Test method development and determination of three-dimensional stiffness properties of polyvinyl chloride structural foams

A study has been conducted to develop proper test methods and to utilize the tests to evaluate three-dimensional mechanical behavior of a polyvinyl chloride structural foam (Divinycell H80 with nominal density of 80 kg/m3). Transversely isotropic foam microstructure was examined and it revealed that the cell size aspect ratio in in-plane directions was near unity but greater than one in the out-of-plane (rise) direction. Foam stiffness properties, i.e. moduli and Poisson’s ratios, were obtained in different loading modes, along both in-plane and out-of-plane directions. The influence of test specimen geometry on compressive properties was studied. Foam specimens with both straight-side and reduced gage sections were designed, fabricated and tested. The effect of specimen gage-section aspect ratio was identified as a critical geometric parameter, affecting foam compressive properties. For foam tensile properties, specimens with different cross-sectional dimensions in the gage section were used. The results revealed transversely isotropic characteristics of the foam material. To evaluate foam shear properties a scaled shear test method was developed. The results indicated a significant difference in in-plane and out-of-plane foam shear stiffness properties.

The Role of Calcareous Soils in SCC of X52 Pipeline Steel

ABSTRACTSusceptibility to external stress corrosion cracking (ESCC) of API X52 pipeline steel in calcareous soil containing different moisture content has been investigated using slow strain rate tests (SSRT). This type of soil is common of the state of Campeche Mexico and has a pH around 8. The results indicate that X52 pipeline steel was susceptible to external SCC only in the saturated calcareous soil, showing some micro cracks in the gage section of the SSR specimen. It was observed that some micro cracks were found at the bottom of micro-pits. Which indicate that first develop a pit and this evolved with time and micro-strain like a crack. Few micro cracks were observed as initiation of SCC close to surface failure. The mechanism of SCC may be influenced by formation and rupture film of carbonates.

Coming Full Circle: The Application of Microtechnology Techniques to Evaluate Bulk Materials

ABSTRACTA tensile test procedure that accommodates specimens with gage section 25 μm thick, 70 μm wide and 360 μm long was developed and demonstrated. The instrumentation and technique were adapted from those previously developed and used to test thin films, by increasing both the force capacity of the load cell and the stiffness of the pull rod. Specimens with bow-tie geometry were fabricated by photolithography from nominally 25 μm thick full hard stainless steel 302 foil. A silicon test frame fabricated by bulk micromachining techniques included tapered grips in the form of recesses in its top surface that accepted and retained the specimen grip sections. One grip was on the fixed outer portion of the frame. The other grip was on a plate suspended in the center of the frame by long slender silicon beams. Force was imposed on this plate by pin loading. The force was measured by use of a custom load cell. The displacement was measured by sub-pixel digital image correlation to surface features on the two ends of the gage section, applied to images with a resolution of approximately 0.8 μm per pixel. Yield and ultimate strengths and elongation values consistent with vendor-provided information were obtained. The values of Young’s modulus were scattered but within the range of expected behavior for the specimen material.

Tensile Test Techniques for a Nuclear Fuel Cladding in a Hot Cell

Modified transverse and longitudinal tensile test techniques are proposed to evaluate the mechanical properties of nuclear fuel cladding materials under a hoop and axial loading condition in a hot cell. The ring specimen with a gage length of 3 mm and a width of 2 mm is designed to limit a deformation within the gage section and to maximize the uniformity of a strain distribution at the gage section. The loading grip is designed such that a constant curvature of a specimen is maintained during a deformation. The contact surface is lubricated with a graphite lubricant (Model P-37, Molykote Co.). A dogbone specimen with a gage length of 25 mm and a gage width of 2.5 mm has been designed for the longitudinal tensile test. The grip is designed such that any slippage at the gripping section does not occur during a test. Through the tensile test of an unirradiated Zircaloy-4 cladding tube and an SUS 316 steel seamless tube, it is found that the proposed techniques are appropriate for an estimation of the tensile properties of an irradiated nuclear fuel cladding in a hot cell.