Simulation Methods Research Articles

Experimental and numerical research on deformation of square plates with circular holes under blast load

The response and failure of plates under blast loads are critical concerns in engineering. Plates with preformed holes may exhibit significantly different behaviors compared to those without holes, and detailed research on this topic remains limited. In this study, the deformation of square plates with circular holes subjected to blast loads was investigated through experiment and simulation methods. Square plates with circular holes were designed with three hole positions and two hole diameters. Far-field explosion experiments measured the displacement fields of the plates and the overpressure on the plate frame. Subsequently, LS-Dyna simulation models were established using a two-dimensional model to three-dimensional model mapping, with numerical results aligning with experimental results. Additional numerical calculations with larger charge mass supplemented the experimental cases, analyzing the influence of holes on plate response. It was found that the presence of a hole influenced the displacement field, with notable local effects such as significantly increased displacement near the hole. The presence of a hole can shift the position of maximum equivalent plastic strain from the plate edge to the hole edge. The influence of the size and position of a hole on the deformation and equivalent plastic strain were discussed.

Simulation Model of One-Parameter Selective Assembly of Two Elements With Multivariate Set-Making

Analytical and simulation methods are used to model assembly processes and technological systems in order to determine and optimize their performance and functioning parameters. The first one, describes an object or process using mathematical relationships indirectly. Simulation modelling is one of the modern methods of production system experimental research, allowing to take the presence of various components in the system, nonlinear characteristics, non-determinism and dynamism of ongoing processes into account. This work is devoted to the simulation model development of the technological process of multivariate one-parameter selective assembly of two elements. Multivariate set-making is defined by generalized rules with a set of weights which elements are set the distribution of elements between sets of different types. Selectively assembled elements have parameters determined by the manufacturing stage, which are independent random variables with known probabilistic characteristics. It is assumed that the input-output relationship is linear with given coefficients, the set-making equations linking the numbers of selective groups and assembly sets are known. A simulation model of the assembly process was built in the GPSS World, which, in contrast to the known one, operates with multivariate set-making rules for the case of assembly of two elements. The model allows to determine the quantitative indicators of the assembly process, in particular, the probabilities of assembly set formation, work-in-progress and preliminary rejects. As an example, the process of multivariate set-making of two parts forming a precision engineering product is considered. The data of parts distributions of both types by selective groups before assembly are given, the technological process indicators are calculated. Based on the modelling results the advantages and disadvantages of the multivariate set-making process are outlined.

Study on the influence of slope morphology on seismic dynamic response based on numerical simulation

Geological disasters frequently occur in our country. Multiple earthquakes have caused landslides on slopes, resulting in serious casualties and property losses. Therefore, it is particularly important to study the dynamic response and instability mechanism of slopes under earthquakes of different frequencies. This paper uses numerical simulation methods to establish a slope model, loads sine waves of different frequencies and amplitudes, collects acceleration and displacement dynamic responses of different profiles, and studies the distribution law of slope acceleration and displacement under dynamic action. Finally, the phenomenon of acceleration amplification effect is discovered. The research results of this paper can provide a basis for slope disaster prevention and mitigation and seismic reinforcement measures.

Optimization Study on Nozzle Selection Based on the Influence of Nozzle Parameters on Jet Flow Field Structure

Currently, the primary method for controlling red tides in the ocean involves spraying water solutions with special chemicals as solutes. High-pressure spraying results in the formation of typical jet structures. In this study, numerical simulation methods are employed to investigate the velocity variations, turbulent characteristics, and gas content distribution of jet flow fields under different initial jet flow pressures, cone angles, and nozzle diameters. Based on practical application scenarios, cluster analysis is used to explore the similarities and differences in jet equivalent diameters under different parameter conditions. The research findings indicate the following. (1) The difference of jet velocity distribution at the far field exit will be enlarged with the increase in the nozzle cone angle. When the nozzle cone angle is 4 mm, the velocity uniformity at the outlet is the best. (2) The TKE of the flow field has no consistent change law along the central axis. At the jet exit, the TKE shows an obvious multi-peak structure. (3) The gas content demonstrates a typical “double-valley” feature at the jet outlet cross-section. Increasing the initial pressure leads to a decrease in the gas content within the jet due to reduced entrainment, while the entrainment range remains largely constant. (4) Cluster analysis reveals that the similarity of jet flow width when it reaches the water surface is minimal compared to other operating conditions when the initial pressure is 0.36 MPa, the cone angle is 115°, and the nozzle diameter is 2 mm. All conditions can be categorized into two or three groups to ensure jet effectiveness. The study results provide scientific guidance for selecting spray devices for controlling red tides in the ocean.

A molecular dynamics investigation of nano-twins and nano-precipitates effects in CoCrFeNi-based high-entropy alloys

Abstract This study systematically investigates the effects of twin boundaries and precipitates on the performance of CoCrFeNi HEAs matrix using molecular dynamics simulation methods. By constructing corresponding HEAs models and conducting simulations of their structural evolution and mechanical behavior at the nanoscale, the influence mechanisms of nanotwins (NTs) and nano-precipitates (NPs) on the mechanical properties of the material were explored through in-depth analysis of simulation results. The findings suggest that twin boundaries effectively impede the movement and slip of dislocations and stacking faults in the material. As a result, this enhances its mechanical properties and inhibits plastic deformation, ultimately improving its ductility. Meanwhile, precipitates also impact the material's performance, and the shape of precipitates may exert different effects on the material, while the phase interface between precipitates and the matrix can hinder the expansion of defects. The presence of twin boundaries can enhance the strengthening effect of precipitates, further improving the material's performance. This study provides a new perspective for understanding the relationship between the microstructure and mechanical properties of HEAs materials, offering important references for the design and optimization of HEAs materials.

A Review of the Degradation Research on the Single-Lap Bolted Joint

Bolted joints, with their advantages of simple structure and convenient disassembly and assembly, are widely used in complex equipment fields such as aerospace systems and weaponry. Subject to complex mechanical loads, the contact surfaces may undergo nonlinear behaviors such as contact–separation and viscous slip, leading to the nonlinear degradation of the connection stiffness, which severely threatens the safety and reliability. These have driven research on bolted joints to span multiple disciplines, from interfacial micro-friction to macro-structural dynamics. Therefore, from the field of micro-friction to macro-dynamics, this review summarizes and analyzes three major degradation models, outlines the experimental development in connected structures, and provides an overview of the numerical analysis methods for degradation simulation. This paper also looks forward to the development directions for future research on the degradation of connected structures.

Improving parameters for achieving uniform cylindrical cup wall thickness in two-step deep drawing processes with SPCC sheet material

Deep drawing processes are essential in modern manufacturing for creating intricate components with deep hollows, particularly cylindrical forms. These processes are widely used in industries such as household appliances, automotive manufacturing, aerospace engineering, and fire safety equipment. This study focuses on the two-step deep drawing of cylindrical cups, utilizing both simulation and experimental methods. The primary goal is to determine optimal geometric and technological parameters for mold design and to address issues like wrinkling and tearing. Key parameters, including punch nose radius (Rpf), die nose radius (Rdf), punch-die clearance (Wf), and blank holder force (BHF), are systematically analyzed. Results show that proper parameters lead to a uniform wall thickness, with deviations reduced to 4.77%. Conversely, improper parameters result in a 12.03% deviation. Improved parameters in the second-step deep drawing yield cylindrical cups that closely match experimental outcomes, free from wrinkling or rim cracking. This research highlights the importance of selecting appropriate parameters to avoid defects.

Investigation of Residual Strength in CFRP Double-Adhesive Single Lap Bonded Joints after Low-velocity Impact

ABSTRACT Single lap adhesive joints are prone to debonding and delamination during impact, affecting the residual tensile strength and mechanical properties. To improve the stress distribution and withstand larger loads, this paper proposes to use Araldite 2015 ductile adhesive at both ends of the joint and AV 138 brittle adhesive in the middle. Through finite element analysis and experiments, the residual strength and damage of the joint under different impact conditions are investigated, and a three-parameter Gram-Charlier model is established. The results show that the model can fit the data points accurately with a coefficient of determination of error above 0.99. As impact energy increases, the residual strength of the joint decreases, especially the AV 138 joint is more sensitive. The residual strength on one side of the impact joint is approximately 20% higher compared to the middle of the impact joint. For the same energy, the residual strength of the secondary impact was about 13% higher than that of the single impact. The main failure mode is cohesive failure, which gradually changes to fiber tear. The numerical simulation matches the experimental results, which verifies the reliability of the simulation and analysis methods.

Prediction of optical properties of uniaxial hyperbolic nanospheres via artificial neural network

In this study, absorption and scattering multilayer perceptron models are developed and validated to predict the optical spectra of uniaxial hyperbolic nanospheres. The finite difference time domain method is used to generate the dataset of the absorption and scattering optical spectra. The models’ optimal performance is achieved for 5 hidden layers and 80 neurons for the absorption and the same hidden layers with 120 neurons for the scattering. The predictions by the model on the test dataset give a low average mean squared error of 0.000145 for the absorption and 0.00071 for the scattering. We also performed a robustness test by using parameters outside the initial parameters used for the training and the predictions are in good agreement with the actual datasets for both absorption and scattering. This research shows the application of artificial neural networks to predict the optical properties of hyperbolic materials and lays the groundwork for developing more complicated neural network models to predict complex phenomena in hyperbolic metamaterials, which are faster and computationally less expensive than using conventional simulation methods. Hyperbolic metamaterials offer unique optical properties that can be used to design new optical devices.

On the Control of Directionality of Myosin.

The origin of the unique directionality of myosin has been a problem of fundamental and practical importance. This work establishes in a conclusive way that the directionality is controlled by tuning the barrier for the rate-determining step, namely, the ADP release step. This conclusion is based on exploring the molecular origin behind the reverse directionality of myosins V and VI and the determination of the origin of the change in the barriers of the ADP release for the forward and backward motions. Our investigation is performed by combining different simulation methods such as steer molecular dynamics (SMD), umbrella sampling, renormalization method, and automated path searching method. It is found that in the case of myosin V, the ADP release from the postrigor (trailing head) state overcomes a lower barrier than the prepowerstroke (leading head) state, which is also evident from experimental observation. In the case of myosin VI, we noticed a different trend when compared to myosin V. Since the directionality of myosins V and VI follows a reverse trend, we conclude that such differences in the directionality are controlled by the free energy barrier for the ADP release. Overall, the proof that the directionality of myosin is determined by the activation barrier of the rate-determining step in the cycle, rather than by some unspecified dynamical effects, has general importance.

Investigating the performance of water-mounted solar photo-voltaic systems using different simulation tools

Water-mounted solar photovoltaics plants, which include canal-top and floating systems, offer several advantages over traditional ground mounted systems. However, studying their feasibility can be challenging due to limitations in commercial simulation tools. These tools often rely on unrealistic parameters, and studies comparing them have concluded that they may not be suitable for simulating these newer systems. This research addresses the above-mentioned gap by developing improved simulation methods for water–mounted solar plants. The study compared the actual performance of a 1 MW canal-top system and a 732 kW floating system in India with simulations from six different commercial tools. The analysis revealed that PVsyst and SolarGIS were the most accurate in predicting performance for the canal-top system, while PVsol and SolarGIS–Prospect performed best for the floating system. By following comprehensive methodology outlined in this study, minimal Root–Mean–Square error values ranging from 0.74 to 3.33 for the canal-top system and 2.13 to 5.20 for the floating system were achieved for different parameters. These results highlight that accurate performance predictions depend on three factors: the precision of meteorological data, the capabilities of the simulation tool for water-mounted systems, and the tool’s ability to be customized for specific system details. This study helps solar developers and researchers choose the most suitable simulation tools and customize them for feasibility studies. It also helps stakeholders predict the energy output of existing water–mounted systems more accurately, reducing the risk of penalties due to deviations from predicted output.

Overview of Theory, Simulation, and Experiment of the Water Exit Problem

The water exit problem, which is ubiquitous in ocean engineering, is a significant research topics in the interaction between navigators and water. The study of the water exit problem can help to improve the structural design of marine ships and underwater weapons, allowing for better strength and movement status. However, the water exit problem involves complex processes such as three-phase gas–liquid–solid coupling, cavitation, water separation, liquid surface deformation, and fragmentation, making it challenging to study. Following work carried out by many researchers on this issue, we summarize recent developments from three aspects: theoretical research, numerical simulation, and experimental results. In theoretical research, the improved von Karman model and linearized water exit model are introduced. Several classical experimental devices, data acquisition means, and cavitation approaches are introduced in the context of experimental development. Three numerical simulation methods, namely, the BEM (Boundary Element Method), VOF (Volume of Fluid), and FVM (Finite Volume Method) with LES (Large Eddy Simulation) are presented, and the respective limitations and shortcomings of these three aspects are analyzed. Finally, an outlook on future research improvements and developments of the water exit problem is provided.

The crossover frequency of acoustic simulation for small-scale enclosures by wave and statistic based methods

In the field of room acoustic simulation, wave-based and statistical numerical methods are pivotal for acquiring sound field characteristics. Although the Schroeder Frequency has been utilized to deduce the suitable frequency range of these methods in large enclosures, the crossover frequency warrants further investigation for the small-scale enclosures with complicated inner structures, such as car cabins. This work aims to explore the applicable frequency range of these acoustic simulation methods for a small-scale model, which means identifying the crossover frequency between wave-based Finite Element Method (FEM) and statistical Ray Tracing Method (RTM). First, the crossover frequency was analyzed by the Schroder Frequency equation and modal density estimated from the room transfer functions (RTFs) in a simplified car model, which considering the interior with and without seat occlusion. Further, the crossover frequency was validated by comparing the magnitude spectra of RTFs simulated by FEM and RTM. This work provides a foundational frequency reference for applying statistical acoustic methods in small-scale enclosures.

Optimised implicit methods for audio rate wave-based acoustic simulation

Wave-based room acoustic computation at an audio rate (i.e., covering the complete range of audible frequencies) is computationally intensive. There is thus a great incentive to develop simulation methods that allow for "accurate" simulation at the lowest possible computational cost, taking into account requirements for massively parallel implementation. Though often formal measures of order of accuracy are employed, in this paper, we examine the optimisation of a locally-defined implicit family of schemes against wideband measures of accuracy, based on the minimisation of numerical dispersion over a specified frequency range. The resulting optimised scheme is defined over a Cartesian grid, and allows performance gains over standard schemes (such as the basic rectilinear scheme, or schemes defined over face-centered cubic grids, and other implicit designs presented in the literature). Numerical stability conditions are easily formulated, and can be built into the optimisation, alongside the computational cost of linear system solution. Simulation results and comparisons of computation times against other known methods are presented.

Numerical investigation of serration angle on trailing edge noise reduction

The influence of serration angle on the three-dimensional flow characteristics and noise attenuation mechanisms of a NACA6512-63 airfoil is explored in this research using large eddy simulation (LES) and spectral proper orthogonal decomposition (SPOD) methods. Analysis of the mean flow field reveals the formation of counter-rotating vortex pairs, resulting from the outward flow towards the serration edges and the downwash flow in the valleys. This flow modification alters the effective angle of the serration, which in turn impacts its noise reduction performance. Furthermore, the noise reduction mechanism is investigated by comparing the general solution of Lyu's semi-analytical equation with the SPOD mode results, and the frequency range associated with noise attenuation is analyzed. The findings indicate that the case with λ/h=0.15 demonstrates the most significant noise reduction effect. This research offers valuable insights into the interplay between serration geometry and the resulting flow characteristics and noise reduction mechanisms.

A human visual attention analysis model for remote interaction interface of unmanned agricultural vehicles

When unmanned agricultural vehicles (UAVs) encounter unexpected failures or incidents during autonomous operations, a highly efficient remote human–machine interaction (HMI) interface is needed to assist in the manual joint control process. The highly complex cognitive mechanisms and visual characteristics of humans make it difficult to design efficient human–machine interfaces. Therefore, a human visual attention analysis model was proposed based on fully convolutional networks for the remote interaction interface of unmanned agricultural vehicles. First, visual attention experimental software combined with gaze-contingent real-time simulation methods was developed to build the dataset. Subsequently, the human visual attention analysis model (HVAAM) is constructed, and the corresponding training strategy is proposed, which is trained on the ILSVRC2012 standard and self-constructed datasets. The accuracy of the HVAAM analysis on the test dataset was validated. Ultimately, a human–machine interaction test of random failure warning for remote monitoring interface of unmanned plowing operation is performed with a self-developed unmanned electric tractor as the carrier. In the test dataset, the average analysis accuracy of HVAAM was 79.2 %, and the proposed training strategy led to a 20.7 % improvement in the model accuracy. In the unmanned electric tractor human–machine interaction test, HVAAM achieved 77.9 % accuracy in the visual attention analysis of the monitoring interface. This study can effectively facilitate the analysis, design, and optimization of remote monitoring interfaces for unmanned agricultural vehicles.

Verification of frequency-dependent impedance boundaries for the Finite-Volume Time-Domain scheme

Numerical simulation methods are widely used to approximate solutions to the wave-equation, taking into account the initial condition ('initial sources') and boundary conditions ('wall materials'). Trustworthy simulations are essential; a primary step is to ensure the correctness of the implementation through a process known as code verification. In this work, we do code verification by studying the convergence of the known finite-volume time-domain (FVTD) method with a frequency-dependent boundary condition modeled as an inductance/resistance/capacitance (LRC) termination. Due to the difficulties of obtaining an analytical solution for frequency-dependent impedance boundaries, we thoroughly derive and implement The Method of Manufactured Solutions tailored to the wave-equation inside a rectangular room for uniform frequency- dependent wall impedance. Asymptotic estimates are found empirically based on a convergence study compared against the manufactured ground truth solution. We investigate the impact of the frequency-dependent boundaries on the convergence affected by the total sum of numerical errors and validate the theoretical properties of the FVTD scheme for various LRC model configurations. The method should also serve as a useful resource for others to verify the correctness of their code implementations.

Most important performance evaluation methods of production lines: A comprehensive review on historical perspective and emerging trends

Production is one of the most significant building blocks that strengthen the sustainable economy of companies and thus contribute to the countries’ welfare. Performance indicators of the production line affect planning operations and the efficiency of the supply chain to which the factory is connected. The key indicators for production line designers and performance analysts to monitor and improve include production rate, resource utilization rate, and average inventory level. The production rate is the most important indicator closely affecting an industrial plant's productivity and efficiency levels. From this perspective, accurate and fast estimation of this indicator is very critical. Production rate can be calculated by simulation, analytical technique, or artificial intelligence methods according to the production line characteristics. In this comprehensive review, the most important performance evaluation methods are discussed historically and systematically about the buffer allocation problem using the snowball sampling method. With this explicit motivation, 145 papers were reviewed and classified according to production line topology, hypothetical/real-case line, machine reliability, previous method on which the method is based, and originality and/or line characteristics. To present a comprehensive comparison, the methods considered were analyzed according to different criteria. This review provides general/in-depth qualitative and quantitative discussions and highlights insights to practitioners and scholars. In addition, the impact of recent key work on production line analysis in the field is assessed along with emerging trends, evolving manufacturing paradigms are discussed, and the challenges associated with performance analysis are addressed.

Pelatihan Pemantauan Pertumbuhan Balita Pada Kader Kesehatan di Puskesmas Muara Tais, Kecamatan Angkola, Muara Tais Tapanuli Selatan

Stunting in Tapanuli Selah district will be 39.4 percent in 2022, and in 2023 it will decrease by 15.6 percent. Community empowerment in the health sector develops Community Resource Health Efforts (UKBM) namely Posyandu. Posyandu organizers are health cadres, elected by the community. Increasing the ability of cadres to manage posyandu activities, especially regarding basic health services to the community, is carried out by training by health workers. Muaratais Health Center was inaugurated on July 15 2023, the newest sub-district expansion in South Tapanuli Regency. The Muaratais Health Center area has 15 villages, in each village there is a posyandu, an average of 4 cadres and there are new cadres who have never attended training. The service team agreed with the Community Health Center to carry out training for posyandu cadres on monitoring the growth of toddlers. Training materials, toddler growth, measuring body length, height and weight using tools available at the posyandu, infant ruler, microtoise, portable electric body weight. The training participants consisted of 20 health cadres, appointed by the community health center to represent the posyandu in their work area. Training activities were carried out for two days in the community health center meeting room. Lecture, question and answer, simulation and demonstration methods. Trainees' knowledge about monitoring toddler growth is getting better. Skills in using the growth monitoring tools available at posyandu category are sufficient. Skills at the advanced stage are continued by the posyandu supervisor.

Alchemical Transformations and Beyond: Recent Advances and Real-World Applications of Free Energy Calculations in Drug Discovery.

Computational methods constitute efficient strategies for screening and optimizing potential drug molecules. A critical factor in this process is the binding affinity between candidate molecules and targets, quantified as binding free energy. Among various estimation methods, alchemical transformation methods stand out for their theoretical rigor. Despite challenges in force field accuracy and sampling efficiency, advancements in algorithms, software, and hardware have increased the application of free energy perturbation (FEP) calculations in the pharmaceutical industry. Here, we review the practical applications of FEP in drug discovery projects since 2018, covering both ligand-centric and residue-centric transformations. We show that relative binding free energy calculations have steadily achieved chemical accuracy in real-world applications. In addition, we discuss alternative physics-based simulation methods and the incorporation of deep learning into free energy calculations.