3 torsion analysis

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FACULTY OF MECHANICAL ENGINEERING“In the name of Allah, The Most Benecent, The Most Mec!f"l#

La$

%&'

Tos!on Anal(s!s

)e*ae+ $(Mohamad Mazwan Mahat

E+!te+ $(Nasrul Azuan bin Alang

Fa-"lt! .e/""teaan Me-an!-al,Un!0es!t! Mala(s!a )ahan1

La$ Locat!onStrength of Materials Lab

La$ O$/ect!0es

By the end of this lab, students should be able to:• Determine the torsion breaking strength of solid bar for

dierent tye of materials!• "dentify the range and the transition from elasti# to lasti#

deformation, the deformation in the elasti# range by illustratingin a searate #hart!

2& 3ate 44444444444444444444

Go"* Mem$es5t"+ent

I3 5ect!on

BMM2521 Engineering Mechanics Lab II_1011/2_Torsion_Test


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89& Into+"ct!on

$orsional Strength is a measure of the ability of a material to withstand atwisting load! "t is the %ltimate Strength of a material sub&e#ted to torsionalloading, and is the ma'imum torsional stress that a material sustains beforeruture! Alternate terms are modulus of rupture and shear strength.

Be#ause many engineering stru#tures, su#h as beams, shafts, and airlanewings, are sub&e#ted to torsional for#es, the torsional roblem has been of ra#ti#al imortan#e in stru#tural analysis for a long time! Saint()enant*+-. was the /rst to ro0ide the #orre#t solution to the roblem of torsionof bars sub&e#ted to moment #oules at the ends! 1e made #ertainassumtions about the deformation of the twisted bar, and then showed thathis solutions satis/ed the e2uations of e2uilibriums and the boundary#onditions! 3rom the uni2ueness of solutions of the elasti#ity e2uations, itfollows that the assumed forms for the disla#ements are the e'a#t

solutions to the torsional roblem!

3irst, #onsider the torsion of a shaft with a #ir#ular #ross se#tion! Assumethat the shaft is /'ed at the origin of the 4artesian #oordinate system! $he x#oordinate is along the shaft a'is! Also note that units in this se#tion areassumed to be #onsistent! $he 0isualization of the bar under torsional loadis shown below5(


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F!1"e 8 C!c"la $a "n+e Tos!onal Loa+

29& E:*e!ment )oce+"e

F!1"e 2 5*ec!men fo the Tos!on Test

F!1"e 6 E;"!*ment 5et"*



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?Note )lease efe to th!s !ll"stat!on fo eas( "n+estan+!n1$he e'eriment ro#edure is di0ided into 6*two. se#tion! 3or the /rstse#tion you need to set u the #onne#tion and load the se#imen #orre#tly!Se#ondly, erform the e'eriment by alying load to the #ir#ular bar!

5ect!on 8

78ou may refer to the re0ious age for numbering illustration+! Make sure that no load is alied to the tor2ue measurement unit! 9ress

and hold the button on the dislay and then ress the 9 button! $hedislay returns to zero!

6! "nsert so#kets *+. into s2uare #onne#tions!;! ! Set the tor2ue dislay to zero using the ?tare@ fun#tion!! Set the ointers on the two angle s#ales *>. to zero!

! Set the dial gauge *+. on the #omensation de0i#e to zero by rotatingthe s#ale ring!C! #orresonds to -! on the se#imen>! $o #on0ert the inut angle on the hand wheel into the angle on the

se#imen, di0ide the inut angle by >;!



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! After ea#h load ste, the deformation of the tor2ue measuring shaftshould be #omensated! $o do this, ad&ust the dolly on the handwheel*++. until the dial gauge *+. shows a 0alue of zero again!

! After ea#h load ste, the torsion moment is read on the dislay and notedalong with the torsional load dislayed!

C! Eith long, thin se#imens, se0eral hundred turns #an be made beforebreakage! "n this #ase, simly read o the 0alue on the re0olution#ounter!

69& Res"lts

Ta$le 8 Res"lts fo M!l+ 5teel

In*"t an1le,T"n =heel

Tos!on an1le !n+e1ee

Tos!on Moment!n Nm

!6- +!=!- 6!!- =!;

+

+!-6!6!-;!=!-!>!!!C!+!+-!6!6-!;!=-!>!+6!



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+-!+!6+! +6


3


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Ta$le 2 Res"lts fo Bass



Tos!on Moment!n Nm

!6- +!=!- 6!C!- =!;

++!-6!6!-;!

=!-!>!!!C!+!+-!


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6!6-!;!=-!>!+6!

+-!+!6+! +6


3


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Ta$le 6 Res"lts fo Al"m!n!"m



Tos!on Moment!n Nm

!6- +!=!- 6!C!- =!;

++!-6!6!-;!

=!-!>!!!C!+!+-!


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6!6-!;!=-!>!+6!

+-!+!6+! +6


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4al#ulation:(

$he ma'imum torsion moment gi0es the following torsion breakingstrength: *4omute all ; materials.

2

3 3

16. 16........... _______ /

. .6

tb tbtb

p

M M Nm N m

W d τ

π π

= = = =

*"nsert the Mtb fra#ture 0alue.

79& 3!sc"ss!ons

+! De/ne the term @tos!onal moment9

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6! Des#ribe the lotted grah result and #omare the materials breakingstrength! 4omment on elasti# and lasti# region as well as the rutureoint!

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;! Ehy do engineers need to ha0e knowledge about failures due totorsional load in designing me#hani#al artsG State any e'amles tosuort your reasons!





=! Assume that same material has #onstant 0alue of torsion breakingstrength! "f the solid #ir#ular bar now is #hanged to hollow #ir#ular


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bar, what would be the 0alue of torsion ma'imum torsion momentsGEhyG





5. Hi0e ; methods on how to minimize and a0oid torsion!




9& Concl"s!on

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Refeences


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3 torsion analysis

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