Types Of Test Specimens Research Articles

Simplified test method for evaluating progressive collapse resistance of precast concrete frame structures

To evaluate the progressive collapse resistance of precast concrete (PC) structures, various test methods have been used in existing experimental studies. However, verification of whether the progressive collapse resistance can be evaluated equivalently by different test methods has been limitedly investigated. In this study, three simplified and three half-frame test specimens were tested under monotonic vertical loading to investigate the effects of the test method on their progressive collapse resistance. As the test parameters, types of test specimens (i.e., sub-frame, simplified, and half-frame specimens), and joint details (i.e., reinforced concrete (RC) continuous joint, PC with continuous joint, and PC with pinned joint) were directly compared. The test results showed that the progressive collapse resistance was primarily affected by the overall lateral stiffness of the exterior columns (Kh) rather than the test setup. When Kh increased in the simplified specimens, the axial force transferred by the beams increased, resulting in an increase in the peak strength (PCAA). Further, the effect of Kh on the peak strength was greater in PC specimens with pinned joints than in RC and PC specimens with continuous joints. To investigate the effect of Kh on the PCAA, a parametric study was conducted using the existing CAA strength model. The parametric study results also indicated that the relationship between the increase in Kh and PCAA was not significantly governed by the test setup for the same joint details. These results indicated that various simplified test methods can be used to evaluate the progressive collapse resistance of PC structures when an adequate range of Kh is provided. Based on the test and parametric study results, recommendations for progressive collapse tests were discussed.

Comparison of Quality of Porous Structure Specimens Produced by Different Additive Technologies and from Different Materials

Lattice and gyroid structures are often subjected to additive technologies to produce various types of products, and the current market has a number of 3D printers that can be used for their production. The quality of the products produced in this way can be assessed on the basis of technical parameters and the filament used. Such an approach, however, is insufficient. In terms of quality, other product parameters need to be assessed, such as the surface texture and the internal structure’s porosity. For such an assessment, we can use the industrial tomography method and the method of roughness measurement via an optical microscope. The paper presents research on the assessment of the surface texture and porosity in lattice and gyroid structures. For the research, two types of test specimens—a specimen with a lattice structure and a specimen with a gyroid structure—were prepared. The obtained results proved that the 3D printing technology directly impacted the surface texture and porosity. For experimental specimens produced by SLS technology, we found that it was very important to carefully remove the excess powder, as unremoved powder can significantly affect the porosity results. For specimens produced by FDM technology, the research confirmed that some “gaps” between the layers were not pores but defects created during specimen production. When analyzing the surface using the Alicon Infinite G5 optical microscope, we found that the measured roughness results were directly impacted by the specimen’s surface color, the structure’s geometry, and the ambient light, which was confirmed by a red lattice experimental specimen, the surface of which could not be scanned. Based on the above, it can be stated that the selection of 3D technology for additive production needs must be given adequate attention regarding the quality of the created structures and textures.

Universal PCR for bacteria, mycobacteria, and fungi: a 10-year retrospective review of clinical indications and patient outcomes.

Our work provides a retrospective analysis of universal PCR orders for bacteria, mycobacteria, and fungi across our institution across a 10-year period. We assessed the positivity rates for this diagnostic tool by test type and specimen type and, critically, studied whether and how the results influenced the outcomes from treatment change, to readmission, to death.

Volume changes measurement of elastomers using 3D DIC

The presented research aims at measuring the volume changes of elastomers using digital image correlation (DIC) in the 3D configuration (stereo DIC). The deformation measurement method in stereo configuration was applied during the mechanical testing of two types of test specimens (dumbbells, cylinders) in uniaxial tension. In this configuration, two cameras were used. The test specimens were measured up to a specified strain value, and the measured data were used to obtain the strain dependence of Poisson’s ratio and the bulk modulus, which are crucial for hyperelastic models. The measurement results reveal that the stereo DIC method provides relatively less scattered data in the low-strain regions for dumbbell-shaped test specimens and is suitable for measuring various test specimen shapes.

Estimation Method for Residual Sodium Amount on Unloaded Dummy Fuel Assembly

This study has researched an estimation method for the amounts of residual sodium film and sodium lumps on dummy fuel pins in the Japanese prototype fast breeder reactor Monju by fundamental experiments and demonstration experiments. The residual sodium amounts on the pin surface were measured using three types of test specimens: (a) single pin, (b) 7-pin assembly, and (c) 169-pin assembly. The single pin and 7-pin assembly experiments revealed that the withdrawal speed of the pins and improvement of the sodium wetting drastically increased the residual sodium amounts. Furthermore, the 169-pin assembly experiments measured the practical amounts of the residual sodium in the Monju dummy fuel assembly and demonstrated sodium draining behavior through small gaps between the pins. The estimation method includes four models such as a viscosity flow model, Landau-Levich-Derjaguin (LLD) model, an empirical equation related to the Bretherton model, and a capillary force model in a tube. These calculation results were comparable to the residual sodium amounts obtained by the experiments. In the tests of improving sodium wetting, the amounts of residual sodium on the test specimen were close to 1.4 times larger than those of the thin sodium film estimated by the LLD model. The increased amount of residual sodium by improving the sodium wetting was explained by the ratio of the adhesion energy ( γ S O − γ S L ).

Predicting Failure of Additively Manufactured Specimens with Holes

Experimental and computational studies were conducted to predict failure loads of specimens containing different-sized holes made using the additive manufacturing (AM) technique. Two different types of test specimens were prepared. Flat specimens, manufactured from polylactic acid (PLA), were subjected to uniaxial loading. Tubular specimens, made of polycarbonate (PC), were subjected to combined loading that was applied using uniaxial testing equipment. Test specimens were uniquely designed and printed to apply the combined bending and torsional loads to tubular specimens. A newly developed failure theory was applied to predict the loads that would result in the fracture of these test specimens. This theory is composed of two conditions related to stress and the stress gradient to be simultaneously satisfied to predict failure. The failure loads predicted using the new failure criteria were compared closely with the experimental data for all test specimens. In addition, a semi-empirical equation was developed to predict the critical failure surface energy for different printing angles. The critical failure surface energy is a material property and is used for the stress gradient condition. Using the semi-empirically determined values for the failure criterion provided close agreement with experimental results.

Effect of Aviation Turbine Fuel Exposure on Interlaminar and Inplane Shear Properties of Glass Fiber Reinforced Epoxy Composite

This study investigated the effect of aviation turbine fuel exposure on interlaminar and in-plane shear properties of E-glass/epoxy composite. The two types of test specimens, namely bare and resin-coated specimens with varying thicknesses as per the ASTM standard, were made out of E-glass/epoxy composite to evaluate their interlaminar and in-plane shear properties. These all types of specimens were immersed inside the aviation turbine fuel for two months and then afterward their effect on the reduction of mechanical properties like interlaminar and in-plane shear tests properties were experimentally investigated. Test results show that ATF fuel exposure has reduced the interlaminar shear strength by 10.04 %, 7.83 %, and 6.01 % for bare, with 0.1 mm and 0.2 mm resin coating, respectively. Similarly, in-plane shear strength was reduced by 14.75 %, 11.22 %, and 7.52 % for bare, with 0.1 mm and 0.2 mm resin coating, respectively, and in-plane shear modulus was reduced by 10.87 %, 8.94 %, and 6.52 % for bare, with 0.1 mm and 0.2 mm resin coating conditions as compared to as-received (without ATF exposure) specimens.SEM micrographs and results too showed that properties were reduced and indicated that the glass/epoxycomposite was resistive to fuel ingression. It was observed that bare specimens exhibited a reduction in shearproperties due to ATF ingression to the polymeric network and induced internal stresses, which not only degraded the matrix and fiber-matrix adherence but created micro-cracks too in the resin at interfaces. Resin-coated specimens limit fuel ingression, which has led to a reduction in properties.

Perilaku Lentur Komposit Beton dan Aspal dengan Kandungan Buton Granular Asphalt (BGA)

This study aims to analyze the behavior of asphalt concrete composites with the addition of Granular Asphal Buton in the asphalt layer as a surface layer on the concrete. The method used in this study was an experimental method with three types of test specimens. Type I of subgrade, Type II of subgrade added to concrete slabs and Type III of subgrade plus concrete asphalt coated plates + BGA 8.5% The results showed Type I reached a peak load of 45.48 kN. Type II reaches a peak load of 142.44 kN. And type III The use of AC-WC + BGA 8.5% concrete layers as surface layers is able to withstand monotonic loads reaching 214.747 kN. The effect of the use of concrete and asphalt layers containing BGA on the subgrade increases the strength of the structure and reduces the stress that occurs in the soil.

Load-Carrying Capacity of Double-Shear Bolted Connections with Slotted-In Steel Plates in Squared and Round Timber Based on the Experimental Testing, European Yield Model, and Linear Elastic Fracture Mechanics

Nowadays, the use of timber as a building material is gaining more prominence. When designing timber structures, it is necessary to pay increased attention to the design of their connections. The commonly used connections are dowel-type connections, which are often used in combination with steel plates slotted into cut-outs in timber members. The presented paper deals with the behavior of double-shear bolted connections of squared timber and round timber with slotted-in steel plates. Several variants of connections with different distances between the fastener and the loaded end were selected for the experimental testing. A total of six types of test specimens were made from spruce timber, for which their selected physical properties were determined and evaluated before the experimental testing. Test specimens of bolted connections were first tested in tension parallel to the grain until failure under quasi-static loading. The connections were broken by splitting. Ductile failure preceded brittle failure. The actual load-carrying capacities were lowest for the lowest end distance. The load-carrying capacities for the middle and the longest end distances were comparable. The results of the experiments were then used for comparison with calculation procedures according to the standard for the design of timber structures and with calculations according to the theory of linear elastic fracture mechanics. The experiments and the analytical models were supported by a simple numerical analysis based on the finite element method.

Tensile behavior of newly developed undercut anchor in cracked and uncracked concrete

The authors have been designing a post-installed anchor that fixes itself into concrete material by expanding the anchor tip in an upward direction, and conducted tensile loading tests to confirm its fundamental dynamic characteristics. The test results on three types of test specimens, with anchor morphology as a parameter, indicate that the final failure modes were all anchor bar fractures, and a stable yield strength was confirmed. Additionally, the yield strength characteristics of the proposed anchor in cases where cracks are present on the concrete surface, wherein the anchors are fixed, were experimentally confirmed.

Design and validation of mixed-mode device for fracture toughness analysis of adhesive joints

In real applications, adhesive joints are subjected to mixed mode I+II loading. The tests developed for mixed-mode loading are complex but considered highly relevant for fracture characterization. There are several mixed-mode tests, of which the Mixed-Mode Bending (MMB) test stands out for its capacity to allow the variation of the mixed-mode ratio practically without limitations. However, although there are several proposals for MMB test device configurations, this test is still considered complex, and some of the current solutions do not allow performing the test on stiffer materials. In this work, the main objective is to design, numerically model and experimentally validate an MMB test equipment to perform structural adhesive tests. Experimentally, it is intended to design and manufacture the MMB test equipment, and subsequently carry out the respective tests. The end result should be an equipment that enables obtaining various mixed-mode combinations, using a single equipment and the same type of test specimen, for further application in the design of adhesively-bonded joints. The equipment was validated by fabricating and testing adhesive joints, although further validation should contemplate estimating the mixed-mode behaviour of adhesive joints and comparing it with literature data.

Study on the effect of annealing on the mechanical properties of nanocrystalline nickel thin films based on X-ray profile analysis

Four types of test specimens of nanocrystalline nickel thin films were prepared: As-deposited material without annealing, and specimens annealed at 473K, 523K, and 573K, respectively. Tensile and fatigue tests were conducted on each specimen, and stress-strain curves and S-N diagrams were created. The effect of annealing on the mechanical properties was investigated based on the difference in crystal structure analyzed from profiles obtained from synchrotron radiation X-rays.

Crack growth simulation in thin plate using simplified strain based damage model

In this study, a simple strain based damage model is applied to simulate the ductile crack growth in thin 590 MPa class steel plates with notch and hole. The model depends only on the stress triaxiality and has two parameters. Determination of two parameters is straightforward by analyzing the tensile test results of flat plate specimen and plate specimen with sharp notches. The determined damage model is then applied to simulate the crack growth in other two types of test specimens containing plates with hole and notch, and a good agreement between the simulated and experimental results is obtained. It is found that the simulation results are primarily affected by the in-plane element size in the crack growth direction. On the other hand, the out-of-plane element size does not affect simulation results. It is found that the use of an in-plane element size of 0.1 mm or less is appropriate.

Analysis on the value of stiffness of the dual joint straightness notch joint of beams due to cyclic lateral load

Precast concrete is an answer to the demands of building structures that save time, but cannot be used widely because of the reliability of the connection, especially during an earthquake, the desired earthquake-resistant building structure must have sufficient strength and rigidity. Stiffness is one of the factors that determine the response of a structure to earthquake loads. When connected with earthquake loads, a structure must have sufficient rigidity so that its movement during an earthquake can be limited. This study aims to determine and analyze the stiffness in the double columns straight joint beam notches due to lateral cyclic load. By dividing 3 (three) types of test specimens, namely Monolithic column Beam, Type 1 Column Joint (SBK), and Type 2 Column Beam Joint (SBK). The connection used is a double straight notch and using the grouting method. Testing and analysis using the Displacement Control Method with the European Convention for Constructional Steelwork (ECCS) 1986 standards. The results showed the monolith column Column (BK) specimens have a greater stiffness value compared to SBK 1 specimens and SBK 2 specimens.

Influence of the Method of Production of Test Specimens on the Result of the Frost Resistance Test of Concrete

The paper deals with a comparison and interpretation of results of frost resistance tests of concrete specimens taken from a structure and test specimens produced in a laboratory using plastic moulds. A concrete block had to be produced for the experiment to simulate a real structure. The concrete used for the production of this block was also used in a laboratory to produce the test specimens. Core samples were drilled out from the concrete block and were subsequently used to make sets of core specimens. The test specimens, which differed in size, shape and the production method in particular, were subjected to frost resistance tests. The output of the paper is both a comparison of the results obtained on individual types of test specimens and a recommendation on how to approach the determination of frost resistance of concrete in a structure.

Comparison of safety margin in LBB design of nuclear pipes based on various types of fracture resistance test specimens

The geometry of cracked pipe, loading condition and crack size all can have a strong effect on its resistance against crack-tip plastic deformation and crack growth. Usually, specimens listed in test standards (e.g. CT specimen) are applied to evaluate the fracture resistance (J-R) curves, which may cause excessive safety margin in leak-before-break (LBB) design of nuclear pipes. In this study, standard (CT) specimen and constraint designed specimens, including curved CT and compact pipe (CP) specimens were applied to measure the J-R curves of nuclear pipes. Finite element analysis (FEA) was applied to derive J-equations to calculate J-R curves for newly designed specimens. Constraint effects in these specimens and full-scale pipes under various loading conditions were compared according to crack-tip plastic deformation level. Then, safety margins in LBB design using these specimens were quantitatively analyzed by constructing the critical crack length lines. Both the tests and FEA results verified the validity of these constraint designed specimens for reducing conservatism.

A constraint correction method based on use of a single test specimen

Commonly, fracture toughness tests on deeply cracked specimens are used to assess defects in large-scale components. The paper presents a method for selection of test specimen type, size and crack length in order to obtain fracture toughness estimates relevant to defects in cracked pipes. The method uses available closed-form T-stress, stress intensity factor and limit load solutions to determine the required specimen dimensions. The paper reports elastic–plastic finite element analyses for single edge notched bend (SENB) and single edge notched tension (SENT) specimens and cracked pipes which demonstrate good agreement of the matching approach, although care is needed in selecting the appropriate limit load solution for SENT geometries.

SARS-CoV-2 Testing Service Preferences of Adults in the United States: Discrete Choice Experiment.

BackgroundAscertaining preferences for SARS-CoV-2 testing and incorporating findings into the design and implementation of strategies for delivering testing services may enhance testing uptake and engagement, a prerequisite to reducing onward transmission.ObjectiveThis study aims to determine important drivers of decisions to obtain a SARS-CoV-2 test in the context of increasing community transmission.MethodsWe used a discrete choice experiment to assess preferences for SARS-CoV-2 test type, specimen type, testing venue, and results turnaround time. Participants (n=4793) from the US national longitudinal Communities, Households and SARS-CoV-2 Epidemiology (CHASING) COVID Cohort Study completed our online survey from July 30 to September 8, 2020. We estimated the relative importance of testing method attributes and part-worth utilities of attribute levels, and simulated the uptake of an optimized testing scenario relative to the current typical testing scenario of polymerase chain reaction (PCR) via nasopharyngeal swab in a provider’s office or urgent care clinic with results in >5 days.ResultsTest result turnaround time had the highest relative importance (30.4%), followed by test type (28.3%), specimen type (26.2%), and venue (15.0%). In simulations, immediate or same-day test results, both PCR and serology, or oral specimens substantially increased testing uptake over the current typical testing option. Simulated uptake of a hypothetical testing scenario of PCR and serology via a saliva sample at a pharmacy with same-day results was 97.7%, compared to 0.6% for the current typical testing scenario, with 1.8% opting for no test.ConclusionsTesting strategies that offer both PCR and serology with noninvasive methods and rapid turnaround time would likely have the most uptake and engagement among residents in communities with increasing community transmission of SARS-CoV-2.

Experimental method and evaluation for interlaminar shear properties of randomly oriented strand thermoplastic composites based on modified double-notch specimen and two dimensional digital image correlation

A new interlaminar shear test method has been proposed based on the double-notch compression test method, in which the test specimen shape with a modified overlap length of the notches is proposed, and the interlaminar shear strain is measured by two-dimensional digital image correlation (2D-DIC) analysis. In order to obtain the interlaminar shear properties in the elastic and non-linear regions of randomly oriented strand thermoplastic composites, we adopted a 2D-DIC analysis system using a bi-telecentric lens, which can accurately measure the strain in a small field of view, and a test system including an interlaminar shear test jig, which can apply a compressive load to the end face of the specimen at high perpendicularity. It is necessary to provide an overlap of the double-notch of 1 mm or more in order to simultaneously obtain the strain in the elastic region and the non-linear region from the actual test results. When numerical analysis by finite element method (FEM) was carried out on four types of test specimen with different shapes used in this research, by using the interlaminar shear property data obtained from actual tests on the optimum test specimen, there was a high level of agreement with the 2D-DIC analysis results for the shear stress – strain diagrams and the interlaminar shear strain distribution. Therefore, the benefits of the test specimen shape and dimensions in the new test method and the validity of the interlaminar shear property values that can be obtained using this method have been confirmed.

The influence of aircraft fluid ingression on tensile properties of aramid fiber composites

Aramid fiber composites that are used in aircraft can be exposed to various fluids from inside and outside the aircraft during maintenance and flight operations. This article investigates how the aircraft fluid affected the tensile properties, including ultimate tensile strength, tensile modulus, and strain at break of aramid fiber composites. Two different types of aramid fiber composite test specimens were prepared; Kevlar® laminate (para-aramid) and Nomex® paper (meta-aramid). The test specimens were soaked in four different types of aircraft fluid, jet fuel, engine oil, hydraulic fluid, and water and tested to measure their tensile properties. The influence of fluid ingression on the test specimens was analyzed by comparing the test data of each fluid group to the control group. Digital image correlation (DIC) was used during the tensile test for strain calculation and better understanding of local strain change during the test. The test results showed that the test specimens soaked in hydraulic fluid and water had an evidence of tensile property change.