Design Optimization of Display Unit Supporting Structure Under Static and Spectrum Loads using FEA

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 10 | Oct -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 669
Design Optimization of Display Unit Supporting Structure under Static
and Spectrum Loads Using FEA
Mahesh B L1, H S Manjunath2, Vijay kumar V3, Surekha A4
1Dept. Of Mechanical Engineering, Dr. Ambedkar Institute of Technology, Bengaluru, Karnataka, India
2Assistant Professor, Dept. Of Mechanical Engineering, Dr. Ambedkar Institute of Technology, Bengaluru,
Karnataka, India
3HOD, Dept. Of Mechanical Engineering, East West Polytechnic, Bengaluru, Karnataka, India
4Lecture, Dept. Of Mechanical Engineering, GPT-Chennapatna, Karnataka, India
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Abstract - Engineering components/assemblies are
mounted over the supporting structures for its functionality.
These supporting structures are subjected to various loads
based on the type of application. Any failure in supporting
structure results to malfunctioning of the mounted
components. So the design considers the safety of the
mounting platforms. Due to the advent of computer based
numerical technology, virtual simulation can be effectively
utilized to improve the safety of the assembly componentsand
the stress condition can be estimated early before the actual
production of the components. In the present work, a display
unit support structure is modeled using a three dimensional
modeling software and later imported to Hypermesh for
quality meshing. The members are grouped to different
components for later designoptimization. Rigidbodyelements
through mass elements are defined for load transfer. Initial
analysis for the given load cases shows failure of some of the
components for the given loading conditions. So design
optimization through design optimizer module is carried out
to improve the problem. Total of 7 design sets in the form of
scalar parameters are represented along with 2 state
variables which defines the limitation for structural safety.
Weight is considered as the objective function with 0.1 kg as
the convergence tolerance. Sub problem approximation
technique is used to find the design sets. Total of 21 sets are
obtained to find the design solution for the requirements. The
results for both initial and final sets are represented.
Key Words: Engineeringcomponents,Malfunctioning,Virtual
simulation, three dimensional modelingsoftware,Hypermesh,
Design optimization, Design optimizer module.
1. INTRODUCTION
Stress analysis is very important part of design of
engineering components. Every structure has its limiting
value based on its internal material structure. Even this
capacity is based on many loading parameters like
temperature and uniformity and method of production.
Based on the limiting values, the design should be carried
out maintaining the structural safety. Many methods are
available to find the structural condition of the problem.
Main methods for structural analysis are as follows.
 Continuum methods
 Experimental methods
 Numerical methods.
1.1 Continuum Methods
These methods are more accurate and are mainly based
on mathematical integral formulae’s. For integration, the
geometry of the problem should be defined with proper
curve fittingfunctionwhichconsumesmaximumtimecoding.
Further continuum methods are classified to exact methods
and approximate methods. Various exact methods are
 Potential energy Method
 Stress function method
 Fourier equations
1.2 Numerical Methods
These are modification of exact or continuum methods.
Based on the same principles of continuum witha difference
of exact integration to partial integration, numerical
methods are becoming more popular in the stress analysis
techniques. Complex integration is simplified withgridtype
of structural geometrical calculations. It can easily
accommodate changes in the geometry, loads and materials.
Various numerical techniques are
 Finite Difference method
 Finite Element Method
 Boundary Element Method
 Finite volume Method etc.
Various commercial and educational software’s are
developed and these methods can be applied to various
branches of engineering like
 Automotive and Aerospace industry
 Medical Industry
 Refrigeration and Air Conditioning
 Nano mechanics
 Fluid Power Engineering

 Nuclear Engineering
 Mechanical Engineering applications etc.
1.3 Experimental Methods
The usage of experimental methods is very essential for
components with large production. At leastfewcomponents
need to be checked for practical testing conditions to know
the nearness of numerical or continuum solution with
practical solution. Various experimental techniques are
 Spring balance Method
 Photo elastic method
 Strain Gauge method
 Load Cell techniques
 X-Ray Diffraction
 Various coating techniques etc.
2. PROBLEM DEFINITION
Structuralanalysis for safetyand design optimisationofa
display unit mainly made of aluminium components is the
main definition of the problem. The main objectives include
 Geometrical Modelling of the Display unit
 Meshing and stress analysis
 Design optimisation
2.1 Methodology
1. Geometrical Modelling of the problem
2. Meshing of the assembly with different
components based on uniform thickness
3. Analysis for static and spectrum loads in different
directions
4. Capturing vonmises stress in the individual
components
5. Design optimisation by variation of thickness of
the assembly components.
2.2 Material
Material selected Aluminium
Elastic Modulus 71Gpa
Poison’s ratio 0.3
Density
7800
kg/m3.
Allowable stress 210 Mpa
Allowable factor of
safety
2
Table -1: Material properties
2.3 Geometrical Modelling of the Display Panel
The geometry is having one meter length with 0.7 m height
along with transverse distance of 0.9 m. The geometry is
built using three dimensional modelling software Solid
works using sketcher, part modeller and assembler. It
contains number of parts which are assembled at the
appropriate places.
Fig -1: Geometrical Plot
2.4 Design Specifications
The structural assembly should with stand 800 kg load on
the top of the panel.
The spectrum loads along longitudinal direction: 15g
Lateral direction: 6g
Transverse Direction: 5g
2.5 Design Requirements
The structure should with standard the loads mentioned in
3.5. The deflection should not exceed9mmandstressshould
not exceed allowable stress of 140Mpa leaving the standard
parts.
2.6 Mesh Plot
Fig -2: Mesh of the Structure.

The figure-2 shows mesh of the system using Hypermesh.
The members are grouped based on the thickness
specification and standard nature. All the standard partsare
meshed using three dimensional solid elements as they
doesn’t need design optimisation.
2.7 Element Types Used
The element is defined with 8 nodes in brick meshing and 4
nodes in tetrahedral meshing. Even it takes 6 nodes during
prism type meshing. Brick meshing is more accurate
compared to other type of meshing.
Fig -3: Solid 45 Elements.
Fig -4: Shell 63 Elements.
3. RESULTS AND DISCUSSION
Structural analysis is the key aspect of finding the safety of
the problem under various cases of loads. Vonmises is the
most appropriate theory for failure prediction of ductile
aluminium material. Various load cases considered for the
problem are as shown below.
1. Self Weight Analysis alone
2. With external load of 800kg
3. With only longitudinal spectrum
4. With only lateral spectrum
5. With only transverse spectrum
6. Combination of all the loads
Fig -5: Deformation under self weight
The figure shows maximum deformation of 0.000223m or
0.223mm deformation due to self weight. This deformation
is less than the allowed deformation of 9mm.
Fig -6: Deformation under ext. load + self weight
(Maximum deformation is 1mm)
Fig -7: Deformation under ext. load + spectrum load
(Maximum Deformation is 5mm)

Fig -8: Deformation under Case 2 and Lateral Spectrum
(Maximum Deformation is 4.5mm)
Fig -9: Deformation plot under case2 and transverse
spectrum
Fig -10: Deformation under all the Loads (Maximum
deformation is 6mm)
The vonmises stress is represented for individual
components are as shown in the table below.
Component
Number
Vonmises Stress
(Mpa)
1 306
2 1040
3 41.4
4 140
5 1320
6 39.2
7 66.8
Table -2: Stress development in non-standard parts
The table shows components 1, 2 and 5 are subjected to
heavy stresses which are higher than the allowable stress of
the material. So these need to be optimised along with low
stress members (Component 3, 6, 7) for even distribution of
stress and maintaining the safety of the assembly for the
given loads.
Fig -11: Design Convergence (Execution of design
optimisation and convergence)
The figure shows convergence of sub problem
approximation through design optimiser module execution.
It shows set number 21 is converging to the requirements
and showing a final weight of 113.82 kgs from the initial
weight of 109.37kgs.
Component
Number
Initial
Thickness
(mm)
Final
Thickness
(mm)
1 3 3
2 0.15 2.84
3 9 5
4 6 5
5 3 8
6 6 4.37
7 3 2.8
Table -3: Comparative Results for Initial and Final
Thickness

Fig -12: Design Iterations to Vonmises Stress
The figure 4.23 shows drop of stress in the initial iterations
itself and finally converging to the required value.
Fig -13: Vonmises Stress Vs Design Parameters
This figure helps in identifying the effect of design variables
on stress generation.
3.1 Results Representation for Final Optimised
Structure:
The figure 14 shows final deformation in the structure. The
maximum deformation is 7.2mm (0.0072m) which is less
then the allowable deformation of 9mm. So deformation
Fig -14: Deformation in the final Optimised Structure
Fig -15: Vonmises stress in the final Optimised Structure
The figure 15 shows final vonmises stress in the assembly.
Maximum stress is 210 and is equal to the allowable stress.
So the assembly is safe for the given resultant loads.
Component
Number
Initial
Vonmises Stress
(Mpa)
Final Vonmises
Stress After Design
Optimization
1 306 138
2 1040 210
3 41.4 36.4
4 140 131
5 1320 186
6 39.2 43.1
7 66.8 62
Table -4: Summary of Stress Results between Initial and
Optimised sets
The table 4 shows redistribution of stresses in the
components and all the stresses in thefinal optimisedsetare

well below or equal to the allowable stress. So the assembly
will be safe for the given loading conditions.
4. CONCLUSIONS
 The assembly is modelled using a three dimensional
modelling software Solid works and imported to
Hypermesh for meshing in ‘step’ file format.
 Hypermesh is used to mesh the components
appropriately with element size of 5mm. All the
standard components are meshed with solid elements
and non standard parts are meshed with shell elements.
A mass element is created to distributethe external load
to the supporting panels through RBE3 element
connection.
 The meshed finite element model is imported to Ansys
software for further analysis in ‘inp’ file format for
further analysis. The results are obtained after
representation of different load steps for self weight,
external load and spectrum in three differentdirections.
The stresses in the nonstandard sections are
represented for individual components.
 The results shows stress exceeding allowable limits in
certain components which need to be improved for safe
working of the support structure. Design optimiser in
Ansys is used after specifying 7 design variables, two
state variables with weightastheobjectivefunction.Sub
problem approximation is used to find the converged
results.
 Totally 21 sets are obtained for converged results. The
final set shows the stress levels within the allowable
limit of the problem for both deformation and stress.
The individual component result also shows safety of
the component for the given loads
REFERENCES
1. Duffin R.J. “Geometric Programming: Theory and
Applications”, Wiley, New York, 1960
2. Morris A.J. “Foundations of Structural Optimisation: A
Unified Approach”, John Wiley & Sons, Isted UK, 1960
3. Gettatly, “ A Procedure for Automated Minimum
Weight Structural Design”, Aero Quart Part 1, vol 17,
pp 332 -342, 1999
4. Jim Patterson, Hendrickson Trailer Suspension
Systems, 2000
5. Hursha Narayan, Robert Bosch Corporation, 2002
6. Joe Metrisin, Florida Turbine Technologies, 2002
7. Arrora J. “Introduction to Optimum Design”, 2nded,
Academic Press, 2004
8. Ravidran A, “ Engineering Optimisation Methods and
Applications”, John Wiley & Sons, UK, 2006

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Design Optimization of Display Unit Supporting Structure Under Static and Spectrum Loads using FEA