Numerical Evaluation of the Shaper Cutter with Cylindrical Rake Face

This paper deals with the geometric built-up of a theoretically profile errorless shaper cutter. Its proposed rake face is a cylindrical surface for each tooth. The setting parameters of this are the axis inclination angle and the grinding wheel’s radius. The possible domain of the setting parameters is computed from geometrical restrictive conditions. The proposed numerical evaluation consists in the computing of the orthogonal rake angle variation, together with the deviation of the generating pro-file from the perfect involute. The obtained results allow the formulation of some conclusions regarding the influence of the cylinder radius and the axis inclination: the best rake angle distributions are obtained when using increased radius values, while profile deviation becomes minimal when using smaller radii and axis inclination angles.

Research on the elastic–plastic external contact mechanical properties of cylinder

Based on Hertz contact theory, an elastic-plastic contact mechanics model of outer cylinder under different contact angles of axis is proposed. The relationship among contact angle, load and contact deformation, contact stiffness and contact area is established. The finite element method is used to simulate the elastic-plastic contact process of the cylinder. The influence of the load and radius of the cylinder model on the contact deformation and the contact stiffness is compared and analyzed under different contact angles. The error of the analysis results of the finite element and the mechanical model is within 9%. On this basis, the influence of contact deformation, contact area and contact angle on the contact stiffness of the outer cylinder in elastic and plastic stage is explored. The results show that in the stage of elastic and plastic deformation, the amount of contact deformation and contact area increase with the increase of load. The contact stiffness decreases with the increase of contact angle and increases with the increase of cylinder radius. The amount of contact deformation decreases with the increase of cylinder radius, and tends to constant gradually. In the elastic stage, the contact stiffness increases with the increase of load. The contact area decreases with the increase of contact angle and increases with the increase of cylinder radius. In the plastic stage, the contact stiffness is constant with the increase of load, and the contact area is independent of contact angle and cylinder radius.

Stimulated emission–based model of fast radio bursts

ABSTRACT Fast radio bursts (FRBs) are bright, short-duration radio transients with very high brightness temperatures implying highly coherent emission. We suggest that the FRBs are caused by the self-focusing of an electron beam interacting with an ambient plasma right beyond the light cylinder radius of a neutron star. The magnetic field at the light cylinder radius is relatively high that can accommodate both young Crab-like systems and old millisecond pulsars addressing the diverse environments of FRBs. At the first stage, the intense pulsed-beam passing through the background plasma causes instabilities such that the trapped particles in local Buneman-type cavitons saturate the local field. The beam is then radially self-focused due to the circular electric field developed by the two-stream instability that leads to Weibel instability in the transverse direction. Finally, the non-linear saturation of the Weibel instability results in the self-modulational formation of solitons due to plasmoid instability. The resonant solitary waves are the breather-type solitons hosting relativistic particles with self-excited oscillations. The analytical solutions obtained for non-linear dispersion and solitons suggest that, near the current sheets, the relativistic bunches are accelerated/amplified by klystron-like structures due to self-excited oscillations by the induced local electric field. Boosted coherent radio emission propagates through a narrow cone with strong focusing due to radial electric field and magnetic pinching. The non-linear evolution of solitons and the stimulated emission are associated with the Buneman instability and the possibility of the presence of nanosecond shots in FRBs are investigated.

Calculation of a thermal stress state, when heating a steel cylindrical object

The paper studies longitudinal strains occurring along the height of a cylindrical object as a result of the temperature difference along the cylinder radius. It describes a particular case of a thermal stress state, when heating a cylinder. A temperature field was measured, when solving an axisymmetric task of heating a cylindrical object. Using the existing analytical dependence, the authors identified mathematical relations to calculate normal, tangential, and equivalent stresses. Such procedure may be applied to determine a stress state of cylinders 0.1 and 0.05 m in radius, when heating up to 400°C. It is shown that changes in a cylinder radius, maintaining the same heating conditions, result in decreasing maximum tension stresses from 45.9 to 23.9 MPa, and compressive stresses from 43.1 to 22.5 MPa. The authors determined principal stresses along a cylindrical rod radius during heating. Applying the Huber–Mises–Hencky criterion, changes in a growth rate of the stress state along a cylinder radius was determined. It is found that at the point of equalizing temperature along the cylinder radius, the highest stresses are in the layer periphery and central areas of the object under study and amount to 40.5 MPa at set conditions of calculations. It is noted that the developed mathematical tool may be used to evaluate a thermal stress state of mill rolls during their heat treatment.

Mapping the Emission Location of the Crab Pulsar’s Giant Pulses

The Crab pulsar has a striking radio profile, dominated by two pulse components (the main pulse and interpulse) which are comprised of giant pulses. These pulses are randomly occurring, they extend to extremely high flux densities, and are closely aligned with emission across the entire electromagnetic spectrum. The Crab, like many pulsars, exhibits scintillation – a pattern in frequency and time arising from interfering scattered images. The pattern varies with location, with the physical scale over which it changes by order unity corresponding to the spatial resolution of the scattering surface. For the Crab, the scattering is in the nebula and the estimated spatial resolution is of order the light cylinder radius. Comparing scintillation spectra of the two components, we infer a difference in physical location of the same order.

The Comparative Analysis of Hydrodynamic Pressures in Cylindrical Tanks

This article presents a comparative study of the values of hydrodynamic pressure and their resultants occurred during the seismic action using P100-1/2013 technical rules and the relations defined in the papers: [1], [3], [5] and the Romanian standard [2] SR EN 1998-4 (silos, tanks and pipelines), which is implemented in Romania. Two cylindrical tanks placed in the same seismic zone have been chosen, with the same amount of storage (about 5000 m3), but of different geometries, to illustrate the influence of hydrodynamic pressures on the construction size (long and short wall behavior) as a function of ratio of the fluid height on the cylinder radius and ratio of corner period on the eigenperiod of the fluid mass. Also in the analyses, in order to evaluate the hydrodynamic convective pressure both the fundamental period of oscillation of the fluid mass and the first ten periods of oscillation were used.

Surface Texturing Through Cylinder Buckling

We consider the axial buckling of a thin-walled cylinder fitted onto a mandrel core with a prescribed annular gap. The buckling pattern develops fully and uniformly to yield a surface texture of regular diamond-shaped buckles, which we propose for novel morphing structures. We describe experiments that operate well into the postbuckling regime, where a classical analysis does not apply; we show that the size of buckles depends on the cylinder radius and the gap width, but not on its thickness, and we formulate simple relationships from kinematics alone for estimating the buckle proportions during loading.