Cyclic Mechanical Behavior Research Articles

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Strain softening observed during nanoindentation of equimolar-ratio Co–Mn– Fe–Cr–Ni high entropy alloy

This research article presents an atomistic study on the cyclic nanoindentation of an equimolar-ratio Co–Mn–Fe–Cr–Ni high-entropy alloy (HEA) using molecular dynamics simulation. The study investigated the effects of indentation depth on the cyclic load versus the indentation depth of the HEA. The results showed that the cyclic response exhibits a pronounced shift towards plasticity with pile-up formation instead of sinking behavior at higher indentation depths. Within the realm of molecular dynamics simulations, the simulated hardness value reached up to 16 GPa for the initial indentation cycle. A steep drop in the load–displacement curve was observed during the elastic–plastic transition, signifying substantial strain softening of the substrate. It was found that the densely clustered stacking faults undergo a reverse transition during cyclic loading, contributing to the backpropagation phase responsible for elastic recovery despite subsequent strain hardening. The study provides important insights into the underlying mechanisms governing the cyclic mechanical behavior of HEAs to guide their improved micromanufacturing.

The novel mechanical and recovery behaviors of 3D printed EVA under cyclic tensile loading

In this study for the first time, the cyclic mechanical properties and shape recovery behavior of 3D printed EVA were investigated. EVA with high elastic capability was successfully printed by direct material extrusion method and then a novel cyclic shape recovery test was conducted in which the tensile test was performed at three different strain levels (250, 500 and 1000%) in six cycles and after the end of each cycle by heating the samples, their recovery was measured. The results showed that in all strain levels and tensile cycles, the full recovery is observed, which is completed in two steps after unloading and after heating the sample. Upon exposure to hot water, the disruption of intermolecular forces facilitated the recovery of the material's original shape through increased molecular mobility and rearrangement of polymer chains. However, it was observed that with increasing strain levels (from 250% to 1000%), the recovery process became less effective, leading to a decline in mechanical properties. Also, by increasing the number of tensile cycles, the tensile stress value at the desired strain level and the rate of change decreases and after the second cycle, the cyclic behavior under tensile loading almost reaches a constant trend.

Mesoscale analysis of aging mechanical behaviors of 3D woven composites

3D orthogonal woven composites (3DOWCs) are inevitably subjected to the severe cyclic hygrothermal aging environment in the application of supersonic aircraft structures and their durability should be proven. However, most current works relating to the hygrothermal aging of 3DOWCs rely on the experimental methods which are of high cost. To address this issue, a matrix-yarn mesoscale model of 3DOWCs was established to investigate the cyclic hygrothermal aging mechanical behaviors in this paper. High-fidelity mesoscale representative volume element (RVE) was constructed with realistic geometric configuration of the reinforcement. Only the aging properties of pure resin were needed in the mesoscale model. The aging properties of fiber yarns were calculated with Chamis formulas accounting for resin aging. Tension-compression asymmetry behavior of resin matrix was accounted in the constitutive model. The damage initiation and propagation of resin matrix, yarn and cohesive interface were modeled by the progressive 3D damage model. The mechanical properties of 3DOWCs before and after aging were predicted by the mesoscale model and validated with experiment. This work can provide effective tool for the design of 3DOWCs applied in harsh environments.

Cyclic mechanical behavior of electro-welded meshes used as structural reinforcement

In this work, the monotonic and cyclic behavior of 6, 7 and 8 mm diameter electro welded meshes manufactured in Colombia and used as reinforcement in construction is studied experimentally. The cyclic mechanical behavior of the material is modeled using the Ramberg-Osgood model, and the model parameters are adjusted based on experimental data and using linear regression. The results show that the material undergoes cyclic softening, and that the Ramberg-Osgood Ramberg -Osgood model accurately predicts the monotonic and cyclic mechanical behavior.

Development of a FEM procedure for evaluating the pressure profile in the industrial wheel and fatigue strength analyses

Industrial wheels are heavily loaded components that undergo severe cyclic stress conditions. Thus, the design of the rims must include a wide fatigue study which articulates in laboratory and field tests, analytical and numerical analyses and comparison of the experimental and computational results. This paper presents the study approach applied in the study of a 25 in rim for earth-moving machines manufactured by Moveero. The rim was subject to a design update which provided the reduction of the thickness from 11 mm to 9 mm. We decided to study the interaction tire-rim because it's a critical zone. The failures affected the area of the seat radius of the fixed flange of the rim, which resulted to be the most stressed part of the rim because of the bending actions of the tire on the flange. In order to deepen the cyclic mechanical behaviour of the component, laboratory inflation and rolling tests were carried out in Woodridge USA considering several combinations of inflation pressure and radial load applied to the wheel. The strain data from the tests were analysed to develop a reverse empirical model for the contact pressure between tire and rim. Once the load diagram applied to the flange for each test was estimated, FEM static simulations could be performed on a 3D model of the rim through SolidWorks Simulation. The stress fields obtained were then used for fatigue FEM numerical analyses which could return an evaluation of the predicted life of the component under several load conditions.

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.

Natural overlaying behaviors push the limit of planar cyclic deformation performance in few‐layer MoS2 nanosheets

AbstractAs a typical two‐dimensional (2D) transition metal dichalcogenides (TMDCs) material with nonzero band gap, MoS2 has a wide range of potential applications as building blocks in the field of nanoelectronics. The stability and reliability of the corresponding nanoelectronic devices depend critically on the mechanical performance and cyclic reliability of 2D MoS2. Although an in situ technique has been used to analyze the mechanical properties of 2D materials, the cyclic mechanical behavior, that is, fatigue, remains a major challenge in the practical application of the devices. This study was aimed at analyzing the planar cyclic performance and deformation behavior of three‐layer MoS2 nanosheets (NSs) using an in situ transmission electron microscopy (TEM) variable‐amplitude uniaxial low‐frequency and cyclic loading–unloading tensile acceleration test. We also elucidated the strengthening effect of the natural overlaying affix fragments (other external NSs) or wrinkle folds (internal folds from the NS itself) on cycling performances and service life of MoS2 NSs by delaying the whole process of fatigue crack initiation, propagation, and fracture. The results have been confirmed by molecular dynamics (MDs) simulations. The overlaying enhancement effect effectively ensures the long‐term reliability and stability of nanoelectronic devices made of few‐layer 2D materials.image

Low Frequency Cyclic Mechanical Loading of Till Deposits from Northern Germany under Oedometric Conditions

Glacial deposits are of significant importance to geotechnical engineers and geologists in northern Europe, North America, and Northern Asia, as vast areas of these land surfaces were historically covered with ice leading to the formation of a wide variety of till deposits. The use of these areas for various engineering purposes warrants their subjection to mechanical loads (of static and cyclic forms) from manmade structures, as well as natural hazards such as earthquakes. This paper focuses on the experimental investigation of the cyclic mechanical loading behavior of two glacial tills from northern Germany under one-dimensional loading or oedometric conditions, and in different soil wetting conditions. The experimental results show a significant dependence of the cyclic mechanical response of the glacial tills on wetting condition and number of loading cycles. The recorded values of accumulated plastic strains of the glacial tills generally increase with an increase in wetting or moisture content, with the highest measured value for the two tills being around 3.9% after 19 cycles of loading. The findings of the experimental cyclic mechanical tests of the glacial tills are discussed in view of the intrinsic soil behavior and fabric.

Effect of Friction Stir Processing on the Fatigue Performance of AZ31 Magnesium Alloy

Herein, the cyclic mechanical behavior of AZ31 magnesium alloy after multipass friction stir processing (FSP) is investigated up to the very high‐cycle fatigue (VHCF) regime. The grain refinement and texture evolution after processing are evaluated to enhance the understanding of the fatigue response. Although ultimate tensile strength and ductility of the friction stir processed AZ31 increase up to about 320 MPa and 25%, respectively, the fatigue performance deteriorates in comparison with that of the as‐received condition due to the low yield strength and texture evolution after processing. Furthermore, analysis of fracture surfaces of the samples after cyclic loading reveals that the as‐received AZ31 is more prone to brittle fracture with multiple‐origin fatigue failure even at low stress amplitudes. On the contrary, the dominant failure mechanisms of the friction stir processed samples are initiation and propagation of cracks originating from the surface, porosities, and grain size inhomogeneity. Nevertheless, the capability of FSP for providing superior crack initiation resistance in the VHCF regime is demonstrated as a significant contribution. Based on a detailed study of prevalent microstructural features, processing–property–damage relationships are established indicating the major effect of FSP on the final performance of the AZ31 magnesium alloy.

Viscoplastic constitutive model considering strain rate sensitivity under multiaxial thermomechanical fatigue loading

AbstractStrain rate sensitivity will change the cyclic mechanical response of materials under multiaxial thermomechanical fatigue loading; thus, it will lead to errors in fatigue life prediction if strain rate sensitivity is not considered in constitutive simulation. In order to more accurately express the time/rate dependence of viscoplastic behavior, a strain rate sensitivity factor is proposed to modify the viscoplastic function of Chaboche model first. On this basis, a viscoplastic constitutive model considering strain rate sensitivity under multiaxial thermomechanical fatigue loading is proposed, which can describe the varying influence of strain rate sensitivity on cyclic mechanical behavior. Meanwhile, the exponential isotropic hardening rule with the linear term is adopted to characterize the initial rapid softening and subsequent stable softening of the material under fatigue loading at elevated temperature. Moreover, the material‐dependent nonproportional hardening coefficient and the loading path‐dependent rotation factor are used in the kinematic hardening rule to consider the effect of nonproportional additional hardening on the cyclic mechanical behavior of materials. Finally, the proposed method is verified by the stress–strain data of titanium alloy TC4 and Ni‐based superalloy GH4169 under uniaxial and multiaxial thermomechanical fatigue loadings, and a good agreement is obtained.

Anisotropy in cyclic behavior and fatigue crack growth of IN718 processed by laser powder bed fusion

This study aims at characterizing the role of strong anisotropy in fatigue crack growth for a superalloy processed by additive manufacturing. The choice has been made to investigate two specimens exhibiting significantly different crystallographic textures, representative of possible variations of microstructures within a real part.Both cyclic mechanical behavior and fatigue crack growth have been investigated at high temperature. As a consequence of the oriented microstructure, high levels of anisotropy of elastic and viscoplastic behaviors were observed. These behaviors have been modeled by the combination of orthotropic elasticity, a Hill’s criterion and linear and non-linear kinematic hardening laws. To assess fatigue crack growth driving forces, in the context of complex crack shape, finite element analysis was proceeded taking care of 3D crack shape description. J was derived from G-θ, this method being convenient for anisotropic material.In most cases, fatigue cracks were found to grow preferentially at the vicinity of grain boundaries, regardless of the crystallographic orientation. An intrinsic fatigue crack growth rate related to this intergranular mechanism has been determined. On the other hand, mostly transgranular crack growth were observed when the loading was applied in the processing direction. In this case, the crystallographic texture appears to be the main factor governing the fatigue crack growth rate.

High Temperature Fatigue Behavior and Failure Mechanism of Ti-45Al-4Nb-1Mo-0.15B Alloy

Strain-controlled low cycle fatigue experiments were carried out on the TiAl alloy Ti-45Al-4Nb-1Mo-0.15B at 400 °C and 750 °C to reveal the cyclic mechanical behavior and failure mechanism. The TiAl alloy presents stable cyclic characteristics under fatigue loading at elevated temperatures. No obvious cyclic softening or cyclic hardening was manifested during experiments. The cyclic stress–strain relationship is well described by the Ramberg–Osgood equation. The fatigue lifetime at different temperatures has a log-linear relationship with the total strain ranges. The fracture morphology indicates the main fracture mode of fatigue specimens at 400 °C is a brittle fracture, while there is a ductile fracture at 750 °C. Meanwhile, the trans-lamellar fracture is dominant for the lamellar microstructure and the percentages of the inter-lamellar fracture decreases with the strain amplitude.

Anisotropic cyclic plasticity modeling for additively manufactured nickel‐based superalloys

AbstractThe additively manufactured materials show anisotropic mechanical properties. In the present paper, a constitutive model for a nickel‐based superalloy made by selective laser melting was established to characterize cyclic mechanical behaviors under multiaxial loading conditions. Detailed material tests revealed that the effects from the building orientation decrease with multiaxial cyclic loads. A cyclic constitutive model based on the Hill criterion was introduced for the superalloy and considered the orthotropic mechanical properties depending on loading cycles. The computation confirms the model can reasonably simulate the cyclic elastic‐plastic behavior under non‐proportional complex loading conditions and provides an applicable method for engineering applications.

Anisotropic cyclic deformation behavior of an extruded Mg-3Y alloy sheet with rare earth texture

Mg-RE (magnesium-rare earth) alloys exhibit pronounced in-plane anisotropy of mechanical response under quasi-static monotonic loading resulting from the RE texture, as extensively reported. In this work, an obvious in-plane anisotropy of cyclic deformation behavior was observed in an extruded Mg-3Y alloy sheet during strain-controlled tension-compression low-cycle fatigue (LCF) at room temperature. The extrusion direction (ED) samples displayed better fatigue resistance with almost symmetrical hysteresis loops and longer fatigue life compared with the transverse direction (TD) samples. The influences of texture on the deformation modes, cracking modes, and mechanical behavior of Mg-Y alloy sheets under cyclic loading were studied quantitatively and statistically. The activation of various slip/twinning-detwinning systems was measured at desired fatigue stages via EBSD observations together with in-grain misorientation axes (IGMA) analysis. The results indicate that the activation of deformation modes in the TD sample was featured by the cyclic transition, i.e., prismatic slip (at the tensile interval) →{10–12}tension twinning (at the compressive reversal) → detwinning + prismatic slip (at the re-tensile reversal). In the case of the ED sample, the cyclic deformation was dominated by the basal slip throughout the fatigue life. For cracking modes, intergranular cracking and persistent slip bands (PSB) cracking were the primary cracking modes in the ED sample while the TD sample showed a high tendency of {10–12} tension twinning cracking (TTW cracking). The underlying mechanisms influencing the activation of various slip/twinning-detwinning systems, as well as cracking modes and cyclic mechanical behavior, were discussed.

Deformation Cycle Resistance of Titanium Nickelide - Polymer Composite Material

The static and cyclic mechanical behavior of samples of composite material with a matrix made of silicone rubber or low-pressure polyethylene reinforced with fibers of titanium nickelide with a martensitic structure has been investigated. It is shown that such composite materials have high deformation cycle resistance.

Finite element analysis of the thermo-mechanical fatigue of DD8 single crystal nickel-based superalloy

Abstract A nonlinear finite element method is presented for analysing the thermo-mechanical fatigue behavior of the DD8 single crystal nickel-based superalloy. The specimens had axial orientations along the [001] direction. In-phase and out-of-phase thermo-mechanical fatigue were simulated under mechanical strain control with a temperature variation from 450 to 900 °C. The cyclic mechanical behavior, the equivalent stress and plastic strain were investigated in both γ' phase and γ matrix.

Experimental And Numerical Modelling of Cyclic Softening and Damage Behaviors for a Turbine Rotor Material at Elevated Temperature

In order to better understand the physical process of deformation and cyclic softening a 12% Cr martensitic stainless steel FV566 has been cyclically tested at high temperature in strain control. Increase in temperature was found to increase the cyclic life, softening rate and viscous stress magnitude. An increase in the dwell time led to the acceleration of the material degradation. The microstructure changes and dominating deformation mechanisms were investigated by means of scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. The results have revealed a gradual sub-grain coarsening, transformation of lath structure into fine equiaxed sub-grains, and misorientation angle development in blocks and packets until material failure. Further, a unified viscoplastic constitutive model coupled with a physically-based damage variable, is proposed to capture the cyclic mechanical behavior and microstructural evolution of the material at elevated temperature. The mechanical strength can be reduced by the decrease in the dislocation density, the coarsening of the martensitic lath and the loss of the martensitic structure under cyclic loading. The proposed physically-based damage variable is driven by the evolutions of dislocation density and martensitic lath width. The good comparisons with test results mean that the proposed model can reasonably model the cyclic elastic-viscoplastic constitutive behavior of the material at high temperature.

An innovative test equipment with rate-dependence in interface damage and its operation under cyclic loading.

An innovative test equipment for analyzing the dynamic damage at the interface of geosynthetic materials is introduced. It provides a result of shear damage on the structural surface of a geosynthetic material that has been subjected to cyclic loading of different amplitudes. First, the experimental data of geosynthetics under cyclic loading are obtained based on the innovative test equipment mentioned above, and a mathematical identification method for the relationship between cyclic loading parameters and shear mechanical behavior of geosynthetics is proposed based on the Mohr-Coulomb criterion, assuming that the micro-element strength of geosynthetics follows Weibull distribution. Moreover, the proposed model, which takes into account repeated loading-unloading conditions, enables this simulated damage process to have properties of reoccurring load cycles, and the proposed method was evaluated by experimental datasets from this study and the existing literature and proved to have a satisfying performance in predicting mechanical behavior of shear stress in geosynthetics under different cyclic loadings. Second, the self-developed test instrument can well solve the direct shear parameters of geosynthetics under dynamic load and can be obtained as a new dynamic statistical model with rate-dependence in interface damage.

Multiaxial low-cycle thermo-mechanical fatigue of a low-alloy martensitic steel: Cyclic mechanical behaviour, damage mechanisms and life prediction

Axial–torsional Low-Cycle Fatigue tests (LCF) and Thermo-Mechanical Fatigue tests (TMF) were performed on a low-alloy martensitic steel for temperatures between 300°C and 600°C, as both proportional and non-proportional. The results show that non-proportional loading leads to an increase in fatigue damage and to a decrease in the observed lifetime. The TMF damage model is proposed here in order to incorporate the effects of multiaxial loading and varying temperatures. This damage model is based on a critical plane approach, and it incorporates the fatigue, oxidation and creep forms of damage. Finally, the proposed model is validated for a large experimental database.