Search Results (6)

During the drilling process of high-temperature geothermal wells, the high temperature at the bottom of the well and the complex lithology of the formation lead to poor tooth loss prevention in cone drill bits. This issue seriously affects the life and efficiency of geothermal drilling. The stability of the wellbore is one of the key issues in the drilling process of high-temperature geothermal wells, and the fixed-tooth strength of the roller drill bit directly affects the stability of the wellbore and drilling efficiency. The heat transfer effect of the wellbore will exacerbate the thermal expansion and performance degradation of the drill bit material in high-temperature environments, leading to a decrease in the strength of the fixed teeth. To address this, this study used a high-temperature experimental apparatus to systematically test the fixed-tooth strength of roller drill bits. By using five types of tooth spacing: 4, 6, 8, 10, and 12 mm, three types of tooth diameters: 12, 14, and 16 mm, and three types of interference fit: 0.075, 0.095, and 0.115 mm, the maximum fastening force of fixed teeth was measured under different conditions, and its variation pattern was analyzed. The experimental results show that the higher the temperature, the weaker the tooth-fixing strength. Under the same perforation distance, the maximum fastening force decreases with increasing temperature. Compared with normal temperature, the maximum fastening force decreases by about 49.6–64.5%. At the same temperature, the maximum fastening force is the largest when the perforation distance is 10 mm. When the temperature increases, the maximum fastening force increases with the tooth diameter; that is, the larger the tooth diameter, the better the tooth-fixing effect. At the same temperature, the maximum fastening force first increases and then decreases with increasing interference. The maximum fastening force is the largest when the interference is 0.095 mm. At 120 °C, 180 °C, and 240 °C, the maximum fastening force is reduced by 21.9%, 29.4%, and 56.6%, respectively, compared to normal temperature. The study reveals the variation law of tooth-fixing strength under high-temperature conditions and proposes tooth-fixing methods and suggestions suitable for high-temperature geothermal wells. This provides a scientific basis for solving the problem of tooth loss of roller bits in high-temperature geothermal drilling and has important theoretical and practical application value. Full article

The rapid development of wearable technologies is increasing research interest in on-body robotics, where relocatable robots can serve as haptic interfaces, support healthcare measurements, or assist with daily activities. However, on-body mobile robotics poses challenges in aspects such as stable locomotion and control. This article proposes a novel small robot design for moving on human limbs that consists of an open grasping mechanism with a spring linkage, where one side holds a pivoting differential drive base (PDDB) with two spherical rollers, and the other side holds an actuated roller for grasping and stabilization. The spherical rollers maintain contact at three points on the limb, optimizing stability with a minimal number of rollers and integrating DC motors within. The PDDB wheels (spherical rollers) enable directional changes on limb surfaces. The combination of the open mechanism, the PDDB, and the spherical rollers allows adaptability to diameter variations along the limb. Furthermore, the mechanism can be easily put on or removed at any point along the limb, eliminating the need to slip the robot over the hand or foot. The kinematic model for the proposed mechanism has been developed. A cascade control strategy is proposed with an outer loop for stable grasping and an inner loop for trajectory adjustments using PDDB roller velocities. An on-limb robot prototype has been built to test its applicability to human arms. Simulation and experimental results validate the design. Full article

This study presents the results of research, the aim of which was to analyze the uniformity of the distribution of selected mechanical properties along the length of a 5.5 mm diameter wire rod of 20MnB4 steel for specific thermoplastic processing parameters. The scope of the study included, inter alia, metallographic analyses, microhardness tests, thermovision investigations, and tests of the wire rod mechanical properties (yield strength, ultimate tensile strength, elongation, relative reduction in area at fracture), along with their statistical analysis, for three technological variants of the rolling process differing by rolling temperature in the final stage of the rolling process (Reducing Sizing Mill rolling block [RSM]) and by cooling rate using STELMOR^® cooling process. The obtained results led to the conclusion that the analyzed rolling process is characterized by a certain disparity of the analyzed mechanical properties along the length of the wire rod, which, however, retains a certain stability. This disparateness is caused by a number of factors. One of them, which ultimately determines the properties of the finished wire rod, is the process of controlled cooling in the STELMOR^® line. Despite technological advances concerning technical solutions (among them, increasing the roller track speed in particular sections), it is currently not possible to completely eliminate the temperature difference along the length of the wire rod caused by the contact of individual coils with each other. From this point of view, for the analyzed thermoplastic processing parameters, there is no significant impact by the production process parameters on the quality of the finished steel product. Whereas, while comparing the mechanical properties and microstructure of the wire rod produced in the different technological combinations, it was found that the wire rod rolled in an RSM block at 850 °C and cooled after the rolling process on a roller conveyor at 10 °C/s had the best set of mechanical properties and the smallest microstructure variations. The wire rod produced in this way had the required level of plasticity reserve, which enables further deformation of the given type of steel in compression tests with a relative plastic strain of 75%. The uniformity of mechanical properties along the length of wire rods designed for further cold plastic working processes is an important problem. This is an important issue, given that wire rods made from 20MnB4 steel are an input material for further cold plastic working processes, e.g., for the drawing processes or the production of nails. Full article

The Double-Disk Straight Groove Lapping (DDSGL) technique, a novel approach to batch processing of bearing rollers, achieves high dimensional consistency by removing material through size comparison between multiple rollers in the processing area. To avoid collision between the rollers, the prevalent practice in DDSGL involves circulating the rollers in fixed linear sequences, an approach that impedes comprehensive size comparison throughout the entire batch of rollers. To counter this, we introduce a Dual-Channel Mixing Scheduling (DCMS) strategy that disrupts the roller sequence without triggering collisions. This strategy promotes extensive size comparison and enhances batch size consistency. To elucidate the operational principles of DCMS, we have developed a computational model grounded in DDSGL, designed simulation test plans under different mixing parameters, and summarized the number of direct comparisons, total comparisons, and differences in roller cycle times to determine the optimal combination of mixing parameters. Finally, structural modifications were made in the DDSGL system for validation studies under different mixing parameters. The test results show that the use of DCHS can reduce processing time by up to 50%, and the batch diameter change of the rollers can converge from 1.15 μm to as low as 0.76 μm. The industrial relevance of this research is significant; these improvements can lead to higher efficiency in the manufacturing process and improved quality of bearing rollers. Full article

Due to the variety of materials used for flat belts of belt conveyors and the further development of material engineering in relation to these belts, the methods of their connection become an increasingly problematic issue. The belts can be connected mainly in three ways: vulcanized (weldable or heat-weldable), glued or mechanically. The latter method is one of the simplest and most universal in terms of the material variety of belts; however, there are many design variations of mechanical fasteners, and each of them has a certain advantage in a narrow group of properties, e.g., the thickness spectrum of a conveyor belt, the minimum diameter of a drive roller or the range of transferable longitudinal loads. The objective of this paper is to analyze the design solutions of commercial mechanical fasteners used mainly for flat rubber-fabric, composite or plastic belts. To fulfill this goal, a preliminary analysis of the stress distribution for an exemplary solid mechanical fastener was carried out in two cases: during ramp-up and during circulating around the roll, followed by a detailed review of commercial solutions available on the market. In addition to determining the current state of knowledge and technology and determining the state of ignorance, special algorithm and design maps have been created, thanks to which the process of selecting the right mechanical fastening will be easier. The overview includes several tables with detailed information on individual connection properties. Additionally, several design aspects were derived, within which individual mechanical connections may differ. This is to enable the generation of customized solutions in the future by proposing an appropriate mathematical model, on the basis of which it will be possible to generate optimal design properties for a given application. Full article

In this study, fluid–structure interaction (FSI) modeling was applied for predicting the fluid flow in a specific peristaltic pump, composed of one metallic roller and a hyperelastic tube pumping a viscous Newtonian fluid. Hyperelastic material dynamics and turbulence flow dynamics were coupled in order to describe all the physics of the pump. The commercial finite element software ABAQUS 6.14 was used to investigate the performance of the pump with a 3D transient model. By using this model, it was possible to predict the von Mises stresses in the tube and flow fluctuations. The peristaltic pump generated high pressure and flow pulses due to the interaction between the roller and the tube. The squeezing and relaxing of the tube during the operative phase allowed the liquid to have a pulsatile behavior. Numerical simulation data results were compared with one cycle pressure measurement obtained from pump test loop data, and the maximum difference between real and simulated data was less than 5%. The applicability of FSI modeling for geometric optimization of pump housing was also discussed in order to prevent roller and hose parts pressure peaks. The model allowed to investigate the effect of pump design variations such as tube occlusion, tube diameter, and roller speed on the flow rate, flow fluctuations, and stress state in the tube. Full article