Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : fatigue


Effect of Oil – Corrosion on Tensile and Fatigue S-N Curve Properties of AA6061-T6

Hussain J.M. Al-Alkawi; Ghgada A. Aziz; Shmoos R. Mazel

Engineering and Technology Journal, 2021, Volume 39, Issue 3A, Pages 407-414
DOI: 10.30684/etj.v39i3A.298

The present study described the effect of shot peening on mechanical properties and rotating corrosion –fatigue behavior (strength and life) of AA6061-T6. Ultimate tensile strength (UTS) and yield stress (YS) were reduced by 4.6% and 1.24% when immersing the tensile samples in crude oil for 60 days. The values of (UTS) and (YS) were raised from 307 to 316 MPa and from 248 to 254 MPa respectively when treated for 10 min. shot peening (SP). Hardness of oil corrosion samples dropped due to pitting corrosion and slightly raised for SP prior to corrosion samples. Oil corrosion reduced the fatigue strength by (-1.25%). This percentage was enhanced due to SP to 2.377%. SP significantly increased the rotating fatigue life by a factor of 1.19 and 1.3 at (UTS) and (Ys) loads respectively. (SP) technique improved corrosion-fatigue resistance due to producing compressive residual stresses at surface layers.

Constant Fatigue Life Under Laser Shot Peening Using Different Surface Coatings

Alakawi H.J.M; Bashar A. Bedaiw; Adel A. Mahmood

Engineering and Technology Journal, 2016, Volume 34, Issue 7, Pages 1275-1283

Laser peening (LP) is a surface treatment technology for metallic materials. LP has shown agreat improvement in the fatigue strength and life.A study of fatigue under constant rotating bending stress programs has been conducted on 7049 AL alloy at a stress ratio (R=-1) and room temperature using laser peening technique .Four groups of tests have been designed.The first group (15 specimens) tested under unpeened condition. The second group (15 specimens) tested under air laser peening (ALP) while the third group (15 specimens) tested under water laser peening (WLP). The last group was designed to examine the fatigue behavior under black paint laser peening (BPLP). All the above groups were designed to establish the S-N curve. The results show no effect of laser peening LP at higher stresses (above 300 MPa), while this effect appears clearly at low stresses (200 and 250 MPa). The results alsoindicated that the WLP is more effective than the ALP. The fatigue life improvement factor (FLIF%) was 39, 18.9 and 4.65 under WLP for 200 MPa, 250 MPa and 300 MPa stress levels respectively.while a clear effect was observed for black paint laser peening (BPLP),it was found that the FLIF % was 93.25 at 300 MPa , 103.24 at 250 MPa and 116 at 200 MPa compared to unpeened data .

Effects of Welding Position, Heat Treatments, and Surface Roughness on the Fatigue Behavior of Welded Aluminum Alloys Using Friction Stir Welding

Shaker Sakran Hassan; Sadeq Hussein Bakhy; Athraa Ali Jawad

Engineering and Technology Journal, 2014, Volume 32, Issue 11, Pages 2773-2787

The present work is aimed to study the fatigue behavior of friction stir welding for the similar and dissimilar joints taking into account the effects of welding position, post welding heat treatments, and surface roughness. The materials were used AA2024T3 and AA6061T6. The maximum welding efficiency achieved at friction stir welding process was 62.8 % of the base metal for the similar 2024-T3 joint, and this value was improved by using post welding heat treatments and reach to 67.9%. Results showed that fatigue strength at 106 cycles depended strongly on welding line position where for welding line at a distance 0.35L from loading side, the reduction in fatigue limit with respect to 2024T3 base material was 45% for similar joint and 58% for dissimilar joints, and for welding line at a distance 0.7 L, the reduction in fatigue strength was 56% for similar joint and 67% for dissimilar joints. While, it was a large reduction in the fatigue strength reaching to 70% in both similar and dissimilar joint for the welding joint at a distance L (i.e at the fixing end). The heat treatments improved the fatigue strength about 31% more than non heat treatments of the similar 2024T3 joint by fsw at 0.7L in high cycle regime. Finally, the non-finishing samples showed a reduction in fatigue strength reaching to 10% more than the finishing samples of the similar 2024T3 joint at 0.7L.

Assessment the Impact of Different Hydrated Lime Addition Methods on Fatigue Life Characteristic

Amjad H. K. Albayati; Ahmed M. Mohammed

Engineering and Technology Journal, 2013, Volume 31, Issue 21, Pages 489-511

The purpose of this study is to evaluate the effect of hydrated lime addition methods as filler replacement on fatigue performance of Hot Mix Asphalt (HMA). Three types of addition methods of hydrated lime were introduced namely dry HL on dry aggregate and saturated surface aggregate above 3% and slurry HL on dry aggregate, ordinary Lime stone powder was reduced by three HL percentage (1.0, 2.0 and 3.0 %). The effect of different methods were investigated on the fatigue properties of HMA using, third-point flexural fatigue bending Test. Pneumatic Repeated Load System (PRLS) was carried out to establish the effect of hydrated lime on the fatigue failure criteria and to select the proper hydrated lime application methods on fatigue behavior of HMA mixtures. The fatigue functions for asphalt mixture with hydrated lime are obtained and compared, and it confirm that the fatigue property of asphalt mixture can be improved using all methods and the addition methods were exhibited different optimality for the result due to its effect . The test results were carried out through the performance analysis using Vesys 5W (2003) to study the long term effectiveness of hydrated lime effect.

The Effect of Tool Geometry for Resistance Spot Welds on Crack Growthin Specimens of Mild Steel

Nadhim M.Faleh

Engineering and Technology Journal, 2013, Volume 31, Issue 12, Pages 2242-2250

A mechanism of crack growth was investigated in resistance spot welds of mild
steel. The experiments in this study were designed to investigate the effects of the
electrode cap geometrieson fatigue life of the resistance spot weld specimens. Two
types of electrode cap geometries were used. These types are 4.8 mm and 6.3 mm
nose,used with the same shank in welding operations of 2mm mild steel plate. To
obtain the goal, operating factors were precisely controlled, especially the electrode
force and welding current of spot welds, to keep the same operating conditions while
changingthe electrode geometries. The life test results showed an improvement in the
fatigue life of resistance spot welds. The increment was 30% in heavy loads and 10%
in low loads based on tool geometry. The improvement in the fatigue life was
produced by reducing the diameter of the nose in the geometry of the tool.

Mechanical Properties of Friction Stir Welded Aluminum Alloy with Butt and Lap Cases

Nadhim M.Faleh

Engineering and Technology Journal, 2013, Volume 31, Issue 11, Pages 2030-2038

Mechanical properties were investigated in base and friction stir linear welds of 7075 aluminum alloy. Welding tools consist of a shoulder with a pin and with-out pin. This work addresses the effects of tool geometry on tensile stress and shear strength of butt and lap welds, and comparing with base material. Also, the effects of process condition on the strength of friction stir processed material are quantitatively characterized. Compared to the butt case, the friction stir lap linear welds, with pin, leads to a 20% increase in optimized weld strength with 1000 rpm of tool revolutions and 200 mm/min of tool speed. The optimizing of operating conditions primarily leads to a 15% increase in optimized weld shear strength, with 1000 rpm of tool revolutions and 200 mm/min of tool speed.

Design and Analysis of Knee Ankle Foot Orthosis (KAFO) for Paraplegia Person

Shaker S. Hassan; Khadim K. Resan; Akeel Zeki Mahdi

Engineering and Technology Journal, 2013, Volume 31, Issue 8, Pages 1521-1533

Knee ankle foot orthoses (KAFOs) are prescribed to paraplegic patients with low level spinal cord injury and with good control of the trunk muscles. Three types of KAFOs were used in this work (plastic-metal, metal-metal and composite materials), the composite materials were depended on the number of perlon layers (13 layers & 9 layers) with one layer of carbon-fiber and (6 layers) without carbon-fiber. The mechanical properties of most of the KAFOs’ materials were tested by tensile test and fatigue machines.
The data of gait cycle (Ground Reaction Force (GRF), and pressure distribution) were collected from one patient with poliomyelitis (wearing brace type KAFO) and one normal subject. In this paper, the FEM (ANSYS) was used to compute the safety factor of fatigue for all types of KAFOs’ models and the equivalent stress (Von-Mises). The interface pressure between the patient’s leg and the brace was tested by using a piezoelectric sensor.
The results obtained from ANSYS gave the profile of safety factor of fatigue, for metal-metal KAFO (3.69), plastic-metal model (0.88). While, the (13) layers for composite material was about (1.4), but (1.07) & (0.41) for (9) layers and (6) layers, respectively. The value of safety factor increased with the composite material for the suggested design.

Residual Stress effect on Fatigue Behavior of 2024- Aluminum alloy

Riyadh A. Al-Taie; Farag Mahel Mohammed; Ahmed N.Al-khazraji

Engineering and Technology Journal, 2011, Volume 29, Issue 3, Pages 567-578

In the present work the effect of residual stress on the fatigue behavior of
2024 Aluminum alloy was studied experimentally and numerically using
finite element method with aid of ANSYS-11 software. All the test
specimens treated by annealing before any process to remove the internal
stresses due to cold work. Residual stresses were imparted to the fatigue tests
specimens by heat treatment, pre-strain and welding. X-Ray diffraction was
used to measure the residual stress.
The heat treatment; done on the test specimens with different temperature of
(420, 450, 480, and 510) oC. After heat treatment; alloy mechanical properties
were improved. For the heat treated specimens as the temperature increased
the compressive residual stress increased to (27.06, 41.43, 72.8 and 85.6)
MPa. That leads to increase the endurance fatigue limit by (32.93%, 40.48%,
50.68% and 61.03%) respectively than other alloy as received. While in pre
strain groups; the test specimens loaded to (265, 290, 315 and 340) MPa by a
tension test machine. As the applied load series were increased the
compressive residual stress increased to (16.51, 25.62, 51.54 and 62.44) MPa
which improve the endurance fatigue limit by (7.68%, 16.19%, 24.98%, and
46.45%), respectively. An electrical arc and metal inert gas were used in
welding series to weld the test specimens, that present a tensile residual stress
of (76.93 and 72.66) MPa, which reduces the endurance fatigue limit by
(23.45% and 16.08%), respectively. The numerical results present fatigue
behavior, deflection and stress at any load, and show a reasonable agreement
results with an experimental one.