Workpiece Surface Temperature Research Articles

Numerical simulation of thermally induced workpiece deformation in turning when using various cutting fluid applications

The paper describes a combined experimental–theoretical approach for modeling heat generation and transfer processes in turning when using various cutting fluid application techniques for cooling and lubrication, i.e. flood type cutting fluid application, minimum quantity cutting fluid application and dry machining. The developed process simulation was based on the finite element (FEM) method applying the ANSYS V5.5.3 program, which provided the workpiece surface temperatures and thermally induced deformation. The development of the physical model was based on a test workpiece of high stiffness to separate thermal deformation from deformation caused by other factors. The simulation and experimental results compared very well and proved the accuracy of the model. The process model and the system approach were also verified on a “real” industrial workpiece.

A Study on the Distribution of Heat in Cool Air Grinding with Porous Metal Bonded Diamond Wheel(Superabrasive/new wheel grinding process)

Influence of cool air on the cooling ability in grinding process has been studied. By blowing cool air through the grinding zone, heat is taken out of the grinding zone and the surface temperature of workpiece also is reduced. This is confirmed by some theoretical and experimental research. However, in order to use cool air on the grinding more effectively, the more theoretical research is necessary. In this research, we try to make clearly the influence of grinding conditions on the heat removed. We also try to make clearly the influence of cool air parameters as temperature, pressure and flow rate on the distribution of heat in grinding as well as the heat removed by cool air in order to give a optimal grinding conditions in cool air grinding. In addition, the application ability of cool air in grinding is apart of this research.

Temperature Measurement in Laser Forming of Sheet Metal

Laser forming is a thermal process for the deformation of sheet metal by thermal stress. Temperature distribution is the most important factor for determining the bending angle of the sheet metal. In the present study, the combined effect of the temperature of the workpiece, the temperature gradient between the two surfaces of the sheet, the size of the zone irradiated with laser beam, and the thickness of the workpiece is investigated both theoretically and experimentally. The temperature at the surface irradiated with C02 laser and at the opposite surface are simultaneously measured using two-color pyrometers with an optical fiber. The bending angle has been found to increase with the spot diameter and workpiece surface temperature and decrease with workpiece thickness. The work surface temperature can be used as a monitoring signal for the purpose of controlling the bending angle.

A study for the constitutive equation of carbon steel subjected to large strains, high temperatures and high strain rates

In this paper, presented is a study for predicting the flow stress during hot deformation of carbon steel where the strain rate reaches as high as 3000 s −1 at high temperature (700–1100 °C). We have analyzed thoroughly Shida’s constitutive equation generally being used within the strain rate limit of 100 s −1 at elevated temperature. It was then assumed possible to obtain the constitutive equation which can depict the flow stress behavior of material beyond strain rate of 100 s −1 by modifying the Shida’s constitutive equation. The validity of the modified constitutive equation has been examined using split Hopkinson pressure bar (SHPB) experiment at high temperature. The high temperatures of SHPB test were obtained by enclosing the specimen in a clam-shell radiant-furnace. It has then been applied to hot rod rolling mill for predicting the surface temperature of workpiece where material throughout rolling experiences high strain rate (3000 s −1) and subsequently significant heat generation due to high strain rate plastic deformation. Results showed the modified constitutive equation could predict the flow stress value with a reasonable extent of error, in comparison with the one obtained from the SHPB experiment. The predicted surface temperatures of the workpiece during hot rod rolling were also in agreement with measured ones.

A thermal model of the wet grinding process

A thermal model of the wet grinding process is presented. The thermal effect of the grain–workpiece interface and the shear plane between the workpiece and the chip is taken into account. By taking all of the parameters needed in the model from the experimental results, the temperature of the workpiece surface in the grinding zone can be predicted. It is shown that the flow rate of the grinding fluid under general grinding conditions is sufficient to cover the thermal boundary layer of the coolant in the grinding zone. The predicted workpiece surface temperatures have been compared to experimental data for some grinding conditions. Good agreement is obtained except for the creep-feed grinding process, when water-based grinding fluid is used. The differences between the theoretical values and experimental results are attributed to constant thermal properties, and neglect of transverse conduction in the development of the thermal model.

Transient Thermal Response of a Rotating Cylindrical Silicon Nitride Workpiece Subjected to a Translating Laser Heat Source, Part I: Comparison of Surface Temperature Measurements With Theoretical Results

Laser-assisted machining (LAM), in which the material is locally heated by an intense laser source prior to material removal, provides an alternative machining process with the potential to yield higher material removal rates, as well as improved control of workpiece properties and geometry, for difficult-to-machine materials such as structural ceramics. To assess the feasibility of the LAM process and to obtain an improved understanding of governing physical phenomena, a laser assisted machining facility was developed and used to experimentally investigate the thermal response of a rotating silicon nitride workpiece heated by a translating CO2 laser. Using a focused laser pyrometer, surface temperature history measurements were made to determine the effect of rotational and translational speed, as well as the laser beam diameter and power, on thermal conditions. The experimental results are in good agreement with predictions based on a transient three-dimensional numerical simulation of the heating process. With increasing workpiece rotational speed, temperatures in proximity to the laser spot decrease, while those at circumferential locations further removed from the laser increase. Near-laser temperatures decrease with increasing beam diameter, while energy deposition by the laser and, correspondingly, workpiece surface temperatures increase with decreasing laser translational speed and increasing laser power, In a companion paper (Rozzi et al., 1998), the detailed numerical model is used to further elucidate thermal conditions associated with laser heating and to assess the merit of a simple, analytical model which is better suited for online process control.

The workpiece temperature, fluid cooling effectiveness and burning threshold of grinding energy in creep feed grinding

In this study, a heat transfer model based on numerical analysis of creep feed grinding is proposed. This model is verified to predict the workpiece surface temperature and to find the fraction of heat entering the workpiece. The fluid cooling effectiveness and the effects of specific grinding conditions on the critical grinding energy when the workpiece burns are also discussed. Meanwhile, scaling analysis is performed to explain the influence that conduction behaviour in the moving direction exerts on creep feed grinding. Compared with the published data, the thermal analysis adopted in this paper is shown to be valid.

On the development of surface temperatures in precision single-point diamond abrasion of semiconductors

This paper presents an analytical, variable-conductivity, thermal model for single-point diamond precision machining of semi conductors. The model is used to calculate the temperature development during the simulated machining of silicon and germanium wafers. The heat generated at a tool-work piece contact is taken as the product of the coefficient of friction, the relative sliding speed, and the contact stress. Whereas, heat partition between the diamond abrasive and the work piece is obtained through a modified Jaeger-Blok analysis that incorporates the coupling of the thermal properties of the tool-work piece system. The results indicate that: for the ranges of nominal loads, cutting speeds and, feeds encountered, the work piece surface temperature rise is well below the thermal softening temperatures for these materials. This, has direct implications to the ductile removal mechanisms. The low values calculated for the work surface are shown to be consistent with several calculations based on the analysis of conventional machining.

水溶性研削油剤の作用に関する研究 ＩＶ 二成分系研削油剤の冷却性と潤滑性

Cooling and lubricating actions of two components mixture type grinding fluids, which contain machine oil and surface active agent, have quantitatively been measured as the cooling and lubricating moduli. Experimental grinding results are compared with grinding results predicted by the model of multipliable effects for cooling and lubricating actions of grinding fluids. Main conclusions are as follows : (1) For two components mixture type grinding fluids, cooling action decreases and lubricating action increases as mixture concentrations increase. (2) The multipliable effects model can quantitatively predict the variations of normal and tangential grinding forces and workpiece surface temperature. (3) This model can accurately predict the optimum mixture concentrations for minimum grinding results of grinding forces and workpiece surface temperature.

水溶性研削油剤の作用に関する研究 Ｖ 潤滑性と冷却性に関する混合則と分離則

In this report proposed is a mixing law with which the lubricating and cooling moduli of mixed type grinding fluids with arbitrary concentration can be predicted from lubricating and cooling moduli of single component type grinding fluid. A separating law is then introduced to separate the lubricating and cooling moduli of each component from those moduli of two-component mixed type grinding fluids which contain mineral oil and surface active agents. By using the mixing and seperating laws on the lubricating and cooling actions, predicted grinding forces and workpiece surface temperature have a close agreement to experimental grindng results. So that mixing and separating laws on the lubricating and cooling actions can be considered as the effective method to establish a standard for proper selection and optimum concentration of several component mixed water soluble type grinding fluids.

A Simple Model for Convective Cooling During the Grinding Process

Heat generated during grinding may cause thermal damage to the workpiece and wheel. To avoid this, grinding fluids are often used, but their effects are not well understood. A simple analytical model of the convective heat transfer between the wheel and workpiece surfaces and the grinding fluid is described. The model predicts the convective heat transfer coefficient at the workpiece surface, the fraction of energy entering the workpiece, and the workpiece surface temperature. Despite its simplicity, the model shows remarkable agreement with published data for conventional and creep feed grinding conditions.

シミュレーションによる研削作業標準設定システムの開発

A very practical simulation system for the establishment of grinding operation standards has been developed in which many practical parameters in actual grinding operations are considered. This computer system simulates such grinding phenomena as dressing, chip geometry, active grains behaviors, wheel surface conditions, wheel wear, grinding force and power, surface roughness, temperature and burning of workpiece, loading on wheel surface, and spark-out grinding. The system can display the simulation results as a graph including both the time-dependent results and the effects of various parameters, having the same effects as many grinding experiments. It is also capable of selecting the optimum grinding wheels and conditions for the grinding operation under the given constraints by exchanging automatically the combinations of the operation parameters and their values. Thus, with the aid of the system, grinding operation standards are able to be established.

水溶性研削油剤の作用に関する研究(第2報)

In this paper propose is a model with which grinding results can quantitatively be given from the viewpoint of cooling and lubricant actions of water soluble type grinding fluids. Experimental results are compared with calculated results by using this model. Main conclusions are as follows: (1) Cooling action is measured as heat transfer rate of grinding fluids and lubricant action is measured as coefficient of lubricant on the grinding wheel surface. (2) Dimensionless grinding results Gr* are given by: Gr*=μ*α·h*-β, where h* and μ* are dimensionless cooling and lubricant moduli defined from heat transfer rate and coefficient of lubricant. (3) Close agreements are obtained between experimental and calculated values of workpiece surface temperature and grinding forces.

Infrared thermographic temperature measurement during laser heat treatment

A commercial infrared thermography system has been used to monitor workpiece surface temperatures during laser heat treatment. A simple optical filtering technique was used to increase the upper temperature limit of the thermography system. Experimental results are presented which demonstrate an accuracy of ±10%. The filtering technique is applicable to most commercial infrared thermographic systems.

On temperature and heat source distributions in sliding contact problems

The heat conduction problem of sliding contact as found in a tool work-piece interaction is analyzed by assuming the presence of a thin boundary layer between the tool wear-flat and the work-piece. Within the layer heat is produced at a constant rate per unit volume of the layer material as a result of large frictional forces. The layer material itself constitutes in the case of cutting of a brittle material a very fine powder whose thermal properties may differ significantly from those of the tool and the work-piece. The presence of the boundary layer permits thus the tool and the work-piece surface temperature distributions to be totally different Furthermore, the evolution in time of these distributions is determined by the heat conduction characteristics of the entire system under consideration and consisting of tool, layer and work-piece.

Statistical evaluation of metal-cutting parameters in hot-machining

SUMMARY The influence of workpiece surface temperature, as also of the cutting velocity, depth of cut and feed, on tool life and surface roughness, in hot-machining, has been investigated, using Factorial Regression Analysis, and a mathematical relationship has been obtained. The equations have been tested for goodness of fit by the Chi-Square Test. Alignment charts have been constructed to evaluate surface roughness and tool life, dependent on other parameters.