MODELING OF ROTATIONAL FACTOR IN NOTCHED BEND SPECIMEN UNDER GENERAL AND LOCAL YIELD SITUATION

The location of the plastic hinge axis in a three point SEN bend speci men is a highly controversial issue. An unambiguous and reliable estim ation of rotational factor (r(p)) is very essential for the accurate d etermination of CTOD data. In contrast to the numerous studies reporte d on the r(p) determination in a cracked situation, limited informatio n is available for a blunt notch situation, although many engineering structures do contain notchlike defects with finite root radius. An at tempt is made to determine r(p) for two situations, namely well below the general yield and around the general yield. The work is based on a theoretical estimation of the plastic zone size using the stress conc entration factor and the elastic as well as the elastic-plastic stress distribution. A theoretical estimation of r(p) in both the pseudo-ela stic and the elastic-plastic situation is estimated through analytical modelling involving factors like plastic zone size, bend angle and no tch opening displacement. The values of the rotational factor are foun d to increase from a small value to around 0.29 in a well below genera l yield situation to 0.53 to 0.54 in a general yield situation with co ntinued loading. A wide discrepancy in the P/P-GY ratio separating the two situations, i.e. well below general yield and around general yiel d, is observed. Consideration of the elastic and the elasto-plastic st ress distribution indicates a much smaller value of P/P-GY as compared to the ratio obtained from experimental load-displacement plots.