Investigation of the effect of residual stresses in the subsurface on process forces for consecutive orthogonal cuts

The quality and surface integrity of machined parts is influenced by residual stresses in the subsurface resulting from cutting operations. These stress characteristics can not only affect functional properties such as fatigue life, but also the process forces during machining. Especially for orthogonal cutting as an appropriate experimental analogy setup for machining operations like milling, different undeformed chip thicknesses cause specific residual stress formations in the subsurface area. In this work, the process-related depth profile of the residual stress in AISI 4140 was investigated and correlated to the resulting cutting forces. Furthermore, an analysis of the microstructure of the cut material was performed, using additional characterization techniques such as electron backscatter diffraction and nanoindentation to account for subsurface alterations. On this basis, the influence of process-related stress profiles on the process forces for consecutive orthogonal cutting strategies is evaluated and compared to the results of a numerical model. The insights obtained provide a basis for future investigations on, e. g., empirical modeling of process forces including the influence of process-specific characteristics such as residual stress

Influence of different alloying strategies on the mechanical behavior of tool steel produced by laser-powder bed fusion

Additive manufacturing is a high-potential technique that allows the production of components with almost no limitation in complexity. However, one of the main factors that still limits the laser-based additive manufacturing is a lack of processable alloys such as carbon martensitic hardenable tool steels, which are rarely investigated due to their susceptibility to cold cracking. Therefore, this study aimed to expand the variety of steels for laser powder bed fusion (L-PBF) by investigating an alternative alloying strategy for hot work tool steel powder. In this study, a comprehensive investigation was performed on the powder and L-PBF processed specimen properties and their correlation with the existing defects. Cubical specimens were created using the following two alloying strategies by means of L-PBF: conventional pre-alloyed gas-atomized powder and a mixture of gas-atomized powder with mechanically crushed pure elements and ferroalloys. The influence of the particle parameters such as morphology were correlated to the defect density and resulting quasi-static mechanical properties. Micromechanical behavior and damage evolution of the processed specimens were investigated using in situ computed tomography. It was shown that the properties of the L-PBF processed specimens obtained from the powder mixture performs equal or better compared to the specimens produced from conventional powder

Combining 2D and 3D characterization techniques for determining effects of HIP-rejuvenation after fatigue testing of SX microstructures

A hot isostatic pressing rejuvenation heat treatment is applied to a CMSX-4 type SX superalloy after it has been subjected to a low cycle fatigue test to rupture. The evolution of microstructural defects, such as pores and cracks which are present after fatigue, has been tracked in 3D by X-ray tomography before and after rejuvenation. From the rejuvenated specimen series of metallographic cross sections were prepared and investigated by scanning electron microscopy for getting complementary 2D information at high resolution. The micrographs were stitched to a panorama which was then matched into the 3D representation of the specimen volume. By combining 3D and 2D data, statistical volume related quantities were achieved while detailed characteristics have been assigned to individual defects present in the 2D panorama micrograph. This technique is in general appropriate for length-scale bridging microstructural investigations. Results of the performed investigations concerning the rejuvenation effect on the microstructure are presented and discussed

Организационная культура в контексте социолого-управленческого подхода: новые аспекты феномена

Рассматриваются особенности нового социолого-управленческого подхода, обосновывается, что он является комплексным, сочетающим системный, деятельностный и феноменологический подходы. Возможность сочетания в одном подходе трех других базируется на полипарадигмальности социологии. Методы. Основу исследования составляют фундаментальные идеи социологии, сравнительный анализ, междисциплинарный подход. Результаты. Организационная культура анализируется с позиции социолого-управленческого подхода. Он позволяет рассматривать организационную культуру как объективно-субъективное образование в единстве трех составляющих. На основе первой составляющей, базирующейся на системном подходе, культура организации рассматривается как сложная система. На основании второй составляющей, базирующейся на деятельностления», как способ деятельности организации. Третья составляющая, базирующаяся на феноменологическом подходе, позволяет говорить о культуре организации как о культурном поле конструирования социальной реальности. Будучи системной, культура организации имеет ряд особенных свойств. Подход к организационной культуре как «субъекту управления» позволяет выявить такие ее особенности, как способность регулировать действия индивидов, упорядочивание организационных социальных процессов, придание смысла существования, объединение индивидов в общие социокультурные пространства, участие в преобразованиях и вещей, и человека. В пределах культуры организации осуществляется постоянное конструирование социальной реальности. В результате организации предстают как системы, в которых коллективные действия сознательно координируются. Социолого-управленческий подход получил эмпирическую проверку в процессе исследования организационной культуры организаций малого бизнеса.The author considers the features of the new sociologic-management approach and justifies that it is integrated, combining system, activity and phenomenological approaches. The possibility of combining three other approaches in one is based on polyparadigmality of sociology. Methods. Fundamental sociological ideas, comparative analysis, interdisciplinary approach are foundation of the research. The results. The sociological and managerial approach is applied to such a phenomenon of social reality as an organizational culture. The sociological and managerial approach focuses on the fact that organizational culture as an objectively-subjective entity is a complex system (a systematic approach), first of all, included in higher-level systems. It has a complex system structure. Secondly, it is a «subject of management» and it characterizes the way the organization works (activity approach). Thirdly, it is a cultural area for construction of social reality (a phenomenological approach). As a complex system, the organization culture has a complex internal structure and is characterized by a number of essential properties. Organizational culture as a «subject of management » regulates the actions of people, social processes in the organization, gives meaning orientation through ensuring the continuity of social experience, socialization, integration of people into unified sociocultural continuums, the common cultural area, participates in the transformation of human beings. As a result, organizations appear as systems in which collective actions are consciously coordinated. The sociological and managerial approach has been empirically tested in investigation of the organizational culture of small business organizations

Manufacturing of W/steel composites using electro-discharge sintering process

Tungsten-steel metal matrix composites are consolidated using electro-discharge sintering. At first steel and tungsten powders are sintered separately and then 25 vol% W, 50 vol% W and 75 vol% W mixed powders are sintered. A thorough process parametric study is carried out involving analysis of the influence of particle size distribution, sintering pressure, and discharge energy on the maximum discharge current and obtained residual porosity. Thermal expansion coefficient and the specific heat capacity of the optimized sintered composites are almost same as their theoretical values, however the thermal conductivities and the mechanical properties are lower than the expected values

Micro-magnetic and microstructural characterization of wear progress on case-hardened 16MnCr5 gear wheels

The evaluation of wear progress of gear tooth flanks made of 16MnCr5 was performed using non-destructive micro-magnetic testing, specifically Barkhausen noise (BN) and incremental permeability (IP). Based on the physical interaction of the microstructure with the magnetic field, the micro-magnetic characterization allowed the analysis of changes of microstructure caused by wear, including phase transformation and development of residual stresses. Due to wide parameter variation and application of bandpass filter frequencies of micro-magnetic signals, it was possible to indicate and separate the main damage mechanisms considering the wear development. It could be shown that the maximum amplitude of BN correlates directly with the profile form deviation and increases with the progress of wear. Surface investigations via optical and scanning electron microscopy indicated strong surface fatigue wear with micro-pitting and micro-cracks, evident in cross-section after 3 × 105 cycles. The result of fatigue on the surface layer was the decrease of residual compression stresses, which was indicated by means of coercivity by BN-analysis. The different topographies of the surfaces, characterized via confocal white light microscopy, were also reflected in maximum BN-amplitude. Using complementary microscopic characterization in the cross-section, a strong correlation between micro-magnetic parameters and microstructure was confirmed and wear progress was characterized in dependence of depth under the wear surface. The phase transformation of retained austenite into martensite according to wear development, measured by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) was also detected by micro-magnetic testing by IP-analysis