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A comparison study on forming limit prediction methods for hot stamping of 7075 aluminum sheet
No full textThis paper provides an experimental and theoretical study of AA7075 hot forming limits. The limits were measured in a wide range of temperature and strain rates using Nakazima test. Elevated temperature tensile testing was performed to capture the constitutive behavior. Two flow models have been calibrated using the tensile data, the Misio\u142ek model and a continuum damage mechanics (CDM) model. Two theoretical forming limit predictions methods have been investigated, the Marciniak\u2013Kaczynski (M\u2013K) method and a method based on CDM. In the M\u2013K model, the constitutive behavior was modeled by the von Mises yield with the Misio\u142ek flow model. The strain rate sensitivity of the groove section was taken into consideration. The CDM forming limit prediction method utilized the corresponding flow model and a simplified plane stress CDM model. Parameters in the constitutive models and the forming limit prediction models were expressed as functions of temperature and strain rate. Both methods accurately predicted the AA7075 forming limits in the hot stamping temperature range and strain rate range.Peer reviewed: YesNRC publication: Ye
Field and numerical investigations of the morpho-hydrodynamic processes of the tidal inlet at Shippagan Gully, New Brunswick, Canada
No full textThis paper presents the result of a multiyear study consisting of field measurements and numerical modeling of a highly dynamic tidal inlet located on the west side of the Gulf of Saint Lawrence near Le Goulet, New Brunswick, Canada. Due to a lack of human intervention in the past few decades, natural processes have taken hold of this tidal inlet and large volumes of sediment have been deposited within the inlet. The Shippagan Gully inlet transects the Acadian Peninsula and is therefore subject to tidal forcing from both ends. An appreciable phase lag present in the two open ocean boundaries results in ebb flows through Shippagan Gully, which regularly exceed 2 m/s, to be twice as strong as the flood flows. This flow imbalance along with a long history of human intervention has created a complex and highly dynamic tidal inlet. The purpose of the study was to develop a numerical model of the hydrodynamic and morphological processes that occur at Shippagan Gully and to use the model to assess alternative engineering measures that could be implemented to promote a safe and navigable channel through the inlet.Peer reviewed: YesNRC publication: Ye
Application of sorptive passive panels for reducing indoor formaldehyde level: effect of environmental conditions
No full textReducing formaldehyde concentration in residential buildings is an important challenge, especially during the summer. In this study, a ceiling tile was used as a sorptive passive panel for formaldehyde removal. The performance of this passive panel was evaluated under different environmental conditions. The results demonstrated that the removal efficiency is comprised between 40% and 71%. Change in the level of relative humidity (30%, 50%, and 75%) had a slight positive effect on the sorption capacity. However, increase in temperature from 21 \ub0C to 26 \ub0C led to approximately 7% decrease in the average formaldehyde removal performance. GC/MS and HPLC analysis revealed the formation of different by-products at low concentrations under extreme environmental conditions. These findings suggest that the passive panel selected for this study holds the potential to be used for formaldehyde removal under various conditions.Peer reviewed: YesNRC publication: Ye
Experimental study of velocity deficit and wake due to single and multiple rectangular porous plates in steady flow
No full textPeer reviewed: YesNRC publication: Ye
Model tests of the United States Coast Guard Heavy Polar Icebreaker indicative designs
No full textThis paper describes the results of model tests carried out in ice and open water conditions to evaluate performance of the United States Coast Guard (USCG) Heavy Polar Icebreaker (HPIB) indicative design. The resistance, propulsion and manoeuvring performance in ice conditions was evaluated at three different ice thicknesses (4, 6 and 8 ft.) with flexural strength 100 psi using two power setups, 36500 HP and 65000 HP. Calm water resistance and propulsion tests were also performed to evaluate open water performance. Models were constructed and tested corresponding to two indicative designs, one with triple shaft propulsion system and the other with one centre shaft and two wing podded propulsors. The present paper describes only the results for the model with triple shaft propulsion system.Peer reviewed: YesNRC publication: Ye
Effect of prior creep strain on high cycle fatigue life of TI 834
No full textRoom-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550\u2009\ub0C and 600\u2009\ub0C, respectively. Microstructural and fractographic examinations on specimens with prior creep strain\u2009>\u20093% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep, followed by fatigue crack propagation in coalescence with the internally distributed damage, leading to the final fracture. The amount of prior creep damage increased with creep strain. The fatigue life of Ti 834 was significantly reduced by prior creep straining. The behavior is rationalized with the integrated creep-fatigue theory.Peer reviewed: YesNRC publication: Ye
Establishing comparability and compatibility in the purity assessment of high purity zinc as demonstrated by the CCQM-P149 intercomparison
No full textFor the first time, an international comparison was conducted on the determination of the purity of a high purity element. Participants were free to choose any analytical approach appropriate for their institute's applications and services. The material tested was a high purity zinc, which had earlier been assessed for homogeneity and previously used in CCQM-K72 for the determination of six defined metallic impurities. Either a direct metal assay of the Zn mass fraction was undertaken by EDTA titrimetry, or an indirect approach was used wherein all impurities, or at least the major ones, were determined and their sum subtracted from ideal purity of 100 %, or 1 kg/kg. Impurity assessment techniques included glow discharge mass spectrometry, inductively coupled plasma mass spectrometry and carrier gas hot extraction/combustion analysis. Up to 91 elemental impurities covering metals, non-metals and semi-metals/metalloids were quantified. Due to the lack of internal experience or experimental capabilities, some participants contracted external laboratories for specific analytical tasks, mainly for the analysis of non-metals. The reported purity, expressed as zinc mass fraction in the high purity zinc material, showed excellent agreement for all participants, with a relative standard deviation of 0.011 %. The calculated reference value, w(Zn) = 0.999 873 kg/kg, was assigned an asymmetric combined uncertainty of + 0.000025 kg/kg and \u2013 0.000028 kg/kg. Comparability amongst participating metrology institutes is thus demonstrated for the purity determination of high purity metals which have no particular difficulties with their decomposition / dissolution process when solution-based analytical methods are used, or which do not have specific difficulties when direct analysis approaches are used. Nevertheless, further development is required in terms of uncertainty assessment, quantification of non-metals and the determination of purity of less pure elements and/or for those elements suffering difficulties with the decomposition process.Peer reviewed: YesNRC publication: Ye
Validating Fricke dosimetry for the measurement of absorbed dose to water for HDR 192Ir brachytherapy: a comparison between primary standards of the LCR, Brazil, and the NRC, Canada
No full textTwo Fricke-based absorbed dose to water standards for HDR Ir-192 dosimetry, developed independently by the LCR in Brazil and the NRC in Canada have been compared. The agreement in the determination of the dose rate from a HDR Ir-192 source at 1 cm in a water phantom was found to be within the k=1 combined measurement uncertainties of the two standards: DNRC/DLCR = 1.011, standard uncertainty = 2.2 %. The dose-based standards also agreed within the uncertainties with the manufacturer\u2019s stated dose rate value, which is traceable to a national standard of air kerma. A number of possible influence quantities were investigated, including the specific method for producing the ferrous-sulphate Fricke solution, the geometry of the holder, and the Monte Carlo code used to determine correction factors. The comparison highlighted the lack of data on the determination of G(Fe3+) in this energy range and the possibilities for further development of the holders used to contain the Fricke solution. The comparison also confirmed the suitability of Fricke dosimetry for Ir-192 primary standard dose rate determinations at therapy dose levels.Peer reviewed: YesNRC publication: Ye
Magnetic materials fabricated by cold spray additive manufacturing
No full textThis presentation discusses the cost effective fabrication of soft and hard magnetic materials using cold spray additive manufacturing. This technique allows for 3D build-up of complex shapes permitting fabrication of high complexity motor designs for enhanced performance. Combination of sprayed soft and hard magnetic materials opens up synergetic design possibilities for additional performance gain and cost savings. Measured hard magnetic properties (coercivity and remanence), soft magnetic properties (permeability and losses) and mechanical properties (adhesion and cohesion) will be presented. Use of the materials for the realization of motor prototypes will be discussed.Peer reviewed: YesNRC publication: Ye
Shortly-branched, linear dextrans as efficient binders for silicon/graphite composite electrodes in Li-ion batteries
No full textThere is a need for new binders that are compatible with both silicon and graphite to enable high energy density silicon/graphite composites for Li-ion batteries. In this work, we have evaluated the shortly-branched, linear polysaccharide dextran with graphite-rich composite electrode and battery testing shows a reversible capacity of about 525 mAh g-1 and an excellent cycling stability unlike the conventional poly(vinylidenefluoride) binder. A study of the interface using Impedance Spectroscopy, X-ray Photoelectron Spectroscopy, and post-mortem Scanning Electron Microscopy analysis shows that the superior performance of Dextran is due to the formation of a solid electrolyte interface layer that completely covers the surfaces of silicon and graphite due to a strong interaction between dextran\u2019s hydroxyl or ethereal groups and silicon surface as evidenced by Infrared spectroscopy. This along with its low cost and environmental friendly nature makes it an attractive binder material for Si/graphite composite electrodes in Li-ion batteries.Peer reviewed: YesNRC publication: Ye