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An integrated HFMEA-DES model for performance improvement of general hospitals: A case study
, Article International Journal of Quality and Reliability Management ; 2020 ; Ershadi, M. J ; Akhavan Niaki, S. T ; Sharif University of Technology
Emerald Group Publishing Ltd
2020
Abstract
Purpose: Healthcare failure mode and effect analysis (HFMEA) identifies potential risks and defines preventive actions to reduce the effects of risks. In addition, a discrete event simulation (DES) could evaluate the effects of every improvement scenario. Consequently, a proposed integrated HFMEA-DES model is presented for quality improvement in a general hospital. Design/methodology/approach: In the proposed model, HFMEA is implemented first. As any risk in the hospital is important and that there are many departments and different related risks, all defined risk factors are evaluated using the risk priority number (RPN) for which related corrective actions are defined based on experts'...
Effect of weld nugget size on overload failure mode of resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 12, Issue 3 , 2007 , Pages 217-225 ; 13621718 (ISSN) ; Asgari, H. R ; Mosavizadch, S. M ; Hoveida Marashi, P ; Goodarzi, M ; Sharif University of Technology
2007
Abstract
In the present paper, effects of welding current, welding time, electrode pressure and holding time on the weld nugget size were studied. A failure mechanism was proposed to describe both interfacial and pullout failure modes. This mechanism was confirmed by SEM investigations. In the light of this mechanism, the effect of welding parameters on static weld strength and failure mode was studied. Then, an analytical model was proposed to predict failure mode and to estimate minimum nugget diameter (critical diameter) to ensure pullout failure mode in shear tensile test. On the contrary to existing industrial standards, in this model, critical nugget diameter is attributed to metallurgical...
An integrated HFMEA-DES model for performance improvement of general hospitals: A case study
, Article International Journal of Quality and Reliability Management ; Volume 38, Issue 1 , 2021 , Pages 1-24 ; 0265671X (ISSN) ; Ershadi, M. J ; Akhavan Niaki, S. T ; Sharif University of Technology
Emerald Group Holdings Ltd
2021
Abstract
Purpose: Healthcare failure mode and effect analysis (HFMEA) identifies potential risks and defines preventive actions to reduce the effects of risks. In addition, a discrete event simulation (DES) could evaluate the effects of every improvement scenario. Consequently, a proposed integrated HFMEA-DES model is presented for quality improvement in a general hospital. Design/methodology/approach: In the proposed model, HFMEA is implemented first. As any risk in the hospital is important and that there are many departments and different related risks, all defined risk factors are evaluated using the risk priority number (RPN) for which related corrective actions are defined based on experts'...
Failure modes of RC structural elements and masonry members retrofitted with fabric-reinforced cementitious matrix (FRCM) system: a review
, Article Buildings ; Volume 12, Issue 5 , 2022 ; 20755309 (ISSN) ; Zhang, D ; Shadabfar, M ; Kontoni, D. P. N ; Iqbal, M ; Sharif University of Technology
MDPI
2022
Abstract
Much research has been conducted and published on the examination of the behavior of reinforced steel and concrete structures with a FRP system. Nevertheless, the performance of FRP differs from that of FRCM, particularly at high temperature and ultimate strength. The present study provides a review of previous research on structural elements (viz. beams, columns, arches, slabs, and walls) retrofitted with FRCM systems, taking account of various parameters, such as layers, composite types, configurations, and anchors for controlling or delaying failure modes (FMs). Additionally, this paper discussed the details of different FMs observed during experimental tests, such as crushed concrete or...
Applying PFMEA in Vehicle Axle Manufacturing Company and Presenting an Effective Model
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Ferydoon (Supervisor)
Abstract
In this thesis we illustrated PFMEA in VAMCO to evaluate effectiveness of applying this standard in this company ,though the results showed better situation but they were not significant then we launch to study the reasons of this matter and to help our survey we used other companies' knowledge via questionnaires and interviews,. After collection of data our conclusion proved that there were both problems in context and application. For solving these problems we investigated about experience of international esteemed companies and finally we decided to apply a new model in form of a software. For designing algorithm of this software we deeply focused on problems and use the recent...
On the failure behavior of highly cold worked low carbon steel resistance spot welds
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 3 , Oct , 2014 , p. 1376-1389 ; 10735623 ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Abstract
Highly cold worked (HCW) low carbon steel sheets with cellular structure in the range of 200 to 300 nm are fabricated via constrained groove pressing process. Joining of the sheets is carried out by resistance spot welding process at different welding currents and times. Thereafter, failure behavior of these welded samples during tensile-shear test is investigated. Considered concepts include; failure load, fusion zone size, failure mode, ultimate shear stress, failure absorbed energy, and fracture surface. The results show that HCW low carbon steel spot welds have higher failure peak load with respect to the as-received one at different welding currents and times. Also, current limits for...
Peak load and energy absorption of DP600 advanced steel resistance spot welds
, Article Ironmaking and Steelmaking ; Volume 44, Issue 9 , 2017 , Pages 699-706 ; 03019233 (ISSN) ; Pouranvari, M ; Salim, R. K ; Hashim, F. A ; Marashi, S. P. H ; Sharif University of Technology
Abstract
The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter...
Prediction of the failure mode of automotive steels resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 25, Issue 6 , 2020 , Pages 511-517 ; Jaderian, S ; Mazaheri, Y ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
In this study, the critical nugget size, at which the failure state in tensile shear test changed from the interfacial failure mode to the pull-out failure one, was estimated as a function of nugget and base metal hardness. The proposed approach could address the effect of various parameters involved in resistance spot welding process, such as sheet thickness, base metal chemical composition and physical properties of electrodes and sheets. The reliability of the present model was evaluated using independent experimental results. Based on the obtained results, the effect of steel composition on critical nugget diameter was found to be more important, especially for the sheets thicker than...
Service life prediction of worn contact wires under multiple failure modes
, Article Structure and Infrastructure Engineering ; 2022 ; 15732479 (ISSN) ; Mahmoodian, M ; Khaloo, A ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Contact wires are critical components of railway overhead infrastructure which provide power for trains. This paper proposes an innovative method to determine the service life of worn contact wires under three failure modes: tension, fatigue, and attrition. The tensile stress, fatigue damage, and cross-section loss of contact wire have been modelled as stochastic processes following lognormal distribution. The first-passage probability method is then used to determine the time-dependent failure probability for contact wires under each failure mode. The service life of the contact wire is determined through system reliability analysis. This method has then been applied to a case study to...
Investigation of Potential Failure Modes of Electric Submersible Pumps and Propose New Methods for Fault Diagnosis and Condition Monitoring of
Electric Submersible Pump
,
M.Sc. Thesis
Sharif University of Technology
;
Behzad, Mehdi
(Supervisor)
Abstract
Despite of many advantages, electro submersible pumps (ESP) have very high costs in maintenance. Since ESP usually operates in deep wells, it should be transported to the surface in order to malfunction. In addition, the state of ESP equipment cannot be determined because of unavailability of vibration measurement on the site. Thus, this equipment fails suddenly. This process costs a lot on country’s oil and water & wastewater industry. so in this thesis, at first, the potential failure modes (PFM) of ESPs are investigated, then proper methods are presented for condition monitoring. Finally, the presented methods are verified by experimental tests and wavelet analysis. The results show that...
Elastoplastic-Damage Model for Hydrostatic Sensitive Metals
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
In this work a model of anisotropic plastic-damage , using thermodynamic framework is going to be proposed. This model was applied in simulating metals behavior. Using this model, besides plastic behavior will help us observe the impact of growth and coalescence of microdefects of material. Generally anisotropic damage application can demonstrate a more realistic behavior in material modeling. To get consistency equation and microdefects growth condition, irreversible thermodynamic will be used. Firstly, the plastic relationships have been written in undamaged configuration; then, using relationships between damaged and undamaged configuration, plastic equations are generalized to damage...
Failure threshold determination of rolling element bearings using vibration fluctuation and failure modes
, Article Applied Sciences (Switzerland) ; Volume 11, Issue 1 , 2021 , Pages 1-18 ; 20763417 (ISSN) ; Feizhoseini, S ; Addin Arghand, H ; Davoodabadi, A ; Mba, D ; Sharif University of Technology
MDPI AG
2021
Abstract
One of the challenges in predicting the remaining useful life (RUL) of rolling element bearings (REBs) is determining a proper failure threshold (FT). In the literature, the FT is usually assumed to be a constant value of an extracted feature from the vibration signals. In this study, a degradation indicator was extracted to describe damage to REBs by applying principal component analysis (PCA) to their run-to-failure data. The relationship between this degradation indicator and the vibration peak was represented through a joint probability distribution using statistical copula models. The FT was proposed as a probability distribution based on the fluctuation increase in the vibration trend....
Force-displacement model for solid confined masonry walls with shear-dominated failure mode
, Article Earthquake Engineering and Structural Dynamics ; Volume 46, Issue 13 , 2017 , Pages 2209-2234 ; 00988847 (ISSN) ; Bakhshi, A ; Ghannad, M. A ; Sharif University of Technology
Abstract
This paper addresses the behavior of confined masonry walls with dominating shear failure mode in walls. For this purpose, failure modes of these walls are classified in details. For each failure mode, complete set of analytical-based relations for deriving parameters related to backbone curves is introduced. Calibrated finite element analyses are utilized as a benchmark for verification of some of the assumptions. The results of the proposed relations are compared with those of several Iranian and non-Iranian experimental data. Sensitivity analysis is performed in order to understand the effects of important behavioral characteristics of these walls. The results of this study indicate that...
Efficient health monitoring of buildings using failure modes and effects analysis case study: Air handling unit system
, Article Journal of Building Engineering ; Volume 29 , 2020 ; Aramoun, F ; Saboohi, Y ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
System health management based on condition monitoring is of great value and significance for improving system performance and reliability. As more data from condition monitoring is obtained, the efficiency of system health monitoring improves. However, increasing the amount of data by installing new sensors on system components is restricted by a variety of factors such as budget, weight and space allowance. Therefore, sensor selection in the most optimal manner in order to achieve maximum valuable information from system is an important issue. In this study, a novel concept is introduced that can be used in sensor combination optimization problems. This concept employs failure modes and...
Failure Modes and Effects Analysis (FMEA) for wind turbines
, Article International Journal of Electrical Power and Energy Systems ; Volume 32, Issue 7 , 2010 , Pages 817-824 ; 01420615 (ISSN) ; Oraee, H ; Tavner, P. J ; Sharif University of Technology
2010
Abstract
The Failure Modes and Effects Analysis (FMEA) method has been used to study the reliability of many different power generation systems. This paper now applies that method to a wind turbine (WT) system using a proprietary software reliability analysis tool. Comparison is made between the quantitative results of an FMEA and reliability field data from real wind turbine systems and their assemblies. These results are discussed to establish relationships which are useful for future wind turbine designs. The main system studied is an existing design 2 MW wind turbine with a Doubly Fed Induction Generator (DFIG), which is then compared with a hypothetical wind turbine system using the Brushless...
Fuzzy ANN Approach to Support Independent Failures of Rotary Equipment Based on Vibration, Temperature Parameters-Case Study: A Centrifugal Pump in offshore Industry
, M.Sc. Thesis Sharif University of Technology ; Ghaemi Osgouie, Kambiz (Supervisor) ; Ebrahimi Pour, Vahid (Co-Advisor)
Abstract
Pump operating problems may be either hydraulic or mechanical and there is interdependence between the failure diagnoses of these two categories. Consequently, a correct diagnosis of a pump failure needs to consider many symptoms including hydraulic or mechanical causes. Nonlinear, time-varying behavior, and imprecise measurement information of the systems makes it difficult to deal with pump failures with precise mathematical equations, while human operators with the aid of their practical experience can handle these complex situations, with only a set of imprecise linguistic if-then rules and imprecise system states, but this procedure is time consuming and needs the knowledge of human...
Structural Reliability in Aging Aircraft Process
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Aging Aircraft with life extension, Conversion or replacing them with new aircrafts are of the decisions in front of airliners after their retirement. Decision making for repairing aircraft to increase its life is depended upon various parameters like its cost and reliability. The thesis evaluated the reliability of the structure of an aircraft before and after life extension. For this purpose, using the statistical data, the predominant failure modes are studied and based on these failure modes the border between fracture and health of the structure which is called limit state function is defined. After this using first order reliability method (FORM), the probability of the failures is...
Evaluation of the Effects of the Flanges on the Strength and the Failure Modes of Masonry Walls
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
Most of the previous studies as well as codes regarding unreinforced masonry walls overlook the effects of perpendicular walls – called flanges – on their behavior; in reality, these transversal walls significantly affect ultimate strength, stiffness, drift capacity, and most importantly the failure modes. In this thesis, numerical finite element modeling was employed in order to investigate the impact of flanges on unreinforced masonry walls subjected to gravity loads and lateral pushover excitation. Moreover, a sensitivity analysis was conducted concerning the effect of different boundary conditions and axial load ratios on failure mode and crack pattern of the flanged walls. First, the...
Microstructure and failure behavior of dissimilar resistance spot welds between low carbon galvanized and austenitic stainless steels
, Article Materials Science and Engineering A ; Volume 480, Issue 1-2 , 2008 , Pages 175-180 ; 09215093 (ISSN) ; Pouranvari, M ; Amirabdollahian, S ; Abedi, A ; Goodarzi, M ; Sharif University of Technology
2008
Abstract
Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode. © 2007 Elsevier B.V. All rights reserved
A fuzzy project buffer management algorithm: a case study in the construction of a renewable project
, Article International Journal of Construction Management ; 2022 ; 15623599 (ISSN) ; Vanhoucke, M ; Khalilzadeh, M ; Amiri, M ; Shadrokh, S ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
One of the major problems with projects is that they are not completed according to schedule. Uncertainty always exists at the heart of real-world project scheduling problems. This paper introduces a fuzzy project buffer management (FPBM) algorithm which is a combination of the adaptive procedure with resource tightness (APRT) and fuzzy failure mode and effects analysis (FFMEA) methods. This paper aims to present an efficient model for project buffer sizing by taking FFMEA into account to reach a more realistic schedule. In this research, for increasing the efficiency of the APRT method, the FFMEA technique is simultaneously applied with them. This research was carried out as a case study in...