Dynamic Behavior of Materials

Abstract

The dynamic behavior of materials is a subject of everincreasing interest to the technical community owing to applications ranging from shock and blast to crash, impact and ballistics. Hence, it has relevance to government, industry and academia. The enhanced interest in dynamic behavior is evident from the increase in the number of papers in Experimental Mechanics on this topic, as well as expansion of the Dynamic Behavior sessions at the SEM annual conferences. Since inauguration of the SEM Dynamic Behavior Technical Division in 2005, presentations on this topic at the annual conference have increased from two sessions (~10 papers) in 2005 to two tracks (~150 papers) in 2009 and 2010. This level of interest prompted the EM editor to suggest a special issue to address current issues on the dynamic behavior of materials. This special issue of Experimental Mechanics includes nine papers addressing topics of immediate interest to this technical community. The papers were selected from the written papers submitted to the Dynamic Behavior track at the 2010 SEM Annual Conference on Experimental and Applied Mechanics, Indianapolis, IN, USA, June 7–10, 2010. The major subject areas are: 1) Advancements in high strain rate testing, 2) Dynamic response of various materials, 3) Dynamic failure and fracture, and 4) Modeling of dynamic events. Hopkinson/Kolsky bar techniques are the most commonly used method for characterizing the high strain rate response of materials. Current dynamic testing methods can be linked to the pioneering work of Hopkinson [1] and Kolsky [2] in applying stress wave experiments to evaluate dynamic material response, and to Lindholm and co-workers [3] in reducing this technique to practice. They [3] developed a methodology for deriving the stress–strain response of a material using transient pulse shapes acquired from strain gages on both bars. The strain rate range for traditional Kolsky bar systems ranges from 10 s to 10 s. Higher strain rates can be achieved by reducing the specimen size and the bar diameter [4]. Small (fewmm or sub-millimeter) diameter Kolsky bar systems have been developed which extend the strain rate range beyond 100,000 s. However, strain gage measurement of the longitudinal stress waves in the bars becomes impractical at the small scale. The paper by Casem, Grunschel and Schuster, in this special issue of Experimental Mechanics, demonstrates the feasibility of optical techniques for replacing traditional strain gage measurements in miniaturized systems. The dynamic tension or compression response of materials is readily obtained with traditional Kolsky bar systems. Pure shear data can also be obtained with a torsion bar. This is detailed in the paper by Hokka, et al. on the high strain rate torsion response of ultra-fine grained aluminum. Modifications to traditional Kolsky bar systems have expanded the types of high strain rate tests that can be conducted using these systems. For example, Anton and Subhash [5] used a modified bar system with a small diameter incident bar to measure dynamic Vickers hardness for brittle materials. Nie, Chen, et al. [6] conducted dynamic flexural strength tests on glass through implementation of a four-point bend configuration in the Hopkinson bar. Nie and Chen also devised a ring-on-ring technique for measuring the dynamic equibiaxial flexural strength of glass at temperatures up to K.A. Dannemann (*) Southwest Research Institute, San Antonio, TX, USA e-mail: kdannemann@swri.org