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Guided wave inspection of dissimilar material joints using time reversal techniques
摘要： Dissimilar material bonding has recently gained a lot of attention in automotive, marine and defense applications. Nevertheless, a major hurdle limiting the full acceptance of such structural components is the lack of non-destructive evaluation (NDE) technique to evaluate their strength, which depends on the integrity of the bonding layer. In this work, guided wave (GW) inspection with surface-mounted piezoelectric sensors (PZT) was employed along with time reversal for Structural Health Monitoring (SHM) of dissimilar material lap-joints. Baseline-free probability imaging was used to identify the location of artificial disbond. The results of GW inspection were further validated with ultrasonic C-scan. Overall, the technique shows great potential in detection of defects in bonded joints.
关键词： guided waves,time reversal,diagnostic imaging,SHM,Dissimilar material joints
更新于2025-09-23 15:22:29
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Laser Brazing of Dissimilar Joint of Austenitic Stainless Steel and Pure Copper
摘要： In many industries, there are applications that require the joining of stainless steel and copper components; therefore, the welding of dissimilar stainless steel/copper joints is a common process. For this investigation, the optimal brazing conditions and suitable filler metals for laser brazing of stainless steel/copper lap joints were studied. Tensile shear force increases with increases in the laser spot diameter or in the laser irradiation angle, which is associated with increased bonding width; however, as bonding width approaches 2 mm, tensile shear force reaches a saturated value due to fracturing at the HAZ of the Cu base plate. In order to obtain joints with high tensile shear strength, laser brazing was optimized by using Cu-Si-based filler metal under the following conditions: laser power: 4 kW; spot diameter: 3mm; laser irradiation angle: 80 degrees; irradiation position shift: 0.6 mm; brazing speed: 0.30 m/min; and filler metal feed speed: 0.30 min. Concerning filler metals, it was found that the Ni-Cu type showed relatively large tensile shear force even at high welding speeds in comparison with those of the Cu-Si, Cu, Cu-Ni, Ni-Cu and Ni types, respectively.
关键词： Laser brazing,Copper,Filler metal,Dissimilar material,Stainless steel,Brazing condition
更新于2025-09-16 10:30:52
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Influence of the laser-based surface modification on the bond strength for friction press joining of aluminum and polyethylene
摘要： Friction press joining is an innovative joining process for the production of plastic-metal joints without additives, in an overlap configuration. In order to achieve a high bond strength, the metallic joining partner is pretreated with laser radiation. Subsequently, heat is induced by friction and pressure during the joining process, causing the thermoplastic material to melt and adhere to the metallic joining partner. In this work, the temperature distribution during the process in the composite is analyzed and characterized. It was found that the occurring temperatures and temperature differences are not only dependent on the rotational speed, but also on the feed rate. It is also shown that the friction surface temperature can be used as an indirect control variable for a model-based, closed-loop control. Based on these findings, various surface modifications for the metallic joining partner were investigated and analyzed with regard to the maximum strength of the joint. It was observed that the highest tensile shear strength can be achieved with a quasi-chaotic nano structure. In addition, the joining compound was characterized by a thin section, facilitating the identification of specific zones in the joint. These investigations show the high potential for friction press joining of plastics and metals, and form the basis for a model-based control of the joining zone temperature.
关键词： Polymer metal joining,Dissimilar material joining,Aluminum,Hybrid bonds,Thermoplastics,Friction press joining
更新于2025-09-12 10:27:22
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Influence of the degree of dilution with laser beam vacuum-welded Cu-Al mixed joints on the electrical properties
摘要： A great potential for light-weight construction lies in the substitution of copper by aluminum. The state of the art, so far, has put the focus only on the identification of the crack-sensitive intermetallic phase. External influential factors, such as temperature, current-feed and time bring about the change of the joining zone structure by diffusion and electro-migration. Moreover, a temporal change of the technological properties (increase of the electric resistance, reduction of strength) of the dissimilar material joint will occur. Findings about this behavior for laser beam under vacuum welds will allow to draw conclusions about the expected life-time.
关键词： Laser beam welding,Dissimilar material joint,Single-moder fiber laser,Copper,Aluminum
更新于2025-09-12 10:27:22
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Nd: YAG Pulsed Laser Dissimilar Welding of UNS S32750 Duplex with 316L Austenitic Stainless Steel
摘要： Duplex stainless steels (DSSs), a particular category of stainless steels, are employed in all kinds of industrial applications where excellent corrosion resistance and high strength are necessary. These good properties are provided by their biphasic microstructure, consisting of ferrite and austenite in almost equal volume fractions of phases. In the present work, Nd: YAG pulsed laser dissimilar welding of UNS S32750 super duplex stainless steel (SDSS) with 316L austenitic stainless steel (ASS), with di?erent heat inputs, was investigated. The results showed that the fusion zone microstructure observed consisted of a ferrite matrix with grain boundary austenite (GBA), Widmanst?tten austenite (WA) and intragranular austenite (IA), with the same proportion of ferrite and austenite phases. Changes in the heat input (between 45, 90 and 120 J/mm) did not signi?cantly a?ect the ferrite/austenite phase balance and the microhardness in the fusion zone.
关键词： Nd: YAG,microstructure,austenitic steel,microhardness,laser welding,dissimilar material,duplex steel
更新于2025-09-11 14:15:04