ANSYS FE procedures and 3D models for thermal and mechanical simulation of both Laser and TIG welding processes are presented. The special features are the applicability to a non uniform gap and the ...use of a fast iterative procedure that assures the constancy of the fixed maximum temperature along the single pass and between each pass and the following, apart from their shapes and sizes. All the thermal and mechanical material properties of both INCONEL 625 and AISI 316 are described till to liquid phase; convection and radiation effects are considered. The 3D ANSYS models use both brick and non linear contact elements and elastic and elastic–plastic materials.
Two full simulation are presented: a laser welding test (taken from ENEA) and a TIG welding one (source W7-X) with the root seam plus 14 passes; thermal and mechanical results are reported in the two cases and for the latter an extensive sensitivity analysis, changing mesh size of the filling material, welding speed and material properties, is explained with results and comparisons. This large sensitivity analysis has been executed for TIG welding because in this case (multi-pass welding) the reduction of CPU time is a strong requirement; but some conclusions are helpful for laser welding too. The mechanical calculation results very sensitive to the mesh shape: this fact implies very fine and regular meshes. The specimens are first restrained and then welded with the foreseen welding procedure; after that it is released and the final linear and angular shrinkages are calculated. The ANSYS birth and death procedure is used and the CPU time was strongly reduced.
Display omitted
•A prototype experimental apparatus reusing CO2 to produce CH4 was assembled.•Experiments and simulations run to a better understanding of the reaction mechanism.•An alternative path ...to a gas-phase-only process to the reduction of CO2 to CH4 has been outlined.
Leveraging on the experience gained by designing and assembling a prototype experimental apparatus reusing CO2 to produce methane in a reaction with H2, we are developing an alternative innovative cost effective and contaminant resistant synthetic strategy based on the replacement of the solid phase catalysis with a homogeneous gas phase process going through the forming CO22+molecular dications.
Leveraging on the experience gained by designing and assembling a prototype experimental apparatus reusing CO2 to produce methane in a reaction with H2, we are developing an alternative innovative ...cost effective and contaminant resistant synthetic strategy based on the replacement of the solid phase catalysis with a homogeneous gas phase process going through the forming CO22+molecular dications.
An Imperative Pure Calculus Capriccioli, Andrea; Servetto, Marco; Zucca, Elena
Electronic notes in theoretical computer science,
04/2016, Volume:
322
Journal Article
Open access
We present a simple calculus where imperative features are modeled by just rewriting source code terms, rather than by modifying an auxiliary structure which mimics physical memory. Formally, this is ...achieved by the block construct, introducing local variable declarations, which also plays the role of store when such declarations have been evaluated. In this way, we obtain a language semantics which is more abstract, and directly represents at the syntactic level constraints on aliasing, allowing simpler reasoning about related properties. We illustrate this possibility by a simple extension of the standard type system which assigns a capsule tag to expressions that will reduce to (values representing) isolated portions of store.
PDF
