Workpiece Temperature Research Articles

Friction stir processing of ZE41 Mg alloy: Optimizing the process parameters

Friction stir processing is a novel processing route used to develop fine grained structures. Processing by FSP is influenced by tool rotational speed, tool travel speed, workpiece temperature, tool tilt angle, etc. Processing at optimum parameters is important to avoid defects and to develop grain refined materials by FSP. In the current research work, ZE41 magnesium alloy was processed by FSP to develop fine grained structure. FSP was done at different tool rotational and travel speeds. Decreased grain size and increased hardness was observed for all FSPed samples. However, variations were clearly observed within the measured grain size, hardness and nugget zone width of the FSPed samples. From Taguchi optimization studies using gray relation analysis; optimum set of parameters which yield smaller grain size and higher hardness were identified. From the results, 1400 rpm and 25 mm/min were observed as optimum. The design model presented in the current study helps to select optimized parameters in producing fine grained ZE41 for upcoming energy efficient applications.

Finite element simulation of deformation and heat transfer during friction stir processing of as-cast AZ91 magnesium alloy

Friction stir processing of as-cast AZ91 magnesium alloy was simulated by a thermomechanical model using DEFORM 3D finite element commercial package V.11. The model accuracy was verified by comparing predicted temperature history with the experiments, which showed an excellent agreement. The model was developed to calculate the effect of pin shape on different aspects of the process. The tracking of several material points was performed at different intervals of the workpiece's thickness, showing that the conical pin prevents points from accumulating the workpiece's top surface at the advancing side, while the points accumulation occurs by the cylindrical pin. The conical pin increases the material displacement, causing more significant effective strain and a greater increase in the workpiece's temperature than the cylindrical pin. Although the contribution of friction and deformation to the heat generation in the retreating side and the advancing side is not the same, their contribution ratio is such that it leads to the symmetrical distribution of temperature. It was found that pin shape affects the deformation and friction contribution on heat generation at both sides of the tool in the workpiece. For this reason, in the case of the cylindrical pin, the temperature at the retreating side was obtained slightly higher than that at the advancing side, while for the conical pin, it was just the opposite. Moreover, the development of vertical, longitudinal, and lateral tool forces was evaluated in detail by the developed model for conical and cylindrical pins during the plunging and traversing (welding) stages.

Прочность и механизм разрушения при кручении технически чистого титана с ультрамелкозернистой структурой

The mechanical behavior and the mechanism of torsional fracture of medical grade titanium Grade4 with an ultrafine-grained (UFG) structure in comparison with a coarse-grained (CG) structure were investigated. CG titanium (dav = 25 μm) was investigated in the hot-rolled state. To obtain the UFG structure, two processing regimes were used. In the first regime, homogenization annealing was carried out at a temperature of 680°C for 1 hour, then equal-channel angular pressing (6 passes) according to the “Conform” scheme (ECAP-С) at a workpiece and tool temperature of 250°C (route Bc, φ =120°). The average grain size is equal to 0.4 μm. In the second regime, after homogenization annealing and six ECAP-C passes, the workpieces were drawn at a temperature of 200°C (ECAP-C+D). The average grain size is equal to 0.2 μm. The torsion test of samples with a diameter of 3 mm (close to the diameter of screws for fixing plates in traumatology) was carried out on a KTS 403‑20‑0.5 installation in accordance with GOST 3565-80. The torque, number of revolutions and angle of twisting of the samples made from CG and UFG titanium, as well as the mechanical properties of titanium during torsion were evaluated. Torsion tests have shown that the torsional strength and the torsional yield strength of UFG titanium increase, and the relative shear decreases in comparison with similar properties of CG titanium. In addition, the mode of nanostructuring (ECAP-C+D) provides higher values of the torsional strength properties of titanium compared to ECAP-C, which is favorable from the standpoint of resistance to fracture of titanium screws by torsion. On the surface of the fractures, there are three regions differing in microrelief: the central part of the fracture, the middle (transitional) and the peripheral parts. In the central part of the fractures, the microrelief consists of equiaxed dimples and structureless areas. In the middle part, shear dimples dominate, and in the peripheral part of fractures, areas of shear dimples alternate with areas of the rubbed surface.

Inverse Identification of the Ductile Failure Law for Ti6Al4V Based on Orthogonal Cutting Experimental Outcomes

Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as a promising approach. To function correctly, they require accurate data related to appropriate material properties (e.g., constitutive models, ductile failure law). Nevertheless, material characterization is usually carried out through thermomechanical tests, under conditions far different from those encountered in machining. In addition, segmented chips observed when cutting titanium alloys make it a challenge to develop an accurate model. At low cutting speeds, chip segmentation is assumed to be due to lack of ductility of the material. In this work, orthogonal cutting tests of Ti6Al4V alloy were carried out, varying the uncut chip thickness from 0.2 to 0.4 mm and the cutting speed from 2.5 to 7.5 m/min. The temperature in the shear zone was measured through infrared measurements with high resolution. It was observed experimentally, and in the FEM, that chip segmentation causes oscillations in the workpiece temperature, chip thickness and cutting forces. Moreover, workpiece temperature and cutting force signals were observed to be in counterphase, which was predicted by the ductile failure model. Oscillation frequency was employed in order to improve the ductile failure law by using inverse simulation, reducing the prediction error of segmentation frequency from more than 100% to an average error lower than 10%.

Modelling and Simulation of Mechanical Loads and Residual Stresses in Deep Rolling at Elevated Temperature

Based on the concept of Process Signatures, the deep rolling process is analyzed, aiming at functional relationships between material modifications and internal material loads during the process. The focus of this work is to investigate the influence of the workpiece temperature on the generated residual stress components. For this purpose, extensive finite element simulations of deep rolling were conducted, taking into account the effect of neighboring tool paths on the internal material loads and residual stress. A kinematic strain hardening model was parameterized and utilized and the simulations were validated experimentally. Simulated residual stresses agree qualitatively well with measurements and show a strong influence of the workpiece temperature as expected. Process Signature Components were generated, taking into account the maximal and minimal residual stress as well as their respective positions beneath the workpiece surface.

A Review of the Boiling Curve with Reference to Steel Quenching

This review presents an analysis and discussion about heat transfer phenomena during quenching solid steel from high temperatures. It is shown a description of the boiling curve and the most used methods to characterize heat transfer when using liquid quenchants. The present work points out and criticizes important aspects that are frequently poorly attended in the technical literature about determination and use of the boiling curve and/or the respective heat transfer coefficient for modeling solid phase transformations in metals. Points to review include: effect of initial workpiece temperature on the boiling curve, fluid velocity specification to correlate with heat flux, and the importance of coupling between heat conduction in the workpiece and convection boiling to determine the wall heat flux. Finally, research opportunities in this field are suggested to improve current knowledge and extend quenching modeling accuracy to complex workpieces.

Modeling and Analysis of Temperature Compensation for Multi-temperature Zone Sintering Furnace Temperature Sensing

The surface temperature of workpieces in a multi-temperature zone sintering furnace is an important parameter to characterize the performances of a multi-temperature zone system. Due to the practical structural properties of the sintering furnace, however, the conventional way of temperature measurement cannot detect the exact surface temperature of the workpieces directly, making it difficult to control the multi-temperature zone system performances precisely. To address such an issue, this paper proposes, for the first time to the best of our knowledge, a temperature compensation algorithm based soft-measurement technique to compensate for the temperature of the measuring points. Specifically, we analyze the heat-transfer mechanism within the electric heating surface and the workpiece surface and establish a mathematical model for it first, and then calculate the radiative heat transfer coefficient between the diffuse gray surface within sintering furnace using the discrete radiation heat transfer method. Finally, the heat transfer mechanism based soft measurement technique is proposed and applied to compensate for the temperature. Both simulations and experiments with a practical sintering furnace are conducted to verify the correctness and effectiveness of the proposed temperature compensation algorithm in different cases. Results show that the proposed algorithm could help maintain the temperature difference within a range limit of ±5°, which is much better as compared with the conventional temperature measurement methods.

Automatic Temperature Measurement and Monitoring System for Milling Process of AA6041 Aluminum Aloy using MLX90614 Infrared Thermometer Sensor with Arduino

Manufacturing process of metal part requires real-time temperature monitoring capability to ensure high surface integrity is upheld throughout the machining process. A smart temperature measurement and monitoring system for manufacturing process of metal parts is necessary to meet quality and productivity requirements. A smart temperature measurement can be applied in machining processes of conventional, non-conventional and computer numerical control (CNC) machines. Currently, an infrared fusion based thermometer Fluke Ti400 was employed for temperature measurement in a machining process. However, measured temperature in the form of data list with adjustable time range setting is not automatically linked to the computer for continuous monitoring and data analysis purposes. For this reason, a smart temperature measurement system was developed for a CNC milling operation on aluminum alloy (AA6041) using a MLX90614 infrared thermometer sensor operated by Arduino. The system enables data linkages with the computer because MLX90614 is compatible and linked to Microsoft Exel via the Arduino. This paper presents a work-study on the performance of this Arduino based temperature measurement system for dry milling process application. Here, the Arduino based temperature measurement system captured the workpiece temperature during machining of Aluminum Alloy (AA6041) and data were compared with the Fluke Ti400 infrared thermometer. Measurement results from both devices showed similar accuracy level with a deviation of ± 2 oC. Hence, a smart temperature measurement system was succeesfully developed expanding the scopes of current system setup.

A Study on the Effects of Temperature, Punch Radius and Punch Stroke on Forming Force When Bending SS400 Steel Plate

Sheet metal forming process is a basic deformation method in the mechanical field. In particular, bending deformation processing is a universal processing method which is widely used to form sheet metal parts such as aviation industry, shipbuilding, automotive and so on. During sheet metal bending process, the forming force is a very important output parameter that needs to be determined to ensure the load capacity of a machining equipment. This forming force magnitude will vary according to machining conditions, Geometric shapes of products, sheet materials, etc. This study examines the influence of technological and geometric parameters such as: work-piece temperature, punch speed and sheet thickness to bending force when forming V-shape of SS400 sheet material.

A 3D analytical thermal model in grinding considering a periodic heat source under dry and wet conditions

Predicting the temperature distribution in the workpiece is of high importance to control and prevent thermally induced damages in grinding. Grinding force has an oscillating nature because of the discrete grit-workpiece interaction. The force fluctuation is more pronounced in macro level when the wheel vibrates due to run out or when segmented, grooved or pattern wheels are utilized. These fluctuations cause a discontinuous or a time-dependent heat source. In this study, the dynamic part of the heat source is included in an analytical thermal model as a new approach to understand detailed workpiece temperature behavior in grinding. Furthermore, heat convection from side surfaces of the workpiece was not included in previous analytical models and is formulated and discussed in this study for the first time. By considering proper boundary conditions an analytical solution for the workpiece temperature distribution by using the periodic heat source concept is proposed. The influential parameters are discussed theoretically, and it is shown that the heat source fluctuations cause an increase in maximum temperature compared to the case with a constant heat source. Furthermore, it is shown that the 2D solution is quite reliable and precise enough to predict the maximum temperature of the slab workpiece having a long width in both wet and dry conditions. Grinding experiments have been carried out to validate the model accuracy by embedding foil thermocouples in a split workpiece setup while using CBN electroplated and aluminum oxide wheels. Validation of discontinuous heat source model was investigated while the wheels have some run out. The effects of grinding conditions on the maximum temperature have been obtained experimentally and compared with the proposed model. The results show that considering a time-dependent heat source not only explains and predicts the cyclic nature of temperature but also improves the prediction of workpiece temperature accuracy.

Thermal and technological aspects of double face grinding of C45 carbon steel

In grinding, the contact zone temperature is a decisive factor influencing the achievable surface quality and the grinding tool wear. In contrast to other grinding processes, only few information regarding double face grinding with planetary kinematics when processing steel is known up to date. Since the successive substitution of industrial double-sided lapping processes by double-sided grinding, it has become necessary to the conducted research in order to provide deeper understanding of the process and factors that influence it. To determine the workpiece temperature during grinding of C45 components, silicon temperature sensors were integrated into the workpiece holders and technological investigations were carried out. The influences and interactions of the mean cutting speed, cooling lubricant flow rate and cutting ability of the grinding wheels on the resulting workpiece temperature were analysed. Subsequently, modelling enabled an empirical estimation of the resulting workpiece temperature for processes in the investigated test area. With regard to the design and optimization of processes for machining plane-parallel workpiece surfaces, this model is a helpful tool for avoiding thermally induced workpiece damage and reduction of tool wear. Furthermore, the method can be used to conduct further examinations on the grinding process and to reduce the amount of cooling lubricant used, to improve life cycle assessment.

Development of Thermo Mechanical Model for Prediction of Temperature Diffusion in Different FSW Tool Pin Geometries During Joining of AZ80A Mg Alloys

Heat generated during the friction stir welding (FSW) process is of complex nature and plays a vital role in influencing the quality of the fabricated joints. In this experimental research, an thermo mechanical process model was formulated to estimate the values of peak temperatures generated during the employment of FSW tools with four different pin geometries (namely cylindrical, taper cylindrical, square and triangle) for joining of AZ80A Mg alloy flat plates, to understand their significant role in influencing the size of the grains, their mechanical strength and in the quality of the joints. The peak temperature values of the formulated thermo mechanical process model are found to be consistent with that of the actual experimental results and exhibited relatively very small variation It was observed that the joints fabricated by taper cylindrical pin geometry was found to possess very fine sized grains, due to the generation of ideal peak temperature (i.e., 348 °C which is nearly 81–82% of the melting temperature of AZ80A Workpiece).

Advances in the understanding of the annular laser beam wire cladding process

This paper experimentally studies the influence of conventional process parameters (laser beam power, P, workpiece, and wire feeding velocities), and the nominal workpiece irradiation proportion WIPN parameter, on ALB-WC process stability and generated clad geometry. The study was based on an extensive set of single clad experiments using stainless steel AISI 316L wire of 0.6 mm diameter and a stainless steel AISI 304 workpiece. The results show that the laser beam power required for a stable process increases non-linearly with WIPN, and this relationship can be described by quadratic regression. An increase in either the workpiece or wire feeding velocity respectively causes a reduction or enlargement of the stability region in the P-WIPN stability diagrams. The influences on stability diagrams are explained by means of the increase in the nominal WIPN to the effective WIPE, as a result of the clad height generated. With respect to clad geometry, it was shown that an increase in the WIPN causes a decrease in the dilution ratio, which is linearly correlated with the workpiece and melt pool temperatures, while clad width and height are not influenced by the WIPN. The paper further explains the complex influences of the process parameters observed on process stability and generated clad geometry using a phenomenological description of the ALB-WC process at a low and high nominal WIPN. For this purpose, heat transfer, Marangoni flow, and laser beam reflections are considered qualitatively and supported by IR and visual images of the wire-end and melt pool as well as the workpiece and melt pool temperatures.

Friction - wear modeling in drilling process of H-13 tool steel

Simulation of metal cutting is complex both from numerical and physical perspective. The scope of this work is to elaborate on the process and physics of metal cutting, and more specifically drilling. The description of H-13 steel dry drilling with the use of a single-layer TiN coated carbide twist drill is presented. H-13 is a high strength alloy steel used in demanding applications and elevated temperatures. A simulation model was developed with use of Deform-3D software, and an experiment was conducted in order to evaluate the acquired simulation results, meaning the wear mechanisms and thermal loads implemented during the process of drilling. The Usui wear model was used for the calculation of the wear rate of the drill. Regarding the experiment, a thermal camera was used in order to record the temperature of the drill after the process. The comparative analysis of the simulation models and the experiment showed that adhesion is the dominant wear mechanism. Higher wear values were observed in the rake faces of the drill, where the coating starts to fade, due to built-up edges (BUE). The tool and workpiece temperatures reach near steady state conditions during process. Elevated temperatures are applied on the removed material. Good chip evacuation and chip length indicate that coated drills with optimized geometry are suitable for drilling tough materials.

Machining mechanism and deformation behavior of high-entropy alloy under elliptical vibration cutting

Molecular dynamics (MD) simulation is applied to investigate the mechanical response of AlCrCuFeNi high-entropy alloy (HEA) under the conventional cutting and ultrasonic elliptical vibration-assisted cutting (UEVAC). The influences of vibration frequency, amplitude ratio, and phase angle on the material removal mechanism are investigated. The results show that the strain and stress are concentrated on the contact area between the workpiece and cutting tool, as well as at the grain boundaries in both cutting methods. The temperature of workpiece under the UEVAC is significantly larger than the conventional cutting, which can have a positive impact on the phase transformation and makes UEVAC easier. The analysis of structure and dislocation exposes that the deformation behavior of polycrystalline is strongly influenced by the grain boundaries, the evolution of stacking fault and dislocation is obstructed by the grain boundaries. Moreover, the average cutting force of the UEVAC is reduced as rising the vibration frequency and amplitude ratio, while the average force under the UEVAC with various phase angles has no significant difference. The number of chip atoms shows that the material removal rate is greater under the UEVAC with a larger vibration frequency, lower amplitude ratio and phase angle. The plastic deformation of chip becomes more serious under the UEVAC with a vibration frequency of 150 GHz, amplitude ratio of 4, and phase angle of 75° due to the smallest cutting ratio.

Experimental evaluation of eco-friendly hybrid cooling methods in slot milling of titanium alloy

Abstract The positive effects of cutting fluids on the machinability performance are well known in machining industry. However, it is also known that their use causes environmental and health problems. Moreover, manufacturers are faced with strict environmental regulations in order to employ dry machining, which is not efficient especially in machining of difficult-to-cut materials such as titanium alloys. Therefore, machining industry developed alternative green machining solutions such as minimum quantity of lubrication, vegetable based cutting fluids, cryogenics and hybrid cooling (combination of cryogenics and minimum quantity of lubrication). Up to now, no work has been documented in the literature on comparison of cryogenics and hybrid cooling with minimum quantity of lubrication. Furthermore, as no information regarding the effects of hybrid cooling on workpiece temperatures during milling of titanium alloy is available, this research aims to demonstrate the feasibility of implementing cryogenics and hybrid cooling method in slot milling of titanium alloy. Thus, the aim of this experimental study was to determine the machining performance of titanium alloy under various green lubricating/cooling methods. In order to do so, minimum quantity of lubrication, cryogenic cooling by spraying liquid nitrogen, cryogenic cooling by spraying carbon dioxide, simultaneous spraying of carbon dioxide and minimum quantity of lubrication, and simultaneous spraying of liquid nitrogen and minimum quantity of lubrication were applied during slot milling process under different cutting speeds. The performance of these methods was evaluated by measuring tool wear, temperature, cutting forces and surface roughness. The results showed that the efficiency of cryogenic cooling was based on the cutting speed where better results were obtained at higher speeds. It was also concluded that the simultaneous spray of cryogenic fluid and minimum quantity of lubrication improved the machinability of titanium alloy as compared to only spray of cryogenics because of both lubricating and cooling effects. In terms of environmental impact of machining operations, hybrid cryogenic methods offer an efficient solution to improve the process sustainability towards cleaner production since the coolant volume is reduced substantially compared to conventional cooling methods decreasing pollutants, and lung and skin diseases experienced by the workers in production facilities. Results showed that the combination of cryogenic and minimum quantity lubrication method provided a balance between productivity and environment. Hybrid method improved the productivity of milling process in terms of cutting speed, tool life, and cost while increasing environmental protection and operator health and reducing material waste.

Quality Can Improve as Productivity Increases: Machining as Proof

Increasing productivity is a crucial task, especially during a crisis when a shortage of products occurs. In addition, a major concern related to higher productivity is the loss of quality that may result in an even worse situation than when there is no product. However, this general common sense is not always true. Beyond their roles during a crisis, quality and productivity are key players after the crisis for competitive advantages and economic recovery. It was initially thought that quality and productivity are opposite to each other and need to be compromised. Once an economic crisis occurred in the 1970s, a novel perspective on the quality–productivity relationship was proposed and played a prominent role in the recovery from that crisis. Researchers such as Deming proposed that productivity can in fact increase as quality increases. This perspective helped people in that crisis and has so far been continually explored in industry and academia. Now, herein, we propose a new perspective that is the reverse of the aforementioned perspective and has its own benefits. We examine it in machining that is a process used in almost all industrial activities. We consider the cutting speed as a productivity (and throughput) measure and the workpiece temperature as a quality metric. We show that why the workpiece temperature may decrease at higher cutting speeds. From various experimental data in the literature, we also realize that the behavior of the workpiece temperature versus the cutting speed is steeper before the peak than that after the peak. We analytically try to explain this observation as well. Then, we analyze our general perspective from three aspects. First, we propose and implement a volume partition analysis. Second, we introduce a new dimension in Taguchi’s view of quality. Third, we introduce the circuit model in the realm of quality and productivity, based on which we develop the mutual interactions between quality and productivity. The proposed perspective in this study is expected to be a helpful mindset change in manufacturing both during and after the COVID-19 crisis.

Multi-objective parameter optimisation to improve machining performance on deep drilling process

Cutting parameters and factors should be selected wisely to increase the quality of a product. Therefore, the optimisation of the deep drilling process was investigated by utilising the Taguchi method on three materials by three different tools. The influences of cutting speed and workpiece temperature are investigated on machining power, surface roughness and tool wear. The results revealed that the application of preheating could provide lower power consumption and a relatively good finished surface. In continuation, analysis of variance demonstrated that all factors are effective, but the workpiece material and speed are the most influential parameters on surface roughness and power consumption, respectively. Workpiece material influenced about 72.24% on machining performance, and its effect was more than tool material (3.64%). For machining power, the effect of speed (55.41%) was higher than others. The preheating and lower speeds reduced tool wear of titanium coated and cobalt coated drills.

3D-Modeling of Hard Turning using Self-Propelled Rotary Tools

This study proposed a three-dimensional finite element (FE) model to simulate hard turning using self-propelled rotary cutting tools (SPRT). A complete tool geometry of the round cutting insert is considered to assess the self-cooling effect of the SPRT while machining hardened steel. A portion of the workpiece is considered according to the cutting parameters and the general contact algorithm has been employed to simulate cutting. Chip formation phase is carried out by coupled temperature displacement analysis using actual boundary conditions according to the experimental setup. The model is able to predict various performance measures like cutting forces, tool and workpiece temperatures, chip morphology and stresses on the workpiece. The model predictions are compared with the published experimental results on hard turning and a close agreement has been found. In addition, models with different feed rates are developed and its effects on cutting forces, chip morphology, stress and temperature distributions have been discussed.

Multi response optimization of nozzle process parameters in MQL assisted face milling of AISI 52,100 alloy steel using TGRA

Abstract The demand for near dry machining increases due to the adverse effect of cutting fluid on health and the environment. MQL technique offers itself as a suitable alternative for cooling and lubrication at the cutting zone during machining. In MQL mixture of a very low quantity of lubricant and compressed air is sprayed at the cutting area. Economic factor also makes it desirable as it reduces the cutting fluid cost. In this paper, the effect of MQL parameters on surface roughness and temperature during face milling of AISI 52,100 alloy steel is studied. The MQL nozzle parameters, the nozzle elevation angle, and the spray distance were selected as a process variable. A full factorial design was used to conduct the experimentations on a vertical machining center; the analysis was done by using the Analysis of variance (ANOVA) approach. A higher value of grey relational grade gives the best combination of MQL parameters for both output responses (surface roughness and temperature). The result shows that the nozzle elevation angle at 450 and a spray distance of 40 mm was the optimum process variable for both the excellent surface finish of the work piece and low temperature at the cutting zone.