Calculated assessment of the impact of geometric deviations from the design on the parameters of mechanical safety of building metal structures within the framework of scientific and technical support for construction

An important part of scientific and technical support of civil engineering facilities at a construction stage - evaluation of influence of fluctuations from a designed geometry onto mechanical safety parameters of load-bearing metal structures - is considered. A multi-tier structure (industrial frame tower) is employed to demonstrate main features of such an assessment. Given is an approach to an analysis of as-built documentation and to a choice of most significant fluctuations of structural metal elements from a designed geometry. Effect of erection sequence being taken into consideration, the so-called genetic non-linearity, during computational estimation of a stress-strain state of metal structures mounted with deviations from their design positions is investigated. Results of static and dynamic analyses of designed and as-built (with geometry fluctuations taken into consideration) models of the multi-level industrial frame tower are obtained and compared with each other. Basing on these results, guidelines for computational assessment of effects of fluctuations from a designed geometry onto mechanical safety parameters of similar frame systems are formulated.

CONVECTION IN SCALED TURBINE INTERNAL COOLING PASSAGES WITH ADDITIVE MANUFACTURING ROUGHNESS

Additive manufacturing processes, such as direct metal laser sintering (DMLS), enable creation of novel turbine cooling internal passages and systems. However, the DMLS method produces a significant and unique surface roughness. Previous work in scaled passages analyzed pressure losses and friction factors associated with the rough surfaces, as well as investigated the velocity profiles and turbulent flow characteristics within the passage. In this study, the heat transfer characteristics of scaled additively manufactured surfaces were measured using infrared (IR) thermography. Roughness panels were CNC machined from plates of aluminum 6061 to create near isothermal roughness elements when heated. Fluid resistance differences between the aluminum roughness panels and roughness panels constructed from ABS plastic using the same roughness patterns from McClain et al. (2020) were investigated. Finally, the overall thermal performance enhancements and friction losses were assessed through calculation of surface averaged “global thermal performance” ratios. The global thermal performance characterizations indicate results in-line with those found for traditional commercial roughness and slightly below traditional internal passage convection enhancement methods such as swirl chambers, dimples, and ribs. The passages investigated in this study do not include compressibility effects or the long-wavelength artifacts and channel geometric deviations observed by Wildgoose et al. (2020). However, the results of this study indicate that, based on the roughness augmentation alone, artificial convective cooling enhancers such as turbulators or dimples may still be required for additively manufactured turbine component cooling.

Evaluation of geometric deviations in rapid prototyped phantoms created from medical imaging data (on the example of computed tomography)

Aim of study. To evaluate the geometric deviations associated with creation of physical objects from computed tomography data using computer-aided design and additive manufacturing. Materials and methods. The source object was created using the FreeCAD application; Blender and Meshmixer software was used for polygon meshes correction and transformation. 3D printing was carried out on an Ender-3 printer with copper-impregnated polylactide plastic BFCopper. Scanning was performed using a 128-slice tomograph Philips Ingenuity CT. A series of tomographic images were processed in 3DSlicer software, used to create virtual models by semiautomatic segmentation with threshold values ​​of 500 HU, 0 HU, -500 HU, -750 HU and manual segmentation. Reproduced and reference polygon meshes were compared using Iterative Closest Point algorithm in CloudCompare software. Results. Reproduced models volume exceeded the volume of respective reference models by 1-27%. The average point cloud linear deviation values of reproduced models from the reference ones were 0.03-0.41 mm. A significant correlation between integral sums of linear deviations and changes in the volume of reproduced models was shown using Spearman's rank correlation coefficient ( = 0.83; temp = 5.27, significance level p = 0.05). Conclusion. The geometry of the reproduced object changes inevitably, while the linear deviations depend more on the chosen segmentation method rather than on the overall size of the model or its structures. Manual segmentation method can lead to greater linear deviations, though it allows to save all the necessary structures.

The Off-Line Simulation on Measuring through Software PC-DMIS CAD++ V4.3

The article analyses and evaluates the ever-important topic of assessing geometric deviation of tolerated formations related to bases with the usage of coordinate measuring machines. The basic system for off-line simulation consists of the coordinate planes of a component’s coordinate system. At the beginning of the measurement, the coordinate system is created by the “3–2–1“alignment. Due to production deviations in real surfaces of the component, each measurement generates mutually different coordinate systems, which is well proven by the experiment on measuring with a coordinate measuring machine DEA Global Performance 12.22.10. An integral part of the article is also the quantification of geometric deviations of ideal tolerated formations related to bases, the estimate of the uncertainty of measurement arising from the placement of points in defining the base system, and the effect of such uncertainty upon the interval of satisfactory values in conformity with the STN EN ISO 14253-1 technical standard. The article also includes a proposal measure in order to ensure the reproducibility of defining the mutual position of coordinate systems.

CONTROL APPROACHES FOR TEMPERING MACHINE TOOL FRAMES WITH MULTIPLE FLUID CHANNELS AND LIMITED, JOINTLY USED ACTUATING VARIABLE

Nowadays, the thermo-energetic design of a machine tool also includes the thermal stabilization of its machine components. In the past, thermal stability was irrefutable connected to minimizing the temperature gradient of machine tools by air conditioning the entire machine or even the factory hall. Today, thermal stability also defines minimal inhomogeneities in the temperature field of the machine tool due to higher energy efficiency requirements. Fluidic tempering systems of machine components offer considerable potential concerning the minimization of thermo-elastic displacements with acceptable energy demand. Hence, intelligent algorithms are required to combine tolerable geometric deviations with minimal energy effort. The scope of this paper is the integration of a demand-oriented fluidic temperature control system into a machine bed. The resulting multi-input-multi-output (MIMO) systems and varying boundary conditions are challenges, which are addressed. Therefore the paper compares two control approaches, a decentralized single-loop control and a multi-loop control by decoupling the control loops and especially focus on the distribution of the jointly used actuating variable, combined with the variation of different boundary conditions.

Convection in Scaled Turbine Internal Cooling Passages With Additive Manufacturing Roughness

Additive manufacturing processes, such as direct metal laser sintering (DMLS), enable creation of novel turbine cooling internal passages and systems. However, the DMLS method produces a significant and unique surface roughness. Previous work in scaled passages analyzed pressure losses and friction factors associated with the rough surfaces, as well as investigated the velocity profiles and turbulent flow characteristics within the passage. In this study, the heat transfer characteristics of scaled additively manufactured surfaces were measured using infrared (IR) thermography. Roughness panels were CNC machined from plates of aluminum 6061 to create near isothermal roughness elements when heated. Fluid resistance differences between the aluminum roughness panels and roughness panels constructed from ABS plastic using the same roughness patterns from McClain et al. (2020) were investigated. Finally, the overall thermal performance enhancements and friction losses were assessed through calculation of surface averaged “global thermal performance” ratios. The global thermal performance characterizations indicate results in-line with those found for traditional commercial roughness and slightly below traditional internal passage convection enhancement methods such as swirl chambers, dimples, and ribs. The passages investigated in this study do not include compressibility effects or the long-wavelength artifacts and channel geometric deviations observed by Wildgoose et al. (2020). However, the results of this study indicate that, based on the roughness augmentation alone, artificial convective cooling enhancers such as turbulators or dimples may still be required for additively manufactured turbine component cooling.