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Crack initiation and stable crack growth under monotonic loading in steels has been studied using an elastic-plastic finite element analysis. The fracture criterion used for crack initiation and stable crack growth was the critical strain energy density. In addition the shift core method for the analysis of crack extension was used. In the shift core modelling method, crack advance is simulated by moving the coordinates of the core region which surrounds the crack tip, to obtain the stiffness reduction. Simultaneously the core itself geometrically undergoes a simple rigid-body motion or translation during the crack extension. The analytically calculated and experimentally measured load for crack initiation and the subsequent stable crack growth agreed well. 相似文献
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Rehan Zahid Masjuki Bin Haji Hassan Mahendra Varman Riaz Ahmad Mufti Md. Abul Kalam Nurin Wahidah Binti Mohd Zulkifli 《固体与材料科学评论》2017,42(4):267-294
Tribological efficiency of industrial applications involving boundary lubrication regime can be improved to an appreciable extent by the deposition of hard coatings on interacting surfaces. Among such coatings, diamond-like carbon (DLC) coatings are considered to be one of the most suitable ones for the said role. DLC coatings possess a unique combination of physical, chemical, and material properties due to which they can help in minimizing friction-induced energy and material losses even under starved lubrication conditions. Since commercial lubricants are optimized for steel surfaces, therefore, a lot of experimental investigations were carried out to analyze the tribological compatibility of these lubricants with various DLC coatings. However, there is still a lack of understanding about how DLC coatings interact with conventional lubricant additives. Some researchers reported tribologically beneficial interactions between DLC coatings and formulated lubricants while others observed no such behavior. To address these inconsistencies, there is a need to rearrange the published data in a more apprehensible and organized manner with a special emphasis on the mechanisms responsible for a particular tribological behavior. In this way, it can be determined whether synergistic or antagonistic correlation exists between a particular DLC-lubricant combination and research on DLC coatings can be continued in a logical way. In this article, most widely investigated non-doped DLC coatings (ta-C, a-C:H, a-C, and ta-C:H) are tribologically analyzed. Average values of friction and wear coefficients are calculated for various DLC-lubricant combinations using already published data and compared to quantify the effectiveness of a particular lubricant additive in enhancing tribological characteristics of symmetrical non-doped DLC contacts. Moreover, tribological performance parameters of non-doped DLC coatings are compared with those of doped-DLC coatings to understand differences in their tribological behavior in combination with additives. 相似文献
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Heru Setyawan Fauziatul Fajaroh W. Widiyastuti Sugeng Winardi I. Wuled Lenggoro Nandang Mufti 《Journal of nanoparticle research》2012,14(4):1-9
In the present study, solid-solution gold?Cplatinum (Au?CPt) nanoparticles with controllable compositions were fabricated by high-intensity femtosecond laser irradiation of an aqueous solution of gold and platinum ions without any chemicals and complicated processes. Transmittance electron microscopy revealed that the single nanometer-sized particles were fabricated by femtosecond laser irradiation of mixed aqueous solutions of gold and platinum ions. The crystalline structure of nanoparticles was characterized by electron and X-ray diffractions. Contrary to the bulk Au?CPt binary systems, which commonly contain a pair of diffraction peaks between pure gold and platinum peaks because of its large miscibility gap in phase diagram, or mixture of Au and Pt, the diffraction peaks of Au?CPt nanoparticles fabricated in the experiment showed a characteristic of the fcc-type lattice. Moreover, the diffraction patterns shifted monotonically from the peak position of pure gold to that of pure platinum as the fractions of platinum ions in the solution were increased. These observations strongly imply that the Au?CPt nanoparticles were solid solution with intended compositions. This technique is not only simple and environmentally friendly, but also applicable to other binary and ternary systems. 相似文献
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N. Mufti 《Journal of magnetism and magnetic materials》2009,321(11):1767-1769
We have investigated the magnetic and dielectric properties of polycrystalline samples of the spinel MnCr2O4. Below the ferrimagnetic ordering temperature at TN∼43 K, both magnetization and dielectric measurements show signatures of the onset of a conical structure at Ts∼17 K and a lock-in temperature at Tf∼14 K. These values are similar to those previously reported for single-crystal samples, where the spiral structure is short-range ordered (SRO) at low temperatures. The application of magnetic field suppresses the dielectric anomaly at Tf indicating that the coherence length of the ordering increases. MnCr2O4 exhibits a symmetrical magnetodielectric response between Tf and Ts that scales with the square of the magnetization. This suggests that the magnetodielectric coupling originates from the P2M2 term in the free energy expansion. The magnetodielectric response becomes asymmetric with respect to field below Tf. 相似文献
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Jorge AB Oró-Solé J Bea AM Mufti N Palstra TT Rodgers JA Attfield JP Fuertes A 《Journal of the American Chemical Society》2008,130(38):12572-12573
We have explored a new strategy to discover materials with large resistive or capacitive responses to magnetic fields by synthesizing EuMO2N (M = Nb, Ta) perovskites that combine ferromagnetic order of S = 7/2 Eu2+ spins with possible off-center distortions of the d0 M5+ cations enhanced by covalent bonding to N. EuNbO2N shows colossal magnetoresistances at low temperatures and a giant magnetocapacitance. However, the latter response originates from a microstructural effect rather than an intrinsic multiferroism. 相似文献
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In the present study a parametric thermal analysis of a single molten metal droplet deposited on a large substrate has been
performed with application to various solid freeform fabrication (SFF) processes employing droplet-based deposition. Simulation
is conducted to investigate the effect of droplet shape, substrate thermal properties, substrate size and thermal boundary
conditions of substrate base on the cooling rate of the droplet and the substrate. It is found that droplet shape and substrate
thermal properties have significant effect only on the solidification time, whereas the steady-state conditions vary significantly
with all the process parameters studied. 相似文献
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Imran Khan Payare L. Sangwan Alamgir A. Dar Rather A. Rafiq Mufti R. Farrukh Jagdish K. Dhar Sheikh A. Tasduq Surrinder Koul 《Journal of separation science》2013,36(16):2602-2610
Betulinic acid ( 1 ), betulinic acid‐3‐acetate ( 2 ), 3‐acetylbetulinaldehyde ( 3 ), oleanolic acid‐3‐acetate ( 4 ), 3‐β‐hydroxy‐28,19‐β‐olenolide ( 5 ), and β‐sitosterol ( 6 ) were isolated from Platanus orientalis and a high‐performance thin‐layer chromatography method was developed for their simultaneous quantification. The markers were first derivatized on the chromatogram with ceric ammonium sulfate and then high‐performance thin‐layer chromatography densitometry was carried out. Chromatographic separation of these markers was carried out on silica gel 60 plates using a ternary solvent system n‐hexane/toluene/acetone (6:3.5:1 v/v/v) as a mobile phase. For marker 1 , a deuterium (D2) lamp and wavelength of 420 nm was used. A tungsten (W) lamp was used for markers 2 and 3 at 550 nm and for 4 – 6 at 500 nm. The method was validated for accuracy, precision, LOD, and LOQ. All calibration curves showed a good linear relationship (r > 0.9919). The precision evaluated by an intra‐ and interday study showed RSDs < 2.51% and accuracy validation recovery between 95.54 and 99.33% with RSDs < 1.55%. The successful application of the validated method showed 1 as the most abundant component (4.63%) and 5 (0.017%) the least. The markers displayed a significant cytotoxic effect against human keratinocyte, mouse melanoma, and human skin epithelial carcinoma cancer cells by using a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. 相似文献
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INHIBITION OF UV AND PSORALEN-PLUS-LIGHT MUTAGENESIS IN PHAGE T4 BY GENE 43 ANTIMUTATOR POLYMERASE ALLELES 总被引:2,自引:0,他引:2
Daniel B. Yarosh Virginia Johns Siraj Mufti Carol Bernstein Harris Bernstein 《Photochemistry and photobiology》1980,31(4):341-350
Abstract— Mutagenesis by UV light or psoralen-plus-light was measured by increases in the reversion of nonsense mutants of phage T4. In the presence of either of two gene 43 antimutator polymerase alleles, ts CB120 or ts CB87, UV-induced reversion was inhibited. Likewise psoralen-plus-light mutagenesis was inhibited when the ts CB120 allele was present. These results imply that the gene 43 DNA polymerase has a role in the formation of mutations from the DNA lesions induced by UV and psoralen-plus-light. 相似文献