Добірка наукової літератури з теми "A non-centroidal bending"

This research presents a theoretical model to analyze the mechanical performance of spherical roller bearings, taking account of the angular and centroidal misalignments between the inner and outer rings. The angular misalignment can be improved by spherical roller bearings self-aligning feature to a certain degree. The interpolation method is used to determine the self-aligning contact angles of the different rollers. The centroidal misalignment is described by the angular and distance deviations. Non-Hertzian contact theory is applied to model and calculate the rollers load-distribution and total contact angles as well as the displacement of the inner ring. The loads of the rollers with the misalignments features and the external loads are included in the equilibrium equations, which is solved by Newton-Raphson method. This research shows spherical roller bearings self-aligning ability can balance the additional bending moment caused by the angular misalignment, which is at the cost of reducing its carrying capacity. But this carrying capacity will be improved to a certain degree by a proper axial load. It also illustrates that any kinds of centroidal misalignments are harmful for the service life of bearings. But the location of the misalignments can be roughly inferred by the external loads and the displacement of the inner ring, which is helpful for spherical roller bearings fault diagnose and elimination.

In this paper, an analytical method based on Timoshenko theory is derived for obtaining the in-plane static closed-form general solutions of deep curved laminated piezoelectric beams with variable curvatures. The equivalent modulus of elasticity is utilized to take into account the material couplings in the laminated beam. The linear piezoelectric effect is considered to develop the static governing equations. The governing differential equations are formulated as functions of the angle of tangent slope by introducing the coordinate system defined by the arc length of the centroidal axis and the angle of tangent slope. To solve the governing equations, defined are the fundamental geometric properties, such as the moments of the arc length with respect to horizontal and vertical axes. As the radius is known, the fundamental geometric quantities can be calculated to obtain the static closed-form solutions of the axial force, shear force, bending moment, rotation angle, and displacement fields at any cross-section of curved beams. The closed-form solutions of the circle beams covered with piezoelectric layers under various loading cases are presented. The results show the consistency in comparison with finite results. Solutions of the non-dimensional displacements for the laminated circular and spiral curved beams with different lay-ups are available. The non-dimensional displacements with geometry and material parameters are also investigated.

ABSTRACTThe leaf petiole is an organ that connects the leaf blade to the stem of a plant. From a structural viewpoint, the petiole resembles a cantilever beam that withstands torsional loading due to wind action and bending deformation due to gravity acting on the leaf blade. During growth, the petiole develops defined structural features at multiple length scales, which synergistically determine its mechanical response to external stimuli. The focus of this study is on the hierarchical level (n=3) of the cellular tissue. The goal is to capture the elastic properties of the cellular tissues of the leaf petiole in Philodendron melinonii at that hierarchy. Since the microstructure of the plant tissues resembles a non-periodic cellular pattern, we resort to a 2-D Finite Edge Centroidal Voronoi tessellation (FECVT) to generate a realistic network of polygonal cells. An analysis based on finite element analysis (FEA) is performed to explore the relation between the effective stiffness of Voronoi model and the properties of the cellular tissue. The effective (homogenized) elastic properties of the cellular tissue can be used to calculate the overall flexural and torsional stiffness of the P. melinonii petiole. The FEA of the Voronoi microstructure depicts the anisotropic stiffness properties of the P. melinonii tissue and its dependence with the graded cellularity.

Робота виконана на кафедрі технології машинобудування, верстатів та інструментів Сумського державного університету Міністерства освіти і науки України.
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціа-льністю 05.02.08 − технологія машинобудування. − Національний технічний універ-ситет України «Київський політехнічний інститут імені Ігоря Сікорського», МОН України, Київ, 2019. Дисертацію присвячено розробленню технології оброблення внутрішніх різей методом безцентроїдного огинання на фрезерних верстатах з ЧПК із застосуванням непрофільного інструмента. На основі аналізу існуючих методів оброблення внутрішніх різей сформульо-вано робочу гіпотезу дисертаційного дослідження, що полягає в обґрунтуванні перспектив використання методу безцентроїдного огинання, як більш продуктивного способу забезпечення показників точності та якості внутрішніх різей. На основі математичного моделювання процесу силової взаємодії обґрунтовано ефективність запропонованої конструкції різального інструмента для реалізації метода безцентроїдного огинання на фрезерних верстатах з ЧПК. Шляхом лінійного програмування та оптимізації за критерієм максимальної продуктивності, з обмеженням по параметрам точності та якості оброблюваних різей визначено область оптимальних режимів різання. Експериментально обґрунтовано застосування технології обробки внутрішніх різей для діапазонів метричної, дюймової та круглої різей. На основі розрахунку оперативного часу встановлено, що запропонована технологія дозволяє скоротити основний час від 2 до 9 разів, а допоміжний – від 2 до 3 разів в порівняні з існуючими технологіям обробки внутрішніх різей.
Thesis for scientific degree of Candidate of Engineering Science on specialty 05.02.08 – Manufacturing Engineering. – National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Ministry of Education and Science of Ukraine, Kyiv, 2019. The dissertation is devoted to the development of the technology of machining of internal threads using the method of non-centroidal bending on CNC milling machines with the use of a non-profile cutting tool. On the basis of the analysis of the ad-vantages and disadvantages of existing methods of machining internal threads with profile cutting tool or comb tool cutters, and multi-pass turning with a non-core cutting tool, the working hypothesis of the dissertation research was formulated. It consisted in justification of the prospects of using the method of non-centroidal bending as a more productive technology of ensuring the accuracy and quality parameters of internal thread. It was justified the area of application of machining method of non-centroidal with a non-core cut-ting tool for the metric thread- in the range of thread steps from 2 to 3,5 mm and diameters from 16 to 64 mm, trapezoidal threads with thread step - 2 mm and diameters from 16 to 28 mm, inch thread - with all standard sizes of steps and diameters from G3/8 to G3 '' and rope thread with a thread step – 12,7 mm and diameters from R22 to 64 mm. In present research by means of calculating the parameters of the spiral trajectory, the kinematic scheme of combining the rotation of the cutting tool, the movement of the axial feed of the cutting tool, the movement of the circular supply of the workpiece around the axis of the cutting tool, and the number of cutting inserts it was theoretically justified condition of bending of cutting inserts for a new method for machining internal threads. Based on mathematical modeling of force interaction, the efficiency of the proposed design of a cutting tool for the implementation of the method of non-centroidal bending on CNC milling machines was justified. As a result of modal analysis of designed cutting tool for machining of rope, metric and inch threads it was determined proved no resonance when using the developed tool. The value of the first internal frequency of a non-core tool for machining rope thread was 2213 Hz, which didn’t coincide with the natural frequency of machining, which was 63 Hz, at spindle speed ni = 1250 rpm for cutting tool with three cutting inserts. The first internal frequency of a non-core cutting tool for machining metric and inch thread was 1537 Hz, which also did not coincide with the natural frequency of the cutting tool during machining – 50 Hz, which corresponds to the spindle speed ni = 1000 rpm for cutting tool with three cutting inserts. By means of linear programming and optimization based on the criterion of maximum productivity, with the limitation on the parameters of accuracy and quality of internal thread, the area of optimal cutting parameters was determined. It was established and experimen-tally confirmed that the proposed manufacturing technology, as well as the design of cutting tools for circular R32 and metric cut M48x3-7N and M48x3-LH-7N, allowed to ensure the accuracy of machining in accordance with the requirements of the relevant standards. The optimal cutting parameters for rope thread R32 was determined for machining of stainless steel 5ХНМ (1.2711, 1.2713, 55NiCrMoV5 in DIN classification): cutting speed – 118 m/min and FPM – mm/min, and for machining steel 40Х (1.7045, 37Cr4 in DIN classifica-tion) cutting speed – 144 m/min, and FRM – 210 mm/min. On the basis of calculation of operating time according to the criteria of the direct manufacture time and auxiliary time it was determined that the proposed technological process allowed to reduce direct manufacture time from 2 to 9 times, and the auxiliary time - from 2 to 3 times in comparison with the existing technological process of machining of internal threads. Implementation of the results of the dissertation research into manufacturing allowed to receive an economic effect, according to the enlarged calculations, for machining bit blank in the amount of 42260 UAH., and when machining double socket – 16550 UAH., with annual output 2000 pcs. of each item. That allowed to reduce the cost of one part by 21,13 UAH. and 8,28 UAH respectively.
Диссертация на соискание научной степени кандидата технических наук по специальности 05.02.08 – технология машиностроения. – Национальный технический университет Украины «Киевский политехнический институт имени Игоря Сикорского» МОН Украины, Киев, 2019. Диссертация посвящена разработке технологии обработки внутренних резьб методом безцентроидного огибания на фрезерных станках с ЧПУ с применением непрофильного инструмента. На основе анализа существующих методов обработки внутренних резьб сформулированы рабочая гипотеза диссертационного исследования, которая заключается в обосновании перспектив использования метода безцентроидного огибания, как более продуктивного способа обеспечения показателей точности и качества внутренних резьб. На основе математического моделирования процесса силового взаимодействия обоснована эффективность предложенной конструкции режущего инструмента для реализации метода безцентроидного огибания на фрезерных станках с ЧПУ. Путем линейного программирования и оптимизации по критерию максималь-ной производительности, с ограничением по параметрам точности и качества, определена область оптимальных режимов резания для диапазонов метрической, дюймовой и круглой резьб. Экспериментально обосновано применение технологии обработки для диапазонов метрической, дюймовой и круглой внутренних резьб. На основе расчета оперативного времени установлено, что предложенная технология позволяет сократить основное время от 2 до 9 раз, а вспомогательного – от 2 до 3 раз в сравнении с существующими технологиям обработки внутренних резьб.

Sloping-sided structures have been used in ice-infested waters to reduce ice loads by inducing flexural failure in the incoming level ice, which can be a fraction of the crushing load of the same level ice on vertical walls [1]. Croasdale’s model [2] has been widely used to predict this type of ice loading, which compares well with available field data, such as that measured at the Confederation Bridge [3]. In Croasdale’s formulation, the problem is idealized as a semi-infinite beam on an elastic foundation and neglects the effects of second-order bending and the edge moment arising from eccentricity of axial loadings, i.e. the distance between the point of ice-structure contact and the centroidal axis of the beam. For thin ice, the edge moment effect is indeed negligible due to the small moment arm. However, the edge moment influence on the structural load increases with the ice thickness, as reported in [4]. This suggests that Croasdale’s model may be inadequate for ice thickness beyond a certain threshold. In this paper, we focus on the plane breaking load of thick ice, taking into account the second order bending of the beam as well as the edge moment effect. We also account for the local crushing of level ice that comes into contact with the sloping structure, which creates a surface parallel to the slope prior to the bending failure of ice sheet. This local crushing is assumed to occur until a sufficient surface area is created to provide the bearing capacity required to induce bending failure in the beam. As a result, the eccentricity of axial loading is reduced, lowering the effects of the edge moment and consequently, the predicted load. Taking the above effects into account, the governing equation and the corresponding deflection equation of the refined model are reformulated, and the system of non-linear equations solved with numerically with the Newton-Raphson method. Additionally, the competition between different failure modes, i.e. flexural, crushing and shear, of a level ice encountering a sloping structure is briefly investigated. It is shown that flexural failure remains the dominant mode of failure even for thick ice, for various practical slope angles, ice material properties and ice-structure contact properties.