Non linear fracture mechanics of polymers: Load Separation and Normalization methods

Frontini, Patricia María; Fasce, Laura Alejandra; Rueda, Federico

doi:10.1016/j.engfracmech.2011.11.020

Cited by 21 publications

(14 citation statements)

References 81 publications

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“…Therefore, the material key curve is a great tool to investigate changes in the constraint level during crack initiation. For the correct application of the material key curve, the load separation principle has to be verified beforehand, as presented for several polymers in the literature [ 11 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. The material key curve is based on the load separation principle [ 9 , 23 , 24 ], in which the load, P, can be expressed as the product of two independent functions for a defined geometry, material and constraint (in the plastic region during a fracture test on a cracked specimen) [ 9 ]:

where G is the geometry function, H the material deformation function, a the notch length, W the specimen width, and u pl the plastic displacement.…”

Section: Theory and Calculationmentioning

confidence: 99%

“…The geometry-independent plastic calibration factor, η pl , is given as two for SENB specimens in the literature [ 24 ]; however, the parameter η pl is only valid if the load can be expressed in its separable form, like in Equation (1) [ 9 , 14 ]. This precondition can be verified experimentally by the separability parameter, S ij , as follows [ 9 , 24 ]:

where a is the remaining ligament length of the tested blunt notched specimens and P(a i ) and P(a j ) are the load values of blunt notched (bN) specimens with identical testing configurations and materials but various crack length over width ratios, a 0 /W (represented as a i and a j in Equation (4)).…”

Section: Theory and Calculationmentioning

confidence: 99%

See 1 more Smart Citation

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

et al. 2021

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Fracture mechanics are of high interest for the engineering design and structural integrity assessment of polymeric materials; however, regarding highly ductile polymers, many open questions still remain in terms of fully understanding deformation and fracture behaviors. For example, the influence of the constraint and specimen size on the fracture behavior of polymeric materials is still not clear. In this study, a polymeric material with an elastic plastic deformation behavior (ABS, acrylonitrile butadiene styrene) is investigated with regard to the influence of constraint and specimen size. Different single-edge notched bending (SENB) specimen sizes with constant geometrical ratios were tested. The material key curve was used to investigate differences in the constraint, where changes for small and large specimen sizes were found. Based on a size-independent crack resistance curve (J–R curve), two apparent initiation parameters (J0.2 and Jbl) were determined, namely, the initiation parameter Jini (based on the crack propagation kinetics curve) and the initiation parameter JI,lim (based on an ESIS TC 4 draft protocol). It was found that J0.2 and Jbl could be used as crack initiation parameters whereby Jini and JI,lim are indicative of the onset of stable crack growth.

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where G is the geometry function, H the material deformation function, a the notch length, W the specimen width, and u pl the plastic displacement.…”

Section: Theory and Calculationmentioning

confidence: 99%

Section: Theory and Calculationmentioning

confidence: 99%

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

et al. 2021

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“…Moreover, both methods could become very difficult or impractical to use in harsh testing conditions, such as high loading rate, high temperature, high-pressure hydrogen, corrosive or other aggressive environments. To overcome the drawbacks of the unloading compliance and electric potential drop methods, a normalization method based on load separation principle was proposed as an alternative technique to determine J -resistance curves by directly using the load-displacement records without the need of instantaneous crack length measurement ( Frontini et al, 2012;Wolfenden et al, 1991;Zhou et al, 1991 ). Recently, Bao et al (2015b )proposed an improved normalization method according to the dimensionless modification of load separation theory.…”

Section: Introductionmentioning

confidence: 99%

Normalization method for evaluating J-resistance curves of small-sized CIET specimen and crack front constraints

Bao

Liu

et al. 2016

International Journal of Solids and Structures

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Available online xxxKeywords: J -resistance curves Normalization method CIET specimen Crack front constraints J -Q -M theory J -A 2 -M theory a b s t r a c t Based on dimensionless load separation principle, the normalization method for estimating J -resistance curves of CIET specimen for ductile materials has been developed. Experiments of ductile crack growth resistance on a typical pressure vessel steel SA-508 are conducted by using CT, SEB and CIET specimens. The resulted J -resistance curves show outstanding influence by load configuration and specimen dimensions. J -Q -M and J -A 2 -M approaches are introduced to quantify the crack front constraint of the three types of specimens. According to finite element analyses (FEA) under plane strain and 3D conditions, the distance-independent constraint parameters are calibrated by matching the FEA results with the J -Q -M and J -A 2 -M solutions using weight average method. The analyses show that the parameters of Q and A 2 are load-independent under plane strain condition, but under 3D condition, the J -A 2 -M approach is incapable of characterizing the stress and deformation fields ahead of crack front of CIET specimen for SA-508 steel, and the parameter Q is no longer load-independent. Because of different crack front constraint, the CIET specimen with B = 10 mm, a 0 = 5 . 8 mm gets the lowest fracture resistance while the SEB specimen with B = 20 mm, a 0 = 11 mm and the CT specimen with B = 15 mm, a 0 = 29 mm obtain the highest fracture resistance for SA-508 steel. The size requirements of J -Q -M dominance for each used CIET, CT and SEB specimens are got. Finally, the constraint-modified J -resistance curves of SA-508 steel based on J -Q -M approach are constructed to predict the crack growth resistance for any fracture specimens or actual flawed structures.

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“…In addition, this group contributed significantly to the development of the experimental determination of J and CTOD values at high loading rates. Furthermore, the working group of ESIS TC4 [25][26][27][28] provided lot of contributions to the experimental determination of J values for polymers.…”

Section: J Integral Definitionmentioning

confidence: 99%

Application of J Integral for the Fracture Assessment of Welded Polymeric Components

Major¹,

Kimpfbeck²,

Miron³

2020

Fracture Mechanics Applications

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For many demanding applications of engineering plastics, fracture behaviour under various loading conditions is of prime practical importance. It is well known that fracture properties of plastics are significantly affected by the loading rate, temperature and both local and global stress states. The limitations associated with conventional fracture test methods may, at least in principle, be overcome by the use of appropriate fracture mechanical approaches, which properly account for the temperature and rate dependence of the mechanical behaviour of plastics and should provide geometry-independent fracture toughness values. To provide an additional contribution to this application, fracture tests were performed on both 15-and 20-mm-thick bulk-extruded sheets of a polypropylene random copolymer (PP(RC)) and on four different configurations of their welded joints.Thefullyductilefracturerangewas determined by rate-dependent tests on single CT specimens, and fracture toughness values were derived at the peak loads (J Fmax and CTOD Fmax). Fracture toughness values were determined for stable crack extension based on the J-Δa and/or CTOD-Δa R-curves using single and multiple specimens in terms of various definitions of the crack initiation (J 0.2 ,J 0.2BL or δ 0.2) toughness values. As expected, both methods revealed distinct differences between the bulk materials and the welded joints. These differences were found to depend on the loading rate, the weld configuration and on thedatareductionmethod(J integral or CTOD).

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Non linear fracture mechanics of polymers: Load Separation and Normalization methods

Cited by 21 publications

References 81 publications

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

Normalization method for evaluating J-resistance curves of small-sized CIET specimen and crack front constraints

Application of J Integral for the Fracture Assessment of Welded Polymeric Components

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