Stress-strain Method Research Articles

Stress-strain curve estimation from micropillar compression with transverse contraction effect

The Focused Ion Beam (FIB) technique and the associated compression testing capabilities provide versatile access to understanding the microstructural behaviour of materials. Among many objectives, determining the stress-strain relationship from experimental or numerical force-displacement data remains a fundamental challenge. However, for micropillers under compression, the inside deformation constraint is complex like in components and the transformation of a measured force-displacement curve into an accurate uniaxial stress-strain curve is not straightforward. In this context, in a previous numerical based analysis for perfect volume constancy or incompressibility the determination of reliable and accurate stress-strain curves from nonlinear load-deformation curves of micropillers was already verified. In the case of transverse contractions, however, numerical simulations of micropillers provide unexpected force-displacement behaviour, i.e. their force-displacement curves are almost superimposing and are very close to the force-displacements for incompressibility. This effect implies, that transverse contraction would have no contributions in micropillar compression. In contrast, independent simulations using a single finite element accurately explore the true uniaxial stress-strain behaviour for the whole range of transverse contractions. These are considered as the reference behaviour and are also treated by an analytical expression. With the presented new stress-strain estimation approach, including transverse contraction, any force-displacement curve from a micropillar under compression can be stepwise corrected. The first step of the new stress-strain curve estimation method, including transverse contraction, is carried out in the same way as in the preceding analysis for incompressibility, followed by further steps to obtain the final true stress-strain curve. Although the presented numerical analysis is exemplarily performed for the behaviour of fused silica, but the stress-strain approach is in the same manner generally applicable for a material behaviour with other stress-strain curves. The assumption behind is isotropic and nonlinear material behaviour.

Study on Axial Fatigue Performance and Life Prediction of High-Strength Bolts at Low Temperatures

High-strength bolts are widely used in outdoor steel structures such as transmission towers and bridges, where they not only endure cyclic wind loads and vehicle loads but also frequently operate in low-temperature environments. However, there is limited research on the axial fatigue performance of high-strength bolts, particularly regarding their mechanical behavior at low temperatures. Therefore, this study conducted a series of fatigue tests on high-strength bolts at 20 °C and 0 °C, both with and without pretension. We established S-N curves and fatigue limits for the three scenarios, revealing that pretension significantly enhances the fatigue life of the bolts, with a 10% increase in fatigue limit at 0 °C compared to 20 °C. However, due to the influence of pretension, the external load has a minimal effect on the actual stress experienced by the bolts, resulting in S-N curves for bolts with pretension being very similar to those for bolts without pretension during cyclic loading. Additionally, we obtained the load–displacement curves and corresponding stiffness degradation patterns of the bolts at both temperatures, finding that all bolts exhibited significant stiffness degradation after reaching 0.8 times their fatigue life. The high-strength bolts at 0 °C demonstrated greater stiffness and faster crack propagation rates, with increases of approximately 6% and 8%, respectively. Furthermore, electron microscope scans were used to clarify the fatigue crack initiation and the evolution of fatigue striations at both temperatures. Finally, by combining refined numerical simulations with the local stress–strain method, the effectiveness of the local stress–strain method for evaluating the fatigue life of bolts without pretension was validated. Building on this, we extended the method to bolts at 0 °C and those subjected to pretension, recommending notch sizes of 0.4 mm and 1.1 mm for fatigue life assessment of bolts with pretension at 0 °C and 20 °C, respectively.

First-principles Calculations of TlCdF3 Compound under Pressure

The present study focused on investigating various properties including structural, elastic, electronic, and optical of TlCdF3 compound under hydrostatic pressure using Density Functional Theory (DFT). The estimated results were consistent with previous investigations. The analysis of the electronic band structures between 0 and 50 GPa revealed that this compound possesses an indirect band gap. The stress-strain method was used to explain elastic properties, and the findings revealed that this compound is ductile, anisotropic and mechanically stable between 0 and 50 GPa. Investigations were done on significant optical features such as refractive index n (𝜔), extinction coefficient k (𝜔), absorption coefficient α (𝜔) and reflectivity R (𝜔) at various pressures between 0 and 50 eV. Our results imply that TlCdF3 compound has the potential for a broad range of technological applications under hydrostatic pressure.

Long-term mechanical properties of sludge-cured lightweight soil under the superimposed effects of drying-wetting and freezing-thawing

ABSTRACT Sludge-cured lightweight soils have unique advantages in roadbed treatment due to their properties such as low density and high strength. Its long-term mechanical law based on the superposition of drying-wetting and freezing-thawing (D-W-F-T) is studied through creep experiment. The test results show that: with the increase of the number of D-W-F-T, the deformation of the soil gradually increases, and the deformation tends to be stable when it reaches a certain number of times; the stress-strain isochronous curves are obviously nonlinear in general; The long-term strength increases with the increase of density and confining pressure, and decreases with the increase of the number of D-W-F-T; by comparing the isochronous stress-strain curve cluster method and the steady state creep rate vs. The comparative analysis suggests that the steady state creep rate versus stress level curve method be used to determine the long term strength.

Prediction of new 212 M2AB2 borides as a promising candidate for future engineering: DFT calculations

The elemental diversity is critical for identifying ternary MAB phases with exceptional properties by tuning bonding types and strength between constitutive atoms. The interactions between M and A atoms significantly impact the physical and chemical properties of MAB phases. M2AB2 (where M = Hf, Zr; A = Ga, Ge) was studied using first-principles density functional theory (DFT). Lattice constants (a, c) and internal coordinates have been found after optimization. The lattice parameters in terms of structure exhibit conformity with findings from earlier research. The electronic band structure (EBS) density of states (DOS) and density of states (DOS) have been determined. According to the band structures and density of states investigation, these compounds are electrical conductors. The elastic constants were computed using the stress-strain method. The computed elastic constants and phonon dispersion patterns support this newly found compound's mechanical and dynamical stability. The isotropic elastic moduli bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (v), and Vickers hardness (Hv) have been explored within the framework of the Voigte-Reusse-Hill approximation. Specific heat capacity, Debye temperature, entropy, Helmholtz free energy, and internal energy changes of M2AB2 (where M = Hf, Zr; A = Ga, Ge) compounds were investigated using thermodynamic characteristics. The minimum thermal conductivity (Kmin) and melting temperature (Tm) of the compounds have also been computed to assess whether they are suitable as thermal barrier coating (TBC) materials or for high-temperature applications. These compounds' optical properties have been studied, demonstrating their usefulness as coating materials for reducing solar heat absorption. The examined physical characteristics of M2AB2 (where M = Hf, Zr; A = Ga, Ge) are contrasted with those of comparable 212 and 211 MAB phases.

Investigation on the stability, mechanism and electronic properties of rutile TiO2 via first-principle calculations

Through first-principles calculations, the structural stability, electrical properties, and mechanical characteristics of TiO2 in the P42/mcm space group under varying external pressures were explored. The dynamical and elastic stability of TiO2 with P42/mcm space group are evaluated based on calculated results of phonon dispersion curves and elastic constants. Furthermore, the evaluation of the theoretical elastic modulus, derived through the stress-strain method, reveals a notable anisotropic characteristic in the TiO2 structure. In light of the ideal strength values ascertained through a range of strain conditions, coupled with the two-dimensional electron localization function maps pertinent to various pivotal structural models, the fundamental mechanism that dictates the mechanical properties of the TiO2 structure has been pinpointed. Meanwhile, the contributions of oxygen (O) and titanium (Ti) atoms to the conduction and valence bands in the band structure of TiO2 have been systematically analyzed. The results of the research will aid in exploring the inherent mechanical and electrical properties of TiO2 compounds.

Quantification and assessment of the error associated with engineering stress-strain analysis in stress accelerated creep tests in 316H stainless steel

ABSTRACT Historically, reduction of area has been neglected during uniaxial creep tests, and engineering rather than true stress-strain and strain rate have been considered. In high load accelerated tests, there is an increasing error associated with the engineering stress and strain, hence this assumption is no longer valid. In this work, uniaxial creep tests on Type 316H austenitic stainless steel at 480–550 °C have been analysed for both engineering and true stress–strain and strain rate. Significantly higher stresses and lower minimum strain rates were determined from true stress-strain rate relationships for as-received 316H. These differences diminish as the material is strain hardened, limiting plastic loading strains and reducing creep ductility. The true stress-strain rate analysis method is shown to be more accurate, however, the engineering stress-strain analysis predicts higher creep strain rates for a given stress and is the more conservative measure for component lifetime assessments.

Phonon softening induced phase transition of CeSiO4: a density functional theory study.

Density functional theory plus Hubbard U (DFT+U) methodology was used to calculate the structures and energetic landscapes of CeSiO4, including its stetindite and scheelite phases from ambient pressure to ∼24 GPa. To ensure accurate simulations of the high-pressure structures, assessments of strain-stress methods and stress-strain methods were conducted in prior, with the former found to have a better agreement with the experimental result. From DFT calculations the equation of states (EOS) of both stetindite and scheelite were further obtained, with the fitted bulk moduli being 182(2) GPa and 190.0(12) GPa, respectively. These results were found to be consistent with the experimental values of 177(5) GPa and 222(40) GPa. Furthermore, the calculated energetics suggest that the stetindite structure is more thermodynamically stable than the scheelite structure at a pressure lower than 8.35 GPa. However, the stetindite → scheelite phase transition was observed experimentally at a much higher pressure of ∼15 GPa. A further phonon spectra investigation by the density functional perturbation theory (DFPT) indicated the Eg1 mode is being softened with pressure and becomes imaginary after 12 GPa, which is a sign of the lattice instability. Consequently, it was concluded that the stetindite → scheelite transition is predominantly initiated by the lattice instability under high-pressure.

Investigating elastic constants across diverse strain-matrix sets

Elastic constants and mechanical properties play a pivotal role across multiple disciplines and engineering applications. We introduced the optimized high-efficient strain-matrix set (OHESS) that determines the second-order elastic constants of materials using the stress–strain method. Herein, we systematically investigate the computational efficiency of OHESS across a broad range of crystal systems and compare it with other notable stress–strain approaches, such as the single-element strain-matrix sets and the universal linear-independent coupling strains. Notably, our data affirm the superior efficacy of OHESS among the strain-matrix sets under consideration. We believe OHESS will markedly improve computational efficiency in determining the elastic constants and mechanical properties, becoming an indispensable tool for material research, design, and high-throughput screening.

Elastic and thermodynamic properties of B2-MgX intermetallics: A high throughput first-principles investigation

Precipitation strengthening is an effective approach in Mg alloys, and hence, it is worthwhile investigating the properties of the Mg-containing intermetallics. In the present work, the thermodynamic and mechanical properties of B2-MgXs (69 different elements) are calculated by high-throughput first-principles calculations. The static properties, including equilibrium volume, equilibrium energy, and bulk modulus, and thermodynamic properties, including linear thermal expansion coefficient (LTEC), are predicted. Meanwhile, the second-order elastic constants (SOECs) and third-order elastic constants (TOECs) are calculated using an efficient strain-stress method. The consistency between our results and the limited experimental or previous theoretic work confirms the high reliability of the present work. Using SOECs and equilibrium energy, the stability of MgXs is assessed from mechanics, energy and lattice dynamics, and 33 (out of 69) stable compounds are screened out. According to Young's and shear modulus, the MgXs are divided into four classes, and the first two classes present high modulus, high ductility, and reasonable anisotropy, equipping those compounds as promising candidates for precipitation strengthening in Mg alloys. In addition, the pressure and temperature dependence of SOECs is estimated using TOECs and LTEC. Furthermore, the present work provides abundant fundamental data for the design of new Mg alloys.

Mechanical Properties of Al–Mg–Si Alloys (6xxx Series): A DFT-Based Study

Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advantages, which include non-corrosivity, low density, relatively low cost, high thermal and electrical conductivity, formability, and weldability. This study investigates the bulk mechanical properties of Al–Mg–Si alloys and the influence of the Si/Mg ratio on these properties. The Al cell was used as the starting structure, and then nine structures were modeled with varying percentages of aluminium, magnesium, and silicon. Elastic constant calculations were conducted using the stress–strain method as implemented in the quantum espresso code. This study found that the optimum properties obtained were a density of 2.762 g/cm3, a bulk modulus of 83.3 GPa, a shear modulus of 34.4 GPa, a Vickers hardness of 2.79 GPa, a Poisson’s ratio of 0.413, a Pugh’s ratio of 5.42, and a yield strength of 8.38 GPa. The optimum Si/Mg ratio was found to be 4.5 for most of the mechanical properties. The study successfully established that the Si/Mg ratio is a critical factor when dealing with the mechanical properties of the Al–Mg–Si alloys. The alloys with the optimum Si/Mg ratio can be used for industrial applications such as plane skins and mining equipment where these properties are required.

Constitutive relations of nanoscale hydration products present in engineered cementitious composites from machine learning assisted experimental nanoindentation

In this work, a method to evaluate the stress-strain properties (at nano-scale) of constitutive phases present in the hydration cement matrix is presented. Using an experimental grid nanoindentation using Berkovich indenter, the constituent phases i.e., Low Density Calcium Silicate Hydrate (LD CSH), High Density Calcium Silicate Hydrate (HD CSH) and clinkers are indented upon during different points of Ordinary Portland Cement (OPC) paste hydration. Further, this study is conducted on four other cement pastes: OPC +20% fly ash, OPC +40% fly ash, OPC +0.5% nanosilica and OPC +1% nanosilica. Using experimental grid nanoindentation technique results in a large dataset depending upon the size of the gird. Three different machine learning algorithms including K-means, Gaussian mixture model (GMM) clustering and, support vector machine (SVM) have been implemented. The developed stress-strain evaluation method has allowed to ascertain the constitutive relations as yield stresses of 354 MPa for LD CSH, 393 MPa for HD CSH and 4340 MPa for clinkers, yield strains of 1.8 × 10−2 for LD CSH, 1.1 × 10−2 for HD CSH and 3.7 × 10−2 for clinkers; ultimate stresses of 371 MPa for LD CSH, 424 MPa for HD CSH and 6085 MPa for clinkers, ultimate strains of 2 × 10−2 for LD CSH, 1.4 × 10−2 for HD CSH and 4.4 × 10−2 for clinkers; and strain hardening exponents of 0.85 for LD CSH, 0.72 for HD CSH and 2.1 for clinkers. Elastic modulus, hardness and the stress-strain values obtained from the load vs. displacement curves are used for the clustering analysis and compared with deconvolution results. These properties have been used to test the feasibility of application of machine learning algorithms to classify the grid nanoindentation data. It was found that the machine learning algorithms were indeed capable of clustering the data obtained from experimental grid nanoindentation. This study presents a novel method to evaluate stress-strain properties of the constituent phases present in the cement microstructure and application of machine learning in the field of material characterisation using nanoindentation technique.

Development of a novel tool used to support design and failure analysis of multiaxial fatigue loading: A case of steering knuckle

The steering knuckle requires a lot of attention when designing because once it is damaged it must be replaced with a new one. In automotive industry, since the structure of steering knuckles is very complex and different from each other; it is difficult to design it separately for each vehicle. In order to address this problem, an innovative idea to solve this problem was developed and named as analysis support tool for steering knuckle of the entire vehicle. In addition to that, the development of computer tool that can assist designers in the analysis phase can save the design time. For this purpose, analysis support tool for steering knuckles of entire vehicles has been developed. The part is first modeled by Free CAD 0.2 software considering the precision of the geometry. Based on scientific approach analysis support tool for steering knuckle of all vehicles is developed which can provide analysis of all forces acting on the component, maximum displacement, fatigue damage, maximum deflection, slope, factor of safety, life expectancy, stress and strain amplitude by stress and strain method and compare the results from Morrow, Smith Watson and Walker equations. In addition to that doing experiment of multiaxial is very expensive and time taking for the designer; therefore, developing simple, accurate and robustness tool used to determine life expectancy and cumulative fatigue damage of multiaxial which can be applied to entire materials is very crucial. The developed tool would be universal, effective, simple, and efficient method used to estimate the life expectancy and Cumulative fatigue damage of multiaxial. Finally, data’s from open literatures are used to validate the accuracy and capabilities of the proposed tool for multiaxial fatigue loading. The end result is a computer tool that can be dedicated and run on any computer without using any internet connection

Elastic properties of A 2Ti6O13 ( H, Li, Na, K and Rb): a computational study

The elastic properties of the alkali hexatitanate family A 2Ti6O13 (A = H, Li, Na, K, and Rb) are investigated based on density functional theory within a generalized gradient approximation plus Hubbard U (GGA+U) approach. The results showed that all members of the family are wide-band semiconductors and the calculated lattice parameters are consistent with experimental values. In terms of mechanical stability, the results indicated that the alkali hexatitanates are highly incompressible to uniaxial stress, with the largest elastic constant C22 reaching values as high as 265 GPa in K2Ti6O13. The obtained elastic constants, using the stress–strain method, were used to calculate bulk modulus, shear modulus, Young’s modulus, brittleness and ductility, elastic anisotropy, Vickers hardness, sound velocities, and the Debye temperature. It was found that the member of the family with the highest atomic number of the alkaline group, Rb2Ti6O13, had the highest values of bulk, shear, and Young’s modulus, as well as the lowest values of shear and compression anisotropy, and a high Vickers hardness.

Experimental study on acoustic emission stress memory function of rock-like specimens under uniaxial compression

The Kaiser effect in rock acoustic emission (AE) test is the most direct manifestation of rock memory function. This article focuses on the influence of different deformation stages and different historical stress conditions on stress memory function, and conducts AE testing of rock-like specimens. It explained the stress memory function in AE testing from the perspectives of crack propagation and damage accumulation. The crack initiation stress σci and crack damage stress σcd of specimens were obtained based on the stress-strain curve method, and the different deformation stages were divided. The damage evolution coefficient [Formula: see text] was proposed to measure the size of the stable development range of damage based on the normalized crack initiation and crack damage stress. The historical stress in the elastic stage could be easily identified from the Kaiser effect during the reloading process, even if the time interval reached 120 hours. The Felicity effect appeared during the reloading process when the historical stress was in the stage of stable crack propagation, and the FR value showed a decreasing trend with the extension of the time interval between loading tests. The loading history in the elastic stage was a training for the AE stress memory function under complex historical stress conditions, which restored the Kaiser effect in the stage of stable crack propagation. The distribution of AE events and CT scanning results were also analyzed in the article, and the damage accumulation information characterized by both are basically consistent. The double Kaiser effect phenomenon appeared in the AE test under complex historical stress conditions, although the criterion for discriminating the AE signal at the Kaiser effect point corresponding to the lower stress remained to be further studied and verified.

INTEGRATION OF ADVANCED METHODS AND MODELS IN THE METHODOLOGY OF ENGINEER-ING CALCULATION OF TORSION SHAFTS OF LIGHT ARMORED VEHICLE SUSPENSION SYSTEMS (REVIEW ARTICLE)

The requirements for the tactical and technical characteristics of the suspension systems of light armored vehicles are constantly growing, taking into account the increase in the intensity of their loads. It is necessary to improve the suspension system, in particular the torsion shafts, which are the most responsible and loaded in the suspension system of light armored vehicles. The existing traditional methods of calculating the torsion shafts of the suspension systems of light armored vehicles do not meet modern requirements. Today, there is a contradiction between the real indicators of strength and durability and those that should be provided for light armored vehicles of the new generation, and especially for future ones. In addition, this contradiction is deepened by the lack of in-depth scientific methods and models of the stress-strain state that would adequately reflect the processes and states in the torsion shafts of the suspension systems of light armored vehicles, and would also become the basis for developing measures to increase their strength and durability. The analysis of literaure showed the absence of a systematic connection of structural solutions, technological modes and load conditions in the calculations of torsion shafts of suspension systems of light armored vehicles. The necessity of creating such a system approach in calculations is shown. Conclusions were made about the need to integrate advanced methods and models in a single methodology for calculating torsional shafts of suspension systems of light armored vehicles. The necessity of linking stress-strain state methods with constructive, technological, and operational factors and developing a suitable specialized software-module complex for carrying out relevant research is shown. Keywords: light armored vehicle; performance characteristics; torsion shaft; suspension systems; stress-strain state; strength; durability; elastic-plastic deformation; contact interaction

Predict the fatigue unloading elastic-plastic reduction mechanism of single crystal 3C-SiC Newton layer by reconstructed multi-dimensional dynamic static combination indenter

To explore the elasto-plastic reduction mechanism of single crystal 3C-SiC Newton layer under fatigue unloading. Reconstructed multi-dimensional single crystal 3C-SiC Newton layer unloading dynamic - static combined head. The evolution law of dislocation loop, the trend of load displacement and the direction of strain concentration expansion during fatigue unloading are analyzed. According to the stress characteristics of nanoindentation process and the requirements of real indentation environment, the NVE ensemble matrix and boundary condition parameters are integrated and optimized. The influence of indenter shape on the evolution process of dislocation ring emergence, fracture and connection and the evolution mechanism are analyzed. Through diamond identification method and stress-strain analysis method, the multi-dimensional force analysis of plastic unloading of nano-indentation is realized. It is found that the yield limit of semi-circular indenter first reaches the yield limit from the elastoplastic loading stage to the plastic loading stage than the normal four-cone. Combined with the load displacement curve, the real stress characteristics of the nano-indentation single crystal 3C-SiC Newton layer are analyzed. The results show that elastoplastic reduction existed in fatigue unloading, and the generation and development of micro-dislocation rings in elastoplastic deformation reduction under fatigue unloading of different dimensions indenter are different. The ultimate yield stress of semi-circular indenter is 3.82GPa and the ultimate strain is 1 %，the ultimate yield stress of positive quad conical indenter is 6.60GPa and the ultimate strain is 1.5 %. The elasto-plastic reduction mechanism of fatigue unloading is directly driven by the plastic evolution mechanism of dislocation ring.

Discussion on Fatigue Life Analysis Methods for Connecting Bolts of the Top Cover of Water Pump Turbines

Under the joint action of dynamic and static loads, the connecting bolts of the top cover of the pump turbine are prone to cumulative damage in local areas such as threads, resulting in cracks or development, and fatigue fracture may occur in severe cases, which will cause serious safety accidents. Therefore, it is necessary to carry out accurate fatigue life estimation analysis for connecting bolts, which has always been a hot spot and difficulty in the industry. This paper introduces several commonly used fatigue life analysis methods of parts, combined with the force characteristics and structural characteristics of the connecting bolts of the top cover, and analyzes and discusses the fatigue life analysis methods suitable for the top cover bolts. Finally, it is believed that the application of stress-strain field strength method can better describe the actual state of the bolt danger area, and the current damage state has an influence on the amount of damage generated by further loading, and the fatigue life analysis of connecting bolts can be combined with the stress-strain field strength method and variable damage linear cumulative damage theory, and the fatigue life and residual fatigue life can be estimated in the design stage or after the phased service of the bolt.

First-principles investigation of phonon spectrum, elastic, mechanical and thermophysical characteristics of an actinide-oxide ceramic

In this paper, first-principles calculations and density functional perturbation theory (DFPT) based on the ab-initio approach, have been utilized to investigate mechanical, elastic anisotropy, dynamical, and thermal properties of nuclear fuel UO. The results reveal that the obtained equilibrium lattice parameter at zero temperature and pressure has a good consistency with the experimental lattice constant. The elastic constants are evaluated using the strain-stress method. These coefficients are estimated to be positive and satisfied the Born-Huang relations, which is indicative of the mechanical stability of this compound. The mechanical properties such as shear modulus, bulk modulus, and Young's modulus of UO are calculated, and the results show the compound's stiffness. Pugh's criterion (B/G) is obtained to be approximately 3.5, which confirms that UO is a ductile substance. Elasticity analysis including universal anisotropy and Zener's anisotropy factor reveals that UO falls into the category of anisotropic materials. The phonon spectrum curve is calculated using DFPT along the high symmetric paths and no negative frequencies are observed in the dispersion relations, implying the dynamical stability of the crystalline structure. The quasi-harmonic Debye (QHD) model is employed to study the thermophysical properties such as Debye temperature, isochoric heat capacity, coefficient of thermal expansion, entropy, and Grüneisen parameter at high pressures and temperatures. We found that molar specific heat was more affected by the temperature than pressure.

Low-cycle tensile fatigue performance of a wire rope strand with an internal flaw in varied position and direction

Taking into account the effects of mean stress, elastic-plasticity and nonlinear contact, the finite element model of the tensile fatigue performance of an internal flawed wire rope strand is built by using the local stress strain method in the present study. A mesh model of the strand with a high-precision feature is established through a block-based method and refinement in the flaw region. The strand with a flaw is investigated to explore its fatigue life distribution, and the effects of the flaw’s position and direction on the strand’s fatigue and bearing performances are analyzed. The numerical results demonstrate that the low-cycle fatigue life zone occurs at the interwire contact region of the intact wire rope strand, while is located at the flaw region of the wire rope strand with an internally flawed wire. The minimum fatigue life of the wire rope strand decreases due to the occurrence of the internal flaw. Moreover, as the internal flaw’s direction angle decreases, the strand’s minimum fatigue life is reduced, and the internal flaw with the major axis perpendicular to the strand axis is the most dangerous. The internal flaw in the outer wire has a more severe influence on the fatigue property of the wire rope strand than a core wire flaw with the same dimension and direction. The wire rope strand is more prone to stress yielding due to the internal flaw, and the effect is getting more significant as the internal flaw’s direction angle decreases.