نشریه فناوری آزمون های غیرمخرب
سال سوم شماره 1 (پیاپی 11، بهار و تابستان 1401)

In this Paper, thermography inspection of carbon fiber reinforced composite parts made by two methods of vacuum infusion and manual layering has been investigated. In this method, composite materials are subjected to a direct electrical stimulation including voltage of 5 volts, current of 1.6 amps for 1-2 seconds and are heated uniformly. By means of an infrared camera, non-destructive evaluation of these parts is conducted. Since the first signs of defects in the electrical stimulation are changes in temperature, this method greatly contributes to the quality of the thermal images taken by the infrared camera and the accuracy of the test. By applying the electrical conductive stimulation directly to the samples, cracks with dimensions of 2 and 1.5 cm in the hand layup parts and cracks with dimensions of 2, 1.5 and 1 cm in parts made by vacuum infusion method were detected. Direct stimulation by means of electrical conductive makes the method more flexible in many real parts that cannot be tested with conventional methods like direct heating or flashlights.

Weld strength is one of the most important goals in the welding industry. Non-destructive testing methods such as Radiography testing (RT) are widely used for weld strength inspection. In RT test, discontinuities and defects appear on the radiograph and are surveyed by interpreters. To increase the contrast of the radiographs, image processing methods are used to sharpen the edges and identify the defects by reducing the fogginess. In this research, two different Fourier algorithms, namely, discrete Fourier transform, and cosine Fourier transform have been used to improve the contrast of welding radiographs and to identify defects and their information. The comparison of the results of the two methods shows that the discrete Fourier transform method has a better efficiency than the cosine Fourier transform method in determining the information of the welding region, IQI lines and welding defects, and its execution time is also less. The evaluation of results by experts show that the contrast of the reconstructed images improves between 5 and 40% for different welding region with the discrete Fourier transform method. According to experts’ opinions, the reconstructed images with the cosine Fourier transform method do not have the necessary efficiency due to the artifact.

Predicting defect detection capability by means of various non-destructive testing methods in test pieces with different geometries and thermal properties is a challenging issue. In this article, the capability of circular defect detection by thermography testing using analytical method has been investigated. Thermal contrasts produced over the surfaces of circular defects in AA 7075, AISI 1015 and SS316 samples by pulsed thermography (PT), step-heating thermography (SHT) and long pulse thermography (LT) were compared. The thermal contrast of defects in samples with thicknesses of 8, 6 and 4 mm made of AISI 1015 were also compared using the three stimulation methods mentioned. Results showed that PT is the best method in samples with high thermal diffusivity. On the contrary, LPT produces a higher thermal contrast in samples with low thermal diffusivity. Also, by increasing of the thickness, more thermal contrast occurs in all three stimulation methods.

Delamination is one of the most common failure types among polymer composites, which occurs in all types of loading, including mode I. For this reason, composite laminates are used in different ways, including the method of using metal Z-pins along the thickness, in order to delay the Delamination time and increase the strain energy release rate. In the present study, the mechanical performance and Acoustic Emission of Delamination in glass/polyester composite have been investigated using the ASTM D5528-01 standard in the manufacture of DCB samples. First, the force-displacement curve and crack growth resulting from Delamination for Z-pinned steel and copper samples were compared with those without pins. The critical load of each sample to obtain the interlayer fracture toughness for mechanical behavior according to the standard D5528-01, as well as the critical load for the Acoustic Emission behavior, was associated with the increase and growth of some signal energy and the jump of cumulative Acoustic Emission energy. It was found that the strain energy release rate increases by using metal pins along the thickness. Also, the fracture toughness obtained from the mechanical method was verified by the Acoustic Emission method.

Mass production of nanocomposites is not possible without proper methods for non-destructive health inspection of these products. It is obvious that the aggregation and agglomeration of nanoparticles in the polymer matrix have a great effect on the quality of the nanocomposite piece. In this article, the accumulation of carbon nanotubes in nanocomposite parts has been investigated with laser interferometry method. This non-contact method is based on the reflection of the laser beam from the sample surface. In this regard, samples with carbon nanotube accumulation defects were made in the epoxy matrix. Also, thermal loading by a halogen lamp has been used for non-contact excitation of these samples. The results prove the capability and feasibility of detecting the nano particle accumulations using the laser interferometric method. Moreover, an acceptable band for both adjustable parameters of the process including loading size and shear distance were found.

Identifying the type of pigments used in historical and cultural artifacts is one of the most important topics facing researchers in this scope, which can answer many questions and concepts in the field of conservation of historical and cultural artifacts. The use of non-destructive analysis methods to investigate and identify the type of materials and pigments used is also one of the most important technical topics in the field of cultural heritage studies, which is less discussed among researchers in this field. For this reason and for studying the historical artifact of the Timurid dynasty, non-destructive methods such as technical imaging (UVF, IRR, VIS), portable Raman spectroscopy, and portable X-Ray fluorescence spectroscopy are used. The studied artwork is a folio from the Timurid Zafarnama manuscript of the 15th century AD. The most important pigments used in this artwork include red, blue, white, green, gold, brown, cream and orang. Data analysis shows the use of Indigi blue, Vermilion and Minium pigments as red, lead white, Malachite green and Litharge yellow. Some other pigments were created by the artist in combination, and some of the existing examples have been identified.

In this study, the quality measurement of a plaster structure armed with steel rods and an internal air cavity was carried out. The scanner system is equipped with a cesium-137 gamma radioactive source with 661.7 keV photopeak energy and a linear array CdWO4 scintillating crystal of detector with 8 x 8 mm2 pixel size. The analysis of the internal structure of the sample was performed in two simulation and experimental phases. MCNPX Monte Carlo code was used to perform the simulation phase.  MLEM and Back Projection methods were used to reconstruct the images. The simulation results were compared with the experimental outputs, their performance in the 3D display inside this phantom was investigated. The results showed that the MLEM reconstruction method is more efficient than the back projection reconstruction method both in the simulation phase and in the experimental phase in providing internal images. The results showed that with modeling, it is possible to evaluate the tomographical pictures of the manufactured samples, and before setting the experimental, it can be used for different materials and geometries.

Natural gas is one of the valuable non-renewable resources in the country, which after sweetening and separation is transferred through pipelines for industrial and domestic use. Since the pressure of the transferred gas decreases due to various factors including friction, slope, etc., along the pipeline, Gas Compression stations are utilized. Operators of gas compression stations urgently need to prioritize the equipment to provide a repair and maintenance plan for the equipment and avoid spending huge inspection costs. In this study, an optimal model for examining and prioritizing critical equipment has been presented. In addition to being quantitative, it also includes more details based on the criteria of safety, health, and environment (HSE). Using the multi-criteria decision-making method, TOPSIS, which generally prioritizes the investigated objectives (equipment) in order of proximity to the ideal solution, it was shown that the turbine, compressor, and scrubbers are the most important (critical) equipment used in stations. Also, the obtained results were compared with the model provided by the gas transmission company, based on which the proposed model, due to its quantitative nature, its use of new decision-making methods, comprehensive details, and prioritization of the studied criteria is a more reliable model than the model of the gas transmission company.