vibration testing
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10.29007/b1th ◽  
2022 ◽  
Author(s):  
Cong Hoa Vu ◽  
Ngoc Thien Ban Dang

Today, freight is an extremely important industry for the world we are living. Fast transportation, large volume...will optimize the cost, time and effort. Besides, ensuring the products safety is a matter of concern. During transporting, it is inevitable that the vibration caused by the engine, rough road surface...the cargo inside can be damaged. Automobile industries have prime importance to vibration testing. Sine vibration testing is performed when we have been given with only one frequency at given time instant. Trend to perform random vibration testing has been increased in recent times. As random vibration considers all excited frequencies in defined spectrum at known interval of time, it gives real-time data of vibration severities. The vibration severity is expressed in terms of Power Spectral Density (PSD). KLT box is an industrial stacking container conforming to the VDA 4500 standard that was defined by German Association of the Automotive Industry (VDA) for the automotive industry. The aim of this paper is study about random vibration and power spectral density analysis, how it can be used to predict the impact of hash road to the KLT box on container / truck during transportation. Finite element model is developed in ANSYS, modal analysis and random vibration analysis were done.


2021 ◽  
Vol 26 (4) ◽  
pp. 316-324
Author(s):  
K. Renji

Equipment that is mounted on a spacecraft is subjected to random vibration tests to verify whether they can withstand the specified random loads. These tests are generally carried out by using shaker systems during which equipment experiences very high responses at the natural frequencies of the equipment. To reduce such over-testing, notching of the input is done. Notching of the input is normally carried out by considering the force generated at the base and limiting it to a specified value. To accomplish the notching, the force spectrum to be limited and measurement of base force during the tests are needed. This work shows that the acceleration input at the interface of equipment gets reduced at its resonance frequency and this feature can be utilized in arriving at the notched input. An expression to determine the depth of notching is derived and the results are compared with those obtained using numerical simulations. The depth of the notch increases with the response of the oscillator and it is sensitive to the stiffness ratios rather than the mass ratios of the oscillator and the mounting panel. This behavior and the expressions derived can be effectively used in arriving at the notched input for an equipment without the need for measuring the base force, especially for random vibration testing, which is demonstrated with an example.


2021 ◽  
pp. 83-95
Author(s):  
Yusuke Fujisaku ◽  
Hideki Naito ◽  
Yu Shirai ◽  
Takuya Maeshima ◽  
Sonoko Ichimaru ◽  
...  

2021 ◽  
Vol 7 ◽  
Author(s):  
Mohammad Royvaran ◽  
Onur Avci ◽  
Brad Davis

The effect of partition walls and non-structural elements on the dynamic response of floors is still not well understood, and there is a need for vibration testing of floors at various stages of construction. The best way to shed some light on the effect of non-structural components is to test additional floors (preferably the same floor) before and after the installation of non-structural elements and compare the dynamic properties. For that purpose, the authors conducted vibration testing on a building floor under construction at various stages of fit-out to quantify the effects of various non-structural elements on the vibration response. An elevated floor of a steel-framed building in the Southeastern United States was tested: the first test was performed for the bare slab conditions with minimal non-structural elements, while the second test was conducted after the installation of non-structural components and in the presence of various construction materials spread over the test floor. The modal tests were conducted by applying measured dynamic forces using an electrodynamic shaker while accelerations were measured at critical locations on the slab. The measurements were post-processed to determine the frequency response functions, which provided general information on the dynamic response. The selection of the test points and excitation functions were primarily to extract maximum data regarding the performance of non-structural elements rather than as part of a standard vibration serviceability assessment of the floor structure. The modal tests were repeated after the installation of non-structural components, electrical and mechanical ductwork, to determine their effect on the vibration characteristics of the floor. The resulting frequency response functions were compared for each condition, and finite element models were created to represent each test condition. As a result, the installation of non-structural components was observed to influence the dynamic response of the floor. Combined with the other test data in the literature, the results of the experimental testing presented in this paper might lead to more effective modeling techniques and provide guidance as to their inclusion into analytical models.


Author(s):  
Gaudentiu Varzaru ◽  
Razvan Ungurelu ◽  
Mihai Branzei ◽  
Bogdan Mihailescu ◽  
Ciprian Ionescu ◽  
...  

2021 ◽  
pp. 107754632110466
Author(s):  
Peng Wang ◽  
Hua Deng ◽  
Yue Liu ◽  
Yi-ming Wang ◽  
Yi Zhang ◽  
...  

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.


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