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Engineering materials commonly suffer from cumulative and irreversible damage during cyclic deformation, leading to fatigue failure. Developing materials with better fatigue resistance is imperative. This work reports a metallic glass network nanomaterial that possesses superior strain‐hardening ability. After a certain number of fatigue tests, the peak stress of the nanomaterial can even be up to four times its original value. This superior strain‐hardening ability originates from the unique plastic mechanism. During cyclic deformation, localized shear transformation zones form and develop, especially in the stress concentration regions. Ligaments crosslinked to these regions cannot sustain their original configurations and contract toward these plastic hinges, resulting in the collapse and coalescence of voids. This densification enhances the engineering stress during each cycle. The fatigue features can be altered by adjusting the cyclic frequency. Stronger strain‐hardening ability can be achieved at lower cyclic frequencies. Highlights: Fatigue responses of nanoporous metallic glass (NPMG) are revealed.The NPMG exhibits superior strain‐hardening ability and remarkable densification.This strain‐hardening behavior is caused by plastic deformation.The fatigue responses of NPMG can be tuned by tailing the cyclic frequency and strain. [ABSTRACT FROM AUTHOR]

The degradation of proton exchange membranes (PEMs) can significantly affect the structural integrity and lifetime of fuel cells. This study investigates the effects of temperature, peak load, initial strain, and loading modes on the mechanical properties of Nafion® 212 PEM using an in‐situ biaxial testing system. The findings indicate that membrane creeping is positively correlated with temperature and peak loads. The stress relaxation rate increases with the increase of initial strain, and an increase in temperature also leads to an apparent decrease in the anti‐relaxation properties of Nafion® 212 membrane. Additionally, the mechanical properties of low‐cycle fatigue at various temperatures were explored under biaxial cyclic loading conditions. When the temperature is fixed, the membrane strain increases and gradually stabilizes with the rise of fatigue cycles. With an increase in temperature, the strain increases at a greater rate. The phase difference increases with temperature growth, and the "hysteresis" phenomenon of the strain becomes more pronounced, resulting in greater energy loss. These results provide valuable insights into the mechanical behavior of Nafion® 212 PEM under different conditions. And can inform the design and optimization of fuel cell systems and contribute to the development of more robust and durable PEM materials. [ABSTRACT FROM AUTHOR]

Electron beam melting (EBM) is a promising three‐dimensional printing technology for the fabrication of components with high complexity and freedom of structural design. However, the major limit for its wider industrial applications is to preclude manufacturing the large‐scale part in one piece. It is because the part size is largely limited by the enclosed vacuum chamber. An alternative option is the use of welding to join EBM‐processed subparts together. In this study, fatigue crack growth (FCG) rate and high‐cycle fatigue (HCF) performance were measured for both EBM‐processed Ti–6Al–4V alloy and its welded joints. An X‐parameter model was then proposed to correlate stress amplitude and geometric parameters (location, size, and shape) of the critical defects at the crack origins with fatigue life. Research framework and result from this work are expected to serve a reference for the defect‐based fatigue life evaluation of welded parts individually manufactured using additive manufacturing. [ABSTRACT FROM AUTHOR]

Chiral metastructures consisting of ring (polygonal or cubic) nodes and elastic bending ligaments exhibit excellent design flexibility for compliant structures. In this paper, based on rigid cubic node rotation and the kinematic geometrical relations of a three‐dimensional (3D) isotropic anti‐tetrachiral structure, an analytical expression for the modulus of the 3D isotropic anti‐tetrachiral structure is derived from strain energy analysis. The nylon powder Selected Laser Sintering (SLS) additive manufacturing technique is employed for fabricating two types of 3D isotropic anti‐tetrachiral specimens with different geometrical parameters; then comparison between experiments, finite element analysis (FEA), and theoretical studies is performed for verifying the analytical formula. The mechanical properties of 3D isotropic anti‐tetrachiral structures can be tuned with two independent dimensionless geometrical parameters. The proposed 3D anti‐tetrachiral structures can be employed for designing advanced structures against impact damages, realizing flexibility of industrial components, and optimizing the vibration attenuation abilities of engineering structures. [ABSTRACT FROM AUTHOR]

Auxetics with negative Poisson's ratio (NPR) can expand dimensions along the direction perpendicular to the tensile direction, such as rigid rotation, reentrant and chiral structures, etc. The mechanical performances of chiral metastructures are closely related to internal defects and interactions between defects. In this paper, two types of irregular chiral structures with Gaussian dispersion of circular node positions and missing ligaments are designed, namely: anti‐tetrachiral metastructure and tetrachiral hybrid metastructure. These two types of chiral metastructures are characterized by node radius, ligament thickness, ligament length, the circular node center dispersion range, and missing ligament percentages. Effects of random node distribution range and cell wall missing percentage on the elastic modulus and Poisson's ratio of chiral metastructures are investigated through experimental tests and finite element (FE) simulation systematically. Through dimensionless analysis, it is found that ligament thickness has remarkable influence on the negative Poisson's ratio. Effect of missing ligament on the mechanical properties of the structure is greater than effect of random node center dispersion. With the increase of ligament missing percentage, the resultant modulus of chiral metastructures decreases, and the corresponding NPR increases. [ABSTRACT FROM AUTHOR]