bluuebunny/crossref_metadata_2025 huggingface dataset:
Concerted, Computing-Intense Novel MFL Approach Ensuring Reliability and Reducing the Need for Dig Verification
Authors: Palmer Johannes , Schartner Aaron , Danilov Andrey , Tse Vincent
Published: January 2021

Magnetic Flux Leakage (MFL) is a robust technology with high data coverage. Decades of continuous sizing improvement allowed for industry-accepted sizing reliability. The continuous optimization of sizing processes ensures accurate results in categorizing metal loss features. However, the identified selection of critical anomalies is not always optimal; sometimes anomalies are dug up too early or unnecessarily, this can be caused by the feature type in the field (true metal loss shape) being incorrectly identified which affects sizing and tolerance. In addition, there is the possibility for incorrectly identifying feature types causing false under-calls.

Today, complex empirical formulas together with multifaceted lookup tables fed by pull tests, synthetic data, dig verifications, machine learning, artificial intelligence and last but not least human expertise translate MFL signals into metal loss assessments with high levels of success. Nevertheless, two important principal elements are limiting the possible MFL sizing optimization. One is the empirical character of the signal interpretation. The other is the implicitly induced data and result simplification.

The reason to go this principal route for many years is simple: it is methodologically impossible to calculate the metal source geometry directly from the signals. In addition, the pure number of possible relevant geometries is so large that simplification is necessary and inevitable. Moreover, the second methodological reason is the ambiguity of the signal, which defines the target of metal loss sizing as the most probable solution. However, even under the best conditions, the most probable one is not necessarily the correct one.

This paper describes a novel, fundamentally different approach as a basic alternative to the common MFL-analysis approach described above. A calculation process is presented, which overcomes the empirical nature of traditional approaches by using a result optimization method that relies on intense computing and avoids any simplification. Additionally, the strategy to overcome MFL ambiguity will be shown. Together with the operator, detailed blind-test examples demonstrate the enormous level of detail, repeatability and accuracy of this groundbreaking technological method with the potential to reduce tool tolerance, increase sizing accuracy, increase growth rate accuracy, and help optimize the dig program to target critical features with greater confidence.
At the Forefront of In-Line Crack Inspection Services: A Highly Versatile Crack Inspection Platform for Complex Flaw Morphologies and Absolute Depth Sizing
Authors: Bott Steven , MacKenzie Rob , Hill Mike , Hennig Thomas
Published: January 2021

In 2014, Enbridge published a request for proposals to develop and provide a solution on a specific type of long seam cracks in a 26” pipeline. In-line inspection technologies available at the time were not able to consistently and accurately characterize the crack threat, although the line was successfully hydrostatically tested in 2015. During the early stages of the project, NDT Global analyzed in detail Enbridge’s requirements, including the specific challenges, spool type, seam weld characteristics etc. and provided different proposals to Enbridge. In 2016, both parties signed a development contract to develop and build a 26” Next Generation Crack Inspection Platform (Proton). The project was divided into various stages to support a successful project that met performance requirements based both on pump tests and a field trial supported by investigative digs and coupon cutouts.

The robot developed is a highly versatile crack inspection platform: it allows to be set up in a configuration optimized for the given threat, pipeline conditions, inspection speed and medium characteristics. This optimization of the configuration allows choosing the optimum measurement modes for flaws in the base material and in the seam weld independently. Additionally, the local wall thickness even in the seam weld is measured accurately. These capabilities allow the operator to collect the best data for each situation. Feeding the information into the crack management program allows Enbridge to maintain the target reliability of the asset.

The robot was utilized successfully in the 26” pipeline. Processing, data analysis and reporting were performed within pre-agreed periods. Initial field findings and lab tests show high correlation of ILI and real flaws and proof the stated accuracy of the new service.

The authors will present in detail some of the specific challenges of the pipeline system and limitations of available crack inspection technologies. Validation results from in-the-ditch non-destructive examination and destructive freeze breaks including cross sections from flaws with complex morphologies will be shown. Performance statistics and comparison to previous inspection results will be used to demonstrate that the new robot can be used as part of an effective crack management program.
Pipeline Steel Fracture Toughness and the Need for a Toughness Database of API 5L Line Pipe
Authors: Lamborn Lyndon , Zhang Shenwei , Limón Sergio , Lai Roger
Published: January 2021

In order for the pipeline industry to usher in the next-level fracture mechanics engineering analysis, reasonable and prudent fracture toughness characterizations are needed to improve burst pressure predictions and fatigue crack growth analysis of pipelines with planar cracks. Converting Charpy V-Notch (CVN) value to fracture toughness via different empirical correlation models derived throughout the years, while laudable, have inherent shortcomings. The main issues being that the Charpy toughness test is not a fracture mechanics-based measurement and the transferability of sub-scale fracture toughness testing is often not completely understood nor is correctly applied. This paper expands on these shortcomings and presents solutions which are supported by fracture toughness data obtained from the pipe boy and seam weld of API 5L line pipe steels. In this manner, best available toughness derivations for mean toughness in base metal and long seam welds are presented. Suggestions for standard fracture mechanics sub-scale coupon testing, such as ASTM E1820, on pipeline steel samples are delineated with rationale for each test type. The transferability of fracture toughness from sub-scale coupon testing results to that exhibits in full-scale pipe failure are demonstrated in the paper. This fracture toughness test database and other similar data sets can be combined and serve as the basis for establishing an industry wide Pipeline Material Database which would mirror established material databases in the aerospace industry such as NASGRO and AFMAT. It is envisioned that a centralized and validated Pipeline Material Database will be expanded to include fatigue crack growth rate data and other pipeline material characterization data sets. These data will support minimizing material assumptions and increase the accuracy of structural integrity predictions to improve the overall pipeline performance. This combined database would be accessible to engineers, analysts, and researchers and updated at regular intervals as more data becomes available.
Establishment and Application of the Pipeline Monitoring System in Permafrost Regions in China
Authors: Liu Jianping , Chen Pengchao , Zhang Hong , Wang Baodong , Liu Xiaoben
Published: January 2021

Buried pipelines in permafrost regions are inevitably subjected to some typical geohazards, such as frost heave, thaw settlement and thaw slumping. The bending or/and longitudinal strains will be induced in pipe under these types ground movement, which is the potential cause of weld joint rupture. Thus, in order to prevent pipe failure, a comprehensive monitoring system was designed and used in the Mohe-Daqing oil pipeline in the permafrost region in northeast China. The Mohe-Daqing oil pipeline is built for importing oil from Russia and its north part of 440km lays in permafrost. The monitoring system includes soil temperature field monitoring system, ground displacement monitoring system and pipe strain monitoring system. The soil temperature field monitoring system, which uses fiber brag grating sensors, can monitor the distribution of surrounding soil temperature in radial direction of pipe in order to detect the change of active ring of permafrost. The ground displacement monitoring system, which is based on a total station, can discover any subsidence or heave of the pipe itself and the embankment along the pipeline. The pipe strain monitoring system, which includes pipe stress monitoring system based on fiber brag grating sensors and inertial measurement unit (IMU) mapping, can inspect the real-time change of pipe stress and the bending strain periodically respectively. Using the comprehensive monitoring system, the important parameters that affect pipeline integrity such as pipeline temperature, stress, strain and displacement of Mohe-Daqing oil pipeline can be supervised timely and effectively. And the accuracy and reliability of the monitoring system have been verified in practical application. In this paper, detail about how these systems are designed and installed on the Mohe-Daqing oil pipeline is elucidated and the monitoring data is analyzed. Through these data, the present mechanical situation of Mohe-Daqing oil pipeline is safe, but the long-term change is critical because of the soaring oil temperature that is far high than the design temperature. The monitoring system is of great significance to ensure the safe operation of Mohe-Daqing pipeline and can provide reference for the pipeline operation in permafrost areas.
Hydrostatic Collapse Tests of Full-Scale Pipeline Specimens With Thickness Metal Loss
Authors: Cunha Divino J. S. , Ferraz Caroline , Netto Theodoro A. , Diniz J. C. , Rosa Diego G. G. , Freire José L. F.
Published: January 2021

The present paper deals with the subject of failure of deep-sea pipelines that have thickness metal-loss areas caused by corrosion and are subjected to high external hydrostatic pressure. An extensive research program was launched to observe failure modes, to examine existing and to develop prediction collapse equations, and to determine their accuracy. The program uses finite element modeling and external hydrostatic collapse tests of full-scale specimens. This paper presents and discusses the results of the first 20 collapse tests, which were performed in a new 103 MPa (15 ksi) hyperbaric chamber (760 mm internal diameter and 7200 mm length). The test results obtained with full scale specimens (324 mm external diameter and 23 mm thickness) made of low carbon steel API 5L X60 with external machined metal loss defects are used to verify the level of accuracy and conservatism of four analytical simple equations used to predict collapse of pipes with corrosion subjected to high external pressure.
Improved Inspection Through Full Matrix Capture Technology
Authors: Bellistri Domenico , Vinyard Jeff , Seward Cameron
Published: January 2021

The ideal Non Destructive Evaluation/Examination process should be carried out using a fully automated system: planning, execution, evaluation and reporting would be all tasks performed by automated technologies and artificial intelligence that don’t need human intervention, thus taking the Human Factor out of the equation. Not yet reaching this level of automation, it is still possible to improve the overall quality of the NDE process to increase both speed and quality, while maintaining safety.

Ultrasonic Testing NDE is considered a safe, portable and reliable inspection method. Detection and characterization depends upon factors like technician’s experience and skills, especially for shear wave UT, where an amplitude vs time signal, the A-Scan, is the only given information from the specimen to be examined. With this technique there is very little digital data saved, often in the form of screenshots.

The evolution of shear wave UT was represented by the use of an array probe with the Phased Array technique: the new capabilities of simultaneously steering the beam in multiple directions and combining all the A-Scans in images together, has made it easier to interpret any anomalies found during inspection.

However, skill and experience are still very important factors to avoid false positive and false negative results. For example, focusing distance from the array probe and false signals from mode conversion may lead to the wrong conclusions.

Ultrasonic imaging technology based on full matrix capture has the intrinsic ability to improve interpretation over more conventional techniques such as PA UT or shear wave UT since it provides information not only about the size of flaws, but also on their geometry in terms of horizontal and vertical extent.
Characterization of Crystallographic Texture of ERW Welded and Heat-Treated API X70 Pipeline Steel
Authors: Sharma Nitin , Wang Yiyu , Li Leijun , Anderson Neil , Rashid Muhammad
Published: January 2021

The impact toughness of high frequency electric resistance welded (ERW) line pipe depends on the steel chemical composition, welding procedure, and post-welding heat treatment. Among several microstructural factors that may influence the impact toughness of high frequency electric resistance welded bond line, the crystallographic texture factor is often assumed, but not sufficiently studied. The evolution of texture during high frequency electric resistance welding and simulated post-welding heat treatments (PWHT) of API X70 pipeline steel was characterized using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). Results of a texture factor calculated using the θ/2θ XRD scans indicated that following the post-weld normalizing treatment, the texture factor of {100} planes for the weld bond line appeared to have increased with the increase in post-weld normalizing temperature. The texture factor results obtained from θ/2θ XRD scans were further verified by using the EBSD on the CVN tested samples in the regions near the fracture path. The XRD texture factor was also used to correlate the evolution of crystallographic texture and Charpy toughness for the PWHT samples. Based on the observations from both XRD and EBSD, the {100} crystallographic orientation of planes in the notched direction correlates well with the cleavage fracture planes of the Charpy impact tested samples. Therefore, the post-weld heat treatment should be designed to minimize any preferred crystallographic texture with {100} planes in the bond line, to promote ductile fracture and improved bond line impact toughness at low temperatures.
Austenite Grain Size Model for the Coarse Grain Heat Affected Zone in Line Pipe Steels
Authors: Romualdi Nicolas , Militzer Matthias , Poole Warren , Collins Laurie , Lazor Robert
Published: January 2021

Pipelines are the safest and most cost-effective method of oil and gas transportation to storage and processing facilities. Large diameter welded pipes fabricated by submerged arc welding (SAW) are the preferred product in many cases for pipeline construction. Furthermore, pipelines are constructed by welding segments of pipe, typically by single or dual torch Gas Metal Arc Welding (GMAW). During welding, both during pipe fabrication and girth welding, the Heat Affected Zone (HAZ) experiences rapid thermal cycles with peak temperatures up to the melting temperature of the base metal. Controlling the microstructure evolution in the HAZ during welding of line pipe steels is critical to ensure that these products meet the Charpy impact testing and CTOD requirements imposed by clients and specifications.

In particular, the Coarse Grain Heat Affected Zone (CGHAZ) is of concern. Here, austenite grain growth occurs readily due to the combination of high temperature and precipitate dissolution. Controlling the CGHAZ austenite grain size is critical to obtain final microstructures with acceptable impact properties. In this study, austenite grain growth has been measured and modeled for thermal conditions relevant for the CGHAZ in 27 steels, including industrial as well as laboratory steels with systematic variations of alloying element content.

Austenite grain size was measured using a Laser Ultrasonics for Metallurgy (LUMet) sensor attached to a Gleeble 3500 Thermomechanical Simulator, which enables high-throughput in-situ monitoring of austenite grain growth. A classical grain growth model has been developed based on a standard test. The grain growth kinetics are described by combining curvature driven grain growth with pinning due to TiN precipitates. A phenomenological relationship has been developed for the grain boundary mobility that decreases with C, Nb and Mo alloying which is consistent with their expected grain boundary segregation. The pinning parameter is rationalized in terms of volume fraction and size of TiN particles. The proposed model has been validated for CGHAZ heat treatment cycles including an industrial welding trial.

The results of this study provide a model to predict the austenite grain size in the CGHAZ as a function of steel chemistries and heat treatment paths, i.e. welding parameters. Austenite grain size maps have been constructed as a function of peak local temperature and line pipe steel chemistry. The model can be used both for steel chemistry design and for optimizing welding of steels with known chemical composition to minimize the CGHAZ austenite grain size both during pipe fabrication and girth welding.
The Influence of Burial Depth and Soil Thermal Conductivity on Heat Transfer in Buried CO2 Pipelines for CCS: A Parametric Study
Authors: Olugunwa Babafemi , Race Julia , Tezdogan Tahsin
Published: January 2021

Pipeline heat transfer modelling of buried pipelines is integral to the design and operation of onshore pipelines to aid the reduction of flow assurance challenges such as carbon dioxide (CO2) gas hydrate formation during pipeline transportation of dense phase CO2 in carbon capture and storage (CCS) applications. In CO2 pipelines for CCS, there are still challenges and gaps in knowledge in the pipeline transportation of supercritical CO2 due to its unique thermophysical properties as a single, dense phase liquid above its critical point. Although the design and operation of pipelines for bulk fluid transport is well established, the design stage is incomplete without the heat transfer calculations as part of the steady state hydraulic and flow assurance design stages. This paper investigates the steady state heat transfer in a buried onshore dense phase CO2 pipelines analytically using the conduction shape factor and thermal resistance method to evaluate for the heat loss from an uninsulated pipeline.

A parametric study that critically analyses the effect of variation in pipeline burial depth and soil thermal conductivity on the heat transfer rate, soil thermal resistance and the overall heat transfer coefficient (OHTC) is investigated. This is done using a one-dimensional heat conduction model at constant temperature of the dense phase CO2 fluid. The results presented show that the influence of soil thermal conductivity and pipeline burial depth on the rate of heat transfer, soil thermal resistance and OHTC is dependent on the average constant ambient temperature in buried dense phase CO2 onshore pipelines. Modelling results show that there are significant effects of the ambient natural convection on the soil temperature distribution which creates a thermal influence region in the soil along the pipeline that cannot be ignored in the steady state modelling and as such should be modelled as a conjugate heat transfer problem during pipeline design.
Burst Pressure Prediction of Pipes With SCC Colonies: Evaluation of Intelligent Flaw Interaction Rules Using Full-Scale Burst Tests
Authors: Wang Bo , Liu Banglin , Wang Yong-Yi , Wang Alex , Rapp Steve
Published: January 2021

This is the second paper in a two-paper series which covers the PRCI-funded work aimed at the development of intelligent flaw interaction rules (termed PRCI-CRES SIA-1-5 rules). The first paper focused on the development of the rules using numerical analyses. This paper covers the evaluation of the rules through full-scale burst tests and accompanying small-scale material tests.

Four full-scale burst tests were conducted on 20” and 18” OD pipe segments with SCC. The SCC colonies on the test sections were inspected using MPI, PAUT, ECA, and IWEX. The small-scale material tests were conducted to measure pipe tensile strength and Charpy impact energy. The four test sections were pressurized until burst. The burst tests were recorded using multiple video cameras to capture the global behavior and detailed crack opening process at the burst locations. With the videos and the post-test examination of the failure surfaces, the full-scale burst tests provide not only the burst pressure but also information for the validation of the fundamental principles of the new interaction rules.

The modified Ln-sec method was used to predict the burst pressure using the equivalent crack size from different flaw interaction rules and the measured pipe material properties. The PRCI-CRES SIA-1-5 rules were found to provide the most accurate and precise burst pressure prediction when factors other than flaw interaction rules remain the same.

The application of the PRCI-CRES SIA-1-5 rules can reduce unnecessary hydrotests and/or other remediation actions with accurate, not overly conservative, burst pressure prediction.
Weld Hydrogen Cracking Susceptibility
Authors: Dinovitzer A. , Moulton J. , Quintana M. , Lazor R.
Published: January 2021

Weld hydrogen cracking has been recognized as an issue of concern and a wide range of hardenability criteria and single pass weld testing techniques have been developed to demonstrate material weldability, however, hydrogen cracks continue to be identified in welds. The potential for hydrogen cracking is related to the presence of hydrogen, the local tensile strain state and the susceptibility of the material microstructure. The weldment slow bend test and hydrogen effusion and cracking model has been used in Pipeline Research Council International (PRCI) research reported in this paper to support the development of an understanding of the interaction of these factors in promoting hydrogen cracking. The slow bend testing procedure is described with examples of the effects of increasing hydrogen and/or strain conditions are used to illustrate hydrogen cracking susceptibility. The slow bend testing procedure was applied to a range of steel weld metals to develop an understanding of the factors which make one more or less susceptible to hydrogen cracking. Combining the results of slow bend testing, the susceptibility of deposited shielded metal arc weld material to hydrogen cracking is defined using a hydrogen susceptibility curve that establishes the critical strain to form a crack as a function of hydrogen concentration. Cracking susceptibility is described through the definition of material ductility and embrittlement indices, which are derived from the hydrogen susceptibility curves. Cracking susceptibility is then correlated with mechanical, chemical and microstructure properties of the deposited welds. This model to predict weld metal hydrogen cracking susceptibility was developed to support electrode selection and welding procedure development to preclude hydrogen cracking. The results in this paper can be used to reduce the risk of hydrogen cracking and support the development of industry guidance.
Microstructure Transformation and Mechanical Properties of X80 Large Diameter Thick Wall Induction Heating Bend for Low Temperature Service
Authors: Liu Yu , You Zongbin , Yan Lijun
Published: January 2021

For the requirement of pipeline station construction project, Grade X80 Longitudinally Submerged Arc Welded (LSAW) induction bend pipe 1422 mm in diameter and wall thickness greater than 25 mm have been developed for pipeline station service applications at −45 °C. The mother pipe of the bends was welded by Ni-Cr-Cu-Mo-Nb-V micro-alloyed Thermo Mechanical Control Process (TMCP) steel plates. After the heat cycle of the bent pipe manufacturing, the microstructure of the base material of the bent pipe consisted of lath bainite ferrite (LBF) and granular bainite (GB). Therefore, it can obtain high strength and excellent low temperature toughness, which can meet the requirements of the project. On the other hand, the welding of the longitudinal seam-welds of the bend mother pipe uses a typical multi-wire two-pass submerged arc welding (SAW) process, which has a large amount of welding heat input. This results in a coarse columnar weld structure with a large amount of fine acicular ferrite so that the seam weld still has a good low temperature impact toughness. However, after the thermal cycling of the bend, the acicular ferrite in the microstructure of the weld metal was greatly reduced, and the grain size was unevenly distributed, which caused the low temperature toughness of the weld metal to deteriorate significantly. In order to solve this problem, the Gleeble3500 thermal simulation test machine was used to test the phase transition critical point Ac3 of the base material and the seam weld metal of the mother pipe. In order to optimize the induction bend process parameters, the influence of heating temperature, cooling rate and tempering temperature on microstructure and mechanical properties were examined. In addition, on the basis of the existing welding process, the welding wire and flux for pipe-making seam-welding were improved, and the pipe-making welding process of the bent mother pipe was improved.
Formulation of 3D Soil Springs for Pipe Stress Analyses
Authors: Barrett John , Phillips Ryan
Published: January 2021

Interdependence between pipe-soil interaction springs in a pipe stress analysis should be considered. This example focused on a single pipe configuration “wished” in place in a clay soil. A conventional pipe stress analyses often idealizes the pipe soil interaction with a beam-spring finite element model where independence is assumed between reactions in axial, lateral and vertical directions. There is however interdependence between these springs as recognized in recent Pipeline Research Council International (PRCI) guidelines. For a frictional interface, axial resistance can be much higher than indicated by PRCI guidelines when accounting for increased lateral and vertical bearing pressure. At the same time, lateral and vertical capacities are shown to be reduced in comparison to pure vertical and lateral loading directions. This paper highlights the development of a 3D soil-spring interaction model based on a continuum finite element analysis approach. By developing a soil capacity envelope based on 3D continuum modeling, updated soil springs can reflect modified capacities depending on the direction of pipe movement. For the landslide scenarios considered in application of the model, the directional dependency is shown to change the accumulated plastic strain profile in the pipe.
Time Dependence of Hydrogen Induced Cracking of X70 Pipeline Steel Under Severe and Mild Sour Service Conditions Using Ultrasonic Analysis
Authors: Gawor S. , Wiskel J. B. , Ivey D. G. , Liu J. , Henein H.
Published: January 2021

A standard NACE hydrogen induced crack test was used to evaluate the resistance of two compositions of X70 steel (X70-X (Ca/S ratio of 2.5) and X70-B (Ca/S ratio of < 0.5)) under severe (pH = 2.7 and 100% H2S) and mild (pH = 5.5 and 100% H2S) sour service conditions. An ultrasonic technique was developed to quantify the severity of hydrogen cracking in both steels as a function of test conditions, steel type and time. In this procedure, a series of local ultrasonic measurements was taken for each test sample to determine a local crack to backwall signal ratio (LCBR). The LCBR values were integrated over the entire sample to give a global crack to backwall ratio (GCBR). A larger GCBR value corresponds to greater hydrogen cracking severity in the sample. Energy dispersive X-ray (EDX) spectroscopy and glancing angle X-ray diffraction (XRD) were used to characterize the surface corrosion products that formed during testing. For severe sour service conditions, the GCBR value reached an asymptotic value of approximately 33% and 47% for X70-X (after 4 days) and X70-B (after 2 days) steels, respectively. For mild sour service conditions, no cracking was observed for testing of less than 16 days. After 32 days, X70-B showed a GCBR of approximately 18%. The onset of cracking of X70-X steel occurred between 32 and 64 days. Samples tested for 64 days showed a GCBR of 30% and 16% for X70-X and X70-B, respectively.

Glancing XRD measurements showed the presence of surface FeS on both steels tested under mild sour service. Quantitative XRD (QXRD) analysis was used to obtain the surface coverage of FeS as a function of test time. EDX mapping confirmed the presence of a high sulfur content over a significant fraction of the surface. XRD measurements of X70-B steel under severe sour service after 8 days did not show a significant amount of FeS. The surface FeS is believed to alter hydrogen ingress into the steel, making it difficult to directly compare measured GCBR values obtained under mild and severe sour service.
Evaluation of Contacting Effect Between Tool and Workpiece on Vibration Characteristics of NC Machine Tools
Authors: Hokazono Taisuke , Sato Ryuta , Nishida Isamu , Shirase Keiichi
Published: January 2021

It is expected that the vibration characteristics of NC machine tools are affected by the contact between the tool and the workpiece during the cutting operations. However, the influences of the contact have not been clarified up to now. In this study, a method to evaluate the contacting effect and evaluated results are described. Frequency response of a vertical type milling machine during cutting operation is evaluated in this study. The evaluation tests of the contacting effect are carried out with and without cutting operations. In order to clearly evaluate the influence of the contact between a tool edge and a workpiece, boring operations of 50 mm diameter are carried out. The frequency responses are measured by using feed motor torque. Impulse signal is applied to the motor torque command during the cutting operations to oscillate the machine tool, and the axial acceleration of the table is measured to obtain the frequency responses. The impulse signal can be applied by refereeing the spindle rotational angle to control the relationships between the cutting edge and workpiece surface. As the results of the evaluations, it is clarified that the proposed method can evaluate the influence of the contact adequately. The natural frequency slightly increases and the vibration amplitude decreases when the tool contacts with the workpiece, regardless of whether non-cutting or cutting. It has also been confirmed that the vibration amplitude of the frequency characteristics is changed due to the contact length and the relative direction of the cutting edge.
Experimental Investigation Into the Spatter Particle Behaviour of Maraging Steel During Selective Laser Melting
Authors: Furumoto Tatsuaki , Egashira Kyota , Oishi Kazushi , Abe Satoshi , Hashimoto Yohei , Koyano Tomohiro , Hosokawa Akira
Published: January 2021

The quality of built parts by selective laser melting (SLM) relies on the comprehension of the phenomena that takes place during the melting and solidification of the metal powder. The scattering of spatter particle as liquid metal during SLM process affects the layer consolidation of powder bed in addition to the surface quality of built part.

The present study is focused on the spatter particle behaviour of maraging steel during SLM to achieve a thorough understanding of the phenomena that occur during the melting and fusing of the metal powder. The spatter particles are tracked using high speed imaging, and the effects of the process parameters on the spatter particle behaviour are investigated. The spatter particles ejected from the melt pool are also physically and chemically evaluated.

The results showed that the spatter particles were classified as being spherical or satellite types, according to their scattered volumes; some spatter particles were larger than the particles in the initial metal powder. Most spatter particles were ejected from the droplet formed around the melt pool and from the melted powder in front of the melt pool; the number of spatter particles ejected from the melt pool was relatively low. The surface roughness affected the generation locations and tracks of the spatter particles, and the substrate surface wettability was the principal factor affecting the spatter particle behaviour.
Fabrication of Flexible Interposer Using Printing Method
Authors: Furuta Atsuhiro , Honjo Kazuki , Taniguchi Jun
Published: January 2021

In recent years, flexible electronic devices such as printed electronics are gathering attention. To make flexible connect between one circuit device and another circuit device, interposer is necessary. However, most of conventional interposers are not flexible, because there are made of silicon or glass substrate. To solve this problem, we have been developed fabrication process of flexible interposer.

Master mold was fabricated by photolithography process. First, SU-8 resist was coated on silicon substrate with 5μm thickness. Then, photolithography process was carried out to SU-8 resist. After development, pillar shape master molds with diameters of 10 or 20 μm were obtained. After release coating of master molds, hole patterns for vias were transferred by UV nanoimprint lithography. The obtained hole patterns were diameter of 10 μm or 20 μm, and pitch of 21.0 μm and 40.1 μm, respectively. Next, these holes were filled with silver ink by roll press method. Then, sintering process was carried out to evaporate of solvent of silver ink. After that, flexible interposer was obtained.

As a result, we have been succeeded in filling the holes array with silver ink. Obtained interposer vias, which were silver region, were 8.2 μm diameter and 3.3 μm height, or 20.3 μm diameter and 5.3 μm height for 10 mm square size.
Tool Path Generation for Five-Axis Controlled Machining of Free-Form Surface Using Barrel Tool: Control of Contact Point on Cutting Edge
Authors: Suzuki Tomonobu , Morishige Koichi
Published: January 2021

This study aimed to improve the efficiency of free-form surface machining by using a five-axis controlled machine tool and a barrel tool. The barrel tool has cutting edges, with curvature smaller than the radius, increasing the pick feed width compared with a conventional ball end mill of the same tool radius. As a result, the machining efficiency can be improved; however, the cost of the barrel tool is high and difficult to reground. In this study, a method to obtain the cutting points that make the cusp height below the target value is proposed. Moreover, a method to improve the tool life by continuously and uniformly changing the contact point on the cutting edge is proposed. The usefulness of the developed method is confirmed through machining simulations.
Influence of Tool Path When Groove Shape Machining Using Ceramic End Mill on Tool Cutting Edge
Authors: Hasegawa Masanobu , Ichikawa Kohei
Published: January 2021

In recent years, the application of ceramic end mill has been studied for the purpose of improving the efficiency of end milling of difficult-to-cut materials such as Ni-base heat resistant alloys. However, although there are cases of application in simple shape and continuous cutting, there are few cases of application in groove shape and intermittent cutting. Because ceramic end mill is not recommend for interrupted cutting. On the other hand, the tool path for actual part machining, such as impeller machining by a conventional carbide end mill, often changes the tool direction by air cutting. In addition, because there are restrictions on the shape of actual parts, air cut may be unavoidable. Therefore, it is important to clarify the effect of intermittent cutting, and to understand the effects and issues when using a continuous cutting tool path.

In this study, the relationship between the tool path and the tool edge condition was verified by the cutting test of the groove shape of Inconel 718 with a ceramic end mill. As a result, it was clarified that the tool path with intermittent air cut has an effect on the cutting edge. In addition, the relationship with the damage to the cutting edge when the number of cutting tooth and the cutting action in the axial direction were changed in a continuous cutting tool path was clarified.
Investigation of Correlation Between Process Energy Balance and Phase Shift Variation of Chatter Vibration in Spindle Speed Variation
Authors: Yamato Shuntaro , Matsuzaki Hirohiko , Ito Takamichi , Kakinuma Yasuhiro
Published: January 2021

It is widely known that the spindle speed variation (SSV) is an effective technology for chatter suppression, especially in the turning or boring process. Its simple optimal design, however, is not a simple task. In the past, certain research works considered the chatter onset from the perspective of process energy balance in a vibration cycle. The phase shift between previous (i.e., outer modulation) and present vibrations (i.e., inner modulation) of chatter is a key factor in the process energy balance. The SSV can be conceptually interpreted as a technique that continuously perturbs the phase shift between the inner and outer modulations, thereby changing the process energy balance. Simply put, the chatter energy can be controlled by applying the SSV to suppress the chatter. This study investigates the correlation between the process energy balance and phase shift behavior in the sinusoidal SSV through numerical energy simulation. The results indicate that the phase shift at the maximum spindle speed is an important factor to minimize the total energy balance (i.e., to dissipate the chatter energy) in the SSV cycle. This probably corresponds to the fact that the beat vibration tends to occur near the maximum spindle speed in the SSV. The insights gained from this study are anticipated to serve as a guideline for shaping the phase shift profile in the SSV to effectively suppress chatter vibration.
On-Machine Estimation of Workpiece Deformation for Thin-Walled Parts Considering Fixture Clamping Sequence
Authors: Zeng Jingkai , Teramoto Koji , Wu Dongjin , Matsumoto Hiroki
Published: January 2021

Due to the higher structure efficiency and lightweight characteristic, thin-walled parts are widely used in the modern manufacturing industry. However, from another point of view, these parts are complex in structure, weak stiffness and high precision demand. During the machining process, because of the material properties and structural characteristics, the action of elastic deformation in machining is heavily affected by the accuracy of thin-walled parts. Recently, novel near-net-shape machining methods which can be applicable to small-lot production such as thin-walled casting, additive manufacturing, and so on becomes common technology.

Finish machining of these thin-walled and complex shape workpiece is an important target of machining. In the small lot production, most of fixturing process is executed as manual operations, which generate large process variations. These variations lead to deteriorate machining accuracy. Especially, the wrong operation for the fixture clamping sequence generates different workpiece deformation. The objective of this research is to estimate actual workpiece deformation by utilizing locally measured strains and fixturing simulation in order to detect unallowable workpiece deformation caused by the wrong clamping sequence.

In this research, workpiece deformations for different clamping sequences are evaluated based on the engineering experiments. Verifications of estimated workpiece deformations are carried out. Through this research, we can effectively estimate the workholding situation of the thin-walled parts during the machining process.
Surface Roughness Analysis for Radius End Mill in Cross Feed Direction Both Contour and Scanning Line Machinings
Authors: Narita Hirohisa
Published: January 2021

An optimum experimental condition, which realize good surface roughness in cross direction both contour and scanning lines, for radius end mill against some inclined surfaces is obtained and some features is these cutting processes is discussed in this paper.

The optimum experimental condition, which consists of cutting type (or feed direction), spindle speed, feed rate, depth of immersion, inclination angle, corner radius of end mill and cross feed, is obtained and the influence degree of these parameters is calculated by using Taguchi method. The experiment is carried out based on L18 orthogonal array. Based on the influence degree and geometric contact status due to unique shape of radius end mill, some feature of radius end milling is introduced.

As a result of the contour line machining, a scallop height is very influenced by the inclination angle and the corner radius, and surface machined by bottom edge must not be remained. Regarding the scanning line machining, “go-up” is good for the feed direction. Big corner radius is also suitable because side edge does not contact to workpiece. In other words, the cutting force in radial direction becomes small. Furthermore, the surface roughness of the scanning line machining is smaller than the one of the contour line machining.
Visualization of Dynamically Changing Cutting Force Under Ultrasonic Cutting Condition
Authors: Isobe Hiromi , Okuda Masataka , Hara Keisuke , Sakurada Akira , Ishimatsu Jun
Published: January 2021

The aim of this study is to investigate the dynamic phenomenon of ultrasonic vibration-assisted cutting condition by utilizing visualization system of stress distribution. The vibrating cutting edge is considered to be cause of dynamic change of cutting force at ultrasonic frequency. However, many researchers have explained the effect of ultrasonic vibration-assisted cutting by evaluating the time-averaged cutting force, because the dynamometers have insufficient frequency characteristics to measure the dynamically changing cutting force in ultrasonic frequency. In this study, the instantaneous stress distribution on workpiece was visualized by photoelastic method in combination of pulse laser emission synchronized with tool vibration. A constructed photographic system is able to capture 360 flames for one ultrasonic vibration period. Dynamic cutting force is calculated by stress distribution by Flamant theory. It was experimentally confirmed that the stress distribution under vibration-assisted condition showed the periodical change synchronized with insert vibration. Because these results are compatible with well-known vibration cutting theories, the imaging system is able to show the periodic change of stress distribution in ultrasonic frequency band. It is considered that the dynamic change of cutting force for ultrasonic vibration period affects intermittent cutting condition. In this report, the vibration direction was adjusted from −9.54° to +9.5° to the cutting direction. When the tool moved in upward for the cutting phase and downward for withdrawal phase, the stress distribution continued to be observed over one period of tool vibration and intermittent cutting did not occurred. The locus of cutting force vector was affected by the ultrasonic vibration direction and rake angle of cutting tool. Negative rake angle showed that the direction of the cutting force vector shifted to the workpiece side near the most advanced position of the cutting edge.
Molecular Dynamics Simulations of Deformation Behavior of AlN in Nanoscratching
Authors: Li Baozhen
Published: January 2021

During the past few years aluminum nitride (AlN) as an important semiconductor material has attracted more and more attention owing to its splendid physical and mechanical properties. In this paper, molecular dynamics simulations of nanoscratching process of AlN are carried out study the deformation behaviors of AlN. The effects of scratching depth on the scratching force, workpiece pile-up and dislocation formation and motion are thoroughly studied. We found that the plastic deformation of AlN is mainly caused by the dislocation nucleation and motion in the nanoscratching process. In this study, we note that the workpiece material undergoes plastic deformation predominant by dislocation activity. In order to investigate the effects of the basic factors that play an important role in the scratching process, we further performed a series of MD simulations of scratching on the AlN(0001) surface along the [-12-10] direction. And it can be seen that there is a critical scratching depth for the transformation from elastic deformation to plastic deformation. The results suggest that the friction and normal force are bigger for a larger scratching depth. We also found the phenomenon of ultra-low friction under shallow scratches of AlN in the scratching process. The ultralow friction force at the scratching depth of 1nm is because of the absence of permanent plastic deformation of workpiece. The deformation under the abrasive begins to recover after the abrasive moves forward. This is the possible reason for the occurrence of ultra-low friction. These results shed light on the material deformation mechanism in nanoscratching process of AlN.
Exploration of Finishing Capability of Developed Polishing Tool in Hybrid Magnetic Field Assisted Finishing Process to Finish Complex Freeform Surfaces of Femoral Component of Prosthetic Knee Joint
Authors: Barman Anwesa , Das Manas
Published: January 2021

Magnetic field-assisted finishing process is a hybrid nanofinishing process that combines the advantages of both magnetorheological finishing process and chemical mechanical polishing process. This process uses magnetorheological fluid combined with chemicals as the polishing medium. The developed novel tool is made of mu-metal which encloses a permanent magnet. The femoral component of the prosthetic knee joint made of titanium alloy is used as the workpiece material in the present study. The surface finish requirement of the femoral knee joint is at the nanometer level. Finishing of the femoral component of the knee joint is a difficult task due to its complex surface conditions. The best final surface roughness of 0.02 μm is obtained after finishing of the knee joint. Also, the femoral knee joint should be hydrophilic in nature. Surface wettability test is conducted using the goniometer to prove the hydrophilicity nature of the finished surface. The formation of the oxide layer is observed on the finished surface. The oxide layer increases the biocompatibility of the implant. The present study proves the capability of the novel tool to provide the required surface properties of the femoral knee implant. Hence, the magnetic field-assisted finishing process can be used to finish the complex freeform surface of the femoral knee implant.