Results Of Full-scale Experiments Research Articles

Piston ring and cylinder liner scuffing analysis in dual-fuel low-speed engines considering liner deformation and tribofilm evolution

The piston ring and cylinder liner (PRCL) system in larger-bore low-speed marine engines frequently experiences scuffing failures, which significantly decrease the engine reliability. To understand this failure mechanism, a scuffing failure model subjected to the PRCL system was developed considering multidisciplinary coupling effects that integrate asperity contact, hydrodynamic lubrication, tribochemistry reactions, thermal effects, friction, and surface wear. The impacts of large-scale deformation and gas-combustion mode on the scuffing performances of the PRCL system were examined. The key findings indicate that the larger-scale liner deformation can markedly reduce oil film thickness and exacerbate local asperity contact, influencing the evolution of the tribofilm by increasing the removal process. Under gas-combustion mode, the oil film thickness is even lower, and the asperity contact pressure further increases due to a more starved lubrication state and higher combustion temperature. This leads to tribofilm breakdown and severe wear near the ring opening area, which are aligning with the full-scale experimental results with scuffing failure.

Математическое моделирование и визуализация сложнонапряженного состояния при переломе диафиза бедренной кости

The purpose of this work is to establish the possibility of using the finite element analysis method to study complex stress states in case of a femur fracture with subsequent data visualization. Experimental data were obtained on a solid-state mathematical parametric model of the femur, created on the basis of computer tomogram data, and repeating studies on native biological objects. As a result of mathematical modeling, oblique transverse and helical fractures of the diaphysis of the femur with elements of helical deformation were studied. The application of finite element analysis made it possible to visualize and predict the stresses arising in bone tissue under the impact of a blunt solid object in a complex stress state and the morphological features of femoral shaft fractures under different torsional loading forces of the proximal part of the femur. The data on the mechanism and morphology of the femoral shaft fracture obtained during modeling are confirmed by the results of original full-scale experiments.

Numerical and semi-empirical models for the stress analysis of flexible pipes tensile armors terminations within end-fittings

The tensile armors of flexible pipes are typically terminated in two configurations, i.e., hook and pigtail, essential to guarantee the tensile armors’ anchorage in the pipe's end-fitting. However, despite its importance for the secure operation of flexible pipes, few works have dealt with the mechanical analysis of these terminations. Hence, this work proposes numerical and semi-empirical models to study the stresses induced on them by operational and extreme loading. Two- and three-dimensional finite element (FE) models are initially proposed, and their advantages and limitations in estimating local stiffness, stresses, and associated failure modes are highlighted. The initial analyses indicated that the two-dimensional model underestimated the terminations’ stiffness, while the detailed three-dimensional model required significant computational effort. However, a simplified three-dimensional model achieved the best compromise between accuracy and computational effort. In common, all models indicated that the hook termination failure is due to a pullout mechanism, while the pigtail induces the tensile armor steel rupture. After that, the simplified three-dimensional model was employed to conduct a parametric study involving several physical and geometric characteristics of the terminations. The importance of these parameters was evaluated using the Design of Experiment (DoE) technique, leading to semi-empirical equations to predict the maximum stresses induced in the terminations due to an axial load imposed on the tensile armor. Finally, the semi-empirical equation obtained for the hook termination was verified using previously presented full-scale experimental test results, showing good agreement.

The interactive force between fat, oil, and grease (FOG) deposits and the effect of food waste disposers on kitchen drainage systems

Food waste disposers (FWDs) streamline kitchen waste management and facilitate waste classification, whether they would increase the potential of blockage in kitchen drainage system is still unknown. This study conducted a theoretical analysis of the interactive forces between fat, oil, and grease (FOG) deposits and their aggregation on pipe walls. The study involved grading food waste particles processed by FWDs using sieving and weighing techniques to determine the mean weight diameter (MWD) of various aggregations. A full-scale experimental system, implemented in a 60-m high test tower, simulated blockages in horizontal pipes of high-rise buildings. The effect of pipeline materials and particle sizes on blockage were examined by measuring the adhesion of deposits on horizontal pipes. Energy dispersive spectrometer (EDS) analysis suggested that liquid bridge force is a primary factor in aggregate formation. Hand-cut particles formed aggregates with the highest MWD value. Particle size analysis revealed that sizes ranging from 2.36 to 4.75 mm, 1.18–2.36 mm, and 0.60–1.18 mm constituted over 80 % of particles ground by FWDs, with an average size of 2.16 mm. Results of full-scale experiment indicate particle diameters, friction coefficients and lipophilic coefficient significantly affected the propensity of these aggregates to adhere to pipes. Notably, particles processed by FWDs tended to cause blockages more frequently than hand-cut particles. These findings elucidate the deposition mechanism of FOG deposits and offer strategies to reduce blockages in kitchen drainage systems, such as reducing current grinding particle size by 18 % to 1.77 mm or selecting pipes like cast iron and high-density polyethylene.

Features and perspectives of application of the rapidly exploring random tree method for motion planning of autonomous robotic manipulators

Objectives. The work analyzes features of one of the most promising approaches to solve the problems for motion planning of autonomous robotic manipulators of various types and purposes using the rapidly exploring random tree (RRT) method. The development of modern robotics is shown to be inextricably linked with the improvement of the designs of the created samples, for which the placement of a manipulator on platform becomes a typical layout option. Prospects for using the RRT method as a constructive basis for creating a universal motion planner are evaluated for mobile and robotic manipulators, including autonomous robotic systems with a manipulator on a moving platform.Methods. The object of the research is the RRT method and its well-known modifications RRT* and RRT-Connect. The effectiveness of applying such methods for solving problems associated with planning the motions of robotic manipulators of various types was evaluated using computer and natural simulation methods.Results. Based on a review of the literature and the results of the research, the wide possibilities of the RRT method can be used for solving motion planning problems not only for mobile and robotic manipulators, but also for robotic systems on whose transport platform an onboard manipulator has been installed (including those having a redundant or reconfigurable structure). The effectiveness of the applied application of the RRT method is confirmed by examples of modeling a mobile platform with an onboard manipulator and the results of full-scale experiments with a prototype of the ARAKS reconfigurable mechatronic-modular robotic manipulators (RTU MIREA, Russia). It can be experimentally demonstrated and theoretically substantiated that the final dimension of the exploring tree, and hence the time of its construction up to reaching a given target state, is largely determined by the value of the growth factor.Conclusions. The generalization of the results obtained opens up real prospects for using the RRT method as a constructive basis not only for creating universal means for motion planning mobile robotic systems with an onboard manipulator, but also for solving the problems of automating the docking of autonomous mobile platforms.

Towards composite suspension control arm: Conceptual design, structural analysis, laminate optimization, manufacturing, and experimental testing

The automotive industry needs composite materials to decrease the weight of new-generation vehicles whilst increasing their strength. In this study, one of the critical (load bearing) components of automobiles, i.e., the suspension control arm made of steel, is fully redesigned for its suitable manufacturing using composite materials. To this end, innovative mechanical simulation methods are developed and coupled to perform the design, analysis, and optimization of the automotive suspension control arm. The main design/optimization criteria are set to reduce no less than 75% weight of the metal control arm and increase its safety by at least 60% by using composite materials and a new geometry suitable for mass production. To predict the deformation-stress state of the control arm, a four-node quadrilateral shell element is implemented based on the kinematics of refined zigzag theory (RZT). Once verified numerically, the computer implementation of the RZT is combined with the optimization algorithm to achieve the optimum laminate stacking sequence of the control arm. Accordingly, prototypes of the composite control arms with optimum lamination plans are manufactured and then experimentally tested under the loading and constraint conditions defined at the conceptual design stage. The numerical and full-scale experimental results are compared, and the RZT models are comprehensively validated. Hence, the advantages of the overarching design-analysis-optimization strategy presented herein are revealed for redesigning and manufacturing automobile parts from composite materials.

Numerical analysis on the lateral resistance and reinforcement of bolted glulam post and beam structures with local cracks

The lateral resistance of bolted glulam timber frame structural system is highly influenced by the mechanical performance of the moment-resisting connections, while local cracks are commonly observed in the bolted glulam connections with the restraint of steel fasteners to wood shrinkage. In this paper, a three-dimensional finite element model was established in business software ANSYS to investigate the influence of cracks on the cyclic behavior of moment-resisting bolted glulam connections and the strengthening effect of friction dampers installed in pre-cracked connections. The numerical model was validated by comparison with full-scale experimental results. Furthermore, a nonlinear numerical model was developed for the glulam timber post and beam structures, and comprehensive analysis was conducted to explore the effect of the number and location of pre-cracked connections and the application of friction dampers on the lateral performance of framed structures. It was found that with local cracks set in the moment-resisting connections, the lateral stiffness and capacity of the framed structures can be reduced by 27% and 30%, respectively. With the installation of friction dampers in pre-cracked connections, the lateral capacity and energy dissipation capacity of the reinforced frame can be up to 1.36 and 2.77 times that of initially perfect frame.

Full-scale experiments on the fire smoke extraction from naturally ventilated shafts for shallow-buried urban road tunnels in hot summer

Shallow-buried urban road tunnels with shafts (URTS) have been operated in large cities of China, and successfully released the traffic congestion. Fire smoke is expected to exhaust out of one-side shaft groups driven by its own thermal buoyancy. However, full-scale test data of the fire smoke spreading in such tunnel are still lacked, and the prediction models needs to be verified. In hot summer of year 2020, three full-scale experiments were carried out on two URTS. A 1.6 m (length) × 1.6 m (width) iron pan was placed on ground with diesel oil used as the fire source. Testing systems were arranged under the ceiling, on top openings of shafts and at bottoms of shafts. Lots of smoke were rapidly exhausted out of the shafts closer to the fire sources, but backflow occurred at bottoms of those shafts farther from the fire sources being not conducive to smoke extraction. Other three results of full-scale fire experiments conducted on one URTS in cold winter are provided here for comparison. The findings are that both the ceiling smoke temperatures and the smoke spreading velocities decayed longitudinally well with the exponential function, and the downstream temperature attenuation coefficient k2 were in range of 0.042 ∼ 0.188 being smaller than that of the upstream, also the hotter the weather, the smaller the k2; maximum values on top openings of the shafts were measured to be 47 °C in temperature, 5 m/s in velocity and 180 ppm in CO concentration; mass flow rates of the unit shafts were measured to decrease away from the fire sources that were 0.30 ∼ 1.77 kg/(s·m2) in Fires 1 and 2, and 0.46 ∼ 1.27 kg/(s·m2) in Fire 3, also the prediction models were confirmed not to be accurate enough; number Ri′ differed among all unit shafts of Shaft 6#, and were about 13.5 ∼ 15.2 in Fire 1, but smaller to be about 1.4 in Fire 2.

Thrust Ripple Suppression Based on Negative Current Control for Short-Primary Low-Speed Large LIM Under Transient Operation

End effect of linear induction motor (LIM) leads to magnetic asymmetry and thrust ripple, which seriously restricts the performance and application of LIM. Existing methods for thrust ripple modeling and compensating have mostly focused on the steady state, which suffer from poor transient performance. Moreover, the influence of asymmetric currents on output thrust is not considered. In this paper, the thrust ripple characteristics and impact factors of a low-speed large LIM with negligible dynamic longitudinal end effect are analyzed in details, firstly. Then, a data-driven extracting and modeling method for transient thrust ripple is proposed. The non-stationary time-varying thrust ripple signal is extracted through wavelet decomposition and reconstruction, the polynomial parameters of thrust ripple model are trained off-line by particle swarm optimization algorithm. Finally, an improved suppressing scheme for transient thrust ripple is proposed, considering the decoupling and feedback control of positive and negative currents, based on the dynamic model of six-phase LIM. Full-scale experimental results have fully demonstrated the accuracy of proposed data-driven transient thrust ripple model is more than 90%. During the high-thrust operating stage, the axial vibration acceleration level of LIM within 100Hz is reduced by more than 12dB, with the adoption of improved control scheme.

Wind pressure on a 45° gabled roof: verifying code provisions with field measurements and wind tunnel data

The wind load provisions for gabled roofs with a slope of 27° < α < 45° in the National Building Code of Canada (NBCC) were derived from wind tunnel studies conducted in the 1970s. The coefficients have remained basically unchanged until this time. The paper presents the results of full-scale measurements and wind tunnel experiments to verify the necessity to update the current NBCC provisions. A full-scale building with a gabled roof of 45° was instrumented with pressure taps, and the wind load was monitored for 15 months. Special attention is given to the roof overhang by considering the simultaneous pressure contribution from both the upper and lower surfaces. The building and surroundings were replicated at a wind tunnel scale and investigated by Concordia University and Western University. Based on these three sources of data, the study concluded that the corner and edge provisions for both cases—a roof with and without overhang—need to be increased. It is suggested to merge the corner and edge into a single “perimeter” load provision. This code simplification would help the roofing industry to reduce misleading interpretations of the code and minimize failure due to installation errors.

Modelling the behaviour of heavy and mass timber members subjected to blast loads

This paper presents a numerical study investigating the behaviour of glued laminated timber (glulam) beams and cross-laminated timber (CLT) panels subjected to shock-tube simulated blast loads. A 3D constitutive material model for wood, which accounts for the anisotropic nature of the material as well as high strain rate effects, was implemented into a finite element (FE) model via user subroutine. Utilizing the continuum damage approach for wood, a total of eight failure criteria were used to describe both ductile and brittle failure modes. A total of 23 full-scale experimental test results were used in the validation of the modelling approach. In general, the FE model was found to be capable of capturing the overall failure mode, damage propagation, as well as predicting the resistance curves with good accuracy.

Numerical and experimental investigation of longitudinal rail creep at turnouts on steep ramps under repeated loads considering realistic braking loads of vehicles

Turnouts on steep ramps are subject to both temperature loads and frequent vehicle braking loads, which may lead to an accumulation of excessive residual longitudinal rail displacement, thereby leading to turnout service failure and threatening vehicle operation safety. In this paper, the following research work was carried out to study the longitudinal rail creep at turnouts on steep ramps: Experiments were conducted to investigate the longitudinal resistance characteristics of fasteners under repeated loading, and based on the experiment results, an MBS-FE simulation model was established for the longitudinal rail creep at turnouts on steep ramps, with real vehicle braking loads and fastener resistance degradation taken into consideration in the model. The change law for longitudinal displacement of turnout rails caused by temperature load and frequent vehicle braking load was studied based on the model. A full-scale experiment was then conducted on the longitudinal rail creep at turnouts on steep ramps under repeated loading conditions in order to verify the results of the simulation. A comprehensive and in-depth study of the longitudinal rail creep at turnouts on steep ramps impacted by repeated loading was conducted through the combination of theoretical analysis and experiment. The following conclusions were drawn: The longitudinal resistance of fasteners displays typical nonlinear characteristics and degrades under repeated loading, these characteristics lead to an obvious accumulation of residual longitudinal displacement of turnout rails on steep ramps under repeated loading, and the increment of residual longitudinal displacement of turnout rails reaches a maximum after the first loading–unloading cycle, and with the increase of the number of load action, the accumulated longitudinal residual displacement of turnout rails increases rapidly in the early stage, and then the growth gradually slows down and eventually stabilizes. The simulation results were found to be very similar to the full-scale experiment results, verifying the accuracy of the analytical model established in this paper.

Modular Multiport Electric-Vehicle DC Fast-Charge Station Assisted by a Dynamically Reconfigurable Stationary Battery

Multi-port Battery-Assisted dc Fast Charger (BA-DCFC) stations enable high charge rates of Electric Vehicles (EVs) at sites that have insufficient grid capacity. However, BA-DCFCs are expensive and inefficient due to the Battery Energy Storage System (BESS) and high-power isolated dc-dc converters that interface the BESS and EV charging ports. This paper presents a modular multi-port dc Linear Fast Charger (LFC) for EVs, which uses a stationary, reconfigurable Battery Energy Storage System (rBESS), a current-mode, digitally controlled bi-directional Linear Regulator (LR), and a contactor matrix. The LFC LR increases the overall station efficiency and eliminates the volume and cooling complexity associated with the high-power magnetics, high-voltage capacitors and high-frequency switches of state-of-the-art (SotA) isolated dc-dc converters. Compared to a SotA isolated dc-dc converter, the LR experiences 83.6% less loss for the same rated EV charge power. Over a day of typical operation, a three-port LFC station is shown to have 28% less loss than a state-of-the-art BA-DCFC, with an average efficiency of 93.4%. The LFC achieves redundancy at the station, BESS and LR levels while also integrating active balancing of state-of-charge/health without auxiliary switched-mode converters. The proposed system is verified using full-scale transient simulations and experimental results from a scaled, hardware-in-loop implementation with a custom LR and series-connected battery modules.

Neutronic and thermohydraulic blanket analysis for hybrid fusion–fission reactor during operation

This work demonstrates the results of full-scale numerical experiments of a hybrid thorium-containing fuel plant operating in a state close to critical due to a controlled source of D–T neutrons. The proposed facility represented a level of generated power (∼10–100 MWt) in a small pilot. In this work, the simulation of the D–T neutron plasma source operation in conjunction with the facility blanket was performed. The fission of fuel nuclei and the formation of spatial-energy release were studied in this simulation, in pulsed and stationary modes of the facility operation. The optimization results of neutronic and fluid dynamics studies to level the emerging offsets of the radial energy formed in the volume of the facility multiplying part due to the pulsed operation of the D–T neutron plasma source were presented. The results will be useful in improving the power control-based subcriticality monitoring method in coupled systems of the “pulsed neutron source–subcritical fuel assembly” type.

Mechanical response of cross-tensioned concrete pavement: experimental study and finite element

ABSTRACT The cross-tensioned concrete pavement (CTCP) has good bearing capacity, anti-crack ability and convenient construction characteristics due to the cross-tenioned prestressed strands placed inside the concrete. In order to study the mechanical response of pavement in construction process, an assembled monolithic structure for CTCP has been proposed and its mechanical response was analyzed through full-scale experiments and finite element model. The results of full-scale experiments show that the longitudinal and transverse compressive strain of concrete respectively exceeds 40μϵ and 20μϵ in the area of laying cross-tensioned prestressed strands with increase of the number of cross-tensioned strands. The end of CTCP is one of the weak areas, which may produce certainly transverse tensile stress. The results of finite element model show that the transverse tensile stress in ending region is mainly affected by the angle of cross-tensioned prestressed strands and its ratio. There is transverse tensile stress at the end of the pavement when the angle of cross-tensioned prestressed strands is small and its ratio is large, which can be offset by arranging transverse prestressed strands. Furthermore, an empirical formula to calculate transverse prestressed strands ratio at the end of pavement is given based on the results of finite element simulation.

Study into torsion compression of hybrid blank made of Al—3Ca—Mn—Zn—Fe—Si alloy

Experimental studies of two blanks made of the same Al—3Ca—Mn—Zn—Fe—Si aluminum alloy are performed. The technology for obtaining a composite (hybrid) blank is associated with a torsion compression scheme and consists in the joint deformation of components from materials assembled into a composite blank, as a result of which they seize under the action of pressure, temperature, and also an increasing deformation in the frictional area of the rotating tool. In this case, the temperature in the joint zone does not reach the values typical for the stir welding process. The results of full-scale experiments and computer simulation modeling performed using the found rheological model of the Al—3Ca—Mn—Zn—Fe—Si alloy are presented. Examples of manufacturing of hybrid blank made of various alloys are given for a comparative comparison of the joint quality.

Mathematical modeling of the fracture along the length of the femur diaphysis

Was to establish a pattern of femur diaphysis fracture with impact force over the entire front surface in an increments of 25 mm. Transverse, oblique and comminuted femur fractures were studied as a result of mathematical modeling. The application of mathematical modeling using the finite element analysis made it possible to visualize and predict the tension arising in the transient material during the impact force of blunt object, as well as the features of fractures' morphology in different sections of femur diaphysis. Modelled data about the mechanism and morphology of femur fracture were confirmed by the results of original full-scale experiments.

Effect of Fouling on the Performance of an Instream Turbine

As the tidal energy industry starts to mature towards commercial projects a key focus is on reliable power performance. As for any marine application, fouling poses a potential performance reduction risk for instream turbine deployments.
 SCHOTTEL HYDRO have developed their current commercial SCHOTTEL Instream Turbines. Four drivetrains with 6.3m rotors were deployed on the surface platform PLAT-I by Sustainable Marine Energy. One of PLAT-Is key features is access to the turbines for inspection and maintenance in situ. The system has undergone sea testing from 2017 to 2021 in Scotland and Nova Scotia (Canada).
 This paper presents the hydrodynamic rotor performance reduction due to fouling based on full-scale experimental results. An in-house blade element momentum model is used to quantify the changes of the hydrodynamic forces in terms of lift and drag for the hydrofoils used. Furthermore, the effect of fouling on the downstream wake was quantified in the field. The performance reduction due to fouling is significant and leads to a power drop of up to 43%, whereas the thrust is reduced by 25%. This is also reflected in a reduction of the turbine’s downstream wake as a “fouled” rotor extracts less energy from the flow. Modifications of the polar data, used for semi-empirical performance predictions, are able to predict the effect of fouling on the rotor performance.
 In general, the results derived from the testing prove the significance of access to the turbines in order to avoid reduction in the turbines’ performance due to fouling.

Experimental and numerical investigations of the ultimate strength of two subsea power-transmission cables

Integration of renewable energies into existing grids must be safe and reliable including the subsea power-transmission cables. Therefore, this paper determines the purely mechanical ultimate strength of a DC and an AC power transmission cable under axial load. Aspects concerning the electrical functionality of these cables are outside the scope of this paper and failure of the cable is defined as rupture of the cable following ultimate strength. At first, the individual components of the cable are tested to obtain the engineering stress strain relationships to derive material model data for the numerical simulation of the components and cables. The latter is compared to full-scale experimental results of the power transmission cables. Very good comparison of the numerical and experimental ultimate strength of the cables was achieved with the presented straightforward procedure.

Study of a local source of autonomous power supply on the basis of a diesel generator

A mathematical model of a local autonomous power supply source based on a diesel generator set is presented. The source of primary mechanical energy is a diesel internal combustion engine with an automatic speed controller, operating on the Polzunov–Watt’s principle. The electric energy converter is an asynchronous motor operating in a generator mode with capacitor self-excitation. The complete set of such devices is carried out from the available and normally working components of technological, electrical and transport equipment. They are formed by the personnel of the relevant enterprises in the period preceding the accident, during its development or at the end of its active phase. Therefore, mathematical models of subsystems of a diesel engine, an asynchronous machine operating in a generator mode, capacitive self-excitation and a number of typical electricity consumers are represented by separate structural blocks with functional relationships and connected according to the principle of subordinate regulation. This form of representation makes it possible to carry out large-scale studies of the qualitative and quantitative indicators of the operation of diesel generator sets with various types of both internal combustion engines and asynchronous machines. The coincidence of the results of numerical simulation and full-scale experiments allows to judge the adequacy of the proposed mathematical model of a local autonomous power supply source with a diesel generator. The presented model combines algorithmic simplicity and high computational precision and will make it possible to determine the criteria for the trouble-free operation of autonomous power supply sources to provide energy to consumers of different categories