Are dykes just filled hydraulic fractures? - Inelastic deformation and emplacement mechanisms of igneous tabular intrusions

<p>Igneous tabular (sheet) intrusions such as dykes, sills and cone sheets, are fundamental elements of volcanic plumbing systems, as they represent the dominant pathways for magma transport and the main feeders of volcanic eruptions. When magma is intruded in the Earth’s crust, it makes its space by pushing and breaking the host rock, which can result in intense inelastic damage and fracturing. To understandand quantify the distribution of such intrusion-induced deformation patterns<em> in the host rock</em> is thus essential to resolve magma emplacement dynamics.</p><p>Sheet intrusions with their low thickness-to-length aspect ratios, resemble fractures. Based on this resemblance, tabular intrusions have been expected to form like (hydraulic) fractures propagating as tensile cracks with sharp and pointy tips, and assuming purely elastic deformation of the host rock. Even if some field observations support this theory, there is growing evidence that other mechanisms, involving significant inelastic deformation of the host rock, accommodate dyke and sill emplacement.</p><p>This contributionprovidesa summary review onthe role of inelastic deformation on the emplacement of tabular intrusions. (1) Field observations show that intrusion tips can be rounded, blunt, and the host deformation accommodating their propagation exhibits inelastic, compressional deformation, in drastic contradiction with theoretical predictions. (2) 3D and 2D laboratory experimentsof magma emplacement in a cohesive Mohr-Coulomb crusthighlightthat magma-induced inelastic deformation, in the form of shear damage and faulting, are first-order transient mechanical precursors for the propagating magma. In addition, these experiments show that the cohesion and friction properties of the model host rock are first-order parameters controlling the formation of intrusions of various shapes, including dykes, plugs, cone sheets, sills and laccoliths. (3) Elasto-plastic numerical models highlight that shear failure is the dominant mechanism to accommodate intrusion growth as soon as heterogeneities are introduced. We conclude that heterogeneities within the host-rock may locally "seed" shear faults ahead of the magmatic intrusion in the propagating direction, in good agreement with field observations. Given that rocks are naturally heterogeneous at multiple scale, these models suggest that shear failure is likely to be a common mechanism for accommodating magma propagation.</p><p>Overall, our field observations andmodelresultsshow that the brittle Coulomb properties of rocks, and their heterogeneities,must be accounted for revealing the nature and distribution of fractures and inelastic damage accommodating the emplacement of igneous tabular intrusions.</p>

Inelastic damage using continuum damage mechanics in composite plate reinforced by unidirectional fibers

It is well that a finite element method is very popular simulation method to predict the physical behavior of systems and structures. In the last years an increase of interest in a new type of numerical methods known as meshless methods was observed. The paper deals with application of radial basis functions on modelling of inelastic damage using continuum damage mechanics of layered plate composite structures reinforced with long unidirectional fibers. For numerical simulations of elastic-plastic damage of layered composite plates own computational programs were implemented in MATLAB programming language. We will use the Newton-Raphson method to solve nonlinear systems of equations. Evaluation damage during plasticity has been solved using return mapping algorithm. The results of elastic-plastic damage analysis of composite plate with unsymmetrical laminate stacking sequence are presented.

The Influence of Inelastic Damage on Tensile Deformation and Creep Crack Growth Behaviour of Type 316H Stainless Steel

Inelastic deformation (combined plastic and creep strain) is known to have significant effects on the tensile and creep deformation behaviour of Type 316H stainless steel. In this work the influence of inelastic strain on the room temperature tensile behaviour of 316H has been examined. Plastic strain was introduced into the material by uniform pre-compression (PC) to 8% plastic strain at room temperature. In addition, creep strain was subsequently introduced into samples by performing uniaxial creep tests on the pre-compressed material. These creep tests were interrupted at various stages of life so that the influence of inelastic damage on the tensile response of the material could be examined. In addition, creep crack growth (CCG) tests have been performed on compact tension C(T) specimens made of 8% pre-compressed material at 550 °C and the results are compared to the existing data on PC material. The results from these tests have been discussed in terms of specimen constraint, initial crack length and loading effects on the CCG behaviour of the PC material.

Inelastic Damage-Involved Response of Colliding Buildings during Earthquakes

Interactions between adjacent, insufficiently separated buildings have been repeatedly observed during major earthquakes. This phenomenon, known as the earthquake-induced structural pounding, may be the reason of local damage at the contact points as well as may lead to the extensive damage at the base of the colliding structure or even initiate its total collapse. In this paper, we examine the importance of inelastic modelling of structural behaviour as the result of damage due to earthquake excitation and structural pounding. The study concerns two adjacent four-storey buildings with different dynamic properties. In the numerical simulations, the nonlinear viscoelastic model is used to model the pounding force during collisions at different storey levels of the structures. The model allows us to take into consideration the dissipation of energy due to damage taking place at the time of collision. Three different ground motion records with different peak ground acceleration levels are used in the study. The comparison between elastic and inelastic damage-involved structural behaviour is investigated. The results of the study show significant changes in the dynamic responses of the inelastic systems as compared to those of elastic ones. The results clearly indicate that modelling the colliding buildings to behave inelastically is really essential in order to obtain accurate damage-involved structural response under earthquake excitation.

Effective shock factors for the inelastic damage prediction of clamped plane plates subjected to non-contact underwater explosion

Shock factors are conventionally used to designate the effect of an underwater explosion on a target. The concept of the effective shock factor was introduced by Rajendran and Narasimhan in a paper entitled ‘A shock factor based approach for the damage assessment of plane plates subjected to underwater explosion’, published in the Journal of Strain Analysis in 2006 (volume 41, issue 6, pages 417–425) for predicting the elastic and yield response of circular and rectangular plates; it was revealed that the coupling factor drastically influences the effect of shock factor on the response of plane plates. It will be of immense use to the designer if effective shock factors are introduced for predicting the inelastic damage of target plates, as shock factors notionally present a pessimistic picture about the damage scenario. The current investigation introduces the concept of effective shock factors to the existing prediction methodologies for estimating inelastic damage of plane plates. Water-backed plate is analysed along with air-backed plates to represent the water-filled side shell of a ship.

Failure Analysis of Miniature Solder Specimen

The effects of specimen geometry size on the behavior of 63Sn-37Pb solder are investigated both experimentally in the laboratory and analytically with finite-element simulations. The simulations are achieved by developing a constitutive model for solder which couples viscoplasticity with a unified damage theory. The unified damage theory is characterized by a damage surface in strain space which separates fatigue damage from inelastic damage. The damage evolution equations are derived within the framework of irreversible thermodynamics. A series of uniaxial tension, tensile creep, and strain-controlled fatigue experiments are performed to obtain material parameters for the solder damage model. The solder damage model is then implemented into a finite element code and used to simulate a uniaxial tension test on a miniature specimen and on a standard ASTM specimen (ASTM Standards, 1999, “Tension Testing of Metallic Materials,” ASTM E8-78). Predictions from these simulations are then compared with each other and with experimental results in order to examine microstructure size effects.