Workpiece Surface Temperature Research Articles

Multi objective optimization of process parameters in hard turning of AISI 52100 steel with surface irregularities using GRA-PCA

Dry hard-turning is a cost-effective, efficient manufacturing method for AISI 52100 hardened bearing steel. Surface Defect Machining (SDM) is a novel approach to address surface roughness, deteriorations, residual stresses, and metallurgical changes on machined steel. SDM involves exposing workpieces to surface irregularities, reducing cutting resistance, and enhancing surface integrity and finish. In the present work, surface irregularities are formed on the surface of the workpiece in the form of indentations. Using the response surface method’s central composite design (CCD), 32 experimental runs were conducted to determine the optimal process parameters by varying the cutting and tool geometry parameters while AISI52100 steel hard turning (HT). Due to its complexity, multi-objective optimization is more challenging to study. The present work aims to evaluate the effects of input parameters on maching force, surface roughness, and workpiece surface temperature. Further, machining parameters optimization is performed employing the Grey relational analysis integrated with principal component analysis (GRA-PCA). Analysis of variance (ANOVA) was used to examine the impact of cutting and tool geometry parameters on grey relational grade (GRG). ANOVA revealed that feed has the highest influence on GRG, followed by depth of cut, nose radius, cutting speed, and negative rake angle. Cutting speed of 800 rpm, feed rate of 0.04 mm/rev, depth of cut of 0.5 mm, nose radius of 1 mm, and negative rake angle of 15° are the optimum combination of process parameters.

Mechanical analysis and machinability evaluation of a new EDM-turning hybrid machining process

This study developed an accurate electrical discharge-assisted turning (EDAT) technique for Ti–6Al–4 V alloy and a precise EDAT cutting force prediction model considering theoretical multi-physics fields with metallurgical transformation. A heat-fluid coupled model of multi-pulse discharge in the EDAT process was developed to obtain the thickness of the removal layer (RL) and modified layer (ML) together with the temperature field of the cutting layer. Subsequently, the shear flow stresses under different machining parameters were obtained using the oblique cutting and flow softening constitutive models. Within the cutting layer, the pure thermal softening effect reduces the flow stresses by more than 25% in the unmodified matrix layer (UML) and by more than 60% in the ML, which is dominated by the metallurgical transformation softening (MTS) effect. Finally, the cutting force model of EDAT under multi-physical fields was established and the accuracy was verified by relevant experiments. The results showed that the increase in discharge number accelerated the rise of workpiece surface temperatures, and the small cutting parameters were favorable to the machining performance of the EDAT. The MTS effect significantly reduces cutting forces while improving the quality of the machined surface.

Finite difference numerical modeling and experimental validation of workpiece surface temperature in micro-grinding

The objective of this work is to characterize the heat transfer and temperature generation into the workpiece during micro-slot grinding. A numerical model for predicting micro-grinding temperature is established based on the finite difference method (FDM). Workpiece volume is divided into small elementary sections and temperature in small sections near and away from the machining zone is calculated using thermo-physical model as well as validated by experimentally measured temperature using infrared technique. Temperature in micro-slot grinding increases during vertical insertion of the tool and becomes stable when the tool transverse in the feed direction. Simulation results show that transient heat transfer becomes dominant on increased feed rate values that result in an overall lowering of heat supply into the surface. Results also reveal that modification in the tool design has a significant impact on the reduction of workpiece temperature due to reduced contact length, reduced cutting forces, friction, and rubbing at the tool-workpiece interface. The proposed model is capable of solving transient problems in micro-slot grinding and is flexible to deal with different boundary conditions. This analysis will help in temperature prediction and establishing temperature reduction strategies that could potentially increase machining precision.

Modeling the effect of workpiece temperature on micromagnetic high-speed-3MA-testing in case of AISI 4140

The growing trend towards industry 4.0 requires in-process identification of the surface properties. The non-destructive highspeed-3MA-testing can be used to characterize surface layers of ferrous materials during turning processes. However, in-process measurements will result in higher workpiece temperatures and thus would interfere with the micromagnetic properties of the workpiece. In the presented study, workpiece surface temperatures will be experimentally determined when turning AISI 4140. Further on, workpieces will be heated up to the respective temperatures, which will then be measured with the 3MA-sensor as they rotate. The effect of temperature will be modelled and used for compensating the associated errors.

Modelling of tool flank−workpiece interface friction considering temperature gradient and particle property for cutting SiCp/Al composites

Currently, friction coefficient at a tool―chip―workpiece interface is simplified to a constant value. However, a friction coefficient that ignores the effects of temperature, pressure, and particle characteristics cannot characterize the frictional behaviours involved in cutting SiCp/Al composites. In this study, based on an inverse solution method, a novel customized device is developed to overcome the shortcoming of the determination of the workpiece surface temperature with a high local gradient. A series of "single-double" cutting inserts experiments are conducted on the device to measure the friction coefficient between the PCD tool―SiCp/Al composites. The friction coefficient model considering the temperature and particle property effects is established for the first time. The influence tendencies of the temperature, particle characteristics, and pressed depth on the friction coefficient are evaluated for varied SiCp/Al composites. The friction force model between the tool flank–workpiece is built considering the temperature gradient and particle characteristic effects. Finally, the analytical model of the cutting temperature subjected to orthogonal cutting SiCp/Al composite is developed by integrating the proposed friction coefficient and friction force models. The analytical results of the cutting temperature agree well with the experimental results, with a relative error smaller than 9.3 %. Compared with our previous study, the analytical model of the cutting temperature proposed in this study can improve the prediction accuracy significantly where the average relative error is reduced by 5%. This study offers a firm foundation for understanding frictional characteristics involved in cutting SiCp/Al composites.

Some Experimental Investigations in the Performance of Electochemical Machining Process.(Dept.M)

A rigid abright drill provided the ratory motion for a brass disc employed as the tool having no embeded abrasive material, Sodium Chloride and Sodium Hydroxide having different concentrating rates between (10% - 50%) were employed as electrolytes covering the gab between the tool and workpieces. Mild steel, free machining -rass and pure aluminum in the as-received conditions were employed as workpieces. Material removal rates were found to be greater for smaller gap widths, higher speed of revolution, greater gap voltage, higher percentages of electrolyte conceration and greater electrolyte velocity for all workpiece materials especially when using sodium chloride. As the material removal rate increases, consequently workpiece surface temperature rises. Such temperature rises all-over the entire range did not exceed + 30°C. Workpiece surface finish were found to improve for higher rates of material removal for mild steel and free machining brass only. No such improvements were noted after aluminum machining except at high tool speeds. Deep scatered scratchs in aluminum specimens were noted at lower tool speeds.

Experimental investigation of the machining characteristics in diamond wire sawing of unidirectional CFRP

Especially for slicing hard and brittle materials, wire sawing with electroplated diamond wires is widely used since it combines a high surface quality with a minimum kerf loss. Furthermore, it allows a high productivity by machining multiple workpieces simultaneously. During the machining operation, the wire/workpiece interaction and thus the material removal conditions with the resulting workpiece quality are determined by the material properties and the process and tool parameters. However, applied to machining of carbon fibre reinforced polymers (CFRP), the process complexity potentially increases due to the anisotropic material properties, the elastic spring back potential of the material, and the distinct mechanical wear due to the highly abrasive carbon fibres. Therefore, this experimental study analyses different combinations of influencing factors with respect to process forces, workpiece surface temperatures at the wire entrance, and the surface quality in wire sawing unidirectional CFRP material. As main influencing factors, the cutting and feed speeds, the density of diamond grains on the wire, the workpiece thickness, and the fibre orientation of the CFRP material are analysed and discussed. For the tested parameter settings, it is found that while the influence of the grain density is negligible, workpiece thickness, cutting and feed speeds affect the process substantially. In addition, higher process forces and workpiece surface temperatures do not necessarily deteriorate the surface quality.

Application of TOPSIS for multi response optimization of Process Parameters in dry hard turning of AISI 52100 steel

In the present work by employing the Technique for order of preference by similarity to ideal solution (TOPSIS) machining parameters optimization is performed with polycrystalline cubic boron nitride (PCBN) tools while AISI 52100 steel hard turning (HT). Based on the CCD of RSM, 32 experimental runs were performed by varying cutting speed, feed, depth of cut, nose radius, and negative rake angle to identify the optimal level of the process parameters. In this study, the multiple performance characteristics measured are machining force, surface roughness, and workpiece surface temperature. To ascertain the impact of cutting parameters on responses, Analysis of Variance (ANOVA) was deployed. An optimum combination of input process parameters for the multiple performance characteristics should be as follows: speed 200 rpm, feed 0.1 mm/rev, depth of cut 0.8 mm, nose radius 1.2 mm, and negative rake angle 45º leading to the value of optimum response variables machining force 561.163 N, Surface roughness 0.507μm and workpiece surface temperature 84.38°C.

Analytical model of workpiece surface temperature prediction in 4-axis milling process

Milling temperature directly affects surface integrity and fatigue life, which is one of the important physical parameters in the process of machining. At present, the prediction of cutting temperature is mainly focusing on orthogonal cutting and turning; there is little research on the prediction of milling temperature of workpiece. The main idea is to discretize the cutting time and heat source, which is learning from the idea of milling force modeling. The moving heat source method is used to predict the workpiece temperature rise in milling process. The geometric kinematics of five-axis machining motion is analyzed. The temperature rise contribution can be calculated in the shear zone based on orthogonal cutting model through coordinate transformation. The proposed model is verified by experiments and 4-axis milling of cylinder surface temperature field is analyzed by simulation. This method can be extended to the temperature prediction of other processing methods, such as five-axis machining and turn-milling compound machining.

Simulation of heat flows in a combined process of plasma spraying and coat hardening

The simulation technique of heat distribution in a detail for applying plasma coating in combination with electro-mechanical treatment and cooling by water jet is worked out. It is shown that water cooling substantially decreases the workpiece surface temperature and provides the formation of more rugged coat by reducing of internal stresses in it.

Multi Response Optimization of Cutting and Tool Geometry Parameters in Hard Turning of Aisi 52100 Steel-Topsis Approach

In the current study, machining parameters optimization is performed in hard turning of AISI 52100 steel with PCBN tools using TOPSIS. Experiments are devised and conducted based on the CCD of the RSM. In this study machining force and workpiece surface temperature are the measured responses. ANOVA is deployed to ascertain the influence of process parameters. Optimal turning parameters are at speed 200 rpm, feed 0.1 mm/rev, depth of cut 0.8 mm, nose radius 1.2 mm and negative rake angle 45o.

White layer analysis of hard turned AISI 52100 steel with the fresh tip of newly developed HSN2 coated insert

As a substitute for grinding, hard turning is becoming attractive in many manufacturing industries, although, it is interrupted by many problems like white layer and tensile residual stress which are generated during hard turning. Due to these reasons, many negative effects like residual stress, wear, and reduced fatigue life are found in the machined components. In the field of hard turning, the study on the white layer is the most interesting research subject among the scientific community. The white layer is one of the main reasons for cutting tool insert failure or excess insert wear. Also, the machined surface quality is affected due to the white layer. This work examines the development of the white layer in hard turning at different cutting speeds. All the experiments are executed on AISI 52100 grade steel (having hardness 55 HRC) with newly developed HSN2 coated carbide insert having a fresh edge for each experiment. Field emission scanning electron microscope, optical microscope and X-ray diffraction are used to analyze white layer at different cutting conditions as well as bulk material. In addition, the micro hardness of the machined surface is measured. Also, the workpiece surface and chip temperatures are studied. Based on analysis of white layers at different cutting speeds, it is observed that low cutting speed is more dominant during hard turning of AISI 52100 steel. The thickness of white layer reduces with increased cutting speed, and its maximum thickness (6.5 μm) is found at 100 m/min cutting speed, and their relationship is justified from analysis of X-ray diffraction peaks. Also, the weight percentage of retained austenite is calculated from XRD analysis and its value is 28.5% at a lower speed (100 m/min), and it reduces to 6.5% with higher cutting speed as compared to the base material.

Achieving Optimal Process Parameters during Hard Turning of AISI 52100 Bearing Steel Using Hybrid GRA-PCA

In the present work hard turning of AISI 52100 steel has been performed using Polycrystalline cubic boron nitride (PCBN) tools. The input parameters considered are cutting speed, feed, depth of cut, nose radius and negative rake angle and the measured responses are machining force and workpiece surface temperature. Experiments are planned as per Central Composite Design (CCD) of Response Surface Methodology (RSM). The effect of input parameters and their interactions are discussed with main effects plot. Further, the multi-objective optimization scheme is proposed by adopting Grey Relational Analysis (GRA) coupled with Principle Component Analysis (PCA). Results demonstrated that speed is the most significant factor affecting the responses followed by negative rake angle, feed, depth of cut, and nose radius. The optimum cutting parameters obtained are cutting speed 1000 rpm, feed 0.02 mm/rev, depth of cut 0.5 mm, Nose radius 1 mm and Negative rake angle 5o.

Influence of Water Cooling on Orthogonal Cutting Process of Ti-6Al-4V Using Smooth-Particle Hydrodynamics Method

Temperature control during the cutting process with different parameters such as cutting velocity and applying water cooling is essential to decrease the cutting force, increase the life of the cutting tool and decrease the machined surface temperature of work-piece. In this research, the temperature of machined surface and the chip-tool interface in orthogonal cutting process of Ti-6Al-4V were investigated using smooth particle hydrodynamics (SPH) method. The effects of cooling with different speeds and temperatures of water flow on the temperature of these surfaces were studied. The non-cooling model is validated using experimental results. According to the results, a water flow with speed of 0.25 m/s at 20°C temperature causes a significant decreasing in the cutting force and the temperature on machined surface and chip-tool interface.

Heat flux distribution and temperature prediction model for dry and wet cylindrical plunge grinding

The grinding heat is generally partitioned into the workpiece, wheel, chips and fluid in grinding process. The total amount of heat flux entering into the workpiece greatly affects the final workpiece surface temperature, which may cause undesirable workpiece burn. Moreover, the variable grinding chip thickness and fluid injection speed along the grinding contact zone could substantially change the specific energy and the shape of the heat source correspondingly. In this article, a Weibull heat flux distribution model for both dry and wet grinding temperature prediction was proposed by analyzing two key parameters: energy partition Rw and shape parameter k. The value of Rw was obtained by considering the real contact length, the active grits number and the average grit radius r0 on the basis of traditional formulas. The relationship between shape parameters k and useful flow was established by a FLUENT simulation of the convective grinding fluid applied in grinding contact zone with wheel-workpiece minimum clearance. The grinding temperature and grinding force experiments were conducted on a grinding machine MGKS1332/H to validate the proposed heat flux model. The calculated workpiece surface temperature distribution was obtained by using the experimental heat flux obtained by the reverse algorithm, and the error between calculated temperature and experimental temperature was analyzed. With the monitored force signals and the proposed temperature prediction model, the grinding temperature for both dry and wet grinding can be predicted, which will be helpful to the optimization and control of temperature in grinding process.

Material removal mechanism of laser-assisted grinding of RB-SiC ceramics and process optimization

Laser-assisted grinding (LAG) is a promising method for cost-effective machining of hard and brittle materials. Knowledge of material removal mechanism and attainable surface integrity are crucial to the development of this new technique. This paper focusing on the application of LAG to Reaction Bonded (RB)-SiC ceramics investigate the material removal mechanism, grinding force ratio and specific grinding energy as well as workpiece surface temperature and surface integrity, together with those of the conventional grinding for comparison. Response surface method and genetic algorithm were used to optimize the machining parameters, achieving minimum surface roughness and subsurface damage, maximum material removal rate. The experiments results revealed that the structural changes and hardness decrease enhanced the probability of plastic removal in LAG, therefore obtained better surface integrity. The error of 3-D finite element simulation model that developed to predict the temperature gradient produced by the laser radiation is found to be within 2.7%–15.8%.

Modeling of grinding wheel topography based on a joint method of 3D microscopic observation and embedded grindable thermocouple technique

The grinding wheel generally has a complicated topography for the irregularity of abrasive grits, which always has an important influence on the final quality of the grinding workpiece. In this paper, a joint method of microscopic observation and grindable thermocouple technique was adopted to model the wheel topography. The grinding wheel topography was first modeled through microscopic observation by an in-position 3D microscope KH-7700 installed on the grinding machine. Based on the measurement of grit sizes, shapes, and distributions through the 3D microscope, a wheel surface model was established and a static grit number model based on Rayleigh distribution was proposed. Moreover, a numerical model was given to validate the proposed Rayleigh distribution model of an active grit number. In order to investigate the real abrasive grit number in a grinding process, an embedded grindable thermocouple was used to detect the dynamic variation of temperature signals, which will reflect the variation of in-process wheel topography under different process parameters, machine status, and even the grit-workpiece interaction status. Through the experimental analysis, it can be concluded that the increase of depth of cut ap could help to greatly increase the active grit number to the grinding process, while the increase of workpiece speed Vw and decrease of wheel speed Vs could lead to a subtle increase of the grit number. Moreover, the active grit number is about one fourth to one third of the static grits. The contact arc length between the wheel (CBN) and the workpiece (Ti-6Al-4V) was calculated by the contact time from the workpiece surface temperature data, and it was found that the actual contact arc length was about 1.5~2 times of the geometric size.

The nature of the change of the surface temperature of the workpiece during hot rolling of pipe steel

The article is devoted the experimental studies of deformation and temperature parameters of rolling the pipe steel on the rolling mill 5000 PJSC “MMK”. Knowledge of the regularities of the change in the surface temperature of work piece during hot rolling under the conditions of thermo mechanical deformation processes is of great theoretical and practical importance. The temperature conditions determine the energy and force parameters of rolling, as well as the mechanical properties and microstructure of the finished products. The experimental rolling was carried out in two stages: roughing at 6 passes at a temperature of 1050-900 ° C and finishing at 18-20 passes at a temperature below the start of the phase transformation of 900 ° C. The finishing rolling has been carried out in a two-phase region at the stage of polymorphic transformation in the steel. Significant differences in the nature of temperature changes at different stages of rolling are revealed.

Multi objective optimization of process parameters for hard turning of AISI 52100 steel using Hybrid GRA-PCA

In this study, multi-objective optimization for a hard turning of AISI 52100 steel has been presented to provide optimum surface quality, Machining force and work piece surface temperature. Cutting speed, feed, depth of cut and Nose radius are considered as input parameters. Experiments are conducted as per Taguchi L9 orthogonal array. The Parametric investigation is carried out for identifying the effect of input parameters on the response using MINITAB14 software package. Further, multi objective optimization is performed with Grey Relational Analysis (GRA) coupled with Principle Component Analysis (PCA). Results demonstrated that nose radius is the most significant factor affecting the response followed by feed, depth of cut and speed. The optimum cutting parameters obtained are cutting speed 900 rpm, feed rate 0.04 mm/rev, depth of cut 0.6 mm and Nose radius 0.8 mm.

Estimation of Heat Transfer Properties for the FE Simulation of Cryogenic Turning

AbstractIn order to shorten the process chain in manufacturing and thus to optimize the manufacturing time, current researches investigate the possibility of combining two process steps, turning and hardening.During cryogenic turning of metastable austenitic steel, deformation induced hardening in the surface layer of the workpiece can be achieved by applying high passive forces onto the workpiece [1]. This leads to an increase in the wear resistance [2] as well as the fatigue strength [3]. For the employed austenite‐martensite phase transformation it is necessary to maintain low process temperatures, typically below room temperature. Thus, cryogenic cooling has to be applied to counteract the heat, generated during machining [4].For a better understanding of the influence of different cutting and cooling parameters on the temperature field during cryogenic turning, and thus martensite formation, knowledge of the exact temperature distribution in the workpiece and the workpiece surface temperature in the contact zone is essential. Since in situ measurements of the latter are hardly possible, an inverse determination via transient finite element simulation is performed [5].In order to model cryogenic turning, material properties, thermal loads and heat transfer coefficients defining convective heat transfer, have to be determined first. These model parameters are investigated independently in stand‐alone experiments, applying only one thermal load at a time. The magnitudes of these values are obtained by iteratively modifying the initial values in the model until correspondence with measured temperature data from the experiment is achieved.The present finite element approach only takes thermal loads into account and is performed in the finite element program FEAP (Finite Element Analysis Program) with an Eulerian mesh, which requires special consideration of the rigid body rotation of the workpiece. The Eulerian treatment results in an unsymmetrical system matrix, and a special stabilisation is required to avoid numerical oscillations in the time integration scheme [5]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)