Papers by Keyword: Cell Size

Abstract: This article shows two examination methods to measure the metal to artery ratio of stents. Our goal was to further develop the previously used measuring method in order to make it suitable for the integration into the quality control process of endovascular stent manufacture to provide more realistic data. The previous method was performed manually using rotating equipment under a stereomicroscope. The new method is an automatic method using an integrated scanner and a rotating engine. Both methods aimed at converting the cylindrical stent into a flattened two-dimensional image in order to enable the measurement of stent surface area by imaging software. From the image we can determine the cell sizes, the maximum achievable stent diameter, and the structure of the stent pattern. Each measurement process was tested on different types of stents. Our findings showed that the methods gave similar results, the largest differences are speed and accuracy.

Abstract: Polyurethane (PU) foams are widely used today in automotive and as insulation system. Due to environmental issues, efforts have been made to replace petrochemical polyol with natural-based polyol in PU foam production, without sacrificing any properties. This study aims to produce palm oil-based PU rigid foam for non-load bearing applications such as wall panel or insulation for buildings. Two parameters studied were percentage of water uptake and surface foam morphology. Palm oil-based polyol (POP) was reacted with polymeric 4,4-diphenylmethane diisocyanate (p-MDI) at 1:1 NCO:OH ratio. Water was used as blowing agent and silicone surfactant was added to produce stable rigid PU foam. The content of silicone surfactant was varied at 2 and 3 part by weight (pbw). The percentage of water uptake increased slightly with increasing surfactant contents due to siloxane portion of the surfactants, is thought able to reduce the surface tension of the cell, thus absorbing more water than 2 pbw surfactant content. The findings were supported with micrographs of scanning electron microscope (SEM) that showed a larger cell window area and thicker strut.

Abstract: This paper researched on multi-period dynamic virtual cell formation problem, and filled the gap on objectives of previous literatures. A developed 0-1 non-linear mixed-integer mathematical model was proposed, it incorporates real-life parameters like alternative routings, operation sequence, duplicate machine, processing time and machine capacity. The advantage of the model is to embed the function relationship between cell size and internal production cost in the model, thus the effects of set-up cost, work-in-process inventory cost, coordination cost and inventory handling cost on VCMS are acted on the model. Finally a numerical example solved by Lingo11.0 software package was presented to verify the model and related discussion was made. The results show that the cell size changes as time in dynamic condition and different scenarios of internal production cost can obtain different cell configurations.

Abstract: Experimental and Finite Element analysis was used for the investigation of the effect of cell size and thickness on the compressive properties of Aluminium honeycomb core. Honeycomb cores were compressed experimentally in in-plane and out of plane directions. The effect of sample size, cell size and thickness on the elastic modulus, yield strength and plateau stress was investigated through FEA. It was found that the mechanical response was independent upon the sample size in in-plane direction. The smallest cell size honeycomb core was deformed at higher yield stress. Similarly, with increase in cell wall thickness, the modulus of the core increased.

Abstract: Formula for microcellular unsaturated polyester using chemical foaming method was studied. With the increase of NaHCO3 content, the cell size of microcellular unsaturated polyester slightly decreased with the increase of styrene content in the range of 1-2 %. The cell size increased in the range of 2-4 %. With the increase of curing agent content, the cell size increased in the range of 0.5-0.9 % and decreased in the range of 0.9-1.3 %. The cell size decreased with the increase of styrene content in the range of 30-40 %. The cell size had little variation when styrene content was in the range of 40-50 %. The average cell size and cell density of microcellular unsaturated polyester were strongly affected by accelerant content. The cell size decreased with the increase of accelerant content. The opposite was for the cell density. The microcellular unsaturated polyester prepared at 2% NaHCO3, 0.3% accelerantt, 0.9% curing agent, 40% styrene had the small cell size, high cell density, and strong compression strength.

Abstract: Microcellular unsaturated polyester was prepared by different foaming agents was studied. Compared with the cell size and density of microcellular unsaturated polyester prepared using azodicarbonamide (AC), the ones of microcellular unsaturated polyester prepared using NaHCO3 were small. For NaHCO3, the cell density of microcellular unsaturated polyester decreased with the increasing temperature. For microcellular unsaturated polyester prepared using NaHCO3 at 100 °C, the average cell size was about 18 μm and the cell density was 1.1×1010 cells/cm3. The compression strength at 100 °C is strongest among that of the materials at the other temperature. The average compression strength was 24.2 MPa. The compression strength-to-weight ratio of microcellular unsaturated polyester prepared at 90 °C and 100 °Cwas about twice that of unsaturated polyester.

Abstract: The tensile model of foams is built using UG software and the tensile deformation processes of microcellular polypropylene foams with different cell sizes are simulated using finite element method (FEM). The effect of cell size on mechanical property is evaluated based on the microstructure of the foams. The cells with small and uniform size are in a state of plane stress, which improved effectively mechanical property of the foams. Whereas the cells with large and nonuniform size are in a state of plane strain, which leads to low mechanical property. The simulation results coincide well with experimental results.

Abstract: The static and dynamic compressive behaviors of open-cell aluminum alloy foams with virtually the same relative density of 0.4 were investigated. The foams have different cell sizes (0.5mm, 1.5mm, 2.5mm) but similar cell morphology and microstructure. The yield strength of these foams was characterized as a function of strain rate and cell morphology. The experimental results indicated that the mechanical responses of foams are sensitive to strain rate, and dependent of the cell size. The present results are compared in details with recent findings obtained from the aluminum foams.