Successive Grinding and Polishing Effect on the Retained Austenite in the Surface of 42CrMo4 Steel

Low-alloy 42CrMo4 steels were studied by 57Fe Mössbauer spectroscopy (MS), X-ray diffractometry (XRD), and Energy Dispersive X-ray Spectroscopy (EDS) measurements. The investigations were performed on metallographic samples, which were subjected to a series of successive grinding and polishing with a progressively finer grit. Conversion X-ray Mössbauer spectroscopy (CXMS) was used to determine the occurrence of austenite in steel samples. It is a unique method detecting the austenite content very sensitively. Six samples with different surface preparation were investigated, starting with 4.8% of austenite on an as-cut sample, and a large decrease in the retained austenite to 2.6% was observed after the first grinding of a hardened cut sample. Additionally, an unexpectedly large decrease in the austenite content to 2.3% was found due to the final polishing. A second time applied successive grinding and polishing of all samples resulted in identical austenite content determined by CXMS of approx. 5%, which proved the applicability of the CXMS method. Generally, the result calls attention to the importance of preparation of metallurgical samples by grinding and polishing where the results can vary significantly on the level of surface processing.

Вплив механічної обробки поверхні на діелектричні та фотодіелектричні властивості кристалів AIIBVI

The subject matter of the study is the dielectric and photodielectric properties of AIIBVI crystals of composition ZnSe and Cd1-хZnхTe, which are grown from the melt, and the structural defects and internal elastic fields associated with these properties. The goal of the article is to study the patterns of influence of surface machining by grinding, polishing, and local loading on the defective structure in the deformation region, and thus on the dielectric and photodielectric properties of AIIBVI crystals of this composition, which is important given the use of these crystals in aerospace engineering. The tasks to be solved are: to investigate the regularities of the influence of grinding, polishing, and local deformation of the chipped surface of ZnSe and Cd1-хZnхTe samples on their defective structure, dielectric and photodielectric properties, including irreversible changes in properties. The problems were solved by the following methods: dielectric and photodielectric properties of crystals were investigated by the capacitive method; scanning photodielectric spectroscopy was used to measure the photoionization energies of localized states of charge carriers in crystals; the distribution of residual elastic stresses in the samples was studied by the polarization-optical method. The following results were obtained. Grinding and polishing cause the transformation of own and impurity maxima of the spectral dependences of the dielectric parameters of AIIBVI crystals, has a characteristic effect on the coordinate dependences of the dielectric parameters of crystals Cd1-хZnхTe. This is due to the transformation of localized states of carriers, which is confirmed by the study of ZnSe crystals. Concentrated deformation of Cd1-хZnхTe crystals significantly affects their dielectric properties, in particular, causes relaxation of dielectric parameters. Conclusions. Mechanical surface treatment of AIIBVI crystals by grinding and polishing, as well as local mechanical loading of Cd1-хZnхTe samples significantly affect their dielectric and photodielectric properties, which is associated with the formation of a system of defects and internal elastic fields in the deformation regions. An explanation of the observed effects is given.

Research on the optical grinding and polishing technology of spherical mirror based on alloy steel materials

In Vietnam, the technology of fabricating spherical surfaces of glass lenses by the loose abrasive grinding method has been researched and widely applied. However, this technology does not really match the needs of grinding and polishing optically the sphere on the basis of alloy steel. This paper introduces some initial results in researching the technology of optical mirror polishing of alloy steel materials. The issues studied include the selection of processing methods and equipment, design and manufacture of auxiliary tools and machining tools, testing and setting up machining processes, and the methodology for characterisation product quality. A spherical mirror of 50 mm in diameter, 70 mm in spherical radius, based on alloy steel material has been optically polished. Test results show that the sample meets the requirements for optical products (N=1; ΔN=1, surface roughness Rz=0.05 μm).

A hybrid control strategy for grinding and polishing robot based on adaptive impedance control

In order to realize the active and compliant motion of the robot, it is necessary to eliminate the impact caused by processing contact. A hybrid control strategy for grinding and polishing robot is proposed based on adaptive impedance control. Firstly, an electrically driven linear end effector is designed for the robot system. The macro and micro motions control model of the robot is established, by using impedance control method, which based on the contact model of the robot system and the environment. Secondly, the active compliance method is adopted to establish adaptive force control and position tracking control strategies under impact conditions. Finally, the algorithm is verified by Simulink simulation and experiment. The simulation results are as follows: The position tracking error does not exceed 0.009 m, and the steady-state error of the force is less than 1 N. The experimental results show that the motion curve coincides with the surface morphology of the workpiece, and the contact force is stable at 10 ± 3 N. The algorithm can realize more accurate position tracking and force tracking, and provide a reference for the grinding and polishing robot to realize surface processing.

Analysis of the error of the optical material removal function in a multivariate mathematical model for controlling the shaping processlarge optical parts

The features of technological processes for controlling the shaping of the optical surfaces of large-sized flat parts at the stages of grinding and polishing on modern machines of continu-ous shaping with a full-size tool.The substantiation of the structure of a multifactorial mathe-matical model of the processes of grinding and polishing of flat optical surfaces is given on the basis of studying the laws of motion of actuators and the processing zone of optical machines of continuous shaping with a full-size tool. The analysis of the influence of technological fac-tors and physicochemical features of the processes of processing surfaces of flat optical parts on the function of removing the optical material of a model of chemical mechanical polishing (CMP) is presented. The analysis of the study of the error of the optical material removal func-tion of the presented multivariate mathematical model with the recommendation for fixing cer-tain values of the main kinematic parameters of machine equipment is carried out.