Using holographic interferometry methods developed, principal stresses separated are acquired at four different time which can be chosen in one blasting loading run, therefore quantitative analysis of full stress field in transient changing process is realized for blasting model. According to the characteristics which stress wave is reflected along free boundary of a hole, the judging methods that are used in the study for two kinds of dynamic fringe patterns are verified. Changing of the stress field is calculated and analyzed when two-holes simultaneously detonated the charge.
En utilisant la methode de l'holographie interferometrique on obtient les contraintes principales separees correspondant ā quatre temps lors d'un essai de chargement explosive, l'an alyse quantitative de contraintes globales au cours d'une processus dynamique pour un modele explosif sest realisee.Selon la nature de reflexion des ondes de contraintes sur le paroi de trou vide, la methode de dechiffrage ā travers de deux sortes de graphe de barres dynamiques differentes appliquees est verifiee, la processus de changement du champ de contraintes,entre les embrasures quard ceux-ci sautent Ii la fois,est calculee et analysee.
Durch Anwendung neues holographisches Interferenzverfahrens werden vier Hauptspannungen,in unterschiedlichen Momente mit einmal explosionsartiger Belastung zu separieren,gewonneu, so dass die Quantitativsanalyse des ganzen Spannungsfeldes des Explosionsmodells im dynamischen Verlauf ansgefuehrt wird. Nach der Reflexionsbeschaffenheit der Spannungswellen, in die leere Lochwand zu stossen, wird die Korrektheit der Unterscheidungsmethode, mit zwei unterschiedlicher dynamischer Streifenbildung im Studium zu benutzen,bewiesen. Der Verlauf des Spannungsfeldes, des zwischen den zwei zu gleicher Zeit detonnierten Sprengloecher liegt,wird Kalkuliert und analysiert.
Dynamic photoelasticity has been proved to be a valuable tool in the study of blasting stress field (Holloway et al. 1972,Reinhardt & Dally 1971, Riley & Dally 1966), but it is very difficult to separate principal stress by Cranz-Schardin camera. Though some researchers applied the methods of holographic interferometry to get isochromatic and isopachic fringe; blasting stress field was not calculated and analyzed actually. Its most disadvantage is that only single time can be recorded. However the result of blasting experiment is usually -different, even though experimental conditions keep the same.
With the aid of the recent developed ruby laser, we study transient stress's changing for blasting model in the paper. Four group of isochromatic and isopachic fringe patterns at different time are acquired in one loading run by the device. In the study, loading system and synchronizing control system are set up; judging methods of dynamic fringe orders are researched and testified. As an example, principal stresses separated are calculated and discussed when two-holes simultaneously detonated the charge.
The experimental system: is composed of a light source, external optical, blasting loading and synchronizing device. The light source is produced by the ruby laser which can emit eight-pulsed laser. The laser cavity is divided into four same parts. Each part laser is emitted independently and the time can be controlled singly. Before lights reach external path, the four parts will be changed into 2x2cm array of light points in space. Two light pulses which are separated by an adjustable delay time are produced at every point. External optical path is the key to separate principal stress, and the optical arrangement is shown in Fig. l (the Figure indicates only horizontal optical paths).
