Issue 32

N. Golinelli et alii, Frattura ed Integrità Strutturale, 32 (2015) 13-23; DOI: 10.3221/IGF-ESIS.32.02 21 used is a silicone-based fluid that is quite compressible (bulk modulus β of about 1000 MPa) so a pressure control not excessively abrupt is allowed. Considering the low compressibility of the fluid, varying the value of pressure requires slider’s strokes of few millimeters. The stroke of the slider is calculated analytically knowing the bulk modulus β, the total volume of the fluid V and the desired pressure variation. The equations involved are:      P V V (14)      V V P (15)    cu V x A (16) By combining Eq. (15)-(16):     cu V x P A (17) In which A cu is the area of the slider. Stepper motors are the most suitable for this application. By knowing the number of steps and the screw pitch an accurate control of the slider’s stroke ∆x is possible without position sensor. R ESULTS AND DISCUSSIONS ig. 10 shows the section of the 3D model of the damper. To allow the assembly, the piston head is composed of two parts: the main body of the piston head and the flange. The flange connects the piston head to the upper-rod using four screws M4x6. Particular attention was paid for the sealing system. A dynamic rod seal was used between the bottom part of the piston head and the bottom rod. Moreover, two static seal (O-Ring) were adopted between the flange and the inner chamber of the piston head. As it can be seen in Fig. 11, the coil wires pass through the drilled screw, the flange and the rod. Figure 10 : Cross-sectional view of the prototype of the damper. Figure 11 : Exploded view. (From the right) Piston head, drilled screw, flange, rod and cylinder head. F