Milling Temperature Research Articles

Experiment and simulation on the high-speed milling mechanism of aluminum alloy 7050-T7451

This study aims to investigate how milling parameters and tool geometric parameters affect the milling mechanism of aluminum alloy 7050-T7451. A two-dimensional high-speed milling model of aluminum alloy 7050-T7451 is established based on Advantedge; the effects of milling parameters (milling speed, cutting depth) and tool geometric parameters (tool rake angle, tool blunt radius) on milling force and milling temperature are identified through single factor experiment. The results show that as milling speed increases, Fx first reduces and then increases, whereas Fy first increases and then reduces; milling temperature first increases and then gradually reduces after a given speed is reached, but the overall change is modest. Milling depth is positively correlated to milling force and milling temperature. As tool rake angle increases, both milling force and milling temperature reduce. Tool blunt radius is positively correlated to Fx and Fy and makes no difference to milling temperature.

Investigation on influence of hybrid nozzle of CryoMQL on tool wear, cutting force, and cutting temperature in milling of titanium alloys

The titanium alloy has a low thermal conductivity of 1/8th that of common metals and half that of stainless steel. The heat dissipation is poor during dry cutting, so the cutting temperature rises above about 600°C. Due to this, the quality of the cutting surface decreases during machining, and rapid tool wear occurs. To solve this, the use of cutting fluid is essential, but the chemical composition of the cutting fluid has a negative effect on the body and the environment. In the current cutting process, in order to minimize this effect, eco-friendly processing using minimum quantity lubrication (MQL) is performed. The machining method using both MQL and a cryogenic gas separately applies the MQL and the cryogenic gas to both sides of the cutting tool. In this case, the oil mist cannot penetrate the cutting zone due to the spray pressure of the cryogenic gas. Therefore, it is necessary to design a hybrid nozzle that can spray oil mist and cryogenic gas into a single flow. Besides, although the study on the effect of MQL and cryogenic machining on the cutting temperature should be preceded, most of the titanium MQL processing papers only study the material surface and tool wear. Accordingly, in this study, we designed and fabricated the hybrid type nozzle of CryoMQL which combined MQL and a cryogenic gas to improve the spraying concentration. And the cutting temperature generated by the process was measured, and the effectiveness of the proposed nozzle on decreasing the cutting temperature was evaluated. Besides, cutting force and tool wear were analyzed according to each cutting method.

Nickel-Based Alloy Dry Milling Process Induced Material Softening Effect.

Improving the cutting efficiency is the major factor for improving the processing of nickel-based alloys. The novelty of this research is the calibrated SiAlON ceramic tool dry milling nickel-based alloy process. Firstly, the nickel-based alloy dry milling process was analyzed through the finite element method, and the required milling force and temperature were deduced. Then, several dry milling experiments were conducted with the milling temperature, and the milling force was monitored. The change in cutting speeds was from 400 m/min to 700 m/min. Experimental results verified the reduction of the dry milling force hypothesized by the simulation. The experiment also indicated that with a cut depth of 0.3 mm, cut width of 6 mm, and feed per tooth of 0.03 mm/z, when milling speed exceeded 527.52 m/min, the milling force began to decrease, and the milling temperature exceeded the nickel-based alloy softening temperature. This indicated that easy cutting could be realized under high-speed dry milling conditions. The interpolation curve about average temperature and average milling forces showed similarity to the tensile strength reduction with the rise of temperature.

Lightweight AlCuFeMnMgTi High Entropy Alloy with High Strength-to-Density Ratio Processed by Powder Metallurgy

In this study, we synthesized a new Al16.6Cu16.6Fe16.6Mn16.6Mg16.6Ti16.6 lightweight high entropy alloy (LWHEA) by high energy ball milling and spark plasma sintering (SPS). The effect of milling time (15, 30, 45, and 60 h) and SPS conditions (600 and 700 °C) on microstructure, hardness, and density of LWHEAs were studied. The results showed that milled LWHEA is base centered cubic (BCC) structured, consisting of dual BCC1/BCC2 matrix with dispersed minor Cu2Mg precipitates and Ti. After SPS of milled samples, the BCC2 phase fraction was increased gradually. The distribution of Ti was uniform up to 45 h milled sample SPSed at 600 °C. However, porosity was built up beyond 45 h milling and higher SPS temperature (700 °C). The presence of finer secondary phases in the HEA matrix contributes to the dispersion hardening. The optimum microhardness and density of LWHEA AlCuFeMnMgTi were around 770 HV and 4.34 g cm− 3 which is superior to other conventional alloys such as Al or Ti-based alloys.

Experimental Research on Milling Temperature of New Cold Saw Blade Milling Cutter

Based on the orthogonal test method and comparative study, the effects of workpiece material, workpiece diameter, milling cutter rotational speed and feed per tooth on milling temperature are investigated when cutting metal bars with new cold saw blade milling cutter. Then this paper reveals the change rule of new cold saw blade milling cutter milling temperature and the essential difference from the traditional hot saw blade milling cutter. Construction of sawing metal bar experiment system at production site, four-factor and three-level orthogonal test method is used to cut 45 steel, 40Cr and Q235B metal materials. The influence curves of workpiece material, workpiece diameter, milling cutter rotational speed and feed per tooth on milling temperature are obtained. By normalizing the experimental data, this paper uses the multiple linear regression method to fit the mathematical model of milling temperature. According to simulation analysis and experimental research, the milling temperature change rule of new cold saw blade milling cutter is obtained. Compared with the traditional hot saw blade milling cutter, the results show that under the same or similar conditions, the highest milling temperature center of new cold saw blade milling cutter is located at the bottom of the chip at a certain distance from the tip and the interface of the corresponding cutting layer adjacent to the bottom layer of the chip. The maximum milling temperature is around 300 °C, which is about 175 °C lower than the maximum milling temperature of traditional hot saw blade milling cutter. Further, it demonstrates that most of the heat generated by cold sawing is discharged from the cutting area along with chips, which keeps the milling cutter and workpiece at a relatively low temperature.

Syntheses of alkali-metal carbazolides for hydrogen storage

Metalorganic hydrides are a new class of hydrogen storage materials. Replacing the H of N–H or O–H functional groups using metal hydrides have been recently reported, which substantially improved the dehydrogenation properties of heteroaromatic organic hydrides by lowering their enthalpies of dehydrogenation (ΔHd), enabling dehydrogenation at much lower temperatures. Among the reported metalorganic hydrides, lithium carbazolide and sodium carbazolide appear to be the most attractive hydrogen storage/delivery material owing to its high hydrogen capacity (>6.0 wt%) and ideal ΔHd. Nevertheless, the interaction of carbazole and corresponding metal hydride to form metallo-carbazolide is a multistep process involving intensive ball milling and high temperature treatment, where the interaction was not investigated in detail. In this paper, both alkali metal hydrides and amides were employed to react with carbazole to synthesize corresponding carbazolides, aiming to broaden and optimize the synthetic method and understand the reaction mechanism. Our experimental results showed that around one equivalent of H2 or NH3 could be released from the reactions of carbazole and corresponding hydrides or amides, respectively. Instrumental spectroscopic analyses proved that metallo-carbazolides were successfully synthesized from all precursors. It is found that the alkali metal amides (i.e., LiNH2 and NaNH2) with stronger Lewis basicities as metal precursors could synthesize the metallo-carbazolides under milder conditions. Furthermore, quasi in situ nuclear magnetic resonance results revealed that alkali metal could replace H (H–N) gradually, donating more electrons to carbazole ring. Additionally, the solubilized alkali cation may unselectively interact with π-electron of aromatic systems of both carbazole molecules and carbazolide anions via electrostatic cation-π interactions.

Relationships between grain physicochemical characteristics and flour particle size distribution for Taiwan rice cultivars

Fourteen cultivars of rice, 5 indica, 6 japonica and 3 waxy types were used to investigate the relationship between grain physicochemical characteristics and particle size distributions of rice flour. The data showed that particle size index (PSI) negatively correlated with the resistance time (RT) and milling temperature of Stenvert hardness test, damaged starch of rice flour, and percentage retained on 60 mesh (> 60 mesh %) (p < 0.05), but positively correlated with percentage that passed through 60 mesh and retained on 100 mesh (60-100 mesh %) (p < 0.05). From principal component analysis (PCA), the first and the second principal components, describing 56.14 and 21.44% of the variance of rice samples, respectively. The first principal component highly correlated with variables including RT, > 60 mesh %, milling temperature of Stenvert hardness test and damaged starch of rice flour, but negatively correlated with hardness index of Brabender micro-hardness test (BMHT), 60-100 mesh % and PSI. The second principal component positively correlated with ash and fat contents, but negatively correlated with shape and thousand-kernel weight (TKW) of rice grains. The effect of protein content was intermediate between the first and second principal component. Based on the results of PCA, the rice grain physical characteristics (i.e., RT and BMHT) are major factors, followed by chemical compositions, affecting the rice flour particle size distributions.

Temperature prediction of ultrasonic vibration-assisted milling

Machining temperature is a key factor in ultrasonic vibration-assisted milling as it can significantly influence tool wear rate and residual thermal stresses. In current study, a physics-based analytical predictive model on machining temperature in ultrasonic vibration-assisted milling is proposed, without resorting to iterative numerical simulations. As the tool periodically loses contact with the workpiece under vibration, three types of tool-workpiece separation criteria are first examined based on the tool trajectory under ultrasonic vibration. Type I criterion examines whether the relative velocity between tool and workpiece in cutting direction is opposite to the tool rotation direction. Type II criterion examines whether the instantaneous vibration displacement in radial direction is larger than instantaneous uncut chip thickness. Type III criterion examines whether there is overlap between current and previous tool paths due to vibration. If no contact, the instantaneous temperature rise is zero. Otherwise, the temperature rise is predicted under shearing heat source in shear zone and secondary rubbing heat source along machined surface. A mirror heat source method is applied to predict temperature rise, considering oblique band heat sources moving in a semi-infinite medium. The proposed predictive temperature model in ultrasonic vibration-assisted milling is validated through comparison to experimental measurements on Al 6063 alloy. The proposed predictive model is able to match the measured temperature with high accuracy of 1.85% average error and 5.22% largest error among all cases. Sensitivity analysis is also conducted to study the influences of cutting and vibration parameters on temperature. The proposed model is valuable in terms of providing an accurate and reliable reference for the prediction of temperature in ultrasonic vibration-assisted milling.

Support vector regression and genetic-algorithm-based multiobjective optimization of mesoscopic geometric characteristic parameters of ball-end milling tool

The poor machinability of titanium alloys results in the serious wear of the rake face of a ball-end milling tool. Previous studies indicated that the mesoscopic geometric characteristics of the tool can effectively improve the wear resistance. Therefore, in this thesis, a milling force model and a milling temperature model of a ball-end milling tool were established to verify the effect of the blunt and negative chamfer tool edges. Setting up a test platform for milling titanium alloy, the influence of mesoscopic geometric characteristic parameters on cutting performance of the ball-end milling tool was analyzed. In addition, based on the support vector regression and genetic algorithm, the optimal mesoscopic geometric characteristic parameters were obtained, which were under the four evaluation indices, such as mechanical–thermal characteristics, tool wear, and surface quality of the workpiece. It was verified experimentally that the tool life of the optimized micro-textured tools with the blunt and chamfer tool edges were improved by 33% and 25%, respectively, and the surface roughness was reduced by 26% and 23%, respectively, which were compared to the non-optimized tools. This thesis provides a reference for improving the processing efficiency and the quality of titanium alloys.

Mechanisms of mechanochemical synthesis of cesium lead halides: pathways toward stabilization of α-CsPbI3

Cesium lead iodide with cubic perovskite structure (α-CsPbI3) is gaining significant interest in photovoltaic applications due to its excellent absorbance of the visible solar light and other attractive optoelectronic properties. However, the synthesis of stable α-CsPbI3 poses a significant challenge. Mechanochemical synthesis is emerging as a suitable method for the preparation of cesium lead halides. This work investigates the ball milling-induced synthesis of cesium lead halides perovskite phase using halide mixing or doping approaches. The synthesis in the CsI + PbI2, CsBr + PbBr2, CsBr + PbI2, and CsI + PbI2 + NdI3 mixtures and halide exchange reactions in the CsPbBr3 + 3KI and CsBr + PbBr2 + 3KI systems are investigated to elucidate the mechanism of this process. Then, CsPb(I1−xBrx)3 and CsPb(1−y)NdyI3 materials with different x and y ratios are prepared, and their stability is probed in the air using light absorption spectroscopy. These results suggest that Nd doping is more efficient in the stabilization of the perovskite structure than partial replacement of iodine with bromine. Microstructure observations reveal the existence of two different product formation mechanisms depending on the mechanical properties of reactants. The results reveal that the milling temperature has a significant impact on the reaction kinetics. The produced particles nucleate and grow at the reactant interface and retard the synthesis reaction by creating a diffusion barrier. Extended milling reduces the product particle size and creates fresh contact between reactants, thus facilitating reaction completion.

An Analytical Approach to Cutter Edge Temperature Prediction in Milling and Its Application to Trochoidal Milling

Cutter edge temperature in milling is an important factor to cutter life. With high cutting speed and feedrate, the cutting efficiency is high; however, the cutter edge temperature is high, shortening the cutter life. Therefore, it is necessary to know the cutter edge temperature in milling. Unfortunately, the cutter edge temperature is difficult to measure and predict in milling. To address the technical challenge, an analytical approach was proposed to predict cutter edge temperature in milling. First, the heat flux into the cutter edge was calculated. Second, by using the Green function, the cutter edge temperature was figured out, and the results obtained from this approach agreed well with that of a recognized test. Then, based on the engagement between the cutter and workpiece in trochoidal milling, the cutter edge temperature was obtained in trochoidal milling. Finally, a temperature comparison was made between trochoidal and side milling based on this analytical approach, and the reasons that trochoidal machining could extend the cutter life were found. This approach is first proposed to calculate the cutter edge temperature in trochoidal milling and can be applied to machining parameters optimization in trochoidal milling and cutter design optimization.

Microstructure and its effect on mechanical and thermal properties of Al-based Gd2O3 MMCs used as shielding materials in spent fuel storage

In this study, novel Al-based Gd2O3 metal matrix composites were designed and synthesized using powder metallurgy to overcome the shortcomings of common neutron absorbers used as shielding materials in spent fuel storage. With an increase in the ball-milling time, the size of powder particles was gradually refined to nanometer scale. Meanwhile, monoclinic Gd2O3 was induced by collision pressure and, according to dynamic analysis, the solid solution was inconspicuous. Al3Gd and Gd3Al5O12 were formed during ball-milling, which was further accelerated during sintering because thermodynamics analysis indicated that the reaction was endothermic. The microstructures of powder mixtures and sintered bulks were seen. Particles of various shapes were found to be dispersed in the bulk matrix; their shapes and sizes varied with milling time, sintering time and temperature, and concentration of Gd2O3. With the increase in sintering temperature and time, the number of porosities and nanoparticles were found to decrease, whereas the sizes of the particles increased. The microhardness of the samples prepared under various conditions was measured, and its relationship with the microstructure was analyzed. It was found that microhardness was positively correlated with the areas of the particles, whereas it was negatively correlated with their sizes. Further, the thermal parameters of the sintered bulks were also measured and the effect of their microstructure and components was analyzed.

Study on Milling Temperature of Titanium Alloy with Micro-Textured Ball End Milling Cutter under Radius of Blunt Edge

A high temperature is produced in the process of precision milling of titanium alloy, and the cutting temperature can be effectively reduced by placing a micro-texture on the tool surface. In order to study the milling temperature of micro-textured ball-end milling cutter in milling titanium alloy under the combined action of a blunt radius with different edges and a micro-texture with different parameters, a new method based on micro-element theory and the generation and transmission of cutting heat has been established. At the same time, the influence of different radii of blunt edges on the milling temperature is simulated by the finite element method and experimentally verified to explore the influence of different radii of a blunt edge and micro-texture parameters on the milling temperature. Taking the milling temperature as the evaluation index, the optimum parameters of micro-circular pit texture are as follows: the diameter of micro-circular pit is 40 micron, pit spacing is 225 micron, distance from cutting edge is 100 microns, and radius of the blunt edge is 60 microns.

Facile fabrication of Si/Sb/Sb2O3/G@C composite electrodes for high-performance Li-ion batteries

Facile fabrication of high-performance Si/Sb/Sb2O3/G@C composite materialviathe ball milling and high temperature calcination process is reported.

High ionic conductivity in CeO2 SOFC solid electrolytes; effect of Dy doping on their electrical properties

Ionic conductors composed of lanthanide-doped ceria with general formula DyyCe1-yO2-δ (y = 0.05, 0.1 and 0.15) were synthesized by mechanochemistry (mechanical milling), and their electrical properties analyzed to be used as solid electrolytes in low-temperature SOFC. Starting oxide reagents were milled at different times in a planetary mill and the evolution of their structures and phases with milling time and temperature (up to 1500 °C) was followed by XRD. Just milled powders were also uniaxially pressed and sintered at different temperatures (1200, 1350 and 1500 °C), and analyzed by FE-SEM, to explore their morphologies as a function of temperature and Dy content. The electrical properties of these materials and undoped commercial CeO2 were analyzed by impedance spectroscopy at different temperatures (200–650 °C) and frequencies (100 Hz - 1 MHz). Results showed that mechanochemistry is a suitable method to obtain the DyyCe1-yO2-δ systems after 20 h of milling, since XRD patterns of these milled powders reveal the formation of fluorite-type cubic solid solutions for all studied compositions. Increasing of temperature generates a higher crystallinity in these materials while the absence of phase transitions in them is corroborated at 1200 °C. Analysis of electrical properties of samples sintered a 1200 °C corroborates the viability of these systems to be used as solid electrolytes in the SOFC technology, being that high dc conductivities (σdc) were obtained for all doped samples, especially for the composition Dy0.1Ce0·9O2-δ, which showed a σdc = 1 × 10−1.91 S cm−1 at 650 °C. This value represents an increase of almost three orders of magnitude for this composition with respect to the undoped CeO2 sample (y = 0, σdc = 1 × 10 −4.83 Scm−1).

Finite element analysis of ultrasonic assisted milling of SiCp/Al composites

SiCp/Al composites have a poor machinability due to the inclusion of the SiC hard particles. Ultrasonic vibration-assisted processing technology has great advantages in processing hard and brittle materials; however, the process of rupture of particles cannot be effectively observed during the test processing, and a large number of tests increase the cost of the test. Using ABAQUS finite element software, a two-dimensional simulation model of single particle, multi-particle, and homogeneous materials was established to investigate the particle rupture process and the temperature variation during the processing of high volume SiCp/Al composites under different processing parameters. The results show that the application of ultrasound improved the particle rupture effect. Furthermore, an appropriate ultrasonic amplitude inhibited the particle breakage and slowed the crack growth. A smoother particle breaking phenomena was observed with the application of a higher frequency. The temperature of ultrasonic assisted milling was found to be lower than that of traditional milling. The conclusions of the milling test were basically consistent with the simulation results, which prove the correctness and feasibility of the simulation results.

Effect of Rolling and Coiling Temperatures on Microstructure and Mechanical Properties of Medium-Carbon Pipeline Steel

Oil country tubular goods (OCTG) steels with a low yield ratio (yield strength/tensile strength) and excellent impact toughness have recently been demanded to ensure mining performance and safety. From this viewpoint, the optimization of the manufacturing conditions is important because they influence the microstructure and mechanical properties of the steels; in particular, in the case of OCTG steels with carbon contents greater than 0.2 wt%, the finishing mill temperature (FMT) and coiling temperature (CT) strongly affect the microstructure of the final products, which are generally composed of ferrite and pearlite phases. In this study, 0.39C-0.23Si-1.56Mn-0.11Cr steel plates were fabricated under various FMT and CT conditions and their yield strength, tensile strength, and impact energy were investigated. In addition, pipes with diameters of 244 and 508 mm were manufactured via an electric resistance welding method using two of these strips fabricated under two different optimized conditions [(1) FMT = 880 °C and CT = 630 °C and (2) FMT = 800 °C and CT = 690 °C] to analyze the change in mechanical properties induced by the work-hardening effect during the piping process. The results revealed that the FMT and CT are closely related to the volume fraction of the ferrite phase, the grain size and lamellar spacing of the pearlite phase, and the tensile and impact properties of the steel strips; the variations in the microstructure and mechanical properties with the FMT and CT were also discussed in detail.

A sterile self-assembled sericin hydrogel via a simple two-step process

In materials science and engineering, designed and well-ordered self-assembled hydrogel with excellent biocompatibility and nontoxic properties is an inviting issue. In this study, a novel self-assembled sericin hydrogel was prepared by a simple-two-step process containing milling and high temperature and high pressure. It is worthwhile pointing out that the sericin with high extraction rate (95%) for fabricating sericin hydrogel was isolated from fibroin-deficient mutant silk cocoons. The hydrogel was formed under a mild condition without introducing any other toxic or harmful substances and its gelling time could be controlled by sericin concentration, temperature or pH values. Moreover, as long as the sericin solution is kept in a bioclean circumstance, the sterile sericin hydrogel can be achieved and no need to sterilize. Furthermore, this hydrogel possesses high porosity, degradation. In addition, the hydrogel system is suitable as a carrier of cells or bioactive molecules contribute from its excellent cell-adhesive capability, effectively promoting cell attachment, proliferation, and a sustained manner for drug release. In summary, our study indicates that the self-assembly sericin hydrogel could be promising candidates in soft tissue engineering applications.

Effect of post-heat treatment on residual stress and tensile strength of hybrid additive and subtractive manufacturing

This paper presents a comprehensive study of the tensile performance, heat treatment, fracture, decrease of residual stress, second-phase particle and microstructures of a 316L stainless steel fabricated by directed laser deposition (DLD) and thermal milling (starting milling temperature at 250 ± 50 °C), a typical hybrid additive and subtractive manufacturing process. Experiments of different post-heat treatment temperatures and tensile tests at room temperature were performed. The residual stress was eliminated with heat treatment at 400 °C for 2 h, and the average residual stress decreased 53.7% while the yield strength and ultimate strength decreased slightly. The fracture surfaces of different heat treatment temperatures were observed. The typical ductile fracture microstructures of dimples were seen in almost all specimens whenever the heat treatment temperature was low or high. The evolution of dimples from formation to destruction by heat treatment was analyzed. The different morphology and composition of the second-phase particles of different heat treatment temperatures were compared. The yield strength of 427.5 MPa, the ultimate strength of 599.27 MPa, and the elongation of 36.48% showed the new hybrid manufacturing technology could be used for further fabrication of components.

An analysis method of cutting heat by transforming from time-varying variable to constant parameter for dry milling of TC4 curved surface

Difficult-to-machine material parts with curved surface are widely used in automobile, aviation, and aerospace fields, and the high-speed milling is the preferred processing method. In high-speed milling process of the curved surface parts, the instantaneous cutting amount is continuously changing due to the geometric feature change of the determined curve toolpath. In this way, the actual processing parameters, including cutting depth, cutting speed, and feed per tooth, are also continuously changing along the curve toolpath, which will result in a severe variation of cutting heat that has negative impact on the tool wear and the surface integrity. For TC4 which is a kind of typical difficult-to-machine material, a novel analysis method of cutting heat is proposed by transforming from time-varying variable to constant parameter for the dry milling of TC4 curved surface. As the actual processing parameters have strong correlational relationship with the instantaneous processing parameters, including instantaneous cutting area, maximum effective cutting radius, and maximum undeformed cutting thickness, the correlational relationship between the actual processing parameters and instantaneous processing parameters is established firstly. By means of fine-tuning the allowance for finish machining and regenerating the curve toolpath, the instantaneous processing parameters can be adjusted to be constant, and the transforming from time-varying variable (actual processing parameters, including cutting depth, actual cutting speed, and feed per tooth) to constant parameter (instantaneous processing parameters, including instantaneous cutting area, maximum effective cutting radius, and maximum undeformed cutting thickness) is realized. Finally, a series of milling experiments are carried out based on the regenerated curve toolpath. The results show that the cutting temperature fluctuation in curved surface milling along the regenerated curve toolpath is decreased by at least 75.81% compared with that in traditional curved surface machining, which is closer to the variation tendency of cutting temperature in plane milling. Consequently, the cutting temperature variation can be smoother by maintaining the instantaneous processing parameters constant, which is of great significance to restrain tool wear and improve surface integrity. Furthermore, the achievement provides theoretical guidance for the allowance distribution of finish machining in the dry milling of TC4 curved surface.