Preface

The X International Geomechanics Conference is jubilee edition of traditional International Geomechanics Conference that Scientific and technical union of mining, geology and metallurgy in Bulgaria with co-operation with other organizations and universities organized. The International Geomechanics Conference has become a traditional scientific event and has proven its authority and importance over the years. The topics of the conference, determined by the members of the National editorial committee, are current and significant. The big challenge facing the mining industry is the rational use of mineral resources. List of Organizing Committee, International Advisory Committee, National Editorial Committee are available in this pdf.

Note 1--Section 2 denotes stress intensity factors as Kic or Kjc. The former implies linear elastic and the latter elastic-plastic stress intensity factor properties. KI~ also implies that larger specimens had to be used.
Section 3 explains the data validity requirements imposed on test data and the number of data required to constitute a statistically useable data set for determining a reference temperature, T o. The temperature, To, has a specific physical meaning with regard to the fracture mechanics properties of a material.
Section 4 describes the test specimens that can be used to develop valid Kjc data. The recommended specimen designs optimize the conditions of constraint, while at the same time they require the least amount of test material to produce a valid Kjc fracture toughness value. Care is taken to explain why certain other specimen types would be unsuitable for this type of work.
Section 5 presents, in simple terms, the fixturing and test equipment needs. Detailed descriptions are not necessary in the present manual, since The Annual Book of ASTM Standards, Volume 03.01, has several standard methods that present detailed information on fixtures that have been used successfully for the past 30 years. However, some of the lesser-known details relative to experience in the use of this equipment for transition temperature determination are presented herein.
Section 6 covers preparation of specimens for testing. The pre-cracking operation is an extremely important step, since, without sufficient care, it is possible to create false Kjc data, influenced more by the pre-cracking operations than by accurately representing the material fracture toughness property.
Section 7 deals with test machines, their mode of operation, and recommended specimen loading rates. The usual practice of measuring slow stable crack growth during loading of test specimens is not a requirement when testing to determine Kjc values. This greatly simplifies the procedure. Post-test visual measurement of the crack growth that has occurred up to the point of Kjc instability is required, however.
Section 8 presents all of the information needed to calculate values of Kj. Some Kjc data may have to be declared invalid due to failing the material performance requirements discussed in Section 3. Contrary to the implication in other ASTM Standards that invalid data are of no use, this method makes use of such data to contribute to the solution for the T o reference temperature. The only data to be discarded as unusable are data from tests that have not been conducted properly.
Section 9 contains the statistical equations that produce the fracture toughness, "scale parameter," for the material tested. The only complexity involved is the determination of substitute (dummy) Kj0 values, which must replace invalid Kjc values to be substituted into the calculations. The "scale parameter" is calculated and used in expressions given in Section 10 to calculate the reference temperature, To, which indexes the Master Curve.
Section 10 includes a second option for calculating the T o temperature that is useable when the Kj~ data have been generated at varied test temperatures. In this case, test temperature becomes an added variable in the calculation.
Section 11 shows how the variability of Kj~ values is handled using the threeparameter Weibull model. Tolerance bounds that will bracket the data scatter can be calculated with associated confidence percentages attached to the bounds. Also included is reality-check information that sets limits, or truncation points, outside of which the ductile to brittle-transition (Master Curve) characterization of a material may not be represented by the test data.
Section 12 presents information on work in progress. The pre-cracked Charpy specimen, if proven to be viable for the production of fracture mechanics data, would greatly expand the applications for the Master Curve procedure. This specimen, because of its small size, taxes the limit of specimen size requirements, so that a classification of work in progress is warranted at the present time. Another subject introduced is a proposal for dealing with macroscopic metallurgical inhomogeneity of the steel being tested. Some steel products, such as heavy-section steel plate, can have fracture toughness property variations that are a significant function of the throughthickness position. The Master Curve concept, unmodified, is not well suited for dealing with such macroscale inhomogeneity. In this particular case, the recommended approach that is suggested herein is only a subject for future evaluation.
Section 13 contains a brief discussion of important considerations involved in directly applying Master Curve fracture toughness data to the fracture-safety analysis of actual structures.
Appendices taken directly from standard E 1921-03 [ 19] have been added to the present document, since they contain example problem solutions for Sections 10.1, 10.2, 11.1, and 11.3 of the present manual. These problems can be used as self educational material to familiarize the user of the manual with the computational steps involved with the determination of the Master Curve reference temperature, T o ,

Ke
Physical crack size; meters, inches Gross thickness of specimens; meters, inches Net thickness of side-grooved specimens; meters, inches Thickness variable, x, that represents the specimen thickness of prediction, meters, inches The thickness of the specimens that were tested; meters, inches Four-inch thick specimen; 0.1016 meters, 4-in., B = 4 Effective thickness of side grooved specimens used in normalized compliance, meters, inches Weibull exponent; sometimes evaluated empirically, but in E 1921, used as a deterministic constant, 4, in all equations where fracture toughness is in units of K, and 2 for toughness in units of J Initial remaining ligament length in specimens; meters, inches Compliance, (VLL/P) normalized by elastic modulus (E') and effective thickness (Be) In Eq 21, a constant established by correlation between T o and Tcv N transition temperature, ~ Coefficient in Eq 30 for establishing tolerance bounds, M P a f m Coefficient in Eq 30 for establishing tolerance bounds, M P a f m Nominal elastic modulus established for ferritic steels; 206, 820 MPa, 30 x 106 psi A dimensionless function that reflects the geometry and mode of loading of the specimen Half height of a compact tension specimen, Fig. 7, meters, inches Incremental order for test data, namely i increments from 1 to N A path independent integral, J-integral; MJ/m 2, in.olb/in.  The peak K e of the fatigue pre-cracking cycle, M P a 4~, ksi ~4~-~. A linear-elastic stress intensity factor, MPa4rm, ksi z4~. In fatigue pre-cracking, the ratio R = Kmin/Kma x Number of data, sum of valid plus invalid data Probability of failure for a specimen, chosen at random from an infinite population of specimens, to fail at or before the Kjc of interest The number of valid Kjc data, exclusive of all invalid data Load; MN, pounds Test temperature; ~ Test temperature of the i th specimen in the incremental order, see Eq 26; ~ The Master Curve reference temperature, see Eqs 10 and 11; ~ For testing with unrecommended specimens, a test temperature at which median Kjc equals 100 MPa,/m. T O is not used to establish the Master Curve Specimen displacement measured on the plane of loading; meters, inches Specimen displacement measured at the front face location, see Fig. 7; meters, inches Specimen width denoted in Figs