Sheet metal forming processes are mechanical processes, designed to make products from metal sheet without material removal. These processes are applied extensively by the manufacturing industry to produce commodities such as heat exchangers or panels for automotive applications. They are suitable for production in large volumes. A typical problem in forming operations is accumulation of local sheet material adherents onto the tool surface, which may deteriorate the subsequent products. This tool failure mechanism is named galling. The aim of this work is to explain the mechanisms behind galling and establish factors how it can be reduced. The focus of this work is on the influence of tool material for minimum risk of galling. Experimental tool steels alloyed with nitrogen were designed and manufactured for systematic tribological evaluation. Reference tool materials were conventional cold forming tool steels and coated tool steels. The sheet material was austenitic stainless steel AISI 304, which is sensitive for galling. A variety of lubricants ranging from low to high viscous lubricants were used in the evaluation. The properties of the tool materials were characterized analytically and their tribological evaluation included industrial field tests and several laboratory-scale tests. The testing verified that nitrogen alloying has a very positive effect for improving galling resistance of tool steels. Tool lives comparable to the coated tool steels were achieved even with low viscous lubricants without poisonous additives. The hypothesis used for the explanation of the positive effect of nitrogen alloying is based on the critical local contact temperature at which the lubrication deteriorates. Therefore, the contact mechanism at the tool-sheet interface and the local energy formation were studied systematically. Theoretical considerations complemented with FEA analysis showed that a small size of hard particles with a high volume fraction gives low local contact loads, which leads to low frictional heating. Also, an even spacing between the hard particles and their frictional properties are of importance. Nitrogen alloyed tool steels have these properties in the form of small carbonitrides. The finding of this work can be applied to a wide range of applications that involve sliding metal contacts under severe tribological loading.

The discovery of the pore-forming toxins produced by Bacillus thuringiensis, which are toxic to insects but not to mammalians, has provided a new successful means to control harmful plant-feeding insects biologically. The toxins are also used on insects that don’t feed on plants, for example on Anopheles. The Bacillus thuringiensis toxins fall into two structural families, named cry and cyt. All of these toxins act by damaging the cell membranes in the mid gut of the insect. In this study, a reliable system for expression and purification of the recombinant Cyt2Aa1 toxin has been developed. The recombinant Cyt2Aa1 toxin has been produced, characterized, followed by the construction of the cysteine mutants V186C and L189C by site directed mutagenesis. The new expression system yields 0.4 g of protein per litre of culture. The activated Cyt2Aa1 toxin is active in the hemolysis assay. Of note, the hemolytic activity of the V186C mutant exceeds that of wild type Cyt2Aa1 toxin and of the L189C mutant. Calcein release assay experiments have been done to examine the activity of the toxin with different artificial liposomes. It was found that Cyt2Aa1 toxin is very active with DMPC, DMPC+DMPG unilamellar liposomes. Surprisingly, however, Cyt2Aa1 toxin showed no activity with liposomes containing cholesterol. With both erythrocytes and sensitive liposomes, the toxin shows a “pro-zone effect”, that is the activity decreases at very high concentrations. The findings are discussed in the context of the toxin’s putative mode of action.

Warm forming of aluminum alloys of has shown promising results for increasing the formability of aluminum alloy sheet. Warm forming is a term that is generally used to describe a sheet metal forming process, where part or all of the blank is formed at an elevated temperature of less than one half of the material’s melting temperature. The focus of this work is to study the effects of warm forming on Novelis X926 clad aluminum brazing sheet. Warm forming of clad aluminum brazing sheet, which is commonly used in automotive heat exchangers has not been studied. This work can be split into three main goals: i) to characterize the material behavior and develop a constitutive model, ii) to experimentally determine the effects of warm forming on deep drawing; and, iii) to create and validate a finite element model for warm forming of Novelis X926. For an accurate warm forming material model to be created, a temperature and rate dependant hardening law as well as an anisotropic yield function are required. Uniaxial isothermal tensile tests were performed on 0.5mm thick Novelis X926at 25°C (room temperature), 100°C, 150°C, 200°C, and 250°C. At each temperature, tests were performed with various strain rates between 7.0 E -4 /sec and 7.0 E -2 /sec to determine the strain rate sensitivity. Tensile tests were also performed at 0° (longitudinal), 45° (diagonal), and 90° (transverse) with respect to the material rolling direction in order to assess the anisotropy of the material. It was found that increasing forming temperature increases elongation to failure by 200%, decreases flow stress by 35%, and increases strain rate sensitivity. Barlat’s Yield 2000 yield function (Barlat et al., 2003a) and the Bergström work hardening law (van den Boogaard and Huétink , 2006) were found to accurately method model the material behavior. Warm deep drawing of 101.6 mm (4”) diameter cylindrical cups was performed using specially designed tooling with heated dies and a cooled punch. Deep drawing was performed on 228.6 mm (9“) and 203.2 mm (8”) diameter blanks of 0.5 mm thick Novelis X926. Deep drawing was performed with die temperatures ranging from 25°C to 300°C with a cooled punch. Teflon sheet and Dasco Cast 1200 lubricants were used in experiments. Different punch velocities were also investigated. 228.6 mm diameter blanks, which could not be drawn successfully at room temperature, were drawn successfully using 200°C dies. Increasing the die temperature further to 250°C and 300°C provided additional improvement in formability and reduced tooling loads. Increasing the punch velocity, increases the punch load when forming at elevated temperatures, reflecting the strong material rate sensitivity at elevated temperatures. A coupled thermal mechanical finite element model was developed using the Bergström hardening rule and the Yield 2000 yield surface using LS-DYNA. The model was found to accurately predict punch force for warm deep drawing using Teflon sheet as a lubricant. Results for Dasco Cast 1200 were not as accurate, due to the difficulties in modeling the lubricant’s behavior. Finite element simulations demonstrated that warm forming can be used to reduce thinning at critical locations, compared to parts formed at room temperature.

The flow of wood fiber suspensions plays an important role during the pulp and paper manufacture process. Considerable research has been carried out in the past 50 years to characterize the fiber suspension flow behavior and to monitor the fiber suspension flow during paper manufacture. However, the above research has been hampered by the lack of techniques to directly characterize fiber suspension flow fields because fibers and fiber flocs tend to interfere with instruments inserted into the flow. The fundamental studies in this thesis concentrated on three parts: (1) examine the feasibility of measuring wood fiber suspension flow by Pulsed Ultrasonic Doppler Velocimetry (PUDV), (2) apply PUDV to characterize fiber suspension flow behavior in a rectangular channel, (3) apply PUDV to measure the forming jet velocity profile along the jet thickness direction (ZD). In the first part, it is demonstrated that PUDV is an accurate technique for the velocity profile measurement of fiber suspension flow. The measurement has high repeatability and sensitivity. Suitable parameters should be selected in order to obtain the optimum measuring results.

The aim of this study was to characterize the interaction between a pulsed ultrasonic wave and a paper forming screen for potential development of a smart paper forming sensor to measure velocity profile of the forming jet as it impinges on the wire. To achieve this goal, a Signal-Processing DOP 2000 pulsed ultrasonic Doppler velocimeter was used to generate a pulsed ultrasonic signal. The signal was transmitted and received using four different ultrasonic transducers: a 2 MHz 10 mm, 4 MHz 5 mm, 4MHz 8 mm focused, and 8 MHz 5 mm. The ultrasonic signals were then analyzed in order to determine the ultrasonic beam echo amplitude and shape. These tests were performed with and without various paper forming screens placed between the ultrasonic transducer and an ultrasonic signal target. Two different paper forming screens were utilized to study the interaction of the ultrasonic beam with the forming screens. The tests showed that the ultrasonic signal passing through the forming screens is greatly attenuated causing a sharp decrease in echo amplitude. To overcome the attenuation of the signal, a much higher amplification of the signal was used causing an increase in the saturation region around the forming screen. This increased the minimum distance that a target had to be away from the forming screen. The closest distance from the plastic sphere to the screen over the widest range of transducer-screen-distances that produced detectable echoes was achieved with the 4 MHz 5 mm transducer. The tests showed for both screens that there is more variation in beam width when the screen is moved laterally than when it is not moved at all. They also show that even though the pores in the forming screen are very small, they seem to have a great effect on the beam width measurements of the ultrasonic transducer.

Advancements in technologies such as microelectromechanical systems (MEMS), display devices, biomedical products have created an increasing requirement for miniature components on the scale of micrometers to nanometers. Currently, a commonly used fabrication for miniaturization is LIGA (Lithographie, Galvanoformung, and Abformung). It is a reliably manufacturing method for high-aspect-ratio microstructures with a precision of less than one micrometer. The use of electroplating within LIGA techniques, however, limits the range of materials that can be used. But the main disadvantage of LIGA is its cost: high-energy X-rays generated by synchrotron equipment. The homogeneous and isotropic characteristics of amorphous bulk metallic glasses (BMGs) due to the absence of crystallites, grain boundaries and dislocations lead to the scale of the metallic-glass structures can be miniaturized down to the atomic scale, which presents very high strength, hardness, elastic strain limit and corrosion resistance. In addition, the excellent workability and surface printability in the supercooled liquid state (the region defined from the glass transition temperature (Tg) to the crystallization temperature (Tx) of BMG) has been considered to be one of the most attractive properties of BMGs. The lighter Mg-based metallic glasses exhibit their superior glass forming ability (GFA). Consequently, the using of Mg-based BMGs can gain the goals of light devices and simplify manufacturing process. In this study, therefore, besides the study of LIGA process, a new process utilize the thermoplastic properties of BMGs is presented. First, UV (ultraviolet) -LIGA, a more economical process than LIGA, is used to fabricate the master mold with nickle-cobalt (Ni-Co) alloy. Then, this mold is applied to hot emboss on Mg58Cu31Y11 amorphous alloy to form a secondary mold. The hot embossing temperature is set at 423 K (150 oC) according to the Tg of the BMG around 413 K (140 oC). This embossing process shows that the thermoplastic forming ability of the BMG material is better than Polymethylmethacrylate (PMMA) which requires high hot embossing pressure. BMG is not only a good material for hot embossing process to fabricate microstructure directly, but also a fast-forming material for mold (or die) fabrication. On the other hand, other replicated-able moulds are presented to demonstrate the multifunctional ability of BMGs. First, a mold of oxygen free copper (OFC) with a very low hardness of 1.606 GPa, which is a popular material for machining due to its good machinability, is used to hot emboss on Mg58Cu31Y11 BMG with a higher hardness of 3.445 GPa. Second, micro triangular-pyramidal array (MTPA) on a tungsten (W) steel mold is transferred on Mg58Cu31Y11 BMG using this modified multi-step hot-embossing method to reduce the pattern size. In addition, scratch test with the Nano Indenter® XP system is used to study the mechanical behavior of the Mg58Cu31Y11 BMG for the application such as surface printability.

Tube hydroforming process is a relatively new technology compared to conventional manufacturing via stamping and welding. However there is not much knowledge available for the product or process designers. The objective of this study will determine the flow stress and forming limit diagram of tubular materials to discuss the formability of tubes. Firstly, a mathematical model is proposed to examine the plastic deformation behavior of a thin-walled tube at different process parameters during the bulge hydroforming process without axial feeding. In the formulation of this mathematical model, an ellipsoidal surface and non-uniform thinning in the free bulged region and sticking friction between the tube and die are assumed. In the sticking friction mode, the elements after contact with the die do not move or slide. The effects of various forming parameters, such as the die entry radius, the bulge length, anisotropy, the initial thickness of the tube, etc., upon the forming pressures are discussed systematically. Secondly, an analytical model combined with hydraulic bulge tests is proposed to evaluate the properties of tubular materials considering anisotropy effect. Annealed AA6011 aluminum tubes and SUS409 stainless steel tubes are used for the bulge test. The tube thickness and radius at the pole and the internal forming pressure are measured simultaneously during the bulge test. The anisotropic values are obtained from tensile tests. From above experimental data, the effective stress - effective strain relations can be derived by this analytical model. The finite element method is used to conduct the simulations of hydraulic bulge forming with the flow stresses obtained by the above-mentioned model. The analytical forming pressures versus bulge heights are compared with the experimental results to validate the approach proposed in this study. Finally, this study also establishes the Forming Limit Diagram (FLD) of aluminum tubular material. An experimental system of tube hydroforming in which axial feed is applied to carry out the hydraulic bulge-forming test of the annealed aluminum alloy tubes. Furthermore, Hill¡¦s new yield criterion is also used to predict the Forming Limit Curves of sheets. The predicted forming limit diagrams are compared with the experimental data. The results of this study can provide useful knowledge for process design. In addition, the process parameters of flow stress and forming limit diagram obtained can improve the accuracy of the simulation results in industrial and academic fields.

The tube hydro-forming (THF) is an innovative manufacturing process which is used to manufacture many industrial components widely. The success of THF is largely dependent on the selection of the loading paths: internal pressure versus time, axial feeding versus time and counter punch (CP) versus time. The finite element analysis is used to simulate the forming result of different loading paths and reduce the cost of die-testing. This paper presents the forming of T-branches and T-branches components with CP. These paper has developed an adaptive simulation algorithm by combining FEM code LS-DYNA 3D with controller subroutine to get ideal bulging height and uniform thickness of the formed tube with multi-stages. Discuss influence under different parameters of process. The results are compared with experimental results to validate accuracy by this adaptive control methods.

The present study aims to determine the optimum blank shape design for the deep drawing of arbitrary shaped cups with a uniform trimming allowance at the flange i.e. cups without ears. This earing defect is caused by planar anisotropy in the sheet and the friction between the blank and punch/die. In this research, a new method for optimum blank shape design using finite element analysis has been proposed. Explicit non-linear finite element (FE) code LSDYNA is used to simulate the deep drawing process. FE models are constructed incorporating the exact physical conditions of the process such as tooling design like die profile radius, punch corner radius, etc., material used, coefficient of friction, punch speed and blank holder force. The material used for the analysis is mild steel. A quantitative error metric called shape error is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. This error metric is then used to decide whether the blank needs to be modified or not. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. In order to verify the proposed method, examples of square cup and cylindrical cup have been investigated. In every case converged results are achieved after a few iterations. So through the investigation the proposed systematic method of optimal blank design is found to be very effective in the deep drawing process and can be further applied to other stamping applications.

Weight reduction is a hot topic in automotive industry. Both the applications of tube hydroforming technique and magnesium alloys offer a large potential for reducing the weight of automotive components. In this research, the relationship between forming pressure and bulge height, the maximum forming pressure and the forming limit during the tube hydraulic bulging process are first analysed. A self-designed warm hydraulic bulge forming equipment and the seamlessly extruted magnesium alloy AZ61 tubes, are used for carrying out a series of warm hydraulic bulge tests, and discussing the formalibility of the magnesium tubes at various temperatures. Furthermore, the flow stress curves are determined by the mathematical model in this paper with the bulge forming test results. Then the validity of the analytical model is verified by comparing the forming pressure and bulge height between analytical and experimental values.