Journal of Surface Engineered Materials and Advanced Technology, 2011, 1, 80-87
doi:10.4236/jsemat.2011.12012 Published Online July 2011 (http://www.SciRP.org/journal/jsemat)
Copyright © 2011 SciRes. JSEMAT
Analysis of Mobile Phone Reliability Based on
Active Disassembly Usin g Smart Ma t erials*
Zhifeng Liu, Liuxian Zhao , Jun Zhong, Xinyu Li, Huanbo Cheng
School of Mechanical and Auto Engineering, Hefei University of Technology, Hefei, China.
Email: zlxlove2008@sina.com
Received March 14th, 2011; revised April 30th, 2011; accept ed May 8th, 2011.
ABSTRACT
When using shape memory materials into active disassembly of actual electronic products, because the elastic modulus
of shape memory materials is affected by the tempera ture is relatively large, th erefore, th e main difference o f environ-
mental reliability between active disassembly products and common products is the impact of collision and vibration
under different temperature. Establishing three-dimensional analysis model, comparing the impact of collision and vi-
bration of mobile phone shells which are made up of PVC materials after casting & radiation and PC/ABS materials
under different temperature. Analyzing the reliability of mobile phone under different temperature and optimizing its
structure according to data of testing.
Keywords: Active Disassembly, Mobile Phone, Environmental Reliability, Analysis of Collision, A nalysis of Vibration
1. Introduction
With the rapid development of electronic technology, it
is growing demand for electronic products and the pace
of elimination of these products is accelerating which
result in the serious pollution of environment. Therefore,
Design for Disassembly (DfD) of products is getting
more and more attention in order to meet the require-
ments of environment protection [1,2]. However, the
current disassembly process of products is only one to
one; that is to say, worker can only disassemble one
product at one time. It is very difficult to achieve the
automation and assembly line of disassembly process of
products. What is more, the disassembly process can
pose threat to human health. So, it is a growing concern
of people about how efficiently to recycle and reuse these
obsolete e le ctronic products [3-5].
In recent years, with the deep research and extensive
application of smart materials, the method of Active
Disassembly using Smart Materials (ADSM) is getting
more and more concerns [6-10]. The technology of
ADSM was put forward by Dr. Chiodo in Brunel Uni-
versity at 1997. Active disassembly using smart material
(ADSM) is a method using shape memory material to
replace fastener, when it is heated to the stimulated tem-
perature, the product can be disassembled actively. The
R&D center of Nokia, Helsinki University of Technolo-
gy and Helsinki University of Art and Design started to
research the active disassembly of mobile phone in co-
operation at 2000-2001, which aimed to develop a ther-
mal stimulated mechanical structure for simplifying the
recycling process of mobile phone. By testing, the aver-
age disassembly time of mobile phone using ADSM is
2s, which is only 1/50 of the average disassembly time
using artificial. Therefore, the method of ADSM can
improve the efficiency of disassembly and achieve the
economic and efficient recycling of mobile phone. The
active disassembly tests of mobile phone and radio are
sho wn in Figure 1 [11].
Any brand of mobile phone needs to go through ri-
gorous testing to verify whether the mobile phone can
meet the required reliability norms before sales in the
market. Environment is one of the most important factors
which affect t he reliability of mobile. According to so me
materials, it is about 52% accidents of electronic prod-
ucts are caused by environment. Including 40% are
caused by temperature, 27% are caused by vibration,
19% are caused by humidity and the remaining accidents
are caused by dust, smoke etc [12].
The main difference between active disassembly mo-
bile phone and common mobile phone is that active dis-
assembly mobile phone is made up of smart drives or
active disassembly fasteners using shape memory alloy
*National Natural Science Foundati on of China (50775064).
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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81
Figure 1 . The active disassembly tests o f mobi le phone and radio [11].
(SMA) or shape memory polymer (SMP). And put the
drives and fasteners into the product when design and
assembly. Because properties of SMA and SMP are easy
to be affected by temperature, so, the main difference of
reliability between active disassembly mobile phone and
common mobile phone is caused by collision and vibra-
tion under different temperature.
2. Constructing the CAD Model of Active
Disassembly Mobile Phone
Constructing active disassembly mobile phone model
used three-dimensional modeling software according to
the structure of bar p hone. As sho wn in Figure 2.
In order to be simple and can explain the problem, this
phone model consists five parts. Number the parts ac-
cording to the order from the outside to the inside, 1 -
front cover, 2 - battery compartment cover, 3 - LCD
screen and the circuit board, 4 - battery, 5 - back cover.
The active disassembly fasteners of front cover and back
cover are made up of PVC material which receives ir-
radiation after casting, the dose of radiation is 4kGy
(SMP for short). There are two L shaped slot in the area
of back cover in order to place Ni-Ti memory alloy films
which act as dr ive of disassembling t he battery, the dr ive
can be changed by changing the size of memory alloy
films, shown in Figure 3.
Here select the stimulation temperature of Ni-Ti
me mor y alloy films as 75˚C. The size of phone model is
105 mm × 45 mm × 8 mm, the screen is 2 inch on stan-
dard, and the thickness of shell is 1 mm. The shell of
common mobile phone is made up of PC/ABS. The
properties of the shell of active disassembly mobile
phone and c ommon phone are s hown i n Table 1.
Table 1. The properties of SMP an d PC/ABS.
Name Density
kg/m 3 Elastic
modulus GPa Tensile
strength MPa Poisson’s
ratio
SMP 1000 3.7 70 0 .4
PC/ABS 1140 2.5 80 0.3
3. Analysis of Collision of Active
Disassembly Mobile Phone
Simulating the free falling body of mobile phone using
computer simulation in order to observe the response of
mobile during the process of free falling body.
3.1. Establishing the Equation of Colli s ion
Establishing the equation of collision before analyzing
the collision of mobile phone using Abaqus. The equa-
tion of collision can be described as below under the
overall coordinate system.
ex
Ma CvKdF++ =, (1)
in which M means the mass matrix of the structure, C
means the damping matrix of the structure, K means the
stiffness matr ix of the structure, a mea ns the vector of the
acceleration, v means the vector of the velocity, d means
the vector of the displacement,
ex
F
means he vector of
the external forces including the force of collision.
If order
in
FCv Kd= +
and suppose
reex in
FFF= −
, then equation of collision can be de-
scribed as below.
re
Ma F
=, (2)
If use concentrated mass, the mass matrix becomes t h e
diagonal matrix, and then each equation of degree of
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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82
freedom is independent. That is,
Figure 2 . The struc ture of mo bile phone .
Figure 3. The Ni-Ti memory alloy films before and after
deformation.
( )
, 1,2,,
re
ii i
Ma Fi==
(3)
Solving the equation of collision using display me-
thod, firstly obtain the following equation by Equation
(3).
, (4)
Then obtaining the velocity (
i
v
) by integration of
time, obtaining the displacement (
i
d
) by integration of
time once again. Here, the integration of time using dis-
play format of central difference. The display format of
central difference is described as below.
( )
( )
1/21/21 21 2
11/212
1/21 2
2
2
nn nnn
n nnn
n nn
vv att
d dvt
t tt
+−+ −
+ ++
++
=+ ∆+∆
= +⋅∆
∆= ∆+∆
(5)
Therefore, obtaining the displacement, velocity and
acceleration of each discrete point of time in the overall
domain of the time used the above recurrence formula.
The display format of integration does not require solu-
tion and reverse solution of matrix, it is not necessary to
solve the simultaneous equations and there is no problem
of convergence. Therefore, the speed of computation is
much fast; the criteria of stability can automatically con-
trol the step of time and ensure the speed of integration
[13].
3.2. The Model of Finite Element Analysis
The experimental condition of the example is shown in
Figure 3. The shell of mobile phone collides with the
rigid plane from a height of 2 mm by free falling body.
The element type of mobile phone shell is C3D8R,
eight-node, reduced integration, linear, solid element,
and the rigid plane uses discrete rigid body for simula-
tion. Selecting the type of parts as discrete rigid body
when constructing the model, therefore, it is not neces-
sary to define the properties of materials. Selecting Ex-
plicit solver in Abaqus [14]. The properties of materials
of mobile phone shel l are shown in Table 1.
3.3. Analy sis of the Result of Collision
Sim ulation
Simulating the mobile p hone collid es with the rigid p lane
by Abaqus finite element method. As shown in Figure 4.
It can been seen from Figure 4 that when the temper-
ature is 20˚C - 60˚C, the maximum stress of mobile
phone shell made up of SMP is 67.1 MP when it falls
from a height of 2 m , and it does not exceed the tensile
strength of SMP which is 70 MP. While the maximum
stress of mobile phone shell made up of PC/ABS is 119
MP under the same condition, which exceeds the tensile
strength of PC/ABS. Therefore, the mobile phone made
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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83
up of PC/ABS can be destro yed falling on the rigid plane
from a height of 2 m at room temperature. Thus, the re- liability of mobile phone mad e up of SMP is hi gher tha n
Figure 4. T he coll ision experiment of mobile phone using SMP and PC/ABS.
the reliabilit y o f mobile phone made up of PC/ABS.
The maximum stress of collision of active disassembly
mobile phone and the common mobile phone under dif-
ferent temperature are shown in Table 2 and Table 3.
4. Analysis of Vibration of Active
Disassembly Mobile Phone
4.1. The Analysis Model of Mobile Phone
The analysis of vibration of mobile phone mainly ana-
lyzes whether the vibration can cause the fasteners be-
tween front cover and back cover to detach. Therefore,
just analyzing the displacement of fasteners between
front cover and back cover is enough. The properties of
materials of mobile phone shell are shown in Table 1.
The parameters of mobile phone motor a re sho wn in Ta-
ble 4. The vibration time of m otor is 5 s.
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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4.2. Analy sis of the Result of Vibration
Sim ulation
The mobile phone can only move alternatively along the
Table 2. The maximum stress of collision of active disas-
sembl y mobil e p ho ne un de r different temperature.
Temperature ˚C The maximum
temperature MPa Tensi le strength
MPa
20 - 60 67.1 70
70 36.5 12.9
Table 3. The maximum stress of collision of common mobile
phone under different temperature.
Temperature ˚C The maximum
temperature MPa Tensi le strength
MPa
20 - 40 119 80
Table 4. The par ame ters of motor .
Rated voltage
V (DC) Rated
Current ( mA)
Rated Speed
R/M Hammer
length mm Mass g
3.0 80 20000 5 2
Z direction using finite element method of Abaqus.
Therefore, it is necessary to define the constraints of X,
Y directions and three rotation directions. The mobile
phone suffers a sinusoid al alternating load, the a mplitude
is 2 mm, the resul t is shown in Figure 5.
It can be seen from Figure 5 that the maximum stress
of front cover made up of SMP is 3.96 MP under the
temperature of 20˚C - 60˚C, and the maximum displace-
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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Figure 5. The collision experiment of mobile phone using SMP.
ment is 1.54 × 102 mm, while the length of connection
between front cover and back cover is 0.8 mm, ther efo re,
the fasteners between front cover and back cover do not
detach and it ensure s the reliabilit y of vibration of mobile
phone. The maximum stress of vibration of active disas-
sembly mobile phone under different temperature is
sho wn in Tabl e 5.
For easy comparison, conducting the same analysis of
mobile phone made up of PC/ABS, the result is shown in
Figure 6.
It can be seen from Figure 6 that the maximum stress
of front cover made up of PC/ABS is 0.12 MP, and the
maximum displacement is 2.74 × 10-2 mm, while the
length of connection between front cover and back cover
is 0.8 mm, therefore, the fasteners between front cover
and back cover do not detach and it ensures the reliability
of vibration of mobile phone. The maximum stress of
vibration of mobile phone made up of PC/ABS under
different te mperature is sho wn in Table 6 .
The vibration reliability of mobile phone made up of
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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Figure 6. The collisio n expe riment of mo bile phone using PC/ABS.
Table 5. The maximum stress of vibration of active disas-
sembl y mobil e p ho ne un de r dif f er e nt te mper ature.
Temperature ˚C Maximum
displacement mm
The length of
connection of
fastener s mm
20 - 60 1.54 × 102 0.8
70 7.15 × 102 0.8
80 3.32 × 102 0.8
90 1.54 0.8
Table 6. The maximum stress of vibration of mobile phone
made up of PC/ABS under dif f erent temperature.
Temperat ure ˚C Maximum
displacement mm
The length of
connection of
fastener s mm
20-40 2.74x 10-2 0.8
90 1.18 x 10-2 0.8
PC/AB S is highe r than t he vibratio n reliabilit y of mobile
phone made up of SMP by comparison.
4.3. Optimizing the Structure of Mobile Phone
In order to expand the stress of collision and vibration
quickly to other locations around the shell and obtain
better mechanical performance, it is necessary to replace
the material of fillet of mobile phone into magnesium
alloy material, as shown in Figure 7 [15]. Currently, the
price of magnesium alloy shell is about the double of
plastic shell. However, the mass of magnesium alloy
is light, the de nsity is low, t he resistance to stress is rela-
tively strong, the hardness is several times more than
traditional plastic, but its weight is only 1/3 of ordinary
plastic. Therefore, it can improve the reliabilit y of mobile
phone using ma gnesiu m allo y shell. What is mor e, it can
make the product more attractive by treating the surface
of magnesium alloy. Therefore, magnesium alloy shell
can be used in high-end mobile phones [15].
5. Conclusions
1) The mobile phone made up of SMP is not destroyed
falling fro m a height of 2 m under the room temperature,
while the mobile pho ne made up of PC/ABS is destr oyed
under the same conditions. Therefore, the collision relia-
bility of mobile phone shell made up of PVC material
which receives irr adiation after castin g is higher than t he
collision reliability of mobile phone shell made up of
PC/ABS. And it can improve the collision reliability us-
ing magnes ium a l loy shell of mobile pho ne.
2) The mobile phone made up of SMP and the mobile
phone made up of PC/ABS both can ensure the reliability
Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials
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Figure 7. Magnesium alloy s hell o f mobi le phone.
of vibration under room temperature. Because the prop-
erty of SMP is easily affected by the temperature, the
elastic modulus of SMP declines sharply under high-
temperature condition which results in the reliability of
mobile phone made up of SMP is relatively low. While
the elastic modulus of PC/ABS affected by the tempera-
ture is not so large, therefore, the mobile phone made up
of PC/ABS can ensure the reliability of vibration under
the temperature of 90˚C.
3) Mobile phone is used under the room temperature
because the electronic components of mobile phone are
easily destroyed under high temperature. The mobile
phone made up of SMP can ensure the reliability of col-
lision and vibration under room temperature, therefore,
the mobile phone made up of SMP meets the environ-
mental reliability.
6. Outlook
It is necessary to analyze the reliability of multi-step ac-
tive disasse mbl y prod ucts, s uch as the i mpact o f collision
and vibration on multi-step active disassembly mobile
phone. What is more, it is necessary to research the im-
pact of active disassembly on the economy and environ-
ment of products.
7. Acknowledgements
Thanks to the suppo rt of NS F C item: 50775064.
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