DESIGN OF MACHINE ELEMENTS- UNIT 3
- 1. Unit - 3 KNUCKLE JOINT
- 2. • A knuckle joint is used to connect two rods which are under the action of tensile loads. • It consists of mainly three elements a fork or double eye rod, a single eye rod and knuckle pin. • Its use may be found in the link of a cycle chain, tie rod joint for roof truss
- 3. Knuckle joint Two or more rods subjected to tensile and compressive forces are fastened together Their axes are not in alignments but meet in a point The joint allows a small angular moment of one rod relative to another It can be easily connected and disconnected Applications: Elevator chains, valve rods, etc
- 9. 1.Failure of solid rod in tension Due to tensile load , the rods are subjected to tensile stresses, and may fail if this stress exceeds the limit
- 10. 2.Failure of Knuckle Pin in Double shear
- 11. The rod may tear along a plane passing through the pin axis 3.Failure of the single eye or rod end in tension
- 12. The rod end may be sheared off as shown in fig. The resisting stress is 4.Failure of the single eye or rod end in double shear
- 13. 5. Failure of single eye or rod end in crushing Due to tension load , the eye end may be crushed to failure. The area resisting crushing is taken as the projected area and the corresponding stress is related to the tensile load is
- 14. 6. Failure of forked end in Tension The fork end may fail in tension across the pin hole
- 15. 7. Failure of forked ends in double shear (as shear of eye)
- 16. 8. Failure of forked ends in Crushing (as Crushing of eye) The forked end is weak in crushing than in other modes, it will result in crushing Failure
- 17. 9. Failure of Knuckle pin by Bending • The loosely fitted knuckle pin experiences bending. • The load on pin uniformly varies over the pin area in the fork. • Maximum bending is at the mid of the pin.