Fatigue Hysteresis Loops Research Articles

Nonlinear viscoelastic mechanical behavior and fatigue hysteresis loops modeling of composite laminates

Fatigue constitutive curve is the presentation of mechanical response and damage mechanism of composites. The hysteresis phenomenon in composites is essentially attributed to the viscoelastic properties of the polymer matrix, causing the strain response to lag behind the stress excitation. Combined with the fatigue damage modes of composites, the contributions of elastic, plastic and viscoelastic strains to the cumulative cyclic strain are analyzed to determine the evolution law of the hysteresis loops with cycling. The hysteresis loops and cyclic hysteresis energy models of composites under tensile-tensile fatigue loads are proposed, and the models are verified by the experimental results of four kinds of laminates under several fatigue loads.

Characterization of multi-step cyclic-fatigue hysteresis behavior of 2D SiC/SiC composite using inverse tangent modulus

Under multi-step cyclic fatigue loading, the mechanical hysteresis loops of ceramic-matrix composites (CMCs) were affected by coupled multiple damage mechanisms. In this paper, the hysteresis-based inverse tangent modulus (ITMs) was developed to characterize the cyclic fatigue mechanical hysteresis behavior in 2D SiC/SiC composite under multi-step loading. The micromechanical multi-step hysteresis constitutive models were developed for the damage state of interface partial and complete debonding. Relationships between the cyclic-dependent interface wear, hysteresis loops, interface slip damage state, and ITMs were established. Effects of multi-step peak stress level, cycle number, and interface properties on the evolution of hysteresis stress-strain curves and ITMs were analyzed. Experimental multi-step cyclic fatigue hysteresis loops and ITMs of 2D SiC/SiC composite under different peak stresses of 1.2, 1.3, 1.4, and 1.5 PLS (proportional limit stress) were predicted. Compared with other hysteresis-based damage parameters, e.g., hysteresis width, hysteresis modulus, peak and residual strain, and loops area, the damage parameter of ITMs can better reveal the interface debonding and slip damage state in CMCs under multi-step cyclic fatigue loading.

Fatigue performance analysis of SiCf/Ti composites under spectrum load

In this study, the fatigue mechanical properties of SiCf/Ti composites under a spectrum load were investigated, and a spectrum load fatigue test of SiCf/Ti composites was carried out, followed by an analysis of the failure mechanism. The evolution law of typical damage modes involving fiber breakage, matrix cracking, and interface wear with the number of spectrum load cycles was investigated with the establishment of a fatigue damage model for each damage under spectrum load. In the combination of the meso-mechanical model and fatigue damage model, the fatigue hysteresis loop, residual stiffness, and residual strength were simulated and compared with practical experiments.

A Back-stress deconvolution method towards modelling of low cycle fatigue behavior of type 316L(N) stainless steel at room temperature

A novel back-stress deconvolution method based on nonlinear-kinematic hardening plasticity theory is proposed to determine the minimum number of back-stresses required to model the low cycle fatigue (LCF) hysteresis loops of 316L(N) stainless steel at room temperature. The deconvoluted back-stresses at different threshold plastic strains corroborate that, three back-stresses can simulate the back-stress vs plastic strain response for all cycles at ± 0.6 % strain amplitude. The variation of kinematic hardening parameters with cycles indicates dynamic evolution of material microstructure and gross microstructural heterogeneity during LCF. The simulated stress–strain hysteresis loops show excellent match with the experiments.

Characterization of cyclic fatigue hysteresis behavior of fiber-reinforced ceramic-matrix composites using inverse tangent modulus

Under cyclic fatigue loading, hysteresis loops appear in fiber-reinforced ceramic-matrix composites (CMCs) due to composite’s internal damage mechanisms. Loading/unloading inverse tangent modulus (ITMs) of the hysteresis loops reflect the composite’s internal damage state and can be used an effective tool to monitor composite’s fatigue damage evolution and fracture. In this paper, characterization of cyclic fatigue hysteresis loops of CMCs using ITMs are investigated. Loading/unloading ITMs are derived using a micromechanical hysteresis constitutive model considering fatigue damage mechanisms of matrix cracking, interface debonding, wear and slip, and fiber’s failure. Relationships between composite’s fatigue hysteresis loops, ITMs and interface slip state (i.e., interface reverse slip ratio (IRSR) and interface new slip ratio (INSR)) are established. Experimental fatigue hysteresis loops, ITMs, and IRSR/INSR of cross-ply SiC/CAS and SiC/MAS composites from the literature are predicted, and the effects of fiber’s volume fraction, matrix crack spacing, and interface debonding energy on composite’s fatigue hysteresis loops, ITMs, and IRSR/INSR are analyzed.

Micromechanical Modeling Tensile and Fatigue Behavior of Fiber-Reinforced Ceramic-Matrix Composites Considering Matrix Fragmentation and Closure

In this paper, micromechanical constitutive models are developed to predict the tensile and fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs) considering matrix fragmentation and closure. Damage models of matrix fragmentation, interface debonding, and fiber’s failure are considered in the micromechanical analysis of tensile response, and the matrix fragmentation closure, interface debonding and repeated sliding are considered in the hysteresis response. Relationships between the matrix fragmentation and closure, tensile and fatigue response, and interface debonding and fiber’s failure are established. Experimental matrix fragmentation density, tensile curves, and fatigue hysteresis loops of mini, unidirectional, cross-ply, and 2D plain-woven SiC/SiC composites are predicted using the developed constitutive models. Matrix fragmentation density changes with increasing or decreasing applied stress, which affects the nonlinear strain of SiC/SiC composite under tensile loading, and the interface debonding and sliding range of SiC/SiC composite under fatigue loading.

A fatigue life prediction method distinguishing fracture modes for Ni-based single crystal superalloys considering porosity defect

Microporosity is one of the most common defects in nickel base single crystal (N-SC) superalloys, which is a great threat to fatigue performance. In this paper, nine porosity-related fatigue damage parameters for N-SC superalloys were selected by referring to those parameters originally proposed for casting and 3D printing metal materials as well as the critical plane damage parameters commonly used in N-SC superalloys. According to the plastic constitutive model of single crystals, a crystal plastic finite element (CPFE) model was established to evaluate these different fatigue damage parameters, and the parameters of CPFE were calibrated by the low cycle fatigue (LCF) hysteresis loop obtained from the fatigue test. The evaluation results showed that the geometric mean of stress–strain concentration factor (GCF) kg was a satisfactory parameter to quantify the effect of porosity defects on fatigue. Inspired by the discovery and considering the slip systems characteristics of N-SC superalloys, the geometric mean of resolved stress–strain concentration factor (GRCF) krg on slip systems was proposed, and it was found that the max(krg,kg) could be used to predict the fracture modes of N-SC superalloys. Based on the max(krg,kg), a porosity-related fatigue life prediction method which can distinguish the fracture modes was put forward. The prediction results showed that the fracture mode prediction results were consistent with the test results, and the life prediction results were also improved compared with the GCF parameter.

Flexural fatigue behavior of bamboo-based products

AbstractBamboo-based products are increasingly used in structural engineering fields. Specifically, their application requires consideration of factors that affect their service life, such as the fatigue behavior. Bamboo-based materials, such as bamboo scrimber, have a high density and uneven stress distribution. These structural properties seriously affect the quality of the bamboo-based materials, and lead to increased fatigue. To solve this problem, the fatigue behavior of bamboo laminated veneer lumber (BLVL) was studied. BLVL was manufactured by arranging rolled and broomed bamboo bundles and hot-pressing. This study describes the flexural fatigue behavior of BLVL at different stress levels. The fatigue was characterized by the fatigue failure, the fatigue hysteresis loops, the energy loss, and stiffness degradation. The results demonstrated that the BLVL material had good fatigue-resisting performances. The fatigue life of BLVL under 80% stress level was estimated to be about 1,700,000 cycles. The main failure modes of the BLVL included fiber tearing, fiber pullout, fiber breakage, and fiber-matrix debonding. The total energy loss at higher stress levels was less than that at low stress levels. Higher stress levels corresponded to a larger drop in stiffness.

A micromechanical tension-tension fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composites considering stochastic matrix fragmentation

A micromechanical tension–tension fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composites (CMCs) is developed considering synergistic effects of stochastic matrix fragmentation and interface debonding. Evolution of matrix fragmentation with applied stress is determined using a numerical method. Fatigue hysteresis loops models for long, medium and short matrix fragmentation are developed based on the interface damage mechanism. Experimental fatigue hysteresis loops of two different CMCs are predicted. With increasing fatigue peak stress, matrix fragmentation density increases, and residual and peak strain, hysteresis area and width increase. Effects of fiber volume and interfacial shear stress on fatigue hysteresis loops are also discussed.

A micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composites

In this paper, a micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composites (CMCs) is developed. Upon unloading or reloading, the stress-strain of tension-compression fatigue hysteresis loops are divided into three different regions. Multiple micromechanical damage parameters of unloading transition stress, closure stress of the matrix cracking, compressive transition stress, complete compressive stress, and reloading transition stress are adopted to characterize the tension-compression stress-strain hysteresis loops. The characteristics of the tension-compression fatigue hysteresis loops of unidirectional SiC/CAS composite are analyzed for different material properties, damage stage, tensile fatigue peak stress, and compression fatigue valley stress. The experimental tension-tension and tension-compression fatigue stress-strain hysteresis loops of unidirectional SiC/CAS composite are predicted using the developed micromechanical models. Under low fatigue valley compressive stress, the tension-compression fatigue hysteresis loop exhibits no closure of matrix cracking; and under high fatigue valley compressive stress, the tension-compression fatigue hysteresis loops exhibit closure of matrix cracking, and complete compressive in the fiber and the matrix. However, the compressive valley stress has no effect on the values of matrix cracking closure stress, compressive transition stress, and complete compressive stress.

Effect of Interface Properties on Tensile and Fatigue Behavior of 2D Woven SiC/SiC Fiber‐Reinforced Ceramic‐Matrix Composites

In this paper, the effect of the fiber/matrix interface properties on the tensile and fatigue behavior of 2D woven SiC/SiC ceramic‐matrix composites (CMCs) is investigated. The relationships between the interface parameters of the fiber/matrix interface debonding energy and interface frictional shear stress in the interface debonding region and the composite tensile and fatigue damage parameters of first matrix cracking stress, matrix cracking density, and fatigue hysteresis‐based damage parameters are established. The effects of the fiber/matrix interface properties on the first matrix cracking stress, matrix cracking evolution, first and complete interface debonding stress, fatigue hysteresis dissipated energy, hysteresis modulus, and hysteresis width are analyzed. The experimental first matrix cracking stress, matrix cracking evolution, and fatigue hysteresis loops of SiC/SiC composites are predicted using different interface properties.

Simulation of tension-compression hysteresis loop of an unidirectionally SiC fiber-reinforced titanium matrix composite

ABSTRACT An approach to simulate the hysteresis loops of an unidirectionally SiC fiber-reinforced titanium matrix composite during tension-compression(T-C) fatigue loading has been developed in this paper. The T-C fatigue process of one cycle was divided into four stages of tension loading (TL), tension unloading (TU), compression loading (CL) and compression unloading (CU). It is assumed that fiber sliding relative to matrix occurs in the whole interfacial debonding area during TL. And there exists a closure stage of matrix crack during CL. Based on the BHE model, the stress–strain relationships during four stages have been derived. By combining the experimental normalized stiffness with the stress–strain relationship during TL, the average matrix crack spacing during various cycles are obtained. Combining the matrix cracking evolution law with another two damage evolution laws, the fatigue hysteresis loops of various cycles under T-C fatigue loading have been acquired. The theoretical results have been compared with experimental data of an unidirectionally SiC fiber-reinforced titanium matrix composite. And the effects of different damages on the hysteresis loops of TMCs have been investigated.

Failure analysis of long-fiber-reinforced ceramic-matrix composites subjected to in-phase thermomechanical and isothermal cyclic loading

In this paper, the failure analysis of long-fiber-reinforced ceramic-matrix composites (CMCs) subjected to the in-phase thermomechanical and isothermal cyclic fatigue loading are investigated using the micromechanical approach. The fiber/matrix interface shear stress is determined as a function of testing temperature and material properties, which affects multiple thermomechanical fatigue damage mechanisms of matrix multicracking, fiber/matrix interface debonding and sliding. The Budiansky-Hutchinson-Evans shear lag model is used to determine the micro stress field of the damaged composite. The matrix stochastic cracking model and the fracture mechanics approach are used to determine the matrix crack spacing and fiber/matrix interface debonding/slip length, respectively, considering the temperature-dependent fiber/matrix interface shear stress. The relationships between the testing temperatures, fiber/matrix interface shear stress, fiber/matrix interface debonding and sliding, and the shape, location and area of fatigue hysteresis loops under in-phase thermomechanical and isothermal cyclic loading are established. The effects of fiber volume fraction, fatigue peak stress, matrix cracking space, fiber/matrix interface frictional coefficient and fiber/matrix interface debonded energy and temperature range on the fatigue hysteresis loops under the in-phase thermomechanical and isothermal cyclic loading are analyzed. The fatigue hysteresis loops of unidirectional SiC/CAS and cross-ply SiC/MAS composite subjected to the in-phase thermomechanical and isothermal cyclic loading are predicted.

Fatigue Hysteresis Loops Simulation of SiCf /Ti Composites under Two-Stage Cyclic Loading

The fatigue hysteresis behavior of SiCf/Ti composites at two-stage cyclic loading has been investigated in present analysis. The effect of fiber volume fraction, loading sequence and fiber shape parameters on the fatigue hysteresis loops of composites were analyzed. Based on the law of interface slip during loading and unloading, the hysteresis loop models considering the failure criterion of fibers and interface shear stress degradation have been developed. Then, the validity of the model was confirmed by experiments. The study provides a basis and reference for further study of mechanical properties under multistage or even random cyclic loading.

Experimental investigation of buckling-restrained steel plate shear walls with inclined-slots

A buckling-restrained steel plate shear wall with inclined slots (simply referred as “slotted SPSW”) consisting of an inner steel plate sandwiched between two precast concrete panels, has been developed as an energy dissipation device of structures. The steel strips between inclined slots behave like a series of buckling-restrained braces to dissipate the energy through inelastic axial deformation when subjected to cyclic loading. This paper experimentally investigated the seismic behavior of slotted SPSWs. Three half-scale specimens were fabricated and tested under quasi-static cyclic loading. Details for proper fabrication of slotted SPSWs were firstly configured. The results illustrated that the slotted SPSW could sustain the target lateral drift ratio (2%) without a reduction of shear force and energy dissipation capacity. Moreover, the tested specimens exhibited stable fatigue hysteresis loops when the cyclic loadings were repeated 30 times at 1.5% peak lateral drift ratio. The maximum drift ratio of tested specimens reached 3.5%, and the cumulative plastic ductility factor was larger than 200. The experimental results indicate that the slotted SPSW is capable of providing high lateral force-resisting and energy dissipation, which can be widely used in engineering structures.

A hysteresis energy dissipation based model for multiple loading damage in continuous fiber-reinforced ceramic-matrix composites

In this paper, a hysteresis energy dissipation based damage model for fiber-reinforced ceramic-matrix composites (CMCs) subjected to multiple loading stress levels is developed. Considering the combination effects of multiple loading sequences and multiple fatigue damage mechanisms, i.e., matrix cracking, fiber/matrix interface debonding and interface wear, the evolution of the fiber/matrix interface debonding and sliding, fatigue hysteresis loops, fatigue hysteresis dissipated energy and fatigue hysteresis modulus changing with increasing applied cycles are analyzed. The effects of fiber volume fraction, matrix crack spacing, fatigue peak stress and fatigue stress range on the damage development inside of CMCs are discussed. The difference of the fiber/matrix interface shear stress existed between the interface wear region and new interface debonded region affects the fiber/matrix interface debonded length and loading carrying ability of intact and broken fibers. The damage evolution for C/SiC and SiC/SiC composites subjected to multiple fatigue loading sequences are predicted using the hysteresis energy dissipation damage model. Under multiple loading stress, the fatigue hysteresis dissipated energy increases when high peak stress and stress range increases due to the increase of fiber/matrix interface sliding range. However, when the low peak stress increases, the evolution of fatigue hysteresis dissipated energy depends on the interface debonding and sliding state.

Synergistic effects of hold time and cyclic loading on fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites at elevated temperatures in oxidizing atmosphere

In this paper, the synergistic effects of the hold time and cyclic loading on the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) at elevated temperatures in air condition are investigated. Based on the analysis of relative frictional sliding between fibers and the matrix in the fiber/matrix interface oxidation and interface wear region, the interface debonded length, interface counter-slip length and interface new-slip length are determined using the fracture mechanics approach. The fatigue hysteresis loops models are developed considering the synergistic effects of hold time and cyclic loading. The relationships between the fatigue hysteresis loops models and internal multiple fatigue damage mechanisms are established. The effects of fiber volume fraction, matrix crack spacing, fatigue stress levels, hold time and oxidation temperature on the fatigue hysteresis loops shape, location and area, fatigue hysteresis modulus and the fiber/matrix interface slip lengths are investigated. The experimental fatigue hysteresis loops, fatigue hysteresis dissipated energy, fatigue hysteresis modulus and the fiber/matrix interface slip lengths of cross-ply SiC/MAS and 2D SiC/SiC composites under cyclic loading for different hold time at elevated temperatures in air condition are predicted.

Comparisons of thermomechanical fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites subjected to different phase angles

In this paper, comparisons of thermomechanical fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) subjected to different phase angles of θ = 0, π/3, π/2, and π have been investigated. The shape, location, and area of fatigue hysteresis loops are affected by the phase angle under the thermomechanical cyclic loading. The effects of fiber volume fraction, fatigue peak stress, matrix crack spacing, interface frictional coefficient, and interface debonded energy on the thermomechanical fatigue hysteresis loops and fiber/matrix interface slip of different phase angles are discussed. The fatigue hysteresis loops of cross-ply CMCs under the phase angles of θ = 0 and π are predicted for different fatigue peak stresses and cycle numbers.

A thermomechanical fatigue hysteresis-based damage evolution model for fiber-reinforced ceramic–matrix composites

In this paper, a thermomechanical fatigue hysteresis-based damage evolution model for fiber-reinforced ceramic–matrix composites has been developed. Upon unloading and reloading, the fiber/matrix interface debonded length, interface counter-slip length, and interface new-slip length change with increasing or decreasing applied stress, which affects the stress–strain fatigue hysteresis loops and fatigue hysteresis-based damage parameters. The reloading/unloading stress–strain relationships when fiber/matrix interface partially or completely debonding are determined as a function of interface debonding/sliding, peak stress, applied cycle number, and thermal cycle temperature. The relationships between thermomechanical fatigue loading parameters (i.e. peak stress, applied cycle number, and thermal cyclic temperature), fiber/matrix interface debonding/sliding lengths, and fatigue hysteresis-based damage parameters (i.e. fatigue hysteresis dissipated energy, fatigue hysteresis modulus, and fatigue peak strain) have been established. The effects of fiber volume fraction, peak stress, matrix cracking space, and thermal cyclic temperature range on damage evolution under the out-of-phase thermomechanical cyclic loading have been discussed. The differences in damage evolution between in-phase/out-of-phase thermomechanical fatigue and isothermal fatigue loading at the same peak stress have been analyzed. The damage evolution of cross-ply SiC/magnesium aluminosilicate composite under the out-of-phase thermomechanical and isothermal fatigue loading has been predicted.

Damage and fracture of a ceramic matrix composite under isothermal and thermomechanical fatigue loading

In this paper, the damage and fracture of long-fiber-reinforced ceramic-matrix composites (CMCs) subjected to the isothermal cyclic fatigue, dwell-fatigue, and in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) have been investigated. The fiber/matrix interface shear stress is determined as a function of testing temperature and material properties, which affects matrix multicracking and fiber/matrix interface debonding/sliding upon unloading/reloading. The relationships between the cyclic testing temperature, applied cycle number, fatigue peak stress level, matrix crack spacing, fiber/matrix interface debonding/sliding, and the shape, location and area of thermomechanical fatigue hysteresis loops have been established. The damage evolution of fatigue hysteresis dissipated energy, fatigue peak strain, fatigue hysteresis modulus and fiber/matrix interface debonding/sliding lengths versus applied cycle numbers subjected to isothermal cyclic fatigue, dwell-fatigue, IP/OP TMF cyclic loading have been compared. The damage and fracture of cross-ply SiC/MAS composite subject to different fatigue loading types have been predicted. The comparison analysis among the isothermal cyclic fatigue, dwell-fatigue with different hold-times, and IP/OP TMF loading have been conducted, and the effects of testing temperature and loading frequencies on fatigue damage and fracture of long-fiber-reinforced CMCs have been discussed.