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Influences of Cyclic Loading on Martensite Transformation of TRIP Steels
W. J. Dan,Z. G. Hu,W.-G. ZHANG 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.2
While austenite transformation into martensite induces increasing of the crack initiation life and restraining of the growth of fatigue cracks in cyclic-loading processes, TRIP-assisted steels have a better fatigue life than the AHSS (Advance High Strength Steels). As two key parameters in the cyclic loading process,strain amplitude and cyclic frequency are used in a kinetic transformation model to reasonably evaluate the phase transformation from austenite into martensite with the shear-band intersections theory, in which strain amplitude and cyclic frequency are related to the rate of shear-band intersection formation and the driving force of phase transformation. The results revealed that the martensite volume fraction increased and the rate of phase transformation decrease while the number of cycles increased, and the martensite volume fraction was almost constant after the number of cycles was more than 2000 times. Higher strain amplitude promotes martensite transformation and higher cyclic frequency impedes phase transformation, which are interpreted by temperature increment, the driving force of phase transformation and the rate of shearband intersection formation.
Kim, K. H.,Watson, Dan M.,Manoj, P.,Forrest, W. J.,Furlan, Elise,Najita, Joan,Sargent, Benjamin,Herná,ndez, Jesú,s,Calvet, Nuria,Adame, Lucí,a,Espaillat, Catherine,Megeath, S. T.,Muz American Astronomical Society 2016 The Astrophysical journal Supplement series Vol.226 No.1
<P>We present our investigation of 319 Class II objects in Orion A observed by Spitzer/IRS. We also present the follow-up observations of 120 of these Class II objects in Orion A from the Infrared Telescope Facility/SpeX. We measure continuum spectral indices, equivalent widths, and integrated fluxes that pertain to disk structure and dust composition from IRS spectra of Class II objects in Orion A. We estimate mass accretion rates using hydrogen recombination lines in the SpeX spectra of our targets. Utilizing these properties, we compare the distributions of the disk and dust properties of Orion A disks with those of Taurus disks with respect to position within Orion A (Orion Nebular Cluster [ONC] and L1641) and with the subgroups by the inferred radial structures, such as transitional disks (TDs) versus radially continuous full disks (FDs). Our main findings are as follows. (1) Inner disks evolve faster than the outer disks. (2) The mass accretion rates of TDs and those of radially continuous FDs are statistically significantly displaced from each other. The median mass accretion rate of radially continuous disks in the ONC and L1641 is not very different from that in Taurus. (3) Less grain processing has occurred in the disks in the ONC compared to those in Taurus, based on analysis of the shape index of the 10 mu m silicate feature (F-11.3/F-9.8). (4) The 20-31 mu m continuum spectral index tracks the projected distance from the most luminous Trapezium star, theta(1) Ori C. A possible explanation is UV ablation of the outer parts of disks.</P>