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The nonlinear rotational behavior of radially deformed double-walled carbon nanotube (DWCNT) bundles is investigated using all-atom molecular dynamics simulations. Results show that the hexagonal packing and transverse collapse of the DWCNTs decelerates the rotating carbon nanotubes (CNTs) or even reverses the rotation direction. The increase in the line-edge roughness and compressive normal pressure between the CNTs act as a brake pad to decrease the linear speed of the rotating CNTs. The maximum breaking power exerted by structural deformation is characterized by the diameters of the DWCNTs and their instantaneous angular velocities. The proposed brake pad model presents a classical yet fundamental mechanism for directly engineering chaotic rotational dynamics in multibody nanosystems. [ABSTRACT FROM AUTHOR]

Nanomaterials, particularly nanofibers produced through electrospinning, have garnered significant attention due to their unique properties and diverse applications. This research explores the influence of collector design, electrode geometry, and collector speed on the properties of electrospun polyacrylonitrile (PAN) nanofibers. Finite element analysis (FEA) was employed to simulate electric fields, revealing the impact of collector geometry on field intensity. The experimental setup, enclosed in an isolated chamber, employed various collector types and electrode configurations. Scanning electron microscope (SEM) analysis showcased the effect of collector speed on fiber alignment and diameter. Furthermore, FEA simulations elucidated the role of electrode geometry and voltage in shaping the electric field, impacting fiber properties. The study introduces a novel, in-house method for producing highly aligned nanofibers and provides insights into optimizing electrospinning parameters for enhanced fiber properties. A testing protocol is devised to minimize surface damage when conducting mechanical tests on nanofiber films, employing a dynamic mechanical analyzer (DMA). Mechanical testing demonstrated the correlation between alignment and tensile strength. Overall, this research contributes valuable insights for tailoring electrospinning processes for tissue engineering and energy storage.

Introduction: A session at the 2023 International Consultation on Incontinence – Research Society (ICI‐RS) held in Bristol, UK, focused on the question: Is the time right for a new initiative in mathematical modeling of the lower urinary tract (LUT)? The LUT is a complex system, comprising various synergetic components (i.e., bladder, urethra, neural control), each with its own dynamic functioning and high interindividual variability. This has led to a variety of different types of models for different purposes, each with advantages and disadvantages. Methods: When addressing the LUT, the modeling approach should be selected and sized according to the specific purpose, the targeted level of detail, and the available computational resources. Four areas were selected as examples to discuss: utility of nomograms in clinical use, value of fluid mechanical modeling, applications of models to simplify urodynamics, and utility of statistical models. Results: A brief literature review is provided along with discussion of the merits of different types of models for different applications. Remaining research questions are provided. Conclusions: Inadequacies in current (outdated) models of the LUT as well as recent advances in computing power (e.g., quantum computing) and methods (e.g., artificial intelligence/machine learning), would dictate that the answer is an emphatic "Yes, the time is right for a new initiative in mathematical modeling of the LUT." [ABSTRACT FROM AUTHOR]

The epithelial-mesenchymal transition (EMT) is a critical step in physiological and pathological processes such as the embryonic development, the wound healing, and the cancer progression, wherein cells transition from a tightly adherent epithelial state to a dispersed mesenchymal state. An EMT core circuit model driven by the synergistic regulation of matrix stiffnesses and growth factors was proposed. The results show that, during the EMT, the matrix stiffnesses and growth factors collaboratively regulate the expression of the E/N-cadherin, a typical cell-cell adhesion molecule, by modulating the EMT-activating transcription factors, thus influencing the progression and reversibility of the EMT. The model elucidates the mechanism of synergistic interactions between mechanical and chemical factors on cell-cell adhesion during the EMT, laying a theoretical foundation for understanding the occurrence, development mechanisms, and preventive strategies against diseases such as cancer. [ABSTRACT FROM AUTHOR]

IntroductionIn the field of orthopedic surgery, the notched continuum robot has garnered significant attention due to its passive compliance, making it particularly suitable for procedures in complex and delicate bone and joint regions. However, accurately modeling the notched continuum robot remains a significant challenge.MethodsThis paper proposes a high-precision mechanical modeling method for the notched continuum robot to address this issue. The flexible beam deflection prediction model based on the beam constraint model is established. The force balance friction model considering internal friction is established. An accurate static model is obtained, which can accurately estimate the deformation and deflection behavior of the robot according to the input driving force. The kinematic model of the notched continuum robot based on the static model is established. This method achieves high accuracywhile ensuring computational efficiency.ResultsExperimental results demonstrate that the static model's error is only 0.1629 mm, which corresponds to 0.25% of the total length of the continuum robot, which is 66 mm.DiscussionThis research provides valuable insights into the modeling and control of continuum robots and holds significant implications for advancing precision in orthopedic surgery.

High-performance polymers are extensively used in various applications undergoing long-term cyclic loadings. The deformation behaviour of an amorphous thermoset epoxy resin undergoing cyclic compressive loading is investigated for a range of applied deformation levels. The measurements indicate significant hysteresis upon repeated loading and unloading cycles with progressive accumulation of plastic strain. Cyclic damage leads to a reduction of the stress needed to reach the peak strain per cycle, while cyclic stiffening corresponding to an increase of elastic modulus with increasing number of cycles is observed, attributed to chain orientation effects. The dissipated energy asymptotically decreases to zero under strain-controlled cycling conditions. Interestingly, when monotonically loaded after cycling, the epoxy exhibits an increase in yield strength. This ‘re-yield’ stress level is closely related to the selected value of the peak (unloading) strain level and increases with increasing number of loading cycles.

Degradation of the mechanical properties of oil-immersed louver contacts is an important cause of exceeding the DC resistance on the valve side of extra-high voltage converter transformers. In this paper, the mapping relationship between force-deformation and force-contact resistance of oil-immersed louver contacts is measured and obtained by utilizing the performance test platform of oil-immersed louver contacts. Based on the stress-strain curves of the stainless steel of the strap under different temperature conditions, a mechanical simulation model of the oil-immersed louver contacts was established. Based on this model, the effects of the plastic deformation temperature of the louver contacts and the stainless steel keel structure on the heating power of the strap are investigated. The results show that the mechanical properties of the louver contacts decrease with the increase in temperature, and the permanent plastic deformation of the strap occurs when the operating temperature reaches 400 °C. Appropriately increasing the torsion angle and thickness of the stainless steel keel can slow down the local overheating of the louver contacts caused by eccentricity. The research results are helpful to understand the mechanism of local overheating failure of oil-immersed electric contact parts, and provide a reference for the design, fault analysis and further research of oil-immersed electric contact parts.

Retaining a waterproof coal pillar is an important measure to defend against water inrush accidents in mining areas and guarantee the safe mining of the next working face. In this paper, the mechanical model of the coal pillar is established and the calculation formula of the waterproof coal pillar width is derived. Then, the development of the water-conducting fracture zone of the overlying rock layer under different coal pillar widths is analyzed using numerical simulation and finally, the integrity of the coal pillar is detected using the geophysical survey method. The main conclusions are as follows: (1) According to the mechanical failure characteristics of the coal pillar, it can be divided into the plastic zone, elastic zone, and water pressure damage zone. The mechanical calculation model for each zone was established, and the formula for calculating the width of the waterproof coal pillar was obtained. (2) Numerical simulation was employed to investigate the development condition of the water conducting fracture zone in the overlying rock strata under the actual width of the waterproof coal pillar; the simulation results indicated that the water conducting fracture zone of two working faces was not connected, which can effectively prevent the accumulation of water in the 2303 goaf. (3) On-site geophysical surveys determined that the influence of water-logged goaf on the coal pillar is between 5 to 15 m; the integrity of the waterproof coal pillar is good, which effectively prevents water accumulation in the previous working face goaf and ensures safe mining in the next working face. [ABSTRACT FROM AUTHOR]

Dowel action of the longitudinal reinforcement in RC beams without and with small amounts of shear reinforcement is typically considered a constant shear contribution determined from the splitting strength of the concrete cover. However, in a recent experimental investigation by the authors, it was shown that the shear force transferred by dowel action for beams without shear reinforcement should be determined from the dowel displacement and a linear elastic model and a rigid plastic dowel model. This article is aimed at extending this model to also cover members with small amounts of shear reinforcement. To that aim, a novel approach to calculate the shear force carried by dowel action of the longitudinal reinforcement in both beams with and without shear reinforcement is presented. The model is derived by establishing an equilibrium of work between the internal stored elastic or dissipated plastic energy and the external work performed by the shear force in the dowel. Additionally, a method to determine the displacement of the dowel from DIC measurements is presented. For the remaining shear‐transfer actions, reasonable constitutive models from the literature are adapted. On the basis of DIC measurements, the shear force carried by each of the shear‐transfer actions is calculated for 16 shear tests of beams without and with small amounts of shear reinforcement. The sum of shear force carried by each of the shear‐transfer actions is shown to predict the applied shear force fairly well, from the development of the critical shear crack until failure. Additionally, it is shown that for beams with shear reinforcement below the minimum requirements according to the current design standards, the shear capacity is governed by aggregate interlock, residual tensile stresses, and the inclination of the compression chord. While for beams with shear reinforcement above the minimum requirements, the shear capacity is governed by the shear reinforcement and dowel action. [ABSTRACT FROM AUTHOR]

Copyright of Revista Iberoamericana de Ingeniería Mecánica is the property of Editorial UNED and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aged individuals and astronauts experience bone loss despite rigorous physical activity. Bone mechanoresponse is in-part regulated by mesenchymal stem cells (MSCs) that respond to mechanical stimuli. Direct delivery of low intensity vibration (LIV) recovers MSC proliferation in senescence and simulated microgravity models, indicating that age-related reductions in mechanical signal delivery within bone marrow may contribute to declining bone mechanoresponse. To answer this question, we developed a 3D bone marrow analog that controls trabecular geometry, marrow mechanics and external stimuli. Validated finite element (FE) models were developed to quantify strain environment within hydrogels during LIV. Bone marrow analogs with gyroid-based trabeculae of scaffold volume fractions (SV/TV) corresponding to adult (25 ​%) and aged (13 ​%) mice were printed using polylactic acid (PLA). MSCs encapsulated in migration-permissive hydrogels within printed trabeculae showed robust cell populations on both PLA surface and hydrogel within a week. Following 14 days of LIV treatment (1 ​g, 100 ​Hz, 1 ​h/day), cell proliferation, type-I collagen (Collagen-I) and filamentous actin (F-actin) were quantified for the cells in the hydrogel fraction. While LIV increased all measured outcomes, FE models predicted higher von Mises strains for the 13 ​% SV/TV groups (0.2 ​%) when compared to the 25 ​% SV/TV group (0.1 ​%). While LIV increased collagen-I volume 34 ​% more in 13 ​% SV/TV groups when compared to 25 ​% SV/TV groups, collagen-I and F-actin measures remained lower in the 13 ​% SV/TV groups when compared to 25 ​% SV/TV counterparts, indicating that both LIV-induced strains and scaffold volume fraction (i.e. available scaffold surface) affect cell behavior in the hydrogel phase. Overall, bone marrow analogs offer a robust and repeatable platform to study bone mechanobiology.

The development of computer-aided facilities has contributed to the optimization of tissue engineering techniques due to the reduction in necessary practical assessments and the removal of animal or human-related ethical issues. Herein, a bone scaffold based on poly (2-hydroxyethyl methacrylate) (PHEMA), gelatin and graphene oxide (GO), was simulated by SOLIDWORKS and ABAQUS under a normal compression force using finite element method (FEM). Concerning the mechanotransduction impact, GO could support the stability of the structure and reduce the possibility of the failure resulting in the integrity and durability of the scaffold efficiency which would be beneficial for osteogenic differentiation. [ABSTRACT FROM AUTHOR]

Summary: This simulation study investigated whether a 4-degrees-of-freedom (DOF) arm could strike a target with a 50-DOF whip using a motion profile similar to discrete human movements. The interactive dynamics of the multi-joint arm was modeled as a constant joint-space mechanical impedance, with values derived from experimental measurement. Targets at various locations could be hit with a single maximally smooth motion in joint-space coordinates. The arm movements that hit the targets were identified with fewer than 250 iterations. The optimal actions were essentially planar arm motions in extrinsic task-space coordinates, predominantly oriented along the most compliant direction of both task-space and joint-space mechanical impedances. Of the optimal movement parameters, striking a target was most sensitive to movement duration. This result suggests that the elementary actions observed in human motor behavior may support efficient motor control in interaction with a dynamically complex object.

Retaining a waterproof coal pillar is an important measure to defend against water inrush accidents in mining areas and guarantee the safe mining of the next working face. In this paper, the mechanical model of the coal pillar is established and the calculation formula of the waterproof coal pillar width is derived. Then, the development of the water-conducting fracture zone of the overlying rock layer under different coal pillar widths is analyzed using numerical simulation and finally, the integrity of the coal pillar is detected using the geophysical survey method. The main conclusions are as follows: (1) According to the mechanical failure characteristics of the coal pillar, it can be divided into the plastic zone, elastic zone, and water pressure damage zone. The mechanical calculation model for each zone was established, and the formula for calculating the width of the waterproof coal pillar was obtained. (2) Numerical simulation was employed to investigate the development condition of the water conducting fracture zone in the overlying rock strata under the actual width of the waterproof coal pillar; the simulation results indicated that the water conducting fracture zone of two working faces was not connected, which can effectively prevent the accumulation of water in the 2303 goaf. (3) On-site geophysical surveys determined that the influence of water-logged goaf on the coal pillar is between 5 to 15 m; the integrity of the waterproof coal pillar is good, which effectively prevents water accumulation in the previous working face goaf and ensures safe mining in the next working face.

This literature review focuses on the primary morphological and structural characteristics, and mechanical properties identified in muscles affected by spastic cerebral palsy (CP). CP is a nonprogressive neurological disorder caused by brain damage and is commonly diagnosed at birth. Although the brain damage is not progressive, subsequent neurophysiological developmental adaptations may initiate changes in muscle structure, function, and composition, causing abnormal muscle activity and coordination. The symptoms of CP vary among patients. However, muscle spasticity is commonly present and is one of the most debilitating effects of CP. Here, we present the current knowledge regarding the mechanical properties of skeletal tissue affected by spastic CP. An increase in sarcomere length, collagen content, and fascicle diameter, and a reduction in the number of satellite cells within spastic CP muscle were consistent findings in the literature. However, studies differed in changes in fascicle lengths and fiber diameters. We also present a conceptual mechanical model of fascicle force transmission that incorporates mechanisms which impact both serial and lateral force production, highlighting the connections between the macro and micro structures of muscle to assist in deducing specific mechanisms for property changes and reduced force production. [ABSTRACT FROM AUTHOR]

Certain assemblies of fibers, called fiber bundles, play a crucial role in the statistical macroscale properties of fibrous structures like natural or artificial materials. Based on the concept of using idealized statistical fiber bundle cells (FBCs) as model elements, the software named FiberSpace was developed by us earlier for the phenomenological modeling of the tensile test process of real fibrous structures. The model fibers of these FBCs had been considered linear elastic, which was suitable for modeling certain textiles and composites. However, the biological tissues are multilevel structures with fiber-like building elements on every structural level where the fiber elements on the dominant level are statistical bundles of elementary fibers. Hence, their modeling required us to introduce model fibers of nonlinear mechanical behavior and derive the proper mathematical formulas for the calculation of the expected tensile force processes of the FBCs. Accordingly, we developed a new version of FiberSpace. The proposed nonlinear FBCs-based modeling method is essentially phenomenological that decomposes the measured and averaged stress–strain curve into the weighted sum of the responses of different idealized nonlinear FBCs. However, this decomposition can give certain information about the fibrous structure and some details of its damage and failure sub-processes. A special application of nonlinear E-bundles, where the measured stress–strain curve is expanded into a product-function series, may give another type of description for the failure process and can be applied to single measurements of structured failure process containing significant peaks and drops as well. The fitted phenomenological FBC models provide a decomposition of the measured force–strain curve, which enables to construct informative damage and failure maps. The applicability of the phenomenological modeling method and the fitting procedure is demonstrated with the tensile test data of some human and animal tissues, such as facial nerves and tendons. [ABSTRACT FROM AUTHOR]

The compression and shear performances of the stitched sandwich thermal protection structure (SSTPS) was systematically investigated through experimental and simulation methods in this study. Compression and shear testing methods were designed, and macroscopic performance data for SiO 2f /SiO 2 thin panels and SSTPS were successfully obtained, thereby validating the rationality of the experimental approach. By establishing mechanical experimental methods, the correlation between microscopic structural features and macroscopic mechanical performance was revealed, and mechanical modeling and analysis work was conducted. The experimental and numerical results indicate that compression and shear failure of thin panels mainly occur at the intersections of fiber bundles, exhibiting non-brittle failure. The delamination of sandwich materials or the buckling deformation of panels is identified as the primary cause of the nonlinear response in SSTPS. Elevated temperatures induce an increase in the modulus and strength of SSTPS and a decrease in toughness, correlated with the high-temperature densification of the matrix structure. Finite element simulations reveal the critical role of component and interface damage in macroscopic nonlinear mechanical responses. The research demonstrates that, the compressive and shear failure mechanisms of SiO 2f /SiO 2 thin panels and SSTPS were successfully elucidated through the implementation of an innovative experimental methodology. [ABSTRACT FROM AUTHOR]

According to the requirements of loading and unloading of safety valve, an automatic guide vehicle for safety valve handling is designed. Aiming at the established mechanical model of in-situ steering of truck, the simulation analysis of virtual prototype is carried out by using ADAMS simulation software. The steering motion under different wheel ground friction coefficient, steering acceleration time and eccentricity is simulated for many times. Based on the simulation curve of rotation center displacement and discrete points of relative displacement value in three-dimensional space, the uncertainty is compared and analyzed The simulation results and prototype tests verify the correctness of the theoretical analysis, which provides a basis for the optimization of the mechanical structure and the design of the control system of the carrier.

In this work, we address the inverse kinetics problem of motion planning of soft biomimetic actuators driven by three chambers. Soft biomimetic actuators have been applied in many applications owing to their intrinsic softness. Although a mathematical model can be derived to describe the inverse dynamics of this actuator, it is still not accurate to capture the nonlinearity and uncertainty of the material and the system. Besides, such a complex model is time-consuming, so it is not easy to apply in the real-time control unit. Therefore, developing a model-free approach in this area could be a new idea. To overcome these intrinsic problems, we propose a back-propagation (BP) neural network learning the inverse kinetics of the soft biomimetic actuator moving in three-dimensional space. After training with sample data, the BP neural network model can represent the relation between the manipulator tip position and the pressure applied to the chambers. The proposed algorithm is more precise than the analytical model. The results show that a desired terminal position can be achieved with a degree of accuracy of 2.46% relative average error with respect to the total actuator length.

Auxetic materials can be exploited for coupling different types of tissues. Herein, we designed a material where the microorganism metabolic activity yields the formation of buckled/collapsed bubbles within gelling silicone cylinders thus providing auxetic properties. The finite element model of such hollow auxetic cylinders demonstrated the tubular structure to promote worm-like peristalsis. In this scenario, the described hybrid auxetic structures may be applied to the longitudinal intestinal lengthening and tailoring procedure to promote enteral autonomy in short bowel syndrome. The presented material and analytical design synergistic approach offer a pioneering step for the clinical translation of hybrid auxetic materials. [ABSTRACT FROM AUTHOR]

Accurate cutting force prediction is crucial in improving machining precision and surface quality in the micro-milling process, in which tool wear and runout are essential factors. A generic analytic cutting force model considering the effect of tool edge radius on tool flank wear and tool runout in the micro-end milling process is proposed. Based on the analytic modeling of the cutting part of the cutting edge in the end face of the micro-end mill bottom, the actual radius model of the worn tool is established, considering the tool edge radius and tool flank wear. The tool edge radius, tool wear, tool runout, trochoidal trajectories of the current cutting edge, and all cutting edges in the previous cycle are comprehensively considered in the instantaneous uncut chip thickness calculation and the cutter–workpiece engagement determination. The cutting force coefficient model including tool wear is established. A series of milling experiments are performed to verify the accuracy and effectiveness of the proposed cutting force model. The results show that the predicted cutting forces are in good agreement with the experimental cutting forces, and it is necessary to consider tool wear in the micro-milling force modeling. The results indicate that tool wear has a significant influence on the cutting forces and cutting force coefficients in the three directions, and the influences of tool wear on the axial cutting force and axial force coefficient are the largest, respectively. The proposed cutting force model can contribute to real-time machining process monitoring, cutting parameters optimization and ensuring machining quality. [ABSTRACT FROM AUTHOR]

Many orally administrated drugs exhibit poor bioavailability due to their limited solubility. The smartFilm technology is an innovative approach to improve the drug aqueous solubility, where the drug is embedded within the matrix of cellulose-based paper in an amorphous state, hence increasing its solubility. Despite its proven effectiveness, smartFilms, i.e., pieces of paper, exhibit limited flowability and are not easy to swallow, and thus oral administration is not convenient. In addition, there is a lack of knowledge of their mechanical behavior under compression. This study aimed to transform unloaded smartFilms, i.e., paper, into a flowable physical form and investigated its mechanical behavior when compressed. Granules made of paper were prepared via wet granulation and were compressed into tablets. The influence of using different amounts and forms of sucrose, as a binder, on the pharmaceutical properties of the produced granules and tablets was studied and the most suitable composition was identified by using instrumented die experiments. For this, the Poisson's ratio and Young's modulus were determined for different compaction force levels and the deformation behavior was estimated with the Heckel mathematical model. All granule batches showed good flowability with angle of repose values between 25–35°. Granule batches with ≤30% dry sucrose content produced tablets that fulfilled the European Pharmacopeia requirements, and the compaction behavior of the granules was found to be comparable to the behavior of classical binders and compression enhancers. Paper can be transferred into granules. These granules can be used as suitable intermediate products for the production of tablets made of paper in large, industrial scale. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the Ahe formation in the DZ area of Tarim Basin, the weak structural plane and natural fractures develop, and the hydraulic fractures are complex. The conventional fracturing model cannot accurately guide the field fracturing design. The guiding idea of this research is the integration of geological engineering. It carried out the core indoor experiment. Based on the imaging logging data, the properties of the weak structural plane were quantitatively characterized. The geomechanical model with the weak structural plane and the spatial distribution model of natural fractures were constructed. The propagation law of hydraulic fracture was studied. The simulation results compared the hydraulic fracture considering the property of weak discontinuity and without considering the property of weak discontinuity. The results showed that the weak structure significantly limited the longitudinal expansion of hydraulic cracks, and the cracks were easier to extend laterally. Based on the geomechanical and natural fracture model considering the property of weak structural plane, the hydraulic fracture morphology of different fracturing parameter combinations was simulated, and the fracturing parameters were optimized. The field application verified the longitudinal restriction of the weak laminar structure on the fracture and the rationality of the fracturing design. [ABSTRACT FROM AUTHOR]

Introduction: In the field of orthopedic surgery, the notched continuum robot has garnered significant attention due to its passive compliance, making it particularly suitable for procedures in complex and delicate bone and joint regions. However, accurately modeling the notched continuum robot remains a significant challenge., Methods: This paper proposes a high-precision mechanical modeling method for the notched continuum robot to address this issue. The flexible beam deflection prediction model based on the beam constraint model is established. The force balance friction model considering internal friction is established. An accurate static model is obtained, which can accurately estimate the deformation and deflection behavior of the robot according to the input driving force. The kinematic model of the notched continuum robot based on the static model is established. This method achieves high accuracywhile ensuring computational efficiency., Results: Experimental results demonstrate that the static model's error is only 0.1629 mm, which corresponds to 0.25% of the total length of the continuum robot, which is 66 mm., Discussion: This research provides valuable insights into the modeling and control of continuum robots and holds significant implications for advancing precision in orthopedic surgery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Pang, Liang, Lin, Zhang and Du.)

Micromechanical characterization of the oxygen-rich layer (ORL) of a Ti-6Al-4V alloy due to high-temperature oxidation was investigated at room temperature. The tensile strength of the pre-oxidized specimens linearly decreased as a function of the surface fraction of ORL in relation to the gage section, demonstrating a competition between oxygen strengthening and embrittlement. Electron-probe microanalyses and nanoindentation testing aimed at locally assessing the elastic and hardness response of the material as a function of the oxygen content. These properties were used in finite element simulations to quantify stress profiles within the oxygen-graded material for different ORL thickness/specimen thickness couples. • Oxygen embrittlement was investigated in Ti alloys using micromechanical testing. • High oxygen-rich layer/specimen thickness ratio was possible using ultrathin specimen. • Competition between oxygen strengthening and embrittlement was observed. • Linear relationship was established between elastic modulus and oxygen concentration. • Numerical simulations on oxygen-graded Ti alloys demonstrated size effects on the "core/shell" response. [ABSTRACT FROM AUTHOR]

According to the requirement of LPG tank car inner wall cleaning,a wall-climbing jet cleaning trolley was designed,which combined high-pressure water jet and mechanical brushing. By establishing the static and dynamic model of car wall cleaning,the minimum adsorption force equation for reliable adsorption of car and the minimum driving force equation for stable operation and steering of car were derived. The example analysis under different wall inclination angles shows that the main instability form of static adsorption is wall sliding,and the minimum adsorption force is 51. 8 N when the wall inclination angle is120 degrees. The main instability form of stable operation is differential steering,and the minimum driving torque is 2. 95 N·m when the wall inclination angle is 50 degrees. The prototype experiment proves that the research results are reliable,which provides a theoretical basis for the development of LPG tank car automatic cleaning equipment and the corresponding technical research.

This paper introduces the modular design and manufacturing method, mechanical model, and test verification of a new type of soft actuator driven by fluid. First, the modular design scheme and driving principle of omnidirectional bending and elongation of the soft actuator are described. Three print-based elastic air cavities constrained by fire lines are distributed radially inside the actuator. The actuator can complete the 3 DOF motions of omnidirectional bending and elongation. From the basic principle of material mechanics, a novel mechanical model of the soft elastomer actuator is established. By numerically solving the nonlinear model, the relationship between actuator elongation/bending angle and driving pressure is obtained. The theoretical prediction and test results show that the deformation of the actuator exhibits a linear relationship with pressure when the chambers are charged. Additionally, the maximum allowable load force on the actuator terminal also exhibits good linearity when the driving pressure increases. Furthermore, the established mechanical model, which considers gravity effects can more accurately describe the features of bend and elongation of the actuator. The results shows that the proposed model is more convenient than the FEM models. This study provides theoretical support for accurate control of a soft actuator.

Auxetic materials can be exploited for coupling different types of tissues. Herein, we designed a material where the microorganism metabolic activity yields the formation of buckled/collapsed bubbles within gelling silicone cylinders thus providing auxetic properties. The finite element model of such hollow auxetic cylinders demonstrated the tubular structure to promote worm-like peristalsis. In this scenario, the described hybrid auxetic structures may be applied to the longitudinal intestinal lengthening and tailoring procedure to promote enteral autonomy in short bowel syndrome. The presented material and analytical design synergistic approach offer a pioneering step for the clinical translation of hybrid auxetic materials.

Accurate cutting force prediction is crucial in improving machining precision and surface quality in the micro-milling process, in which tool wear and runout are essential factors. A generic analytic cutting force model considering the effect of tool edge radius on tool flank wear and tool runout in the micro-end milling process is proposed. Based on the analytic modeling of the cutting part of the cutting edge in the end face of the micro-end mill bottom, the actual radius model of the worn tool is established, considering the tool edge radius and tool flank wear. The tool edge radius, tool wear, tool runout, trochoidal trajectories of the current cutting edge, and all cutting edges in the previous cycle are comprehensively considered in the instantaneous uncut chip thickness calculation and the cutter–workpiece engagement determination. The cutting force coefficient model including tool wear is established. A series of milling experiments are performed to verify the accuracy and effectiveness of the proposed cutting force model. The results show that the predicted cutting forces are in good agreement with the experimental cutting forces, and it is necessary to consider tool wear in the micro-milling force modeling. The results indicate that tool wear has a significant influence on the cutting forces and cutting force coefficients in the three directions, and the influences of tool wear on the axial cutting force and axial force coefficient are the largest, respectively. The proposed cutting force model can contribute to real-time machining process monitoring, cutting parameters optimization and ensuring machining quality.

Many orally administrated drugs exhibit poor bioavailability due to their limited solubility. The smartFilm technology is an innovative approach to improve the drug aqueous solubility, where the drug is embedded within the matrix of cellulose-based paper in an amorphous state, hence increasing its solubility. Despite its proven effectiveness, smartFilms, i.e., pieces of paper, exhibit limited flowability and are not easy to swallow, and thus oral administration is not convenient. In addition, there is a lack of knowledge of their mechanical behavior under compression. This study aimed to transform unloaded smartFilms, i.e., paper, into a flowable physical form and investigated its mechanical behavior when compressed. Granules made of paper were prepared via wet granulation and were compressed into tablets. The influence of using different amounts and forms of sucrose, as a binder, on the pharmaceutical properties of the produced granules and tablets was studied and the most suitable composition was identified by using instrumented die experiments. For this, the Poisson’s ratio and Young’s modulus were determined for different compaction force levels and the deformation behavior was estimated with the Heckel mathematical model. All granule batches showed good flowability with angle of repose values between 25–35°. Granule batches with ≤30% dry sucrose content produced tablets that fulfilled the European Pharmacopeia requirements, and the compaction behavior of the granules was found to be comparable to the behavior of classical binders and compression enhancers. Paper can be transferred into granules. These granules can be used as suitable intermediate products for the production of tablets made of paper in large, industrial scale.

A novel anti-tetrachiral with L-type ligaments (LATC) meta-structure was proposed in this work by a combination of the classical anti-tetrachiral (ATC) and anti-tetra-missing rib (ATMR) meta-structures. Finite element (FE) analyses and experimental tests were then carried out to investigate the mechanical performance and the underlying deformation mechanisms of the proposed meta-structure by adopting Polyamide 6/carbon-fiber (PA6/CF) as the base material. The results indicated that the proposed meta-structure exhibited a tunable constant negative Poisson's ratio (NPR) over a relatively large strain range. To enhance the understanding of the underlying microstructural mechanisms, theoretical formulas for the in-plane effective elastic constants (i.e., effective Poisson's ratio, elastic modulus and shear modulus) of the meta-structure were further derived by employing the energy method. The accuracy of the theoretical formulas was subsequently validated through FE analysis and experimental tests. • A novel auxetic meta-structure was proposed. • The proposed design achieves adjustable and constant NPRs within extreme large strains. • A mechanics model for the effective elastic constants of the proposed design has been established. [ABSTRACT FROM AUTHOR]

Summary: Somitogenesis is often described using the clock-and-wavefront (CW) model, which does not explain how molecular signaling rearranges the pre-somitic mesoderm (PSM) cells into somites. Our scanning electron microscopy analysis of chicken embryos reveals a caudally-progressing epithelialization front in the dorsal PSM that precedes somite formation. Signs of apical constriction and tissue segmentation appear in this layer 3-4 somite lengths caudal to the last-formed somite. We propose a mechanical instability model in which a steady increase of apical contractility leads to periodic failure of adhesion junctions within the dorsal PSM and positions the future inter-somite boundaries. This model produces spatially periodic segments whose size depends on the speed of the activation front of contraction (F), and the buildup rate of contractility (Λ). The Λ/F ratio determines whether this mechanism produces spatially and temporally regular or irregular segments, and whether segment size increases with the front speed.

This article presents a microfluidic system with multiple constriction channels in parallel capable of characterizing cortical tension of single cells in a continuous manner. Single cells are forced to travel through constriction channels (cross-sectional area smaller than single cells) in a quasi-static manner with front/rear membrane curves of deformed cells captured. Then the front/rear membrane curves are translated into cortical tension based on a home-developed mechanical model illustrating the relationship among cortical tension, cell deformation, aspiration pressure and geometrical parameters of constriction channels. Based on this microfluidic platform, cortical tension with sample sizes as large as thousands of single HL-60 cells were quantified for the first time where a variety of experimental conditions were used for comparison. Specifically, comparable values of cortical tension were obtained from both front and rear membrane portions of single cells while aspiration pressure rather than channel length can affect the quantified values of cortical tensions to an extent. As a demonstration, the microfluidic system was used to process HL-60 cells under a variety of cell treatments, producing higher cortical tension for the cells treated with paraformaldehyde for fixation and lower cortical tension for the cells treated with cytochalasin D for cytoskeleton compromise in comparison to wild-type counterparts. In summary, the developed microfluidic system can quantify cortical tension from single cells in a continuous fluid flow, which may function as an enabling tool in the field of single-cell analysis. [ABSTRACT FROM AUTHOR]

Numerous models have been developed in the literature to simulate the thermomechanical behavior of amorphous polymers at large strain. These models generally show a good agreement with experimental results when the material is submitted to uniaxial loadings (tension or compression) or in the case of shear loadings. However, this agreement is highly degraded when they are used in the case of combined load cases. A generalization of these models to more complex loads is scarce. In particular, models that are identified in tension or compression often overestimate the response in shear. One difficulty lies in the fact that 3D models must aggregate different physical modeling, described with different kinematics. This requires the use of transport operators complex to manipulate. In this paper, we propose a mechanical model for large strains, generalized in 3D, and precisely introducing the adequate transport operators in order to obtain an exact kinematic. The stress–strain duality is validated in the writing of the power of internal forces. This generalized model is applied in the case of a polycarbonate amorphous polymer. The simulation results in tension/compression and shear are compared with the classical modeling and experimental results from the literature. The results greatly improve the numerical predictions of the mechanical response of amorphous polymers submitted to any load case. [ABSTRACT FROM AUTHOR]

The stress mechanism of a straight mortise-and-tenon joint with wooden pegs in traditional residential wooden structures was analyzed, and a theoretical moment-rotation model of the joint was derived. To verify the model, three full-scale joint specimens were fabricated and subjected to low-cycle reversed loading tests. All specimens showed tensile cracking parallel to the grain at the top or bottom of the tenon neck. The theoretical calculation results are consistent with the experimental results. The results of the parametric analysis based on the theoretical model show the following: the rotational stiffness and bending moment of the joint increase as the beam width increases; as the beam height increases, the moment increases, but the initial stiffness of the joint is only slightly impacted; as the column diameter increases, the initial stiffness and moment increase, and the free rotation of the joint decreases; as the gap between the mortise and tenon increases, the initial stiffness and moment decrease; as the sliding friction coefficient increases, both the rotational stiffness and moment of the joint increase, and the increase is greater after the joint yields than before.

Aerogels are solids with exceptional characteristics, such as ultra-low density, high surface area, high porosity, high adsorption and low-thermal conductivity. Due to these characteristics, aerogels are emerging to be a popular material among the scientific community, since their discovery in 1931. However, their applicability has remained questionable due to the poor mechanical characteristics, such as brittleness and low tensile strength. In the last three decades, due to the rapid development in the computational resources and numerical methods, a deeper understanding of physical behavior and properties of these materials have been extensively investigated. In this work, an effort is made to critically analyze and categorize the computational models and simulation results available for silica, carbon, carbon nanotubes, graphene, and cellulose aerogels. This work focused on a better understanding of how these materials were computationally modeled and simulated over the time-period and at different length-scales, wherein primary approaches, such as molecular dynamics (MD), coarse-grained, micromechanical multiscale and continuum mechanics modeling, were discussed. It also strives to give an insight into the areas where further computational studies are required, which could lead to numerous other application fields. The systematic review provides a mechanistic basis for reliable applications of aerogels. [ABSTRACT FROM AUTHOR]