IRANIAN JOURNAL OF MANUFACTURING ENGINEERING
Year:2019 | Volume:6 | Issue:7 |Papers Count:6

Error compensation using software methods is an effective and low-cost solution for increasing machining accuracy in CNC machine tools. In current research, the main goals are to develop a method for measuring geometric error, modeling, and geometric error compensation for the Rotary table of a 4-axis machine tools by implementing Homogeneous Transformation Matrix (HTM) method. After designing parametric-error model, empirical data is experimentally obtained, required for calculating unknown parameters of the model. Then, data measurement tests were carried out by a BallBar Measurement mechanism according to ISO 230-7 standard on the four-axis CNC milling machine. BallBar mechanism can measure the movement deviations of a constant radius circular path for different directions. After substituting experimental data in the proposed error model, by using matrix and computational relations the complete error model of the process is achieved. Finally, geometric errors for different angles of the rotary table are extracted from the error model and presented. Among achievements of this research, the new error model and the method of verification could be mentioned. Based on the validated model, compensations on the tool path can be carried out in order to reach higher accuracy. In addition, the error compensation method used for equipment installation, and the type of movement selected for BallBar mechanism on the 4-axis machine tool, will elevate the precision and accuracy of results. From the innovative outcomes of the present study, optimum error model and its validation to investigate the consistency of the results in both empirical and theoretical approaches is absolutely worth mentioning.

In the past two decades, the development of layered composites as well as their manufacturing methods has become a fascinating subject for researchers. The CRB is a solid-state welding to create a bonding between a wide ranges of metals using a simple rolling. In this study, the multi-layered Al5052/MgAZ31B composite was produced by CRB and its formability was studied. Rolling operations were performed by applying a 70% reduction in room temperature. The formability of Al/Mg composite was carried out using stretch test with semi-circular punch in different loading and the forming limit diagram was drawn. FLDs are the most practical method for obtaining sheet formability, which determines the strain before necking and fracture. In addition to formability, mechanical properties and fracture surface of Al/Mg were also studied using a tensile test, microhardness, optical and scanning electron microscopy. Due to low formability of magnesium and the production of Al/Mg composite at room temperature, the surfaces of the FLD is desirable due to the lack of separation between the aluminum/magnesium interfaces and the compensation tightness of magnesium with high formability of aluminum. Also, the results of mechanical properties showed that strength and microhardness of Al/Mg composite compare to initial aluminum improved 149. 5% and 80%, respectively, due to the cold working and increasing density of dislocations. The images of the fracture surfaces showed that the aluminum before and after rolling had a ductile fracture with different size, number of dimples that after the rolling the size and depth of the dimples decreased.

Vibro-thermography is an emerging and promising technique that uses ultrasonic elastic waves as an excitation source to detect and evaluate surface and subsurface defects. Friction of the edges of defects, viscoelastic behavior and non-linear vibrations of the defect region are the main sources of heating and the temperature gradient that shows up synchronously with variations of non-linear elastic energy. The temperature gradient in the defect region can be imaged by an infrared camera in order to estimate the location and size of the defects. In this paper, the vibro-thermography is simulated in COMSOL Multiphysics software. Lamb waves are used to excite an aluminum plate containing a flat-bottomed hole. First, the resonance frequency of the defect is found by means of the theory of vibrations and also by finite element method (FEM). An algorithm that incorporates frequency analysis as a function of out-of-plane displacements is used to verify this frequency and the results are compared with the eigenfrequency analysis results. The agreement observed between the theoretical and numerical models is found to be very good. The plate is then excited by an amplitude modulated sine-burst at the local defect resonance (LDR) frequency and a frequency related to the thermal penetration depth. Thermal image processing is carried out on the thermal waves to obtain their amplitude and phase images. By considering a four-point algorithm, the location, size and geometry of the defect is estimated with good accuracy.

Due to the increasing use of tubular components in various industries such as automotive and military industries, tube hydroforming process has been widely welcomed due to its advantages over traditional methods. The Y-shaped product is an asymmetric part that requires expensive asymmetric axial feed control equipment for its production. In this paper, by designing the tube in symmetric pairs and applying the same axial force on two sides of the tube, the hydroforming process of the double of Y-shaped is improved. Then, the process is three-dimensionally simulated using the Abaqus software by finite element method and the conditions for the improvement of the shape were investigated. In order to validate the modeling, the experimental product and the simulation model were compared, which showed a good agreement. Using the design of experiment method, the effects of tube length, the distance between the two bulges, internal pressure and axial feeding are investigated on the height of the bulge and the thinning percentage.

The method for producing amorphous / ultrafine grain microstructure by underwater friction stir processing is a new method, which uses a rotating tool to severely deform the base metal which immersed in water. Due to the high temperature created as a result of friction, dynamic recrystallization wants to occur in severely deformed material but rapid quenching by water prevents nucleation or growth of new recrystallized grains. In the present study, the base metal was commercial pure copper and copper alloy. The applied tool was made from tungsten carbide. The microstructural evolution and tribological properties of the specimens were investigated before and after the application of the process. Microstructural evaluation by optical microscope showed a significant reduction in grain size by processing pass increment. Similarly, the hardness of the crosssectional area showed an increase up to 45% higher than the base metal. The x-ray diffraction pattern of the underwater friction stirred processed samples in comparison to the base metal pattern exhibits shorter and wider peaks, while the background of the pattern has increased. The sum of these factors represents the formation of an amorphous / ultra-fine grained structure. Also, the wear behavior of the samples was investigated by means of pin on the disk method and the results showed that the friction coefficient of processed samples decreased by at least 48% compared to the base metal. The results of wear and hardness tests show that the underwater friction stir processing can significantly improve the wear resistance and hardness of commercial pure copper and brass alloys.

Application of traditional methods for the separation and sorting of healthy products from defective is a tedious and laborious, which needs fast and low cost non-destructive diagnostic system to overcome this problem. The present study was conducted with the aim of determining the internal quality of the tuber agricultural product (potato, Banba variety) with nondestructive sound test during the storage duration of 44 days with 78% moisture content. In order to determine the internal quality of the product during shelf life storage, sound and pressure test (as a control) were used. The results showed that the acoustic test has the ability to determine the quality of potato during the storage period. Also the effect of two independent variables of storage time and sample mass was compared on the bio-yield force (pressure test) and the firmness index using acoustic test. The results of this research revealed that the storage duration and mass of samples were significant at 1% probability level on quality parameters. In this study, the correlation coefficient between the firmness index and bio-yield force and the modulus of elasticity was 66% and 63%, respectively. The overal results of this research revealed sound test is capable for diagnostic internal quality of potato during 44 days of storage.