Interfacial Gap Research Articles

The influence of different bond primers on the bond strength of concrete overlays and the microstructure of the overlays transition zone

This study investigated the effect of different bond primers (BP) and the thickness of BP on bond performance. The mechanical and microstructural properties of BP were studied systematically using compressive strength, drying shrinkage, X-ray diffraction, and other methods; bond strength was evaluated using the slant shear test, and the failure modes were observed. Further, kernel density estimation was performed to qualify the crack width of the repair interface statistically characterised by analysing images obtained using the backscattered-electron method. The results indicated that when the BP was modified using silica fume, nano-silica, and Portland cement after ball milling, the modified BP pores were refined because of the combined filler, packing, and pozzolanic effects. The drying shrinkage of BP modified by an expansive agent was reduced; the BP could narrow the repair interface gap or even disappear, and the modified BP made the interfacial zone denser and improved bond strength. The results of the microscopic characterisation method of the repair interface verify the multi-scale characterisation of the new and old concrete interface.

Effect of FSW process parameters on microstructure and mechanical properties of the dissimilar AA2024 Al alloy and 304 stainless steel joints

Abstract The effect of friction stir welding (FSW) parameters on microstructure and mechanical properties of the dissimilar AA2024 Al alloy and 304 stainless steel joints was elucidated. The results showed that tool offset had a crucial effect on the properties. The optimum condition was obtained at a rotational speed of 750 rpm, a traverse speed of 65 mm/min, and a zero tool offset. At positive offsets and lower heat inputs, tunnel and interfacial gap defects were formed. At negative offsets and higher heat inputs, thick intermetallics compounds (IMCs) were formed. However, at optimum condition, sound and serrated interface, composite like the structure of stir zone (SZ), and thin IMCs around steel particles in Al matrix caused higher strength and ductility with a dimple like a fracture mode. During FSW, a high-strained ultra-fine grained (UFG) layer with a thickness of 5 μm is formed in the interfacial area, which causes micro cracks poor in iron. Aluminum fills these micro cracks, and then large steel particles dispatch towards the SZ. Finally, IMCs form around the dispatched steel particles concurrent with their further fragmentation in SZ. Thus, a composite structure composed of dynamically recrystallized aluminum matrix and UFG steel particles surrounded by IMCs forms in SZ.

Modular Heat Sinks for Enhanced Thermal Management of Electronics

Abstract Power electronics are vital for the generation, conversion, transmission, and distribution of electrical energy. Improving the efficiency, power density, and reliability of power electronics is an important challenge that can be addressed with electrothermal codesign and optimization. Current thermal management approaches utilize metallic heat sinks (HSs), resulting in parasitic load generation due to different potentials between electronic components on the printed circuit board (PCB). To enable electrical isolation, a thermal interface material (TIM) or gap pad is placed between the PCB and HS, resulting in poor heat transfer. Here, we develop an approach to eliminate TIMs and gap pads through modularization of metallic HSs. The use of smaller modular heat sinks (MHSs) strategically placed on high power dissipation areas of the PCB enables elimination of electrical potential difference, and removal of electrical isolation materials, resulting in better cooling performance due to direct contact between devices and the HS. By studying a gallium nitride (GaN) 2 kW DC–DC power converter as a test platform for electrothermal codesign using the modular approach, and benchmarking performance with a commercial off-the-shelf HS design, we showed identical power dissipation rates with a 54% reduction in HS volume and a 8 °C reduction in maximum GaN device temperature. In addition to thermal performance improvement, the MHS design showed a 73% increase in specific power density with a 22% increase in volumetric power density.

Photoelectronic Properties of End-bonded InAsSb Nanowire Array Detector under Weak Light

A simple fabrication of end-bonded contacts InAsSb NW (nanowire) array detector to weak light is demonstrated in this study. The detector is fabricated using InAsSb NW array grown by molecular beam epitaxy on GaAs substrate. The metal-induced gap states are induced by the end-bonded contact which suppresses the dark current at various temperatures. The existence of the interface dipole due to the interfacial gap states enhances the light excitation around the local field and thus upgrades the photoresponsivity and photodetectivity to the weak light. The light intensity of the infrared light source in this report is 14 nW/cm2 which is about 3 to 4 orders of magnitude less than the laser source. The responsivity of the detector has reached 28.57 A/W at room temperature with the light (945 nm) radiation, while the detectivity is 4.81 × 1011 cm·Hz1/2 W−1. Anomalous temperature-dependent performance emerges at the variable temperature experiments, and we discussed the detailed mechanism behind the nonlinear relationship between the photoresponse of the device and temperatures. Besides, the optoelectronic characteristics of the detector clarified that the light-trapping effect and photogating effect of the NWs can enhance the photoresponse to the weak light across ultraviolet to near-infrared. These results highlight the feasibility of the InAsSb NW array detector to the infrared weak light without a cooling system.

Influence of Silane Pretreatment and Warm Air-Drying on Long-Term Composite Adaptation to Lithium Disilicate Ceramic

Background: Repair bonding to lithium disilicate ceramic (LDS) remains an issue. This study examined whether the adaptation of a resin composite to LDS can be improved by a silane pretreatment and warm air-drying. Methods: LDS blocks (IPS e.max CAD) with prefabricated tapered cavities were bonded using a silane-containing universal adhesive (Clearfil Universal Bond Quick ER; UBQ) or the bonding agent of a two-step self-etch adhesive (Clearfil SE Bond 2), with and without a silane pretreatment (Clearfil Ceramic Primer; CP). CP and the adhesives were air-dried with normal air (23 ± 1 °C) or warm air (60 ± 5 °C), light-cured, and the cavities were filled with a flowable composite. Interfacial gap formation was evaluated using swept-source optical coherence tomography immediately after filling, after 24 h, 5000 and 10,000 thermal cycles, and an additional 1 year of water storage. Results: Without the silane pretreatment, all specimens soon detached from the cavities. Warm air-drying significantly decreased gap formation compared to normal air-dried groups (p < 0.001) and improved long-term stability (p < 0.001). The lowest gap formation was observed with UBQ when the silane pretreatment was combined with warm air-drying. Conclusions: Composite adaptation to LDS was insufficient without silanization, but it was stable in the long term if the silane pretreatment and warm air-drying were combined.

Effects of the positive pre-swirl purge flow on endwall aero-thermal performance of a gas turbine blade

The harsh thermal environments and the complicated near-endwall secondary flows pose great challenges to the thermal management of a blade endwall. To improve the endwall aero-thermal performance, a series of inclined guide fins are mounted inside the interface gap, generating a positive pre-swirl purge flow. The effects of the guide fins' inclined angle on aerodynamic losses, film cooling effectiveness and heat transfer performance of an endwall are investigated under three coolant-to-mainstream mass flow ratios (MFR). Results indicate that the guide fins’ inclined angle exerts significant impacts on the flow-thermal interplay between the secondary flow structures and the coolant ejection. A positive pre-swirl purge flow stimulates the boundary layer fluid to weaken the near-endwall cross flows and thereby significantly reduces the blade aerodynamic losses, especially for MFR >1.0%. More importantly, increasing the inclined angle improves both the effectiveness and coverage of endwall film cooling dramatically when MFR <1.0%, although the cooling performance downstream of the slot exit is lowered when MFR = 1.5%. Besides, increasing the inclined angle marginally enhances the endwall heat transfer level when MFR = 0.5%, but significantly decreases that when MFR >1.0%. Overall, a positive pre-swirl purge flow is beneficial to improve the endwall thermal protection level.

Comparative evaluation of 6% cranberry, 10% green tea, 50% aloe vera and 10% sodium ascorbate on reversing the immediate bond strength of bleached enamel: In vitro study

ObjectivesThe present study aimed to assess antioxidant activity of herbal antioxidants namely 6% cranberry extract, 10% green tea, 50% aloe vera and 10% sodium ascorbate and their effect on reversal of bond strength in bleached enamel. Materials and methodFrom one hundred and twenty extracted maxillary central incisors enamel blocks of 5 ​× ​5 ​mm were prepared and arbitrarily divided into six experimental groups (n ​= ​20): Group A: no bleaching, Group B: only bleaching protocol, Group C – bleaching ​+ ​6% cranberry extract solution, Group D – bleaching +10% Green Tea extract, Group E − bleaching ​+ ​50% aloe vera extract, Group F – bleaching ​+ ​10% Sodium Ascorbate. After bleaching antioxidants were applied for 10 ​min and were subjected to bonding procedures. The specimens were sectioned into 120 small strips of size (1 ​× ​1 ​× ​8 ​mm). Sixty sticks were analyzed to micro tensile bond strength using Universal testing machine and fractured segment were observed for failure modes (Adhesive, Cohesive and Mixed) under stereomicroscope. Remaining 60 sticks were observed for interface gap between tooth and composite resin under SEM. The %AA (antioxidant activity) was assessed with spectrophotometric analysis. ResultsData was statistically analyzed using ANOVA and Post Hoc Tukey’s test. Group A (91.68 ​± ​2.24 Mpa) showed higher mean micro tensile bond strength versus group D (82.14 ​± ​1.45 Mpa), followed by group E (75.26 ​± ​1.92Mpa), group F (63.89 ​± ​1.95Mpa), group C (57.58 ​± ​1.96 Mpa) and least in group B (31.5 ​± ​1.27 Mpa). The %failure mode inferred maximum adhesive mode of failure (86.25%). ConclusionAll the four antioxidants were able to reverse the compromised bond strength comparatively after bleaching maximum being green tea followed by aloe vera, sodium ascorbate, and minimum in cranberry. Clinically significance-Easily available, biocompatible, cost effectual, and potent herbal antioxidants could be used considerably for immediate esthetic cases where time is a restricting factor.

Simulations of melting performance enhancement for a PCM embedded in metal periodic structures

To overcome the inherent poor thermal conductivity of most phase change materials (PCM), inserting highly thermally conductive wire nets with periodic structures into them have been proposed. Numerical simulations have been extensively conducted to determine critical cell size and the effect of cell height and interface gap thickness on the heat transfer within the PCM. In addition, predictive correlations of the effective thermal conductivity were put forward. The simulated results indicate that: for structures with the same porosity, the critical cell size gradually decreases as the thermal conductivity of the wire net (ligament material) increases. For the proposed periodic structure embedded in the considered computational domain with 0.90 porosity, the critical pores per inch (PPI) for copper ligaments is approximately 10 PPI, while for stainless steel, it is approximately 3-5 PPI; a shorter cell height with a lower porosity shortens the melting time, therefore, stacking inexpensive metal wire is considered as an interesting alternative to commercially produced metal foams. Moreover, non-brazed scenarios lead to longer melting times, more than three times, compared to a perfectly brazed case. Furthermore, the effective thermal conductivity of the proposed periodic structure has been numerically calculated, which agrees well with some models available in the literature.

Resistance to dynamic and static loading of the implant mounts on its respective implant

Introduction: Implant restorations should endure a variable range of forces over a long period of time. Some commercial brands offer the implant together with an accessory called “implant mount” or “implant holder,” which might be used as a temporary abutment. However, scientific literature in the use of implant holders as abutments for restorations is scarce.Objectives: The purpose of this in vitro study was to compare the load at which implant holders of Implant Direct® and Zimmer® fail under static compression after being subjected to fatigue, and to compare the gap produced between the implant–holder complexes after dynamic loading.Materials and Methods: The test protocol was based on the recommendation of ISO 14801. Five implant–implant holder assemblies of each brand were subjected to dynamic loading. A load of 250 N was applied at 5 × 106 cycles and at 15 Hz stress frequency (Eden Prairie, MN, USA). The gap (μm) at the interface was measured postfatigue using scanning electron microscopy (S-3700N, HITACHI, Japan), and afterward, static loading was applied and the maximum load (N) after the point of failure was established. Implant–definitive abutment complexes were used as controls. Data were analyzed by means of a central tendency measurement test Mann–Whitney U-test (nonparametric).Results: There was no difference between both the implant holder groups (P ≤ 0.05); however, a slight trend of greater resistance was observed for the Zimmer® group. The gap in the interface was greater for Implant Direct® implants, but the difference was not statistically significant.Conclusion: No significant differences were found in terms of the maximum load under compression or the interface gap after the dynamic loading in the two experimental groups.

Bridging the interfacial gap in mixed-matrix membranes by nature-inspired design: precise molecular sieving with polymer-grafted metal–organic frameworks

Porous nanoparticles with interfacial adhesiveness boost the selectivity of separation membranes to achieve size-selective nanofiltration.

Effect of nano-biomaterials silk-collagen sponge scaffold on the tendon and ligament healing of patients with anterior cruciate ligament injuries

With the rapid development of nanotechnology, the application of nanomaterials is more and more extensive, and the contact between humans, animals and plants and nanomaterials is inevitable. Anterior cruciate ligament (ACL) is an important intra-articular ligament of the knee joint, which plays a very significant role in the normal movement and functional stability of the knee joint. ACL is generally difficult to heal after injury and the main treatment method currently is use auto-graft or allograft and synthetic materials for ACL reconstruction, but there exist problems such as large demand but limited sources. Nanotechnology development provides new ideas and approaches for ACL reconstruction. This technology inoculates certain cells from autologous tissues into scaffold materials, and then implants the grown cell scaffold complex into defect or injury sites for completing the tissue or organ defect repair and functional reconstruction. On the basis of summarising and analysing previous research results, this paper selected silk and collagen sponges as experimental materials to prepare nano-biological scaffolds, then observed the surface structure of the prepared scaffolds under scanning electron microscope and conducted histological analysis and biomechanical testing, and finally applied this nano-silk-collagen sponge biomaterial scaffold (NNSCSBS) to the tendon ligament repair surgery of patients with ACL injury. The results showed that collagen fills fibrous spaces with relatively uniform distribution after NSCSBS hybridisation, and the NSCSBS cultured in vitro had more abundant skin fibroblasts growth; the NSCSBS had the porosity of (77.63 ± 1.82)%, the moisture of (78.24 ± 1.19)%, the maximum load of (122.48 ± 12.66) N, the stiffness of (26.07 ± 2.58) N/mm without statistically significant differences (P > 0.05); postoperative ACL's bone mineral density and collagen fibre composition both increased; the graft tendon was surrounded by new bone tissue, and the tendon and bone were connected by fibrous collagen with narrower interface gap and more mature new bone tissue. Therefore, the NSCSBS can provide mechanical support with silk scaffolds as the core, increase the scaffold's three-dimensional space with composite collagen as bio-component, promote more cell adhesion and improve biocompatibility of nano-biomaterial scaffold, and better repair ligament-osseous junction to form a bionic structure, having a good application prospect.

Influence of biofilm removal from the tooth-restoration interface on the progression of secondary caries lesions: a preliminary in vitro model study

This study investigated the effects of biofilm removal from the tooth-restoration surface on secondary caries lesion progression. Biofilms were grown for up to 28 days on resin-restored enamel-dentin disks with an interfacial gap with DMM or DMM + 1% sucrose under five different protocols of Visible Biofilm Removal (V-BR; n = 7): (1) without V-BR, (2) with partial V-BR, (3) with total V-BR, (4) with total V-BR and saliva reinoculation, and (5) without V-BR under 9 h of cariogenic challenge. V-BR was performed at 7, 14 and 21 days. ΔS and CFU counts served as outcome variables. Linear regression models showed that ΔS values were higher for outer lesions than wall lesions, and outer lesion progression generally increased over time (p < 0.01). All protocols tested, except total V-BR, increased the lactobacilli count (p < 0.005). V-BR did not influence the progression of caries lesions on the cavity wall in this biofilm model.

High Temperature Sealing of Silicon Oxide/Oxide Bonding Interfaces

High temperature (>1000°C) annealing is necessary to completely close a bonding interface. Using interface synchrotron high energy X-ray reflectivity, we have investigated the sealing behavior of silicon thermal oxide/ silicon thermal oxide interfaces, with different surface roughnesses. Interface X-ray reflection is able to measure accurately the width and the depth of the electron density gap across a bonding interface with a sub-nanometer accuracy, whose product is a good marker of the interface closure.The uncomplete closure of the interface is the result of a balance between attractive and repulsive force between the two bonded solids. These two forces depend on the statistics of asperity and on the mechanical behavior of individual asperity [1]. For attraction, at high temperatures, a key factor is the gain of contact surface area which reduces the surface energy due to uncontacted zones. Repulsion is due to compression of contacting asperities. At high temperature, both elastic and plastic behavior can be expected, with some yield of the asperities compressed above the elastic limit.In the elastic solid regime, we have shown that equilibrium distance of rough silicon oxide to rough siliconoxide bonding can be predicted using standard adhesive contact models such as Johnson-Kendall Roberts (JKR) or Deryagin-Müller-Toporov (DMT) with Gaussian roughness statistics[2]. The equilibrium distance is dependent and sensitive to the Fuller Tabor adhesion parameter, θ=E σ3/2 R1/2 / 2γR where E is the Young modulus, σ the mean roughness, R the radius of the asperity, while 2γ is the adhesion energy at contact points. When θ>>1 , the equilibrium distance is large and the contact area is small (unclosed interface) . When θ<<1 the adhesion energy is strong and the system will have a strong tendency to seal.In the plastic regime, both repulsive and attractive curves share the same dependence with distance so that the system is expected to be unstable, between a weakly evolving unsealed interface and a fully sealed interface when the asperity pressure stress is above the elastic limit.The kinetics of the sealing can also be modeled in this case, monitoring the interfacial gap as a function of time (Figure). It is found that the sealing characteristic time scales directly with the silicon oxide viscosity (Figure insert). This dependence can be understood using the plastic asperity contact model, assuming the fluid part flows according to the Stokes equation around asperities.

Effect of Thermomechanical Loading on the Cementation Interface of Implant-Supported CAD/CAM Crowns Luted to Titanium Abutments.

To investigate the effect of aging on the morphology of the interface between monolithic implant crowns and standardized titanium base abutments. Four groups of hybrid abutment crowns differing in restorative material (lithium disilicate [LD] or polymer-infiltrated ceramic network [PICN]) and in fabrication procedure of the interfacial zone for luting to a titanium abutment (milled during CAD/ CAM procedure [M] or prefabricated [P]) were formed: LDS-M, LDS-P, PICN-M, and PICN-P (n = 10 each). The morphology of the crown-abutment interface was examined before and after artificial aging using scanning electron microscopy. The total gap length per specimen was measured at both time points, and intergroup (Kruskal-Wallis [KW]) plus pairwise (Wilcoxon Mann-Whitney [WMW]) comparisons were performed (α = .05). Before aging, statistically significant differences in gap length were identified among groups (KW: P = .0369) for PICN-P > LDS-P (WMW: P = .0496) and LDS-M > LDS-P (WMW: P = .0060). The effect of aging among the groups, expressed as an increment of total gap length, was 50% in LDS-M, 30% in LDS-P, 20% in PICN-M, and 30% in PICN-P. After aging, the statistically significant differences in gap length identified among groups (KW: P = .0048) were for PICN-P > LDS-P (WMW: P = .0134); LDS-M > PICN-M (WMW: P = .0204); PICN-P > PICN-M (WMW: P = .0486); and LDS-M > LDS-P (P = .0022). However, comparison of the difference in gap length from before to after aging among the groups was not statistically significant (KW: P = .3549). The cementation interfaces of CAD/CAM crowns on standardized titanium base abutments demonstrated a high percentage of gaps before and after thermomechanical loading. The composition of the restorative material and the nature of the interface influenced the interfacial gap dimension.

Long-term evaluation of warm-air treatment effect on adaptation of silane-containing universal adhesives to lithium disilicate ceramic.

The effect of warm air-blowing on the sealing ability of two one-bottle and one two-bottle silane-containing universal adhesives (UAs) applied to lithium disilicate ceramics (LDS) was evaluated. Tapered cavities prefabricated in LDS blocks (IPS e.max CAD) were treated by the adhesives, air-blown either with normal air (23±1°C) or warm air (60±5°C), and filled with a flowable resin composite. Interfacial gap formation was observed using swept-source optical coherence tomography immediately after filling, after 24 h, 5,000 and 10,000 thermal cycles, and an additional 1-year water storage. Specimens bonded using normal air-blown one-bottle UAs exhibited a significantly higher gap formation than the two-bottle UA (p<0.001), and detached within 24 h. Warm air-blowing significantly decreased the gap formation of one-bottle UAs (p<0.001), but the specimens dislocated within 24 h or during thermocycling. The two-bottle UA withstood all aging procedures and warm air-blowing significantly decreased its 1-year gap formation compared to normal air-blowing (p=0.002).

Primal interface debonding formulation for finite strain isotropic plasticity

A framework is developed for modeling ductile damage of nonlinear materials whose plastic deformation is characterized using rate independent classical plasticity. This method relies on the assumption that the free energy can be decomposed into elastic, plastic and damage parts. A thermodynamically consistent method is derived which satisfies the second law of thermodynamics in the Clausius–Duhem inequality form. The dissipation associated with plasticity takes place in the domain only, while damage dissipation is localized to the interface. The method is developed using Variational Multiscale ideas to obtain definitions of the interface fluxes within a primal formulation analogous to the Discontinuous Galerkin method, which ensures weakly vanishing interface gap prior to reaching a damage initiation criterion. The local nonlinear problem to calculate both plastic deformation gradient and damage variable follows an incremental approach similar to classical plasticity return mapping algorithm. This elastoplastic damage formulation is developed for material undergoing finite strain, and it naturally accommodates a trapezoidal traction separation law (TSL) whose shape can be varied to model either ductile interface behavior or brittle interface behavior. The formulation's performance is assessed through modeling a patch test and a compact tension specimen.

Mechanical performance of rubberized cement paste with calcium sulfoaluminate cement addition

Due to an increasing amount of waste tires produced yearly, environmental concerns arise as waste tires in landfills pose both a fire hazard, and a habitat for rodents and mosquitos. As a result, the reuse of waste tires in the form of waste rubber in concrete has been attempted. Previous research work has shown that the inclusion of waste rubber in concrete results in a drastic decrease in compressive strength. The limitations regarding the use of rubberized concrete are related to the interfacial transition zone between rubber and paste. Due to mismatch in free surface energy between rubber and cement paste, an interfacial gap is often reported to be present. This investigation aims to determine the effect of expansive cement, specifically calcium sulfoaluminate cement (CSA), has on the performance on rubberized cement samples, and its effect on the interfacial transition zone. A comprehensive experimental plan was carried out including pullout and compressive tests, scanning electron microscopy (SEM) imaging of fractured surface, and non-destructive tests through resonant frequency and dynamic mechanical analysis (DMA); furthermore, a temperature sweep via DMA was done to determine damping factor as a function of temperature. Results from compressive strength indicate a marked increase in the performance of rubberized samples with expansive cement. Pullout results, dynamic modulus and damping ratio values, shrinkage measurements, and scanning electron microscopy (SEM) imaging validate the hypothesis that a decreased interfacial gap at the rubber-paste interface obtained from using expansive cement results in increased mechanical performance.

Enhanced Reproducibility of Positive Temperature Coefficient Effect of CB/HDPE/PVDF Composites with the Addition of Ionic Liquid

Developing an effective method for improving the reproducibility of positive temperature coefficient (PTC) effect is of great significance for large-scale application of polymer based PTC composites, owing to its contribution to the security and reliability. Herein, we developed a carbon black (CB)/high density polyethylene (HDPE)/poly(vinylidene fluoride) (PVDF) composite with outstanding PTC reproducibility, by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIm][NTf2]) into the composite. After multiple repeated temperature cycles, the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%. Our studies revealed that [OMIm][NTf2] contributes to the improvement of PTC reproducibility in two ways: (i) it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends; (ii) it inhibits the crystallization of PVDF through the dilution effect, leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF. This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.

Microscale diffusion-mechanics model for a polymer-based solid-state battery cathode

A non-linear microscale diffusion-mechanics model combining mass transport and linear momentum balance equations, with elasto-viscoplastic polymer constitutive law and interfacial traction-separation law is proposed to provide a new insight into the effects of viscoplasticity and interfacial damage on the in situ diffusive-mechanical behaviour of a polymer-based cathode for a solid-state battery (SSB). Diffusion and mechanics are coupled through two mechanisms: (1) active particle (AP) volumetric change dependence on Li concentration, and (2) interfacial flux dependence on mechanical opening. The model is resolved for a simple cathode microstructure using an axisymmetric unit cell concept, and integrated with the non-linear finite-element solver ABAQUS with the help of its user subroutines (UMAT and UINTER). Finite-element simulations reveal that plastic deformations of the polymer due to volumetric changes of the AP reduce the value of the interfacial opening displacement, which is desirable for maintaining interfacial flux. The results also demonstrate that slower battery charging rates may lead to a softer polymer response, and thus a smaller interfacial gap. Moreover, a comparison between the linear elastic and current elasto-viscoplastic models for the polymer electrolyte shows that even 5% volumetric shrinkage of the AP leads to an overprediction of the interfacial opening with the linear elastic material law, which limits its validity in modelling polymer-based SSBs.

Thermal analysis of a Gramme‐ring‐winding high‐speed permanent‐magnet motor for pulsed alternator using CFD

Due to the merit of very-short end turns, Gramme-ring windings are widely used in high-speed permanent-magnet motors (HSPMMs). This study investigated the thermal issues of a 300 kW, 12,000 rpm Gramme-ring-winding HPSMM with housing water jacket and forced air cooling, based on the computational fluid dynamics (CFD) and numerical heat-transfer calculations. The reasons that cause the overheat of the prototype in the experimental test are thoroughly analysed. The high wind resistance of air gap as the ventilation duct and the large interface gap between the stator lamination and housing water jacket is thought to be the main reasons. Then improvement of the ventilation structures is studied to decrease the wind resistance. Besides, the modification of water channels is also investigated to avoid the influence of a large interface gap on the water cooling performance. Finally, a new cooling structure, combining the slot ventilation ducts and inside water channels, is proposed for the HSPMM with Gramme-ring windings. With the new cooling structure, the temperature rise of the motor is decreased, and the power density can be increased.