• Title/Summary/Keyword: Button Fracture

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Simulation on Spot Welding Behavior of Car Body Sheet (자동차용 판재의 점 용접시 용접거동 Simulation)

  • 이재갑;강춘식
    • Journal of Welding and Joining
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    • v.12 no.2
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    • pp.76-86
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    • 1994
  • Spot welding behavior of galvanized steel has been studied using both numerical and experimental techniques. The model that used to calculate temperature distribution within weldment is two-dimensional axis-symmetric finite difference method, and nugget sizes of specimen welded in condition of welding current and time has been estimated by experiment Results have shown that nugget sizes are increased in proportion to welding current and time, but the growth rate of nugget is decreased. Shear-tensile strength tests have shown interface fracture when welding current is 7, 9KA, welding time is 8-14cycle and 11KA, 8-10cycle respectively, but above 7, 9KA fracture shows button type. In button fracture, shear-tensile strengths have been proportional to nugget sizes.

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MECHANICAL PROPERTIES OF REUSED LITHIUM DISILICATE GLASS-CERAMIC OF IPS EMPRESS 2 SYSTEM

  • Oh Sang-Chun
    • The Journal of Korean Academy of Prosthodontics
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    • v.40 no.6
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    • pp.572-576
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    • 2002
  • This investigation was designed to estimate the biaxial flexure strength and fracture toughness of lithium disilicate glass-ceramics of IPS Empress 2 system pressed with as-received ingots and their sprue buttons. Two groups of the lithium disilicate glass-ceramics were prepared as follows: group 1 is ingot-pressed group; group 2 is sprue button-pressed group. A ball-on-three-ball test was used to determine biaxial flexure strength (BFS) of disks in wet environment. Scanning electron microscopy(SEM) analysis was conducted to observe the microstructure of the ceramics. Unpaired t-test showed that there were no differences in the mean biaxial Hem strength (BFS) and KIC values between group 1 and 2 (p > 0.05). Two groups showed similar values in the KIC and the strength at 5% failure probability. The SEM micrographs of the IPS Empress 2 glass-ceramic showed a closely packed, multi-directionally interlocking pattern of numerous lithium disilicate crystals protruding from the glass matrix. The lithium orthophosphate crystals could not be observed on the fracture surface etched. There was no a marked difference of the microstructure between group 1 and 2. Although there were no tests including color stability, casting accuracy, etc., the results of this study implied that we could reuse the sprue button of the pressed lithium disilicate glass-ceramic of IPS Empress 2 system.

Mechanical Properties of Zirconia Reinforced Glass-Ceramic (지르코니아 강화형 Glass-Ceramic의 기계적 성질)

  • Park, Eun-Eui;Dong, Jin-Keun;Lee, Hae-Hyoung;Song, Ki-Chang;Oh, Sang-Chun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.17 no.3
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    • pp.199-204
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    • 2001
  • This study was to investigate the reused possibility of zirconia reinforced glass-ceramic(IPS Empress Cosmo ceramic) with sprue button in the flexure strength and fracture toughness. 40 disk-shaped ceramic specimens (20 specimens: as-pressed material; 20 specimens: reused material) with approximately 1.7 mm thickness and 15 mm diameter were prepared by "lost wax" technique. The remnants(sprue buttons) were used for repressing. The surface treatments for the discs were gradually abraded with 320, 800, 1200, and 2000 grit SiC sandpaper. The specimens were evaluated their flexure strength with the biaxial flexure jig(ball-on-three balls) and their fracture toughness with Vickers Indentation-microfracture test. The Weibull moduli were calculated for biaxial flexural strength. The mean flexure strength and fracture toughness of each group were $122.2{\pm}18.3MPa$, $1.00{\pm}0.09MPa{\cdot}m^{0.5}$ (as-pressed ceramics), and $122.2{\pm}20.3MPa$, $1.01{\pm}0.10MPa{\cdot}m^{0.5}$ (reused ceramics). There were no significant differences in the strength and the fracture toughness between the as-pressed and the reused IPS Empress Cosmo ceramic (P>0.05). This implied zirconia reinforced glass-ceramic(IPS Empress Cosmo ceramic) could be used one more time by reusing of sprue button in the flexure strength and fracture toughness.

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Characterization of Partial Interfacial Fracture on Resistance Spot-Welded TRIP Steels for Automotive Applications (자동차 차체용 TRIP강판의 저항 점용접부 Partial Interfacial Fracture 특성에 관한 연구)

  • Choi, Chul Young;Kim, In-Bae;Kim, Yangdo;Park, Yeong-Do
    • Korean Journal of Metals and Materials
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    • v.50 no.2
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    • pp.136-145
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    • 2012
  • Resistance spot welding of TRIP780 steels was investigated to enhance understanding of weld fracture mode after tensile shear testing (TST) and L-shape tensile testing (LTT). The main failure mode for spot welds of TRIP780 steels was partial interfacial fracture (PIF). Although PIF does not satisfy the minimum button diameter (4${\surd}$t) for acceptable welds, it shows enough load carrying capacity of resistance spot welds for advanced high strength steels. In the analysis of displacement controlled L-shape tensile test results, cracks initiated at the notch of the faying surface and propagated through the interface of weldments, and finally, cracks change path into the sheet thickness direction. Use of the ductility ratio and CE analysis suggested that the occurrence of PIF is closely related to high hardness and brittle welds, which are caused by fast cooling rates and high chemical compositions of TRIP steels. Analysis of the hold time and weld time in a welding schedule demonstrated that careful control of the cooling rate and the size of a weld nugget and the HAZ zone can reduce the occurrence of PIF, which leads to sound welds with button fractures (BFs).

Arthroscopic Stabilization for Displaced Lateral Clavicular Fractures: Can It Restore Anatomy?

  • Khan, Prince Shanavas;Yoo, Yon-Sik;Kim, Byung-Su;Lee, Seong-Jin;Ha, Jong Mun
    • Clinics in Shoulder and Elbow
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    • v.19 no.3
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    • pp.143-148
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    • 2016
  • Background: The purpose of our study was to evaluate the accuracy of reduction based on postoperative computed tomography (CT) images after arthroscopic stabilization using tightrope system for unstable distal clavicle fracture. Methods: Twelve patients with distal clavicle fracture combined with coracoclavicular (CC) ligament injury (type II, V) who received arthroscopically assisted fixation using a flip button device were evaluated for accuracy of reduction using 3-dimensional postoperative CT scan by measuring the degree of distal clavicular angulation and clavicular shortening. Results: Immediate postoperative plain radiograph confirmed restoration of the CC distance (CCD) in 10 patients. At final follow-up, the CCD remained reduced anatomically on plain radiographs in these patients. All patients showed excessive posterior angulation and shortening compared to the opposite side. The average Constant score recovered to 94.8 at final follow-up. Conclusions: Indirect reduction and arthroscopic subacromial approach with flip button fixation of unstable distal clavicle fractures demonstrated favorable clinical results despite unavoidable posterior angulation of distal clavicle and shortening the total length of clavicle.

A Study on the Resistance Spot Weldability of 590 MPa Grade DP Steel with Modified Electrode Tip (가공 전극을 적용한 590 MPa급 DP강의 저항 점용접에 관한 연구)

  • Lee, Sang-Min;Park, Yeong-Do
    • Korean Journal of Metals and Materials
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    • v.48 no.1
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    • pp.71-76
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    • 2010
  • The use of advanced high-strength steels (AHSS) in automotive applications has steadily increased over the past few years. Two different failure modes are generally observed in shear-tension tests for resistance spot welds of AHSS. interfacial fractures and full button pullout. Despite high load-carrying capacity. the resistance spot welds in AHSS cue prone to interfacial fractures. To improve the load carrying ability of welds during shear-lap and cross tension tests. the tip surface of the electrode was grooved in a round shape. The electrode tip surface was modified so as to concentrate the current now in the central and circumferential portion of the electrode force. The results showed that the interfacial fracture was suppressed in welds using the modified electrode. In a comparison of failure mode during mechanical tests. the welds made with the modified electrode showed a higher tendency to fail via full button pullout fracture.

Syndesmotic Injury (원위경비인대결합의 손상)

  • Ahn, Jungtae;Park, Moon Su;Jeong, Bi O
    • Journal of Korean Foot and Ankle Society
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    • v.26 no.1
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    • pp.9-15
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    • 2022
  • Syndesmotic injuries are found frequently in clinical practice, and they remain controversial because of the variety of diagnostic techniques and management options. Bony avulsions or malleolar fractures are commonly associated with syndesmotic disruptions. Even unstable isolated syndesmosis injuries are associated with a latent or frank tibiofibular diastasis and should not be ignored in the early phase. A relevant instability of the syndesmosis with diastasis results from collateral ligaments tears and requires operative stabilization. The treatment involves an anatomic reduction of the distal tibiofibular articulations followed by stable fixation. Syndesmotic transfixation screws or suture button implants are being proposed as a means of fixation. Recently, suture button fixation has shown more favorable outcomes, but the outcomes can still be controversial. Syndesmotic malreduction can lead to hardware failure, adhesions, heterotopic ossification, tibiofibular synostosis, chronic instability, and posttraumatic arthritis. In particular, the correct diagnosis and evidence-based treatment options for unstable syndesmotic injury should be considered.

All-arthroscopic, Guideless Single Suture-button Fixation of Acute Acromioclavicular Joint Dislocation: A Description of the Technique and Early Treatment Results

  • Altintas, Burak;Yildiz, Fatih;Uzer, Gokcer;Kapicioglu, Mehmet;Bilsel, Kerem
    • Clinics in Shoulder and Elbow
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    • v.20 no.2
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    • pp.59-67
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    • 2017
  • Background: The purpose of this study was to examine the clinical and radiological results of the all-arthroscopic, suture-button fixation technique to treat acute acromioclavicular (AC) joint separations. Methods: All patients with acute AC joint separations received all-arthroscopic, single suture-button (TightRope) procedure without a special guide. Postoperative Constant score (CS), pain level according to visual analogue scale, and range of motion (ROM) were evaluated. For radiological evaluation, coracoclavicular distances were measured bilaterally. Results: Between December 2010 and June 2012, 18 consecutive patients (4 women and 14 men; mean age, 29.3 years) with acute AC joint separations underwent surgical treatment after 6.4 days (range, 2-20 days) following the initial trauma. The average postoperative follow-up was 16.9 months. The mean CS was 92.4 (range, 84-96). The mean external rotation, forward flexion, and abduction were $75.8^{\circ}$ (range, $50^{\circ}-90^{\circ}$), $170^{\circ}$ (range, $150^{\circ}-180^{\circ}$), and $163.8^{\circ}$ (range, $140^{\circ}-180^{\circ}$), respectively. Five patients exhibited coracoclavicular ossifications. In two patients, superficial wound infections were successfully treated with antibiotic therapy. In one patient, a coracoid fracture was observed. No significant differences were found regarding pain, ROM, or strength parameters between both sides. The coracoclavicular distance was discovered to be approximately 2.8 mm greater on the affected side; however, this minimal reduction loss did not affect the functional results. Conclusions: The findings of this study suggests that all-arthroscopic treatment of AC joint separations using the single suture-button technique without a drill guide is safe, yielding good to excellent clinical results.

Effect of Paint Baking on the Strength and Failure of Spot Welds for 780 TRIP Steels (780 MPa급 TRIP강의 저항 점용접부 강도 및 파단에 미치는 Paint Baking의 영향)

  • Son, Jong-Woo;Nam, Dae-Geun;Kim, Dong-Cheol;Park, Yeong-Do
    • Journal of Welding and Joining
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    • v.28 no.2
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    • pp.66-73
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    • 2010
  • Conventional fracture test of resistance spot weld had been performed without consideration of paint baking process in automobile manufacturing line. This study was aim to investigate the effect of paint baking on fracture mode and load carrying capacity in fracture test for resistance spot welded 780TRIP steels. With paint baking cycle after resistance spot welds, peel tests and microhardness were conducted on the as-welded and baked samples. Resistance spot welds in AHSS (Advanced High Strength Steels) are prone to display partial interfacial fractures during fracture test or vehicle crash. Baking cycle increased the load-carrying capacity of the resistance spot welded samples and improved the fracture appearance from partial to full button fracture for the L-type peel tests. Specially, the differences in fracture appearance are apparent when the nugget size of spot welds is small enough to produce the partial interfacial fracture. The comparison of macrohardness and microstructure between as-welded and baked samples showed that there are no large difference in change the fracture mode. However, the results of the instrumented indentation test suggested that fusion zone and HAZ of baked sample have less tensile and yield strength and proves that the tempering effects are applied and enhanced the resistance to fracture on welds with application of baking cycle.