EFFECT OF STRAIN RATE AND ANNEALING ON PROPAGATING CRACKS IN PMMA USING SHADOW OPTICAL METHOD
EBTISAM HASAN HASAN YOUNES;
Abstract
The study consisted of two parts. The first one dealt with stationary cracks where as the second one focused on investigating, experimentally, the dynamic stress intensity
factor (Ko), crack velocity (a•) and crack acceleration (a•)•
and their inter-relation
using the caustic method on two different specimens configurations for both Casted and Extruded types of PMMA having artificial and natural crack in each type of configuration. The study extends to investigate the effect of annealing on those parameters. This entails the determination of the critical annealing temperature leading to the critical value of stress intensity factor (minimum K1c). The effect of applying different cross head speeds (i.e. different strain rates) and different specimen thicknesses are also investigated. Moreover, the study extends further to investigate the roughness of fractured surfaces as a function of different dynamic fracture parameters in both "as produced" and "annealed" material. An attempt to set an empirical correlation of the annealing temperatures with the dynamic stress intensity factor (Ko) is presented as a model for further development of more correlation.
The study, in both parts, arrived at a set of important conclusions that could be utilized in further studies on the behavior of polymeric materials. The study on stationary cracks showed, first of all, that the use of an artificial crack with tip radius small enough to fulfill fracture mechanics requirements is an economical alternative to the introduction of natural cracks. It is also concluded that strain rate affects the value of the stress optical constant of the material where as the change of thickness is of little effect on the same parameter.
Experimental study, on two types of PMMA revealed that the annealing temperature corresponding to a minimum (critical) value of stress intensity factor is 80°C for 24 hours. Hence, this value is used to study the effect of annealing on the dynamic crack propagation parameters in both types of PMM.A (Casted and Extruded) using two specimens configurations.
factor (Ko), crack velocity (a•) and crack acceleration (a•)•
and their inter-relation
using the caustic method on two different specimens configurations for both Casted and Extruded types of PMMA having artificial and natural crack in each type of configuration. The study extends to investigate the effect of annealing on those parameters. This entails the determination of the critical annealing temperature leading to the critical value of stress intensity factor (minimum K1c). The effect of applying different cross head speeds (i.e. different strain rates) and different specimen thicknesses are also investigated. Moreover, the study extends further to investigate the roughness of fractured surfaces as a function of different dynamic fracture parameters in both "as produced" and "annealed" material. An attempt to set an empirical correlation of the annealing temperatures with the dynamic stress intensity factor (Ko) is presented as a model for further development of more correlation.
The study, in both parts, arrived at a set of important conclusions that could be utilized in further studies on the behavior of polymeric materials. The study on stationary cracks showed, first of all, that the use of an artificial crack with tip radius small enough to fulfill fracture mechanics requirements is an economical alternative to the introduction of natural cracks. It is also concluded that strain rate affects the value of the stress optical constant of the material where as the change of thickness is of little effect on the same parameter.
Experimental study, on two types of PMMA revealed that the annealing temperature corresponding to a minimum (critical) value of stress intensity factor is 80°C for 24 hours. Hence, this value is used to study the effect of annealing on the dynamic crack propagation parameters in both types of PMM.A (Casted and Extruded) using two specimens configurations.
Other data
| Title | EFFECT OF STRAIN RATE AND ANNEALING ON PROPAGATING CRACKS IN PMMA USING SHADOW OPTICAL METHOD | Other Titles | تأثير معدل الانفعال والتخمير على الشروخ المنتشرة فى البولى ميثيل ميثاأكربلات باستخدام طريقة الظلال الضوئية | Authors | EBTISAM HASAN HASAN YOUNES | Issue Date | 2001 |
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