Optical detection of impact contact times with a beam deflection probe

Tomaž Požar (Author), Janez Rus (Author), Rok Petkovšek (Author)

Abstract

We present an optical detection technique, called the beam deflection probe, to accurately measure contact times of normal-incidence impacts of steel and sapphire spheres with a transparent glass block. It exploits the deformation of the area that is in a mechanical touch during the rebound. The deformation of the surface acts as a dynamic contact mirror. When illuminated by a laser beam, total internal reflection takes place at the contact mirror, the beam is deflected from it, and its angular deflection history is moni- tored by a quadrant photodiode. A simple threshold-level data processing of the photodiode signals is used to determine the impact duration. It is shown that the shape of the signal is highly dependent on the location of the impact relative to the center of the laser-beam illuminated area while the determination of the contact time does not depend on the impact position. Using an automated ball release mechanism, the contact time of low-velocity impacts was measured for various ball diameters and approach velocities conforming to the Hertz contact theory. The proposed optical detection of contact times supplements the existing measurement techniques and represents the only alternative to the piezoelectric detection when contact times are to be measured on the microsecond scale.

Keywords

contact time;Hertz contact theory;beam deflection probe;elastic impact;contact mirror;

Data

Language:	English
Year of publishing:	2017
Typology:	1.01 - Original Scientific Article
Organization:	UL FS - Faculty of Mechanical Engineering
UDC:	531.3:620.1/.2(045)
COBISS:	15512859
ISSN:	0014-4851
Views:	676
Downloads:	562
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary abstract:	Predstavljamo optično merilno metodo, imenovano laserska odklonska sonda, za natančno merjenje kontaktnih časov pravokotnih udarcev jeklenih in safirnih kroglic s prozorno stekleno kocko. Metoda izrablja deformacijo območja, ki je pri odboju v mehanskem kontaktu. Deformacija površine deluje kot dinamično kontaktno zrcalo. Ko je osvetljeno z laserskim žarkom, pride na kontaktnem zrcalu do totalnega notranjega odboja, žarek se odkloni, njegovo časovno kotno odvisnost pa spremlja kvadrantna fotodioda. Za določitev trajanja trkov uporabljamo preprosto pragovno procesiranje signalov. Pokazali smo, da je oblika signala močno odvisna od mesta udarca glede na središče območja, ki ga osvetljuje laserski žarek, medtem ko določitev časa kontakta ni odvisna od položaja udarca. Z avtomatiziranim mehanizmom za spuščanje kroglic smo določili čas stika pri udarcih z nizko hitrostjo pri različnih premerih kroglic in različnih vpadnih hitrostih. Rezultati so skladajo s Hertzevo teorijo. Predlagana optična detekcija kontaktnih časov dopolnjuje obstoječe merilne tehnike in predstavlja edino alternativo piezoelektrični detekciji, kadar je kontaktne čase potreba meriti na mikrosekundni skali.
Secondary keywords:	čas trka;Hertzeva kontaktna teorija;odklonska soda;elastični trk;kontaktno zrcalo;
Type (COBISS):	Article
Embargo end date (OpenAIRE):	2018-05-23
Pages:	str. 1225-1238
Volume:	ǂVol. ǂ57
Issue:	ǂiss. ǂ8
Chronology:	2017
DOI:	10.1007/s11340-017-0289-8
ID:	10991295