A Theory for Mathematical Framework of Fatigue Damage on S-N Plane

2014 ◽  
Vol 627 ◽  
pp. 117-120 ◽  
Author(s):  
Hoda Eskandari ◽  
Ho Sung Kim
Keyword(s):  
Fatigue Life ◽  
Boundary Conditions ◽  
Fatigue Damage ◽  
Fatigue Loading ◽  
Mathematical Framework ◽  
Accumulated Damage ◽  
Damage Quantification ◽  
Damage Equation

A theory for mathematical framework is developed with axioms for fatigue damage, quantification and relativity concept, boundary conditions, and compatibility, allowing us to evaluate the validity of candidate damage equations/quantities on S-N plane for prediction of fatigue life. Manifestation points for accumulated damage were defined for boundary conditions by differentiating between damage accumulated before failure, and failure caused by damage at quantised fatigue loading cycles. A selected damage equation leading to a theoretical S-N curve was validated as an example.

A Multi-Level Low Cycle Fatigue Damage Model for Forging Die Material

2006 ◽  
Vol 514-516 ◽  
pp. 804-809
Author(s):  
S. Gao ◽  
Ewald Werner
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Die Material ◽  
Multi Level ◽  
Loading Sequence ◽  
Forging Die

The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

Stiffness Degradation of Digital Polypropylene Under Fatigue Loading: Investigations via 3-Dimensional Polyjet Printed Coupons

2020 ◽  
Author(s):  
Ravi Pratap Singh Tomar ◽  
Furkan I. Ulu ◽  
Ajit Kelkar ◽  
Ram V. Mohan
Keyword(s):  
Experimental Data ◽  
Regression Analysis ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Damage State ◽  
3 Dimensional ◽  
Accumulated Damage ◽  
Polyjet Printing

Abstract The utilization of additively manufactured parts is gaining popularity in functional applications. Polymer-based additive manufacturing (AM) parts are utilized in a variety of engineering applications for automotive, aerospace, and energy. AM printed parts are however newer class of materials, and structural performance of these materials is not fully understood completely, and very limited exists currently on precisely performance of Polyjet printed parts and associated digital materials under fatigue loading. This paper investigates the stiffness degradation under tension-tension fatigue loading of digital polypropylene using homogenous 3-Dimensional test coupons formed using PolyJet printing. Homogeneous 3-Dimensional test configuration employed in the present study eliminates the process-induced limitations of traditional ASTM D638 2D fatigue test coupons for AM processed materials. Fatigue data is analyzed to present an empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclic loading. Further, the actual damage accumulation due to cyclic loading with the predicted model is compared. Modeling of the S-N diagram provides a better estimation of fatigue life and fatigue life modeling of AM printed test coupons and is obtained via linear regression analysis of experimental data with high correlation coefficient R2 (0.9971). The analytical model of the accumulated damage state is based on the stiffness degradation and is derived from the regression analysis of experimental data of stiffness degradation at different loading percentages assuming a polynomial of degree 4. Present study provides insight into the fatigue damage state and cyclic performance of digital polypropylene from Polyjet printing.

Load Spectrum Compiling and Practical Application of Output Flange for Wheel Loader Gearbox

2011 ◽  
Vol 346 ◽  
pp. 483-489
Author(s):  
Ying Shuang Zhang ◽  
Guo Qiang Wang ◽  
Ji Xin Wang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Prediction Method ◽  
Fatigue Loading ◽  
Load Spectrum ◽  
Element Analysis ◽  
Wheel Loader ◽  
Program Load Spectrum ◽  
Program Load

To realize the structural light weighting design of the transmission components of engineering vehicles on the basis of life in control, this paper took wheel loader as an example, collected the time-domain load signals of the transmission system in typical working conditions, provided processing steps for load spectrum synthesis by a certain percentage, and generated the program load spectrum which consisted of various amplitudes and means. The load spectrum can be used for fatigue loading at the output flange of gearbox. Then, the finite element model of the flange was established, and the stress analysis was carried out in the stress concentration location such as fillet. The prediction method of fatigue life on the base of program load spectrum was given. After the fatigue life prediction based on the compiled load spectrum and the theory of cumulative fatigue damage, the fatigue life of outside fillet of the flange, where is of maximum stress, is obtained. It was possible to obtain adequately fatigue prediction results in engineering vehicle design, using load spectrum, finite element analysis, and a stress-life approach to fatigue damage calculations.

Experimental Damage Mechanics of Microelectronic Solder Joints Under Fatigue Loading

2002 ◽  
Author(s):  
Cemal Basaran ◽  
Hong Tang ◽  
Shihua Nie
Keyword(s):  
Elastic Modulus ◽  
Fatigue Life ◽  
Thermal Cycling ◽  
Fatigue Damage ◽  
Solder Joints ◽  
Fatigue Loading ◽  
Damage Mechanism ◽  
Load Drop ◽  
Material Degradation ◽  
Elastic Modulus Degradation

Fatigue damage is a progressive process of material degradation. The objective of this study is to experimentally qualify the damage mechanism in solder joints in electronic packaging under thermal fatigue loading. Another objective of this paper is to show that damage mechanism under thermal cycling and mechanical cycling is very different. Elastic modulus degradation under thermal cycling, which is considered as a physically detectable quantity of material degradation, was measured by Nano-indenter. It was compared with tendency of inelastic strain accumulation of solder joints in Ball Grid Array (BGA) package under thermal cycling, which was measured by Moire´ interferometry. Fatigue damage evolution in solder joints with traditional load-drop criterion was also investigated by shear-strain hysteresis loops from strain-controlled cyclic shear testing of thin layer solder joints. Load-drop behavior was compared with elastic modulus degradation of solder joints under thermal cycling. Following conventional Coffin-Manson approach, S-N curve was obtained from isothermal fatigue testing with load-drop criterion. Coffin-Manson curves obtained from strain controlled mechanical tests were used to predict fatigue life of solder joints. In this paper it is shown that this approach underestimates the fatigue life by an order of magnitude. Results obtained in this project indicate that thermal fatigue and isothermal mechanical fatigue are completely different damage mechanism for microstructurally evolving materials.

scholarly journals Thermo-mechanical fatigue damage behavior for Ni-based superalloy under multiaxial loading

2018 ◽  
Vol 165 ◽  
pp. 19002
Author(s):  
Dao-Hang Li ◽  
De-Guang Shang
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Tensile Stress ◽  
Fatigue Damage ◽  
Mechanical Strain ◽  
Creep Damage ◽  
Fatigue Loading ◽  
Shear Stresses ◽  
Damage Behavior ◽  
Von Mises

The fatigue damage behavior was experimentally investigated in different axial-torsional thermo-mechanical loading conditions for Ni-based superalloy GH4169. The strain controlled tests were carried out with the same von Mises equivalent mechanical strain amplitude of 0.8% in the temperature range from 360°C to 650°C. The results show that the fatigue life is drastically reduced when the axial mechanical strain and the temperature are in-phase, which can be due to that the creep damage is induced by the tensile stress at high temperature. Moreover, the fatigue life is further decreased when the axial mechanical strain and the shear strain are out-of-phase, which can be attributed to that the non-proportional hardening can increase the creep and the oxidation damages. Furthermore, the tensile stress is crucial to the nucleation of creep cavities at high temperature compared with the shear stress. The tensile and shear stresses all can increase the creep damage under fatigue loading at high temperature. In addition, the oxidation damage can be induced during cyclic loading at high temperature, and it can be increased by the tensile mean stress caused in non-isothermal loading.

scholarly journals Mode II Behavior of High-Strength Concrete under Monotonic, Cyclic and Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7675
Author(s):  
Henrik Becks ◽  
Martin Classen
Keyword(s):  
Fatigue Life ◽  
Compressive Stress ◽  
Fatigue Damage ◽  
High Strength Concrete ◽  
High Strength ◽  
Fatigue Loading ◽  
Mode Ii ◽  
Shear Tests ◽  
Strength Concrete ◽  
Mode Ii Loading

An economically efficient yet safe design of concrete structures under high-cycle fatigue loading is a rather complex task. One of the main reasons is the insufficient understanding of the fatigue damage phenomenology of concrete. A promising hypothesis states that the evolution of fatigue damage in concrete at subcritical load levels is governed by a cumulative measure of shear sliding. To evaluate this hypothesis, an experimental program was developed which systematically investigates the fatigue behavior of high-strength concrete under mode II loading using newly adapted punch through shear tests (PTST). This paper presents the results of monotonic, cyclic, and fatigue shear tests and discusses the effect of shear-compression-interaction and load level with regard to displacement and damage evolution, fracture behavior, and fatigue life. Both, monotonic shear strength and fatigue life under mode II loading strongly depend on the concurrent confinement (compressive) stress in the ligament. However, it appears that the fatigue life is more sensitive to a variation of shear stress range than to a variation of compressive stress in the ligament.

Durability of Concrete Under the Combined Action of Carbonization and Fatigue Loading of Vehicles

2019 ◽  
Vol 11 (12) ◽  
pp. 1781-1787
Author(s):  
Yuan-Yao Miao ◽  
Di-Tao Niu ◽  
Ning Cheng
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Fatigue Loading ◽  
Atmospheric Environment ◽  
Climate Simulation ◽  
Concrete Durability ◽  
Loading Level ◽  
Damage Degree ◽  
Vehicle Loading ◽  
Combined Action

Natural factors such as environments gradually cause the aging of structural materials of concrete bridges and mechanical properties of the components are constantly degraded. When highway bridge structures are under the combined with vehicle loading and environmental diversities, the degradation of structural performance is further aggravated. In this study, according to the deterioration trend of concrete durability in atmospheric environment, durability tests for concrete under the combined action of fatigue loading of vehicles and carbonization were performed by artificial climate simulation. A bending fatigue test for concrete under vehicle loading was carried out, and the trend of fatigue life change with vehicle loading level and the trend of fatigue strain development were obtained. The results show that the fatigue life increases with the decrease in fatigue loading level of vehicles, and the logarithmic value of fatigue life Nf is linear with the fatigue stress level S. Fast carbonization tests for concrete were performed with respect to the fatigue damage degree D of 0, 0.2, 0.4, 0.6, and 0.8. It was found that the carbonization trend of fatigue damaged concrete under vehicle loading follows the Fick first law. The carbonization depth increases with the increase in carbonization time, relatively fast at the initial stage and then slowly at the later stage. When the fatigue damage degree D is less than 0.4, the effects of fatigue damage on carbonization is relatively small. When D is more than 0.4, the effect of fatigue damage on carbonization is relatively significant. The extension of interior micro-cracks and micropores caused by fatigue damage is a significant factor affecting the carbonization performance of fatigue damaged concrete. The change trend of carbonization depth of damaged concrete with time was fitted and analyzed. An influencing factor of fatigue damage was introduced, and a durability prediction model for concrete under the combined action of carbonization and fatigue loading of vehicles was established.

Fatigue Life Prediction of Composite Pin Joints

2014 ◽  
Vol 697 ◽  
pp. 57-61
Author(s):  
Peng Gang Mu ◽  
Xiao Peng Wan
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Composite Structures ◽  
Degradation Process ◽  
Damage State ◽  
Damage Propagation ◽  
Damage Models ◽  
Damage Quantification ◽  
Arbitrary Loading ◽  
Damage Process

In this research, new progressive fatigue damage models are established to calculate the fatigue life and simulate damage process of composite pin joints. The proposed models based on residual strength and residual stiffness of unidirectional laminates, have three parameters to present the different damage state, which can accurately describe the growth process of fatigue damage propagation by the mathematical method. The fatigue damage models combining with stress analysis, failure analysis, and material property degradation process, can predict the fatigue life, damage state and residual material properties of composite structures under arbitrary loading conditions. Using the models, composite pin joints with different stacking sequence are analyzed, fatigue life and damage quantification are concluded simultaneously. The proposed models and the process of analysis provide a way to solve the fatigue durability of composite structures.

scholarly journals New Nonlinear Cumulative Fatigue Damage Model Based on Ecological Quality Dissipation of Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Hongsong Li ◽  
Yongbao Liu ◽  
Xing He ◽  
Wangtian Yin
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Damage ◽  
Damage Model ◽  
Fatigue Loading ◽  
Ecological Quality ◽  
Aircraft Structures ◽  
Variable Amplitude ◽  
Fatigue Damage Accumulation ◽  
Cumulative Fatigue Damage

The failure of many aircraft structures and materials is caused by the accumulation of fatigue damage under variable-amplitude cyclic loading wherein the damage evolution of materials is complicated. Therefore, to study the cumulative fatigue damage of materials under variable-amplitude cyclic loading, a new nonlinear fatigue damage accumulation model is proposed based on the ecological quality dissipation of materials by considering the effects of load interaction and sequence. The proposed new model is validated by the test data obtained for three kinds of material under multilevel fatigue loading. Compared with the Miner model and Kwofie model, the proposed model can more effectively analyse the accumulative damage and predict fatigue life of different materials under variable-amplitude cyclic loading than others. The study provides a basis for predicting fatigue life accurately and determining reasonable maintenance periods of aircraft structures.

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