scholarly journals Large-Scale Molecular Simulations on the Mechanical Response and Failure Behavior of a defective Graphene: Cases of 5–8–5 Defects

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Shuaiwei Wang ◽  
Baocheng Yang ◽  
Jinyun Yuan ◽  
Yubing Si ◽  
Houyang Chen
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Molecular Simulations ◽  
Failure Behavior ◽  
Defective Graphene

scholarly journals On the effects of membrane viscosity on transient red blood cell dynamics

Soft Matter ◽  
2020 ◽  
Vol 16 (26) ◽  
pp. 6191-6205 ◽  
Author(s):  
Fabio Guglietta ◽  
Marek Behr ◽  
Luca Biferale ◽  
Giacomo Falcucci ◽  
Mauro Sbragaglia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Blood Circulation ◽  
Hydraulic Properties ◽  
Large Scale ◽  
Mechanical Response ◽  
Cell Dynamics ◽  
Membrane Viscosity

Computational Fluid Dynamics is currently used to design and improve the hydraulic properties of biomedical devices, wherein the large scale blood circulation needs to be simulated by accounting for the mechanical response of RBCs at the mesoscale.

Continuum Description of the Time- and Strain-Dependent Poisson’s Ratio of Ligament Under Finite Deformation

2013 ◽  
Author(s):  
Aaron M. Swedberg ◽  
Shawn P. Reese ◽  
Steve A. Maas ◽  
Benjamin J. Ellis ◽  
Jeffrey A. Weiss
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Large Strain ◽  
Fiber Direction ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
Strain Dependent

Ligament volumetric behavior controls fluid and thus nutrient movement as well as the mechanical response of the tissue to applied loads. The reported Poisson’s ratios for tendon and ligament subjected to tensile deformation loading along the fiber direction are large, ranging from 0.8 ± 0.3 in rat tail tendon fascicles [1] to 2.98 ± 2.59 in bovine flexor tendon [2]. These Poisson’s ratios are indicative of volume loss and thus fluid exudation [3,4]. We have developed micromechanical finite element models that can reproduce both the characteristic nonlinear stress-strain behavior and large, strain-dependent Poisson’s ratios seen in tendons and ligaments [5], but these models are computationally expensive and unfeasible for large scale, whole joint models. The objectives of this research were to develop an anisotropic, continuum based constitutive model for ligaments and tendons that can describe strain-dependent Poisson’s ratios much larger than the isotropic limit of 0.5. Further, we sought to demonstrate the ability of the model to describe experimental data, and to show that the model can be combined with biphasic theory to describe the rate- and time-dependent behavior of ligament and tendon.

Experimental Analysis of Ratcheting Failure Based on the Piezomagnetic Response of X80 Pipeline Steel

2017 ◽  
Author(s):  
Sheng Bao ◽  
Shengnan Hu ◽  
Yibin Gu
Keyword(s):  
Magnetic Field ◽  
Hysteresis Loop ◽  
Mechanical Response ◽  
Pipeline Steel ◽  
Failure Process ◽  
Failure Behavior ◽  
X80 Pipeline Steel ◽  
Test Analysis ◽  
Number Of Cycles ◽  
The Magnetic Field

The objective of this research is to explore the correlation between the piezomagnetic response and ratcheting failure behavior under asymmetrical cyclic stressing in X80 pipeline steel. The magnetic field variations from cycle to cycle were recorded simultaneously during the whole-life ratcheting test. Analysis made in the present work shows that the piezomagnetic hysteresis loop evolves systematically with the number of cycles in terms of its shape and position. Corresponding to the three-stage process in the mechanical response, piezomagnetic response can also be divided into three principal stages, but the evolution of magnetic parameter is more complex. Furthermore, the loading branch and unloading branch of the magnetic field-stress hysteresis loop separate gradually from each other during ratcheting failure process, leading to the shape of hysteresis loop changes completely. Therefore, the progressive degradation of the steel under ratcheting can be tracked by following the evolution of the piezomagnetic field. And the shape transition of the hysteresis loop can be regarded as an early warning of the ratcheting failure.

Molecular Dynamics Modeling the Nano-Identation of Titanium

2021 ◽  
Author(s):  
Peiqiang Yang ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Rajiv Shivpuri
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Titanium Alloys ◽  
Large Scale ◽  
Mechanical Response ◽  
Pure Titanium ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Nano Indentation ◽  
Molecular Dynamics Modeling

Abstract Titanium alloys’ excellent mechanical and physical properties make it the most popular material widely used in aerospace, medical, nuclear and other significant industries. The study of titanium alloys mainly focused on the macroscopic mechanical mechanism. However, very few researches addressed the nanostructure of titanium alloys and its mechanical response in Nano-machining due to the difficulty to perform and characterize nano-machining experiment. Compared with nano-machining, nano-indentation is easier to characterize the microscopic plasticity of titanium alloys. This research presents a nano-indentation molecular dynamics model in titanium to address its microstructure alteration, plastic deformation and other mechanical response at the atomistic scale. Based on the molecular dynamics model, a complete nano-indentation cycle, including the loading and unloading stages, is performed by applying Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The plastic deformation mechanism of nano-indentation of titanium with a rigid diamond ball tip was studied under different indentation velocities. At the same time, the influence of different environment temperatures on the nano-plastic deformation of titanium is analyzed under the condition of constant indentation velocity. The simulation results show that the Young’s modulus of pure titanium calculated based on nano-indentation is about 110GPa, which is very close to the experimental results. The results also show that the mechanical behavior of titanium can be divided into three stages: elastic stage, yield stage and plastic stage during the nano-indentation process. In addition, indentation speed has influence on phase transitions and nucleation of dislocations in the range of 0.1–1.0 Å/ps.

scholarly journals Simulation of Cyclic Loading on Pipe Elbows Using Advanced Plane-Stress Elastoplasticity Models1

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Konstantinos Chatziioannou ◽  
Yuner Huang ◽  
Spyros A. Karamanos
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Mechanical Response ◽  
Low Cycle Fatigue ◽  
Constitutive Relations ◽  
Cyclic Plasticity ◽  
Integration Scheme ◽  
Repeated Loading ◽  
Finite Element Software ◽  
Hardening Models

Abstract This work investigates the response of industrial steel pipe elbows subjected to severe cyclic loading (e.g., seismic or shutdown/startup conditions), associated with the development of significant inelastic strain amplitudes of alternate sign, which may lead to low-cycle fatigue. To model this response, three cyclic-plasticity hardening models are employed for the numerical analysis of large-scale experiments on elbows reported elsewhere. The constitutive relations of the material model follow the context of von Mises cyclic elasto-plasticity, and the hardening models are implemented in a user subroutine, developed by the authors, which employs a robust numerical integration scheme, and is inserted in a general-purpose finite element software. The three hardening models are evaluated in terms of their ability to predict the strain range at critical locations, and in particular, strain accumulation over the load cycles, a phenomenon called “ratcheting.” The overall good comparison between numerical and experimental results demonstrates that the proposed numerical methodology can be used for simulating accurately the mechanical response of pipe elbows under severe inelastic repeated loading. Finally, this paper highlights some limitations of conventional hardening rules in simulating multi-axial material ratcheting.

The Belgian Demonstration Programme for the Disposal of High-Level and Long-Lived Radioactive Waste

2006 ◽  
Vol 932 ◽  
Author(s):  
Bernier Frédéric ◽  
Demarche Marc ◽  
Bel Johan
Keyword(s):  
Radioactive Waste ◽  
Thermal Load ◽  
Large Scale ◽  
Mechanical Response ◽  
Boom Clay ◽  
Geological Formation ◽  
Important Input ◽  
Clay Layers ◽  
High Level ◽  
Large Scale Tests

ABSTRACTThe EIG EURIDICE is responsible for performing large-scale tests, technical demonstrations and experiments so as to assess the feasibility of a final disposal of vitrified radioactive waste in deep clay layers. This programme is part of the Belgian Research and Development programme managed by ONDRAF/NIRAS. The research infrastructure includes the Underground Research Facilities HADES (URF HADES) in the Boom Clay geological formation and surface facilities. The achievements of the demonstration programme are the demonstration of the construction of shafts and galleries at industrial scale, the characterisation of the hydro-mechanical response of the host rock, and the “OPHELIE mock-up” a large scale hydration test under thermal load of pre-fabricated bentonite blocks. The future works will consist mainly in the realisation of the “PRACLAY experiments” including a large scale heater test. The large scale heater test has to demonstrate that Boom Clay is suitable, in terms of performance of the disposal system, to undergo the thermal load induced by the vitrified waste. The combined effect of the excavation and the thermal load will be investigated. A long term (more than 10 years) large scale heater test would be representative of the most penalizing conditions that could be encountered in the real disposal. The results of this test will constitute an important input for the Safety and Feasibility Cases 1 (SFC-1, 2013) and 2 (SFC-2, 2020).

scholarly journals Dynamic design: manipulation of millisecond timescale motions on the energy landscape of cyclophilin A

2020 ◽  
Vol 11 (10) ◽  
pp. 2670-2680 ◽  
Author(s):  
Jordi Juárez-Jiménez ◽  
Arun A. Gupta ◽  
Gogulan Karunanithy ◽  
Antonia S. J. S. Mey ◽  
Charis Georgiou ◽  
...  
Keyword(s):  
Large Scale ◽  
Energy Landscape ◽  
Molecular Simulations ◽  
Cyclophilin A ◽  
Dynamic Design ◽  
Loop Motions

Molecular simulations were used to design large scale loop motions in the enzyme cyclophilin A and NMR and biophysical methods were employed to validate the models.

Field testing of rocking foundations in cohesive soil: cyclic performance and footing mechanical response

2020 ◽  
Vol 57 (6) ◽  
pp. 828-839 ◽  
Author(s):  
Keshab Sharma ◽  
Lijun Deng
Keyword(s):  
Field Test ◽  
Large Scale ◽  
Mechanical Response ◽  
Field Testing ◽  
Cohesive Soil ◽  
Superior Performance ◽  
Unit Weight ◽  
Moment Capacity ◽  
Contact Areas ◽  
Rocking Foundations

This paper presents a field test program of a large-scale soil–footing-structure system designed with a rocking foundation in a cohesive soil to examine the behaviour of the system and to provide case histories for possible performance-based seismic design of foundations. The rocking system was subjected to slow cyclic loadings at various drift ratios up to 7%. Twenty-four tests were conducted for foundations with varying initial factors of safety against the bearing failure, loading directions, rotation amplitudes, and embedment. A geotechnical investigation was carried out to determine soil properties before and after the experiments. The system performance indices, such as damping, stiffness, settlement, and re-centering capability, were quantified and compared with the published literature. Field test results showed that the strength and unit weight of soils at footing edges were increased due to rocking, for the present cohesive soil. The rocking moment capacity increased slightly with the increasing soil strength. An empirical equation for the secant stiffness was developed. The rocking system on the cohesive soil exhibited superior performance in terms of small residual settlement and large re-centering capability. Footing’s mechanical response was quantified using strain gauge readings. The footing remained elastic in tension; the transient soil–footing contact areas were estimated with strain gauges, and they agreed very well with the measured or calculated contact areas.

Wrinkling and failure behavior of single-layer MoS2 sheets under in-plane shear

2019 ◽  
Vol 21 (35) ◽  
pp. 19115-19125 ◽  
Author(s):  
Yao Li ◽  
Peijian Chen ◽  
Hao Liu ◽  
Juan Peng ◽  
Feng Gao ◽  
...  
Keyword(s):  
Molecular Simulations ◽  
Single Layer ◽  
Failure Behavior ◽  
Nonlocal Model ◽  
Plane Shear

In this paper, the wrinkling and failure behavior of single layer MoS2 (SLMoS2) sheets under in-plane shear is investigated using molecular simulations and the nonlocal model.

Properties of Highly Filled, Highly Plasticized, Semicrystalline Polymer Networks

1991 ◽  
Vol 64 (2) ◽  
pp. 181-201 ◽  
Author(s):  
Richard D. Vargo ◽  
Frank N. Kelley
Keyword(s):  
Tensile Strength ◽  
Mechanical Response ◽  
Polymer Networks ◽  
Three Dimensional ◽  
Important Variable ◽  
Failure Behavior ◽  
Energy Data ◽  
Viscoelastic Effects ◽  
Tearing Energy ◽  
Increasing Temperature

Abstract 1. Component reactivity of ingredients such as fillers and plasticizers is significant and is measurable by a technique developed during this work. 2. The undesirable syneresis problem common to these highly plasticized materials can be controlled through adjusting equivalence ratios. Syneresis can be controlled primarily by decreasing the crystallinity of the material. 3. Changing percent crystallinity with temperature is a very important variable controlling the physical properties, i.e., ultimate properties, tearing energy, and dynamic-mechanical response. 4. The tearing energy data did not display simple amorphous behavior, and, as such, could not be shifted using a reduced variables technique such as WLF shifting. All variables were needed to represent the data. Three dimensional plotting developed previously by von Merrwall et al. was utilized to represent the data. The resulting tear-energy data exhibit the normal viscoelastic effects of rate and temperature as well as the superposition of the effects of crystallinity on the tearing energy. A decrease in tearing energy with increasing temperature is primarily due to increasing crystallinity in the samples. Plasticizer decreased the tearing energy, while filler increased the tearing energy. Filler lessened the effects of temperature and plasticizer on tearing energy. 5. Ultimate property measurements using ring samples for these model propellants revealed that these materials did not behave in a simple thermo-rheological manner, since crystallinity effects are predominant in the tensile mode. Because of crystallinity and strain-induced crystallinity, the data could not be represented by a failure envelope as proposed by Smith. The presence of plasticizer has the effect of decreasing the tensile strength, while filler tends to increase the tensile strength for the plasticized systems. 6. A model is presented to explain the high strain-to-failure behavior of these systems. Further details of this work can be found in Reference 22.

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