Considerable changes have occurred in metal forming in the last decade. A record of these changes can be found in keynote papers presented by the members of the Scientific Technical Committee—Forming, at the CIRP Annual General Meeting each year. The keynote papers are excellent references on important developments in metal forming and are used as a reference, globally. Not only is this paper a compendium of most of the keynotes presented, but from 2001 onward, it has updates on new information on five keynote subject areas. The authors of each keynote have written an update with new information that has developed since the writing of the keynote. The authors of each section are shown in order of presentation.

Metal forming progress since 2000

Single point incremental forming: An assessment of the progress and technology trends from 2005 to 2015

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments.

Single point incremental forming: state-of-the-art and prospects

Incremental sheet forming (ISF) is an emerging metal-forming technology in which the tool motion is controlled numerically. The process is economical to form complex parts in small to medium batches and provides a short and inexpensive way of forming products having a relatively simple but interesting shape. In this article, a review of the present state-of-the-art technologies and the potential applications of incremental sheet metal forming are presented in brief. This article seeks to address the approaches and methods that are prevalently applied. Furthermore, the article also seeks to guide researchers for future work, by identifying inadequacies of the current approaches and potential for valuable contributions in the field of incremental forming.

Research and Progress in Incremental Sheet Forming Processes

Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the yield locus of DC06 steel, based on a biaxial tensile test on a perforated cruciform specimen. The hardening behavior is described by a Swift type hardening law and the yield locus is modeled with a Hill 1948 yield surface.

Identification of Mechanical Material Behavior Through Inverse Modeling and DIC

A five stage forming strategy for Single Point Incremental Forming of a circular cylindrical cup with a height/radius ratio of one is presented. Geometrical relations are discussed and theoretical strains are calculated. The influence of forming direction (upwards or downwards) is investigated for the second stage comparing explicit FE analysis with experiments. Good agreement is found between calculated and measured thickness distribution, overall geometry and strains. Using the proposed multi stage strategy it is shown possible to produce a cup with a height close to the radius and sides parallel to the symmetry axis in about half of the depth.

Multi Stage Strategies for Single Point Incremental Forming of a Cup

A novel feedback control system – Controlling the material flow in deep drawing using distributed blank-holder force

Experimental verification of a deep drawing tool system for adaptive blank holder pressure distribution

Full and partial penetration welding using high power lasers exhibit different melt pool geometries. The main difference is that full penetration welds tend to widen at the root side. In recent years, full penetration laser welding has been modeled using sophisticated multiphase numerical models. However, less computationally-complex thermo-mechanical models that are capable of accounting for the root widening phenomenon in full penetration laser welding are lacking. In this study, hybrid laser welding was performed for full and partial penetration modes on butt joints of structural steel. A numerical model was presented that used a three-dimensional transient Finite Element (FE) analysis and thermal conduction heat transfer for calculating the temperature fields in both full and partial penetration welding modes. For this purpose, a double-conical volumetric heat source was developed based on the three-dimensional conical (TDC) heat source in the literature. The model was validated and calibrated with different experiments. The results show that the model is capable of calculating the transient temperatures for the common melt pool geometries obtainable by the full and partial penetration hybrid laser welding of thick-section steels. The model can potentially be employed as the basis for predicting e.g. microstructural properties or residual stresses for a given welding procedure.

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Benny Ørtoft Endelt

Papers

Multi Stage Strategies for Single Point Incremental Forming of a Cup

A novel feedback control system – Controlling the material flow in deep drawing using distributed blank-holder force

Experimental verification of a deep drawing tool system for adaptive blank holder pressure distribution

A numerical model for full and partial penetration hybrid laser welding of thick-section steels

New framework for on-line feedback control of a deep-drawing operation