Determination Method of a Proper Small-Load-Omitting Criterion Based on the Extreme Load

2013 ◽  
Vol 694-697 ◽  
pp. 278-283
Author(s):  
Zhi Qiang Xu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
High Frequency ◽  
Life Prediction ◽  
Time History ◽  
Fatigue Life Prediction ◽  
Threshold Theory ◽  
Small Load ◽  
Extreme Load ◽  
Peak Over Threshold

A crucial step to obtain a reliable fatigue life prediction is to determine a proper small load threshold below which the cycles at small loads or stresses with high frequency causing little fatigue damage are truncated from the original load time history. By taking both the peak over threshold theory and the endurance limit threshold into account, a proper small load threshold is proposed in this paper. The optimal threshold should be high enough to remove the high-frequency small cycles and low enough to minimize the loss of the fatigue damage which maybe be truncated by the empirical small-load omitting threshold. Based on this proper threshold, the fatigue life prediction will be more reliable.

scholarly journals Strain energy-based rubber fatigue life prediction under the influence of temperature

2018 ◽  
Vol 5 (10) ◽  
pp. 180951 ◽  
Author(s):  
Jingnan Zhang ◽  
Fengxian Xue ◽  
Yue Wang ◽  
Xin Zhang ◽  
Shanling Han
Keyword(s):  
Fatigue Life ◽  
Prediction Model ◽  
Fatigue Damage ◽  
Strain Energy ◽  
Life Prediction ◽  
Least Square ◽  
Fatigue Life Prediction ◽  
Uniaxial Tensile ◽  
Influence Of Temperature ◽  
Different Temperatures

Aiming at the problem of the fatigue life prediction of rubber under the influence of temperature, the effects of thermal ageing and fatigue damage on the fatigue life of rubber under the influence of temperature are analysed and a fatigue life prediction model is established by selecting strain energy as a fatigue damage parameter based on the uniaxial tensile data of dumbbell rubber specimens at different temperatures. Firstly, the strain energy of rubber specimens at different temperatures is obtained by the Yeoh model, and the relationship between it and rubber fatigue life at different temperatures is fitted by the least-square method. Secondly, the function formula of temperature and model parameters is obtained by the least-square polynomial fitting. Finally, another group of rubber specimens is tested at different temperatures and the fatigue characteristics are predicted by using the proposed prediction model under the influence of temperature, and the results are compared with the measured results. The results show that the predicted value of the model is consistent with the measured value and the average relative error is less than 22.26%, which indicates that the model can predict the fatigue life of this kind of rubber specimen at different temperatures. What's more, the model proposed in this study has a high practical value in engineering practice of rubber fatigue life prediction at different temperatures.

Fatigue Life Prediction of Composite Laminate

2012 ◽  
Vol 472-475 ◽  
pp. 591-595 ◽  
Author(s):  
Jun Liu ◽  
Feng Peng Zhang
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Composite Laminates ◽  
Life Prediction ◽  
Plate Theory ◽  
Damage Model ◽  
Prediction Method ◽  
Fatigue Life Prediction ◽  
Fatigue Properties ◽  
Adjacent Layer

Abstract. based on the accumulating fatigue damage model, with single ply plate theory and experiment data as the foundation, consider the interaction between adjacent layer and material degradation, a kind of fatigue life prediction method of fiber reinforced composite laminates is developed. The stiffness decline of each ply during cyclic loading is determined by the fatigue damage variable and the load amplitude and the fatigue life of any laminates can be predicted using the fatigue properties of single ply plate. Using this method a 3D Finite element model is established by ABAQUS software and the fatigue life and the fatigue damage evolution of a T300 / QY8911 laminats are analyzed, the results are more closer to the experimental results.

Fatigue Life Prediction of Composite Laminates Based on Progressive Damage Analysis

2014 ◽  
Vol 1064 ◽  
pp. 108-114 ◽  
Author(s):  
Jun Kang ◽  
Zhi Dong Guan ◽  
Zeng Shan Li ◽  
Zhun Liu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Material Property ◽  
Composite Laminates ◽  
Life Prediction ◽  
Shear Failure ◽  
Fatigue Life Prediction ◽  
Progressive Damage ◽  
Damage Analysis ◽  
Fatigue Damage Analysis

A three dimensional analysis model is developed on the fatigue life prediction of composite laminates based on a progressive damage analysis. This model consists of stress analysis, fatigue failure analysis and material property degradation. Teserpe’s failure criteria is used to fatigue damage analysis. Fiber tensile/compressive breakage, matrix tensile/compressive cracking, matrix/fiber shear failure and tension/compression delamination are considered in fatigue damage analysis. The methodologies of sudden degradation and gradual degradation are both applied in the material property degradation. The stiffness and strength gradual degradation is based on the Shokrieh fatigue model, which is based on fatigue test for unidirectional laminates. In order to consider the scatter of the material in the practical structures, the stiffness and strength of the material are randomly distributed using normal distribution in the numerical model. The progressive fatigue damage model is developed in finite element code ABAQUS through user subroutine UMAT, which can simulate the fatigue damage process. Fatigue life of different ply stacking sequences and geometries composite laminates under different cycle loading are predicted. The predicted fatigue life is in good agreement with the experimental results.

Fatigue Behaviour of Lead-Free Solder Interconnections in Life Prediction of Trilayer Structures Subjected to Thermal Cycling

2015 ◽  
Author(s):  
Alireza Shirazi ◽  
Hua Lu ◽  
Ahmad Varvani-Farahani
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Life Prediction ◽  
Damage Parameter ◽  
Fatigue Life Prediction ◽  
Lead Free Solder ◽  
Critical Plane ◽  
Trilayer Structure ◽  
Fatigue Damage Parameter ◽  
Free Solder

Trilayer structures such as flip chip plastic ball grid array (FC-PBGA) packages are bodies made of a large variety of dissimilar materials. Due to the coefficients of thermal expansion (CTE) mismatches between and temperature gradients within the layers, thermally induced interaction becomes a typical type of the loads for the joint layer made of lead-free solder joint interconnections. Thermal stresses and strains at the interfaces of solder joints and neighboring adhesive layers are the cause for solder joint fatigue failures, which account for the most common package failures. The current study puts forward a fatigue life prediction method for a trilayer structure using the critical plane-energy fatigue damage parameter in combination with the modified Coffin-Manson life model. The proposed method of calculated fatigue damage parameter for the samples of study, along with their experimental life (Nf50%) under two different thermal conditions is presented. The values of life in (0–100°C) condition and (25–125°C) with the same temperature ramp rate and dwell conditions are found to differ by a factor of 1.3 where the structures tested under (0–100°C) condition show lower lives. The present study further correlated the fatigue damage parameters with the Coffin-Manson type equation to calculate/predict the fatigue life of structures under (25–125°C) condition. The results of the Nf50 fatigue life prediction versus the experimental cycles show that the predicted lives of samples with SAC305 solder joints fall apart with a factor ranging from (1.24)∼(−1.45). The advantage of the proposed method in comparison with the existing methods in life prediction of the trilayer structure with solder alloy is that there are no empirical parameters involved in energy-critical plane damage parameter in life prediction of the trilayer structure. Parameters within the proposed approach purely involves mechanical and fatigue properties of the midlayer alloy.

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