• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.4
• /
• pp.91-96
• /
• 2001

In this paper, an investigation was performed on the dynamic interlaminar fracture toughness of CFRP(carbon filber rein-forcement plastics). Specimens used in this experiments are CF/PEEK laminated plates. In this experiments, Split Hopkin-sons Bar(SHPE) tes was apply to dynamic and notched flexure test. The model II fracture toughness of each unidirectional CFRP was estimated by the analyzed deflection of the specimen and J-integral with the measured impulsive load and reac-tions at the supported points. As an experimental results the vibration amplitude of [$0^{\circ}_10 /F_4 0^{\circ}_10 $] j-aminates appear more than that of [$0^{\circ}_10 /F_2 0^{\circ}_10 $ laminates for the j-integral and displacement velocity at a measuring point. Also, it is thought that the dynamic fracture toughness of two kind specimen(CF/PEEK) with the crease of displacement velocity becomes great at a measuring point with in the range of measurement.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.4
• /
• pp.125-133
• /
• 1998

The objective of this study is to propose a new approach for modelling of burr formation process during orthogonal cutting when the tool exits the workpiece. This approach is based on the rigid-plastic finite element method combined with the ductile fracture criterion and the element kill method. This approach is applied to orthogonal cutting process to predict the fracture location and the fracture angle as well as the cutting force. To validate this approach, orthogonal cutting tests inside SEM(scanning electron microscope) at very low speed are carried out using A16061-T6 to observe the behavior of the material during the chip and the burr formation. The results of the experiment are compared with those of the finite element simulation.

• Journal of Mechanical Science and Technology
• /
• v.14 no.2
• /
• pp.207-214
• /
• 2000

Fracture phenomenon has been reported on blades, rotors, connections and rotor discs of LP turbines of nuclear power plants, which is caused by fatigue, stress corrosion and erosion. In this study, as a tool of reliability evaluation, a number of stress and fracture analyses were performed on the defected area under various operating conditions using the finite element method. Possible defects on key-way and rotor disc were assumed to be two-dimensional cracks and centrifugal force, temperature distribution and shrink-fit effect were included as external loads. From stress analysis results, stress intensity factors were obtained and these values can be utilized to evaluate reliability and predict remaining lifetime of the turbine discs.

• Journal of Chest Surgery
• /
• v.14 no.2
• /
• pp.123-126
• /
• 1981

190 cases of the thoracic injuries experienced at the department of chest surgery, Chungnam National University Hospital, for 5 years from Jan. 1976 till Dec 1980, were analysed. The results are as follows; 1. The incidence rate of male to female was 5.1:1. The common age groups were 3rd, 4th and 5th decades, and the most common age group in the penetrating injury was 3rd decade. 2. The most common mode of the nonpenetrating injuries was a traffic accident [63.0%], and the most commonly used tool in the penetrating injuries is a knife [66.7%]. 3. The most common nonpenetrating injury was rib fracture [73.9%], and the common fracture sites were 5th, 6th, 7th and 8th ribs [especially, 7th rib]. The incidence rate of flail chest was 15% of the cases of the rib fractures. 4. The common associated injuries of the nonpenetrating were long bone fracture [18.3%], brain contusion [15.9%], and clavicle fracture etc.. 5. The common method of surgical treatment were closed thoracostomy [46.7%], thoracentesis, and open thoracotomy [7.4%] etc.. 6. The overall mortality was 2.8%. [Nonpenetrating; 0.8%, Penetrating; 6.3%]

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.269-273
• /
• 1997

In order to maker unmanned machining systems with satisfactory performances, it is necessary to incorporate appropriate condition monitoring systems in the machining workstations to provide the required intelligence of the expert. This paper deals with condition monitoring for chatter, tool wear and fracture during turning operation. To develop economic sensing and identification methods for turning processes, sound pressure measurement and digital signal processing technique were proposed. We suppressed chatter by stability control methodology, which was studied through manipulation of spindle speeds regarding to chatter frequencies. It was shown that tool wear and fracture were identified and to be estimated by using the wear indices. The validity of the proposed system was confirmed through the large number of cutting tests.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.12 no.6
• /
• pp.36-43
• /
• 2003

In machining of ceramic materials, they are very difficult-to cut materials because of there high strength and hardness. Machining of ceramics are characterized by cracking and brittle fracture. Generally, ceramics are machined using conventional method such as finding and polishing. However these processes are generally costly and have low MRR(material removal rate). This paper focuses on determining the optimal levels of process parameters for products with CNC machining center. For this purpose, the optimization of cutting parameters is performed based on experimental design method. A design and analysis of experiments is conducted to study the effects of these parameters on the surface roughness by using the S/N ratio, analysis of ANOVA and F-test. Cutting parameters, namely, cutting speed, feed and depth of cut are optimized with consideration of the surface roughness.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.6 s.249
• /
• pp.722-727
• /
• 2006

Bone fracture healing is one of the important topics in biomechanics, demanding computation simulations due to the difficulty of obtaining experimental or clinical results. In this study, we adopt the design space optimization method which was established by the authors as a tool for the simulation of bone growth using its evolutionary characteristics. As the mechanical stimulus, strain energy density is used. We assume that bone tissues over a threshold strain energy density will be differentiated and bone tissues below another threshold will be resorbed. Under compression and torsion as loadings, the filling process of the defect is well illustrated following the given mechanical criterion. It is shown that the design space optimization is an excellent tool for simulating the evolutionary process of bone growth, which has not been possible otherwise.

• Economic and Environmental Geology
• /
• v.28 no.5
• /
• pp.503-512
• /
• 1995

Groundwater flow in fracture networks is simulated using a discrete fracture (DF) model which assume that groundwater flows only through the fracture network. This assumption is available if the permeability of rock matrix is very low. It is almost impossible to describe fracture networks perfectly, so a stochastic approach is used. The stochastic approach assumes that the characteristic parameters in fracture network have special distribution patterns. The stochastic model generates fracture networks with some characteristic parameters. The finite element method is used to compute fracture flows. One-dimensional line element is the element type of the finite elements. The simulation results are shown by dominant flow paths in the fracture network. The dominant flow path can be found from the simulated groundwater flow field. The model developed in this study provides the tool to estimate the influences of characteristic parameters on groundwater flow in fracture networks. The influences of some characteristic parameters on the frcture flow are estimated by the Monte Carlo simulation based on 30 realizations.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.4 s.247
• /
• pp.393-401
• /
• 2006

The influences of stress triaxiality on ductile fracture have been investigated for various specimens and structures. With respect to a transferability issue, recently, the interests on local approaches reflecting micromechanical specifics are increased again due to rapid progress of computational environments. In this paper, the applicability of the local approaches has been examined through a series of finite element analyses incorporating modified GTN and Rousselier models as well as fracture toughness tests. The ductile crack growth of nuclear carbon steels is assessed to verify the transferability among compact tension (CT) specimens with different in-plane size. At first, the basic material constants were calibrated for standard CT specimens and used to predict fracture resistance (J-R) curves of larger CT specimens. Then, the in-plane size effects were examined by comparing the numerically estimated J-R curves with the experimentally determined ones. The assessment results showed that the in-plane size effect should be considered for realistic engineering application and the damage models might be used as useful tool for ductile fracture evaluation.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.365-371
• /
• 2004

Generally, fracture of a material is influenced by plastic zone size developed near the crack tip. Hence, according to the relative size of plastic zone in the material, the mechanics as a tool for analyzing the fracture process are classified into three kinds, that is, Linear Elastic Fracture Mechanics, Elastic Plastic Fracture Mechanics, Large Deformation Fracture Mechanics. Even though the plastic zone size is such an important parameter, the practical measurement techniques are very limited and the one for in-situ measurement is not virtually available. Therefore, elastic-plastic FEA has been performed to estimate the plastic zone size. In this study, it is noticed that side necking at the surface is a consequence of plastic deformation and lateral contraction and the relation between the plastic zone and side necking is investigated. FEA for modified boundary layer models with finite thickness, various mode mixities $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$ and strain hardening exponent n=3, 10 are performed. The results are presented and the implication regarding to application to experiment is discussed.