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61.
Ductile failure of heterogeneous materials, such as cast aluminum alloys and discretely reinforced aluminums or DRA’s, initiates with cracking, fragmentation or interface separation of inclusions, that is followed by propagation in the matrix by a ductile mechanism of void nucleation and growth. Damage localizes in bands of intense plastic deformation between inclusions and coalesces into a macroscopic crack leading to overall failure. Ductile fracture is very sensitive to the local variations of the microstructure morphology. This is the first of a two part paper on the effect of microstructural morphology and properties on the ductile fracture in heterogeneous ductile materials. In this paper the locally enhanced Voronoi cell finite element method (LE-VCFEM) for rate-dependent porous elastic–viscoplastic materials is used to investigate the sensitivity of strain to failure to loading rates, microstructural morphology and material properties. A model is also proposed for strain to failure, incorporating the effects of important morphological parameters. 相似文献
62.
Swati Ghosh Vishav Preet Singh Rana Vivekanand Kain Vivek Mittal S.K. Baveja 《Materials & Design》2011,32(7):3823-3831
Effect of residual stress generated during tube fabrication, roll expansion and machining of stainless steel on the stress corrosion cracking (SCC) susceptibility was studied by testing fabricated tubes, tube–tube sheet joint and heavily machined plate of austenitic stainless steel (SS) in boiling MgCl2. U bend samples of machined plate were exposed to acidified SO4 + Cl? environment at room temperature to study its ambient temperature SCC behavior. The results correlate the SCC behavior of the SS tubes and roll expanded joints to the nature and magnitude of residual stresses present. The study also highlights the distinct difference in ambient temperature SCC behavior of machined vs. nonmachined surfaces. 相似文献
63.
In this investigation, crack density and wear performance of SiC particulate (SiCp) reinforced Al-based metal matrix composite (Al-MMC) fabricated by direct metal laser sintering (DMLS) process have been studied. Mainly, size and volume fraction of SiCp have been varied to analyze the crack and wear behavior of the composite. The study has suggested that crack density increases significantly after 15 volume percentage (vol.%) of SiCp. The paper has also suggested that when size (mesh) of reinforcement increases, wear resistance of the composite drops. Three hundred mesh of SiCp offers better wear resistance; above 300 mesh the specific wear rate increases significantly. Similarly, there has been no improvement of wear resistance after 20 vol.% of reinforcement. The scanning electron micrographs of the worn surfaces have revealed that during the wear test SiCp fragments into small pieces which act as abrasives to result in abrasive wear in the specimen. 相似文献
64.
S. Palit Sagar A.K. MetyaM. Ghosh S. Sivaprasad 《Materials Science and Engineering: A》2011,528(6):2895-2898
Influence of microstructural changes on the second harmonics of sinusoidal ultrasonic wave during low cycle fatigue (LCF) deformation in pearlitic steel was studied. Fatigue tests were interrupted and at every interruption, non-linear ultrasonic (NLU) parameter (β) was determined. Microstructures of cyclically deformed specimens at various cycles were examined by transmission electron microscopy (TEM). The variation of β with fatigue cycles was correlated with the microstructural changes and the results were explained through the variation in dislocation morphology and carbon content of the steel. 相似文献
65.
G. Balakrishnan P. Kuppusami S. Murugesan Chanchal Ghosh Divakar Ramachandran E. Mohandas D. Sastikumar 《Transactions of the Indian Institute of Metals》2011,64(3):297-299
Multilayers of CeO2/ZrO2 thin films were deposited on Si (100) substrates using pulsed laser deposition at an optimized oxygen partial pressure of 3×10−2 mbar and at room temperature. The CeO2 layer thickness was 10 nm, while the ZrO2 layer thickness was varied as 10, 20 and 30 nm. CeO2 and ZrO2 layers were deposited alternately to obtain 25 bilayers. High temperature x-ray diffraction (HTXRD) results showed that the multilayer films had cubic ceria and tetragonal ZrO2. Thermal expansion coefficients were calculated for CeO2 and t-ZrO2 and found to increase with the decrease of ZrO2 layer thickness. The cross sectional transmission electron microscopy (XTEM) of CeO2/ZrO2 multilayer also indicated that ceria was found to be in cubic phase while zirconia contained predominantly tetragonal phase along with cubic phase in thermally annealed specimen. 相似文献
66.
67.
The tracer diffusion coefficients of the elements as well as the integrated interdiffusion coefficients are determined for the Cu3Sn and Cu6Sn5 intermetallic compounds using incremental diffusion couples and Kirkendall marker shift measurements. The activation energies are determined for the former between 498 K and 623 K (225 °C and 350 °C) and for the latter between 423 K and 473 K (150 °C and 200 °C). Sn is found to be a slightly faster diffuser in Cu6Sn5, and Cu is found to be the faster diffuser in Cu3Sn. The results from the incremental couples are used to predict the behavior of a Cu/Sn couple where simultaneous growth of both intermetallics occurs. The waviness at the Cu3Sn/Cu6Sn5 interface and possible reasons for not finding Kirkendall markers in both intermetallics in the Cu/Sn couple are discussed. 相似文献
68.
Shenyan Huang Gautam Ghosh Xin Li Jan Ilavsky Zhenke Teng Peter K. Liaw 《Metallurgical and Materials Transactions A》2012,43(10):3423-3427
Ultra-small-angle X-ray scattering (USAXS) is employed to quantify the average size, interparticle spacing, and volume fraction of the primary B2 precipitates in Fe-based superalloys with varying Al concentration. The results are analyzed with a model incorporating polydispersity and interference effects and verified by transmission electron microscopy (TEM) characterizations. As the Al amount increases from 4 to 10?mass pct, there is an approximately 40?pct decrease in the average interparticle spacing and?~30?pct reduction in the average particle diameter. 相似文献
69.
70.
The fate of [1-14C] linoleic acid and [1-14C] linolenic acid in the liver slices and also in the liver tissues of live carnivorous catfish,Heteropneustes fossilis andClarias batrachus, was studied. Incorporation of the fatty acids into different lipid classes in the live fish differed greatly from the tissue
slices, indicating certain physiological control operative in vivo. The extent of desaturation and chain elongation of linoleic
and linolenic acids into long-chain polyunsaturated fatty acids was low. Linolenic acid was oxidized (thus labeling the saturated
fatty acid with liberated14C-acetyl-CoA) in preference to linoleic acid, and this oxidation also seemed to be under physiological control since both
of the fatty acids were poorly oxidized in the tissue slices and in the killed fish. These fish can therefore recognize the
difference in the acyl chain structures of linoleate and linolenate. The higher oxidation of liolenic acid and poor capacity
for its conversion to longer chain, highly unsaturated derivatives indicates a higher demand for the dietary supply of these
essential fatty acids in these two species. 相似文献