• Korean Journal of Metals and Materials
• /
• v.56 no.11
• /
• pp.805-812
• /
• 2018

High pressure die casting is one of the precision casting methods. It is highly productivity and suitable for manufacturing components with complex shapes and accurate dimensions. Recently, there has been increasing demand for efficient heat dissipation components, to control the heat generated by devices, which directly affects the efficiency and life of the product. Die cast aluminum alloys with high thermal conductivity are especially needed for this application. In this study, the influence of elements added to the die cast aluminum alloy on its thermal conductivity was evaluated. The results showed that Mn remarkably deteriorated the thermal conductivity of the aluminum alloy. When Cu content was increased, the tensile strength of cast aluminum alloy increased, showing 1 wt% of Cu ensured the minimum mechanical properties of the cast aluminum. As Si content increased, the flow length of the alloy proportionally increased. The flow length of aluminum alloy containing 2 wt% Si was about 85% of that of the ALDC12 alloy. A heat dissipation component was successfully fabricated using an optimized composition of Al-1 wt%Cu-0.6 wt%Fe-2 wt%Si die casting alloy without surface cracks, which were turned out as intergranular cracking originated from the solidification contraction of the alloy with Si composition lower than 2 wt%.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.6
• /
• pp.1053-1059
• /
• 2002

The purpose of this study is to suggest how the machining technique of constant control of cutting speed can improve precision machining and tool life in high speed machining using a ball end mill. Cutting speed is changed in machining fee form surfaces such as connecting rod die. So, we don't have supreme surface form and tool life on machining. To solve this problem we should settle on optimal cutting speeds in free form surface machining. And, to improve precision machining, We must execute high speed machining methods to output optimum NC data using developed constant control of cutting speed program after modeling by CAD/CAM. In this paper, a comparison was made of the cutting precision and tool life in conventional cutting and those in connecting rod machining applying the program developed.

• Design & Manufacturing
• /
• v.2 no.6
• /
• pp.43-48
• /
• 2008

Magnesium alloys have given high attention to the industry of light-weigh as automobile and electronics with aluminium, titanium and composite alloys due to their high strength, low specific density and good damping characteristics. But the magnesium contained structures under high temperature have the problems related to creep deformation and rupture life, which is a reason of developing the new material against creep deformation to use them safely. The purpose of this study is to predict the creep deformation mechanism and rupture time of AZ31 magnesium alloy. For this, creep tests of AZ31 magnesium alloy were done under constant creep load and temperature with the equipment including automatic temperature controller with acquisition computer. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined over the temperature range below 0.5Tm and stress range of 109~187MPa, respectively, in order to investigate the creep behavior. AZ31 Magnesium alloy identify the activation energy for creep deformation and the stress dependence to creep rate at below 0.5Tm, and then investigate the mechanism for creep deformation and creep rupture life of AZ31 Magnesium alloy.

• Korean Journal of Metals and Materials
• /
• v.48 no.7
• /
• pp.651-659
• /
• 2010

When high-speed interrupted cutting is carried out for die and mold steels with high hardness, CBN tools manifested a significantly longer wear life than carbide, ceramic, or cermet tools in an experiment of face milling characteristics. In addition, it was also found that they secured a stable surface roughness within a range of 1.6 S~6.3 S, an acceptable range for precision machining for polished machining parts. And it makes them acceptable in the precision machining field, except in industries where very high machining accuracy is required. In the high hardness interrupted cutting, it was advantageous to perform a negaland treatment and a honning treatment on the tools' cutting edge to extend tool life and surface roughness. Also, severe crater development was found on the sloped face in CBN tools following high-speed machining. This caused the cutting edge to be weakened and damaged, and ultimately resulted in a shorter tool life. Finally, as a result of EDX mapping inspection, Cr component was detected evenly on the entire crater wear area, which can be included only in STD 11.

• The Korean Society of Law and Medicine
• /
• v.9 no.1
• /
• pp.413-459
• /
• 2008

The Law has intervened to define rare circumstances in which a person should choose continuing life in United States. On the one hand, the law has traditionally acted to preservelife and to respect the sanctity of life. On the other hand, one's control over one's own body, and the right to determine what kind of medical care one will receive, is equally well respected and historically grounded. The competent patients have the right to forgo life-sustaining treatment, courts in United States have left many unanswered questions about the nature of that right. The right to choose to forgo life-sustaining treatment is a manifestation of a patient's autonomy interest. In United States, The Karen Quilan case gave rise to legislative activity in the host of state capitals, and several states had adopted statutes that formally recognized some forms of written directives describing some circumstances in which certain kinds of medical care could be terminated. These statues were sometimes dominated 'living will' acts, sometimes 'right to die' acts and ocasionally 'natural death' acts. Today virtually every state has produced a living will statue. In Korea, courts do not permit a terminally ill person to withhold or withdraw life-sustaining treatment. Living wills apply in case of terminal illness owing to a defect in legislation. Now In Korea, these lively dispute of legal policy on the preconditions and concrete procedure of living will act and natural death act. Through the legislation of living will act and natural death act, we should prepare some circumstances to respect patient's autonomy on the right to die. We should frame the cultural standard to make a decision of forgoing life-sustainin1g treatment under the discreet procedure.

• Journal of Korean Medical classics
• /
• v.3
• /
• pp.1-150
• /
• 1989

Oriental medicine thinks life and death as the following. 1. The universe seems to be a kind of organism which is divided into 3 branches, as Heaven, Earth and Man. Man is not created from nihil by the Creator. Heaven and Earth by their interaction operate to produce man. This is similiar that zygote is not created from nihil, and that sperm and ovum are transformed into zygote by their interaction. The symbolic meaning of sperm is Heaven, and that of ovum is Earth. Mind and body, as well as spirit and body, are not the real, but artificial words for the purpose of observing and expressing one man. So there is not spiritual substance as distinct from body. The expected life span of man is subjected to change, and is always becoming through life. Fate, the Creator and the world to come cannot be said to be. 2. After one's death, man is transformend into Heaven and Earth. Dying is this process of transformation. Although man comes into existence and closes one's life, the total life of the universe does not change. The criteria of determination of death is not in cell death, but in somatic death. Somatic death divided into 2 branches, one is heart-lung death, the other is brain death. For the standard of health changes ceaselessly as time goes by, aging and dying is not the process of losing health. Because of mind cannot be seperated from body, we'll feel at ease bodily and mentally in healthy dying. The completion of lifetimes is the value of healthy dying. 3. From the viewpoint of these, we must think to let a person die healthily is the right medical ethics. The way to let a person die healthily is divided into 3 branches, one is treatment, another is prevention and the other is promotion of health. We should treat and prevent death of sickness, but take care of healthy dying.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.2
• /
• pp.38-43
• /
• 2007

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of $0.4{\mu}m$) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated A ground surface roughness Rz of 0.14 um was achieved Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish $5000mm^2$ of die steel surface without any deterioration of the ground surface roughness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.05a
• /
• pp.163-168
• /
• 2002

Hot forging is widely used in the manufacturing of industry machine component. The mechanical, thermal load and thermal softening which are happened by the high temperature in hot forging process. Tool life decreases considerably due to the softening of the surface layer of a tool caused by a high thermal load and long contact time between the tool and billet. Also, tool life is to a large extent limited by wear, heat crack and plastic deformation in hot forging process. These are one of the main factors affecting die accuracy and tool life. That is because hot forging process has many factors influencing tool life, and there was not accurate in-process data. In this research, life prediction of hot forging tool by wear and plastic deformation analysis considering tempering parameter has been carried out for automobile component. The new developed technique in this study for predicting tool life can give more feasible means to improve the tool life in hot forging process.

• Journal of the Daesoon Academy of Sciences
• /
• v.16
• /
• pp.69-85
• /
• 2003

Death has been one of the basic objects in philosophy and religion. Why do people feel afraid about death? Maybe it is because they don't know the situation after death or because they have a wrong idea about it. Someone may think that he/she doesn't care the situation. But this attitude is wrong. We must understand that our attitude about life is shaped by our knowledge of the situation after death. A recurrent theme about death in popular thought is the idea that death is mysterious. As we have seen, it is difficult to formulate a satisfactory philosophical analysis of the concept of death. If it is impossible to analyse the concept of death, then it is impossible to explain precisely what we mean when we say that something dies. It might be said therefore that, in virtue of this fact, death is mysterious. Of course, death is not distinctively mysterious - all other unanalysable concepts are equally mysterious in this way. Reflection on death gives rise to a variety of philosophical questions. One of the deepest of these is a question about the nature of death. Typically, philosophers interpret this question as a call for an analysis or definition of the concept of death. Plato, for example, proposed to define death as the separation of soul from body. However, this definition is not acceptable to those who think that there are no souls. It is also unacceptable to anyone who thinks that plants and lower animals have no souls, but can nonetheless die. Others have defined death simply as the cessation of life. This too is problematic, since an organism that goes into suspended animation ceases to live, but may not actually die. The eastern philosophers proposed to define death as the nonduality of life and death. Taoists, for example, do not believe in the Wheel of Life of the Buddhists nor in the Heaven or Hell of Christianity. Taoists view existence as glorious. The whole Universe, they teach, is a marvelous, vibrant Unity wherein everything, visible and invisible, pulses with energy and changes. As being develops through the experience of existence, its vessels are swept onwards by the mighty stream of the eternal TAO to other forms of expression and activity. Man does not die; he merely extends into new fields. Taoists teach that the end of a person is the return to the Ultimate Reality. "Life is uncertain - Death is certain": This is a well known saying in Buddhism. Knowing very well that death is certain and it is a natural phenomenon that everyone has to face, we should not be afraid of death. Yet, instinctively, all of us fear death because we do not know how to think of its inevitability. We like to cling to our life and body and so develop too much craving and attachment.

• Transactions of Materials Processing
• /
• v.12 no.1
• /
• pp.18-25
• /
• 2003

This paper explains the process design for improving tool life in the conventional hot forging process. The thermal load and the thermal softening are happened by contact between the hotter billet and the cooler tools in hot forging process. Tool life decreases considerably due to the softening of the surface layer of a tool was caused by a high thermal load and long contact time between the tools and the billet. Also, tool life is to a large extent limited by wear, heat crack and plastic deformation in hot forging process. Above all, the main factors which affect die accuracy and tool life we wear and the plastic deformation of a tool. The newly developed techniques for predicting tool life are applied to estimate the production quantity for a spindle component and these techniques can be applied to improve the tool life in hot forging process.