Search Results (9)

Traditional hydro-pneumatic spring suspensions are limited to a single vertical degree of freedom, which cannot accommodate the significant technological changes introduced by the new in-wheel motor drive mode. Integrating the motor into the vehicle’s hub creates a direct motor drive mode, replacing the traditional engine–transmission–drive shaft configuration. Together with the dual in-wheel motor wheelset structure, this setup can achieve both drive and differential steering functions. In this study, we designed a six-arm suspension wheel-leg device based on hydro-pneumatic springs, and its structural composition and functional characteristics are presented herein. The external single-chamber hydro-pneumatic springs used in the six-arm structure suspension were analyzed and mathematically modeled, and the nonlinear characteristic curves of the springs were derived. To overcome the instability caused by inconsistent extension lengths of the hydro-pneumatic springs during horizontal steering, the spring correction force, horizontal rotational torque, consistency, and stiffness of the six-degree-of-freedom hydro-pneumatic spring wheel-leg device were analyzed. Finally, with the auxiliary action of tension springs, the rotational torque of the hydro-pneumatic springs and the tension resistance torque of the tension spring counterbalanced each other, keeping the resultant torque on the wheelset at approximately 0 N∙m. The results suggest that the proposed device has excellent self-stabilizing performance and meets the requirements for straight-line driving and differential steering applications. This device provides a new approach for the drive mode and suspension design of the dual in-wheel motor wheelset. Full article

This paper investigates the failure mechanism of the rear drive shaft in a modified pickup truck which had operated for about 3000 km. The investigation included macroscopic and microscopic evaluation to document the morphologies of the fracture surface, measurement of the material composition, metallographic preparation and examination, mechanical testing, and finite element modelling and calculations. The results obtained suggest that rotation-bending fatigue was the primary cause of the drive shaft failure. The crack initiation is located in the root of the machined threads on the drive shaft surface and expanded along the side of the machining line surface. The main cause of fatigue cracks is attributable to a high stress concentration owing to a large unilateral bending impact under overload. Meanwhile, the bidirectional torsional force also produces a higher stress concentration and thus accelerates the fatigue crack to expand radially along the surface. Furthermore, the hardness of the central section of the drive shaft was marginally below standard. This deficiency results in harm to the bearings and other mechanical components, as well as expediting the enlargement of cracks. Finite element analysis revealed significant contact stress between the bearing and drive shaft, with stress levels exceeding the fatigue limit stress of the parent material. This highlights the need for reevaluation of the heat treatment process and vehicle loading quality to enhance the drive shaft’s longevity. Full article

Based on the composite shaft lining structure, the research on the electromagnetic and negative pressure coupling adsorption technology of wall–climbing robots is of great significance to improve the level of safety monitoring during the construction and service of coal mine shafts. On the basis of theoretical research and computational data, the numerical simulation and simulation experiments of the coupled adsorption system of a wall–climbing robot are conducted in this research. In the ANSA software environment, of experimental models and experimental environments of electromagnetic and negative pressure adsorption devices are constructed to investigate, parameters such as air flow and the law behavior of fan pressure under different system conditions, including negative pressure and varying fan speeds. The intensity distribution of the magnetic flux inside the electromagnetic circuit under different working conditions and the law of change in the direction of movement are explored. Furthermore, the power consumption and power increment of the electromagnetic and negative pressure adsorption system under the same adsorption force output are compared and analyzed. Based on the experimental results, a series of conclusions are verified; firstly the negative pressure of the system should be formed under certain basic specific fundamental conditions; secondly, the main velocity of the negative pressure adsorption system and the full pressure of the fan are determined by the internal and external pressure difference and the fan speed, respectively; lastly, the adsorption efficiency of electromagnetic adsorption is significantly higher than that of negative pressure adsorption. These research findings are expected to introduce a new technical means approach for the safety monitoring of vertical shafts and shafts in coal mines, thereby demonstrating the theoretical significance and practical value of the application and development of an underground multi–scenario robot automation system in coal mines. Full article

The working conditions and environment of coal mine shafts are intricate and special. Currently, manual inspections or fixed-point monitoring is generally applied for daily safety monitoring, and intelligent and automated inspection equipment and its supporting technologies are not available. Starting from the technical requirements of the electromagnetic adsorption device of the wall-climbing robot for safety monitoring of the coal mine shaft, based on the structural characteristics and chemical composition of the composite shaft lining of the coal mine, the fundamental structure of the electromagnetic array and the electromagnetic unit are clarified, and a multi-layer matrix simulation point overlap mapping analysis method is proposed. Based on the system modeling and simulation calculations in MATLAB software, the number and distribution law of effective mapping points between the endpoints of the electromagnetic array and the reinforced frame in the shaft lining are inferred, which leads to the establishment of a calculation model of the equivalent adsorption area. The NSGA-II algorithm, a non-dominant elite strategy based on a genetic algorithm, is used to calculate the optimum combination scheme of various genetic parameters of individual electromagnetic units. Through the statistical analysis of the optimal individual data of each generation in the iterative process, the accuracy of the algorithm process and constraints, as well as the fitness function, are verified. Based on the research results of this paper, the electromagnetic adsorption issue of the mine shaft wall-climbing robot on the composite shaft lining structure has been effectively solved, which has theoretical significance and practical value for improving the autonomous ability and monitoring level of coal mine shaft safety monitoring. Full article

A theoretical study of the formation of water build-up, or water blanketing, and its influence on the ventilation of mine upcast shafts was carried out. Two scenarios for droplet moisture accumulation in the shaft were considered: condensation from saturated air rising up the shaft and groundwater inflows through the leaky shaft lining. Analytical dependencies of the pressure drop due to the influence of water build-up versus the outgoing air flow velocity and the height of the groundwater source were obtained, taking into account the fractional composition of the droplet moisture. Practical arrangements are proposed to reduce the influence of the effect of water build-up in upcast shafts in the case of groundwater inflows through the leaky shaft lining. Full article

There are numerous traces of mining activity in the Miedzianka Mountain (Świętokrzyskie Mountains, Poland), because copper and silver ores have been mined in this region since at least the 13th century. The history of scientific research on the Miedzianka Mountain ore deposit spans almost 200 years. Almost 40 minerals have been found: ore minerals of Cu and Fe, and also secondary minerals, including carbonates, sulphates and even very rare arsenates, phosphates and vanadates. Three new minerals have been found, staszicite, lubeckite and miedziankite, but their chemical composition has not been precisely determined and therefore their names have not been approved by the International Mineralogical Association (IMA). The Miedzianka Mountain deposit is an important area on the map of educational activities. It is included in the “Świętokrzyskie Archaeological and Geological Trail” as a site of historical (mining and metallurgy) and natural (geological sciences) heritage. Despite the large potential, none of the underground workings (adits and shafts) are currently available to the public. Our research and exploration of the Teresa adit, which is one of the historical underground complexes of the Miedzianka Mountain, show that this adit displays a wide spectrum of topics in the field of mineralogy, geology and mining history. The Teresa adit, which is a 523 m system of underground corridors, contains 270 m of natural karst caves altered by mining works and is constituted of Upper Devonian limestones, locally cut by cherry shales. In several sites of the adit unique features can be observed, such as: (1) old mining works—galleries carved in the rock back in the 19th century; (2) interesting vein mineralization with secondary-colored copper carbonates and multi-colored calcite veins; (3) mineralization with azurite domination; and (4) karst phenomena (coatings, flowstone, dripstones and stalactites) in a cave part of the adit. The sites with unique features suggest that the Teresa adit is highly suitable to be presented to tourists. That is why we propose seven sites on the underground route that could be the basis for further projects to create a “geotouristic trail” in the Teresa adit. The proposal to make the Teresa adit available to tourists is in line with the tendency to protect the post-industrial landscape associated with former mining activities. Full article

One of the crucial issues affecting the structural safety of propeller vehicles is the propeller tonal excitation and related vibrations. Propeller rotation during flight generates vibrating sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust, and blade geometry. Generally, the higher energy levels generated are confined to 1st blade passing frequency (BPF) and its harmonics, while additional broadband components, mainly linked with the blade shape, the developed engine power, and the turbulent boundary layer (TBL), also contribute to the excitation levels. The vibrations problem takes on particular relevance in the case of composite structures. The laminates in fact could exert damping levels generally lower than metallic structures, where the greater amount of bolted joints allow for dissipating more vibration energy. The prediction and reduction of aircraft vibration levels are therefore significant considerations for conventional propeller aircrafts now entering the commercial market as well as for models currently being developed. In the Clean Sky 2 framework, the present study focuses on a practical case inherent to the AIRBUS-Racer program aiming to design and develop a multi-tasking fast rotorcraft. This paper defines a finite elements (FE)-based procedure for the characterization of the vibration levels of a main landing gear (MLG) composite door with respect to the expected operating tonal loads. A parametric assessment was carried out to evaluate the principal modal parameters (transfer functions and respective resonance frequencies, mode shapes, and damping coefficients) of the landing gear-door assembly in order to achieve reduced vibration levels. Based on the FE analysis results, the influence of the extra-damping, location, and number of ballast elements, the boundary conditions were investigated with respect to failure scenarios of the kinematic line opening the study towards aeroelastic evaluations. Further experimental ground test results serve as a validation database for the prediction numerical methods representative of the composite door dynamic response. Full article

To address the support problem of large-diameter drilling shafts in the west area of Zhangji coal mine, a thinner shaft lining structure composed of double layers of steel plate and high-performance concrete is proposed herein. Firstly, a series of tests of high-performance concrete preparation were carried out, and the optimized mix ratio of pumping concrete with 60–70 MPa strength for shaft lining of the drilled shaft was obtained. Then, shaft lining models were designed according to the similarity theory, and the mechanical properties of the shaft lining were experimentally studied by loading test. The test results showed that the stress state of concrete in the shaft was obviously improved, and the compressive strength of concrete was increased by 1.97–2.52 times. Finally, the results of the study were applied to a shaft in the control strata of the inlet shaft in the west area of Zhangji coal mine, which made it possible to use the drilling method to construct the shaft. The following field measurement showed that the annular strain of the shaft lining concrete was −487 με, which is far less than the ultimate strain value of C65 concrete, and the shaft lining structure was kept safe and reliable. Full article

To address the cracking and leaking of concrete in frozen shaft linings in deep and thick topsoil layers in coal mines, hybrid-fiber-reinforced concrete (HFRC) was developed. First, the composition of the reference concrete was obtained by investigating high-strength concrete commonly used in shaft linings, and two dosages of polyvinyl alcohol fiber (PVAF) and polypropylene plastic steel fiber (PPSF) were obtained by the mixing test. Then, tests of early cracks of concrete were conducted; results showed that HFRC could almost avoid early cracks, exhibiting an advantage in early crack resistance. Thus, HFRC can play a significant role in improving the durability of frozen shaft linings in complex underground environments. Furthermore, a series of mechanical property tests were carried out. The results showed that the compressive strength of HFRC was similar to that of the reference concrete, but the tensile and flexural strength of HFRC was 42.7% and 35.1% higher than that of the reference concrete, respectively. Finally, an analog simulation model test of shaft linings was conducted. The new type of shaft lining structure containing hybrid fibers (HFs) exhibited plastic deformation characteristics under load, and the maximum hoop strain was −3562 με. It addressed the problem of high brittleness of frozen shaft lining structures of ordinary high-strength concrete and improved the toughness and crack resistance. HFRC is an ideal material for frozen shaft lining structures in deep and thick topsoil. Full article