Journal articles on the topic 'Tow Angle Placement'
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1
Bourgeois, Mark E., and Donald W. Radford. "Consolidation and Tow Spreading of Digitally Manufactured Continuous Fiber Reinforced Composites from Thermoplastic Commingled Tow Using a Five-Axis Extrusion System." Journal of Composites Science 5, no. 3 (March 5, 2021): 73. http://dx.doi.org/10.3390/jcs5030073.
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During the development of digitally manufactured, commingled tow continuous fiber reinforced composites, consolidation force was controlled using a controlled spring force that yielded a repeatable tow width. However, the use of the extruder face to consolidate the material requires that the extruder remain perpendicular to the placement surface throughout the process. When considering more complex tool contours including sloped surfaces, more than three axes of motion are necessary to maintain the perpendicularity of the extruder tip to the surface. In this effort, a five-axis system is developed and used to demonstrate the ability to consolidate over complex contours. In addition, the nozzle face temperatures required for good consolidation and wetout result in poor tow path fidelity when complex paths are introduced. The implementation of an automated, computer-controlled localized cooling system enables both good wetout and consolidation while also enabling more accurate changes in tow path due to improvements in local tow tack. With the development of the five-axis system it is also shown that the tow width can be adjusted by rotating the existing placement nozzle to angles not equal to 90°. Thus, through a combination of controlled localized cooling and real-time control of the nozzle angle, a possible approach to control of tow width, independent of the tow placement angle and radius of curvature during tow steering, is described.
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Zhu, Yingdan, Shijie Qi, Hongli Jia, Pengcheng Shi, Youqiang Yao, Junfeng Hu, Philippe Boisse, and Haibing Xu. "Assessing tensile behavior of open-hole variable angle tow composites using a general gradient property simulation methodology." Journal of Reinforced Plastics and Composites 39, no. 19-20 (June 26, 2020): 742–57. http://dx.doi.org/10.1177/0731684420929094.
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Variable Angle Tow placement is a way to steer individual curvilinear fibers. This work presents the assessment of tensile behavior of open-hole composite laminates with Variable Angle Tow reinforcement. A new multi-scale finite element method, consisting of a microscale unit cell model and a macroscale gradient property model, is developed to simulate Variable Angle Tow structures with various fiber trajectories. The tensile strength and the failure process of open-hole reinforced laminates with Variable Angle Tow reinforcement under tensile loading are predicted and analyzed. Experiments are also conducted to investigate reinforcing efficiency and failure modes of the open-hole laminates. The comparison of predicted and experimental results for the tensile strength and failure modes of T700/Epoxy laminates demonstrates clearly that the mechanical behavior of Variable Angle Tow structure can be simulated very well by the proposed multi-scale model. Moreover, it is found that the tensile strength of Variable Angle Tow laminates is closely related to the eccentricity and it reaches the maximum value only when the trajectories of curvilinear fibers keeps consistent with maximum principal stress trajectories of the open-hole plate.
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Haavajõe, Anti, Madis Mikola, and Meelis Pohlak. "Design and Manufacturing of Variable Angle Tow Laminate." Key Engineering Materials 674 (January 2016): 59–64. http://dx.doi.org/10.4028/www.scientific.net/kem.674.59.
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Variable angle tow (VAT) laminates have shown enhanced stiffness/strength performance compared to conventional straight fiber laminates. Employment of VAT allows utilizing variable stiffness design of composite structure, thus it widens the design possibilities. As a result, composite structure with improved mechanical characteristics can be manufactured. The main aims of the current study are to give an overview on methods and algorithms used for analysis and design of VAT laminates, and to develop technology and equipment for manufacturing laminate with improved structural performance. In order to improve the accuracy of the compaction process, a set of experiments were carried out using a simple testing device. For measuring the compaction force, a pneumatic cylinder, pressure regulator and digital manometer were used. The temperature of the consolidation area and the heat distribution were screened with the thermal camera. Infrared heater was used as a heating source. Material used in the experiment was carbon fiber reinforced polyamide.Findings show that in addition to the main parameters – the compaction force and temperature, there are many minor factors, such as the compaction wheel diameter, material and surface roughness of the compaction roller, the material and surface roughness of the mold and the pretension in the laminating tape and also the laminating speed, all influence the quality of the final product.Key words: Advanced Fiber Placement Technology, Automated Fiber Placement, Automated Tape Laying, Fiber Reinforced Composites, Laminates
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Yi, Minghui, Fei Liu, Wuxiang Zhang, and Xilun Ding. "Formation Mechanism and Modeling Method of Wrinkling Defects in Variable Angle Tow Steering Fiber Placement." Aerospace 9, no. 10 (October 19, 2022): 620. http://dx.doi.org/10.3390/aerospace9100620.
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Variable angle tow steering technology is capable of manufacturing complex aviation parts with a trajectory of intricate curvature planned based on stress or profile characteristics, which greatly improves the forming efficiency, design flexibility and mechanical properties of composite structures. In view of the forming defects such as buckling and wrinkles caused by the lateral bending of fiber prepreg tow, a theoretical buckling model based on the Rayleigh Ritz method, the principle of minimum potential energy and the viscoelastic foundation is established, in which the adhesion coefficient is characterized by the degree of intimate contact to introduce process parameters. On the basis of the contact mechanics analysis, the distribution of the compaction pressure and bending stress is studied to improve the theoretical model, and the critical buckling load and the minimum radius of the tow under the normal and tangential contact conditions are determined precisely. Finally, the finite element models of compaction and variable angle steering placement are proposed, and the theoretical model and simulation model are verified by corresponding trials. It is demonstrated that defects can be effectively suppressed through optimizing process parameters.
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Carvalho, João, Abdolrasoul Sohouli, and Afzal Suleman. "Fundamental Frequency Optimization of Variable Angle Tow Laminates with Embedded Gap Defects." Journal of Composites Science 6, no. 2 (February 20, 2022): 64. http://dx.doi.org/10.3390/jcs6020064.
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Variable stiffness composite laminates can improve the structural performance of composite structures by expanding the design space. This work explores the application of variable stiffness laminated composite structures to maximize the fundamental frequency by optimizing the tow angle. To this end, an optimization framework is developed to design the fiber angle for each layer based on the maximization of the fundamental frequency. It is assumed that the design process includes the manufacturing constraints encountered in the automated fiber placement process and a linear fiber angle variation. The current study improves existing results by considering embedded gap defects within the optimization framework. The plates are assumed symmetric, with clamped and simply supported boundary conditions. The optimal results and a comparison between the non-steered and steered plates with and without gaps are presented. Results show that, although gaps deteriorate the structural performance, fiber steering can still lead to an increase in the fundamental frequency depending on the plate’s geometry and boundary conditions.
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Bittrich, Lars, Axel Spickenheuer, José Humberto S. Almeida, Sascha Müller, Lothar Kroll, and Gert Heinrich. "Optimizing Variable-Axial Fiber-Reinforced Composite Laminates: The Direct Fiber Path Optimization Concept." Mathematical Problems in Engineering 2019 (February 19, 2019): 1–11. http://dx.doi.org/10.1155/2019/8260563.
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The concept of aligning reinforcing fibers in arbitrary directions offers a new perception of exploiting the anisotropic characteristic of the carbon fiber-reinforced polymer (CFRP) composites. Complementary to the design concept of multiaxial composites, a laminate reinforced with curvilinear fibers is called variable-axial (also known as variable stiffness and variable angle tow). The Tailored Fiber Placement (TFP) technology is well capable of manufacturing textile preforming with a variable-axial fiber design by using adapted embroidery machines. This work introduces a novel concept for simulation and optimization of curvilinear fiber-reinforced composites, where the novelty relies on the local optimization of both fiber angle and intrinsic thickness build-up concomitantly. This framework is called Direct Fiber Path Optimization (DFPO). Besides the description of DFPO, its capabilities are exemplified by optimizing a CFRP open-hole tensile specimen. Key results show a clear improvement compared to the current often used approach of applying principal stress trajectories for a variable-axial reinforcement pattern.
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Zhao, Wei, and Rakesh K. Kapania. "Buckling Analysis and Optimization of Stiffened Variable Angle Tow Laminates with a Cutout Considering Manufacturing Constraints." Journal of Composites Science 6, no. 3 (March 4, 2022): 80. http://dx.doi.org/10.3390/jcs6030080.
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Variable angle tow laminates (VAT) and stiffeners are known to redistribute the in-plane load distribution and tailor the buckling mode shapes, respectively, for improving structural performance. To leverage the benefits of using VAT laminates in the practical applications, in the present paper, we discuss buckling load maximization conducted for a stiffened VAT laminated plate with a central cutout considering VAT laminate manufacturing constraints. Three representative boundary conditions as seen in the aerospace structures are considered: in-plane axial displacement, in-plane pure shear, and in-plane pure bending displacements. Two common manufacturing constraints, the one on the automatic fiber placement (AFP) manufacturing head turning radius and the other on the tow gap/overlap, while fabricating VAT laminates are considered in the laminate design. These two manufacturing constraints are modeled by controlling the fiber path radius of curvature and tape parallelism in optimizing the fiber path orientations for the VAT laminates. Stiffener layout and fiber path angle for the VAT laminated plates are both considered in the buckling load maximization study. To avoid using a fine mesh in modeling the stiffened VAT laminates with a cutout when employing the finite element analysis during the optimization, the VAT laminated plate and the stiffeners are modeled independently. The displacement compatibility is enforced at the stiffener–plate interfaces to ensure that the stiffeners move with the plate. Particle swarm optimization is used as the optimization algorithm for the buckling load maximization study. Optimization results show that, without considering AFP manufacturing constraints, the VAT laminates can increase the buckling loads by 21.2% and 12.4%, respectively, comparing to the commonly used quasi-isotropic laminates and traditionally straight fiber path laminates for the structure under the in-plane axial displacement case, 19.7% and 12.5%, respectively, for the in-plane shear displacement case, and 62.1% and 26.6%, respectively, for the in-plane bending displacement case. The AFP manufacturing constraints are found to have different impacts on the buckling responses for the VAT laminates, which cause the maximum buckling load to be 9.3–10.1%, 3.0–3.2%, and 23.2–29.8% less than those obtained without considering AFP manufacturing constraints, respectively, for the present studied model under in-plane axial, shear, and bending displacements.
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Sánchez-Majano, Alberto Racionero, Rodolfo Azzara, Alfonso Pagani, and Erasmo Carrera. "Accurate Stress Analysis of Variable Angle Tow Shells by High-Order Equivalent-Single-Layer and Layer-Wise Finite Element Models." Materials 14, no. 21 (October 28, 2021): 6486. http://dx.doi.org/10.3390/ma14216486.
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New concepts of lightweight components are conceived nowadays thanks to the advances in the manufacture of composite structures. For instance, mature technologies such as Automatic Fibre Placement (AFP) are employed in the fabrication of structural parts where fibres are steered along curvilinear paths, namely variable angle tow (VAT), which can enhance the mechanical performance and alleviate the structural weight. This is of utmost importance in the aerospace field, where weight savings are one of the main goals. For that reason, shell structures are commonly found in the aerospace industry because of their capabilities of supporting external loadings. Straight-fibre composite shell structures have been studied in recent decades and, now, spatially varying composite shells are attracting the attention of manufacturers. This work analyses the mechanical behaviour of VAT composite shells subjected to different external loadings and boundary conditions. The Carrera Unified Formulation (CUF) is employed to obtain the different structural models in a systematic and hierarchic manner. The outcomes of such numerical models are discussed and compared with commercial software Abaqus.
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Wang, Huaqiao, Jihong Chen, Zhichao Fan, Jun Xiao, and Xianfeng Wang. "Experimental Investigation on the Influence of Fiber Path Curvature on the Mechanical Properties of Composites." Materials 14, no. 10 (May 17, 2021): 2602. http://dx.doi.org/10.3390/ma14102602.
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Automated fiber placement (AFP) has been widely used as an advanced manufacturing technology for large and complex composite parts and the trajectory planning of the laying path is the primary task of AFP technology. Proposed in this paper is an experimental study on the effect of several different path planning placements on the mechanical behavior of laminated materials. The prepreg selected for the experiment was high-strength toughened epoxy resin T300 carbon fiber prepreg UH3033-150. The composite laminates with variable angles were prepared by an eight-tow seven-axis linkage laying machine. After the curing process, the composite laminates were conducted by tensile and bending test separately. The test results show that there exists an optimal planning path among these for which the tensile strength of the laminated specimens decreases slightly by only 3.889%, while the bending strength increases greatly by 16.68%. It can be found that for the specific planning path placement, the bending strength of the composite laminates is significantly improved regardless of the little difference in tensile strength, which shows the importance of path planning and this may be used as a guideline for future AFP process.
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Hashimoto, Kenji, Kentaro Hattori, Takuya Otani, Hun-Ok Lim, and Atsuo Takanishi. "Foot Placement Modification for a Biped Humanoid Robot with Narrow Feet." Scientific World Journal 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/259570.
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This paper describes a walking stabilization control for a biped humanoid robot with narrow feet. Most humanoid robots have larger feet than human beings to maintain their stability during walking. If robot’s feet are as narrow as humans, it is difficult to realize a stable walk by using conventional stabilization controls. The proposed control modifies a foot placement according to the robot's attitude angle. If a robot tends to fall down, a foot angle is modified about the roll axis so that a swing foot contacts the ground horizontally. And a foot-landing point is also changed laterally to inhibit the robot from falling to the outside. To reduce a foot-landing impact, a virtual compliance control is applied to the vertical axis and the roll and pitch axes of the foot. Verification of the proposed method is conducted through experiments with a biped humanoid robot WABIAN-2R. WABIAN-2R realized a knee-bended walking with 30 mm breadth feet. Moreover, WABIAN-2R mounted on a human-like foot mechanism mimicking a human's foot arch structure realized a stable walking with the knee-stretched, heel-contact, and toe-off motion.
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McClay, Irene, and Kurt Manal. "The Influence of Foot Abduction on Differences between Two-Dimensional and Three-Dimensional Rearfoot Motion." Foot & Ankle International 19, no. 1 (January 1998): 26–31. http://dx.doi.org/10.1177/107110079801900105.
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The advantage of a three-dimensional over a two-dimensional approach to rearfoot analysis has been questioned in the past. The purpose of this study was to examine differences in typical rearfoot variables obtained using a two-dimensional analysis compared with a three-dimensional approach. In addition, the influence of foot placement angle on these differences was assessed. Two- and three-dimensional rearfoot kinematics were collected from 18 recreational runners. Two-dimensional values for eversion at toe-off and time to peak eversion were found to be significantly different from the three-dimensional results. Differences between two-dimensional and three-dimensional variables were magnified with increased toe-out. Differences between eversion values were found to be minimal when the foot was abducted between 7 and 10°. The premise that excessive pronators have more pronounced toe-out was not supported by this study. Results suggest that caution should be exercised when assessing two-dimensional rearfoot motion in subjects with excessive toe-out.
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Cotic, Matthias, Korbinian Ksoll, Knut Beitzel, Wolfgang Seiberl, Andreas B. Imhoff, Ansgar Schwirtz, Florian Kreuzpointner, and Andrea Achtnich. "Objective visualization of the effect of different knee flexion angles on medial-lateral displacement of the knee center in frontal plane during single-Leg Squat." Orthopaedic Journal of Sports Medicine 8, no. 9_suppl7 (September 1, 2020): 2325967120S0051. http://dx.doi.org/10.1177/2325967120s00514.
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Introduction: The subjective single-leg squat (SLS) test can be used as a functional diagnostic agent to prevent knee injuries. [1] However, there are missing objective data about its functional rating, performance, squat depth and medio-lateral knee displacement in the frontal plane. [2] There-fore, the purpose of this pilot study was to evaluate the medio-lateral knee displacement in the frontal plane with a 3D motion capture system at different knee flexion angles during the SLS in healthy patients. Hypotheses: The hypothesis was that according to different knee flexion angles, there is a variability of medial knee displacement (= valgus positions) in healthy patients. Methods: 17 healthy and sporty subjects (9 ♀/ 8 ♂, age 25±4 years, BMI 24±2 kg/m2) participated in this study. Exclusion criteria were balance disorders, hip knee and/ or ankle complaints, sur-gery history, high deviation in lower extremity axis (i.e. Genu varum/ Genu valgus). Knee dis-placement was measured by 3D motion analysis system (Vicon Motion Systems, Oxford, UK) using a modified method of Krosshaug et al. [3] Thus, knee displacement was defined as distance between knee joint center and reference plane including the calculated hip and ankle joint center and the fixed toe marker on the second metatarsal head. A positive knee dis-placement was associated with a knee valgus, a knee varus was described as negative knee displacement. Every participant did 12 single-leg squats on each side. Results: The following knee flexion angles of all SLSs were captured (°, mean and standard deviation (±)): start position at 11 ± 6; downward phase at 40 ± 0 and 60 ± 0; maximum at 86 ± 16; up-ward phase at 60 ± 0 and 40 ± 0; end position at 8 ± 6. The medio-lateral knee displacement of all SLSs showed at the mentioned knee flexion an-gles the following values respectively (mm, median, interquartile range (25th - 75th quartile)): -12 (-19 to -5); 0 (-9 to 7); 13 (-2 to 28); 38 (8 to 61); 17 (0 to 36); 4 (-6 to 16); -15 (-22 to -7). Conclusion: According to different knee flexion angles, there is a variability of medio-lateral knee dis-placements in healthy patients. This variability should be included in the functional rating of a SLS as well as in the interpretation of different knee pathologies. Moreover, it provides an objective basis in the prediction of knee injuries.
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Wilding, Thomas, Stefan Grebien, Ulrich Mühlmann, and Klaus Witrisal. "Accuracy Bounds for Array-Based Positioning in Dense Multipath Channels." Sensors 18, no. 12 (December 3, 2018): 4249. http://dx.doi.org/10.3390/s18124249.
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The accuracy of radio-based positioning systems will be limited by multipath interference in realistic application scenarios. This paper derives closed-form expressions for the Cramér–Rao lower bound (CRLB) on the achievable time-of-arrival (ToA) and angle-of-arrival (AoA) estimation-error variances, considering the presence of multipath radio channels, and extends these results to position estimation. The derivations are based on channel models comprising deterministic, specular multipath components as well as stochastic, diffuse/dense multipath. The derived CRLBs thus allow an evaluation of the influence of channel parameters, the geometric configuration of the environment, and system parameters such as signal bandwidth and array geometry. Our results quantify how the ToA and AoA accuracies decrease when the signal bandwidth is reduced, because more multipath will then interfere with the useful LoS component. Antenna arrays can (partly) compensate this performance loss, exploiting diversity among the multipath interference. For example, the AoA accuracy with a 16-element linear array at 1 MHz bandwidth is similar to a two-element array at 1 GHz , in the magnitude order of one degree. The ToA accuracy, on the other hand, still scales by a factor of 100 from the cm-regime to the m-regime because of the dominating influence of the signal bandwidth. The position error bound shows the relationship between the range and angle information under realistic indoor channel conditions and their different scaling behaviors as a function of the anchor–agent placement. Specular multipath components have a maximum detrimental influence near the walls. It is shown for an L-shaped room that a fairly even distribution of the position error bound can be achieved throughout the environment, using two anchors equipped with 2 × 2 -array antennas. The accuracy limit due to multipath increases from the 1–10-cm-range at 1 GHz bandwidth to the 0.5–1-m-range at 100 MHz .
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Recanati, Maurice-Andre, Arvind K. Agnihotri, Jennifer K. White, James Titus, and David F. Torchiana. "Optimization of Vessel Orientation for Robotic Coronary Artery Bypass Grafting." Heart Surgery Forum 8, no. 1 (February 16, 2005): 9. http://dx.doi.org/10.1532/hsf98.20041039.
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The availability of telemanipulation robots has not yet resulted in the emergence of a reliable endoscopic coronary bypass procedure. A major challenge in performing a closed-chest coronary operation is creating a high-quality anastomosis in a reasonable period of time. In this experimental study, the impact of distal vessel orientation on the speed and accuracy of anastomosis was quantifed. We found that vessel orientation and the relative angle of the surgical plane influence anastomosis speed, the trauma to the vessel, the accuracy of stitch placement, and the eventual achievement of hemostasis. Our results suggest that the speed and accuracy of a robotically performed anastomosis of a vessel graft to a coronary artery can be improved by making small changes in vessel orientation. Vessels should be positioned between the horizontal and diagonal orientation and inclined between the horizontal and +45. Because the 6-o'clock stitch is particularly challenging, surgeons may benefit from an orientation that moves the heel or the toe of the anastomosis away from this critical position.
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Neunteufel, Daniel, Stefan Grebien, and Holger Arthaber. "Indoor Positioning of Low-Cost Narrowband IoT Nodes: Evaluation of a TDoA Approach in a Retail Environment." Sensors 22, no. 7 (March 30, 2022): 2663. http://dx.doi.org/10.3390/s22072663.
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The localization of internet of things (IoT) nodes in indoor scenarios with strong multipath channel components is challenging. All methods using radio signals, such as received signal strength (RSS) or angle of arrival (AoA), are inherently prone to multipath fading. Especially for time of flight (ToF) measurements, the low available transmit bandwidth of the used transceiver hardware is problematic. In our previous work on this topic we showed that wideband signal generation on narrowband low-power transceiver chips is feasible without any changes to existing hardware. Together with a fixed wideband receiving anchor infrastructure, this facilitates time difference of arrival (TDoA) and AoA measurements and allows for localization of the fully asynchronously transmitting nodes. In this paper, we present a measurement campaign using a receiver infrastructure based on software-defined radio (SDR) platforms. This proves the actual usability of the proposed method within the limitations of the bandwidth available in the ISM band at 2.4 GHz. We use the results to analyze the effects of possible anchor placement schemes and scenario geometries. We further demonstrate how this node-to-infrastructure-based localization scheme can be supported by additional node-to-node RSS measurements using a simple clustering approach. In the considered scenario, an overall positioning root-mean-square error (RMSE) of 2.19 m is achieved.
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İnceoğlu, Serkan, William H. Montgomery, Selvon St Clair, and Robert F. McLain. "Pedicle screw insertion angle and pullout strength: comparison of 2 proposed strategies." Journal of Neurosurgery: Spine 14, no. 5 (May 2011): 670–76. http://dx.doi.org/10.3171/2010.11.spine09886.
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Object Minimally invasive pedicle screws inserted vertically (that is, dorsoventrally) through the pedicle, as opposed to the more common coaxial technique, offer potential advantages by minimizing soft-tissue stripping during screw placement. The screws are designed for insertion through a medial starting point with vertical trajectory through the pedicle and into the vertebral body. As such, no lateral dissection beyond the insertion point is necessary. However, the effects of this insertion technique on the screw biomechanical performance over a short- and long-term are unknown. The authors investigated the pullout strength and stiffness of these screws, with or without fatigue cycling, compared with comparably sized, traditional screws placed by coaxial technique. Methods Twenty-one lumbar vertebrae (L-3, L-4, and L-5) were tested. Each pedicle of each vertebra was instrumented with either a traditional, coaxial pedicle screw (Group A), placed through a standard starting point, or a vertically oriented, alternative-design screw (Group B), with a medial starting point and vertical trajectory. The specimens were divided into 2 groups for testing. One group was tested for direct pullout (10 specimens) while the other was subject to pullout after tangential (toggle) cyclic loading (11 specimens). The screws were cycled in displacement control (± 5 mm producing ~ 4-Nm moment) at a rate of 3 Hz for 5000 cycles. Pullout tests were performed at a rate of 1 mm/minute. Results Two-way ANOVA showed that Group B screws with a medial starting point (2541 ± 1090 N for cycled vs 2135 ± 1323 N for noncycled) had significantly higher pullout loads than Group A screws with a standard entry point (1585 ± 766 N for cycled vs 1417 ± 812 N noncycled) (p = 0.001). There was no significant effect of cycling or screw insertion type on pullout stiffness. Tangential stiffness of the Group B screws was significantly less than that of the Group A screws (p = 0.001). The stiffness of both screws in the toe region was significantly affected by cycling (p = 0.001). Conclusions The use of Group B screws inserted through a medial starting point showed greater pullout load than a Group A screw inserted through a standard starting point. The greater pullout strength in Group B screws may be due to screw thread design and increased cortical bone purchase at the medial starting point. Nevertheless, anatomical considerations of the medial starting point, that is, pedicle or lateral vertebral body cortex breach, may limit its application. The medial starting point of the Group B screw was frequently in the facet at the L-3 and L-4 pedicle entry points, which may have clinical importance.
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Oliinyk, I. Yu, O. V. Tsyhykalo, and O. A. Koval. "Features of Blood Supply to the Bones of the Lower Leg in the Ankle Joint Region." Ukraïnsʹkij žurnal medicini, bìologìï ta sportu 6, no. 6 (December 25, 2021): 74–79. http://dx.doi.org/10.26693/jmbs06.06.074.
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The purpose of the study was to investigate the topography of permeable (nutrition) arteries in the lower third of leg during human ontogenesis. Materials and methods. The research was conducted on 30 specimens of human prefetuses and fetuses aged 3-9 months of prenatal development; 28 bone specimens of adult tibia and fibula and 27 series of computerized tomography scans of lower extremities of adults aged 21-72 were used. We have used a complex of methods for morphological research: anthropometry, morphometry, macromicroscopy, injections of blood vessels of X-ray contrasting mixtures, three-dimensional reconstruction and statistical analysis. Results and discussion. Cartilage osteogenesis occurs in the prefetal period of prenatal human development, in which blood vessels play a crucial morphofunctional role. During endochondral ossification of the tibia, the vessels of the bone cuff grow into the diaphysis of the cartilaginous model of the bone and osteogenic cells go beyond their limits. In the third trimester of prenatal development, blood vessels grow into the epiphyseal part of the cartilaginous model and an epiphyseal centre of ossification forms. Between the epiphysis and diaphysis centers of ossification, a metaphysical growth plate forms that develops intraosseous anastomosis between the diaphyseal and metaphysical blood vessels. In the metaphysis region, there are extra-skeletal anastomoses. Often, the insertion of nutrition arteries into the bone of the tibia is usually the middle third of bones (55%) and distal metaphysis (37%). In 10%, there were nutrition foramina in the upper third of the tibia. Three-dimensional reconstruction also clearly shows a more extensive and developed network of vessels in the bone marrow canal in metaphysical regions. In the middle third of the tibia and fibula, 1-3 nutrient foramina can be traced on most specimens. On the fibular, in addition to the posterior-medial localization of the nutrient arteries, there were variants with a "high" (above the metaphysis) placement of the entrance of the vessel into the bone substance. Conclusion. The most common places where arteries enter the bones of the lower leg are the middle third of the bones (55%) and the distal metaphysis (37%). In 10%, there were nutrient foramina in the upper third of the tibia. The three-dimensional reconstruction also clearly shows a more extensive and developed network of vessels in the bone marrow canal in metaphysical regions. During the postnatal period, we most often encountered the localization of nutritional arteries on the anterior-lateral surface of the tibia (23%), or their combination – the presence of both nutrient arteries on the posterior and medial bone surfaces (18.3%)
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Rabuffetti, Marco, Alberto Marzegan, Alessandro Crippa, Ilaria Carpinella, Tiziana Lencioni, Anna Castagna, and Maurizio Ferrarin. "The LAMB gait analysis protocol: Definition and experimental assessment of operator-related variability." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 233, no. 3 (February 1, 2019): 342–53. http://dx.doi.org/10.1177/0954411919827033.
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Gait analysis has demonstrated to efficaciously support clinical investigations. The patterns of the outcome variables (joint angles, moments and powers) are characterized by an intrinsic and extrinsic variability. Particularly, extrinsic variability is induced by operator-dependent differences in markers’ placement, with errors propagating non-linearly to alter outcome variable patterns. The aims of this study are (1) to consider a specific gait analysis protocol named LAMB and provide a description of its procedures, (2) to experimentally assess the between-operator and within-operator variability induced by operator-dependent marking of required anatomical landmarks and (3) to evidence how such inaccuracies propagates to the gait analysis kinematic and kinetic outcome variables. Six expert gait analysis operators performed LAMB anatomical landmarks marking on three healthy adult participants; moreover, one operator repeated three times the marking on one participant. The participants then performed a set of locomotor tasks including stair negotiation and heel- and toe-walking. An anatomical calibration approach let to register each marking and to compute, starting from one single raw data set, a set of outcome variables for each marking/operator. The between-operator variability of gait analysis outcome was assessed in terms of mean absolute variability to quantify offsets and minimal correlation coefficient to quantify patterns’ similarity. The results evidence average minimal correlation coefficient ranging from 0.857 for moments to 0.907 for angles and average mean absolute variability accounted for few degrees in angular variables (worst between-operator mean absolute variability is 7.3°), while dynamic variables mean absolute variability, relative to the variable range, was below 5% for moment and below 10% for powers. The variability indexes are comparable to those related to previously published protocols and are independent from the considered task, thus suggesting that the LAMB is a reliable protocol suitable for the analysis of different locomotor tasks.
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DO, HUNG, AMAL A. OWIDA, and YOSRY S. MORSI. "INTIMAL HYPERPLASIA AND WALL SHEAR IN ARTERIAL BYPASS Y-GRAFTING AND CONSEQUENCE GRAFTING: A NUMERICAL STUDY." Journal of Mechanics in Medicine and Biology 14, no. 03 (March 13, 2014): 1450044. http://dx.doi.org/10.1142/s0219519414500444.
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The progression of intimal hyperplasia is considered to be the main cause of bypass failure and is directly related to the individual blood rheology, local arterial geometry and placement of the junctions, graft diameter and graft surface characteristics as well as the degree of compliance. In this paper we use commercial computational fluid dynamics (CFD) ANSYS to examine under the correct physiological flow conditions the hemodynamic forces of composite bypass with internal mammary artery in Y-grafting and consequence grafting which is known to achieve high patency rate and highly recommended by clinicians. Particular emphasis is given here on the parameters that could initiate the development of intimal hyperplasia within these bypass configurations. The hemodynamic flow patterns between the consequence grafting and the composite Y-grafting are observed here to be different. Moreover, on both end-to-side and side-to-side configurations, the circulating flows are detected in the vicinity of the junction area, while the Dean flow vortexes are only observed on the end-to-side configuration. Likewise, the hemodynamic flow on the end-to-side configuration on the LCX of both 45° and 90° Y-grafting is found to be smoother than that of the junction on the LCA, regardless of the changing of anastomosis angles. The high WSS gradients are observed at the vicinity of the toe and on the bed of the junction, while the low WSS are presented at the distal of the stenosis and at the stagnation point. The clinical relevance of the results are presented and discussed with particular focus on the factors and the flow patterns that trigger the development of intimal hyperplasia.
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Stavetska, R., Y. Dynko, M. Bushtruk, I. Starostenko, O. Babenko, and N. Klopenko. "Linear type trait evaluation of firstborns of Ukrainian Black-and-White Dairy breed depending on the body build." Tehnologìâ virobnictva ì pererobki produktìv tvarinnictva, no. 1(147) (May 29, 2019): 24–34. http://dx.doi.org/10.33245/2310-9289-2019-147-1-24-34.
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It has been experimentally proven that the strength and direction of the connection between the linear type traits evaluation of the Ukrainian black-and-white dairy breed cows and their body build depends on the type of the build and the sign of the exterior. The study was conducted in 2018 on a breeding plant of the Ukrainian Black-and-White Dairy breed SPC named Shchorsa in Kiev region (n=89). Differentiation of cows on types of their body build was conducted by the method proposed by Chernenko (low-capacity, mid-capacity and high-capacity types) and Kolesnik (by the massiveness index – on the friable and dense, the bone index – delicate and rough, the wide-breast and wide-rump indices – on narrow-body and wide-body types). It was found that the cow-heiferswere well-developed, had intermediate stature and optimum body condition score, deep body, and wide, slight slope rump. They alsohad desirable rear legs, set and foot angle but some toe-out, the udder was well-balanced. Under the good total score of the exterior of studied cows there were some animals with short stature (134– 136 cm), very wide rump, straight rear legs side view and toe-out, extremely steep foot angle, loose fore udder attachment, deep udder below hocks and front teat placement inside of quarter. The degree of development of the studied linear traits of cow-heifers confirms their in-herd variability. The variability of the exterior traits varies from 10,7 % (body depth) to 38,6 % (stature). In addition to the stature of a significant variability was characterized of angularity (22,4 %), rear legs set (22,5 %), body condition score (21,8 %), as well as traits that describe udder: rear udder attachment (31,4 %), udder depth (32,6 %) and front and rear teat position (31,3 % and 25,1 %, respectively). The high variability of linear traits indicates the possibility of effective their selection. As a result of the research, it has been established that the strength and direction of the correlations between the linear type traits evaluation of Ukrainian Black-and-White Dairy breed cows and the type of their body build depends on the type of the body build and the linear trait. The low-, mid- and high-capacity bodies build types (according to Chernenko) reliably correlate with chest width (r=0,58) and body depth (r=0,48), rear legs rear view (r=0,30), the central ligament (r=0,28), udder depth (r =-0,22) and teat length (r=0,25), P˂0,01–0,001. Friable and dense bodies build (according to Kolesnik) were most strongly associated with stature (r=-0,28), chest width (r =-0,70), and body depth (r=-0,38), as well as with rear legs rear view (r=-0,23), P˂0,05...0,001; delicate and rough bodies build – with stature (r=-0,51), angularity (r=-0,22),rump width (r=-0,35), udder depth (r=-0,27) and rear udder attachment (r =0,20), P ˂ 0,05–0,001; narrow-body and wide-body types – with chest width (r=0,30) and rump width (r=0,23), P˂0,05–0,01. Linear type trait evaluation of cows depends on the body build. The strength and direction of the correlations between types of body build and linear traits showed that the most informative is the classification of the body build by low-, mid- and high-capacity according to Chernenko – on the average η2x=17,5 %. The less informative – by narrow-body and wide-body types according to Kolesnik – η2x=7,6 %. The classification of cows on delicate-rough, narrow-body and wide-body types (according to Kolesnik) according to informativeness and reliability can have the intermediate position – η2x=10,0–11,5 %. The strongest influence on the body build has the cows’ height (η2x=27,9 % on average for all studied types of body build), chest width (η2x=33,5 %), body depth (η2x=21,8 %), rump width (η2x=24,1 %) and rear legs (η2x=18,7 %). Key words: cows, linear type trait evaluation, body build, correlation, power of influence.
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Qu, Weiwei, Jiaxin Gao, Yaoyao Ye, Di Yang, Ruming He, Qian Yang, Liang Cheng, and Yinglin Ke. "Determination and application of posture adjustable domain under constraints of placement quality." Journal of Reinforced Plastics and Composites, June 3, 2022, 073168442211056. http://dx.doi.org/10.1177/07316844221105657.
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This paper defines the adjustable domain of placement posture during automatic fiber placement process and determines the critical size of the adjustable domain under the constraints of placement quality. The influence of the posture deflection on the placement quality is analyzed first, and compaction and slippage of tows are determined as the main constraints. Simulation models of tow compaction under variable deflection angles are established, and the influence of deflection angle and direction on tow compaction is analyzed. The friction coefficient is measured by experiments to characterize the friction behavior of the tow, and a tow slip criterion was established to avoid unacceptable defects. Combining the above constraints, posture adjustable domain is obtained and the influence of various parameters is analyzed. A searching method is established to calculate the collision-free posture in the adjustable domain and applied on a complex mold surface. The results show that the posture adjustable domain can effectively ensuring the placement quality when the placement head is deflected to avoid collision.
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Punera, Devesh, and Paulomi Mukherjee. "Recent developments in manufacturing, mechanics, and design optimization of variable stiffness composites." Journal of Reinforced Plastics and Composites, April 15, 2022, 073168442210829. http://dx.doi.org/10.1177/07316844221082999.
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The functional advantages of tailored stiffness, often seen in nature, are also utilized in composite structures. Advancements in the multiaxis tow placement and automated fiber placement (AFP) machines led to the development of variable angle tow (VAT) composites, also referred further as variable stiffness composites (VSC). These composites are shown to effectively enhance the stress distribution and buckling load capacity of structures with greater flexibility on the design space. This review systematically presents the status of recent research on the topic of VSCs. Various manufacturing techniques of VSC are discussed; constraints and the defects associated with the manufacturing processes are enlisted. The review highlights the optimization studies based on the fiber profile and macro-scale stiffness invariants. Several studies existing in the domain of buckling, vibration, and aeroelastic tailoring of angle tow composites are summarized to connect the important aspects of analysis and present a holistic approach for future studies in this area.
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Rajasekaran, Aadhithya, and Farjad Shadmehri. "Steering of carbon fiber/PEEK tapes using Hot Gas Torch-assisted automated fiber placement." Journal of Thermoplastic Composite Materials, February 14, 2022, 089270572110679. http://dx.doi.org/10.1177/08927057211067962.
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In-situ manufacturing of thermoplastic composites using Hot Gas Torch (HGT)-assisted Automated Fiber Placement (AFP) has the potential to produce laminates in an efficient manner by avoiding a secondary process, like autoclave consolidation. One of the advantages of AFP technique is its capability to steer fiber path and to manufacture Variable Angle Tow (VAT) laminates which have shown to have improved mechanical performance. This study investigates the process parameters that affect steering of carbon fiber reinforced thermoplastic tapes (AS4/polyether ether ketone) using an HGT-assisted AFP machine. The effect of the steering radius, laydown speed, number of repasses, and substrate angle on the geometry and bond strength of steered tape was investigated through observation and testing. A modified lap shear test was devised and used to study the bond strength between the steered tape and the substrate and the results were compared with autoclave treated samples which served as a reference. It was found that with a decrease in the steering radius of the tape, there was a decrease in the tape width and an increase in the tape thickness. A significant reduction in the steering-induced defects was observed at higher laydown speeds where the defects were intermittent unlike in the case of lower laydown speeds. Performing a repass over the steered tape smoothed some of the tape defects caused by steering. Furthermore, the lap shear strengths of the steered tapes were found to be functions of laydown speed and substrate angle.
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Kolle, J. J., A. C. Mueller, S. Baumgartner, and D. Cuthill. "Modeling Proppant Transport in Perforated Casing Based on Surface Testing." SPE Drilling & Completion, October 1, 2022, 1–12. http://dx.doi.org/10.2118/209178-pa.
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Summary The results of a series of proppant transport surface tests (PTSTs) were used in conjunction with Eulerian multiphase-computational fluid dynamics (EMP-CFD) modeling to develop an engineering model of proppant distribution. The PTSTs were carried out to evaluate proppant placement through perforated casing. In these tests, sand slurry was pumped at realistically high flow rates through perforated casing, and the distribution of sand and slurry from each perforation cluster was observed. The tests show that gravitational settling in horizontal casing, proppant slip past perforations, and the viscoelastic properties of slickwater fluids strongly affect the distribution of proppant from the heel to the toe of the completion. The EMP-CFD modeling was used to estimate the gravitational settling of sand in fully developed turbulent slurry flow in horizontal casing as a function of casing velocity. A survey of 36 calculations was carried out to generate tables of sand concentration in a cross section through the casing as a function of flow rate and particle size. A single-phase CFD analysis showed how sand exiting each perforation is taken from a limited ingestion area, which is proportional to the ratio of flow through the perforation to total flow in the casing. A detailed EMP-CFD analysis of flow through single perforations showed how sand slips past the perforation. The results of 28 EMP-CFD calculations provided slip factors as a function of particle size, casing flow velocity, and perforation flow velocity in straight and angled perforations. The EMP-CFD settling tables and a parameterization of the slip factors were integrated into an engineering model. The model predicts the distribution of slurry and sand through each perforation based on the proppant size, perforation phase angle, and pump rate. The engineering model was used to predict the sand distributions observed in the PTSTs. The PTSTs were conducted with a range of sand sizes and with friction-reducing (FR) polymer additives, while the EMP-CFD analysis assumed water. A weight factor is introduced in the settling model to account for the increased dispersion of sand in water with FR and to match the observed sand distributions in the PTSTs. The observed slip of 100 and 40/70 mesh sand is consistent with the EMP-CFD calculations in water. The model reflects the PTST observations that fine sand is distributed relatively uniformly throughout the length of a perforated completion, while coarser sand tends to slip past the heel perforations and concentrate at the bottom toward the toe of the completion.
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Đurić, Neđo, Milan Perisić, and Dijana Đurić. "LANDSLIDE ON LOCATION OF WATER SOURCE STUDENAC NEAR BIJELJINA, REPUBLIKA SRPSKA." Archives for Technical Sciences 1, no. 8 (November 15, 2012). http://dx.doi.org/10.7251/afts.2013.0508.001d.
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ABSTRACTThe landslide is located in the hinterland of water source "Studenac" in the local community GornjaCadjavica near Bijeljina. The field where the triggered landslide occurred is conditionally stable slope.It is overgrown with forest trees and therefore it was not a subject of interest in terms of its stabilityuntil the water source and accompanying local road have been constructed in the lower part of theslope. Additionally the slope was undercut resulting in jeopardizing its conditional natural stability. Atfirst, it was about some slight ground movements requiring no significant interventions.As the time was passing by site conditions have been changing. During winter and spring timemovement of rock blocks is more intense due to large amount of surface and underground waterwhereby such a process was significantly slower and almost calm in the summer time. Such a cycle wasrepeated for several years until late 2010 when massive collapse of the unstable zone, which might becalled ‘landslide’, endangered not only the local road but also the water source.For the purposes of overviewing the site and landslide characteristics as a whole, exhaustive researcheswere carried out within the part of the site affected by sliding at the surface of about 0,4 ha. A fieldsurveying of wider area was also conducted. The landslide is located at relatively steep slope where theheight distance between the crown and the toe of the landslide is 14,0 m. General slope angle is up to100 and in those parts where landslides occur they are up to 250. Sliding plane has been formed at depthof 2,5 to 4 m depending on terrain morphology, in clay of high plasticity (CH groups). The main causeof landslides is surface and underground water.Within the scope of remediation project two restorative measures were applied. The main recoverymeasure was placement of AB retaining concrete wall which was intended to accept the pressures ofsoil mass and to prevent it from slipping, namely to maintain the slope in stable condition. The otherremedial measure was construction of an open perimeter canal at the slope above the retaining wall forthe purposes of collecting surface water flowing towards the main body of the landslide and itsdiversion outside the sliding area. Key words: landslide, slope, water source, research, rehabilitation
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"Stress Distribution Along the Implant-Bone Interface: A Pilot Study using Finite Element Analysis to Compare Tilted and Non-Tilted Implants under Different Loads." Advances in Bioengineering and Biomedical Science Research 4, no. 4 (October 1, 2021). http://dx.doi.org/10.33140/abbsr.04.04.04.
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Introduction: This study used finite element analysis to evaluate stress distribution of implants placed at different angulations under two loadings. Stress was measured at the implant-bone interface. Methods: Four models of implant and bone were manufactured via three-dimensional optical scanning and point cloud data extraction. They included implants placed: 1) Without tilt 2) tilted at 15o, 3) tilted at 30o, and 4) tilted at 45o. A tissue-level implant was scanned, and a mandible bone model was extracted from cone-beam computed tomography systems. A 3D model of the implants in the mandible were constructed. The finite element analyses were carried out using simulation software. The physical interaction at implant-bone interfaces during loading were considered through bonded surface-to-surface contacts. Static loading (with axial forces of 150N and 300N) were applied to evaluate the implant-bone model. Results: The amount of stress along the implant-bone interface was greater under 300N loading than 150N loading. The stress along tilted implants were greater than that of non-tilted implants under both 150N and 300N. There was no significant variance among the various angles of implants. The displacements along the tilted implants were larger than those of nontilted implants. The stress distribution along the implant-bone interface increased when the loading increased. Conclusion: The tilted implants presented greater stress distribution. The in vitro stress distribution analysis using FEA will provide clinical guidance for implant placement.