Project 1

Aim

To conduct design and analysis study on a plastic stool using solidworks simulation tool to improve our design to better suite our functional needs.

Objectives

• To reduce the material weight of the object in our design by doing a design study.
• To withstand a total weight of 100kg.

Introduction

Finite element analysis is used to solve numerical differential equations of complex parameters used in engineering and mathematical models. Key feature of FEA is using differential equations as it simplifies and provide the following:

• Accurate representation of complex geometry
• Inclusion of dissimilar material properties
• Capture of circumscribed effects
• Uncomplicated total solution

Basic theory

FEA involves dividing the problem into small number of smaller sub domain that represent a set of element equations to the original problem. Thus, unifying set of element equations to form the final calculation. The FEM approximates a solution by minimizing an associated error function via the calculus of variations. Typical problem areas of interest include structural analysis, heat transfer, fluid flow ...etc. Studying or analyzing a phenomenon with FEM is known as finite element analysis (FEA).

Methods of solving engineering problems:

• Analytical method

Usage of derived mathematical formulae.

• Experimental method

Requires performing experiments and recording the solutions as long the setup is well defined.

• Numerical method

Using mathematical tools to obtain approximate solutions for complex areas and volumes.

General steps in analysis:

1. Pre-processing
   • Geometry check

After importing the CAD model, it is made sure that there are no alterations in our model.

• Meshing

Model is discretized into smaller elements for meshing.

• Quality check

Quality of the meshing is checked during this step.

• Boundary conditions

This includes the fixtures, loads, values of loads, initial conditions of the model, material of

the model… etc.

2. Processing

Software computes the mathematical calculations based on the boundary conditions provided for FEA.

3. Post-processing

Visualization of the data form the simulation to obtain result or verify the hypothesis or redesign to obtain the desired outcome.

Solidworks simulation

• Create a new study under simulation choose static option.
• Apply the type of material to the part to imbued with mechanical, chemical and thermal properties, in our case we use custom plastic with the following properties.

Elastic Modulus	2000000000	N/m^2
Poisson's Ratio	0.394	N/A
Shear Modulus	318900000	N/m^2
Mass Density	1020	kg/m^3
Tensile Strength	30000000	N/m^2
Compressive Strength		N/m^2
Yield Strength	4150000	N/m^2
Thermal Expansion Coefficient		/K
Thermal Conductivity	0.2256	W/(m·K)
Specific Heat	1386	J/(kg·K)
Material Damping Ratio		N/A

• Fixtures helps in constraining our design. We have to define the faces to be fixed in our design.

• Under external loads apply compressive force of 980N in our model. Thus, translating to 100kg on the plastic stool.

• We mesh our object next to provide us with better simulation result

• We run the simulation now to obtain the stress, strain and displacement plots for the simulation study.

Observation

With the above simulation plot details, it is safe to say that the design holds good for the give load conditions. Now that we have obtained the simulation results, we can do an evaluation design study to further improve our design.

Solidworks New design study

• Create a new design study to reduce the material in our design without affecting the load supporting capacity.
• The following variable parameters, constrains and goals are set to improve the in our design.

Our prime objective of this design study is to reduce the material weight of our design as you can in under the goals of this study.

• Once our design study tabulates all the iterations we are provided with the optimal design. In our case we obtain the following.

This lets us know that these dimensions can be altered in our original design to obtain the best possible result with low mass of the object as well as maintain a factor of safety more than 2.

Now that our design is optimized for the reduced mass and to with stand the force of 980N.

The resulting stress, strain and displacement of the optimized design is as follows.

Observation & Result

With the resulting study of the optimized model, we can see that the stress, strain and displacement values have slightly increased in our optimized model but nevertheless our main goal is to reduce the weight of our object. Which we have achieved without compromising the design integrity of our model.