Bogdan Kruszyński

Residual stress in grinding

Abstract Results of investigations on residual stress in surface grinding are presented in the paper. A coefficient “B” combining power density and wheel/workpiece contact time was developed. Experimental set-up and software to estimate the coefficient during grinding are described in the paper. Experiments were carried out for surface plunge grinding for several workmaterials in a wide range of grinding conditions. The influence of process parameters on the coefficient B as well as the relation between B and maximum residual stress were experimentally evaluated. The usefulness of the coefficient to predict residual stress in surface grinding was proved.

An Intelligent Supervision System for Cylindrical Traverse Grinding

The paper presents a supervision system that uses techniques of artificial intelligence to monitor, control and optimise the traverse grinding operation. The system consists of two levels which act in parallel to produce parts satisfying the geometrical and surface finish requirements with maximum possible productivity. The objective of the first optimisation level is to maximize the material removal rate, simultaneously satisfying restrictions on surface roughness, out-of-roundness and waviness errors and on grinding temperature. At the same time the second, geometrical control level is responsible for the removal of the initial shape error by stabilising the motion trajectory of the grinding wheel in relation to the part being ground. The performance of the supervision system was evaluated by extensive experiments to prove its effectiveness.

An Attempt to Predict Residual Stresses in Grinding of Metals with the Aid of a New Grinding Parameter

Residual stresses are considered as the most representative parameter of all properties in the surface layer created by grinding processes and which allow a relatively good assessment of the performance of ground parts. The damage caused by the creation of residual stress in the surface layer of metals has been analysed from the point of view of the thermal aspects of the process with the purpose of finding a representative parameter which combines the most important grinding parameters and which is strongly connected with the residual stress created in the surface layer. Such a parameter may be useful when selecting grinding conditions of critical parts. The suggestion of such a parameter has been developed. The evidence based on analysis of available data found in literature - of its good functional correlation to the residual stress generated in different work materials in different grinding operations is presented and discussed in the paper. It seems that the proposed new grinding parameter may be helpful in a better control of surface integrity in grinding in the industrial practice.

Surface integrity of machined surfaces

This chapter presents the basic knowledge on surface integrity produced in traditional and non-traditional machining processes. An extended overview of fundamental characteristics of surface finishes and surface integrity including surface roughness/surface topography, specific metallurgical and microstructure alterations and process-induced residual stresses is carried out. Surface roughness was determined by many important 3D roughness parameters and representative scanned surface topographies were included. They allow recognizing the structural features, i.e., determined and random components of the machined surfaces. Moreover, some practical formulae for prediction of the theoretical surface roughness in typical cutting operations (turning and milling) and grinding operations are provided. On the other hand, possible surface alterations resulting from abusive machining operations are demonstrated. Finally, the state-of-the-art of machining technology is addressed to many finishing cutting, abrasive and non-traditional (EDM, ECM, LAM, USM, etc.) operations to show how the manufacturing processes can be effectively utilized and optimized in practice.

Forces in Generating Gear Grinding-Theoretical and Experimental Approach

Abstract Results of investigations carried out on the generating gear grinding process, the so-called Niles method, are presented in the paper. A detailed analysis of tooth profile generation shows that, due to the complex kinematics, grinding conditions vary substantially during the cycle of gear tooth creation which may, in turn, influence the grinding forces. It was found that workspeed and dimensions of the layer being removed in a particular generating stroke are the factors having the greatest influence on the grinding forces. On the basis of extensive analytical and experimental work the equations were proposed which allow the calculation of the normal and tangential grinding forces in each particular generating stroke of grinding wheel during tooth profile generation. The analysis of maximum grinding forces in the tooth profile grinding cycle as a function of process parameters is also presented in the paper.

THE INFLUENCE OF GRINDING CONDITIONS ON THE DISTRIBUTION OF RESIDUAL STRESS IN THE SURFACE LAYER OF 17crni6-6 STEEL AFTER CARBURIZING

This paper presents the results of a study aimed at determining the residual stress which results from developing the surface layer by low-pressure and conventional carburizing and grinding of 17CrNi6-6 steel. A synergistic effect of thermochemical and abrasive treatment was examined on ring samples used to study residual stress by Davidenkov’s method. Samples were subjected to vacuum carburizing and conventional carburizing, which was followed by grinding with a 38A60K8V aloxite grinding wheel and a CBN grinding wheel RNB80/63B75V. The following cutting fluids were used during the grinding process: oil emulsion 5%, supply rate ca. 20 l/min, Micro5000 oil supplied at the minimum quantity lubrication (MQL) of ca. 25 ml/h, dry machining. The study determined the effect of the type of grinding wheel and the cooling and lubricating agent on the distribution of residual stress in the surface layer. The best effects of grinding with respect to the residual stress were achieved with flood cooling with oil emulsion and grinding with a CBN grinding wheel.

Application of Principal Component Analysis and Decision Trees in Diagnostics of Cylindrical Plunge Grinding Process

In the grinding process, information about the process state may be derived from many measurement signals. As a result of these signals preprocessing, it is possible to obtain a high number of features of which only a part is related to the monitored process. This paper deals with the feature selection problem and modeling of relationships of selected features with grinding process states and grinding results. Firstly, time–frequency signal processing techniques are analyzed. Using the Hilbert-Huang transform, force, vibration, and acoustic emission signals are decomposed into separate intrinsic mode functions, and then the statistical features are extracted from these functions. Next, principal component analysis is used to select the most relevant features and to remove redundant data. Finally, decision trees are applied to additionally decrease the number of features and to model the grinding process. Using the proposed approach, it is possible to automate the feature selection process and to effectively diagnose the process state and predict final part quality parameters.

Temperatures in Grinding of Magnetic Composites - Theoretical and Experimental Approach

Abstract The present paper is concerned with grinding temperatures and surface Integrity for grinding of magnetic composites consisting of sandwich-like layers of brittle magnetic material and soft steel. High temperatures which are generated during grinding of these magnetic composites may have a detrimental effect on their magnetic properties if the grinding temperature exceeds the Curie point of the magnetic component. A thermal model was developed to calculate the grinding temperatures in the magnetic composite workplace. Temperatures measured in the magnetic composite using embedded thermocouples were found to be consistent with predictions from the thermal model. Crucial regions in the magnetic composite were found where the highest temperatures and temperature gradients occur and where surface integrity may be destroyed. The range of grinding conditions providing both high efficiency and good surface quality were found.