A Procedure for the Determination of Ductile Fracture Toughness Values Using J Integral Techniques

Abstract The effect of gel on the fracture toughness of four PVC/NBR (50/50) blends was characterized by two different J- integral methods. Three of these blends are compatible blends with 33% acrylonitrile in NBRs, and the fourth with 21% acrylonitrile content, is an incompatible blend. Two types of gel are involved in this study microgels and macrogels. The J-integral methods are (1) conventional method proposed by Bagley and Landes and (2) crack initiation locus method proposed by Kim and Joe. The same load-displacement curves are used in both methods. However, the latter eliminates the energy dissipation away from the crack tip in the determination of Jc, while the former does not. Both methods produced almost the same results indicating that the energy dissipation away from the crack tip is negligible in these samples. The fracture toughness of a macrogel-containing blend is much greater than that of a microgel-containing blend, which, in turn, is only slightly greater than that of a gel-free blend. This implies that the two gel-containing blends have different fracture processes. The incompatible blend has the lowest fracture toughness due to weak interaction at the boundaries of the two phases.

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About Relation Between Irradiation Hardening of Ferritic Steels and Ductile Fracture Toughness Decrease

Volume 3: Design and Analysis ◽

10.1115/pvp2009-77026 ◽

2009 ◽

Author(s):

Jiri Novak

Keyword(s):

Fracture Toughness ◽

Temperature Dependence ◽

Ductile Fracture ◽

Stress Level ◽

Deformation Theory ◽

Strain Curve ◽

Stress Strain Curve ◽

Stress Strain ◽

Irradiation Hardening ◽

Ductile Fracture Toughness

We showed recently that temperature dependence of the ductile fracture toughness can be predicted on the base of two assumptions: 1) assumption of constant characteristic length, 2) assumption of proportionality between J-R curve slope and deformation work in unit volume, evaluated from zero to critical strain for initiation of deformation bands determined in plane strain geometry for material modeled by deformation theory of plasticity. Temperature dependence of ductile fracture toughness results simply from temperature dependence of the stress-strain curve. Irradiation hardening changes stress-strain behavior in a qualitatively different way: It is observed that irradiation hardening to certain yield stress level changes the stress-strain curve of the material in the same way as prestraining of the unirradiated material to the same flow stress level does. Equivalence of irradiation and prestraining concerns all key properties of deformation theory; namely the secant modulus should be taken from the stress-strain curve of unirradiated material. With exception of this specific feature, the task of finding relative fracture toughness decrease by irradiation is the same as prediction of relative decrease of fracture toughness by temperature change. In the frame of the corresponding theory, relative decrease of ductile fracture toughness expressed by J-R curve slope can be obtained from the stress-strain curve of unirradiated material and irradiation hardening level. Quantitative results are presented for the weld metals 72W and 73W, studied in the Fifth Irradiation Series in the Heavy-Section Steel Irradiation Program, and compared with experimental data.

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Determination of Material Fracture Toughness by Circular Pre-Cracked Small Punch Test Specimens

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.795.165 ◽

2019 ◽

Vol 795 ◽

pp. 165-171

Author(s):

Wu Lin Wang ◽

Du Wei Wang ◽

Kai Shu Guan

Keyword(s):

Fracture Toughness ◽

Empirical Correlation ◽

Fracture Toughness Test ◽

J Integral ◽

Small Punch Test ◽

Small Punch ◽

Punch Test ◽

Determination Procedure ◽

Material Fracture

Fracture toughness empirical correlation between SPT(Small Punch Test) with non-crack sample and standard fracture toughness test has been established in recent years. In order to compensate the imperfection of empirical correlation, such as absence theoretical basis, poor repeatability and universality, in this paper, an O-type pre-cracked sample was adopted to evaluate fracture toughness. The mechanical model of the sample is in compliance with plane strain condition in the direction of crack propagation. In this paper a determination procedure was studied and established, and the J-integral of steel Q345R was calculated using the procedure.

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Small punch test to predict ductile fracture toughness JIC and brittle fracture toughness KIC

Scripta Metallurgica et Materialia ◽

10.1016/0956-716x(91)90053-4 ◽

1991 ◽

Vol 25 (11) ◽

pp. 2481-2485 ◽

Cited By ~ 76

Author(s):

X. Mao ◽

M. Saito ◽

H. Takahashi

Keyword(s):

Fracture Toughness ◽

Brittle Fracture ◽

Ductile Fracture ◽

Small Punch Test ◽

Small Punch ◽

Punch Test ◽

Ductile Fracture Toughness

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Establishment of Unified Correlation of In-Plane and Out-of-Plane Constraints with Ductile Fracture Toughness of Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.853.22 ◽

2016 ◽

Vol 853 ◽

pp. 22-27 ◽

Cited By ~ 4

Author(s):

Bo Rui Yan ◽

G.Z. Wang ◽

Fu Zhen Xuan ◽

Shan Tung Tu

Keyword(s):

Fracture Toughness ◽

Ductile Fracture ◽

Structural Integrity ◽

Damage Model ◽

Equivalent Plastic Strain ◽

Specimen Thickness ◽

Wide Range ◽

Out Of Plane ◽

Correlation Line ◽

Ductile Fracture Toughness

In this paper, the finite element method (FEM) based on GTN damage model was used to obtain ductile fracture toughness and investigate the establishment method of unified correlation of in-plane and out-of-plane constraints with ductile fracture toughness of steels. The unified constraint parameter Ap at different equivalent plastic strain (εp) isolines has been calculated and analyzed for SEN(B) specimens with a wide range of in-plane and out-of-plane constraints. The results show that the average Ap along the specimen thickness (Apave) can well characterize a wide range of in-plane and out-of-plane constraints. The suitable εpisolines range for establishing the unified correlation between Apave and ductile fracture toughness of the steel has been obtained. For the specimens with lower constraint, the higher εp values should be used. The results also show that the correlation line of JC/Jref-Apave1/2is independent of the selections of the suitable εp isolines and the reference specimen. This may bring convenience for the establishment and application of the JC/Jref-Apave1/2correlation lines. Using ductile fracture toughness data of a small number of specimens with different constraints (such as three specimens with different a/W) together with FEM calculations of the parameter Ap, the correlation line of JC/Jref-Apave1/2can be established. The correlation line may be used in structural integrity assessments incorporating both in-plane and out-of-plane constraints.

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