F. Ghodusi Borujeni , H. Jalalifar, S. Jafari, A. Rafati,
Volume 19, Issue 12 (12-2019)
Abstract
Casing collapse is major problem of the oil fields which causes increase of costs to oil companies. This problem can be seen not only at drilling time in some formations but also after the completion and production may cause problems. exact prediction of collapse pressure is a very important factor in the casing design. Casing Collapse generaliy is a function of the geomechanical properties of the formation and the properties of the solid mechanics of the casing. One of the properties of solid mechanics that affects the testing of the collapse can be the ovality of the casing and the difference in the thickness of the casing and the existence of residual stress during the construction of the casing. In this paper, using numerical methods, the effect of each of the above-mentioned solid mechanics parameters and formation creep on the collapse of the casing has been investigated. The results of this study indicate that pipe defects, such as casing ovality, eccentricity and the presence of residual stress, reduce the strength of the casing.
This reduces the resistance to the extent that the casing at the time of installation due to high plastic strain will collapse and also it was found that the pipe imperfections is more effective than rock salt creep in casing collapse.
Sh. Darzi, M.j. Mirnia, M. Elyasi,
Volume 20, Issue 8 (8-2020)
Abstract
Single point incremental forming is a cost-effective process with high flexibility and as a result, would be a proper selection for low-batch and high-customized production compared to traditional processes such as pressing. The target market of this process usually consists of medical, automotive, and aerospace industries in which metals with high strength to weight are highly in demand. These materials are usually formed at elevated temperatures due to their low formability at room temperature. In this study, the AA6061 aluminum sheet was homogeneously heated at 25-400°C. In addition, the effects of important process variables of heat-assisted SPIF including temperature, vertical pitch, feed rate, and three types of lubricants were investigated on formability of truncated cones with various wall angles. According to the results, despite the inability of local heating in enhancing the formability of the AA6061 sheet (37% improvement of formability under optimal conditions), the homogenous heating approach which was used in this article leads to a significant improvement in formability (528%). Temperature is the most important parameters effective on the formability, while lubricant and vertical pitch are ranked as the second and third parameters, respectively and the effect of feed rate is negligible. The critical wall angle increases from 60 to 65 degrees with increasing the temperature from 25 to 400°C. In order to choose a suitable set of parameters, the surface roughness should be taken into account, which may alter the results from 1.18 to 4µm as the best and worst surface conditions, respectively. Furthermore, a truncated cone with a wall angle of 65 degrees was successfully formed to 44mm depth using an appropriate combination of process parameters. This demonstrates an outstanding improvement in formability.
Seyed Javid Zakavi, Esmaeil Bakhshipour,
Volume 22, Issue 7 (7-2022)
Abstract
In this paper, by using the Chaboche kinematic hardening model with the isotropic hardening law, the effect of temperature and bending moments is investigated on the strain accumulation behavior of carbon steel piping branch. Carbon steel branch junctions under internal pressure and temperature with dynamic bending moment are tested at five temperatures of 20, 50, 100, 150 and 200 ° C. The results obtained by numerical analysis show that the highest amount of ratcheting occurred near the branch junctions in the circumferential direction. The strain ratcheting occurred mainly because of dynamic moments and high temperatures. The results show that in all three samples, the amount of strain ratcheting increases with increasing of dynamic moment level and temperature. With increasing of the ratio of diameter to thickness in branch junctions, the onset of strain accumulation occurs at low moment levels. It can be concluded that initially, the rate of strain ratcheting is high and with the increase of loading cycles, this rate decreased due to the strain hardening phenomenon. The increase of strain ratcheting at high temperatures is due creep strain because of high temperature and mainly accumulated plastic strain under dynamic bending moments because of cyclic plasticity.
Amirhosein Abasi, Rasoul Safdarian,
Volume 23, Issue 6 (5-2023)
Abstract
Single point incremental forming (SPIF) is a cost-effective process with high flexibility and as a result, it is a suitable choice for low-batch production compared to traditional metal forming methods. In the present experimental research, the warm SPIF with ball nose tool was used in the forming of aluminum tailor welded blanks (TWB) that were joined together by the argon welding process. Aluminum sheets of 6061 and 5083 with an equal thickness of 1.5 mm were used as base metals and joined together using the butt welding method. In this research, the effect of four parameters of temperature, lubricant, step down, and feedrate were investigated on the formability and appearance of aluminum. The temperature range is between room temperature and 290 degrees Celsius, and three types of lubricants are used in the experimental tests. The Taguchi method was used for the design of the experiment. The results of the tests indicated that an increase in the temperature as the most effective parameter led to an increase in the formability of TWB by 79%. The lubrication, step down, and the feedrate was in the next ranks of effectiveness in the formability of aluminum TWB.
Hamidreza Rezaei Ashtiani, Naser Meyghani, Omid Khalili,
Volume 23, Issue 12 (12-2023)
Abstract
At the end of the forming process, when the part is removed from the mandrel and the matrix and the part is loaded, a deformation occurs in the part, and this deformation after forming is called spring back. This research was carried out in order to experimentally determine the spring return of stainless steel 316 and carbon steel ST37 with different thicknesses in C-die forming and compare it with finite element simulation. The parts with three thicknesses of 1, 1.5, and 2 mm, forming and the geometrical dimensions of the spring back of the sheets have been verified. The results showed that the experimental spring back in the finite element simulation is consistent with the test, and also by reducing the thickness, spring back increases, which is affected by perfect elastic zone and surface plastic strain and membrane and bending stress.
Mahnaz Dabaghi, Maryam Morakabati,
Volume 24, Issue 2 (1-2024)
Abstract
In This study, in order to evaluation of ductility and consequently the optimum workability region of novel Ti-3Al-8Mo-7V-3Cr titanium alloy (Ti-3873), the hot tensile tests were performed at a constant strain rate of 0.1 s-1 and the temperature range of 650-850 ℃ . To establish the relationship between microstructural evolution and ductility, the microstructure of the specimen was examined by optical microscopy (OM) and scanning electron microscopy (SEM) after and before hot deformation. The results showed that ductility at the temperatures of 650-750 ℃ , increased from 33% to 54% as a consequence of transformation of α to β phases and gradually eliminating the α phase. The maximum ductility obtained at 850 ℃ with a 71% increase in ductility. Microstructural studies showed the elongated and serrated boundaries confirmed the occurrence of dynamic recovery. Recrystallized grains were also observed at 850 ℃ . Therefore, it can demonstrate that the restoration mechanism of the Ti-3873 alloy during hot tension is dynamic recovery and partial dynamic recrystallization. Finally, according to tension results, the appropriate range of deformation deformation of the Ti-3873 alloy in this study is 800-850 ℃ .
Sajjad Lohrasbi, Soheil Nakhodchi,
Volume 24, Issue 8 (7-2024)
Abstract
Inconel 718 superalloy is widely used in various industries due to its excellent high-temperature properties. The production of components made from Inconel 718 superalloy through the Selective Laser Melting (SLM) method enables the fabrication of parts with complex geometries. Therefore, improving the mechanical properties of parts produced by SLM using secondary strengthening processes is of great importance. This study investigates the effect of cold pre-strain on the tensile and compressive strength of Inconel 718 superalloy samples produced by SLM. The test specimens were produced by the SLM method and subjected to single-stage (5%-15%-30%) and two-stage (4%-12%-16%) loading. To examine the impact of initial loading on mechanical properties, tensile, compression, and hardness tests were performed, and the microstructure behavior was analyzed using an optical microscope. The results indicate that the yield strength and ultimate tensile strength of the Inconel 718 superalloy in the Y-axis (XY plane) increased by 31.8% and 11.6%, respectively, after applying a 30% initial strain along the Z-axis. The compressive yield strength of Inconel 718 superalloy increased by 79.3% in the Z-direction with a 30% pre-strain. In other words, applying pre-strain along the Z-axis affects the compressive strength in the XZ plane as the principal strain and the tensile strength in the XY plane as the shear strain. Increasing pre-strain to 30% has a minimal effect on the hardness properties of Inconel 718 superalloy. The results from the two-stage loading process indicate an enhancement in strength with the increase in the number of loading stages, attributed to the work-hardening phenomenon
