Metallurgical and Materials Transactions A

, Volume 40, Issue 5, pp 1118–1125 | Cite as

Using Thermomechanical Conditioning Cycles to Improve Fracture Toughness of Low Carbon Steel

  • F. W. Wu
  • R. N. Ibrahim
  • R. K. Singh Raman
  • R. Das
Article
First Online:
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Abstract

The improvement of material toughness has significant industrial applications. In this article, the thermomechanical conditioning (TMC) cycle (which involves simultaneous application of heat to a moderate temperature combined with a tensile load, followed by unloading and cooling to room temperature) was used to improve the fracture toughness of the material. Apparent fracture toughness (K a ) is denoted to represent the fracture toughness of cracked components after the application of TMC cycles. The TMC cycles result in a significant increase in the apparent fracture toughness (K a ) of AS 1548 grade 7-460R steel as compared to the fracture toughness (K IC ) of the original material. It is found that the improvement in the apparent fracture toughness of the material was due to the increase in plastic strain and the plastic zone size ahead of the crack tip that occurred after applying TMC. In this study, both the apparent and original fracture toughness (K a and K IC ) are evaluated using the cylindrical notched tensile (CNT) technique, which is considerably cost effective over the standard compact tension specimens (ASTM E399).

Keywords

Fracture Toughness Stress Intensity Factor Compressive Residual Stress Plastic Zone Size Stable Crack Growth 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

a

actual crack length

aeff

effective crack length

CNT

cylindrical notched tensile (specimen)

CTOD

crack tip opening displacement

d

equivalent diameter of the ligament

D

specimen outside diameter

F

parametric function describing specimen geometry for the concentric case

FO

parametric function describing specimen geometry for an eccentric ligament

FEA

finite element analysis

Ka

apparent fracture toughness

KCON

applied stress intensity factor during TMC cycles

KI

mode I stress intensity factor

KIC

mode I critical stress intensity factor (fracture toughness)

(KIC)est

first estimate of K IC

P

tensile force applied to the specimen

ry

Irwin correction factor (plastic zone radius)

SEM

scanning electron microscope

TCON

conditioning temperature

TMC

thermomechanical conditioning cycles

α

constant

ε

eccentricity of the ligament

σb

nominal bending stress in the specimen

σt

nominal axial stress in the specimen

σuts

material ultimate strength

σys

material yield strength

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2009

Authors and Affiliations

  • F. W. Wu
    • 1
  • R. N. Ibrahim
    • 1
  • R. K. Singh Raman
    • 1
    • 2
  • R. Das
    • 3
  1. 1.Department of Mechanical and Aerospace EngineeringMonash UniversityClaytonAustralia
  2. 2.Department of Chemical EngineeringMonash UniversityClaytonAustralia
  3. 3.CSIRO Mathematical and Information SciencesClaytonAustralia

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