Wall Thickness Distribution Research Articles

Mechanics of double-sheet die-less shear spinning: a novel potential method for wall thickness control in spinning process

Die-less spinning has high flexibility in aeronautics, aerospace vehicles and other manufacturing fields; however, the wall thickness of the workpiece is hard to control in die-less shear spinning. A flexible control method of wall thickness distributions on the truncated cone shape is attempted using double-sheet shear spinning. The fundamental approach entails the adjustment of original thickness during forming. In double-sheet die-less shear spinning, two aluminum disk blanks arranged concentrically are formed for truncated cone. The cover thicknesses of the spun workpieces are smaller than the value that conforms to the sine law using the same blank thickness. The wall thicknesses of base spun workpieces are bigger than the sine law value under the same circumstances. The theoretical mechanics analysis of the double-sheet shear spinning process is carried out through mechanics and finite element analysis.

Hydrogen Transport and Metal Embrittlement Risk in Storage and Industrial Applications

A physical model studying the diffusion of interstitial atoms has been used in the study of hydrogen redistribution, in order to predict the risk of hydrogen damage in a range of manufacturing processes. In this work, conditions representative of hydrogen storage and some scenarios in the nuclear or chemical industries are considered. A singular advantage of this model is that, contrary to some simplified commercial and academic models, it contemplates diffusion in its most comprehensive description, i.e., with the driving force for atom diffusion being the gradient in chemical activation instead of simply considering it occurs down a composition gradient. Because the model also incorporates thermal history, microstructure, matrix solubility, multiple trapping distributions, interaction with the atmosphere and others, it is ideally suited to study real industrial applications. In this work, several simulations of hydrogen permeation are considered. Hydrogen permeation in industrial applications may introduce damage within the metal structure, leading to delayed failure. In the cases studied hydrogen is transported through a metal wall separating one volume with high hydrogen pressure and/or high temperature from another volume with low hydrogen pressure and temperature. By using such comprehensive physical model, it is possible to study the effects of hydrogen pressure and temperature gradient, wall thickness, metal microstructure and trap distribution on the flux across the wall and on the accumulation of hydrogen within the metal. Furthermore, it makes possible to estimate the embrittlement risk and when necessary the time to fracture. Keywords: hydrogen, steel, permeation, physical model, hydrogen storage, nuclear industry

Effect of Interface Friction on Overlapping Sheets Bulging Formability and Microstructure of 5A02 Aluminum Alloy

Aluminum alloy 5A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability and microstructure of target sheet in overlapping sheets bulging process. Sheet sliding experiment was performed to measure interface friction coefficient of 5A02/SUS304 in different lubricating conditions and normal pressure. Overlapping sheets bulging experiment of 5A02/SUS304 was carried out to investigate the influence of interface friction on limit bulging height, wall thickness distribution, microstructure and fracture morphology of 5A02 bulging specimens. The results showed that increase of the interface friction coefficient of 5A02/SUS304 could effectively improve the limit bulging height and deformation uniformity of 5A02. And the fracture style of 5A02 transformed from toughness fracture of dimples-micropores gathered to fault slip separation fracture. Therefore, target sheet bulging formability is improved with the increase of interface friction coefficient.

Numerical simulation study on multi-pass non-axisymmetric spinning of cylindrical parts with oblique flange

A non-axisymmetric cylinder with an oblique flange has broad application prospects. Spinning is the main production process for this kind of workpiece. Finite element modeling is a necessary method to study some key problems that are difficult to be solved merely through experiments, such as the strain and stress fields in the development of this spinning technology. In this study, the spinning process of a non-axisymmetric oblique flange cylindrical part was established and simulated using ABAQUS/explicit software. The credibility of the simulation result was validated through an experiment. The influence of the axial roller feed along the cylinder wall on the distribution of wall thickness and stress and strain during the forming process was analyzed. The change in stress field and strain field with time was analyzed, and the quantitative relationship between forming conditions and forming results was described. Furthermore, the forming principle of the flange was analyzed. It would be beneficial for flange forming to reduce the increasing distance of the cylinder wall in the 180° direction (parameter c) and the vertical distance from the closest point to the spindle as the roller returns back in the 180° direction (parameter d), to a certain extent. Hence, a workpiece with an ideal appearance was obtained. By comparing the wall thickness distribution, the design and optimization of the roller path were once again verified to be reasonable.

Analysis of the influence of cold pipe rolling technological factors on the change in Q-factor distribution along the deformation cone

The paper provides the results of studying the effect of technological factors of the cold pipe rolling process on the changingof Q-factor distribution along the deformation cone. The Q-factor value, which is the relationship between actual deformation on the wall thickness and actual deformation on the pipe mean diameter, and the pattern of its distribution along the deformation cone are controlledvalues when rolling pipes from titanium and zirconium alloys of a certain range. The Q-factor defines whether metal grains will be oriented radially or tangentially. It is desirable that Q-factor f luctuate around its definite value with low amplitude along the entire deformation cone. It is determined that the method used to calculate the pipe wall thickness distribution along the deformation cone has a significant effect on the change in the Q-factor distribution along the deformation cone. The advantages of using mandrels with a curvilinear generatrix of the working surface profile are confirmed. Dependences ascertained in the article can be used to calculate the schedules of rolling and calibration of cold pilgering mill tools.

ẢNH HƯỞNG CỦA MỘT SỐ THÔNG SỐ CÔNG NGHỆ ĐẾN SỰ PHÂN BỐ CHIỀU DÀY THÀNH KHI TẠO HÌNH SIÊU DẺO CHI TIẾT BÁN CẦU TỪ HỢP KIM NHÔM HỆ Al-Zn-Mg-Cu

This paper presents the research results on forming simulation in blow forming of a hemispherical part from aluminum alloy in superplastic conditions. The 2D Deform software is used for numerical simulation. The results are intended to assess to influence of process parameters (such as deformation temperature T, forming pressure p, back pressure p0) on the distribution of wall thickness. Based on the research results allow to determine the reasonable process parameters (superplastic forming use back pressure and deformation temperature of 530°C, forming pressure of 25 atm) that improve the degree of uniformity wall thickness in superplastic forming of a hemispherical part from Al-Zn-Mg-Cu aluminum alloy.

Influence of radiation-crosslinking on the elongation behaviour of glass-fibre-filled sheets in the thermoforming process

Abstract Thermoforming is one of the most important processes in polymer processing. In the packaging industry, thermoformed parts such as blister packs are manufactured from amorphous plastics such as polystyrene (PS) or polyvinyl chloride (PVC). In the field of semi-crystalline thermoplastics, mainly standard thermoplastics, such as, for example, polypropylene (PP), polyethylene (PE), or polyethylene terephthalate (PET), are used. There is limited literature dealing with the thermoforming of thin filled systems. Filler bonding, in particular, represents a major challenge in strain rheology. Electron irradiation is a way to generate improved filler-matrix bonding. In this study, the influence of fillers and radiation-crosslinking on the elongation behaviour and on the wall thickness distribution was investigated. At higher areal draw ratios, an enormous benefit of radiation-crosslinking of thin filled sheets is shown. While non-crosslinked specimens could not be formed, it was possible to thermoform radiation-crosslinked sheets filled with 10 vol.% glass fibres. Furthermore, with the higher areal draw ratio, the influence of the filler orientation on the stretching behaviour became more apparent.

Study on die-less spinning of cone–cylinder combined hollow parts

Die-less spinning can achieve the thin-walled parts with the regular shape of cone and cylinder or even some non-axisymmetric shapes. And it has advantages in forming some difficult demolding shapes. In this study, die-less spinning in a cone–cylinder combined hollow part and its forming mechanism were investigated. A ball-crown-shape roller was used to replace a conventional roller in the spinning process. The roller movement and spindle rotation were controlled by a computer numerical control spinning machine to achieve a planned roller path. The pass sets of tilted and horizontal lines were designed to form the cone and cylinder shape, respectively. Further, two methods were adopted to link the two forming pass sets and spin the cone–cylinder combined shape. One is to connect the cone and cylinder forming lines directly (Schemes A); the other is to connect the cone and cylinder forming lines by transition lines (Schemes B). The effects of two key parameters (roller path and feed ratio f) on the wrinkling and wall thickness distribution were analyzed. The product exhibited wrinkling on the wall using the roller path of Scheme A with f = 0.5 mm/r. f affected the occurrence of wrinkling considerably. Larger f made the flatness of the cylinder wall worse, no matter which roller path (in Scheme A or B) was used. When f was set to 0.25 mm/r (f was lower than LT1 in this study) with a blank thickness of 2.05 mm, wrinkling could be suppressed in the roller path of Scheme A. The product had an increasing thickness distribution on both the cone and the cylinder. The cylinder wall was even thicker than the disk blank with a blank thickness of 2.05 mm.

Evaluation of an ancient cast-iron Buddha head by step-heating infrared thermography

The authors report on the development of a step-heating infrared thermography method for nondestructive evaluation of a cast-iron Buddha head made in the Song Dynasty (AD 960–1279) in China. In particular, this method measures the wall-thickness distribution, which can be used as an indicator for the condition of the object. Unlike other areas of analysis, inspection of cultural relics requires special attention to safety. To avoid the heat shock associated with traditional flash thermography, a step-heating method with a mild heating process is considered to be more acceptable for evaluating cultural relics made from various materials. Before application to inspection of the Buddha head, a numerical analysis and experimental tests were performed to verify the accuracy of this step-heating thickness measurement method. Finally, thickness images of the Buddha head were acquired and analyzed. The step-heating thickness measurement method has a high accuracy and can be safely used for inspecting cultural relics.

Detection of extended blockages in pressurised pipelines using hydraulic transients with a layer-peeling method

Water distribution systems (WDSs) are one of society’s most important infrastructure assets. They consist of buried pipes that are often old and their condition is extremely difficult and expensive to determine. This research proposes a non-invasive layer-peeling method using hydraulic transient waves to detect extended blockages in pressurised pipelines. In the numerical study, hydraulic transient pressure waves are injected into a pipeline at a dead-end. Wave reflections caused by multiple extended blockages (uniform and non-uniform) are simulated using the method of characteristics (MOC). The impulse response function (IRF) of the pipeline is then obtained using the simulated pressure response at the dead-end. The original layer-peeling method previously applied to tubular music instruments is further developed by considering the differences between the instruments and pressurised pipelines (boundary conditions, fluid properties). Using the IRF and the modified layer-peeling method, the internal pipe diameter values are estimated section by section from the dead-end to the upstream end of the pipeline. The blocked pipe sections are then accurately identified from the reconstructed pipe wall thickness distribution profile.

Continuous reducing and sizing process of hot rolled steel-copper clad tube

Steel-copper clad tubes with small diameters and super lengths are in widespread used as heat exchange elements because of good performances of corrosion resistance, thermal conductivity, and high strength. The key problems affecting clad tube quality are poor dimensional precision and low adhesion strength. In this paper, these problems were analytically solved by performing continuous reducing and sizing through Y-type rolling. The main procedure involved pretreatment, assembling, heating, continuous rolling, and heat treatment. The changes in diameter and wall thickness distributions of the external and internal tubes were predicted by executing a finite simulation for steel-copper clad rolling. Rolling trials were then conducted on the clad tube for the comparison of the simulation and real rolling results, both of which indicated the good compatibility between the shape and dimensions of the finished tube. Finally, the bonding surface was observed byVhx-2000 ultra-depth of field microscope. The adhesion strength of the steel-copper tube was checked on WDW-E100D electronic universal tensile machine. The result showed that the hot fusion has occurred on the surface of steel-copper, and the clad tube rolled from the Y-type mill was strong and the adhesion strength has far exceeded the requirement.

Analysis of tubes with rectangular section forming process by fluid–solid coupling method

Owing to the advantages of favorable forming stiffness, light weight, and high production efficiency, hydroforming technology has extensive application prospects in the automobile and aerospace fields. This study designs and develops an experimental test system, which continuously injects oil into a quartz tube with favorable transparency, and then captures the flow characteristics of the liquid in the tube in real time using an ultra-high-speed camera. The fluid–solid coupling method of the MSC.Dytran finite element software is used for the experiment. The correctness of the simulation analysis method is verified by comparing the experimental and simulation results. Thus, a hydraulic bulging experiment of 20# steel tube without axial feed and a simulation analysis of the hydraulic bulging process of the rectangular section tube through the fluid–solid coupling method were conducted. A comparison between the experimental and simulation results verified the correctness of the finite element modeling and numerical calculation. In addition, the effects of forming pressure, loading time, and hydraulic loading path on wall thickness change in fillet filling was studied. Results showed that pressure drop exists in the pipe, and the velocity of the fluid changes rapidly with the deformation. The forming pressure clearly influences the forming effect. The maximum thinning rate of the middle section wall thickness initially decreases and then increases given an extended hydraulic loading time. Therefore, the optimal loading time should be determined to achieve the optimal forming effect. The effect of hydraulic loading path on the thickness reduction of wall thickness is not apparent but significantly influences the uniformity of wall thickness distribution.

3D FEM-DEM coupling analysis for granular-media-based thin-wall elbow tube push-bending process

The granular-media-based thin-wall elbow push-bending process involves filling a tube with granular media and pushing the tube into a die to bend a tubular blank into an elbow shape. By means of the mechanical characteristics of granular filler, an elbow tube with t/D < 0.01 (the ratio of wall thickness to outer diameter) and R/D < 1.5 (the ratio of bending radius to outer diameter) can be formed. To investigate the interaction between thin-wall elbow and granular filler, A 3D FEM-DEM coupling numerical model is developed, which takes into account both the deformation behavior of tubular blank (continuum, finite element method FEM) and mechanical characteristics of granular filler (discrete media, discrete element method DEM). By means of the coupling model, the key forming parameters of an elbow tube such as forming force, wall thickness distribution, wrinkling are simulated and compared to experimental results.

Enhancement on deformation uniformity of the target sheet by bulging process with magnetic medium and overlapping sheet

In the field of sheet forming, how to improve its performance is one of long-term goals. It is also an important basis for determining the quality and reliability of sheet forming. In this paper, the influence of overlapping sheet conditions on bulging behavior of Al1060 sheet using force-transmitting medium has been studied. That is, it uses a “soft-and-hard” double-side pressure loading method. The results show that the bulging behavior and forming ability of the aluminum sheet may be changed by adding an overlapping sheet. Compared with the condition without overlapping sheet, when the thickness of the overlapping sheet is 0.5 mm, the maximum thinning rate reduces from 43.95 to 38.16%. It improves the deformation uniformity of the entire target aluminum sheet, and the forming performance also increases with it. Compared with the situation of 1 mm overlapping sheet thickness under the same condition, the uniformities of the wall thickness distribution and the forming properties of the target aluminum sheet with an overlapping sheet thickness of 0.5 mm are significantly better and it reveals the causes. It also establishes that a theoretical model of the warp stress varies with angle, and provides scientific guidance for the improvement of light alloy forming performance and the expanding of the implementation about thin-sheet magnetic media pressure technology.

Integration of neural models in the process of technological preparation of the production of castings

The methodical application of neural network modeling in preparation and optimization of casting technology is described. A new technique for classifying castings based on geometric relationships of the geometry of parts and information on the distribution of wall thickness in castings.

Influence of an Increased Fiber Filler Content on the Elongation Behavior of Filled Films in the Thermoforming Process

Thermoforming belongs to one of the most important processes in polymer processing, especially in the packaging industry. It enables the forming of thermoplastic components into shaped parts at high temperatures. Since the thermoforming of films takes place in the rubbery state, amorphous thermoplastics are mainly processed, which have a wide rubbery state. Radiation crosslinking can be used to widen the thermoforming window of semi-crystalline thermoplastics. A benefit of the crosslinking is the increased short-term temperature resistance. In general, there are only a few investigations concerning the thermoforming of filled thin films. Within this investigation, the influence of an increasing glass fiber content up to 15 vol.-% as well as the effect of radiation crosslinking on the elongation behavior and the wall thickness distribution was examined. It can be summarized that especially thermoforming with an increased filler content at high areal draw ratios represents a challenge. Whereas non-crosslinked glass fiber filled films are thermoformable only at low areal draw ratios, radiation crosslinked films can be also formed at higher areal draw ratios without difficulties. For high filler contents and high areal draw ratios, no forming is possible at high areal draw ratios, although the films have been crosslinked. The use of radiation crosslinking enables the process limit in thermoforming of thin filled films to be increased and thus the range of applications to be extended greatly.

Experimental study of single point incremental forming with dummy sheet

The present article focuses on single point incremental forming (SPIF) process with dummy sheet. Influence of process parameters namely dummy sheet thickness, tool size, step size, wall angle and feed rate on minimum thickness of formed parts is investigated. After experimentation and analysis, it is found that the wall angle, tool size, dummy sheet thickness and step size are significant parameters. Based on the analysis mathematical model is developed to predict minimum thickness of formed part. Further optimisation of process parameters is performed using desirability function in order to maximize the minimum thickness. In SPIF process with dummy sheet, it is observed that the variation in wall thickness is small and overall wall thickness distribution along the depth of formed parts is almost uniform. Also, wall thickness distribution obtained is close to the value predicted by sine law.

An Investigation into the Formability and Processes of GLARE Materials Using Hydro-bulging Test

Our research mainly focuses on investigating the formability and processes of GLARE materials in the hydro-bulging test. Finite element simulation software ABAQUS/Explicit is applied to study the state of stress and strain as well as wall thickness distribution while experiments have done to validate the simulation results. The results indicate that cavity pressure and blank holder force have a significant effect on the forming behavior compared with traditional metal blanks. Curing process is also introduced in the production stage after first forming step. This study will increase the application of composite laminate manufacturing and open new ways for specialists working on high-strength lightweight material for future research.

Corrosion Failure Analysis of Elbow in LPG Desulfurization Unit

The elbow plays a crucial role in changing the flow direction of the medium in pipeline system and is one of the most commonly used pipeline components in the oil and gas transportation. This paper focuses on the corrosive failure mechanism of the elbow of regeneration tower of LPG desulfurization unit in a refinery. Aiming at the failure elbow, based on the macro and micro perspectives, the physical laws of the inner layer of the elbow, including the distribution of corrosion holes and wall thickness, are summarized and analyzed. The further characterization methods were used to study the corrosion mechanism, including mechanical properties, metallographic examination, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy spectrum analysis (EDS). Taking the thief hole as center, the elbow was divided into 4 rows. It is found that the maximum diameter was 21.1 mm while the minimum was 7.76 mm, and the vast majority of holes were 16 ~ 19 mm. The average size of the middle section was larger, meanwhile, possessed most holes over 19 mm. The corrosion thickness first increased then decreased along the flow direction and reached the maximum in completely destroyed area of the 1st and 2nd row. The corrosion thickness increased gradually along the flow direction of the 3rd and 4th row. Erosion corrosion is the main cause of elbow failure. Fluid erosion plays a dominant role in the failure process while electrochemical corrosion plays a dominant role in the formation of corrosion holes. Besides, the presence of heat-stable salts (HSS) also aggravates the corrosion of elbow.

Wall thickness and mucous cell distribution in the rabbit large intestine.

To achieve a better understanding of rabbit large intestinal functions, such as production of hard and soft feces and cecal fermentation, knowledge of the intestinal wall structure is essential. However, such knowledge is far from complete. Therefore, the aims of this study were to measure the thickness of the wall and its constituent layers and describe distribution of mucous cells in each segment of the large intestine in New Zealand White rabbits. Results showed that the cecum had the thinnest entire wall throughout the large intestine, and the fusus coli and rectum had a thicker entire wall in comparison to the cecum, the first segment of the proximal colon, the second segment of the proximal colon, and the distal colon. Moreover, the thickness of the mucosa in the fusus coli and that of the inner and outer layers of the tunica muscularis in the rectum were greater than that of the other segments. Mucous cells in the mucosa were the fewest in the cecum and most numerous in the fusus coli. This study provides detailed knowledge of the wall thickness and distribution of mucous cells in the large intestine of the rabbit. These findings are important for improving our understanding of rabbit intestinal physiology and pathology.