Abstract: A tribological test apparatus has a supporting structure, to which are fitted a central shaft rotating about a respective axis, and three peripheral shafts rotating about respective axes equally spaced angularly about the axis of the central shaft; the central shaft and peripheral shafts respectively support a central specimen and three peripheral specimens facing one another radially; and the apparatus has three actuators, each for exerting on a relative peripheral specimen a force directed towards the central specimen, and a guide and slide device associated with each peripheral shaft to enable each peripheral specimen, in use, to translate radially towards the central specimen and exert a contact pressure on the central specimen by virtue of the force generated by the relative actuator.

Abstract: An evaluation method in which a capacitive sensor is placed in a region of a container, into which a granular material is fed so as to contact the sensor, and the variation in the impedance of the sensor caused by feeding in the material is evaluated. The method is particularly useful for evaluating the compactness of sand in a formwork for making metal castings. The evaluation system includes a sensor defined by plates sensitive to the variation in the dielectric; and a conditioning and control circuit for indicating the variation in the capacitance of the plates, or more generally the total impedance of the system, when the granular material is fed into the container. In one embodiment, the plates of the sensor are defined by two combs made of conducting material, having two numbers of interlacing segments, and located on a rigid or flexible support.

Abstract: A tribological test apparatus has a supporting structure, to which are fitted a central shaft rotating about a respective axis, and three peripheral shafts rotating about respective axes equally spaced angularly about the axis of the central shaft; the central shaft and peripheral shafts respectively support a central specimen and three peripheral specimens facing one another radially; and the apparatus has three actuators, each for exerting on a relative peripheral specimen a force directed towards the central specimen, and a guide and slide device associated with each peripheral shaft to enable each peripheral specimen, in use, to translate radially towards the central specimen and exert a contact pressure on the central specimen by virtue of the force generated by the relative actuator.