Search results for "Strain Distribution"

Strain field measurements in polycrystalline tantalum

2013

National audience; The unterstanding and the local quantification of surface strain distribution is a key element of crack initiation analysis. Experiments following up the local strain distribution have been carried out, based on the construction of several hundred micrometers wide strain maps ; and using gratings of regularly spaced micrometric markers deposited by lithography. The strain maps are computed using a specific routine, allowing to quantify the local strain distribution at the grain scale for different interrupted tensile loads.

Dilatation Sites: Fibrous Veins, Strain Shadows, Strain Fringes and Boudins

1998

Many deformed rocks contain sites with a deviant mineralogy and fabric, interpreted as an effect of rearrangement of material by local dilatation and precipitation during deformation. Such ‘dilatation sites’ can be isolated and elongate (veins), flanking rigid objects (strain shadows) or occur in the neck of boudinaged layers or elongate crystals (Fig. 6.1). Strain shadows are also referred to in the literature as pressure shadows. Most veins and many strain shadows and boudin necks have sharp contacts with the wall rock and may form by precipitation of material from an aqueous solution in a fracture, as outlined below. Such sites are usually filled with polycrystalline material which may b…

Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study.

2006

The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry. Volumes of the triceps surae muscles and strain distribution of the soleus aponeurosis and the Achilles tendon at a constant submaximal plantar flexion (20% pre-maximal voluntary contraction) were measured by using MRI and velocity-encoded, phase-contrast MRI techn…

Influence of strain in the reduction of the internal electric field in GaN/AlN quantum dots grown ona-plane 6H-SiC

2006

The strain state of stacks of GaN/AIN quantum dots (QDs) grown on (0001) and (1120) 6H-SiC has been investigated by means of Raman spectroscopy. Depending on the orientation of the wurtzite axis with respect to the growth direction it is found that the piezoelectric contribution to the electrostatic potential may either reinforce that arising from the spontaneous polarization or oppose it. The experimental results are compared with a theoretical model for the strain and polarization field in QDs of both orientations that allows the calculation of the electrostatic potential in the QDs. Both the experimental results and the theoretical model indicate that the internal electric field and elec…

Stress and strain distribution in perforated plate loaded in median plane

2019

Influence of bone parameters on peri-implant bone strain distribution in the posterior mandible

2014

Objectives: The success rate of dental implants depends on the type of bone at the implant site. The purpose of the present study was to investigate the effects of the bone parameters at the implant-placement site on peri-implant bone strain distributions. Study Design: The morphologies and bone densities of seventy-five potential implant sites in the posterior man - dible were measured using computed tomography (CT). Based on the CT data, we defined bone parameters (low and high in terms of cancellous-bone density and crestal-cortical bone density, and thin and thick in terms of crestal-cortical bone thickness), and we constructed finite-element models simulating the various bone types. A …

Optimal die Design for Cold Extrusion Processes

1999

The design of cold extrusion processes requires the optimisation of several process variables in order to obtain a defect free product. The fulfilment of different objectives, such as the minimisation of forming loads or the homogeneity of the deformations, is highly requested. Nevertheless, several other relevant aspects of extrusion processes have to be taken into account and require a suitable optimisation of the process parameters and in particular of the die shape. In this paper, tool life has been assumed as the most relevant goal and an effective die design procedure as been setup. It is well known that fatigue cracking of the dies is the principal cause of dies failure in cold extru…

Quantification and visualization of finite strain in 3D viscous numerical models of folding and overthrusting

2020

Abstract Finite strain analysis and three-dimensional (3D) numerical modeling are important methods to understand the deformation history of rocks. Here, we analyze finite strain in 3D numerical simulations of power-law viscous folding and overthrusting. Simulations with different and laterally varying detachment geometries cause a lateral transition from folding (for thicker detachments) to overthrusting. We compute the 3D finite strain tensor, the principal strain values and their orientations. We compute the Nadai strain, e S , and the Lode’s ratio, ν , representing the strain symmetry (constriction or flattening). We apply Hsu diagrams to visualize strain distribution in e S - ν space, …

A Comparative Analysis of Different Robust Design Approaches in Sheet Stamping Operations

2011

A crucial issue in sheet stamping optimization problems is related to the process robustness improvement: critical scattering in the investigated performances arises due to some noise variables influence, often evolving up design failure itself. In fact, strong variations in the final stamped part or fluctuations of strain distribution may lead to an uncontrolled process design. Such variability cannot be controlled but anyway it is possible to develop proper design tools able to identify robust process calibrations above which the noises variations effects are admissible. In this paper, a multi‐objective optimization problem was analyzed, with the aim to minimize both excessive thinning an…