Fracture mechanics nonlinear

Nonlinear chemometrics methods, 6 53-54 Nonlinear dielectrics, 11 91-92 Nonlinear fracture mechanics, 20 350 Nonlinear interaction, 14 680... 

Nonlinear Fracture Mechanics, ASTM Technical Publication 995, American Society for Testing and Materials, Philadelphia, PA, 1986, pp. 7-26. 

J. L. Bassani, D. E. Hawk, and F.-H. Wu, Crack Growth in Small-Scale Creep, in Nonlinear Fracture Mechanics Volume I—Time Dependent Fracture, eds. A. Saxena, J. D. Landes, and J. L. Bassani, ASTM STP 995, American Society for Testing and Materials, Philadelphia, PA, 1988, pp. 68-95. 

Equilibrium tests at the local deformation stage of a sample provide adequate changes of external forces to internal efforts of a material to resist with corresponding static development of the main crack. These tests are most appropriate when using bending or tension of the samples, because the fracture process will be defined by development of a unique breakaway type of crack, which allows determination of the actual surface area of the fracture. This means that the tests correctly provide the real physical processes of fracture of a concrete and the principles of nonlinear fracture mechanics with traditional mechanical characteristics of concrete and allows determination of a set of power and energy parameters of the material fracture. 

No crack instability developed in the tests of load vs. crack opening displacement (COD), and all specimens fractured in a ductile manner after general yielding. Neither the concept of linear elastic fracture mechanics (K) nor that of nonlinear fracture mechanics (COD, /-integral) for unstable fracture can be applied to the phenomenon such as a stable fracture of 5083-0. 

Excellent texts on fracture mechanics are available [9-11]. Related topics are failure criteria for the onset of cracking in laminated systems [55], dynamic fracture mechanics [56], and nonlinear fracture mechanics [9,11]. 

Hutchinson, J. W. (1979) A Course on Nonlinear Fracture Mechanics, L5mgby Department of Solid Mechanics, Technical University of Denmark, pp. 1-101. 

The problem of secondary flexure in axial tensile tests is considered in view of the tension-softening process. The procedures aimed at elimination of that parasite effect were studied by Akita et al. (2001) and Novak et al. (2006) who have shown possibilities of nonlinear fracture mechanics simulation in analysis of the experimental data, including post-peak descending branch of the load-displacement curves, taking into consideration material imperfections and heterogeneities. 

The Irwin s similarity relationship of Rc = Kc /E and the deviation from this relationship in nonlinear fracture mechanics regime were studied as functions of the dimensions and geometries of test specimens. In nonlinear fracture regime, Rc is always larger than jE (or Kq jE ). The excess energy, Rc — fE, was experi-... 

For refined finite element analysis, the fracture behavior of concrete and masonry can be simulated with continuum elements based on the nonlinear fracture mechanics concept. In these elements, cracks are modeled in a smeared fashion, i.e., with a material stress—strain law representing distributed crack development in... 

Saxena A. Nonlinear fracture mechanics for engineers CRC Press 1997. 

M. Wecharatana and S.P. Shah, Nonlinear fracture mechanics parameters , in... 

Saxena, A. (1998). Nonlinear Fracture Mechanics for Engineers, Boca Raton, FL CRC Press, Chap. 2, p.27. 

In most composites with desirable tensile properties, linear elastic fracture mechanics (LEFM) criteria are violated.30,31 Instead, various large-scale nonlinearities arise, associated with matrix damage and fiber pull-out. In consequence, alternate mechanics is needed to specify the relevant material and loading parameters and to establish design rules. Some progress toward this qbjective will be described and related to test data. This has been achieved... 

A. S. Kobayashi, Dynamic Fracture Analysis by Dynamic Finite Element Method-Generation and Propagation Analysis, in Nonlinear and Dynamic Fracture Mechanics, eds. N. Perrone and S. N. Atluri, ASME, New York, 1979, pp. 19-36. 

Polymers which yield extensively under stress exhibit nonlinear stress-strain behavior. This invalidates the application of linear elastic fracture mechanics. It is usually assumed that the LEFM approach can be used if the size of the plastic zone is small compared to the dimensions of the object. Alternative concepts have been proposed for rating the fracture resistance of tougher polymers, like polyolelins, but empirical pendulum impact or dart drop tests are deeply entrenched forjudging such behavior. 

Because the existence and extent of the nonlinear regime, b, is highly dependent on the fraction of the modifying phase and the test speed, it is believed to play an important role in thet kinetics of toughening and thus is considered for fracture characterization. In order to apply the same analysis over the entire range of test speeds, the standard linear elastic fracture mechanics... 

These analyses and associated experiments demonstrate that fracture mechanics can be used to provide information and insight into the value of the failure load, the locus of likely crack growth, and the path along which the crack will then grow. Where analytical analyses of stress, strain, and energy release rates are difficult or impossible, modern numerical methods can be very useful. In the opinion of the authors, the utility of these combined tools has hardly been exploited. The inclusion of nonlinear, nonelastic effects in the analyses is feasible is such materials are carefully characterized and/or properties become available. 

In special cases, such as elastomers or other high-elongation materials, bulk plastic or nonlinear behavior of the material does occur. For these cases there have been theories proposed. Chapter 1 discussed the generalized fracture mechanics theory developed by Andrews in which the effect of variables such as crack speed, temperature, and magnitude of strain on the strain energy release rate is considered. ... 

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