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Shearography is one of the recent methods of non-destructive technique based on the interference of laser beams that have been reflected from the surface of the specimen. This method, which has high speed and accuracy, can evaluate the displacement derivative on the sample surface at once. In this paper, the possibility of sub-surface cracks detection with different lengths and angles in composite samples was investigated by shearography method and thermal stimulation system. For this purpose, in composite samples, manufactured and controlled cracks were created with different lengths and angles. After calibration of the performance of the shearography setup, two heat sources of radiation were used to load samples. Loading quantity, the amo
In this study, the growth of induced delamination in off axes composite laminates has been investigated. Glass-Epoxy composite laminates and Glass-Kevlar-Epoxy hybrid composite laminates with cross-ply [04/90n]s and angle-ply [304/90n]s and [454/90n]s composite layup, containing a low density matrix crack in 90? layers have been made. Then they have been subjected to tensile loading in experimental tests in order to investigate the growth delamination from the location of the matrix cracking and to measure the stiffness degradation. The experimental observations reflect the effects of hybridization and staking sequences on the induced delamination growth for the first time. In addition, the growth of delamination in the considered composite
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 internal 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
Turbine blades are one of the most sensitive and important hot parts of gas turbines, so that the efficiency and life of turbines are directly related to the operation of these components. Therefore, to prevent damage caused by high temperatures, they must be properly cooled. The common method of cooling these parts is to pass the cooling fluid through their complex internal channels. Non-destructive testing of thermography, is one of the new methods for detecting imperfections in these cooling paths which is considered in this article. Thermal loading is applied in an active manner by hot steam generator system. In order to identify the capability of this system in the detection of the residuals in the cooling system of blades, 3 kinds of
In this paper, the effects of the joint type on the driven-out bead of the roll-formed pipes, welded by high-frequency induction welding process are studied. The main goal is to predict and reduce the volume of the bead driven out in the weld seam. Moreover, it aims to move the semi-solid bead during welding to the outer diameter of the pipe. This study has two prior aims: to produce a defect-free joint and to improve the mechanical and metallurgical properties. In order to optimize the weld joint, various joint types have been investigated by experimental tests and simulation. Lastly, destructive tests were used to determine if the desired mechanical properties of the weld joint were obtained. The metallurgical properties and the derivatio
In this paper, shearography or speckle pattern shearing interferometry, which is one of the moders optical and non-contact methods in non-destructive testings (NDT) of materials, is investigated. To this purpose, the workpeace should be subjected to a kind of loading. Some of the conventional loading methods in are relative vacuum loading, thermal loading, and Acoustic Loading. In this paper, The Acoustic loading method has been developed to stimulate and identify the defects. Two methods of thermal loading and Acoustic loading were compared on polyethylene and Teflon pieces with Delamination created behind them, thereafter, The effect of the type of loading on the capability to identify defects, as well as the quality of scanning results,
In this paper, ultrasonic welding of glass fiber reinforced thermoses, co-cured whit a thermoplastic has been studied. Co-curing process forms a connection between the thermoset and the thermoplastic while curing the composite. Considering that the calculated stress should not be related to the dimensions of the sample, a horn with a tip dimension smaller than the standard overlap was used. The results show that the actual weld dimensions are bigger than the intended weld dimensions. This has happened due to the movement of the melted thermoplastic to the sideways during the welding. The design of experiment has been done using response surface central composite, and a quadratic equation based on the lap shear strength of the welds containi
In recent years, limitations such as the inability to inspect composite materials in common non-destructive testing methods (NDT) have led to the development of new methods such as optical thermography (OPT) and digital shearography (DISH) which are able to resolve these limitations with non-contact and full field inspection. The aim of this paper is to compare the new and traditional NDT methods and also to mention the main features of these new methods such as detection of the defects by stimulating the specimen and receiving its response as out-of-plane displacement derivative (strain) and temperature gradients. The results show that the loading conditions, type of inspected defects, shear amount and the studied material are effective pa
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
Welding residual stresses are considered as significant factors for the reduction of fatigue life and load bearing of welded structures. In this article, characterization of a low-temperature stress-relief method called vibratory stress relief process was investigated. In this regard, welding of a butt joint of two steel plates was simulated and induced welding residual stresses were calculated. An experimental residual stress measurement was conducted to verify the numerical results. It was established that the simulated residual stresses are in good agreement with the measured results obtained from the hole drilling strain gauge measurements. In the following, the vibratory stress relief process of the welded joint was simula
The cold roll forming is a continuous metal forming process to produce a large variety of profiles. A major product of the cold roll forming is wide profiles whose application is expanding in the construction of houses, bridges, airports, sports arenas, etc. The edge wrinkling is one of the common defects in the cold roll forming of the wide profiles. The edge wrinkling leads to several problems, such as decrease of dimensional tolerances, abrasion of forming rolls due to contact with the wrinkled edge, non-uniform distribution of forming through the production line, and unsuitable energy consumption. In this paper, the mechanics of edge wrinkling in the cold roll forming of the wide profile is investigated, and the effect of
In this paper, the application of pre-heating process on the reduction of residual stress in the repair welding of steel pipes is investigated. In this purpose, a thermo-elastic-plastic molding of the repair welding process is developed using finite element method. In order to verify this modeling method, experimental data of repair welds of a carbon steel pipe, measured by deep hole drilling method, were utilized. The verified results indicated that the developed computational method can be beneficially used as an effective tool to predict the residual stress of the pipes undergo the repair welding. The verified finite element model was utilized in the repair welding of carbon steel and stainless steel pipes to consider the effects of preh
In this article, the influence of SiC nanoparticles on the friction stir welding of AZ91 magnesium alloy has been studied. For this purpose, a groove was designed to incorporate the nanoparticles into the weldment without requiring any additional tool to cover the weld surface. The welding process was carried out with and without nanoparticles in different process conditions. The mechanical properties and microstructure of the prepared joints were also studied. The results indicated that without using the nanoparticles, the minimum grain size of 2.79??m along with the strength of 99% of the base metal can be achieved by applying the highest examined welding traverse speed and the lowest rotational speed. By using the SiC nano
High-frequency induction welding (HFIW) is among the most commonly used methods for producing roll formed pipes. In this paper, weld quality is evaluated through examining the weld properties, in order to obtain the effect of edge preparation on improvement of weld quality. Temperature distribution in the weld zone is studied through the groove shape of the weld joint, and the other parameters such as current, frequency, and linear speed, considered constant, are equal to 1400?A, 150?kHz, and 25?m/min respectively. The mechanical and metallurgical properties of the weld metal were evaluated by tensile test and metallography. The appropriate temperature distribution resulted from modifying the shape of the connecting edges, le
In this paper, thermo-mechanical behavior of the welding process was analyzed to determine the effect of preheating on the distortion magnitude and distribution in dissimilar joints. By using a verified finite element model, an efficient user subroutine was developed to consider the effects of phase transformation. In order to verify the model, experimental data for dissimilar joints, obtained by CMM measuring device method, were utilized. Good agreement was observed between the finite element and experimental data. The results indicated that the developed computational method is an effective tool to predict the distortion of dissimilar weld joints. The present finite element model was developed in a butt-welded plate to consider the effect
In this research, the twist and the longitudinal bow defects were studied by finite element analysis in the asymmetrical channel sections. Effects of the geometrical properties including the strip thickness, the web width, and the flange width were investigated on the above effects. Some experiments were performed on an industrial roll-forming machine to verify the accuracy of the finite element model. The results showed that the twist angle decreases with the increase of both strip thickness and web width. However, the twist angle increases with the increase of flanges width. Also the variations of the longitudinal bow height are similar to those of the average residual longitudinal strain of both flange edges.
In this paper, we examine the method of Digital Image Correlation (DIC) and introduce a new theory for measuring residual stresses in non-destructive mechanical parts. In this regard, with the aim of scientific proof, the new theory introduced into the review of the article related to the idea presented in this study and its details have been discussed. First, the principles of the method of digital image correlation and methods for calculating correlation coefficients are presented. With the aim of evaluating the authenticity of the outputs of digital imaging, by constructing the required equipment and performing empirical tests to perform the process, comparing the output results of the digital imaging overlap method and the finite elemen
Laser shear interferometry or shearography is one of the novel NDE methods that is used to inspect and estimate the size of subsurface defects. In this research, a new method for estimating the size of plane defects was presented. In order to verify and compare the proposed method with conventional methods and studying the effect of defect depth and shear size on the accuracy of the measurements, different plane defects were tested. The size of the defects was measured in different conditions and the estimation error was reached in each case. Also, Finite element simulation was used to study the effect of loading time estimation error. The results showed that the proposed method was able to predict the defect more accurately than the conven