Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : fatigue

Applying Non-linear Damage Model for Predicating Corrosion Effect on Fatigue Life of (carbon + glass) Fibers / PMMA Composite

Husin .J.M. Al-Alkawi; Amer Hameed Majeed; Saisaban Ali Fahad

Engineering and Technology Journal, 2012, Volume 30, Issue 16, Pages 2898-2909

The objective of this work is to investigate the salt water effects on fatigue
degradation, and stress-life relationship. A series of reversed fatigue experiments were
conducted on (carbon+ glass) / PMMA of salt water environments. Results indicate that
the composite degrade during cycling. Exposure to salt water (salt water is used to
simulate the sea water) provides the most significant reduction in fatigue life. The
corrosion environment reduces the fatigue strength by 61% compared to dry fatigue.
Based on previous damage model [16], corrosion – fatigue nonlinear damage model is
presented in this paper, which contains one material constant; the inverse slope (α) of the
S-N curve. Six specimens of two levels loading of composite material were used to verify
the present model; the results showed that the predicted life is in good agreement with the
experimental results.

Seismic Response Damage of Nuclear Tower

Kadhim Karim Mohsen

Engineering and Technology Journal, 2012, Volume 30, Issue 6, Pages 1029-1047

The seismic response of the nuclear tower is analyzed by investigating the frequency response during the main recorded events. The dynamic characteristics of the nuclear tower under seismic response with higher intensity are pointed out the dominant seismic time history components determines the response characteristics of the tower. The nuclear tower coupled with the seismic loadings will amplify the damages to
the structure. These results are consistent with field observations after major seismic response, this explains the symmetry of the nuclear tower damage during seismic response. Seismic resistance measures, such as viscous damping or energy dissipation, dynamic properties and nuclear tower vibration elements will help to increase the
accuracy of the life model. In this paper, improvement in using computing program and mathematical algorithms will increase both the accuracy and confidence of the results. The contact problem of the nuclear tower structure is another direction for a detailed understanding the mechanism of the nuclear tower structure interaction, such as mode shapes, eigenvalues/vectors, deformation, propagation and non-propagation of cracks, and the stresses slip of the foundation caused by random seismic loading that can lead to damage. This study is helpful for designing new seismic resistant nuclear towers structures to reduce damage.

Influence of Annealing, Normalizing Hardening Followed By Tempering And Laser Treatments on Some of The Static and Dynamic Mechanical Properties of Medium Carbon Steel

Sanna A. hafeed; AbdulKhaliq F. Hamood

Engineering and Technology Journal, 2010, Volume 28, Issue 21, Pages 6274-6287

This research illustrates the influence of different heat treatments on the mechanical properties such as stress-strain curves ,wear resistance and fatigue properties of medium carbon steel,. This steel was treated by annealing, normalizing, hardening followed by tempering and laser treatments. The bulk mechanical properties of ultimate ,fracture and yield tensile strength were evaluated. Surface mechanical properties of fatigue, wear resistance and hardness were evaluated as well. Microstructure of treated alloys also were inspected. Results showed that (hardened -tempered) steel had improved tensile strength,
fatigue{limit, life}, wear resistance, hardness then laser surface treated alloy, then the normalized alloy came in order ,but annealed alloy had the lowest mechanical properties. Annealing caused softening and growth of alloy structure. It was found that the microstructure of treated alloy play an important role in the improvement
or deterioration of bulk and surface mechanical properties and by analyzing the obtained results. For (Quenched -tempered) alloy found fine tempered martensititic structure, laser surface treated alloy had martensititic structure in the skin and ferritic- pearlitic structures in the core .Normalized alloy had ferriticpearlitic structures, Annealed alloy had coarse ferritic- pearlitic structures

Effect of Hold Time Periods at High Temperature on Fatigue Life In Aluminum Alloy 2024 T4

Mahir H. Majeed; Dhafir S. Al-Fattal; Husain J. Al-alkawi

Engineering and Technology Journal, 2010, Volume 28, Issue 13, Pages 2608-2621

In some applications, the aluminum alloy 2024 T4 may be subjected to an
interaction of fatigue and creep effects at high temperature. This paper investigates
the effect of this interaction by studying the effect of constant amplitude fatigue
(CAF) and creep separately, and then fatigue-creep interaction is introduced by
testing the alloy under constant amplitude with some holding time periods through
the test at high temperature (150 oC). The results showed that the life time of the
alloy decreases due to fatigue-creep interaction as compared to creep alone in
about 77%, and in about 80% as compared with fatigue alone. This is a result of
accumulated fatigue damage superimposed on creep damage. Creep allows more
free spaces for fatigue cracks paths that accelerate failure. A theoretical model to
calculate the time to failure due to fatigue-creep interaction has been proposed.
This theoretical interaction model predicts very close time to failure values to the
experimental results.

Effect of Heat Treatment on Notch Sensitivity Factor for Aluminum Alloys

Ahmed. N. Al-Khazraji; Emad Abdul Hussein Al-mudhafar

Engineering and Technology Journal, 2010, Volume 28, Issue 3, Pages 509-519

This study is concerned with the effect of heat treatment (precipitation
hardening) on notch sensitivity factor for aluminum alloy (7075). Tests were
conducted on four configurations of specimens, three of them which had external
circumferential notches with notch radii of 0.5 mm, 0.7 mm, and 1 mm. The
fourth configuration is un-notched specimens. The alloy samples which were used
in fatigue test were subjected to cold working before heat treatment. Dimensions
and roughness of the specimens were measured. The fatigue tests were performed
for different types of specimens. The (S-N) equation was derived for each group to
estimate the fatigue life under any applied stress amplitude. In addition, the
strength reduction factor (kf )and notch sensitivity factor (q) were calculated.
The results showed that the fatigue strength reduction factor were
increased after heat treatment and with decreasing notch radius. Also the notch
sensitivity factor increased with increasing notch radius and after heat treatment.
The enhancement percentage in notch sensitivity factor after the heat treatment for
1 mm radius notch was (22.616%).