Sharif Digital Repository

This paper presents, various parameters of the composite patch for repairing and reinforcement the damaged composite pipe have been investigated. There are various parameters of the composite patch such as Laminate orientation, length, width, material and thickness of the patch. by changing these parameters in each analysis and comparing the results, the optimal patch for the damaged pipe is determined  

Due to well mechanical properties and high resistance to environmental conditions, metal pipes are used to transport oil and gas products, water and sewage, as well as hydraulic systems in aircraft or aerospace systems. Therefore, maintenance of oil and gas transmission lines in energy-related industries and pressurized tanks in the aviation industry has always been a concern of engineers. Due to the problems of old methods for repairing damaged pipelines or aerial structures, it seems necessary to provide new, safe and cheap methods for repairing them. Various engineering standards for pipelines and their repairs have been presented so far which have analytical solutions to determine the... 

An aerial structure can be at the disposal of the owners of damage or intellectual property during its lifetime, under the supervision of static and dynamic loads and providing information in the field of recognizing temperature, humidity and environmental pressure with high-speed gradient. Capable Composite patches are used to repair damaged areas. Composite patches have unique properties such as high strength to weight ratio and corrosion resistance. In structures modified with a composite patch, various failures occur during loading, including: fiber breakage, matrix fracture, separation of fibers from the matrix or the latest patch from the main structure and failure of the metal... 

In this project, first of all the Axiomatic Design approach, then the Scarf Repair and papers about it so far have been explained. Then Scarf Repair design with Axiomatic Design approach has been done and at the end a damaged plate sample has been repaired with developed way. Axiomatic Design is a systematic approach to design or judge existing designs for choosing the best design. This approach, says that a good design is the one that satisfys Independence and Information axioms. Independence axiom says that the better design is the one that its functional requierments are independent from each other and Information axiom says that from designs that satisfy the Independence axiom, the... 

Nowadays, composite pressure vessels are used in different industries that are deal with high pressure technologies such as aerospace, petroleum, gas and petrochemical. Composite pressure vessels structural health is checked in specified time duration with respect to standard processes. If vessels structure is damaged, its condition should reconciling with standards. If the damage is repairable, composite pressure vessel will repair, else it should be replaced. The companies repair these types of damages only in several outer layers of vessel. If the damage is deeper than a specific value, it is unusable. The purpose of this thesis is composite patch repair design on damaged composite... 

The phenomenon of aging causes a great deal of damage to the airborne structures for which there is a specific maintenance instruction, or if an unexpected damage occurs in specific area of a structure, this damage must be repaired and a special repair process must be designed for it. However, due to the diversity of damages and also variations of the implemented loads, the load is transferred to other structural elements, hence, it is necessary to extend the life of the structure in order to identify these loaded elements and reinforce the applied forces. First, this phenomenon involves a design of a large number of metal patches, where a large number of drills have to be made in the body... 

Application of composite patches in repair of damaged/aged aircraft structures is one of the most popular repairing methods in aerospace engineering and because of its advantages the use of this type of repair is increasing today. However, to use these patches in life extension of aged aircraft, the added weight to the structure should be strictly controlled. This could be best done if achieving the optimum and smart design by using optimization and structural health monitoring methods. These two concept about pre-designed of composite patch repair are investigated in this thesis. The simulation by Abaqus software and experimental results and tests will be used for this purpose. In first... 

Turbochargers are industrial devices that widely are used in aviation, marine and automotive industry. Manufacturing cost and technology of their components vary according to their application fields. One of the most important components of these devices is turbine wheel, which needs to be solid, strong and have a high resistance in critical extraordinary conditions. In these days, it can be seen that superalloys are used remarkably in manufacturing of turbine wheels. When this part of turbine is damaged due to some different reasons, turbine wheel must be quit of circle Process according to repair instructions. In these conditions either turbine must be repaired or replaced by a new one;... 

When today’s aircrafts reach the end of their service lifes, fatigue cracks are found to have developed along rivet holes and other highly stressed regions of the aircraft. In order to extend life of these aircrafts, repairs have been made to arrest these cracks. Composite repair patches provide an innovative repair technique, which can enhance the way aircrafts are maintained. In this thesis, composite patch design is presented based on axiomatic design technique. Axiomatic design is investigated design methodology for large or complex system design. Tools to enable successful application of axiomatic design are expressed as axioms and process for axiomatic system design. The patch design... 

Today, the material selection process plays an important role in all engineering design branches. Generally, in transition from concept design to detail design, designers and engineers need to find specific materials to optimize performance of the systems. There are introduced nearly 80000 engineering materials up to now, i.e. metallic alloys, composite materials, plastics, ceramics, glass and etc. These large amounts of materials and the wide range of manufacturing processes causes engineers always seek new material selection methods. In material selection it’s require to consider advantages, restrictions, necessities of method and this phenomenon appear because of design problem that... 

The main purpose of this text is to develop a method for health monitoring of patch-repaired structures. The method consists of usage of piezoelectric wafer active sensors (PWAS) in the mean of stress waves in plate-like structures and processing the obtained results gathered from these sensors using finite element method. During this analysis, effect of different parameters has been investigated by sensitivity analysis methods. The main kind of stress waves that used are lamb wave of different kind. The behavior of main structure due to propagation of symmetric and anti-symmetric modes of lamb wave was investigated. Beginning with finding the results of un-damaged and un-repaired... 

Debugging programs is a time-consuming and error-prone activity. So far, much research has tried to repair the programs automatically. Many of them try to change the location of the fault for a faulty program that fails at least one of its test cases so that all cases in the test suite pass. However, in real projects, the test suite is usually not enough, and the methods that aim to pass the test suite, often lead to the production of incorrect repairs, which is known as overfitting or weak test suite. In this regard, attention to methods based on program specification and the use of static code analysis have shown promising results. In this thesis, a method is presented that recommends... 

Cloud and distributed storage systems can provide large-scale data storage and high data reliability by adding redundancy to data. Redundant data may get lost due to the instability of distributed systems such as hardware failures. In order to maintain data availability, it is necessary to regenerate new redundant data in another node, referred to as a newcomer and this process reffered to repair process. Repair process is expected to be finished as soon as possible, because the regeneration time can influence the data reliability and availability of distributed storage systems. In this context, the general objective is to minimize the volume of actual network traffic caused by such... 

Assessing the seismic loss incurred by structures post-earthquake, or to evaluate structural performance vis-à-vis potential seismic events, constitutes an imperative and pivotal measure for informed decision-making geared towards enhancing community resilience. However, large-scale assessments targeting risk analysis at citywide levels necessitate significant temporal and computational resources. To expedite this process and mitigate associated costs, this study introduces a machine learning-based methodology for estimating seismic loss and repair time of special steel moment-resisting frames. Six distinct machine learning models were trained based on results derived from nonlinear time... 

The repair of pipes that deteriorate over time or due to various factors is a critical issue in engineering. Consequently, effective and novel repair methods, especially using FRP (Fiber-Reinforced Polymer) composites, have gained significant importance. In this research, the repair and connection of pipes using FRP are examined. In the pipe repair section, through hydrostatic testing, various factors such as the damaged area, the number of sharp corner points, the width of the sheets, the number of layers, and the pre- stress condition of the FRP are studied for their impact on the pipe's ultimate pressure tolerance. Also, in the pipe connection section, with hydrostatic tests, the ultimate... 

This research investigates the impact of a new type of latex called Carboxylated Styrene Butadiene Rubber (XSBR) on the mechanical properties and permeability of latex-modified concrete. Latex-modified concretes offer numerous advantages, but a key challenge is the reduction in compressive strength, hindering their widespread use, especially in structural applications. In the initial phase of this study, the influence of XSBR latex is examined, and four different dosages of XSBR latex are incorporated into concrete. Keeping other parameters constant, especially the water-to-cement ratio, a comparison is made between different mix designs. All specimens are subjected to two different curing... 

This study aims to investigate the cost and time uncertainty of the seismic repair process of structural elements in earthquake damaged buildings in Iran. In order to identify the most important type of structural system in the country, using the method of analytic hierarchy process (AHP), 39 activists in the field of construction were interviewed. Based on the results, in buildings with reinforced concrete materials, concrete moment frames and in buildings with steel materials, steel moment frames and braced steel braced frames are the most important structural systems. By selecting the structural component of lateral load-bearing in each of the mentioned structural systems and considering... 

The development of the methods to evaluate the seismic resilience of communities, infrastructures, and structures has attracted many researches. To estimate the resilience with accuracy, developing a model that can simulate the events during the recovery time is very important. For the same, modelling the aftershocks with their accumulative effects on the damaged buildings during the recovery time has been the main focus of the current study. The proposed approach to simulate the aftershocks’ effect utilizes the Monte-Carlo sampling, in which each sample includes the two following steps. The first step is the simulation of the cumulative damage caused by the mainshock-aftershocks sequence... 

Occurrence of earthquakes constantly has and still causes damage, human casualties and financial loss around the globe. Therefore finding a solution which enables structures to withstand destructive earthquakes while sustaining the least possible damage to their primary elements, would prove invaluable. In conventional connections of moment-resisting frames, dissipation of seismic energy is accomplished by development of plastic deformations at pre-determined hinge locations on beam and columns, which means damage to these elements is deemed both reasonable and acceptable. However, recently “damage avoidance” principle has recieved close attention, where non-linear behaviour manifests itself... 

In this research, seismic loss of eccentrically braced frame buildings is assessed by using reliability methods. For this end, first, Bayesian linear regression is utilized to characterize the epistemic uncertainty of the problem in the form of damage models. The input of these models are mechanical and physical properties of the components, and the outputs are damage ratios. In the second step, by using the developed models and the comprehensive library of probabilistic models of Rt, reliability analysis is conducted on 4, 8, and 16 stories building located in San Jose. The limit state function is seismic loss, including repair loss, collapse loss, and demolition loss, and analysis method...