Accumulated Lifetimes in Single-Axis Vibration Testing

Bouma, Adam; Campbell, A.B.; Roberts, Thomas C.; Taylor, Stuart G; Haynes, Colin; Harvey, Dustin

doi:10.1007/978-3-030-12676-6_12

Cited by 4 publications

(4 citation statements)

References 2 publications

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“…This is specifically to compare the results that are obtained from all locations and the effects that the accelerometer has on the calculated values for the natural frequencies and displacements. For example, in several previous studies [ 14 , 15 , 16 , 42 , 43 ], the accelerometers are often seen in the middle of the beam connecting the two c-channels on the Removable Component, or near the top bolted connections. These observations, with a particular focus on the first mode of vibration, lead to the conclusion of testing the three locations shown in Figure 2 .…”

Section: System’s Description and Experimental Setupmentioning

confidence: 99%

“…Because the BARC has multiple bolted joints, it serves as a complex nonlinear system in which small changes in boundary conditions or laboratory instrumentation may have significant impacts on its dynamical responses. Researchers have heavily studied the BARC system since its inception and many variations in experimental setup exist in the literature, one of the most notable being the variations in boundary conditions between the BARC and shaker [ 14 , 15 , 16 , 17 ]. These variations present a challenge for researchers to compare results as shown in [ 18 ] where the authors proved that decreasing the distance between bolted joints connecting the box assembly significantly decreases the resulting natural frequencies of the system and may cause contact nonlinearities with the fixture.…”

Section: Introductionmentioning

confidence: 99%

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Insights on the Impacts of Accelerometer Location on the Dynamics and Characteristics of Complex Structures

Takeshita,

Madrid,

Granillo

et al. 2023

Sensors

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There exists a high level of difficulty in understanding the physical responses of complex dynamical systems. To this end, researchers have previously used different measurement techniques, such as displacement sensors or accelerometers, in the laboratory to capture a system’s dynamics. A well-known structure in the literature is the Box Assembly with Removable Component (BARC) whose purpose is to gain a deep understanding of testing complex systems. Further breaking down the structure, the Removable Component (RC) portion is often used as a relatively simplified version which retains significant complexity from the original system. However, the placement of accelerometers on the RC have varied greatly throughout the literature which presents a challenge in comparing results and may not accurately represent the system’s dynamics. Finite Element Analysis (FEA) is performed for three common accelerometer locations to determine how their placement affects the frequencies and mode shapes for the RC and results are compared against those without accelerometers. Free vibration experiments are carried out to understand the variation of frequencies and damping for each accelerometer location to obtain the overall response for the first mode of vibration. Next, random vibration experiments are run to gain insight on the interaction between linear and nonlinear responses based on excitation level, while showing the influence of an accelerometer’s location on system dynamics. The results demonstrate that the location of the accelerometer is highly influential on the linear and nonlinear characteristics of the system. It is proved that for the first mode of vibration, nonlinear softening and nonlinear damping behaviors may take place due to the interaction between the location of accelerometers, direction of excitation, and response axis analyzed.

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Section: System’s Description and Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Insights on the Impacts of Accelerometer Location on the Dynamics and Characteristics of Complex Structures

Takeshita,

Madrid,

Granillo

et al. 2023

Sensors

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show abstract

“…Recent work has confirmed that there is usually a substantial increase in test severity 4 when cross-axis responses are considered (Bouma et al, 2019). Published work that attempts to understand the difficulty of replicating field environments in the lab began in the 1960s, in the Apollo era, when huge advances in component qualification testing were made.…”

Section: Multi-axis Testingmentioning

confidence: 99%

Rapid, Approximate Multi-axis Vibration Testing

Cramer,

Harvey,

Zhang

2023

Conference Proceedings of the Society for Experimental Mechanics Series

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Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS May 2023 Cramer, Ethan Savoy. Rapid, Approximate Multi-Axis Vibration Testing. Master of Science (Mechanical and Energy Engineering), May 2023, 43 pp., 9 tables, 23 figures, 41 numbered references.Sequential single-axis vibration testing strategies often produce over-testing when qualifying system hardware. Multi-axis excitation techniques can simulate realistic service environments, but the hardware and testing strategies needed to do so tend to be costly and complex. Test engineers instead must execute sequential tests on singleaxis shaker tables to excite each degree of freedom, which the previous two decades of vibration testing literature have shown to cause extensive over-testing when considering cross-axis responses in assessing the severity of the applied test environments.Traditional assessments assume that the test article responds only in the axis of excitation, but often significant response occurs in the off-axes as well. This paper proposes a method to address the over-testing problem by approximating a simultaneous multi-axis test using readily-available, single-axis shaker tables. By optimizing the angle of excitation and the boundary condition through dynamic test fixture design, the test article can be tested using a Single-Input, Multiple-Output (SIMO) test in a way that approximates a Multiple-Input, Multiple-Output (MIMO) test. This paper shows the proposed method in simulation with a 2D finite element box assembly with removable component (BARC) model attached to springs with variable stiffness.The results include quantified test quality assessment metrics with comparison to standard sequential testing. The proposed method enables access to rapid, approximate, multi-axis testing using existing hardware, thereby reducing the overconservatism of sequential single-axis tests and requisite over-design of systems.

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“…In a complex structure, such as the BARC, seemingly insignificant changes to boundary conditions and fixtures can have large effects on the response of the system. Boundary conditions across the literature of this structure do not have common test fixtures or fixture dimensions [4][5][6] which may not be ideal when comparatively discussing results. To explore the impacts of the test fixture connections on the system's dynamical response, the locations of the bolts fixing the box assembly to the shaker during experiments are deeply investigated in this work.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Test Fixture Connections of the BARC Structure on Its Dynamical Responses

Jankowski

Sedillo

Takeshita

et al. 2021

Sensors and Instrumentation, Aircraft/Aerospace, Energy Harvesting &Amp; Dynamic Environments Testing, Volume 7

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The Box Assembly with Removable Component (BARC) structure has been recently introduced as a challenge problem for the study of the effects of boundary conditions on vibrational testing and modal analysis. Current efforts in studying shaker input excitations on the BARC structure have focused on either varying the degrees of freedom of the test or varying the input signal. The effects that the bolted joints introduced into the BARC's dynamical response have not been fully investigated. This study presents an investigation on the influences of test fixture connections on the dynamical responses of BARC systems for the purpose of establishing a standard fixture connection for general testing and test replication. This investigation is done by varying the distance between bolted connections to compare the effects of stiffness of fixture contribution on the dynamic response. In addition to modal analysis, experimental random vibrations are carried out to determine the dominant frequencies in the system. The experimental measurements are compared to finite element simulations in order to determine the possible variability and the reason behind that. The finite element simulations show that the wider connection geometry leads to a softening effect in natural frequencies of the system. On the other hand, the experimental measurements indicate that the effects of gap between the fixture connections have a negligible impact on the system's dominant frequencies. This study shows the importance of accurately considering the same experimental setup as the computational modeling and vice versa.

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Accumulated Lifetimes in Single-Axis Vibration Testing

Cited by 4 publications

References 2 publications

Insights on the Impacts of Accelerometer Location on the Dynamics and Characteristics of Complex Structures

Insights on the Impacts of Accelerometer Location on the Dynamics and Characteristics of Complex Structures

Rapid, Approximate Multi-axis Vibration Testing

Impacts of Test Fixture Connections of the BARC Structure on Its Dynamical Responses

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