Full-Scale Test and Analysis of a PRSEUS Fuselage Panel to Assess Damage-Containment Features

Stitched composite technology has the potential to substantially decrease structural weight through enhanced damage containment capabilities. The most recent generation of stitched composite technology, the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept, has been shown to successfully arrest damage at the sub-component level through tension testing of a three stringer panel with damage in the form of a two-bay notch. In a joint effort undertaken by the National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), and the Boeing Company, further studies are being conducted to characterize the damage containment features of the PRSEUS concept. A full-scale residual strength test will be performed on a fuselage panel to determine if the load capacity will meet strength, deformation, and damage tolerance requirements. A curved panel was designed, fabricated, and prepared for residual strength testing. A pre-test Finite Element Model (FEM) was developed using design allowables from previous test programs to predict test panel deformation characteristics and margins of safety. Three phases of testing with increasing damage severity include: (1) as manufactured; (2) barely visible impact damage (BVID) and visible impact damage (VID); and (3) discrete source damage (DSD) where the panel will be loaded to catastrophic failure. This paper presents the background information, test plan, and experimental procedure. This paper is the first of several future articles reporting the test preparations, results, and analysis conducted in the test program

Baseline new bone formation does not predict bone loss in ankylosing spondylitis as assessed by quantitative computed tomography (QCT) - 10-year follow-up

<p>Abstract</p> <p>Background</p> <p>To evaluate the relationship between bone loss and new bone formation in ankylosing spondylitis (AS) using 10-year X-ray, dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT) follow-up.</p> <p>Methods</p> <p>Fifteen AS patients free from medical conditions and drugs affecting bone metabolism underwent X-ray, DXA and QCT in 1999 and 2009.</p> <p>Results</p> <p>In spine QCT a statistically significant (p = 0,001) decrease of trabecular bone mineral content (BMC) was observed (change ± SD: 18.0 ± 7.3 mg/cm³). In contrast, spine DXA revealed a significant increase of bone mineral density (change ± SD: -0.15 ± 0.14 g/cm²). The mean BMC, both at baseline and follow-up was significantly lower (p = 0.02 and p = 0.005, respectively) in advanced radiological group as compared to early radiological group. However, in multiple regression model after adjustment for baseline BMC, the baseline radiological scoring did not influence the progression of bone loss as assessed with QCT (p = 0.22, p for BMC*X-ray syndesmophyte scoring interaction = 0.65, p for ANOVA-based X-ray syndesmophyte scoring*time interaction = 0.39). Baseline BMC was the only significant determinant of 10-year BMC change, to date the longest QCT follow-up data in AS.</p> <p>Conclusions</p> <p>In AS patients who were not using antiosteoporotic therapy spine trabecular bone density evaluated by QCT decreased over 10-year follow-up and was not related to baseline radiological severity of spine involvement.</p

Torque ripple analysis in brushless DC motor with skewed magnets

The paper examine the prediction of cogging torque and electromagnetic torque in a brushless dc motor with a skewed magnet structure. The skew can readily be accounted for in a 3-D finite element (FE) model. This requires creation of a three-dimensional model with a fine mesh. I.e. a more workable alternative is to use two-dimensional multi-slice FE modeling, which comprises several cross-sections along the machine's shaft, so that each slice is a 2-D magnetic field problem. Additionally the influence of a segmented magnet rotor on the electromagnetic and cogging torque is investigated. In this case three-dimensional computations are used. The multi-slice FE model with skewed magnets and a segmented magnet rotor are used to compute cogging torque by the virtual work method. The FE simulations have been carried out with a multi-slice model comprising 5 slices and with a segmented magnet rotor comprising 2-3 segments. Using optimal magnet skew angle for a multi-slice model it has been shown that cogging torque can be reduced to 95% compared to a prototype (un-skewed motor) with the same average torque

Analysis of the integral parameters in the small power 3-phase slotless axial flux generator with double rotor core

Design of axial-flux generators with magnets is a part of on-going energy storage research project for wind energy applications. In this paper axial flux 3-phases small power generator with magnets and double rotor has been analysed. Presented machine consist slotless stator core which is made of lamination. Electromagnetic requirements of the electric machine were achieved by doing three-dimensional finite element analyses. A three- dimensional analysis was necessary by nature of arrangement coils such as end-winding effect. The main goal of electromagnetic field investigation was achieve high enough induced rectifier DC voltage from three phase winding and high efficiency

Torque ripple reduction by using multi-slice Fe modelling of brushless DC motor with skewed magnets

The intention of this paper is to look at multi-slice two-dimensional finite element modeling of a brushless DC motor with and without magnet skew. The results obtained are compared with experimental measurements on a typical machine without skew structure of the magnet. A standard approach to reducing cogging torque is to skew the magnet structure with respect to the rotor. Alternatively, the stator core can be skewed as well. This paper will consider the case of magnet skew only. From the finite element analysis (FEA) results, it shows that the brushless DC motor with 10° magnet skew angle with 5 slices had better performance than the motor with different values of skew angle. Additionally the difference between a physical machine with un-skewed magnets and a model of skewed magnet machine are shown

Vibrations of stator structure of BLDC motor due to magnetic sources

Vibrations and acoustic noise are some of the fundamental problems in the design and exploitation of rotating electrical machines. The aim of this paper is to use finite element multi-physical model – electromagnetic and mechanic – in order to predict the forced vibrations due to Maxwell forces in stator structure of BLDC. In aim of verification numeric calculations experimental measurements was made by sensors measuring radial component of acceleration in selected point. A vibration prediction model for the BLDC motor is constructed in this paper, the model is verified be experiments, with acceptable accuracy