The influence of fatigue loading history and microstructural damage on the magnitude of frictional heating and interfacial shear stress in a unidirectional Sic fiber/calcium aluminosilicate matrix composite was investigated. The extent of frictional heating was found to depend upon loading frequency, stress range, and average matrix crack spacing. The temperature rise attained during fatigue can be significant. For example, the temperature rise exceeded 100 K during fatigue at 75 Hz between stress limits of 220 and 10 MPa. Analysis of the frictional heating data indicates that the interfacial shear stress undergoes an initially rapid decrease during the initial stages of fatigue loading: from an initial value over 20 MPa, to approximately 5 MPa after 25 000 cycles. Over the range of 5 to 25 Hz, the interfacial shear stress was not significantly influenced by loading frequency. The implications of frictional heating in fiber-reinforced ceramics are also discussed. [

The elastic stress and strain fields of finite thickness large plate containing a hole are systematically investigated using 3D finite element method. It is found that the stress and strain concentration factors of the finite thickness plate are different even if the plate is in elasticity state except at notch root of plate surface. The maximum stress and strain do not always occur on the mid plane of plate. They occur on the mid plane only in thin plate. The maximum stress and strain concentration factors are not on mid plane and the locations of maximum stress and strain concentration factors are different in thick plate. The maximum stress and strain concentration factors of notch root increase from their plane stress value to their peak values, then decrease gradually with increasing thickness and tend to each constant related to Poisson's ratio of plate, respectively. The stress and strain concentration factors at notch root of plate surface are the same and are the monotonic descent functions of thickness. Their values decrease rapidly and tend to each constant related to Poisson's ratio with plate thickness increasing. The difference between maximum and surface value of stress concentration factor is a monotonic ascent function of thickness. The thicker the plate is or the larger the Poisson's ratio is, the larger the difference is. The corresponding difference of strain concentration factor is similar to the one of stress concentration factor. But the difference magnitude of stress concentration factor is larger than that of strain concentration factor in same plate.

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High ductility in traditional beam-to-column connections is often coupled with beam local buckling. These plastic local buckling deformations are difficult and very costly to repair in any post-disaster reconstruction. This paper investigates a new connection consisting of an extended end-plate, long shank SMA bolts, continuity plates, beam flange ribs and web stiffeners. Advanced 3D models of traditional end-plate bolted connection and the SMA connection are created, and the behavior of the two types of connections is compared. The results show obvious cyclic elongations of the bolts in the SMA connection compared to the beam local buckling in the traditional connection. Rather than the plastic hinge forming away from the column face in the traditional connection, a superelastic hinge forms just at the beam-to-column interface in the SMA connection with the moment-carrying capacity of bolt cluster controlled below the elastic flexural capacity of the connecting beam. The connection deformations are recoverable upon unloading. Moreover, the SMA connection ductility is significantly influenced by the length of the SMA bolts. For SMA bolts which are 1.2 times longer than the standard bolt, the inelastic interstory drift angle reaches 0.035 rad, which indicates that the proposed connection can be designed with sufficient ductility.

A new approach for estimating the interfacial frictional shear stress in fiber-reinforced ceramics is presented. The approach is based upon measurement of the temperature rise which occurs during the cyclic loading of ceramic composites. This temperature rise, which is caused by the frictional slip of fibers within the composite, is related to the level of frictional shear stress which exists along debonded interfaces. To illustrate the technique, the interfacial shear stress in a unidirectional Nicalon-fiber calcium aluminosilicate matrix composite was determined at ambient temperature. [

Some shape memory alloys like NiTi show noticeable high damping property in pseudoelastic range. Due to its unique characteristics, a NiTi alloy is commonly used for passive damping applications, in which the energy may be dissipated by the conversion from mechanical to thermal energy. This study presents a shape memory alloy based micro-damper, which exploits the pseudoelasticity of NiTi wires for energy dissipation. The mechanical model and functional principle of the micro-damper are explained in detail. Moreover, the mechanical behavior of NiTi wires subjected to various temperatures, strain rates and strain amplitudes is observed. Resulting from those experimental results, the damping properties of the micro-damper involving secant stiffness, energy dissipation and loss factor are analyzed. The result indicates the proposed NiTi based micro-damper exhibits good energy dissipation ability, compared with conventional materials damper.

This study presents the deflection, resonant frequency and stress results of rectangular, triangular, and step profile microcantilevers subject to surface stress. These cantilevers can be used as the sensing element in microcantilever biosensors. To increase the overall sensitivity of microcantilever biosensors, both the deflection and the resonant frequency of the cantilever should be increased. The effect of the cantilever profile change and the cantilever cross-section shape change is first investigated separately and then together. A finite element code ANSYS Multiphysics is used and solid finite elements cantilever models are solved. A surface stress of 0.05 N/m was applied to the top surface of the cantilevers. The cantilevers are made of silicon with elastic modulus 130 GPa and Poisson’s ratio 0.28. To show the conformity of this study, the numerical results are compared against their analytical ones. Results show that triangular and step cantilevers have better deflection and frequency characteristics than rectangular ones.

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