suc ben vat lieu_ tinh toan truc shaft
DESCRIPTION
Tinh toan chon kich co truc dua theo suc benTRANSCRIPT
Machine ElementShaft
Shaft
1. Strength of Shaft
(2) Bending load
2. Strength of Key
(3) Torsion load
(1) Material
3. Fracture surface
Shaft
𝑊 : h𝑊𝑒𝑖𝑔 𝑡𝐹 :𝐹𝑜𝑟𝑐𝑒𝜎=
𝑀𝑍
𝑀 :𝑀𝑜𝑟𝑚𝑒𝑛𝑡𝜎 :𝑆𝑡𝑟𝑒𝑠𝑠
Strength of Shaft (1) Bending load
Shaft
I: geometrical moment of inertia, Z: section modulus
Shaft
Formula of statically determinate beam
BMD: Bending Moment Diagram SFD: Shear Force Diagram
Shaft
BMD: Bending Moment Diagram SFD: Shear Force Diagram
Shaft
𝑊=12 𝑡𝑜𝑛𝜎 𝑎=46𝑁
How much diameter we need ?
allowable stress
< Q. 1 >
Shaft
𝑊 : h𝑊𝑒𝑖𝑔 𝑡𝐹 :𝐹𝑜𝑟𝑐𝑒𝑀 :𝑀𝑜𝑟𝑚𝑒𝑛𝑡𝜎 :𝑆𝑡𝑟𝑒𝑠𝑠
Strength of Shaft
𝑇 :𝑇𝑜𝑟𝑠𝑖𝑜𝑛
𝑇
(2) Torsion load
Shaft
Shaft
Stress concentration
Fig. Stepped Shaft
fatig
ue n
otch
fact
or β
Shaft
Stress concentration
Fig. Torsion of Shaft having key
stre
ss c
once
ntra
tion
fact
or α
Shaft
Stress concentration
Fig. Torsion of Stepped shaft
stre
ss c
once
ntra
tion
fact
or α
Shaft
< Q. 2 >
𝜏𝑎=98𝑁
How much torsion each shaft resist ?
allowable stress
𝜏=𝑇𝑍𝑃
=16𝑇𝜋 𝑑3
This shift have stress concentration
Shaft
Stress concentration
boss
shaft
Shape and stress distribution of Tight fit
contact edge
Distance from contact edge r
Stre
ss σ
Shaft
Countermeasure
boss
shaft
boss
shaft
boss
shaft
ditchditch
Shaft
𝐹=12h𝑙𝑝
𝐹=𝑏𝑙𝜏 𝑘
(2) contact pressure strength
(1) shear strength
Strength of Key
𝑙≥1.5𝑑
Shaft
ShaftFatigue Fracture Surface
Chevron Pattern
Beach Mark
Chevron Pattern
Beach Mark
starting point
Final fracture section
Shaft
Fracture surface
pulsating bending
fully-reversed bending
rotary bending
pulsating tension, tension and compression
cyclic torsion
high stress low stressnotch
(sharp)notch (dull)smooth
notch (sharp)
notch (dull)smooth
ShaftMaterial for Shaft
small shaft, motor shaft car shaft, common shaft crank shaft, induction hardening shaft cam shaft, piston shaft small shaft, piston pin crank shaft, cam shaft, drive shaft, common shaft small shaft, middle shaftcommon shaftcrank shaft, large shaft, piston pin cam shaft, spline shaft middle shaft, large shaft
common shaft, piston pin piston pin
crank shaft, car shaft, various shaft large shaft
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