1) The document presents a finite element study that develops a 3D model of the human foot and investigates the stress and strain distributions under various loading conditions and surfaces. 2) The model is created using CATIA software and analyzed using ANSYS. The study finds that peak stress and strain occur on the bottom of the foot. 3) The results show that stress and strain decrease as the Young's modulus value increases under the same loading. Running produces higher stresses and strains than standing, and concrete surfaces produce lower loading than artificial grass or rubber surfaces.

1. Finite Element Study of Foot When Running on
Various Surface.
M.Najib and A.Hassan
Mohamad Najib bin Ali Amran
Mechanical Engineering
Universiti Malaysia Perlis
Perlis,Malaysia
mohamadnajibaliamran@gmail.com
Abstract—The main purpose of this project is to investigate the
mechanical stress and strain distribution of foot during running
on various surface. The human foot is adaptable structures of
bones, joints, muscles and soft tissue that let us stand upright and
perform exercises like walking, running and jumping. To
perform a direct investigation or experiment on human foot, it
seems very difficult since the structures are very complex
compared to other human part body. The study of human foot
behavior is significant to identify the location of injury
occurrence and the cause in order to increase the knowledge in
the improvement the way to prevent an injury and very useful to
improve footwear design as well as enhance its development. The
purposes of this study are to develop a finite element model of the
human foot and investigate the effect of various loadings produce
on various surfaces such as artificial grass, concrete and rubber
toward the biomechanical response of the human foot. The foot
model reconstruct in CATIA software while 3D Finite Element
Model as well as the analysis has done in ANSYS 14.5 software.
The peak of stress and strain distribution was occurring on below
of human foot. Straining and stress effect were decreasing when
Young’s Modulus value increase with the same amount of
loading.
Keywords—3D Finite Element Model; mechanical stress;
mechanical strain; Young’s Modulus;
I. INTRODUCTION
Foot is a complex structure in human body structure. Most
human activity is using a foot for example standing, walking
and running. Running is a healthy activity can benefit almost a
part of human body. If human do a running activity regularly
it will give benefit to physical and mental for example help to
build strong bones, strengthen muscles, improve
cardiovascular muscle, reduce stress, can enjoy a sense of
freedom and improve mental stamina.
At a certain condition, a running activity can give an injury
to human foot if we do wrong step or do this activity on non-
suitable surface condition. The surface of running of running
is most factors in determining how well they perform and how
likely injured them are to get. That’s why we must understand
running an activity where collisions occurs between human
foot and ground.
When a human start running, the muscles in human right
foot will contract and reverse the downward velocity of human
body. This process will make a human more easily and faster
to moving on running. After that, the muscle in the left leg
will do a job for descending the acceleration on human foot.
So, human must know to choosing the surface of running to
prevent an injury such as not running on uneven surface.
A structure of human foot combines mechanical complexity
and structural strength. The ankle function as shock absorber
for foot can maintain when large pressure produce and
provides flexibility and resiliency. Besides that, there are
many vertebrates have on human leg structure. The total
vertebrates contain in leg and ankles are 26 bones, 33 joints
and have more 100 muscles, tendons and ligaments.
When the injury occur on foot, it is difficult to investigate
the injury of foot during experimental because the size of bone
on plantar fascia (PF) too small. Analysis need to be made to

2. ensure the force produce on foot when running on various
surfaces such as artificial grass, concrete and rubber which
surfaces will lower the risk of injury on foot.
II. METHODOLOGY
A. CATIA modelling of the human foot
For the analysis of the human foot related to the find
mechanical stress and strain on below human foot part, a
suitable software need to be use in order to obtain the
desire outcome. Thus, various software has been
shortlisted for the purpose of the project. The software
used includes CATIA in which the human foot with the
ground support has been modelled by using this software.
This software is a computer aided drawing which widely
used around the world. CATIA is drawing software which
enables the user to draw the complex part as well as
establishing a simulation. It is also easy to use because the
command prompt for the software is in properly manner.
The foot with ground support as shown in Figure 1 has
been modelled by using CATIA CAD software before the
simulation and analysis can be done by using other suitable
software that has been dedicated to the distribution stress
and strain analysis.
Figure1: Foot with ground support.
B. ANSYS 14.5 Software
ANSYS 14.5 is one of the software has been widely
used in the engineering field. ANSYS software used in
order to determine the stress and strain on the human foot
model analysis. There are several step must be follows
when development Finite Element Model (FEM). FEM
used to predict the mechanical behavior of structures and
material in engineering application.
The first step are building a new material in
engineering data because human foot(skin) structure and
ground support(rigid body) not consist in ANSYS
software. For this material, all was considered as linear
elastic and isotropic. The property of all materials was
derived from Young’s Modulus and Poisson’s ratio. The
mechanical property of human foot and rigid body are
tabulated in Table 3.1.
Table 3.1: Mechanical properties structure of human foot
model
Next, imported and generate model by click at
geometry column under static structural system in project
schematic and then the geometry window will appear. Now,
change the format to .IGS from .CAT because ANSYS only
can read a folder with .STEP and .IGS format.
The next process is defined material and contact of
human foot model with ground support. The materials in this
column were taken from the engineering data that has build in
pevious step build a new material process. For stiffness parts,
all components set as flexible by click at eometry definition
column.
Figure 2: Define manually contact on surface model.
For meshing process, convergence test must perform
to get perfect number of element size to be use in analysis.
The function of convergence test to know the optimum size of
mesh so the mesh size is not too small or excessively large.
Effect if element size to large are take very long time to
complete mesh and if too large the result for analysis is not
accurate and have a higher percentage of error. For perform
this convergence test used the strain analysis. The result of
convergence test shows the element size start converge at
element size 1.2-1.0mm. So, for this analysis used element
size 1.1mm because in the range of converge value, it produce
the lowest value of maximum strain.
Structure Young’s
Modulus(Mpa)
Poisson’s
ratio(v)
Human Foot 0.15 0.45
Ground
Support
2100000 0.4

3. Table 1: Element size and maximum strain value from
convergence test
The model consist two components which is human
foot and ground support. The mesh type for human foot are
tetrahedral and for ground support are hexahedral. For the
surface have a contact, applied a sizing contact meshing
method because it creates elements of relatively the same size
on bodies from the faces of a face to edge contact region.
Figure 3: Complete meshing of model
After finished meshing, check the quality of meshing by
produce the skewness or orthogonal mesh metric spectrum.
The high value of skewness or low value of orthogonal of a
model are not recommendation for simulation work process
because will affect the result of analysis. The range of
skewness and orthogonal as shown in Table 2 and Table 3.
Table2: The range skewness mesh metric spectrum
Table 3: The range orthogonal mesh metric spectrum
After checked the quality of meshing, apply the
boundary condition. For this cases, fixed support need to
construct by drawing the plate above the human foot model
for avoid the changes or deformation when analysis occur
when analysis process. Next, to make sure the result of
deformation only focus on human foot part put the ground
support as rigid body because this analysis is focussing on
any changes of stress and strain on human foot when running
on various model.
Next, apply the force below the ground support by selecting
define by component and the load is applied on –Z direction.
The value of force is different depend on surface. There are
three surface are choosen there are rubber,artificial grass and
concrete. After finished select all components, analysis is
perfomed as Figure 3.
Figure 3: Running the analysis.
III. RESULT AND DISCUSSION
A. Determine peak load from experiment.
From the experiental result, peak load from rubber surface
and artificial grass is nearly same. But, for the concrete the
peak load value is much lower compared to rubber and
artificial grass.
Figure 4: Graph of peak load (N) running in three different
surface

4. Table 4: Summary result of peak load.
B. Stress and strain response of human foot
There are two condition analysis for analysis there are
normal standing and running condition. There are three
different weight of human is considered in this analysis
which is (a) 50Kg, (b) 60Kg and 70Kg. From the human
weight, the calculation for value of force produce by
human for one foot are use a formula:
F=
Where; F= Force of human foot
m= Mass of human
g= Gravitional value
The result from the contour were same because the
boumdary condition applied for these model are same only the
value of force is different. So, only the value of minimum and
maximum of equivalent stress and strain of human foot model
is different. As conclusion, the higher the weight of human
will produce the higher value of stress and strain as shown in
Figure 5 and Figure 6.
Figure 5: Equivalent (Von-Mises) stress for human foot under
normal standing with three different weight. (a) 50Kg, (b)
60Kg, (c) 70Kg
Figure 6: Equivalent elastic strain for human foot under
normal standing with three different weight. (a) 50Kg, (b)
60Kg, (c) 70Kg
Table 5: Result of equivalent stress and strain for normal
standing.
For running condition, there are three different
surface choosen such as rubber, artificial grass and concrete.
There are three value of Young’s Modulus is choosen from
previous study E=0.15 Mpa, E=0.20Mpa and E=0.25Mpa. The
value of peak load is same for each Young’s Modulus analysis
which is for rubber F=1520N, for artificial grass F=1480N and
for concrete F=1380N. Figure 7 and Figure 8 shows the stress
and strain analysis for rubber surface because at rubber surface
produce a higher load.
Figure 7: Comparison between three different strain
distribution contours.

5. Figure 8: Comparison between three different strain
distribution contours.
The result for running condition for different value of
E on all three surface shows a very similar stress and strain
distribution and concentration contours. The significant
different among these two result are the minimum and
maximum value of stress and strain. The red circle indicated
the highest point where stress and strain in concentrated.
Stress and strain contours on these three conditions shows that
the stress value becomes lower when it comes to medial and
every finger of human foot. The strain contour is looking
nearly same for every analysis but the value is different
because ANSYS software cannot to set he limit manimum and
maximum strain value.
Table 6: Result of equivalent strain and stress for
running in three different surface.
Figure 9: The graph of stress vs. Young Modulus
Figure 10: The graph of Strain v. Young Modulus
IV. CONCLUSION
The study of Finite Element model on human foot
behavior is very useful because the experimental study on
this part is very limited. By using Finite Element model, we
are able to quantify and predicting various type of
biomechanics behavioue without ung real subject. High
quality of Finite Element odel is ery essential and must be
emphasized when conducting the study. The perfect model of
Finite Element model come out with high accuracy and
reliable result. Besides that, the margin of error also able to
reduce with a superior and perfect model of Finite Elment. If
lack of accuracy with lead to bad result and the esult cannot
be used as reference. As conclusion, it is important
stabilizing structure of human foot during standing and
running, the study of human foot throughout Finite Element
ethod must be enhanced to gain more understanding about its
biomechanics as well as helpful in devopment of footwear
industry.