DISK MATCHING DEVICES FOR METHODS OF EXTERIOR LEVELLING OF CAR BODY PANELS

. The basic equipment of the given methods consists of the power source, the levelling tool and the matching device for exterior levelling methods of car body panels is presented in the paper. Using the obtained analytical expressions, the numerical estimations of the basic characteristics of the considered matching device have been plotted. The schematic solution as to technical realization of the disc matching device is proposed. The experimental approbation of the elaborated tool of the exterior magnetic and pulse levelling has been carried out.


Introduction
At present of special interest are methods of reconditioning and repair of car body panels which make it possible to perform so-called the exterior levelling without dismantling of body elements and disturbance of the existing protective paint coating [1,2].

Analysis of publications
The greatest promise of them are magnetic and pulse methods based on energy application of pulse magnetic fields [3][4][5][6][7]. The basic equipment of the given methods consists of magnetic and pulse plant (MPP) -the power source, the inductor system (IS) -the levelling tool and the pulse step-up current transformer -the matching device (MD). The last-mentioned matches the MPP with the tool by inductive load which allows levelling operation to be performed effectively [3,4]. Fundamentally, the MD is the stepup current transformer which makes it possible to change the current amplitude in the IS and vary values of the operating frequency of working fields [8].
Developments of powerful tools for magnetic and pulse attraction of sheet metals were initiated by increase in demand to production operations by body coating levelling of cars and aeroplane frames [3][4][5][6][7]. Levelling process efficiency depends on value of current and its parameters (amplitude value, frequency, discharge pulse form) in the tool -the inductor system. Consequently, problems, connected with the attainment of necessary parameters of the discharge current pulse in the inductor system are rather urgent and one of ways of their solution is to bring into the equipment exterior magnetic and pulse levelling methods of different hardware components -the MD [9].

Purpose and problem statement
Analysis of electromagnetic processes in the disk matching device for methods of exterior levelling of car body panels. The development and suggestion of schematic designs as to technical realization of the disk matching device as a tool of exterior magnetic and pulse levelling. The experimental approbation of the development tool of exterior magnetic and pulse levelling.

Design model of the disc matching device
One of a variation of a possible practical MD construction is a structure which consist of the massive metal disk with the radial sectional view (the secondary winding), on one the side of which the multiturn coil (the primary winding) is located. The primary winding is connected up to the MPP lead. The inductor system is connected up to the secondary winding in the field of the radial section. Schematically, the MD with the connected IS is shown on the block diagram of the magnetic and pulse levelling complex ( fig. 1) [3,9].
For an analysis of electromagnetic processes in the disk MD and calculation of its basic characteristics, we set a design physical and mathematical model in the cylinder coordinate system shown on fig. 2 [8,[10][11][12].
We perform calculation by the use of integration equation methods of mathematical physicsclassical methods of boundary-value problem solution of electrodynamics [8,12,13].
Without dwelling on the deduction of calculation relationships the final expression for the induced current density in metal of the secondary winding may be written as We integrate expression (1), by sheet metal . We obtain dependence for radial distribution of linear density of the induced current Obtained results are illustrated by numerical estimations for situations which are real in magnetic and pulse levelling of car body panels [8,9,12]. b) with increasing conductivity the transformation ratio value increases, for example, steelaluminium increase is 20 %.

Construction and the principle of tool operation of exterior levelling on the basis of the disk compatible MD
The made analysis of electromagnetic processes in the MD and performed numerical estimations make it possible to develop and propose one of possible technical implementations of the tool of exterior magnetic and pulse levelling on the basis of the disk MD ( fig. 5). The given MD has been developed in the KhNAHU laboratory of electromagnetic technologies and it is protected by the patent.
In the outlined technical implementation of the tool ( fig. 5) the second winding of the disk MD is combined with the inductor which has an internal hole in the form of the truncated cone. The given tool is rather a powerful one in work-ing of thin-walled ferromagnets in the low frequency mode of operating fields. The tool for exterior magnetic and pulse levelling of frame and body elements of transport facilities [9] is an example of one of the ways of its practical application.

The principle of the tool operation
Electrical leads 5 of the primary winding 1 of the combined disk MD which is applied in the form of spiral on the dielectric frame are connected to the power source -the MPP [14,15]. In current flowing along the spiral primary winding 1 the magnetic field is formed around it, which excites electric current in the inductortool with the internal hole in the form of the truncated cone 3 (the secondary winding of the MD).

Experiments by magnetic and pulse leveling
Experimental investigations by the serviceability checking of the developed tool of the exterior magnetic and pulse levelling have been carried out by the magnetic and pulse plant MIUS-2. The given plant has been designed in the KhNAHU laboratory of electromagnetic technologies and it is a source of power for the exterior magnetic and pulse levelling complex of car body panels [3,9].
The specifications of magnetic-pulse installation MIUS-2 ( fig. 6): stored power W = 2 kJ; mains voltage ~ 380/220 V; capacity of condensers C = 1200 μF; self-frequency f 0 = 7 kHz; self-inductance L = 440÷500 nH; charge voltage of capacitive storages U c =100÷2100 V; repetition rate of discharge pulses f i =1÷10 Hz. In the first part of experimental investigations using the developed tool deformations on body panel elements of Citroen car have been created, fig. 7, a. In the second part of experimental investigation obtained deformations were removed, fig. 7 Performed experimental investigations showed that the developed tool of magnetic and pulse levelling on the basis of the combined disk MI-US a powerful one and it can be used both for creation of necessary deformations and for removal of dints on the car body panel bringing formed craters to the level of the surface.

Conclusions
Performed investigations make it possible to formulate the following conclusions.
1. The analysis of electromagnetic processes in the disc matching device for exterior levelling methods of car body panels has been performed.
2. It was determined that time and amplitude characteristics of the induced current are defined by the electrical conduction and metal thickness of the secondary winding of the matching device.
3. It has been found that the circle through the centre of the primary winding of the matching device (r/R ≈ 0,6) is the place of the most powerful signal current pick off with the secondary winding.
4. The schematic handling on the technical implementation of the disc matching device, as the exterior magnetic and pulse levelling tool has been developed and proposed.
5. The experimental approbation of the developed tool of the exterior magnetic and pulse levelling has been carried out. Results of the conduced investigations showed that the developed tool is a powerful one and it can be used both for creation of necessary deformation and for dint removal from car body panel elements.