Application of micropolar theory to the description of the skin effect due to hydrogen saturation

A model is proposed for the description of a highly inhomogeneous distribution of hydrogen within a saturated metal specimen (the so-called skin effect due to hydrogen saturation). The model is based on the micropolar continuum approach and results in a nonuniform stress–strain state of a cylindrical metal specimen due to distributed couples or microrotations. The dependence of the diffusion coefficient on the strain energy is considered in order to model stress-induced diffusion. Accumulation of hydrogen within a thin boundary layer results in a highly nonuniform distribution of hydrogen across the specimen. The mutual influence of the stress–strain state and hydrogen accumulation is taken into account. The estimated thickness of the surface layer containing hydrogen is comparable to the thickness observed in experiments. The predicted average concentration coincides with experimental data.

Stress Triaxiality and Lode Angle Parameter Characterization of Flat Metal Specimen with Inclined Notch

The stress state has an important effect on the deformation and failure of metals. While the stress states of the axisymmetric notched bars specimens are studied in the literature, the studies on the flat metal specimen with inclined notch are very limited and the stress state is not clearly characterized in them. In this paper, digital image correlation and finite element simulations are used to study the distribution of strain and stress state, that is stress triaxiality and Lode angle parameter. Flat specimen with inclined notch was tested to extract the full field strain evolution and calculate stress state parameters at three locations: specimen centre, notch root and failure starting point. It is found that compared with the centre point and the notch root, the failure initiation point can better characterize the influence of the notch angle on the strain evolution. Conversely, the centre point can more clearly characterize the effect of the notch angle on stress state, since the stress states at the failure point and the notch root change greatly during the plastic deformation. Then the calculated stress state parameters of the flat metal specimen with inclined notch at the centre point are used in Wierzbicki stress state diagram to establish a relationship between failure mode and stress state.

Effect of Surface Roughness and Oxidation Conditions on Wettability of Borosilicate Glass Sealant

One of the major challenges in the fabrication of glass-metal Joint is the wettability of glass sealant over the metal surface. The aim of the work was to study the wetting and spreading behavior of borosilicate glass sealant over austenitic stainless steel SS 304 and copper substrates with different surface roughness and oxidation conditions. During the wettability study of borosilicate glass sealant over the metal specimen, glass pallets were melted over the different oxidized metal specimens. The wetting behavior of borosilicate glass over metal specimen was measured in terms of contact angle and spreading area. The types of oxide and change in microstructure after oxidation were examined with the help of XRD analysis and optical microscopy. Tensile strength and hardness of the metal substrates after oxidation was also evaluated .

Study of a New Kind Compound Inhibitor

It has a significant practical value to research a compound inhibitor for low temperature for the protecting of power plant devices with low working-temperature. In this paper, a new kind of film-forming inhibitor based on octadecylamine for low temperature has been proposed. Coupon test has been taken with autoclave simulating the on-site water-vapor environment; the film-forming effect of the metal specimen has been evaluated by hydrophobic test, acid copper sulfate drip test and AC impedance test. The result shows that the inhibitor filmed well after compounded, and has an important practical value.