bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Developments in Numerical Modeling of Transduction Materials
Authors: Hladky-Hennion Anne-Christine , Bossut Régis , Debus Jean-Claude
Published: March 2021

Recent research work in sonar system performance, coupled with achievements in the field of acoustic quieting, has led to the development of new ceramics that are promising for both hydrophone and projector applications. Other materials have also been studied like piezoelectric composite materials, magnetostrictive and electrostrictive materials. To design transducers using these materials, the finite element method seems to be the best suited approach. Using this method, it is possible to analyze, characterize and tailor new materials as well as to design a full transducer or an array. Recent developments in the ATILA finite element code allow the modeling of new transduction materials. The aim of this paper is to present the theoretical formulation in numerical modeling of materials used either for hydrophone or active sonar applications.
Investigation of an OHC Valve Train With Respect to Sound Quality
Authors: Suh In-Soo , Debost Sophie
Published: March 2021

Although the vibration generated by high speed dynamic movement of a valve train (VT) in an overhead camshaft SI engine is not a major source of engine noise, it still affects the overall sound quality of the engine, which is important to the subjective response of the customer.

The purpose of this research is to determine the specific mechanism of the valve train dynamic behavior, which is responsible for noise generation, and the vibration transmission characteristic to engine surfaces. Dynamic simulation with a lumped mass model is developed to analyze the dynamic behavior of VT during operation, and reveal the resonance frequencies of VT modeshapes excited by the cam harmonics. Also, experimental measurements of the valve acceleration, transfer functions of vibration, and the structural response have been performed in the valve train rig.

Based on the spectral analysis, two distinct noise generating mechanisms are determined. Vibration from VT components’ interaction, which is mainly excited by the harmonics of the cam profile during valve opening period, is dominant in the frequency range less than 6 kHz. On the other hand, valve seating is the dominant source in the frequency range from 6 kHz to 20 kHz. The more vibration energy from these two sources is transmitted through the structure via the VT system, rather than directly via the valve seat to the surfaces where sound is radiated, especially around the frequency of 5 kHz and 11 kHz. This fundamental investigation on the vibration sources and its transmission characteristics provides a new insight on the VT noise, which is an essential step toward the design of an engine with better sound quality.
Experimental Study for Extraction of Normal Modes
Authors: Chen S. Y. , Ju M. S. , Tsuei Y. G.
Published: March 2021

A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.
Vibroacoustical Analysis of Flow in Pipes
Authors: Charley J. , Carta F. , Caignaert G.
Published: March 2021

This paper is concerned with the study of pressure and flow rate fluctuations propagation within ducts. A new transfer matrix model for a pipe taking into account the fluid-structure interactions effects is presented and compared to other formulations; significant gains have been realized. An extension of acoustic intensity technique using four transducers is presented.
Modal Analysis Method for Determination of Elastic Constants
Authors: Marchand V. , Pouyet J.
Published: March 2021

The purpose of this paper is to present an original means to determine materials elastic constants using a free vibration method. This experimental device enables us to obtain the natural frequencies of a free circular plate subject to heating at temperatures ranging from 20 to 1000 °C. The vibrations of the sample are recorded by a microphone. The identification of experimental natural frequencies is obtained by comparison with frequency spectrum resulting from two experimental means. A grid method consists in determining the elastic constants of the materials by comparing the experimental frequency with the frequencies calculated analytically using Ritz method.
Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions
Authors: Morgan Jeffrey A. , Pierre Christophe , Hulbert Gregory M.
Published: March 2021

This paper shows how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method and the use of a Maclaurin series expansion to represent the residual effects of the omitted modes. It was developed as a base-band method for structures exhibiting normal modes of vibration determined from free boundary vibration tests. Of particular importance is the procedure developed for the estimation of the Maclaurin series expansion coefficients and for the recovery of the Craig-Bampton matrices from the residual flexibility formulation. This allows accurate dynamic models to be determined for measured systems that can be used to predict the effects of structural modifications and in substructure coupling analyses. The performance of the new method is demonstrated by comparison of experiment and analysis for two simple beams.
Modal Testing and Parameter Identification of Active Magnetic Bearing System
Authors: Lee Chong-Won , Ha Young-Ho , Kim Cheol-Soon , Joh Chee-Young
Published: March 2021

Complex modal testing is employed for parameter identification of a four-axis active magnetic bearing system. In the test, magnetic bearings are used as exciters while the system is in operation. The experimental results show that the directional frequency response function, which is properly defined in the complex domain, is a powerful tool for identification of bearing as well as modal parameters.
Adaptive Synchronization Control Design for High-Speed Magnetic Bearings
Authors: Yang Li-Farn , Tsao Jeen-Gwo
Published: March 2021

The performance of actively controlled magnetic bearings is greatly degraded if subjected to unpredictable disturbances or system dynamic variations. This paper present an adaptive synchronization control on a magnetically suspended rotor system for disturbance rejection and plant variation compensation. The rotor system consists of a rotating disk mounted on a shaft which is actively positioned in the radial directions via two magnetic bearings at both ends. Under the synchronizing control, four displacements of shaft along bearing axes are coordinated such that the disturbed displacement can promptly be recovered with those undisturbed in a complementary way. Such motion synchronization requires strict regulation and adaptation through four local controllers with an adaptive feedforward control scheme. The local controllers can be linked by the coupling law, in which an error along one bearing axis can affect overall control loop of four axes. Two control algorithms are developed under the biaxial and quadaxial synchronization conditions, and their adaptation laws are optimized in an attempt to minimize the adaptation errors. Simulations of disturbance rejection responses will also be presented.
Experimental Modal Analysis of Rotating Disk Systems
Authors: Irretier Horst , Reuter Frank
Published: March 2021

A completely non-contact testing technique is presented to perform experimental modal analysis on rotating disk systems to identify modal parameters as eigenfrequencies, modal damping ratios and mode shapes due to rotation. Theoretical frequency response functions of rotating structures are presented which form the basis of the modal analysis. Experimental results of a rotating circular disk and a rotating radial impeller are presented and the influence of rotation on the modal parameters due to centrifugal, gyroscopic and aerodynamic effects is shown.
Development of an Electromagnetic Impactor for Structures With Large Rigid Body Motions
Authors: Wassermann J. , Mokesch H. , Springer H.
Published: March 2021

A PC-controlled electromagnetic impactor (PCC-EMI) is developed that can be used for broad band excitation of rotating structures from a stationary system. Begin, magnitude and position of the force impact exerted to the moving structure are automatically and precisely controlled by a personal computer through a new electronic circuit device. Bouncing effects of the hammer tip are electronically suppressed and an impact can be aimed to any desired point on the rotating structure with high accuracy and high repeatability. Experiments are carried out to test the positioning and repeatability capabilities of the system. Common frequency response functions are measured for a rotating disk and natural bending frequencies are experimentally determined in terms of the speed of rotation of the disk.
A New Methodology for the Accurate and Consistent Identification of Modal Parameters Using Multi-FRF Analysis
Authors: Lin R. M. , Ling S.-F.
Published: March 2021

A new method for the estimation of modal parameters is presented in this paper. Unlike the majority of the existing methods which involve complicated curve fitting and interpolative procedures, the proposed method calculates the modal parameters by solving eigenvalue problem of an equivalent eigensystem derived from measured frequency response function (FRF) data. It is developed based on the practical assumption that only one incomplete column of the FRF matrix of the test structure has been measured in a frequency range of interest. All the measured FRFs are used simultaneously to construct the equivalent eigensystem matrices from which natural frequencies, damping loss factor and modeshape vectors of interest can be directly solved. Since the identification problem is reduced to an eigenvalue problem of an equivalent system, natural frequencies and damping loss factors identified are consistent. Further procedures for normalizing the identified eigenvectors so that they become mass-normalized are developed. Numerical case examples are given to demonstrate the practicality of the proposed method and results obtained are indeed very promising. It is believed that with the availability of such identification method, modal analysts’ dream of intelligent and full automatic modal analysis will become a reality.
A Generalized Treatment of the Energetics of Translating Continua
Authors: Lee Seung-Yop , Mote C. D.
Published: March 2021

The energetics of translating, one-dimensional continua, like uniform strings or tensioned beams, that travel between two supports is analyzed in this paper. The non-conservative interaction between the supports and the translating continua causes energy flux at the boundaries. The total mechanical energy is not conserved, and a periodic transfer of energy into and out of the system occurs. From the power flows in traveling waves, the energy flux for a string translating through fixed, free, elastic and viscous damping boundary conditions is obtained explicitly in terms of the transport speed and the ratio of the reflected to incident amplitudes. The time-dependent character of the total energy of a translating tensioned beam is complex because the beam is dispersive. The energy variation in the beam is represented in terms of the mechanical impedance and the amplitude ratio between the reflected and incident propagating waves. At low frequency, frequency-dependent energy ratios are identical to those of translating strings. The amount of energy flux at boundaries decreases with frequency, and increases with transport speed. Numerical simulations verify the analytically predicted energy variations for the different supports.
Vibration Analysis of Mindlin Plates by the Superposition-Galerkin Method
Authors: Gorman D. J. , Ding Wei
Published: March 2021

In the first part of this paper, it is demonstrated how the superposition of four judiciously selected forced vibration solutions to rectangular mindlin plate vibration problems permits the obtaining of an eigenvalue matrix from which the resonant frequencies of fully clamped mindlin plates can be extracted. Subsequently, it is shown how the same forced vibration solutions can be obtained much more efficiently by the Galerkin Method. After superposition of the latter solutions, it is shown how the same resonant frequencies are obtained. The vast advantages of exploiting this latter “Superposition-Galerkin” method are enumerated and discussed in detail.
On the Formulation and Solution of a Class of Magneto-Viscoelasto-Dynamics (MVD) Governing Equations of Motion
Authors: Wong Po Kee , Wong Adam , Wong Anita
Published: March 2021

The paper is to provide the formulation and solution of a class of linear viscoelastic, isotropic, homogeneous, three-dimensional, magnetic conducting materials’ governing displacement equations of motion by means of the spectral operator theory in order to find the answers for the perplexing phenomena of plasma instabilities in those materials.
Dynamic Response of Soil Under S.H.P.B. Loading
Authors: Semblat J. F. , Gary G. , Luong M. P.
Published: March 2021

Soil dynamic response has been little investigated under fast loading conditions. Split Hopkinson Pressure Bar method leads to the determination of dynamic behaviour of various materials. A special experimental device called three-dimensional S.H.P.B provides dynamic response of soil specimens in both axial and radial directions (oedometric tests). Comparisons with other loading paths (mean and deviatoric stresses) give usefull elements on granular soil behaviour under high strain rates. The results are also analysed at grain-size scale (grain-size distribution, fracture energy). Experimental results show that 3D-Split Hopkinson Pressure Bar is a promising tool for laboratory dynamic testing on soils.
Modal Loss Factors of Thick Three-Layer Cylinders With Viscoelastic Core
Authors: Hamidzadeh Hamid R. , Jiang Yanfei
Published: March 2021

An analytical solution to the free vibration of a damped three-layer thick sandwiched cylinder of infinite extend is presented. The constrained layer damping is accomplished by sandwiching a linear viscoelastic material between two isotropic elastic cylinders with the same properties. The governing equation is derived based on elasto-dynamic theory utilizing complex elastic moduli. Dimensionless natural frequencies and modal loss-factors are extracted.

Special case for a three-layer sandwiched cylinder with similar elastic properties is considered. The computed dimensionless frequencies are compared with previously established results. The comparison indicates the validity of the proposed mathematical procedures. In addition, the effects of various values of material damping for the core layer and ratio of the core shear modulus to the shear modulus of the elastic cylinders on natural frequencies and modal loss-factors are studied. For a given configuration, modal information for the first two modes for n = 0, 1, 2, 3 and 4 are presented for a wide range of core material damping and G2/G1 ratio.
Transient Vibration Reduction Through the Use of Dual Absorbers
Authors: Bursal Faruk H.
Published: March 2021

The dual absorber configuration is shown to exhibit considerable improvements with respect to transient vibration over the conventional, single-absorber design for the same amount of total absorber mass. The term transient as used in this paper refers to monotonic changes in frequency during the start-up and shut-down of rotating machinery. The use of the frequency response as a design tool for this kind of transient is motivated by a quasi-staticity argument, which presumes the change in the operating frequency to be slow relative to the natural period of the oscillations. New tuning rules for dual absorbers are presented that yield near-optimal levels of transient vibration reduction along with significant steady-state attenuation. The improvements obtainable by using dual absorbers become more pronounced when the system changes its speed of rotation more slowly. The dual absorber design appears to exhibit the best overall vibration reduction characteristics among all passive absorbers tested and can also be installed retroactively onto an existing absorber setup. Because the design shares the simplicity of construction and maintenance of other passive absorbers, it is believed to be an excellent alternative to more complicated active or semi-active absorbers in many situations.
System Identification of Torsionally-Coupled Structures
Authors: Lin Chi-Chang , Ueng Jin-Min , Lin Pao-Lung
Published: March 2021

In this paper, the Ibrahim Time Domain technique is employed to calculate the modal frequencies and damping ratios of torsionally-coupled buildings based only on partial free vibration response measurements. To obtain the complete mode shapes, an interpolation method is developed to calculate the mode shape value for the locations without measurement. All mode shapes obtained are mutually orthogonal. The structural seismic responses are also estimated. Numerical results show that the proposed method is able to identify structural dominant modal parameters accurately even with highly coupled modes and noise contaminations. Small number of response measurements (no need of input measurement) and simple on-line calculation make the proposed method favorable to real implementation.
Vibration Control With Neural Network Dynamic Compensator
Authors: Shiotsuka Toshinari , Yoshida Kazuo , Nagamatsu Akio
Published: March 2021

An approach is presented on designing the dynamic compensator-type controller, using two kinds of neural networks. One is used for identification of system dynamic characteristics of the control object. A time history of response under sine-sweep input is used as the teaching signal of this neural network.

The other is used as the neural network controller. The control input is determined with this neural network in order that a performance index concerning the state variable and the input force takes the minimum value.

These two neural networks are combined reciprocally in a cascade type in designing the controller. Validity and usefulness of the presented approach are verified by both an computer simulation and an experiment with an active suspension model.
Nonstationary Robust Positioning Control of Flexible Structures
Authors: Hara Susumu , Yoshida Kazuo
Published: March 2021

For positioning control of such vibrating system as flexible structures, it is important to reduce vibration. In the problem, influences of such uncertainties as variations of parameters of controllers possess nonstationary characteristics. This paper presents an integrated synthesis method of both motion and vibration controller maintaining the robustness of the control by using a time-varying criterion function. In this method, a smooth change from H2 positioning control to H vibration control is realized by solving time-varying Riccati equations in stead of time-invariant Riccati equations. This method is applied to a positioning problem of flexible tower-like structure. In comparison with the former methods proposed by the authors, the usefulness of the method is verified theoretically and experimentally.
An Optimal Design Method for Rubber Dynamic Vibration Absorber
Authors: Satoh Yoshihiro , Misawa Hiroshi
Published: March 2021

A dynamic vibration absorber can be used for suppression of excessive amplitude of structures at the resonance. This paper deals with an optimal design method for the dynamic vibration absorber which consists of a mass and a carbon-black filled rubber vulcanizate. First, a system which consists of a main system and the dynamic vibration absorber was analyzed, considering nonlinear dynamic properties possessed by the rubber vulcanizate. Frequency response functions of the system were derived in the form including the rubber geometry and a mass ratio as design parameters. Next, an objective function was composed of the frequency response functions. Minimizing the objective function with respect to the parameters of the rubber geometry for given mass ratio, the optimal values were determined. From the consideration of the results, a new convenient method to determine the optimal values was derived. This method was examined by the experiments. As a result, the validity of the analysis method was verified, and the availability of the present design method for the suppression of vibration was confirmed.
Contact Impedance Sensors: Applicability for the Evaluation of Flexible Structures
Authors: Daugela Antanas , Fujii Hiroshi , Misaki Akitsugu
Published: March 2021

The Mechanical Contact Impedance Evaluation (MCIE) method has not been throughly explored in order to test elastic polymers. In this paper the applicability of MCIE for defining the mechanical properties of elastic materials and structures is discussed in detail. The analytical solution of the resonance state equation shows that the MCIE method is effective in the case of piezo active flexural vibrators which excite the surface of the specimen in the normal direction. The results received from the FEM modal and harmonic analysis, where longitudinal, flexural and torsion vibrators were simulated, support the conclusion above. Experimental results received from the analysis of flexural vibrator show that the MCIE can be successfully used in a comparator to evaluate elastic polymers when quick and nondestructive testing is required.
Sensorless Active Suppression of Transverse Vibration of Flexible Plate
Authors: Matsuda Ken-ichi , Okada Yohji
Published: March 2021

In rolling processes, flexible steel sheet is supported by rollers and is bound to produce structural vibration. This vibration can cause severe problem to surface finish and affect the quality of the product. To overcome this problem, active vibration control has been proposed. This usually requires both sensors and actuators. The location of sensors and actuators play a very important role in active vibration control. Moreover, a reliable sensor can be very expensive. This paper proposes a self-sensing vibration control using a push-pull type electromagnet to control the transverse vibration of the steel plate. The construction of the electromagnet has two types of coils, namely the bias coil and the control coil. Vibration displacement is estimated by using the mutual inductance change between the bias and the control coils. The estimated signal is proportional to the gap displacement. The proportional and derivative signal of which is fedback to the control coil to control the transverse vibration of the steel sheet. The proposed method is applied to a simple test rig to confirm the capability of the device. The results obtained are showing high possibility for reducing the sheet steel vibration.
Active and Regenerative Control of Electrodynamic Vibration Damper
Authors: Okada Yohji , Harada Hideyuki
Published: March 2021

A new method of regenerating electric power from the vibration energy is presented. An electro-dynamic actuator is controlled by a relay controller to regenerate electric power during the highspeed motion of the actuator. For the lowspeed motion, an active control algorithm is applied to the same actuator to achieve good damping performance. This idea can be applied to a vehicle suspension system which is composed of electrodynamic actuator and spring. The system is simulated on a computer to evaluate the vibration damping property and energy regenerative capability. A simple experimental apparatus is made to confirm its capability.
Response of Piezoelectric Solids to Unitary Impulsive Loads: A Computational Approach
Authors: Khutoryansky Naum , Sosa Horacio
Published: March 2021

Fundamental solutions for transient dynamic piezo-electricity are derived through the plane wave decomposition and represented in three alternative manners, namely over the unit sphere, over the material’s slowness surface and over a line of the latter. The computational virtues of the uni-dimensional integral representation are exposed through a numerical example concerning a transversely isotropic piezoelectric ceramic subjected to unitary impulsive applied forces.
Piezoelectric Actuation of von Karman Circular Plates With Thermal Deformation and Nonlinear Oscillation
Authors: Tzou H. S. , Zhou Y.-H.
Published: March 2021

Linear dynamics and distributed control of piezoelectric laminated continua have been intensively studied in recent years. In this study, dynamics, electromechanical couplings, and control of thermal buckling of a piezoelectric laminated circular plate with an initial nonlinear large deformation are investigated. It is assumed that the von Karman type geometrically nonlinear deformation is considered. In addition, the piezoelectric layers are uniformly distributed on the top and bottom surfaces of the circular plate. Accordingly, control effect is introduced via an equivalent control moment on the circumference. Dynamic equations and boundary conditions including elastic and piezoelectric couplings are formulated, and solutions are derived. Active control of plate’s nonlinear deflections, thermal buckling, and natural frequencies using high control voltages are studied, and their nonlinear effects are evaluated.
Simultaneous Use of Piezoelectric Ceramics As Sensor and Actuator for Through-Plate Sound Transmission Control
Authors: Akishita Sadao , Aoyama Satoru , Yokoi Kenji , Ma Chris C. H.
Published: March 2021

Externally applied electric field in piezoelectric material causes mechanical stress in addition to electric charge displacement. This effect is bidirectional in that mechanical strain can in turn cause electric charge displacement. The bidirectionality suggests that a piezoelectric element can be used simultaneously as both a sensor and an actuator for bending vibration control of a thin plate. To do this, the key problem that needs to be solved is to separate the two kinds of electric charge displacement generated in the piezoeoectric element due to the mechanical strain and the electric control signal. By introducing a dummy piezo-electric element to provide a reference on the effect due to the electric control signal only, successful separation of the two kinds of charge displacement signals has been accomplished. The effectiveness of the simultaneous use for the control system is demonstrated in substantial reductions of the sound pressure transmitted and the bending vibration in the plate.
Identification of a Significantly Non-Proportionally Damped Structure Using Force Appropriation
Authors: Holmes P. S. , Wright J. R. , Cooper J. E.
Published: March 2021

Dynamic tests were carried out on an aluminium plate with significant non-proportional damping applied via two oil filled dampers. Normal mode force appropriation (phase resonance) methods were used to measure the undamped normal modes of the plate and the results compared with corresponding complex modes obtained using a standard curve fitting (phase separation) approach.

It is demonstrated that, as long as suitable excitation positions are chosen, high quality undamped normal modes can be identified while the curve fitted modes are highly complex. A Finite Element analysis of the plate was used to show how the results of normal mode force appropriation are directly comparable, particularly when damping is non-proportional.
The Frequencies and Damping of a Cantilever Composite Plate With a Viscoelastic Layer
Authors: Cupiał P. , Nizioł J.
Published: March 2021

In the paper the natural frequencies and modal loss factors of a three-layered rectangular cantilever plate with high-modulus composite face layers and a viscoelastic mid-layer are discussed. Two analysis approaches are considered, the Ritz method and the finite element method. The Ritz analysis is based on an appropriate 2-D plate model. Algebraic polynomials are used which satisfy the necessary geometric boundary conditions. The discretized eigenvalue problem is then solved for complex eigenvalues, from which damped frequencies and modal loss factors are extracted. Both frequencies and loss factors are shown to converge with an increasing number of the polynomials used. Apart from the Ritz method, frequencies and modal loss factors are calculated by the finite element method based on the so-called strain energy method. Comparison between the two approaches is then given.
The Method of Trajectories for Finding Eigenfrequencies of Damped Structures
Authors: Pesterev Alexander V. , Tavrizov Grigorii A.
Published: March 2021

The method of finding complex eigenfrequencies of distributed parameter structures with finite number of lumped dampers is presented. The approach used is based upon the structural analysis method in the context of which the problem of investigation of a system degenerates into investigation of some complex characteristic matrix. Multiplication of all damping coefficients by a real scalar parameter α results in consideration of a family of α-parametrized intermediate systems. When α varies eigenfrequencies of the intermediate systems describe trajectories in the complex plane. The differential equation governing the trajectories is established. Given the eigenfrequencies of the conservative system those of the damped structure can be obtained by integrating the differential equation.
Transient and Steady-State Response of Constrained Translating Strings
Authors: Zhu W. D. , Mote C. D.
Published: March 2021

The exact expression describing the constraint force in a constrained translating string is derived using the Green’s function formulation. Discontinuity of the initial velocity at a boundary of the string due to a disturbance causes discontinuity in the constraint force history for any constraint that is not modeled by a single spring element. The discontinuities in the constraint force occur at instants when those propagating wave-fronts in the string with non-vanishing slope interact with the constraint. A model of a magnetic tape-recording head system is analyzed. Tape-head contact loss is predicted, depending on the amplitude and frequency of the disturbance, the head location and the preload of the tape against the head. The transient response to a harmonic end excitation is compared at the steady state to the closed-form prediction of a steady forced analysis.
Applications of Electrical Impedance Tomography to Nondestructive Evaluation
Authors: Santosa Fadil
Published: March 2021

Electrical impedance tomography is a technique for imaging the interior of a region using DC current and voltage measurements collected on the boundary of the region. The image obtained corresponds to the conductivity of the material in the region. This tomographic method has its origins in geophysical exploration and in biomedical imaging.

In this paper, we describe two applications of this technique for NDE. In the first application, we devise a method for determining the length and the location of a straight-line crack in a circular domain. The second application concerns the use of electrical impedance tomography for imaging corrosion in plates.
Stability and Resolution in Thermal Imaging
Authors: Bryan Kurt , Caudill Lester F.
Published: March 2021

This paper examines an inverse problem which arises in thermal imaging. We investigate the problem of detecting and imaging corrosion in a material sample by applying a heat flux and measuring the induced temperature on the sample’s exterior boundary. The goal is to identify the profile of some inaccessible portion of the boundary. We study the case in which one has data at every point on the boundary of the region, as well as the case in which only finitely many measurements are available. An inversion procedure is developed and used to study the stability of the inverse problem for various experimental configurations.
Estimating the Interaction Kernel in a Mathematical Model for a Beam With Internal Damping Mechanism
Authors: Lin Tao , Russell David L.
Published: March 2021

Beams formed by long fiber composite materials have certain internal damping torque. A mathematical model for the displacement of this type of beams in cantilever configuration is the following initial-boundary value problem of an integro-differential equation [1, 14]:

(1) ρ ( x ) w t t ( x , t ) − 2 ( ∫ 0 L h ( x , y ) [ w t x ( x , t ) − w t x ( y , t ) ] d y ) x + ( E I w x x ( x , t ) ) x x = f ( x , t ) ,

(2) w ( 0 , t ) = 0 , w x ( 0 , t ) = 0 ,

(3) w x x ( L , t ) = b l 1 ( t ) ,

(4) − ( E I w x x ( x , t ) ) x | x = L + 2 ∫ 0 L h ( L , y ) [ w t x ( L , t ) − w t x ( y , t ) ] d y = b l 2 ( t ) ,

(5) w ( x , 0 ) = w 0 ( x ) , w t ( x , 0 ) = w 1 ( x ) ,

where L is length of the beam, w(x, t) is the transverse displacement of the beam at time t and position x, ρ(x) is the mass density, EI is the stiffness parameter. The interaction integral kernel h(x, ξ) is introduced in this model by considering a restoring torque which comes from spatially variable bending of the beam. This kernel h(x, ξ) depends on the material properties of the beam. Choosing a different material (different h(x, ξ)) can realize a different damping effect for the beam.
Identification of Vehicle-Bridge Interactive Forces From Measured Bridge Responses: Theoretical Studies
Authors: Law S. S. , Chan Tommy H. T. , Zeng Q. H.
Published: March 2021

Information of the vehicle-bridge interaction force is an important parameter in the design and evaluation of highway bridges. However it is difficult to directly measure or accurately calculate the force which is a moving force. The objective of this paper is to explore the theory of force identification based on the response of the structure to acquire a time history of the moving force. The force will be identified in time domain using a modal superposition method. A moving force on a simply supported beam is simulated, and the computational results show that the method is noise sensitive, and yet acceptable results can be obtained by combining the use of vibration data of the bending moment and acceleration measurements.
Model Verification and Validation in Engineering: Updating of Mathematical Models by the Use of Test Data
Authors: Natke H. Günther
Published: March 2021

Mathematical models are uncertain. Therefore they have to be verified and validated in order to obtain usable models.

Models are maps of systems. Thus, one first has to define the expressions, and secondly, one has to give the relations between them.

The best available information about the system stems from the existing system: measurements. Consequently, system identification methods are used for model verification and validation.

The uncertainties of the prior model and of the measurements have to be modelled. This is done probabilistically. The resulting updating methods are discussed, including the problems arising, and procedures for overcoming them.
Parameterisation of Joints and Constraints for Finite Element Model Updating
Authors: Friswell Michael I. , Mottershead John E. , Ng Gary H. T. , Smart Mark G.
Published: March 2021

The sensitivity method is applied to update finite element models of welded and bolted joints, and the boundary condition of a cantilever plate. Careful parameterisation is found to be critical in updating the joints and boundary conditions. Updating geometric parameters has considerable potential in updating. The use of nodal offset dimensions results in an updated model of the welded joint with physical interpretation. Similarly the ‘rigid’ boundary in a cantilever plate is successfully updated using the effective length of the elements closest to the joint. In all cases an improvement on the analytical natural frequencies is demonstrated.
Structural Fault Localization Using Direct Stiffness Update Methods
Authors: Verçosa Carlson Antonio M. , Arruda José Roberto F.
Published: March 2021

The problems caused by experimental data incompleteness when using optimal-matrix update methods are well known. Since the advent of laser-based vibration measurements, the number of measured degrees-of-freedom may be very large, even larger than the number of degrees-of-freedom in a finite element model. Considering that the incompleteness problem may now be partly solved, this paper revisits some well-established direct stiffness update methods, as well as a method recently proposed by the authors, for use in structural fault localization applications. The methods are appraised using a simulation example consisting of a clamped-free beam. The force cancellation between adjacent finite elements, which is known to create an impossible situation for Kabe’s method, is solved by introducing the concept of pseudo sparsity. The effects of modal truncation, expansion, and additive noise are investigated.
Updating a Non-Conservative Finite Element Model: Two Modal Methods
Authors: Moine Pascal , Billet Laurent , Aubry Denis
Published: March 2021

Two updating methods using modal data are proposed to update damped F.E. models. The first one is based on a sensitivity approach whereas the second one minimises some energy error. It is possible to derive from the second method a density error function which allows to localise erroneous structural parameters. Numerical tests are presented in order to evaluate the performances of the two methods.
Error Localization Methods With Static Modes and Thermographic Data
Authors: Thouverez F. , Humbert L. , Jezequel L.
Published: March 2021

The goal of updating methods in dynamic is to improve the finite element models by means of experimental tests. In fact, we try to estimate a better value of the mass (M) and stiffness (K) matrices. Several ways are possible to complete the updating of M and K :

- Global techniques which consist to correct the entire matrices without keeping a physical meaning of the M and K modifications. This approach transforms the finite element “knowledge” models into “representation” models which are more accurate in the measured frequency range but don’t represent the actual structure. This kind of method has been developed first by Baruch (1978) and Berman (1979) and improved by lots of researchers (Kabe, 1985 and Wei, 1990).

- Local techniques try to compute the best values of the physical parameters defined on each element of the modelling. This method is a very stiff one since the optimization of the numerical modes is required over a very large number of parameters. To be able to use this approach we must select only the elements which must be modified to reduce the size of the optimization problem. To do so, we will apply the localization methods. In this paper we will present two ways to locate the modelling errors as well as a new approach based on thermographic, data. Each localization methods will be tested and we will show the influence of the expansion technique and the improvement due to the use of the static modes. The thermographic measurements give us a large number of data but partial because the information gathered by the camera concernes only the sum of the principal strains (Olivier et al, 1988 and Ryall et al, 1992). But the advantages of this method are the number of points which is important and the nature of the data which is a strain information (very sensitive to the local defaults of modelling).
The Laser Torsional Vibrometer: Successful Operation During Lateral Vibrations
Authors: Miles Toby J. , Lucas Margaret , Rothberg Steven J.
Published: March 2021

Torsional vibration of rotating shafts can contribute significantly to machinery noise and vibration levels. The Laser Torsional Vibrometer has been developed for accurate non-contact measurement of the torsional oscillation of rotating components, with advantages over conventional techniques. Its optical geometry offers inherent immunity to lateral shaft vibration in most cases but the instrument is sensitive to specific types of lateral shaft vibration under certain circumstances. Theory is presented to illustrate this effect on the Vibrometer measurements and close agreement with experimental results is found. The significance of this cross-sensitivity is discussed and illustrated with experimental results from two different engine applications, allowing the specification of optimum configurations to ensure effective immunity to all lateral vibration.
Mamba in the Mirror: Black Masculinity, Celebrity, and the Public Mourning of Kobe Bryant
Authors: Williams A. Lamont
Published: March 2021

In this manuscript, the author describes their unexpected grieving process in dealing with the death of Kobe Bryant. In particular, the author focuses on the mourning process on tragic celebrity deaths and the relationship between celebrity, mortality, and the ways in which people make sense of themselves through celebrity figures. The author attempts to highlight the complicated nature of mourning celebrity figures who are not personally known, especially those that have a complicated history in the public eye. The author moves into and through their own personal experiences as a Black man in order to make sense of public mourning, race, and the Black Masculinity of Kobe Bryant.
Response to Comment on “Increased growing-season productivity drives earlier autumn leaf senescence in temperate trees”
Authors: Zani Deborah , Crowther Thomas W. , Mo Lidong , Renner Susanne S. , Zohner Constantin M.
Published: March 2021

Our study showed that increases in seasonal productivity drive earlier autumn senescence of temperate trees. Norby argues that this finding is contradicted by observations from free-air CO
2
enrichment (FACE) experiments, where elevated CO
2
has been found to delay senescence in some cases. We provide a detailed answer showing that the results from FACE studies are in agreement with our conclusions.
Management of severe traumatic intrusion in the permanent dentition
Authors: Rovira-Wilde Alex , Longridge Nick , McKernon Sarah
Published: March 2021

Traumatic intrusion is considered one of the most severe luxation injuries to the permanent dentition. There are limited studies based on minimal evidence supporting suggested management protocols, owing to the rare occurrence of intrusion. The following case report details the multidisciplinary management and 18-month follow-up, in line with current UK guidelines, of a 23-year old adult male who sustained severe intrusion injuries to both permanent maxillary central incisor teeth. Timely, accurate diagnosis and subsequent appropriate management correlates with improved outcomes for traumatic injuries and it is therefore imperative those involved with the acute and long-term management of dentoalveolar trauma are aware of current guidelines.
Bilateral alveolar rhabdomyosarcoma of breast: a rare entity
Authors: Varshney Bharti , Kumar Abhishek , Deka Lopamudra , Aiyer Hema Malini
Published: March 2021

Sarcomas of breast constitute less than 1% of all malignant breast tumours. Alveolar rhabdomyosarcoma (RMS) is very rare in breast with limited case reports in literature, and primary alveolar RMS arising from breast is still less common than metastatic RMS. Here, we report a case of primary bilateral alveolar RMS of breast in an adolescent female where the correct diagnosis was obfuscated by an overlap in the histological features of RMS and high-grade invasive ductal carcinoma.
Unusual cause of severe iron deficiency anaemia in a child: paraoesophageal hernia
Authors: Bolia Rishi , Srivastava Yash , Yadav Renu , Sherwani Poonam
Published: March 2021

Iron deficiency anaemia is a known complication of a large hiatal hernia in adults. It occurs as a result of erosions on the gastric mucosa secondary to traction at the hiatus during respiration and/or gastric acid-related injuries to the mucosa. Even though anaemia occurs as a result of chronic gastrointestinal blood loss, testing for faecal occult blood is often negative and upper gastrointestinal endoscopy normal as the bleeding is intermittent. In children, a hiatus hernia as a rare cause of iron deficiency anaemia and has been described only in case reports. Here, we describe a 5-year-old boy who presented with severe transfusion-dependent iron deficiency anaemia caused by a paraoesophageal hernia. Surgical repair of the hiatus hernia led to complete resolution of anaemia. One should consider a hiatus hernia as a diagnostic possibility when evaluating a child with refractory iron deficiency anaemia.
Addison’s disease with primary hypothyroidism in a case of visceral leishmaniasis and HIV coinfection
Authors: Rani Monu , Garg Rakesh , Agraharabachalli Nanjunde Venkatesh Darshan , Rajput Rajesh
Published: March 2021

A 41-year-old man presented with vomiting and loose stools. He had a history of long-term intermittent fever, generalised skin hyperpigmentation, dragging sensation in the left hypochondrium and unintentional weight loss. He was receiving combination antiretroviral therapy since 2010 for HIV infection. He also received antitubercular therapy for tuberculous spondylitis. During the hospital stay, he was found to have postural hypotension, hypoglycaemia, hyponatraemia, hyperkalaemia, pancytopenia, hypothyroidism, hyperglobulinaemia and hypoalbuminaemia with reversal of serum albumin/globulin ratio. The morning plasma cortisol was lower than normal and could not be appropriately stimulated after the Synacthen test. The bone marrow histopathology was suggestive of visceral leishmaniasis. He was diagnosed as a case of visceral leishmaniasis and HIV coinfection with primary adrenal insufficiency (Addison’s disease) and primary hypothyroidism, as a rare and unusual presentation.
Necrotising fasciitis of the thoracic wall: a rare case with favourable outcome
Authors: Nemésio Rodrigo Athayde , Ruivo Ana , Monteiro Alexandre , Tralhão José Guilherme
Published: March 2021

Necrotising fasciitis (NF) is a severe infection of the subcutaneous tissue and fascia that can rapidly lead to sepsis and shock with high mortality rates. Its initial signs are often non-specific making it difficult for an early diagnosis to be reached. Nevertheless it is of the utmost importance to begin proper treatment including wide surgical debridement as soon as possible in order to avoid death. We present the case of a patient with NF of the thoracic wall which is a rare location for this disease but often associated with worse prognosis. Even though he progressed to septic shock within less than 24 hours of its presentation, due to early surgical management, aggressive resuscitation and intensive care support, he reached a favourable outcome. After three surgical revisions and 2 weeks in an intensive care unit, the patient was discharged from hospital 35 days after admission.