CALCULATING AND MODELING ROPE MECHANISM OF A MOBILE CRANE TELESCOPIC BOOM

Power analysis and computer modeling of moving the telescopic boom rope mechanism using the “Universal Mechanism” software package, considering the mechanical characteristics of the ropes, boom sections and their contact interaction, have been carried out. The dependences for calculating the preliminary tension of the ropes are obtained, the regularities of operating the cable mechanism of the crane telescopic boom are established.

Piecewise linear approximation of boundary conditions and solutions in problems of 1d nonstationary dynamics of heteromodular elastic media

Рассматривается динамика одномерных деформаций разномодульной упругой среды под действием нестационарной граничной нагрузки в режиме «растяжение - сжатие». Исследуются особенности построения кусочно-линейной функции, аппроксимирующей нелинейное краевое условие. Указан критерий выбора узловых точек разбиения аппроксимирующей функции, позволяющий управлять режимами взаимодействия волновых фронтов всех типов в решении краевой задачи. Получена итерационная формула изменения скорости ударной волны в результате ее попутного столкновения с медленными фронтами предварительного растяжения, а также итерационные соотношения для построения поля перемещений на всех стадиях деформирования. The one-dimensional deformation dynamics in an elastic heteromodular medium under nonstationary boundary loading in the <tension and compression> mode is considered. The features of constructing a piecewise linear approximation of a nonlinear boundary condition are investigated. A selection criterion for the nodal partition points of the approximating function is indicated; it allows us to control the modes of collision between wave fronts of all types when the boundary value problem is solved. An iterative formula for the change in the shock wave velocity as a result of its collision with slow fronts of preliminary tension is obtained; the iterative relations for constructing the displacement field at all stages of deformation are written.

MODELING OF SPOKE STIFFNESS FOR EXTERNAL FIXATION DEVICES

A nonlinear calculation of the stiffness of the spokes of external fixation devices in traumatology is proposed. Taking into account the geometric nonlinearity of the spoke, the finite element method is used in the calculations of stiffness and stresses arising in the spoke fasteners. Under the action of the transverse force and its preliminary tension, deflections of the spoke and stresses in the attachment points are determined.

About Errors Engineering and Deviceing Anchor Piles, Performed by Discharge-Pulse Technology

The article examines a case from the practice of geotechnical construction, when errors in the calculations of anchor piles performed by discharge-pulse technology (DPT anchor) and deviations from engineering solutions could lead to an emergency. During excavation of the foundation pit, an underground parking lot under construction, the enclosing structure, fixed with DPT anchors, received unacceptable displacements. Calculations established that the bearing capacity of the DPT anchors on the ground was overestimated up to 3 times. In addition, the analysis of the available materials on this object allowed the authors to identify serious violations in the construction of the latter. It is shows that when carrying out work on the preliminary tension of the DPT anchors, in some cases, already with an effort of 10 tons, there is a loss of their bearing capacity along the ground. As a result, it became necessary to redesign the anchorage.

Analytical model of liner with previous loads

Purpose. Development analytical model of the liner, taking into account its previous tension, structural and technological parameters and physical-mechanical characteristics of the rubber material, for modeling its deformations in the radial, longitudinal and circular planes. Methods. Analytical, mathematical modeling. Results. On the basis of the equilibrium equations for a cylindrical shell, taking into account the isotropy of the medium and the without momentary stress state, the spatial of forces and the preliminary tension of the liner, a system of analytic equations is developed that enables modelling of the deformations of the liner, which is the factor of its closure. The analytical dependences of the deformation of the liner in the longitudinal, circular and radial planes, depending on its structural parameters and physical and mechanical characteristics of the material, are developed. Parameters for deformation simulation are: R – radius of liner, Е – modulus of elasticity, h – thickness of liner, рн – vacuum pressure, l – the length of the active part of liner, ν – Poisson's coefficient for rubber, Fн force of tension of liner. Depending on the central angle in the radial plane of the section, the shape of the deformation of the liner is simulated along its entire working length. Conclusions. The obtained dependences allow simulating the deformation of the liner in the longitudinal, circular and radial planes, depending on its structural parameters and physical-mechanical characteristics of the material. The developed analytical dependences take into account the preliminary tension of the liner, the vacuum pressure and makes it possible to model, depending on the central angle in the radial plane of the cross-section of rubber. The use of developed analytical dependencies makes it possible to substantiate the basic parameters that influence the technological process of milk yield cows Keywords: liner, vacuum pressure, modulus of elasticity, radial deformation, coordinate system, tension of rubber, the cylindrical shell, the isotropic medium.

Stretch properties of elastic knitted fabric with pillar stitch

Knitted fabrics and products are subjected to a variety of stresses and loads/deformation during their usage. The loads are different by value, by direction, and by duration. The alternations of loading and unloading or resting processes affect the knitted structure and could bring about changes in the linear dimensions of the fabric or result in the deformation of the knitted items and ultimately the loss of product appearance or its functional properties. A wide range of textile materials resistant to multiply loads was produced by using elastomeric yarn that has an elongation of more than 95% and is able to attain full recovery after relaxation due to its chemical composition. This case study examines two existing test methods for evaluating the stretch properties of textile materials produced with the elastomeric yarns with emphasis on warp knitted abdominal binder-type fabrics. It was found that the linear density of the weft in-laying threads and the preliminary tension of the ground yarn which formed pillar stitch affect stretch properties of elastic warp knitted fabric: the full deformation and its constituent parts. The change in the preliminary elongation of the bare spandex in the 210%–270% range does not have a significant effect.