Author: S. Bhattacharya Publisher: ISBN: Category : Area measurement Languages : en Pages : 10
Book Description
The standard methods of estimating the average size of the slow crack growth region as described in BS 5762 (Crack Opening Displacement (COD)) and ASTM E 1290 (Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement) are cumbersome, painstaking, time consuming, and dependent on several factors; e.g., section thickness, the nature of crack front profile, and the number of measurements. Often errors are introduced in determining the average crack size which in turn affect the determination of critical CTOD value.
Author: NV. Challenger Publisher: ISBN: Category : Continuum mechanics Languages : en Pages : 19
Book Description
This paper presents the results of an experimental program to study size and geometry effects in CTOD R-curves. The results were obtained from room temperature unloading compliance R-curve tests on different-sized single-edge-notch-bend (SENB) specimens made from Ti-3Al-2.5V alloy, HY100 steel, and nickel-aluminum-bronze (NAB). The crack growth resistance was measured in terms of conventional CTOD, ?0 (i.e., as defined in BS 5762), CTOD corrected for crack growth, ?R, and CTOD derived using a double clip gage arrangement, ?dc. It was found that all the CTOD R-curves exhibited upswings after crack extensions corresponding to approximately 15% of the initial uncracked ligament. Based on the results obtained in this study, it is postulated that the crack growth limit for CTOD controlled crack growth in R-curves is 15% of the initial uncracked ligament. This condition alone, however, is not sufficient to guarantee size/geometry independent results. It is also necessary to have the same level of specimen constraint.
Author: S. Bhattacharya Publisher: ISBN: Category : Crack size Languages : en Pages : 7
Book Description
ASTM Committee E-24 on Fracture has recently standardized the crack tip opening displacement (CTOD) measurement method. Three major differences between the ASTM E 1290-89 method and British Standard BS5762:1979 are outlined, and the influence of these differences on the critical crack initiation CTOD value is studied. The study is based on a typical fatigue crack and slow crack growth front profile. A difference of up to 6% in the CTOD values between the two standards, irrespective of the slow crack growth size, was found in the present study. However, a marginal ditterence of only 2% in the initiation CTOD value could be observed for the slow crack growth situation considered.
Author: Juan R. Donoso Publisher: ISBN: Category : Common format Languages : en Pages : 21
Book Description
A new method of construction of the J-R curve has been proposed recently that makes use of a postulated crack growth law relating stable crack extension, ? a, to plastic displacement, vpl. An analytical treatment of both the J-?a curve and the force-displacement, P-v, curve, is now possible even under circumstances in which the sole inputs are the P-v curve and the initial and final crack size values. Based upon this crack growth law concept, and on the common and the concise format equations of Donoso and Landes, an alternative way of estimating the amount of stable crack growth is presented. This alternative method, which allows for the evaluation of the crack size at any value of force or displacement along the P-v curve, has been applied to some examples of C(T) fracture test specimens that have crack extension values obtained by the unloading compliance method. The results are quite encouraging, and the method is extended here to cases in which there are no crack extension measurements available.
Author: George C. Sih Publisher: Springer Science & Business Media ISBN: 9400961529 Category : Science Languages : en Pages : 289
Book Description
Concrete has traditionally been known as a material used widely in the construction of roads, bridges and buildings. Since cost effectiveness has always been one of the more important aspects of design, concrete, when reinforced and/or prestressed, is finding more use in other areas of application such as floating marine structures, storage tanks, nuclear vessel containments and a host of other structures. Because of the demand for concrete to operate under different loading and environmen tal conditions, increasing attention has been paid to study concrete specimens and structure behavior. A subject of major concern is how the localized segregation of the constituents in concrete would affect its global behavior. The degree of nonhomogeneity due to material property and damage. by yielding and/or cracking depends on the size scale and loading rate under consideration. Segregation or clustering of aggregates at the macroscopic level will affect specimen behavior to a larger degree than it would to a large structure such as a dam. Hence, a knowledge of concrete behavior over a wide range of scale is desired. The parameters governing micro-and macro-cracking and the techniques for evaluating and observing the damage in concrete need to be better understood. This volume is intended to be an attempt in this direction. The application of Linear Elastic Fracture Mechanics to concrete is discussed in several of the chapters.
Author: G. Pluvinage Publisher: Springer Science & Business Media ISBN: 9401008809 Category : Science Languages : en Pages : 361
Book Description
As Directors of this NATO Workshop, we welcome this opportunity to record formally our thanks to the NATO Scientific Affairs Division for making our meeting possible through generous financial support and encouragement. This meeting has two purposes: the first obvious one because we have collected scientists from East, far East and west to discuss new development in the field of fracture mechanics: the notch fracture mechanics. The second is less obvious but perhaps in longer term more important that is the building of bridges between scientists in the frame of a network called Without Walls Institute on Notch Effects in Fatigue and Fracture". Physical perception of notch effects is not so easy to understand as the presence of a geometrical discontinuity as a worst effect than the simple reduction of cross section. Notch effects in fatigue and fracture is characterised by the following fundamental fact: it is not the maximum local stress or stress which governs the phenomena of fatigue and fracture. The physic shows that a process volume is needed probably to store the necessary energy for starting and propagating the phenomenon. This is a rupture of the traditional "strength of material" school which always give the prior importance of the local maximum stress. This concept of process volume was strongly affirmed during this workshop.
Author: S. Bhattacharya
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Author: NV. Challenger
Author: S. Bhattacharya
Author: Juan R. Donoso
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Author: George C. Sih
Author: G. Pluvinage