The effect of weld stresses on weld quality

A narrow heat source raises the temperature of a spot on a solid piece of material like metal. The high temperature of the spot decreases with distance from the spot. This is true whether the heat source is an arc, a flame, an electron beam, a plasma jet, a laser beam, or any other source of intense, narrowly defined heat. Stress and strain fields around a moving heat source are organized into a coherent visible system. It is shown that five stresses act across the weld line in turn as an arc passes. Their proportions and positions are considerably altered by weld parameters or condition changes. These pushes and pulls affect the metallurgical character and integrity of the weld area even when there is no apparent difference between after-the-fact examples

Evaluation of Second-Stage Contactor Media for Manganese Removal

The focus of this research was to determine the performance of different types of media for a post-filter second-stage contactor for the removal of manganese from a drinking water source. The Aquarion Water Company’s Lantern Hill (LH) water treatment facility in Stonington, CT served as the motivation for this study. The groundwater at this site contains significant concentrations of manganese, averaging 0.2 mg/L, as well as iron, 2.3 mg/L, and total organic carbon (TOC), 3.5 mg/L. Currently, the Lantern Hill facility is using a combination of pH adjustment, potassium permanganate, chlorine, and cationic polymer addition prior to down flow through a dual media, anthracite over green sand, direct filtration process. Levels of prefilter chlorine required to maintain a filter effluent manganese concentration of 0.02 mg/L or less result in unacceptable levels of disinfection byproducts (DBPs), specifically trihalomethanes (THMs) and haloacetic acids (HAAs). Prior UMass/AWC research has shown that a two-stage approach, with a first-stage dual media (DM) filter for the removal of particulate matter, including oxidized iron and some TOC, followed by a second-stage media contactor for manganese removal, is effective. Addition of chlorine after the first-stage filter results in much lower DBP levels compared to the addition of chlorine to the raw water at a level that yields effective manganese control. The design of a facility upgrade is in progress, which requires more information on media performance

Finding Through NDE the Thermal History and Metallurgical Status of a Heat Treatable Aluminum Alloy

In heat-treatable aluminum alloys it has long been accepted that decreased values of strength were accompanied by increases in electrical conductivity (C). In quality or processing control and trouble-shooting situations this has been useful for finding anomalies in or among aluminum alloy maill products. But the regression was always found as a wide scatterband where conductivity could not give a narrow range of possible strengths. It was discovered for several alloys and quantified for 2219, that the scatterband formed by data from several lots and sources actually could be divided into groups with different histories. When specimens produced by created combinations of quenching-time and aging-time had their Hardness (H) vs Conductivity plotted on a H vs C format a fan-like dispersion of coordinated points was seen. Drawing locuses thru like times divided this fan into age-time and quench-time grids. Any particular C-H coordinate in this envelope then was seen as identifying the thermal history of the piece with that of C-H value. It was also found that progress in one direction on this format marked out the increase in the 2219 hardening precipitates θ″ and θ′. Progress in the other direction marked out the increase in the softening precipitate θ. So that even the particular metallurgical status could be found from the C-H coordinate of the specimen. This work taught that the large C-H variations seen in accumulations of data most often represented variations in the material itself, not in measurement systems. The work also taught that variation in production material was tracible mainly to variation in quench quench times. Should such variations be reduced the standard deviation of strength would be reduced and higher design strengths could be assigned to the alloy. In practical situations increases in design strengths (which conversely means reductions in assembly weight) are seen at 12%. The NDE measurements can serve this end by identifying and certifying grades of material before pieces are put into service. This strategy involves avoiding that apparently sound material which will fail early in its service life.</p

Corrigendum: Cadmium and lead in tissues of scallops from Port Phillip Bay, Australia, (Water Science and Technology 30)

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Applications of NDE to the Processing of Metals

Presently conceived automated metals processing systems have reached a high degree of complexity and incorporate not only control hardware but algorithms based on computer simulations and models of processes and a multiplicity of sensors for monitoring process and geometrical parameters, as well as material properties during the various stages of processing1-4. In such systems, sensors which can nondestructively measure material properties during processing provide information which can be used to verify, simplify and eventually improve the control algorithms. Also by directly providing the quantities of interest, such sensors relax the requirements on other measurements (such as temperature) from which material properties are traditionally inferred. In addition, material property sensors used near the end of the process insure that specifications are being met, regardless of the performance of automated systems upstream. In some cases the availability of new techniques capable of monitoring the evolution of microstructure during initial phases of processing may also help develop new and simpler metallurgical processes resulting in simultaneous improvements of quality and productivity