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Designing the roller and determining the required passes to manufacture the bar depend on the estimation of the pressure value during the bar rolling operation. Numerous researchers have proposed a mean unit pressure formula based on the flat rolling process formula. However, it is challenging to predict the pressure accurately using these formulas. Hence, the principle of sticking and slipping friction as well as weak plane strain is applied to derive the analytical formula based on slab analysis. To apply the proposed formula for different types of passes, the given pass shape is converted into an equivalent rectangular bar and assumed that it is pressed between two flat plates. Prediction of metal flow stress value is calculated by using Shida's formula with the proposed equation for the correction in input temperature of the hot metal. The constitutive formula of the roll separating force (RSF) is proposed based on these parameters. A comparison is made between the suggested formula and the experimental values which is available in the literature. The findings reveal that the RSF values obtained by applying the suggested method offer a reliable approximation for different kinds of passes. [ABSTRACT FROM AUTHOR]

Pure magnesium and Mg-(0.2-0.9 at%) Y rolled sheets were subjected to three-point bending tests to individually investigate the effects of texture and yttrium addition on bending deformation behavior. Yttrium addition increased bending yield stress in both Specimen TR with the neutral plane parallel to the ND (normal direction of the rolled sheets) plane and Specimen TN with the neutral plane perpendicular to the ND plane, resulting from the increase in critical resolved shear stresses (CRSSs) for basal slip and f10-12g twinning with yttrium addition. Bending ductility increased with increasing yttrium addition until 0.5 at% yttrium addition, and then decreased at 0.9 at% yttrium addition in Specimen TN. On the other hand, bending ductility increased until 0.9 at% yttrium addition in Specimen TR since non-basal slip activities increased with increasing yttrium addition. Since the neutral plane in Specimen TN with 0.9 at% yttrium addition moved more to the center than that in Specimen TN with 0.5 at% yttrium addition, resulting in the higher tensile strain at the tension side. Therefore, the bending ductility in 0.9 at% yttrium addition was lower than that in 0.5 at% yttrium addition. [ABSTRACT FROM AUTHOR]

Piled embankments are becoming widely used to cope with engineering problems (e.g., excessive settlements, bearing failure) caused by soft soil subgrade to maintain the safety and stability of the constructed facilities. This study focused on an international motor-racing circuit currently under construction, where the underlying soft soil substratum characterized by a high void ratio and compressibility may largely influence the long-term performance of the project. Pretensioned high-strength concrete (PHC) pile-supported embankment is designed to improve this project, and its effectiveness remains to be studied. In addition, this study specifically focused on negative skin friction (NSF) and neutral plane (NP) position development, which significantly influence the bearing capacity of the pile foundation and have not been fully understood. As such, two large-scale field tests were performed on the PHC pile-supported embankments to monitor the settlement of piles and the surrounding soils. According to the monitored layered settlements, the NP development with time was quantitatively analyzed, and NP gradually moved up toward the pile top during soil consolidation. Comparison between the measurements of two test sites with and without geogrid reinforcement indicated that geogrids could not only alleviate total and differential settlements of the foundation but also contribute to the shallower final NP position. A numerical model, whose effectiveness was validated by comparing with the field measurements, was established to predict the complete variation of NP positions and explore the effects of various influencing factors through a parametric study. This study enhances the comprehension of NSF and NP development in pile foundations and provides valuable guidance for this motor-racing circuit and other related projects in the future. [ABSTRACT FROM AUTHOR]

Piles transmit structural loads through skin friction, end-bearing, or both to deeper and stronger soil layers. Surcharge loads, site grading, or dewatering activities induce downward movement in the soil that is adjacent to piles installed in a compressible soil layer. This movement causes negative skin friction stresses that act downward at the pile–soil interface, which causes an additional force denoted the drag force (Qn) that is applied to the pile, which results in a larger axial load in the pile shaft. The end-bearing force and positive skin friction that develops in the pile part within stable (incompressible) soil resist the applied loads [e.g., dead load (Qd) and Qn]. This paper aimed to evaluate Qn that was mobilized on driven H-piles that were installed in soft clay with three-dimensional (3D) nonlinear finite-element analysis. Two numerical models were validated against the field data from two instrumented H-piles, which were part of a three-span bridge (E-21) on Highway 418, Ontario, Canada. The calculated settlements and Qn agreed well with measured field data. The validated numerical models were employed to conduct a parametric analysis to investigate the location of the neutral plane (NP) at which the skin friction changed from negative to positive. In addition, the performance of the piles that were installed in small and large groups was investigated, which considered Qn and group effects. It was found that the group effect was negligible for piles that were installed in one row but were significant for piles that were installed in large groups. Finally, a group factor was proposed to calculate the drag force for piles in a group (Q(n)pile in group). [ABSTRACT FROM AUTHOR]

Abstract We proposed new basic equations and the approximate model for gravitational ventilation through a single openingm which can be incorporated into a ventilation network analysis. The new basic equations are the mass flow balance and the conversion equations of pressure difference and dynamic pressure at an indoor‐outdoor boundary. In order to calculate the mass flow rate by gravitational ventilation using these equations, the following two values at the boundary are required: (1) windward speed, (2) temperature profile. 1. We have shown calculation methods based on the one‐dimensional flow for (1), and used a flow tube model for (2). 2. The neutral pressure level and the inflow‐outflow wind speed can be obtained by steady‐state analysis of basic equations. The coefficients that optimize the calculation results were also shown. 3. We compared the approximate model with the CFD and verified their validity. Finally, the basic characteristics of single‐opening gravitational ventilation were discussed.

Blue ghosting flame and self-extinguishing are two typical flame behaviors in ventilation-controlled compartment fires. However, the study of the evolution of these two behaviors with opening factor and heat release rate (HRR) is incomplete. In this study, the experiments were performed in a 1/2-scale compartment model with openings of six different sizes. The temperature, oxygen concentration and carbon monoxide concentration in the compartment under different propane supply rates were recorded and analyzed. The results showed that the flame transformed from the stable stage to blue ghosting flame or extinguishment with the increase of the total HRR. When there is a blue ghosting flame and self-extinguishing, the combustion spontaneously regulates the oxygen concentration in the compartment and changes the trend of the oxygen concentration decreasing with the total HRR. The blue flame not only reflects that the real HRR is in an unstable state, but also changes the evolutionary trend of the ceiling temperature. The critical HRR for the appearance of blue ghosting flame and self-extinguishing behavior increases linearly with the opening factor. The value of the Global Equivalence Ratio stabilized around 0.73 only after the opening factor was greater than 0.0145. The blue ghosting flame cannot return to stability and is extinguished when the difference between the entrainment rate and the air consumption rate exceeds the limit of spontaneous regulation of combustion. [ABSTRACT FROM AUTHOR]

Foldable perovskite solar cells (PSCs) have promising applications in self‐powered wearable and portable electronic devices. However, the folding stability requires further improvement through mitigating the strain in brittle layers under folding deformation. Herein, sandwich‐structured PSCs (SS‐PSCs) are constructed by coating a protection layer at the back of the device, to tune the neutral plane (NP) place into the brittle perovskite films. To accurately regulating the NP place, the effect of protective layer thickness on the strain distribution in PSCs is simulated. The SS‐PSCs are experimentally prepared using Al2O3/polyethylene terephthalate (PET) protection layer with optimum thickness, combined with ultrathin silver foldable electrodes. Benefitting from the water‐resisting Al2O3/PET, the SS‐PSCs demonstrate high environment stability which maintains 85.1% of original efficiency after 700 h in humidity of 50% ± 10%. More importantly, the SS‐PSCs exhibit excellent mechanical stability, which maintains >90% of the initial efficiency after bending with 4000 cycles at radius of 0.2 mm, and even 67.2% of the initial efficiency after 50 direct folding cycles. As far as it is known, it is one of the best mechanical stable devices. The findings pave the way for realizing not only foldable PSCs but also other foldable optoelectronic devices, such as sensors and organic light emitting devices. [ABSTRACT FROM AUTHOR]

Large structures such as tall buildings, towers, and bridges transfer their loads to competent soil layers through pile skin friction and/or end bearing. When a pile is installed in a compressible soil layer, it may experience additional skin frictional force called drag force due to excessive soil settlement relative to the pile. This paper reports the results of a comprehensive long-term monitoring program of instrumented bridge piles and adjacent soil to evaluate the development of drag forces along the shafts of three piles. The data collected from the monitoring program are presented and discussed in terms of measured responses with time and load distribution along the pile shafts. The data were used to compute and locate the extent of the drag force for each of the three piles and to determine the end of the consolidation process. In addition, the results were used to examine the unified design method and assess the design codes with respect to drag force. [ABSTRACT FROM AUTHOR]

A new excavation retaining structure, referred to as an outward inclined-vertical framed retaining wall (OIVFRW), has been developed and adopted in practice. This retaining structure can limit excavation-induced ground movement and protect adjacent infrastructures. A case history shows that it performs well in controlling wall deflection, but its retaining mechanism and the factors influencing its performance are not fully understood. Therefore, this paper aims to investigate the behaviour of an OIVFRW to provide a better understanding of the retaining mechanism of this newly developed retaining structure. A case history of an OIVFRW in soft soil is first introduced, and a finite element model is then established. Parametric studies are carried out to investigate the relationship between influencing factors and the performance of an OIVFRW. Subsequently, the location of the neutral plane, the mobilization of the skin friction and the distribution of the axial force are analysed. Moreover, the retaining mechanism of this structure is discussed on the basis of the parametric investigation, and the contribution of pile length to the retaining mechanism is investigated. The results show that an OIVFRW structure performs well in limiting deformation, and the length of the vertical pile and the inclination angle show significant contributions to limit the structure movement. Moreover, the axial force of the vertical pile, which stems from the relative displacement between the soil and vertical pile, acting on the head of the inclined pile is beneficial to resist the deformation of the OIVFRW. [ABSTRACT FROM AUTHOR]

There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay, which may pose a risk of instability of retaining systems. The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meter-deep braced excavation of a subway station in thick soft clay (total thickness up to 42 m) in Shanghai. In this case, a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile foundation. Efforts were first made to examine the complex relationships between the post uplift with the excavation depth (H), Terzaghi’s safety factor against base heave (Fs) and maximum deflection of retaining wall. A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative research. The working characteristics of the long pile foundation under low safety factor against base heave (Fs

We proposed new basic equations and the approximate model for gravitational ventilation through a single openingm which can be incorporated into a ventilation network analysis. The new basic equations are the mass flow balance and the conversion equations of pressure difference and dynamic pressure at an indoor‐outdoor boundary. In order to calculate the mass flow rate by gravitational ventilation using these equations, the following two values at the boundary are required: (1) windward speed, (2) temperature profile. 1. We have shown calculation methods based on the one‐dimensional flow for (1), and used a flow tube model for (2). 2. The neutral pressure level and the inflow‐outflow wind speed can be obtained by steady‐state analysis of basic equations. The coefficients that optimize the calculation results were also shown. 3. We compared the approximate model with the CFD and verified their validity. Finally, the basic characteristics of single‐opening gravitational ventilation were discussed. [ABSTRACT FROM AUTHOR]

The study and analysis of tectonic activities on regional structures is of great significance to mine prospecting and production safety in mine work. We take the No. 3 coal seam in the Yangquan mining area as the object of study. The methods of fractal dimension, structural curvature and trend surface analysis are applied to quantitatively evaluate and predict the mine structure. The folded meso-plane analysis is also carried out. The results show that the trend surface reflects that the monoclinic structure is high in the NE direction and low in the SW direction. The dip angle is small, and the overall structure is characterized by an NNE−NE trend. The curvature value of the coal seam in the mining area is generally small. The northwest structure is relatively simple. The eastern fracture is more developed. The southern structure is relatively simple. A large nearly EW direction Taohe syncline is developed in the middle and south. Several large fractures in the NE direction are developed in the southwest. The capacity dimension of fractures in the mine field is mostly between 0.6 and 1.6. It indicates that the complexity of the fracture structure in the mine field has obvious heterogeneity. The neutral surface of the mine is in the third section of Taiyuan formation, and the No. 3 coal seam is above it. The research results have reference significance for the evaluation and prediction of safe mining and gas outburst danger zones in mining areas. [ABSTRACT FROM AUTHOR]

Sticker‐type anti‐reflective (AR) film is a powerful route to achieve the highest efficiency and commercialization of perovskite solar cells (PSCs) by improving the light transition efficiency (LTE). However, conventionally used AR film has high flexural rigidity owing to its limitation of material and thickness, thereby hindering its application to high‐efficiency flexible devices. This paper proposes a sticker‐type ultra‐thin perfluoropolyether (PFPE) AR film (SUPA) made of PFPE (n = 1.34) that is fabricated through a well‐designed two‐step peeling propagation method. The proposed SUPA demonstrates superior properties in terms of LTE (≈98.3%) and film thickness (≈20 µm), exhibiting the best performance among the existing AR films for PSCs. The SUPA‐assisted rigid and flexible PSC guarantees high short‐circuit current density (rigid ≈26.63 mA cm−2, flexible ≈23.05 mA cm−2) and power conversion efficiency (rigid ≈24.31%, flexible ≈20.05%). The SUPA sustains over 97.5% of its initial transmittance under exposure to the light (168 h) and damp heat condition (1000 h), and devices with SUPA show remarkable flexibility maintaining their initial efficiency after 10 000 cycles of a bending test (2 mm radius). [ABSTRACT FROM AUTHOR]

A theory is proposed to study the vibrations of homogenous isotropic circular cylindrical shells based on a developed plate vibration theory. By proposing a novel distribution of the shear stress and strain across the thickness of the shell, the arguments are adjusted such that the transverse shear strains and stresses equal zero at the shell surfaces. Due to the existing curvature in the circumferential direction, the defined shear stress and strain distributions consider a change in the position of the neutral plane toward the center of curvature. In the presented Two-Separated Lateral Displacement (TSLD) theory, the lateral displacement is defined by two bending and shear parts to provide an analytical model, referred to as the four-variable refined plate theory. The similarity to classical theory and involving only four unknowns are significant features of the introduced theory. The TSLD theory is verified against the available data in the literature. It is shown that the provided stress and stress distributions lead to more accurate results, especially in moderately thick cylinders. The proposed theory is remarkably more precise than classical shell theory and First-order Shear Deformation Theory (FSDT). Results of the TSLD theory are as accurate as the Higher-Order Shear Deformation Theory (HOST12) for the higher frequency parameters and more thick shells, while the TSLD theory implementation is much simpler than the HOST12. [ABSTRACT FROM AUTHOR]

The flexible printed OLED TV display technology will be able to create new application market, such as rollable/foldable TV, in the future. It's TV Mobiles. Recently, the TCL (Guangdong Juhua Printed Display Technology Ltd. Co, TCL CSOT & TCL Corporate Research) has successfully demonstrated the 31″ FHD flexible printed OLED TV in CES 2020. The product is fabricated by ink jet printing technology with top emission OLED device architecture, advanced encapsulation technology and is driven by IGZO oxide TFT B/P technology. The panel performance of 31″ flexible printed OLED TV has continuously improved drastically after demonstration at CES based on optimization of top emission OLED device architecture including printing OLED material development, MURA free printing technology, Oxide TFT B/P technology and advanced thin film encapsulation technology. The RGB device performance of 31" FHD flexible printed OLED TV has high current efficiency and long‐life time, R:(0.68,0.32), 46.3cd/A, LT95>8khrs@1knits, G:(0.28,0.70),115.5cd/A, LT95>6khrs@1knits, B:(0.13,0.062),5.35cd/A, LT95 >0.35khrs@1knits respectively. It is getting closer and closer to meet the commercial requirement of flexible OLED TV target specification. The technical challenges of 31″ FHD flexible printed OLED TV are also identified. In this paper, the technology development status and technical challenges are discussed [ABSTRACT FROM AUTHOR]

In this study, the impact of Negative Skin Friction (NSF) on composite piles concerning different variables such as different pile sections, the amount of concrete and steel consumption, and various interaction coefficients of the pile-soil system in both solid and hollow conditions are evaluated using numerical methods. Besides, the effect of the variables considered on the negative skin friction and pile’s settlement is investigated. Numerical analyses were performed using ABAQUS and MATLAB. The results showed that the amount of frictional stress on the pile decreases if the hollow sections are used. However, the hallow pile experiences more settlements than other piles’ models. On the other hand, if the amount of consumed steel in a pile is reduced, the amount of negative skin friction induced in a pile decreases, while the pile settlement increases. After examining the Finite Element of concrete piles in fine-grained soils, the safety surface of the suggested numerical relationship was considered in the phenomenon of negative friction on the pile. For this purpose, considering the uncertainty parameters such as mean, variance and probability function for overcharge, soil parameters, dimensions and different types of the single pile, the amount of settlement, the stress created on the pile, the position of neutral plane on the pile and drag load were calculated using the proposed relationship. Finally, the safety surface of the proposed relationships or comparisons of a Finite Element results in a close approximation to the real models was computed.

This study investigates numerically the impact of the longitudinal location as well as the heat release rate (HRR) of the fire source on the neutral plane and induced flow within a longitudinal sloping tunnel under natural ventilation. Research shows that neutral plane height in longitudinal sloping tunnels is mainly influenced by the longitudinal location of the fire source and the longitudinal slope and is relatively insensitive to the HRR. The nearer the fire source location is to the low entrance and the greater the slope, the higher the neutral plane position at the high entrance of the tunnel will be. In addition, the induced flow between the fire source and the low entrance of the tunnel was compared for all conditions. Results indicated that the induced flow velocity was positively correlated with the longitudinal slope of the tunnel and the HRR, and negatively correlated with the distance between the fire source and the low entrance of the tunnel. Eventually, a non-dimensional model was established to estimate the velocity of the induced flow between the low entrance of the tunnel and the fire source. These conclusions have implications for the field of tunnel fire safety engineering. [ABSTRACT FROM AUTHOR]

Bidirectional reinforced embankment (BRE) technology, pile supporting in vertical and geosynthetic reinforcement in horizontal, has been widely adopted in engineering practice to control total and/or differential settlement. In design, the load distribution of BRE is essential for determining pile size (i.e., diameter and length), pile spacing, pile cap details (if any), and properties of geosynthetic reinforcement, et al. Several methods have been proposed in previous studies to investigate the load bearing mechanism in the BRE platform. However, resistance of foundation soil is typically neglected, which implies that the load on piles would be overestimated if the resistance of foundation soil is neglected or over weakened. The reason for this overestimation is that larger geosynthetic deflection would be expected without the reaction of foundation soil, which would cause a more significant soil arching and thus more load would be transferred to piles. To minimize this overestimation, a method for analyzing load transfer mechanism in the BRE was proposed, considering the subsoil resistance as well as the existence of neutral plane (i.e., zero skin friction). An equal settlement was assumed for soils at the embankment bottom and the foundation top. The iteration process was adopted to solve equations to determine the load shared by piles and soils. In derivation, the soil arch height in the embankment was calculated instead of being assumed in existing methods. A flow chart was developed to solve equations of the proposed method and two case histories from literatures were used to compose the rationality verification. Compared with the field measurement and numerical calculation, this study can be more effective in calculating loads shared by piles and soils in the BRE for the working condition with better pile end bearing stratum. [ABSTRACT FROM AUTHOR]

Three-point bending tests were performed on pure zinc single crystals with different crystal orientations to investigate orientation dependence on bending deformation behavior. With basal planes parallel to the neutral planes, the specimens deformed due to basal slips and formed a gull shape after deformation. On the other hand, specimens whose neutral planes are perpendicular to the basal planes and neutral axes are perpendicular to [0001] deformed due to second order pyramidal ©c + aª slips, {10112} twinning and basal slips within {10112} twins, displaying a V shape. The bending deformation behavior of pure zinc single crystals was found to show strong orientation dependence. Also, the bending deformation behavior of pure zinc single crystals was found to differ from that of pure magnesium single crystals when the neutral plane and neutral axis are respectively perpendicular to the basal planes and [0001]. [ABSTRACT FROM AUTHOR]

The present design method in various codes for axially loaded piles embedded in consolidating soil is not satisfactory. It is too conservative in calculating the maximum pile force. Furthermore, the additional pile settlement due to the consolidation is neglected in ascertaining whether the requirements of allowable settlement have been met. This is because the behavior of such piles is not well understood. A new step-by-step design method based on the combination of results of extensive parametric studies of an elastoplastic load transfer model incorporating pile–soil slip reported previously is presented. In contrast to the iterative procedure required by some existing methods to determine the neutral plane location, these design charts can be used to determine the pile top settlement, neutral plane location, and maximum pile load directly. Further saving in the design of pile foundation is obtained with the concept of a compensating-pile foundation. [ABSTRACT FROM AUTHOR]

• An asymptotic analysis is performed for modeling radial forging process. • It can predict the material flow inhomogeneity and deviation of neutral points profile. • A process feasibility criterion is developed in terms of the die angle, friction and back-push stress for the 1st time. • A breakthrough method is proposed that can effectively find the location of the neutral plane far easier and faster. In this paper, an analytical approach based on the asymptotic analysis is proposed to develop an axisymmetric model for the radial forging process of rods. This model is able to predict the deformation inhomogeneity in the radial direction and approves that the profile of the neutral plane is not a planar cross section of the workpiece. For the first time, a relationship has been developed between the die angle, friction coefficient and back-push stress that can be used as a criterion for examining the feasibility of the radial forging process. A breakthrough method has also been proposed that can effectively find the location of the neutral plane far easier and faster than the traditional approach. Finite element simulation of the process has been performed to validate the deformation pattern obtained by the asymptotic model. Models are also verified against available experimental data. The findings of this study are especially useful for online design, analysis and control of the radial forging process. [ABSTRACT FROM AUTHOR]

It is recognized that NSF on a pile affects the structural and geotechnical design. The formation of NSF on a pre-stressed high-strength concrete (PHC) pile under a control building in a Vietnamese project was investigated using a verified numerical model in FLAC3D. The height of backfills, the consolidation degree of soil, working loads on the PHC pile, and the pile diameter were analyzed in sensitivity analyses to investigate the influence on NSF. It was found that higher backfills and higher consolidation degree were dominant in the formation of NSF, causing an increase of the dragload and an upward movement of the neutral plane. The working load and the pile diameter affected the dragload and the position of the neutral plane less. A limit decrease of the dragload induced by NSF was observed when the working load increased. Accelerating the soil consolidation process would be suggested to avoid great displacement due to NSF.

This study conducted parametric analyses to investigate the influence of structural loading (pile-head loading) on the development of negative skin friction in friction single piles and friction-end-bearing single piles in consolidating ground. Numerical effective stress-based mechanical-flow analysis models were built in ABAQUS software. The appropriateness of the modeling approach was verified by applying it to simulate a field model test described in the literature. For small surcharges, pile-head loading considerably reduces the depth of the neutral plane and therefore drag load for the friction pile. Under the same pile-head loads, the reduction in total drag load for the friction-end-bearing pile is smaller than that for the friction pile. However, when the friction-end-bearing pile is subjected to larger pile-head loads, the degree of total drag load reduction is comparable to that of the friction pile. Considerable pile-head displacement occurs under the combined action of pile-head and surcharge loadings. In contrast to the friction pile, the friction-end-bearing pile, because of the greater stiffness and strength of its bearing stratum, exhibits a significant reduction in negative skin friction, no bearing failure, and a smaller pile-head displacement when it is subjected to large pile-head loading. [ABSTRACT FROM AUTHOR]

Neutral plane strategies have been studied to reduce the tensile strain of brittle films in foldable electronics under bending. However, those strategies depend on the dimensions of components in devices, implying that they could be limited to application to various designs of devices. Herein, the glass fabric's position in a glass fabric–reinforced siloxane hybrid substrate is shifted to control the neutral plane of the substrate. Due to the stiffness difference between the glass fabric and epoxy siloxane hybrid matrix, the neutral plane of the substrate is affected by the position of the glass fabric. Therefore, the glass fabric is asymmetrically impregnated to be located at the substrate surface so as to shift the neutral plane of the substrate toward the surface. The effectiveness of the newly developed substrate is proved by comparison with a conventional colorless polyimide substrate. The neutral plane position and maximum tensile strain of the substrates are investigated by analytical calculation, digital image correlation analysis, bending test, and finite element method simulation. The results clearly show that the newly developed substrate–based structure can reduce the maximum tensile strain under bending. Consequently, the cracking of the brittle hard coating is effectively prevented. [ABSTRACT FROM AUTHOR]

In this study, an improved multi-layer structure was proposed to prevent delamination and permanent deformation in a rollable display. After obtaining the equivalent material properties of the OLED panel using homogenization method, the strain of each layer in rollable display was estimated through finite element analysis, and the possibility of delamination and plastic deformation was predicted based on the yield strain in each film layer and the shear strain in adhesives between film layers. As the display module rolls, the difference of displacement between layers accumulates and the shear strain in adhesives increases. The delamination and the permanent deformation has been resolved using high modulus adhesives and hyper-elastic cover film material. [ABSTRACT FROM AUTHOR]

Pure magnesium and MgY alloy single crystals were subjected to three-point bending tests to investigate the effect of crystal orientation and yttrium on bending deformation behavior. Specimens whose neutral planes are parallel to (0001) and neutral axes are [112̅0] deformed due to basal slips, displaying a gull-shape. Their bending yield stresses increased by addition of yttrium and were controlled by the shear stress on the basal plane. Conversely, neutral planes parallel to (11̅00) and neutral axes are [112̅0] resulting in specimens deformed due to (101̅2) twins occurred at the compression side, basal slips within the twins and finally showed a V-shape. In MgY alloys, first order pyramidal ©c + aª slips (FPCS) and (101̅1)-(101̅2) double twins were also activated in the tension area. Their bending yield stresses and bending ductility increased by yttrium addition. Strain induced by (101̅1)-(101̅2) double twins at the tension side was very low. FPCS was found to be activated by addition of yttrium and to increase bending ductility. [ABSTRACT FROM AUTHOR]

The market for next-generation flexible displays is rapidly expanding with the launch of foldable electronic products. Consequently, the flexible electronic material and device industries are continuously growing. Specifically, the cover window used in foldable displays is a very important component that must have excellent optical, physical, and mechanical characteristics while withstanding high external stresses caused by the bending radius, unlike the existing rigid-type cover windows. Considerable research efforts have been dedicated toward improving their performance. In this study, a cover window substrate for a foldable display having high flexibility was developed. To this end, ultra-thin glass (UTG) with excellent flexibility and transparency was used to overcome the low surface hardness of the typical polymer substrate used in existing foldable substrates. In addition, for efficient stress control, the design of the multilayer structure was optimized by generating multiple neutral planes through the use of an optical clear adhesive (OCA) buffer layer. The structure of the cover window was designed using the finite element simulation technique, and actual samples of the cover window with the optimized structure were produced to evaluate their physical, mechanical, and optical characteristics. As a result, the optimized foldable cover window showed a surface hardness of 9 H and a light transmittance of 90 %; especially, it exhibited an excellent bending reliability with 200000 bending repetitions without failure at the small bending radius of 1.5 R. [ABSTRACT FROM AUTHOR]

For indirect‐bandgap germanium (Ge), strain‐engineering provides a controllable means to transform Ge into direct‐bandgap material with strongly enhanced light emission efficiency. Flexible electronics offer a powerful platform for introducing external strain into semiconductor nanomembranes (NMs) through deformation with flexible substrates. So far, the Ge/GexSi1−x alloy quantum well (QW) NMs have not been sufficiently investigated to comprehend how the external deformation tunes the wavelength and light‐emitting properties. Herein, a theoretical model based on the elasticity theory and k·p method is established to analyze the strain‐optoelectronic properties of the externally deformed Ge/GexSi1−x QW NMs via neutral plane (NP) modulation in both embedded and sticked form. Calculated results reveal that the elastic strain is linearly distributed, inducing tilt of the band edge similar to the electric field. Considering the fracture limit of the material, the NP layout determines the critical bending curvature that the NM can achieve. Large tunable range of wavelength Δλ of 1615 nm and enhanced transverse electric (TE)/transverse magnetic (TM) peak gain of 949/3778 cm−1 are predicted for r = 1000 nm (the distance between NP and QW) under the bending limit. Further calculations conclude that larger r allow for smaller bending curvature to achieve wider range of wavelength and more enhanced optical gain. [ABSTRACT FROM AUTHOR]

In this study, the film stacks of rollable AMOLED display are analyzed and designed by FEA (finite element analysis). The control for the layer thicknesses and stiffness of film stacks are two of the key designs for rollable AMOLED display. Also, the use of OCA (optically clear adhesives) brings a particular effect to the setting of neutral plane. In the FEA, constitutive model of hyperelasticity is chosen to describe the mechanical behavior of adhesives since the nonlinear elastic behavior and large deformation characteristics of adhesives. A 7.4‐inch WQHD prototype rollable AMOLED display has been successfully rolled up more than 15,000 cycles in dynamic at 10mm rolling radius without damages. [ABSTRACT FROM AUTHOR]

Based on a new categorization, significancy and feasibility of vector-acting foundations for offshore challenging substructures are emphasized. A marine challenging status is typically related to loading, investigations, subsurface, environment, construction and sustainability requirements. The issue of the interaction of piles and complex subsoil is discussed in this paper. Three scenarios are studied comprising sensitive deposits at the full depth, the most impressive one, compressible deposits at the top layer and soft soil underlain by strong deposits. The role of CPTu records is addressed in recognition of problematic layers, geotechnical design and embedment depth designation. The effect of soil sensitivity on shaft and toe resistance is quantified through static analysis and reduction factors are suggested. Since bearing capacity, settlement and axial load are interactive, the neutral plane concept is applied, unifying the mentioned aspects. Through the neutral plane approach and considering the downdrag force due to the collapse of sensitive soil, primary design criteria incorporating sensitivity are discussed and quantified. Applying ground modification as a supplement for deep foundations is realized through two case studies, leading to enhancement in geotechnical performance. Overall, the mentioned phenomena must be discovered comprehensively in extraordinary conditions, aiming for a safe, reliable, knowledge-based and optimum design. • Introducing novel classification for foundations based on the form and load transfer mechanism. • Presenting influential factors in marine challenging substructures. • Incorporating soil sensitivity for modifying bearing capacity in undrained condition. • Quantifying and discussing the effect of sensitivity on pile performance via neutral plane concept. • Assessment the performance of ground improvement and deep foundations combination. [ABSTRACT FROM AUTHOR]

The current general accepted view is that the delayed installation of piles after the commencement of consolidation leads to a reduction of drag load acting on piles. Despite the extensive studies reported in the literature, no work that focussed on the quantitative effect of delayed installation of piles after the commencement of the consolidation on pile behavior was reported. A study on the effect of the delayed pile installation after the commencement of the consolidation is undertaken using a load transfer theory. Pile-soil slip is accounted for by limiting shear stress at the pile-soil interface to the average undrained shear strength of the consolidating soil. The effect of pile-soil slip in limiting the drag load is accounted for once the location of the neutral plane resulting from the delayed pile installation after the commencement of the consolidation is known. Contrary to the current generally accepted understanding that delayed installation of piles after the commencement of the consolidation will lead to a reduction of drag load on such piles, the present study finds that the drag load on piles may not be reduced for consolidating soft clay with two ways drainage or one way bottom drainage conditions. [ABSTRACT FROM AUTHOR]

In this study, the film stacks of foldable AMOLED display are analyzed and designed by finite element analysis (FEA). Controlling the position of neutral plane is one of the key designs for foldable AMOLED display. However, the use of optically clear adhesives (OCA) has a particular effect on the prediction of neutral plane. In the FEA, traction‐separation law is chosen to describe the mechanical behavior of adhesives; also the material parameters and failure strength of adhesives are obtained by basic material tests in advance. A 5.99‐inch WQHD prototype foldable AMOLED display has been successfully folded more than 100,000 times in dynamic and static mixing at 3mm inward folding radius without damages. [ABSTRACT FROM AUTHOR]

The development of negative skin friction on circular piles in a consolidating layered soil is investigated by an elasto-plastic load transfer theory which accounts for slippage of the soil. The elastic load transfer theory is premised on the compatibility condition that the vertical displacement of the 'pile' is equal to the summation of the vertical displacement of the layered soil due to the consolidation of the upper soil layer and the vertical displacement in the 'soil layers' along the pile's centroidal axis caused by a system of pile-soil interactive forces. Slippage of the soil is accounted for by imposing the shear strength of the clay layer as the limit of the pile-soil interface shear stress. The saturated upper clay is consolidating under a uniform surcharge in accordance with Terzaghi's one-dimensional consolidation theory. The validity of the proposed solution is confirmed by comparison with field measurements. Extensive parametric studies with regard to the effect of pile-soil slip on pile behaviour are presented. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesters have been studied extensively because they show considerable promise for use in both military and commercial applications. In this work, research was conducted into the core component of a piezoelectric energy harvester, i.e., the piezoelectric cantilever. The phenomenon where the piezoelectric cantilever has a very low output when no substrate layer is present can be explained using neutral plane theory. The relationship between the neutral plane's position and the piezoelectric cantilever’s output power can be studied in depth through analysis of this phenomenon. A mathematical model of a vibrating piezoelectric cantilever is established and the neutral plane position and open-circuit voltage of a vibrating piezoelectric cantilever are deduced based on Euler-Bernoulli beam theory. Calculations and finite element simulation results show that the neutral plane's position in the piezoelectric cantilever is dependent on the elastic moduli and thicknesses of the piezoelectric and substrate layers and that the output of the piezoelectric cantilever is also closely related to the neutral plane's position. To study how the neutral plane's position affects the output power of the piezoelectric cantilever, polyvinylidene fluoride (PVDF) piezoelectric cantilevers with different substrate layers but the same piezoelectric layer were fabricated and the output powers of these layers were measured. Experimental results show that the composite piezoelectric cantilever’s performance is enhanced in terms of its output voltage, average power and power density as the neutral plane is gradually moved further away from the mid-plane of the piezoelectric layer. [ABSTRACT FROM AUTHOR]

The present study included the finite element analysis and optimal design of a multi-layered foldable structure (foldable display) to satisfy stress, neutral plane, and delamination requirements under a 2.5 mm radius of curvature (i.e., 2.5R) due to static bending load. Two bending types (inner folding and outer folding) were considered to accommodate the repeated bending, and their maximum stress values were evaluated. In the approximate optimization for the thickness and Young’s modulus of multiple film layers, the objective was to minimize the folding stress subjected to constraints on the positioning of the largest stress value to a neutral plane and prevention of delamination. Through the simultaneous change in thickness and Young’s modulus, the study identified the new position of a neutral axis so that a 16% improvement in the stress magnitude was obtained. A simulation-based T-peel test was also performed to analyze the fracture behavior of the adhesive, and the relation between the fracture toughness GC and separation load LP could be expressed as Lp = 12.687Gc. The optimized objective function value of von Mises stress was improved by 18% compared to an initial design, and constraints of the delamination indicator and positioning of the neutral plane were satisfied. [ABSTRACT FROM AUTHOR]

An internal fire whirl (IFW) can be generated readily in a tall vertical shaft model under appropriate ventilation provisions. IFW inside a shaft model with corner gap ventilation and closed roof has been reported earlier. It is demonstrated in this paper by scale modeling experiment that an IFW can also be generated even when the ceiling is partly open for smoke extraction. A shaft model of width 34 cm, length 35 cm and height 145 cm, with a 3.6-cm corner gap to provide ventilation on the side. A 7-cm diameter fuel tray of n-propanol was used. Fire in the shaft model was studied under two scenarios, with front-half covered roof and rear-half covered roof (relative to the position of the gap). Background-oriented Schlieren (BOS) technique was applied to measure the neutral plane height across the corner gap. Thermocouples were used to measure smoke temperature and to counter-check results from the BOS technique. Compared with the closed-roof model, IFW was generated at an earlier time, and fuel burning rate was higher in the partly opened roof scenarios. In addition, the smoke layer was kept at a higher level and had a lower temperature. [ABSTRACT FROM AUTHOR]

Construction of foundations close to each other, which results in substantial interaction between them, has become a common practice. However, not much literature is available for practicing engineers to analyse and design deep and shallow foundations when they are constructed adjacent to each other. This study analyses one such scenario where a structure supported on drilled shafts was supposed to be constructed adjacent to another structure supported on a large mat foundation with heavy floor load. A detailed parametric study using finite element techniques was performed to better understand stress distributions and develop simplified methods to analyse this type of problems. Lateral stress and drag forces on the shafts resulting from the heavy load on the mat foundation were identified to be the key factors. This paper is focused on estimating the drag forces. A deformation bulb under a uniformly loaded square foundation, similar to the well-known pressure bulb, is proposed. A new term ‘Isodefers’ has been proposed to refer the lines of equal deformation. Isodefers are a significant tool for practicing engineers to understand vertical deformation distribution below a uniformly loaded square area and estimate drag forces on nearby deep foundations by determining its neutral plane. [ABSTRACT FROM AUTHOR]

We investigated the effects of repetitive mechanical bending stress on top-gate amorphous InGaZnO thin-film transistors (TFTs). Electrical parameters were gradually degraded under repetitive tensile bending stress. After 50 000 bending cycles, some TFTs showed gate leakage current increase during positive gate bias thermal stress. After 60 000 bending cycles, conduction path was physically severed to an open state. However, when an additional organic layer was deposited on the TFTs as a stress-reduction layer, device characteristics were unaffected by repetitive mechanical stress up to 100 000 cycles. Finite element structural simulations show the vulnerable stress-concentrated regions that cause leakage current, contact resistance increase, and interface traps. Electrical deterioration under repetitive bending is significantly mitigated by applying a stress-reduction layer. [ABSTRACT FROM AUTHOR]

Conventional beam elements based on the mid-plane formulation are often used to predict vibration frequencies of beams. Recently published work on the vibration of functionally graded materials (FGM) beams shows that if the positions of immovable end supports are at a different plane to the middle-plane, beam elements based on mid-plane formulation will yield inaccurate results. This paper extends this work further by critically examining the effect of end support positions along the height of the beam in the context of vibration analysis. A formulation for vibration analysis of beams based on reference-plane formulation is proposed. In order to verify the proposed formulation, we considered FE modelling of beams based on generalized beam elements, composite shell elements and 3D solid elements that are able to accurately capture the effect of end support height position on vibration frequencies. Two vibrating beam examples are considered. The first problem deals with a single layer beams and the second problem deals with a double layer beam. Both problems are analyzed using the proposed method and FE models based on generalized beam elements, composite shell elements and 3D solid elements for different end support conditions and heights. Single layer beam was also modelled in FE using conventional beam elements. The results clearly showed that if one uses conventional beam elements for vibration analysis of beams, the results will not be accurate if immovable end supports are applied at an eccentricity to the mid-plane. Vibration frequencies predicted from the proposed reference-plane formulation were shown to agree well with the results from FE models based on generalized beam elements, composite shell elements, and 3D solid elements. [ABSTRACT FROM AUTHOR]

Undesirable vibrations that occurred in cold rolling mills, widely known as chatter, are studied in this article by considering the interaction of three types of vibrations, namely, the longitudinal vibration of the rolled strip and the torsional and vertical vibrations of the upper work roll. The dynamic component of rolling force is determined using the quasi-static model under the assumption that the changes in roll gap and strip tension produce the variation of rolling force. The coupled vibrations of the work roll and rolled strip are mathematically governed by a set of 3-degree-of-freedom non-linear equations. Under chatter conditions, a new variable is introduced to represent the motion of the quasi-neutral point. A stability criterion for the motion of the quasi-neutral point is developed by studying the eigenvalues of the corresponding characteristic equation of the linearized parts of the non-linear equations. The chatter stability can then be examined by evaluating the determinants of five matrices. Numerical examples are given to show the stable and unstable vibrations in the cold rolling process. The unstable vibration would lead to skidding phenomenon and even break the rolled strip. The results presented in this article provide new insights into the dynamic interaction of the coupled vibrations and the dynamics of the rolling process. [ABSTRACT FROM AUTHOR]

A hydrodynamics method (HM) has been developed to predict the contact stresses in hot strip rolling. This method is based on that materials deformed in hot rolling present properties of viscous fluid. The contact stress formulas are derived from Navier-Stokes equation (N-S equation) by using HM. The contact stresses predicted by these formulas agreed well with the experiment data, which verified the validity of these formulas. By comparisons of experiment data with the results predicted by the derived formulas, the Amontons-Coulomb friction model (ACM) and the Absolute constant friction model (AFM), it is found that formulas derived by HM can smooth the friction hill and has higher accuracy in predicting the neutral plane positon than the ACM and the AFM did. It is believed that the contact stress formulas derived by HM can be used to solve on line hot rolling problems. [ABSTRACT FROM AUTHOR]

There has been a controversial claim that the beam model formulation for functionally graded materials (FGM) beams must be based on the neutral plane for correct solutions. This claim cuts across well accepted mid-plane formulation for FGM beams. Presented herein is a critical examination of the mid-plane and neutral plane formulations for the vibration analysis of FGM beams. It will be shown herein that the problem arises from a misconception that the immovable supporting points are located at the mid-plane when the supporting points are actually at the neutral plane when basing the formulation on the neutral plane. The positioning of the immovable simple supports at two different planes leads to the difference in results. However, in the case of movable simple supports, the mid-plane formulation furnishes the same vibration solutions as the neutral plane formulation, even though the supports are located on different planes. Both formulations furnish the same frequency results for clamped ends. The conclusion is that there is nothing wrong with using the mid-plane formulation for FGM beams. In fact, by using the neutral plane formulation, it would be difficult to solve FGM beams with a constraint on the longitudinal displacement at the midplane. [ABSTRACT FROM AUTHOR]

This paper presents the characteristics of the spill plume in a compartment fire with high-low opposing openings. Three sizes of doors (low openings), six sizes of windows (high openings), and three heat release rates were adopted. Mass flow rates through the openings were calculated with new length scales considering the effect of bidirectional airflow at the door, and then the expression of the neutral plane height was derived. The calculated results had good agreement with the experimental results. To reveal the effect of the opening sizes on the energy proportion, the heat fluxes from the openings were calculated based on the new length scales, and the heat lost through compartment boundaries was also obtained. It was found the size variation of any opening would affect the proportion of each part of the energy and the ratio of heat flow through openings can be represented by the 5/2 power of the ratio of the new length scales. The fire spill plume thickness is related to the horizontal velocity of the plume ejected from the window, and one linear relationship was established. Moreover, the heat flux along the façade and the temperature distribution of the fire spill plume outside the window were given with the new length scale. • The characteristics of the spill plume in a compartment fire with high-low opposing openings were investigated. • Mass flows through the openings were calculated with new length scales, and the expression of neutral plane height was derived. • The effect of the opening sizes on the energy proportion through the opening was revealed. • Establishing the correlation between the fire spill plume thickness and the horizontal velocity of the plume ejected. • The heat flux along the façade and the temperature distribution of the fire spill plume outside the window were given with new length scale. [ABSTRACT FROM AUTHOR]

The generation of negative skin friction (NSF) induces the additional axial force on the pile, which exerts a detrimental load rather than a beneficial one. However, the effect of soil creep on the long-term development of NSF has remained poorly understood. The study uses numerical analysis to investigate this effect. First, an elasto-viscoplastic model with an enhanced time integration algorithm is successfully implemented into a finite element code. Next, the two-dimensional axisymmetric pile-soil interaction model is established and properly calibrated with a known field case. Finally, parametric studies are conducted to examine different degrees of creep effect on the variation in NSF and neutral plane (NP) within the primary and secondary consolidation periods. According to the findings, a high creep coefficient of the soil results in an increase in NSF and descending trend of the NP. The creep induced delay of NSF is observed attributed to the increase in excess pore pressure during the early stage of consolidation. The NP position varies drastically at the commencement of consolidation when taking creep into consideration. Lastly, the study proposes an exponential prediction model to reflect the time dependence of the location of the NP. [ABSTRACT FROM AUTHOR]

Negative skin friction is considered one of the problems in the design of piled foundations in soft soil. The negative skin friction induces an additional compressive force on the pile called the dragload as well as, an additional pile movement called the downdrag. Ignoring the effect of negative skin friction in the design of piles leads to structural, and serviceability problems. The dragload depends on various factors such as, pile characteristics (method of installation, material, and surface treatment), soil properties (shear strength and compressibility), pile–soil relative movement, and degree of consolidation. In this paper, an axisymmetric finite element model was used to simulate, and analyze the pile–soil interaction problem of negative skin friction. The soft soil was simulated by the double hardening soil model, and the pile was described by a linear elastic model. A field case study for two instrumented end bearing driven pipe precast concrete piles in Bangkok soft clay was back analyzed. The various approaches to model the pile element, and load configurations were analyzed, and compared. An extensive parametric study was carried out to investigate the effect of different factors on the dragload value, neutral plane location, slip length, and pile movement.

Working in the context of Hilbert's axiomatic system, we prove that the Tzitzeica-Johnson configuration has sense in neutral geometry. The elements of a Tzitzeica-Johnson configuration allow us to analyse the Euclidean or the non-Euclidean character of the metric of the plane