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Master of the DNTU Myshov Maksim

MYSHOV MAKSIM

Donetsk national technical university

Faculty: "Mechanical"

Speciality: "Mechanical engineering"

The abstract of the master's thesis on the theme: "Development of the technological provision and increasing quality of abrasive machining thin wall production on the basis of the using ultrasound effects"

Scientific Leader: Doctor of Technical Science, professor Michaylov Alexandr

URGENCY OF THE THEME

         The cardinal problems of the modern mechanical engineering are relate the receipt in the stage of making machine elements such characteristics of quality, which would satisfy the requirements to the service properties. At the same time it is necessary to exclude the formation causes of failures and to learn take part in formation of adjusted in advance of the performance attributes. It is known that the main cause of failure of machines is not breakage, and it is a wear of mobile couplings under the action of frictional forces. The wear-resistance of rubbing pairs, particularly, to a great extent is to take shape with the microrelief of the surface layers, which is received as a result of machining, and with the microhardness and residual stresses. It is the most complicated to control by process the formation of performance attributes of the machine elements, which is produced from inclined to phase transformation the material in the processes of mechanical machining, differing the high thermal tenseness. To such processes, first of all, the grinding is relate. There is arise the momentary contact temperatures in the work area, amounting to 800-10000C, and pressure, exceeding two-three times the yield strength of material. By comfortable tool for influence on process formation of the operating characteristics when the grinding is follows to consider a rational application the energy of ultrasound field.

THE PURPOSES AND AIMS OF MASTER'S THESIS

         The purpose of master’s thesis is to increase the abrasive machining quality of thin wall production on the basis of the using ultrasound effects and to develop for ultrasound abrasive machining necessary technological provision, which will enable to machine the thin wall production. The aims are

  1. The theoretically research of factors, which influence on the abrasive machining quality of thin wall production.
  2. The development of the technological provision for ultrasound abrasive machining of thin wall production.
  3. The selection of the abrasive rational operating conditions of thin wall production on the basis of the using ultrasound effects.
  4. The research of the influence ultrasound vibration on:
    -the roughness of the machined surface;
    -the temperature in the operating zone;
    -the geometrical deviation of thin wall surface production.
  5. The simulation of the heat generation for machining and processes of the temperature and force strains.

         Now it is known three fields of application ultrasound vibrations when the grinding. There are:

  1. A stimulation of forced ultrasound vibrations small amplitude in the system “grinding wheel - workpiece”.
  2. An influence on the work surface of grinding wheel for cleaning and smearing wheel’s grains and pores.
  3. A dressing of the shaped section of grinding wheels with the thin plate (with the small static force an equal 4…8 N); at the same time on the slowly rotating wheel feeds the coolant liquid.
         When the surface grinding of the heat-resistant alloys, use the ultrasound vibration small amplitude raise the machined surface smoothness, ensuring the bigger stability value of the roughness. At the same time the cutting forces are decrease, the wear of grinding wheel is raise 1.5 times; the relative metal removal remains about constant. When the ultrasound grinding, the temperature of machined surfaces are decrease twice, the temperature of chips decreases too. All this results in full liquidation of the grinding burn and cracks.
         When the grinding of the pre-production model, which was accomplished the high-frequency vibrations, though great depth of cutting the maximum temperature of the pre-production model is twice less in the explored zone, than when the common grinding. When the vibrations grinding, the decrease of temperature can illustrate with the decrease angle of contact abrasive grains, and with the decrease constant of friction grinding wheel’s grains and detail material. In the process of tool grinding from carbonaceous, alloyed and high-speed steels the main factors, influencing on the heat production and the temperature of grinding surface, are the specific pressure and the time contact of wheel with detail. Smaller temperatures during the grinding with the vibrations cause smaller residual stresses.
Figure 1 – The plan of grinding with ultrasound vibrations


         When tools grinding with the ultrasound vibrations (Figure 1), the surface smoothness of the high-speed plates is increase more than twice; resistance of cutter VK8, sharpened with this method, is increase twice the resistance of cutter, sharpened with the common method; increase the productivity of the process. More effect would expect, when tools grinding with the cooling. The high-frequency vibrations with small amplitude improve the condition of access in the cutting zone of the cutting emulsion and it must provide the improvement quality of the machined surface.

CONCLUSIONS

         The broad use of material with the specific properties, the high requirements to the dimensional accuracy and geometric patterns, structural complexity of details frequently result in, that the traditional methods of shaping details surfaces with the cutting are ineffective, and, sometimes, unacceptable.
         When the machining, the use of ultrasound is being a perspective and a progressive direction in the modern technology. The output would work well to raise by means the intensification of machining condition (by reduction of cutting time) and would work well to improve the quality, precision and machines reliability. It is determined too, that the temperature, which is arising in the cutting area with the ultrasound, is reduced about twice. It results in the improvement of surface smoothness, and the absence of burn and microcracks as compared with the common grinding.
         When the grinding of the workpieces, which is inclined to the structural- phase transformations in the surface layers, the use of ultrasound field allows to realize the defect-free grinding of workpieces on the forced (accelerated) conditions without the unwanted changes of structural- phase composition of the surface layer (the probability of rise defects is reduced in 1.4-1.6 times).
         The ultrasound allows to raise the scientific and technical level of processes machining the details from the intractable materials in the mechanical engineering, and in the others cases, the ultrasound allows in principle new to solve a problems their production.
         Now this theme of the masters thesis is researching and it will be complrted at the end of the December 2008.
Figure 2 - The simulation of surface grinding with the ultrasound effects (22 sequences)
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