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New pyrotechnic smoke compositions, containing only environmentally benign materials, have been demonstrated to produce thick white smoke clouds upon combustion. These compositions use powdered boron carbide (B4C) as a pyrotechnic fuel, KNO3 as a pyrotechnic oxidizer, and KCl as a combustion temperature moderator. Small amounts of calcium stearate and polymeric binders may be added to moderate burning rate and for composition granulation. Prototype tests involving three preferred compositions were conducted in end- and core-burning grenade and canister configurations. Smoke release times ranged from 3.5 to 70 s for the grenades and from 8 to 100 s for the canisters. Notably, any desired smoke release time within these ranges may be obtained by fine adjustment to the calcium stearate content of the compositions and/or small changes to the device containers. Aerosolization efficiency and quantitative performance, as determined by smoke chamber measurements, remain consistent regardless of smoke release time. Impact, friction, and electrostatic discharge tests show that the compositions are insensitive to accidental ignition and are safe to handle.

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Elastic and plastic strain evolution under four-point bending has been studied by synchrotron energy dispersive x-ray diffraction. Measured strain profiles across the specimen thickness showed an increasing linear elastic strain gradient under increasing four-point bending load up to ϳ2 kN. The bulk elastic modulus of Ti-6Al-4V was determined as 118 GPa. The onset of plastic deformation was found to set in at a total in-plane strain of ϳ0.008, both under tension and compression. Plastic deformation under bending is initiated in the vicinity of the surface and at a stress of 1100 MPa, and propagates inward, while a finite core region remains elastically deformed up to 3.67 kN loading. The onset of the plastic regime and the plastic regime itself has been verified by monitoring the line broadening of the ͑100͒ peak of ␣-Ti. The effective compression/tension stress-strain curve has been obtained from the scaling collapse of strain profile data taken at seven external load levels. A similar multiple load scaling collapse of the plastic strain variation has also been obtained. The level of precision in strain measurement reported herein was evaluated and found to be 1.5ϫ 10 −5 or better.

Strain localization in the presence of a stress gradient is a phenomenon common to many systems described by continuum mechanics. Variations of this complex phenomenon lead to interesting nonlinear effects in materials/engineering science as well as in other fields. Here, the synchrotron based energy dispersive x-ray diffraction (EDXRD) technique is used for high spatial resolution profiling of both compression and tension induced strain localization in important materials/engineering problems. Specifically, compression induced strain localization in shot peened materials and tension induced strain localization in the plastic zones adjoining the faces of a fatigue crack are profiled. The utility of the EDXRD synchrotron technique for nondestructively cross-sectioning strain variations on small length scales (down to 10–20μm) is described. While the strain field profiling relies on the shift of the Bragg lines, the data show that plastic deformation regions can also consistently be seen in the broadening of the Bragg peaks through the full width at half maximum parameter. Quantitative correlations between the synchrotron based x-ray determined deformations and surface deformations, as measured by optical surface height profiling, are also made.

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