Clamp Region Research Articles

Minimum loss modulation method for various power factor angles

In recent years, the energy crisis has prompted widespread attention to electric vehicles (EVs). As a core component of electric drive system in EV, motor controller has a significant impact on vehicle energy consumption. In such situation, this paper proposes a minimum loss modulation method for all power factors and reduces current THD by dead-band compensation. Firstly, the mechanism model of the controller is established for loss calculation, and the relationship between the clamping region and the current peak is analyzed based on the traditional modulation methods. Secondly, a discontinuous pulse width modulation considering power factor angle method (CPFA-DPWM) is proposed to ensure that clamping region always falls at the peak current at all power factors. Furthermore, the adoption of current vector method instead of direct sampling for current polarity determination effectively reduces judgment error and avoids false dead-band compensation. The effectiveness of the proposed method is verified by simulation and thermal measurement experiment. Under China Light-duty Vehicle Test Cycle (CLTC), the controller loss of CPFA-DPWM is reduced by 18.61 % compared to SVPWM.

Dynamic mechanical response and failure behavior of solid propellant under shock wave impact

Solid rocket motor propellants are typically subjected to shock wave loads during ignition. To analyze the dynamic mechanical response and failure behavior of hydroxyl-terminated polybutadiene (HTPB) propellant under varying shock intensities, this study innovatively employed a shock tube apparatus in conjunction with schlieren imaging and 3D-DIC techniques. Shock loading experiments were conducted on propellant samples of three different thicknesses under pressures ranging from 0.3 to 0.7 MPa, capturing the dynamic deformation processes. Results revealed that deformation initiated at the clamped region, extending towards the center and forming a parabolic shape. The maximum deformation of the samples shows an approximately linear relationship with the launch pressure and decreases with increasing sample thickness. The 5 mm sample failed under a 0.6 MPa shock pressure, with electron microscopy images identifying matrix damage, particle debonding, and particle fracture as the principal failure mechanisms. Finite element simulations based on the generalized Maxwell linear viscoelastic constitutive model were conducted, demonstrating good agreement with experimental data. The critical stress for fracture was determined to be 4.12 MPa, and the ultimate shock wave pressures for 3, 6, 9, and 12 mm thicknesses were approximately 0.3 MPa, 0.65 MPa, 1.1 MPa, and 1.4 MPa, respectively. These findings provide valuable insights for assessing the structural integrity of solid rocket motors under ignition shock conditions.

Analysis of multi-scale failure behavior of SiCf/SiC composite clad tube under flexible clamping damage

The intricate spatial fiber winding structure of SiCf/SiC ceramic matrix composite (CMC) cladding tubes makes it difficult to investigate in depth the inherent evolutionary mechanism of damage failure under specific operating conditions. Therefore, in this study, based on X-ray computed tomography (X-CT) reconstruction and cross scale numerical simulation methods, combined with clamping failure experiments under specific conditions for the cladding tubes, we conduct an in-depth analysis of the material's damage, failure, and mechanical behavior in different clamped regions. The research indicates that variations in the clamped regions have a minimal impact on the overall mechanical feedback of the material, and the maximum clamping load remains essentially around 500 N. The tube damage exhibits a unique " regional progressive damage evolution mechanism," where stress differentials of 108.49–115.33% appear between the inner and outer surfaces in different regions, leading to variations in the initiation and propagation of cracks within these areas. Furthermore, based on the minimum potential energy principle and semi-geodesic line theory, the intricate macroscopic tube structure formed by the spatial stacking and winding of SiCf/SiC cladding tube fibers is accurately reconstructed, which is combined with macroscale and microscale local feature models to capture the fibre/matrix morphology of the material with dynamic mechanical feedbacks, and experimentally validated in this work. The results indicate that the numerical model can effectively characterize the complex mechanical damage morphology and progressive failure lows of SiCf/SiC CMC at multiscale. Simultaneously, it is observed that stress concentrations in the fiber crossover region result in a load-bearing capacity 112–283% higher than in other areas. This phenomenon often leads to the first occurrence of failure in this region after clamping overload, exhibiting more pronounced damage characteristics.

Bistable hybrid symmetric laminates with a clamped-clamped boundary condition: An experimental and numerical investigation

In this work, a clamped-clamped boundary condition is considered for a family of bistable hybrid symmetric laminates in which the direction of curvature does not change during the snap-through process between the two stable configurations. The laminates were modeled using finite element analysis to predict the characteristics of stable configurations, including the distributions of curvatures and out-of-plane displacement in two directions, and then the results were validated by experiments. The snap-through behaviors of the bistable laminates under the clamped-clamped boundary condition were investigated numerically and experimentally and then compared with the preloaded laminates with the same boundary condition. The results showed that the bistable laminates require a lower snap-through load than the preloaded laminates when they have a similar maximum out-of-plane displacement. The loading position, lay-up design, and length of the clamped region were employed as variables to discover the features of snap-through behavior. It was found that the unsymmetric deformation mode was present regardless of the load position during the snap-through behavior of these bistable laminates. At last, a variable cross-section tube consisting of two bistable laminates was proposed, and the area of the cross-section could be increased by 80% after the snap-through of the two bistable laminates

Effect of fixture boundary conditions for low-velocity impact: A focus on composites with different matrix and fibers

It has been noted that the matrix may have a significant effect on the impact resistance of composite material. Replacing a brittle polymer with a more “flexible” one can improve the impact resistance of composite. However, composites with soft polymer as matrix may challenge the standard experimental methods for tests, such as the low-velocity impact. Due to the extremely large elastic deformation, a standard fixture can hardly grip the sample due to severe slip of the sample at the clamping region. To address this issue, a new fixture was designed and implemented for testing highly deformable composite laminates subjected to low-velocity impacts that can adequately clamp the sample with a set of ‘bolt teeth’. The new fixture, however, provides a different boundary condition. Therefore, an investigation on the effect of the fixture on the low-velocity impact of “soft” composite was performed. This work can help to understand the influence of different boundary conditions on the mechanical performance during the low-velocity impact tests. Thus, the current work was performed with epoxy-based composites, which can fit both standard and designed fixtures. The analysis was carried out on experimental results with different types of fibers (glass/aramid) as well as different energy levels for the two fixtures. Through analysis of the experimental data, it was found that a smaller permanent deformation, as well as a higher peak force, were obtained from specimens tested with the standard fixture, indicating a stiffer boundary condition, compared with the designed fixture for soft composites.

Dynamic modelling and quality factor evaluation of hemispherical shell resonators

A novel strategy is proposed for the dynamic modelling and quality factor evaluation of the hemispherical shell resonators (HSR) considering the coupling of hemispherical shell and support rod. The artificial spring technique is introduced to realize the coupling connection of substructures and simulate the arbitrary boundary conditions. Hamilton's principle with the Rayleigh-Ritz method is employed to establish the equation of motion of the HSR, and the natural frequencies of the HSR are obtained by solving the eigenvalue problem of the equation of motion. The thermal energy method is applied to evaluate the thermoelastic damping (TED) of the HSR. The model of anchor loss is based on a separation and transfer method, in which the HSR and its substrate are first separated for analysis and then the stress from the clamped region of the support rod is transferred to the substrate for determining the vibration displacement across the clamped region. The energy losses to the substrate are formulated as the integral of the product of the stress and the vibration displacement across the clamped region per cycle of vibration. The results calculated from the present theoretical method are compared with those from the published literature and the finite element method (FEM), which validates the correctness and feasibility of the present theoretical model. The effects of the boundary conditions and geometrical parameters on the vibration behaviors of the HSR are analyzed, and the influences of the boundary conditions, geometrical parameters and material properties of the HSR on the quality factors related to the TED and anchor loss are investigated. The present model can be used to optimize the design of the HSR with a high quality factor.

On the link between mechanics and thermal properties: mechanothermics

We report on the theoretical derivation of macroscopic thermal properties (specific heat, thermal conductivity) of an electrically insulating rod connected to two reservoirs, from the linear superposition of its mechanical mode Brownian motions. The calculation is performed for a weak thermal gradient, in the classical limit (high temperature). The development is kept basic as far as geometry and experimental conditions are concerned, enabling an almost fully analytic treatment. In the modeling, each of the modes is subject to a specific Langevin force, which enables to produce the required temperature profile along the rod. The theory is predictive: the temperature gradient (and therefore energy transport) is linked to motion amplitude cross-correlations between nearby mechanical modes. This arises because energy transport is actually mediated by mixing between the modal waves, and not by the modes themselves. This result can be tested on experiments, and shall extend the concepts underlying equipartition and fluctuation–dissipation theorems. The theory links intimately the macroscopic size of the clamping region where the mixing occurs to the microscopic lengthscale of the problem at hand: the phonon mean-free-path. This clamping region, which is key, has received recently a renewed attention in the field of nanomechanics with topical works on ‘phonon shields’ and ‘soft clamping’. We believe that our work should impact the domain of thermal transport in nanostructures, with future developments of the theory toward the quantum regime.

Nano-beam clamping revisited

Within recent years, the field of nano-mechanics has diversified in a variety of applications, ranging from quantum information processing to biological molecules recognition. Among the diversity of devices produced these days, the simplest (but versatile) element remains the doubly clamped beam: it can store very large tensile stresses (producing high resonance frequencies f0 and quality factors Q), is interfaceable with electric setups (by means of conductive layers), and can be produced easily in clean rooms (with scalable designs, including multiplexing). Besides, its mechanical properties are the simplest to describe. Resonance frequencies and Qs are being modeled, with as specific achievement the ultrahigh quality resonances based on “soft clamping” and “phonon shields.” Here, we demonstrate that the fabrication undercut of the clamping regions of basic nano-beams produces “natural soft clamping,” given for free. We present the analytic theory that enables to fit experimental data, which can be used for {Q,f0} design: beyond finite element modeling validation, the presented expressions provide a profound understanding of the phenomenon, with both Q enhancement and a downward frequency shift.

Numerical Investigation of Step Size Effect on Formability of 2024-T3 Aluminum in Incremental Forming

Incremental forming (IF) is an advanced manufacturing process in which a forming tool locally deforms sheet material into a desired geometry through successive passes at incremental depths. An inherent benefit to the IF process is its formability improvement over conventional stamping; however, further enhancements will enable the forming of increasingly complex geometries. To progress the IF process towards heavy industrial use, the modeling of such processes must be further developed. Single point incremental forming (SPIF) of AA2024-T3 was modeled herein utilizing explicit formulations. The model geometry featured a nominally rectangular-shaped clamping region. A friction factor was experimentally determined and utilized within the model, which is a novel addition to this work. Formability was determined and forming limit diagrams were composed. It was found that the present model shows greater formability and underestimates plastic strain compared to experimental testing. The generation of forming limit diagrams for this material processed by IF is also a novel addition to this field.

Lateral Transport During Membrane Permeation in Diffusion Cell: In Silico Study on Edge Effect and Membrane Blocking

Membrane transport in diffusion cell studies is not one-dimensional from the donor to the receptor. Lateral diffusion within the membrane into the surrounding clamped region can lead to edge effect. Lateral diffusion can also affect the impact of an object blocking the membrane in a diffusion cell. The effects of lateral transport on permeation across a two-layer membrane in diffusion cells were investigated in this study under edge effect and membrane blocking conditions that could be encountered in previous gingiva and hypothetical skin permeation studies. Model simulations of time-dependent and steady-state transport were performed using COMSOL Multiphysics. The simulations indicated edge effect could increase the steady-state flux across the membrane up to 35% with a relatively thick membrane and small diffusion cell opening (e.g., gingiva study). The edge effect decreased when the relative thickness and permeability of the major barrier (top layer in the two-layer membrane) decreased. When the membrane was partially blocked by an object, lateral diffusion within the membrane could mitigate its impact: e.g., when the object was in the receptor, the impact caused by membrane blocking was reduced more than half. Therefore, membrane lateral transport should be considered under certain circumstances in permeation studies using diffusion cells.

Performance Evaluation of SiC-Based Two-Level VSIs with Generalized Carrier-Based PWM Strategies in Motor Drive Applications

Currently, silicon carbide (SiC) MOSFETs are several times higher in cost than the equivalent silicon (Si)-IGBTs; however, the gains in power conversion efficiency, simplification of thermal management, and energy savings in general bring the advantages of lower total cost of ownership. The implementation of discontinuous PWM (DPWM) techniques for controlling the motor drive brings further reductions for the semiconductor switching losses; however, most existing techniques have limited performance on the optimized clamping region, particularly at a low power factor, which is a common operation condition for motor drives employing the widely used V/f control, particularly at partial- or low-load conditions. This paper evaluates the performance of a SiC-based two-level voltage-source inverter (2L-VSI) motor drive operated with generalized carrier-based PWM methods. Theoretical analysis and experimental measurements are conducted in a 2.2 kW heatsink-less 2L-VSI prototype and induction machine, which demonstrates that the minimum switching losses DPWM (MSL-DPWM) is the most favorable solution in practice in terms of the achievable power conversion efficiency and harmonic distortions and also produces the least common-mode current, which is critical in motor drives.

Tailoring structural inhomogeneities in Al90Sm10 metallic glass nanowire via torsional deformation

Structural evolution of Al90Sm10 metallic glass (MG) nanowire (NW) has been investigated in great details by employing Molecular dynamics to simulate the torsion deformation for varying torsion speed i.e., 1/360 revolution/ps, 1/600 revolution/ps and 1/900 revolution/ps. The structural evolution has been evaluated via employing certain techniques such as atomic strain and Voronoi Tessellation method. Shear transformation zones (STZs) nucleate homogenously near the vicinity of the clamped regions, grow and coalesce into the wide shear bands (SB) that grow along the interior of the NW specimen with increasing degree of rotation. The atomic strain gradient in the Al90Sm10 MG NW also varies radially. With increasing torsion speed the STZ nucleation become inhomogeneous and the width of SBs are constricted to narrow bands. The amelioration of Voronoi polyhedral (VPs) with increasing torsional angle possessing liquid like character such as Z13<0, 2, 8, 4>, Z13<0, 3, 6,4>, Z12<0, 2, 8, 2> encourages collective shear transformation and thereby enhancing plastic deformation under torsion load. A transformation pathway of VPs has been mapped out for Al90Sm10 MG NW under the subjugation of torsion load.

A critical review on damage modeling and failure analysis of pin joints in fiber reinforced composite laminates

Fiber-reinforced composite material plays a vital role in structural engineering due to its lightweight and high strength ratio which becomes a key material in a mechanically fastened pin joint. Recent review articles in this area were restricted to the numerical and experimental approaches which are used for strength prediction of pin joints in polymer matrix composites. The present study begins with an extensive analysis of relevant studies in the provided structurally clamped joint region using numerous numerical approaches and theories of failure. Numerous experimental and numerical approaches are available nowadays and have been cited by the researchers in their respective research to foretell the damage initiation and failure mode in the composite joint. The study gives the review of different numerical analyses of composite joints by utilizing interactive criteria for failure analysis, viz. Tsai-Wu, Tsai-Hill, Yamada Sun’s theory predicts failure using higher-order polynomial equations that comprise all stress or strain components, whereas limit stress criteria i.e. Maximum stress criterion which uses linear equations for finding the solution. Progressive Damage Analysis (PDA) quantifies matrix and fiber failure using the material depletion rule preceded by Hashin’s theory which offers a good interpretation irrespective of the types of composite material. In the end, various parameters are discussed which enhance joint performance under different loading conditions.

Performance evaluation of Reinforced honeycomb structure under blast load

In this study, numerical simulations were carried out to explore the response of the reinforced honeycomb sandwich structure with varying cell size (7, 10 and 15 mm), node length (25, 37.5 and 50 mm) and cell wall thickness (0.1, 0.2, 0.3 and 0.4 mm). The honeycomb structure made of aluminum alloy 8011 were subjected to low intensity blast loads by varying mass of TNT (10 g, 15 g, 20 g and 25 g) and standoff distance (200 mm, 250 mm and 300 mm). Commercial finite element code LS-DYNA was employed to carry out numerical simulations for both conventional and reinforced honeycomb sandwich structure keeping identical geometrical and blast load parameters. The deformation of the back face sheet was a major parameter to establish blast resistance of the core. Failure mechanisms of reinforced honeycomb was characterized as fully folded region, partially folded region, and clamped region. Reinforced honeycomb sandwich outperformed the conventional honeycomb sandwich structure of identical geometry parameters under similar blast loads. Increase in cell-wall thickness and node length enhanced the blast resistance whereas, increment in cell size reduced the blast resistance of the reinforced honeycomb sandwich structure.

Demarcating the Exact Midplane of the Liver Using Indocyanine Green Near-Infrared Fluorescence Imaging During Laparoscopic Donor Hepatectomy.

Indocyanine green (ICG) near-infrared fluoroscopy has been recently implemented in pure laparoscopic donor hepatectomy (PLDH). This study aims to quantitatively evaluate the effectiveness of ICG fluoroscopy during liver midplane dissection in PLDH and to demonstrate that a single injection of ICG is adequate for both midplane dissection and bile duct division. Retrospective analysis was done with images acquired from recordings of PLDH performed without ICG (pre-ICG group) from November 2015 to May 2016 and with ICG (post-ICG group) from June 2016 to May 2017. 30 donors from the pre-ICG group were compared with 46 donors from the post-ICG group. The operation time was shorter (P = 0.002) and postoperative peak aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were lower (P = 0.031 and P = 0.019, respectively) in the post-ICG group than the pre-ICG group. Within the post-ICG group, the color intensity differences between the clamped versus nonclamped regions in the natural, black-and-white, and fluorescent modes were 39.7 ± 36.2, 89.6 ± 46.9, and 19.1 ± 36.8 (mean ± SD, P < 0.001), respectively. The luminosity differences were 37.2 ± 34.5, 93.8 ± 32.1, and 26.7 ± 25.7 (P < 0.001), respectively. Meanwhile, the time from when ICG was injected to when the near-infrared camera was turned on for bile duct visualization was 85.6 ± 25.8 minutes. All grafts received from the 46 donors were successfully transplanted. In conclusion, ICG fluoroscopy helps to reduce operation time and lower postoperative AST/ALT levels. ICG injection visualized with black-and-white imaging is most effective for demarcating the liver midplane during PLDH. A single intravenous injection of ICG is sufficient for midplane dissection as well as bile duct division.

Cyclobutanone Inhibitor of Cobalt-Functionalized Metallo-γ-Lactonase AiiA with Cyclobutanone Ring Opening in the Active Site.

An α-amido cyclobutanone possessing a C10 hydrocarbon tail was designed as a potential transition-state mimetic for the quorum-quenching metallo-γ-lactonase autoinducer inactivator A (AiiA) with the support of in-house modeling techniques and found to be a competitive inhibitor of dicobalt(II) AiiA with an inhibition constant of Ki = 0.007 ± 0.002 mM. The catalytic mechanism of AiiA was further explored using our product-based transition-state modeling (PBTSM) computational approach, providing substrate-intermediate models arising during enzyme turnover and further insight into substrate–enzyme interactions governing native substrate catalysis. These interactions were targeted in the docking of cyclobutanone hydrates into the active site of AiiA. The X-ray crystal structure of dicobalt(II) AiiA cocrystallized with this cyclobutanone inhibitor unexpectedly revealed an N-(2-oxocyclobutyl)decanamide ring-opened acyclic product bound to the enzyme active site (PDB 7L5F). The C10 alkyl chain and its interaction with the hydrophobic phenylalanine clamp region of AiiA adjacent to the active site enabled atomic placement of the ligand atoms, including the C10 alkyl chain. A mechanistic hypothesis for the ring opening is proposed involving a radical-mediated process.

Dynamics of pantographic sheet around the clamping region: experimental and numerical analysis

The experimental and numerical analyses of the linear time-invariant dynamical behavior of the clamping region of a 2D pantographic material are presented. The experimental observations of the clamping area, obtained by means of a specialized stereo microscope, are compared with the results of a second gradient linear model enforcing the same symmetries as the system microstructure.

DEMARCATING THE EXACT MIDPLANE OF THE LIVER USING INDOCYANINE GREEN NEAR-INFRARED FLUORESCENCE IMAGING DURING LAPAROSCOPIC DONOR HEPATECTOMY

Background: Indocyanine green (ICG) near-infrared fluoroscopy has been widely implemented in laparoscopic donor hepatectomy for precise demarcation of the liver midplane. The aim of this study is to show the effectiveness of ICG fluoroscopy in comparison to the traditional demarcation method used in laparoscopic donor hepatectomy and also to confirm that a single injection of ICG is adequate for completion of both midplane dissection and bile duct division. Method: Retrospective analysis was done with images acquired from recordings of 46 laparoscopic living donor hepatectomies performed between June 2016 and May 2017. Intraoperatively, vascular inflow of the targeted hemiliver was temporarily clamped so that the ischemic line dividing the right and left lobes would become visible. ICG was then injected intravenously (0.025mg/kg) and the near-infrared camera was switched on for visualization in the black-and-white mode and fluorescent mode. Images were captured in the natural, black-and-white, and fluorescent views, and the color values of the clamped vs non-clamped regions were quantitated. Additionally, the time from ICG injection to bile duct illumination and that from bile duct illumination to fluoroscopy termination were measured. Results: The color differences between the clamped vs non-clamped regions in the natural, black-and-white, and fluorescent views were 39.7±36.2, 89.6±46.9, and 19.1±36.8 (P< 0.001), respectively, demonstrating that ICG visualized in the black-and-white view is most effective for demarcation of the liver midplane. Furthermore, the time from ICG injection to bile duct illumination and that from bile duct illumination to fluoroscopy termination were 85.6±25.8mins and 8.7±4.8mins, respectively, indicating that a single injection of ICG is adequate for midplane dissection followed by bile duct division. Conclusion: ICG injection visualized with black-and-white imaging is most effective for demarcating the exact liver midplane during laparoscopic donor hepatectomy. Also, a single injection of ICG is sufficient for midplane dissection as well as bile duct division.

Shear behavior of woven and non-crimp fabric based thermoplastic composites at near-processing conditions

In intra-laminar shear testing of continuous fiber reinforced thermoplastic composites at near-processing conditions, several factors influence the measured forces in picture frame tests. These influences mostly result from tight clamping of the specimen in the frame and, depending on the heating strategy, possible unmelted areas near the clamping regions, yielding in a shift of the point of rotation of the fibers. An approach to compensate these effects has recently been suggested, but generally valid compensation settings could not yet be deducted. In addition, research on the shear properties of continuous fiber reinforced thermoplastics has been limited to quasi-static deformation speeds and thermodynamically stable temperature levels. This study examines the effect of high deformation speeds and temperature levels in the transitional region between melting point and recrystallization on the intra-laminar shear behavior of different types of continuous fiber reinforced thermoplastics to deduct a material behavior, which better resembles actual processing behavior by using a custom-built picture frame setup. The edge effects are analyzed to deduct generally recommendable compensation settings using a statistical approach. In addition, variations of the pathways of individual fibers in pre-forms are measured, revealing elongation reserves of 0.4–0.5%, which can be confirmed in picture frame tests. The results furthermore show the importance of performing material tests at near-processing conditions to deduct reliable material data for usage in forming simulation. Further research is necessary to understand the complex deformation behavior in the transitional region below melting point and before recrystallization is complete.

Trench Shielded Planar Gate IGBT (TSPG-IGBT) With Self-Biased pMOS Realizing Both Low On-State Voltage and Low Saturation Current

A novel trench shielded planar gate IGBT (TSPG-IGBT) with self-biased pMOS is proposed in this paper. It features a P-layer beneath the trench of the TSPG-IGBT to form a self-biased pMOS, which provides an additional path for the hole current and clamps the potential of the nMOS's intrinsic drain for lower saturation current. In the off-state, with the increasing potential of the N-cs (N-doped carrier store layer), the self-biased pMOS turns on and the potential of the P-layer will be clamped by the hole channel. Then, the reverse voltage is sustained by the P-layer/N-drift junction and the potential of the N-cs is shielded by the clamped P-layer region. Therefore, the N-cs can be heavily doped to reduce the on-state voltage (Von) without decreasing the breakdown voltage. Compared with the conventional TSPGIGBT, the Von of the proposed TSPG-IGBT is reduced by 0.3 V at the current density of 200 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with the same turn-off loss. Besides, the saturation current density of the proposed one is decreased by 24%.