29 research outputs found
Investigation on Aging of Metallic Surface Integrated Micro-POFs
No full textAbstractSurface integrated optical waveguides present a possibility to realize inherent communication structures. Optical communication is used particularly by smart parts exposed to humidity, high vibration or electromagnetic fields. We developed a method to integrate micro-polymer optical fibers (μ-POFs) into metallic surfaces using the dispensing process. After positioning, the μ-POFs are bonded to the surface by dispensing UV-curing adhesives. The bonded optical waveguide is coupled at its end-facets respectively to sender or receiver elements. Efficiency of the coupling depends on the alignment stability of the polymer fiber to beam sender or receiver. In operating conditions the smart parts undergo aging due to thermal and mechanical stress. We investigated the possible influence of this aging on the position stability of bonded μ-POFs, and consequently on the optical communication efficiency. The experimental set-up as well as the measurements are presented and discussed in this article
InUse – Intelligent Ring Washer for Measurements of Forces in Screw Connections
No full textDie lösbare Verbindung von mechanischen Komponenten innerhalb von Maschinen und Anlagen wird zumeist über Schraubverbindungen realisiert. Um eine ausreichende Verbindung zu erzielen werden derzeit die Klemmkräfte durch ein definiertes Anzugsmoment aufgebracht. Bei der Berechnung des Momentes entsprechend der benötigten Kraft finden Reibbeiwerte innerhalb der Schraubverbindung Berücksichtigung, welche nur bedingt ermittelt werden können. In kritischen Maschinenkomponenten wird daher eine Überdimensionierung der Schrauben zur Erhöhung der Sicherheit akzeptiert. Die direkte Kraftmessung mittels einer intelligenten Unterlegscheibe und eine transpondergestützte Datenübertragung ermöglicht es, die Kräfte genau einzustellen und somit die Sicherheit zu erhöhen.Releasable connections between mechanical components inside machinery are mainly accomplished with screws. The necessary clamping forces to achieve a sufficient connection are produced by an applied torque. To calculate the applied torque according to the required forces, the friction coefficient within the screw needs to be taken into account, which can only be conditionally determined. Therefore, in critical machine components the employed screws are commonly over-dimensioned to increase safety. The herein presented device comprises a force-measuring washer with an onboard RFID tag for passive and wireless data transmission. In this way, the safety of the connection can be enhanced by accurately measuring the force and adjusting the applied torque accordingly
Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding
No full textAbstractAs an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented
Conditioning of Surface Energy and Spray Application of Optical Waveguides for Integrated Intelligent Systems
No full textAbstractNetworks of optical waveguides allow for data transmission and sensing applications. Therefore, this technology is a key element for the integration of intelligent systems and structural health monitoring. Optical waveguides are the essential backbone to connect these structures.The flexible and high-resolution manufacturing of waveguides, also on three-dimensional substrates, is accomplished by a combination of two printing processes. In the first step, flexible substrates are conditioned by a printing technology with an adapted flexographic printing mechanism. To produce the optical waveguide itself, the Aerosol-Jet-Printing process of liquid polymer or varnish is used on pre-conditioned areas with hydrophobic or hydrophilic behaviour. Waveguides fabricated by this two-stage process reach parabolic cross sections with a minimum width down to 10μm. This paper shows the mechanism for the use of the processes and latest results concerning the choice of materials, which allow the operability for this kind of manufacturing. We show the adaption of the local surface energy by the printing technology to achieve a self-configuration of UV varnishes for high-resolution waveguides
Additive manufacturing of copper vertical interconnect accesses by laser processing
No full textThis paper introduces a new manufacturing process for vertical interconnect accesses (VIA). In contrast to industrially established VIA metallization technologies, the presented approach takes place without any chemical plating by combining copper ink and epoxy insulator coating with CO2 laser processing for VIA drilling and copper ink sintering. The minimum VIA resistances are less than 50 mΩ, fitting the theoretically calculated value. A laboratory application scenario testing a 10 × 10 contact pad array with a pitch of 800 µm successfully demonstrates routing across five printed metallization layers, including 128 blind and 112 buried VIA. © 2021 The Author
High-power Laser Welding of Thick Steel-aluminum Dissimilar Joints
No full textAbstractAccording to the Intergovernmental Panel on Climate Change (IPCC), a worldwide reduction of CO2-emissions is indispensable to avoid global warming. Besides the automotive sector, lightweight construction is also of high interest for the maritime industry in order to minimize CO2-emissions. Using aluminum, the weight of ships can be reduced, ensuring lower fuel consumption. Therefore, hybrid joints of steel and aluminum are of great interest to the maritime industry.In order to provide an efficient lap joining process, high-power laser welding of thick steel plates (S355, t = 5mm) and aluminum plates (EN AW-6082, t = 8mm) is investigated. As the weld seam quality greatly depends on the amount of intermetallic phases within the joint, optimized process parameters and control are crucial. Using high-power laser welding, a tensile strength of 10 kN was achieved. Based on metallographic analysis, hardness tests, and tensile tests the potential of this joining method is presented
Closed-loop Process Control for Laser Patterning of Thin Film Strain Sensors
No full textAbstractThis work presents a laser based bridge balancing method for strain sensor circuits which are applied directly on component surfaces by means of thin film deposition and laser patterning. The balancing process is integrated in the patterning process and consists of iterative cycles of laser scanning and bridge measurement operations until a balanced bridge circuit is generated. It is shown that a balanced bridge circuit on the surface of a non-planar surface can be generated within few scan cycles, and thus, allows for short processing times and high-throughput manufacturing of integrated thin film strain sensors on the surface of mechanical components
The Influence of Laser Welding Processes on the Weld Seam Quality of Thermoplastic Composites with High Moisture Content
No full textAbstractPresently, fiber reinforced materials are used for many industrial applications. Laser transmission welding (LTW) is a suitable method to join these materials. For multiple thermoplastics, the weld seam quality is affected by the amount of moisture content in the joining members. For LTW, heat is applied to the welding members and water in the composite changes phase from liquid to gas. Increasing the gas content can lead to detrimental cavities in the weld seam.Therefore, experiments were performed to investigate the influence of the laser focal geometry on the generation of cavities. Different focal geometries lead to different levels of process heat generation which affects the amount of vaporization. The experiments were conducted with endless glass fiber reinforced polyetherimide and endless carbon fiber reinforced polyetherimide. These samples were tested for their weld seam strength and the results were correlated to the moisture content and laser beam geometry
Optimising Process Efficiency During Remote Laser Cutting of CFRP by Utilisation of a Double-scan-head
No full textAbstractA double-scan-head was developed combining two pairs of galvo-mirrors into one device. One pair controls the laser beam's position, while the other in this setup is used for a pyrometer. Thus, a pyrometer's optical path can be controlled independently from a laser's path as well as being locked to the same geometrical path during CFRP processing.Using such a double-scan-head, a comparison between locked pyrometry and independent scanning pyrometry is performed during multi-pass laser cutting on multiple geometries. Carbon fibre reinforced epoxy and PPS are cut with pre-selected threshold surface temperatures ranging from T = 80-120°C to interrupt and optimise the process in order to reduce the material's thermal strain. Both locked and scanning pyrometry are compared based on total processing time, heat affected zone, and the influence of fibre orientation.The study shows a double-scan-head allows improved process monitoring strategies leading towards more efficient laser material processing in terms of quality and time
Studies on the Robustness of Underwater Laser Cutting of S355J2+N Using a Yb:YAG Disk Laser Source
No full textAbstractIn this paper, an underwater laser cutting process for maintenance and replacement operations is presented and investigated regarding process robustness for the application in rough environments. A Yb:YAG laser is used with 4 kW laser power in an active cutting process with oxygen as cutting gas. For 10 mm thick constructional steel plates a process window is determined with the focus on robustness for distance interferences. The examined parameter sets include the nozzle clearance, focus positioning and cutting gas pressure adjustment, as they are significant factors of influence in underwater laser cutting. By adjusting the developed parameter sets, sheets with thicknesses up to 50 mm, as well as plates that are fixed to a concrete backing are cut. The used equipment, which completely consists of standard components, is presented along with its preparation for underwater operation
