Finite element modelling of the laser forming of AISI 1010 steel

Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfil this promise in a manufacturing environment the process must have a high degree of controllability, which can be achieved through a better understanding of its underlying mechanisms. One area of limited understanding is that of the variation in bend angle per pass observed during multi-pass laser forming along a single irradiation track, notably the decrease in bend angle per pass after many irradiations. Finite element (FE) modelling can be used to ascertain which of the various process parameters (such as graphite burn-off, geometrical effects, variation in absorption, etc.) contribute towards this phenomenon and subsequently the magnitude of their contribution

Alternative Fabrication Routes toward Oxide-Dispersion-Strengthened Steels and Model Alloys

The standard powder metallurgy (PM) route for the fabrication of oxide-dispersion-strengthened (ODS) steels involves gas atomization to produce a prealloyed powder, mechanical alloying (MA) with fine oxide powders, consolidation, and finally thermal/thermomechanical treatment (TMT). It is well established that ODS steels with superior property combinations, for example, creep and tensile strength, can be produced by this PM/MA route. However, the fabrication process is complex and expensive, and the fitness for scaling up to the industrial scale is limited. At the laboratory scale, production of small amounts of well-controlled model systems continues to be desirable for specific purposes, such as modeling-oriented experiments. Thus, from the laboratory to industrial application, there is growing interest in complementary or alternative fabrication routes for ODS steels and related model systems, which offer a different balance of cost, convenience, properties, and scalability

CO2 Diffusion Inside Photosynthetic Organs

In the present chapter, we review the current state-of-the-art of knowledge on mesophyll (internal) CO2 diffusion conductance of photosynthetic tissues (for simplification, gm). We show that, despite concerns regarding the methodological approaches currently used for its estimation, a large and consistent body of evidence has accumulated showing that gm is finite and significantly limiting for photosynthesis, as well as being highly variable among photosynthetic organisms and in response to environmental changes. Part of this variation results from different anatomies of the photosynthetic tissues, with a particularly strong influence of chloroplast distribution and cell wall thickness. Besides these, it appears that a biochemical modulation of gm also occurs, likely involving aquaporins and, possibly, carbonic anhydrases and other metabolic components.Further efforts are needed in the near future to improve CO2 diffusion models, both for the estimation of gm and for the precise physiological understanding of the CO2 assimilation process in different plants, as well as to increase our knowledge of the mechanistic base for gm and its regulation