26G IIHill AND U>\V TK.MI'KltATURE TESTS. 



and to pour it into the casing when the test bar has been 

 placed in position for the test. When the test is complete 

 the alloy must be poured out again before it has time to 

 solidify. Owing to the fact that there is little free convec- 

 tion of the fluid in the case of an alloy, it is not easy to 

 preserve a uniform temperature at all points. 



For low temperature tests, a freezing mixture must be 

 used in place of the hot fluid. 



Experiments were made on the effect of temperature 

 on the strength of metals as long ago as 1856, by Sir 

 William Fairbairn, who tested iron for boiler plates and 

 rivets at temperatures varying from 30 deg. Fah. to 435 deg. 

 Fah.* These tests were carried in an extemporised vertical 

 testing machine of the single lever type. The specimens 

 tested were reduced in cross-section at the part exposed to 

 the heating and cooling influences, so that fracture at that 

 point was rendered certain. The rod coming from the 

 lower shackle and attached to the lower end of the speci- 

 men was made to pass through the bottom of vessel 

 containing the heating fluid, in the case of hot tests. In 

 the box was a quantity of oil or water which was. kept at 

 the required temperature by means of a fire grate placed 

 beneath and around it. The position of the test bar was 

 such that the part upon which the test was to be made was 

 immersed so as to be throughout the test kept at the 

 temperature of the fluid. For the tests in which the 

 temperature was maintained below that of the surrounding 

 atmosphere, the hot liquid was replaced by a freezing 

 mixture. 



A number of tests have been more recently made by 

 Mr. Thomas Andrews-f- on railway axles at both high and 

 low temperatures. In the cases where these axles were 

 tested whole under a falling load, they were first exposed 

 for an hour to either the cooling action of a freezing 

 mixture or to the heating effect of the warm bath. When 

 an axle was to be tested it was immediately lifted out of 

 the bath by means of a small crane, placed in position, and 

 the test carried out at once. As the axles were relatively 

 large masses of metal, and the test was carried out imme- 

 diately after being lifted out of the bath, there was little 

 change in temperature. The tests were carried out at two 

 distinct temperatures, namely, the cold tests at 7 deg. 

 Fah. and the warm tests at 120 deg. Fah. The freezing 



* Brir. Asso. Report, 1856. 

 t Min. Proc. Inst. C.E., Ixxxvii. and xciv. 



