Deformation and Fracture of a Silicate Melt Around Tg: Implications to Dynamics of Volcanic Eruptions

2008 ◽  
Author(s):  
Mie Ichihara ◽  
Daniel Rittel ◽  
M. B. Rubin
Keyword(s):  
Strain Rate ◽  
Work Hardening ◽  
High Strain ◽  
Elastic Solid ◽  
Volcanic Eruptions ◽  
Strain Rates ◽  
Stress Strain Relation ◽  
Deformation And Fracture ◽  
Fracture Transition ◽  
Low Strain Rate

The mechanical properties of magma around the glass transition temperature have not been characterized yet, though this subject is considered to be important in dynamics of volcanic eruptions. In this paper, we present an experimental investigation of stress-strain relation of synthetic magma at various temperatures and strain rates. The material behaves as an elastic solid at low temperature and/or high strain rate, and as a viscous fluid at high temperature and/or low strain rate. In the transition, it reveals work-hardening response. Although the work-hardening nature has not been reported for noncrystalline magma, it is important in constructing a mathematical model to represent the flow-to-fracture transition of magma, namely the transition of eruptions from effusive to explosive styles.

Three-Parameter Viscoelasticity Models for Ballistic Fabrics

2008 ◽  
Author(s):  
N. V. David ◽  
X.-L. Gao ◽  
J. Q. Zheng ◽  
K. Masters
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Constitutive Relations ◽  
Viscoelastic Behavior ◽  
Strain Rates ◽  
Rheological Models ◽  
Maxwell Element ◽  
In Series ◽  
Low Strain Rate

Ballistic fabrics are made from high performance polymeric fibers such as Kevlar®, Twaron® and Spectra®. These fibers often behave viscoelastically in high strain rate deformations. The Kelvin-Voigt and Maxwell rheological models have been used to characterize such viscoelastic responses at different strain rates. However, these two-parameter models have been found to be inadequate and inaccurate in some applications. As a result, three-parameter rheological models have been utilized to develop constitutive relations for viscoelastic polymeric fabrics. In this study, a generalized Maxwell (GM) model and a generalized Kelvin-Voigt (GKV) model are proposed to describe the viscoelastic behavior of a ballistic fabric, Twaron® CT716, at the strain rates of 1 s−1 and 495 s−1. The GM model consists of a Maxwell element (including a viscous dashpot and a spring in series) and a second spring in parallel to the Maxwell element, while the GKV model is an assembly of a Kelvin-Voigt (KV) element (containing a viscous dashpot and a spring in parallel) and a second spring in series with the KV element. The predictions by the GM and GKV models are compared with existing experimental data, which shows that the two sets of results are in fairly good agreement. In particular, the comparison reveals that the GKV model gives more accurate results at the low strain rate, whereas the GM model performs better at the high strain rate while still providing accurate predictions for the low strain rate responses.

An Investigation of Microstructure Inhomogeneity in Waspaloy Subjected to Plane Strain Compression Testing

2007 ◽  
Vol 558-559 ◽  
pp. 589-594 ◽  
Author(s):  
M.J. Thomas ◽  
Bradley P. Wynne ◽  
Eric J. Palmiere ◽  
Ken P. Mingard ◽  
Bryan Roebuck
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Plane Strain ◽  
High Strain ◽  
Plane Strain Compression ◽  
Strain Rates ◽  
Nickel Based Superalloy ◽  
Nominal Strain ◽  
Plane Strain Compression Test ◽  
Low Strain Rate

An assessment of the inhomogeneity of microstructure generated within plane strain compression test specimens has been performed using the nickel based superalloy, Waspaloy. Two variables were investigated: the effect of strain rate and the effect of friction at the tool/specimen interface. Tests were performed at 1040°C at nominal strain rates of 0.01 and 1 s-1 with and without a glass based lubricant. At the low strain rate the microstructure was relatively homogeneous regardless of the friction conditions. At the high strain rate there was significant microstructure variation from surface to mid plane which was further exaggerated by increased friction. Quantification of the inhomogeneity, however, is non-trivial in this alloy due to the complicated recrystallisation behaviour it exhibits and difficulty in differentiating between recrystallised and non-recrystallised grains.

scholarly journals Investigation on Mechanical Properties of GH4720Li at High Strain Rates at Wider Temperature Range

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Chen ◽  
Haifeng Zhang ◽  
Yunlong Zhang ◽  
Hongtao Zhang ◽  
Qingxiang Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
True Stress ◽  
Strain Rates ◽  
Hot Compression Test ◽  
Strength And Plasticity ◽  
Low Strain Rate

In this paper, the dynamic mechanical properties of GH4720Li nickel-base alloy under a large temperature range and high and low strain rates were studied by the hot compression test. The difference of mechanical properties of GH4720Li alloy under high and low strain rates was analyzed from the perspective of microstructure. The hot compression test experimental results showed that the true stress of GH4720Li alloy decreased at a low strain rate as the trial temperature elevated. Nevertheless, it was abnormal that the true stress increased at high strain rate condition as temperature elevated. By comparing the microstructure under high and low strain rates, it was found that the precipitates under low strain conditions contained a large amount of Cr (Mo). However, the content of Cr (Mo) in the precipitates at a high strain rate decreased, while the content of Fe increased. It would be concluded that Cr (Mo) would reduce the compressive strength and plasticity of GH4720Li alloy, while Fe would increase the compressive strength and plasticity of GH4720Li alloy. In addition, under the condition of a low strain rate, the shape of Cr (Mo) precipitates obtained at 20°C was lamellar, but it was spherical at 800°C. The compressive strength of GH4720Li composites with lamellar precipitates was higher than that of spherical precipitates.

BRITTLE FRAGMENTATION OF AN EXPANDING RING BY MOLECULAR DYNAMICS

2013 ◽  
Vol 02 (02) ◽  
pp. 1350010
Author(s):  
GUOWU REN ◽  
TIEGANG TANG ◽  
ZHAOLIANG GUO ◽  
YUANSHUAI YANG ◽  
QINGZHONG LI
Keyword(s):  
Strain Rate ◽  
Physical Mechanism ◽  
High Strain ◽  
Fragmentation Process ◽  
Strain Rates ◽  
Anisotropic Behavior ◽  
Wide Range ◽  
Low Strain Rate ◽  
Brittle Fragmentation ◽  
Random Defect

In this paper, the brittle fragmentation of an expanding ring is numerically studied by a simple atomistic model. We investigate the statistical distribution of fragment spanned over a wide range of strain rates when damage related to broken bond reaches a steady state. It is shown that at low strain rate limited number of heavy fragments can be generated because of anisotropic behavior while for high strain rate fragment can be well fitted with Weibull distribution. The physical mechanism of fragmentation process reveals that damage accompanying with numerous microcracks is found to initiate in the inner regime of the expanding ring. Furthermore, we discuss the effect of random defect on the fragmentation process.

Temperature-Dependent Tension Plastic Deformation and Fracture Behavior of Ti-6.6Al-3.3Mo-1.8Zr-0.29Si Alloy at High Strain Rates

2014 ◽  
Vol 626 ◽  
pp. 115-120
Author(s):  
Jun Zhang ◽  
Qi Wei Zhang ◽  
Yang Wang
Keyword(s):  
Strain Rate ◽  
Titanium Alloys ◽  
High Strain ◽  
Impact Resistance ◽  
Strain Rates ◽  
Temperature Dependent ◽  
High Strain Rates ◽  
Tension Tests ◽  
Deformation And Fracture ◽  
Split Hopkinson

Titanium alloys have received great interest in the engineering applications requiring light weight and high impact resistance components. It is necessary to understand the mechanical properties of titanium alloys at high strain rates and various temperatures in the structural design. In the present paper, uniaxial tension tests at strain rates of 190, 500 and 1150s-1 and temperatures of 20, 150, 300°C are carried out using a modified split hopkinson tension bar system to investigate the effects of strain rate and temperature on tension behavior of the Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy. Experimental results indicate that the alloy has the rate and temperature sensitivity and still keeps high strengths and toughness at temperature up to 300°C under high strain rate. SEM observations reveal that ductile fracture is the major fracture mode when the alloy is deformed at high strain rates.

Mechanical Behavior of Rubber at High Strain Rates

2006 ◽  
Vol 79 (3) ◽  
pp. 429-459 ◽  
Author(s):  
C. M. Roland
Keyword(s):  
Hydrostatic Pressure ◽  
Strain Rate ◽  
Mechanical Response ◽  
High Strain ◽  
Glassy State ◽  
Hopkinson Bar ◽  
Strain Rates ◽  
Rate Data ◽  
Split Hopkinson ◽  
Low Strain Rate

Abstract Methods to obtain the mechanical response of rubber at high rates of strain are reviewed. These techniques include the extrapolation of low strain, low strain rate data, the limitations of which are discussed, extrapolations to elevated hydrostatic pressure, and direct determinations using split Hopkinson bar and drop weight testers, as well as miscellaneous methods. Some applications involving rubber at strain rates sufficient to induce a transition to the glassy state are described.

A Study on High Speed Tension Property of C-Grade Bullet Proof Steel Plate

2014 ◽  
Vol 1063 ◽  
pp. 59-64
Author(s):  
Ming Tu Ma ◽  
Yan Zhao ◽  
Gang Fang ◽  
Yi Feng
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Speed ◽  
Steel Plate ◽  
High Strain ◽  
High Strength ◽  
Sem Analysis ◽  
Strain Rates ◽  
Deformation And Fracture ◽  
Tension Experiments

In this paper, the high speed tension experiments have been performed on ultra high strength bullet proof steel. The samples were cut from the bullet proof steel plate after hard-module quenching with thickness of 3.7 mm. The mechanical properties at strain rates of 0.001 s-1, 0.01 s-1, 0.1 s-1 and 1 s-1 were carried out on MTS810, while those at higher strain rates of 200 s-1, 500s-1 and 1000s-1 were tested on HTM5020 high speed tension tester and Hopkinson bar. The data from the high-speed tension experiments were fitted via Johnson-Cook constitutive equation, and the fracture surface of each sample was analyzed by SEM. The results indicate that, the shoot-resistance capability of bullet proof steel is closely related to its strength, thickness and flow behaviors under high strain rate. The shoot-resistance will be improved in the case of higher strength and better matching between strength and elongation. The Johnson-Cook equation fitted via experimental data provides fundament to numerical simulation. With the increase of strain rate, the size and depth of dimple trend to decrease and the depth of dimple changes less in steel with lower strength and higher elongation. The SEM analysis of fracture is benefit for further understanding of deformation and fracture mode under high strain rate.

High Strain Rate Behavior of Sn3.8Ag0.7Cu Solder Alloys and Its Influence on the Fracture Location Within Solder Joints

2009 ◽  
Author(s):  
Dennis Chan ◽  
Xu Nie ◽  
Dhruv Bhate ◽  
Ganesh Subbarayan ◽  
Indranath Dutta
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Solder Alloy ◽  
High Strain ◽  
Strain Rates ◽  
Solder Alloys ◽  
Snagcu Solder ◽  
Rate Behavior ◽  
Strain Rate Behavior ◽  
Low Strain Rate

Significant work has been done on the characterization of SnAgCu solder alloys at low strain rates (10−6 to 10−2s−1), and as a result, the behavior of solder over these strain rate regimes is well understood. On the other hand, there is a lack of accurate and consistent data for solder at high strain rates. In this paper, we will present data obtained using a servo-hydraulic mechanical tester and split-Hopkinson bar for the Sn3.8wt%Ag0.7wt% Cu solder alloy over strain rates spanning 0.001 to 500s−1. It is shown that the saturation stress correlates well with strain rate over nine decades on a log-log plot. It is also shown that a fit using Anand model based on low strain rate regime (4×10−6 to 2×10−4s−1) data captures the high strain rate results to a reasonable accuracy. It is commonly observed that in low strain rate failure, as in thermo-mechanical fatigue, failure tends to occur through the bulk of the solder. However in high strain rate failures, as those seen in drop tests, fractures occur through the intermetallic layer. We present finite element simulations of ball shear and ball pull tests using the above high strain rate data. It is demonstrated how the shift in failure mode from the bulk solder to intermetallic compound may be explained based on the high strain rate behavior of the SnAgCu solder alloy.

Compressive Behavior of ME20M Magnesium Alloy at Low Temperatures

2021 ◽  
Vol 902 ◽  
pp. 15-19
Author(s):  
Jin Wang ◽  
Yang Wang ◽  
Zi Ran Li
Keyword(s):  
Flow Stress ◽  
Magnesium Alloy ◽  
Strain Rate ◽  
Low Temperatures ◽  
High Strain ◽  
Rolling Direction ◽  
Strain Rates ◽  
Compressive Behavior ◽  
Main Fracture ◽  
Low Strain Rate

The compressive behavior of ME20M alloy along rolling direction (RD) at a wide strain rates under low temperatures is investigated in this paper. Compressive stress-strain results reveal that the effect of strain rate on yield strength and flow stress is not obvious, especially at low temperatures. Moreover, the temperature plays an important role in compressive responses. SEM observations indicate that brittle fracture is the main fracture mode at low strain rate, and ductile fracture occurs in the failure of the alloy at high strain rate.

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