Photopolymer additive manufacturing has become the subject of widespread interest in recent years... more Photopolymer additive manufacturing has become the subject of widespread interest in recent years due to its capacity to enable fabrication of difficult geometries that are impossible to build with traditional manufacturing methods. The flammability of photopolymer resin materials and the lattice structures enabled by 3D printing is a barrier to widespread adoption that has not yet been adequately addressed. Here, a water-based nanobrick wall coating is deposited on 3D printed parts with simple (i.e., dense solid) or complex (i.e., lattice) geometries. When subject to flammability testing, the printed parts exhibit no melt dripping and a propensity toward failure at the print layer interfaces. Moving from a simple solid geometry to a latticed geometry leads to reduced time to failure during flammability testing. For nonlatticed parts, the coating provides negligible improvement in fire resistance, but coating of the latticed structures significantly increases time to failure by up to ≈340% compared to the uncoated lattice. The synergistic effect of coating and latticing is attributed to the lattice structures’ increased surface area to volume raito, allowing for an increased coating:photopolymer ratio and the ability of the lattice to better accommodate thermal expansion strains. Overall, nanobrick wall coated lattices can serve as metamaterials to increase applications of polymer additive manufacturing in extreme environments.
International Journal of Pressure Vessels and Piping, Sep 1, 2017
The single edge-notched tension (SENT or SE(T)) test uses a low-constraint specimen geometry to d... more The single edge-notched tension (SENT or SE(T)) test uses a low-constraint specimen geometry to determine the elastic-plastic fracture toughness of relevant linepipe steels. Application of the results include, but are not limited to, design methods, material selection, structural integrity assessment, fitness for service (FFS) and engineering critical assessment (ECA). Until recently, industry and government researchers have developed and published recommended practices without consensus from standard development organizations. A test standard was recently issued in 2014 by the British Standards Institution as BS 8571, and there is an ongoing effort to publish a robust standard test method within the American Society of Testing and Materials (ASTM International). Standardization of any test method should consider the influence of physical measurements on the results of the test. Generically, all measurements have uncertainty, and a standardized test method endeavors to produce results with a minimum uncertainty, as well as known precision and bias so that the results can be intelligently used for their intended purpose. This paper reviews the measurement techniques and procedures from each of the published recommended practices and BS 8571 and provides further guidance on specific techniques and procedures with respect to uncertainty.
In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, ex... more In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI and the MATH-1 contractors assume no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. By accepting the report and utilizing it, you agree to waive any and all claims you may have, resulting from your voluntary use of the report, against PRCI and the MATH-1 contractors.
Pipeline and Hazardous Materials Safety Administration2019PDFTech ReportWeeks, TimothyNational In... more Pipeline and Hazardous Materials Safety Administration2019PDFTech ReportWeeks, TimothyNational Institute of Standards and Technology (U.S.)United States. Department of Transportation. Pipeline and Hazardous Materials Safety AdministrationUnited States. Dept. of Transportation. Pipeline and Hazardous Materials Safety AdministrationUnited StatesCrackingHigh strength steelMaterials testsPipelinesState of the artProceduresPromoting SafetyDTPH56-13-X-000013Final ReportThe development of high toughness linepipe materials is reducing the relevance of current material test methods and their application to design. Current fracture mechanics models, plastic collapse schemes and test methods are inadequate to determine the crack arresting capacity of a particular steel alloy/linepipe component. Furthermore, relatively inexpensive tests that are quick to perform are simply not available to accurately assess the fracture behavior of today's high strength and high toughness linepipe steels.111
In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, ex... more In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI and the MATH-1 contractors assume no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. By accepting the report and utilizing it, you agree to waive any and all claims you may have, resulting from your voluntary use of the report, against PRCI and the MATH-1 contractors.
The clamped single edge-notched tension (SE(T)) specimen has been widely used in a single-specime... more The clamped single edge-notched tension (SE(T)) specimen has been widely used in a single-specimen testing scheme to generate fracture resistance curves for high strength line-pipe steels. The SE(T) specimen with appropriate notch geometry is a low-constraint specimen designed to reduce conservatism in the measurement of fracture toughness. The crack driving force is taken as either the J-integral or crack tip opening displacement (CTOD); it is generally accepted that the two parameters are interchangeable and equivalent using a simple closed form solution. However, the assumption that they are interchangeable, and to what extent, hasn’t been previously investigated experimentally on the same SE(T) specimen. This paper presents multiple test methods that were simultaneously employed on the same SE(T) specimens. The instrumentation includes: clip-gauges to measure surface crack mouth opening displacements (CMOD) and CTOD by the double-clip-gauge method; strain-gage arrays for direct J-integral measurements; and direct-current potential-drop (DCPD) instrumentation for supplementary crack size measurement. A direct comparison of ductile crack-growth resistance curves generated using J-integral and CTOD is presented here where each represents a different experimental and analytical approach. The two methods are in reasonable agreement over a narrow range of crack growth, differing slightly at initiation and diverging with increasing crack growth. Analysis of the supplementary instrumentation (i.e., strain gages, extensometers and DCPD) will be provided in a future publication.
A feasibility study was performed to evaluate a novel method of accurately fatigue-cracking steel... more A feasibility study was performed to evaluate a novel method of accurately fatigue-cracking steel plates to generate proposed fatigue-crack reference standards. Fatigue cracks were introduced into low-carbon steel reference plates and the actual size of the fatigue cracks were accurately predicted by the fatigue-crack introduction technique. Flaw sizing of the fatigue cracks in the plates was conducted by industrial collaborators through use of various nondestructive evaluation (NDE) techniques. As part of the feasibility study, a limited round robin analysis was conducted that included NDE sensor manufacturers and users, that demonstrated the fatigue cracks in the reference plates could be located and sized. The round robin demonstrated significant scatter in the NDE data, and the crack depth and surface breaking length values (a × 2c) were both over-and underpredicted as compared to the actual values of the reference plates. The NDE community acknowledges a genuine need for a fatigue crack reference standard by which NDE sensors and technologies can be calibrated and verified for the accurate sizing of fatigue flaws in structural components.
Materials Performance and Characterization, Aug 28, 2014
single-specimen technique that includes formulas for calculating the J-integral and crack-tip ope... more single-specimen technique that includes formulas for calculating the J-integral and crack-tip opening displacement, as well as for estimating crack size using rotationcorrected elastic unloading compliance. Here, crack-resistance curves and critical toughness values obtained from shallow-crack SE(T) specimens (a 0 /W % 0.25) are compared to shallow-crack (a 0 /W % 0.25) SE(B) specimens. We believe that the SE(T) methodology is mature enough to be considered for inclusion in future revisions of EPFM standards such as ASTM E1820 and ISO 12135, although additional work is needed to establish validity limits for SE(T) specimens.
International Journal of Pressure Vessels and Piping, Sep 1, 2017
This special issue on fracture toughness testing and applications to modern pipelines using singl... more This special issue on fracture toughness testing and applications to modern pipelines using single edge notched tension (SENT) specimens aims to provide a technical platform to present recent results with regard to development and progress of SENT fracture toughness test methods and applications. Fracture toughness is an important material property in fracture mechanics methods and has been used for materials selection, engineering critical analysis, fitness for service evaluation and structural integrity assessment. Traditional fracture toughness test methods as specified by American Society for Testing and Materials (ASTM) or British Standards Institution (BSI) were developed for bending dominant specimens to determine lower-bound fracture toughness. For modern pipeline steels, however, both material strength and fracture toughness are high, and the standard lower-bound fracture toughness can be overly conservative for application to real cracks in pipelines. In order to reduce conservatism, the oil and gas industry has favored the use of SENT toughness in the strain-based design and structural integrity assessment of pipelines so as to save material and maintenance costs. While BSI recently published a SENT test standard BS 8571, ASTM work is ongoing on its standardization of SENT testing and facing challenges of consensus on experimental technology and evaluation methodology. Therefore, internationally recognized experts from different countries, including Belgium, Brazil, Canada, UK and USA, were invited to make contributions to this special issue, and eight papers were finally accepted with regard to SENT test methods, test procedures, experimental evaluation, validation and challenges so as to improve SENT toughness testing standardization and applications. The first paper by Dr. Moore and Mr. Pisarski summarizes the current status of the SENT testing standard BS 8571 since its publication and the changes planned for its ongoing development. The second paper by Dr. Park et al. reviews the CANMET SENT test method and applications in comparison with other existing procedures and updating experimental evaluation equations for J-R curve measurements. The third paper by Dr. Panico et al. summarizes the ExxonMobil SENT test procedure using a double clip gage approach for measuring a Crack Tip Opening Displacement (CTOD) resistance curve and its application to strain-based design of pipelines. The fourth paper by Prof. Ruggieri presents a brief review of current progress in fracture resistance test procedures to measure low-constraint fracture toughness using SENT and single edge notched bend (SENB) specimens in terms of J-integral and CTOD resistance curves. The fifth paper by Dr. Zhu presents a more detailed technical review of existing SENT test methods focused on experimental evaluations for the DNV practice, CANMET procedure, ExxonMobil method and BS 8571 standard as well as recent progress with comparisons and suggestions for further studies. The sixth paper by Mr. Weeks reviews the measurement techniques and processes of existing SENT test methods, and provides further guidance on specific techniques and processes with respect to uncertainty for standardized SENT testing of line pipe steels. The seventh paper by Dr. Minnebruggen et al. describes the direct current potential drop technique using experimental and numerical approaches for determining crack growth measurement in a single SENT specimen test. The eighth paper by Dr. Hioe et al. describes the direct current electrical potential method to measure crack extension during a single SENT specimen test with comparison of the unloading compliance results. The guest editors would like to express their gratitude to Professor Robert Ainsworth, the Editor-in-chief of International Journal of Pressure Vessels and Piping, for offering us the opportunity to publish this special issue and for his invaluable advice and help in paper solicitation, review and organization. We hope this special issue provides a useful source of information on SENT testing and applications for researchers and engineers in the fracture mechanics community and in the oil and gas industry.
The influence of microstructure on pipe flattening response was assessed using two different comm... more The influence of microstructure on pipe flattening response was assessed using two different commercially produced U-ing, O-ing, and expansion (UOE) pipes from API X65 steels having either a bainitic microstructure (steel B) or a ferrite/pearlite microstructure (steel FP). A four-point bending apparatus and distinctive procedure were used to minimize strain localization during flattening. The flattened specimens were sectioned at different positions through the thickness, and tensile tested in both the longitudinal (LD) and transverse directions (TD) to assess the through-thickness variation in properties. Yield strength (YS) distributions in the LD show V-shaped profiles through thickness in both steels, whereas the YS in the TD nearest the outside diameter (OD) surface is reduced. These variations in YS are due to the Bauschinger effect associated with the compressive flattening pre-strain. The uniform elongation (UE) of steel FP is almost independent of specimen position through the thickness, but for steel B there is a substantial reduction of the UE at both the inside and outside diameter positions and this reduction is greater in the LD. This work confirms that flattened pipe mechanical properties exhibit an important dependence on their microstructure type and it is postulated that the flattening procedure also influences the mechanical properties.
Ethanol fuel production and consumption are expected to increase significantly in the near future... more Ethanol fuel production and consumption are expected to increase significantly in the near future. Existing pipeline infrastructure could be repurposed to transport ethanol and other biofuels from production sources, such as those located in the Midwest, to end users across the country. The effects of ethanol fuel, including its ability to harbor corrosion-inducing microbiological life, are not well established in relation to degrading the fatigue properties of pipeline materials. In this work experiments were performed to evaluate crack growth behavior of pipeline steels in several ethanol environments. The environments included a simulated fuel grade ethanol and an ethanol-water solution inoculated with a microbiological species (Acetobacter aceti) isolated from industrial ethanol storage tanks. Fatigue crack growth rates of API 5L X52 and X70 pipeline steels were determined as a function of the stress intensity amplitude (ΔK) during exposure to the various ethanol environments. Significant increases in fatigue crack growth rate were found above ΔK levels of approximately 17 MPa m 1/2 and 20 MPa m 1/2 during testing of X52 and X70 in simulated fuel grade ethanol, respectively. Fatigue crack growth rates were increased by almost two orders of magnitude, relative to air, during testing of X52 and X70 in ethanol-water solutions inoculated with acetic acid producing bacteria. Concurrent research suggested that glutaraldehyde may be an effective biocide for controlling acid producing bacteria in pipelines. The data presented are useful for reliability models to ensure safe fuel transport of ethanol.
NIST work developed processes to identify the stress/strain/crack velocity conditions for unstabl... more NIST work developed processes to identify the stress/strain/crack velocity conditions for unstable high-rate ductile crack propagation found in a full-scale pipeline burst test and duplicate those conditions in a medium-scale test. With modeling to validate conditions and assumptions used in reducing the scale of the tests. A medium-scale test to elucidate material property data necessary to qualify high-strength high-toughness steels based on the correlation to large-scale tests. Parametric determination of the material properties governing fracture propagation or arrest-ability was developed. This will assist researchers to determine a relevant and effective small-scale test (or tests) that provides enough information for material selection, design, reliability, as well as integrity and risk assessment. Pipe evaluated includes API5L X70 and X80 pipe. The strain was measured by a three-dimensional digital image correlation system. This project takes a phased approach with complemen...
A variety of mechanical property tests are performed in the design, construction and maintenance ... more A variety of mechanical property tests are performed in the design, construction and maintenance phase of a pipeline. Most of the tests are performed by use of small-scale specimens with size typically in the range of a few inches to tens of inches (1 in = 25.4 mm). There are numerous test labs capable of performing most small-scale tests. These tests can be performed effectively under a variety of conditions, e.g., test temperature, strain rate, and loading configuration. More importantly, most routine small-scale tests are performed in accordance with national and international standards, ensuring the consistency of testing procedures. To confirm pipeline designs and validate material performance, it is desirable to test girth welds under realistic service conditions. Full-scale tests can incorporate certain realistic features that small-scale specimens cannot. However, these tests can be time-consuming and expensive to conduct. Very few labs can perform the tests, even with month...
Volume 3: Operations, Monitoring and Maintenance; Materials and Joining, Sep 26, 2016
This paper reports an extension of a previous study that compared methods of evaluating J by the ... more This paper reports an extension of a previous study that compared methods of evaluating J by the crack mouth opening displacement and by surface strain gradients. Here, the surface strain gradients are measured by three-dimensional digital image correlation. The results herein represent a small test matrix that involved evaluation of the J-integral for clamped single-edge notched tensile specimens from API 5L X65 base-metal, weld metal and the adjacent heat affected zone; the J-integral was evaluated by a standardized procedure utilizing the crack mouth opening displacement (CMOD) and by the contour integral method on an external surface strain contour. Digital image correlation provides sufficient full-field strain data for use by this method and is considerably more robust than surface-mounted strain gage instrumentation. A series of validity checks are presented that demonstrate that the data are useful and valuable. Experimental determination of the J-integral is not limited to thoroughly analyzed test geometries and may be achieved with limited instrumentation. Furthermore, the method described does not require a determination of crack size nor any instrumentation that requires access to the crack mouth.
Photopolymer additive manufacturing has become the subject of widespread interest in recent years... more Photopolymer additive manufacturing has become the subject of widespread interest in recent years due to its capacity to enable fabrication of difficult geometries that are impossible to build with traditional manufacturing methods. The flammability of photopolymer resin materials and the lattice structures enabled by 3D printing is a barrier to widespread adoption that has not yet been adequately addressed. Here, a water-based nanobrick wall coating is deposited on 3D printed parts with simple (i.e., dense solid) or complex (i.e., lattice) geometries. When subject to flammability testing, the printed parts exhibit no melt dripping and a propensity toward failure at the print layer interfaces. Moving from a simple solid geometry to a latticed geometry leads to reduced time to failure during flammability testing. For nonlatticed parts, the coating provides negligible improvement in fire resistance, but coating of the latticed structures significantly increases time to failure by up to ≈340% compared to the uncoated lattice. The synergistic effect of coating and latticing is attributed to the lattice structures’ increased surface area to volume raito, allowing for an increased coating:photopolymer ratio and the ability of the lattice to better accommodate thermal expansion strains. Overall, nanobrick wall coated lattices can serve as metamaterials to increase applications of polymer additive manufacturing in extreme environments.
International Journal of Pressure Vessels and Piping, Sep 1, 2017
The single edge-notched tension (SENT or SE(T)) test uses a low-constraint specimen geometry to d... more The single edge-notched tension (SENT or SE(T)) test uses a low-constraint specimen geometry to determine the elastic-plastic fracture toughness of relevant linepipe steels. Application of the results include, but are not limited to, design methods, material selection, structural integrity assessment, fitness for service (FFS) and engineering critical assessment (ECA). Until recently, industry and government researchers have developed and published recommended practices without consensus from standard development organizations. A test standard was recently issued in 2014 by the British Standards Institution as BS 8571, and there is an ongoing effort to publish a robust standard test method within the American Society of Testing and Materials (ASTM International). Standardization of any test method should consider the influence of physical measurements on the results of the test. Generically, all measurements have uncertainty, and a standardized test method endeavors to produce results with a minimum uncertainty, as well as known precision and bias so that the results can be intelligently used for their intended purpose. This paper reviews the measurement techniques and procedures from each of the published recommended practices and BS 8571 and provides further guidance on specific techniques and procedures with respect to uncertainty.
In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, ex... more In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI and the MATH-1 contractors assume no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. By accepting the report and utilizing it, you agree to waive any and all claims you may have, resulting from your voluntary use of the report, against PRCI and the MATH-1 contractors.
Pipeline and Hazardous Materials Safety Administration2019PDFTech ReportWeeks, TimothyNational In... more Pipeline and Hazardous Materials Safety Administration2019PDFTech ReportWeeks, TimothyNational Institute of Standards and Technology (U.S.)United States. Department of Transportation. Pipeline and Hazardous Materials Safety AdministrationUnited States. Dept. of Transportation. Pipeline and Hazardous Materials Safety AdministrationUnited StatesCrackingHigh strength steelMaterials testsPipelinesState of the artProceduresPromoting SafetyDTPH56-13-X-000013Final ReportThe development of high toughness linepipe materials is reducing the relevance of current material test methods and their application to design. Current fracture mechanics models, plastic collapse schemes and test methods are inadequate to determine the crack arresting capacity of a particular steel alloy/linepipe component. Furthermore, relatively inexpensive tests that are quick to perform are simply not available to accurately assess the fracture behavior of today's high strength and high toughness linepipe steels.111
In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, ex... more In publishing this report, PRCI and the MATH-1 contractors make no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI and the MATH-1 contractors assume no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. By accepting the report and utilizing it, you agree to waive any and all claims you may have, resulting from your voluntary use of the report, against PRCI and the MATH-1 contractors.
The clamped single edge-notched tension (SE(T)) specimen has been widely used in a single-specime... more The clamped single edge-notched tension (SE(T)) specimen has been widely used in a single-specimen testing scheme to generate fracture resistance curves for high strength line-pipe steels. The SE(T) specimen with appropriate notch geometry is a low-constraint specimen designed to reduce conservatism in the measurement of fracture toughness. The crack driving force is taken as either the J-integral or crack tip opening displacement (CTOD); it is generally accepted that the two parameters are interchangeable and equivalent using a simple closed form solution. However, the assumption that they are interchangeable, and to what extent, hasn’t been previously investigated experimentally on the same SE(T) specimen. This paper presents multiple test methods that were simultaneously employed on the same SE(T) specimens. The instrumentation includes: clip-gauges to measure surface crack mouth opening displacements (CMOD) and CTOD by the double-clip-gauge method; strain-gage arrays for direct J-integral measurements; and direct-current potential-drop (DCPD) instrumentation for supplementary crack size measurement. A direct comparison of ductile crack-growth resistance curves generated using J-integral and CTOD is presented here where each represents a different experimental and analytical approach. The two methods are in reasonable agreement over a narrow range of crack growth, differing slightly at initiation and diverging with increasing crack growth. Analysis of the supplementary instrumentation (i.e., strain gages, extensometers and DCPD) will be provided in a future publication.
A feasibility study was performed to evaluate a novel method of accurately fatigue-cracking steel... more A feasibility study was performed to evaluate a novel method of accurately fatigue-cracking steel plates to generate proposed fatigue-crack reference standards. Fatigue cracks were introduced into low-carbon steel reference plates and the actual size of the fatigue cracks were accurately predicted by the fatigue-crack introduction technique. Flaw sizing of the fatigue cracks in the plates was conducted by industrial collaborators through use of various nondestructive evaluation (NDE) techniques. As part of the feasibility study, a limited round robin analysis was conducted that included NDE sensor manufacturers and users, that demonstrated the fatigue cracks in the reference plates could be located and sized. The round robin demonstrated significant scatter in the NDE data, and the crack depth and surface breaking length values (a × 2c) were both over-and underpredicted as compared to the actual values of the reference plates. The NDE community acknowledges a genuine need for a fatigue crack reference standard by which NDE sensors and technologies can be calibrated and verified for the accurate sizing of fatigue flaws in structural components.
Materials Performance and Characterization, Aug 28, 2014
single-specimen technique that includes formulas for calculating the J-integral and crack-tip ope... more single-specimen technique that includes formulas for calculating the J-integral and crack-tip opening displacement, as well as for estimating crack size using rotationcorrected elastic unloading compliance. Here, crack-resistance curves and critical toughness values obtained from shallow-crack SE(T) specimens (a 0 /W % 0.25) are compared to shallow-crack (a 0 /W % 0.25) SE(B) specimens. We believe that the SE(T) methodology is mature enough to be considered for inclusion in future revisions of EPFM standards such as ASTM E1820 and ISO 12135, although additional work is needed to establish validity limits for SE(T) specimens.
International Journal of Pressure Vessels and Piping, Sep 1, 2017
This special issue on fracture toughness testing and applications to modern pipelines using singl... more This special issue on fracture toughness testing and applications to modern pipelines using single edge notched tension (SENT) specimens aims to provide a technical platform to present recent results with regard to development and progress of SENT fracture toughness test methods and applications. Fracture toughness is an important material property in fracture mechanics methods and has been used for materials selection, engineering critical analysis, fitness for service evaluation and structural integrity assessment. Traditional fracture toughness test methods as specified by American Society for Testing and Materials (ASTM) or British Standards Institution (BSI) were developed for bending dominant specimens to determine lower-bound fracture toughness. For modern pipeline steels, however, both material strength and fracture toughness are high, and the standard lower-bound fracture toughness can be overly conservative for application to real cracks in pipelines. In order to reduce conservatism, the oil and gas industry has favored the use of SENT toughness in the strain-based design and structural integrity assessment of pipelines so as to save material and maintenance costs. While BSI recently published a SENT test standard BS 8571, ASTM work is ongoing on its standardization of SENT testing and facing challenges of consensus on experimental technology and evaluation methodology. Therefore, internationally recognized experts from different countries, including Belgium, Brazil, Canada, UK and USA, were invited to make contributions to this special issue, and eight papers were finally accepted with regard to SENT test methods, test procedures, experimental evaluation, validation and challenges so as to improve SENT toughness testing standardization and applications. The first paper by Dr. Moore and Mr. Pisarski summarizes the current status of the SENT testing standard BS 8571 since its publication and the changes planned for its ongoing development. The second paper by Dr. Park et al. reviews the CANMET SENT test method and applications in comparison with other existing procedures and updating experimental evaluation equations for J-R curve measurements. The third paper by Dr. Panico et al. summarizes the ExxonMobil SENT test procedure using a double clip gage approach for measuring a Crack Tip Opening Displacement (CTOD) resistance curve and its application to strain-based design of pipelines. The fourth paper by Prof. Ruggieri presents a brief review of current progress in fracture resistance test procedures to measure low-constraint fracture toughness using SENT and single edge notched bend (SENB) specimens in terms of J-integral and CTOD resistance curves. The fifth paper by Dr. Zhu presents a more detailed technical review of existing SENT test methods focused on experimental evaluations for the DNV practice, CANMET procedure, ExxonMobil method and BS 8571 standard as well as recent progress with comparisons and suggestions for further studies. The sixth paper by Mr. Weeks reviews the measurement techniques and processes of existing SENT test methods, and provides further guidance on specific techniques and processes with respect to uncertainty for standardized SENT testing of line pipe steels. The seventh paper by Dr. Minnebruggen et al. describes the direct current potential drop technique using experimental and numerical approaches for determining crack growth measurement in a single SENT specimen test. The eighth paper by Dr. Hioe et al. describes the direct current electrical potential method to measure crack extension during a single SENT specimen test with comparison of the unloading compliance results. The guest editors would like to express their gratitude to Professor Robert Ainsworth, the Editor-in-chief of International Journal of Pressure Vessels and Piping, for offering us the opportunity to publish this special issue and for his invaluable advice and help in paper solicitation, review and organization. We hope this special issue provides a useful source of information on SENT testing and applications for researchers and engineers in the fracture mechanics community and in the oil and gas industry.
The influence of microstructure on pipe flattening response was assessed using two different comm... more The influence of microstructure on pipe flattening response was assessed using two different commercially produced U-ing, O-ing, and expansion (UOE) pipes from API X65 steels having either a bainitic microstructure (steel B) or a ferrite/pearlite microstructure (steel FP). A four-point bending apparatus and distinctive procedure were used to minimize strain localization during flattening. The flattened specimens were sectioned at different positions through the thickness, and tensile tested in both the longitudinal (LD) and transverse directions (TD) to assess the through-thickness variation in properties. Yield strength (YS) distributions in the LD show V-shaped profiles through thickness in both steels, whereas the YS in the TD nearest the outside diameter (OD) surface is reduced. These variations in YS are due to the Bauschinger effect associated with the compressive flattening pre-strain. The uniform elongation (UE) of steel FP is almost independent of specimen position through the thickness, but for steel B there is a substantial reduction of the UE at both the inside and outside diameter positions and this reduction is greater in the LD. This work confirms that flattened pipe mechanical properties exhibit an important dependence on their microstructure type and it is postulated that the flattening procedure also influences the mechanical properties.
Ethanol fuel production and consumption are expected to increase significantly in the near future... more Ethanol fuel production and consumption are expected to increase significantly in the near future. Existing pipeline infrastructure could be repurposed to transport ethanol and other biofuels from production sources, such as those located in the Midwest, to end users across the country. The effects of ethanol fuel, including its ability to harbor corrosion-inducing microbiological life, are not well established in relation to degrading the fatigue properties of pipeline materials. In this work experiments were performed to evaluate crack growth behavior of pipeline steels in several ethanol environments. The environments included a simulated fuel grade ethanol and an ethanol-water solution inoculated with a microbiological species (Acetobacter aceti) isolated from industrial ethanol storage tanks. Fatigue crack growth rates of API 5L X52 and X70 pipeline steels were determined as a function of the stress intensity amplitude (ΔK) during exposure to the various ethanol environments. Significant increases in fatigue crack growth rate were found above ΔK levels of approximately 17 MPa m 1/2 and 20 MPa m 1/2 during testing of X52 and X70 in simulated fuel grade ethanol, respectively. Fatigue crack growth rates were increased by almost two orders of magnitude, relative to air, during testing of X52 and X70 in ethanol-water solutions inoculated with acetic acid producing bacteria. Concurrent research suggested that glutaraldehyde may be an effective biocide for controlling acid producing bacteria in pipelines. The data presented are useful for reliability models to ensure safe fuel transport of ethanol.
NIST work developed processes to identify the stress/strain/crack velocity conditions for unstabl... more NIST work developed processes to identify the stress/strain/crack velocity conditions for unstable high-rate ductile crack propagation found in a full-scale pipeline burst test and duplicate those conditions in a medium-scale test. With modeling to validate conditions and assumptions used in reducing the scale of the tests. A medium-scale test to elucidate material property data necessary to qualify high-strength high-toughness steels based on the correlation to large-scale tests. Parametric determination of the material properties governing fracture propagation or arrest-ability was developed. This will assist researchers to determine a relevant and effective small-scale test (or tests) that provides enough information for material selection, design, reliability, as well as integrity and risk assessment. Pipe evaluated includes API5L X70 and X80 pipe. The strain was measured by a three-dimensional digital image correlation system. This project takes a phased approach with complemen...
A variety of mechanical property tests are performed in the design, construction and maintenance ... more A variety of mechanical property tests are performed in the design, construction and maintenance phase of a pipeline. Most of the tests are performed by use of small-scale specimens with size typically in the range of a few inches to tens of inches (1 in = 25.4 mm). There are numerous test labs capable of performing most small-scale tests. These tests can be performed effectively under a variety of conditions, e.g., test temperature, strain rate, and loading configuration. More importantly, most routine small-scale tests are performed in accordance with national and international standards, ensuring the consistency of testing procedures. To confirm pipeline designs and validate material performance, it is desirable to test girth welds under realistic service conditions. Full-scale tests can incorporate certain realistic features that small-scale specimens cannot. However, these tests can be time-consuming and expensive to conduct. Very few labs can perform the tests, even with month...
Volume 3: Operations, Monitoring and Maintenance; Materials and Joining, Sep 26, 2016
This paper reports an extension of a previous study that compared methods of evaluating J by the ... more This paper reports an extension of a previous study that compared methods of evaluating J by the crack mouth opening displacement and by surface strain gradients. Here, the surface strain gradients are measured by three-dimensional digital image correlation. The results herein represent a small test matrix that involved evaluation of the J-integral for clamped single-edge notched tensile specimens from API 5L X65 base-metal, weld metal and the adjacent heat affected zone; the J-integral was evaluated by a standardized procedure utilizing the crack mouth opening displacement (CMOD) and by the contour integral method on an external surface strain contour. Digital image correlation provides sufficient full-field strain data for use by this method and is considerably more robust than surface-mounted strain gage instrumentation. A series of validity checks are presented that demonstrate that the data are useful and valuable. Experimental determination of the J-integral is not limited to thoroughly analyzed test geometries and may be achieved with limited instrumentation. Furthermore, the method described does not require a determination of crack size nor any instrumentation that requires access to the crack mouth.
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Papers by Timothy Weeks