Papers by Keyword: Strain

Abstract: In this article four samples of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ were prepared and irradiated with different doses of gamma radiation 6, 8 and 10 Mrad. The effects of gamma irradiation on structure of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ samples were characterized using X-ray diffraction. It was concluded that there effect on structure by gamma irradiation. Scherrer, crystallization, and Williamson equations were applied based on the X-ray diffraction diagram and for all gamma doses, to calculate crystal size, strain, and degree of crystallinity. It is observed through the results that gamma irradiation causes a change in the atomic density, crystal size, strain, degree of crystallinity and thus a change in the diffraction angle and intensity peaks. It was found that the highest crystal size was 69.3269 nm at 4MRad dose, crystallization is 69.3269 at 4MRad and the strain is 0.0068 when sample without radiation.

Abstract: In this manuscript, the effect of substituting strontium with barium on the structural properties of Tl_0.8Ni_0.2Sr_2-xBr_xCa₂Cu₃O_9-δ compound with x= 0, 0.2, 0.4, have been studied. Samples were prepared using solid state reaction technique, suitable oxides alternatives of Pb₂O₃, CaO, BaO and CuO with 99.99% purity as raw materials and then mixed. They were prepared in the form of discs with a diameter of 1.5 cm and a thickness of (0.2-0.3) cm under pressures 7 tons / cm², and the samples were sintered at a constant temperature of 860 ° C. The structural properties were studied using X-ray diffraction for all samples, and the results showed that the samples have tetragonal structure and the change of the parameters structure with the change of the barium concentration. Full Width Half Maximum (FWHM) was calculated by Orange Pro using X-RAY data. The crystal size was calculated using Scherrer and Willeamson-Heall methods, where the results showed that the crystal size, compliance and degree of crystallinity changed with the change of barium concentration, and the highest average for the crystal size was 70.0271nm at x=0, and crystallization at 61.46% at x=0.6, and the strain decreased to 0.0037 when barium concentration equals 0.4.

Abstract: The scheme of non-equal channel angular pressing (non-ECAP) of a magnesium billet has been analyzed. The modeling was performed by DEFORM-2D software. A high level of strain is shown to be achieved during non-ECAP. It leads to more homogenous structure refinement of magnesium and plasticity improvement that could favorably affect the subsequent deformation of a Mg-strip by cold rolling. At non-ECAP-process, the upper part of the strip is noted to be hardened more than the lower one. The lower part is supposed to be formed by extensional strain mainly, meanwhile for the upper one, the prime mechanism is likely to be shear strain. Based on hardness measurement of the samples cut from the obtained Mg-strip, conclusions have been made about the influence of the accumulated strain during non-ECAP on the strength properties of the strip.

Abstract: This study aims to analyze the stress that occurred on the automotive coil spring made of SAE 5160 carbon steel due to various types of road surfaces. The 60-second strain signals measured on a coil spring of a car being driven on a flat, uphill, and downhill road surface were used as the loads in these dynamic analyses. The analysis results showed that the maximum stress occurred on the inside of the spring in the second coil from the top. The results of this dynamic analysis also showed that the three types of road surfaces provided almost the same stress. The downhill road surface gave the highest stress, which was 0.622 GPa, followed by flat road (0.621 GPa) and uphill road (0.62 GPa). The reasons for this are the shifting of the vehicle load to the front wheels together with the braking effect when driving downhill.

Abstract: In this paper, the structural strain of the beam shear stress sensor is optimized, and the average strain of the strain sensor is simulated by Ansys Workbench. Firstly, the mathematic model of the beam sensor is established, and the stress and strain of the model are analyzed theoretically. Secondly, the finite element modeling of the sensor is carried out, and the finite element simulation of Ansys Workbench is carried out. The key dimensions of strain measurement are studied by parameter driven. Then the simulation results show that the effect of the production patch error on the output is quantitatively analyzed. Finally, the feasibility of mathematical model theory and finite element simulation is verified by calibration experiment.

Abstract: Composite over-wrapped pressure vessel (COPV) with ultra-thin metal liner and high strength carbon fiber reinforced plastic (CFRP) structure was widely used in space system. Meanwhile, there are some difficulties in the calculation of COPV stress-strain state related to the elastic-plastic liner and elastic composite. In this paper a novel design theory was proposed for calculating stress distribution in the bi-material COPV and determining the optimal thickness parameters of COPV based on traditional grid theory optimization. This new theory named Parameters Correspondence Relationship Structure Design Method (PCRSDM) can increase the design precision and structure performance factor of COPV compared to traditional grid theory. The correct models of mechanical characteristic between liner and CFRP are established from the view of optimized grid theory, the present theory is useful to develop a theoretical framework to calculate and design the COPV double shells. The COPV stress-strain behavior is also systemically studied by the ANSYS finite element analysis (FEA), the results show good agreement between FEA simulation and PCRSDM calculation. Both FEA and PCRSDM can meet the design requirements of COPV. A complete design, development and qualification testing of a specialized COPV used to satellite propulsion system was successfully conducted to verify the COPV design in terms of PCRSDM and FEA, the result show that PCRSDM is suitable for the design of COPV.

Abstract: The measurement of the modulus of elasticity is a technologically demanding test and its correct implementation has a fundamental effect on the resulting measured value. The main influences that may affect the proper performance of the test include, for example, the shape and size of the test specimen, the method of obtaining the test specimen, the method of adjustment of contact area between specimen and hydraulic equipment, but also the eccentricity of the specimen in the test apparatus. The paper presents the results of an experiment focused on the influence of the eccentricity of the test specimen and the observance of standard measurement conditions. The standard determines the maximum strain difference on individual measuring sensors when the maximum test force is reached.

Abstract: Creep tests using a simple jig have been performed on 63 wt.% tin-37 wt.% lead solder wires of diameters 1 mm and 2 mm at room temperature (23°C). Coils containing 5 or 10 rings were allowed to creep under their own weight for 60 minutes. It was noted that for either of these diameter wires, the coil with 10 rings had significantly large vertical displacements as compared to those with 5 rings. In each particular coil, the highest vertical displacements were in the bottom rings. The overall maximum vertical displacement was 76.5 mm and this was in a bottom ring of the 2 mm diameter wire with 10 rings. However, in all cases, the amount of horizontal displacement was negligible. The bottom ring of the 2 mm diameter wire had the largest initial strain of 0.151 at 5 minutes and final strain of 0.546 at 60 minutes; this was in the coil with 10 rings. Although no consistent pattern in change between the initial and final diameters was noted for the rings in any coil even after 24 hours of creep, it was quite apparent that in a majority of cases a change in diameter occurred. The main factor responsible for the observed creep is attributed to the weight of the rings in the coils rather than capillary flow.

Abstract: This study aims to identify the effect of road surface to coil spring fatigue life using the strain-life approach. Strain signals were measured by attaching a strain gauge at the critical point of the component. The car was driven on a flat road, as well as uphill, and downhill paths. The results show that the downhill road provided the lowest fatigue life, of 1.5E+4 cycles to failure, which was 53 % lower than that of the uphill and 2,233 % lower than the flat road owing to the braking factor which resulted in a higher stress to the coil spring.

Abstract: The article is devoted to the testing of samples for tensile, namely the formation of the neck. The objective of the study is to establish the qualitative level of influence of the nature of the hardening curve of the material on the shape and size of the neck. By using computer simulation, testing of samples of the two test materials, selected so as to provide the possibility of direct comparisons, forming the necks of the same diameter in the minimum section and the section near the neck, is worked over. It is found that the nature of the hardening curve determines the shape and size of the neck, including the radius of its curvature. This makes it possible to recover the hardening curve for large values of the strain. At the same time, it is established that the equation of the forming neck is invariant to the nature of the hardening curve of the material.