Papers by Keyword: Compression

Abstract: Powder metallurgical (PM) route is one of the methods for metal foam fabrication. In this paper, we report the fabrication of Zn alloy foams with 0~50wt.% Mg via powder metallurgical approach by using CaCO₃ as the blowing agent. The fabrication process included 5 steps: powders mixing, cool-pressing, heat treatment, hot-pressing, foaming and cooling. The effects of Mg addition, foaming temperature on the foaming process were discussed. Finally, the compressive behavior of Zn alloy foam was evaluated.

Abstract: This paper presents a method for acquiring true stress–strain curves using engineering strain curves obtained from upset forging of cylindrical specimens. The main problem deals with determination the true strain in upset hot forging on hummers when the values of strain rates are differ in the range from 0 to 10^-3s. At such strain rates due to wave processes strain distribution in cylindrical specimen will be uneven. The purpose of this publication is to analytically determine the strain distribution in compressed cylindrical specimen.

Abstract: The paper presents a new method for processing of cast composites reinforced with ceramic particles in order to improve the microstructure homogeneity and material properties. The presented forming method consists in compression aided by additional shear stress that is caused by transverse motion of a punch. As a result, severe plastic deformation can be obtained in a workpiece. A series of experiments was conducted for previously cast Al-Mg-Cu matrix composites containing 15% reinforcement in a form of the mixture of SiC and glassy carbon particles. It was found that the applied method allows to refine the particles and to obtain a good-quality bonding on the particle-matrix interface.

Abstract: The authors of presented research case focused on possibilities of sealing porous as well as non – porous materials and analysed the measured results. It is the second article of the above mentioned authors dealing with sealed joints, however, in this case study the focus was placed on a group of industrially manufactured modified silyl polymer and polyurethane sealants. The research is based on the modified test procedure for the determination of adhesion and cohesion properties during maintained extension at variable temperatures, i.e. a high temperature of (70 + 2) °C and a temperature simulating freezing, i.e. (-20 + 2) °C, according to the European standard EN ISO 9047. The degree of specimen extension was set to amplitude of 20.0 % and the aim of the research case was to discover any differences that might appear in the resistance. The measured results demonstrate that there are significant differences between individual sealants in the results they provide in combination with specific material, e.g. wood appears to be a problematic substrate as well as glass cement or aluminium.

Abstract: In this work parametric modelling was utilized to design and produce two types of porous microarchitectures with auxetic compressive properties suitable for deformation energy mitigation applications such as blast and bullet protection. The samples were directly produced from acrylic material using a high resolution 3D printer and their compressive mechanical characteristics were tested. Two different structures exhibiting in-plane negative strain dependent Poisson’s ratio were selected for the analysis: i) two-dimensional inverted (re-entrant) honeycomb and ii) two-dimensional cut missing-rib. Stress-strain relationships were established from a set of quasi-static compression experiments where the strain fields were evaluated using digital image correlation applied to measure the full-field displacements on the samples' surface. From the displacement fields true strain – true stress curves were derived for each sample and relative elastic moduli were evaluated.

Abstract: The uniformly cross-linked gellan gum hydrogel with sodium montmorillonite (Na-MMT), organo-montmorillonite (CTAB-MMT) and Cloisite 15A were successfully prepared. The compression performances of the hydrogels were investigated. The results show that the GG hydrogels containing Cloisite 15A required smallest volume to achieve optimum compression stress, modulus and compression strain at 5% (w/w) compared to both Na-MMT and CTAB-MMT at 10% (w/w), respectively. The decrease in compression performances of gellan gum hydrogel at higher concentration containing those clays could be due to agglomeration process which created the entangled structure and bring up the brittleness of hydrogel properties. Overall, the presence of the clays significantly improved the mechanical performances of gellan gum hydrogels which beneficial to be used in tissue engineering.

Abstract: Aluminium foams are of interest due to their ultra low density, high structural stiffness per unit weight. Like conventional Al foams having Ca, ceramic particle (e.g. SiC, Al₂O₃) containing Al alloy metal matrix composite (MMC) foams can be produced. In this approach, parameters such as particle type, size, and volume fraction need to be optimized to get good quality foams with high foam expansions. However, the role of them on the compression properties of MMC foams is seldom reported. With this objective, the present study explores the effect of SiC_P size and vol. % on compression behavior of various Al-Si/SiC_P foams prepared at DMRL. From the large number of compression tests, it is observed that the reinforcement parameters don’t seem to play any effective role with respect to foam properties, although they are very important in foam manufacture.

Abstract: Thin-walled structures are widely used in building structures such as thin-walled vessels or storage tower, beam-columns of houses and halls, as components for cars, boats or airplanes and in sport industry. These types of structures are made not only as steel, but nowadays of composite materials.This paper deals with buckling and postbuckling behaviour and presents the experimental results for thin-walled composite columns with channel cross-section subjected to compression.

Abstract: The river sediments from the Chi River basin, including Chi River and Nam Phong River, are valuable to comprehend the brick process, physical and chemical properties which lead to its strength. Study areas cover three different regions in Maha Sarakham, Kalasin and Roi Et provinces nearby six brickyards which are separated in two areas Nam Phong and Chi River area. Mechanical property is referred to compressive strengths of a brick unit. These compressive strengths of the fired brick unit increase with increasing their densities. Elastic moduli of original fired brick at the ultimate stress and strain corresponding by time in submersion test show that any solutions filled in void or pore can enhance the apparent density of bricks. Thus, fired bricks are capable to resist compressive force than the normal condition. The ratio of modulus in submersion test for 4 hours, expressed in the original fired brick to water, acidic saline and saline is 1: 1.1: 1.2: 1.6, respectively. The stress level depends on the fracture plane over particular long space fabricating by manufacturing process. These results are related only to the linearity plot.

Abstract: Carbon black suspension is investigated using a squeezing test, which compresses a disk of paste between two parallel plates, one of which is moving at a constant speed. From this test, the two-phase nature of carbon black suspension can be evidenced. Liquid migration is observed at low compression speed. This test is also a good tool for constructing a two-phase model for paste flow modeling. The concentrated suspension is composed of a powder of activated carbon black and a Newtonian liquid phase.