Volume 3 Issue 4
Authors: Basel Younes
Abstract: This research investigates the influence of the hot-drawing process on the thermal shrinkage and mechanical properties of the bio-polymer fibers. As-spun fibers made of biodegradable linear aliphatic-aromatic co-polyester (LAAC) were drawn under a fractional factorial design as a function of hot-drawing conditions, the LAAC fibers were characterized and statistically modeled using appropriate experimental and statistical methods. According to the analysis, the most effective and significant parameters influencing the fiber mechanical properties are the drawing ratio and the drawing temperature. The significant factors affecting the thermal shrinkage are the total number of drawing stages (DS), the drawing temperature (DT), relaxing stage ratio (RS) and the plate temperature (PT). A new forecasting data source was achieved to optimize the hot drawing of as-spun aliphatic-aromatic co-polyesters (LAAC) fibers, and to specify the direction of increasing or decreasing of the significant process parameters. From the results and analysis, a combination of factor levels was designed for controlling the mechanical properties of the studied material using the regression equations obtained. With their elastical properties, the optimized aliphatic-aromatic co-polyester fibers with other biodegradable/bio-based materials could be used in agricultural, horticultural and other textile applications for sustainable development.
Keywords: Biodegradable Polymer; Hot Drawing; Mechanical Properties; Thermal Shrinkage; Aliphatic-Aromatic Co-Polyester; Statistical Modeling; Bio-based Polymer Applications
Authors: V. M. Kornev
Abstract: Critical stresses for quasi-brittle bimaterial with edge cracks have been obtained. Cracks along the plane interface of the bimaterial are simulated as bilateral cuts. The critical stresses correspond to necessary and sufficient fracture criteria and those are lower-bound and upper-bound estimates for critical states of a system. The embrittlement effect is revealed by comparison of fracture between bimaterial and homogeneous material. Estimates for effective diameters of grain separation have been obtained. It is noted that -stress affects critical stresses for very short cracks, so for cracks occupying the most of a specimen width. Critical stresses have been derived above which specimens are broken apart. Subareas on the plot of external load versus crack length are singled out where damage accumulation in material takes place after single loading. Comparison of critical stresses with the subareas mentioned above for homogeneous materials and bimaterials has been performed.
Keywords: Brittle and Quasi-Brittle Fracture; Structured Materials; Edge Crack; Bimaterial
Authors: Pesin Alexander; Pustovoitov Denis; Pesin Ilya
Abstract: The main goal of the investigation is to determine key technological parameters, necessary for producing required curvature of sheets up to 4000 mm in width with the required mechanical properties. Investigation into dynamics of the process' main technological parameters allowed to define its three characteristic stages: asymmetric rolling, asymmetric rolling in combination with initial unsettled plastic bending, and asymmetric rolling combined with settled plastic bending. It was found out that the intensity of the deformations changes unevenly, depending on the height of the deformation zone, on all three stages, with its highest value being in the lower part of the sheet, and with the lowest value being in its center. In the second stage, the intensity of the deformation abruptly increases, and a significant asymmetry on the sheet thickness occurs. In the third stage, the non-uniformity of the intensity deformations fields decreases. Similar results can be also observed for stress intensities. Casings on two converters were produced and installed in the oxygen-converter plant. Economic effect from the installation of the developed technology was more than 1 million dollars.
Keywords: Asymmetric Rolling; Plastic Bending; Large-size Bodies of Rotations; Curvature; Mathematical Modeling