Numerical investigation on fatigue life of aluminum brazing structure with fin-plate-side bar under the low temperature thermal-structure cyclic stress

2021 ◽  
pp. 105918
Author(s):  
Hongqiang Ma ◽  
Jiwei Jia ◽  
Ruixiang Ding ◽  
Xinmei Luo ◽  
Donggen Peng ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Low Temperature ◽  
Numerical Investigation ◽  
Thermal Structure ◽  
Cyclic Stress

Rate Dependent Constitutive Equations of Cyclic Softening

1985 ◽  
Vol 40 (7) ◽  
pp. 653-665
Author(s):  
J. S. Mshana ◽  
A. S. Krausz
Keyword(s):  
Stress Relaxation ◽  
Low Temperature ◽  
Constitutive Equations ◽  
Strain Softening ◽  
Structural Characteristics ◽  
High Stress ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Stress Softening

Constitutive equations of cyclic strain and stress softening for materials with low internal stress levels are derived from the rate theory. The study shows that over the high stress and low temperature range where the description of plastic flow in cyclic softening can be approximated with activation over a single energy barrier, cyclic strain softening is well related to stress relaxation process while cyclic stress softening is related to creep process. The material structural characteristics for cyclic strain softening, cyclic stress softening and stress relaxation are identical. Subsequently, it is shown that cyclic stress and strain softening within the high stress and low temperature range can be evaluated from the constitutive equations using the material structural characteristics measured from a simple stress relaxation test.

scholarly journals Impact of Graphene Oxide on Zero Shear Viscosity, Fatigue Life and Low-Temperature Properties of Asphalt Binder

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3073
Author(s):  
Abbas Mukhtar Adnan ◽  
Chaofeng Lü ◽  
Xue Luo ◽  
Jinchang Wang
Keyword(s):  
Graphene Oxide ◽  
Fatigue Life ◽  
Low Temperature ◽  
Shear Viscosity ◽  
Storage Stability ◽  
Asphalt Binder ◽  
Asphalt Binders ◽  
Test Results ◽  
Zero Shear Viscosity ◽  
Modified Asphalt

This study has investigated the impact of graphene oxide (GO) in enhancing the performance properties of an asphalt binder. The control asphalt binder (60/70 PEN) was blended with GO in contents of 0%, 0.5%, 1%, 1.5%, 2%, and 2.5%. The permanent deformation behavior of the modified asphalt binders was evaluated based on the zero shear viscosity (ZSV) parameter through a steady shear test approach. Superpave fatigue test and the linear amplitude sweep (LAS) method were used to evaluate the fatigue behavior of the binders. A bending beam rheometer (BBR) test was conducted to evaluate the low-temperature cracking behavior. Furthermore, the storage stability of the binders was investigated using a separation test. The results of the ZSV test showed that GO considerably enhanced the steady shear viscosity and ZSV value, showing a significant contribution of the GO to the deformation resistance; moreover, GO modification changed the asphalt binder’s behavior from Newtonian to shear-thinning flow. A notable improvement in fatigue life was observed with the addition of GO to the binder based on the LAS test results and Superpave fatigue parameter. The BBR test results revealed that compared to the control asphalt, the GO-modified binders showed lower creep stiffness (S) and higher creep rate (m-value), indicating increased cracking resistance at low temperatures. Finally, the GO-modified asphalt binders exhibited good storage stability under high temperatures.

scholarly journals Effect of Mean Stress on the Fatigue Life Prediction of Notched Fiber-Reinforced 2060 Al-Li Alloy Laminates under Spectrum Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Weiying Meng ◽  
Liyang Xie ◽  
Yu Zhang ◽  
Yawen Wang ◽  
Xiaofang Sun ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Linear Model ◽  
Life Prediction ◽  
Piecewise Linear ◽  
Forecast Accuracy ◽  
Cyclic Stress ◽  
Fatigue Life Prediction ◽  
Fiber Reinforced ◽  
Piecewise Linear Model ◽  
Spectrum Loading

This paper presents a study on the fatigue life prediction of notched fiber-reinforced 2060 Al-Li alloy laminates under spectrum loading by applying the constant life diagram. Firstly, a review on the state of the art of constant life diagram models for the life prediction of composite materials is given, which highlights the effect on the forecast accuracy. Then, the fatigue life of notched fiber-reinforced Al-Li alloy laminates (2/1 laminates and 3/2 laminates) is tested under cyclic stress, which has different stress cycle characteristics (constant amplitude loading and Mini-Twist spectrum loading). The introduced models are successfully realized based on the available experimental data of examined laminates. In the case of Mini-Twist spectrum loading, the effect of the constant life diagram on the life prediction accuracy of examined laminates is studied based on the rainflow-counting method and Miner damage criteria. The results show that the simple Goodman model and piecewise linear model have certain advantages compared to other complex models for the life prediction of notched fiber metal laminates with different structures under Mini-Twist loading. From the engineering perspective, the S-N curve prediction based on the piecewise linear model is most applicable and accurate among all the models.

scholarly journals Influence of the microstructure on the cyclic stress-strain behaviour and fatigue life in hypo-eutectic Al-Si-Mg cast alloys

2018 ◽  
Vol 165 ◽  
pp. 15004 ◽  
Author(s):  
Jochen Tenkamp ◽  
Alexander Koch ◽  
Stephan Knorre ◽  
Ulrich Krupp ◽  
Wilhelm Michels ◽  
...  
Keyword(s):  
Solid Solution ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Weight Ratio ◽  
Cyclic Stress ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Eutectic Morphology ◽  
Cast Alloys ◽  
Incremental Step

Aluminium alloys are promising candidates for energy-and cost-efficient components in automotive and aerospace industries, due to their excellent strength-to-weight ratio and relatively low cost compared to titanium alloys. As modern cast processing and post-processing, e.g. hot isostatic pressing, result in decreased frequency and size of defects, the weakest link depends on microstructural characteristics, e.g. secondary dendrite arm spacing (SDAS), Si eutectic morphology and α-Al solid solution hardness. Hereby, fatigue investigations of the effect of the microstructure characteristics on the cyclic stress-strain behaviour as well as fatigue mechanisms in the low cycle and high cycle fatigue regime are performed. For this purpose, samples of the aluminium cast alloy EN AC-AlSi7Mg0.3 with different Si eutectic morphology and α-Al solid solution hardness were investigated. To compare the monotonic and cyclic stress-strain curves, quasistatic tensile tests and incremental step tests were performed on two microstructure conditions. The results show that the cyclic loading leads to a hardening of the material compared to monotonic loading. Based on damage parameter Woehler curves, it is possible to predict the damage progression and fatigue life for monotonic and cyclic loading in hypo-eutectic Al-Si-Mg cast alloys by one power law.

Mesodamage Evolution in Polycrystals

2005 ◽  
Vol 127 (2) ◽  
pp. 214-221 ◽  
Author(s):  
M. Chadli ◽  
A. Abdul-Latif
Keyword(s):  
Fatigue Life ◽  
Micromechanical Model ◽  
Small Strain ◽  
Cyclic Stress ◽  
Damage Variable ◽  
Thermodynamic Force ◽  
Inelastic Behavior ◽  
Loading Paths ◽  
Localized Plastic Deformation ◽  
Phase Angles

A micromechanical model of damaged elasto-inelastic behavior is proposed to predict the plastic fatigue life for fcc metallic polycrystals under multiaxial loading paths. This model is expressed in the time-dependent plasticity for a small strain assumption. In order to generalize and then to increase the model applicability (with respect to other works of the author) in describing the cyclic stress-strain evolution during plastic fatigue, it is therefore assumed that a damage variable initiates and then evolves at the grain level where the phenomenon of the localized plastic deformation occurs. The associated thermodynamic force of the damage variable is determined as a total granular energy (elastic and inelastic). The transition of the elastic strain from the single to the polycrystal, which is classically performed by averaging procedures in this type of modeling, is modified due to the coupling of such a strain with damage. The developed model is tested under different multiaxial cyclic loading situations (tension-compression and tension-torsion with different out-of-phase angles). The effects the loading paths and the grains aggregate type on the fatigue life are appropriately investigated. It is demonstrated that the model can correctly describe the overall and local damaged behavior of polycrystals.

Precision Evaluation for Thermal Fatigue Life of Power Module Using Coupled Electrical-Thermal-Structural Analysis

2011 ◽  
Author(s):  
Tomohiro Takahashi ◽  
Qiang Yu ◽  
Masahiro Kobayashi
Keyword(s):  
Fatigue Life ◽  
Temperature Distribution ◽  
Solder Joint ◽  
Thermal Fatigue ◽  
Thermal Structure ◽  
Inelastic Strain ◽  
Power Module ◽  
Thermal Fatigue Life ◽  
Power Cycling ◽  
Precision Evaluation

For power module, the reliability evaluation of thermal fatigue life by power cycling has been prioritized as an important concern. Since in power cycling produces there exists non-uniform temperature distribution in the power module, coupled thermal-structure analysis is required to evaluate thermal fatigue mechanism. The thermal expansion difference between a Si chip and a substrate causes thermal fatigue. In this study, thermal fatigue life of solder joints on power module was evaluated. The finite element method (FEM) was used to evaluate temperature distribution induced by joule heating. Higher temperature appears below the Al wire because the electric current flows through the bonding Al wire. Coupled thermal-structure analysis is also required to evaluate the inelastic strain distribution. The damage of each part of solder joint can be calculated from equivalent inelastic strain range and crack propagation was simulated by deleting damaged elements step by step. The initial cracks were caused below the bonding Al wire and propagated concentrically under power cycling. There is the difference from environmental thermal cycling where the crack initiated at the edge of solder layer. In addition, in order to accurately evaluate the thermal fatigue life, the factors affecting the thermal fatigue life of solder joint where verified using coupled electrical-thermal-structural analysis. Then, the relation between the thermal fatigue life of solder joint and each factor is clarified. The precision evaluation for the thermal fatigue life of power module is improved.

Experimental and numerical investigation on RAP mixtures at low temperature

2018 ◽  
pp. 141-144
Author(s):  
Augusto Cannone Falchetto ◽  
Ki Hoon Moon ◽  
Di Wang ◽  
Riccardi Chiara ◽  
Yoo Byeong Soo ◽  
...  
Keyword(s):  
Low Temperature ◽  
Numerical Investigation

The Reliability of a Component Under Multiple Cyclic Stress Levels With Distributed Cyclic Numbers

2016 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Life ◽  
Probabilistic Models ◽  
Random Variable ◽  
Fatigue Loading ◽  
Cyclic Stress ◽  
Initial Crack ◽  
Stress Levels ◽  
Single Constant ◽  
Unsolved Issue ◽  
Loading Spectrum

Fatigue damage is initiated through some “defects” on the surfaces of and/or inside the component and induced by the fatigue cyclic loadings. These “defects” are randomly scattered in components, and one of these “defects” will be randomly “activated” and finally developed to become the initial crack which causes the final fatigue failure. Therefore, the fatigue strength is inherently a random variable and should be treated by probabilistic models such as typical P-S-N curves. The fatigue cyclic loading could be presented or described in any form. But the fatigue loading spectrum can generally be grouped as and described by these five models: (1) a single constant cyclic stress (loading) with a given cyclic number, (2) a single constant cyclic stress with a distributed cyclic number, (3) a distributed cyclic stress (loading) at a given fatigue life (cyclic number), (4) multiple constant cyclic stress levels with given cyclic numbers, and (5) multiple constant cyclic stress levels with distributed cyclic numbers. The approaches for determining the reliability of components under fatigue loading spectrum of the models 1∼4 are available in literature and books. But few articles and books have addressed an approach for determining the reliability of components under the fatigue loading spectrum of the model 5. This paper will propose two approaches for addressing this unsolved issue. Two examples will be presented to implement the proposed approaches with detailed procedures.

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