Middle Bar Research Articles

A Simplified Test Device for Thermal-stress Ratcheting (a Three Bars Specimen) and Some Results

A special plate-shaped specimen with two symmetrical, straight air gaps in the center portion and a pair of holes for load chucks at the end is proposed, fabricated and examined for thermal-stress ratcheting. Effective portion of the specimen is divided into three bars by a couple of slender air gaps. Two side bars out of three are enveloped with special trace heaters. Testing is made by on-off cycling of the heaters under a constant steady membrane stress. When thermal loading is applied by heating, the middle bar becomes a cold element and the other side bars hot elements. Descriptions and characteristics of the specimen, the test procedures and typical results are presented.

An experimental study on thermal-stress ratchetting of austenitic stainless steel by a three bars specimen

A new test specimen for thermal-stress ratchetting is proposed and tested for standard AISI-304 stainless steel. Its purpose is to avoid the drawbacks of a tubular specimen. It is a special plate-shaped specimen with two symmetrical, straight air gaps in the center portion and load chucks at the ends. Since three surfaces out of four on the side bars are enveloped by sheathed trace heaters, the middle bar becomes a cold element and the rest side bars hot elements during thermal loading. Experiments on thermal-stress ratchetting are performed with this specimen. Interesting incremental strain growth behaviour of the specimen subjected to cyclic thermal stresses under a steady primary load is obtained with regard to an actual strain-hardening material. It was confirmed that incremental strain growth decreased with increase in the cumulative strain growth. There is expected to be an asymptotic cumulative strain growth for any test condition. It is also found that the tendency for theoretical strain growth is fairly similar to that found experimentally. However, the experimental data are considerably greater than the theoretical data. This can be explained qualitatively by a decrease in both yield strength and Young's modulus at high temperature for the hot elements.

Design of partial denture components. I. Middle palatal bars.

An analysis of the effect of length and curvature on the load deformation characteristics of palatal bars that can be represented by arcuate beams is presented. The width and thickness required to produce palatal bars of equal rigidity for different lengths are deduced and presented as a nomogram.

小形並びに中形壓延機に於けるレピーターに關する考案

The author studied the new designed oval and A.K. type repeaters (this terms named by this plant to the new type repeaters), the former used for the mill producing φ12m/m-φ22m/m steel bars, the latter for the mill producing 50×50m/m equal angle steel.In the case of the oval repeater for small section bar mill, the author studied on the shape of repeater, on the special devices of guard and box guide.In the case of the A.K. type repeater for middle section bar mill, the author studied on square repeater, revolution repeater, 3 Kal. repeater.Especially in the case of revolution repeater, the author applied the principle of "Schoepf's repeater", and obtained very good results.