CO2 Adsorption–Desorption Kinetics from the Plane Sheet of Hard Coal and Associated Shrinkage of the Material

The paper presents the results of studies on sorption and CO2 desorptions from coals from two Polish mines that differed in petrographic and structural properties. The tests were carried out on spherical and plane sheet samples. On the basis of the sorption tests, the effective diffusion coefficient was calculated on the plane sheet samples based on a proper model. Similar tests were performed on the spherical samples. Mathematical model results for plane sheet samples were compared with the most frequently chosen model for spherical samples. The kinetics of CO2 desorption from plane sheet samples were compared with the kinetics of sample shrinkage. In both samples, the shrinkage was about 0.35%. The size change kinetics and CO2 desorption kinetics significantly differed between the samples. In both samples, the determined shrinkage kinetics was clearly faster than CO2 kinetics.

Preparation of Mg-TM-Y (TM=Transition Metal) Alloys with Long Period Stacking Ordered Phase and their Superior Mechanical Properties

Mg-Ni-Y alloy with composition ratio of 1 : 2 (Ni : Y) consisted of Mg, and 18R-type long period stacking ordered (LPSO) phases, whereas composition ratio of 1 : 1 (Ni : Y) consisted of Mg,14H-type LPSO and Mg2Ni phases, respectively. After hot-rolling at 693K, strong basal texture parallel to the plane sheet was formed in the LPSO, and Mg phases. Tensile test was performed along rolling direction (R.D) from room temperature (R.T) to 573K. The Mg98Ni1Y1, Mg96Ni2Y2, Mg94Ni3Y3, Mg97Ni1Y2 and Mg94Ni2Y4 rolled sheets exhibited 0.2% proof stress (σ0.2) of 232MPa, 255MPa, 358MPa, 337MPa and 393MPa, and elongation (δ) of 6%, 5%, 7%, 15% and 7% at R.T, respectively. The σ0.2 of the Mg-Ni-Y rolled sheet tend to increase with increasing of area fraction of the LPSO phase. After annealing at 773K for 0.6ks, the δ of Mg-Ni-Y rolled sheet tend to increase, while the σ0.2 decreased due to randomization of the Mg phase by re-crystallization. The Mg-Ni-Y rolled sheets exhibited high σ0.2 above 200MPa at 473K. Additionally, it was noted that σ0.2 of the Mg94Ni2Y4 rolled sheet exhibited 329MPa at 473K and 211MPa at 573K. Thus, the LPSO phase have high thermal stability and is attribute to strengthening of the Mg-Ni-Y alloy sheet at high temperature.

Influence of Geometrical Shapes and Sheet Thicknesses on the Dimensional Accuracy of Single and Assembled Parts

Based on elastic stress and strain states after forming and joining processes, single and assembled parts show deviations regarding their dimensional accuracy. Therefore an analysis of selected influencing factors and their influence on the dimensional accuracy of assembled parts is performed in this paper. In this article a novel approach is presented that characterizes the impact of three geometrical shapes (convex/concave/straight) and different sheet thicknesses on the dimensional accuracy along a linked forming and joining process chain. The process chain consists of a deep drawing and a clinching process. Depending on sheet thickness, material and geometrical shape, the dimensional accuracy of single parts and joined assemblies varies. For the single parts the geometry of the specimen S-rail is used. Several types of assemblies are used for the proposed approach combining this specimen with a plane sheet or a second S-rail. The FEM-tools LS-DYNA and Abaqus, are used to demonstrate this approach. Simulations and experiments with aluminum alloy 6014, mild steel CR3 and sheet thicknesses of 0.7, 1.0 and 2.0 mm are conducted for single and assembled parts. In summary, a significant improvement of the dimensional accuracy of an S-rail assembly is demonstrated using two non-dimensional accurate single parts. Future work will be to analyze frequently occurring part segmentations for the joining technologies and to optimize material mix and sheet thicknesses in order to improve deviations of the assembly to the nominal CAD geometry.

On the cusps bordering liquid sheets

The edge of a stationary radially expanding liquid sheet and the receding rim bordering a plane sheet are naturally indented. It presents a collection of cusps at the extremity of which the liquid concentrates and is expelled. An experimental description of these cusps for a stationary flat inviscid Savart sheet is given. We identify the stable node–jet structure responsible for the deflection of the incoming flow at the rim and demonstrate how these cusps are the structures that accommodate for both mass and momentum conservation at the sheet edge. Their shape, their number around the sheet, and the residual momentum carried by the ejected liquid are computed.