TOPOLOGY OPTIMIZATION OF BRAKE PEDAL ARM USING ANSYS WORKBENCH

TOPOLOGY OPTIMIZATION OF BRAKE PEDAL ARM USING ANSYS WORKBENCH

Objective:

To optimize for the structural layout of a brake pedal arm within a given design space by using Topology optimization module in ANSYS workbench.

In this project a linear static analysis is carried out to minimize the compliance of the brake pedal arm generally used in the automotive industry based on only 50% of its initial mass/volume.

This is similar to that of a cantilever beam subjected to a tip load.

Hence we look for a light weight design of the brake arm pedal.

Procedure:

• The brake pedal arm model is initially carried out with a static structural analysis system for a certain set of constraints and loads.
• The stress and strain results are found by solving the static structural system.
• The model is then optimized for areas of minimally developed stress.
• The excess weight is cut and an optimized design is carried over which meets the defined criteria.

Static structural analysis of brake pedal arm:

Engineering Material:

Since the problem is dealt with structural topology optimization,the analysis is carried out with Structural steel material as default.

Geometry:

The brake pedal arm model which is obtained from grabcad website can be used for the analysis.

The model can be downloaded from this link.

https://grabcad.com/library/brake-pedal-18

The model is imported into the Design modeler of the Geometry tab and it is generated in order to check if any abnormalities are present in the model.

Meshing:

In the Mechanical tab,the model is subjected to meshing and setup for boundary conditions.

The model is meshed with 2mm element size of tetrahedral elements.Face meshing is applied to lateral faces.

Cylindrical coordinate system:

A new cylindrical coordinate system is defined for the cylindrical face of the brake arm where the shaft is to be attached.

It allows displacement only in defined DOF.

Boundary conditions:

The analysis system is left as default to run for 1 second.

A force of 100N is applied normally to the face of the brake pad.

The cylindrical face of the model is given a displacement constraint as follows.

Results:

The following results are requested to solve.

Total deformation

Equivalent stress

Equivalent strain

Topology Optimization:

Structural topology optimization is a mathematical method of retrieving an optimal solution to a design problem with suitable constraints and loads.

The topology optimization formulation uses a finite element method to evaluate the design performance.

Advantages of topology optimization:

1.Maximizes the performance of the system

2.Increase in sustainability

3.Weight reduction.

Optimization formulation:

Before solving an optimization problem, an optimization formulation has to be made and a model for calculation created.

A structural optimization requires an optimization formulation. This should include; design variables, response, constraint and an objective function.

Design variables:

The design variables might be anything that influences the performance of the investigated structure. The number of design variables may vary from the minimum of one to several millions and the structural properties will be dependent on the design variables.

Response:

For any given values of the design variables a response from the structure might be retrieved. Common types of responses are displacement, stress, mass and compliance. Responses are used to evaluate the performance and properties of the structure.

Objective function:

The objective function is a response used to decide how good a design is. In an optimization formulation, the objective function is usually to be minimized (minimization problem). Due to this, only one objective function is allowed per optimization formulation. Although, it does exist multi-objective functions, which are functions of several responses. Typically used objective functions are mass and compliance.

Constraints:

Each design variable and response might be constrained with an allowed minimum and maximum value. Constraints are used on the response and design variables to make sure that the properties of the structure are in an allowed interval. Typical constraints are maximum allowed mass, stress, displacement or minimum allowed stiffness or dimensions.A constraint that always has to be fulfilled is the static equilibrium equation.

Optimization results:

The optimization result of topology density gives the idea of regions to be excluded and marginal areas supposed to keep.

The regions of minimum stress are set to exclusion as they over-constraint the model.

The brake pedal arm model is redesigned with Design modeler with the idea of optimized results.

A few portions of the brake arm are excluded from the model and set to static structural analysis once again.

In this problem, mass is set to define a response constraint with 50% to retain.

The optimization formulation is defined with 500 iterations by default with convergence accuracy of 0.1%.

Optimized design:

It is found that the optimized brake pedal arm model successfully carries out the analysis with high performance.

Total deformation

Equivalent stress

Equivalent strain

Comparison:

From the obtained results, it is evident that

It can be seen from the comparative table that stress and strain produced in the optimized design model is quite higher than that of the original design.

Also the total deformation in the optimized model is approximately thrice than that of the original design.This is because of the lowering of stiffness of the optimized design which leads to reduction in overall weight of the model.

Conclusion:

Thus,the structural layout of a brake pedal arm within a given design space is created and it is optimized by using Topology optimization module in ANSYS workbench.