Papers by Keyword: Strain Gauges

Abstract: Residual stress is one of the main reasons for failure of automotive cylinder blocks and engine heads. These failures are typically associated with in-service distortion or cracking occurring in engines during operation cycles. The problem becomes more pronounced for engines that are running at elevated operating pressures and temperatures, limiting R&D options in developing and implementing higher-efficiency engines. New aluminum alloys and manufacturing methods have been introduced with varying degree of success, in many cases affected by the stress magnitudes and stress distribution in the component. Therefore, active research is ongoing internationally on finding the most reliable methods of stress analysis as a basis for developing efficient methods for stress mitigation. The current study presents a comparison between two experimental strain measurements techniques: a destructive method that is based on application of strain gauge sensors, and a non-destructive method using neutron diffraction. The results indicate that although the strain gauge method provides an indication of the nature (i.e. compression or tension) of strain within a component, this method should primarily be used for surface measurements and qualitative analyses only. Neutron diffraction remains the superior technique for strain analysis, particularly for engineering components with complex geometries. The results from this study provide the transportation industry with a more comprehensive understanding of the efficacy of utilizing strain gauge sensors, neutron diffraction or finite element modelling for measuring the residual strain in cast components. The results will help manufacturers to develop the next generation of powertrain systems with increased efficiency and improved performance.

Abstract: A reasonably accurate, low-cost system for the monitoring of strains in simple physical models within the field of Structural Engineering, based on Internet of Things, is presented, calibrated and discussed. The system only requires average, economic devices as Arduino microcontroller and strain gauges. Several tests on a case study of a scaled-cantilevered aluminium beam with different loading are conducted. Governing parameters are calibrated aimed at an optimization when benchmarked against theoretical and experimental results obtained with a reference device. Results show great accuracy; however, the need of setting of the parameters campaign-by-campaign, especially aimed at dealing with thermal drift, becomes a shortcoming. Still, its minimum cost and user-friendly management makes it a suitable solution for different applications.

Abstract: The paper is devoted to the study of the nonlinearity of the output signal of the pressure sensor on the silicon on sapphire structure (SOS). The authors constructed a mathematical model of the strain-gauge and carried out numerical simulation by using the ANSYS 12.1 software. For comparative analysis, the problem was solved both in a geometrically nonlinear and in a geometrically linear formulation. To account for the elastic-plastic properties of the silver solder PSR72, the Prandtl diagram was used. As a result, the maximum stresses and deformations in the sapphire crystal, solder, and titanium membrane under which the design successfully works were determined, and also the nonlinearity of the output signal was estimated in depending of the applied pressure. According to calculations, the nonlinearity of the output signal is 11.3%. The received value is unacceptable for this type of sensor, and requires further tuning, which negatively affects the accuracy of the product and its cost.

Abstract: Conventional strain gauges made of constantan or CuCr for instance have a low value for structural health monitoring issues in plastic composites. These strain sensor materials exhibit small elastic regions and show fatigue when dynamically loaded with strain levels over 0.3 percent. For this reason, these sensors would break or fail before the composite life-time and thus cannot be integrated into this kind of composite materials. Pseudoelastic thermal shape memory alloys are therefore used as strain sensors and integrated into composites in order to allow piezoresistive strain measurement and structural health monitoring in such materials. Thermal treatments are used to create sensor structures out of shape memory alloy wires. Pseudoelastic shape memory wires can be strained up to 8 percent repeatedly. Their gauge factor is higher than 5. Shape memory strain sensors are successfully embedded into glass fibre reinforced plastics and show a significant and reproducible resistance change when the composite is strained. The dynamic strength is magnificently higher compared to conventional strain gauges. Shape memory strain sensors are an efficient alternative to fiber-bragg-grating sensors and can potentially be used for strain measurements in different plastics and textile materials. Shape memory sensor structures can be embedded or applied and are good candidates for structural characterisation and monitoring applications.

Abstract: Interaction analysis between foundation structure and subsoil and credential assessment of stress in the subsoil and internal forces in foundation structure are discussed in research conferences and scientific journals in the long term. Since 2012 research team at Faculty of civil engineering VSB - TU Ostrava has tested a few slabs with dimensions 2 x 2 m with thickness from 0.12 to 0.2 m. Complex testing comprises measurement of slab deformations, stress in the subsoil and measurement of stress in foundation slab using strain gauges. Slabs were made of plain concrete, reinforced concrete, pre-stressed concrete and fibre concrete. In the paper there are particular test results of stress measured in the foundation structure. Measured values are compared with calculated values. Strain gauge measurement efficiency and optimisation is discussed.

Abstract: The paper presents some results of experimental program focused on drying and shrinkage of large concrete specimens. Segments of walls with thicknesses 200, 400 and 800 mm and standard cylinders 150x300 mm were used as specimens. Each segment has embedded 4 vibrating wire strain gauges in axis plane for measurements of shrinkage strain and plastic tubes of various lengths for measurements of pore relative humidity in different depths. Relative humidity and temperature of ambient environment were not controlled, however they were recorded very closely. Measure shrinkage strains are compared with prediction based on shrinkage models. The most important predictive models are used for comparison: Model Code 2010, Eurokód 2, Model ACI 209-R92, Model B4 a Model B4s.

Abstract: This paper presents an investigation of possibilities of using regression analysis and genetic algorithms in modelling the cutting force values in cylindrical grinding. The process included measurement of cutting forces during cylindrical grinding and later calculating their values using abovementioned techniques. It was concluded that both techniques can be used for cutting forces modelling with genetic algorithms having a slight advantage.

Abstract: This article includes the brief analysis of the problems in area of long-time process loading measuring in service and also explains the processing of the measured strain state without re-calculation the strain into stress in detail and presents the results from the installed in-time monitoring system of the fatigue damage in a real operation of gas pipelines.

Abstract: The monitoring of stiffened composite panels behavior using resistance strain gauges (SG), fibre optic Bragg grating sensors (FOBG) and contactless optical measurements based on digital image correlation (DIC) principle is discussed in the paper. Both the panel structure and different load cases are specified. Mechanical tests include different load-scenarios like static and fatigue loading in compression of reference and impacted panels. The main reason of failure is buckling. The measurements taken from the sensors captured all changes in the buckling modes of the panel. Moreover, they showed a good correlation between FOBG and SG strain measurements.

Abstract: This paper is focused on determination of load sharing in planetary transmission during the test and usual operation. Load sharing is one of examined items in transmission. That is investigation of power flow uniformity through satellites in planetary transmission.