Статті в журналах: "Multiaxial damage and failure"

1

Socie, D. "Multiaxial Fatigue Damage Models." Journal of Engineering Materials and Technology 109, no. 4 (October 1, 1987): 293–98. http://dx.doi.org/10.1115/1.3225980.

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Two multiaxial fatigue damage models are proposed: a shear strain model for failures that are primarily mode II crack growth and a tensile strain model for failures that are primarily mode I crack growth. The failure mode is shown to be dependent on material, strain range and hydrostatic stress state. Tests to support these models were conducted with Inconel 718, SAE 1045, and AISI Type 304 stainless steel tubular specimens in strain control. Both proportional and non-proportional loading histories were considered. It is shown that the additional cyclic hardening that accompanies out of phase loading cannot be neglected in the fatigue damage model.

2

Lu, Chun, Jiliang Mo, Ruixue Sun, Yuanke Wu, and Zhiyong Fan. "Investigation into Multiaxial Character of Thermomechanical Fatigue Damage on High-Speed Railway Brake Disc." Vehicles 3, no. 2 (June 1, 2021): 287–99. http://dx.doi.org/10.3390/vehicles3020018.

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The multiaxial character of high-speed railway brake disc thermomechanical fatigue damage is studied in this work. Although the amplitudes and distributions of temperature, strain and stress are similar with uniform and rotating loading methods, the multiaxial behavior and out-of-phase failure status can only be revealed by the latter one. With the help of a multiaxial fatigue model, fatigue damage evaluation and fatigue life prediction are implemented, the contribution of a uniaxial fatigue parameter, multiaxial fatigue parameter and out-of-phase failure parameter to the total damage is discussed, and it is found that using the amplitude and distribution of temperature, stress and strain for fatigue evaluation will lead to an underestimation of brake disc thermomechanical fatigue damage. The results indicate that the brake disc thermomechanical fatigue damage belongs to a type of multiaxial fatigue. Using a uniaxial fatigue parameter causes around 14% underestimation of fatigue damage, while employing a multiaxial fatigue parameter without the consideration of out-of-phase failure will lead to an underestimation of about 5%. This work explains the importance of studying the thermomechanical fatigue damage of the brake disc from the perspective of multiaxial fatigue.

3

Ellyin, F., and K. Golos. "Multiaxial Fatigue Damage Criterion." Journal of Engineering Materials and Technology 110, no. 1 (January 1, 1988): 63–68. http://dx.doi.org/10.1115/1.3226012.

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A multiaxial fatigue failure criterion is proposed based on the strain energy density damage law. The proposed criterion is hydrostatic pressure sensitive; includes the effect of the mean stress, and applies to materials which do not obey the idealized Masing type description. The material constants can be evaluated from two simple test results, e.g., uniaxial tension, and torsion fatigue tests. The predicted results are compared with biaxial tests and the agreement is found to be fairly good. A desirable feature of this criterion is its unifying nature for both short and long cyclic lives. It is also consistent with the crack initiation and propagation phases of the fatigue life, in the sense that both of these phases can be related to the strain energy density either locally or globally.

4

Liu, Jianhui, Xin Lv, Yaobing Wei, Xuemei Pan, Yifan Jin, and Youliang Wang. "A novel model for low-cycle multiaxial fatigue life prediction based on the critical plane-damage parameter." Science Progress 103, no. 3 (July 2020): 003685042093622. http://dx.doi.org/10.1177/0036850420936220.

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Multiaxial fatigue of the components is a very complex behavior. This analyzes the multiaxial fatigue failure mechanism, reviews and compares the advantages and disadvantages of the classic model. The fatigue failure mechanism and fatigue life under multiaxial loading are derived through theoretical analysis and formulas, and finally verified with the results of multiaxial fatigue tests. The model of multiaxial fatigue life for low-cycle fatigue life prediction model not only improves the prediction accuracy of the classic model, but also considers the effects of non-proportional additional hardening phenomena and fatigue failure modes. The model is proved to be effective in low-cycle fatigue life prediction under different loading paths and types for different materials. Compared with the other three classical models, the proposed model has higher life prediction accuracy and good engineering applicability.

5

Zheng, Shan Suo, Wen Yong Li, Qing Lin Tao, and Yu Fan. "A Multiaxial Damage Statistic Constitutive Model for Concrete." Applied Mechanics and Materials 166-169 (May 2012): 56–59. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.56.

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In order to apply the uniaxial damage evolution equation that established with the variable of strain to the multiaxial damage quantitative analysis, this paper bases on the Hsieh-Tang-Chen four-parameter failure criterion and adopts the way of making the triaxial equivalent strain combining with the uniaxial damage evolution equation to analyze and deduce the uniaxial damage evolution equation of SRHSHPC, and which is expanded to multiaxial condition as well. A function considered triaxial stress state and a related correction value are suggested, then, improving the damage evolution equation from triaxial to multiaxial form, finally proposing the multiaxial damage statistic constitutive equation for concrete, taking numerical simulation with the complete decoupling method and the result shows that the model is effective.

6

Habtour, Ed, William (Skip) Connon, Michael F. Pohland, Samuel C. Stanton, Mark Paulus, and Abhijit Dasgupta. "Review of Response and Damage of Linear and Nonlinear Systems under Multiaxial Vibration." Shock and Vibration 2014 (2014): 1–21. http://dx.doi.org/10.1155/2014/294271.

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A review of past and recent developments in multiaxial excitation of linear and nonlinear structures is presented. The objective is to review some of the basic approaches used in the analytical and experimental methods for kinematic and dynamic analysis of flexible mechanical systems, and to identify future directions in this research area. In addition, comparison between uniaxial and multiaxial excitations and their impact on a structure’s life-cycles is provided. The importance of understanding failure mechanisms in complex structures has led to the development of a vast range of theoretical, numerical, and experimental techniques to address complex dynamical effects. Therefore, it is imperative to identify the failure mechanisms of structures through experimental and virtual failure assessment based on correctly identified dynamic loads. For that reason, techniques for mapping the dynamic loads to fatigue were provided. Future research areas in structural dynamics due to multiaxial excitation are identified as (i) effect of dynamic couplings, (ii) modal interaction, (iii) modal identification and experimental methods for flexible structures, and (iv) computational models for large deformation in response to multiaxial excitation.

7

Mao, Xue Ping, Yang Yu, Chao Li, Sai Dong Huang, Hong Xu, and Yong Zhong Ni. "Study on Creep Behaviors of T92 Steel under Multiaxial Stress State." Advanced Materials Research 860-863 (December 2013): 774–79. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.774.

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Creep tests for smooth specimens and notched specimens of T92 steel were carried out to study the effect of multiaxial stress state on creep rupture behaviors at 650°C. Creep rupture life was estimated by representative stress at multiaxial state of stress, the failure behavior of multiaxial creep was analyzed, and Kachanov creep damage formula was used to analyze the experimental data. The results show that the notch strengthens rupture life, multiaxial rupture behavior is controlled by mixed parameters, the creep ductility of the smooth and notched specimen decreases with rupture time, and damage factors of the smooth specimen and notched specimen are similar according to Kachanov formula.

8

Santecchia, E., A. M. S. Hamouda, F. Musharavati, E. Zalnezhad, M. Cabibbo, M. El Mehtedi, and S. Spigarelli. "A Review on Fatigue Life Prediction Methods for Metals." Advances in Materials Science and Engineering 2016 (2016): 1–26. http://dx.doi.org/10.1155/2016/9573524.

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Metallic materials are extensively used in engineering structures and fatigue failure is one of the most common failure modes of metal structures. Fatigue phenomena occur when a material is subjected to fluctuating stresses and strains, which lead to failure due to damage accumulation. Different methods, including the Palmgren-Miner linear damage rule- (LDR-) based, multiaxial and variable amplitude loading, stochastic-based, energy-based, and continuum damage mechanics methods, forecast fatigue life. This paper reviews fatigue life prediction techniques for metallic materials. An ideal fatigue life prediction model should include the main features of those already established methods, and its implementation in simulation systems could help engineers and scientists in different applications. In conclusion, LDR-based, multiaxial and variable amplitude loading, stochastic-based, continuum damage mechanics, and energy-based methods are easy, realistic, microstructure dependent, well timed, and damage connected, respectively, for the ideal prediction model.

9

Karolczuk, Aleksander, and Ewald Macha. "Critical Planes in Multiaxial Fatigue." Materials Science Forum 482 (April 2005): 109–14. http://dx.doi.org/10.4028/www.scientific.net/msf.482.109.

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The paper includes a review of literature on the multiaxial fatigue failure criteria based on the critical plane concept. The criteria were divided into three groups according to the distinguished fatigue damage parameter used in the criterion, i.e. (i) stress, (ii) strain and (iii) strain energy density criteria. Each criterion was described mainly by the applied the critical plane position. The multiaxial fatigue criteria based on two critical planes seem to be the most promising. These two critical planes are determined by different fatigue damage mechanisms (shear and tensile mechanisms).

10

Ellyin, Fernand. "Multiaxial Fatigue--A Perspective." Key Engineering Materials 345-346 (August 2007): 205–10. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.205.

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Research on the fatigue resistance of mechanical components/structures has been proceeding for nearly a century and a half. Yet, there is no universally agreed upon theory that can predict most aspects of fatigue failure. The reason is the complexity of phenomenon and its dependence on the microstructure. Here, we present a strain energy based damage parameter which has an underlying microscopic basis. A master life curve is subsequently defined which correlates very well with experimental data.

11

Camara, Aliou Badara, Fabienne Pennec, Sébastien Durif, Jean-Louis Robert, and Abdelhamid Bouchaïr. "Bolt fatigue parametric study of a bolted assembly." MATEC Web of Conferences 300 (2019): 04002. http://dx.doi.org/10.1051/matecconf/201930004002.

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Structural integrity of aircraft, nuclear power plants, space rockets, ships, automotive structures, biomedical devices, and many other applications, is a major design purpose and concerns various components subjected to cyclic loads for which fatigue is generally the dominant factor leading to its failure. The fatigue damage cumulation phenomenon is a process which may lead to cracks initiation and possibly to the structure failure under the action of variables stresses cycles. The mechanical components are generally subjected to multiaxial stress states. Taking into account this stress states triaxiality generally deals with multiaxial fatigue criteria. They are suitable tools for assessing the material fatigue resistance against periodical stress states, especially when they are multiaxial. The study carried out in this paper aims to analyze the fatigue behaviour of pre-stressed bolts involved in a so-called tee-stub bolted assembly that is subjected to variable loads. A multiaxial fatigue post-processing tool using two multiaxial fatigue approaches (integral approach and critical plan approach) is developed and implemented on Matlab software in order to assess the bolt fatigue damage and then its fatigue life through an iterative process. The tool is validated by fatigue test results on bolted assemblies found in the literature, which are additionally compared with those obtained by standards (Eurocode, VDI). A parametric study on the tee-stub is then performed.

12

Zolochevsky,, Alexander, Takamoto Itoh,, and Yoichi Obataya,. "A Continuum Damage Mechanics Model for Multiaxial Low Cycle Fatigue Failure." Journal of the Mechanical Behavior of Materials 12, no. 1 (February 2001): 1–20. http://dx.doi.org/10.1515/jmbm.2001.12.1.1.

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13

Liu, Shu Li, Takamoto Itoh, and Noriyuki Fujii. "Visualization of Multiaxial Stress/Strain State and Evaluation of Failure Life by Developed Analyzing Program under Non-Proportional Loading." Advanced Materials Research 891-892 (March 2014): 1391–96. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1391.

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This study presents definitions of principal stress/strain range and mean stress/strain introduced by utilizing Itoh-Sakane criterion for multiaxial loading including non-proportional loading, and shows the method of calculating the non-proportional factor which expresses the severity of non-proportional loading under the multiaxial 3D loading. This paper also shows a method of visually presenting the stress/strain, the non-proportionality of loading and the damage evaluation.

14

Zeng, Chongyang, and Xiangfan Fang. "Experimental analysis and modelling of dynamic deformation and failure behaviour of steel." EPJ Web of Conferences 250 (2021): 02020. http://dx.doi.org/10.1051/epjconf/202125002020.

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New specimen geometries with various stress states are designed and applied for dynamic loading tests. Oscillation-free force is measured during multiaxial loading tests in the strain range of 10-4 – 103 s-1. The deformation and local strain fields of specimens have been measured using high-speed camera and evaluated by digital image correlation (DIC) techniques. It is found that the strain rate effects on fracture strain are stressstate dependent. To model the material plasticity and ductile fracture behaviour during dynamic tests, an extended damage mechanics model (eMBW model) is used. In this work, the model is enhanced and implemented into LS-DYNA. To cover the strain rate effects on plasticity at a large strain rate range, a modified Johnson–Cook-type rate-dependency and exponential temperature-dependency are used. In addition, the influences of both stress state and strain rate on fracture locus are considered. The enhanced damage mechanics model successfully predicts the deformation and fracture behaviour of the investigated steel under dynamic multiaxial loading.

15

Brighenti, Roberto, and Andrea Carpinteri. "Damage Mechanics and Critical Plane Approach to Multiaxial Fatigue." Key Engineering Materials 592-593 (November 2013): 239–45. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.239.

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The mechanical behaviour of structural components subjected to multiaxial fatigue loading is very important in modern design. Several approaches have been introduced in recent decades to analyse this problem. The so-called critical plane approach, based on the stresses acting on the plane where the crack nucleation is expected to occur, is widely used. This criterion can give us a fatigue damage measurement, which can be used to evaluate fatigue life. On the other hand, fatigue life under general multiaxial stress histories can also be assessed by applying the damage accumulation method. In such a method, a scalar damage parameter is quantified through the damage increments which develop during the fatigue process up to the critical damage value corresponding to the final failure of the structures. The damage increment approach to fatigue has recently been discussed and connected to the classical crack propagation approach. In the present paper, the interpretation of the critical plane approach based on the continuum damage mechanics concepts is examined. In particular, the physical meaning of the critical plane approach is shown, that is, such an approach can be interpreted as a damage method which takes into account the scalar damage parameter evaluated along preferential directions. Finally, the fatigue behaviour of a metallic material under multiaxial cyclic load histories is analysed through the two above approaches.

16

YATOMI, M., A. D. BETTINSON, N. P. O'DOWD, and K. M. NIKBIN. "Modelling of damage development and failure in notched-bar multiaxial creep tests." Fatigue Fracture of Engineering Materials and Structures 27, no. 4 (April 2004): 283–95. http://dx.doi.org/10.1111/j.1460-2695.2004.00755.x.

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17

Donadon, Maurício V., Sérgio Frascino M. de Almeida, Mariano A. Arbelo, and Alfredo R. de Faria. "A Three-Dimensional Ply Failure Model for Composite Structures." International Journal of Aerospace Engineering 2009 (2009): 1–22. http://dx.doi.org/10.1155/2009/486063.

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A fully 3D failure model to predict damage in composite structures subjected to multiaxial loading is presented in this paper. The formulation incorporates shear nonlinearities effects, irreversible strains, damage and strain rate effects by using a viscoplastic damageable constitutive law. The proposed formulation enables the prediction of failure initiation and failure propagation by combining stress-based, damage mechanics and fracture mechanics approaches within an unified energy based context. An objectivity algorithm has been embedded into the formulation to avoid problems associated with strain localization and mesh dependence. The proposed model has been implemented into ABAQUS/Explicit FE code within brick elements as a userdefined material model. Numerical predictions for standard uniaxial tests at element and coupon levels are presented and discussed.

18

Rösch, Peter, Halvar Schmidt, and Thomas Bruder. "A novel approach to simulate the stiffness behaviour of spot welded vehicle structures under multi axial variable amplitude loading." MATEC Web of Conferences 165 (2018): 17005. http://dx.doi.org/10.1051/matecconf/201816517005.

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Under cyclic loading in combination with high local stress levels a change in stiffness of connection points, e.g. spot welds, self-piercing rivets or flow drill screws can be observed. This paper introduces a numerical approach for the simulation of stiffness changes in vehicle structures under multiaxial cyclic loading as a result of the stiffness degradation of individual spot welds. The basic approach is based on a conventional damage accumulation combined with a power law representing the change in the spot weld’s stiffness. Instead of an accumulated damage value D a residual stiffness is set as failure criterion. Extensions to the approach are presented for its application to multiaxial loading with variable amplitudes. A conventional multiaxial fatigue test of a complete vehicle, focusing on its rear end including global stiffness and local strain measurements at the beginning, median and at the end of the test are presented and compared to the simulated results. This computation approach allows a more reliable fatigue assessment in comparison to a fatigue analysis which does not consider stiffness changes. The damage propagation after the crack initiation at an individual spot weld is represented more accurately as subsequent changes in the load paths are considered.

19

McLendon, W. Ross, and John D. Whitcomb. "Characteristic progressive damage modes in a plain weave textile composite under multiaxial loads." Journal of Composite Materials 51, no. 11 (August 20, 2016): 1539–56. http://dx.doi.org/10.1177/0021998316662132.

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A finite element-based model was developed to predict progressive damage evolution within a plain weave textile composite subjected to various combinations of in-plane tension and shear. Cracking in the tows, matrix, and interfaces was accounted for through cohesive zone modeling. Shear damage in the tows was accounted for through a continuum damage model. The damage behavior in the tows was stochastic in nature with properties determined from prior investigations of composite microstructures that included randomness in fiber positions. The predicted progressive damage evolution was found to qualitatively match well with experimental observations performed on similar material systems. The effect of temperature change, which modifies the thermally induced stresses in the tows as well as the apparent strength of the tows (due to changes in thermally induced microstresses at the fiber–matrix scale) was examined. Finally, the progressive failure responses under different loadings were compared to identify common characteristic behaviors. The effect of these characteristic behaviors on the textile’s effective response was investigated along with approaches to incorporate the behaviors into a structural scale progressive failure model.

20

Cichosz, Jörg, Tobias Wehrkamp-Richter, Hannes Koerber, Roland Hinterhölzl, and Pedro P. Camanho. "Failure and damage characterization of (±30°) biaxial braided composites under multiaxial stress states." Composites Part A: Applied Science and Manufacturing 90 (November 2016): 748–59. http://dx.doi.org/10.1016/j.compositesa.2016.08.002.

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21

Nahrmann, Marvin, and Anton Matzenmiller. "Modelling of nonlocal damage and failure in ductile steel sheets under multiaxial loading." International Journal of Solids and Structures 232 (December 2021): 111166. http://dx.doi.org/10.1016/j.ijsolstr.2021.111166.

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22

Newaz, G. M., and Ke Zhang. "Inelastic Response of Off-Axis MMC Lamina." Journal of Engineering Materials and Technology 120, no. 2 (April 1, 1998): 163–69. http://dx.doi.org/10.1115/1.2807006.

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Damage evolution and failure characteristics were investigated for a 10 deg off-axis SiC/It unidirectional metal matrix composite (MMC) lamina subjected to monotonic loading. A replica technique was used to monitor sequential damage evolution under monotonic loading for the 10 deg MMC lamina. The replicas were then examined under a Scanning Electron Microscope (SEM). Characteristic debonding along the fiber—a dominant damage mechanism, matrix plasticity in the form of slip bands and fiber cracks were observed at various strain levels and were rationalized based on the state of stress in the off-axis lamina. This investigation provides an insight into the off-axis material response for MMC lamina and associated damage mechanisms and can guide mechanism-based multiaxial constitutive model and failure criteria development.

23

Sharifimehr, Shahriar, and Ali Fatemi. "Interaction Between Normal and Shear Stresses and Its Effect on Multiaxial Fatigue Behavior." MATEC Web of Conferences 300 (2019): 16007. http://dx.doi.org/10.1051/matecconf/201930016007.

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Interaction between normal and shear stresses plays an important role in multiaxial fatigue damage. The aim of this study was to investigate this interaction effect on fatigue behavior of shear failure mode materials under multiaxial loading conditions. In order to model the influence of normal stress on fatigue damage, the present study introduces a method based on the idea that the normal stress acting on the critical plane orientation causes two types of influence, first by affecting roughness induced closure, and second, by a fluctuating normal stress affecting the growth of small cracks in mode II. The summation of these terms could then be used in shear-based critical plane damage models, for example FS damage model, which use normal stress as a secondary input. In order to investigate the effect of the method, constant amplitude load paths with different levels of interaction between the normal and shear stresses were designed for an experimental program. The proposed method was observed to result in improved fatigue life estimations where significant interactions between normal and shear stresses exist.

24

Ó Murchú, C., SB Leen, PE O’Donoghue, and RA Barrett. "A precipitate evolution-based continuum damage mechanics model of creep behaviour in welded 9Cr steel at high temperature." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 1 (April 4, 2018): 39–51. http://dx.doi.org/10.1177/1464420718762607.

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A multiaxial, physically based, continuum damage mechanics methodology for creep of welded 9Cr steels is presented, incorporating a multiple precipitate-type state variable, which simulates the effects of strain- and temperature-induced coarsening kinematics. Precipitate volume fraction and initial diameter for carbide and carbo-nitride precipitate types are key microstructural variables controlling time to failure in the model. The heat-affected zone material is simulated explicitly utilising measured microstructural data, allowing detailed investigation of failure mechanisms. Failure is shown to be controlled by a combination of microstructural degradation and Kachanov-type damage for the formation and growth of creep cavities. Comparisons with experimental data demonstrate the accuracy of this model for P91 material.

25

Averbeck, Stefan, Daniel Spriestersbach, and Eberhard Kerscher. "Crack growth and microstructural changes in AISI 52100: white etching cracks (WEC) and fine granular area (FGA)." MATEC Web of Conferences 300 (2019): 18001. http://dx.doi.org/10.1051/matecconf/201930018001.

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The service life of rolling element bearings can usually be predicted with good accuracy. However, the damage phenomenon „white etching cracks” (WEC) can lead to premature and unforeseeable failures. The formation of zones with strongly decreased grain sizes at the crack faces is a characteristic of this type of failure. An earlier study showed that it is possible to reproduce this type of failure by multiaxial fatigue experiments with superposed cyclic compression and torsion. The present study shows the analysis of the stress state of those multiaxial fatigue tests with stress-based critical plane criteria. Using the critical plane results as a basis for a fracture mechanical analysis, a correlation is found between the crack length, the associated plastic zone size, and the extent of the transformed microstructure. This correlation is very similar to our results of the study of fine granular areas (FGA), a very high cycle fatigue phenomenon in bearing steels. It is argued that a plasticity-driven mechanism similar to the one proposed for FGA formation is responsible for WEC formation, too. Additional factors that are often cited as promoting WEC formation could explain the shift from very high cycle fatigue in the case of FGA to the early failures due to WEC.

26

Ozdemir, Huseyin, and Kadir Bilisik. "Experimental Study on Angular Flexural Performance of Multiaxis Three Dimensional (3D) Polymeric Carbon Fiber/Cementitious Concretes." Polymers 13, no. 18 (September 11, 2021): 3073. http://dx.doi.org/10.3390/polym13183073.

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Multiaxis three-dimensional (3D) continuous polymeric carbon fiber/cementitious concretes were introduced. Their angular (off-axis) flexural properties were experimentally studied. It was found that the placement of the continuous carbon fibers and their in-plane angular orientations in the pristine concrete noticeably influenced the angular flexural strength and the energy absorption behavior of the multiaxis 3D concrete composite. The off-axis flexural strength of the uniaxial (C-1D-(0°)), biaxial (C-2D-(0°), and C-2D-(90°)), and multiaxial (C-4D-(0°), C-4D-(+45°) and C-4D-(−45°)) concrete composites were outstandingly higher (from 36.84 to 272.43%) than the neat concrete. Their energy absorption capacities were superior compared to the neat concrete. Fractured four directional polymeric carbon fiber/cementitious matrix concretes limited brittle matrix failure and a broom-like fracture phenomenon on the filament bundles, filament-matrix debonding and splitting, and minor filament entanglement. Multiaxis 3D polymeric carbon fiber concrete, especially the C-4D structure, controlled the crack phenomena and was considered a damage-tolerant material compared to the neat concrete.

27

Gyekenyesi, A. L. "Isothermal Fatigue Behavior and Damage Modeling of a High Temperature Woven PMC." Journal of Engineering for Gas Turbines and Power 122, no. 1 (October 20, 1999): 62–68. http://dx.doi.org/10.1115/1.483176.

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This study focuses on the fully reversed fatigue behavior exhibited by a carbon fiber/polyimide resin woven laminate at room and elevated temperatures. Nondestructive video edge view microscopy and destructive sectioning techniques were used to study the microscopic damage mechanisms that evolved. The elastic stiffness was monitored and recorded throughout the fatigue life of the coupon. In addition, residual compressive strength tests were conducted on fatigue coupons with various degrees of damage as quantified by stiffness reduction. Experimental results indicated that the monotonic tensile properties were only minimally influenced by temperature, while the monotonic compressive and fully reversed fatigue properties displayed greater reductions due to the elevated temperature. The stiffness degradation, as a function of cycles, consisted of three stages; a short-lived high degradation period, a constant degradation rate segment covering the majority of the life, and a final stage demonstrating an increasing rate of degradation up to failure. Concerning the residual compressive strength tests at room and elevated temperatures, the elevated temperature coupons appeared much more sensitive to damage. At elevated temperatures, coupons experienced a much larger loss in compressive strength when compared to room temperature coupons with equivalent damage. The fatigue damage accumulation law proposed for the model incorporates a scalar representation for damage, but admits a multiaxial, anisotropic evolutionary law. The model predicts the current damage (as quantified by residual stiffness) and remnant life of a composite that has undergone a known load at temperature. The damage/life model is dependent on the applied multiaxial stress state as well as temperature. Comparisons between the model and data showed good predictive capabilities concerning stiffness degradation and cycles to failure. [S0742-4795(00)01001-2]

28

Liu, Fang, Ming Xie, Yanjun Ji, and Mengzhen Zhou. "Progressive fatigue damage analysis of composite bolted joint using equivalent stress model." Science Progress 103, no. 1 (September 16, 2019): 003685041987423. http://dx.doi.org/10.1177/0036850419874234.

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Composite bolted joints are quite necessary for composite structures connection, which has become the main limit for the use of composites in main load-bearing structures. In this article, a fatigue model of composite bolted joint based on equivalent stress is established by programming in ABAQUS USDFLD subroutine to simulate the progressive failure of composite bolted joints. By introducing three-dimensional Tsai–Hill static failure criterion, equivalent stress is calculated for investigating effects of multiaxial stress on fatigue life. In the subroutine of progressive failure for fatigue model, fatigue life of composite bolted joint and damage state of elements that are meshed in the process of modelling are connected by defining field variable. Different fatigue modes are predicted here by changing stress amplitude and ratio loading, in which simulation results agree well with that obtained in corresponding experiments.

29

Halici, Dilek, Daniel Prodinger, Cecilia Poletti, Daniel Huber, Martin Stockinger, and Christof Sommitsch. "Modelling of the Ductile Damage Behaviour of a Beta Solidifying Gamma Titanium Aluminide Alloy during Hot-Working." Materials Science Forum 783-786 (May 2014): 556–61. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.556.

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Gamma titanium aluminides are innovative materials for high temperature and light weight applications [1]. On the other hand, their hot workability can be limited by failure during hot deformation processes. The prediction of ductile damage in metallic materials can be performed by macromechanical ductile damage criteria [2-4]. If the calculated damage D parameter exceeds a critical value Dc, the material fails. Some macromechanical ductile damage criteria are shown in Table 1, with σ as effective stress, ε as effective strain, σmax as maximum principal stress, σm as hydrostatic stress (mean stress) and εf as equivalent fracture strain. The damage responds to strain localization and thus, to multiaxial stress concentration that increases fracture probability.

30

Song, Yongsheng, Youliang Ding, Fei Jiang, Zhiwen Wang, Jun Lu, and Huijuan Jia. "Multiaxial Fatigue Assessment for the Hanger Deck Connection of a High-Speed Steel-Truss-Arch Railway Bridge." Applied Sciences 11, no. 3 (January 26, 2021): 1142. http://dx.doi.org/10.3390/app11031142.

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Steel-truss-arch bridges have been applied in high-speed railway bridges due to their excellent dynamic and static structural performance. Under the action of high-speed trains, the steel connections between hangers and decks suffer from repeated stresses, inducing potential fatigue problems or even fatigue failure. In this study, a multiaxial fatigue evaluation method was first created and established based on critical damage-plane methodology, following which the fatigue evaluation procedure was also created and recommended. The methodology was applied to real-life strain data from a high-speed railway bridge from which an assessment of fatigue damage and predicted fatigue life was estimated. The connection between the shortest hanger and deck on the downstream side was selected as the target due to its relatively high stress. A multiscale finite-element model of this bridge was created according to the design profile and monitoring results of traffic flow, where the finite-element model was calibrated and validated by comparing the calculation results with the monitoring data. Influence analysis was then carried out to investigate two factors—i.e., the total traffic flow and compositions of freight trains—having effects on the fatigue life of the steel connection. The results indicate that the applied multiaxial fatigue method is suitable for online fatigue evaluation of actual bridges. In addition, by using the multiaxial fatigue method, the fatigue-damage accumulation rate can be nearly 60 times that obtained by the uniaxial fatigue method. If freighting is taken into consideration, the fatigue damage will increase rapidly, and for the case 10% of proportion traffic as freighting, the actual fatigue life is estimated to be shorter than the design life.

31

Chen, Qingqing, Yuhang Zhang, Tingting Zhao, Zhiyong Wang, and Zhihua Wang. "Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour." Materials 14, no. 5 (February 26, 2021): 1099. http://dx.doi.org/10.3390/ma14051099.

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The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.

32

Majid, Mohd Shukry Abdul, M. Afendi, R. Daud, N. A. M. Amin, Azizul Mohamad, E. M. Cheng, A. G. Gibson, and M. Hekman. "General Lifetime Damage Model for Glass Fibre Reinforced Epoxy (GRE) Composite Pipes under Multiaxial Loading." Key Engineering Materials 594-595 (December 2013): 624–28. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.624.

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This paper presents the modelling of a general lifetime performance for glass fibre reinforced epoxy (GRE) composite pipes similar to the well-known Tsai-Hill interactive failure criterion. Tsai Hill criterion is based on the Von Misses distortional energy criterion which was modified to satisfy the orthotropic nature of GRE composite pipes. The effects of stress developed in each ply from ultimate elastic wall stress (UEWS) test were expressed in a single quadratic term of axial and hoop stress through laminate theory. The term then solved to produce limits with respect to axial and hoop stress, which represented in a graphical form of failure envelope. The modelled envelop shows a good agreement with experimental data from the multiaxial UEWS test of ±55° GRE composite pipes. This indicates that such model can be used to predict the long-term performance of GRE pipes under combine loadings.

33

Hamandi, Farah, and Tarun Goswami. "Macrodamage Accumulation Model for a Human Femur." Applied Bionics and Biomechanics 2017 (2017): 1–19. http://dx.doi.org/10.1155/2017/4539178.

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The objective of this study was to more fully understand the mechanical behavior of bone tissue that is important to find an alternative material to be used as an implant and to develop an accurate model to predict the fracture of the bone. Predicting and preventing bone failure is an important area in orthopaedics. In this paper, the macrodamage accumulation models in the bone tissue have been investigated. Phenomenological models for bone damage have been discussed in detail. In addition, 3D finite element model of the femur prepared from imaging data with both cortical and trabecular structures is delineated using MIMICS and ANSYS® and simulated as a composite structure. The damage accumulation occurring during cyclic loading was analyzed for fatigue scenario. We found that the damage accumulates sooner in the multiaxial than in the uniaxial loading condition for the same number of cycles, and the failure starts in the cortical bone. The damage accumulation behavior seems to follow a three-stage growth: a primary phase, a secondary phase of damage growth marked by linear damage growth, and a tertiary phase that leads to failure. Finally, the stiffness of the composite bone comprising the cortical and trabecular bone was significantly different as expected.

34

Mantilla, C. A., J. A. Valdés, and F. Casanova. "Multiaxial fatigue analysis for the shaft of a 100 MW hydro-power generator." Journal of Mechanical Engineering and Sciences 13, no. 2 (June 28, 2019): 4928–45. http://dx.doi.org/10.15282/jmes.13.2.2019.12.0409.

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This paper presents a stress and fatigue life analysis for the shaft of a 100 hydro-generator. Normal and shear stresses were measured at the cylindrical section of the shaft at several power levels. A finite element model was developed to find points with stress concentration and the corresponding stress concentration factor. Analytical models taken from the literature were implemented to calculate stresses during phase-to-ground and phase-to-phase failure. Stresses were linked with the generation history of the machine taken each hour during one year to obtain the stress history. With the stress history, the Wang-Brown multiaxial fatigue model and the Miner’s rule were used to estimate the fatigue life. Stresses on the shaft were found to be dependent on the generated power. Operation at partial load (between 30 and 60% of full load) was found to produce higher vibration in comparison with operation at power greater than 60% of full load. Changing the power level produced higher damage than the vibration produced during operation at a steady state condition. It was found that the shaft has a practically infinite life even when the damage produced during electrical failure was considered.

35

Dubourg, M.-C., Y. Berthier, and L. Vincent. "Cracking under fretting fatigue: Damage prediction under multiaxial fatigue." Journal of Strain Analysis for Engineering Design 37, no. 6 (August 1, 2002): 519–33. http://dx.doi.org/10.1243/030932402320950134.

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Fretting is one of the plagues of modern industry. It occurs whenever a junction between components is subjected to cyclic sliding, with small relative displacements at the interface of the contacting surfaces. Further cyclic bulk stresses may be superimposed on to one or both components. The investigation of fretting wear and fretting fatigue started in the early 1970s. It is responsible for premature fatigue failures and often limits the life of a component. Crack initiation and growth under fretting contact conditions have been investigated. The fretting map concepts allow the first degradation responses of the material—no degradation, cracking and wear—to be related to a fretting regime with its corresponding local contact conditions during fretting tests. The fretting fatigue prediction models have been developed and compared to experiments conducted either on metallic or photoelastic materials. A special emphasis has been directed towards crack nucleation and early growth during stage I, the stage I-stage II transition and stage II crack growth (crack initiation sites, orientation, growth path, formation of a branch, growth mechanism). The analysis of the different stages that comprise the crack lifetime has been carried out in order to understand the effects of diverse parameters that are thought to influence the fretting damage.

36

Rigon, Daniele, Filippo Berto, and Giovanni Meneghetti. "Crack paths in multiaxial fatigue of C45 steel specimens and correlation of lifetime with the thermal energy dissipation." Frattura ed Integrità Strutturale 16, no. 59 (December 22, 2021): 525–36. http://dx.doi.org/10.3221/igf-esis.59.34.

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The work reports the observed fatigue damage of C45 steel specimens tested in a previous work under multiaxial loading conditions and its relationship with the thermal energy dissipation which has been used in the last decades to estimate the uniaxial fatigue behavior of metals. For this purpose, fatigue data relevant to thin-walled samples made of quenched and tempered C45 steel tested under completely reversed combined axial and torsional cyclic loadings with different biaxiality ratios and phase-shift angles have been analysed. The analyses of crack paths at the initiation point of failure were performed after a 50% stiffness loss that corresponded to a crack size ranging from 7 to 15 mm; afterwards, the characteristic crack paths of each loading condition were analysed by using a digital microscope to identify the orientation of the crack initiation plane. After having broken all fatigue tested specimens under static tensile loading, the fracture surfaces were inspected close to the crack initiation point using a digital microscope. Despite the stress states and fatigue damage mechanisms dependent on the load condition, the Q parameter applied to the present experimental results proved to correlate all multiaxial fatigue test results in a single fatigue scatter band.

37

Liu, Tianqi, Xinxin Qi, Xinhong Shi, Limin Gao, Tian Zhang, and Jianyu Zhang. "Effect of Loading Frequency Ratio on Multiaxial Asynchronous Fatigue Failure of 30CrMnSiA Steel." Materials 14, no. 14 (July 15, 2021): 3968. http://dx.doi.org/10.3390/ma14143968.

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Multiaxial asynchronous fatigue experiments were carried out on 30CrMnSiA steel to investigate the influence of frequency ratio on fatigue crack initiation and propagation. Test results show that the surface cracks initiate on the maximum shear stress amplitude planes with larger normal stress, propagate approximately tens of microns, and then propagate along the maximum normal stress planes. The frequency ratio has an obvious effect on the fatigue life. The variation of normal and shear stress amplitudes on the maximum normal stress plane induces the crack retardation, and results in that the crack growth length is longer for the constant amplitude loading than that for the asynchronous loading under the same fatigue life ratio. A few fatigue life prediction models were employed and compared. Results show that the fatigue life predicted by the model of Bannantine-Socie cycle counting method, section critical plane criterion and Palmgren-Miner’s cumulative damage rule were more applicable.

38

Zhu, Zhiwu, Chenxu Cao, and Tiantian Fu. "SHPB test analysis and a constitutive model for frozen soil under multiaxial loading." International Journal of Damage Mechanics 29, no. 4 (August 9, 2019): 626–45. http://dx.doi.org/10.1177/1056789519867471.

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A split Hopkinson pressure bar is adopted to test the dynamic mechanical behavior of frozen soil at different temperatures and high strain rates. An aluminum sleeve is used as a passive confining pressure device. Comparing the results of this test with those under the uniaxial state shows that besides the temperature and strain rate effects, frozen soil exhibits obvious stress strengthening characteristics. In addition, the failure mode is viscoplastic instead of brittle. If frozen soil is regarded as a particle-reinforced composite material, then the debonding damage of ice particles and rate-dependent damage of soil matrix are taken into account. Based on this, a dynamic constitutive model of frozen soil under a multiaxial state is proposed. The theoretical results of the model agree well with the experimental results, verifying the rationality and applicability of the model.

39

Reis, Luís G., Bin Li, and Manuel de Freitas. "Crack Growth Orientation in Two Structural Materials under Multiaxial Fatigue Loading." Materials Science Forum 587-588 (June 2008): 892–97. http://dx.doi.org/10.4028/www.scientific.net/msf.587-588.892.

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In real engineering components and structures, many accidental failures are due to unexpected or additional loadings, such as additional bending or torsion, etc. Therefore, it has attracted more research attentions to study the mechanical behavior of materials under complex loading conditions. Two typical structural materials are studied and compared in this paper: AISI 303 stainless steel and 6060-T5 Aluminum alloy. The objective is to study the effects of multiaxial loading paths on the crack initiation and orientation of the two materials studied. Fatigue tests were conducted in a biaxial testing machine. Fractographic analyses of the fracture surface were carried out by optical microscope and SEM approaches. In addition to the experimental studies, theoretical predictions of the damage plane were made using critical plane approaches. Comparisons of the predicted orientation of the damage plane with the experimental observations are shown. The applicability of the multiaxial fatigue criteria for the two materials is discussed. It was shown that the two materials studied have different crack orientations under the same loading path. This observation appears to show that the applicability of the fatigue models is dependent on the material type and multiaxial microstructure characteristics.

40

Ellyin, F., K. Golos, and Z. Xia. "In-Phase and Out-of-Phase Multiaxial Fatigue." Journal of Engineering Materials and Technology 113, no. 1 (January 1, 1991): 112–18. http://dx.doi.org/10.1115/1.2903365.

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In this investigation, thin-walled circular cylindrical specimens fabricated from a low alloy pressure vessel steel (ASTM A-516 Gr. 70) were subjected to various multiaxial loading conditions. The tests were conducted under strain-controlled condition, and loading was provided through an axial actuator and internal and external pressure across the specimen wall. Four in-plane strain ratios (ρ = Δεt/Δεa) were tested, and the most damaging case was the equi-biaxial in-plane straining, ρ = 1. For the latter condition, 90 deg out-of-phase loading was also investigated. These tests indicated a dramatic decrease in the number of cycles to failure, Nf, as a result of out-of-phase loading. The influence of the plastic strain path on life is thus clearly demonstrated. It is shown that the total strain energy density, ΔWt = ΔWe+ + ΔWp, correlates with both the in-phase and out-of-phase cyclic tests, and therefore is a proper damage parameter to be used for life predictions. A brief description of how ΔWt can be calculated is given for the case of proportional loading. The predicted results are compared with the experimental data, and the agreement is found to be very good indeed.

41

Pisati, Marco, Marco Giuseppe Corneo, Stefano Beretta, Emanuele Riva, Francesco Braghin, and Stefano Foletti. "Numerical and Experimental Investigation of Cumulative Fatigue Damage under Random Dynamic Cyclic Loads of Lattice Structures Manufactured by Laser Powder Bed Fusion." Metals 11, no. 9 (September 3, 2021): 1395. http://dx.doi.org/10.3390/met11091395.

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Lattice structures are lightweight engineering components suitable for a great variety of applications, including those in which the structural integrity under vibration fatigue is of paramount importance. In this work, we experimentally and numerically investigate the dynamic response of two distinct lattice configurations, in terms of fatigue damage and life. Specifically, Face-Centered-Cubic (FCC) and Diamond lattice-based structures are numerically studied and experimentally tested under resonant conditions and random vibrations, until their failure. To this end, Finite Element (FE) models are employed to match the dynamic behavior of the system in the neighborhood of the first natural frequency. The FE models are employed to estimate the structural integrity by way of frequency and tip acceleration drops, which allow for the identification of the failure time and a corresponding number of cycles to failure. Fatigue life under resonant conditions is well predicted by the application of conventional multiaxial high cycle fatigue criteria to the local state of stress. The same approach, combined with the Rainflow algorithm and Miner’s rule, provides good results in predicting fatigue damage under random vibrations.

42

Zhu, Shun-Peng, Zheng-Yong Yu, Qiang Liu, and Ayhan Ince. "Strain energy-based multiaxial fatigue life prediction under normal/shear stress interaction." International Journal of Damage Mechanics 28, no. 5 (July 13, 2018): 708–39. http://dx.doi.org/10.1177/1056789518786031.

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Through characterizing the interaction of normal/shear stress–strain behavior on material planes of TC4 alloys, a new strain energy critical plane model describing mean stress effects is proposed for life prediction under tension–compression, pure torsion, and tension–torsion loadings. Moreover, a modified Ince–Glinka model is elaborated through considering crack surface close to the maximum shear strain plane. Three simple solutions are presented to determine cracking failure mode using the concepts of life, damage, and strain. Comparing with lifing models of Liu, Smith–Watson–Topper, and modified Ince–Glinka, the proposed model provides more accurate life predictions for TC4 and a compressor turbine disc by full-scale fatigue testing.

43

Wang, Feng Hui, Qiong Wu, Ying Xi Wu, and Sheng Yin Song. "Fatigue Life of Thread Connection for Casing Drilling under Tension and Torsion." Advanced Materials Research 33-37 (March 2008): 255–60. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.255.

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Casing drilling technique which has been dramatically developing is a revolution in petroleum industry and has aroused great concerns. The fatigue failure of casing thread connection is a critical issue for using. Therefore, to study the fatigue failure of casing connection is an important issue for understand the life of casing drilling. For the notched element, how to estimate the life and which parameter (equivalent stress, equivalent strain ,or the strain in the root )represent the damage under fatigue condition is still a problem. The purpose of this paper is to investigate the fatigue life of notch element under multiaxial stresses and to find out the damage parameter so as to predict the life of notch element. First specimen were machined with the same notch geometer dimension as the casing thread connection, fatigue tests with tension and torsion loading were carried out by fatigue test machine , for stress levels designed to obtain S-N lifetime curve. The stress and strain for the connections subjected to proportional loading were analyzed by elastic-plastic finite element method. The stress-strain state for notched specimens subjected to constant amplitude proportional multiaxial loadings was also calculated and analyzed by the finite element model. Take the equivalent stress, equivalent strain and the strain by FEM in the root into the prediction model, the strain by FEM has a good agreement with the experiment.But the results from the equivalent stress and equivalent strain also in good agreement with the experiment and is thought to be a simple prediction way.

44

Algarni, Mohammed, Yuanli Bai, Mohammed Zwawi, and Sami Ghazali. "Damage Evolution Due to Extremely Low-Cycle Fatigue for Inconel 718 Alloy." Metals 9, no. 10 (October 17, 2019): 1109. http://dx.doi.org/10.3390/met9101109.

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This paper evaluates the damage evolution process under extremely low-cycle fatigue (ELCF). The study explores the damage behavior under different stress states. The influence of the multiaxial state of stress on the metal’s life is determined. Two different stress states were examined: (a) axisymmetric and (b) plane-strain. The study is based on the modified Mohr–Coulomb (MMC) ductile fracture criterion that was extended to cover the ELCF regime in a previous research study. Four distinctive geometries are designed to study the effect of different stress states on ELCF life and damage evolution. The damage model is calibrated for life prediction to agree with the ELCF experimental results. The investigation of the damage evolution behavior is dependent on equivalent plastic strain, stress triaxiality, Lode angle, and cyclic loading effect. The damage evolution is extracted from Abaqus finite element simulations and plotted versus the equivalent plastic strain. The damage accumulation shows nonlinear evolution behavior under cyclic loading conditions. SEM images were taken to further study the microscopic failure mechanisms of ELCF.

45

Makhutov, N. A., V. S. Kossov, E. S. Oganyan, G. M. Volokhov, M. N. Ovechnikov, and A. L. Protopopov. "Prediction of contact-fatigue damage to rails using computational-experimental methods." Industrial laboratory. Diagnostics of materials 86, no. 4 (April 23, 2020): 46–55. http://dx.doi.org/10.26896/1028-6861-2020-86-4-46-55.

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Analysis of the operational data related to rails failure showed that contact-fatigue defects consistently hold a prominent place. The goal of the study is to show the possibilities of using modern numerical methods in calculation assessment of the service life of rails before the onset of contact fatigue crack formation on a running surface depending on the values of axial load. To calculate a stress-strain state in the area of contact interaction between the wheel and rail a detailed finite-element model implemented in the MSC. Marc software package is used. The analysis revealed complex multiaxial and non-proportional nature of the stress-strain state. The Brown – Miller multiaxial fatigue model implemented in the MSC. Fatigue software package was taken to determine accumulation of the contact fatigue damages on a rail running surface. The model is based on the assumption that maximum fatigue damages in the metal occur in the area with the maximum shear stress. The impact of normal stresses in this area is also taken into account. The results of a comparative computational analysis of the rail life time confirm that the service life decreases with increasing axial loads, all other conditions being the same. With a share of 20% of freight trains with axle loads of 25 tonf in a daily pattern one should expect a decrease in the contact fatigue life of rails by 3 – 4 %. It is possible to improve the method for prediction of the contact fatigue life of rails in terms of experimental definition of the fatigue and strength characteristics of the rail steel depending on the degree of hardening of the running surface, their probabilistic properties and the use of a cumulative distribution of vertical forces taking into account the structure of the freight traffic passing through the section.

46

Anes, Vitor, Luis Reis, and Manuel Freitas. "Effect of Shear/Axial Stress Ratio on Multiaxial Non-Proportional Loading Fatigue Damage on AISI 303 Steel." Metals 12, no. 1 (January 4, 2022): 89. http://dx.doi.org/10.3390/met12010089.

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In this paper, we investigate the cyclic response of AISI 303 stainless steel subjected to non-proportional loads with different amplitude ratios between shear stresses and normal stresses. Based on the experiments, a relationship between the proportional reference load and a varied range of non-proportional loads was established. To achieve this objective, an experimental program was implemented to evaluate the non-proportional parameter Y. Then, the evolution of this parameter was analyzed with the number of cycles to failure and with the ratio between shear and normal stresses, finally, the evolution of the non-proportional parameter Y was mapped by two functions. The results show that the non-proportional response of the AISI 303 can be estimated using the two functions obtained. This allows the estimation of the relationship between non-proportional and proportional stresses as a function of the number of cycles to failure together with the relationship between shear and normal stresses. The results obtained have direct application in the evaluation of accumulated damage, assessed in real-time, resulting from variable amplitude loading spectra. This is of particular interest for the evaluation of structural health monitoring of structures and mechanical components.

47

Li, Dian-sen, Zhuo Wang, Hong-wei Duan, and Lei Jiang. "Temperature effects on the compression behavior and failure of 3-D MWK glass fabric-reinforced epoxy composites." High Performance Polymers 31, no. 4 (June 19, 2018): 449–61. http://dx.doi.org/10.1177/0954008318781952.

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This article reports the temperature effects on the in-plane and out-of-plane compression behavior and failure of 3-D multiaxial warp-knitted glass fabric-reinforced epoxy composites. The damage and fracture morphology are observed from macroscopic and microscopic views, and the failure mechanism is demonstrated. The results show that the temperature has significant effect on in-plane and out-of-plane compression properties, the stress versus strain curves decline, and the properties decrease significantly with increasing the temperature. The temperature of 75°C is a key point, at which change in compression properties occurs, and at 150°C, the materials become plastic. Moreover, fiber architecture and loading modes are also important factors on compression properties of composites. The results also show that the damage and failure patterns vary with temperature, fiber architecture, and loading modes. Under in-plane compression, material A shows local 0° fiber layers delaminating and becomes softening and plasticity with increasing temperature. Material B shows delaminating between 0°, 90°, +45°, and −45° fiber layers along 45° angle and exhibits multiple delaminating at elevated temperatures. Under out-of-plane compression, material A shows multiple local shear fracture with 45° angle and experiences softening, roughness, and expansion at elevated temperatures. Material B exhibits shear brittle failure clearly, and delaminating dominates the main failure with increasing the temperature.

48

Zhou, Jie, Hong-Zhong Huang, and He Li. "A Novel Energy-Critical Multiaxial Fatigue Life Prediction for Low Cycle Fatigue under Mixed-Mode Loading." Metals 8, no. 12 (December 14, 2018): 1066. http://dx.doi.org/10.3390/met8121066.

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Fatigue failure evolution is a process of damage accumulation under continued stresses and forces. The mechanical component is always subjected to various loadings and the lifespan is mainly governed by fatigue. The low cycle fatigue (LCF) is a key failure mode of many components. In order to estimate the LCF life under multiaxial loadings in practical design, a modified model is proposed, based on the Fatemi-Socie (FS) and Smith-Watson-Topper (SWT) models, which considers the effects of shear and tensile behaviours. Then a novel judgment criterion is presented to distinguish the mixed-mode loadings and the procedures to employ the proposed model are also presented. Furthermore, two types of materials (TC4 and GH4169) and comparisons with the FS, Wang-Brown (WB) and redefined SWT (Re-SWT) models are employed to verify the accuracy and effectiveness of the proposed model, which has shown more reasonable predictions than the other models.

49

Brevis, W., L. Susmel, and J. Boxall. "Investigating in-service failures of water pipes from a multiaxial notch fatigue point of view: A conceptual study." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 7 (October 7, 2014): 1240–59. http://dx.doi.org/10.1177/0954406214553020.

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Many mechanisms and processes can cause deterioration and ultimately failure of water distribution pipes during in-service operation, amongst these is damage caused by metal fatigue. This paper summarises an attempt at formalising a novel methodology suitable for estimating the number of years taken for a through thickness fatigue crack to form in this complex scenario. The devised method is based on the so-called modified Wöhler curve method and can be applied to estimate fatigue damage of water pipes independently from the degree of multiaxiality and non-proportionality of the load history. The computational approach of the proposed fatigue life estimation technique makes full use of an incremental procedure: fatigue damage is evaluated year by year by assuming that all variable involved in the process can change over time. The detrimental effect of corrosion pits is directly accounted for by treating them as conventional notches whose size increases with time. Finally, by taking as reference information the number of years for a blowout hole to form, the proposed approach is used to show how the lifetime of grey cast iron pipes can be remarkably shortened by fatigue.

50

Saber, M., D. W. J. Tanner, W. Sun, and T. H. Hyde. "Determination of creep and damage properties for P92 at 675 °C." Journal of Strain Analysis for Engineering Design 46, no. 8 (September 13, 2011): 842–51. http://dx.doi.org/10.1177/0309324711413012.

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In order to predict the service life of components that operate at high temperatures, such as steam carrying pipes in conventional power plants, the material creep behaviour needs to be determined. There are little creep data available on grade P92 (9Cr2W) steel (a potential successor to P91) as it is a relatively new material; therefore a testing programme has been undertaken. This paper presents the results of uniaxial and notched bar creep tests on P92 parent material (PM) and P92 weld metal (WM) at 675 °C. The PM had higher failure times and lower minimum creep strain rates for tests in the same stress range (80–100 MPa) as the WM, but the PM and WM values tend to converge at high stress, with a significant difference between the failure times as applied stress decreases. The notch strengthening effect was found to decrease as the applied stress decreased. Processing of the test data including the calculation of the minimum creep strain rates has been performed to determine the material constants required for Norton’s steady state creep and both the Kachanov and the Liu and Murakami creep damage models. Material constant sets for creep of P92 PM and WM at 675 °C, including a parameter to describe the effect of a multiaxial stress state, have been obtained that give a good fit to the test data. Validation was achieved using finite element analysis.

Статті в журналах з теми "Multiaxial damage and failure"

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