Porosity in composites is a critical manufacturing defect that leads to a reduction of mechanical performance. Non-destructive testing (NDT) techniques are used to inspect composites after manufacture to identify defects and to help assess their impact on mechanical performance. Micro X-ray computed tomography is a promising NDT technique which provides information about pore location, size and morphology. To identify and characterise voids, an image 'segmentation' must be applied to the full CT dataset, which is simply a rule-based decision about whether a voxel is inside a pore or not. This work uses a simple model to analyse and compare the effectiveness of previously accepted threshold methods for segmentation across a range of material and porosity parameters. A new CT-segmentation thresholding method is proposed and evaluated for characterising voids in a wider range of composites.The sources of uncertainties are investigated and recommendations are made to minimise these uncertainties.
To investigate and evaluate the effect of void features on the mechanical performance of composite materials, it is important to be able to manufacture samples with a range of controlled void content. A criterion of less than 2% of porosity is typically acceptable for industry. However, it is important to investigate the effect of void content above and below this range, as voids are typically unevenly distributed in composite parts, and so there are likely to be local void concentrations higher than 2% in some sections of the structures. In this paper, a novel manufacturing process that allows panels with a range of void contents to be manufactured in a controlled manner is introduced. This allowed an investigation of the effect of manufacturing parameters, such as time, pressure and temperature and material systems on the void content and morphology of the voids in specimens produced.
In the submitted scientific work, the existing types of stator fastening design of turbogenerators and the main causes of the stressed state of the stator suspensions are considered. A detailed calculation of the complex stressed state of the turbogenerator stator suspension was carried out for a number of electrical sheet steels, taking into consideration the unevenness of the heat distribution along the horizontal axis of the unit. It is proposed that the calculation of the mechanical stress is carried out by means of the mechanical and thermal calculation, coordinated with the electrical one. The possibility of replacing steel 38Х2Н2ВА with steel 34CrNiMo6 and 40NiCrMo7 is indicated, subject to compliance with GOST 8479-70 for the same strength group.
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