Load History Effects Resulting from Compression Precracking

2005 ◽  
Vol 2 (9) ◽  
pp. 12025 ◽  
Author(s):  
MA James ◽  
SC Forth ◽  
JA Newman
Keyword(s):  
Load History ◽  
History Effects

Load History Effects on Fretting Contacts of Isotropic Materials

2004 ◽  
Vol 126 (2) ◽  
pp. 385-390 ◽  
Author(s):  
P. T. Rajeev ◽  
H. Murthy ◽  
T. N. Farris
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Singular Integral Equations ◽  
Contact Problems ◽  
Two Dimensional ◽  
Load History ◽  
Jet Engine ◽  
Isotropic Materials ◽  
History Effects ◽  
Cauchy Singular Integral

The load history that blade/disk contacts in jet engine attachment hardware are subject to can be very complex. Using finite element method (FEM) to track changes in the contact tractions due to changing loads can be computationally very expensive. For two-dimensional plane-strain contact problems with friction involving similar/dissimilar isotropic materials, the contact tractions can be related to the initial gap function and the slip function using coupled Cauchy singular integral equations (SIEs). The effect of load history on the contact tractions is illustrated by presenting results for an example fretting “mission.” For the case of dissimilar isotropic materials the mission results show the effect of the coupling between the shear traction and the contact pressure.

Sliding-Load History Effects on the Friction of MoS2in Vacuum

1971 ◽  
Vol 14 (2) ◽  
pp. 156-161 ◽  
Author(s):  
Warren E. Jamison ◽  
Harold S. Weber
Keyword(s):  
Load History ◽  
History Effects

Adaptive Neural Network Modelling in Fatigue life Prediction under Load History effects

2011 ◽  
Vol 284-286 ◽  
pp. 1266-1270
Author(s):  
M. Abdul Razzaq ◽  
Kamal A. Ariffin ◽  
Ahmed El Shafie ◽  
Shahrum Abdullah ◽  
Z. Sajuri ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Prediction ◽  
Experimental Tests ◽  
Fatigue Life Prediction ◽  
Load History ◽  
Adaptive Neural Network ◽  
Network Modelling ◽  
History Effects ◽  
Point Bend

Artificial intelligence (AI) techniques and in particular, adaptive neural networks (ANN) have been commonly used in order to Fatigue life prediction. The aim of this paper is to consider a new crack propagation principle based on simulating experimental tests on three point-bend (TPB) specimens, which allow predicting the fatigue life and fatigue crack growth rate (FCGR). An important part of this paper is estimation of FCG rate related to different load histories. The effects of different load histories on the crack growth life are obtained in different representative simulation and experiments.

Efficient Modeling of Fretting of Blade/Disk Contacts Including Load History Effects

2004 ◽  
Vol 126 (1) ◽  
pp. 56-64 ◽  
Author(s):  
H. Murthy ◽  
G. Harish ◽  
T. N. Farris
Keyword(s):  
Frictional Contact ◽  
Contact Region ◽  
Singular Integral Equations ◽  
Numerical Approach ◽  
Design Tool ◽  
Load History ◽  
Near Surface ◽  
History Effects ◽  
Geometric Transitions ◽  
Fretting Damage

Fretting is a frictional contact phenomenon that leads to damage at the contact region between two nominally-clamped surfaces subjected to oscillatory motion of small amplitudes. The region of contact between the blade and the disk at the dovetail joint is one of the critical locations for fretting damage. The nominally flat geometry of contacting surfaces in the dovetail causes high contact stress levels near the edges of contact. A numerical approach based on the solution to singular integral equations that characterize the two-dimensional plane strain elastic contact of two similar isotropic surfaces presents itself as an efficient technique to obtain the sharp near-surface stress gradients associated with the geometric transitions. Due to its ability to analyze contacts of any two arbitrary smooth surfaces and its computational efficiency, it can be used as a powerful design tool to analyze the effects of various factors like shape of the contact surface and load histories on fretting. The calculations made using the stresses obtained from the above technique are consistent with the results of the experiments conducted in the laboratory.

scholarly journals SMILE: A European R&D Program for the Inclusion of Warm Pre-Stress in RPV Assessment

2005 ◽  
Author(s):  
Dominique Moinereau
Keyword(s):  
Beneficial Effect ◽  
Brittle Failure ◽  
Structural Integrity ◽  
Development Program ◽  
Experimental Results ◽  
Load History ◽  
Local Approach ◽  
Integrity Assessment ◽  
History Effects ◽  
Energy Community

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at an European level generally do not take necessary into account the beneficial effect of load history (warm pre-stress WPS). A 3-year Research & Development program — SMILE — has been started in January 2002 as part of the Fifth Framework of the European Atomic Energy Community (EURATOM). The SMILE project (“Structural Margin Improvements in aged-embrittled RPV with Load history Effects”) is one of a “cluster” of Fifth Framework projects in the area of Plant Life Management. It aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Finally, this project aims to harmonize the different approaches in the European Codes and Standards regarding the inclusion of the WPS effect in a RPV structural integrity assessment. Within the framework of the project, an important experimental work has been conducted including WPS type experiments on CT specimens and also a PTS type transient experiment on a large component. The experimental results on CT specimens confirm the beneficial effect of warm pre-stress, with an effective significant increase of the material resistance regarding the risk of brittle failure. The WPS type experiment on the cylinder has been successfully conducted, with a final brittle failure during the reloading. The present paper describes the aims and objectives of the SMILE project, the main experimental results, and the corresponding analyses based on engineering methods, finite element elastic and elastic-plastic computations, and local approach to fracture.

Load-History Effects on Deformation Capacity of Flexural Members Limited by Bar Buckling

2010 ◽  
Vol 136 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Despina V. Syntzirma ◽  
Stavroula J. Pantazopoulou ◽  
Mark Aschheim
Keyword(s):  
Deformation Capacity ◽  
Load History ◽  
Flexural Members ◽  
History Effects ◽  
Bar Buckling

Fatigue Threshold Behavior of Stainless Steel in High Temperature Air and Water

2016 ◽  
Author(s):  
Elaine West ◽  
Heather Mohr ◽  
Erik Lord
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Crack Closure ◽  
Austenitic Stainless Steels ◽  
Fatigue Threshold ◽  
Threshold Behavior ◽  
Load History ◽  
History Effects ◽  
Stress Ratios ◽  
Type 304

The fatigue threshold behavior of stainless steel was assessed in high temperature air and hydrogenated deaerated water environments as a function of stress ratio (R). Fatigue threshold experiments were conducted on four different heats of type 304, 304/304L, and 308L austenitic stainless steels in 250°C air and water environments at stress ratios ranging from 0.1 to 0.8. Air and water experiments showed that operational threshold ΔK (ΔKTH) values ranged from 4.3–6.0 and 3.9–5.3 MPa√m, respectively. ΔKTH values were observed to generally decrease with increasing R which is attributable to crack closure effects. The water ΔKTH measurements were either consistent with or lower than air threshold measurements, and the potential roles of the competing effects of crack closure and hydrogen enhanced planar slip will be discussed in the context of these results. Load history effects in the form of overloads and underloads were shown to significantly impact ΔKTH measurements and these results motivated testing aimed at characterizing material property based intrinsic ΔK threshold (ΔKTH*) values. The ΔKTH* values for stainless steel fatigue crack growth in 250–288°C air and water environments are estimated to be 3 and 2 MPa√m, respectively.

NESC VII: A European Project for Application of WPS in RPV Assessment Including Biaxial Loading

2010 ◽  
Author(s):  
Dominique Moinereau ◽  
Ste´phane Chapuliot ◽  
Ste´phane Marie ◽  
Philippe Gilles
Keyword(s):  
Beneficial Effect ◽  
Brittle Failure ◽  
Large Scale ◽  
Biaxial Loading ◽  
Numerical Models ◽  
Development Program ◽  
Sufficient Evidence ◽  
Load History ◽  
Integrity Assessment ◽  
History Effects

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at a European level do not necessarily take into account the beneficial effect of load history (warm pre-stress WPS) on the resistance of RPV material regarding the risk of brittle failure. A 4-year European Research & Development program — SMILE — was successfully conducted between 2002 and 2005 as part of the 5th Framework of the European Atomic Energy Community (EURATOM). The objective of the SMILE project (‘Structural Margin Improvements in aged-embrittled RPV with Load history Effects’) was to provide sufficient evidence in order to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Numerous experimental, analytical and numerical results have been obtained which confirm the beneficial effect of warm pre-stress on RPV steels, with an effective significant increase of the material resistance regarding the risk of brittle failure. In addition to SMILE, a new project dealing with WPS — NESC VII — has been launched in 2008 (linking with the European Network of Excellence NULIFE) with the participation of numerous international organizations (R&D, Utilities and Manufacturers). Based on experimental, analytical and numerical tasks, the project is focused on topics generally not covered by past experience on WPS: biaxiality of loading on large-scale specimens, effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models) … Among these tasks, some new novel WPS experiments are being conducted on large scale cruciform bend bar specimens in order to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel). After a synthesis of main WPS results available from previous projects on representative RPV steels, a description of the NESC VII project is presented in this paper together with the corresponding organization, including the present status of the project.

scholarly journals Load history effects on fatigue crack propagation: Its effect on the R-curve for threshold

2015 ◽  
Vol 9 (33) ◽  
pp. 209-214 ◽  
Author(s):  
X. Zhou ◽  
A. Hohenwarter ◽  
T. Leitner ◽  
H.P. Gänser ◽  
R. Pippan
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Load History ◽  
History Effects
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