Induced Energy Dissipation Research Articles

Experimental study on energy dissipation characteristics of adiabatic shear evolution in high-speed machining of U75V steel

As one of the main characteristics in high-speed machining process, the adiabatic shear evolution induced energy dissipation influences the development of serrated chip and tool failure, which was further investigated experimentally in this work. Through the high-speed machining experiment of U75V rail steel by applying the cemented carbide insert, the development of chip morphology accompanying with the adiabatic shear evolution and tool failure with the cutting speed increasing were investigated microscopically. Based on the adiabatic shear saturation limit analysis, the energy dissipation theory was further proposed to evaluate the energy dissipation accumulation and energy dissipation rate of adiabatic shear evolution. The influences of energy dissipation characteristics related to physical and mechanical properties on the tool failure were revealed and discussed. It was concluded from the analysis of experimental results that the energy dissipation of adiabatic shear evolution from adiabatic shear banding to fracture, resulting in the thermal and mechanical coupling, mainly influenced the mechanisms of tool failure on the rake face. The occurrence of adiabatic shear fracture weakened the friction effect on the rake face. The energy dissipation theory of adiabatic shear evolution reasonably assessed the tool failure characteristics in high-speed machining process.

A numerical method for axisymmetric adhesive contact based on kalker’s variational principle

A numerical method for axisymmetric adhesive contact of elastic bodies is proposed. It allows computing the size of the contact spot, the force of interaction as well as the contact pressure distribution unrestricted to any particular form of the initial gap between the bodies. Therefore, compared to the existing analytical theories, it is a more versatile research tool that can be used to study such phenomena as adhesive strength of conjugate bodies and stability loss induced energy dissipation in oscillating contact. A variational principle that can be used to construct an approximate solution is proposed. The derived nonlinear equations of the discretized mini-max problem determine the unknown radius of the circular contact spot and the nodal values of the thought-for contact pressure. Unlike other numerical methods where contact domain is updated by subtracting or adding separate boundary elements of finite size, the proposed approach enables gradual continuous variation of the contact area. The arc-length method was implemented in the numerical routine in order to solve for the unstable sections of the adhesive interaction process. Besides the distance and force variables, the increment of the contact area is included in the control for the sake of convergence. The numerical error of the approximate method with respect to the known analytical solutions is evaluated. Linear convergence with mesh refinement in computed force and contact area is observed. Extension of the proposed approach for arbitrary three-dimensional shape of the contacting bodies is planned for the future. This is required to study the impact of the random surface roughness on their adhesive properties.

Thermal coupling effect on the vortex dynamics of superconducting thin films: time-dependent Ginzburg–Landau simulations

In this paper, vortex dynamics of superconducting thin films are numerically investigated by the generalized time-dependent Ginzburg–Landau (TDGL) theory. Interactions between vortex motion and the motion induced energy dissipation is considered by solving the coupled TDGL equation and the heat diffusion equation. It is found that thermal coupling has significant effects on the vortex dynamics of superconducting thin films. Branching in the vortex penetration path originates from the coupling between vortex motion and the motion induced energy dissipation. In addition, the environment temperature, the magnetic field ramp rate and the geometry of the superconducting film also greatly influence the vortex dynamic behaviors. Our results provide new insights into the dynamics of superconducting vortices, and give a mesoscopic understanding on the channeling and branching of vortex penetration paths during flux avalanches.

Experimental Generation of Focusing Wave Groups on Following and Adverse-Sheared Currents in a Wave-Current Flume

Focused waves are often used in physical and numerical studies as a representative condition for extreme waves or as a means to generate very steep and breaking waves at a prescribed location in space and time. They have also been combined with depth-varying currents in investigations of incipient wave breaking, wave breaking–induced energy dissipation, and wave–current induced loads on marine structures. A focused wave is created when all the components in a transient wave group come into phase. In the past, linear wave theory and iterative methodologies coupled with the linear Doppler-shifted dispersion relationship have been suggested to account for the presence of a current and achieve the required phase and amplitude focusing. In the majority of cases, linear or constant steepness spectra are used, which, compared to measured or theoretical spectra like the Joint North Sea Wave Project (JONSWAP), Gaussian, and Pierson-Moskowitz (PM) can be termed unrealistic. The effectiveness of these methodologies also decreases as the nonlinearity increases; therefore, in most studies, either weakly nonlinear conditions are used or the focus location is determined empirically. Here, an iterative methodology is suggested that can focus waves of any height at a predetermined temporal and spatial location even for wave groups propagating on a strong following or adverse current. An experimental apparatus developed to generate relatively stable sheared velocity profiles is also described. The depth-varying profile of the resulting currents diverges from that of classical wind-driven currents and comes closer to profiles measured in field sites important for the deployment of, for instance, tidal and wind energy converters. The methodology is successfully applied to wave groups traveling on still water, following, and adverse currents, and the results presented refer to linear, weakly nonlinear, and strongly nonlinear–focused waves generated for a range of realistic target spectra. The capability to generate wave groups with the same amplitude spectrum at a fixed location for a variety of flow conditions—still water, following, and adverse sheared currents—is also illustrated.

Impact of anticipation in dynamical systems.

Many animals, including humans, have predictive capabilities and, presumably, base their behavioral decisions-at least partially-upon an anticipated state of their environment. We explore a minimal version of this idea in the context of particles that interact according to a pairwise potential. Anticipation enters the picture by calculating the interparticle forces from linear extrapolations of the particle positions some time τ in the future. Simulations show that for intermediate values of τ, compared to a transient time scale defined by the potential and the initial conditions, the particles form rotating clusters in which the particles are arranged in a hexagonal pattern. Analysis of the system shows that anticipation induces energy dissipation and we show that the kinetic energy asymptotically decays as 1/t. Furthermore, we show that the angular momentum is not necessarily conserved for τ>0, and that asymmetries in the initial condition therefore can cause rotational movement. These results suggest that anticipation could play an important role in collective behavior, since it may induce pattern formation and stabilizes the dynamics of the system.

Design and Fabrication of a Tip‐Like ZnO Nanotube Array Structure with Condensate Microdrop Self‐Propelling Function

AbstractHere, we present a type of tip‐like nanotube array with condensate microdrop self‐propelling (CMDSP) function. Based on the basic principle that condensate microdrops can self‐remove via coalescence‐released weak surface energy as long as interface adhesion induced energy dissipation is sufficiently low, we design tip‐like nanotubes with extremely low solid–liquid interface adhesion. To verify the feasibility of this idea, we propose a strategy of preferential etching of six corners and the interior of ZnO nanopencils to achieve tip‐like nanotubes. Our studies demonstrate that this nanostructure can be achieved by immersing ZnO nanopencils in 0.006 m HCl aqueous solution at 80 °C for 3 h. After silane modification, the resulting nanostructure shows CMDSP function. This work offers a new avenue for developing CMDSP functional films, which can find a variety of technological applications such as moisture self‐cleaning, antifrosting and enhancing heat transfer.

The fetch effect on aeolian sediment transport on a sandy beach: a case study from Magilligan Strand, Northern Ireland

AbstractExperiments were conducted on Magilligan Strand, Northern Ireland, to assess the influence of the fetch effect on aeolian sediment transport. During each experiment surface sediments were uniformly dry and unhindered by vegetation or debris. The leading edge of erodible material was well defined, with the limit of wave up‐rush demarcating the wet–dry boundary; the work was conducted during low tides. A number of electronic and integrating traps were utilised, with two ultrasonic anemometers used to measure wind direction and velocity at 1 Hz. The combination of 1o direction data and trap locations resulted in a range of fetch distances, from 2 to 26 m. Data integrated over 15‐minute intervals (corresponding to the integrating trap data) revealed a distinct trend for all the experiments. An initial rapid increase in the transport rate occurred over a short distance (4–9 m). This maximum transport rate was maintained for a further 5–6 m before a steady decay in the flux followed, as fetch distance increased. A measured reduction in wind speed (6–8%) across the beach suggests a negative feedback mechanism may be responsible for the diminishing transport rate: the saltating grains induce energy dissipation, thus reducing the capability of the wind to maintain transport. For one experiment, the presence of compact sediment patches may also have contributed to the reduction of the transport rate. The decay trend calls into question the utility of the fetch effect as an important parameter in aeolian studies that seek to understand sediment budgets of the foredune‐beach zone. Copyright © 2016 John Wiley & Sons, Ltd.

Process Signatures of EDM and ECM Processes – Overview from Part Functionality and Surface Modification Point of View

The concept of Process Signatures, which aggregates information on material modifications caused by thermal, mechanical and chemical process-induced loadings, is a promising new strategy to achieve a knowledge-based solution of the so-called inverse surface integrity problem. This paper presents an overview on the projection of the above mentioned concept on selected research activities for state-of-the-art Electrical Discharge Machining (EDM) as well as Electrochemical Machining (ECM) technologies. Within the paper representative process application examples are used to briefly discuss the process induced energy dissipation and the resulting surface modifications. Similarities and differences due to the distinct active physical principle of material removal are analyzed. Finally, a methodology to enable a standardized comparison of material loadings and resulting surface integrity in future will be introduced.

Experiments and numerical simulations of nonlinear vibration responses of an assembly with friction joints – Application on a test structure named “Harmony”

In presence of friction, the frequency response function of a metallic assembly is strongly dependent on the excitation level. The local stick-slip behavior at the friction interfaces induces energy dissipation and local stiffness softening. These phenomena are studied both experimentally and numerically on a test structure named “Harmony”.Concerning the numerical part, a classical complete methodology from the finite element and friction modeling to the prediction of the nonlinear vibrational response is implemented. The well-known Harmonic Balance Method with a specific condensation process on the nonlinear frictional elements is achieved.Also, vibration experiments are performed to validate not only the finite element model of the test structure named “Harmony” at low excitation levels but also to investigate the nonlinear behavior of the system on several excitation levels. A scanning laser vibrometer is used to measure the nonlinear behavior and the local stick-slip movement near the contacts.

Sestrin2 inhibits uncoupling protein 1 expression through suppressing reactive oxygen species.

Uncoupling protein 1 (Ucp1), which is localized in the mitochondrial inner membrane of mammalian brown adipose tissue (BAT), generates heat by uncoupling oxidative phosphorylation. Upon cold exposure or nutritional abundance, sympathetic neurons stimulate BAT to express Ucp1 to induce energy dissipation and thermogenesis. Accordingly, increased Ucp1 expression reduces obesity in mice and is correlated with leanness in humans. Despite this significance, there is currently a limited understanding of how Ucp1 expression is physiologically regulated at the molecular level. Here, we describe the involvement of Sestrin2 and reactive oxygen species (ROS) in regulation of Ucp1 expression. Transgenic overexpression of Sestrin2 in adipose tissues inhibited both basal and cold-induced Ucp1 expression in interscapular BAT, culminating in decreased thermogenesis and increased fat accumulation. Endogenous Sestrin2 is also important for suppressing Ucp1 expression because BAT from Sestrin2(-/-) mice exhibited a highly elevated level of Ucp1 expression. The redox-inactive mutant of Sestrin2 was incapable of regulating Ucp1 expression, suggesting that Sestrin2 inhibits Ucp1 expression primarily through reducing ROS accumulation. Consistently, ROS-suppressing antioxidant chemicals, such as butylated hydroxyanisole and N-acetylcysteine, inhibited cold- or cAMP-induced Ucp1 expression as well. p38 MAPK, a signaling mediator required for cAMP-induced Ucp1 expression, was inhibited by either Sestrin2 overexpression or antioxidant treatments. Taken together, these results suggest that Sestrin2 and antioxidants inhibit Ucp1 expression through suppressing ROS-mediated p38 MAPK activation, implying a critical role of ROS in proper BAT metabolism.

Excited States of the Inactive and Active Forms of the Orange Carotenoid Protein

The orange carotenoid protein (OCP) is a crucial player in the process of nonphotochemical quenching in a large number of cyanobacteria. This water-soluble protein binds one pigment only, the keto carotenoid 3'-hydroxyechinenone, and needs to be photoactivated by strong (blue-green) light in order to induce energy dissipation within or from the phycobilisome, the main light harvesting system of these organisms. We performed transient-absorption spectroscopy on OCP samples frozen in the inactive and active forms at 77 K. By making use of target analysis we determined the excited state properties of the active form. Our results show that OCP photoactivation modifies the carotenoid excited state energy landscape. More specifically the photoactivated OCP is characterized by one state with predominantly ICT character (ICT/S1) and a lifetime of 2.3 ps, and another state with mainly S1 character (S1/ICT) with a lifetime of 7.6 ps. We also show that the kinetic model is fully consistent with the RT data obtained earlier (Berera et al., J. Phys. Chem. B 2012, 116, 2568-2574). We propose that this ICT/S1 state acts as the quencher in the OCP mediated nonphotochemical quenching.

Morphology and properties of the biosourced poly(lactic acid)/poly(ethylene oxide‐b‐amide‐12) blends

AbstractBiosourced poly(lactic acid) (PLA) blends with different content of poly(ethylene oxide‐b‐amide‐12) (PEBA) were prepared by melt compounding. The miscibility, phase structure, crystallization behavior, mechanical properties, and toughening mechanism were investigated. The blend was an immiscible system with the PEBA domains evenly dispersed in the PLA matrix. The PEBA component suppressed the nonisothermal melt crystallization of PLA. With the addition of PEBA, marked improvement in toughness of PLA was achieved. The maximum for elongation at break and impact strength of the blend reached the level of 346% and 60.5 kJ/m2, respectively. The phase morphology evolution in the PLA/PEBA blends after tensile and impact tests was investigated, and the corresponding toughening mechanism was discussed. It was found that the PLA matrix demonstrates obvious shear yielding in the blend during the tensile and impact tests, which induced energy dissipation and therefore lead to improvement in toughness of the PLA/PEBA blends. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers

Decoherence Window and Electron-Nuclear Cross Relaxation in the Molecular MagnetV15

Rabi oscillations in the V(15) single molecule magnet embedded in the surfactant (CH(3))(2)[CH(3)(CH(2))(16)CH(2)](2)N(+) have been studied at different microwave powers. An intense damping peak is observed when the Rabi frequency Ω(R) falls in the vicinity of the Larmor frequency of protons ω(N). The experiments are interpreted by a model showing that the damping (or Rabi) time τ(R) is directly associated with decoherence caused by electron-nuclear cross relaxation in the rotating reference frame. This decoherence induces energy dissipation in the range ω(N) - σ(e) < Ω(R) < ω(N), where σ(e) is the mean superhyperfine field induced by protons at V(15). Weaker decoherence without dissipation takes place outside this window. Specific estimations suggest that this rapid cross relaxation in a resonant microwave field, observed for the first time in V(15), should also take place, e.g., in Fe(8) and Mn(12).

Energy Dissipation in Nearly Saturated Poroviscoelastic Soil Columns during Quasi-Static Compressional Excitations

AbstractThis paper presents a theoretical investigation on the energy dissipation in a nearly saturated poroviscoelastic soil column under quasi-static compressional excitations. Different components of the energy dissipation are evaluated and compared. The magnitude of fluid- induced energy dissipation is primarily a function of a normalized excitation frequency Ω. For small values of Ω, a drained soil column is fully relaxed and essentially behaves as a dry column with negligible pore pressure. For such a soil column, fluid-induced energy dissipation is negligible, and the total damping ratio of the column is essentially the same as that of the solid skeleton. For very high values of Ω, a drained soil column is fully loaded and the excitation-generated pore pressure decreases as the fluid becomes more compressible. For such a soil column, the fluid pressure gradient only exists in a thin boundary layer near the drainage boundary, where drainage occurs and fluid induces energy dissipation, whereas the re...

Vortex nucleation induced phonon radiation from a moving electron bubble in superfluidH4e

We construct an efficient zero-temperature semi-local density functional to dynamically simulate an electron bubble passing through superfluid 4He under various pressures and electric fields up to nanosecond timescale. Our simulated drift velocity can be quantitatively compared to experiments particularly when pressure approaches zero. We find that the high-speed bubble experiences remarkable expansion and deformation before vortex nucleation occurs. Accompanied by vortex-ring shedding, drastic surface vibration is generated leading to intense phonon radiation into the liquid. The amount of energy dissipated by these phonons is found to be greater than the amount carried away solely by the vortex rings. These results may enrich our understanding about the vortex nucleation induced energy dissipation in this fascinating system.

Vibrations of microscale circular plates induced by ultra-fast lasers

In this study, the vibration phenomena during pulsed laser heating of a microscale circular plate are investigated. The circular plate is made of silicon and is heated uniformly on the upper surface by a non-Gaussian laser beam with a pulse duration of 2 ps, which incites vibration due to the thermoelastic coupling effect. The coupling between the temperature field and stress field induces energy dissipation and converts mechanical energy into heat energy, which is irreversible. An analytical–numerical technique based on the Laplace transform is utilized to calculate the vibration of the deflection and thermal moment. The size effect is analyzed. Finally, the vibration behaviors of the circular plate under different environmental temperatures are compared.

Laser-induced vibrations of micro-beams under different boundary conditions

In this study, the vibration phenomenon during pulsed laser heating of a micro-beam is investigated. The beam is made of silicon and is heated by a non-Gaussian laser beam with a pulse duration of 2 ps, which incites vibration due to the thermoelastic damping effect. The coupling between the temperature field and stress field induces energy dissipation and converts mechanical energy into heat energy, which is irreversible. An analytical–numerical technique based on the Laplace transform is used to calculate the vibration of the deflection and thermal moment. A general algorithm of the inverse Laplace transform is developed. The validation of this algorithm is obtained through comparison with numerical results obtained by the FEMLAB software package. The effect of laser pulse energy absorption depth is studied. The size effect and the effect of different boundary conditions are also analyzed. Finally, the damping ratio and resonant frequency shift ratio of beams due to the air damping effect and the thermoelastic damping effect are compared.

Characterization of PNA and DNA Immobilization and Subsequent Hybridization with DNA Using Acoustic-Shear-Wave Attenuation Measurements

We report here how the quartz crystal microbalance with dissipation monitoring (QCM-D) technique, simultaneously measuring changes in the induced energy dissipation, D (cf. viscoelastic properties), and the frequency, f (cf. coupled mass), can be used to characterize the bound state of single-stranded peptide nucleic acid (PNA) and deoxyribose nucleic acid (DNA) in relation to their ability to function as selective probe(s) for fully complementary and single-mismatch DNA. The possibility to use the QCM-D technique for detection of binding kinetics and structural differences in the formed duplexes is also presented. We found that thiol-PNA and thiol-DNA attached via a sulfur group directly on a bare-gold surface are less efficient as probes for DNA than are biotin-PNA and biotin-DNA, coupled on top of a two-dimensional (2-D) arrangement of streptavidin, formed on a biotinylated phospholipid bilayer on a SiO2 surface. The fully complementary and singly mismatched DNA oligomers hybridize with the immobilized PNA and DNA. A single mismatch is discriminated via a significant difference in the binding and dissociation kinetics, demonstrating a high selectivity and thus successful immobilization of functional single strands. The observed ratios between hybridization-induced energy dissipation (DeltaD) and the frequency shift (Deltaf) made it possible to discriminate thiol-PNA directly attached to a gold surface from biotin-PNA coupled to the streptavidin 2-D arrangement, where the former were shown to be inefficient for detecting subsequent hybridization. Structural differences of the immobilized layers composed of biotin-PNA-DNA and biotin-DNA-DNA were clearly reflected by the DeltaD and Deltaf response.

Uncoupling protein-2 (UCP2): molecular and genetic studies.

Thermogenesis is associated to oxygen consumption and cellular respiration. This process is coupled to adenosine-diphosphate (ADP) phosphorylation through the existence of a proton gradient across the inner mitochondrial membrane. It was postulated that proton leaks through this membrane would uncouple respiration from adenosine-triphosphate (ATP) synthesis and induce energy dissipation as heat. Such a mechanism was identified in thermogenic brown adipose tissue mitochondria which contain a unique proton carrier referred to as uncoupling protein (UCP). This UCP is activated by fatty acids and its synthesis is positively controlled by retinoids, thyroid hormones, catecholamines and rexinoids. In fact, in most types of cells, respiring mitochondria release heat and the coupling of substrate oxidation to ADP phosphorylation is under 100%. It suggested that the partial coupling of respiration to ADP phosphorylation was due to proton leaks possibly related to the brown fat UCP. This approach led to the identification of UCP2 and UCP3, two homologues of the brown fat UCP (renamed UCP1). UCP2 gene is widely expressed in tissues and cell types, whereas the UCP3 gene is dominantly expressed in skeletal muscles (and brown fat in mice). Recent genetic, biochemical and physiological studies suggest that these novel UCP2 contribute to resting metabolic rate, fat oxidation and may represent new targets for anti-obesity compounds.

Simultaneous frequency and dissipation factor QCM measurements of biomolecular adsorption and cell adhesion.

We have measured the energy dissipation of the quartz crystal microbalance (QCM), operating in the liquid phase, when mono- or multi-layers of biomolecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy dissipation are discussed. Three main contributions to the measured increase in energy dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy dissipation of the same magnitude as the measured ones.