Residual Stress in Wheels: Comparison of Neutron Diffraction and Ultrasonic Methods, with Trends in RCF

The critical damage mechanism on many GB passenger train wheels is Rolling Contact Fatigue (RCF) cracking in the rim. Evidence from field observations suggests that RCF damage occurs much more quickly as the wheelsets near the end of their life. Wheel manufacturing processes induce a compressive hoop stress in the wheel rim; variations in residual stress through the life of a wheel may influence the observed RCF damage rates. This paper describes experiments to measure residual stresses in new and used wheel rims to identify whether this could be a significant factor, and compares the findings from neutron diffraction and ultrasonic birefringence methods. The scope goes beyond previous applications of neutron diffraction to railway wheels and identifies key considerations for future testing. Assuming that the as-manufactured stress distribution was similar for all three wheels tested, it is found that the stresses are redistributed within the wheel rim during its life as material is removed and plastic flow occurs. However, the hoop stress near the running surface remains compressive and may not have a large influence on the RCF damage rates

Asymmetric Cuts In The Contour Method For Residual Stress Measurement

The standard contour method is limited to sectioning test components into two symmetric halves. In this study a new approach is developed to deal with asymmetric cuts in the contour method of residual stress measurement. The proposed approach is demonstrated using finite element (FE) simulations and is validated experimentally using a series of asymmetric contour cuts and neutron diffraction measurements

Characterization of the residual stresses in spray-formed steels using neutron diffraction

Neutron diffraction was used to characterize the residual stresses in an as-sprayed tube-shaped steel preform. The measured residual stress distributions were compared with those simulated using finite element method by taking into account the effects of the thermal history, porosity and different phases of the sprayed preform. The porosity was measured using X-ray microcomputed tomography. The study revealed for the first time the correlation between the distribution of porosity and residual stress developed in the as-sprayed preform

Arrested States formed on Quenching Spin Chains with Competing Interactions and Conserved Dynamics

We study the effects of rapidly cooling to T = 0 a spin chain with conserved dynamics and competing interactions. Depending on the degree of competition, the system is found to get arrested in different kinds of metastable states. The most interesting of these has an inhomogeneous mixture of interspersed active and quiescent regions. In this state, the steady-state autocorrelation function decays as a stretched exponential $\sim \exp(-{(t/\tau_{o})}^{{1}\over{3}})$, and there is a two-step relaxation to equilibrium when the temperature is raised slightly.Comment: 4 pages, Latex, 3 postscript figures. Phys. Rev. E to appear (1999

Gallium nitride nanoparticles for solar-blind detectors

We investigate the properties of GaN semiconducting nanoparticles as a potential candidate for photodetection in the solar- blind region. The photocurrent spectral response is studied spanning the range 1·6-5·5 eV. A significant fraction of the response is in the range 4-5·5 eV. The results are compared to other optical properties and the origins of the features observed in the spectra are speculated upon

Studies in Sulphonamides Part VII: Synthesis of 1,3 diary1 2 (substituted sulphonamidobenzeneazo) propane 1, 3 diones and evaluation of their antibacterial properties

Different 1, 3-diarylpropane-1, 3-diones, 1-(P-nitropheny1) 3-phenyI-, p-nitropheny1) 3-(p-methyI-pheny1)- 1,)p-nitropheny1-3-(p-methoxypheny1)-, and 1-(m-nitropheny)-3- (p-methyIpheny1) propane 1, 3-diones have synthesised and coupled with a number a diazotised sulphonamide bases to yield the respective 1,3-diaryI-2-(substituted sulphonamidozeneazo) propane. All these substituted sulphonamidobenzence propane-1,3- diones have been screened in vitro for their antibacterial properties using cup plate agar diffusion method and some of these have been found active

Studies in Sulphonamides Part X

The present paper describes the synthesis of four differently substituted dibenzoylmethanes, viz., 1(m-nitropheny1)-3-(p-chloropheny1)-, 1-(m-notropheny1)-3-(p-bromopheny1)-, 1,3-di(p-methoxypheny1) and 1-(p-ethoxypheny1)-3-pheny1 propane-1,3-diones and study of their coupling reactions with different diazotised sulphonamide bases. The resulting 2-sulphonamidobenzeneazo derivatives were subjected to biological assay in vitro against S. aureus and E. coli and some of these found to posses considerable activity

Studies in Heterocyclic Compounds -Part VIII

Different azo compounds, 1-(m-nitrophenyl)-3-(p-bromophenyl)-and 1-(m-nitrophenyl) 3-(p-chlorophenyl)-2-(substituted sulphonamidobenzeneazo) propane-1,3-dinoes on condensation with hydrazine hydrate (100%), phenylhydrazine, p-nitrophenyllhydrazine and benzoylhydrazine yield the corresponding 1-simple/substituted-3-(m-nitrophenyl)-5-(p-bromo chlorophenyl)-4-(substituted sulphonamidobenzeneazo) pyrazoles. The homogeneity and purity of these was confirmed by TLC and these on screening in vitro against S. aureus and E. coli were found to exhibit antibacterial activity