Dynamic Excitation Forces Research Articles

Simulation and experimental investigation on vibration of a radial turbine wheel using a two-way FSI approach

When turbine blades of a radial turbocharger are subjected to an unsteady aerodynamic load excitation force, high cycle fatigue of the turbine blades will occur when the excitation force reaches a certain level. The fatigue of the radial turbine wheel is affected by both static and dynamic stresses, and high cycle fatigue occurs when the dynamic stress reaches a certain amplitude. In this study, a two-way fluid–structure interaction (FSI) analysis method was used to predict the dynamic excitation force and dynamic response of the turbine wheel, which can precisely predict the forced vibration of the turbine wheel under the condition of rotor–stator interaction. A resonance intersection point was excited by the stator (turbine housing vortex tongue) of the radial turbocharger as the operating boundary condition, and the aerodynamic excitation caused by the rotor–stator interaction and the vibration amplitude of the turbine blade was predicted and analysed. A turbine blade dynamic measurement system (tip timing) was used to measure the dynamic deformation of turbine blades for turbochargers in real time. The simulation and measurement results showed that the errors of the predicted vibration displacements and measured mistuning blades were within the acceptable range, and the two-way FSI analysis method can precisely predict the forced vibration of the model.

Influence of Misalignment on Beveloid Gear Tooth Contact and Dynamic Characteristics in Transfer Case Transmission of AWD Vehicle

Beveloid gears are usually employed to transfer motion of small shaft angle, but the assembly errors or misalignment can affect the gear tooth contact and dynamic performance. A dynamic model and tooth contact analysis model of the intersecting beveloid gear pair are established, the defects of the theoretical tooth surface in the meshing are analyzed, and a microgeometry modification method to improve the meshing performance is proposed. At the same time, the effects of system misalignment and manufacturing errors on its meshing characteristics are considered. By studying the sensitivity of the static and dynamic characteristics of beveloid gear on different misalignment components, the influence laws of misalignment on the contact pattern, transmission error, mesh stiffness, and dynamic excitation force are obtained, which give suggestions for tooth surface modification and support structural stiffness design of beveloid gear with a good NVH performance.

Coupling of dynamic reaction forces of a heavy load crane and ship motion responses in waves

ABSTRACT The conventional approach to dynamic analysis of ship motion response with shipboard operation equipment is usually done by establishing combined equations of motion of the multi-body system. The weakness of such methods is usually associated with the effectiveness of modelling and the simulation efficiency of computing the dynamic ship responses in waves in the time domain. In recent years, time domain simulation of nonlinear ship motion response in waves has become more and more popular. In this paper, we present coupled simulation of a heavy load crane with interactive ship motion responses in waves. The static gravitational forces of the crane system and dynamic excitation forces from the payload are applied to the ship as external forces on varying attack points of the hull during crane operations. Simulation of the crane operation is implemented in the digital twin ship platform and demonstrated meaningful physical behaviours.

Optimum design of large-scale systems considering material nonlinearities and uncertainties

A novel optimum design procedure for uncertainty quantification and validation, applicable in large-scale mechanical systems or industrial structures with material or structural nonlinearities is proposed in this work. Its implementation is presented through the research and optimal development of a full glass panoramic car elevator under real operational fail-safe loading scenario, including accurate dynamic analyses, placing emphasis on high fidelity FE models, uncertainty quantification and efficient handling of material nonlinearities. At first, a small-scale laboratory experimental arrangement of a single glass panel was examined, in order to develop high fidelity FE models of the laminated glass system and the point-support contact mechanism based on the level of dynamic excitation forces. Structural identification along with effective computational model updating and uncertainty quantification techniques were applied, in order to finely tune and estimate the parameters (material properties and damping ratios) of the numerical FE models and assess their uncertainties. The material nonlinearity of the natural rubber was examined at three forcing levels and excitation frequencies. Using maximum stress-strain pairs and updated moduli of elasticity a stress-strain curve, defining the nonlinear elastic behavior of the rubber was applied in the implicit nonlinear analysis of the full-scale elevator system. Based on the results of this analysis the elevator chassis was redesigned and optimized, in order to achieve minimum design stresses at the glazing components under emergency safety gear engagement. The stress levels developed on the optimal design of the elevator car were validated, in order to test the reliability of the applied method.

Theoretical investigation of the contributions of the excitation forces to the vibration of an axial piston pump

Abstract A theoretical dynamic model of an axial piston pump was developed in this paper. The axial piston pump was modeled as a dynamic system with four masses and 19 degrees of freedom (DOFs). The dynamic excitation forces were calculated using the piston chamber pressures simulated with a three-dimensional computational fluid dynamics (CFD) model. A test rig was constructed to validate both the CFD model and the dynamic model. The CFD model was validated by a comparison of the discharge pressure ripples, and the dynamic model was validated by a comparison of the vibration velocities. The vibration characteristics and the contributions of the excitation forces to the vibrations of the housing were analyzed. The results demonstrated that the vibration velocity along the XF- axis is larger than the vibration velocities along the YF- and ZF- axes, and the vibration angular velocity around the XF- axis is smaller than that around the YF- axis. The excitation moments of forces MCY and MPY have large contributions to most of the vibrations, and the excitation moments of forces MCX and MPX have negligible contributions to most of the vibrations. In addition, the vibrations are found to be significantly reduced by optimizing the bolt mounting positions.

Measurements on the Vehicle-Track Interaction and the Excitation of Railway-Induced Ground Vibration

Two railway measurement campaigns have been performed in Germany and Switzerland which yield insight in the vehicle-track-soil interaction. The campaign in Germany has included simultaneous measurement of vehicle, track, and soil vibrations during train runs with 16, 25, 40, 63, 80, 100, 125, 140, 160 km/h, and impulse measurements of the passenger car, three track sections and the soil. Two ballast tracks, one on the soil surface and one on a concrete bridge, have been investigated as well as a slab track in a tunnel. Ten different sites in Switzerland have been measured for soil properties and train-induced ground vibrations, which allow to determine the excitation forces of the railway traffic. New axle-box measurements at some of the Swiss sites have been analysed to get further experimental evidence. All these measurements have been evaluated to characterize the excitation processes. Relations between vehicle vibration and ground vibration can be observed. The vehicle vibrations, namely the accelerations of the wheelsets, yield the dynamic forces due to the passage over the irregularities of the vehicle and the track. The ground vibrations are correlated to these dynamic forces to a certain extent. Some mid-frequency ground vibration amplitudes, however, are higher than expected from the dynamic excitation forces. The experimental observations can be explained by an irregular response to the passage of the static loads, that means the passage of the static loads over an irregular ballast or soil. This correct understanding of the excitation processes is important for the prediction as well as for the mitigation of railway induced ground vibrations.

Simultaneous Measurements of the Vehicle, Track, and Soil Vibrations at a Surface, Bridge, and Tunnel Railway Line

A complex measuring campaign has been performed including the simultaneous measurement of vehicle, track, and soil vibrations during train runs at 16, 25, 40, 63, 80, 100, 125, 140, and 160 km/h and impulse measurements of the passenger car, three track sections, and the soil. A ballast track on the soil surface and on a concrete bridge has been investigated as well as a slab track in a tunnel. The evaluation and comparison of all these data show a generally good agreement for all components if the strong low- and high-frequency cut-off characteristics of the layered and damped soil are incorporated. There is a strong causal correlation between the vehicle and the soil by the dynamic excitation forces and a weak relation between the track and the soil by the axle-sequence spectrum of the train. However, the similarity between the axle-impulse spectrum observed at the track and the spectra of the ground vibration leads to the special excitation component of “scattered axle impulses” which is predominant at the far field points of the soil.

A Study on the Dynamics and Vibration Behavior of an Axial Piston Pump Using Combined MBD/FE Approach

In the present work a combined multibody dynamics(MBD) and finite element(FE) approach is developed for modeling the dynamics and vibration behaviour of an axial piston type hydraulic pump. A MBD model of the pumping mechanism is developed to predict the dynamic excitation forces at the bearings and control piston locations. The dynamic excitation forces in the frequency domain are obtained using fast fourier transform (FFT) with a rectangular type windowing function. A detailed FE model of the pump is developed consisting of the internal components, housing, and end cover. The dominant mode shapes and natural frequencies of the pump assembly are studied. The forced vibration behaviour of the pump is predicted by using the dynamic excitation forces from the MBD model. The numerical results are compared with the experimental results and a good agreement is found. Further, numerical studies are carried out to study the influence of component mass and stiffness on the vibration response.

NUMERICAL SIMULATION OF RAILWAY TRACK SUPPORTING SYSTEM USING FINITE-INFINITE AND THIN LAYER ELEMENTS UNDER IMPULSIVE LOADS / GELEŽINKELIO BĖGIŲ SISTEMOS SKAITMENINIS MODELIAVIMAS NAUDOJANT BAIGTINIUS BEGALINIUS IR PLONASIENIUS ELEMENTUS, VEIKIAMUS DINAMINĖMIS APKROVOMIS

The present study deals with two dimensional, numerical simulation of railway track supporting system subjected to dynamic excitation force. Under plane strain condition, the coupled finite-infinite elements to represent the near and far field stress distribution and thin layer interface element was employed to model the interfacial behavior between sleepers and ballast. To account for the relative debonding, slipping and crushing that could take place in the contact area between the sleepers and ballast, modified Mohr-Coulomb criterion was adopted. Furthermore an attempt has been made to consider the elasto-plastic material non-linearity of the railway track supporting media by employing different constitutive models to represent steel, concrete and supporting materials. Based on the proposed physical and constitutive modeling a code has been developed for dynamic loads. The applicability of the developed F.E code has been demonstrated by analyzing a real railway supporting structure. Santrauka Šiame straipsnyje nagrinėjama geležinkelio bėgių dvimatė sistema, veikiama dinaminės žadinančios jėgos. Pagal plokštuminę deformacijų sąlygą suporuoti baigtiniai begaliniai elementai aprašo artimą ir tolimą įtempių pasiskirstymo sritis, o plonasienis sąsajos elementas yra įvestas sąveikai tarp pabėgių ir balasto aprašyti. Yra naudojamas modifikuotas Mohr-Coulombo kriterijus, kuris įvertina atplėšimo, nuslydimo ar išspaudimo galimybes kontaktiniame pabėgių ir balasto paviršiuje. Taip pat yra pabandyta įvertinti tampriai plastinės medžiagos netiesiškumą, sudarant skirtingus sudėtinius sistemos modelius (pavyzdžiui, iš plieno, betono, atramų medžiagų). Remiantis pasiūlytu fiziniu ir sudėtiniu modeliavimu sudarytas skaičiavimo algoritmas dinaminėms apkrovoms įvertinti. Sudaryto baigtinių elementų algoritmo pritaikymas yra pademonstruotas išnagrinėjus realią geležinkelio bėgių sistemą.

Resonant Bending Fatigue Test Setup for Pipes With Optical Displacement Measuring System

Pipes and tubular members are used in offshore applications as structural elements, such as columns or in transport pipelines, risers, etc. When subjected to dynamic loads, weld defects or geometrical stress raisers can initiate fatigue cracks, causing the columns or pipelines to fail prematurely. In order to investigate the fatigue behavior of pipe joints, a resonant bending fatigue setup was designed, suitable for testing pipes within a diameter range from 6 in. to 20 in. In this setup, the pipe, filled with water, is subjected to a dynamic excitation force with a frequency close to the natural frequency of the filled pipe. The force is applied using a unique drive unit with excentric masses. The pipe is supported in the nodes of its natural wave-form, so that no dynamic forces are transmitted to the setup. The deformation of the pipe is measured at discrete locations using an optical 3D dynamic measuring system. Through-thickness fatigue cracks can be detected by pressurizing the water in the pipe and applying a pressure gauge. In this paper, some unique aspects of the design of the resonant bending fatigue setup are discussed by presenting the results of a semianalytical model used for calculating the deformation and bending stress in the excitated pipe and by comparing these results to the deformation measurements made by the dynamic measuring system. The working principles of the setup are illustrated by showing the preliminary test results for a 12 in. diameter X65 steel pipe with a wall thickness of 12.7 mm. It is demonstrated that the model predicts the behavior of the pipe in the setup very accurately.

System identification of steel framed structures with semi-rigid connections

A novcl system identification and structural hcalth assessment proccdurc of steel finn~ed structures with semi-rigid connectiol~s is prescntecl in tliis paper. It is capable of ilctecting damages at the local elc~ncr~t level under nonnal operating conditions; i.e., serviceability limit state. The procedure is a linear time-domain system identification tecllnique in which the structure responses arc required, whereas the dynamic excitation force is not recluircd to identifjl thc strtlctural parameters. The procedure hacks changcs in the stiffiiess properties of all the elements in a stnlcture. It can identify damage-frec ancl (lamaged stnictural elemenls vely accurately whcn excited by different types of' dy~ramie loadings. 'l'he method is elaborated witli the llclp of' several numerical examples. Tlle results indicate that the proposed i~lgoritll~n identified tlle structures correctly and detected the prc-imposed danlages in the frames when excited hy earthquake, impact, and harmonic loadings. '1:Ile algorithm can potentially be used for structural llealtli asse,ss~rie~~t and monitoring of existing shxctures witli lninimum clisnlption of operations. Since the procedure requires only a few time points of response infotmation, it is cxpccted to be economic and efficient.

Development of a piezoelectric polymer film sensor for plantar normal and shear stress measurements

We have developed a new sensor prototype for plantar pressure measurements during gait. The mechanical stress at the plantar surface has two components, pressure acting normal to the surface and shear stress acting tangential to the surface. The shear stress can be further divided into anterior–posterior (AP) and medial–lateral (ML) components. The developed sensor simultaneously measures both normal and shear stresses. It utilizes commercial polyvinylidenefluoride (PVDF) material and consists of four separate sensor elements. This paper presents the sensor development and calibration for each force components. A shaker providing dynamic excitation force was used in the calibration. Average sensitivities computed from the results were (12.6 ± 0.8) mV/N for the normal force, (223.9 ± 20.3) mV/N for the AP shear force and (55.2 ± 11.9) mV/N for the ML shear force. A preliminary plantar pressure measurement was also done. The results obtained were promising. However, the sensor developed here is the first prototype. In future, a matrix sensor based on this principle is planned to be constructed.

Input force identification: Application to soil-pile interaction

An identification method for estimating the time varying excitation force acting on a structural system based on its response measurements is presented in this study. The method employs the simple Kalman filter to establish a regression model between the residual innovation and the input excitation forces. In applying the method, first, the ambient vibration measurement of a structural system is collected, then the stochastic subspace identification is applied to estimate the system matrix ‘A’ and the measurement matrix ‘H’. Incorporated with the identified ‘A’ and ‘H’ matrices the dynamic excitation forces are estimated from the measured structural responses by using Kalman filter with a recursive least-square estimator to update the estimation in the sense of real-time computation. Verification of the method on numerical simulation through MIMO system is conducted first. Identification of soil forces during the shaking table test of soil–pile interaction is also demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.

Internal flow-induced behaviour of flexible risers

It has been found in recent years that the pressure distribution and flow behaviour of fluid inside the bore of a flexible riser has a substantial effect on its static and dynamic behaviour. This paper is concerned with examining the contributions of internal flow to both the governing equations and the dynamic excitation forces applied to a flexible riser. A derivation from first principles of the full governing equations for a flexible riser in two dimensions is presented, together with equations for riser excitation due to slug flow through the riser bore. A frequency-domain numerical solution scheme is also described and its results are compared with model tests for both riser global behaviour due to external disturbances (such as surface vessel motions and waves) and due to internal flow.