B&K  Impact Hammer  Type-8202 Impact testing for measuring frequency responsefunctions, to be used for :

Dynamic structural testing such as modal analysis

FEATURES:

- Individually calibrated force transducer that can beremoved and used for other purposes
- Three different tips and an additional mass fortailoring the excitation spectrum
- Cable routed through hammer handle for protection
- Balanced design to maximize impact precision andminimize hammer bounce

 

Introduction

 The Impact Hammer Type 8202 is aninstrumented hammer for testingstructural behaviour when used inconjunction with a dual- or mul-tichannel spectrum analyzer. An im-pact from such a hammer imparts tothe test structure a smooth excitationspectrum over a broad frequencyrange. The force is measured by thebuilt-in Force Transducer Type 8200while the structural response ismeasured by separate means, for ex-ample an accelerometer fitted to thetest object. The frequency bandwidth of the

first lobe of an impact’s spectrum isinversely proportional to the width of the impulse. This is determined bythe duration of the impact force,which in turn depends on factorssuch as the mass and structure of thehammer, and in particular the hard-ness of the contacting surfaces (thehammer tip and the impact area, seeFig.1). The three different tips (steel,plastic and rubber, seeFig.2) and theadditional mass supplied with the Type 8202 enable the pulse durationto be varied from 0.2ms to 5ms witha maximum force of 5000N(1124.10lbf) on a massive, hard ob- ject. The tip material, frequency range,pulse duration and the correspondingforce ranges are given inFig.1.The force spectra obtained when impact-ing an aluminium plate using varioushammer tips, with and without theadditional mass, are shown inFig.4. The Impact Hammer Type 8202may be used to excite structures withmasses in the range of approximately2kg to 3000kg (4.5lb to 6600lb).However, this range is very much de-pendent on the structure’s mechani-cal properties and the mechanicalbackground noise imparted to it byambient conditions. The construction of the hammer isextremely robust. The handle is of anodized aluminum, the hammerhead and the additional mass are of stainless steel and the seatings of theplastic and rubber tips (which reducelateral deformation of the tip materi-al during impact) are of titanium. The miniature socket and cable fromthe force transducer to the hammerhandle are protected by a clip-onguard. The cable is conveniently ledthrough the handle to the socket onthe base of the handle. The charge signal from the forcetransducer is reduced (by a factor of approximately 4) by a simple circuitwithin the handle to prevent the fol-lowing amplifier from being overload-ed. When used with Brüel&Kjær’sSignal Analyzer Unit Type 2035 (partof Multichannel Analysis System Type 3550), the transducer signal canbe connected directly to one of theanalyzer’s accelerometer inputs via aUNF to TNC cable (AO0231). The main specifications of the ham-mer are determined by the Force