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The fatigue behavior of TC17 titanium alloy under different test environments: The effect of saltwater on fatigue failure characteristics and life estimation

The study of fatigue behavior in saltwater for TC17 titanium alloy has become a potential research issue in practical engineering and theoretical scientific research. In this study, it is found from the designed fatigue test that the corrosiveness of the test environment has a significant negative effect on the fatigue life of titanium alloy, and the distributions of fatigue life in 3.5%NaCl solution and 5%NaCl solution are similar. Typical surface failure characteristics and obvious corrosion traces are detected due to the coupling effect of corrosion and fatigue load. Then, electron back scatter diffraction (EBSD) is performed to figure out the change of micro grains from fine grains to coarse grains with the test environment changes from water to NaCl solution, and the strain concentration regions are detected at grain boundary and internal of coarse grains. Finally, the comparison of S-N curve with different models are carried out, Basquin model is proved to be suitable for the S-N curve estimation of TC17, and S-N models for different test environments are established. The micro test results provide a clear understanding of the corrosion fatigue failure behavior, and the newly established model considering the corrosiveness of test environment is novel and essential to the further fatigue study in theoretical research and engineering practice.

The low-carbon vehicle routing problem with dynamic speed on steep roads

The low-carbon vehicle routing problem with dynamic speeds on steep roads (LCVRPDS-SR) considers the combined effects of dynamic speeds, steep roads, and loads on carbon emissions. Earlier low-carbon vehicle routing problems typically assumed that vehicles travel at a constant speed on flat roads. However, such models do not apply in urban or rural areas with steep roads. Although the subsequent studies further explored the effect of steep roads, their performance are still suboptimal since they fail to take into account the varying speeds on the terrain. This paper proposes an extended LCVRPDS-SR model that tackles dynamic speed decisions on steep roads for the low-carbon vehicle routing problem. The objective function is non-linear and considers only environmental factors. Then an improved adaptive large neighborhood search algorithm is presented, including a new speed optimization algorithm and several improved removal and insertion operators. Extensive experiments are conducted on the generated instances to verify the effectiveness of the model and algorithm and derive managerial insights. The significant reduction in greenhouse gas emissions is achieved when considering dynamic speeds.

Design of Glass Handrails

Glass handrail loading and design in the United States lags behind best practice in other parts of the world. Improvements are possible for the design load, residual capacity and damage-event loading, each of which could be based on occupancy. Neither static loading nor impactor testing accounts for the dynamic effects of sustained loading to handrails during crowd load events. Alternate configurations for improved robustness at similar size and cost are presented.

Fatigue performance testing and life prediction of welded fuel pipes

The external piping system which connects power devices, valve control devices, actuators, etc. is an essential system on the aero engine. Under the combined effects of high fluid pressure and external vibration, multiaxial fatigue failure is the main factor that seriously affects the safety of the piping system. The objective of this paper is to establish the multiaxial fatigue life model for the typical welded fuel pipe of the piping system by combining fatigue testing, simulation and theoretical analysis which is of great guiding significance for the engineering application of the piping system. Firstly, the fatigue limits of welded fuel pipes under no and 13.5 MPa internal pressure are obtained by rotational bending fatigue tests using the up-and-down method. Three additional stress levels of rotational bending fatigue tests under no internal pressure are supplemented and then the S-N curve is further obtained by the group method. Since the corresponding fracture surface of the specimens locates at the weld toe near the fixed end, peak stress method is adopted to evaluate the fatigue performance of the weld toe on the pipe specimens. In addition, by comparing the fatigue limit with no and 13.5 MPa internal pressured pipes, it is obvious that the equivalent uniaxial stress corrected by Gerber formula is not applicable for the multiaxial fatigue condition which is caused by the combined effect of fluid pressure and displacement load. The local stress concentration factor caused by the weld toe is determined and based on Findley critical plane model, the multiaxial fatigue life model is established which simultaneously takes the local stress concentration effect, mean stress effect and multiaxial stress effect into consideration. The results of rotational bending fatigue tests under 13.5 MPa internal pressure are within the triple error dispersion band and the accuracy of the proposed life model are verified.

Fabrication of a novel hydrophobic zinc borate/polydopamine/talc nanocomposite with sandwich-like structure for enhanced tribological properties

Two-dimensional layered materials (2DLMs) as lubricant additives have received increasing attention due to their low interlaminar shear stress, outstanding chemical stability and lubrication effects, but the extreme pressure properties, dispersion and dispersion stability in base oils are poor. Herein, a hydrophobic zinc borate/polydopamine/talc (OA-ZB/PDA/TA) nanocomposite with sandwich-like structure is prepared by hydrothermal-assisted intercalation combined with mechanical activation process using natural talc 2DLMs as substrate and oleic acid (OA) as a surface hydrophobic modifier and peeling aid. No obvious sedimentation of OA-ZB/PDA/TA occurs in the rapeseed oil after 15 d, while pure TA is significantly deposited after 12 h, showing superior dispersion and dispersion stability. The OA-ZB/PDA/TA used as a lubricant additive in rapeseed oil exhibits excellent tribological performances under the loads from 147 to 784 N, particularly, wear scar diameter and coefficient of friction reduce by 51.4 and 33.7 % under 392 N, respectively, and the maximum nonseizure load (PB) increases by 27.0 % relative to pure TA. The TA-ZB-TA "sandwich-like" structure gives full play to the synergistic lubrication between ZB NPs and TA, resulting in the sliding and rolling effects under low load, friction film and rolling effect under medium load, and friction film under high load. Our work provides a new avenue for the enhanced extreme pressure properties and dispersion stability of 2DLMs in base oil.

Research on Temperature Rise Characteristics Prediction of Main Shaft Dual-Rotor Rolling Bearings in Aircraft Engines

Traditional aero-engine bearings rotate simultaneously with their inner and outer rings, which makes the temperature rise prediction model computationally large with low accuracy, and it cannot be accurately verified due to the means of testing. This paper presents a method for predicting the temperature rise characteristics of aero-engine bearings under composite load conditions. Firstly, the local method is used to calculate the heat generation from heat sources such as bearing spin, lubricant drag, and the differential sliding of steel ball and collar, respectively, then finite element modelling and steady-state thermal analysis are carried out for aero-engine bearings under the simultaneous action of axial and radial external loads, a double-rotor test setup is designed and the predictive model is validated, and finally, the influences of rotational speed and load on the temperature rise characteristics of the bearings are investigated. The study shows that the aero-engine bearing prediction model proposed in this paper has high accuracy; with the increase in the rotational speed of the inner ring of the bearing, the temperatures of both the inner and outer rings of the bearing increase significantly; the temperatures of the inner and outer rings of the bearing increase with the increase in the axial load, and the effect of the radial load on the temperature of the bearing is not obvious.

Shear behavior of thin-walled concrete-filled steel tubular columns

Shear failure is a brittle type of failures, which should be avoided in any structure as it could cause property loss and human casualties. The shear behavior of thin-walled concrete-filled steel tubular (CFST) columns was hence investigated in this study, involving the tests of 24 thin-walled CFST columns and considering the following parameters: shear span-to-depth ratios = 0.15, 0.3, 0.5, 1, 1.5, and 2; confinement factor = 0.63, 1.27, 1.44, and 1.70; and axial load ratios = 0, 0.2, 0.4, and 0.6. The test results revealed the insights of the initial shear stiffness, failure modes, ultimate bearing capacity, load-deflection curves, load-strain curves, and ductility of the specimens. Based on the failure modes, a method is proposed to evaluate the load resistance, and explain the relationship between the shear span-to-depth ratio and the peak bearing capacity. A compression strut mechanism considering the confinement provided by the steel tube flange is also proposed. The effect of axial load on the shear strength of the concrete core is negligible when the axial load ratio doesn’t exceed 0.4. The predicted results from using the proposed simple model agree generally well with the experimental results.

Enhanced boron removal via seed-induced crystal growth of barium perborate in sequential fluidized-bed crystallization

Chemical oxo-precipitation (COP) is an enhanced precipitation method for boron removal with the conversion of boric acid to perborate anions. When using barium-based precipitant, the boron can be effectively precipitated as barium perborates (BaPBs). The phase transformation of BaPBs from amorphous (A-BaPB, Ba(B(OH)3OOH)2) to crystalline (C–BaPB, BaB2(OO)2(OH)4) form is crucial for effective boron removal. However, scaling up this phase transformation of BaPBs is hindered by poor diffusion. This study aims to promote the growth of C–BaPB through seed-induced crystal growth, eliminating the need for phase transformation. By examining the relationship between crystal growth rate and supersaturation, surface spiral growth was identified as the rate-limiting step of the growth of micron-sized seeds near pHpzc. To enable continuous crystal growth, granular seeds of C–BaPB were prepared and employed as the medium for fluidized-bed crystallization (FBC). The system reached steady state 3 hydraulic retention times, achieving 90% boron removal. The effect of surface loading, ionic strength, and dosages on steady-state crystal growth rate was studied, revealing a shift of the rate-limiting step in FBC to diffusion. Lastly, the system that constituted of two FBCs in-series for sequential crystallization of A-BaPB and C–BaPB was demonstrated. The integrated system provided 97.8% of boron removal from synthetic wastewater containing 500 mg-B/L, with 92.3% of boron crystallized on the granular seeds of BaPBs.

Investigation of notch position and fiber ratio on the fracture mode and energy of sfrc beam under the impact load

When the literature is examined, it is seen that a lot of study has been done on the crack propagation and fracture modes that occur under the influence of static loads in reinforced concrete (RC) structures. Studies in the literature show the effect of crack initiation, concrete compressive strength, and fiber volume fraction on the tension mode (Mode-I), shear mode (Mode-II), and mixed fracture mode that occurs in crack propagation under static load. However, the literature has not found a comprehensive study in which the fracture modes are examined under the effect of dynamic impact loading. For this reason, an experimental study has been planned in which hybrid steel fiber reinforced concrete (SFRC) notched beams with varying compressive strength will be tested under impact loading with a free-fall drop weight device designed by the authors. The experimental variables studied were determined as the change of the crack initiation point in the beams, the compressive strength of the concrete used to produce the beams, and the fiber volume fraction in the concrete mixture. The acceleration and impact load-time histories under the constant-energy-level impact loading applied to the beams were measured. Also, the crack shape, fracture mode, crack angle, and energy absorption capacities of the beams under impact load were interpreted. While the transition from Mode-I fracture form to Mode-II fracture form occurs under impact loading, the effects of concrete compressive strength and steel fiber ratio variables on energy absorption capacity, crack angle, and crack shape are studied. Increasing the distance of the notch from the beam midpoint in notched beams produced with concrete without fiber from 0 to 40, 80 and 120 mm caused the energy absorption capacity values to increase by an average of 39 %, 66 % and 86 %, respectively. Increasing the distance of the notch to the beam midpoint from 0 to 40, 80 and 120 mm in beams with 0.75 % and 1.5 % fiber ratio increased the energy absorption capacity values by an average of 40 %, 65 % and 86 %, respectively. In beams with 2.25 % fiber ratio, increasing the notch distance from 0 to 40, 80 and 120 mm increased the energy absorption capacity values by an average of 38 %, 62 % and 83 %, respectively.

Effect of axial load and shear span on seismic performance of CFT columns reinforced with end-fixed ultra-high strength rebars

Effect of axial load and shear span on seismic performance of CFT columns reinforced with end-fixed ultra-high strength rebars

Vicious Circle With Venous Hypertension, Irregular Flow, Pathological Venous Wall Remodeling, and Valve Destruction in Chronic Venous Disease: A Review.

Substantial advances occurred in phlebological practice in the last two decades. With the use of modern diagnostic equipment, the patients' venous hemodynamics can be examined in detail in everyday practice. Application of venous segments for arterial bypasses motivated studies on the effect of hemodynamic load on the venous wall. New animal models have been developed to study hemodynamic effects on the venous system. In vivo and in vitro studies revealed cellular phase transitions of venous endothelial, smooth muscle, and fibroblastic cells and changes in connective tissue composition, under hemodynamic load and at different locations of the chronically diseased venous system. This review is an attempt to integrate our knowledge from epidemiology, paleoanthropology and anthropology, clinical and experimental hemodynamic studies, histology, cell physiology, cell pathology, and molecular biology on the complex pathomechanism of this frequent disease. Our conclusion is that the disease is initiated by limited genetic adaptation of mankind not to bipedalism but to bipedalism in the unmoving standing or sitting position. In the course of the disease several pathologic vicious circles emerge, sustained venous hypertension inducing cellular phase transitions, chronic wall inflammation, apoptosis of cells, pathologic dilation, and valvular damage which, in turn, further aggravate the venous hypertension.

INFLUENCE OF PROPELLER-ICE LOADS ON THE WEAR DEVELOPMENT IN STERN TUBE BEARINGS OF MARINE PROPULSION SYSTEMS AND IDENTIFICATION OF CRITICAL OPERATING CONDITIONS

Abstract Increasing ship traffic in ice-covered waters leads to more frequent collisions between ship propellers and sea ice which causes extreme impulse loads on the propeller. Theses loads are transferred through the propeller shaft to the sliding bearings of the stern tube, especially, the aft stern tube bearings. Extreme bearing loads can lead to mixed-friction regimes which cause wear in the bearings and eventually results in a failure of the entire propulsion system. The effect of ice-induced loads on the contact conditions in the sliding bearings is widely unknown. Thus, a study of the influence of these loads on the contact conditions and wear behavior in stern tube bearings resulting from observed sea ice conditions and operating conditions of the ship is necessary. This paper aims to investigate the influence of ice collision loads on the contact conditions in the bearings of the stern tube of the research vessel SA Agulhas II. For this purpose, an elastohydrodynamic simulation and a multibody simulation based on field measurements were performed. As a result, this paper identifies the operating condition thresholds (i.e. propeller torque and rotational speed) during propeller-ice collisions that cause mixed-friction conditions in the bearings. On the basis of these conditions, a risk map is generated to assess the actual wear risk by including the frequency of occurrence of the corresponding mixed-friction condition over the duration of a voyage.

Analysis of Vibration Characteristics and Influencing Factors of Complex Tread Pattern Tires Based on Finite Element Method

The vibration of the tires significantly impacts a vehicle’s ride comfort and noise level; however, the current analysis of tire vibration characteristics often involves excessive simplification in their models, leading to a reduction in model accuracy. To analyze the tire vibrational properties and the influence of its design and service conditions, a combined modeling technology was developed to construct a three-dimensional (3D) finite element model of a 205/55R16 specification radial tire with intricate tread patterns. The accuracy and reliability of the simulation model was verified through vibration modal tests. Based on the vibration mode theory, the Lanczos method provided by ABAQUS was adopted to analyze the modal characteristics of the tire under free inflation and grounded conditions, and the effects of different inflation pressures, loads, operating conditions, and belt cord angles on the tire vibration characteristics were analyzed. The results indicate that grounding constraints will suppress the low order radial modal frequency of the tire and enhance the lateral modal frequency. The higher the order of the tire vibration mode, the greater the impact of inflation pressure. As the operating conditions change, the modal frequencies of all directions have the same trend of change, and as the ground load increases, the tire is prone to misalignment at lower lateral frequencies. The radial and lateral grounding modes of the tire are slightly affected by the change of the cord angle in the belt layer, but the circumferential grounding frequency decreases as the belt layer angle increases. These research findings offer a crucial foundation for the structural design of complex tread pattern tires, and also serve as a reference for addressing vibration and comfort issues encountered in the tire matching process.

Elucidating solvent effects on lipase-catalyzed peroxyacid synthesis through activity-based kinetics and molecular dynamics.

Peroxyacid synthesis is the first step in Prilezhaev epoxidation, which is an industrial method to form epoxides. Motivated by the development of a kinetic model as a tool for solvent selection, the effect of solvent type and acid chain length on the lipase-catalyzed peroxyacid synthesis was studied. A thermodynamic activity-based ping-pong kinetic expression was successfully applied to predict the effect of the reagent loadings in hexane. The activity-based reaction quotients provided a prediction of solvent-independent equilibrium constants. However, this strategy did not achieve satisfactory estimations of initial rates in solvents of higher polarity. The lack of compliance with some assumptions of this methodology could be confirmed through molecular dynamics calculations i.e. independent solvation energies and lack of solvent interaction with the active site. A novel approach is proposed combining the activity-based kinetic expression and the free binding energy of the solvent with the active site to predict kinetics upon solvent change. Di-isopropyl ether generated a strong interaction with the enzyme's active site, which was detrimental to kinetics. On the other hand, toluene or limonene gave moderate interaction with the active site rendering improved catalytic yield compared with less polar solvents, a finding sharpened when peroctanoic acid was produced.

Finite element analysis-based blast and seismic performance evaluation for RC frame with retrofitted ENTA damper systems

Blast loading and seismic excitations are widely recognized as the most detrimental occurrences that a building structure may encounter throughout its lifespan. Therefore, this study investigated the retrofitting capacity of external devices (ENTA damper systems) for reinforced concrete (RC) frames in term of enhancing their resistance under the combined effects of blast and seismic loads. This study presents the establishment of finite element (FE) models for retrofitted RC frames with ENTA damper systems through the utilization of the dynamic analysis software LS-DYNA. The investigation involved the validation for blast performance of RC column in order to identify the most effective method for modeling blasts. Additionally, the study aimed to validate the performance of RC frame models through effects of ENTA damper systems under seismic loading. Subsequently, a performance evaluation of RC frame structures was carried out to examine the impact of the ENTA damper systems when subjected to blast loading. The findings of the study indicate that the use of external ENTA damper systems effectively enhanced the rigidity and structural integrity of RC frames, while maintaining their ability to resist deformation. Finally, the damage assessment of blast and seismic performance is investigated based on various parameters such as ductility, drift and energy-based damage limits.

Recent progress in polyvinyl alcohol (PVA)/nanocellulose composite films for packaging applications: A comprehensive review of the impact on physico‐mechanical properties

AbstractAs society advances, the demand for innovative and sustainable food processing techniques and materials has grown significantly. The food industry, especially the food packaging sector, faces the challenge of developing cost‐effective and sustainable packaging materials to meet consumers' increasing demands. One promising solution for this is the use of biodegradable polymers such as polyvinyl alcohol (PVA), but standalone PVA cannot meet the required properties of packaging materials. The use of nanocellulose (NC) as fillers has been intensively studied recently. This review article provides a comprehensive overview of existing studies focusing on the preparation of PVA/NC composite films for packaging applications. The effects of NC loading on the physico‐mechanical properties of these films, including tensile strength, elongation, water absorption/swelling behavior, barrier properties, and optical properties, have been thoroughly examined. Overall, the general findings suggest that the reinforcement of NC in the PVA polymer matrix leads to improvements in the films' properties. Specifically, the addition of NC enhances tensile strength, reduces O2, CO2, and water vapor transmission rates, and decreases the films' propensity to absorb moisture or swell under wet conditions. However, it is important to note that the presence of NC compromises the optical properties of the films by reducing transparency, and the NC content beyond threshold level reduces the feasibility of the composite film. By synthesizing these findings, this review underscores the potential of PVA/NC composite films as promising materials for packaging applications. Moving forward, further research efforts are warranted to optimize the formulation and processing of these composite films to strike a balance between mechanical strength and optical clarity, thus advancing their practical utility in the packaging industry.

Cobalt Promotion and Ni+Co Loading Effects of γ-Al2O3-Supported Ni–Co Catalysts for the Flue Gas Reforming of Methane

Cobalt Promotion and Ni+Co Loading Effects of γ-Al₂O₃-Supported Ni–Co Catalysts for the Flue Gas Reforming of Methane

A new method of rapid-intelligent assessment for the dynamic service performance in high-speed railway subgrade

ABSTRACT There is a lack of a rapid, advanced, and comprehensive method for assessing the dynamic service performance in high-speed railway subgrade, which leads to an inability to pre-assess the health state of the subgrades in advance. In this paper, an innovative method of rapid-intelligent assessment for the dynamic service performance (RADSP) in high-speed railway subgrade was proposed. Firstly, a large-scale exciter was used to simulate the train loading effect, which could rapidly obtain the assessment metrics for subgrade dynamic service performance, including subgrade dynamic response (SDR) and subgrade cumulative deformation (SCD), where the SDR includes dynamic stress and acceleration. Then, to explore the future development trend of SCD during operation, an intelligent and advanced prediction of SCD was conducted using the optimal machine learning (ML) prediction model. Finally, by combining the results of the SDR and SCD assessments to achieve the RADSP in high-speed railway subgrade. Moreover, the method was applied to assess the dynamic service performance of diatomaceous earth subgrade structures with four different waterproofing structure layers (WSL): the middle of subgrade surface layer (WSL-1), the bottom of subgrade surface layer (WSL-2), the middle of subgrade bottom layer (WSL-3), and the bottom of subgrade bottom layer (WSL-4). The results indicate that: 1) During the excitation experiments, the maximum values for SDR (dynamic stress, acceleration) and SCD exceed the respective limits of 50 kPa, 10 m/s2, and 15 mm under WSL-1 and WSL-4. 2) The ensemble model, AdaBoost-GPR, is selected as the optimal ML model to predict the SCD values. Notably, the prediction SCD value exceeds the 15 mm limit under WSL-3, indicating that the SCD during future operation does not meet the requirements for pre-assessment. 3) Under WSL-2, both SDR and SCD assessments satisfy the limit value requirements, indicating that the dynamic service performance is better. Based on the proposed method, it is found that when designing waterproof-drainage subgrade structures in diatomaceous earth areas, it is recommended to position the WSL at the bottom of subgrade surface layer. The research findings serve as a crucial reference and valuable lesson for the health monitoring of high-speed railway subgrades.

Effect of Torsional Load on Electrical and Mechanical Properties/Behaviour of Stretchable GNP-Ag Conductive Ink

Stretchable conductive inks (SCIs) have gained significant attention in recent years due to their potential applications in flexible and wearable electronics. Graphene nanoplatelet (GNP) hybridization conductive ink is a promising material for stretchable electronics due to its high electrical conductivity and excellent mechanical properties. However, the resistivity of GNP ink on flexible substrates can be affected by various factors, such as the torsion of the substrate. This paper aims to investigate the effect of torsional load in terms of the electrical and mechanical behaviour of hybridization conductive ink between GNP and Ag. The research was carried out on the formulation and performance of GNP hybrids using GNP and silver flakes (Ag). The GNP hybrid ink was printed on a copper substrate using a mesh stencil method and cured at 250 °C for an hour. The resistivity was evaluated at room temperature before and after the torsional tests in terms of electrical characteristics. The finding exposed that the resistivity values for each of the three samples of torsional tests significantly changed after 1000 cycles. Eventually, the resistance value at cycle 5000 rose due to the damaging impact of increasing the number of torsional cycles on the sample. In future work, it is recommended that the evaluation is made under temperature dependence and supported by SEM images.

Supported copper nanoarchitecture for selective ethylbenzene oxidation (EBO) reaction

Copper-based (Cu-NP) uniformly dispersed on various inorganic supports (alumina, silica, titania, and zirconia) were prepared by the reverse microemulsion technique. These nanoparticles were used for the selective oxidation of ethylbenzene (EB) to produce acetophenone (AP) as the main product in the presence of Tert‑butyl hydroperoxide(TBHP) as an oxidant. This study focused on creating Cu-nanoparticles evenly dispersed on alumina using varying Cu-loadings (5 %, 10 %, and 15% wt.) and Brij-35 as the surfactant. The resulting catalytic material was characterized using various physicochemical techniques like XRD, FESEM, HRTEM, XPS and physisorption techniques. Various parametric studies were conducted, such as the effects of temperature, catalyst support, catalyst loading, and TBHP loading to optimize the EB conversions and AP selectivity. Among the various catalyst loadings, 15 % CuO/Al2O3 (15 % of the copper content) nanocomposites showed exceptional performance, with the highest EB conversion rate (99.7 %) and AP selectivity (98.5 %) compared to other nanocomposites. The catalyst's stability and recyclability over four cycles were attributed to the strong copper oxide-alumina interaction. These findings suggest that this nanocomposite material is a promising candidate for catalytic applications, offering high selectivity and consistent EB conversion rates.