CRACK PROPAGATION UNDER INITIAL MODE II CONDITIONS

2020 ◽  
pp. 49-56
Author(s):  
D.V. Fedotova ◽  
◽  
R.M. Khamidullin ◽  
Keyword(s):  
Crack Propagation ◽  
Material Properties ◽  
Crack Path ◽  
Plastic Material ◽  
Compact Tension ◽  
Mode Ii ◽  
Curvilinear Crack ◽  
Inclined Crack ◽  
Kinked Crack ◽  
Elastic Plastic Material

Series of tests for compact tension shear specimens under mode II and following mixed mode was carried out. Compact tension shear specimens made of steels 34X and P2M, Ti-6Al-4V titanium and 7050 aluminum alloys. During experiments the behavior of the inclined crack angles, kinked crack angles and crack propagation angles, as a function of dimensionless crack length for the curvilinear paths was obtained. The influence of elastic-plastic material properties on the form the curvilinear crack path is established.

Structural Integrity Research for Reactor Pressure Vessel Under In-Vessel Retention of a Core Melt

2016 ◽  
Author(s):  
Yongjian Gao ◽  
Yinbiao He ◽  
Ming Cao ◽  
Yuebing Li ◽  
Shiyi Bao ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Material Properties ◽  
Power Plants ◽  
Structural Integrity ◽  
Plastic Material ◽  
Plastic Region ◽  
Reactor Pressure Vessel ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Reactor Pressure

In-Vessel Retention (IVR) is one of the most important severe accident mitigation strategies of the third generation passive Nuclear Power Plants (NPP). It is intended to demonstrate that in the case of a core melt, the structural integrity of the Reactor Pressure Vessel (RPV) is assured such that there is no leakage of radioactive debris from the RPV. This paper studied the IVR issue using Finite Element Analyses (FEA). Firstly, the tension and creep testing for the SA-508 Gr.3 Cl.1 material in the temperature range of 25°C to 1000°C were performed. Secondly, a FEA model of the RPV lower head was built. Based on the assumption of ideally elastic-plastic material properties derived from the tension testing data, limit analyses were performed under both the thermal and the thermal plus pressure loading conditions where the load bearing capacity was investigated by tracking the propagation of plastic region as a function of pressure increment. Finally, the ideal elastic-plastic material properties incorporating the creep effect are developed from the 100hr isochronous stress-strain curves, limit analyses are carried out as the second step above. The allowable pressures at 0 hr and 100 hr are obtained. This research provides an alternative approach for the structural integrity evaluation for RPV under IVR condition.

Hole-Drilling Method for Residual Stress Measurement - Consideration of Elastic-Plastic Material Properties

2013 ◽  
Vol 768-769 ◽  
pp. 174-181 ◽  
Author(s):  
David von Mirbach
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Yield Stress ◽  
Material Properties ◽  
Plastic Material ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Elastic Plastic Material ◽  
Ring Core

Two commonly used mechanical methods for the determination of residual stresses are the hole-drilling method and the ring-core method, which can be regarded as semi-destructive. The most restricting limitation for the general applicability of both methods, according to the current state of science and technology, is the fact that the scope for relatively low residual stress under 60% of the yield stress is limited.This is a result of the notch effect of the hole or ring core, which leads to a plastification around and on the bottom of the hole and ring shaped groove already at stresses well below the yield stress of the material. The elastic evaluation of the resulting plastic strains leads consequently to an overestimation of the delineated residual stresses. In this paper the influence of elastic-plastic material properties no the specific calibration function for the hole-drilling method using the differential method is studied, and the method of adaptive calibration functions is presented.

Fracture Toughness of Northeast China Larch

2012 ◽  
Vol 517 ◽  
pp. 661-668 ◽  
Author(s):  
L.P. Qiu ◽  
En Chun Zhu ◽  
Hua Zhang Zhou ◽  
L.Y. Liu
Keyword(s):  
Numerical Simulation ◽  
Fracture Toughness ◽  
Stress Intensity ◽  
Crack Propagation ◽  
Material Properties ◽  
Northeast China ◽  
Numerical Approach ◽  
Mode I ◽  
Mode Ii ◽  
Full Size

Wood, as a green and environment-friendly building material, is widely used in building engineering. Naturally grown, wood has various defects like knots, cracks and inclined grain. Fracture Mechanics is thus an efficient tool to investigate the mechanical behavior of wood and wood-based composite products. According to Linear-elastic Fracture Mechanics (LEFM), fracture toughness can be introduced to measure the resistance to crack propagation. Crack was assumed to occur when the stress intensity factorKreached a critical valueKC.Fracture in wood usually involves not only the Mode I type (open) fracture, but also the Mode II type (shear) fracture. For getting a better understanding of the crack growth phenomenon of Northeast China Larch, it is, therefore, essential to assess theKICandKIIC, which are the critical stress intensity factors for Mode I and Mode II type fracture, respectively. In the current study,KICandKIIC, of Northeast China Larch were determined through tests with compact tension specimens and tests with compact symmetric shear specimens, respectively. In addition, the material properties tests were also performed. All of the specimens were cut from the same batch of Glulam beams. Based on the obtained data from experiments, LEFM was employed to explain the fracture failure in the form of crack propagation. Using Extended Finite Element Method (XFEM), simulation of the crack propagation in Mode I and Mode II was performed incorporating ABAQUS. The crack propagation and the load-displacement curves of numerical simulation were in good agreement with experiments, which validated that the proposed numerical approach is suitable for analysis of crack growth in the specimens. As part of a larger program to investigate the fracture behavior of Glulam beams made of Northeast China Larch, this study provides the material properties and validation of the numerical simulation approach. A series of experiments of full-size curved Glulam beams subject to bending and the corresponding simulations extending the numerical approach of this study to the cases of full-size wood composite members are under development.

On a Study of the Use of the (T˙) Integral in Fracture Analysis of Solids With Inelastic Rate-Constitutive Laws

1982 ◽  
Vol 104 (4) ◽  
pp. 331-337 ◽  
Author(s):  
M. Nakagaki ◽  
S. N. Atluri
Keyword(s):  
Plastic Material ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Constitutive Law ◽  
Fracture Criteria ◽  
Elastic Plastic ◽  
Infinitesimal Deformations ◽  
History Of ◽  
Elastic Plastic Material ◽  
Radial Loading

Here, the following topics are discussed: (i) a new integral (ΔT1) of relevance in the presence of cracks in an elastic-plastic material characterized by a rate-independent incremental constitutive law under the assumption of infinitesimal deformations, (ii) the conditions for path-independency of this integral, (iii) the physical meaning of (ΔT1) whether or not it is path-independent, (iv) its relation to J under conditions of radial loading when deformation theory of plasticity may be valid. The features of this new parameter (ΔT1) are brought out in a numerical solution of a compact tension specimen which is subject to a history of (displacement-controlled) loading/unloading/reloading. The implications of the present results in the context of more rational elastic-plastic fracture criteria are briefly discussed.

Analysis of the spherical indentation cycle for elastic–perfectly plastic solids

2004 ◽  
Vol 19 (12) ◽  
pp. 3641-3653 ◽  
Author(s):  
L. Kogut ◽  
K. Komvopoulos
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Material Properties ◽  
Deformation Behavior ◽  
Plastic Material ◽  
Elastic Plastic ◽  
Loading And Unloading ◽  
Elastic Plastic Material

A finite element analysis of frictionless indentation of an elastic–plastic half-space by a rigid sphere is presented and the deformation behavior during loading and unloading is examined in terms of the interference and elastic–plastic material properties. The analysis yields dimensionless constitutive relationships for the normal load, contact area, and mean contact pressure during loading for a wide range of material properties and interference ranging from the inception of yielding to the initiation of fully plastic deformation. The boundaries between elastic, elastic–plastic, and fully plastic deformation regimes are determined in terms of the interference, mean contact pressure, and reduced elastic modulus-to-yield strength ratio. Relationships for the hardness and associated interference versus elastic–plastic material properties and truncated contact radius are introduced, and the shape of the plastic zone and maximum equivalent plastic strain are interpreted in light of finite element results. The unloading response is examined to evaluate the validity of basic assumptions in traditional indentation approaches used to measure the hardness and reduced elastic modulus of materials. It is shown that knowledge of the deformation behavior under both loading and unloading conditions is essential for accurate determination of the true hardness and reduced elastic modulus. An iterative approach for determining the reduced elastic modulus, yield strength, and hardness from indentation experiments and finite element solutions is proposed as an alternative to the traditional method.

Shakedown Bounds of Structures Using Linear and Nonlinear Methods

2008 ◽  
Author(s):  
Dan Vlaicu
Keyword(s):  
Material Properties ◽  
Plastic Material ◽  
Nonlinear Material ◽  
Upper And Lower Bounds ◽  
The Finite Element Method ◽  
Periodic Loading ◽  
Elastic Plastic Material ◽  
Compensation Approach ◽  
Elastic Shakedown ◽  
Loaded Structure

For a cyclically loaded structure made of elastic-plastic material it is considered elastic shakedown if plastic straining occurs in the first few cycles and the sequent response is wholly elastic. In this paper the finite element method is used to develop upper and lower bounds limits for the elastic shakedown of structures under periodic loading conditions. Linear methods using elastic compensation approach and the residual stress method derived from Melan’s theorem are used to generate the lower bound limit for the shakedown load while the upper bound is found through a method derived from Koiter’s theorem. Furthermore the results are compared with cycle-by-cycle method based on nonlinear material properties.

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