On Relevant Ramberg-Osgood Fit to Engineering Nonlinear Fracture Mechanics Analysis

Abstract

The present paper proposes a robust method for the Ramberg-Osgood (R-O) fit to accurately estimate elastic-plastic J from the engineering fracture mechanics analysis based on deformation plasticity. The proposal is based on engineering stress-strain data to determine the R-O parameters, instead of true stress-strain data. Moreover, for practical applications, the method is given not only for the case when full stress-strain data are available but also for the case when only yield and tensile strengths are available. The reliability of the proposed method for the R-O fit is validated against detailed three-dimensional FE analyses for through-wall cracked pipes under global bending using five different materials, three stainless steels and two ferritic steels. Taking the FE J results based on incremental plasticity using actual stress-strain data as the reference, the FE J results based on deformation plasticity using various R-O fits are compared with reference J values. Comparisons show that the proposed R-O fit provides more accurate J values for all cases, compared to existing methods for the R-O fit. Advantages of the proposed R-O fit in practical applications are discussed, together with its accuracy.

Elastic–plastic J and COD estimation schemes for 90° elbow with throughwall circumferential crack at intrados under in-plane opening moment

“…Figures 6 and 7 show typical cases where it is seen that predictions of J and COD estimation schemes and the finite element values are reasonably close in spite of the load dependence of the plastic influence functions. Another manifestation of the violation of Ilyushin's theorem is the overprediction of plastic J and COD in the elastic to fully plastic transition regime for α 1 (Zahoor 1987;Kim et al 2001Kim et al , 2004. Chattopadhyay (2006) has recently investigated this issue in detail and proposed the modified plastic J -integral and COD equations by changing the α terms.…”

From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling

“…[] and Fan et al . []) and numerical models [e.g., Kim et al ., ]. In the elastic regime, our model undergoes no permanent deformation and the stresses are below a yielding threshold.…”

True stress–strain curve acquisition for irradiated stainless steel including the range exceeding necking strain

“…Particularly, it is difficult to get the stressestrain curve of the actual components. Several procedures have been proposed for estimating the stressestrain curve from the yield and ultimate strengths for structural integrity assessment of a cracked component [14,15]. However, these procedures did not focus on irradiated or hardened materials.…”