Fatigue Analysis Design Approach, Manufacturing and Implementation of a 500 kW Wind Turbine Main Load Frame

The main load frame of a wind turbine is the primary mount for all nacelle equipment and is used as the principal load transmitter. This frame should have a reliable fatigue safety rating because it is a load-bearing component. In this work, the fatigue life design, manufacturing and implementation process for the main load frame of a 500 kW wind turbine are studied. The weight of the main load frame and static safety factors are preserved while the cyclic life of the bedplate is kept infinite. Modified Goodman theory is applied to achieve an effective fatigue design using a commercial finite element software package. Analytical calculations are carried out to obtain the safety factors of the bedplate and dynamic strength of the materials. A finite element approach is employed to perform stress analysis. Stress oscillations are established for both welded and cast parts of the hybrid bedplate, and the maximum and minimum stress values are established. Fatigue safety factors are calculated via fatigue analysis iterations. The obtained safety factors are adequate from the perspective of commonly accepted fatigue safety standards. Welding and casting techniques are applied together for manufacturing of the frame. On-site testing indicates that the wind turbine does not show any signs of fatigue. Rupture, cracks, and abrupt accelerometer reading variations are not observed.

Modeling of Piezoceramic Actuators for Control

In this chapter a full electromechanical model of piezoceramic actuators is presented. This model allows for easy integration of the piezo stack with a structural finite element model (FEM) and includes the flow of energy into and out of the piezo element, which is governed by the transducer constant of the piezo element. Modeling of the piezo stack capacitive hysteresis is achieved using backlash basis functions. The piezo model can also be used to predict the current usage of the PZT which depends on the slew rate of the voltage applied to the PZT. Data from laboratory experiments using a load frame and free response tests is used to estimate the PZT model parameters. In addition, a simplified model of a modulated full bridge strain gauge is derived based on test data which includes the effect of intrinsic bridge imbalance. Sensors of this type are often used with feedback control to linearize the behavior of the device. Taken together, the actuator and sensor model can be used for the development of piezo actuated control algorithms.

The Influence of Calcaneal and First Ray Osteotomies on the Contact Pressures of the Ankle Joint

Category: Ankle, Hindfoot Introduction/Purpose: Medial displacement calcaneal osteotomies (MDCO) and first ray plantarflexion osteotomies, such as a Cotton osteotomy, are frequently used realignment procedures for hindfoot and ankle joint valgus malalignment. Multiple studies demonstrated the effects of calcaneal osteotomies on the contact pressures of the ankle joint (CPAJ), with slight medial displacement of the center of pressure and lateral unloading of the ankle joint. However, the influence of a first ray plantarflexion osteotomy on the CPAJ is yet to be determined. In this cadaveric study we compared the effects of calcaneal and first ray osteotomies in the CPAJ. Methods: Fifteen bellow-knee cadaveric specimens were dissected to expose the ankle joint and isolate the flexor and peroneal tendons. Tekscan 5033 sensors were placed in the ankle joint and held in place with cyanoacrylate. Specimens were loaded in a servohydraulic load frame. The following loads were applied to the tendons: Achilles (200 N), PTT (40 N), peroneals combined (44 N), FHL/FDL combined (35 N). Ankles were tested in an intact position, after isolated MDCO (6, 8, 10 and 12 mm), isolated Cotton osteotomies (4, 8 and 12 mm) as well as combined osteotomies (10 mm and 12 mm, respectively). Specimens were then cyclically load from 100N-700 N at a rate of 0.5 Hz for 30 cycles while CPAJ data was collected at a rate of 20 Hz. Average and maximum pressure data were extracted as well as the center of pressure (CoP) movement in the AP and ML directions. Results: There was a significant (p<0.05) and progressive decrease in respective maximum and average contact pressures of the ankle joint when comparing intact ankle (1608 and 1312kPa), calcaneal osteotomy (1291 and 1034 kPa), Cotton osteotomy (1165 and 962 kPa) and combined osteotomies (1134 and 903 kPa). Cotton osteotomy and combined osteotomies showed similar contact pressures. Regarding CoP measurements of the ankle joint, native ankle and MDCO demonstrated similar positionings in the sagittal and coronal planes. Cotton and combined osteotomies caused a significant shift of the CoP anteriorly and laterally when compared respectively to the intact/MDCO and MDCO ankles. Conclusion: The results of this study demonstrate that the Cotton osteotomy has a greater effect on the contact pressures of the ankle when compared to the MDCO. There is an overall decrease in the maximum and average pressures as well as a deviation of the center of pressure toward the anterior and lateral aspect of the ankle joint. These findings should guide surgeons when deciding between first ray and calcaneal osteotomies as realignment procedures for hindfoot and ankle valgus deformities.

Investigation of a deadweight force standard machine with a 1 mN – 10 N range

<p>A 10 N small force standard machine with air-bearing support has been developed by NIM. Differing from traditional deadweight force standard machines, this machine is equipped with a balance beam supported by air bearing. The weights of the load frame and deadweight hanging system are balanced, and the initial force is extended to 1 mN. Furthermore, there are innovative designs in the load frame and tension force joint. Performance experiments such as sensitivity, repeatability, and rotation effect are carried out. The uncertainty of this machine is evaluated as 1.0×10^-4 (<em>k</em> = 2) in the range of 1 mN – 0.5 N, 4.0 × 10^-5 (<em>k</em> = 2) in the range of 0.5 N – 10 N. The structure of this force standard machine and its key components are introduced in detail. The performance experimental results and uncertainty evaluation are demonstrated in this paper.</p>

The Middle and Distal Aspects of the Ulnar Footprint of the Medial Ulnar Collateral Ligament of the Elbow Do Not Provide Significant Resistance to Valgus Stress: A Biomechanical Study

Background: The medial ulnar collateral ligament (UCL) insertion of the elbow has been shown to extend distally beyond the sublime tubercle. The contribution to valgus stability of the distal aspect of the footprint is unknown. Purpose/Hypothesis: The purpose of this study was to determine the contribution of each part of the UCL footprint to the elbow valgus stability provided by the UCL. It was hypothesized that the distal two-thirds of the ulnar UCL footprint would not contribute significantly to valgus stability provided by the UCL. Study Design: Descriptive laboratory study. Methods: Fifteen cadaveric arms were dissected to the capsuloligamentous elbow structures and potted. A servohydraulic load frame was used to place 5 N·m of valgus stress on the intact elbow at 30°, 60°, 90°, and 120° of flexion. The UCL insertional footprint was measured and divided into thirds (proximal, middle, and distal). One-third of the UCL footprint was elevated off the bone (leaving the ligament in continuity), and the elbow was retested at the same degrees of flexion. This was repeated until the entire UCL footprint on the ulna was sectioned. Each elbow was randomized for how the UCL would be sectioned (sectioning the proximal, then middle, and then distal third or sectioning the distal, then middle, and then proximal third). Ulnohumeral joint gapping (millimeters) was recorded with a 3-dimensional motion capture system using physical and virtual markers. Two-group comparisons were made between each sectioned status versus the intact condition for each flexion angle. Results: When the UCL was sectioned from distal to proximal, none of the ligaments failed prior to complete sectioning. When the UCL was sectioned from proximal to distal, 3 of the 6 ligaments failed after sectioning of the proximal third, while 2 more failed after the proximal and middle thirds were sectioned. Of the specimens with the distal third of the ligament sectioned first, no significant differences were found between intact, distal third cut, and distal plus middle thirds cut at all flexion angles. Conclusion: The middle and distal thirds of the insertional footprint of the UCL on the ulna did not significantly contribute to gap resistance at 5 N·m of valgus load. The proximal third of the footprint is the primary resistor of valgus load. Clinical Relevance: This cadaveric biomechanical study demonstrated that the middle and distal thirds of the native UCL insertion onto the ulna did not significantly contribute to valgus resistance at the elbow. When a UCL reconstruction is performed, the proximal third of the UCL insertion may be the most clinically important portion of the ligament to reconstruct.

Kuat Tarik Sambungan Bambu Celah Berpengisi Dengan Alat Sambung Baut Pada Berbagai Variasi Jarak Ujung

Kekuatan sambungan bambu salah satunya ditentukan oleh jarak ujung alat sambung. Jarak ujung alat sambung sangat penting untuk diperhatikan pada sambungan bambu dengan baut karena bambu yang berbentuk tubular dan mempunyai gaya geser sejajar serat yang rendah. Kendala tersebut dapat diatasi dengan memberi pengisi disekitar lubang sambungan. Namun demikian, efektifitas dari bambu berpengisi yang diberi celah untuk menempatkan pelat buhul pada sambungan perlu dikaji lebih lanjut. Tujuan dari penelitian ini adalah untuk mengetahui kuat tarik sambungan bamboo celah berpengisi dengan alat sambung baut pada berbagai variasi jarak ujung dan mengetahui pola kegagalan sambungan. Lima variasi benda uji dibuat dengan jarak ujung masing-masing sebesar 50 mm, 60 mm, 70 mm, 80 mm dan 90 mm. Pengujian benda uji dilakukan pada load frame dan pembebanan diberikan secara bertahap melalui hydaulic jack sampai terjadi kegagalan. Hasil pengujian menunjukkan bahwa kuat tarik sambungan meningkat seiring dengan meningkatnya jarak ujung alat sambung. Kuat tarik maksimum yang dihasilkan pada variasi jarak ujung50 mm, 60 mm, 70 mm, 80 mm dan 90 mm berturut-turut sebesar 1997, 352 Kg, 2124, 36 Kg, 2336, 04 Kg, 2381, 4 Kg, dan 2411, 64 Kg dengan prosentase kenaikan berkisar sebesar 6%, 17%, 19%, dan 21%. Pola kegagalan yang terjadi pada seluruh benda uji relatif sama yaitu baut tertekuk atau patah.