Dynamic Crack Initiation in Ductile Steels
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چکیده
The goal of the work presented here is to study dynamic crack initiation in ductile steels "NiÐCr steel and 293 stainless steel# at di}erent loading rates and to establish appropriate dynamic failure criteria[ A variety of infrared and visible optical methods and high!speed photography are used in this study[ Precracked steel specimens are subjected to dynamic three!point bend loading by impacting them in a drop weight tower[ During the dynamic deformation and fracture initiation process the time history of the transient temperature in the vicinity of the crack tip is recorded experimentally using a high!speed infrared detector[ The dynamic temperature trace in conjunction with the HRR solution is used to determine the time history of the dynamic J!integral J"t#\ and to establish the dynamic fracture initiation toughness\ Jc [ The measure! ments made using high!speed thermography are validated through comparison with determination of J"t# by dynamic optical measurements of the crack tip opening displacement "CTOD#[ Finally\ the micromechanisms of fracture initiation are investigated by studying the fracture surface using scanning electron microscopy[ Þ 0887 Elsevier Science Ltd[ All rights reserved[
منابع مشابه
On Macroscopic and Microscopic Analyses for Crack Initiation and Crack Growth Toughness in Ductile Alloys
Relationships between crack initiation and crack growth toughness are reviewed by examining the crack tip fields and microscopic (local) and macroscopic (continuum) fracture criteria for the onset and continued quasi-static extension of cracks in ductile materials. By comparison of the micromechanisms of crack initiation via transgranular cleavage and crack initiation and subsequent growth via ...
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