SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
New definitions are proposed for some terms in State Standard GOST 25762–83. Additional terms and definitions are proposed to describe surface shaping by cutting tools. The new terms eliminate some omissions in our general concepts regarding the kinematics of cutting and surface shaping.
The cutting time and speed in the abrasive lapping of zirconia ceramics are investigated. Their influence on the productivity and final surface roughness is considered. The optimal cutting time and speed are determined.
The ease of cutting of high-chromium ferrite steels is considered. In cutting, the productivity is found to be satisfactory, but it is difficult to obtain a machined surface of acceptable quality. Recommendations are made for improving the quality of the machined surface.
Hydroabrasive cutting may be intensified by swirling of the working jet of suspension. In addition to fatigue failure of the machined material, the swirling activates abrasive cutting.
The influence of the supply on the cutting force is established in the machining of quenched steel by VOK-60 cutting ceramic. The optimal machining conditions for quenched 40Kh and KhVG steel workpieces are determined.
Vorontsov’s plastic-flow method permits the derivation of a model of cutting for the region where the tool exits the blank. The stress–strain state of the blank is determined, and the dimensions of the plastic-deformation zone are calculated. The main cutting parameters are shown to be variable.
An analytical formula is derived for determining the frictional coefficient at cutter–blank contact, on the basis of the cutting equations and the shear angle, and is verified by means of experimental data. This formula may be used to calculate the cutting parameters, without constraints on the significant factors.
Vorontsov’s plastic-flow method permits the derivation of a model of cutting for the region where the tool enters the blank. The stress–strain state of the blank is determined, and the dimensions of the plasticdeformation zone are calculated. The main cutting parameters are shown to be variable.
In research on thread cutting, the flaws inevitably arising in the first two and last two turns of the thread, when the process is unsteady, are analyzed. Specifically, insertion and removal of the tool from the workpiece are accompanied by abrupt change in thread diameter: abrupt decrease in the case of threads on shafts; and increase for threads in holes. That leads to the appearance of slots on assembly, thereby increasing the likelihood of accidents and other problems in thread operation. A method of eliminating such gaps is proposed and tested: control of the machining precision in the course of thread cutting. In particular, the thread diameter and pitch are controlled by compensation of the axial and radial elastic displacements of the tool, based on timely correction of the transverse and longitudinal supply during the unsteady stage of the process. Compensation of the machining errors improves the dimensional precision of the thread and decreases the systematic errors and spread in the thread dimensions.
The relation between the cutting properties of superhard tool inserts and their eigenfrequency is studied. The relation between the life of inserts and their acoustic properties is confirmed experimentally in the turning of high-temperature nickel alloys and quenched steels. A method is developed for determining the eigenfrequency of cutting inserts, along with the corresponding equipment.
The evolution of the dynamic cutting system is simulated with different trajectories of the power of irreversible transformations in performing work. The evolutionary changes associated with change in tool wear and in surface precision and quality depend on the dynamic properties, on the subsystems that interact through cutting, and also on the initial dynamic relationship formed by the process.
The actual cutter geometry in precision cutting is described, and the corresponding model of the mechanical characteristics of cutting is presented.
This paper describes the dynamic stability evaluation of a constrained-motion dynamometer (CMD) with passive damping. The CMD’s flexure-based design offers an alternative to traditional piezoelectric cutting force dynamometers, which can exhibit adverse effects of the complex structural dynamics on the measurement accuracy. In contrast, the CMD system’s structural dynamics are nominally single degree of freedom and are conveniently altered by material selection, flexure element geometry, and element arrangement. In this research, a passive damping approach is applied to increase the viscous damping ratio and, subsequently, the stability limit. Cutting tests were completed and the in situ CMD displacement and velocity signals were sampled at the spindle rotating frequency. The periodic sampling approach was used to determine if the milling response was synchronous with the spindle rotation (stable) or not (chatter) by constructing Poincaré maps for both experiment and prediction (time-domain simulation). It was found that the viscous damping coefficient was increased by 130% and the critical stability limit was increased from 4.3 mm (no damping) to 15.4 mm (with damping).
Significant progress has been made in our understanding of the analytic structure of FRW wavefunction coefficients, facilitated by the development of efficient algorithms to derive the differential equations they satisfy. Moreover, recent findings indicate that the twisted cohomology of the associated hyperplane arrangement defining FRW integrals overestimates the number of integrals required to define differential equations for the wave-function coefficient. We demonstrate that the associated dual cohomology is automatically organized in a way that is ideal for understanding and exploiting the cut/residue structure of FRW integrals. Utilizing this understanding, we develop a systematic approach to organize compatible sequential residues, which dictates the physical subspace of FRW integrals for any n -site, ℓ-loop graph. In particular, the physical subspace of tree-level FRW wavefunction coefficients is populated by differential forms associated to cuts/residues that factorize the integrand of the wavefunction coefficient into only flat space amplitudes. After demonstrating the validity of our construction using intersection theory, we develop simple graphical rules for cut tubings that enumerate the space of physical cuts and, consequently, differential forms without any calculation.
We reformulate differential equations (DEs) for Feynman integrals to avoid doubled propagators in intermediate steps. External momentum derivatives are dressed with loop momentum derivatives to form tangent vectors to unitarity cut surfaces, in a way inspired by unitarity-compatible IBP reduction. For the one-loop box, our method directly produces the final DEs without any integration-by-parts reduction. We further illustrate the method by deriving maximal-cut level differential equations for two-loop nonplanar five-point integrals, whose exact expressions are yet unknown. Finally, we speed up the computation using finite field techniques and rational function reconstruction.
We elaborate on aspects of a new positive geometry proposed recently, which was conjectured to be the four-point amplituhedron for ABJM theory. We study generalized unitarity cuts from the geometry, and in particular we prove that (1) the four-point integrand satisfies perturbative unitarity (or optical theorem) to all loops, which follows directly from the geometry, and (2) vanishing cuts involving odd-point amplitudes follow from the “bipartite” nature of the associated “negative geometries”, which justifies their appearance in ABJM theory. We also take a first step in integrating the forms of these negative geometries and obtain an infrared-finite quantity up to two loops, from which we extract the cusp anomalous dimension at leading order.
We consider the Riemann–Hilbert-type boundary-value problems in the case of several unknown functions and obtain solvability conditions and index formulas for the linear conjugation problem, the Riemann–Hilbert problem, and the Riemann–Hilbert–Poincaré problem on a plane cut along several regular arcs in various weighted functional classes. We also examine the general differential boundary-value problem for analytic functions and boundary-value problems with shifts and complex conjugation on a cut plane.
Commercial TiAlN-coated carbide tools were post-treated using the high current pulsed electron beam irradiation method. The influence of the energy density of the electron beam on the morphology, phase composition, surface roughness and Vickers hardness were investigated. The higher energy density imposed on TiAlN-coated carbide tools resulted in a flatter and harder modified surface. After the beam irradiation, the XRD diffraction peak intensity of the hardening phase (Ti,Al)N was changed, and the diffraction peak position was shifted; these changes are attributed to the improved microhardness of the irradiated coatings. Investigations on the cutting experiments of turning Ti-6Al-4V alloy showed that the irradiated TiAlN-coated carbide tool exhibited longer cutting life and better wear resistance than those of an unirradiated tool. This improvement is attributed to the combined effect of low surface roughness and high microhardness that resulted from the high current pulse electron beam irradiation.