Iraqi journal of mechanical and material engineering

The monthly time series of the Total Dissolved Solids (TDS) and Chloride(CL) concentrations in Euphrates River at Babylon were analyzed as a time series. The data used for the analysis was the monthly series during (2000-2013). The series was tested for non-homogeneity and found to be nonhomogeneous. A significant positive jump was observed at 2002 for Total Dissolved Solids (TDS) and at 2006 for Chloride (CL). This non homogeneity was removed using a method suggested by Yevichevich (7). The homogeneous series was then normalized using Box and Cox (2) transformation. The periodic component of the series was fitted using harmonic analyses, and removed from the series to obtain the dependent stochastic component. This component was then modeled using first order autoregressive model (Markovian chain). The above analysis was conducted using the data for the period (2001-2011), the remaining 2-years (2012-2013) of the observed data was left for the verification of the model. The observed model was used to generate future series. Those series were compared with the observed series using t-test. The comparison indicates the capability of the model to produce acceptable future data.

This paper is aimed to study the effect of heat treatment for submerged arc welding joint in
the dimension of 100*50*16 mm on corrosion resistance in sea water at different
temperatures.
Submerged arc welding is carried out for Low carbon steel St37 under welding conditions of
750 Amper DC current straight polarity (DCSP) and 32 volt, welding wire type EM12K.70-
18 in diameter of 4mm and wire speed of 4.2m/min with Flux . A joint geometry of single
V at 45P
o
P butt joint welded two passes was adopted. The welded pieces were tested by X-ray
radiography and faulty pieces were excluded.
After welding, the joints without defects have be submitted to heat treatment including
quenching where the joint heated to 900 C⁰ for one hour then water cooled and followed
by normalizing heat treatment by heating to 900 C⁰ for one hour then air cooled. Corrosion
specimens prepared from the weld joint with the dimensions of (15*15*3) mm according to
ASTM G71-31 then optical microscopy was used to observe the welded joint microstructure.
Corrosion tests were investigated by electrochemical potential state cell in a prepared salt
water (sea water) at different temperatures (25, 50.75) C⁰. Tafle equation was adopted to
calculate the corrosion rate.
Results show that heat treatment contributed in reducing corrosion rate and normalizing gives
better results than quenching but the effects of media temperature give the opposite

In this study, dissimilar sheets of commercial pure aluminum and copper, 4 mm thickness were butt joined by Friction Stir Welding (FSW) to experimentally explore the effect of tool rotational speeds on the mechanical properties. Three rotational speeds of 1200, 1700 and 2200 rpm were applied. The transverse speed and the axial force were kept constant at 50 mm/min and 5 KN, respectively. X-ray diffraction (XRD), Vickers microhardness and tensile strength were investigated at these different rotational speeds. The joint welded at 1700 rpm was compared with their counterparts and observed significantly better. The formation of relatively hard brittle intermetallic compounds AlCu and Al4Cu9

Tensile modulus and strength of 60% constant volume fraction of carbon fiber reinforced
aluminum matrix composite materials have been investigated under room temperature (RT),
zeroP
°
PC, -15 P
°
PC and -30 P
°
PC using Testometric M500 tensile testing machine equipped with an
environmental chamber. Three samples of different laminate arrangement and orientation
were employed, namely SR1Rand SR2R, which included both woven and unidirectional fibers, and
SR3R, which contained only unidirectional fibers. The results showed that the tensile modulus
was slightly increased with decreasing temperatures. The tensile strength showed a slight
decrease for samples SR1 Rand SR2R with decreasing temperature, but for sample SR3R, the tensile
strength increased as the temperature decreased from (RT) to -15 P
°
PC and then decreased at -
30 P
°
PC. The SR3R laminate orientation with only unidirectional carbon fibers possessed the
highest tensile modulus and strength.

This work focuses on the study the effect of data seeds (DS) and olive seeds (OS) on
thermal and water absorption properties of epoxy resin. Olive and dates seeds were added to
epoxy matrix at weight fraction (0, 8, 13&18%wt) with grain size (300, 450 & 600ىm). The
composite specimens were prepared by Hand-Layup technique according to standard test.
The results show that the thermal and water absorption properties of composites increasing
with increase weight fraction of particles. Also its found the higher value of thermal
conductivity, thermal diffusivity, specific heat and water absorption happened at ( =18 wt%)
and grain size (300ىm) for specimens reinforced with olive seeds. The mathematical model
results show that the weight fraction of particles have higher effect than grain size on
properties.

This paper investigates the linear static and modal analysis of a helical machined spring using the finite element method with the aid of SolidWorks software. A comparison between a conventional helical spring with rectangular cross section area and a machined helical spring was performed. A helical spring with square cross section area was modeled with different spring index, while for the machined helical spring two cases were modeled, one with different slot hole diameter and the other with different end extension length. Results obtained were verified with different analytical formulas for shear stress, deflection and natural frequency. There was a good agreement between the theoretical and numerical results, the maximum deviation in shear stress, deflection and the fundamental natural frequency of the numerical results were (3.6%), (2.6%) and (0.19%) respectively. For the machined helical spring it was concluded that the tangent hole configuration is better than the center hole configuration and changing the extension length has no considerable effect on spring characteristics. The machined spring with any slot hole and any extension length is better than the identical helical spring with rectangular cross section.