Search results for "deformation"
showing 10 items of 515 documents
Crystallographic preferred orientation development by dissolution–precipitation creep
2000
Abstract Crystallographic preferred orientations (CPOs) in deformed rocks are commonly interpreted as resulting from crystal plastic deformation mechanisms, where deformation is achieved by the movement of dislocations. In this paper we investigate the possibility of CPO-development by dissolution–precipitation creep or pressure solution. A numerical model is presented, which simulates the development of a grain aggregate that deforms by reaction-controlled dissolution–precipitation creep. Grains are simulated as rectangular boxes that change their shape by growth, or dissolution of their surfaces, depending on the normal stresses acting on the individual surfaces. Grains can also rotate du…
Instabilities of the deformation process in cold drawing of poly(ethylene terephthalate) and other polymers
1981
The relationship between drawing rate and drawing stress was studied for amorphous poly(ethylene terephthalate) (PET) under various experimental conditions. Three types of expriments were performed: simple drawing with necking at constant rate, drawing through a conical die, and drawing at constant stress. Under constant stress conditions a transition between two stable regimes of drawing can be observed. The transition occurs at a critical stress σc at which the rate of neck propagation changes by some orders of magnitude. Such a transition was found both below and above the glass transition of PET. With constant drawing rates instabilities of neck propagation were observed under certain e…
Seismic moment tensors and regional stress in the area of the December 2013–January 2014, Matese earthquake sequence (Italy)
2014
Abstract The main goal of this study is to provide moment tensor solutions for small and moderate earthquakes of the Matese seismic sequence in southern Italy for the period of December 2013–January 2014. We estimate the focal mechanisms of 31 earthquakes with local magnitudes related to the Matese earthquake seismic sequence (December 2013–January 2014) in Southern-Central Italy which are recorded by the broadband stations of the Italian National Seismic Network and the Mediterranean Very Broadband Seismographic Network (MedNet) run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The solutions show that normal faulting is the prevailing style of seismic deformation in agreeme…
Stylolite interfaces and surrounding matrix material: Nature and role of heterogeneities in roughness and microstructural development
2010
Rough pressure solution interfaces, like stylolites, are one of the most evident features of localized slow deformation in rocks of the upper crust. There is a general consensus that the development of these rough structures is a result of localized, stress enhanced, dissolution of material along a fluid filled interface, but little is known on the initiation of this roughness. The aim of this article is to reveal the role of heterogeneities initially present in the host-rock on roughness initiation. This should give insights on whether stylolite roughness is generated by a stress-induced instability or by the presence of disorder in the material (i.e. quenched noise). We use a microstructu…
An empirical model for free surface energy of strained solids at different temperature regimes.
2006
Abstract We have developed an empirical formulation, based on the elastic theory, to calculate the variation of the surface free energy when a crystal is strained in the elastic regime. The model permits to obtain the variation of the surface energy at different strains and temperatures when are known the thermal dependence on the bulk and surface elastic constants. Molecular dynamics (MD) simulations were performed using the three low index surfaces of Al, to validate the accuracy of the model. The comparison between the empirical model and the MD simulations shows a good agreement for temperatures ranging between 0 and 900 K, and for deformation between −2% and 2%.
From A Medial Surface To A Mesh
2012
Medial surfaces are well-known and interesting surface skeletons. As such, they can describe the topology and the geometry of a 3D closed object. The link between an object and its medial surface is also intuitively understood by people. We want to exploit such skeletons to use them in applications like shape creation and shape deformation. For this purpose, we need to define medial surfaces as Shape Representation Models (SRMs). One of the very first task of a SRM is to offer a visualization of the shape it describes. However, achieving this with a medial surface remains a challenging problem. In this paper, we propose a method to build a mesh that approximates an object only described by …
Curvilinear constraints for free form deformations on subdivision surfaces
2010
This paper presents a method to deform a subdivision surface with curvilinear constraints. It combines an intuitive free form deformation with a Loop subdivision algorithm. The main advantage of this method of deformation is that it uses only vertices of an object and satisfies the geometrical constraints provided by the user. It permits us to control the final shape of the deformed object, defining the range (i.e. the impact) of the deformation before applying it. The deformation takes into account the Loop properties to follow the subdivision scheme, allowing the user to fix some curvilinear constraints at the subdivision level he works on and to render the final object at the level he wa…
Self-Consistent Tilted-Axis-Cranking Study of Triaxial Strongly Deformed Bands inEr158at Ultrahigh Spin
2012
Stimulated by recent experimental discoveries, triaxial strongly deformed (TSD) states in $^{158}\mathrm{Er}$ at ultrahigh spins have been studied by means of the Skyrme-Hartree-Fock model and the tilted-axis-cranking method. Restricting the rotational axis to one of the principal axes---as done in previous cranking calculations---two well-defined TSD minima in the total Routhian surface are found for a given configuration: one with positive and another with negative triaxial deformation $\ensuremath{\gamma}$. By allowing the rotational axis to change direction, the higher-energy minimum is shown to be a saddle point. This resolves the long-standing question of the physical interpretation o…
Constraining the surface properties of effective Skyrme interactions
2016
The purpose of this study is threefold: first, to identify a scheme for the determination of the surface energy coefficient a_surf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for a_surf and the characteristic energies of the fission barrier of Pu240; and third, to lay out a procedure how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. There are several frequently used possibilities to define and calculate the surface energy coefficient a_surf of effective interactions. The most direct access is provided by the model system of se…
Tree Singularities: Limits, Series and Stability
2013
A tree singularity is a surface singularity that consists of smooth components, glued along smooth curves in the pattern of a tree. Such singularities naturally occur as degenerations of certain rational surface singularities. To be more precise, they can be considered as limits of certain series of rational surface singularities with reduced fundamental cycle. We introduce a general class of limits, construct series deformations for them and prove a stability theorem stating that under the condition of finite dimensionality of T 2 the base space of a semi-universal deformation for members high in the series coincides up to smooth factor with the “base space of the limit”. The simplest tree…