STP1072

    Precracking and Strain Rate Effects on HSLA-100 Steel Charpy Specimens

    Published: Jan 1990


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    Abstract

    Improved predictions of the ductile-to-brittle transition behavior of structures are possible using Charpy specimens that have increased constraint. This report contains the results of an investigation into the combined effects of a change in notch acuity and a change in loading rate on the transition curve of a high-strength, low alloy (HSLA) steel. Specifically, the changes in absorbed energy and ductile-to-brittle transition temperature were noted. Standard Charpy V-notch specimens were fatigue precracked to a total crack depth (notch and precrack) of approximately 0.280 cm. The specimens were subsequently tested using an impact loading rate of 5.1 m/sec over a wide range of temperatures to fully develop the transition temperature curve. The transition temperature was determined using the 50% Fracture Appearance Transition Temperature (FATT). As expected, the level of absorbed energy was lower for precracked specimens as compared to standard specimens. The transition temperature of the precracked specimens was shifted upward by approximately 40°C. Both standard V-notch specimens and fatigue precracked specimens were tested at a slower loading rate of 0.0025 cm/sec to determine the combined effects of the sharper crack tip and the change in loading rate on both the energy absorbed and the transition temperature. At the slow loading rate the absorbed energy was lower for precracked specimens while the transition temperature was shifted upward by approximately 20°C. The results were also compared with those from 1.6-cm thick dynamic tear (DT) tests. It was found that the transition curve developed through fracture appearance for the DT test was identical to that of the precracked CVN tested at the impact loading rate.

    Keywords:

    ductile-to-brittle transition, Charpy, notch acuity, loading rate, transition temperature, dynamic tear, energy absorption, precracking, impact testing


    Author Information:

    Mikalac, S
    research engineershead of the Materials Engineering Department, David Taylor Research CenterDrexel University, AnnapolisPhiladelphia, MDPA

    Vassilaros, MG
    research engineershead of the Materials Engineering Department, David Taylor Research CenterDrexel University, AnnapolisPhiladelphia, MDPA

    Rogers, HC
    research engineershead of the Materials Engineering Department, David Taylor Research CenterDrexel University, AnnapolisPhiladelphia, MDPA


    Paper ID: STP24143S

    Committee/Subcommittee: E28.02

    DOI: 10.1520/STP24143S


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