• 期刊

Analysis on Temperature Field Simulation for Offset Cutting a Nanochannel at a Fixed Down Force on Single-crystal Silicon Using Three-dimensional Quasi-steady Molecular Statics Nanocutting Model

The paper develops three-dimensional quasi-steady molecular statics nanocutting model to simulate offset cutting a nanochannel trapezium groove on single-crystal silicon at a fixed down force by a small probe. It is set that after a cutting pass is performed at a fixed down force on each cutting layer, the probe offsets rightwards to perform one more cutting pass, and then offsets leftwards to the middle position between the two passes aforesaid to perform cutting - this process is regarded as an offset cutting. The down force and cutting force of each cutting pass on the first cutting layer obtained from simulation of three-dimensional quasi-steady molecular statics nanocutting model are compared with the down force and cutting force of the cutting pass on the first cutting layer obtained from SDFE theoretical equation. The comparison has proved that it is feasible to use the three-dimensional quasi-steady molecular statics nanocutting model developed by the paper to simulate offset cutting of nanochannel trapezium groove at a fixed down force on single-crystal silicon by a small probe. The paper considers that plastic heat and friction heat would be produced during cutting of every cutting pass. The plastic deformation heat of the paper can be calculated by multiplying the equivalent stress and equivalent strain of the workpiece of single-crystal silicon being cut. Focusing on the production method of friction heat on the surface of cutting tool for nanocutting of single-crystal silicon, the paper finds the calculation method of temperature rise produced from friction heat. After finding the sum of temperature rise produced from two heat sources, the paper achieves the total temperature rise of each atom of the single-crystal silicon workpiece being cut, and then analyzes the temperature field of each cutting pass on the first cutting layer when performing offset cutting at a fixed cutting force.

• 期刊

Type Synthesis of Five Degree-of-Freedom Hybrid Mechanism

With the introduction of fractal theory and topological graph, this paper deals with the type synthesis and kinematic analysis of closed-loop 5-DoF (five degree-of-freedom) HMs (hybrid mechanisms). Firstly, the concept of fractal theory and topological graph are introduced. Then, theoretical grounds which consist of motional feature and algorithm for the type synthesis of HMs are presented in detail. The motional feature is composed of route, branch and kinematic pairs represented by a 8-bit binary string, while the algorithm is composed of route rule for dealing with the topological graph and calculation rule of union-intersection-preserving. Meanwhile, a mathematic model for both fractal and HMs is developed considering the interaction and correlation between them. Furthermore, the concrete procedure of type synthesis of 5-DoF HMs can be structured base on a selected topological graph and a flowchart is recommended in detail. Finally, the analysis of the motional characteristic for the end-effector is proposed and applied to an example chosen from type synthesis to demonstrate the validity of the methodology in this paper.

• 期刊

Effects of HHO Particulate Morphology from Diesel Engine Fueled with Bio-Diesel

To provide a theoretical basis for reducing particulate pollutants from diesel engines fueled with bio-diesel, this paper examines the topographical characteristics of biodiesel combustion particulates, focusing on HHO (brown gas). A 186F trial diesel engine is run at the calibration conditions, and a particle size sampling device is used to collect particulate pollutants when the diesel engine burns biodiesel and conducts co-combustion of biodiesel and HHO. Scanning electron microscopy and transmission electron microscopy are applied to analyze the influence of co-combustion with HHO on the particle morphology and the equivalent area diameter, to examine the change law of the microstructures, such as the spacing of the particles and the crystallite size, with HHO co-combustion and to analyze the functional mechanism of HHO in the generation of particulates. The results show that when the diesel engine is fueled with biodiesel, the surface morphology of the particles is predominantly distributed in lumps, chains and branches, and so on; upon the blending combustion of HHO, the cluster structure is reduced, and the particulates are mostly in a linear and branched distribution. The soluble organic matter on the particle surface is reduced, and the number of particles per unit area is reduced. Co-combustion with HHO can decrease the average equivalent area diameter of the particles by approximately 71.1%, moving the particle diameter in the direction of a small particle size. The increased area of the microcrystalline carbon layer widens the basal advantageous for the process of particle oxidation, and the reduced microcrystalline dimension of the particles increases the curvature and weakens the ordering of the microcrystalline structure on the surface. When biodiesel is blended with HHO, the hydroxyl can accelerate the oxidation of soluble organic matter on the particle surface as well as of the carbon component, reducing the fractal dimension of the particles by 0.04, indicating that the combustion of an HHO blend can reduce the structural tightness of particles. HHO affects the topographical characteristics of biodiesel combustion particles and can effectively reduce the particulate contaminants of bio-diesel.

• 期刊

Stress Calculation and Fatigue Life Evaluation on Cup-Type Flexspline under Bending and Torsion in Harmonic Drive

This paper describes a composite method of calculating multi-tooth root stress and evaluating fatigue life of flexspline (FS) in harmonic drive (HD). In order to accurately describe the stress state of the flexible gear root, a mathematical method combined with simulation method is applied. FS is divided into two parts, the cup part and the teeth part, according to the type of stress. On the cup part, the stress is caused by the support of the wave generator (WG). The bending stress is analyzed using differential equations and appropriately set boundary conditions. The theoretical analysis of meshing teeth in a harmonic drive is brought into the finite element model of FS that is deformed by the outer contour of the wave generator. The simulation is conducted under the action of torque and the meshing generated stress is obtained. Finally, the stress spectrum of the tooth root is acquired according to the flexural and torsion stress, while the maximum radial, the circumferential and shear stress are obtained. After applying the fourth strength theory to calculate the Von-Mises stress, the safety factors of several materials are compared according to the S-N curve and fatigue limit formula.

• 期刊

Robust Optimization for Suspension Parameters of Suspended Monorail Vehicle Using Taguchi Method and Kriging Surrogate Model

This study proposes an effective method to robust optimize the vehicle suspension parameters. To implement this method, firstly, a multi-body dynamics model of the suspended monorail vehicle was constructed as a simulation model to obtain the vehicle running stability index. Then, the multi-combination suspension parameters obtained by the orthogonal experimental design method are brought into the simulation model to obtain the training samples of the surrogate model, and the Kriging surrogate model on the vehicle running stability is constructed. Finally, the Taguchi method is used to find the optimal combination of suspension parameters based on the Kriging surrogate model, and the running stability index values of the suspension parameters corresponding to the initial and optimal combinations is compared. The results show that the robust optimization method proposed in this paper improves the lateral and vertical running stability of suspended monorail vehicle by 10.08% and 9.18%, respectively.

• 期刊

A Ground Surface Roughness Model Considering Grit and Vibration Variances

By combining the kinematic grit and spindle vibration effects, an analytical ground surface roughness model representing their individual effects on the ground surface was developed. In this model, the surface profile is treated as the superposition of variances of the kinematic grit and vibration profiles. By summing the variance of the two profiles, the root-mean-square ground surface roughness can be estimated. The transmitting factor, which defines the amount of power transmitted from spindle vibration to the ground surface, was derived from the dynamic grinding system and is related to the stiffness of the process, namely the workpiece cutting stiffness and wheel contact stiffness. An experimental procedure for identifying the stiffness in the process was also developed. Due to its analytical nature, the model estimates the ground surface roughness as well as allowing for the analysis of the contribution and effects of the grinding conditions, machine vibration and stiffness within the process. Procedures for identifying the process parameters were developed and a series of experiments with varying parameters were performed in order to validate the model. Discussions regarding the grinding conditions for the surface roughness based on experimental and model analysis results are presented. The model predictions and experimental results support the finding that a greater grinding depth and width increases the grinding force and hence deteriorates the ground surface. Furthermore, although a greater feed of the workpiece results in a larger grinding force and spindle vibrations, it also increases the cutting stiffness and thus reduces the transmitting factor of the spindle vibration, diminishing its adverse effects on the ground surface roughness.

• 期刊

Modeling and Simulation of Tubular Steam Methane Reformer

Steam methane reforming is a major hydrogen production process to convert the methane-rich hydrocarbon-containing gases into hydrogen. This paper presents the numerical model of a tubular steam methane reformer. By solving the mass transport, chemical reactions, and conjugated heat transfer in a double-pipe type of reformer with computational fluid dynamics scheme, the characteristics and performance of steam methane reforming process are investigated. The simulation results are in good agreement with the experimental data as the simulation parameters are adjusted to fit the specific catalysts. In the study cases of the present work, the calculated methane reforming rates are ranged from 63% to 99% with the hydrogen production rate in the range of 62%~87% by the various simulation parameters. It shows that the present numerical model has enough accuracy and is suitable for different catalyst beds for steam methane reforming process.

• 期刊

Arm Equipped Exploring Robot

In this study, LabVIEW and KNR are used to develop an arm equipped exploring robot with different control modes for operating the arm. Each sensor and the robot arm are controlled through wireless transmission. The exploring robot is also equipped with a webcam, ultrasonic distance sensor, lithium battery, and wireless USB adapter for robot vision, distance sensing, power supply and wireless signal transmission, respectively. Robot arm control comprises two modes, namely, keyboard and motion control modes. The keyboard control mode collects keyboard input information through Wi-Fi wireless transmission to KNR for operating the robot arm control and mobile robot. A learning function in also included in the keyboard control mode. The user can customize a number of arm positions, so that the robot arm can repeat movements. Motion control collects information from a leap motion sensor through Wi-Fi wireless transmission to KNR, and the implementation of motion control can simulate the hand movement.

• 期刊

Tolerance Design of Low Noise Humidifier using Monte Carlo and Multi-body Dynamic Simulation

In case of general home appliance product, resin parts are widely used due to economic efficiency and structural design freedom. However, Resin parts have shape and dimensional variations depending on the injection and cooling conditions when they are injected. When various parts are assembled, the accumulated tolerances may cause degradation of product performance or NVH problem. Particularly, the tolerance of the system in which its operating conditions are varied during operation becomes greater. In this study, Monte Carlo simulation is used to obtain the tolerance variation of the humidifier parts considering the changing operating conditions. And multibody dynamics analysis is also used to secure the operability of the driving part and low noise level. Experiments were also carried out to verify the noise and vibration level. This study is expected to be useful in the early stage of research before prototyping.

• 期刊

Plastic Behavior Laws of Aluminum Aerospace Alloys: Experimental and Numerical Study

The aim of this work is to study the anisotropic behavior of an aluminum alloy using a behavior model. The identification of this model requires an appropriate set of experimental database. Thus, the simple tensile tests (in and off axis) are carried in three loading directions relative to the rolling direction. This database consists of various curves of hardening for tensile tests interpreted as homogeneous and their Lankford coefficients. In order to further refine the experimental part of this work, microstructural observations were conducted through Transmission Electronic Microscopy to show interactions between the precipitates and dislocations in studied material. The experimental results obtained from uniaxial tensile tests are first described in order to show anisotropic behavior. Subsequently, an identification strategy will be implemented with regard to several hypotheses using a non-quadratic anisotropic yield function and isotropic hardening laws. The results show a good agreement between the theoretical results and experimental data.