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STRUCTURAL DESIGN AND OPTIMIZATION OF

CHASSIS

INTRODUCTION:-

Chassis is a French turn and was initially used to denote the frame or main structure of a vehicle. It is now extensively used to denote the complete vehicle except the body for the heavy vehicle having a separate body. The chassis contain all the major units necessary to propel the vehicle, direct its motion, stop it, and allow it to run smoothly over uneven surfaces.

It is the main mounting for all the components including the body. It is also known as carrying unit.

The chassis include following components as shown in fig: 1.1Frame,Front suspension,Steering mechanism,Radiator,Engine, clutch, gearbox,Propeller shaft,Rear spring,Road wheels,Differential, half shaft, universal joints,Brakes end braking system,Storage battery,Silencer,Shock absorbers, fuel tank, petrol and hydraulics pipe cables and some means of mounting these components.

Chassis components

1.1 Importance of chassis Frame [3]

The frame or under body is the main part of the chassis, on which the remaining parts of chassis are mounted. It is a rigid structure that forms a skeleton to hold all the major part together. The engine is mounted in the forward end of the frame end of the frame and is connected to the clutch and transmission units to form a complete power assembly. At the rear end of the frame, the rear axle housing is attached through the rear spring. The wheels and tyre assemblies supports the frame. The steering system has some parts bolted to the frame and some to the body. The petrol tank is fastened to the rear of the frame.

Functions of chassis frame

• To carry load of the passengers or goods carried in the body

• To with stand stresses caused due to bad road condition

• To with stand forces caused due to the sudden braking or acceleration

• To with stand centrifugal force while cornering• To support load of body, engine, gear box etc..

Types of chassis frames

• There are three types of chassis frames 1.Conventional Frame 2.Integral Frame 3.Semi-integral frame

1.Conventional frames

It has two long side members and 5 to 6 cross side members joined together with the help of rivets and bolts

In this conventional frame construction the body and frame are separated In this the engine is at the frontDriver sits behind the engineFrame sections may solid round or rectangular cross section frames

Conventional frame

2.Integral frameUsed in most of the carsNo frame and all the assembly units are attached to the bodyBody will carry the entire function of the frameDue to elimination of frame it is cheaper and due to less weight of body it is most economic also

3.Semi integral frame

In this it has divided it into two section of half frames one half frame is fixed at the in the front end on which engine gear box and front suspension is mounted The main advantage of this frame is when we met with an accident the damaged chassis frame can be easily replaced This type of frames is used in FIAT cars in some of the EUROPEAN and AMERICAN cars

Main requirements of body for various types of vehicle

It should be light in weight It should provide minimum number of components It Should provide sufficient space for passengers and luggage It should with stand vibrations while in motion It should offer minimum resistance to air Should be cheaply available and easily manufacturing Load should be uniformly distributed Should have good vision and ventilation

since to get all the main requirements ,optimization of a body is must .

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What is meant by optimization

. Optimization:-• Optimization can be defined as

the automatic process to make a system or component as good as possible based on an objective function and subject to certain design constraints.

• There are many different methods or algorithms that can be used to optimize a structure.

e.g.:- Gradient Method.

Types of OPTIMIZATION

Topology:- It is a mathematical technique that optimized the material distribution for a structure within a given package space

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Topography: Topography optimization is an advanced form of shape optimization in which adesign region for a given part is defined and a pattern of shape variable-based reinforcementswithin that region is generated using OptiStruct

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Free Size: It is a mathematical technique that produces an optimized thickness distribution perelement for a 2D structure

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Shape: It is an automated way to modify the structure shape based on predefined shapevariables to find the optimal shape.

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Size: - It is an automated way to modify the structure parameters (Thickness, 1D properties,material properties, etc…) to find the opt

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Free Shape: It is an automated way to modify the structure shape based on set of nodes that canmove totally free on the boundary to find the optimal shape.

Design Variables:-

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Design Variables or DVs are system parameters that can vary to optimize system performance.

There will be different DVs for different type of optimization

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TOPOLOGY: It is a mathematical technique that optimized the material distribution for a structure within a given package space.

• DVs are defined as a fictitious density for each element,and these values are varied from 0 to 1 to optimize thematerial distribution.

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TOPOGRAPHY: Topography optimization is an advanced form of shape optimization in which a design region for a given part is defined and a pattern of shape variable-based reinforcements within that region is generated.

FREE-SIZE: This is a special method designed by Altair to optimize 2D structure where the design variables are the thickness of each element. This method is very useful for aerospace structures where shear panels are preferable to truss structures.

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SHAPE: is an automated way to modify the structure shape based on predefined shape variables to find the optimal shape.

• DVs are used to modify the geometry shape of thecomponent.

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SIZE: It is an automated way to modify the structure parameters to find the optimal design. DVs are any Scalar parameter(Thickness, 1D properties, material properties, etc…) that affects the system response.

FREE-SHAPE: It is an automated way to modify the structure shape based on set of nodes that can move totally free on the boundary to find the optimal shape. DVs are defined based a set of nodes.