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The increasing complexity of technical consumer products has led to the integration of Model-Based Systems Engineering (MBSE) approaches into sectors that are not viewed as classic users of Systems Engineering. The approach helps grasping the complexity and keeping costs at a low level. However, many companies struggle with the implementation of the approach into their processes. A regularly mentioned reason for this is a missing visibility of a clear benefit. Especially smaller enterprises are facing these problems within the value chain. This paper presents an approach to contribute towards the enhancement of MBSE accessibility. It shows different strategies for the integration of tacit knowledge into system models and discusses their feasibility and contribution towards this enhancement.

Due to the increasing requirements on lightweight constructions, the demands for efficient joining processes are constantly rising. Therefor cold forming processes provide a faster and less expensive alternative to established thermal joining methods. In order to guarantee the joining reliability, not only the selection of a suitable process, but also the design and dimensioning of the joint is crucial. As a possible solution, data-driven methods offer procedures for the structuring of data and the targeted analysis of product features and key variables. Motivated by this, the paper shows a literature-based approach by using the example of clinching to illustrate the potentials and limits of data-based methods for the design and optimization of mechanical joining processes.

Additive Fertigung ist zum etablierten Prozess geworden. Durch schichtweisen Aufbau werden nicht mehr nur Prototypen gefertigt, sondern auch Bauteile mit hohen Steifigkeits- und Festigkeitsanforderungen. Im Fused Filament Fabrication (FFF)-Verfahren gefertigte Bauteile werden schichtweise durch Extrusionspfade aufgebaut und besitzen in Pfadrichtung ublicherweise bessere mechanische Eigenschaften als quer dazu. Unterschiedliche Extrusionspfade, insbesondere im Bauteilinneren („Infills“) besitzen daher einen hohen Einfluss auf die mechanischen Bauteileigenschaften. Um diese bereits vor der eigentlichen Fertigung abschatzen zu konnen, wurde ein Simulationsansatz entwickelt, der ausgehend von Fertigungsinformation (G-code) ein Simulationsmodell aufbaut, welches die lokal unterschiedlichen Materialorientierungen berucksichtigt. Dieser Ansatz soll detailliert vorgestellt und anhand eines Demonstratorbauteils mit unterschiedlichen Infill-Mustern angewandt werden.

Due to scarce resources coupled with increasing mobility requirements, resource-efficient machine and motor elements are vital. Therefore, surfaces in lubricated tribological contacts can be microtextured, enabling improved lubricating conditions and friction behavior. While this has already been shown for lower loaded contacts, the effects for higher loaded, application-oriented EHL contacts are topic of basic research. Therefore, geometrically defined microtextures are adapted to the tribological system of the tappet/camshaft contact in the valve train of combustion engines as a demonstrator. The tribological performance in respect to lubricating conditions, friction and wear behavior is analyzed on single cam/tappet component test-rigs. EHL simulation is used as ‘numerical zoom’ into a section of the contact area contributing to better understanding of effects and observed phenomena.

Optimization specifically for fiber reinforced plastics (FRP) is becoming more and more important for creating high-quality composite structures. Yet, in spite of the increasing use of topology optimization (TO) within product development, specific TO methods for transversely isotropic materials like FRP are scarce in research and even more scarce in practical application. This is amongst other reasons caused by the challenge of simultaneous optimization of mutually dependent material distribution and fiber orientations, which poses an obstacle to established gradient-based optimization routines in terms of iterations (run time) and gradient formulation. Thus, based on bionic methods, an efficient, empirical optimization method is proposed to enable fast and FRP-suitable geometry propositions. Case studies show efficiency and effectiveness: the new approach offers very fast convergence; plus perceptible stiffness gains compared to established topology optimization for isotropic materials.

The embodiment of mechanical joints is a demanding activity during the design of mechanism. In this context, particularly the assessment of the effects of geometrical deviations on the behaviour of the mechanical joint is of strong importance. This paper presents an approach to the gap hull estimation for mechanical joints considering form deviations. The novelty of this approach lies in the ability to analyse the behaviour of mechanical joints considering multiple pairs of mating surfaces. The application of this method to a prismatic as well as to a cylindrical joint prove the versatility of the method regarding different kinds of joints with multiple pairs of contact surfaces. Moreover, the results of the application of this approach to the tolerance analysis of a two-pin-two-hole assembly confirm the importance of considering form deviations in the tolerance analysis and in the design of mechanical joints and mechanism.

Additive Fertigungsverfahren haben sich aufgrund ihrer losgrosenunabhangigen Fertigungskosten und der grosen Gestaltungsfreiheit sowohl in der Forschung als auch in der industriellen Anwendung erfolgreich etabliert. So werden die verschiedenen additiven Verfahren nicht mehr nur fur die Herstellung von Prototypen, sondern vermehrt zur Fertigung komplexer, endkonturnaher Bauteile und gesamter Baugruppen angewendet. Dabei konnten in den letzten Jahren zahlreiche Richtlinien fur die Gestaltung der schichtweise aufgebauten Bauteile hergeleitet werden. Eine umfassende Betrachtung additiv gefertigter Gelenke fehlt jedoch bisher. Um den Produktentwickler bzw. Konstrukteur bei der Gestaltung von mittels Fused Deposition Modeling (FDM) hergestellten Drehgelenken zu unterstutzen, werden im nachfolgenden Beitrag relevante Aspekte, wie z. B erforderliche Mindestspalte zur Trennung von nicht- und einfach-gekrummten Elementen, aufgezeigt. Versuchsergebnisse dienen dabei als Basis fur die Ableitung von Richtlinien fur das Design FDM-gedruckter Gelenke und erganzen dadurch die Grundsatze des Design for Additive Manufacturing. Die Umsetzung der erarbeiteten Gestaltungsrichtlinien wird anschliesend exemplarisch an einem ebenen Mechanismus dargelegt.

Tolerance-cost-optimizations help to find optimal tolerances for a given tolerance design, which achieve minimum total costs while satisfying the quality requirements. These requirements are commonly expressed as scrap rates in ppm-range. This paper presents several methods for the scrap rate estimation in sampling-based tolerance-cost-optimizations. Moreover, the proposed approaches are applied to a typical case study and compared in terms of their required computation time and the obtained optimization results. The novelty of the contribution can be found in comparing different scrap rate estimation techniques for sampling-based tolerance-cost-optimizations and giving recommendations to researchers as well as practitioners.

Today the market environments require products to be developed by multidisciplinary teams, which have to consider contradictory requirements in drastically reduced times-to-market. In this context, the importance of robust design ambitions, which strive for developing products that are insensitive to variations from manufacturing, assembly and use processes, increases. In this paper, a novel methodology for the robust-design optimization of a mechanism is introduced, which allows optimizing the mechanism so that contradictory requirements are met despite the presence of geometrical deviations and uncertainties during use. The result of this optimization process are mechanisms, which do not only fulfill kinematic requirements, but are also insensitive to geometrical part deviations and uncertain ambient parameters.

Product realization processes are undergoing radical change considering the increasing digitalization of manufacturing fostered by cyber-physical production systems, the internet of things, big data, cloud computing, and the advancing use of digital twins. These trends are subsumed under the term “industry 4.0” describing the vision of a digitally connected manufacturing environment. The contribution gives an overview of future challenges and potentials for next generation geometry assurance and geometrical variations management in the context of industry 4.0. Particularly, the focus is set on potentials and risks of increasingly available manufacturing data and the use of digital twins in geometrical variations management.

Inhalt: Die Qualität 3D-gedruckter Bauteile ist von einer Vielzahl an Einflussparametern abhängig. Nach Identifikation der Haupteinflussparameter auf die relevante Zielgröße, wie zum Beispiel Maß- und Formhaltigkeit, mechanischen Eigenschaften oder Optik, können geeignete Maßnahmen dabei helfen, die Anforderungen an das 3D-gedruckte Bauteil zu erfüllen. Der nachfolgende Beitrag zeigt am Beispiel des Bausatz-Druckers Anet A8, dass neben den Prozessparametern der mechanische Aufbau des Druckers einen erheblichen Einfluss auf die Bauteilqualität hat.

Tolerancing is commonly performed in late design stages, in which the product geometry is fully defined. However, this often leads to high manufacturing costs or expensive design changes. Therefore, motivated by the idea of frontloading, a new approach for first tolerance evaluations in conceptual design stages is developed, which enables a first tolerance specification and analysis based on the few geometry data available. Together with semantic information of the interface notations of adjacent parts, graphs including relevant geometry elements and tolerance information are generated. These graphs support designers with a first assessment of tolerance situations before the geometry is finally defined.

In tolerance and variation simulations, sensitivity analyses are used to assess the influences of tolerance specifications and geometrical deviations on the assembly key characteristics and to support product and process developers in deriving more suitable tolerancing decisions and in optimizing manufacturing and assembly processes. However, established methods to the sensitivity analysis in the context of variation simulations disregard important statistical dependencies, which occur when considering form deviations. To overcome these shortcomings, an approach to the density-based sensitivity analysis in variation simulations considering form deviations based on Skin Model Shapes is presented. The method is highlighted and discussed employing a typical tolerance analysis case study.

Kegelrollenlager eignen sich hervorragend für tragfähige und führungsgenaue Lagerungen. Wie jedes reale Bauteil unterliegen jedoch auch Kegelrollenlagerkomponenten Maß-, Form- und Lageabweichungen. Diese Abweichungen haben Einfluss auf das Betriebsverhalten von Kegelrollenlagern. In einer Kooperation mit Schaeffler Technologies AG & Co. KG hat der Lehrstuhl für Konstruktionstechnik der Friedrich-Alexander-Universität Erlangen-Nürnberg das Softwarewerkzeug „MAGMAKegel“ entwickelt, mit welchem sich Toleranzanalysen durchführen lassen, um ebendiese Auswirkungen geometrischer Abweichungen auf Kegelrollenlager zu quantifizieren. Im vorliegenden Beitrag wird das Softwarewerkzeug genauer beschrieben.

Im Rahmen der Zusammenarbeit der Friedrich-Alexander-Universität Erlangen-Nürnberg und der Technischen Universität Berlin wurde eine interaktive Studie mit 20 Experten aus großen und kleinen Unternehmen aus dem deutschsprachigen Raum durchgeführt. Ein Ziel der Studie war die Feststellung von Lücken und Herausforderungen, welche die bereits seit einigen Jahren bestehenden wissenschaft-lichen Erkenntnisse und damit verbundene neue digitale Fähigkeiten in der industriellen Praxis limi- tieren. Der vorliegende Artikel beschreibt sowohl das Vorgehen als auch die Erkenntnisse der Studie. Darüber hinaus leitet sich weiterer Handlungsbedarf ab.

Two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, known as MXenes, are a growing class of 2D materials, which offer great solid lubrication ability for low friction applications due to their weakly bonded multi-layer structure and tribo-layer formation with self-lubricating characteristics. To date, most studies have assessed their tribological response in basic laboratory tests. However, these tests do not adequately reflect the complex geometries, kinematics, and stresses present in machine components. Here, we aim at bridging this gap through assessment of the friction and wear performance of multi-layer Ti3C2Tx MXene solid lubricant coatings used in rolling bearings. MXenes’ tribological response is compared with state-of-the art solid lubricant coatings, which include molybdenum disulfide (MoS2), tungsten-doped hydrogenated amorphous carbon (a-C:H:W), and hydrogen-free, more graphite-like amorphous carbon (a–C). Multi-layer Ti3C2Tx MXene coatings reduce wear on the bearing washers by up to 94%, which can be attributed to the transfer of the lubricious MXene nano-sheets to secondary tribo-contacts of the bearing. While the frictional torque of all solid lubricant coatings is similar during steady-operation, the MXene-coated bearings extend the service life by 30% and 55% compared to MoS2 and DLC, respectively. This contribution demonstrates the ability of MXene solid lubricant coatings to outperform state-of-the-art solid lubricants in dry-running machine components such as rolling bearings.

Musculoskeletal multibody models are increasingly used to analyze and optimize physical interactions between humans and technical artifacts. Since interaction is conveyed by contact between the human body and the artifact, a computationally robust modeling approach for frictional contact forces is a crucial aspect. In this contribution, we propose a parametric contact model and formulate an associated force optimization problem to simultaneously estimate unknown muscle and contact forces in an inverse dynamic manner from a prescribed motion trajectory. Unlike existing work, we consider both the static and the kinetic regime of Coulomb's friction law. The approach is applied to the analysis of a leg extension training machine with the objective to reduce the stress on the tibiofemoral joint. The uncertainty of the simulation results due to a tunable parameter of the contact model is of particular interest.

In commercial injection moulding simulation software only tools for glass fibre-reinforced thermoplastics exist, but not for natural fibres. In our research, we adapted a simulation software for sisal fibre-reinforced polypropylene. To evaluate our simulation results, three experimental methods, to measure fibre orientation are compared to each other using injection moulded sisal fibre-reinforced polymer parts: terahertz spectroscopy, μ-CT and light microscopy measurements (LMM) of microtome sections. Terahertz spectroscopy determines the main orientation over the plate thickness, but it neglects variances of fibre orientation across the plate thickness. Using μ-CT and LMM allows measuring fibre orientation at different layers across the plate thickness and to detect a shell-core effect. Care has to be taken comparing results from μ-CT and LMM, due to their differences in the slice thicknesses. The orientation found with the μ-CT correlates well with the injection moulding simulation developed for sisal fibre-reinforced polypropylene.

International audience; The digitalization of manufacturing fuels the application of sophisticated virtual product models, which are referred to as digital twins, throughout all stages of product realization. Particularly, more realistic virtual models of manufactured products are essential to bridge the gap between design and manufacturing and to mirror the real and virtual worlds. In this paper, we propose a comprehensive reference model based on the concept of Skin Model Shapes, which serves as a digital twin of the physical product in design and manufacturing. In this regard, model conceptualization, representation, and implementation as well as applications along the product life-cycle are addressed. In today's highly competitive markets, the ambitions for shortening the time to market and for increasing the product development performance fuel the application of sophisticated virtual product models, which are frequently referred to as digital twins. Enabled by the digitalization of manufacturing, cyber-physical production systems, model-based system engineering, and a growing endeavour for data gathering and processing, these models are increasingly enriched with production and operation data. Moreover, they allow the efficient prediction of the effects of product and process development as well as operating and servicing decisions on the product behaviour without the need for costly and time-expensive physical mock-ups [1-3]. Particularly in design, such realistic product models are essential to allow the early and efficient assessment of the consequences of design decisions on the quality and function of mechanical products. However, current approaches to the implementation of digital twins lack of a conceptual basis, which hinders the applicability of the digital twin vision to various activities in design and production engineering. Motivated by this need, this paper proposes a comprehensive reference model, which serves as a digital twin of the physical product in design and production engineering. In this regard, important model properties, such as scalability, interoperability, expansibility, and fidelity, as well as different operations on this reference model along the product life-cycle, such as composition, decomposition, conversion, and evaluation are addressed. Moreover, the application of this reference model to geometrical variations management is highlighted. The paper is structured as follows. In the next section, the vision of the digital twin and its evolution is reviewed. After that, a comprehensive reference model for the digital twin is introduced, which is then applied to geometrical variations management. Finally, a conclusion and an outlook are given.

Dimensional management deals with the fact that the real geometry of every manufactured part deviates from its ideal shape. To evaluate the effects of these deviations tolerance analysis, which are often based on vectorial models, are carried out. Nevertheless the use of vectorial models has one major disadvantage – they cannot adequately represent form deviations. As a consequence new concepts of representations based on the GPS’ Skin Model have been established. Since the use of Skin Model Shapes (SMS) is time-consuming and does not always offer advantages over vectorial models, the Hybrid Tolerance Representation (HTR) which combines the advantages of vectorial and discretely represented tolerances is introduced in this paper. The HTR is based on a classification of the contact situation of the cinematic chain into lower and higher kinematic pairs. Based in this classification all higher kinematic pairs are going to be represented by SMS whereas lower pairs, are represented by vectors. Besides the simulation of the contact situation of all higher kinematic pairs the coupling of vectorial and discrete geometry representations is a challenge. The practical implementation of the presented method is shown on an X-ray shutter.

Geometrical variations are inevitably introduced during manufacturing and can thus be observed on every manufactured artefact. Although it is widely acknowledged that these part deviations distinctly affect the function and quality of mechanical assemblies, the majority of virtual product validation activities still rely on the modelling and analysis of the nominal product geometry without considering such geometrical part deviations. In order to overcome this shortcoming, the aim of this paper is to highlight the current status of geometrical variations modelling approaches for virtual product realization and to carve out future challenges in this domain. For this purpose, different geometry representation schemes, which are nowadays used during virtual product realization, are discussed. Furthermore, they are linked to the various virtual product realization activities and potentials for improvements for their use and exchange are highlighted. The novelty of the contribution can be found in the comprehensive review of approaches for geometrical variations modelling, their placement into a changing virtual product development landscape, and the exposition of elaborated challenges for future research in this domain.

Inhalt: Die Toleranzsimulation ist ein essentielles Werkzeug zur frühzeitigen Analyse der Auswirkungen von Bauteil- abweichungen auf funktions- und qualitätskritische Baugruppenmaße. Dieser Beitrag stellt einen neuen Ansatz zur Toleranzsimulation auf Basis von Punktwolken und Ober-flächennetzen unter Berücksichtigung von Formabweichungen und in Übereinstimmung mit Toleranznormen vor und erläutert das, diesem Ansatz zugrundeliegende, Konzept der Skin Model Shapes.

With the aim to fulfill legal regulations concerning energy efficiency and greenhouse gas emissions, diamond-like carbon (DLC) coatings are increasingly used on highly stressed components of internal combustion engines to reduce friction and prolong component lifetime. The valve train is one of a key system of the combustion engine considerably contributing to frictional losses, especially under boundary and mixed lubrication conditions at lower crankshaft speeds. In this regard, the tribological contact bucket tappet/camshaft offers high potential for friction reduction but imposes high demands on DLC coatings due to highly complex kinematics and repetitive loads depending on the cam contours and the camshaft angle and speed. The aim of this work was to analyze the influence of DLC coatings on the frictional and wear behavior within the contact bucket tappet/camshaft. This tribological contact was analyzed in a one tappet/one cam friction test-rig using series-production tappets, cams and valve springs ensuring high transferability of the results into the real application. Two amorphous hydrogen containing carbon based coatings were deposited on series-production bucket tappets. The zirconium based DLC coating a-C:H/ZrC g was compared to a DLC coating system a-C:H:X deposited under industrial conditions. One mineral motor oil of SAE viscosity grade 0W20 and one synthetic motor oil polyalphaolefin (PAO) of SAE viscosity grade 5W30 formulated with different additive packages containing the anti-wear (AW)/extreme pressure (EP) additive zinc dialkyl dithiophosphate (ZDDP) and the friction modifier (FM) additives molybdenum dialkyl dithiocarbamate (MoDTC) and glycerol monooleate (GMO) were used in the test-rig. Special attention was paid to the interactions of the additive packages in the low viscosity oils with the functional surfaces of the a-C:H:ZrC g coated bucket tappets. The frictional behavior determined by time-resolved measurements of friction forces reveals that higher camshaft speeds led to increased lubrication film formation contributing to reduced frictional losses. Higher motor oil temperature resulted in temperature induced reduced viscosity of the motor oils leading to higher frictional losses. The DLC coatings a-C:H:ZrC g and a-C:H:X caused significant reduction of frictional losses under the operating conditions in the test-rig. The a-C:H:ZrC g coated bucket tappets caused higher frictional losses than uncoated bucket tappets at low camshaft in boundary friction conditions. Friction reduction at all operating points was ensured by a-C:H:X regardless of camshaft speed, motor oil temperature and the choice of motor base oil and additive package proving the great potential for application on components under challenging lubricating and loading conditions. The wear of the uncoated and a-C:H:ZrC g coated functional surfaces was analyzed by means of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The a-C:H:ZrC g coating contributed to wear protection in the highly loaded tribological contact despite the different lubricating and loading conditions regardless of the base oil and additive packages. The a-C:H:X coating revealed similar favorable behavior. Comprehensive surface sensitive analysis of the uncoated and a-C:H:ZrC g coated bucket tappets by means of Raman spectroscopy and XPS indicated that no tribo-chemical reaction layer was formed from the motor oil and the additive packages on a-C:H:ZrC g coated bucket tappets under the operating conditions. Moreover, the combination of additives ZDDP and GMO in PAO appears to be disadvantageous in terms of reaction layer formation since no tribo-chemical reaction layer was found on uncoated steel bucket tappets after tribological tests in contrast to the mineral oil containing ZDDP and MoDTC.

Virtual product validation ensures that products fulfil their function under different varying conditions. Within the framework of virtual product validation, variation simulation represents the specific area that deals with the consequences of geometric part variations on functional key characteristics. In addition to the nominal geometry of the parts, the permissible part deviations in the form of tolerances, the joining sequence and process variations during assembly are required to simulate the effects of geometrical part deviations on assembly or product key characteristics. If the required quality targets are not achieved, the part tolerances usually have to be tightened, which goes hand in hand with increased production costs. The achievable part tolerances depend, among other things, on the material used, the workpiece dimensions, the manufacturing process, but also on the interaction between these factors. Therefore, the prediction of specific manufacturing process dependent deviations is hardly possible. However, if predictions should be made as exactly as possible, there is also the possibility to integrate measurement data directly or indirectly into the tolerance analysis. This has the advantage that material- and production-specific deviations can be considered in the best possible way for a certain part geometry. However, if measurement data is integrated into tolerance analysis, the problem arises that, in addition to the actual component deviation, the measurement uncertainty as part of the measurement result, must be implicitly determined in order to also be taken into account. Conversely, the tolerance analysis results are also influenced by the measurement uncertainty. To tackle this issue a novel procedure is presented which allows the quantification of the influence of the measurement uncertainty on the result of the tolerance analysis. In addition, it is shown how the measurement uncertainty is determined, whereby in particular the single point measurement uncertainty is dealt with. Since the measurement uncertainty can be different for each measuring point, Skin Model Shapes are used for tolerance analysis in order to have the possibility for defining point specific information. The developed procedure is then applied to a suitable case-study. CT measurements are used as the measurement method for determination of the single point measurement uncertainties. Finally, different scenarios for the tolerance analysis are compared in order to quantify the influence of the measurement uncertainty in the best possible way.

Efficient and systematic design methods are indispensable aids on the way to effective lightweight solutions. In this article. the necessity of providing the product developer with a design method for the design of endless fibre-reinforced plastic [FRP] components to fulfil fatigue requirements is highlighted. Existing damage models and test methods could be used and extended within such approaches. A suitable method should take into account particularly the variety of requirements for FRP components and consider other influences. e.g. from multi-layer composite design or load introduction. preferably supported by CAE tools. The simple applicability of an effective approach should be demonstrated both on test specimens and on demonstrator components.

Due to increasing market transparency. companies are mainly focusing on development of customized products. In this course. a competitive advantage should be achieved through the automated adaptation of product characteristics. In order to achieve this. development engineers focus primarily on modifying existing designs and refrain from re-running the entire product development process [PDP]. However. this approach is primarily limited to the CAD environment. Previous phases of the PDP are not integrated. leading to a lack of traceability and continuity. Media breaks and API conflicts arise which increase costs. In order to make use of this potential. this article shows a concept for integration of all phases of the RFLP approach into a tool for customization of adaptation constructions.

This paper presents a holistic approach to structure and classify requirements of the product life cycle systematically and make them accessible for the evaluation process. In a first analysis step. process models of selected literature are analyzed regarding classification and structuring of requirements as well as their derivation into evaluation criteria. In a subsequent synthesis step. the classification system is developed with a consistent consideration of the multi-criteria evaluation process. This approach therefore contributes to raise the awareness of an appropriate handling of requirements and to minimize forgotten requirements as well as evaluation criteria. As a result. costly iterations in the development process can be reduced sustainably by using the proposed approach.

The automotive industry electrifies a huge variety of previously mechanically-actuated car functions. While sharing the same function. the used electric motors often differ in customer related geometries and interfaces. The suppliers have to cope with this huge external variance using an appropriate variant management. With this paper. the support of the variant management of electric drives by knowledge-based systems is proposed. Therefore. a combination of two systems containing the knowledge of the configuration and design of motors are used. The concept is applied and evaluated on the example of the shaft rotor lamination connection. As a result. the amount of internal variants can be reduced and controlled as well as the designer can be supported during the development process.

Testing sports equipment with athletes is costly, time-consuming, hazardous and sometimes impracticable. We propose a method for virtual testing of running shoes and predict how midsoles made of BO...

Although mass production parts look the same at first sight, every manufactured part is unique, at least on a closer inspection. The reason for this is that every manufactured part is inevitable subjected to different scattering influencing factors and variation in the manufacturing process, such as varying temperatures or tool wear. Products, which are built from these deviation-afflicted parts, consequently show deviations from their ideal properties. To ensure that every single product nevertheless meets its technical requirements, it is necessary to specify the permitted deviations. Furthermore, it is crucial to estimate the consequences of the permitted deviations, which is done via tolerance analysis. During this process, the imperfect parts are assembled virtually and the effects of the geometric deviations can be calculated. Since the tolerance analysis enables engineers to identify weak points in an early design stage, it is important to know which contribution every single tolerance has on a certain quality-relevant characteristic to restrict or increase the correct tolerances. In this paper, four different methods to calculate the sensitivity are introduced and compared. Based on the comparison, guidelines are derived which are intended to facilitate a selection of these different methods. In particular, a newly developed approach, which is based on fuzzy arithmetic, is compared to the established high–low–median method, a variance-based method, and a density-based approach. Since all these methods are based on different assumptions, their advantages and disadvantages are critically discussed based on two case studies.

The development of hybrid trusses made of carbon-fiber-reinforced plastic struts and aluminum knots is currently not standardized, and there is no overall method for the design, although it has been proven that mass reduction is feasible. This paper introduces a new method for computer-aided engineering based design of hybrid trusses using carbon-fiber-reinforced plastic struts and metal nodes based on a modular system. The method includes all design steps from topology optimization to computer-aided design model generation and offers support to the engineer. The method is discussed in theory. A case study is done with a beam-shaped truss. It shows that if the bisection optimization method is combined with further constraints, it is suitable for selecting the optimum struts from a modular system for the truss. The developed approach is a suitable method for designing hybrid trusses. The basis of the method has been developed and will be further detailed and extended.

This contribution is aimed at the detailed understanding of lubrication mechanisms within total knee replacement. While Part I is focused on the experimental investigation, Part II deals with the development of a predictive numerical model. Here, a knee simulator was used for direct optical observation of the contacts between a metal femoral and a transparent polymer components. Transient dynamic conditions were applied. Mimicked synovial fluids with fluorescently labelled constituents were used as the test lubricants. The results showed that -globulin forms thin boundary lubricating film, being reinforced by the interaction of phospholipids and hyaluronic acid. Further development of lubricating film is attributed to albumin layering. Based on the results, a novel lubrication model of the knee implant is proposed. Tato studie je zaměřena na detailní porozumění mechanismů mazání v náhradě kolenního kloubu. Zatímco část I představuje experimentální pozorování, část II se zabývá vývojem prediktivního numerického modelu. V této části studie byl využit kolenní simulátor pro přímé optické pozorování kontaktu kovové femorální komponenty a vložky zhotovené z průhledného polymeru. Byly aplikovány proměnné dynamické podmínky. Jako mazivo byly využity modelové synoviální kapaliny s fluorescenčně označenými složkami. Výsledky ukázaly, že -globulin má tendenci formovat tenkou meznou vrstvu, která je vyztužená fosfolipidy v interakci s kyselinou hyaluronovou. Další nárůst mazacího filmu je připisován vrstvení albuminu. Na základě výsledků je představen nový teoretický model mazací vrstvy v kolenní náhradě.

Total knee replacements are an effective surgical treatment to restore the function of the knee. For an adequate design, knowledge about stresses and lubrication conditions is vital. Part II proposes a fully-coupled transient 3D model for the soft elastohydrodynamically lubricated contact based upon the generalized Reynolds equation and Finite Element Method while Part I of this study focused on experimental observations. Within the scope of this contribution, a numerical model is presented and validated with experimental data. Good agreement between model predictions and experimental data was found. A strong influence of fluid and geometry assumptions and transient effects were found. Besides, it was demonstrated that the rheological synovial fluid properties have a decisive role in the tribological behavior.

Despite the excellent clinical performance of joint replacements, wear-induced aseptic loosening is a main cause of premature implant failure. Tribological testing is usually carried out using bovine serum as an artificial synovial fluid. In order to gain new insights into the suitability to simulate human synovial fluid and provide recommendations for the conditions of tribological testing, accurate rheological measurements on the influence of temperature, shear rate and pressure on density and viscosity were performed. Thus, a temperature dependence of density and viscosity could be verified, whereas both values decreased with higher temperatures. The temperature dependency of viscosity could be approximated by an Arrhenius model. Moreover, shear-thinning characteristics could be demonstrated and fitted to a Cross model, which agreed well with investigations on human synovial fluid reported in literature. Furthermore, an anomaly of pressure dependence of viscosity was found and correlated with the behavior of water as a main constituent. At room temperature, the viscosity initially decreased to a minimum and then increased again as a function of pressure. This was no longer distinct at human body temperatures. Consequently, the present study confirms the suitability of bovine serum as a substitute synovial fluid and emphasizes the importance of realistic testing conditions in order to ensure transferability and comparability.

The dynamic behavior of a cage can have a significant influence on the performance and the noise of a rolling bearing. In case of an unstable or high-frequency cage movement, vibrations are transmitted to the adjacent machine elements and the environment, which can influence the operating behavior of the whole system. In addition, a loud noise can often be perceived, which is referred to in the literature as cage rattling or squealing. In this paper, characteristics of different cage movements are investigated using multibody simulations and experimental investigations. For this purpose, essential properties of the fundamentally observable cage movement types “stable”, “unstable” and “circling” are presented. The calculated cage dynamics and the type of cage motion are used to show dependencies between the operating conditions and the resulting cage movement such as inner ring rotational speed, bearing load or cage characteristics such as pocket clearance. Based on the simulations, interactions between the input parameters can also be determined. The results are used to identify operation-critical conditions and cage properties that lead to high cage dynamics. Finally, a comparison between the results of the multibody calculations and optical measurements is made. The optical measurements are performed using high-speed cameras. Reference markers fixed on the cage and digital image correlation allow the evaluation of the kinematics as well as the deformation of the cage. These results are compared with the simulation data to ensure a high quality of dynamics simulation.

Diamond-like carbon (DLC) coatings, frequently used to reduce wear and friction in machine components as well as on forming tools, are often subjected to cyclic loading. Doping of DLC coatings with metals or metal carbides as well as the usage of multilayer architectures represent promising approaches to enhance toughness, which is beneficial for the coatings' behavior under cyclic loading. In this study, we utilized cyclic nanoindentation to characterize the tribologically induced surface fatigue behavior of single-layer tungsten-doped (a-C:H:W) and multilayer silicon oxide containing (a-C:H:Si:O/a-C:H)25 amorphous carbon coatings under cyclic loading. Columnar growth was observed for both coatings by focused ion beam microscopy and scanning electron microscopy, while the multilayer architecture of the (a-C:H:Si:O/a-C:H)25 coating was verified by the silicon content using glow-discharge optical emission spectroscopy. In cyclic nanoindentation of the (a-C:H:Si:O/a-C:H)25 multilayer coating, stepwise small changes in indentation depth were observed over several indentation cycles. The surface fatigue process of the single-layer a-C:H:W covered a smaller number of indentation cycles and was characterized by an early steep increase of the static displacement signal. Microscopical analyses hint at grain deformation, sliding at columnar boundaries, and grain detachment as underlying fatigue mechanisms of the a-C:H:W coating, while the (a-C:H:Si:O/a-C:H)25 multilayer coating showed transgranular crack propagation and gradual fracturing. In case of the (a-C:H:Si:O/a-C:H)25 multilayer coating, superior indentation hardness (HIT) and indentation modulus (EIT) as well as a higher HIT3/EIT2 ratio suggest a higher resistance to plastic deformation. A high HIT3/EIT2 ratio, being an indicator for hindered crack initiation, combined with the capability of stress relaxation in soft layers contributed to the favorable surface fatigue behavior of the (a-C:H:Si:O/a-C:H)25 multilayer coating observed in this cyclic nanoindentation studies.

Sheet-bulk metal forming (SBMF) is characterized by successive and/or simultaneous occurrence of quite different load conditions regarding stress and strain states. These conditions significantly influence the material flow and thus the geometrical accuracy of the components. To improve the product quality a control of the material flow is required. An appropriate approach is given by locally adapted tribological conditions due to surface modifications of tool and workpiece, so-called tailored surfaces. Within the present study different methods to adapt the surfaces are presented and investigated with respect to their tribological effectiveness in SBMF. In a first step, requirements regarding necessary adaptions of the friction values for two SBMF processes are numerically defined. Based on the requirements different tailored surfaces are presented and analyzed regarding their tribological influence. Finally, the potential of surface modifications to improve SBMF processes is shown.

Internal clearance is a functional key characteristic of bearings. The bearing clearance can be evaluated using rigid body movements of the inner ring. Due to the deviations of dimension and roundness the contact areas between the bearing components cannot be predicted. Hence contact detection is necessary. For this purpose the herein presented concept is based on a raytrace algorithm. The concept can be used for the simulation of the bearing clearance for deviated bearing components. This enables the evaluation of the influence of dimensional and form deviations on the bearing clearance.

The additive manufacturing (AM) model factory's aim is to establish a leading-edge learning academy for the digital and generative production of innovative mechatronic products, where the complete value chain is integrated on a single site. Short courses and deep dives enable easier access to the state of the art technologies and increase the awareness for their potentials. Anchored in key industries such as automotive, aerospace, and medical by major OEMs and regional SMEs, the AM model factory cooperates with world-class partners and leading market players. This paper displays the model factory's setup, selected technologies, exemplary courses, and benefits.

Due to springback, deviations compared to the designed ideal modal occur during pipe bending processes. With quality control gauges no quantitative statements can be made regarding the process stability. The components are either good or bad and no production trends can be determined. This leads to high scrap rates and in addition, the real performance of the produced components may differ from the target behaviour of the initially designed CAD model. As addressed within this contribution, with integrating optical 3D measuring systems into the bending process, the actual state can be detected continuously. This enables to give feedback to the bending device for automatically readjust of bending parameters and thus prevent producing defective components. Moreover, the digitalisation of the actual contour allows a parametric correction of the designed CAD model, whereby the functional behaviour can be closer to reality within simulation models.

When talking about a large batch production of a certain mechanical product it generally comes along with specific requirements in terms of dimensional management to guarantee a consistently high product quality ensuring that customer requirements are met. Therefore, this contribution is about the effect that the elasticity of the observed assembly has on the formation of the limiting positions of the considered key product characteristics arising from tolerance analysis. On the example of an automotive door assembly a developed approach based on existing methodologies is explained in detail containing CAT and FEM simulations.

Kurzfassung Das Toleranzmanagement umfasst alle Tätigkeiten zur Steuerung geometrischer Bauteilabweichungen entlang des Produktlebenszyklus und ist daher von großer Bedeutung für produzierende Unternehmen. Gewohnte Wertschöpfungsketten befinden sich jedoch angesichts der vierten industriellen Revolution im Umbruch. Der Beitrag gibt daher einen Überblick über die Chancen und Herausforderungen für das Toleranzmanagement im Kontext von Industrie 4.0 und stellt mögliche Lösungsansätze vor.

Newly emerging Ti3C2Tx–nanosheets (MXenes) have attracted considerable attention in energy storage, catalysis and, more recently, tribology. MXene nanosheets are characterized by a weakly-bonded multi-layered structure with self-lubricating ability, making them a suitable candidate for solid lubrication. This contribution aims at addressing for the first time their application in higher loaded steel/steel dry sliding contacts by investigating the influence of contact pressure and relative humidity on friction and wear performance. Compared to the uncoated reference, a 2.3-fold friction reduction and a 2.7-fold reduction of the wear volume were verified for MXene-coated specimens for moderate contact pressures and low relative humidity. This was due to the in-situ formation of a compacted tribo-film consisting of densified Ti3C2Tx–nanosheets. In contrast, too high pressures induced a partial rupture of the wear-protecting tribo-layer, thus reducing its beneficial effects. Additionally, no beneficial effects regarding friction and/or wear were found at higher relative humidities, which was correlated with the expansion of the basal spacings. Therefore, this study summarizes favorable operating conditions for MXene nanosheets when used as solid lubricant to improve friction and/or wear thus making them excellent candidates for advanced, next-generation solid lubricants.

Solid lubricants like carbon-based materials, transition metal dichalcogenide compounds, polymers and soft metals, each with their specific merits and limitations, pursue the goal of reducing friction and wear between two rubbing surfaces under substantially dry conditions. Newly emerging early transition metal carbides and carbonitrides, such as Ti3C2Tx-nanosheets (MXenes), seem to be a promising candidate to be used as a solid lubricant due to their weakly bonded multilayer structure with self-lubricating character. For the first time, this paper aims at addressing the application of MXene nanosheets in higher loaded rolling-sliding contacts of machine elements by investigating their friction and wear behavior in thrust ball bearings under ambient conditions. Thereby, a reduction of the frictional torque by a factor of up to 3.2, an extension of the service life by about 2.1 times and a decrease of the linear cumulative wear rate by up to 2.9 compared to uncoated references have been verified. Thus, the Ti3C2Tx-coating already featured results comparable to reports on graphene, amorphous carbon coatings or advanced transition metal dichalcogenide, which demonstrates the tremendous potential of MXene nanosheets as outstanding, next-generation solid lubricant in machine elements.

In many technical systems, rolling bearings are critical machine elements concerning accuracy and lifetime. Their load distribution and radial displacement are directly linked to the accuracy and the fatigue life of rolling bearings. However, load distribution and radial displacement form a complex interdependency. Geometric deviations further influence this mutual connection. Although there are several approaches to determine the load distribution and the radial displacement, most of them are either too simplistic, allowing only the consideration of dimensional deviations, or too sophisticated and therefore unsuitable for a statistical evaluation of geometric deviations. Hence, the main purpose of this contribution is to provide a method for the determination of load distribution and radial displacement of cylindrical roller bearings that allows the consideration of geometric deviations as well as statistical evaluation of these deviations. Moreover, applying the method to a use case shows, whether the consideration of geometric deviations in the determination of load distribution and radial displacement is reasonable. The novelty of the contribution is, therefore, the provision of a statistical variational simulation framework for the analysis of load distribution and radial displacement of rolling bearings.

Associated with manufacturing and assembly processes, inevitable geometric deviations have a decisive influence on the function and quality of products. Therefore, their consideration and management are important tasks in product development. Moreover, to meet the demand for short development times, the front-loading of design processes is indispensable. This requires early tolerance analyses evaluating the effect of deviations in a design stage, where the product’s geometry has not yet been finally defined. Since such an early tolerance consideration allows quick and economic design changes seeking for robust designs, it is advisable that the design engineer, who is entirely familiar with the design, should take this step. For this purpose, this paper presents an easy-to-use CAD-based tolerance analysis method for skeleton models. The relevant part deviations are represented by varying geometric dimensions with externally driven family tables. The approach comprises the strength of vector-based methods but does not require an expensive set-up of tolerance analysis models. Particularly, the novelty of this method lies in the CAD-internal sampling-based tolerance analysis of simple geometries without the use of expensive CAT software. This enables designers to evaluate the effect of tolerances already at the preliminary design stage. Using a case study, the presented approach is compared with the conventional vector-based tolerance analysis.

Nowadays, ergonomic evaluation of work can be done using Digital Human Models (DHM). One advantage is to reduce the need for corrective measures by supporting a more prospective ergonomic work design. Although ergonomic models provide useful information for risk assessment, single working tasks with minor changes in work place design are difficult to evaluate. Instead, biomechanical models can analyze single movements or body postures, taking internal forces in muscles and joints into account. Therefore, the main goal of this work is to establish an interface between a biomechanical human model (AnyBody) and the “Editor for manual work activities” (ema) to enrich ergonomic evaluation with biomechanical parameters. First results demonstrate that the automatically generated movements of ema showed some specific deviations relative to the subjects’ movements in experimental conditions. Optimization of kinematic data in AnyBody is necessary to ensure more physiological movements which are highly valuable for ergonomic evaluation.

Real components always deviate from their ideal dimensions. This makes every component, even a serial production, unique. Although they look the same, differences can always be observed due to different scattering factors and variations in the manufacturing process. All these factors inevitably lead to parts that deviate from their ideal shape and, therefore, have different properties than the ideal component. Changing properties can lead to major problems or even failure during operation. It is necessary to specify the permitted deviations to ensure that every single product nevertheless meets its technical requirements. Furthermore, it is necessary to estimate the consequences of the permitted deviations, which is done via tolerance analysis. During this process, components are assembled virtually and varied with the uncertainties specified by the tolerances. A variation simulation is one opportunity to calculate these effects for geometric deviations. Since tolerance analysis enables engineers to identify weak points in an early design stage, it is important to know the contribution that every single tolerance has on a certain quality-relevant characteristic, to restrict or increase the correct tolerances. In this paper, a fuzzy-based method to calculate the sensitivity is introduced and compared with the commonly used extended Fourier amplitude sensitivity test (EFAST) method. Special focus of this work is the differentiation of the sensitivity for the total system and the sensitivities for the subsystems defined by the α-cuts of the fuzzy numbers. It discusses the impact of the number of evaluations and nonlinearity on sensitivity for EFAST and the fuzzy-based method.