STRAIN RATE–DEPENDENT BEHAVIOR OF UNCURED RUBBER: EXPERIMENTAL INVESTIGATION AND CONSTITUTIVE MODELING

2022 ◽  
Author(s):  
Sanghyeub Kim ◽  
Thomas Berger ◽  
Michael Kaliske
Keyword(s):  
Strain Rate ◽  
Evolution Equations ◽  
Cyclic Creep ◽  
Tensile Tests ◽  
Internal Variables ◽  
Creep Tests ◽  
Rate Dependent ◽  
Nonlinear Viscosity ◽  
Dependent Behavior ◽  
Building Process

ABSTRACT The strain rate dependence of uncured rubber is investigated through a series of tensile tests (monotonic, multistep relaxation, cyclic creep tests) at different strain rates. In addition, loading/unloading tests in which the strain rate is varied every cycle are carried out to observe their dependence on the deformation history. A strain rate–dependent viscoelastic–viscoplastic constitutive model is proposed with the nonlinear viscosity and process-dependent recovery properties observed in the test results. Those properties are implemented by introducing evolution equations for additional internal variables. The identified material parameters capture the experiments qualitatively well. The proposed model is also evaluated by finite element simulations of the building process of a tire, followed by the in-molding.

Constitutive Modeling of the Rate-Dependent Behavior of Ti-6Al-4V Using an Arrhenius-Type Law

2012 ◽  
Vol 591-593 ◽  
pp. 949-954
Author(s):  
Jun Jie Xiao ◽  
Dong Sheng Li ◽  
Xiao Qiang Li ◽  
Chao Hai Jin ◽  
Chao Zhang
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Tensile Tests ◽  
Alloy Sheet ◽  
Uniaxial Tensile ◽  
Thin Wall ◽  
Rate Dependent ◽  
Hot Environment ◽  
Dependent Behavior ◽  
Element Simulation

Uniaxial tensile tests were performed on a Ti-6Al-4V alloy sheet over the temperature range of 923K-1023K with the strain rates of 5×10-4s-1-5×10-2s-1 up to a 25% length elongation of the specimen. The true stress-strain curves reveal that the flow stress decreases with the increase of the temperature and the decrease of the strain rate. In the same process, the accompanying softening role increases. It is found that the Ti-6Al-4V shows the features of non-linearity, temperature sensitivity and strain rate dependence in hot environment. Finally, an Arrhenius-type law has been established to predict the experimental data and the prediction precision was verified by the plotting of parameter and flow stress, which revealed that the error of stress exponent was only 4.99%. This indicates the flow stress model has high precision and can be used for the process design and the finite element simulation of hot forming thin-wall Ti-6Al-4V alloy components.

scholarly journals Influence of strain rate and heat treatments on tensile and creep properties of Zn-0.15Cu-0.07Ti alloys

DYNA ◽  
2016 ◽  
Vol 83 (195) ◽  
pp. 77-83 ◽  
Author(s):  
María José Quintana Hernández ◽  
José Ovidio García ◽  
Roberto González Ojeda ◽  
José Ignacio Verdeja
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Strain Rates ◽  
Creep Tests ◽  
Design Problems ◽  
Creep Properties ◽  
Heat Treated ◽  
Zn Alloys

The use of Cu and Ti in Zn alloys improves mechanical properties as solid solution and dispersoid particles (grain refiners) may harden the material and reduce creep deformation. This is one of the main design problems for parts made with Zn alloys, even at room temperature. In this work the mechanical behavior of a Zn-Cu-Ti low alloy is presented using tensile tests at different strain rates, as well as creep tests at different loads to obtain the value of the strain rate coefficient m in samples parallel and perpendicular to the rolling direction of the Zn strip. The microstructure of the alloy in its raw state, as well as heat treated at 250°C, is also analyzed, as the banded structure produced by rolling influences the strengthening mechanisms that can be achieved through the treatment parameters.

scholarly journals Strain Rate Dependent Behavior of Vinyl Nitrile Helmet Foam in Compression and Combined Compression and Shear

2020 ◽  
Vol 10 (22) ◽  
pp. 8286
Author(s):  
Nicolas Bailly ◽  
Yvan Petit ◽  
Jean-Michel Desrosier ◽  
Olivier Laperriere ◽  
Simon Langlois ◽  
...  
Keyword(s):  
Strain Rate ◽  
Shear Loading ◽  
Combined Loading ◽  
Impact Behavior ◽  
Rate Variation ◽  
Shear Stresses ◽  
Absorbed Energy ◽  
Static Compression ◽  
Rate Dependent ◽  
Dependent Behavior

Vinyl nitrile foams are polymeric closed-cell foam commonly used for energy absorption in helmets. However, their impact behavior has never been described in isolation. This study aims to characterize the strain rate dependent behavior of three VN foams in compression and combined compression and shear. Vinyl nitrile samples of density 97.5, 125, and 183 kg/m3 were submitted to quasi-static compression (0.01 s−1) and impacts in compression and combined compression and shear (loading direction of 45°). For impacts, a drop test rig was used, and a method was developed to account for strain rate variation during impactor deceleration. Young’s modulus and stress at plateau were correlated with foam density in both compression and combined loading. Vinyl nitrile foams were strain rate dependent: The absorbed energy at the onset of densification was two to four times higher at 100 s−1 than at 0.01 s−1. In combined loading, the compressive stress at yield was reduced by 43% at a high strain rate. Compared to expanded polypropylene, vinyl nitrile foams transmitted less stress at the onset of densification for equivalent absorbed energy and presented a larger ratio between the compression and shear stresses in combined loading (0.37 at yield). This larger ratio between the compression and shear stresses might explain why vinyl nitrile helmet liners are thought to be better at reducing head rotational acceleration than expanded polypropylene helmet liners.

Strain-Rate Sensitive Constitutive Modeling of Anisotropic Visco-Hyperelastic Materials

2012 ◽  
Author(s):  
Sahand Ahsanizadeh ◽  
LePing Li
Keyword(s):  
Strain Rate ◽  
Evolution Equations ◽  
Mechanical Response ◽  
Viscoelastic Behavior ◽  
Biological Tissues ◽  
Internal Variables ◽  
Current Configuration ◽  
Hyperelastic Materials ◽  
History Of ◽  
Viscoelastic Constitutive Model

Integral-based formulations of viscoelasticity have been widely used to describe the mechanical behavior of soft biological tissues and polymers. However, it is suggested that they are not suitable to be used under high strain rates. On the other hand, strain-rate sensitive models with an explicit dependence on the strain-rate have been developed for a certain class of materials. They predict the viscoelastic behavior during ramp loading more accurately while fail to account for the relaxation response. In order to overcome these drawbacks, a viscoelastic constitutive model has been proposed in this study based on the concept of internal variables. While the behavior of elastic materials is uniquely determined by the current state of deformation or external variables, the mechanical response of inelastic materials are regulated also by internal variables. The internal variables are associated with the dissipative mechanisms in the material and along with the evolution equations introduce the effect of history of the deformation to the current configuration. The current study employs short-term and long-term internal variables to account for the viscoelastic response during loading and relaxation respectively.

Effect of Fiber Orientation and Strain Rate on the Nonlinear Uniaxial Tensile Material Properties of Tendon

2003 ◽  
Vol 125 (5) ◽  
pp. 726-731 ◽  
Author(s):  
Heather Anne Lynch ◽  
Wade Johannessen ◽  
Jeffrey P. Wu ◽  
Andrew Jawa ◽  
Dawn M. Elliott
Keyword(s):  
Stress Relaxation ◽  
Strain Rate ◽  
Material Properties ◽  
Poisson’S Ratio ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Poisson's Ratio ◽  
Fiber Direction ◽  
Linear Region ◽  
Rate Dependent

Tendons are exposed to complex loading scenarios that can only be quantified by mathematical models, requiring a full knowledge of tendon mechanical properties. This study measured the anisotropic, nonlinear, elastic material properties of tendon. Previous studies have primarily used constant strain-rate tensile tests to determine elastic modulus in the fiber direction. Data for Poisson’s ratio aligned with the fiber direction and all material properties transverse to the fiber direction are sparse. Additionally, it is not known whether quasi-static constant strain-rate tests represent equilibrium elastic tissue behavior. Incremental stress-relaxation and constant strain-rate tensile tests were performed on sheep flexor tendon samples aligned with the tendon fiber direction or transverse to the fiber direction to determine the anisotropic properties of toe-region modulus E0, linear-region modulus (E), and Poisson’s ratio (ν). Among the modulus values calculated, only fiber-aligned linear-region modulus E1 was found to be strain-rate dependent. The E1 calculated from the constant strain-rate tests were significantly greater than the value calculated from incremental stress-relaxation testing. Fiber-aligned toe-region modulus E10=10.5±4.7 MPa and linear-region modulus E1=34.0±15.5 MPa were consistently 2 orders of magnitude greater than transverse moduli (E20=0.055±0.044 MPa,E2=0.157±0.154 MPa). Poisson’s ratio values were not found to be rate-dependent in either the fiber-aligned (ν12=2.98±2.59, n=24) or transverse (ν21=0.488±0.653, n=22) directions, and average Poisson’s ratio values in the fiber-aligned direction were six times greater than in the transverse direction. The lack of strain-rate dependence of transverse properties demonstrates that slow constant strain-rate tests represent elastic properties in the transverse direction. However, the strain-rate dependence demonstrated by the fiber-aligned linear-region modulus suggests that incremental stress-relaxation tests are necessary to determine the equilibrium elastic properties of tendon, and may be more appropriate for determining the properties to be used in elastic mathematical models.

Athermal and Thermal Limits of the Grain Refinement by SPD

2008 ◽  
Vol 584-586 ◽  
pp. 938-943 ◽  
Author(s):  
Martin Hafok ◽  
Reinhard Pippan
Keyword(s):  
Strain Rate ◽  
Grain Refinement ◽  
Single Phase ◽  
High Pressure Torsion ◽  
Bulk Materials ◽  
Microstructural Refinement ◽  
Thermal Limits ◽  
Rate Dependent ◽  
Dependent Behavior ◽  
Saturation Region

Severe plastic deformation, SPD, enables the grain refinement of bulk materials. However, at strains larger than a critical value, no further microstructural refinement can be observed. This regime is denoted as saturation region of the microstructural size. It will be shown that this regime can be divided into a thermal and an athermal part. The transition between these two regimes was examined in an Al-3wt.%Mg alloy. The single phase alloy was deformed by high pressure torsion (HPT) at various temperatures and different rotational speeds. During the HPTdeformation the flow stress was measured by a torque cell in a temperature range between -196°C (evaporation temperature of the liquid nitrogen) and 450°C. The temperature and the strain rate dependent behavior reveal a shift of the onset of the thermal activated regime towards higher temperatures by an increase of the strain rate.

scholarly journals Characterization of Strain Rate-Dependent Behavior of 63Sn-37Pb Solder Using Split Hopkinson Torsional Bars (SHTB)

2001 ◽  
Author(s):  
Shi-Wei Ricky Lee ◽  
Lan Hong Dai
Keyword(s):  
Solder Joint ◽  
Strain Rate ◽  
Shear Loading ◽  
Rate Dependent ◽  
Dependent Behavior ◽  
Split Hopkinson ◽  
Dynamic Shear Strength ◽  
Torsion Bar ◽  
Dependent Behaviour

Abstract The present study is aimed at the experimental characterization of strain-rate dependent behaviour of solder materials under impulsive shear loading. In order to achieve this objective, a unique testing technique, namely, split Hopkinson torsion bar (SHTB) is employed. The solder material under investigation is 63Sn-37Pb. The experimental results indicate that the shear behavior of the solder joint is very sensitive to the strain rate and the dynamic shear strength of the solder joint is much higher than the static one.

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