• Journal of Mechanical Science and Technology
• /
• v.19 no.spc1
• /
• pp.265-271
• /
• 2005

Randomness exists in engineering. Tolerance, assemble-error, environment temperature and wear make the parameters of a mechanical system uncertain. So the behavior or response of the mechanical system is uncertain. In this paper, the uncertain parameters are treated as random variables. So if the probability distribution of a random parameter is known, the simulation of mechanical multibody dynamics can be made by Monte-Carlo method. Thus multibody dynamics simulation results can be obtained in statistics. A new concept called functional reliability is put forward in this paper, which can be defined as the probability of the dynamic parameters(such as position, orientation, velocity, acceleration etc.) of the key parts of a mechanical multibody system belong to their tolerance values. A flexible mechanical arm with random parameters is studied in this paper. The length, width, thickness and density of the flexible arm are treated as random variables and Gaussian distribution is used with given mean and variance. Computer code is developed based on the dynamic model and Monte-Carlo method to simulate the dynamic behavior of the flexible arm. At the same time the end effector's locating reliability is calculated with circular tolerance area. The theory and method presented in this paper are applicable on the dynamics modeling of general multibody systems.

• Journal of Powder Materials
• /
• v.21 no.4
• /
• pp.307-312
• /
• 2014

This study is focused on investigating the relation between the particle size of silver flake powder and mechanical milling parameters. Mechanical milling parameters such as ball size, impeller rotation speed and milling time of the attrition ball-mill were controlled to produce silver flake powder. The particle size of the silver flake powder increased with increasing ball size and impeller rotation speed. The change of the particle size of the silver flake powder with mechanical milling parameters was analyzed based on balls motion in the mill container of the attrition ball-mill. The silver flake particles were formed at the elastic deformation area of the ball due to the collision between balls. The change of the particle size of the silver flake powder with mechanical milling parameters well consists with the change of the collision energy of ball with parameters mentioned above.

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.106-108
• /
• 2009

In this paper, we handle automatic estimation of mechanical parameters for mobile robots. Most estimation methods are based on the sequence and move-measurement-estimation. Estimated accuracy is largely dependent on the paths. Mathematical conditions minimizing estimation errors are derived, and then a method finding optimal paths for mechanical parameters estimation is proposed.

• International Journal of Automotive Technology
• /
• v.7 no.7
• /
• pp.859-866
• /
• 2006

This study employed the perturbation method, the Edgeworth series, the reliability optimization, the reliability sensitivity technique and the robust design to present a practical and effective approach for the robust reliability design of vehicle components with arbitrary distribution parameters on the condition of known first four moments of original random variables. The theoretical formulae of the robust reliability design for vehicle components with arbitrary distribution parameters are obtained. The reliability sensitivity is added to the reliability optimization design model and the robust reliability design is described as a multi-objection optimization. On the condition of known first four moments of original random variables, the respective program can be used to obtain the robust reliability design parameters of vehicle components with arbitrary distribution parameters accurately and quickly.

• Proceedings of the KWS Conference
• /
• 2003.05a
• /
• pp.29-31
• /
• 2003

Generally, the Quality of a weld joint is strongly influenced by process parameters during the welding process. In order to achieve high quality welds, mathematical models that can predict the bead geometry to accomplish the desired mechanical properties of the weldment should be developed. To achieve this objectives, a sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.6
• /
• pp.951-960
• /
• 1997

Package crack caused by the soldering process in the surface mounting plastic package is evaluated by applying the maximum energy release rate criterion. It could be shown that the crack propagation from the lower edge of the ie pad is easily occurred at the maximum temperature during the soldering process, where the pressure acting on the crack surface is assumed by the saturated vapor pressure at maximum temperature. The package crack formation depends on various parameters such as chip size, relative thickness, material properties, the moisture content and soldering temperature etc. The quantitative measure of the effects of the parameters could be easily obtained by using the taguchi's method which requires only a few kinds of combinations with such parameters. From the results, it could be obtained that the more significant parameters to effect the package reliability are the orders of Young's modulus, die pad size, down set, chip thickness and maximum soldering temperature.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.20 no.3
• /
• pp.269-278
• /
• 2022

The buffer is a critical barrier component in an engineered barrier system, and its purpose is to prevent potential radionuclides from leaking out from a damaged canister by filling the void in the repository. No experimental parameters exist that can describe the buffer expansion phenomenon when Kyeongju bentonite, which is a buffer candidate material available in Korea, is exposed to groundwater. As conventional experiments to determine these parameters are time consuming and complicated, simple swelling pressure tests, numerical modeling, and machine learning are used in this study to obtain the parameters required to establish a numerical model that can simulate swelling. Swelling tests conducted using Kyeongju bentonite are emulated using the COMSOL Multiphysics numerical analysis tool. Relationships between the swelling phenomenon and mechanical parameters are determined via an artificial neural network. Subsequently, by inputting the swelling tests results into the network, the values for the mechanical parameters of Kyeongju bentonite are obtained. Sensitivity analysis is performed to identify the influential parameters. Results of the numerical analysis based on the identified mechanical parameters are consistent with the experimental values.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.321-322
• /
• 2002

This paper presents study of effects of cutting parameters such as cutting speed, feed rate and depth of cut on the surface roughness in hard turning. Taguchi Method and linear regression model of design parameters were utilized to identify the controlling process parameters that can monitor the surface roughness in the hard turning operation. In the process optimization, experimental planning was performed using the orthogonal array and concept of the signal-to-noise ratio. Cutting parameters such as speed, feed rate, and depth of cut were selected as process parameters and the ANOVA analysis showed that feed rate and cutting speed had more effect on the roughness variation that depth of cut.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.9
• /
• pp.1462-1469
• /
• 1997

This study presents a genetic algorithm-based method for optimizing control parameters in fluid power systems. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics. A genetic algorithm seeks control parameters maximizing a measure that evaluates system performance. Five control gains of the PID-PD cascade controller fr an electrohydraulic speed control system with a variable displacement hydraulic motor are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that optimization of the five gains by manual tuning should be a task of great difficulty and that a genetic algorithm is an efficient scheme giving economy of time and in labor in optimizing control parameters of fluid power systems.

• Journal of Mechanical Science and Technology
• /
• v.16 no.1
• /
• pp.46-59
• /
• 2002

The main purpose of this study is to investigate the variation of tool electrode edge wear and machining performance outputs, namely, the machining rate (workpiece removal rate), tool wear rate and the relative wear, with the varying machining parameters (pulse time, discharge current and dielectric flushing pressure) in EDM die sinking. The edge wear profiles obtained are modeled by using the circular arcs, exponential and poller functions. The variation of radii of the circular arcs with machining parameters is given. It is observed that the exponential function models the edge wear profiles of the electrodes, very accurately. The variation of exponential model parameters with machining parameters is presented.