torsion test1

8/10/2019 Torsion Test1

1/6

1979

EASTERN MEADITERRANEAN UNIVERSTY

DEPARTMENT OF MECHANICALENGINEERING

LABORATORY HANDOUT

COURSE STRENGTH OF MATERIALS- MENG222

Semester: Spri! 2""#-2""$

L%&' N(: )

N%me (* E+p:Torsion Test

Istr,t(r: Ass(' Le' C%*er .i/i0(rsAssist%t: G10%3 T%e0

Submitted by:

Student No:

Date: ..

-------------------------------------------------------------------------------------------------------------

EVALUATION

PROCEDURERESULTS & GRAPHSDSCUSSONREPORTPRESENTATONOVERALL MAR.

1


2/6

Name and !i"natu#e $o% ea'uato#(:OBJECT:

To carry out a torsion test to destruction in order to determine the following for aspecimen.

a) The modulus of rigidity.b) The shear stress at the limit of proportionality.c) The general characteristics of the torque ,angle of twist relationship.

APPARATUS:

Tecquipment Torsion Testing Machine and Torsiometer ,steel rule and micrometer.

Standard torsion specimen for use with the torsion testing machine and torsiometer

THEORY:

From the general torsion theory for a circular specimen.

rL

G

J

T =

=

Where,

T !pplied Torque """"""""""""""" #m or lbf in

$ %olar second moment of area"""""""""" &mm or &in

' Modulus of rigidity """"""""""""". (mmN or

(inlbf

!ngle if twist o*er length +)""""""""".. radians

(


3/6

Shear stress at radius r-"""""""""""(

mm

N or

(in

lbf

r radius""""""""""""""""""". mm or in

EXPERIMENTAL PROCEDURE ( In instruti!n "!r#$

1) Measure the o*erall length and test diameter of the specimen.() raw a line down the length of the degree of the section of the specimen with a

pencil this ser*es as a *isual aid to the degree of twist being put on the specimenduring loading.

/) Mount the specimen firmly in the Torsion Testing Machine as indicated in theoperating instructions0see later.

f the Torsimeter is to be used the fi2ing procedure should be carried out asprescribed.

For each increment of strain record the following 3a) angle of twist of the specimen ) in degrees.b) !pplied torque"""""..T)c) !ngle of twist o*er the 45 millimeter or (.55 inch gauge length in radians, as

recorded by the dial gauge indicator""".. ) in radians.d) When the elastic limit has been passed continue to test to destruction with e*er

increasing increments of strain, recording for each strain increment,i) !ngle of twist in degrees.ii) !pplied torque.

NOTE3 n some tests it may be found unnecessary to use the Torsiometer after theelastic limithas been reached. The Torsiometer, if this is the case, can be remo*edfrom the specimen and readings of twist ta6en direct from the machine scales. Toremo*e the Torsiometer unclamp the two cap screws securing it to the specimen andslip each end clamp of the Torsiometer off the specimen. The end clamps ha*e beenslotted for this purpose. t is not possible to remo*e the center cylindrical spacer ofthe Torsimeter as this would in*ol*e disturbing the end fi2ing of the specimen ,i.e.releasing it from the chuc6, and this S789+ #8T :; 8#; 9#;< !#=>9MST!#>;S 9


4/6

To ensure that an adequate number of *alues are obtained from the test ,particularlyduring the elastic region of strain, the following is recommended3

OPERATIN% INSTRUCTIONS &OR THE TORSION TESTIN% MACHINE AND

TORSIOMETER (In instruti!n "!r#$

1) !llow the spring balance to hang free of the torque arm and ?ero the balance byad@usting the small 6nurled screw at the top right hand of the balance.

() Slide balance along the supporting framewor6 until the two engra*ed lines, oneon the hori?ontal cross member of the frame and the other on the balanceassembly bloc6 which is sliding along this member, coincide.

/) Slid the hoo6 of the balance under the 6nife edge on the torque arm with the hoo6hanging free at its lowest position.

&) >lamp the specimen in to the @aws of the Torsion Machine and fit the Torsiometer

on to the specimen a full account of this is found earlier in the bulletin under themean heading A9se and 8peration of the TorsiometerB.

t is essential when using the Torsion Machine to ma6e sure that the whole lengthof the he2agonal ends of the specimen are contained fully within the chuc6 @aws.!lso when the straining head, specimen and Torsiometer are pushed along the bedso that the end of the specimen enters the headstoc6 chuc6, enter the specimen into the chuc6 until the light compression spring behind the headstoc6 chuc6 @ustbeings to compress.

4) when the specimen has been firmly fi2ed in position clamp the straining head tothe bed.

C) Turn the handle on the straining head until the torque arm is in the hori?ontal asshown by the spirit le*el.

D) Turn the spring balance hand wheel to raise the balance until the hoo6 on thebalance is @ust contacting the 6nife edge on the torque arm. This will be seen bymo*ement of the spirit le*el bubble.

>are should be e2ercised to carry out this operation so that the torque arm andspring balance are ?eroed-

:oth balance hand wheel and straining head hand wheel may ha*e to be ad@ustedtogether to obtain this condition.

E) ero the fine and course angular displacement dials on the input and output shaftsof the straining head. ! 6nurled nut is pro*ided behind each dial to loc6 the dial inposition.

G) ero the re*olution counterHby turning cloc6wise .15) !d@usting the arm on the Torsiometer so that it @ust contacts the dial gauge

plunger. ! 6nurled nut is pro*ided for this purpose and a full description is found

&


5/6

under the main heading A9se and 8peration of TorsiometerB earlier in thisbulletin.

11) ero the dial gauge indicator by rotating the dial.1() The apparatus is now ready for use and the test specimen can be loaded, in the

desired increments, by turning the handle on the straining head until the specimen

has been rotated the requisite number of degrees as shown on the fine angulardisplacement on the machine. :;F8; 7#W7;;+.

1/) When testing the more elastic materials the Torsiometer dial needs to be resetperiodically to ?ero due to the limitation on the plunger tra*el. See Ause and8peration of the TorsiometerB.

NOTE ON THE CONTENT O& THE LABORATORY REPORT

8nce again the content of the report will depend largerly on the type of test carriedout and the detailed in*estigation required, but for a test similar to that describedabo*e the following suggestion are offered3

nclude in the report a dimensioned drawing of the specimen .9sing the tabulated results,

a) %lot a graph of applied Torque T- against angle of twist as a base for theelastic region. 9se the slope of this graph to determine the *alue of the modulusof rigidity. !lso from this graph determine the torque, and then calculate theshear stress at the limit of proportionality.

b) %lot a graph of applied torque against angle of twist of the specimen as a base,for the complete test to destruction.

DISCUSSION O& RESULTS

1. State and comment upon the *alues obtained from the test .(. >omment upon the o*erall result obtained from the test./. >omment upon the apparatus an procedure.&. iscuss the errors in*ol*ed in determining the modules rigidity using the angle of

twist from the machine dial, and compare the result obtained with the *alue foundby using the Torsiometer.

4


6/6

Tabulate the results as follows3

;+!ST>

torsion test1

Documents