Determination of the stress acting on the individual cells of open-cell stainless steel foams

A series of tensile tests was performed on powder metallurgical processed open cell stainless steel foams with different densities and average pore sizes of 150, 300 and 600 μm, respectively to examine the effect of porosity as well as the cell wall thickness on the foams tensile mechanical properties. Moreover, a state of the art strain measuring device, which is not in touch with the sample's surface, was used to determine the strain and the other tensile properties accurately. The function of this device is based on the usage of a laser (CCD) camera. The laser (CCD) camera monitors the dimensional changes during loading by detecting the positional changes of special markers clipped on the sample's surface representing the gauge length. Thus we can avoid the constraint effects caused by using the conventional extensometers of contact type. By using the Weibull distribution function, the average fracture stress of the individual foam cells was statistically measured. The results showed a strong dependence of foams' mechanical properties on their porosity and thickness of their cell walls. Foams with small pores displayed higher mechanical properties than foams with larger ones. Foams with thick cell walls failed at larger stresses than foams having thin cell walls or struts.