Modeling of pipe-drawing tool for drawing the multifaceted pipes of nonferrous metals on an immediate arbor

A method of mathematical modeling of a pipe-drawing tool for drawing the multifaceted pipes of nonferrous metals and alloys using the vector-matrix apparatus, which can be applied for the analytical description of the bulk deformation region, is presented. Arbors with various geometries of the reduction zone are considered. As a result of modeling the deformation region, which appears when manufacturing the profiled multifaceted pipes by arbor drawing using all types of considered arbors, it is established that the best result with the smallest rounding radii is attained for arbors with a pyramidal input into the reduction zone. © 2013 Allerton Press, Inc

Applying Gaussian distributions on SO(3) for modeling the texture and predicting the properties of texturized polycrystalline materials

This paper considers a quantitative description of the crystallographic texture. When the crystallographic texture is modeled, the generalized Gaussian distribution is applied on Riemannian manifolds. A simple model of the orientation distribution function (ODF) is obtained, which corresponds to the Gaussian distribution of the axial crystallographic texture. It is demonstrated that an equally probable distribution of crystallographic axes and an ideal axial texture are realized as special cases of the ODF model. An anisotropy evaluation of elastic modulus is carried out. The indicatrix transformation of Young's modulus is demonstrated. © 2016 Author(s)

Texture parameter variation region for orthotropic polycrystals with cubic symmetry of the crystal lattice

The variation region of texture parameters (which are integral characteristics of the preferable orientation of crystallographic axes) allows solutions to be found for managing anisotropic properties, illustrating all possible textured states of an orthotropic polycrystalline material with a crystal lattice of cubic symmetry. Each point in this region is matched by certain anisotropy of both elastic and plastic properties. The region of texture parameter variation is defined both analytically and using a numerical experiment of statistic simulation. Analytically, the solution is found via determining the effective eigenvalues of the elasticity operator for a textured anisotropic cubic polycrystal. The algorithm to be followed for visualizing the region-forming elements implies determining the lines of intersection of planes with a conical surface. The numerical solution is based on the determination of texture parameters, i.e, on the starting assumption that the variation region is bounded and lies in the first octant. The task of constructing the variation region is solved via finding the texture parameters using the Monte-Carlo method according to the density of distribution of crystallographic axes in space. When modeling the variation region, octets are used, which are symmetrical reflections of randomly taken orientations in all the octants of space. The constructed regions have the required symmetry. The numerically obtained cloud of textured states and the analytically constructed variation region have geometric centers coinciding at the point corresponding to the non-textured state. At various stages of thermal and mechanical treatment of metallic materials, texture evolution can be represented geometrically as a texture state trajectory that is seen to be within the determined texture parameter variation region. © 2018 Author(s)

Geometric representation of polycrystalline material texture by axis-angle parametrization

Texture is the preferential orientation of crystallographic axes in polycrystal. For its mathematical modeling, the orientation distribution function of the crystallographic axes is used. Traditionally, the orientation distribution function is written with the help of directional cosine matrices, Miller indices or Euler-Krylov angles. Recently, texture has increasingly often been described using quaternions, Rodrigues parameters and the vector space of axis-angle parameters. Axis-angle parameters allow us to describe all possible rotations of the SO(3) group, which corresponds to all possible orientations of crystallographic axes in polycrystalline materials. The SO(3) group is a set of rotations to all possible angles around all possible axes given by all vectors of the unit sphere. The set of such rotations corresponds to points set on a ball of radius π in three-dimensional Euclidean space. The description of the crystallographic texture using axis-angle parameters made it possible to visualize the distribution of crystallographic axes and obtain a new geometric representation of the texture. © 2018 Author(s)

Construction of a programmed trajectory in the configuration space of rotations for solving the problem of the solid rotation

The paper proposes method of programmed control based on the concept of solving the inverse dynamic problem. As a configurational space of rotations, it is proposed to consider a sphere with a radius of 2 π in the three-dimensional Euclidean space, which is the image of the unit Sp(1) quaternions. A linear relationship has been established between the angular velocity vector of a solid in its spherical motion and the velocity of a point in a sphere allowing to relate the rotation of a solid to the motion of a point inside a three-dimensional sphere. This approach allows to clearly interpret the spherical motion of a solid by the movement of a point inside this sphere, which is used by the authors to describe the rotation of a solid at arbitrary given boundary conditions for angular positions, velocities and accelerations. An example of a smooth turn from one position to another in the case when the turn is set in the sphere in the form of a polynomial of the fifth degree is given. © Published under licence by IOP Publishing Ltd

A quaternionic description of kinematics and dynamics universal joint

The purpose of the work is figuring out the kinematic and dynamic equations of u-joint motion in the quaternion parametrization. The quaternion description of u-joint kinematics allowed us to formulate the claims about the crosspiece angular velocity projections. We've also determined the principle point projection acting on the crosspiece by solving the inverse problem from Euler's dynamic equations with the found driving shaft's angular velocity and the inertial crosspiece characteristics. The modeling results are verified in the computer software-Mathcad and can be used for creating optimal u-joint designs by changing its geometry. © Published under licence by IOP Publishing Ltd

Mathematical modelling of the spatial network of bone implants obtained by 3D-prototyping

In this paper, the mathematical model suitable for bone implants 3D-prototyping is proposed. The composite material with the spatial configuration of reinforcement with matrix of hydroxyapatite and titanium alloys fibers is considered. An octahedral cell is chosen as an elementary volume. The distribution of reinforcing fibers is described by textural parameters. Textural parameters are integrated characteristics that summarize information on the direction of reinforcing fibers and their volume fractions. Textural parameters, properties of matrix and reinforcing fibers allow calculating effective physical and mechanical properties of the composite material. The impact of height and width of the octahedral reinforcement cells on textural parameters of the composite material is investigated in this work. The impact of radius of fibers is also analyzed. It is shown that the composite becomes quasi-isotropic under certain geometrical parameters of cell. © 2016 Author(s)

Designing the program trajectory for steering a spacecraft under arbitrary boundary conditions

A problem is considered of designing the program trajectory of a spacecraft turning from an arbitrary initial orientation to an arbitrary final orientation, with the orientations being defined with unit quaternions. A projection of a group of unit quaternions Sp(1) on a sphere with the radius of 2π is used to represent rotation of a body as a motion of a point inside the given sphere. Polynomials of the fifth degree are considered as a class of functions to define the program trajectories in the sphere. The suggested class of trajectories is demonstrated to be effective to provide the possibility of meeting boundary conditions at arbitrary values of velocities and accelerations. © 2020 Institute of Physics Publishing. All rights reserved

Quaternion model of programmed control over motion of a Chaplygin ball

This paper deals with the problem of program control of the motion of a dynamically asymmetric balanced ball on the plane using three flywheel motors, provided that the ball rolls without slipping. The center of mass of the mechanical system coincides with the geometric center of the ball. Control laws are found to ensure the motion of the ball along the basic trajectories (line and circle), as well as along an arbitrarily given piecewise smooth trajectory on the plane. In this paper, we propose a quaternion model of ball motion. The model does not require using the traditional trigonometric functions. Kinematic equations are written in the form of linear differential equations eliminating the disadvantages associated with the use of Euler angles. The solution of the problem is carried out using the quaternion function of time, which is determined by the type of trajectory and the law of motion of the point of contact of the ball with the plane. An example of ball motion control is given and a visualization of the ball-flywheel system motion in a computer algebra package is presented. © 2019 Udmurt State University. All rights reserved

Smooth movement of a rigid body in orientational space along the shortest path through the uniform lattice of the points on SO(3)

Many tasks of motion control and navigation, robotics and computer graphics are related to the description of a rigid body rotation in three-dimensional space. We give a constructive solution for the smooth movement of a rigid body to solve such problems. The smooth movement in orientational space is along the shortest path. Spherical solid body motion is associated with the movement of the point on the hypersphere in four-dimensional space along the arcs of large radius through the vertices of regular four-dimensional polytope. Smooth motion is provided by the choice of a special nonlinear function of quaternion interpolation. For an analytical presentation of the law of continuous movement, we use the original algebraic representation of the Heaviside function. The Heaviside function is represented using linear, quadratic and irrational functions. The animations in the computer program MathCad illustrate smooth motion of a rigid body through the nodes of a homogeneous lattice on the group SO(3). The algorithm allows one to change in a wide range the time intervals displacements between nodes, as well as the laws of motion on these intervals