Explore the vast range of titles available.

Thin fiber networks are widely represented in nature and can be found in man-made materials such as paper and packaging. The strength of such materials is an intricate subject due to inherited randomness and size-dependencies. Direct fiber-level numerical simulations can provide insights into the role of the constitutive components of such networks, their morphology, and arrangements on the strength of the products made of them. However, direct mechanical simulation of randomly generated large and thin fiber networks is characterized by overwhelming computational costs. Herein, a stochastic constitutive model for predicting the random mechanical response of isotropic thin fiber networks of arbitrary size is presented. The model is based on stochastic volume elements (SVEs) with SVE size-specific deterministic and stochastic constitutive law parameters. The randomness in the network is described by the spatial fields of the uniaxial strain and strength to failure, formulated using multivariate kernel functions and approximate univariate probability density functions. The proposed stochastic continuum approach shows good agreement when compared to direct numerical simulation with respect to mechanical response. Furthermore, strain localization patterns matched the one observed in direct simulations, which suggests an accurate prediction of the failure location. This work demonstrates that the proposed stochastic constitutive model can be used to predict the response of random isotropic fiber networks of arbitrary size.

Purpose Esophageal pressure (Pes) is a minimally invasive advanced respiratory monitoring method with the potential to guide management of ventilation support and enhance specific diagnoses in acute respiratory failure patients. To date, the use of Pes in the clinical setting is limited, and it is often seen as a research tool only. Methods This is a review of the relevant technical, physiological and clinical details that support the clinical utility of Pes. Results After appropriately positioning of the esophageal balloon, Pes monitoring allows titration of controlled and assisted mechanical ventilation to achieve personalized protective settings and the desired level of patient effort from the acute phase through to weaning. Moreover, Pes monitoring permits accurate measurement of transmural vascular pressure and intrinsic positive end-expiratory pressure and facilitates detection of patient–ventilator asynchrony, thereby supporting specific diagnoses and interventions. Finally, some Pes-derived measures may also be obtained by monitoring electrical activity of the diaphragm. Conclusions Pes monitoring provides unique bedside measures for a better understanding of the pathophysiology of acute respiratory failure patients. Including Pes monitoring in the intensivist’s clinical armamentarium may enhance treatment to improve clinical outcomes.

Based on the comprehensive analysis of the origin and structural characteristics, this study established the physical and mechanical models of an unstable rock mass with sandstone and mudstone interbeds as its base (also referred to as an unstable rock mass with an interbed base) and proposed the retreat mechanisms of the base, i.e., the softening and compressive deformation of mudstones within it induces the tensile failure of the thin-bedded sandstones in it. Moreover, this study explained the sliding-shear and toppling failure modes of an unstable rock mass with an interbed base and put forward the mechanical criteria for the two failure modes. The case analysis showed that the base retreat of the Leijiagou unstable rock mass conforms to the mechanical mechanisms of base retreat proposed in this study and that this unstable rock mass will not undergo sliding-shear or toppling failures under the current situation. The preliminary prediction indicates that the Leijiagou unstable rock mass will lose stability after 15.2 years due to toppling failures, when the critical depth of its rock cavity will be 4.1 m.

This paper presents a numerical model of an integrated 3D casing-cement-formation system, to evaluate the mechanical tensile and shear failure of the cement at the casing-cement interface as the pressure and temperature conditions of the formation and borehole vary during production. The model which includes the formation pressure, unlike others proposed, was developed by stages under finite element discretization and compared to analytical models. Results show that increasing the formation temperature increases the probability of tensile and shear failure in the cement, while increasing the wellbore temperature decreases these probabilities. On the other hand, the decrease in the well pressure reduces the probability of shear failure and increases the tensile failure. In the case of formation pressure, the opposite occurs.

Acoustic emission (AE) monitoring was used during indentation tests on the cross section of plasma-sprayed 8 wt.% yttria-stabilized zirconia (8YSZ) thermal barrier coatings to investigate the relationship between AE signals and the associated deformation or single cracking events. The damage evolution in 8YSZ was studied by examining signal characteristics with the aid of AE parameter analysis and wavelet packet decomposition. The results show that the coatings were firstly elasto-plastically deformed, and microcracks gradually developed around the indentation. Then, delamination occurred and the fracture was made up of some longer cracks and dozens of microcracks. AE signals originating from coating deformation, formation of microcracks and longer cracks show different amplitudes and frequencies. The results indicate that the features of AE parameters differ depending on the mechanical failure mechanism, and AE responses are closely related to the fracture behavior and are dependent on splat microstructure of the coatings.

Purpose - The purpose of this paper is to encourage the integration of Lean principles with reliability models to sustain Lean efforts on a long-term basis. It seeks to present a modified FMEA that will allow Lean practitioners to understand and improve the reliability of Lean systems. The modified FMEA approach is developed based on the four critical resources required to sustain Lean systems: personnel, equipment, materials, and schedules.Design methodology approach - A three-phased methodology approach is presented to enhance the reliability of Lean systems. The first phase compares actual business and operational conditions with conditions assumed in Lean implementation. The second phase maps potential deviations of business and operational conditions to their root cause. The third phase utilizes a modified Failure Mode and Effects Analysis (FMEA) to prioritize issues that the organization must address.Findings - A literature search shows that practical methodologies to improve the reliability of Lean systems are non-existent.Research limitations implications - The knowledge database involves many tedious calculations and hence needs to be automated.Originality value - The paper has defined Lean system reliability, developed a conceptual model to enhance the Lean system reliability, developed a knowledge base in the form of detailed hierarchical root trees for the four critical resources that support our Lean system reliability, developed a Risk Assessment Value (RAV) based on the concept of effectiveness of detection using Lean controls when Lean designer implements Lean change, developed modified FMEA for the four critical resources.

Silicon is a promising anode material due to its high theoretical specific capacity, low lithiation potential and low lithium dendrite risk. Yet, the electrochemical performance of silicon anodes in solid-state batteries is still poor (for example, low actual specific capacity and fast capacity decay), hindering practical applications. Here the chemo-mechanical failure mechanisms of composite Si/Li 6 PS 5 Cl and solid-electrolyte-free silicon anodes are revealed by combining structural and chemical characterizations with theoretical simulations. The growth of the solid electrolyte interphase at the Si|Li 6 PS 5 Cl interface causes severe resistance increase in composite anodes, explaining their fast capacity decay. Solid-electrolyte-free silicon anodes show sufficient ionic and electronic conductivities, enabling a high specific capacity. However, microscale void formation during delithiation causes larger mechanical stress at the two-dimensional interfaces of these anodes than in composite anodes. Understanding these chemo-mechanical failure mechanisms of different anode architectures and the role of interphase formation helps to provide guidelines for the design of improved electrode materials. Although silicon anodes are promising for solid-state batteries, they still suffer from poor electrochemical performance. Chemo-mechanical failure mechanisms of composite Si|Li 6 PS 5 Cl and solid-electrolyte-free silicon anodes are now revealed and should help in designing improved electrodes.

Catastrophically mechanical failure of soft self-healing materials is unavoidable due to their inherently poor resistance to crack propagation. Here, with a model system, i.e., soft self-healing polyurea, we present a biomimetic strategy of surpassing trade-off between soft self-healing and high fracture toughness, enabling the conversion of soft and weak into soft yet tough self-healing material. Such an achievement is inspired by vascular smooth muscles, where core-shell structured Galinstan micro-droplets are introduced through molecularly interfacial metal-coordinated assembly, resulting in an increased crack-resistant strain and fracture toughness of 12.2 and 34.9 times without sacrificing softness. The obtained fracture toughness is up to 111.16 ± 8.76 kJ/m 2 , even higher than that of Al and Zn alloys. Moreover, the resultant composite delivers fast self-healing kinetics (1 min) upon local near-infrared irradiation, and possesses ultra-high dielectric constants (~14.57), thus being able to be fabricated into sensitive and self-healing capacitive strain-sensors tolerant towards cracks potentially evolved in service. Catastrophically mechanical failure, of soft self-healing materials often stems from its poor resistance to crack, propagation. Here, the authors present a strategy of surpassing trade-off, between soft self-healing and high fracture toughness, enabling the, conversion of soft and weak into soft yet tough self-healing materials.

Graphene is often referred to as the strongest material in existence. That may be so for a perfect crystal, but most graphene sheets are polycrystalline, and the grain boundaries affect their mechanical properties. A new study reveals that both the density and detailed arrangement of the defects that form the grain boundaries play a significant part in determining the strength of a polycrystalline graphene sheet. The two-dimensional crystalline structures in graphene challenge the applicability of existing theories that have been used for characterizing its three-dimensional counterparts. It is crucial to establish reliable structure–property relationships in the important two-dimensional crystals to fully use their remarkable properties. With the success in synthesizing large-area polycrystalline graphene 1 , 2 , 3 , 4 , 5 , understanding how grain boundaries (GBs) in graphene 2 , 3 , 4 alter its physical properties 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 is of both scientific and technological importance. A recent work showed that more GB defects could counter intuitively give rise to higher strength in tilt GBs (ref.  10 ). We show here that GB strength can either increase or decrease with the tilt, and the behaviour can be explained well by continuum mechanics. It is not just the density of defects that affects the mechanical properties, but the detailed arrangements of defects are also important. The strengths of tilt GBs increase as the square of the tilt angles if pentagon–heptagon defects are evenly spaced, and the trend breaks down in other cases. We find that mechanical failure always starts from the bond shared by hexagon–heptagon rings. Our present work provides fundamental guidance towards understanding how defects interact in two-dimensional crystals, which is important for using high-strength and stretchable graphene 14 for biological and electronic applications.

Applying high stack pressure (often up to tens of megapascals) to solid-state Li-ion batteries is primarily done to address the issues of internal voids formation and subsequent Li-ion transport blockage within the solid electrode due to volume changes. Whereas, redundant pressurizing devices lower the energy density of batteries and raise the cost. Herein, a mechanical optimization strategy involving elastic electrolyte is proposed for SSBs operating without external pressurizing, but relying solely on the built-in pressure of cells. We combine soft-rigid dual monomer copolymer with deep eutectic mixture to design an elastic solid electrolyte, which exhibits not only high stretchability and deformation recovery capability but also high room-temperature Li-ion conductivity of 2×10 −3  S cm −1 and nonflammability. The micron-sized Si anode without additional stack pressure, paired with the elastic electrolyte, exhibits exceptional stability for 300 cycles with 90.8% capacity retention. Furthermore, the solid Li/elastic electrolyte/LiFePO 4 battery delivers 143.3 mAh g −1 after 400 cycles. Finally, the micron-sized Si/elastic electrolyte/LiFePO 4 full cell operates stably for 100 cycles in the absence of any additional pressure, maintaining a capacity retention rate of 98.3%. This significantly advances the practical applications of solid-state batteries. Applying high stack pressure is primarily done to address the mechanical failure issue of solid-state batteries. Here, the authors propose a mechanical optimization strategy involving elastic electrolyte to realize solid-state batteries operating without external pressurizing.