A method of real-time bi-axial strain control in fatigue testing of elastomers

2011 ◽  
pp. 409-414 ◽  
Author(s):  
N Murphy ◽  
J Hanley ◽  
S Jerrams
Keyword(s):  
Real Time ◽  
Fatigue Testing ◽  
Axial Strain ◽  
Strain Control

Strain Control Correction for Fatigue Testing in LWR Environments

2020 ◽  
Author(s):  
Marc Vankeerberghen ◽  
Alec Mclennan ◽  
Igor Simonovski ◽  
German Barrera ◽  
Sergio Arrieta Gomez ◽  
...  
Keyword(s):  
Correction Factor ◽  
Fatigue Testing ◽  
Crack Nucleation ◽  
Gauge Length ◽  
Correction Factors ◽  
Element Analysis ◽  
Cross Sectional ◽  
Strain Control ◽  
Specimen Diameter ◽  
Contact Points

Abstract During strain-controlled fatigue testing of solid bar specimens in a LWR environment within an autoclave, it is common practice to avoid the use of a gauge length extensometer to remove the risk of preferential corrosion and early crack nucleation from the extensometer contact points. Instead, displacement- or strain-control is applied at the specimen shoulders, where the cross-sectional area of the specimen is higher and so surface stress levels are lower. A correction factor is applied to the control waveform at the shoulder in order to achieve approximately the target waveform within the specimen gauge length. The correction factor is generally derived from trials conducted in air by cycling samples with extensometers attached to both the shoulders and the gauge length; typically, the average ratio between the strains or the ratio at half-life in these locations is taken to be the correction factor used in testing. These calibration trials may be supplemented by Finite Element Analysis modelling of the specimens, or by other analysis of results from the calibration trials. Within the INCEFA+ collaborative fatigue research project, a total of six organizations are performing fatigue testing in LWR environments within an autoclave. Of these, one organization is performing tests in an autoclave using extensometers attached to both the specimen shoulders and the specimen gauge length. Therefore the INCEFA+ project provides a unique opportunity to compile and compare methods of shoulder control correction used by different organizations when fatigue testing in LWR environments. This paper presents the different methods of correcting shoulder control waveforms used by partners within the INCEFA+ project, compares the correction factors used, and assesses sensitivities of the correction factor to parameters such as specimen diameter. In addition, correction factors for air and PWR environments are compared. Conclusions are drawn and recommendations made for future fatigue testing in LWR environments within autoclaves.

scholarly journals Standards-Based Technologies for Exchanging Fatigue Test Data

2018 ◽  
Author(s):  
Tim Austin ◽  
Lianshan Lin ◽  
Thomas Métais
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Nuclear Power ◽  
Power Plants ◽  
Ad Hoc ◽  
Fatigue Testing ◽  
Axial Strain ◽  
Engineering Systems ◽  
Data Formats ◽  
Engineering Materials

Fatigue testing campaigns are a common feature in the design and operation of advanced engineering systems in the aerospace and power generation sectors. The resulting data are typically of a high inherent technical and financial value. Presently, these data are typically transferred between departments and companies by way of ad-hoc solutions reliant on obsolete or proprietary technologies, including CSV files, MS Excel® files, and PDFs. In these circumstances there is significant potential for data loss, inconsistency, and error. To address these shortcomings, there is a need for a systematic means of transferring data between different digital systems. With this in mind, a series of CEN Workshops on engineering materials data have taken place with a view to developing technologies for representing and exchanging engineering materials data. Most recently, a CEN Workshop on the topic of fatigue test data has delivered data formats derived from the ISO 12106 standard for axial strain-controlled fatigue testing. This paper describes the methodology for developing the data formats and demonstrates their use in the scope of the INCEFA-PLUS project on increasing safety in nuclear power plants by covering gaps in environmental fatigue assessment.

Strain Control Correction for Fatigue Testing in Lwr Environments

2021 ◽  
Author(s):  
Marc Vankeerberghen ◽  
Alec Mclennan ◽  
Igor Simonovski ◽  
Sergio Arrieta Gomez ◽  
German Barrera ◽  
...  
Keyword(s):  
Fatigue Testing ◽  
Strain Control

scholarly journals Real-Time GPU-Based Digital Image Correlation Sensor for Marker-Free Strain-Controlled Fatigue Testing

2019 ◽  
Vol 9 (10) ◽  
pp. 2025 ◽  
Author(s):  
Andreas Blug ◽  
David Joel Regina ◽  
Stefan Eckmann ◽  
Melanie Senn ◽  
Alexander Bertz ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Real Time ◽  
Digital Image ◽  
Graphics Processing Units ◽  
Fatigue Testing ◽  
Sampling Rate ◽  
Surface Preparation ◽  
Image Correlation ◽  
Marker Free ◽  
Path Dependent

Digital image correlation (DIC) is a highly accurate image-based deformation measurement method achieving a repeatability in the range of   σ =   10−5 relative to the field-of-view. The method is well accepted in material testing for non-contact strain measurement. However, the correlation makes it computationally slow on conventional, CPU-based computers. Recently, there have been DIC implementations based on graphics processing units (GPU) for strain-field evaluations with numerous templates per image at rather low image rates, but there are no real-time implementations for fast strain measurements with sampling rates above 1 kHz. In this article, a GPU-based 2D-DIC system is described achieving a strain sampling rate of 1.2 kHz with a latency of less than 2 milliseconds. In addition, the system uses the incidental, characteristic microstructure of the specimen surface for marker-free correlation, without need for any surface preparation—even on polished hourglass specimen. The system generates an elongation signal for standard PID-controllers of testing machines so that it directly replaces mechanical extensometers. Strain-controlled LCF measurements of steel, aluminum, and nickel-based superalloys at temperatures of up to 1000 °C are reported and the performance is compared to other path-dependent and path-independent DIC systems. According to our knowledge, this is one of the first GPU-based image processing systems for real-time closed-loop applications.

scholarly journals Real-Time Well-Integrity Monitoring Using Fiber-Optic Distributed Acoustic Sensing

SPE Journal ◽  
2019 ◽  
Vol 24 (05) ◽  
pp. 1997-2009 ◽  
Author(s):  
T.. Raab ◽  
T.. Reinsch ◽  
S. R. Aldaz Cifuentes ◽  
J.. Henninges
Keyword(s):  
Life Cycle ◽  
Strain Rate ◽  
Real Time ◽  
Fiber Optic ◽  
Axial Strain ◽  
Fiber Optic Cable ◽  
Integrity Monitoring ◽  
Well Integrity ◽  
Distributed Acoustic Sensing ◽  
Cement Integrity

Summary Proper cemented casing strings are a key requirement for maintaining well integrity, guaranteeing optimal operation and safe provision of hydrocarbon and geothermal resources from the pay zone to surface facilities. Throughout the life cycle of a well, high–temperature/high–pressure changes in addition to shut–in cyclic periods can lead to strong variations in thermal and mechanical load on the well architecture. The current procedures to evaluate cement quality and to measure downhole temperature are mainly dependent on wireline–logging campaigns. In this paper, we investigate the application of the fiber–optic distributed–acoustic–sensing (DAS) technology to acquire dynamic axial–strain changes caused by propagating elastic waves along the wellbore structure. The signals are recorded by a permanently installed fiber–optic cable and are studied for the possibility of real–time well–integrity monitoring. The fiber–optic cable was installed along the 18⅝–in. anchor casing and the 21–in.–hole section of a geothermal well in Iceland. During cementing operations, temperature was continuously measured using distributed–temperature–sensing (DTS) technology to monitor the cement placement. DAS data were acquired continuously for 9 days during drilling and injection testing of the reservoir interval in the 12¼–in. openhole section. The DAS data were used to calculate average–axial–strain–rate profiles during different operations on the drillsite. Signals recorded along the optical fiber result from elastic deformation caused by mechanical energy applied from inside (e.g., pressure fluctuations, drilling activities) or outside (e.g., seismic signals) of the well. The results indicate that the average–axial–strain rate of a fiber–optic cable installed behind a casing string generates trends similar to those of a conventional cement–bond log (CBL). The obtained trends along well depth therefore indicate that DAS data acquired during different drilling and testing operations can be used to monitor the mechanical coupling between cemented casing strings and the surrounding formations, hence the cement integrity. The potential use of DTS and DAS technology in downhole evaluations would extend the portfolio to monitor and evaluate qualitatively in real time cement–integrity changes without the necessity of executing costly well–intervention programs throughout the well's life cycle.

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