Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session S4: Materials Strength IV: Dynamic Material Strength |
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Chair: William Buttler, Los Alamos National Laboratory, Christopher Neel, Air Force Research Laboratory Room: Grand H |
Thursday, June 18, 2015 9:15AM - 9:30AM |
S4.00001: Effect of dilute tungsten alloying on the dynamic strength of tantalum under ramp compression C.S. Alexander, J.L. Brown, J.C.F. Millett, G. Whiteman, J.R. Asay, N.K. Bourne The strength of tantalum and tantalum alloys are of considerable interest due to their widespread use in both military and industrial applications. Previous work has shown that strength in these materials is tied to dislocation density and mobility within the microstructure. Accordingly, strength has been observed to increase with dilute alloying which serves to increase the dislocation density. In this study, we examine the effect of alloying on the strength of a dilute tantalum-tungsten alloy (2.5 weight percent W) under ramp compression. The strength of the alloy is measured using the ``self-consistent'' technique which examines the response under longitudinal unloading from peak compression. The results are compared to previous studies of pure tantalum and dilute tantalum-tungsten alloys under both shock and ramp compression and indicate strengthening of the alloy when compared to pure tantalum. [Preview Abstract] |
Thursday, June 18, 2015 9:30AM - 9:45AM |
S4.00002: Isothermal Volume Expansion of a TATB-Based Composite and the Effect on Compressive Strength Darla Thompson, Ricardo Schwarz, Racci DeLuca It has long been known that compacted composites containing TATB crystals undergo ``ratchet growth,'' an irreversible volume expansion upon thermal cycling. A mechanism has not been established but is believed to arise from the highly-anisotropic CTE of TATB crystals and the interactions caused by compaction. Because explosive performance depends fundamentally on bulk density, the details of this phenomenon are important to understand. PBX 9502 is a plastic bonded explosive containing 95 wt{\%} TATB crystals. We have used a TA Instruments thermal mechanical analyzer (TMA) to monitor uniaxial length changes of PBX 9502 specimens as a function of temperature and thermal cycling. Previous ``ratchet growth'' work has focused on irreversible expansion as a function of temperature range and number of thermal cycles (1). In the work reported here, we demonstrate that irreversible growth also occurs during extended isothermal conditions and especially at elevated temperatures. We explore PBX 9502 irreversible expansion as a function of time and temperature, in the form of thermal ramps and holds. Post-test specimens are then subjected to quasi-static compression testing to determine whether the mechanical properties correlate with the final bulk density, or depend in a more complex way on the detailed thermal history of the specimen. [1] H.F. Rizzo, J.R. Humphrey, and J.R. Kolb, ``Growth of 1,3,5-Triamino-2,4,6- Trinitrobenzene (TATB), Control of Growth by Use of High Tg Polymeric Binders,'' Propellants and Explosives, 1981, 6, 57-62. [Preview Abstract] |
Thursday, June 18, 2015 9:45AM - 10:00AM |
S4.00003: Shock Induced Shear Strength in Two HMX Based Polymer Bonded Explosives Jeremy Millett, Peter Taylor, Gareth Appleby-Thomas The response of energetic materials to shock loading has largely concentrated on their detonation behaviour. However, they can also be considered to be structural materials in their own right, and hence their response to a purely mechanical shock loading is also of interest. Therefore we present results from two HMX based polymer bonded explosives, EDC37 and EDC32, where we investigate the shock induced shear strength behind the shock front. Results are discussed in terms of microstructure and differences of the binder phases. [Preview Abstract] |
Thursday, June 18, 2015 10:00AM - 10:15AM |
S4.00004: Experimental study on the dynamic mechanical behaviors of polycarbonate Wei Zhang, Yubo Gao, Xuanming Cai, Nan Ye, Wei Huang Polycarbonate (PC) is a widely used engineering material in aerospace field, since it has excellent mechanical and optical property. In present study, both compress and tensile tests of PC were conducted at high strain rates by using a split Hopkinson pressure bar. The high-speed camera and 2D digital speckle correlation method (DIC) were used to analyze the dynamic deformation behavior of PC. Meanwhile, the plate impact experiment was carried out to measure the equation of state of PC in a single-stage gas gun, which consists of asymmetric impact technology, manganin gauges, PVDF, electromagnetic particle velocity gauges. The results indicate that the yield stress of PC increased with the strain rates. The strain softening occurred when the stress over yield point except the tensile tests in the strain rates of 1076s-1 and 1279s-1. The ZWT model can describe the constitutive behaviors of PC accurately in different strain rates by contrast with the results of 2D-DIC. At last, The D-u Hugoniot curve of polycarbonate in high pressure was fitted by the least square method. And the final results showed more closely to Cater and Mash than other previous data. [Preview Abstract] |
Thursday, June 18, 2015 10:15AM - 10:45AM |
S4.00005: Shear Strength Measurements During Shock Loading Using Laterally Mounted Stress Gauges. Invited Speaker: Jeremy Millett The shear strength during shock loading of materials is of the utmost importance as it can be used to inform on resistance to ballistic attack. As such a number of techniques have been developed to determine this parameter. One method to do achieve this is the use of stress gauges mounted such that they are sensitive to the longitudinal and lateral components of stress, with shear strength being the difference between the two. A major advantage of this technique is that it places the gauge within the material flow, and as such it is possible to infer materials deformation mechanisms by observing how shear strength changes with time. However, it should also be realised that this technique is invasive as it requires the sample be sectioned such that the stress gauge can be placed in location. This presentation will therefore discuss results generated using this technique in a range of materials, and situations where the conditions of stress are known precisely. Results will also be discussed in context, both with other techniques and known materials response. [Preview Abstract] |
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