Circular Bulge Research Articles

SEM study on the dorsal lingual surface of the common tree shrew, Tupaia glis.

The dorsal lingual surface of the common tree shrew was examined by SEM after treating it with HCl to remove the mucous substance. Filiform (FI), fungiform (FU) and circumvallate papillae (CI) were observed. The FI exhibited a small circular bulge surrounded by anterior and posterior filamentous processes. FU were scattered among the FI. There were 3 CI separating the anterior 4/5 from the posterior 1/5 of the tongue. In addition, a group of conical projections with caudal orientation was found anterior to the palatoglossal fold on each side of the tongue. Microridges were widely observed on the entire dorsal lingual surface, except on the free surface of FI processes.

Electromagnetic induction in a spherical earth with a circular bulge in the upper mantle

Results of computing the anomalies of the variable magnetic field, generated by a harmonically variable field of the H1,0-type in the model of a spherical Earth with an expressive bulge in the well-conducting part of the mantle, are presented. It was found that not only the radial, but also the tangential component of the magnetic field is disturbed above the bulge. The largest amplitudes of these changes can be observed over the area of the largest slope of the conductivity boundary if the exciting magnetic field is perpendicular to the surface of the interface.

Noninvasive visualization of the left main coronary artery by cross-sectional echocardiography.

Real time cross-sectional echocardiographic studies of the left main coronary artery (LMCA) were performed in 15 normal patients, 15 patients with angiographically proven coronary artery disease but normal left main coronary segments, three patients with greater than 75% obstruction of the left main coronary artery, and one patient with a larger aneurysm of the left main coronary artery. In normal subjects the LMCA evaginates from in inferolateral wall of the aorta. The artery appears as two dominant parallel linear echoes separated by a clear space representing the lumen of the vessel. The LMCA courses beneath the right ventricular outflow tract and can generally be followed to its expected point of bifurcation. Confirmation that this structure was in fact the LMCA was obtained by injection of cardiogreen dye directly into the LMCA in two cases and by visualization of dye in this structure following aortic flush in one case. In the three cases with obstructive lesions of the LMCA, there was an area of inward bending of the parallel vessel wall echoes resulting in varying degrees of narrowing of the arterial lumen. In the case with the aneurysmal dilatation of the LMCA, an echo-free circular bulge in the distal portion of the LMCA was recorded. This study demonstrates the fesibility of recording the left main coronary artery using the cross-sectional echocardiographic technique.

Variability of forming limit curves

Summary The forming limit curve indicates the maximum uniform strain which can be achieved in an element of a sheet which is strained in a proportional biaxial straining process; it refers to the strain in a region adjacent to, but not within, any area of localized straining associated with rupture. In this work forming limit curves were determined for four different grades of mild steel; gridded test pieces were stretch formed to failure in elliptical and circular hydrostatic bulge dies. Each test was repeated twenty times for each material and each die, in order to provide data for statistical investigation of scatter in measured forming limits. It is shown that the variation in forming limits is much greater than that due to the experimental error and it is proposed that this scatter reflects an intrinsic property of the material which is important in determining material formability. A three-dimensional forming limit diagram is presented which can be used to determine the probability of failure of an element which is stretch formed to a particular strain level. The experimental data are also employed to determine the number of tests required to determine the mean forming limit curve within a specified accuracy.

Strength and Failure Characteristics of Metal Membranes in Circular Bulging

Abstract Circular hydraulic bulges were formed from a group of materials having widely varying strain-hardening rates. The complete development of the shapes and strain distributions was determined experimentally, and the stress and radius of curvature at the pole were calculated as a function of the maximum strain. An analysis of the data revealed that strain gradients and, therefore, the bulge heights were influenced by the stress-strain characteristics of the metal. It was also found that the bulge contour was closely approximated by a sphere only at strains in the vicinity of the instability strain. Instability was exhibited by all materials having a sufficient ductility at strains varying from ϵ3 = −0.47 for 75S-O to ϵ3 = −0.64 for annealed low-carbon steel. The phenomenon of instability was related to both the development of the shape and the strain distribution. The previously reported differential equation for instability in a circular bulge was found to yield strains which agreed with the maximum load strain and the instability strains derived from the analysis of the shape and strain distributions. These instability strains were not found to be simply related to the necking strains in uniaxial tension. The height and maximum strains (forming limits) obtainable in bulging were found to be greatly reduced by the presence of surface flaws or a large grain size.

Strength and Failure Characteristics of Thin Circular Membranes

Abstract The problem treated in this paper concerns the deformation and failure characteristics of thin circular metal membranes. The problem originated in a research project on the elevated-temperature bulging of aluminum alloys, conducted at Case Institute of Technology under contract with the Office of Production Research and Development of the War Production Board. Commercially the problem relates to the design of safety diaphragms used for the protection of pressure vessels. Also, similar conditions of loading and geometry are present in certain structures subjected to underwater explosion or high hydrostatic pressure. The circular bulging of metal membranes also offers the possibility of investigating the fundamental properties of metal in biaxial stress and strain states. In this paper the instability phenomena encountered in the deformation of such shapes is analyzed in terms of strain distribution and also by previously developed equations relating the stress-strain and radius-strain functions. The paper also develops the fact that the circular bulge test appears particularly suitable for determining basic stress-strain relations to much higher strain values than are obtainable by conventional methods.

Circular Bulging of Aluminum-Alloy Sheet at Room and Elevated Temperatures

Abstract In this paper preliminary results are reported on the strength characteristics and forming limits of various aluminum-alloy sheet, when subjected to hydraulic pressure over a circular area at temperatures up to 500 F. The strain distributions were analyzed by means of a photo-grid, after these bulges failed. The bulges exhibited a practically balanced biaxial strain state over most of the contour with the exception of a very narrow range of local deformation in the vicinity of the fractures. The maximum meridional strain outside the necked area observed at the pole of a bulge, in spite of its biaxial nature, generally exceeded the uniform elongation known from tensile tests. The forming limits for all annealed conditions increased considerably with increasing temperature if the temperature exceeded a certain critical value, between 250 and 400 F, depending upon the alloy. The heat-treated conditions of the alloys 24S and 61S were only slightly affected by the testing temperature, while the forming limits (uniform stretch) of 75S-T, R301W, and R301T were materially increased at elevated temperatures. The reduction of thickness, which is a measure of the ductility of an alloy, followed approximately the same trend as the forming limit.