resistência dos materiais (Ásia)
Post on 01-Jun-2018
225 Views
Preview:
TRANSCRIPT
-
8/9/2019 Resistncia dos Materiais (SIA)
1/51
1
Mechanics of MachineryMechanics of Machinery
. .
-
8/9/2019 Resistncia dos Materiais (SIA)
2/51
2
1. ! " #$ %&'(). !*" +$ % ,'(
-. % /01"2 !3 4'( 4''(
4. A5t65r 7. 8r9man:7;oran9@M; 6anism 9;si nt6;sisE FoC5m; 4G? )n9 89itiM 7raHIJiCC? 4KK4
-
8/9/2019 Resistncia dos Materiais (SIA)
3/51
-
8/9/2019 Resistncia dos Materiais (SIA)
4/51
4
!Z [1"21 %\ ] ^c # "_
-
8/9/2019 Resistncia dos Materiais (SIA)
5/51
5
Mechanism AnalysisMechanism Analysis
Kinematics motion position velocity acceleration
Kinetics F=ma
Mechanics
DynamicsStatics
MechanismMechanism
AnalysisAnalysis
Object is inObject is inmotionmotion
Object isObject is
motionless ormotionless ormovin
g with a = 0moving with a = 0
-
8/9/2019 Resistncia dos Materiais (SIA)
6/51
6
Object types
1. Particle a point mass, m2. Rigid body a finite body that is not
fle ible.
3. !le ible body " a finite body that isfle ible, not considered in this class.
#ote$ %n this class, &e &ill loo' at ho& a particleand a rigid body mo(e in t&o dimensionalspace)2*+ or plane.
-
8/9/2019 Resistncia dos Materiais (SIA)
7/51
Motion types in 2D
4. jransCation ` 3 Z # `%"\ l Z lc #Z 0! 02" p2cq ; tiCin;ar transCation ` 3Z #
`%"\ l Z lc #Z0 `*d 1!!` 3 #Z lcq V5r iCin;ar transCation I ` 3Z #
`%"\ l Z lc #Z0 `*d 1!!` 3 %3#Z lc). otation `%"\ l Z lZ l 2+2 b #0 0
/ !1 + l# \0 %b%#Z l\l l
-
8/9/2019 Resistncia dos Materiais (SIA)
8/51 -
Translation motion !
-
8/9/2019 Resistncia dos Materiais (SIA)
9/51
-
8/9/2019 Resistncia dos Materiais (SIA)
10/51 1
"otational motion
-
8/9/2019 Resistncia dos Materiais (SIA)
11/51
-
8/9/2019 Resistncia dos Materiais (SIA)
12/51 12
echanism ynthesis
"e&'ire$ Motion
#omponents types
('mber)si*e)shape
MechanismSynthesis(design)
Mechanisms are the basis of allmachine design
-
8/9/2019 Resistncia dos Materiais (SIA)
13/51 13
echanism synthesis
%n some de(ices, e.g. instr0ments, controlmechanisms the correct motion is the mostimportant thing. he po&er )force+ transmitted issmall and so strength si e of parts is not theprime concern.
%n other machines, the 'inematic analysis is onlyone step in the design process. 7nce &e ha(e&or'ed o0t ho& parts sho0ld mo(e together &em0st then calc0late the forces that areprod0ced. he re80ired strength and si e shapeof parts can then be determined
-
8/9/2019 Resistncia dos Materiais (SIA)
14/51 14
+asicMechanisms
-
8/9/2019 Resistncia dos Materiais (SIA)
15/51 15
9in'agesSli$er,#ran-.in- / frame )reference+.in- 2 cran'.in- connecting"rod )con"rod+.in- 1 slider
4 " Reciprocating motion)bac' : fore+
2 " Rotation
Kinematic $iagrams simpli3ie$ b't acc'rate!$iagrams showing geometry o3 motion
#ran-,"oc-er .in- / frame )reference+.in- 2 cran'.in- connecting"rod )con"rod+.in- 1 roc'er
-
8/9/2019 Resistncia dos Materiais (SIA)
16/51 16
4"bar lin'age e amples
/ran'"roc'er *o0ble"roc'er
http://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cdoublerocker_assembly.avihttp://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cgrashof_crank_rocker.avi -
8/9/2019 Resistncia dos Materiais (SIA)
17/51
1
lider"cran' e amples
%n(ersiontandard slider"cran'
http://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cinverted_sc_assembly.avihttp://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cslidercrank_assembly.avi -
8/9/2019 Resistncia dos Materiais (SIA)
18/51
1-
/am
(+4 A cam can only p'sh the 3ollower not p'll!the ret'rn action re&'ires spring)gravity etc5
#am rotates at constant ang'lar velocityFollower moves 'p an$ $own
-
8/9/2019 Resistncia dos Materiais (SIA)
19/51
1
/am"follo&er e amples
!lat faced translating follo&er !lat faced reciprocating follo&er
http://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cflat_faced_cam.avihttp://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CAnimation%5Cff_translating_follower.avi -
8/9/2019 Resistncia dos Materiais (SIA)
20/51
2
;ears
;ears are 0sed to transmit motion from one shaftto another &ith a constant ang0lar (elocity ratio)gear ratio+.
;ears trains canbe 0sed &hen alarge o(erall gearratio is re80ired
driver
driven
http://var/www/apps/conversion/tmp/scratch_6/C:%5CMonsak%5CMachinery%5CCt%20&%20Br.avi -
8/9/2019 Resistncia dos Materiais (SIA)
21/51
21
;ears
-
8/9/2019 Resistncia dos Materiais (SIA)
22/51
22
De3initions
-
8/9/2019 Resistncia dos Materiais (SIA)
23/51
-
8/9/2019 Resistncia dos Materiais (SIA)
24/51
24
9in'
< rigid body ha(ing t&o or more pairing elements )=oints+ thatconnect to other bodies for the p0rpose of transmitting force ormotion
+ell,#ran- < simple lin' ha(ing threeconnections 0sed to formotion red0ction
-
8/9/2019 Resistncia dos Materiais (SIA)
25/51
25
!rameFi6e$,.in-4 re3erence 3rame7 .in- no5 /not always shown as a lin-!
>oint )?inematic pair+#onnection o3 2 or more lin-s allowing relative
motion
-
8/9/2019 Resistncia dos Materiais (SIA)
26/51
26
?inematic pairs)>oints or connections+
@a(e 2 basic types$ .ower pair a =oint connected 2 members
ha(ing s0rface contact )e.g. b0sh, pin+ 8igher pair a connection that ta'es place at
a point or along a line )ball bearing, gearteeth, cam+
These classifications are not really important forkinematic analysis
-
8/9/2019 Resistncia dos Materiais (SIA)
27/51
2
ypes of pairs )=oints+
"evol'te pair/ $o3!
9rismatic sli$ing! pair/ $o3!
"olling pair / $o3!, witho't slip
#ams 2 $o3!,with slip
Lower pairs
higher pairs
-
8/9/2019 Resistncia dos Materiais (SIA)
28/51
2-
ype of >oints, @igher Pairs%ears sliding and rotation motion bet&een t&o teeth, 2 *7!
-
8/9/2019 Resistncia dos Materiais (SIA)
29/51
2
ype of >oints, @igher Pairs+elt an$ p'lley no sli$ing! or chain an$ sproc-et 1 *7!
Spring no effect on mechanism *7!
-
8/9/2019 Resistncia dos Materiais (SIA)
30/51
3
/ommon types of >oint
-
8/9/2019 Resistncia dos Materiais (SIA)
31/51
31
*egrees 7f !reedom )dof+ obility )!+
The n'mber o3 motion variables 's'ally joint variables s'ch as angles! which canbe controlle$ in$epen$ently to bring the$evice to a partic'lar positioncon3ig'ration!
:3 F = / the mechanism can be $riven by asingle inp't motion
:3 F = 2 the mechanism re&'ires twoseparate inp't motions to pro$'ceconstraine$ $e3inite! motion
-
8/9/2019 Resistncia dos Materiais (SIA)
32/51
32
obility of planar machanisms
#0mber of lin'sn A 6
#0mber of =ointf 1 A
/an &e calc0late themobility from thisinformationB
-
8/9/2019 Resistncia dos Materiais (SIA)
33/51
33
link ! " dof # links ! " x# !$ dof
# links % &oint ! " x#' #x ! ( dof
'dof'&oint
-
8/9/2019 Resistncia dos Materiais (SIA)
34/51
34
2 ?? ?????????
)x ,y *
1
link ! " dof
)x ,y * )x#,y#*
12
# links ! " x# !$ dof
)x ,y * )x#,y#*
1
#'dof'&oint
# links % &oint ! " x#' x ! + dof
-
8/9/2019 Resistncia dos Materiais (SIA)
35/51
35
!orm0la for dof
! A 3)n"1+ 2f 1 f 2
! A obility )dof+
n A n0mber of lin's
f 1 A n0mber of =oints &ith 1 dof
f 2 A n0mber of =oints &ith 2 dof
To calc'late the total n'mber o3 $o3 3or aplanar mechanism4
K't*bach;s criteriaOr %r'bler;s criteria
-
8/9/2019 Resistncia dos Materiais (SIA)
36/51
-
8/9/2019 Resistncia dos Materiais (SIA)
37/51
3
D amplesn = 7 3 / = 7 3 2 = 0F = 0 motion is impossible$ mechanism formsa str0ct0re
F = n,/! 23 / 3 2
n = 17 3 / = 17 3 2 = 0F = / mechanism can be dri(en by a singleinp0t motion$ constrained mechanism
n = 17 3 / = 17 3 2 = 0F = / mechanism can be dri(en by a singleinp0t motion$ constrained mechanism
-
8/9/2019 Resistncia dos Materiais (SIA)
38/51
-
8/9/2019 Resistncia dos Materiais (SIA)
39/51
3
f f f
f 3 / = ?
3 2 = 0
F = >,/!,2 ?,0
F = 2
D f F d DOF! h h
-
8/9/2019 Resistncia dos Materiais (SIA)
40/51
4
Degrees of Freedom DOF! trench hoe#0mber of lin's, n A 12, #0mber of one *7! =oints, f 1 A 12 )pins+ E 3 )slider+ A 15,
#0mber of t&o *7! =oints, f 2 A
! A 3)n
1+ 2f 1 f 2 A 3)12"1+ "2)15+ A 3
/2 //
/0
@?
>
top related