scholarly journals EVALUATION OF FATIGUE LIFE AND SERVICE LIFE OF THE BOAT BODY OUTER COMPOSITE SKIN

2021 ◽  
Vol 13 (6) ◽  
pp. 858-866
Author(s):  
Vitaly E. Strizhius ◽  
Keyword(s):  
Fatigue Life ◽  
Service Life

scholarly journals Fatigue performance of nanoclay filled glass fiber reinforced hybrid composite laminate

2017 ◽  
Author(s):  
◽  
John Olumide Olusanya
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Glass Fiber ◽  
Residual Strength ◽  
Composite Structures ◽  
Fatigue Performance ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Glass Fiber Reinforced

In this study, the fatigue life of fiber reinforced composite (FRC) materials system was investigated. A nano-filler was used to increase the service life of the composite structures under cyclical loading since such structures require improved structural integrity and longer service life. Behaviour of glass fiber reinforced composite (GFRC) enhanced with various weight percentages (1 to 5 wt. %) of Cloisite 30B montmorillonite (MMT) clay was studied under static and fatigue loading. Epoxy clay nanocomposite (ECN) and hybrid nanoclay/GFRC laminates were characterised using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties of neat GFRC and hybrid nanoclay/GFRC laminates were evaluated. Fatigue study of the composite laminates was conducted and presented using the following parameter; matrix crack initiation and propagation, interfacial debonding, delamination and S–N relationship. Residual strength of the materials was evaluated using DMA to determine the reliability of the hybrid nanoclay/GFRC laminates. The results showed that ECN and hybrid nanoclay/GFRC laminates exhibited substantial improvement in most tests when compared to composite without nanoclay. The toughening mechanism of the nanoclay in the GFRC up to 3 wt. % gave 17%, 24% and 56% improvement in tensile, flexural and impact properties respectively. In the fatigue performance, less crack propagations was found in the hybrid nanoclay/GFRC laminates. Fatigue life of hybrid nanoclay/GFRC laminate was increased by 625% at the nanoclay addition up to 3 wt. % when compared to neat GFRC laminate. The residual strength of the composite materials revealed that hybrid nanoclay/GFRC showed less storage modulus reduction after fatigue. Likewise, a positive shift toward the right was found in the tan delta glass transition temperature (Tg) of 3 wt. % nanoclay/GFRC laminate after fatigue. It was concluded that the application of nanoclay in the GFRC improved the performance of the material. The hybrid nanoclay/GFRC material can therefore be recommended mechanically and thermally for longer usage in structural application.

A life test method and result analysis for slewing bearings in wind turbines

2015 ◽  
Vol 229 (18) ◽  
pp. 3499-3514 ◽  
Author(s):  
Haiyong Zong ◽  
Hua Wang ◽  
Shuhua Tian ◽  
Xuehai Gao
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Wind Turbines ◽  
Test Method ◽  
Test Equipment ◽  
Life Test ◽  
Complex Load ◽  
Slewing Bearing ◽  
Remaining Service Life ◽  
Slewing Bearings

Slewing bearings generally consist of the rotational connection between two substructures and are usually used for complex load at very low speeds. If the slewing bearing has some faults during the working lifecycle, the machine will have to be stopped and the slewing bearing will be disassembled for checking the internal surface damage of the rings or rolling elements to prevent serious accidents. However, this is a very difficult process and will cost a lot of manpower, time, and money. Although there is a large number of traditional or modern techniques used widely in general bearings, they may not be able to predict the remaining service life of slewing bearings precisely due to the huge difference between the general bearings and the slewing bearings, thus, the experiments are the most effective and reliable methods. In this paper, a special test table for slewing bearings applied in wind turbine generators is presented and an accelerating fatigue life test method based on the test equipment is proposed to study the fatigue properties and predict the remaining service life of the slewing bearings used in wind turbines. It is shown that the presented test equipment can realistically reflect the state of slewing bearings under the actual working conditions. What’s more, the experimental results show that the proposed method is conservative and provides a more accurate prediction of the fatigue life for the slewing bearings and also can meet the high reliability requirements of the slewing bearings in wind turbines.

Effects of Carbon Fibre Geogrid Reinforcement on Propagation of Cracking in Pavement and Augmentation of Flexible Pavement Life

2014 ◽  
Vol 891-892 ◽  
pp. 1533-1538 ◽  
Author(s):  
Amir Barry Dizaj ◽  
Hasan Ziari ◽  
Mahmood Ahmadi Nejhad
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Crack Propagation ◽  
Carbon Fibre ◽  
High Speed ◽  
Flexible Pavement ◽  
Fatigue Specimen ◽  
Four Point Bending ◽  
Bending Loading

Most of the distresses in flexible pavement are due to cracking and rutting. Geogrids distribute the street and loads to adequate area and cause augmentation bearing capacity. This project surveys the function of carbon and Glass fiber Geogrids on Delay of Crack propagation in flexible pavement and placement configuration in pavement structure. Four point bending loading applied to beams with dimension 50.8*63.5*381 mm and 6.5 mm tolerance (AASHTO TP8-96). According to the received specimen from cutting slabs of case study toward chart fatigue life, for each condition reinforced and unreinforced beams 3 sample in 4-strain level were experimented. Simulatedrepeated loading with a frequency 10 Hz simulate high-speed traffic was applied to beam fatigue specimen. Based on definition (AASHTO T321-07) assumed achieving to 50% first bending stiffness for end of the fatigue life indicate a significant reduction in the rate of crack propagation in reinforced samples with carbon geogrids compared to unreinforced ones, augmentation service life is up to 3.5fold and placing the geogrid at a one-third depth of overlay thickness from the bottom provide the maximum service life.

Numerical Investigation on Fatigue Problem of Cable Net Structure of Five-Hundred-Meter Aperture Spherical Radio Telescope

2014 ◽  
Vol 936 ◽  
pp. 1351-1355 ◽  
Author(s):  
Peng Jiang
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Active Control ◽  
Radio Telescope ◽  
Stress Amplitude ◽  
Stress Range ◽  
Relative Standard ◽  
Reflector Surface ◽  
Reflector System ◽  
Residual Fatigue

The reflector of Five-hundred-meter Aperture Spherical radio Telescope (FAST) is supported by cable-net structure, so that to enable its reflector surface to form a paraboloid from a sphere in real time through active control. However, such form-changing operation would lead to about 500MPa stress range for the cable-net structure. Such stress range is nearly twice as much of that defined by the relative standard. So the cable-net structure is the most critical and expendable part of FAST reflector system. So, the service life of FAST would directly depend on the residual fatigue life of its cable-net structure. The present paper would make an effort to find a more appropriate deformation strategy to decrease the stress amplitude of the cable during form-changing operation.

scholarly journals Design of circular flexible plates under of corrosion wear

2021 ◽  
Vol 263 ◽  
pp. 03007
Author(s):  
Vladimir Mavzovin ◽  
Igor Ovchinnikov
Keyword(s):  
Fatigue Life ◽  
Optimal Design ◽  
Service Life ◽  
Quadratic Programming ◽  
Sequential Quadratic Programming ◽  
Minimax Problem ◽  
Corrosive Wear ◽  
Optimal Thickness ◽  
Programming Technique ◽  
Metal Structures

The problems of optimal design of metal structures are usually formulated as the problem of finding such values of the selected parameters of structures that provide the smallest (or largest) value of the selected optimality criterion in the area of admissible design solutions. In most works on the optimization of metal structures, parametric problems are considered, limited by the preliminary assignment of a constructive form with the possibility of changing its parameters. To solve these problems, both deterministic and probabilistic optimization models can be used. A deterministic problem of optimal design of flexible round metal plates exposed to the combined action of a load and an aggressive environment causing corrosive wear of one of the plate surfaces is considered. A feature of the statement is that it takes into account the effect of the stressed state of the plates on the kinetics of their corrosive wear. Due to the insufficient efficiency of random search methods, the sequential quadratic programming technique is used. Two formulations of the optimal design problem are formulated, which are reduced to the minimax problem. 8 optimization projects were considered, their comparative analysis was carried out. It is shown that the realization of the found optimal thickness profiles leads either to a significant decrease in the stress level at the end of the plate’s service life, or to a significant increase in the service life. Calculation results show that maximum fatigue life designs are equal at end-of-life, and the maximum increase in fatigue life for hard- pinned inserts along the contour is 59%. As a result of the study, it was found that the problems of optimal design of flexible round plates under conditions of corrosive wear (the rate of which depends on the level of stresses in the plates), presented in the form of a minimax problem, can be effectively solved using the sequential quadratic programming technique, and the study of time evolution is intense -strain state can be carried out using a combination of the mesh method and the Adams method. Realization of the found optimal thickness profiles leads either to a significant decrease in the stress level at the end of the plate’s service life, or to a significant increase in the service life.

scholarly journals Numerical Evaluation of Structural Safety for Aged Onshore Wind Foundation to Extend Service Life

2020 ◽  
Vol 10 (13) ◽  
pp. 4561
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Sung-Hoon Song ◽  
Jeongsoo Kim
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Safety Evaluation ◽  
Life Extension ◽  
Structural Safety ◽  
Material Strength ◽  
Design Strength ◽  
Onshore Wind ◽  
Service Period ◽  
Service Life Extension

In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.

Failure analysis and fatigue life prediction of high-speed rail clips based on DIC technique

2021 ◽  
Vol 13 (12) ◽  
pp. 168781402110662
Author(s):  
Yan Liu ◽  
Xiujie Jiang ◽  
Qiutong Li ◽  
Huan Liu
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Fatigue Failure ◽  
High Speed ◽  
Experimental Tests ◽  
Image Correlation ◽  
Fe Model ◽  
Rail Transportation ◽  
High Speed Rail ◽  
Dic Technique

With the development of rail transportation, the fatigue failure of rail clips has become an issue, which affects the operational safety of trains. In this study, reasons for the fatigue failure of rail clips were investigated to improve their service life. A digital image correlation (DIC) technique was conducted to obtain strain fields, vibration modes, and natural frequencies of a rail clip. The strain and displacement of a rail clip under dynamic cyclic loading were also obtained. A fastener system refinement model was developed to analyze the static, dynamic, and modal responses of the clip. The experimental tests and modal simulation results were mutually verified. The fatigue life was analyzed based on the verified FE model. The results revealed that the maximum strain and minimum fatigue life occur at the heel of the clip, in good agreement with the actual fracture position. As the amplitude and frequency of dynamic cyclic load increased, the fatigue life of the clip decreased sharply. Moreover, the normal wheel–rail force accompanied by high-frequency rail corrugations accelerated crack initiation and reduced the fatigue life. The findings of this study provide guidance for improving the service life of rail clips.

Applying Digital Technologies Beyond Design Life

2021 ◽  
Author(s):  
Luiz Paulo Feijo ◽  
Suqin Wang ◽  
Christiane Machado
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Digital Technology ◽  
Predictive Analytics ◽  
Life Extension ◽  
Structural Behaviour ◽  
Structural Evaluation ◽  
Design Service Life ◽  
Remaining Fatigue Life ◽  
Extension Process

Abstract This paper focuses on Floating Production Installations, which are assets designed based on site-specific environmental conditions to determine their design service life. The longevity of these assets depends on the fatigue aspects related to the structural elements and mooring systems. Among the challenges involving the continued services of ageing assets is the integrity of these elements. When an asset reaches its end of design service life, Operators often decide to undergo a life extension process for safe continued operations. Alife extension process generally includes three phases: investigation, determination and implementation. Following a baseline inspection to determine the present conditions of the structures, engineering assessments are to be carried out to evaluate the fatigue damage through the lifecycle of the installation and therefore determine the remaining fatigue life. Collecting information to execute these assessments is challenging and can be automated with the use of digital technology. Digital tools allow an accurate collection of data, providing a continuous evaluation of the remaining fatigue life and supporting an informed decision-making process. Observing the operation of several aging assets and their structural behaviour, the parameters to be measured during the installation's lifecycle have been identified along with other aspects that also contribute to the determination of its continued service. The recommended data acquisition for relevant measurements is summarized in this paper. The application of sensors and monitoring systems on the installations allows measuring these parameters on a continuous basis, and consequently, Operators are able to determine the degradation pattern that the structure is subject to. An estimation of the remaining fatigue life can be achieved by using predictive analysis, which, along with insights of the future expected corrosion, provides Operators the necessary basis to implement corrective measures and mitigations to avoid the occurrence of a failure. This paper offers an innovative, forward-looking technology that allies physics-based processes with digital technology, supported by predictive analytics and continuous structural evaluation, to assess the integrity of an offshore asset in support of safe continued services.

Is Titanium Drillpipe Applicable to Offshore Drilling? A Question from a Corrosion Fatigue Perspective

SPE Journal ◽  
2021 ◽  
pp. 1-17
Author(s):  
Hao Yu ◽  
Yisheng Mou ◽  
Zhanghua Lian ◽  
Qiang Zhang
Keyword(s):  
Corrosion Resistance ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Service Life ◽  
Corrosion Fatigue ◽  
Field Application ◽  
Drilling Mud ◽  
Offshore Drilling ◽  
Rotary Drilling ◽  
Short Period

Summary In offshore horizontal well drilling, one of the major challenges is the large dogleg severity in the buildup section due to the shallow depth of reservoirs. In such a case, the drillstring has to bend itself to fit the borehole trajectory and suffers greatly from the high alternating stress while rotary drilling. This could lead to fatigue fracture of the drillpipe within a short period. The corrosion from drilling mud may exacerbate the failure risk. Titanium alloy, as a new drillpipe material, has the characteristics of excellent corrosion resistance and low elastic modulus, which can theoretically extend the fatigue life. To study the performance of titanium alloy drillpipe quantitatively, titanium alloy material, and G105 steel of the same grade are compared to obtain the microscopic characteristics and macroscopic properties through experimental tests. Moreover, the mechanism of passive film formation of the two materials is analyzed in the corrosion fatigue (CF) environment. Then, the experimental results are extended to modeling the actual drillstring assembly and simulating its service life in the field practice of offshore drilling. Our numerical results indicated that the titanium alloy drillpipe has much better corrosion resistance but only half the stress level of G105 steel under the same dogleg severity and axial force, which makes its fatigue life over 23 times longer. Eventually an economic appraisal is given by considering the full-service life of the drillpipe. The research results of this paper can provide a detailed theoretical basis and reference for field application and can popularize the use of titanium alloy drillpipe.

Effect of Joint Behavior on the Reassessment of Fixed Offshore Platforms in the Bay of Campeche, Mexico

2005 ◽  
Author(s):  
Partha Chakrabarti ◽  
Adinarayana Mukkamala ◽  
Ibrahim Abu-Odeh ◽  
Juan de Dios de la O. Rami´rez
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Oil And Gas ◽  
Gas Production ◽  
Strength Analysis ◽  
Offshore Platforms ◽  
Inspection Planning ◽  
Oil And Gas Production ◽  
Joint Flexibility ◽  
Joint Behavior

Pemex Exploration y Produccio´n owns and operates several fields in the Bay of Campeche, located in the south Gulf of Mexico, for oil and gas production. Many of these fixed offshore platforms were built during the 70s and 80s and have already exceeded their design service life. To meet the growing demand for oil and natural gas it was found economic to extend the service life for these platforms by at least another 15 to 30 years. To meet this extended service life, thorough and systematic reassessment studies need to be conducted leading to identification of any structural weakness and possible locations of fatigue problems. To extend the fatigue life of the welded joints, inspections are required to be performed according to a risk based inspection planning procedure. As a part of the reassessment study non-linear pushover and spectral fatigue analyses are conducted. The effect of joint behavior, viz. the local joint flexibility and strength, on the structural ultimate capacity and fatigue life is discussed in this paper. In conventional analysis the tubular joints are assumed to be rigid and the flexibility effects due to shell deformations are ignored. In this present paper, the effect of the joint behavior is included in the analysis and its implications on the results are discussed. For the ultimate strength analysis both API and MSL formulations for the load-deformation behavior of the joint are studied and compared. For the fatigue analyses, local joint flexibility modeling using Buitrago’s formulation is used. Results including and excluding these effects are compared. Effect of grouting of the joint is also studied. Comprehensive results of the study for a number of platforms, which cover the categories of Drilling, Production, Gathering and Habitation, are presented. The effects of local joint flexibility and joint strength on structural behavior have been recognized to be important in the recent publications of the recommended practices and the codes such as the API RP 2A. However, comprehensive discussions and the results of application of these aspects are rare in the published literature. This paper addresses these issues and presents the results of a large number of platforms of different configurations, indicates some noticeable trends and suggests some general conclusions.

Sign in / Sign up

Export Citation Format

Share Document