مجله مهندسی ساخت و تولید ایران
سال هفتم شماره 1 (فروردین 1399)

Due to the increasing applicant of special polymers in industries, especially in the medical and aerospace industries, it is necessary to study and investigate the production and machining of these materials. Polyether ether ketone is a heat resistant polymer that is used in the medical industry nowadays. Grinding is one of the important machining processes of this material. Using conventional lubricants and cooling liquids is not optimal in machining of PEEK, because grinded workpiece must be cleaned several steps before use. In this paper, cryogenic cooling technology, as one of the newly emerging cooling systems in the field of machining that have a very high ability, does not have a negative environmental impact, and greatly reduces need to clean machining parts, has been used for cooling of the machining zone. One of the important issues of machining output parameters is surface integrity. Surface Integrity and roughness have a high importance in the performance of the finished product and is an important parameter for investigation the machinability. Comparison of the results of using compressed air and cryogenic cooling on surface roughness and surface conditions indicate the significant effect of cryogenic cooling on the output of this study

Application of metal matrix composites reinforced by ceramic phase is increasing rapidly in different industries. Recently, dynamic compaction has been considered as one of the complementary methods of powder metallurgy in production of composite materials. Moreover, aluminum, as one of the most important industrial metals, is widely used in manufacture of metal matrix composites. In this study, the effects of dynamic compaction on pure and composite aluminum powders are studied. To produce composite specimens, pure aluminum and nano-silicon carbide powders are used as matrix and reinforcement respectively. Dynamic compaction experiments are performed using gas-gun apparatus in different velocities. Afterwards, density, strength and microstructure of compacted samples are evaluated. The obtained results show density, strength and spring back of pure samples are increased with increasing compaction velocity. Ceramic particles increase porosity in microstructure of composite samples. Adding 1 weight percentage of ceramic increases the strength of samples and leads to uniform distribution of particles into metal matrix, whereas adding more than 1% causes significant decrease in strength. In the following of the study, experimental results obtained from dynamic compaction and the difference between experimental and predicted results are considered as input and objective function of artificial neural networks optimization method. The obtained results show that this empirical-numerical method is able to predict density of specimens obtained from dynamic compaction with a good accuracy.

One of the most important parameters that can be considered when creating a hole is the surface roughness. Many factors, such as drill transverse vibration, temperature, and tool geometry, play a role in creating surface roughness. In this paper, the effects of the factors include spindle speed, feed and pre-drill with associated variables including axial force and cutting torque are considered. The main purpose of this paper is to determine the significance of each of the factors and dependent variables in the variation of surface roughness. The material of workpiece is selected from the 7000 series Al Alloy. The simultaneous analysis of all the factors and dependent variables has been done using the Manova method. In the first step, the results show that the use of this method can reveal the effect of factors on creating simultaneously the axial force and cutting torque, and then determines the effectiveness of each of the factors and dependent variables in determining the surface roughness at 95% confidence level. The results indicate that considering axial force and cutting torque in model can increase the ability of prediction model in surface roughness by 37.39% compared to the prediction performed based on factors. On the other hand, the results show that the axial force has a greater effect than the cutting torque on the surface roughness of the hole. Therefore, in order to improve the surface quality of the produced hole, it is necessary to pay attention to methods that reduce the axial forces.

The thermography inspection is the most modern non-destructive test method that has been expanding in the industry in recent years. There are several benefits such as high-speed testing, along with high precision and the ability to inspect without conduct. The advantages of this method, which leads to lower costs and increase accuracy in testing, make us able to use this method to detect the defects in the gas turbine blade channels to increase the accuracy of the fault diagnosis and it reduces the maintenance costs. Gas turbines have many uses in the industry. The efficiency of these turbines increases with increasing combustion temperature. The goal is to achieve more efficiency, but there are limitations to this goal. When shape of cooling channels has a complex geometric shape, maybe the ceramic muscle cannot completely exit at the casting stage and it will break. Remaining these particles in the cooling channels can seriously affect the turbine performance. So it's very important to detect this defect before using a defective blade. In this paper, it was aimed to detect existed channels in the workpiece to examine the effect of injected vapor pressure into the channels as temperature stimulus and to investigate the influence of channel distance from the surface from the results obtained by thermography.

Digital shearography is a laser interferometry method that is used to detect and measure defects non-destructively. In this study, a new approach was presented to measure planar defects using digital shearography method. A total of 16 shearography tests were carried out in order to verify the proposed method and study the effect of shear size and depth of defect on measurement accuracy. Defect size was varied in four level and depth of defect and shear size were changed in two levels. The defects size were measured in different conditions and the estimation error was obtained in each case. The proposed method was able to predict defect size with good precision and the lowest error percentage was obtained in 15 mm size 0.5 mm depth defect at shear size of 15 mm. The results showed that as the shear size is approached the defect size, the error percentage is reduced and the maximum accuracy of prediction is obtained when the shear size is equal to the size of the defect. Also, varying the depth of defect led to variation of estimation error, and in most cases the prediction of defect size with a depth of 1 mm was more precisely due to the better shape of the shearography fringes.

CMT process is a new developed gas metal arc welding (GMAW) process which has low dilution and heat input. This method is useful for expensive electrodes which are used in surfacing. In this research 1, 2 and 3 layer of flux cored Stellite 6 is deposited on A516-Grade 70. Same type of this steel with hard faced Stellite 6 is widely used in oil, gas and petrochemical industries especially where there is a need for wear and oxidation resistance at high temperatures. Chemical composition of layers is explored and the changes in dilution and iron content versus layer number and final thickness of deposited weld are investigated. Similar samples were prepared with conventional GMAW process for comparison. The results showed that heat affected zone (HAZ) in CMT samples are thinner and reduces by 28% which means less heat input in this process. In CMT process Dilution and weld penetration are 39% and 41% respectively less than conventional welding process. By using this method, the desired chemical composition is achievable with less number of thinner layers and leads to reduction of welding electrode consummation