• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.112-119
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• 1995

Early fracture and cutting force of ceramic tool for hardened STC3 steel was investigated in this study. It was found that early fracture of ceramic tool was mostly occurred before normal wear was progressed beyond a critical cutting speed and normal wear was performed under the critical cutting speed. The relationships among critical cutting speed, which was a cause of early fracture, suggested cutting cross section, that is, maximum thickness of cut and width of cut, and cutting force were examined. The following conclusions were obtained: (1)Critical cutting speed showed a high value in the case of small maximum thickness of cut and large nose radius, but was not influenced by width of cut, (2)Principal, feed and radial force, respectively, showed the proportional value to constant cutting area, width of cut and maximum thickness of cut orderly, (3)Occurrence of early fracture was dependent upon radial force.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.215-220
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• 2001

The objective of this study is to examine the fracture characteristics of concrete at early ages such as critical stress intensity factor, critical crack-tip opening displacement, fracture energy based on the concepts of the effective-elastic crack model and the cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By varying strength and age, load-crack mouth opening displacement curves were obtained and the results were analyzed by linear elastic fracture mechanics. The results from the test and analysis showed that critical stress intensity factor and fracture energy increased, and critical crack-tip opening displacement decreased with concrete age from 1 day to 28 days. The obtained fracture parameters at early ages may be used as a fracture criterion and an input data for finite element analysis of concrete at early ages.

• Computers and Concrete
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• v.13 no.1
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• pp.31-47
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• 2014

This research is focused on obtaining the fracture property of steel fiber reinforced concrete(SFRC) specimens at early ages of 1, 2, 3 and 7-day, respectively. For this purpose, three point bending tests of nine groups of SFRC beams with notch of 40mm depth and different steel fiber ratios were conducted. The experimental results of early age specimens were compared with the 28-day hardened SFRC specimens. The test results indicated that the steel fiber ratios and curing age significantly influenced the fracture properties of SFRC. A reasonable addition of steel fiber improved the fracture toughness of SFRC, while the fracture energy of SFRC developed with curing age. Moreover, a quadratic relationship between splitting strength and fracture toughness was established based on the experiment results. Additionally, afinite element (FE) method was used to investigate the fracture properties of SFRC.A comparison between the FE analysis and experiment results was also made. The numerical analysis fitted well with the test results, and further details on the failure behaviors of SFRC could be revealed by the suggested numerical simulation method.

• International Journal of Concrete Structures and Materials
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• v.18 no.3E
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• pp.191-198
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• 2006

The objective of this study is to examine fracture characteristics of concrete at early ages, i.g. critical stress intensity factor, critical crack-tip opening displacement, fracture energy, and bilinear softening curve based on the concepts of effective-elastic crack model and cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By experimenting with various strengths and ages, load-crack mouth opening curves were obtained, and the results were analyzed by linear elastic fracture mechanics and FEM(finite element method). The results from the test and analysis showed that critical stress intensity factor and facture energy increased while critical crack-tip opening displacement decreased with concrete aging from 1 day to 28 days. Four parameters of bilinear softening curve from 1 day to 28 days were obtained from a numerical analysis. The obtained fracture parameters and bilinear softening curves at early ages from this study are to be used as a fracture criterion and an input data for the finite element analysis of concrete at early ages.

• Journal of Korean Foot and Ankle Society
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• v.21 no.1
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• pp.21-26
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• 2017

Purpose: To evaluate the clinical outcome of an operation with early rehabilitation from ankle fracture in accordance with the injury type. Materials and Methods: A total of 136 patients (70 males and 66 females) who underwent surgery and early rehabilitation for ankle fractures between December 2008 and December 2013 were retrospectively reviewed. The average age was 47.9 years, with a range of 18~79 years. The mean follow-up period was 28.7 months, with a range of 24~102 months. All patients were classified in accordance with the Lauge Hansen classification and anatomic fracture site. Moreover, the presence of ligament injuries were documented. A short-leg cast was applied postoperatively for two weeks; thereafter, patients began the range-of-motion exercises after cast removal. Full weightbearing was allowed at 2 weeks postoperatively. Each patient was assessed radiologically and clinically based on the OlerudMolander score, visual analogue scale (VAS) for pain, joint stiffness, and capability of single heel raising. Results: Seventeen patients (12.5%) complained of postoperative pain (VAS score 1~3), and the incidence was higher in patients with trimalleolar fractures or associated ligament injuries. Twenty-three patients (16.9%) complained of postoperative ankle stiffness. The mean Olerud-Molander score was 75.4/80 (range, 55~80). Olerud-Molander scores were lower in patients with ligament injuries than in those with fracture alone. There was no nonunion or fracture displacement even after early weightbearing walking. Conclusion: In this retrospective series, early rehabilitation after surgical restoration of ankle mortise by anatomical reduction and stabilization was shown to be successful. Earlier motion exercise and weightbearing walking can minimize fracture complications like joint stiffness or weakness in ankle fracture.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.58-66
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• 2002

The objective of this study is to examine the fracture characteristics of concrete at early ages such as critical stress intensity factor, critical crack-tip opening displacement, fracture energy, and bilinear softening curve based on the concepts of the effective-elastic crack model and the cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By taking various strengths and ages, load-crack mouth opening displacement curves were obtained, and the results were analyzed by linear elastic fracture mechanics and the finite element method. The results from the test and analysis showed that critical stress intensity factor and fracture energy increased, and critical crack-tip opening displacement decreased with concrete ages from 1 day to 28 days. By numerical analysis four parameters of bilinear softening curve from 1 day to 28 days were obtained. The obtained fracture parameters and bilinear softening curves at early ages may be used as a fracture criterion and an input data for finite element analysis of concrete at early ages.

• Journal of Korean Neurosurgical Society
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• v.38 no.1
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• pp.77-79
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• 2005

We report a case of early stress fracture of the pelvic ring following an extension of a multilevel instrumented lumbosacral fusion in an osteopenic female. Surgeons should be aware of possibilities of pelvic complications in osteopenic patients with lumbosacral arthrodesis and should take care when harvesting iliac bone graft.

• Journal of Korean Neurosurgical Society
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• v.59 no.2
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• pp.137-142
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• 2016

Objective : To evaluate whether an early bone marrow edema pattern predicts vertebral deformity types and prognosis in osteoporotic vertebral compression fracture (OVCF). Methods : This retrospective study enrolled 64 patients with 75 acute OVCFs who underwent early MRI and followed up MRI. On early MRI, the low SI pattern of OVCF on T1WI were assessed and classified into 3 types (diffuse, globular or patchy, band-like). On followed up MRI, the vertebral deformity types (anterior wedge, biconcave, crush), degree of vertebral body height loss, incidence of vertebral osteonecrosis and spinal stenosis were assessed for each vertebral fracture types. Results : According to the early bone marrow edema pattern on T1WI, 26 vertebrae were type 1, 14 vertebrae were type 2 and 35 vertebrae were type 3. On followed up MRI, the crush-type vertebral deformity was most frequent among the type 1 OVCFs, the biconcave-type vertebral deformity was most frequent among the type 2 OVCFs and the anterior wedge-type vertebral deformity was most frequent among the type 3 OVCFs (p<0.001). In addition, type 1 early bone marrow edema pattern of OVCF on T1WI were associated with higher incidence of severe degree vertebral body height loss, vertebral osteonecrosis and spinal stenosis on the follow up MRI. Conclusion : Early bone marrow edema pattern of OVCF on T1WI, significant correlated with vertebral deformity types on the follow up MRI. The severe degree of vertebral height loss, vertebral osteonecrosis, and spinal stenosis were more frequent in patients with diffuse low SI pattern.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.4 no.1
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• pp.24-27
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• 2011

Late rupture of the extensor pollicis longus (EPL) tendon is an occasional complication following a distal radius fracture. Early rupture of the EPL tendon as a complication of distal radius fracture is rare. We report one case of early rupture of the EPL tendon after distal radius fracture.

• The Korean Journal of Nuclear Medicine
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• v.21 no.1
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• pp.39-46
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• 1987

The stress fracture is a disease caused by and abnormal stress to the normal bone with constant, repeated pull. Early detection of stress fracture plays an important role in treatment and prevention of its complication. Bone scintigraphy was performed to evaluate 18 patients with stress fracture of the lower extremities from May, 1985 to April, 1987, in the Department of Internal Medicine of National Police Hospital. The results were as follows: 1) Seventeen of the 18 cases showed positive bone scans at the initial study performed from 1 week to S months after the onset of symtom. 2) Ten of the 18 patients had findings of stress fracture at the initial X-ray film. Two out of 8 negative case revealed positive findings in the follow-up studies. 3) The bone scans in the 2 cases taken 5 months after the onset of symton; the one showed only slightly increased radiouptake, the other showed no abnormal findings. In conclusion, bone scanning is a more sensitive indicator of early stress fracture than radiologic study. The healing phase is characterized by a gradual decline in radioactivity at the fracture site in concordance with subsidence of symptom.