Temperature effect on nanotwinned Ni under nanoindentation using molecular dynamic simulation

Temperature effect on atomic deformation of nanotwinned Ni (nt-Ni) under localized nanoindentation is investigated in comparison with nanocrystalline Ni (nc-Ni) through molecular simulation.The nt-Ni exhibits enhanced critical load and hardness compared to nc-Ni,where perfect,stair-rod and Shockley dislocations are activated at (111),(111) and (111) slip planes in nt-Ni compared to only SSockley dislocation nucleation at (111) and (111) slip planes of nc-Ni.The nt-Ni exhibits a less significant indentation size effect in comparison with nc-Ni due to the dislocation slips hindrance of the twin boundary.The atomic deformation associated with the indentation size effect is investigated during dislocation transmission.Different from the decreasing partial slips parallel to the indenter surface in nc-Ni with increasing temperature,the temperaturedependent atomic deformation of nt-Ni is closely related to the twin boundary:from the partial slips parallel to the twin boundary (~10 K),to increased confined layer slips and decreased twin migration(300 K–600 K),to decreased confined layer slips and increased dislocation interaction of dislocation pinning and dissociation (900 K–1200 K).Dislocation density and atomic structure types through quantitative analysis are implemented to further reveal the above-mentioned dislocation motion and atomic structure alteration.Our study is helpful for understanding the temperature-dependent plasticity of twin boundary in nanotwinned materials.

FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA

S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper （SWT）Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis （FEA） of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life.

Critical anomaly and finite size scaling of the self-diffusion coefficient for Lennard Jones fluids by non-equilibrium molecular dynamic simulation

We use non-equilibrium molecular dynamics simulations to calculate the self-diffusion coefficient, D, of a Lennard Jones fluid over a wide density and temperature range. The change in self-diffusion coefficient with temperature decreases by increasing density. For density ρ＊ = ρσ3 = 0.84 we observe a peak at the value of the self-diffusion coefficient and the critical temperature T＊ = kT/ε = 1.25. The value of the self-diffusion coefficient strongly depends on system size. The data of the self-diffusion coefficient are fitted to a simple analytic relation based on hydrodynamic arguments. This correction scales as N-α, where α is an adjustable parameter and N is the number of particles. It is observed that the values of a 〈 1 provide quite a good correction to the simulation data. The system size dependence is very strong for lower densities, but it is not as strong for higher densities. The self-diffusion coefficient calculated with non-equilibrium molecular dynamic simulations at different temperatures and densities is in good agreement with other calculations fronl the literature.

Optimal Design and Dynamic Simulation of Mountain Bike with Rear Suspension

This paper investigates the dynamic design methodology of mountain bikes with rear suspension. Firstly, a multi-rigid body dynamic model of rider and mountain bike coupled system is constructed. The rider model includes 19 skeletons, 18 joints and 118 main muscles. Secondly, to validate the feasibility of the model, an experiment test is designed to reflect the real cycling status. Finally, aiming at enhancing the performance of the rider vibration comfort, the scale parameters of rear suspension are optimized with computer simulation and uniform design. The mathematical model in the vibration performance and the design variables is constructed with regression analysis. The result shows that when the length of side link is 90 mm, the length of connected rod is 336.115 1 mm and the included angle between absorber and side link is 60°, the mountain bike has better vibration comfort. This study and relevant conclusions are of practical importance to the design of the mountain bike＇s rear suspension system.

Process Modeling and Dynamic Simulation for EAST Helium Refrigerator

In this paper,the process modeling and dynamic simulation for the EAST helium refrigerator has been completed.The cryogenic process model is described and the main components are customized in detail.The process model is controlled by the PLC simulator,and the realtime communication between the process model and the controllers is achieved by a customized interface.Validation of the process model has been confirmed based on EAST experimental data during the cool down process of 300-80 K.Simulation results indicate that this process simulator is able to reproduce dynamic behaviors of the EAST helium refrigerator very well for the operation of long pulsed plasma discharge.The cryogenic process simulator based on control architecture is available for operation optimization and control design of EAST cryogenic systems to cope with the long pulsed heat loads in the future.

Dynamic simulations of the late MIS 3 transgressions in the East China Sea and southern Yellow Sea,China

Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3（MIS 3） and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level（H_S） was defined as the glaciation-climateforced sea levels, and the relative sea level change（H_R） was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±（2.5–4.5） m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.

DYNAMIC SIMULATION OF FLUID-STRUCTURE INTERACTION PROBLEMS INVOLVING LARGE-AMPLITUDE SLOSHING

An effective computational method is developed for dynamic analysis offluid-structure interaction problems involving large-amplitude sloshing of the fluid andlarge-displacement motion of the structure. The structure is modeled as a rigid container supportedby a system consisting of springs and dashpots. The motion of the fluid is decomposed into twoparts: the large-displacement motion with the container and the large-amplitude sloshing relative tothe container. The former is conveniently dealt with by defining a container-fixed noninertiallocal frame, while the latter is easily handled by adopting an ALE kinematical description. Thisleads to an easy and accurate treatment of both the fluid-structure interface and the fluid freesurface without producing excessive distortion of the computational mesh. The coupling between thefluid and the structure is accomplished through the coupling matrices that can be easilyestablished. Two numerical examples, including a TLD-structure system and a simplified liquid-loadedvehicle system, are presented to demonstrate the effectiveness and reliability of the proposedmethod. The present work can also be applied to simulate fluid-structure problems incorporatingmultibody systems and several fluid domains.

DYNAMIC SIMULATION OF ROTATING SHELLS COUPLED WITH LIQUID

The dynamic behaviors of rotating shells coupled with liquid areshown. The shell under con- sideration has arbitrary boundaryconditions and a complex shape. A modified boundary element methodand finite strip technique are used to improve the computingefficiency and to guarantee the continuity conditions on theliquid-shell interaction plane. The effects of various parameterssuch as shell's thickness and liquid depth are investigated. Dynamicsimulations are applied to several typical shell-liquid systems, andthe natu- ral frequencies, mode shapes and response of vibration arecalculated numerically.

Spatio-temporal Dynamic Simulation of Urban Land Use in Karst Areas Based on CLUE-S Model——A Case Study of Dahua Yao Nationality Autonomous County in Guangxi Zhuang Autonomous Region

This article uses TM images in 1999 and 2006 in Dahua County,selects the driving factors having great impact on urban land use change,and conducts data processing using GIS software.It then uses CLUE-S model to simulate land use change pattern in 2006,and uses land use map in 2006 to test the simulation results.The results show that the simulation achieves good effect,indicating that we can use CLUE-S model to simulate the future urban land use change in karst areas,to provide scientific decision-making support for sustainable development of land use.

Dynamic simulation and modeling of PCP transport between sediment and water

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Molecular dynamic simulation of lubricant spreading： effect from the substrate and endbead

Molecular dynamic simulations based on a coarse-gralned, bead-spring model are adopted to investigate the spreading of both nonfunctional and functional perfluoropolyether （PFPE） on solid substrates. For nonfunctional PFPE, the spreading generally exhibits a smooth profile with a precursor film. The spreading profiles on different substrates are compared, which indicate that the bead-substrate interaction has a significant effect on the spreading behaviour, especially on the formation of the precursor film. For functional PFPE, the spreading generally exhibits a complicated terraced profile. The spreading profiles with different endbeads are compared, which indicate that the endbead-substrate interaction and the endbead-endbead interaction, especially the latter, have a significant effect on the spreading behaviour.

Behavioural analysis and dynamic simulation of the debris flow that occurred in Ganluo County(Sichuan, China) on 30 August 2020

On August 30, 2020, a high-intensity storm that dropped 45.4 mm of rain in 5 hours hit the Heixiluo basin and triggered a landslide-generated debris flow event, causing fatalities and damage. The original source of the debris flow was a large slope collapse on a steep hillside. The fallen debris mass was enlarged through sediment entrainment and slope collapse and ultimately buried a bridge at the gully entrance. Approximately 6.9×10;m;of material, including sediments and collapsed slope deposits in the gullies, was entrained, and the maximum erosion depth reached 17 m. A geomorphological analysis was initially performed based on a detailed field investigation to recognize the liquid and solid sources of the debris flow and the areas subjected to deposition and erosion. A map of the erosiondeposition distribution was obtained based on preand post-event DEMs. Using the rainfall estimated by the nearest rain gauge and the solid source estimated by the DEMs, runoff and debris flow propagation was simulated using a liquid-solid two-phase model that considers the effects of runoff and entrainment. The similarity between the estimated and simulated deposition-erosion volumes was satisfactory. The behaviour of debris flows captured in the simulation is broadly in line with the main features of the observed event.

Study of structural and magnetic properties of Fe(80)P-9B(11) amorphous alloy by ab initio molecular dynamic simulation

The structural and magnetic properties of Fe80P9B11 amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe（80）P9B（11） amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe–B partial pair distribution functions（PDFs） becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.

Dynamic Simulation Analysis of the Working Device of a ZL50 Loader

In this study,assuming a certain type of wheel loader as the main objective of the research,the performances of the working device of the loader are investigated on the basis of an in-house code.After creating a three-dimensional model of the working device using Solidworks,this model has been imported into the dynamic simulation software ADAMS,and the simulation problem has been completed by adding the relevant constraints and loadings.The load stress curve relating to the main connecting point of the working device has been obtained in the frame work of this approach and it has been shown that the movement characteristics are compatible with(i.e.,they match)the actual working conditions.The present study may be regarded as a theoretical basis for the design and improvement of the working device of a vast category of wheel loaders.

Molecular dynamic simulation of the thermodynamic and kinetic properties of nucleotide base pair

A nucleotide base pair is the basic unit of RNA structures. Understanding the thermodynamic and kinetic properties of the closing and opening of a base pair is vital for quantitative understanding the biological functions of many RNA molecules. Due to the fast transition rate, it is difficult to directly observe opening and closing of single nucleic acid base pair in experiments. This review will provide a brief summary of the studies about the thermodynamic and kinetic properties of a base pair opening and closing by using molecular dynamic simulation methods.

CAS-based Water Resources Optimal Allocation and Dynamic Simulation for Sewage Irrigation Area

Based on the theory of complex adaptive system(CAS),the optimal allocation model of water resources in sewage irrigation areas was established,which provided new ideas and application value for the rational utilization of agricultural production and waste water resources.The results demonstrated that the difference of crop energy capture mainly depended on the development stage.Waste water with a certain concentration was able to promote crop growth,while excessive concentration inhibited crop growth.The correlation between water absorption rate and leaf area index was close(R=0.9498,p<0.01).The amount of bad seeds increased at a speed of 34.7·d^-1,when system irrigated randomly in the seedling stage,while it tended to remain stable at a speed of 0.3·d^-1 after plants entering the mature stage which impacted the total yields of crops.

Dynamic Simulation of Cracked Buildings for Damage Detection

A dynamic simulation method for cracked structures is implemented to determine their dynamic response with the purpose of evaluating their structural behavior.The procedure makes possible the si mulation of three-dimensional cracked structures.The excitation force is randomly generated to simulate wind gusts.It is assumed the structure remains in the elastic range,which allows for each mode that contributes to its dynamic response to be decoupled.The results indicate that the presence of damage causes changes in the modals parameters of the structure as accurate as other similar methods proposed for simpler structures.Therefore,it is concluded that the proposed method is a reliable way to evaluate the dynamic behavior of three-dimensi onal cracked building structures.

Stochastic dynamic simulation of railway vehicles collision using data-driven modelling approach

Using stochastic dynamic simulation for railway vehicle collision still faces many challenges,such as high modelling complexity and time-consuming.To address the challenges,we introduce a novel data-driven stochastic process modelling(DSPM)approach into dynamic simulation of the railway vehicle collision.This DSPM approach consists of two steps:(i)process description,four kinds of kernels are used to describe the uncertainty inherent in collision processes;(ii)solving,stochastic variational inferences and mini-batch algorithms can then be used to accelerate computations of stochastic processes.By applying DSPM,Gaussian process regression(GPR)and finite element(FE)methods to two collision scenarios(i.e.lead car colliding with a rigid wall,and the lead car colliding with another lead car),we are able to achieve a comprehensive analysis.The comparison between the DSPM approach and the FE method revealed that the DSPM approach is capable of calculating the corresponding confidence interval,simultaneously improving the overall computational efficiency.Comparing the DSPM approach with the GPR method indicates that the DSPM approach has the ability to accurately describe the dynamic response under unknown conditions.Overall,this research demonstrates the feasibility and usability of the proposed DSPM approach for stochastic dynamics simulation of the railway vehicle collision.

Quasimolecular Dynamic Simulation for Bending Fracture of Laminar Composite Materials

Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous