Damping capacity of metallic materials Drd. Nicanor Cimpoesu Faculty S.I.M. Iasi

Damping capacity  High damping capacity has been one of the most important properties of materials used in engineering structures where undesirable noise and vibration are to be passively attenuated.

Materials with damping capacity  Rubbery membrane type EPDM used as elastic ecologic sheets proofing for accumulation reservoirs of residual waters results from different technological fabrication processes, ornamental lakes, swimming pools, fishy pools, ecological garbage holes, roofs, canals, tunnels which on internal friction test have 0.8 value at 1 Hz testing frequency for -40 °C temperature and value of 0.85 at 100 Hz frequency and -25 °C.  A steel sample was analyzed as extreme value of internal friction which has a maximum value of at 1 Hz but also an adhesive with low viscosity with a value 6 for internal friction at –20 °C. between this value tests reveal a value of 0.2 for internal friction at a quartz material at 580 °C and for an composite between a epoxy resin and carbon fibers with values at 190 °C for first test and still for 190 °C but second test.

Shape memory materials  This unusual property for a metallic material author named “rubbery behavior” and after year 1951 scientific people study many different alloys most common being Ni-Ti (nitinol), Cu-Al-Zn and Cu-Al-Ni which have a lot of practical applications.

Internal friction and shape memory alloys  A particularly interesting class of devices is linked to the application of particular kinds of ‘‘smart materials’’ to engineering structures.  Particularly interesting for their properties, linked to microcrystalline phase transition processes, are the shape memory alloys (SMA-s).  SMA-s exhibit a particular behaviour that makes them quite promising for civil engineering applications, especially for the realization of new semi-active control devices.  Internal friction is measured frequently with a system moved with certain amplitude and after that left free to vibrate so the amplitude will decrease.

Shape memory alloy used in structures applications

Internal friction versus temperature

Chemical analysis of SMA-s

Dilatometry tests

Optical microscope micrographs

Scanning electron microscopy's

EDX study of investigated alloys

EDX study of investigated alloys second part

EDX study of investigated alloys third part    

Equipment for internal friction study type torsion pendulum

Results obtained with torsion pendulum

Equipment for internal friction study type DMA

Internal friction measured with DMA of a SMA based CuZnAl

Application of a shape memory alloy memory effect + big internal friction

Concluzions Concluzions  Un aliaj cu memoria formei, obtinut cu costuri reduse si care poseda un bun efect de memoria formei, a fost realizat din metale de puritate ridicata cupru, zinc si aluminiu.  Aliajul obtinut Cu 68,6 Zn 13,2 Al 4,85 prezinta efect de memoria formei ceea ce reprezinta un avantaj in utilizarea acestuia in diferite aplicatii ca element de disipare a energiei datorita valorilor ridicate pe care le prezinta frecarea sa interna.  Valoarea frecarii interne la temperatura camerei este relativ scazuta pentru aplicatii practice dar mai mare decat a materialelor metalice in general. Valoarea ridicata a frecarii interne (0.116) la temperatura de 89,73 °C face din acest aliaj o posibila solutie a problemelor de seismica si vibratii putand fi utilizat ca element de disipare a energiei mentinand in acelasi timp proprietatile de material metalic.  Este prezentata si influenta temperaturii asupra valorilor frecarii interne cu punerea in evidenta a domeniului unde intalnim cea mai mare valoare a amortizarii punand in evidenta punctele de transformare ale aliajului si domeniul unde faza martensitica este impreuna cu cea austenitica.  In investigatiile legate de frecarea interna se observa si legatura dintre modulul de elasticitate a unui material si capacitatea sa de amortizare fiind coordonate de cauze similare.

 This paper was sustain by PCE-IDEI grant 616, project 83/ Thanks : Thanks : - Prof. Dr. Ing. Hopulele Ion - Conf. Dr. Ing. Stanciu Sergiu THE END