Sections Of Bars Research Articles

The skin‐core morphology and structure–property relationships in injection‐molded polypropylene

AbstractTensile bars of an isotactic propylene homopolymer and an ethylene–propylene copolymer were prepared by injection molding under a variety of melt temperatures and injection pressures. The effects of these processing variables on morphology and crystalline orientation were studied using optical microscopy and x‐ray diffraction. Microscopy of microtomed thin sections of the tensile bars revealed the presence of three distinct crystalline zones, namely, a highly oriented nonspherulitic skin, a row or shear‐nucleated spherulitic intermediate layer, and a typically spherulitic core. The thickness of the oriented skin layer is a function of the polymer melt temperature and varies inversely with temperature. The thickness of the intermediate layer varies with injection pressure, but in a complex manner. Preferred crystallite orientation in the skin and intermediate layers exerts profound effects on mechanical properties. Tensile yield strength, impact strength, and shrinkage increase with increasing combined thickness of the two oriented outer layers.

Distortion of cross sections during deformation of oriented glass-reinforced plastics

Test pieces equipped with wire strain gauges were used to investigate the distortion of cross sections of bars made of oriented glass-reinforced plastics (GRP) in tension and bending. The need for modified design formulas, obtained without use of the simplifying hypothesis of plane sections, is demonstrated. The previously obtained theoretical results of [2, 3] are experimentally confirmed. The effect of the free ends on beam deflection is found to be unimportant.

鐵鋼の再結晶軟化に及ぼす合金元素の影響

The present report supplys some data on the recrystallization softening of cold-rolled alloyed iron and steels, with'a point of view to survey the effect of the alloying elements on the rigidity of steel at high temperature.The samples were prepared by induction melting in magnesia-lining crucibles, using 0.08% C Swedish steel and the best grade of metals or ferro-alloys as the alloying materials. After complete annealing, these alloyed iron bars were subjected to cold rolling of 20% and 50% reduction in thickness. And Brinell hardness tests were carried out upon the sections of these rolled bars, which were reannealed at various temperatures (300 to 1000°C) for a constant period of time (2hr), and also at a constant temperature (550, 600, 650 or 700°C) for vafious periods of time (2min to 100hr).The results obtained were shown in Figs. 1, 2, 4 and 5, from which the following conclusions were drawn.(1) Nb, Ti, Mo, W, V, Cr and Co raised the recrystallization temperature, and retarded the softening of steel accompanied by annealing.(2) Ni, Mn, Si, Al, Sn and P hardly changed the range of softening temperature of ferritic steel.(3) Cu, added more than the solubility limit for iron, raised the softening temperature of steel.(4) Cold rolled 0.65%C steel having spheroidal structure was easily softened than the lamellar one by annealing.(5) High Ni-or high Mn-steel having austenitic structures showed higher softening temperatures than the ferritic ones.