Effect Of Loading Research Articles

Direct observation of deformation and resistance to damage accumulation during shock loading of stabilized nanocrystalline Cu-Ta alloys

Energy absorption by matter is fundamental to natural and man-made processes. However, despite this ubiquity, developing materials capable of withstanding severe energy fluxes without degradation is a significant challenge in materials science and engineering. Despite recent advances in creating alloys resistant to energy fluxes, mitigating the damage caused by the absorption and transfer of mechanical energy remains a critical obstacle in both fundamental science and technological applications. This challenge is especially prominent when the mechanical energy is transferred to the material by shock loading. This study demonstrates a phenomenon in which microstructurally stabilized nanocrystalline Cu-Ta alloys can undergo reversal or nearly complete recovery of the dislocation structure after multiple shock-loading impacts, unlike any other known metallic material. The microstructure of these alloys can withstand repeated shock-wave interactions at pressures up to 12 GPa without any significant microstructural damage or deterioration, demonstrating an extraordinary capacity to be virtually immune to the detrimental effects of shock loading.

Predicting the Effects of Cryogenic Treatment and Impact-Oscillatory Loading on Changes in the Strength Properties of Stainless Steels

Abstract New experimental results concerning the strength properties of stainless steels are analyzed. In particular, the strength properties of steels were improved at room temperature using the preliminary impact-oscillatory loading (IOL) in liquid nitrogen. Mechanical tests performed on stainless steel 12Kh18N10T have found the IOL conditions (deformation of the material during pulse loading—εimp = 9.69%), under which the ultimate strength of steel increases by 32.2% compared to the initial state under subsequent static tensioning. Metallographic analysis of the deformed steel revealed twinning in the microstructure. This accounts for a significant increase in ultimate strength under subsequent static tensioning. A method for estimating the ultimate strength of stainless steels of different chemical compositions by changing the percentage of the main chemical elements is proposed. To test this technique, stainless steel 12Kh18N9 was chosen. Similar studies using this steel at εimp = 9.5% in liquid nitrogen followed by static tensioning at room temperature have confirmed the effectiveness of the proposed approach.

Economic Load Dispatch Problem Analysis Based on Modified Moth Flame Optimizer (MMFO) Considering Emission and Wind Power

In electrical power system engineering, the economic load dispatch (ELD) problem is a critical issue for fuel cost minimization. This ELD problem is often characterized by non-convexity and subject to multiple constraints. These constraints include valve-point loading effects (VPLEs), generator limits, emissions, and wind power integration. In this study, both emission constraints and wind power are incorporated into the ELD problem formulation, with the influence of wind power quantified using the incomplete gamma function (IGF). This study proposes a novel metaheuristic algorithm, the modified moth flame optimization (MMFO), which improves the traditional moth flame optimization (MFO) algorithm through an innovative flame selection process and adaptive adjustment of the spiral length. MMFO is a population-based technique that leverages the intelligent behavior of flames to effectively search for the global optimum, making it particularly suited for solving the ELD problem. To demonstrate the efficacy of MMFO in addressing the ELD problem, the algorithm is applied to four well-known test systems. Results show that MMFO outperforms other methods in terms of solution quality, speed, minimum fuel cost, and convergence rate. Furthermore, statistical analysis validates the reliability, robustness, and consistency of the proposed optimizer, as evidenced by the consistently low fitness values across iterations.

Experimental Study on Fretting Wear Behaviors of H62 Brass under Pre-stressed conditions

The fretting wear behavior of H62 brass encountered with GCr15 steel under pre-stressed conditions was studied using a self-developed fretting wear device in this study. The effects of normal loads, pre-stresses, fretting frequencies and fretting movement amplitudes were studied. Simultaneously, the changes of the coefficient of friction, depth of the worn scar, the surface morphologies of the worn scar and the wear mechanisms were analyzed. Experiments results showed that the coefficient of friction decreased as the normal loads and pre-stresses increased and increased as the fretting frequencies and fretting movement amplitudes increased. The depth of the worn scars clearly increased as the normal loads and pre-stresses increased and decreased as the fretting movement amplitudes increased. The oxygen contents slightly increased in the annular area of the worn scars. And the main wear mechanisms of H62 brass encountered with GCr15 under different fretting parameters used in this study were abrasive wear, adhesion wear and local spallings.

A novel framework for elucidating the effect of mechanical loading on the geometry of ovariectomized mouse tibiae using principal component analysis.

Murine models are used to test the effect of anti-osteoporosis treatments as they replicate some of the bone phenotypes observed in osteoporotic (OP) patients. The effect of disease and treatment is typically described as changes in bone geometry and microstructure over time. Conventional assessment of geometric changes relies on morphometric scalar parameters. However, being correlated with each other, these parameters do not describe separate fractions of variations and offer only a moderate insight into temporal changes. The current study proposes a novel image-based framework that employs deformable image registration on in vivo longitudinal images of bones and Principal Component Analysis (PCA) for improved quantification of geometric effects of OP treatments. This PCA-based model and a novel post-processing of score changes provide orthogonal modes of shape variations temporally induced by a course of treatment (specifically in vivo mechanical loading). Errors associated with the proposed framework are rigorously quantified and it is shown that the accuracy of deformable image registration in capturing the bone shapes (∼1 voxel = 10.4μm) is of the same order of magnitude as the relevant state-of-the-art evaluation studies. Applying the framework to longitudinal image data from the midshaft section of ovariectomized mouse tibia, two mutually orthogonal mode shapes are reliably identified to be an effect of treatment. The mode shapes captured changes of the tibia geometry due to the treatment at the anterior crest (maximum of 0.103mm) and across the tibia midshaft section and the posterior (0.030mm) and medial (0.024mm) aspects. These changes agree with those reported previously but are now described in a compact fashion, as a vector field of displacements on the bone surface. The proposed framework enables a more detailed investigation of the effect of disease and treatment on bones in preclinical studies and boosts the precision of such assessments.

Nonlinear finite element formulation for thin-walled conical shells

This study presents a novel finite element formulation to predict the geometrically nonlinear response of conical shells under a wide range of practical loading conditions. The formulation expresses the discretized equilibrium equations in terms of the first Piola-Kirchhoff stress tensor and its conjugate gradient of the virtual displacements, is based on the kinematics of Love-Kirchhoff thin shell theory and the Saint-Venant-Kirchhoff constitutive model, and captures the follower effect of pressure loading. The formulation takes advantage of the axisymmetric nature of the shell geometries by adopting a Fourier series to characterize the displacement distributions along the circumferential direction while using Hermitian interpolation along the meridional direction. Comparisons with general shell models show the accuracy of the formulation under various loading conditions with a minimal number of degrees of freedom, resulting in a significant computational efficiency compared to conventional general-purpose shell solutions.

Dynamic response characteristics of proton exchange membrane fuel cell during transient loading: An experiment study

The dynamic performance of Proton Exchange Membrane Fuel Cell (PEMFC) is crucial for safe and efficient operation and remains a major barrier to commercialization. In this paper the dynamic response characteristics of PEMFC under serpentine flow field (SFF) and parallel flow field (PFF) are discussed. The effects of current loading, operating pressures, anode and cathode stoichiometric ratios, as well as operating temperatures on the dynamic response characteristics of PEMFC are systematically studied through experimental methods. Furthermore, the principle and mitigation strategies for voltage undershoot are investigated. It shows that lower current density, higher back pressure and higher temperature are benefit to alleviate voltage undershoot. Compared with the SFF, the Second-stage time delay of PFF is shortened by 9.2 s, the VU is decreased by 17.27 mV, and the energy loss is reduced by 0.71%. Moreover, Pearson correlation coefficient is proposed to evaluate the correlation between index and PEMFC performance.

Dynamic modeling and robust control of a multi-cable payload transfer system for offshore cranes subjected to random waves and wind loads

The payload often experiences unpredictable motion due to the combined effects of random waves and wind loads, significantly impacting the safety and efficiency of offshore operations. To expand the effective working window for offshore transfer operations, this study introduces a multi-cable payload transfer system (MPTS). Using a 45-ton offshore crane mounted on a multipurpose vessel from COSCO Shipping Group as a prototype, this study establishes a dynamic model of MPTS, considering the effects of vessel motion, crane actions, and wind loads. The payload remains in an unstable state due to external disturbances. Additionally, variations in payload specifications and mass lead to considerable uncertainties in the dynamic parameters of MPTS. To address these uncertainties, a second-order linear observer is developed. Subsequently, an improved computed torque controller is proposed, and the boundedness of the tracking errors is proven using the Lyapunov theory. The transfer process is divided into three distinct phases: lifting, slewing, and lowering. The feasibility of the transfer scheme is verified through high-fidelity simulations and prototype experiments. This research provides a solid theoretical foundation for the subsequent engineering application of MPTS.

Nonlinear dynamic characteristics of smart FG-GPLRC sandwich varying thickness truncated conical shell with internal resonance for first three order modes

This paper examines the 1:1:1 internal resonant nonlinear dynamic characteristic of the simply supported varying thickness functionally graded graphene platelets reinforced composite (FG-GPLRC) smart truncated sandwich conical shell subject to the combined effects of transverse load and in-plane force. The truncated smart sandwich conical shell is composed of an FG-GPLRC varying thickness core and two magneto-electro-elastic face layers, whose material properties and constitutive relations are individually identified by the rule of mixture, improved Halpin-Tsai approach and generalized Hooke's law. Utilizing the first-order shear deformation theory (FSDT), von Karman's geometrical nonlinearity, Hamilton's principle and Galerkin technique, the 3DOF dimensionless nonlinear dynamic formulations for the truncated smart FG-GPLRC conical shell are established. The multiple-scale technique is applied to developing the averaged equations for the truncated smart FG-GPLRC conical shell under combined resonance. The frequency-response and force-response curves, Poincare maps, phase portraits, time history diagrams, bifurcation and maximum Lyapunov exponent diagrams can be portrayed by the nonlinear equation solver and Runge-Kutta approach. The effects of the damping and tuning parameters, transverse and in-plane forces on the 1:1:1 internal resonant nonlinear dynamic characteristic of truncated smart varying thickness FG-GPLRC sandwich conical shell are examined.

Waste rubber recycling in concrete-filled steel tube members: Mechanical performance, reliability and life cycle assessment

This paper focuses on the axial compression mechanical performance, reliability analysis and environmental impact of rubber concrete-filled circular steel tube (RuCFST) columns. Initially, the research of the axial compression performance reveals that enhancing the wall-thickness or yield strength of steel tubes variably increases the yield, peak, and ultimate loads of RuCFST columns. The degree of enhancement of each characteristic point by growing the wall thickness of the steel tube is 5 %–44 %, 6 %–44 %, and 9 %–44 %, respectively; while the degree of enforcement is 5 %–55 %, 23 %–53 %, and 24 %–61 %, respectively, upon yield strength increase. Reliability analysis indicates that higher concrete grades decrease the probability of axial compression failure in RuCFST columns. Raising the yield strength and wall-thickness of steel tubes leads to a reduction in the reliability index. Both larger and smaller live-to-dead load effect ratios adversely impact the reliability index. In addition, the life cycle assessment method was used to evaluate the environmental impact of RuCFST columns, and the analysis was made after considering the superposition effect of waste rubber incineration and recycling into rubber aggregates.

Effect of vanadium loadings in the textural and structural properties of Mg–Al–V mixed oxides

Effect of vanadium loadings in the textural and structural properties of Mg–Al–V mixed oxides

Comparative assessment of pollution control measures for urban water bodies in urban small catchment by SWMM

Under the current increasingly serious water pollution situation in urban, the comprehensive treatment and protecting measures in urban small catchment are the necessary step to the water pollution treatment, not only focus on the water bodies themself. In this paper, the Luojiagang river channel and its catchment in Wuhan, which has been heavily impacted by water pollution, are taken as an example for the comparative assessment of pollution control measures in order to explore the effective and sustainable schemes including the LID (Low Impact Development---LID) by using SWMM model (Storm Water Management Model---SWMM). Through the comparison of pollution treatment measures based on scenarios simulation with the baseline scenarios, it was found that the reduction effects of pollutant peak concentrations at the outlet node of Luojiagang River had the decreasing order of: the combined measures (COS) > LID control > the water diversion from Donghu Lake (WAD) > the sewage treatment (SET) > the sediment dredging (SED), and the reduction effects of total pollutant load had the decreasing order of: LID > COS > SET > SED > WAD. The results show that the control of non-point source pollution is the key for the improvement of water quality in Luojiagang River, and LID plays important role in the reduction of both pollutant peak concentrations and load. This study has the implication for the decision making of the water pollution controlling schemes in urban small catchment.

Assessment of impact load effect on self-sensing of cement composites incorporating hybrid silicon carbide-graphite under various environmental conditions

This study investigates the self-sensing abilities of hybrid silicon carbide-graphite cement composites (HSCGC) under various environmental conditions, focusing on dynamic impacts. Integrating silicon carbide (SiC) and graphite enhances the mechanical and electrical properties of these composites. Tests showed that composites with 30 % SiC and 2 % graphite had a 14.1 % increase in compressive strength and up to 85 % decrease in electrical resistivity. Water absorption reduced by 3.25 %, indicating better durability. Impact resistance ratios (IRR) varied with humidity and impact angles, with the highest IRR observed at 70 % humidity and a 30-degree angle. Self-sensing responses indicated that higher SiC and graphite content maintained stable conductivity, especially at 60 and 90-degree angles. Temperature changes affected resistivity, negligible at −10°C and increased at 45°C. The study concludes that HSCGCs are suitable for smart construction materials, capable of real-time environmental and structural monitoring, advancing predictive models and control systems.

Performance of Combined Woven Roving and Mat Glass-Fiber Reinforced Polymer Composites Under Absorption Tower Lifting Loads.

This study investigates the structural integrity of a glass-fiber reinforced polymer absorption tower during lifting operations, evaluating factors of safety and stress distribution for both horizontal and vertical scenarios. A key focus is the comparative analysis of surface and volumetric meshing techniques in finite element modeling. Results demonstrate that surface models achieve comparable stress predictions to computationally intensive volumetric models, significantly reducing computational demands without compromising accuracy. For instance, stress at the flange edge with holes was accurately captured using a surface model with 5675 elements (12.79 MPa), yielding similar results to a volumetric model requiring over 94,000 elements (13.37 MPa). Similar computational efficiency and agreement between modeling approaches were observed at the packing support ring-shell joint. Finite element analysis employing Hashin's failure criterion, informed by industry-standard experimental data, revealed safety factors ranging from 1.9 to 2.5 for horizontal lifting and four for vertical lifting. These safety factors indicate sufficient margins for safe operation. While these findings support the feasibility of both lifting methods, further investigation is recommended to address the lower safety factors observed in specific horizontal lifting scenarios. A comprehensive assessment incorporating industry standards, dynamic load effects, and potential mitigation strategies is crucial to ensure the long-term structural integrity of the GFRP absorption tower.

Morphology and Effect of Load on Bridge Piers Impacted by Continuous Sea Ice

Morphology and Effect of Load on Bridge Piers Impacted by Continuous Sea Ice

Gilding the Lily: Studies on the Effects of Successive Loading of Light Energy‐Storing Molecules with Norbornadiene Units

The photochromic norbornadiene‐quadricyclane cycle has emerged as a promising basis for molecular solar thermal (MOST) energy storage. In this context, it has been estab­lished that multifunctional photoswitches with several norborna­diene units at one central aromatic core have favorable photochemical properties and storage capacities. Nevertheless, a maximum number of three norbornadiene units has been combined in one molecule, so far. In this work, scope and limits of this approach should be further assessed. Thus, exemplary polyfunctionalized derivatives have been synthesized by Suzuki‐Miyaura reactions, and their suitability for MOST applications was investigated. These compounds were converted into the correspon­ding quadricyclanes by direct UV irradiation (λex = 315 nm) with moderate quantum yields, whereas the reaction is more efficient upon irradiation with λex = 520 nm in the presence of photosensitizers. But these molecules showed low stabilities and short half‐lifes of 1 to 2 days. Moreover, the photo­chemical reaction is hampered by the close vicinity of photoactive units. Therefore, it appears that in such assemblies, a maximum number of three norbornadiene units is the limit to keep the optimal balance of photochemical properties required for MOST applications.

Coal‐wall spalling prevention mechanism using advance‐grooving pressure relief in the large‐mining‐height working face of a shallow coal seam

AbstractIn mining, the roof structure of a working face with a large mining height in a shallow‐buried coal seam is prone to cutting instability in front of the support, which causes support crushing and coal‐wall spalling. This study analyzes 2201 working faces with large mining heights in the Haiwan No. 3 Mine by investigating the mechanical response law of coal walls under the transient excitation of roof structure instability. A mechanical model of coal walls under dynamic and static load coupling is established, revealing the formation mechanism of coal wall spalling and its main influencing factors. Prevention and control technologies of advanced grooving and pressure relief are proposed, and grooving parameters are determined. The results show that: During the mining process of large mining height working face in shallow buried coal seam, the step change of static response of coal wall is induced by the transient instability of roof structure, and the high abutment pressure is formed on the coal wall. At the same time, the strain energy and gravitational potential energy of roof cutting instability are released to form a dynamic load. Under the action of dynamic and static load, the plastic failure dissipation power of the coal wall is greater than the critical power, and the coal wall spalling occurs. The main influencing factors are mining load, mining height, and internal friction angle of the coal wall. The method of advanced grooving pressure relief can change the roof structure and coal force mechanism, by cutting off the connection between the coal wall and immediate roof, reducing the height of the coal wall force, effectively controlling the position of the roof cut off break line, reducing the static load effect of the roof on the coal, and transferring the position of the dynamic load response to the depth of the coal wall. When the grooving height‐depth ratio k is 0.75, the peak value of the abutment pressure moves 5.57 m to the front of the working face, and the pressure relief effect is the best. The above research results provide an effective active protection method for controlling coal wall spalling in fully mechanised working face with large mining height.

Investigating mental workload across task modalities: a multimodal analysis using pupillometry

Understanding mental workload is challenging due to its multidimensional nature and varying sensitivities of its primary measures: task performance, perceived workload, and physiological responses. This study investigates the effects of task load on performance, perceived workload, and pupil measures across different information modalities. A within-subjects experiment involving three tasks (digit span, matrix span, and dual n-back) was conducted with three task load levels. Workload measures included accuracy/sensitivity, reaction time, NASA-TLX, peak pupil diameter, and peak pupil latency. Consistent patterns of associations between task load and these workload measures were found across the three modalities. Workload measures revealed a nuanced interplay between task modality and task load. Robustness of peak pupil latency, accuracy, and NASA-TLX was highlighted across verbal and visual modalities, while peak pupil diameter showed a weaker impact with differences between modalities. The findings encourage multivariate assessment of mental workload to account for different task modalities.

Microstructural Evolution and Mechanical Properties of Extruded AZ80 Magnesium Alloy during Room Temperature Multidirectional Forging Based on Twin Deformation Mode.

This study investigates the preparation of ultrahigh-strength AZ80 magnesium alloy bulks using room temperature multidirectional forging (MDF) at different strain rates. The focus is on elucidating the effects of multidirectional loading and strain rates on grain refinement and the subsequent impact on the mechanical properties of the AZ80 alloy. Unlike hot deformation, the alloy subjected to room temperature MDF exhibits a lamellar twinned structure with multi-scale interactions. The key to achieving effective room temperature MDF of the alloy lies in combining multidirectional loading with small forging strains per pass (6%). This approach not only maximizes the activation of twinning to accommodate deformation but ensures sufficient grain refinement. Microstructural analysis reveals that the evolution of the grain structure in the alloy during deformation results from the competition between {101¯2} twinning or twinning variant interactions and detwinning. Increasing the forging rate effectively activates more twin variants, and additional deformation passes significantly enhance twin interaction levels and dislocation density. Furthermore, at a higher strain rate, more pronounced dislocation accumulation facilitates the transformation of twin structures into high-angle grain boundaries, promoting texture dispersion and suppressing detwinning. The primary strengthening mechanisms in room temperature MDF samples are grain refinement and dislocation strengthening. While increased dislocation density raises yield strength, it reduces post-yield work hardening capacity. After two passes of MDF at a higher strain rate, the alloy achieves an optimal balance of strength and ductility, with a tensile strength of 462 MPa and an elongation of 5.1%, significantly outperforming hot-deformed magnesium alloys.

Effects of hemodynamic load on cardiac remodeling in fish and mammals: the value of comparative models.

The ability of the vertebrate heart to remodel enables the cardiac phenotype to be responsive to changes in physiological conditions and aerobic demand. Examples include exercise-induced cardiac hypertrophy, and the significant remodeling of the trout heart during thermal acclimation. Such changes are thought to occur in response to a change in hemodynamic load (i.e. the forces that the heart must work against to circulate blood). Variations in hemodynamic load are caused by either a volume overload (high volume of blood returning to the heart, impairing contraction) or a pressure overload (elevated afterload pressure that the heart must contract against). The changes observed in the heart during remodeling are regulated by multiple cellular signaling pathways. The cardiac response to these regulatory mechanisms occurs across levels of biological organization, affecting cardiac morphology, tissue composition and contractile function. Importantly, prolonged exposure to pressure overload can cause a physiological response - that improves function - to transition to a pathological response that causes loss of function. This Review explores the role of changes in hemodynamic load in regulating the remodeling response, and considers the cellular signals responsible for regulating remodeling, incorporating knowledge gained from studying biomedical models and comparative animal models. We specifically focus on the renin-angiotensin system, and the role of nitric oxide, oxygen free radicals and transforming growth factor beta. Through this approach, we highlight the strong conservation of the regulatory pathways of cardiac remodeling, and the specific conditions within endotherms that may be conducive to the development of pathological phenotypes.