Wall Thickness Thinning Research Articles

Numerical Simulation Study of Wall Thickness Change Rule of Single Point Progressive Molding of Al5083

With the development and progress of science and technology, the application of single-point progressive molding is more and more extensive, but single-point progressive molding still exists the problem of excessive thinning of wall thickness of molded parts, which seriously affects the quality of molded parts. The article takes Al5083 plate forming cone as the research object, uses Abaqus finite element simulation software, according to the principle of single variable, respectively explores the influence of process parameters such as tool head diameter, layer spacing, feed rate and residual height on the average wall thickness reduction rate and the maximum wall thickness reduction rate of the molded parts. The results show that: increasing the tool head diameter, the average wall thickness reduction rate increases and the maximum wall thickness reduction rate decreases; the average wall thickness reduction rate and the maximum wall thickness reduction rate increase with the increase of ply spacing; the average wall thickness reduction rate and the maximum wall thickness reduction rate increase with the increase of the tool feed rate; the average wall thickness reduction rate decreases and the maximum wall thickness reduction rate increases with the increase of the residual height.

Research of eddy current inspection system for condenser titanium tubes in nuclear power plant

Condenser titanium tubes are easily to generate many defects in nuclear power plants, such as corrosion, damage, and wall thickness thinning. Eddy current technology is the main method of condenser titanium tubes in-service inspection, but manual operation has the problem of low efficiency. This article designed one new titanium tube eddy current inspection system based on automatic push-puller, and successfully applied in the nuclear power plant in China. The results show that this system can realize eddy current inspection in the condenser tubes with push-puller machine.

Study on forming process of equal wall thickness metal spiral pipe by single screw pump

To solve the problems of poor high temperature resistance of conventional screw pump stator and difficult machining of screw pump stator with equal wall thickness, this paper created a finite element model of equal wall thickness metal spiral pipe for single screw sump with 42CrMo based on tube hydroforming (THF). In this paper, the forming effects of different processes were evaluated by analysing the average pitch, wall thickness thinning rate and inner contour accuracy. Due to the particularity of design section and irregular plastic flow of material, the wall thickness of internal high pressure forming decreases seriously; on the other hand, because the diameter of the designed section is relatively large, the minimum ratio of D2 to Dmin is 1.12, which shows that wrinkles appear in external high pressure forming. As a result, based on the problems of internal and external high pressure forming, a coupling forming process was proposed. The results show that different parameters of coupling forming have little effect on the average pitch of metal spiral tube, and its maximum deviation is 1.08%; while thickness reduction ratio is proportional to initial diameter and thickness. Besides, when the liquid pressure is 350 MPa, the diameter is 60 mm and the wall thickness is 7.5 mm, the contour matching degree is higher; but the material accumulation and wrinkling will happen when the pipe diameter greater than 60 mm.

Study on the Law of Blank and Material Properties on the Free Bending of Pipes

To explore the impact of various material parameters on the three-dimensional free bending behavior of metal pipes and enhance the quality of such bending processes, this study focused on TP2 copper pipes with dimensions Φ12mm×1mm. Under uniform conditions of process parameters, free bending equipment, and key component characteristics, pipes with varying wall thicknesses and materials were investigated. The evaluation criteria were based on the maximum wall thickness thinning rate and maximum ellipticity of the pipes. The investigation aimed to understand how alterations in different material parameters affect bending radius, propulsive force, and wall thickness of the pipes. The results revealed that smaller bending radii correlate with more pronounced influences of wall thickness on pipe curvature. Additionally, an increase in wall thickness led to a decrease in pipe forming quality. The bending radius of the pipe was determined by multiple parameters, including the material's elastic modulus, yield strength, pipe hardening index, and strength coefficient. The maximum ellipticity of the pipe was found to be associated with material strength, while the alteration of pipe wall thickness was influenced by the hardening index, denoted as 'n'.

A thickness reduction testing method for ferromagnetic materials based on variable intensity DC magnetization

The assessments of internal thickness reduction of ferromagnetic components are extremely important. Traditional nondestructive testing (NDT) methods are usually non-linear and sometimes the electromagnetic parameters of components are required. In this paper, a thickness reduction testing method based on variable intensity DC magnetization (VIDC-MAG) is proposed. Both theoretical modeling analysis and simulation modeling analysis show that a pole point of magnetic permeability μm appears with the increase of DC magnetization intensity, which corresponds to an inflection point magnetizing current im. The im decreases with the increase of the defect depth of the wall thickness reduction and shows a linear relationship. The experimental results show that the method performs well for the inner wall thickness thinning and the relative error of the measurement results is small. Additionally, the measurement results are related to the width of the thickness reduction, the probe excitation frequency, the magnetic properties of ferromagnetic material and the lift-off distance of the magnetizer. The method is applicable to the thickness variation of the cover layer and does not need to know the electromagnetic parameters of the components in advance, which has greater practical application value.

Analysis of the Cause of Gas Pipeline Burst in a Gas Production Plant

In order to reduce the failure of pipes, the macroscopic morphology, macroscopic crack, chemical composition, hardness, microstructure and so on were tested through the macroscopic analysis, physical and chemical property inspection, hydrogen-induced cracking test and sulfide stress cracking test. The SEM was used to analyze the microscopic cracks, fractures and element distribution at the failure site. The results show that the cracking zone of the failed pipe section has the characteristics of bulging deformation and thinning of wall thickness. The macroscopic fracture of the fracture is a typical 45° shear shape. The fracture was observed under the high magnification of scanning electron microscope and showed dimple morphology. The failure mode of the failed pipe segment is plastic fracture. The reason for the failure of this pipe is the special geographical location of this section of the pipeline, and the sudden increase of pipeline pressure after the well opening operation causes the water hammer phenomenon, which causes the local bulging of the pipe body, which further leads to burst failure.

Study on In-Service Inspection of Nuclear Fuel Assembly Failure Using Ultrasonic Plate Wave.

As protection for nuclear power plants is quite necessary, the nuclear fuel is sealed in zirconium alloy thin wall cladding. During service, fuel rods might be damaged caused by wall-thickness thinning, cladding corrosion and cracking, etc. This will cause the coolant to enter into the fuel rod, which may lead to the failure of the fuel assembly. However, current diagnostic methods have limitations due to the special structure of the fuel assembly and the underwater and radioactive environment. In this paper, a novel inspection method is proposed to recognize the failure of a fuel rod. The fuel rod failure can be detected based on the presence or absence of coolant inside the fuel rod by using an ultrasonic plate wave. The inspection model and process algorithm are proposed for in-service inspection. The relationship between signal and scanning position is established and analyzed. Both ultrasound field simulation and experiment have been carried out for validation. The corresponding results illustrate that the failed nuclear fuel rod of the whole fuel assembly (including the internal rods) can be effectively detected without the influence of the near-field region by using the proposed method.

Analysis of influence of bending radius on strength of titanium alloy tube

Titanium alloy has excellent performance, and the application of titanium alloy in aviation hydraulic pipeline could meet the requirements of high performance and light weight of the hydraulic system. However, the titanium alloy is difficult to be processed and formed, and the titanium alloy tube is easy to be thinned and distorted during the bending process, which affects the performance of the tube. In this paper, the forming process of TA18 titanium alloy tube with three bending radii was simulated, and the influence of bending radius on the thickness thinning rate and ovality of the bent tube was studied. Based on the forming simulation results, the bearing capacity of each bent tube after forming was studied, and the influence of bending radius on the service strength of the hydraulic tube was analyzed then. The results showed that increasing the bending radius could reduce the wall thickness thinning rate and ovality of the bending part, and enhance the service strength, which would provide data support for the bending forming and performance evaluation of titanium alloy tube.

Subregional flexible-die control in magnetorheological pressure forming

Magnetorheological pressure forming (MRPF) has shown great flexibility in process control by adjusting the mechanical property of MR fluid. However, the regulation of flexible-die property at present is holistic. In this paper, MRPF based on subregional flexible-die control was proposed, which makes the MR fluid show different force transfer characteristics to meet the requirements of flexible-die performance in different areas. Two kinds of non-uniform magnetic fields were established using the combination of coil and iron core groups based on the measurement and finite element simulations. The MRPF experiments of the Al1060-O sheet using the holistic and subregional flexible-die control methods were conducted. The effects of subregional flexible-die control on loading curve, strain distribution, configuration, wall thickness thinning rate, and fracture characteristics were analyzed. Compared with the case that the specimen ellipticity changes little under the central-dominated magnetic field (CMF), the ellipticity gradually decreases under the fringing-dominated magnetic field (FMF) with the increase of the current. The fracture modes can be divided into three types, and the fracture position transfers from the center of the specimen to the circle of R10mm and then to the die fillet area. The influence mechanism of subregional flexible-die control on sheet deformation behavior and fracture mode is further clarified. The non-uniform distribution of cavity pressure and friction conditions caused by the magnetorheological effect is the main factor affecting the stress states and final deformation behavior of sheet metal. This study provides a new path for intelligent control in sheet metal forming of complex thin-walled parts.

Investigation by numerical modeling of the mechano-electrochemical interaction at a dent-corrosion defect on pipelines

Dent-corrosion combination defect causes the curvature change and wall thickness thinning on the pipeline simultaneously, which poses a higher threat to pipeline integrity than a single type of defect. In this work, a finite element (FE) based multi-physical field coupling model was developed to investigate the mechano-electrochemical (M-E) interaction at the dent-corrosion defect on an operating X80 pipeline. Parameter effects, including internal pressure, the diameter-to-thickness ratio of the pipe, and the geometries of the defect, were determined. Results demonstrate that the local equivalent plastic strain and anodic current density are insensitive to practical operating pressure but highly dependent on the diameter-to-thickness ratio and the geometries. A critical dent depth of 4% of the pipe diameter existed, exceeding which the increase of dent depth hardly affects the maximum equivalent plastic strain of the pipeline. The size of the indenter is negatively correlated with the equivalent plastic strain and the anodic current density at the defect center. There is also a critical threshold of 10% pipe diameter, below which the distribution of equivalent plastic strain and anodic current density at the defect is significantly affected. The effect of the circumferential dent is significant, while that of the axial dent is marginal.

Non-axisymmetric die-less spinning using ball-crown-shape roller

The non-axisymmetric cone has broad application prospects. However, the severe wall thickness thinning has been the bottleneck problem restricting the application of non-axisymmetric parts which are manufactured via die-less shear spinning. In order to control the spun wall thickness distribution, the ball-crown-shape roller is adopted to carry out the non-axisymmetric spinning. The spun workpiece with the non-axisymmetric cone shape is obtained, and the deviation of the maximum and minimum half cone angles α and β between the experimental results and the theoretical values is no more than 4.11%. The wall thicknesses are much greater than that of the shear spinning value with the corresponding half cone angles, and basically maintain at (even locally exceed) the initial blank thickness. At the same time, the half cone angle is considered to have small effect on the wall thickness distribution. The finite element model for this spinning process is established and verified to reveal the wall thickness distribution mechanism which is illustrated as that the BCSR causes the complementary relationship between the metal outflow and circumferential replenishment in the each half cone angle direction.

Research on the active pressurized forced lubrication deep drawing process and evaluation of the lubrication effect

Friction and lubrication are important parameters that affect the quality of sheet metal forming; excellent lubrication conditions and less harmful friction can reduce local thinning, delay fracture, and improve surface quality. Aiming at the poor friction conditions and difficult lubrication in the flange area during deep drawing, an active pressurized forced lubrication deep drawing (FLDD) process was proposed in this paper. A hydraulic system was employed to flush high-pressure lubricating oil into the contact gap between the die and sheet in the flange area. The high-pressure hydrostatic oil film in the contact gap can reduce the real contact area and effectively improve the lubrication conditions. The equipment is simple, the cost is low, and the lubricating oil pressure can be measured and controlled. Under the conditions of 20-kN, 35-kN, and 50-kN blank holder force (BHF), FLDD testing of box parts was carried out with 5-MPa and 9-MPa pressure using water-based lubricating oil. The horizontal comparison experiment was conducted with vegetable oil and water-based lubricating oil under the same process conditions. The test results illustrated that the lubrication effect of vegetable oil was the worst, whereas the lubrication effect of water-based mineral lubricant was significantly improved after pressurization. The maximum forming height was increased by 17.97%, the maximum forming force was reduced by 8.9%, the maximum wall thickness thinning rate was decreased by 7%, and the lubrication effect at 9-MPa pressure was superior to that of 5 MPa. The FLDD process has definite application value in improving the production environment, pollution control, and automatic production.

Precision forming of thin-walled hollow components with the complex surface by self-adaptive non-uniform pressure

The precision forming of thin-walled hollow components with the complex surface is difficult due to the excessive thinning of small radius circular arcs and the springback of small curvature surfaces. The difficulty is because the pressure required for forming a small radius circular arc is larger than that needed for other regions, while the pressure supplied inside the hollow blank in a conventional hydroforming process is equal everywhere causing the forming pressure cannot meet the requirements of different deformation regions. To solve this problem, the thin-walled hollow component with the complex surface is formed precisely by employing self-adaptive non-uniform pressure. Herein, theoretical analysis of the self-adaptive non-uniform pressure of viscous medium acting on the blank and the stress distribution of blank during the circular arc filling process is conducted. Then, different viscous medium parameters are employed in the forming of hollow components with different circular arc radii by numerical simulation. The results indicate that the non-uniform pressure is formed during the forming process, and is affected by the mechanical properties of viscous medium. The stress and strain distribution of blank are uniform, as well as the wall thickness thinning ratio and springback are small when the appropriate viscous medium is selected. As an application, the thin-walled hollow turbine blade is manufactured. The wall thickness is uniform and the dimensional deviation is kept at a lower level.

Fatigue detection and analysis of drilling tools based on metal magnetic memory method

With the vigorous development of offshore oil and gas resources in the world, underwater extended reach horizontal wells have been widely used. However, due to the complicated stress and serious corrosion of drill pipes in horizontal wells, drill pipes are vulnerable to damage. After a period of service at sea, some drill tools will be placed in coastal areas for a long time. The cumulative fatigue of drilling tools is not easy to master. In the past year or two, drilling tool failure has become more and more frequent. In order to evaluate the fatigue of drilling tools in different periods and master the quantitative fatigue of drilling tools, the metal magnetic memory method has its unique advantages in detecting the stress concentration and early damage of ferromagnetic materials. The self-developed metal magnetic memory detection device is used to detect the drilling tools in the drilling tool base. The results show that the gradient peak value and ladder are used to detect the drilling tools in the drilling tool base. The average degree can be used to classify the fatigue of drilling tools, and the metal magnetic memory method is more than sensitive to various defects of drilling tools, such as penetration, internal corrosion, external corrosion, wall thickness thinning, etc.

A semi-empirical model for underground gas storage injection-production string time series remaining useful life analysis in process safety operation

Time series risk analysis in digitalized process operations offers a useful means to transform the unordered data information into actions and practices related to process safety. A method for easily implementing time series degradation state analysis is proposed and described in terms of the remaining useful life (RUL) counting process based on a digitization semi-empirical probabilistic model. The well logs are used to inform a case study describing underground gas storage (UGS) injection-production string degradation risk. The corrosive effect of carbon dioxide in a complex environment is also considered, which leads to the decrease of internal pressure strength (IPS) with wall thickness thinning as well as RUL. The relationship between the residual IPS and RUL of the injection-production string at different rates of wall-thinning is analyzed. Based on the Gamma process method, the key empirical parameter information with time series degradation process and the probability density functions of different degradation under corresponding conditions are obtained. Then based on the Sequential Monte Carlo algorithm, the degradation trajectory of time series with confidence belt is obtained, and the confidence interval quantization of the wall thinning rate of injection-production string under different working conditions is realized. The results show that a semi-empirical time series RUL analysis could be used to more realistically evaluate the degradation state of the injection-production string. The residual strength with the Klever-Stewart calculation model has high stability for the uncertainty characteristics of the stochastic process. The proposed model is expected to calculate and determine the RUL of string with different thinning rates of wall thickness, and then further determine the time series corrosion degradation state for risk early warning. It is thus concluded that the proposed digitization semi-empirical remaining useful life prediction model provides a highly intuitive and quantitative tool for assessing the risk of degradation at the RUL level in the injection-production string of UGS.

Numerical simulation and experimental research on rubber flexible-die forming limitation with new position-limited backpressure mechanism

The forming limitation and the wall thickness distributions are the two main parameters for estimating the forming quality of T-shaped tubes. In this paper, the effects of three key factors on the forming limitation and the wall thickness distributions are investigated, which are punch front distance l1, reverse height h1, and the matching relationship between rubber hardness and axial feed Δl. A new position-limited backpressure mechanism is proposed, which is made up of the rigid position-limited lever, the flexible backpressure medium, and the rigid spacer. The simulations and experiments are carried out. Both results show that the thinning rate of the wall thickness decreases first and then increases, and the thickening rate decreases gradually with the increase of l1. The branch reaches the highest with the l1 of 5mm under the requirements of thinning rate and thickening rate. With the rise of reverse height h1, the bigger h1 is beneficial to the wall thickness thinning suppress at the top of the branch, and the branch reached the highest when h1 is 7mm. When Δl is fixed, the rubber hardness has a significant influence on the forming defects. The exorbitant rubber hardness causes the branch to rupture, and the excessive axial feed causes the wall to wrinkle. When rubber hardness is fixed, the thickening rate decreases with the increase of Δl. The best forming limitation and thickness distribution are achieved with the punch front distance l1 of 5mm, the reverse height h1 of 7mm, the rubber hardness of 75HA, and the axial feed Δl of 24mm.

Modeling the impact of shell wall thickness thinning on the stress state

A large number of fire-flame-proof substances, complex technological processes, characterizes oil and gas industry. Ensuring safety and preventing accidents are important issues for oil and gas industry. Modeling in modern software systems contributes to assessing the current situation and making the right decisions to extend safe operation life and increase equipment reliability. The wall thickness of a shell, even before putting in operation, is differential. In this paper, the effect of shell wall thickness thinning on the stress state is considered, taking into account the possible permissible deviation within the limits of GOST. The purpose of research is to prove the necessity and importance of taking into account uneven distribution of wall thickness for calculations. The object of study is cylindrical shell made from steel 09G2S. The thinning zone varied along the length of the study object. According to calculations result in SolidWorks software package, thinning, within the permissible possible deviation, at low pressures does not pose a danger. In case of increase in pressure up to 6 MPa and above, which is often used in complex technological processes, it leads to stress increasing in shell wall, which can contribute to strength characteristics deterioration. The results of research emphasize the importance of taking into account all features of a research object in 3D modeling, because it is at the heart of a new promising method of production management, like a digital twin.

Heterogeneous microstructure and mechanical property of thin-walled tubular part with cross inner ribs produced by flow forming

Flow forming was employed to manufacture the 2219 aluminium alloy thin-walled tubular parts with cross inner ribs (longitudinal and transverse inner ribs, LTIRs) integrally, which have been widely used in the aviation and aerospace fields. Electron backscattered diffraction (EBSD) examination along with micro-hardness tests was conducted on the typical zones of the flow formed part, thus to make a detailed study on the deformation modes as well as strain gradient induced heterogeneous microstructure and mechanical property. The wall thickness thinning is dominant at non-rib zone, while it is the die filling that mainly prevails at TIR and LIR zones, resulting in the occurrence of three different deformation modes. The plane strain deformation contributes to the severe fragmentation of ribbon-like grains at non-rib zone, while the axial tensile strain during longitudinal inner rib (LIR) forming and small radial tensile strain during transverse inner rib (TIR) forming cannot make the large ribbon-like grains refined effectively. In order to refine the microstructure and obtain uniform mechanical property, modifying the initial microstructure and changing the strain types at rib zones by full die filling, as well as subsequent annealing treatment should be considered.

Parametric Simulation Analysis of the Electromagnetic Force Distribution and Formability of Tube Electromagnetic Bulging Based on Auxiliary Coil

Tube electromagnetic bulging has been given much attention due to its superior advantages in the field of light alloy processing. However, the conventional tube electromagnetic bulging process exhibits some critical issues that restrict its wide industrial applications. This includes non-uniform axial deformation and poor forming performance such as wall thickness thinning. This article proposes a cost-effective solution for such issues through simultaneous radial and axial electromagnetic force loading using an auxiliary driving coil. In this regard, the influence of the auxiliary coil geometrical parameters on the electromagnetic force distribution and tube forming performance is investigated using electromagnetic-structure coupling model of the bulging process. The robustness of the new proposed method is validated by comparing its electromagnetic force distribution and tube forming performance with the traditional cylindrical coil method, currently used by industry practice. Numerical results show that the introduction of the auxiliary coil may effectively weaken the radial electromagnetic force at the end of the tube and solve the uneven axial deformation issue. Based on the obtained results, the maximum uniform deformation area is increased from 6.9mm to 35.1mm. The tube relative wall thinning issue is reduced and the relative wall thickness reduction of the pipe is found to be 0.01661. The axial electromagnetic force can be further improved by adjusting the geometrical parameters of the coil and the proposed electromagnetic bulging can effectively increase the uniform deformation range of the tube.

Texture evolution and controlling of high-strength titanium alloy tube in cold pilgering for properties tailoring

Abstract As one of the preferred fabrication technologies for high-strength titanium alloy tubes, cold pilgering has unique advantages of large deformation, fine surface, and close dimensional tolerance since materials are incrementally experiencing compressive stress states dominated local loading throughout entire rolling process. However, both complex external loading history and low symmetric hexagonal close-packed (HCP) crystal structure induce heavy crystallographic reorientation of polycrystalline significantly influencing formability and performance of titanium tubular products. How to achieve a bespoken tailoring of texture related properties is still a challenge. Accordingly, taking high-strength Ti-3Al-2.5 V tubes as the case material, this study focuses on the tube texture evolution and the texture controlling guidelines for properties tailoring in cold pilgering. By coupling validated and verified three dimensional finite element (3D-FE) model and viscoplastic self-consistent (VPSC) crystal plasticity model, a macro-meso scaled computation platform is established to predict the inhomogeneous deformation flow and texture evolution during pilgering. Then the tube texture evolution characteristics along rolling process with three typical initial textures are investigated, and the correlation between texture evolution and spatial inhomogeneous deformation allocation is explored, in which the deformation history is fully featured by strain vector, viz., strain ratio α and equivalent plastic strain ee as well as ratios of wall thickness thinning to outer diameter reduction (total Q value and transient Q value). Taking the contractile strain ratio (CSR) as the most important indicator for evaluating the texture and properties, the effect of final texture features of the tube on its tensile mechanical properties is revealed, and then the texture controlling guidelines for properties tailoring of the tube are proposed. To obtain the desired near radial texture and the reasonable CSR, the different pass rolling specifications can be considerably designed to coordinate the spatial strain components based on reasonable range of total Q value and ee, then the rolling tools can be designed for further fine tuning of the transient Q value and strain ratio α.