Flexible Pin Research Articles

Quantitative reliability measures determination of a steel-reinforced concrete beam taking into account fatigue damage accumulation in flexible pin stops

Reliability is one of the most important properties of road bridges due to their degree of responsibility and strategic importance for the transport system. For steel-reinforced concrete bridges, which are widespread nowadays, the question of their overall structure reliability dependence on the element’s condition of steel beam and reinforced concrete slab connection remains not fully studied. The authors have performed fatigue damage accumulation numerical modelling in the conjunction elements of steel-reinforced concrete beam from the cyclic temporary loads influence and analysed this process influence on the overall structure reliability. Based on the previous studies data, a relationship model between the conjunction element shear rigidity and the amount of damage accumulated by it is proposed. The nonlinear finite element calculation algorithm with regard to the conjunction element’s rigidity reduction is proposed and tested on the model of the steel-reinforced concrete superstructure. The selection method of the equivalent time load for modelling the accumulation of fatigue damage process from traffic flow is proposed. In order to optimise the computational resources used it is proposed to use loading process clusterization into enlarged cycles groups and the rational group size is determined. A numerical experiment on the simply supported steel reinforced concrete beam model with different loading cycles number (from 1 loading to 100 million loading cycles) to determine the reliability index β under the assumption of variability of two parameters — design steel resistance and the value of temporary load. FORM (First Order Reliability Method) was used for probabilistic analysis. The study results have shown that the accumulation of fatigue damage in the elements of steel-reinforced concrete superstructures has a significant effect both on the load-bearing capacity of the superstructure beams and on the quantitative indicators of structural reliability (increase in the probability of structural failure, decrease in the reliability index β).

Influence analysis of the connective elements failures on the road bridges steel reinforced superstructures service reliability

The paper considers the influence issues of connective elements failures, in particular flexible pin stops, on the road bridges steel reinforced superstructures service reliability. The authors have formulated possible criteria for the superstructure failure both for the first and the second groups of limit states, and also developed scenarios of connective elements exclusion from the structures operation, that are modeling the failure of individual connective elements in the operation process. For five finite element models of road bridges steel reinforced superstructures a numerical experiment on modeling of the connective elements exclusion from the operation of the structure was carried out. The calculation results for each scenario and for the partial scenario realization levels were analyzed in terms of possible superstructures failures as a whole. Numerical experiment results have shown that at the exclusion of a separate small group of connective elements increases the maximum stresses in the over-supported beams sections by up to 3 %, and further development of the connective elements disconnection scenario can lead to an increase in stresses by 20 %. It is concluded that for existing steel reinforced superstructures the risk of superstructures failure under normal operating conditions due to disconnection of connective elements is low, even in the case of almost unlikely complete disconnection of all connective elements. Nevertheless, the exclusion from operation of connective elements may be more critical in cases of abnormal bridge structure operation or in cases of significantly lower engineering reserves of the structure in terms of strength and stiffness.

Operating regime investigational study of steel-reinforced concrete superstructure flexible pin stops of the existing road bridge

In the article, the author published the full-scale experiment results on an existing steel-reinforced concrete road bridge, carried out to determine the actual parameters of the operation regime of the interconnection elements — flexible pin stops. This work was carried out as part of the author's dissertation research in the field of improving methods for testing the elements' endurance of the steel-reinforced concrete superstructures interconnection and is a development of the previously conducted comprehensive comparative analysis of existing models for testing endurance. The article gives a detailed description of the conditions for conducting and methods of a two-stage experiment, which includes short-term and long-term parts, as well as a detailed description used for processing experimental data for each of the stages. Based on the results of the experiment's short-term part, when compared with the results of finite element modeling of the operation of the stops, the possibility of using existing computational models to describe the actual model operation was confirmed. Also, within the framework of the short-term part, according to the conducted dynamic tests results with the moving load passage through the threshold, the presence of a significant dynamic component of the resulting forces in the interconnection stops was revealed. During the second long-term part of the experiment, a continuous recording of stresses in the interconnection elements from the passage of an unregulated traffic flow over the bridge was made. The article presents both direct survey data (tensograms) and the results of their further processing in terms of damage accumulation analysis; also, the accumulated damages values from actual traffic loads are compared with the expected values in the calculation according to some design standards. Intermediate conclusions based on the experiment results are formed and directions for future work within the scope of this study are indicated.

Application of flexible pin for planetary gear set of wind turbine gearbox

Wind turbines are eco-friendly energy sources that generate electricity from wind power. Among their various components, gearboxes constitute the most critical loss owing to their longest downtime. To guarantee their durability, a flexible pin was designed based on the original straddle-mounted pin for enhanced tooth load sharing and distribution in the planetary gear set (PGS) of a wind turbine gearbox (WTGB). The improved durability was evaluated by calculating the mesh load factor and face load factor for contact stress and comparing these values with those of the original straddle-mounted pin. The mesh load factor decreased from 1.37 to 1.08, whereas the maximum face load factor decreased slightly, moderating the overall safety factor variation. Furthermore, the structure of the proposed flexible pin model was analyzed and verified that no static failure or interference occurred. Additionally, microgeometry optimization was applied to improve the load distribution. Therefore, it was verified that a flexible pin applied to a single helical-geared PGS, thus far considered impossible, enhances the durability of WTGBs by improving the load sharing and distribution of a PGS. Consequently, the possibility of designing single helical-geared planetary gearboxes with flexible pins to take advantages of both helical gears and flexible pins was shown analytically.

The load sharing structure design and FE analysis of planetary gearbox with flexible pin

The paper first introduced the unequally load sharing in the planetary gear set and explained the cause of unequally load sharing in traditional design. Then a new floating structure of planetary gear with flexible pin has been designed to improve unequally load sharing of planetary gear set. In order to verify the flexible pin structure effects on the load sharing, two integrated finite element models have been built. Each one consists of two coupled planetary gear sets. One finite element model has been built with flexible pin structure and the other with fixed pin. The same load and boundary conditions have been applied to the two different finite element models. After analysis, the vonmises stresses of different parts such as ring gear, planetary gear, bearing and pin etc. in two different models have been compared. From the analysis result verification, the maximum vonmises stress of flexible pin of planetary gear set is much higher than that of planetary gear set with fixed pin in different mesh position. Although it is in the design range of material strength, its increase indicates that flexible pin structure makes the higher unequal mesh load of planetary gear shared with other pinions, the deflection of flexible pin make the load sharing with other pinions possible. Whereas the maximum vonmises stresses of other parts such as ring gear, planetary gear, bearing and sun gear decreases in a certain degree with the flexible pin deflection. It really indicates that the effect of flexible pin in the planetary gear set is obvious against fixed pin. When the higher unequally sharing load becomes smaller, maximum vonmises stresses of all planetary gear set parts except flexible pin become smaller and safer.

Experimental study of SSS of a steel concrete beam taking into account the rigidity of the connecting seam

The article presents the test results of a scale model of a single-span steel-reinforced concrete beam, which is as close as possible to the real structures of bridge spans with the combination of a reinforced concrete slab with steel beams using flexible pin stops. The distribution of the experimental values of shear deformations and normal stresses in the beam flanges is in good agreement with the calculated data, taking into account the shear stiffness of the joint, and differ in a number of values from those calculated by the classical approach.

Combined electrohydraulic and flexible pin die forming: a novel high strain rate forming die setup

Electrohydraulic forming (EHF) is one of the high-velocity metal forming processes that can significantly increase the formability of metals compared with quasi-static forming processes. On the other way, multi-point forming (MPF) is one of the flexible forming methods that provides different sheet metal geometries by varying the height of the pins. The purpose of this study is to take the advantages of both the EHF and MPF processes by presenting a design for flexible dies to be used in the electrohydraulic forming process. As the first step, electrohydraulic free-forming was performed to investigate the reproducibility and to obtain some of the parameters needed for simulations. Then, the ABAQUS finite element software and Coupled Eulerian-Lagrangian method were used to simulate this process. Afterward, the experimental tests were undergone to determine the defects of the forming process using a flexible pin die. Various geometries were produced by conducting experiments and inserting the proper elastic layer to eliminate the dimpling. The reproducibility and validity of the flexible pin die forming simulation was investigated by analyzing the dome height and final profile of the specimens. After ensuring the accuracy of the simulation, a thicker elastic layer was used to remove the dimpling defect completely. The results of the experiments and simulations illustrated that the use of flexible pin die is possible in the process of EHF and the proper final forms can be obtained by applying the appropriate thickness of the polyurethane layer.

Strengthening effect of different fiber placement designs on root canal treated and bleached premolars

To evaluate the strengthening effect of five different fibers with different placement designs in root canal treated and intracoronally bleached premolars. Seventy extracted single-rooted premolars were distributed into 7 groups (G1-G7). Group 1 (G1) included the intact (I) teeth as the negative control. Group 2 (G2) included root canal treated, intra-coronally bleached and composite (C) restored teeth as the positive control. In the other five test groups after root canal treatment the teeth were intra-coronally bleached and fiber materials were placed into standard MOD cavities in the following different designs: an intracanal rigid fiber/Reforpost (G3,RF), an intracanal flexible fiber/ Everstick (G4, FF), four intracanal flexible pin fibers/Dentapreg Pin (G5,PF), an intercuspal flexible fiber /Dentapreg SFU (G6, IF) or an intra-coronal horseshoe-shaped/ Dentapreg SFU (G7,CF). All cavities were filled with a microfilled resin composite. Fracture resistance was tested using a universal testing machine under a crosshead speed of 1mm/minute. One-way ANOVA and Duncan's Multiple Range tests were used for statistical analysis. Fracture types were recorded. The fracture resistance values in descending order were G1(I): 1190.97N > G6 (IF): 1138.78N > G5 (PF): 942.45N > G3 (RF): 737.40N > G4 (FF):694.29N > G2 (C): 611.83N > G7 (CF): 542.78N. There were statistically significant differences among the groups (p ≤ 0.05). In all groups, repairable coronal oblique fractures were mostly observed. Flexible fibers placed intercuspally exhibited a significantly better strengthening effect than those of the intracanal flexible and rigid fibers (p < 0.05).

Load Sharing Performance of Herringbone Planetary Gear System with Flexible Pin

To study the load distribution mechanism of the power-split transmission, and improve the carrying capacity of the herringbone star gear transmission system, the dynamic model of the planetary gear system for a geared turbofan engine with the flexible pin was established based on the node finite element method. The model considered the comprehensive influence of meshing error, time-varying meshing stiffness, bearing supporting stiffness and meshing phase. The dynamic load sharing performance of the system were studied in the equivalent meshing error, and the influence of the error incentives and structure of pins on the load sharing characteristics was analyzed. The results indicate that the vibration track of the center gears deviates from the origin because of the eccentricity error. The load sharing performance of the system can be improved by improving gears’ manufacturing precision. Moreover, the influence of manufacturing errors is larger than that of assembling errors. The flexible pin improved by Montestruc has the best load sharing performance among the four types of pin models designed in the study. The load sharing performance declines with an increase of in input speed and a decrease in input power.

Design and Tests of a Multi-pin Flexible Seedling Pick-up Gripper for Automatic Transplanting

HighlightsA multi-pin flexible pick-up gripper with a four-jaw chuck having four pick-up pins has been developed.The gripper can effectively grasp, hold and release plug seedlings with low damages to the plants and the root soil.Based on a typical on-off control and cylinder stroke position detection, the control system for timely response was designed to automate the process of picking up and releasing seedlings.Abstract. A multi-pin flexible seedling pick-up gripper for automatic transplanting was developed and evaluated. The gripper having a four-jaw chuck mainly consists of a parallel-type air gripper with four fingers, four fork frames, four cylinder fingers, and several connecting/supporting parts. The air gripper moves to open and close the cylinder fingers, and the cylinder fingers each having a flexible pin grasp and release the seedling. When the pick-up gripper extracts seedlings from the tray cells, its four cylindrical fingers push out four pick-up pins to penetrate deep into the root soil and then close, making the pick-up pins to firmly hold the root soil for lifting. When the pick-up gripper releases seedlings, its fingers open, making the pick-up pins loosen the root soil and then pull back for discharging. An electrical and pneumatic control system was designed to coordinate the execution of each action. The pick-up gripper attached to a robotic manipulator was tested on a range of plug seedling transplanting parameters and conditions. The results showed that penetration depth, seedling species, and the interaction of working pressure and seedling species significantly influenced the successful automatic transplanting. On the whole, the seedling integrity ratio in automatic transplanting was found to be up to 93.37%. For optimum performance of the device in transplanting seedlings, the pick-up pins of the multi-pin gripper need to grasp the maximum amount of root soil at their maximum penetration depth. Keywords: Gripper, Flexible, Multi-pin, Seedlings, Transplanting.

Dynamical load sharing behaviors of heavy load planetary gear system with multi-floating components

To investigate the dynamical load sharing behaviors of multi-floating components in the heavy load planetary gear system, a multi-floating planetary gear system that includes a floating central component and a quasi-floating planet flexible supporting pin is employed. Then a 21 degree of freedom lumped parameters dynamical model of this system is presented to study the dynamical load sharing behaviors. Some influencing factors, such as supporting stiffness, positions error of sun or carrier, and external input load are analyzed on the dynamical load sharing of the planetary gear system with multi-floating components. The results demonstrate that the load sharing condition of the system is best when both the sun gear and planet gears are multi-floating at the same time. When the planet gear position errors remain constant, reducing the flexible pin stiffness of planet gear or increasing external input load can effectively improve the load sharing. These conclusions are verified by the relevant experiments.

Avoidance of Reamer Breakage During ACL Reconstruction With Flexible Reamer System: Response.

Authors’ Response: We greatly appreciate the viewpoints of Dr Jaiman concerning the timing/use of the 4.5-mm reamer when utilizing a flexible reamer for establishing a femoral tunnel. Using a flexible reamer system is very advantageous in creating a low femoral tunnel especially in the current context of concomitant anterolateral ligament (ALL) reconstruction or posterolateral corner reconstruction, as can often be needed with revision anterior cruciate ligament (ACL) surgery. Furthermore, avoiding knee hyperflexion facilitates placement of the femoral guide pin, as visualization and graft passage is almost never compromised as is often seen with straight pins/reamers placed using the necessary hyperflexion to avoid a short femoral tunnel. Furthermore, with modern flexible reamers and experience, the ACL tunnel length is maximized, with most condylar distances 35 to 40 mm with use of standard offset guides. As the reader suggests, utilizing the appropriate graft size reamer first is quite acceptable as it does seat the femoral tunnel/socket when the pin is placed ideally. We often utilize this first step. However, in those situations when the nitinol pin is too posterior or low on the lateral wall, using the 4.5-mm reamer first across the intercondylar distance allows adjustability of the femoral tunnel anteriorly or superiorly without having to replace the flexible pin. In our experience, redirecting a slightly low or posterior nitinol wire can be difficult as the nitinol pin often drops into the same track. Furthermore, there are advantages to knowing the condylar width (especially if too short or in the case of a less experienced surgeon) before seating the femoral tunnel. If the surgeon does elect to ream first with the 4.5-mm reamer, the femoral tunnel can still be seated in an accurate position, despite the mobility. One advantage of reaming with the 4.5-mm first, in our experience, is that it allows the flexible final-sized reamer to seat itself within the condyle in the scenario where the pin is too posterior. We agree that placement of the final socket centered on the bifurcate ridge is most critical, and we often ream with the final-sized reamer first then follow with the 4.5-mm reamer. We discussed in the article reaming with the 4.5-mm reamer first as it is a very nice technical trick to adjust the final socket without having to replace the nitinol pin when the initial attempt/placement could be adjusted slightly anteriorly or superiorly, which is often the case. When using a bone-tendon-bone autograft, this technique modification helps avoid posterior wall blow out from a posteriorly placed nitinol wire. Although using the final-sized reamer first works extremely well when the pin is placed accurately, we find that reaming with the 4.5-mm reamer first prevents the larger, final-sized reamer from kinking on the nitinol wire and is often easier to ream. With our change to the Stryker flexible system we have not had reamer or wire breakage regardless of the order of reaming. As to the use of the tibial guide, the proper selection of tibial angle we agree can be variable and is best adjusted to replicating the ACL tibial footprint. We find the 55° setting very useful when performing hamstrings autografts but have utilized other angles of approach, when appropriate, as suggested by the readers’ comment.

Posterolateral portal tibial tunnel drilling for posterior cruciate ligament reconstruction: technique and evaluation of safety and tunnel position.

To evaluate the safety for neurovascular structures and accuracy for tunnel placement of the posterolateral portal tibial tunnel drilling technique in posterior cruciate ligament (PCL) reconstruction. Fifteen fresh-frozen human cadaveric knees were used. The tibial tunnel for the PCL was created using a flexible reamer from the posterolateral portal. Then, the flexible pin was left in place, and the distance from the posterolateral portal, the flexible pin, and the tibial tunnel to the peroneal nerve and popliteal artery was measured. Additionally, the distance between the tibial tunnel and several landmarks related to the PCL footprint was measured, along with the distance from the exit point of the flexible pin to the superficial medial collateral ligament and gracilis tendon. The peroneal nerve and the popliteal neurovascular bundle were not damaged in any of the specimens. The median (range) distance in mm from the peroneal nerve and popliteal artery to the posterolateral portal and flexible pin was: 52 (40-80) and 50 (40-61), and 35 (26-51) and 22 (16-32), respectively. The median (range) distance from the tibial tunnel to the popliteal artery was 21mm (15-38). The tibial tunnel was located at a median (range) distance in mm of 3 (2-6), 6 (3-12), 5 (2-7), 4 (1-8), 9 (3-10), 10 (4-19), and 19 (6-24) to the champagne-glass drop-off, lateral cartilage point, shiny white fibre point, medial groove, medial meniscus posterior root, lateral meniscus posterior root, and posterior aspect of the anterior cruciate ligament, respectively. The posterolateral portal tibial tunnel technique is safe relative to neurovascular structures and creates an anatomically appropriate tibial tunnel location. The clinical relevance of study is that this technique may be safely and accurately used in PCL reconstruction to decrease the risk of neurovascular damage (avoid use of a posteriorly directed pin), avoid the use of intraoperative fluoroscopy, and avoid the sharp turn during graft passage.

Inside-Out Antegrade Tibial Tunnel Drilling Through the Posterolateral Portal Using a Flexible Reamer in Posterior Cruciate Ligament Reconstruction

Posterior cruciate ligament (PCL) reconstruction using the transtibial drilling or arthroscopic tibial-inlay technique has a risk of injury to the popliteal neurovascular bundle because a pin is drilled anterior to posterior. Intraoperative fluoroscopy is used to decrease the risk of neurovascular injury. In addition, graft passage in the transtibial technique may be problematic because of a sharp turn when placing the graft into the tibial tunnel, which may damage graft fibers. In the surgical technique described in this report, the posteromedial portal is used for visualization and the posterolateral portal is used for debridement of the PCL tibial footprint and the synovial fold closest to the PCL. A curved guide is placed from the posterolateral portal to the tibial footprint, and a flexible pin is drilled across the tibia. The tibial tunnel is then created using a flexible reamer under direct visualization up to the desired length, and a graft can be positioned in the tibial tunnel through the posterolateral portal. This technique has the potential advantages of decreasing the risk of injury to the popliteal neurovascular bundle (use of anteriorly directed, inside-out drilling), avoiding a sharp turn during graft passage, and allowing accurate and anatomic tibial tunnel placement without intraoperative fluoroscopy.

The nonlinear effects of flexible pins on wind turbine gearboxes

The structure of flexible pin-type planetary gear systems used in wind turbine gearboxes can improve the load sharing ability of planets while saving space unlike straddle-type carriers. However, the nonlinear dynamic characteristic of this type of system is not fully developed. This work presents a coupled lumped-parameter dynamic model to demonstrate nonlinear effects. Gear contact loss nonlinearity and bearing clearance nonlinearity are integrated into this dynamical model, and the effects of flexible pins on the nonlinear dynamic responses are discussed. The conclusions made are as follows: lower flexible pin stiffness can significantly reduce nonlinear effects; when pin stiffness is increased, contact loss still occurs in positions of strong vibration even if the planet gear bearings have higher orders of magnitude of tangential load in the wind turbine gearbox; dynamic response peaks are asymmetric with a frequency sweep; only left oblique "Soft" jumps occur, and the right oblique “Hard” jump phenomena rarely occur; planet gear supporting the bearing clearance exists; and vibration chaos occurs in positions of strong vibration.

Avoiding Flexible Reamer Breakage During Anatomic ACL Reconstruction.

As outlined in our January 16, 2013 editorial, “The Case Report Redefined with JBJS Case Connector ,” one important role of JBJS Case Connector is to alert the orthopaedic community about a potentially problematic device or therapy. When two or more such cases with similar mechanisms appear, we will identify the procedure or implant as a “watchable” intervention. While this system is not statistically conclusive and may or may not be supported by other published case reports or registry data, the intention is to sharpen the focus of clinicians on the potential for similar problems and thereby enhance clinical outcomes and patient safety. The “Watch” designation may also encourage others to report related difficulties and enlist the orthopaedic community to either demonstrate that these are isolated, unrelated cases or sharpen the focus further on rigorously evaluating the intervention. Where appropriate, we may identify brand, model, or implant-lot specifics. Anatomic reconstruction of ruptured anterior cruciate ligaments (ACLs) offers well-documented advantages over nonanatomic approaches. Optimal tunnel parameters contribute much to the success of anatomic ACL reconstruction. For single-bundle anatomic techniques, some surgeons have begun to curve tunnels slightly rather than drill straight ones. Users of the curved approach say it allows them to achieve longer tunnel lengths, reduce the risk of iatrogenic injury, and avoid the need for knee hyperflexion and notchplasty. The desire among some surgeons to create curved tunnels has prompted manufacturers to develop flexible drill guides and reamers. In the October 22, 2014 JBJS Case Connector , Lee et al. report on two cases of …

Pitfalls in Single-Bundle Anterior Cruciate Ligament Reconstruction with the Flexible Reamer System: A Report of Two Cases and Review of the Literature.

We present two cases of anterior cruciate ligament reconstruction with use of the flexible reamer system. In both patients, the starting reamers were broken during femoral reaming. The location of the breaks was approximately 60 mm from the tip of the reamer, which is the transitional zone between the proximal and distal portions of the reamer. We believe that several conditions could have resulted in abnormal stress concentration on the flexible reamers, including engagement of the flexible reamer with a physeal scar or the posterior cortex, an inappropriate flexion angle of the knee, and acute bending of the flexible pin.

Application of Axiomatic Design Theory in Multi-Planetary Gear Transmission Design

Development of product innovation design theory, especially the axiomatic design, has changed the pattern depending upon accumulated experience in product design. Independence rule and information rule are the necessary rules of axiomatic design theory. In design of multi-planetary gear transmission, axiomatic design has been applied to determinate type of even-loading mechanism, being important in evenly dividing power into planetary gears to greatly reduce vibration and impact of gear transmission process. By axiomatic design, flexible pin even-loading system and sun gear floating system were compared, and the best scheme has been decided to realize great power transmission.

Research on Even-Loading Mechanism of Multi-Planetary Gear Transmission

Multi-planetary gear transmission is usually used in construction equipment, metallurgical machinery and wind-driven generator. Driving mechanism of heavy-duty equipment without even-loading system is badly loading, resulting in great impact force and severe vibration. To study characteristic of power dividing, multi-planetary gear transmission without any even-loading mechanism and that with flexible pin even-loading mechanism were simulated in commercial gear drive design software and dynamics analysis software. The simulation results are shown in this paper and conclusions are drawn useful for design and manufacture of heavy-duty multi-planetary gear transmission.

70.4L: Late‐News Paper: Flexible Amorphous Silicon PIN Diode Sensor Array Process Compatible with Indium Gallium Zinc Oxide Transistors

AbstractA flexible PIN diode sensor array process has been successfully demonstrated. Device fabrication of the thin film transistor (TFT) backplane occurred below 200 °C on a polyethylene naphthalate (PEN) substrate using indium gallium zinc oxide (IGZO) with a saturation mobility of 13.5 cm2/V‐s as the active semiconductor. The increased mobility enables the fabrication of higher speed and higher resolution sensor arrays in comparison to current amorphous silicon (a‐Si) technology.