Suchergebnisse

This paper presents the large deformation, and failure response of a thin flat scored metallic disc (FSMD) subjected to a pressure impulse as experienced in a break-away disc or an explosion vent. The response of this thin FSMD is numerically simulated for a loading rate and validated with an experiment, where a good agreement is found on plastic strains, burst pressure, and deformation pattern. The loading rate and several geometric parameters of FSMD significantly influence its response. Therefore, the influence of loading rate ( P& ), score depth and width-todisc thickness ratio (t 1 /t and b/t), diameter-to-disc thickness ratio (D/t), score length-to-disc radius ratio (l/R), score pattern, and score geometry on the deformation and failure response of the thin FSMD is thoroughly investigated. The studies demonstrate that 1) the failure initiation point shifts from disc centre to between 1/5th and 1/3rd radius for loading rates ≤ 25 MPa/s; 2) the responses such as burst pressure, burst time, central deflection, and equivalent strain are i) sensitive to the loading rates up to 100 MPa/s, ii) sensitive to score's depth, only up to 0.6t and insensitive to score's width, iii) significantly unaffected for the number of scores N > 8, iv) stabilised for l/R > 0.5 and D/t > 250, v) almost the same for semi-circular, rectangular and triangular score geometries, and vi) very minimal for the number of scores N = 3; and 3) the failure do not initiate and propagate along all scores for N > 4 in the disc.

Dynamic (DRX) operative duringdeformation and static recrystallization (SRX) operative after deformation are considered responsible for the changes in microstructure and texture of deformed materials. Especially in the case of advanced steels that are required in the form of plates of various thicknesses, hot rolling is the main manufacturing process during which the steel undergoes DRX under the rolls and SRX between rolling passes/strands. Knowledge on DRX and SRX characteristics of such steels is crucial for optimisation of hot rolling parameters,achieving the desired microstructure and consequently the targeted mechanical properties.In this study, certain key aspects of both dynamic (DRX) and static recrystallisation (SRX) behaviour of aCu-bearing HSLA steel, which was developed at DMRL, have been explored through high temperature deformation studies using Gleeble thermo-mechanical simulator. Through uniaxial compression testing in the austenitic regime, domains of continuous and discontinuous DRX prevalent in the steel were identified and critical parameters for initiation of dynamic recrystallisation viz., critical strain (ec), critical stress (sc), peak stress (sp) and peak strain (ep) were determined as a function of temperature and strain rate. SRX characteristics were assessed through uniaxial double hit compression tests with fixed strain rate and strain per hit but at different temperatures and with different imposed intermediate static recrystallisation (ISRT) times. From the fractional softening data, parameters such as time for 50% recrystallisation, t0.5, temperature for 50% recrystallisation, T0.5, and activation energy, QSRX have been estimated.Although the steel exhibited good plastic deformation characteristics, the results suggest that the role of copper in retarding recrystallisation is significant.