Dynamic Finite Element Model Research Articles

Dynamic Analysis of Outer and Inner Race Defects on Thermoplastic Rolling Bearing System Using Implicit Finite Element Method

This paper proposes an improved finite element dynamic model to analyze the vibration response of a rolling bearing system. The vibration responses of defect free and defective polypropylene (PP) bearings are analyzed using the finite element analysis and compared with the experimental results using the in house developed bearing fatigue test rig. The boundary conditions of this model are imposed to ensure an adequate homogeneity with the experimental apparatus. This study considers the viscoelastic property of thermoplastic to investigate the effect of the flexibility and damping viscosity of material. The three-dimensional dynamic analysis detects the vibrations produced in a rolling bearing system. Modal frequencies and the vibration modes shapes which must be avoided had been determined. Monitoring the evolution of vibration signatures as a function of defect location is also carried out using Finite Element Analysis (FEM). Test results reveal that peak vibration amplitudes are more pronounced in an inner ring defect than in an outer ring defect. Vibration signals of stainless-steel bearings are investigated to compare the performance of the thermoplastic bearings with its metallic counterparts. Both test and simulation results reveal that a lower level of vibration is observed with PP bearings compared to that of metal. The PP bearings not only dampen vibrations, but also accommodate shaft misalignments unlike their steel counterparts. Once overall vibration spectrums results are validated, Von Mises stresses within the rings are evaluated under excessive loading conditions. The simulation results show that stress is high in raceways where the balls are compressed between the raceways. Computational results agree well with the experimental tests for the test scenarios.

Quantifying robustness in tall timber buildings: A case study

Robustness research has become popular, however very little is known on its explicit quantification. This paper summarises a quantification method previously published by the main author and proceeds in demonstrating its step-by-step application with a case study tall timber building. A hypothetical 15-storey post-and-beam timber building with a central core is designed for normal loads, and four improved options are designed to account for abnormal loads in order to increase the building’s robustness. A detailed, nonlinear, dynamic Finite Element model is set up in Abaqus® to model three ground floor column removal scenarios, and a Random Forest classifier is set up to propagate uncertainties, to efficiently estimate the probability of certain collapse classes occurring, and to calculate the importance of each input parameter. The results show how design improvements at the whole building scale (e.g., strong floors) have a higher impact on robustness performance than just improving the strength and ductility of some selected connections, although these results are exclusive to the building studied. The case study reinforces the importance of a sound conceptual design for achieving robustness in tall timber buildings.

Configuration-controllable porous metamaterial and its bandgap characteristics: Experimental and numerical analysis

Metamaterials that can tune the bandgap by controlling the configuration have prospects for the security of engineering structures. A configuration-controllable metamaterial is developed in this study to achieve effective vibration reduction, and its bandgap characteristics are investigated through experiments and numerical analysis. The metamaterial specimen is designed and fabricated using silicone rubber. A corresponding experimental platform is constructed to achieve a controllable configuration of the metamaterial. Subsequently, the vibration transmission of the specimen with different deformations is tested. The commercial software COMSOL is used to simulate finite-element dynamic models of the unit cell, and the entire structures of the metamaterial is established to analyze their bandgaps and frequency response characteristics. Both the numerical and experimental results demonstrate that the configuration change can significantly affect the bandgap characteristics. With increasing compression, the existing low-frequency bandwidth of the metamaterial narrow, whereas the high-frequency bandwidth broadens. When the metamaterial deformation is larger, a new bandgap appears at a lower frequency. In addition, the effects of the geometric parameters on the bandgaps are revealed. It shows that the frequency range, width and number of bandgaps of the developed metamaterial can be effectively adjusted through configuration control.

Deformation Stability of GH4033 Superalloy in the Hot Continuous Rolling Process Based on Dynamic Material Model and Finite Element Model

Deformation Stability of GH4033 Superalloy in the Hot Continuous Rolling Process Based on Dynamic Material Model and Finite Element Model

Vibration Test and Control of Factory a Building under Excitation of Multiple Vibrating Screens

In order to reduce the excessive vibration responses of a reinforced concrete frame structure induced by several vibrating screens working simultaneously, field vibration monitoring and some vibration reduction measures are carried out. The results of field vibration monitoring show that the maximum vertical vibration of the structure exceeds 106% of the limitation of building vibration. The results of the structural response analysis show that the excessive structural vibration is attributed to the resonance, as the frequency of the vibrating screens coincides with vertical natural frequency of the floors of the factory structure. Based on this fact, three vibration control measures, including damping, active vibration isolation of vibrating screens and structural vibration absorption, are proposed to mitigate the excessive vibration. In order to analyze the vibration control performance of the proposed schemes, the finite element dynamic model of the factory building structure is established, and the model is verified by the results of vibration and mode tests. Then, the damping system, vibration isolation system and vibration absorption system are set up in the models, and the vibration control performance of the three schemes are investigated. The results show that the measures, including vibration isolation and absorption, can reduce the vibration by more than 80%. Combined with the demand for a short construction period, the active vibration isolation of vibrating screens is finally selected. After the implementation of the scheme, the field monitoring data show that the structural vibration response is consistent with the finite element result and obviously weakened to meet the limitation. This study can provide a reference for the vibration control design for similar screening factory buildings.

Static and dynamic effects of train-track-bridge system subject to environment-induced deformation of long-span railway bridge

Laying ballastless tracks on a long-span railway bridge with a main span greater than 300 m is a challenge in engineering practice and has aroused significant concerns. Influenced by complicated environmental factors, long-span railway bridges in service deform with large amplitudes and complex shapes, which may result in damage to the track structure and threaten the running safety and ride comfort of trains. In this study, we investigate some typical statics and dynamics problems under the actual conditions of a long-span cable-stayed high-speed railway bridge with a main span of 400 m and laying ballastless track. The track-bridge finite element model and dynamic interaction model of the train-track-bridge system are first established. Furthermore, the influences of the complicated environment-induced bridge deformations are comprehensively investigated using the curvature method that reveals the deformation compatibility of the bridge-track system and indicates the dynamic interaction behavior of the train-track-bridge system subject to train running speeds and bridge deformations. Results indicate that excellent dynamic performance of the train-track-bridge system can be achieved by setting an elastic cushion of 0.1 N/mm3 under the track bed. Interface damage between track layers will not occur directly because of the complex deformations of the bridge decks. The bridge deformations induced by the environmental temperature and the concrete creep are qualified. The dynamic responses of the train-track-bridge system are also excellent under the excitations of bridge deformations. Dynamic simulations of the train-track-bridge system are proposed to evaluate long-span bridge deformations subject to complicated service situations in comparison with an oversimplified statics evaluation.

A finite element modelling approach for the numerical analysis of switch rail contact loading and cyclic profile degradation

A dynamic 3D finite element model for the calculation of profile degradation in the switch panel is presented. The model includes the contact between wheel and rail, as well as the contact between switch rail and stock rail to allow an elastic relative movement between the two rails. Break-outs of the switch rail tip can be facilitated by this relative movement and the stresses and strains at this interface are calculated. The profile degradation of the switch rail due to contact loading between wheel flange and switch rail is numerically simulated considering the cyclic plastic deformation of the rail material. The sliding wear is evaluated separately and superimposed to the geometrical change caused by the plastic deformation.

Prediction of the temperature sensitivity of strawberry drop damage using dynamic finite element method

In this study, the textural mechanics of strawberry tissues were analyzed using a uniaxial compression test at six temperature levels, and a dynamic finite element model of the strawberry drop system was developed to investigate the collision-damage sensitivity of the fruit. The strawberry geometric model included two parts of the receptacle: the cortex and the pith. The fruit finite element model with average tissue mechanical data was found to be capable of reproducing four key collision mechanical parameters (maximum impact force and contact area, drop damage area, percentage of damage volume) with an average relative error of 1.76%, 8.45%, 2.99% and 4.74%, respectively. Five covariance analysis models also showed that the drop direction was the most important factor affecting the occurrence of the fruit drop damage, followed by fruit temperature and drop height. Specifically, in a low temperature range (1 ~ 7 °C), the fruit collision damage degree did not change significantly with temperature change, but when the temperature was between 14 °C and 35 °C, the damage area and percentage of damage volume increased by 0.82 mm2 and 0.06%, respectively, for every 1 °C increase in temperature. Furthermore, it was found that there is a strong linear correlation between internal and surface damage in the strawberry fruit, and the obtained mathematical models can be utilized to predict the internal damage degree of fruit based on the surface damage area. This study incorporated dynamic finite element technology with statistical analysis to provide a systematic approach for investigating the collision-damage sensitivity of fresh fruit in relation to fruit temperature.

Experimental Research and Fatigue Life Prediction of Ultra-High-Strength Steel Aermet100

This study concentrates on the fatigue performance of ultra-high-strength steel Aermet100 under different loading rates. The standard specimen measured the static mechanical properties of Aermet100 steel, based on which the basic mechanical properties and fracture characteristics of the sample before and after necking was obtained. To take the strain rate effect into account, this study uses the dynamic constitutive model Johnson-Cook. The equation parameters are fitted through dynamic mechanical tests and quasi-static tests. This model is input into ABAQUS user-defined program afterward. Referring to the work done above, along with the extended finite element method (XFEM), this study establishes the dynamic fracture finite element model of the Aermet100 steel specimen on the basis of the continuous damage mechanics. Five groups of specimen fatigue tests were carried out in the laboratory. Simulation results show the feasibility and accuracy of the integrated XFEM model with the same loading and boundary conditions. The experimental data and simulation results prove that, in the loading time range of 0.0001 ~ 1s, the life cycles increase as the loading rate increases. It is worth mentioning that when the loading time is in the order of 0.0001s, the life changes significantly.

Dynamic Finite Element Modeling and Simulation of Soft Robots

Soft robots have become important members of the robot community with many potential applications owing to their unique flexibility and security embedded at the material level. An increasing number of researchers are interested in their designing, manufacturing, modeling, and control. However, the dynamic simulation of soft robots is difficult owing to their infinite degrees of freedom and nonlinear characteristics that are associated with soft materials and flexible geometric structures. In this study, a novel multi-flexible body dynamic modeling and simulation technique is introduced for soft robots. Various actuators for soft robots are modeled in a virtual environment, including soft cable-driven, spring actuation, and pneumatic driving. A pneumatic driving simulation was demonstrated by the bending modules with different materials. A cable-driven soft robot arm prototype and a cylindrical soft module actuated by shape memory alley springs inspired by an octopus were manufactured and used to validate the simulation model, and the experimental results demonstrated adequate accuracy. The proposed technique can be widely applied for the modeling and dynamic simulation of other soft robots, including hybrid actuated robots and rigid-flexible coupling robots. This study also provides a fundamental framework for simulating soft mobile robots and soft manipulators in contact with the environment.

Electromechanical coupling modeling and analysis of piezoelectric damping laminated structures based on zig-zag hypothesis

Based on the zig-zag theory and Hamiltonian principle, the electromechanical coupling dynamic finite element(FE) model of piezoelectric damping laminated structure is established, the natural frequency and loss factor of the structure is accurately calculated. The eight nodes quadratic element is adopt for FE modeling, each node with seven DOFs, which considers the complex elastic modulus of damping layer. The correctness of model is verified by the calculation and simulation of an example in the literature. The effects of reinforcement orientation angle, thickness of damping layer and structure curvature on the frequency and loss factor of piezoelectric damping laminated structure are investigated. This study can provide references for vibration control and optimization design of piezoelectric damping laminated structures.

Finite Element Model Modification of the Mount Bracket Based on Modal Test

<div class="section abstract"><div class="htmlview paragraph">The mount bracket is an important part of the mount system, and its dynamic characteristics will affect dynamic characteristics of the mount system, which means it will affect NVH(Noise, Vibration, Harshness) of the vehicle. Based on the large error between the test result and the finite element analysis(FEA) result, the dynamic finite element model of the mount bracket can be modified from the material parameters and the equivalent boundary of the bolt joint. In this paper, a method to identify the parameters of the mount bracket model by combining modal test, FEA, and the mathematical optimization model was presented. Firstly, based on HyperStudy platform, the optimization objective was minimizing the natural frequency error between FEA and free mode test, and the material parameters of the bracket to be identified were used as design variables to build the optimization function. The global response surface method was used for iteration to complete the identification. Then, because the dynamic characteristic parameters of the bolt joints of the mount bracket have an important influence on the test results, an equivalent model using spring element to simulate the stiffness of bolt joints was established. Again, based on the equivalent model and the parameter identification method, the optimization objective was minimizing the natural frequency error between FEA and modal test under constraint conditions, and the stiffness parameters of spring elements were identified by iterative optimization to finish the modification of the mount bracket boundary model. At last, the modified finite element model was applied to the dynamic characteristics analysis of two different mount brackets. The results showed that the maximum error of natural frequency between the simulation value and the test value could satisfy the engineering requirement well, which indicated that the modified model had a good prediction accuracy and engineering application.</div></div>

Dynamic Finite Element Model Updating Based on Correlated Mode Auto-Pairing and Adaptive Evolution Screening

A method for dynamic finite element (FE) model updating based on correlated mode auto-pairing and adaptive evolution screening (CMPES) is proposed to overcome difficulties in pairing inaccurate analytical modal data and incomplete experimental modal data. In each generation, the correlated mode pairings (CMPs) are determined by modal assurance criterion (MAC) values and the symbiotic natural frequency errors, according to an auto-pairing strategy. The objective function values constructed by correlated and penalized subitems are calculated to screen the better individuals. Then, both the updating parameters and the CMPs can be adjusted adaptively to simultaneously approach the ideal results during the iteration of population evolution screening. Three examples (a thin plate with small holes, an F-shaped structure, and an intermediate case with multi-layer thin-walled complex structure) were presented to validate the accuracy, effectiveness, and engineering application potential of the proposed method.

Prediction of Dynamic Stick-Slip Events in Belt-Drives Using a High-Fidelity Finite Element Model

AbstractA high-fidelity dynamic finite element model of a one-pulley belt-drive system is used to study how Coulomb friction coefficient and adhesion stress affect belt stick-slip events over driver and driven pulleys. The model shows that at Coulomb friction coefficient below a certain critical value, the belt undergoes pure sliding in the slip arc on driver and driven pulleys with no stick-slip dynamic events. Above that critical friction coefficient value dynamic stick-slip events start to occur in both driver and driven pulleys resulting in torque pulses, which for practical belt-drives may cause nonsmooth operation, excessive belt noise and/or excessive belt wear. For driver pulleys the dynamic stick-slip events are in the form of Schallamach waves, while for driven pulleys the dynamic stick-slip events are in the form of expansion pulses. The model results are validated using recently generated experimental results.

In situ determination of the extreme damage resistance behavior in stomatopod dactyl club.

The structure and mechanical properties of the stomatopod dactyl club have been studied extensively for its extreme impact tolerance, but a systematic in situ investigation on the multiscale mechanical responses under high-speed impact has not been reported. Here the full dynamic deformation and crack evolution process within projectile-impacted dactyl using combined fast 2D X-ray imaging and high-resolution ex situ tomography are revealed. The results show that hydration states can lead to significantly different toughening mechanisms inside dactyl under dynamic loading. A previously unreported 3D interlocking structural design in the impact surface and impact region is reported using nano X-ray tomography. Experimental results and dynamic finite-element modeling suggest this unique structure plays an important role in resisting catastrophic structural damage and hindering crack propagation. This work is a contribution to understanding the key toughening strategies of biological materials and provides valuable information for biomimetic manufacturing of impact-resistant materials in general.

Dynamic modeling of the gear-rotor systems with spatial propagation crack and complicated foundation structure

Considering both spatial crack fault and complex foundation structure, the dynamic finite element model and multi-body dynamic model are established simultaneously to analyze the dynamic characteristics of gear-rotor systems. Firstly, the extended finite element method is used to simulate the three-dimensional crack propagation paths of spur gears under partial load. Then, based on the proposed three-dimensional loaded tooth contact analysis (3D-LTCA) method, the mesh stiffness of spur gears with the spatial crack and complex foundation is calculated and the results are verified by the finite element method. Finally, the dynamic finite element model and multi-body dynamic model of the gear-rotor system are established. The dynamic responses under different crack levels are analyzed. The advantages and disadvantages of these two dynamic models are evaluated. According to the above analysis, it is indicated that the 3D-LTCA can accurately consider the influence of complex foundation and spatial crack on mesh stiffness. The finite element model and multi-body dynamic model can effectively analyze the influence of crack fault and foundation structure on dynamic responses.

Crashworthiness Analysis and Multi-Objective Optimisation of Multi-Cell Windowed Structures under Dynamic Impact Loading

Applying a windowed design in a thin-walled structure is a method to further enhance the crashworthiness of the structure. In this study, two kinds of windowed designs were introduced into different regions of a multi-cell energy absorption structure to form a multi-cell windowed structure, and its crashworthiness under dynamic impact was studied. Dynamic impact testing and LS-DYNA finite element modelling were combined to calculate the crashworthiness response of the structure. The simulation results show that the use of the windowed multi-cell structure can improve the crashworthiness response of the multi-cell structure. The influence of the windowed design on the structural deformation mode was analysed in detail. In addition, the multi-objective optimization design of different windowed structures was carried out to obtain a comprehensive crashworthiness evaluation, and the results show that the windowed design at the front end of the structure yields good results regarding the initial peak force (PCF), while the windowed design in the middle of the structure can effectively improve the specific energy absorption (SEA) and energy absorption (EA).

Pile group in clay under cyclic lateral loading with emphasis on bending moment: Numerical modelling

Pile foundations supporting major structures are often founded in soft compressible clays. Apart from usual super-structural loading, these piles are subjected to cyclic lateral loads originating from actions of waves, ship impacts, winds or moving vehicles. Such repetitive loading induces stress reversal in adjacent soft clay initiating progressive degradation in soil strength and stiffness. This not only deteriorates the pile capacity with unacceptable displacements, the bending moments also increase. Although past studies investigated the response of single pile under lateral cyclic loading, a detailed study on pile group in clay under cyclic lateral loading with emphasis on bending moment is of immense practical interest. This paper focuses on detailed study of the response of pile group in clay under cyclic lateral loading, with emphasis on bending moment, through numerical modelling via a three-dimensional dynamic finite element (FE) approach and simplified boundary element modelling (BEM). Comparisons of computed results with available test data imply that the results obtained by 3 D dynamic FE model are better than the BEM. Extensive parametric studies with field data indicate that pile bending moment has been significantly influenced by cyclic loading parameters (number of cycles, frequency and amplitude). Relevant conclusions are drawn from the entire study.

Dynamic Finite Element Modelling and Vibration Analysis of Prestressed Layered Bending–Torsion Coupled Beams

Free vibration analysis of prestressed, homogenous, Fiber-Metal Laminated (FML) and composite beams subjected to axial force and end moment is revisited. Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) models are developed and presented. The frequency results are compared with those obtained from the conventional FEM (ANSYS, Canonsburg, PA, USA) as well as the Homogenization Method (HM). Unlike the FEM, the application of the DFE formulation leads to a nonlinear eigenvalue problem, which is solved to determine the system’s natural frequencies and modes. The governing differential equations of coupled flexural–torsional vibrations, resulting from the end moment, are developed using Euler–Bernoulli bending and St. Venant torsion beam theories and assuming linear harmonic motion and linearly elastic materials. Illustrative examples of prestressed layered, FML, and unidirectional composite beam configurations, exhibiting geometric bending-torsion coupling, are studied. The presented DFE and FEM results show excellent agreement with the homogenization method and ANSYS modeling results, with the DFE’s rates of convergence surpassing all. An investigation is also carried out to examine the effects of various combined axial loads and end moments on the stiffness and fundamental frequencies of the structure. An illustrative example, demonstrating the application of the presented methods to the buckling analysis of layered beams is also presented.

Numerical analysis of thermo-mechanical behavior in flow forming

Flow forming is a metal forming process for cylindrical workpieces where high velocity deformation leads to radial thinning and axial extension. In the current study, a thermomechanical, dynamic and explicit finite element model of a flow forming process is developed on ABAQUS software. The model is validated through the comparison of reaction forces and geometry obtained from the experiments. Coolant convection effect is analyzed in conjunction with roller and mandrel conduction cooling to study the thermal variations in the deformation zone during the process. The methodology detailed in this study facilitates a deeper understanding of the evolution of heat during the flow forming process and lays the groundwork for further exploration into the possible role of a material’s thermal properties in the definition of flow formability.