Fatigue behavior of conventional and stationary shoulder friction stir welded EN AW-5754 aluminum alloy using load increase method. - In: Metals, ISSN 2075-4701, Bd. 10 (2020), 11, 1510, insges. 11 S.
https://doi.org/10.3390/met10111510
Thermal efficiency in laser-assisted joining of polymer-metal composites. - In: Materials, ISSN 1996-1944, Bd. 13 (2020), 21, 4875, insges. 16 S.
https://doi.org/10.3390/ma13214875
Statistical analysis of pulsed laser beam welding repair strategies of nickel-base superalloys. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 638-643
Pulse shaping is a suitable option to adapt energy input and temperature gradients in the base material during filler wire assisted laser beam welding, although the influence on the temperature-depended microstructure and γ-precipitation strengthening of Nickel-base superalloys as well as the process windows are not sufficiently understood so far. Therefore, the influence of pulse parameters, preheating temperature, hot-wire heating power and wire feeding rate on the deposition process and the resulting macro- and microstructure of similar Nickel-base superalloy joints of Inconel 738 low carbon (IN 738 LC) with Haynes (HS 282) filler are investigated. The statistical analysis of the multidimensional parameter space with respect to the geometric properties of the weld seams (dilution, aspect ratio and wetting angle) and hot-crack formation revealed high reliability and predictability concerning individual choice of suitable parameters in field repair application.
https://doi.org/10.1016/j.procir.2020.09.099
Effect of reduced ambient pressure and atmospheric composition on material removal mechanisms of steel and aluminum by means of high-speed laser processing. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 487-492
Balancing processes require highly precise mass corrections especially in case of high-speed turning rotors. Material removal by means of cw-mode laser radiation represents a novel approach for industrial balancing applications in order to achieve sufficient removal rates. Thereby, spatter formation was identified as primary removal mechanism. In this study, the effect of reduced ambient pressures and atmospheres with varying concentrations of argon, nitrogen and oxygen on spatter formation and loss of mass were investigated for AISI304 (1.4301, X5CrNi18-10) and EN AW-2618 (DIN 3.1924) under the use of a 400W single mode-fiber laser.
https://doi.org/10.1016/j.procir.2020.09.169
Acoustic process monitoring in laser beam welding. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 763-768
Structure-borne acoustic emission (AE) measurement shows major advantages regarding quality assurance and process control in industrial applications. In this paper, laser beam welding of steel and aluminum was carried out under varying process parameters (welding speed, focal position) in order to provide data by means of structure-borne AE and simultaneously high-speed video recordings. The analysis is based on conventionally (e.g. filtering, autocorrelation, spectrograms) as well as machine learning methods (convolutional neural nets) and showed promising results with respect to the use of structure-borne AE for process monitoring using the example of spatter formation.
https://doi.org/10.1016/j.procir.2020.09.139
Laser-assisted joining of AISI 304 thin sheets with polymers. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 531-536
Laser-assisted metal-polymer joining gains importance in several applications due to the possibility of a direct connection between both materials. Aside from lightweight construction, a direct metal-polymer connection shows a high economic potential especially in large series production, e.g. domestic appliances. Based on this motivation, laser-assisted simultaneous joining of AISI 304 thin sheets (0.3 1.0 mm, X5CrNi18-10) with unreinforced polypropylene (PP) as well as acrylonitrile butadiene styrene (ABS) is carried out. Starting from a generally valid process description based on the energy per sheet thickness, the distortion as well as the mechanical properties are examined, whereby up to 17.4 MPa are reached and the tensile shear strength drops by at least 15 % during alternating climate test (-20 75 ˚C, 40 75 % rel. humidity). Further investigations under cyclic load showed, that long life fatigue strength (5 106 cycles) is achieved at about 47 % of the initial tensile shear strength.
https://doi.org/10.1016/j.procir.2020.09.177
Process control by real-time pulse shaping in laser beam welding of different material combinations. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 769-774
Joining of metallic material combinations with limited solubility is a challenging task. Because of low solubility, such material combinations lead to the formation of intermetallic compounds (IMC) during common weld bath. IMC then lead to increased hardness and brittleness. Generally, these properties are undesirable and the aim is to reduce intermetallics to a minimum. In this contribution, a process control by real-time pulse shaping is realized, whereby the power is adjusted in each individual pulse. The material-specific emissions are continuously detected by photodiodes and used as control variable. By equipping the photodiodes with band-pass filters, the wavelength can be selected in a material-dependent manner. The control loop including data processing and pulse shaping as well as the connection to the power supply of the laser beam source is realized by a novel system in less than 10 µs. This enables laser welding of different metals with a nearly constant penetration depth at the boundary layer and, therefore, the limitation of IMC.
https://doi.org/10.1016/j.procir.2020.09.137
Strategies for increasing the productivity of pulsed laser cladding of hot-crack susceptible nickel-base superalloy Inconel 738 LC. - In: Journal of manufacturing and materials processing, ISSN 2504-4494, Bd. 4 (2020), 3, 84, S. 1-23
A novel repair strategy based on decoupled heat source for increasing the productivity of wire-assisted pulsed laser cladding of the [gamma]'-precipitation strengthening nickel-base superalloys Inconel 738 low carbon (IN 738 LC, base material) and Haynes 282 (HS 282, filler material) is presented. The laser beam welding process is supported by the hot-wire technology. The additional energy is utilized to increase the deposition rate of the filler material by increasing feeding rates and well-defining the thermal management in the welding zone. The simultaneous application of laser pulse modulation allows the precise control of the temperature gradients to minimize the hot-crack formation. Accompanying investigations such as high-speed recordings and numerical simulations allow a generalized statement on the influence of the adapted heat management on the resulting weld seam geometry (dilution, aspect ratio and wetting angle) as well as the formation of hot-cracks and lack of fusion between base and filler material. Statistical analysis of the data - the input parameters like laser pulse energy, pulse shape, hot-wire power and wire-feeding rate in conjunction with the objectives like dilution, aspect ratio, wetting angle and hot-cracking behavior - revealed regression functions to predict certain weld seam properties and hence the required input parameters.
https://doi.org/10.3390/jmmp4030084
Feasibility study of using integrated fiber optical sensors to monitor laser-assisted metal-polymer joining. - In: Welding in the world, ISSN 1878-6669, Bd. 64 (2020), 9, S. 1565-1578
The possibilities and challenges of using fiber optical sensors to monitor the laser-assisted joining of metal-polymer joints have been described in this article. Fundamental investigation proves the basic suitability of the measuring method for this application and studies the effect of essential influencing variables of the joining process - e.g., the clamping force - on the resulting sensor signals. In addition, the strain state (because of the process temperature and shrinkage of the polymer) of the parts to be joined can be traced as a function of the joining partners, the process parameters, and the material thicknesses. It is shown that the fiber optical method is suitable for process monitoring directly in the joining zone of metal-polymer hybrids and providing a tool for detailed strain measurements in the joint zone during subsequent component testing.
https://doi.org/10.1007/s40194-020-00942-y
A novel approach for the detection of geometric- and weight-related FSW tool wear using stripe light projection. - In: Journal of manufacturing and materials processing, ISSN 2504-4494, Bd. 4 (2020), 2, 60, S. 1-20
https://doi.org/10.3390/jmmp4020060