Improved Techniques for Uniaxial and Multiaxial Vibration Test Profile Definition

2020 ◽  
Vol 63 (1) ◽  
pp. 53-62
Author(s):  
Kurthan Kersch ◽  
Andreas Wagner ◽  
Thomas Kuttner ◽  
Elmar Woschke
Keyword(s):  
Fatigue Damage ◽  
Field Data ◽  
Vibration Test ◽  
Phase Information ◽  
Vibration Testing ◽  
Additional Phase

Abstract This work aims to improve profile derivation methods for uniaxial and multiaxial vibration testing. Thereby, the focus is put on the inclusion and processing of phase information between the excitation axes. An inherent necessity is the availability of field data. Two existing methods are independently extended by additional phase information and an appropriate processing. The first method is the Fatigue Damage Spectrum for a uniaxial profile derivation. The second method is the enveloping technique for a multiaxial profile derivation. Both methods are theoretically discussed and then evaluated with a fatigue damage calculation of an exemplary structure.

scholarly journals Comparison of seismic interferometry techniques for the retrieval of seismic body waves in CO2 sequestration monitoring

2019 ◽  
Vol 16 (6) ◽  
pp. 1094-1115
Author(s):  
Haitao Cao ◽  
Roohollah Askari
Keyword(s):  
Co2 Sequestration ◽  
Field Data ◽  
Cross Correlation ◽  
Time Lapse ◽  
Body Waves ◽  
Seismic Interferometry ◽  
Storage Site ◽  
Phase Information ◽  
Wave Data ◽  
The Cross

Abstract Ambient noise seismic interferometry performed by cross-correlation has been proven to be a potential cost-effective technique for geological studies. To improve the resolution of images created by interferometry, additional techniques using deconvolution and cross-coherence have been introduced. While all three methods have previously been evaluated using surface wave data for shear-wave imaging of the near surface, comparatively little study has been devoted to assess the three methods for the retrieval of body waves in reflection surveys for time-lapse application. Moreover, although the application of seismic interferometry to CO2 sequestration by cross-correlation has been investigated by many researchers, to our knowledge, similar time-lapse studies have not been conducted using deconvolution and cross-coherence methods. We evaluate the three methods of cross-correlation, deconvolution and cross-coherence for the retrieval of phase information contained in virtual seismic records by applying seismic interferometry to synthetic data, using a model reservoir before and after CO2 injection. By examining two approaches of regularization and smoothing factors to suppress spurious reflection events observed on the deconvolution and cross-coherence results, we note that both approaches provide similar results. We investigate noise effects by adding random noise independently at each geophone. Finally, we apply these techniques to field data recorded near the CO2 storage site in Ketzin, Germany. For both our numerical and field data studies, we find that the cross-coherence technique retrieves the phase information of body-wave data more effectively than the cross-correlation and deconvolution techniques, and is less sensitive to uncorrelated noise from shallow sources.

Synthesis of a Time History Based on the Sine-on-Random Prediction Methodology Defined in MIL-STD-810 Method 519

2017 ◽  
Vol 60 (1) ◽  
pp. 31-41
Author(s):  
Michael T. Hale
Keyword(s):  
Time Domain ◽  
Laboratory Tests ◽  
Field Data ◽  
Time History ◽  
Environmental Engineering ◽  
New Technique ◽  
Vibration Test ◽  
Temporal Characteristics ◽  
New Time ◽  
Exponentially Weighted

Abstract Method 519.7, Annex D of MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests, Change Notice 1 (MIL-STD-810G/CN1) outlines a prediction methodology for establishing a sine-on-random (SoR) structured spectrum that is intended to be representative of gunfire for use in cases in which there is an absence of field data. From that spectrum, the ramp modulated pulse (RMP) technique is proposed as a methodology to synthesize a time history with temporal characteristics that more realistically represent the temporal characteristics of gunfire than that of a SoR time history synthesized via classical SoR generation techniques. This paper provides an alternate technique to the RMP methodology presented in Method 519. The alternate technique is based on normalized exponentially weighted (NEW) time history generated via classical time domain techniques for a SoR vibration test. An outline of the NEW technique and an associated example are provided.

Quadratic Mode Shape Components From Ground Vibration Testing

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
L. H. van Zyl ◽  
E. H. Mathews
Keyword(s):  
Mode Shape ◽  
Ground Vibration ◽  
Axial Displacement ◽  
Vibration Test ◽  
Transverse Displacement ◽  
Vibration Testing ◽  
Linear Mode ◽  
Quadratic Mode ◽  
Acceleration Signals ◽  
Shape Component

Points on a vibrating structure generally move along curved paths rather than straight lines. For example, the tip of a cantilever beam vibrating in a bending mode experiences axial displacement as well as transverse displacement. The axial displacement is governed by the inextensibility of the neutral axis of the beam and is proportional to the square of the transverse displacement; hence the name “quadratic mode shape component.” Quadratic mode shape components are largely ignored in modal analysis, but there are some applications in the field of modal-basis structural analysis where the curved path of motion cannot be ignored. Examples include vibrations of rotating structures and buckling. Methods employing finite element analysis have been developed to calculate quadratic mode shape components. Ground vibration testing typically only yields the linear mode shape components. This paper explores the possibility of measuring the quadratic mode shape components in a sine-dwell ground vibration test. This is purely an additional measurement and does not affect the measured linear mode shape components or the modal parameters, i.e., modal mass, frequency, and damping ratio. The accelerometer output was modeled in detail taking into account its linear acceleration, its rotation, and gravitational acceleration. The response was correlated with the Fourier series representation of the output signal. The result was a simple expression for the quadratic mode shape component. The method was tested on a simple test piece and satisfactory results were obtained. The method requires that the accelerometers measure down to steady state and that up to the second Fourier coefficients of the output signals are calculated. The proposed method for measuring quadratic mode shape components in a sine-dwell ground vibration test seems feasible. One drawback of the method is that it is based on the measurement and processing of second harmonics in the acceleration signals and is therefore sensitive to any form of structural nonlinearity that may also cause higher harmonics in the acceleration signals. Another drawback is that only the quadratic components of individual modes can be measured, whereas coupled quadratic terms are generally also required to fully describe the motion of a point on a vibrating structure.

scholarly journals Efficient retrieval of phase information from real-valued electromagnetic field data

2019 ◽  
Vol 1 ◽  
pp. 100019
Author(s):  
Alexander Blinne ◽  
Stephan Kuschel ◽  
Stefan Tietze ◽  
Matt Zepf
Keyword(s):  
Electromagnetic Field ◽  
Field Data ◽  
Phase Information ◽  
Efficient Retrieval

Method for increasing the speed of an electrodynamic shaker for vibration test of rolling stock equipment

2021 ◽  
pp. 107754632110466
Author(s):  
Peng Wang ◽  
Hua Deng ◽  
Yue Liu ◽  
Yi-ming Wang ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Input Impedance ◽  
Vertical Direction ◽  
Maximum Velocity ◽  
Rolling Stock ◽  
Vibration Test ◽  
Vibration Testing ◽  
High Frequencies ◽  
Electrodynamic Shaker ◽  
Long Life ◽  
The Impact

The velocity required in IEC 61373 for long-life random vibration testing of Category-3 rolling stock equipment in the vertical direction is 2.7821 m/s, but the maximum velocity of existing electrodynamic shakers falls in the range of 2–2.5 m/s. In this study, an electrodynamic shaker with a velocity satisfying the requirements for vibration testing of Category-3 rolling stock equipment was developed. First, mechanical and equivalent circuit models of an electrodynamic shaker were developed. On this basis, reducing the impedance of the armature coil was identified as the best option for increasing the velocity of the shaker. However, owing to the impact of the back electromotive force of the armature coil, a decrease in the input impedance of the armature coil at low frequencies leads to an increase in its input impedance at high frequencies. To reduce the input impedance at high frequencies, a shading coil was incorporated into the circuit. The shading coil-incorporated new design was modeled using equivalent circuits and simulated numerically. The results showed that the improvement measures—incorporating a shading coil, increasing the cross-sectional area, and reducing the number of turns of the armature coil—effectively reduced the input impedance of the armature coil, thereby increasing the armature coil current and the velocity of the shaker. Finally, a shaker with a maximum velocity of 3.2 m/s was fabricated based on the new design and was validated to satisfy the high-velocity requirement for the long-life vibration test of Category-3 equipment in the vertical direction as specified in IEC 61373.

Vibration Test Time Compression and MIL-HDBK-781 vs. MIL-STD-810E

1994 ◽  
Vol 37 (1) ◽  
pp. 24-30
Author(s):  
H. Caruso ◽  
E. Szymkowiak
Keyword(s):  
Fatigue Life ◽  
Test Time ◽  
Vibration Test ◽  
Vibration Testing ◽  
Test Program ◽  
Compression Algorithms ◽  
Time Compression

This paper defines test time compression issues associated with vibration testing as described in MIL-STD-810E and MIL-HDBK-781. Differences and similarities associated with the test goals and application of each document are examined. Use of these documents for establishing test time compression algorithms related to fatigue life (durability) and reliability evaluations is discussed. Specific inconsistencies between the vibration models in each document for jet aircraft equipment are identified. Recommendations are offered for bringing these documents into agreement to provide increased uniformity and correlation of results throughout a test program.

Fatigue damage evaluation of short fiber CFRP based on phase information of thermoelastic temperature change

2017 ◽  
Author(s):  
Takahide Sakagami ◽  
Daiki Shiozawa ◽  
Yu Nakamura ◽  
Shinichi Nonaka ◽  
Kenichi Hamada
Keyword(s):  
Temperature Change ◽  
Fatigue Damage ◽  
Short Fiber ◽  
Damage Evaluation ◽  
Phase Information
Sign in / Sign up

Export Citation Format

Share Document