Deformation Behavior of FCC Crystalline Metallic Nanowires Under High Strain Rates

1998 ◽  
Vol 554 ◽  
Author(s):  
Yue Qi ◽  
Hideyuki Ikeda ◽  
Tahir Cagin ◽  
Konrad Samwer ◽  
William L. Johnson ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
Deformation Process ◽  
High Strain ◽  
Shear Instability ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Size Mismatch ◽  
Alloy Crystal ◽  
Critical Strain Rate ◽  
Pure Cu

AbstractWe used molecular dynamics (MD) methods to study the deformation behavior of metallic alloy crystal nanowires of pure Cu, NiCu alloy and NiAu alloy, under high rates of uniaxial tensile strain, ranging from 5* 108/s to 5* 10/s. These nanowires are just about 2 nm thick and hence cannot sustain dislocations, instead we find that deformation proceeds through twinning and coherent slipping mechanisms. NiAu has a 13% size mismatch whereas NiCu only 2.5%. As a result the critical strain rate at which the “nanowire crystals” flow like a “liquid” is 100 times smaller for NiAu. We also calculated the elastic constants at each strain state for all strain rates to identify the relation between mechanical “shear” instability and deformation process.

Dynamic Deformation Behavior of As-Extruded Mg-Gd-Y Magnesium Alloy and the Microstructural Evolution

2011 ◽  
Vol 284-286 ◽  
pp. 1579-1583
Author(s):  
Ping Li Mao ◽  
Zheng Liu ◽  
Chang Yi Wang ◽  
Feng Wang
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Strain Rates ◽  
Compression Axis ◽  
Deformation Localization ◽  
Dynamic Deformation Behavior

The dynamic deformation behavior of an as-extruded Mg-Gd-Y magnesium alloy was studied by using Split Hopkinson Pressure Bar (SHPB) apparatus under high strain rates of 102 s-1 to 103s-1 in the present work, in the mean while the microstructure evolution after deformation were inspected by OM and SEM. The results demonstrated that the material is not sensitive to the strain rate and with increasing the strain rate the yield stress of as-extruded Mg-Gd-Y magnesium alloy has a tendency of increasing. The microstructure observation results shown that several deformation localization areas with the width of 10mm formed in the strain rates of 465s-1 and 2140s-1 along the compression axis respectively, and the grain boundaries within the deformation localization area are parallel with each other and are perpendicular to the compression axis. While increasing the strain rate to 3767s-1 the deformation seems become uniform and all the grains are compressed flat in somewhat. The deformation mechanism of as-extruded Mg-Gd-Y magnesium alloy under high strain rate at room temperature was also discussed.

Impact tensile behavior and frequency response of 3D braided composites

2011 ◽  
Vol 82 (3) ◽  
pp. 280-287 ◽  
Author(s):  
Xuehui Gan ◽  
Jianhua Yan ◽  
Bohong Gu ◽  
Baozhong Sun
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Tensile Properties ◽  
High Strain ◽  
Tensile Modulus ◽  
Tensile Failure ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Braided Composites ◽  
3D Braided Composites

The uniaxial tensile properties of 4-step 3D braided E-glass/epoxy composites under quasi-static and high-strain rate loadings have been investigated to evaluate the tensile failure mode at different strain rates. The uniaxial tensile properties at high strain rates from 800/s to 2100/s were tested using the split Hopkinson tension bar (SHTB) technique. The tensile properties at quasi-static strain rate were also tested and compared with those in high strain rates. Z-transform theory is applied to 3D braided composites to characterize the system dynamic behaviors in frequency domain. The frequency responses and the stability of 3D braided composites under quasi-static and high-strain rate compression have been analyzed and discussed in the Z-transform domain. The results indicate that the stress-strain curves are rate sensitive, and tensile modulus, maximum tensile stress and corresponding tensile strain are also sensitive to the strain rate. The tensile modulus, maximum tensile stress of the 3D braided composites are linearly increased with the strain rate. With increasing of the strain rate (from 0.001/s to 2100/s), the tensile failure of the 3D braided composite specimens has a tendency of transition from ductile failure to brittle failure. The magnitude response and phase response is very different in quasi-static loading with that in high-strain rate loading. The 3D braided composite system is more stable at high strain rate than quasi-static loading.

Research on Numerical Algorithm of Constitutive Equation under High Speed Deformation in Hadfield Steel

2012 ◽  
Vol 562-564 ◽  
pp. 688-692 ◽  
Author(s):  
Deng Yue Sun ◽  
Jing Li ◽  
Fu Cheng Zhang ◽  
Feng Chao Liu ◽  
Ming Zhang
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Speed ◽  
High Strain ◽  
Equivalent Stress ◽  
Hadfield Steel ◽  
Stress And Strain ◽  
Strain Rates ◽  
The Finite Element Method

The influence of the strain rate on the plastic deformation of the metals was significant during the high strain rate of loading. However, it was very difficult to obtain high strain rate data (≥ 104 s-1) by experimental techniques. Therefore, the finite element method and iterative method were employed in this study. Numerical simulation was used to characterise the deformation behavior of Hadfield steel during explosion treatment. Base on experimental data, a modified Johnson-Cook equation for Hadfield steel under various strain rate was fitted. The development of two field variables was quantified during explosion hardening: equivalent stress and strain rates.

Deformation behavior of Al/Cu in-situ metal-intermetallic laminates at low and high strain rates

2021 ◽  
pp. 159767
Author(s):  
Kartheek. S.M. Sonti ◽  
Biswaranjan Dash ◽  
K.V. Vamsi ◽  
H. Bandyopadhyay ◽  
B. Ravisankar ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
High Strain ◽  
Strain Rates ◽  
High Strain Rates

A New Instrument for Tensile Testings of Thin Free Standing Films at High Strain Rates

2008 ◽  
Author(s):  
Eran Ben-David ◽  
Doron Shilo ◽  
Daniel Rittel ◽  
David Elata
Keyword(s):  
Mechanical Response ◽  
High Strain ◽  
Measurement Techniques ◽  
Experimental System ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
High Strain Rates ◽  
Optical Encoder ◽  
Free Standing ◽  
New Instrument

The design of more reliable and sophisticated Micro Electro Mechanical Systems (MEMS) relies on the knowledge, understanding, and ability to control their mechanical response. In recent years, enormous progress has been made in developing new measurement techniques for studying the mechanical response of sub-micro scale specimens. However, there is still a lack of knowledge and testing techniques regarding the response of MEMS structures to mechanical shocks, which can appear during fabrication, deployment, or operation. We present an instrument for testing the mechanical response of thin free standing films under uniaxial tensile stress at high strain rates of up to 2×103 sec-1. The experimental system consists of a micro-device, which contains the freestanding specimen, and an external system, which includes instrumentation for measuring its mechanical response. The components of the external system are controlled by a single interface, and allow for a variety of displacement profiles to be applied to the specimens. All the instrumentation operates at high sampling rates (above 1 MHz) to allow for high strain rate application. The freestanding specimen is produced by MEMS fabrication techniques on a micro-device that also includes S-springs to protect the specimen and aluminum grating lines for measuring the displacement. One side of the chip is pulled by a piezoelectric translation stage, which allows controlling the displacement with a nanometric resolution and applying high velocities and accelerations. The specimen displacement is monitored by an optical encoder device that measure the displacement of the aluminum grating located on the micro-device close to the specimen with an accuracy of about 10 nm. The load is determined by measuring the charge on a piezoelectric PMN-30%PT shear plate, which is connected to the pin that holds the micro-device. The new instrument is applied for studying the response of thin aluminum films with thickness of 0.5–1 μm, width that varies between 5 to 50 μm, and length of 120 μm. The mechanical response of these specimens is measured at different strain rates and is compared to measurement done by nanoindentation.

Evolution of Anand Parameters With Elevated Temperature Aging for SAC Leadfree Alloys

2019 ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Thermal Aging ◽  
High Strain ◽  
Lead Free ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
High Strain Rates ◽  
Free Solder ◽  
Sac Solder

Abstract Electronic components in downhole oil drilling and gas industry applications, automotive and avionics may exposed to high temperatures (> 150°C) and high strain rates (1–100 per sec) during storage, operation and handling which can contribute to the failures of electronics devices. Temperatures in these applications can exceed 200°C, which is closed to melting point for SAC alloys. The microstructure for lead free solder alloys constantly evolves when subjected to thermal aging for sustained periods with accompanying degradation in mechanical properties of solder alloys. In this paper, evolution of microstructure and Anand parameters for unaged and aged SAC (SAC105 and SAC-Q) lead free solder alloys at high strain rates has been investigated induced due to thermal aging. The microstructure of the SAC solder is studied using scanning electron microscopy (SEM) for different strain rate and elevating temperature. The thermal aged leadfree SAC solder alloys specimen has been tested at high strain rates (10–75 per sec) at elevated temperatures of (25°C–200°C). The SAC leadfree solder samples were subjected to isothermal aging at 50°C up to 1-year before testing. To describe the material constitutive behavior, Anand Viscoplastic model has been used. Effect of thermal aging on Anand parameters has been investigated. In order to verify the accuracy of the model, the computed Anand parameters have been used to simulate the uniaxial tensile test. FEA based method has been used to simulate the drop events using Anand constitutive model. Hysteresis loop and Plastic work density has been computed from FEA.

Excessive damage increase in dual phase steels under high strain rates and temperatures

2020 ◽  
pp. 105678952095805
Author(s):  
Merve Çobanoğlu ◽  
Rasim K Ertan ◽  
Caner Şimşir ◽  
Mert Efe
Keyword(s):  
Deformation Behavior ◽  
High Strain ◽  
Damage Parameter ◽  
Dynamic Strain ◽  
Dual Phase ◽  
Strain Rates ◽  
Dual Phase Steels ◽  
Complex Process ◽  
Ultrasonic Sound ◽  
Void Shape

Damage formation in dual phase steels is a complex process and it may be sensitive to the deformation conditions and mechanisms. In this study, the damage parameter is measured and compared under quasi-static and industrial forming conditions (temperatures: 25 vs 200, 300°C and strain rates: 10−3 vs 10 s−1) for DP590 and DP800 steels. Resonance frequency and ultrasonic sound velocity techniques are utilized for the measurements to test the effectiveness and validity of each technique. At a given strain, the damage values can be up to 700% higher at industrial forming conditions, under which dynamic strain aging (DSA) controls the deformation behavior. DSA results in lower formability and is the likely mechanism responsible from the abnormal damage evolution. Measured damage parameters are also confirmed with the void fraction characterization by microscopy, which also provided details on the void shape and distribution with respect to the deformation conditions.

A quantitative criterion for predicting solid-state disordering during biaxial, high strain rate deformation

2021 ◽  
Author(s):  
Michael Becker ◽  
Desiderio Kovar
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Strain State ◽  
Biaxial Loading ◽  
High Strain ◽  
Md Simulations ◽  
Strain Rates ◽  
Critical Strain Rate ◽  
Wide Range ◽  
High Strain Rate Deformation

Abstract A criterion to predict the onset of disordering under biaxial loading based on a critical potential energy per atom was studied. In contrast to previous theories for disordering, this criterion incorporates the effects of strain rate and strain state. The strain state (or stress state) is defined by the combination of strain (or stress) magnitudes and directions that are applied to each sample during the simulation. Τhe validity of this criterion was studied using molecular dynamic (MD) simulations of Ag conducted over a wide range of biaxial strain rates, strain configurations, and crystal orientations with respect to the applied stress state. Biaxial strains were applied in two different planes, (112 ̅) and (001) in eight directions in each plane. Results showed that, when larger strain rates were applied, there was a transition from plastic deformation driven by the nucleation and propagation of dislocations to disordering and viscous flow. Although the critical strain rate to initiate disorder was found to vary in the range of ε ̇ = 1×1011 s-1 to ε ̇ = 4×1011 s-1, a consistent minimum PE/atom of -2.7 eV was observed over a broad range of strain states and for both crystallographic orientations that were studied. This indicates that the critical PE/atom is a material property that can be used to predict the onset of disordering under biaxial loading. Further, the results showed that this criterion can be applied successfully even when non-uninform strain states arise in the crystal.  

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