Effect of Rate Sensitivity on Necking Behavior of a Laminated Tube Under Dynamic Loading

2013 ◽  
Vol 81 (5) ◽  
Author(s):  
Y. Shi ◽  
P. D. Wu ◽  
D. J. Lloyd ◽  
D. Y. Li
Keyword(s):  
Dynamic Loading ◽  
High Speed ◽  
Volume Fraction ◽  
Numerical Study ◽  
Rate Sensitivity ◽  
Element Model ◽  
Localized Necking ◽  
Rate Dependent ◽  
Positive Rate ◽  
Laminated Materials

An elastic-viscoplastic based finite element model has been developed to study the necking behavior of tube expansion for rate independent materials, rate dependent monolithic materials, and laminated materials during dynamic loading. A numerical study shows that for rate independent materials, the dynamic loading will not delay diffused necking but localized necking; for rate dependent materials, high strain rate sensitivity can significantly delay the onset of localized necking for both monolithic and laminated sheets and affect the multiple-neck formation in high-speed dynamic loading. The model also shows that a higher volume fraction of a clad layer with positive rate sensitivity material in a laminated sheet improves the sheet ductility.

Effective thermal conductivity of silicone/phosphor composites

2011 ◽  
Vol 45 (23) ◽  
pp. 2465-2473 ◽  
Author(s):  
Qin Zhang ◽  
Zhihua Pi ◽  
Mingxiang Chen ◽  
Xiaobing Luo ◽  
Ling Xu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Numerical Study ◽  
Element Model ◽  
Interfacial Thermal Resistance ◽  
Conductivity Measurements ◽  
The Monte Carlo Method ◽  
Random Particle

The effective thermal conductivity of silicone/phosphor composites is studied experimentally and numerically. Thermal conductivity measurements are conducted from 30°C to 150°C for the composites with phosphor volume fraction up to 40%. In the numerical study, a finite element model with empirical particle size distribution and random particle position is constructed using a probability density function and the Monte Carlo method, and the interfacial thermal resistance layer between phases also introduced in the model. The results indicate that when phosphor concentration is below 25 vol.%, the conductivity of the composite increases slightly with either phosphor volume fraction or temperature, and the Kapitza radius of the composite is 0.8 µm. When phosphor concentration is above 25 vol.%, the increase of conductivity correlates positively with phosphor volume fraction significantly but negatively with the temperature, and the Kapitza radius is 0.032 µm.

Simulation of Oblique Cutting in High Speed Turning Processes

2016 ◽  
Vol 3 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Usama Umer
Keyword(s):  
High Speed ◽  
Cutting Tool ◽  
Rate Sensitivity ◽  
Material Model ◽  
Element Model ◽  
Adaptive Meshing ◽  
Oblique Cutting ◽  
High Speed Turning ◽  
Inclination Angles ◽  
And Performance

A Finite Element Model is developed for Oblique cutting process in high speed turning of H-13 tool steel. The material model used for workpiece is elastic-thermoplastic including the strain rate sensitivity effect. In order to predict the tool performance, tool is considered as non-rigid and direct stresses are determined around the tool tip. Lagrangian approach is utilized along with adaptive meshing to minimize element distortion around the tool tip. The model predicts cutting forces in 3-directions at different inclination angles. The results are compared with experimental data and found to be in good agreement. The model is also able to predict stress and temperature contours in the workpiece and the cutting tool which help in predicting workpiece surface integrity and performance of the cutting tool.

An Experimental and Numerical Study on Orthogonal Machining of Ti–6Al–4V Alloy

2016 ◽  
Vol 16 (4) ◽  
pp. 209-213 ◽  
Author(s):  
Vijayan Krishnaraj
Keyword(s):  
Titanium Alloy ◽  
High Speed ◽  
Numerical Study ◽  
Cutting Temperature ◽  
Element Model ◽  
Dry Cutting ◽  
Factors Affecting ◽  
Numerical Result ◽  
Orthogonal Machining ◽  
Major Factors

AbstractIn this work experimental and numerical result of high speed orthogonal machining of Ti-6AL-4V titanium alloy is presented. High speed orthogonal turning is carried in a lathe using uncoated carbide inserts under dry cutting conditions. Experimental study is carried out by focusing on the measurement of cutting force and cutting temperature. The experimentation is supplemented by simulations from 2D finite element model (FEM) using Third Wave AdvantEdge software. The measured cutting forces and temperature are compared with FEA results. The major factors affecting the machinability of titanium alloy such as spindle speed, feed and cutting tool rake angles are investigated. Numerical results agree with the experimental results at higher speeds and feed levels. These results can be used for further study in high speed turning of titanium alloys.

scholarly journals Bubble Flow Analysis of High Speed Cylindrical Roller Bearing under Fluid-Solid Thermal Coupling

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Li Cui ◽  
Wenxia Wang ◽  
Zhang Yanlei
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Numerical Study ◽  
Roller Bearing ◽  
Generation Model ◽  
Bubble Flow ◽  
Thermal Coupling ◽  
Air Volume ◽  
Cylindrical Roller Bearing ◽  
Cylindrical Roller

Heat generation model of high speed cylindrical roller bearing is constructed by calculating the local friction in the bearing. Bubble flow calculation model of roller bearing considering fluid-solid thermal coupling is constructed based on two-body fluid model and k-ε turbulent model, in which diameter and size of bubbles, breakup, and coalescence model of bubbles are considered. Using dynamic mesh method, a new method for evaluating bearing temperature is set up treating the rolling elements as moving heat sources. Based on these models and finite element method, bubble flow of a high speed roller bearing is studied based on FLUENT software. The numerical study reveals the relationship between velocity of bearing, air volume fraction, and velocity and pressure of oil-air flow. An increase of air content in the oil produces a lower pressure at the bearing outlet while the exit fluid velocity increases. When fluid-solid thermal coupling effect is considered, velocity and pressure at outlet of the bearing both become larger, while temperature of bearing is lower than that without coupling. In comparison, the coupling effects on flow pressure and temperature are obvious. For a given rotating speed, there is an optimal value for air volume fraction, such that temperature rise of the bearing reaches the lowest value. Experiments verify the outcomes of the method presented in this paper.

scholarly journals Combined Viscoplasticity-Embedded Discontinuity Model for 3D Description of Rock Failure Under Dynamic Loading

2020 ◽  
Vol 53 (11) ◽  
pp. 5095-5110
Author(s):  
Timo Saksala
Keyword(s):  
Dynamic Loading ◽  
Shear Failure ◽  
Yield Criterion ◽  
Model Performance ◽  
Rate Sensitivity ◽  
Rock Failure ◽  
Inertia Effects ◽  
Loading Rates ◽  
Rate Dependent ◽  
Heterogeneous Rock

Abstract This paper presents a combined viscoplasticity-embedded discontinuity model for 3D analyses of rock failure processes under dynamic loading. Capabilities of a rate-dependent embedded discontinuity model, implemented with the linear tetrahedral element, for mode I (tension) loading induced fractures is extended to compressive (shear) failure description by viscoplastic softening model with the Drucker–Prager yield criterion. The return mapping update formulas are derived for the corner plasticity case exploiting the consistency conditions for both models simultaneously. The model performance is demonstrated in 3D numerical simulations of uniaxial tension and compression test on a heterogeneous rock at various loading rates. These simulations corroborate the conception that the rate sensitivity of rock is a genuine material property in tension while structural (inertia) effects play the major role in compression at high loading rates (up to 1000 s−1). Finally, the model is validated with predicting the experiments of dynamic Brazilian disc test on granite.

scholarly journals Numerical Study of Tire Hydroplaning Based on Power Spectrum of Asphalt Pavement and Kinetic Friction Coefficient

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Shengze Zhu ◽  
Xiuyu Liu ◽  
Qingqing Cao ◽  
Xiaoming Huang
Keyword(s):  
Friction Coefficient ◽  
Power Spectrum ◽  
High Speed ◽  
Complex Modulus ◽  
Numerical Study ◽  
Asphalt Pavement ◽  
Water Film ◽  
Element Model ◽  
Kinetic Friction ◽  
Inflation Pressure

Hydroplaning is a driving phenomenon threating vehicle’s control stability and safety. It happens when tire rolls on wet pavement with high speed that hydrodynamic force uplifts the tire. Accurate numerical simulation to reveal the mechanism of hydroplaning and evaluate the function of relevant factors in this process is significant. In order to describe the friction behaviors of tire-pavement interaction, kinetic friction coefficient curve of tire rubber and asphalt pavement was obtained by combining pavement surface power spectrum and complex modulus of tread rubber through Persson’s friction theory. Finite element model of tire-fluid-pavement was established in ABAQUS, which was composed of a 225-40-R18 radial tire and three types of asphalt pavement covered with water film. Mechanical responses and physical behaviors of tire-pavement interaction were observed and compared with NASA equation to validate the applicability and accuracy of this model. Then contact force at tire-pavement interface and critical hydroplaning speed influenced by tire inflation pressure, water film thickness, and pavement types were investigated. The results show higher tire inflation pressure, thinner water film, and more abundant macrotexture enhancing hydroplaning speed. The results could be applied to predict hydroplaning speed on different asphalt pavement and improve pavement skid resistance design.

Dynamic Indentation Hardness and Rate Sensitivity in Metals

1999 ◽  
Vol 121 (3) ◽  
pp. 257-263 ◽  
Author(s):  
G. Subhash ◽  
B. J. Koeppel ◽  
A. Chandra
Keyword(s):  
Vickers Hardness ◽  
High Speed ◽  
Rate Sensitivity ◽  
Indentation Hardness ◽  
Dynamic Indentation ◽  
Rate Dependent ◽  
Static Hardness ◽  
Rate Processes ◽  
Engineering Materials ◽  
Static Conditions

An experimental technique for determining the dynamic indentation hardness of materials is described. Unlike the traditional static hardness measurements, the dynamic hardness measurements can capture the inherent rate dependent material response that is germane to high strain rate processes such as high speed machining and impact. The dynamic Vickers hardness (DHV) of several commonly used engineering materials is found to be greater than the static Vickers hardness (HV). The relationship between the hardness and yield stress under static conditions, i.e., HV =3σy, is also found to be valid under dynamic conditions. It is suggested that this simpler technique can be used to assess the rate sensitive nature of engineering materials at moderate strain rates in the range of around 2000/s.

Unsteady Numerical and Experimental Study of Cavitation in Axial Pump

2014 ◽  
Vol 4 (1) ◽  
pp. 55-68
Author(s):  
Mohamed Adel ◽  
Nabil H. Mostafa
Keyword(s):  
Numerical Simulation ◽  
Void Growth ◽  
High Speed ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Two Phase ◽  
Impeller Blade ◽  
Axial Pump

This paper presents an experimental and three-dimensional numerical study of unsteady, turbulent, void growth and cavitation simulation inside the passage of the axial flow pump. In this study a 3D Navier-Stokes code was used (CFDRC, 2008) to model the two-phase flow field around a four blades axial pump. The governing equations are discretized on a structured grid using an upwind difference scheme. The numerical simulation used the standard K-e turbulence model to account for the turbulence effect. The numerical simulation of void growth and cavitation in an axial pump was studied under unsteady calculating. Pressure distribution and vapor volume fraction were completed versus time at different condition. The computational code has been validated by comparing the predicated numerical results with the experiment. The predicted of cavitation growth and distribution on the impeller blade also agreed with that visualized of high speed camera.

An experimental and numerical study of the mechanical properties of a cross-linked polyethylene subject to low-velocity impacts

2018 ◽  
Vol 233 (8) ◽  
pp. 1604-1618
Author(s):  
Andrew Cummings
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Numerical Study ◽  
Element Model ◽  
Dynamic Mechanical Properties ◽  
Small Scale ◽  
Analysis Model ◽  
Low Velocity ◽  
Element Analysis ◽  
Rate Dependent

The response of a thermosetting cross-linked polyethylene, commercially referred to as Vitrite, has been studied experimentally and numerically. Two different testing programmes have been carried out; the first to characterise the mechanical properties of the material, and the second to provide information to validate a finite element model. Strain-rate dependent stress–strain curves have been obtained to determine the static and dynamic mechanical properties of Vitrite in tension and compression. Guided drop testing of a mass onto small scale samples has been used to study their deformation and rebound response. This has been compared to the deformation results of a finite element analysis model of the drop tests using the data obtained from the material characterisation tests as input to the model.

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