Search

The purpose of this paper is to study the anti-corrosion properties of a novel pre-treatment CeO2/ZrO2 nanometric film coating on the surface of cold-rolled plate at room temperature. A novel coating agents involved elements Zr,Ce and additional surfactants were prepared and used in the field of cold-rolled plate pretreatment. The surface of the coating sample was investigated by using X-ray Photon Spectrum (XPS), X-ray Diffraction (XRD) and Scanning Electronic Microscope (SEM)，respectively. The Ce3+ doted ZrO2 nanofilm could improve the anti-corrosion performance of coated plate. This dipping coating process satisfied the energy-saving and green chemistry requirement of modern cold-rolled plate pre-treatment technology.

This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of tool material on the characteristics of Electrical Discharge Machining process of AISI H13 tool steel. The studied process characteristics included the tool wear ration and thickness of the white layer on the workpiece after the EDM process. The experiments carried out under the designed full factorial procedure and the considered EDM input parameters included pulse on-time and pulse current. The results of this study could be utilized to choice a set of pulse on-time and pulse current according to the outcomes that suit the requirements of tool-workpiece combination processed by the EDM.

Monodispersed silica spheres have attracted much attention because of their widely applications in the areas of catalysis, adsorption, chromatography packing materials and advanced ceramics. This paper focused on its application as a packing material of function coatings for space applications. Nanosized monodispersed silica spheres can be fabricated by Stöber method. However, microsized monodispersed silica spheres are not easy obtained. In this paper monodispersed silica spheres with the size between 200nm to 2000nm were fabricated by hydrolysis of tetraethoxy silane (TEOS) in isopropyl alcohol solvent and using ammonia as catalyst through multi-step growth method. The influence of silica seed number density and TEOS concentration on monodispersity and size of silica sphere were studied. The result shows that monodispersed silica spheres could be obtained through control the concentration of TEOS and the silica seed number density during every growth step. The diameter of monodispersed silica spheres increased with the steps of growth.

The Deep Surface Rolling (DSR) technology can substantially increase the fatigue life of metallic materials due to the introduction of deep compressive residual stresses in the material surface. These beneficial compressive residual stresses can be achieved up to a depth of 1 mm. The DSR technology also produces a good surface finish unlike bead peening technology. In this study, the main objectives were: (1) to study the feasibility of DSR for fatigue life improvement of high strength aluminium alloy (7075-T651) repaired with laser cladding technology, and (2) to investigate the effect of thermal stressing on the fatigue life improvement of DSR. Previously published results have shown that post-heat treatment of laser clad high strength Al alloy coupons improved their fatigue life. The experimental results in this paper show that the fatigue life was substantially increased using the DSR technique on laser clad 7075-T6 aluminium alloy compared to laser cladding alone and laser cladding followed by post heat treatment.

Dynamic properties of Nanostructured Metal Matrix Composites (NMMCs) materials consisting of nanograined aluminum matrix with nano or micro-sized ceramics particulates are calculated using Ansys/LS-DYNA in this paper. There are three conditions for the mechanics analysis involved the target with 10 vol. % SiC, 30 vol. % SiC and 50 vol. % SiC. It is assumed that the SiC particles uniformly distributed in the matrix. According to the analysis, the strength of NMMCs material is reduced, and the deformation of target is weakened by the vol. % of SiC increasing.

Graft copolymerization of acrylamide (AM) and methyl acrylacyl oxyethyl trimethyl ammonium chloride (DMC) onto gelatin under microwave radiation was studied. The resultant ternary graft copolymer was used as wood pulp dry-strengthening agent. The application results showed that the optimum synthesis conditions was that microwave radiation power was 500W, microwave radiation time was 120S, the concentration of CAN(initiator) was 3mmol/L, m(CS): m(AM): m(DMC) =1:6:2. The breaking length and broken index of hand sheet made of wood pulp was respectively increased by 24.5% and 22.3% when the dosage of the graft copolymer was 0.8% of dry fiber weight.

In this paper, the keyhole of YAG laser welding 5A90 Al-Li alloy was observed and measured through the high speed camera. The characteristics of the keyhole and the effects of welding parameters were studied. The characteristics of the absorption of laser energy and the susceptivity for heat input in welding 5A90 were given. The results show that in this welding condition, the keyhole of laser welding 5A90 is nearly a taper and the highest temperature area is in the bottom. There are clear effects of heat input on the characteristics, especially the surface radius of keyhole and plasma/vapor in keyhole. Another phenomena is observed that sometime plasma/vapor could disappear in 0.3ms welding time, and this feature will be more remarkable as decrease of heat input. It shows that the absorption of energy is unsteady. It is known that when this instability reaches a certain value, an unsteady weld will be formed.

Dielectrophoresis (DEP) has been verified to be an efficient means of assembling carbon nanotubes (CNTs) for various applications. This paper simulates the electric field distribution of the quadruple electrode structure when the external AC voltage is applied between a pair of opposite electrodes. There exist induced electric potentials between high voltage electrodes and floating electrodes and thus floating electrodes seriously change the field distribution. For a pair of wide parallel electrodes, the deposition of one CNT bridging the electrode pair will greatly alter the local electric field and repel the further deposition of CNTs in the vicinity. The screening distance is relevant with the width of the electrode gap, which provides a way to estimate the density of assembled CNTs between the electrode pair.

Some tests including tensile test, bending test and shear test have been done to fibre-reinforced sandwich core boards which are ready applied to high speed train. Fibre laying craftwork is introduced in the paper and the test results show that the uniformity of fibre laying craftwork is good. The laying fibres have effective enhanced axial strength and modulus of fibre-reinforced sandwich core board. The reinforce influence degree to modulus is greater than strength.

In this paper we prepared electroless Ni-plated wood veneers using two Pa activation methods. One is the traditional Pa colloid activation and the other uses Pa2+ions. SEM-EDS results indicated that the coatings were continuous, uniform and compact with a P content of lower than 4 wt.%. XRD analysis showed that the coatings were crystalline, which was related to the low P content. The plated wood veneers exhibit good electro-conductivity with surface resistivity of lower than 0.3 Ω cm-2and higher electromagnetic shielding effectiveness of over 60 dB in frequencies from 10 MHz to 1.5 GHz.

Modified anaerobic-anoxic-aerobic (A2O) technology for dye wastewater was studied. The effects of Hydraulic retention times (HRT), sludge retention time (SRT) and carbon source on treatment efficiency were discussed. Scanning electron microscopes (SEM) for different sludge and UV-visible spectrum analysis for influent and effluent were investigated respectively. The results showed that when COD of influent was 600~1200 mg/L and the dye concentration was 20~40 mg/L, HRT had the obvious effect on treatment efficiency of modified A2O system. Total treatment efficiency of the improved system was more than 90% at the optimal HRT (29 h). The dye structure was demonstrated to be changed during the process. Finally, the dye and its intermediates were transformed and mineralized respectively.

PC1D software, which was developed by the University of New South Wales, has been used to simulate photovoltaic properties of crystalline semiconductor devices. The paper focuses on the simulation of silicon solar cell by PC1D. The simulation of silicon solar cell is carried out by setting up key parameters, which include device area, thickness, band gap, etc. Several important characteristics of silicon solar cells are obtained by simulation.

The use of aluminium alloys rose in the last decade, as its specific mechanical properties allow a reduction of mass as for example in automotive. Moreover aluminium, due to its high corrosion resistance, is a very important material class in plant construction, where it is used for pipes or container till 250 °C. Aluminium can be welded with different technologies. Nowadays TIG and MIG are mainly used for example in plant construction or in mechanical engineering. Laser beam welding is a widely established technology in automotive. The advantage is the high energy concentration, which leads to a high welding speed and a narrow heat affected zone. Plasma welding is applied when joining aluminium with alternating current, as an easy removal of the oxide layer in the surface of the weld pool is possible. Plasma-Powder-Arc-Welding (PPAW) method has been developed from Plasma Transferred Arc (PTA) weld surfacing and Plasma Arc Welding (PAW) methods by combining a small PAW torch (PAW is traditionally performed with wire as filler material) with powder filler material feeding as used in PTA-equipment. The coupling leads to a better mechanisation of the welding process as the consumable is fed directly through the welding torch. In this paper investigations on aluminium sheets (£ 2 mm) AA5xxx and AA6xxx using different powder materials are reported. The influence of the processing parameters and conditions on the process reliability, when welding with industrial robots butt and corner welds is investigated. Conventional PPAW of aluminium is performed with AlSi12 filler material. A post processing of the joint, as for example anodising in order to improve corrosion resistance, leads to a very different optical aspect, as the colouration of the weld seam after anodising differs from the base material. Thanks to a correct choice of filler material it is possible to reduce the colour differences between base materials/heat affected zone and bead, so that the weldment can be set for high quality optical applications, too.

The problem of a piezoelectric screw dislocation emitted from a blunt crack is dealt with in this paper. For an arbitrary distribution of the residual dislocation, the series-form solutions are derived. The results show that the force acting on the dislocation decreases with the value of the dielectric constant within the crack increasing. And the increase of the dielectric constant within the crack helps dislocation emission effectively.

In this paper, (Ba,Ti)-doped lanthanum silicate nano-sized powders have been synthesized via microwave assisted sol-gel auto-combustion route by using TEOS and lanthanum nitrate as the starting materials, citric acid and glycol as chelators. Both the phase compositions and morphologies of the obtained powders have been characterized. The results indicated that: the synthesized nano powders were characterized as fluffy aggregates with the particle size ranging from 50 to 100nm. As the doping contents of Ba increased, the crystalline sizes decreased and the aggregation were deteriorated, while the particle size decreased from 120nm to 80nm and the aggregation between particles were halted as the doping contents of Ti increased.

This paper briefly reports on the improved properties and bettered applications of some piezoelectric ceramics (i. e. S-PZT, etc.) of ferro/piezoelectric community by means of bettering their technological process links, especial superfine grinding of powder of raw materials, and sintering technique of piezoelectric ceramics in them. These piezoelectric ceramic materials have obtained the better effect in their newly and widely applied aspects, such as, acoustoelectric transducing; electrical to mechanical to electrical transducing; acoustooptic effect; electrooptic technique, and, piezoelectric ceramics for high voltage generators, ignition and detonation purposes, and some original applications (e.g., combining the electrorheological fluids) etc.. As far as appropriate measure of the improving sintering and other technique processes in present work is concerned, they also have reference value to electronic ceramics of having similar manufacturing technological process, such as capacitor ceramics, resistance ceramics, magnetic ceramics, and oxide ceramic superconducting materials, etc..

In this paper, the degradation of Salix psammophila is used to make the polyurethane elastomer and study on the process involving changes in molecules with SPM. Compared with the pure polyurethane, it can be concluded that the polymerization of particles′ size, height and measurement have got bigger visibly. But the cured particles change nothing and retain the natural polymer’s linear permutation. And this polyurethane elastomer′s fracture profile is brittle.

Displacement is traditionally deemed to be equivalent to deformation. However, displacement is not exactly deformation, for example, the tip of a workpiece illustrates big displacement, but, it caused by the deformation of main body. In this paper, theory of active and passive deformation is proposed for the evaluation of the deformation of workpiece during heat treatment process and the corresponding algorithm was established. The deformation consists of active and passive deformation; the former is the actual deformation, while the latter is caused by the deformation of other areas. This algorithm was applied to the deformation analysis of a hydraulic turbine blade which is a large thin-walled workpiece. And the real deformation area of the blade is found.

The influence of incident beams polarization degree on the SPR phase sensor is theoretically and experimentally studied in this paper. The results indicate that the decrease of the polarization degree will lead to the phase difference curves jump decrease near the resonance angle for the ellipsometry method. Besides, the lower the polarization degree, the smaller the jump, which can also lead to reduced sensitivity of the SPR phase sensor. For example, the sensitivity with the polarization degree of 0.9 is 90% that of the polarization degree of 1.

Microwave heating technology is a cost-effective alternative way for heating and curing of used in polymer processing of various alternate materials. The work presented in this paper addresses the attempts made by the authors to study the glass transition temperature and curing of materials such as casting resins R2512, R2515 and laminating resin GPR 2516 in combination with two hardeners ADH 2403 and ADH 2409. The magnetron microwave generator used in this research is operating at a frequency of 2.45 GHz with a hollow rectangular waveguide. During this investigation it has been noted that microwave heated mould materials resulted with higher glass transition temperatures and better microstructure. It also noted that Microwave curing resulted in a shorter curing time to reach the maximum percentage cure. From this study it can be concluded that microwave technology can be efficiently and effectively used to cure new generation alternate polymer materials for manufacture of injection moulds in a rapid and efficient manner. Microwave curing resulted in a shorter curing time to reach the maximum percentage cure.

SOL (stand-off layer) damping treatment is the most effective method to improve the damping characteristics of the base structure compared with unconstrained and constrained layer damping treatment. In this case, the viscoelastic layer is sandwiched between the SOL and the constraining layer. During vibration, the SOL acts as a strain magnifier which magnifies the shear strain in the viscoelastic layer by increasing the distance between the viscoelastic layer and the neutral axis of the base structure thus dissipates more vibration energy. The equations of motion root in kinematic equations, constitutive equations and equilibrium equations of force and moment, and constitute one variable (lateral deflection) with order differential equation and two variables (axial deflections of the base beam and the constraining layer) with order differential equation of motion. Together with the boundary conditions, the transfer function method and the finite element method are adopted to analyze the damping characteristics of the composite structure. In distributed function method, the equations are transferred to state space form. In finite element method, the lateral deflection is interpolated by Hermite interpolation function and the axial deflections of the base layer and the constraining layer are interpolated by Lagrange interpolation function. At last, the predictions of the two analytical methods are validated against the commercial software ANSYS. Close agreements are found among the three methods. To achieve the expected effect, the SOL must have high shear stiffness and low bending stiffness so it does not significantly influence the flexural rigidity of the base structure but does not absorb the shear stress desired to be passed on to the viscoelastic layer. This paper is focus the application of SOL damping treatment on cantilever beam model, but it is essential to note that the model can be extended to complex structures such as plates and shells. We can select the slotted SOL damping treatment which could effectively avoid the increase in bending stiffness but also maintain high shear stiffness as the substitute.

The assembly force in a proton exchange membrane fuel cell (PEMFC) stack affects the characteristics of the porosity and electrical conductivity. Generally, the stack is assembled at room temperature while it’s operated at about 80 °Cor even higher. As a result, the assembly pressure can’t keep constant due to thermal expansion. This paper focuses on the contact pressure between membrane electrode assembly (MEA) and bipolar plates in real operations. A three-dimensional finite element (FE) model for the assembly process is established with coupled thermal-mechanical effects. The discipline of contact pressure under thermal-mechanical effect is investigated. A single cell stack is fabricated in house for the analysis of contact pressures on gas diffusion layer at different temperatures. The results show that as the temperature increases, contact pressure increases due to thermal expansion. It indicates that the influence of thermal expansion due to temperature variation should be taken into consideration for the design of the stack assembly process.

This paper mainlyintroduces the basic optical principles of light. Using He-Ne laser and pinhole configure collimated illumination, measuring the index of refraction by minimum deviation method, and measuring the birefringence use of wedge method by transmission optical microscope. In addition, give the results and discussion of the whole experiments.

This paper proposes a method based on vector calculation of flux density to evaluate the specific load capacity (SLC) of radial hybrid magnetic bearing (RHMB). The vector sum of the flux densities generated by the permanent magnet and the control current is calculated in this method, and then the functional expression of the SLC is built up via the flux densities. The influence of outer rotor diameter, fraction of circumferential rotor surface covered by poles and the length of the air gap are analyzed. It turns out that the SLC decreases with the maximum force of the bearing, and increases first and then decreases with the increase of pole area and length of the air gap. The maximum attainable SLC for RHMB of all sizes does not vary substantially from 23:1. The results of the analysis provide basis for the prediction of volume and mass for the RHMB in application.

Little attention has been paid to the nano-TiO2as corrosion inhibitor before. In this paper, Myristic acid-modified nano-TiO2(MA-TiO2) were synthesized by Myristic acid and tetrabutyl titanate via the sol-gel method, and it was characterized by IR and TEM. MA-TiO2was dispersed in oil, and used as a corrosion inhibitor. From the Tafel plots and EIS spectra, we can know that the values of the current densities decreased by the addition of MA-TiO2. Because of the MA-TiO2formed a deposition layer in the surface of 45#carbon steel panels, the current density of the the base oil with MA-TiO2is much smaller than the base oil. The inhibition efficiency was over 90% with added 5 wt % TiO2.

Activated carbons to be used as electrode in electrochemical double-layer capacitors were fabricated using amphiphilic carbonaceous material (ACM) as precursor. To study the significance of functional groups and microcrystalline of the precursor in preparing AC, we applied pre-carbonization upon the ACM under different conditions to control these two parameters in this paper. FTIR and XPS spectra showed functional groups on the precursors decreased as the increase of pre-carbonization temperature. After carbonization at 800 °C, the growth of graphitic microcrystallites was noticeable. Porous structure parameters of final ACs inferred that the functional groups on the precursors have a more significant effect than microcrystalline size on formation of mesopores during activation process not only for its role as active sites but also the homogeneous activation profited from the solubility of samples in alkaline solutions. The sample AC0 with almost half mesopores showed the best electrochemical behavior with a specific gravimetric capacitance of 255 F/g at current density of 1000mA/g and kept rectangular shape cyclic voltammetry curve even at scan rate high as 400 mV/s.

The paper has been retracted due to double publication. The original has been published in " Cocurrent Engineering Approach to Materials Processing", Ed Dwivedi SN et al. (1992), pp.217-229.

The compressive strength of the cementitious materials doubly with alkaline slag and fly ash are investigated in this paper. The optimum mixing way and ratio of weight were found. The hydration properties of cement binders with alkaline slag and fly ash are studied using XRD and SEM. The result shows that alkaline slag can stimulate the activity of fly ash, increase the hydration velocity of clinker mineral and improve the second hydration of fly ash.

This paper examines the effects of cyclic bending on the deformation and failure of layers that are relevant to flexible organic solar cells (with Polyethylene Terephthalate (PET) substrates and Poly-3-hexylthiophene: [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) active layers). The deformation and cracking mechanisms are elucidated along with the stresses and crack driving forces associated with the bending of flexible organic solar cells. The changes in the optical properties (transmittance) of the individual layers and multilayers are then explored for layers/multilayers deformed to flexural strains and stresses that are computed using finite element models. The implications of the results are then discussed for the design of flexible organic solar cells.

In the paper, taking the particles suspension for filtered object, the effect of the long fiber bundles bulk density on filtration efficiency was studied through the filtration experiments with the designed experimental equipment. And combining with the filtering model of long fiber bundle filter to do fluid analysis, the result show that, for the filtering velocity is 72m / h, in the filtration efficiency, filtration cycle, backwashing and other aspects of comprehensive performance of long fiber high efficient filter are best when the packed density is 73kg/m3.

SiJiaYing's iron ore is fine grain hematite and gangue mineral is quartz,chlorite,black mica and parts of clay mineral.Grinding process is tend to argillation,which seriously impact the subsequent strong magnetic and flotation thick operation.This paper mainly conduct ball mill sphere diameter,ball ratio and the grinding effect factor test,which including medium filling ratio,grinding concentration and so on.By compared experiments optimize,grinding process and improve the grinding effect.

In this paper, Tessier sequence extract procedure (SEP), toxicity leaching procedure (TCLP) and simple bioaccessibility extraction test (SBET) were employed to evaluate the immobile efficiencies for As, Cu and Pb contaminated soils. Experimental results indicated that the TCLP was efficient to extract the most active part heavy metal and evaluate the risk of the samples; the Tessier method divided heavy metals in soils to different fractions. Monitoring the changes of different fractions during the immobilizing procedure could help fully understand the mechanism of stabilization. The SBET method simulated the human digest system, thus it could be used to evaluate the risk changes to human during the immobilizing process; and to reveal the potential risk of chemical stability. In our project, these three evaluate method should be utilized properly to help accessing the risk, electing suitable immobilizing method and evaluating the efficiency of stabilization.

This paper comprises of the characterizations of superabsorbent polymer hydrogels based on sago starch (SS) prepared via graft copolymerization method with acrylic acid (AA) in the presence of ammonium persulphate (APS) and N, N-metylenebisacrylamide. The morphology of sago-g-acrylic (SAG) was evidenced by scanning electron microscope (SEM) images. The remarkable feature of this SAG is the porosity distribution with different amount of crosslinker. Less amount of crosslinker leads to increment in porosity distribution as well as water absorbency. This SAG with excellent water absorbency properties, being biodegradable in nature could be useful in sanitary products, horticulture and agriculture.

Al-22Si-5Fe-4Mn-3Cu-1Mg alloy billet was prepared by spray forming processing, and the morphology and microstructure development of the over-spray powder were investigated in this paper. The results show that the diameter of the most powder was about 38um. With the decreasing of the powder size, its shape became more round and surface more smooth. Heterogeneous nucleation was the main nucleation way and the microstructures were dendrite grains for the most of over-spray powder. The formation mechanisms of the different microstructures were investigated through comparison with the microstructure of the spray formed ingot.

The objective of this research was to study on charcoal block production from eucalyptus bark using screw press unit. The physical and thermal properties of charcoal and factors affecting the testing units performance, which were mixing ratios by weight of eucalyptus bark charcoal: cassava starch: water content (1: 0.10: 0.75, 1: 0.15: 0.75 and 1: 0.20: 0.75) and screw pressing speeds (90, 105, 120 and 135 rpm) were studied. The optimum of screw press unit was screw pressing speed of 120-135 rpm and a mixing ratio by weight of eucalyptus bark charcoal: cassava starch: water content of 1: 0.15: 0.75. The test result at the feed rate of 140 kg/hr indicated that the machine had a capacity of 119.71-121.95 kg/hr, specific energy consumption of 12.33-12.73 W-hr/kg, charcoal block bulk density of 467.55 to 468.88 kg/m3, charcoal strength of 152.58 to 153.60 kPa and heating value of 21.95 MJ/kg for charcoal block moisture content of 7.46 % (w.b.)

The use of computers in manufacturing has enabled the development of several new sheet metal forming processes. This paper describes modifications that have been made to traditional forming methods such as conventional spinning and shear forming, where deformation is localized. Recent advances have enabled this localized deformation to be accurately controlled and studied. Current developments have been focused on forming asymmetric parts using CNC technology, without the need for costly dies. Asymmetric Incremental Forming has the potential to revolutionize sheet metal forming, making it accessible to all levels of manufacturing.

Zinc coated steels are nowadays used for different applications as for example for household appliances, automotive or offtakes. Due to the boiling temperature of zinc (907°C), which is lower than the steel melting point, the welding of zinc coated steel sheets presents many difficulties. As a result of the violent evaporation of zinc, pores in the weld seam are present after solidification and the zinc coating near the weld is damaged. Brazing of zinc coated steels with CuSi-alloys offers some advantages, as the joining temperature is about 950-1000°C. Nevertheless the high melting point of these filler materials requires very restricted process strategies and damaging of the zinc coating near the brazing seam can’t be avoided. Although laser-, plasma- and MIG-joining with CuSi and CuAl are performed nowadays. ZnAl-alloys are characterized through low melting temperature, which are comparable to the melting point of zinc, so that the damaging of the zinc coating can be reduced. In this paper investigations carried out with ZnAl-materials for joining zinc coated steel sheets as DC04ZE75/75 and DX56Z (thickness 0,9 mm) are reported. First investigations were performed by resistance spot soldering and show that using low temperature melting materials leads to a lower damaging of the zinc coating. Further the process reliability of laser soldering with ZnAl-alloys and a Nd:YAG as well as a diode laser is reported and confirms the suitability of these alloys for a damaging free joining zinc coated steels. The low surface tension leads to a wide bearing section, so that advantageous properties are expected. The mechanical properties of edge welds are evaluated in this paper through tensile tests as well.

Compared to welding, laser brazing offers a suitable possibility to lower the working temperature and to join unweldable material combinations, while maintaining the numerous advantages of the laser joining process. Beside an acceptable joint strength, the brazed joints are characterised by a smooth surface and seams with almost no pores. As a result of this laser brazing combines the advantages of conventional brazing and laser welding. Within the scope of this paper the laser brazing process and its characteristics are explained in detail. In particular the interrelation of temperature progress, available processing time for brazing/diffusion and the thickness of the diffusion layer is discussed. Subsequently the material specific particularities of laser brazing aluminium alloys are described and discussed with respect to recently gained results.

Against the background of the required weight reduction in transportation through lightweight construction, the application of hybrid structures, where dissimilar materials are joined together, has a high technical and economical potential. In the field of sheet machining, combinations of steel and aluminium are especially interesting. In comparison to conventional steels, the application of aluminium alloys as supporting materials makes a distinct weight reduction possible. On the other hand, steels have advantages in the fields forming and welding. The application of modern high-strength steels with reduced sheet thicknesses allows weight reduction, too. But joining of material combinations of steel and aluminium is problematic. On the one hand brittle intermetallic compounds are formed between steel and aluminium. On the other hand the aluminium melt has a bad wetting behaviour. Different physical properties of both materials have to be considered, too. To achieve sufficient mechanical properties of such joinings it is necessary to limit growth of intermetallic compounds between steel and aluminium. This can be actualized by an exact energy supply. With the electron beam on atmosphere a precise and easily controllable energy supply is possible. The publication demonstrates successful investigations, which were performed with the 175 kVNVEBW (Non Vacuum Electron Beam Welding) installation at Institut of Materials Science, University of Hanover. With NVEB joining hybrid structures between zinc coated steels and 5.xxx and 6.xxx aluminium alloys were produced. In a welding-brazing process (the steel remained in the solid phase whereas the aluminium was molten) combinations with acceptable mechanical properties could be joined. By use of optimized joining parameters as well as a surface activating flux, both, a good wetting and a thin intermetallic compound < 10 µm were attained. Another possible strategy is a pure brazing process, for which an example is also given in the paper. The paper shows metallurgical and mechanical investigations, among other things results of element distribution analysis and tensile tests.

The customers’ demand for high quality and low cost products with rising functionality forces the enterprises to cost savings. In production these cost savings can be accomplished by simplification or omission of handling operations in the process chain. In laser beam welding of stamped sheet metals a previous cleaning of the sheets is usually necessary to guarantee a sufficient seam quality at a lap joint. Due to the recent trend towards low use of lubricants in forming operations the question arises, whether this process could be avoided in order to lower the production costs. The disadvantage of this measure would be a degradation of the seam quality. This reduction shows up in a falling strength of the weld due to inclusions and pore formation. This paper deals with the impact of different types of contaminations on the quality of laser welding. Therefore several liquid (oils) and solid (metallic and non-metallic) contaminants are examined. Zinc coated sheets are investigated too, because a zinc contamination arises with these sheets in the welding operation. The zinc coating evaporates because of the high temperature and this leads to a high porosity in the welding seam. In both cases also the height of the gap between the two sheets is varied in order to investigate its influence on the weld. To reduce the effort of the investigations, but not the accuracy of the results, the laboratory trials were supported by the methods of design of experiments. After the welding operation, the quality of the welding seam is evaluated by means of its mechanical properties and tightness. The results of the investigations are discussed and the developed solution strategies are presented.

During the joining process of complex body components in the automobile industry, dimensional accuracy is essential. In order to predict the behavior and to improve the geometrical quality of joined sheet metal parts during the welding and cooling process, a simulation method by means of finite elements is applied. This should be done in the early stage of the product’s life cycle to reduce process adjustments, which are time and money consuming. In recent years the simulation of welding was basically feasible by models consisting of volume elements. This way the metallurgical phase transformation, which is responsible for the behavior of the treated parts during the cooling process, can be established for a specific material. The use of volumes has a negative influence on the calculation time and it is not applicable for sheet metals. Especially, if effects from previous forming processes are to be considered. Additionally, the application of shells can meet the requirements of an analysis of the effects of welding when the metallurgical material properties are taken into account. In this paper an example of a sheet metal (DC04, former St 14) will be examined with the aid of a finite element analysis. Firstly, a transient temperature field is calculated in a thermal simulation by applying a certain method. In this calculation only the thermal properties of the material are used. Secondly, the transient temperature field is used as the initial load for the thermo-mechanical analysis. The distortion and the residual stresses of the work piece can be calculated using thermo-mechanical properties and material phase transformations.

The technology of Laminated Object Manufacturing (LOM) is not very new. For hundreds of years wooden parts are built by stacking layers together. Nowadays also paper, plastic, ceramic composite and metal sheets are treated in layers. For the manufacture of prototypes and especially technical tools, e. g. moulds for gravity casting, die casting or injection molding, out of metallic foil however the low self stiffness of this material is a great challenge. In this case it is useful to produce the parts in a two step process. The first subprocess is the stacking of the layers, which can be realised by laser beam spot welding to determine the position of the layer in combination with generating the defined contour by a laser beam cutting process. This procedure is done in a fully automated machine where the CAD-file of the desired part and the building parameters like the laser parameters and the cutting velocity are needed as input. However the stability of the produced green part is insufficient for most kind of application. Hence, a second sub-process to enhance the mechanical properties of the part is necessary. This can for example be realised by high temperature soldering or by diffusion welding in a furnace with inert gas or vacuum. During these kinds of joining processes the green part is homogeneously pressed with the help of a powder bed and at the same time it is tempered for a defined term. In this paper the principle of sheet metal LOM is described as well as the process chain of Laminated Object Manufacturing of metal foil. For each sub-process of metal foil LOM the results of the experimental work for qualifying and optimizing the sub-process are shown. Finally some examples of possible applications especially in the field of Rapid Tooling and Rapid Manufacturing are discussed.

Aluminum alloys, due to their low density compared to steels, are an important group of materials, in particular for light weight construction of transport vehicles. However, aside from their low specific weight, drawing of car body components made from aluminum alloys is limited by an inferior formability. To enable a modern car body design, it is necessary to enhance the formability of aluminum sheet metal. One basic approach to reach this aim is to adapt the mechanical properties of the blank for the drawing process. The general idea is to soften the deformation zone relative to the force transferring zone, which results in an improved material flow and thus to larger drawing depths. In this paper the process sequence consisting of local induction heat treatment followed by deep drawing of precipitation hardenable aluminum alloy is presented. Using an induction system, it is possible to change the mechanical properties of the 6xxx aluminum blanks in a restricted area by influencing the precipitation structure. Tensile tests characterize the conversion from the stable naturally aged condition T4 to reversible solution heat treated W conditions of AA6016 as function of temperature and time. This effect leads to a reduction of flow stress, which is used to design an material property distribution adapted for the subsequent deep drawing process. A process characterization study provides detailed information concerning induction heating parameters, to improve the deep drawing of cylindrical cups, which results in a decisive increase of the limiting drawing ratio. Accompanying the experimental investigations, a finite element analysis approach is realized as a process design and optimization tool. Following the presented strategy, it is possible to enhance the forming capability of aluminum alloys. This leads to advanced manufacturing processes, which extend the field of applications for aluminum car body parts.

Tube hydroforming is an advanced technology for the manufacturing of lightweight components with complex shape. The forming results can be usually improved if axial feeding at the tube ends is enabled. For very long parts, however, due to the high friction forces acting at high pressure in the feeding zone between tube and die, no material movement towards the expansion area occurs. The tube is only upset in the feeding zone, no compressive stresses take place in the expansion area and the forming results are not satisfactory. This can be avoided by eliminating friction and by inducing additional tangential stresses in axial direction on the tube surface of the feeding area. This paper presents the investigations performed in this direction by using a high viscous fluid flowing along the internal and external surface of the tube. The flow helps to reduce the friction force and allows the sliding between the tube and the tool surface. Experimental tests of tube upsetting under pressure will show the effects of the medium flow on the thickening of the tube wall. Not only increased sliding and homogeneous thickening will be obtained, but even an increase of the wall thickness in the area close to the expansion zone will be shown. This effect is even stronger when the yield stress in the expansion zone is reduced by means of a previous local heat treatment.

A new process technology for stretch-forming of thin sheet metals is presented within this paper. This new technology is based on shock waves as a source for the forming energy, which are created through laser pulses. The results of some preliminary experiments show, that stretchforming with laser pulses is possible. The influence of parameters like defocussing, power density, pulse energy, number of pulses and material are worked out with excimer-laser pulses. The results show, that uniform shaped domes with a dome height over 250 µm with diameters of 1.4 mm could be produced. More recent studies show that even better results can be reached through the use of TEA-CO2-Lasers, since no confinement is needed and ablation at the surface is avoided. The absence of ablation at the surface makes this new technology even more interesting, since not only the surface remains accurate, but also since several pulses can be applied at one point and thus higher forming degrees can be reached without increasing the power density.

The production of automotive body parts and panels is a very complex process, starting with the raw materials and ending in the paint shop. Due to the fact that aluminium sheet metal has to be lubricated before forming, all of the following processes have to be considered. Lubricants, such as oils, dry-film lubricants or recently introduced hotmelts have to protect the material’s surface, reduce friction whilst drawing the panels and should not compromise further treatments [1]. Different types of lubricants show different characteristics. This difference is especially noticeable when comparing liquid and dry-film lubricants. As dry-film lubricants do not run off the blanks’ surface and are distributed homogeneously, they show different tribological properties compared to conventional liquid lubricants. The effect on friction of aluminium sheet metal is shown through several basic experiments [2, 3]. In addition, the paper shows the effect of further operations within the production chain. The advantages and disadvantages not only for drawing, but also for assembly lines and the painting process are described in this paper. Assembly issues are carried out on stability testings of riveted and clinched assemblies. These trials show how the assembly process is affected by different proceedings. The fact that every car body has to be completely free of grease before painting, signifies the necessity to get lubrication off the car body’s surface before painting. The interactions between lubrication and paint shop are shown on typical process parameters. Most typical characteristics considering bonding and riveting were tested out on a hood assembly of the current BMW 7-series. In addition to that, experiences made in the press shop at BMW’s Dingolfing plant were figured out and carried over to a long-term strategy of pre-lubrication of aluminium sheet metal. This includes adhesive compatibility as well as the above mentioned assembly process.

Tribological aspects strongly influence the deep drawing behaviour of sheet metal, being responsible for both the punch force and the material draw-in from the flange. Recent developments in lubrication technology have shown that dry film lubricants can be a good alternative to conventional fluid lubricants in case of aluminium sheets. Their main advantages are the homogeneous distribution on the blank surface, the good adhesion to the surface and the possibility of applying it already in the rolling mill. In order to introduce this technology in series production also for steel sheets more knowledge concerning the influence of the lubricant amount on the drawing forces is needed. A further important aspect to be considered is the surface quality of the steel grades and its interactions with the dry lubricant. In this paper four steel grades with different mechanical and/or surface properties are considered. After a microscopical and topographical investigation of the surface the materials were tested in a cup drawing test after applying two different amounts of the dry film lubricant Drylube E1. Further process parameters which were varied are the blank holder force FN and the drawing ration b. In this way, information about the influence of the lubricant amount on both the drawing force and on the maximum blank holder force FZ could be obtained for three different values of b. The experimental results have shown how a strong decrease of the lubricant amount (from 1.0 down to 0.5 g/m2) causes, at a given drawing ratio, only a small increase in the maximum drawing force as well as a small increase in the maximum blank holder force.

In the paper the thermal characterization of friction stir welding processes (FSW) of aluminium alloys is presented. In particular both embedded thermocouples and a thermography analysis were utilized in order to acquire the temperature vs. time curves in point of interests of the joints and the temperature distributions, respectively. Such kind of results are very important in order to investigate the material conditions during the FSW process.

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.

The multifarious applications of aluminum alloys in different industrial domains are based on the mechanical properties as well as the light weight characteristics, which allow energy saving for the products in use. Nevertheless aluminum alloys are considered to be difficult to weld by conventional welding processes. This paper deals with cost-effective friction stir welding of thin sheet aluminum alloys in thicknesses of about 1 mm to widen the possible range of applications. Based on former studies results will be shown how an optimized tool geometry increases the mechanical properties of friction stir welded parts. The characteristics of these friction stir welded thin sheets will be analysed in a statistical evaluation in order to detect the interactions and dependencies of the process parameters. By highlighting the main process parameters and their significances a process window for friction stir welded blanks of AA5182 and AA6016 is presented.