Probabilistic Static Failure of Composite Material.

Cassenti, Brice N.

doi:10.2514/3.48422

Cited by 44 publications

(20 citation statements)

References 6 publications

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“…Shima and Oyane [2] proposed a plasticity theory for porous metals, which represents the basis for most of the powder consolidation modelling work. Cassenti [3] investigated HIPping modelling using an elasto-plastic large-deformation model with implicit thermal calculations. The ability of his model to predict the shape and geometrical changes was inadequate.…”

Section: Introductionmentioning

confidence: 99%

An iterative approach of hot isostatic pressing tooling design for net-shape IN718 superalloy parts

Essa

Khan

Hassanin

et al. 2015

Int J Adv Manuf Technol

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Powder Hot Isostatic Pressing is a resource-efficient approach for netshape manufacture of high-value Nickel-based superalloy structures. One of the key challenges to its application is the availability of modelling tools that can predict the geometrical changes that occur during the consolidation process in order to design the tooling required. In this work, the utility of a finite element code, based on the plastic collapse model, was assessed. The finite element model was then combined with an optimisation toolbox to design (in an iterative process) the tooling required to accommodate the powder consolidation process. The model was validated for IN718 superalloy, using a demonstrator with complex features. Microstructural characterisation was also performed to assess the degree of densification. Although the finite element model did not account for creep deformation, good predictions were obtained. Nevertheless predictions of the dimensions of consolidated samples were obtained, which were typically within 1% of the observations, suggesting that plastic collapse accounts for 99% of the geometrical changes due to the densification process for the range of hot isostatic pressing parameters investigated.

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Section: Introductionmentioning

confidence: 99%

An iterative approach of hot isostatic pressing tooling design for net-shape IN718 superalloy parts

Essa

Khan

Hassanin

et al. 2015

Int J Adv Manuf Technol

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“…The development of weakest-link theory for static structures presented here will follow the discussion provided in the literature [6]. Consider an infinitesimal volume element, d V , at a point x in a total volume V , and let the stress be s ij at point x .…”

Section: Basic Theory For Static Structuresmentioning

confidence: 99%

“…See Cassenti [6] for a discussion of materials with finite unequal failure loads in tension and compression. The stress is now a function of the through-thickness direction, z , and is given by where h is the thickness of the rectangular cross section and .…”

confidence: 99%

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Weakest-Link Probabilistic Failure

Cassenti¹

2004

Engineering Design Reliability Handbook

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In 1939, Weibull [1] proposed a model for the failure of materials that could be used to predict the increased strength observed in bending specimens when compared with tensile specimens. The model was based only on the statistical scatter in experimental results and the assumption that the weakest point in the structure governs the failure of the entire structure. The weakest-link assumption implies that there is a greater probability for failure in larger structures than in equally stressed smaller structures. This follows from the fact that there is a greater probability for a critical flaw in the volume of the larger structure. Of course, weakest-link theory will result in conservative predictions for the failure probabilities, since stress can be redistributed when the weakest point fails. Hence, the conservatism may significantly overpredict the failure probability in metallic structures, but it should be accurate in ceramic structures. Composite material structures should lie intermediate between metallic and ceramic structures. Many aspects of the effects of size on strength have been examined. Harter [2] has produced a review of the early literature on size effects in material structures. Weakest link has been extended to the prediction of failure locations [3], time dependent failure [4], multi-axial stress states [5], and composite material structures [6].This chapter will first present the basic theory, and then this will be extended to the prediction of failure locations. Time-dependent failure will then be discussed, and the results will be extended to composite materials. Basic Theory for Static StructuresThe development of weakest-link theory for static structures presented here will follow the discussion provided in the literature [6]. Consider an infinitesimal volume element, d V , at a point x in a total volume V , and let the stress be s ij at point x . Assume that the infinitesimal probability for failure, d f , in volume element d V is proportional to the volume element and is a function of the stress state. ThenFinally, weakest-link failure can be readily applied to the design of composite material structures. Although the accuracy for composite structures is not as good as for ceramic structures, it still provides considerable accuracy and can be readily adapted to represent the large number of competing failure mechanisms present. An excellent guide for developing these models is the use of existing damage models.

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“…Some research works have focused on the cracks and failure of random composites [9]. Regarding the failure probability or reliability, Onkar et al [10,11], Cassenti [12], Kam et al. [13] and Lekou and Philippidis [14] have demonstrated the effect of random material properties.…”

Section: Introductionmentioning

confidence: 97%