Facetting value of helical thread surface received by enveloping

В морской технике применяются различные резьбовые соединения. Детали судовых механизмов подвергаются в процессе работы вибрациям и переменным нагрузкам, которые приводят их к разрушениям, потере герметичности и к внеплановым остановкам судовых машин.. Для повышения эксплуатационных свойств и увеличения срока службы резьбовых соединений проводят анализ качества сопрягаемых поверхностей, в частности, параметров шероховатости. В предлагаемой статье исследуется величина огранки винтовой поверхности резьбы образующаяся при осуществлении нового метода изготовления резьбы огибанием. Процесс обработки металла, к которому относится новый метод нарезания, заключается в касании лезвия инструмента и обрабатываемого материала прерывистым касанием. Нарезание резьбы осуществляется, специальной червячной фрезой. При прерывистом резании обрабатываемая поверхность оказывается, как бы составленной из отдельных криволинейных площадок (граней), Линия стыка граней имеет определенную высоту по нормали к поверхности, при нарезании резьбы - к винтовой поверхности. Высота стыка граней определяет качественный показатель шероховатости поверхности, называемый волнистостью. При нарезании резьбы червячной фрезой высота стыка граней (волнистость винтовой поверхности) зависит от числа зубьев фрезы. Задача исследования состоит в том, чтобы выяснить, каким должно быть число зубьев фрезы для получение заданной шероховатости винтовой поверхности резьбы и как это влияет на качество поверхности резьбы. Так же в статье рассмотрено графическое описание процесса получения огранки резьбы и пример расчета числа гребенок фрезы. There are many different thread joints used on marine facilities. While in operation, components of the mechanisms undergo vibrations with repeated stresses that leads to their failures, loss of tightness, and unscheduled shutdowns of the equipment. The analyses of joint surfaces quality, e.g. roughness parameters, are conducted to enhance serviceability of the thread joints and to prolong their lifespan. The article studies facetting value of a helical thread surface while applying a new method of thread production – enveloping. The new method of cutting that is a process of metal treatment involves non-continuous contacting an instrument blade and the material being cut. The cutting of the thread is done with a special hob cutter. Due to the non-continuous cutting, a treated surface becomes as if consisting of curved pads or faces. The faces junction line has a specific normal line level towards the surface and towards the helical surface during the cutting. The height of the junction defines qualitative indicator of the surface roughness known as undulation. When cutting the thread with a hob cutter the height of the faces junction - undulation of a helical surface – depends on a cutter teeth number. The research objective is to specify the cutter teeth number needed to achieve the required roughness of a thread helical surface as well as to determine how it influences on the quality of the thread surface. The paper also provides several drawings illustrating the process of obtaining the thread facetting and the example of calculation of a cutter chaser number.

Roller Profiling for Generating the Screw of a Pump with Progressive Cavities

Progressive cavity pumps are used in industry for the circulation of high viscosity fluids, such as crude oil and petroleum products, sewage sludge, oils, salt water, and wastewater. Also known as single screw pumps, these pumps are composed of a single rotor which has the shape of a rounded screw, which moves inside a rubber stator. The stator has an double helical internal surface which, together with the helical surface of the rotor, creates a cavity that moves along the rotor. The movement effect of the cavity inside the stator is the movement of the fluid with a constant flow and high pressure. In this paper, an algorithm for profiling the rollers for generating the helical surface of the pump rotor with progressive cavities is proposed. These rollers are constituted as tools for the plastic deformation of the blank (in case the pump rotor is obtained by volumetric deformation) or for its superficial hardening.

Meshing theory of axial arc tooth profile cylindrical worm drive

In this paper, the axial arc tooth profile cylindrical worm drive is proposed, whose worm is cut by turning tool. Due to the simple processing equipment, short manufacturing time and low cost, this kind of worm can replace the cylindrical worm ground by grinding wheel under some conditions. The meshing theory of the worm drive is founded comprehensively. Moreover, a movable orthogonal frame is established on the non-orthogonal parametric curves net helical surface. Based on the founded meshing theory, the simulating study on the meshing quality of the worm drive is performed systematically. The numerical outcome shows that the meshing quality of this worm drive is quite favorable, and the condition of forming lubricating oil film is excellent. The working orthogonal clearance of the turning tool is decreased with the increase of the worm thread number, which must be a positive value in the process of worm cutting. This explains that the number of the worm thread is ≤4.

Theoretical aspects of obtaining a helical surface from a thin strip during sheet stamping

В статье рассмотрены теоретические аспекты получения винтовой поверхности из тонкой полосы при листовой штамповке. Также предложена модель для расчета компонентов напряженно-деформированного состояния полосы и отдельных технологических параметров. Для удобства расчетов предполагается, что полоса имеет достаточную длину и угол закручивания по всей длине полосы одинаков. Несмотря на значительные упрощения геометрического характера, задача о кручении полосы остается сложной, вследствие двумерности напряженного состояния, геометрической и физической нелинейности процесса деформирования. Ее дальнейшее решение целесообразно основывать на методе конечных элементов, ориентируясь на применение ЭВМ. Для замыкания системы уравнений, описывающих поведение дискретной модели полосы на шаге нагружения, необходимо связать напряжения и малые приращения деформаций в середине каждого элемента. Для этого используем теорию пластического течения, пренебрегая упругими составляющими деформаций вследствие их малости по сравнению с большими пластическими деформациями. The article deals with the theoretical aspects of obtaining a helical surface from a thin strip during sheet stamping. A model is also proposed for calculating the components of the stress-strain state of the strip and individual technological parameters. For convenience of calculations, it is assumed that the strip has a sufficient length and the angle of twisting along the entire length of the strip is the same. Despite significant geometric simplifications, the problem of band torsion remains complex due to the two-dimensionality of the stress state, the geometric and physical nonlinearity of the deformation process. Its further solution should be based on the finite element method, focusing on the use of computers. To close the system of equations describing the behavior of the discrete band model at the loading step, it is necessary to relate the stresses and small increments of deformations in the middle of each element. To do this, we use the theory of plastic flow, neglecting the elastic components of deformations due to their smallness in comparison with large plastic deformations.

EXTERNAL ROLLING OF A POLYGON ON CLOSED CURVILINEAR PROFILE

The design of a helical surface tillage tool made of a developable helicoid section has been calculated using the methods of analytical and differential geometry, the theory of surfaces, the systems of computer-generated graphics and mathematics. A helical tool in the form of a skeleton cylinder made of bars, where there is a helical surface made of arranged sheet metal, has been developed. Such a design prevents a helical surface from becoming clogged with soil. The suggested tool operates as a roller and the soil can easily pass through the gaps between the bars. New helical harrow tools have been designed and made for this experiment. An experimental harrow equipped with helical tools has been made and used to conduct a field research. The research was aimed at determining the optimal kinematic parameters and the pattern of field movement, which allow performing the technological process of soil tillage with the performance indices that meet the agricultural requirements.

MULTI-FACTOR EXPERIMENTAL RESEARCH OF THE GRAIN DRYING PROCESS BY INDUCTION HEATERS

This is a method of drying grain related to agriculture and can be used as a grain dryer on an elevator. Increasing the efficiency of the process of heating the grain material and reducing energy costs is due to the fact that there is a uniform distribution of moisture in the dried product. The induction drying method has the advantage that it does not have heat transfer from the heater. Ensuring the quality of the heat treatment process, in compliance with operational and technological requirements with minimal energy costs, an idealized contact type installation for heat treatment of grain should include the following main elements in its structural composition. For the study, the entire design of the grain dryer with direct induction heaters was assembled. The installation of a cylindrical shape with a helical surface auger includes all the above elements – this is the supply of grain to the hopper, the method of heat supply, the determination of the distance. Inside this cylinder is a fixed helical surface, on which the grain from the hopper is filled from the top. Due to the gravitational forces, the grain moves down the helical surface. There is one feature here – the helical surface must have a variable pitch, decreasing from the top to the bottom. This is due to the fact that as the grain dries, the coefficient of friction of the grain on the material of the helical surface decreases. High-frequency grain dryers have been designed, tested, and even put into practice. The grain dried in such installations meets all technological requirements, and in some cases surpassed the grain dried in the traditional, convective way in quality. Economic changes in our country have revealed the demand for miniaturization of plants, mini grain dryers have been created, mobile grain dryers with relatively low power consumption, highly economical, easy to use and maintain, and most importantly-quite cheap.

Meshing Characteristic of Arc-Toothed Cylindrical Worm Pair and Cutting Geometric Condition of Its Worm

The arc-toothed cylindrical worm has an arc tooth profile in a section, which may be the axial section, the normal section, or an offsetting plane of the worm helical surface. The meshing principle for a gearing containing such a worm is established. The normal vector of instantaneous contact line is determined in the natural frame and the meshing performance parameters are obtained without the help of the curvature parameters of the worm helical surface to ensure the established meshing principle is concise and practical. The numerical results show that the worm working length can be beyond half of the thread length and the meshing zone of the worm pair can cover most of the worm gear tooth surface. The instantaneous contact lines are uniformly distributed and the worm pair forms double-line contact. The numerical outcomes of the induced principal curvature show that the contact stress level between the teeth is higher in the middle of the worm gear tooth surface and near its dedendum. The forming condition of the lubricating oil film is poorer in the middle of the worm gear tooth surface and from addendum to dedendum as demonstrated by the numerical results of the sliding angle. The normal arc-toothed worm lathed by an offsetting cutter is recommended to apply in industry after various researches and analyses. The cutting geometric condition of the worm is investigated quantitatively. It is discovered that the rule of the cutter working relief angle changes along the cutting edge during lathing the worm.

Research of particle movement on rough surface formed by screw movement of sinusoid under action of own weight

The differential equations of particle movement on a rough surface which is formed by the helical motion of a sinusoid under the action of the force of own weight were obtained in the article. The sinusoid is the axial cross-section curve of the helical surface and is located in the vertical plane. The obtained equations were solved by numerical methods and the trajectories of the particle on the helical surface were constructed. In addition, graphs of the change in the particle velocity and its distance from the axis of the surface were found, as a result of which the conditions when stabilization of the particle movement is possible were found. It is shown that in the general case, as a result of acceleration, the particle moves away from the axis of the surface and stops in one of its gutters. The depth and density of the gutters are controlled by changing the constant coefficients parameters. Also, a partial case at zero depths of the gutter, when the sinusoid turns into a straight line and the particle moves on the surface of the helical conoid, were considered.