﻿540 Mr. W. A. Scoble on the Strength and Behaviour 



readings of the twist directly. The length of the beam, or 

 the distance from the centre line of the pins to the rollers, 

 was 30 inches. The load was applied at the centre and the 

 deflexion measured at 14 inches from the roller support. 

 The end mirror was 1-J inches from the roller support. The 

 pin joints at the one bearing, and the combined roller and 

 pulley arrangement, were tested to determine the amount 

 of constraint due to friction. This was in each case small, 

 but has been allowed for in working out the results. 



9. The Tests Grouped. 



The tests may conveniently be divided into three classes. 

 The first includes the tests with one kind of loading only, 

 these giving the loads necessary to cause yield either by 

 bending or twisting. For the second class a definite fraction 

 of the critical bending load was put on and the specimen then 

 twisted to yield. In the third set a given part of the yield 

 twisting moment was applied and then sufficient bending load 

 put on to cause the bar to give. Each kind of load was 

 applied directly by weights, so that it increased by stages and 

 not gradually. When the elastic limit was reached the load 

 added was considerably smaller than those put on at first, it 

 being of the order of one pound. The pulley was lightly 

 tapped after the addition of each twisting load to minimize 

 the effect of friction or sticking. If a result appeared 

 doubtful, or if the increments of load had been too large at 

 the yield-point, preventing its accurate measurement, the test 

 was repeated on a new T bar. 



10. Table of 'Results. 

 The results of the tests are tabulated below : — 



Group 



of 

 Test. 



Number 



of 



Test, 



Bending 

 Moment. 



Twisting 

 Moment. 



Tensile 



Stress 



due to 



Bending. 



Shear 



Stress 



due to 



Twisting. 



Max. | Min. 

 Principal 



Stress. 



Max. 

 Shear 

 Stress. 



1. 



i. ... 

 in... 



2660 

 





 2400 



64600 

 





 29170 



64600 

 29170 







-29170 



32300 

 29170 



2. 



IV. ... 



V. ... 



vi. ... 



VII.... 

 XII. ... 



667-5 

 1331 



2000 

 2420 

 2000 



22S0 

 2120 

 1899 

 1171 

 1720 



16220 



32350 

 48600 

 58750 

 486U0 



28250 

 25750 

 23050 

 14240 

 20900 



37500 

 48200 

 57800 

 619S0 

 56740 



-21S00 

 -15S00 



- 9200 



- 3220 



- 8140 



29400 ! 



32000 



33f,00 



32600 



32440 



32030 

 32400 

 30400 



3. 



VIII. ... 

 IX. ... 

 XL... 



2f>58 

 2310 

 1454 



64,') 

 1335 

 2033 



62100 

 56100 

 35330 



7840 

 16220 

 24700 



63080 

 60450 

 48060 



- 980 



- 4350 

 -12740 



