An Experimental Measurement of Toughness Locus for a Ductile Material

Kim, Dong Hak; Lee, Jeong Hyun; Kim, Ho Dong; Kang, Ki‐Ju

doi:10.4028/www.scientific.net/kem.297-300.2410

Cited by 1 publication

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“…Figure 1 shows an example of displacement field due to side necking measured by SDSP (Lee and Kang 16 ). Kim et al 18 . have used the side necking displacement to estimate the parameter Q , a measure of the near‐tip stress triaxiality during ductile fracture.…”

Section: Introductionmentioning

confidence: 99%

Geometrical relationships between side necking and plastic zone size near a crack tip in ductile metals. Part I: Modified boundary layer solutions

Kim

Kang

2008

Fatigue Fract Eng Mat Struct

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A B S T R A C TThe plastic zone size is regarded as the measure of a material's resistance, and it also determines the fracture behaviour. Recently, stereo digital speckle photography (SDSP) has been found to be useful for measuring in-situ the side necking developed on the lateral surfaces of a specimen during a standard fracture test procedure for J IC . Because plastic deformation occurs without any volume change, the in-plane plastic zone developed around a crack tip should be accompanied by out-of-plane deformation, that is, side necking. With the aid of the new measurement technique, side necking is expected to act as a gauge for indicating the plastic zone size. As a preliminary study, the geometrical relationships between side necking and the plastic zone size near a crack tip in ductile metals are explored by using a finite element model with modified boundary conditions. As parameters representing the geometrical similarity between side necking and the plastic zone, the shapes of each region, the distances from the crack tip to the boundaries of each region, r p and r s and the areas of each region, A p and A s are examined for their sensitivities to variables such as mode mixity, hardening exponent and so on. Among them, the areas, A p and A s seem to be the best for application because an excellent linearity between them is maintained in a wide range of mode mixity and load level regardless of the hardening exponent, specimen thickness and yield stress.Keywords crack tip blunting; ductile fracture; plastic zone; side necking. N O M E N C L A T U R E A p = plastic zone areaA s = area of side necking region B = thickness of disk E =Young's modulus K = linear elastic stress intensity factor K I = mode-I stress intensity factor K II = mode II stress intensity factor n = strain hardening exponent ρ = notch radius Q = Q parameter R = radius of disk r p = distance from the crack tip to the plastic zone boundary r s = distance from the crack tip to the side necking region u x = boundary displacement in direction x u y = boundary displacement in direction y u z = out-of-plane displacement on side necking region ν = Poisson's ratio

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Section: Introductionmentioning

confidence: 99%