HIGH AND LOW TEMPERATURE TESTS. 263 



The following is an example of a test of a hemp rope : 

 TEST OF AN ITALIAN HEMP ROPE. 



Of course it must be remembered that this sectional 

 area is only nominal, and does not refer to a solid section 

 but to the area of the circle representing the outer 

 circumference of the rope. 



TESTING OF METALS AT ABNORMAL 

 TEMPERATURES. 



14- It is important in some cases to test samples of metals 

 at temperatures either above or below the normal tempera- 

 ture of the atmosphere, in order to discover their properties, 

 at the temperatures at which they may be expected to be 

 used under the ordinary conditions of working. Examples 

 of such are to be found in copper and bronze firebox 

 stays for locomotives, and steel which is to be used for 

 boiler making. These are cases of parts of structures 

 exposed to high temperatures ; the axles of railway 

 vehicles are to some extent affected by exposure to frost, 

 and tests of these at temperatures below the normal have 

 been made. 



141. High and Low Temperature Tests. It is known 

 that many metals, when exposed to temperatures much above 

 the normal, are affected to a considerable extent as regards 

 their strength properties. The gradual increase in the 

 pressures, and consequently the temperatures at which 

 steam boilers are worked makes the testing of metals at 

 high temperatures most important. 



The objects to be aimed at in carrying out a test of 

 this kind satisfactorily are : 



(a) The application and measurement of the loads on 

 the test bar. 



(b) The maintaining of the bar at a uniform and pre- 

 arranged temperature during the whole of the test. 



