Joining of hybrid semi-finished products from sheet metal by orbital forming

Contrary demands like a reduction of carbon dioxide emissions and an increase in functionality are facing the manufacturing industry with growing challenges. When processing functional components, like synchronizer rings, conventional process chains, like shearing and subsequent joining, are reaching their limits due to an increased complexity of the components and a lack in efficiency, referring to the long process time. To meet these challenges, the strategy of lightweight construction combines the application of lightweight materials with efficient manufacturing processes and an innovative product design. One possibility within lightweight construction is the utilization of load-adapted hybrid components, featuring different material strength classes. In previous research, the process of orbital forming is used to manufacture semi-finished products with a varying thickness profile due to the specific radial material flow. This material flow should now be used to realize a permanent joint between materials of two different strength levels. Therefore, the process of orbital forming is modified to manufacture hybrid semi-finished products from a dual-phase steel DP600 and a naturally rigid aluminum alloy EN AW 5754, both with an initial thickness of 2.0 mm. Different joint geometries are cut by laser into a steel ring and the part is coaxially positioned around a basic aluminum disc inside a die and subsequently formed. The joint is investigated regarding the geometrical and mechanical properties, comparing a radial cross-section and the micro hardness distribution. In order to reveal the potential of orbital forming for a combined forming and joining operation, the axial as well as the peeling strength of the multi-material components are investigated and evaluated.

Comparison Between Homogenous and Heterogeneous Reservoirs: A Parametric Study of Water Coning Phenomena

Water coning is the biggest production problem mechanism in Middle East oil fields, especially in the Kurdistan Region of Iraq. When water production starts to increase, the costs of operations increase. Water production from the coning phenomena results in a reduction in recovery factor from the reservoir. Understanding the key factors impacting this problem can lead to the implementation of efficient methods to prevent and mitigate water coning. The rate of success of any method relies mainly on the ability to identify the mechanism causing the water coning. This is because several reservoir parameters can affect water coning in both homogenous and heterogeneous reservoirs. The objective of this research is to identify the parameters contributing to water coning in both homogenous and heterogeneous reservoirs. A simulation model was created to demonstrate water coning in a single- vertical well in a radial cross-section model in a commercial reservoir simulator. The sensitivity analysis was conducted on a variety of properties separately for both homogenous and heterogeneous reservoirs. The results were categorized by time to water breakthrough, oil production rate and water oil ratio. The results of the simulation work led to a number of conclusions. Firstly, production rate, perforation interval thickness and perforation depth are the most effective parameters on water coning. Secondly, time of water breakthrough is not an adequate indicator on the economic performance of the well, as the water cut is also important. Thirdly, natural fractures have significant contribution on water coning, which leads to less oil production at the end of production time when compared to a conventional reservoir with similar properties.

Influence of layered structure of composite timber floor boards on their hardness

The possibility of using composite elements of flooring pine veneers with knotholes for the production of supporting layers has been determined. This assessment was made on the basis of the Brinell hardness measurement of the face layer of five-layer composites with empty spots in their structure imitating knotholes of various diameters (10, 20 and 50 mm). The dependencies obtained from empirical determinations were supported by numerical analysis. It was found that it is possible to use veneers with defects (empty spots) with a diameter of up to 20 mm to produce composites of three and more layers of wood (counting from the face layer). The anatomical section of the exposed wood on the face (radial cross-section, tangential section) of the layered composite does not affect the obtained hardness values.

Fractal planetary rings: Energy inequalities and random field model

This study is motivated by a recent observation, based on photographs from the Cassini mission, that Saturn’s rings have a fractal structure in radial direction. Accordingly, two questions are considered: (1) What Newtonian mechanics argument in support of such a fractal structure of planetary rings is possible? (2) What kinematics model of such fractal rings can be formulated? Both challenges are based on taking planetary rings’ spatial structure as being statistically stationary in time and statistically isotropic in space, but statistically nonstationary in space. An answer to the first challenge is given through an energy analysis of circular rings having a self-generated, noninteger-dimensional mass distribution [V. E. Tarasov, Int. J. Mod Phys. B 19, 4103 (2005)]. The second issue is approached by taking the random field of angular velocity vector of a rotating particle of the ring as a random section of a special vector bundle. Using the theory of group representations, we prove that such a field is completely determined by a sequence of continuous positive-definite matrix-valued functions defined on the Cartesian square [Formula: see text] of the radial cross-section [Formula: see text] of the rings, where [Formula: see text] is a fat fractal.

Self-similar growth of a bimodal laboratory fan

Using laboratory experiments, we investigate the growth of an alluvial fan fed with two distinct granular materials. Throughout the growth of the fan, its surface maintains a radial segregation, with the less mobile sediment concentrated near the apex. Scanning the fan surface with a laser, we find that the transition between the proximal and distal deposits coincides with a distinct slope break. A radial cross section reveals that the stratigraphy records the signal of this segregation. To interpret these observations, we conceptualize the fan as a radially symmetric structure that maintains its geometry as it grows. When combined with slope measurements, this model proves consistent with the sediment mass balance and successfully predicts the slope of the proximal–distal transition as preserved in the fan stratigraphy. While the threshold-channel theory provides an order-of-magnitude estimate of the fan slopes, driven by the relatively high sediment discharge in our experimental system, the actual observed slopes are 3–5 times higher than those predicted by this theory.

Self-similar growth of a bimodal laboratory fan

Using laboratory experiments, we investigate the growth of an alluvial fan fed with two distinct granular materials. Throughout the growth of the fan, its surface maintains a radial segregation, with the less mobile sediment concentrated near the apex. Scanning the fan surface with a laser, we find that the transition between the proximal and distal deposits coincides with a distinct slope break. A radial cross-section reveals that the stratigraphy of the deposit bears the mark of this consistent segregation. To interpret these observations, we conceptualize the fan as a radially symmetric structure that maintains its geometry as it grows. When combined with slope measurements, this model proves consistent with the sediment mass balance and successfully predicts the slope of the proximal-distal transition as preserved in the fan stratigraphy. The threshold channel theory provides an order-of-magnitude estimate of the fan slope, but relatively high sediment discharges manifest themselves in the form of slopes 3–5 times higher than those predicted from the theory.

Studi Mutu Kayu Jati di Hutan Rakyat Gunungkidul. V. Sifat Kimia Kayu

Penelitian ini bertujuan untuk mengeksplorasi sifat kimia kayu jati dari hutan rakyat Kabupaten Gunungkidul. Pohon (dbh 28-37 cm) diambil dari tempat tumbuh berbeda yaitu Nglipar, Panggang, dan Playen. Setiap tempat diambil 3 pohon sebagai ulangan dan sampel yang digunakan adalah disk yang diambil dari bagian pangkal. Penampang radial disk dibagi menjadi 3 bagian, yaitu gubal, teras luar, dan teras dalam. Sifat kimia yang diuji adalah kadar holoselulosa, á-selulosa, hemiselulosa, lignin, ekstraktif etanol-toluena, kelarutan dalam air panas, kelarutan dalam NaOH 1%, dan abu. Sebagai pembanding, digunakan kayu jati dewasa dari tegakan Randublatung (Perhutani). Kisaran nilai kimia dari komponen dinding sel kayu jati Gunungkidul adalah kadar holoselulosa 75,76-79,74%, á-selulosa 46,72-50,90%, hemiselulosa 27,41-30,14%, lignin 29,22-32,80%, dan kelarutan dalam NaOH 1% sebesar 16,43-17,35%. Selanjutnya, kadar ekstraktif etanol-toluena, kelarutan dalam air panas, dan abu adalah 5,04-10,77%, 2,74-7,85%, dan 0,60-1,66%, secara berurutan. Interaksi antara kedua faktor berpengaruh nyata pada kadar holoselulosa, á-selulosa, hemiselulosa, dan ekstraktif etanol-toluena. Faktor tempat tumbuh berpengaruh nyata pada kadar abu sedangkan faktor radial berpengaruh nyata pada kadar kelarutan dalam air panas dan abu. Kayu jati dari Gunungkidul memberikan nilai rerata kadar ekstraktif etanol-toluena dan abu yang lebih rendah sedangkan nilai di parameter lainnya masih dalam kisaran nilai kayu jati dari Randublatung.Kata kunci: Tectona grandis, sifat kimia, hutan rakyat, arah radial, Gunungkidul AbstractThis study aimed to explore the chemical properties of teak wood grown in community forests from Gunungkidul Regency. Trees (dbh 28-37 cm) were selected from three different sites i.e. Nglipar, Panggang, and Playen. Three trees were cut from each site and disks were taken from the base of the trees. The disk in radial cross section was divided into 3 parts: sapwood, outer heartwood, and inner heartwood. Chemical properties tested were holocellulose, á-cellulose, hemicellulose, lignin, ethanol-toluene extractives, hot-water soluble extractives, solubility in NaOH 1%, and ash contents. Mature teakwoods from Randublatung (Perhutani plantation) were used for comparison purpose.The values range of chemical composition in the cell wall components of the Gunungkidul teak wood were holocellulose content 75.76-79.74%, , á-cellulose content 46.72-50.90%, hemicellulose content 27.41-30.14%, lignin content 29.22-32.80%, and solubility in NaOH 1% 16.43-17.35%. Further, the ethanol-toluene extractive, hot-water soluble, and ash content values ranged from 5.04 to 10.77%, 2.74-7.85%, and 0.60-1.66%, consecutively. Interaction between two factors affects significantly to holocellulose, á-cellulose, hemicellulose, and ethanol-toluene extractive contents. The growth-site significantly influence on the ash contents as radial factor has significantly affect on the levels of hot water soluble extractives and ash content. The amounts of ethanol-toluene extractive and ash contents of Gunungkidul teak wood showed the lower values than those of teak from Randublatung. The values of other parameters were remain in the range of value of teak from Randublatung.

Visualization Investigation of Secondary Flow on Heat Transfer Deterioration in Horizontal Heat Tube

Mixed convection heat transfer in heated tubes has been studied extensively in the past decades, which is widely used in various industrial fields such as cooling of a nuclear reactor core. The secondary flow, which is induced by buoyancy force, has been found in previous research to have profound influence on the heat transfer difference on circumferential position and occurrence of heat transfer deterioration in horizontal heated channel. Therefore, understanding the secondary flow velocity field has important implications to prevent heat transfer deterioration and ensure the safe operation of nuclear power plants. Numerical methods have been adopted in literature to analyze the complex interaction between secondary flow and heat transfer deterioration. However, to the knowledge of the author, experimental measurement of secondary flow in the radial cross-section of a horizontal tube does not exist. In this paper, a novel measurement method, which combines the transparent heating and PIV (Particle Image Velocimetry) technology, has been adopted to experimentally investigate the secondary flow velocity field on the radial cross-section in a horizontal heated tube. The heat transfer deterioration mechanism is revealed through analysis of the distribution of secondary flow along circumference direction at low mass flow rates and high heat flux conditions. We found that the buoyancy force lead the hot fluid to rise along the tube wall from bottom to top. While the secondary flow is most intensive near the middle of the interface, the secondary velocities are high at the bottom of the cross-section, where the tube wall is well cooled by cold fluid descends from the central part of the cross-section. Near the top of the tube wall, the secondary velocities are very small and the thermal acceleration effect makes the fluid rise. As a result, the mixed convection of top and center part of cross-section is weak and heat is primarily transferred by conduction, which leads the occurrence of thermal stratification of fluid. Consequently, the thermal accumulation of fluid in the top leads to heat transfer deterioration. Moreover, thermal properties differences between Freon (FC-72) and water, especially the Prandtl number (Pr), make the occurrence of heat transfer deterioration much easier for FC-72 than water with same working conditions.

Micro-Scale Numerical Model of Bovine Cortical Bone: Analysis of Plasticity Localization

Evolution of damage and fracture in a bone is affected by its microstructure. A non-uniform distribution of osteons in a cortical bone tissue results in a localization of deformation processes. Such localization can affect bone performance under external load and initiate fracture. In this paper, a two-dimensional numerical (finite-element) model for osteonal bovine cortical bone was developed with account for its microstructure. The topology of a transverse-radial cross section of a bovine cortical bone was captured with optical microscopy. The elastic-plastic data for the microstructural features of the cross section was obtained with a use of the nanoindentation technique. Both the topology and nanoindentation data were used as input to the model formulated with the Abaqus finite-element software. The area, directly reflecting micro-scale information, was embedded into the region with homogenised properties of the cortical bone. Different scenarios of the loading were tried: (i) tension in transverse direction, (ii) tension in radial direction and (iii) tension in both directions. The calculated stress and strain fields for various cases of loading demonstrate different patterns due to implementation of microstructural features in the finite-element model. There are obvious signs of localization of the plastic regions at the micro-structure level that can be considered as fracture precursors. The suggested approach emphasizes the importance of microstructural features in development of bone failure.