Brian Wilshire

Flake Metal Powders for Revealing Latent Fingerprints

Fine flake powders, having flake diameters ranging from 50 to 1 μm and stearic acid/powder ratios varying from 0 to 50 weight percent, were produced by laboratory-scale milling of aluminum, zinc, copper, and iron powders. The effectiveness of these flakes for detection of latent fingerprints was then assessed by comparing the print qualities obtained when using these flake powders with those achieved using commercial aluminum, commercial black, and commercial dark magnetic dusting powders. While the commercial aluminum powder was found to have an average flake diameter and stearic acid level close to the optimum values required to obtain bright fingerprints, several potential avenues of development were identified which could lead to the commercial availability of superior black powders.

Long term creep life prediction for Grade 22 (2·25Cr—1Mo) steels

Using new data analysis procedures, 100 000 h creep strengths are estimated by extrapolation of stress rupture values with creep lives <5000 h for Grade 22 tube as well as for annealed/tempered and quenched/tempered plates. In addition to allowing accurate prediction of long term strengths, the resulting property sets can be discussed sensibly in terms of the deformation and damage processes controlling creep and creep fracture.

Magnetic Flake Powders for Fingerprint Development

Different types of fine magnetic flake powders, which could be applied to latent fingerprints using a standard magnetic applicator, were produced with the aim of identifying product ranges suitable for bright fingerprint development on dark surfaces. Impressive bright print qualities were achieved with the smooth-surfaced flake manufactured by milling of spherical carbonyl iron and austenitic stainless steel powders. Compared with the results obtained for commercial aluminum fingerprint powders, these new magnetic flake products proved almost equivalent for print development on smooth surfaces and superior for print detection on rough surfaces.

Creep and creep fracture of an oxide-dispersion-strengthened 13% chromium ferritic steel

Abstract Short-term creep data for the oxide-dispersion-strengthened 13% chromium ferritic steel, DT2203YO5, have been analysed using the ϑ Projection Concept. The ϑ methodology is shown to rationalize the complex behaviour patterns recorded when traditional power-law equations are used to describe the creep characteristics of ODS alloys. Moreover, the robust form of the ϑ relationships allows estimates of long-term creep and creep-fracture properties to be obtained, despite the variability of the property values recorded for alloy DT2203YO5 in tests of short duration.

Obliteration of Latent Fingerprints

Comprehensive trials have established that latent fingerprints can be rendered partially or totally unidentifiable during print development by the following: (a) ridge smearing, which depends on the type and age of the latent print and also on the type of brush and brushing procedures used, and (b) overpowdering and/or overbrushing of the print. These causes of pattern obscuration are discussed in terms of their implications for fingerprint development procedures, since up to 10% of prints developed at crime scenes can be difficult or even impossible to identify.

Deformation and failure processes during tensile creep of fibre and whisker reinforced SiC/Al2O3 composites☆

Abstract The tensile creep and creep fracture properties in air from 1473 to 1673 K are reported for an alumina matrix composite, reinforced with interwoven bundles of silicon carbide (Nicalon™) fibres aligned parallel and normal to the stress axis. The creep strength of this 0/90° SiC f /Al 2 O 3 composite is determined by the longitudinal fibres, with creep of the fibres accompanied by crack development in the weak porous matrix. Oxygen penetration then promotes failure of the fibres bridging the developing cracks, with creep fracture occurring when a crack becomes long enough to cause sudden failure by fibre pull-out. These behaviour patterns are discussed in relation to tensile creep data available for SiC whisker-reinforced alumina, allowing comparisons to be made between the effects of whisker and fibre reinforcement on the high-temperature creep and creep fracture characteristics of SiC/Al 2 O 3 composites.

Prediction of Long Term Stress Rupture Data for 2124

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.

Development of Latent Fingerprints on Paper Using Magnetic Flakes

For various types of paper differing in color and surface texture, a study has been made of the factors governing the developed print qualities achieved using a magnetic applicator to apply fine iron flake powders and the subsequent retrieval of the magnetic flake from the papers using a rare-earth permanent magnet.

Grain boundaries: their influence on creep strain accumulation

Abstract Understanding the role of grain boundaries has been impeded by continued adoption of power law equations for identification of the processes governing creep and creep fracture of metals and alloys. In contrast, the dominant mechanisms can be clarified through new relationships which involve normalisation of the applied stress by the yield and ultimate tensile strengths determined from high strain rate tests at the creep temperatures.

Design Data Prediction for Grade 92 Steel

For Grade 92 steel (9Cr-0.5Mo-1.8W-V-Nb), multi-batch stress-rupture measurements are shown to be rationalized through relationships which involve only the activation energy for matrix diffusion (300 kJmol−1 ) and the ultimate tensile stress values at the creep temperatures. The resulting ‘master curve’ is at least as impressive as those obtained using traditional parametric methods, but with the empirical parameters replaced by physically-meaningful properties. These approaches lead to straightforward procedures for extended extrapolation of short-term data, with analyses of test results for creep lives less than 5000 hours predicting 100,000-hour rupture strengths. Indeed, noting that the allowable creep strengths for Gr. 92 steel have been reduced progressively as longer-term fracture data have become available, the present predictions coincide well with the lower limits of the most recent estimates determined for stress-temperature combinations producing failure in times up to 100,000 hours and more. Validation of the new methodologies can be achieved by independent analyses of standard property sets for other creep-resistant steels, introducing the prospect of a marked reduction in the scale and costs of the experimental programs currently undertaken to provide long-term engineering design data.Copyright