Review of Single Bubble Motion Characteristics Rising in Viscoelastic Liquids

The emphasis of this review is to discuss three peculiar phenomena of bubbles rising in viscoelastic fluids, namely, the formation of a cusp, negative wake, and velocity jump discontinuity, and to highlight the possible future directions of the subject. The mechanism and influencing factors of these three peculiar phenomena have been discussed in detail in this review. The evolution of the bubble shape is mainly related to the viscoelasticity of the fluid. However, the mechanisms of the two-dimensional cusp, tip-streaming, “blade-edge” tip, “fish-bone” tip, and the phenomenon of the tail breaking into two different threads, in some special viscoelastic fluids, are not understood clearly. The origin of the negative wake behind the bubbles rising in a viscoelastic fluid can be attributed to the synergistic effect of the liquid-phase viscoelasticity, and the bubbles are large enough; thus, leading to a very long relaxation time taken by the viscoelastic stresses. For the phenomenon of bubble velocity jump discontinuity, viscoelasticity is the most critical factor, and the cusp of the bubbles and the surface modifications play only ancillary roles. It has also been observed that a negative wake does not cause velocity jump discontinuity.

Heat development at the knife roller during leather shaving

Leather, which is regularly tanned from whole hides of up to 5 m2, needs a constant thickness over the entire surface in order to be processed into high-quality consumer goods such as shoes, furniture and car interiors. Precise adjustment of the thickness is achieved by shaving. On an industrial scale, rotating knife rollers are used to remove chips from the flesh side of semi-finished leathers whereby adjusting the specified thickness and generating a smooth surface. Care must be taken to prevent the temperature from rising above the denaturation temperature of the leather during shaving in order to avoid any loss of quality. Beside this, temperature rise is always a sign of friction showing avoidable energy expenditure. In order to localize the source of friction during shaving, actual temperature development at the roller knife is studied. Different measuring methods are used to evaluate the temperature increase at the blade roll of the shaving machine. The finite element method is used to thermally simulate the process. Measured temperatures, the geometry of the blade roll and process data are taken into account for modelling the temperature development close to the blade edge. The obtained results enhance the understanding of temperature generating processes during machine operation and allow conclusions about potential improvements in the design of the machine and blades. Graphical abstract

Features of the wear of the working bodies of the Viking tillage unit

It is shown that the most uniform wear of the bit blade occurs when soil particles move perpendicular to the blade edge. It has been determined that the width of the edge affects the traction resistance of the body, the penetration ability, and the strength of the blade. It has been found that in case of loamy soils, the optimal width of the blade part is in the range between 70 and 80 mm at an acute angle of 50 degrees between the bit blade and the side edge.

Evaluation of cutting force of high-performance fibers’ dynamic cutting behaviour

An analysis of fiber mechanics during cutting is conducted using a rotating cutting set up. It was found that high cutting speeds, low cutting angles, and high cutting normal forces lead to low values of cutting force. In this study, a set of high performance organic and inorganic fiber types are tested throughout different conditions of cut testing. Inorganic fibers gave the lowest specific cutting force. Values of cutting stresses on the edge of the blade were proved to be a function of fibers’ Young’s moduli. Higher Young’s moduli give lower cutting stresses on the blade edge while cutting fibers. Organic fibers were found to have a higher cutting resistance than carbon and glass fibers. A significant indirect correlation was found between the shear stress of the fibers and the fiber Young’s modulus. The value of the cutting force is significantly affected by both normal force and cutting velocity. The analysis of fiber mechanics during cutting is conducted using a rotating cutting set-up. It was found that high cutting speeds, low cutting angles, and high cutting normal forces lead to low values of cutting force. In this study, a set of high performance organic and inorganic fiber types are tested throughout different conditions of cut testing. Inorganic fibers gave the lowest specific cutting force. Values of cutting stresses on the edge of the blade were proved to be a function of fibers Young’s modulus. Higher Young’s modulus gives lower cutting stresses on the blade edge while cutting fibers. Organic fibers were found to have a higher cutting resistance than carbon and glass fibers. A significant indirect correlation was found between the shear stress of the fibers and the fibers Young’s modulus. The value of the cutting force is significantly affected by the normal force, cutting angle, and cutting velocity.

Hydromechanics, Aerodynamics and Thermodynamics: Critical Numerical Analysis of Aerodynamics of BLE Turbine Blade

This contribution presents a numerical analysis based on the effects of aerodynamics of the bump-based humpback whale fins available on the turbine blade edge. In this research, performance comparisons have been made based on dual sequestered blades. One of the blades was sinusoidal in shaped with Bumped Lead Edge (BLE) and the other one with Upright Leading Edge (ULE). However, all the blades are based on a similar cross-sectional profile i.e. NACA-012. This research has been based on simulations of Reynold’s number i.e. 1.8.105 of Attack Angle (AA) i.e. from ‘0º - 30º’. At this angle, especially greater than 10º, the BLE has indicated an enhancement in about 3.5% to 9.0% lift and a reducing drag whereas the negligible variation in lifts and minor drag is displayed for AA less than 10º. The findings in this result for BLE have indicated a substantial achievement in aerodynamic features for particular AA.

Fault Analysis for Reliability Centered Maintenance (RCM) in Machining

This contribution presents a numerical analysis based on the effects of aerodynamics of the bump-based humpback whale fins available on the turbine blade edge. In this research, performance comparisons have been made based on dual sequestered blades. One of the blades was sinusoidal in shaped with Bumped Lead Edge (BLE) and the other one with Upright Leading Edge (ULE). However, all the blades are based on a similar cross-sectional profile i.e. NACA-012. This research has been based on simulations of Reynold’s number i.e. 1.8.105 of Attack Angle (AA) i.e. from ‘0º - 30º’. At this angle, especially greater than 10º, the BLE has indicated an enhancement in about 3.5% to 9.0% lift and a reducing drag whereas the negligible variation in lifts and minor drag is displayed for AA less than 10º. The findings in this result for BLE have indicated a substantial achievement in aerodynamic features for particular AA.

Design of Crushing Mechanism of Mobile Straw Granulator

Background: Crop straw is a valuable renewable biological resource. In this study, a mobile straw granulator was designed to fully and efficiently use crop straw. The key crushing mechanism device of the mobile straw granulator was also designed in detail. Methods: The first three natural frequencies and vibration modes of the crushing roller are obtained by applying ANSYSWorkbench software to the modal analysis of the crushing roller. Results: The lowest natural frequency of the crushing roller was 165.83 Hz, which was higher than its working frequency of 30 Hz and would not cause resonance. Three factors and three levels were tested using the average resistance of the blade as an index and the blade edge angle, the blade thickness, and the blade end width as the test factors. Conclusion: The optimal parameter combination obtained by software analysis is blade edge angle of 30°, blade thickness of 8 mm, and blade width of 75 mm. With this parameter combination, the blade power consumption is the smallest, the service life is the largest, and the crushing effect is the best.

An Auto-Regressive Exogenous-Based Temperature Controller for a Hybrid Thermoplastic Microforming of Surgical Blades From Bulk Metallic Glass

Temperature control is critical in manufacturing of the multifacet bulk metallic glass (BMG) knife edge. The temperature control in thermoplastic forming process could make a significant effect on the type of deformation, which ultimately results in the final blade edge shape. The controller selection is based on the knowledge of the model from system identification, the performance of the controllers, and the feasibility of the implementation to the testbed. In this study, temperature control, using fuzzy logic, is implemented along with auto-regressive exogenous, ARX model, which can maintain the steady-state temperature within the range of ±2.5 K. With this proposed controller, experiments have shown similar or better results of multifacet blade geometries than those manufactured using proportional–integral–derivative (PID) controller. The blade edge samples are successfully manufactured with the average straightness and the edge radius of the blade of 3.66 ± 0.5 μm and 25.7 ± 6 nm, respectively.

Behavior of Different Grafting Strategies Using Automated Technology for Splice Grafting Technique

Even though the splicing graft technique is relatively recent, it has become the most commonly used grafting method for solanaceae, and in particular, for tomato. Today, almost everyone has standardized the use of plastic or silicone grafting clips, equipped with manipulating wings and a frontal opening, to ensure proper bonding and allow for wound healing. Numerous factors influence the success or failure of the grafting process, factors such as the seedling varieties combined, climatic conditions, pre-graft and post-graft care, cutting point, cutting angle, pressure of the clips, blade edge, or substrate water content, among others. In this work, several alternatives in the graft assembly and coupling protocol were evaluated. Having studied the different working alternatives for grafting using a robotic system, two modes of joining order were analyzed. It has been shown that there are 20% more recorded successes if one first joins the graft seedlings and then places the grafting clip to guarantee their union. In addition, we studied the different orientation alternatives for the cutting line and the seedling union with respect to the clip opening—there were approximately 10% more successes obtained in grafts where the splice-union cutting line between the two plants faced the clip opening.

A method for evaluating the edge strength of soil-cutting parts of forestry machines

One of the main factors that determine the resistance of blade working bodies against damage under dynamic loads is their resistance to plastic crumpling, brittle or fatigue failure. Hard alloys that strengthen the blades of tillage parts are more brittle materials than steel, so the blunting of their edges is caused by the formation of cracks, their gradual growth or microchipping, even from a possible single impact of a solid inclusion in the soil. In addition to the usual brittle fracture of hard alloys, fatigue failure occurs under cyclic impact conditions. (Research purpose) The research purpose is in identifying the pattern of destruction of the blade edge of soil-cutting parts of forestry machines and theoretically justifying the algorithm for assessing the strength to determine the rational thickness of the wear-resistant coating during hardening. (Materials and methods) The article presents the main regularities of the influence of material properties and geometric parameters of the blade on the radius of rounding. (Results and discussion) The process of breaking the edge of the blade of hardened working bodies of forestry machines has been studied. The claim that the blunting of the blades is mainly due to its destruction and not to wear has been proved. The article presents a method for evaluating the strength of bimetallic blades of soil-cutting parts of forestry machines. It was found that the blunting of the blade occurs as a result of edge destruction in the process of multiple impacts of solid soil inclusions along the edge of the blade. (Conclusions) The article shows that the destruction of the edge of the blade leads to blunting of soil-cutting parts, which affects their performance. It was found that the sharpness of a self-sharpening hardened blade is determined by the thickness of the reinforcing layer and its ability to resist destruction under impact.