Browsing by Author "HSU, HC"

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A HIERARCHICAL MODEL-GUIDED GENERATION OF CHINESE CHARACTERS
(1994)
LEE, HJ
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HSU, HC
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資訊工程學系
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Department of Computer Science
EFFECT OF POLYCARBONATE MOLECULAR-WEIGHT ON PRECRACK HYSTERESIS ENERGY IN DETERMINING ITS DUCTILE-BRITTLE TRANSITION
(1991-09-20)
CHANG, FC
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HSU, HC
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交大名義發表
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應用化學系
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National Chiao Tung University
The distinctive ductile-brittle transition behavior of pseudoductile polymeric materials such as polycarbonate (PC) has been discovered to be closely related to the precrack hysteresis loss energy. The higher molecular weight (MW) PC with higher ductility also results in higher precrack hysteresis energy and therefore greater precrack plastic volume under condition of constant loads. If the precrack plastic volume exceeds a critical value, crack initiation thereafter will propagate within the domain of the plastic zone and results in ductile fracture. The deformation displacement is closely related to the precrack plastic volume, and the critical displacement actually determines the critical plastic volume. The higher molecular weight polycarbonate with higher entanglement density is able to withstand earlier crack initiation more effectively. Toughening plastics, such as rubber modification, is simply the result of delaying or retarding the crack initiation and allows the precrack plastic zone to grow over its critical value. A model of crack criterion based on precrack plastic zone is proposed to interpret the ductile-brittle transition phenomenon.
PRECRACK HYSTERESIS ENERGY IN DETERMINING ITS DUCTILE-BRITTLE TRANSITION .3. EFFECT OF TEMPERATURE
(1994-06-27)
CHANG, FC
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HSU, HC
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交大名義發表
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應用化學系
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National Chiao Tung University
A temperature variable has been used to correlate the precrack hysteresis energy and the corresponding ductility in terms of ductile-brittle transition behavior for polycarbonate. When the precrack plastic zone exceeds a critical value, crack extension thereafter will be effectively contained within the domain of the plastic zone and result in ductile fracture. Whether a specimen will fail in a ductile mode or a brittle mode is actually already being decided before the onset of crack initiation. The precrack elastic storage energy, total input energy minus hysteresis energy, is the major driving force to strain the crack tip for crack initiation. A higher testing temperature with lower yield stress converts a greater fraction of the input energy into the precrack hysteresis energy and relieves the storage strain energy available for crack initiation. A polycarbonate-toughening mechanism of increasing temperature is very similar to the presence of rubber by reducing yield stress and increasing the precrack plasticity. (C) 1994 John Wiley & Sons, Inc.
PRECRACK HYSTERESIS ENERGY OF ELASTOMER-MODIFIED POLYCARBONATES IN DETERMINING ITS DUCTILE BRITTLE TRANSITION
(1993-03-20)
CHANG, FC
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HSU, HC
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交大名義發表
;
應用化學系
;
National Chiao Tung University
For ductile fracture, the precrack plastic zone has to exceed a critical value, and precrack hysteresis energy has been employed to characterize the plastic zone. The presence of elastomer in polycarbonate is able to enhance precrack hysteresis and, therefore, toughens the polycarbonate matrix. Higher precrack hysteresis means that a greater fraction of the input energy converts into plasticity and leaves less storage energy available to strain the crack tip for crack initiation. If the precrack plastic zone is above the critical value before onset of initiation, the crack growth developed thereafter will be effectively contained within the domain of the plastic zone and results in mass shear, yielding ductile fracture. In this paper, the elastomer toughening is classified as promotion of ductile failure through mass shear yielding and the localized energy dissipation processes. The localized energy dissipations are further divided into the activities occurring on and underneath the fracture surface. A different approach in interpreting the elastomer-toughening mechanism is discussed in detail.