chapter 1 strength of materials

8/19/2019 Chapter 1 Strength of Materials

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DAT 2023:STRENGTH OFMATERIALS

TOPIC 1: STRESS & STRAINBY: PUAN NUR AINI SYAKIMAH BINTI

AHMAD SHUYUTI


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CONTENT

Introduction

Force

Support Reaction

Free Body Diagram

Equilibrium of a Rigid Body


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INTRODUCTION

Mechanics of mateia!s A branch of mechanc! I" !"#$e! "he re%a"on!h of:

E'"erna% %oa$! a%e$ "o a $eformab%ebo$() an$

The n"en!"( of n"erna% force! ac"n*+"hn "he bo$(

Are #!e$ "o com#"e $eforma"on! of abo$(

S"#$( bo$(,! !"ab%"( +hen e'"erna% force!are a%e$ "o "


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INTRODUCTION

Mechanics of mateia!s A branch of mechanc! I" !"#$e! "he re%a"on!h of:

E'"erna% %oa$! a%e$ "o a $eformab%ebo$() an$

The n"en!"( of n"erna% force! ac"n*+"hn "he bo$(

Are #!e$ "o com#"e $eforma"on! of abo$(

S"#$( bo$(,! !"ab%"( +hen e'"erna% force!are a%e$ "o "


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-ORCE

S#rface forceConcen"ra"e$

D!"rb#"e$ E'"erna% force In"erna% force A%e$ force Reac"on force


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S#or" Reac"on


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E.#%br#m of a R*$Bo$( Rigid body a body that does not deform

under the action of applied loads

Deformable body a body that deforms

under the action of applied loadsEquations of equilibrium For equilibrium

balance of forces balance of moments

Draw a free-body diagram to account for allforces acting on the body

Apply the two equations to achieeequilibrium state ! F " 0

! MO " 0


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-ree Bo$( Da*ram! No"e!


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ne"ton) N# #n" of force n "he m/! !(!"em of #n"!)+hch ! ba!e$ on "he me"rc !(!"em0 " ! "he force"ha" ro$#ce! an acce%era"on of 1 me"er er!econ$ er !econ$ +hen e'er"e$ on a ma!! of 1

/%o*ram The ne+"on ! name$ for Sr I!aacNe+"on

mass# n h(!c!) "he .#an""( of ma""er n a bo$(re*ar$%e!! of "! 2o%#me or of an( force! ac"n* on

" The "erm !ho#%$ no" be conf#!e$ +"h +e*h")+hch ! "he mea!#re of "he force of *ra2"( ac"n*on a bo$(

"ei$ht# mea!#re of "he force of *ra2"( on a bo$(

%e& Tems

http://www.factmonster.com/ce6/sci/A0819139.htmlhttp://www.factmonster.com/ce6/sci/A0833496.htmlhttp://www.factmonster.com/ce6/sci/A0833496.htmlhttp://www.factmonster.com/ce6/sci/A0832931.htmlhttp://www.factmonster.com/ce6/sci/A0832931.htmlhttp://www.factmonster.com/ce6/sci/A0833496.htmlhttp://www.factmonster.com/ce6/sci/A0833496.htmlhttp://www.factmonster.com/ce6/sci/A0819139.html


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#hat is a scalar $ A scalar is simply a number% a magnitude alone&

#hat is a force and how is it illustrated$

A force is usually shown as a ector% which includes

both magnitude and a direction&

#hat is a free-body diagram$ A free-body diagram illustrates the relatie

magnitude and direction of all forces acting upon an

ob'ect& (he ob'ect must be isolated and )free* of its

surroundings&

%e& Tems


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Weight (W) aries depending upon the location of the body in the

earth+s graitational field ,or the graitational field of some other

astronomical body& A gien body will hae the same mass on the

earth and on the moon% but its weight on the moon will be only about./0 of the weight as measured on the earth&

(he acceleration of graity on earth is appro1imately23&4. m5s6 in SI units and78&8 ft5s6 in 9S :ustomary units&

(o calculate the weight of an ob'ect you hae to multiply it;s mass times the acceleration of gravity.

W m ! g

'hat (oes $a)it& ha)e to (o"ith the "ei$ht of an o*+ect,


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# " m ! g#rite the formula2

Substitute %???


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(his is a free-body diagram of the Statue of iberty& She

is represented by a simple bo1& (he forces acting on herare labeled with a magnitude and the arrow shows

direction& otice the surrounding ob'ects are stripped

away and the forces acting on the ob'ect are shown&

C3/8.? lb

C3/8.? lb

Free-Body Diagram


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637 here rere!en"! "he force of "he +e*h" of "he!"a"#e

6N7 ! "he norma% force) +hch rere!en"! "he force

8ber"( I!%an$ ! #!hn* bac/ # on "he !"a"#e

+,&'000 lb

+,&'000 lbF

FW

Free-Body Diagram

The !%an$ ha! a *rea" re!!"ance "o comre!!on The*ro#n$ ! e'er"n* a force #+ar$ on "he !"a"#eeren$c#%ar) or norma%) "o "he !#rface

Norma%: mean! eren$c#%ar "o) 9e' The +a%%! "o "heoor;

The force of "he e$e!"a% "o "he !"a"#e ! norma% "o"he !#rface of "he *ro#n$


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(hin< of the diagram on an plane&

If )up* is assumed to be the positie direction%then is positie and # is negatie&

-C3>%??? lb

C3>%??? lbF "

F# "

,=ositie y-directiony

1,=ositie 1-direction

Free-Body Diagram


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Free-Body Diagram

(he first line of this calculation reads%

)(he sum of the Forces in the positie y direction is# * ( Σ is the Greek symbol for “sum” )

↑ ΣFy " #

ΣFy " ,-C3>%??? lb ,C3>%??? lb

ΣFy " ?

(he sum of the forces in the y is Gero&

(he forces acting on the ob'ect cancel each other out&

-C3>%??? lb

C3>%??? lb "

# "

,=ositie y-directiony

1,=ositie 1-direction


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•#e


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Crea"e a free bo$( $a*ram 9-BD; of "he *or%%a:

Force/Free Body Diagrams

Sitting Horilla

Free Body Diagram of the Sitting

Horilla ,(he bo1 represents the

gorilla% # " weight of the gorilla% "

ormal force


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"his is also an accetable

diagram.

F

F#

Sitting Horilla

No"ce "ha" "he arro+ hea$! of "he +e*h" an$norma% force ha2e chan*e$ a! +e%% a! "her%oca"on


F#

F

Pre2o#!


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Bungee 'umpingfrom crane

Dra+ a -BD of b#c/e" "he bungee 'umper leaped from2

Free Body Diagram of the buc


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(raffic ight

supported by cables

Dra+ a -BD of "he rn* a" on" C:

A B

:

D

Free Body Diagram of the ring at

point : ,( represents the force of the

cables that are in tension acting on

the ring

F(:A

F(:D

F(:B


3here are "he force! on "he rn*=


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Dra+ a -BD of "he "ra>c %*h":

Free Body Diagram of the traffic light

,F(/ represents the force of the cables

acting on the light and F# is the weight

acting on the light

F#

F(:D

8*h"

(raffic ight

supported by cables

A B

:

D


3here are "heforce! on "he

%*h"=


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=in-:onnected =ratt (hrough (russ

Bridge

Dra+ a -BD of "he n a" on" A:

A B

E

D

:

Free Body Diagram of pin A

,If you consider the third dimension% then

there is an additional force acting on point

A into the paper2 (he force of the beam

that connects the front of the bridge to the

bac< of the bridge&

F(AEF(A:

F(AB

F(AD


3here are "heforce! on on" A=

? O


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?@

.oce(/e fo Ana!&sis

Me"ho$ of !ec"on!

1 Choo!e !e*men" "o ana%(e

? De"ermne S#or" Reac"on!

Dra+ freebo$( $a*ram for +ho%e bo$(

A%( e.#a"on! of e.#%br#m

1? EUI8IBRIUM O- ADE-ORMAB8E BODY

1 ? EUI8IBRIUM O- A


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?F

.oce(/e fo ana!&sis

-reebo$( $a*ram

1 Kee a%% e'"erna% %oa$n*! n e'ac"%oca"on! before 6!ec"onn*7

? In$ca"e #n/no+n re!#%"an"!) N) ) M)an$ T a" "he !ec"on) norma%%( a"cen"ro$ C of !ec"one$ area

Co%anar !(!"em of force! on%( nc%#$eN) ) an$ M

E!"ab%!h x, y, z coor$na"e a'e! +"hor*n a" cen"ro$

1? EUI8IBRIUM O- ADE-ORMAB8E BODY


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chapter 1 strength of materials

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