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For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

This paper introduces a new approach for parallel loading of distribution transformers with different impedance voltages and power ratings while considering all other relevant paralleling conditions. This approach is constructed to assist design and maintenance engineers in making informed decisions when a required transformer with specific impedance, voltage, and power rating is unavailable. The primary objective of this paper is to minimize partial stoppages and energy supply shortages resulting from the unavailability of appropriate transformers. Additionally, the study aims to enhance operational reliability in the event of unexpected failures in one or more transformers operating in parallel. The proposed approach optimizes new load sharing for transformers when a new or temporary unit replaces a failed one. The analysis aims to balance the costs of production losses and lifestyle disruptions resulting from energy shortages. These impacts are evaluated against the reduction in total transformer capacity and the operational constraints introduced by the newly installed transformer with a different impedance voltage. The proposed method’s effectiveness is demonstrated through a numerical example involving four different scenarios. The paper concludes with results, conclusions, and recommendations based on the proposed approach.

Due to the extremely complex load distribution form and evolution law of soft-rock tunnels under high geo-stress, there has been a long-term lack of theoretical support for designing supporting structures and preventing large deformation disasters. Therefore, it is significant to explore the interaction between surrounding rock and supporting structures for soft-rock tunnels under a high geo-stress environment. Firstly, the evolution characteristics of the supporting structure load and surrounding rock damage were analyzed using the field measurement and the proposed composite viscoelastic-plastic creep damage model. Then, the load sharing and transfer mechanisms were discussed based on the decreasing evolution process of the bearing capacity after the primary support yields. Furthermore, a theoretical solution method that can reflect this load evolution mechanism was derived by synthesizing elastic–plastic constitutive, creep damage constitutive, and concrete damage constitutive models. The results showed that the load grows with the development of the surrounding rock damage. Hence the surrounding rock damage is an intrinsic factor leading to load growth. If a supporting component yields, the bearing mode will change from cooperative sharing to load transfer. In other words, part of the load originally acting on the yielded component will be transferred to the other unyielded components. During 55 days after the primary support yielded, a total load of 381 kPa was transferred to the secondary lining, accounting for 61.3% of the total load of the secondary lining. Calculation examples showed that the proposed theoretical solution method could reflect the progressive yield process of each supporting component and the load sharing and transfer processes.

Arrays of pillars fabricated on flat substrates belong to a class of multicomponent systems composed of many interconnected elements functioning in parallel. Under sudden loading, their load-bearing capacity depends not only on the intrinsic strength of individual pillars but also on the mechanism by which loads released from crushed pillars are redistributed to surviving ones. Following the initial application of load, pillars with thresholds below the applied stress collapse, and their loads are transferred according to a prescribed load-sharing rule, triggering bursts of failures. These bursts may either drive the system to complete collapse or stabilise it in a partially damaged configuration. In this work, we introduce a novel phenomenological load transfer rule that explicitly incorporates the system geometry and the elastic properties of the substrate. When the pillars are placed on a homogeneous, isotropic substrate and crushing occurs instantaneously, the redistributed loads are transferred to intact pillars located within the Voronoi cells defined by the ones failed simultaneously. Since the locations of crushed pillars evolve during the loading process, the Voronoi load sharing (VLS) rule is inherently dynamic rather than static. Within the fibre bundle model framework, we simulate suddenly loaded pillar arrays to evaluate their overall strength and to characterise the spatio-temporal evolution of damage under the VLS rule. These findings are systematically compared with those obtained from other established load-transfer rules.

One of the major disadvantages of micropiles is their low lateral stiffness and flexural rigidity due to the small diameter. This limitation can be handled in current practice, by installing the micropile with inclined condition or providing a steel casing. Additional steel casings will increase the lateral load capacity of micropiles but increase the project cost as well. Thus, inclination of micropile which is relatively simple and cheap is recommended. In this paper, a comprehensive numerical analysis is conducted on the behavior of micropiled rafts installed with inclined condition under combined vertical and lateral loading. A FEM calibrated against full-scale axial and lateral field tests is used to conduct the analysis. The soil profile is soft clay soil underlain by a layer of dense sand. The study investigates the impact of several parameters which are as follows: magnitude of vertical loading, reinforcement type, inclination angle of micropiles, and number of inclined micropiles. The study reveals that increasing vertical loads causes continuous decrease in the lateral load capacity of micropiled rafts. When all micropiles installed are inclined, the positively inclined micropiles carry 79–86% of the total lateral load carried by micropiles, whereas the negatively inclined ones carry 14–21%. Inclined micropiles offer greater lateral load sharing ratio (α h ) than that of vertical ones, largest at θ = 45°. The effect of micropile reinforcement on improving the lateral performance is low compared to the effect of micropile inclination angle.

As surface wear is one of the major failure mechanisms in many applications that include polymer gears, lifetime prediction of polymer gears often requires time-consuming and expensive experimental testing. This study introduces a contact mechanics model for the surface wear prediction of polymer gears. The developed model, which is based on an iterative numerical procedure, employs a boundary element method (BEM) in conjunction with Archard’s wear equation to predict wear depth on contacting tooth surfaces. The wear coefficients, necessary for the model development, have been determined experimentally for Polyoxymethylene (POM) and Polyvinylidene fluoride (PVDF) polymer gear samples by employing an abrasive wear model by the VDI 2736 guidelines for polymer gear design. To fully describe the complex changes in contact topography as the gears wear, the prediction model employs Winkler’s surface formulation used for the computation of the contact pressure distribution and Weber’s model for the computation of wear-induced changes in stiffness components as well as the alterations in the load-sharing factors with corresponding effects on the normal load distribution. The developed contact mechanics model has been validated through experimental testing of steel/polymer engagements after an arbitrary number of load cycles. Based on the comparison of the simulated and experimental results, it can be concluded that the developed model can be used to predict the surface wear of polymer gears, therefore reducing the need to perform experimental testing. One of the major benefits of the developed model is the possibility of assessing and visualizing the numerous contact parameters that simultaneously affect the wear behavior, which can be used to determine the wear patterns of contacting tooth surfaces after a certain number of load cycles, i.e., different lifetime stages of polymer gears.

Pitch error is inevitable in gear machining, and it will aggravate the vibration and noise of the herringbone star gear train (HSGT). Although the machining accuracy is limited, the dynamic performance of the system can be further improved by appropriately combining the error phases. In this work, according to the periodicity of the pitch error and its influence on the backlash, the different backlash formed by the meshing tooth pairs during the transmission is deduced, then the meshing state and error excitation force of each tooth pair are considered, respectively. A new dynamic model of HSGT considering multi-tooth with different backlash under the influence of pitch error is established, and the reliability of the model is verified by the vibration experiment of the gearbox. Based on the proposed model, the influence mechanism of the error phase adjustment on two-sides of the herringbone center gear on the load-sharing performance is analyzed, and the optimal error phase combination of three parallel star gears is explored. When the pitch error value is constant, this research can guide the error phases combination of each herringbone gear in the HSGT, thereby reducing the vibration and improving the load-sharing performance of the system.

A finite element analysis (FEA) was conducted to examine the behaviour of single-lap quasi-isotropic (QI) and cross-ply (CP) hybrid bolted/bonded (HBB) configurations subjected to tensile shear loading. Several critical design factors influencing the composite joint strength, failure conditions, and load-sharing mechanisms that would optimise the joining performance were assessed. The study of the stress concentration around the holes and along the adhesive layer highlights the fact that the HBB joints benefit from significantly lower stresses compared to only bolted joints, especially for CP configurations. The simulation results confirmed the redundancy of the middle bolt in a three-bolt HBB joint. The stiffness and plastic behaviour of the adhesive were found to be important factors that define the transition of the behaviour of the joint from a bolted type, where load sharing is predominant, to a bonded joint. The load-sharing potential, known as an indicator of the joint’s performance, is improved by reducing the overlap length, using a low-stiffness, high-plasticity adhesive, and using thicker laminates in the QI layup configuration. Enhancing both the ratio of the edge distance to the hole diameter and washer size proves advantageous in reducing stresses within the adhesive layer, thereby improving the joint strength.

As multilevel inverters are gaining increasing importance, newer topologies are being proposed to reduce part count for large number of levels in output voltage. A simplified five-level inverter has been recently reported in the literature to reduce component count. The topology comprises of floating input DC sources connected in opposite polarities through power switches. The structure requires lesser active switches as compared with conventional cascaded H-bridge topology with much reduced switching losses. Available literature present generalisation of the topology with symmetrical sources, but no investigations are made for equal load sharing and asymmetrical configurations. This study presents a comprehensive analysis of the aforementioned topology, referred to as cross-connected sources-based multilevel inverter (CCS-MLI). The topology is analysed for both symmetric and asymmetric source configurations. Also, a new algorithm for asymmetric source configuration suitable for CCS-MLI is proposed. A control scheme is also proposed for equal load sharing in five-level topology. Investigations are made for possibility of equal load sharing in higher level structures and fundamental frequency switching of switches bearing higher voltage stresses. Various concepts are verified with simulations and experimental studies.

Piled raft foundations are a reliable solution for improving load distribution and minimizing settlement, particularly in soils where shallow foundations are inadequate. This study focuses on the performance of floating piled raft systems in sandy soils, where controlling settlement is critical. A calibrated three-dimensional finite element (FE) model was developed and validated using experimental load–settlement data to investigate the effect of key parameters, including the number of the pile and the stiffness of the piled-raft foundations. The results show that an optimal configuration of 10 piles achieves a balanced load-sharing ratio of approximately 50% between the raft and piles, which effectively minimizes the settlement without any unnecessary structural redundancy. Beyond this point, additional piles reduce settlement by only 3–5%. The stress distribution analysis highlights the importance of raft–soil interactions, while parametric studies demonstrate how pile numbering and piled-raft stiffness affect the performance of the foundations. This research reinforces the value of numerical modeling as a predictive tool and offers practical design recommendations for cost-effective and sustainable foundation systems in sandy ground conditions.