scholarly journals Biomechanical analysis of the cancellous screws implantation schemes in surgical treatment of flexible flatfoot in children

2016 ◽  
Author(s):  
Gennadiy Koshman ◽  
Vladimir Barsukov ◽  
Viktor Anosov ◽  
Jolanta Pauk
Keyword(s):  
Operational Reliability ◽  
Biomechanical Analysis ◽  
Supporting Surface ◽  
Core Diameter ◽  
Strained Condition ◽  
Heat Treated ◽  
Calculated Stress ◽  
Flexible Flatfoot ◽  
Wide Range ◽  
Cancellous Screws

Carry out comparative biomechanical analysis of influence of the implantation scheme and characteristic sizes of cancellous screws on parameters of its strained condition, and elaborate guidelines for optimization of implantation parameters and decision for a material metalware choice. Performed mathematical modelling and comparative numerical analysis of the parameters of strained condition, slant and cantilevered schemes of implantation of cancellous screws, applied to a wide range of support loads variations acting on a screw. Made analysis of influence of size parameters (length of the overhanging part, angle with normal at supporting surface, core diameter) on the magnitude of the calculated stress that appear in compressed and extended zones of slant implanted screw. Carried out investigations reveal that short screws, installed on the hard circuit, from the standpoint of operational reliability according to the criteria of strength under static loading (occasional overload) and multicyclic loading have the highest capacity for work. Least favourable in application are slant and cantilevered implanted screws. With increasing length of cantilevered part and angle between axis of a screw and line of loading force calculated values of stress also increases. Screws of heat-treated stainless steel are preferred from the standpoint of saving bearing capacity with unit congestion due to increased plasticity in 4–5 times (residual strain at failure) compared with titanium alloys.

scholarly journals Two-Segment Foot Model for the Biomechanical Analysis of Squat

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
E. Panero ◽  
L. Gastaldi ◽  
W. Rapp
Keyword(s):  
Body Weight ◽  
Inverse Dynamics ◽  
Statistical Significance ◽  
Lower Limbs ◽  
Biomechanical Analysis ◽  
Wide Range ◽  
Foot Model ◽  
Partial Body ◽  
The One ◽  
Midtarsal Joint

Squat exercise is acquiring interest in many fields, due to its benefits in improving health and its biomechanical similarities to a wide range of sport motions and the recruitment of many body segments in a single maneuver. Several researches had examined considerable biomechanical aspects of lower limbs during squat, but not without limitations. The main goal of this study focuses on the analysis of the foot contribution during a partial body weight squat, using a two-segment foot model that considers separately the forefoot and the hindfoot. The forefoot and hindfoot are articulated by the midtarsal joint. Five subjects performed a series of three trials, and results were averaged. Joint kinematics and dynamics were obtained using motion capture system, two force plates closed together, and inverse dynamics techniques. The midtarsal joint reached a dorsiflexion peak of 4°. Different strategies between subjects revealed 4° supination and 2.5° pronation of the forefoot. Vertical GRF showed 20% of body weight concentrated on the forefoot and 30% on the hindfoot. The percentages varied during motion, with a peak of 40% on the hindfoot and correspondently 10% on the forefoot, while the traditional model depicted the unique constant 50% value. Ankle peak of plantarflexion moment, power absorption, and power generation was consistent with values estimated by the one-segment model, without statistical significance.

scholarly journals Pressure losses and oscillations in a compact valve of a steam turbine

2021 ◽  
Vol 345 ◽  
pp. 00027
Author(s):  
Václav Sláma ◽  
David Šimurda ◽  
Lukáš Mrózek ◽  
Ladislav Tajč ◽  
Jindřich Hála ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pressure Oscillation ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Valve Seat ◽  
Pressure Losses ◽  
Oscillation Analysis ◽  
Seat Angle ◽  
Wide Range

Characteristics of a new compact valve design for steam turbines are analysed by measuring pressure losses and oscillations on the valve model. It is the model of an intercept valve of the intermediate-pressure turbine part. This valve is relatively smaller hence cheaper than usual control and intercept valves. Besides, four different valve seat angles were tested in order to investigate the valve seat angle influence. In order to further clarify measured phenomena, the wide range of numerical simulations were also carried out. Measurements were performed in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences in an air test rig installed in a modular aerodynamic tunnel. Numerical simulations were performed in the Doosan Skoda Power Company using a package of ANSYS software tools. Measurement results are compared with numerical and generalized in the form of valve characteristics and pressure oscillation maps. As a result of the pressure loss analysis, pressure losses in similar valve assemblies can be predicted with required accuracy for each new turbine where modern compact valves are used. As a result of the pressure oscillation analysis, operating conditions at which dangerous flow instabilities can occur were identified. Thanks to this, the areas of safe and dangerous operating conditions can be predicted so that the operational reliability of the valve can be guaranteed.

Experimental Investigation of Various Chip Parameters during Machining of the Ti25Nb3Mo3Zr2Sn Beta Titanium Alloy

2012 ◽  
Vol 622-623 ◽  
pp. 366-369 ◽  
Author(s):  
Rizwan Abdul Rahman Rashid ◽  
Shou Jin Sun ◽  
Gui Wang ◽  
Matthew Simon Dargusch
Keyword(s):  
Titanium Alloy ◽  
Chip Thickness ◽  
Shear Angle ◽  
Beta Titanium Alloy ◽  
Solution Treated ◽  
Beta Titanium ◽  
Heat Treated ◽  
Wide Range ◽  
Thickness Shear ◽  
Cutting Speeds

Machining of Ti25Nb3Mo3Zr2Sn beta titanium alloy is carried out under two different heat treatments, solution treated, and solution treated and aged conditions. The chips formed after machining were cold mounted, polished and etched to reveal their microstructures. Different chip parameters such as average chip thickness, shear angle, undeformed chip length, and distance between serrations were measured and reported for both the heat treated samples for a wide range of cutting speeds, ranging from 5 m/min to 175 m/min. The results obtained were explained in terms of the heat treatment (hardness) of the samples and the cutting speeds.

Risk-Based Assessment of Unplanned Outage Events and Costs for Combined-Cycle-Plants

2012 ◽  
Author(s):  
Dale Grace ◽  
Thomas Christiansen
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Cash Flow ◽  
Gas Turbines ◽  
Operational Reliability ◽  
Combined Cycle ◽  
Maintenance Costs ◽  
Wide Range ◽  
Turbine Equipment ◽  
The Impact

Unexpected outages and maintenance costs reduce plant availability and can consume significant resources to restore the unit to service. Although companies may have the means to estimate cash flow requirements for scheduled maintenance and on-going operations, estimates for unplanned maintenance and its impact on revenue are more difficult to quantify, and a large fleet is needed for accurate assessment of its variability. This paper describes a study that surveyed 388 combined-cycle plants based on 164 D/E-class and 224 F-class gas turbines, for the time period of 1995 to 2009. Strategic Power Systems, Inc. (SPS®), manager of the Operational Reliability Analysis Program (ORAP®), identified the causes and durations of forced outages and unscheduled maintenance and established overall reliability and availability profiles for each class of plant in 3 five-year time periods. This study of over 3,000 unit-years of data from 50 Hz and 60 Hz combined-cycle plants provides insight into the types of events having the largest impact on unplanned outage time and cost, as well as the risks of lost revenue and unplanned maintenance costs which affect plant profitability. Outage events were assigned to one of three subsystems: the gas turbine equipment, heat recovery steam generator (HRSG) equipment, or steam turbine equipment, according to the Electric Power Research Institute’s Equipment Breakdown Structure (EBS). Costs to restore the unit to service for each main outage cause were estimated, as were net revenues lost due to unplanned outages. A statistical approach to estimated costs and lost revenues provides a risk-based means to quantify the impact of unplanned events on plant cash flow as a function of class of gas turbine, plant subsystem, and historical timeframe. This statistical estimate of the costs of unplanned outage events provides the risk-based assessment needed to define the range of probable costs of unplanned events. Results presented in this paper demonstrate that non-fuel operation and maintenance costs are increased by roughly 8% in a typical combined-cycle power plant due to unplanned maintenance events, but that a wide range of costs can occur in any single year.

A Biomechanical Comparative Analysis of Two Techniques for Tibiotalar Arthrodesis

1994 ◽  
Vol 15 (6) ◽  
pp. 301-305 ◽  
Author(s):  
Robert L. Friedman ◽  
Richard R. Glisson ◽  
James A. Nunley
Keyword(s):  
Laboratory Testing ◽  
Biomechanical Analysis ◽  
Torsional Motion ◽  
Bending Tests ◽  
Torsional Testing ◽  
Fusion Site ◽  
Fresh Frozen ◽  
Tibiotalar Arthrodesis ◽  
Cancellous Screws ◽  
Cantilever Bending

Two commonly used techniques for tibiotalar fusion were quantitatively compared using instrumented testing of the strength of the construct. The tibiae and tali from 10 pairs of fresh-frozen cadaveric limbs were used. One joint of each pair was fused using two 6.5-mm crossed cancellous screws from proximal to distal while the contralateral joint was fused using two 6.5-mm parallel cancellous screws from distal to proximal. Each specimen was subjected to cantilever bending and torsional testing by servohydraulic actuators. The bending tests included plantarflexion, dorsiflexion, inversion, and eversion, and measured the load during deflection applied 10 cm distal to the fusion site. The rigidity was expressed as newtons per millimeter of deflection. The torsional tests measured construct stiffness in external and internal rotation, and were expressed as newton-meters per degree of rotation. For the bending tests, the crossed screw construct was more rigid in eversion (23.1 N/mm, P = .0004) and dorsiflexion (16.9 N/mm, P = .02), while the parallel screw construct was more rigid in inversion (22.8 N/mm, P = .02) and plantarflexion (22.3 N/mm, P = .0007). In torsional testing, the crossed screw construct was at least 1.5 times stiffer than the parallel screw construct in resisting internal (1.7 N-m/deg versus 0.9 N-m/deg, P = .0001) and external (1.4 N-m/deg versus 0.9 N-m/deg, P = .02) rotation. In laboratory testing, the crossed screw technique is more rigid than the parallel screws, especially in resisting torsional stresses. Assuming that a stronger construct is desirable, and given that short leg casts commonly used after such fusions do not completely restrict torsional motion, this biomechanical analysis suggests that the crossed screw technique improves the likelihood of a successful arthrodesis.

scholarly journals Modeling the Recovery of Heat-Treated Bacillus licheniformis Ad978 and Bacillus weihenstephanensis KBAB4 Spores at Suboptimal Temperature and pH Using Growth Limits

2014 ◽  
Vol 81 (2) ◽  
pp. 562-568 ◽  
Author(s):  
C. Trunet ◽  
N. Mtimet ◽  
A.-G. Mathot ◽  
F. Postollec ◽  
I. Leguerinel ◽  
...  
Keyword(s):  
Heat Resistance ◽  
Bacillus Licheniformis ◽  
Content Type ◽  
Bacillus Weihenstephanensis ◽  
Heat Treated ◽  
Wide Range ◽  
Growth Limits ◽  
Cardinal Temperature ◽  
Resistance Data ◽  
Recovery Temperature

ABSTRACTThe apparent heat resistance of spores ofBacillus weihenstephanensisandBacillus licheniformiswas measured and expressed as the time to first decimal reduction (δ value) at a given recovery temperature and pH. Spores ofB. weihenstephanensiswere produced at 30°C and 12°C, and spores ofB. licheniformiswere produced at 45°C and 20°C.B. weihenstephanensisspores were then heat treated at 85°C, 90°C, and 95°C, andB. licheniformisspores were heat treated at 95°C, 100°C, and 105°C. Heat-treated spores were grown on nutrient agar at a range of temperatures (4°C to 40°C forB. weihenstephanensisand 15°C to 60°C forB. licheniformis) or a range of pHs (between pH 4.5 and pH 9.5 for both strains). The recovery temperature had a slight effect on the apparent heat resistance, except very near recovery boundaries. In contrast, a decrease in the recovery pH had a progressive impact on apparent heat resistance. A model describing the heat resistance and the ability to recover according to the sporulation temperature, temperature of treatment, and recovery temperature and pH was proposed. This model derived from secondary mathematical models for growth prediction. Previously published cardinal temperature and pH values were used as input parameters. The fitting of the model with apparent heat resistance data obtained for a wide range of spore treatment and recovery conditions was highly satisfactory.

Mechanical Behavior of Alloy AA6111 Processed by Severe Plastic Deformation: Modeling and Experiment

2007 ◽  
Vol 129 (3) ◽  
pp. 380-389 ◽  
Author(s):  
Yuri Estrin ◽  
KiHo Rhee ◽  
Rimma Lapovok ◽  
Peter F. Thomson
Keyword(s):  
Mechanical Response ◽  
Uniform Elongation ◽  
Internal Variable ◽  
Uniaxial Tensile ◽  
Variable Model ◽  
Angular Pressing ◽  
Heat Treated ◽  
Wide Range ◽  
Before And After ◽  
Constitutive Parameters

An established dislocation density related, one-internal variable model was used, with some modifications, as a basis for modeling the mechanical response of aluminum alloy AA6111. In addition to conventional rolling, equal channel angular pressing (ECAP) was used to produce a wide range of grain sizes, down to the submicrometer scale. The samples were heat treated before and after both processes to optimize tensile ductility. Implementation of the model to uniaxial tensile response of the conventionally rolled and the ECAP processed materials confirmed its good predictive capability. The model was further used to formulate simple relations between true uniform strain and the constitutive parameters that allow reliable prediction of the uniform elongation.

Hydroxyapatite Scaffolds Produced by Hydrothermal Deposition of Monetite on Polyurethane Sponges Substrates

2011 ◽  
Vol 493-494 ◽  
pp. 820-825 ◽  
Author(s):  
Fernanda Danielle Mishima ◽  
Luis Henrique Leme Louro ◽  
Felipe Nobre Moura ◽  
Luciano Andrade Gobbo ◽  
Marcelo Henrique Prado da Silva
Keyword(s):  
Electron Microscopy ◽  
Aqueous Solution ◽  
Tricalcium Phosphate ◽  
Porous Scaffolds ◽  
New Bone Formation ◽  
Total Conversion ◽  
X Ray ◽  
Heat Treated ◽  
Wide Range ◽  
Scanning Electron

Hydroxyapatite scaffolds have been being produced by a wide range of processes. The optimun material to be used as bone graft has to be partially resorbable, with resorption rates similar to new bone formation ones. The samples must have porosity compatible with tissue ingrowth. Hydroxyapatite and tricalcium phosphate ceramics are good choices for designing such materials. In the present study, polymeric sponges were coated with hydroxyapatite and sintered. The method consists of coating polyurethane sponges substrates in an aqueous solution rich in phosphate (PO4)3-and calcium (Ca)2+ions. The solution is composed by 0.5M Ca(OH)2, 0.3M H3PO4and 1M CH3CHCO2HOH (lactic acid) at pH of 3.7. The sponges were immersed in a beaker with the solution and heated up to 80°C to precipitate monetite on the sponge. Continuous and adherent coatings were formed on the surface of sponges interconections. These coatings were characterised by X-ray diffractometry and the only identified phase was monetite. The substrates were converted to hydroxyapatite in an alkali solution.The total conversion from monetite to hydroxyapatite was confirmed by XRD analyses. The struts were heat treated in order to eliminate the organic sponge and sinter the scaffolds. After sintering, hydroxyapatite and tricalcium phosphate were identified on the struts. Optical microscopy revealed the morphology of the struts, while scanning electron microscopy (SEM) showed the precipitates morphology. The method showed to be efficient in the production of porous scaffolds.

scholarly journals The Primary Metatarsalgia: Pathogenesis, Biomechanics and Surgical Treatment

2017 ◽  
Vol 72 (1) ◽  
pp. 53-58
Author(s):  
D. S. Bobrov ◽  
L. J. Slinjakov ◽  
N. V. Rigin
Keyword(s):  
Surgical Treatment ◽  
Treatment Options ◽  
Supporting Surface ◽  
Excessive Pressure ◽  
Functional Changes ◽  
Treatment Techniques ◽  
Tendon Lengthening ◽  
Metatarsal Bones ◽  
Wide Range ◽  
The One

This paper presents a comprehensive review on the current concept of the diagnosis and treatment of central metatarsalgia on the basis of medical literature analyses. Metatarsalgia is the term for pain in the forefoot. This is a set of symptoms corresponding to a wide range of diseases. Central metatarsalgia is a kind of metatarsalgia which arises from structural-functional changes that lead to excessive pressure in the area of metatarsal heads. The data analysis demonstrated that presently various types of osteotomies of metatarsal bones are the main surgical treatment options with the chance of complication ranging from 6 to 50%. Weil-osteotomy is known to be the most popular type of osteotomy for treatment of central metatarsalgia. The most common complication of Weil-osteotomy is floating toe, the one that doesn’t contact with the supporting surface. In case Weil-osteotomy and intraphalangeal arthrodesis with trans acticular fixation are both performed, the complication of floating toe increases up to 50%. When Weil osteotomy, plantar plate repair, extensor digitorum longum tendon lengthening and triple Weil-osteotomy are performed simultaneously, the complication rate is 15% approximately which is much lower. Using combined osteotomy techniques as well as taking into account structural-functional pathologic changes of the forefoot and ligaments repair of metatarsalphalangeal joint will ensure the most successful development of surgical treatment techniques for central metatarsalgia.

scholarly journals Numerical and Experimental Investigation of Formability in Incremental Sheet Forming of Particle Reinforced Metal Matrix Composite Sheets

2021 ◽  
Author(s):  
Shakir Gatea ◽  
Thana Abdel Salam Tawfiq ◽  
Hengan Ou
Keyword(s):  
Metal Matrix ◽  
Room Temperature ◽  
Single Point ◽  
Weight Ratio ◽  
High Strength ◽  
Operating Conditions ◽  
Particle Composite ◽  
Heat Treated ◽  
Wide Range ◽  
Sic Particle

Abstract Metal matrix composites (MMCs) have a high strength-to-weight ratio, high stiffness, and good damage resistance under a wide range of operating conditions, making them a viable alternative to traditional materials in a variety of technical applications. Because of their high strength, composite materials are hard to deform to a significant depth at room temperature. As a result, additional treatments are required to enhance the composite's room ductility prior to deformation. In this investigation, as-received 6092Al/SiCp composite sheets (T6-condition) are heat treated to O-condition annealing to enhance its ductility in order to assess the influence of single point incremental forming (SPIF) parameters on the formability and fracture behavior of the Al/SiC particle composite sheets at room temperature. Then the annealed sheets are heat treated to T6-condition to enhance the strength and achieve properties equivalent to as-received sheets properties. The results demonstrate that the Al/SiC particle composite sheets with T6 treatment could not be deformed to the specified depth at room temperature due to low room ductility and that further treatment, such as O-condition annealing, is required to enhance the room ductility. When annealed Al/SiCp composite sheets are heat treated to T6, the sheets exhibit properties comparable to the as-received sheets. Al/SiC particle composite sheets with low SPIF parameters may have greater formability and fracture depth with low strain hardening curve.

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