Publication detail

Analysis of operational deflection shapes of the shaker armature near upper frequency limit

HAVRÁNEK, Z. BENEŠ, P.

Original Title

Analysis of operational deflection shapes of the shaker armature near upper frequency limit

Czech Title

Analýza provozních tvarů kmitů armatury vibračního budiče blízko horního mezního kmitočtu

English Title

Analysis of operational deflection shapes of the shaker armature near upper frequency limit

Type

conference paper

Language

en

Original Abstract

The paper deals with practical analysis of operational deflection shape of the top surface of the electrodynamic shaker armature near upper frequency limit below main resonance. The vibration test system with maximal sine force of 35 kN has been examined for excessive difference of vertical vibration acceleration between the center of circular shaker armature with diameter of 640 mm and its edges. With the control accelerometer in the center of the armature, there was thirty times higher acceleration on the edges at upper frequency limit of the shaker (2000 Hz). This difference has been firstly examined by contact measurement with piezoelectric accelerometers in certain points and afterwards with single point laser Doppler vibrometer enhanced with galvo-mirror system for the fast scanning of the whole armature surface. With scanning measurement procedure the operational deflection shape of the armature has been evaluated during sine force excitation of the vibration system. Detected deflection of the tabletop surface has umbrella-shape with very high displacement on the edges. This excessive difference in acceleration between recommended control point and the rest of the armature led to the armature damage in the past. The umbrella-shape vibrations of the armature indicate high friction in the central bearing or very high damping in the armature internal support which is necessary for handling heavy loads on the shaker table. To avoid further damage of the armature and equalization of the vibration amplitude on the whole surface, special dural stiffening plate with bolts arranged in concentric circles has been made. After several measurements of the deflection shapes of the armature equipped with the plate, necessary positions of the mounting bolts has been identified. Finally only half the number of bolts has been fitted and it led to the vibration acceleration variance on the whole tabletop within 20 percent.

Czech abstract

Článek se věnuje praktické analýze provozních tvarů kmitů horní plochy armatury elektrodynamického budiče vibrací v blízkosti horního mezního kmitočtu tesně pod hlavním rezonančním kmitočtem. Vibrační testovací systém s maximální sinusovou silou 35 kN byl analyzován z důvodu přílišného rozdílu mezi středem kruhové armatury budiče o proměru 640 mm a jejími okraji. Při použití řídicího akcelerometru v ose armatury a buzení na kmitočtu blízkém maximálnímu limitu (2000 Hz) bylo naměřeno na jejích okrajích 30x větší zrychlení než bylo požadované. Tento rozdíl byl nejdříve ověřován kontaktním měřením s piezoelektrickými akceleromery v několika málo bodech a později pomocí jednobodového Dopplerovského vibrometru rozšířeného o optický vychylovací systém pro rychlé skenování celého horního povrchu armatury. Z naměřených hodnot vibrací pomocí skenovacího systému byly následně vyhodnoceny provozní tvary kmitů armatury při sinusovém buzení vibračního systému. Zjištěné výchylky horní desky měly deštníkový tvar s vysokými hodnotami na okrajích desky. Tento výrazný rozdíl zrychlení mezi doporučeným řídicím bodem a zbytkem armatury způsobil její poškození v minulosti. Deštníkový tvar kmitů indikuje vysokou hornotu tření v centrálním ložisku nebo vysoký činitel tlumení ve vnitřní podpoře armatury, která je nezbytná při instalaci velmi hmotných obejktů na stole budiče. Aby se zabránilo poškození armatury v budoucnu a zároveň se vyrovnaly amplitudy vibrací na celém jejím horním povrchu, byla vyrobena speciální duralová ztužovací deska s šrouby rozmístěnými v soustředných kruzích. Po několika měřeních tvarů kmitů armatury doplněné o ztužovací desku byly identifikovány potřebné pozice upevňovacích šroubů. Závěrem byla osazena pouze polovina šroubů a rozptyl hodnoty zrychlení vibrací na celém povrchu stolu byl maximálně 20% od průměrné hodnoty.

English abstract

The paper deals with practical analysis of operational deflection shape of the top surface of the electrodynamic shaker armature near upper frequency limit below main resonance. The vibration test system with maximal sine force of 35 kN has been examined for excessive difference of vertical vibration acceleration between the center of circular shaker armature with diameter of 640 mm and its edges. With the control accelerometer in the center of the armature, there was thirty times higher acceleration on the edges at upper frequency limit of the shaker (2000 Hz). This difference has been firstly examined by contact measurement with piezoelectric accelerometers in certain points and afterwards with single point laser Doppler vibrometer enhanced with galvo-mirror system for the fast scanning of the whole armature surface. With scanning measurement procedure the operational deflection shape of the armature has been evaluated during sine force excitation of the vibration system. Detected deflection of the tabletop surface has umbrella-shape with very high displacement on the edges. This excessive difference in acceleration between recommended control point and the rest of the armature led to the armature damage in the past. The umbrella-shape vibrations of the armature indicate high friction in the central bearing or very high damping in the armature internal support which is necessary for handling heavy loads on the shaker table. To avoid further damage of the armature and equalization of the vibration amplitude on the whole surface, special dural stiffening plate with bolts arranged in concentric circles has been made. After several measurements of the deflection shapes of the armature equipped with the plate, necessary positions of the mounting bolts has been identified. Finally only half the number of bolts has been fitted and it led to the vibration acceleration variance on the whole tabletop within 20 percent.

Keywords

operational deflection shapes, vibrodiagnostics, non-contact vibration measurement, electrodynamic vibration exciter, shaker armature

RIV year

2013

Released

07.07.2013

Publisher

International Institute of Acoustic and Vibration

Location

USA

ISBN

978-616-551-682-2

Book

Proceedings of the 20th International Congress on Sound and Vibration

Pages from

1

Pages to

8

Pages count

8

BibTex


@inproceedings{BUT101904,
  author="Zdeněk {Havránek} and Petr {Beneš}",
  title="Analysis of operational deflection shapes of the shaker armature near upper frequency limit",
  annote="The paper deals with practical analysis of operational deflection shape of the top surface of the electrodynamic shaker armature near upper frequency limit below main resonance. The vibration test system with maximal sine force of 35 kN has been examined for excessive difference of vertical vibration acceleration between the center of circular shaker armature with
diameter of 640 mm and its edges. With the control accelerometer in the center of the armature, there was thirty times higher acceleration on the edges at upper frequency limit of the shaker (2000 Hz). This difference has been firstly examined by contact measurement with piezoelectric accelerometers in certain points and afterwards with single point laser Doppler
vibrometer enhanced with galvo-mirror system for the fast scanning of the whole armature surface. With scanning measurement procedure the operational deflection shape of the armature has been evaluated during sine force excitation of the vibration system. Detected deflection of the tabletop surface has umbrella-shape with very high displacement on the edges. This excessive difference in acceleration between recommended control point and the rest of the armature led to the armature damage in the past. The umbrella-shape vibrations of the armature indicate high friction in the central bearing or very high damping in the armature internal support which is necessary for handling heavy loads on the shaker table. To avoid further damage of the armature and equalization of the vibration amplitude on the whole surface, special dural stiffening plate with bolts arranged in concentric circles has been made. After several measurements of the deflection shapes of the armature equipped with the plate, necessary positions of the mounting bolts has been identified. Finally only half the number of bolts has been fitted and it led to the vibration acceleration variance on the whole tabletop within 20 percent.",
  address="International Institute of Acoustic and Vibration",
  booktitle="Proceedings of the 20th International Congress on Sound and Vibration",
  chapter="101904",
  howpublished="electronic, physical medium",
  institution="International Institute of Acoustic and Vibration",
  year="2013",
  month="july",
  pages="1--8",
  publisher="International Institute of Acoustic and Vibration",
  type="conference paper"
}