A Microstructure-Level Material Model for Simulating the Machining of Carbon Nanotube Reinforced Polymer Composites

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Ashutosh Dikshit ◽  
Johnson Samuel ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Carbon Nanotube ◽  
Weight Fraction ◽  
Material Model ◽  
Material Behavior ◽  
Compression Tests ◽  
Linear Elastic ◽  
Rate Dependent ◽  
Wide Range ◽  
Parametrization Scheme ◽  
Fraction Length

A continuum-based microstructure-level material model for simulation of polycarbonate carbon nanotube (CNT) composite machining has been developed wherein polycarbonate and CNT phases are modeled separately. A parametrization scheme is developed to characterize the microstructure of composites having different loadings of carbon nanotubes. The Mulliken and Boyce constitutive model [2006, “Mechanics of the Rate Dependent Elastic Plastic Deformation of Glassy Polymers from Low to High Strair Rates,” Int. J. Solids Struct., 43(5), pp. 1331–1356] for polycarbonate has been modified and implemented to capture thermal effects. The CNT phase is modeled as a linear elastic material. Dynamic mechanical analyzer tests are conducted on the polycarbonate phase to capture the changes in material behavior with temperature and strain rate. Compression tests are performed over a wide range of strain rates for model validation. The model predictions for yield stress are seen to be within 10% of the experimental results for all the materials tested. The model is used to study the effect of weight fraction, length, and orientation of CNTs on the mechanical behavior of the composites.

A Viscoelastic Correspondence Principle for Plane Membranes Subjected to Lateral Pressure

1983 ◽  
Vol 50 (4a) ◽  
pp. 740-742 ◽  
Author(s):  
B. Stora˚kers
Keyword(s):  
Time Dependence ◽  
Viscoelastic Material ◽  
Lateral Pressure ◽  
Correspondence Principle ◽  
Material Model ◽  
Material Behavior ◽  
Linear Elastic Material ◽  
First Order ◽  
Linear Elastic ◽  
Consistent Approximation

The classical Fo¨ppl equations, governing the deflection of plane membranes, constitute the first-order consistent approximation in the case of linear elastic material behavior. It is shown that despite the static and kinematic nonlinearities present, for arbitrary load histories a correspondence principle for viscoelastic material behavior exists if all relevant relaxation moduli are of uniform time dependence. Application of the principle is illustrated by means of a popular material model.

Influence of strain rate, temperature and fatigue on the radial compression behaviour of Norway spruce

Holzforschung ◽  
2017 ◽  
Vol 71 (6) ◽  
pp. 505-514 ◽  
Author(s):  
Carolina Moilanen ◽  
Tomas Björkqvist ◽  
Markus Ovaska ◽  
Juha Koivisto ◽  
Amandine Miksic ◽  
...  
Keyword(s):  
Strain Rate ◽  
Linear Model ◽  
Norway Spruce ◽  
Material Model ◽  
Radial Compression ◽  
Compression Tests ◽  
Static Compression ◽  
Rate Dependent ◽  
Compression Model ◽  
Wood Compression

Abstract A dynamic elastoplastic compression model of Norway spruce for virtual computer optimization of mechanical pulping processes was developed. The empirical wood behaviour was fitted to a Voigt-Kelvin material model, which is based on quasi static compression and high strain rate compression tests (QSCT and HSRT, respectively) of wood at room temperature and at high temperature (80–100°C). The effect of wood fatigue was also included in the model. Wood compression stress-strain curves have an initial linear elastic region, a plateau region and a densification region. The latter was not reached in the HSRT. Earlywood (EW) and latewood (LW) contributions were considered separately. In the radial direction, the wood structure is layered and can well be modelled by serially loaded layers. The EW model was a two part linear model and the LW was modelled by a linear model, both with a strain rate dependent term. The model corresponds well to the measured values and this is the first compression model for EW and LW that is based on experiments under conditions close to those used in mechanical pulping.

scholarly journals Experimental and Numerical Characterization of the Cyclic Thermomechanical Behavior of a High Temperature Forming Tool Alloy

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Sean B. Leen ◽  
Aditya Deshpande ◽  
Thomas H. Hyde
Keyword(s):  
High Temperature ◽  
Life Prediction ◽  
Material Constant ◽  
Superplastic Forming ◽  
Material Model ◽  
Fatigue Tests ◽  
Material Behavior ◽  
Future Application ◽  
Rate Dependent ◽  
Numerical Characterization

This paper describes high temperature cyclic and creep relaxation testing and modeling of a high nickel-chromium material (XN40F) for application to the life prediction of superplastic forming (SPF) tools. An experimental test program to characterize the high temperature cyclic elastic-plastic-creep behavior of the material over a range of temperatures between 20°C and 900°C is described. The objective of the material testing is the development of a high temperature material model for cyclic analyses and life prediction of SPF dies for SPF of titanium aerospace components. A two-layer viscoplasticity model, which combines both creep and combined isotropic-kinematic plasticity, is chosen to represent the material behavior. The process of material constant identification for this model is presented, and the predicted results are compared with the rate-dependent (isothermal) experimental results. The temperature-dependent material model is furthermore applied to simulative thermomechanical fatigue tests, designed to represent the temperature and stress-strain cycling associated with the most damaging phase of the die cycle. The model is shown to give good correlation with the test data, thus vindicating future application of the material model in thermomechanical analyses of SPF dies for distortion and life prediction.

On Modeling the Mechanical Behavior of Amorphous Polymers for the Micro-Hot-Embossing of Microfluidic Devices

2008 ◽  
Author(s):  
Vikas Srivastava ◽  
Lallit Anand
Keyword(s):  
Three Dimensional ◽  
Amorphous Polymers ◽  
Hot Embossing ◽  
Compression Tests ◽  
Predictive Capability ◽  
Finite Element Program ◽  
Rate Dependent ◽  
Wide Range ◽  
Element Program ◽  
Simple Compression

In this paper, a brief summary of some of our recent work [1, 2] is presented, with the goal of developing an engineering science-based process-simulation capability for micro-hot-embossing of amorphous polymers. To achieve this goal: (i) a three-dimensional thermo-mechanically-coupled large deformation constitutive theory has been developed to model the temperature and rate-dependent elastic-viscoplastic response of amorphous polymers; (ii) the material parameters in the theory were calibrated by using new experimental data from a suite of simple compression tests on Zeonex-690R (cyclo-olefin polymer), that covers a wide range of temperatures and strain rates; (iii) the constitutive model was implemented in the finite element program ABAQUS/Explicit; and (iv) the predictive capability of the numerical simulation procedures were validated by comparing results from the simulation of a representative micro-hot-embossing process against corresponding results from a physical experiment.

Rate-Dependent Constitutive Modeling of Polymer Subjected to Dynamic Loading

2012 ◽  
Vol 185 ◽  
pp. 119-121
Author(s):  
Jian Ming Yuan ◽  
Jan Ma ◽  
Geoffrey E.B. Tan ◽  
Jian Fei Liu
Keyword(s):  
Test Data ◽  
Constitutive Modeling ◽  
Dynamic Compression ◽  
Fem Simulation ◽  
Material Model ◽  
Strain Rates ◽  
Compression Tests ◽  
Material Models ◽  
Rate Dependent ◽  
Tension Tests

This paper proposes an effective and systematical method to obtain reliable rate-dependent material models used in FEM simulation for polymers. Compressive stress-strain curves of two types of polymer are obtained at different strain rates. Rate-dependent elastic-plastic models are applied to describe the observed rate-dependent behaviors, whereby the input data of material model are determined from the test data obtained. Verification of the material models is proposed via comparing FEM simulation with test data of quasi-static tension tests and dynamic compression tests of different strain rates.

scholarly journals The simplified approach to numerical modeling of polyurethane foam shock absorbers of complex structure: determination of effective mechanical properties and preparation of mathematical models of a homogenized material

2021 ◽  
Vol 2131 (4) ◽  
pp. 042056
Author(s):  
A Semenov ◽  
A Smirnov ◽  
M Stepanov ◽  
N Kharaldin ◽  
A Borovkov
Keyword(s):  
Strain Rate ◽  
Polyurethane Foam ◽  
Shock Absorber ◽  
Complex Structure ◽  
Material Model ◽  
Material Behavior ◽  
Stress Strain ◽  
Simplified Approach ◽  
Shock Absorbers ◽  
Wide Range

Abstract The first part of this paper is devoted to modeling foam taking into account the effect of strain rate on material behavior in the LS-Dyna software package for solving dynamic problems in a wide range of speeds. The MAT_083 material model was used, which analyzes the stress-strain state considering the dependence on the strain rate. The process of adaptation of experimental data for use in the MAT_083 material model is described. The second part of this study touches upon the homogenization of the properties of a shock absorber consisting of SKU-PFL-100 polyurethane (the modeling approach is described in the previous article) and polyurethane foam, the model of which is described in the first part of this paper. Homogenization of the shock absorber is carried out in order to reduce the number of elements in the problem and, accordingly, to improve the calculation performance. The stress-strain curves obtained during the compression of a shock absorber are used in the material MAT_083.

Experimental Methods for Characterizing of Sheet Metals at High Strain Rates

2011 ◽  
Vol 473 ◽  
pp. 474-481
Author(s):  
Lothar W. Meyer ◽  
Shawky Abdel-Malek ◽  
Norman Herzig
Keyword(s):  
Optical Measurement ◽  
Biaxial Tension ◽  
Shear Loading ◽  
Tension Test ◽  
Material Behavior ◽  
Tension Stress ◽  
Strain Rates ◽  
Compression Tests ◽  
Sheet Plane ◽  
Wide Range

Beside tension tests and measuring of Lankford coefficients (r-values), compression tests on small cubes in the sheet plane over a wide range of strain rates are also performed using special devices. The material behavior under shear loading is measured according to Miyauchi using appropriate equipment with the application of optical measurement of speckle strain field. A biaxial tension/tension stress state can be realized in the layer compression test. Through the compression, shear and layer compression tests, large deformations are reached, which can not be measured in the tension test due to necking. These four test types are performed not only quasi-statically but also quasi-dynamically on a servo hydraulic machine and under impact loading in a drop weight machine and rotary tensile impact tester (flywheel) with a precise measurement of force and displacement to determine the strain rate dependency of the investigated materials. Extra points of the yield loci can be measured in the plane strain tension test using a specimen ratio of B/L ≥ 20.

scholarly journals Characterization of the Mechanical Behavior of a Lead Alloy, from Quasi-Static to Dynamic Loading for a Wide Range of Temperatures

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2357
Author(s):  
Yann Coget ◽  
Yaël Demarty ◽  
Alexis Rusinek
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Digital Simulation ◽  
Armed Forces ◽  
Material Behavior ◽  
Lead Alloy ◽  
Behavioral Models ◽  
Compression Tests ◽  
Wide Range ◽  
The Impact

The current needs in terms of ballistic protection for armed forces require an almost constant improvement in performance to face the constantly evolving threats and scenarios. Ballistic tests are conventionally carried out in order to assess and validate the levels of protection. The challenge is to be able to set up a digital protocol and only carry out final validation tests. Indeed, the advantage of digital simulation lies in the possibility of being able to evaluate a wide variety of configurations. In order to obtain reliable results, it is necessary to use sufficiently precise material behavior models to transcribe the phenomena observed during the impact. Our study focuses on the behavior of a small caliber ammunition with a ductile core impacting personal protection. More particularly on the mechanical behavior of the lead alloy core. Thus, compression tests have been carried out on a wide range of deformation rates, from quasi-static behavior to dynamic regime, at different temperatures. The study in dynamic conditions was carried out using split Hopkinson pressure bars. Due to the material properties, the experimental device had to be adapted in order to optimize the propagation of the waves allowing to measure signals (elastic waves). These tests demonstrate the dependency of the stress with strain rate and temperature. Dynamic restoration and recrystallization phenomena, characteristic of a material deformed in its hot working area, have also been identified. The associated oscillations due to Pochhammer–Chree effect, observable on the stress–strain curves, constitute the major problem for the implementation of behavioral models. Finally, a constitutive model sensitive to strain rate and temperature is investigated for ballistic purposes.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Influence of filler hybridization on thermomechanical properties of hemp/silver epoxy composite

2020 ◽  
pp. 096739112097811
Author(s):  
Munjula Siva Kumar ◽  
Santosh Kumar ◽  
Krushna Gouda ◽  
Sumit Bhowmik
Keyword(s):  
Thermal Conductivity ◽  
Silver Nanoparticles ◽  
Epoxy Polymer ◽  
Hybrid Composites ◽  
Conductive Filler ◽  
Weight Fraction ◽  
Mechanical Analysis ◽  
Thermomechanical Properties ◽  
Material Behavior ◽  
Good Crystallinity

The polymer composite material’s thermomechanical properties with fiber as reinforcement material have been widely studied in the last few decades. However, these fiber-based polymer composites exhibit problems such as fiber orientation, delamination, fiber defect along the length and bonding are the matter of serious concern in order to improve the thermomechanical properties and obtain isotropic material behavior. In the present investigation filler-based composite material is developed using natural hemp and high thermal conductive silver nanoparticles (SNP) and combination of dual fillers in neat epoxy polymer to investigate the synergetic influence. Among various organic natural fillers hemp filler depicts good crystallinity characteristics, so selected as a biocompatible filler along with SNP conductive filler. For enhancing their thermal conductivity and mechanical properties, hybridization of hemp filler along with silver nanoparticles are conducted. The composites samples are prepared with three different combinations such as sole SNP, sole hemp and hybrid (SNP and hemp) are prepared to understand their solo and hybrid combination. From results it is examined that, chemical treated hemp filler has to maximized its relative properties and showed, 40% weight % of silver nanoparticles composites have highest thermal conductivity 1.00 W/mK followed with hemp filler 0.55 W/mK and hybrid 0.76 W/mK composites at 7.5% of weight fraction and 47.5% of weight fraction respectively. The highest tensile strength is obtained for SNP composite 32.03 MPa and highest young’s modulus is obtained for hybrid composites. Dynamic mechanical analysis is conducted to find their respective storage modulus and glass transition temperature and that, the recorded maximum for SNP composites with 3.23 GPa and 90°C respectively. Scanning electron microscopy examinations clearly illustrated that formation of thermal conductivity chain is significant with nano and micro fillers incorporation.

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