Konferenzbeiträge ab 2018

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Sennewald, Martin; Hasieber, Michael; Szallies, Konstantin; Bergmann, Jean Pierre
Influence of microstructure and microgeometry of the probe on friction stir welding of AA 6060 T66. - In: Engineering for a changing world, (2023), 2.1.114, S. 1-2

https://doi.org/10.22032/dbt.58854
Rohe, Maximilian; Hildebrand, Jörg; Bergmann, Jean Pierre
Investigation of a quantified sound probe for stud weld quality measurement with numerical simulation data. - In: Engineering for a changing world, (2023), 2.1.065, S. 1-8

Drawn arc stud welding with ceramic ferrules is a widely used joining process for joining sheet metal to studs, which can be threaded or sheared. During the welding process, various irregularities can occur which adversely affect the resulting mechanical properties. Arc blowing is one of the most common process defects. Arc blowing can result in an asymmetric weld bead which can increase the failure rate of the stud. An approach to stud testing is given in DIN ISO EN 14555. A sound probe carried out by an experienced welder provides qualitative information about the weld bead. The sound probe causes the stud to vibrate at its natural frequencies. If the eigenfrequencies can be calculated for each weld bead shape, the sound probe can be quantified. To this end, a new simulation approach is presented which allows the rapid calculation of the eigenfrequencies of the stud with different weld bead shapes. A data set is also generated and analyzed.



https://doi.org/10.22032/dbt.58853
Reimann, Jan; Rohe, Maximilian; Rauch, Alexander; Hildebrand, Jörg; Bergmann, Jean Pierre
Directed energy deposition-arc (DED-Arc) and numerical welding simulation as a method to determine the homogeneity. - In: Engineering for a changing world, (2023), 2.1.036, S. 1-17

This research presents a hybrid approach to for the prediction of the homogeneity of mechanical properties in 3D metal parts manufactured using directed energy deposition-arc (DED-Arc). DED-Arc is an additive manufacturing process which can offer a cost-effective way to manufacture 3D metal parts, due to high deposition rate of up to 8 kg/h. Regression equations developed in a previous study were used to predict the mechanical properties of a wall structure using only the cooling time t8/5 calculated in a numerical welding simulation. The new approach in this research paper contains the prediction of the homogeneity of the mechanical properties, especially hardness, in 3D metal parts, which can vary due to localized changes in t8/5 cooling time provoked by specific geometrical features or general changes in dimensions. In this study a method for the calculation of the hardness distribution on additively manufactured parts was developed and shown.



https://doi.org/10.22032/dbt.58852
Sturm, Kerstin; Husung, Stephan; Wünsche, Christine
Error classification as a basis for automating the conformity of production process in the automotive industry. - In: Engineering for a changing world, (2023), 2.1.011, S. 1-16

In the automotive industry, the complexity of ensuring production conformity has increased significantly. Reasons for this are a growing number of vehicle variants in combination with increasing regulatory requirements in import markets. Violations of the "Conformity of Production" (CoP) can result in drastic penalties. This is contrasted by a partially random and manual inspection process that is currently not sufficiently automated and digitalized. According to the BMW Group CoP expert workshop there is not enough error analysis and classification in the current situation to comprehensively perform automated inspections. To gain more insight into this manual inspection process, a comprehensive error analysis and classification must first take place to derive measures. Based on the requirements for the CoP process and the findings from the state of the art, the objective of this contribution is to analyze the status quo regarding error frequencies and to derive possible measures from the findings.



https://doi.org/10.22032/dbt.58850
Hebenstreit, Roman; Theska, René
Calibration of positioning microsystems with subatomic accuracy. - In: Engineering for a changing world, (2023), 1.4.117, S. 1-6

Multidimensional positioning, measuring and manipulation with a spatial resolution in the subatomic range are an upcoming demand in the area of nanotechnology. Nanopositioning and measuring machines (NMM) enable to measure and manipulate objects within a large addressable 3D-range of up to a few hundred millimetre in each dimension with a specified spatial resolution of down to 0.1 nm [1]. New approaches are needed to extend the potential of NMM technology to even smaller scales. In previous work [2] a proof-of-concept positioning system has been designed to achieve reproducibility and resolution for precise motion on subatomic scale. In a first approach, a scanning probe microscope will be used to measure a nanosized periodic lattice that serves as a scale for the position according to [3]. Here, we present a microsystem design with an addressable positioning range of ±100 μm that will carry the lattice structure. In order to precisely control the motion, the electrostatic drive and position sensor characteristics of the demonstrator must be calibrated thoroughly by means of an optical measuring system. A focused, range-resolved fibre-optic laser interferometer is comprised as the calibration standard. An uncertainty estimation for the measurement setup is carried out. It is shown that the desired positioning accuracy for the first tip- and grating-based setup can be achieved with the presented microsystems.



https://doi.org/10.22032/dbt.58741
Darnieder, Maximilian; Wittke, Martin; Pabst, Markus; Fröhlich, Thomas; Theska, René
Monolithic compliant mechanism for an EMFC mass comparator weighing cell. - In: Engineering for a changing world, (2023), 1.4.112, S. 1-14

Mass comparator weighing cells based on electromagnetic force compensation (EMFC) find application in the most demanding force and mass measurement applications. The centerpiece of these devices is a highly sensitive compliant mechanism with thin flexure hinges. The compliant mechanism forms the mechanical part of the mechatronic overall system. A novel mechanism based on an advanced adjustment concept has been developed, manufactured, and experimentally investigated. The adjustment is designed to further reduce the measurement uncertainty for mass comparisons by canceling out first-order error components. The focus is on the mechanical properties: stiffness, tilt sensitivity, and off-center load sensitivity. The elastic stiffness of the compliant mechanism is compensated by introducing a negative gravitational stiffness to enable the compensation of manufacturing deviations and to increase mass resolution.



https://doi.org/10.22032/dbt.58738
Keck, Lorenz; Seifert, Frank; Newell, David; Theska, René; Haddad, Darine
Preliminary characterization of anelastic effects in the flexure mechanism for a new Kibble balance at NIST. - In: Engineering for a changing world, (2023), 1.4.101, S. 1-13

A new Kibble balance is being built at the National Institute of Standards and Technology (NIST). For the first time in one of the highly accurate versions of this type of balance, a single flexure mechanism is used for both modes of operation: the weighing mode and the velocity mode. The mechanism is at the core of the new balance design as it represents a paradigm shift for NIST away from using knife edge-based balance mechanisms, which exhibit hysteresis in the measurement procedure of the weighing mode. Mechanical hysteresis may be a limiting factor in the performance of highly accurate Kibble balances approaching single digit nanonewton repeatability on a nominal 100 g mass, as targeted in this work. Flexure-based mechanisms are known to have very good static hysteresis when used as a null detector. However, for larger and especially longer lasting deformations, flexures are known to exhibit anelastic drift. We seek to characterize, and ideally compensate for, this anelastic behavior after deflections during the velocity mode to enable a 10 accurate Kibble balancemeasurement on a nominal 100 g mass artifact with a single flexure-based balance mechanism.



https://doi.org/10.22032/dbt.58743
Layher, Michel; Bliedtner, Jens; Theska, René
A laser beam deflection system for heat treatments in large scale additive manufacturing. - In: Engineering for a changing world, (2023), 1.4.082, S. 1-15

Large Scale Additive Manufacturing (LSAM) based on plastic raw material is known for high material output and thus, increased productivity. For an improvement of part properties LSAM is combined with a laser process. Depending on the deposition direction, the laser beam needs to be repositioned to reach the space between two adjacent and consecutively printed strands. Therefore, an optomechanical design is required that allows variable orientation of the laser beam. It consists of a combination of an elliptical, tube-like mirror with an additional, rotatable flat mirror in one of its focal axes. The deflected laser beam hits the second focal axis where the extruder nozzle is located. Thus, > 75% of the nozzle circumference is covered during a laser beam treatment. Both mirrors are individually designed custom-made parts. Its functional verification lays the foundation for an improved additive manufacturing process, which aims to homogenize the component structures to improve the mechanical properties of 3D-printed components.



https://doi.org/10.22032/dbt.58739
Miettinen, Mikael; Vainio, Valtteri; Haverinen, Petteri; Leutonen, Onni; Viitala, Raine; Theska, René
Validation of experimental setup for aerostatic bearing simulation. - In: Engineering for a changing world, (2023), 1.4.079, S. 1-10

Aerostatic bearings are extensively used in precision engineering applications that require high positional accuracy and low friction motion. In these bearings, externally pressurized gas is fed through a restrictor into the bearing gap. The viscous shear in the gap restricts the flow, thus forming a pressurized film between the bearing and the guide surface. In the development of models and in investigations of, for example, effects of manufacturing errors and porous material permeability properties, characterization of bearing performance is required. The performance is commonly characterized with a measurement setup, either under static or dynamic conditions. In the present study, an experimental setup for the measurement performance of aerostatic bearings is presented. The investigated measurement setup is validated with a comparison to a literature model. The results of the present study include the load capacity, stiffness, air consumption, and pressure distribution of a commercially available axisymmetric graphite thrust bearing. The results show good agreement between the measurements and the model. Thus, the results show corroborative evidence on the usability of the measurement setup in future aerostatic bearing research.



https://doi.org/10.22032/dbt.58841
Hahm, Christoph; Erbe, Torsten; Theska, René
Cement-bound mineral casted parts in precision engineering. - In: Engineering for a changing world, (2023), 1.4.077, S. 1-14

The design of a machine frame, supporting a plurality of components/modules, is a major challenge during the development of precision systems. The geometric stability of the supporting parts under thermal and mechanical loads has a decisive influence on the achievable accuracy. Common materials like cast iron or natural stone have preferable properties but often come with high costs and long lead times due to sourcing or manufacturing process and required geometric precision. Concrete is an interesting alternative. Polymer concrete and cement-based concrete such as self-compacting concrete have been considered as cost-effective alternatives for quite a while now. This paper summarizes recent research and findings on these alternative materials and reviews their applicability in machine frame design. Aspects of the cold primary shaping process will be covered with an emphasis on ready-to-use features with geometric tolerances in the order of magnitude of micrometers. The potential for integrating functional elements is discussed. The advantages of concrete as an alternative material are summarized with regard to the application of the design principle "functional material at the location where functionality is required".



https://doi.org/10.22032/dbt.58740