Numerical and analytical investigation of an ultrasonic assisted ECAP process

One of the great challenges in the processing of materials using Equal Channel Angular Pressing (ECAP) is the high forming forces required to produce large shear deformation in the material. Researchers show that the friction forces between the die and the sample constitute a great part of the total forming forces. Recently, ultrasonic vibrations are successfully implemented into the ECAP process with the aim of reducing the friction forces. However, there is still need to optimize the parameters of ultrasonic vibrations in the ECAP process using numerical methods. FE simulation of the ultrasonic assisted ECAP process is very time-consuming and during simulation, the constant ram speed has interaction with the vibration speed. A virtual increase in the ram speed for simulation of ultrasonic assisted ECAP process will affect the results. By using Coulomb and Dahl friction models, it is analytically shown how vibration speed and constant ram speed interact with each other during FE simulation. The results clearly suggest against using virtually higher speeds in numerical modelling of the vibrated ECAP process. The conclusion is reached through comparing several simulations, as well as an analytical formulation, with experimental data from literature. The required friction coefficient values to be used in FE simulation at high contact forces are measured experimentally. An alternative strategy is then offered to speed up FE simulation of the vibrated ECAP process without the need for a virtual increase in the ram speed. The proposed strategy can increase the simulation speed of the ultrasonic assisted ECAP process up to ten times <br /

Experimental and numerical evaluation of influencing parameters on the manufacturing of lined pipes

The amount of residual contact stress between an inner corrosion-resistant alloy pipe and its external carbon steel counterpart is the main challenge when manufacturing lined pipes. This study outlines the experimental and numerical evaluation of the manufacturing parameters of mechanically bonded double-walled pipes, produced by the thermo hydraulic shrink fit process. The measurements indicate that the gripping force between the outer 4-inch carbon steel and inner 3-inch stainless steel pipes was 33.94 MPa when processed at 350°C with a hydraulic pressure of 30 MPa. The experimental results correlate with those of finite element method simulations for gripping force. The magnitudes of the measured gripping forces in the experiment are sufficiently high for most scenarios. The cross-sections of the final lined pipes were inspected for possible defects with the most common being the lamination-type defect for this production process

Development of a Procedure for Risk-Based Qualification of Additively Manufactured ‎Components: Adopting to Oil and Gas Industrial Applications

Recent advances in additive manufacturing (AM) technology provide the potential for on-demand and rapid production of spare parts during urgent repair times. Recently, big oil and gas companies have shown early progress in using additive technology in manufacturing specific heat exchangers, downhole cleanout tool nozzles, offshore risers, gas turbine nozzles, and subsea chemical stick injection tools. Despite the mentioned progress, the current adoption level of additive technology for the offshore oil and gas industry is very limited. Non-destructive and destructive evaluation methods of additively manufactured metallic components have been studied extensively. However, the technique selection procedure and scope of the required test methods have not been studied sufficiently. This paper discusses various elements related to the qualification of additively manufactured components for application in the oil and gas industry. A risk-based qualification method for identifying the scopes of required non-destructive and destructive tests and the resulting qualification procedure for additively manufactured spare components in offshore oil and gas applications is suggested.Development of a Procedure for Risk-Based Qualification of Additively Manufactured ‎Components: Adopting to Oil and Gas Industrial ApplicationspublishedVersio

A new designed incremental high pressure torsion process for producing long nanostructured rod samples

High pressure torsion (HPT) is one of the most important and effective severe plastic deformation (SPD) processes for producing nanostructured (NS) and ultrafine grained (UFG) metals. Whereas HPT presents excellent mechanical properties, its applications are limited to small disk-shaped samples. In this study a new design of incremental HPT (IHPT) process entitled SIHPT is developed which is much convenient for the production of large NS and UFG metallic rods. In this new design, some steppers along the length of the rod-shaped sample are used while applying an axial load from two ends of it. Step twisting of stepper parts with simultaneous axial loads extend the deformed region to the whole length of the sample. The five turn IHPT process was applied to a 50 mm length and 10 mm diameter pure copper sample and microstructure, and mechanical properties were evaluated. The microstructural study of SIHPT processed samples using TEM and EBSD micrographs clearly reflected the NS sample having an average grain size of less than 100 nm. Also, microhardness measurements showed that the sample has fairly good homogeneity through both axial and radial directions. Besides, tensile test measurements indicate that there is about four times improvement in yield strength of nanostructured sample compared to unprocessed metal which is accompanied with satisfactory ductility as a result of high hydrostatic compressive stresses

A Response Surface Methodology Model for Optimizing Electromagnetic Acoustic Transducers’ Parameters

Flaw detection is one of the most important problems that pipeline industries are concerned. Conventional ultrasonic method needs coupling medium, and is not more suitable for in-line inspection systems. Electromagnetic acoustic transducers can be used as a good alternative technique in the applications of in-line inspection. However, it is relatively new technique and effectively needs more research. The response resolution is directly related on amplitude of ultrasonic waves. This paper presents signal amplitude model in inspection of steel plate in terms of magnetic current, static magnetic field and thickness of plate using response surface methodology. The established equation shows that the magnetic current was found to be main influencing factor on the signal amplitude. The variance analysis for the polynomial model reveals that the interaction terms and the square terms for static magnetic field except the interaction with magnetic current were statistically insignificant. However, it could be seen that the second-order effect of static magnetic field is significant. After magnetic current, thickness of plate is the most influencing factor on signal amplitude while the impact of static magnetic field is negligible

Comparison between frictional behavior of the soft and brittle materials at different contact pressures

Miavaghi, A. Kangarlou, H. and Eskandarzade, M. 2017. Comparison between frictional behavior of the soft and brittle materials at different contact pressures. Lebanese Science Journal. 18(1): 98-105. Coefficient of friction changed significantly by the change in contact pressure. Experimental measurement of the coefficient of friction in different contact pressures can be useful in numerical and analytical analysis of many engineering problems, such as metal forming process. This study dedicated to investigate the sensitivity of the friction coefficient to changes in contact pressures. To aim this goal the special tribometer device has been fabricated and the coefficient of friction of the soft and brittle metals when sliding with a low speed on a rigid body are measured for different contact pressures. The friction sensitivity of the soft (copper and aluminum) and brittle (steel) samples to changes in contact pressure are compared and discussed. The results showed that both brittle and soft metals are highly sensitive for change in contact pressure but their behaviour is slightly different. While the coefficient of friction of the steel sample when sliding on a steel substrate is reduced sharply by a little increase in contact pressure; the coefficient of friction of the soft material when sliding on a steel substrate is reduced slowly depending on the magnetude of the applied normal load

Risk assessment of electrofusion joints in commissioning of polyethylene natural gas networks

The application of polyethylene pipes and equipment in the natural gas networks is continuously increasing due to their competitive weight and cost compared to metallic materials. Electrofusion welding is an effective and fast approach for the production of polyethylene joints with high safety and endurance. However, recently intermittent failures have reported in underground polyethylene piping networks. Although the failure frequencies are low, but disasters could happen due to the failure in gas pipelines as they usually buried in populated areas. In this study a combination of Failure Mode and Effects Analysis (FMEA), and empirical methods were used to identify main damage mechanisms incorporated to intermittent failures of polyethylene natural gas networks. After performing the FMEA process, based on the obtained risk ranking, three most critical damage mechanisms, including improper scraping, lipid contaminations, and humidity existence in weld zones were investigated experimentally to determine their practical severity. According to empirical evaluations, improper scraping was the most severe damage mechanism, followed by the contaminated welding surfaces during the weld construction

The Effect of Long Term Starvation on Galanin, Leptin, Thyroid Hormones, Insulin, Prolactin, Growth Hormone, Ghrelin and Factors Involved in Energy Metabolism in Adult Goats

Some hormonal disturbances have been demonstrated in starvation, but in ruminants such as goats, the role of galanin in adaptation to starvation or endocrine functions is not well studied. The present study was conducted to assess the effect of long term starvation on galanin, leptin, thyroid hormones, insulin, prolactin, growth hormone, ghrelin and factors involved in energy metabolism including HDL, Cholesterol, β-hydroxybutyrate, glucose, NEFA, TG and VLDL concentrations in adult goats. Eight non-lactating non-pregnant goats aged 4-5 years and BCS 3 were randomly divided to control and test groups. The animals were trained to eat their daily forage ration during a 10 day period. The experimental procedure was applied for 20 days, during which control group received 120% of maintenance energy, while the test group was supplied with 80% of maintenance energy for the first 10 days and with 40% of maintenance energy for another 10 days. Blood samples were collected at day 10 of training and 2, 4, 10, 12, 14 and 20 days after beginning of starvation. Blood parameters were measured according to standard procedures. No significant difference was observed in the concentrations of cholesterol, fT3, T4, T3, growth hormone, NEFA, insulin and ghrelin between control and test groups (P=0.05). There was significant difference in galanin, leptin, fT4, HDL, glucose, TG, VLDL and prolactin concentrations between control and test groups (P=0.05). Control of energy balance and the role of galanin in adaptation to long starvation or endocrine functions in goat are different from other species

Development of a Procedure for Risk-Based Qualification of Additively Manufactured ‎Components: Adopting to Oil and Gas Industrial Applications

Recent advances in additive manufacturing (AM) technology provide the potential for on-demand and rapid production of spare parts during urgent repair times. Recently, big oil and gas companies have shown early progress in using additive technology in manufacturing specific heat exchangers, downhole cleanout tool nozzles, offshore risers, gas turbine nozzles, and subsea chemical stick injection tools. Despite the mentioned progress, the current adoption level of additive technology for the offshore oil and gas industry is very limited. Non-destructive and destructive evaluation methods of additively manufactured metallic components have been studied extensively. However, the technique selection procedure and scope of the required test methods have not been studied sufficiently. This paper discusses various elements related to the qualification of additively manufactured components for application in the oil and gas industry. A risk-based qualification method for identifying the scopes of required non-destructive and destructive tests and the resulting qualification procedure for additively manufactured spare components in offshore oil and gas applications is suggested