scholarly journals Simple Modelling of Undrained Shear Response of Granular Materials

2018 ◽  
Author(s):  
Yang Wu ◽  
Liwei Wen
Keyword(s):  
Granular Materials ◽  
Internal State ◽  
Shear Behaviour ◽  
Experimental Investigations ◽  
Model Framework ◽  
Hardening Law ◽  
Confining Pressures ◽  
Parametric Studies ◽  
Simulation Results ◽  
Undrained Shear

A vast amount of past experimental investigations reported that the internal peak angle of sand was jointly governed by the density and effective stress level. Several relationships were proposed between these elements. The dependence of dilatancy characteristics on the internal state of a granular material was examined and revealed. A simple constitutive model framework was established on a basis of several well-proven and experienced relationships for granular materials to simulate their undrained shear behaviour. A basic hardening law connecting the varying tendency of the stress ratio with shear strain was employed. This model is capable of predicting the undrained monotonic stress-strain relationship of granular materials at different densities and various confining pressures. A series of parametric studies are conducted to investigate the susceptibility of the simulation results to the selected parameters. The simulation results also confirm the influential influences of dilatancy and deformability on the shear characteristics of granular materials at the critical state.

A SIMPLE CONSTITUTIVE MODEL FOR UNDRAINED SHEAR CHARACTERISTICS OF SANDY SOILS

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Yang Wu
Keyword(s):  
Constitutive Model ◽  
Granular Materials ◽  
Internal State ◽  
Model Framework ◽  
Hardening Law ◽  
Confining Pressures ◽  
Parametric Studies ◽  
Shear Characteristics ◽  
Simulation Results ◽  
Undrained Shear

A vast amount of past experimental examinations reported that the internal peak angle of sand was jointly affected by the density and effective stress level. Several relationships were proposed between these elements. The dependence of dilatancy characteristics on the internal state of a granular material was examined and revealed. A simple constitutive model framework was established on a basis of several well-proven and experienced relationships for granular materials to simulate their undrained shear behavior. A basic hardening law connecting the varying tendency of the stress ratio with shear strain was employed. This model is capable of predicting the undrained monotonic stress-strain relationship of granular materials at different densities and various confining pressures. A series of parametric studies are conducted to investigate the susceptibility of the simulation results to the selected parameters. The simulation results also confirm the influential influences of dilatancy and deformability on the shear characteristics of granular materials at the critical state.

Modeling and Simulation of Microstructure Evolution in Extruded Aluminum Profiles

2009 ◽  
Vol 424 ◽  
pp. 43-50
Author(s):  
Farhad Parvizian ◽  
T. Kayser ◽  
Bob Svendsen
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloys ◽  
Modeling And Simulation ◽  
Microstructure Evolution ◽  
Internal State ◽  
Extrusion Process ◽  
State Variables ◽  
Cooling Process ◽  
Microstructure Parameters ◽  
Simulation Results

The purpose of this work is to predict the microstructure evolution of aluminum alloys during hot metal forming processes using the Finite Element Method (FEM). Here, the focus will be on the extrusion process of aluminum alloys. Several micromechanical mechanisms such as diffusion, recovery, recrystallization and grain growth are involved in various subsequent stages of the extrusion and the cooling process afterward. The evolution of microstructure parameters is motivated by plastic deformation and temperature. A number of thermomechanical aspects such as plastic deformation, heat transfer between the material and the container, heat generated by friction, and cooling process after the extrusion are involved in the extrusion process and result in changes in temperature and microstructure parameters subsequently. Therefore a thermomechanically coupled modeling and simulation which includes all of these aspects is required for an accurate prediction of the microstructure evolution. A brief explanation of the isotropic thermoelastic viscoplastic material model including some of the simulation results of this model, which is implemented as a user material (UMAT) in the FEM software ABAQUS, will be given. The microstructure variables are thereby modeled as internal state variables. The simulation results are finally compared with some experimental results.

scholarly journals An Investigation of Dynamic Responses and Head Injuries of Standing Subway Passengers during Collisions

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yong Peng ◽  
Tuo Xu ◽  
Lin Hou ◽  
Chaojie Fan ◽  
Wei Zhou
Keyword(s):  
Numerical Simulation ◽  
Head Injury ◽  
Head Injuries ◽  
Dynamic Responses ◽  
Passive Safety ◽  
Friction Coefficients ◽  
Safety Design ◽  
Parametric Studies ◽  
Simulation Results ◽  
Set Up

With the development of the subway and the pressing demand of environmentally friendly transportation, more and more people travel by subway. In recent decades, the issues about passenger passive safety on the train have received extensive attention. In this research, the head injury of a standing passenger in the subway is investigated. Three MADYMO models of the different standing passenger postures, defined as baseline scenarios, are numerically set up. HIC15values of passengers with different postures are gained by systematic parametric studies. The injury numerical simulation results of various scenarios with different friction coefficients, collision acceleration, standing angle, horizontal handrail height, and ring handrail height are analyzed. Results show that the horizontal handrail provides better protection in the three different standing passenger postures. Different friction coefficients and the standing angle have great impact on the head injuries of passengers in three different scenarios. The handrail height also has some effects on head injury of passengers with different standing postures, so it is necessary to be considered when designing the interior layout of the subway. This study may provide guidance for the safety design of the subway and some advices for standing subway passengers.

scholarly journals Design and Manufacture of a Novel Sunlight Guiding Panel

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 562
Author(s):  
Wei-Hsuan Hsu ◽  
Yi-Zhang Xie
Keyword(s):  
Energy Consumption ◽  
Nanoimprint Lithography ◽  
Window Glass ◽  
Elevation Angle ◽  
Experimental Investigations ◽  
Technological Advancement ◽  
Total Energy Consumption ◽  
Application Potential ◽  
Simulation Results ◽  
Design And Manufacture

With technological advancement, energy consumption and lack of energy supply are inevitable. Approximately 20% of total energy consumption is used for artificial light in standard office buildings. To reduce energy consumption for illumination purposes, a sunlight guiding panel was used to increase the amount of sunlight available indoors. However, in most designs of a sunlight guiding panel, the panel has to be placed on the outdoor surface of a window glass. This type of design is inconvenient for assembling and cleaning. To enhance the practicality of a sunlight guiding panel, we attempted to place the sunlight guiding panel on the indoor surface of a window glass. The simulation results revealed that when the sunlight guiding panel was placed on the indoor surface of a window glass, the aspect ratio of the light-guiding structure of the sunlight guiding panel had to be increased for guiding the sunlight from outdoors so as to increase the amount of sunlight indoors. To fabricate the proposed sunlight guiding panel, UV nanoimprint lithography was applied to pattern the light-guiding structure of the sunlight guiding panel. Moreover, a mold with a high-precision light-guiding structure was used in UV nanoimprint lithography. The mold was fabricated using ultraprecision machining technology. Both analytical and experimental investigations were conducted to confirm the proposed design. The average light-guiding efficiency was 89.9% with a solar elevation angle range of 35° to 65°, and the experimental results agreed well with the simulation results. This study elucidates light-guiding efficiency when the sunlight guiding panel is placed on the indoor surface of a window glass, which can increase the usage convenience and application potential of sunlight guiding panels.

Effect of particle type on the shear behaviour of granular materials

Particuology ◽  
2020 ◽  
Author(s):  
Shunkai Liu ◽  
Zhihong Nie ◽  
Wei Hu ◽  
Jian Gong ◽  
Peng Lei
Keyword(s):  
Granular Materials ◽  
Shear Behaviour ◽  
Particle Type

The influence of particle elongations on direct shear behaviour of granular materials using DEM

2019 ◽  
Vol 21 (4) ◽  
Author(s):  
Shiva Prashanth Kumar Kodicherla ◽  
Guobin Gong ◽  
Z. X. Yang ◽  
Kristian Krabbenhoft ◽  
Lei Fan ◽  
...  
Keyword(s):  
Granular Materials ◽  
Shear Behaviour ◽  
Direct Shear

Thermal Performance Measurement for Confined Heat Sinks by Using a Modified Transient Liquid Crystal Technique

2003 ◽  
Author(s):  
S. T. Kuo ◽  
M. P. Wang ◽  
M. C. Wu ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Heat Sink ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Preheating Temperature ◽  
Parametric Studies

A series of experimental investigations with a new modified transient liquid crystal method on the studies related to the fluid flow and heat transfer characteristics in a channel installed with a heat sink have been successfully performed. The parametric studies on the local and average effective heat transfer characteristics for confined heat sinks have been explored. The influencing parameters and conditions include air preheating temperature at channel inlet, flow velocity and heat sink types. Besides, a concept of the amount of enhanced heat transfer (AEHT) is introduced and defined as the ratio of j/f. The j/f ratio is almost independent of Reynolds number for a specific confined heat sink. The j/f ratios are 0.0603 and 0.0124 for fully-confined and unconfined heat sinks, respectively.

A Numerical Study on the Ultimate Strength of Damaged Tubular Bracing Members Under Axial Compression

2018 ◽  
Author(s):  
Ling Zhu ◽  
Jieling Kong ◽  
Qingyang Liu ◽  
Han Yang ◽  
Bin Wang
Keyword(s):  
Ultimate Strength ◽  
Axial Compression ◽  
Numerical Study ◽  
Load Capacity ◽  
Approximate Equation ◽  
Offshore Structures ◽  
Experimental Investigations ◽  
Pipe Length ◽  
Axial Load Capacity ◽  
Parametric Studies

The tubular bracing members of offshore structures may sustain collision damages from the supply ships, which lead to the deterioration of the load carrying capacity of tubular bracing members. This paper presents a numerical simulation of the ultimate strength of damaged tubular bracing members under axial compression with the nonlinear finite element code ABAQUS, based on previous experimental investigations. Parametric studies are conducted to investigate the load capacity of damaged tubular bracing members, by considering the effects of diameter (D), wall thickness (H), pipe length (L) and the damage positions on the ultimate strength of tubular members. It is found that lateral damage can cause great reduction of the axial load capacity of tubular members. In addition, an approximate equation to predict the ultimate strength of tubular members based on the given damage depth is proposed.

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