An Experimental/Numerical Study on the Sensitivity of Axial Compressive Load Bearing Response of Steel Tubular to Geometrical Imperfections (original) (raw)
Related papers
Thin-Walled Structures, 2016
In in this paper, cyclic behavior of SS316L cubic shells under pure torsional load was experimentally and numerically studied. Experimental tests were carried out by a servo-hydraulic NSTRON 8802 machine under torsional load-control condition. In this loading condition and based on experimental results, due to the existence of larger shear stress along the shell thickness, increasing of torsional torque amplitude caused the enhancement of ratcheting angle and reduction of shells's life. Also, the effect of cutout and its size on ratcheting behavior of cubic shell were investigated , According to experimental results, it was seen that the sensitivity of ratcheting angle to cutout position near the applied load was high and the shell's life decreases in this condition. Numerical analysis was done by Abaqus software and using the nonlinear isotropic/kinematic hardening model. There is a good agreement with that of experimental results.
Investigation of Stability of Noncircular Lobed Journal Bearings Lubricated by Ferrofluid
2019
Nowadays, the demand for journal bearings operating at high speeds and also the importance of their stability in practical usage has caused a need for noncircular lobed bearings instead of circular bearings. This makes the extreme effects of lubrication kind in bearing performance more important. For this reason, choosing appropriate lubricant is of great significance. Ferrofluids as a result of having unique features can be considered as one of the choices. The aim of this paper is to study the stability of two, three and four lobe noncircular journal bearings lubricated with ferrofluids considering parameters such as eccentricity ratio, the ratio of length to diameter and also the magnetic force coefficient. In this work, by considering small perturbation of journal about its static equilibrium position and using the numerical method of finite elements to solve the equations, whirling frequency and stability domain are obtained. The results show that by increasing the eccentricity...
2019
Nowadays, simulation of viscoelastic flows at high Weissenberg numbers is one of the most obstacles and important issues for rheologists to observe the rheological properties at sufficiently high weissenberg number. It is well known that the conformation tensor should, in principle, remain symmetric positive definite (SPD) as it evolves in time. In fact, this property is crucial for the well-posedness of its evolution equation. In practice, this property is violated in many numerical simulations. Most likely, this is caused by the accumulation of spatial discretization errors that arise from numerical integration of the governing equations. In this research, we apply a mathematical transformation, the so-called hyperbolic tangent, on the conformation tensor to bound the eigenvalues and prevent the generation of negative spurious eigenvalues during simulations. The flow of FENE-P fluid through a 2D channel is selected as the test case. Discrete solutions are obtained by spectral/hp e...
Hydraulic and Structural Analysis of Babolrud River Training Using Some Applied Software
DOAJ (DOAJ: Directory of Open Access Journals), 2019
Occurrence of heavy floods in rivers causes a lot of damages and losses. In this research, to highlight the river-training reaches in 10.9 km of Babolrud River, first, using topographic map of the area, the Tin layer was created in GIS software. Then, using the HEC-GeoRAS extension, the main route and cross sections of the river were prepared and introduced to the HEC-RAS model. River discharge with return periods of 2 to 200 years was calculated. Flow analysis in the agricultural and urban areas was performed and the areas which need training measures such as flood-retaining walls and levees were specified and designed. The structural design, stability control and sliding was performed based on the Standard No. 518, using RetainWall software, and design and control of levee stability was performed based on the Standard No. 214, using GeoStudio software. The cost of project implementation was estimated based on the Price List of 2017. The output of HEC-RAS software showed that height of flood-retaining wall in 3 urban reaches ranged between 1.73 to 2.8 m and in 5 agricultural reaches ranged between 1.46 to 2.25 m. It was concluded that the overall cost of levee implementation is about 9.01 billion Rials, of gravity concrete flood-retaining wall is about 9.26 billion Rials and of concrete cantilever inverted T shape flood-retaining wall is about 10.05 billion Rials. Thus, using floodretaining levee is the most economical option.
Identification of Underwater Vehicle Hydrodynamic Coefficients Using Model Tests
Volume 8: Dynamic Systems and Control, Parts A and B, 2010
Predicting the hydrodynamic coefficients of an autonomous underwater vehicle (AUV) is important during vehicle design. SUT-2 is an AUV, being developed by the Marine Engineering Research Center of Sharif University of Technology in Iran (MERC). Model tests are done in the marine engineering laboratory towing tank. In this research, hydrodynamic coefficients are calculated using model test results of an autonomous underwater vehicle. Hydrodynamic forces are also analyzed. These coefficients are used for dynamic modeling and autonomous controller design.
Design and Manufacturing Magnetic Damper and Active Control of Beam Vibrations using Eddy current
There is different methods to damp the vibration. However, the numbers of contactless methods are limited. Eddy current dampers are of these procedures. Eddy current is produced in a nonmagnetic conductive material when it is subjected to a time varying magnetic field. In this research, active and semi-active types of eddy current dampers are manufactured and input impulse responses for different damping modes are determined experimentally and numerically. The Aluminium cantilevered beam is stimulated by an eddy current impact. The stiffness and damping coefficient are derived by a reduced logarithmic method according to the time response. The response to impulse is simulated by Simulink of MATLAB and the outcomes are compared with experimental results. Both results show significant decrease in the peak of frequency responses. The results of modal semi-active experiments show the effective suppress of vibration by more than 10 dB. Experiments on the active damper demonstrate a remarkable decrease in the first and second peak of frequency spectrum and increase in bandwidth over previously used eddy current methods.
تعيين موقعيت لولههای تراشه دابل لومن در جراحی توراکس: کمپليانس بگ در مقايسه با برونکوسکوپ فيبراوپتيک
مجله دانشکده پزشکی دانشگاه علوم پزشکی تهران, 2012
Lung separation is the basis of thoracic anesthesia, which is performed by different instruments. Checking probable malpositioning of tracheal tube needs fiberoptic bronchoscopy. The aim of this study was to compare respirator suggested compliance with fiberoptic findings in detecting major tracheal tube malpositioning. Methods: A total of 256 patients undergoing thoracic surgery with double-lumen tracheal tube insertion in Imam Khomeini Hospital, Tehran, Iran, during 2010-11 were divided into three groups (n=86). We used left-sided double-lumen tube (DLT) for left or right-sided surgeries (groups 1 and 2), and right-sided DLT for left-sided surgeries (group 3). The position of the tubes was evaluated and compared using bag compliance versus fiberoptic bronchoscopy. Results: The mean age of the study population was 44.7±13.4 (16-73) years, while 155 (59.9%) were male. The sensitivity, specificity, positive and negative predictive values, and the accuracy of bag compliance test for left-sided DLT in supine position were 40% (95% CI: 20-60%), 99% (95% CI: 96-99%), 84% (95% CI: 54-94%) 92% (95% CI: 88-95%) and 92% (95% CI: 87-95%), respectively. The above-mentioned variables for lateral decubitus position respectively were 27%, 98%, 76%, 89%, and 88%. Malpositioning was more prevalent in right-sided DLTs (P=0.02). Conclusion: Based on the results of this study, and the high specificity, positive predictive value, and accuracy of bag compliance test, its use is encouraged as an alternative to fiberoptic bronchoscopy for checking DLT position, specially, in emergent surgeries or when fiberoptic bronchoscopy is unreachable due to lack of expertise or personnel.
2010
هعلاطم نيا رد يشنكاو حلاصا تيزوپماك ياه نليپورپ ـ كلات زا هدافتسا اب يسكوپا يردوپ ششوپ تاعياض ـ يلپ رد رتسا ود ردورتسـكا كـي ماجنا هچيپرام و يكيناكم صاوخ و تخير تسا هتفرگ رارق يسررب دروم اهنآ يسانش . هعلاطم تخير يم ناشن يسانش يردوـپ تاعياض هك دهد يلپ رتسب رد كلات تارذ شخپ دوبهب بجوم تهج رد ليهست بجوم و هدش نليپورپ بلاق نايرج تهج رد كلات تارذ يريگ يـم يريگ دوـش . يسكوپا زا يراع هنومن ـ يلپ نامز شيازفا اب رتسا يگدوسرف يسكوپا ندوزفا اب هك دراد يديدش صاوخ شهاك ـ يلپ رتسا عياض رد دوجوم تا يردوپ ششوپ يـلپ هـنومن رد و هداد ناشـن تفا يرتمك رايسب نازيم هب صاوخ نيا يواـح نليپورـپ 20 % ندوزـفا اـب كـلات 20 % ،تاعياـض ًابيرقت تيزوپماك تسا هدش مواقم يترارح يگدوسرف لباقم رد . تـيزوپماك رد يكيناكم صاوخ تمواقم دوبهب يگدوـسرف تارـثا رـبارب رد اـه يم سچ زا يشان دناوت نيزر يگدنب يلپ ياه سم نيا هك دشاب كلات يور رب تاعياض رد دوجوم يسكوپا و رتسا أ يصلاخان دوجو هب هجوت اب هل ياه هدننكرپ رد يزلف يم اهرميلپ يترارح يگدوسرف عيرست بجوم هك يندعم ياه تسا هيجوت لباق ،دوش . نيزر تخپ يسـكوپا ياه ـ يـلپ رتـسا بجوم ي...