Experimental Study On The Vibration Damping And Noise Reduction Performance Of Aluminum Foam-polyurethane Composites

As a new type of functional material,aluminum foam(AF)has been attached great importance and rapidly developed in recent years.A new kind of high-performance Aluminum Foam-Polyurethane composite material(AF-PU)was manufactured in this thesis,using AF as the matrix material and filling the holes of AF with polyurethane(PU).This composite material was fabricated for the purpose of employing AF in the field of structural vibration and nosie reduction more widely.From the sound absorption and friction damping in both directions,a series of experiments,theoretical derivations and numerical simulations were carried out in order to understand the vibration damping and noise reduction performance of this new material,and the related conclusions are as follows:(1)The sound absorption tests of the aluminum foam and AF-PU composites resonance sound absorption structure were carried out.The porosity of foam aluminum,sample thickness and back cavity thickness on the influence of foam aluminum sound absorption performance was studied,and sample thickness of AF-PU composites,the back cavity thickness and perforation rate on the influence of AF-PU composites resonance sound absorption structure was also researched.With the increase of the sample thickness,thickness of back cavity and porosity,sound absorption performance of foam aluminum had a certain improvement.However,aluminum foam used in this test was not suitable for sound absorption of low and medium frequency.The sound absorption performance of AF-PU composites resonance sound absorption structure around the resonant frequency had an excellent performance.When the sample thickness increased from 10mm to 30mm,resonant frequency of AF-PU composites resonance sound absorption structure decreased from 470Hz to 380Hz,under back cavity thickness of 20mm.When back cavity thickness increased from 20mm to 60mm,resonant frequency of AF-PU composites resonance sound absorption structure decreased from 470Hz to 265Hz,under sample thickness of 20mm.When the perforation rate increased from 3.2%to 7.1%,resonant frequency increased from 470Hz to 680Hz and peak absorption coefficient decreased from 0.99 to 0.56,under sample thickness and back cavity thickness of 20mm.So,with the increase of the sample thickness and thickness of back cavity,the resonant frequency decreased.With the increase of the perforation rate,the resonant frequency increased,but peak absorption coefficient decreasing.(2)The sound absorption mechanism of the AF-PU composites resonance sound absorption structure was analyzed.According to the principle of helmholtz resonator,resonant frequency equation of AF-PU composites resonance structure was derived.The correctness of the theoretical formula was verified by comparing the theoretical formula and experimental results.Based on finite element simulation of AF-PU composites resonance sound absorption structure,the error of resonant frequency obtained with the test was very small,and the maximum error was 8.58%.In engineering application,high peak absorption coefficient was ensured according to the low perforation rate,the resonant frequency was determined by changing the AF-PU composites thickness and back cavity thickness.(3)Friction devices of AF-PU composites were made and the frictional properties of AF-PU composites were tested.The force and deformation curves were full and symmetric,so the composites had excellent friction energy dissipation characteristics.The performance of the device tended to be stable after five cycles.With the increase of cycles,the curve showed a trend of shrink,and friction decreased to 5000N.The ideal elastic-plastic model was put forward.According to the characteristics of the model,AF-PU composites friction mechanism can be described well.Under the small displacement,force and deformation curves show the strong viscoelasticity.Under medium displacement,force and deformation curves show the frictional-viscoelastic properties.Under large displacement,force and deformation curves more show frictional properties.(4)The force-deformation curves of the AF-PU composites were analyzed.The relation between composites friction performance and load frequency was small.The relation between composites friction performance and load amplitude was larger.With the increase of the load amplitude,the energy consumption and equivalent damping ratio increased.Due to the defects of the friction device,high strength bolts loosened slightly in the process of vibration,which lead to lower energy with the increase of cycling times.But according to the test data,the equivalent damping ratio reduced tinily under control.According to good friction performance of the AF-PU composites,its application in the wheel damping ring was put forward.Friction and damping had a great effect on reducing vibration response.There was a optimal equivalent damping coefficient and sliding friction force.