Dissertations / Theses on the topic 'Micro forming process'

Le succès de l'industrialisation des micro-produits dépend des processus de conception et de fabrication. Une étape cruciale est la caractérisation du matériau utilisé dans les simulations numériques. Bien qu’il confère certaines propriétés mécaniques au matériau, l’essai de traction est loin de représenter la déformation complète subie par le matériau. Par conséquent, un autre test, Micro Incremental Deformation (Micro InDef), test présentant une déformation non homogène et riche en information, est développé sur la base du micro formage incrémental mono-point (µSPIF).Pour modéliser la formabilité du matériau (en particulier l'endommagement de matériaux), le modèle de Lemaitre est choisi en raison de sa capacité à modéliser le comportement du matériau en s'appuyant sur la mécanique des milieux continus et la thermodynamique de processus irréversibles. Dans cette étude, le Micro InDef test en tant que test de caractérisation de matériau est validé. De plus, en utilisant une méthode d’identifiabilité, il est prouvé que les paramètres matériaux identifiés sont des paramètres physiques, et non un simple lissage mathématique. Une fois le modèle de Lemaitre identifié, des tests expérimentaux et des simulations éléments finis sont effectués sur des tests de traction, des tests de cisaillement, des courbes limites de formage et des essais hors plan, afin de vérifier la fiabilité et l'adaptabilité de notre identification.Cette étude est finalement appliquée à un projet industriel dans le domaine des connecteurs, qui utilise principalement les alliages de cuivre comme matériau constitutifs
The success of micro product's industrialization depends on the conception, design and manufacturing process. A crucial step is the characterization of the material used in the numerical simulations. Although it gives some mechanical properties of material, tensile test is far from representing the complete deformation produced in the material. Therefore another test, Micro Incremental Deformation (Micro InDef), test which has non homogeneous deformation and which is rich in charactérization data is developped, based on Micro Single Point Incremental Forming (µSPIF).To modelise the limit of formability (especially the damage of materials), Lemaitre's constitutive model is chosen due to its possibility to define the material behaviour by using continuum mechanics and thermodynamics of irreversible processes. Within this study, Micro InDef as material characterization test is validated. Moreover, the material parameters identified are proven to be physical parameters, instead of only mathematical fitting, using an identifiability method. Once Lemaitre's model is identified, experimental tests and finite element simulations are performed on tensile tests, shearing tests, forming limit tests and out-of-plane tests, to verify the reliability and adaptability of our identification.This study is applied in an industrial project within the connector domain, which use copper alloys

La miniaturisation fait maintenant partie intégrante des problématiques actuelles de notre société. Afin de combler l'attente des industries demandeuses de plus en plus de composants de petites tailles, tout en respectant des délais de fabrication courts, les procédés par déformation plastique se sont révélés être les plus efficaces. Pour éviter de nombreux tests expérimentaux la simulation de ces procédés est une alternative importante. L'objectif de cette thèse vise à la définition d'une loi de comportement dédiée aux tôles ultra-fines d'alliages cuivreux présents dans les industries et en particulier l'horlogerie. Une campagne expérimentale est ainsi menée dans le but d'observer le comportement de tôles en cuivre de 0,25 mm d'épaisseur et d'un alliage de cuivre béryllium de 0,20 mm d'épaisseur. La caractérisation microstructurale permet de valider le cadre des tôles ultra-fines grâce à l'étude du nombre et de la taille des grains dans l'épaisseur. Les tests expérimentaux mettent quant à eux en avant le comportement isotrope du cuivre, le CuBe possède pour sa part un comportement anisotrope et une prédominance d'écrouissage cinématique. En relation avec les observations expérimentales, deux modèles utilisant une loi élastoviscoplastique sont proposés et comparés, un dans le cadre de la plasticité associée et l'autre employant la plasticité non-associée. Ces modèles prennent notamment en compte un écrouissage mixte. Les paramètres matériaux sont ensuite identifiés à l'aide d'un algorithme de minimisation. Les différentes analyses sur les méthodes de simulations et d'identification indiquent que le modèle de plasticité non-associée est le plus adapté. Des simulations et identifications sur des éléments de volume représentatifs sont suffisantes dans notre cas. Enfin différents procédés de mise en forme sont étudiés et simulés grâce à l'implémentation de la loi de comportement proposée dans un code de calcul par la méthode des éléments finis. Ils mettent en évidence le développement du modèle proposé permettant de prendre en compte un écrouissage mixte. Ce modèle peut donc être utilisé pour la simulation de procédés de mise en forme de tôles ultra-fines d'alliages cuivreux de petites dimensions sous sollicitations complexes
Miniaturization is now an integral part of the current issues of our society. To meet industries expectation which are looking for more small-sized components with shorter manufacturing deadlines, plastic deformation processes have proven to be the most effective. To avoid a lot of experimental tests, simulation of these processes is an important alternative. The goal of this thesis is to define a behaviour law dedicated to ultra-thin sheets of copper alloys which are present in industries and particularly in the watchmaking industry. An experimental campaign is thus carried out to notice the behaviour of a of 0,25 mm thick copper sheet and of a 0,20 mm thick copper beryllium alloy. The micro-structural characterisation makes it possible to validate the framework of ultra-thin sheets thanks to the study of the number and size of the grains in the thickness. Experimental tests highlight the isotropic behaviour of copper. The CuBe has an anisotropic behaviour and a predominance of kinematic work hardening. Regarding to the experimental observations, two models using an elastoviscoplastic law are proposed and compared, one within the framework of associated plasticity and the other employing non-associated plasticity. These models especially take into account a mixed work hardening. Material parameters are then identified using a minimisation algorithm. The different analyses on the simulation and identification methods indicate that the non-associated plasticity model is the most suitable. Simulations and identifications on representative volume elements are sufficient in our case. Finally, the several forming processes are studied and simulated thanks to the implementation of behaviour laws in a computer code by the finite element method. They highlight the development of the proposed model allowing to take into account a mixed work hardening. This model can therefore be used for the simulation of forming processes of ultra-thin sheets, especially of small-sized copper alloys under complex stresses

碩士
國立勤益科技大學
機械工程系
102
Based on different friction coefficients, this study aims to analyze the stamping simulation with various die angles (88°, 89°, 90°, 91°, and 92°), distinct plate thicknesses (0.05mm, 0.078mm, and 0.1mm), and different die radii (0.4mm, 0.5mm, 0.6mm, 0.7mm, and 0.8mm) for the difference in the micro equilateral vertical steel process of the stainless steel plate (SUS304). The micro equilateral vertical steel process is simulated with the application of Prandtl-Reuss flow rule and the combination of Finite Element deformation theory and Updated Lagrangian formulation (ULF) to establish an incremental elasticoplastic deformation finite element analysis program with Coulomb law of friction. Generalized rmin algorithm is utilized for dealing with the elasticoplastic state and the contact problem with the die contact surface in the forming process. From the simulated data, the relations among deformation history, punch load, and punch stroke and the stress and strain distribution in the forming process are acquired. Regarding the comparison of the thinnest thickness with changing friction coefficients, the effect of friction coefficients on the thinnest thickness is not significant. Such Finite Element Analysis could precisely analyze the entire deformation process of the equilateral vertical steel stamping forming, meaning that the history of the deformation process could be successfully depicted. With such deformation history, the forming situation of the metal plate could be acquired and the forming problem in the actual stamping process could be predicted. The research findings show that the thinnest plate part in the micro equilateral vertical steel forming process appears on the vertical corner of the central point that cracks, if any, would appear on the vertical corner of the central point. The simulation and experiments in this study present that the proposed calculation could be effectively applied to the micro equilateral vertical steel forming process analysis. In Finite Element Analysis, the entire deformation process and the stress and strain distribution in the deformation process could be simulated. The research results obviously prove the calculation being able to effectively simulate the equilateral vertical steel stamping forming process.

碩士
清雲科技大學
機械工程研究所
96
In general, the electromagnetic forming process mostly relies on the use of the electromagnetic force to deform metallic workpieces at high speed. The force is induced by the high current and voltage with a coil set. This, however, would result the high design cost and the temperature rising problem. In this study, an electromagnetic micro-forming process is designed that the induced electromagnetic force will attract the ferromagnetic punch to contact the workpiece, and then forced the workpiece to deform. To build a generalized interface program for transferring the correspondent data between two commercial F.E. code, ANSYS and LS-DYNA, is the first goal of this study. Then, the experimental apparatus for the electromagnetic micro-forming process will be designed and manufactured. Meanwhile, the dynamic finite element analysis of the micro-forming process coupled with structure and electromagnetic fields is examined. The size effect in the micro-forming processes and the spring back phenomenon will be observed and discussed in details. With the different distances being variations between the coil and punch, the effects on the predicted shape are assessed. Through comparison with the experiments, the numerical results have a same tendency as in the test works. And the method used in this study is available in the relative micro-forming processes.

碩士
清雲科技大學
機械工程研究所
96
The development in science and technology is fast now; the products are designed and manufactured by nanometer scale, it makes the micro-forming processes more important today. In micro-forming, the using of nontraditional technologies such as EDM, WEDG, PVD, PVC etc..., is rather normal. In this study, an electromagnetic micro-forming process is designed that the induced electromagnetic force will attract the ferromagnetic punch to contact the workpiece, and then forced the workpiece to deform. The experimental apparatus for the electromagnetic micro-forming process will be designed and manufactured. Meanwhile, the analysis of the micro-forming process by the dynamic FEM is examined. The relative experiment will proceed simultaneously. The sizes and shapes of the forming die and punch are discussed in details. Two solving methods for spring back phenomenon will be observed and assessed. These analytical results have been rather useful in the tools design, the products control and forming limit prediction. The most significant advantage is developing the precise analysis technology to suit for the future necessity of manufacturing processes in 3C industries.

碩士
國立高雄應用科技大學
模具工程系
106
Nosing process reducing the dimension of the open end of tube or tubular container is one of important methods for the assembly of micro metal components. A typical application of the nosing process is the assembly of micro pins and tubes for manufacturing micro electrical connectors, such as Pogo pins, which have been widely used in electronics products and precision instruments. However, the characteristics of the nosing process at micro scale may be different from those at macro scale and have not been fully understood. 　　This study used finite element simulations and experiments to investigate the forming limit in the nosing process of micro copper cups, and to establish the forming limit curves in terms of nosing ratio (the ratio of the final diameter to the initial diameter), die angle, and friction factor. Two-stage processes, including backward extrusion and nosing processes, were considered in simulations and experiments at micro scale. The backward extrusion processes were employed to produce the 1 mm diameter cups with different wall thickness. The cups were later used in the nosing processes under different conditions. By analyzing the results of the deformed cups from the simulations, it is possible to identify the failure conditions in the processes and establish the forming limit curves for the nosing processes. The cups with 1 mm diameter and 0.1 mm wall thickness, which were obtained from the backward extrusion processes, were used in the experiments of the nosing processes under two conditions, the nosing ratios of 0.70 and 0.88, and the same die angle of 30°. 　　The simulation results show that the limit of the nosing ratio decreases as the die angle or friction factor reduces. Moreover, the cases with the nosing ratio of 0.70 are more sensitive to lubricating conditions and to form the defects of bugling in the wall and rim of the cup than those cases with the nosing ratio of 0.88, as shown in the experimental results. The study not only explores the characteristics of the noise process of micro copper cups but also establishes the forming limit curves which can be the guidelines for the design of micro metal components.

碩士
國立虎尾科技大學
動力機械工程系機械與機電工程碩士在職專班
107
The aim of this study is to develop a parametric desktop metal micro-forming servo press, and to investigate the influence of stamping parameters on the forming limit of copper sheet to obtain the maximum forming limit for making micro drawing components. The developed servo press system uses a servo motor to drive the screw, so that the screw drives the punch to perform the movement of the punching curve, and then receives the reaction force through the force sensor, and transmits it back to the system for data analysis. The experimental results show that the larger R angle of punch corner, the deeper of drawing depth. Therefore, the R-angle of the punch affects the forming limit. In the analysis of the results of different stamping curves, the motion curve of the pulse punch press and the constant velocity of punch lift can obtain lower punching force and good quality of product. In addition, increasing punch speed can increase the drawing depth. In the experiment, the worst processing parameters were selected to add R32 oil to lubricate for stamping. However, it was found that open lubrication is ineffective in improving the forming limit, which may be due to incorrect lubricant selection or open lubrication mode that does not provide effective lubrication.

碩士
北臺灣科學技術學院
機電整合研究所
99
As a result of products trending miniaturization in recent years, micro technology has been widely used in various areas. On the field of micro-forming of sheet metal, processing scale is close to hundreds of even dozens of micron scale. Due to the feature size of the finished product is almost as the microscopic size, so the deformation behavior of materials may not be very consistent to the macroscopic deformation behavior of traditional homogeneous material. In other words, the grain size will affect the behavior of macroscopic deformation. This article aims at the discussion of deformation behavior considering size effect on bead forming process of sheet metal. In this study, the test specimens were made by phosphor bronze sheets for bead forming test. The specimens with different thickness were firstly heated at different temperatures for obtaining the objective grain sizes. And the mechanical properties of specimen were acquired by using tensile test. Through the bead forming test with a bead forming machine, the curled angles, springback and curling load were measured and analyzed for investigating the geometric size effect and grain size effect during the bead forming process. In addition, this study adopted the finite element method with the macro deformation module of DEFORM-3D software code to simulating the bead forming process. The simulation results were compared with experimental results to estimate the validity of simulation with the macro deformation module considering the grain size effect in micro bead forming proces.

碩士
國立臺灣科技大學
機械工程系
99
The demands of micro-forming process in modern manufacturing technology have increased in the past decade. However, the cost of materials in the micro-forming process has also increased with the decreased dimension of parts. In this study, the microstructure, plastic strain ratio (r-value) and spring-back of nickel foils fabricated in two different ways, electrodeposited(ED) nickel foils and rolled nickel foils are described. The thickness of electrodeposited nickel foils used were 0.05mm, 0.075mm and 0.1mm respectively. The thickness of rolled nickel foils used were 0.05mm and 0.1mm. In the results, the plastic strain ratio of ED nickel foils showed lower anisotropy than rolled nickel foils. Moreover, the spring-back angel of rolled nickel foils was affected by the rolling direction but the ED nickel foils showed good consistence of spring-back in varied direction.

碩士
國立臺灣科技大學
機械工程系
99
The flexible forming process has the following advantages: only one rigid die must be manufactured, the product shape can be changed easily by changing the die, flexible medium and rigid die do not need to be assembled precisely, and high surface quality. Therefore, the time and cost required for forming process can be greatly reduced. This study investigated the feasibility of AISI 304 thin stainless steel sheet for micro-channel under flexible forming process. For the fabrication of a single channel, there were two different deformation styles: concave and convex. The deformation characteristics of the two deformation styles were analyzed with experimental method. Two different flow channel designs including both four parallel flow channel and interdigitated flow channel were presented in this study to compare the depth of forming of the micro-channel. The flexible mediums of different hardness were used in the experiment to study the micro-forming process. It can be found that the convex deformation style has better formability in flexible forming process. Both Four parallel flow channel and interdigitated flow channel have different depth in each channel after forming. The thickness distribution of the formed micro-channel is uneven, and the most dangerous position occurs at the side of the micro-channel. The punch load increases with decreasing hardness in TPU(flexible medium). This will serve as reference for further research on flexible forming process.

碩士
北臺灣科學技術學院
機電整合研究所
99
The capability of predicting the sheet metal part final geometry as well as springback amount is an important feature in the sheet metal bending processes. The occurrence of grain size effect make the application of a traditional process design methodology difficult. Therefore, the design of micro-forming operations is still largely performed through empirical techniques. While the design work is made by way of tools and processes, for effectively compensating and eliminating the springback, to understand the influence of grain size effects on springback is an important and powerful way. In this paper, the heat treatment was carried out for 99.5% Ferrum specimens at different temperature to obtain the objective grain size. A V-bending process was conducted for investigating the different objects. One of the objects is to discuss the springback considering the geometric size effect based on the same grain size while the specimens were bent with different thickness. In another object, discussion of grain size effect with springback measurement based on a same thickness situation is expressed. In the third object, the illustrations of experimental results are detailed with the punch radius and springback in sheet metal bending processes. The expression of the fourth object is detailed with the effect of punching speed during the V-bending process. Furthermore, this paper adopted the finite element method with the macro deformation module of DEFORM-3D software code to simulating the V-bending process.

碩士
國立臺灣科技大學
機械工程系
97
Metal microforming process is a developing technology in precision manufacturing. This technology has many advantages, such as high producing efficiency, low cost, and the ability to produce products with complicated geometrical shape. But when the dimensions reduce to the micro scale, the forming parameters and material properties change due to the reduction of dimensions. This is called the “size effect”. A methodology of formulating an elastic-plastic three-dimensional finite element model to simulate sheet metal forming process is developed using Prandtl-Reuss flow rule and von Mises yield criterion respectively in association with an updated Lagrangian formulation. The shape function derived from a four-node quadrilateral degenerated shell element was combined into the stiffness matrix to constitute the finite element model. An extended algorithm was proposed to formulate the boundary condition, such as nodal penetration and separation, strain increment and rotation increment, and altered elasto-plastic state of material. This study will discuss thickness respectively the pure iron sheet of 0.2mm, 0.1mm, 0.075mm, 0.05mm, after different temperature and time recrystallization annealing, its micro stretch forming the formability change, and compare with the analysis result of numerical simulation, the relationship between punch load and punch stoke, the breakage stroke, the distribution of stress, the distribution of thickness. In order to obtain the minimum suitable range of plasticity theory at present, and discuss the accuracy and suitability in micro scale.

碩士
國立高雄應用科技大學
模具工程系碩士班
102
Microstructure device has been widely used in various applications such as optical communication, optoelectronics, flat panel display and bio-technology. Micro-injection molding, micro-casting and micro-hot embossing are regarded as the best mass-production methods to replicate microstructures and micro-parts. However, the processes involve high temperature, high pressure and require expensive facilities. They are complicated, time-consuming batch-wise processes. From this perspective, an innovative vacuum assisted capillary molding technology for rapid fabricating microstructure devices has been proposed and developed. During the capillary forming operation, the UV curable resin is coated on the substrate. The stack of PDMS mold with microstructure and the substrate coated with UV-curable resin is then placed in the vacuum assisted capillary molding facility. The UV curable resin is filling in the microstructure of the PDMS mold due to the capillary phenomenon and surface tension. After curing, the PDMS mold is removed from the substrate, and the substrate with microstructure device on its surface can be obtained. Finally, the vacuum assisted capillary molding facility with UV exposure capacity is designed, constructed and tested. The effects of processing conditions on the shape and quality of formed microstructure devices are investigated and researched. These experimental results show the potential of the vacuum assisted capillary molding process for mass production of microstructure devices with high productivity and low cost.

碩士
淡江大學
機械與機電工程學系碩士班
100
This study applied the dynamic-explicit finite element method to perform the forming limit analysis on the electrodeposited copper foil and the rolled copper foil in the micro deep drawing process of a square cup. Under the condition of isotropic materials, the numerical analyses were performed to explore the relationships between the punch load and the stroke, the distribution of cup heights, the forming limit, and the deformation process in the micro deep drawing process of a square cup. To verify that the finite element analysis program could reasonably predict the forming limits in micro deep drawing of a square cup, a set of square die and three sets of square punches were designed to perform the experiment. This study compared the forming loads, maximum cup heights, and forming limits of electrodeposited copper foil and rolled copper foil with different corner radii of punch. According to the results of the numerical analyses and the experiments results, when arc radius of punch increased, the forming load of the electrodeposited copper foil and rolled copper foil decreased, while the cup height increased. According to the definition of limit drawing ratio (LDR), when arc radius of punch increased from 0.2mm to 0.8mm, LDR of the electrodeposited copper foil increased from 2.075 to 2.273. And that of the rolled copper foil increased from 1.845 to 1.911. The numerical analyses could all reasonably simulate the experiment results. Therefore, the dynamic-explicit finite element analysis program proposed by this study could reasonably predict forming limits for electrodeposited copper foil and rolled copper foil in the micro deep drawing process of a square cup.

碩士
國立中興大學
機械工程學系
94
A single transformer coupled plasma dry etching (TCP) process for forming a micro-channel with a pair of silicon tips was investigated. This micro-channel can act as a floating gate in a flash memory to increase erase speed. In each experiment, a substrate with a silicon layer was carefully prepared. This substrate was placed in the reaction chamber of a TCP etching machine. By passing an etching gas mixture through the substrate and processing it with a radio frequency power, a concavity was formed on the silicon layer. The middle region at the bottom of the concavity would be lower than the edge region, a silicon tip was thus obtained. In this work, the effects of etching gas composition, chamber pressure and radio frequency power on the angle of silicon tip and bottom dimple were investigated. The considered etching gas mixture comprises of Cl2, O2, HBr, and He. The upper radio frequency power was fixed at 600 W and the lower radio frequency power was either at 10 W or at 20 W. Three chamber pressures, 4.5, 6, and 10 mTorr, were individually considered. The result shows that for the case with the lower radio frequency power of 20 W, chamber pressure of 10 mTorr and the Cl2, O2, HBr, and He composition setting at 20.4%, 5.5%, 12.9%, 61.2%, a silicon tip without bottom dimple can be formed.