Abstract: An insert (10) for use in clothing designed to protect against bullets or knife attacks includes an upper layer (14) having a ceramic matrix. A pair of plugs (20) are fitted to the ceramic layer (14), the plugs (20) being made from a material having an impedance to vibration substantially the same as that of the ceramic matrix at the point of manufacture. The plugs (20) are configured for conducting mechanical vibration through the ceramic layer (14), for recording a vibration-related signature for the insert (10). By comparing a series of such signatures recorded over time, it is possible to assess whether the internal structure of the ceramic matrix has become damaged, which is useful in determining whether the insert needs to be replaced or repaired.

Abstract: A bearing comprises two opposing ring and a single row of rolling balls accommodated in the raceways of each of the rings. At least one of the rings carries an ultrasonic scanning device for scanning specific areas of the other ring upon relative rotation of the rings. The ultrasonic scanning device is opposite the other ring next to the raceway of said ring, and is directed such that ultrasonic waves produced thereby impinge upon the raceway of the other ring sidewardly.

Abstract: An improved pivot ring assembly which has a first and second annular member, one of which is mounted within the other, the first and second annular members having a first and second spaced apart race, respectively, that face one another, and rolling elements positioned to roll on the races between the first and second annular members. The improvement comprises an aperture being provided in the first annular member for receiving an ultrasonic probe, the aperture having a hole therein which is directed toward a critical area of the assembly. This critical area includes an edge of the race of the second annular member. Furthermore, the races lie in planes perpendicular to the centerline of the annular members, and the first annular member is mounted within the second annular member.