Investigation of chip formation of Ti–6Al–4V in oxygen-free atmosphere

Titanium and titanium alloys have high strength at low density, good corrosion resistance and excellent biocompatibility. Therefore, the use of titanium materials is well established in high-performance applications such as aerospace and biomedical. However, titanium and titanium alloys such as Ti–6Al–4 V have low thermal conductivity, exhibit unfavorable chip formation with typical segmented chips and have high chemical affinity to surrounding elements such as oxygen. Tool wear and the properties of the component surface and sub-surface are significantly influenced by the presence of oxygen and resulting chemical interactions. Among other things, chemical reactions such as oxidation occur due to the high temperatures and presence of oxygen. In this work, the chip formation of Ti–6Al–4 V at different cutting speeds in discontinuous orthogonal cutting process under different atmospheres is investigated. A conventional air atmosphere, a pure argon atmosphere and a silane-doped atmosphere were used. The oxygen content of the silane-doped argon atmosphere corresponds to an extremely high vacuum (XHV), which is practically oxygen-free. It was found that chip formation is affected by the surrounding atmosphere. At the cutting speed vc = 80 m/min, non-periodic segmentation is present under oxygen-free atmosphere, while segmental chip formation occurs under air. This is accompanied by up to 16.5% lower feed force under inert gas atmosphere, which is due to reduced friction caused by the use of an oxygen-free atmosphere

IT Project Portfolio Management Tools: Towards Taxonomy-based Archetypes

To achieve organizational goals and remain competitive, evaluating, selecting, and managing IT projects and proposals to build a value-driven portfolio is a critical activity. IT project portfolio management (ITPPM) tools assist these portfolio-related activities, support strategic decision-makers, and help complete more IT projects successfully. Despite existing research on this topic, knowledge about the characteristics and design elements of ITPPM tools is still limited. We develop a taxonomy based on scientific literature and 60 real-word ITPPM tools with four perspectives, 20 dimensions, and 51 characteristics. Subsequently, we perform a cluster analysis and identify five ITPPM tool archetypes. Our results and findings contribute to the knowledge base and integrate scientific and practical knowledge to build the basis for further research on ITPPM tools. Further, we structure the ITPPM tool market, guide practitioners in selecting an appropriate ITPPM tool and support the development of new solutions or develop existing ones further

IT Project Portfolio Management Tools: Towards Taxonomy-based Archetypes

To achieve organizational goals and remain competitive, evaluating, selecting, and managing IT projects and proposals to build a value-driven portfolio is a critical activity. IT project portfolio management (ITPPM) tools assist these portfolio-related activities, support strategic decision-makers, and help complete more IT projects successfully. Despite existing research on this topic, knowledge about the characteristics and design elements of ITPPM tools is still limited. We develop a taxonomy based on scientific literature and 60 real-word ITPPM tools with four perspectives, 20 dimensions, and 51 characteristics. Subsequently, we perform a cluster analysis and identify five ITPPM tool archetypes. Our results and findings contribute to the knowledge base and integrate scientific and practical knowledge to build the basis for further research on ITPPM tools. Further, we structure the ITPPM tool market, guide practitioners in selecting an appropriate ITPPM tool and support the development of new solutions or develop existing ones further

FEM-based simulation of continuous wear of CrAlN-coated tools

The understanding of the correlation between the coating-specific properties of PVD-coated cutting tools, the thermomechanical loads on the cutting wedge and the resulting tool wear, is necessary to avoid costly iterative test series. To obtain this knowledge a hybrid approach based on experimental tests and FEM-based chip formation is used in this study. In this respect, in a first step, a suitable wear rate model is derived and parameterized on the basis of wear analogy tests and experimental machining investigations. This wear rate model is then coupled with the FEM-based chip formation simulation to predict continuous tool wear

WEB SURVEY GAMIFICATION – INCREASING DATA QUALITY IN WEB SURVEYS BY USING GAME DESIGN ELEMENTS

Researchers and survey designers face the challenge of low data quality as web surveys are often not compelling. Thus, participants’ engagement declines while completing a survey resulting in participants tend to apply satisficing behavior (e.g., speeding, straight-lining) in order to complete the questionnaire or even break-off the completion of the questionnaire. Due to satisficing behavior, researchers are faced with the challenge of low data quality. Addressing this challenge, survey gamification promises to make web survey participation enjoyable, which might also engage participants to complete questionnaires by providing high-quality data. However, the research on the effects of gamifying web surveys (in particular on behavioral outcomes) is still inconclusive. Addressing this short-coming, we propose to examine the effects of two common game design elements – badges and a meaningful story – in an experimental study. Based on the theoretical background of gamification and the theory of cognitive absorption, we derive hypotheses and outline in detail our experimental design in this research-in-progress paper. Our proposed research study will contribute to research and practice by addressing an important challenge when conducting online surveys: the motivation to process surveys accurately

IT Project Portfolio Management Tools: Towards Taxonomy-based Archetypes

To achieve organizational goals and remain competitive, evaluating, selecting, and managing IT projects and proposals to build a value-driven portfolio is a critical activity. IT project portfolio management (ITPPM) tools assist these portfolio-related activities, support strategic decision-makers, and help complete more IT projects successfully. Despite existing research on this topic, knowledge about the characteristics and design elements of ITPPM tools is still limited. We develop a taxonomy based on scientific literature and 60 real-word ITPPM tools with four perspectives, 20 dimensions, and 51 characteristics. Subsequently, we perform a cluster analysis and identify five ITPPM tool archetypes. Our results and findings contribute to the knowledge base and integrate scientific and practical knowledge to build the basis for further research on ITPPM tools. Further, we structure the ITPPM tool market, guide practitioners in selecting an appropriate ITPPM tool and support the development of new solutions or develop existing ones further

Similarities in social calls during autumn swarming may facilitate interspecific communication between Myotis bat species

Bats employ a variety of social calls for communication purposes. However, for most species, social calls are far less studied than echolocation calls and their specific function often remains unclear. We investigated the function of in-flight social calls during autumn swarming in front of a large hibernaculum in Northern Germany, whose main inhabitants are two species of Myotis bats, Natterer’s bats (Myotis nattereri) and Daubenton’s bats (Myotis daubentonii). We recorded social calls in nights of high swarming activity and grouped the calls based on their spectro-temporal structure into ten types and verified our visual classification by a discriminant function analysis. Whenever possible, we subsequently assigned social calls to either M. daubentonii or M. nattereri by analyzing the echolocation calls surrounding them. As many bats echolocate at the same time during swarming, we did not analyze single echolocation calls but the “soundscape” surrounding each social call instead, encompassing not only spectral parameters but also the timbre (vocal “color”) of echolocation calls. Both species employ comparatively similar social call types in a swarming context, even though there are subtle differences in call parameters between species. To additionally gain information about the general function of social calls produced in a swarming context, we performed playback experiments with free-flying bats in the vicinity of the roost, using three different call types from both species, respectively. In three out of six treatments, bat activity (approximated as echolocation call rate) increased during and after stimulus presentation, indicating that bats inspected or approached the playback site. Using a camera trap, we were sometimes able to identify the species of approaching bats. Based on the photos taken during playbacks, we assume one call type to support interspecific communication while another call type works for intraspecific group cohesion

Exponential Modular Multilevel Converter for Low Voltage Applications

This paper presents the structure and control of a single phase Exponential Modular Multilevel Converter (EMMC), which works as a bidirectional AC/DC converter. In addition to the main H-bridge converter, it uses series connected H-bridges with DC link capacitors. The nominal voltage rating of the capacitors is increased with each module by factor of two. In this manner, the number of output voltage levels exponentially increases with the number of series connected H-bridges. By using low-voltage MOSFETs it is possible to achieve a very high efficiency, especially at partial loading. The high number of voltage levels reduces the output voltage THD, while using a low switching frequency. Thus, the required grid filter size can be substantially reduced. Furthermore, the additional capacitor modules increase the nominal output voltage at the AC side, so that the flow of the active and reactive power can be dynamically adjusted. Therefore, the EMMC could be used, for instance, as a vehicle charger directly connected to the grid