Set Of Static Tests Research Articles

Experimental validation of inertial twist concept for rotor blade application

The present study performs a set of static tests to demonstrate a novel passive morphing concept. The concept introduces a bend–twist coupled composite spar to rotor blades, allowing for twist morphing to be achieved by imposing a lagwise bending moment using centrifugal forces produced by a movable mass at the blade tip. First, three composite spars are fabricated using a symmetric layup configuration with varied ply orientations. A set of static tests are designed to replicate the effect of the centrifugal forces during rotation, where the detailed distribution of twist, deflection and strain are measured on each spar with varied loading conditions. The experimental results suggest that the blade twist can be well controlled by the position of the tip mass and rotational speed. It was also found the distribution of the twist is linear when the spar deflection is small, whereas a quadratic twist distribution was observed for a large tip deflection due to the induced lateral restoring forces. Furthermore, the influence of the ply angle upon the coupled twist is demonstrated from the experimental and numerical results.

Procedure of hydrogen and mixture impact assessment on the changes of mechanical parameters and errors of household gas meters

The article describes the method of conducting representative research to determine the effect of pure gaseous hydrogen and a mixture of hydrogen and natural gas (methane) on the performance and metrological characteristics of household gas meters. The experimental research has been carried out in two stages. 84 membrane and rotary meters have been selected for research. The main aspect of the need for such research is the safety of meters. Before the start of the tests and after each stage, the metrological characteristics of all gas meters on the reference prover are determined. At the first stage, a set of static tests is performed, according to which the internal and external short-term and long-term (42 days) tightness of gas meters are checked. A prototype of the installation layout has been developed to conduct experiments on determining the tightness. The second stage is to conduct a dynamic series of tests. Gas meters are assembled according to the developed scheme and installed for testing on the model of the gas distribution network system. It is recommended to use a drum-type meter as a reference gas meter. The criterion for determining the effect of hydrogen and gas meter is the established change in metrological characteristics after the study.

On the issue of ensuring reliability of reinforced concrete structures of “northern execution”

The work is devoted to the design justification of the required resource of bearing capacity of bent reinforced concrete elements of “northern execution” based on ensuring the required reliability at the time of exhaustion of the frost resistance of concrete. The dynamic model of functioning of structure in severe climatic conditions is considered as a set of static tests at individual stages of cyclic temperature and humidity effects (FTC) formed on the basis of corresponding experimental samples of strength and deformability of concrete. For the criterion for reliability of structure, it is taken the value of strength and deformability of concrete, at which its bearing capacity over a normal section has a probability of at least 99.7%. Using graphic-analytical modeling, limit (failure) values were established and correction of the normative dependency by introducing a differentiating coefficient of reliability, accounting for the level of reinforcement and design negative air temperature, was proposed. The technical and economic unreasonableness of excessive, more than 80% of the boundary, reinforcement of normal sections of bent reinforced concrete elements of “northern execution” is established.

Development of prestressed unbonded and bonded CFRP strengthening solutions for tensile metallic members

In this study, a novel unbonded mechanical clamping system was developed for the strengthening of tensile metallic members using prestressed carbon fiber reinforced polymer (CFRP) plates. The system clamps a pair of prestressed CFRP reinforcement to a metallic substrate and provides an almost uniform contact pressure over the CFRP plate along the anchorage length. A finite element simulation was used to optimize the design of the mechanical components of the system. Subsequently, a set of static and fatigue tests was performed to evaluate the performance of the optimized design. Experimental results revealed that the proposed mechanical clamping system is capable of transferring the entire tensile capacity of the CFRP plates to the steel substrate, even after experiencing 10 million fatigue cycles. The comparative performance of the developed clamps was further investigated by a set of static tests on steel plate specimens strengthened with the prestressed bonded reinforcement (PBR) and the newly developed prestressed unbonded reinforcement (PUR) systems. Furthermore, simple analytical models are proposed to formulate the stress state in prestressed unbonded and bonded CFRP-strengthened tensile metallic members. The accuracy of the proposed analytical formulations was verified by the experimental results obtained during the current study. Experimental results revealed that the efficacy of having relatively high prestressing forces in the normal modulus (NM) CFRP reinforcements is much higher than the stiffness improvement obtained by using ultra-high modulus (UHM) CFRPs. However, the available capacity of the PBR system before debonding failure is far lower than that of the developed PUR solution.

Detecção automática de cenários internos e externos utilizando mensagens NMEA de receptores GNSS

Detecção de cenários internos e externos é um importante recurso para diversos tipos de atividades como navegação multisensor e serviços baseados em localização. Esta pesquisa apresenta o uso de dados NMEA fornecidos por receptores GPS para caracterizar diferentes tipos de cenários automaticamente. Um conjunto de testes estáticos é realizado para avaliar métricas obtidas dos dados NMEA como quantidade de satélites, diluição da precisão e razão densidade sinal-ruído, com o objetivo de detectar possíveis padrões de comportamento que permitam determinar tipos de cenários de operação.

Tomographic examination of auxetic polyurethane foam structures

Polyurethane foams processed according to a hybrid mechanical–chemical–thermal (M–Ch–T) process developed at Air Force Institute of Technology (AFIT) have been tested to verify the inner structure deformation after the process. The X-ray microtomography of both the original EUROFOAM S28280 foam and the processed specimens allowed the creation of three-dimensional virtual models of tested specimens and enabled evaluation of homogeneity of foam structures. In order to examine variations in the processed material's inner structure, samples from different locations of the specimen were scanned. Moreover, a foam specimen was divided into nine subspecimens to perform a set of static tests on each of them separately and to check the gradient of properties throughout the sample volume. Presented methods allowed to visualize the inner structure of the processed foams as well as to estimate inhomogeneity. Obtained results will be used for optimization of the manufacturing process.

An experimental investigation of static and fatigue behaviour of sandwich composite panels joined by fasteners

Abstract An experimental investigation has been carried out to estimate the static and fatigue behaviour of specimens made up of steel plates and sandwich composite panels joined together by either blind or mechanical lock fasteners. A preliminary study was carried out in order to analyse the drilling operation of sandwich panels to determine the best values of parameters to use for fastener installation. A first set of pull-out and shear static tests was performed in 1992, using sandwich panels composed of a nomex honeycomb core between two laminates of glass/graphite/kevlar fibres in epoxy matrix. The investigation was completed in 1998. It consisted of performing a set of pull-out and shear fatigue tests on joints with blind fasteners, and of performing a new set of static tests on identical specimens with the same loading conditions as in 1992 so as to evaluate the possible ageing effect on mechanical proprieties of sandwich panels tested.

Test Set and Fault Partitioning Techniques for Static Test Sequence Compaction for Sequential Circuits

We propose a new static test set compaction method based on a careful examination of attributes of fault coverage curves. Our method is based on two key ideas: (1) fault-list and test-set partitioning, and (2) vector re-ordering. Typically, the first few vectors of a test set detect a large number of faults. The remaining vectors usually constitute a large fraction of the test set, but these vectors are included to detect relatively few hard faults. We show that significant compaction can still be achieved by partitioning faults into hard and easy faults, and compaction is performed only for the hard faults. This significantly reduces the computational cost for static test set compaction without affecting quality of compaction. The second key idea re-orders vectors in a test set by moving sequences that detect hard faults to the beginning of the test set. Fault simulation of the newly concatenated re-ordered test set results in the omission of several vectors so that the compact test set is smaller than the original test set. Experiments on several ISCAS 89 sequential benchmark circuits and large production circuits show that our compaction procedure yields significant test set reductions in low execution times.