Orientation effects of anisotropy, stress, excitation, bias and residual fields on Barkhausen noise generation in pipeline steel

Abstract

Magnetic Barkhausen noise (MBN) measurements were made on a semicircular section of pipe applying the Barkhausen excitation field in different directions through 360". A DC bias field was then applied in the axial and circumferential directions and MBN measurements were made. A circumferential tensile stress of 129 MPa was then applied and MBN measurements were made with and without the DC bias field. The MEN data were analysed in the light of changes in the domain configuration due to the application of tension and/or the DC bias field. The relative orientations of preferred easy axis, Barkhausen excitation field, bias and residual fields and stress were all found to influence MBN generation.

Efeito Do Cisalhamento Cíclico Na Resposta Magnética Do Aço Go

“…A criação de novos sítios de aprisionamento bem como a intensificação dos sítios já existentes dificultou a orientação dos domínios na direção do campo magnético, ocasionando deste modo, a degradação das propriedades magnéticas do aço GO [7]. No gráfico exibido na Figura 5 verifica -se que o valor de pico foi maior è medida que os corpos de prova foram submetidos a uma quantidade maior de deformação plástica.…”

A Study of Stress – Induced Subtle Magnetic Changes in a Mild Steel using Barkhausen Emission-Aided Analysis Approaches

“…Today, despite extensive and intensive theoretical and experimental investigations, [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], the applied stressinduced micromagnetic effects in ferromagnetic steels are complex and not yet fully understood. In general, the investigation of stress effects on polycrystalline ferromagnetic materials needs a basic reduction to a formulated set of problems solvable by detailed experimental investigations and/or mathematical analysis concerning the dynamics of domain wall motion.…”

“…In general, the investigation of stress effects on polycrystalline ferromagnetic materials needs a basic reduction to a formulated set of problems solvable by detailed experimental investigations and/or mathematical analysis concerning the dynamics of domain wall motion. As such, the application of stress to material results in a modification of strain state and a corresponding change of its elastic energy, [1], [2], [3], [4], [5], [6], [7], [8], [11], [12], [13], [14], [15] as well as in variations of effective strength levels of domain wall pinning sites, [3], [19]. This is related to the general fact that in ferromagnetic materials, the modification of internal stressstrain results in a change in the free energy and consequent changes in the micromagnetic response of the material, [8], [12], [28].…”

“…In particular, applied stress may modify the energy of domain wall configuration, e.g. the pattern of 180 O and 90 O domain walls within the grain, [5], [7], [8], [17]. In these materials, position magnetostriction implies that for reasons of energy minimization, domain magnetization should be along the cubic crystal axis that is closest to the direction of applied stress.…”

Σχέση µικροδοµής, µηχανικών και µαγνητικών ιδιοτήτων σε χάλυβες χαµηλής περιεκτικότητας σε άνθρακα (Low carbon steels)

“…Είναι όµως φανερό πως ο αριθµός (βαθµός) διασπορά της ενέργειας κίνησης των τοιχωµάτων θα πρέπει γενικώς να αυξάνεται συναρτήσει της αύξησης των παραµορφώσεων, διότι µε την αύξηση των παραµορφώσεων αυξάνεται η πυκνότητα των εξαρµόσεων (dislocations) και συνεπώς των εµποδίων στην κίνηση των τοιχωµάτων. Η αντίθεση αυτή στο πρώτο στάδιο θα µπορούσε να εξηγηθεί µε την ύπαρξη ενός «ανταγωνιστικού» παράγοντα όπως αυτού της «τασικής πόλωσης» (stress-bias) που σηµαίνει, όπως είναι γνωστό, ότι εφαρµόζοντας µια εξωτερική τάση, δηµιουργείται ένας επιπλέον αντίστοιχος άξονας ανισοτροπίας, ο οποίοςγια λόγους ελαχιστοποίησης της συνολικής µαγνητοελαστικής ενέργειας -τείνει να προσανατολίσει τις µαγνητικές περιοχές προς αυτόν τον άξονα, βοηθώντας αυτές να κινούνται πιο εύκολα, δηλαδή να έχουν αυξηµένη, συνδυασµένη-οµαδική κίνηση [31][32][33][34]. Ταυτόχρονα είναι γνωστό ότι ακόµα και οι χαµηλές εφελκυστικές τάσεις δρουν ευεργετικά στη δηµιουργία (στον πολλαπλασιασµό) διαµηκών (longitudinal) τοιχωµάτων τύπου 180 ο σε βάρος των εγκάρσιων (transverse) τοιχωµάτων [5,[35][36][37].…”