Visualization of Tensile Stress Induced Material Response at a Crack Tip in Polymers under Critical Load by NMR Imaging

2000 ◽  
Vol 33 (13) ◽  
pp. 4836-4841 ◽  
Author(s):  
P. Adriaensens ◽  
L. Storme ◽  
R. Carleer ◽  
D. Vanderzande ◽  
J. Gelan ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Critical Load ◽  
Crack Tip ◽  
Nmr Imaging ◽  
Material Response

scholarly journals Fracture Mechanical Analysis of Thin-Walled Cylindrical Shells with Cracks

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 592
Author(s):  
Feng Yue ◽  
Ziyan Wu
Keyword(s):  
Fracture Mechanics ◽  
Tensile Stress ◽  
Failure Modes ◽  
Cylindrical Shells ◽  
Crack Tip ◽  
Mechanical Analysis ◽  
J Integral ◽  
Thin Walled Structures ◽  
Circumferential Tensile Stress ◽  
Thin Walled

The fracture mechanical behaviour of thin-walled structures with cracks is highly significant for structural strength design, safety and reliability analysis, and defect evaluation. In this study, the effects of various factors on the fracture parameters, crack initiation angles and plastic zones of thin-walled cylindrical shells with cracks are investigated. First, based on the J-integral and displacement extrapolation methods, the stress intensity factors of thin-walled cylindrical shells with circumferential cracks and compound cracks are studied using linear elastic fracture mechanics, respectively. Second, based on the theory of maximum circumferential tensile stress of compound cracks, the number of singular elements at a crack tip is varied to determine the node of the element corresponding to the maximum circumferential tensile stress, and the initiation angle for a compound crack is predicted. Third, based on the J-integral theory, the size of the plastic zone and J-integral of a thin-walled cylindrical shell with a circumferential crack are analysed, using elastic-plastic fracture mechanics. The results show that the stress in front of a crack tip does not increase after reaching the yield strength and enters the stage of plastic development, and the predicted initiation angle of an oblique crack mainly depends on its original inclination angle. The conclusions have theoretical and engineering significance for the selection of the fracture criteria and determination of the failure modes of thin-walled structures with cracks.

Features Testing of Stud Material Under Low Constraint Ductile Tearing

2017 ◽  
Author(s):  
P. James ◽  
M. Jackson ◽  
P. Birkett ◽  
C. Madew
Keyword(s):  
Structural Integrity ◽  
High Stress ◽  
Crack Tip ◽  
Pressure Vessels ◽  
Materials Testing ◽  
Screw Thread ◽  
Surface Point ◽  
Defect Tolerance ◽  
Material Response ◽  
Crack Tip Constraint

Defect tolerance assessments are carried out to support the demonstration of structural integrity for high integrity components such as nuclear reactor pressure vessels. These assessments often consider surface-breaking defects and assess Stress Intensity Factors (SIFs) at both the surface and deepest points. This can be problematic when there is a high stress at the surface, for example due to the stress concentration at the root of a screw thread. In the past this has led to the development of complex and costly 3D finite element analyses to calculate more accurate SIFs, and still resulting in small apparent limiting defect sizes based on initiation at the surface point. Analysis has been carried out along with supporting materials testing, to demonstrate that the increased SIF at the surface point is offset by a reduction in crack-tip constraint, such that the material exhibits a higher apparent fracture toughness. This enables a more simplistic assessment which reduces the effective SIF at the surface such that only the SIF at the deepest point needs to be considered. This then leads to larger calculated limiting defect sizes. This in turn leads to a more robust demonstration of structural integrity, as the limiting defect sizes are consistent with the capability of non-destructive examination techniques. The high SIF at the surface location, and the concomitant reduction in crack-tip constraint, meant that it was not possible to demonstrate the material response with conventional tests, such as those using shallow-notched bend specimens. Instead it was necessary to develop modified specimens in which semielliptical defects were introduced into a geometry which replicated the notch acuity at the root of a screw thread. These feature tests were used to demonstrate the principle, prior to testing with more conventional specimens to fit more accurately the parameters required to represent the material response in a defect tolerance assessment. Margins in defect tolerance assessments are usually measured against the initiation of tearing, even though the final failure for the material may occur at a higher load following stable crack extension. This work measured and assessed the benefit of reduced crack-tip constraint on both the point of initiation and on the development of the tearing resistance curve. This demonstrated that the effect of constraint was valid with tearing for this material and that there was additional margin available beyond the onset of tearing. The feature test geometry also provided evidence of the tearing behaviour at the surface and deepest points of a surrogate component under representative loading. This paper provides an overview of the range of tests performed and the post-test interpretation performed in order to provide the R6 α and k constraint parameters.

NMR Imaging Study of Stress-Induced Material Response in Rubber Modified Polyamide 6

2002 ◽  
Vol 35 (1) ◽  
pp. 135-140 ◽  
Author(s):  
P. Adriaensens ◽  
L. Storme ◽  
R. Carleer ◽  
J. D'Hae ◽  
J. Gelan ◽  
...  
Keyword(s):  
Imaging Study ◽  
Polyamide 6 ◽  
Nmr Imaging ◽  
Material Response

Governing factors of the local tensile stress in the vicinity of a rapidly propagating crack tip in elastic-viscoplastic solids

2019 ◽  
Vol 218 ◽  
pp. 106548 ◽  
Author(s):  
Fuminori Yanagimoto ◽  
Kazuki Shibanuma ◽  
Toshiyuki Matsumoto ◽  
Katsuyuki Suzuki
Keyword(s):  
Tensile Stress ◽  
Crack Tip ◽  
Propagating Crack ◽  
Viscoplastic Solids

Stress Distribution Characteristics of Runway Pavement under New Generation Large Aircrafts

2013 ◽  
Vol 811 ◽  
pp. 218-222
Author(s):  
Li’an Zhang ◽  
Lei Zhang ◽  
Cao Shi ◽  
Shun Xin Yang
Keyword(s):  
Sensitivity Analysis ◽  
Stress Distribution ◽  
Tensile Stress ◽  
Critical Load ◽  
Contact Pressure ◽  
Pavement Design ◽  
Distribution Characteristics ◽  
Parameter Sensitivity Analysis ◽  
New Generation ◽  
High Contact Pressure

New Generation Large Aircrafts became a new member of China large airports. However, its heavy weight and high contact pressure would have great impact on the flexible runway pavement. in this paper, based on the multilayered elastic theory, the tensile stress distribution under different airplane was studied to obtain the critical load positions. Furthermore, parameter sensitivity analysis was conducted, including thickness and modulus of Asphalt Stabilized Base (ATB) layer. Results indicated that increasing ATB thickness can only decrease the tensile stress a little, and increasing the modulus of the ATB layer will be more efficient than increasing its thickness. Finally pavement design suggestions composing of both the structural and material considerations were proposed.

Brittle-Ductile Transition in Heterogeneous Metallic Materials [PowerPoint Submission]

2006 ◽  
Vol 978 ◽  
Author(s):  
Silvester John Noronha ◽  
Nasr M Ghoniem
Keyword(s):  
Fracture Toughness ◽  
Tensile Stress ◽  
Size Distribution ◽  
Crack Tip ◽  
Transition Curve ◽  
Crack Plane ◽  
Metallic Materials ◽  
Brittle Ductile Transition ◽  
Discrete Dislocation ◽  
The Matrix

AbstractWe present a model for the brittle - ductile transition in heterogenous metallic materials based on two dimensional discrete dislocation simulations of crack-tip plasticity. The sum of elastic fields of the crack and the emitted dislocations defines an elasto-plastic crack field. Effects of crack-tip blunting of the macrocrack are included in the simulations. The plastic zone characteristics are found to be in agreement with continuum models, with the added advantage that the hardening behavior comes out naturally in our model. The present model is composed of a macrocrack with microcracks ahead of its tip. These microcracks represent potential fracture sites at internal inhomogenities, such as brittle precipitates. Dislocations that are emitted from the crack-tip account for plasticity. When the tensile stress at the microcrack situated along the crack plane attains a critical value over a distance fracture is assumed to take place. The brittle-ductile transition curve is obtained by determining the fracture toughness at various temperatures. Factors that contribute to the sharp upturn in fracture toughness with temperature are found to be: the decrease in tensile stress ahead of the crack tip due to increase in blunting, and the increase in dislocation mobility. The inherent scatter in fracture toughness measurements are studied by using a size distribution for microcracks, distributed on the crack plane of the macrocrack. The scatter in fracture toughness measurements is found to be an effect of the size distribution of microcracks rather than their spatial distribution on the matrix ahead of the crack plane. When compared, the obtained results are in agreement with the existing experimental data.

Simulative Study of Evolution Behavior of Transverse Surface Crack in Rolling Process

2011 ◽  
Vol 403-408 ◽  
pp. 88-92
Author(s):  
Ya Gao ◽  
Jian Lin Sun ◽  
Bing Yun
Keyword(s):  
Tensile Stress ◽  
Surface Crack ◽  
Rolling Direction ◽  
Crack Tip ◽  
Element Model ◽  
Rolling Process ◽  
Friction Coefficients ◽  
High Crack ◽  
Explicit Finite Difference ◽  
Evolution Behavior

Based on explicit finite difference algorithm, finite element model of steel plate with transverse surface crack in rough rolling was found. The evolution regularity of transverse surface crack in rolling process was calculated with the model, and effect of different crack sizes, different friction coefficients and different roll diameters on crack evolution were studied. The research indicated that, in rolling direction, the crack tip stress changed from tensile stress to compression stress and then tensile stress again; length and depth of crack both had effect on the healing and propagation of the crack, and mostly in the way of influencing displacement of freedom surface of the crack; different friction coefficients showed no effect on crack tip propagation, but low friction coefficient would be in favor of crack healing at crack bottom; small roll diameter would lead to high crack tip tensile stress and more propagation at crack tip.

Diffusive Crack Growth at a Bimaterial Interface

1996 ◽  
Vol 63 (3) ◽  
pp. 796-803 ◽  
Author(s):  
Tze-jer Chuang ◽  
June-Liang Chu ◽  
Sanboh Lee
Keyword(s):  
Tensile Stress ◽  
Crack Growth ◽  
Crack Tip ◽  
Ceramic Composites ◽  
Bimaterial Interface ◽  
Self Diffusion ◽  
Interfacial Sliding ◽  
Stress Solution ◽  
Microcrack Growth ◽  
Loading Parameter

The high temperature microcrack growth behavior along a planar interface between two elastic dissimilar media is investigated with an aim at estimating service life of advanced ceramic composites under creep-rupture conditions. The crack is assumed to grow along the interface normal to a remote applied tensile stress via a coupled surface and grain-boundary diffusion under steady-state creep conditions. The crack-tip conditions were first derived from the asymmetric tip morphology developed by surface self-diffusion. The governing integro-differential equation containing the unknown tensile stress distribution along the interface ahead of the moving crack tip was derived and it was found that a new length parameter exists as a scaling factor for the interface for which the solution becomes identical to that of the single-phase media when plotted on the nondimensional physical plane. In contrast to the elastic stress solution which shows singularity at the tip and oscillatory character away from the tip, the creep stresses have a peak value away from the tip due to a wedging effect and interfacial sliding eliminates stress oscillation resulting in a decoupling between mode I and mode II stress fields. This stress solution ties the far-field loading parameter to the crack-tip conditions in terms of the unknown crack velocity to give a specific V-K functional relationship. It was shown that a stress exponent of 12 in the conventional power-law crack growth emerges at higher applied stress levels. An analysis on energy balance shows that the energy release during crack growth amounts to the J-integral which derives mostly from work done by “wedging,” not from strain energy loss. A constraint on interfacial diffusivities of the two species was found and its implications on possible microstructural developments were discussed.

New crack generation phenomena by crack collision in 10 mm thick tempered glass

2021 ◽  
pp. 1-13
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Tensile Stress ◽  
Crack Propagation ◽  
High Speed ◽  
Crack Tip ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Crack Generation ◽  
Caustics Method ◽  
Thick Glass ◽  
Collision Angle

High speed photography by Caustics method using Cranz–Schardin camera was used to study crack propagation and divergence in thermally tempered glass. Tempered 10 mm thick glass plates were used as a specimen. New crack generation by two crack collision was observed. Regarding the presence/absence of new cracks, the dependence of the two cracks on the collision angle was confirmed. Considering that it is based on the synthesis of stress 𝜎CR generated at the crack tip, tensile stress necessary for the generation of new cracks could be created.

Sign in / Sign up

Export Citation Format

Share Document