Acoustic performances of silicone foams for sound absorption

The aim of this study is to investigate the link between the elaboration process, the microstructure and the acoustic behaviour of silicone foams obtained using a two-component silicone. Different parameters such as the ratio of components, the addition of a thinning agent and the curing temperature are varied, with the objective of understanding the influence of each parameter in the foam’s acoustic absorption. The microstructure is analysed using scanning electron microscopy and acoustic properties are measured. Two non-acoustical properties of the porous material are also investigated, namely the porosity and the flow resistivity. Pore cell size and interconnected porosity have great impact on acoustical properties. Significant enhancements of the absorption properties could be obtained in the low-frequency band by increasing the rate of agent B through an increase in the amount of interconnected porous cells. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. Representative models of the foam for acoustic simulations are obtained allowing estimation of the tortuosity, viscous and thermal characteristic length from acoustic measurements. These models are able to simulate the acoustic behaviour of the silicone foams when embedded in sound packages.

Effect of Pore Architecture of Titanium Implants on Stress-Strain State upon Compression

The problem of stress-strain state upon compression of implant of titanium alloy with cellular architecture was formulated by means of ABAQUS software and finite element analysis. The volume of the material was segmented on the unit cells characterized by specific configuration. The boundary conditions and physical equations were stated to describe the correlation between stresses and strains. The calculations of stress values, area reduction and mean stress were performed. The increased strain rates were revealed in horizontal pore cell walls. Joint simulating of several individual unit cells was provided. Zone seeing tensile stresses were observed in the segment of radius of the unit cell. The estimation of threatening sections location of the construction was conducted.

Surfaces with pores: hydrodynamic lubrication

Purpose This paper aims to assess the hydrodynamic lubrication of two opposing surfaces with identical pores having a semicircular profile. The surfaces are treated with more than one pore that allows clarification of whether there exists interaction between the pores. Design/methodology/approach A transient, spatial, one-dimensional model of surfaces with regular pores was developed and applied in the context of fluid lubrication. MATLAB software has been used. Findings Calculations show that a lubricating film between two surfaces with pores provides better hydrodynamic conditions in comparison to that on one surface with pores. It was also shown that the pores of one surface act as separate objects and can take into account only the interaction between the pores of the opposite surfaces. In addition, it was found that there are optimum values of the pore radii, gap and pore cell dimensions at which the bearing capacity of the film is maximal. Practical implications The computer program used for the pore parameter calculations provided the optimal lubrication. Originality/value This is the first study of the lubricating film hydrodynamic behavior of two opposite surfaces with pores having a semicircular profile.

Manufacturing Process and Geometric Model of Porous Metal Fiber Sintered Felts

Using the designed multi-tooth tool, a novel porous metal fiber sintered felt (PMFSF) with three-dimensional reticulated structure has been produced by solid-state sintering of copper fibers. The copper fibers were fabricated using the cutting method. According to the SEM results, it was found that there were two kinds of sintering joints of surface contact and crossing fiber meshing among the fibers in the PMFSF. The coarser sintering joints will help to enhance the mechanical strength of PMFSF. Based on the structure characteristic, a three-dimensional model with the cubic pore cell structure was established to describe the structure of PMFSF. In addition, the effectiveness of geometric model was verified by the test results of specific surface area of PMFSF.