جستجوی مقالات مرتبط با کلیدواژه « کوبش فراصوتی » در نشریات گروه « فنی و مهندسی »

Wire EDM (WireCut) is a machining process utilizing electric discharge to gradually cut a workpiece with a spark-generating thin wire. It offers benefits like non-contact cutting, versatility with materials, and precise dimensional accuracy. However, it is important to note that surfaces cut by WireCut process may exhibit tensile residual stresses with significant values in the surface layers. Ultrasonic Peening Treatment (UPT) can be employed as a new approach to modify the surface structure of wire EDMed workpieces. UPT, which induces compression in the surface layers of the workpiece, generates compressive residual stress and enhances mechanical properties including hardness. In this study, UPT was performed on wire EDMed workpieces made of alloy steel Mo40 (DIN 1.7225) using an ultrasonic vibrating tool on a lathe, at 3 levels: finishing, semi-finishing, and roughing. The impact of parameters such as the number of passes, feeding rate, and the type of wire EDM cut on the constant amplitude of vibration were studied to understand their effect on the residual stress generated. The experiments conducted using the Taguchi method revealed that in every case, this process resulted in the conversion of tensile residual stresses into substantial compressive residual stresses in wire EDMed workpieces. The compressive residual stress also reached 1654 MPa. More passes lead to higher compressive residual stress, while a higher feeding rate leads to a decrease. Surface hardness increased by 30%, 31%, and 48% for the semi-finishing, finishing, and roughing workpieces in the initial pass. This trend continued with each subsequent pass.Key words: Residual stress - Surface hardness -Wire Electric Discharge Machining (WEDM) - Ultrasonic Peening Treatment (UPT) - Mo40 alloy steel

Nowadays, Aluminum alloys are chosen for various industrial applications due to their special properties and high corrosion resistance. By optimizing the surface properties of Aluminum alloys, the performance and reliability of using these materials can be effectively improved. Therefore, investigating the surface mechanical treatment has been the focus of researchers and various mechanical methods have been used to improve the surface characteristics of Aluminum alloys. Among these methods, ultrasonic hammer peening is a cold work process in which many impacts are applied to the surface of the sample in a short period with high frequency. In this research, the effect of ultrasonic hammer peening on the wear properties of Aluminum alloy Al6061-T6 has been investigated. To carry out the process of ultrasonic hammering, three parameters of vibration amplitude, rotational speed of the work piece, and feed rate of the tool were selected and their effect on the wear resistance was investigated. The obtained results showed that the ultrasonic hammer peening increased the surface hardness by about 141.4%. With the increase of the vibration amplitude and the feed rate, the wear resistance increased and the increase of the rotational speed decreased the wear resistance. The highest wear resistance has been obtained in the vibration amplitude of 11 µm, rotational speed of 500 rpm, and feed rate of 0.8 mm/rev. As a result, the wear resistance has increased by about 46% compared to the raw material in these conditions.

Ultrasonic needle penning is a modern technique that enhances the surface properties of metallic components by imposing static and dynamic loadings. The efficiency of this technique dramatically is dependent on the process parameters. In this study an experimental and numerical investigation on ultrasonic needle penning was carried out. The numerically predicted residual stress profile was verified using X-ray diffraction measurement of residual stress. A 3D finite element model of ultrasonic needle penning was simulated by ABAQUS software. Moreover, a parametric study was performed to investigate the effects of needle diameter, amplitude, device moving speed and static force on residual stress distribution. In order to design of experiments and determine the optimized process parameters of ultrasonic needle penning, Taguchi’s method was implemented. Based on the results, needle diameter had the lowest impact on maximum compressive residual stress and residual stress increases by increasing amplitude and reducing device moving speed. The maximum residual stress was achieved for the needle diameter of 4mm, the amplitude of 16µm, the device moving speed of 1.5cm/s and the static force of 10N. For the optimum case, compressive residual stress was improved 24%.