analysis of lifting machine
TRANSCRIPT
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ME 351A PROJECT
Team members
Ankit Shrivastava (11113)
Ankit Yadav (11115)
Ahsen Parwez (11416)
Deepak Dalakoti (11235)
Shivam Patel (11683)
Anurag Bhatt (11135)
Project Title – Transporters
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OBJECTIVE
Design of transporter system in Southern Labs
Analyzing critical failure locations of the assembly
Estimating present load capacity of the machine
Proposed design changes for a load of 3 tonnes
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SUB SYSTEMS
Pneumatics and Pulley Primarily lifting mechanism
Pneumatic piston cylinder arrangement
Powered by motor
Main Frame Supports carriage and pulleys
Safety features like anti roll bar
Carriage Platform reinforced by square steel bars
Connected to chain and pulley assembly
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Design Specifications
FBD and Analysis of sub-system
Is allowable load under 3 tonnes?
Identify critical locations with n =3
Proceed to next sub system
Design alterations
NO
YES
Choose minimum of all loads as the rated load
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PNEUMATICS AND PULLEY
Possible modes of failure
Rupture of pneumatic cylinder Buckling of piston rod Weld failure of Pulley shaft T section yielding Chain Design
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ESTIMATING CRITICAL LOADS
Failure Mode Critical load with n = 3 (in tonnes)
Rupture of pneumatic cylinder 10.72
Buckling of piston rod 81
Weld failure of Pulley shaft 3.05
T section yielding 9.9
Chain failure ASTM 60 designed for 3 tons
Critical element - pulley shaft Maximum allowable load = 3.05 tonnes Satisfies design requirement of 3 tonnes No design modifications required
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MAIN FRAME
Modes of failure
Failure of load carrying bar Weld failure of welded chain Anti roll bar failure
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ESTIMATING CRITICAL LOADS
Modes of failure Critical loads with n =3 (in tonnes)
Failure of load carrying bar 1.1
Weld failure of welded chain 9.8
Anti roll bar 4.2
Critical location – load carrying bar Maximum allowable load < 3 tonnes Design changes required
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DESIGN CHANGES FOR WEIGHT CARRYING BAR
Increase weld length and leg size Maximum Load is 2.4 tons for h =5mm and d = 5mm
Maximum length and leg size limited by dimensions of bar
Change material 440 Q&T steel
Maximum load is 7.32 tonnes
Economically unfeasible
Change weld pattern Square weld
Maximum load = 3.26 tonnes
Most feasible solution
Compromised Factor of Safety Measure of last resort
For n = 2 , critical 4.8 tons
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CARRIAGE
Modes of failure
Weight sharing by square reinforcing side bars
Shear failure of reinforcing side bars
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ESTIMATING CRITICAL LOADS
Modes of failure Maximum load with n = 3 (in tonnes)
Weight sharing by square reinforcing side bars
26.42
Shear failure of reinforcing side bars 6.73
Critical location – shear failure of reinforcing side bars
Maximum allowable load = 6.73 tonnes Satisfies design requirement of 3 tonnes No design changes required
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FINITE ELEMENT ANALYSIS
Analysis done using design principles was cross checked using Finite element packages commercially available.
Inventor was used to create a CAD model of the critical systems and analysis was done.
We plotted the factor of safety for the structure while taking load as 3 tonnes.
Also, displacements of critical elements were plotted to check assumptions made during theoretical analysis
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LOAD CARRYING BAR
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LOAD CARRYING BAR
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LOAD CARRYING BAR
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LOAD CARRYING BAR
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CARRIAGE WELDS & BENDING
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CARRIAGE WELDS & BENDING – Y displacements
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CARRIAGE WELDS & BENDING- Safety factors
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CARRIAGE WELDS & BENDING- Safety factors
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DESIGN SHORTCOMINGS & PROPOSED CHANGES
Exact length of Piston rod unknown
Novel Use of chain with pulley modelled as pulley with cable
Mixture of butt & fillet welds in reinforcement bars taken as all fillet welds (inherently conservative as fillet welds are weak)
PROPOSED CHANGE :
Load carrying bar most critical & fails at weld to connecting plate
Design change made : weld pattern change
Alternative: Add reinforcement to bar like in a truss for load sharing and larger capacity enhancement and reliability
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THANK YOU