Design analysis of Cotter joint used in piston rod and crosshead a.pptx

Design analysis of Cotter joint
used in piston rod and crosshead

1.Abstract
2.Introduction
3.Literature survey
4.Design of cotter joint
5.Cotter joint to connect piston rod and crosshead
6.Example problem statement
7.3d modelling of cotter joint
8.Analysis of cotter joint
9.Result and discussion
10.Conclusion
11.Suggestion for future
12.References

1. TOPIC:- Design analysis of Cotter joint used in piston rod and crosshead

2. CONTENT Abstract Introduction Literature survey Design of cotter joint Cotter joint to connect piston rod and crosshead Example problem statement 3d modelling of cotter joint Analysis of cotter joint Result and discussion Conclusion Suggestion for future References

3. ABSTRACT The subject of this project is the modeling and analysis of cotter joint. Cotter joint is used to connect two rods subjected to axial tensile or compressive loads. Cotter joint is widely used to connect the piston rod and cross head of the steam engine, so as a joint between the piston rod and the tailor pump rod, foundation bolt etc. Failure of cotter joint may causes accident, so it is necessary to design cotter joint to withstand under tension without failure the effective design of mechanical device or assembly demand the predictive knowledge of its behavior in working condition. In this project we use theoretical method for finding dimensions of cotter joint. After the design of cotter joint, The modeling of cotter joint is done by using 3D software. Here we will be using CREO for modeling. After modeling on CREO, we will analyze cotter joint on software named as “ANSYS V15”.

4. a INTRODUCTION The Failure of cotter joint may causes accident so it is necessary to design cotter joint to withstand under tension without failure. The effective design of mechanical device or assembly demand the predictive knowledge of its behavior in working condition. It became necessary for the designer to know the forces and stress developed during its operation. In this project we use theoretical method for finding dimensions of cotter joint. After the design of cotter joint, the modeling of cotter joint is done by using CREO. Here we will be using CATIA V5R19 for modeling. After modeling on CREO, We will analyze cotter joint on software named as “ANSYS V15”. A cotter is a flat wedge shaped piece of rectangular cross-section and its width is tapered (Either on one side or both sides) from one end to another for an easy adjustment. The taper varies from 1 in 48 to 1 in 24 and it may be increased up to 1 in 8, If a locking device is provided. The locking device may be a taper pin or a set screw used on the lower end of the cotter. The cotter is usually made of mild steel or wrought iron. A cotter joint is a temporary fastening and is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces. It is usually used in connecting a piston rod to the cross- head of a reciprocating steam engine, A piston rod and its extension as a tail or pump rod, Strap end of connecting rod etc. [6] INTRODUCTION

5. LITURATURE SURVEY Saxena N, Raj Vaidya R, “Study and analysis of cotter joint with the replacement of material by using Teflon”, journal of engineering research & application, The objective of this paper is to study the various stresses and strain by replacing of material by using Teflon. In many industries use cotter joint which is combination of two materials cast iron is stainless steel. In this paper the replacement of cast iron into composite polymer material, Polymer is the most similar to property of metal. Composite polymers are characterized by a high flexibility material they conclusion that the result appropriate equal or closer theoretical and ANYSYS Ravindra S. Dharpure, Prof D. M. Mate, “Study and Analysis of Pin of cotter Joint In Train”, The main motive of this paper is to improve the performance of the cotter pin in the couplings of the railway couplings. The current mechanism of coupling is briefly defined and methodologically treatment is determined for failure of cotter pin in the coupling. The aim of this chapter is to conceptually define remedy for the failure problem of the cotter coupling. As per the company’s present requirement the cotter joint should be efficiently used to reduce the cost of production, improve the quality of the product, Increase the production rate and Increase the service life of the cotter joint.

6. DESIGN OF COTTER JOINT The socket and spigot cotter joint is shown in Fig . Let, P = Load carried by the rods, D = Diameter of the rods, d 1 = Outside diameter of socket, d 2 = Diameter of spigot or inside diameter of socket, d 3 = Outside diameter of spigot collar, T 1 = Thickness of spigot collar, d 4 = Diameter of socket collar, c = Thickness of socket collar, b = Mean width of cotter, T = Thickness of cotter, L = Length of cotter, A = Distance from the end of the slot to the end of rod, σ t = Permissible tensile stress for the rods material, τ = Permissible shear stress for the cotter material, σ c = Permissible crushing stress for the cotter material.

7. Cotter Joint to Connect Piston Rod and Crosshead Following is the cotter joint which is used to connect the Piston rod and Crosshead. The piston rod is tapered in order to resist the thrust. The taper we can use for the piston rod may be from 1 in 24 to 1 in 12. The piston rod and crosshead may be subjected to a tensile or compressive load. All components of the joint are assumed to be of the same material. We know that maximum load on the piston, P = (π/4) × d 2  × p where, D = Diameter of the piston, and p = Effective steam pressure on the piston. In designing a cotter joint to connect Piston rod and crosshead, the following modes of failure may occur. Or at least we need to consider these failures in order to determine the design parameters of the Cotter joint to connect Piston rod and Crosshead. Failure of piston rod in tension at cotter Failure of cotter in shear Failure of the socket in tension at cotter Failure of socket in crushing

8. Piston Rod Diameter The piston rod may fail in tension at the cotter due to the maximum load on the piston. We know that area resisting tearing at the cotter will be The Tearing strength of the piston rod at the cotter will be the product of the cross-section area that resists the tensile stress and the induced tensile stress. Let us equate the tearing strength to the maximum load (P), we can write             From this relation, we can determine the diameter of the piston rod at the cotter (d 2 ). The thickness of cotter (t) is taken as 0.3 d 2 .

9. Width of the Cotter By assuming the Failure of the cotter in shear, we can obtain the width of the Cotter. As you can see the above schematic representation of the Cotter being pulled away by the two equal opposite loads results in double shear. The shearing area of the cotter will = 2 b × t and shearing strength of the cotter will be the product of the permissible shear stress of the  = 2 b × t × τ Now equate this relation to the load (P), we can write as P = 2 b × t × τ From this relation, we can determine the width of cotter (b).

10. Diameter Of Socket (d 3 ) By considering the Failure of the socket in tension at the cotter, we can determine the Diameter Of the Socket. We know that area that resists the tearing of the socket at the cotter is and the tearing strength of the socket at the cotter will be the product of the area that resists the tearing of the socket at the cotter and the induced tensile stress. we can write the relation as follows. Equating this to maximum load (P), we have From this equation, the diameter of the socket (d3) is obtained.

11. Induced Crushing Stress In The Socket The induced crushing stress in the socket may be checked by considering the Failure of the socket in crushing. We know that area that resists crushing of socket = (d 3  – d 2 ) t and crushing strength of the socket = (d 3  – d 2 ) t × σ c Equating this to maximum load (P), we have P = (d 3  – d 2 ) t × σ From this relation, the induced crushing stress in the socket may be checked. The length of the tapered portion of the piston rod (L) is taken as 2.2 d 2 . The diameter of the parallel portion of the piston rod (d) =  d 2  + (L/2) × Taper The diameter of the piston rod at the tapered end (d 1 ) =  d 2  – (L/2) × Taper By the way, the taper on the piston rod is usually taken as 1 in 20. from this also the d 1  can be obtained.

12. Example Problem Statement Q. Design a cotter joint to connect the piston rod to the crosshead of a double-acting steam engine. The diameter of the cylinder is 300 mm and the steam pressure is 1 N/mm2. The allowable stresses for the material of the cotter and piston rod are as follows. σ t  = 50 MPa τ = 40 MPa σ c  = 84 Mpa Answer: Given data: Cylinder diameter (D) = 300 mm Steam pressure inside cylinder (p) = 1 N/mm2 σt= 50 MPa = 50 N/mm2 τ = 40 MPa = 40 N/mm2 σc= 84 MPa = 84 N/mm2 We know that maximum load on the piston rod, P = (π/4) × d2 × p = (π/4) × (300)2 × 1 = 70695N The various dimensions for the cotter joint to connect Piston rod and crosshead of the double-acting steam engine are obtained by considering the different modes of failure as mentioned above.

13. Answer: 1. Diameter of piston rod at cotter Let us say d2 = Diameter of piston rod at cotter, and t = Thickness of cotter. It may be taken as 0.3 d2. Considering the failure of the piston rod in tension at the cotter. We know that load (P)                      70695 = [(π/4) × (d 2 ) 2  – d 2  × (0.3 d 2 )] × 50 70695 = [(π/4) × (d 2 ) 2  – 0.3 (d 2 ) 2 ] × 50 70695 = 24.27 (d 2 ) 2 (d 2 ) 2  = 70 695 / 24.27 (d 2 ) 2 = 2913 d 2  = 53.97 We got the Diameter of the Piston rod at the cotter as 53.97mm, let us take this value as 55mm. The thickness of the Cotter (t) will be = 0.3 d2 = 0.3 × 55 = 16.5 mm

14. Answer: 2. Width of cotter Let us say b = Width of cotter. Considering the failure of cotter in shear. Since the cotter is in double shear, therefore load (P), P = 2 b × t × τ 70695 = 2 b × t × τ 70695= 2 b × 16.5 × 40 70695= 1320 b b = 70 695 / 1320 b = 53.5 We got the width of the cotter as 53.5mm , let us round it up to 54mm.

15. Answer: Diameter of socket Let us take d3 = Diameter of the socket. Considering the failure of socket in tension at cotter. We know that load (P),                          70695 = [(π/4) {(d 3 )  2  – 55 2 } – ( d 3  – 55) 16.5] 50 70695 = 39.27 (d 3 )  2  – 118792 – 825 d 3  + 45375 (d 3 )  2  – 21 d 3  – 3670 = 0 d 3  =73mm. Let us now check the induced crushing stress in the socket. We know that load (P), P = (d 3  – d 2 ) t × σ 70695 = (d 3  – d 2 ) t × σ c 70695= (72 – 55) 16.5 × σ c 70695= 280.5 σ c σ c  = 70 695 / 280.5 σ c  = 252 N/mm

16. Answer: Since the induced crushing is greater than the permissible value of 84 N/mm2, therefore let us find the value of d 3  by substituting σ c = 84 N/mm 2  in the above expression, P = (d 3  – d 2 ) t × σ 70695 = (d 3  – 55) 16.5 × 84 70695 = (d 3  – 55) 1386 d 3  – 55 = 70 695 / 1386 d 3  – 55 = 51 d 3  = 55 + 51 = 106 The diameter of the socket we get is (d 3 ) 106mm

17. Answer: We know the tapered length of the piston rod is (L) = 2.2 d 2  = 2.2 × 55 = 121 mm. Assuming the taper of the piston rod as 1 in 20, therefore the diameter of the parallel portion of the piston rod is d =  d 2  + (L/2) × Taper d = 55 + (121/2) × (1/20) d =58mm. The diameter of the piston rod at the tapered end is d 1  =  d 2  – (L/2) × Taper d 1  = 55 – (121/2) × (1/20) d 1  = 52mm. These are all the parameters to design the Cotter Joint to Connect Piston Rod and Crosshead

18. 3D MODELLING OF COTTER JOINT Assembly of Cotter Joint

19. Detail Of Cotter Joint

20. ANALYSIS OF COTTER JOINT Fig : Project Schematic Fig : Meshed Assembly Fig : Equivalent (von-mises) stress at 40kN load Structural analysis at 40 KN

21. Fig : Total deformation at 40KN load Fig : Equivalent (von-mises) stress at 50kN load Fig : Total deformation at 50KN load Structural analysis at 50 KN

22. Structural analysis at 60 KN Fig : Equivalent (von-mises) stress at 60kN load Fig : Total deformation at 60KN load

23. Load (KN) Max. Deformation (mm) Von-Mises Stress (MPA) Remark 40 0.02998 77.98 SAFE 50 0.03731 97.47 SAFE 60 0.04477 117 SAFE Result and Discussion The maximum permissible value of stress of structural steel is 400 MPA. From this it is clear that the design of cotter joint is safe for 50kN as there is minimum acceptable deflection. The stress is also less than the permissible stress of the material. Hence design of cotter joint Assembly is safe.

24. Conclusion Cotter joint is widely used in application in automobiles and other field. So it should be strong enough so if it can’t sustain that amount of load, otherwise there is possibility of accidents. So we designed the cotter joint. Then by CATIA V5R20 we had done the modeling with gives correct design then design we are going to check by ANSYS R15 to find stress in the cotter so we got perfect design of cotter joint. Based on the analysis results, following conclusion points are summarized, The maximum permissible value of stress of 30C8 steel is 400 MPA. From the results achieved at loads 40kN, 50kN and 60kN it has given lower stress values and deformation for the 30C8 steel.

25. References Shaikh J, vanka H, [2015], “Modeling and analysis of knuckle joint”, International journal & magazine of engineering, Technology, Management and research , Vol. 2, Issue 11, Page no. 292-298 Saxena N, Rajvaidya R, [2015],“Study and analysis of knuckle joint with the replacement of material by using Teflon”, Journal of engineering research & application, Vol. 5, Issue 3, Page no. 67-71 Xianguang KONG, Yuanying QIU [2012] , “Research and implementation of CATIA tool integration technology based on CAA." Dev dutt dwivedi, V.K. Jain [2016] ,“Design and analysis of automobile leaf spring using ansys." Vol. 3, Issue 1. Mahajan Vandana N, Shekhawat Sanjay P "Analysis of blades of axial flow fan using ANSYS." "A text book of machine design."R.S khurmy & J.K Gupta. “Design of machine element”, V.B Bhandari – 3 rd edition.