Discrete-continuous three-element model of impact device

There have been examined the mathematic model of the impact device provided for geological materials destruction. Basic elements of the impact device are variable cross-section tool, striker and impact device body. The interaction of these elements is described as a movement of two discrete mass and the rod in the presence of rigid and dissipative connections. One equation in partial derivatives and two ordinary differential equations associated by initial and boundary conditions represent the initial-boundary problem. The numerical method parameters of which are determined at tests problems solution by Fourier method is used for looking for solutions of mixed initial-boundary problem. Researches are made, and parameters determining the damping efficiency of tool, striker and impact device body oscillations are evaluated.

Regulation of Phosphorylated State of NMDA Receptor by STEP61 Phosphatase after Mild-Traumatic Brain Injury: Role of Oxidative Stress

Traumatic Brain Injury (TBI) mediates neuronal death through several events involving many molecular pathways, including the glutamate-mediated excitotoxicity for excessive stimulation of N-methyl-D-aspartate receptors (NMDARs), producing activation of death signaling pathways. However, the contribution of NMDARs (distribution and signaling-associated to the distribution) remains incompletely understood. We propose a critical role of STEP61 (Striatal-Enriched protein tyrosine phosphatase) in TBI; this phosphatase regulates the dephosphorylated state of the GluN2B subunit through two pathways: by direct dephosphorylation of tyrosine-1472 and indirectly via dephosphorylation and inactivation of Fyn kinase. We previously demonstrated oxidative stress’s contribution to NMDAR signaling and distribution using SOD2+/− mice such a model. We performed TBI protocol using a controlled frontal impact device using C57BL/6 mice and SOD2+/− animals. After TBI, we found alterations in cognitive performance, NMDAR-dependent synaptic function (decreased synaptic form of NMDARs and decreased synaptic current NMDAR-dependent), and increased STEP61 activity. These changes are reduced partially with the STEP61-inhibitor TC-2153 treatment in mice subjected to TBI protocol. This study contributes with evidence about the role of STEP61 in the neuropathological progression after TBI and also the alteration in their activity, such as an early biomarker of synaptic damage in traumatic lesions.

DEVELOPMENT AND BENCH TESTS OF A PHYSICAL MODEL OF REVERSIBLE HYDRAULIC IMPACT DEVICE

The paper presents a physical model of reversible one-way hydraulic impact device (with two striker movement limiters). The researches helped to develop the design of the device and a test bench simulating the resistance of the medium in case of possible body movement. Tests of a hydraulic impact device with a rigidly sealed body showed its efficiency in the operating modes obtained in the calculations: when changing the flow rate of the liquid, the striker strikes both in the forward and reverse directions.

Investigation on fracture toughness of polytetrafluoroethylene with impact essential work of fracture method

Polytetrafluoroethylene (PTFE) polymer has a wide range of applications in various industries. Therefore, for designers it is essential to know the strength properties of the material under dynamic loads. In this study, pure-PTFE, bronze and carbon filled-PTFE are tested under dynamic load. In addition, pure and carbon filled specimens were used to determine the temperature effect of PTFE. All tests were carried out in the Charpy impact device according to impact essential work of fracture method. At 23°C, pure-PTFE showed the highest impact strengths, bronze filled-PTFE and carbon filled-PTFE showed lower respectively and it has been found that the carbon filler increases the fracture toughness approximately two times at high temperature (150°C). On fracture surfaces phase transitions effects of PTFE and behavior of fillers used were investigated with Scanning Electron Microscope.

Segregation of the bulk cargo on a belt conveyor under the vibro-pulse impact

The dynamics of interaction of the large lumps of the bulk cargo with a conveyor belt while passing through roller supports of the conveyor linear sections is often a cause of damage on the conveyor belt. In order to reduce the negative impact it is proposed to isolate the conveyor belt surface from the large lumps by filling small fractions of the bulk cargo by means of adding a shock device to the conveyor structure that causes increased segregation of the bulk cargo. A mathematical model of the segregation of the bulk cargo located on the conveyor belt and in zone of impact of the shock pulses has been developed. The model considers a change in the rotation direction of the large lump when applying shock pulses to the characteristic points of the lump lower face. Herewith it takes into consideration weakening of the shock pulse by a layer of the bulk cargo small fractions. The presented model has received experimental confirmation. Analytically and experimentally the height of filling of the bulk cargo small fractions under a large lump when passing the vibrating impact device located on the conveyor belt has been determined.

Analysis of non-contact electromagnetic impact device connected to boosting circuit

We propose a non-contact electromagnetic impact-torque device (EMI device) using induced currents, and its characteristics have been verified using 3-D finite element method (FEM) analysis and carrying out measurements on a prototype. This paper describes a new EMI device with a regenerative circuit. A boosting chopper circuit is connected to the proposed EMI device, and the impact torque is controlled using the regenerated power.

RESEARCH OF THE IMPACT DEVICE MODEL OF THE ROD TYPE BY DIFFERENCE METHOD

Приводится анализ механических колебаний элементов ударного устройства с помощью модели стержневого типа. Ударник и инструмент связаны упругими и диссипативными элементами, которые имитируют их взаимодействие. Аналогично моделируется взаимодействие инструмента с рабочей средой. Сформулирована начально-краевая задача для системы двух волновых уравнений с учетом переменных поперечных сечений стержней. Площади поперечных сечений определяются параметрическими формулами при сохранении объемов стержней. Параметрические формулы позволяют получать различного вида зависимости площади поперечного сечения стержня от его длины. Начальные условия отражают физическую картину взаимодействия инструмента с ударником и рабочей средой. Краевые условия описывают контактные взаимодействия ударника с инструментом и последнего с рабочей средой. В качестве модельной задачи рассматривается соударение ударника и инструмента через элемент большой жесткости. Начально-краевая задача исследуется разностным методом. Проводится сравнение решений задачи, полученных с помощью двухслойной и трехслойной разностных схем. Такие схемы реализованы в общей компьютерной программе в системе Mathcad. Показано, что при вычислениях распределения нормальных напряжений по длине стержня лучшими свойствами относительно устойчивости обладает двухслойная схема The article gives the analysis of mechanical vibrations of the impact device elements using the model of the rod type. The hammer and the tool are connected by elastic and dissipative elements that simulate their interaction. The interaction of the tool with the processing medium is simulated in a similar way. An initial boundary-value problem is formulated for a system of two wave equations taking into account the variable cross sections of the rods. Cross-sectional areas are determined by parametric formulas maintaining the volume of the rods. Parametric formulas allow one to obtain various dependence types of the cross-sectional area of the rod on its length. The initial and boundary conditions reflect the physical phenomenon of the tool interaction with the processing medium, and also describe the contact interactions of the hammer with the tool. The impacting of the hammer and the tool through an element of high rigidity is considered as a model problem. To control the limiting values, the solution of the model problem by the Fourier method is used. The initial-boundary-value problem is investigated by the difference method. A comparison of solutions obtained for the two-layer and three-layer difference schemes is given. Such schemes are realized in a common computer program in the Mathcad. It is shown that the two-layer scheme has the best properties in relation to stability while calculating the distribution of normal voltage along the length of the rod