[show abstract][hide abstract] ABSTRACT: This paper discusses stress intensity factor (SIF) calculations for surface cracks in round bars subjected to combined torsion and bending loadings. Different crack aspect ratios, a/b, ranging from 0.0 to 1.2 and relative crack depths, a/D, ranging from 0.1 to 0.6 were considered. Since the loading was non-symmetrical for torsion loadings, a whole finite element model was constructed. Then, the individual and combined bending and torsion loadings were remotely applied to the model. The equivalent SIF method, F*EQ, was then used explicitly to combine the individual SIFs from the bending and torsion loadings. A comparison was then carried out with the combined SIF, F*FE, obtained using the finite element analysis (FEA) under similar loadings. It was found that the equivalent SIF method successfully predicted the combined SIF for Mode I. However, discrepancies between the results determined from the different approaches occurred when F
III was involved. It was also noted that the predicted F*FE using FEA was higher than the F*EQ predicted through the equivalent SIF method due to the difference in crack face interactions.
Journal of Zhejiang University - Science A: Applied Physics & Engineering 08/2013; 13(1). · 0.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper describes the modeling of multiaxial ultimate elastic wall stress (UEWS) at
room temperature for glass fibre reinforced epoxy (GRE) composite pipes. The model developed,
predicts the stress-strain response caused by the combined, static and cyclic of UEWS loading taking
into effects of transverse matrix cracking within the laminates. The procedure, although not a standard
method, seems to provide a good alternative to the current raw materials' re-qualification procedure
delineated in ISO 14692 through ASTM D2992. The effective transverse and shear modulus of the
lamina due to increasing presence of transverse matrix cracking were estimated. Classical laminate
analysis was then applied to compute the corresponding ply properties as a function of increasing
stress and strain. The model shows a good agreement with the experimental results of multiaxial
UEWS tests on ±55° filament wound glass-reinforced epoxy pipes.
Applied Mechanics and Materials 07/2013; 367:113-117.
[show abstract][hide abstract] ABSTRACT: This paper presents an experimental investigation into the influence of winding angles in multiaxial ultimate elastic wall stress (UEWS) tests of glass-fibre reinforced epoxy (GRE) composite pipes. Currently, UEWS test is one of the alternative methods used to the 1000-hour test procedure detailed in ASTM D2992 for the detection of manufacturing changes and reconfirmation of the design basis of composite pipes. A stress-strain response was obtained for each winding angle and the results then compared with those computed through conventional laminate theory. Experimental data showed that the UEWS point varies for each winding angle, and the difference becomes even more pronounced, especially when the angles deviated from the ideal ±55°. It is also concluded that the UEWS stresses, which represent the onset of non-linearity were very much dependent on the transverse and shear stress responses, and these values were found to be consistent with the predicted values from the commonly used Tsai Wu failure criterion.
Advanced Materials Research 01/2013; 795(424):428.
[show abstract][hide abstract] ABSTRACT: Stress shielding interaction effect of two parallel edge cracks in finite body under uniaxial loading is analysed using developed finite element (FE) analysis program. In present study, the stress shielding interaction is formulated as a mathematical model called stress shielding damage (SSD) model. SSD model used to define the combination and re-characterization of crack interaction from multiple cracks to single crack. Focus is given to weak crack interaction state as the crack interval exceed the length of cracks (b > a). The crack interaction factors are evaluated based on Griffith strain energy release rate and mode I SIF using J-integral analysis. For validation, the stress shielding factor parameters are compared to single edge crack SIF as a state of zero interaction in a form of crack unification limit (CUL) and crack interaction limit (CIL).