bluuebunny/crossref_metadata_2025 huggingface dataset:
Achieving Consistent Safety by Using Appropriate Safety Factors in Corrosion Management Program
Authors: Al-Amin Mohammad , Zhang Shenwei , Kariyawasam Shahani , Yan Jason Z. , Matchim Tammie
Published: January 2021

Pipeline operators assess metal-loss corrosion anomalies identified on pipelines to determine whether such anomalies require remediation. The assessment of metal-loss anomalies can be performed using deterministic or probabilistic approach. In deterministic method, the failure pressure ratio (FPR) for a metal-loss corrosion anomaly is evaluated against a predetermined safety factor, where FPR is defined as the predicted burst pressure of the anomaly divided by the maximum allowable operating pressure (MAOP) or maximum operating pressure (MOP). Conservative characteristic values are used for the variables such as measurements of metal-loss, pipe geometry, material properties, operating pressure and assessment model in calculating FPR. Safety factors in deterministic assessment are used to account for residual uncertainties, human error and consequence levels. Safety factors are established in various codes and standards in North America. However, those safety factors are not consistent across codes and standards as demonstrated in this paper. This paper describes the fundamentals of how appropriate safety can be assured for pipelines containing metal-loss anomalies by selecting appropriate safety factors. The effect of using different safety factors on the reliability level of the pipeline system is examined in this study. A set of new safety factors to ensure consistent safety level for pipelines containing metal-loss corrosion are proposed in this paper. The impact of the proposed safety factors on the integrity decisions are also demonstrated.
An Engineering Assessment Methodology to Evaluate Arc Burns
Authors: Kohandehghan Alireza , Prescott Jonathan , Guest Stuart , Lepine Sean
Published: January 2021

Arc burns, also known as arc strikes, are caused by momentary interaction of an electric arc, e.g., welding electrode or welding ground clamp, and a pipe or fitting, upon which a minimal or no amount of weld metal is deposited. Arc burns typically correspond with localized alteration of microstructures, shallow pitting, sharp surface contours, re-melting, and/or cracking. The damaged microstructures manifest in the form of a locally harder material due to accelerated cooling rates. Arc burns mainly form during the pipeline construction and are typically located adjacent to manually installed girth welds. The hard microstructures associated with arc burns are susceptible to hydrogen-induced cracking (HIC) in the presence of atomic hydrogen. Pipeline maintenance codes consider arc burns as defects and require their complete removal by grinding.

Due to the relatively small dimension of arc burns, removal by grinding followed by etching contrast test is often the simplest and most reliable permanent repair for such defects. However, in some circumstances grinding to the maximum allowable depth may not completely remove the affected microstructures. Also, removal of arc burns often requires grinding near girth welds and significant grinding depths may require through-thickness inspection of the welds to ensure safety. Type B pressure containing steel sleeves are another permanent repair method that can be used to repair arc burns or partially removed arc burns within grinding metal loss features. Installation of permanent repairs over an arc burn is costly and may introduce additional or higher risks to the integrity of pipeline when scarce industry studies are available that conclusively demonstrate the dangers of leaving arc burns or partially removed arc burns in pipes.

Despite the need, there is no validated engineering assessment method for the evaluation of arc burns. This paper will summarize an engineering assessment methodology and the findings of the evaluation of crack-free arc burns and partially removed arc burn features for two scenarios on vintage liquid pipelines. A combination of one- and three-dimensional finite element models was utilized to investigate the effect of arc burns and/or partially removed arc burns on the integrity of the pipeline based on plastic collapse, local yielding, and fatigue failure modes. The effect of the buried pipeline profile and soil was considered in the assessment of the axial load capacity of the pipeline. The geometrical and metallurgical stress concentrations of the features were considered in the engineering assessment. The engineering assessment determined if the pipeline with the arc burns and/or partially removed arc burns can survive rupture, brittle fracture, and fatigue damage mechanisms during its operation and if reinforcement of the area or cut-out is required.
Establishing a Detection Threshold for Acoustic-Based External Leak Detection Systems
Authors: Bussière Mathew , Stephens Mark , Derakhshesh Marzie , Cheng Yue , Daniels Lorne
Published: January 2021

A better understanding of the sensitivity threshold of external leak detection systems can assist pipeline operators in predicting detection performance for a range of possible leak scenarios, thereby helping them to make more informed decisions regarding procurement and deployment of such systems. The analysis approach described herein was developed to characterize the leak detection sensitivity of select fiber optic cable-based systems that employ Distributed Acoustic Sensing (DAS). The detection sensitivity analysis consisted of two steps. The first step involved identifying a suitable release parameter capable of providing a defensible basis for defining detection sensitivity; the second step involved the application of logistic regression analysis to characterize detection sensitivity as a function of the chosen release parameter. The detection sensitivity analysis described herein provides a means by which to quantitatively determine the leak detection sensitivity threshold for each technology and sensor deployment position evaluated in a set of full-scale tests. The chosen sensitivity threshold measure was the release parameter value associated with release events having a 90% probability of being detected. Thresholds associated with a higher probability level of 95% were also established for comparison purposes. The calculated sensitivity thresholds can be interpreted to mean that release events associated with release parameter values above the sensitivity threshold have a very high likelihood (either 90 or 95%) of being detected.
Evaluation and Acceptability Criteria for Pneumatic Pressure Tests
Authors: Li Guohua , Tupper Michael , Wei Hong-Chan , House Robert , Bidmus Hamid
Published: January 2021

A pneumatic pressure test can be performed when hydrotesting a pipe is infeasible and/or impracticable. Despite its use throughout the industry, little published reference material is available regarding this important and ubiquitous topic with no known industry codes, standards or criteria identified to provide guidance related to stabilization time, test evaluation, and acceptance criteria.

This paper provides an evaluation of minimum stabilization time for various pipe sizes and lengths obtained from transient, parametric simulation results. By evaluating typical test parameters, the paper concludes that gas mass should be used as the principal evaluation criterion, since it is conserved during testing if there is no leak. This paper introduces an acceptance index for which a test can be accepted provided the acceptance index is within defined lower and upper limits obtained from the accuracy of the pressure and temperature measuring devices.

Field test data from three cases studies are successfully presented to verify the feasibility and validity of the proposed acceptance criteria for natural gas mains pneumatically tested with nitrogen at test pressures in the range of 300 psig (2,068 kPag) to 900 psig (6,205 kPag).
Cracks in Dents: How Can I Use an ILI Robot to Detect Them?
Authors: Guajardo Rogelio , Hennig Thomas , Mendez Carlota , Tarramera Beatriz
Published: January 2021

Cracks in dents or linear anomalies interacting with dents are a major pipeline threat. These combined anomalies represent challenges to the Mechanical Engineers that design ILI tools as they need to keep the sensor in an optimal position towards the inner pipe wall. Ultrasonic Crack (UC) tools consist in a sensor plate with a fixed incidence angle that depends on the coupling medium. This plate is then attached to the skids; these are in constant contact with the internal pipe wall. When the tool interacts with a dent, the incidence angle is not optimal; therefore, detection of any interacting feature is compromised.

By not having the optimum angles in the pipe wall, the amplitudes from the reflections caused by cracks will be attenuated. Depending on the magnitude of the attenuation, these might be below analysis thresholds meaning that an algorithm and/or analyst will not consider them as relevant signals. Up to this point, detection of interacting features sounds like a “guess “ or “luck”. So, how can we use UC inspection to detect the interacting features? How can operators manage their assets knowing that they have dents but there is an uncertainty if there are interacting features?

To answer these questions, a systematic approach had to be used. It consisted of multiple phases where 1.- The mechanical design of the tool was understood, 2.- Simulation campaigns to understand the ultrasonic pulse while interacting with the dent, 3.- Pump tests with artificial features, and 4.- Pump test with real features.

All of the data gathered through the different phases allowed the authors to understand the attributes from the features and conditions that influence detection and identification of cracks in dents. This derived in a performance specification stating the truth capabilities to detect interacting features in a dent. These learnings were applied to commercial inspections where the feedback loop is closed with the field verifications.
Getting to Know Your Bends to Support SCC Management
Authors: Wood Chris , Merotto Fernando , Kerrigan Brian , Loback Ramon , Gea Pedro
Published: January 2021

Nova Transportadora do Sudeste (NTS) own and operate a gas transmission system in Brazil constructed in 1996. One of the confirmed primary integrity threats to this system is axial stress corrosion cracking. The pipelines vary in diameter, weld type, manufacturer and age. One of the pipelines failed in 2015 due to an axial stress corrosion crack. Since the failure, NTS have executed an intense inspection campaign to detect and size axial cracking within their network.

The 2015 failure occurred on a field bend. The inspection campaign and following dig campaign has confirmed that cracking (both axial and circumferential) within field bends is the primary integrity threat. Brazil has a challenging terrain and approximately 40% of joints within the network were subject to cold field bending. The influences of the pipeline geometry within these areas have resulted in localised elevated stresses where the axial stress corrosion cracking colonies are initiating and growing. To date, no cracking (axial or circumferential) has been verified within their straight pipe joints.

NTS initially took a conservative baseline assessment approach using API 579 Part 9, due to the limited information regarding the pipe material and complex stress state. In addition to the hoop stress from internal pressure, the baseline assessment also considered weld residual stress and bending stress due to ovalization to determine immediate and future integrity.

An intensive dig campaign is underway following a crack detection in-line inspection campaign using electromagnetic acoustic transducer technology. A large number of deep cracks were reported by the in-line inspection system, these were verified to be deep and repaired with a type B sleeve. However, at one site an entire joint was removed for further analysis, to investigate the crack morphology, confirm material properties and refine the predictive failure pressure modelling.

This paper outlines how NTS have combined a burst test, mechanical testing, FEA modelling, fractography and metallographic examination to further understand the feature morphology and stresses within these areas and how they have been able to reduce conservatism from their baseline assessment with confidence and adopt a plastic collapse approach to accurately predict failure.
The Application of Numerical Simulation to Liquid Pipeline Leakage at LNG Terminal in China
Authors: Guo Zhichao , Li Zhaoci
Published: January 2021

In 2018, China’s natural gas import reached 90.39 million tons, and the liquefied natural gas (LNG) import was 53.78 million tons, accounting for 59.5% of total natural gas imports. With the construction of LNG terminals, more studies on the leakage of LNG storage and transportation facilities have emerged to prevent catastrophic consequences such as explosions and frostbite. However, most of previous researches focused on gas pipeline leakage after LNG gasification, and few of those have been done on LNG liquid pipeline leakage. In this paper, Fluent software is used to numerically simulate the process of LNG liquid pipeline leakage. After the occurrence of LNG leakage, it will suffer the process of endothermic, evaporation, and diffusion, which is considered as a two-phase diffusion process. The Euler-Lagrangian method is introduced to simulate the diffusion process of gas phase and liquid phase separately. In the simulation, the liquid phase is regarded as discrete droplets for discrete processing. The movement trajectory, heat transfer process and evaporation process of each droplet are tracked respectively. Different from the liquid phase, the gas phase is regarded as a continuous phase and the Navier-Stokes equations are adopted for calculation. Thereafter, coupling calculations of two phase are performed to determine the concentration field and temperature field of the LNG liquid pipeline leakage. As a supplement to this research, the influence of wind speed on LNG leakage and diffusion process is analysed in detail. Finally, the numerical simulation method is applied to a coastal LNG terminal in northern China to determine the distribution of natural gas concentration and temperature, as well as delimit the combustion range. The results can provide scientific reference for the delimitation of risky zones and the formulation of emergency response strategy.
Pipeline Plain Dent Fatigue Assessment: Shedding Light on the API 579 Level 2 Fatigue Assessment Methodology
Authors: Shirband Zeynab , Gosselin Adrian , Guest Stuart , Falcon Lee
Published: January 2021

For continued safe operation of pipelines, thousands of integrity digs are conducted every year to repair ILI detected defects. Integrity-driven pipeline excavations can be quite costly, present significant scheduling challenges with landowner consultation and seasonal access limitations, and an unmitigated defect may have required a pressure reduction or service outage, resulting in a loss of revenue from the asset. Dents are known to be one of the drivers for many integrity excavations, especially for liquid pipelines. A pipeline with a minimal mechanical deformation is not expected to fail immediately, however, severe pressure cycles combined with the geometric distortion can cause fatigue crack initiation and growth that can lead to failure. To account for the possibility of fatigue failure, recent changes to pipeline codes, such as CSA Z662, are requiring pipeline operators to repair any dent susceptible to fatigue failure unless an engineering assessment proves it is fit for service.

A commonly used dent fatigue assessment methodology is outlined in API RP 579, also known as the EPRG-2000 model. The assessment methodology uses an S-N curve from DIN 2413 part 1 with a safety factor of 10, which has been derived from undamaged pressurized pipe sections experiencing pressure cycles with stress ratios of zero, and separate stress enhancement factors for dents and gouges which take into account the shape of dents and gouges. To account for the effect of mean stress, Gerber mean stress correction, which has been developed for pressure cycles with stress ratios of −1 (i.e., for fatigue bar specimens), is also applied on pressure cycles. According to the literature, API 579 Level 2 fatigue assessment methodology results in very conservative estimates of fatigue lives compared to experimental data. This paper will discuss the potential factors resulting in conservative assessments and propose refinements in the methodology. This will include the safety factor used for pipes with known operating pressure fluctuations and the mean stress correction model suitable for a pipeline with pressure cycles that have R ratios greater than zero. The acceptable number of cycles obtained using the proposed refinements were compared to experimental data and EPRG-1995 model’s predictions — the comparison revealed that the proposed methodology results in a more realistic safety margin for dented pipelines. The proposed methodology can be used as a part of engineering assessments in mechanical damage integrity management programs to improve the pipeline operator’s understanding of a dent’s remaining life and enable a more appropriate repair timeline.
Preserving Critical Stormwater Storage Assets at Pipeline Terminal
Authors: Huang Vincent , Walter David J. , Treen Curtis R. , Richmond John A.
Published: January 2021

A slope failure compromised the integrity of a critical stormwater storage facility at a petroleum storage terminal within northern Alberta. Through periodic ground inspections and a review of LiDAR and aerial imagery, significant lateral deformation of a lined stormwater pond was identified. The potential for pond overflow and uncontrolled stormwater release into the natural environment due to compromised discharge outlets and liner integrity posed an operational and environmental risk. A fast-tracked review and assessment of both the historical and as-built construction details, a good understanding of the regional geology, and geotechnical investigation and instrumentation were required to identify remedial measures that could be implemented to restore the pond prior to the onset of major storm events.

Geotechnical investigation and assessment showed weak zones in the bedrock at shallower depths than were historically encountered at the site. Spatial constraints, uncontrolled fill placement in close proximity to the pond, expansion of the pond following original construction, and compromised subsurface drainage were identified as factors that may have contributed to the failure. Assessment of remedial options considered impacts relative to both local and global factors of safety. The selected remedial option was a combination of slope unloading, shear key construction, and improved drainage with the design and construction occurring within a timeframe of 3 months to minimize the time that the pond was out of service.

The paper highlights the challenges associated with the slope unloading and shear key construction that were required to control the ground movements. An approach involving sequential excavation and replacement was adopted to manage the risks associated with shear key construction. In addition, directional drill methods were incorporated to install some of the drainage measures due to the risk associated with an open cut approach. The project was fast-tracked to minimize exposure to high precipitation and limited stormwater storage capacity.
Dent Screening Criteria Based on Dent Restraint, Pipe Geometry and Operating Pressure
Authors: Tiku Sanjay , Rana Arnav , John Binoy , Dinovitzer Aaron
Published: January 2021

A safety advisory (2010-01), issued by the National Energy Board (NEB) in June 2010, referenced two incidents which were a result of a fatigue crack failure that occurred within shallow dents [1]. The dents in both instances were less than 6% (of the OD). Currently, there is no consensus on how shallow dents or shallow dents with stress concentrators, as called by the ILI tool, are assessed and acted upon.

BMT Canada Ltd. (BMT) was contracted by the Canadian Energy Pipeline Association (CEPA) to develop a definition for shallow dents, and two levels of screening method for the integrity assessment of shallow restrained dents and unrestrained dents. These two levels are known as CEPA Level 0 and CEPA Level 0.5 dent integrity assessment techniques that may be applied without finite element modelling or detailed calculations. The BMT dent assessment finite element (FE) modeling method was used to develop an extensive database of dents for different pipe geometries (OD/t), indenter shapes, pipe grades, and indentation depths. The results of the FE modelling were used to develop trends for the stress magnification factors (KM) across the range of pipes and dents modelled. These trends are used as the basis for the Level 0 and Level 0.5 dent screening and assessment approaches that can be used for both unrestrained dents and shallow restrained dents. The results show that for low OD/t pipe geometry and/or low spectrum severity indicator (SSI) [2] dent fatigue life may not pose an integrity threat.

These dent screening approached have been adopted in the API Recommended Practice 1183 Dent Assessment and Management, that is currently under development.
Full-Scale Fatigue Testing of Crack-in-Dent and Framework Development for Life Prediction
Authors: Arumugam Udayasankar , Gao Ming , Krishnamurthy Ravi , Zarea Mures
Published: January 2021

Dents containing crack fields (colonies) were often observed in liquid pipelines. A recent PRCI research “Study of the Mechanism for Cracking in Dents in a Crude Oil Pipeline” showed evidence of corrosion fatigue cracking mechanism in dents and estimated the crack growth rate as a function of stress intensity factor using the measured spacings of fatigue striations from fracture surfaces based on the assumption that the formation of fatigue striations on a cycle-by-cycle basis. However, due to the lack of full-scale fatigue crack growth data, the success was limited in this study. This gap prompted PRCI to launch a full-scale experimental investigation of cracks-indents under cyclic pressure load in the simulated groundwater (NS4 solution) environment. The objective of the study is to determine the crack growth rate in dent as a function of stress intensity factor, the number of cycles to failure, and the failure modes of crack-in-dent. The investigation is aimed at establishing a framework for the remaining fatigue life prediction of cracks-in-dents in liquid pipelines. This framework would benefit liquid pipeline operators to manage the integrity of dents associated with corrosion fatigue cracking exposed to groundwater in a timely manner.

A total of six pipe samples containing cracks in shallow dents excavated from a 24-inch diameter liquid transmission pipeline were selected for full-scale fatigue tests. The test system developed under the project consisted of (1) a computer-controlled hydraulic pressure cycling system, (2) an environment chamber containing NS4 solution mounted on the dent region to provide a simulated field environment condition, (3) real-time crack growth monitoring systems including direct current potential drop (DCPD) system, Clip gage, and Strain gage, and (4) a data acquisition system. The cyclic pressure range used in the fatigue test was between 78 psig (7.2%SMYS, minimum) and 780 psig (72%SMYS, maximum) with R = 0.1, which was based on historical operational pressure fluctuation data. A constant frequency of 0.0526 Hz was selected for the testing to ensure the frequency requirement for corrosion fatigue was met.

In this paper, the objective, along with the background of this research, is discussed first. Then, the pipe sample preparation, experimental setup, and test results are presented. The fatigue crack growth rate as a function of the stress intensity factor is then discussed. Following this, the fatigue crack growth coefficients were estimated using the full-scale test data and FEA. Finally, the fatigue test results are summarized and presented the framework for the life prediction of corrosion fatigue cracks in shallow dents.
Repair of Leaks in Thin Wall High Pressure Pipelines Using Composite Reinforcing Technologies
Authors: Alexander Chris , Talbi Salem , Kania Richard , Rickert Jon
Published: January 2021

A study was conducted to evaluate two composite repair technologies used to reinforce severe corrosion and thru-wall leaking defects in thin-walled pipe materials; conditions where the welding of conventional Type B steel sleeves cannot be conducted. This program involved the reinforcement of simulated 85% corrosion defects in 6.625-inch × 0.157-inch, Grade X52 pipe materials subjected to cyclic pressure and burst testing. The test matrix also included repaired pipe samples with thru-wall defects that were pressurized using nitrogen gas and buried for 90 days. The program was comprehensive in that it evaluated the following elements involving a total of 81 reinforced corrosion defects.

• Corrosion features with a depth of 85% of the pipe’s nominal wall thickness in thin-walled pipe material (i.e., 0.157 inches, or 4 mm).

• Thru-wall defects having a diameter of 0.125 inches (3 mm).

• Repairs made with leaking defects having 100 psig (690 kPa) internal pressure.

• Strain gage measurement made in non-leaking 85% corrosion defects; it should be noted that the remaining “15%” ligament was 0.024 inches (0.6 mm); to the author’s knowledge, no high-pressure testing has ever been conducted on such a thin remaining wall.

• Long-term 90-day test that included pressurization with nitrogen gas, followed by relatively aggressive pressure cycling up to 80% SMYS followed by burst testing.

This is the first comprehensive study conducted by a major transmission pipeline operator evaluating the performance of competing composite technologies used to reinforce severe corrosion features with thru-wall defects. The reinforcement of leaks has not been accepted by regulatory bodies such as the Canadian Energy Regulator (CER), or the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA). A goal of the current study is to validate composite repair technologies as a precursor to regulatory approval.

The results of this study indicate that viable composite repair technologies exist with capabilities to reinforce leaks in pipelines that experience operating conditions typical for gas transmission systems (i.e., minimal pressure cycling).
Developing a Representative Soil Response Model
Authors: Phillips Ryan , Martens Michael
Published: January 2021

A testing procedure and methodology has been developed to provide more realistic pipe-soil response curves which account for differing soil types, pipe and trench geometries and backfill conditions. Such curves increase the reliability of the pipe-soil interaction analyses, and help to reduce overall conservatism in definition of springs for pipe-soil interaction.

Pipe-soil spring response is now generally determined by geotechnical engineering estimation of the soil properties which are used as inputs to simple pipe-soil interaction guidelines. A new dual axis field test procedure, including equipment and interpretative methodology has been developed to directly measure soil response curves for bearing and shear interactions. A numerical modelling protocol interprets these measurements to directly assess pipe-soil spring responses, rather than relying on simplified guidelines.

This paper includes the field and laboratory testing and associated numerical modelling used in the development of the pipe-soil spring response process, as well as the initial results of trials with the new dual axis testing system. The next step for this initiative will be the development of a database of field test data, from which significant advancements can be made to further improve pipe spring recommendations.
Calibration and Compensation of Rotary Axis Angular Positioning Deviations on a SCARA-Type Industrial Robot Using a Laser Tracker
Authors: Zhao Nan , Ibaraki Soichi
Published: January 2021

In general, the “absolute” positioning accuracy of industrial robots is significantly lower than its repeatability. In the past research, in order to improve a robot’s positioning accuracy over the entire workspace, the compensation for the link length errors and the rotation axis angle offsets are often employed. However, the positioning error of the compensated industrial robot is still much higher than that of a typical machine tool. The purpose of this study is to propose a new kinematic model and its calibration scheme to further improve the absolute positional accuracy of an industrial robot over the entire workspace. In order to simplify the problem, this study only targets the 2D positioning accuracy of a SCARA-type robot. The proposed model includes not only link length errors and rotary axis angular offsets but also the “error map” of the angular positioning deviation of each rotary axis. The angular error deviation of each rotary axis is identified by measuring the robot’s end-effector position by a laser tracker at many positions. To verify the validity of the identified model, the effectiveness of the compensation based on it is also investigated.
Graph-Based Feature Recognition and Combination Method for Automatic Process Planning System
Authors: Xie Da , Zhu Jiang , Tanaka Tomohisa
Published: January 2021

Generating the Numerical Control (NC) tool path for machining a complex shaped component is highly dependent on the proficiency of a Computer-Aided Manufacturing (CAM) programmer in manufacturing field, although the CAM systems now are highly integrated. A Computer-Aided Process Planning (CAPP) system, which can automatically extract the manufacturing features from the Computer-Aided Design (CAD) model and generate the machining process planning, has been expected for a long time. In this research, a graph-based CAPP system was proposed. It mainly includes four modules, data conversion module, feature classification module, feature combination module and process planning module. The first two modules claim a graph-based feature recognition method, output the recognized manufacturing features which are classified into four classes and defined as specific types. The feature combination module generates different paths to combine manufacturing features from a goal model into raw material shape by four kinds of combination methods corresponding to the four classes. Finally, the process planning module will give a cost estimation of all those paths with the consideration of manufacturing resources and time cost. A relatively optimized machining method and machining sequence will be generated as the output of this proposed system.
Tribological Properties Between a-C:H Coatings and SiO2 at High Temperature
Authors: Umehara Noritsugu , Konishi Kota , Murashima Motoyuki , Tokoroyama Takayuki
Published: January 2021

Tribological properties of a-C:H coatings has been investigated in various friction conditions. It is clear that temperature and mating materials give effects on tribological properties. In this study, we especially focus on the effect of mating material on its tribological properties of a-C:H coatings. Ball-on-disk friction test is conducted between a-C:H coating and 5 kinds of mating material, which is SiC, SiC(O)_800 (SiC oxidized at 800°C), SiC(O)_1050°C, SiC(O)_1300°C, and Quartz glass. It is found that a-C:H coatings shows low friction coefficient and low specific wear rate when O/Si ratio of the element content of mating material is 2, in other words, mating material is SiO2. In the wear scar of a-C:H coating after friction test with SiC, severe damage was confirmed. It is considered that a-C:H coating and SiO2 show low adhesion even at high temperature, which leads low friction and wear. Compared SiC(O) with Quartz, the friction coefficients with a-C:H coatings are respectively 0.013 and 0.038. Even though SiC(O) and Quartz are both SiO2, the tribological properties are different. On the wear track of SiC(O), transferred things from a-C:H coating are confirmed.
Proposal of a Tool Path Generation Method to Ensure Workpiece Stiffness for Efficient Rough Machining
Authors: Kumanotani Maho , Kusino Hitoshi , Nakamoto Keiichi
Published: January 2021

Recently, the demand of complex shape parts has increased in the aircraft and medical industries. In these parts machining, the displacement and vibration of workpiece that strongly affect the machining efficiency are induced due to the heavy change of the unmachined workpiece shape and stiffness during rough machining. However, it is difficult to automatically determine machining parameters of operation planning by using a commercial CAM software because there is a large number of combinations. Therefore, in order to improve the efficiency of complex parts machining, the authors proposed a determination method of workpiece shapes during rough machining based on topology optimization relevant to maximizing static stiffness. On the other hand, tool paths that directly affect the workpiece stiffness are not generated automatically to create the calculated workpiece shapes in the previous study. From these reasons, this study proposes a generation method of tool paths by using design variables obtained through the calculation of topology optimization. The tool paths are simply generated based on design variables and enables to ensure the workpiece stiffness during rough machining because design variables are strongly related to the objective function. By conducting a machining experiment assuming complex parts machining, it is confirmed that the proposed method has a potential to realize efficient rough machining.
Error Analysis by Square 3 x 3 Machining Method for Five-Axis Machining Centers
Authors: Sakamoto Shigehiko , Yokoyama Atsushi , Nakayasu Kazumasa , Suzuki Toshihiro , Koike Shinji
Published: January 2021

The establishment of international standards for 5-axis control machining centers has been supported by the high interest of each country. Internationally, various accuracy inspection methods have been proposed and widely discussed. Accuracy measuring devices for these purposes have also been proposed. In 2014, inspection methods for 5-axis machines were published in ISO 10791-6 and 10791-7.

In this research, we propose a test method to process 9 square faces as a new accuracy evaluation method. We simulate the influence of assembly error by the proposed square 3 × 3 machining method on the machined surface. By processing 9 square faces with different tool angle on the same plane, it was possible to evaluate the influence of assembly errors in the 5-axis machining center on the machined surface.

Nine surfaces machined by the square 3 × 3 processing method cause differences in surface height due to alignment errors. In addition, nine machined surfaces become all diagonal not parallelism. The alignment errors of the 5-axis machining center is identified by evaluating the orientation of the machined surfaces. Specifically, we propose a newly method to measure the height difference of nine surfaces. Then, the possibility of identifying the alignment error of the 5-axis machining center using the measurement results is shown.
Effects of the Size of Built-Up Layer on the Wear of Uncoated Cemented Carbide Tools in Dry Cutting of SUS304 Stainless Steel
Authors: Song Xiaoqi , Takahashi Yukio , Ihara Tohru , He Weiming
Published: January 2021

Built-up layer (BUL) formed on the tool rake face during cutting has the tool protective effect. As BUL can change the shape of tool resulting in variation of rake angle and edge radius during cutting, it also has significant influences on the cutting phenomena such as tool wear, cutting forces and surface integrity. SUS304 stainless steel is very difficult to cut, leading to the rapid tool wear and poor surface quality. It also has a high tendency to form BUL during cutting due to its high work hardening rate and high chemical affinity. To actively and purposely utilize BUL, the effects of the size of BUL on the wear of uncoated cemented carbide tools in dry cutting of SUS304 were investigated using experimental and analytical methods in this study. The cutting parameters were chosen to induce the stable BUL formation. After cutting, the worn cutting tools were analyzed using the laser confocal microscopy and scanning electron microscopy. It was confirmed that BUL can reduce the tool flank wear rate in the steady-state wear when its height is equal to or less than the uncut chip thickness. The results also showed that BUL formed at cutting speed 40 m/min can not only reduce the tool flank wear rate but also induce a significant improvement in cutting forces and surface integrity. Meanwhile, using the obtained experimental results and proposed model, simulation was conducted to evaluate the effects of the size of BUL on the tool flank wear formation. It was confirmed that BUL, especially when its height is close to the uncut chip thickness, which reduces the real rake angle to negative, can reduce the normal stress on the tool flank face and lead to a decrease in the tool flank wear rate.
Measuring Optical Properties of Advanced Nano/Micro-Periodic Structures Fabricated by Multi-Exposure Interference Lithography
Authors: Masui Shuzo , Michihata Masaki , Takamasu Kiyoshi , Takahashi Satoru
Published: January 2021

Functional optical elements based on nano/micro-periodic structures have attracted much attention. Since the fabrication of these dual-periodic structures requires precise control of periodicity, the semiconductor process such as an electron beam lithography has been mainly employed. However, these techniques have problems with expensive and low throughput for industrial applications. Therefore, there remains a need for low cost and high throughput fabrication methods of dual-periodic structures. Then we developed a multi-exposure interference lithography (MEIL) system using rotational Lloyd’s mirror interferometer to overcome these problems. The advantages of interference lithography are a large processing area and low cost. Our developed rotational Lloyd’s mirror setup enables us to a highly precise superposition of multiple interference fringes by multi-exposure. Furthermore, we developed a measurement setup for reflective diffractive elements using a two axial rotating stage and measured the diffraction properties of the fabricated dual-periodic diffraction gratings. In this paper, as a demonstration, we succeeded in the fabrication of high-dispersion diffraction grating with an enhanced diffraction efficiency of the −3rd order light. The fabricated shapes have a periodicity of 1997 nm and 665 nm. Furthermore, it was confirmed that the intensity of the −3rd order light was enhanced by about 10 times compared to the single periodic grating.
Measurement of Rake Face Temperature in Cryogenic Machining of Titanium Alloy
Authors: Sato Masahiko , Kamoto Masashi
Published: January 2021

Titanium alloys are widely used as mechanical components, since they have superior properties such as high strength-to-weight ratio. They are regarded as difficult-to-cut materials. Their low thermal conductivity increases the temperature near the cutting edge, which causes excessive tool wear during cutting. Recently, many studies on cryogenic machining have been conducted. Cryogenic machining has emerged as an environmentally friendly alternative to traditional emulsion coolants. In this study, the rake face temperatures of cutting tool in the turning of titanium alloy under dry, soluble coolant, cryogenic carbon dioxide coolant and liquid nitrogen coolant conditions were measured to clarify the effect of coolant on cutting temperature. Turning tests were performed using a precision lathe. Tool insert was made by a translucent alumina. A small hole was drilled into the tool insert. An infrared radiation pyrometer with an optical fiber was used. The optical fiber was inserted into the hole. During chip formation, the infrared rays, radiated from the tool-chip interface and transmitted through the cutting tool, were accepted and transmitted by the optical fiber. The effects of cryogenic coolant on the rake face temperature were investigated. The rake face temperatures under carbon dioxide cooling and liquid nitrogen cooling were approximately 60 °C and 90 °C lower than that in dry cutting, respectively.
Investigation of Fracture Behavior of Piezoelectric Ceramics Embedded in Metal Matrix
Authors: Iijima Karin , Yanaseko Tetsuro , Kuboki Isao , Sato Hiroshi , Asanuma Hiroshi
Published: January 2021

In recent years, there is considerable interest in the Structural health monitoring. This is a technique to diagnose and evaluate the damage and deterioration of a structure by attaching sensors to the structure, and is useful for judging whether building can be reused or not at that time of a disaster such as an earthquake. There are several types of sensors such as piezoelectric type, optical fiber and strain gauge type and piezoelectric sensors are very suitable for this purpose because they do not require an energy source considering that they produce electrical power by themselves. However, the application range of piezoelectric ceramics used for piezoelectric sensors is narrow because of its fragility. Then, the researches and developments of the piezoelectric ceramics embedded in the matrix that has excellent mechanical strength are carried out. The metal-core piezoelectric fiber/aluminum composite was developed by Asanuma et al. to overcome the problems associated with piezoelectric ceramics, such as poor mechanical properties, reliability; brittleness and low fracture strain. The fracture strain of piezoelectric ceramics fiber significantly improved due to residual compressive stress caused by difference of coefficient of thermal expansion between the ceramics and the matrix during embedding process. However, there is few statistical data on the mechanical properties of piezoelectric ceramic fibers, and the improvement in the properties due to the embedding has not been quantitatively evaluated. In this study, to overcome this problem, the simplified model of metal matrix piezoelectric composite was fabricated and used to compare strengths before and after embedding by 3-point bending test. As a result, it is found that Weibull parameters of piezoelectric ceramics are improved by embedding in the matrix.
Precision Coating of ta-C Films on Quartz Surfaces
Authors: Kawai Kotaro , Hirata Yuki , Akasaka Hiroki , Ohtake Naoto
Published: January 2021

Diamond-like carbon (DLC) films have excellent properties such as high hardness, low friction coefficient, high wear resistance, chemical inertness and so on. Because DLC film is considered as an effective coating material to improve their surface properties, this films are used in various applications such as parts for automobiles engines, hard disk surfaces, cutting tools and dies, and so on. DLC films consist of a mixture of sp2 bonded carbon atoms and sp3 bonded carbon atoms. Among them, ta-C film is known as the hardest and strongest film since it mainly consists of sp3 bonded carbon atoms. One of deposition methods to form ta-C is Filtered Cathodic Vacuum Arc (FCVA). The characteristic of this method is that it is possible to remove the droplets and form a high-quality film.. However, even though lots of mechanical components which require ta-C coating have three-dimensionally shapes, it is difficult to coat ta-C film three dimensionally by using FCVA process. At present, researches on 3D deposition of amorphous carbon films on three dimensional components is still insufficient, and investigation reports on the deposition mechanism and characterization of the deposited films are even more limited. In this study, we tried to deposit films on 3D components by the FCVA method and evaluated the microstructure and surface morphologies of films. Although films were coated successfully in the entire surfaces, different properties were showed depending on the location of components. These properties were investigated by Raman spectroscopy and laser microscope.
Development of Curved Hole Electrical Discharge Machining Method: Automatic Generation of Device Operating Command in Consideration of Realizing the Machining
Authors: Ishida Tohru , Kaide Yusuke , Mizobuchi Akira , Takeuchi Yoshimi
Published: January 2021

Aiming to enhance the degree of freedom of hole shapes which can be realized by machining methods, our research group has developed a new device that can fabricate curved holes by means of electrical discharge machining. The previous studies have shown that the device has the ability of fabricating curved holes and have developed the manner for fabricating curved holes with desired shapes by use of the device. This manner is built on the basis of the teaching playback method. So, the manner contains the teaching process for generating the operating commands that can make the device fabricate desired curved holes. However, the teaching process just built needed troublesome manual works. Not to need such works, the last study has devised the manner for automatizing the teaching process. Contrary to our expectation, however, the operating command generated by the automatized teaching process could not fabricate a desired curved hole due to the lack of the consideration to the motion capacity of the device and so on. To overcome this problem, this study has improved the algorithm to generate the operation command. The machining experiment employing the operating command generated by using the improved algorithm can fabricate the desired curved hole. This proves that the improved algorithm is effective to the fabrication of desired curved holes by means of the device.
Surface Texturing Process by High Speed Ultrasonic Turning to Obtain Low Friction Surface
Authors: Hara Keisuke , Isobe Hiromi
Published: January 2021

Tribological properties such as lubrication, friction and wear resistance are important to improve machine operating efficiency, machine performances and machine life. To improve tribological properties of sliding surface, scraping is available. Scraping fabricates many small depression on target surface evenly, the depression will function oil hole which promote lubrication of flat bearing surface. Many researchers have reported the surface texturing method which aim is similar to scraping. For example, the techniques fast tool servo turning with diamond insert tool and turn mill processing by dual spindle turning center were reported to fabricate periodically micro dimple. However, these techniques employ expensive high precision machine tools. This paper introduces a more cheaply and rapidly surface texturing technique which employs ultrasonic vibration turning to obtain low friction surface and improve tribological properties. In ultrasonic turning, cutting tool tip is vibrated in principal direction and radial direction simultaneously origin from poisons deformation of ultrasonic transducer. The radial direction tool vibration functions to squeeze workpiece surface in workpiece radial direction periodically, textured surface will be obtained. The results of ultrasonic turning experiments, textured surfaces were obtained. In order to evaluate the tribological performance of the turned surface, friction coefficient between stainless steel pin and turned surface were measured under oil dipping condition. It was confirmed that friction coefficient of ultrasonic turned surface is drastically reduced compared with ordinary turned surface. And proposed technique is available to perform surface texturing for several materials.