A Conjectured Solder Fatigue Law Based on Nonlinear Dynamics

1992 ◽  
Vol 114 (2) ◽  
pp. 122-127
Author(s):  
S. Russell ◽  
R. Caroselli ◽  
J. Mason ◽  
M. Shah
Keyword(s):  
Nonlinear Dynamics ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Simple Relationship ◽  
Quadratic Map ◽  
Quadratic Maps ◽  
Curve Fit ◽  
Solder Fatigue ◽  
Erratic Motion ◽  
Special Case

A discipline of nonlinear dynamics (Chaos Theory), not traditionally used in the study of solder, is applied here in developing a conjectured general form for fatigue based on creep. Solder joint data are analyzed which demonstrates two strain-rate regimes. In the literature, this is recognized as related to the two modes of grain boundary and matrix creep. In this paper, the behavior is treated as a “bifurcation” and a quadratic normal form identified which addresses qualitative features of the observed data. The resulting mathematical model is transformed into a quadratic map (difference equation) which is a classic paradigm for chaotic motion. This model addresses not only the two distinct rate regimes but also an unstable intermediate range of erratic motion which is observed in the data. Correlation between solder fatigue behavior and onset of model instability regarding effects of solder dwell (model relaxation) and solder grain size (assumed to be associated with model time increment) has been discussed in previous work. This has motivated examination of the classic Coffin-Manson (C.M.) low cycle fatigue law for elastic, plastic deformation in terms of appropriate quadratic maps. The result is a “curve-fit” representation of the C.M. forms in terms of map parameters. In particular, a simple relationship appears to exist between the “universal slopes” of the C.M. law and the “universal” Feigenbaum constant δ = 4.66920..., so called because it is associated with a wide class of maps which includes the quadratic as a special case. With this approach, a conjectured form of solder fatigue law under creep deformation is generated. General properties of the resulting form are discussed and compared with some of the fatigue models currently in use.

scholarly journals Influence of turning tool wear on the surface integrity and anti-fatigue behavior of Ti1023

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110112
Author(s):  
Li Xun ◽  
Wang Ziming ◽  
Yang Shenliang ◽  
Guo Zhiyuan ◽  
Zhou Yongxin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Tool Wear ◽  
Surface Integrity ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Machined Surface ◽  
Deformation Layer

Titanium alloy Ti1023 is a typical difficult-to-cut material. Tool wear is easy to occur in machining Ti1023, which has a significant negative effect on surface integrity. Turning is one of the common methods to machine Ti1023 parts and machined surface integrity has a direct influence on the fatigue life of parts. To control surface integrity and improve anti-fatigue behavior of Ti1023 parts, it has an important significance to study the influence of tool wear on the surface integrity and fatigue life of Ti1023 in turning. Therefore, the effect of tool wear on the surface roughness, microhardness, residual stress, and plastic deformation layer of Ti1023 workpieces by turning and low-cycle fatigue tests were studied. Meanwhile, the influence mechanism of surface integrity on anti-fatigue behavior also was analyzed. The experimental results show that the change of surface roughness caused by worn tools has the most influence on anti-fatigue behavior when the tool wear VB is from 0.05 to 0.25 mm. On the other hand, the plastic deformation layer on the machined surface could properly improve the anti-fatigue behavior of specimens that were proved in the experiments. However, the higher surface roughness and significant surface defects on surface machined utilizing the worn tool with VB = 0.30 mm, which leads the anti-fatigue behavior of specimens to decrease sharply. Therefore, to ensure the anti-fatigue behavior of parts, the value of turning tool wear VB must be rigorously controlled under 0.30 mm during finishing machining of titanium alloy Ti1023.

scholarly journals Experimental and Computational Approach to Fatigue Behavior of Polycrystalline Tantalum

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 416 ◽  
Author(s):  
Damien Colas ◽  
Eric Finot ◽  
Sylvain Flouriot ◽  
Samuel Forest ◽  
Matthieu Mazière ◽  
...  
Keyword(s):  
Free Surface ◽  
Low Cycle Fatigue ◽  
Large Strain ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Field Measurements ◽  
Test Sample ◽  
Lattice Rotation ◽  
Element Simulation ◽  
Crack Initiation Criterion

This work provides an experimental and computational analysis of low cycle fatigue of a tantalum polycrystalline aggregate. The experimental results include strain field and lattice rotation field measurements at the free surface of a tension–compression test sample after 100, 1000, 2000, and 3000 cycles at ±0.2% overall strain. They reveal the development of strong heterogeneites of strain, plastic slip activity, and surface roughness during cycling. Intergranular and transgranular cracks are observed after 5000 cycles. The Crystal Plasticity Finite Element simulation recording more than 1000 cycles confirms the large strain dispersion at the free surface and shows evidence of strong local ratcheting phenomena occurring in particular at some grain boundaries. The amount of ratcheting plastic strain at each cycle is used as the main ingredient of a new local fatigue crack initiation criterion.

Effects of Surface Finish and Loading Conditions on the Low Cycle Fatigue Behavior of Austenitic Stainless Steel in PWR Environment for Various Strain Amplitude Levels

2009 ◽  
Author(s):  
Jean Alain Le Duff ◽  
Andre´ Lefranc¸ois ◽  
Jean Philippe Vernot
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Strain Amplitude ◽  
Surface Finish ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Complex Loading ◽  
Loading Conditions ◽  
Test Results ◽  
Cycle Fatigue

In February/March 2007, The NRC issued Regulatory Guide “RG1.207” and Argonne National Laboratory issued NUREG/CR-6909 that is now applicable in the US for evaluations of PWR environmental effects in fatigue analyses of new reactor components. In order to assess the conservativeness of the application of this NUREG report, Low Cycle Fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in air environment a fatigue behavior consistent with the ANL reference “air” mean curve, as published in NUREG/CR-6909. LCF tests in a PWR environment were performed at various strain amplitude levels (± 0.6% or ± 0.3%) for two loading conditions corresponding to a simple or to a complex strain rate history. The simple loading condition is a fully reverse triangle signal (for comparison purposes with tests performed by other laboratories with the same loading conditions) and the complex signal simulates the strain variation for an actual typical PWR thermal transient. In addition, two various surface finish conditions were tested: polished and ground. This paper presents the comparisons of penalty factors, as observed experimentally, with penalty factors evaluated using ANL formulations (considering the strain integral method for complex loading), and on the other, the comparison of the actual fatigue life of the specimen with the fatigue life predicted through the NUREG report application. For the two strain amplitudes of ± 0.6% and ± 0.3%, LCF tests results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates give “Fen” penalty factors close to those estimated using the ANL formulation (NUREG/6909). However, for the lower strain amplitude level and a triangle loading signal, the ANL formulation is pessimistic compared to the AREVA NP test results obtained for polished specimens. Finally, it was observed that constant amplitude LCF test results obtained on ground specimens under complex loading simulating an actual sequence of a cold and hot thermal shock exhibits lower combined environmental and surface finish effects when compared to the penalty factors estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins, whereas the current ASME approach seems sufficient to cover significant environmental effects for representative loadings and surface finish conditions of reactor components.

Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Adrian Willuweit ◽  
Steffen Bergholz ◽  
Christian Philippek ◽  
Jevgenij Kobzarev
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hybrid Approach ◽  
Combined Cycle ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Constitutive Material Model ◽  
Standard Design ◽  
Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

Thermomechanical Fatigue Behavior of Bare and Coated CMSX-4

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
T. Coppola ◽  
S. Riscifuli ◽  
O. Tassa ◽  
G. Pasquero
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Thermomechanical Fatigue ◽  
Tensile Creep ◽  
Thermal Gradients ◽  
Test Program ◽  
Complete Set ◽  
Comparison Of The Results ◽  
Very High

Highly cooled turbine blades undergo very high thermal gradients during rapid engine idle-max-idle cycling. Traditional isothermal fatigue data are often insufficient for predicting service lives. A complete set of high temperature tests, in the range of 750–1050°C, was performed on single crystal alloy CMSX-4. The test program comprised tensile, creep, low cycle fatigue, and thermomechanical fatigue (TMF) tests. In particular the cycle time for TMF was 3 min, aiming to simulate the real high-power transient conditions in aircraft engines. Clockwise and counterclockwise diamond cycle types were applied on bare and coated specimens to investigate their influence on the fatigue limit. The comparison of the results obtained with the available ones from open literature is discussed.

LOW CYCLE FATIGUE BEHAVIOR AND LIFE PREDICTION OF A CAST COBALT-BASED SUPERALLOY

2012 ◽  
Vol 06 ◽  
pp. 251-256
Author(s):  
HO-YOUNG YANG ◽  
JAE-HOON KIM ◽  
KEUN-BONG YOO
Keyword(s):  
Fatigue Life ◽  
Strain Energy ◽  
Life Prediction ◽  
Prediction Models ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Different Temperatures

Co -base superalloys have been applied in the stationary components of gas turbine owing to their excellent high temperature properties. Low cycle fatigue data on ECY-768 reported in a companion paper were used to evaluate fatigue life prediction models. In this study, low cycle fatigue tests are performed as the variables of total strain range and temperatures. The relations between plastic and total strain energy densities and number of cycles to failure are examined in order to predict the low cycle fatigue life of Cobalt-based super alloy at different temperatures. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

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