Shock compression of solids

Experimental study of energy absorption in a close-celled aluminum foam under dynamic loading

The compressive deformation behavior of open- and closed-cell aluminum foams was assessed under static and dynamic loading conditions. High strain rate experiments were conducted in our laboratory using a split Hopkinson pressure bar system at strain rates ranging from 400 to 2500 s−1. A strain rate effect was demonstrated for Alporas, a closed-cell aluminum. foam. The strain-rate effect was more significant for a higher density (i.e. 15% relative density) Alporas foam and is attributed to the kinetics of gas flow through the cell structure. The experimental results are discussed in reference to recent findings by other investigators on the dynamic behavior of similar open- and closed-cell aluminum foams.

High strain rate compression of closed-cell aluminium foams

The mechanical properties of polymers are becoming increasingly important as they are used in structural applications, both on their own and as matrix materials for composites. It has long been known that these mechanical properties are dependent on strain rate, temperature, and pressure. In this paper, the methods for dynamic loading of polymers will be briefly reviewed. The high strain rate mechanical properties of several classes of polymers, i.e. glassy and rubbery amorphous polymers and semi-crystalline polymers will be reviewed. Additionally, time–temperature superposition for rate dependent large strain properties and pressure dependence in polymers will be discussed. Constitutive modeling and shock properties of polymers will not be discussed in this review.

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High Strain Rate Mechanics of Polymers: A Review

Low-strength and low-impedance materials pose significant challenges in the design of experiments to determine dynamic stress-strain responses. When these materials are tested with a conventional split Hopkinson pressure bar, the specimen will not deform homogeneously and the tests are not valid. To obtain valid data, the shape of the incident pulse and the specimen thickness must be designed such that the specimens are in dynamic equilibrium and deform homogeneously at constant strain rates. In addition, a sensitive transmission bar is required to detect the weak transmitted pulses. Experimental results show that homogeneous deformations at nearly constant strain rates can be achieved in materials with very low impedances, such as a silicone rubber and a polyurethane foam, with the experimental modifications presented in this study. ©2002 ASME

Dynamic Compression Testing of Soft Materials

Tensile and compressive properties of polystyrene bead (PSB) foams at room temperature for strain rates from 10−3 to 105 min−1 can be represented as nearly linearly increasing functions of modulus or stress versus the logarithm of the strain rate. The shear modulus and tensile data, including failure properties, on 0.054 g/cc PSB foam at various temperatures and strain rates can be represented by master curves of log (stress or modulus) versus log (reduced strain rate). These master curves are formed by a time and temperature superposition method, wherein data at one temperature are superposed on data at another temperature by a shift along the log (strain rate) axis. These time–temperature shift factors are calculated using a form of the Arrhenius equation.

Time and temperature dependence of the mechanical properties of polystyrene bead foam

Elastic Precursor Decay in Tantalum

The Hopkinson split bar, instrumented with both a set of piezoelectric X‐cut quartz crystal pressure transducers and a set of strain gauge transducers, was developed to enable investigation of the stress—strain—strain rate behavior in compression of brittle and/or low strength materials. The approach was applied to the study of a brittle, strain rate sensitive, polycrystalline, organic solid, and for purposes of comparison a relatively ductile, highly filled polymer. Comparison and discussion of data from the two materials illustrate the advantage of the technique to obtain valid, more accurate stress and modulus information at strain levels significantly lower than those satisfactorily obtained by using the split bar instrumented with strain gauges alone.

Combined Strain Gauge—Quartz Crystal Instrumented Hopkinson Split Bar

Effect of strain rate on tension and compression stress-strain behavior in a TRIP alloy☆

The shear storage modulus has been determined for 0.05, 0.10, and 0.22 g/cc polystyrene bead foams and for the full density polymer at frequencies from 0.005 to 0.5 Hz at temperatures from −5° to 84°C. These data are superposed to form master curves of log modulus versus log temperature-reduced frequency, using shift factors calculated by the Arrhenius equation. A plot of log modulus versus log density is linear for the three density foams; however, the modulus value for the solid polymer does not follow this relationship.

Kenneth G. Hoge

Papers

Time and temperature dependence of the mechanical properties of polystyrene bead foam

Elastic Precursor Decay in Tantalum

Combined Strain Gauge—Quartz Crystal Instrumented Hopkinson Split Bar

Effect of strain rate on tension and compression stress-strain behavior in a TRIP alloy☆

Dynamic shear modulus of polystyrene bead foams