Thin Sheet Part Research Articles

Design of joints of thin sheet parts with mechanical connections (according to EN 1993-1-3)

The main direction of development of steel building structures is to reduce the cost of implementation of buildings without changing their load-bearing capacity and value in use. Therefore, an essential factor in the development is the introduction of modern technologies. Solutions from other industries such as automotive or aerospace, have been adapted to perform building structures. As a result, today in the construction industry we use lightweight steel profiles from cold-bent elements. Modern technology and advanced calculation theory make it possible to build these structures much more economically than previous conventional systems. Elements and products made of thin sheets allow to reduce costs of construction, but at the same time is associated with the possibility of defects resulting in the appearance of a state of failure of structural elements or the entire facility. Connection zones of thin-walled elements are always the critical points, hence the need for a particularly thorough assessment at the design stage, and then at the implementation of the investment. Correct application of the presented calculation procedure in article will allow the design and realization of modern structures, which will be durable and safe in operation for the expected period of time.

Two-stage magnetic-elasto-pulse stamping of thin sheet parts

The article substantiates the use of preliminary static loading and subsequent forging force when stamping thin sheet parts of complex shape with an elastic punch. The static load provides a relative deformation of the order of 20– 30% in the processing zone, which guarantees the stability of the position of the workpiece during subsequent pulsed loading. This technique is very important in the manufacture of asymmetric parts with a thickness of 0.01 – 0.3 mm. As a result, the accuracy of the products obtained corresponds to the 7th grade.The article provides a schematic diagram and a description of the proposed design of a double-action press, and analyzes the cyclogram of the device.It is recommended to carry out a static load with an electric drive, a pulsed one with a magnetic hammer, which is connected to a generator of impulse currents with a capacitive storage with an energy capacity of up to 40 kJ with a natural discharge frequency of the current of 20 kHz.

КОНСТРУКТОРСЬКО-ТЕХНОЛОГІЧНА ПІДГОТОВКА ВИРОБНИЦТВА ДЕФЛЕКТОРА З ВИКОРИСТАННЯМ ІМПУЛЬСНИХ ТЕХНОЛОГІЙ

The development of explosion punching processes is a rather complicated task for preparing the production of aircraft engines. The relatively large complexity and duration of production preparation, as well as the relatively high cost of the dies, require careful development of technological processes and an informed choice of a technically rational and cost-effective version of the technological process that corresponds to a certain scale of production. Even small further changes in technological processes usually lead to the processing of dies or the design and manufacture of new ones that require considerable time and are quite expensive. The design features of the thin-sheet part, which is an integral part of the D-136 turboshaft engine, which is used on Mi-26 heavy transport helicopters, are analyzed. The deflector has a domed shape, stiffening ribs are provided for stiffening the shape of the part - axisymmetric. After stamping-hoods, it is necessary to apply machining (drilling holes on the flange for mounting the deflector). The accuracy of the part is determined by the accuracy of processing the working surface of the matrix. Deviation of the part profile from the working profile of the matrix depends on the dimensions of the part. The technological process of stamping by the explosion of a deflector is developed, which consists of several stages: analysis of the structural and technological features of the part; determination of the shape and size of the workpiece, as well as the consumption of material; the choice of a rational technological process that ensures the manufacture of the necessary parts; determination of the type of equipment needed; selection of type and technological scheme of the stamp, and determination of the complexity of manufacturing stamped parts. A mathematical for describe the design of the deflector, which consists of several levels of complexity model is developed. Each level of the design description is responsible for its own stage of the technological process. Based on the developed model, an algorithm and a program for calculating the parameters of the technological process are created.

Investigation on Springback Behavior of Cu/Ni Clad Foils during Flexible Die Micro V-Bending Process

With the increasing demand for micro parts using metal laminates in modern production, the manufacturing processes of thin sheet parts have been elevated. However, it is difficult to predict the deformation behavior with miniaturization because of size effects in micro-scale. In this study, the flexible die micro V-bending behavior of Cu/Ni clad foils was investigated. The bending experiments with three different punch angles and Cu/Ni clad foils under different annealed temperatures were performed. The results show that the springback angle increases with the increase of bending angle and annealing temperature. The placement of Cu/Ni clad foils induced compressive stress results in the more obvious thinning of thickness and decreasing of springback angle. The interactive effects of the distribution of deformation zones and compressive stress induced by the interface layer result in the springback behavior of Cu/Ni clad foils during the flexible die micro V-bending process.

Comparison of Technological Methods for Small Diameter Hole Perforation in Titanium Alloys

There is a huge number of methods for hole obtaining. In view of the fact that an increasing number of parts demand an increased accuracy and roughness in the obtained holes, especially concerning thin sheet parts, there is the need of research in this field. The main goal of the work is to establish the most optimal method for small-diameter hole obtaining in titanium alloys. The sheet of titanium alloy OT4-1 is studied with the thickness of 0.5 mm. At the same time, rigid tolerances are established both for the holes themselves and for their location. Drilling, laser treatment and electroerosion ("super drilling") were chosen as the drilling methods. Other methods were not considered due to the possibility of aperture rupture between holes and other profile distortions for the part and the holes. The most optimal modes of hole obtaining were selected. The productivity, the quality and the accuracy of the holes were evaluated. They studied in detail the technologies for the obtaining of holes with the purpose of processing mode setting. The main recommendations were presented for an optimal method selection concerning the obtaining of small diameter holes in thin-sheet titanium alloys.

A study of incremental sheet forming by using water jet

In this work, a variant of the incremental sheet forming (ISF) process, namely the incremental sheet forming by using water jet (ISF-WJ), was studied. In the investigation, an ISF-WJ prototype machine was designed and developed. Different design concepts of the water jet nozzle were proposed and evaluated to achieve the maximum forming pressure by performing computational fluid dynamic (CFD) simulations. Based on the forming pressure distribution modeled by CFD simulations, finite element (FE) models were developed to study the sheet deformation behavior under the ISF-WJ process condition. Based on the understanding gained from the numerical study, experiments were conducted to validate the ISF-WJ process and the developed prototype machine. The results suggest that ISF-WJ is a feasible process to achieve improved surface finish of thin sheet parts. In addition, this study has found that water jet pressure plays an important role in preventing sheet wrinkling and obtaining an accurate geometry of formed parts.

Experimental Researches on the Limit Angle of Conical Parts Manufactured by Single Stage Incremental Forming on CNC Lathes

ncremental sheet forming (ISF) is one the manufacturing methods for sheet metal parts which has an increased rate of flexibility combined with relatively simple and cheap common technological equipment. This paper presents the results of researches on ISF performed on a CNC lathe, for thin sheet parts made of DC04Am mild steel. The main objective of the paper was to establish the maximum wall angle of the parts and its dependence on the main parameters of the process: thickness and diameter of the part, the tool radius, the feed rate, the spindle speed and the lubricating/cooling conditions. The tests were performed with original equipment designed by the authors and the results were commented and presented in diagrams and images of the parts. The main conclusion is that ISF on a CNC lathe can be successfully used for manufacturing conical shaped parts made of mild steel thin sheet, having a certain maximum angle of the parts wall, for small sized batches. The limit values of the parameters analyzed are a useful technological database for engineers.

Planar Contour Primitive Recognition of Thin Sheet Part Dimensional Inspection System

According to the two indices of inspection accuracy and inspection speed, a planar contour primitive recognition method of thin sheet part dimensional inspection system based on curvature and HOUGH transform is proposed. A contour point classification algorithm based on neighborhood values is developed, and a curvature threshold method is selected to filter the contour points, and a projection height method is selected to distinguish the property of the primitive and classify the contour points, and the straight line primitive and arc primitive segmentation and merging algorithms are constructed respectively by HOUGH transform. The inspection accuracy and inspection speed of the proposed method are compared and analyzed by contrast experiments between the proposed method and four dominant point detection methods such as Chung & Tsai method and so on. The dominant point detection ability of the proposed method is tested by a simulation planar contour which includes all kinds of dominant points. The experimental results indicate that the proposed method can recognize primitives exactly, the inspection speed is fast and the universality is good.

Research on Dimensional Inspection System of Thin Sheet Part Based on Machine Vision

Key technologies of dimensional inspection system of thin sheet part based on machine vision are investigated, and an entire machine vision inspection system is developed. A cad information-based line scanning step adaptive optimization method used for image grabbing of inspected part is proposed. A rectangle lens subpixel edge detection method based on cubic spline interpolation used for edge detection is advanced. A planar contour primitive recognition method based on curvature and HOUGH transform used for image recognition is raised. The inspection accuracy of the inspection system can reach to 1μm, and the inspection time can satisfy the requirements of on-line real-time inspection, so the inspection system is feasible.

Research on Edge Detection of Thin Sheet Part Dimension Inspection System Based on Machine Vision

Aiming at the edge detection of thin sheet part dimension inspection system based on machine vision, a contrast research on edge detection is investigated. The Gaussian blurred simulation image and thin sheet part image are took as evaluation images, and the edge detection are done with Roberts operator, Sobel operator, Prewitt operator, Kirsch operator, Laplacian operator, LOG operator and mathematical morphology edge detection method. The results of edge detection are analyzed deeply, and the edge location accuracy, noise resisting ability and calculation time of each algorithm are compared. The single-pixel width connected contour is acquired with mathematical morphology edge detection method, the detection time are 0.0521 second and 0.457 second respectively. It is appropriate that taking the mathematical morphology edge detection method as the edge detection method of thin sheet part dimension inspection system based on machine vision.

Conception automatique et optimisation des surfaces additionnelles pour le procédé d’emboutissage

Lors de la fabrication, à l’aide d’un procédé d’emboutissage, de pièces en tôles minces telles que les carrosseries automobiles ou les composants d’électroménager, certaines surfaces doivent être ajoutées à la pièce désirée afin d’éviter des défauts comme la rupture, le plissement et la rayure. Ces surfaces additionnelles sont constituées de murs de protection et de surfaces sous serre-flan. L’objectif principal de cette étude est de proposer une méthodologie d’aide à la conception des surfaces additionnelles s’appuyant sur le développement d’une procédure numérique automatique de conception et d’optimisation de ces surfaces additionnelles dans le cadre d’un procédé d’emboutissage de tôles minces. La conception automatique des surfaces additionnelles s’appuie sur la création des courbes de profil et de surfaces de COONS. Ces surfaces sont ensuite maillées automatiquement et la simulation du problème d’emboutissage est résolue avec l’Approche Inverse. Enfin, les paramètres géométriques nécessaires à la création des surfaces sont optimisés afin de satisfaire des critères mécaniques propres au procédé d’emboutissage. Ces outils paramétriques de conception-simulation-optimisation permettent d’aboutir rapidement à des surfaces additionnelles optimales.

Moment–curvature measurement in thin sheet—part I: equipment

The measurement of the moment–curvature characteristic for thin sheet metal in the elastic–plastic range provides important information which is not readily obtained from the tensile test. Steel sheet which is roll-formed to products such as roofing typically contains a residual stress distribution and is subject to strain ageing; these conditions can be identified from bend tests. The accurate determination of the moment–curvature diagram is not easy as the limiting elastic curvature is large and the magnitude of the moment is small. Part I of this paper describes equipment and data processing which have been developed for this purpose and in Part II, results obtained in sheet which has been progressively aged and stress-relieved are presented.

Moment–curvature measurement in thin sheet—part II: yielding and kinking in aged steel sheet

The bending equipment described in Part I is used to study the behaviour of a sample of galvanised steel sheet. The sheet is known to have an internal stress distribution and to exhibit ageing. Tensile and bend behaviour is measured for the sheet in the “as-received” condition, after ageing at 170°C and 300°C and after ageing and stress relieving at 450°C. In the bend test, attention is focussed on the imposed outer fibre bending stress at the limit of linear, elastic bending. In the “as-received” condition, this is substantially less than the tensile yield stress, but increases rapidly with ageing and for ageing at 300 °C it is approximately 200 MPa greater than the lower yield stress in the tensile test. Samples treated at 300 and 450°C showed maxima in the moment/curvature characteristic and unstable “kinking” was observed in bending. The bending moment versus curvature diagrams presented indicate material characteristics of importance in technological forming processes which are not easily identified in tensile tests.

Permeation of gases and vapours through films and thin sheet—part II

Methods used to measure the permeation of vapours through polymers are reviewed. Some theoretical and practical aspects of current British standards are discussed together with the units in which gas and vapour transport are usually expressed.

Permeation of gases and vapours through polymer films and thin sheet—part I

The many techniques for measuring the permeation of gases and vapours through polymer films and thin sheets are reviewed in detail. An outline of the basic theory is followed by consideration of each experimental method in terms of the physics of the method and of the practical aspects of operation.