Application Of Cyclic Loading Research Articles

A Full-Scale Tidal Blade Fatigue Test using the FastBlade Facility

Fatigue testing of tidal turbine blades requires the application of cyclic loads without the ability to match the natural frequency of the blade due to their high stiffness and the associated thermal issues of testing composite materials at those frequencies (i.e., 18–20 Hz). To solve this, loading the blades with an auxiliary system is necessary; in most cases, a conventional hydraulic system tends to be highly energy-demanding and inefficient. A regenerative digital displacement hydraulic pump system was employed in the FastBlade fatigue testing facility, which saved up to 75 % compared to a standard hydraulic system. A series of equivalent target loads were defined using Reynolds-Averaged Navier Stokes (RANS) simulations (based on on-site collected water velocity data) and utilised in FastBlade to demonstrate an efficient way to perform fatigue testing. During the test, a series of measurements were performed on the blade response and the Fastblade test structure itself, providing novel insights into the mechanical behaviour of a blade, and enabling improved testing practice for FastBlade. Without catastrophic failure, the blade withstood the principal tidal loading for 20 years (equivalent). This test data will enable FastBlade to identify improvements to the testing procedures, i.e., control strategies, load introduction, instrumentation layout, instrument calibration, and test design.

Subgrade soil response to rail loading: Instability mechanisms, causative factors, and preventive measures

The demand for more efficient heavy-haul rail networks over soft subgrades poses significant geotechnical challenges and requires a comprehensive understanding of stress conditions as well as the failure potential of subgrade soil under moving wheel loads and increasing rail speeds. Unfavourable stress conditions in the subgrade can result in various types of failures, three of which are identified in this article: (i) excessive plastic settlement, (ii) progressive shear failure, and (iii) subgrade fluidisation (mud pumping). Through a series of advanced testing schemes using cyclic triaxial, hollow cylinder, and an in-house dynamic filtration apparatus, critical stress conditions and soil characteristics prone to subgrade instability are discussed. The results demonstrate that under adverse combinations of loading frequency (f) and cyclic stress ratio (CSR) the continuous application of cyclic loads can lead to an unstable state of soil where excess pore pressure and axial strain increase rapidly. This study also reveals that low to medium plasticity soils (PI < 22) are more vulnerable to subgrade fluidisation, where the rapid internal migration of pore water transforms the upper soil to a fluid-like state with substantial loss in soil stiffness. The layered response of soil through dynamic filtration tests showed larger hydrodynamic forces induced by differential hydraulic gradients in the top layer during cyclic loading causes moisture to move upwards. Various factors that can influence soil instability such as the degree of compaction degree, clay content, soil fabric and stress rotation are also addressed in this paper. Finally, novel solutions for stabilising subgrade such as a vertical drain-composite system and the use of eco-friendly biopolymers are presented.

Characterisation of bond between cement paste and steel fibres with different surface roughness using SEM.

The performance of cementitious composites reinforced with fibres or/and bars depends on the bond strength between inclusion and cementitious matrix. The nature of formation of fibre-matrix bond is crucial for enhancing the reliability and utilisation of reinforced composites. The research provides a review on the recently published result about the changes in the microstructure of cement matrix surrounding steel fibres with different surface roughness, using a scanning electron microscope (SEM) coupled with k-means clustering algorithm for image segmentation. The debonding pattern of the fibre-matrix bond after the tensile loading cycles was discussed by observing the amount of adhered cement paste to the pulled out fibre surface with SEM. Therefore, analysis of SEM images enabled to explain the connection between the micro-scale properties of cement paste and fibre after application of cyclic loading.

Experimental study on the seismic performance of GFRP reinforced concrete columns actively confined by AFRP strips

This paper proposes a new type of concrete columns, which are reinforced with GFRP bars and actively confined by Aramid Fiber-Reinforced Polymer (AFRP) strips. FRP reinforcement is a non-corrosive material and has the advantages of having lighter weight, higher tensile strength, and long-term durability as compared to steel reinforcement. Active confinement has advantages over non-confined concrete columns and it is expected that the active confinement in the critical area increases the adhesion between the concrete and the rebars, strengthens the concrete cover portion of the rebars, and increases the shear capacity of the column. The literature does not show a comprehensive examination of the actively confined concrete columns that are reinforced by polymer and steel bars. Six reinforced concrete columns were cast, loaded, and tested under simultaneous application of axial and cyclic loads. Four columns were actively confined by AFRP strips at 10% and 30% of the AFRP ultimate strain in the critical area. Two columns were reinforced with steel bars, and the other two were reinforced with GFRP bars. Also, two columns with steel bars and GFRP bars, but without confinement, were utilized as the control specimens. Experimental results showed that the strain in the cover portion of the actively confined columns was reduced due to the effect of active confinement, and the strength of the concrete core increased. The active confinement increased the adhesion between the concrete and the bars and also reduced crack width, which ultimately resulted in increasing concrete strength, ductility, and energy absorption.

Crystal plasticity enhanced direct cyclic analysis of cyclic behaviour of LPBF-manufactured AISI 316L

The fatigue performance of Laser Powder Bed Fusion manufactured 316L stainless steel is critical for cyclic loading applications. Additive manufacturing of 316L produces a characteristic microstructure consisting of grains with a fine cellular structure within. This microstructure shows a comparatively high fatigue strength combined with a high defect tolerance. The purpose of this paper is to numerically analyse the local response of this microstructure to cyclic loading and, in particular, the joint action between lack of fusion defects and the surrounding grain structure. The traditional incremental analysis method for polycrystalline alloys is computationally expensive. Therefore, a direct cyclic analysis combined with a phenomenological crystal plasticity model is used in this work to predict the stable cyclic response of the material, resulting in a much lower computational cost. Three statistically equivalent representative volume elements are generated. The considered crystal plasticity parameters are calibrated using experimental tensile stress–strain curves. The comparison with incremental analysis demonstrates the accuracy and efficiency of the proposed method. The shakedown limit, based on the maximum load that allows the convergent cyclic response, significantly depends on the local grain orientation around lack of fusion defects, revealing a reason for the large scatter in the fatigue strength.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study.

The present study compared three different implant and abutment sets of type Morse taper (MT) connection, with- and without-index, were analyzed regarding their mechanical behavior without and with cyclic load application simulating the masticatory function. Ninety implant and abutment (IA) sets were used in the present study, divided into three groups (n = 30 samples per group): Group A, Ideale solid straight abutment (one piece) without index; Group B, Ideale abutment with an angle of 30-degree (two pieces) without index; Group C, Ideale abutment with an angle of 30-degree (two pieces) with index. The abutment stability quotient (ASQ) values, detorque value and rotation angle were measured before and after the cycling load. Twenty IA sets of each group were submitted to mechanical load at 360,000 cycles. The ASQ without load were 64.7 ± 2.49 for the group A, 60.2 ± 2.64 for the group B, 54.4 ± 3.27 for the group C; With load were 66.1 ± 5.20 for the group A, 58.5 ± 6.14 for the group B, 58.9 ± 2.99 for the group C. Detorque values were lower in groups B and C compared to group A (p < 0.05). In conclusion, the presence of the index did not influence the stability values. However, solid straight abutments (group A) showed higher values of stability compared to groups of angled abutments (groups B and C).

Influence of high frequency on the fatigue life of metallic single lap joints

Polymer adhesives are known to exhibit time dependent mechanical behaviour, that becomes more and more evident approaching the glass transition temperature, Tg. When subjected to fatigue, bonded joint lifetime can be therefore affected by the loading frequency and amplitude. According to the literature, the influence of the frequency on the fatigue behavior manifests as a rise of the temperature in the adhesive due to the hysteretic heating, which is related in turn to Tg and to the viscoelastic properties of the adhesive. In this paper, cyclic loading was applied to single lap shear joints until failure at frequencies in the range of 70–90 Hz, that are little explored by the existing literature. The aim is twofold: on one side, to investigate the possibility to speed up fatigue tests in comparison to tests performed in the range of 7–9 Hz; on the other side, to explore the possibility to generate stress-life data in a range of number of cycles between 106 and 108, therefore two order of magnitude higher then usual, without exceeding with the time required for the tests. The joints were made with both aluminum and stainless-steel substrates bonded with a structural epoxy adhesive, to manufacture a Single Lap Joint (SLJ). Two loading ratios R (respectively 0.1 and 0.4, defined as the minimum over the maximum force of the fatigue cycle) and different load ranges were applied. Digital Image Correlation (DIC) technique was used to assess the presence of creep strains. A preliminary investigation consisting in a Dynamic Mechanical Analysis (DMA) of bulk adhesive for the range of frequency of interest, and in the measurement of the temperature of the adhesive layer during some selected fatigue tests was carried out. No significant changes of the viscoelastic properties of the adhesive were found for the frequency of interest, and, at the same time, temperature measurements revealed that the temperature increased by a few degrees, remaining in any case far from the glass transition temperature. The test results showed that only small effect due to the application of a high frequency cyclic loading on the fatigue life apparently occurs for tests carried out at the lowest load ratio, in particular when the applied loads were relatively low, and the number of cycles at failure relatively high. On the opposite, the results of tests carried out at the highest load ratio are affected by the loading frequency, and it has been related to the presence of significant creep deformation within the adhesive layer.

Methodology for simulating the elastoplastic behavior in crack propagation problems using dual formulations of the boundary element method

Due to the application of cyclic loads, the existing crack length in a structure increases with time, resulting in greater stress concentration around the crack tip and therefore causing an increase in propagation velocity and a decrease in residual strength of the structure which, at a given time, becomes so low that the structure can no longer support the service loads. This paper presents a new approach to evaluate two-dimensional elastoplastic models in a crack propagation scenario, based on the boundary element method and its dual formulations. The methodology adopted consists of two stages: firstly, the simulation of the elastoplastic behavior, which considers the process of initial stresses and allows the treatment of several flow criteria, without taking into account the incompressibility of inelastic deformations. In this step, the domain integral due to non-homogeneous terms in the plastification region is transformed into a boundary integral by the Dual Reciprocity Method (DRM) using the polyharmonic splines functions due to its local behavior and, from the plastic calculus, the J-Integral is used to compute the SIF's. The second stage aims to simulate, in an incremental way, the crack propagation path using homemade software for crack modeling and analysis based on ElastoPlastic Fracture Mechanics (EPFM) and the Dual Boundary Element Method (DBEM). To validate the adopted methodology, as well as correctly simulate the mechanical behavior of cracks in the plastic regime of the material, three 2D models with straight and inclined cracks are used. Initially, the von Mises criterion for perfectly plastic materials is used and the numerical results compared with classic models from the literature, showing the effectiveness of the program in crack treatment and in the prediction of the propagation path, as well as the non-linear algorithm in the region plastification using the DRM.

A ELASTO-PLASTIC CONSTITUTIVE MODEL BASED ON CHABOCHE KINEMATIC HARDENING OF ALUMINUM ALLOY 7050-T7451

The elasto-plastic behavior of the aluminum alloy 7050-T7451 subjected to cyclic loading was investigated and modeled. The objective of this work is to improve the constitutive model of Chaboche with a special emphasis in the compression. In the proposed model, the part under tension of the stress-strain curve in the stable hysteresis cycle is modeled separately from the compressed one, where it is considered that they have different Modulus of Elasticity. The work includes both simulation and experimental data, and they are compared to each other. The values were collected experimentally by the application of symmetric cyclic strain-driven loading in the strain range between 0.75% and 2.25%. The experimental results were used to calculate the parameters of the constitutive model in a MATLAB® software. The responses obtained with the proposed model have greater adherence to the experimental results than those obtained with the Chaboche model.

Cyclic Load Impact Assessment of Long-Term Properties in Compression to Steel and Polyvinyl Alcohol Fibre-Reinforced Geopolymer Composites.

This study investigates the cyclic load application impact on fly-ash-based geopolymer composites that are reinforced with a low amount of fibre reinforcement. For reinforcement purposes, polyvinyl alcohol and steel fibres are used. For testing purposes, four geopolymer composite mixes were made, three of which had fibre reinforcement. Simultaneously, specimens were tested for shrinkage, static-load-induced creep, and cyclic-load-induced creep. For static and cyclic creep testing, specimens were loaded with 20% of their strength. For cyclic creep testing, load application and release cycles were seven days long. When each cycle was introduced, the load was applied in steps. Necessary load application or unloading lasted for 5 min and consisted of four steps, each 25% of the necessary load. From the long-term static and cyclic creep tests, it was seen that only the plain specimens showed that static creep strains are within cyclic creep strains. For all the other specimens, the static load was higher than the cyclic-load-induced creep amplitude. Also, 1% polyvinyl alcohol fibre-reinforced specimens showed the most elastic characteristics under cyclic load, and 1% steel fibre-reinforced specimens appeared to be the most resistant to the cyclic load introduction.

Multi-Actuator Full-Scale Fatigue Test of a Tidal Blade

Fatigue testing for tidal turbine blades involves the application of cyclic loads without matching the blade's natural frequency, which is challenging due to their high stiffness and associated thermal issues of composite materials at those frequencies (typically around 18Hz cycles). An auxiliary system is required to load the blades to address this challenge. However, traditional hydraulic systems tend to be highly energy-demanding and inefficient.&#x0D; To solve this problem, researchers utilized real on-site data to define a series of equivalent target loads and implemented them in FastBlade, which proved an efficient way to perform fatigue testing. They used a regenerative digital displacement hydraulic pump system and achieved a remarkable 75% energy savings compared to a standard hydraulic system. During the testing, they utilized a system of 3 actuators instead of the traditional single actuator system, which produced more realistic and complex loads. We also address such changes in temperature along large composite structures during the test and mechanisms to address these issues. &#x0D; Throughout the test, a series of measurements were taken on the blade response and FastBlade itself, which revealed exciting results on the mechanical behaviour of the blade and best testing practices for FastBlade. Impressively, the blade withstood 40 years' worth of accelerated fatigue loading without catastrophic failure.

Dynamic crack growth propagation of Al 2024 thin plates reinforced with carbon nanotube subjected to non-proportional cycling loading

In this study, the dynamics crack growth in a thin plate made of aluminum alloy 2024T3, which was coated with two types of coating, electrocoating (Ni-CNTs) and electroless coating (Ni-CNTs), were investigated under a non-proportional cyclic loading. Pure multi-walled carbon nanotubes (MWCNTs) were added to the coating solution at a concentration of 2 g/l to enhance the mechanical properties and study the effect of adding carbon nanotubes to the coating solution.Fracture mechanics analysis was performed using two methods. First, a novel apparatus was designed for experimental analysis of the application of a non-proportional cyclic loading, consisting of a repeated, cyclic inplane shear stress with constant tension stress. Secondly, the numerical analysis was carried out using ABAQUS 2019 programming to obtain numerical results and compare them with the experimental results to validate the study. Paris law parameters, including Paris law constants c and m, K (change in stress intensity factor), and da/dN (crack growth per cycle), which were included in the ABAQUS software to simulate the model and compare the results with the experimental data.The specimens were analyzed using XRD, FESEM, and EDXRF after the coating process to determine the quality, distribution, and thickness of the coating layer on the specimen's surface. The hardness tests showed a 57% increase in the hardness of the specimens coated with electrocoating and a 72% increase in the hardness of specimens coated with electroless coating. The Young's modulus also showed an increase of 37.5% for specimens coated with electrocoating and 50% for specimens coated with electroless coating, compared to specimens without coating.

Metallurgical evaluation and failure analysis of turbo expander Tie-bolt

Failure in a turbo-expander Tie-Bolt (stud) made of superalloy A-286 was investigated. The evaluation of the chemical composition and tensile properties confirmed compliance with the relevant standard. However, the coarsening of γ′ due to over aging condition, the non-uniform grain size and banded coarse MC carbide particles, the segregation of phosphorus to grain boundaries and the growth of carbide particles at the grain boundaries led to a decrease in fatigue strength of the alloy. Fractography studies showed that fracture occurred due to primary axial and secondary bending loads. Multiple ratchets and tire tracks on the fracture surface were consistent with low-cycle fatigue (LCF) failure mechanism. Fatigue striations spacing and micro hardness profile of the threads were used to calculate the stress amplitude and estimate the fatigue strength of Tie-bolt. Neuber’s rule was used to estimate the local stress and strain in the thread root. The calculation results showed that the failure occurred due to the application of cyclic loads at a stress level lower than fatigue strength of the stud. A large amount of sulfur detected at the multiple cracks initiation areas by EDS analysis, indicated the presence of H2S in the environment, which has caused cathodic hydrogen charge and reducedthe steel ductility and accelerated fatigue crack nucleation and growth.

Dynamic biomechanical investigation of a novel sulcus bicipitalis plate in combination with a conventional locking plate for the treatment of complex proximal humerus fractures

BackgroundComplex proximal humerus fractures place high demands on osteosynthetic treatment. In some cases, double plating has already been used to increase primary stability of the osteosynthesis. This approach was advanced in the present study by developing an additive plate for the sulcus bicipitalis. To demonstrate the superior primary stability of the newly developed plate osteosynthesis, a biomechanical comparison against a conventional locking plate with an additional calcar screw was performed. MethodsTen pairs of cadaveric humeri were treated proximally with a locking plate (PENTA plate small fragment, INTERCUS). Each had a two-part fracture model with a fracture gap of 10 mm. All right humeri were treated with an additive novel plate that extends along the bicipital sulcus and encircles the lesser tuberosity proximally. First, the specimens were loaded sinusoidally at 250 N in 20° abduction for 5000 cycles. Afterwards quasi-static loading until failure was applied. FindingsThe movement at the fracture gap due to the cyclic loading occurred mainly as rotation around the z-axis, corresponding to a tilt medially and distally. The double plate osteosynthesis reduces the rotation by approximately 39%. For all load cycles observed, except 5000 cycles, medial and distal rotation of the head was significantly reduced by the double plate. The failure loads showed no significant differences between the groups. InterpretationIn the tested scenario under cyclic loading, the novel double plate osteosynthesis showed a significant superiority of primary stability over the conventional treatment with one locking plate. Furthermore, the study showed the advantages of cyclic load application over quasi-static load application until failure.

Depth-dependent soil fluidization under cyclic loading—an experimental investigation

Past studies have shown that shallow subgrade soil can transform to a slurry (i.e., fluidization) under unfavourable cyclic loading. However, the depth-dependent behaviour of soil parameters during this process has not been properly understood. The current study utilised a large-scale cylindrical test rig, where instrumentation was installed to observe the soil behaviour along the depth of the test specimens under cyclic loading, to examine and quantify the onset of soil fluidization. The results show that excess pore water pressure tends to rise more at the upper layers causing zero-effective stress, while void ratio expands rapidly within the deteriorated soil fabric, making the water content approach the liquid limit of soil when internal moisture migration occurs from the bottom to the top of the specimen. The larger the cyclic load, the deeper the fluidized zone and the faster the fluidization. The study also suggests that the zero-effective stress condition alone cannot interpret the inception of soil fluidization; hence, the change in void ratio and the liquidity index during the application of cyclic loading should also be considered in tandem.

Review of human supraspinatus tendon mechanics. Part I: fatigue damage accumulation and failure.

Repetitive stress injuries to the rotator cuff, and particularly the supraspinatus tendon (SST), are highly prevalent and debilitating. These injuries typically occur through the application of cyclic load below the threshold necessary to cause acute tears, leading to accumulation of incremental damage that exceeds the body's ability to heal, resulting in decreased mechanical strength and increased risk of frank rupture at lower loads. Consistent progression of fatigue damage across multiple model systems suggests a generalized tendon response to overuse. This finding may allow for interventions before gross injury of the SST occurs. Further research into the human SST response to fatigue loading is necessary to characterize the fatigue life of the tendon, which will help determine the frequency, duration, and magnitude of load spectra the SST may experience before injury. Future studies may allow invivo SST strain analysis during specific activities, generation of a human SST stress-cycle curve, and characterization of damage and repair related to repetitive tasks.

Mechanical characterization of a multi-layered zirconia: Flexural strength, hardness, and fracture toughness of the different layers

This study compared the flexural strength under monotonic (static - sσ) and cyclic load application (fatigue - fσ), hardness (H) and fracture toughness (KIC) of different layers of a multi-layered zirconia (IPS e.max ZirCAD MT Multi, Ivoclar). Each layer was sectioned, classified into three groups according to yttria content (4-YSZ, 4/5-YSZ and 5-YSZ), and shaped on samples for flexural strength and fracture toughness tests (bars: 1.0 × 1.0 × 11 mm); and Vickers hardness test (plates: 1.5 × 4.0 × 5.0 mm). Flexural strength under monotonic load application (sσ; n = 10) was obtained through two different devices (three-point-bending and ball-in-hole device) and fatigue flexural strength (fσ; n = 15; initial load: 10 N; step-size: 5 N; 10,000 cycles/step) was assessed using a ball-in-hole device under cyclic load application. Vickers hardness test (n = 5), fracture toughness test (n = 10), and additional analyzes (Finite Element Analysis - FEA, Energy-dispersive X-ray spectroscopy - EDS and Scanning Electron Microscopy - SEM) were also performed. No differences were found between the different devices in the monotonic flexural strength test, and FEA showed similar tensile stress distribution for the two devices. 4-YSZ showed higher values of flexural strength under monotonic and cyclic load application modes (sσ = 1114.73 MPa; fσ = 798.84 MPa), and fracture toughness (KIC = 3.90 MPa√m). 4/5-YSZ had an intermediate sσ; however, fσ was similar to 5-YSZ (404.00–429.36 MPa) and KIC similar to 4-YSZ (KIC = 3.66 MPa√m). No statistical differences were found for hardness and Weibull modulus for fatigue flexural strength data. The amount of yttria in the layer compositions increased from 4-YSZ to 5-YSZ, and larger zirconia crystals were observed in the topographic images of 5-YSZ. Failures in the flexural strength and toughness tests started from the face subjected to tensile stress. Different layers of the multi-layered zirconia blank presented distinct mechanical properties. 4-YSZ (cervical layer) presented the highest flexural strength under monotonic and cyclic loads (fatigue), and higher fracture toughness even similar to the transition layer (4/5-YSZ). Hardness was similar between the layers. The ball-in-hole device performed similarly to the three-point bending device and can be used as an alternative to the traditional method.

A micromechanical study of the fatigue behavior of MWCNT-modified carbon fibers/epoxy resin single filament composites subjected to cyclic loadings

This paper presents a comprehensive study on the impact of surface modification of carbon fibers using multiple-walled carbon nanotubes (MWCNTs) to improve the load-transfer capacity of the fiber-matrix interface of an epoxy matrix composite subjected to dynamic loads. The single-fiber fragmentation technique (SFFT) was utilized to characterize the length of interfase damage (IDL) produced by quasi-static and dynamic loadings for linear elastic and plastic strains and the residual efficiency of interfacial stress transfer. A finite element model was used to validate the optical measurement and the extent of interfase damage. Scanning electron microscopy (SEM) corroborated the presence of the MWCNTs on the surface of the carbon fibers. The interfacial shear strength (IFSS) increased by approximately 27.5%, attributed to the carbon nanotubes and a more significant fiber-matrix stress transfer. The application of dynamic loads decreased the mechanical properties of the matrix, premature fragmentation of the carbon fiber, and interfacial damage, which led to a reduction in the interfase load-transfer capacity. However, the incorporation of carbon nanotubes in the interface decreased the adverse effects generated by the application of cyclic loads, mainly the propagation of interfacial damage.

Accumulation of irreversible deformation of soils as a result of repeated loading

Objective. The purpose of the study is to establish the patterns of accumulation of irreversible soil deformations from repeated loading.Method. When loading soils, the balance between external and internal forces is established gradually over a more or less long time. Therefore, with a single application of a cyclic load, such an equilibrium can be achieved only in a relatively long time.Result. An approximate method is proposed for calculating the magnitude of the deformation developed as a result of the action of a cyclic load. The cases are determined when it is necessary to take into account the viscous component of deformation and when the latter can be neglected. It has been established that when determining the deformation of soils that has developed during a single application of such cyclic loads that are characteristic of the process of their compaction by machines, in all cases, except for rolling them with rollers on pneumatic tires, the viscous component of deformation can be ignored.Conclusion. In a relatively short time of the load, the state of equilibrium can be achieved only in the process of soil deformation by repeated loading. With an increase in the number of loading repetitions, the soil gradually hardens, and the deformation decreases. This occurs both due to the irreversible and reversible parts of the deformation. Consequently, the soil deformation modulus increases from cycle to cycle.

Crack initiation and growth simulations of functionally graded dental implant subjected to cyclic axial loads

AbstractTwo essential characteristics in designing dental implants are having high fracture resistance and being compatible with jawbone. One of the best implant choices to achieve this aim is titanium‐hydroxyapatite functionally graded (FG) material. Also, fracture of implants under cyclic loads is one of the most common causes of destruction of dental implants. However, the crack initiation location and growth path as well as the optimum material distribution for the FG implants are questions that have not been answered yet. The aim of this study was introducing a new and powerful numerical approach to predict the crack initiation behavior and progressive damage in the FG dental implants, subjected to cyclic axial loadings. The approach is developed by employing extended finite element method (XFEM) in ABAQUS software, Visual Studio, and FORTRAN Compiler. Also, the Python code was modified for crack growth modeling in fatigue fracture analysis based on Paris law. The result showed that the micro‐cracks below the outer surface of FG implant are created, due to the application of cyclic load, which is invisible. This research shows that FG implants with power factor less than 1 show much more resistance to crack growth under pre‐tightening and cyclic loadings.