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.

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.

Strength of frozen sand containing tetrahydrofuran hydrate

1989 ◽  
Vol 26 (3) ◽  
pp. 479-483 ◽  
Author(s):  
V. R. Parameswaran ◽  
M. Paradis ◽  
Y. P. Handa
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Creep Behavior ◽  
Peak Stress ◽  
Strain Rates ◽  
Rate Region ◽  
Frozen Sand ◽  
Cylindrical Samples ◽  
Low Strain Rate

Cylindrical samples of frozen sand containing tetrahydrofuran hydrate were tested under uniaxial compression at 267 K and strain rates between 10−6 and 10−3 s−1. In the low strain rate region the compressive strength of the samples was higher than that of frozen sand containing ice. For example, at 267 K and a strain rate of 10−6 s−1 the peak stress for the frozen sand containing hydrate was about 16 MPa, whereas the corresponding value for the frozen sand containing ice was only 10.5 MPa. The strain rate dependence of stress for the frozen sand containing hydrate was much smaller than that of frozen sand containing ice, so that at higher strain rates the compressive strengths of the two materials become almost the same. Key words: tetrahydrofuran hydrate, frozen sand, mechanical properties, compressive strength, creep behavior.

A Study on the Evolution of the High Strain Rate Mechanical Properties of SAC105 Leadfree Alloy at High Operating Temperatures

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Lead Free ◽  
Electronic Systems ◽  
Strain Rates ◽  
High Strain Rates ◽  
Solder Interconnects

Electronics products may often be exposed to high temperature during storage, operation and handling in addition to high strain rate transient dynamic loads during drop-impact. Electronics subjected to drop-impact, shock and vibration may experience strain rates of 1–100 per sec. There are no material properties available in published literature at high strain rate at elevated temperature. High temperature and vibrations can contribute to the failures of electronic system. The reliability of electronic products can be improved through a thorough understanding of the weakest link in the electronic systems which is the solder interconnects. The solder interconnects accrue damage much faster when subjected to Shock and vibration at elevated temperatures. There is lack of fundamental understanding of reliability of electronic systems subjected to thermal loads. Previous studies have showed the effect of high strain rates and thermal aging on the mechanical properties of leadfree alloys including elastic modulus and the ultimate tensile strength. Extended period of thermal aging has been shown to affect the mechanical properties of lead free alloys including elastic modulus and the ultimate tensile strength at low strain rates representative of thermal fatigue [Lee 2012, Motalab 2012]. Previously, the microstructure, mechanical response and failure behavior of leadfree solder alloys when subjected to elevated isothermal aging and/or thermal cycling [Darveaux 2005, Ding 2007, Pang 2004] have been measured. Pang [1998] has showed that young’s modulus and yield stress of Sn-Pb are highly depending on strain rate and temperature. The ANAND viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components. Previously, Mechanical properties of lead-free alloys, at different high strain rates (10, 35, 50, 75 /sec) and elevated temperature (25 C-125 C) for pristine samples have been studied [Lall 2012 and Lall 2014]. Previous researchers [Suh 2007 and Jenq 2009] have determined the mechanical properties of SAC105 at very high strain rate (Above 1000 per sec) using compression testing. But there is no data available in published literature at high strain rate and at elevated temperature for aged conditions. In this study, mechanical properties of lead free SAC105 has been determined for high strain rate at elevated temperature for aged samples. Effect of aging on mechanical properties of SAC105 alloy a high strain rates has been studied. Stress-Strain curves have been plotted over a wide range of strain rates and temperatures for aged specimen. Experimental data for the aged specimen has been fit to the ANAND’s viscoplastic model. SAC105 leadfree alloys have been tested at strain rates of 10, 35, 50 and 75 per sec at various operating temperatures of 50°C, 75°C, 100°C and 125°C. The test samples were exposed to isothermal aging conditions at 50°C for different aging time (30, 60, and 120 Days) before testing. Full-field strain in the specimen have been measured using high speed imaging at frame rates up to 75,000 fps in combination with digital image correlation. The cross-head velocity has been measured prior-to, during, and after deformation to ensure the constancy of cross-head velocity.

scholarly journals Microstructure and Mechanical Properties of Laser Welded 6061-T6 Aluminum Alloy under High Strain Rates

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1145
Author(s):  
Jincheng Nie ◽  
Shengci Li ◽  
Huilong Zhong ◽  
Changjing Hu ◽  
Xiangsong Lin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Aluminum Alloy ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Base Material ◽  
Strain Rates ◽  
High Strain Rates ◽  
Plastic Deformation Region

Laser welding is widely used for the joining of aluminum alloy in the automotive industry, and the vehicles produced are inevitably subjected to high strain rate loading during their service. Therefore, this paper studied the mechanical properties of 6061-T6 aluminum alloy and its laser welded joint at strain rates between 0.0003 and 1000 s−1. Results showed that the microstructure of welded material (WM) was much finer than base material (BM), typical columnar crystals grew perpendicularly to the fusion line, and the minimum hardness value (~56 HV) was obtained inside WM. The strength and dynamic factors of BM and WM increased with increasing strain rate, and the strength of WM was less sensitive to strain rate compared with BM. The strain rate effect was not homogenous in the plastic deformation region. The modified Johnson–Cook (J–C) model which introduced the term C = C1 + C2·ε could well describe the dynamic plastic deformation of BM. However, the fitted results of the simplified J–C model were overall better than the modified J–C model for WM, especially for high strain rate (1000 s−1). These findings will benefit the determination of the dynamic deformation behavior of laser welded aluminum alloy under high strain rates, and could provide a better understanding of lightweight and the safety of vehicles.

Dynamic Characterization of Additively Manufactured Polylactide (PLA)

2021 ◽  
pp. 146442072110651
Author(s):  
GTL Priyanka ◽  
Ch. Saideep ◽  
T. Tadepalli
Keyword(s):  
Compressive Strength ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Fused Deposition Modelling ◽  
Strain Rates ◽  
Simple Modification ◽  
Fused Deposition ◽  
Softening Behavior ◽  
3D Printed

Additively manufactured materials have excellent properties with wide applications in many industries. For designing components exposed to extreme loading situations, it is essential to characterize the high strain rate response of 3D printed (fused deposition modelling) materials. In this study, uniaxial quasi-static and dynamic compressive tests were carried out at various strain rates (10−2 s−1 and 200 s−1 to 1800 s−1) for 3D printed PLA. Strain rate dependent compressive response of Polylactide acid (PLA) disk specimens 3D printed at 0°, 45° and 90° orientations was obtained using the Split Hopkinson bar technique. The results show that the compressive strength increases with corresponding strain rates for 0° and 45° print orientations. PLA printed at 0° has higher compressive strength compared to 45° and 90° orientations under quasi-static as well as high strain rate loading. Toughness was observed to increase with strain rate in all three orientations. A simple modification to the Johnson-Cook model is proposed, which accounts for the effects of print orientation, porosity and strain softening behavior.

scholarly journals Study on the Effect of Sample Temperature on the Uniaxial Compressive Mechanical Properties of the Brain Tissue

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Fengjiao Guan ◽  
Guanjun Zhang ◽  
Xiaohang Jia ◽  
Xiaopeng Deng
Keyword(s):  
Mechanical Properties ◽  
High Strain Rate ◽  
Strain Rate ◽  
Brain Tissue ◽  
High Strain ◽  
Material Behavior ◽  
Sample Temperature ◽  
Temperature Dependency ◽  
The Brain ◽  
Low Strain Rate

Craniocerebral injury has been a research focus in the field of injury biomechanics. Although experimental endeavors have made certain progress in characterizing the material behavior of the brain, the temperature dependency of brain mechanics appears to be inconclusive thus far. To partially address this knowledge gap, the current study measured the brain material behavior via unconstrained uniaxial compression tests under low strain rate (0.0083 s-1) and high strain rate (0.83 s-1) at four different sample temperatures (13°C, 20°C, 27°C, and 37°C). Each group has 9~12 samples. One-way analysis of variance method was used to study the influence of sample temperature on engineering stress. The results show that the effect of sample temperature on the mechanical properties of brain tissue is significant under the high strain rate, especially at low temperature (13°C), in which the hardening of the brain tissue is very obvious. At the low strain rate, no temperature dependency of brain mechanics is noted. Therefore, the current results highlight that the temperature of the brain sample should be ensured to be in accordance with the living subject when studying the biomechanical response of living tissue.

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.

scholarly journals Static Mechanical Properties of Expanded Polypropylene Crushable Foam

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 249
Author(s):  
Przemysław Rumianek ◽  
Tomasz Dobosz ◽  
Radosław Nowak ◽  
Piotr Dziewit ◽  
Andrzej Aromiński
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Experimental Tests ◽  
Absorption Capacity ◽  
Strain Rates ◽  
Foam Density ◽  
Energy Absorption Capacity ◽  
Closed Cell

Closed-cell expanded polypropylene (EPP) foam is commonly used in car bumpers for the purpose of absorbing energy impacts. Characterization of the foam’s mechanical properties at varying strain rates is essential for selecting the proper material used as a protective structure in dynamic loading application. The aim of the study was to investigate the influence of loading strain rate, material density, and microstructure on compressive strength and energy absorption capacity for closed-cell polymeric foams. We performed quasi-static compressive strength tests with strain rates in the range of 0.2 to 25 mm/s, using a hydraulically controlled material testing system (MTS) for different foam densities in the range 20 g/dm3 to 220 g/dm3. The above tests were carried out as numerical simulation using ABAQUS software. The verification of the properties was carried out on the basis of experimental tests and simulations performed using the finite element method. The method of modelling the structure of the tested sample has an impact on the stress values. Experimental tests were performed for various loads and at various initial temperatures of the tested sample. We found that increasing both the strain rate of loading and foam density raised the compressive strength and energy absorption capacity. Increasing the ambient and tested sample temperature caused a decrease in compressive strength and energy absorption capacity. For the same foam density, differences in foam microstructures were causing differences in strength and energy absorption capacity when testing at the same loading strain rate. To sum up, tuning the microstructure of foams could be used to acquire desired global materials properties. Precise material description extends the possibility of using EPP foams in various applications.

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