Evaluation of Dynamic Fracture Toughness Using the Normalization Method PDF Download

Author: G. Carcagno
Publisher:
ISBN:
Category : Dynamic fracture testing
Languages : en
Pages : 17

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Book Description
This paper presents a simple technique to determine dynamic J-R curves from a single, precracked Charpy-type specimen by means of an instrumented Charpy testing machine. This technique is based on the normalization method proposed originally by Landes and Herrera. This method eliminates the need for crack length monitoring that makes it particularly suitable under dynamic loading conditions.

Author: SM. Graham
Publisher:
ISBN:
Category : Alloy 718
Languages : en
Pages : 14

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Book Description
The fracture toughness and tensile properties of Alloy 718 were measured at quasi-static and dynamic loading rates for two different heat treatments and two product forms. Two different methods for conducting the dynamic tests were investigated; one involving interrupted tests and the other utilizing a single impact. The interrupted test method used multiple impacts with displacement limits to enable measurement of crack lengths at intermediate points. The normalization method was used to generate tearing resistance curves for the dynamic tests following the guidelines in ASTM Standard Test Method for measurement of Fracture Toughness (E 1820). The analysis pointed out the importance of obtaining a good measurement of load, displacement, and crack length at the point of maximum displacement (the anchor point). As the amount of ductile crack extension increased, the uncertainty in the plasticity function fit also increased. Methods to improve the fit were investigated, including the addition of anchor points from multiple tests, and use of a tangency point to estimate initiation. The resulting curves are compared to ascertain the variability obtained from nominally identical specimens, and to evaluate the effect of loading rate on the plasticity function. The normalization tearing resistance curves are compared with curves generated from the interrupted tests using compliance measurements during unloads to determine crack extension. Good agreement was obtained between the two methods of measuring tearing resistance, thereby validating the normalization analysis. The tests showed that multiple impacts drive down the tearing resistance, which may be significant in applications where a dynamic event causes load fluctuation.

Author: SM. Graham
Publisher:
ISBN:
Category : Dynamic fracture toughness
Languages : en
Pages : 19

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Book Description
This study examined fracture behavior of two HY-100 under-matched welds under dynamic loading. A new test fixture that provided greater control of specimen deflection during impact testing of SE(B) specimens was developed, as was a procedure for applying the Normalization Method to the analysis of dynamic fracture toughness tests. Successful application of Normalization involved using multiple specimens with varying ductile crack growth to establish the correct form for the plasticity function. The accuracy of the measured JId was verified by comparing with multi-specimen JId values.

Author: Welding Institute
Publisher:
ISBN:
Category : Fracture mechanics
Languages : en
Pages : 364

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Book Description

Author: Ravinder Chona
Publisher: ASTM International
ISBN: 0803118678
Category : Electronic book
Languages : en
Pages : 864

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Book Description
The proceedings of the 23rd National Symposium on Fracture Mechanics, held in College Station, Texas, June 1991, present a broad overview of the current state of the art in fracture mechanics research. Following the Swerdlow Lecture (Structural Problems in Search of Fracture Mechanics Solutions by

Author: T. Ochiai
Publisher:
ISBN:
Category : Brittle fracture
Languages : en
Pages : 34

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Book Description
Fracture toughness properties of structural steels of 490-MPa strength class and weld metals under dynamic loading are studied in the light of the near crack tip stress fields. The loading rate in toughness tests range from 0.1 to 500 mm/s. The near-tip stress fields are analyzed by 3D-FEM considering the strain rate effect on the flow properties of materials. Temperature rise caused by high-speed plastic deformation is also included in the FE analysis. The critical CTOD at brittle fracture initiation decreases when increasing the loading rate. This is due to the elevation of a local stress near the crack tip. The local approach is applied to the dynamic fracture toughness evaluation. It is shown that the brittle fracture resistance evaluated in terms of the Weibull stress, an integrated stress over a highly stressed region near the crack tip, is a material property independent of the loading rate. Based on the Weibull stress fracture criterion, the dynamic fracture toughness can be predicted from static toughness results. An engineering procedure to estimate the loading rate effect on the fracture toughness is also presented.

Author: U. Mayer
Publisher:
ISBN:
Category : Compact tension specimen
Languages : en
Pages : 14

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Book Description
ASTM E1921-15a describes the determination of the reference temperature T0,X for the loading rate X for ferritic steels in the transition range, where X is the order of magnitude of the average loading rate of the tests evaluated. Because this rate is defined for the linear-elastic part of a test only, the definition of the loading rate, valid for tests showing not only linear-elastic but also plastic behavior, is important. In a research project investigating the correlation of dynamic crack initiation and crack arrest funded by the German government, tests at -20°C on specimens of 22 NiMoCr 3 7 steel (A 508 Cl.2) were performed with different specimen geometry and loading devices in the range from 105 MPa?m s-1 to 3 x 106 MPa?m s-1. Evaluation according to ASTM E1921 shows differences of up to 30 K in T0,X obtained from linear-elastic test series and T0,X obtained from elastic-plastic test series with comparable dK/dt. New results were obtained in the current follow-up joint IWM-MPA project from test series at a loading rate of 5 x 105 MPa?m s-1. Results from tests with 1T C(T)-specimen at various test temperatures in the transition region are presented, analyzed, and reference temperature T0,5 is evaluated. The statistical distribution of the determined dynamic fracture toughness values KId resp., KJc,d and the determination of the characteristic loading rate in the case of elastic-plastic tests is discussed. This analysis shows the need of modifications of the standard evaluation method in ASTM E1921, if used for tests at elevated loading rate. The assumed statistical distribution has to be adapted and the actual loading rate at fracture initiation has to be taken into account. Suggestions for the considerations and requirements for the evaluation of data determined at elevated loading rates are presented.

Author: https://www.chinesestandard.net
Publisher: https://www.chinesestandard.net
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 44

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Book Description
This Standard stipulates the principles, specimens, testing machines, test procedures and measurements, calculation of fracture mechanical parameters and test reports of instrumental impact and evaluation of fracture toughness of prefabricated cracked Charpy specimens of metal materials by fracture mechanics methods. This Standard is applicable to the determination of fracture toughness of the prefabricated cracked Charpy-type specimens of metallic materials.

Author: WJ. Wright
Publisher:
ISBN:
Category : Crack length measurement
Languages : en
Pages : 19

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Book Description
Crack extension during fracture toughness tests of ferritic structural steels cannot be determined from measurements of unloading compliance or electric potential change when the specimen is dynamically loaded. Measurements of crack extension in fracture toughness tests are also very difficult when the test temperature is high or the test environment is aggressive. To circumvent this limitation, researchers for years have been developing key curve and normalization function methods to estimate crack extension in standard elastic-plastic fracture toughness test geometries.

Author: T. Kobayashi
Publisher:
ISBN:
Category : Absorbed energy
Languages : en
Pages : 9

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Book Description
Instrumented Charpy impact test has been widely used as a simple method for semi-empirically evaluating material impact toughness. The authors have developed a new instrumented Charpy impact testing system, which is called CAI (Computer Aided instrumented Charpy Impact testing) system. Using the CAI system, dynamic fracture toughness parameters such as Kd, Jd, Tmat, and various absorbed energies can be obtained from the load-deflection curve of a single precracked specimen for both ductile and brittle materials. It has been already put into practical use in Japan. This paper introduces the details of the toughness evaluation procedures in the CAI system.