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Conventional energy sources like fossil fuels are no longer viable due to their limitations and environmental impact. The demand for cleaner, more efficient energy solutions has led to the development of electric machines with smaller volumes and higher output. The family of permanent magnet Vernier motors have high torque output at very low speeds while being very small in volume. In conventional SVPM, the core losses are high, which leads to heating and reducing the efficiency of the motor, and the power factor of the motor is also low, and the torque can increase in relation to the motor volume. The reluctance torque theory, along with the normal output torque of the motor, increases the final torque of the motor. In addition, the toothing of the rotor reduces the cross-sectional area and weight of the rotor. With the reduction of the cross-sectional area, the eddy currents in the core are reduced, the power factor increases and the efficiency of the motor improves. Therefore, in this paper, a spoke-type permanent magnet Vernier motor with a rotor similar to the reluctance rotor has been designed, which has higher torque, lower losses, and higher power factor compared to conventional spoke-type permanent magnet Vernier motors. [ABSTRACT FROM AUTHOR]

Electric machines, particularly induction motors, are widely used in industry as they are robust in construction and require less maintenance. These machines are continuously operated under high loading conditions, which may result in machine vibrations. The Experimental-Modal-Analysis (EMA) technique is employed in this research to determine electrical machine vibrations. The hammer test is a popular EMA approach for locating the exact location of winding looseness. EMA test is executed on the stator winding to extract the modal parameters to find exact deformation in machine windings. Mathematical calculations and a numerical model are developed to validate the experimental data. The EMA’s Operational Deformation Structure (ODS) validates the winding’s looseness precisely. Two test machines’ MA and MB windings are tested with EMA to evaluate the stator slot structure’s looseness. Finally, the proposed technique is compared with the finite element technique along with mathematical calculations for verification. [ABSTRACT FROM AUTHOR]

Assessment of verification concepts acc. to EC7 for excavation retaining walls in sand based on the finite element method The current draft of the new version of EN 1997 distinguishes for the numerical calculations of retaining structures between verification approaches with different application of partial safety factors: either on the effects of actions, or on the shear strength parameters of the soil. Comprehensive numerical studies based on the finite element method for representative system geometries were carried out and the results were evaluated. Various systems with different boundary conditions with regard to support, groundwater level, excavation depth and embedment depth were considered. Internal forces were determined for all systems. Overall, it was found that both verification methods deliver similar values for shear forces and bending moments along the wall. The two variants for the approach using reduction factors for the shear strength of the soil were compared; both variants yielded different results due to the different initial conditions with an a priori reduction of the shear parameters of the soil on the one hand and a reduction only in decisive calculation phases on the other. A comparison with the current analytical method according to Blum in accordance with the recommendations of the EAB showed that other embedment lengths are necessary in the FEM due to different stress distributions along the wall in order to fulfill the verification of the embedment length. The degree of earth support fixity in the FEM calculations is less than in an analytical calculation acc. to Blum. [ABSTRACT FROM AUTHOR]

The contribution at hand introduces computational modeling and realistic simulation concepts for a comprehensive description of the manufacturing and application of densified wood and wooden structures made from molded densified wood. Wood, as a natural material, is characterized by e.g. a very good mechanical load-bearing capacity related to its density. Nevertheless, the ratio between its mechanical properties and its density can be optimized by densification technology for an expanded use of wood in structural engineering. The wood densification process is not only a mechanical process with large and irreversible deformations, it is also denoted by temperature- and moisture-dependent treatments of the wooden specimens. Thus, the introduced approaches to predict the material and structural characteristics of compressed and molded wood consist of an inelastic and multi-physical constitutive modeling of wood at finite deformations as well as the computation of effective structural properties of wood after the thermo-hygro-mechanical densification process. A successful implementation of the modeling concepts into the finite element method (FEM) is presented, which is verified by numerical investigations. A validation of the numerical results is carried out by use of experimental data at beech wood (Fagus Sylvatica, L.), taken from literature. [ABSTRACT FROM AUTHOR]

Applications of soft materials are customarily linked to complex deformation scenarios and material nonlinearities. In the bioengineering field, soft materials typically mimic the low stiffness of biological matter subjected to extreme deformations. Computational frameworks surge as a versatile tool to assist the design of functional applications. The constitutive model lies at the core of such frameworks. In this regard, the customary extreme non-linear behavior of elastomers poses an additional challenge to thoroughly capture the material behavior. Here, data-driven methodologies hold considerable promise for enhancing constitutive modeling when contrasted with phenomenological approaches. In this investigation, we introduce a versatile data-adaptive method tailored to the modeling of hyperelastic soft materials at finite strains. Specifically, our method substitutes an a priori chosen model for the strain energy function by a flexible interpolant defined on a discretized invariant space. Within this framework, the interpolation values assume the role of material parameters and are determined through finite element model updating to conform to measured experimental data — comprising full-field displacements coming from Digital-Image-Correlation and global reaction forces. We validate the method on uniaxial experimental tests of soft elastomers, encompassing ELASTOSIL TM , DOWSIL TM , and V HB TM. Overall, we aim to establish a new route for the construction of hyperelastic energy functions, untethered from any predefined existing models or assumptions regarding the shape of the energy. [ABSTRACT FROM AUTHOR]

The importance of numerical investigations in joining processes increases with the development of advanced joining technologies, process designs and tool concepts. To predict the load bearing capabilities for fibre-reinforced thermoplastic (TPC) structural components, the knowledge of the resultant material structure is essential. In this paper, a forming process of a carbon fibre/polyamide 6-preform into a structured mould is investigated. An adapted integral bladder-assisted moulding process is used and numerically investigated by combination of an Arbitrary-Lagrangian-Eulerian method and a multi-filament approach. The objectives are to analyse the forming phenomena of bridging, compression and rearrangements of the fibres while forming. Due to the application of the Arbitrary-Lagrangian-Eulerian method, flow process of the matrix can be investigated. The proposed multi-filament modelling approach is presented in detail and the main phenomena of fibre rearrangement and flow processes during the forming process are discussed on the basis of micrographic and surface analyses of the experimental investigations. It is shown that the chosen numerical approach is suitable to model and analyse the phenomena of fibre bridging and the flow process to determine matrix rich zones. The quantitative comparison of the experimental and numerical results reveals, that the compaction of the fibre bundles is overestimated in the simulations. Furthermore, numerical parameters regarding contact behaviour and leakage significantly impact the modelling performance.

The robust crash design of plastic components is of great interest in automotive engineering. For an efficient development, a prototype-free development is aimed at, whereby at the same time the test programme can be strongly reduced and in the future possibly completely omitted, if the virtual design delivers robust results. Based on the plastic component design of a head box, a possible procedure consisting of finite element calculation and artificial neural networks is described exemplarily. The head box is the load-bearing part of the head restraint of a car seat. It can be shown that, if these methods are used correctly, components can be designed very quickly to fulfil the specified objective functions. [ABSTRACT FROM AUTHOR]

As damage occurs in the context of high stresses that are also related to the presence of plastic strains, it is natural to investigate the effect of plasticity on damage evolution and to thus achieve a more realistic model. In this work, the existing and new damage model presented in [Junker P, Schwarz S, Makowski J, Hackl K. Continuum Mech. Therm. 2017, 29 (1), 291–310] is enhanced with plasticity and isotropic hardening. The damage model is based on a relaxation-based approach and does not require additional complex regularization techniques besides considering viscous effects. The benefit of the model are mesh-independent results for the rate-dependent case, even without considering, e.g. gradient terms for mathematical regularization. The enhancement with plasticity and isotropic hardening was investigated for a representative volume element that considerd a damaging matrix material and non-damaging hard precipitates. Two different loading types, pure tension and pure shear, yielded the homogenized stress/strain response for the material at various loading rates. Hereto, several finite discretizations in terms of finite-element meshes were used. The results underline the mesh-independence for physically reasonable loading rates and viscosities.

Monitoring and Modeling of a Wind Turbine Support Structure to Create a Digital Twin The basis for creating a digital twin is a suitable model with a close connection to reality in the form of measurement data. In this paper it is explained how model and measurement data of the support structure of a wind turbine can be obtained. The procedure is implemented on a real wind turbine with a concrete/steel hybrid tower. The monitoring includes the acquisition of vibrations, strains and temperature as well as the determination of the dynamic Young's modulus of the concrete structure by sound velocity measurements. For modeling, a finite element model with shell elements was chosen, which takes into account stiffening effects from static loads. A comparison between model and reality is the most important premise for the use of a digital twin: Therefore, a multi‐stage model validation based on modal parameters and local material stresses is performed. The Digital Twin offers different usage scenarios; here one is carried out: the fatigue calculation and remaining useful life (RUL) estimation. For this purpose, material stresses at highly stressed positions are determined using measurement data and model. The results are currently still unrealistically high lifetimes for the concrete part. The results are based on relatively short (1 h, 24 h) stress time series. This could be one reason for the high values. It could also be an indication that fatigue is a non‐critical load case for the concrete part. [ABSTRACT FROM AUTHOR]

Structural fire design as a level‐3‐analysis of the listed ML machine laboratory at ETH Zurich At ETH Zurich, scientists are researching the innovative processes of tomorrow. For this reason, it goes without saying that modern simulation methods are used to solve a special problem in the refurbishment of the listed ML machine laboratory in the heart of Zurich. The steel structure of the hall was erected in 1933 and is one of the first fully welded steel structures in Switzerland. Since the use in the course of the current transformation must take fire protection measures into account, but at the same time the construction must remain in its original state for reasons of monument conservation, a structural fire design based on natural fire methods was used to prove the fire resistance of the steel hall. Prof. Dr. Mario Fontana was involved in this ambitious project, which until recently held the professorship for steel, wood and composite construction at the institute for structural analysis and design at ETH Zurich and is one of the internationally renowned scientists for structural fire design from Switzerland. With the help of simulation methods, the prove of the load‐bearing capacity in the event of a fire of the machine hall is currently in progress to maintain its original state with visible steel structure in the future. [ABSTRACT FROM AUTHOR]

An ancient landslide, situated in Deqin County, Yunnan Province, China, was used to investigate the reactivation by water infiltration. This study considers the infiltration process and landslide stability using finite-element method (FEM)-based models. The results show that the reactivation of old landslide deposit was triggered by the long-term leakage of diversion ditch before October 2012, and the reactivation was triggered again by the intense rainfall on 7–9 October 2012. The old cracks, which formed in the earlier reactivation of landslide, played a key role for the rainfall infiltration. They offered a preferential path for much more rainfall to infiltrate fast into deep soil, and caused wetting front to move down faster in landslide. The old slip zone with lower permeability was another important factor to cause the infiltrated water to accumulate and form a high pore water pressure above slip zone. Then the high pore water pressure decreased the shear strength of slip zone and triggered the reactivation of the old landslide deposit again. [ABSTRACT FROM AUTHOR]

This paper presents a new design of microelectromechanical systems (MEMS) based low-g accelerometer utilizing mode-localization effect in the three degree-of-freedom (3-DoF) weakly coupled MEMS resonators. Two sets of the 3-DoF mechanically coupled resonators are used on either side of the single proof mass and difference in the amplitude ratio of two resonator sets is considered as an output metric for the input acceleration measurement. The proof mass is electrostatically coupled to the perturbation resonators and for the sensitivity and input dynamic range tuning of MEMS accelerometer, electrostatic electrodes are used with each resonator in two sets of 3-DoF coupled resonators. The MEMS accelerometer is designed considering the foundry process constraints of silicon-on-insulator multi-user MEMS processes (SOIMUMPs). The performance of the MEMS accelerometer is analyzed through finite-element-method (FEM) based simulations. The sensitivity of the MEMS accelerometer in terms of amplitude ratio difference is obtained as 10.61/g for an input acceleration range of ±2 g with thermomechanical noise based resolution of 0.22 μμg/Hz and nonlinearity less than 0.5%.

Assessment of pseudo‐static methods for the bearing capacity of footings under seismic loading The common method for assessing the bearing capacity of foundations under seismic loading is based on the assumption of pseudo‐static acceleration forces which represent the inertial forces from the superstructure and those in the ground. The components of the classic tripartite bearing capacity equation in DIN 4017 are provided with suitable reduction factors for this purpose. Results from recent numerical studies are compiled. An alternative representation is a dome‐shaped 3‐D bearing strength surface in terms of combinations of vertical load, horizontal load, and bending moment that lead to failure. The equation in the DIN can also be converted into such a surface. 3‐D surfaces are compared and evaluated for the case of a purely cohesive and a cohesionless soil. A widely used FEM code with a Mohr‐Coulomb constitutive model is then applied to numerically capture for typical configurations the effects of load inclination and eccentricity as well as of the inertial forces in the soil. The suitability of the FEM as a robust calculation means is confirmed, provided that all modelling details are adequately considered. The influence of the dilation angle is discussed separately. It is shown that the extended bearing capacity equation is particularly suitable for the application in design, and also offers the advantage of a steady transition from the static to the seismic loading case. [ABSTRACT FROM AUTHOR]

Since structural engineering requires highly developed and optimized structures, the thickness dependency is one of the most controversially debated topics. This paper deals with stability analysis of lightweight thin structures combined with arbitrary geometrical imperfections. Generally known design guidelines only consider imperfections for simple shapes and loading, whereas for complex structures the lower-bound design philosophy still holds. Herein, uncertainties are considered with an empirical knockdown factor representing a lower bound of existing measurements. To fully understand and predict expected bearable loads, numerical investigations are essential, including geometrical imperfections. These are implemented into a stand-alone program code with a stochastic approach to compute random fields as geometric imperfections that are applied to nodes of the finite element mesh of selected structural examples. The stochastic approach uses the Karhunen-Loève expansion for the random field discretization. For this approach, the so-called correlation length lc controls the random field in a powerful way. This parameter has a major influence on the buckling shape, and also on the stability load. First, the impact of the correlation length is studied for simple structures. Second, since most structures for engineering devices are more complex and combined structures, these are intensively discussed with the focus on constrained random fields for e.g. flange-web-intersections. Specific constraints for those random fields are pointed out with regard to the finite element model. Further, geometrical imperfections vanish where the structure is supported. [ABSTRACT FROM AUTHOR]

Immunoassay is a biochemical test that measures the presence or concentration of biomolecule in a solution by the means of the antibody (or antigen). Most immunoassays involve chemically linking antibodies or antigens with some kind of detectable labels which produce measurable signals in response to the binding. The use of labels creates problems, including complexity in the screening process and probable influence on the nature of target molecular. To overcome the drawbacks, we theoretically demonstrate an integrated Mach–Zehnder interferometer (MZI) with $n$ -shaped slot waveguide based on finite-element method. Dual polarization can be strongly confined in the slot where the analytes are accommodated. The interaction between the optical field and tested solution is greatly enhanced, resulting in high sensitivity of the device. The detection of surface adsorbed molecule densities is down to 0.176pg/mm2 for transverse electric mode and 1.27pg/mm2 for transverse magnetic mode. The integrated MZI with identical configuration of both arms make the parallel-control trial available thereby effectively preventing the unspecific binding and background from biological materials. Wavelength interrogation was taken to monitor the antibody-antigen recognition. [ABSTRACT FROM AUTHOR]

Phenomenological constitutive modeling is prone to uncertainty and results in loss of information as data coming from experiments are not used directly in calculations. Data-driven approaches are a promising alternative to constitutive modeling. We present a new data-adaptive approach to model hyperelastic rubber-like materials at finite strains. Our proposed modeling procedure combines the advantages of phenomenological hyperelasticity with the data-driven paradigm of directly including experimental data in calculations. We suggest formulating a finite-element-like approximation of the strain energy function as a sum of basis functions expanded over a set of invariants multiplied by unknown parameters. The parameters are determined by an optimization algorithm to match measured experimental data (full-field displacements and global reaction forces) in a least-squares sense. We verify our approach and show that computation times are similar compared to those of phenomenological models. By numerical examples, we demonstrate the ability of our approach to re-identify O (10) parameters. [ABSTRACT FROM AUTHOR]

We theoretically investigate the intensity-dependent optical nonlinearity in graphene-aided D-microfiber, by tuning the chemical potential of graphene and varying radial distance and radii of the D-microfiber. Utilizing an interplay between graphene and the enhanced evanescent field of a guided mode in the waveguide of interest, the net utility of nonlinear coefficient is harnessed up to a very high value of 10 6 W − 1 m − 1 . Importantly, which is ∼ two orders of magnitude larger than in PMMA–graphene–PMMA waveguide. The highly dispersive nature of the waveguide, D ∼ 10 3 ps/nm-km, and large nonlinear figure-of-merit, FOM NL ∼ 1.29, have raised the possibilities of utilizing slow light structures to operate devices at few watts power level with microscale length. These studies have opened one window towards the next-generation all fiber-optic graphene nonlinear optical devices. [ABSTRACT FROM AUTHOR]

Edge cracks are a well-known problem in the series production of vehicle body components. Various approaches were developed to predict the sensitivity of edge cracks and to improve the forming behavior of shear cut edges. The two-stage shear cutting process has become a popular method for reducing the edge crack sensitivity of steels and thus maximizing the formability of the shear cut edge. The application of this method with adapted shear cutting parameters has the advantage that the severely damaged shear affected zone is cut off in the second stage and the scrap is less stiff than in a normal shear cutting process. In the second stage only a small amount of deformation, and thus damage, is generated in the final component edge, as forming mainly occurs in the scrap. In this work a simulation model is presented and validated as well as the results of the numerical parameter analysis using the material HCT780X. The influence of the radius of the cutting line, the wear condition of the active elements of the shear cutting tool as well as the width of the cutting-offset on the resulting damage within the shear affected zone were investigated. It was found that using adapted two-stage shear cutting parameters lead to the formation of two separate shear zones and therefore can reduce the hardening of the shear affected zone by more than half. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents numerical and experimental studies on modal behavior of cylindrical, lightly damped beam structures containing a notch-like crack with variable position and geometry. The numerical investigation utilizes the Finite-Element-Method (FEM) and a discretization strategy is developed that enables a crack to be represented in three dimensions. A test procedure capable of delivering a broadband impulse excitation to a flexible supported test specimen was developed. The customized excitation unit was used in conjunction with a Laser-Scanning-Vibrometer (LDV) to analyze a frequency range up to 40 kHz. The first 15 bending mode shape pairs with their corresponding eigenfrequencies are numerically and experimentally identified. The model updating is performed for the elastic parameters and the boundary conditions to minimize the deviation between experimentally determined and numerically calculated results in terms of eigenfrequencies. The acquired data are used in a two-stage damage identification procedure, in which suitable start vectors are found by the evaluation of objective function plots. Subsequently, geometrical crack parameters are identified. The deviations between real and determined crack positions range between 0.05 and 0.28 percent for crack depth/diameter ratios of less than 7 percent. [ABSTRACT FROM AUTHOR]

Torsion bars are used in automotive engineering as well as in other industrial applications. Such elements are produced by bending cold drawn wires. In conventional drawing processes tensile residual stresses occur near the surface of the wire. Small bending radii, which are required in limited assembly spaces, result in component failure due to reduced formability. Additional operations such as heat treatment or shot peening are necessary to influence the residual stress of the wire and to improve the dynamic stability of the torsion bar. The aim of the research is to reduce tensile residual stresses near the surface of the wire in order to eliminate process steps and to enhance formability. Therefore, a forming technology is developed by using a modified drawing die geometry on the basis of gradation extrusion. Finite element simulation is used to investigate the influences of element geometry, number of elements and process modification on the resulting residual stresses after wire drawing of a steel alloy. The results are evaluated and compared with the conventional wire drawing process. Furthermore, the requirements for the design of an experimental test device will be outlined as well as the measurement of the residual stresses by using X-ray diffraction.

Nonsmooth modes of vibration allow for identification of resonant behaviours and attendant vibratory frequencies in structures prone to unilateral contact conditions on the boundary. The prominent approach for finding nonsmooth modes of vibration entails finding continua of periodic solutions to the system in question. In this paper, nonsmooth modes of a one-dimensional bar of varying cross-sectional area prone to unilateral contact with a rigid obstacle are determined. While numerical and analytical techniques were previously proposed, they were limited to constant cross section bar and could not be applied on the varying area bar for which the classical d'Alembert solution no longer exists. In this article, nonsmooth modal analysis of the varying area bar is performed via a novel treatment of the Signorini conditions within the finite element framework: the nodal boundary method. The nodal boundary method solves the Signorini problem by switching between two sets of shape functions describing either (1) inactive contact motion (motion away from the rigid obstacle) or (2) active contact motion (bar in contact with the rigid obstacle). In the proposed nodal boundary method, the motion of the contacting node does not participate in the resulting governing Ordinary Differential Equation (ODE). Instead, its motion is prescribed by the boundary conditions and is dictated by the motion of internal nodes. The nodal boundary method results in a discontinuous ODE in the internal nodes which can be solved both analytically and via numerical techniques. Solutions obtained by the nodal boundary method exhibit several advantages over existing numerical techniques: no chattering at contact, no penetration of the rigid obstacle, and existence of periodic solutions. Specifically, these periodic solutions are readily detectable via the shooting method with sequential continuation. The nodal boundary method is used successfully for the nonsmooth modal analysis of different models of the varying area bar. Besides, application of the nodal boundary method for nonsmooth modal analysis of the uniform area cantilever bar in Dirichlet or Robin boundary conditions is also demonstrated for comparison with existing literature. • Nodal boundary method introduced for treatment of Signorini problem. • Nodal boundary method does not exhibit numerical chattering at contact. • Periodic solutions for bar prone to contact exist in nodal boundary method. • Nonsmooth modes of the bar in contact are detected for different configurations. • Obtained nonsmooth modes are validated against SICONOS solutions. [ABSTRACT FROM AUTHOR]

This paper focuses on the optimal structural design of a hybrid permanent-magnet-electro-magnetic suspension system (PEMS) for a magnetic levitation (Maglev) transportation system in order to decrease the suspension power loss. First, the nonlinear magnetic force expression of a PEMS system is obtained by developing the magnetic equivalent circuit of the hybrid structure. The proposed analytical framework accounts for leakage fluxes and material properties such as iron reluctances. A number of design considerations are also presented to attain more practical results. Genetic algorithm is then employed to optimize the lifting force while reducing the system power loss. Moreover, 3-D finite element method (FEM) is utilized in the analyses and it is shown that the results calculated from the proposed model match well with those obtained from FEM. In addition, superiorities of the implemented model over the existing approaches are demonstrated. The outcomes show that the proposed method has increased the magnetic force, while significantly reducing the suspension power loss compared with those in the conventional pure electromagnet structure and in a previously proposed hybrid structure. [ABSTRACT FROM AUTHOR]

This article reports a comprehensive study on four point bending and temperature experiments and their correlation with numerical simulation. The test vehicle is a printed circuit board (PCB) with 16 Quad Flat No Leads Packages (QFNs) components mounted on top and bottom side. Each QFN has 120 stress sensing cells distributed over the surface of the silicon die. In our experiments we have investigated the stress state in the QFN utilizing these piezoresisitve stress sensors for thermal, four point bending and combined loading conditions. In our study we compare these measurements with the numerical model. Stress analysis for the isothermal bending case showed that components very close to the edge are exposed to slightly higher stresses (20 %) compared to the components placed in the center of the PCB. • Iso-thermal four point bending, thermal-cycle and combined load experiments with on-chip stress sensor • Resulting stresses from experiment and simulation • Superposition of individual load cases (four point bending and temperature) leads to same results as combined load case. [ABSTRACT FROM AUTHOR]

Roebel cables made of high temperature superconducting (HTS) coated conductors can carry high currents with a compact design and reduced ac losses. Therefore, they are good candidates for manufacturing coils for HTS applications such as motors and generators. In this paper, we present the experimental dc and ac characterization of several coils assembled from a 5-m-long Roebel cable built at Karlsruhe Institute of Technology, which differ in the number of turns and turn-to-turn spacing. Our experiments, which are supported by finite-element-method calculations, show that a more tightly wound Roebel coil, despite having a lower critical (and therefore operating) current, can produce a higher magnetic field than a loosely wound one. For a given magnetic field produced at the coil's center, all the coils have similar ac losses, with the exception of the most loosely wound one, which has much higher losses due to the relatively large current needed to produce the desired field. The experiments presented in this paper are carried out on the geometry of pancake coils made of Roebel cables, but they are exemplary of a more general strategy, based on coupling experiments and numerical simulations, that can be used to optimize the coil design, with respect to different parameters, such as tape quantity, size, or ac loss, the relative importance of which is dictated by the specific application. [ABSTRACT FROM PUBLISHER]