Determination of the Depth of Hardened Layer After Centrifugal Rolling of Low-Rigid Shafts

Theoretical or theoretical-experimental methods are widely used when studying various techniques for processing materials, cutting among them. The physical and mechanical properties of the materials being processed are to be taken into account along with the process parameters (mode, geometric parameters of the machining tool, etc.). The resistance of the material to plastic shear present in the calculated dependences for determination of the force and temperature in the cutting zone and the temperature in the surface layer of the workpiece, as well as for determination of the quality parameters of the surface layer of the part (the residual stresses, degree and depth of work hardening, roughness, and others) and the accuracy of processing is used in all the aforementioned methods in addition to the ultimate tensile strength and the modulus of elasticity of the processed material. Previously, when determining the numerical value of the resistance of the processed material to plastic shear, the latter was considered as a function of the tensile strength of the processed material. However, an increased temperature observed in the cutting area which depends on the combination of the processed and tool materials, the mode of processing, and on the geometry of the cutting part of the tool was not taken into account. The value of the effective cutting force was also ignored though this value is determined by the same parameters which determine the temperature in the cutting zone. The mechanical characteristics of the processed material are known to depend on the temperature. In this regard, the resistance of the processed material to plastic shear was assessed at a certain temperature determined by the technological conditions of processing. The goal of the study is to prove the necessity of determining the resistance of the processed material to plastic shear to be used in theoretical determination of cutting forces, temperature in the cutting zone, and the quality parameters of the surface layer of the part. The dependence is given to determine the value of the resistance of the processed material to plastic shear under optimal processing conditions that ensure the minimum wear of the cutting tool taking into account the parameters of the cutting process and the geometry of the cutting part of the tool. Processing conditions that determine the temperature and force in the cutting zone are taken into account by chip shrinkage in the formula for determining the value of the resistance of the processed material to plastic shear. The use of the proposed technique can improve the accuracy of calculations of the quality parameters of the material of the surface layer of the part and the accuracy of processing.

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Wear resistance of composite materials based on ultra-high molecular polyethylene with combined filling

Vasilev,

Danilova,

Okhlopkova

et al. 2023

Zavod. lab., Diagn. mater.

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Polymer composite materials (PCM) of antifriction duty with self-lubricating properties are used for the manufacture of various parts in friction units of machines and mechanisms. PCM can partially replace parts made of metals and alloys, increasing the reliability and service life of the equipment when the use of oils or external lubricants is limited or prohibited. The goal of the study is the effect of fillers (sulfenamide, sulfur, magnesium and zinc oxides) on the tribological parameters of polymer composite materials based on ultra-high molecular weight polyethylene (UHMWPE). Samples were prepared by hot pressing at a temperature of 175°C and a pressure of 10 MPa. Composites with filler concentrations 0.5 and 1 wt.% were considered (for sulfenamide, sulfenamide with sulfur, and combinations of 0.5 and 1 wt.% sulfenamide with sulfur and zinc oxide or magnesium oxide). It is shown that the introduction of sulfenamide leads to an increase in the wear resistance by six times, and the introduction of a combination of fillers of 0.5 wt.% sulfenamide, sulfur, and magnesium oxide — by 1.5 times. The friction surfaces of composites were studied using methods of scanning electron microscopy and IR-spectrometry. The formation of an oriented ordered structure in the form of clusters of wear products was revealed on the friction surfaces of composites filled with sulfenamide. In the case of combined filling, secondary structures were found on the friction surface, which visually differ from the UHMWPE friction surface. The appearance of peaks in IR spectra corresponding to oxygen-containing groups (–C=O, –COOX) was observed on the friction surface of composites with combined filling. It is shown that IR spectra of composites with mono- and binary fillers have peaks of less intensity due to the formation of secondary structures. The introduction of sulfenamide into UHMWPE, together with zinc and magnesium oxides, promotes the crosslinking of polymer macromolecules in the friction zone due to frictional heating, shear loads, and the action of a counterbody. The developed materials can be used as parts of friction units for cars and transport equipment that can withstand harsh operating conditions in a sharply continental climate.

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Determination of the Depth of Hardened Layer After Centrifugal Rolling of Low-Rigid Shafts

Cited by 3 publications

References 2 publications

Modern Methods of Finishing and Hardening Processing of Cycloidal Helical Surfaces

Modern Methods of Finishing and Hardening Processing of Cycloidal Helical Surfaces

A technique for experimental determination of the resistance of materials to plastic shear upon their processing by cutting

Wear resistance of composite materials based on ultra-high molecular polyethylene with combined filling

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