Modares Mechanical Engineering
Year:2015 | Volume:15 | Issue:13 (SUPPLEMENT)|Papers Count:24

This study aims to simulate the orthogonal machining process of titanium alloy using finite element method. Simulation with finite element method makes the cutting process easy to understand, increases tool life and reduces the cutting forces. Three-dimensional simulation was performed using the Abaqus software. The effects of machining parameters include the cutting speed and feed rate on the cutting and feed forces, shear stress and tool life were assessed. To validate the results of the application, the experiments were carried out in the field and the results were compared with the values obtained from the tests. The results showed that the simulation results are in good agreement with the experimental data.

Machining of thin-walled monolithic parts made of aluminum alloys is a key process in industries such as aerospace. In the final machining process, the cutting forces and machining temperature produce deflection for workpiece which results in the dimensional inaccuracies and distortion on the finished component. The purpose of this paper is to study the thermal and mechanical behavior in machining of aluminum alloys (Al7075-T0) using PCD (polycrystalline diamond) and K10 (cemented carbide) tools to investigate the correlation between both parameter on distortion. The study was made using a three-dimensional finite element method model in Abaqus software under orthogonal cutting conditions. The results represented the direct effect of the force and temperature on level of distortion in thin-walled workpieces. However, the mechanical loads have more influence on work piece distortion in comparison to the thermal loads. It was concluded that the polycrystalline tool has a superior performance in terms of cutting forces and temperature when compared to the cemented carbide tool. To validate the FEM model, the results were compared with experiments of the other papers. Results showed a good agreement with experiments.

The main problems in the machining of thin walled parts made of aluminum alloys are the distortion and dimensional instability after machining which lead to an increase in the production costs. In general, distortion in machined parts made of aluminum alloy is a function of the residual stresses. In this study, a three-dimensional FEM model in Abaqus under orthogonal cutting conditions is used for investigating the correlation between machining induced residual stresses and the distortion in thin-walled cylinder made of AL7075-T6 alloy. To compare and validate the FEM model with experimental results of other papers, several simulation are carried out under different conditions using K10 and PCD tools. Machining force, temperature and distortion were measured. Correlation between residual stress and distortion was studied by measurement on some workpieces. The results represented the direct effect of stresses on level of distortion. Unlike experimental, there is no limitation in FEM model to compute amount of residual stresses in all directions. Results showed a good agreement with experiment. This indicates that the FEM model can be used to simulate machining process to predict its distortion with no limitation with saving of 600 euros for each test considering the equipments limitation in Iran.

Distribution of thermal loads during the machining process leads to reducing the surface quality and rapid tool wear. Therefore, optimization of thermal loads in machining has always been important. On the other hand depth of the restructured layer can improve mechanical and metallurgical properties and of the workpiece. Since experimental investigation in machining operations is expensive and time-consuming procedure, finite element method is also used as an efficient tool in this regard. Therefore, at the first part of this study, experimental machining tests was carried on Inconel 718 alloy at the different cutting depth, cutting speed and the feed rate to measure machined surface temperature. The results of experiments were used to simulate machining process using commercial software of DEFORM-3D-V10. After calibration and validation of the results of 3D simulation with corresponding experiments, the effect of tool edge radius, tool nose radius, and workpiece hardness was investigated. To improve the accuracy of the simulations, heat transfer coefficient was calibrated by experimental result of temperature and it was defined as function of cutting parameters. Finally, the effect of machining parameters was investigated on the depth of the recrystallized layer using the critical strain criterion.

Surface and subsurface cracks in part are induced by mechanical cutting of brittle material specially glass which decrease part's life-cycle. The goal of this research is to present a finite element model for predicting induced median cracks as the most deterministic cracks on the BK7 glass subsurface in micromachining. Bilinear Cohesive Zone Method (CZM) was used for simulation of crack and its specifications. CZM's parameters were obtained and calibrated by micro-Vickers experiment and the results were validated by micro-scratch test. Finite element model demonstrated median cracks dramatically increase from ductile-to-brittle-changing-regime point in micro-scratch. Finally, the validated finite element model facilitated the prediction of the depth of median cracks with respect to tool cutting depth in micromachining.

In this study, 3D 8inite element simulation of reaming process has been carried out on the hard steel. The cutting parameters in the simulation process were selected based on the optimum experimental results which lead to the smaller cutting forces, lower vibration of the reaming tool and better surface quality. This simulation was used to predict cutting forces as one of the most important reaming output variables. Simulation of material removal process was performed by commercial finite element software SFTC DEFORM-3D and using the explicit Lagrangian code. In addition, some empirical experiments were done on the hardened D2 tool steel workpieces to 8ind the optimum reaming condition and validation of finite element model. Cutting parameters including feed rate and cutting speed were changed and cutting forces were measured, experimentally. The results showed that the numerical results have a good consistency with the experimental one and average difference of 10% was seen. Finally, the effect of input parameters on the cutting force at the simulation and experimental test were investigated. It was seen that the cutting forces error is reduced between two analyses by increasing the feed rate. This indicates that the meshes with higher quality and density are required in lower removal rate.

Broaching is a specific method of removing metal by tools that have successively increasing cutting edges, the part is made through tool moving in a certain path. The cutting force is high as a result of high removal rate in the broaching process. The process may have too many surface errors since high displacement arose by this cutting force. For this reason, proper attention should be paid in the broaching tool design, geometry analysis and the process conditions. Considering the broach machining table and accessories, the dynamometer installation is complicated. Therefore, the finite element modeling can be used for evaluating the cutting force. In this study, the simulation of broaching process is done using Abaqus Software. After modeling the process, the effect of rake angle and cutting speed parameters on cutting forces are investigated.

Cutting forces that affects the cutting tool during machining are one of the important parameters must be known to select the economical cutting conditions and mount the workpiece on machine tools, securely. In this paper, the effects of the feed rate in machining of aluminum alloy 5083, used in lightweight structural application in automotive, shipbuilding and aerospace industries, on the cutting tool stresses have been investigated. Cutting forces were measured by a series of experimental measurements while stress distributions on the cutting tool were analyzed using a commercial finite element method (FEM) (ABAQUS). The results showed that the feed rate is the most relevant cutting parameter affecting cutting tool stresses.

Due to a need for a 3D 7inite element simulation model and having a high solution time, simulation of an oblique cutting process has some limitations and has been studied less. In this study, for solving these limitations, a 2.5D model was developed for analyzing the oblique cutting process and simulation of chip formation in this cutting process was established. Two deformable parts were modeled as tool and workpiece. Johnson-Cook material model and Johnson-Cook damage criteria were used. Then the effect of tool-rake angle, cutting edge inclination angle and cutting depth on aluminum-alloy chip morphologies were analyzed and it was seen that by decreasing the rake-angle, the chips became smaller. The increase in cutting edge inclination angle causes the chips become more conical and more continuous. There were segmented chips by increasing the cutting depth, as a result of increasing the undeformed chip thickness and amount of stress.

Meanwhile damages on machine, the created vibrations during the machining process will effect on the significant results of the process, such as surface finishing.6ptimized design of the machine tool and high quality of the workpiece would be possible by determining the vibration characteristics of machine structure. In this paper, transient and harmonic dynamic behavior of gantry CNC milling machine (DMC 1000) has been studied. For this reason, rudimentary structure of the machine and its main complex are modeled in the commercial Solidworks software. Then, the natural frequency and dynamic response are evaluated in both transient and harmonic moods using ABAQUS.Finally, the stability condition is investigated for the current machine. Results showed that the system response is more sensitive under frequency of 400 Hz and the largest displacement occurs at first locating position of spindle.

Hydraulic valves have very important role in hydraulic industry. Spool is one of the main parts of these valves which defines the valve efficiency and application by determining the fluid flow. The dimensional tolerance and surface quality of spool are the main effective parameters concerning the valve application. Spool requires heat treatment after machining for achieving the desired level of hardness and getting ready for grinding. In this paper, the hydraulic valves spools have first been machined to reach to the desired dimensions. Then, heat treatment has been performed on them to obtain the appropriate hardness. Finally, the spool distortion induced by heat treatment and its surface quality after grinding has been measured has been measured and compared with each other.

One of the new ways to improve the machining parameters in turning processes methods is the minimum quantity lubrication (MQL) method. In this study, the machining process of Monel K500 super alloy has been investigated using wiper type ceramic tool under dry and minimal lubrication with nano-fluid conditions. First, the necessary equipment was provided to perform the tests in dry and relatively dry (minimal lubrication) conditions. Then, the tests were completed in each of these conditions to determine the shear and feed rates. The utilized tool in experiments is the Wiper Ceramic Insert with the code CNGA 12 04 08 T01020WG-650 that is manufactured by Sandvik. The parameters of machining forces and surface roughness were measured during the tests. The results showed that the machining in the conditions of minimal quantity lubrication using nano-fluid not only reduced the amount of surface roughness, but also reduce shear force at low shear rates.

High pressure hybrid jet assisted machining is an efficient method to improve the machining conditions. The significant advantage of this method is concentration of high pressure fluid on machining zone and reduction in tool-chip interface. In this research, a collection of pumps and water jet pump was used in order to supply a high pressure jet. A specific tool holder was designed and manufactured. Experiments were designed to investigate the process parameters such as jet pressure, cutting speed, feed rate and depth of cut. During the experiments, the cutting forces and surface roughness were measured. Results showed the existence of the optimum conditions of the minimum cutting force and surface roughness in hybrid jet assisted machining. Thus, the optimization of process parameters is necessary in order to use hybrid machining more efficiently. A neural network with suitable topology was utilized which was trained by genetic algorithm to obtain the predictive model. Ultimately, genetic algorithm was applied to optimize process parameters. Results showed the ability of employed algorithm to predict the optimum parameters with considerable accuracy.

Having unique properties such as high melting point and hardness, Inconel 718 superalloy has been found a widespread application in turbines and aerospace industries. Due to these properties, Inconel 718 superalloy cutting with traditional methods is difficult and costly. Therefore, novel cutting methods such as laser cutting have been considered. Geometrical characteristics of the cutting kerf and the surface roughness are important factors in the cutting process. These parameters have not been widely investigated in the laser cutting of Inconel 718. In this study, Inconel 718 superalloy was cut via laser, and the effect of cutting parameters including cutting speed, nitrogen gas pressure, and the power and focal distance of the laser beam, on the cutting kerf width and surface roughness was investigated through experimental investigations and artificial neural network. The results implied the high precision of the model in the estimation of kerf width and surface roughness.

The surface roughness is a widely used index of surface quality which depends entirely on the input parameters and cutting conditions. This paper presents an approach for determining the optimum cutting speed, feed rate, radial depth of cut and milling type leading to minimum surface roughness in milling process of AIsI 420 stainless steel by integrating Artificial Neural Network (ANN) and Imperialist Competitive Algorithm (ICA). The combination of these two methods to optimize the cutting process is provided for the first time in this article. 54 different cases were tested and surface roughness was measured in each experiment. The predicted results using ANN indicated good agreement between the predicted values and the experimental values. ICA was used to determine the optimal machining parameters leading to minimum surface roughness. The obtained results proved that the ANN-ICA approach is capable of predicting the optimum machining parameters to minimum surface roughness in milling process.

Micromilling is a suitable method for fabrication of miniature parts with 3D complex geometries. This method has wide applications in fabricating of medical micro tools. Titanium alloys were used in medical applications extensively due to their high strength-to-weight ratio, corrosion resistance and biocompatibility. Owing to the fabricating of micro parts in implants and medical tools, studying the micromilling of titanium alloys becomes more important. In this study, the surface roughness produced by micromilling of Ti6Al4V alloy is investigated. Spindle speed, feed rate and axial depth of cut have been considered as cutting parameters. Micromilling has been done with three lubricating and cooling conditions: dry, wet and minimum quantity lubrication (MQL). TiAlN coated carbide micro-end mill tool with the diameter of 0.5mm were used. Taguchi method has been used to design and analyze the experiments. The results showed that the surface roughness is minimized by the use of the minimum quantity of lubricant. Surface roughness decreased with the increase in cutting speed and feed, regardless of the lubrication and cooling condition. The minimum surface roughness was 118 nm in the condition of spindle speed=30000 rpm, feed rate=0.8mm/tooth and depth of cut=60mm.

Ultimate surface quality in machining process has a great effect on the workpiece performance and is the most important characteristic of machined surface. Using cutting fluid, as an effective factor on surface integrity improvement, has environmental problems and is harmful for operator’s health. As a result, using minimum quantity lubrication (MQL) is considered as an alternative method. In this study, surface roughness of Ti-6Al-4V alloy workpieces were investigated in high speed milling process and using MQL method. full factorial experiments including 5 levels of cutting speed and 2 levels of feed rate were implemented. Results revealed that a surface roughness of 0.2mm could be achieved in high speed milling of Ti-6Al-4V alloy in proper cutting conditions and in presence of MQL method. furthermore, minimum surface roughness was reported in cutting conditions of Vc=450 m/min and fz=0.08 mm/tooth.

High speed machining has many advantages such as increasing productivity, reducing production cost and improving final workpiece properties. On the other hand, final surface roughness is one of the most important of machined workpiece. In present study, relationship between high speed milling parameters and workpiece surface quality made of 1.7765 steel alloy and hardness of 50 HRC in presence of minimum quantity lubrication method was investigated. Cutting speed, feed rate and axial and radial cutting depth were studied and totally 30 experiments were done. Results showed that among main cutting parameters, feed rate and cutting speed had the most effect on surface roughness and surface roughness reduced with increasing cutting speed. In addition, using minimum quantity lubrication had a good performance in high cutting speed and cutting depth.

In the last years hexapod machine tool with six degrees of freedom has got the attention of experts for achieving high dexterity and high speed machining. Free form surfaces are widely used in today industries. These surfaces are much encountered in aerospace, auto and other industries. Therefore machining of these surfaces is very important. For interpolation of free form surfaces, NUR5S curves are commonly used. For investigating the quality of machined surface, final surface roughness is very important and is the most important feature of machined surface. In this study the effect of machining parameters such as cutting depth, feed rate and cutting speed on surface roughness were investigated. Design of experiments was done using Taguchi method. Then with using of neural network and genetic algorithm the best case for surface roughness was achieved. The cutting tool used in this study was ball end-mill and the work piece was aluminum of three thousand series. The results showed that cutting speed and depth of cut had the most effect on the surface roughness.

High-speed milling is widely used in the manufacturing industry. This method is faster and more precise than the traditional milling. The feature of precision and speed in the method of manufacturing has made it suitable for manufacturing of bigger and high precision milling parts. This research studies the effect of tool length on stable materials removal rate in high speed milling processes. It is shown that the tools length is highly affected the natural frequency of the most flexible mode and the high material removal rate is obtained when the tools length in the stable region is accessible with the fastest speed. Furthermore, sometimes longer tools provide higher material removal rate than the short ones.

As a single-pass machining operation, broaching is extensively used to produce simple and complicated profiles with finished surface quality. Broaching is often used for mass production. Since, it is a special manufacturing process, few researches has been reported in this area. In this research, the dynamic effects of cutting forces for different cutting speeds on Aluminum 7075 have been theoretically and experimentally analyzed using MATLAB. Moreover, to make sure of the results, experimental setup has also been designed to investigate the effect of cutting speed on surface quality and cutting force. For this purpose, a servo hydraulic system based on position control has been designed. With the increase of cutting speed from 2 m/min to 8 m/min, an undeniable decrease in cutting force is observable, while the surface quality experiences an interesting increase. It can be concluded that the higher cutting speeds are to be preferred for processing this material. In practice, it is applicable for especially car manufacturing industry to shorten the time and lower the cost of production.

The objective of this work is to investigate the influence of cutting speed (rpm), feed rate (mm/min) and tool diameter (mm) on the uncut fiber and delamination damage of a type of composite sandwich structures including PVC foam, Trapezoidal corrugated sheets and faces made of E-Glass/polyester. VARTM method has been used for manufacturing of samples. A design of experiments (full factorial) was used to assess the importance of the drilling parameters. The drilling operation was assessed based on two introduced factors including the delamination factor (DF) and uncut fiber factor (UCFF). Minitab software has been used for obtaining the role of each parameter on output factor. Analysis of the experimental results for DF indicated that the feed rate and drill diameter were the most significant and insignificant parameters, respectively. But, experimental results for UCFF showed that the tool diameter has greatest influence where UCFF increased with increasing diameter, too. Also, the results revealed that the both factors increase with the increase of feed rate. There is an optimum point for cutting speed and tool diameter in evaluation of UCFF. Whereas, increasing tool diameter leads to decrease of DF and generally there is a maximum point in variation of cutting speed for UCFF.

bone drilling is one of the common processes in orthopedic operations for therapy and maintaining different parts of a broken bone with together. The most important possible problem during operation is the unwanted increase in drilling process temperature (higher than 47oC) which causes thermal necrosis or cell death and local burnt in bone tissue. Applying higher forces to the bone may lead to break or crack and consequently serious damage in the bone. In this paper, a second order linear regression model is introduced to predict process temperature during bone drilling as a function of drilling speed, feed rate and effective interactions. This model can specify the maximum speed of the surgery to stay within the acceptable range. Applying design of experiments, modeling and optimization of effective parameters using response surface method in bone drilling, optimized drilling speed and feed rate were obtained to minimize force and surface roughness. Using multi objective optimization, this was done within the acceptable temperature range without tissue damage which can remarkably reduce the regeneration of the bone cells and less therapy period. Drilling speed and feed rate variations were considered in wide ranges of 500 to 2500 rpm and 40 to 60 mm/s, respectively. results showed that the minimum temperature increase and the best surface roughness are obtained when drilling speed and feed rate is minimum. Increasing these two parameters induced to the higher temperatures. At high drilling speeds, “temperature increase rate” decreases in the way that the response surface model represents horse saddle shape. Also, the minimum force imposed to bone tissue is ascertained in lower feed rates and the most tool drilling speed. It is noted that the lowest damage to the bone during orthopedic surgery occurs with drilling speed of 500 rpm and feed rate of 40 mm/min considering all aforementioned parameters.