Acoustic Properties of 316L Stainless Steel Hollow Sphere Composites Fabricated by Pressure Casting

Abstract

In this study, we prepared metal hollow sphere composites (MHSCs) using metal hollow spheres (MHSs) by pressure casting under vacuum conditions, and investigated the acoustic properties. The density of the MHSCs was measured using the mass to volume ratio, the microstructure of the MHSCs was observed using a scanning electron microscope, and the acoustic properties of the MHSCs were tested using an impedance tube. The measured MHSCs showed that the densities of the MHSCs with the random distribution of MHSs with diameter ~3.28 mm (1.74 g/cm3 to 1.77 g/cm3) (MHSC-3.28) were nearly equal to that of the MHSCs with the random distribution of MHSs with diameter ~5.76 mm (1.74 g/cm3 to 1.76 g/cm3) (MHSC-5.76), and lower than that of the MHSCs with the layered structure of MHSs with diameter ~3.28 mm (1.93 g/cm3 to 1.97 g/cm3) (MHSC-LS). Microstructural observations confirmed that the interface region between the MHSs and matrix demonstrated a simple physical combination pattern with pores. The acoustic properties of the MHSCs showed that the sound absorption coefficient of MHSC-LS was lower than that of MHSC-3.28 and higher than that of MHSC-5.76 at off-resonance. The sound absorption coefficient peak value of MHSC-3.28 was higher than that of MHSC-LS, and lower than that of MHSC-5.76 at resonance. The sound transmission loss of MHSC-3.28 was lower than that of MHSC-5.76, which shows the rules are independent from the resonance. The sound transmission loss of MHSC-LS was higher than that of MHSC-5.76 at resonance, but lower than that of MHSC-3.28 at off-resonance. In addition, we discuss the propagation mechanism of the sound waves in the MHSC, which is mainly determined by the distribution of the MHSs in the MHSC.

Sound insulation of a novel laminated polymer matrix composite containing metallic hollow spheres based on phononic crystal structure design

“…The bulk modulu B of every component can be calculated by formula 6. In the above formula 6, E represents the elastic modulus and μ represents the Poisson ratio. In this study, the elastic modulus and Poisson ratio of the matrix material and single layer composites were obtained from our previous researches 31–35 through ultrasonic method and quasi‐static compression method. Table 2 lists the elastic modulus ( E ), Poisson ratio ( μ ), and bulk modulus ( B ) of SR, PU, single layer MHSSR and MSHP.…”

“…In the above formula 6, E represents the elastic modulus and μ represents the Poisson ratio. In this study, the elastic modulus and Poisson ratio of the matrix material and single layer composites were obtained from our previous researches [31][32][33][34][35] through ultrasonic method and quasi-static compression method. Table 2 lists the elastic modulus (E),…”

“…In this experiment, according to ASTM D72‐08 standard, the density of single layer material was measured by drainage method and Archimedes principle 31–35 . The density of SR, PU, single layer MHSSR and MSHP were 1.13, 1.09, 2.22, and 2.18 g·cm −3 , respectively.…”

“…The sound insulation performance of the one-dimensional phononic crystal laminated composites in this study were tested by BSWA422/477 impedance tube. The principle of sound insulation test was based on ASTM E2611-09 standard, [31][32][33][34][35] that is, the sound signal and data are collected by four microphones, and the STL was calculated by the transfer matrix method. The size of low frequency (64$1000 Hz) sample was 100 mm in diameter and 18 mm in thickness, and the high requency (1000$6300 Hz) sample is 30 mm in diameter and 18 mm in thickness.…”

“…However, most of the above researches on one‐dimensional phononic crystals are focused on the design and theoretical analysis, there are few reports on the one‐dimensional phononic crystal with good sound insulation properties actually prepared. Recently, our team found that metallic hollow spheres can effectively improve the acoustic performance of silicone rubber, polyurethane, and aluminum alloy 31–35 . The elastic silicon rubber and the harder polyurethane may be arranged periodically to form a one‐dimensional phonon crystal.…”