Papers by Keyword: Shear Deformation

Abstract: Friction stirring is a fundamental process in the friction stir welding (FSW), and moreover, high strain rate deformation in elevated temperature to lead to extremely high ductility and fine grain size. In the present study, friction stirring process has been successfully modelled as a high temperature deformation depending on strain rate and temperature, assuming shear deformation of material in stir zone and generation of frictional heat by rotating tool. Axial load and torque during the process were estimated based on the model, and compared with the experimental data at two kinds of combination ratio in FSW of aluminum and Al-Mg alloy. It was, consequently, confirmed that the model could evaluate flow stress and strain rate from the experimental load and torque.

Abstract: Theoretical and practical aspects of fabrication and processing of bulk metallic nanomaterials are presented. The effect of different deformation modes on the structure formation is shown. Development of nanotechnology with respect to fabrication of gas turbine engines (GTE) parts made of nanostructured superalloys is exemplified.

Abstract: The fracture behavior and fatigue limit in notched specimens of C/C composites were investigated. Also, the effect of specimen thickness on fatigue limit was discussed. Two plates of different thicknesses of plates of C/C composites using fine-woven carbon fiber laminates with α=0°/90° direction were used for testing. α is the angle between the carbon fiber direction and specimen axis. The crack growth behavior and failure mechanism of specimens are derived from the shear damage in the fiber bundle and matrix. Slits of several sizes were cut on both sides of a test section and different geometries of the specimens were prepared. Specimens with slits and blunt-notches were used to compare the fatigue strength. The fatigue limit is related to the method of making the plate of carbon composites. Large sizes of voids are observed in the case of specimens of thinner thickness. The fatigue limit was related to the void fraction, and thinner specimens showed a lower fatigue limit.

Abstract: The shear deformation behavior of the course-grained Cu-8wt%Ag alloy processed by one pass of equal channel angular pressing (ECAP) was revealed through the metallurgical microscope and the scanning electron microscope. Through the macro-level and micro-level synthesis analysis, it is confirmed that there are two shear deformation during the ECAP processing: the one along the intersection plane (IP) and the other along the vertical plane to the IP. And it is estimated that theoretical ranges of two shear angles are-32°<θ₁<0° and 43°<θ₂<58° respectively. Finally, it is also proved that the evolution of the shear bands is affected by the parallel and vertical shear to the IP of the ECAP die, and that, besides the shear along the IP, the shear along the vertical plane to the IP also plays an important role during the plastic deformation.

Abstract: For the model of the nonlinear elastic medium with inhomogeneous properties represented by a continuous change of the elastic moduli and density, the motion problems of a plane longitudinal or transverse shock waves are considered. The matched asymptotic expansions method allows to determine the evolution equations reflecting the nonlinearity of the wave processes and the inhomogeneity of the medium. The transition to the limiting inner problem of the small parameter method is dictated by the chain of inner problems, the solutions of which require a changes in all of the independent variables and their scales.

Abstract: We carried out simulations of contact interaction between BCC iron crystallite and various pure FCC metals under shear loading by means of molecular dynamics. It was shown that the result of this interaction is the transformation of FCC atomic lattice of contacted material into BCC one within a thin layer in the contact zone. The results of simulations can be used to control strength of the interfacial layers of coated materials, as well as to understand the processes which are taking place in surface layers of materials under the contact.

Abstract: The dry sliding friction test of normalized T10 steel against hardened quenched and tempered 20CrMnTi steel under normal load of 60 N and sliding speed of 0.29m/s was carried out on a pin-on-disc tribo-tester. The microstructures in the worn surface layer of T10 steel pin and 20CrMnTi steel disc were analyzed by OM, SEM, and TEM, which were all severely plastically deformed. The ultrafine and even nanoferrite grains (5 nm to 200 nm) were observed in the worn surface layer of T10 steel pin, which was considered to be the result of severely shear deformation.

Abstract: Taking a rise steel as a study, study response of the structure to the dynamic characteristics under fluctuating wind load. The results showed that: deformation of structure under the fluctuating wind load is shear deformation; Structural displacement response curve is similar to the curve of the pressure time history. Because of consider different heights the structure of spatial correlation affect, Displacement positions on different floors response curves are differ.

Abstract: Dissimilar joints between 1050 Al alloy and Cu were prepared by ultrasonic spot welding technique to understand the joint characteristics. The joint strength was evaluated by tensile shear strength test. The joint strength increased with increasing joining energy and the joint produced with sufficiently high energy was fractured at the base metal region of Al alloy. The interface microstructure in Al alloy consists of severely deformed region due to ultrasonic vibration. In addition, the fine and equiaxed grains were observed near the joint interface in the specimens fractured at the base metal. These characteristics were significantly different from the microstructure in the bulk region of Al alloy. In contrast, the microstructure in Cu was hardly changed around the interface after ultrasonic welding. Additionally, thin intermetallic compound layer with the thickness of 40 nm was found to be formed at the joint interface in the specimens fractured at the base metal. Peak temperature during ultrasonic welding was found to be approximately 480 K at the interface, which was measured using embedded thermocouple.

Abstract: Analytical formulations and solutions for natural frequency analysis of functionally graded material (FGM) plates based on two higher-order refined shear deformation theories with 9 and 12 degrees-of-freedom are presented. The displacement model with 12 degrees-of-freedom considers the effect of both transverse shear and normal strain/stress while the other considers only the effect of transverse shear deformation. In addition another higher-order model and the first-order model developed by other investigators and available in the literature are also presented for the evaluation purpose. For mathematical modeling purposes, the Poissons ratio of the material is considered as constant whereas Youngs modulus is assumed to vary through the thickness according to the power law function. The equations of motion are derived using Hamiltons principle. Solutions are obtained in closed-form using Naviers technique and solving the eigenvalue equation. The accuracy of the theoretical formulations and the solution method using the present two higher-order refined models is first established by comparing the results generated in the present investigation with the 3D elasticity solutions already reported in the literature. After establishing the accuracy of predictions, benchmark results for the natural frequencies using all the four models are presented for single layer FGM plate and multi layered FGM sandwich plate with varying edge ratios and side-to-thickness ratios.