Cyclic creep and creep-fatigue interaction in sandwich beams

1997 ◽  
Vol 32 (1) ◽  
pp. 1-18 ◽  
Author(s):  
R A Shenoi ◽  
H G Allen ◽  
S D Clark
Keyword(s):  
Cyclic Creep ◽  
Creep Model ◽  
Long Term Effects ◽  
Burger Model ◽  
Reinforced Plastic ◽  
Main Emphasis ◽  
Creep Fatigue ◽  
Cyclic Waveform ◽  
Damage Rule

The main emphasis of this paper is to identify long-term effects such as creep and creep-fatigue interaction for a typical sandwich structure incorporating FRP (fibre-reinforced plastic) faces and a PVC (polyvinyl chloride) foam core. For the creep modelling a Bürger model and a power law model are investigated and compared with experimental results. Fatigue results pertaining to a cyclic trapezoidal waveform are presented in the context of the creep-fatigue interaction. A cyclic creep model is developed in order to investigate the effect of cyclic creep deformation on a response containing elements of fatigue and creep. A simple linear damage rule separating the creep and fatigue components for the chosen cyclic waveform is used in order to quantify the relative influence of both components on the lifetime of the structure. Finally conclusions are drawn regarding the aptness of the chosen creep and creep-fatigue interaction models.

Unified Viscoplastic Model Coupled With Damage for Evaluation of Creep-Fatigue of Grade 91 Steel

2017 ◽  
Author(s):  
Nazrul Islam ◽  
David J. Dewees ◽  
Tasnim Hassan
Keyword(s):  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Creep Model ◽  
Damage Evaluation ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Term Creep ◽  
Grade 91 Steel

A continuum damage mechanics (CDM) coupled unified viscoplasticity model has been developed to predict the creep-fatigue life of modified Grade 91 steel. A tertiary creep model termed MPC-Omega codified in Part 10 of API (and also implemented in the ASME BP&V Code for Grade 22V and more recently Grade 91 Steel) is also employed for creep damage evaluation. As MPC-Omega has a direct relationship with Larson-Miller parameter (LMP) coefficients, creep damage coefficients in the unified constitutive model (UCM) are tied with MPC-Omega coefficients in order to utilize WRC and API 579-1 Grade 91 creep rupture database. The model is validated against long-term creep, LCF, creep-fatigue and TMF experimental responses at T = 20–600°C.

Sensitivity Study on Parameters for Fatigue-Creep Modeling of Stainless Steel Materials

2012 ◽  
Vol 628 ◽  
pp. 217-220
Author(s):  
Xiao Cong He
Keyword(s):  
Stainless Steel ◽  
Prediction Models ◽  
Strain Range ◽  
Sensitivity Study ◽  
Summation Method ◽  
Creep Model ◽  
Fatigue Life Estimation ◽  
Creep Fatigue ◽  
Fatigue Endurance

In present paper, sensitivity study on parameters for fatigue-creep model of stainless steel materials has been carried out. An analytical model has been established to predict fatigue-creep life of AISI347 stainless steel. Manson’s Universal Slopes equation has been used as an empirical correlation which relates fatigue endurance to tensile properties. Different creep prediction models have been studied in order to correlate the results of shout-time elevated temperature tests with long-term service performance at more moderate temperatures. Comparison between the different creep prediction models and experimental results were carried out for a range of stresses and temperatures. A linear damage summation method has been used to combined fatigue and creep. The results of sensitivity analysis indicate that strain range and temperature have very significant influence on creep-fatigue life estimation.

Ovarian Dysfunction in Fetally Irradiated Beagles

1977 ◽  
Vol 35 ◽  
pp. 658-659
Author(s):  
T. M. Seed ◽  
M. H. Sanderson ◽  
D. L. Gutzeit ◽  
T. E. Fritz ◽  
D. V. Tolle ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Low Dose ◽  
Long Term Effects ◽  
Ovarian Dysfunction ◽  
Dose Rates ◽  
Highly Sensitive ◽  
Microscopic Evaluation ◽  
Ovarian Pathology ◽  
Normal Offspring

The developing mammalian fetus is thought to be highly sensitive to ionizing radiation. However, dose, dose-rate relationships are not well established, especially the long term effects of protracted, low-dose exposure. A previous report (1) has indicated that bred beagle bitches exposed to daily doses of 5 to 35 R 60Co gamma rays throughout gestation can produce viable, seemingly normal offspring. Puppies irradiated in utero are distinguishable from controls only by their smaller size, dental abnormalities, and, in adulthood, by their inability to bear young.We report here our preliminary microscopic evaluation of ovarian pathology in young pups continuously irradiated throughout gestation at daily (22 h/day) dose rates of either 0.4, 1.0, 2.5, or 5.0 R/day of gamma rays from an attenuated 60Co source. Pups from non-irradiated bitches served as controls. Experimental animals were evaluated clinically and hematologically (control + 5.0 R/day pups) at regular intervals.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Long-Term Effects of Head Lice Tx Unknown

2012 ◽  
Vol 43 (3) ◽  
pp. 42
Author(s):  
MITCHEL L. ZOLER
Keyword(s):  
Head Lice ◽  
Long Term Effects

The response of skin perfusion and of rheological and immunological variables to intravenous prostanoid administration in Raynaud’s phenomenon secondary to collagenosis

VASA ◽  
2005 ◽  
Vol 34 (4) ◽  
pp. 243-249 ◽  
Author(s):  
Drinda ◽  
Neumann ◽  
Pöhlmann ◽  
Vogelsang ◽  
Stein ◽  
...  
Keyword(s):  
Laser Doppler Flowmetry ◽  
Raynaud’S Phenomenon ◽  
Raynaud's Phenomenon ◽  
Plasma Viscosity ◽  
Laser Doppler ◽  
Erythrocyte Aggregation ◽  
Control Group ◽  
Long Term Effects ◽  
Doppler Flowmetry

Background: Prostanoids are used in the treatment of Raynaud’s phenomenon and acral perfusion disorders secondary to collagenosis. In subjective terms, intravenous administration of these agents produces success in more than 50% of patients. The therapeutic outcome of clinical administration of alprostadil or iloprost may vary from individual to individual. Patients and methods: The following variables were analysed in a cross-over study in 27 patients with collagenosis and Raynaud’s phenomenon: plasma viscosity and erythrocyte aggregation (rheological variables), partial pressure of oxygen and laser Doppler flowmetry in the finger region, and lymphocyte phenotyping and interleukin (IL) determinations (immunological variables). Results: Laser Doppler flowmetry revealed significant differences between patients with secondary Raynaud’s phenomenon and a control group of 25 healthy subjects. Laser Doppler readings did not change significantly as a result of the treatments. Therapy with iloprost produced a reduction in IL-1beta, L-selectin (CD 62 L) and IL-6. Conclusion: The change in immunological variables due to iloprost may explain the long-term effects of prostaglandins in the treatment of Raynaud’s phenomenon. From our results it is not possible to infer any preference for iloprost or alprostadil.

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