Influence of Vickers tip imperfection on depth sensing indentation tests

In the last decade, the development of depth sensing indentation equipment has permitted two of the most conventional mechanical properties of materials to be easily determined: hardness and Young's modulus. Some care is needed to accurate results from the experimental determination of the aforementioned mechanical properties. In this study, numerical simulations were performed on two well-known materials (Bk7 glass, AISI M2 steel) and on fictitious materials with a wide range of mechanical properties, using Vickers indenters with different sizes of tip imperfections. The purpose is to estimate the influence of the size of the defect on the hardness and Young's modulus results obtained by ultramicro and nanoindentation tests.http://www.sciencedirect.com/science/article/B6VJS-4KPN470-4/1/046a4e2ab8ab1a360f1fb902158d564

Single Laser Detection of CO and OH via Laser Induced Fluorescence

Two-photon laser-induced fluorescence detection of carbon monoxide with excitation in the Fourth Positive System near 280 nm is demonstrated in carbon monoxide/nitrogen mixtures at ambient conditions and in a methane/air Bunsen flame. Fully resolved rotational spectra are presented for the A–X (5,0) and (4,0) bands near 279 and 284 nm, respectively. Energy transfer from excited molecular nitrogen to carbon monoxide with subsequent fluorescence from carbon monoxide that was reported for low pressure conditions in the literature has also been observed at atmospheric conditions. It was further demonstrated that overlaps of some CO A–X (4,0) rotational lines with OH A–X (1,0) rotational lines allow simultaneous excitation of both species with a single laser. The fluorescence bands are completely separated, enabling detection without crosstalk. Detection limits are adequate to detect CO in nascent state in a flame and it is expected that for application in high-pressure, low-temperature combustion environments, where high quantities of CO are present, this approach can provide advantages compared to the excitation of CO at shorter wavelengths due to decreased laser beam attenuation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86784/1/Sick6.pd