INTERACTION OF HIGH-STRAIN AND HIGH-CYCLE FATIGUE IN TURBINE MATERIALS

Abstract— An investigation has been conducted to examine the interaction between high-strain and high-cycle fatigue under combined cycling conditions on 2% NiCrMoV and a 12% CrNiMo alloy. The results reveal that the application of high-strain fatigue cycles prior to low-strain high-cycle fatigue is significantly less damaging than the equivalent number of single high-strain cycles applied between periods of high-cycle fatigue, indicating a much greater damaging interactive effect under the combined cycling condition. A damage summation, based on high-strain and high-cycle fatigue initiation curves and calculated at various endurances, was found to approach zero under combined cycling conditions indicating that a prediction of damage using the Palmgren-Miner linear damage rule is inapplicable. Cumulative damage curves, based on an assessment of hypothetical crack growth behaviour under high-strain and high-cycle fatigue conditions, can be constructed to explain the large departure from the Palmgren-Miner prediction of unity. Such curves, however, fail to predict the more damaging interactive effect observed under combined cycling conditions. The apparent contradiction between experimental results and theoretical assessment is discussed and a mechanism proposed to account for the observed interactive effect.     

Combined salience based person re-identification

Human eye perceives an object as the entity with global information and local information. Human salience is distinctive local information in matching pedestrians across disjoint camera views, and matching on overall foreground guarantees reliable and robust identification. In this paper, we propose a strategy for the matching of mean salience to identify pedestrians. Also, we consider that person re-identification based on the local single directional matching suffers from the variations of pose, illumination and overlapping, and propose a global bi-directional matching to solve the challenging problems of person re-identification. Furthermore, our matching of mean salience is tightly combined with the global bi-directional matching. Patch matching is utilized to handle the misalignment problem in pedestrian images. We test our feature and matching approaches in person re-identification scenario. Experimental results demonstrate that the mean salience and the global bi-directional matching have promising discriminative capability in comparison with other ones.     

Use of Nanoindentation,Finite Element Simulations,and a Combined Experimental/Numerical Approach to Characterize Elastic Moduli of Individual Porous Silica Particles

This article describes the use of a combination of experimental nanoindentation and finite element numerical simulations to indirectly determine the elastic modulus of individual porous, micron-sized silica (SiO₂) particles. Two independent nanoindentation experiments on individual silica particles were employed, one with a Berkovich pyramidal nanoindenter tip, the other with a flat punch nanoindenter tip. In both cases, 3D finite element simulations were used to generate nanoindenter load–displacement curves for comparison with the corresponding experimental data, using the elastic modulus of the particle as a curve-fitting parameter. The resulting indirectly determined modulus values from the two independent experiments were found to be in good agreement, and were considerably lower than the published values for bulk or particulate solid silica. The results are also consistent with previously reported modulus values for nanoindentation of porous thin film SiO₂. Based on a review of the literature, the authors believe that this is the first article to report on the use of nanoindentation and numerical simulations in a combined experimental/numerical approach to determine the elastic modulus of individual porous silica particles.     

Isolation and characterization of natural Ara h 6: evidence for a further peanut allergen with putative clinical relevance based on resistance to pepsin digestion and heat

Peanut allergy is a significant health problem because of its prevalence and the potential severity of the allergic reaction. The characterization of peanut allergens is crucial to the understanding of the mechanism of peanut allergy. Recently, we described cloning of the peanut allergen Ara h 6. The aim of this study was isolation and further characterization of nAra h 6. We purified nAra h 6 from crude peanut extract using gel filtration and anion exchange chromatography. The preparation was further characterized by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) with subsequent immunoblotting. Stability of nAra h 6 was studied by an in vitro digestibility assay as well as by resistance against thermal processing. Sequencing of nAra h 6 identified the N-terminal amino acid sequence as MRRERGRQGDSSS. Further results clearly demonstrated stability of nAra h 6 against pepsin digestion and heating. Immunoglobulin G (IgE) binding analysis and its biological activity shown by RBL 25/30-test of natural Ara h 6 supported the importance of this peanut allergen. Investigation of nAra h 6 revealed evidence for a further peanut allergen with putative clinical relevance based on resistance to pepsin digestion and heat.     

Effects of openings on the punching shear strength of RC flat‐plate slabs without shear reinforcement

Openings in RC flat‐plate slabs are one of the critical factors that influence the punching shear strength of the slab and determine its thickness in the vicinity of the slab‐column joint. This study experimentally investigates the effects of openings on the punching shear strength of flat‐plate slabs without shear reinforcement. Tests were performed on eight flat‐plate slab specimens considering the layout and number of openings as test variables. The failure characteristics of each specimen are examined, and the effects of the test variables on the punching shear strengths of the test specimens are investigated. The measured punching shear strengths of the test specimens are compared with the predictions of several concrete design codes, including the American Concrete Institute (ACI), Comité Euro‐International du Béton and Fédération Internationale de la Précontrainte (CEB‐FIP) model and fédération internationale du béton (fib) model codes. This indicates that the reductions in punching shear strength due to the existence of openings are generally proportional to the loss of effective critical sections, and an L‐shaped opening layout around the corner of the column may further reduce the punching shear strength and may contribute to the loss of effective critical sections due to the existence of openings. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of X-ray diffraction patterns from mechanically alloyed Al-Ti powders

X-ray diffraction (XRD) method is one of the most versatile tools to characterize various forms of materials. Simplicity and wealth of information from the spectrum makes it attractive for the evaluation of mechanical alloyed powders. However, careful interpretation of the solubility of minor phase is necessary due to the effect of particle size on the detection limit in XRD method. In this study, we demonstrate the inaccuracy of solubility from XRD analysis of nanosized particle system using Al-Ti as a model. Using transmission electron microscopy (TEM), it is confirmed that large amount of nanosized Ti in Al matrix is not detected by XRD. The peak disappearance of minor phase can not be used to determine the solubility of mechanically alloyed powders. Lattice parameter change of the major phase should be used to assess the solubility limit of the minor phase in nanosized particle system. In addition, the possible sources of error are addressed when mechanically alloyed powders of Al-Ti system are characterized by the XRD method. Proper XRD analysis methods are suggested to determine the lattice parameter, solubility of minor elements, crystallite size and strain variance in the MA Al-Ti samples. Pure A1 is used as an internal standard to correct instrumental broadening, the Al {111} peak is used to determine lattice parameter of A1, and the lattice parameter of Al is recommended to estimate the solubility of Ti in Al. The calculation of crystallite size and strain variance in the MA powders using Williamson-Hall equation is also discussed in detail.