Mechanical properties of cellular solids produced from hollow stainless steel spheres
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Mechanical properties of cellular hollow sphere structures are studied in this work. The material was fabricated by coating the metallic powder slurry on expanded polystyrol (EPS) spheres, drying, forming under compression, debinding, and final sintering of the spheres to each other. Longitudinal elastic wave velocities were measured using ultrasound phase spectroscopy while compression tests were carried out up to a homologous temperature of 0.6. Dependence of the relative Young’s modulus on the relative density is similar to conventional open-cell foams. Compression stress–strain plots show the three stages of elastic deformation, plateau, and densification. With increasing temperature the overall level of the compressive stress–strain plots shifts to lower stresses. The hollow sphere solids show slightly better high temperature strength in comparison to the base metal. However, due to the considerable scatter in the experimental data points, this improvement seems to be insignificant. Structural observations on samples deformed to within the plateau region clearly show the heterogeneous progress of deformation.
KeywordsFoam Electrical Discharge Machine Hollow Sphere Cell Wall Material Plateau Stress
Co-author SR is grateful to DAAD (Deutscher Akademischer Austausch Dienst) for funding his stay in Karlsruhe, Germany under DAAD—Masters sandwich Model Scholarship and thanks Prof. B. P. Kashyap (Department of Metallurgical Engineering and Materials Science, IIT Bombay) for his guidance and for introducing him to the topic of metallic foams. The authors also thank Dr. K. A. Weidenmann (IAM-WK, KIT) for cross-reading the manuscript and for giving valuable suggestions.
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