Wavelet-like analysis in the frequency-damping domain for modal parameters identification

Modal analysis and parametric model identification play a fundamental role in many fields, especially for the optimization and vibration control of civil structures and complex mechanical systems. In the last decades these techniques have been frequently applied for the development of innovative cutting tools and CNC machine tools. Although several methodologies are available in literature for parametric model identification, there is still a lack of an effective and robust algorithm. In this paper a new algorithm for automatic identification of a parametric model of a linear dynamic Single Input Single Output system with Multiple Degrees of Freedom is presented. Some recent approaches perform the Wavelet decomposition of the Impulse Response in the time-frequency domain. Here a Wavelet-like decomposition of the Frequency Response in the frequency-damping domain is introduced for vibration modes recognition. Afterwards, advanced statistical approaches are applied for vibration modes selection and model generation. The method was successfully tested on a complicated frequency response characterized by several vibration modes, which was obtained from experimental modal analysis performed on a circular saw blade

Divergence, at what cost?

The EU-UK Trade and Cooperation Agreement is a free trade agreement like no other: the first between parties negotiating from a position of regulatory convergence; the first trade deal in which the EU has accepted the principle of no tariffs and no quotas, but also the first trade deal which not only incorporates provisions that can broaden and deepen the Agreement’s scope, but also narrow it. However, at what cost are the parties willing to increase divergence, asks Totis Kotsonis (Pinsent Masons LLP)

Development of a universal, machine tool independent dynamometer for accurate cutting force estimation in milling

When integrating a dynamometer into a machining system, it is necessary to identify the dynamic relationship between the effective input forces and the measured output signals (i.e., its transmissibility) through dedicated experimental modal analysis. Subsequently, a filter can be derived and applied to reconstruct the effective input forces from the measured signals. Unfortunately this identification phase can be complex, posing challenges to the device's applicability in both laboratory and industrial conditions. Here this challenge is addressed by introducing a novel dynamometer concept based on both load cells and accelerometers, along with a Universal Inverse Filter. Notably, this filter is independent of the dynamic behavior of the mechanical system where the device is installed. A single calibration suffices, ideally conducted by the device manufacturer or by an expert, allowing the dynamometer's integration by a non-expert user into any machining system without the need for repeating the identification phase and the filter generation. Furthermore, this new concept offers another significant advantage: it attenuates all inertial disturbances affecting the measured signals, including those arising from the cutting process and those originating from exogenous sources such as spindle rotation, linear axes’ movements, and other vibrations propagating through the machine tool structure. To illustrate, a simplified model is introduced initially, followed by an overview of the novel dynamometer design, innovative identification phase, and filter construction algorithm. The outstanding performance of the novel (non-parametric) Universal Inverse Filter – about 5 kHz of usable frequency bandwidth along direct directions and 4.5 kHz along cross dir. – was experimentally assessed through modal analysis and actual cutting tests, compared against state of the art filters. The efficacy of the new filter, which is even simpler than its predecessors, was successfully demonstrated for both commercial and taylor-made dynamometers, thus showing its great versatility

Influence of the Experimental Setup on the Damping Properties of SLM Lattice Structures

Background: Metal lattice structures obtained through Selective Laser Melting may increase the strength-to-weight ratio of advanced 3D printed parts, as well as their damping properties. Recent experimental results showed that AlSi10Mg and AISI 316L lattices are characterized by higher Rayleigh damping coefficients with respect to the fully dense material. However, some unclear or contradictory results were found, depending on the experimental setup adopted for modal analysis. Objective: In this work the influence of the experimental setup when performing modal analysis on different SLM AISI 316L lattice structures was deeply investigated. The study provides a critical comparison of various experimental modal analysis approaches, allowing to evaluate the influence of external damping sources and material internal damping phenomena. Methods: The dynamic behaviour of SLM AISI 316L specimens incorporating lattice structures was estimated by means of pulse testing and sinusoidal excitation through an electromagnetic shaker. The validity of the viscous damping model was assessed by means of sinusoidal excitation with different levels of vibration velocity. Moreover, the influence of experimental setup on modal analysis results was critically evaluated, by considering different actuators, contact and non-contact sensors and boundary/clamping conditions. Results: The classical viscous damping model describes with good approximation the damping properties of SLM lattice structures. When exciting single specimens in free-free conditions, those embedding lattice structure and unmelted metal powder filler were characterized by superior internal damping properties with respect to the specimens incorporating the lattice structure without any filler, which was however more effective than the full density equivalent material. Most of the other experimental setups introduced additional external damping sources, that could alter this important outcome. Conclusions: SLM lattice structures embedded into 3D printed components provide superior damping properties against mechanical and acoustic vibrations and the metal powder filler does significantly enhance such damping capacity. A correct estimation of material internal damping was achieved by applying non-contact sensors and free-free boundary conditions, whereas other experimental setups were partly inadequate

Upgraded Kalman filtering of cutting forces in milling

Advanced piezoelectric dynamometers with a wide frequency bandwidth are required for cutting force measurement in high-speed milling and micromilling applications. In many applications, the signal bandwidth is limited by the dynamic response of the mechanical system, thus compensation techniques are necessary. The most effective compensation techniques for a full 3D force correction require an accurate and complex identification phase. Extended Kalman filtering is a better alternative for input force estimation in the presence of unknown dynamic disturbances. The maximum bandwidth that can be currently achievable by Kalman filtering is approximately 2 kHz, due to crosstalk disturbances and complex dynamometer\u2019s dynamics. In this work, a novel upgraded Kalman filter based on a more general model of dynamometer dynamics is conceived, by also taking into account the influence of the force application point. By so doing, it was possible to extend the frequency bandwidth of the device up to more than 5 kHz along the main directions and up to more than 3 kHz along the transverse directions, outperforming state-of-the-art methods based on Kalman filtering

Utjecaj skladištenja plodova masline u vrećama na kakvoću ulja i sastav hlapljivih sastojaka

The composition of olive oil volatile components depends on genetic factors, ripening grade of the fruit, fruit storage and processing conditions. Storage of olives in reticular or plastic bags is still a frequently used practice that has negative effects on oil quality, particularly on sensory characteristics. The changes of volatile compounds during this procedure were determined using headspace solid phase microextraction (HS-SPME). The method was optimised as regards sample conditioning and extraction time, and verified by testing the repeatability and linearity of the response. The main changes during fruit storage in bags are increase of methanol and ethanol concentration and decrease of 1-penten-3-one, trans-2-hexenal and cis-3-hexenyl acetate concentration. The changes in plastic bags are more evident and significant differences between the two types of storage are established.Sastav hlapljivih sastojaka maslinovog ulja ovisi o genetičkim faktorima, stupnju zrelosti plodova i njihovu skladištenju te uvjetima preradbe. Još uvijek se često primjenjuje skladištenje maslina u mrežastim ili plastičnim vrećama, što negativno utječe na kakvoću ulja, osobito na senzorska svojstva. Promjene hlapljivih sastojaka tijekom ovoga postupka utvrđene su primjenom mikroekstrakcije na čvrstoj fazi u natprostoru (HS-SPME). Metoda je optimirana s obzirom na kondicioniranje uzorka i vrijeme ekstrakcije, te provjerena utvrđivanjem ponovljivosti i linearnosti odgovora. Glavne su promjene tijekom skladištenja plodova u vrećama povećanje koncentracije metanola i etanola, te smanjenje koncentracije 1-penten-3-ona, trans-2-heksenala te cis-3-heksenil acetata. Promjene u plastičnim vrećama više su izražene, a uočene su i bitne razlike između dvaju načina skladištenja

Effects of different cross-sections of Body Centered Cubic cells on pressure drop and heat transfer of additively manufactured heat sinks

In many industrial applications, heat loads management requires the design and production of compact heat exchangers which are expected to handle high thermal loads with acceptable pressure losses, while assuring good mechanical performances. These challenging targets can be achieved by filling the cavities where the cool/hot fluid circulates with lattice structures promoting the heat exchange between the fluid and the cavity boundaries. Such lattice structures can be only produced through Additive Manufacturing due to their high geometric complexity. Recent experimental investigations proved the effectiveness of some kinds of lattice structures having a circular cross section. Here the aerothermal behaviour of Body-Centred Cubic (BCC) lattice stagger arrays in a rectangular channel was experimentally investigated by considerably extending the previous studies to higher Reynolds numbers (up to 30′000) and to new types of lattice structures. Specifically, three new BCC structures having a cam-like, drop-like and elliptical cross section were explored in this work and compared against those having circular cross section. All the samples were manufactured by means of Laser Powder Bed Fusion and made from AlSi10Mg. At first, the heat exchangers were comprehensively characterized by means of optical non-destructive methods. Successively they were tested in a dedicated rig by imposing constant heat flux boundary conditions. The characteristics of the transitional or fully turbulent approaching flow to the test section are also reported thanks to dedicated flow field measurements performed by Particle Image Velocimetry. According to the obtained results, the BCC structure with the circular cross section of larger diameter is the most effective in terms of heat transfer, although it is largely penalized by the pressure losses. Similar heat transfer performances were achieved by the tapered cross section of elliptical shape with the advantage of a considerably lower friction factor. Pressure losses resulted almost identical for all the tapered cross sections but lower than those of the circular one having an equal frontal dimension. When considering the thermal performance factor the circular shape becomes unfavourable for Re>20′000, while the elliptical cross section is the best choice to efficiently promote heat transfer up to Re=30′000

State aid and Brexit: the temptation for political intervention

State aid is currently regulated by the EU and, after Brexit, the government intends to transpose the rules into UK legislation, with the Competitions and Markets Authority overseeing the issue. Totis Kotsonis (Eversheds Sutherland) explains why future governments could be tempted to allow political intervention that EU membership precludes

The immunogenic potential of carbon ions and the involved mechanisms in tumor cells

Triple-negative breast cancer and osteosarcoma are aggressive, highly metastatic, and radioresistant tumors that require innovative therapeutic approaches to improve clinical outcomes. Radiotherapy is a cornerstone of cancer treatment, used in nearly half of all cancer patients. The immunogenic signals elicited by X-ray exposure in cancer cells are relatively well-documented and form the basis for combined radiotherapy and immunotherapy approaches. Radiotherapy with charged particles, particularly carbon ions, hold promise for overcoming radioresistance due to the prevalence of direct DNA damage and the reduced dependency on oxygen, while at the same time sparing the healthy tissues to a higher extent. The impact of carbon ions on the immunogenicity of cancer cells is understudied but represents an important area of research for combinations of charged particle therapy with immunotherapy for radioresistant cancers in advanced stages. This work addresses the limited knowledge of the immunogenic potential of carbon ions analyzing immunogenic molecules and mechanisms activated in murine triple-negative breast cancer (4T1 cells) and osteosarcoma (LM8 cells). For most of the endpoints, different doses and time points were analyzed and the results of carbon ions were compared to X-rays. The results highlighted that carbon ion irradiation effectively overcomes the radioresistance of both cell lines. In LM8 cells with a functional p53 protein, carbon ions induce more effectively regulated cell death than X-rays. In contrast, in 4T1 cells with a non-functional p53, radiation predominantly triggers mitotic catastrophe, which can delay radiation-induced cell death (in the form of apoptosis, ferroptosis, or necroptosis). Irradiation of both cell lines with carbon ions also results in an enhanced or similar release of immunostimulatory molecules, such as cytokines and chemokines, compared to X-rays. In particular, the in vitro mechanisms underlying the higher efficiency of carbon ions compared to X-rays in reducing lung metastasis in an in vivo osteosarcoma model (Helm et al., 2021) were investigated. This work revealed a higher induction of adjuvant molecules after irradiation with carbon ions of osteosarcoma cells, in the form of damage-associated molecular patterns (DAMPs), cytokines, and chemokines compared to X-rays. Moreover, the occurrence of cytoplasmic dsDNA and the activation of the cGAS-STING pathway, which results in immunostimulatory interferon-β release, were analyzed in triple-negative breast cancer cells based on the results of Vanpouille-Box and colleagues (Vanpouille-Box et al., 2017). The results indicate that the occurrence of cytoplasmic dsDNA is correlated with the features of mitotic catastrophe observed in 4T1 cells and that carbon ions induce more efficiently cytoplasmic dsDNA and interferon-β release than X-rays. The influence of a fractionated irradiation scheme with X-rays was also investigated with respect to the cGAS-STING pathway and the release of interferon-β. The higher immunogenicity of a 3x8 Gy over a single high dose demonstrated by Vanpouille-Box and colleagues (Vanpouille-Box et al., 2017) could not be reproduced in this work. This points to other effects besides the immunogenic signals released by cancer cells (e.g. on the tumor microenvironment or adjacent tissues) that can additionally explain the advantages of fractionation observed in vivo (Vanpouille-Box et al., 2017). One of the factors inducing radioresistance is intratumoral hypoxia, which is present in some solid tumors including osteosarcoma. Carbon ions, having a more direct effect on the target molecule (DNA), have the potential to reduce radioresistance but the data on their immunogenicity in reduced oxygen concentrations are limited. Therefore, the interplay between hypoxia, the linear energy transfer of the particle, and immunogenic cell death was additionally investigated in this study. The results indicate that the enhanced immunogenic potential of carbon ions may be limited by reduced oxygen levels and that increasing the linear energy transfer may not trigger a higher level of immunogenic signals. Overall, this study integrates data on damage-associated molecular patterns, immune ligands, cytokines, and chemokine release, indicating a higher or similar immunogenicity of carbon ions compared to X-rays. These findings highlight that carbon ion radiotherapy is a powerful modality for potentially overcoming the limitations of conventional radiotherapy and its combination with immunotherapies can be an asset, particularly for the treatment of advanced and radioresistant tumors