STP1248

    Effect of Surface Finish of Charpy Anvils and Striking Bits on Absorbed Energy

    Published: Jan 1995


      Format Pages Price  
    PDF Version (164K) 10 $25   ADD TO CART
    Complete Source PDF (4.9M) 10 $96   ADD TO CART


    Abstract

    Some new Charpy impact testing machines often report higher energy values than machines which have been in service for a period of time. An investigation into the cause of this phenomenon revealed that a major contributing factor was the surface finish of the Charpy anvils and the striking bit. Depending on the trajectory of the Charpy specimen halves after impact and the configuration of the testing machine, a considerable amount of friction may occur between the specimen and the anvils as the specimen is broken. Friction may also occur between the specimen and the striking bit as the specimen exits the machine. Polishing the anvils and the striking bit minimizes the friction between these parts. As a Charpy impact testing machine tests many samples, the striking bit and anvils become burnished and energy absorption due to friction is reduced. If new parts are highly polished prior to installation, the burnishing, normally caused by testing many samples, is simulated. In this way energy absorption associated with friction during the wear-in period is minimized and remains more constant during the life of the anvils and striking bit. ASTM Standard Test Methods for Notched Bar Impact Testing of Metallic Materials (E 23) requires the surface finish of the anvil and striking bit to be better than 4 μm (125 μin.). Specifying a 0.1 μm (4 μin.) surface finish as a requirement in E 23 will not only eliminate the wear-in period, but will minimize shifts in test results when anvils and/or striking bits are replaced in Charpy impact testing machines.

    Keywords:

    anvils, Charpy impact test, energy loss, friction, impact test, striker, surface finish


    Author Information:

    Ruth, EA
    Manager, Engineering & Systems, Tinius Olsen Testing Machine Co., Inc., Willow Grove, Pennsylvania

    Vigliotti, DP
    Technician and Supervisory Metallurgist, Materials Reliability Division, National Institute of Standards and Technology, Boulder, Colorado

    Siewert, TA
    Technician and Supervisory Metallurgist, Materials Reliability Division, National Institute of Standards and Technology, Boulder, Colorado


    Paper ID: STP14658S

    Committee/Subcommittee: E28.07

    DOI: 10.1520/STP14658S


    CrossRef ASTM International is a member of CrossRef.