Accuracy of mercury-alloy proportioning systems.
To measure the reproducible accuracy of some commercially available mercury/alloy proportioning systems, a study was made of several mercury dispensers, alloy pellets, and disposable capsules. This study included a consideration of some human variables that were introduced in manipulating the systems. Most of the systems that were tested provided acceptable accuracy when used correctly.
Plasticity of Amalgam Mixes
The plasticity of an amalgam mix prior to and during condensation could have a significant influence on the homogeneity and adaptation of the amalgam restoration. One of the difficulties in investigating the possible significance of mix plasticity is the absence of a quantitative test to measure this property. Presently used tests include such subjective evaluations as rolling the amalgam mix into a rope, dropping the mix from a certain height to a flat surface, rolling the mix between the fingers, or sensing the way in which the mix behaves under forces of condensation. In view of the possible significance of mix plasticity, it was the purpose of this investigation to devise and evaluate a test to quantitate mix plasticity and to determine subsequently the influence of various factors on this property. No attempt was made at this time to determine either a value for optimum plasticity or a difference of plasticity that might be significant to the efficacy of the amalgam restoration. A study to demonstrate the true significance of the property of mix plasticity would necessarily follow the establishment of a valid test. Thus, the objective of this investigation was the development and evaluation of a plasticity test only.
Review of Literature on Probability of Detection for Magnetic Particle Nondestructive Testing
Abstract : A critical review of the available literature concerning the minimum reliably detectable defect size aNDI for magnetic particle testing (MPT) in aerospace applications is presented. Four probability of detection (POD) studies relevant to detection of fatigue cracks in aircraft components were found over the period 1968 to 2011. As the statistical methods used in these four previous studies were either outdated or otherwise deficient, the original data were reanalysed using currently accepted techniques. A meta-analysis of the results is presented, with emphasis on statistical inferences for the defect size expected to be detected with 90% POD. It is shown that the minimum reliably detectable defect size aNDI = 2.0 mm currently specified by the Royal Australian Air Force for wet fluorescent magnetic particle inspection using the continuous method is consistent with estimates of the average performance of MPT derived from the reanalysis of the literature.