Numerical investigations of the stepped double torsion fracture toughness specimen

This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical bone. This study also provides some recommendations along with the critical review, which would be beneficial for future research of fracture analysis of cortical bone. Cortical bone fractures due to sports activities, climbing, running, and engagement in transport or industrial accidents. Individuals having different diseases are also at high risk of cortical bone fracture. It has been observed that osteon orientation influences cortical bone fracture toughness and fracture mechanisms. Apart from this, recent studies indicate that fracture parameters of cortical bone also depend on many factors such as age, sex, temperature, osteoporosis, orientation, location, loading condition, strain rate, and storage facility, etc. The cortical bone regains its fracture toughness due to various toughening mechanisms. Owing to these factors, several experimental, clinical, and numerical investigations have been carried out to determine the fracture parameters of the cortical bone. Cortical bone is the dense outer surface of the bone and contributes to 80%–82% of the skeleton mass. Cortical bone experiences load far exceeding body weight due to muscle contraction and the dynamics of motion. It is very important to know the fracture pattern, direction of fracture, location of the fracture, and toughening mechanism of cortical bone. A basic understanding of the different factors that affect the fracture parameters and fracture mechanisms of the cortical bone is necessary to prevent the failure and fracture of cortical bone. This review has summarized the advancement considered in the various experimental techniques and numerical methods to get complete information about the fracture mechanisms of cortical bone.

Download Full-text

Standardization of CTOD Toughness Correction for Constraint Loss in Steel Components

Volume 1: Codes and Standards ◽

10.1115/pvp2008-61076 ◽

2008 ◽

Author(s):

Fumiyoshi Minami ◽

Mitsuru Ohata

Keyword(s):

Fracture Toughness ◽

Fracture Criterion ◽

Shape Parameter ◽

Pipeline Steel ◽

Fracture Initiation ◽

Failure Assessment ◽

Fracture Assessment ◽

Steel Welds ◽

Weibull Stress ◽

Fracture Toughness Specimen

A standardized procedure for correction of CTOD fracture toughness for constraint loss in steel components is presented. The equivalent CTOD ratio β = δ/δWP is developed on the basis of the Weibull stress fracture criterion, where δ and δWP are CTODs of the standard fracture toughness specimen and the wide plate component, respectively, at the same level of the Weibull stress. With the CTOD ratio β, the critical CTOD δWP, cr of the wide plate that is equivalent to δcr at brittle fracture initiation is given as δWP, cr = δcr/β. Nomographs of β are provided as a function of the crack type and size in the component, the yield-to-tensile ratio of the material and the Weibull shape parameter m. The fracture assessment with β is shown within the context of a failure assessment diagram (FAD), which includes the pipeline steel welds with a notch in the weld metal.

Download Full-text

Measurement of dynamic fracture toughness by double torsion testing

Mechanical Engineering Journal ◽

10.1299/mej.17-00529 ◽

2018 ◽

Vol 5 (2) ◽

pp. 17-00529-17-00529 ◽

Cited By ~ 1

Author(s):

Tadaharu ADACHI ◽

Zoltan MAJOR ◽

Kenji FUJII ◽

Kohei MIKUMA ◽

Markus Karamoy UMBOH ◽

...

Keyword(s):

Fracture Toughness ◽

Dynamic Fracture ◽

Dynamic Fracture Toughness ◽

Torsion Testing ◽

Double Torsion

Download Full-text

An evaluation of the chevron bend bar fracture toughness specimen

Engineering Fracture Mechanics ◽

10.1016/0013-7944(81)90094-1 ◽

1981 ◽

Vol 14 (4) ◽

pp. 821-832 ◽

Cited By ~ 17

Author(s):

T.T. Shih

Keyword(s):

Fracture Toughness ◽

Fracture Toughness Specimen

Download Full-text

Constraint Based Assessments of Large-Scale Cracked Straight Pipes and Elbows

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2015-45948 ◽

2015 ◽

Author(s):

Marius Gintalas ◽

Robert A. Ainsworth

Keyword(s):

Fracture Toughness ◽

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Large Scale ◽

Initiation Point ◽

T Stress ◽

Advanced Analysis ◽

Material Fracture ◽

Fracture Toughness Specimen

The paper presents T-stress solutions developed to characterize constraint levels in large-scale cracked pipes and elbows. Stress intensity factor, KI, solutions for pipes and elbows are normalised by material fracture toughness to define the Kr parameter in fitness-for-service procedures, such as R6. Adding knowledge on levels of T-stress allows more advanced analysis through a normalised constraint parameter βT. The paper presents analyses for 6 pipes and 8 elbows. Values of the normalised constraint parameter βT are calculated for each pipe and elbow at the experimentally measured crack initiation point. Comparison of constraint levels in the pipes and elbows with those in various types of fracture toughness specimen are used to predict the initiation loads using the R6 method and to provide guidelines for transferability.

Download Full-text

Use of Small Specimens for Evaluation of Irradiated Materials

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-98089 ◽

2013 ◽

Author(s):

Mikhail A. Sokolov ◽

Randy K. Nanstad

Keyword(s):

Fracture Toughness ◽

Small Volume ◽

Radioactive Material ◽

Surveillance Programs ◽

Series Of Experiments ◽

Point Bend ◽

Impact Data ◽

Surveillance Specimens ◽

Reactor Pressure ◽

Fracture Toughness Specimen

Small specimens are playing the key role in evaluating properties of irradiated materials. The use of small specimens provides several advantages. Typically, only small volume of material can be irradiated in a reactor at desirable conditions in terms of temperature, neutron flux, and neutron dose. Small volume of irradiated material may also allow for easier handling of specimens. Smaller specimens reduce the amount of radioactive material, minimizing personnel exposures and waste disposal. However, use of small specimens imposes variety of challenges as well. These challenges are associated with proper accounting for size effects and transferability of small specimen data to the real structures of interest. The PCVN specimen as well as any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of RPVs. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Precracking and testing of Charpy surveillance specimens would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. However, there is a growing number of indications that there might be a bias in the reference fracture toughness transition temperature, To values derived from PCVN and compact specimens. The present paper summarizes data from the series of experiments that use subsize specimens for evaluation of the transition fracture toughness of reactor pressure vessel (RPV) steels. Two types of compact specimens and three types of three-point bend specimens from five RPV materials were used in these subsize experiments. The current results showed that To determined from PCVN specimens with width (W) to thickness (B) ratio W/B = 1, on average, are lower than To determined from compact specimens with W/B = 2. At the same time, three-point bend specimens with W/B = 2 exhibited To values that were very similar to To values derived from compact specimens. Constraint corrections developed by Dodds et al. are applied to assess the bias.

Download Full-text