EXPERIMENTAL EXPERIMENTAL STRESS ANALYSIS OF O F TOGGLE JACK USING FEA APPROACH 1
Mr.A.Tamilarasan Mr.G.Keerthi RAJ 1 2
2
Lecturer, Dept.of.Mech .Engg, Pallavan College of Engineering, Engineering, Kanchipuram-631502,Tamilnadu. Kanchipuram-631502,Tamilnadu. Lecturer, Dept.of.Mech .Engg, Pallavan College of Engineering, Engineering, Kanchipuram-631502,Tamilnadu. Kanchipuram-631502,Tamilnadu.
ABSTRACT This paper presents the analysis of screw rod of Toggle jack taking into account the estimation of the effects of a screw and joint elements load. The Toggle Jack is a device used to raise all or part of a vehicle into the air in order to facilitate repairs. Initially the jack is experimentally tested at certain load to obtain induced stress values. Further the model is created in CATIAV5 R11and imported to ANSYS9.0 for static stress analysis, has been devised in the course of investigation. This paper compares the predicted results from Finite Element Analysis (FEA) of the mechanical behavior and experimental results from the test.
Key words: Toggle jack, Power screw, Modeling, Structural analysis.
1. INTRODUCTION
Automobile jacks are used to lift the vehicle at certain level from the earth surface. These jacks are readily available in the market for different tonnage capacities. Among all of them, the Toggle jack or scissors jack is mainly used to lift the medium weight vehicles. A typical example of toggle jack as shown in Fig1.
The jack consists of base plate, bottom and top bracket, power screw, nuts, links, crank etc. The channel shaped bottom bracket is centrally fixed on the base plate either welding or joined by bolt and nut. Two links are connected; one on each end of bottom bracket, other end of the links is joined with two nuts. Also, the the top side of two links links is tied with nuts and and top bracket.
The four links are joined by link pins in the holes of nuts and brackets. The screw rod engaged with nuts. When screw is rotated the nuts are moved either towards of the centre or away from the centre. When the jack is in top position, the distance between the nuts are minimum, where as in the jack in bottom position the distance is maximum. The toggle jack is a symmetrical object.so; all the loads are equally distributed distributed in each side of the jack. 2. EXPERIMENTAL SETUP
Fig.1
Fig.2
Fig.3
The aim of this experimental setup is used to measure the rising load, and corresponding displacement occurs. A typical example of experimental setup is depicted as shown in Fig.1, 2, and 3. In this, we have tested a jack in the car (Maruthi ZEN) at our laboratory. From the test, we have observed a structural performance of the jack.
Since, the jack is brought into the below of the rear axle of the car. In order to measuring the load, the load cell is placed in between rear axle and jack. Strain gauges are also patched on the circumference of power screw. Then, these wires are directly connected to data acquisition box.
By operating the crank of the jack, the rear axle gradually is lifted from the initial position. After that, the jack is positioned at certain height. In this stage, the tire of the axle is raised in the air on one side. Now the readings (like raised load, axial displacement) are noted form the acquisition box. The following data’s are obtained from the test. 1. Raised Load = 113.576Kg =1135.76N 2. Displacement = 0.913mm 3. MANUAL CALCULATION CALCULATION 3.1 Design Data of Toggle jack:
Type of car
: Maruthi ZEN (Gasoline engine)
Weight of Vehicle
: 1160.67Kg
Type of thread
: Square thread, fine series.
No.of.Links
:4
Material
: C45
Young’s Modulus
: 2.1×10 N/mm
Poisson’s Ratio
: 0.3
Co-Efficient of Friction
: 0.15
Distance between Nuts
: 1.When in Bottom position =310mm
5
2
2. When in Top Position
=250mm
For C45 Steel material: 1. Yield point Stress,
σy = 360N/mm2 [PSG DB1.9]
2. Factor of Safety,
FS = 3 2
3. Allowable Tensile Stress, [σ t] = σy / FS =120 N/mm
2
4. Allowable Shear Stress, [τ] = [σt] / 2 = 60 N/mm N/mm 3.2 Design for Strength 1. Design 1. Design of Power Power Screw:
The magnitude of pull is acting on two sides of the screw. For safe design; we have taken twice the load on each side.
W = 2Raised load =21135.76 =2271.98N
To estimate screw diameter, tensile load alone considered. 2
W = ( ∏ / 4)dc [σt ] 2
2271.98 = ( ∏ / 4)dc
120
dc = 5.290mm
The Next nearest Standard Mean diameter, dm = 12mm and Pitch, p=2mm. Core diameter, dc
= 10mm and Lead, L= 2mm.
2. Calculation of Torque:
2.1. Lead Angle, Ф
-1
= Tan [L/ ∏ dm ] = 3.03
°
2.2. Friction Angle, α = Tan -1(µ) = 8.5 ° 2.3. Torque
T = W( dm /2) Tan (α+ Ф) = 2271.98 (12/2) Tan (8.5+ 3.03) = 2780.30N-mm.
3. Torsion Shear Stress:
τ
3
3
2
= (T16/ ∏ dc ) = (2780.30 16/ ∏ 10 ) =14.16N/mm
4. Direct Tensile Stress: St ress:
σt
2
2
= W (∏ /4 dc ) = 2271.98 (∏ /4 10 ) = 33.20N/mm
2
5. Induced Max.Principal Stress:
σmax
= (σt/2)+ sqrt (σt+4 τ2) 2 = (33.20/2)+ sqrt (33.20+4 14.16 ) 2
= 60.320 N/mm < [σt] =120 N/mm
2
There fore, Maximum Induced stress value is LESS THAN the allowable stress. Hence, Design is safe against the strength.
4. MODELING OF TOGGLE JACK
Fig.4
In CATIAV5, the power screw part file and the entire model of jack are created using bottom-up approach. The individual components are drawn and stored in part file. The components are brought together and assembly in assembly design workbench by applying suitable parametric assembly constrains to them. Then the jack assembly and screw model are converted to IGES file for the purpose of analysis in ANSYS. The Model of To ggle jack as shown in Fig.4.
5. FEA APPROACH
Mainly, the structural analysis is used to determine the displacements, stresses, strains, and forces in structures or components caused by loads. The IGES File model of power screw is opened in ANSYS Window environment. In Pre-processing stage, the input data’s like Young’s Modulus and Poisson’s ratio are given and choosing proper element (SOLID92) for this model. Because, the 10 node SOLID92 is quadratic displacement behavior and is well suitable for irregular meshes. The element is defined by ten nodes having three degrees of freedom at each node: translations in the nodal x, y, and z d irections as shown in Fig.5.
Then, free meshing is applied to the screw model. Further Boundary conditions are applied ¼ of the distance at the eac h end along the screw length. Finally, the Loads are applied axially, there by the component is analyzed .In post processing stage, we have observed structural behavior of
screw analyzed to get individual stresses, displacements, etc. Fig.5
The power screw induced stress values and displacement are shown in Fig.6
Fig.6
Then, the entire model of jack is tested at same load, we have obtained induced stress values of the entire model and identified where the maximum stress occurs. The stress and displacement are shown in Fig.7
Fig.7
5. RESULTS AND DISCUSSION
From the experimental investigation, the load and displacement are measured using these values and assuming suitable materials, the manual calculation is done. From this, we have obtained the induced stress value is less than t he permissible stress. Where as in FEA approach, we have chosen proper element and good meshing is done. By applying the same load on the power screw model, there by, the behavior of the screw is analyzed successfully. successfully. The Experimental result and ANSYS result is given in Table1. Sl.no
Description
Manual Result
ANSYS Result
1
Induced Stress
60.320N/mm
60.231 N/mm
0.089
2
Displacement
0.913mm
1.011mm
0.098
2
2
Deviation
Table1.
From the table1, we have obtained the ANSYS result is closer to manual result; therefore the deviation is very less. Hence, the ANSYS result proves as far as close to manual result always.
The comparison charts are shown in Fig.8 and Fig.9 respectively.
INDUCE IND UCED D STRESS VALUE VALUES S Manua Manuall
ANSYS NSYS
60.35 s s e r t s s e u d l e a c v u d n I
60.3 60.25 60.2 60.15
Method
Fig.8 DISPLACEMENT VALUES Manu Ma nual al
ANSY ANSYS
1.05
t n e 1 m e c 0.95 a l p s 0.9 i D 0.85 Method
Fig.9
6. CONCLUSION
The experimental test is done successfully. After that, we have done the modeling of screw rod and toggle jack in CATIAV5 and analyzed the same model in ANSYS9.0.From this, we have been concluding the induced stress values and displacement values are coming closer to each other.
REFERENCE:
1. Joseph E.Shigley, C.R.Mischke,” Mechanical engineering Design”, TATA McGraw- Hill Publishing company limited, New Delhi. 2. M.F.Spotts,”Design of Machine Elements”, Prentice- Hall India Private Limited, New Delhi. 3. Robert L.Norton,”Machine Design”, Prentice- Hall India Private Limited, New Delhi. 4. WilliamC.Orthwein,”Standard Hand book of Machine Design”Jaico Publishing House, New Delhi. 5. V.B.Bhabdari,”Introduction V.B.Bhabdari,”Introduction To Machine Design”’TATA McGraw-Hill Publishing Company Limited, New Delhi. 6. PSG DESIGN DATA DAT A BOOK,”PSG College of Technology”, Coimbatore. 7. www.Roton.com 8. www.designofmachinery.com 9. www.powertransmission .com 10. www.powerjack.com
