• International Journal of Concrete Structures and Materials
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• v.18 no.3E
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• pp.183-189
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• 2006

Many researchers have recently proposed various parameters, variables of models and experimental methods to evaluate fracture properties of concrete, and their developments allow us to analyze the non-linear and quasi-brittle fracture mechanisms. This paper presents a brief treatment of the fracture parameters. Additionally, three-point bending tests were conducted to compare J-integral($J_{Ic}$) with other parameters($K_{Ic},\;G_{Ic},\;and\;G_F$). The change in parameter values with respect to the width and notch length of concrete beam specimens was also considered. The load-displacement curves were used to measure the concrete fracture toughness experimentally. From the results of experiment, it was found that the value of $G_F\;and\;J_{Ic}$ decreased as the notch depth increased and that $G_F$ was less sensitive than $J_{Ic}$. Therefore, the former, $G_F$, is more appropriate in using it as the concrete fracture toughness parameter. The values of $G_F\;and\;J_{Ic}$ increased when the width of concrete specimens increasing from 75 mm to 150 mm. Thus, the effects of the specimen width should be considered in determining the fracture toughness of concrete.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.42-51
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• 1985

The dynamic fracture toughness, fracture characteristics, impact tension and tensile properties of Al-Mg-Si T5 alloy and Al-Zn-Mg T6 alloy respectively welded with filler metal of Alcan 4043 were investigated. The dynamic fracture toughness values were obtained rapidly and simply for the specimen of small size by using instrumented Chirpy impact testing machine. the testing temperatures of the specimen were a range of room temperature and-196.deg. C. The results obtained in this experiment are summarized as follows. With decreasing the testing temperatures, dynamic tensile stress and fracture load were increased, on the other hand the deflection and impact value showed decreasing tendency in order of base metal>HAZ>weld. Changes of total absorbed energy were more influenced by the crack propagation energy than the crack initiation energy. At the low temperatures, the unstable rapid fracture representing the crack propagation appeared for the specimens of Charpy press side notched in Al-Zn-Mg alloy, but it was difficult to obtain the unstable rapid fracture in Al-Mg-Si alloy. Because of the development of plastic zone at the notch root, it was difficult to obtain thevalid $K_{1d}$ value in Al-Mg-Si alloy. Therefore the fatigue cracked specimens were effective in both Al-Mg-Si and Al-Zn-Mg alloys. With decreasing the impact testing temperatures, specimens underwent a transition from dimple-type transgranular fracture to lamella surface-type intergranular fracture because of the precipitate at the grain boundaries, impurities and crystal structure of the precipitates.s.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• Transactions of Materials Processing
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• v.26 no.2
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• pp.121-126
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• 2017

The hot stamping process is an innovative forming method that could prevent the cracking of high strength steel sheets. The formability test of boron steel sheet using forming limit diagrams at elevated temperature is very complicated and time consuming job. In this paper, an alternative test method to evaluate the formability of boron steel in hot stamping has proposed. It measured the FLD0 instead of whole strain combinations of FLD with the tensile test machine and specially designed test rig. Test results shows that the proposed test method can simulate the plain strain condition fracture and can make the FLD of boron steel sheet at elevated temperature with less effort.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1172-1182
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• 1993

In orthogonal machining a quantitative model for burr formation process and fracture when tool exits workpiece is proposed. When no fracture during burr formation burr formation process is divided by three parts; Initiation, Development and Final burr formation. According to the properties of workpiece fracture will happen or not after initiation of burr formation. Considering the fact that fracture depends on the ductility of workpiece, the fracture strain obtained from ductile fracture criterion is used for prediction. It is verified that the fracture strain from tension test can be used as fracture criterion in burr formation without large error. For detailed observation of burr formation an experimental stage for micro orthogonal cutting inside SEM (Scanning Electron Microscope) is built. Through the comparison between model prediction and experimental result from orthogonal machining in milling machine the model is verified.

• Journal of Korean Physical Therapy Science
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• v.8 no.1
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• pp.841-850
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• 2001

This study was conducted to find out current status and characteristics, so that the result could provide basic data to establish prevention programs for hip fracture among the elderly. The data were coolected from 199 cases hospitalized in 4 university hospitals in Pusan during three years period from January, 1966 to December, 1998. The data were obtained from medical records and by using questionnaires through telephone contact or direct personal interview with the subjects or their family, and were analyzed with x2-test. The results were as follow: The mean age of elderly hip fractured cases was 75.7 years, and 61.8% were female. The average hospital stay of the cases was 30.8 days, and 73.9% survived. Femur neck fracture cases comprised 51.7% of the toral cases, while trochanteric fracture cases comprised 48.3%. The hip fracture occurred more frequently during the day, shown as 66.9%, and the most frequently due to trips(44.2%), followed by slips(322%), c1ash(14.6%), dizziness(7.5%), and 00 on. Femur neck fracture, however, occurred the most frequently due to trips(51.5%) and, on the other hand, trochanteric fracture due to slips(40.6%) and trips(36.5%). About two third of hip fracture(67.8%) occurred inside of the building. The most frequently mentioned location for hip fractures was rooms or floors(32.1%), followed by streets(24.1%), bathrooms(17.6%), stairways(13.1%), and so on. Trochanteric fracture, especially, more frequently occurred inside of the building(71.9%) as compared to femur neck fracture(64.1 %). The rate of independent indoor walking in femur neck fractured cases reduced from 88.3% to 74.8% after fracture incidences, while the rate reduced from 86.0% to 45.8% in trochanteric fracture cases. It indicated that trochanteric fractures affected the walking ability of the elderly more severely that femur neck fractures. In conclusion, hip fracture occurs as a combined result of aging characteristics, environmental factors, and health related characteristics. Future studies that investigaterisk factors of hip fracture in elderly are recommended.

• Journal of the Korean Society of Safety
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• v.6 no.4
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• pp.21-27
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• 1991

Acoustic Emission was monitored during tensile test and loading-holding-unloa-ding cycle test for two types (notched and unnotched) of CFRP specimens. AE activities showed that the fiber breakage during tensile tests depended upon the specimen geometry. We obtained new AE parameter such as the ration (damage ratio= AE events during unloading test / AE events during loading test) and the felicity ratio from which we investigated dynamic fracture process of CFRP specimens. The damage ratio of AE events was shown to be a good indicator to distinguish the generated fracture mechanism, such as fiber breakage and delamination. Also, ultrasonic testing results after loading-holding-unloading cycle test were good agreement with AE test results to detect defects or fiber breakage.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.121-129
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• 1993

Plane strain punch stretching test (PSST) was developed to evaluate stamping formability of sheet materials. In this test, the rectangular specimen of sheet material is uniformly stretched up to fracture by raising a specially designed punch to certainly assure plane strain stretching deformation along the longitudinal direction of the specimen. The stamping formability was evaluated by limit punch height(LPH) in plane strain punch stretching test compared to limit dome height(LDH) in hemispherical punch stretching test. LPH-value in PSST well ranks the stamping formability of various material and correlates with press performance. Moreover by using ultrasonic thickness gauge the plane strain intercept-limit plane strain(FLCo)-in forming limit curve can be accurately determined from thickness measurement around the fracture area. The FLCo derived from thickness measurement well correlates with the results from circle grid analysis for the deformed circle grid marked on the surface of the specimen.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.1
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• pp.10-20
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• 2018

The aim of this study was to evaluate the factors affecting the healing of root fracture in immature permanent teeth and the prognosis of root fracture by statistically analyzing the relationship with the pulp and root healing. The radiographs of 51 root-fractured maxillary anterior permanent teeth were collected. In radiograph, locations of root fracture, apical foramen width and width of diastasis between the fragments were measured. The value of the studied parameters were compared by independent t-test and rogistic regression test. In conclusion, there was no difference in the prognosis of pulp healing according to the location of root fracture. However, root healing occurs well as the root fracture is located at the root apex (p < 0.05). Lastly, the smaller the width of diastasis between the fragments after reduction, the better the pulp healing was (p < 0.05).

• The Journal of the Korean dental association
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• v.53 no.5
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• pp.360-367
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• 2015

Purpose : The purpose of this study was to evaluate the effect of amount of cantilever in intra-crown according to implant fixture position on mechanical strength of internal conical joint type implant. Materials and Methods : Internal conical joint type implant fixture, abutment screw, abutment was connected and gold alloy prostheses were fabricated and cemented on abutment. For fatigue fracture test, the specimens were loaded to the 350 N, 2,000,000 cycle on 3, 4, 5, and 6 mm off-center of gold alloy prostheses. The fracture pattern of implant component was observed. Results : No fatigue fracture found on 3 and 4 mm group. But initial crack pattern found on 3 specimens of 4 mm group. Fatigue fracture found on all specimens of 5 mm group. But complete fracture was not observed. One specimen of 6 mm group fracture completely. Implant fixture fracture wax not observed. Conclusion : The mechanical failure of implant prostheses increased with the loading area farther from center of implant fixture. To reduce mechanical problem of internal joint type implant, surgical and prosthetic consideration is needed.