Process and machine system development for the forming of miniature/micro sheet metal products

This paper reports on the current development of the process for the forming of thin sheet-metal micro-parts (t < 50µm) and the corresponding machine system which is part of the research and technological development of an EU funded integrated project - MASMICRO ("Integration of Manufacturing Systems for the Mass-Manufacture of Miniature/Micro-Products" (/www.masmicro.net/). The process development started with qualification of the fundamentals related to the forming of thin sheet-metals in industrial environment, for which a testing machine and several sets of the testing tools were developed. The process was further optimised, followed by new tool designs. Based on the experience gained during the process development, a new forming press which is suitable for industrial, mass-customised production, has been designed

Electromagnetic Forming of Longitudinal Strengthening Ribs in Roll Formed Automotive Profiles

In the automotive industry, increasing ecological concerns and demands for higher performance have become lightweight construction a key aspect. Due to the gradual introduction of high strength materials on the one side, and greater consideration with regard to continuous manufacturing technologies on the other side, it is possible nowadays to address the demands that structural and complex automotive parts have to face, from the standpoint of lightweight manufacturing. Thickness, shape and impact conditions constitute the main aspects to consider for such parts and shape conditions in particular require from complex, costly and lengthy procedures, especially when discontinuous forming operations such as stamping and hydro forming procedures are selected. However, continuous forming operations like Roll Forming (RF) can prove to be advantageous and suited for scalable parts (e.g in length) and at the same time be economically reasonable. RF lines as well generally incorporate additional installations to perform multiple forming operations destined to imprint strengthening ribs perform punching operations or weld certain parts. It is in this context where the usefulness of the electromagnetic forming technology for completion of auxiliary operations can be proven, given its flexibility and reasonable investment costs. Electromagnetic forming (EMF) is a contact-free technique where large forces can be imparted to a conductive metallic workpiece by a pure electromagnetic interaction. The produced electromagnetic pressure can produce stresses in the workpiece that are several times larger than the material flow stress. Ultimately this can cause the workpiece to deform plastically and to be accelerated achieving high velocities. Once the velocity is imparted to the workpiece, the shape can be developed either by free or die forming. The work described in this paper explores the potential of the EMF process to adequately form shallow longitudinal ribs or stiffeners in components previously formed utilizing an innovative concept called Flexible Roll Forming, developed at The Technical University of Darmstadt in Germany, by means of magnetic pulse forming, maintaining the integrity of the workpiece while trying to meet industry standard tolerances. Profiles exhibiting hat-like cross sections made of AHSS steels were subjected to localized impulses in order to achieve strengthening features in the roll formed part. ZStE340 steel alloy profiles were first roll formed and then inserted in the EM forming installation designed for the occasion. A high strength copper alloy (Cr-Zr-Cu) was used as a conductor for the single turn coil, placed opposite to the sidewall in the moment of the energy delivery. Formed specimens were subsequently measured to account for existing dimensional deviations

Study of Useful Life of Dry-Type WTSU Transformers

Dry-type transformers are rapidly becoming popular as wind turbine step-up (WTSU) transformers, especially in offshore wind farms. Cast resin transformers are not flammable and are also resistant to moisture. However, their thermalelectrical degradation must be carefully analysed given the special conditions of wind farm installations. The present paper studies the remaining useful life (RUL) calculation of dry-type WTSU transformers based on the most thermally stressed location i.e. the winding hot-spot. The estimation of the loss of life of the transformer can be used for diagnostic and prognostic monitoring purposes in the framework of digital twins. The methodology is then applied to a typical WTSU load profile and the impact of several transformer characteristics and operating conditions are compared to the reference case.The authors gratefully acknowledge the support of the Basque Government (project ELKARTEK KK2018/00096 and GISEL research group IT1191-19), as well as of the University of the Basque Country UPV/EHU (research group funding GIU18/181)

Development of a new machine system for the forming of micro-sheet-products

Most of the developed micro-forming machines were based on standalone concepts which do not support efficient integration to make them fully automated and integrated. At present, material feeding in micro-forming is not of sufficient precision and reliability for high throughput manufacturing applications. Precise feeding is necessary to ensure that micro-parts can be produced with sufficient accuracy, especially in multi-stage forming, while high-speed feeding is a must to meet the production-rate requirements. Therefore, design of a new high-precision and high-speed feeder for micro-forming is proposed. Several possible approaches are examined with a view to establishing feasible concepts. Based on the investigation, several concepts for thin sheet-metal feeding for micro-forming are generated, they being argued and assessed with applicable loads and forces analysis. These form a basis of designing a new feeder

Analysis of loss of life of dry-type WTSU transformers in offshore wind farms

Currently, dry-type transformers are commonly installed as wind turbine step-up (WTSU) transformers, especially in offshore wind farms. Due to their low flammability and resistance to moisture, their performance is optimal in offshore platforms. Nonetheless, their thermal-electrical degradation must be carefully considered given the special wind and weather conditions in marine environments. The present paper studies the thermal aging of dry-type WTSU transformers in offshore wind farms considering the most thermally stressed location i.e. the winding hot-spot. The estimation of the transformer lifetime consumption introduced in this work can be applied in the framework of digital twins for diagnostic and prognostic monitoring purposes The thermal degradation study is based on a typical offshore load profile and includes the analysis of the impact of several transformer characteristics and operating conditions. As a result of the analysis, it can be concluded that lower temperature insulations, forced air cooling systems, a lower mean winding temperature rise and cool ambient temperatures lead to decreased loss of life values. Also, the present work suggests the suitability of considering thermal degradation studies as an optimal sizing factor for offshore WTSU given the low ambient temperatures in marine environment and the low capacity factors.The authors gratefully acknowledge the Support of the Basque Government (project ELKARTEK KK - 2018/00096 and GISEL research group IT1191-19), as well as of the University of the Basque Country UPV/EHU (research group unding GIU18/181)

Endogenous agendas and seniority advantage

We study a legislative assembly that chooses its agenda protocol endogenously. We generalize McKelvey and Riezman’s (1992) seminal theory on seniority in legislatures, by allowing for a large class of ordinal agenda rules that assign different recognition probability to each legislator. We consider two stages — the selection of agenda rules, and the decision making that transpires under them. We predict that the agenda rules chosen in equilibrium preserve seniority distinctions, disproportionately favor more senior legislators, and generate an incumbency advantage to all legislators.Governmen

Freshwater prawn research at SEAFDEC/AQD

The Philippines lags behind Thailand and Indonesia as far as research and commercial production of the freshwater prawn, Macrobrachium sp., are concerned. Although studies on Macrobrachium sp. (or ulang as it is locally known), started at the Binangonan Freshwater Station of SEAFDEC/AQD in the mid-1980’s, research efforts were discontinued soon thereafter because of a) inadequate technical skills; b) problems with larval rearing and the domestication of wild stocks; and among others, c) the Macrobrachium sp. being considered in the Philippines as a low priority species in contrast to commercially important freshwater commodities like tilapia and milkfish. This was two decades ago and in retrospect, had researches continued, the freshwater prawn in the Philippines could have been successfully domesticated and current problems concerning limited aquaculture production of genetically depauperate non-indigenous stocks could have been resolved. With the renewed interest in the culture of alternative species like the freshwater prawn, researchers at the Binangonan Freshwater Station started to conduct some studies on the refinement of breeding, larval rearing and culture of Macrobrachium rosenbergii in late 2003. These studies are briefly described here

Fault detection based on ROCOV in a multi-terminal HVDC grid

Protection of a meshed VSC-HVDC grid is a challenge due to the behaviour of DC current and voltage signals during fault conditions. Protection systems must operate in a very short time range. Since fault detection should be very fast, local measurement based algorithms are mostly used; communication based algorithms lack the needed speed as a result of the communication time delay. This way, a ROCOV algorithm is proposed in this paper. This algorithm is analysed for different fault conditions.The authors gratefully acknowledge the support from the Spanish Ministry of Economy, Industry and Competitiveness (project ENE2016-79145-R AEI/FEDER, UE), the Basque Government (GISEL research group IT1191-19), as well as from the University of the Basque Country UPV/EHU (research group funding GIU18/181)

Efficiency Improvement and Analysis of Changes in Microstructure Associated to a Uniform Pressure Actuator

During the 1st international Conference on HIGH SPEED FORMING held in Dortmund in 2004 a new forming coil giving significant advantages was presented in the framework of ongoing R&D programs at OSU (The Ohio State University). It established the improvement provided by the return path for currents induced in the workpiece. To quantify the mentioned improvement, Labein has performed classical cone forming experiments with both configurations and analyzed energetic efficiency using well known alloys, more precisely AA 6016 and 1050. Both deformation mechanisms and contour analysis of the specimens were studied. General purpose multi-turn coils provide pressure distributions not extended to the whole forming area, resulting in zones undergoing significant delay as die the deformation sequence is referred. As a result, varied deformation patterns can be found along the contour of a cone specimen formed in such way. Firstly, a macroscopic survey of the specimens shows that uniform pressure distributes deformation over the entire formed area during the deformation process. Secondly, the effect on efficiency provided by this new coil concept is focuses not only on the ability for distributing deformation, but on the energy required to create such deformation. Finally, to validate the whole simulation, the predicted strain level, shape, and internal energy of the workpiece are compared with the experimental specimens. A key point in the validation process is checking the internal energy. It is known that the ratio of stored energy to deformation energy ranges in the order of 30 %. The procedure for the experiments follows this methodology