Limit Load Research Articles

Effect of the Nanoparticles h-BN on Improving the Tribological Properties of Biodegradable Vegetable Oils

Lubricants are substances that reduce friction and heat dissipation between operating machine parts. The purpose of the paper is to investigate the possibility of improving the tribological properties of biodegradable vegetable oils. The objects of the research were lubricating oils produced based on selected plant oils (rapeseed, sunflower, corn, soybean) and Priolube ester oil containing nanoparticle hexagonal boron nitride (h-BN) and a dispersant. The research assesses the physicochemical properties, the wear load limit, the welding load, and the friction coefficient of the prepared oil compositions. The article compares the results with those obtained during the CB30 engine and PAO4 oil tests. The test results confirm that lubricating oils prepared in this way are characterized by promising tribological properties, are easy to prepare, and are environmentally friendly. The appropriate method of preparation has a significant impact on the quality of the obtained oils.

Applications of machine learning techniques to broaden operating envelope of biodiesel-fueled HCCI engines

A significant shortcoming of Homogeneous charge compression ignition (HCCI) engines is their narrow operating envelope, particularly with high-reactivity fuels like biodiesel. Additionally, the compositional variability of biodiesels, reflected in cetane number variations based on different source feedstocks, poses another challenge. While various strategies have successfully extended the maximum load limit in diesel-HCCI engines, they have not been adequately explored in biodiesel-fueled HCCI engines. This study is the first to comprehensively investigate the interplay of biodiesel composition, cetane number, engine compression ratio, and charge dilution strategy for extending the operating envelope of a light-duty HCCI engine. Given the impracticality of controlling multiple variables experimentally, this work focuses on the potential of machine learning (ML) algorithms to predict the operational limits of an HCCI engine using neat biodiesels derived from diverse sources. Among the ML models explored, artificial neural networks were the most accurate in predicting the minimum stable load, with prediction errors of 3.5% (calibration) and 3.9% (validation). Support vector machine models predicted the maximum load (with and without dilution) with errors below 5%. Notably, biodiesel produced from a blend of linseed, karanja, coconut, and mustard oils in specific proportions (42%, 3%, 25%, and 30% mass, respectively) yielded a wide HCCI operating range from 0.4 to 3.25 bar (without dilution) and up to 3.67 bar BMEP with charge dilution. This study highlights the novelty and practicality of using ML to predict and extend the operating envelope for biodiesel-fueled HCCI engines, demonstrating their suitability for future applications.

Mixed Finite Element Formulation in Nonlinear Geometrical Analysis of Space Trusses and Application to Trusses With Member Length Imperfection

Abstract Space trusses usually have a significant number of elements. As a result, it is inevitable that some elements have imperfections. In this study, the authors proposed a mixed finite element method for nonlinear geometrical analysis of space trusses. The post-buckling behavior of space trusses with length imperfections was predicted using a code list written in the programming software. The numerical results indicate that when the length imperfection approaches zero, the results converge to those obtained in studies on standard trusses. A second approach based on the displacement model is also proposed, in which the Lagrange multiplier method is used to deal with the member length imperfection. The results show that the two approaches proposed by the authors are effective, in which the mix formulation based on the finite element model is superior to that based on the displacement model. These results verify the accuracy of the method. Based on the proposed method, the effects of imperfections in the element layers on the truss were studied. The results show that the imperfections in the top two element layers have the maximum influence on the limit load value, whereas the remaining layers have a negligible influence. The combination of the imperfect lengths of these two layers of elements can produce results in which the limit load value is much larger than in the case of a perfect system. Based on the obtained results, it is possible to provide a solution for improving the overall stability of truss structures by creating reasonable imperfections.

Legal Study on the Oversight of Overloaded Motor Vehicles: Efforts to Protect Road Safety and Infrastructure

The oversight of motor vehicles exceeding weight limits is critical in safeguarding road safety and protecting infrastructure from premature damage. Overloaded vehicles are a common issue, contributing significantly to accidents and accelerated road deterioration, which incurs high repair costs and disrupts public transport and logistics. This study examines the legal frameworks and regulatory practices aimed at controlling vehicle overloading in Indonesia. Utilizing a normative juridical approach, the research reviews pertinent laws, regulations, and real-world cases involving load limit violations to gain insights into the effectiveness of existing policies. Findings reveal that while stringent load regulations are in place, enforcement remains inconsistent due to various limitations, including outdated monitoring technology, insufficient human resources, and challenges in coordinating between regulatory agencies. The research identifies critical obstacles in the current oversight mechanisms, such as a lack of real-time data collection and limited roadside weighing facilities, which hinder comprehensive monitoring. Furthermore, penalties for overloading are often inadequate to deter repeat violations. Based on these findings, this study recommends a multi-faceted approach to strengthen vehicle load regulation enforcement. Suggested improvements include upgrading monitoring technology, such as installing automatic weigh-in-motion systems, increasing the frequency and coverage of roadside inspections, and implementing more severe penalties to enhance deterrence. Additionally, the study emphasizes the need for inter-agency coordination and public awareness campaigns to foster compliance among vehicle operators. Through these initiatives, Indonesia can better protect its roadways, ensuring both road safety for all users and the long-term sustainability of its infrastructure.

Design and Test of a Traction Side-Pull Square Straw Bale Pick-Up-and-Stack Truck

To address the issues of limited one-time loading capacity, single functionality, and low automation level in existing square straw bale pickers, a large automated square straw bale pick-up-and-stack truck that integrates picking, stacking, transporting, and bundling functions has been developed, combining the technical advantages of one-time field removal and storage of bales. We innovatively designed a side-pulling traction mechanism that can realize the rapid transition between the transporting state and working state of the machine; a picking device that can complete the continuous action of forking, lifting, turning positioning, and de-forking; and a bundling device that can realize the adjustment of the attitude of square straw bales. Response surface tests were conducted on the prototype to determine the key structural and operational parameters, using the bundle completion rate and regular bale rate as evaluation indicators. Regression and significance tests were performed on the machine’s forward speed, chassis frame offset, and the ground clearance of the fork tine to determine the influence and priority of these factors on the evaluation indicators. Through multi-objective function optimization of the regression model, the optimal parameter combination was found to be a machine forward speed of 15.5 km/h, a chassis frame offset of 2126 mm, and a fork tine ground clearance of 225 mm, resulting in a bundle completion rate of 98.85% and a regular bale rate of 96.96%. Subsequent field tests with the optimized parameters showed that at a machine forward speed of 15.5 km/h, a chassis frame offset of 2126 mm, and a fork tine ground clearance of 225 mm, the bundle completion rate was 98.37% and the regular bale rate was 95.83%, meeting the relevant design requirements. This study can provide a reference for the design and development of straw collection and storage machinery.

Development of a Load‐Bearing, Terrain‐Adaptive Hexapod Robot With Chebyshev‐Linkage Legs

ABSTRACTThis study introduces an exploratory design for a hexapod load‐carrying robot, aiming to address challenges commonly associated with quadruped robots, including limited load capacity and high control complexity. By leveraging a Chebyshev linkage‐based overconstrained leg‐foot architecture that combines high rigidity and low friction, along with a multi‐drive system for lateral movement, we propose a robot with improved adaptability to diverse terrains, such as snow, sand, puddles, ice, and deserts. This versatility suggests potential applications in areas such as factory inspection, field reconnaissance and transport, and desert exploration. Using static and dynamic analyses, we evaluated the leg structure's stress distribution and motion requirements, employing simulations in Workbench and Adams to cross‐validate our theoretical calculations. The development of a prototype and its subsequent testing under various environmental conditions aimed to demonstrate the design's practicality and the robot's operational capabilities in real‐world settings. Although the findings indicate progress toward enhancing load‐bearing capabilities and terrain adaptability with reduced control complexity, further research and development are necessary to fully realize the potential of such robotic systems in practical applications.

Load Limiting Control for Component Life Extension

This paper presents the development of a novel life-extending control scheme for critical helicopter components subjected to significant fatigue loading. The primary objective is to synthesize a more efficient and less conservative life-extending control scheme than those currently available in the literature. The proposed load limiting control (LLC) scheme is a viable solution that addresses several issues that current life-extending control schemes suffer from, such as the neglect of fatigue damage induced by the harmonic component of loads and the inability to distinguish between aggressive and nonaggressive maneuvers. The proposed LLC scheme treats desired harmonic load limits as limit boundaries and recasts the problem of load limiting as a vehicle limit by computing a control margin (CM) using a limit detection and avoidance module. The computed CM is used as a cue to the pilot. The limit detection and avoidance module comprises an optimization algorithm, a model predictive controller, and a computationally simple onboard dynamical model. Simulations were conducted to demonstrate the effectiveness of the LLC scheme in limiting harmonic pitch link loads during flight. One significant outcome is that, with sufficient training, the pilot can skillfully track the cue within 0.5 s of initiating the tracking task.

A Minimalist Pathogen-Like Sugar Nanovaccine for Enhanced Cancer Immunotherapy.

Pathogen-mimicking nanoparticles have emerged at the forefront of vaccine delivery technology, offering potent immune activation and excellent biocompatibility. Among these innovative carriers, mannan, a critical component of yeast cell walls, shows promise as an exemplary vaccine carrier. Nevertheless, it faces challenges like unpredictable immunogenicity, rapid elimination, and limited antigen loading due to high water solubility. Herein, mannan with varying carbon chain ratios is innovatively modified, yielding a series of dodecyl chains modified mannan (Mann-C12). Through meticulous screening, a mannan variant with a 40% grafting ratio is pinpointed as the optimal vaccine carrier. Further RNA sequencing confirms that Mann-C12 exhibits desired immunostimulatory characteristics. Coupled with antigen peptides, Mann-C12/OVA257-280 nanovaccine initiates the maturation of antigen-presenting cells by activating the TLR4 and Dectin-2 pathways, significantly boosting antigen utilization and sparking antigen-specific immune responses. In vivo, experiments utilizing the B16-OVA tumor model underscore the exceptional preventive capabilities of Mann-C12/OVA257-280. Notably, when combined with immune checkpoint blockade therapy, it displays a profound synergistic effect, leading to marked inhibition of tumor growth. Thus, the work has yielded a pathogen-like nanovaccine that is both simple to prepare and highly effective, underscoring the vast potential of mannan-modified nanovaccines in the realm of cancer immunotherapy.

A perception-guided CNN for grape bunch detection

Precision Viticulture (PV) is becoming an active and interdisciplinary research field since it requires solving interesting research issues to concretely answer the demands of specific use cases. A challenging problem in this context is the development of automatic methods for yield estimation. Computer vision methods can contribute to the accomplishment of this task, especially those that can replicate what winemakers do manually. In this paper, an automatic artificial intelligence method for grape bunch detection from RGB images is presented. A customized Convolutional Neural Network (CNN) is employed for pointwise classification of image pixels and the dependence of classification results on the type of input color channels and grapes color properties are studied. The advantage of using additional perception-based input features, such as luminance and visual contrast, is also evaluated, as well as the dependence of the method on the choice of the training set in terms of the amount of labeled data. The latter point has a significant impact on the practical use of the method on-site, its usability by non-expert users, and its adaptability to individual vineyards. Experimental results show that a properly trained CNN can discriminate and detect grape bunches even under uncontrolled acquisition conditions and with limited computational load, making the proposed method implementable on smart devices and suitable for on-site and real-time applications.

Nitrogen leaching losses from pasture and winter forage crops in the West Matukituki Valley

In 2013 the Otago Regional Council (ORC) entered mediation with local farmers on changes to their Water Plan, Plan Change 6A, which sought to apply nitrogen load limits within the catchments of Lake Wanaka and Lake Hawea for all farm systems. There was little information available on nitrogen leaching losses in the high rainfall environments (c 2500 mm pa) of the South Island's high country. Agreement after mediation with the ORC and local farmers required a research project to examine differences between measured losses and outputs from OVERSEER® at a paddock and farm scale. To address this knowledge gap, a series of monitoring sites were set up in November 2014 in the West Matukituki Valley, west of Lake Wanaka. Porous soil solution samplers were installed to a depth of 50 cm in (i) a sheep- and cattle-grazed pasture, (ii) a cattle-grazed winter forage crop, and (iii) a native bush site. Results for 2015 showed that rainfall totalled 2240 mm, with calculated drainage estimated at 1330 mm. The total fluxes of dissolved N from the crop and pasture sites during the 12 months from June 2015 were 157 and 43 kg N/ha, respectively. Dissolved organic N (DON) made an unexpectedly large contribution to these fluxes, accounting for 20 and 67% of the total fluxes of dissolved N in drainage from the crop and pasture sites, respectively. Gaining a better understanding of the bioavailability of dissolved forms of organic N in leachate would help determine the risks that these forms of nutrients pose to water quality, and if they should be incorporated into models such as Overseer which do not account for DON. The project’s initial findings enabled an informed discussion on the use of modelled results from Overseer for the mitigation of N loss at a farm scale in the lakes’ catchments. It also focussed farmers’ attention on management of the nitrogen leaky parts of their farm systems, especially winter crops.

Measurement of fracture toughness in high-strength alloys via modified limit load analysis using flat-end cylindrical indenter

In this paper, fracture toughness (KJ) was measured for high strength rail steels and AL2024-T351 via chamfered cylindrical flat-end indentation. The indentation loading focused on applying the J-integral approach to curves of load versus indentation depth up to the crack initiation point based on a modified limit load via multiple indenter sizes. To promote single indenter size for practical use, virtual indenter sizes were proposed based on geometrical similarities, where the stress intensity factors according to J-integral approach were extrapolated to minimize the contribution of the plastic component of J-integral (JP). However, when the indentation method for KJ is applied to high strength rail steels, a consideration for the modification of the J-integral approach is suggested with the inclusion of stress triaxiality effect to accommodate the pressure sensitivity experienced in compression-based testing for some materials. The KJ values were seen to agree well with fracture toughness from conventional testing (KIC) for all materials in the study showing a relative difference below 5% except the JP rail steel, which showed only a relative difference of 16%. This is based on the condition that pressure sensitivity effect is present for the rail steels and not for AL2024-T351. The study also compares different indenter sizes, which show similar pressure and normalized depth profiles consequently offering the potential for a non-destructive means to measure mechanical properties and fracture toughness via micro-sized indenters. This opens an opportunity for further studies in material characterization capabilities across a wide range of industries in the future.

Guidance for structural integrity assessment of smooth pipe elbows containing defects using R6

Recently, guidance for fracture assessment of defective elbows using the R6 failure assessment diagram (FAD) method has been included in R6 Revision 4 Amendment 13 (2023). This paper provides an overview of the new guidance and supporting validation. The guidance is validated using 75 cases of 3-D finite element (FE) elastic-plastic J results of smooth pipe elbows of various geometries with axial/circumferential internal/external semi-elliptical/extended/fully-circumferential surface cracks under internal pressure, in-plane/out-of-plane bending moment, torsion and various load combinations, by comparing the FE-based Option 3 failure assessment curves (FAC) with the R6 Option 2 FAC. The results show that, for 74 out of 75 cases, the FE-based Option 3 data points are above the R6 Option 2 FAC with reasonable conservatism when the guidance for evaluating the elbow stress intensity factor and limit load is followed. In other words, following the new guidance can lead to reasonably conservative assessment results.

Damage mechanism identification and failure behavior of 2D needle-punched SiCf/SiC composites based on acoustic emission and digital image correlation

In order to improve the reliability of damage analysis for SiCf/SiC composites, an identification method of damage mechanism was established by combining in-situ acoustic emission (AE) and digital image correlation (DIC). The corresponding failure behavior of 2D needle-punched SiCf/SiC composites during ambient-temperature tensile test was investigated in detail. Through a machine learning k-means algorithm, AE signals could be effectively divided into five clusters: friction and sliding, interface damage, matrix cracking, individual fiber breaks and collective fiber breaks. DIC results show that the surface strain of composites increased non-uniformly during the tensile process, and the architecture of the composites had a significant influence on the initiation and propagation of cracks. To summarize, the tensile process consisted of three stages: the elastic stage, the rapid propagation of matrix cracks, the coordinated fiber fracture within the large strain bands. The failure of composites was dominated by the limited load transferring ability of the interface.

Transverse compressive behavior of plain and polypropylene fiber-reinforced concrete infilled steel tubes as hybrid steel-concrete nodes for discrete reticulated shell structures

This study investigates using concrete infilled steel tubes as hybrid nodes for discrete reticulated shell structures under compressive loading transverse to the tube axis. Three configurations were tested: empty, plain concrete infilled and polypropylene fiber-reinforced concrete infilled steel tubes. Displacement-controlled loading was applied through welded steel plates. Simplified beam theory models and nonlinear finite element analysis were used to evaluate the structural behavior. The concrete infilled steel tube specimens had higher stiffness and load-bearing capacity than the empty ones. The structural behavior of the concrete infilled specimens could be split into pre- and post-split-tensile cracking phases. No significant difference was found between the plain and fiber-reinforced concrete specimens under loads up to 1500 kN, which was the load limit of the testing machine. An additional fiber-reinforced concrete specimen, tested on a higher capacity machine, had a load-bearing capacity of 2400 kN and exhibited ductile failure.

Tackle power outage effects for Egypt's energy crisis via localized optimum load shedding

This paper presents an approach for selecting optimal load-shedding values for individual subscribers or consumers. Implementing this method can bring positive outcomes for consumers by minimizing risks and economic losses caused by power outages. It enables network operators to address power supply deficits and overcome network issues, especially those affecting weaker areas. The optimal load-shedding values are determined by employing IGWA (Improved grey wolf algorithm) through a Graded Objective Function Strategy. The proposed method essentially centered on categorizing loads into two levels based on their importance. The first level includes essential loads, the disruption of which results in risks or significant economic losses. The second level comprises less critical loads, and they do not have more risks or economic losses when power outages. This approach applies specifically to residential loads. The control scheme diagram of disconnecting and reconnecting the current is established by estimating the critical load limit during power outage periods. The necessary arrangements can be made, leading to a proactive measure against risks and losses. The proposal has been implemented in Egypt's electricity network. this proposed method provides a simple and effective solution to the ongoing crisis and provides permanent resolution of problems arising from power outages.

Analysis and experimental evaluation framework for buckling and post-buckling of composite stiffened panels

The composite thin-walled stiffened panel exhibits considerable potential for post-buckling bearing capacity. However, due to the limitations in post-buckling analysis and experimental evaluation capabilities, local buckling under limited loads is not permissible for current aircraft composite panels, significantly diminishing the weight reduction effect of composite panels. In this paper, experimental research on composite fuselage curved panels under combined compression and shear loads was conducted with an experimental system. The buckling analysis and failure prediction of composite fuselage curved panels were performed by the finite element method, using the interlaminar failure criterion and an improved Tsai-Wu failure criterion. Meanwhile, interaction formulaes were utilized to predict buckling correlation curves and failure envelopes. The results show that the finite element model with improved criteria and the rapid analysis method based on interaction formulaes exhibit high accuracy, which are available for properties analysis of composite panels. The experimental techniques and analytical methods proposed in this paper can provide a way to evaluate the buckling and post-buckling performance of composite stiffened panels.

3D limit analysis of reinforced concrete with sliding along smeared cracks

Limit analysis (LA) is successfully used for investigating the bearing capacity of reinforced concrete (RC) structures. Some cautions must be taken when using this method for RC since the concrete component exhibits a softening behavior with decreasing strength and limited ductility. A commonly adopted provision consists of considering isotropic reduced values of concrete strength to be input in the analysis (empirical effectiveness factors). In this paper, an alternative and completely new approach is proposed and investigated in which concrete strength is weakened in a more targeted manner. To that purpose, the commonly used 3D truncated Mohr-Coulomb (TMC) criterion is adopted to classically describe the compressive, tensile, and shear failure of concrete. However, TMC is here in an original way enriched by additional constraints that allow to account for weakness and anisotropy induced by preferential failure patterns, assumed a priori. The limit analysis approach is then formulated for two dual analyses in the convex optimization framework, making it possible to quantify the numerical error and obtain a lower and an upper bound of the limit load. Numerical examples illustrate the agreement of the formulation with academic results and laboratory tests.

Preparation and Characterization of Universal Liquid Proliposomes Encapsulating Water-soluble Efficacious Substances.

Liposomes were extensively used for cosmetics and pharmaceuticals due to their versatility, biocompatibility, and biodegradability, as well as the ability to encapsulate water-soluble and fat-soluble substances. However, some challenges remain unsolved, including poor stability, complex preparation process, limited encapsulation efficiencies (EE%) and drug loading capacity (DLC%). We herein prepared universal liquid proliposomes by rotary evaporation method and optimized formulations with different pH, glycerol content, ethanol content and preparation process. The EE% of water-soluble substances was above 85%, and the maximum DLC% was 37.5%. In 7 different conditions, the optimal formulation of the proliposomes remained stable over 60 days. The excellent stability of proliposomes and nicotinamide liposomes and their essence, when applied to cosmetic formulations, was confirmed by the Turbiscan stability analyzer. The proposed universal liquid proliposomes can form liposomes encapsulating a variety of water-soluble substances rapidly, making them an accessible and versatile tool for improving the stability and applicability of water-soluble raw materials.

A Comprehensive Review of Challenges in Oral Drug Delivery Systems and Recent Advancements in Innovative Design Strategies.

The oral route of drug administration is often preferred by patients and healthcare providers due to its convenience, ease of use, non-invasiveness, and patient acceptance. However, traditional oral dosage forms have several limitations, including low bioavailability, limited drug loading capacity, and stability and storage issues, particularly with solutions and suspensions. Over the years, researchers have dedicated considerable effort to developing novel oral drug delivery systems to overcome these limitations. This review discusses various challenges associated with oral drug delivery systems, including biological, pharmaceutical, and physicochemical barriers. It also explores common delivery approaches, such as gastroretentive drug delivery, small intestine drug delivery, and colon-targeting drug delivery systems. Additionally, numerous strategies aimed at improving oral drug delivery efficiency are reviewed, including solid dispersion, absorption enhancers, lipidbased formulations, nanoparticles, polymer-based nanocarriers, liposomal formulations, microencapsulation, and micellar formulations. Furthermore, innovative approaches like orally disintegrating tablets (ODT), orally disintegrating films (ODF), layered tablets, micro particulates, self-nano emulsifying formulations (SNEF), and controlled release dosage forms are explored for their potential in enhancing oral drug delivery efficiency and promoting patients' compliance. Overall, this review highlights significant progress in addressing challenges in the pharmaceutical industry and clinical settings, offering novel approaches for the development of effective oral drug delivery systems.

Mechanical Robustness Analysis of Semiconductors with a Single Needle Probe Card Using Acoustic Emissions

The combination of indentation testing and acoustic emission (AE) is widely used to analyze the fracture toughness of test substrates. In the manufacturing of semiconductor devices this material parameter also plays an important role. During the so-called wafer testing inside a wafer prober small probe tips are pressed onto the chip surface to check its performance. To prevent damaging the chip by that, the fracture toughness and load limit of it has to be defined in a prequalification step. This paper presents a test system that imitates the wafer testing process as close as possible and uses acoustic emission to detect appearing cracks and thereby also the load limit. The frontend of the test setup consists of a modular single needle probe card which can be placed in a wafer prober. Also, the indenter properties (tip diameter, stiffness, etc.) can be adjusted to the probe used later on during productive wafer testing to ensure realistic probing conditions. A piezoelectric sensor and a full strain gauge Wheatstone bridge are implemented close to the single indenter to measure the AEs and the applied contact force respectively. The signal-to-noise-ratios (SNRs) of both sensors are improved with an own analog amplifier module before recording them with an USB oscilloscope. A developed measurement software (LabVIEW) is used to adjust measurement parameters (trigger limit, record length, conversion factors, etc.) and automatically store and separate measurement data from different acoustic events and imprints. To evaluate the result files a second software tool (MATLAB) reads the files out and clusters the recorded events to separate crack signals from electrical and mechanical disturbances. With a prototype first test results are generated and the functionality and accuracy of the measurement concept is proven.