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.

AN IMAGE BASED INERTIAL IMPACT TEST TO EXTRACT VISCOELASTIC CONSTITUTIVE PARAMETERS

2021 ◽  
Author(s):  
ANDREW MATEJUNAS ◽  
LLOYD FLETCHER ◽  
LESLIE LAMBERSON
Keyword(s):  
Strain Rate ◽  
Polymer Matrix ◽  
Mechanical Response ◽  
High Strain ◽  
High Rate ◽  
Strain Rates ◽  
High Strain Rates ◽  
Full Field ◽  
Viscoelastic Parameters ◽  
Constitutive Parameters

Polymer matrix composites often exhibit a strong strain rate dependance in their mechanical response. In many of these materials, the viscoelastic behavior of the polymer matrix drives the rate dependence in the composite, however identifying these parameters at high strain rate presents a significant challenge. Common high-rate material characterization techniques such as the Kolsky (split-Hopkinson pressure) bar require a large test matrix across a range of strain rates. Kolsky bars also struggle to identify constitutive parameters prior to the yield due to inertial effects and the finite period of time required to reach force equilibrium. The Image Based Inertial Impact (IBII) test has been successfully used to identify linear elastic constitutive behavior of composites at high strain rates, but, to date, has only been used to extract constitutive properties at a single nominal strain rate in each test. Here, we propose an adaptation of the IBII test to identify viscoelastic parameters at high strain rates using full-field displacement data and the nonlinear virtual fields method (VFM). We validate the technique with finite element simulations of an IBII test on a model viscoelastic material that is characterized with a Prony series formulation of the generalized Maxwell model. The nonlinear VFM is then used to extract the Prony pairs for dynamic moduli and time constants from the full-field deformation data. The nonlinear viscoelastic identification allows for characterization of the evolution of mechanical response across a range of strain rates in a single experiment. The experimentally identified viscoelastic parameters of the matrix can then be used to predict the behavior of the composite at high strain rates. This approach will also be validated experimentally using a single-stage gas-gun to characterize the high-rate viscoelastic response of PMMA.

Mechanical response of kerogen at high strain rates

2021 ◽  
pp. 103905
Author(s):  
Xiaohe Wang ◽  
Xianfu Huang ◽  
Mengni Gao ◽  
Ya-Pu Zhao
Keyword(s):  
Mechanical Response ◽  
High Strain ◽  
Strain Rates ◽  
High Strain Rates

Anisotropic Behaviour of AZ31B Sheet at High Strain Rates

2012 ◽  
Vol 151 ◽  
pp. 726-730 ◽  
Author(s):  
Iram Raza Ahmad ◽  
Dong Wei Shu
Keyword(s):  
Maximum Stress ◽  
Mechanical Response ◽  
High Strain ◽  
Rate Sensitivity ◽  
Tensile Loading ◽  
Strain Rates ◽  
High Strain Rates ◽  
Anisotropic Behaviour ◽  
Strain Behaviour ◽  
Tension Compression Asymmetry

The anisotropic effects on the mechanical response of AZ31B sheet at high strain rates have been analyzed. The experimental results indicate that the stress-strain behaviour of the alloy is highly anisotropic and rate sensitive. However, anisotropy of the mechanical properties of the alloy is less significant at higher strain rates. Under tensile loading, the anisotropic behaviour of the alloy is less significant as compare to its behaviour under compression. In both compression and tensile loading the alloy shows significant rate sensitivity as compare to quasi-static strain rates but at higher rates it is less significant. The maximum stress is observed to reach nearly 600 MPa for transverse direction impact. The tension-compression asymmetry is observed in the alloy.

scholarly journals Development of an experimental system to apply high rates of loading

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Pedro Barata ◽  
Aldina Santiago ◽  
João P. C. Rodrigues ◽  
Constança Rigueiro
Keyword(s):  
Design Methodology ◽  
High Strain ◽  
Impact Force ◽  
Experimental System ◽  
Experimental Tests ◽  
Pneumatic Cylinder ◽  
Strain Rates ◽  
High Strain Rates ◽  
Ongoing Research ◽  
Set Up

Purpose The purpose of this paper is to develop an experimental system to apply high rates of loading, in order to characterize the behaviour of bolted steel connections subjected to accidental loads, such as impact. The work presented in this paper is part of an ongoing research project at the University of Coimbra IMPACTFIRE PTDC/ECM/110807/2009. Design/methodology/approach The experimental set-up was designed to test under tension T-stubs andis capable to apply high strain rates. The test rig comprises a series of beams and steel elements placed horizontally, providing resistance and stiffness for the proposed tests. The loading system is operated by high pressure nitrogen and it comprises three main components: pneumatic reservoir, pneumatic cylinder and a rapidly opening valve, which and allows the instantaneous nitrogen flow from the reservoir to the cylinder. This paper presents a detailed description of the experimental components developed, designed and fabricated at University of Coimbra. Furthermore, the data acquisition system, the methodology for analysis of the results and the results of preliminary tests are also reported. Findings The results of the tests showed that the developed system is capable to apply an impact force in the specimens, the shape of the force and acceleration, in terms of duration and magnitude provided by the system showed that the system is capable to apply and simulate an impact force in specimens under tension. Moreover, the results reached under high rates of loading are compared with those reached under quasi-static loading; an increase of the plastic and ultimate resistances and a decrease of the deformation capacity are noticed. Originality/value The value of this paper is to describe the development of a new experimental system to perform tests at high strain rates. The results of the experimental tests of T-stub under tension are presented herein.

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