Search Results (18)

Marine propulsion shaft alignment is affected by bearing offsets, hull deformation, thermal growth, and condition-dependent propeller and gear loads. An alignment scheme optimized for a single condition may therefore lead to unbalanced bearing reactions or excessive shaft-line deformation in service. To improve multi-condition alignment performance while reducing the reliance on repeated direct finite element evaluations during optimization, this study proposes a hybrid surrogate-assisted multi-objective optimization framework for a container-ship propulsion shafting system. A beam finite element model based on Euler–Bernoulli theory is established and numerically checked using jack-up calculations. Cold static, hot operating, and zero-pitch conditions are considered. Bearing-load uniformity, maximum coupling vertical offset, and maximum shaft slope are selected as objectives. According to response characteristics, an extremely randomized trees model is used for the nonlinear load-uniformity response, whereas response surface models are used for the smoother coupling-offset and shaft-slope responses. The Pareto front is obtained using multi-objective particle swarm optimization, and a compromise scheme is selected using entropy-weighted TOPSIS. For the investigated case, the preferred scheme reduces the three objectives by 44.36%, 38.62%, and 8.65%, respectively, relative to the pre-optimization scheme, and finite element recalculation gives prediction deviations below 5%. The proposed framework provides a practical reference for propulsion shaft alignment optimization under operating conditions. Full article

Heat pump technology can efficiently recover waste heat from oil and gas gathering, processing, and transportation. However, the energy transfer mechanism of high-speed rotating internal flow in the scroll compressor remains unclear under unbalanced load conditions, leading to low equipment energy efficiency and high operation and maintenance costs. This study adopted dynamic grid technology, finite element analysis and one-way thermal–fluid–solid coupling method to quantitatively study the flow field characteristics and mechanical response of four characteristic phases. The results showed that the internal pressure and temperature fields of the compressor presented a non-uniform distribution. The deformation of the scroll wraps was mainly concentrated in the compression chamber, and the maximum stress was concentrated at the wraps’ root. Further analysis revealed that temperature loading played a dominant role in the structural responses. At a spindle rotation angle of 0°, under temperature loading alone, the maximum deformation and maximum stress were 28.605 μm and 521.81 MPa, respectively, while the corresponding values under pressure loading alone were small. In addition, the deformation and stress under coupled loading were not a linear superposition of the individual loading effects, with a deformation deviation of 0.938 μm and a stress deviation of 7.18 MPa at a spindle rotation angle of 0°. In this study, a numerical model of the scroll compressor was established and experimentally verified, which provided a theoretical basis for optimizing scroll profile design, suppressing wrap tip wear and improving the energy efficiency of heat pump systems. Full article

To address the vibration and noise issues induced by inertial forces in marine V-type air compressors during operation, this study systematically investigates inertial force balancing and optimization. Based on dynamic analysis, analytical expressions for the first- and second-order reciprocating inertial forces and the rotating inertial force under unbalanced conditions are precisely derived. Considering the characteristics of a V-type air compressor with a V-angle of γ = 60°, the synthesis model of the first-order reciprocating inertial force is modified. The positive–negative rotating wheel system method is employed for preliminary balancing design, and the rigid–flexible coupling dynamics theory is innovatively introduced to construct a high-precision multi-body dynamics model that accounts for the flexible deformation of the crankshaft and connecting rod. Through joint simulation using ANSYS (2024R1) and Adams (2024.2), the dynamic responses of the pure rigid-body model and the rigid–flexible coupling model are compared to determine the optimal balancing configuration. The Adams/Insight module is utilized to perform multi-objective optimization of the balance iron mass. Results indicate that the rigid–flexible coupling model more accurately reflects the dynamic characteristics of the air compressor compared to the pure rigid-body model, significantly enhancing simulation accuracy. The optimized balance iron configuration effectively suppresses system vibration, with the peak X-direction bearing reaction force decreasing from 3750 N to 3610 N (a reduction of 3.7%), the vibration intensity reducing by 45.3%, and the radiated noise sound power level decreasing by 7.45%. This study provides a systematic theoretical approach and technical pathway for vibration and noise reduction, as well as for structural reliability design of marine air compressors. Full article

Steel slag is a major solid waste generated by the steelmaking industry. Its characteristics, including high hardness and large specific surface area, offer the potential to replace traditional mineral fillers in asphalt mixtures. However, the high alkalinity of unmodified steel slag often leads to unbalanced rheological properties and insufficient moisture stability in asphalt mastic. In this study, a modified steel slag filler was prepared using a process involving crushing and screening, water washing for dealkalization, and surface modification with a silane coupling agent. Using limestone powder and hydrated lime as control groups, the modification effects on base asphalt mastic were systematically investigated. Rheological properties were characterized using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Interfacial performance was evaluated through pull-off tests and water immersion dispersion tests. Furthermore, mechanisms were elucidated using X-ray Fluorescence (XRF), BET specific surface area analysis, and surface free energy (SFE) tests. The results indicate that the modified steel slag significantly enhances the high-temperature deformation resistance of the asphalt mastic. At 58 °C, the complex modulus reached 7.3 MPa, representing increases of 43.3% compared to limestone powder mastic. At −18 °C, the creep stiffness increased by only 3.0%, suggesting that low-temperature cracking resistance remained fundamentally stable. The water immersion dispersion loss rate was 2.12%, and the attenuation rate of pull-off strength after water immersion was 12.5%, indicating that its resistance to moisture damage is superior to that of limestone powder and comparable to that of hydrated lime. Mechanism analysis reveals that the large specific surface area of the modified steel slag strengthens physical adsorption, while the basic oxides undergo a weak acid–base reaction with the acidic components of the asphalt. Additionally, surface modification improves compatibility. The preparation process for modified steel slag is simple; it can be used as a standalone substitute for traditional mineral fillers, balancing both performance and environmental benefits. Full article

The air turbine starter (ATS) of an aero-engine incorporates a high-speed, high-energy rotor. An uncontained failure of the ATS could lead to catastrophic consequences, making containment capability research critically important. This study proposes a comprehensive evaluation methodology for ATS containment. A full-scale finite element model of the whole structure of an ATS was established to analyze containment characteristics and structural deformation patterns. Furthermore, an experimental method for ATS containment testing was designed to investigate the containment process and critical structural damage. By integrating simulation and experimental results, the load transfer paths and structural dynamic response of the ATS were systematically analyzed. The results demonstrate that sudden high-energy loads primarily follow two distinct transfer paths, each causing completely different structural damage behaviors. After the turbine wheel is broken, the resulting unbalanced load causes turbine shaft oscillation, which, in turn, compresses the bearings and damages their inner and outer rings. This research provides valuable guidance for the structural design of air turbine starters. Full article

The model explicitly incorporates boundary conditions that account for the complex interplay between sections experiencing varying degrees of reduction. This interaction significantly influences the overall deformation behavior and force loading. The control effect is associated with boundary conditions determined by the unevenness of the compression, which have certain quantitative and qualitative characteristics. These include additional loading, which is less than the main load, which implements the process of plastic deformation, and the ratio of control loads from the entrance and exit of the deformation site. According to this criterion, it follows from experimental data that the controlling effect on the plastic deformation site occurs with a ratio of additional and main loading in the range of 0.2–0.8. The next criterion is the coefficient of support, which determines the area of asymmetry of the force load and is in the range of 2.00–4.155. Furthermore, the criterion of the regulating force ratio at the boundaries of the deformation center forming a longitudinal plastic shear is within the limits of 2.2–2.5 forces and 1.3–1.4 moments of these forces. In this state, stresses and deformations of the plastic medium are able to realize the effects of plastic shaping. The force effect reduces with an increase in the unevenness of the deformation. This is due to a change in height of the longitudinal interaction of the disparate sections of the strip. There is an appearance of a new quality of loading—longitudinal plastic shear along the deformation site. The unbalanced additional force action at the entrance of the deformation source is balanced by the force source of deformation, determined by the appearance of a functional shift in the model of the stress state of the metal. The developed theory, using the generalized method of an argument of functions of a complex variable, allows us to characterize the functional shift in the deformation site using invariant Cauchy–Riemann relations and Laplace differential equations. Furthermore, the model allows for the investigation of material properties such as the yield strength and strain hardening, influencing the size and characteristics of the identified limit state zone. Future research will focus on extending the model to incorporate more complex material behaviors, including viscoelastic effects, and to account for dynamic loading conditions, more accurately reflecting real-world milling processes. The detailed understanding gained from this model offers significant potential for optimizing mill roll designs and processes for enhanced efficiency and reduced energy consumption. Full article

Carbon staple fiber composites are materials reinforced with discrete-length carbon fibers processed using traditional textile technologies, offering moderate mechanical properties and flexibility in manufacturing. These composites can be produced from recycled carbon staple fibers, aligned into yarn and tape-like structures, providing a more sustainable alternative while balancing performance, cost-effectiveness, and environmental impact. Aligning staple fibers into tape-like structures enables similar applications to those of continuous-fiber-based products, while allowing control over fiber orientation distribution, fiber volume fraction, and length distribution, which are all critical factors influencing both mechanical and thermo-mechanical properties. This study focuses on the experimental characterization and numerical investigation of Coefficients of Thermal Expansion (CTEs) in aligned carbon staple fiber composites. The effects of fiber orientation and volume fraction on coefficients of thermal expansion under different fiber alignment parameters are analyzed, revealing distinct thermal expansion behavior compared to typical aligned unidirectional continuous carbon fiber composite laminates. Unlike continuous unidirectional laminates, which typically exhibit transversely isotropic behavior without tensile–shear coupling, staple fiber composites demonstrate different in-plane axial, transverse, and out-of-plane CTE characteristics. To explain these deviations, a modeling approach is introduced, incorporating detailed experimental information on fiber distributions and microstructural features rather than averaged fiber orientation values. This involves a multi-scale analysis based on a laminate analogy through which all composite thermo-elastic properties can be predicted, accounting for variations in fiber orientations, volume fractions, and tape thicknesses. It is shown that while the local variation of fiber volume fraction has a small effect on the homogenized value of the coefficients of thermal expansion, fiber misalignment, tape thickness, and asymmetry in fiber orientation distribution will significantly affect the measurements of CTEs. For the case of carbon staple fiber composites, the asymmetry in fiber orientation distribution significantly influences the measurements of axial CTE. Fiber orientation asymmetry causes tensile–shear coupling under mechanical and thermal loading, leading to an unbalanced laminate with in-plane shear–tensile deformation. This coupling disrupts uniform displacement, complicating strain measurements and the determination of composite properties. Full article

During the transient process of load rejection, the hydraulic pressure applied to the pump-turbine and plant concrete changes dramatically and induces high dynamic stress on the spiral case. The preloading spiral case has been widely used in large-scale pumped-storage power stations due to its excellent load-bearing capacity. However, studies on the impact of preloading pressure on the structural response during load rejection are still few in number. In this paper, 3D flow domain and structural models of a prototype pump-turbine are designed to analyze the hydraulic characteristics and flow-induced dynamic behavior of the preloading steel spiral case under different preloading pressures during load rejection. The results show that the asymmetric design of the logarithmic spiral lines ensures an axially symmetric potential flow within the spiral case domain with uniform pressure distribution. Higher preloading pressure provides larger preloading clearance, leading to greater flow-induced deformation and stress, with their maximum values located at the mandoor and the inner edge, respectively. The combined effect of the asymmetrical shape, internal hydraulic pressure and unbalanced hydraulic force leads to an asymmetrical preloading clearance distribution, resulting in an asymmetrical distribution along the axial direction but a symmetrical characteristic near the waistline of the structural response. Stress variations at sections and between sections share similar characteristics during load rejection. It follows the same trend as the hydraulic pressure under lower preloading pressures, while there is a delayed peak of stress due to the delayed contact phenomenon when the preloading pressure reaches the maximum static head. The conclusions provide scientific guidance for optimizing the preloading pressure selection and structural design for the stable operation of units. Full article

The hydrodynamic characteristic of the multiphase mixed-transport pipeline is essential to guarantee safe and sustainable oil–gas transport when extracting offshore oil and gas resources. The gas–liquid two-phase transport phenomena lead to unstable flow, which significantly impacts pipeline deformation and can cause damage to the pipeline system. The formation mechanism of the mixed-transport pipeline slug flow faces significant challenges. This paper studies the formation mechanism of two-phase slug flows in mixed-transport pipelines with multiple inlet structures. A VOF-based gas–liquid slug flow mechanical model with multiple inlets is set up. With the volumetric force source term modifying strategy, the formation mechanism and flow patterns of slug flows are obtained. The research results show that the presented strategy and optimization design method can effectively simulate the formation and evolution trends of gas–liquid slug flows. Due to the convective shock process in the eight branch pipes, a bias flow phenomenon exists in the initial state and causes flow patterns to be unsteady. The gas–liquid mixture becomes relatively uniform after the flow field stabilizes. The design of the bent pipe structure results in an unbalanced flow velocity distribution and turbulence viscosity on both sides, presenting a banded distribution characteristic. The bend structure can reduce the bias phenomenon and improve sustainable transport stability. These findings provide theoretical guidance for fluid dynamics research in offshore oil and gas and chemical processes, and also offer technical support for mixed-transport pipeline sustainability transport and optimization design of channel structures. Full article

Micropile groups have been progressively more frequently adopted in the construction of transmission tower bases due to their compact size and flexible construction advantages. However, the load-bearing characteristics and deformation mechanisms of micropile groups are complex, and the study of their coupling effects under combined loads remains unclear. Consequently, this paper presents a field static load test of micropile groups in a highland mountainous area. The analysis encompasses the axial force distribution and load-sharing ratio of micropiles. With a focus on micropile groups subjected to both uplift and horizontal combined loads, the coupled effects under different load combination ratios are examined using numerical simulation methods. The key findings are as follows: During the uplift loading process, the load distribution among individual piles is relatively uniform, with lower side friction resistance gradually coming into play to counterbalance the top load. The load–uplift displacement curve exhibits a steep characteristic, making it susceptible to sudden failure in practical engineering applications. Under the simultaneous action of uplift (V) and horizontal (H) loads, the unbalanced lateral frictional resistance on both sides of the pile segment induces additional bending moments, which is an important part affecting the load-coupling mechanisms. The uplift resistance capacity of micropile groups decreases with an increase in horizontal load, while the horizontal load-carrying capacity initially decreases and then increases with an increase in uplift load. The space enclosed by the yield envelope under combined load, and the vertical line of the ultimate load, is divided into a ‘failure zone’ and a ‘safety zone.’ In the design of the pile foundation, the uplift bearing capacity reduced by the ‘failure zone’ should be taken into account. Full article

The fracturing behaviors of serial coal pillars is significant for understanding their failure mechanism. To reveal this, the bearing stress, acoustic emission, electrical resistivity, local strain, force chain distribution, and cracks evolution of serial coal pillars under uniaxial compression were evaluated by experiment and numerical simulation. The results show that four bearing stages are observed during the fracturing process (i.e., nonlinear growth, linear growth, yielding growth, and weakening stages). The acoustic emission features, electrical resistivity responses, strain develops, force chain distributions, cracks evolutions, and local displacement are highly consistent to illustrate the fracturing behaviors. System fracturing of serial coal pillar specimens is appeared along with the collapse of lower uniaxial compressive strength coal pillar specimen. The limit bearing capacity of serial coal pillar specimens is almost equal to the strength of lower uniaxial compressive strength coal pillar specimen. The unbalanced deformation characteristics of serial coal pillar specimens are presented due to the strength differences. The evolution of the key deformation element is the rooted reason for the overall fracturing mechanism of serial coal pillar specimens. For serial coal pillar specimens with different strengths, the critical condition of system fracturing is that the sum of secant modulus of upper and bottom coal pillars is zero, which is expected to predict the system fracturing of serial pillars in the underground coal mining. Full article

In view of the occurrence conditions of inclined coalbed, the deformation and failure characteristics of the main roof will affect the safe production of the working face. Therefore, the study of the deformation and failure characteristics of the main roof in the inclined coalbed has guiding significance for the control of surrounding rock. This paper takes the II1042 working face of Taoyuan Coal Mine as the research background, adopts the methods of theoretical analysis, numerical calculation, and field practice to analyze the evolutionary characteristics of the initial failure of the main roof of the working face under the background of the inclined coalbed, and explores the mechanical behavior characteristics of the working face roof during the mining of inclined coalbed. Based on the elastic thin plate theory, a mechanical model of the overlying rock roof of a large-angle coal seam is established, and the mechanical characteristics of the surrounding rock under the initial failure of the main roof under the unbalanced load are studied. The stress distribution characteristics of the lower surface are summarized, and the evolution law of the initial fracture of the main roof is summarized. According to the actual geological conditions of the II1042 working face of Taoyuan Coal Mine, the failure characteristics of the main roof and the initial breaking step distance are obtained by analysis, and the analysis results are verified by monitoring the mine pressure of each part of the target working face on site. The research results show that: ① Under the unbalanced load of the inclined coalbed, the deflection surface of the main roof of the coal seam is asymmetrical with respect to the arrangement direction of the working face, and the maximum deflection point is located at the upper middle position of the working face, namely (a/2, 1.836 b/π), and the main roof of the working face breaks for the first time when it advances to 35 m. ② With the advancement of the working face, the two long sides of the roof break first. With the deflection and deformation of the roof, the tensile stress in the middle of the main roof reaches the tensile strength of the rock and breaks, and then the two short sides of the roof break under the action of the breaking and turning of the rock, and the upper short side will break before the lower one. ③ According to the monitoring and analysis of the rock pressure at each part of the working face, it is judged that the initial pressure step distance is between 28.2 m and 34.6 m, which is consistent with the theoretical analysis results. Full article

The motion information of blades is a key reflection of the operation state of an entire wind turbine unit. However, the special structure and operation characteristics of rotating blades have become critical obstacles for existing contact vibration monitoring technologies. Digital image correlation performs powerfully in non-contact, full-field measurements, and has increasingly become a popular method for solving the problem of rotating blade monitoring. Aiming at the problem of large-scale rotation matching for blades, this paper proposes a modified speeded-up robust features (SURF)-enhanced digital image correlation algorithm to extract the full-field deformation of blades. Combining an angle compensation (AC) strategy, the AC-SURF algorithm is developed to estimate the rotation angle. Then, an iterative process is presented to calculate the accurate rotation displacement. Subsequently, with reference to the initial state of rotation, the relative strain distribution caused by flaws is determined. Finally, the sensitivity of the strain is validated by comparing the three damage indicators including unbalanced rotational displacement, frequency change, and surface strain field. The performance of the proposed algorithm is verified by laboratory tests of blade damage detection and wind turbine model deformation monitoring. The study demonstrated that the proposed method provides an effective and robust solution for the operation status monitoring and damage detection of wind turbine blades. Furthermore, the strain-based damage detection algorithm is more advantageous in identifying cracks on rotating blades than one based on fluctuated displacement or frequency change. Full article

Close extra-thick coal seams are subject to the broken overburden of mined coal seams, and the deformation and damage of the roadways is serious, which affects the safe operation of the mine. To reduce the deformation and damage of the roadways, this paper studied the deformation and damage law of the gob-side roadway in close extra-thick coal seams through numerical simulation and field monitoring, compared and analyzed the deformation and damage characteristics of the roadway under different reinforcement support methods, determined the optimal reinforcement support method, and carried out field verification. The obtained results indicated that the deformation and damage of the gob-side roadway showed asymmetric characteristics. The large deformation of the coal body in the deep part of the roadway wall is an important reason for the continuous occurrence of roadway wall heave in the coal pillar. Under the action of unbalanced support pressure, the floor is subject to the coupling effect of horizontal extrusion pressure and vertical stress that cause extrusion mobility floor heave. The horizontal and vertical displacement of the coal pillar side of the roadway under different support methods is much larger than that of the solid coal side. Increasing the anchor cable length and fan-shaped arrangement can improve the support effect. Grouting at the coal pillar side can significantly improve the bearing capacity and stability of the coal pillar. The effect of floor grouting is much better than the anchor cable in controlling the floor heave. The integrated reinforcement method of anchor cable + coal pillar side grouting + floor grouting has the best effect with the least horizontal and vertical deformation. The research results are of great significance for ensuring the stability of similarly endowed roadways. Full article

This paper presents a comparison of two variants of an axial flux magnetic gear (AFMG), namely, with integer and fractional gear ratios. Based on calculations derived with the use of three-dimensional numerical models, the torque characteristics of the analyzed AFMGs are computed and verified on a physical model. The greatest emphasis is put on the detailed decomposition and analysis of local forces in modulator pole pieces (also used in the structural analysis) within the no-load and maximal load conditions. The authors also describe the unbalanced magnetic forces (UMF) in the axial and radial directions resulting from the construction of the considered AFMGs variants, and their possible effects in the context of the use of additive manufacturing (AM) in prototypes. The paper also proposes an effective method for limiting the axial strain by using the asymmetry of the air gaps, which slightly reduces the torque transmitted by AFMGs. Finally, a static strength analysis was presented that allows us to assess the effects of local forces in the form of modulator disc deformation for selected cases of air gap asymmetry. Full article