Evaluation of a Vibration Text Fixture

Abstract

Mechanical vibration tests require the use of vibrators, power amplifiers, accelerometers, and closed loop control systems. A device is needed to connect physically the specimen to be tested to the vibrator table referred to as vibration test fixture. To verify and validate a fixture to be used, an evaluation of its dynamical behaviour is mandatory. The fixture natural frequencies must be higher than the maximum test frequency. In this work, some issues about electrodynamic vibrators and fixtures are revised and the behaviour of a real fixture is analysed numerically and experimentally. The fixture natural frequencies and its response to a harmonic acceleration applied on its bottom surface are evaluated by using the finite element method. A real test was performed by applying slow swept sine acceleration to the fixture mounted in an electrodynamic vibrator and measuring its response. The effect of the closed loop control system on the fixture response is evaluated. It is shown that the control system plays an important role in the definition of the fixture useful operating frequency range.

Analysis on Vibration Characteristics of Air Film Damping with Open Boundaries

“…Aluminium alloy fixture is chosen to improve the test efficiency since it is of good stability and it can be conveniently installed and removed. In addition, the resonance frequency of the specially designed aluminum alloy fixture is 4475.6 Hz, which is far greater than the measured resonance frequency of the plate specimens; therefore the measurement accuracy stays high [20]. During each test, the resonance modes of the plate specimens were measured at first, and the frequency step is then set to 0.5 Hz near the resonance band, while the frequency step is set to 2 Hz outside the resonance band for convenience of experiment.…”

Dynamical Characteristics Of A Head Expander For Vibration Testing In Pustekbang Laboratory

“…Pengujian getaran merupakan sebuah pengujian yang dilakukan untuk mengetahui karakteristik dinamik dari sebuah struktur atau benda [1]. Selain untuk mengetahui karakteristik dinamik dari sebuah benda, pengujian getaran juga bisa digunakan untuk mengetahui kekuatan struktur saat dikenai getaran secara kontinyu [2].…”

“…Selain itu, head expander juga berfungsi untuk menyalurkan energi dalam bentuk getaran dari alat uji getaran ke benda uji [6]. Input getaran yang diberikan pada Head expander sebisa mengkin tidak berubah saat diteruskan pada benda uji, oleh karenanya Head expander haruslah sekaku mungkin sehingga tidak menyebabkan resonansi [1]. Head expander juga harus seringan mungkin karena semakin kaku dan semakin kecil massa sebuah benda maka frekuensi natural dari benda tersebut akan semakin besar [7].…”

“…Verifikasi ini dilakukan agar peneliti memiliki gambaran mengenai rentang frekuensi serta batasan-batasan lainya yang bisa dilakukan dengan baik oleh head expnader yang ada di Laboratorium Suhu dan Vibrasi Pustekbang-LAPAN. Pada penelitian kali ini, validasi dilakukan terhadap sifat homogenitas head expander.Menjelaskan kronologis penelitian, meliputi desain penelitian, prosedur penelitian (dalam bentuk algoritma, pseudocode atau lainnya), cara pengujian dan perolehan data [1][2][3]. Uraian jalannya penelitian harus didukung referensi, sehingga penjelasannya dapat diterima secara ilmiah [2,4].…”

Development of Shock Test Fixture for a Heavy Rocket Valve

“…Sine vibration testing involves subjecting the EUT to a swept sine input over a frequency range. Mechanical shock is a sudden, non-periodic disturbance occurring when environmental accelerations are applied for short but definite period of time [1].The different parts of a electrodynamic shaker is detailed in [2]. Testing of a component for any kind of vibration involves mounting it on a shaker with the help of an intermediate element called a Fixture [3].The fixture transmits the forces produced by shaker table to EUT.…”