Magnetic Leakage Field of an Elastically Bent Ferromagnetic Steel Pipe

Experimental study of stray fields of elastically and inelastically bent steel tubes with hinged ends

“…The sag should then decrease sharply with a further increase in the sag and, finally, should tend toward some constant value commensurable to (4). The experiment in [9] completely confirmed this character of dependence σ cr (y 0 ). The negative sign in (4) is related to the fact that the stress in (4) is a compressing stress.…”

“…For tubes made from steel 20, we obtained satisfactory agreement between experimental and theoretically-calculated curves [9,10] in the case of elastic bending. Additionally, in [8] the tangential and normal components of the stray field were measured for high sag values ( y 0 = 13 and 19.2 cm), where the bending stress in a considerable part of the tube was higher than the yield stress; as a result, IDRs were observed in both the extended and compressed parts of the tube [4].…”

“…It is seen that the main features of these curves coincide with those of curves ∆H x (x) presented in [8] for both elastic bending (curve with y 0 = 2 cm in Figs. 2a and 2c [9]; curves with y 0 = 1.4, 3, and 4 cm in Fig. 1 of the present article) and inelastic bending (see the other curves in the figures mentioned).…”

“…It is known [4,[8][9][10] that the exponential dependence of ∆M σ on σ 2 is the strongest (see, e.g., expression (18) in [8]) in the vicinity of the first of these points, which results in the corresponding specific features of dependence ∆H x (x) [4,[8][9][10].…”

“…As follows from the above description, the yield stress of steel 20 (σ y = 250 MPa) was first achieved at different sag values for extended and compressed parts of the tube y y according to the equation (5) where R for our tube (its parameters are described in [9]) is 70 MPa/cm. As a result, for the extended part of the tube, the yield stress was first achieved at point x = 0, α = 0°, and r = r 2 at = 4.1 cm; whereas = 3 cm was required for its compressed part.…”