Numerical Modeling Techniques Research Articles

Distinct element modeling of the in-plane and out-of-plane response of ordinary and innovative masonry infill walls

Masonry infill walls (MIWs) are essential partition components that are often damaged during earthquakes because of their brittle nature. As a result, innovative solutions are attractive to improve performance of MIWs by reducing damage during in-plane drift or increasing damping. Examples of innovative solutions have been investigated experimentally, but mesoscale or microscale numerical modelling techniques could also be useful to evaluate performance and investigate the principal failure mechanisms of both ordinary and innovative MIWs, and subsequently optimize their design. This paper employs the Distinct Element Method (DEM) to predict the in-plane (IP) and out-of-plane (OOP) response of ordinary and innovative MIWs within RC frames. The DEM methodology used in this study account for the crushing of concrete and masonry, the shear-compression behavior of mortar and the shear behavior of a novel damping layer joint (DLJ) inserted in the MIW (named damped masonry infilled wall (DMIW)). DEM results are compared against experimental results for both MIWs and DMIWs. Two IP and four OOP experimental tests were simulated in total. The DEM simulation methodology is capable of predicting the IP and OOP load–displacement response as well as the damage patterns of the ordinary MIWs and DMIWs, although the local displacement mechanism at the DLJ locations of the DMIW varied for the OOP tests. Local stress distribution differences, as well as modeling modifications for simulating the damage pattern of DMIWs, are further discussed. Overall, the effectiveness of the DEM simulation provides confidence that it could be used to improve upon the DMIW design in the simulation environment.

Experimental and Numerical Studies on Dynamic Response of Parallel Wire Cables Subjected to Close-In Explosions

The recent trend of increasing global terrorist attacks and identified vulnerabilities associated with critical bridges highlights the necessity to protect cable-stayed bridges from terrorist assaults. The cables are the most crucial load-carrying components within the envelope of a cable-stayed bridge, whose failure could result in the progressive collapse of the whole bridge structure with disastrous consequences. However, there is a very limited understanding of the blast effects on cables. This paper presents an experimental and numerical investigation of the blast performance of parallel wire cables under close-in explosions. Field blast tests were conducted on three identical parallel wire cable specimens with varying explosive charge weights. An equivalent beam–shell model was developed in LS-DYNA to reproduce the dynamic response of parallel wire cables subjected to close-in explosions and was comprehensively validated against the experimental results. With the validated numerical modeling techniques, the dynamic behavior of parallel wire cables in a realistic blast scenario of vehicle-borne improvise explosive devices (VBIEDs) detonated on the bridge deck was investigated. The results showed that high bending stress was induced in the cable end near the deck, indicating that the cable-to-girder anchorage zone is the most vulnerable position under the close-in blast scenario. Parametric analyses were carried out to further investigate the effects of cable dimension, prestressing force, cable length, and anchorage angle on the dynamic response of the parallel wire cables. It was found that the cables with smaller dimensions and higher prestressing force are more vulnerable, while the cable length and anchorage angle have limited effects on the performance. The results could be used in the safety evaluation and preliminary protective design of cable-stayed bridges under potential blast threats.

Seismic fragility functions for RC As-built and eccentric steel brace frames

Quasi-static cyclic loading tests were performed on single-story reduced-scale reinforced concrete as-built (un-retrofitted) and eccentrically steel braced (retrofitted) frames. The frames damage mechanism, force–displacement hysteretic response and capacity backbone envelopes were studied and a damage scale was developed. A simplified numerical modeling technique was proposed in the finite element-based package SeismoStruct and the model was evaluated, calibrated and validated with the test data. The proposed modeling technique was employed further to perform incremental dynamic time history analysis on two-story as-built and eccentric steel braced frames. Fragility functions for the frames in terms of immediate occupancy, life safety and collapse prevention were developed using a probabilistic-based methodology. The as-built frame was more fragile in terms of immediate occupancy, life safety and collapse prevention damage states as opposed to the retrofitted frame.

METHODS AND TECHNIQUES COMBINATION WORKING BODIES OF COMPLEX SOIL PROCESSING MACHINES

The article establishes that the combination of working bodies in tillage machines can be optimized with the help of mathematical models and algorithms. These expressions provide valuable information about the performance of tillage machines and can be used to improve their efficiency and productivity. Using mathematical models and algorithms, engineers and inventors can optimize the design of tillage machines and improve their performance, leading to improved quality in field operations. In addition, the combination of working organs in tillage machines can also be analyzed using numerical simulation methods. These methods use mathematical models and algorithms to simulate the behavior of tillage machines in a virtual environment. Numerical modeling techniques provide valuable information about the behavior of tillage machines and their components, allowing engineers and designers to optimize their design and increase productivity. Using numerical simulation techniques, engineers and designers can verify the mathematical models and algorithms used in the analysis of tillage machines and improve their accuracy and reliability. Thus, the combination of working bodies in tillage machines can be analyzed and optimized with the help of mathematical models, algorithms and numerical modeling methods. These methods provide valuable information about the performance of tillage machines and can be used to improve their efficiency and productivity. Using these methods, engineers and designers can optimize the design of tillage machines and improve their performance, leading to increased efficiency and productivity in field operations. In addition, numerical modeling techniques can also be used to analyze the environmental impact of tillage. For example, modeling can be done to determine the impact of tillage on soil erosion and greenhouse gas emissions. By analyzing the results of this simulation, engineers and designers can improve the sustainability of tillage operations and reduce their environmental impact.

Tropical cyclone risk assessment of Port Blair, Andaman Islands, India by using numerical modelling and geospatial techniques

Tropical cyclone risk assessment of Port Blair, Andaman Islands, India by using numerical modelling and geospatial techniques

An integrated approach to evaluate mechanical performance of date palm filler reinforced polypropylene

In this study, the mechanical properties of newly developed bio-composites comprising both untreated and chemically treated date palm agro-residue fillers and polypropylene matrix are experimentally evaluated. Then, the experimental results are integrated into a numerical technique using a spring network model to estimate the tensile properties of the date palm filler in a powder form. Indeed, experimentally measuring these properties is a tedious task and time consuming. Besides, the spring network is employed to predict the effective mechanical properties of the bio-composite and simulate progression of fracture including crack onset and evolution in a two-dimensional model of the material. Next, the elastic modulus and strength as obtained numerically are fed into proper analytical models after adjusting relevant input parameters to calculate both stiffness and strength of the bio-composites. The best analytical models along with their adjusted empirical constants that closely fit the experimental outputs are identified. Both numerical and analytical modeling techniques exhibited excellent agreement with the experimental counterparts and as such could act as efficient tools in producing natural fiber polymeric composites with tailored mechanical properties. Besides, the derived bio-composites serve as eco-friendly, renewable, economically competitive material that can be used to design a broad range of products in industries including, construction, automotive, sport and others.

Design and development of high-speed rotating impeller for turbo-molecular pump through topology optimization

Additive Manufacturing (AM) process has potential to manufacture complex structures to cater the design requirement and process requirement for any specific application. However, this process is expensive as compared to the traditional and on-going advanced manufacturing process. The cost of AM process depends on volume/mass and size of the parts, and due to this, the AM manufactured part needs to be topologically optimised before manufacturing. In view of this, the manufacturer has to ensure the functionality and acceptability of design parameters about the computer aided design (CAD) model through a reliable numerical modelling technique for the topology optimisation (TO). Moreover, the CAD model also needs to be compatible for ease of manufacturing by AM process which is possible by post analysis and CAD modification. In the present paper, TO was implemented for a high-speed rotating impeller of a turbo-molecular pump (TMP) followed by manufacturing to achieve better performance.

Numerical Modeling Technique of Damage Behavior of MaSonry-Infilled RC Frames

The damage pattern of masonry-infilled reinforced concrete (RC) frame structures in earthquake events is complicated, and understanding the detailed failure behavior of these structures and modeling it accurately has been a challenging task. In this paper, the extended finite element method (XFEM) is introduced to reproduce arbitrary cracks initiating and propagating in concrete frame and masonry units, combined with interface elements to model various behaviors of masonry-infilled RC frames. Within the finite element analysis program FEAP, a user element subroutine is adopted for the incorporation of XFEM and two types of extended finite elements with and without crack tip enrichments are built to simulate the behavior of concrete material for frame members and masonry blocks for the infill panel, respectively. In addition, a macro command is created to check the crack-propagation criterion and update crack and enrichment information. Furthermore, numerical examples are performed with existing test data, which reveal the efficiency of the implementation procedure. A comparison of the analytical and experimental results show that the proposed modeling can be used to predict the crack and failure process and the load-bearing capacity curves of the structures and reflect accurately the interaction of masonry infill and RC frames.

Comparing a single pile's axial bearing capacity using numerical modeling and analytical techniques

It has become crucial to study the different pile types in terms of their performance and bearing capacity due to the growing use of different types of piles throughout numerous construction projects. The bearing capacity of piles has been determined for this purpose using various analytical, numerical (finite element and finite difference), and field approaches. To determine pile-bearing capacity, geotechnical engineers and accountants prefer to utilise analytical pile design methods, which take into consideration a variety of methodologies and the soil conditions for each method (such as adhesion, internal friction angle, etc.) Design decisions are made depending on the opinions that are expressed. By comparing the analytical and software results using Plaxis 2D software, using the design results of more than 30 heaps, and analysing prior studies, we attempted to gauge the validity of each of these approaches in this study. For the analyzed piles, the greatest relative error between the theoretical technique and the numerical approach utilised in this study was around 14%; however, this error can be greatly decreased by modifying the meshing and making it finer since the method answers the method. Based on the findings, it was concluded that accurate calculations of the bearing capacity of piles could be made using numerical models and appropriate behavior models for the soil and piles. Therefore, it is somewhat true, rational, and appropriate that numerical models can prevent costly loading tests on piles.

Development of the simplified spring‐based nonlinear models for full‐connection cold‐formed steel‐framed gypsum partition walls

AbstractThe role of nonstructural components in performance‐based earthquake engineering is undeniable because of their significant contribution to the total investments in buildings. Gypsum partition walls are one of the main sources of seismic damage among other nonstructural components. As a result, researchers developed various detailed numerical modeling techniques for simulating the seismic performance of these walls. Although detailed characteristics of the walls are considered in these models by means of different nonlinear elements, these micro‐models are not appropriate to be incorporated into their parent building models due to their extensive computational cost. Therefore, this study proposes a simplified spring‐based modeling technique to facilitate the simulation of gypsum partition walls in macro building models. For this purpose, the hysteresis behavior of full‐connection gypsum partition walls is modeled using a nonlinear springs element with a parametric material model designated in the “” platform as the “” constitutive model. The proposed spring‐based models are then validated through the hysteresis behavior of the micro‐finite element models available in the literature. These spring models are developed to consider several construction and geometric variations such as the stud/track thickness, the distance from the center of screws to the edge of the gypsum board, the distance from the center of screws to the edge of the stud/track flanges, construction quality, and the aspect ratio of the walls. Results from this study prove that the proposed technique shows a promising accuracy besides its simplicity and effective computational cost.

Numerical modelling technique for rock mass in underground coal mine by using grain-based model

The stability of rock mass around longwall or excavation in underground coal mine is a prerequisite for the safe and continuous coal production. In practice, instability incidents commonly occur at longwall face or longwall roof that causes serious occupational injury or even death. Current research on the instability has not sufficiently interpreted the formation and propagation of rock mass failure, mostly due to the discontinuous, anisotropic, inhomogeneous and non-elastic nature of rock mass. To assist interpretation of the above stability behaviour, this paper presents a study to improve the numerical modelling technique of rock mass around longwall by using Grain-Based Model. The modelling technique uses Discrete Element Methods and the grain structure Voronoi. A procedure for calibrating rock properties in modelling technique is proposed and validated through application for field rock mass at Ha Lam coal mine, Quang Ninh province, Vietnam. The paper also presents a technique for selecting grain size and monitoring the modelling efficiently. The proposed procedure along with the modelling code are useful for investigation of rock mass around underground excavations from which technical solutions for safe and continuous production can be established.

Effect of carbon fiber reinforcement on dimensional variations of 3D printed polyamide-6 composites: A simulation study.

Due to material design and fabrication flexibility, additive manufacturing (AM) or 3D printing (3DP) processes and polymer composites have paved their way into several industrial sectors. The quality of 3D printed polymer composites is highly dependent on the reinforcement content of polymers and 3DP process parameters. Several experimental studies are performed to optimize the reinforcement contents and process parameters; however, exploring the numerical modeling and simulation techniques is vital to lower the research and development costs. In the study, the numerical simulations for the 3DP process were performed using Digimat® software for carbon fiber-reinforced polyamide-6 (PA6) composites fabricated via the fused filament fabrication (FFF) process to evaluate the effect of reinforcement content on deflections, warpages, and process-induced residual stresses. The FFF process simulations were performed to fabricate tensile testing coupons with pure PA6 and 10%-28% CF-reinforced PA6 composites. A significant impact of CF-reinforcement was observed on the deflections, warpages, and residual stresses. The maximum displacement of 4.518 mm and critical warpage of 3.012 was observed for pure PA6 material. However, with the addition of CF reinforcement, a maximum deflection of 3.369 mm and critical warpage of 2.246 was achieved for PA6 reinforced with 28% CF (PA6-CF28). The improved 3D printed specimen quality was acquired at the cost of increased residual stresses of 14.53 MPa compared to 11.75 MPa in pure PA6 specimen. The CF reinforcement significantly improved the 3DP manufacturing performance of PA6/CF composites, reducing deflections and warpages.

Self-heating of viscous dampers under short- & long-duration loads: Experimental observations and numerical simulations

Similar to other energy dissipating devices, fluid viscous damper converts its input kinetic energy to heat which in turn results in temperature rise of the device. Damper self-heating may result in excessive internal pressure due to the thermal expansion of the internal fluid. Moreover, the elevated temperature might have a detrimental effect on the sealing system of the damper. In this study, two full-scale viscous dampers are tested under short- and long-duration loading protocols. A thermal camera is used to monitor temperature rise during different loads. Based on the tests of this study, the temperature rise of the considered dampers can be neglected in the case of short-duration seismic loads, but the self-heating can be significant during long-duration loading. A numerical modeling technique is also proposed by which thermal behavior of fluid viscous dampers can be thoroughly examined. Numerical simulations are able to estimate temperature of internal and external components of the damper considering different heat transfer mechanisms. Validity of the numerical results are investigated by comparing them to the results from thermal camera. Finally, energy-temperature curves are developed to estimate thermal behavior of viscous dampers during short- and long-duration loads.

Experimental validation of numerical model for thermomechanical performance of material extrusion additive manufacturing process: Effect of infill design & density

The optimum selection of process parameters, materials, and product design is essential to achieve the desired response of 3D-printed structures, especially in functional components. The current practices of the experimental optimization process require significant resources, which can be limited through numerical modeling and simulation techniques. In this study, a thermomechanical numerical model is used to predict the performance of the additive manufacturing (AM) process, i.e., fused filament fabrication (FFF). 3D printing (3DP) process simulations were performed for tensile testing coupons using carbon fiber-reinforced polyamide-6 (PA6-CF) material. The numerical model predicted the effect of infill patterns and densities on the deflections and distortions during the FFF process. The numerical model predictions were validated via experiments performed under similar conditions. The results conclude that the numerical model can adequately predict the process-induced deflections and distortions during the FFF process. Generally, higher dimensional control was observed for rectangular infill patterns and increased infill density. However, the numerical model overestimates the shrinkage as the stress-relaxation effect is not considered in the numerical model and underestimates the warpages as perfect build plate adhesion is assumed.

Low coercivity magnetoplasmonic crystal based on a thin permalloy film for magnetic field sensing applications

This research is devoted to the fabrication of 5-nm thick permalloy film-based magnetoplasmonic crystal for magnetic field sensing applications. Optical and magneto-optical activity of the magnetoplasmonic crystal is studied with the means of numerical modeling and spectroscopy techniques. The studied sample achieves sensitivity to an external DC magnetic field of 7.5 mOe in the 5.1 Oe required modulation AC magnetic field. Obtained experimental and modeling results can be used for the fabrication of cheaper and more energy-efficient sensing elements for magnetoplasmonic crystal-based magnetic field sensors due to the reduction of required ferromagnetic material and modulation magnetic field.

On the influence of time-dependent behaviour of elastomeric wave energy harvesting membranes using experimental and numerical modelling techniques

The transient response of elastomeric polymers is dependent on polymer composition, temperature and the loading history. In particular, hysteresis, dissipation and creep are significant in the choice of material for elastomer membrane wave energy converters. Natural rubber is a good candidate when looking for material for a wave energy harvester since it has an excellent stretchability, is almost resistant to the environment in which the harvester will be used and has good fatigue properties. The mechanical behaviour of the natural rubber used in this work has been deeply characterised: the material resulted to have a very little hysteretical behaviour (that is a very low energy dissipation during stretching) but also to show a strain-dependency, stress softening, and relaxation at constant stretch. Low dissipation represents the best case scenario for energy harvesting; in reality reinforcement of the material is required which adds to the dissipative behaviour. Afterwards, an extended finite strain viscoelastic constitutive model is proposed that is calibrated analytically to the experimental data to identify the relevant material parameters resulting in non-linear viscosity functions in the evolution equations of the constitutive model. The model was able to capture the minimal dissipation behaviour with good degrees of accuracy. Results are shown for a flexible membrane wave energy converter under creep and cyclic loading. A parametric study is made comparing the experimentally characterised polymer with different amounts of viscous dissipation. The response of the wave energy converter shows that even minimal amounts of dissipation manifests itself into changes in the pressure–volume function and reduction in energy capture through hysteresis. The new material model shows, for the first time, that the control of internal pressure in wave energy membranes must take into account transient material effects.

Numerical Simulation of Photoacoustic Effect in One-Dimensional Carbon Nanostructures

The paper describes methods for theoretical and numerical simulation of the photoacoustic effect that occurs in one-dimensional carbon micro- and nanostructures under an action of pulsed laser radiation. The proposed numerical modeling technique is based on solving the equations of motion of continuous media in the Lagrange form for spatially inhomogeneous media. This model makes it possible to calculate fields of temperature, pressure, density, and velocity of the medium depending on the parameters of laser pulses and characteristics of micro- and nanostructures.

Numerical investigations to assess ground subsidence and fault reactivation during underground coal gasification

Abstract. This paper aims to assess potential environmental impacts associated with commercial-scale application of in situ coal conversion in a target area in Hungary. The site is an environmentally protected forested area. Parametric numerical modelling techniques were employed using a discrete element method (DEM) to evaluate the surface subsidence and fault activation during mining processes. The Mohr–Coulomb elastic–plastic material model adopted to simulate rock formations. Zero-thickness interfaces with friction and cohesive characteristics were employed to simulate geological faults. A sensitivity study on rock formations and fault properties was conducted to address the importance of geological parameters that have an impact on surface subsidence as well as fault activation, which could in turn result in pollutant migration from the deep coal seams to the surface. The analysis of the results demonstrated that surface subsidence is affected by the average Young's modulus of the geological strata, whereby the activation of the faults is influenced by the friction angle between faults. Also, it was found that shallower seams are more likely to produce surface subsidence; i.e. as excavation depth increases, the surface subsidence decreases. Finally, computational outputs from this work were used to develop the web-based and interactive Environmental Hazards and Risk Management Toolkit (EHRM) for planning and decision-making processes during in situ coal conversion.

Field measurement and simplified numerical model for vibration response of subway superstructure

The residents near subway lines may be influenced by subway-induced vibration to a large extent. A simplified numerical modelling technique of the subway superstructure with a high-precision Caughey damping was proposed based on finite element software ANSYS in this paper, aiming to simulate the above-ground vibration response related to residents’ comfort under subway operation. Firstly, the two-stage field measurement of “free field-floor slabs of superstructure”, spanning four years, was carried out on a frame structure building above Guangzhou Metro Line 3. The time domain and frequency domain data of the measured vibration were analysed. A simplified numerical finite element (FE) model of the superstructure was then established, in which a high-precision Caughey damping was constructed using seven control frequencies. The comparative analysis of the simulated and measured results of the building verified that the simplified FE model for simulating the subway superstructure’s vibration response worked well and facilitated engineering applications. Additionally, another superstructure model of the shear wall was established by the same method to explore further the difference in the propagation characteristics of subway-induced vibration in the structure of two different forms. Finally, design recommendations for vibration control of subway superstructure were provided.

Optical Imaging and Analytical Design of Localized Topological Structures in Chiral Liquid Crystals

We combine numerical modeling and analytical design techniques to study several of the most common localized topological structures in frustrated chiral nematic liquid crystal cells. An energy minimization procedure is applied to the lattice model to simulate the director field distributions. These distributions are also approximated using the suitably designed analytical ansatz. We present both simulated and approximated results for optical polarizing microscopy textures and different visualizations of director field structure such as distributions of the azimuthal director angle and isolines for the normal component of the director in coordinate planes. The ansatz correctly mimicked the geometry and optical properties of the solitonic structures under consideration.