FE calculations on a three stage metal forming process of Sandvik Nanoflex

Sandvik NanoflexTM combines good corrosion resistance with high strength. This steel has good deformability in\ud austenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-induced\ud transformation into martensite takes place. After deformation, transformation continues as a result of internal stresses. Both\ud transformations are stress-state and temperature dependent. A constitutive model for this steel has been formulated, based\ud on the macroscopic material behaviour measured by inductive measurements. Both the stress-assisted and the strain-induced\ud transformation into martensite have been incorporated in this model. Path-dependent work hardening has also been taken\ud into account. This article describes how the model is implemented in an internal Philips FE code called CRYSTAL, which is\ud a dedicated robust and accurate finite element solver. The implementation is based on lookup tables in combination with\ud feed-forward neural networks. The radial return method is used to determine the material state during and after plastic\ud flow, however, it has been extended to cope with the stiff character of the partial differential equation that describes the\ud transformation behaviour

Iterative springback compensation of NUMISHEET benchmark #1

Upon unloading after the forming stage, a sheet metal product will spring back due to internal stresses. Springback\ud is a major problem for process-planning engineers. In industrial practise, deformations due to springback are compensated\ud manually, by doing extensive measurements on prototype parts, and altering the tool geometry by hand. This is a time\ud consuming and costly operation. In this paper the application of two compensation algorithms, based on the finite element\ud simulation of the forming process are discussed. The smooth displacement adjustment (SDA) method and the springforward\ud (SF) method have been applied to several industrial products, such as the NUMISHEET 2005 benchmark#1. With the SDA\ud method successful compensations have been carried out. For the SF method some principal problems remain

Preliminary investigation on homogenization of the thickness distribution in hole-flanging by SPIF

A drawback of the hole-flanging process by single-stage SPIF is the non-uniform thickness obtained along the flange. Multi-stage strategies have been used to improve it, however they increase notably the manufacturing time. This work presents a preliminary study of the tool paths for a hole-flanging process by SPIF in two stages. An intermediate geometry of the piece is proposed from the analysis of the thickness distribution observed in previous single-stage process. A simple optimization procedure is used to automate the intermediate part design, the NC code generation for the tool path and the validation of the optimal forming strategy by means of FEA

Strategies and limits in multi-stage single-point incremental forming

Abstract: Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufac-turing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large effect on the location of strain points in the principal strain space. Strain paths are linear in the first stage and highly non-linear in the subsequent forming stages. The overall results show that the experimentally determined FFLCs can successfully be employed to establish the forming limits of multi-stage SPIF

Numerical study on the thickness homogenization in hole-flanging by single-point incremental forming

Incremental sheet forming is a novel technology that has significant benefits compared to conventional forming. However, it is a time-consuming process that is usually carried out in several forming stages to homogenize deformation and avoid material failure. In hole-flanging operations by SPIF, a single-stage strategy might provide functional flanges in considerably less time, however a non-uniform thickness is obtained along the flange. This work proposes a two-stage process as the best strategy to increase production rate, and an optimization methodology to produce a homogeneous thickness distribution of the flange. The procedure is used to automate the design process of parts and tool trajectories by CAD/CAM, and validate the optimal forming strategy by FEAGobierno español DPI2015-64047-

The Lifetimes of Phases in High-Mass Star-Forming Regions

High-mass stars form within star clusters from dense, molecular regions, but is the process of cluster formation slow and hydrostatic or quick and dynamic? We link the physical properties of high-mass star-forming regions with their evolutionary stage in a systematic way, using Herschel and Spitzer data. In order to produce a robust estimate of the relative lifetimes of these regions, we compare the fraction of dense, molecular regions above a column density associated with high-mass star formation, N(H2) > 0.4-2.5 x 10^22 cm^-2, in the 'starless (no signature of stars > 10 Msun forming) and star-forming phases in a 2x2 degree region of the Galactic Plane centered at l=30deg. Of regions capable of forming high-mass stars on ~1 pc scales, the starless (or embedded beyond detection) phase occupies about 60-70% of the dense, molecular region lifetime and the star-forming phase occupies about 30-40%. These relative lifetimes are robust over a wide range of thresholds. We outline a method by which relative lifetimes can be anchored to absolute lifetimes from large-scale surveys of methanol masers and UCHII regions. A simplistic application of this method estimates the absolute lifetimes of the starless phase to be 0.2-1.7 Myr (about 0.6-4.1 fiducial cloud free-fall times) and the star-forming phase to be 0.1-0.7 Myr (about 0.4-2.4 free-fall times), but these are highly uncertain. This work uniquely investigates the star-forming nature of high-column density gas pixel-by-pixel and our results demonstrate that the majority of high-column density gas is in a starless or embedded phase.Comment: 10 pages, accepted to Ap

Numerical explicit analysis of hole flanging by single-stage incremental forming

The use of Single-Point Incremental Forming (SPIF) technology in hole flanging operations using multi-stages strategies have been widely studied in the last few years. However, these strategies are very time-consuming, limiting its industrial application.In a very recent work of the authors, the capability of SPIF process to successfully perform hole-flanges using a single-stage strategy has been experimentally investigated. The aim of the present work is to develop a numerical model of this process to beable to predict the sheet failure as a function of the size of the pre-cut hole. The numerical results are compared and discussed in the light of experimental tests over AA7075-O metal sheets with 1.6mm thickness.Ministerio de Economía y Competitividad DPI2015-64047-

Justification Of Conditioning Volitional Development Of Children\u27s Mastering Their Language Skills And Functions

The article analyzes the scientific approaches of domestic scientists to understanding the problem of will and the interrelated aspects of its development in ontogenesis. When studying ways of forming volitional behavior at its first stages, special attention is drawn to the fact that the child\u27s volitional behavior arises with the emergence of the skills to build speech utterances, with which he begins to plan his activities and regulate the process of its implementation, that is, the mastering of planning and regulating functions of speech takes place. By analyzing the ways of forming language skills in preschool and early school age, structures for creation a speech utterance, the author clarified the term "expression speech" (stages of its construction) and language skills, provided for the implementation of each stage of verbal expression. Also it is justified the condition of volitional development of children mastering their language skills and functions; relationship stages of planning and regulatory functions of broadcasting in preschool and early school age. The paper presents the author\u27s functional-structural model of the optimization process of development of the planning and regulatory functions in the formation of children\u27s speech in their language skills

Supernova Propagation And Cloud Enrichment: A new model for the origin of 60^{60}Fe in the early solar system

The radioactive isotope $^{60}$Fe ($T_{1/2} = 1.5$ Myr) was present in the early solar system. It is unlikely that it was injected directly into the nascent solar system by a single, nearby supernova. It is proposed instead that it was inherited during the molecular cloud stage from several supernovae belonging to previous episodes of star formation. The expected abundance of $^{60}$Fe in star forming regions is estimated taking into account the stochasticity of the star-forming process, and it is showed that many molecular clouds are expected to contain $^{60}$Fe (and possibly $^{26}$Al [$T_{1/2} = 0.74$ Myr]) at a level compatible with that of the nascent solar system. Therefore, no special explanation is needed to account for our solar system's formation.Comment: 15 pages, 3 figure