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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),

ISSN 0976 – 6359(Online), Volume 5, Issue 9, September (2014), pp. 440-454 © IAEME

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STRUCTURAL ANALYSIS AND DESIGN OFA MOBILE MAST

Siva Krishna.N1, Amara Nageswara Rao.N

2

1, 2

(Department of Mechanical Engineering, Nimra Institute of Science & Technology/jntuk, Jupudi

Village, Krishna Dt A.P, India)

ABSTRACT

“Mobile mast for The Radar carrier Vehicle”, the working object is taking the images and

giving the information to costal security services. This FE Assembly has the different sub-

assemblies. Those names are Aerial Antenna Assembly, Aerial rotary Assembly, and Azimuth drive

Assembly, Chassis & Sub frame, 4-Bar mechanism and Palette without riggers. The total Wight of

this model is 30.590 tones. This FE Model can be configuration into two FE Models. These are

Deployed 0 Degrees and Deployed 90 Degrees.For the static analysis in the deployed condition, the

assembly rests on outriggers. For several models, the outrigger-bases were modeled as “clamped”.

This is a reasonable assumption when the dead-weight of the model acts in the “Y” direction. The

Structural Analysis and Design has been carried out for contrast loads to find out the displacement

and stress contour plots; we can do FE Modeling, materials, physical properties, Boundary

conditions and Loading conditions and Load steps .After completion of load steps we can go for run

model by using Nastran tools. The Nastran solver can be generated. The post processor can be used

for viewing the animation results and take the displacement and Stress contour plots.

Keywords: Design Modifications and Structural Analysis, Radar Carrier Vehicle, Nastran.

INTRODUCTION

“MAST” means multi axis simulation table, mast having the multi degree of freedom and

Simultaneous multi-axis motion. It is a very flexible, reliable, fast orientation changing table.

General applications of a mast areMilitary Applications, HomelandSecurity, Law-Enforcement

Applications, Intelligence Gathering Applications, Research& Scientific Applications, Security&

Surveillance Applications, Border Security Applications, Commercial Applications and Data

Collection/Sensors.

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING

AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)

ISSN 0976 – 6359 (Online)

Volume 5, Issue 9, September (2014), pp. 440-454

© IAEME: www.iaeme.com/IJMET.asp

Journal Impact Factor (2014): 7.5377 (Calculated by GISI)

www.jifactor.com

IJMET

© I A E M E



441

Background

GOWRA ENGINEERING TECHNOLOGIES PVT. LTD. Has designed a 10m mobile mast

for the Radar Vehicle. Preliminary analysis of this design have been carried out by GOWRA

ENGINEERING TECHNOLOGIES PVT. LTD. As a part of the design activity, undertook the tasks

of further improvement of the model and carrying out additional analysis. This report covers the first

phase of this activity, the models for the static analysis and the results of these analysis.

Given the availability of Nastran models of the preliminary analysis, and the unavailability of

3D CAD models, the selected approach was as follows:

a) Treat the GOWRA ENGINEERING TECHNOLOGIES PVT. LTD. Nastran models as the

starting point

b) To verify these models, and note areas of potential improvements and / corrections

c) Create “improved” models incorporating these improvements / corrections

d) Perform analysis and report the results

For step 2, the models were reviewed against assembly drawings supplied by GOWRA

ENGINEERING TECHNOLOGIES PVT. LTD., and further discussed with them. The selected

modeling approach was the outcome of these discussions.

With respect to step 3, note that the number of elements to be used consists of conducting

component level analysis with different mesh densities and evaluating the change in deformation

under a gravity load. Based on these studies, suitable element densities were selected for each

component.

Further, correctness of the assembly models was verified by applying gravity loads along

each of the X, Y and Z directions to check that element connectivity was correct. These results too,

are not included in this report. However these load cases are included in the models delivered to

them.

With respect to Step 4, several load cases are included in the scope of this project. These

include linear static analysis. This report covers the static analysis, including different cases. The

load cases are summarized in the relevant sections below.

Reference Model



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Design Modifications

1. Diameter of the cylindrical pads in-between the azimuth and palette were increased to 150

mm from 75 mm and the position was adjusted so as to represent their pattern position in

drawing.

The cylindrical pads of 75mm Diameter The cylindrical pads of 150mm Diameter

2. Gussets were added on the upper link and lower link near the cross-member near the Pylon

side. The dimensions of the gussets are 200 x 200mm and thickness of the gusset plate is

12mm.

Upper and lower-link before adding gussets Upper and lower-link after adding gussets



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3. Gussets were added to Pylons in order to minimize the stresses in the Driver side of pylons

regions. The dimensions of the Gussets are 62 X 90mm with Thickness =20mm. The Pylon

plate’s extension material has been removed near the Gussets.

Pylons before adding gussets Pylons after adding gussets

4. Azimuth Base plate thickness has been updated to 20mm, 3mm from 16mm, 8mm, and 3mm.

T=16m

m

T=8mm T=3mm

Azimuth Base before modification Azimuth Base after modification



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5. The mass of 7.77 tons has been re-distributed over the front end of the Chassis as shown.

The Mass distribution over-the The Mass Re-distribution over-

Front End of Chassis the Front End of Chassis

6. Added vertical supports inside the Aerial Antenna Frame.

The Aerial Antenna Frame before adding The Aerial Antenna Frame after adding

Internal supports Internal supports



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7. Added supports between the outriggers (in folded Condition) and Palette

Showing the supports between the outriggers and the Palette

FINITE ELEMENT MODELS

Comparison between initial and final models: This section summarizes the Nastran models

supplied by GOWRA ENGINEERING TECHNOLOGIES PVT. LTD. and the final modified

models are

The “reference” model contained 8, 48,434 elements and 7, 45,149 nodes.

61 mass elements

470 rigid link elements

416895 quadrilateral 4-noded shell elements

5135 triangular 3-noded shell elements

202435 4-noded tetrahedral elements

800 5-noded pentahedral elements

201010 8-noded hexahedral elements

108523 6-noded tetrahedral elements

3105-D elements

The elements in the final models are as below:

• Deployed condition:

Zero-Degree Model: 1, 62,500 elements, 1, 61,250 nodes

Ninety-Degree Model: 1, 62,435 elements, 1, 61,368 nodes

Apart from corrections to some meshed components, the significant changes were as follows:

a) Avoid usage of tetrahedral elements

b) Reduce the number of elements used for flanges etc., since these are considered

relatively stiff.



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As detailed earlier, the elements of the final models were arrived at using convergence

estimates. A direct-comparison between the number of elements in the reference model and those in

the improved models can be misleading. For example, the reference models contained 1, 01,879

tetrahedral elements for the U-bolts, 1, 75,714 tetrahedral elements in “flanges”, 1, 09,008 elements

in the path between the sub-frame and the vehicle chassis. These 3 components represent 51.38 % of

the total elements in the model. In comparison, the palette and sub-frame contained 1, 15,765

elements (or 12.5% of the elements) in the reference model as against 85, 258 elements (or 49% of

the elements) in the “improved” model.

c) Avoid the use of rigid elements

d) Ensure compatibility of element types and continuity in connections across

components

Note that the final models do not contain any tetrahedral or pentahedral. All elements are

concentrated mass elements, 4-noded quadrilateral shell elements, 3-nodded triangular shell

elements, 8-nodes hexahedral elements or 2-nodded beam elements. Further, the GOWRA

ENGINEERING TECHNOLOGIES PVT. LTD. The models used Steel, Aluminum. The final

models use Steel and Balata only.

Material Properties

All materials use linear constitutive models. Data used is as shown below

Material

Young's

Modulus

(E, MPa)

Poisson's

Ratio

Density

kg/mm3 Notes

Steel 2.1e+05 0.3 7.83e-9

Steel 2.1e+05 0.3 2.4e-08

Used for some components to ensure

weight of elements is consistent with

weight of sub-assembly

Steel 2.5e+04 0.310 5.9e-10

Steel 9.6e+04 0.300 3.2e-09

Aluminum 7.0e+04 0.3 2.7e-09

Balata 1300.00 0.400 1.1e-09

Estimated properties (supplied by

Gowra Engineering Technologies Pvt.

Ltd.)



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Beam Cross-sections

Some components were modeled using beam elements. The data used for these elements is as

below:

Section

Name Type Data

Density

(kg/mm3) Notes

U-bolt Circular,

solid Dia = 19mm 7.90E-09

Sub-frame and chassis sub-

assemblies are attached together

with the help of U-bolts

Hollow

Beam

Circular,

hollow

I.D=100mm,

O.D=115mm 2.40E-08

Hollow Cylinder of Hydraulic

Actuator

Beam Circular,

solid Dia =80mm 7.90E-09 Piston in the Hydraulic Actuator

Beam Circular,

solid Dia=30mm 7.90E-09

Part of a sliding Cylindrical rod

in the Rotary frame Assembly

Beam Circular,

solid Dia=40.8mm 7.90E-09

Beam Circular,


Beam Circular,


Beam Circular,

solid Dia=50mm 7.90E-09

Beam Circular,


Beam Circular,


Beam Circular,


Summary of weights and elements

Sub-assembly Earlier Weight of mast

(103 kg)

Added Weight of mast

(103 kg)

Aerial Antenna

Assembly 1.5854 1.6500

Aerial Rotary

Assembly 1.0256 1.230

Azimuth Drive

assembly 1.309 1.309

Chassis and sub-frame 14.468 14.468

Four-bar mechanism 1.3408 1.356

Palette with

Outriggers 10.575237 10.577

Total 30.304 30.590



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The load cases and forces are summarized in the table below:

Fig.No. Configuration Restraints Forces

1 Deployed, 0

degrees

Outriggers clamped Self-weight (gravity)

2 Deployed, 0

degrees

Outriggers clamped Self-weight and 90 kmph gust load

3 Deployed, 0

degrees


4 Deployed, 90

degrees

Outriggers clamped Self-weight (gravity)

5 Deployed, 90

degrees


6 Deployed, 90

degrees


RESULTS

Case 1

Deployed, 0 degrees / Outriggers clamped / Self-weight (gravity)

Deformed shape Stress Contours

Fig.No 1: Isometric-View



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Summary of results

Direction

Before modification structure

results

Before modification structure results

applied

forces

reaction forces applied forces reaction forces

X-force (N) 0 0 0 7.50E-05

Y-force (N) -2.980E+05 -2.980E+05 -3.001E+05 3.001E+05

Z-force (N) 0 0 0 -1.168E-06

X-moment(N-mm) -1.495E+08 -1.495E+08 -1.51E+08 1.51E+08

Y-moment (N-mm) 0 0 0 -3.645E-02

Z-moment (N-mm) -8.489E+08 -8.489E+08 -8.554E+08 8.554E+08

Case 2

Deployed, 0 degrees / Outriggers clamped / Self-weight and 90 kmph gust load





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Summary of results

Direction


results


results

applied forces reaction forces applied forces reaction forces

X-force (N) .04E+03 -4.68E+035 4.86E+03 -4.860E+03

Y-force (N) -3.135E+ 052.887E+05 -3.011E+05 3.011E+05

Z-force (N) -6.631E-03 6.031E-03 -6.331E-03 6.332E-03

X-moment (N-mm) -1.71E+08 1.31E+08 -1.51E+08 1.51E+08

Y-moment (N-mm) -1.962E+06 1.662E+06 -1.962E+06 1.962E+06

Z-moment (N-mm) -9.003E+08 8.843E+08 -8.923E+08 8.923E+08

Case 3:



Fig.no 3: Isometric-View



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Summary of applied forces

Direction


results


results

applied

forces

reaction

forces

applied

forces

reaction forces

X-force (N) 8.941E+03 -8.341E+03 8.641E+03 -8.641E+03

Y-force (N) -3.519E+05 2.519E+05 -3.019E+05 3.019E+05

Z-force (N) 5.712.E-06 -4.255E-06 6.E-06 -3.967E-06

X-moment (N-mm) -1.462E+08 1.558E+08 -1.51E+08 1.51E+08

Y-moment (N-mm) -3.889E+06 3.089E+06 -3.489E+06 3.489E+06

Z-moment (N-mm) -9.420E+08 9.0E+08 -9.210E+08 9.210E+08

Case 4

Deployed, 90 degrees / Outriggers clamped / Self-weight (gravity)





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Direction


results


results

applied

forces

reaction

forces

applied

forces

reaction forces

X-force (N) 0 9.75E-05 0 9.48E-05

Y-force (N) -3.219E+05 2.7831E+05 -3.001E+05 3.001E+05

Z-force (N) 0 2.921E-05 0 2.633E-05

X-moment (N-mm) -1.54E+08 1.35E+08 -1.45E+08 1.45E+08

Y-moment (N-mm) 0 -1.531E-01 0 -1.374E-01

Z-moment (N-mm) -8.957E+08 8.237E+08 -8.597E+08 8.597E+08

Case 5






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Summary of applied forces:

Direction


results


results

applied

forces

reaction

forces

applied

forces

reaction forces

X-force (N) -6.3E-03 6.248E-03 -6.33E-03 6.428E-03

Y-force (N) -3.211E+05 2.099E+05 -3.011E+05 3.011E+05

Z-force (N) -4.620E+03 4.460E+03 -4.860E+03 4.860E+03

X-moment (N-mm) -1.99E+08 1.59E+08 -1.79E+08 1.79E+08

Y-moment (N-mm) 2.477E+07 -1.277E+07 1.877E+07 -1.877E+07

Z-moment (N-mm) -8.936E+08 8.336E+08 -8.636E+08 8.636E+08

Case 6






454


Direction


results


results

applied

forces

reaction

forces

applied

forces

reaction forces

X-force (N) 6.589E-06 8.953E-06 6.300E-06 9.169E-05

Y-force (N) -3.038E+05 3.0E+05 -3.019E+05 3.019E+05

Z-force (N) -8.21E+03 8.02E+03 -8.641E+03 8.641E+03

X-moment (N-mm) -1.85E+08 1.69.05E+08 -2.05E+08 2.05E+08

Y-moment (N-mm) 3.008E+07 -2.88E+07 3.338E+07 -3.338E+07

Z-moment (N-mm) -8.127E+08 7.989E+08 -8.667E+08 8.667E+08

CONCLUSION

The Structural Analysis has been carried out for different load cases to find out the stress

contour plots; from this task first we carried out the Design improvements. The FE Model and

carrying out the additional analysis. In Additional Analysis, we added the gust load for different

directions by using different load cases has to be made.

In our project we have done the structural analysis for a 10 m MAST. We have performed a

static analysis at different conditions with a gust load. Structural analysis, we analyze the forces and

momentum of MAST. By observing the results, by changes done in the design of MAST we get

MAST more stable conditions and equilibrium. When comparing to privies loads force and

momentums are more advantageous to MAST.

REFERENCES

[1] Robort.D.Cook, Davis S Malkus, Michael E Plesha: Concepts and applications of Finite

element Analysis, 3rd

Ed, John Wiley and Sons.

[2] W.C.Young, R.G.Budynas: Roark’s Formulas for Stress and Strain, 7th

Edition, McGraw Hill.

[3] R.S.Khurmi, J.K.Gupta: A text Book of machine Design for Design Methodology.

[4] William J Anderson: MSC Nastan is a comprehensive simulation solution for the test.

[5] Rao V Dukkipati, M A Rao, Rama Bhat (2000): Computer Aided Analysis and Design of

machine elements, New Age international publishers.

[6] R.D.Cook (1995): Finite Element modeling for stress Analysis, John Wiley and Sons.

[7] T.J.R. Hughes (2000): The Finite Element Method, Linear Static Analysis, Dover Publications.

[8] John Anderson Jr: Fundamentals of Aerodynamics, 4th

Edition, McGraw Hill.

[9] Amir Javidinejad, “Structured Teaching of Machine Design for Future Design Engineers”,

International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2,

2012, pp. 120-127, ISSN Print: 0976-6340, ISSN Online: 0976-6359.

[10] N. Rishi Kanth, Dr.C.V.Mohan Rao and G. Yedukondalu, “New Method in Predictive

Maintenance of a Machine”, International Journal of Mechanical Engineering & Technology

(IJMET), Volume 3, Issue 1, 2012, pp. 142-149, ISSN Print: 0976-6340, ISSN Online:

0976-6359.

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