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Stress fractures

Norihiko L Okamoto, Shu Fujimoto, Yuki Kambara, Marino Kawamura, Zhenghao M T Chen, Hirotaka Matsunoshita, Katsushi Tanaka, Haruyuki Inui, Easo P George
High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33-43 MPa, ~10 times higher than that of pure nickel...
October 24, 2016: Scientific Reports
Evelise M Souza, Jan De Munck, Pong Pongprueksa, Annelies Van Ende, Bart Van Meerbeek
OBJECTIVES: To determine the interfacial fracture toughness (iFT) and micro-tensile strength (μTBS) of composite cements bonded to dentin. METHODS: Fifty feldspar ceramic blocks (Vita Mark II, Vita Zahnfabrik) were luted onto dentin using two self-adhesive (G-CEM LinkAce, GC; SpeedCEM, Ivoclar Vivadent), two self-etch (Multilink Primer & Multilink Automix, Ivoclar Vivadent; Scotchbond Universal & RelyX Ultimate, 3 M ESPE), and one etch-and-rinse (Excite F DSC & Variolink II, Ivoclar Vivadent) composite cement (n=10)...
October 19, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Jie Gao, John L Williams, Esra Roan
Growth plate chondrocytes are responsible for bone growth through proliferation and differentiation. However, the way they experience physiological loads and regulate bone formation, especially during the later developmental phase in the mature growth plate, is still under active investigation. In this study, a previously developed multiscale finite element model of the growth plate is utilized to study the stress and strain distributions within the cartilage at the cellular level when rapidly compressed to 20 %...
October 21, 2016: Biomechanics and Modeling in Mechanobiology
Li Li, Yang Lu, Min Li, Xunwei Liu, Peng Jin, Lijun Wang, Gang Sun
STUDY DESIGN: A retrospective study. SUMMARY OF BACKGROUND DATA: Percutaneous vertebroplasty (PV) changes mechanical stress of vertebral column and can cause recurrent pain at the treated level. However, there were a few reports on the therapeutic effects of the repeat PV for patients with recurrent pain at the treated level. OBJECTIVE: To evaluate the therapeutic effects of repeat PV at previously treated vertebral level for patients with osteoporotic vertebral compression fractures (OVCFs) having recurrent pain after initial PV...
November 2016: Clinical Spine Surgery
Weihua Xie, Songhe Meng, Hua Jin, Chong Du, Libin Wang, Tao Peng, Fabrizio Scarpa, Chenghai Xu
This paper presents a simple methodology to perform a high temperature coupled thermo-mechanical test using ultra-high temperature ceramic material specimens (UHTCs), which are equipped with chemical composition gratings sensors (CCGs). The methodology also considers the presence of coupled loading within the response provided by the CCG sensors. The theoretical strain of the UHTCs specimens calculated with this technique shows a maximum relative error of 2.15% between the analytical and experimental data. To further verify the validity of the results from the tests, a Finite Element (FE) model has been developed to simulate the temperature, stress and strain fields within the UHTC structure equipped with the CCG...
October 13, 2016: Sensors
Brian R Waterman, Baris Gun, Julia O Bader, Justin D Orr, Philip J Belmont
PURPOSE: To comprehensively quantify established risk factors for the development of lower extremity stress fractures within a contemporary U.S. military cohort. METHODS: Using the Defense Medical Epidemiological Database, all U.S. service members diagnosed with tibia/fibula, metatarsal, other bone, femoral neck, and femoral shaft stress fractures were identified based on International Classification of Diseases, 9th Revision, Clinical Modification code from 2009 to 2012...
October 2016: Military Medicine
Leo Fradet, Xiaoyu Wang, Lawrence G Lenke, Carl-Eric Aubin
BACKGROUND: Proximal junctional failure is a severe proximal junctional complication following adult spinal instrumentation and involving acute proximal junctional kyphotic deformity, mechanical failure at the upper instrumented vertebra or just above, and/or proximal junctional osseoligamentous disruption. Clinical studies have identified potential risk factors, but knowledge on their biomechanics is still lacking for addressing the proximal junctional failure issues. The objective of this study was to develop comprehensive computational modeling and simulation techniques to investigate proximal junctional failure...
October 11, 2016: Clinical Biomechanics
Wenhao Song, Dongsheng Zhou, Yu He
BACKGROUND: The aim of this study was to compare the biomechanical characteristics between bilateral and unilateral lumbo-iliac fixation in unilateral comminuted sacral fractures (USF) by finite element analysis. METHODS: A 3-dimensional finite element model of unilateral sacral fractures was simulated. Three kinds of implants were instrumented into the model, including the unilateral lumbopelvic fixation (ULF), bilateral lumbopelvic fixation (BLF), and unilateral iliac fixation with bilateral lumbar pedicle screws (UBF)...
October 2016: Medicine (Baltimore)
Fumihiko Watanabe, Kazuhiko Hiroyasu, Kazuhiko Ueda
BACKGROUND: Fractured connections between implants and implant abutments or abutment screws are frequently encountered in a clinical setting. The purpose of this study was to investigate fracture strength using a torsion test at the interface between the implant and the abutment. METHODS: Thirty screw-type implant with diameters of 3.3, 3.8, 4.3, 5.0, and 6.0 mm were submitted to a torsion test. Implants of each size were connected to abutments with abutment screws tightened to 20 N · cm...
December 2015: Int J Implant Dent
Stefano C Meliga, Jacob W Coffey, Michael L Crichton, Christopher Flaim, Martin Veidt, Mark A F Kendall
: In-depth understanding of skin elastic and rupture behavior is fundamental to enable next-generation biomedical devices to directly access areas rich in cells and biomolecules. However, the paucity of skin mechanical characterization and lack of established fracture models limits their rational design. We present an experimental and numerical study of skin mechanics during dynamic interaction with individual and arrays of micro-penetrators. Initially, micro-indentation of individual skin strata revealed hyperelastic moduli were dramatically rate-dependent, enabling extrapolation of stiffness properties at high velocity regimes (>1ms(-1))...
October 13, 2016: Acta Biomaterialia
Sajjad Jafari, R K Singh Raman, Chris H J Davies, Joelle Hofstetter, Peter J Uggowitzer, Jörg F Löffler
Magnesium (Mg) alloys have attracted great attention as potential materials for biodegradable implants. It is essential that an implant material possesses adequate resistance to cracking/fracture under the simultaneous actions of corrosion and mechanical stresses, i.e., stress corrosion cracking (SCC) and/or corrosion fatigue (CF). This study investigates the deformation behaviour of a newly developed high-strength low-alloy Mg alloy, MgZn1Ca0.3 (ZX10), processed at two different extrusion temperatures of 325 and 400°C (named E325 and E400, respectively), under slow strain tensile and cyclic tension-compression loadings in air and modified simulated body fluid (m-SBF)...
September 28, 2016: Journal of the Mechanical Behavior of Biomedical Materials
Yang Lu, Jong Ho Lee, Xiang Yang, I-Wei Chen
Resistance random access memory (RRAM) is a rapidly developing emergent nanotechnology. For practical applications and basic understanding, it is important to ascertain whether RRAM undergoes uniform or filamentary switching, but on this point previous area-scaling studies have often shown ambiguous and conflicting findings. Here we demonstrate a simple test-physically breaking the device into two and studying their characteristics individually-can make a definitive determination. Our experiment on two prototypical RRAMs found that one (the nanometallic memory) switches and conducts uniformly while the other (the filamentary memory) does not...
October 13, 2016: Nanoscale
Isaac J Larsen, Michael P Lamb
The surfaces of Earth and Mars contain large bedrock canyons that were carved by catastrophic outburst floods. Reconstructing the magnitude of these canyon-forming floods is essential for understanding the ways in which floods modify planetary surfaces, the hydrology of early Mars and abrupt changes in climate. Flood discharges are often estimated by assuming that the floods filled the canyons to their brims with water; however, an alternative hypothesis is that canyon morphology adjusts during incision such that bed shear stresses exceed the threshold for erosion by a small amount...
October 12, 2016: Nature
Carolina A Moreira, John P Bilezikian
CONTEXT: Stress fractures are repetitive use injuries in which recurrent strains lead to material fatigue and microarchitectural discontinuities. Stress fractures account for up to 20% of athletic injuries, more commonly sustained by women and in those who engage in track-and-field events. The pathogenesis of stress fractures is multifactorial. Although most stress fracture are reported among women who may experience menstrual disturbances, low body mass index, low energy intake and sometimes low bone mass, these individuals do not regularly seek endocrinological attention...
October 12, 2016: Journal of Clinical Endocrinology and Metabolism
Kristin L Popp, William McDermott, Julie M Hughes, Stephanie A Baxter, Steven D Stovitz, Moira A Petit
PURPOSE: To determine differences in bone geometry, estimates of bone strength, muscle size and bone strength relative to load, in women runners with and without a history of stress fracture. METHODS: We recruited 32 competitive distance runners aged 18-35, with (SFX, n=16) or without (NSFX, n=16) a history of stress fracture for this case-control study. Peripheral quantitative computed tomography (pQCT) was used to assess volumetric bone mineral density (vBMD, mg/mm(3)), total (ToA) and cortical (CtA) bone areas (mm(2)), and estimated compressive bone strength (bone strength index; BSI, mg/mm(4)) at the distal tibia...
October 10, 2016: Bone
Tarek M Hegazi, Jeffrey A Belair, Eoghan J McCarthy, Johannes B Roedl, William B Morrison
Injuries of the hip and surrounding structures represent a complex and commonly encountered scenario in athletes, with improper diagnosis serving as a cause of delayed return to play or progression to a more serious injury. As such, radiologists play an essential role in guiding management of athletic injuries. Familiarity with hip anatomy and the advantages and limitations of various imaging modalities is of paramount importance for accurate and timely diagnosis. Magnetic resonance (MR) imaging is often the modality of choice for evaluating many of the injuries discussed, although preliminary evaluation with conventional radiography and use of other imaging modalities such as ultrasonography (US), computed tomography, and bone scintigraphy may be supplementary or preferred in certain situations...
October 2016: Radiographics: a Review Publication of the Radiological Society of North America, Inc
Hao Sun, Sankha Mukherjee, Chandra Veer Singh
Two new graphene allotropes, penta-graphene and phagraphene, have been proposed recently with unique electronic properties, e.g. quasi-direct band gap, direction-dependent Dirac cones and tunable Fermi velocities. However, their mechanical properties have not been fully studied yet. In this work, we have performed extensive density functional theory calculations to evaluate the mechanical properties of these two materials and compared with graphene, graphane, and pentaheptite. Our simulations show that the ultimate tensile strength (UTS) and the strain corresponding to UTS in both penta-graphene and phagraphene are smaller than that of graphene...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
Yong Seok Hwang, Valery I Levitas
The external surface of metallic particles is usually covered by a thin and strong oxide shell, which significantly affects superheating and melting of particles. The effects of geometric parameters and heating rate on characteristic melting and superheating temperatures and melting behavior of aluminum nanoparticles covered by an oxide shell were studied numerically. For this purpose, the multiphysics model that includes the phase field model for surface melting, a dynamic equation of motion, a mechanical model for stress and strain simulations, interface and surface stresses, and the thermal conduction model including thermoelastic and thermo-phase transformation coupling as well as transformation dissipation rate was formulated...
October 10, 2016: Physical Chemistry Chemical Physics: PCCP
Ashraf Idkaidek, Vineet Agarwal, Iwona Jasiuk
Reference Point Indentation (RPI) is a novel technique aimed to assess bone quality. Measurements are recorded by the BioDent instrument that applies multiple indents to the same location of cortical bone. Ten RPI parameters are obtained from the resulting force-displacement curves. Using the commercial finite element analysis software Abaqus, we assess the significance of the RPI parameters. We create an axisymmetric model and employ an isotropic viscoelastic-plastic constitutive relation with damage to simulate indentations on a human cortical bone...
September 14, 2016: Journal of the Mechanical Behavior of Biomedical Materials
Mehmet Nuri Erdem, Sinan Karaca, Seckin Sarı, Feridun Yumrukcal, Ruhat Tanli, Mehmet Aydogan
BACKGROUND CONTEXT: Application of pedicle screws with cement in order to strengthen the fixation of the osteoporotic spine has increasingly gained popularity. However, the technique has also led to an increase in cement-related complications. PURPOSE: The aim of this study was to compare the clinical and radiological results of the patients with degenerative spinal pathologies who were treated with pedicle screws and cement injections on all segments versus those who were treated with cement injections only on the strategic vertebrae selected...
October 5, 2016: Spine Journal: Official Journal of the North American Spine Society
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