Search Results (315)

This paper presents field investigations of a corrugated steel soil–steel arch structure with a span of 25.7 m and a rise of 9.0 m—currently the largest single-span structure of its kind in Europe. The structure, serving as a wildlife crossing along the DK16 expressway in northeastern Poland, was constructed using deep corrugated steel plates (500 mm× 237 mm) made from S315MC steel, without additional reinforcements such as stiffening ribs or geosynthetics. The study focused on monitoring the structural behavior during the critical backfilling phase. Displacements and strains were recorded using 34 electro-resistant strain gauges and a geodetic laser system at successive backfill levels, with particular attention to the loading stage at the crown. The measured results were compared with predictions based on the Swedish Design Method (SDM). The SDM equations did not accurately predict internal forces during backfilling. At the crown level, bending moments and axial forces were overestimated by approximately 69% and 152%, respectively. At the final backfill level, the SDM underestimated bending moments by 55% and overestimated axial forces by 90%. These findings highlight limitations of current design standards and emphasize the need for revised analytical models and long-term monitoring of large-span soil–steel structures. Full article

As the core component of ultra-precision machine tools, the manufacturing errors of aerostatic spindles are inevitable due to the limitations of machining and assembly processes, and these errors significantly affect the spindle’s static and dynamic performance. To address this issue, a force model of the unbalanced air film, considering the straightness errors of the rotor’s radial and thrust surfaces, was constructed. Unlike conventional studies that rely solely on idealized error assumptions, this research integrates actual straightness measurement data into the simulation process, enabling a more realistic and precise prediction of bearing performance. Rotors with different tolerance specifications were fabricated, and static performance simulations were carried out based on the measured geometry data. An experimental setup was built to evaluate the performance of the aerostatic spindle assembled with these rotors. The experimental results were compared with the simulation outcomes, confirming the validity of the proposed model. To further quantify the influence of straightness errors on the static characteristics of aerostatic spindles, ideal functions were used to define representative manufacturing error profiles. The results show that a barrel-shaped error on the radial bearing surface can cause a load capacity variation of up to 46.6%, and its positive effect on air film load capacity is more significant than that of taper or drum shapes. For the thrust bearing surface, a concave-shaped error can lead to a load capacity variation of up to 13.4%, and its enhancement effect is superior to those of the two taper and convex-shaped errors. The results demonstrate that the straightness errors on the radial and thrust bearing surfaces are key factors affecting the radial and axial load capacities of the spindle. Full article

Simulation is an important technical tool in corn threshing operations, and the establishment of the corn kernel model is the core part of the simulation process. The existing modeling method is to treat the whole kernel as a rigid body, which cannot be crushed during the simulation process, and the calculation of the crushing rate needs to be considered through multiple criteria such as the contact force, the number of collisions, and so on. Aiming at the issue that kernel crushing during maize threshing cannot be accurately modeled in discrete element simulations, in this study, a sub-area crushing model was constructed; representative samples with 26%, 30% and 34% moisture content were selected from a double-season maturing region in China; based on the physical dimensions and biological structure of the maize kernel, three stress regions were defined; and mechanical property tests were conducted on each of the three stress regions using a texturometer as a way to determine the different crushing forces due to the heterogeneity of the maize structure. The correctness of the model was verified by stacking angle and mechanical property experiments. A discrete element model of corn kernels was established using the Bonding V2 method and sub-area modeling. Bonding parameters were calculated by combining stacking angle tests and mechanical property tests. The flattened corn kernel was used as a prototype, and the bonding parameters were determined through size and mechanical property tests. A 22-ball bonding model was developed using dimensional parameters, and the kernel density was recalculated. Results showed that the relative error between the stacking angle test and the measured mean value was 0.31%. The maximum deviation of axial compression simulation results from the measured mean value was 22.8 N, and the minimum deviation was 3.67 N. The errors between simulated and actual rupture forces at the three force areas were 5%, 10%, and 0.6%, respectively. The decreasing trend of the maximum rupture force for the three moisture levels in the simulation matched that of the actual rupture force. The discrete element model can accurately reflect the rupture force, energy relationship, and rupture process on both sides, top, and bottom of the grain, and it can solve the error problem caused by the contact between the threshing element and the grain line in the actual threshing process to achieve the design optimization of the threshing drum. The modeling method provided in this study can also be applied to breakable discrete element models for wheat and soybean, and it provides a reference for optimizing the design of subsequent threshing devices. Full article

In this study, an axial flux double airgap permanent magnet-assisted synchronous reluctance motor (AF-Pma-SynRM) was designed for electric vehicles (EVs). The AF-Pma-SynRM model employs a forced liquid cooling method (cooling jacket) for a high current density. The model was tested using multi-objective optimization and multi-physics analysis. The AF-Pma-SynRM design has achieved 95.6 Nm of torque, 30 kW of power, and 93.8% efficiency at a 3000 rpm rated speed. The motor exhibits a maximum speed of 10,000 rpm, 253.1 Nm of torque, and 65 kW of output power. This study employs a novel barrier structure for axial motors characterized by fixed outer and inner dimensions, and is suitable for mass production. In the final stage, the motor was cooled using the cooling jacket method, and the average temperature of the winding was measured as 73.83 °C, and the average magnet temperature was 66.44 °C at a nominal power of 30 kW. Also to show variable speed performance, an efficiency map of the AF-Pma-SynRM is presented. Full article

Conventional bolts frequently fail under large deformations due to stress concentration in soft rock tunnels. In contrast, yielding bolts incorporate energy-absorbing mechanisms to sustain controlled plastic deformation. This study employed FLAC3D to numerically investigate the pull-out, shear, and bending behaviors of yielding bolts, evaluating their support effectiveness in soft rock tunnels. Three-dimensional finite difference models incorporating nonlinear coupling springs and the Mohr–Coulomb criterion were developed to simulate bolt–rock interactions under multifactorial loading. Validation against experimental pull-out tests and field measurements confirmed the model accuracy. Under pull-out loading, the axial forces in yielding bolts decreased more rapidly along the bolt length, reducing stress concentration at the head. The central position of the maximum load-bearing capacity in conventional bolts fractured under tension, resulting in an hourglass-shaped axial force distribution. Conversely, the yielding bolts maintained yield strength for an extended period after reaching it, exhibiting a spindle-shaped axial force distribution. Parametric analyses reveal that bolt spacing exerts a greater influence on support effectiveness than length. This study bridges critical gaps in understanding yielding bolt behavior under combined loading and provides a validated framework for optimizing energy-absorbing support systems in soft rock tunnels. Full article

In the case of strengthening building structures, the process usually involves elements that have a certain loading history and are typically subjected to loading during the strengthening process. In scientific research, on the other hand, strengthening is usually applied to elements that are not representative of real structures. This article presents a study of the effect of pre-damage on the behavior of eccentrically compressed concrete cylinders confined with PBO-FRCM (fabric-reinforced cementitious matrix with PBO fibers) composite. Concrete confinement introduces a favorable triaxial stress state, which leads to an increase in the compressive strength of concrete. FRCM systems are an alternative to FRP (fiber-reinforced polymer) composites. Replacing the polymer matrix with a mineral matrix primarily improves the fire resistance of the strengthening system. The elements were made of concrete with a compressive strength of about 40 MPa, which is typical for current reinforced concrete columns. Pre-damage was induced by loading the test elements to 80% of the average compressive strength and then fully unloading. The elements were then strengthened with three layers of PBO-FRCM composite and subjected to axial or eccentric compression with force applied at two different eccentricities. In addition to electric strain gauges, a digital image correlation system was used for measurements, to identify the initiation of PBO mesh overlap delamination. This study analyzed the elements in terms of load-bearing capacity, deformability, ductility, and failure mechanisms. In general, there was no negative effect of pre-damage on the behavior of the tested elements. Full article

The human neck is highly vulnerable in motor vehicle crashes, and cervical spine response data are essential to improve injury prediction tools (e.g., crash test dummies, human body models). This feasibility study aimed to implement the use of pressure sensors in whole-body post-mortem human subject (PMHS) cervical spine intervertebral discs (IVDs) to confirm the feasibility and repeatability of cervical IVD pressure response to biomechanic research. Two fresh frozen whole-body PMHSs were instrumented with miniature pressure sensors (Model 060S, Precision Measurement Company, Ann Arbor, MI, USA) at three cervical IVD levels (C3/C4, C5/C6, and C7/T1) using minimally invasive surgical insertion techniques. Each PMHS underwent three quasistatic motion test trials, and each trial included multiple head/neck motions (i.e., gentle traction, flexion/extension, lateral bending, axial rotation, and forced tension/compression). Results showed marked pressure differences between both the cervical level assessed and the motion undertaken as well as successful intra-subject repeatability between the three motion trials. This study demonstrates that changes in cervical IVD pressure are associated with motion events of the cervical spine. Cervical IVD response data could be utilized to assess and supplement the characterization of the head/neck complex motion, and data could facilitate the continued improvement of injury prediction tools. Full article

External fixators are frequently used to treat complex fractures with multiple bone fragments and soft tissue injuries. Inaccurate assessment of bone union and premature removal of the fixator may necessitate revisions and prolong treatment. The decision to remove an external fixator typically depends on an orthopedist’s experience. The accuracy of diagnosis can be improved by using a force sensor integrated into the modified external fixator according to Mitkovic. A sensor measuring axial compressive force is mounted between two vertical rods. Experiments with the modified external fixator were carried out using three different axial loads delivered by the universal electromechanical testing machine (UETM) and a sensor that detected the corresponding axial force. Springs with variable rigidity were used to simulate bone callus stiffness. Low rigidity springs represented a high elasticity callus, whereas high rigidity springs represented a callus with lower elasticity. The results show that the force detected by the sensor was nearly identical to the force delivered by the UETM while the callus did not form, decreased as spring rigidity increased, and eventually zeroed out as the leg healed. The findings indicated that using modified external fixator according to Mitkovic can help orthopedists assess bone healing more accurately. Full article

With the rapid development of the national economy, the construction of super high-rise buildings, long-span bridges, high-speed railways, and transmission towers has become increasingly common. It is also more frequent to build structures on karst foundations, which imposes higher demands on foundation engineering, especially pile foundations. To study the influence of the roughness factor (RF) on the bearing characteristics of rock-socketed pile, model pile load tests were conducted with different RF values (0.0, 0.1, 0.2, and 0.3) to reveal the failure modes of the test pile, analyze the characteristics of the load–displacement curves and the axial force and resistance exertion law of the pile, and discuss the influence of the RF on the ultimate bearing capacity of the test pile. Based on the load transfer law of test piles, a load transfer model considering the relative pile–soil displacement and the shear dilatancy effect of pile–rock is established to analyze its load transfer characteristics. The results show that the failure mode of the test pile is splitting failure. The load–displacement curves are upward concave and slowly varying. The pile side resistance and the pile tip resistance mainly bear the load on the pile top. As the load on the pile top increases, the pile tip resistance gradually comes into play, and when the ultimate load is reached, the pile tip resistance bears 72.12% to 79.22% of the upper load. The pile side resistance is mainly borne by the rock-socketed section, and the pile side resistance increases sharply after entering the rock layer, but it decreases slightly with increasing depth, and the peak point is located in the range of 1.25D below the soil–rock interface. Increasing the roughness of the pile can greatly improve the ultimate bearing capacity. In this study, the ultimate bearing capacity of the test pile shows a trend of increasing and then decreasing with the gradual increase in RF from 0.0 to 0.3, and the optimal RF is 0.2. The load transfer model of pile–soil relative displacement and pile–rock shear dilatancy effect, as well as the pile tip load calculation model, were established. The calculation results were compared with the test results and engineering measured data, respectively, and they are in good agreement. Full article

Rainfall-induced landslide mitigation remains a critical research focus in geotechnical engineering, particularly for safeguarding buildings and infrastructure in unstable terrain. This study investigates the stabilizing performance of slopes reinforced with negative Poisson’s ratio (NPR) anchor cables under rainfall conditions through physical model tests. A scaled geological model of a heavily weathered rock slope is constructed using similarity-based materials, building a comprehensive experimental setup that integrates an artificial rainfall simulation system, a model-scale NPR anchor cable reinforcement system, and a multi-parameter data monitoring system. Real-time measurements of NPR anchor cable axial forces and slope internal stresses were obtained during simulated rainfall events. The experimental results reveal distinct response times and force distributions between upper and lower NPR anchor cables in reaction to rainfall-induced slope deformation, reflecting the temporal and spatial evolution of the slope’s internal sliding surface—including its generation, expansion, and full penetration. Monitoring data on volumetric water content, earth pressure, and pore water pressure within the slope further elucidate the evolution of effective stress in the rock–soil mass under saturation. Comparative analysis of NPR cable forces and effective stress trends demonstrates that NPR anchor cables provide adaptive stress compensation, dynamically counteracting internal stress redistribution in the slope. In addition, the structural characteristics of NPR anchor cables can effectively absorb the energy released by landslides, mitigating large deformations that could endanger adjacent buildings. These findings highlight the potential of NPR anchor cables as an innovative reinforcement strategy for rainfall-triggered landslide prevention, offering practical solutions for slope stabilization near buildings and enhancing the resilience of building-related infrastructure. Full article

During long-span arch bridge construction, repeated adjustments of large cantilevered segments and nonuniform cable tensions can lead to deviations from the desired arch profile, reducing structural efficiency and increasing labor and material costs. To precisely control the process of cable-stayed buckle construction in long-span arch bridges and achieve an optimal arch formation state, a constrained optimization for the buckle and anchor cable forces under one-time tension is developed in this paper. First, by considering the coupling effect of the cable-stayed buckle system with the buckle tower and arch rib structure, the control equations between the node displacement and cable force after tensioning are derived based on the influence matrix method. Then, taking the cable force size, arch rib closure joint alignment, upstream and downstream side arch rib alignment deviation, tower deviation, and the arch formation alignment displacement after loosening the cable as the constraint conditions, the residual sum of squares between the arch rib alignment and the target alignment during the construction stage is regarded as the optimization objective function, to solve the cable force of the buckle and anchor cables that satisfy the requirements of the expected alignment. Applied to a 310 m asymmetric steel truss arch bridge, the calculation of arch formation alignment is consistent with the ideal arch alignment, with the largest vertical displacement difference below 5 mm; the maximum error between the measured and theoretical cable forces during construction is 4.81%, the maximum difference between the measured and theoretical arch rib alignments after tensioning is 3.4 cm, and the maximum axial deviation of the arch rib is 5 cm. The results showed the following: the proposed optimization method can effectively control fluctuations of arch rib alignment, tower deviation, and cable force during construction to maintain the optimal arch shape and calculate the buckle and anchor cable forces at the same time, avoiding iterative calculations and simplifying the analysis process. Full article

Background/Objectives: The conventional practice in clinical settings involves using multi-use surgical instrumentation (SI). However, there is a growing trend towards transforming these multi-use SIs into disposable surgical instruments, driven by economic and environmental considerations without considering the biomechanical aspects. This study focuses on redesigning an SI kit for implanting cervical spinal facet cages. Understanding the boundary conditions (forces, torques, and bending moments) acting on the SI during surgery is crucial for optimizing its design and materials. Therefore, this study aims to develop a measurement system (MS) to record these loads during implantation and validate it through in vitro testing. Methods: A combined numerical–experimental approach was used to design and calibrate the MS. Finite element analysis (FE) was used to optimize the geometry of the sensitive element of the MS. This was followed by the manufacturing phase using 3D printing and then by calibration tests to determine the stiffness of the system. Finally, the MS was used to measure the boundary conditions applied during SI use during in vitro tests on a cervical Sawbone spine. Results: After designing the measurement system (MS) via finite element analysis, calibration tests determined stiffness values of K_F = 1.2385 N/(µm/m) (axial compression), K_T = −0.0015 Nm/(µm/m) (torque), and K_B = 0.0242 Nm/(µm/m) (non-axial force). In vitro tests identified maximum loads of 40.84 N (compression) and 0.11 Nm (torque). Conclusions: This study developed a measurement system to assess surgical implant boundary conditions. The data will support finite element modeling, guiding the optimization of implant design and materials. Full article

The development of rotordynamic systems with reduced energy dissipation is a key challenge in modern applications, such as Flywheel Energy Storage Systems. This paper investigates a fully passive vertical rotor system supported by two passive magnetic bearings whose configuration provides radial stability while minimising power losses due to their thrust effect. A numerical model describes the forces and stiffness of the magnetic bearings, identifying the operational range of the thrust–radial support configuration. A test rig is developed for the experimental characterisation of the rotor and passive magnetic bearings in both static and dynamic conditions. Different magnetic thrust force levels are tested by varying the axial distance between the rotor and stator magnetic rings of the bearings. Static tests are performed to measure the weight force compensation corresponding to the different bearing configurations, validating the numerical model. Dynamic tests analyse the rotor power losses with a non-invasive approach via optical sensor measurements. Full article

The hydraulic support is one of the most crucial pieces of equipment at the working face. To achieve the intelligentization of the attitude-monitoring system, we have designed and developed a Fiber Bragg Grating (FBG) inclinometer for the hydraulic support. This innovation offers a brand-new monitoring tool and approach for measuring the attitude angle of the hydraulic support. The FBG inclinometer for the hydraulic support integrates passive grating sensing technology with an inclination force element. It not only fulfills the inclination measurement function but also employs passive sensing technology, rendering it safer and more reliable compared to electromagnetic inclinometers. First, we delved into the sensing principle of the grating based on its structure, and investigated its sensing characteristics under uniform axial stress and temperature variations. We analyzed the strain–temperature cross-sensitivity issue and applied a temperature compensation technique. Second, we carried out a novel structural design and proposed two design alternatives: the cantilever beam type was selected after a comprehensive comparison. Subsequently, we deduced the corresponding theoretical formulas and ultimately adopted the temperature compensation method using an unstressed reference grating. Finally, on-site verification was conducted on the hydraulic support in the general mining face of Delong Mine, and the FBG inclinometer successfully passed the test. Finally, an actual test was carried out at the Delong Coal Mine site, and the subsequent use yielded quite satisfactory results. An analysis of the data collected on-site by the FBG inclinometer for the hydraulic support revealed that the newly developed FBG inclinometer for the hydraulic support can be effectively applied in the field of intelligent monitoring in underground coal mines. The monitoring data can serve as a reliable data foundation for assessing the operating attitude of the hydraulic support. This indicates that the FBG inclinometer is highly suitable for wide-scale industrial applications. Full article

The surface texture technology has been applied to ball screws. However, the rough grinding surface of ball screws is not considered, and the elastohydrodynamic lubrication (EHL) characteristics and anti-friction and anti-wear mechanisms are not comprehensive and in-depth. Theoretical simulation and experimental measurement of the ground surface topography of the screw raceways are conducted to take into account the impact of the grinding surface on the EHL interaction between the ball and the raceway. The EHL model and friction torque model of ball screws have been established simultaneously, considering the ground surface topography of the raceway and the geometric features of the textures manufactured on the raceway surface. The friction reduction mechanism of the textured raceway of ball screws is elucidated in detail from the microscopic point of view, and the influence of the geometric features of the textures on the anti-friction characteristics of ball screws under different axial loads and rotation speeds is further analyzed and discussed. The proof-of-principle experiments of the friction-reducing performances of the textured raceways of the ball screws are conducted. The textured raceway of the ball screws provides an effective anti-friction effect that reduces the friction coefficient of the contact system of the ball screws by 15.2% at a normal contact force of 60.23 N, an entrainment speed of 167.5 m/s, a texture diameter of 40 μm, a texture depth of 10 μm and a texture areal density of 10%. Full article