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PSNA COLLEGE OF ENGINEERING AND TECHNOLOGY, DINDIGUL – 624 622 DEPARTMENT OF MECHANICAL ENGINEERING ME6503

UNIT I

DESIGN OF MACHINE ELEMENTS

STEADY STRESSES AND VARIABLE STRESSES IN MACHINE

MEMBERS Sl. N (

T!"#$

PSGDB P%&'

Preferred numbers, ts and tolerances

N. 3.( ) 3.6,

2

Direct, Bending and torsional stress equations,

*.(+ *.(, 6.2, *.(

3 4 5

eccentric loading curved beams Principal stress, theories of failure stress concentration – Design for variable loading

6.2 %- 6.3 *.2, *.3 *.4 ) *.6

CURVED BEAM PROCEDURE 1. The bending bending stress stress in the curved curved beam beam is zero, zero, at a point other other than at the centroidal ais !"#$. %. &f the sectio section n is s'mmetr s'mmetrica icall such such as circle, circle, recta rectangl ngle, e, &( Beam Beam )ith )ith equal *anges, then the ma. bending stress )ill al)a's occur at the inside bre. 3. Based on given section to nd the r n, + from PSGDB 6.2 %- 6.3 . &f the the sect sectio ion n is uns' uns'mm mmet etri rica cal, l, then then the the ma. ma. bend bendin ing g str stress ess ma' ma' occur at either inside or the outside bre. The ma. bending stress at the inside bre is given b' σ bi =

 M b hi  A e r i

hi - i/ ri - +i/ +n - rn e - distance from the "# to the 0# !0eutral ais$ e - + – +n !or$ + – r n hi - i - distance from the 0# to the inside bre - r n ( ri ri - +i - radius of curvature of the inside bre

b - 2  3 3 - distance bet)een the load and "# - 4 5 + 6. Direct tensile stress at a section σ d =

 P  A

7. a. bending stress at the outside bre is  M b ho σ bo =  A e r o

ho - o/ ro - +o/ ho - o - distance from the 0# to the outside bre +o – +n or ro - +o/ ro - +o - radius of curvature of the outside bre 8. +esultant stress on inner and outer surface &nner 9 - 9d 5 9bi :uter 9 - 9d ( 9bo