• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4A
• /
• pp.529-536
• /
• 2008

The failure behavior of structures is changed under different loading rates, which might arise from the rate dependency of materials. This phenomenon has been focused in the engineering fields. However, the failure mechanism is not fully understood yet, so that it is hard to be implemented in numerical simulations. In this study, the numerical experiments to a brittle material are simulated by the Molecular Dynamics (MD) for understanding the rate dependent failure behavior. The material specimen with a notch is modeled for the compact tension test simulation. Lennard-Jones potential is used to describe the properties of a brittle material. Several dynamic failure features under 6 different loading rates are achieved from the numerical experiments, where remarkable characteristics such as crack roughness, crack recession/arrest, and crack branching are observed during the crack propagation. These observations are interpreted by the energy inflow-consumption rates. This study will provides insight about the dynamic failure mechanism under different loading rates. In addition, the applicability of the MD to the macroscopic mechanics is estimated by simulating the previous experimental research.

• Journal of Korean Foot and Ankle Society
• /
• v.12 no.2
• /
• pp.189-196
• /
• 2008

Purpose: Nonunions and delayed unions are possible complications of fractures of fifth metatarsal base. We tried to report the results of the surgical treatment, which is not prevalent yet. Materials and Methods: Retrospective study of thirty nine patients undergoing operation at our institution between 2003 and 2008 was conducted. Six patients were excluded with loss of follow up before bony union, multiple trauma, pediatric fractures, stress fracture, open fracture. There were 18 males and 15 females with 45.1 years old mean age. The average follow-up period was 18.3 months. We used a midfoot scoring system of AOFAS for clinical assessment and radiologic findings to evaluate bony union, alignment. Results: According to Lawrence's classification, Zone 1 fractures were thirteen and Zone 2 were twenty. Average AOFAS score was 93.61. Conclusion: Early operative treatment with cannulated screw fixation in fractures of the fifth metatarsal base is thought to be an useful and easy treatment option with faster rates of union.

• Journal of Korean Foot and Ankle Society
• /
• v.16 no.2
• /
• pp.87-93
• /
• 2012

Fractures located at the metaphyseal/diaphyseal junction at the base of the fifth metatarsal were first described by Sir Robert Jones in 1902. However, ever since, there has been disagreement and debate regarding the diagnosis, classification, pathomechanics, the incidences, and potential causes of delayed unions and nonunions, and the optimal method of treatment. It appears to be widely agreed that proximal fractures of the metaphyseal/diaphyseal region of the fifth metatarsal are prone to delayed union or even nonunion. Several classifications of proximal fifth metatarsal stress fractures have been devised. Torg et al. classified fractures involving the proximal part of the diaphysis of the fifth metatarsal into three types. The Torg classification is a good grading system that can be used to determine the type of surgery needed as well as for the prediction of prognosis. The ''plantar gap'' might add to the decision-making process for surgery and improve the prediction of patient prognosis. In addition, the new classification using 'plantar gap' might be used for classification of fifth metatarsal stress fracture. Fifth metatarsal stress fractures can be treated conservatively or surgically, and excellent results have been reported for surgery with rapid recovery in athletes. Intramedullary screw fixation has become a popular form of fixation for fifth metatarsal stress fractures. Bone grafting presents the problems of a longer recovery time and additional skin incision for harvesting. The modified tension band wiring is an useful and simple option for surgical treatment of challenging fifth metatarsal stress fractures.

• Journal of Korean Foot and Ankle Society
• /
• v.12 no.2
• /
• pp.185-188
• /
• 2008

Purpose: Zone I fractures of the fifth metatarsal bone can generally be treated by conservative methods while both surgical and conservative methods are used for zone II fractures. However, the clinical results of conservative treatment have been rarely reported. The purpose of this study is to report the clinical results of conservative treatment for zone I and II nondisplaced fractures. Materials and Methods: Between July 2007 and August 2008, consecutive thirty seven patients (38 fractures) with zone I and II fractures of the fifth metatarsal bone were treated with tolerable weight bearing and minimum duration of immobilization based on pain on weight bearing. We evaluated the duration of immobilization, time to clinical and radiographic union, and time to pre-injury activity level. Results: Clinical and radiological union were achieved in all patients without any complications including malunion or nonunion. The mean duration of immobilization was 28.7 days. The mean 33.1 days and 48.9 days were required for clinical union and radiographic union respectively, after the initial injury. The mean time to pre-injury activity level was 4.8 months. Conclusion: Our study shows that the acute nondisplaced zone I, II fracture of fifth metatarsal bone can be treated effectively using tolerable weight bearing and minimum duration of immobilization, which is based on the pain on weight bearing.

• Steel and Composite Structures
• /
• v.8 no.3
• /
• pp.179-200
• /
• 2008

This paper reports the results of a recent experimental study into the behavior of welded fin-plate connections to both hollow and concrete filled tubular (CFT) columns under shear. Experiments have been performed at both ambient and elevated temperatures with the aid of an electric kiln. The observed failure modes include fracture of the fin plate and tearing out of the tube around the welds. By considering the results of previously published research, the current design method for similar connections under purely tensile load, in CIDECT Guide 9, based on a deformation limit of 3% of the tube width is shown to be inadequate when evaluating the ultimate strength of such connections. By comparing the results from the current test program which failed in the fin-plate with Eurocode guidance for failure of a fin-plate alone under shear and bending load it is shown that the column face influences the overall connection strength regardless of failure mode. Concrete in-fill is observed to significantly increase the strength of connections over empty specimens, and circular column specimens were observed to exhibit greater strength than similarly proportioned square columns. A finite element (F.E.) model, developed using ABAQUS, is presented and validated against the experimental results in order that extensive parametric tests may be subsequently performed. When validating the model against elevated temperature tests it was found that using reduction factors suggested in published research for the specific steel grades improved results over applying the generic Eurocode elevated temperature steel strength reduction factors.

• Structural Engineering and Mechanics
• /
• v.30 no.2
• /
• pp.177-190
• /
• 2008

Material failure behavior is generally dependent on loading rate. Especially in brittle and quasi-brittle materials, rate dependent material behavior can be significant. Empirical formulations are often used to predict the rate dependency, but such methods depend on extensive experimental works and are limited by practical constraints of physical testing. Numerical simulation can be an effective means for extracting knowledge about rate dependent behavior and for complementing the results obtained by testing. In this paper, the failure behavior of a brittle material under different loading rates is simulated by molecular dynamics analysis. A notched specimen is modeled by sub-million particles with a normalization scheme. Lennard-Jones potential is used to describe the interparticle force. Numerical simulations are performed with six different loading rates in a direct tensile test, where the loading velocity is normalized to the ratio of the pseudo-sonic speed. As a consequence, dynamic features are achieved from the numerical experiments. Remarkable failure characteristics, such as crack surface interaction/crack arrest, branching, and void nucleation, vary in case of the six loading cases. These characteristics are interpreted by the energy concept approach. This study provides insight into the change in dynamic failure mechanism under different loading rates.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.23 no.2
• /
• pp.389-397
• /
• 1993

This is a report of multiple myeloma occurred in the left mandibular body and skull. 66-year-old patient was referred to our hospital with a complaint of painful swelling on the left mandibular body area. The author diagnosed it as a multiple myeloma by the clinical examination, radiographic findings, laboratory findings and the histopathological findings. The purpose of this report is to aid in the diagnosis of multiple myeloma and to aid to differentiate it from malignant tumours. The characteristic features are as follows: 1. In clinical examination, painful swelling was observed in left mandibular body area. 2. In radiographic findings, radiograms showed relatively ill-defined radiolucency without sclerotic border in left mandibular body area. And also represented multiple punched-out radiolucency in the skull and pathologic fracture of vertebral body on lumbar 3 level. 3. In histopathologic findings, infiltration of abnormal plasma cells was observed. 4. In laboratory findings, decreasing of albumin/globulin ratio, hypercalcemia, renal impairment was observed, but we could not find the Bence-Jones protein in urin.

• Archives of Plastic Surgery
• /
• v.50 no.5
• /
• pp.501-506
• /
• 2023

This article portrays the authors' experience with a complex lower limb bone and soft tissue defect, following chronic osteomyelitis and pathological fracture, which was managed by the multidisciplinary orthoplastic team. The decision for functional amputation versus limb salvage was deemed necessary, enhanced by the principles of "spare parts" in reconstructive microsurgery. This case describes the successful use of the osteocutaneous distal tibia turn-up fillet flap that allowed "lowering the level of the amputation" from a through knee to a below-knee amputation (BKA) to preserve the knee joint function. We comprehensibly review reports of turn-up flaps which effectively lower the level of amputation, also applying "spare-parts" surgery principles and explore how these concepts refine complex orthoplastic approaches when limb salvage is not possible to enhance function. The osteocutaneous distal tibia turn-up fillet flap is a robust technique for modified BKA reconstructions that provides sufficient bone length to achieve a tough, sensate stump and functional knee joint.

• Archives of Craniofacial Surgery
• /
• v.10 no.2
• /
• pp.67-70
• /
• 2009

Purpose: Anatomical basis around orbit can be helpful in periorbital surgery, and there are many articles about measurement between periorbital reference points. In 1967, Jones and Evans measured the orbital wall thickness of Asian cadavers and this article has been cited more than 50 times. But there is no research in orbital thickness in Vivo. Author's idea was based on difference between live human and human cadaver. Material & Method: We conducted this study from 63 consecutive blow out fracture patients between January, 2000 to june, 2005 by collecting the bone fragments and measured the thickness of that fragment using vernia calipers. Anatomically, orbital floor is separated two area by inferior orbital fissure and we measured each area. Three areas were zone I (medial wall), zone II (medial to inferior orbital fissure) and zone III (lateral to inferior orbital fissure). Result: When the overall results were considered, the thickness of Zone I (medial wall of orbit) was average $0.131{\pm}0.006mm$ in male and $0.129{\pm}0.007mm$ in female and Zone II (medial side of orbital floor) was $0.251{\pm}0.005mm$ in male and $0.245{\pm}0.006mm$ in female, Zone III (lateral side of orbital floor) was $0.237{\pm}0.006mm$ in male and $0.226{\pm}0.006mm$ in female. There were no statistical difference between orbital wall thickness of male and female. Also, orbital wall thickness of adults measured $0.130{\pm}0.005mm$, $0.250{\pm}0.005mm$, $0.232{\pm}0.006mm$ in Zone I, Zone II, Zone III and $0.128{\pm}0.006mm$, $0.233{\pm}0.005mm$, $0.215{\pm}0.007mm$ in Zone I, Zone II, Zone III from childs, and there were no statistical difference between adult and child. Conclusion: This article is the first study about Korean orbital wall thickness, and can be helpful to periocular surgery.