scholarly journals The Effect of Material Present in the Void for Thermography Inspection in Concrete

In the previous study by the author, a numerical model to predict the thermal contrasts resulting from subsurface voids (i.e. delaminations) in concrete under a given set of environmental conditions was developed using the finite element method. The model was verified using the experimental test data, and the results indicated that the model could be an effective tool to support the thermography inspection of the concrete. In this present study, the use of the verified model to evaluate the effects of materials present in the void created by the delamination expected to influence the detectability of the subsurface voids. The effect of this parameter on the thermal contrast developed on the surface above a subsurface delamination was assessed under a specific set of environmental conditions. The results indicated that air-filled void produced a significant thermal contrast compared to water-filled void, ice-filled void, and epoxy adhesive-filled void.

Author(s):  
Виктор Григорьевич Чеверев ◽  
Евгений Викторович Сафронов ◽  
Алексей Александрович Коротков ◽  
Александр Сергеевич Чернятин

Существуют два основных подхода решения задачи тепломассопереноса при численном моделировании промерзания грунтов: 1) решение методом конечных разностей с учетом граничных условий (границей, например, является фронт промерзания); 2) решение методом конечных элементов без учета границ модели. Оба подхода имеют существенные недостатки, что оставляет проблему решения задачи для численной модели промерзания грунтов острой и актуальной. В данной работе представлена физическая постановка промерзания, которая позволяет создать численную модель, базирующуюся на решении методом конечных элементов, но при этом отражающую ход фронта промерзания - то есть модель, в которой объединены оба подхода к решению задачи промерзания грунтов. Для подтверждения корректности модели был проделан ряд экспериментов по физическому моделированию промерзания модельного грунта и выполнен сравнительный анализ полученных экспериментальных данных и результатов расчетов на базе представленной численной модели с такими же граничными условиями, как в экспериментах. There are two basic approaches to solving the problem of heat and mass transfer in the numerical modeling of soil freezing: 1) using the finite difference method taking into account boundary conditions (the boundary, for example, is the freezing front); 2) using the finite element method without consideration of model boundaries. Both approaches have significant drawbacks, which leaves the issue of solving the problem for the numerical model of soil freezing acute and up-to-date. This article provides the physical setting of freezing that allows us to create a numerical model based on the solution by the finite element method, but at the same time reflecting the route of the freezing front, i.e. the model that combines both approaches to solving the problem of soil freezing. In order to confirm the correctness of the model, a number of experiments on physical modeling of model soil freezing have been performed, and a comparative analysis of the experimental data obtained and the calculation results based on the provided numerical model with the same boundary conditions as in the experiments was performed.


Aviation ◽  
2010 ◽  
Vol 14 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Tadeusz Markowski ◽  
Stanislaw Noga ◽  
Stanislaw Rudy

The development of computer techniques and computational systems based on the finite element method allows one to conduct a free vibration analysis of large systems like an aviation gearbox test rig. The object of this paper is to present a free vibration analysis of a gear fatigue test rig working in a closed loop configuration. A numerical model of the test rig based on the finite element method is presented in this paper. The base model contains all the essential structures of the real system. After the numerical results of the natural frequencies of the rig were obtained, they were then verified by the experimental results on a real object. Numerical analysis was performed using the ANSYS code. Santrauka Baigtiniu elementu metodu paremtas kompiuterines technikos ir kompiuteriniu sistemu kūrimas leidžia atlikti laisvuju svyravimu analize tokios dideles sistemos, kaip aviacines pavaru dežes, testavimo irenginys. Šio darbo tikslas buvo atlikti pavaru dežes nuovargio bandymu irenginio, veikiančio uždaro kontūro konfigūracijoje, laisvuju svyravimu analize. Taip pat pateikiamas testavimo irenginio skaitinis modelis, kurio veikimas yra pagristas baigtiniu elementu metodu. Pagrindinis modelis turi visas tikrosios sistemos svarbiausias struktūras. Gavus irenginio savuju dažniu kiekybinius rezultatus, buvo patikrinti realaus objekto eksperimentiniai rezultatai. Naudojantis ANSYS sistema buvo atlikta skaitine analize.


2019 ◽  
Vol 294 ◽  
pp. 05006
Author(s):  
Dmytro Bannikov ◽  
Anatoliy Radkevich ◽  
Antonina Muntian

The purpose of the work is to evaluate the spatial distribution of the rigidity of the carrier frame and the body of the Ukrainian electric locomotive DC3 as a single system during operation and repair. The research was carried out on the basis of the finite element method with the application of design and computing complex SCAD for Windows. The numerical model of the electric locomotive was built, tested and then used to identify the causes and providing guidance on solving some specific operational questions. They are included, for example, the possibility of eliminating the body skew when jacking up on jacks and jamming the door as a result. The researches showed that the structure of the electric locomotive DS3 in general has a rather high spatial rigidity, both in transverse and longitudinal directions, and on torsion. However, for some practical repair tasks there is not enough for that rigidity. It was recommended to increase the thickness of the shell of its body up to 4 mm or the roof up to 8 mm, which leads to an increasing in the total mass of the machine by about 2,5 and 3,5 tons, respectively.


2013 ◽  
Vol 486 ◽  
pp. 239-244 ◽  
Author(s):  
Martin Svoboda

The article deals with the influence of manufacturing and geometric asymmetry on the vertical oscillation of symmetric and asymmetric systems consisting of rigid bodies linked flexibly with different kinematic excitation. The solution was performed using experimental and numerical analysis (with application of oscillation of vehicles and flexibly coupled machines). Numerical solutions were carried out by finite element method (FEM) on a simple model and experimental solutions on laboratory model of a mechanical system. The aim of the work was to create a numerical model and its solution using the finite element method. The experimental solution was used to verify the numerical model.


Mechanik ◽  
2018 ◽  
Vol 91 (7) ◽  
pp. 549-551
Author(s):  
Waldemar Dudda

Presented are the results of strength analysis of the Pilmet boom sprayer. After creating the numerical model of the boom, a static analysis was carried out. Stresses and displacements were determined using the finite element method for different variants of the folding boom position.


2005 ◽  
Vol 490-491 ◽  
pp. 667-671 ◽  
Author(s):  
Xiao Ling Zheng ◽  
Min You ◽  
Yong Zheng ◽  
Hai Zhou Yu ◽  
Chun Mei Yang

The residual stress in epoxy adhesive layer deposited on metal and other substrate at room temperature is studied. With embedded strain gauges in arranged depth of epoxy layer, the strain changes in the adhesive layer induced by the curing procedure and the changes of ambient temperature were measured to evaluate the changes of residual stress in place during a period after the curing procedure finished. The actual strain in epoxy adhesive layer from curing is used to estimate the residual stresses in it. While taking the strain obtained from the surface of the adhesive layer as free strain, the residual stress can be calculated and presented a strongly cyclic variation with a period of 24 h. The inner stress is also analyzed using the finite element method.


2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mourad Nahal ◽  
Rabia Khelif

PurposeThe aim of this paper is to investigate the failure probability in an irregular area in pipeline (elbow) over its lifetime. The reliability analysis is performed by using of an enhanced first-order reliability method / second-order reliability method (FORM/SORM) and Monte Carlo simulation methods: a numerical model of a corroded pipeline elbow was developed by using finite element method; also, an empirical mechanical behavior model has been proposed. A numerical case with high, moderate and low corrosion rates was conducted to calculate the deferent reliability indexes. The found results can be used in an application case for managing an irregular area in pipeline lifetime. Hence, it is necessary to ensure a rigorous inspection for this part of a pipeline to avoid human and environmental disasters.Design/methodology/approachThe present paper deals a methodology for estimating time-dependent reliability of a corroded pipeline elbow. Firstly, a numerical model of corroded elbow is proposed by using the finite element method. A mechanical behavior under the corrosion defect in time is studied, and an empirical model was also developed.FindingsThe result of this paper can be summarized as: a mechanical characterization of the material was carried out experimentally. A numerical model of a corroded pipeline elbow was developed by using the finite element method. An empirical mechanical behavior model has been developed. The reliability of a corroding pipe elbow can be significantly affected by corrosion and residual stress. A proportional relationship has been found between probability of failure and corrosion rate. The yield stress and pressure service have an important sensitivity factor.Originality/valueAiming to help Algerian gas and oil companies' decision makers, the present paper illustrates a methodology for estimating time-dependent reliability of a corroded pipeline elbow over its lifetime using numerical models by applying the finite element method. Firstly, a numerical model of a corroded pipe elbow was developed and coupled with an empirical mechanical behavior model, which is also proposed. A probabilistic is then developed to provide realistic corrosion parameters and time modeling, leading to the real impact on the lifetime of an elbow zone in pipeline. The reliability indexes and probability of failure for various corrosion rates with and without issued residual stress are computed using Monte Carlo simulation and FORM.


Author(s):  
ZhiYong An ◽  
Yenwen Lu

This paper reports a theoretical study of the pneumatic balloon-jointed actuation, which has been utilized in the microfinger and the microhand to perform an out-of-plane rotation [1]. The finite element method (FEM) is utilized to describe and to predict the performance of this actuation, in terms of the actuation angles, forces, and structure stiffness. Several related geometrical parameters have been studied, providing the guidelines of the micro balloon-jointed actuation.


Nanoscale ◽  
2019 ◽  
Vol 11 (43) ◽  
pp. 20868-20875 ◽  
Author(s):  
Junxiong Guo ◽  
Yu Liu ◽  
Yuan Lin ◽  
Yu Tian ◽  
Jinxing Zhang ◽  
...  

We propose a graphene plasmonic infrared photodetector tuned by ferroelectric domains and investigate the interfacial effect using the finite element method.


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