This document mainly introduces the evaluation of vehicle noise, noise sources and noise control. The development of fibers used for noise reduction materials is described as well. Besides, it analyzes the advantages and the necessities of the natural fibre nonwoven materials applied for the noise control, illustrates the present research status and the factors that introduces the sound absorption properties of the natural fibre nonwoven composites used for noise reduction. The paper also gives some reference point for advice to the development of automotive nonwoven materials. it shows that natural fibre nonwoven materials have a huge potential market and worthy for scholars to make a further study.
A comprehensive two-dimensional (2D) mathematical model based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT was developed to describe the interaction of the multiple physics fields during DC casting process. ANSYS was for calculation of the stress field and FLUENT was for calculation of the fluid flow, heat transfer of the solidification. The results show that: the model is reliable and accurate to simulate the multiple physics of DC casting. Consequently, the position, which was prone to hot tearing, was confirmed and the max velocity, at which the hot cracking might not occur, was determined. The numerical simulations will be very useful for preventing crack, optimizing casting parameters and obtaining high-quality ingots.
Hot-ductility tests of the microalloyed Q345B structural steel were performed in a tensile machine of Gleeble-1500D at different strain rates of 1.5•10-3/s 、2.5•10-3/s and 2•10-2/s and at temperature range from 1300°C to 700°C(Δ T=100°C ), which are close to the continuous casting condition of steel. Fracture surfaces were examined using a scanning electron microscope; it was found that the hot decrease as strain rate decrease, because the void growth mechanism predominates over void nucleation, giving time for nucleation cracks to grow. The minimum ductility was found at about 800°C for the strain rates of 1.5•10-3/s and 2.5•10-3/s, and the fracture was intergranular. The steel has good plasticity in temperature range from 1200°C to 900°C which is suitable for straighten operation.
Retroreflective film are used widely in traffic and municipal field as information carrier, the retroreflection index is considered the most important parameter, test methods of this parameter including absolute and relative method, traditional instruments are consisted of light source, photometric detector, angle adjust device, etc. The complex structure of instrument add the uncertainty component, so reflectance spectrum is used to calculated the film retroreflection index, this method would improve the testament accuracy and provide more light sources choices without structure adjustment.
The functions of hydroentangled nonwovens are determined by the degree of the fiber entanglement, which depend mainly on parameters of the water jet. According to the spun lacing technology, this paper set up the numerical model based on the simplified water jetting model, establishing the governing equations, and the blended two-phase flow as the multiphase flow model. This paper simulation the water needle after the water jetting from the water needle plate in the different pressure (100bar, 60bar, 45bar, 35bar).
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