Tension-compression Cyclic Loading Research Articles

Compressive residual strength of the pultruded glass-fiber composite after tension-compression fatigue

We experimentally determined the decrease of residual compressive strength of the pultruded glass-fiber laminate after tension-compression cyclic loading. The adapted Arcan rig was used for tension-compression fatigue tests. The cyclic load was applied with the critical stress ratio R=−0.87. The residual compressive strength was determined after applying the predefined number of loading cycles with the stress amplitudes of 242 MPa and 173 MPa. The results indicated that the residual compressive strength was reduced about 20% at 77% of fatigue life under the stress amplitude of 242 MPa and at 83% of fatigue life under the stress amplitude of 173 MPa. The microstructural analysis showed that the crack growth path and failure mode depend on the stress amplitude.

Cyclic behaviour of circular CFT-SG columns under axial tension-compression: Novel FE modelling and design methods

The ultra-high concrete-filled steel tubular (CFT) power transmission tower is popularly applied in engineering practice, which may be under a typical cyclic axial tension-compression loading condition due to the dynamic wind load. Nonetheless, the CFT columns of the tower may be accompanied by significant gap defects due to the influence of structural feature, material property, and service environment. Hence, to figure out the performance of circular CFT columns with spherical-cap gaps (CFT-SG) subjected to cyclic axial tension-compression, this paper investigates a constitutive relationship for the gapped core concrete, which is verified by several existing experiments. A novel numerical modelling approach for simulating the irregular cross-section of the circular CFT-SG columns under cyclic axial load was following established based on the triangulation method and code programming. The influence of important parameters such as gap ratio, material strength, and diameter to thickness ratio on the hysteresis characteristics, load-bearing capacity, elastic stiffness, energy dissipation and ductility of circular CFT-SG columns under cyclic axial tension-compression force is studied. Moreover, the restoring force model of the circular CFT-SG columns under cyclic axial tension-compression is finally presented. Research results declare that the compressive bearing capacity, stiffness, ductility, and energy dissipation of circular CFT-SG columns under cyclic axial tension-compression are gradually weakened with the increment in the gap ratio. The numerical modelling approach and restoring force model proposed in this article can accurately evaluate the hysteresis performance of circular CFT-SG columns subjected to cyclic axial tension-compression.

Акустические свойства мартенситно-стареющей стали XM-12 после энергетических воздействий

The study of the acoustic properties of maraging steels operated under various energy force and temperature actions is a critical task, since it is the method of acoustic structuroscopy that provides the most reliable connection with the structure, stress-strain state and mechanical properties of steels. The paper is devoted to research of the acoustic properties of the 15-5 PH maraging steel samples under various types of heat treatment under the conditions of mechanical tensile and cyclic loads. Samples of the 15-5 PH maraging steel were studied in three structural states: solid solution annealing and subsequent aging at 470 and 565 °C; during tensile tests; during cyclic tension-compression loading. The research used a unique scientific installation “Information-measuring complex for investigation of acoustic properties of materials and products”. It implements the acoustic mirror-shadow multiple reflections method using electromagnetic-acoustic and piezoelectric transducers based on polyvinylidene fluoride film to excite and receive waves and allows determining the velocity of wave propagation with an error of no more than 2 m/s. The acoustic (wave velocity, elastic moduli, electromagnetic-acoustical (EMA) transformation coefficients, acoustic anisotropy coefficients, acoustoelastic coupling coefficients) and electromagnetic (coercive force and electrical conductivity) characteristics of the samples were examined. The samples were studied in the initial state (before loading); stepwise in the process of tensile loads and subsequent unloading; after tensile tests; during cyclic tension-compression loading. It was revealed that the following acoustic parameters of 15-5 PH steel samples are the greatest structural sensitivity to mechanical tensile load and cyclic loading: transverse wave velocity, Poisson’s ratio, double EMA-transformation coefficient, and acoustic anisotropy coefficient.

A novel defect-related cyclic damage model driven by strain energy density for LPBF titanium alloy

The unavoidable defects in additive manufacturing (AM) material have an impact on the deformation behavior and fatigue lifetime. In this study, a series of experiments on Laser powder bed fusion (LPBF) Ti-6Al-4 V under symmetrical tension–compression cyclic loading were conducted, and the corresponding damage mechanism was then investigated. It is revealed that due to the nucleation, growth, and coalescence of micro-voids, LPBF Ti-6Al-4 V exhibits accelerated softening behavior after reaching cyclic stability. Based on the physical mechanism, a cyclic damage model with a critical initiation criterion was developed using fracture mechanics principles, in which plastic strain energy as the driving parameter is introduced to describe the defect evolution, and the void’s closure effect during the tension–compression cycle is considered. Experimental validation has demonstrated that the damage model can accurately predict the cyclic stress–strain curves for LPBF Ti-6Al-4 V vertical and horizontal specimens, with errors in predicting crack initiation and growth lifetime falling within the ± 1.6 and ± 2.5 scatter bands.

Experimental study of shape memory alloy plates under cyclic tension–compression loading scenarios

Shape memory alloys (SMAs) have garnered significant attention for their potential in earthquake-resistant structures, primarily due to their superelastic effect and exceptional self-centring capabilities. However, the mechanical properties of SMA plates, especially under cyclic tension–compression loading, remain underexplored. This research aims to bridge this gap by designing and testing 33 SMA plates equipped with buckling-restrained devices. The study varied parameters such as specimen thickness (4 mm, 6 mm, and 8 mm), loading protocols (seven in total), and test temperatures (25 °C and 0 °C). The findings reveal that the stress–strain curves under cyclic tension–compression loading exhibited asymmetric characteristics. For instance, at 25℃, a 4 mm thick specimen at 4% strain had a compressive peak stress that was 22.2% higher than its tensile counterpart, and its compressive residual strain exceeded the tensile residual strain by 99.0%. Furthermore, when compared to SMA plates under cyclic tension-release loading, those under cyclic tension–compression loading had reduced tensile residual strains. At 0 °C, the peak stress saw a decrease ranging from 2.4 to 43.1%, while the residual strain surged by 11.9–591.4% compared to the tests at 25℃. This study provides novel insights into the behavior of SMA plates under varied conditions, emphasizing their potential for seismic applications.

Improving low-cycle fatigue life of ZK61 magnesium alloy via basal texture weakening by the compression-extrusion process

In response to the problem that intense basal texture seriously affects the low-cycle fatigue life of magnesium alloys, the compression-extrusion process for basal texture weakening was implemented in ZK61 magnesium alloys. The low-cycle fatigue life under uniaxial symmetrical tension-compression cyclic loading was dramatically improved by basal texture weakening, up to 1.5∼3 times that in an intense-textured state. Basal texture weakening promoted basal slip to dominate the cyclic deformation, thus significantly reducing the cyclic tension-compression asymmetry caused by the {10–12} twinning-detwinning. Further, the suppression of {10–12} twinning and the decrease of compressive plastic strain slowed down dislocation accumulation inhibiting the cyclic hardening and fatigue crack initiation. The Manson-Coffin equation was feasible to predict the fatigue life of the intense-textured and weak-textured ZK61 magnesium alloys. The promotion of basal slip arising from basal texture weakening led to the decrease of fatigue ductility coefficient and the increase of fatigue ductility exponent contributing to the higher fatigue life.

Low cycle fatigue response and fracture mechanism in a novel Al-3.5Si-0.5Mg-0.4Cu casting alloy

The LCF (low-cycle fatigue) behavior of a T6-treated low silicon cast aluminum alloy Al-3.5Si-0.5Mg-0.4Cu was investigated under axial symmetric tension-compression cyclic loading conditions. LCF behavior and results of experiment (under 6 different total strain amplitudes from 0.25 % to 0.5 %) are included. OM (Optical Microscopy), SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscope) are employed to observe and analyze the fracture morphology and microstructure evolution. The results demonstrate that cracks were initiated from surface or subsurface defects. A higher total strain amplitude led to a smaller sum area of fatigue crack initiation region as well as a steady crack propagation regime, and a larger fatigue striation bandwidth. Furthermore, crack propagates along the interface between eutectic silicon and α-Al matrix under lower strain amplitudes. Otherwise, it extends through eutectic silicon particles if higher strain amplitudes are applied.

Mechanical properties and constitutive models of shape memory alloy for structural engineering: A review

Shape Memory Alloys (SMAs) are an innovative material with the unique features of superelasticity and energy dissipation capabilities under extreme loads. Due to their unique features, they have a great potential to be employed in structural engineering applications under different conditions. However, in order to effectively use SMAs in civil engineering structures and model their behaviors accurately in Finite Element (FE) packages, it is crucial for structural engineers to comprehend the mechanical properties and cyclic behavior of different SMA compositions under varying loading conditions. While previous studies have focused mainly on the cyclic behavior of SMAs under tensile loading, it is important to evaluate their fatigue behavior under cyclic tension-compression loading for seismic applications. This literature review aims to discuss the current gaps in the existing literature on the behavior of SMA rebars under low-cycle fatigue (LCF). The review provides a comprehensive overview of the primary characteristics of SMAs, summarizes the mechanical properties of SMAs presented in the literature and the parameters that affect them, and critically evaluates the effects of cyclic loading and LCF on SMAs. The review also provides a summary of the different constitutive models of SMAs and compares their advantages and limitations, which helps structural engineers to employ an appropriate constitutive model for predicting the accurate behavior of SMAs in FE software.

Compression and Fatigue Testing of High-Strength Thin Metal Sheets by Using an Anti-Buckling Device

BackgroundThe modelling of the sheet metal forming operations requires accurate and precise data of the material plastic behaviour along non-proportional strain paths. However, the buckling phenomenon severely limits the compressive strain range that could be used to deform thin metal sheets.ObjectiveThe main aim of this paper was to propose an effective device, that enables to determine of accurate stress-strain characteristics of thin metal sheet specimens subjected to axial deformation without buckling and with a special emphasis on friction correction.MethodsIn this paper, an anti-buckling fixture was proposed to assess the deformation characteristics of X10CrMoVNb9-1 (P91) power engineering steel, and DP500 and DP980 dual-phase steels, under compression loading. The fixture enables monitoring of the friction between the specimen and supporting blocks during the test, and thus the precise stress response of the material could be determined.ResultsThe effectiveness of the fixture was evaluated under tension–compression cyclic loading and during the compression tests in which high-strength thin metal sheets were successfully deformed up to 10% without specimen buckling. Furthermore, the successful determination of a friction force variation between supporting blocks and the specimen during tests enabled to determine an actual force acting on the specimen.ConclusionsThe proposed testing fixture was successfully assessed during the compression and cyclic tension–compression of high-strength thin metal sheets as no buckling was observed. Its advantage lies in adapting to change its length with specimen elongation or shrinkage during a test. The friction force generated from a movement of both parts of the device could be effectively monitored by the special strain gauge system during testing and thus its impact on the stress-strain characteristics could be successfully eliminated.

Experimental test and simulation calculation of fatigue properties of aluminum–titanium-steel explosive welded connector under tension-compression cyclic loading

The three-layer clad plate (aluminum alloy layer/commercial pure titanium layer/CCSB steel layer) was prepared by explosive welding as marine transition connector. The fatigue properties of clad plate were studied by experiment and finite element simulation. The fatigue limit and S–N curve were obtained by axial high-cycle fatigue test under tension-compression loading. The up-and-down method and group method were used respectively. Combining Static Structural module and DesignLife module based on the ANSYS Workbench Platform, the stress distribution, safety factor and fatigue life of clad plate under different loads were calculated. The results show that fatigue limit of Al–Ti-steel clad plate is 55 MPa, and the fatigue fracture mainly occurs in the 104∼106 cycles period in the stress range of 65 MPa∼100 MPa. The maximum relative error of fatigue life is 7.05%, and the relative error of fatigue limit is 0.45% between model and test fitting values. The results of finite element simulation have good agreement with the results of experimental method, which proves the feasibility and reliability of finite element simulation to analyze and forecast fatigue property of explosive welded clad plate. The position of the stress concentration is at the connection part between steel and pure titanium, while fatigue fracture occurs in the 3003 aluminum alloy layer because of the low tensile strength. Improving the tensile strength of Al-steel joint material is a key measure for solving the fracture problem of hull foundation.

An anomalous compression-induced softening behavior of AA6014-T4P during cyclic loading

This paper investigated the cyclic plasticity of AA6014-T4P with the tension-compression (T-C) and compression-tension (C-T) cyclic loading tests. A new compression-induced softening behavior is found and modeled. Specifically, the material was softened permanently during the tensile load when a compressive pre-strain was applied, whereas such an abnormal phenomenon was not observed when the loading sequence is reversed. Moreover, the magnitude of the permanent softening scale linearly with the compressive pre strain. Therefore, we term this phenomenon as compression-induced softening in this paper. Based on this compression-induced softening phenomena, a modified Y–U model is formulated by introducing a correction factor that modifies the hardening rate of the boundary surface to describe the permanent softening effect, which can predict the compression-induced softening well. Our work reveals a new phenomenon for the cyclic loading of metal sheets and stimulates further efforts on the path-dependence of metal plasticity.

Investigation on fatigue cracks of diaphragm cutout in bridge orthotropic steel deck

Fatigue cracks were found at the diaphragm cutouts in the orthotropic steel deck (OSD) of a self-anchored suspension bridge while the in-service time of the bridge was less than 10 years. The causes of fatigue cracks of the diaphragm cutout are investigated in this study. The fatigue cracks initiated from the intersections of the arc curves and the straight lines, which form the geometrical discontinuity to the cutout edge. The in situ monitoring and finite element analysis under fatigue load model indicate that the cracking region in the cutout is in bidirectional compression. However, the thermal-structural analysis and tests show that the rib-to-diaphragm welding process produces high tension residual stress at the cracking points of the cutouts. The cutouts are under tension-compression cyclic loading because of the coupled stress, which is derived from the vehicle-induced stress and the welding residual stress. The results show that the strain energy method can present a reasonable fatigue life estimation for the diaphragm cutouts with full consideration of the residual stress.

An experimental and modelling study of cyclic tension-compression behavior of AA7075-T6 under electrically-assisted condition

Electrically-assisted (EA) forming is an effective method to improve forming quality of sheet metal. In order to reveal the effects of current on material flow behavior under complex strain paths and develop corresponding constitutive model, the EA tension-compression cyclic loading tests with particularly designed setup were carried out. Then, the effects of current on the elastic modulus degradation and cyclic deformation were investigated. Further, corresponding modulus degradation model and constitutive model were developed. The results showed that the flow stress under EA uniaxial tension was lower than that under warm uniaxial tension. Moreover, the current-induced growth of precipitate and the decrease of dislocation occur under EA uniaxial tension. Regarding the EA cyclic deformation behavior, the elastic modulus decreases with the increase of plastic strain, temperature and current density, which is described by a proposed modified modulus degradation model. The Bauschinger effect and permanent softening effect are weakened with the increase of temperature and current density. The asymmetric tension-compression behavior becomes more obvious with the increase of temperature and current density. Based on above results, a modified Y-U model was established and verified with EA draw-bending process. The above research work can provide some research basis for the application of electrically-assisted forming.

Deformation of thin metal and composite sheets by using anti-buckling fixture for large deformation under tension–compression cyclic loading

In this paper, an anti-buckling fixture was proposed to assess the deformation characteristics of DP500 and DP980 dual-phase steels, and AZ31B magnesium composite under tension–compression cyclic loading. The advantage of the device lies in the possibility of monitoring friction between the specimen and supporting blocks during the test. In consequence, it allows to avoid an error during stress determination. The full cyclic loading capacity for each material can be executed at the displacement amplitude within the range ±2.5 mm which corresponds to the maximum strain amplitude of ±0.2 for the specimen with the gauge length of 21.5 mm. It is concluded, that the technique proposed is promising since the thin sheet material can be tested under tension–compression in a wide range of deformation without the buckling effect. Furthermore, useful data for modelling cyclic deformation behaviour for shell structures can be obtained.

Experimental study on cyclic hardening characteristics of structural stainless steels

This paper studies the cyclic hardening characteristics of commonly used structural stainless steel types and grades including austenitic stainless steel grades S30408 and S31608 (equivalently to EN 1.4301 and EN 1.4401) as well as duplex stainless steel grade S22053 (equivalently to EN 1.4462) under tension-compression cyclic loading. A total of twenty-four monotonic loading tests and thirty-six cyclic loading tests were performed and two different cyclic loading protocol types were selected, namely cyclic ascend (CA) loading and cyclic constant (CC) loading with strain amplitudes ranging from ±0.5% to ±5%. Specimens with plate thicknesses of 6 mm and 8 mm were tested. The test results indicate that the cyclic hardening/softening behavior of the three grades of structural stainless steel generally shows obvious strain amplitude dependence and unsaturation before fracture under large strain amplitudes, which are significantly different from carbon steel. Meanwhile, there is a huge difference between the cyclic skeleton curves and the monotonic constitutive curves for different stainless steel grades. The effects of strain amplitude, stainless steel grade and loading history on the cyclic hardening/softening characteristics have been thoroughly studied. It should be noted that the seismic performance of stainless steel structures is greatly affected by the loading history. From the viewpoint of the seismic design of stainless steel structures, this paper proposes an equation to predict the maximum cyclic hardening degree at various strain amplitudes under constant amplitude loading.

Fatigue Life of Miniature SAC Solder Specimen Affected by Distribution Morphology of Primary Tin Crystal

Miniature specimens of Sn-3.0Ag-0.5Cu (SAC) solder show large variation in tensile strength even though they are under the same loading conditions. We have found that this phenomenon can be correlated to the difference in the distribution morphology of primary Tin crystals in the specimens. Such a different could affect the fatigue strength of the miniature specimen. Then, in this study, we carried out fatigue tests with cyclic tension-compression loading using the miniature SAC solder specimen to investigate the relationship between the fatigue life and the distribution morphology of primary Tin crystals. The results show that the stress amplitudes of the hysteresis loops under the same loading condition show large variations and the fatigue life becomes shorter with the increase in the stress amplitude. The specimens having a high-stress amplitude in their hysteresis loops contain a high proportion of the primary Tin crystals which grow in directions vertical to or parallel to the loading direction. Namely, the fatigue strength of the specimen containing a large number of such primary Tin crystals tends to become lower.

High-Temperature Deformation Characteristics of Cu<sub>3</sub>Sn Evaluated by the Tests Using Composite Copper Wire Specimen.

In recent years, the propulsive movement of electrification of automobiles and airplanes is accelerating to realize a decarbonized society. Along with this movement, lightening of electric mobility is also required to reduce electricity consumption. The power modules used in electric mobility control high voltage and great current and are subjected to high temperature. Since most of the power modules employ Si semiconductor chips which can’t work in such a high-temperature range, cooling systems must be installed to prevent their failure. Therefore, next-generation power semiconductor chips using SiC or GaN, which can work properly in a high-temperature environment of over 200 ℃, are expected to be mounted in power modules to lighten them by eliminating cooling system. Cu3Sn intermetallic bonding technique which can form joints having a high melting point has attracted attention to achieve the mounting of the chips. To put the technique into practical use, the high-temperature deformation characteristics of Cu3Sn must be clarified. We previously proposed a materials testing method using a composite copper wire (CCW) specimen having a Cu3Sn layer to estimate the tensile characteristics of Cu3Sn. In this study, we conducted tensile tests, tension-strain maintenance tests, and cyclic tension-compression loading tests using the CCW specimen to evaluate the deformation characteristics of Cu3Sn in the temperature range between room temperature and 200 ℃.

Cyclic behavior of iron-based shape memory alloy bars for high-performance seismic devices

As a new member of the shape memory alloy (SMA) material family, iron-based SMAs (Fe-SMAs) show great potential in seismic applications due to their favorable properties. The thermomechanical behavior of Fe-SMAs has been extensively studied over the past decades. However, the relevant research regarding the use of Fe-SMAs in the community of earthquake engineering is still in an early stage, particularly on their mechanical behavior under cyclic tension–compression loadings. This study conducted a systematic experimental investigation of the cyclic behavior of Fe-SMA bars with a buckling-restrained device, which was cyclically tested under tension–compression loadings. The cyclic properties, such as hysteretic response, recovery capability, fatigue behavior, and fracture behavior were evaluated with varying strain amplitudes and different loading protocols. Test results show that satisfactory hysteretic loops with excellent deformation capability are obtained under cyclic tension–compression loadings. Fe-SMA bars exhibit acceptably stable behavior under multistage loadings. Moreover, they possess unique inherent properties, including moderate shape memory effect, high “post-yield” stiffness, and excellent fatigue behavior, thereby providing a promising solution to develop high-performance seismic devices. These properties are conducive to limit peak drifts, mitigate residual drifts of structures, and withstand long-duration ground motions and strong repeated aftershocks.

Experimental Study on Mechanical Properties of Novel FRP Bars with Hoop Winding Layer

Due to the fact that steel reinforcement is vulnerable to corrosion, FRP bars with light weight, high strength, and excellent durability have become a good substitute for ordinary steel bars. FRP bars have high tensile strength, but their compressive strength is relatively low and often neglected, so the application of FRP bars in compression members has been restricted. This paper proposes a new pultrusion-winding-pultrusion method to improve the compressive ability of FRP bars. A hoop FRP layer is winded on the outer surface of the pultruded FRP core, and a longitudinal pultruded layer and ribs are also added on the outermost surface. In this paper, mechanical properties of this novel FRP bar with hoop winding layer are investigated. First, monotonic tensile and compressive tests on traditional and novel GFRP bars were conducted. Then, cyclic tension-compression loading tests were also carried out on the two types of GFRP bars. Test results showed that the compressive ultimate bearing capacities of GFRP bars with winding layers were 10∼20 kN greater than those of the traditional GFRP bars, and the compressive ductility of the novel GFRP bars was also improved. Furthermore, the tensile stress-strain behaviors of both GFRP bars were linear-elastic and the added winding layer did not greatly influence the tensile properties of the GFRP bars. Moreover, for the cyclic loading test, the compressive ultimate load of GFRP bars was 80%∼90% of that under monotonic compressive test, and the tensile ultimate load was 45%∼65% of that under monotonic tensile test. Compared with the GFRP bar without winding layer, the overall stiffness of the novel GFRP bar was greater than that of the traditional one and the ultimate load of the novel GFRP bar was also greater. In addition, seeing that the residual displacement of the novel GFRP bar was greater than that of the traditional GFRP bar, winding hoop fibers on the outer surface of the core is a useful way to improve the energy dissipation capacity of the GFRP bar.

Effect of inclusions on the fatigue strength of a bearing steel

Here are presented results of experimental investigation about effect of inclusions on the fatigue strength of a bearing steel 100Cr6. Fatigue tests were carried out at sinusoidal cyclic tension-compression loading, f = 190 Hz, R = −1, room temperature, in the region ranged from N ≈ 3.5 × 105 to N ≈ 1.0 × 108 cycles of loading. Initiation of the fatigue cracks was observed in the bulk of the tested specimens and the so-called “fish eyes” were observed, mainly on the TiN inclusions (66 % Ti, 19 % N, 9 % Cr, remainder Fe, V, Zr). The TiN inclusions are hard, with sharp edges causing a significant stress concentration in a small localized area, resulting in an initiation of a fatigue crack. On the other hand, in standard for the chemical composition of this steel, the content of Ti was not prescribed.