Accession Number : ADA255684


Title :   Modeling of Microstructural Effects on Fracture Processes at High Loading Rates


Descriptive Note : Final technical rept. 1 Feb 1989-31 May 1992


Corporate Author : SRI INTERNATIONAL MENLO PARK CA


Personal Author(s) : Giovanola, Jacques H ; Klopp, Richard W ; Shockey, D A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a255684.pdf


Report Date : Jun 1992


Pagination or Media Count : 201


Abstract : We extended classical dynamic fracture mechanics to a class of new commercially useful titanium microstructures and demonstrated that their dynamic fracture behavior differs significantly from that of previously studied model materials. By combining continuum measurements (obtained using the torsion split Hopkinson bar and one-point-bend fracture test methods) and fractogaphic measurements (obtained using fracture surface topography analysis, FRASTA), we generated a complete data base on static and dynamic strength and fracture toughness for various microstructures of the alloy Ti-IOV-2Fe-3AI. We determined effects of microstructural features on microfailure behavior and we modeled some of the observed microfailure processes using finite element analysis. Whereas the dynamic initiation toughness was only moderately higher than the static initiation toughness (at most 20%), a very strong rise was found in the crack propagation toughness with crack extension (as much as a 100% increase) for velocities as low as 100 m/s. This rate dependent resistance curve effect is an intrinsic material property (in contrast to a structural effect) and a strong function of microstructure. We demonstrated that the formation of shear lips is also a strongly rate dependent phenomenon and that shear lips, when they develop, make only a modest contribution to the propagation toughness (on the order of 20% for the case studied here). Our results also showed that, in general, there is not a direct correlation between the dynamic initiation and propagation toughnesses.


Descriptors :   *MICROSTRUCTURE , *MODELS , *ALLOYS , *TITANIUM , *FRACTURE(MECHANICS) , TEST AND EVALUATION , SHEAR PROPERTIES , VELOCITY , DATA BASES , PARAMETERS , RESISTANCE , CRACKS , CORRELATION , MECHANICS , SURFACES , STRENGTH(MECHANICS) , TOPOGRAPHY , GRAIN SIZE , TOUGHNESS , TEST METHODS , RATES , CURVES(GEOMETRY) , TORSION , STATICS , RODS , BEHAVIOR , CRACK PROPAGATION , FINITE ELEMENT ANALYSIS , MATERIALS , DYNAMICS , FUNCTIONS , PROPAGATION , MEASUREMENT , CONTRAST


Subject Categories : Inorganic Chemistry
      Properties of Metals and Alloys
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE