Patent GB-1031972-A (GB)
Title: Improvements in or relating to valve devices for
IPC: G01N3/40
Filed: 1964-03-25
Abstract: 1,031,972. Testing materials. C. KLEESATTEL. March 25, 1964, No. 12733/64. Heading H4D. [Also in Division G1] Surface characteristics of a test piece T (Fig. 1) are derived from the resonance frequency of a member 11 provided with a rounded contact surface tip 12 (Fig. 2, not shown) held against the test piece by a force F which, in this embodiment, is provided by a mass 16 supported by a nodal flange 18. The member 11 which is of magnetostrictive material polarized by a permanent magnet 15, or by a bias voltage in a drive coil 13, is caused to vibrate by means of the drive coil 13 supplied from a tunable generator 14 the resonance frequency being indicated by a frequency meter 24 when the output from a coil 23 as read on a voltmeter 25 is a maximum. Alternatively, the output from coil 23 may be " fed-back " to generator 14 via a filter 26 so that the system is always resonant. When the generator is tunable the coil 23 may be omitted and resonance indicated by a voltmeter connected across an impedance in series with the drive coil 13 (Fig. 5, not shown). In operation the resonance frequency of member 11 above or in contact with a standard test piece is determined and the required surface characteristics are then deduced from the difference between such frequency and that measured when the unknown test-piece T is contacted by the tip 12. The Specification includes the mathematical theory of the operation and shows that the compliance ratio (i.e. the degree of coupling between the tip 12 and the test-piece) is a function of the resonant frequency and that when the tip 12 is rounded so that the area of contact is a function of the force F the resonant frequency is also a function of this force. This relationship is utilized in the embodiment of Fig. 7 (not shown) in which the force F is provided by a compression spring 30 acting on a nodal flange 18b and adjustably controlled by a knob 35. In operation member 11b is vibrated via coil 13b at a fixed frequency above free resonance or at the frequency at which it resonates when tip 12b is urged against a standard piece of known characteristics by a predetermined force as read on scale 42. The unknown test-piece T is then inserted and the required characteristics determined from the new force or change of force necessary to again cause member 11b to resonate. In a further application of this relationship the vibrating member 11c (Fig. 9, not shown), is provided with a rounded contact end 12e resting on a curved seat 50 in a cup-shaped base 49 and the change in the resonant frequency of member 11c when a compressive force F is applied is utilized as a measure of such force (e.g. in a dynamometer load indicator). When the force is a tension the arrangement of Fig. 10 (not shown) may be employed. In a further embodiment for measuring the shear compliance of an unknown test-piece S (Fig. 11, not shown), the vibrating member 11e is provided with two tips 12e against which the test-piece S and a piece T of known shear compliance are urged by a constant force F, any difference in the compliances producing a bending wire in member 11e which produces a signal in the pickup coil 23e of twice the resonant frequency. Such frequency which is selected by a filter 26e is indicated on a frequency meter 24e and its magnitude, which is indicative of the difference in shear compliance, is indicated on a voltmeter 25e. In another arrangement (Fig. 12, not shown), two members 11 are urged against a test-piece strip T by constant forces F and vibrated in the same phase (arrows A) to produce a bending wire in the strip so that the resonant frequency (as read on meter 24) is mainly determined by the mechanized impedance of the strip T. The latter is proportioned to the thickness so that the arrangement operates as a thickness gauge. In a similar arrangement but with the vibrating members phased to vibrate in opposition the resonant frequency is mainly determined by the surface compliance of the test strip so that a surface hardness sensing device results (Fig. 13, not shown). By forming the vibrating member 11 (Fig. 15, not shown) with the mechanical impedance Z, of the portion 11a provided with the rounded contact surface tip at least one-tenth that of the impedance Z 2  of portion 11b an improvement in sensitivity and resolving power results since the amplitude of vibration at the support flange 18 as when the nodal position is varied (e.g. N 1 , N 2 , N 3 ) by increasing the force with which the tip is urged against the test piece is much less than the amplitude at the support flange when the member is symmetrical about the flange as shown at 11 (Fig. 1). When the test-piece is of relatively soft material the tip on the vibrating member may be of relatively large radius (Fig. 2, not shown) or it may be annular as in Fig. 4 (not shown). When hard material is to be tested a tip with a hardened insert (Fig. 3, not shown) e.g. of tungsten carbide, diamond or sapphire having a small radius of curvature is necessary.