جستجوی مقالات مرتبط با کلیدواژه « milling » در نشریات گروه « فنی و مهندسی »

This research investigates tool wear, elemental analysis (EDAX) on the machined surface, surface roughness, microhardness and microstructural changes in the cross-section of milled 304L stainless steel samples under dry and Minimum quantity lubrication (MQL) methods. The MQL process was able to improve the surface roughness for all milling parameters from 17% to 41% compared to the corresponding dry conditions. In dry machining, defects such as built up edge, severe flank wear and tool chipping were created. In MQL mode, these defects were significantly reduced and tool chipping was almost eliminated. By increase of cutting speed and depth, the surface hardness has increased. Compared to the dry method, the MQL reduces the hardness values and hardened depth below the machined surface. According to EDAX analysis on dry and MQL machined surfaces, applying the roughest cutting parameters, it was determined that no change of chemical elements occurred on machined surfaces. Increasing cutting parameters or dry machining causes the plastic deformation to intensify, the microstructure is flattened and the microstructure grains are compressed in the vicinity of the machined surface. The maximum reduction in thickness of deformed layer in MQL compared to dry method is 39%. For each milling sample, there is a direct relationship between the hardened depth and thickness of the corresponding microstructurally deformed layer.

The present research has aimed to investigate the effect of Ti3AlC2 reinforcing MAX phase on the electromagnetic behavior of TiC matrix composites. In this case, the milling process and secondary heat treatment were used for the synthesis of the composite. The resulting structures were examined by scanning electron microscope, differential thermal analysis, and X-ray diffractometer. Electromagnetic behavior was investigated by vector network analyzer. The investigations showed that it is possible to create a TiC/Ti3AlC2 composite structure in situ after milling. Electromagnetic investigations revealed that the electromagnetic absorption behavior of TiC/Ti3AlC2 ceramic matrix composite was improved compared to the original TiC. So that the lowest reflection loss of the milled composite was equal to -19.46 dB in the frequency range of 1 to 18 GHz band. After annealing at 1400 °C, it was found that the Ti3AlC2 phase resulting from the milling process was not stable and turned into the single phase solid solution of TiCx. Electromagnetic investigations of the annealed sample showed that after removing the MAX phase, the electromagnetic absorption behavior was weakened. Thus, the lowest reflection loss of the annealed sample was equal to -9.82 dB.

Achieving the required dimensional and geometrical accuracy as well as the appearance and performance quality in the production of industrial parts and the availability of interchangeability in the assembly and supply of spare parts for products has been one of the important challenges of the industry. In this research, the effect of adding axial ultrasonic vibration to the tool on the geometric accuracy of the Al6061-T6 work piece in the milling process was investigated. By analyzing the results, it was found that the presence of axial ultrasonic vibration improves the parallelism and flatness of the wall and the smoothness of the bottom surface as well as the perpendicularity of the wall with the bottom. It was also observed that a higher feed speed increases geometric deviations and surface roughness, while a higher cutting speed reduces them. By comparing the graphs, it was found that the positive effect of ultrasonic vibrations on the quality of the surface and the geometric accuracy of the work piece is more noticeable in the conditions of lower cutting speed and higher feed; That is, the condition in which we face the worst surface quality and the lowest geometric accuracy in conventional milling.

Today, the machining and milling of composites is of great importance; Because composites are used in various sectors and have found great efficiency in various industries. Considering this, in this article, in order to save the cost of milling composites, the effectiveness of various parameters that affect the cutting force and tool wear, including spindle speed (rpm), feed rate (mm/rev), cutting depth (mm) and percentage of sic, has been discussed; To minimize tool wear and cutting force by creating optimal conditions. Performing a sensitivity analysis according to the regression equations of cutting force and tool wear has shown that spindle speed with 63% and the percentage of composite silicon carbide with 22% have the greatest effect on tool wear and depth of cut with 47% and advance with 23% have the greatest effect on cutting force.

Advances in many engineering fields depend on materials with appropriate properties. The use of metal-matrix composites is rapidly growing as a suitable alternative to conventional materials due to their strength-to-weight ratio, resistance to wear and creep, etc. Machining of metal-based composites is a difficult task due to the presence of very abrasive reinforcing particles in its based metal. Therefore, it is necessary to investigate the factors affecting these materials. In this research, a methodical study has been conducted to investigate the effect of the parameters of spindle  speed, feed rate, depth of cut and the percentage of reinforcing particles on the behavior of cutting force and tool wear using experimental design methods, modeling and statistical sensitivity analysis methods. . Detailed analysis of behaviors has been done by providing statistical regression equations and optimization by Deringer's method and E-Fast-Sensitivity Analysis. According to the obtained results, the cutting depth had the greatest effect on the machining force. Also, cutting speed with 77%, advance rate with 9% percent and cutting depth and weight percent of reinforcing particles with 7% percent are other parameters affecting tool wear in the milling process of this composite.

Today, various military, aerospace, automotive, etc. industries need materials with a high strength-to-weight ratio. The use of metal-based composite materials, especially aluminum-based composites, has increased greatly. Machining is needed to achieve high dimensional accuracy in products made with aluminum-based composites. Due to the presence of reinforcing material such as silicon carbide, machining of this type of material is difficult. Therefore, it is important to study the parameters affecting the machining of aluminum-based composites. In this study, the effect of spindle speed, feed rate, depth of cut and percentage of reinforcing particles were discussed using experimental and statistical test methods. The responses of surface roughness and material removal rate were investigated. The behavior of the input parameters on the responses of the process has been carefully investigated quantitatively and qualitatively. Answers have also been optimized. According to the obtained results, the spindle speed has the greatest effect on the surface roughness. Also, feed rate 33%, spindle speed 28%, depth of cut 26% and the percentage of reinforcing particles 13% have an effect on the chipping rate.

In this paper, the error of tool deflection in perpendicular to a milling process feed direction is investigated and novel compensation method to this error is proposed. While the end mill tool is machining, due to the existence of perpendicular disturbing force on the feed path while the endmill tool is machining, a deflection which reduces machining accuracy. If a compensation force is exerted to the middle of tool, the deflection can be reduced. By using a hydraulic actuator, the compensation force would be proportional to the disturbing machining force, in the opposite direction so that this error can be reduced. It is necessary to estimate disturbing forces and tool deflection magnitude in lateral side of machining precisely before applying the proportional force to the endmill. The first step endmill is modeled on SolidWorks and in the next step The machining operation is simulated to calculate the error causing force in which both the milling tool and the workpiece are 3D flexible. By obtaining the force results of the tool under different machining modes from Abaqus, a semi -analytical model is established on Simscape Multibody module of matlab software. By comparing Abaqus results the parameters of the lumped model are adjusted. The output force is extracted from Abaqus and put in tabular form the tool deflection is extracted from MATLAB SimScape which calculation speed is faster than the numerical model in this method. To find the compensating force, the beam theory obtains a factor of 3.2 times the machining force applied to the middle of the tool. This force is applied in open loop to the MATLAB model and the result indicates almost 70 percent reduction in the tool tip lateral deflection.

One approach for the preparation of Mg-3Zn-1Mn nanobiocomposite is powder metallurgy. After preparing the alloy by the milling process, hardening is conducted during the sintering process. The condition for obtaining high strength and corrosion resistance of as-sintered specimens is the uniform distribution of zinc and manganese elements in the magnesium matrix and the maximum particle size reduction to increase the surface area. In this research, under certain conditions, the milling process has been conducted to fabricate this nanocomposite. The result of XRD analysis exhibited that the optimal sample is obtained after 25 h milling. At this time, the grain size was 27 μm, and the crystallite size was 24 nm. Evaluation of X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and field emission scanning electron microscopy (FE-SEM) results for samples shows uniform distribution of zinc and manganese particles in the matrix of magnesium and confirms the reduction of particle size with spherical shape for nanobiocomposite specimens.

Today, Carbon fiber-reinforced polymer composites (CFRP) have extensive use in different fields such as aerospace, automotive, oil, gas, and defense industries compared to metals, due to the high ratio of strength to weight. Machining of these materials regard to their non-homogeneity structure is complicated. Due to the different thermal expansion coefficients between the fibers and resin polymer composite milling materials difficult to create one of the final parts. Achieve optimal machining conditions, with high efficiency, which need proper analysis and careful investigation. Minimizing the machining time became important Due to developments in CNC technology. One of the time minimizing methods is high-speed machining technology. In this study, composite plates made of carbon/epoxy to a thickness of 10 millimeters, which are often used in the body of Aerospace structures and missiles, have been manufactured by hand layup. The cutting parameters used during the milling operation of the CFRP panel ranged from 1000 rpm to 7000 rpm for the spindle speed, feed rate from 1000 mm/min to 3000 mm/min, and lastly 1.0 mm to 3.0 mm range for depth of cut. the combination of spindle speed, feed rate, and depth of cut are studied at five different levels. 20 runs of experiments are performed based on Response Surface Methodology (RSM). the milling process with two-flute tungsten carbide - coated diamond insert with a 20 mm diameter was performed. their surface quality after milling process is measured. So after roughness, material removal rate and required analysis were performed. Spindle speed has a greatest effect on surface roughness. In conclusion, the influence of the cutting parameters is higher spindle speed, lower feed rate, and lower depth of cut resulting in low surface roughness. The optimized cutting parameters were spindle speed, feed rate, and depth of cut of 7000 rpm, 1000 mm/min and 1 mm respectively with the surface roughness of 1.9 um.

Determination of machining forces in order to calculate the required power and torque for cutting and select the right tools, equipment, and cutting parameters (feed rate, cutting depth, cutting speed) for machining the desired geometry and material prior to the process is significant. The analysis of machining forces is necessary to determine the forces to reduce the cost of performing multiple empirical experiments. In this study, the components of, , and  milling forces with two cutting edges with main adjustment angle were predicted by the mechanistic modeling method by calculating cutting and edge force coefficients. Also, for the first time, the cutting section of the workpiece was designed in order to eliminate the calculating error of the round corner of inserts.To avoid the interaction of the parameters, simultaneous change of cutting speed with feed rate was avoided and 8 experiments with different feed rates but with the same cutting speed were performed. A comparison of the modeled forces curve with the results obtained from the dynamometer shows acceptable agreement.As the feed rate increases, the difference between the predictive and experimental force decreases relative to the increase of force.

Milling process of the thin-walled structures has broad applications in aerospace, automotive industries and etc. One of the main problems in their machining is unstable chatter vibrations, which causes not only the poor machined surface quality but also decreases the system life span and machining efficiency. So, lots of researchers are interested in investigating the dynamic behavior of the thin-walled structures during the machining processes and restrain its pernicious effects. In this regard, the main purpose of this paper is to l the effects of geometrical parameters of machining system including workpiece height, thickness, and tool overhang and its diameter on the chatter stability. To this end, first by utilizing relative transfer function concept, dynamic models of tool and workpiece were derived. Then experimental tests conducted to extract cutting force coefficients. Finally, stability lobe diagrams were constructed under impression of tool and workpiece dimensions. Results proved that by increasing tool overhang length, chatter stability decreases.

In this study, cobalt-alumina composite was prepared in-situ by mechanochemical process using cobalt oxide as a raw material in the presence of aluminum and carbon as reducing agents, for this purpose released heat from aluminothermic reaction was used in order to activate the carbothermic reaction. In this respect, milling the powder mixture of Co3O4-Al-C was done by a high energy ball milling device (fast mill) and also, the effect of different parameters such as speed, time, and ball-to-powder ratio on the final production was investigated. The milled powders were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). According to the results of XRD analysis and distribution map of elements after 12 hours of milling, the redox reaction completely occurred and as a result, the peaks corresponding to the cobalt and alumina phases appeared in the diffraction pattern. The increase in milling time from 12 to 36 resulted in a decrease in the crystallites size of the cobalt and alumina phases up to 9 and 20.3 nm, respectively. On the other hand, with an increase in the speed of 350 to 450 rpm, the particle size distribution has been uniformly and size of the agglomerates produced in the powder mixture has decreased. Also, according to SEM images, increasing the ball to powder ratio from 15:1 to 40:1 resulted in a reduction in the average particle size below 1 μm and a more uniform distribution of the alumina reinforce phase in the cobalt background.

In this research, the effect of different substitution quantities of zinc cations on electromagnetic and microwave absorption properties of Z-type barium hexaferrite with chemical composition of Ba3Co2-xZnxFe24O41 (x=0, 1.2, 1.3, 1.4, 1.5, 2) generated by high energy milling method was studied. X-ray diffraction (XRD) method was used to verify the formation of Z type Ba-hexaferrite phase in the synthesis conditions. Magnetization properties of different compositions were studied by alternative gradient force magnetometery (AGFM). X-ray diffraction (XRD) method was used to confirm the formation of Z-type Ba-hexaferrite phase. The investigations by AGFM showed that the amount of magnetization increased by substituting the desired composition. So that the amount of magnetization (67 emu/g) for an unsubstituted sample will reach its maximum (84 emu/g) for the sample with composition of . In addition, complex permeability and permittivity coefficients of the samples were studied by vector network analyzer (VNA). Using the measured coefficients, reflection loss curves were plotted. The results of the reflection loss (RL) plots showed that, on average, the maximum absorption bandwidth occurred among the samples at a frequency range of 4-8 GHz. The best absorption (the most negative reflectance loss) was observed at -47 dB and at a frequency of 7 GHz for the sample with an index of substitution of x=1.3.

Nowadays, with the advancement of materials science and the production of materials with special properties such as super alloys, composites and ceramics used in advanced industries, the use of traditional machining methods for the production of these parts is not possible. Therefore, the use of modern methods has been considered. One of these methods, which has the ability to add to traditional cutting processes, is the use of ultrasonic vibrations during the machining process. In this paper, analytical relations have been derived to calculate machining forces associated with ultrasonic vibration based on the undeformed chip thickness. Then numerical simulation of ultrasonic assisted milling process is performed by applying the vibrations to the workpiece in the feed direction by using the ABAQUS finite element software and the machining forces are determined. The results obtained by analytical and numerical data show that the use of ultrasonic vibrations can change the direction of movement of the tool and change the thickness of the undeformed chip and thus reduce the machining forces in the milling process. Also, based on the results, it was found that there is a good agreement between the results obtained from analytical analysis and 3D FEM modeling in macro scale.

Reducing energy consumption in production is an urgent need. In manufacturing processes, especially machining, more than 90% of the environmental impacts are due to energy consumption in machine tools. The purpose of the present study is to estimate and compare the energy consumption of AISI 316 steel milling process in conventional (wet) and minimum quantity lubrication (MQL) modes as well as the experimental measurement of energy consumption in each of these two modes. Studies have suggested different types of energy consumption modeling in machining but few studies have been conducted on the use of these modeling techniques and the minimum quantity lubrication method has been rarely compared with the wet state in terms of energy consumption. Empirical experiments were used to confirm the modeling performed to predict energy consumption in the milling process. The results show that the proposed method is efficient and practical for predicting energy consumption with 5% error. After confirming the modeling, using two levels for feed rate and spindle speed and applying full factorial design of experiments, energy and power consumption in MQL and wet cutting modes using the power meter connected to the input 3-phase power cable of the milling machine were experimentally measured. Energy consumption in the minimum quantity lubrication method was decreased by 16% compared to the wet state. The average power consumption in MQL milling is 33% lower than in wet milling.

In the milling of sculptured surfaces, cutting forces and the final part accuracy can be affected by surfaces curvatures. In this paper, an analytical formulation containing the explicit form of the principal curvatures of the surface is developed for extracting the engagement boundaries between a ball-end mill and a sculptured surface, and the effect of surface curvatures on the milling forces is investigated. To this end, first, a mechanistic cutting force model is presented for calculating the milling forces acting on a ball-end tool. Orthogonal to oblique cutting technique is used to calculate the cutting force coefficients, and the model is verified by comparing the predicted milling forces with the existing ones in the literature. Then, parametric studies are performed to investigate the effects of cutting depth and surface curvatures on the milling forces. The results show that at a constant cutting depth, the milling forces are more influenced by the surface curvatures at the concave and saddle regions of the surface in comparison with the convex regions. Furthermore, for constant values of curvatures, the effect of surface curvatures on the milling forces increases as the cutting depth decreases. In other words, as the cutting depth decreases, neglecting the effect of surface curvatures results in more relative error in the calculated milling forces. Furthermore, the obtained results show that the surface curvature perpendicular to the feed direction has more influence on the milling forces than the curvature in the feed direction.

In this research perovskite phase of strontium titanate was produced from celestite concentrate (strontium sulphate). At first stage, the precursor of strontium carbonate was prepared from celestite-sodium carbonate mixture using mechanochemical process. Strontium titanate was synthesized using strontium carbonate-TiO2 mixture in the second stage. The results indicated that high energy ball milling plays a significant role in the chemical reaction and results in decreasing the temperature of post-heat treatment for producing of strontium titanate. Although some traces of rutile phase were overlapped with strontium carbonate, however no sign of chemical reaction observed in the10 hours milled mixtures of strontium carbonate-TiO2. TGA results showed that milling results in decreasing the formation temperature of perovskite strontium titanate phase in the milled mixtures. Although the traces of strontium titanate phase were revealed in the 5 hours milled mixture after isothermal heating at temperature of 600℃, the signs of un-reacted raw materials (TiO2 and SrCO3) were observed in un-milled mixture at this temperature. The traces of SrTiO3 were observed in un-milled and milled mixtures after heating at temperature of 900℃. XRD and FT-IR results indicated that strontium titanate can be synthesized form celestite concentrate (SrSO4) at lower temperatures using mechanochemical process. SEM micrographs showed that the ultrafine particles of strontium titanate (SrTiO3) can be formed in the milled samples.