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The experimental modal analysis requires good knowledge of various engineering fields, such as mechanical vibrations, transducers used in vibration measurement, transducers and system calibration methods, data acquisition systems, digital signal processing and system identification. Test facilities constitute a key factor for improving the quality of the estimated modal model. This paper aims to describe the experimental facilities at the Institute of Aeronautics and Space (IAE) Modal Testing Laboratory in terms of associated instrumentation and data acquisition system, metrological aspects and computational resources. The discussion is completed with a practical application showing a ground vibration testing (GVT) of an unmanned aerial vehicle (UAV).

The experimental facilities were evaluated in a typical GVT, using three shakers in both vertical and horizontal excitations and 88 response measurement points. The global excitation method was used to excite all desired modes. The reliability of the experimental modal model was validated by an auto modal assurance criterion matrix for the measured modes of the structure.

The experimental facilities were successfully used for validating the dynamical characteristics of the UAV under testing.

The modal test facilities of the Modal Testing Laboratory at the IAE, the main research center of the Brazilian Air Force, are described in this paper.

The main purpose of this study is to examine the damage behavior of flexural members under different loading conditions. The finite element model is proposed for the prediction of modal parameters, damage assessment and damage detection of flexural members. Moreover, the analysis of flexural members has been done for the sensor arrangement to accurately predict the damage parameters without the laborious work of experimentation in the laboratory.

Beam-like structures are structures that are subjected to flexural loadings that are involved in almost every type of civil engineering construction like buildings, bridges, etc. Experimental Modal Analysis (EMA) is a popular technique to detect damages in structures without requiring tough and complex methods. Experimental work conducted in this study concludes that a structure experiences high changes in modal properties once when cracking occurs and then at the stage where cracks start at the critical neutral axis. Moreover, among the various modal parameters of the flexural members, natural frequency and mode shapes are the viable parameters for the damage detection.

For torsional mode, drop in natural frequency is high for higher damages as compared to low levels. This is because of the opening and closing of cracks in modal testing. When damage occurs in the structure, there is a reduction in the magnitude of the FRF plot. The measure of this drop can also lead to damage assessment in addition to damage detection. The natural frequency of the system is the most reliable modal parameter in detecting damages. However, for damage localization, the next step after damage assessment, mode shapes can be more helpful as compared to all other parameters.

Effect on Dynamic Properties of Flexural Members during the Progressive Deterioration of Reinforced Concrete Structures is studied.

Traditional dynamic and flutter analysis demands a detailed finite element model of the aircraft in terms of its mass and stiffness distribution. However, in absence of these details, modal parameters obtained from experimental tests can be used to predict the flutter characteristics of an aircraft. The purpose of this paper is to develop an improved and reliable method to predict the flutter characteristics of an aircraft structure of unknown configuration under an anticipated aerodynamic loading using software such as MSC Nastran and experimental modal parameters (such as mode shapes, natural frequencies and damping) from ground vibration tests.

A finite element model with nodes representing the test points on the aircraft is created with appropriate boundary constraints. A direct matrix abstraction program has been written for NASTRAN software that carries out a normal modes analysis and replaces the mass normalized eigenvalues and vectors with the experimentally obtained modal parameters. The flutter analysis proceeds with the solution of the flutter equation in the flutter module of NASTRAN.

The method has been evaluated for a light composite aircraft and its results have been compared with flight flutter tests and the flutter speeds obtained from the finite element model with actual stiffness and mass distributions of the aircraft.

The methodology developed helps in the realistic prediction of flutter characteristics of a structure with known geometric configuration and does not need material properties, mass or stiffness distributions. However, experimental modal parameters of each configuration of the aircraft are required for flutter speed estimation.

The proposed methodology requires experimental modal parameters of each configuration of the aircraft for flutter speed estimation.

The paper shows that an effective method to predict flutter characteristics using modal parameters from ground vibration tests has been developed.

The purpose of this paper is to propose an alternative test board design with only one loading condition and sufficiently large sample size, which is more suitable for the statistical package qualification. With the exception of the board shape and size and package component layout, all other aspects of the design strictly follow the JEDEC standard so that the board design can be easily implemented.

A test board in a round shape was introduced. First, drop tests were carried out. Then, the dye stain test and metallurgical analysis were performed in order to study the failure mechanism of lead‐free solder joint under drop impact.

The test results indicate that the combined effect of mechanical shock and PCB bending vibration is the root cause of solder joint failure under drop impact, and that the maximum peeling stress of the critical solder joint could be considered to be the dominant failure factor. On the other hand, the fracture of BGA lead‐free solder joints occurs at intermetallic compound (IMC) interface near the package side, and failure mode is brittle fracture.

These results are the same as those of JEDEC standard test board. Furthermore, the solder joint loading conditions in this design are simplified from six to one. The round test board can take the place of JEDEC standard test board to carry out drop test and to enable good solder joint life prediction and statistical analysis.

The purpose of this paper is to capture the actual structural behavior of the longest timber footbridge in Spain by means of a multi-scale model updating approach in conjunction with ambient vibration tests.

In a first stage, a numerical pre-test analysis of the full bridge is performed, using standard beam-type finite elements with isotropic material properties. This approach offers a first structural model in which optimal sensor placement (OSP) methodologies are applied to improve the system identification process. In particular, the effective independence (EFI) method is used to determine the optimal locations of a set of sensors. Ambient vibration tests are conducted to determine experimentally the modal characteristics of the structure. The identified modal parameters are compared with those values obtained from this preliminary model. To improve the accuracy of the numerical predictions, the material response is modeled by means of a homogenization-based multi-scale computational approach. In a second stage, the structure is modeled by means of three-dimensional solid elements with the above material definition, capturing realistically the full orthotropic mechanical properties of wood. A genetic algorithm (GA) technique is adopted to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

An overall good agreement is found between the results of the updated numerical simulations and the corresponding experimental measurements. The longitudinal and transverse Young's moduli, sliding and rolling shear moduli, density and natural frequencies are computed by the present approach. The obtained results reveal the potential predictive capabilities of the present GA/multi-scale/experimental approach to capture accurately the actual behavior of complex materials and structures.

The uniqueness and importance of this structure leads to an intensive study of its structural behavior. Ambient vibration tests are carried out under environmental excitation. Extraction of modal parameters is obtained from output-only experimental data. The EFI methodology is applied for the OSP on a large-scale structure. Information coming from several length scales, from sub-micrometer dimensions to macroscopic scales, is included in the material definition. The strong differences found between the stiffness along the longitudinal and transverse directions of wood lumbers are incorporated in the structural model. A multi-scale model updating approach is carried out by means of a GA technique to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

This study aims to reduce the weight of the door, improve the operating efficiency and ensure the safety of vehicle operation.

Based on traditional aluminium alloy doors, a new type of honeycomb composite material was developed. Tests were conducted to determine the honeycomb compression resistance, honeycomb and skin shear performance, plate bending, thermal conductivity and environmental protection. Eight doors were developed based on the full-side open structure, and static strength and stiffness analyses were performed simultaneously. To solve door vibration problems, modal analysis and test were carried out.

The test results showed that the weight of the door was reduced by more than 40% whilst ensuring the strength and stiffness of the vehicle. The first–sixth-order test mode of the door was increased by more than 14% compared with existing aluminium alloy doors.

A new type of honeycomb composite material was used in this study. The test results showed that the weight of the door was reduced by more than 40% whilst ensuring the strength and stiffness of the vehicle. The 1st-to-6th order test mode of the door was increased by more than 14% compared with the existing aluminium alloy door.

This paper aims to improve the life of the printed circuit boards (PCB) used in computers based on modal analysis by increasing the natural frequency of the PCB assembly.

In this work, through experiments and numerical simulations, an attempt has been made to increase the fundamental natural frequency of the PCB assembly as high as practically achievable so as to minimize the impacts of dynamic loads acting on it. An optimization tool in the finite element software (ANSYS) was used to search the specified design space for the optimal support location of the six fastening screws.

It is observed that by changing the support locations based on the optimization results the fundamental natural frequency can be raised up to 51.1% and the same is validated experimentally.

Manufacturers of PCBs used in computers fix the support locations based on symmetric feature of the board not on the dynamic behavior of the assembly. This work might lead manufacturers to redesign the location of other surface mount components.

This work provides guidelines for PCB manufacturers to finalize their support locating points which will improve the dynamic characteristics of the PCB assembly during its functioning.

This study provides a novel method to improve the life of PCB based on support locations optimization which includes majority of the surface mount components that contributes to the total mass the PCB assembly.

The purpose of this paper is to propose a virtual testing strategy in order to predict damping due to the joints which are present in the ARIANE 5 launcher.

Since engineering finite element codes do not give satisfactory results, either because they are too slow or because they cannot calculate dissipation accurately, a new computational tool is introduced based on the LArge Time INcrement (LATIN) method in its multiscale version.

The capabilities of the new strategy are illustrated on one of the joints of ARIANE 5. The damping predicted virtually is compared to experimental results, and the approach appears promising.

The tool which has been developed gives access to calculations which were previously unaffordable with standard computational codes, which may improve the design process of launchers. The code is transferred into ASTRIUM‐ST, where it is being used to build a database of dissipations in the joints of the ARIANE 5 launcher.

The purpose of this paper is to propose the pressure fluctuation to further evaluate and predict the dynamic and static characteristics of the aerostatic slider and improve the calculation accuracy of the aerostatic slider.

First-order velocity slip is introduced into the traditional gas-film fluid equation, and the numerical analysis method is used to solve the static performance of the aerostatic slider. The finite element analysis method is used to solve its dynamic characteristics.

It can be concluded from the simulation and experimental results that the model considering the velocity slip in the gas film flow is more accurate. The errors between the modal detection results and the vibration detection results (0.8%–5.8%) under speed slip are smaller than the traditional cases (23.7%–210%), which also verifies the correctness of the above conclusions.

In this paper, the method of simulation and experiment is used to prove that the first-order velocity slip model is more suitable to predict the dynamic response of the aerostatic slider than the condition without slip.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0059/

The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation performance is limited due to the weight, size and cost. The dramatic attenuating wave propagation characteristic of hull base without adding weight is essential to the vessel acoustic stealth.

The characteristics of vibration wave propagated from typical shape base link structures have been investigated according to impedance mismatch and wave conversion in non‐homogeneous structure. The hull base is simplified to three degrees of freedom damped system through the mechanical impedance method. The influence of blocking mass weight, as well as location properties to the base vibration isolation performance have been discussed. Furthermore, the structure‐borne sound design of a typical hull base is carried out.

The impedance mismatch of the hull base is further increased by the comprehensive use of high transmission loss base link structures, blocking mass as well as damping layer. The effectiveness of structure‐borne sound design is verified through numerical calculation together with underwater model test. The test data show that the noise has been reduced larger than 3 dB.

The paper describes what is believed to be the first application of the high transmission loss base in hull structures based on the literature survey. The method of structure‐borne sound design of a typical hull base can be applied in different types of vessels.