Mechanical Impedance Analysis Research Articles

Development of an Open-Source Robotic NDT Solution for Automated Composite Repair Testing

Abstract Non-destructive testing (NDT) plays an important role in aircraft maintenance and repair processes, ensuring the structural integrity necessary for safe operation. The paper presents the design and evaluation of an animated, low-cost robotic NDT system tailored for inspecting composite bonding agents. The system integrates commercially available components, including a three-degree-of-freedom robotic arm and a Raspberry Pi 4B, managed by custom Python software with a user-friendly graphical interface. Mechanical Impedance Analysis (MIA) and Eddy Current Testing (ET) methods were employed to assess the system’s performance on representative test specimens. Results indicate that the system delivers reliable and accurate measurements comparable to commercial tools like the MAUS V, while offering simplicity and modularity. Limitations such as scanning speed and handling of complex geometries are acknowledged, with potential solutions proposed for future enhancement. The system provides an affordable and customizable alternative for NDT automation in the aerospace industry.

Defect detection within filling layer of subway slab ballastless track based on impulse response method

The impulse response method, as a mechanical impedance analysis method with high-impact energy, can provide a rapid assessment of structural integrity. For this reason, the impulse response method is applied to subway slab ballastless tracks, and the theory behind this method, as well as the applicability of detecting the voids within the self-compacting concrete (SCC) filling layer, are deeply studied. The theoretical derivation of the mobility function of subway slab ballastless track under impact load is performed. The finite element model is established and the propagation of elastic waves in the process of impulse response method is simulated. The study also investigates the sensitivity of various characteristic parameters and the frequency analysis range to void identification in the SCC filling layer. Furthermore, the characteristic parameters for defect identification in the SCC filling layer are constructed and subsequently validated through a full-scale test. The results reveal that the impulse response method is capable of generating elastic waves with higher energy and longer wavelengths within the structure. This characteristic is advantageous for the detection of concealed defects in the multi-layer structure. The mobility spectrum of subway slab ballastless track exhibits multi-frequency peak characteristics, and the calculated cut-off frequency of the peak-mean mobility ratio should be extended to more than 1600 Hz. Among the three characteristic parameters of peak mobility, dynamic stiffness, and peak-mean mobility ratio, the peak-mean mobility ratio has the advantage of accurately identifying the void position and providing a more precise range.

Performance Evaluation of Inerter-Based Dampers for Bridge Flutter Control: A Comparative Study

As the number of long-span bridges continues to grow, wind-induced vibration issues have become increasingly intensified. Among them, flutter is a serious wind-induced vibration that can lead to bridge collapse. To address this problem, this paper proposes inerter-based dampers as a solution for flutter control and compares their performance to traditional tuned mass dampers (TMDs). Firstly, eight distinct inerter-based dampers were proposed, based on various combinations of mass-inerter-spring-damper (MISD) components. Secondly, the equations of motion of the bridge-MISD system were derived based on the two-mode coupled flutter theory and the mechanical impedance analysis method. Thirdly, the flutter control performance of the eight proposed MISDs is examined using a simply supported beam, with the six better-performing dampers further evaluated using the Jiangyin Bridge. The results show that inerter-based dampers can effectively improve the critical flutter wind speed of bridges, with performance sensitive to frequency. Additionally, incorporating an inerter decreases the static displacement of the mass block, while increasing the mass of MISD and the distance between the damper and the section center improves flutter control performance. The optimal spring stiffness ratios for the six MISDs are identified, largely dependent on the damper’s inertance and mass. In conclusion, this paper offers a promising solution to addressing flutter in long-span bridges and provides insights into the design and optimization of inerter-based dampers.

Hybrid skyhook mass damper

The objective of this study is to increase the efficiency of an initial passive Tuned Mass Damper (TMD) by adding an active control unit. A critical issue in many engineering domains is the design of fail-safe active systems. The proposed hybrid system aims to address this issue and realizes the said objective. It emulates the behavior of a skyhook damper parallel to a passive TMD. Skyhook dampers acts like viscous dampers connected to the ground, reducing the vibration amplitudes without any overshoot. It can be difficult to design a specific control law to obtain a desired dynamical behavior. The paper presents two ways to understand and design the hyperstable control law for Hybrid Mass Damper (HMD) (also called Active TMD), using the power flow formulation or the mechanical impedance analysis. These approaches are illustrated through the synthesis of this hybrid device and the emulation of the Skyhook damper. It is shown that a well-designed control law for this kind of system may result in high damping performance, ensuring stability and a fail-safe behavior. In addition, the amplitude of the primary system’s response is reduced over the entire frequency range which is not the case for the usual active or hybrid systems. Robustness is analyzed and compared to that of the classical active mass damper, and an experimental set up validates the proposed hybrid system.

The Influence of Composite Polymeric Materials Topology Over the Shearing Modulus Using Virtual Instruments

This study presents research regarding the calculation of the mechanical characteristics of composite polymeric materials. By using LabVIEW� software a virtual instrument was created used for monitoring in real time the process of cross-linking the composite polymeric materials. The experiments were realized based on composite materials containing epoxy/fiberglass resin of different topologies. By means of the virtual instrument and of a sensor created based on the mechanical impedance analysis, implanted in the composite material, it was determined the G shearing module of the composite material at different temperatures.

Viscoelastic Measurement in High Frequency Range with New Rheometer Based on Mechanical Impedance Analysis.

A new rheometer measuring viscoelasticity of liquids at high frequencies with a surface loading method was constructed and applied to a waterborne polymer. An impedance head that could simultaneously detect force and acceleration was employed in this rheometer. A small glass plate was attached to a vibrator through the impedance head. The mechanical impedance of liquids was evaluated from difference between the transfer functions for the two cases, one with the plate being immersed in the sample and the other with the plate in the air. Then, the storage and loss moduli were calculated from the mechanical impedance as functions of frequency in the range of 102 to 104 rad s-1. As a calibration, the moduli data for a solution of polystyrene in diethylphthalate obtained with this rheometer were compared with those with a conventional rheometer. Agreement of the two sets of data indicated a good performance of the new rheometer. Viscoelasticity of aqueous solution of associating polymer was determined at frequencies 103-104 rad s-1 with this rheometer and at 10-1-103 rad s-1 with a conventional rheometer. This associating polymer solution was found to possess single relaxation viscoelasticity.

THE MECHANICAL IMPEDANCE ANALYSIS METHOD OF NONDESTRUCTIVE TESTING (A REVIEW)

The mechanical impedance analysis (MIA) method is nowadays widely used for detecting debonds in multilayer structures made of advanced composites, metals and other materials in different combinations, delaminations in plastics and some other defects. Testing is carried out with one-sided access, no liquid couplant is required. In tested objects bending waves of sonic and low ultrasonic frequencies are excited. For about 12 years the MIA method has been used in Russia only. But since 1973 the MIA flaw detectors have been produced in the West too, first by INSPECTION INSTRUMENTS (U.K.) and then by STAVELEY. This review article gives brief systematic information about the up-to-date state of MIA method, its basic principles, types of probes and their characteristics, capabilities and applications. A newly developed pulse version of the MIA method is described, which enables the design of portable flaw detectors, especially suitable for in-service testing.

Real time cure monitoring of composite structures using the techniques of mechanical impedence analysis

AbstractA dynamic mechanical apparatus, based on the concept of mechanical impedance analysis (MIA), was constructed for real‐time cure monitoring of composites. The frequency response function (FRF), in terms of the inertance, impedance or admittance value, can be obtained from the ratio of the Fourier Transforms of excitation and response signals. Spectra during curing of several different kinds of composite materials were obtained with the Fast Fourier Transform spectrum analyzer while the material was continually excited with a random input generated by an electro‐magnetic shaker. The dynamic properties, such as storage modulus (E′) and loss tangent (tan δ), of the composite can be obtained from the FRF spectra as a function of cure time and temperature. Variations of the inertance spectra with cure time, reflecting the changes in the dynamic mechanical properties, for the composite materials under various isothermal cure conditions are discussed. Optimal cure cycles of a new resin can be determined by characterizing the phase transformation of the material, which can be identified from the MIA measurement results. The MIA technique is found to be a sensitive and direct means for monitoring the overall cure state of composites. The signals obtained can be integrated in real‐time in a closed‐loop feedback control system for composite fabrication.

Design of New Viscoelastic Spectrometer in Audiofrequency Range Based on Mechanical Impedance Analysis

Design of New Viscoelastic Spectrometer in Audiofrequency Range Based on Mechanical Impedance Analysis

Monitoring the dynamic mechanical behavior of polymers and composites using mechanical impedance analysis (MIA)

AbstractThe techniques of mechanical impedance analysis (MIA) have been evaluated in terms of its potential for use as a reliable dynamic mechanical methodology. The method involves measuring the relation between a force input (excitation) and a motion output (response) between various points on the structure. In its most common and simple form, the force input and velocity output are measured at a single point of the structure and the values of the mechanical admittance (velocity/force) are plotted as a function of frequency. Rapid measurements and analysis of the dynamic mechanical properties of polymers and composites can be obtained by using a dual‐channel FFT spectrum analyzer interfaced with a personal computer. It is demonstrated that the technique can be used to analyze polymer viscoelasticity, to study phase transformation of thermosetting resins, and to monitor cure of integrated composite structures. Also discussed are the potential advantages and limitations of the MIA technique when applied in the fields of polymer science and engineering.