A DEVICE AND METHOD OF CHARACTERIZATION OF THE ELASTIC PROPERTIES OF A FRICTION MATERIAL

A device (100) of characterization of the elastic properties of a friction material, comprising: —a support yoke (1) having a body (2) with a monoblock structure surrounding an inner chamber (3); —said inner chamber (3) being defined superiorly by a first monoblock body portion (2) or upper crossbar (4); —said inner chamber (3) being defined inferiorly by a second monoblock body portion (2) or lower crossbar (5); —said upper (4) and lower (5) crossbars being mutually connected by two side columns (6, 7) formed by a third and a fourth monoblock body portions (2); —said monoblock body comprising at least one access opening (8) to the inner chamber (3); —said upper crossbar comprising a threaded through hole (9) defining a device axis (X-X) arranged substantially orthogonal to said upper crossbar (4) and said lower crossbar (5) fully passing through the inner chamber (3); —said support yoke <(1) houses, substantially completely in said inner chamber (3), a measuring column (10); said measuring column (10) comprising transmission components of a static and dynamic actions, said components being arranged not necessarily in the order indicated herein below and being mutually arranged stacked substantially along said device axis (X-X) and suitable to be packed together between said upper (4) and lower (5) crossbars so as to transmit a static or dynamic action from one and the other: a preloading screw (11) suitable to engage in said threaded through hole (9) with at least one threaded length (22) thereof to enter said inner chamber (3) according to a predetermined displacement with respect to said upper crossbar (4) along substantially said device axis (X-X) to exert, once the measuring column (10) has been packed, a predetermined static preloading action; an actuator (12) capable of exerting, substantially along said device axis (X-X) an oscillatory thrust action having a predetermined period that is also variable in time in a controlled manner; —at least one load cell—(13) suitable to detect the preloading action and the oscillatory thrust action exerted by said actuator; at least one specimen support portion (14) to support a specimen of material to be tested (15) suitable to receive the preloading action by the preloading screw (11) and/or the oscillatory action of the actuator (12) and to transmit it to the specimen of material to be tested (15); at least one acceleration sensor or accelerometer (16) connected to said at least one support portion (14) to detect at least the acceleration of the support portion (14) generated by said oscillatory thrust action of the actuator (12); wherein—said measuring column (10) comprises a centering shaft (18). coupled to the end (17) of said preloading screw (11) projecting into said inner chamber (3); said centering shaft having a geometry substantially with a symmetry plane parallel to the device axis (X-X); said centering shaft (18) comprises at least one pair of geometric coupling portions (19) mutually arranged in opposite positions and for the direct or indirect geometric coupling to the monoblock body (2) of the support yoke (1), so as to be coupled to said centering screw to receive therefrom the axial preloading thrust but to avoid transmitting torsion actions to the remaining part of the measuring column (10), so as to transmit to said actuator (12) substantially a direct preloading action substantially along said device axis (X-X); —said measuring column (10) further comprises at least a ball joint (42) suitable to compensate for possible thrust misalignments between said preloading screw (11) and said actuator (12), and/or between said actuator (12) and said specimen support portion (14).