scholarly journals ПОШКОДЖЕННЯ ВІД ЩІЛИННОЇ КОРОЗІЇ В КОНСТРУКЦІЯХ ЛІТАКІВ ТА ЇХ ВИЯВЛЕННЯ

2019 ◽  
pp. 143-155
Author(s):  
Микола Савович Топал ◽  
Володимир Михайлович Андрющенко
Keyword(s):  
Optical Sensors ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Corrosion Damage ◽  
Fatigue Loading ◽  
Chloride Ions ◽  
Integrated Sensor ◽  
Aluminum Ions ◽  
Internal Structures ◽  
And Control

Presented examples of destruction of aircraft designs due to corrosion of metals under conditions of fatigue loading. It is shown that slit corrosion, which is an increase in corrosion in crevice and gaps between two metals, as well as in places of untight contact of metal with a nonmetallic material resistant to corrosion, leads to the appearance of corrosion products in the joints of the skin with the power suite, which supports it , which can lead to the swelling of some elements of the joint relative to other elements and provoke the tearing off of the heads of rivets with the further development of fatigue cracks and the destruction of aircraft structures. Shown, that visual inspection is not always effective for the detection of corrosion damage, and sometimes impossible, for example, in closed internal structures. New developments in the field of sensors and equipment for the detection of corrosive substances and corrosion damage are presented. Among them is information on the sensor (organic-ceramic composite) containing the conducting complex. When the composite is exposed to water liquids, its conductivity is lost. When the composite dries, the sensor reaches its initial values of resistance. Information is provided on the optical sensor for detecting corrosion in the construction of the airframe. This sensor is based on the remote detection of aluminum ions formed during corrosion. The development of a multi-parameter integrated sensor for assessing the structural integrity of aluminum alloys, the recording of the concentration of chloride ions, the release of hydrogen, changes in humidity and degradation of the material is presented. Information is provided on fluorescence-based optical sensors used to detect specific ions such as aluminum, indicating the beginning of corrosion of an aluminum alloy. Information is provided on the development of advanced digital X-ray methods for the detection of corrosion in the design of aircraft. The conclusion is made on the necessity of combining visual control and control with the use of means and methods for detecting corrosive substances and corrosion damage.

Environment-assisted corrosion damage of steel bridges: a conceptual framework for structural integrity

2020 ◽  
Vol 38 (1) ◽  
pp. 49-65
Author(s):  
Nirosha D. Adasooriya ◽  
Tor Hemmingsen ◽  
Dimitrios Pavlou
Keyword(s):  
Conceptual Framework ◽  
Structural Integrity ◽  
Corrosion Damage ◽  
Steel Bridges ◽  
Lessons Learned ◽  
Control Measures ◽  
Steel Bridge ◽  
St52 Steel ◽  
Corrosion Of Steel ◽  
And Control

AbstractA framework is presented in this paper to assess the structural integrity of steel bridges for environment-assisted corrosion damage. Forms of corrosion of steel bridges and their effects, possible locations of occurrence, and most appropriate inspection techniques are first studied and the lessons learned from past steel bridge failures are discussed. A review of the corrosion damage of steel bridges, including causes, effects, and control measures, is presented along with guidelines for the recognition and investigation of environment-assisted cracking (EAC) of steel bridges. Experimental approaches are proposed to investigate the EAC of structural steel. The proposed approach is used to investigate the EAC susceptibility of cathodically protected ST52 steel. In addition, the feasibility of the proposed approach is tested. Hence, the conceptual framework is proposed. The framework aims to support the inspection and maintenance practices of steel bridges.

Managing Fatigue from Corrosion Pits in Aircraft Structures

2014 ◽  
Vol 891-892 ◽  
pp. 261-266 ◽  
Author(s):  
Lorrie Molent
Keyword(s):  
Pitting Corrosion ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Cost Driver ◽  
Major Advance ◽  
Corrosion Prevention ◽  
Management Plans ◽  
Corrosion Pits ◽  
And Control ◽  
Analytical Tools

Despite corrosion prevention or protection schemes/treatments and corrosion prevention and control plans, in-service corrosion does occur and has the potential to impact the structural integrity of aircraft. Whilst the fatigue management of the aircraft is generally well understood as reflected in typical Aircraft Structural Integrity Management Plans (ASIMP), which in some cases contain environmental degradation plans, limited provision beyond find and fix exists for corrosion repair. Thus the repair of corrosion can be a major through life cost driver as well as an aircraft availability degrader. This find and fix policy exists largely because tools are currently considered too immature to accurately assess the structural significance of corrosion when it is detected. In this paper a process is described which should allow an alternative to the current find (corrosion) and fix philosophy for pitting corrosion. The method is intended to maintain a probability of failure consistent with ASIMP structural certification requirements for fatigue cracks initiating from corrosion pits for a specific period. Unanticipated maintenance costs significantly more than planned maintenance. Thus delaying the repair of pitting corrosion until the next scheduled maintenance, should save considerable resources and improve aircraft availability. The development of analytical tools capable of accurately assessing the effect of corrosion on the durability of a structure would be considered a major advance for the ASIMP.

Sustainment Engineering and Residual Life Prediction of Aluminum Alloy Structure at Service Environment

2013 ◽  
Vol 661 ◽  
pp. 124-127
Author(s):  
Qian Zhang ◽  
Gang Liu ◽  
Cun Li Wu
Keyword(s):  
Aluminum Alloy ◽  
Life Prediction ◽  
Structural Integrity ◽  
Residual Life ◽  
Fatigue Cracks ◽  
Corrosion Damage ◽  
Life Extension ◽  
Alloy Structure ◽  
Service Environment ◽  
Residual Life Prediction

The effects of service environment will cause corrosion damage and fatigue cracks to initiate and grow, compromising structural integrity of the aircraft aluminum alloy structure. To develop an effective inspection and maintenance-scheduling program that takes advantage of life extension technologies, the sustainment engineering and residual life prediction method of aging aircraft aluminum alloy structure at service environment was proposed in this article. The whole algorithm of the sustainment engineering was described and the included situations of repairs, corrosion damage and widespread fatigue damage on aircraft structures were presented. At last, combining the results of FEM calculation with the AFGROW software of crack growth analyses, the residual life of corroded aluminum alloy structure was estimated.

scholarly journals Management of Airframe In-Service Pitting Corrosion by Decoupling Fatigue and Environment

2021 ◽  
Vol 2 (3) ◽  
pp. 493-511
Author(s):  
Loris Molent ◽  
Russell Wanhill
Keyword(s):  
Corrosion Fatigue ◽  
Pitting Corrosion ◽  
Structural Integrity ◽  
Corrosion Damage ◽  
Fatigue Loading ◽  
Cost Driver ◽  
Service Environments ◽  
Corrosion Pits ◽  
The Impact ◽  
Fatigue Corrosion

Corrosion-induced maintenance is a significant cost driver and availability degrader for aircraft structures. Although well-established analyses enable assessing the corrosion impact on structural integrity, this is not the case for fatigue nucleation and crack growth. This forces fleet managers to directly address detected corrosion to maintain flight safety. Corrosion damage occurs despite protection systems, which inevitably degrade. In particular, pitting corrosion is a common potential source of fatigue. Corrosion pits are discontinuities whose metrics can be used to predict the impact on the fatigue lives of structural components. However, a damage tolerance (DT) approach would be more useful and flexible. A potential hindrance to DT has been the assumption that corrosion-induced fatigue nucleation transitions to corrosion fatigue, about which little is known for service environments. Fortunately, several sources indicate that corrosion fatigue is rare for aircraft, and corrosion is largely confined to ground situations because aircraft generally fly at altitudes with low temperature and humidity Thus, it is reasonable to propose the decoupling of corrosion from the in-flight dynamic (fatigue) loading. This paper presents information to support this proposition, and provides an example of how a DT approach can allow deferring corrosion maintenance to a more opportune time.

scholarly journals The size effect of rebars, on the structural integrity of reinforced concrete structures, which are exposed to corrosive environments

2018 ◽  
Vol 188 ◽  
pp. 03009
Author(s):  
Argyro Drakakaki ◽  
Charis Apostolopoulos
Keyword(s):  
Reinforced Concrete ◽  
Structural Integrity ◽  
Chloride Concentration ◽  
Seismic Energy ◽  
Corrosion Damage ◽  
Chloride Ions ◽  
Exposed Surface ◽  
Plastic Hinges ◽  
Corrosive Environments ◽  
Critical Regions

The goal of the present study is to mention the importance of underestimation of the corrosion damage developed in critical load bearing areas, on the column bases, where formation of plastic hinges is attended, mainly during strong seismic events (Figure 1). In such cases, plastic hinges are expected to absorb the seismic energy, owed to seismic vibration. However, chloride induced corrosion is responsible for significant degradation of concrete infrastructures located in coastal areas. Forecasting the life expectancy of such structures, in corrosive environments, is a challenge in engineering, given the fact that existing internal, external, as well as subcutaneous defects, in combination with the aggressive environmental factors, may be responsible for the development of subcutaneous damage on steel reinforcement [1], which may diminish the tolerance of the critical regions of the structures. Moreover, it is widely known that penetration of chloride ions into reinforced concrete varies according to its porosity and its permeability, however, the major factor for corrosion initiation is the threshold of chloride concentration, which strongly depends on the exposed surface area of steel. In the present experimental study, the variation of corrosion damage, on bare specimens, was evaluated and correlated with the geometry of the exposed surface of steel in corrosion [2]. Finally, a correlation between short bare specimens and the “injured” areas of the long embedded specimens is estimated as well.

scholarly journals Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4380
Author(s):  
Alirio Andres Bautista Villamil ◽  
Juan Pablo Casas Rodriguez ◽  
Alicia Porras Holguin ◽  
Maribel Silva Barrera
Keyword(s):  
Crack Propagation ◽  
Structural Integrity ◽  
Crack Propagation Rate ◽  
Fatigue Loading ◽  
Propagation Rate ◽  
Operating Conditions ◽  
Impact Testing ◽  
Mode I ◽  
Mode I Crack ◽  
Constant Amplitude

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

scholarly journals The durability of flexible eddy current array (FECA) sensors in harsh service environments

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yujian Song ◽  
Tao Chen ◽  
Ronghong Cui ◽  
Yuting He ◽  
Xianghong Fan ◽  
...  
Keyword(s):  
Eddy Current ◽  
Fatigue Cracks ◽  
Radiation Environment ◽  
The Finite Element Method ◽  
Integrated Sensor ◽  
High Durability ◽  
Vibration Experiment ◽  
Service Environments ◽  
Salt Fog Corrosion ◽  
Salt Fog

AbstractSensors for structural health monitoring (SHM) need to be permanently integrated on structures and withstand the harsh service environments, which has been a big challenge for the application of SHM in aircrafts. This paper focuses on the durability of flexible eddy current array (FECA) sensors in harsh service environments of aircrafts, including vibration environment and several typical exposed environments. First, a kind of FECA sensor is illustrated and its integration method is proposed. Moreover, in order to study the durability of the sensor in vibration environment, the modal analysis is performed by the finite element method. According to the simulation results, the durability experiment in vibration environment is carried out under the fourth order vibration mode, which makes the sensor suffer the harshest vibration loads. During the vibration experiment, output signals of the sensor keep stable and the sensor is well bonded to the structure, which shows the integrated sensor has high durability in vibration environment. Finally, the durability of integrated sensors is separately tested in three exposed environments, including salt fog corrosion environment, fluid immersion environment, as well as hygrothermal and ultraviolet-radiation environment. After these environmental exposure experiments, all sensors are well bonded to structures and can effectively monitor fatigue cracks, which shows great durability. Therefore, FECA sensors can survive in harsh service environments of aircrafts, which provides important support for the engineering applications of FECA sensors.

Relaxation of Residual Stresses in and around Mechanical Fasteners Due to Fatigue Loading

2006 ◽  
Vol 524-525 ◽  
pp. 153-158 ◽  
Author(s):  
Matthew E. Fox ◽  
Philip J. Withers
Keyword(s):  
Residual Stresses ◽  
Hoop Stress ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Far Field ◽  
Synchrotron Diffraction ◽  
Fastener Hole ◽  
Single Plate ◽  
Mechanical Fasteners ◽  
Hoop Stresses

The residual stresses around clearance-fit mechanical fasteners have been found to be similar to those around cold expanded holes where compressive hoop stresses close to the fastener hole are balanced by far-field tensile stresses. This compressive zone has been shown to prolong fatigue lifetimes around fastener holes. Constant amplitude fatigue loading was applied to single plate rivet specimens for varying numbers of cycles to investigate the redistribution of these stresses after fatiguing. Synchrotron diffraction was used to map the evolution of the residual stresses around the rivets. Little change in the hoop stress local to the rivets occurred until visible fatigue cracks were observed suggesting that relaxation of these stresses is due to the cracks rather than their cause.

scholarly journals Integrity Management of Marine Structures; With Emphasis on Design for Structural Robustness

2018 ◽  
Author(s):  
Torgeir Moan
Keyword(s):  
Structural Damage ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Design Standards ◽  
Limit States ◽  
Fabrication Errors ◽  
Integrity Management ◽  
Operational Errors ◽  
And Control

Based on relevant accident experiences with oil and gas platforms, a brief overview of structural integrity management of offshore structures is given; including an account of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. The focus is on developing research based design standards for Accidental Collapse Limit States to ensure robustness or damage tolerance in view damage caused by accidental loads due to operational errors and to some extent abnormal structural damage due to fabrication errors. Moreover, it is suggested to provide robustness in cases where the structural performance is sensitive to uncertain parameters. The use of risk assessment to aid decisions in lieu of uncertainties affecting the performance of novel and existing offshore structures, is briefly addressed.

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