Local identification of the stress–strain curves of metals at a high strain rate using repeated micro-impact testing

This paper presents data obtained from a newly-developed instrument to test the quality of solder interconnections at high strain rate – the ‘micro-impactor’. This shear test of the interconnection at high strain rate mimics the stress experienced by the solder joint when undergoing shock due to drop-impact. Instrumented with a load cell and linear variable displacement transducer (LVDT), it also has the ability to provide dynamic impact force and displacement data. Earlier concepts to characterise the solder joint at high strain rates such as the miniature pendulum impact tester [1] lacked this capability. This micro-impactor was used to study the effect of increasing silver (Ag) and copper (Cu) concentration in solder alloys on the shear strength of the solder joint. The performance of these lead-free alloys was also compared to that of the well-established leaded solder. It was found that increasing the silver content increases the yield strength of the solder, causing the failure to occur at the brittle intermetallic layer instead of in the bulk of the solder.

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High strain rate stress-strain response of soils - A review

Japanese Geotechnical Society Special Publication ◽

10.3208/jgssp.v03.i13 ◽

2015 ◽

Vol 3 (2) ◽

pp. 80-85

Author(s):

Sunita Mishra ◽

Tanusree Chakraborty ◽

Dipanjan Basu

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Strain Response ◽

Stress Strain

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High Strain-Rate Compressive Behavior and Constitutive Modeling of Selected Polymers Using Modified Ramberg-Osgood Equation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.566.80 ◽

2014 ◽

Vol 566 ◽

pp. 80-85

Author(s):

Kenji Nakai ◽

Takashi Yokoyama

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Compressive Stress ◽

Constitutive Modeling ◽

High Strain ◽

Strain Rates ◽

Stress Strain ◽

Strain Behavior ◽

Least Squares Fit ◽

Wide Range

The present paper is concerned with constitutive modeling of the compressive stress-strain behavior of selected polymers at strain rates from 10-3 to 103/s using a modified Ramberg-Osgood equation. High strain-rate compressive stress-strain curves up to strains of nearly 0.08 for four different commercially available extruded polymers were determined on the standard split Hopkinson pressure bar (SHPB). The low and intermediate strain-rate compressive stress-strain relations were measured in an Instron testing machine. Six parameters in the modified Ramberg-Osgood equation were determined by fitting to the experimental stress-strain data using a least-squares fit. It was shown that the monotonic compressive stress-strain behavior over a wide range of strain rates can successfully be described by the modified Ramberg-Osgood constitutive model. The limitations of the model were discussed.

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High strain-rate behavior of natural fiber-reinforced polymer composites

Journal of Composite Materials ◽

10.1177/0021998311414946 ◽

2011 ◽

Vol 46 (9) ◽

pp. 1051-1065 ◽

Cited By ~ 31

Author(s):

Wonsuk Kim ◽

Alan Argento ◽

Ellen Lee ◽

Cynthia Flanigan ◽

Daniel Houston ◽

...

Keyword(s):

Energy Dissipation ◽

High Strain Rate ◽

Strain Rate ◽

Polymer Composites ◽

Natural Fiber ◽

High Strain ◽

Split Hopkinson Pressure Bar ◽

Natural Fibers ◽

Hopkinson Pressure Bar ◽

Stress Strain

The high strain-rate constitutive behavior of polymer composites with various natural fibers is studied. Hemp, hemp/glass hybrid, cellulose, and wheat straw-reinforced polymeric composites have been manufactured, and a split-Hopkinson pressure bar apparatus has been designed to measure the dynamic stress–strain response of the materials. Using the apparatus, compressive stress–strain curves have been obtained that reveal the materials’ constitutive characteristics at strain rates between 600 and 2400 strain/s. Primary findings indicate that natural fibers in thermoset composites dissipate energy at lower levels of stress and higher strain than glass-reinforced composites. In the case of thermoplastic matrices, the effect on energy dissipation of natural fibers vs. conventional talc reinforcements is highly dependent on resin properties. Natural fibers in polypropylene homopolymer show improved reinforcement but have degraded energy dissipation compared to talc. Whereas in polypropylene copolymer, natural fibers result in improved energy dissipation compared to talc. These data are useful for proper design, analysis, and simulation of lightweight biocomposites.

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