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| Blacha L., Fröhlichova M., Buzek J. |
| METAL EVAPORATION FROM LIQUID ALLOYS |
| Keywords: metals evaporation|kinetics of evaporation|pressure|atmospheare|mass transport| |
| No 2 (2003), p. 105-115 |
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| Kropuch S., Peterka P., Krešák J. |
| MAGNETISING PROCESSES DURING NONDESTRUCTIVE STEEL WIRE ROPES TESTING |
Abstract
Steel wire ropes are because of their working properties very often used in the industries as mining, engineering , building or power engineering as well as in the personal transport or as anchoring and hoisting ropes in the ship transport. During the life of the steel wire rope it is exposed to different negative forces [3]. Because of these forces the working environment in which the rope is used is very rough. From the reliability point of view rope must be one of the safest parts of the equipment. From the operating point of view very high requirements are imposed on ropes, besides their high safety also the possibility of their testing in the operation.
Nondestructive testing of the ropes, mainly magnetic nondestructive methods of tests can contribute to the high quality ropes testing during the life of the rope.
Nondestructive testing of the steel wire ropes used on drilling rigs, mining hoisting equipment, cable railways and cranes is very important from the safety point of view of this equipment. The article is dealing with magnetising processes of the ropes during their nondestructive testing. In order to determine optimal magnetising it is necessary to know the maximum value of the measured rope differential permeability in which neighbourhood the maximal signal during the nondestructive testing at the sensor can be found. So far the magnetic properties of the steel wire ropes can be found only in the technical papers. For this reason we have performed 624 measurements of the steel wire ropes in our laboratory. The results were stored in the database in the form of mathematic-physical model for steel wire ropes magnetic properties. The database is the basis for the determination of the steel wire ropes optimum magnetising during nondestructive tests.
13 types of ropes were used for the primary research on magnetic properties. By sample selection it was respected that the selection included different strength classes of steel wire ropes, new ropes tested before their loading on the hoisting or transport equipment, the ropes loaded on the mining hoisting equipment and on the equipment used for personnel transport. The ropes summary is shown in the table 1. It was emphasised to have possibility to compare magnetic properties of new and used steel wire ropes. At the same time the ropes used in the most often equipment as the hoisting equipment, ski lifts, cable ways and drilling rigs were selected. In the literature are published the approximate values of magnetic properties for structural steel, cylindrical material but the values for the field of steel wire ropes are missing. The selection was chosen in order to at least partially covered the field of steel wire ropes for the needs of the next research and practical magnetic defectoscopy. Measured magnetic material parameters are used as a basis for mathematical modelling of magnetising processes and for the development of the equipment used in the steel wire ropes testing at the same time.Used mathematical model of the physical process of ferromagnetic materials magnetising expressed in the equation (4) can be evaluated as very good as the results of the acquired correlation coefficient of the regress model in the range 0,99943-0,99999 reflect. The created physical-mathematical models of the hysteresis loops and the behaviour of the differential permeability preserve with the sufficient accuracy the behaviour of the magnetic parameters (B-H a µ-H) of the measured ropes by the necessity to store the minimum amount of data. For the magnetising parameters behaviour (B-H and µ-H) plot it is only necessary to input in the computer programme Excel appropriate coefficients A-E and Hmax. ( Tab.2) and the it is possible to plot the requested behaviour of the hysteresis loops or the behaviour of the differential permeability for the steel wire rope.Database of the measurements is available for the determination of the steel wire rope magnetising optimum intensity and the settings of the optimal working point of the defectoscopic equipment. It was confirmed by measurements that the magnetic properties of the steel wire ropes are approaching to the properties of the steel sheets in the direction of their rolling. By the change of the maximal differential permeability depending on the magnetising frequency ( after adjusting to the relative velocity of the rope and the defectoscopic equipment) the value of the optimum magnetising intensity is changing . That means that by testing it is necessary to make corrections of the steel wire rope magnetising H with taking into the account its relative velocity to the idle value Ho.
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| Keywords: steel wire ropes|diagnostics|optimal magnetising| |
| No 2 (2003), p. 122-130 |
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