Crack face sliding displacement (CSD) as an input in exact GLOB-LOC expressions for in-plane elastic constants of symmetric damaged laminates

2019 ◽  
Vol 29 (4) ◽  
pp. 547-569 ◽  
Author(s):  
Mohamed Sahbi Loukil ◽  
Janis Varna
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Opening Displacement ◽  
Crack Opening ◽  
Crack Density ◽  
Opening Displacement ◽  
Crack Face ◽  
Out Of Plane ◽  
Crack Sliding Displacement ◽  
Element Method

The crack opening and crack sliding displacements of both faces of an intralaminar crack are the main parameters defining the significance of each crack in laminate stiffness degradation, according to the previously published GLOB-LOC approach for symmetric laminates with an arbitrary number of cracks in all plies. In the exact stiffness expressions of this approach, the crack density is always multiplied by crack opening displacement and crack sliding displacement. The dependence of crack opening displacement on geometrical and elastic parameters of adjacent plies was studied previously and described by simple fitting functions. The crack sliding displacement has been analyzed for low-crack densities only and the proposed finite element method-based fitting expressions are oversimplified not including the out-of-plane ply stiffness effects. Based on finite element method analysis, more accurate expressions for so-called non-interactive cracks are suggested in the presented article. For the first time the shear stress perturbations are analyzed and interaction functions are presented with the feature that they always lead to slightly conservative predictions. The presented simple fitting functions, when used in the GLOB-LOC model, give predictions that are in a good agreement with finite element method results and with experimental data for laminates with damaged off-axis plies in cases when crack face sliding is of importance. The significance of including crack sliding displacement in stiffness predictions is demonstrated.

Effective shear modulus of a damaged ply in laminate stiffness analysis: Determination and validation

2019 ◽  
Vol 54 (9) ◽  
pp. 1161-1176
Author(s):  
Mohamed Sahbi Loukil ◽  
Janis Varna
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Shear Modulus ◽  
Crack Density ◽  
Accurate Solution ◽  
Effective Stiffness ◽  
Crack Face ◽  
Plane Shear ◽  
Stiffness Reduction ◽  
Element Method

The concept of the “effective stiffness” for plies in laminates containing intralaminar cracks is revisited presenting rather accurate fitting expressions for the effective stiffness dependence on crack density in the ply. In this article, the effective stiffness at certain crack density is back-calculated from the stiffness difference between the undamaged and damaged laminate. Earlier finite element method analysis of laminates with cracked 90-plies showed that the effective longitudinal modulus and Poisson’s ratio of the ply do not change during cracking, whereas the transverse modulus reduction can be described by a simple crack density dependent function. In this article, focus is on the remaining effective constant: in-plane shear modulus. Finite element method parametric analysis shows that the dependence on crack density is exponential and the fitting function is almost independent of geometrical and elastic parameters of the surrounding plies. The above independence justifies using the effective ply stiffness in expressions of the classical laminate theory to predict the intralaminar cracking caused stiffness reduction in laminates with off-axis plies. Results are in a very good agreement with (a) finite element method calculations; (b) experimental data, and (c) with the GLOB-LOC model, which gives a very accurate solution in cases where the crack face opening and sliding displacements are accurately described.

Uncertainty Characterization of the CrCOD Circumferential Crack Opening Displacement Module for xLPR

2015 ◽  
Author(s):  
Richard Olson ◽  
Paul Scott
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Opening Displacement ◽  
Crack Face ◽  
Pipe Surface ◽  
Circumferential Crack ◽  
The Us ◽  
Experimental Values ◽  
Metal Weld

The US NRC/EPRI xLPR (eXtremely Low Probability of Rupture) probabilistic pipe fracture analysis program uses deterministic modules as the foundation for the calculation of the probability of pipe leak or rupture as a consequence of active degradation mechanisms, vibration or seismic loading. The circumferential crack opening displacement module, CrCOD, estimates crack opening displacement (COD) at the inside pipe surface, at the mid-wall thickness location, and at the outside pipe surface using a combined tension/crack face pressure/bending GE/EPRI-like solution. Each module has an uncertainty beyond the uncertainty of the xLPR data inputs. This paper documents the uncertainty for CrCOD. Using 36 pipe fracture experiments, including: base metal, similar metal weld, and dissimilar metal weld experiments; bend only and pressure and bend loading; static and dynamic load histories; cracks that range from short to long, the uncertainty of the CrCOD methodology is characterized. Module uncertainty is presented in terms mean fit and standard deviation between prediction and experimental values.

Flexibility of Trunnion Piping Elbows

1990 ◽  
Vol 112 (2) ◽  
pp. 184-187 ◽  
Author(s):  
G. D. Lewis ◽  
Y. J. Chao
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Chemical Plants ◽  
The Finite Element Method ◽  
Flexibility Analysis ◽  
Piping Systems ◽  
Out Of Plane ◽  
Element Method

Trunnion piping elbows are commonly used in piping systems in power and chemical plants. The flexibility of the trunnion piping elbows is normally less than that of the plain piping elbows. In this paper, the finite element method is used to derive the in-plane and out-of-plane flexibility factors of trunnion piping elbows. The results can be easily adopted into the piping flexibility analysis.

Regular papers / Articles ordinaires A numerical approach for the static analysis of the body of pressurized dry gas holders

2003 ◽  
Vol 30 (2) ◽  
pp. 381-390
Author(s):  
L H You ◽  
J J Zhang ◽  
H B Wu ◽  
R B Sun
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Plane Deformation ◽  
Numerical Approach ◽  
Gas Pressure ◽  
The Body ◽  
The Finite Element Method ◽  
Out Of Plane ◽  
Plane Bending ◽  
Element Method

In this paper, a numerical method is developed to calculate deformations and stresses of the body of dry gas holders under gas pressure. The deformations of the wall plates are decomposed into out-of-plane bending and in-plane deformation. The out-of-plane bending of the wall plates is described by the theory of orthotropic plates and the in-plane deformation by the biharmonic equation of flat plates under plane stress. The theories of beam columns and beams are employed to analyze the columns and corridors, respectively. By considering compatibility conditions between the members and boundary conditions, equations for the determination of deformations and stresses of dry gas holders under gas pressure are obtained. Both the proposed approach and the finite element method are used to investigate the deformations and stresses of the body of a dry gas holder under gas pressure. The results from the proposed method agree with those from the finite element method. Because far fewer unknowns are involved, the proposed method is computationally more efficient than both the finite element method and the series method developed from the theory of stiffened plates.Key words: numerical approach, body of dry gas holders, gas pressure.

Numerical Computation of the Overall Moduli of Two Dimensional Infinite Media with Cracks

2009 ◽  
Vol 417-418 ◽  
pp. 241-244
Author(s):  
H.P. Yin
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Crack Density ◽  
Crack Size ◽  
Numerical Results ◽  
Two Dimensional ◽  
Opening Displacement ◽  
Consistent Method ◽  
Differential Scheme ◽  
Cracked Solids

The overall elastic moduli of a solid are changed when the solid is damaged by cracks. For a finite solid, the size influence has been investigated and it has been found that for a given crack density, increasing crack size reduce the overall moduli [1]. For an infinite solid, it is obviously impossible to make the computation with all cracks. Classical methods suggest computing the overall moduli with the solution of the crack opening displacement of one single crack. The interaction between cracks is neglected or taken into account approximately. In this paper, the overall moduli of two dimensional infinite solids with cracks are computed numerically. From numerical simulations, it has been found that the interaction between cracks can be neglected if the distance between them is three times larger than the crack size. So one can compute the opening displacement on one crack with the presence of cracks nearby and use the crack opening displacement to compute the overall moduli. The numerical values are smaller than those of the method of diluted distribution but greater than those of the differential scheme and the self consistent method. They are also slight greater than the numerical results of bounded cracked solids. For small values of crack density however, the numerical results of both infinite solids and bounded solids are close to the estimation of the differential scheme.

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