Experimental Study on Inverse Fracture in Drop-Weight Tear Test and Other Laboratory Test: Current Activities in HLP Committee, Japan, Report 2

2016 ◽  
Author(s):  
Tetsuya Tagawa ◽  
Taishi Fujishiro ◽  
Toshihiko Amano ◽  
Shuji Aihara ◽  
Satoshi Igi
Keyword(s):  
High Speed ◽  
Crack Arrest ◽  
Image Correlation ◽  
Correlation Technique ◽  
Brittle Crack ◽  
Fracture Surfaces ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Shear Area ◽  
The Impact

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against long brittle fracture propagation. However, there is an ambiguity in its evaluation if the inverse fracture appears (100% shear area prior to cleavage fracture from the notch) on the DWTT fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer has been discussed as a possible cause. In the present work, DWTTs for X65, X70 and X80 were performed. In addition to conventional DWTT specimen with a pressed notch (PN), PN specimen with a back slot and specimens with a chevron notch (CN) or a static pre-cracked (SPC) were examined. The fracture appearances were compared in the different strength and in the different initial notch type. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen type, but there were no cases free from the inverse fracture. The inverse fracture was investigated by fractography and the hardness profiles along the under layer of the fracture surfaces. Also, the strain histories during impact in DWTTs were measured by the digital image correlation technique based on the high-speed camera images. The DWTT specimen purpose is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. The DWTT results should be examined with a manner of a running brittle crack in a pressurized linepipe. A large scale brittle crack arrest test, so called temperature gradient ESSO test was also performed for X65 mother plate. The shear area fraction measured in DWTT fracture appearance was compared with the local shear lip thickness fraction in ESSO test. The count of the inverse fracture was discussed in comparison with the long brittle crack arrest behavior in ESSO test.

Effect of Notch Type in Drop-Weight Tear Test Specimen on Crack Propagation and Arrest Behavior

2018 ◽  
Author(s):  
Satoshi Igi ◽  
Toshihiko Amano ◽  
Takahiro Sakimoto ◽  
Yasuhiro Shinohara ◽  
Tetsuya Tagawa
Keyword(s):  
Crack Propagation ◽  
Large Scale ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Chevron Notch ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Shear Area ◽  
The Impact ◽  
Crack Propagation And Arrest

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle fracture propagation. However, in the recent years there is an ambiguity in its evaluation if inverse fracture appears on the specimen fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer and existing tiny split have been discussed as a possible cause. In this paper, machined notch in brittle weld DWTT for X65 was performed and compared with various notch types of DWTTs such as conventional DWTT specimen with a pressed notch (PN), a chevron notch (CN) and a static pre-cracked (SPC). The fracture appearances were compared with different strength X65 - X80 grades linepipes and with different initial notch types. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen types, but there were no cases where the inverse fracture did not occurs. The purpose of DWTT is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. A large scale brittle crack arrest test, so called West Jeferson test is generally used to reproduce crack propagation and arrest behavior in an actual pipeline material. A middle scale test so called Crack Arrest Temperature (CAT) test was also proposed to check the shear area fraction measured in DWTT with API rating with that the local shear lip thickness fraction in those tests. CAT test can well reproduce crack propagation and arrest behavior under the condition of brittle crack initiation from the initial notch.

The Influence of Facet Size on the Accuracy of Modal Parameters Determined by Digital Image Correlation Technique

2014 ◽  
Vol 611 ◽  
pp. 496-500 ◽  
Author(s):  
Róbert Huňady ◽  
Martin Hagara ◽  
František Šimčák
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Modal Parameters ◽  
Correlation Technique ◽  
Correlation System ◽  
Correlation Process ◽  
The Impact ◽  
Facet Size

The paper deals with measurements of modal parameters using high-speed digital image correlation and assesses how the size of image elements (facets) influences the accuracy of modal parameters of the analyzed structure. The facet size is an important parameter that significantly affects the correlation process and its results. In the paper the experimental modal analysis of steel circular plate that has been excited by the impact hammer is described. Correlation system Q-450 Dantec Dynamics was used to measure the responses of the analyzed structure.

Inverse Fracture in DWTT and Brittle Crack Behavior in Large-Scale Brittle Crack Arrest Test

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Tetsuya Tagawa ◽  
Toshihiko Amano ◽  
Takashi Hiraide ◽  
Takahiro Sakimoto ◽  
Satoshi Igi ◽  
...  
Keyword(s):  
Large Scale ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Specimen Type ◽  
Chevron Notch ◽  
Drop Weight Tear Test ◽  
Shear Lip ◽  
Local Shear ◽  
Shear Area ◽  
Linepipe Steels

The drop weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle fracture propagation. Although there is an ambiguity in the evaluation of DWTT results if inverse fracture appears on the fracture surfaces, the cause of inverse fracture is not yet fully understood. In the present work, DWTTs were performed with X65, X70, and X80 steel linepipes. In addition to the conventional DWTT specimen with a pressed notch (PN), PN specimens with a back slot (BS) and specimens with a chevron notch (CN) or static precrack (SPC) were also examined, and the fracture appearances in different strengths and different initial notch types were compared. Although the frequency of inverse fracture in these DWTTs was different with each material and each specimen type, there was no material or specimen type that was entirely free from inverse fracture. The purpose of the DWTT is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. Therefore, the DWTT results should be examined with a running brittle crack arrest (BCA) test. A large-scale BCA test with temperature gradient was also performed with the X65 mother plate, and the shear area fraction measured in the DWTT fracture surface was compared with the local shear lip thickness fraction in the BCA test. Based on the results, the count of inverse fracture in the DWTT was discussed in comparison with the long BCA behavior in the BCA test.

scholarly journals Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1602
Author(s):  
Ángel Molina-Viedma ◽  
Elías López-Alba ◽  
Luis Felipe-Sesé ◽  
Francisco Díaz
Keyword(s):  
Modal Analysis ◽  
Energy Absorption ◽  
High Speed ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Image Correlation ◽  
Composite Panel ◽  
Impact Excitation ◽  
Full Field ◽  
The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

New Computational Procedures for Evaluation of Fracture Surfaces of the Drop Weight Tear Test of the Piping Steel

2011 ◽  
Author(s):  
Pavel Zˇidli´k ◽  
Petr Ferfecki ◽  
Bohumi´r Strnadel
Keyword(s):  
Fracture Surface ◽  
Ductile Fracture ◽  
Unstable Fracture ◽  
Fracture Surfaces ◽  
Drop Weight ◽  
Highly Sensitive ◽  
Drop Weight Tear Test ◽  
Computational Procedures ◽  
New Procedures

Drop weight tear test (DWTT) is one of the standard methods for evaluation of the ductility of large-dimensional structural components, such as pipelines used for gas and/or oil transportation. In general, the pipelines are even used in places with temperatures close to −40 °C, and in such environments, it is necessary to guarantee the resistance of the material used for pipeline against the initiation of unstable fracture. Currently, the percentage portion of the ductile fracture of the DWTT specimen is determined by an expert evaluator. The objective of this paper is to introduce new procedures working on the principle of deterministic, statistical and fractal description of the fracture surface. For the proposed computational procedures, the fracture surface of the test specimen is scanned at the macroscopic level using the 3D-Cam scanner. The newly investigated procedures show highly sensitive to the determination of the percentage portion of the ductile fracture on the tested DWTT specimens. The developed procedures to assess the fracture surfaces of the DWTT specimens contributes to making the results of this test more correct, objective and also increases the reliability and safety of the manufactured pipelines.

Dynamic Analysis of Thin Glass Under Ball Drop Impact With New Metrics

2013 ◽  
Author(s):  
Liang Xue ◽  
Claire R. Coble ◽  
Hohyung Lee ◽  
Da Yu ◽  
Satish Chaparala ◽  
...  
Keyword(s):  
High Speed ◽  
Impact Testing ◽  
Image Correlation ◽  
Thin Glass ◽  
Fea Model ◽  
Wear And Tear ◽  
Local Measurements ◽  
Drop Impacts ◽  
Global And Local ◽  
The Impact

Response of brittle plate to impact loads has been the subject of many research studies [1–7]. Specifically, glass presents a wide variety of applications in daily life, and helps to protect the displays of smartphones, tablets, PCs, and TVs from everyday wear and tear. Therefore, the necessity of glass to resist scratches, drop impacts, and bumps from everyday use leads to the importance of investigation of the glass response under dynamic impact loading. The ball drop test has been applied in the past, specifying an energy threshold as a prediction metric. Use of energy as the key parameter in impact testing is limited, since it does not account for the time spent in contact during the impact event. This study attempts to establish a reliable metric for impact testing based on a momentum change threshold. The deformation and the strain of the glass will be obtained by the Digital Image Correlation (DIC) system, while the rebound velocity will be measured with the high speed cameras. The global and local measurements are conducted to verify the accuracy of the experimental results. Finally, the FEA model is developed using ANSYS/LS-DYNA to provide a comprehensive understanding of the dynamic response of the glass. Excellent correlation in deflection is obtained between the measurements and predictions.

scholarly journals Experimental investigation of the impact response of novel steelbiocomposite hybrid materials

2018 ◽  
Vol 183 ◽  
pp. 02040
Author(s):  
KarthikRam Ramakrishnan ◽  
Mikko Hokka ◽  
Essi Sarlin ◽  
Mikko Kanerva ◽  
Reijo Kouhia ◽  
...  
Keyword(s):  
High Speed ◽  
Structural Integrity ◽  
Metal Layer ◽  
Rear Surface ◽  
Impact Resistance ◽  
Natural Fibre ◽  
Image Correlation ◽  
Impact Response ◽  
High Speed Camera ◽  
The Impact

Recent developments in the production of technical flax fabrics allow the use of sustainable natural fibres to replace synthetic fibres in the manufacture of structural composite parts. Natural fibre reinforced biocomposites have been proven to satisfy design and structural integrity requirements but impact strength has been identified as one of their limitations. In this paper, hybridisation of the biocomposite with a metal layer has been investigated as a potential method to improve the impact resistance of natural fibre composites. The impact response of biocomposites made of flax-epoxy is investigated experimentally using a high velocity particle impactor. A high-speed camera setup was used to observe the rear surface of the plates during impact. Digital Image Correlation (DIC) of the high speed camera images was used for full-field strain measurement and to study the initiation and propagation of damage during the impact. The different modes of damage in the hybrid laminate were identified by postimpact analysis of the section of the damaged composite plate using optical microscopy. The study shows the difference in impact response for different material combinations and configurations. The hybrid construction was shown to improve the impact resistance of the flax composite.

Measurement of Transient Dynamic Response of Circuit Boards of a Handheld Device During Drop Using 3D Digital Image Correlation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
S. B. Park ◽  
Chirag Shah ◽  
Jae B. Kwak ◽  
Changsoo Jang ◽  
Soonwan Chung ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Impact Response ◽  
Experimental Methodology ◽  
Full Field ◽  
Handheld Device ◽  
3D Digital Image Correlation ◽  
The Impact

In this work, a new experimental methodology for analyzing the drop impact response is assessed using a pair of high-speed digital cameras and 3D digital image correlation software. Two different test boards are subjected to Joint Electron Device Engineering Council (JEDEC) standard free-fall impact conditions of half-sine pulse of 1500 G in magnitude and 0.5 ms in duration. The drop is monitored using a pair of synchronized high-speed cameras at a rate of up to 15,000 frames per second. The acquired images are subsequently analyzed to give full-field dynamic deformation, shape, and strain over the entire board during and after impact. To validate this new methodology for analyzing the impact response, the in-plane strain as well as the out-of-plane acceleration at selected locations were measured simultaneously during the drop using strain gauge and accelerometers and were compared with those obtained using high-speed cameras and 3D digital image correlation presented in this paper. Comparison reveals excellent correlation of the transient behavior of the board during impact and confirms the feasibility of using the full-field measurement technique used in this study.

Stent Expansion in Curved Vessel and Their Interactions: An In Vitro Study

2014 ◽  
Author(s):  
Shijia Zhao ◽  
Shengmao Lin ◽  
Linxia Gu
Keyword(s):  
High Speed ◽  
In Vitro Study ◽  
Image Correlation ◽  
Correlation Technique ◽  
Digital Image Correlation Technique ◽  
Stent Expansion ◽  
Curved Artery ◽  
Induced Changes ◽  
Stenting Procedure

The objective of this work is to characterize the interaction between balloon-expandable stents and curved artery simulants. The deformation at the outer surface of the curved artery simulant was monitored using two high-speed cameras, and the corresponding strain map was obtained with 3-D digital image correlation technique. The anisotropic variations in the arterial mechanics were clearly observed. Results indicated three distinct phases during the stenting procedure, i.e., expansion, recoil and stabilization. The stent expansion dramatically altered the strain field of the curved artery simulant, and larger strain was observed around the center of stent than its two ends. In addition, the change in curvature of the simulant during the implantation of stent was quantified. This work characterized and quantified the interaction between stent and artery simulant in a laboratory setting, which could facilitate the optimization of the stent design for minimizing the stent-induced changes in the mechanical environment of artery.

scholarly journals EXPERIMENTAL AND THEORETICAL RESEARCH ON REINFORCED LIGHTWEIGHT CONCRETE FLEXURAL ELEMENTS / ARMUOTOJO LENGVOJO BETONO LENKIAMŲJŲ ELEMENTŲ EKSPERIMENTINIAI IR TEORINIAI TYRIMAI

2014 ◽  
Vol 6 (5) ◽  
pp. 480-487
Author(s):  
Deividas Rumšys ◽  
Darius Bačinskas ◽  
Edmundas Spudulis ◽  
Eugenijus Gudonis ◽  
Aleksandr Sokolov
Keyword(s):  
High Speed ◽  
Lightweight Concrete ◽  
Image Correlation ◽  
Theoretical Research ◽  
Correlation Technique ◽  
Video Cameras ◽  
Strain Behavior ◽  
Four Point Bending ◽  
Vertical Displacements ◽  
Bending Loading

The paper deals with analysis of structural lightweight concrete. New lightweight concrete mixture made with expanded clay aggregate has been proposed and applied for experimental rein-forced concrete beams. Totally 8 beams with different rein-forcement ratios (0.309%, 0.557%, 0.895% and 1.255%) were tested under short-term four point bending loading. Stress-strain behavior of the beams under considerations has been investigated. Average strains at 4 different levels of pure bend-ing zone and vertical displacements at 12 different points of the beam were measured. During the test, deformations and crack-ing of the pure bending zone were additionally observed using high-speed digital video cameras. The data obtained by cameras were analyzed using digital image correlation technique. Applying the test data bending moments and curvature diagrams were derived for each beam. The obtained relationships were compared with theoretical results calculated using design code methods LST EN and STR. Using the inverse algorithm developed by VGTU, tension reinforced lightweight concrete stress and strain diagrams were obtained, which were adapted to numerical modeling by software ATENA. Moment and curvature diagrams obtained by finite elements program were compared with experimental moment and curvature diagrams. Good agreement between both diagrams has been obtained. Straipsnyje aprašytas naujai sukurtas konstrukcinis lengvasis betonas ir jo panaudojimas eksperimentinių armuotojo lengvojo betono sijų gamybai. Atlikti trumpalaike apkrova veikiamų plieniniais strypais armuotų lengvojo betono sijų eksperimentiniai tyrimai, kuriuose nagrinėtas sijų įtempių ir deformacijų būvis. Laboratorijoje išbandyti 8 lenkiamieji elementai, kurių armavimo procentai: 0,309 %, 0,557 %, 0,895 % ir 1,255 %. Tyrimų metu matuotos vidutinės elemento deformacijos grynojo lenkimo zonoje 4 skirtinguose lygmenyse bei sijų poslinkiai ties atramomis, jėgos pridėjimo vietose ir viduriniame pjūvyje (iš viso 12 matavimo taškų). Bandymo metu grynojo lenkimo zonos deformacijos bei pleišėjimas papildomai stebėti greitaeige vaizdo kamera. Gauti rezultatai panaudoti sudarant eksperimentines lenkimo momentų ir kreivių diagramas, kurios palygintos su teoriškai apskaičiuotomis taikant Lietuvoje galiojančių LST EN ir STR projektavimo normų metodikas. Taikant VGTU sukurtą atvirkštinio uždavinio algoritmą, gautos tempiamo armuotojo lengvojo betono įtempių ir deformacijų diagramos, kurios pritaikytos atliekant skaitinį modeliavimą baigtinių elementų programa ATENA. Gautos momentų ir kreivių diagramos baigtinių elementų programa palygintos su eksperimentų metu gautomis momentų ir kreivių diagramomis. Gautas geras šių diagramų sutapimas.

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