DESIGN AND ANALYSIS OF THE STEM TUBE OF THE BIKE (Part 1)
Abstract
The design process has many important steps, one of the
most important steps is the simulation analysis. This process save much time
and money and help the designers to reach the optimized design with the cost
of only computerized calculation. Solidworks simulation tool is a finite
element analysis tool that gives fast and approximated solution for the design
problem. In this project, the stem part of the bike will be analyzed to reach
the optimized thickness of the middle tube that gives factor of safety less
than 2.5.
Table of
Contents
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---------- Part 1 ---------------------------------------------------------------
1. Model Components
The model is composed of three main
parts (figure 1), the first is the steering tube. This tube is attached to the
stem using two M4 bolts. The stem itself is composed of 2 parts that will be
called the main body and the flat plate, the main body is composed of a tube
with bulk ends, the tube length is 152 mm. The other part of the stem (flat
plate) is used to fix the stem with third main part of the model which is the
handlebars, only two M5 bolts is used for this fixation.
The
material for this parts are assigned as follow, firstly, the steering tube is
assigned to Steel alloy with modulus of elasticity of 210 GPa, shear modulus of
79 GPa, density of 7700 kg/m^2 and yield strength of 620 MPa. The assignment of
the stem is Aluminum 2024 with modulus of elasticity of 72.4 GPa, shear modulus
of 28 GPa, density of 2800 kg/m^2 and yield strength of 415 MPa. The Aluminum
7075 is assigned to the handlebars which has the following characteristics,
modulus of elasticity of 72 GPa, shear modulus of 26.9 GPa, density of 2810
kg/m^2 and yield strength of 505 MPa.
The aim of this analysis is to reach
the optimum thickness of the stem main body tube that gives factor of safety
doesn’t go below 2.5. Therefore, the other parts, except stem main body and
flat plate, will be ignored. To do this, the applied forces will be moved to
the main body end and flat, each force will be translated with a force in the
same directions and moment in opposite directions so the moments will remove
each other and the forces will add at the main body end. The other end will
have fixed constraint at the area with the contact with the steering tube. The
forces and constraints will be discussed in more details in the constraints
section.
In the model, the handlebars and the
steering tubes will be suppressed (Figure 2). In addition, another two
constraints will be added to the bolts holes to make them concentric to manage
to add bolts effects inside.
3. Constraints
and Boundary conditions
AS discussed in the previous
section, the forces will be translated to one end of the main body and the flat
plate, in addition, the moment will cancel each other. The forces of 656 N at
the handlebar ends will add up so the applied forces will equal 1312 N.
Regarding the fixation, fixed constraint will be added at the contact area with
the steering tube, as the applied forces is only vertical and there are no
expected deformation in any other sides, there will be no difference if the
constrained degrees of freedom were translations only or translations and
rotations degrees of freedom.
The contact between the flat plate
and the main body is simulated by 2 bolts at the bolts hole (figure 3), each
bolt have pre-load axial force of 4 KN. The material of the bolts is steel
alloy, its properties are pre-defined in the model section for the steering
tube. The diameter of the bolt head is estimated of 6.3 mm, in addition, the
nominal shank diameter is estimated of 4.2 mm.
4. Defeaturing
After deciding on the areas and
holes that will be used in the simulation, the unimportant and unused features
will be suppressed in this section. This process will help in reducing
calculations’ time, in addition, it will reduce the meshing elements and complexity.
The features will be mainly small holes that was not used for the connections.
In addition, fillets that are in unimportant places.
The
following table shows the part before and after the suppressing of the unwanted
feature,
Table
1
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