Thanh-Phong Dao

Bio: Thanh-Phong Dao is an academic researcher from Ton Duc Thang University. The author has contributed to research in topics: Compliant mechanism & Taguchi methods. The author has an hindex of 17, co-authored 95 publications receiving 758 citations. Previous affiliations of Thanh-Phong Dao include National Kaohsiung University of Applied Sciences.

Design and computational optimization of a flexure-based XY positioning platform using FEA-based response surface methodology

Abstract: This paper presents the mechanical design and computational optimization for a flexure-based XY positioning platform that is capable of performing planar translational motion with two degrees of freedom in the-x and-y axes. During the mechanical design, the hybrid leaf spring and right circular hinges are adopted to increase the travel displacement and reduce the cross-axis coupling errors. These hybrid joints create the parallelogram structures which provide the functions of joint and transmission mechanisms with excellent decoupling properties. The statistics and dynamics of the mechanism are analyzed, and these analyses are validated with FEA and experimental results. A finite element analysis-based response surface methodology is utilized to solve the multi-objective optimization problems and thus the static and dynamic characteristics of the positioning platform are improved. The prototype is fabricated using a wire electric discharge machining technique. The experimentations are carried out to investigate the performance of the platform and verify the established performance characteristics and optimization methodologies. The experimental results reveal that the platform has a broad workspace range in excess of 125 μm × 125 μm with a first-order natural frequency of 740 Hz. The cross-axis coupling ratio is less than 0.6% verifying the excellent decoupling property.

Machining parameter optimization in shear thickening polishing of gear surfaces

Abstract: The non-Newtonian fluid polishing is an advanced method that is applied to machining the complex surfaces. This method significantly improves the surface quality and mechanical properties of the material. In addition, it also reduces the concentrated stress at the root of the gear, so the fatigue resistance of the material is increased. The characteristics of shear thickening fluid are applied to machining the alloy steel SCM435 gears in this study. Firstly, the relationships between main machining parameters (distance D, velocity V, and inclination angle I) and responses (pressure and surface roughness of gear) is investigated in the polishing process. The effect of three machining parameters to the polishing process is carried out by conducting the simulation and experiment. The simulations results found that the pressure area is distributed throughout all the gear surfaces and maximum pressure value is achieved about 16.3 kPa with inclination angle of 26 degrees. In addition, experimental results indicated that the surface roughness of the gear surfaces can be reach 12 nm after 25 min polishing. Finally, the multi-responses optimization is utilized to optimize the pressures on the gear surfaces in machining process. The experimental results illustrated that the surface roughness is achieved the smallest at maximum pressure area. The best surface roughness of the gear surfaces can be reach 13 nm under optimal machining parameters such as the distance of 15 mm, velocity of 1.5 m/s and inclination angle of 32 degrees.

Multi-objective Optimal Design of a 2-DOF Flexure-Based Mechanism Using Hybrid Approach of Grey-Taguchi Coupled Response Surface Methodology and Entropy Measurement

Abstract: A large displacement and a high first natural frequency are two main concerns for any flexure-based positioning system. A two-degree-of-freedom (DOF) flexure-based mechanism (FBM) with a modified double-lever amplification mechanism is first designed. This study then proposes a multi-objective optimal design of the 2-DOF FBM using the hybrid approach of grey-Taguchi coupled response surface methodology and entropy measurement. The design variables of the 2-DOF FBM include the thickness of the flexure hinges and the length of lever amplification, both of which play vital roles in determining quality responses. The quality responses of the 2-DOF FBM are assessed by measuring the displacement and first natural frequency. The experimental plan is carried out using the Taguchi $${L_{25}}$$ orthogonal array. An integrated approach of grey-Taguchi- based response surface methodology and entropy measurement is then applied for the multi-objective optimization of the 2-DOF FBM. To illustrate the relation between the design variables and the output responses, mathematical regression models are developed. The entropy measurement technique is applied to calculate the weight factor corresponding to each response. Then, an analysis of variance (ANOVA) is conducted to determine the significant parameters affecting the responses. In addition, the ANOVA and experimental validations are conducted to validate the statistical adequacy and the prediction accuracy of the developed mathematical models, respectively. The results reveal that the regression models have good statistical adequacy and excellent prediction accuracy. The confirmation results of the grey relational grade fall within 95 % of the confidence interval. It is strongly believed that the proposed approach has great potential for the optimal design of related flexure-based mechanisms.

Multiresponse Optimization of a Compliant Guiding Mechanism Using Hybrid Taguchi-Grey Based Fuzzy Logic Approach

Abstract: Because of a lack of precisely miniaturized guiding mechanism, micro/nanoindentation devices are now difficult to integrate inside scanning electron microscope. A compliant guiding mechanism (CGM) with a compact size, serving as an accurate positioning platform, is hence proposed in this paper. The displacement and first natural frequency are the most important quality responses of CGM. The geometric parameters of CGM and applied force play a vital role in determining those responses. The experiment plan is firstly designed by Taguchi’s orthogonal array. A hybrid approach of Taguchi-grey based fuzzy logic is then developed to optimize two responses, simultaneously. The grey relational analysis based on the fuzzy logic is used to achieve a grey-fuzzy reasoning grade (GFRG) that combines all the quality characteristics. The GFRG, serving as a performance index, determines optimal parameter levels. Analysis of variance is conducted to assess the significant parameters affecting the responses. The confirmation results revealed that the 195 μm displacement of the CGM was many times greater than that of the previous mechanisms. It could be concluded that the quality responses of CGM can be significantly improved through the hybrid optimization approach. The proposed methodology has great applications for related compliant mechanisms and engineering sciences. Taking benefits of a compact structure into account, CGM has a great ability for micro/nanoindentation device inside scanning electron microscope.

Mechanism and machine theory

Abstract: Kinematic analysis of mechanisms kinematic synthesis of mechanisms simple mechanisms and coupler curves cams spur gears helical, spiral, worm and bevel gears gear trains hydrodynamic lubrication static force analysis inertia force analysis combined static and inertia force analysis turning moment diagram and flywheel balancing of rotating components balancing of reciprocating components gear forces.

The rheology of shear thickening fluid (STF) and the dynamic performance of a STF-filled damper

Abstract: This paper presents a study of the rheological properties of shear thickening fluid (STF) and its application as a damper. The STF samples, with different weight fractions, were prepared by dispersing nanosized silica particles in a solvent. By using a parallel-plate rheometer, both steady-state and dynamic experiments were carried out to investigate the rheological properties of STFs. Experimental results indicated that these suspensions show an abrupt increase in complex viscosity beyond a critical dynamic shear rate, as well as this increase being reversible. Working with the fabricated STF materials, a prototype damper was fabricated and its dynamic performances were experimentally evaluated. An equivalent linear model through effective elastic stiffness and viscous damping was developed to address both the damping and the stiffness capabilities of the damper. Also, a mathematical model was developed to investigate working mechanisms of STF-based devices.

Kinetostatic and Dynamic Modeling of Flexure-Based Compliant Mechanisms: A Survey

Abstract: Flexure-based compliant mechanisms are becoming increasingly promising in precision engineering, robotics, and other applications due to the excellent advantages of no friction, no backlash, no wear, and minimal requirement of assembly. Because compliant mechanisms have inherent coupling of kinematic-mechanical behaviors with large deflections and/or complex serial-parallel configurations, the kinetostatic and dynamic analyses are challenging in comparison to their rigid-body counterparts. To address these challenges, a variety of techniques have been reported in a growing stream of publications. This paper surveys and compares the conceptual ideas, key advances, and applicable scopes, and open problems of the state-of-the-art kinetostatic and dynamic modeling methods for compliant mechanisms in terms of small and large deflections. Future challenges are discussed and new opportunities for extended study are highlighted as well. The presented review provides a guide on how to select suitable modeling approaches for those engaged in the field of compliant mechanisms.