A thermomechanical stress analysis of a superplastic forming (SPF) tool is performed by means of the finite element simulation of the whole forming process. The distributions of residual stress and distortion within the tool are investigated in order to evaluate the damage effects of thermomechanical loading. The effect of cyclic loading is related to the fact that residual stress and distortion in the tool accumulate as loading cycles proceed. The characteristics of the typical forming parameters of the sheet are described too. Meanwhile, the numerical simulation can be employed to compare various materials that can be used to manufacture forming tools.
Numerical simulation was performed on an axi-symmetric metallic die during a whole life cycle. It was shown that most important stresses are generated by the thermal gradients during heating up and repeated die removal from the press furnace and also by the clamping pressure during forming. The forming itself causes non dimensioning stresses. Creep relaxation during forming induces plastic deformation and distortion of mould after cooling down. To increase simulation relevance, new behaviour models are investigated for three classes of materials candidate for SPF dies: heat resistant cast steels, fibre reinforced refractory concretes and low cost monolithic ceramics.
Glasses-free light field displays have significantly progressed due to advances in high-resolution microdisplays and high-end graphics processing units (GPUs). However, for near-eye light-field displays requiring portability, the fundamental trade-off regarding achieved spatial resolution remains: retinal blur quality must be degraded; otherwise, computational consumption increases. This has prevented synthesizing the high-quality light field from being fast. By integrating off-the-shelf gaze tracking modules into near-eye light-field displays, we present wearable virtual reality prototypes supporting human visual system-oriented focus cues. An optimized, foveated light field is delivered to each eye subject to the gaze point, providing more natural visual experiences than state-of-the-art solutions. Importantly, the factorization runtime can be immensely reduced, since the image resolution is only high within the gaze cone. In addition, we demonstrate significant improvements in computation and retinal blur quality over counterpart near-eye displays.
In this paper, damages accumulated in superplastic forming (SPF) tools during the forming cycles were investigated in various aspects. Finite element simulations were performed on an axisymmetric mould of heat resistant cast steel to evaluate thermomechanical stresses and strains during the forming cycles, which cause accumulated residual stress and deformation damage in the mould. The dimensional changes due to microstructure evolution of the tool material were studied on specimens for typical thermal cycles. And high temperature corrosion destroying the surfaces of the tool was investigated too.
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