Crack Propagation Prediction Using Haensel Damage Model

2012 ◽  
Author(s):  
Piotr Bednarz ◽  
Jaroslaw Szwedowicz
Keyword(s):  
Cyclic Loading ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Damage Model ◽  
Lifetime Prediction ◽  
Dissipated Energy ◽  
Mathematical Approach ◽  
Loading Conditions ◽  
Stored Energy ◽  
Tensile Stresses

The Haensel damage model correlates lifetime of a component until crack initiation to the dissipated and stored energy in the material during cyclic loading. The crack initiation is influenced by mean stresses. The Haensel damage model considers the mean stress effect by including compressive and tensile stresses in calculations of elastic strain energy during cyclic loading conditions. The goal of the paper is to extend the above model to predict crack propagation under large cyclic plasticity and non-proportional loading conditions. After voids initiation onset of necking, voids growth and linking takes place among them. During this process a mesocrack is created. This stage of fracture involves the same amount of released energy for new crack surface creation as dissipated energy for mesocrack initiation. The amount of dissipated and stored energy is related to the process zone size and to the number of cycles. Ilyushin’s postulate is used to calculate the amount of dissipated energy. In order to consider a contribution of tensile stresses only during loading to crack propagation, tensile/compressive split is performed for the stress tensor. One of the key drivers of this paper is to provide a straightforward engineering approach, which does not require explicit modelling of cracks. The proposed mathematical approach accounts for redistribution of stresses, strains and energy during crack propagation. This allows to approximate the observed effect of distribution of dissipated energy on the front of a crack tip. The developed approach is validated through FE (Finite Element) simulations of the Dowling and Begley experiment. The Haensel lifetime prediction of Dowling’s experiment is in good agreement with the experimental data and the explicit FE results. Finally, the proposed mathematical approach simplifies significantly the engineering effort for Nonlinear Fracture Mechanics lifetime prediction by avoiding the requirement to simulate real crack propagation using node base release methods, XFEM or remeshing procedures.

scholarly journals Experimental and Numerical Study of Fracture Behavior of Rock-Like Material Specimens with Single Pre-Set Joint under Dynamic Loading

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2690
Author(s):  
Bo Pan ◽  
Xuguang Wang ◽  
Zhenyang Xu ◽  
Lianjun Guo ◽  
Xuesong Wang
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Joint Angle ◽  
Simulation Software ◽  
Dissipated Energy ◽  
Energy Structure ◽  
Joint Angles ◽  
Crack Penetration ◽  
Before And After ◽  
The Impact

The Split Hopkinson Pressure Bar (SHPB) is an apparatus for testing the dynamic stress-strain response of the cement mortar specimen with pre-set joints at different angles to explore the influence of joint attitudes of underground rock engineering on the failure characteristics of rock mass structure. The nuclear magnetic resonance (NMR) has also been used to measure the pore distribution and internal cracks of the specimen before and after the testing. In combination with numerical analysis, the paper systematically discusses the influence of joint angles on the failure mode of rock-like materials from three aspects of energy dissipation, microscopic damage, and stress field characteristics. The result indicates that the impact energy structure of the SHPB is greatly affected by the pre-set joint angle of the specimen. With the joint angle increasing, the proportion of reflected energy moves in fluctuation, while the ratio of transmitted energy to dissipated energy varies from one to the other. NMR analysis reveals the structural variation of the pores in those cement specimens before and after the impact. Crack propagation direction is correlated with pre-set joint angles of the specimens. With the increase of the pre-set joint angles, the crack initiation angle decreases gradually. When the joint angles are around 30°–75°, the specimens develop obvious cracks. The crushing process of the specimens is simulated by LS-DYNA software. It is concluded that the stresses at the crack initiation time are concentrated between 20 and 40 MPa. The instantaneous stress curve first increases and then decreases with crack propagation, peaking at different times under various joint angles; but most of them occur when the crack penetration ratio reaches 80–90%. With the increment of joint angles in specimens through the simulation software, the changing trend of peak stress is consistent with the test results.

Crack initiation and crack propagation under thermal cyclic loading

1990 ◽  
Vol 8 (2) ◽  
pp. 98-104 ◽  
Author(s):  
K. Bethge ◽  
D. Munz ◽  
J. Neumann
Keyword(s):  
Cyclic Loading ◽  
Crack Initiation ◽  
Crack Propagation

Crack propagation in ceramic materials under cyclic loading conditions

1975 ◽  
Vol 6 (11) ◽  
pp. 2161-2163 ◽  
Author(s):  
Y. W. Mai ◽  
A. G. Atkins
Keyword(s):  
Cyclic Loading ◽  
Crack Propagation ◽  
Ceramic Materials ◽  
Loading Conditions

Numerical Investigations of Phenomena Caused by the Closure and Growth Behavior of Short Cracks Under Thermal Cyclic Loading

2010 ◽  
Author(s):  
Ju¨rgen Rudolph ◽  
Kai Bauerbach ◽  
Michael Vormwald
Keyword(s):  
Cyclic Loading ◽  
Crack Propagation ◽  
Crack Closure ◽  
Thermal Loading ◽  
Hysteresis Loops ◽  
Local Stress ◽  
Damage Parameter ◽  
Loading Conditions ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

Thermal cyclic loading conditions of nuclear power plant components cause local stress-strain hystereses which are considered to be fatigue relevant events. The contributions of the hysteresis-loops to the fatigue process are evaluated using a damage parameter based on the effective cyclic J-integral which also includes the effects of crack closure. The successful application of such a short crack propagation approach essentially depends on the realistic description of the crack closure. In this context a finite element based algorithm is presented to simulate the opening and closure effects under special consideration of thermal cyclic loading conditions. The concept is based on node release and contact mechanisms. The implications of the crack propagation on the temperature at the crack tip are to be considered. In this context, the consequences of the altered temperature profile as the crack propagates have to be taken into account. It is the aim to formulate Newman-type analytical equations in order to incorporate the influence of crack closure into an engineering approach. Furthermore, the peculiarities of transient thermal loading on the crack propagation behavior are considered. The reduced crack propagation rates due to the temperature gradient in the direction of the wall are investigated numerically in order to describe the reduction of the damage contribution and decelerated crack propagation rates. The effects of changing thermal conditions in the wall on the crack propagation behavior are considered within the numerical algorithm.

Fatigue Crack Growth of Notched Tubular Specimen under Biaxial Loading Conditions

2006 ◽  
Vol 306-308 ◽  
pp. 139-144
Author(s):  
Hyun Woo Lee ◽  
Se-Jong Oh
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Biaxial Loading ◽  
Fatigue Crack Initiation ◽  
Growth Direction ◽  
Crack Growth Behavior ◽  
Loading Conditions ◽  
Tubular Specimen

Crack growth behavior of S45C notched tubular specimen was studied to predict fatigue crack initiation and crack propagation under biaxial loading conditions. Stress-strain field near the hole was analyzed by ANSYS. The crack initiation lives and the crack initiation locations were predicted from strain based theories, and the analysis results were compared with the test results. Crack propagation behaviors were studied to understand the reason of crack branching and crack growth rates changing under biaxial loading conditions. Crack growth direction was also observed to find the governing factors of the fatigue damage under biaxial loading conditions.

Reduced-thickness CVN testing to represent slant failure of pipelines

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Philippe Thibaux ◽  
Patrick Goes
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Propagation Speed ◽  
High Strength ◽  
Dissipated Energy ◽  
Specimen Thickness ◽  
Absorbed Energy ◽  
Element Analysis ◽  
The Difference ◽  
Energy Dissipated

To avoid longitudinal ductile crack propagation along a gas pipeline, the Batelle Two Curve method is used during pipeline design. This method states that a running crack will be arrested if the gas decompression velocity exceeds the crack propagation speed at the internal gas pressure. The crack propagation curve is scaled by impact energy values obtained through Charpy V-Notch (CVN) testing. However, for high-strength steel grades this scaling leads to unconservative predictions, because the experiment does not sufficiently represent the pipeline failure mode. The CVN specimen exhibits mainly mode I failure, without significant shear lips, while real failure is a combined mode often described as slant failure. In the present study, instrumented CVN tests are carried out on samples with different thickness reduction levels. To get a better insight in the crack initiation and propagation behaviour, the CVN test is simulated by finite element analysis. The dissipated energy and resulting fracture surfaces can be successfully represented. It is observed that slant failure is promoted by reducing the specimen thickness. In addition, the specific absorbed energy is decreased. However, most of the difference of absorbed energy is in crack initiation. This means that the fraction of the total energy dissipated in crack propagation is increased for reduced thickness specimens, making it a possible tool to assess the resistance of a material to crack propagation, provided that brittle fracture is avoided.

Computational Analysis of Fatigue Crack Propagation at Elevated Temperature for IN718

2011 ◽  
Vol 110-116 ◽  
pp. 29-32
Author(s):  
Guo Bin Zhang ◽  
Huang Yuan
Keyword(s):  
Fatigue Crack ◽  
Elevated Temperature ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Damage Model ◽  
Complex Loading ◽  
Creep Damage ◽  
Loading Conditions ◽  
Creep Fatigue ◽  
Creep Damage Model

Creep damage is an important failure factor of high-temperature alloy. The fatigue crack growth under elevated temperature of the material is investigated for life prediction. In this paper, the numerical simulation of the crack propagation in nickel-based super alloy, IN718, was presented. A modified creep damage model was employed to accumulate the creep damage under cyclic loading conditions. The numerical results exhibit a reasonable agreement in the comparison with the experimental data. The cohesive zone approach, combining with the extended finite element method, has the ability to simulate the creep-fatigue crack propagation even for more complex loading conditions and specimen geometries.

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