force definition for the stopper’s longevity test.
Figure 9 Establishment of the equivalent stress.
Setup of the Experimental Test for the Hinge Stopper
To verify the accuracy of the numerical stress simulated by the FEM (Ansys program), experimental
work of the destruction test for the hinge stopper is required. Here, three kinds of auto-closed type
hinges (type-1, type-2, and type-3) are adopted in the experimental work. As indicated in Fig. 10,
prototype hinges are used for inspecting the maximum destruction force using a push/pull meter. The
push/pull meter is reset before the destruction test is performed.
Figure 10 The destruction test for the hinge stopper joint.
Experimental Results and Discussion
Ten sets of type-1 notebooks are tested. The results of the type-1 hinge stopper in the destruction test
are shown in Table 2. In addition, the simulated results (using FEM) are shown in Table 3. As
indicated in Table 3, the maximum stress at the hinge stopper joint (at the right rotating axle) will
reach 1387.1 Mpa when the external force implemented at the notebook’s cover is 37.044 N. The
above stress is beyond the maximum allowable tensile stress (1387.1 Mpa) of the rotating axle which
is already broken. The profile of the related stress with respect to the acting force is shown in Fig. 11.
In comparing the simulated results with the experimental data, it is found that the error percentage
shown in Table 4 reaches 3.8%.
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Table 2 Results of the hinge stopper force in the destruction test (type-1).
Item no.
stopper damage force (N)
1
2
3
36.75
37.24
38.22
4
37.35
5
6
7
8
9
10
average
40.57
40.18
38.71
38.22
37.73
40.18
38.51
Table 3 The stress analysis of the hinge stopper (type-1).
step
Stopper force
(N)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
0.0
0.88
1.76
3.09
4.41
5.29
6.17
7.50
8.82
9.70
10.58
11.91
13.23
14.11
14.99
16.32
17.64
18.52
19.40
20.73
22.05
22.93
23.81
25.14
Rotating
axle-left
(Mpa)
0.0
165.65
277.44
412.99
522.54
602.39
682.04
802.02
921.93
999.65
1078.30
1039.90
1117.60
1084.20
1099.10
1077.80
1073.40
1079.50
1078.00
1081.10
1083.00
1083.70
1086.90
1095.2
24
25
26
26.46
26.901
27.122
27
28
29
30
31
32
33
34
35
27.232
27.342
27.507
27.756
28.127
28.686
29.523
30.36
30.87
Rotating axle-right
(Mpa)
Upper saddle-left
(Mpa)
Upper saddle-right
(Mpa)
0.0
212.66
355.76
527.95
669.21
771.24
872.72
1025
1178.2
1034.3
1040.6
1061.3
1075.8
1093.5
1101
1090.1
1087.2
1089.2
1090.7
1092.6
1094.5
1095.7
1097
1104.7
0.0
116.17
205.77
317
412.48
478
543.4
640.79
737.94
800.88
864.23
959.98
1056.8
1127.7
1200.4
1262.2
1418.1
1552.7
1456.7
1352.2
1362.8
1394.8
1397.9
1437
0.0
91.304
146.1
220.99
285.03
330.7
396.21
494.12
592.38
656.53
721.46
820.2
883.23
945.83
827.66
905.26
995.25
1059.6
1128.6
1234.7
1340.7
1411
1455.5
1469.5
1103.6
1106.5
1111.7
1115.5
1119
1120.8
1464.7
1476.3
1482.4
1387.7
1393.4
1372.6
1117.4
1123.3
1131.8
1134.1
1130.9
1119.3
1126.2
1135.1
1140.9
1124.8
1122.6
1125.7
1130.2
1136.8
1147.1
1166.4
1187.8
1201.1
1485.6
1488.9
1493.6
1500.6
1510.6
1525.5
1552.2
1586
1606.6
1373.9
1359.6
1360.2
1361.1
1384.9
1388
1385.5
1405
1417.4
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Materials, Mechatronics and Automation II
36
37
38
39
40
41
42
43
44
45
46
47
31.752
32.634
33.957
35.28
36.162
37.044
38.367
39.69
40.572
41.454
42.777
44.1
1147.9
1174.7
1218
1264.6
1302.8
1341.9
1398.5
1455.8
1496
1613.1
1660.9
1710.7
1226.3
1252.3
1291.1
1329.4
1358.5
1387.1
1430.3
1474.2
1503.9
1538.4
1586.6
1634.7
1620.5
1651.3
1708.6
1758.2
1793.8
1826.7
1872.9
1916
1944
1971
2012.2
2050.9
1440.3
1461.1
1497.7
1541.2
1573.9
1605.5
1652.2
1697.6
1727.8
1762.1
1807.3
1850.9
Figure 11 Profile of the related stress with respect to the acting force [type-1 auto-closed hinge].
Table 4 Accuracy between FEM and experimental data (type-1).
FEM data
Experimental data
absolute error
Error percentage (%)
Stopper force (N)
37.04
38.51
1.47
3.8%
Similarly, ten sets of type-2 notebooks are tested. The simulated results indicated that the
maximum stress at the hinge stopper joint (at the right rotating axle) will reach 1843.6 Mpa when the
external force implemented at the notebook’s cover is 34.104 N. The above stress is near the
maximum allowable tensile stress (1865 Mpa) of the rotating axle which is already broken. The
profile of the related stress with respect to the acting force is shown in Fig. 12. In comparing the
simulated results with the experimental data, it is found that the error percentage shown in Table 5
reaches 4.1 %.
Figure 12 Profile of the related stress with respect to the acting force [type-2 auto-closed hinge].
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Table 5 Accuracy between FEM and experimental data (type-2).
FEM data
Experimental data
absolute error
Error percentage (%)
Stopper force (N)
34.10
35.57
1.47
4.1%
Likewise, ten sets of type-3 notebooks are tested. According to the FEM’s simulated results, the
maximum stress at the hinge stopper joint (at the right rotating axle) will reach 1863.2 Mpa when the
external force implemented at the notebook’s cover is 44.57 N. The above stress is beyond the
maximum allowable tensile stress (1865 Mpa) of the stopper which is already broken. The profile of
the related stress with respect to the acting force is shown in Fig. 13. In comparing the simulated
results with the experimental data, it is found that the error percentage shown in Table 6 reaches 4.4
%.
Figure 13 Profile of the related stress with respect to the acting force [type-3 auto-closed hinge].
Table 6 Accuracy between FEM and experimental data (type-3).
FEM data
Experimental data
absolute error
Error percentage (%)
Stopper force (N)
44.57
42.68
1.89
4.4%
Conclusion
A numerical stress analysis of the auto-closed hinge stopper for a notebook has been assessed.
Because of the numerical prediction, the time spent in the product design process and cost of
manufacturing will be shortened without tedious trials and errors in a laboratory. In addition, it is
essential to assure that the stopper joint can endure maximum stress. Maximum stress is induced due
to a sudden pushing force when the monitor of the notebook is opened at its maximum angle.
Therefore, the required hinge stopper joint is specified by the notebook’s client. As mentioned in
section 5, three kinds of auto-closed hinge stoppers (type-1, type-2, and type-3) are assessed. The
results reveal that for a type-1 auto-closed hinge, the maximum stress at the hinge stopper joint (at the
right rotating axle) will reach 1387.1 Mpa when the external force implemented at the notebook’s
cover is 37.044 N. The above stress is beyond the maximum allowable tensile stress (1387.1 Mpa) of
the rotating axle which is broken. Additionally, for a type-2 auto-closed hinge, the maximum stress at
the hinge stopper joint (at the right rotating axle) will reach 1843.6 Mpa when the external force
implemented at the notebook’s cover is 34.104 N. The above stress is near the maximum allowable
tensile stress (1865 Mpa) of the rotating axle which is broken. Also, for a type-3 auto-closed hinge,
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Materials, Mechatronics and Automation II
the maximum stress at the hinge stopper joint (at the right rotating axle) will reach 1863.2 Mpa when
the external force implemented at the notebook’s cover is 44.57 N. The maximum allowable tensile
stress of the stopper is 1865 Mpa. Moreover, the accuracy of the numerical results for three kinds of
auto-closed hinges (type 1~3) shown in Tables 4, 5, and 6 has been been executed. As indicated in
Tables 4, 5, and 6, the resulting error percentages between the simulated results and the experimental
data are between 3.8%~4.4%. Consequently, this study indeed can provide a quick design for the
hinge stopper of a notebook. Moreover, it will reduce costs caused by tedious trials and errors in the
laboratory.
References
[1] J.M. Paros, L. Weisbord: Machine Design Vol. 35 (1965), p. 151
[2] S.T. Smith, D.G. Chetwynd, and D.K. Bowen: J. Phys. E. Vol. 20 (1987), p. 977
[3] S.E. Kim, M.K. Kim, and W.F. Chen: Engineering Structures Vol. 22 (2000), p. 15
[4] X. Shifu, L. Qingsing: Precision Instrument Design, Tsinghua University Press. Beijing (1991)
[5] H.H. Lee: Finite Element Simulations with ANSYS Workbench 12, GOTOP INFORMATION
INC. (2010)