Measurements Of Coercive Force Research Articles

Changes in magnetic characteristics of pipes during hydraulic and pneumatic tests of trunk pipelines

To identify the zones with the highest tensile stresses and deformations, a two-parameter magnetic method based on the measurement of coercive force and residual magnetic induction was applied. For realization of the method a mobile hardware and software complex DIUS-1.21M with an electromagnetic U-transducer was used, which was located along the pipe axis and along the pipe ring. Measurements were carried out on three pipes: in the first one magnetic characteristics were measured in the absence and under the influence of internal pressure; in the second and third ones — before the test and after the pipe fracture. It was revealed that internal pressure leads to the growth of residual magnetic induction in all zones both along the axis and along the ring, which indicates the occurrence of axial and circular tensile stresses in these zones, and the change of coercivity occurred ambiguously. It was found that fracture significantly increases the scatter of magnetic characteristics, which is explained by the complex nature of the stress-strain state of the fractured object.

Non-destructive Evaluation of Tube-to-Tube Sheet Roller Expanded Joint Quality Using Magnetic Coercive Force Measurements

Non-destructive Evaluation of Tube-to-Tube Sheet Roller Expanded Joint Quality Using Magnetic Coercive Force Measurements

APPLICATION OF COERCYTIMETRY METHOD FOR EVALUATION OF RESIDUAL STRESSES IN FLAT KNIVES

With the help of high-frequency currents, hardening coatings of increased hardness are applied to the working bodies of agricultural machines. When evaluating the effectiveness of these methods, along with studying the basic physical and mechanical properties of coatings, it is necessary to know the level of residual stresses in the coatings obtained. (Research purpose) The research purpose is studying the features and evaluate the possibilities of using coercimetry as an objective and reliable method for determining the stress state of flat knives hardened by HDPE boration. (Materials and methods) Samples of 65G steel in the initial state and flat mower knives reinforced with HDPE boration were prepared for the study. Performed the work in accordance with the current GOST 58599-2019 "Technical diagnostics. Diagnostics of steel structures. Magnetic coercive method. General requirements". Bursting machines, a magnetic structroscope (coercitimeter) were used KRM-C-K2M and devices for determining hardness and microstructure. (Results and discussion) At the first stage, the expected values of the coercive force for 65G steel were calculated depending on the chemical composition. As a result of mechanical tests of 65G steel samples for tensile strength with simultaneous measurement of coercive force, experimental data were obtained for constructing calibration curves, which were used to determine stresses in hardened knife samples after HDPE boration. It was determined that the residual stresses in hardened flat knives vary from 400 to 730 megapascals. These stresses can be considered acceptable (safe), since the yield strength for 65G steel is 685-785 megapascals. (Conclusions) The method of measuring coercive force makes it possible to estimate the degree of change in residual stresses in parts hardened by HDPE boration methods.

Express evaluation of the quality of producing caterpillar tracks by the results of coercive force measurement

The Paton Welding Journal, 2022, №11. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Study on Coercivity-Stress Relationship of X80 Steel under Biaxial Stress

Buried pipelines are prone to deformation under surface displacement, pressure occupation, and/or other actions, resulting in stress concentration. Conducting regular stress detection is an important approach to reducing pipeline accidents. This study performed experiments on measuring the coercivity stress of X80 steel, the most commonly used material for high-pressure large-diameter gas transmission pipelines. The coercivity of the specimen under different stress combinations was measured using the DC-driven coercive force measurement system, and the variation of coercive force with biaxial stress was also analyzed. The modified coercive force-stress expression of the generalized Hooke’s law was proposed; the model for the coercive force-stress relationship of X80 steel under the biaxial stress state was established based on this expression. The study indicates that the coercive force method is reliable for accurately measuring the stress of pipeline steel and evaluating the safety margin of in-service pipelines.

A new Cr25Ni35Nb alloy critical failure time prediction method based on coercive force magnetic signature

High-temperature damage in Cr25Ni35Nb alloys can be differentiated into four stages: the almost perfect stage, Carbide grain boundary coarsening stage, early creep stage and critical failure stage. In this paper, a novel approach based on a magnetic signature to monitor the alloy transitions between the four stages is proposed. Since the difference (ΔNi/Cr) between the content ratio of Ni to Cr in grains and the average value of the ratio of Ni to Cr of the alloy vary at different stages, these variations are highly correlated to the magnetic signature, coercive force (Hc). Thus, the curve of Hc vs ΔNi/Cr, which is “M” shaped over the whole life of the alloy, can be used to estimate the remaining life of the alloy tube using the easy measurement of coercive force. The first “U” inflection point indicates that the early creep stage has started and the second inverted “U” inflection point indicates that the critical failure stage is coming up. By identifying the inflection points, the alloy critical failure time can be predicted.

A method for quickly evaluating heat treatment quality of 35CrMo steel cylinder using magnetic properties

Seamless steel cylinders are widely used in real-life situations, and heat treatment has an important effect on their service life. The common methods used for heat treatment quality monitoring have many shortcomings, such as destructive operation, high cost and low coverage. To quickly and accurately evaluate the performance of the cylinder after heat treatment, a fast non-destructive testing method is introduced based on the coercive force measurement. The amount of residual stress for 35CrMo steel cylinder before and after heat treatment was evaluated quantitatively by the Metal Magnetic Memory technique, and the structural-mechanical dependence of coercive force was also revealed. Due to the grain refinement and the stress relief, the modified magnetic field index △H and k(x)of 35CrMo steel after heat treated are significantly decreased by 54% and 56%, respectively. Correspondingly, the magnetic coercive force is inversely proportional to the grain size, which is verified by hardness test. The structural-mechanical states of 35CrMo steel cylinder can be justified by measuring their coercive force, which is potential to be used as a reliable, accurate and non-destructive tool for mass production.

On the Advantages of Local Measurement of Coercive Force of Ferromagnetic Objects Based on Internal Field

It has been shown that locally measuring coercive force $${{H}_{{\text{c}}}}$$ based on the magnitude of demagnetizing current has a fundamental limitation on the measurement range. We have demonstrated the expediency of measuring coercive force in ferromagnetic objects locally, based on the magnitude of the tangential component of the magnetic field in the interpole space on the surface of the test object, that is, based on the internal field. This allows one to expand the range of measured values $${{H}_{{\text{c}}}}$$ by several times. Also, the influence of the gap between the transducer and the object, as well as the shape and size of test objects on the measurement results is significantly reduced. This makes it possible to measure the absolute values of $${{H}_{{\text{c}}}}$$ of homogeneous ferromagnetic objects, as well as the coercive force of objects with nonferromagnetic coatings of considerable thickness.

Діагностування пошкодженості феромагнітних сталей при механічному навантаженні по результатам вимірювання коерцитивної сили

Діагностування пошкодженості феромагнітних сталей при механічному навантаженні по результатам вимірювання коерцитивної сили

Damage evaluation for AISI 304 steel under cyclic loading based on coercive force measurements

The authors present the results of experimental investigations on the damage evaluation of AISI 304 steel under tension and cyclic loading based on coercive force measurements. It was established that kinetics of the coercive force demonstrates descending and ascending sections on the kinetic curve independently on the loading type. The increase of coercive force is caused by the deformation-induced transformation of the paramagnetic austenite into ferromagnetic martensite. The increasing coercive force is observed during the deformation process up to the loss of metal continuity (initiation and propagation of cracks and voids). While the coercive force shows a decreasing tendency due to the loss of metal continuity (stage of crack propagation). In the coercive force monitoring, it is required to pay attention to the variation in the direction of the kinetic curve and not to the absolute values of coercive force. Thus, the coercive force monitoring in the most critical zones of the structural elements allows one to control for the damage accumulation at each stage of crack initiation or propagation.

Microstructure and Crystallographic Texture of Silicon Iron Modified by Torsion Under Quasihydrostatic Pressure

The electron backscatter diffraction, X-ray diffraction analysis, electromotive force instantaneous measurement, microhardness and coercive force measurement techniques are used to explore the development of the microstructure, crystallographic texture and physico-mechanical properties of silicon iron (Fe-3% Si) alloy under quasi-hydrostatic pressure in a Bridgman anvil. It is found that the alloy deformation is accompanied by its significant hardening. In-plane torsion test shows that the average grain size rapidly decreases down to 185 nm after a quater turn of the movable anvil. With the number of turns increased up to six the grain size gradually decreases down to 150 nm. At the same time, the average size of subgrains is less dependent on the deformation degree. The crystallographic texture evolution involves the formation of the strong {001} texture component after comparatively small megaplastic deformation followed by the simple shear texture formation. Such a behavior can be correctly described in terms of non-equilibrium thermodynamics.

Oscillographic modeling of characteristics of magnetic materials

The question of using an oscilloscope to measure the characteristics of magnetic materials using computer simulation techniques is considered. The work is used in the training of specialists in metrology, carried out by the department of information-measuring equipment of the National Technical University ‟Igor Sikorsky Kyiv Polytechnic Institute” in the specialty ‟Metrology and information-measuring equipment”. The bachelor’s program contains the course “Methods and Measuring Instruments”, which includes learning of methods and measuring instruments for electrical, magnetic and non-electrical quantities.Characterization of magnetic materials is made by various methods. One of them is a method with using an oscilloscope. The method of indirect measurement of magnetic induction and coercive force by integrating a secondary electromotive force is used. The method allows to estimate the maximum intensity and induction of the sample, the absolute and relative magnetic permeability, residual induction and coercive force, that is convenient for students, allows remote execution of laboratory practical work.The task of creating a computer workshop was solved by using the LabVIEW software package. A simulation model, a measurement experiment technique, and a procedure are described.The use of computer technology in the training of specialists has allowed to acquire the skills of visual observation of the dynamic magnetic loop of the test sample on the screen of the oscilloscope, to determine the main characteristics of the test material by the loop of the dynamic cycle, as well as, if necessary, to perform laboratory work remotely and to provide the opportunity to use this course while training the specialists in other specialties.

Определение напряженно-деформированного состояния участка трубопровода под давлением по результатам измерения коэрцитивной силы

Определение напряженно-деформированного состояния участка трубопровода под давлением по результатам измерения коэрцитивной силы

Development of electromagnetic NDT methods for structural integrity assessment

Nondestructive testing (NDT) methods are widely used for inspection of long term exploited structures as important part of maintenance strategy. NDT methods can create the background for material optimization under the engineering procedures (e.g., welding) influence also. Principal attention taken into consideration is the investigation of the correlations between measured nondestructively material properties (e.g., specific electrical conductivity, coercive force) and parameters of fatigue crack growth resistance (FCGR) needed for residual life estimation. In this study the evaluation of aluminum alloys (AA) degradation in aging aircraft and AA welded joints characterization based on the specific electrical conductivity (SEC) measurements are presented. Eddy current (EC) device for local noncontact SEC with lift off suppression was developed. For ferrous steel components (steam pipelines, ship bearing elements) the NDT method based on coercive force (CF) measurements by attachable type probes are applied. The EC method based on the magnetic anisotropy (MA) changes under mechanical stress was proposed.

Measuring coercive force in local domains of a sample

A method has been proposed for determining the coercive force in local domains of bulk samples magnetized normally to the surface. The method is based on local measurement of the normal magnetic-field component at the sample surface, in the gap between the sample and the pole of a magnetizing device. The coercive force is determined by the magnetic field for which local magnetization in the measured domain becomes zero. Conditions for the correctness of coercive-force measurements have been established.

Оценка остаточной прочности стали AISI304 при статическом и циклическом нагружении по измерениям коэрцитивной силы

Оценка остаточной прочности стали AISI304 при статическом и циклическом нагружении по измерениям коэрцитивной силы

Non-destructive testing of residual stresses by magnetic methods under conditions of simple stressing

We have shown how crucial it is to determine the residual stresses (RS) at the stages of the product life cycle by means of the non-destructive testing (NDT) magnetic methods and to create computational algorithms and models. The experimental results of the RS in rod-shaped specimens after the 3-point-bending by magnetic-noise analysis and coercive force measurement are proved as being topical. The interrelations between the value of the change undergone by magnetic characteristics that are measured by the NDT magnetic methods and the value of the axial RS resulted from modeling by finite element method are revealed.

Опыт применения коэрцитиметрии при обследовании технического состояния строительных металлоконструкций

Опыт применения коэрцитиметрии при обследовании технического состояния строительных металлоконструкций

Освоение технологии термической обработки центробежнолитых валков с рабочим слоем из хромникельмолибденового чугуна

The paper is dedicated to analysis of heat treatment of cast iron products. It is noted that heat treatment is performed for reduction of internal stresses, graphitization, decarurization, to change structure and properties. During the experiments technological parameters of heat treatment of centrifugally cast rolls with working layer of chromium-nickel-molybdenum cast iron have been determined. They are necessary to develop effective process in special car bottom gas furnaces. It is shown that such treatment contributes to reduction of residual stresses in the rolls after casting. The aim of this paper was to study the effect of heat treatment on the structure, hardness level and stress state of sheet-rolling rolls. Studies of as-cast rolls showed that various combinations of matrix with secondary carbide inclusions were observed depending of proportions of chemical components in the analyzed cast iron and cooling rate of the cast billet. Hardness level changed depending on their quantitative relations. Results of stressed state study of castings by means of coercive force measurement showed a non-uniform distribution of its values along the working surface of roll barrels. A regime of low-temperature ( T = 673 K) annealing proposed in the work permitted to obtain a more uniform structure of the working layer of rolls. As a result, inhomogeneity of properties along working layer surface decreased two times compared to as-cast state.

Применение коэрцитиметров для диагностики оборудования

Introduction. Changes of metal structure commonly result in equipment failures; early recognition of such changes is necessary in order to prevent emergency situations. Coercimetry is a simple and informative method for metal structure estimation.
 Method. The coercive force measurement method was used for estimation of the metal fatigue state.
 Results. The article presents the results of coercive force measurement application for the diagnosis of blast furnace jackets, overhead cranes, load-bearing elements of buildings and structures, pressure vessels, industrial pipelines, chimney stacks, ropes of hoisting devices. Manual testing of the equipment working under metallurgical production conditions is complicated; in hard-to-reach places and gas hazardous areas the stationary testing system has been used; the system has included permanently installed sensors connected to the switchboard. The equipment residual life has been determined by the coercive force maximum values with the use of nomograms.
 Conclusions. The coercive force measurement method for diagnostic survey of the equipment working under considerable thermal effect makes it possible to determine the metal stress state, predict zones of corrosion cracks formation and development, estimate the residual operation life, plan worn areas replacement/repair and as the final result – reduce unplanned and emergency shutdowns.