Characterization of the Fracture Behaviour of Elastomers Under Complex Loading Conditions

2007 ◽  
pp. 223-224
Author(s):  
Z. Major ◽  
K. Lederer ◽  
R. W. Lang
Keyword(s):  
Fracture Behaviour ◽  
Complex Loading ◽  
Loading Conditions

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.

The Effect of Muscle Loading on Internal Mechanical Parameters of the Lumbar Spine: A Finite Element Study

2011 ◽  
Author(s):  
Benjamin C. Gadomski ◽  
John Rasmussen ◽  
Christian M. Puttlitz
Keyword(s):  
Annulus Fibrosus ◽  
Critical Role ◽  
Complex Loading ◽  
Tissue Level ◽  
Mechanical Parameters ◽  
Loading Conditions ◽  
Additional Stability ◽  
Muscle Loading ◽  
Pure Moment

The human spine experiences complex loading in vivo; however, simplifications to these loading conditions are commonly made in computational and experimental protocols. Pure moments are often used in cadaveric preparations to replicate in vivo loading conditions, and previous studies have shown this method adequately predicts range of motion behavior (1, 2). It is unclear what effect pure moment loading has on the tissue-level internal mechanical parameters such as stresses in the annulus fibrosus and facet contact parameters. Recent advances in musculoskeletal modeling have elucidated previously unknown quantities of the musculature recruitment patterns such as times, forces, and directions. The advancements are especially relevant in cases of surgical intervention because the spinal musculature has been reported to play a critical role in providing additional stability to the spine when defects such as discectomy and nucleotomy are involved (2). Thus, the aim of the study was to determine the importance of computational loading conditions on the resultant global ranges of motion, as well as the tissue-level predictions of annulus fibrosus stresses, and facet contact pressures, forces, and areas.

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