Investigation of Fracture Criterion for HTPB Propellant

2012 ◽  
Vol 591-593 ◽  
pp. 745-749
Author(s):  
Bo Han ◽  
Yu Tao Ju ◽  
Chang Sheng Zhou
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Cohesive Zone ◽  
Fracture Criterion ◽  
Cohesive Zone Model ◽  
Rate Effect ◽  
Zone Model ◽  
J Integral ◽  
Loading Rates ◽  
Htpb Propellant

The fracture toughness of HTPB propellant has a significant rate effect. In order to establish a fracture criterion considering rate effect for HTPB propellant, experiments were conducted at different loading rates. Two kinds of specimens were used to get the fracture properties. Stress intensity factor and J-integral were obtained by the single edge notched tension specimen test. A power law cohesive zone model was obtained by the experiment based inverse method. Through comparing we found that the stress intensity factor and J-integral cannot model the rate effect in fracture process. The cohesive zone model (CZM) has a constant critical separation distance at different loading rates and has a capability to model the rate effect during the crack initiation and propagation process. A finite element simulation in ABAQUS was given to demonstrate its capability to model the crack propagation.

scholarly journals Critical value of the generalized stress intensity factor for a crack perpendicular to an interface

2015 ◽  
Vol 471 (2183) ◽  
pp. 20150571 ◽  
Author(s):  
George G. Adams
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Critical Value ◽  
Zone Model ◽  
Cohesive Stress ◽  
Generalized Stress Intensity Factor

When a crack tip impinges upon a bi-material interface, the order of the stress singularity will be equal to, less than or greater than one-half. The generalized stress intensity factors have already been determined for some such configurations, including when a finite-length crack is perpendicular to the interface. However, for these non-square-root singular stresses, the determination of the conditions for crack growth are not well established. In this investigation, the critical value of the generalized stress intensity factor for tensile loading is related to the work of adhesion by using a cohesive zone model in an asymptotic analysis of the separation near the crack tip. It is found that the critical value of the generalized stress intensity factor depends upon the maximum stress of the cohesive zone model, as well as on the Dundurs parameters ( α and β ). As expected this dependence on the cohesive stress vanishes as the material contrast is reduced, in which case the order of the singularity approaches one-half.

scholarly journals Adhesion and pull-off force of an elastic indenter from an elastic half-space

2014 ◽  
Vol 470 (2169) ◽  
pp. 20140317 ◽  
Author(s):  
George G. Adams
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Half Space ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Elastic Half Space ◽  
Work Of Adhesion ◽  
Zone Model ◽  
Generalized Stress Intensity Factor ◽  
Elastic Punch

The adhesion between an elastic punch and an elastic half-space is investigated for plane and axisymmetric geometries. The pull-off force is determined for a range of material combinations. This configuration is characterized by a generalized stress intensity factor which has an order less than one-half. The critical value of this generalized stress intensity factor is related to the work of adhesion, under tensile loading, by using a cohesive zone model in an asymptotic analysis of the separation near the elastic punch corner. These results are used in conjunction with existing results in the literature for the frictionless contact between an elastic semi-infinite strip and half-space in both plane and axisymmetric configurations. It is found that the value of the pull-off force includes a dependence on the maximum stress of the cohesive zone model. As expected, this dependence vanishes as the punch becomes rigid in that case the order of the singularity approaches one-half. At the other limit, when the half-space becomes rigid, the stresses become bounded and uniform and the pull-off force depends linearly on the cohesive stress and is independent of the work of adhesion. Thus, the transition from fracture-dominated adhesion to strength-dominated adhesion is demonstrated.

scholarly journals The J-integral for mixed-mode loaded cracks with cohesive zones

2020 ◽  
Vol 227 (1) ◽  
pp. 79-94
Author(s):  
Johannes Scheel ◽  
Alexander Schlosser ◽  
Andreas Ricoeur
Keyword(s):  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Constitutive Law ◽  
Zone Model ◽  
J Integral ◽  
Cohesive Law ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

AbstractThe J-integral quantifies the loading of a crack tip, just as the crack tip opening displacement (CTOD) emanating from the cohesive zone model. Both quantities, being based on fundamentally different interpretations of cracks in fracture mechanics of brittle or ductile materials, have been proven to be equivalent in the late 60s of the previous century, however, just for the simple mode-I loading case. The relation of J and CTOD turned out to be uniquely determined by the constitutive law of the cohesive zone in front of the physical crack tip. In this paper, a J-integral vector is derived for a mixed-mode loaded crack based on the cohesive zone approach, accounting for the most general case of a mode-coupled cohesive law. While the $$J_1$$ J 1 -coordinate, as energy release rate of a straight crack extension, is uniquely related to the cohesive potential at the physical crack tip and thus to the CTOD, the $$J_2$$ J 2 -coordinate depends on the solution of the specific boundary value problem in terms of stresses and displacement gradients at the cohesive zone faces. The generalized relation is verified for the Griffith crack, employing solutions of the Dugdale crack based on improved holomorphic functions.

Deformation Behavior and J-Integral of Macroscopic Hydride Platelet Clusters in Hydrided Zr-2.5Nb Pressure Tube Materials Under Plane Strain Conditions

2019 ◽  
Author(s):  
Shengjia Wu ◽  
Jwo Pan ◽  
Douglas A. Scarth ◽  
Sterling St. Lawrence
Keyword(s):  
Mechanical Behavior ◽  
Plane Strain ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Early Stage ◽  
Pressure Tube ◽  
Zone Model ◽  
Fracture Parameter ◽  
J Integral ◽  
Hydride Platelet

Abstract The mechanical behavior and J-integral of macroscopic hydride platelet clusters in hydrided Zr-2.5Nb pressure tube materials are investigated by two-dimensional finite element analyses with cohesive zone model under plane strain conditions. The hydride platelets are assumed to be separated at the early stage of the loading and are treated as cracks. The cohesive zone model with a trapezoidal traction-separation law is adopted. The macroscopic mechanical behavior is quantified by the macroscopic stress-strain relations and the fracture parameter of the bulk radial hydride is specified by the J integral-stress relations. The hydride platelet spacing has major effects while the cohesive energy and cohesive strength have minor effects on the mechanical behavior and fracture properties of the bulk hydrides. The computational results suggest that the hydride platelet cluster can be viewed as a soft region with a reduced load carrying capacity at large stress under plane strain loading conditions. A hydride platelet cluster may be treated as a cracked bulk hydride but with a reduced crack tip driving force for fracture.

Numerical analysis of cracked aluminum plate repaired with multi-scale reinforcement composite patches

2020 ◽  
Vol 54 (28) ◽  
pp. 4341-4357
Author(s):  
A Yousefi ◽  
M Mosavi Mashhadi ◽  
M Safarabadi
Keyword(s):  
Mechanical Properties ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Aluminum Plate ◽  
Zone Model ◽  
Composite Patch ◽  
Different Thickness

In this study, numerical modeling is used to investigate the performance of a single-sided composite patch with different scale fillers, as reinforcement of a cracked aluminum plate under static tension. The main concerns of previous studies are about the geometry of patches, composite layups, and failure of adhesive. In this research, the effect of patch properties such as size and fiber volume fraction, the thickness of patch, and thickness of adhesive on the overall performance of the cracked aluminum plate are investigated numerically. Indeed, first, a 3 D representative volume element (RVE) is adopted to calculate the mechanical properties of carbon nanotube (CNT)/epoxy and carbon fiber (CF)/epoxy composite patch at each specified volume fraction for investigating the effect of patch properties on the performance of a single-sided patch for crack repairing. In this regard, the cohesive zone model is adopted to analyze the debonding between the epoxy matrix and reinforcement to characterize the mechanical properties of composite patches. Finally, a linear 3 D finite element analysis is performed to calculate the stress intensity factor (SIF) for cracked aluminum plate repaired by a single-sided composite patch at each specified reinforcement volume fraction for different thickness of patch and different thickness of adhesive. The results demonstrated that the stress intensity factor highly depends on the patch properties (patch stiffness) in addition to patch thickness and adhesive thickness.

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