670 Industrielle Fertigung
Effects of local gas shielding on induction brazing of stainless steel: an experimental approach
(2024)
Ni-based brazing fillers are primarily utilized in vacuum furnaces or continuous furnaces. However, the application of such furnace techniques imposes technical and economic limitations on the size of brazeable components. Induction brazing offers an alternative to overcome these limitations, enabling the brazing of large components by means of localized heating and gas shielding. This study aims to improve the understanding of process control and required gas quality for effective brazing by conducting experiments on tube-to-tube joints using Ni-based brazing alloys. To determine their impact on brazing outcomes, process gases with varying oxygen contents were systematically tested. The microstructure of the brazed joints was analyzed by light microscopy. The influence of process gas quality on corrosion behavior was examined using a capillary microcell. High residual oxygen contents in the process gas led to a shift in the corrosion potentials. Additionally, the mechanical properties of the joints are affected. Therefore, the monotonic mechanical properties were investigated at ambient temperature. The findings of this research offer practical recommendations and present a newly developed shielding gas nozzle for industrial applications. These insights support the optimization of induction brazing processes and highlight the potential for increasing the quality and efficiency of brazing large components.
In the field of modern drive technology, conventional form-fit shaft-hub connections, such as the standardized keyway connection, are reaching their mechanical limits due to the space-saving design. The trochoidal profiles are elegant modern shaft-hub connections with a compact design for high-power transmission. This article deals with an analytical approach to determining the stress state in trochoidal profiles under shear bending. The solution completes the existing analytical attempts at the load cases of pure bending and torsion. Similar to the torsional loading case, a conformal mapping must be found that can completely transform the unit circle to the non-circle profile area. The conformal mapping function is deduced from the contour equation of the profile. To check the analytical results, in addition, numerical investigations were carried out. The results of the complementary numerical studies show very good agreement with the analytical solutions. The equations derived for the maximum stresses enable a reliable and cost-effective design of the profile shafts subjected to shear force loading.
Manufacturing companies are experiencing many challenges with regard to customer-oriented and on-time production, especially in the context of an intensified global business and while advancing the digital transformation. Accordingly, the ongoing development and deployment of Industry 4.0 solutions for customisable products in small batch sizes, not only pose new problems for work preparation, but also for operative production planning in connection with high cost, time and quality pressure. Modern, complex and highly automated production systems (in this case from the semiconductor domain) must be operated close to an optimal operating state in order to be economically reasonable. Promised delivery dates and throughput times specified in contracted service agreements must be ensured and require a permanent and effective adjustment of production planning and control in daily execution. All other general conditions of an economic production remain unchanged. Today, the question of whether the production target is realistic and whether all promised delivery dates are met are today still answered with rather simple backward-oriented approaches, mostly without taking into account uncertainties, stochastic behaviour of the manufacturing system or alternatives that arise during operation. As shown in previous publications, these questions can be answered in more detail and more resilient using a backward-oriented discrete event-based simulation approach (SimBack). This article presents additional findings. The results show and deepen the impression, that the SimBack-approach can be successfully solve scheduling questions for customer-specific orders in a real-world environment.
Dynamically loaded structures made of thermoplastic polymers have been extensively exploited in several demanding industries. Due to the viscoelastic and thermal properties of thermoplastic polymers, self-heating is generally inevitable, especially during dynamic deformations at high frequencies. Therefore, the thermoplastic polyether ether ketone (PEEK), with its high temperature resistance and high specific strength, is a particularly ideal candidate for dynamically loaded applications. Using scanning laser Doppler vibrometry and infrared thermography, an experimental study of the vibration characteristics and the vibration-induced heating of flat-sheet PEEK specimens was carried out. The specimens were base-excited by means of a piezoelectric actuator at high frequencies in the range between 1 and 16 kHz. As a result, a maximum temperature rise of approximately 6.4 K was detected for the highest investigated excitation. A high correlation between the spatial distribution of the velocity along the beam’s axial direction and the resulting temperature increase was measured. To summarize, the occurring self-heating of PEEK due to the dissipation of vibrational energy has to be critically considered for dynamically loaded structural applications, especially areas with high displacement amplitudes, such as antinodes, which yield the highest temperature increase.
To increase productivity when joining galvanised sheet metal, metal inert gas (MIG) and tungsten inert gas (TIG) arc brazing are combined in a hybrid process. This coupling of two arc processes increases brazing speed and reduces weld reinforcement and the tendency to spatter. Because the arcs are 6 mm apart, they influence each other. Therefore, the blowing action is a major challenge in hybrid arc brazing. A current modulation and the optimal relative position of the arcs to each other are compulsory conditions. Selected brazing parameters are tested in order to verify the hybrid arc brazing. Overlap joints are brazed on galvanised sheets. The mechanical-technological properties of the brazed joints are determined. It has been shown that hybrid brazing can achieve significantly higher brazing speed with the same or better brazing quality compared to standard arc brazing. For the realisation of the hybrid arc brazing process, software-controlled welding machines are used, which will replace conventional power sources in the future.
The atomizing gas dynamics and the applied process energy have a significant influence on the produced particles. The melting process of the two wires can be influenced by current modulation. As for arc welding processes, more and more electronic and software-controlled machines are being used for arc spraying and will have replaced conventional power sources in the future. Due to the highly dynamic, fast regulating computing technology in the latest energy source, technology arcs can be operated with different current forms and types. The modern machines allow process-stable, reproducible variation of the particles and heat input into the substrate. Constant and pulsed current can be used as current forms. Usable current types are direct current (DC) and alternating current (AC). The electrical parameters must be analyzed to evaluate the process behavior. The consumable used is a wire-shaped iron-based alloy with a diameter of 1.6 mm. Relevant process parameters such as basic current Iground, pulse current Ipulse, pulse duration tpulse, impulse frequency fpulse, and alternating current frequency, fAC, are varied and recorded using appropriate measurement technology. The aim is to change the process performance and thereby the particle formation in a broad band. High-speed images are used to observe the arc and the deposition process. In addition, particle sizes are determined.
