Articles written in Sadhana

    • Design and multi-objective optimization for a broad self-amplified 2-DOF monolithic mechanism


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      This paper proposes a structural design and multi-objective optimization of a two-degree-of-freedom (DOF) monolithic mechanism. The mechanism is designed based on compliant mechanism with flexure hinge and is compact in size (126 mm by 107 mm). Unlike traditional one-lever mechanisms, a new doublelever mechanism is developed to increase the working travel amplification ratio of the monolithic mechanism. The ideal amplification ratio, the working travel, the statics and the dynamics of the mechanism are taken into consideration. The effects of design variables on the output responses such as the displacement and first natural frequency are investigated via finite-element analysis based on response surface methodology. The fuzzy-logicbased Taguchi method is then used to simultaneously optimize the displacement and the first natural frequency. Experimental validations are conducted to verify the optimal results, which are compared to those of the original design. On using a finite-element method, the validation results indicated that the displacement and frequency are enhanced by up to 12.47% and 33.27%, respectively, over those of the original design. The experiment results are in a good agreement with the simulations. It also revealed that the developed fuzzy-logic-based Taguchi method is an effectively systematic reasoning approach for optimizing the multiple quality characteristics of compliant mechanisms. It was noted that the working travel/displacement of the double-levermechanism is much larger than that of the traditional one-lever mechanism. It leads to the conclusion that the proposed mechanism has good performances for manipulations and positioning systems.

    • Investigation on lap-joint friction stir welding between AA6351 alloys and DP800 steel sheets


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      With continuous growth and stringent demand for weight reduction in automotive structures, the automotive industry has shown an increasing interest in dissimilar aluminium–steel welding. Dissimilar lap joint between AA6351 alloys of 2 mm thickness and DP800 advanced high-strength dual-phase steel of 1 mmthickness has been attempted and joined successfully by friction stir welding with different combinations of parameters. The experimental results of this research work clearly indicate that joining of advanced high strength steel and aluminium in lap-joint configuration is quite feasible with friction stir welding. Microstructuralcharacterization has been performed by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). An intermetallic compounds layer was found in the interface of steel and aluminium with thickness of less than 7 μm and it was identified as Al2Fe and Al3Fe by XRD method. Thermal cycle has been measured and correlated with the microstructure. Shear tensile test has been performed for determining the maximum failure load for different combinations of parameters. Finally, mechanical properties and microstructural observation are correlated with each other.

    • Design variables optimization effects on acceleration and contact force of the double sliders-crank mechanism having multiple revolute clearance joints by use of the Taguchi method based on a grey relational analysis


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      This study developed a mechanism with two sliders for a planer machine, in order to enhance productivity. First, the effects of the clearance size and seven imperfect revolute joints on the dynamic characteristics of the proposed mechanism were analyzed by finite element analysis in ANSYS software. In order to improve the dynamic behavior, an optimal design was carried out via the Taguchi method with grey relational analysis. The simulation results demonstrated that the clearance size has a slight effect on the velocity andgreatly affects the accelerations of the two sliders and contact forces in the seven revolute clearance joints. The values of velocity, acceleration of the two sliders and contact force increased when the clearance size increased,as compared with an ideal joint. It was found that the optimal design parameters for both the acceleration of the first slider and the contact force in the first revolute clearance joint (RCJ) are an input velocity at 500 rpm, a length of bearing at 15 mm, a journal radius at 9.7 mm, the material’s structural steel with a Young’s modulus of 69 GPa and a clearance at 0.1 mm. The optimal results of acceleration and contact force are 186.45 (m/s2) and 106.854 (N) respectively, with a 3.92% error for acceleration and 9.99% for contact force compared with the simulation results.

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