Frequency Dependency of Beam Collapse Due to Vibration Loads

Evaluation of flight equipment acceleration caused by random vibration loads

AIAA Journal ◽

10.2514/3.14925 ◽

2001 ◽

Vol 39 ◽

pp. 2001-1758

Author(s):

Romualdo Ruotolo ◽

Massimiliano Cotterchio

Keyword(s):

Random Vibration ◽

Vibration Loads

Download Full-text

Prediction of acoustically induced random vibration loads for Shuttle payloads

10.2514/6.1995-1200 ◽

1995 ◽

Cited By ~ 2

Author(s):

K Leung ◽

B Foist

Keyword(s):

Random Vibration ◽

Vibration Loads

Download Full-text

LATERAL VIBRATIONS OF BEAMS ON AN ELASTIC BASE AT CHANGING THE SUPPORTING CONDITIONS

Building and reconstruction ◽

10.33979/2073-7416-2020-91-5-70-76 ◽

2020 ◽

Vol 91 (5) ◽

pp. 70-76

Author(s):

E.V. LEONTIEV ◽

◽

Keyword(s):

Dynamic Behavior ◽

Elastic Foundation ◽

Dynamic Problem ◽

Static Problem ◽

Elastic Base ◽

Design Model ◽

Lateral Vibrations ◽

Internal Forces ◽

Vibration Loads ◽

The Right

The paper considers the system "beam - elastic foundation", in which a beam with free edges was at first on a solid elastic foundation, but when a defect suddenly forms in the foundation under the right side of the beam, part of foundation was removed from design model. As a result of calculations performed by the method of initial parameters, the displacements and internal forces for the static problem are determined. The dynamic problem of determining the forces and displacements was solved, taking into account the three vibration loads F (t) = F sinγt applied at arbitrary points d when the conditions for supporting the right side of the beam on an elastic foundation were changed, the values of the dynamics coefficients were determined. Conditions are formulated that must be taken into account when analyzing the dynamic behavior of a structure under the influence of vibration loads in the case of a change in the conditions of bearing on an elastic foundation.

Download Full-text

Mechanical Consequences of Dynamically Loaded NiTi Wires under Typical Actuator Conditions in Rehabilitation and Neuroscience

Journal of Functional Biomaterials ◽

10.3390/jfb12010004 ◽

2021 ◽

Vol 12 (1) ◽

pp. 4

Author(s):

Umut D. Çakmak ◽

Zoltán Major ◽

Michael Fischlschweiger

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Storage Modulus ◽

Loss Factor ◽

Empirical Relation ◽

Material Behavior ◽

Chemical Compositions ◽

Loading Frequency ◽

Frequency Dependency ◽

Controlled Conditions

In the field of rehabilitation and neuroscience, shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase transforming alloy. Hence in this work, dynamic thermomechanical material behavior of temperature-triggered phase transforming NiTi shape memory alloy (SMA) wires with different chemical compositions and geometries was experimentally investigated. Storage modulus and mechanical loss factor of NiTi alloys at different temperatures and loading frequencies were analyzed under force-controlled conditions. Counterintuitive storage modulus- and loss factor-dependent trends regarding the loading frequency dependency of the mechanical properties on the materials’ composition and geometry were, hence, obtained. It was revealed that loss factors showed a pronounced loading frequency dependency, whereas the storage modulus was not affected. It was shown that force-controlled conditions led to a lower storage modulus than expected. Furthermore, it turned out that a simple empirical relation could capture the characteristic temperature dependency of the storage modulus, which is an important input relation for modeling the rehabilitation device behavior under different dynamic and temperature loading conditions, taking directly into account the material behavior of the shape memory alloy.

Download Full-text

Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors

Sustainability ◽

10.3390/su13052865 ◽

2021 ◽

Vol 13 (5) ◽

pp. 2865 ◽

Cited By ~ 1

Author(s):

Sungryong Bae ◽

Pilkee Kim

Keyword(s):

Energy Harvester ◽

Load Resistance ◽

Oscillation Period ◽

Ambient Vibration ◽

Ambient Vibrations ◽

Frequency Dependency ◽

Energy Harvesters ◽

Piezoelectric Energy ◽

Optimal Load ◽

Bistable Energy Harvester

In this study, optimization of the external load resistance of a piezoelectric bistable energy harvester was performed for primary harmonic (period-1T) and subharmonic (period-3T) interwell motions. The analytical expression of the optimal load resistance was derived, based on the spectral analyses of the interwell motions, and evaluated. The analytical results are in excellent agreement with the numerical ones. A parametric study shows that the optimal load resistance depended on the forcing frequency, but not the intensity of the ambient vibration. Additionally, it was found that the optimal resistance for the period-3T interwell motion tended to be approximately three times larger than that for the period-1T interwell motion, which means that the optimal resistance was directly affected by the oscillation frequency (or oscillation period) of the motion rather than the forcing frequency. For broadband energy harvesting applications, the subharmonic interwell motion is also useful, in addition to the primary harmonic interwell motion. In designing such piezoelectric bistable energy harvesters, the frequency dependency of the optimal load resistance should be considered properly depending on ambient vibrations.

Download Full-text

Experimental modeling of adjacent parallel shield tunnels subjected to train-induced vibration loads

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409720986269 ◽

2021 ◽

pp. 095440972098626

Author(s):

Junchen Zhang ◽

Qixiang Yan ◽

Kai Yang ◽

Minghui Sun

Keyword(s):

Experimental Studies ◽

Bimodal Distribution ◽

Dominant Frequency ◽

Experimental Modeling ◽

Load Curve ◽

Hilbert Huang Transform ◽

Frequency Peak ◽

Train Speed ◽

Vibration Loads ◽

Train Induced Vibration

Previous studies have performed numerical simulations of adjacent parallel shield tunnels under train-induced vibration loads. However, few experimental studies have been performed for the interaction mechanisms. In this study, experimental modeling is conduced to explore the interaction of adjacent parallel shield tunnels subjected to different train-induced vibration loads. A new Hilbert-Huang transform (HHT) is applied to obtain the instantaneous responses of tunnels. The results show that the acceleration of the tunnel follows the trend of the train load curve. The peak accelerations of the tunnels experience a unimodal distribution along the train speed, while the dominant frequencies of the tunnels follow a bimodal distribution. The interaction between the adjacent parallel tunnels is significant. The transform of the vibration loads to the adjacent tunnel is through the soil below the tunnel. The farther away from the train load is, the greater the train speed corresponding to the dominant frequency peak.

Download Full-text