MIDTERM

is a branch of
mechanics that studies the internal effects of
stress and strain in a solid body that is
subjected to an external loading

longitudinal stress/circumferential formula

lb/in^2 convert to lb/ft^2

N-kN

psi-ksi

is associated with the strength of the
material from which the body is made, while

is a measure of the deformation of the
body.

performed experiments to
study the effects of loads on rods and beams

A body is subjected
to only two types of external loads;
namely surface forces AND body
forces.

are caused by the
direct contact of one body with
the surface of another.

is developed when one
body exerts a force on
another body without direct physical
contact between the bodies.

The surface forces that develop
at the supports or points of
contact between bodies are

Equilibrium of a body requires
both these, to prevent the
body from translating or having
accelerated motion along a straight or
curved path

this is required to prevent the body from rotating

Four types of resultant loadings:

This force acts perpendicular to the area.

tend to cause the two
segments of the body to slide
over one another.

This effect is developed when
the external loads tend to twist
one segment of the body with
respect to the other about an
axis perpendicular to the area.

caused by the external
loads that tend to bend the
body about an axis lying
within the plane of the area.

includes the study of the body’s stability when a body
is subjected to compressive loading.

This subject expanded into other areas of
mechanics, such as the

which is applied to a
point on the body

if the surface loading is
applied along narrow strip of area.

is equivalent
to the area under the distributed loading
curve, and this resultant acts through the
centroid C or geometric center of this area

Procedure for Analysis

stress represents a force per unit area,
in the International Standard or SI system, the
magnitudes of both normal and shear stress are
specified in the basic units of

Foot-Pound-Second system of
units, engineers usually express stress in

where 1 kilopound (kip) = lb?

will occur to members that are axially loaded. applied force is perpendicular
to the resisting area.

Two types of Normal Stress

Forces parallel to the area resisting the force cause shearing stress.

is the contact pressure between the separate bodies. It differs from
compressive stress, as it is an internal stress caused by compressive forces.

A tank or pipe carrying a fluid or gas under a pressure is subjected to tensile
forces, which resist bursting, developed across longitudinal and transverse
sections.

Also known as unit deformation, is the ratio of the change in
length caused by the applied force,
to the original length.

From the origin O to the point called
p ro p o rtio n a l lim it, th e s tre s s- s tra in
c u rve is a s tra ig h t lin e . Th is lin e a r
re la tio n b e twe e n e lo n g a tio n a n d th e
a xia l fo rc e c a u s in g wa s firs t n o tic e d
b y

fo r s m a ll d e fo rm a tio n s , th e
s tre s s a n d s tra in a re p ro p o rtio n a l to e a c h o th e r,
a n d th is is kn o wn a s

formula for Hooke’s Law?

is the limit beyond
wh ic h th e m a te ria l will n o lo n g e r g o
b a c k to its o rig in a l s h a p e wh e n th e
lo a d is re m o ve d , o r it is th e m a xim u m
s tre s s

s tra in d ia g ra m fro m O to E

Th e re g io n

fro m E to R is c a lle d

is the point at which
th e m a te ria l will h a ve a n

a p p re c ia b le e lo n g a tio n o r

yie ld in g with o u t a n y in c re a s e in

lo a d .

The maximum ordinate in the

stre ss- s tra in d ia g ra m

the
s tre n g th o f th e m a te ria l
a t ru p tu re . Th is is a ls o
kn o wn a s th e b re a kin g

stre ng th.

is the work done on a
u n it vo lu m e o f m a te ria l a s th e fo rc e is

g ra d u a lly in c re a s e d fro m O to P, in N·m / m 3.

is the work done
o n a u n it vo lu m e o f m a te ria l a s th e fo rc e

is g ra d u a lly in c re a s e d fro m O to R, in
N·m / m 3.

A body is subjected to only two types of external loads; namely,

What are the various types of strain?

is the ratio of the steady force acting
o n a n e la s tic b o d y to th e re s u ltin g
d is p la c e m e n t. It h a s th e u n it o f N/ m m .

is a measure of the amount
o f la te ra l s tra in c a u s e d d u e to th e
lo n g itu d in a l s tra in o f m a te ria l.

is one
ha ving re la tive ly la rg e te nsile stra ins up
to th e p o in t o f ru p tu re like s tru c tu ra l
ste e l a nd a lum inum , whe re a s b rittle
m a te ria ls ha s a re la tive ly sm a ll stra in
u p to th e p o in t o f ru p tu re like c a s t iro n
a n d c o n c re t e .