Experimental Study on the Mechanical Performance of Mortise-Tenon Joints Reinforced with Replaceable Flat-Steel Jackets

The mortise-tenon joint is an important hub transmitting and distributing external loads for load-bearing components(beams,columns et al.)in the ancient-timber frame structure system.However,the conventional steel hoop reinforcement methods often insert wood screws into the timber components.When the reinforced joint rotates greatly,the anchoring failure of the screws will cause damage to the timber joint.To solve this problem,this study proposes a detachable and replaceable non-destructive flat-steel jacket reinforcement method in which horizontal flat steel is placed in the center of the joint,and the bolt is extended to the outside of the timber beam.Nine 1:3.52 scaled straight-tenon joint specimens were subjected to monotonic loading of beam ends,including three unreinforced reference joints,three joints with flat-steel jacket and three carbon fiber-reinforced plastic(CFRP)reinforced joints.The mechanical behaviors of the novel joints with flat-steel jacket were experimentally studied by comparing with those of the joints without strengthening and retrofitted with CFRP,based on the failure modes,the initial stiffness,the ultimate bearing capacity,and the moment-rotation relationship curves.Results indicated that the mortise-tenon joints reinforced with flat-steel jackets maintain the original semi-rigid properties of the unreinforced mortise-tenon joints and can effectively prevent the tenon from pulling out.The initial stiffness and ultimate bearing capacity were improved markedly.The column and beam of the reinforced joints remain intact providing the reference for the practical application of joints reinforcement.The mortisetenon joints reinforced with CFRP lose the semi-rigid properties of the unreinforced tenon-mortise joints.The joints reinforced with CFRP have the largest initial stiffness,while the unreinforced joints have the lowest stiffness.The initial stiffness of the proposed joint is in between the joints reinforced with CFRP and unreinforced joints.The ultimate bearing capacity of the joints reinforced with flat-steel jacket is larger than the other two joints,whereas the unreinforced joints have the lowest ultimate bearing capacity.

MEASUREMENT OF ANGULAR VIBRATION AMPLITUDE BY ACTIVELY BLURRED IMAGES

A novel motion-blur-based method for measuring the angular amplitude of a high-frequency rotational vibration is schemed. The proposed approach combines the active vision concept and the mechanism of motion-from-blur, generates motion blur on the image plane actively by extending exposure time, and utilizes the motion blur information in polar images to estimate the angular amplitude of a high-frequency rotational vibration. This method obtains the analytical results of the angular vibration amplitude from the geometric moments of a motion blurred polar image and an unblurred image for reference. Experimental results are provided to validate the presented scheme.

Modelling self-sensing of a magnetostrictive actuator based on a terfenol-D rod

A simplified quasi-static computational model for self-sensing applications of magnetostrictive actuators based on terfenol-D rods is presented. Paths and angle changes in the magnetic moments rotation of Tb0.3Dy0.7Fe2 alloy are studied as functions of compressive stress and magnetic field, and then used to determine the magnetization in its actuation. Then sensing of magnetic induction picked from a driving coil in an actuator is derived. The model is quick and efficient to solve moments rotation and its magnetization. Sensing results of compressive stress and magnetostriction calculated by the model are in good agreement with experiments and will be helpful in the design and control of self-sensing applications in actuators.