Search results for "CLOSURE"
showing 10 items of 411 documents
The Application of CFD Methods for Modeling of a Three-Phase Fixed-Bed Reactor
2018
The mathematical model of the three-phase fixed-bed reactor (TBR) consisting of the continuity equation, the momentum balances of each phase and mass balances of reaction mixture components were presented and discussed. These balances are the result of averaging by means of Euler’s procedure and form the basis of the Computational Fluid Dynamics (CFD). Although the CFD model is based on fundamental principles some empirical relations (closure lows) must be implemented into the momentum balance in order to ensure a proper description of the dynamics of very complex three-phase system. Therefore, the sensitivity of a multiphase CFD model with respect to relations defining drag forces between …
Investigation of the crack tip stress field in a stainless steel SENT specimen by means of Thermoelastic Stress Analysis
2019
Abstract In this work a Thermoelastic Stress Analysis (TSA) setup is implemented to investigates the Thermoelastic and Second Harmonic signals on a fatigue loaded Single Edge Notched Tension (SENT) specimen made of stainless steel AISI 304L. Three load ratios are in particular applied, R=-1, 0, 0.1. The thermoelastic signal is used to evaluate the Stress Intensity Factor via two approaches, the Stanley-Chan linear interpolation method and the over-deterministic least-square fitting (LSF) method using the Williams’ series expansion. Regarding least-square fitting, an iterative procedure is proposed to identify the optimal crack tip position in the thermoelastic maps. The SIF and T-Stress are…
A model for predicting the mixed-mode fatigue crack growth in a bonded joint
2013
Bonded joints are highly sensitive to the presence of defects and to the degradation phenomena, and this aspect represents the primary obstacle to their use in different structural engineering applications. Delamination in a bonded joint represents, in fact, one of the primary, most common and insidious causes of damage. In this paper, a numerical–experimental study on the crack propagation along the adhesive layer of a bonded joint specimen is carried out. Experimental study is focused on the evaluation of the damage modalities of a bonded joint when the specimens are subject to fatigue load. Experimental tests are compared with the results of several numerical analysis performed in ANSYS …
Elastic-plastic fatigue crack growth in 18G2A steel under proportional bending with torsion loading
2006
The paper presents the results of fatigue crack growth on low-alloy 18G2A steel under proportional bending with torsion loading. Specimens with square sections and a stress concentration in the form of external one-sided sharp notch were used. The tests were performed under the stress ratios R = -1, -0.5 and 0. The test results were described by the ΔJ-integral range and compared with the ΔK stress intensity factor range. It has been found that there is a good agreement between the test results and the model of crack growth rate, which includes the ΔJ-integral range.
Comparison of frictional forces during the closure of extraction spaces in passive self-ligating brackets and conventionally ligated brackets using t…
2019
Background This study compared the frictional force resulting from the bracket/archwire interface and the stress at the root/periodontal ligament/bone interface, between passive self-ligating brackets and conventionally ligated brackets, during the space closure stage. Material and methods A cone beam tomography was taken to a female patient that required extraction of upper first premolars and passive self-ligating system; three months after its activation, a cone beam tomography was taken again. The designs of the maxillary bone and the entire system were possible through tomography images and stereomicroscopic photographs. Validation of the Finite Element Method (FEM) was achieved compar…
ΔJ-integral range estimation for fatigue crack growth rate description
2004
Abstract The paper presents an equation for fatigue crack growth rate description taking into account the ΔJ-integral range, which was verified experimentally for variable bending. Plane, notched specimens were tested under unilaterally restrained bending for different values of stress ratio R. The results of tests and numerical calculations were presented as characteristics of fatigue crack growth rate. It has been shown that in the case of a change of stress ratio from R=−1.0 to R=0.0, the crack rate increases twice for 10HNAP steel and five times for 18G2A steel. The empirical formula presented in the paper describes well the test results of fatigue crack rate in the steels.
Non Gaussian closure techniques for the analysis of R-FBI isolation system
1997
The Resilient-Friction Base Isolator (R-FBI) stochastic response under severe ground motion modelled as a stationary and non-stationary zero mean stochastic white noise processes is performed. The moment equation approach is applied and the non-normal response is obtained by means of a non-Gaussian closure technique, based on the Gram-Charlier asymptotic expansion of the response probability density function. Results are compared with the equivalent non linearization technique and with results obtained by means of Monte Carlo simulation.
A new definition of well-behaved discrimination functions
2009
Abstract A discrimination function shows the probability or degree with which stimuli are discriminated from each other when presented in pairs. In a previous publication [Kujala, J.V., & Dzhafarov, E.N. (2008). On minima of discrimination functions. Journal of Mathematical Psychology , 52 , 116–127] we introduced a condition under which the conformity of a discrimination function with the law of Regular Minimality (which says, essentially, that “being least discriminable from” is a symmetric relation) implies the constancy of the function’s minima (i.e., the same level of discriminability of every stimulus from the stimulus least discriminable from it). This condition, referred to as “well…
Feuilletages deCP(n) : de l’holonomie hyperbolique pour les minimaux exceptionnels
1992
Let ℱ be a holomorphic foliation ofCP(n). If ℱ has a leaf L, the closure L of which is disjoint from the singular set of the foliation, we prove that there exists a loop in a leaf contained in L with contracting hyperbolic holonomy.