IIW History 1948-1958

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this at the time, in 1953 the Commission recommended that, during fatigue tests, measurements of additional bending stresses should be carried out with resistance strain gauges. To this end, it was laid down where the strain gauges should be placed on the specimens to take these measurements. Finally, and also with a view to unification, the Commission recommended a certain number of conditions with regard to the actual execution of pulsating tensile fatigue tests on welded assemblies. It fixed z kg/mm 2 as the lower limit of the cycle, it laid down a range of standard sections for specimens and it clari– fied the definition of the completion of a fatigue test, the fatigue strength being determined at two million cycles without fracture. In the meantime, the Commission collected the results of comparative tests on butt-welded joints, these tests having been decided upon in 1951 at Oxford. An important report presented in 1956 by Mr. CAZAUD (France) allowed the Commission to make certain comparisons which resulted in important differences being detected between the fatigue strengths measured in the different countries for butt-welded joints. The fact that the tests thus analysed had been under– taken before the testing technique was finally fixed did, however, make variations inevitable between the results from one country and those from another. The Commission thought that the experience gainecl as a result of these tests and of the comparison of their results would make it possible to carry out, under exactly comparable conditions, a new series of tests; it therefore made a working group responsible for drawing up a programme of tests t o be carried out in collaboration by the various member countries; this subject is mentioned below In 1952, Commission XIII asked the member societies of the IIW to send it information about fatigue failures which had occurred in service in welded con– structions. It was difficult at the beginning to obtain such information becau e those in a position to supply it feared that, if they passed it on, they would brina discredit on certain applications of welding or even on certain under– taki~gs, the products of which might be identified. For this reason the Com– mission, at the Copenhagen assembly in 1953, adopted a resolution stressing the educational value of the information sought and asking the Governing Council to approve in principle the publication of a special memorandum to draw attention to the necessity for a genuine effort to exchange information on this subject. This resolution, which was approved by the Governing Council, was follo\ved during the course of the year 1954 by the circulation of a questionnaire prepared in liaison with the Scientific and Technical Secretariat and containing a stan– dard form for the replies to the Commission's enquiry. This questionnaire was intended to make possible the collection of information about the appearance of fractures, the circumstances in which they occurred, the service conditions of the constructions which had failed, the nature of the materials, etc. The Commi sion received various interesting replies to this questionnaire in 1955· At first, the intention was to gather the e replies together in the form of a number of monoaraphs. In 1956, hov,·ever, the Commission thought that, as relatively few c;ses were reported to it, it would be better to publish the reports separately as they v.·ere received so that users should not be deprived of documentary information \Yhich , even though fragmentary, might be useful to them; it 1rns also hoped, and this hope seems to have subsequently been justified, that the first publications, with \vhich great care was taken t o preserve anonymity, would encourage further replies. Up to the pre ent, seven reports have, at the request of the Commission, been circulated; these relate to cases of fatig ue failure and to the st eps taken or recommended for preventing the reccurrence of this type of accident in the cases mentioned . Among the information asked for in the c1uestio1111aire, the most difficult in connexion with the future work of the Commission. C. Investigation of fatigue failures in service.