A NUMERICAL AND EXPERIMENTAL INVESTIGATION OF COALESCENCE BETWEEN CYLINDRICAL HOLES

2014 ◽  
Vol 38 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Joel S. Griffin ◽  
Clifford J. Butcher ◽  
Zengtao Chen
Keyword(s):  
Finite Element Analysis ◽  
Experimental Investigation ◽  
Digital Image ◽  
Micromechanical Model ◽  
Image Correlation ◽  
Far Field ◽  
Element Analysis ◽  
Cylindrical Holes ◽  
Image Technique ◽  
Local Work

A sequential digital image technique was employed to detect the onset of coalescence between pairs of holes in tensile specimens. The coalescence event was induced between cylindrical holes that were positioned with various spacing and ligament orientations. Using finite-element analysis as a framework, the coalescence predictions of a classic micromechanical model were compared with the experimental coalescence results. It was found that the predicted strains at coalescence could be significantly improved by accounting for local work-hardening in the ligament region between the two holes. Digital image correlation was used to extract strain values from the digital image record, for both the far-field and the intervoid ligament.

Characterization and Validation of Fatigue Strains for Superelastic Nitinol using Digital Image Correlation

2021 ◽  
Author(s):  
Koray Senol ◽  
Hengchu Cao ◽  
Sakya Tripathy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Digital Image Correlation ◽  
Strain Amplitude ◽  
Digital Image ◽  
Fatigue Testing ◽  
Image Correlation ◽  
Element Analysis ◽  
Local Material ◽  
Mean Strain

Abstract Fatigue is a major challenge encountered in cardiovascular implant design. While the properly heat-treated Nitinol can exhibit up to 6-7% recoverable strains allowing for minimally invasive transcatheter delivery of cardiovascular implants, the cyclic in-vivo loading can cause premature fracture of the implant if the fatigue strain is too high. Strain-based criteria have been adopted for the development of Nitinol fatigue resistance. Lacking experimental tools to characterize the local material fatigue strain, fatigue testing of Nitinol specimens has largely relied on the finite element analysis to compute the cyclic strain amplitude and mean strain based on experimentally derived constitutive parameters using phenomenological strain energy theory. Without a consistent computational standard, previous works have resulted in controversy and inconsistency in the impact of mean strain on the fatigue resistance of Nitinol in terms of strain amplitude limit at high cycle fatigue regime. In this paper, digital image correlation (DIC) technique is used to experimentally determine local material strains of Nitinol fatigue specimens using monotonic and cyclic loading conditions. These local strains are compared with strains computed from finite element analysis. It was found that strains from DIC and FEA are comparable in the single-phase states (pure austenitic or martensitic), whereas the measured strains can show significant difference from simulation computed strain during the transformation stage where both austenite and martensite phase co-exist. These observations have significant implications to nitinol fatigue testing and implant reliability assessment.

scholarly journals A New Method Combining Finite Element Analysis and Digital Image Correlation to Assess Macroscopic Mechanical Properties of Dentin

Materials ◽  
2015 ◽  
Vol 8 (2) ◽  
pp. 535-550 ◽  
Author(s):  
Wenlong Wang ◽  
Nicolas Roubier ◽  
Guillaume Puel ◽  
Jean-Marc Allain ◽  
Ingrid Infante ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
New Method ◽  
Element Analysis
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