Weld residual stresses near the bimetallic interface in clad RPV steel: A comparison between deep-hole drilling and neutron diffraction data

The inner surface of ferritic steel reactor pressure vessels (RPV) is clad with strip welded austenitic stainless steel primarily to increase the long-term corrosion resistance of the ferritic vessel. The strip welding process used in the cladding operation induces significant residual stresses in the clad layer and in the RPV steel substrate, arising both from the thermal cycle and from the very different thermal and mechanical properties of the austenitic clad layer and the ferritic RPV steel. This work measures residual stresses using the deep hole drilling (DHD) and neutron diffraction (ND) techniques and compares residual stress data obtained by the two methods in a stainless clad coupon of A533B Class 2 steel. The results give confidence that both techniques are capable of assessing the trends in residual stresses, and their magnitudes. Significant differences are that the ND data shows greater values of the tensile stress peaks (∼100 MPa) than the DHD data but has a higher systematic error associated with it. The stress peaks are sharper with the ND technique and also differ in spatial position by around 1 mm compared with the DHD technique. © 2014 Elsevier B.V

Designing aluminium friction stir welded joints against multiaxial fatigue

The present paper investigates the accuracy of the Modified Wöhler Curve Method (MWCM) in estimating multiaxial fatigue strength of aluminium friction stir (FS) welded joints. Having developed a bespoke joining technology, circumferentially FS welded tubular specimens of Al 6082-T6 were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out using the experimental results have demonstrated that the MWCM applied in terms of nominal stresses, notch stresses, and also the Point Method is accurate in predicting the fatigue lifetime of the tested FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands

Corrosion fatigue of Ti-6Al-4V coupons manufactured by directed energy deposition

Titanium is a versatile biocompatible metal that is desirable in additively manufactured medical implant devices. However, additively manufactured parts have particular microstructures, porosity, residual stress, and surface conditions which can have a strong impact on fatigue performance. Implants have an added complexity from the saline operating environment and the associated impact on the safe design life. Equally, direct energy deposition induces a complex thermal history which, if not carefully controlled, can significantly alter the mechanical/material properties of the component. This study investigates the decrease in fatigue life, in an in vitro body fluid simulation using Ringer's solution, observed in Ti-6Al-4V specimens extracted from coupons manufactured by directed energy deposition. An interrupted deposition strategy was employed to control build regularity, which appeared to influence certain mechanical properties, including corrosion fatigue life. An ≈50% decrease in fatigue life was observed in Ringer's solution at 6 Hz loading frequency, clearly important in designing implants

Evaluation of pseudoephedrine pharmacy sales before and after mandatory recording requirements in Western Australia: a case study

Background: A community pharmacy real-time electronic recording program, ProjectSTOP, enables Australian community pharmacists to verify pseudoephedrine requests. In Western Australia the program was available for voluntary use from April 2007 and became mandatory November 2010. This case study explores the effectiveness of the program by reviewing the total requests for pseudoephedrine products, and the proportion of requests which were classified as ‘denied sales’ before and after mandatory implementation. Seasonal and annual trends in these measures are also evaluated. Methods: ProjectSTOP data recordings for Western Australia pharmacies between 1 December 2007 and 28 February 2014 were analysed. Data included a de-identified pharmacy number and date of each pseudoephedrine product request. The total number of requests and sale classification (allowed, denied, safety, or not recorded) were calculated for each month/pharmacy. The potential influence of mandatory reporting using ProjectSTOP was investigated using a Regression Discontinuity Design. Correlations between sales from the same pharmacy were taken into account by classifying the pharmacy number as a random effect. The main effects of year (continuous variable), and season (categorical variable) were also included in the model. Results: There was a small but steady decline in the total requests for pseudoephedrine per month per 100,000 population (per pharmacy) from the time of mandatory reporting. The number of denied sales showed a steady increase up until mandatory reporting, after which it showed a significant decline over time. Total sales were heavily influenced by season, as expected (highest in winter, least in summer). The seasonal pattern was less pronounced for denied sales, which were highest in winter and similar across other seasons. The pattern over time for safety sales was similar to that for denied sales, with a clear change occurring around the time of mandatory reporting. Conclusion: Results indicate a decrease in pseudoephedrine product requests in Western Australia community pharmacies. Findings suggest ProjectSTOP has been successful in addressing suspicious sales and potential diversion however ongoing data review is recommended

Case studies in marine concentrated corrosion

This paper outlines the problem and analysis techniques in three exemplar case studies of marine concentrated corrosion. The intended audience is failure analysts or forensic engineers, who might occasionally come across examples of concentrated corrosion and are seeking relevant background information. In particular, it demonstrates the advantages in problem identification and solution that can accrue from the use of the highly sophisticated spectrographic instrumentation that is currently available. These techniques include energy dispersive spectroscopy (EDS) mapping in a scanning electron microscope (SEM), Fourier transform infrared (FT-IR) and Raman spectroscopy. Confocal laser scanning microscopy (CLSM) is also useful in surface metrology. The main case study presented is one of accelerated low water corrosion (ALWC) on the tubular steel piles of a marina. The paper includes an outline of some of the relevant literature relating to the use of these modern techniques in identifying marine corrosion products