GB491056A - Improvements in and relating to constructional members in the form of metal bars - Google Patents

Abstract

491,056. Altering physical structure. UMLAUF, A. Jan. 26, 1938, Nos. 2504 and 2505. Convention dates, Aug. 25, 1937 and Dec. 20, 1937. [Classes 83 (ii) and 83 (iv)] Constructional members in the form of metal bars have the yield point increased by twisting the bars cold so as to stretch them beyond the elastic limit and then, still in the cold, untwisting the bars by reversing the direction of rotation while simultaneously applying an axially directed pulling force. An I-section bar 1 may be twisted as shown in Fig. 2 by gripping the ends in chucks and rotating one of the chucks whilst maintaining them at the same distance apart so as to preserve the original length l of the bar. The other chuck is then rotated in the opposite direction and moved away from the first chuck so to produce a straight bar 2, Fig. 4, of an increased length #<l>. Alternatively the bar may first be twisted without axial tension so as to decrease its length by #<l1>, Fig. 9, and then untwisted with axial tension so as to resore it to the original length l<1> or to a greater length. The stretched bars may be used in pure steel construction or as reinforcement for concrete, and for the latter purpose the process may be applied to pairs of round rods as shown in Fig. 7, in which case the rods may be given a further stretch-twisting operation to leave them in a twisted condition with a further increased yield point. The first stretch-twisting operation may also include additional stretching which may be effected prior to, during or after the stretch-twisting, and the process may be applied to bars of T, angle, channel or other section.