• Elastomers and Composites
• /
• v.39 no.2
• /
• pp.142-152
• /
• 2004

Tensile tests of two types of injection-molded polystyrene(PS) samples have been carried out over a wide range of temperature and strain rates in order to characterize their crazing behaviors. Mechanical properties were affected by the formation of crazes as well as test variables. Below the brittle-ductile transition temperature, the tensile stress and the ultimate elongation increased with the molecular weight, strain rate, and with decreasing temperature while the number and average length of crazes also increase. The crazing stress increased with molecular weight, strain rate, and with decreasing temperature. However, the dependence was small compared to the tensile stress. The gap between crazing stress and tensile stress which represents time fur craze formation and growth increased with molecular weight, strain rate, and with decreasing temperature. Crazing was activated near the ${\beta}$-relaxation temperature; crazing stress abruptly decreased at this temperature. During the tensile test, the craze density changed exponentially with the applied stress. At the initial stage, crazes formed slowly. Once a certain number of craze formed, however, the craze density increased rapidly. Craze nucleation and growth occur simultaneously.

• Elastomers and Composites
• /
• v.39 no.4
• /
• pp.324-329
• /
• 2004

The phase morphology, degree of craze and impact property in Polycarbonate (PC)/Acrylonitrile-Butadiene- styrene (ABS) blend containing the phosphate based flame retardant were studied in terms of injection molding temperatures. As the injection molding temperature increases, significant amount of coalescences and crazes were observed and impact strength decreased. It was also observed that the addition of compatibilizer into the blends suppresses the coalescence and craze.

• Korean Journal of Materials Research
• /
• v.30 no.3
• /
• pp.105-110
• /
• 2020

Cu/PET composite films are widely used in a variety of wearable electronics. Lifetime of the electronics is determined by adhesion between the Cu film and the PET substrate. The formation of an anisotropic nanostructure on the PET surface by surface modification can enhance Cu/PET interfacial adhesion. The shape and size of the anisotropic nanostructures of the PET surface can be controlled by varying the surface modification conditions. In this work, the effect of Cu/PET interface nanostructures on the failure mechanism of a Cu/PET flexible composite film is studied. From observation of the morphologies of the anisotropic nanostructures on plasma-treated PET surfaces, and cross-sections and surfaces of the fractured specimens, the Cu/PET interface area and nanostructure width are analyzed and the failure mechanism of the Cu/PET film is investigated. It is found that the failure mechanism of the Cu/PET flexible composite film depends on the shape and size of the plasmatreated PET surface nanostructures. Cu/PET interface nanostructures with maximal peel strength exhibit multiple craze-crack propagation behavior, while smaller or larger interface nanostructures exhibit single-path craze-crack propagation behavior.

• Journal of the Korean Society for Precision Engineering
• /
• v.3 no.1
• /
• pp.40-49
• /
• 1986

Crack, craze and void are common defects which may be found in the bulk of polymeric materials such as either themoplastics or thermosets. The healing phenomena, autohesion, of these defects are known to be a intrinsic material property of various polymeric materials. However, only a few experimental and theoretical investigations on crack, void and craze healing phenomena for various polymeric materials have been reported up to date [1, 2, 3]. This may be partly due to the complications of healing processes and lacking of appropriate theoretical developments. Recently, some investigators have been urged to study the healing phenomena of various polymenic materials since the significance of the use of polymer based alloys or composites has been raised in terms of specific strength and energy saving. In the earlier published reports [1, 2, 3, 4], the crack and void healing velocity, healing toughness and some other healing mechanical and physical properties were measured experimentally and compared with predicted values by utilizing a simple model such as the reptation model under some resonable assumptions. It seems, however, that the general acceptance of the proposed modeling analyses is yet open question. The crack healing processes seem to be complicate and highly dependent on the state of virgin material in terms of mechanical and physical properties. Furthermore, it is also strongly dependent on the histories of crack, craze and void development including fracture suface morphology, the shape of void and the degree of disentanglement of fibril in the craze. The rate of crack healing may be a function of environmental factors such as healing temperature, time and pressure which gives different contact configurations between two separated surfaces. It seems to be reasonable to assume that the crack healing processes may be divided in several distinguished steps like stress relaxation with molecular chain arrangement, surface contact (wetting), inter- diffusion process and com;oete healing (to obtain the original strength). In this context, it is likely that we no longer have to accept the limitation of cumulative damage theories and fatigue life if it is probable to remove the defects such as crack, craze and void and to restore the original strength of polymers or polymer based compowites by suitable choice of healing histories and methods. In this paper, we wish to present a very simple and intuitive theoretical model for the prediction of healed fracture toughness of cracked or defective polymeric components. The central idea of this investigation, thus, may be the modeling of behavior of chain molecules under healing conditions including the effects of chain scission on the healing processes. The validity of this proposed model will be studied by making comparisons between theoretically predicted values and experimentally determined results in near future and will be reported elsewhere.

• Restorative Dentistry and Endodontics
• /
• v.11 no.1
• /
• pp.33-41
• /
• 1985

The purpose of this study was to determine the extent of tooth structure crazing when pinhole were drilled in dentin at various distances from the dentionenamel junction, and when pins were inserted by hand wrench and Auto-klutch handpiece. Sixty freshly extracted teeth were embedded in blocks of cold-curing acrylic resin to a level 1mm apical to the cementoenamel junction, the crown of the teeth were removed to a level 1.5mm coronal to the cementoenamel junction. After being sectioned, the cut surface of the teeth were smoothed, and they were divided into 4 groups. Group I : 4 pinholes were drilled with self-threading Minim spiral drill and pins were inserted with hand wrench in fifteen teeth. Group II : 4 pinholes were drilled with self-threading Minim spiral drill and pins were inserted with Auto-klutch handpiece in fifteen teeth. Group III : 4 pinholes were drilled with self-threading Regular spiral drill and pins were inserted with hand wrench in fifteen teeth. Group IV : 4 pinholes were drilled with self-threading Regular spiral drill and pins were inserted with Auto-klutch handpiece in fifteen teeth. The cut surface were then examined microscopically for the presence or absence of craze line. The results were as follows: 1. The self-threading Minim pin groups (Group I & II) produced less craze lines than did the self-threading Regular pin groups (Group III & IV). 2. In the self-threading Minim pin groups, there was more craze lines with hand wrench (Group I) than with Auto-klutch handpiece (Group 11). 3. In the self-threading Regular pin groups, there was more craze lines with hand wrench (Group III) than with Auto-klutch handpiece (Group IV). 4. Placement of the pinhole at 0.0mm from the dentionenamel junction produced more craze lines than placed at 0.5mm, 1.0mm (p<0.05), however there was no statistically significant between the 0.5mm and 1.0mm distance.

• International Journal of Internet, Broadcasting and Communication
• /
• v.15 no.3
• /
• pp.52-57
• /
• 2023

In the restaurant industry, along with the fourth industry, there is a food technology craze due to IT development. In addition, many prospective restaurant founders are increasing due to restaurant start-ups with relatively low entry barriers. And ChatGPT is causing a craze for chatbots. Therefore, the purpose of this paper is to analyze factors for restaurant start-ups with big data and implement a system to make it easier for prospective restaurant start-ups to recommend restaurant start-ups that suit them and further increase the success rate for restaurant start-ups. Therefore, this paper is meaningful in analyzing the start-up factors desired by prospective restaurant founders with big data, turning them into text, and furthermore, designing and studying the start-up factors shown as big data into a restaurant start-up chatbot system.

• Archives of design research
• /
• v.21
• /
• pp.109-121
• /
• 1997

The poster in America was considered merely a means of advertising until the late 1880s, and was not thought to have any intrinsic value. During the 1890s, the poster in America came into its own as a medium of artistic expression, and it was recognized anew as an medium of advertising. The production and circulation of posters became active, and it won the popularity of poster collectors. But the American poster renaissance flourished for a few brief years in the 1890s. In this thesis, I paid attention that the art poster in America was mainly a product of the publishing trade, and that it's rise and fall was connected with the circumstances of the publishing business. In chapterII, I discussed the growth of publishing business and the phenomenon of poster craze, and tried to figure out the characteristic of American poster design in 1890s. The American poster boom was formally initiated in Spring 1893, when Edward Penfield published the first of his monthly designs advertising Harper's Magazine. Penfield created a native American tradition of realism in the series of Harper's posters, his figures are realistic though anonymous, and are drawn without distortion or grotesquery, and details are reduced to essentials but not eliminated. In chapterIII, I discussed the change in book cover design in the 1890s. The rapid evolution of book and magazine covers was largely a reaction to the poster craze. Most magazines were issued with the same standard covers month after month at that time. In 1894, when William Bradley was asked to design a standard cover for the Inland Printer, he convinced the publishers to change the cover with every issue instead of designing one permanent cover. With the poster craze at its height, posters became big business, but still they were not very successful as advertisements. Because collectors of the 1890s were more interested in acquiring posters than in buying books. Significantly, this was also the moment when poster like designs began to appear on the covers of books and mass magazines. Publishers took notice of an idea. If the eye-catching design was on the cover itself rather than on a separate poster, the customer who wished to acquire the design would be obliged to buy the magazine. So there was no distinction stylistically between the posters of the 1890s and the magazine covers of the early 1900s. At the same time, the artistic poster was beginning to decline. While the most typical advertisements of the 1890s were the book and magazine posters of Bradley and Penfield, after 1900 advertisements for manufacturers' products played an increasingly prominent role. They would never again assume the leading role that they had played in the 1890s.

• Electrical & Electronic Materials
• /
• v.1 no.2
• /
• pp.136-148
• /
• 1988

본 논문은 Epoxy수지에 무기물을 첨가하여 tracking 특성에 미치는 자외선 조사의 영향을 연구하였다. 시료는 Bisphenol A형 Epoxy수지에 충진제 MgO와 Al(OH)$_{3}$를 각각 첨가한 시료와 무기물을 첨가하지 않은 무층진 시료에 대하여 자외선을 조사하여 산화 및 열화현상과 tracking현상을 비교 연구 검토하였다. 그 결과 자외선조사로 인하여 carbonyl기의 생성과 craze의 발생이 있었고 이는 tracking 파괴와 침식을 용이하게 한다. 그리고 Epoxy수지에 충진제를 첨가하므로서 자외선에 의한 열화를 감소시키고 내 tracking성을 향상시킨다.

• Annual Conference of KIPS
• /
• 2011.11a
• /
• pp.730-732
• /
• 2011

최근 전 세계적으로 스마트폰의 열풍이 거세게 불고 있다. 본격적으로 출시된 지 얼마 되지 않은 스마트폰이 이렇게 인기를 끌게 된 원인을 분석하고, 스마트폰의 가장 큰 문제점인 보안 사고의 심각성과 원인, 해결 방안에 대해 연구한다.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.403-404
• /
• 2023

In an era where everything is digitalized using AI(Artificial Intelligence), such as the ChatGPT craze, the evacuation guidance system still uses an analog and fixed method, so there is a limit to quick response in case of fire. In order to overcome this, we introduce a digitally transformed evacuation guidance system using AI and discuss its effectiveness.