structural optimization of drive unit bracket using … · 1 simulate to innovate structural...

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Simulate to Innovate

Structural Optimization of Drive Unit Bracket Using OptiStruct

Abstract

This paper deals with optimization of Drive Unit Bracket Assembly for Tow Truck. Drive Unit Bracket Assembly is the important part of the Tow Truck Chassis .The motor which provides the traction to the Equipment is mounted on the Subject Drive Unit Bracket. This paper describes development of a Finite element model and subsequent analysis and simulation of Drive Unit Bracket Assembly consisting of structural members which are designed using basic principles of structural design. Topology & Size optimization is applied to Drive Unit Bracket Assembly considering volume as the objective along with stress constraints. Manufacturing constraints are considered to provide the manufacturability and interpretable design proposal. From the interpretations of Topology & Size optimization, one conservative design is proposed. Drive Unit Bracket Structure is optimized to minimize the mass and the stress requirements.

Introduction

Tow trucks are a vital part of the material handling chain in many operations like large factories, plants,

warehouses, airports and ports where goods have to be transported over significant distances. Tow

trucks offer exceptionally high productivity and economics compared to options like transporting goods

on various types of forklift trucks.

This advantage is even more pronounced when the load to be transported consists of a relatively large

number of small items. Tow trucks are a very efficient and cost competitive form of transporting goods

because they do not carry any goods themselves but pull the load placed in trolleys. A trolley train can

transport a large number of items at a time, something other mobile material handling equipment cannot

do.

Always conscious of the impact on the environment and the rapidly growing need for clean, quiet and

energy efficient material handling equipment, Godrej brings to you electric battery powered towing

solutions with 3 models of tow trucks in capacities of 2,5 and 6 tonne with variants for stand-on and sit-

down operation.

Electric powered tow trucks to cut your transportation costs and time. Godrej Electric Tow Trucks are

ideally suited for indoor work on industrial flooring due to their compact profile and high degree of

manoeuvrability.

The 5 and 6 tonne sit-down models are also available with higher ground clearance and pneumatic

tyres for outdoor use on concrete or paved surfaces. The emphasis on safety, operator comfort,

efficiency and serviceability ensures that the user gets a productive, cost effective and durable towing

solution.

Ms. Nazia .S. Ansari Manager

Godrej Material Handling Div Godrej & Boyce Mfg Co Ltd

Mr. Naushad Ansari Manager

Godrej Material Handling Div Godrej & Boyce Mfg Co Ltd

Mr. Vinay Kulkarni Assistant Vice President Godrej Material Handling

Godrej & Boyce Mfg Co Ltd

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Application

The Drive Motor which is the Main power source for the Tow Truck is mounted on the Drive Unit Bracket Assembly as shown in Fig 1 below

Objective

The main objective of this simulation is the re-design of Drive Unit Bracket Assembly with optimum mass while maintaining Stress constraints.

Drive Unit

Bracket Assembly

Drive Unit

Mountings on

Frame

Drive Unit

Fig2 Geometric Model Of Drive Unit Bracket Assembly

Fig1 Layout for Drive Unit Bracket Assembly

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Fig 3 Finite Element Model

The elements used for FE model are 2d shell elements for sheet metal components like Drive Unit Plate,Gusset,Channels & Back Plate & 1d rigid elements are used for Welded connections. The material defined for all components is Steel with following properties: Young’s modulus, E =210 GPa Poisson’s ratio, ν =0.30 Density, ρ = 7900 kg/m3 Yield strength, σ =260 MPa Gravity has been defined in the model

Gusset(2 No's)

Drive Unit Plate(1 No)

Fig 3 Shows the Finite Element Model for the Bracket. FE Model Description Total No of Elements= 10256 Total No of Nodes = 10645

GFfIG 3

Design Space

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Fig 4 Boundary Conditions:

Process Methodology Design & Non-Design space has been defined for the Optimization Setup in OptiStruct Initially Size Optimization is performed on the Bracket to determine the Optimum material thickness of components used in the Bracket. Size Optimization is a concept level design method that determines the optimum material Thickness for a give optimization problem within the identified Design space. In Size optimization, the thickness of each Element is a Design variable. The problem is solved using several problem formulations to have a better understanding of Underlying physics. Parameters defined during Size Optimization Setup are Design Variables - Gauges of all Parts in Design space Design Constraints - Stress < 130 N/mm2 Objective - Minimize Volume Size Optimization is followed by Topology Optimization in OptiStruct. Design space is again defined for Topology Optimization setup in OptiStruct. Topology Optimization method helps to determine the optimal material Distribution for a given optimization Problem. Parameters defined during Topology Optimization Setup are Design Variables - Density of each element in Design space Design Constraints - Stress < 130 N/mm2 Objective - Minimize Volume

Tractive Effort=538

N

Constraints at 4

Mounting points

Impact exerted during

Bumping =8000 N

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The Optimization Process Flowchart is as shown below:

Static Analysis

Design Modification based on Static

Analysis Results

Size optimization

Optimized design

Converged

Topology Optimization

Converged

Optimized Design

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Concept Design & Optimization Process

Original Design

Design Modification based on

Static Results

Size Optimization gives

Optimum thickness of 10 mm

for all plates

of the Bracket

Topology Optimization gives

Optimum Material

Distribution for all 10mm

plates


Size Optimization Results

Fig5Density Plots from Size Optimization show that all the plates can be reduced to 10mm

Topology Optimization Results (Fig 6)

Density Plots from Size Optimization show that all the plates can be reduced to 10mm

Final Design Concept based

on results from Optimization

Optimization Parameters

Design Variables design space

Design Constraints

Objective -

Topology optimization was performed to find the material densities for all the

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Density Plots from Size Optimization show that all the plates can be reduced to 10mm Thickness

on results from Optimization

Optimization Parameters

Design Variables - Gauges of all Parts in

Design Constraints- Stress < 130 N/mm2

- Minimize Volume

Topology optimization was performed to find the material densities for all the

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(Fig 7) Result & Discussion

Due to Manufacturing Constraint, Fabricated design of Bracket was recommended as shown in Fig below

Displacement Plots

Stress Plots

Max Displacement= 1.3mm

Max Stress= 156 MPa which will be shared by mounting

Final Design derived based on Outputs from Topology & Size Optimization

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Fig 8 Displacement & Stress Plots For The Fabricated Design

Table for Material Savings

Sr no Part description Thickness(mm) Weight(Kgs)

Material Savings(Kgs)

1 Motor Mounting Plate

Vertical Plates Mounting Plates

16 10 20

9.5 6.4 4.5

-

2 Bend Design of Bracket 10 8

12.4

3 Fabricated Design of Bracket 10 9 11.4

Fabricated Design Of Mounting Bracket

Max Stress= 166 Mpa which will be shared by mounting Bolts

20.4


Conclusion Using Concept Design & Optimization techniques the weight of the Bracket was reis significant savings in weight and these savings amount to Rs 1240/bracketMonthly production of Tow Truck is 5 Nos. The work presented in this paper is in the early phases of ongoing work and it is important to promising results will strongly demand more detailed Analysis as mentionStudy Benefit Summary • Reduce Development Time

Through OptiStruct's design synthesis approach,CAE is development cycle, thereby driving the design process and enabling a reduction in the number of design iterations • Improve Design Performance

OptiStruct helps to develop structurally sound, lightweight products by applyin advanced optimization methods to solve the design problem. • Explore More Design Alternatives

OptiStruct's advanced optimization engine allows users to combine topology, topography, size and shape optimization methods to create more requirements can also be defined as input to the simulation to create designeasier to interpret and to manufacture.

• Higher Productivity Through

OptiStruct's integrated analysis and optimization approach enables computationally efficient concept design synthesis and design optimization studies. A highly organized and intuitive interface greatly simplifies user effort through the optimization process.

Further Scope of Study

The study was extended to Motor Mounting Brackets used on other Equipments. Topology & Size optimizations techniques of optimization were

plates Density Plots of Size Optimization Results are as shown in Fig

Using Concept Design & Optimization techniques the weight of the Bracket was reand these savings amount to Rs 1240/bracket

Monthly production of Tow Truck is 5 Nos. Hence Annual Savings =74400 Rs (5*1240*12)

The work presented in this paper is in the early phases of ongoing work and it is important to trongly demand more detailed Analysis as mentioned in the further scope of

ct's design synthesis approach,CAE is applied upfront in the product development cycle, thereby driving the design process and enabling a reduction in the number

Design Performance OptiStruct helps to develop structurally sound, lightweight products by applyinadvanced optimization methods to solve the design problem.

Explore More Design Alternatives advanced optimization engine allows users to combine topology, topography, size

and shape optimization methods to create more alternative design proposals. Manufacturing requirements can also be defined as input to the simulation to create design proposals that are easier to interpret and to manufacture.

Higher Productivity Through Hyper Works Integration ted analysis and optimization approach enables computationally efficient

concept design synthesis and design optimization studies. A highly organized and intuitive interface greatly simplifies user effort through the optimization process.

Motor Mounting Brackets used on other Equipments.Topology & Size optimizations techniques of optimization were used to arrive at Optimum sizes

Density Plots of Size Optimization Results are as shown in Fig

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Using Concept Design & Optimization techniques the weight of the Bracket was reduced by 61% which

=74400 Rs (5*1240*12)

The work presented in this paper is in the early phases of ongoing work and it is important to note these ed in the further scope of

applied upfront in the product development cycle, thereby driving the design process and enabling a reduction in the number

OptiStruct helps to develop structurally sound, lightweight products by applying the most

advanced optimization engine allows users to combine topology, topography, size alternative design proposals. Manufacturing

proposals that are

ted analysis and optimization approach enables computationally efficient concept design synthesis and design optimization studies. A highly organized and intuitive user-

Motor Mounting Brackets used on other Equipments. used to arrive at Optimum sizes of

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Initial (Base Design ) Final (Optimised Design) Using optimization, thickness of plates used in the bracket were reduced to 8mm & 6mm.Total Weight reduction of 61% achieved from the Final Optimized Design of Bracket Annual savings from this Analysis amounted to 4,68000 INR ACKNOWLEDGEMENTS The authors would like to acknowledge our company M/s. Godrej and Boyce Mfg. Co. Ltd, Material Handling Equipment Division and Altair’s Technical support. REFERENCES 1. OptiStruct –User’s Manual-Altair Engineering 2. Practical Finite Element Analysis- Nitin S.Gokhale, Sanjay S. Deshpande, Sanjeev V.Bedekar, Anand N.Thite. 3.Altair HyperWorks 3.RADIOSSv11 help Manual.

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