This part of ISO 12680 specifies a method for determining the dynamic Young's modulus of rectangular cross-section bars and circular cross-section specimens of refractories by impulse excitation of vibration. The dynamic Young's modulus is determined using the resonant frequency of the specimen in its flexural mode of vibration. NOTE Although not specifically described in this part of ISO 12680, this method can also be used at high temperatures with suitable equipment modification. This part of ISO 12680 does not address the safety issues associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices.