Effect of crack-tip region constraint on fracture in the ductile-to-brittle transition

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U.S. Dept. of Commerce, National Bureau of Standards, Order from National Technical Information Service] , [Washington, D.C.], [Springfield, VA
Steel -- Fracture., Fracture mechanics., Steel -- Brittle
StatementT.L. Anderson.
SeriesNBSIR -- 84-3001., NBSIR -- 3001.
ContributionsUnited States. National Bureau of Standards.
The Physical Object
Paginationxii, 199 p. :
ID Numbers
Open LibraryOL18037933M

Get this from a library. Effect of crack-tip region constraint on fracture in the ductile-to-brittle transition. [T L Anderson; United States. National Bureau of Standards.]. Ductile-to-brittle transition is not an intrinsic phenomenon of material and it depends not only on the temperature and strain rate but also on crack tip constraint.

In order to study the crack tip constraint effect on the fracture toughness, SENB and SENT specimens with different crack depths are selected as the fracture mechanics specimens. The geometrical configurations are schematically drawn in Fig.

2 for both SENB and SENT specimens. (a) (b) Fig. This study examines crack front length and constraint loss effects on cleavage fracture toughness in ferritic steels at temperatures in the ductile-to-brittle transition region.

A local approach for fracture at the micro-scale of the material based on the Weibull stress is coupled with very detailed three-dimensional models of deep-notch bend by:   In this paper to establish a more precise fracture evaluation method in DBTT region for an irradiated RPV with a postulated surface flaw, fracture analysis procedures considering constraint effect, the Beremin model and damage mechanics model and a coupled model of these models were applied to the specimens with different constraints, which Author: Kiminobu Hojo, Takatoshi Hirota, Naoki Ogawa, Kentaro Yoshimoto, Yasuto Nagoshi, Shinichi Kawabata.

The effect of both factors on the stress/strain behavior in the vicinity of a crack tip is discussed systematically based on previous research and numerical analyses.

It is clarified that the common fracture parameters such as J and CTOD do not always represent material constants because of the change of stress/strain behavior as a result of the difference in plastic : M.

Toyoda. Ductile-to-brittle transition is not an intrinsic phenomenon of material and it depends not only on the temperature and strain rate but also on crack tip constraint. The effect of crack tip constraint on ductile brittle transition has been widely studied by both experiments and numerical simulation,, e.g., the influence of T-stress on crack resistance curve at Cited by: 2.

An effect of constraint on fracture toughness has therefore been demonstrated by this work, but the effect (an increase in fracture toughness by a factor of around ) is dominated by an increased amount of ductile tearing prior to cleavage Size: KB.

The effects of crack depth (a/W) and specimen width W on the fracture toughness and ductile–brittle transition have been investigated using three-point bend element analysis is employed to obtain the stress–strain fields ahead of the crack tip.

Description Effect of crack-tip region constraint on fracture in the ductile-to-brittle transition PDF

The results show that both normalized crack depth (a/W) and specimen width (W) affect the fracture toughness Cited by: effect on the fracture toughness (J c) of a material in the ductile-to-brittle transition temperature region as a difference in the crack tip constraint What is the loss of constraint.

This paper presents a modified Weibull stress model, which accounts for the effects of plastic strain and stress triaxiality at the crack tip region. The proposed model is applied to predict cleavage fracture in a modified A pressure vessel steel.

It is demonstrated that the Weibull modulus (m) remains constant in the temperature range considered, while the threshold Author: Xiao Sheng Gao, Gui Hua Zhang, T.S. Srivatsan. 1 1. Crack tip constraints in a weldment and their effect on ductile crack growth. Zhiliang Zhang and Erling Østby.

Norwegian University of Science and Technology (NTNU) and SINTEF Materials and Chemistry. The ductile-to-brittle transition can be measured by impact testing: the impact energy needed for fracture drops suddenly over a relatively narrow temperature range – temperature of the ductile-to-brittle transition.

Details Effect of crack-tip region constraint on fracture in the ductile-to-brittle transition PDF

Ductile-to-brittle transition Impact Energy BCC metals (e.g., iron at T E/). Constraint Effects on Brittle Fracture in SEeS) and C(T) Specimens Specimen size and geometry effects on cleavage fracture offerritic steels tested in the ductile-to-brittle transition region remain an important technological impediment in industrial applications of fracture typical dependence ofQ on distance ahead of crack tip.

E/ao. At this depth rock becomes less likely to fracture, and more likely to deform ductilely by creep. This happens because the brittle strength of a material is increased by the confining pressure, whilst the ductile strength of a material decreases with increasing temperature.

3. For ceramics, this type of transition occurs at much higher temperatures than for metals. The ductile-to-brittle transition can be measured by impact testing: the impact energy needed for fracture drops suddenly over a relatively narrow temperature range – temperature of the ductile-to-brittle transition.

region and the surrounding continuum: as a result, the crack-tip region was subjected to unphysical constraint. The purpose of this paper is to present the results of a recent molecular-dynamics study of the brittle-to-ductile transition [5,6].

Abstract. This work was motivated by the fact that although fracture toughness of a material in the ductile-to-brittle transition temperature region exhibits the test specimen thickness (TST) effect on, frequently described as, experiences a contradiction that is deduced from this empirical formulation; that is, = 0 for large TST.

On the other hand, our previous works have Cited by:   Specimen size and geometry effects on cleavage fracture of ferritic steels tested in the ductile-to-brittle transition region remain an important technological impediment in industrial applications of fracture mechanics and in the on-going development of consensus fracture testing standards.

This investigation employs 3-D nonllinear finite element analyses Cited by: Crack tip opening displacement is widely used and quite specific in that it is the only standardized test that covers all fracture behaviors that occur between the extremes associated with the stress intensity factor K and J-integral tests.

Effect of crack-tip region constraint on fracture in the ductile-to-brittle transition, NBSIR The effect of constraint on the ductile-brittle transition is investigated numerically under small scale yielding conditions in plane strain. An elastic-viscoplastic constitutive relation for a porous plastic solid is used to model ductile fracture by the nucleation and subsequent growth of voids to coalescence.

Two populations of second phase particles are represented, large inclusions with. The crack-tip constraint approach to the TST effect on J c assumes that the effect is a result of the out-of-plane crack-tip constraint.

Guo [5, 6] proposed a parameter T z = 33 /(11 + 22) to measure the magnitude of the out-of-plane crack-tip constraint, and. A Micromechanics Approach to Assess Effects of Constraint on Cleavage Fracture Toughness: a temperatures in the ductile-to-brittle transition (DBT) region, fracture by transgranular cleavage along well defined, low index stress fields and crack-tip constraint.

Microstructural Effect on the Ductile-to-Brittle Transition in Body Centered Cubic Metals Investigation by Three Dimensional Dislocation Dynamics Simulations A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Mechanical and Aerospace Engineering by Jianming Huang Author: Los Angeles.

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The Charpy test has been used for many years to characterize both the transition temperature and fracture energy for Ductile Iron, and a large body of Charpy impact energy data has been accumulated.

The Charpy test is a dynamic fracture test in which a notched (see Figure ) or unnotched test piece is struck an impact blow by a swinging.

UNSW Sydney NSW Australia Tel: (+61 02) CRICOS Provider Code G | ABN 57 Last update on Wed, 11/12/ Authorised by the Head, School of Materials Science and Engineering. Prediction of Cleavage Fracture in the Ductile-to-Brittle Transition Region of Pressure Vessel Steels: A Probabilistic Model Authors: Xiao Sheng Gao, Gui Hua Zhang, T.S.

Srivatsan Abstract: This paper presents a modified Weibull stress model, which accounts for the effects of plastic strain and stress triaxiality at the crack tip region. Some materials have the ability to behave as ductile materials at higher temperature and as brittle material below it.

This phenomenon is known as "ductile to brittle transition" and the temperature at which it occurs is called as the transition t. Figure 1. Fracture behavior of different materials as a function of temperature. The characterization of fracture resistance of ferritic steels in this region is problematic due to scatter in results, as well as size and temperature dependences [2–9].Size effects imply decreasing of the median value of fracture toughness and a larger scatter in small specimen than in larger Author: Carlos Berejnoi, Juan E.

Perez Ipiña. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality).

In the mid-to-upper transition region, small amounts of ductile crack extension (often fracture. @article{osti_, title = {Application of fracture toughness scaling models to the ductile-to- brittle transition}, author = {Link, R.E.

and Joyce, J.A.}, abstractNote = {An experimental investigation of fracture toughness in the ductile-brittle transition range was conducted.

A large number of ASTM A, Grade B steel, bend and tension specimens with varying crack lengths .In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension.

The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality).There has been some uncertainty in the field of fracture mechanics as to whether shifts in the ductile-to-brittle transition with specimen size are caused by statistical sampling effects or constraint effects.

Fracture toughness data for three carbon-manganese steels were analyzed to examine the effectiveness of each model in predicting the Cited by: 1.