A Fast Automated Impact Hammer Test Method for Modal Parameter Extraction: Implementation on a Composite Bridge Beam (original) (raw)
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In the context of the SERIES project (Task 2.3: “software development for data processing”) concerning the availability of simple tools and techniques for real-time data analysis and interpretation, the present report discusses the use of the Fast Impact Hammer Testing method (FIHT) with the purpose of providing to the partners of SERIES the opportunity to use the FIHT method on the structures of the project, and at the same time to improve the method for the dynamic characterisation of structures. The method is illustrated using a practical example of a novel type of structure tested at ELSA, named PROMETEO, composed of a concrete and fibre glass deck supported by a carbon fibre beam 13 meters long. The results obtained with the FIHT method was compared with the results obtained by others existing methods and on other types of structures, confirming the validity of the new methodology employed. The ease of use, and the reduced test and processing time, are the main advantages and i...
Tutorial. Signal processing aspects of structural impact testing
1992
! analysis analysis frequency (Hz) ! sample digital sample ra te (Hz) !l.f frequency re solution (Hz) G�F (w, �) auto spectrum of transient force G '1'x (w, T) auto spectrum of vibration re sponse signal G�x (w, T) cross spectrum of force and vibration response signal G� (ro, T) auto spectrum of general transient signal H(ro) theoretical frequency response function
Time Effective Structural Frequency Response Testing With Oblique Impact
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Structural frequency response testing is accurate in identifying the dynamic characteristic of a machinery structure. In practical perspective, conventional structural frequency response testing such as experimental modal analysis with impulse technique (also known as "impulse testing") has limitation especially on its long acquisition time. The high acquisition time is mainly due to the redundancy procedure where the engineer has to repeatedly perform the test in 3 directions, namely the axial-, horizontal- and vertical-axis, in order to comprehensively define the dynamic behavior of a 3D structure. This is unfavorable to numerous industries where the downtime cost is high. This study proposes to reduce the testing time by using oblique impact. Theoretically, a single oblique impact can induce significant vibration responses and vibration modes in all the 3 directions. Hence, the acquisition time with the implementation of the oblique impulse technique can be reduced by a...
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Acta Polytechnica, 2020
This paper presents a comparative experimental-analytical study on the performance of Multi-Input Single-Output (MISO) and Single-Input Multi-Output (SIMO) techniques to identify the modal properties of a cantilever beam. A 2-D laser interferometry was employed to perform the SIMO modal test, while for the MISO test configuration, a conventional accelerometer was used to measure the response of the structure. Comparing the experimentally-measured natural frequencies with those calculated by the FEM model, a maximum difference of 4% between natural frequencies was observed. The repeatability of both techniques is also investigated in this paper and it is shown that the difference between modal properties identified under different operators is less than 0.5% for both the MISO and SIMO techniques.
New Tools for Structural Testing: Piezoelectric Impact Hammers and Acceleration Rate Sensors
Journal of Guidance, Control, and Dynamics, 1998
Small-size ultra-high-precision mechanical systems demand special testing methodologies, such as a better highfrequency response, a precise impact position, an extremely high repeatability, etc. Utilizing the fact that signals obtained from piezoelectric sensing elements are strongly in uenced by the interfacing circuitry, piezoelectric sensors that can be used to measure acceleration rate were developed. Both analytical and experimental results indicate that acceleration rate sensors can detect the arrival of realistic shock earlier than conventional accelerometers can. An ultra-high-precision high-speed piezoelectric impact system with an on-line load cell was also modeled, designed, and built. The sensitivity of this on-line load cell was calibrated by using a standard quartz load cell. This innovative high-speed impact hammer system was found to have a timing accuracy in the range of microseconds and a positioning accuracy in the range of micrometers.
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The impact test in structural parts for dynamic applications is an essential procedure for their certification in the presence of time dependent loads. In the case of beam elements, either built with one material or as an assembly of different material members joined with recent developed bonding techniques, an impact test is of leading importance, once the dynamic resistance of the joints involved in the beam fabrication is assessed and evaluated. The pseudodynamic method is an alternative to dynamic analysis of structures, here offering to the researcher the possibility of examining with detail the specimen in test for the initiation and progress of eventual damage mechanisms arising in the beam element joints whenever included in the design.
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The characterisation of vibration in buildings often involves exciting the building structure with a force and measuring the vibration response. The two common non-destructive force excitation methods are the use of an instrumented impact hammer or an electromagnetic vibration shaker. This paper contains a discussion on how to build a low cost instrumented hammer, and compares the performance of the hammer with a commercially available impact hammer and a commercially available electromagnetic shaker for vibrating buildings. The merits and disadvantages of each of these three instruments are discussed and it is the opinion of the author that for the vibration analyses often conducted in semiconductor manufacturing facilities, laboratories, and offices, the use of an instrumented impact hammer can provide higher quality measurements at a lower cost than the use of an electromagnetic shaker.
Structural Health Monitoring, 2010
This article presents a basic experimental technique and simplified finite element (FE)-based models for the detection, localization, and quantification of impact damage in composite beams around the barely visible impact damage level. Detection of damage is carried out by shift in modal parameters. Localization of damage is done by a topology optimization tool, which showed that correct damage locations can be found rather efficiently for low-level damage. The novelty of this article is that we develop an all in one package dedicated to impact identification by modal analysis. The damaged zones in the FE models are updated by reducing the most sensitive material property, in order to improve the experimental/ numerical correlation of the frequency response functions. These approximate damage models (in terms of equivalent rigidity) give us a simple degradation factor that can serve as a warning regarding the safety of the structure.