Showing 5 results for Ultrasonic
M. Bekrani,
Volume 6, Issue 1 (8-2020)
Abstract
One of the novel ultrasonic phased array based scanning methods for ultrasonic imaging in non-destructive test is total focusing method (TFM). This method employs maximum available information of the phased array elements and leads to an improved defect detection accuracy compared to conventional scanning methods. Despite its high detection accuracy, TFM behaves weak in distinguishing the real defects from noise which is because of its high background noise level. In this paper, a low complexity technique is presented for performance improvement of TFM which employs a beamforming method on the phased array received signals and leads to a reduction of the background noise and increase in the accuracy of the defect detection. To this end, a thresholding technique along with three-level clipping of the array received data is applied for low-complexity approximation of the correlation matrix inverse employed in the beamforming. Experimental results for detection of drilled holes on a steel pipe show a background noise reduction of 4.45 dB and improvement in the hole distinction of about 3 dB in comparison to those of TFM. In addition, as shown in the simulation results, the minimum distinguishable distance between two neighbor reflector points for the proposed method is 0.21 mm which is 0.23 mm lower than that for TFM.
A. Jabarirad, D. Akbari, M. Golzar,
Volume 6, Issue 2 (12-2020)
Abstract
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 containing three principle parameters time, force and amplitude was suggested, as well as predicting the optimum values. The equation shows that the force is an insignificant factor. In the samples with a higher time value the thermosetting resin started to degrade. The dominant failure mode of the specimens is segregation between the thermoset and fibers. The results show that the optimum parameters can result in a lap shear strength of 28.2 MPa, which is a very decent value compared to other methods of joining.
Hamed Tirband, Davood Akbari, Mohammad Golzar,
Volume 7, Issue 1 (8-2021)
Abstract
In this research, tensile strength of ultrasonic welded parts made of thermoset polymer-reinforced glass fiber with surface preparation has been investiagted. In order to elevate the adhesion of two surfaces laser grooving method has been applied. Two type of thermoplastic materials including Plymethyl methacrylate (PMMA) and polypropylene (PP) have been used as interlayers. Influences of main welding parameters were investigated. The results show that the force and compression parameters in these joints have been ineffective parameters and in higher weld welds, the thermosetting resin has started thermal degradation. The pressure considered constant and set at 2 bar, welding time set at 1.6 seconds and holding time considered 3 seconds. The results showed that the minimum tensile strength of welded samples with laser surface preparation method is 1286 N, which is much more than maximum tensile strength of welded samples without any surface preapration. This indicates that laser beam surface preparation is an effective method in improving of the adhesion strength of thermoset polymeric parts.
H.r. Masoumi, H. Razavi, A.h. Meysami, M. Khodaei,
Volume 7, Issue 1 (8-2021)
Abstract
The aluminum alloys of Al1050 with thickness of one millimeter and Al3105 with thickness of half millimeter were joined via ultrasonic spot welding (USW). To create a suitable welding, a vibrating horn (welding tool) fit to transducer and ultrasonic generator was designed using ANSYS software. Due to mechanical and thermal cycles during USW, both diffusion and mechanical mixing facilitated the formation of welded interfaces. The alloying element, Mn, in Al3105 diffused into Al1050 during USW, and diffusion behavior varied with selection of top sheet. The fracture mechanism during lap shear testing, i.e. debonding or pullout fracture, varied based on welding power, time and pressure of jack. The optimal point for the existing welding conditions was obtained. The best welding conditions were for 750 W at 2 and 3 seconds when the horn was held on the overlap of the sheets. Also, in the tensile test, sheet rupture was performed around the welding spot (out of welding spot).
M. N. Sadraee Far, F. Kolahan,
Volume 9, Issue 2 (1-2024)
Abstract
In this study, we employed the active TIG method with ultrasonic vibration (UV) for welding 316L steel. Throughout the active tungsten inert gas (A-TIG) welding process, a high-frequency ultrasonic generator produced high-intensity acoustic waves at an optimal frequency of 20.3 kHz and a vibration amplitude of 8 micrometers. These waves were directed into the molten weld pool, covered by SiO2 nanoparticles serving as an activating flux. The effect of UV and nanoparticles on weld geometry and weld microstructure was analyzed and compared with conventional TIG welding proces. The results indicated that the use of nanopowder not only increased weld penetration by approximately 17.5% but also reduced the Weld Bead Width (WBW) by 28% compared to Conventional TIG. These values increased by 25% and decreased by 35%, respectively, in the presence of ultrasonic waves. Additionally, the introduction of nanomaterials into the molten pool led to finer grains. The ultrasonic waves played a crucial role in ensuring the uniform distribution of these nanomaterials in the melt, ultimately resulting in an enhanced microstructure of the weld.
