332 REPORTS ON THE STATE OF SCIENCE, ETC. 
is restricted during a brief stage of the test are only slight, and not 
of practical importance. 
(4) The determination of the lower yield-point during the course of an 
ordinary tensile test should not add greatly to the total time required 
for the test. 
(5) In structural members such as tie-bars, columns, beams, tubes and 
the like, of mild steel or moderately high-tensile steel, subject to 
determinate conditions of loading, the overloads required to cause 
undue plastic overstrain are readily calculated in terms of the lower 
yield-point of the steel employed. 
(6) In welded structures comprising members subject to determinate 
loading, the calculated overloads required to cause undue plastic 
overstrain are closely confirmed in tests, when the joints between 
the members are of reasonable design. 
(7) In welded structures of complex design the margin between the 
actual load and the calculated overload (at which undue plastic over- 
strain may be expected to occur in the light of calculations based on 
the lower yield-point of the steel) affords a serviceable guide to the 
designer. 
In view of these considerations based upon investigation and experience, 
it is considered that the tensile lower yield-point offers advantages that 
justify its more general application in connection with structural design in 
mild and moderately high-tensile steel ; but its application at present is 
restricted by the lack of an accepted British Standard Specification. 
A draft of such a specification is submitted for consideration : 
‘ After yield has commenced in a tensile test on a standard piece 
(comprising a portion that is tolerably uniform in section) and before it 
has spread along the whole of the portion of uniform section, the load 
shall be readjusted to a new, steady value (being reduced if necessary) 
so that yield spreads along the uniform portion while the machine 
continues to elongate the piece slowly (at a rate not exceeding ;'; in. 
per minute). The stress value deduced by dividing the readjusted 
load by the initial cross-sectional area of the uniform portion of the 
test-piece shall be known as the lower yield-point.’ 
Recommendation —The Committee recommends that the desirability of 
adding a specification of the lower yield-point to the specifications of other 
properties of mild and moderately high-tensile steel, be brought to the notice 
of the British Standards Institution. 
* * * * * 
The terms of reference ‘to investigate the stresses in overstrained 
materials’ were extremely wide. The Committee has investigated one 
important aspect of the problem. They do not ask to be reappointed, but 
suggest that further investigation of some of the special problems involved 
deserves serious consideration. 
