Articles de revues : « Cyclic tests, push-over tests »

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Lin, S. S., C. H. Lai, C. H. Chen et T. S. Ueng. « Derivation of Cyclic p-y Curves From Instrumented Dynamic Lateral Load Tests ». Journal of Mechanics 26, n^o 2 (juin 2010) : 123–33. http://dx.doi.org/10.1017/s1727719100002987.

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AbstractIn this paper, an efficient method is proposed to derive cyclic p-y curves from either push-over or shaking table test results. The Fourier series function, satisfying the boundary conditions of a pile, is used to represent deflection behavior of the pile-soil system at each instant of time during loading interval. In order to obtain soil reaction along the pile shaft, convergence of the series after differentiation is guaranteed by applying the Cesaro sum technique. Results of four push-over tests and two other shaking table test results, conducted at the National Center for Research on Earthquake Engineering in Taiwan, are then used to verify the feasibility of the proposed method.

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Nezamian, Abolghasem, Riadh Al-Mahaidi et Paul Grundy. « Bond strength of concrete plugs embedded in tubular steel piles under cyclic loading ». Canadian Journal of Civil Engineering 33, n^o 2 (1 février 2006) : 111–25. http://dx.doi.org/10.1139/l05-091.

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Investigation of the load transfer of concrete plugs to tubular steel piles subjected to tension and compression and cyclic loading has been conducted at Monash University over the past 3 years. The work presented in this paper reports on the results of the combination of pull-out, push-out, and cyclic loading tests carried out on 15 steel tube specimens filled partially with reinforced concrete with variable lengths of embedment. The pull-out force was applied through steel reinforcing bars embedded in the concrete plug, and push-out forces were applied through a thick top circular plate on the top of the concrete plug. Test results included the cyclic loading, ultimate pull-out and push-out forces, slip of concrete plugs, and longitudinal and hoop strains along the piles for some specimens. The tests clearly showed that average bond strength significantly exceeds expectations and is higher than the results of previous investigations using plugs without reinforcement. The test results also indicated that cyclic loading tests reduced the bond strength due to the accumulation of damage to the plug–pile interface. The push-out and pull-out tests conducted under symmetric cyclic loading demonstrated that slip between the concrete plug and the steel tube increased with repeated loading, and the rate of slip growth increased with an increase in the peak load.Key words: tubular steel pile, reinforced concrete plug, bond, cyclic loading.

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Tokimasa, Katsuyuki. « Life Estimation of SUS304 Steel Subjected to Nonproportionally Combined Push-Pull and Cyclic Torsion at 973K ». Key Engineering Materials 345-346 (août 2007) : 323–26. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.323.

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The present paper summarizes the fully reversed strain-controlled creep-fatigue tests conducted on thin-walled tubular specimens of SUS304 austenitic stainless steel at 973K in air under push-pull, cyclic torsion, in-phase straining and 90deg out-of-phase straining of push-pull and cyclic torsion. It is shown that, as the results of analysis of the experimental data by the strain-range partitioning methodand the critical plane model parameter, a new inelastic-strain based parameter was proposed for life estimation of SUS304 subject to nonproportionally combined push-pull and cyclic torsion by the strain-range partitioning method.

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Vaško, A. « Fatigue Properties of Nodular Cast Iron at Low Frequency Cyclic Loading ». Archives of Metallurgy and Materials 62, n^o 4 (1 décembre 2017) : 2205–10. http://dx.doi.org/10.1515/amm-2017-0325.

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Abstract Three melts of ferrite-pearlitic nodular cast iron with different charge composition were used for fatigue tests. Wöhler fatigue curves and fatigue strength were obtained, and microstructure and fracture surfaces were investigated. The aim of the paper is to determine the influence of charge composition on microstructure, mechanical and fatigue properties of synthetic nodular cast irons and their micromechanisms of failure. Fatigue tests were realised at low frequency sinusoidal cyclic push-pull loading (stress ratio R = −1) at ambient temperature (T = 20 ±5°C). They were carried out with using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz. The results of fatigue tests at low frequency cyclic loading are compared with fatigue properties at high frequency cyclic loading.

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Fan, Jian Sheng, et Wen Liu. « Tests on Shear Studs Using Profiled Steel Sheeting Subjected to Cyclic Loading ». Applied Mechanics and Materials 578-579 (juillet 2014) : 196–200. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.196.

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Push-out tests were conducted to study the performance of shear studs in composite beams with profiled sheeting. All stud specimens were through-deck welded on steel beams. Three variables, i.e. the presence of profiled sheeting, the direction of the steel sheeting and the loading patterns were studied. Comparison between test results and predictions according to design specifications were also proposed. The research shows that, direction of the profiled steel sheeting has little influence on the ultimate load with shank shearing failure; shear failure of concrete rib decreases the shear strength; and the shear resistance of a parallel concrete rib is about twice of a transverse one.

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Itoh, Takamoto, Fumio Ogawa et Takahiro Morishita. « Fatigue Testing and Evaluation of Fatigue Strength under Multiaxial Stress State ; Why do we need fatigue testing ? » MATEC Web of Conferences 159 (2018) : 01050. http://dx.doi.org/10.1051/matecconf/201815901050.

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Types of multiaxial fatigue tests and their experimental results are presented in this paper. There are typical three types in multiaxial fatigue tests: the combining push-pull and reversed torsion loading test using hollow cylinder specimen, the biaxial tension-compression test using cruciform specimen and the inner pressure applied the push-pull loading test using the hollow cylinder specimen. In the combining a push-pull loading and a reversed torsion loading test, failure life under non-proportional loading in which principal directions of stress and strain were changed in a cycle was shortened compared to proportional loading in which those are fixed. Fatigue lives were well-correlated using a non-proportional strain range considering the effect of strain path and material dependence. In the biaxial tension-compression test, the failure life decreased with increase of the principal strain ratio. In the inner pressure applied the push-pull loading test, cyclic deformation behaviour due to complex loading paths of multiaxial fatigue tests with the inner pressure associated with push-pull and rev. torsion acted to reduce the failure lives. Experimental investigation of multiaxial failure life and elucidation of their governing mechanism is essential and it can broaden the applicability of structural components.

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Noster, Ulf, et Berthold Scholtes. « Isothermal strain-controlled quasi-static and cyclic deformation behavior of magnesium wrought alloy AZ31 ». International Journal of Materials Research 94, n^o 5 (1 mai 2003) : 559–63. http://dx.doi.org/10.1515/ijmr-2003-0098.

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Abstract The low-cycle and high-cycle fatigue behavior of the Mg-base wrought alloy AZ31 is investigated in the temperature range 20– 300 °C using total-strain-controlled push – pull tests. It is shown that the mechanical properties of the material are substantially influenced by the direction dependent formation of deformation twins and resulting deformation asymmetry. As a consequence tensile mean stresses develop during total-strain-controlled fatigue tests without mean strain.

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Valente, Marco. « Steel-Concrete Bond Deterioration under Repeated Loading for Different Confinement Levels ». Applied Mechanics and Materials 217-219 (novembre 2012) : 188–91. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.188.

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This paper presents the results of experimental tests and numerical analyses concerning the influence of repeated cyclic loading and reinforcement confinement on bond between steel rebar and concrete. Experimental tests of push-pull type were carried out at the Politecnico di Milano on concrete specimens provided with a steel cage of longitudinal bars and stirrups, and reinforced with a single steel rebar. The experimental tests were conducted under monotonic and repeated loading history. Bond strength degradation was observed due to repeated cyclic loading. Detailed three-dimensional finite element models of the specimens were developed to reproduce laboratory tests and parametric analyses were performed to provide a better understanding of the experimental results. The numerical analyses showed good agreement with the experimental results and confirmed that the applied repeated loading history caused significant bond deterioration. High values of reinforcement confinement enhanced bond strength and delayed the onset of bond deterioration.

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Saito, Shunsuke, Fumio Ogawa et Takamoto Itoh. « Fatigue Life Properties of Stainless Steels in Wide Ranged Biaxial Stress State ». Key Engineering Materials 795 (mars 2019) : 60–65. http://dx.doi.org/10.4028/www.scientific.net/kem.795.60.

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Multiaxial fatigue tests consisting of push-pull loading and cyclic inner pressure were carried out using hollow cylinder specimens of type 430 stainless and type 316 stainless steels at room temperature. 7 types of cyclic loading paths were employed by combining axial and hoop stresses: a Pull, an Inner-pressure, a Push-pull, an Equi-biaxial, a Square-shape, a LT-shape and a LC-shape. Fatigue lives vary depending on the loading path when those were evaluated by the maximum Mises’ equivalent stress on inner surface of the specimen. The fatigue lives of both the steels showed a similar tendency although some Pull tests take longer fatigue life when cracks initiated from inside surface of the specimen. This study investigated the crack initiation and propagation behaviors as well as the initiation of oil leakage to prove the behavior and discusses life evaluation for two steels under wide ranged biaxial stress state, too.

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Vaško, Alan, Juraj Belan et Eva Tillová. « Study of the fatigue behaviour of synthetic nodular cast irons at low and high frequency cyclic loading ». MATEC Web of Conferences 157 (2018) : 07014. http://dx.doi.org/10.1051/matecconf/201815707014.

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The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. High frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both of them were carried out at sinusoidal cyclic push-pull loading (stress ratio R = -1) at ambient temperature (T ≈ 20 °C). The relationship σa = f (N) and fatigue strengths were determined experimentally; mechanical properties, microstructures and fracture surfaces were investigated.

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Siller, I., W. Waldhauser et R. Ebner. « Numerical modelling and physical simulation of the softening behaviour of hot work tool steels during thermal fatigue ». Journal de Physique IV 120 (décembre 2004) : 649–56. http://dx.doi.org/10.1051/jp4:2004120074.

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Fatigue due to thermal cycling is one of the main reasons for the damage of tools used in die casting processes. In order to investigate the thermal fatigue behaviour of tool steels a thermal fatigue testing facility was designed and built up. For better understanding of the mechanisms of thermal fatigue finite element-simulations were carried out. To specify the cyclic material behaviour push-pull-tests at different temperatures were performed. The Chaboche-model was used to describe the kinematic material response. Isotropic softening is also taken into account. Depending on the arising accumulated plastic strain stable cyclic deformation or continuous softening occurs. The results are consistent with the accomplished thermal fatigue tests on different hot work tool steels.

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Zhang, Jianwei, Zhengfa Li, Fan Wang, Saiyang Zhuo et Tao Wang. « Seismic Resilience Study of Piers Enhanced by Ultrahigh-Performance Concrete Jackets Based on Cyclic Loading Test and Static Push-Over Curves ». Science of Advanced Materials 14, n^o 11 (1 novembre 2022) : 1679–91. http://dx.doi.org/10.1166/sam.2022.4385.

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The efficiency of novel retrofitting of constructed reinforced concrete piers with ultra-high performance concrete (UHPC) jackets was investigated. Pier specimens were subjected to a series of cyclic quasi-static stress tests, whereby two tests employed UHPC jackets with a single width (UHPC-W), while the other two used UHPC jackets with several narrow widths (UHPC-N). The seismic responses were compared in terms of energy dissipation, ductility, hysteresis curves, and skeleton curves. The seismic capability of reinforced concrete piers is increased by both W-type and N-type UHPC jackets by reducing concrete damage. Reinforced concrete piers with a UHPC-W jacket offer greater lateral strength but are more vulnerable to plastic hinge movement. On the other hand, the UHPC-N jacket increases the ductility of concrete and conceals concrete damage. However, construction quality was critical to ensure tight contact between the multiple strips and the reinforced concrete shaft. Based on the implicit method, a 3D finite element model is recommended for nonlinear static elasticplastic analysis. The nonlinear reinforcement model, bond-slip behavior, and concrete damage plastic model are all included in the finite element model. In order to assess the seismic susceptibility of the retrofitted piers, various limit states were defined, and fragility curves unique to the particular structure were produced.

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Taklas, Mohamad, Moussa Leblouba, Samer Barakat et Zaid A. Al-Sadoon. « Concrete-to-concrete shear friction behavior under cyclic loading ». E3S Web of Conferences 347 (2022) : 01001. http://dx.doi.org/10.1051/e3sconf/202234701001.

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The main objective of this paper was to study the concrete-to-concrete shear friction behavior under cyclic loading and different test rates. Eight dynamic push-pull tests were performed on concrete specimens with as-cast surface roughness type applying four different test rates. The test results include the hysteresis loops of the friction force-displacement relations. It is concluded that the dynamic coefficient of friction decreased with the increased test rate. This reduction in the dynamic coefficient of friction should be considered in the design of structural elements under cyclic or dynamic loading.

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He, Xing, Junfeng Chen, Wei Tian, Yuebing Li et Weiya Jin. « Low Cycle Fatigue Behavior of Steam Generator Tubes under Axial Loading ». Materials 11, n^o 10 (11 octobre 2018) : 1944. http://dx.doi.org/10.3390/ma11101944.

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Compared with the fatigue properties of the material (Inconel Alloy 690), the real fatigue lives of tubes are more meaningful in the fatigue design and assessment of steam generator (SG) tube bundles. However, it is almost impossible to get a satisfactory result by conducting fatigue tests on the tube directly. A tube with a uniform and thin wall easily fails near the clamping ends under cyclic loading due to the stress concentration. In this research, a set-up for fatigue tests of real tubes is proposed to overcome the stress concentration. With the set-up, low cycle fatigue tests were conducted in accordance with an existing fatigue design curve for Alloy 690. Strain control mode was applied with fully reversed push–pull loading under different strain amplitudes (0.15%, 0.2%, 0.3%, and 0.4%). A favourable result was obtained, and the low cycle fatigue behavior was investigated. The results showed that the fatigue life tested by the real tube was below the strain–life curve of Alloy 690 which was fitted by conventional solid specimens. A cyclic hardening behavior was found by the cyclic stress–strain curve when compared with the monotonic stress–strain curve.

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Ali, Qaisar, Tom Schacher, Mohammad Ashraf, Bashir Alam, Akhtar Naeem, Naveed Ahmad et Muhammad Umar. « In-Plane Behavior of the Dhajji-Dewari Structural System (Wooden Braced Frame with Masonry Infill) ». Earthquake Spectra 28, n^o 3 (août 2012) : 835–58. http://dx.doi.org/10.1193/1.4000051.

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This paper presents experimental and numerical investigations conducted on typical dhajji buildings found in the northern mountainous areas of Kashmir and surrounding regions to evaluate their in-plane lateral load response. The experimental work included an in-plane quasistatic cyclic test on three full-scale walls as well as monotonic tension and bend tests on main connections. The test results show that the dhajji-dewari system of buildings possesses tremendous resilience against lateral forces. The function of connections, especially the connections between the vertical posts and bottom plate, control the performance of the system. The test results also indicate that although masonry infill does not contribute to lateral load capacity, it significantly increases the energy dissipation capacity of system. The data accrued from the tests has been used in nonlinear static push-over analysis of the numerical models to develop simplified analytical tools for facilitating lateral load performance evaluation of dhajji structures.

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Figueira, Diogo, Carlos Sousa, Rui Calçada et Afonso Serra Neves. « Push-Off Tests in the Study of Cyclic Behavior of Interfaces between Concretes Cast at Different Times ». Journal of Structural Engineering 142, n^o 1 (janvier 2016) : 04015101. http://dx.doi.org/10.1061/(asce)st.1943-541x.0001364.

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Moosburger-Will, Judith, Michael Greisel, Michael Schulz, Mario Löffler, Wolfgang M. Mueller et Siegfried Horn. « Investigation of the fiber-matrix interaction in carbon fiber-reinforced polyether ether ketone by cyclic single fiber push-out and push-back tests ». Composite Interfaces 27, n^o 2 (23 mai 2019) : 227–47. http://dx.doi.org/10.1080/09276440.2019.1620542.

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Šulák, Ivo, Karel Obrtlík, Ladislav Čelko et Pavel Gejdoš. « Degradation of YSZ/EUCOR TBC Coating System during High Temperature Low Cycle Fatigue Tests ». Solid State Phenomena 258 (décembre 2016) : 420–23. http://dx.doi.org/10.4028/www.scientific.net/ssp.258.420.

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Thermal barrier coatings are widely used to protect the substrate from high temperature and extremely aggressive environments in gas engines. In the present article, authors have been studied degradation of complex thermal barrier coating system deposited on polycrystalline nickel superalloy IN 713LC. The substrate material was grit blasted with alumina (Al2O3) particles prior to air plasma deposition of CoNiCrAlY bond coat. Top coat consists of conventional zirconia (ZrO2) stabilized by yttria (Y2O3) -YSZ ceramic in combination with a eutectic nanocrystalline ceramic Eucor made of zirconia (ZrO2), alumina (Al2O3) and silicia (SiO2) –in the ratio of 50/50 in wt. %. The top coat was deposited using water stabilized plasma. Test specimens with the TBC coating system were fatigued under strain control condition in fully reversed symmetrical push-pull cycles at 900°C in air. The microstructure of TBC was characterized with scanning electron microscopy and energy dispersion X-ray analysis. The coating hardness and thickness were measured. Fracture surface and polished sections parallel to the specimen axis were examined to study damage mechanisms in coatings under cyclic loading at high temperature. TBC delamination was observed at the top coat/bond coat interface after cyclic loading at high temperature. Fatigue crack initiation sites are documented. Majority of fatigue cracks start from the surface and top coat/bond coat interface.

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Klemenz, Manuel, Volker Schulze, Otmar Vöhringer et Detlef Löhe. « Finite Element Simulation of the Residual Stress States after Shot Peening ». Materials Science Forum 524-525 (septembre 2006) : 349–54. http://dx.doi.org/10.4028/www.scientific.net/msf.524-525.349.

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In a three-dimensional Finite-Element-Simulation of shot peening, a combined isotropickinematic viscoplastic material description was introduced in order to describe the cyclic softening effects during peening. After verifying the model in the simulation of push-pull tests at different strain amplitudes it could be used for the shot peening simulation. The simulated residual stress profile is compared with experimental results determined by X-ray diffraction and with simulated results of a simpler isotropic viscoplastic material model.

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Seracino, R., D. J. Oehlers et M. F. Yeo. « Behaviour of Stud Shear Connectors Subjected to Bi-Directional Cyclic Loading ». Advances in Structural Engineering 6, n^o 1 (janvier 2003) : 65–75. http://dx.doi.org/10.1260/136943303321625748.

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Almost all stud shear connectors in composite steel-concrete bridge beams are subjected to bi-directional cyclic loading at some stage during the fatigue life of the structure. In the assessment of an existing structure, it is desirable to predict the extent of fatigue damage experienced by the stud shear connectors as accurately as possible as this component of the structure can not be visually inspected. However, very little research has been carried out to quantify the fatigue behaviour of stud shear connectors subjected to bi-directional cyclic loading. This paper presents a new push-pull specimen that was developed to provide a better understanding of the bidirectional cyclic fatigue behaviour of stud shear connectors. The tests confirmed that for a given range of load, the fatigue life of connectors subjected to bi-directional cyclic loading is longer than those subjected to unidirectional loads only, and that the strength and stiffness of the connectors reduce immediately upon cyclic loading and continues to do so throughout the fatigue life. It was also shown that the rate of increase in slip per cycle is constant over most of the fatigue life with a rapid increase near the end so that, if monitored, can be used to provide adequate warning of failure.

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Prasad, Y. V. S. N., et S. Narasimha Rao. « Pullout behaviour of model pile and helical pile anchors Subjected to lateral cyclic loading ». Canadian Geotechnical Journal 31, n^o 1 (1 février 1994) : 110–19. http://dx.doi.org/10.1139/t94-012.

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This paper presents the effect of lateral cyclic loading on the pullout capacity of model and helical piles in clayey soil. The tests were conducted on short rigid model piles in the laboratory in three phases, namely lateral static load tests, lateral cyclic load tests, and vertical pullout tests. From the test results it was found that the lateral cyclic loading affects the pullout capacity of piles substantially. Reduction in pullout capacity mainly depends upon the lateral deflection of the pile during cyclic loading and the embedment ratio of the pile. This reduction in the pullout capacity of model piles is presented in terms of nondimensional parameters, viz., degradation factor, lateral deflection ratio, and embedment ratio of pile. However, in the case of helical piles under similar conditions, it was found that the lateral cyclic loading has very little influence on the pullout capacity. The reasons for the better performance of helical piles over ordinary piles are explained. Key words : clay, degradation factor, helical pile, lateral cyclic loading, lateral deflection, Joading level, pile, pullout capacity.

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Xu, Jun, Huahuai Sun, Weizhen Chen et Xuan Guo. « Experiment-Based Fatigue Behaviors and Damage Detection Study of Headed Shear Studs in Steel–Concrete Composite Beams ». Applied Sciences 11, n^o 18 (7 septembre 2021) : 8297. http://dx.doi.org/10.3390/app11188297.

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Many in-service bridges with steel–concrete composite beams are currently aging and experiencing performance deterioration. Under long-term cyclic loads from traffic on bridges, headed shear studs in steel–concrete composite beams are vulnerable to fatigue damage. The comprehensive understanding of fatigue behaviors and the feasible detection of fatigue damage of headed shear studs is, thus, crucial for the accurate numerical simulation of the fatigue crack propagation process. The paper, thus, experimentally investigates the fatigue behaviors of headed shear studs through push-out tests of three specimens. The fatigue failure modes and cyclic strain evolution of specimens are analyzed. The fatigue lives of headed shear studs are compared with the S–N curves of the AASHTO, Eurocode 4 and BS5400 codes. The fatigue crack details of shear studs in push-out tests are then detected using the ultrasonic non-destructive testing. The results show that the root fracture is the main fatigue failure mode of shear studs under fatigue loading. The fatigue life estimations based on the three current codes (i.e., AASHTO, Eurocode 4 and BS5400) can be safely guaranteed only with different safety redundancies. The strain at the shear stud with fatigue damage shows a consistent increasing trend followed by decreasing behavior after reaching the peak value with the loading cycles. Moreover, the feasibility of the ultrasonic non-destructive testing with the combination of a strain measurement for fatigue crack details detection of headed shear studs in composite beams is proved.

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Saito, Shunsuke, Fumio Ogawa et Takamoto Itoh. « Fatigue Life Properties of Stainless Steels in Wide Ranged Biaxial Stress States using a Hollow Cylinder Specimen ». MATEC Web of Conferences 300 (2019) : 09004. http://dx.doi.org/10.1051/matecconf/201930009004.

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Stress controlled multiaxial fatigue tests were carried out using hollow cylinder specimens of type 430 and 316 stainless steels at room temperature. A newly developed fatigue testing machine which can apply push-pull loading and inner pressure to the specimen was used. For inner pressure, oil was put inside of the specimen. 7 types of cyclic loading paths were employed by combining axial and hoop stresses; a Pull, an Inner-pressure, a Push-pull, an Equi-biaxial, a Square-shape, a LT-shape and a LC-shape. Fatigue lives vary depending on the loading path when those were evaluated by the maximum Mises’ equivalent stress range on inner surface of the specimen. The fatigue lives of both the steels showed a similar tendency. However, the following difference was identified. Specifically, differences in fatigue lives of type 430 stainless steel between the uniaxial loading and the multiaxial tests were large, while those of type 316 stainless steel were small. To discuss difference in fatigue life properties between both steels, this study investigates the effect of the shear stress range, mean stress and additional hardening and which leads to evaluate the lives suitably.

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Vaško, Alan, Libor Trško et Mária Chalupová. « Influence of Charge Composition on the Structure and Fatigue Properties of Nodular Cast Irons ». Materials Science Forum 782 (avril 2014) : 295–300. http://dx.doi.org/10.4028/www.scientific.net/msf.782.295.

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The contribution deals with comparison of microstructure and fatigue properties of synthetic nodular cast irons with a different ratio of steel scrap in a charge. Chemical composition of individual meltages was regulated alternatively by ferrosilicon (FeSi) and carburizer or metallurgical silicon carbide (SiC). The fatigue tests were run at high-frequency sinusoidal cyclic push-pull loading (frequency f 20 kHz, load ratio R = 1, temperature T = 20 ± 5 °C) using the ultrasonic testing equipment KAUP-ZU. The paper shows the influence of charge composition on microstructure, fatigue properties and micromechanisms of failure.

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Sasaki, Katsuhiko, Ken-ichi Ohguchi et Hiromasa Ishikawa. « Viscoplastic Deformation of 40 Pb/60Sn Solder Alloys—Experiments and Constitutive Modeling ». Journal of Electronic Packaging 123, n^o 4 (24 août 1999) : 379–87. http://dx.doi.org/10.1115/1.1371927.

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This study first proposes a simple constitutive model for viscoplasticity, which includes the elastic, plastic, and creep strains independently. The plastic strain is evaluated by the flow rule employing back stresses evolved with a Ziegler type of hardening rule. The creep strain is evaluated by the modified Norton’s law. The applicability of this constitutive model is evaluated with pure tensile tests, creep tests and cyclic tension-compression loading tests, to demonstrate the progress of viscoplastic deformation of 40Pb/60Sn solder alloys. The tests were conducted over both several temperature ranges and strain rates. As a result, it was found that the material constants used in the constitutive model could be determined by simple tests such as pure tensile and cyclic tension-compression loading tests. The simulation by the constitutive model explains accurately the viscoplastic deformation of the 40Pb/60Sn solder alloys.

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Meola, Carosena, Giovanni Maria Carlomagno, Carmela Bonavolontà et Massimo Valentino. « Monitoring Composites under Bending Tests with Infrared Thermography ». Advances in Optical Technologies 2012 (7 novembre 2012) : 1–7. http://dx.doi.org/10.1155/2012/720813.

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The attention of the present paper is focused on the use of an infrared imaging device to monitor the thermal response of composite materials under cyclic bending. Three types of composites are considered including an epoxy matrix reinforced with either carbon fibres (CFRP) or glass fibres (GFRP) and a hybrid composite involving glass fibres and aluminium layers (FRML). The specimen surface, under bending, displays temperature variations pursuing the load variations with cooling down under tension and warming up under compression; such temperature variations are in agreement with the bending moment. It has been observed that the amplitude of temperature variations over the specimen surface depends on the material characteristics. In particular, the presence of a defect inside the material affects the temperature distribution with deviation from the usual bending moment trend.

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Zhou, Z., D. J. White et C. D. O’Loughlin. « The changing strength of carbonate silt : parallel penetrometer and foundation tests with cyclic loading and reconsolidation periods ». Canadian Geotechnical Journal 57, n^o 11 (novembre 2020) : 1664–83. http://dx.doi.org/10.1139/cgj-2019-0066.

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This paper describes a centrifuge study using novel penetrometer tests (T-bar and piezoball) and model foundation tests to explore through-life changes in the strength of a reconstituted natural carbonate silt. The test procedures include episodic cyclic loading, which involves intervals of pore pressure dissipation between cyclic packets. These loads and the associated remoulding and reconsolidation cause significant changes in the soil strength and foundation capacity. Soil strength changes from penetrometer tests differed by a factor of 15 from the fully remoulded strength to a limiting upper value after long-term cyclic loading and reconsolidation. For the model foundation tests, the foundation capacity of a surface foundation and a deep-embedded plate were studied. The soil strength interpreted from the measured foundation capacity varied by a factor of up to three due to episodes of loading and consolidation, with an associated order of magnitude increase in the coefficient of consolidation. The results show a remarkable rise in soil strength over the loading events and provide a potential link between changes in soil strength observed in penetrometer tests and the capacity of foundations, allowing the effects of cyclic loading and consolidation to be predicted.

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Wang, Jian Jun, et Wei Guo Guo. « Pseudo-Elastic Behavior of NiTi SMA under the Quasi-Static and the Impact Cyclic Tests ». Advanced Materials Research 560-561 (août 2012) : 13–19. http://dx.doi.org/10.4028/www.scientific.net/amr.560-561.13.

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Abstract. To characterize the thermomechanical cyclic response, especially Pseudo-elastic behavior of NiTi shape-memory alloy (SMA) at different temperatures and different loading frequencies, a series of tests of both quasi-static and dynamic uniaxial compression cyclic loading have been performed on cylindrical samples, using an Instron servohydraulic testing machine and the Hopkinson technique. Transformation temperature, after dynamic loading is measured and compared with that of as-received state. The influence of the annealing temperature on the fatigue response is also examined. A few noteworthy conclusions are as follows: (1) Transformation temperature, can be changed under higher strain rates; (2) By changing the annealing temperature, the transformation stress and the dissipated energy of NiTi can also be obviously changed, so as it changes the transformation temperature, Af ;(3) In cyclic loading, the dissipated energy over cycles tends to be a minimum stable value, and it seems that cyclic loading leads to a stable Pseudo-elastic behavior of the alloy; (4) Repeated impact tests of the alloy produce slightly changes in the shape of the Pseudo-elastic loop and in the dissipated energy comparing with the quasi-static cyclic tests.

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Beck, Tilmann, Marcus Klein, Marek Smaga, Frank Balle et Dietmar Eifler. « Innovative Experimental Approaches and Physical Measurement Methods for Fatigue Monitoring and Life Assessment ». Materials Science Forum 879 (novembre 2016) : 205–10. http://dx.doi.org/10.4028/www.scientific.net/msf.879.205.

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The present contribution gives an overview on innovative methods to characterize cyclic deformation and lifetime behavior of metallic materials and hybrid joints based on high precision measurement of electrical resistance, temperature and magnetic properties during fatigue testing. General aim is to minimize the number of fatigue tests for reliable S-N curve calculation. Moreover, instrumented cyclic hardness tests allow short-time assessment of cyclic hardening in case of limited availability of test material. The methods are applied to a wide range of materials, from carbon steels, over cast iron and metastable austenitic steels to ultrasonically welded Al-alloy/polymer matrix composites.

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Leen, Sean B., Aditya A. Deshpande et Thomas H. Hyde. « Finite Element Modelling and Experimental Testing of Thermomechanical Behaviour and Failure of Titanium Superplastic Forming Dies ». Key Engineering Materials 433 (mars 2010) : 247–56. http://dx.doi.org/10.4028/www.scientific.net/kem.433.247.

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This paper describes high temperature cyclic and creep relaxation testing and modelling of a high nickel-chromium material (XN40F) for application to life prediction of superplastic forming (SPF) tools. An experimental test programme to (i) characterise the high temperature cyclic elastic-plastic-creep behaviour of the material over a range of temperatures between 20oC and 900oC, including cyclic controlled strain-range tests at different strain-rates and creep relaxation tests, and (ii) identify the material constants relevant to thermo-mechanical fatigue (TMF) life prediction, is described. The objective of the material testing is the development of high temperature material and failure models for cyclic analyses and life prediction of SPF and diffusion bonding (DB) dies for titanium aerospace components.

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Gladskyi, Maksym, Kateryna Barandych, Volodymyr Frolov et Serhii Yurenko. « INFLUENCE OF STRESS CONCENTRATION ON STEEL DEFORMATION 20 UNDER CYCLIC LOADS ». Technical Sciences and Technologies, n^o 1(27) (2022) : 60–66. http://dx.doi.org/10.25140/2411-5363-2022-1(27)-60-66.

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The effect of stress concentration on fatigue behavior of steel 20 is studied. Experimental study is carried out on tubular smooth and notched specimens under uniaxial cyclic loading and alternating torsion. Load and strain controlled fatigue tests were carried out at room temperature using servohydraulic machine with independent control of push-pull and torsion loads with frequency of 0.5-3 Hz. One basic geometry for two different types of specimens shown in Figure 1 with 1.1 mm wall thickness, 22 mm inside diameter, and 40 mm gauge length was used in this work. One type was a tubular smooth thin-walled specimens, the other type was the same thin-walled specimen with 3.4 mm circular through-thickness hole at the middle of gauge length. The 5% load drop for uniaxial strain control tests and 5% strain and rotation angle increment for uniaxial and torsion load control tests respectively, as compared to midlife stable cycle for smooth specimens were considered as a small crack initiation life. The criterion of maximum principal stress was used as a control parameter of the test program. Torque loading was accompanied by a significant decrease in durability compared to uniaxial loading due to conservative methodology. Although maximum principal stress criterion could correlate axial and torsion constant amplitude data of notched specimens with a factor of 4, it could not correlate axial with torsion data of smooth specimens. It is found that the prediction of fatigue life can be successfully performed according to the shear form of Fatemi-Soci criterion by taking into account the mechanism of destruction of samples. The shear strain-life curve was generated based on von Mises criterion. The FS parameter was associated with local stress-strain condition based on FE analysis results.

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Šulák, Ivo, Karel Obrtlík et Ladislav Čelko. « Comparative Study of Microstructure and High Temperature Low Cycle Fatigue Behaviour of Nickel Base Superalloys Inconel 713LC and MAR-M247 ». Key Engineering Materials 713 (septembre 2016) : 86–89. http://dx.doi.org/10.4028/www.scientific.net/kem.713.86.

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The present work is focused on the study of microstructure and low cycle fatigue behavior of the first generation nickel-base superalloy IN 713LC (low carbon) and its promising second generation successor MAR-M247 HIP (hot isostatic pressing) at 900 °C. Microstructure of both alloys was studied by means of scanning electron microscopy (SEM). The microstructure of both materials is characterized by dendritic grains, carbides and casting defects. Size and morphology of precipitates and casting defects were evaluated. Fractographic observations have been made with the aim to reveal the fatigue crack initiation place and relation to the casting defects and material microstructure. Low cycle fatigue tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of both materials were obtained. Cyclic stress-strain curve of MAR M247 is shifted approximately to 120 MPa higher stress amplitudes in comparison with IN 713LC. Significantly higher fatigue life of MAR-M247 has been observed in Basquin representation. On the other hand IN 713LC shows prolonged lifetime compared with MAR-M247 in the Coffin-Manson representation. Results obtained from high temperature low cycle fatigue tests are discussed.

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Jen, Ming Hwa, Che Kai Chang, Yi Chun Sung et Feng Chi Hsu. « Manufacturing and Mechanical Responses of Ti/APC-2 Nanocomposite Cross-Ply and Quasi-Isotropic Laminates at Elevated Temperature ». Advanced Materials Research 150-151 (octobre 2010) : 796–99. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.796.

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Both Ti/APC-2 cross-ply and quasi-isotropic nanocomposite laminates were successfully fabricated. Basically, the tensile tests at elevated temperature were conducted to obtain the baseline data of mechanical properties, such as strength and stiffness. The results for both types of laminates of longitudinal stiffness predicted by the rule of mixtures (ROM) were in good agreement with experimental data, whilst, those ultimate strength predicted by ROM were lower than the measured data. Then, the tension-tension (T-T) constant stress amplitude cyclic tests were performed at elevated temperature to receive the S-N curves, fatigue strength and life. It is a surprise that almost no delaminations were observed in tensile and cyclic tests, even at elevated temperature and over a million cycles.

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Fossum, A. F., P. T. Vianco, M. K. Neilsen et D. M. Pierce. « A Practical Viscoplastic Damage Model for Lead-Free Solder ». Journal of Electronic Packaging 128, n^o 1 (19 août 2005) : 71–81. http://dx.doi.org/10.1115/1.2160514.

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This paper summarizes the results of a program to construct an internal variable viscoplastic damage model to characterize 95.5Sn–3.9Ag–0.6Cu (wt.%) lead-free solder under cyclic thermomechanical loading conditions. A unified model is enhanced to account for a deteriorating microstructure through the use of an isotropic damage evolution equation. Model predictions versus experimental data are given for constant strain-rate tests that were conducted at strain rates of 4.2×10−5s−1 and 8.3×10−4s−1 over a temperature range from −25°Cto160°C; cyclic shear tests; and elevated-temperature creep tests. A description is given of how this work supports larger ongoing efforts to develop a predictive capability in materials aging and reliability, and solder interconnect reliability.

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Jeong, Yoseok, WooSeok Kim, Viktor Gribniak et David Hui. « Fatigue Behavior of Concrete Beams Prestressed with Partially Bonded CFRP Bars Subjected to Cyclic Loads ». Materials 12, n^o 20 (15 octobre 2019) : 3352. http://dx.doi.org/10.3390/ma12203352.

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The lack of ductility is the greatest concern in the applications of carbon fiber reinforced polymer (CFRP) materials, when used as pre-stressing reinforcements. To improve the ductility, a partially bonded FRP system which is intentionally unbonded in the middle part of the beam and bonded in both end parts of the beam has been developed and applied to prestressed concrete beams. While, many researchers investigated the instantaneous performance of partially bonded CFRP prestressed concrete beams, this study intended to evaluate the fatigue performance, the static load-carrying capacity after fatigue loading and ductility. Based on the fatigue loading tests followed by static loading tests, over-reinforced and web-confined partially bonded CFRP prestressed concrete beams exhibited satisfactory fatigue performance without cracks and stiffness degradation during fatigue loading. In addition, no degradation of load-carrying capacity was observed in static loading tests after the fatigue tests. The ductility index of concrete beams, prestressed with partially bonded CFRP bars, is combined with over-reinforcements and web-confinements, similar to that of beams prestressed with steel bars.

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Cai, Hongda, Stevens Marion A. Kalceff, Bryan M. Hooks, Brian R. Lawn et Kenneth Chyung. « Cyclic fatigue of a mica-containing glass-ceramic at Hertzian contacts ». Journal of Materials Research 9, n^o 10 (octobre 1994) : 2654–61. http://dx.doi.org/10.1557/jmr.1994.2654.

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Fatigue damage in a mica-containing glass-ceramic is examined using Hertzian contact tests. For the material in its base glass state, such tests indicate that fatigue occurs solely by chemically enhanced cone crack extension. In the glass-ceramic, fatigue is evident as an expansion of a macroscopic subsurface microfracture zone. Comparative observations of the subsurface damage in static and cyclic loading, and tests in different environments, indicate that the fatigue in the glass-ceramic is mechanical in origin, although it is enhanced by moisture. This result is reinforced by load-point-displacement data, which reveal significant hysteresis in the glass-ceramic but not in the base glass. Flexure tests on Hertz-indented glass-ceramic specimens show only a slight loss of strength, <5%, over 105 cycles. This contrasts with the base glass which, although of higher laboratory strength, is subject to abrupt and severe strength degradation from cone crack pop-in. High magnification examination of the subsurface damage in the glass-ceramic suggests the underlying cause of the mechanical fatigue mechanism to be attrition of frictional tractions at closed microcrack interfaces.

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Hasebe, Tadashi, Masao Sakane et Masateru Ohnami. « High Temperature Low Cycle Fatigue and Cyclic Constitutive Relation of MAR-M247 Directionally Solidified Superalloy ». Journal of Engineering Materials and Technology 114, n^o 2 (1 avril 1992) : 162–67. http://dx.doi.org/10.1115/1.2904156.

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This paper investigates the effect of solidification direction on cyclic constitutive relation and low cycle fatigue life for a directionally solidified (DS) superalloy Mar-M247LC at 1173 K in air. Strain controlled push-pull low cycle fatigue tests were carried out for three kinds of specimens of which loading direction was 0, 45 and 90 deg to DS axis. The 0 deg specimen exhibited the largest fatigue strength, the 45 deg specimen the smallest and the 90 deg specimen the intermediate. The difference in the fatigue strength due to the loading direction was discussed in detail from the viewpoint of the anisotropy of Young’s modulus. A life prediction method for DS specimens, considering the anisotropy of the Young’s modulus, was proposed and successfully applied to the low cycle fatigue data.

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Vaško, Alan, et Marek Krynke. « Fatigue Properties Of Nodular Cast Irons Alloyed By Si, Mo And Cu ». System Safety : Human - Technical Facility - Environment 1, n^o 1 (1 mars 2019) : 738–44. http://dx.doi.org/10.2478/czoto-2019-0094.

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AbstractIn recent years, the research of nodular cast iron has been focused on increasing fatigue resistence. In the paper, two types of alloyed nodular cast irons have been investigated – SiMo-nodular cast iron alloyed by 4% of silicon and 1% of molybdenum and SiCu-nodular cast iron alloyed by 4% of silicon and 1.5% of copper. SiMo-nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines. SiCu-nodular cast iron is used in various components of tribotechnical units. These components are often loaded by fatigue. The mechanical and fatigue behaviour of both nodular cast iron types has been studied by means of tensile test, impact bending test, hardness test and fatigue tests. Fatigue tests were realised at low frequency cyclic push-pull loading up to 10 million cycles. The relationship between the amplitude of stress and number of cycles to failure was investigated and the fatigue strength was determined. Mechanical and fatigue properties of both nodular cast iron types are correlated with the microstructure of specimens.

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Law, K. T., Y. L. Cao et G. N. He. « An energy approach for assessing seismic liquefaction potential ». Canadian Geotechnical Journal 27, n^o 3 (1 juin 1990) : 320–29. http://dx.doi.org/10.1139/t90-043.

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An energy method for assessing liquefaction potential of granular soils was developed based on laboratory tests and observational data obtained in past major earthquakes. Cyclic triaxial and cyclic simple shear tests were conducted and the results show that a unique relation exists between the dissipated energy during cyclic load and the excess pore pressure that eventually led to liquefaction failure. This unique relation has been combined with an energy attenuation equation to develop a criterion for defining the liquefaction potential of a site. Parameters for the criterion were evaluated from 136 sites involved in 13 major earthquakes over the world. A comparison was made between the energy method and the commonly used stress method. The energy method was found to be simpler to apply and more reliable. Key words: energy, earthquake, liquefaction potential, standard penetration test, laboratory cyclic test, excess pore pressure, granular soils, case records.

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Wang, Yuanqing, et Zhongxing Wang. « Experimental Investigation and FE Analysis on Constitutive Relationship of High Strength Aluminum Alloy under Cyclic Loading ». Advances in Materials Science and Engineering 2016 (2016) : 1–16. http://dx.doi.org/10.1155/2016/2941874.

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Experiments of 17 high strength aluminum alloy (7A04) specimens were conducted to investigate the constitutive relationship under cyclic loading. The monotonic behavior and hysteretic behavior were focused on and the fracture surface was observed by scanning electron microscope (SEM) to investigate the microfailure modes. Based on Ramberg-Osgood model, stress-strain skeleton curves under cyclic loading were fitted. Parameters of combined hardening model including isotropic hardening and kinematic hardening were calibrated from test data according to Chaboche model. The cyclic tests were simulated in finite element software ABAQUS. The test results show that 7A04 aluminum alloy has obvious nonlinearity and ultra-high strength which is over 600 MPa, however, with relatively poor ductility. In the cyclic loading tests, 7A04 aluminum alloy showed cyclic hardening behavior and when the compressive strain was larger than 1%, the stiffness degradation and strength degradation occurred. The simulated curves derived by FE model fitted well with experimental curves which indicates that the parameters of this combined model can be used in accurate calculation of 7A04 high strength aluminum structures under cyclic loading.

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Peloso, Simone, Chiara Casarotti, Filippo Dacarro et Giuseppe Sinopoli. « Response of an Existing Two-Storey RC Frame Designed for Gravity Loads : In Situ Pushover Tests and Numerical Analyses ». Buildings 10, n^o 12 (4 décembre 2020) : 227. http://dx.doi.org/10.3390/buildings10120227.

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The purpose of the research was to study the response of existing constructions, designed for gravity loads only in the South of Italy, more precisely in the Sicily Region. The building is an existing two-story reinforced concrete structure, built in the ‘80s. In order to design the test, numerical study on the structure has been conducted, using information reported on original design drawings or derived by in situ geometric and material investigation. A number of numerical models and pushover analyses of the structure have been carried out, in order to account for the uncertainties related to possible different responses. The numerical analyses aimed at estimating the capacity of the structure in terms of both force and displacement, the ductility reserve, and the most likely sequence of formation of plastic hinges. The pseudo-static cyclic test was designed to push and pull the building in one direction at increasing displacement levels, up to a drift of about 2%. At the end of the test, the infill panels were completely collapsed. Beams, columns, and joints showed plastic hinges and shear failures in different parts of the structure, with spread spalling of the concrete. Numerical and experimental results were found in fair agreement.

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Belan, Juraj, Lenka Kuchariková, Eva Tillová, Denisa Závodská et Mária Chalupová. « Effect of Fatigue Loading Mode on 718 Alloy Fatigue Properties ». Periodica Polytechnica Transportation Engineering 47, n^o 4 (23 mai 2018) : 335–41. http://dx.doi.org/10.3311/pptr.12114.

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In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators such as the surface, persistent slip bands (PSBs), interfaces of constituents in the case of composites, and grain interfaces in the case of metals. Eventually a crack will reach a critical size, the crack will propagate suddenly, and the structure will fracture. The first works about fatigue phenomenon were published since 1837 and intensively was investigated by Wöhler in 1860. With needs of using the progressive materials such titanium and Ni-base superalloys become more significant to put under the various fatigue loading these sorts of alloys. Presented article deals with how the various condition of loading influenced an IN718 alloy fatigue lifetime especially. The fatigue tests provided on this kind of material was done via low frequency loading and push-pull or rotation-bending stress up to this time. Fatigue tests of experimental material was carried out at two different frequencies, 20 kHz with stress ration R = - 1 (push – pull, σm = 0 MPa) as well as the three-point bending load R ˂ 1 (σom = 526.8 MPa) at low frequency 150 Hz at room temperature. The microstructure characterization and Scanning Electron Microscopy (SEM) fractography analysis of fatigue process were done as well. The main goal of study was analyze obtained data after fatigue test and consider, if the various loading modes have influence on fatigue lifetime (initiation sites, crack propagation character, etc.).

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Yoo, Yun Ha, et Jung Gu Kim. « Aqueous Corrosion Characteristics of Iron Aluminides ». Advanced Materials Research 26-28 (octobre 2007) : 23–26. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.23.

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Aqueous corrosion behaviors of Fe3Al-based iron aluminides were investigated. From the result of cyclic anodic polarization tests conducted in 3.5 wt.% NaCl solution at 25, 48, 72 and 95°C, as the temperature increased, the resistance to pitting corrosion decreased significantly, especially over the range of 25~48°C. From the result of crevice corrosion tests, no crevice corrosion occurred on FAL-Mo in the lower chloride-containing solution (200 ppm Cl-), however, FAL-Mo did not perform as well as the 304L SS in the higher chloride-containing solution (3.5 wt.% NaCl). From the result of anodic polarization tests performed in sulfur-compound solutions, additions of Cr and Mo to the Fe3Al-based iron aluminides tend to improve the aqueous corrosion resistance. Aqueous corrosion behaviors with different Al content evaluated by cyclic anodic polarization test in the chloride-containing solution exhibited the more stable passive behavior and the higher pitting resistance as Al contents increased.

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Brookfield, D. J., D. N. Moreton et D. G. Moffat. « Shakedown and Cold Creep of Stainless Steel Type 316 Torispherical Drumheads Subjected to Internal Pressure ». Journal of Pressure Vessel Technology 108, n^o 3 (1 août 1986) : 289–96. http://dx.doi.org/10.1115/1.3264788.

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The results from cyclic internal pressure tests on two nominally identical stainless steel type 316 torispherical drumheads are presented. The effect of cold creep is investigated and is shown to contribute most of the accumulated strain during pressure cycling. The experimental shakedown pressure is compared with the design pressures from BS 5500 and the effect of over-pressure testing on subsequent cyclic behavior is discussed.

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Bowman, Elisabeth T., et Kenichi Soga. « Mechanisms of setup of displacement piles in sand : laboratory creep tests ». Canadian Geotechnical Journal 42, n^o 5 (1 octobre 2005) : 1391–407. http://dx.doi.org/10.1139/t05-063.

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A series of triaxial creep tests is described, with the aim of shedding light on the mechanisms behind displacement pile setup in granular soils. The stress path leading to the creep stages has been designed to mimic, as far as possible, the installation of a pile adjacent to an element of soil. A complex strain response is found with creep in dense sands at high stress ratio, with rotation of the creep strain vector over time. A new hypothesis, involving kinematically restrained dilation of the soil close to the pile shaft and soil ageing, is proposed to explain pile setup. Influences on the creep behaviour, and hence degree of setup, are found to be particle shape and strength, relative density, and rate of loading. The application of small cyclic perturbations during creep is found to accelerate the onset of volumetric dilation and hence is proposed to accelerate setup.Key words: creep, setup, displacement piles, laboratory testing, sands.

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Greisel, M., J. Jäger, J. Moosburger-Will, M. G. R. Sause, W. M. Mueller et S. Horn. « Influence of residual thermal stress in carbon fiber-reinforced thermoplastic composites on interfacial fracture toughness evaluated by cyclic single-fiber push-out tests ». Composites Part A : Applied Science and Manufacturing 66 (novembre 2014) : 117–27. http://dx.doi.org/10.1016/j.compositesa.2014.07.010.

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Zhang, Wei Chang, Ming Liang Zhu et Fu Zhen Xuan. « Experimental Characterization of Competition of Surface and Internal Damage in Very High Cycle Fatigue Regime ». Key Engineering Materials 754 (septembre 2017) : 79–82. http://dx.doi.org/10.4028/www.scientific.net/kem.754.79.

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Axially push-pull cyclic tests of a low strength rotor steel were performed up to the very high cycle fatigue regime at ambient environment under ultrasonic frequency. Fatigue tests were interrupted at selected number of cycles for surface morphology observation and roughness measurement with the help of a 3D surface measurement system (Alicona InfiniteFocusSL). The fatigue extrusions and slip band developed on the specimen surface were recorded. The influence of stress level on the number and morphology of slip band was discussed. The surface roughness of fatigue specimens was found to be increased with the increasing of fatigue cycles. The fatigued specimens were finally cracked from surface or interior micro-defects after observation of fracture surface by scanning electron microscopy. The internal damage behavior consists of crack initiation and early propagation from micro-defect, crack growth within the fish eye, and fast crack growth. It is observed that there exists a competition between surface and internal fatigue damage in the very high cycle fatigue regime, i.e., surface damage is gradually developed with the increasing of fatigue cycles, while the critical interior micro-defect can be dominant for fatigue cracking.

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Bressan, Stefano, Javad Razavi, Fumio Ogawa, Takamoto Itoh et Filippo Berto. « Multiaxial fatigue strength under non-proportional loading of additively manufactured notched components of Ti-6Al-4V ». MATEC Web of Conferences 300 (2019) : 03005. http://dx.doi.org/10.1051/matecconf/201930003005.

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In this study fatigue tests have been conducted on additively manufactured notched specimens made of titanium alloy Ti-6Al-4V under uniaxial loading and multiaxial non-proportional loading. Laser powder bed fusion technique has been employed to fabricate cylindrical specimens which have been successively machined to obtain a circumferential notch. Four varieties of specimens were fabricated depending on the build orientation and the application of a post-fabrication stress-relief heat treatment. The influence of layer orientation and heat treatment on the material microstructure has been analyzed. Strain controlled tests were performed with both proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path. The number of cycles to failure under both proportional and non-proportional loadings seemed not depending on layer orientation and heat-treatment. The cyclic plastic behavior of the material has been verified through the observation of the softening and hardening curves. The surface of the crack has been finally analyzed to verify the crack initiation position which has been detected on voids or defects located in the vicinity of the notch tip.

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Komatsu, Kohei, Qicheng Teng, Zherui Li, Xiaolan Zhang et Zeli Que. « Experimental and analytical investigation on the nonlinear behaviors of glulam moment-resisting joints composed of inclined self-tapping screws with steel side plates ». Advances in Structural Engineering 22, n^o 15 (28 juin 2019) : 3190–206. http://dx.doi.org/10.1177/1369433219858722.

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Glulam moment-resisting joint composed of inclined self-tapping screws with steel side plates were designed and its nonlinear moment-rotational skeleton curve was predicted by taking nonlinear load ( P)–deformation ( u) relationships of all moment-resisting components into considerations within step-wise linear calculation process. P-u relationships of all moment-resisting components were estimated by the fundamental shear joint tests or appropriate empirical relationships, and they were approximated by the tetra polygonal line curves or bi-linear curves. The extended Normalized Characteristic Loop model, which was originally developed for reinforced concrete construction, was applied to describe the hysteresis loops. For predicting failure load, the design equations for a mechanical joint loaded with inclination to the grain direction were applied. Three replications of T-shaped beam-column joint specimens were fabricated using Canadian spruce glulam beam and column. Connections of steel plates to glulam members were all composed of full-threaded inclined self-tapping screws. Static push-pull cyclic loading tests were conducted and observed behaviors were compared with step-wise linear analytical results. Agreements between predicted nonlinear behaviors and observed ones were good on the whole.

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Juneja, A., et A. K. Mohammed-Aslam. « Application of a Cyclic Degradation Model for Pore Pressure Accumulation in Loose Sands and Silts Subjected to Dynamic Loading ». Journal of Earthquake and Tsunami 12, n^o 05 (décembre 2018) : 1850014. http://dx.doi.org/10.1142/s1793431118500148.

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Most cyclic soil models which are used to estimate strain and pore pressure accumulations, are soil specific and, often evaluate the accumulation model either as a function of the number of load cycles or they tend to utilize parameters which can only be obtained by using detailed laboratory tests. This paper attempts to enhance the capabilities of a simple plasticity model which can approximate the trend of pore pressure accumulation. This function uses a stress dependent degradation parameter which allows the yield loci to adjust and reduce its size at the end of each load cycle. The cyclic degradation model which was originally developed for clays, was adapted for sands and silts in this work with the use of two new parameters. The model was tested by using the cyclic triaxial data of three non-plastic soils. These samples were subjected to cyclic load amplitudes which are normally used in most seismic studies. The modified degradation model could predict fairly well the pore pressure accumulation in high-load amplitude tests but lead to over-prediction in low-load amplitude tests, unless the function was allowed to taper off at large cycles. Notwithstanding the above, the above cyclic model using the degraded yield surface, was incapable of correctly predicting the stress paths which were close to the sample’s ultimate state as it failed to permit phase transformation which is generally observed in sands and silts.

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