An Investigation on Monitoring Methods of Creep Damage Using Ultrasonic Technique

2004 ◽  
Author(s):  
Yoshikazu Yokono ◽  
Yoshihiro Nagano
Keyword(s):  
Continuous Monitoring ◽  
Ultrasonic Method ◽  
Creep Damage ◽  
Ultrasonic Technique ◽  
Monitoring Methods ◽  
Material Degradation ◽  
Creep Life ◽  
Term Operation ◽  
Safety Operation ◽  
Life Fraction

The reliability of facilities under long-term operation, that is to prevent trouble or accident, is one of the most important matters in the field of petroleum and petrochemical plants. For this purpose, some kinds of non-destructive inspection methods are carried out periodically to detect damages or degradation of material. Moreover, to enrich the reliability of safety operation of the plants, continuous monitoring methods to detect material degradation without mistiming are required. Recently, ultrasonic method has been developed as a key technology to detect and evaluate the damage of materials. One of the advantages of ultrasonic technique is to obtain much information about microstructure change due to material degradation when ultrasounds travel through the material. Further, ultrasonic technique has also the potential ability to be applied for continuous monitoring methods. The objective of this study is to accomplish monitoring methods of creep damage using ultrasonic technique. A novel technique to acquire the ultrasonic data during uni-axial creep test is investigated as the first step of monitoring of creep damage. As a result, it is confirmed that the sound velocity in time domain decreases gradually in creep acceleration stage which starts at the creep life fraction of 0.6 and the gravity frequency in frequency domain begins to increase at the creep life fraction of 0.8. Therefore, the possibility to monitor the creep damage under continuous operation by ultrasonic technique is suggested.

A Practical Ultrasonic Inspection Method for Detecting and Characterising Defects Found Within Composite Repairs

2018 ◽  
Author(s):  
J Downing ◽  
A Hook
Keyword(s):  
Wall Thickness ◽  
Steel Substrate ◽  
Ultrasonic Method ◽  
Ultrasonic Inspection ◽  
Heat Exposure ◽  
Matrix Cracking ◽  
Ultrasonic Technique ◽  
Inspection Method ◽  
Composite Repairs ◽  
Layered Matrix

Two steel substrate test panels were developed to represent common plate thicknesses found on naval vessels and scanned using the Babcock developed ultrasonic technique. One sample comprised of a series of slotted surface breaking flaws of varying widths and through thicknesses to represent fracturing/cracking. The inspection method detected simulated cracking to a depth of 2mm and 0.5mm in width. The second sample included numerous loss of wall thickness areas of varying diameters and through thicknesses, with the smallest detectable loss of wall thickness being 0.1mm at a 15mm diameter. After proving confidence in detection, there was a need to characterise flaws to provide support and ascertain a repair action. Samples were produced that were subjected to either impact or heat exposure to induce realistic representative damage. The practical ultrasonic method was successfully used to independently characterise between the samples, with induced de-laminations caused by blisters, and multi layered matrix cracking caused by varying levels of projectile impacts, due to their unique morphology.

scholarly journals Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 623
Author(s):  
Xiaoyan Wang ◽  
Meng Li ◽  
Yuansheng Wang ◽  
Chengjiang Zhang ◽  
Zhixun Wen
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Creep Damage ◽  
Primary Creep ◽  
Single Crystal Superalloy ◽  
Secondary Creep ◽  
Creep Life ◽  
Phase Coarsening ◽  
Damage Repair ◽  
Creep Time

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

Laser-Generated Ultrasonic Technique for Inspecting Delamination in CFRP

2006 ◽  
Vol 321-323 ◽  
pp. 968-971
Author(s):  
Won Su Park ◽  
Sang Woo Choi ◽  
Joon Hyun Lee ◽  
Kyeong Cheol Seo ◽  
Joon Hyung Byun
Keyword(s):  
High Frequency ◽  
Ultrasonic Method ◽  
Piezoelectric Sensor ◽  
Frequency Component ◽  
Guided Wave ◽  
Center Frequency ◽  
High Frequency Component ◽  
Ultrasonic Technique ◽  
Non Destructive Evaluation ◽  
Non Destructive

For improving quality of a carbon fiber reinforced composite material (CFRP) by preventing defects such as delamination and void, it should be inspected in fabrication process. Novel non-contacting evaluation technique is required because the transducer should be contacted on the CFRP in conventional ultrasonic technique during the non-destructive evaluation and these conventional contact techniques can not be applied in a novel fiber placement system. For the non-destructive evaluation of delamination in CFRP, various methods for the generation and reception of laser-generated ultrasound are applied using piezoelectric transducer, air-coupled transducer, wavelet transform technique etc. The high frequency component of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. Air-coupled transducer was tried to be adopted in reception of laser-generated guided wave generated by using linear slit array in order to generate high frequency guided wave with a frequency of 1.1 MHz. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled transducer and linear slit array. Transmitted laser-generated ultrasonic wave was received on back-wall and its frequency was analyzed to establish inspecting technique to detect delamination by non-contact ultrasonic method. In a frequency spectrum analysis, intensity ratio of low frequency and center frequency was approvable parameter to detect delamination.

Creep Damage Evaluation of Fine-Grained HAZ in Mod. 9Cr Ferritic Heat-Resistant Steel Weldments

2007 ◽  
Author(s):  
N. Yoneyama ◽  
K. Kubushiro ◽  
H. Yoshizawa
Keyword(s):  
Creep Damage ◽  
Life Time ◽  
Creep Life ◽  
Creep Tests ◽  
Boundary Density ◽  
Fine Grained ◽  
Type Iv ◽  
Fine Grain ◽  
Type Iv Cracking ◽  
Rupture Mechanism

9Cr steel weldments are concerned with evaluation of creep life time and creep rupture mechanism. In fine grain HAZ (FG-HAZ) of weldments, TYPE IV cracking and creep voids occurred at lower stress than rupture stress level of base metal. In the crept specimen, FG-HAZ sometime has large coarsening grains near creep voids. These recovery phenomena are localized in FG-HAZ, and recovered microstructures are dependent on heat input of welding. In this study, creep tests are examined in two types of weldments, and relations between creep life time and coarsened sub-grains or grains have been studied by microstructural changing with EBSP analysis. In crept specimens, boundaries are moved and boundary density is decreasing in the fine-grained HAZ. Maximum grain size and creep life time have linear function, and EBSP can evaluate creep life time of 9Cr weldments. These microstructural changing are considered by morphology of precipitates in the several crept specimens.

The Effects of Cooling Holes on the Creep Life in a Modeling Specimen of Single Crystal Air-Cooled Turbine Blade

2011 ◽  
Vol 284-286 ◽  
pp. 1678-1683 ◽  
Author(s):  
Da Shun Liu ◽  
Bai Zhi Wang ◽  
Zhi Xun Wen ◽  
Zhu Feng Yue
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Damage Model ◽  
Creep Damage ◽  
Creep Life ◽  
Damage Development ◽  
User Subroutine ◽  
Initial Rupture ◽  
Creep Deformations ◽  
Sem Analyses

This paper presents the study of the influences of cooling holes on the creep life behavior in the modeling specimen of single crystal cooling turbine blade at high temperature. Thin-walled cylindrical specimens with holes are tested to model the air-cooled turbine blade. Specimens without holes are also studied to make comparisons. Experimental results show that at 900°C, the creep lives of specimens with holes are longer than those of specimens without holes. Scanning Electron Microscopy (SEM) analyses reveal that creep deformations occur firstly around the cooling holes and finally rupture at the region with low stress and strain. Finite element analyses are used to study the creep damage development by a K-R damage model which has been implemented into the Abaqus user subroutine (UMAT). Simulation results show that stress concentration and redistribution occur around the cooling holes during the creep development. It is also shown that the maximum strain and stress are around the cooling holes which are the initial rupture region in the experiments.

scholarly journals Non-Contact Video-Based Neonatal Respiratory Monitoring

Children ◽  
2020 ◽  
Vol 7 (10) ◽  
pp. 171
Author(s):  
Scott L. Rossol ◽  
Jeffrey K. Yang ◽  
Caroline Toney-Noland ◽  
Janine Bergin ◽  
Chandan Basavaraju ◽  
...  
Keyword(s):  
Neonatal Intensive Care ◽  
Continuous Monitoring ◽  
Improve Patient Care ◽  
Neonatal Intensive Care Units ◽  
P Value ◽  
Monitoring Methods ◽  
Iatrogenic Complications ◽  
Impedance Pneumography ◽  
Clinical Changes ◽  
Improve Patient

Respiratory rate (RR) has been shown to be a reliable predictor of cardio-pulmonary deterioration, but standard RR monitoring methods in the neonatal intensive care units (NICU) with contact leads have been related to iatrogenic complications. Video-based monitoring is a potential non-contact system that could improve patient care. This iterative design study developed a novel algorithm that produced RR from footage analyzed from stable NICU patients in open cribs with corrected gestational ages ranging from 33 to 40 weeks. The final algorithm used a proprietary technique of micromotion and stationarity detection (MSD) to model background noise to be able to amplify and record respiratory motions. We found significant correlation—r equals 0.948 (p value of 0.001)—between MSD and the current hospital standard, electrocardiogram impedance pneumography. Our video-based system showed a bias of negative 1.3 breaths and root mean square error of 6.36 breaths per minute compared to standard continuous monitoring. Further work is needed to evaluate the ability of video-based monitors to observe clinical changes in a larger population of patients over extended periods of time.

RECTAL PCO2 MONITORING: A COMPARISON OF CONTINUOUS MONITORING METHODS

2004 ◽  
Vol 32 (Supplement) ◽  
pp. A31
Author(s):  
Elaine M Fisher ◽  
Richard P Steiner
Keyword(s):  
Continuous Monitoring ◽  
Monitoring Methods ◽  
Pco2 Monitoring

Degradation Evaluation of 2.25Cr-1Mo Steel Using Nondestructive Method

2005 ◽  
Vol 297-300 ◽  
pp. 1951-1957
Author(s):  
Jong Seo Park ◽  
Un Bong Baek ◽  
Jeong Min Kim ◽  
Seung Hoon Nahm ◽  
Bong Young Ahn
Keyword(s):  
Electrical Resistivity ◽  
Ultrasonic Attenuation ◽  
Indentation Test ◽  
Creep Damage ◽  
Nondestructive Method ◽  
Magnetic Characteristics ◽  
Isothermal Heat Treatment ◽  
Material Degradation ◽  
Aging Parameter ◽  
Degradation Evaluation

Several nondestructive evaluation methods were attempted for the estimation of the creep damage of degraded 2.25Cr-1Mo steel. The specimens of three different aging periods were prepared by an isothermal heat treatment at 430°C, 482°C, and 515°C. The effect of probe configuration on the electrical resistivity was studied. Single configuration method and dual-configuration method were utilized for measuring electrical resistivity. The electrical resistivity was determined by a standard DC four-point probe method at 24±0.5°C. Indentation test, magnetic characteristics test and ultrasonic test were carried out to investigate the correlation between the major characteristics and aging parameter. Unlike the electrical resistivity characteristics, ultrasonic attenuation coefficient and indentation characteristics did not show a relation to Larson-Miller parameter. However, a correlation between the electrical resistivity and aging parameter was identified, which allows one to estimate the extent of material degradation.

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