Damping Characterization of Magnesium Based Composites Using a New Circle-Fit Approach

Abstract

In the present study, a new methodology of using free–free beam method coupled with circle-fit approach is used to determine damping of ceramic reinforced magnesium composites. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency is predicted accurately for the test specimen. An attempt is made to rationalize the increase in damping capability of the MMC when compared against the monolithic specimen in terms of increase in dislocation density and presence of plastic zone at the matrix–particulate interface.

FEM based damping studies of metastable Al/Ti composites

“…Thus, the damping factor η r can be expressed using the angles shown in Fig. 1(a) of [20], as follows: Table 2 lists the damping loss factor η free for the monolithic and MMC samples.…”

“…Fig. 1(a) of [20] shows the typical circle plot from which two points are selected for damping loss factor calculation, denoted as points a and b corresponding to frequencies ω a and ω b , respectively, which are lesser and greater than the natural frequency ω n , respectively. Thus, the damping factor η r can be expressed using the angles shown in Fig.…”

“…Using least square technique a circle was fit and based on hysterically damped vibrating system the circle diameter can be shown to be inversely dependent on the damping coefficient. The exact location and determination of the natural frequency and the corresponding damping factor 'η' was calculated using frequency spacing technique [20]. Fig.…”

“…The coefficient of thermal expansion was determined on extruded composite sample using thermal-mechanical analyzer [20] and the results are listed in Table 1. Results show that the coefficient of thermal expansion of the aluminium matrix decreases with an increase in Ti weight percentage.…”

“…Micro-hardness measurements [20] in the matrix and at the Al-Ti interface were conducted on polished samples and are listed in Table 1. The results also revealed that the interface hardness in all the three composite samples was higher when compared to the matrix hardness.…”