A fabrication history based strain-fatigue model for prediction of crack initiation in a radial loading wheel

A strain-based fatigue model concerning fabrication history is applied to predict the fatigue life of a commercial car wheel under radial loads. As the prior conditions, the strain fatigue testing is performed on standard specimen of DP590 and FB540 steels at various fabrication states, including raw materials, pre-strain and pre-strain + bake. Furthermore, the strain distribution of car wheel during its rotation under radial loads is simulated via ANSYS. The fatigue properties mainly determined by crack initiation of car wheels at various fabrication states are predicted via local stress–strain method, in which the scale and surface factors are also taken into account. The radial fatigue testing is carried out, and the results are used to validate the present model. The fracture mechanism is analysed using FEI Nova 400 field emission gun scanning electron microscope

The lives of FR I radio galaxies

After a brief introduction to the morphological properties of FRI radio sources, we discuss the possibility that FRI jets are relativistic at their bases and decelerate quickly to non-relativistic velocities. From two-frequency data we determine spectral index distributions and consequently the ages of FRI sources. We show that in the large majority of cases synchrotron theory provides unambiguous and plausible answers; in a few objects re-acceleration of electrons may be needed. The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources. The linear sizes of FRI and FRII sources make it unlikely that many FRII's evolve into FRI's. A brief discussion is given of the possibility that radio sources go through different cycles of activity.Comment: 19 pages, including 13 figures, to appear in `Life Cycles of Radio Galaxies', ed. J. Biretta et al., New Astronomy Review

Integrated disease management of leaf spots and crown rust of oat

Non-Peer ReviewedCrown rust and leaf spots can reduce the yield and quality of oats. The objective of this research was to determine the effect of conventional fungicides, Actigard® and oat cultivars that vary in resistance to crown rust on leaf spot and crown rust severity, and oat yield and quality. Two experiments were established at each location in Saskatchewan: Saskatoon and Melfort. Experiment one consisted of three oat varieties: AC Morgan (crown rust susceptible), CDC Dancer (intermediate) and CDC Morrison (resistant) and three fungicide treatments: check (unsprayed), propiconazole and pyraclostrobin. Experiment two consisted of the application of Actigard® at two rates: 8.75 g ai/ha and 26.25 g ai/ha; three crop growth stages: seedling, boot and heading; on two varieties: CDC Dancer and CDC Morrison, with an unsprayed check for each variety. At Saskatoon, crown rust was observed while leaf spot severity was low. At Melfort, no crown rust was observed but leaf spot severity was low to moderate. Fungicide reduced the severity of crown rust and increased yield and quality of oat at Saskatoon for the susceptible variety (AC Morgan) and somewhat for the moderately susceptible variety (CDC Dancer). The crown rust resistant variety (CDC Morrison) did not benefit from fungicide. Leaf spots were reduced by fungicide application at Melfort, but little increase in yield or quality was detected. There was little difference between AC Morgan and CDC Morrison for leaf spot symptoms, but CDC Dancer appeared to suffer slightly more than the other varieties. There was no impact of fungicide on beta-glucan content at either location, although there were differences among varieties, but only at Saskatoon. Actigard® was not observed to have any positive or negative effects on disease severity (crown rust or leaf spots) or any of the factors measured, including nutritional characteristics, at either location, although there were differences among varieties for many of the factors measured

Integrated disease management of leaf spots and crown rust of oat

Non-Peer ReviewedCrown rust and leaf spots can reduce the yield and quality of oats. The objective of this research was to determine the effect of conventional fungicides, Actigard® and oat cultivars that vary in resistance to crown rust on leaf spot and crown rust severity, and oat yield and quality. Two experiments were established at two locations in Saskatchewan: Saskatoon and Melfort. Experiment 1 consisted of three oat varieties: AC Morgan (crown rust susceptible), CDC Dancer (intermediate) and CDC Morrison (resistant) and three fungicide treatments: check (unsprayed), propiconazole and pyraclostrobin. Experiment 2 consisted of the application of Actigard® at two rates: 8.75 g ai/ha and 26.25 g ai/ha; three crop growth stages: seedling, boot and heading; on two varieties: CDC Dancer and CDC Morrison, with an unsprayed check for each variety. At Saskatoon, crown rust was observed while leaf spot severity was low. At Melfort, no crown rust was observed and leaf spot severity was low. Fungicide reduced the severity of crown rust and increased yield and quality of oat at Saskatoon for the susceptible variety (AC Morgan) and somewhat for the moderately susceptible variety (CDC Dancer). The crown rust resistant variety (CDC Morrison) did not benefit from fungicide. Leaf spots were reduced by fungicide application at Melfort, but little increase in yield or quality was detected. There was little difference between AC Morgan and CDC Morrison for leaf spot symptoms, but CDC Dancer appeared to suffer slightly more than the other varieties. There was no impact of fungicide on beta-glucan content at either location, although there were differences among varieties, but only at Saskatoon. Actigard® was not observed to have any positive or negative effects on disease severity (crown rust or leaf spots) or any of the factors measured, including nutritional characteristics, at either location, although there were differences among varieties for many of the factors measured

Continuum limit of amorphous elastic bodies: A finite-size study of low frequency harmonic vibrations

The approach of the elastic continuum limit in small amorphous bodies formed by weakly polydisperse Lennard-Jones beads is investigated in a systematic finite-size study. We show that classical continuum elasticity breaks down when the wavelength of the sollicitation is smaller than a characteristic length of approximately 30 molecular sizes. Due to this surprisingly large effect ensembles containing up to N=40,000 particles have been required in two dimensions to yield a convincing match with the classical continuum predictions for the eigenfrequency spectrum of disk-shaped aggregates and periodic bulk systems. The existence of an effective length scale \xi is confirmed by the analysis of the (non-gaussian) noisy part of the low frequency vibrational eigenmodes. Moreover, we relate it to the {\em non-affine} part of the displacement fields under imposed elongation and shear. Similar correlations (vortices) are indeed observed on distances up to \xi~30 particle sizes.Comment: 28 pages, 13 figures, 3 table

Near Threshold Enhancement of p pbar System and p pbar Elastic Scattering

The observed enhancement of $p\bar p$-production near the threshold in radiative decays of $J/\psi$ and $e^+e^-$-annihilations can be explained with final state interactions among the produced $N\bar N$ system, where the enhancement is essentially determined by $N\bar N$ elastic scattering amplitudes. We propose to use an effective theory for interactions in a $N\bar N$ system near its threshold. The effective theory is similar to the well-known one for interactions in a $NN$ system but with distinctions. It is interesting to note that in the effective theory some corrections to scattering amplitudes at tree-level can systematically be summed into a simple form. These corrections are from rescattering processes. With these corrected amplitudes we are able to describe the enhancement near the threshold in radiative decays of $J/\psi$ and $e^+e^-$-annihilations, and the $p\bar p$ elastic scattering near the threshold.Comment: Discussions and References added, Fig.2 redrawn. Published version in Phys. Lett.

3D FEA modelling of laminated composites in bending and their failure mechanisms

keywords: 3D keywords: 3D keywords: 3D keywords: 3D keywords: 3DAbstract This paper developed three-dimensional (3D) Finite Element Analysis (FEA) to investigate the effect of fibre lay-up on the initiation of failure of laminated composites in bending. Tsai-Hill failure criterion was applied to identify the critical areas of failure in composite laminates. In accordance with the 3D FEA, unidirectional ([0]16), cross-ply ([0/90]4s) and angle-ply ([±45]4s) laminates made up of pre-preg Carbon Fibre Reinforced Plastics (CFRP) composites were manufactured and tested under three-point bending. The basic principles of Classical Laminate Theory (CLT) were extended to three-dimension, and the analytical solution was critically compared with the FEA results. The 3D FEA results revealed significant transverse normal stresses in the cross-ply laminate and in-plane shear stress in the angle-ply laminate near free edge regions which are overlooked by conventional laminate model. The microscopic images showed that these free edge effects were the main reason for stiffness reduction observed in the bending tests. The study illustrated the significant effects of fibre lay-up on the flexural failure mechanisms in composite laminates which lead to some suggestions to improve the design of composite laminates

Disease survey of cereal crops in Saskatchewan in 2013

Non-Peer ReviewedCereal crops in Saskatchewan can suffer a number of diseases that reduce yield and quality. A disease survey was conducted in 2013 to identify pathogenic agents and assess disease severity on oat, canaryseed, barley and winter and spring wheat. Crown rust was detected at trace levels in four of 32 oat crops and the most common leaf spotting pathogens were Pyrenophora avenae and Stagnospora avenae, similar to previous years. On canaryseed, Septoria triseti was observed from plating of leaf samples and appeared to be highest in west-central SK and lowest in the north-east. Fusarium avenaceum was identified from plating of seeds in four of 26 crops, but only at low levels. In barley, only two crops were affected by stripe rust, but leaf spots symptoms observed on most crops, most commonly caused by Cochliobolus sativus and Pyrenophora teres; Septoria passerinii was identified in a few samples. Severe stripe rust infection was observed in seven of 89 winter wheat crops, but 60 crops were stripe rust-free. In winter wheat fusarium head blight was generally low in most regions of SK, except near Outlook, where severity was much higher. In spring wheat, stripe rust infection was observed in eight of 17 crops and was severe in one crop

Transonic Shocks In Multidimensional Divergent Nozzles

We establish existence, uniqueness and stability of transonic shocks for steady compressible non-isentropic potential flow system in a multidimensional divergent nozzle with an arbitrary smooth cross-section, for a prescribed exit pressure. The proof is based on solving a free boundary problem for a system of partial differential equations consisting of an elliptic equation and a transport equation. In the process, we obtain unique solvability for a class of transport equations with velocity fields of weak regularity(non-Lipschitz), an infinite dimensional weak implicit mapping theorem which does not require continuous Frechet differentiability, and regularity theory for a class of elliptic partial differential equations with discontinuous oblique boundary conditions.Comment: 54 page