Fracture Prediction of Welded Steel Connections Using Traditional Fracture Mechanics and Calibrated Micromechanics Based Models

Yuanqing Wang,Hui Zhou,Yongjiu Shi,Jun Xiong 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.3

Fracture resistance is of primary concern in the seismic design of beam-to-column connections in steel moment resisting frames (SMRFs). Micromechanics based fracture models such as the void growth model (VGM) and the stress modified critical strain (SMCS) model provide alternative approaches for ductile fracture prediction by relating micro-mechanisms of void nucleation, growth and coalescence to macroscopic stresses and strains. In this study, the VGM and SMCS models were calibrated for Q345 structural steel and the corresponding weld, through smooth notched tensile (SNT) tests and complementary continuum finite element models (FEMs). A series of seven local connections representing beam-to-column connections in SMRFs were tested under monotonic tensile loading and the specimen elongations at fracture critical point were obtained. The traditional J-integral based fracture mechanics and micromechanics based fracture models (VGM and SMCS) were applied to predict fracture in each tested local connection through refined three-dimensional FEM. Comparisons between these numerical approaches and experimental observations in prediction of fracture critical displacement, indicated that the VGM and SMCS models were able to predict fracture of welded connection with good accuracy, while the J-integral based approach resulted in quite conservative fracture prediction. This paper has bridged the gap between small-scale material tests and large-scale structural experiments in fracture evaluations

Is ankle fracture related to low bone mineral density and subsequent fracture? A systematic review

Atiporn Therdyothin,Nacharin Phiphopthatsanee,Wiwat Wajanavisit,Patarawan Woratanarat,Sukij Laohajaroensombat,Tulyapruek Tawonsawatruk 대한골다공증학회 2020 Osteoporosis and Sarcopenia Vol.6 No.3

Objectives: Ankle fractures are common in the elderly. However, their association with osteoporosis remains controversial. This systematic review aims to determine the relationship between ankle fracture and bone mineral density (BMD), and to investigate the risk of subsequent fractures after ankle fracture. Methods: MEDLINE and Scopus publications were searched from inception to March and April 2019, respectively. Articles were selected by 2 independent reviewers for cross-sectional, cohort, or casecontrol studies comparing BMD or subsequent fracture risk in low-energy ankle fractures patients with that of the normal population. Data extraction was performed by 2 investigators. Discrepancies were resolved with the third reviewer. Quality assessment was conducted using the modified NewcastleOttawa Scale. Results: Overall, 19 articles were included. The quality assessment showed a generally low-to-moderate risk of bias among studies, mainly due to potential confounders and inadequate follow-up. Of 13 studies exploring BMD in ankle fractured-patients, lower central and peripheral BMD was found in 3 and 2 studies, respectively. The risk of subsequent fracture was examined in 11 studies with relative risks ranging from 0.7 to 4.59. An increased risk of any subsequent fractures in women, both genders, and men was found in 5, 2, and 1 articles, respectively. Conclusions: Despite the lack of clear association with BMD, the contribution of ankle fracture to increased subsequent fracture risk and its associated microarchitectural changes cannot be overlooked. Moreover, its potential role as an early predictor of future fracture may promote secondary prevention. Further studies with longer follow-up and stricter confounder control are recommended.

흉골 골절 환자에서 심혈관계 동반 손상의 예측 인자와 응급 심장 초음파의 적응증

김찬웅,류지영,전영진 梨花女子大學校 醫科大學 醫科學硏究所 2001 EMJ (Ewha medical journal) Vol.24 No.1

Objective : To determine the predicting factors related to cardiovascular injuries and To suggest a clinical indication for emergency echocardiography in sternal fractures. Materials and Results : A total mumber of 40 patients with sternal fractures a over 5-year period were retrospectively assessed on clinical, echocardiographic and biochemical status. We analyzed the following 4 factors as predicting factors for cardiovascular injuries in sternal fractures : 1) presence of restraint, 2) presence of associated injuries, 3) presence of a past medical history involving cardiovascular system, 4) Revised Trauma Score(RTS). We, also, assessed the utility of conventional diagnostic methods for cardiovascular injuries, such as ECG, chest X-ray, and enzyme levels. Based on the methods, we tried to infer an indication for emergency echocardiography in sternal fractures. Results : The presence of a past medical history involving cardiovascular system and abnormal RTS on admission were significant predicting factors. Emergency echocardiography was performed according to the predicting factors and the results from conventional evaluations. These data can suggest that indications for emergency echocardiography in sternal fractures include as 1) if more than two studies reveal abnormality without any significant predicting factors. 2) if more than one study reveal abnormality with any significant predicting factors. Conclusion : The past medical history involving cardiovascular system and initial vital signs imply the presence of associated cardiovascular injuries in sternal fractures. And if possible, emergency echocardiography is recommended.

A Predictive Method for the Femoral Head Necrosis by the Observation of the Bleeding from the Cannulated Screw in Patients of the Femoral Neck Fractures

Sang-Wook Lee(이상욱),Myung-Rae Cho(조명래),Byoung-Kwan Lee(이병관),Sang-Bong Ko(고상봉),Dong-Kyu Shin(신동규),Koing-Woo Kwon(권굉우) 대한정형외과학회 2004 대한정형외과학회지 Vol.39 No.5

목적: 대퇴 경부 골절 환자에서 수술시 고정을 위해 사용하는 유관 나사를 이용하여 향후 대퇴 골두 골 괴사의 예측 방법에 대하여 조사하였다. 대상 및 방법: 1999년 3월부터 2001년 2월까지 44명을 대상으로 최소 25개월 이상 추시 관찰하였으며, 평균 나이는 51세(18-76세)였다. 근위부에 삽입된 유관 나사의 두부에 있는 관으로부터 출혈 유무를 관찰하였는데, 출혈군은 38예, 비 출혈군은 6예였다. 추시에서 대퇴 골두 골 괴사는 단순 방사선 사진으로 판독하였다. 두 군에서 유관나사 부위의 출혈 유무와 무혈성 괴사의 발생 관계에 있어 민감성, 정확성, 양성 예측도, 음성 예측도를 조사하였다. 결과: 대퇴 골두 골 괴사는 7예(16%)에서 발생하였다. 출혈군은 38예 중 1예(2.6%), 비 출혈군은 6예 모두에서 대퇴 골두골 괴사가 발생하였다. 비 출혈군과 골두 골 괴사의 관계에서는 민감도 86%, 정확도 100%, 양성 예측도 100%, 음성 예측도가 97%였다. 결론: 대퇴 경부 골절 환자에서 추후 발생할 수 있는 대퇴 골두 골 괴사에 대한 예측 방법으로 수술 중 유관 나사의 두부관 출혈 유무가 단순하면서 유용한 방법으로 판단된다. Purpose: The aim of this study was to examine the validity of using cannulated screws as a method for predicting avascular necrosis of the femoral head after a fixation of fractures in patients with femoral neck fractures. Materials and Methods: Between March 1999 and January 2001, 44 patients with a femoral neck fracture that had been fixed with cannulated screws were enrolled in this study. The follow up period was more than 25 months and the mean age of the patients was 51 years (range, 18 to 76 year). Blood drainage in the holes of the screw head was checked. There were 38 cases in the bleeding group, and 6 cases in the non-bleeding group. The development of head necrosis was evaluated using plain radiography. The validity of the relationship between the two groups and head necrosis was evaluated by the sensitivity, specificity, the positive predictive value, and the negative predictive value. Results: An avascular necrosis of the femoral head developed in 7 cases (16%). Only one of the 38 patients in the bleeding group developed head necrosis (2.6%). However, all those in the non-bleeding group developed head necrosis (100%). The sensitivity was 86%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 97%. Conclusion: Bleeding from holes in the cannulated screws is a simple and accurate perfusion assessment for predicting the development of an avascular necrosis of the femoral head after a femoral neck fracture.

Ultra-Low Cyclic Fatigue Fracture of Q235B and Q345B Steels and Their Butt Welded Joints

Xiyue Liu,Yidu Bu,Yuanqing Wang,Yang Guan 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.2

Earthquake-induced fractures in steel structures are characterised by high-strain low-cycle conditions. In order to investigate the ultra-low cyclic fatigue fracture of steel welded joints under earthquakes, two most commonly used structural steels (Q235B and Q345B) and the corresponding welds were studied by experiments and numerical analysis in this paper. Specimens were extracted from the base material, the weld metal and the heat aff ected zone to investigate the behaviour in diff erent parts of the welded joint. Eighteen smooth round bars were tested under large strain amplitudes, the hysteretic properties, damage degradation characteristics and failure process were analyzed. Constitutive model named Chaboche model was calibrated to describe the cyclic hardening behaviour of these materials. Seventy-two notched round bars with three diff erent notch sizes and two loading protocols were tested to study the fracture behaviour of diff erent materials at different stress triaxialities and diff erent strain amplitudes. Two micromechanical fracture models: cyclic void growth model and degraded signifi cant plastic strain model were calibrated based on the test results. The micromechanical models and Chaboche model were incorporated into numerical simulations by software ABAQUS with subroutine VUMAT to predict the materials fracture. The results show that the failure process under cyclic loads is opposite to that of monotone loads. The dissipation capacity of Q345B is superior to that of Q235B. The fracture resistance deteriorate more in the weld zone under the same loading conditions. The validated models can be used to eff ectively and accurately evaluate the fracture in steel welded connections under ULCF conditions.

Risk factor analysis for predicting vertebral body re-collapse after posterior instrumented fusion in thoracolumbar burst fracture

Jang, Hae-Dong,Bang, Chungwon,Lee, Jae Chul,Soh, Jae-Wan,Choi, Sung-Woo,Cho, Hyeung-Kyu,Shin, Byung-Joon Elsevier 2018 SPINE JOURNAL Vol.18 No.2

<P><B>Abstract</B></P> <P><B>Background Context</B></P> <P>In the posterior instrumented fusion surgery for thoracolumbar (T-L) burst fracture, early postoperative re-collapse of well-reduced vertebral body fracture could induce critical complications such as correction loss, posttraumatic kyphosis, and metal failure, often leading to revision surgery. Furthermore, re-collapse is quite difficult to predict because of the variety of risk factors, and no widely accepted accurate prediction systems exist. Although load-sharing classification has been known to help to decide the need for additional anterior column support, this radiographic scoring system has several critical limitations.</P> <P><B>Purpose</B></P> <P>(1) To evaluate risk factors and predictors for postoperative re-collapse in T-L burst fractures. (2) Through the decision-making model, we aimed to predict re-collapse and prevent unnecessary additional anterior spinal surgery.</P> <P><B>Study Design</B></P> <P>Retrospective comparative study.</P> <P><B>Patient Sample</B></P> <P>Two-hundred and eight (104 men and 104 women) consecutive patients with T-L burst fracture who underwent posterior instrumented fusion were reviewed retrospectively. Burst fractures caused by high-energy trauma (fall from a height and motor vehicle accident) with a minimum 1-year follow-up were included. The average age at the time of surgery was 45.9 years (range, 15–79). With respect to the involved spinal level, 95 cases (45.6%) involved L1, 51 involved T12, 54 involved L2, and 8 involved T11. Mean fixation segments were 3.5 (range, 2–5). Pedicle screw instrumentation including fractured vertebra had been performed in 129 patients (62.3%).</P> <P><B>Outcome Measures</B></P> <P>Clinical data using self-report measures (visual analog scale score), radiographic measurements (plain radiograph, computed tomography, and magnetic resonance image), and functional measures using the Oswestry Disability Index were evaluated.</P> <P><B>Methods</B></P> <P>Body height loss of fractured vertebra, body wedge angle, and Cobb angle were measured in serial plain radiographs. We assigned patients to the re-collapse group if their body height loss progressed greater than 20% at any follow-up time compared with immediate postoperative body height loss; we assigned the remaining patients to the well-maintained group. The chi-square test and <I>t</I> test of SPSS were used for comparison of differences between two groups and multiple logistic regression analysis for risk factor evaluation. Through the decision tree analysis of statistical package R, a decision-making model was composed, and a cutoff value of revealed risk factors and re-collapse rate of each subgroup were identified. The present study wassupported by the University College of Medicine Research Fund (university to which authors belong). There was no external funding source for this study. The authors have no conflict of interest to declare.</P> <P><B>Results</B></P> <P>Re-collapse occurred in 31 of 208 patients (14.9%). In this group, age, the proportion of male gender, preoperative height loss, and preoperative wedge angle were significantly greater than the well-maintained group. Multivariable logistic regression analysis identified two independent risk factors: age (adjusted odds ratio 1.084, p=.002) and body height loss (adjusted odds ratio 1.065, p=.003). According to the decision-making tree, age (>43 years) was the most discriminating variable, andpreoperative body height loss (>54%) was the second. In this model, the re-collapse rate was zero in ages less than 43 years, and among those remaining, nearly 80% patients with greater than 54% of body height loss belonged to the re-collapse group.</P> <P><B>Conclusions</B></P> <P>The independent predictors of re-collapse after posterior instrumented fusion for T-L burst fracture were the age at operation (>43 years old) and preoperative body height loss (>54%). Carefu

FATIGUE LIFE PREDICTION OF RUBBER MATERIALS USING TEARING ENERGY

Kim, H.,Kim, H.Y. The Korean Society of Automotive Engineers 2006 International journal of automotive technology Vol.7 No.6

It has been almost impossible to predict the fatigue life in the field of rubber materials by numerical methods. One of the reasons is that there are no obvious fracture criteria and excessively various ways of mixing processes. Tearing energy is considered as a fracture criterion which can be applied to rubber compounds regardless of different types of fillers, relative to other fracture factors. Fatigue life of rubber materials can be approximately predicted based on the assumption that the latent defect caused by contaminants or voids in the matrix, imperfectly dispersed compounding ingredients, mold lubricants and surface flaws always exists. Numerical expression for the prediction of fatigue life was derived from the rate of rough cut growth region and the formulated tearing energy equation. Endurance test data for dumbbell specimens were compared with the predicted fatigue life for verification. Also, fatigue life of industrial rubber components was predicted.

FATIGUE LIFE PREDICTION OF RUBBER MATERIALS USING TEARING ENERGY

H. KIM,H. Y. KIM 한국자동차공학회 2006 International journal of automotive technology Vol.7 No.6

It has been almost impossible to predict the fatigue life in the field of rubber materials by numerical methods. One of the reasons is that there are no obvious fracture criteria and excessively various ways of mixing processes. Tearing energy is considered as a fracture criterion which can be applied to rubber compounds regardless of different types of fillers, relative to other fracture factors. Fatigue life of rubber materials can be approximately predicted based on the assumption that the latent defect caused by contaminants or voids in the matrix, imperfectly dispersed compounding ingredients, mold lubricants and surface flaws always exists. Numerical expression for the prediction of fatigue life was derived from the rate of rough cut growth region and the formulated tearing energy equation. Endurance test data for dumbbell specimens were compared with the predicted fatigue life for verification. Also, fatigue life of industrial rubber components was predicted.

Effects of anisotropic properties on bursting behavior of rectangular cup with a V-notch

Jeong-Tai Kim,Sang-Mok Kim,강범수,구태완 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

Effects of mechanical anisotropic properties on bursting failure and its pressure of rectangular deep-drawn cup fabricated by using AA3005-H14 thin sheet are investigated to utilize for electrolyte container of lithium-ion secondary batteries. The V-notch shape with a depth of 0.1 mm and an angle of 20.0˚ is defined on the rectangular cup, which has a thickness of 0.20 mm on the major surface and that of 0.30 mm on the minor surface. With the measured mechanical properties by uni-axial tensile tests and the defined V-notch geometry, a series of numerical prediction models considering isotropic, planar and normal anisotropic characteristics, are built-up and the bursting simulations are performed. Thereafter, the bursting fracture behavior is investigated by adopting ductile fracture criterion proposed by Cockcroft and Latham. The results predicted for the planar and the normal anisotropic models show that the bursting fracture pressure is well matched to 0.400 MPa, and the isotropic and the planar anisotropic models present a bursting fracture height of about 4.95 mm and 4.92 mm, respectively. A series of experimental investigations are undertaken to verify the bursting deformation that had been predicted. The bursting pressure and its height during experimental verifications are shown to be in good agreement with each variation of about 5.88% and roughly 0.20% with respect to the numerical results obtained using the planar anisotropic model.

Analysis of Predictors of Results after Surgical Treatment of Acetabular Fractures

신종기,안성진,고태식,이정섭 대한고관절학회 2015 Hip and Pelvis Vol.27 No.2

Purpose: The aim of this study was to analyze the factors affecting the outcomes after surgical treatment of acetabular fractures. Materials and Methods: Between January 2000 and December 2012, 106 patients with acetabular fractures were treated with open reduction and internal fixation. We performed a retrospective cohort study to analyze the factors which may influence a patient’s prognosis after surgical treatment of an acetabular fracture. The factors examined included age, femoral head injury, fracture type, dislocation, initial displacement, delay to injuryrelated surgery (in days), and quality of reduction. Additionally, we investigated clinical and radiological outcomes, as well as the development of osteoarthritis. Results: Patients included 85 males (80.2%) and 21 females (18.8%) with a mean age of 50.4 (17-78) years. The mean follow-up period was 2.6 (1-10) years. In a univariable regression analysis, quality of reduction, age, and initial displacement were significantly associated with radiological and clinical outcomes. In a multivariable regression analysis, quality of reduction (P<0.001) and initial displacement (P=0.001) were found to be factors predictive of clinical and radiological outcomes. Additionally, the quality of reduction (P=0.005) was found to be predictive of osteoarthritis development. Conclusion: Study results indicated that the quality of reduction was the most important factor influencing the prognosis of patients with acetabular fractures.