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Advances in the use of in situ transmission electron microscopy (TEM) to study mechanical deformation have enabled a direct correlation of mechanical properties with microstructures, in particular, atomic-level defect dynamic processes. Shear deformation of metallic materials has been noticed to lead to unique microstructural features with superior properties that would be difficult to achieve by traditional metallurgical processes. However, in contrast to the case of in situ TEM studies of structural evolution under tension, compression, and bending, in situ TEM probing of dynamic processes during direct shear loading, especially at microscales and nanoscales, is very limited. This paper reviews recent progress on the development of in situ TEM for studying shear deformation in terms of both the technique and the scientific insights that have been gained. In addition, we discuss current challenges encountered in the use of in situ TEM for shear deformation, such as the limited total strain, strain rate, and spatial and temporal resolution. To provide perspective, we present promising opportunities for in situ TEM studies with pure shear loading by taking advantage of the integration of advanced imaging techniques both in TEM and scanning transmission electron microscopy domains, advanced electron detectors, highly efficient chemical analysis, data-driven machine learning, and environmental conditions. [ABSTRACT FROM AUTHOR]

Although tension-shear coupling of weave fabrics in large deformation has been observed in experiments, most constitutive models for weave fabrics often ignore this coupling effect for simplicity. In this paper, a nonlinear anisotropic hyperelastic constitutive model is proposed to consider this tension-shear coupling effect. Draping experiments of a plain weave fabric over a tetrahedron mold are carried out to validate the proposed coupling constitutive model. Subsequently, the influences of tension-shear coupling on draping processes are investigated. Numerical simulation results indicate that the tension-shear coupling effect significantly changes fiber reorientation during draping process, which makes shear deformation tend to be uniform and reduces the local shear deformation concentration and should not be neglected in woven fabric stamping with salient double curvatures. [ABSTRACT FROM AUTHOR]

The role of deformation twinning in the formation of a fine-grained structure in cold-rolled 310S steels has been investigated by using transmission electron microscopy. When 310S steels were rolled at room temperature, a deformation twin appeared in the early stage of the rolling process. A fine lamellar structure consisting of the deformation twin and matrix (T-M) developed with increased rolling strain. At moderate strain, micro shear bands appeared in the area of the T-M lamellar structure, and the shear bands grew and multiplied during further cold-rolling. Such multiplication of shear bands destroyed the T-M lamellar structure, which caused the development of a fine-grained structure. In shear bands, a highly misoriented structure with a submicron grain size was generated. In this paper, the mechanism of the transmutation process from the T-M lamellae into the fine-grained structure is discussed. Particular emphasis is laid on the role of deformation twinning in the formation of the fine-grained structure. [ABSTRACT FROM AUTHOR]

In this paper, the effect of thermal cycle on the interlaminate shear strength (ILSS) and impact behaviour of unidirectional carbon fibre reinforced polyetherimide (PEI) matrix composites were studied. Samples were subjected to 100 thermal cycles (by immersing from boiling water (100°C) to ice water (0°C). The effects of thermal cycles were characterized by short beam shear and instrumented impact testers. Also Fractographic investigations were done using a scanning electron microscope (SEM). It is observed that the plastic deformations at the fibre/matrix and interlaminar interface as well as residual stresses lower the ILSS and flexural modulus of the material proportional with the number of thermal cycles. Up to the first 20 thermal cycles the material shows a brittle fracture with lower fracture energy, but after the 20th thermal cycles it is possible to observe that the material fractures with higher fracture energy at longer fracture time. A remarkable difference in the fracture morphology between the thermal cycled and un-treated materials has been observed. It is found that thermal cycles strictly affect the fracture morphology. [ABSTRACT FROM AUTHOR]

A new method has been developed for measuring not only bending but also shear flexibility of pulp fibers by using confocal laser scanning microscopy. Based on the Steadman and Luner method, a two-stage wet pressing process was used which enabled both bending and shear flexibility and both bending and shear modulii of fibers to be determined with a single test. Three types of fibers, i.e., bleached spruce Kraft Pulp (BKP), aspen bleached chemi-themomechanical pulp (BCTMP), and aspen themomechanical pulp (CTMP), were tested. Results show that the longitudinal elastic modulii of the fibers are in a range of 3–37 GPa, and the transverse shear modulii of them are in a range of 27–103 MPa. It was also found that the shear contribution to the overall fiber deformation ranged from 60% to 90% for the fibers measured. This substantiates the concept of shear contribution to measured fiber flexibility as proposed by Waterhouse and Page. [ABSTRACT FROM AUTHOR]