Change In Deflection Research Articles

Implementation of Legendre wavelet method for the size dependent bending analysis of nano beam resonator under nonlocal strain gradient theory

The bending analysis due to thermoelastic loading in nanoscale materials is primarily determined by the physical aspect of the material and the modeling of structures. This paper examines the prediction of bending characteristics of the Euler-Bernoulli beam using Moore-Gibson-Thompson (MGT) thermoelasticity theory in conjunction with nonlocal strain gradient theory (NSGT). The coupled equations for dimensionless deflection and temperature change with ramp-type heating boundary conditions are formulated and solved using the Laplace transform method and the wavelet approximation method. The stiffness softening and hardening effects due to nonlocal and length-scale parameters are assessed, and their discrepancies are discussed. Findings further reveal that the impact of the thermal relaxation parameter on deflection and temperature is negligible. Moreover, the different aspect ratios of the beam's structure depict the prominently behavior of structural simulations in bending.

Development of a Multi-Suspension Unit for Solar Cleaning Robots to Mitigate Vibration Impact on Photovoltaic Panels

Numerous studies about solar panel cleaning robot (SPCR) have been conducted globally to enhance the performance of photovoltaic panels (PV panels). However, there is a reality: scant attention has been paid to the large pressure and vibration that SPCR movements induce, not only on the photovoltaic panel surface but also on the mounting structure. Most of the research is focused on evaluating the “cleanliness” of the PV surface by using a clearing robot or the effects of natural factors (wind, dust, etc.) on the PV panels. Nonetheless, the large pressure and vibration constitute one of the primary factors contributing to the degradation of photovoltaic panel longevity and efficiency, especially affecting poorly installed PV arrays. To address these issues, this study proposes the design of a multi-suspension unit for the SPCRs equipped with track-wheeled, which might reduce vibration on the PV panel surface generated by the SPCRs’ motion and brushing action during operation. The multi-suspension unit facilitates the expansion of the contact area between the track-wheeled and the PV panel surface; hence, the negative effect is reduced owing to the vibration-absorbing properties of the rubber track pads. In the case of a static SPCR state, with only the impact of rotating brushes on vibration, the effectiveness of the multi-suspension unit can reduce vibration by a maximum of 72.63. Moreover, a metric (Δz) is proposed to evaluate the change in deflection of PV panels over time. The results show that the number of significant changes in PV panel deflection gradually decreases or disappears, while the number of small changes increases. In the case of SPCR operating on portrait PV modules, the number of occurrences of Δz (greater than 0.5 mm) is reduced from 18 counts to 5 counts, while the number of occurrences of Δz (less than 0.5 mm) increased from 61 counts to 91 counts. Overall, the proposed multi-system suspension is effective in reducing or eliminating large deflections while keeping the vibration frequency constant.

A Study on the Characteristics about Shaft Deflection According to the Change in Manufacturing Sequences

Recently, the amount of orders for large container ships based on eco-friendly fuel is increasing. Container ships have very different characteristics of cargo as comparing other type cargo carriers, having a unique arrangement of structural members. In this reason, the classification societies propose major governing conditions that affect independent shaft alignment calculations based on detailed analysis. In this study, the change in displacement around the shaft system, which occurs in the manufacturing process, was investigated using structural analysis modeling. The manufacturing process is divided into PE (Pre-erection), welding according to the erection sequences, lifting the block, setting on the dock, and finally reviewing the launching conditions. The results of this study, the displacement of the shaft system during the manufacturing stages were confirmed. The change in the number of block supports had the greatest effect on the change in deflection rather than the effect of welding heat, and the final results were similar to those of the PE condition. The shaft centering analysis can be predicted correct value in advance if the characteristics of deflection change according to the process are known, and accurate prediction can be made in a short time by using the proposed procedure.

Label free detection of vitamin D by microcantilever-based aptasensor

Vitamin D deficiency or insufficiency is a growing public health problem. In this work, a novel and sample approach based on microcantilever for measuring the level of 25-hydroxyvitamin D (25(OH)D) was proposed. The Bruno aptamer was utilized to functionalize the microcantilevers, serving as a sensing layer for detecting 25(OH)D. The working principle of the sensor is based on the changes of the microcantilever deflection and frequency as a result of the aptamer removal from the surface of the microcantilever resulting from its interaction with vitamin D. The results showed a linear dependence between vitamin D concentration and the microcantilever deflection and frequency shift in a range of concentrations from 1 to 300 nM. For this biosensor, the limit of detection (LOD) was calculated to be ∼ 0.3 nM. The biosensor selectivity was tested against vitamin C and the sensor showed high selectivity towards vitamin D.

The J2 evolution model and control technology of the main roadway surrounding rock under superimposed influence of double-coal seam mining

Under double-seam mining, the main roadway surrounding rock is affected by the superposition of the advanced stress of the two-seam coal working faces. The stress superposition mode and degree are of great significance to the width calculation of the protective coal pillar and the determination of the critical control direction of the surrounding rock. This paper uses theoretical analysis, numerical simulation, and site engineering practice to carry out targeted research. The conclusions are as follows: Under different lateral pressure coefficients, the superposition evolution law of maximum principal stress direction of two coal seams with different offsets; Two developmental trends and three types of evolution models of J2 peak zone (the critical area of the stress increase and deflection changes) under different superimposed loading modes are summarized. Based on the typical asymmetric evolution model of the J2 peak zone, an asymmetric truss-cable co-anchoring method is proposed aimed at the J2 critical zone. The field monitoring results show that the main roadway surrounding rock is stable after support when the upper coal seam protective coal pillar is left 80 m, and the lower one is 60 m wide. It is of great reference importance for similar engineering practices.

A novel approach of bending behavior of carbon nanotubes by combining the effects of higher-order boundary conditions and coupling through doublet mechanics

This article presents the bending behavior of carbon nanotubes (CNTs) based on doublet mechanics (DM) and Euler–Bernoulli beam theory to analyze how deflection changes with higher-order boundary conditions and the coupling, which have not been previously investigated. The governing equations and associated boundary conditions are obtained using the principle of minimum potential. Numerical solutions show an important effect of higher-order boundary conditions on the deflection of cantilever CNTs, unlike simply supported CNTs. A paradox in which DM shows a stiffening behavior for cantilever CNTs is resolved using higher-order boundary conditions. The coupling significantly effects the bending behavior of armchair CNTs.

Steering Control Improvement of Active Surgical Needle Using Mosquito Proboscis-Inspired Cannula

Abstract Active needles have demonstrated superior tip deflection and improved accuracy compared to passive needles enhancing the efficacy of percutaneous needle insertion procedures. Successful navigation of these needles through tissues to reach targets relies on factors such as the actuation mechanism, tip shape, and surface geometry. In this study, we investigated the advantages of modifying the surface geometry of the active needle shaft, focusing on two improving crucial aspects: (a) needle tip deflection and (b) trajectory tracking during tissue insertion. Prior research had shown that modifying the surface geometry of passive needles reduced friction force, tissue displacement, and tissue damage. Building on this knowledge and being motivated by the surface geometry of mosquito proboscis, our study proposed a bio-inspired design modification on the active needle cannula. The active needle with the mosquito proboscis-inspired cannula was tested to measure the changes in insertion force, tip deflection, and trajectory tracking during polyvinyl chloride (PVC) phantom tissue insertions. Results showed that passive bevel-tip needles reduced insertion force by up to 10.67%. In active needles, tip deflection increased by 12.91% at 150 mm insertion depth when the cannula was modified. The bio-inspired cannula improved trajectory tracking error in the active needle by 39.00% while utilizing up to 17.65% lower control duty cycle. The enhancement of tip deflection and tracking control is expected to improve percutaneous procedures by achieving better patient outcomes and significantly mitigating the risk of complications.

Sensitive detection of heavy metal stress in aquatic plants by dissolved oxygen-quenched fluorescence/materials movement-induced beam deflection method.

Sensitive detection of heavy metal (HM) stress in aquatic plants by dissolved oxygen (DO)-quenched fluorescence/materials movement-induced beam deflection method is demonstrated. Egeria densa Planchon and Cu2+ were used as a model aquatic plant and HM ion, respectively. Reproducibility and experimental errors of the method were first investigated in a control culture solution only containing 10-6M Ru (II) complex (Tris (2,2'-bipyridyl) ruthenium (II) chloride) without addition of any fertilizer and Cu2+. Changes of DO concentration (∆DO) and deflection (∆DE) during the monitoring periods were used as parameters to quantitatively evaluate the experimental errors and detection limits. Averages or means ([Formula: see text], [Formula: see text]) and standard deviations (σ∆DO, σ∆DE) of ∆DO and ∆DE in seven control experiments with different aquatic plants sheets during both the respiration and photosynthesis processes were obtained. Next, DO and deflection at the middle vicinities of the aquatic plant were monitored during 2h of both respiration and photosynthesis in presence of 10-10 ~ 10-6M Cu2+. Experimental results showed that the aquatic plant began to suffer from the HM stress in some extent in presence of 10-9M Cu2+. When the concentration of Cu2+ was higher than 10-8M, changing trends of both DO and deflection with time were not reversed during the respiration and photosynthesis, implying that the materials movements in the physiological activities had been altered greatly. It is demonstrated that the method could sensitively detect the HM stress in the aquatic plants given by nM HM ions in culture solution without addition of a fertilizer. Furthermore, detection limits of the method were quantitatively discussed by considering [Formula: see text] σ∆DO and [Formula: see text] σ∆DE as the minimum detectable changes of DO and deflection caused by the HM stress, respectively.

Experimental Study on Mechanical Behavior of Gas Transmission Shield Tunnel Segments

To analyze the mechanical behavior of the shield tunnel segment lining of underwater pipelines, based on the prototype segment structure practically applied in a project, a local model test of the combined shield segment considering front and rear ring staggered joints was designed. The internal forces and strains, joint opening and misalignment, and structural deflection change with the axial pressure ratio at different locations of the segment in the range of axial pressure ratio 0.02–0.54 were investigated, and the final failure form of the segment structure was also obtained. The experiment results show that in the assembly segments, the middle segment has the highest stiffness, followed by the side segments. When the segments are damaged, the maximum opening of the longitudinal joint is 1.75 mm. Because the overall damage of the segments is earlier than the joint damage, it is suggested that the development of structural cracks, joint misalignment, and structural deflection be taken as the basis for evaluating the safety of tunnel segments. When the axial compression ratio is loaded above 0.50, top concrete crush damage occurred in the middle segment, while the concrete on both sides happened to incur an oblique 45° shear damage.

An experimental study of bending resistance of multi-size PFRC beams

Abstract To study the effects of macro- and micro-fiber on the concrete beams, bending resistance tests were conducted on the polypropylene fiber-reinforced concrete beams. Stepwise loaded tests were carried out to obtain the load–deflection curves for different test pieces, cracking load values of the first inclined crack, recording and depicting crack development, changes in mid-span deflection of the test pieces, load–strain relationships of concrete, etc. The crack patterns and failure modes were observed. The research findings have shown that the ultimate load of the concrete beams doped with multi-size polypropylene fiber is 58.31 and 34.08% higher than that of ordinary concrete beams and concrete beams with single macro-fiber, respectively. Notably, the ultimate anti-bending bearing capacity of the beams significantly improves following the addition of macro-fiber. Polypropylene fiber can offset the defects caused by macro-fiber, remarkably suppress the development of cracks, and control the deformation of beams due to the effects of micro-fiber of different dimensions.

Coupled Excitation Strategy for Crack Initiation at the Adhesive Interface of Large-Sized Ultra-Thin Chips

The initial excitation of interface crack of large-size ultra-thin chips is one of the most complicated technical challenges. To address this issue, the reversible fracture characteristics of a silicon-based chip (chip size: 1.025 mm × 0.4 mm × 0.15 mm) adhesive layer interface was examined by scanning electron microscope (SEM) tests, and the characteristics of a cohesive zone model (CZM) unit were obtained through peel testing. The fitting curve of the elastic bilinear model was in high agreement with the experimental data, with a correlation coefficient of 0.98. The maximum energy release rate required for stripping was GC = 10.3567 N/m. Subsequently, a cohesive mechanical model of large-size ultra-thin chip peeling was established, and the mechanical characteristics of crack initial excitation were analyzed. The findings revealed that the larger deflection peeling angle in the peeling process resulted in a smaller peeling force and energy release rate (ERR), which made the initial crack formation difficult. To mitigate this, a coupling control method of structure and force surface was proposed. In this method, through structural coupling, the change in chip deflection was greatly reduced through the surface coupling force, and the peeling angle was greatly improved. It changed the local stiffness of the laminated structure, made the action point of fracture force migrate from the center of the chip to near the edge of the chip, the peeling angle was increased, and the energy release rate was locally improved. Finally, combined with mechanical analysis and numerical simulation of the peeling process, the mechanical characteristics of peeling were analyzed in detail. The results indicated that during the initial crack germination process, the ERR of the peel interface is significantly increased, the maximum stress value borne by the chip is significantly reduced, and the peel safety and reliability are greatly improved.

Fourth AIAA High-Lift Prediction Workshop: Fixed-Grid Reynolds-Averaged Navier–Stokes Summary

The current state-of-the-practice technology for high-lift aerodynamic simulations is to solve the Reynolds-averaged Navier–Stokes (RANS) equations on a fixed grid or a refinement sequence of fixed grids. The Fixed-Grid Reynolds-Averaged Navier–Stokes Technology Focus Group set out to determine meshing requirements and best practices, whether RANS can accurately predict the change in aerodynamic performance with changes in flap deflection, whether RANS modeling can produce accurate results near CLmax, and the effects of underconvergence and solution strategy on computed results. Eighteen groups of participants submitted over 100 datasets. Challenges with grid convergence and iterative convergence made it impossible to definitively answer all the questions we had posed. Despite this, we can conclude that meshes with at least half a billion cells (more than one billion degrees of freedom) are required for grid convergence away from stall; that RANS simulations cannot currently be reliably used to predict aerodynamic coefficients near stall, nor changes in coefficients with changes in flap angle; that iterative underconvergence remains a significant source of uncertainty in outputs; and that solution initialization can have an important effect on solution behavior, including flow separation patterns.

Size-dependent thermal bending of bilayer microbeam based on modified couple stress theory and Timoshenko beam theory

The bilayer microbeam can be assigned with two different thermal expansion coefficients, so that the microbeam can be used as a thermal actuator, which can provide bending with thermal loading. As a microdevice, the size effect plays an important role. In addition, the length height ratio L/h of the microbeam has to be smaller than 20, to provide sufficient support. With this ratio, the shear effect of the beam can not be ignored. In this work, considering both the size and shear effects, we modified the couple stress and Timoshenko beam theories to study the thermal bending of bilayer microbeams. By using the principle of minimum potential energy, we derived the higher-order governing equations under thermal load. Then with specified boundary conditions, we adopted the differential quadrature method to solve the governing equations. Finally, using a bilayer microbeam made of aluminum and polysilicon as an example, we verified effects of transverse shear and beam size. Results show that the size effect on beam stiffness is significant when the beam height is on the order of equivalent length scale (leq). Moreover, considering the transverse shear effect indicates that the lateral deflection of the Timoshenko beam depends on the ratio L/h: as L/h increases, the tip deflection increases and converges to the classical solution. Specifically, for a Timoshenko beam with h/leq = 15, the change in deflection can reach 44.6% when L/h is increased from 5 to 25.

A computational iterative design method for bend-twist deformation in composite ship propeller blades for thrusters

Abstract This study investigates the feasibility of utilising common composite material layup techniques in ship propeller blade design to achieve an automatic pitch adjustment through bending-induced twist deformation. A comprehensive design approach, including various reinforcement materials and arrangements, was employed to attain the desired foil pitching, while minimising other undesirable deformation modes. The design process involved iterative computational analysis using finite element analysis and a deformation mode analysis based on foil shape parameters. The research showed that the proposed design approach effectively found options to improve the desired foil parameter pitch, while minimising undesirable deformation modes such as blade deflection and foil shape change. Furthermore, the proposed blade design was tested in thruster steering operational conditions and was found to have a pitch change well matched, potentially countering some changes in fluid flow. When compared to Kumar and Wurm’s design, which only focused on the angular orientation of glass reinforcement, the proposed design was found to outperform the twisting by achieving the same twist for a blade half the length. This study provides valuable insights into the utilisation of composite materials in ship propeller design and highlights the potential for further improvement through a composite engineering design approach.

Fabry-Perot İnterferometre Tabanlı Sensörlerde Mesa Boyutlarının MEMS Diyaframlar Üzerine Etkisi

In this study, the effects of mesa dimensions on sensor response in diaphragm-based Fabry-Perot fiber optic sensors (FOSs) were investigated in detail. Mesa diaphragms, also called center-embossed diaphragms, have been discussed sufficiently in the literature, but the effect of mesa thickness on sensor performance has not been discussed in detail. Moreover, there is no precise analytical solution for such diaphragms. For this reason, diaphragms with different thicknesses and radii were selected, and the deflection and frequency responses of the diaphragm according to the applied acoustic pressure were analyzed using the ANSYS software, depending on whether the mesa is thinner or thicker than the diaphragm. If the thickness of the mesa is smaller than the thickness of the diaphragm, the center deflection changes drastically. However, if the thickness of the mesa is two times greater than the thickness of the diaphragm, there is no significant change in the deflection results. Similarly, if the mesa thickness is thinner than the diaphragm, the sensor’s frequency response changes drastically with increasing mesa radius. In cases where the mesa thickness is larger than the diaphragm thickness, the frequency response changes less. According to the results, mesa dimensions should be considered when designing a mesa diaphragm-based Fabry-Perot FOS.

Time-dependent modelling of thin poroelastic films drying on deformable plates

AbstractUnderstanding the generation of mechanical stress in drying, particle-laden films is important for a wide range of industrial processes. One way to study these stresses is through the cantilever experiment, whereby a thin film is deposited onto the surface of a thin plate that is clamped at one end to a wall. The stresses that are generated in the film during drying are transmitted to the plate and drive bending. Mathematical modelling enables the film stress to be inferred from measurements of the plate deflection. The aim of this paper is to present simplified models of the cantilever experiment that have been derived from the time-dependent equations of continuum mechanics using asymptotic methods. The film is described using nonlinear poroelasticity and the plate using nonlinear elasticity. In contrast to Stoney-like formulae, the simplified models account for films with non-uniform thickness and stress. The film model reduces to a single differential equation that can be solved independently of the plate equations. The plate model reduces to an extended form of the Föppl-von Kármán (FvK) equations that accounts for gradients in the longitudinal traction acting on the plate surface. Consistent boundary conditions for the FvK equations are derived by resolving the Saint-Venant boundary layers at the free edges of the plate. The asymptotically reduced models are in excellent agreement with finite element solutions of the full governing equations. As the Péclet number increases, the time evolution of the plate deflection changes from $t$ to $t^{1/2}$ , in agreement with experiments.

Study on the effect of loading conditions on the fracture behavior of pipeline with girth weld

There is increasing attention on the fracture of pipelines with girth weld, as a result of the accidents caused by additional loads occurring occasionally. However, there is little research on the dynamic cracking behavior of girth welds under different load forms. To further understand the fracture process of girth weld, the crack initiation and dynamic fracture behavior of welded pipe under pure bending load are firstly analyzed by numerical simulation method based on Gurson-Tvergaard-Needleman (GTN) model. It is found that the bearing capacity of the pipeline is reduced due to the existence of the weld. Subsequently, the distribution of the axial stress and strain and the fracture morphology are analyzed, which indicates that the softening of HAZ donated to the brittle fracture of the pipe. The opening angle and displacement are studied respectively, from which can be obtained that WOD is linearly related to the deflection change, and the fracture resistance of the pipe girth weld can be characterized by the slope. Finally, the bearing capacity and fracture toughness of the pipe in different loading conditions are analyzed. The results show that the bearing capacity of pipeline girth weld is greatly reduced due to shearing.

Solving and Numerical Simulations of Fractional-Order Governing Equation for Micro-Beams

This paper applies a recently proposed numerical algorithm to discuss the deflection of viscoelastic micro-beams in the time domain with direct access. A nonlinear-fractional order model for viscoelastic micro-beams is constructed. Before solving the governing equations, the operator matrices of shifted Chebyshev polynomials are derived first. Shifted Chebyshev polynomials are used to approximate the deflection function, and the nonlinear fractional order governing equation is expressed in the form of operator matrices. Next, the collocation method is used to discretize the equations into the form of algebraic equations for solution. It simplifies the calculation. MATLAB software was used to program this algorithm to simulate the numerical solution of the deflection. The effectiveness and accuracy of the algorithm are verified by the numerical example. Finally, numerical simulations are carried out on the viscoelastic micro-beams. It is found that the viscous damping coefficient is inversely proportional to the deflection, and the length scale parameter of the micro-beam is also inversely proportional to the deflection. In addition, the stress and strain of micro-beam, the change of deflection under different simple harmonic loads, and potential energy of micro-beam are discussed. The results of the study fully demonstrated that the shifted Chebyshev polynomial algorithm is effective for the numerical simulations of viscoelastic micro-beams.

Beam vibration due movement of overweight cargoes on reinforced concrete bridges at different ground conditions

The article deals with the vibrations of a reinforced concrete bridge whose supports are located in soils with different properties under the action of overweight cargoes. The assumption is made that the structure deformed in the elastic zone when Hooke's law is valid. The Fourier method is used to solve the problem. The results are presented as graphs of changes in stresses and deflections along the coordinate and time, which are accompanied by analysis. When a concentrated load is applied, depending on the stiffness coefficient of the connection between the supports and the ground, stresses exceeding the limit load can occur in the middle of the beam cross-section. Thus, in the calculations, it is necessary to consider the nature of the interaction of the supports with the surrounding soils when calculating the beams for the action of moving loads.

Метод исследования формоизменения шатунных вкладышей коленчатого вала автомобильного двигателя в эксплуатации (на примере КамАЗ-740)

The relevance of the topic of the article is due to the unresolved problem of failures of automobile engines, in particular, modern mass-produced engines of the KAMAZ-740.10, 7403 families, due to cranking of the connecting rod bearings, and the need for deeper studies of the processes and phenomena that lead to them, and the development of solutions that exclude them in operation. The purpose of the study is to ensure the reliability of automobile engines by reducing the risk of crankshaft connecting rod bearings turning in operation by developing a method for studying their shape change and applying it when substantiating and implementing various design, technological and operational solutions. A prototype is described and a developed method and device for determining the clearance in a connecting rod bearing, suitable for studying the formation of connecting rod bearings under engine test bench conditions. The prototype was a differential-type pneumatic device used in active control devices for honing cylinder liners. With the use of the described device, a method for studying the formation of connecting rod bearings under the conditions of bench tests of KAMAZ-740.10 diesel engines was developed and tested. The use of new methods, devices and techniques makes it possible to investigate the patterns of shape changes of connecting rod bearings in relation to lubrication conditions, temperature and load conditions of the engine, and other factors. The presented experimental results show that the gap in the connecting rod bearing is not stable, is caused not only by wear, but also by the resulting deflection of the liner, and significantly depends on the temperature regime of the engine - with an increase in oil temperature, the gap decreases due to an increase in deflection. The authors explain the formation of deflection and shape change of the liners by the loss of its stability from the action of loads and internal stresses under conditions of instability of the oil supply. The results of experimental studies presented in the article have a scientific novelty, since a previously undescribed and not fixed decrease in the gap due to the deflection of the liners, which is formed immediately from the start of operation after the engine is assembled, is established, and its value is variable and determined by the temperature regime. Practical significance – the developed method makes it possible to study the formation patterns of crankshaft connecting rod bearings to test the effectiveness of design, technological and operational solutions to prevent their turning during the operation of an automobile engine. The main directions of promising research is the substantiation of practical solutions to ensure the stability of the shape of the liners during long-term operation of the engine.