Abstract: The present invention is a method and apparatus for measuring the average hardness of a metal. This method capitalizes on the discovery that a longitudinal wave will travel roughly twice as fast as a transverse (shear) wave, the times-of-flight of the two waves are affected to different degrees by hardness, and there is a linear relationship between velocity and hardness. Longitudinal and transverse ultrasonic signals are applied to a first end (face) of the metal. The longitudinal and transverse signals are detected at this same first end of the metal after they are reflected off of the second end (face) of the metal. The time-of-flight for each of the longitudinal and transverse waves is measured. The hardness, H, in the metal is then determined by applying substantially the following equation: ##EQU1## where: H.sub.1 =known hardness for the hard phase of the metal;h=a constant for the metal alloy;R=measured ratio of shear and longitudinal times of transit; andR.sub.

Abstract: A method and apparatus for measuring tensile stress in a fastener already in place. This method capitalizes on the discovery that a longitudinal wave will travel roughly twice as fast as a transverse wave and the times-of-flight of the two waves are affected to different degrees by tensile stress. Longitudinal and transverse ultrasonic signals are applied to a first end of the fastener. The longitudinal and transverse signals are detected at this same first end of the fastener after they are reflected off of the second end of the fastener. The time-of-flight for each of the longitudinal and transverse waves is measured. The tensile stress, T, in the fastener is then determined by applying substantially the following equation: ##EQU1## where v.sub.10 and v.sub.20 =the velocities of the longitudinal and transverse signals, respectively, in a similar fastener not under stress;k=the length of the unstressed portion of the fastener;.lambda. and .mu.=Lame' constants for the fastener material; andD.sub.1 and D.sub.