Complex Loading Research Articles

Preparation, characterization, stability, and antioxidant of quercetin-loaded hyaluronic acid complexes via pH-induced co-assembly

The purpose of this study was to investigate the feasibility of constructing an oral delivery system for quercetin (QUT) using hyaluronic acid (HA) as the wall material. The findings revealed that when the mass ratio of QUT to HA was 1:10, the prepared QUT-HA complexes exhibited excellent stability (particle size of 802 nm, zeta potential of -36 mV) and QUT loading capacity (encapsulation efficiency of 79.77%, loading capacity of 89.65 mg/g). The characterization of QUT-HA complex confirmed the formation of hydrogen bond between QUT and HA, resulting in a homogeneously dispersed coral-like complex and leading to the transformation of QUT's crystal structure into an amorphous state. Environmental stability analysis demonstrated that the QUT-HA complex maintains good stability within an ionic concentration range of 0-500 mM, a pH range of 3-8, and at temperatures of 50-90°C. In vitro simulations of gastrointestinal digestion indicated that the QUT-HA complex aggregates during simulated gastric fluid digestion and dissociates following simulated intestinal fluid digestion, effectively enhancing the bioaccessibility of QUT. Antioxidant assays showed that the scavenging ability of QUT against DPPH and ABTS radicals was significantly improved by complex loading. Therefore, the QUT-HA complex developed in this study possesses a high QUT loading capacity, excellent processing and digestive stability, and can effectively enhance the bioaccessibility and antioxidant activity of QUT, making it a promising candidate for use as an oral nutritional supplement in the field of functional foods.

Bending moment calibration for rotational bending fatigue testing machine based on strain measurement

Abstract Rotational bending fatigue testing is an important method to evaluate the fatigue of metal materials under cyclic loading. Specifically, the fatigue strength is evaluated through repeated rotational bending under complex loads with the accuracy affected by the bending moment. Here, a method based on strain measurements is proposed for calibrating the bending moment of rotational bending fatigue testing machines. Specifically, the strain of a metal sample under loading with resistance strain gauges was recorded using a strain acquisition system to measure the bending moment. The positions of strain gauges were designed according to the principle of strain measurements to establish a calibration program. Three metal samples of different sizes were tested on two types of rotational bending fatigue testing machines, and the measurement uncertainty was evaluated and verified. The experimental results showed that the proposed method measured and calibrated the bending moment of rotational bending fatigue testing machines rapidly, conveniently, and accurately. The results also provide a practical reference for research and application in related fields.

CONTRIBUTION TO IMPROVING OF MACHINE PARTS MECHANICAL PROPERTIES BY THERMOMECHANICAL HARDENING

Current industrial production is characterized by requirements for improving the physical and mechanical properties of the used material. This causes a workload creating a rather complex load on all types of machines and mechanisms during operation. The design of such objects is currently based on a wide range of computational and experimental methods that allow modelling their state and behaviour even in the case of complicated non-stationary loading conditions. In this paper, the authors focus on the statistical evaluation of selected manufacturing operations related to mechanical and thermomechanical processing of products [Kuric 2011]. For example, in the case of long pipe billets with a thickness coefficient of 2-4, practically the only way of their production in the metallurgical cycle is cross-roll piercing followed by reduction. This process has high productivity but at the same time certain disadvantages. These disadvantages limit the efficiency and the range of use of the pipe blanks obtained by piercing, which leads to a consequent shortening of the machine production cycle. The presented approaches allow changing the structure of technological processes of production of axisymmetric metal products, by modifying the thermomechanical processing at the beginning of the production cycle.

Study of the residual stress distribution in SiCp/Al composites under thermal cycling conditions

In this study, a three-dimensional random representative volume element model was constructed using the finite element method combined with Python script to investigate the residual stress distribution in SiCp/Al composites with varying volume fractions, particle shapes, and particle size under thermal cycling conditions. The model has two different particle morphologies: spheres and irregular polygons. The results show that the irregular polygonal SiC particles exhibit higher residual stresses than spherical particles before and after thermal cycling due to their complex load transfer pathways and higher stress concentration at particle corners, which makes them more consistent with the characterization of SiCp/Al composites under practical application conditions. As the volume fraction of SiC particles increases, the particle spacing decreases, hindering the release of thermal stresses through plastic deformation. Notably, the relief rate of residual stress reached 53% in the 12 vol% SiCp/Al composites, with the stress decreasing from 698 MPa to 328 MPa after 50 thermal cycles. In contrast, the reduction rate for 18 vol% composites is only 13% after thermal cycling. Furthermore, compared to larger particles (7.3 µm, 8.9 µm), the smaller particles (4.3 µm, 5.9 µm) exhibit a more uniform stress distribution and lower thermal stresses before and after thermal cycling. Consequently, our work provides a significant theoretical basis for the design and application of SiCp/Al composites, especially for the application of materials under extreme temperature changes.

Mechanistic Insights into the cis-Selective Catalytic Ring-Opening Metathesis Polymerization.

Cis-selective ring-opening metathesis polymerization (ROMP) with the commercial Grubbs "nitrato catalyst" has shown promise for synthesizing stereoregular materials, but it comes with the drawback of losing control over the molecular weight due to the poor initiation rate of the catalyst and the need for stoichiometric ruthenium complex loading. To address these issues, we developed a chain transfer polymerization method that allows for the catalytic synthesis of polymers while controlling the degree of polymerization. This allowed us to produce shorter polymers with exceptional chain-end control. Analysis of the polymers revealed a novel double monomer addition mechanism for this catalyst. MALDI-ToF mass spectrometric measurements showed that when using small monomers like norbornene, the polymer chains contained only odd numbers of monomers. In contrast, the polymerization of norbornene-imide-type monomers shows a major distribution with odd numbers of monomers along with a minor distribution of even numbers. This unique distribution of polymer chain types had not been previously observed in ROMP. We explain this phenomenon by the chiral nature of the catalyst that yields two isomeric catalytic species with dissimilar reactivities toward monomer and chain transfer agents.

Multifunctional and tunable bandpass filters with RF codesigned isolator and impedance matching capabilities

Abstract This paper presents the radio frequency (RF) design and experimental validation of a multifunctional bandpass filtering (BPF) concept with center frequency tunability and RF codesigned isolator and impedance matching functionality. The multifunctional bandpass filter/isolator (BPFI) concept combines frequency-tunable reciprocal resonators and nonreciprocal frequency-selective stages (NFSs) to realize center frequency tunability and fully directional transfer characteristics. The NFS, as the core component of the BPFI concept, exhibits frequency-selective transmission response in the forward direction and signal cancellation in the reverse direction. Its tunability is achieved by combining a transistor-based network with a tunable capacitively loaded coupled-line section. Furthermore, the NFS facilitates matching of different source loads allowing for the BPFIs to be used as reconfigurable matching networks. For experimental validation, an NFS and two BPFIs were designed, manufactured, and measured at L band. Their features include (i) NFS: center frequency tuning from 1.55 to 1.9 GHz with maximum directivity from 20 to 52 dB and gain from 0.3 to 1.3 dB. (ii) BPFI (topology A): center frequency tuning from 1.52 to 1.9 GHz with maximum directivity from 20 to 44 dB and gain from −1.5 to −0.5 dB. (iii) BPFI (topology C): ability to match complex loads with 26 + j18 Ω and 26 − j14 Ω.

Anisotropy cyclic plasticity constitutive modelling for Ni-based single-crystal superalloys based on Kelvin decomposition

Nickel-based single-crystal (SC) superalloys exhibited excellent exceptional mechanical properties at high temperatures due to the elimination of internal grain boundaries, contributed a strong orientation-dependent material response. The anisotropy of SC superalloys was modeled viscoplastically from a macroscopic viewpoint based on the Kelvin decomposition theory [1] which was a decomposition of the stress space according to the elastic matrix eigen-directions to control the viscoplastic flow by Kelvin stress decoupled from each other. Compared to the classical phenomenological macro model, the proposed model effectively captures the slip deformation mechanism of SC superalloys with the inherent ability to simulate anisotropic because of the two criterions framework controlled by Kelvin stress. Compared with others, the proposed model was able to simulate time-dependent inelastic deformation and cyclic deformation behavior under complex loading. The kinematic hardening and isotropic hardening models incorporated microscopic quantities, such as dislocation density and channel phase width, connecting the macroscopic mechanical response with the microscopic state to achieve multiscale constitutive modelling. The parameter identification and finite element implementation were conducted on a SC superalloy [2]. Simulation results demonstrated the accuracy of the proposed model in predicting deformation behavior under various orientations, rate-dependent effects, isothermal and non-isothermal cyclic deformation. Comparison with the classical anisotropic matrix macroscopic phenomenological approaches highlights the superior capability of the proposed model to simulate the orientation-dependent mechanical properties of single-crystal alloys.

Multiple shock and acceleration processes of high-velocity flyers driven by the HEAVEN-I laser facility

The experiments of high-velocity flyer acceleration were performed on the HEAVEN-I KrF laser facility with a long-pulse duration (∼ 28 ns). Double-layered flyers consisting of polystyrene and aluminum films can be accelerated to more than 10 km/s measured by VISAR. The polystyrene layer is used as the ablative material, insulation layer, and shock wave regulator. Multiple shock and acceleration processes were observed by adjusting the thickness of the polystyrene layer. We simulated and analyzed the multiple shock processes driven by the long laser pulses and square pressure pulses. The results indicate that the reverberation processes can be induced by the alternating shock and rarefaction waves due to the wave–interface interactions. The reverberations in the Al layer can modulate the pressure evolution and the fine structure of flyer acceleration history. Similar processes in the polystyrene layer can lead to a secondary or multiple shock loading process when the driving pulse duration is several times longer than the shock round trip time in the double-layered flyer. Multiple accelerations can effectively enhance the final velocities in the experimental and simulation results. However, multiple accelerations involve more complex shock loading and unloading processes, and flyers are more prone to breakup compared with single acceleration.

Analysis of Vibrational Characteristics of the Bank of China Tower in Hong Kong with ANSYS

Abstract. With the rapid urbanization and technological advancements in construction, modern high-rise buildings have become a symbol of urban development. However, these structures face unprecedented challenges due to their increasing height and the complex dynamic loads they must withstand. This paper presents a comprehensive analysis of the Bank of China Tower in Hong Kong, a prominent architectural landmark, using ANSYS software to perform modal and transient structural analyses. The primary structure of the tower consists of five steel-reinforced concrete columns, designed to resist dynamic responses under extreme conditions such as high wind speeds and seismic activities. The modal analysis identified multiple natural frequencies and vibration modes, providing insights into the dynamic behavior of the structure. The transient structural analysis, conducted under seismic wave loading, demonstrated the tower's admirable performance under specified seismic conditions, highlighting its sufficient safety margins. This study emphasizes the importance of advanced materials and innovative structural designs in ensuring the stability and safety of high-rise buildings. The findings contribute significantly to the field of structural engineering, offering valuable insights for the design and analysis of future high-rise structures.

Data-driven homogenisation of viscoelastic porous elastomers: feedforward versus knowledge-based neural networks

A computational framework is established to implement time-dependent data-driven surrogate constitutive models for the homogenised mechanical response of porous elastomers at large strains. The aim is to enhance the computational efficiency of multiscale analyses through the use of these surrogate models. To achieve this, explicit finite element (FE) simulations are conducted to predict the homogenised response of a cubic unit cell of a porous elastomer, using two different viscoelastic descriptions of the parent material, subject to pseudo-random, multiaxial, non-proportional histories of macroscopic strains. The histories of homogenised variables extracted from each set of FE predictions form a training dataset, which is used to train two different surrogate models, both relying on artificial neural networks (NNs). The first model predicts the increment in macroscopic stress over a simulation step, as a function of the macroscopic stress and strain at the beginning of the step, of the prescribed macroscopic strain increment, and of the corresponding time increment. The second model uses the same inputs and outputs but tests a knowledge-based modelling approach: it relies on the aid of an additional nonlinear elastic constitutive model, which is time- and path-independent and known a priori. This model represents an existing base of knowledge which is augmented and corrected by an NN after training on viscoelastic data. The data-driven surrogate model, therefore, learns the viscoelastic behaviour of the unit cell starting from knowledge of its elastic response. The two surrogate models are found to have comparable and very high accuracies at capturing the homogenised unit cell response to highly complex loading cases across a range of viscoelastic properties. Hyperparameter optimisation shows that the second, knowledge-based model requires a simpler NN and therefore incurs a smaller computational cost.

Plasmon-Enhanced Photoelectrochemistry of Photosystem II on a Hierarchical Tin Oxide Electrode for Ultrasensitive Detection of 17β-Estradiol.

Despite its excellent efficiency in natural photosynthesis, the utilization of photosystem II (PSII)-based artificial photoelectrochemical (PEC) systems for analytical purposes is hindered due to the low enzyme loading density and ineffective electron transfer (ET) processes. Here, we present a straightforward and effective approach to prepare a PSII-based biohybrid photoanode with remarkable photoresponse, enabled by the use of a hierarchically structured inverse-opal tin oxide (IO-SnO2) electrode combined with gold nanoparticles (Au NPs). The porous, carbon-containing IO-SnO2 structure allows for a high density and photoactivity loading of PSII complexes, while also providing strong electrical coupling between the protein film and the electrode. A new electron transfer pathway mediated by Au NPs was identified at the protein-electrode interface, which efficiently shuttles the photogenerated electrons from the enzyme to the IO-SnO2 electrode. Furthermore, the PEC response of the electrode was significantly enhanced by the surface plasmon resonance (SPR) effect of Au NPs. Upon light irradiation, this PSII-based photoanode exhibited an impressively high and stable photocurrent output, which was utilized to fabricate an aptasensor for 17β-Estradiol (E2) detection. Under optimal conditions, a detection limit of 0.33 pM was obtained, along with a broad detection range from 15 pM to 30 nM. The applicability of the aptasensor was assessed by measuring E2 in water and urine samples, demonstrating its feasibility in environmental monitoring and clinical tests.

Mechanical Behaviors of Orthogonal Spiral Metal Skeleton–Polyurethane Elastomer Composites under Complex Loading Modes

Herein, a novel material design strategy is proposed: an interpenetrating composite composed of a woven orthogonal spiral metal skeleton and polyurethane (PU) elastomer. This interpenetrating composite combines rigidity and flexibility, exhibiting excellent elasticity and deformation recovery. The deformation behavior and mechanical properties of the composites under various loading conditions are investigated through experiments and numerical simulations. Different degrees of warping behaviors occur in composites with various structural parameters under uniaxial tension. Alternating rotations and double spiral arrangements can significantly limit the warping phenomenon, with a maximum reduction of 78%. The bending load capacity is regularly increased by increasing the wire diameter and decreasing the pitch. Increasing the number of loaded spiral wires enhances the bending load capacity of the composites. Uniaxial compression tests demonstrate that the composites have excellent load‐carrying capacity and strain recovery, with compressive strength 1.5 times that of pure PU. Cyclic compression tests further illustrate the excellent energy consumption capacity and stability of the composites. Overall, the introduction of orthogonal spiral skeletons into the composites demonstrates the potential to achieve enhanced load‐carrying capacity and large strain recovery simultaneously.

Driving response analysis of twisted and coiled polymer actuators by considering the viscoelastic behavior of their precursor fibers

Twisted and coiled polymer actuators (TCPA) represent a type of artificial muscle predominantly composed of viscoelastic polymers in their precursor fibers. An integral form of the viscoelastic constitutive model has been developed to predict the mechanical deformation of the precursor fibers. The model successfully accounts for the first-cycle effect and the creep deformation near the glass transition temperature of the precursor fibers. Combined with the multilayer model by Gao and Wang (2024 Smart Mater. Struct. 33 045031), which predicts the effective mechanical and thermal properties of TCPA, the proposed viscoelastic constitutive model accurately predicts the thermo-mechanical response of TCPA under the heating and cooling cycle and applied loads. It is noted that the driving strain of TCPA is sensitive to the heating and cooling cycles. When the cycle duration is short, the proposed viscoelastic model can be simplified to a linear elastic model. The numerical implementation of the viscoelastic constitutive model is detailed, with validation conducted on two polymer materials, polypropylene, and polyamide 66. The proposed constitutive model can effectively predict the driving response of TCPA under complex loading conditions.

Electrocoagulation treatment of wastewater collected from Haldia industrial region: Performance evaluation and comparison of process optimization

This study investigates the treatment of oil-contaminated wastewater with high levels of inorganic substances, suspended solids and turbidity, collected from the Haldia industrial region of India in February 2023. The wastewater, originating from industries such as chemical, petrochemical, textile, and battery manufacturing, presents a complex pollutant load that challenges traditional treatment methods. Electrocoagulation was employed as the treatment technique, with process optimization conducted using Box-Behnken design (BBD) and central composite design (CCD) for key parameters: pH, initial oil concentration, current density, and electrolysis time. The study comprehensively examined the effects of these parameters on turbidity removal. The optimal conditions were determined to be a pH of 7.5, an initial oil concentration of 275 mg/L, a current density of 17.5 mA/cm², and an electrolysis time of 20 min. Under these conditions, CCD outperformed BBD, achieving a desirability score of 93 % compared to 80 % for BBD. The process successfully reduced turbidity from 450 NTU to 56 NTU and total suspended solids (TSS) from 300 mg/L to 102 mg/L. The operation cost of the process was found to range from ₹0.904/m³ to ₹2.71/m³ as the electrolysis time increased from 0.17 to 0.5 h. The study presents a viable solution for industrial wastewater treatment in this region, aligning with the United Nations Sustainable Development Goal (UN SDG) 2030. Additionally, combining electrocoagulation with membrane filtration may enhance comprehensive pollutant removal.

Behaviour of paddled energy-absorbing rockbolts under complex loading laboratory conditions

Since their introduction in 2010, paddled energy-absorbing rockbolts have been widely used in seismically active hard rock mines. This paper provides new data and reviews previous work to quantify the performance of paddled energy-absorbing rockbolts under controlled laboratory conditions. Of significance is the realization that the typical split location in impact tests, at the centre between two paddle anchor points can at best provide an upper limit value. This inherent variability in performance under different testing configurations should be acknowledged and taken into consideration in the design of ground support in seismic conditions. This paper discusses the reduction in capacity of paddled rockbolts as a function of loading angle from a maximum value during axial tests (0° loading angle) to the lowest value during pure shear (loading angle of 90°). A significant reduction in displacement capacity is observed as the loading angle changes between axial (0°) and 40°. Beyond a 40° loading angle up to shear (90°) loading the reduction in displacement capacity is less significant. Due to the variances in the capacity observed through the variance of the testing configuration: loading mechanism, direction of loading, location / presence of a discontinuity, it must be recognized that results from laboratory-based testing are not independent of the testing configuration. This should be acknowledged when extrapolating anticipated performance in the field.

Three-dimensional fracture mechanics model of conch shells with hierarchical crossed-lamellar structures

Conch shells, characterized by a highly mineralized hierarchical crossed-lamellar structure that represents the pinnacle of molluscan evolution, exhibit exceptional crack resistance to protect their soft bodies from predatorial attacks. In this paper, we present a three-dimensional fracture mechanics model to establish a correlation between fracture toughness and the crossed-lamellar structure, elucidating the hierarchical crack bridging mechanism of aragonite lamellae. We find that increased fracture toughness is achieved through the energy dissipation contributed by the interfacial debonding of both first-order and second-order lamellae. The conch shells demonstrate outstanding resistance to cracking in two principal directions, featuring a locally stacked structure of flat plates that effectively withstand complex loads. The vertically alternating stacking structure of macroscopic layers of equal thickness inspires a biomimetic design with more balanced mechanical properties, accompanied by enhanced crack resistance observed as the lamellae become thinner. The theoretical results are in good agreement with relevant experimental measurements. This work not only sheds light on the physical mechanisms responsible for the remarkable fracture toughness of crossed-lamellar structures but also provides guidelines for designing high-performance biomimetic structural materials.

Stacking BSRG-PLS: A physical and data-driven real-time stability safety analysis of arch dams during operation

Anti-sliding stability is the foundation for the normal operation of arch dams. In recent years, extreme weather has occurred frequently. It is important to grasp the anti-slide stability of arch dam (ASSAD) under complex load conditions in time. Currently, the ASSAD safety factor is primarily analyzed through the finite element method (FEM), which are time-consuming, labor-intensive, and lack timeliness. To address this, this paper proposes a real-time ASSAD analysis method during operation based on the Stacking BSRG-PLS model, which integrates a Bidirectional long short-term memory network, Residual neural network, Support vector machine, Gaussian process regression model and Partial Least Squares regression method. Firstly, based on the Stacking BSRG-PLS model and measured temperature combing with FEM, the transient temperature field of arch dam is established. Subsequently, a sample dataset containing the load data and the corresponding ASSAD safety factors calculated by FEM is constructed. Whereafter, using the Stacking BSRG-PLS model again, the real-time ASSAD safety factor is obtained based on the sample dataset. Case studies indicate that this method is effective and feasible, and has high analysis precision. It provides an effective way to quickly evaluate the ASSAD safety based on the measured data.

Kinematic Patterns of Different Loading Profiles Before and After Total Knee Arthroplasty: A Cadaveric Study

One of the major goals of total knee arthroplasty (TKA) is to restore the physiological function of the knee. In order to select the appropriate TKA design for a specific patient, it would be helpful to understand whether there is an association between passive knee kinematics intraoperatively and during complex activities, such as ascending stairs. Therefore, the primary objective of this study was to compare the anterior–posterior (AP) range of motion during simulated passive flexion and stair ascent at different conditions in the same knees using a six-degrees-of-freedom joint motion simulator, and secondary, to identify whether differences between TKA designs with and without a post-cam mechanism can be detected during both activities, and if one design is superior in recreating the AP translation of the native knee. It was shown that neither TKA design was superior in restoring the mean native AP translation, but that both CR/CS and PS TKA designs may be suitable to restore the individual native kinematic pattern. Moreover, it was shown that passive and complex loading scenarios do not result in exactly the same kinematic pattern, but lead to the same choice of implant design to restore the general kinematic behavior of the native individual knee.

Analysis and evaluation of suitability of high-pressure dynamic constitutive model for concrete under blast and impact loading

Concrete demonstrates complex dynamic mechanical behaviors under the influence of blast or impact loads, and there are inherent limitations in experimental and theoretical methods when dealing with highly nonlinear problems. As computational technologies and mechanics continue to evolve, it is possible to conduct high-fidelity simulations of the transient response of concrete structures subjected to intense dynamic loads. Such simulations play a crucial role in revealing the propagation laws of stress waves, the progression of damage, the mechanisms of structural failure, and in conducting protective engineering design. An accurate concrete material model is essential for conducting numerical studies. This article reviews the development of high-pressure dynamic constitutive models for concrete in recent years from both experimental research and theoretical modeling perspectives, focusing on the analysis and evaluation of the modeling methods and main shortcomings of the equation of state(EOS), strength model, and damage model. Using single-element numerical simulations under a single loading path and numerical calculations of engineering cases under complex loading paths, a systematic analysis and comparison were conducted on the predictive capabilities of the HJC, RHT, KCC, and CSC models, as well as the newly developed Kong-Fang and Yan-Chen models. It pointed out the impact of high-pressure mechanical behavior of concrete and the cumulative effect of damage under hydrostatic pressure on the calculation results. Finally, a discussion was conducted on the inherent flaws, applicability, and research difficulties of local constitutive models of concrete in the finite element method. This provides a reference for the selection and research of constitutive models when conducting numerical analysis of the blast and impact resistance of concrete structures.

Analysing Flexural Response in RC Beams: A Closed-Form Solution Designer Perspective from Detailed to Simplified Modelling

This paper presents a detailed analytical approach for the bending analysis of reinforced concrete beams, integrating both structural mechanics principles and Eurocode 2 provisions. The general analytical expressions derived for the curvature were applied for the transverse displacement analysis of a simply supported reinforced concrete beam under four-point loading, focusing on key limit states: the initiation of cracking, the yielding of tensile reinforcement and the compressive failure of concrete. The displacement’s results were validated through experimental testing, showing a high degree of accuracy in the elastic and crack propagation phases. Deviations in the yielding phase were attributed to the conservative material assumptions within the Eurocode 2 framework, though the analytical model remained reliable overall. To streamline the computational process for more complex structures, a simplified model utilising a non-linear rotational spring was further developed. This model effectively captures the influence of cracking with significantly reduced computational effort, making it suitable for serviceability limit state analyses in complex loading scenarios, such as seismic impacts. The results demonstrate that combining detailed analytical methods with this simplified model provides an efficient and practical solution for the analysis of reinforced concrete beams, balancing precision with computational efficiency.