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The present article is focused on the condensation process of exhaust gases to reduce the air pollution to a possible extent. It is accomplished by circulating liquid N2 through copper tubes inside a chamber that is designed to condense the oncoming exhaust gases from the muffler of automobiles, thereby condensing a significant portion of exhaust gases. The condensed gases can be stored and processed at any industrial premises for recycling in a cost-effective manner. The work reported herein compares the design and analysis of two different mechanisms to achieve the effective condensation of automobile exhausts (i.e.)., one involves the employment of copper tubes with Liquid N2, and other involves porous bed kept inside copper tubes with Liquid N2. It is observed that a significant improvement in the heat transfer characteristics of the later version with porous bed over the other counterpart. The modelling and meshing of copper tubes with porous material is a tedious process, because it requires a huge number of nodes to capture the geometry. Hence, the non-equilibrium porous bed module available in the ANSYS Fluent tool is used to carry out the numerical analysis of the entire model. Further, the performance characteristics of the porous bed model are validated with a small sectional model of copper tube with porous bed and by a novel experimental technique involving distilled water in copper tubes. The outcomes of the studies are presented with different colour band metrics and trial experimental results. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The failure behavior and the failure mechanisms of the copper tube used in the air conditioning heat exchanger were analyzed using macrostructure and microstructure examination and the chemical composition analysis of the corrosion products. Results showed that the corrosion of the exterior surface of the copper tube should be responsible for the failure of the air conditioning heat exchanger. The chemical compositions of the corrosion products mainly included Cu, O, C, P, S, Cl, and so forth. The corrosion mechanisms were electrochemical corrosion under the circumstances of a humid environment, oxygen, and some corrosive medium. The corrosive media were organic carboxylic acids, Cl−, H2S, and SO2, which came from air pollutants, the combustion of fuels, the automobile exhaust, and the industrial waste gas. One or more electrochemical corrosion destroyed the integrity of the copper tube and led to the failure of the air conditioning heat exchanger in advance. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the performance increase of evacuated solar collector with nano fluid. Solar collector includes absorber unit to transfer the heat energy to a working fluid. In this research it was intended to evaluate performance considering with nano fluid. Improving the heat collection efficiency, efficient extraction of the heat from the solar collector, controlling the operating temperature, long maintenance free life of the device are some of the major challenges in collecting and extracting heat from the evacuated solar collectors. Using nano fluids as working fluids are interesting and challenging. Improvement in the performance of the evacuated heat pipe was obtained using heat transporting nano fluid consisting of aqueous dispersion (3 weight %) of Copper Oxide (CuO) nanoparticles; in comparison with the device without utilizing the nano fluid. From the past research, authors have analysed the performance with numerous trials. The result shows that evacuated tube heat pipe collector with nano fluid give the better result than heat pipe collector without nano fluid. [ABSTRACT FROM AUTHOR]

Sequential knurling and cutting-bending method is proposed to manufacture leaf-like integral outside finned tubes (LIOFT). The numerical analysis method was used to explore the material fracture and plastic forming processes. Single-factor experiments were used to establish quantitative relationships between process parameters and forming quality to guide the design of experimental parameters. The results of the numerical analysis revealed that the teeth of the knurled tube were cut by the tool's main cutting edge and then slide-bent along the rake face and minor cutting edge during the forming process. The knurling direction significantly affects the fin height and shift, a reasonable knurling direction increases the fin height by 40.1% while reducing the fin shift by 94.0%. Increasing the friction coefficient and tool feeding speed slightly increases the fin height but reduces the fin strength and finning ratio. The combination of experimental parameters was optimized based on the numerical analysis results, and a LIOFT with a maximum fin height of 3.46 mm was manufactured accordingly. [ABSTRACT FROM AUTHOR]

Due to its excellent processability, thermal conductivity and high corrosion resistance, the copper tube applied to the heat exchanger is joined by the brazing process. In order to improve the performance of heat exchangers, it is essential to inspect the joint quality of copper tubes, but it is difficult to identify defects in tube-shaped joints without cutting. To solve this problem, this study proposes a new detection method based on the Convolutional Neural Network (CNN) model to detect joint defects that occur in brazing joints of copper tubes. In the experiment, a brazing joint using high-frequency induction heating was performed on a 12.71 mm diameter copper tube, which is mainly used in heat exchangers, and the joint failure was judged based on the penetration depth of the filler material measured by vertically cutting the joined copper tube. In addition, thermal image data having a data structure of 80 × 80 pixels per frame was collected to be used as data to determine whether the brazing joint is defective in real time. Finally, using the collected thermal image data, we developed a CNN model with a structure that applies different hyperparameters to determine whether or not the joint of copper tube is defective. The selected CNN model produced an f1 score of 0.991 and a recall of 99.73%, and formed the basis for developing a system that identifies defects in brazing joints of copper tubes through thermal image data obtained in real time. [ABSTRACT FROM AUTHOR]

The utilization of Solar Water Heating Systems (SWHS) is a potential solution to use as an alternative to fuel and electricity in areas where these resources are scarce, costly, and not easily accessible. Research was conducted in Duhok City, Kurdistan of Iraq to evaluate the efficiency of a traditional type of SWHS, namely the serpentine collector variant. An active system collector that employed a moving water pump to facilitate the circulation of water inside the systems was used in the experiment. An analysis was conducted to assess the performance of the collector concerning solar irradiation, wind speed, and mass flow rate. This study utilized a Flat Plate Collector (FPC) with a tubular serpentine shape absorber made of steel sheet and copper tube. The serpentine collector had a maximum total heat loss coefficient of 5.53 . The serpentine collector demonstrated its highest level of practical heat gains at 561W. Its performance was observed to improve with increasing solar irradiation and water mass flow rate, but declined when wind speed exceeded the rated values. The serpentine collector achieved maximum efficiency with a flowrate of 0.042 kg/s, resulting in a productivity of 66.6%. While the maximum increase in water tank temperature in the serpentine collector was 25.8 ℃ at the mass flowrate 0.05 kg/s.

The effects of joining methods on the microstructure and corresponding stress corrosion cracking (SCC) behavior of copper tubes used in heat exchangers are evaluated by microstructure characterization and the slow strain rate testing (SSRT). The results show that the brazed joint (BJ) had worse SCC behavior and poorer fracture toughness than the mechanical joint (MJ). The fracture surfaces of the BJ and MJ samples after SSRT demonstrated the different fracture behaviors of the samples, especially intergranular brittle fracture in the BJ. Copper oxide layer on BJ is found to be extremely detrimental to the SCC behavior. Furthermore, a numerical model is established to predict and analyze the onset of the SCC along the surface of BJ. [ABSTRACT FROM AUTHOR]

The Parallel Tubular Channel Angular Pressing Process (PTCAP) has emerged as a promising method for refining the grain structure and enhancing the mechanical properties of metallic materials through severe plastic deformation. This study focuses on a comprehensive investigation of the PTCAP process, combining experimental and numerical analysis to gain insights into its underlying mechanisms. Experimental investigations involve processing a commercially pure copper tube using PTCAP under controlled conditions. In parallel, an explicit numerical analysis is developed using ABAQUS software to simulate the deformation behavior during PTCAP. The model incorporates material constitutive equations and accounts to describe the material response under high strain rates and large deformations. The research aims to investigate how multi-pass PTCAP affects hardness, strain homogeneity, and stress distribution. A comparison between the load punch from the experimental and FEM is conducted to validate the FEM results, and there is a good correlation between both. Hardness measurements are conducted at various stages to quantify the changes in material hardness resulting from the successive PTCAP passes. The hardness of the Cu tube increased by 63.45, 94.51, 103.98, and 105.64% after 1 to 4 passes, respectively.

Copper tubes used in air‐conditioners and refrigerators often fail due to ant nest corrosion (ANC) in formic acid environment. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) were analyzed by vapor corrosion tests, optical microscopy (OM), scanning electron microscope (SEM), energy‐dispersive X‐ray spectrometry (EDS). The effects of the surface condition on ANC of copper tube were also investigated. Results showed that ANC of copper tube was a spontaneous process. The surface integrity of copper tube surface oxide layer is not the decisive factor of ANC. ANC originated from the dissolution of the surface oxide layer in HCOOH, which exposed fresh copper matrix. ANC is a special electrochemical corrosion, where the copper matrix acts as an anode and the undissolved surface oxide layer acts as a cathode due to the potential difference. The accumulation of corrosion products consisting of Cu(HCOO)2 and Cu2O can produce a wedge effect and generate many microcracks until to penetrate the copper tube wall. These findings would provide a deep understanding of the corrosion behavior of copper and copper alloys. [ABSTRACT FROM AUTHOR]

The welding process is one of the fabrication processes in which tubes can be performed for structural purposes and transport liquids or gases. This study is focused on the manufacturing, characterization, and evaluation of mechanical properties of welded tubes made from oxygen-free copper (C1020) sheets using friction crush welding. The welded tubes were produced using different tool rotation speeds (1500, 1600, and 1700 rpm) and feed rates (130, 140, and 150 mm/min). The flanged edge height of 2.5 mm and 0.5 mm gap between the ends of the copper sheet was used. All examinations on welded tubes were achieved using different instruments such as optical microscopy, SEM, hardness, and tensile testers. The microstructure study showed good weld quality and good material flow between the two ends of the copper sheet in the weld zone. Moreover, the weld zone was not defective. The lowest hardness was identified in the crush zone due to the coarseness of the copper grains. The highest tensile strength of 105 MPa was obtained at the tool rotation speed of 1500 rpm and 130 mm/min feed rate. The results also showed that ductile fracture is the main source of failure.

In the Urals, there are more than a hundred products with large-diameter holes, some of which are made using a copper tube. Experiments on hollow drilling in the expedition of S. A. Semenov have shown great complexity of this method. In experiments on drilling it was planned to identify labor costs for the manufacture of copper tube, and also reveal various aspects of drilling techniques. The article presents the results of experiments on drilling different types of stone (soapstone, marble, serpentine and jade) with a copper tube. Experiments have shown that drilling with a brace is 1.5 times more effective than drilling with a borer. And using a copper tube as a drill increased the speed of making holes by 4–7 times. It also turned out that the abrasive used is very important for drilling efficiency. The most effective abrasive was emery, whose deposits are known in the southern Urals. The results obtained allow the authors to establish with great accuracy what drills and with application of what equipment stone axes of Bronze Age were drilled. A comparison of the experimental drills with bronze age drills shows that drilling with a copper tube was often, but not always, performed using a special machine tool. Labor-intensive making stone axes with large diameter holes especially made of strong row materials attest about high social status of their owners.

Forensic engineers investigating water loss incidents, caused by water leaking from damaged copper tube piping systems inside buildings, are tasked with determining if that damage is from the piping being exposed to subfreezing temperatures or some other cause. This paper provides guidance for such investigations and factual basis for such opinions, including presenting the results of experimental testing of water-filled copper tube piping systems exposed to subfreezing conditions. It also discusses piping standards and building codes. When ice forms a solid plug inside a pipe, the portion of the piping downstream of that plug becomes isolated. As the ice plug grows, the pressure in the isolated portion of the piping system increases dramatically from hydraulic pressure until the strength of the "weak link" is exceeded, which causes a rupture that relieves the pressure. Oftentimes, no significant water flows through the rupture at that time because the ice plug prevents water flow through the pipe. However, significant water flow occurs once the plug melts. This paper demonstrates why it is critically important for forensic engineers to understand this sequence of events. [ABSTRACT FROM AUTHOR]

An experimental study is conducted to show the influence of the tubes material type of the heat exchanger on the refrigeration system performance. The system is operated by using R134a as a working fluid, 2 mm internal diameter, and different lengths of capillary tubes which were 120, 135, and 150 cm. The experimental results showed that when increasing the refrigerant mass flowrates led to reducing each of the performance coefficient COP, number of transfer unit NTU and evaporator effectiveness ε. However, the highest improvement had appeared for each parameter COP, NTU, and ε which were 21%, 113.38%, and 59.42% respectively at a capillary tube length of 120 cm and m ˙ = 3.19 g/s compared to the length of capillary tube 150 cm. Besides, it was found an increase in W ˙ c with the incrementing in the capillary tube length from 120 cm to 150 cm. The biggest percentage of compression power was 23% at the capillary tube length of 150 cm compared to others at m ˙ = 3.71 g/s. Finally, the experimental results of COP and W ˙ c were validated by comparing them with other publications. [ABSTRACT FROM AUTHOR]

The texture evolution of copper tube manufactured by floating plug drawing process was investigated by Electron Backscatter Diffraction techniques and Visco-Plastic Self-consistent (VPSC) modelling method. The results obtained from experimentation indicate that the initial textures of copper tube transformed sharply after the first pass of the drawing process, and the final textures in the tube consist of Goss {110} <001> and P {110} <111> components. The VPSC model was established in order to study the texture transformation and the activity of slip systems of the tube during the drawing process. Two types of transformation paths were proposed to explain the mechanism of the texture evolution, which has a good agreement with the VPSC simulation results. [ABSTRACT FROM AUTHOR]

Deposition of well-adherent diamond-like‑carbon (DLC) films on copper is relatively difficult due to weak bonds between copper and carbon. The Cu-O-Si-C nanostructure was proposed to improve the adhesion and the corrosion-resistance of multilayer Si-DLC/DLC film on an inner surface of copper tube prepared by PECVD. First, the copper alloy was pretreated by oxygen. Then mixture gas of tetramethylhexylsilane (TMS) and oxygen was used to deposit interlayer, and finally multilayer Si-DLC/DLC film was deposited using the gas C 2 H 2 and argon. Transmission Electron Microscope (TEM) demonstrated that there existed CuSiO 3 , CuO, SiC, SiO 2 nanostructures in the interlayer. And X-ray Photoelectron Spectroscopy (XPS) proved that there were actually Cu O, Si C and Si O bonds at the interface. These bonds and compounds enhanced the adhesion between multilayer Si-DLC/DLC film and copper substrate. The polarization potential was significantly improved to −0.07 V, achieved through the process of oxygen pre-implantation and the combined deposition of oxygen and TMS. Furthermore, the adhesion of the film was estimated by the Rockwell test and reached HF1-HF2. The Cu-O-Si-C microstructure plays a crucial role in enhancing the adhesion and corrosion resistance of multilayer Si-DLC/DLC film. • The Cu-O-Si-C nanostructure was proposed to improve the adhesion of DLC coatings on copper substrate. • Oxygen was used to pretreat the surface of copper alloy before depositing. • The Cu-O-Si-C nanostructure enhanced the corrosion resistance of DLC films on copper substrate. [ABSTRACT FROM AUTHOR]

In this paper, cyclic flaring and sinking (CFS) as a new severe plastic deformation (SPD) method was employed to produce the ultrafine grain (UFG) copper tubes. The extra friction has eliminated in the CFS method that provided the possibility for production of longer UFG tubes compared to the other SPD methods. This process was done periodically to apply more strain and consequently finer grain size and better mechanical properties. The CFS was performed successfully on pure copper tubes up to eleven cycles. Mechanical properties of the initial and processed tubes were extracted from tensile tests in the different cycles. The remarkable increase in strength and decrease in ductility take placed in the CFS-ed tubes. The material flow behavior during CFS processing was analyzed by optical microscopy (OM), and a model was presented for grain refinement mechanism of pure copper based on multiplication and migration of dislocations (MMD). This mechanism caused that the initial grains converts to elongated dislocation cells (subgrains) and then to equiaxed ultrafine grains in the higher cycles. The CFS method refined the microstructure to fine grains with the mean grain size of 1200nm from initial coarse grain size of 40µm

In this paper, the effects of various parameters on the process of T-shaped copper tube bulge forming have been investigated. This evaluation is based on the properties of the copper tubes, properties of polyurethane rod and practical conditions of a bulge forming process such as the friction coefficient between die and tube, between tube and rod, boundary conditions and their constraints. The effect of each condition on a T-shaped copper tube has been explicitly simulated using the Abaqus software. The experimental results have been validated by conducting a series of experiments. After simulating the process, the effect of other parameters such as die corner radius, friction coefficient, thickness of the tube and counterpoise can be evaluated and used in practical experiments. Then, the simulation results have been compared with the obtained results from the experiments. Once the accuracy of the simulation results has been endorsed, the optimal values of different parameters have been determined using simulations. The optimal values for die corner radius, friction coefficient and counterpoise are 5 mm, 0.05 and 200 N, respectively. The findings shows the positive effect of utilization of optimal value for die corner radius, optimal value for counterpoise and lubricate on optimize forming process properties.

High precision dimensionality tubes are required for a number of applications. Nevertheless, there are some troubles and challenges to produce high quality tubes in a cost-effective way. In recent works done at the Institute of Metallurgy at Clausthal University of Technology, the tube drawing process was optimized by introducing dynamic tilting and shifting of the die. These methods made it possible to control the wall-thickness variation and even residual stresses (RSs) evolution. A possible influence on texture evolution, however, has not yet been investigated, though it is well known that the crystallographic texture has a remarkable effect on materials' properties. Furthermore, the initial texture clearly influences the microstructural evolution during plastic deformation, affecting the RSs evolution and dimension accuracy, too. In this paper the evolution and heterogeneity of the texture are introduced for tube drawing performed with a tilted die. The measurements were done using synchrotron and neutron diffraction methods. The aim was to understand the behavior of the material during the asymmetrical tube drawing, caused by the tilted die, and connect the effects between eccentricity and residual stresses. Pole figures and ODF densities were studied and the creation and variation of different texture components were analyzed as well. Unlabelled Image • Anisotropic behavior, crystallographic and texture evolution before and after drawing with tilting were studied. • Macro- and micro-texture were investigated. For macro-texture, crystallographic orientations were compared before and after drawing. • Micro-texture was studied for through-wall-thickness analyses. • Concerning the gradient over the wall-thickness, the cube component was the most dominant one at Max and Min positions. • After the first drawing step with tilting, the ODF intensity of the cube and Bs components were reduced. [ABSTRACT FROM AUTHOR]

The first process in the production, namely, horizontal continuous casting process, directly influences the performances of finished copper tubes. Numerical calculation and comparative analysis were conducted for the flow field and microstructural field of the flow and solidification of casting liquid in two kinds of crystallizers for horizontal continuous casting. It was found that the internal factors influencing the internal heat exchange effect of crystallizer and the microstructural uniformity of casting billets are swirl effect, and turbulence intensity. The structural parameters of liquid inlet of a crystallizer with lateral opening, i.e., the forward tilt angle and lateral tilt angle of liquid inlet, were analyzed from the source, and the reasonable parameter values of liquid inlet for improving the quality of casting billets were finally obtained with the mean value of maximum spin speed, the turbulence intensity, and the microstructural grain size of casting billet as evaluation criteria. The accuracy of the numerical calculation was visually verified through metallographic experimental analysis. This study provides measurable reference theoretical basis for production of inner grooved copper tube with efficient heat exchange. [ABSTRACT FROM AUTHOR]

The susceptibility of copper to stress corrosion cracking is increased by the addition of Zn, P, As, Sb, Si, and other elements. Among these, P, As, and Sb can lead to substantial increases even when present in extremely small amounts. P is an important additive element used in copper tubes, recently found to enhance resistance to ant nest corrosion in Cu-P alloys with concentrations increased tenfold. The problem of stress corrosion cracking in copper heat transfer tubes, typically used in air conditioner heat exchangers, is known to be a rare phenomenon. However, its relationship to high-phosphorus alloys is not yet understood. In this study, the relationship between high-phosphorus copper tubes and stress corrosion cracking was analyzed by investigating the effects of P concentration and tube shape on stress corrosion cracking in a hairpinbending copper tube. We confirm that alloys with small amounts of added P (0.027%) were prone to grain boundary corrosion. However, no clear difference in the degree of corrosion progression between Cu- 0.027%P and Cu-0.38%P alloys was observed. While the segregation of P to grain boundaries in high-phosphorus alloys is a clear cause for concern, no segregation was observed in alloys with concentrations from 0.02 to 0.4% in our FE-EPMA analysis. We conclude that residual stress in hairpin-bending copper tubes is a rare phenomenon. Similar results were found for thin-walled copper tubes. But the stress corrosion cracking in Cu-P alloys tended to occur when there were abnormalities in the bending process. As the shape of hairpinbent tubes became non-uniform, stress concentrated around local area, resulting in residual stress and stress corrosion cracking. In summary, it was found that while shape defects in hairpin bending process reduce the resistance to stress corrosion cracking in Cu-P alloy tubes, variations in P concentration from 0.02-0.4% produced no significant effect on stress corrosion cracking. [ABSTRACT FROM AUTHOR]

Copper is generally known as a metal which is excellent in workability and resistant to corrosion. Copper tube is used in a wide range of heat transfer field. However, when ant nest corrosion occurs on copper tube, the progression rate of corrosion is enough fast to penetrate the tube prematurely. In recent years, phosphorus added to the copper has been found to have an influence on progression of ant nest corrosion. Test of ant nest corrosion on different low phosphorus content in the copper clarified the influence of low phosphorus content in copper for ant nest corrosion. [ABSTRACT FROM AUTHOR]

Copyright of Al-Khawarizmi Engineering Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present study, copper tubes were subjected to severe plastic deformation through integrated extrusion-equal channel angular pressing (Ex-ECAP). Plastic deformation characteristics were analyzed using finite element simulation and resultant microstructures were characterized by optical microscopy. Also, X-ray diffraction patterns were utilized to calculate crystallite size. Results showed that integrated Ex-ECAP could be successfully applied on metallic tubes. Meanwhile, the resultant sub-grain size was measured to be in the range of 360-550 nm by Williamson-Hall method. Optical micrographs taken from the cross section of deformed sample demonstrated that initial grains in the plane perpendicular to flow direction remained equiaxed after deformation by Ex-ECAP and their sizes were decreased from 16 to 4 μm after deformation. [ABSTRACT FROM AUTHOR]

Condensation heat transfer performance can be significantly enhanced by patterning the condenser surface with different wettability regions as shown by numerous studies, including part I of this study. In part I of this study, some patterned surfaces with alternative parallel straight stripes consist of hydrophobic (β) and less-hydrophobic (α) regions at different ratios exhibited higher heat transfer rate than others. In this Part II of the study, our objective is to analyse the droplet dynamics during water vapor condensation on hybrid-wettability patterned horizontal tube surfaces under saturation conditions near the atmospheric pressure. Three major outlines were found in the course of the droplets dynamic investigation. First, the existence of an optimum (β/α) ratio that maximized the condensation heat transfer rate, as demonstrated in part I of a sample carrying β and α-regions widths of 0.6 mm and 0.3 mm, respectively is justified. This is because the optimum ratio exhibits the maximum droplet departure frequency and the minimum droplet area coverage rate among other samples. Second, the reduction in the heat transfer rate resulting from any deviation from the optimum ratio is also identified. We observed that by increasing the α-regions width on the hybrid patterned surface, the condensation was dominated by the filmwise mode, thus reducing the condensation rate. In contrast, decreasing the width of α-regions less than the optimum ratio was found to be unfavourable due to the increase in the bridging droplets observed and discussed herein. Lastly, the undesirable observed bridging phenomenon found to occur on all tested hybrid patterned surfaces, can significantly influence the condensation heat transfer performance. A bridging droplet can be referred to a droplet joined (bridged) by two, three, or four neighboring α-stripes. Increasing these unwanted droplets formation frequency can induce additional thermal resistance which can reduce the condensation rate. The most dominant and frequent bridging droplet type observed herein was found to be for droplets that were bridged by two α-regions, followed by those between three and four α-regions. A quantitative method (i.e. Bridging coverage area rate) was adapted herein to quantify the influence of the velocity, frequency, and size of the three types of bridging droplets on the condensation rate of the hybrid patterned surfaces. [ABSTRACT FROM AUTHOR]

In this paper, cyclic flaring and sinking (CFS) as a new severe plastic deformation (SPD) method was employed to produce the ultrafine grain (UFG) copper tubes. The extra friction has eliminated in the CFS method that provided the possibility for production of longer UFG tubes compared to the other SPD methods. This process was done periodically to apply more strain and consequently finer grain size and better mechanical properties. The CFS was performed successfully on pure copper tubes up to eleven cycles. Mechanical properties of the initial and processed tubes were extracted from tensile tests in the different cycles. The remarkable increase in strength and decrease in ductility take placed in the CFS-ed tubes. The material flow behavior during CFS processing was analyzed by optical microscopy (OM), and a model was presented for grain refinement mechanism of pure copper based on multiplication and migration of dislocations (MMD). This mechanism caused that the initial grains converts to elongated dislocation cells (subgrains) and then to equiaxed ultrafine grains in the higher cycles. The CFS method refined the microstructure to fine grains with the mean grain size of 1200nm from initial coarse grain size of 40μm. [ABSTRACT FROM AUTHOR]

In this paper, the effects of various parameters on the process of T-shaped copper tube bulge forming have been investigated. This evaluation is based on the properties of the copper tubes, properties of polyurethane rod and practical conditions of a bulge forming process such as the friction coefficient between die and tube, between tube and rod, boundary conditions and their constraints. The effect of each condition on a T-shaped copper tube has been explicitly simulated using the Abaqus software. The experimental results have been validated by conducting a series of experiments. After simulating the process, the effect of other parameters such as die corner radius, friction coefficient, thickness of the tube and counterpoise can be evaluated and used in practical experiments. Then, the simulation results have been compared with the obtained results from the experiments. Once the accuracy of the simulation results has been endorsed, the optimal values of different parameters have been determined using simulations. The optimal values for die corner radius, friction coefficient and counterpoise are 5 mm, 0.05 and 200 N, respectively. The findings shows the positive effect of utilization of optimal value for die corner radius, optimal value for counterpoise and lubricate on optimize forming process properties. [ABSTRACT FROM AUTHOR]

Inner grooved copper tubes have been widely applied as a kind of enhanced heat transfer tube. Annealing in a copper-tube pit furnace has a relatively high cost to performance ratio, and its operation at elevated temperature and the temperature uniformity of workpieces inside the furnace are difficult to control. Considering the structural characteristics of a pit furnace and using the wall function method, we establish a three-dimensional turbulent flow fluid–structure interaction heat transfer model and compute and analyze the flow field and temperature field inside the furnace. Methods for improving the fan speed, the heights of the gas-guiding cylinder, and the load frame are given. The temperature of critical points inside the furnace during annealing of the copper tubes has been measured and then compared with simulated values, directly validating the accuracy of the computation results. This study not only offers specific methods for improving the annealing quality of inner grooved copper tubes but will serve as a reference basis for quantifying pit furnace improvement. [ABSTRACT FROM AUTHOR]