792 SUMMARY OF CURRENT RESEARCHES. 



Consequently there can be no uniform relation between static tensile test 

 and notched bar impact test. 



P. Welikhow * finds that impact tensile tests give numerical values 

 which agree with the results of static tensile tests, and give in addition 

 the kinetic strength of the material. 



Irregular Stresses due to Non-homogeneity.f — A. Leon summarises 

 the results of mathematical investigations concerning the irregular 

 stresses which arise in elastic bodies owing to the presence of inclosures, 

 hollow spaces, and superficial flaws. Inclosures of any kind will cause 

 local increase of stress, and thus a diminution in the strength of the 

 material. These increases in stress are greatest within the elastic range, 

 and diminish rapidly when permanent deformations occur. 



Thermo-electric Measurement of Elastic Limits — E. Rasch deduces 

 from theoretical considerations that when a metal is stressed in tension 

 its temperature falls so long as its deformation is purely elastic, but rises 

 when inelastic permanent deformation begins. A method of determin- 

 ing elastic limit founded on this property is described. The change of 

 temperature of a tensile test-piece when submitted to increasing stress is 

 followed by means of a thermo-couple placed in contact with the test- 

 piece and connected to a delicate galvanometer. The critical stress — 

 i.e. elastic limit — is indicated by a reversal in the temperature record. 



Influence of Increased Temperature on the Mechanical Qualities 

 of Metals. § — M. Rudeloff describes the various methods which have 

 been employed for carrying out tensile and other mechanical tests at 

 high temperatures. The results of high temperature mechanical tests 

 made by the author and others on steel, cast iron, copper, brass, bronze, 

 manganese bronze, and delta metal are summarised. A comprehensive 

 bibliography is appended. 



Portevin, A. — Binary Alloys. 



[A. Portevin has continued his account of the investigations carried oat in 

 G. Tammann's laboratory at Gottingen (see this Journ., 1908, pp. 522 

 and 787). The alloys of nickel, lead, antimony, silicon, tin, and zinc are 

 here dealt with.] 



Rev. Melallurgie, v. (1908) pp. 838-56, 909-27 ; 

 vi. (1909) pp. 241-71, 951-82 (127 figs.). 



* Proc. Inst. Assoc, for Testing Materials, No. 10 (1909) 9 pp. (2 figs.) 

 t Op. cit., No. 9(1909) 6 pp. J Op. cit., No. 11 (1909) 7 pp. (2 figs.). 



§ Op. cit., No. 12 (1909) 30 pp. (25 figs.). 



