Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : stress

Crack Propagation in Cement Mortar Exposed to External Sulfate Attack

M.H. Abedalrazzaq

Engineering and Technology Journal, 2017, Volume 35, Issue 4, Pages 411-420

This study displays experimental investigation to find out the effect of the external sulfate attack on crack propagation in cement mortar cubes exposed to two sulfate solutions. For this purpose, five mixes of mortar are designed to cast 90 cubes (18 cubes of each mix) and two sulfate solutions (magnesium sulfate MgSO4 and sodium sulfate Na2SO4), each of 34000 p.p.m SO4-2 concentration are prepared. The cubes are evenly distributed in each of the solutions and in tap water as well. The testing technique is carried out compressive strength and Ultrasonic Pulse Velocity (UPV) tests simultaneously to specify the stress/strength ratio at which cracks propagate. The tests are carried out after 56 and 150 days of exposing to sulfate solutions. The results show that crack propagation takes place in specimens exposed to sulfate solutions at stress/strength ratios higher than those which are kept in tap water. The main conclusion, according to this study results, is that sulfate particles delay the propagation of cracks in cement mortar cubes.

Dynamic Crack Growth Analysis of Aluminum Thin Plates Using Analytical and Finite Element Analysis

Bassam Ali Ahmed; Fathi A. Alshamma

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 1065-1078

In this work, the stresses and dynamic crack growth were studied and analyzed in thin flat plate with a surface crack at the center, subjected to cycling low velocity impact loading for two types of aluminum plates (2024, 6061). Analyticalsolution using classical plate theory by using Levy solution employed to determine stresses induced in plate due to the impact load. The impact load applied at the center of surface plate, was calculated by Hertzian contact law. Stresses with respect to time at the crack tip and the velocity of crack growth were calculated through elastic plastic fracture mechanics equations.The size of plastic zone around the crack tip which caused by impact loadingwas found by Dugdal’s model theory.Numerical analysis using program (ANSYS11-APDL) based on finite element method used to analysis the stresses with respect to time at crack tip and then find the velocity of the crack growth under cycling impact loading.The results show that the stresses increase withincreasing in the crack length (i.e:160Mpa at 7mm and 175Mpa at 10mm for Al-6061 also 140Mpa at 7mm and 165Mpa at 10mm for Al-2024).. It was found that the cumulative number of cycles leads to increase in the stress values with increasing in crack growthvelocity.

Mechanical and Tribological Behavior of Glass- Polyester Composite System under Graphite Filler Content

Farag M. Mohammed; Drai A. Smait

Engineering and Technology Journal, 2012, Volume 30, Issue 4, Pages 672-683

Experimental investigations had been done in this work to demonstrate the effect of
graphite filler contents on the mechanical and tribological behavior of (30% volume
fraction) glass-polyester composite system. The stress-strain relations, modulus of
elasticity, yield stress, ultimate tensile strength and ultimate compression strength were
studied according to ASTM-D 638-87and ASTM-D 695 to present the composite
mechanical behavior. The wear rate and wear resistance were investigated according to
ASTM-D 5963 using pin on disc machine to present the composite tribological behavior.
The results showed that the mechanical and tribological properties behavior was
improved when the graphite filler content was increased up to 7.5% and then decreased
after that. At 7.5% filler content the modulus of elasticity, yield stress, ultimate tensile
strength, ultimate compression strength and wear resistance increased by (41%, 64%,
24%, 60% and 38%) greater than unfilled composite, while the wear rate was decreased
by 27% less than the unfilled one.