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Contact problem of herringbone gears is complex due to the sensitivity to the inevitable manufacturing errors and elasticity deformation. A new semi-analytical slice (SAS) model of herringbone gears is developed in this paper for analyzing the elastic contact behavior with errors. The geometry model of herringbone gears is established, in which the herringbone gears are discretized into slices and errors are explicitly depicted. The elasticity of herringbone gears is efficiently and accurately addressed by the semi-analytical method combining the advantage of analytical method and finite element (FE) method. Based on the geometry and elasticity modeling, the SAS model of herringbone gears is developed by the derivation of compatibility and equilibrium equations. Upon the model, the mesh stiffness, transmission error (TE) and load distribution behavior of herringbone gears considering the elasticity and errors are analyzed. The effectiveness of the SAS model is verified by the FE model in ANSYS software. It is expected that the proposed SAS model is significant to the analysis and optimization for the herringbone gear transmission. [ABSTRACT FROM AUTHOR]

The increasing emphasis on environmental sustainability and stricter gas emissions regulations has made the optimization of fuel and emissions a crucial factor for marine propulsion systems. This paper investigates the potential to improve fuel efficiency and reduce emissions of LNG ship propulsion systems by using different load sharing strategies in Dual-Fuel Diesel-Electric (DFDE) propulsion systems. Using data collected from on-board cyclic measurements and an optimization model, the effects of different load sharing strategies for various types of fuel, such as HFO, MDO, and LNG, under different engine load conditions were investigated. The results of these strategies are compared with those of on-board power management systems (PMS), which evenly allocate power among the engines, irrespective of fuel usage and emission levels. The results show that load adjustments according to the optimization model can considerably increase fuel economy and contribute to the reduction of CO2 and NOx compared to standard practice at the equal load in different ship operating modes. Our approach introduces an innovative optimization concept that has been proven to improve fuel efficiency and reduce emissions beyond standard practices. This paper demonstrates the robustness of the model in balancing environmental and operational objectives and presents an effective approach for more sustainable and efficient ship operations. The results are in line with global sustainability efforts and provide valuable insights for future innovations in energy optimization and ship emission control. [ABSTRACT FROM AUTHOR]

This study investigated the failure mode of pre-tensioned bonded hybrid joints in steel structures using Digital Image Correlation (DIC) alongside Finite Element Analysis (FEA) and compared the results with those of adhesive bonded joints of identical geometry. While all joint types initially exhibited ideal adhesive joint behaviour at low loading levels, with linear elastic response, differences emerged as loading increased. In particular, hybrid joints exhibited out-of-plane deformations near the ends of the splice plates, a feature not observed in bonded joints. Shear deformations consistently peaked at the ends of the overlap for all joint types and increased with increasing load levels. In contrast to bonded joints, hybrid joints demonstrated resilience under escalating loads, maintaining resistance due to the presence of bolts despite the increased deformations. This study contributes to the understanding of the observed failure mode: while hybrid joints initially resembled ideal bonded joints at lower loads, increasing loads caused critical cracks to initiate at the overlap ends in the adhesive layer, culminating in bonded joint failure. In conclusion, this study has elucidated the failure mode of hybrid joints, providing insights for modelling and dimensioning in steel structures. [ABSTRACT FROM AUTHOR]

Introduction: Urban power load forecasting is essential for smart grid planning but is hindered by data imbalance issues. Traditional single-model approaches fail to address this effectively, while multi-model methods mitigate imbalance by splitting datasets but incur high costs and risk losing shared power distribution characteristics. Methods: A lightweight urban power load forecasting model (DLUPLF) is proposed, enhancing LSTM networks with contrastive loss in short-term sampling, a difference compensation mechanism, and a shared feature extraction layer to reduce costs. The model adjusts predictions by learning distribution differences and employs dynamic class-center contrastive learning loss for regularization. Its performance was evaluated through parameter tuning and comparative analysis. Results: The DLUPLF model demonstrated improved accuracy in forecasting imbalanced datasets while reducing computational costs. It preserved shared power distribution characteristics and outperformed traditional and multi-model approaches in efficiency and prediction accuracy. Discussion: DLUPLF effectively addresses data imbalance and model complexity challenges, making it a promising solution for urban power load forecasting. Future work will focus on real-time applications and broader smart grid systems. [ABSTRACT FROM AUTHOR]

An effective approach to deal with the structural failures of transmission towers in tornadic events is to develop good structural health monitoring (SHM) systems for them. However, the strategy for SHM of transmission towers against tornados should be different from the conventional atmospheric boundary layer (ABL) winds oriented ones, as the non-stationary nature of the tornados significantly differentiates them from the ABL winds. To satisfy the need of obtaining the highly time-varying whole-field stress on the structure in the course of the tornadic event for effective SHM, an innovative transient tornadic load distribution identification method is proposed for use, which is based on the field structural mode shape measurement and dynamic finite-element (FE) model updating. Via a numerical case study, it is noted that good effectiveness is achieved for the new load distribution identification method. Employing the Modal Assurance Criteria based FE model updating technique, the new method has the advantage of being easily embraced in practical SHM systems. It is found that when the transient tornadic velocity profile to be identified is noticeably different from the mode shape of the structure without undertaking external loads, the identified load pattern is very accurate for the new approach. [ABSTRACT FROM AUTHOR]

With the rapid growth and development of Internet of Things (IoT) and smart mobile devices, the volume of data generated at the network edge has increased significantly. Mobile edge computing (MEC) has emerged as a pivotal technology to address the computational limitations of these devices by bringing cloud capabilities closer to end users. However, MEC still faces two critical challenges: edge server placement (ESP) and load distribution. The first problem involves determining the optimal locations for a set of heterogeneous computational servers within a given network of base stations (BSs) and their associated workload. The objective is to strategically position these servers to ensure efficient computational resource allocation and to enhance the quality of service (QoS) for end users. The second problem is the distribution of computational tasks/requests, which itself comprises two sub-problems: (a) identifying the most suitable server for the requests arriving at each BS, and (b) scheduling these requests on the selected servers. This paper addresses these challenges through a comprehensive approach. We model these problems using a mixed-integer nonlinear programming (MINLP) framework. For the ESP problem, the goal is to achieve load balancing among servers. For the load distribution problem, the objectives are to minimize response time and ensure that user request deadlines are met. To address these problems, we propose an ant colony optimization (ACO) algorithm to efficiently solve the ESP problem, ensuring balanced load among servers. For the load distribution problem, we introduce two heuristic algorithms: one for selecting the most suitable server to distribute incoming workloads from devices, and another for scheduling requests on each server based on their urgency and importance. We validate our proposed approach through extensive experiments using real-world data from Shanghai Telecom base stations. The experimental results demonstrate that our approach significantly outperforms state-of-the-art methods in terms of load standard deviation, average request response time, and the percentage of deadlines successfully met. Specifically, our method improves load balancing by 57.6%, reduces the average response time by 50.7%, and increases deadline compliance by 35.2%. These findings underscore the efficacy of our proposed methods in enhancing MEC system performance, thereby delivering superior QoS and user experience in IoT and mobile computing applications. [ABSTRACT FROM AUTHOR]

In modern cloud-based computing through pooled resources, service providers must ensure resource accessibility. The migration of workloads to the cloud necessitates careful planning, including the provision of a sufficient number of easily available virtual machines (VMs). This paper addresses the NP-hard problem of load distribution by proposing an advanced scheduling technique designed to tackle this issue directly. The main goal of the investigation is to maximize the assignment of tasks among virtual machines (VMs), ensuring an evenly distributed workload throughout the entire system. We proposed a new method to enhance the distribution of work in cloud-based structures, leveraging insights from spider monkey foraging habits. The proposed optimization technique tries to increase efficiency by strategically distributing jobs to the VMs with the least workload. The algorithm demonstrates robust performance in simulations evaluating load distribution, response time, and efficiency across several task types. The suggested load distribution technique demonstrates substantial enhancements compared to current methods, with an amazing 85% effectiveness in distributing the workload across 20 concurrent tasks. The proposed method outperforms existing algorithms, such as Improved Ant Colony Optimization and Particle Swarm Optimization—Artificial Bee Colony, which achieve load-balancing rates of 70% and 75%, respectively. This paper elucidates the intricacies of workload distribution in cloud-based computing systems while proposing a comprehensive method to improve resource consumption and overall system efficiency, hence advancing distributed computing settings. [ABSTRACT FROM AUTHOR]

Load distribution is a very important indicator that has a great effect on bearing service performance. Unreasonable load distribution is likely to accelerate the bearing failures. The dynamic effects of the moving parts of the rolling bearing have significant influence on the load distribution. In order to study the load distribution of rolling bearings, the dynamic interaction between raceways and balls is considered in detail and a dynamic model of ball bearings subjected to radial loads is presented. The results of the proposed model are compared with those of the traditional static model and the quasi‐static model. The dynamic load coefficient and the dynamic angular extent coefficient are defined to show the characteristics of the dynamic load distribution. The effects of radial clearance, the radial load, and the rotational speed on the dynamic load distribution are studied. Through the above research, this paper concludes that the load distribution is greatly influenced by the dynamic effects of moving parts, especially under the conditions of large clearance, light load, or high speed. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In a sustainable energy system, managing the charging demand of electric vehicles (EVs) becomes increasingly critical. Uncontrolled charging behaviors of large-scale EV fleets will exacerbate loads imbalanced in a multi-microgrid (MMG). At the same time, the time cost of users will increase significantly. To improve users' charging experience and ensure stable operation of the MMG, we propose a new joint scheduling strategy that considers both time cost of users and spatial load balancing among MMGs. The time cost encompasses many factors, such as traveling time, queue waiting time, and charging time. Meanwhile, spatial load balancing seeks to mitigate the impact of large-scale EV charging on MMG loads, promoting a more equitable distribution of power resources across the MMG system. Compared to the Shortest Distance Matching Strategy (SDMS) and the Time Minimum Matching Strategy (TMMS) methods, our approach improves the average peak-to-valley ratio by 9.5% and 10.2%, respectively. Similarly, compared to the Load Balancing Matching Strategy (LBMS) and the Improved Load Balancing Matching Strategy (ILBMS) methods, our approach reduces the average time cost by 31.8% and 25% while maintaining satisfactory spatial load balancing. These results demonstrate that the proposed method achieves good results in handling electric vehicle scheduling problems. [ABSTRACT FROM AUTHOR]

It is important to study damage evolution as well as failure of carbon fiber reinforced polymer (CFRP) plates bolted joints. Therefore, the quasi‐static tensile test on single‐lap and double‐lap CFRP plates bolted joints was conducted. Meanwhile, the tensile strength prediction model for titanium alloy bolted joint of CFRP plates was established based on the improved 3D Hashin failure criterion, then a theoretical model was proposed to accurately predict the load distributions and tilt angle of bolted joints. Thus, the load–displacement curves were divided into four stages, and load distributions at different stage points as well as the relationship between tilt angle of bolt and load variation were obtained. The damage evolution of single‐lap and double‐lap at different stage points was analyzed respectively, and failure mechanisms were revealed based on load distribution. The results show that the ultimate failure of single‐lap is caused by the intrusion of bolt head into CFRP plates, while double‐lap is caused by the compression deformation of central plate. The numerical simulation works are in high agreement with the experimental results. Highlights: Calculate the load distribution at single‐lap and double‐lap bolted joints.Obtain the relationship between bolts tilt angle and load variation.Analysis of damage evolution in bolt‐hole wall of carbon fiber reinforced polymer (CFRP) plates.Using loads to reveal the failure mechanisms of single‐lap and double‐lap bolted joints of CFRP plates. [ABSTRACT FROM AUTHOR]

(1) Background: Alpine skiing, with its long history, has experienced numerous innovations and developments on all levels ranging from technology to fashion over the past 120 years. However, teaching approaches for beginners remained quite consistent for many decades and are mainly grounded in experience. The One-Ski-Method (OSM) is an alternative approach to the predominant snowplow (SP) method with the strategy to initially experience and acquire the elementary positions and actions on one ski in order to subsequently transfer these to two skis. The aim of the study was to compare the effects of the SP and the OSM by assessing the position of the ski via load distribution sensors. (2) Methods: A total of 33 participants were groupwise randomly assigned to the two methods and tested via load insoles on the first and the fifth day on a moderate slope for six turns. Between the two measurements, the groups were instructed according to the SP or the OSM methods, respectively. The data were analyzed via Matlab and SPSS. (3) Results: The OSM group showed a significantly greater forefoot load than the SP group (p = 0.029). The SP group developed a greater rearfoot loading from pre- to post testing. (4) Conclusions: The findings make it perceivable that OSM learners acquire a beneficial specific position on the ski due to the exercises of the OSM. [ABSTRACT FROM AUTHOR]

This study investigates adhesive bonding as a crucial engineering technique for joining materials, with a focus on load distribution, structural enhancement, and weight reduction. Advances in adhesive formulations, surface preparation, and application techniques continue to expand its capabilities. The research addresses stresses in hybrid joints resulting from pre-tensioning bolts and subsequent axial loading, emphasizing the influence of normal stresses on the critical adhesive-steel interface. Off-axis samples are bonded to mild steel using four different adhesives: SW7240, S370, DP460 (2K-epoxies), and SF479 (2K polyurethane). The choice of adhesive significantly influences shear strength under various loading conditions. Formulating this interaction in terms of maximum shear or von Mises stresses leads to relatively complex failure criteria that make the further analysis dependent on each adhesive. On the other hand, expressing strength at maximum principal stress significantly simplifies comparative analysis, as it consistently exhibits an almost linear trend, indicating strength reduction with increasing hydrostatic pressure for all adhesives, potentially simplifying subsequent strength predictions of hybrid joints. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Skewed steel I-girder bridges experience complex load distribution under live load that is not thoroughly understood, while standard design practice for such bridges consists of simplifications that should be further evaluated and verified. Commonly used line girder analysis (LGA) can estimate strong-axis bending stress through the application of a live load distribution factor (LLDF) that considers the skew effect from 30° to 60°, and it accounts for skew-related lateral response by simply adding a flange lateral bending stress for skew exceeding 20°. Since LGA calculations related to skew do not account for bridge width, and because girder lateral bending response is considered in a simplified fashion, further refinement may be possible. In addition, the widely used practices of designing exterior and interior girders with the same demand and analyzing stub and integral abutment bridges in a similar way need to be further assessed. This paper evaluates the effect of bridge geometric parameters—including skew of 0°–70°, bridge width ranging from 8 to 26 m (27–84 ft), and abutment type (stub versus integral)—on skewed steel I-girder bridge response through a numerical parametric study (using field-validated models), considering live load positioning across the width of a bridge. The distribution of girder strong-axis and lateral bending stress was analyzed, with peak stress compared to LGA calculations. Exterior girders were generally observed with larger strong-axis bending stress but smaller lateral bending stress (versus interior girders) when directly loaded; estimating girder strong-axis bending stress using LGA with a controlling LLDF for all girders can be overly conservative for interior girders. The distribution of strong-axis and lateral bending stress on a skewed bridge with either stub or integral abutments was also found to be dependent on live load positioning, with peak stress closer to bridge obtuse corners (away from bridge midspan) as skew increases. The standard practice of providing a minimum distance between the bridge end and the first intermediate cross-frame was confirmed to be important to avoid lateral bending stress concentration near bridge obtuse corners. Girder response near the bridge pier was generally less significant than that along bridge spans under live loading, except for exterior girder flange lateral bending stress. Near the pier, bottom flange lateral bending stress increases with increasing skew, while interior and exterior girders behave differently under the skew effect for strong-axis bending stress. [ABSTRACT FROM AUTHOR]

The combination of metal and composite in threaded couplings increases the reliability of the structure operating under conditions of intensive internal pressure. Strength analysis of threaded metal – composite couplings based on the application of modern finite element modeling methods at the stage of design documentation development allows to create more efficient structures that better meet the operational requirements. The strength of threaded couplings of cylindrical shells made of composite material and metal under the action of gas-dynamic internal pressure is analyzed in this paper. A methodology for numerical study of the problem in Ansys / Explicit Dynamics software package is proposed. Detailed modeling of threaded couplings is used. The developed model takes into account the following: dependence of material properties on ambient temperature; nonlinear relations between the components of stress and strain tensors in metal elements, orthotropic properties of composite materials; peculiarities of contact interaction in the zones of threaded couplings of prefabricated shell elements made of different materials. The stress state of a cylindrical structure with a central shell made of carbon fiber-reinforced plastic or fiberglass and with steel shells at the edges, loaded with gas-dynamic internal pressure with a maximum value of 20 MPa at a maximum ambient temperature of 100 °С was studied. It was obtained that plastic deformations are concentrated on the edges of the threaded couplings of steel shells. At the same time, the magnitude of plastic coupling deformations with the inner metal shell is an order of magnitude higher than for couplings with the outer metal shell. The magnitude of plastic deformations in couplings with an inner metal shell is twice less when using fiberglass than when using carbon fiber reinforced plastic. Localization of critical stresses was observed only in metal shells at threaded couplings. In this case, in the thread zone they are within the elasticity limits, and the stress state of the FRP shell is not critical. No local material failure was observed in the structure.

Abstract Background While measuring meniscal extrusion quantitatively is an early risk factor for knee osteoarthritis (KOA), the biomechanics involved in this process are not well understood. This study aimed to investigate the effects of varying degrees of medial and lateral meniscal extrusion and their material softening on knee osteoarthritis progression. Methods Finite element analysis (FEA) was utilized to simulate varying degrees of meniscal extrusion (1–5 mm) in 72 knee joint models, representing progressive meniscal degeneration and material softening due to injury. Changes in von Mises stress of the cartilage and menisci and the load distribution on the tibial plateau’s meniscus and cartilage were studied under balanced standing posture in both healthy and injured knees, and statistical analysis was performed using Spearman correlation. Results Compared to healthy knees, peak stress in medial compartment tissues increased by over 40% with 4 mm of medial meniscus extrusion, and in lateral compartment tissues with 2 mm of lateral meniscus extrusion. Meniscus extrusion reduced the contact load between the meniscus and femoral cartilage but increased it between the tibial and femoral cartilages, with a maximum increase up to fivefold. Spearman correlation analysis indicated that meniscal extrusion significantly affected peak stress and contact loads in the respective knee compartment (p

It has been proved by experiments that the soft layers can effectively adjust the load distribution ratio of composite pre-tightened tooth connection, but theoretical research on the composite pre-tightened tooth connection embedded with soft layers has not been carried out. Therefore, in this work, the load distribution theory of composite pre-tightened tooth connection embedded with soft layers is studied by spring stiffness method. First, based on deformation compatibility condition, the theoretical calculation formula of load distribution ratio of each tooth is derived by spring stiffness method. Then, load distribution ratio is obtained by experiments, and the theoretical calculation results are verified. Finally, through the derived formula, the load distribution ratio of the composite pre-tightened tooth connection embedded with soft layers is parameterized. Research shows that (1) The theoretical value is in good agreement with the experimental value, and the maximum error of calculation result of the load distribution of the joint is 8%; (2) Under the action of soft layers, each tooth of two-teeth and three-teeth joints are damaged at the same time, the ultimate bearing capacity is increased by 29.0 and 21.6%, respectively, compared with the traditional two-teeth and three-teeth joints; (3) The elastic modulus and thickness of soft layers have a significant impact on the load distribution ratio of each tooth.

Highlights Carbon Fiber Reinforced Polymer (CFRP) Hybrid Bonded/Bolted (HBB) joint structures are distinguished for their superior jointing performance among current mechanical joint systems, making them a favored option for mechanical joints. These structures are characterized by many structural parameters, with the relationship between these parameters and jointing performance being notably complex. Additionally, the laminate's brittleness and the uneven distribution of bolt loads in multi‐bolt joint structures impair the overall jointing performance. To investigate the impact of structural parameters on the uneven load distribution within CFRP HBB joint structures and improve their jointing performance, a finite element analysis (FEA) model grounded in 3D Hashin failure criterion is developed. Validation of the model with experimental data confirmed the uneven load distribution among bolts in multi‐bolt joints. The study elucidated the influence of changes in structural parameters (overlap length, bolt‐hole spacing, and clearance fit) on the uneven load distribution and the connection strength of CFRP HBB joint structures. A negative correlation is found between the unevenness of load distribution and connection strength, offering insights for enhancing and researching connection strength in CFRP HBB joint structures. Developed a FEA model based on the 3D Hashin failure criterion for CFRP Bonded‐Bolted joints. Identified key factors affecting HBB joint load distribution and jointing performance. Evaluated the impact of overlap length, bolt‐hole spacing, and clearance fit on CFRP joints. Suggested design optimizations for enhancing the performance of HBB joints. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: While measuring meniscal extrusion quantitatively is an early risk factor for knee osteoarthritis (KOA), the biomechanics involved in this process are not well understood. This study aimed to investigate the effects of varying degrees of medial and lateral meniscal extrusion and their material softening on knee osteoarthritis progression. Methods: Finite element analysis (FEA) was utilized to simulate varying degrees of meniscal extrusion (1–5 mm) in 72 knee joint models, representing progressive meniscal degeneration and material softening due to injury. Changes in von Mises stress of the cartilage and menisci and the load distribution on the tibial plateau's meniscus and cartilage were studied under balanced standing posture in both healthy and injured knees, and statistical analysis was performed using Spearman correlation. Results: Compared to healthy knees, peak stress in medial compartment tissues increased by over 40% with 4 mm of medial meniscus extrusion, and in lateral compartment tissues with 2 mm of lateral meniscus extrusion. Meniscus extrusion reduced the contact load between the meniscus and femoral cartilage but increased it between the tibial and femoral cartilages, with a maximum increase up to fivefold. Spearman correlation analysis indicated that meniscal extrusion significantly affected peak stress and contact loads in the respective knee compartment (p < 0.001), with a lesser impact on the opposite compartment. Notably, medial meniscal extrusion also significantly increased peak stress in the lateral tibial cartilage (p < 0.05). Conclusions: The quantitative analysis revealed that meniscal extrusion significantly affected the biomechanics of soft tissues within the same compartment, with limited impact on the opposite side. Specifically, Medial extrusion beyond 4 mm significantly affected the biomechanics of the medial compartment, while lateral extrusion over 2 mm had a similar impact on the lateral compartment. Meniscal softening, without altering joint contact characteristics, primarily affected the biomechanics of the meniscus itself, with minimal impact on other soft tissues. [ABSTRACT FROM AUTHOR]

A novel static model of planetary roller screw mechanisms (PRSMs) is proposed to obtain the load distribution over threads by an energy method. The energy method consists of the structural potential energy and an optimization problem. The potential energy is calculated by structural discretization. And the optimization problem, whose objective is the structural potential energy, is obtained by combining the principle of minimum potential energy with the forces balance constraints. The load distribution is the result of the optimization problem. A finite element model is established for validation. Compared with previous models, the proposed model has lower complexity and higher precision. To further verify the reliability and practicability of the proposed model, effects of the nut position, shaft diameter, and number of roller threads on the load distribution are analyzed based on the proposed model. The results show that the nut position has little influence on the load distribution. The shaft diameter and number of roller threads significantly impact the load distribution. [ABSTRACT FROM AUTHOR]

Methods of mathematical modeling of the dependence of fuel consumption on the load of diesel gensets are considered. Accounting for such dependence in simulating the operation of solar-diesel hybrid power systems can reduce the consumption of diesel fuel and the operating hours of diesel generators. [ABSTRACT FROM AUTHOR]

Wave-induced forces pose significant challenges to marine structures, especially pile groups, where cap structures and pile spacings play critical roles in load distribution and structural stability. A physical wave flume experiment was conducted to investigate the influences of cap structures and pile spacings on wave load distributions under different wave conditions. Spatial and temporal variations in wave load distributions, including temporal variations in horizontal force, were measured as wave pressure rather than force. The results demonstrate that cap structures significantly alter the distributions of wave loads on pile groups. The integration of the cap increases the horizontal forces on the front pile and slightly reduces the vertical pressures across the pile group, particularly on the rear pile at relatively low elevations. The cap also delays the peak moment of horizontal force, especially in shallow water depths, where impact loads are more prominent and the cap induces water splash-back. Additionally, reducing pile spacing mitigates interference effects, optimizing the load distribution across piles by modulating flow velocity and pressure. The vertical pressure distribution exhibits a tiered pattern, with lower sections experiencing consistent loading, middle sections being subjected to higher loads at larger spacings, and upper sections being more affected by the cap at smaller spacings. As wave velocity and water depth increase, the differences in pressure intensity between pile groups with and without cap structures decrease, indicating the stabilizing effect of wave characteristics on structural response. This study provides insights into the design of marine pile group structures to optimize their performance characteristics under dynamic wave loading conditions. [ABSTRACT FROM AUTHOR]

The operational safety and stability of wind turbines are highly determined by the characteristics of main bearings, which are influenced by the axial clearance. In this paper, for the arrangement type of double-supported tapered roller bearings on the wind turbine main shaft, the actual clearance distribution assumption is established, and a new method of calculating the internal load distribution taking into account the axial clearance is proposed. Firstly, the mathematical relationship between the clearance of tapered roller bearings and ring displacement, contact deformation, and load interval is described. Secondly, the load components of main bearings are calculated by force balance equation and load-displacement condition. Finally, a mathematical model of main bearings including axial clearance is established, and it is numerically solved to obtain the internal load distribution of the bearings. The calculation results of a large megawatt wind turbine example show that: the axial load of both main bearings is negatively correlated with the sum of axial clearances; the number of loaded rolling elements is negatively correlated with the sum of axial clearances; and there exists an optimal value of the sum of axial clearances for main bearings to reach the optimal load carrying state. [ABSTRACT FROM AUTHOR]

Time-varying loads, manufacturing errors, and assembly errors are the main factors leading to the performance degradation of the planetary roller screw mechanism. This paper proposes a comprehensive analysis method for the performance degradation of the planetary roller screw mechanism caused by time-varying loads and manufacturing and assembly errors. Firstly, a simulation analysis model of the planetary roller screw mechanism was established and its effectiveness was verified. A quantitative analysis was conducted on the influence of manufacturing and assembly errors on the load distribution, revealing the load-bearing mechanism under the influence of errors. Secondly, loading experiments were conducted on the planetary roller screw mechanism, and the degradation of its load-bearing performance was divided into the normal degradation stage, the accelerated degradation stage, and the failure stage. The experimental results prove that the initial transmission accuracy has a significant impact on the degradation of the load-bearing performance, determining the occurrence of the node where the accelerated degradation stage appears in the load-bearing performance. Thirdly, the wear status of the threads and gears was examined, and the results showed that material peeling was the main factor causing the degradation of load-bearing performance. [ABSTRACT FROM AUTHOR]

Highlights The CFRP/Ti multi‐bolt joints are commonly used in important structural parts of aircraft. These structure often adopts an integrated drilling method to improve manufacturing efficiency and avoid assembly problems. However, significant differences in material properties between CFRP and titanium alloy can affect hole accuracy, leading to deviations in hole‐size that impact joint performance. In response to these challenges, this study conducted experiments on the hole‐making process for CFRP/Ti laminated multi‐bolt joints and analyzed hole‐size characteristics and precision. The research investigated the effect of hole‐making processes on the static tensile and fatigue performance of CFRP/Ti three‐bolt single‐lap joints specimens and revealed the influence of hole‐size characteristics on load distribution among bolts. Results indicated that titanium alloy chip formation during CFRP hole drilling induced a microcutting effect on CFRP hole walls, resulting in stepped holes. The use of low‐frequency vibration‐assisted drilling improved chip removal and enhanced hole‐making precision. The use of the LDR‐LDR‐CD combined hole‐making process can mitigate the secondary bending phenomenon of critical bolt in CFRP/Ti three‐bolt, single‐lap joints specimens, thereby reducing local stress concentrations. This process combination effectively distributes bolt loads evenly, resulting in a reduction of the bolt load ratio in critical holes by 6.2%, and increases ultimate load and fatigue life by 6.7% and 47.7%, respectively. Therefore, in the hole‐making process of CFRP/Ti multi‐bolt joints, it is crucial to ensure that the precision of critical holes is lower than that of auxiliary holes to decrease the bolt load ratio in critical holes and enhance structural joint performance. Novel method for uniformly distributing load based on controlling drilling precision. The formation process of CFRP/Ti hole diameter characteristics in different processes. The LDR‐LDR‐CD can optimize load distribution, improve ultimate load and fatigue life. [ABSTRACT FROM AUTHOR]

The contact properties of the screw-nut pair play a decisive role in the wear rate and service life of ball screws. The difficulty of the ball contact loads directly detected has resulted in the development of many flexible contact models to predict what happens inside the ball screw during its working process. However, few contact models account for nut flexibility when axial load is applied. This article proposes a screw-nut pair contact model with the flexible screw and nut, which are modeled as elastic beams with axial deformations. The geometric relationship of the centers of the raceways and balls is used to describe the variation of the contact loads with the positions of the balls. Effects of the axial, transverse, and torsional deformations of the screw and nut and the geometric error of balls on centers of the raceways and balls are taken into account in the model. For the dynamic model of the feed system, the screw is considered a continuum rod, while the worktable and bearings are treated as lamped masses. The effect of the contact stiffness of the screw-nut pair on the axial and torsional vibration modes of the screw is investigated using a numerical simulation. Moreover, the influences of the worktable position on vibration modes of the feed systems are discussed for the screw with fixed-free and fixed–fixed support modes, respectively. The load-deformation and dynamic experiments are conducted to verify the effectiveness of the proposed models. [ABSTRACT FROM AUTHOR]

Precast prestressed hollow core (HC) floors are widely used in various applications within the construction sector. Such floors are usually designed as single, simply supported elements, although it is known that individual elements forming the floor interact with each other. This article presents the state of the art regarding load redistribution in HC floors in the light of experimental data, current analytical models and code provisions. While this phenomenon is widely known and recognized, only sparse, and often poorly documented experimental data are available, which represent the basis for the assessment and calibration of analytical models. Moreover, even though the available models and code provisions share similar assumptions, their outcomes are in some cases conflicting. Having recognized the existing knowledge gap, the authors outline future perspectives for the development of consistent analytical and numerical approaches supplemented by new experimental data. [ABSTRACT FROM AUTHOR]

Load distribution is affected by distortion of contact continuity along the face width due to deformations of the system elements. In this study, a coupled lumped parameter model is studied for a pair of spur gears to demonstrate tooth load distribution continuity with system deformation components. A loaded tooth contact analysis is made analytically in iterative progress. Shaft bending, the torsional deformation of the gear body, and the profile gap between mating surfaces are investigated to specify effects on load distribution. A nonlinear time-variant dynamic model of a pair of spur gears is established using the Lagrange method to see contact loss effects on dynamic transmission error. A lumped parameter model with coupling stiffness is utilized to obtain equivalent mesh stiffness. The nonlinear model considering torsional deformation and gear profile gap with the complete analytical approach is proposed as considering parabolic load distribution in contact that differs from existing literature. Shaft bending deformation is investigated in symmetrical and asymmetrical gear positioning. As the ratio of the distance of the gear to the bearings on the shaft increases, its partial loading also increases. The response of the system is adversely affected by the decreasing gear mesh stiffness with partial contact loss. The results are validated by the finite element analysis and experimental test results from the literature. [ABSTRACT FROM AUTHOR]

Various approaches to mechanical modeling are available in practice to calculate the dynamic response of railway bridges under high-speed traffic, differing significantly in their complexity and accuracy. Very simple models often overestimate the vibrations occurring in reality but are much more computationally efficient and dependent on only a few input parameters than more complex and accurate models. Modeling the high-speed train as a multi-body system can represent the beneficial vehicle-bridge interaction, but it requires knowledge of numerous vehicle parameters, which manufacturers rarely disclose. In contrast, the track-bridge interaction can also be depicted by a simple coupling beam modeling of the structure, requiring only a few input parameters representing the dynamic stiffness and damping of the track. Several calculations on different single-span steel girder bridges demonstrate the influence of different model variants and input parameters on the acceleration results of the structure. Additionally, an approach for determining a dynamic distribution of the train axle loads affecting the bridge depending on the assumed vertical track stiffness is presented. [ABSTRACT FROM AUTHOR]

Double-row tapered roller bearings are one of the main bearings for semi-direct drive wind turbines. Its performance is directly related to its service life. At present, the research of double-row tapered roller bearings is mainly focused on single bearing, and the research of multicomponent bearing system is rarely considered comprehensively. In this paper, a rigid-flexible hybrid multi-force analysis model considering multiple components is proposed, which can be used for the analysis and research of system models. The results show that the contact load is similar to the theoretical contact load. The contact stress distribution of the left row roller along the prime line is more uniform, and there is only one row bearing near zero of the roller. The error between the simulation results and the theoretical calculation results is 4.56%, which is within the allowable range of error, so it is feasible to analyze the contact stress of the proposed rigidflexible mixed multi-mechanical system model. [ABSTRACT FROM AUTHOR]

The modified teeth are deliberately manufactured to mitigate the stress concentration generated by offset components, which makes equipment more susceptible to localized failures. Therefore, this paper presents a model aimed at investigating the meshing characteristic of gear pair with modification and crack failure. In this model, the tooth deformation and force transmission are determined based on slice coupling theory. The torsional deformation of teeth produced by eccentric load distribution is considered and complemented to the calculation method. Finally, the approach is proven through the experimental tests and FE model. The result shows that when the equipment is operated in misalignment condition, eccentric load distribution, and stress concentration at tooth edge are generated, the meshing stiffness will be reduced drastically, which can be suppressed by appropriate modification, and the rapid decline of meshing stiffness is weakened by increasing the effective contact length. Although the contact stiffness would be further reduced by the crack failure and the tooth surface deformation is increased, it seems to alleviate the stress concentration and eccentric load effectively. [ABSTRACT FROM AUTHOR]

Abstract Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque (more than 100 kN m). A multi-row cam roller bearing (MCRB) is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor. However, compact geometry and complex loads render MCRB susceptible to fatigue failure, highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability. Therefore, this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life. In this method, a quasi-static model was developed to calculate the load distribution, with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution. Subsequently, a genetic algorithm was used to obtain the optimized geometry parameters, which significantly improved the fatigue life of the MCRB. Finally, a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method. This study provides a theoretical guideline for optimizing the design of MCRB, thereby increasing the fatigue life of hydraulic motors.

To reveal the dynamic load distribution characteristics of planetary roller screw mechanism under the high-speed operating conditions, based on the spiral surface equation and deformation coordination relationship, a static contact force calculation method of the roller-screw and roller-nut thread at the contact point is proposed, and a formula for calculating the contact angle after bearing is derived. On this basis, further considering the inertial force generated by using high-speed operation, a dynamic load distribution model for planetary roller screw mechanism thread was established. By comparing with the finite element contact model of planetary roller screw mechansim, the error is below 5%, which verifies the correctness of the model established. Finally, the influence of the parameters such as screw speed, axial load, pitch, and tooth flank angle on the distribution of dynamic load was analyzed. The results show that the inertia force causes the roller to have a tendency to move closer to the nut and away from the screw resulting in a decrease in dynamic contact force on the roller screw side and an increase in dynamic contact force on the roller nut side. The degree of uneven distribution of dynamic load is positively correlated with the screw speed and pitch, and negatively correlated with the tooth side angle. The size of axial load has a significant impact on the distribution of dynamic load.

Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque (more than 100 kN m). A multi-row cam roller bearing (MCRB) is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor. However, compact geometry and complex loads render MCRB susceptible to fatigue failure, highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability. Therefore, this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life. In this method, a quasi-static model was developed to calculate the load distribution, with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution. Subsequently, a genetic algorithm was used to obtain the optimized geometry parameters, which significantly improved the fatigue life of the MCRB. Finally, a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method. This study provides a theoretical guideline for optimizing the design of MCRB, thereby increasing the fatigue life of hydraulic motors. [ABSTRACT FROM AUTHOR]

Aiming at the traditional bearing life calculation method which is difficult to investigate the influence of working radial clearance on the life of cylindrical roller bearings, a theoretical calculation model of the working clearance of cylindrical roller bearings and a bearing life calculation model considering the working radial clearance were proposed. Firstly, after studying the influence mechanism of interference fit, centrifugal force, temperature, radial load and dynamic pressure lubricant film on radial clearance, the theoretical calculation model of cylindrical roller bearing working clearance was established. Then, according to the theoretical calculation model of bearing working clearance, the bearing life calculation model considering the working radial clearance was established by linking the maximum rolling element load with the bearing working clearance. Finally, the cylindrical roller bearing SKF N324 on the main shaft of SFW250-8 / 850 horizontal hydroelectric generator was taken as the research object, five original radial clearance groups defined in the standard were calculated based on the theoretical calculation model of bearing working clearance. Based on the bearing life calculation model considering working radial clearance, the load distribution and life of the five working radial clearance groups were analyzed to determine the optimal working clearance group. Lastly, the model results were compared with the calculation results of ISO/ TS 16281: 2008 and the simulation results of RomaxDesigner, verifying the reliability of the calculation model. The results indicate that the interference fit has the greatest effect on the radial clearance of bearings under light and medium load conditions, with respective changes of - 30. 768μm and - 16. 413μm. Temperature has the greatest effect on the radial clearance of the bearings under heavy load conditions with a variation of - 16. 866 μm. When the clearance value is - 43 μm under light load condition, the number of rollers that can bear the load is 9, and the life reaches the maximum value of 48 187 h, the change of radial clearance will affect the distribution of contact stress and the number of loaded rollers of the bearing, which will affect the life of the bearing, and the optimal working clearance value of the bearing is different under different loads. The calculation results of the bearing life calculation model have an error of 3. 48% with the calculation results of ISO/ TS 16281:2008 and an error of 4. 71% with the Romax simulation results. This model is closer to the actual working conditions, which can provide a reference for the bearing design, and can choose the appropriate clearance according to the actual working conditions to extend the bearing service life. [ABSTRACT FROM AUTHOR]