Modeling of Crack Growth With Dwell Time for Aero-Engine Spectra Loadings in a Ni-Based Superalloy

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Erik Storgärds ◽  
Kjell Simonsson ◽  
Sören Sjöström ◽  
David Gustafsson ◽  
Tomas Månsson
Keyword(s):  
Cyclic Load ◽  
Sustained Load ◽  
Cyclic Loads ◽  
Surface Cracks ◽  
Multiple Tests ◽  
Linear Elastic ◽  
Modeling Concept ◽  
Aero Engine ◽  
Elastic Fracture ◽  
Good Agreement

Testing and simulation of aero-engine spectra with dwell times are reported in this paper. The modeling concept used is built on linear elastic fracture mechanics (LEFM) and provides a history-dependent evolution description of dwell damage and its interaction with cyclic load. The simulations have been carried out for three spectra: (1) cyclic loads, (2) combined sustained load and cyclic loads, and (3) slow load ramps and cyclic loads, all for surface cracks at 550 °C for Inconel 718. All simulations show reasonable good agreement with experimental results. Prediction of multiple tests of several batches is also provided to show statistical scatter.

Modelling of Crack Growth With Dwell Time for Aero Engine Spectra Loadings in a Ni-Based Superalloy

2015 ◽  
Author(s):  
Erik Storgärds ◽  
Kjell Simonsson ◽  
Sören Sjöström ◽  
David Gustafsson ◽  
Tomas Månsson
Keyword(s):  
Crack Growth ◽  
Inconel 718 ◽  
Dwell Time ◽  
Cyclic Load ◽  
Sustained Load ◽  
Cyclic Loads ◽  
Surface Cracks ◽  
Multiple Tests ◽  
Aero Engine ◽  
Good Agreement

Testing and simulation of aero engine spectra with dwell times are reported in this paper. The modelling concept used is built on LEFM and provides a history dependent evolution description of dwell damage and its interaction with cyclic load. The simulations have been carried out for three spectra, 1) cyclic loads, 2) combined sustained load and cyclic loads and 3) slow load ramps and cyclic loads, all for surface cracks at 550°C for Inconel 718. All simulations show reasonable good agreement with experimental results. Prediction of multiple tests of several batches is also provided to show statistical scatter.

Influence of the Interface and Residual Stresses on the Apparent Fracture Toughness of Layered Ceramic Composites Based on Alumina-Zirconia

2014 ◽  
Vol 606 ◽  
pp. 209-212
Author(s):  
Luboš Náhlík ◽  
Bohuslav Máša ◽  
Pavel Hutař
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Ceramic Composites ◽  
Layered Composites ◽  
Material Interfaces ◽  
Linear Elastic ◽  
Apparent Fracture Toughness ◽  
Elastic Fracture ◽  
Layered Ceramic ◽  
Good Agreement

This paper deals with the fracture behaviour of layered ceramic composite with residual stresses. The main goal is to investigate the effect of residual stresses and material interfaces on crack propagation by more complex 3D finite element models. The crack behaviour was described by analytical procedures based on linear elastic fracture mechanics (LEFM) and generalized LEFM. The influence of laminate composition with residual stresses on critical values for crack propagation through the laminate interfaces was also determined. Good agreement has been found to exist between numerical results and experimental data. The results obtained can be used for a design of new layered composites with improved resistance against crack propagation.

Analysis of creep-induced strains and stresses in notches subjected to a cyclic load

2007 ◽  
Vol 42 (5) ◽  
pp. 361-375 ◽  
Author(s):  
J E Nuñez ◽  
G Glinka
Keyword(s):  
Finite Element ◽  
Plane Stress ◽  
External Load ◽  
Cyclic Load ◽  
Time Dependent ◽  
Cyclic Loads ◽  
Creep Response ◽  
Stress Components ◽  
Estimation Of Time ◽  
Good Agreement

A method for the estimation of time-dependent strains and stresses in notches subjected to a cyclic load is discussed in the paper. The proposed solution is an extension of the methodology proposed previously for notches under a steady external load. A new algorithm is proposed to predict the creep response near notches in plane stress components subjected to cyclic loads. Predictions were compared with finite element data, and good agreement was obtained for various geometrical and material configurations.

Estimation of the Crack Behaviour in the Compressive Layer of the Alumina-Zirconia Ceramic Laminate

2014 ◽  
Vol 627 ◽  
pp. 41-44
Author(s):  
Luboš Náhlík ◽  
Bohuslav Máša ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Direct Method ◽  
Zirconia Ceramic ◽  
Finite Element Models ◽  
Linear Elastic ◽  
Dimensional Finite Element ◽  
Density Factor ◽  
Elastic Fracture ◽  
Energy Density Factor ◽  
Good Agreement

This paper deals with a description of the crack behaviour in the layered alumina-zirconia ceramic laminate. The main aim is to investigate the crack behaviour in the compressive layer. The crack propagation was investigated on the basis of linear elastic fracture mechanics. Two dimensional finite element models were developed in order to obtain a stress distribution around the crack tip. The stress intensity factors were computed numerically employing the direct method. The change in the crack propagation direction was estimated using criterion based on the strain energy density factor. Sharp crack deflection in the compressive layer was predicted by mentioned approach. The determined crack behaviour is qualitatively in a good agreement with experimental observations.

scholarly journals Combined Visibility and Surrounding Triangles Method for Simulation of Crack Discontinuities in Meshless Methods

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
H. Pirali ◽  
F. Djavanroodi ◽  
M. Haghpanahi
Keyword(s):  
Diffraction Method ◽  
Meshless Methods ◽  
Standard Test ◽  
The Finite Element Method ◽  
Linear Elastic ◽  
Element Free Galerkin ◽  
Elastic Fracture ◽  
Element Free ◽  
Crack Faces ◽  
Good Agreement

In this paper a combined node searching algorithm for simulation of crack discontinuities in meshless methods called combined visibility and surrounding triangles (CVT) is proposed. The element free Galerkin (EFG) method is employed for stress analysis of cracked bodies. The proposed node searching algorithm is based on the combination of surrounding triangles and visibility methods; the surrounding triangles method is used for support domains of nodes and quadrature points generated at the vicinity of crack faces and the visibility method is used for points located on the crack faces. In comparison with the conventional methods, such as the visibility, the transparency, and the diffraction method, this method is simpler with reasonable efficiency. To show the performance of this method, linear elastic fracture mechanics analyses are performed on number of standard test specimens and stress intensity factors are calculated. It is shown that the results are in good agreement with the exact solution and with those generated by the finite element method (FEM).

An Analysis of the Fatigue Strength of Metals Containing Small Defects

2007 ◽  
Vol 353-358 ◽  
pp. 323-326 ◽  
Author(s):  
Masahiro Endo ◽  
A.J. McEvily
Keyword(s):  
Fatigue Limit ◽  
Threshold Level ◽  
Plastic Behavior ◽  
Al Alloy ◽  
Threshold Condition ◽  
Rational Basis ◽  
Linear Elastic ◽  
Small Cracks ◽  
Elastic Fracture ◽  
Good Agreement

A modified linear-elastic fracture mechanics approach proposed by McEvily has been applied to predict the effects of small defects on the fatigue limit and the threshold level. In the analysis, three modifications were taken into account (1) the effect of elastic-plastic behavior of small cracks, (2) the Kitagawa effect where in the very small crack regime the required stress for propagation is controlled by the fatigue limit of a smooth specimen rather than by the long-crack threshold condition, and (3) the effect of crack closure development from zero up to the macroscopic level as a newly formed crack extends. Three steels, a brass and an Al alloy were investigated. Good agreement between predicted and experimental results has been obtained and a rational basis for the area parameter model was shown.

scholarly journals Stress intensity factors for multiple cracks in thick-walled cylinder

2015 ◽  
Vol 3 (2) ◽  
pp. 207
Author(s):  
Krunal G. Girase ◽  
Navneet K. Patil ◽  
Dinesh Shinde ◽  
Kanak Kalita
Keyword(s):  
Stress Intensity ◽  
Crack Size ◽  
Diameter Ratio ◽  
Multiple Cracks ◽  
Intensity Factors ◽  
Structural Geometry ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Walled Cylinder ◽  
Good Agreement

<p>The stress intensity factor (SIF) is the linear elastic fracture mechanics parameter that relates remote load, crack size and structural geometry. It predicts very accurately the stress state. In this work, cylinders with multiple cracks are considered. The following parameters are varied during the analysis of the cylinders: the number of cracks, (the variation in number of cracks ultimately led to a variation in the inter-crack spacing), the crack length to cylinder thickness ratio (a/t), the diameter ratio of the cylinders. Very good agreement between the finite element stresses and the theoretical stresses is seen.</p>

scholarly journals Elastic Fracture Toughness for Ductile Metal Pipes with Circumferential Surface Cracks

2017 ◽  
Vol 730 ◽  
pp. 489-495 ◽  
Author(s):  
Chun Qing Li ◽  
Guo Yang Fu ◽  
Shang Tong Yang
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Linear Elastic Fracture Mechanics ◽  
Surface Cracks ◽  
Steel Pipes ◽  
Ductile Metal ◽  
Linear Elastic ◽  
Fracture Failure ◽  
Metal Pipes ◽  
Elastic Fracture

Surface cracks have long been recognized as a major cause for potential failures of metal pipes. In fracture analysis, the widely used method is based on linear elastic fracture mechanics. However, for ductile metal pipes, it has been known that the existence of plasticity results in easing of stress concentration at the crack front. This will ultimately increase the total fracture toughness. Therefore, when using linear elastic fracture mechanics to predict fracture failure of ductile metal pipes, the plastic portion of fracture toughness should be excluded. Otherwise, the value of fracture toughness will be overestimated, resulting in an under-estimated probability of failure. This paper intends to derive a model of elastic fracture toughness for steel pipes with a circumferential crack. The derived elastic fracture toughness is a function of crack geometry and material properties of the cracked pipe. The significance of the derived model is that the well-established linear elastic fracture mechanics can be used for ductile materials in predicting the fracture failure.

Flaw Proximity Rules for Parallel Surface Cracks Based on Elastic, Elastic-Plastic Fracture Mechanics and Limit Load Analyses

2006 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Structural Reliability ◽  
Limit Load ◽  
Crack Size ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Offset Distance ◽  
Bending Load ◽  
Elastic Fracture

When multiple cracks approach one another, the stress intensity factor, J integral value of cracks and limit load of cracked component are likely to change due to the interaction of the stress field. Since the changes in these parameters are not always conservative in structural reliability evaluations, the interaction between multiple cracks must be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code provides a flaw characterization rule for interacting multiple cracks. In Sec. XI, adjacent cracks are replaced by a coalesced single combined crack if they are located within the distance of half depth of deeper crack. However, the criterion for offset distance is given by an absolute value, although magnitude of the interaction is inevitably dependent on the crack size. In current study, an alternative criterion for the offset distance is examined. The linear-elastic fracture, elastic-plastic fracture and limit load analyses are performed for interacting semi-circular and semi-elliptical surface cracks by using the finite element method under a tensile and bending load. Based on the relationship between fracture strength and relative position of the two cracks, the allowable condition for the offset distance is discussed.

Fracture-mechanics-based analytical prediction of remaining life of tubular T- and Y-joints

2005 ◽  
Vol 219 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A R C Murthy ◽  
G S Palani ◽  
N R Iyer
Keyword(s):  
Fracture Mechanics ◽  
Life Prediction ◽  
Analytical Prediction ◽  
Remaining Life ◽  
Constant Amplitude ◽  
Linear Elastic ◽  
Tubular Joints ◽  
Elastic Fracture ◽  
Experimental Values ◽  
Good Agreement

This paper presents methodologies for analytical prediction of remaining life of tubular T- and Y-joints by using linear elastic fracture mechanics principles. Bowness and Lee proposed expressions for the computation of the stress intensity factor (SIF) for T-butt plates which can be used for SIF computation of tubular joints and which are also recommended in BS 7910. It is observed from the literature that these expressions have not been used for the remaining life prediction of tubular joints. In this paper, these expressions have been used for analytical prediction of remaining life of tubular T- and Y-joints under constant amplitude loading. The predicted remaining life for T- and Y-joints is found to be in good agreement with those of experimental values reported in the literature. The effect of the degree of bending (DoB) on remaining life has been studied. It is observed from the studies that, the higher the DoB, the longer is the remaining life.

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