Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : crack growth

Strain Behavior at Crack Tip in Thin Plate Using Numerical and Experimental Work

Bassam Ali Ahmed; Fathi A.Alshamma

Engineering and Technology Journal, 2016, Volume 34, Issue 3, Pages 513-526
DOI: 10.30684/etj.34.3A.7

In this work, strains were studied and analyzed in a thin flat plate with a surface crack at the center, subjected to cycling of low velocity impact loading for two types of aluminum plates (2024, 6061). Experimental and numerical methods were implemented to achieve this research. Two cases of boundary conditions were used in this study; clamped-clamped with simply supported at the other edges, and clamped-clamped with free at the other edges. Numerical analysis using program (ANSYS11-APDL) based on finite element method used to analyze the strains with respect to time at crack tip. In the experimental work, a rig was designed and manufactured for cyclic impact loading on the cracked specimens. The grid points was screened in front of the crack tip to measure the elastic-plastic displacements in the x and y directions by grid method, from which the strains are calculated. The results show that the strains increase with increasing the crack length. It was found that the cumulative number of cycles leads to increase in the strain values.

Study of Short Cracks Growth Behavior for Duralumin 7075- T6 Enhanced by Artificial Ageing as Thermal and Chemical Treatments Under Rotating Bending Loading

Mustafa Sami Abdullateef

Engineering and Technology Journal, 2013, Volume 31, Issue 11, Pages 2166-2182
DOI: 10.30684/etj.31.11A12

The fatigue life of ductile metals is controlled mainly by the propagation life of a short surface crack; to clarify the growth behavior of short cracks is crucial factor to the safe design of smooth surface members. However, little has been reported on the growth behavior of short surface cracks in thermal-chemical treated duralumin. In the present study, stress-controlled fatigue tests (under rotating bending load) for 70 hours artificial aged duralumin 7075-T6 without chemical treatment case (1) and with chemical treatment case (2). The growth behavior of short cracks was monitored by a plastic replication technique and the surface damage (short crack propagation) during cyclic stressing was observed by optical microscopy. The physical background of fatigue damage for case (1) and case (2) was discussed from the viewpoints of the initiation and growth behavior of short cracks.

Crack Growth Model for Estimating the Fatigue Life under Variable loading

Hassan Abd- ALRsoul; Basim H. Abbas; Khairallah S. Jabur

Engineering and Technology Journal, 2011, Volume 29, Issue 13, Pages 2773-2782
DOI: 10.30684/etj.29.13.15

This paper examines the fatigue short and long cracks behaviour in 2024 T4 aluminum alloy under rotating bending loading and stress ratio R = -1. In the short cracks region, cracks grow initially at a fast rate but deceleration occurs quickly and, depending on the stress level, they either arrest or are temporarily halted at a critical length. This critical length is shown to conincide with the value of the microstructure parameter, grain size diameter, An empirical model which describes short and long cracks rates is developed and
is seen in good agreement with the experimental observations in this alloy. Comparison of the empirical model lives results with cumulative fatigue results has shown encouraging experimentally agreement while liner rule gave a non – reasonable prediction.