This work was concerned with evaluating the behavior of thermoplastics reinforced with melt processable phosphate glasses processed by techniques including injection molding, compression molding, and thermoforming. Thermoplastic resins consisting of polyphenylene sulfide (PPS), polyetherimide (PEI) and polyetheretherketone (PEEK) were combined with phosphate glasses having glass transition temperatures (Tg) that ranged from 230-290°C to form composite systems where both the matrix and reinforcing phase were deformable during processing. For the process of injection molding, several factors were examined to maximize the mechanical properties obtained with the addition of the phosphate glasses. The influence of variables such as the glass and matrix viscosity, glass loading, melt temperature, and mold fill rate were examined for a variety of composite blends consisting of the PPS, PEI, and PEEK reinforced with a lower Tg (234°C) phosphate glass and PEEK blended with a higher Tg (282°C) glass. From this work, it was determined that the best mechanical properties were generally produced by using processing temperatures and material combinations that minimized the viscosity differences between the thermoplastic resin and phosphate glass. Variations in the material combinations and processing conditions utilized were also found to result in the formation of a variety of glass phase morphologies that consisted of droplets, ribbons, and an interpenetrating network structure. The addition of the phosphate glass to the neat thermoplastics resins was found to be an effective way to produce injection moldable composite blends. The stiffness of the composite blends increased with glass loading with composites containing up to 45 vol% phosphate glass exhibiting machine direction tensile and flexural moduli in the range of 3-5 times greater than that those of the neat thermoplastics. Additionally, these composites were found to offer moduli and strengths that ranged from 25-50% lower than conventional E-glass fiber reinforced materials of the same loading. The lower mechanical properties of the neat phosphate glasses coupled with a lack of adhesion between the matrices and the glasses helped contribute to the lower mechanical properties exhibited by the phosphate glass reinforced composites. Still, the phosphate glass reinforced blends offered certain advantages including lower mechanical anisotropy, smoother surfaces, and lower viscosities. The processing behavior of phosphate glass reinforced thermoplastics was also examined at temperatures commonly used in forming and shaping operations such as compression molding and thermoforming. It was determined that it was possible to deform the phosphate glass reinforcing phase along with the matrix resin at temperatures only 30-50°C above the Tg of the glass. The deformable phosphate glass reinforcing phase resulted in composite blends that exhibited greater extensibility than a solid E-glass fiber reinforced material. The elongation of the phosphate glass into a higher aspect ratio reinforcing morphology was found to result in an almost 25% increase in the tensile modulus for a polyphenylene sulfide based composite. / Ph. D.

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In recent years, there has been an increase in the use of press hardened steel (PHS) in the body-in-white of automobiles, namely in parts such as side impact beams, roof rails, engine firewalls, and the floor area. As these parts are expected to possess corrosion resistance, Al-Si coatings are utilized on them. The implementation of Zn coatings is limited, despite possessing improved corrosion resistance attributed to cathodic corrosion protection, due to the detrimental effects of liquid metal embrittlement (LME) and microcracking. LME can be mitigated if stamping occurs at a temperature lower than the Fe-Zn peritectic temperature of 782 °C, as this ensures that the conditions of LME are not met and the cathodically-protective Γ-Fe3Zn10 phase is formed. The objective of this work was to determine a process window for stamping at lower temperatures for a GA80-coated prototype steel (steel K) with the composition of 0.19C-1.92Mn-0.20Si-0.003B-0.03Ti (wt.%). The target mechanical properties in this process window were UTS ≥ 1400 MPa, and YS ≥ 1000 MPa. To achieve robust cathodic corrosion protection, more than 15 vol% of Γ-Fe3Zn10 in the coating was desired. Furthermore, it was aimed to determine the robustness of this process and the industrial feasibility of it through pilot-scale trials for the GA80-coated prototype steel. To this end, a bare prototype steel (steel I) with the composition of 0.20C-1.96Mn-0.25Si-0.003B-0.01Ti was compared to GA-coated steel K. It was found that stamping a direct hot press forming (DHPF) temperature of 650 °C produced similar mechanical properties such as tensile strengths and ductilities. Microstructural analysis of laboratory-scale DHPF for steel K showed that both the coating and the substrate microstructures were not a strong function of the DHPF temperatures of 550 – 700 °C. The substrate predominantly consisted of martensite with small amounts of ferrite and the coating consisted of α-Fe(Zn) and ≥ 15 vol.% Γ-Fe3Zn10. Based on the fraction of Γ-Fe3Zn10 and the coating thickness, robust cathodic corrosion protection is expected from GA80-coated steel K. Furthermore, no evidence of LME or severe microcracking was observed in the microstructure for DHPF temperatures of 550–700 °C for steel K and ductile fracture was observed in tensile coupons. Tensile testing for laboratory-scale DHPF for steel K showed that the mechanical properties such as YS, UE and PUE were not significantly affected by DHPF temperatures of 550-700 °C. Moreover, the targets of UTS ≥ 1400 MPa, and YS ≥ 1000 MPa were met for all DHPF temperatures of 550 – 700 °C. Through pilot-scale tensile testing of steel K, it was determined that the targets for tensile strengths (UTS and YS), were achieved across various conditions involving austenitization at 890 °C for 60 – 240 s and DHPF temperatures ranging from 550 – 700 °C. These findings strongly suggest that industrial feasibility is attainable for DHPF of GA-coated steel K at lower temperatures, enabling the attainment of desirable mechanical properties and robust corrosion protection. Thus, it can be concluded that the process window yielding desirable properties for steel K was determined to be austenitization at 890 °C for 60 – 240 s and DHPF temperatures between 550 – 700 °C. / Thesis / Master of Applied Science (MASc) / The forming process of the steels used in the automotive industry is not suitable for zinc coatings because it requires pressing at high temperatures to ensure obtaining strong steels. Thus, zinc coatings cannot be utilized despite the desirable cathodic corrosion protection properties they can provide. This study aimed to determine a suitable process window for a zinc-coated prototype steel that would have both high strength and desirable corrosion protection. The zinc-coated prototype steel was pressed at lower temperatures. It was observed that the target mechanical properties were met for all the temperatures tested. Moreover, robust cathodic corrosion protection is expected for all the temperatures. Furthermore, pilot-scale tests yielded comparable results to those obtained in the laboratory, indicating that this process can be successfully applied in the industry as it possesses a sufficiently large process window.

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<p>Metal forming processes have been widely applied in many industries. With the severe competition in the market, a reliable and robust metal forming process becomes crucial for the manufacturer to reduce product development time and cost. For the purpose of supplying engineers with an effective tool for a reliable and robust design of metal forming process, this research investigates the application of traditional reliability theory and robust design methods in metal forming processes for the ultimate goal of increasing quality and reducing cost in manufacturing.</p> <p> A method to assess the probability of failure of the process based on traditional reliability theory and the forming limit diagram (FLD) is presented. The forming limit of a material is chosen as the failure criteria for analysis of reliability.</p> <p> A study of prediction of forming limit diagrams using finite element simulation without pre-defined geometrical imperfection or material imperfection is presented. A 3D model of the dome test is used to predict the FLD for AA 5182-0. The FE predicted forming limit diagram is in good agreement with the experimental one. The uncertainty sources for the scatter of forming limits are categorized and investigated to see their effects on the shape of FLD.</p> <p>A novel method of improving the reliability of a forming process using the Taguchi method at the design stage is presented. The thickness-thinning ratio is chosen as the failure criteria for the reliability analysis of the process. A Taguchi orthogonal array is constructed to evaluate the effects of design parameters on the thinning ratio. A series of finite element simulations is conducted according to the established orthogonal array. Based on the simulation results, Taguchi S/N analysis and ANOVA analysis are applied to identify the optimal combination of design parameters for minimum thinning ratio, minimum variance of thinning ratio, and maximum expected process reliability.</p> <p> A multi-objective optimization approach is presented, which simultaneously maximizes the bulge ratio and minimizes the thinning ratio for a tube hydroforming process. Taguchi method and finite element simulations are used to eliminate the parameters insignificant to the process quality performance. The significant parameters are then optimized to achieve the multiple optimization objectives. The optimization problem is solved by using a goal attainment method. An illustrative case study shows the practicability of this approach and ease of use by product designers and process engineers.</p> / Thesis / Doctor of Philosophy (PhD)

<p>In sheet metal forming processes, friction has decisive effects on the strain distribution in the deformed sheets and the quality of the final product due to the large surface/thickness ratio of the blank sheets. It is well known that friction in sheet forming operations is dependent on local contact conditions such as surface roughness, contact pressure and sliding velocity. Adding complexity to this frictional behavior, some rolled sheets have oriented surface roughness and show considerable frictional anisotropy. A constant friction model without consideration of these relevant phenomena is regarded as the reason why sheet metal forming simulations often fail to produce satisfying results despite the well developed material models. </p> <p>To develop a friction model which considers both of the varying conditions of local contact and the frictional anisotropy was the aim of this thesis. For this purpose, the analysis method of the friction test (draw-bend test) had to be examined for the capability to evaluate these parameters independently. Through careful study using finite element simulations, it was found that the conventional method has shortcomings in addressing pressure dependent friction due to the pressure non-uniformity existing in the test. Therefore, a new analysis method, which can evaluate pressure dependency of a friction coefficient, was developed. In the new method, contact pressure maps obtained from simulations were included in the analysis of test data.</p> <p>The new analysis method was applied to friction measurement of aluminum sheets with known anisotropic mill finish, and friction coefficients were obtained as functions of contact pressure, sliding velocity and sliding direction. In the obtained friction model, a friction coefficient is a continuous surface over the domain of contact pressure and sliding velocity. Lastly, the new friction model was implemented into a finite element code and the model was validated through circular cup drawing experiments and simulations. The comparisons showed good agreements in the aspects of punch force, cup size and failure location. Thus, the newly developed model can accurately predict the effects of anisotropic friction in sheet metal forming processes. </p> / Thesis / Doctor of Philosophy (PhD)

<p> This thesis deals with the analytical and experimental study of the influence of residual stress due to cold bending on the behaviour of thin-walled open sections. The residual stress distribution caused by cold forming the sections is predicted theoretically. The influence of this residual stress on the load-displacement characteristic, and load carrying capacity of similarly curved tension and compression specimens is then analyzed. A local buckling analysis based on the virtual work and incremental theories is performed to predict the collapse load of compression specimens containing residual stresses.</p> <p> The experimental work consisted of tests to confirm theoretical elastic springback strains due to cold bending of steel sheet to various radii. Tension and compression tests were then performed on various cold formed sections to observe the effects of residual stress and to confirm analytical predictions. </p> <p> Conclusions have been deduced from the theory and from these tests, and suggestions made for further research.</p> / Thesis / Master of Engineering (MEngr)

<p>The field of superplasticity is reviewed, with particular reference to the mode of deformation and viability for industrial application. Superplastic and conventional Zn-Al eutectoid alloys are compared with regard to the pressures and time required and the problems associated with the production of shaped hollow components from billet material, using extrusion followed by pressure forming. A possible industrial process is suggested and economically assessed in a Supplement to the Dissertation. </p> / Thesis / Master of Engineering (ME)

Flugzeuge sind üblicherweise als Rahmenstrukturen aus Leichtbauwerkstoffen wie faserverstärktem Kunststoff, Titan- oder Aluminiumlegierungen gestaltet. Je nach Anwendungsfall reicht die Tragfähigkeit der eingesetzten Streben von wenigen Kilonewton bis zu mehr als 250 kN. Die Verbindungen der Streben mit Anschlussstücken sind häufig komplex, sodass hohe Kosten für die montierten Bauteile entstehen. Fügen durch elektromagnetische Kompression (EMK) stellt aufgrund der verfahrensspezifischen Vorteile eine vielversprechende Alternative dar, um Verbindungen deutlich einfacher zu realisieren, insbesondere wenn Streben aus Aluminiumrohr eingesetzt werden.