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In soft devices, complex actuation sequences and precise force control typically require hard electronic valves and microcontrollers. Existing designs for entirely soft pneumatic control systems are capable of either digital or analog operation, but not both, and are limited by speed of actuation, range of pressure, time required for fabrication, or loss of power through pull-down resistors. Using the nonlinear mechanics intrinsic to structures composed of soft materials—in this case, by leveraging membrane inversion and tube kinking—two modular soft components are developed: a piston actuator and a bistable pneumatic switch. These two components combine to create valves capable of analog pressure regulation, simplified digital logic, controlled oscillation, nonvolatile memory storage, linear actuation, and interfacing with human users in both digital and analog formats. Three demonstrations showcase the capabilities of systems constructed from these valves: 1) a wearable glove capable of analog control of a soft artificial robotic hand based on input from a human user’s fingers, 2) a human-controlled cushion matrix designed for use in medical care, and 3) an untethered robot which travels a distance dynamically programmed at the time of operation to retrieve an object. This work illustrates pathways for complementary digital and analog control of soft robots using a unified valve design.

Anisotropic materials are widely found in nature and engineering, and their crack paths often exhibit complex morphologies such as deflection, kinking, and zig-zag propagation. The formation of these patterns is governed not only by the anisotropic fracture toughness but also by the external loading, whose influence on the crack path is still not fully understood. In this work, we analysed crack propagation in a strongly anisotropic plate with an edge crack under three external loading modes: uniaxial tension (UT), a stationary K-field boundary (Stat-KB), and a surfing K-field boundary (Surf-KB) that moves with the nominal crack tip. A strongly anisotropic high-order phase-field model was used to simulate crack propagation, with the anisotropy degree controlled by a scalar χ . The results show that UT gives an almost straight crack, and Stat-KB leads to a single kinked but non-stationary path, whereas Surf-KB produces a quasi-steady zig-zag path whose kink angle and amplitude increase with χ .

Thin-ply composite failure modes also significantly differ from conventional ply composite failure modes, with the final failure mechanism switching from irregular progressive failure to direct fracture characterized by a uniform fracture with the reduction of the ply thickness. When open holes and bolt joints are involved, thin-ply-laminated composites exhibit more complex stress states, damage evolution, and failure modes. Compared to the experimental study of thin-ply-laminated composite-bolted joints, there are few reports about numerical analysis. In order to understand the damage evolution and failure mechanism of thin-ply-laminated composites jointed by single-lap bolt, a progressive damage model based on three-dimensional (3D) LaRC failure criterion combined with cohesive element is constructed. Through an energy-based damage evolution method, this model can capture some significant mechanical characteristics in thin-ply-laminated structures, such as the in situ effect, delamination inhibition, and fiber compressive kinking failure. The comparisons between the numerical predictions and experimental observations are made to verify the accuracy of the proposed model. It is found that the predicted stress-displacement curves, failure modes, damage morphologies, etc., are consistent with the experimental results, indicating that the presented progressive damage analysis method displays excellent accuracy. The predicted stress at the onset of delamination is 50% higher than that of the conventional thick materials, which is also consistent with experimental results. Moreover, the numerical model provides evidence that the microstructure of thin-ply-laminated composite performs better in uniformity, which is more conducive to inhibiting the intra-layer damage and the expansion of delamination damage between layers. This study on the damage inhibition mechanism of thin-ply provides a potential analytical tool for evaluating damage tolerance and bearing capabilities in thin-ply-laminated composite-bolted joints.

The LaRC02 criterion is a classical criterion for determining fiber kinking failure of UD laminates under longitudinal compression (LC), but its basis for determining matrix cracking in a fiber kinking coordinate system is based on stress-invariant theory rather than on a physical mechanism. Herein, three Puck-like physical-mechanism-based inter-fiber failure criteria are extended to LC failure of UD composites, and thus three failure criteria (denoted as LC-Guo, LC-Li, and LC-Puck failure criteria) are constructed for fiber kinking failure determination. The stresses in the global coordinate system are transformed to the fiber kinking coordinate system by a three-level coordinate system transformation, and then the failure determination is performed using the three Puck-like criteria. The results show that the overall accuracy of the three proposed criteria is higher than that of the LaRC02 criterion, especially the LC-Guo criterion. Additionally, an analysis of the influence of material properties shows that the failure envelope curves tend to be conservative, and the predicted off-axial compression strength decreases as the transverse compression strength and in-plane shear strength increase and the transverse tensile strength decreases. This work proposes a more reasonable assessment methodology for the determination of LC failure of UD composites, which has important theoretical significance and engineering value.

An experimental investigation was focused on the failure behavior of unidirectional fiber-reinforced polymers when subjected to combined longitudinal/transverse compression and in-plane shear due to off-axis loading. Block-shaped and end-loaded specimens, spanning ten different fiber orientations (0°, 5°, 10°, 15°, 20°, 30°, 45°, 60°, 75°, and 90° with respect to the loading direction), were loaded to ultimate failure using a dedicated fixture. Different failure modes, including longitudinal compression, in-plane shear, and transverse compression, were identified, along with distinctive characteristics of the corresponding failure envelopes. Four physically based failure theories—Hashin, Camanho, Puck, and LaRC05—were subjected to a comparative analysis. Criteria derived from the concept of the action plane consistently outperformed in describing matrix-dominated failures, providing both qualitative and quantitative predictions of failure stresses and fracture plane orientation. However, for fiber-dominated failures, these theories seem to fall short in providing satisfactory predictions, particularly in accurately describing the influence of shear on fiber compression failure. Although criteria based on fiber-kinking theory can reasonably explain the formation of kink bands, they tend to yield overly conservative results. Recalibrations and minor refinement based on experimental results were implemented, leading to an improved agreement. Finally, the constructive role of off-axis compression tests in characterizing the failure behavior of unidirectional composites is discussed.

The origins of the various outbursts of hard X-rays from magnetars (highly magnetized neutron stars) are still unknown. We identify instabilities in relativistic magnetospheres that can explain a range of X-ray flare luminosities. Crustal surface motions can twist the magnetar magnetosphere by shifting the frozen-in footpoints of magnetic field lines in current-carrying flux bundles. Axisymmetric (2D) magnetospheres exhibit strong eruptive dynamics, i.e., catastrophic lateral instabilities triggered by a critical footpoint displacement of ψ crit ≳ π. In contrast, our new three-dimensional (3D) twist models with finite surface extension capture important non-axisymmetric dynamics of twisted force-free flux bundles in dipolar magnetospheres. Besides the well-established global eruption resulting (as in 2D) from lateral instabilities, such 3D structures can develop helical, kink-like dynamics, and dissipate energy locally (confined eruptions). Up to 25% of the induced twist energy is dissipated and available to power X-ray flares in powerful global eruptions, with most of our models showing an energy release in the range of the most common X-ray outbursts, ≲1043 erg. Such events occur when significant energy builds up while deeply buried in the dipole magnetosphere. Less energetic outbursts likely precede powerful flares, due to intermittent instabilities and confined eruptions of a continuously twisting flux tube. Upon reaching a critical state, global eruptions produce the necessary Poynting-flux-dominated outflows required by models prescribing the fast radio burst production in the magnetar wind—for example, via relativistic magnetic reconnection or shocks.

Fibre kinking is the most prevalent failure mode observed in UD composites. The accurate prediction of kinking failure is of paramount importance in industrial applications. To address this challenge, we develop a non-linear mean-field debonding model (NMFDM) based on our previous work, which efficiently captures the non-linear material behaviour of UD composites under longitudinal compression leading to kinking failure. Building upon the foundation of our earlier mean-field model, this enhanced NMFDM incorporates geometric non-linearity due to fibre rotation under longitudinal compression and the non-linear elasticity of fibres in the fibre direction. These additions address crucial aspects in kink band formation and the typically non-linear elastic behaviour of carbon fibres, which were not considered in our previous work. Additionally, we introduce a fibre kinking model (FKM) to predefine initial fibre misalignments in the geometries, allowing us to study the formation of kink bands. The FKM considers the effects of initial misalignments and fibre rotations during kinking by proposing a transformation law for off-axis cases. As a representative example, we investigate the initiation and evolution of kink band formation in an AS4/8552 UD composite by predefining various initial misalignments. The results demonstrate that our newly proposed NMFDM yields reliable predictions of kink band formation in UD composites, outperforming other existing models and even comparing favorably to micrograph observations of kink bands. Compared to our previous work, this enhanced model offers a more comprehensive understanding of kink band formation, particularly under large strains, by incorporating the non-linear elasticity of fibres in the fibre direction. This advancement opens up potential applications in designing composite structures with improved resistance to compressive failure, paving the way for broader applications in aerospace, automotive, and other industries where high-performance composite components are crucial.

Turbulence plays a key role in forming the complex geometry of the large-scale current sheet (CS) and fast energy release in a solar eruption. In this paper, we present full 3D high-resolution simulations for the process of a moderate coronal mass ejection (CME) and the thermodynamical evolution of the highly confined CS. Copious elongated blobs are generated owing to tearing and plasmoid instabilities, giving rise to a higher reconnection rate, and undergo the splitting, merging, and kinking processes in a more complex way in 3D. A detailed thermodynamical analysis shows that the CS is mainly heated by adiabatic and numerical viscous terms, and thermal conduction is the dominant factor that balances the energy inside the CS. Accordingly, the temperature of the CS reaches to a maximum of about 20 MK, and the range of temperatures is relatively narrow. From the face-on view in the synthetic Atmospheric Imaging Assembly 131 Å, the downflowing structures with similar morphology to supra-arcade downflows are mainly located between the post-flare loops and loop top, while moving blobs can extend spikes higher above the loop top. The downward-moving plasmoids can keep the twisted magnetic field configuration until the annihilation at the flare loop top, indicating that plasmoid reconnection dominates in the lower CS. Meanwhile, the upward-moving ones turn into turbulent structures before arriving at the bottom of the CME, implying that turbulent reconnection dominates in the upper CS. The spatial distributions of the turbulent energy and anisotropy are addressed, which show a significant variation in the spectra with height.

Extracranial internal carotid artery (EICA) kinking and coiling are the most frequently reported carotid anomalies in the literature. Embryogenic and acquired causes for such anomalies have been postulated but the prevalence of kinking and coiling has not been well characterized across age categories. The aim of this study is to evaluate the prevalence of EICA coiling and kinking among different age groups to better understand its potential causes and changes during the course of life. A total of 2856 subjects aged 0 to 96 years were studied by echo-color Doppler (ECD). Morphology and anatomical anomalies of the EICA were assessed. Patients with anatomical anomalies were stratified by age groups and the prevalence of EICA abnormalities was calculated. The maximal velocity recorded at the level of the kinking was compared with that measured in the common carotid artery and the peak systolic velocity kinking ratio (PSVKR) was calculated. A total of 284 subjects (9.94% of the sample) were found to have kinking or coiling of the EICA. The prevalence was significantly higher at the extremes of age (≤ 20 and > 60 years old, p < 0.001) supporting the hypothesis of a reduction with growth and a new increase in the elderly. PSVKR was higher in subjects with more severity kinking. This study showed a higher prevalence of EICA coiling and kinking in the very young and in the elderly. This bimodal prevalence distribution supports the hypothesis of a congenital anomaly that resolves with somatic growth, while advanced age with its many anatomical changes leads to its reappearance or worsening. Studies with longitudinal follow-up and paired observation are required to support this hypothesis.

The hot deformation behavior and structural evolution of the Ti-48Al-2Cr-2Nb with duplex and lamellar initial microstructures were investigated by hot compression test at temperature ranging from 1000 to 1150°C and strain rates from 0.001 to 0.1 s −1 . Both the work hardening and dynamic softening were observed simultaneously during hot deformation of Ti-48Al-2Cr-2Nb with duplex and lamellar microstructures. The peak stress increased with increasing Z parameter for both initial microstructures. Activation energy of deformation (Q) was calculated about 166 and 238 kJ/mol for duplex and lamellar microstructure, respectively. The lowest value of Q appeared at the temperature of 110 °C and strain rate of 0.001s −1 for both duplex and lamellar microstructures. The workability of alloy at strain rate of 0.1s −1 was poor at all temperatures. Bending and kinking the lamellae and partial dynamic recrystallization were the dominant softening mechanisms during hot deformation up to order/disorder transformation temperature (between 1120 and 1130°C). At the upper temperatures, softening occurred by forming shear bands and bending the lamellae. Maximum workability of both duplex and lamellar microstructures appeared at the temperature of 1100°C, where the maximum amount of recrystallized and decomposed γ phase existed.