AbstractFabric-reinforced cementitious matrix (FRCM) composites are a new class of materials used to repair and strengthen existing structures. Mechanical performance varies widely based on the type ...and volume of fibers, fabric architecture, mortar properties, and bond characteristics. Moreover, test setup and boundary conditions are of the utmost importance for their mechanical characterization because of the complex interaction between fabric and brittle matrix. Therefore, the challenge is to define characterization and acceptance criteria that are (1) suitable for a wide spectrum of existing FRCM systems, and (2) produce representative values for the design of strengthened members. In this paper, three FRCM systems comprising carbon, glass, and steel fabrics were tested in accordance with two different acceptance methods. One method, which has been developed and adopted in the United States, is based on tensile tests on FRCM coupons with a clevis-grip mechanism that allows slippage at the fabric–matrix interface and provides mechanical properties that are directly used for design. The other method, developed within RILEM TC 250-CSM, combines the results of clamping-grip tensile tests on bare textile specimens with those of FRCM-to-substrate shear bond tests to obtain mechanical properties accounting for a broad range of possible failure modes. The results provided by the two methods are discussed and compared in relation to FRCM field applications.
The strength and ductility of two tungsten products, developed for application in nuclear fusion environment, are studied before and after neutron irradiation using uniaxial tensile tests. The first ...product is a commercially pure tungsten, produced by AT&M company according to ITER specification, and the second one is reinforced with zirconium carbide (W–ZrC) particles. The addition of ZrC particles leads to a reduction of the ductile to brittle transition temperature (DBTT) in non-irradiated conditions down to 50–100 °C without loss of strength and of other attractive properties of tungsten.
The neutron irradiation was performed in the range 625–700 °C up to 1.125 dpa. The tests were performed to screen the shift of the DBTT as well as to characterize the evolution of the strength and ductility at the irradiation temperature. In addition, a series of interrupted tensile tests were performed in order to determine the variation of the yield strength as a function of temperature using an original single specimen test method.
The neutron irradiation causes the reduction of the total elongation of both tungsten products. The DBTT range, which was evaluated from the tensile test results, of W–ZrC lies in the 300–500 °C range (while it is ∼100 °C in non-irradiated state). The DBTT range of pure tungsten is between 400 and 575 °C i.e. higher than that of W–ZrC. The irradiation hardening, measured at ∼600 °C, which is close to the irradiation temperature, leads to an increase of the proof stress by a factor of two in both studied grades. Despite that the irradiation induced hardening, both products retain a total elongation of about 10% prior to fracture. W–ZrC exhibits a similar total elongation at 500 °C, thus maintaining a significant ductility resource, while pure W becomes brittle at 500 °C and below.
•Ductile-to-brittle transition was revealed by small punch and miniature tensile tests.•Miniature tensile tests demonstrated high consistency and repeatability.•An inverse method developed to ...determine the temperature-dependent mechanical properties.•Finite element modelling was carried out to predict damage evolution and fracture.
Small punch tensile (SPT) tests have been carried out for a CoNiCrAlY coating at room temperature (RT), 500 °C and 700 °C. Highly re-producible results have been obtained for SPT at 700 °C while the formation of early cracking at lower temperatures tends to compromise the repeatability of the tests. An alternative novel miniature specimen testing method has been developed and used for the miniature tensile tests of the CoNiCrAlY coating in the same temperature range. Good agreements have been achieved between the SPT and miniature tensile testing results regarding the ductile to brittle transition temperature (DBTT). Excellent repeatability has been achieved over the full range of the temperature for the miniature tensile tests. An inverse approach has been developed and used to extract the mechanical properties of the material from the miniature tensile tests, using a temperature-dependent Johnson-Cook model. Finite element (FE) modelling of the SPT tests, including damage evolution, has been carried out using the extracted material properties to give comparable predictions of the SPT testing results, such as the load-displacement curves and the approximate locations of the fracture failures.
The paper presents the results of testing the properties of HY 80 steel from the hull of a Kobben class 207 submarine after 60 years of operation in extreme sea conditions. Steels from the HY family ...in the post-war period were used to build American and German submarines. For the obtained fragment of steel from the hull of the Polish submarine ORP Jastrząb (ORP-Boat of the Republic of Poland), static tensile tests were performed on an MTS testing machine. Dynamic tensile tests were carried out on a rotary hammer for the strain rate in the range of 500~2000 s−1. Results: Based on the obtained results, the Johnson–Cook model and the failure parameters of HY 80 steel in terms of the finite element method (FEM) were developed. Conclusion: This model can be used to simulate fast-changing processes such as resistance of structures to collisions, shelling, and the impact of pressure waves caused by explosions in water and air related to submarines.
Sprayed concrete is important construction material in tunnelling. Primary lining is essential in NATM where the sprayed concrete can be loaded by tension due to bending moments. The tension is ...common reason of failure because concrete has a relatively low tensile strength. The tensile strength is usually determined by splitting tensile test in laboratory. However, the results can be distorted because the specimen is not loaded by pure tension in this case. The paper compares results of concrete tensile strength determined by two methods: indirect by the splitting tensile test and direct by the modified tensile test.
Abstract
Tensile tests on fabric-reinforced cementitious matrix (FRCM) coupons are used to evaluate the tensile mechanical properties of the composite. Bond tests, typically single-lap shear tests, ...are used to characterize the interfacial properties between the FRCM composite and the substrate and to identify the interface at which debonding takes place. Some FRCM composites exhibit debonding at the fiber–matrix interface, which is characterized by a cohesive material law (CML) that can be obtained from bond tests. The authors have shown that for these composites, the CML can be fed into an analytical model to predict the results of tensile tests. In this paper, the same model is used to highlight some critical aspects of the clevis-grip tensile test. In particular, it will be shown that the length of the gripping devices, the length of the specimen, and the gauge length adopted to measure the deformation of the specimen have a strong influence on the results of the tensile tests. In addition, an analogy between the clevis-grip tensile test and single-lap shear test will point out that the tensile test is a bond test and can be used to determine the bond capacity rather than the tensile properties, which will be proven to be non-uniquely defined by this test.
Developing high temperature technology increases the need for high temperature resistant materials. Nimonic 80A alloy is generally preferred due to its high creep resistance, oxidation resistance and ...high resistance to high temperature corrosion. The study determines the tensile constitutive equation (JC parameters) of Nimonic 80 A superalloys. Johnson Cook (JC) model is preferred amongst the various material constitutive equations (Zerille Armstrong, Bordner Partom, JC model). Three different kinds of tensile experiment were performed to identify the model parameters. These are quasi-static tensile experiments applied at room temperatures. These experiments were carried out at 0.001, 0.01 and 0.1 s−1 strain rates. Therefore, the reference strain rate for all experiments was selected to be 10−3. As a second test, tensile experiments were conducted at room temperature at high strain rates (102–103 s−1) using the Split Hopkinson pressure bar (SHPB). Lastly, tensile experiments were conducted at high temperatures (300–900 °C) at 0.001 s−1. It was observed whether all tests are compatible with each other or not, and so five Johnson-Cook (JC) parameters of Nimonic 80 A alloy were identified via the data found from the experiments. After determination of parameters, tensile test simulations by finite element method (FEM) were performed in ANSYS Workbench. As a result, the accuracy of the JC parameters is verified since there is a deviation of %2.84 between the experimental and the simulation results.
•The material tensile constitutive model (Johnson-Cook) of Nimonic 80A superalloy.•Three different types of tensile tests to determine the tensile equation parameters.•The microstructural developments during the all tension tests.•The FE simulations of tensile tests by using JC parameters of Nimonic 80A alloy.•Verification of tensile JC parameters of Nimonic 80A superalloy.
The tensile properties of quartz fiber fabric-reinforced resin composites at high temperature were studied. The effects of specimen type and dimension, temperature loading procedure, holding time and ...loading rate on the tensile properties of the composites at high temperatures were analyzed through series of comparative experiments, the tensile test parameters were determined. Chinese national standard for high-temperature tensile property testing of the composites was compiled based on the data collected. According to the established standard, the tensile testing at 500°C was carried out. Compared with the tensile properties at room temperature, the tensile strength and tensile modulus of the composite at high temperature decreases significantly, with the tensile strength decreasing by about 42.32% and the tensile modulus decreasing by about 24.18%. This is mainly due to the high temperature which causes part of the resin matrix to pyrolyze and detach from around the fiber, thus losing the integrity of the material. In addition, this national standard for high-temperature tensile properties has some general applicability to different types of fiber-reinforced resin composites.
•A new UHPC grout-filled pipe sleeve with bolts is developed for large-diameter deformed bars.•21 specimens are tested to validate the feasibility and study the effect of design parameters.•The ...working mechanism of the pipe sleeve is investigated according to the test results.•The pipe sleeve can connect large-diameter deformed bars with an embedded length of 5db.•The existence of bolts can enhance bar-grout and grout-pipe wall bond strengths.
Grouted sleeve splice is a competitive alternative to reinforcement connections of accelerated bridge construction (ABC). When it is used to connect large-diameter deformed bars, overlong development length is required, although the decreased amount of connected bars and increased construction tolerance can accelerate construction speed. This paper aims to develop a novel ultra-high performance concrete (UHPC) grout-filled pipe sleeve with bolts for large-diameter deformed bars. It is expected to shorten the embedded length and delay grout crushing and splitting caused by bolts using UHPC's high material properties. A direct tensile test was conducted on 21 specimens to validate the feasibility, investigate the design parameters' effects, and explore the working mechanism of the pipe sleeve. Results show that the proposed pipe sleeve is feasible to connect large-diameter deformed bars with an embedded length of 5db. There are four failure modes including grout bond failure without/with bolts as well as bar bond failure without/with bolts in this test. UHPC without steel fiber is a preferred grout for the pipe sleeve because steel fiber can weaken grout fluidity and reduce bar-grout bond strength as well as grout-pipe bond strength. The existence of bolts can significantly enhance bar-grout bond strength as well as grout-pipe bond strength. The grout-pipe bond performance is sensitive to the depth of bolts in grout, amount of bolts, and distance of bolts to the end. When the pipe sleeve is used for deformed bars with higher strength, bearing capacity is slightly increased and deformation capacity is markedly weakened for bar-grout bond behavior. A greater cross dimension of the steel pipe is a good choice to avoid grout bond failure.
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