Sound Absorption Properties Of Single-Hole Hollow Polyester Fiber Reinforced Hydrogenated Carboxyl Nitrile Rubber Composites

A series of single-hole hollow polyester fiber (SHHPF) reinforced hydrogenated carboxyl nitrile rubber (HXNBR) composites were fabricated. In this study, the sound absorption property of the HXNBR/SHHPF composite was tested in an impedance tube, the composite morphology was characterized by scanning electron microscope (SEM), and the tensile mechanical property was measured by strength tester. The results demonstrated that a remarkable change in sound absorption can be observed by increasing the SHHPF content from 0% to 40%. In the composite with 40% SHHPF in 1 mm thickness, the sound absorption coefficient reached 0.671 at 2,500 Hz; the effective bandwidth was 1,800-2,500 Hz for sound absorption coefficient larger than 0.2. But the sound absorption property of the composite deteriorated when the SHHPF content increased to 50% in 1 mm thickness. While with 20% SHHPF proportion, the sound absorption property was improved by increasing the thickness of composites from 1 to 5 mm. Compared with the pure HXNBR of the same thickness, the tensile mechanical property of the composite improved significantly by increasing the SHHPF proportion. As a lightweight composite with excellent sound absorption property, the HXNBR/SHHPF composite has potential practical application value in the fields of engineering.

Effects of Filtration Purification and Solution Treatment on the Microstructure and Mechanical Property of AZ91D Alloy

As-cast and solution-treated microstructures of AZ91D alloy before and after the purification by MgO ceramic foam filter (CFF) with different thicknesses at the range from 15 mm to 35 mm were investigated by optical microscopy and scanning electron microscopy. Meanwhile, the tensile mechanical property and impact toughness were tested. The results show that the impurities in the alloy melt could be eliminated by the filtration purification effectively. With increasing the thickness of CFF, the tensile mechanical property and impact toughness first increased significantly, and then decreased slightly. The AZ91D alloy purified by the CFF with the thickness of 20 mm and the porosity of 10 ppi exhibited the best comprehensive mechanical property. The tensile strength σb, elongation δ and impact toughness αnK at ambient temperature reached 205 MPa, 8.5% and 16 J/cm2, with the improving amplitude of 13%, 31% and 46% comparing with the corresponding unpurified value, respectively. At the same time, σb and δ at elevated temperature reached 195 MPa and 31.5%, with the improving amplitude of 9% and 174%, respectively. After the alloy was solution treated, the mechanical property was enhanced further, and the improving amplitude was larger for the alloy by the filtration purification. σb reached 260 MPa and 205 MPa at ambient and elevated temperatures, with the improving amplitude of 32% and 5% comparing with the unpurified value, respectively. αnK reached 27 J/cm2, with the improving amplitude of 69%.

Study about the Effects of Cryogenic Treatment on the Mechanical Properties of PCrNi3MoVA Steel

On the basis of processing the PCrNi3MoVA steel with cryogenic treatment and then experimenting with the static tensile and impulse at room temperature, the effects of cryogenic treatment on macro-mechanical properties of the material is studied. The test results show that tensile mechanical property of PCrNi3MoVA steel can be improved with appropriate number of cryogenic treatment, otherwise can be weakened if the number is inappropriate; at the same time, there is no influence of cryogenic treatment on impact toughness of the material

Microstructures and Mechanical Properties of ZK60-XHo Wrought Magnesium Alloys

Microstructures and phase compositions of as-cast and extruded ZK60-xHo (x=0~5) alloys were analyzed by X-ray diffraction, differential scanning calorimetry, optical microscope, scanning electron microscope and transmission electron microscope. Meanwhile, tensile mechanical property and impact toughness were tested. The results showed that as-cast microstructure was refined gradually with increasing the Ho content. Mg-Zn-Ho new phase increased gradually, while MgZn2 phase reduced gradually to disappear. Second phase tended to distribute along grain boundary by continuous network. As-cast tensile mechanical property remained almost unchanged and impact toughness value αnK was low (9~17 J/cm2). After extrusion by λ=40/T=593 K, grain size reached the micron level (1~5 μm) and broken second phase distributed dispersedly. Extruded tensile mechanical property was enhanced obviously. Tensile strength σb at ambient temperature increased gradually from 355 MPa for ZK60 alloy to 375 MPa for ZK60-4.77Ho alloy, while elongation δ decreased gradually from 19.5% to 12.5%. σb at 473 K increased gradually from 120 MPa to 169 MPa. Meanwhile, αnK was enhanced to 26~54 J/cm2. Fine grain and few fine dispersed second phase enhanced the tensile mechanical property and impacted toughness of magnesium alloys effectively.