On heat lines or lines of thermal discontinuity

Shear Localization: A Historical Overview

“…Such sheets or bands have historically been described by various names, e.g., ''heat lines'' or ''thermal crosses'' seen, for example, in steel forging operations [7][8][9][10] and ''white etching bands'' (due to their appearance in chemically etched specimens of deformed steels [11] ). Shear bands have been reported in many metals and alloys e.g., steels, brass, alloys of aluminum, titanium and its alloys, magnesium, and uranium.…”

“…[7] No doubt similar observations had been made many times previously, but either not reported by men of science or written up in places no one has looked for some time. As a token of this, the articles by Massey [8] and Adcock [15] on phenomena observed in metal forging lay forgotten in the archives until Johnson et al [9] and Hatherly [16] rediscovered them.…”

Thermal Effects in Plasticity. Part II: Uniqueness and Applications

“…From now on we shall t,a,kc y12 = 0 when making further siniplifications. locally acliabatir process the last t'wo terms in (7) disappear. We shall look more closely on bhe second term, t'hus eventually on XijmlZ.…”

“…For steel, at 4' = 330 "K, it is r, w 0 , l . Hence, when T, Q 1 we can put y12 = 0 in the connt'itutive relations (7) through (9). From now on we shall t,a,kc y12 = 0 when making further siniplifications.…”

“…Information regarding the temperature distribution both in the workpiece and in the tool may help to explain certain observed phenomena. We mention such defects as "hot-shortness" resulting in circumferential cracking of the surface of extruded materials [l] and generation of patterns of "heat lines" in forging of mild steel a t about 700 "C [7]. Unfortunately a precise study requires the solution of complicated system of equations describing plane or axi-symmetrical problems of thermoplasticity.…”