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Comparison of Resistive and Optical Strain Measurement for Early Fracture Detection

Current Directions in Biomedical Engineering 2020年第3期6卷

作者： Carabello, Alina Neupetsch, Constanze Werner, Michael Rotsch, Christian Drossel, Welf-Guntram Zajonz, Dirk Chemnitz University of Technology Adaptronics and Lightweight Design in Production Chemnitz Germany Fraunhofer Institute for Machine Tools and Forming Technology Iwu Chemnitz/ Dresden Germany Zeisigwaldkliniken Bethanien Chemnitz Germany

To increase learning success in surgical training, physical simulators are supplemented by measurement technology to generate and record objective feedback and error detection. An opportunity to detect fractures following hip stem implantation early can be measurement of occurring strains on bone surface. These strains can be determined while using strain gauges, digital image correlation (DIC) or photoelasticity. In this research strain gauges and DIC were compared regarding their suitability as strain measurement tools for use in physical simulators. Therefore a testing method was described to replicate the implantation of a hip stem. Testing devices modelled on a realistic prosthesis were pressed into prepared porcine femora in a two-step procedure with a material testing machine. The local strains occurring on bone surface were determined using an optical measurement system for DIC and strain gauges. The initial fractures in the tested femora are located medial-anterior in most cases (73,6%). With increasing indentation depth of the test device, the strains on bone surface increase. Comparing the local strains determined by DIC and strain gauges consistencies in curves are noticeable. Maximal determined strains before fracturing amount to 0,69% with strain gauges and 0,75% with DIC. In the range of the fracture gap, strain gradients are determined by using DIC. However the detected surfaces are of low quality caused by gaps and motion artefacts. The results show strains on bone surfaces for early fracture detection are measurable with strain gauges and DIC. DIC is assessed as less suitable compared to strain gauges. Furthermore strain gauges have greater level of integration and economic efficiency, so they are preferred the use in surgical training simulators. © 2020 by Walter de Gruyter Berlin/Boston 2020.

关键词： Image correlation

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How Distributed Ledger Technologies affect business models of manufacturing companies

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Procedia CIRP 2021年 104卷 152-157页

作者： Johannes Mayer Philipp Niemietz Daniel Trauth Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of the RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

Industry 4.0 is characterized by the transformation and networking of production systems as a result of utilizing digital technologies and processing huge amounts of data. The features of Distributed Ledger Technologies have the potential to revolutionize production by creating trust and transparency in stored data, eliminating dependence on single entities and performing automated transactions in real time. Due to the disruptive change coming with an implementation, manufacturers remain skeptical about the technology. To raise awareness of the potential of Distributed Ledger technology, this paper describes valid use cases and examines the interactions with business models in real world manufacturing scenarios.

关键词： Distributed Ledger technology Manufacturing Data Marketplace Subscription Quality-Tracking Audit

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Three Dimensional Numerical Modeling of Face Turning Using the Coupled-Eulerian-Lagrangian Formulation

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Procedia CIRP 2021年 102卷 162-167页

作者： M. Hardt T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstraße 17 52074 Aachen Germany

Modeling the cutting process by means of Finite Element (FE) simulations found wide acceptance in the scientific community. Most of these studies focused on the simulation of the orthogonal cutting process. However, the orthogonal cutting process has only limited application in the metal cutting industry. Simulations of three-dimensional processes, such as face turning, are characterized by high computational times. In this study, a FE-model of face turning is presented, wherefore the Coupled-Eulerian-Lagrangian formulation is used. The computational time of the simulations was reduced to approximately 6 h, which allowed a time-efficient use of FE-simulations to analyze the face turning process. The results of the simulations are evaluated by comparing them with corresponding experimental cutting tests. The comparison of the results revealed a good agreement between the simulated and the experimental cutting forces, whereas the simulated passive and feed force deviated to a larger extend from the experimental counterparts.

关键词： Face turning AISI 1045 Coupled-Eulerian-Lagrangian Finite Element simulation

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Influence of Abrasive Properties on Erosion in Waterjet Machining

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Procedia CIRP 2021年 102卷 375-380页

作者： M. Schüler M. Dadgar T. Herrig T. Bergs Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 Aachen 52074 Germany Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany

In the recent decades abrasive waterjet (AWJ) machining has been successfully established as a highly flexible, non-conventional production technique with significant productivity advantages for hard-to-machine materials. However, the remaining challenging issue with this technology is how to control the influencing factors affecting the erosion process. For AWJ machining, the abrasive grit interaction is considered to be the most important factor during the erosion process. To attain a more profound understanding of the AWJ erosion process, the physical phenomena of grit interaction on the machining result need to be investigated. Therefore, diverse abrasive grit of individual shape and mechanical properties were used in the course of the experiments with subsequent visual analyses of the machining results supplemented by residual stress measurements. This study has identified essential process mechanisms required for the modeling of AWJ machining operations.

关键词： Abrasive waterjet Material modification Modeling

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Three-dimensional multi-physical modelling of the influence of the cutting fluid on the chip formation process

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Procedia CIRP 2021年 102卷 216-221页

作者： Hui Liu Bingxiao Peng Markus Meurer Daniel Schraknepper Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 52074 Aachen Germany

In today’s manufacturing, cutting fluid systems are widely used in modern machine tools to improve the process performance. The influence of cutting fluids on the specific cutting force components as well as the resulting heat distribution is a complicated physical phenomenon, which is difficult to experimentally investigate due to the restricted optical accessibility in the machining process. To better understand the working principle of the cutting fluid system, a three-dimensional fluid-structure interaction simulation approach for orthogonal cutting processes was developed in this work. The simulation approach overcomes the underestimation of the fluid velocity perpendicular to the cutting direction in conventional two-dimensional simulations and allows a more accurate resolution of the flow behavior in the cutting zone. This method provides a detailed investigation of the mechanical effect of the coolant jet on the chip formation process. To evaluate the simulation results, orthogonal cutting experiments were conducted on a lathe under both wet and dry conditions. The comparison of chip shapes between simulation and experiment shows that the three-dimensional model can accurately predict cutting fluid induced chip breakage. Furthermore, the simulative investigation showed that chip formation is strongly dependent on the orientation of the nozzle jet. This result provides first findings for improving chip removal by varying the coolant supply parameters.

关键词： Cutting Fluid Simulation Fluid-Structure-Interaction Multiphysics Modelling Orthogonal Cutting

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Generation and evaluation of automation concepts of additive process chains with Laser Powder Bed Fusion (L-PBF)

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Procedia CIRP 2021年 96卷 97-102页

作者： Rainer Horstkotte Florian Heinrich Marcel Prümmer Kristian Arntz Thomas Bergs Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany Laboratory for Machine Tools and Production Engineering (WZL) RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany

Laser Powder Bed Fusion (L-PBF) is an additive manufacturing (AM) technology that plays a major role in the production of mass customized metal components and products. A significant disadvantage of AM is the required post-processing of the additive manufactured parts, which is necessary to remove auxiliary structures, separate the workpieces from the substrate plate and achieve high precision as well as low surface roughness. Automation of these post-processes is a crucial factor for increasing productivity and thus for further industrialization of L-PBF. This paper presents a methodology to model and evaluate the manufacturing process chain of post-processing with regard to automation. For this purpose, a uniform notation is introduced to model the sequence of manufacturing processes and handling operations. The notation allows the representation of different automation concepts and integrates typical post-processes for L-PBF manufactured parts. A reference scale is used to evaluate different concepts with regard to their level of automation. The focus on lead time estimation enables the methodology to generate and evaluate different automation concepts.

关键词： Laser Powder Bed Fusion L-PBF automation automation concepts process chain additive manufacturing AM post-processing lead time estimation

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Modelling of Energy Distribution in SEDM on the Basis of Gas Bubble Observations

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Procedia CIRP 2021年 102卷 293-298页

作者： T. Petersen S. Schneider A. Klink T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

The energy distribution in electrical discharge machining is still subject to discussions. On the one hand, it is important to know the exact amount of energy that is applied to a workpiece, since solely this heat is responsible for the loads that are applied to the material and result in material modifications. On the other hand, it is very difficult to directly measure the heat due to the diminutive temporal and spatial scales. Hence, a method was developed to measure the size of the gas bubble that evolves during the discharge and used to model the energy fraction that dissipates during the formation of named bubble. With the easily measurable general energy input and the developed model, the number of unknown fractions of the energy distribution can be reduced. This step allows for a better assumption of the energies that load and modify the workpiece material.

关键词： EDM Gas Bubble Process Signatures High-Speed Camera

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Simulation of friction between diamond and polycrystalline cubic boron nitride

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Procedia CIRP 2021年 104卷 44-49页

作者： Ulrich Müller Sebastian Prinz Sebastian Barth Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

Grinding is a key technology in the manufacturing chain of polycrystalline cubic boron nitride (PCBN) cutting tools. However, high wear and low material removal rates during grinding lead to high manufacturing costs of PCBN cutting tools. Since friction is a major driver of grinding wheel wear, the friction related temperature between diamond as abrasive grain and PCBN as cutting tool material was investigated using the finite element method. Maximum temperatures of up to 720 °C and average temperatures of up to 165 °C were found on the PCBN surface depending on the PCBN specification, the friction coefficient, and the relative velocity.

关键词： Friction grinding polycrystalline cubic boron nitride

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Visualization of Spatially Resolved Energy in Wire Electrical Discharge Machining

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Procedia CIRP 2021年 104卷 1512-1517页

作者： Ugur Küpper Tim Herrig Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 Aachen 52074 Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

For the development of a process monitoring system in wire EDM, a model for mapping the material removal based on process data is necessary. In order to use the causal relationship between the process energy and the material removal, the individual discharges must first be digitally mapped on the machined surface. In the context of this work, the discharge position is detected considering the individual discharge energy in order to allow the mapping of the spatially resolved process energy. For this purpose, test series are carried out to correlate the discharge position with the difference between the upper and lower current using a real-time capable measuring system.

关键词： Electrical Discharge Machining (EDM) Wire EDM Monitoring Energy Digital Manufacturing System

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Development of handling system concepts for additive process chains with Laser Powder Bed Fusion (L-PBF)

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Procedia CIRP 2021年 104卷 1173-1178页

Laser Powder Bed Fusion (L-PBF) is an additive manufacturing (AM) technology that enables the production of highly complex and individualized metal components. Since these components need post-processing, L-PBF is usually utilized within a manufacturing process chain. The automation of this process chain is a crucial step towards the industrialization of L-PBF. This paper presents a methodology for the conceptual design of handling systems for the automated handling of L-PBF components. It includes the selection of gripping and clamping devices, robots, and other peripheral systems. Restrictions that arise from the complexity of the components and the technologies are considered.

关键词： Additive manufacturing AM Laser Powder Bed Fusion L-PBF Process chain Automation Automated handling Automated gripping Automated clamping Automation concepts Post-processing Handling systems

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