New method of lifetime prediction for brittle fracture of polyethylene

Chudnovsky, A.; Shulkin, Y.; Baron, D.; Lin, Kaiming

doi:10.1002/app.1995.070561108

Cited by 28 publications

(4 citation statements)

References 15 publications

(9 reference statements)

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“…As the crack tip velocity becomes finite, the singularity disappears, the driving force vanishes, and the crack stops its propagation, waiting until the driving force becomes critical again due to the loading process. This qualitative feature agrees well with numerous experimental evidences of nonmonotonic crack propagation with intermediate crack arrests in polymers [1]. Thus, the subclass of soft materials with n < 1 exhibits the quasistatic regime of crack propagation.…”

supporting

confidence: 78%

“…The paper is motivated by an experimental observation [1], according to which cracks propagate in polymers in a discontinuous manner under both constant and cyclic loadings. Since crack propagation or crack arrest is caused mainly by the driving force acting on the crack tip [2][3][4], it is interesting to study the latter within nonlinear elasticity.…”

Section: Introductionmentioning

confidence: 99%

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Driving force acting on a running crack

2002

Proc. Appl. Math. Mech.

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The asymptotic analysis of the dynamic crack problem for the anti-plane shear mode is provided. The field near the crack tip is studied in detail for a nonlinear elastic incompressible material whose stored energy behaves asymptotically as a power of the first invariant of the strain tensor at large strains. It is shown that the hardening parameter characterizes fully the singularity degree of the near-crack-tip field. Based on the latter knowledge the driving force acting on the crack tip is calculated. Possible scenarios of the crack propagation are discussed.

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supporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Driving force acting on a running crack

2002

Proc. Appl. Math. Mech.

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“…The crack propagation is commensurate with the formation and growth of a process zone surrounding the crack [57][58][59][60][61]. The process zone in front of a crack is considered to be a zone of allotropically transformed material: the deformation process thins the sample in the area of the crack tip and the thinning zone at different stages can be observed in Figure 4.…”

Section: Tom Resultsmentioning

confidence: 99%

Analysis of the Damage Mechanism around the Crack Tip for Two Rubber-Toughened PLA-Based Blends

et al. 2021

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The toughening mechanisms of poly(lactic acid; PLA) blended with two different elastomers, namely poly (butylene adipate-co-terephtalate; PBAT) and polyolefin elastomers with grafted glycidyl methacrylate (POE-g-GMA), at 10 and 20 wt.%, were investigated. Tensile and Charpy impact tests showed a general improvement in the performance of the PLA. The morphology of the dispersed phases showed that PBAT is in the form of spheres while POE-g-GMA has a dual sphere/fibre morphology. To correlate the micromechanical deformation mechanism with the macroscopical mechanical behaviour, the analysis of the subcritical crack tip damaged zone of double-notched specimens subjected to a four-point bending test (according to the single-edge double-notch four-point bend (SEDN-4PB) technique) was carried out using several microscopic techniques (SEM, polarized TOM and TEM). The damage was mainly generated by shear yielding deformation although voids associated with dilatational bands were observed.

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“…[8,12] More information could be gained, if the distribution of process zone size through the whole thickness of the specimen were known. The results of such investigations on PE100-1 are shown in Figure 3 and Figure 4.…”

Section: Fcg Kineticsmentioning

confidence: 99%

Fatigue Crack Growth and Process Zone Development in a PE‐HD Pipe Grade in Through‐Thickness Direction

Balika¹,

Pinter²,

Lang³

2006

Adv Eng Mater

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Improvements in the polymerisation process of polyethylene (PE) over the last two decades have led to commercial PE materials (PE 80, PE 100), which continuously gain importance as pipe materials in gas and water supply systems. It is generally acknowledged that the resistance of thermoplastics pipes against quasi-brittle failure determines their long-term performance. This failure phenomenon consisting of crack initiation and crack propagation can be realized in principle under laboratory conditions by various mechanical approaches. Despite the basic difference in loading conditions, some research groups favour fatigue test approaches in evaluating new pipe grades and in evaluating the long-term performance under constant amplitude loading conditions for the following reasons: Firstly, fatigue loading principally leads to accelerated crack growth; secondly, similar characteristics have been found in creep crack growth and fatigue crack growth (FCG) in various PE materials. [1±5] Many fatigue investigations on PE, based on cyclical pressurized pipe tests [2,6,7] and fracture mechanics methods [4,8±10] have shown that FCG in PE occurs either by a quasi-continuous mechanism or by a discontinuous (stepwise) mechanism. As different work groups have shown, [10,11] the crack growth mode depends on various test parameters such as the R-ratio (minimum to maximum load), test temperature and the stress level.The objectives of the research reported here were (1) to characterize the fatigue crack growth behaviour of a high density polyethylene (PE-HD) pipe grade using a method based on a linear elastic fracture mechanics (LEFM) approach and (2) to examine the development of the crack front and the front of the process zone ahead of the crack in the thickness direction of the specimen during the fatigue tests. In contrast to other research reports in the literature, [10±14] the novelty of this work was the determination of a very dense array of data points in the through-thickness direction. The effects of the stress intensity factor and frequency were investigated systematically. The experimental data were determined in order to calculate the effective crack length based on compliance relationships. Results and Discussion FCG KineticsA typical fracture surface of a specimen tested at 5 Hz is shown in Figure 1. Striations on the fracture surface document the stepwise crack growth mechanism. The fracture surface is characterised by the typical attributes of craze formation and breakdown (voids and fibrils). No clear differences in the details of fracture surfaces could be found as a result of the variation of frequency.When examining the FCG data in Figure 2, where FCG rates, da/dN, are shown as function of the stress intensity factor range, DK I , it becomes apparent that with increasing test frequency there is a noticeable increase in crack growth resistance in the low crack-growth regime. At higher crackgrowth rates, the curves coincide. This frequency sensitivity of FCG in polymers can be explained in terms of the eff...

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New method of lifetime prediction for brittle fracture of polyethylene

Cited by 28 publications

References 15 publications

Driving force acting on a running crack

Driving force acting on a running crack

Analysis of the Damage Mechanism around the Crack Tip for Two Rubber-Toughened PLA-Based Blends

Fatigue Crack Growth and Process Zone Development in a PE‐HD Pipe Grade in Through‐Thickness Direction

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