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This research aims to study the surface characteristics of low carbon steel JIS G3101 SS400 processed by sandblasting using steel grit G25. The sandblasting process is conducted at a fixed nozzle pressure of 5 bar and pressure angle of 90o, and varying nozzle-to-surface distances at 15, 25, and 30 cm, and blasting durations of 25, 45, and 120 s. Surface characterization is firstly carried out by conducting observation on the surface’s morphology by SEM and chemical composition by EDS. Subsequently, visual inspection and measurement on surface roughness and hardness profile identification by Rockwell and micro-Vickers hardness tests are conducted. A paint thickness test using ASTM D7091 was undertaken to observe the surface characteristics related to the coating process. Based on the result, SEM found valleys, granules, micro-cracks, and grits embedded on the surface. The visual inspection shows the roughness is within the range of Sa2 - Sa3 of ISO 8501 with values are Ra 18.1 and Ra 21.4 µm. The hardened layer exhibits a maximum hardness value of 332 HV and a depth of more than 50 µm by sandblasting parameters of 15 cm distance and 120 s duration. Both roughness and hardness profiles are confirmed, increasing with closer nozzle-to-surface distance and longer blast duration. It is concluded that sandblasting using steel grit G25 is effective in improving the mechanical strength and surface hardness of low carbon steel SS400. These mechanical properties are essential in the paint coating of machinery applications such as pump, tank, ship, and pipeline.

This study evaluated the correlation between crystallite size and micromechanical characteristics of micrometer-sized monoclinic WO3 particles. To avoid the existence of other parameters in the measurement (such as impurities and porous structure in the particle), micrometer WO3 particles were prepared using a direct heat treatment of ultrapure micrometer-sized ammonium tungstate powders. The crystallite size was controlled independently in a constant WO3 particle outer diameters to obtain a precise measurement result. The mechanical properties, i.e., hardness and Young’s modulus, were measured by load-controlled nanoindentation test on the singular WO3 particles. The force and displacement relationship data was plotted and analyzed to obtain the correlation between crystallite size and mechanical properties. The results revealed that the micro-mechanical properties of WO3 particles were strongly dependent on the crystallite size. The hardness and Young’s modulus values increased more than 40 and 15 times, respectively, when increasing the crystallite size to about 40 nm. The study was completed with a proposed mechanism of crack propagation inside the particle due to static load. The study demonstrates the important role of crystallite size in determining the micro-mechanical characteristics of WO3 particles. The result is useful especially when utilizing WO3 microparticles for various processes involving extreme conditions, such as high pressure reaction.

The elastic behavior of aluminum alloy foam under uniaxial loading and bending conditions is studied by experimental investigations and theoretical analyses. It is found from the experiments that the elastic moduli measured from three- and four-point bending tests as well as flexural vibration tests are significantly larger than the corresponding elastic moduli measured from uniaxial compression tests. This discrepancy cannot be described by the well-known elastic modulus equation introduced by Gibson and Ashby for foam materials. Theoretical analyses are carried out to explain the discrepancy and to improve the elastic modulus equation of Gibson and Ashby. In the analyses, unit-cell models are proposed, and elastic modulus equations for both uniaxial loading and bending conditions are derived. The derived equations offer a good description of the discrepancy as well as reveal the prominent role of cell local deformation under bending condition. Furthermore, the present work offers clear evidence that the classical continuum theories, such as Bernoulli–Euler beam theory, are inadequate for describing the elastic bending behavior of metal foams.