Static Simulation Research Articles

Bio-inspired design and performance evaluation of a novel morphing nose cone for aerospace vehicles

An effective way to improve the flight capability and environmental adaptability of aerospace vehicles is to design a morphing aircraft structure, which can actively change their aerodynamic shape. During different physiological activities, the abdomens of bees are regularly deformed to improve the efficiency of movement. This was used as an inspiration for the design of a nose cone for aerospace vehicles. Based on the deformation mechanism of the bee abdomen, a bionic design of a variable configuration morphing nose cone (MNC) mechanism with high sensitivity is proposed, which can realize real-time reverse self-locking of the mechanism via auxiliary branch chains. Theoretical models for the kinematics and dynamics of the MNC mechanism under two configurations are derived, verifying that the proposed mechanism has good kinematic and dynamic characteristics. The theoretical models are validated through simulation studies. In addition, static finite element simulations are performed to verify that the auxiliary locking branch chain can significantly improve the bearing capacity of the proposed mechanism. Moreover, the force and thermal parameters of different configurations of the MNC under corresponding typical working conditions are analyzed, enabling the improvement of the aerospace vehicle aerodynamic characteristics by the morphing of its nose cone. Finally, based on the analytic hierarchy process, different drag and heat flux reduction schemes are comprehensively evaluated.

Design and optimization of medium-high frequency FBG acceleration sensor based on symmetry flexible hinge structure

A flexible hinge fiber Bragg grating (FBG) acceleration sensor based on the symmetry mass block is proposed to address poor transverse performance and lower sensitivity in medium- and high-frequency. The dual mass block design causes the FBG fiber to vibrate while simultaneously being stretched or compressed in the reverse direction. Thus, the FBG's sensitivity is greatly improved, and its deformation is double that of the single hinge construction. MATLAB software theoretically investigates and optimizes the sensor's natural frequency and sensitivity. In contrast, ANSYS analyzes static structural stress and simulation. The implementation of the sensors is assessed through an experimental test. The accelerometer's natural frequency is 1550 Hz, and its working stability frequency range is flat at 400–1000 Hz. The amplitude anti-interference of the sensor is approximately 3.27%, and the average sensitivity's linearity is roughly 66 pm/g. Developing medium and high-frequency vibration data is essential for the health monitoring and evaluation of constructions such as bridges, railroads, and tunnels.

Dynamic Equilibrium at the HCOOH-Saturated TiO2(110)-Water Interface.

Carboxylic acids bind to titanium dioxide (TiO2) dissociatively, forming surface superstructures that give rise to a (2 × 1) pattern detected by low-energy electron diffraction. Exposing this system to water, however, leads to a loss of the highly ordered surface structure. The formate-covered surface was investigated by a combination of diffraction and spectroscopy techniques, together with static and dynamic ab initio simulations, with the conclusion that a dynamic equilibrium exists between adsorbed formic acid and water molecules. This equilibrium process is an important factor for obtaining a better understanding of controlling the self-cleaning properties of TiO2, because the formic acid monolayer is responsible for the amphiphilic character of the surface.

A Comparison between the Molecularly Imprinted and Non-Molecularly Imprinted Cyclodextrin-Based Nanosponges for the Transdermal Delivery of Melatonin.

Melatonin is a neurohormone that ameliorates many health conditions when it is administered as a drug, but its drawbacks are its oral and intravenous fast release. To overcome the limitations associated with melatonin release, cyclodextrin-based nanosponges (CD-based NSs) can be used. Under their attractive properties, CD-based NSs are well-known to provide the sustained release of the drug. Green cyclodextrin (CD)-based molecularly imprinted nanosponges (MIP-NSs) are successfully synthesized by reacting β-Cyclodextrin (β-CD) or Methyl-β Cyclodextrin (M-βCD) with citric acid as a cross-linking agent at a 1:8 molar ratio, and melatonin is introduced as a template molecule. In addition, CD-based non-molecularly imprinted nanosponges (NIP-NSs) are synthesized following the same procedure as MIP-NSs without the presence of melatonin. The resulting polymers are characterized by CHNS-O Elemental, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric (TGA), Differential Scanning Calorimetry (DSC), Zeta Potential, and High-Performance Liquid Chromatography (HPLC-UV) analyses, etc. The encapsulation efficiencies are 60-90% for MIP-NSs and 20-40% for NIP-NSs, whereas melatonin loading capacities are 1-1.5% for MIP-NSs and 4-7% for NIP-NSs. A better-controlled drug release performance (pH = 7.4) for 24 h is displayed by the in vitro release study of MIP-NSs (30-50% released melatonin) than NIP-NSs (50-70% released melatonin) due to the different associations within the polymeric structure. Furthermore, a computational study, through the static simulations in the gas phase at a Geometry Frequency Non-covalent interactions (GFN2 level), is performed to support the inclusion complex between βCD and melatonin with the automatic energy exploration performed by Conformer-Rotamer Ensemble Sampling Tool (CREST). A total of 58% of the CD/melatonin interactions are dominated by weak forces. CD-based MIP-NSs and CD-based NIP-NSs are mixed with cream formulations for enhancing and sustaining the melatonin delivery into the skin. The efficiency of cream formulations is determined by stability, spreadability, viscosity, and pH. This development of a new skin formulation, based on an imprinting approach, will be of the utmost importance in future research at improving skin permeation through transdermal delivery, associated with narrow therapeutic windows or low bioavailability of drugs with various health benefits.

Influence of Capping Ligands, Solvent, and Thermal Effects on CdSe Quantum Dot Optical Properties by DFT Calculations.

Cadmium selenide nanomaterials are very important materials in photonics, catalysis, and biomedical applications due to their optical properties that can be tuned through size, shape, and surface passivation. In this report, static and ab initio molecular dynamics density functional theory (DFT) simulations are used to characterize the effect of ligand adsorption on the electronic properties of the (110) surface of zinc blende and wurtzite CdSe and a (CdSe)33 nanoparticle. Adsorption energies depend on ligand surface coverage and result from a balance between chemical affinity and ligand-surface and ligand-ligand dispersive interactions. In addition, while little structural reorganization occurs upon slab formation, Cd···Cd distances become shorter and the Se-Cd-Se angles become smaller in the bare nanoparticle model. This originates mid-gap states that strongly influence the absorption optical spectra of nonpassivated (CdSe)33. Ligand passivation on both zinc blende and wurtzite surfaces does not induce a surface reorganization, and thus, the band gap remains nonaffected with respect to bare surfaces. In contrast, structural reconstruction is more apparent for the nanoparticle, which significantly increases its highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap upon passivation. Solvent effects decrease the band gap difference between the passivated and nonpassivated nanoparticles, the maximum of the absorption spectra being blue-shifted around 20 nm by the effect of the ligands. Overall, calculations show that flexible surface cadmium sites are responsible for the appearance of mid-gap states that are partially localized on the most reconstructed regions of the nanoparticle that can be controlled through appropriate ligand adsorption.

Design and Simulation of a Customize Three-axis Gimbal Structure using Finite Element Analysis Method

This paper presents a Finite Element Analysis (FEA) on a customized three-axis gimbal design application. Examples of applications of the gimbals such as drones, camera stabilizers, and spacecraft. The SolidWorks software checked the gimbal’s FEA characteristics with no existing load or normal conditions. Using the FEA method, a static simulation analysis where the material of this assembly design uses Polylactic Acid (PLA), used mainly by 3D printer machines. The force is given to the gimbal structure and obtains the results of the maximum value of stress in MPa, displacement in mm, and strain. Thus, based on the results obtained from SolidWorks, the structure will not fail. The maximum stress value between parts is 2.31 MPa for the support part and 3.09 MPa for the assembly model when the yield stress value of the PLA material properties is at 70 MPa. The new design structure for the gimbal hardware focuses on academic purposes based on PLA material and is easy to build using a 3D printer. In the summary, the customized three-axis gimbal design using SolidWorks will not fracture when the design is in normal condition which has a total force of 6.87 N, which is equal to 0.70 kg at 3.09 MPa where the weight of the base, O-ring, and servo motors at the U-shape part. In addition, the design can hold up to 230.87 N, which is equal to 23.54 kg at 69.90 MPa of the stress value before it will fail at 70 MPa.

Geometric and Material Modelling Aspects for Strength Prediction of Riveted Joints

The aim of this study is to develop a methodology for static strength and failure mode simulation of hot-driven riveted joints. The purpose is to be able to accurately estimate a rivet joint’s static strength behaviour and its failure mode without relying on experiments, to save both time and resources during the design of joints. The non-linear finite element analysis modelling framework considered the rivet joint configurations and geometry, the material properties of the plate and rivet as well as the clamping force of the hot-driven rivet. A ductile damage model was also implemented to capture the stress softening of the materials and the failure modes of the joints. Using experimental data from literature, the modelling framework is validated, and it is shown that it is able to capture the strength behaviour and failure modes of different configurations of rivet joints markedly well. The effect of the rivet pre-load on the mechanical response of the joint is also studied and it is shown that the strength of the joint increased with the increase in rivet pre-load. The modelling framework is then applied to an industrial component. The modelling framework is used to compare welding and riveting as joining methods in a component built in two grades of high-strength steel. It is found that the welded joint possessed greater strength compared to the proposed riveted joint. However, using the proposed simulation methodology developed, a riveted joint with matching strength to the welded joint could be designed.

Route Optimization Equalization Scheme Based on Graph Theory for Liquid Metal Battery Strings

In order to solve the inconsistency problem of series connected liquid metal battery (LMB) strings, a route optimization equalization scheme is proposed in this article. In terms of balancing topology, a modular double-layer cell-to-cell balancing topology based on inductor and flyback multi-winding transformer is designed, which can transfer energy between any two batteries within or among modules. For control strategy, an equalization strategy based on graph theory and ant colony optimization (ACO) is proposed, which has been compared with the traditional maximum/minimum equalization control strategy. The static condition simulation results show that compared with traditional equalization strategy, the balancing speed of the route optimization control strategy is improved by 88.62%, and the balancing efficiency is increased by 19.43%. Moreover, the inconsistency problem of the battery strings can be significantly improved under both static and dynamic conditions. Therefore, by improving the balancing effect, the proposed scheme can not only effectively avoid overcharging or discharging problems, but also increase the consistency, available capacity and service life of liquid metal battery strings.

Research on Improvement of Clamping Device for Online Nondestructive Tensile Testing of Braided Wire Rope

The online nondestructive tensile testing machine can crush wire ropes, during the safety tension test of braided wire ropes. To solve this problem, this paper analyzes the reasons for crushing phenomena from the aspects of static simulation and geometric analysis of wire ropes. In terms of static simulation of the tensile process, the equivalent stress, contact pressure and contact gap cloud map of the wire rope in the clamping jaw range are obtained. It is found that both equivalent stress and contact pressure of the wire rope reach maximum values at the transition section between the adjacent peak and trough of the sinusoidal curve, while both reach minimum values at the position of the peak and trough, where the wire rope is in a non-contact state. Concerning the geometrical analysis of the clamping surface of the jaws, the results show that the normal distance between the sinusoidal curves of the movable jaw and the fixed jaw is not constant in one period, which is the smallest at the transition section between the peak and the trough. Therefore, our group determine the destruction resulted from the unreasonable curve shape of the clamping surface, further improve the jaw curve and realize the non-damaged safety tension test of wire ropes.

Analysis and mitigation of spatial integration errors for the material point method

SummaryThe material point method (MPM) is a robust numerical simulation approach for continuum mechanics problems involving large material deformations coupled to changing surface topographies. These types of problems are present in many different engineering contexts, from understanding the failure processes of earthen slopes to predicting the strengths and failure mechanisms of body armor to modeling the impact forces of waves in fluid tanks. By using a set of persistent material point tracers to follow the motion and deformation of the continuum material while solving the equations of motion on a static simulation grid, the MPM avoids several shortcomings of more traditional numerical approaches including blurring of material surfaces — as in Eulerian finite element or finite volume methods (FEMs or FVMs) — and mesh tangling — as in Lagrangian FEMs. Despite its robustness, MPM is known to develop significant numerical errors: namely, (i) the particle ringing instability and (ii) solution dependent discretization and integration errors. In this work, we present an analysis of local‐in‐time, spatial integration errors in the MPM and several techniques designed to mitigate these errors. Error mitigation approaches previously described in the literature are compared to a new method we propose for problems involving very large material deformations. The proposed method is shown to offer substantial improvement over standard MPM for simulations of fluid‐like materials without requiring significant augmentation of existing MPM frameworks.

Offshore, Unmanned Auto-Leveling Sea-Surface Drifting Platform with Compact Size

This paper proposes an offshore, unmanned auto-leveling sea-surface drifting platform, with a compact size of 0.7 m in diameter, used for obtaining air-sea interface environmental parameters. The platform was designed based on the parallel mechanism with limited degrees of freedom. The mechanical structure, control system hardware, and software of the principal prototype are introduced. A ground-based device was developed to simulate wave disturbance, based on which the static and dynamic simulation experiments were carried out. Experimental results show that the auto-leveling system can achieve real-time leveling against the angle deviation induced by waves, with a leveling accuracy of 0.2° in a simulated wave with an angle of 12°, which meets the requirements of observation equipment.

Research on performance optimization method of human-machine physical interaction system considering exoskeleton wearing comfort

In order to improve the wearing comfort and bearing effectiveness of the exoskeleton, based on the prototype and working mechanism analysis of a relaxation wearable system for knee exoskeleton robot, the static optimization synthesis and its method are studied. Firstly, based on the construction of the virtual prototype model of the system, a comprehensive wearable comfort evaluation index considering the factors such as stress, deformation and the proportion of stress nodes was constructed. Secondly, based on the static simulation and evaluation index of system virtual prototype, multi-objective genetic optimization and local optimization synthesis of armor layer topology were carried out. Finally, the model reconstruction simulation data confirmed that the system had good wearing comfort. Our study provides a theoretical basis for the bearing performance and prototype construction of the subsequent wearable system.

First-principle insights of initial hydration behavior affected by copper impurity in alite phase based on static and molecular dynamics calculations

Copper tailings have been used as a raw material for cement clinker production. The Cu element can enter into the cement phase and change its hydration behavior. In this study, the influence of Cu-doping on the structure and hydration characteristics of alite phase (tricalcium silicate, C3S) are disclosed by combining the density functional theory (DFT)-based static and molecular dynamics calculations. In the static simulation, local Oi atoms move closer to doped Cu atom with Cu–O distance of 1.84–1.93 Å and forms Cu-Oi bonds, resulting the decrease of surface electrophilic reactivity. A single water molecule exhibits lower adsorption energies (0.92–2.12 eV) on the Cu-doped C3S surface than on the pure C3S surface (0.62–1.69 eV), as the chemical bonds of Ca-OW and HW-OS were weakened. Further ab-initial molecular dynamics (AIMD) simulations cover the shortcomings of static calculations and obtain new discoveries: (a) Cu-doping promotes hydroxylation of C3S surface and stabilizes fluctuation of dissociated proton. (b) Ca-OW bond concentration is raised after Cu-doping, whereas the constraint effect of the C3S surface on OW is weakened. (c) Cu-doping accelerates the diffusion of Oi into water layer by ∼2 Å within 13 ps, facilitating the dissolution of clinker. These findings contribute in several ways to our understanding of the hydration properties of Cu-doping C3S and provide theoretical support for the sustainable and greener development of the construction industry.

Choice of the stress integration scheme for accurate large-deformation finite element analysis

The use of computational structural models that include geometrical non-linearity in many application cases may require high reliability in prediction of displacements. Nevertheless, large differences up to 60% on maximum total displacement have been found among results of static large-deformation analyses performed by means of the major commercial software packages in a simple benchmark study with linear material properties. In order to investigate the causes of such disagreement, the present work compares different finite element formulations including well-established stress update schemes. The various formulations are tested, and results are compared in three test cases. Rodriguez stress update algorithms have shown the best performance among methods reported in literature. Finally, the cause of the large differences found in the predictions of commercial codes is identified. It is linked to the energetic inconsistency of some stress update methods in the simulation of extension/compression loading conditions. Such inaccuracy is reproduced analytically by formulating and integrating the corresponding inconsistent constitutive equations. The identified problem is very important for designers, as it affects almost all the static simulations, which are the most common type of large-deformation analyses and usually involve extension/compression loading.

Loading on a wind turbine high-speed shaft gearbox bearing: Ultrasonic field measurements and predictions from a multi-body simulation

Wind turbine gearbox failures, many of which result from load-driven rolling element bearing failures, account for long downtimes and high maintenance costs. Non-invasive, in-situ measurement of bearing roller loads using ultrasound facilitates better understanding of the load history and failure mechanisms these gearbox bearings experience. In this study, ultrasonic load measurements from an instrumented high-speed shaft bearing were compared against results from a static multibody simulation. Measurements taken under steady operating conditions were found to agree well with the model. After quantification of the error in ultrasonic measurements the model enabled identification of load outliers which were attributed to transient events. Over- and under-loading instances may act to promote a variety of failure mechanisms, leading to premature bearing failure.

A Beam Finite Element for Static and Dynamic Analysis of Composite and Stiffened Structures with Bending-Torsion Coupling

This research presents a new beam finite element capable of predicting static and dynamic behavior of beam structures with bending-torsion coupling. The model here derived establishes a relation between the bending and torsional nodal degree of freedom of a two node beam element. The equilibrium equations are derived neglecting the non-linear terms while the stiffness and mass matrices are derived with Galerkin’s method. The shape functions are obtained considering Timoshenko’s hypothesis and the torsional moment constant along the element. The model has been validated through numerical and experimental results for static and dynamic simulation. The comparison revealed a relative difference mostly lower than 5% for static deformations and natural frequency prediction, while the Modal Assurance Criterion (MAC) confirmed the consistency with numerical and experimental results in terms of mode shape similarity.

Static numerical simulation of radial deformation of ultra-thin dicing blade

Grinding with dicing blade is an important method to cut or slot electronic and optical devices. The deformation of grinding tools will definitely affect the processing of workpiece. However, this effect has been disregarded during processing. In order to improve the machining accuracy in the precision grinding method, this deformation is worth considering. In this research, the grinding state of the ultra-thin dicing blade was simplified as a static problem. The force model of the ultra-thin dicing blade during grinding was established, which centrifugal force was adopted in the whole blade and triangular distribution grinding forces were adopted in the grinding area. The radial deformation of the ultra-thin dicing blade was determined by finite element simulation, and the influence of grinding parameters on its radial deformation was analyzed. The simulation results showed that the grinding area of the ultra-thin dicing blade occurred radial expansion deformation at high rotational speed (more than 8000 rpm), and the value could reach 1.75 μm (rotational speed at 23,000 rpm, feed speed at 600 mm/min, and grinding depth at 0.12 mm). The deformation increased in a form of power function with the increase of rotational speed, and decreased linearly with the increase of feed speed and grinding depth. This work can provide reference data for deformation compensation, which is helpful to improve the dimensional accuracy of grinding groove.

Stress Relaxing Simulation on Digital Rock: Characterize Attenuation Due To Wave‐Induced Fluid Flow and Scattering

AbstractDigital rock physics (DRP) is essential to understand the wave elastic and attenuation characteristics of complex porous rocks, offering insights into interpreting seismic and sonic logging data. Most of the existing DRP technology can only simulate wave‐induced fluid flow (WIFF) or scattering effects separately in a relatively narrow or single‐frequency band. To incorporate both the effects of WIFF and elastic scattering simultaneously, we develop a stress relaxing simulation (SRS) technique on digital rocks to characterize the P wave dispersion and attenuation signatures in a broad frequency band. We propose to use the combined methodology of curve resampling and wavelet‐packet denoising to suppress the high‐frequency noise of the stress relaxation curve. For a digital rock containing pore‐crack elements, we demonstrate that SRS is capable of characterizing the attenuation due to squirt flow and scattering as well as their interactions. The simulation results of wave dispersion and attenuation using SRS are overall consistent with other well‐developed DRP technology of transmitted wave simulation (high‐frequency band), forced oscillating simulation (intermediate‐frequency band), and static simulation (low‐frequency band), suggesting the reliability and robustness of the developed methodology. We also apply the SRS on a realistic 2D digital rock of porous sandstone. It is found that the attenuation due to elastic scattering of the microscopic heterogeneities is significantly higher than that caused by squirt flow, which might be caused by the lack of pore connectivity impeding the fluid exchange at the microscopic scale due to the limitation of 2D digital porous rocks.

Investigation of Corroded Bond-Slip Effects for Corroded RC Columns

Steel bar corrosion is one of the most common causes of structural performance degradation for reinforced concrete (RC) columns subjected to extreme loads such as earthquakes. Due to the different characteristics of corrosion effects, a comprehensive and efficient finite element (FE) modeling approach is necessary for the performance assessment of corroded RC columns. To this end, this study provides an effective FE modeling approach using a recently developed geometrically nonlinear fiber-based frame element that considers bond-slip, allowing for explicit representation of corrosion-affected bonding. This aspect necessitates the use of an explicit material model for corroded bond-slip and its associated corroded properties. Since the existing models of corroded bonding properties in the literature were developed based on the highly scattered and limited experimental data, this study develops a new probabilistic model for corroded bonding properties based on more experimental data compiled from the literature and quantifies the prevailing uncertainties. To facilitate its use for modeling corroded RC structures, a cyclic corroded bond-slip model in an open-source FE software framework is implemented. In this paper, the FE modeling approach is first used to model two corroded RC columns tested in the literature, with comparison to the conventional modeling approach (i.e., assuming perfect bonding). The influence of corroded bonding on the static and dynamic behaviors of RC columns is further explored deterministically. Furthermore, the impact of uncertainty in corroded bonding properties on the static and dynamic behavior simulations of RC columns is examined. This work is concluded that (1) the FE modeling approach provided for corroded RC columns proves to be effective in capturing corrosion effects; and (2) corroded bonding plays an important role in simulating the behavior of corroded RC columns, and thus cannot be neglected. This is particularly true considering its associated uncertainty and its impact on the performance assessment of RC columns under severe corrosion conditions.

Energy Response Characteristics of Laterally Loaded Piles

A bounding surface plasticity p − y model is used to examine the internal energy responses of a laterally loaded pile in static and dynamic simulations. The model response is first compared with those observed in physical centrifuge tests, including monotonic and cyclic loading, in a normally consolidated fine-grained soil. Then, the model is used to examine hypothetical static and dynamic situations. The monotonic load capacities determined by the model and an upper-bound limit analysis method are in agreement with that inferred from the physical test. The work done by external loads in static conditions is principally balanced by the plastic work in the p − y springs and the elastic strain energy in the structural pile elements, which are comparable in the cases examined. The numerical model is capable of reproducing accurately the observed test structural responses as well as the characteristics of plastic energy dissipation. In a dynamic free-vibration simulation, the pile is highly damped as a result of the significant plastic energy dissipation. The simple work-hardening elastic–plastic p − y model is theoretically sound, applicable to arbitrary loading histories, and requires the same level of effort to use as traditional p − y methods.