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Determination of Crack-Tip Opening Displacement in T-Type Wedge Opening Loaded Specimen

  • W. Sochu
  • N. Noraphaiphipaksa
  • A. Manonukul
  • C. KanchanomaiEmail author
Brief Technical Note
  • 52 Downloads

Abstract

The protective layer at the crack tip of an alloy component can be damaged, and the resistance to crack propagation can be reduced by the combined effects of stress and a corrosive environment. Therefore, the measurement of crack-tip opening displacement (CTOD) can be applied to characterize the crack propagation rate (da/dt) during stress corrosion cracking (SCC) experiments. In the present work, CTOD of a T-type wedge opening loaded (T-WOL) specimen with a built-in loading bolt was initially determined using three-dimensional elastic-plastic finite element analysis (FEA). The influence of stress concentration from side groove on CTOD was clearly evaluated, i.e., the fluctuation of CTOD occurred near the groove-tip plane. However, CTOD became stable on >90% of thickness of T-WOL specimen. Therefore, CTOD at mid-thickness plane of T-WOL specimen could be applied for SCC experiment.

Keywords

Crack-tip opening displacement T-type wedge opening loaded specimen Stress corrosion cracking Finite element analysis 

Nomenclature

ASTM

American Society for Testing and Materials

a

Crack length

α

Constant of the Ramberg-Osgood relationship

Bn

Net thickness of T-WOL specimen

BS

British standards

CMOD

Crack-mouth opening displacement

CTOD δ5

Crack-tip opening displacement defined for a gage length of 5 mm

CTOD 45o

Crack-tip opening displacement defined as a distance between two intersections of ±45o lines from the crack tip with crack surfaces

CT

Specimen compact-tension specimen

da/dt

Crack propagation rate

∆K

Stress intensity factor range

ε

Strain

εbf

Back-face strain

E

Modulus of elasticity

F

Applied force

FL

Limit force corresponding to a fracture

FEA

Finite element analysis

ISO

International Organization for Standardization

KI

Stress intensity factor under opening mode

KC

Critical stress intensity factor or fracture toughness

LEFM

Linear-elastic fracture mechanics

μ

Friction coefficient

n

Constant of the Ramberg-Osgood relationship

R

Stress ratio

SCC

Stress corrosion cracking

σ

Stress

σn

Normal stress

σY

Yield stress

T-WOL

Specimen T-type wedge opening loaded specimen

τ

Shear stress

τc

Critical shear stress

W

Width of T-WOL specimen

WES

Japan welding engineering society standard

Notes

Acknowledgements

The authors would like to acknowledge the discussions and supports from Dr. J.T.H Pearce, the Thailand Research Fund (TRF), the Thailand Commission on Higher Education of Thailand (National Research University Project), the National Research Council of Thailand (NRCT), The Thammasat School of Engineering Research Fund, and the Thammasat University Research Fund.

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Copyright information

© Society for Experimental Mechanics 2019

Authors and Affiliations

  1. 1.Center of Materials Engineering and Performance, Department of Mechanical Engineering, Faculty of EngineeringThammasat UniversityPathumthaniThailand
  2. 2.Nitikorn Research Partner Co. Ltd.LumlukkaThailand
  3. 3.National Metal and Materials Technology Center (MTEC)National Science and Technology Development Agency (NSTDA)Klong LuangThailand

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