نشریه فناوری آزمون های غیرمخرب
سال سوم شماره 3 (پیاپی 13، بهار و تابستان 1402)

Nowadays, flying objects engines are harmed and malfunctioned due to aging phenomenon. One of the most important problems lies in the hot part of these engines. Turbines of these engines have creep and metallurgical difficulties which lead to cracks and part failure. In case of one engine blade failure, the whole engine will be out of operational line. Thus, proposing a method for aging determination and longing the lifetime of these engines’ parts can play a significant role in keeping the military helicopters of the country continuously operating. In this study, Eddy current non-destructive method was utilized to evaluate the microstructural changes of Rene80 super alloy turbine blades of J85 engine. The microstructural changes that occurred in this sample by aging phenomenon at a temperature above 800 ℃ for 1600 h under service was studied through destructive and non-destructive routes. To this end, changes of 4 turbine blade parts which were under service for the same periods of times were compared together as well as with an intact blade sample (as the control sample). Metallography studies, scanning electron microscopy (SEM), EDS element analysis, and micro hardness test were done to assess microstructural changes and destructions and phases characterizations. It was found that there was a good correspondence between the results obtained from destructive studies and Eddy current evaluations. The results show that the volume fraction and grain size of the precipitates of the under-service samples were considerably increased compared to the intact specimen and the morphology of 'γ precipitates were transformed from cubic to spherical shape. Likewise, the hardness of the under-service samples was decreased compared to the intact one. The Eddy current results show that the impedance amount of the under-service samples was decreased compared to the control which is in correspondence with the hardness test results. And the induction resistance parameter in Eddy current test closely correlates with hardness test results (R2=0.95). Altogether, it can be concluded that Eddy current non-destructive method is capable of separating different samples of this super alloy and distinguishing of microstructural changes.

One of the most important and challenging processes of manufacturing industrial parts has always been the process of creating various joints, including permanent joints by welding method. Considering the sensitivity of the welded joints in terms of defects and cracks caused by the process, checking the accuracy, precision and health of the created weld is one of the most important concerns of researchers and craftsmen. For this reason, the development of non-destructive methods to check the integrity and quality of the joints created by the welding process has been increasing in recent years. But each of these methods have always shown certain limitations in evaluation welded parts. Among these limitations is the need to cool down the part before the inspection process and the need for direct contact with the part. The infrared thermography method, as one of the advanced non-destructive inspection methods, has been widely used in the inspection of welded joints in recent years due to its many advantages. Among the advantages of the infrared thermography, it can be mentioned that it is non-contact, online, and has the ability to quickly evaluate a very large area of the part. Also, this process can check the health of the part during its working life in an assembled set. These unique features have turned the infrared thermography method into a method with a very high potential in the testing, process control and automation of the welding process .In addition, the ability to synchronize with the methods of artificial intelligence, machine learning, deep learning and signal and image processing has shown the potential of this method to be used more and more in modern industries in the future. Also, the research fields in this area are very untouched and many research gaps are felt in this field. In the upcoming research, an attempt has been made to create a suitable background for this process by presenting an overview of the principles of infrared thermography. Also, the applications of infrared thermography in the welding process, especially in non-destructive inspections, have been investigated, in which different methods of infrared thermography in non-destructive inspections have been described and explained.

Investigating the integrity of structures and equipment such as airplanes, the pipelines, the oil platforms, the bridges and the pressure vessels is an essential task in the industry. Employing a reliable and accurate methods for investigating the health of the industries equipment’s is vital to increase the health and reduce the financial hazards. Nowadays, the use of thermographic inspection technique or the inspection using infrared waves as a useful and advanced tool among the various methods of condition monitoring and nondestructive evaluations is expanding. Infrared thermography is performed with the help of thermal information analysis using non-contact thermal imaging devices. The infrared thermography is used to detect hot spots, heat losses, leaks, insulation defects, etc., so that the nondestructive men and maintenance personnel can take appropriate actions to fix the problems. In this research, a steel plate with 20 flat bottom holes (FBH) with diameters of 2 to 10 mm and distances from the test piece surface (Defect depth) ranging from 0.5 to 2 mm was used as a test sample. A flash lamp and two projectors were used as heating sources and then the thermal image sequences were recorded. It was observed that only 11 defects can be detected in the thermal raw image. In order to improve capability of thermography test, 6 techniques of Thermal contrast including absolute thermal contrast, running contrast, normalized contrast (final value), normalized contrast (maximum value), standard contrast and differentiated absolute contrast (DAC) have been applied to the of thermal raw images. Thermal contrast based techniques found to be useful in improving defect detection by increasing contrast between the image of the defect and sound area and reducing effects of non-uniform heating. Normalized contrast (final value) had the best performance in terms of increasing the number of detected defects and was able to reveal 16 defects.

High strength aluminum alloy pipes (AA7075-T6) has been widely used in various industries due to their favorable properties, Such as high strength to weight ratio, excellent machinability and proper forming. On the other hand, according to the susceptible to phenomenon of stress corrosion cracking, the evaluation and monitoring of mechanisms related to this issue is of considerable importance in the industry. In this research, Fuzzy clustering method (FCM) has been used to detect acoustic emission signals related to stress corrosion cracking mechanisms of aluminum pipe. Using this method, while revealing the clusters in an unsupervised method, leads to more appropriate classification and separation of data. In this regard, a laboratory system including waveguide, corrosive solution chamber, and arc-shaped aluminum samples according to ASTM-E399 standard along with acoustic emission equipment was designed and prepared. Then, using the slow strain rate test (SSRT) and receiving AE signals simultaneously, the AA7075-T6 aluminum sample was placed in two corrosive environments (HCL9% and HCL33%) to identify the two main mechanisms of stress corrosion cracking, including anodic dissolution and hydrogen embrittlement (cathodic). Five descriptive acoustic parameters including rise time, count, energy, amplitude and duration were used to analyze the obtained signals. In order to select the most effective acoustic characteristics and reduce the amount of information, principal component analysis was used. Subsequently, with the fuzzy method (FCM clustering) based on the optimized data from the analysis of the main components, it was possible to distinguish and separate these two types of corrosion mechanisms. According to the obtained results, it was found that the dominant mechanism in the phenomenon of stress corrosion cracking in HCL corrosive solution is the anodic dissolution mechanism, which in addition to increasing the corrosion current density, increases the dependence of stress corrosion on this mechanism by increasing the concentration of H+ and C- ions.

Industrial gamma radiography is used to test the defect of thick pipes in the oil and gas industry. Due to the high energy of the gamma sources used in radiography, the permeability is high in parts with a thickness of several inches and gives a good image of the internal characteristics of the pipe. Due to various factors such as the scattering of gamma rays and the stages of emergence and proofing of the film, the recorded image is usually blurred. The resolution and contrast of radiographic images have an important rule for precise interpretation and better defect detection. Different methods of image processing, both in the frequency and spatial domains, can be useful for improving the quality of radiographs. Various types of total variation-based methods have been used to improve the quality of images in different types of image processing problems. In this research, the weighted isotropic-anisotropic total variation method (WAITV) has been used to process and improve the contrast of radiographic images. This method works on the basis of horizontal and vertical differential operators and isotropic and anisotropic conversion functions and provides fast algorithmic coefficients for optimization using the alternating path method. This algorithm was applied to 24 prepared radiographic images and the original and processed images were evaluated by experts. The results of the evaluation show that, according to specialists, the use of the WAITV method has an effect of 10 to 20% in improving the contrast of radiographic images. In general, the edges of the images are sharper and different regions such as IQI lines and defects are better seen in the processed images. Experts also emphasize that due to the changes in brightness in the pixels and the possibility of creating false defects, the use of this method and other processing methods can only be interpreted when compared with the original radiographic image.

Modeling and simulation are crucial in designing and developing complex systems, such as cargo scanner systems. A cargo scanner is a device used to scan and inspect cargo transported by air, land, and sea. These scanners are usually used by customs and security centers to identify potential threats such as weapons, explosives, and contraband. One of the key benefits of using modeling and simulation is that it allows designers to test different scenarios and configurations without the need for physical prototypes. This can save time and money, as well as reduce the risk of costly mistakes. This study examines how the parameter angle affects detector responses in truck cargo scanner systems using the MCNPX code. The angle refers to the angle at which the beam generated from the beam generator interacts with the detector's normal surface, an important factor in ensuring the accuracy and reliability of cargo scanning systems in imaging. Initially, the X-ray spectrum output was calculated from the accelerated 6 MV electrons due to tungsten target impact and validated against spectra from other studies. The results demonstrated good agreement between the output spectra. The changes in counts recorded in the vertical direction of the detector arrays showed that the count difference between the lowest pixel and highest pixel is approximately 33%, while the count changes from the closest pixel to the farthest pixel to the beam generator in the horizontal direction are about 60%. Subsequently, the angle of each array was adjusted so that the emitted rays from the cone beam generator were perpendicular, and this case was compared to cases where the array angle was 20 and 30 degrees. The results revealed that when exposed to perpendicular radiation, the signal recorded in detectors is greater than that of a rotated detector, and the count rate in the detector decreases as the angle increases.

A fire extinguisher is a critical piece of safety equipment used to suppress or extinguish small fires in emergency situations to prevent large and deadly fires. This study examines the possibility of using a measurement system based on a transmitted gamma ray and a linear pixel needle detector of a vehicle cargo scanner based on gamma ray technology to inspect fire extinguishers.. The aim is to determine the effectiveness and accuracy of this approach in detecting any defects or irregularities in fire extinguishers, which would enhance the safety and reliability of these crucial emergency devices. The study involves testing the system on four different models of fire extinguishers and analyzing the results to assess its viability as an inspection method. The results were analyzed, with output in the form of images and intensity profiles recorded in one direction from the images. The findings of this research could have a significant impact on the field of fire safety. They could help to contribute to the development of more advanced and efficient inspection techniques for fire extinguishers, in conjunction with other non-destructive inspection methods. In this study, the capabilities, limitations and potential applications of a transmission gamma based imaging system for fire extinguisher inspection were investigated.The imaging unit utilized a gamma source of cesium-137 and a linear detector array. The study discusses the potential applications of this technology in the field of fire safety and its limitations. The research highlights the importance of developing more advanced and efficient inspection techniques for fire extinguishers, as well as the need for ongoing research in this field. Ultimately, this study provides valuable insights into the potential use of vehicle cargo scanner systems for the inspection of fire extinguishers, and its findings have important implications for the field of fire safety. The results provide valuable insights into the feasibility of using gamma-ray technology-based automotive cargo scanner systems and pixel linear detectors as a reliable method for fire extinguisher inspection, ultimately enhancing public safety and emergency preparedness.

Early detection of sub surface defects is very important in the maintenance and development of structures made of composite materials. Therefore , it becomes necessary to use non - destructive tests to improve system reliability and prevent untimely failure of components during operation. However , due to the multi-component nature of the configuration , its complexity , and the extent of various defects in these materials , the detection of defects in composite materials is always difficult .So , there is important to develop some new and advanced methods to detect many of defects in these types of materials . Shearography or laser shearing interferometery , with internal excitation of the defect is one of the novel methods of non - destructive testing of subsurface defects , which detects defects by receiving the defect's surface response to the loading. In this article, a glass fiber-reinforced polymer specimen was subjected to non-destructive inspection using shearography with modulated ultrasonic loading. The parameters influencing the detectability of plane defects were studied , and the obtained results were compared with the usual constant - amplitude ultrasonic loading method . In shearography tests using the amplitude modulation technique , in contrast to the constant amplitude ultrasonic loading , the defect was easily detected at all three excitation frequencies and through the phase and amplitude images . Additionally , the highest resolution of defect detection was achieved at the 43 k Hz excitation frequency . The amplitude image results showed that the defect has higher detect - ability at lower modulation frequencies, regardless of the piezoelectric stimulation frequency . Furthermore , the phase difference changes and defect detect - ability in the phase images are not significantly affected by the piezoelectric excitation frequency , demonstrating the independence of the phase image and the modulating method from the loading conditions .

In recent years, with the increase in the price of non-renewable petroleum products and strict environmental laws, the application of natural fibers as reinforcement in composite materials has been increased. In the current study, the effect of adding natural fibers on the resilience to delamination, which is the most common type of failure in laminated composites, is investigated in mode Ⅰ loading using features extracted and evaluated from acoustic emission non-destructive method. The samples were made using the hand lay-up method. The double edge cantilever beam test was used to test the samples. Using the methods provided in the ASTM D5528 standard, the occurrence of initiation of delamination is determined in the samples. The results show that only the use of the mechanical methods provided in the mentioned standard is not enough to determine the initiation of delamination, and for an easier and more accurate determination of the initiation of delamination. Thus, the assessment of delamination defect initiation and fracture toughness by means of features measured by acoustic emission test should be applied. Then, using the energy method, cumulative energy, count and cumulative count are used to determine the initiation of delamination in the samples. Then, using the critical load and critical displacement determined by different mechanical and acoustic emission methods, the interlaminar fracture toughness values of the samples are calculated. At the end, the results of the present study are compared with previous studies. According to the obtained results, the usage of kenaf fibers does not show a significant increase in the interlaminar fracture toughness of glass/epoxy composites, but application of cotton fibers causes a significant increase in the interlaminar fracture toughness. Among the different acoustic emission methods, the count method shows the lowest error of 1.8 percent regarding the method proposed in the standard, nonlinear method, among the other acoustic emission methods.

Additive manufacturing (AM) is based on the deposition of materials with high precision to make a final part or component using different methods. This process is considered one of the main developments in the fourth industrial revolution and is still growing. There are many different types of additive manufacturing methods, and today, the use of efficient inspection methods is required to ensure a certain level of quality and detect defects and discontinuities in the industry. Today, in industry, non-destructive testing (NDT) is widely used, especially in additive manufacturing, to ensure efficient quality control and predictive maintenance without changing the properties and initial state of materials. Each non-destructive testing method is based on different physical principles and the correct selection and use of each test depends on the application, manufacturing process, type of material and possible discontinuities and many other things. The most common defects created in AM parts in terms of appearance include porosity, entrapped impurity, cracks, and material defects, which are mainly caused by changes in manufacturing parameters, injection parameters, and initial material properties. In this article, the performance of non-destructive tests was investigated to inspect the parts produced by the additive manufacturing method. These tests include visual inspection, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing, XCT, acoustic emission testing and thermography test. The application of each of the mentioned NDT methods in additive manufacturing and their suitability for detecting the defects of parts manufactured by AM method were investigated. Also, the sensitivity, advantages and disadvantages of each method were evaluated and the types of defects and the ability to detect these defects by NDT methods were mentioned. Considering that there are 7 categories of production methods in additive manufacturing, in this research, the application of each NDT test for different categories of AM process was discussed and the challenges in each were mentioned.