Thin Copper Sheets Research Articles

Strain-Controlled Fatigue Behavior in Thin Pure Copper Sheet for Smart Stress-Memory Patch

A new sensing method called “smart stress-memory patch” has been proposed for fatigue damage evaluation of structures. This patch estimates the number of cycles and stress amplitude using its crack length. In this study, fatigue crack growth behavior in thin pure copper sheet was investigated under strain-controlled testing to evaluate the sensor characteristics when the patch is attached to structure. Electrodeposited (ED) copper of 99.96% purity with an average grain size of 2µm provided a stable crack propagation and easy observation of crack length. The relationship between stress intensity factor range and crack growth rate was fitted on one curve regardless of strain amplitude. The scattering in fatigue crack growth was evaluated by a stochastic model, and it demonstrated that the error of fatigue cycles estimated by the patch is small enough. Furthermore, stress transfer between the patch and structure was calculated on the simple assumption that the patch is perfectly bonded on the structure, and it was shown that the patch attached to structure can estimate the number of cycles and stress amplitude on the structures.

Properties of DLC Film Deposited on Mould with Micro-Cavity Used in Microforming

Micro-forming as a kind of metal forming process is very suitable for massive production of micro-parts with high mechanical properties. To eliminate the scaling effects of friction in micro-forming, diamond-like carbon (DLC) film of nano-thickness was deposited on the micro mould with plasma based ion implantation and deposition (PBII&D) method for its excellent tribological behaviors. The effects of mould cavity dimensions were investigated, for example distribution of thickness, surface topography and microstructure of DLC film. The result shows that the thickness of DLC film decreases from 554 nm to 47 nm with the increasing of depth into mould cavity. And ripple topography appears when the cavity dimension is small. The ratio between ID and IG increases with the increasing of cavity dimension, which means that the amount of SP3 bonds becomes smaller. With the DLC film deposited female die, micro-cups of 1.1 mm in diameter were manufactured successfully using copper thin sheet of 0.04 mm in thickness with a blanking-deep drawing process. And the surface quality and dimension accuracy of micro-cup were analyzed in details. The results show that DLC film is feasible alternative to micro-forming.

Study on single-discharge machining characteristics of non-conductive engineering ceramics in emulsion with high open voltage and large capacitor

This paper presents a new process for the machining of non-conductive engineering ceramics that is based on electrical discharge machining. It uses a thin copper sheet as an assisting electrode and a high capacitance value capacitor that is directly discharged into the machining process i.e. there are no current-limiting resistors in the discharge circuit. This configuration creates a high discharge energy and discharge force which enables electronically insulating engineering ceramics to be effectively machined. Single-discharge experiments were performed using an emulsion as the dielectric machining fluid. The effects of the dielectric fluid, polarity, open voltage, capacitance, and current-limiting resistance on the process performance in terms of the volume and depth of the crater created in the surface of the workpiece, tool wear, and assisting electrode wear were investigated. In addition, the microstructure of the crater was examined using a scanning electron microscope. The results show that the crater is the result of a spalling process on the surface of the non-conducting ceramic workpiece. However, at the centre region of the crater some material is removed by melting and vaporization, and this type of material removal is enhanced by an increase in the open voltage.

Micro bulging of thin T2 copper sheet by electromagnetic forming

Electromagnetic micro bulging experiments on T2 copper were achieved in order to find the effects that different voltages and depths of mold work on deformation characters. Laser scanning confocal microscope and contourgraph were used to study the effects of electromagnetic forming parameters such as voltage and die depth on material. Results show that width and depth of micro channel increase with the increases of voltage with a certain die depth, moreover, forming depth reaches the maximum at 7 500 V. And then rebound emerges and forming depth decreases. Forming depth and width of channel increase with the decease of die depth at a certain voltage; and forming depth reaches maximum at 0.5 mm of die depth. Therefore, rebound is weakened and the traces caused by bad exhaust disappears gradually, and surface roughness decreases simultaneously in electromagnetic bulging experiments.

A Process Investigation for Micro-EDM Fabrication of through Holes in Thin Copper Sheets

This paper reports a study of a micro-EDM process to fabricate micro-through holes in 30 micron thick copper sheets. Circular holes in various micro-sizes were produced by a micro-EDM machine and with tungsten electrodes. Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDX) were used to identify the influence of electric sparks on the quality of the fabricated features by careful study of resulted cavitation, adhesion of debris, and re-solidification of molten materials, etc. Such analyses allow the generalization of the relevant fabrication mechanisms. In addition, measurements of overcut of the holes facilitate a working model to be developed for predicting the overcut as a function of process parameters including the discharge capacitance and the working voltage of the circuitry. Results of this study enable the derivation of proper settings for fabricating holes of good quality and permit the precision fabrication of the range of micro-throughholes.

Determination of Uniaxial Flow Stress Curve Using Aero-Bulge Test for Very Thin Copper Sheet

Determination of the flow stress curve is an important step for precisely describing material behavior in Finite Element simulations. The flow stress curve is generally determined by taking a uniaxial tensile test as a standard. In the case of very thin sheet, since the fracture is generated at a low strain, there is not enough uniaxial data obtained to be applied in the FE simulation. The reason for this is that charactering plastic deformation at a large strain values by extrapolating a flow stress curve which is based on insufficient measurement data is highly susceptible to error. Bulge test is useful method for determining the equivalent biaxial flow stress curve up to a large strain. In this paper, the biaxial flow stresses curve for very thin copper sheet with thickness 35 and 50 μm were determined using the aero-bulge test. A new empirical model was derived for the estimation of the sheet thickness at the pole. After the compatibility between uniaxial and biaxial flow stresses was verified, the uniaxial flow stress curve was determined from the aero-bulge test using reverse engineering. The methodology of extrapolation of the flow stress curve at a large strain was finally proposed for application in FE simulations.

Light Metal in High-Speed Stamping Tools

The required number of punched and blanked parts in the electronic industry, such as leadframes, contact pins or plugs often reach several million pieces. According to this, the production process has been sped up to frequencies up to 2000 parts per minute. At this production rate parts of thin steel or copper sheets are produced with high-speed stamping presses and blanking tools. Because of the high gating velocities in the blanking tool there is a recurring acceleration at the moment, when the blank holder contacts the sheet metal. A second shock in the blanking tool arises, when the sheet cracks. This is also known as the impact shock during the blanking process. Trough these two impulses and through the cycle of the plunger movement a periodic oscillation arises in the tool. Horizontal vibrations can lead to an undefined position between punches and die-plate, while vertical movement leads to increased wear because of friction forces between the blanked surface and the lateral area of the punches. The goal of this project was to minimize these oscillations in cutting tools by the usage of lightweight materials in the flux of forces. An experimental cutting tool was designed with alternative top and bottom plates for the comparison of the oscillation status in the cutting process when using plates of steel, aluminium or magnesium. The centre plate of the tool remains constant. Experiments were accomplished for several velocities and tool setups with different plate materials. To determine the influence of the materials with different density and elasticity acceleration, force and acoustic emission sensors were integrated in the tool. The set of problems was investigated by analyzing the measured data and by determining the wear in practical tests.

EDXRF analysis of metal artefacts from the grave goods of the Royal Tomb 14 of Sipán, Peru

AbstractSeveral metallic sheets (about 1 mm thick) from the grave goods of the Royal Tomb 14 (Sipán, Peru) were characterised by energy dispersive X‐ray fluorescence analysis, using both a portable instrument and a capillary collimated spectrometer to investigate details, and micro‐Raman spectroscopy. The samples, belonging to the clothing of the warrior priest, resulted composed of thin copper sheets or tumbaga (natural alloy of copper, silver and gold). They were unearthed covered with typical green patina, formed during their long burial and characterised mainly by copper minerals, such as malachite, atacamite and magnetite identified with micro‐Raman spectroscopy. Due to deterioration of the original alloy, the artefacts analyzed in this work were rather fragile and could not resist hard polishing aimed at cleaning off corrosion products. So a non‐destructive qualitative EDXRF analysis was performed to identify the elemental composition of the metal alloy and a quantitative estimation was made applying the fundamental parameter method. The presence of superficial patina layer and the non‐homogeneous composition was also taken into account during calculation. The data obtained, compared to published results from several artefacts found in the nearby tombs, have been treated with a hierarchical statistic analysis. Copyright © 2011 John Wiley & Sons, Ltd.

Fatigue crack behavior of thin copper sheet and its application for smart stress-memory patch

A new sensor called “smart stress-memory patch” which can measure the stress amplitude and the number of fatigue cycles and the maximum stress related to a structure subjected to fatigue loading for efficient structural health monitoring has been proposed. However, there are two problems in the real applications of smart patch. Firstly, when the sensor is adhered to the structure, the sensing property of smart patch may change because the restrained condition of the sensor would be intricately changed. Secondly, high-precision crack measurement of smart patch by optical microscope is too cumbersome in the real field. In this study, thin electrodeposited (ED) Cu specimen was prepared and attached to steel bar as a sensor of smart patch. The fatigue test was performed to examine the fatigue crack growth of the sensor attached to the structure. Furthermore, wireless devices using low power wireless modules have been developed for efficient crack measurements, and wireless devices results give close agreement with the results by microscope.

Material flow in heterogeneous friction stir welding of aluminium and copper thin sheets

The aim of this investigation was to study material flow during dissimilar friction stir welding of AA 5083-H111 to deoxidised high phosphorus copper plates of 1 mm thickness. The welds were performed using different tool geometries and welding parameters. The positions of the copper and aluminium plates, relative to the advancing and retreating sides of the tool, were also changed. It was found that the tool geometry and relative position of the plates deeply influence the morphology of the aluminium and copper flow interaction zones, influencing the distribution of both materials in the weld and the formation of intermetallic compounds. The material accumulated under the tool during welding was found as another important aspect determining weld morphology.

Investigation of size effects of very thin aluminum and copper sheets using aero-bulge test

Material behavior is heavily influenced by its microstructure. For very thin sheets, the ratio of the sheet thickness to the average grain size is usually small. In this case, the influence of surface grains on the material strength, which is normally lower strength than inner grains, is relatively large, so that the material strength further decreases by increasing grain size. In this paper, the change of the material behavior for very thin aluminum (99.5%) with thicknesses of 50 and 95 μm and copper (99.9%) sheet with thicknesses of 35 and 50 μm depending on the grain size were discussed. To this end, the material strength and the work hardening exponent were determined using a modified bulge test (aero-bulge test). For both materials, material strength decreases with increasing grain size and decreasing sheet thickness. For copper sheets, an additional size effect due to the amount of phosphorous was observed. The work hardening exponent of aluminum sheets changes similarly with the change of material strength. For copper sheets, the work hardening exponent was changed however anomalously vis. the work hardening exponent changes inversely with respect to the material strength.

베릴륨동 극박판의 드로잉 성형성과 품질특성 연구

The present study is focused on the deep drawability and product qualities of ultra thin beryllium copper sheet metal. The goal of this research is to investigate the limit drawing ratio in deep drawing of ultra thin beryllium copper metal. For the experiment, beryllium copper(C1720, <TEX>$50{\mu}m$</TEX> in thickness) is used. Tensile test are also carried out to find out the material properties. Deep drawing experiments are carried out in Universal Testing Machine(UTM) to obtain limit drawing ratio. Deep drawing tests are carried out for various specimen sizes. Teflon film is used as a lubricant and constant blank holding force is imposed. Sheet thickness and surface hardness are measured along radial direction after deep drawing. Thickness is measured using optical microscope. For beryllium copper(C1720), the maximum LDR of 2.4 is obtained when the die shoulder radius is 20 or 30 times of sheet thickness.

Reversible Bending Motion of Unimorph Composites Driven by Combining LaNi&lt;SUB&gt;5&lt;/SUB&gt; Alloy Powders Dispersed Polyurethane and Thin Supporting Copper Sheet under Partial Hydrogen Gas Pressure

The polyurethane composites dispersed with powders mixture of LaNi S hydrogen storage alloy (35 vol% of LaNi 5 ) and Pd-Al 2 O 3 catalyst powders were prepared by solution cast method, which easily controlled the shape and mixed ratio of the composites. In order to generate the bending strain of reversible up motions at vertical and horizontal directions, the unimorph (PU+LaNi 5 /Cu) sheet constructed with the driving polyurethane composite and supporting copper thin sheet of 10 μm thickness with high specific stiffness (apparent hardening modulus per specific weight) was prepared. Although the bending motion of the unimorph sheet operated by hydrogenation under 0.3 MPa H 2 gas was irreversible, the reversible motion was detected under 0.2 MPa H 2 gas. The maximum strain of reversible bending motion (e max ) of the PU+LaNi 5 /Cu sheet is more than 1520 and 1120ppm on vertical and horizontal directions, respectively. The e max of the PU+LaNi 5 /Cu sheet at vertical direction was slightly higher than that of the ABS resin unimorph (ABS+LaNi 5 /ABS) sheet constructed with the driving ABS resin composites and pure ABS resin supporting sheet, whereas it was slightly lower than that of the silicone rubber unimorph (SR+LaNi 5 /SR) sheet constructed with the driving silicone rubber composites and pure silicone rubber supporting sheet. It can be estimated that the responsiveness (de/dt) of cyclic motion of the (PU+LaNi 5 /Cu) sheet is slightly higher than ABS+LaNi 5 /ABS sheet.

Processing Micro-Gear Based on Bio-Etching Method

A bio-etching method using Thiobacillus ferrooxidans (T.f.) for processing micro-gear has been developed. The principle of bio-etching method is that certain microorganisms in nature consume some metal ions to be energy during their growth. The strain of Thiobacillus ferrooxidans consume elemental ferric and cooper ions as its energy source, so T.f. is selected as bio-etching tool, Leathen culture medium is selected as culture medium of T.f., and the thin copper sheet is used as the processed material. During the micro-gear is processed, firstly, thin copper sheet of 0.05mm is cleaned in the acid liquid and some materials such as dirt and grease are cleaned away, then, the anti-erode film is applied to the surface of thin copper sheet, then the surface of thin copper sheet is irradiated by ultraviolet under the condition that the surface is covered by mask film and developed, the anti-erode film that not covered by mask film will be dissolved and cleaned away, after that, thin copper sheet is put into the T.f. liquid and agitating, after the 3h, micro-gear is obtained. The result is showed that micro-gear can be processed by bio-etching method.

Penetration resistance of steel fiber reinforced concrete containment structure to high velocity projectile

Containment structures not only are leak-tight barriers, but also may be subjected to impacts caused by tornado-generated projectiles, aircraft crashes or the fragments of missile warhead. This paper presents the results of an experimental study of the impact resistance of steel fiber-reinforced concrete against 45 g projectiles at velocity around 2500 m/s. An explosively formed projectile (EFP) was designed to generate an equivalent missile fragment. The formation and velocity of EFP are measured by flash x-ray. A switch made of double-layered thin copper sheets controlled the exposure time of each flash x-ray. The influence of the fiber volume fraction on the crater diameter of concrete slab and the residual velocity of the projectile were studied. The residual velocity of the projectile decreased as the fiber volume fractions increased. In this work, the residual velocity of the projectile was to 44% that of plain concrete when the fiber volume fraction exceeded 1.5%. Based on the present finding, steel fiber reinforced concrete with the fiber volume fraction exceeding 1.5% appear to be more efficient in protection against high velocity fragment impact.

Numerical simulation of single pulse discharge machining insulating Al2O3 ceramic

The technique of electrical discharge milling insulating ceramics with instantaneous high temperature generated by a discharge channel flowing along a workpiece surface has been developed by the authors. The process uses a thin copper sheet fed to the tool electrode along the workpiece surface as the assisting electrode, using a water-based emulsion as the machining fluid. It is able effectively to machine a large surface area on insulating ceramics, as well as other advanced non-conductive materials such as cubic boron nitride (CBN) and polycrystalline diamond (PCD). The mathematical models of thermal eroding non-conductive Al2O3 ceramic with a single pulse discharge are esta lished. The thermal erosion characteristics of insulating Al2O3 ceramic with a single pulse discharge have been numerically simulated. The numerical simulation results have been validated by experiment.

The study of deformation and stress—strain distribution of nano-scale thin sheet copper under the biaxial tensile loads by using molecular dynamics and finite-element method

This paper investigates the strain and stress distributions in a nano-scale copper thin sheet under the biaxial tensile action, within the range of elasticity, by employing the molecular dynamics (MD) and finite-element method (FEM). Each atom is regarded as a node and the lattice as an element. The nano-scale copper thin sheet model, established in this study, is based on the face centered cubic lattice structure, and divides the lattice into 24 constant strain tetrahedron elements. After MD simulation, the biaxial force is found to be almost the same during the biaxial tensile action. Simulation results reveal that the stress and strain are highly closer at the edge of the sheet. The presence of strain around the upper and lower surfaces in the central region of the thin sheet indicates that after exhibiting biaxial tensile activity, contraction occurs in the region. The FEM/MD model, constructed in this paper directly melts the FEM spirit in MD computation. This facilitates the analysis of stress and strain in the entire nano-scale range for the nano-scale copper thin sheet.

Superconducting cyclotron and its vacuum system

A large superconducting cyclotron is under construction at this Centre and will be used to accelerate heavy ion beams to energy up to 80 MeV/A for light heavy ions and about 10 MeV/A for medium mass heavy ions. The vacuum system for this accelerator has several different aspects. The main acceleration chamber will be evacuated to a level of about 10−7 torr using both turbo molecular pumps and specially designed cryopanels. The surfaces exposed to this ‘vacuum’ are mostly made of OFE copper. The cryogenic transfer lines, to cool the cryopanels, are of several meters in length and they pass through RF resonators extending below the magnet. The cryostat that will house the superconducting coils has an annular vacuum chamber, which is evacuated to a level of approximately 10−5 torr using a turbo molecular pump. Cryopumping action starts once the coils are cooled to low temperatures. A differential pumping is provided below the RF liner that encloses the pole tip of the main magnet. The space that is pumped in this case contains epoxy-potted trim coils wound around the pole tips. Crucial interlocks are provided between the differential vacuum and the acceleration chamber vacuum to avoid distortion of the RF liner, which is made of thin copper sheets. The other important vacuum system provides thermal insulation for the liquid helium transfer lines. In this paper a brief description of the superconducting cyclotron will be given. Details of various vacuum aspects of the accelerator and the logistics of their operation will be presented. Introduction of some of the improved equipment now available and improved techniques are also discussed.

Electric discharge milling of insulating ceramics

Ceramics have been used widely in modern industry. However, the manufacture of ceramic blanks is not an efficient process. The shaping of ceramic blanks with conventional machining methods (such as grinding) is a long, labour-intensive, and costly process. Electromachining processes promise to be effective and economical techniques for the production of tools and parts from ceramic blanks. Wire electric discharge machining (WEDM) is able to slice ceramics effectively. Electrical discharge machining (EDM) and electrical discharge grinding (EDG) shape ceramic blanks at a lower cost. With the help of some assisting methods, WEDM, EDM, and EDG can be used to machine insulating ceramics. However, WEDM, EDM, and EDG of insulating ceramics show lower efficiency, especially for a large surface area on insulating ceramics. This paper presents a new process of machining insulating ceramics using electrical discharge (ED) milling. ED milling uses a thin copper sheet fed to the tool electrode along the surface of the workpiece as the assisting electrode, and uses a water-based emulsion as the machining fluid. This process is able effectively to machine a large surface area on insulating ceramics, as well as other advanced non-conductive materials such as cubic born nitride (CBN) and polycrystalline diamond (PCD). The machining principle and characteristics of the technique are introduced. The effect of pulse on-time, pulse off-time, and peak current on the process performance has been investigated.

Effect of technological parameter on the process performance for electric discharge milling of insulating Al 2O 3 ceramic

Engineering ceramics have been widely used in modern industry. However, the manufacture of ceramic blanks is not an efficient process. The shaping of ceramic blanks with conventional machining methods (such as grinding), is a long, labour-intensive and costly process. Wire electric discharge machining (WEDM) is able to effectively slice conducting ceramics. Electrical discharge machining (EDM) and electrical discharge grinding (EDG) of conducting ceramic show lower cost. With the help of some assisting methods, WEDM, EDM and EDG can be used to machine insulating ceramics. However, EDM and EDG of a large surface area on insulating ceramics show lower efficiency. This paper presents a new process of machining insulating ceramics using electrical discharge (ED) milling. ED milling uses a thin copper sheet fed to the tool electrode along the surface of workpiece as the assisting electrode, and uses a water-based emulsion as the work fluid. This process is able to effectively machine a large surface area on insulating ceramics. The machining principle of the process is introduced. The effects of tool polarity, peak voltage, rotational speed of tool electrode and feed speed of workpiece on the process performance have been investigated.