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Compact Tension Specimens (compact + tension_specimen)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Influence of Ramberg,Osgood fitting on the determination of plastic displacement rates in creep crack growth testing

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 4 2007
NAM-SU HUH
ABSTRACT This paper investigates the effect of the Ramberg,Osgood (R-O) fitting procedures on plastic displacement rate estimates in creep crack growth testing, via detailed two-dimensional and three-dimensional finite-element analyses of the standard compact tension specimen. Four different R-O fitting procedures are considered: (i) fitting the entire true stress,strain data up to the ultimate tensile strength, (ii) fitting the true stress,strain data from 0.1% strain to 0.8 of the true ultimate strain, (iii) fitting the true stress,strain data only up to 5% strain and (iv) fitting the engineering stress,strain data. It is found that the first two fitting procedures can produce significant errors in plastic displacement rate estimates. The last two procedures, on the other hand, provide reasonably accurate plastic displacement rates and thus should be recommended in creep crack growth testing. Several advantages of fitting the engineering stress,strain data over fitting the true stress,strain data only up to 5% strain are discussed. [source]

The evolution of the stress,strain fields near a fatigue crack tip and plasticity-induced crack closure revisited

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2004
L. G. ZHAO
ABSTRACT The evolution of the stress,strain fields near a stationary crack tip under cyclic loading at selected R -ratios has been studied in a detailed elastic,plastic finite element analysis. The material behaviour was described by a full constitutive model of cyclic plasticity with both kinematic and isotropic hardening variables. Whilst the stress/strain range remains mostly constant during the cyclic loading and scales with the external load range, progressive accumulation of tensile strain occurs, particularly at high R -ratios. These results may be of significance for the characterization of crack growth, particularly near the fatigue threshold. Elastic,plastic finite element simulations of advancing fatigue cracks were carried out under plane-stress, plane-strain and generalized plane-strain conditions in a compact tension specimen. Physical contact of the crack flanks was observed in plane stress but not in the plane-strain and generalized plane-strain conditions. The lack of crack closure in plane strain was found to be independent of the material studied. Significant crack closure was observed under plane-stress conditions, where a displacement method was used to obtain the actual stress intensity variation during a loading cycle in the presence of crack closure. The results reveal no direct correlation between the attenuation in the stress intensity factor range estimated by the conventional compliance method and that determined by the displacement method. This finding seems to cast some doubts on the validity of the current practice in crack-closure measurement, and indeed on the role of plasticity-induced crack closure in the reduction of the applied stress intensity factor range. [source]

Evaluating the linear normalization technique for deriving J -resistance curves

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2003
J. R. TARPANI
ABSTRACT In this paper, results from the linear normalization (LN) technique of Reese and Schwalbe for deriving J- crack resistance (J,R) curves have been compared, related to J,,a (J -integral,ductile crack growth) data points, to those obtained from traditional elastic compliance technique. Research results regarding a nuclear grade steel exhibiting a wide range of elastic,plastic fracture resistance agree quite well for both techniques until a certain level of toughness of the material. Below this critical level, LN produces inconsistent results for the sub-sized compact tension specimens (0.4T C[T]). The evidence suggests that the loss of applicability of the LN technique can be determined on the basis of the , plastic factor (,pl) for the best linear correlation achieved for ,PN,,a (normalised load gradient,ductile crack growth) data. [source]

Ductile fracture of commercial purity titanium at room temperature

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2000
G. Shatil
An experimental and numerical program was carried out to examine and assess the deformation and fracture behaviour of alloys of commercial purity (CP) titanium. The material rate-dependent deformation under constant displacement rates and under sustained loads was directly simulated in finite element analyses using an implemented unified material model. The simulations predicted the fracture of compact tension specimens subjected to J,R tests and sustained load tests employing a dimensional analysis and strain-hardening approach. Differences between two batches with different oxygen contents were examined and the limitation of the material model was investigated. [source]

Subcritical Crack Growth in Lead Zirconate Titanate

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004
William S. Oates
Subcritical crack growth in terms of velocity,stress intensity factor (v,K) curves in lead zirconate titanate (PZT) were experimentally characterized on poled and unpoled compact tension specimens. The poled specimens were tested under open- and short-circuit electrical boundary conditions, which resulted in an increase in fracture toughness by 0.2 MPa·m1/2 for the accessible velocity range (v= 10,9 to 10,4 m/s) in the open-circuit case. Subcritical crack growth of unpoled specimens was obtained under ambient (relative humidity = 35%) and dry (relative humidity , 0.02%) conditions over a regime in stress intensity factor of 0.5 MPa·m1/2. [source]