PART II 



PHYSICAL PROPERTIES OF MATERIALS 

 CHAPTER XII 



IRON AND STEEL 



166. Introductory. A study of the properties of materials used in 

 engineering construction involves a study of the machines used for 

 making the tests and the method of conducting these tests. From 

 the time of Galileo, in 1600 A.D., tests have been made to determine 

 the strength of materials, but only during the past fifty years has any 

 very great advance been made. The rapid development of the past 

 half century has been due to the notable increase in the construction 

 of large buildings, bridges, etc. ; for where engineers were formerly 

 content to use material without being tested, the importance of modern 

 constructions demands that the physical properties of the materials 

 used shall be determined for each large contract. 



The early testing machine consisted of little more than an ordinary 

 scalebeam with the test piece attached to one end and the load 

 applied at the other. These were used for making tension tests, and 

 machines equally as simple were used for compression and flexure 

 tests. Fig. 144 shows a type of these machines which was used by 

 Kirkaldy about 1860. The specimen to be tested was held in the 

 jaws g while the lever F was in the position of the dotted lines 

 (Fig. 144). A load N was then applied to the end of the lever and 

 gradually increased until the specimen was ruptured. 



Testing machines have been much improved during the past twenty 

 or thirty years in the United States by Kiehle Bros, and Olsen & Co., 



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