Springback in simple axisymmetric stampings

A series of experiments was conducted to measure springback (calculated from dome height measurements) in a simple, stretched sheet metal part formed using a 50.8-mm-radius hemispherical punch. Parts were formed from three materials [5182-0 aluminum, 2036-T4 aluminum, and aluminum-killed (AK) steel] using three different binder geometries (lockbead, stinger, flat), and punch penetration was varied between 1.27 and 21.6 mm, limited by failure of the aluminum sheet. The steel and 5182-0 aluminum were chosen to possess similar gage and tensile properties to highlight the effect of elastic modulus, while the 5182-0 and 2036-T4 aluminum were chosen to possess similar gage and modulus but different tensile behavior to highlight the effect of strength differences. Springback increased with increasing strength and decreasing modulus. A major finding was that, for a specific material, a primary factor influencing spring-back was the binder geometry, with the lockbead showing the least springback and least variation with punch penetration: by contrast, the stinger and flat binders exhibited much greater springback, and the magnitude of the springback was strongly influenced by the extent of punch penetration. In the worst case, the springback was more than 30 pct of punch penetration. The effect of binder region restraint on springback was evaluated by comparing the part geometry both before and after strain-free removal of the binder region by electrodischarge machining. The magnitude and sign of the binder region restraint depended on binder geometry and punch penetration but was always less than the springback observed in removing the part from the die initially.     

Laboratory and field evidence for maleproduced aggregation pheromone inRhynchophorus cruentatus (F.) (Coleoptera: Curculionidae)

Laboratory and field assays were conducted to determine if palmetto weevil,Rhynchophorus cruentatus (F.), adults produce an aggregation pheromone. Attraction of females in a Y-tube olfactometer to conspecific males was greater than to clean air. Male and female attraction to conspecific male volatiles combined with host-palm,Sabal palmetto (Walter), volatiles was greater than to host-palm volatiles alone. Similarly, more weevils were caught in the field in traps baited with conspecific males plus host-palm tissue than in similar traps baited with only males, or palm tissue, or females, or females plus palm tissue. These results suggest thatR. cruentatus males produce an aggregation pheromone(s) that is highly attractive to conspecific adults of both sexes when combined with host-palm volatiles. This study is an important step towards understanding the chemical ecology ofR. cruentatus.     

Investigation of selected baseline removal techniques as candidates for automated implementation

Observed spectra normally contain spurious features along with those of interest and it is common practice to employ one of several available algorithms to remove the unwanted components. Low frequency spurious components are often referred to as 'baseline', 'background', and/or 'background noise'. Here we examine a cross-section of non-instrumental methods designed to remove background features from spectra; the particular methods considered here represent approaches with different theoretical underpinnings. We compare and evaluate their relative performance based on synthetic data sets designed to exemplify vibrational spectroscopic signals in realistic contexts and thereby assess their suitability for computer automation. Each method is presented in a modular format with a concise review of the underlying theory, along with a comparison and discussion of their strengths, weaknesses, and amenability to automation, in order to facilitate the selection of methods best suited to particular applications.     

Deposition and characterization of nickel–niobium composite electrocoatings

Ni–Nb composite electrocoatings were obtained on carbon steel from Watts bath, containing suspended 20 μm size niobium powders. The effect of cathodic current density, electrolyte stirring rate and concentration of Nb particles in the bath on the deposit morphology and texture, volume fraction of co-deposited Nb particles and microhardness was investigated. The Ni–Nb composite layers presented a rough morphology with randomly oriented Ni grains, whereas pure Ni coatings obtained under the same experimental conditions were smooth and showed highly preferred orientation in the [110] or [100] direction. Stirring rate of the electrolyte and concentration of Nb particles in the bath are the main parameters affecting the incorporation of Nb particles. The Nb incorporated volume fraction was 11–14%, 17–19%, 27–32% and 34–37% for the 20 g L⁻¹ Nb/550 rpm, 20 g L⁻¹ Nb/400 rpm, 40 g L⁻¹ Nb/400 rpm and 40 g L⁻¹ Nb/550 rpm conditions, respectively. The microhardness of the Ni–Nb composite coatings obtained at 20 and 40 mA cm⁻² was higher than that of pure Ni layers, due to grain refining. Incorporation of Nb particles in Ni coatings improved the corrosion resistance of the deposits in NaCl and H₂SO₄ solutions.     

Etude physicochimique et electrochimique de la protection d'un acier au carbone par les monofluorophosphates. I. Influence d'un traitement de conversion chimique

Résumé A l'aide de méthodes électrochimiques stationnaires (relevé des courbes courant-tension, mesure de la résistance de polarisation) nous avons étudié le comportement en milieu NaCl 3% d'un acier au carbone (XC 38) ayant subi une phosphatation cristalline ou amorphe puis un post-traitement par les monofluorophosphates de zinc ou de potassium. Nous avons montré que tous les traitements rédusaient la corrosion du substrat métallique mais à des degrés différents selon le type de traitement.L'analyse physico-chimique des couches issues des différents traitements a été conduite par analyse chimique, microscopie électronique à balayage et spectroscopie de photoélectrons (ESCA). Dans le cas de la phosphatation cristalline nous avons montré qu'il y a formation d'une solution solide Fe_xZn_3–x(PO₄)₂-4H₂O(1x3); un post-traitement par le monofluorophosphate de potassium entraine la formation d'un composé de formule moyenne Zn_0.5K_1.1PO_3.35F_0.4.

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Different chemical conversion treatments have been applied to a XC 38 carbon steel. Using electro-chemical methods (steady-state cathodic polarization curves, polarization resistance measurements) it has been shown that all the treatments reduce the corrosion rate of the metallic substrate; nevertheless, great differences in the degree of protection provided were found depending upon the treatment used. A physico-chemical analysis of the layers resulting from different treatments has been carried out using chemical analysis, scanning electron microscopy and photoelectron spectroscopy.It has been shown that, in the case of zinc phosphatation, there is formation of a solid solution Fe_xZn_3–x(PO₄)₂-4H₂O(1x3); in the case of zinc phosphatation with a potassium monofluorophosphate post-treatment there is formation of a compound with average stoichiometric formula Zn_0.5K_1.1PO_3.35F_0.4.

     

Assessing the value of human factors initiatives

This paper examines the effectiveness of human factors initiatives and addresses some difficulties reported in calculating the value of such interventions. Company representatives and researchers applied a novel probabilistic assessment tool to estimate the financial impact of two macro-ergonomic projects. Key benefits of the company intranet project include reduced administrative and operational costs compared to a paper-based system; time savings for users asking for, providing and receiving information; and improved system usability and higher levels of usage. The communities of practice project demonstrates value through more efficient distribution and retrieval of information; reduced duplication by re-using technical knowledge to solve similar problems and improved sharing of good working practices, lessons and resources. The strengths of the tool include transparency, being quick and easy to learn and the collaborative workshop format, involving researches and key representatives from the organization. It makes a useful contribution to the challenge of assessing the financial value of ergonomic interventions, and, by exploiting its diagnostic and planning capabilities, could be extended to other domains.     

Preparation,characterisation and activity of an iron/sodalite catalyst for the oxidation of methane to methanol

An iron sodalite catalyst similar to that reported to have good selectivity for the oxidation of methane to methanol by Lyons et al. has been prepared, tested and characterised. In a limited range of temperature at 34 bar total pressure the selectivity of the catalyst to methanol is a little better than that of an empty silica glass reactor. Before reaction, X-ray powder diffraction and Mössbauer spectroscopy confirm the presence of Fe(III) in the sodalite framework. After reaction Mössbauer spectroscopy identifies Fe(II) and also small particles of iron(III) oxide, < 1 m in size.     

On approximate triangular decompositions in dimension zero

Triangular decompositions for systems of polynomial equations with n$n$ variables, with exact coefficients, are well developed theoretically and in terms of implemented algorithms in computer algebra systems. However there is much less research concerning triangular decompositions for systems with approximate coefficients.