Mechanical Engineering Reviewer.pdf

I

ALCORCON ENGINEERING REVIEW CENTER· Manila: 4th FIr,

Anadeta Bidg. 891 Galicia St. cor:Espana AVe.

Sampaloc Mli!nila (leI. 742-5fS..OO)

'Cebu: 4TH FIr. Vlllacam~a-Capuras Bldg., Sanciangco St. Cabu City (Tel # 254-33-84)

MACHiNE ELEMENTS RqlUng Cylinders 1. Cylinders Rolling in opposite direction:

~

. Tangential speed

Vi "" Va :::: 11: 01 Nt :::: '";&

1t

Dz N2

"Relatioflof diameter and speed 01 N1 :: D:.! N2

,

$peedRatlo:::' SpeedofDIi?l~r . eM) SpeedoftbeDnven

"

CenierDistance '" R1 + Rz = o!+ °2 2

;&

Tangential speed

V1 ::: V:;: := 11: 01 Nl

.. := 11:

D:iNz

(;; Relation of diameter and speed

D1 N1 :::: DzN2 ". Spee d R81.0= t' ..,.,

Speed .of Driver Speed .of the Driven

G Center Distance :::: R; _ R2 "" 0 1 - D2 2

STRESSES DEFINITIONS:

.Force 1'-1':;: ? :;: 1. Stress (S):::: - - . .., In , kgfcm-, KN/m . Area Stress::: a total resistance that a material .offers to an applied load.

2. Ultimate stress (Su) -

is the s~ess tMt

would cause failure

,

,

3. Yieldstress(Sy) - maximum stress without causing deformation 4. Allowable stress(Sall) ::: Ultimate stress/Factor of SafetY

Types 'of. Stresses A. Tensile Stress

CSt)

S, Compressive Stress(Sc)

Fe , A

D .

.

,

:;,>-"

'.

, F -

\..

JI'

.

t~'", t

o A ::: n D ~ (fof'punching a hole)

flo

D. Bearing Stress(Sb)

L

where: A::: DL E. Factor of ~fety(FS)

A Based on yield strength:

D

S

FS:::: - Y San

B. Based on ultimate strength:

where:

Sail ::: allowable stress

S...::: ultimate stress

Sy ::: yield stress

F. Torsional Shear stress(Ss)

s.. : :

Tc J

where:

=:

16T'

7tD3

T :: torque J.:: polar moment of inertia 1I:D4

32 (for sofid shaft)

J :::

c :: r (for circular cross section) d :: diameter:

G. Bending Stress(St)

F

t

St:: Me ~

.'

For rectangular beam:

l..

aM

St::

bh 2

"lhere: M :::: moment c :: distance of farthest fiber from neutral axis :: moment of inertia aboutthe neutral axis f ;;;; bh3112 (for rectangular cross section)

4 ==

sectio~ modulus

of rectangular shaft : :.:

,.

T

M

c

nd 3

=-16S

Z :: section modulus of circular shaft ::: -

*.

.

~Of~~ @ ~fAvK} Strain and Elongation A. Strain :::: y

l

S. Stress::::

c.

F

A

Stress Modulus of elasticity, E :: - - Strain

FL AY

F

D. Y:: FL

AE

where:

Y:: elongation due to applied load L :::: original length F :: force For steel: E = 30 X 106 psi

A= area

S

= stress

DtN,"'-

nNz.

!it :. 0-N"Iv

OJ

D~-c.. (£0.[

k ::: coefficient of thermal expansion, wJm-"C 1/ /'

h ::: final temperature, °C ,

\ _I",

'-' ~ lIISX C ~I

Relation between shearing and tensile stress based on theory of failure: Stmax ::

~

Variable Stress

8m-:::

~1tth~::. ~~td~~~

~

~ .rk~ ~ ~ lei ot 61rCSS/~

_1_ '" 8 m + Sa FS Sy. Sn

where:

Sy. ::.: yield point

FS :: factor of safety

Sm ::: mean stress :::

So ::: endurance limit

Smax +SmltL

2 Smax -Smin

vo ::: variable component stress:::

t:;,

--"-"~-

Smax ::: maximum stress

Smin ::: minimum stress

2

/

" Poisson's Ratio(u) ::: is the ratio of lateral unit deformation to axial unit deformation.

where:

u•

2~ -1

fll. Psteel ill> :!~!ii~~

G::;

shear modulus of elasticity

- I "

0:;;J4(;

r ~l~eJ ~

~ o.;/G !t>~

E ::: modulus of elasticity

~ pa)~:C l{~oY r~~eJ ~ D.'~r

h>

o.e_

ALCORCON ENGINEERING REVIEW CENTER Manila: 41i> Fir. Anacleta Bldg. 891 Galicia St. cor. Espana Ave. Sampaloc Manila (Tel. 742-56-00) Cebu: 4TH Fir. Villacampa-Capuras Bldg., Sanciangco Sf. Cebu City (Tel # 254-33-84)

Machine Design Problems - DAY 1 MACHINE ELEMENTS 1. PROBLEM (ME Bd. Apr. 91) Two parallel shafts connected by pure rolling tum in the same direction having a speed ratio of 2.75. What is the distance of the shafts if the smaller cylinder is 22 em in diameter? 2. Two cylinders rolling in opposite direction has a speed ratio of 3 .. If center distance is 40 in, find the diameter of smaller cylinder.

, ','

l~

J:;

, ,

-= ',G, s X )6~ ~I. .•. , ( &t>';f) ( ::zq-~'t ",'jOr xld

(cln (J.

CXkf;

~ ~Slf1b

~

J

\w

Pr ~ O. 'db 'VI ~ ~_

¥lOY)- tL

O=j;f

l.

Q l.\ I (g t ~ 38 ~ . ~ Q

t}.

&\ ~ -l= :: -

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