Fatigue improvement of aluminium welds by means of deep rolling and diamond burnishing

Deep rolling is an industrially widely established mechanical surface treatment process for the modification of roughness and fatigue resistance. However, the process has not been considered as a potential method for the mechanical post welded treatment of welded joints yet. Even, the potential of deep rolling for increasing the fatigue strength is comparably well-known in the case of non-welded components. Therefore, the effect of deep rolling (hydrostatic mounted tool) and diamond burnishing (mechanical mounted tool) to increase the fatigue strength of butt joints was approved in this work for aluminium alloy AlMg4,5Mn0,7 (EN AW 5083). For this purpose, fatigue tests under full tensile loading were performed in as-welded and deep rolled, burnished and ultrasonic impact treated conditions. Different residual stress states as well as work hardening states are determined in deep rolled and burnished condition. However, similar and significant fatigue life improvement was determined for both processes.

Contribution In Determining The Fatigue Endurance of Slide Diamond Burnishing AISI52100 Steel Components

The present paper is an investigation on the effect of slide diamond burnishing on the fatigue endurance of a component made of AISI52100 steel. Burnishing operation has been performed on cylindrical specimens using optimal parameters statistically selected such as burnishing force, burnishing feed and number of tool passes. Bending fatigue tests in air at R= -1 and S-N curves have been plotted by incrementing the applied stress from a maximum stress level of about 66% of the ultimate tensile stress to a stress value below which fatigue does not occur. Results show that slide diamond burnishing has increased the fatigue resistance comparing to unburnished specimens. The fatigue endurance is respectively 222 MPa and 190 MPa. At high stress levels, the fatigue resistance improvement is clearly observed and the fatigue trends are in good agreement with those reported in literature. However, the present results are slightly lower and that is attributed to the shoulder fillet value of the specimen. For small fillet radius, fatigue resistance is lowered.

Modeling of the Contact Interaction of the Tool Indenter with the Part Surface when Processing by Surface Plastic Deformation Methods

There are results of studying the parameters of the indenter contact interaction with the surface when processing cylindrical parts made of 45 steel of different hardness by surface plastic deformation (SPD) methods with single-indenter elastic tools (diamond burnishing, ball burnishing). There were considered such characteristics as the resistance force when the indenter starts and in the steady state of SDP, the range of force fluctuations during processing, friction factor when the indenter starts and in the steady state, as well as some derivative coefficients. Adequate physical-statistical models for the quantitative estimation of the contact interaction parameters from SPD processing factors are obtained.

JUSTIFICATION OF APPLICATION MODES OF MACHINING ATTACHMENTS FOR PROCESSING PARTS BY THE METHOD OF PLASTIC DEFORMATION

Проблема и цель. Установлено, что функциональное действие машин в значительной мере определяется параметрами качества их поверхностного слоя. Цель работы – обеспечение качества поверхностного слоя деталей одним из наиболее эффективных способов, обеспечивающих управление в широком диапазоне показателями качества обработки деталей поверхностным пластическим деформированием (ОУО ППД). Одни и те же параметры качества поверхностного слоя можно получить, используя различные методы и режимы ОУО ППД. Для их оценки необходимо определение трудоемкости операции. Следовательно, имеет место совокупность научно-технических задач, решение которых позволяет разработать методологию, алгоритм и программу выбора оптимального метода и условий ОУО ППД, обеспечивающих требуемые параметры качества поверхности при минимальной технологической себестоимости, что дает значительный экономический эффект. Методология. Одним из способов обработки деталей при восстановлении служит алмазное выглаживание после процесса шлифования. Выглаживатель – кристаллический алмаз – перераспределят металл поверхностного слоя, при этом меняется микрорельеф. После алмазного выглаживания увеличивается надежность, долговечность деталей, износостойкость. Для достижения цели предлагается использование двухзвенных оправок, которые позволяют исключить биение обрабатываемой поверхности. Структурный эквивалент механизма близок к кривошипно-шатунному механизму, в отличие от которого радиус обрабатываемой детали распределяется по дуге. Изменения силы выглаживания устанавливают связь между статической силой и силой инерции. Статическую силу сглаживания можно определить, зная основные технологические параметры и процессы. Сила инерции зависит от массы подвижного звена оправки. Результаты. Результаты настоящего исследования показали: к числу задаваемых параметров относятся масса подвижного звена оправки, диаметр детали, скорость скольжения, эксцентриситет, постоянная механизма и сила инерции. Найдены разрешенные частоты вращения в зависимости от диаметра детали. Заключение. Данная методика может быть применена для восстановления рабочих поверхностей поршневых пальцев автотракторных дизельных двигателей сельскохозяйственного назначения и позволяет снизить уровень шероховатости поверхности обрабатываемых деталей. Problem and purpose. Problem and purpose. It has been established that the functional action of machines is largely determined by the quality parameters of their surface layer. The purpose of the work is to ensure the quality of the surface layer of parts by one of the most effective methods that provides control over a wide range of quality indicators for processing parts by surface plastic deformation (SPD). The same parameters of the quality of the surface layer can be obtained using different methods and modes of SPD. To assess them, it is necessary to determine the complexity of the operation. Consequently, there is a set of scientific and technical problems, the solution of which makes it possible to develop a methodology, an algorithm and a program for choosing the optimal method and conditions for SPD, which provide the required surface quality parameters at a minimum technological cost, that gives a significant economic effect. Methodology. One of the methods of processing parts during restoration is diamond burnishing after the grinding process. The smoother or the crystal diamond will redistribute the metal of the surface layer, thus changing the microrelief. After diamond burnishing, reliability, durability of parts, and wear resistance increase. To achieve the goal, it is proposed to use two-link mandrels, which allow to exclude the beating of the treated surface. The structural equivalent of the mechanism is close to the crank gear, in contrast to which the radius of the workpiece is distributed along the arc. Changes in the smoothing force establish a relationship between static force and inertial force. The static smoothing force can be determined by knowing the basic technological parameters and processes. The force of inertia depends on the mass of the moving link of the mandrel. Results. The results of this study showed that the parameters set included the mass of the movable link of the mandrel, the diameter of the part, the sliding speed, the eccentricity, the constant of the mechanism and the force of inertia. The permitted speeds were found depending on the diameter of the part. Conclusion. This technique can be used to restore the working surfaces of the piston pins of automotive diesel engines for agricultural purposes and can reduce the level of surface roughness of the processed parts

ДОСЛІДЖЕННЯ ВПЛИВУ ПОКРИТТІВ І ТЕХНОЛОГІЧНИХ МЕТОДІВ ВИГОТОВЛЕННЯ НАПРЯМНИХ ЕЛЕМЕНТІВ НА ЇХ ЗНОСОСТІЙКІСТЬ

The matter of the experimental studies of the effect of coatings and technological methods of manufacturing guide elements of universal prefabricated readjustable tooling on their wear resistance are presented. The coatings investigated were made of VK15 carbide powder, which were applied by detonation spraying, and a titanium nitride-based coating produced by condensation with ion bombardment, as well as the surface hardening of guide elements by diamond burnishing for various steels: 20V, 12KhN3A, 40Kh, 38KhMYuA-B and others.During the process of diamond smoothing the roughness improves by 2 - 3 classes and the very nature of the roughness changes: a surface microrelief is created with rounded peaks and valleys instead of microroughness with sharp peaks and valleys, which are characteristic of surfaces after grinding. In this case the bearing surface of the samples increases essentially, and their running-in is accelerated. According to the results of tests under a load of 50, 75 and 100 kgf, a graph of the dependence of wear on the specific pressure was built and it was found that the wear of samples after burnishing decreases by 25 ... 40% compared to polished and at a load of 20 kgf/cm, respectively, is for steel 20 ... 2.7 and 1.9 μm, for steel 12XN3A – 2.3 and 1.6 μm, for steel 40X – 1.8 and 1.3 μm and for steel 38XMYUA – 1.4 and 0.8 μm.With increasing the load the wear of the ground specimens increases sharply, and for the flattened specimens this process is much slower. Based on the test results, graphs of the wear rate were plotted depending on the test duration, as well as for wear in relation to the number of cycles. According to the test results, it was found that steel 38KhMYuA has less wear, which is associated with its high hardness and insignificant tendency to metal seizure. Based on the research results, it was found that different methods of processing parts (previous) grinding and diamond burnishing have different wear. It has been found that diamond burnishing is a very effective surface hardening process.As a result of the tests carried out, it was found that the best performance in testing for wear resistance obtained for a column with TiN coating, the thickness of which does not exceed 0.1 μm, is 5 - 6 times less than the wear resistance of columns with a hard-alloy coating. For the system of directly changeable dies, a pair is recommended, which includes a guide column with a detonation coating VK15 and a holder (sleeve) with a CIB coating based on TiN, since these coatings showed high performance properties and had practically no wear.