Internal Geometry Research Articles

Integrated geophysical approach for detection and size-geometry characterization of a multiscale karst system in carbonate units, semiarid Brazil

Abstract The karstification of carbonate rocks creates 3D maze voids that are normally controlled by fracture networks and sedimentary bedding. The spatial distribution and density of karst systems are usually complex and difficult to predict, demanding multidisciplinary studies at different scales of investigation to determine the spatial distribution and density of karst features and their possible links with cave systems controlled by the regional structural setting. The present study integrates geophysical datasets (gravity, electrical resistivity tomography - ERT, and ground penetrating radar - GPR) with a digital elevation model to investigate a karst system in the Irecê basin, a semiarid region of Brazil. Morphostructural lineaments reveal a NNW-SSE- and E-W-oriented structural setting of the crystalline basement, which is imprinted on the internal basin architecture, and surface drainage network. Negative gravity anomalies and high-gradient gravity zones indicate the main karstic zone, where karst landforms are concentrated. In addition, 2.5D gravity modeling provides the internal basin geometry, demonstrating that the karst system has evolved in the thickest sector of the basin. ERT profiles delineate the underground passages that connect dolines at depth. Finally, GPR data image shallow subsurface ghost-rock karstification that spread out from the surface to depth and that took advantage of vertical fractures and slightly arched bedding planes. Our results point out the role of the fracture corridors in channelizing hydrodynamic energy at a sufficiently high level to create caves by the total removal of dissolved material, whereas in the surrounding areas under low hydrodynamic conditions, overall shallow ghost-rock karstification took place, creating residual weathered rocks (alterites).

Towards Structural and Aeroelastic Similarity in Scaled Wing Models: Development of an Aeroelastic Optimization Framework

The pursuit of more efficient transport has led engineers to develop a wide variety of aircraft configurations with the aim of reducing fuel consumption and emissions. However, these innovative designs introduce significant aeroelastic couplings that can potentially lead to structural failure. Consequently, aeroelastic analysis and optimization have become an integral part of modern aircraft design. In addition, aeroelastic testing of scaled models is a critical phase in aircraft development, requiring the accurate prediction of aeroelastic behavior during scaled model construction to reduce costs and mitigate the risks associated with full-scale flight testing. Achieving a high degree of similarity between the stiffness, mass distribution and flow field characteristics of scaled models and their full-scale counterparts is of paramount importance. However, achieving similarity is not always straightforward due to the variety of configurations of modern lightweight aircraft, as identical geometry cannot always be directly scaled down. This configuration diversity has a direct impact on the aeroelastic response, necessitating the use of computational aeroelasticity tools and optimization algorithms. This paper presents the development of an aeroelastic scaling framework using multidisciplinary optimization. Specifically, a parametric Finite Element Model (FEM) of the wing is created, incorporating the parameterization of both thickness and geometry, primarily using shell elements. Aerodynamic loads are calculated using the Doublet Lattice Method (DLM) employing twist and camber correction factors, and aeroelastic coupling is established using infinite plate splines. The aeroelastic model is then integrated within an Ant Colony Optimization (ACO) algorithm to achieve static and dynamic similarity between the scaled model and the reference wing. A notable contribution of this work is the incorporation of internal geometry parameterization into the framework, increasing its versatility and effectiveness.

Classification, main types of structures and purpose of capillary means to ensure fuel perfection

The flight of a spacecraft is characterized by the alternation of active sections of the trajectory, when the propulsion system is operating, and passive sections, in which the liquid components of the fuel in the tanks are under the influence of microgravity and, as a result, various disturbing factors (actions: aerodynamic forces, solar wind, internal gravitational forces, disturbances from the engines of the orientation and stabilization system, etc.) can occupy any position in them. At the same time, the situation is not ruled out when the gas phase can get into the flow line, which in the future can lead to a failure to restart the propulsion system and an emergency end of the mission. Therefore, an almost obligatory element of the systems for storing and supplying liquid rocket fuel components of the propulsion system of a spacecraft is the means of ensuring fuel continuity, the main criterion for the perfection of which is the amount of residual fuel components that cannot be produced due to a violation of the fluid continuity at the inlet to the propulsion system. The design of the fuel continuity means is directly determined by the internal geometry of the tank and the characteristics of the pneumohydraulic system of the spacecraft. A significant complication of the design of the fuel continuity means occurs in the presence of several factors that are present when a spacecraft performs a flight task: multiple launch and stop of the propulsion system, performing complex maneuvers under conditions of multidirectional external force impulses, which is just inherent in spacecraft. The position uncertainty and heterogeneity of the boundaries between the boost gas and fuel components at the time of launching the propulsion system require additional measures to prevent premature gas breakthrough into the flow line with its subsequent entry into the propulsion system. Therefore, over more than five decades, fuel continuity tools have been developed, the operation of which is based on various principles. At the same time, capillary-type fuel continuity means are most widely used. During this time, the basic physical principles of the behavior of a liquid under the action of capillary forces under weightless conditions were studied, the main types of designs of means for ensuring fuel continuity were determined, and the range of tasks they solved was described.

Embedding a surface acoustic wave sensor and venting into a metal additively manufactured injection mould tool for targeted temperature monitoring

Injection moulding (IM) tools with embedded sensors can significantly improve the process efficiency and quality of the fabricated parts through real-time monitoring and control of key process parameters such as temperature, pressure and injection speed. However, traditional mould tool fabrication technologies do not enable the fabrication of complex internal geometries. Complex internal geometries are necessary for technical applications such as sensor embedding and conformal cooling which yield benefits for process control and improved cycle times. With traditional fabrication techniques, only simple bore-based sensor embedding or external sensor attachment is possible. Externally attached sensors may compromise the functionality of the injection mould tool, with limitations such as the acquired data not reflecting the processes inside the part. The design freedom of additive manufacturing (AM) enables the fabrication of complex internal geometries, making it an excellent candidate for fabricating injection mould tools with such internal geometries. Therefore, embedding sensors in a desired location for targeted monitoring of critical mould tool regions is easier to achieve with AM. This research paper focuses on embedding a wireless surface acoustic wave (SAW) temperature sensor into an injection mould tool that was additively manufactured from stainless steel 316L. The laser powder bed fusion (L-PBF) “stop-and-go” approach was applied to embed the wireless SAW sensor. After embedding, the sensor demonstrated full functionality by recording real-time temperature data, which can further enhance process control. In addition, the concept of novel print-in-place venting design, applying the same L-PBF stop-and-go approach, for vent embedding was successfully implemented, enabling the IM of defectless parts at faster injection rates, whereas cavities designed and tested without venting resulted in parts with burn marks.

Equivariant volume extremization and holography

In a previous paper two of us (D.M. and A.Z.) proposed that a vast class of gravitational extremization problems in holography can be formulated in terms of the equivariant volume of the internal geometry, or of the cone over it. We substantiate this claim by analysing supergravity solutions corresponding to branes partially or totally wrapped on a four-dimensional orbifold, both in M-theory as well as in type II supergravities. We show that our approach recovers the relevant gravitational central charges/free energies of several known supergravity solutions and can be used to compute these also for solutions that are not known explicitly. Moreover, we demonstrate the validity of previously conjectured gravitational block formulas for M5 and D4 branes. In the case of M5 branes we make contact with a recent approach based on localization of equivariant forms, constructed with Killing spinor bilinears.

Integrating artificial intelligence with numerical simulations of Cattaneo-Christov heat flux on thermosolutal convection of nano-enhanced phase change materials in Bézier-annulus

The numerical analysis based on incompressible smoothed particle hydrodynamics (ISPH) is introduced to examine the impacts of Cattaneo-Christov (Ca-Ch) heat flux and exothermic chemical reaction on thermosolutal convection of nano-enhanced phase change materials (NEPCM) in Bézier-annulus. The used annulus is formed between inner connected Bézier curves and outer connected spline-Bézier curves. The inner shape of connected Bézier curves is maintained at Th&Ch, left/right walls of spline-Bézier curves are kept at Tc&Cc and other walls are adiabatic. The governing equations, after being converted into non-dimensional form, have been solved by ISPH which is an accurate meshless algorithm the treatment of internal flows inside complex geometries. The simulations are executed for Frank-Kamenetskii number FK, Ca-Ch heat flux δC, buoyancy ratio parameter N, Soret-Dufour numbers SrDu, Rayleigh number Ra, and nanoparticle parameter φ on thermosolutal convection of a suspension fluid. From the numerical simulation values for the average Nusselt and Sherwood numbers (Nu¯, Sh¯) were obtained for some fluid flow scenarios. Then, based on those values an artificial neural network (ANN) model was developed to predict the values of Nu¯, and Sh¯ without the need to perform the ordinary simulations again for the new cases which is a high cost compared to ANN. From the obtained simulations, it was concluded that the ANN model is an accurate tool to be used to predict the needed values. Also, the Frank-Kamenetskii number significantly influences the enhancement process of the temperature distributions and velocity field as well as phase change material in Bézier-annulus.

Heat transfer optimization of uo2-mo fuel using genetic algorithms

Two genetic algorithm (GA) methods were applied to thermal finite element models to optimize the heat transfer efficacy of a UO2-Mo composite fuel pellet with typical pressurized water reactor fuel geometry. Mo additions to UO2 have been shown to increase the thermal conductivity, thus reducing centerline temperatures and temperature gradients. Previous studies evaluated uniformly dispersed Mo or continuous Mo internal geometries (e.g., fins, plates, discs) that were selected using engineering intuition. The current study uses two different implementations of the same GA to optimize Mo placement and minimize the fuel temperature with the only constraint being a maximum 10% Mo volume fraction. One approach superimposed Mo line elements onto the monolithic UO2 pellet model, and the other converted entire UO2 volume elements to Mo. The former method generated 1D heat transfer connections between nodes, whereas the latter method allowed for the formation of 3D structures. Features of the optimal fuel design produced by the GAs included dispersed Mo near the centerline that shifted the peak fuel temperature outward by 0.6 mm, Mo chains in the high-heat-flux region in the mid-to-outer radial zone, and a large continuous structure that spanned the full radius and height of the pellet and accounted for 87.7 % of the total Mo in the pellet. Analysis of this design indicates that the optimal Mo configuration is a balance between creating continuous heat transfer pathways and optimally dispersing Mo to minimize the heat transfer distance through UO2. This architecture ultimately produced an effective thermal conductivity of 11.3 W/m·K under the assumed boundary conditions. This result is higher than any previous values from the literature. Potential fabrication methods and challenges are discussed in addition to the implications on fuel performance.

Parameterisation and Prediction of Intra-canal Cochlear Structures

Accurate 3D models of the cochlea are useful tools for research in the relationship between the electrode array and nerve fibres. The internal geometry of the cochlear canal plays an important role in understanding and quantifying that relationship. Predicting the location and shapes of the geometry is done by measuring histologic sections and fitting equations that can be used to predict parameters that fully define the geometry. A parameter sensitivity analysis is employed to prove that the size and location of the spiral lamina are the characteristics that most influence current distribution along target nerve fibres. The proposed landmark prediction method more accurately predicts the location of the points defining the spiral lamina in the apical region of the cochlea than methods used in previous modelling attempts. Thus, this technique can be used to generate 2D geometries that can be expanded to 3D models when high-resolution imaging is not available.

Assessment of the energy performance of a solar/biomass hybrid system for the climatization of smalland medium-scale buildings

The H2020 EU-funded project Hybrid-BioVGE aims to develop an efficient system entirely based on solar energy and biomass for the climatization of buildings during both the heating and cooling seasons. The most innovative component of the concept is a solar-driven Variable Geometry Ejector (VGE) cooling cycle, which can adjust its internal geometry with two degrees of freedom, according to the effective operating conditions. This paper presents the components of the Hybrid-BioVGE concept and describes a demonstrator of the proposed solution installed in a single-family house in Porto (Portugal). The main characteristics of the building, the size and typology of thermal energy storages included in the system are presented as well. In order to demonstrate the energy-saving potential of the Hybrid-BioVGE concept, the numerical model of the demonstrator was implemented in the TRNSYS 18 environment. Outcomes of simulations include the system’s energy performance for both heating and cooling seasons, the achievable solar fraction and the VGE efficiency. Numerical results show that up to 98% of the system energy input derives from renewable sources, with a solar fraction of 61.5%, during the heating season. On the contrary, the seasonal performance factor in cooling operating mode is lower than expected. The VGE cooling cycle efficiency is mainly penalised by the heat rejection loop, which should be optimised to achieve the best performance.

Virtual Surgical Planning for Point-of-Care Manufacturing

Two factors motivating the achievement of safe and effective Point-of-Care Manufacturing (POCM) are (1) to provide personalized medical devices to patients with short treatment windows (e.g., trauma, advanced stage cancer) and (2) to ensure that those devices improve outcomes and reduce revision surgery rates. In-hospital use of Virtual Surgical Planning (VSP) now commonly includes the production of surgical models and procedure guides (e.g., cutting, drilling, or placement guides and tool jigs). As this technology becomes widely available, we envision the FDA approving VSP software with tools for personalized, implantable, medical device design and POCM. Indeed, VSP for local optimization of device shape (external surfaces and internal pore geometry), placement (anatomical location), materials (via interactive simulation of post-operative device performance), and the fabrication process engineering plan can be executed in real time. This is nothing short of a paradigm shift from manual personalization of off-the-shelf devices or the factory-based fabrication of personalized medical devices. As an example of this new paradigm, we present here a hypothetical VSP pathway for the design and POCM of personalized mandibular graft fixation devices where optimized performance avoids both stress shielding-induced bone loss as well as stress concentration-induced device failure.

Evaluation of low-loss alumina material for high-power RF windows

Conventional RF vacuum windows are made of metalized ceramics, hermetically brazed to a pillbox cavity. High-power windows, operating in ultra-high frequency (UHF) band, require the fabrication of ceramic disks with diameters on the order of 9”. Furthermore, a Titanium Nitride (TiN) multipactor suppression coating must be applied to the ceramic surfaces. The large size and complex internal geometry of these windows create challenges in validating the coating in the fully fabricated assembly. This study evaluates a novel low-loss alumina AO479U, provided by Kyocera, and a reactive sputtering process suitable to deposit a 10-20 nm thick TiN coating on a large diameter window. The paper will report the changes in the TiN coating through chemical cleaning and vacuum braze processes using stylus profilometry, optical microscopy, Scanning Electron Microscopy (SEM), and Rutherford Backscattering Spectroscopy (RBS).

Heat Transfer Analysis for Combustion under Low-Gradient Conditions in a Small-Scale Industrial Energy Systems

The issue of maintaining low-gradient combustion in the conditions of high heat extraction has been investigated numerically in this work. The analyses include the application of a convective boundary condition at the wall (with estimated boiling heat transfer coefficient); analysis of the Internal Recirculation Device’s impact on combustion products and heat transfer under low-gradient conditions; and comparison of both traditional and low-gradient combustion modes. It was shown that the Internal Recirculation Device material and geometry has a significant impact on the nitrogen oxide (NOx) formation mechanism, as NO2 emission becomes predominant and can rise up to several hundreds ppm. What is more, along with decrease in thermal resistance of the IRD, CO emissions also increase rapidly, even achieving over 2000 ppm. Additionally, the convective heat transfer rate decreased by about 25% after switching from traditional to low-gradient combustion, whereas the radiative mechanism increased by ≈40% compared to traditional mode. It should also be mentioned that the low-gradient combustion applied in this work achieved approximately 10% higher efficiency than conventional combustion.

3D Electrothermal Model for Internal Temperature Distribution in Lithium-Ion Battery Cell and Module

In recent years, lithium-ion batteries (LIBs) have been massively developed in many applications as they provide high energy and power densities, high efficiency and long lifespan compared to other battery technologies. Despite remarkable improvements, Li-ion batteries still face thermal issues, which cause performance drop, limited calendar life, safety concerns and temperature-caused degradation. Therefore, proper thermal management for a LIB is necessary to control its temperature and to extend its lifetime. Internal temperature measurement remains very challenging for LIB. So, electrothermal LIB models, developed to forecast both electrical performances and temperature distributions, seems to be a powerful and complementary tool to experiments, in particular to obtain battery temperatures in use. Most of models, assume simplified approach considering that heat sources are either located in the center of the cell or uniformly distributed in the volume of the cell and so do not consider the real internal geometry of the cells.In this work, a 3D electrothermal model of a large commercial prismatic NMC-type lithium-ion cell (25 Ah) is developed based on the internal geometry reconstructed from tomography. The electrothermal model, developed with the COMSOL Multiphysics® software with the real internal geometry as well as the anisotropy of the thermal properties, accounts for irreversible and reversible heat sources. The entropy variation profiles were estimated by Entroview™ using their patented method. The validation of the model is performed thank to temperature measurement during charge and discharge at several currents in a climatic chamber at 25°C. Simulation results highlight exothermal and endothermal behaviors related to the entropy change along with the charge and discharge stages. Moreover, the internal temperature distribution is thoroughly impacted by the internal geometry of the cell and the anisotropy of the thermal properties.Finally, the 3D electrothermal model is extended to a module of 12 cells in series (12S) to evaluate the heterogeneities of internal temperatures considering the real geometry of each cell. Once validated, simulation (as shown of figure 1) underline the heterogeneous temperature distribution at the module scale and the importance of having an efficient battery thermal management system to limit an excessive increase of the temperatures which can cause performance drops until irreversible degradations. Figure 1

Internal Flow Characteristics of Novel Turbine Performance Enhancement Method through Specific Fluid Injection

Gas turbine engines are an essential component for many industries, such as aerospace, marine propulsion, energy generation, etc., with modern engines capable of achieving high powers, efficiencies and reliability. However, these high performances are achieved on a narrow interval of working regimes; when operating at partial loads, a drastic decrease in performance is expected. In order to mitigate this drawback, a novel injection method has been proposed to improve axial turbine and gas turbine engine performance at these regimes. The method consists of the injection of a fluid in specific sections of turbine vanes to accelerate the flow, modify the velocity triangles and increase the generated power at partial loads. In this paper, the authors discuss the internal flow characteristics of the injection channels using numerical studies to determine the flow fields for different working regimes. The results show that the power generated by the rotor can be improved by 10% to 21% for different operating regimes without considering the internal geometries. The introduction of internal flow configurations led to smaller improvements in power generation, obtaining injection system pressure losses of between 10% and 20%. The paper concludes that the flow through channels is not uniform, with smaller dimensions of the internal geometries leading to higher pressures and an increased influence of the injection system.

Assessment of Microgap and Bacterial Leakage of Two Types of Internal Implant-Abutment Union.

The current research was done to assess microbial seepage of two types of internal implant-abutment connections. Twenty dental implants are categorized into two groups. Group A fixtures with an internal hexagonal geometry and group B fixtures with a tri-lobe internal connection. All implant-abutment assemblies underwent a three-week incubation period at 37°C in sterile tubes containing 5 mL of Staphylococcus aureus broth culture. Through the use of Gram stain and biochemical processes, the resultant colonies were recognized. The mean Log10 colony forming unit (CFU) in group A was 8.4 and in group B was 7.2. The variation between both groups was found to be considerable (P < 0.05). Microgap was more in group B compared to group A. Bacteria may infiltrate the small area between the implant and the abutment. Compared to dental implant fixtures with a tri-lobe internal connection, there was a noticeably higher Log10 CFU in dental implant fixtures with an internal hexagonal geometry.

Fluid Flow Analysis of Neonatal Dual-Lumen Cannulas for Venovenous Extracorporeal Membrane Oxygenation.

Hemolysis persists as a common and serious problem for neonatal patients on extracorporeal membrane oxygenation (ECMO). Since the cannula within the ECMO circuit is associated with hemolysis-inducing shear stresses, real-world internal fluid flow measurements are urgently needed to understand the mechanism and confirm computational estimates. This study appears to be the first experimental study of fluid flow inside commercial ECMO dual-lumen cannulas (DLCs) and first particle image velocimetry (PIV) visualization inside a complicated medical device. The internal geometries of four different opaque neonatal DLCs, both atrial and bicaval positioning geometries each sized 13 Fr and 16 Fr, were replicated by three-dimensional printing clear lumen scaled-up models, which were integrated in a circuit with appropriate ECMO flow parameters. PIV was then used to visualize two-dimensional fluid flow in a single cross section within the models. An empirical model accounting for shear stress and exposure time was used to compare the maximum expected level of hemolysis through each model. The maximum measured peak shear stress recorded was 16±2 Pa in the top arterial bicaval 13 Fr model. The atrial and 16 Fr cannula models never produced greater single-pass peak shear stress or hemolysis than the bicaval and 13 Fr models, respectively, and no difference was found in hemolysis at two different flow rates. After 5 days of flow, small DLC-induced hemolysis values for a single pass through each cannula were modeled to linearly accumulate and caused the most severe hemolysis in the bicaval 13 Fr DLC. Engineering and clinical solutions to improve cannula safety are proposed.

Architectural rift geometry of the Rio do Peixe Basin (Brazil): Implications for its tectonic evolution and Precambrian heritage

Preexisting shear zones in the basement may influence the formation of normal faults in rift environments. However, the specific role and interaction between these preexisting shear zones and younger rift faults in controlling the growth of normal faults remain an area of limited understanding. The Rio do Peixe Basin (RPB), located in Brazil, was the subject of a comprehensive study using integrated airborne magnetic analysis, 2D and 3D seismic interpretation, and 3D gravity modeling. This study investigated tectonic evolution and Precambrian heritage by examining the role of basement structures in controlling the internal geometry of the RPB. The integration of geophysical data supported by field data showed that the underlying basement structures significantly influence the geometry of the basin sedimentary fill. E–W-striking structures controlled the opening of the RPB and the development of the depocenters of the basin. NE–SW-striking structures influenced the segmentation of the depocenters and, consequently, the internal geometry of the basin. Furthermore, the study revealed the migration of depocenters toward the NE associated with developing the NE–SW-striking segment of the Portalegre Fault attributed to the basin-opening process. By investigating the underlying crustal architecture, this comprehensive geophysical study sheds light on the architectural rift geometry of the RPB. The findings underscore the influence of basement structures on the internal basin architecture and provide valuable insights into its tectonic evolution and Precambrian heritage.

Fundamentals of low-cost aerosol sensor design and operation.

Most evaluations of low-cost aerosol sensors have focused on their measurement bias compared to regulatory monitors. Few evaluations have applied fundamental principles of aerosol science to increase our understanding of how such sensors work and could be improved. We examined the Plantower PMS5003 sensor's internal geometry, laser properties, photodiode responses, microprocessor output, flow rates, and response to mono- and poly-disperse aerosols. We developed a physics-based model of particle light scattering within the sensor, which we used to predict counting and sizing efficiency for 0.30 to 10 μm particles. We found that the PMS5003 counts single particle scattering events, acting like an imperfect optical particle counter, rather than a nephelometer. As particle flow is not focused into the core of the laser beam, >99% of particles that flow through the PMS5003 miss the laser, and those that intercept the laser usually miss the focal point and are subsequently undersized, resulting in erroneous size distribution data. Our model predictions of PMS5003 response to varying particle diameters, aerosol compositions, and relative humidity were consistent with laboratory data. Computational fluid dynamics simulations of the PurpleAir monitor housing showed that for wind-speeds less than 3 m s-1, fine and coarse particles were representatively aspired to the PMS5003 inlet. Our measurements and models explain why the PurpleAir overstates regulatory PM2.5 in some locations but not others; why the PurpleAir PM10 is unresponsive to windblown dust; and why it reports a similar particle size distribution for coarse particles as it does for smoke and ambient background aerosol.

Helical Electrodes for Electro-Discharge Drilling: Experimental and CFD-Based Analysis of the Influence of Internal and External Flushing Geometries on the Process Characteristics

The electro-discharge (ED) drilling of precision boreholes in difficult-to-machine materials, particularly with respect to the cost-effectiveness of the overall process, is still a challenge. Flushing is one key factor for the precise machining of boreholes, especially with high aspect ratios. Therefore, the influence of internal and external flushing geometries for six types of brass tool electrodes with a diameter of 3 mm with and without a helical groove was analyzed experimentally and numerically. Using this helical external flushing channel, drilling experiments in X170CrVMo18-3-1 (Elmax Superclean) with an aspect ratio of five revealed a material removal rate (MRR) that was increased by 112% compared with a rod electrode, increased by 28% for a single-channel tool electrode and decreased by 8% for a multi-channel tool electrode. Signal analyses complemented these findings and highlighted correlations between classified discharge event types and the experimental target parameters. Amongst others, it was verified that the arcing frequency ratio drove the electrode wear rate and the beneficial frequency ratio correlated with the MRR and the surface roughness Ra. Sophisticated 3D computational fluid dynamics (CFD) models of the liquid phase were introduced and evaluated in great detail to demonstrate the validity and further elucidate the effect of the external flushing channel on the evacuation capability of debris and gas bubbles. The presented methods and models were found to be suitable for obtaining in-depth knowledge about the flushing conditions in the ED drilling working gap.

Extension of a shell‐like RVE model to represent transverse shear effects in textile reinforced composites

AbstractTextile reinforcements have long been used in shell‐like components like tires, belts, hoses and, in particular, air spring bellows. These bellows consist of a certain number of cords embedded in soft rubber, resulting in high membrane stiffness to absorb tensile forces and low resistance to changes in curvature. The embedded cords are produced by twisting multifilament yarns. Modelling and simulation of bellows is a challenging task. Thereby, the complex internal geometry, large deformations as well as the strongly anisotropic and nonlinear material behavior have to be taken into account in a computationally efficient manner. One approach is the application of multiscale analyses in conjunction with representative volume elements (RVE). Within this study, a through‐thickness RVE based on in‐plane periodic microstructures is applied. The local behavior of the cords is represented by an anisotropic constitutive model that regards directions and mechanical properties of filaments, which result from previous cord twisting simulations. In this contribution, an extension of the classical periodic boundary conditions (PBC) is presented, which considers curvature, pressure load, and, in particular, transverse shear. The RVE is used to simulate the stresses and strains in cord‐rubber composites under realistic load conditions. Moreover, it is employed for homogenizing the mechanical behavior and, thus, for developing a suitable constitutive model for shells.