Process reliability and reproducibility of pneumomechanical and electrohydraulic forming processes

A sufficiently high process reliability and reproducibility is mandatory if a high-speed forming process is to be used in industrial production. A great deal of basic research work into pneumo-mechanical and electrohydraulic forming has been successfully performed in different institutions in the past. There, the focus has been more on process related correlations, such as the influence and interaction of different parameters on the course and result of those processes. The aspects of reliability and reproducibility have not been examined to a sufficient extent. Hence, in the case of pneumo-mechanical forming, insufficient investigations have been conducted into the effect that key parameters like the kinetic energy level, the filling height of the working media or the conditions inside the acceleration tube have on the reproducibility and course of the process. For electrohydraulic forming, the repeatability has worsened on occasions up to now. To improve the forming results and, in particular, the reputability of the process, it is necessary to examine the tool parameters associated with the electrodes and the working media. That is why research of this type is currently ongoing at the LUF. One important issue here is examining the options that exist for visualising the way the spark takes hold in the discharge chamber

Combined Working Media-Based Forming on a Pneumo-Mechanical High Speed Forming Machine

Quasi-static working media-based forming processes (WMF) permit the production of complex sheet metal parts with relatively little expense. The associated need for very high pressures and hence complex tools and machines for the production of fine geometrical details is often problematic. The use of high speed forming processes (HSF) can offer many benefits, including a reduced financial outlay on equipment and better part properties in this case. But these processes also have disadvantages, of course, such as if they are used for the production of complex large-surface parts. Consequently, a combination of both approaches would be ideal. This paper describes a new approach to combining high pressure sheet metal forming (HPF) and pneumo-mechanical HSF for the production of complex sheet metal parts

Исследование пневмомеханического высокоскоросного процесса

In the area of metal forming technology, the pneumomechanical high-speed-forming process is a promising approach for manufacturing of thin walled workpieces made of high strength materials. This process uses a pneumatic accelerated plunger that dives into a working media filled pressure chamber for the generation of a short pressure pulse. This pulse can be influenced, on the one hand, by evacuating the acceleration tube and as a consequence higher plunger energy and on the other hand by varying process parameters such as working media characteristics as e.g. density, oxygen content and type as well as the plunger geometry. The influence of these parameters on the process is subject of intense research work at the Chair of Forming and Machining Technology (LUF) at University of Paderborn. Recent results show that pneumomechanical and electrohydraulic forming allows for manufacturing of complex geometrical details in aluminum alloys that cannot be produced by conventional stamping processes. Due to the high homogeneity of the pressure distribution in the pressure chamber, it is possible to achieve high quality workpieces with low dimensional deviations. This paper presents the results of basic research conducted on pneumomechanical high-speed-forming as well as a comparison with electrohydraulic forming.В статье рассматриваются различия обработки листового металла в разных плотностях и видах рабочей среды. В работе было исследовано влияние изменения содержания кислорода в рабочей среде и различных геометрий плунжера на деформацию листового металла. Опытным путем была установлена возможность изготовления сложных геометрических деталей из алюминиевых сплавов с помощью пневмомеханической и электрогидравлической штамповки, обычными способами не производимые. Благодаря точной равномерности распределения давления в радиальном направлении, достигается незначительное геометрическое отклонение заданной формы заготовки. В данной работе представлены результаты фундаментальных исследований пневмомеханической штамповки в сравнение с электрогидравлической формовкой. Результаты исследований были использованы для достижения соответствующих процессов и разработки инструментов для пневмо-механической высокоскоростной штамповки

Исследования высокоскоростного пневмомеханического просесса по формовки сложно структурированых листовых и трубчатых компонентов

У зв'язку з суворими нормами викиду вуглекислового газу і економії ресурсів в автомобільній і аерокосмічній промисловості усе більш вирішальну роль грають полегшені конструкції. Таким чином, на сьогоднішній день необхідність виробництва конструкцій із складною геометрією з високоміцних матеріалів є високоактуальною. У цьому плані, неминуча розробка нових процесів для високоміцних матеріалів тих, що відповідають вищевикладеним вимогам. Процеси високошвидкісного формування показують більш високі показники відносно формування комплексних гострокрайових деталей і є важливим ключем до зниження ваги компонентів, при цьому відповідаючи високим вимогам викиду вуглекислового газу, а також сприяючи збереженню важливих природних ресурсів. Дослідження пневмомеханічного і електрогідравлічного процесу формування металу є важливим предметом інтенсивної дослідницької роботи кафедри формування і обробки технологій університету Падерборн. Для інтеграції вказаних процесів в промисловості, дуже важливе визначення впливу різних параметрів процесу на формування результату, який не лише сприяє оптимізації самого процесу, але і призводить до кращого розуміння явищ цих процесів. У статті розглядається вплив прискорення стислого повітря і рівня заповнення робочого середовища на формування деталей з листової і трубчастої геометрії. Досвідченим шляхом була встановлена можливість виготовлення складних гострокрайових і квадратоподібних геометричних деталей з алюмінієвих сплавів за допомогою пневмомеханічного штампування. Результати дослідження роблять явним факт ефективного впливу тиску стислого повітря і рівня заповнення камери тиску, що змінюється, на формування деталей. У цій роботі представлені результати ґрунтовних досліджень пневмомеханічного штампування в порівняння з конвенціональним гідроформінгом.Lightweight design is playing an increasing role in the automotive and aerospace industries due to the stringent emission regulations. Hence it is necessary to produce parts with complex geometries from sophisticated high-strength materials. In this context, and especially when high strength materials have to be formed into highly complex geometries, it is inevitable that new manufacturing processes will need to be developed which meet these requirements. High speed forming processes have a very high potential when it comes to shaping complex, sharp-edged parts and constitute a key means of reducing a component’s weight and hence of complying with the stringent emission regulations and also saving on essential resources. These processes and, in this case, pneumo-mechanical and electrohydraulic forming in particular, are a major subject of intense research at the University of Paderborn's Chair of Forming and Machining Technology (LUF). To be able to bring these processes into industrial use, it is necessary to identify the influence of different process parameters on the forming result. This will not only help to optimize the process itself, but will also lead to a better understanding of the process phenomena. This paper presents recent results relating to the influence of different process parameters, such as the acceleration pressure and the filling level of the working media, on the forming result of sharp-edged, sheet metal parts and square-formed tube geometries in aluminium using a pneumo-mechanical, high speed forming process. It is seen that the forming result can effectively be influenced by varying the acceleration pressure and the filling level. Furthermore, this paper presents the results of basic research conducted on pneumo-mechanical high speed forming and its comparison with conventional hydroforming.В связи со строгими нормами выброса углекислового газа и экономии ресурсов в автомобильной и аэрокосмической промышленности все более решающую роль играют облегченные конструкции. Таким образом, на сегоднишний день необходимость производства конструкций со сложной геометрией из высокопрочных материалов является высокоактуальным. В этом плане, неизбежна разработка новых процессов для высокопрочных материалов отвечающих вышепоставленым требованиям. Процессы высокоскоростной формовки показывают более высокие показатели относительно формирования комплексных острокраевых деталей и являются важным ключом к снижению веса компонентов, при этом соответствуя высоким требованиям выброса углекислового газа, а также способствуя сохраненю важных природных ресурсов. Исследования пневмомеханического и электрогидравлического процесса формовки металла является важным предметом интенсивной исследовательской работы кафедры формирования и обработки технологий университета Падерборн. Для интеграции указаных процессов в промышленности, очень важно определение влияния различных параметров процесса на формирование результата, который не только способствует оптимизации самого процесса, но и приводит к лучшему пониманию явлений этих процессов. В статье рассматривается влияние ускорения сжатого воздуха и уровня заполнения рабочей среды на формирование деталей из листовых и трубчатых геометрий. Опытным путем была установлена возможность изготовления сложных острокраевых и квадратнообразных геометрических деталей из алюминиевых сплавов при помощи пневмомеханической штамповки. Результаты исследования делают очевидным факт эффективного влияния изменяющегося давления сжатого воздуха и уровня заполнения камеры давления на формовку деталей. В данной работе представлены результаты основательных исследований пневмомеханической штамповки в сравнение с конвенциональным гидроформингом

Some aspects regarding the use of a pneumomechanical high speed forming process

A promising approach to the production of thin-walled workpieces in high strength materials is the use of a special pneumomechanical high-speed-forming process. This process uses a pneumatically accelerated plunger that dives into a pressure chamber filled with the working media in order to generate a short pressure pulse. Ways in which the pressure pulse can be influenced include e.g. varying the type of working media, the density of the working media, the accelerating pressure distance and the plunger geometry. The influence of these parameters on the process formed the subject of intense technological research at the Chair of Forming and Machining Technology (LUF) at Paderborn University. The results of these investigations were used to achieve an appropriate process and tool design for the pneumomechanical high-speed forming process. It thus proved possible to manufacture complex workpieces and geometrical details from thin-walled, high strength stainless steel or aluminium alloys that cannot be produced by conventional stamping processes. Because of the high uniformity of the pressure distribution in the radial direction, it is possible to achieve just small dimensional or geometrical deviations in respect of the desired shape of the workpiece. The planned paper will present results of the basic research conducted into pneumomechanical high-speed-forming as well as a comparison with electrohydraulic forming

A Distinct Layer of the Medulla Integrates Sky Compass Signals in the Brain of an Insect

Mass migration of desert locusts is a common phenomenon in North Africa and the Middle East but how these insects navigate is still poorly understood. Laboratory studies suggest that locusts are able to exploit the sky polarization pattern as a navigational cue. Like other insects locusts detect polarized light through a specialized dorsal rim area (DRA) of the eye. Polarization signals are transmitted through the optic lobe to the anterior optic tubercle (AOTu) and, finally, to the central complex in the brain. Whereas neurons of the AOTu integrate sky polarization and chromatic cues in a daytime dependent manner, the central complex holds a topographic representation of azimuthal directions suggesting a role as an internal sky compass. To understand further the integration of sky compass cues we studied polarization-sensitive (POL) neurons in the medulla that may be intercalated between DRA photoreceptors and AOTu neurons. Five types of POL-neuron were characterized and four of these in multiple recordings. All neurons had wide arborizations in medulla layer 4 and most, additionally, in the dorsal rim area of the medulla and in the accessory medulla, the presumed circadian clock. The neurons showed type-specific orientational tuning to zenithal polarized light and azimuth tuning to unpolarized green and UV light spots. In contrast to neurons of the AOTu, we found no evidence for color opponency and daytime dependent adjustment of sky compass signals. Therefore, medulla layer 4 is a distinct stage in the integration of sky compass signals that precedes the time-compensated integration of celestial cues in the AOTu

Factors Affecting the Clinical Measurement of Visuo-Spatial Neglect

The present study examined a battery of tests to evaluate unilateral spatial neglect; the tests included different tasks involving several modalities of spatial exploration mapping perceptual, motor, attentional and personal or extrapersonal space dimensions. The subjects, 121 right-brain-damaged patients with unilateral neglect, were studied in seven laboratories in four European countries. Relationships among the various tests were examined by correlations, a cluster analysis and by an analysis of individual cases. Different sensitivity was found among various tests for detecting neglect performances. Both the cluster analysis and the single case analysis clearly showed a segregation between personal and extrapersonal neglect. Analysis of the large cluster, including a variety of tests of extra personal neglect, together with the study of single cases, suggests the possibility of differentiating the various manifestations of spatial neglect which can be interpreted on the basis of the descriptions of other individual cases previously reported in the literature. Finally, the present study indicated the relative stability of neglect following the acute phase and its independence from age

Why We Can No Longer Ignore Consecutive Disasters

In recent decades, a striking number of countries have suffered from consecutive disasters: events whose impacts overlap both spatially and temporally, while recovery is still under way. The risk of consecutive disasters will increase due to growing exposure, the interconnectedness of human society, and the increased frequency and intensity of nontectonic hazard. This paper provides an overview of the different types of consecutive disasters, their causes, and impacts. The impacts can be distinctly different from disasters occurring in isolation (both spatially and temporally) from other disasters, noting that full isolation never occurs. We use existing empirical disaster databases to show the global probabilistic occurrence for selected hazard types. Current state‐of‐the art risk assessment models and their outputs do not allow for a thorough representation and analysis of consecutive disasters. This is mainly due to the many challenges that are introduced by addressing and combining hazards of different nature, and accounting for their interactions and dynamics. Disaster risk management needs to be more holistic and codesigned between researchers, policy makers, first responders, and companies

Competition-based model of pheromone component ratio detection in the moth

For some moth species, especially those closely interrelated and sympatric, recognizing a specific pheromone component concentration ratio is essential for males to successfully locate conspecific females. We propose and determine the properties of a minimalist competition-based feed-forward neuronal model capable of detecting a certain ratio of pheromone components independently of overall concentration. This model represents an elementary recognition unit for the ratio of binary mixtures which we propose is entirely contained in the macroglomerular complex (MGC) of the male moth. A set of such units, along with projection neurons (PNs), can provide the input to higher brain centres. We found that (1) accuracy is mainly achieved by maintaining a certain ratio of connection strengths between olfactory receptor neurons (ORN) and local neurons (LN), much less by properties of the interconnections between the competing LNs proper. An exception to this rule is that it is beneficial if connections between generalist LNs (i.e. excited by either pheromone component) and specialist LNs (i.e. excited by one component only) have the same strength as the reciprocal specialist to generalist connections. (2) successful ratio recognition is achieved using latency-to-first-spike in the LN populations which, in contrast to expectations with a population rate code, leads to a broadening of responses for higher overall concentrations consistent with experimental observations. (3) when longer durations of the competition between LNs were observed it did not lead to higher recognition accuracy