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Die Zukunft ist virtuell
(2020)
Der Beitrag skizziert einleitend grundlegende Defizite in Lerneinheiten der Automatisierungstechnik. Als Lösungskonzept werden Digitale Zwillinge der Maschinen vorgeschlagen, die mit realer Steuerungsalgorithmik und AR/VR kombiniert werden. Die informationstechnische Umsetzung dieses Konzepts in der `Digital Twin as a Service ́ Plattform ermöglicht die Entwicklung und Bereitstellung von AR/VR-Lernszenarien. Auf Basis der technologischen Beschreibung werden vier Lernszenarien aus der Robotik aufgezeigt, die bereits in der beruflichen Bildung, der Hochschulbildung und der industriellen Bildung erfolgreich eingesetzt werden. Am Beispiel eines ausgewählten Lernszenarios werden die Lernziele und das didaktische Design detailliert betrachtet. Abschließend wird auf die Evaluierung eingegangen. Ergänzend zu diesem schriftlichen Beitrag ist unter https://www.virtual-automation-lab.de/avril2020 ein Kurzvideo über das Lösungskonzept, die Software-Plattform sowie die Lernszenarien abrufbar.
Moderne Visualisierungsmethoden wie bspw. Mixed Reality Methoden in Kombination mit Digitalen Zwillingen eröffnen neue Formen der Mensch-Roboter-Interaktion bei der Offline-Programmierung von Industrierobotern. Durch die Verschmelzung von realen und virtuellen Inhalten ist eine intuitivere dreidimensionale Interaktion zwischen Mensch und Digitalem Zwilling möglich. Bislang verhindern jedoch die plattform- und endgeräteabhängige Entwicklung der Anwendungen sowie die fehlenden Schnittstellen zwischen modernen Endgeräten, Digitalen Zwillingen und der industriellen Steuerungstechnik den breiten Einsatz dieser Technologien. Mit diesen Herausforderungen beschäftigt sich das Forschungslabor Virtual Automation Lab (VAL) der Fakultät Maschinenbau an der Hochschule Esslingen. Kernkompetenz des VAL ist die Erforschung und der Einsatz von Mixed Reality Methoden im Maschinenbau. Ergänzend wird im Rahmen der vom Land BW finanzierten Transferinitiative „Transferplattform BW Industrie 4.0“ Forschungstransfer für kleine und mittelständische Unternehmen (KMU) geleistet. Das in Kooperation mit den Hochschulen Aalen und Reutlingen und der Steinbeis-Stiftung durchgeführte Transferprojekt soll einen niederschwelligen Zugang für KMU zu Themen wie servicebasierter Einsatz von Digitalen Zwillingen im industriellen Umfeld, webbasiertes 3D-Maschinenmonitoring und Mixed Reality Anwendungen ermöglichen. Im Rahmen dieses Beitrags wird die am VAL entwickelte Digital Twin as a Service – Plattform, die Interaktionsabstraktion und -modellierung zur eingabegeräteunabhängigen intuitiven Mensch-Roboter-Interaktion sowie ein auf Basis dieser Plattform entwickelter Digitaler Zwilling der Maschinenbaulabore der Hochschule Esslingen mit Anbindung an Offline-Programmiersysteme von Roboterherstellern, vorgestellt.
Processing of liquid silicone rubber (LSR) in the injection molding process has a high economic potential. Since there are some fundamental differences compared to classical thermoplastic injection molding, up to now there is a lack of well‐founded knowledge of the process which allows an estimation of the cycle time. Because, in addition to reverse temperature control, LSR processing also involves an irreversible temperature‐ and time‐dependent chemical reaction. In this paper, the complex cross‐linking reaction is first modelled phenomenologically using dynamic differential scanning calorimetry (DSC) measurements and the well‐fitting Kamal‐Sourour model. Afterwards, a temperature and cross‐linking simulation is set up, which reliably simulates the time‐ and travel‐dependent temperature profile and degree of cross‐linking in the mold. Therefore, the released exothermic cross‐linking heat is also taken into account. The simulated temperature values are verified with measurements in the cavity during the injection molding process. The measured values correspond very well with the simulated values at different mold temperatures. It is shown that the influence of the cross‐linking heat on the overall temperature profile in the LSR component during the injection molding process is relatively low. Nevertheless, the model is necessary to determine the degree of cross‐linking ‐ it can be used to calculate the cycle time at which the component of a certain cross‐section can be ejected at a known tool temperature and is fully cross‐linked. With this knowledge, existing processes can be optimized in terms of mold temperature and curing time, but also new components can be calculated economically.
In this chapter, to investigate the tensile behavior of CNTs, finite element models of single-walled carbon nanotubes (SWCNTs) in perfect and doped modes for common types of carbon nanotube (CNT) configuration, i.e., the armchair, zigzag, and chiral models, were generated using a commercial finite element software (MSC Marc). To create the computational models, nodes were placed at the locations of carbon atoms and the bonds between them were modeled using three-dimensional elastic generalized beam elements. Doped models were simulated by three different heteroatoms including silicon, nitrogen, and boron separately with the doping concentration ranging from 0 to 5%. Young’s moduli of all models were obtained and compared with the perfect structures. The results indicated that Young’s modulus of chiral SWCNTs is larger than the moduli of the armchair and zigzag SWCNTs in all models and incorporating the silicon and boron atoms into CNT led to a linear reduction in Young’s modulus which was most significant for silicon and less noticeable for boron. Regarding nitrogen doping, a different trend was observed that was a negligible and less conspicuous increment in the value of Young’s modulus by increasing the percentage of doping. Besides, this behavior was the same for all armchair, zigzag, and chiral configurations with the same dopant atom. The investigations also revealed that the structural irregularity and ripples, which are induced by dopant atoms, are a key factor which influences the tensile behavior of CNTs. Our results for Young’s modulus of doped CNTs are in good agreement with recent investigations.
We consider the mixed initial-boundary value problem in the context of the
Moore-Gibson-Thompson theory of thermoelasticity for dipolar bodies. We consider the case of heat conduction with dissipation. Even if the elasticity tensors
are not supposed to be positively defined, we have proven both, the uniqueness
and the instability of the solution of the mixed problem. In the case that the mass
density and the thermal conductivity tensor are positive, we obtain the uniqueness
of the solution using some Lagrange type identities.
Mobilitätshilfen sind allgegenwärtig und existenziell für Menschen, die aufgrund von Krankheit und Pflegebedürftigkeit in ihren Alltagsbewegungen und -fortbewegungen eingeschränkt sind. Mobilität steht in einem direkten Zusammenhang zur Selbstständig-keit und Selbstbestimmung im Alltag. Für viele pflegebedürftige Menschen sind Mobili-tätshilfen entscheiden dafür, ob sie ihren Alltag (wieder) selbst gestalten können. Dabei müssen sie sich innerhalb und außerhalb von Räumen ganz unterschiedlichen Heraus-forderungen stellen. Teilhabe am sozialen, möglicherweise auch am beruflichen Leben wird für viele Betroffene erst dann möglich, wenn die unterschiedlichen Mobilitätshilfen aufeinander und auf die jeweiligen Aktivitäten abgestimmt sind. Für Angehörige und für Pflegefachpersonen stellt sich täglich die Frage, mit welchen Mobilitätshilfen eine siche-re und angemessene Unterstützung möglich ist. Dabei gilt es, die Ausstattung mit Hilfen dem aktuellen Mobilitätsprofil der Betroffenen anzupassen; die Folgen von Über- oder Unterversorgung mit Mobilitätshilfen kann für die Betroffenen gravierende negative Folgen haben!
Effect of voids in a heat-flux dependent theory for thermoelastic bodies with dipolar structure
(2020)
Due to the good mechanical properties, flax fiber-reinforced epoxy composites
are being widely used as a green alternative to glass fiber composites. However,
plant fibers absorb moisture from the environment, being in a higher moisture
uptake as the relative humidity (RH) increases. This absorbed moisture deteriorates the mechanical properties of the composites. In this study, geometric
and displacement potential function (DPF) approaches are used to predict the
mechanical properties of flax fiber-reinforced epoxy composites under environmental conditions, in particular, different RH values. The tensile properties
that were measured experimentally strongly agreed with the analytical findings.
Almost similar results were found for the tensile strain those were measured
experimentally and the one predicted by the geometric function.
However, the predicted strain values were 38% and 42% less than the experimental ones for 0% and 95% RH conditioned composites, respectively, when
DPF was used. Good conformity between the experimental, analytical, and
DPF formulation for predicting mechanical properties ensures the practical
applicability of this study. The formulations established in this work could,
therefore, be utilized to analytically solve laminated composites under specific
boundary conditions in structural applications.
The moisture absorption behavior of flax fiber-reinforced epoxy composites is deliberated to be a serious issue. This property restricts their usage as outdoor engineering structures. Therefore, this study provides an investigation of moisture in flax fibers on the performance of the flax/epoxy composite materials based on their shear responses. The ±45° aligned flax fibers exposed to different relative humidities (RH) and the vacuum infusion process was used to manufacture the composite specimens. The optimum shear strength (40.25 ± 0.75 MPa) was found for the composites manufactured with 35% RH-conditioned flax fibers, but the shear modulus was reduced consistently with increasing RH values. Although shear strength was increased because of fiber swelling with increased moisture absorption rate until 35% RH environments with good microstructures, nonetheless, strength and modulus both started to decrease after this range. A very poor microstructure has been affirmed by the SEM images of the composite samples conditioned at 90% RH environments.
In our present paper, we approach the mixed problem with initial and boundary conditions, in the context of thermoelasticity without energy dissipation of bodies with a dipolar structure. Our first result is a reciprocal relation for the mixed problem which is reformulated by including the initial data into the field equations. Then, we deduce a generalization of Gurtin’s variational principle, which covers our generalized theory for bodies with a dipolar structure. It is important to emphasize that both results are obtained in a very general context, namely that of anisotropic and inhomogeneous environments, having a center of symmetry at each point.
The objective of this study is to investigate the influence of veneering technique (hand-layering vs. milling) on the fracture resistance of bi-layer implant-supported zirconia-based hybrid-abutment crowns. Mandibular molar copings were anatomically designed and milled. Copings were then veneered by hand-layering (HL) (n = 20) and milling using the Cad-On technique (LD) (n = 20). Crowns were cemented to zirconia hybrid-abutments. Ten samples of each group acted as a control while the remaining ten samples were subjected to fatigue in a chewing simulator. Crowns were loaded between 50 and 100 N for 1.2 million cycles under simultaneous temperature fluctuation between 5 and 55 °C. Crowns were then subjected to static load a to fracture test. Data were statistically analysed using the one-way ANOVA. Randomly selected crowns from each group were observed under scanning electron microscopy to view fractured surfaces. Study results indicate that during fatigue, LD crowns had a 100% survival rate; while HL crowns had a 50% failure rate. Fracture resistance of LD crowns was statistically significantly higher than that of HL crowns at the baseline and after fatigue (p ≤ 0.05). However, fatigue did not cause a statistically significant reduction in fracture resistance in both LD and HL groups (p > 0.05). Copings fractured in the LD crowns only and the fracture path was different in both LD and HL groups. According to the results, it was concluded that milled veneer implant-supported hybrid-abutment crowns exhibit significantly higher fracture resistance, and better withstand clinical masticatory loads in the posterior region compared to the hand-layered technique. Also, fatigue application and artificial aging caused no significant strength reduction in both techniques. Clinical significance: Different veneering techniques and materials (hand-layering or milling) act differently to clinical forces and environment and may be prone to early chipping during service. Therefore, practitioners are urged to consider the appropriate veneering protocol for posterior implant-supported hybrid-abutment restorations.