No abstract

Abstract. The article considers the influence of the surface layer characteristics on the regularities of the cutting process and the formation of the quality of the surface machined. This effect has been confirmed by the study results of the combined cutting method with advanced plastic deformation (APD). The work estimates the impact of the change in the surface layer properties on the forces and temperature of cutting, stability of the chip formation and quality parameters of the surface machined. The rise in the tech level specifies the challenges of increasing the effectiveness of the parts production and formation of the required performance characteristics of their surfaces. It is noteworthy that at present, inadequate attention is paid to all the parameters of the machine part surface both in construction, process design, and production. Machining considers for the most part the geometrical parameters and surface roughness. To improve the surface performance parameters such as the surface structure, hardness, wear resistance, etc., some special operations are assigned, including the strengthening treatment, honing finishing operations and heat treatment of various types. However, in certain cases, the desired surface parameters can be achieved by less number of operations and at less cost.Besides, the concept of machining design, in our view, requires some updating and improvements. Despite the continuing technological advance and potential of certain branches of machine-building industry, which are the basis for any industrial production (first of all, machine tool building, metallurgy, cutting tool production, etc.), for upward movement, they cannot fully ensure the necessary stability of all technological system parameters in course of machining operations. So, this fact causes the parameter instability of the surface machined, and hence the performance instability of the manufactured parts, assemblies, mechanisms, and machines.The machining procedure of a part can be considered as a sequence of operations on a workpiece. Each operation to some extent changes a set of the surface parameters of the workpiece machined, with the processing result to depend not only on the type and mode of exposure and the tool applied, but also on the previous state and the surface layer of the workpiece. The processing result depended not only on the type and modes of action and the tool applied, but also on the previous state of the workpiece and the surface layer. The effectiveness of the cutting process was considerably influenced by the properties of the material being processed, the workpiece and the cutting tool. The indicated properties given in the reference literature and certificates for tool and construction materials were averaged and allowed for a wide range of characteristics [1,2]. This significantly reduced the reliability and effectiveness of the technological preparation of production and also affected the stability of the processing results.For a better understanding the essence of this issue, let's l...

310Machined surfaces of very high quality are required in honing the most important and most precise machine parts (for example, cylinder linings in internal-combustion engines for cars, trucks, and tractors), whose operational reliability is a primary concern in competitive markets.We know that the formation of even one deep scratch on the cylinder surface requires additional finishing (honing by bars with micropowder or lapping), with considerable loss of production time.Such scratches are due to the considerable size variation of the cutting grains that is permitted by the standard regarding the manufacture of diamond and abrasive honing bars. As a rule, the time required for the elimination of such scratches is up to 30% of the total machining time. Therefore, there is a pressing need to reduce the likelihood that large cutting grains will form part of the abrasive tool.The standard size distribution of diamond and abrasive grains in the tool does not permit the elimination of such defects in machining important parts (such as the linings of hydraulic cylinders in heavy-duty mechanisms within excavators, bulldozers, cranes, and other transport systems).One promising approach is to use a new single-component abrasive tool based on white corundum [1]. In the manufacture of this tool, boron-carbide powder must be added to white-electrocorundum abrasive powder (10-20 wt % boron carbide). Then a compressive shock wave is passed through the powder mixture, with subsequent high-temperature sintering in an electrovacuum furnace.When the shock wave passes through the powder mixture, the particles of each component are crushed.The size distribution of the white-electrocorundum and boron-carbide grains will be different.However, under the action of the impact force, the electrocorundum grains briefly move at enormous speed toward the boron-carbide grains (whose hardness is 37-43 GPa, as against 20-24 GPa for the electrocorundum) and are further crushed, which considerably changes their size distribution, since additional pores are formed in the high-temperature sintering of boron-carbide powder.After honing the 40 ï steel parts (the cylinder linings of A-type motors and hydraulic cylinders) by the new abrasive tool, the following results are obtained: the number of surface scratches is reduced to 0.1% (in other words, practically to zero); and the stable mean surface roughness of the machined part is Ra = 0.14-0.2 µ m, which is 2.4-3.2 times less than the value after machining with a diamond tool. CONCLUSIONSThe action of a compressive shock wave on whiteelectrocorundum grains or on boron-carbide grains is insufficient to permit the use of these powders individually for abrasive tools in finishing. However, the application of a fast compressive shock wave to a mixture of white-electrocorundum and boron-carbide grains changes the size distribution of the grains at the working surface so that the machined surfaces obtained exhibit high performance. REFERENCES 1. Russian Patent 2293013.

The article considers the issues of determining the elastic characteristics of a single-component abrasive tool depending on the porosity of the abrasive tool after pressing the abrasive compound studied; the method of determining the modulus of elongation and porosity based on theoretical and experimental data has been used; the dependency graph between the modulus of elongation and porosity, as well as experimental formulas reflecting these dependencies are presented. Based on the experimental and calculated data on the density, porosity and the size of the modulus of elongation, depending on the pressure of the shock wave during pressing and the initial aluminium oxide grains sizes, empirical dependences of elastic characteristics have been determined in order to predict the production of a single-component abrasive tool without a bond with predetermined properties.

No abstract

Both in the manufacture and repair of critical parts of mechanical engineering and engine building, great attention is paid to the formation of a trace on the surface, the surface layer quality and the geometric shape accuracy. However, methods of achieving high accuracy in the parts manufacture and their repair after operation differ significantly. The article assesses the possibility of implementing the honing method with a variable height speed of tool rotation (hon) patented by the author, and analyses the productivity of this method when repairing the internal combustion engines cylinder liner at a taper value of 0.20 mm.

The article presents the results of residual stresses measurements in the material of the internal combustion engine (ICE) sleeves. The studies have been carried out for new sleeves, sleeves after processing with diamond and single-component abrasive tools (SCAT) and sleeves that have exhausted their service life. The results of the research have established the fact that processing of the sleeves with a single-component abrasive tool substantially increases the values of internal residual compressive stresses, which contributes to the life extension of the engine in whole.

No abstract