Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : vibration

Effect of Re-vibration Process on Axial Capacity of Short Reinforced Concrete Circular Columns

S.A. Abbas

Engineering and Technology Journal, 2017, Volume 35, Issue 7, Pages 776-787

A considerable amount of research work has been performed on the effects of vibrating of fresh concrete on the reduction of shrinkage and creep, the improvement bond stress between reinforcing bar and concrete, reduction the concrete permeability and improvement of the mechanical properties of concrete (tension and compression). Series of tests on reinforced concrete circular column, cubes and cylinders were carried out to study the effect of re-vibration duration on axial strength of column, compression strength of concrete cubes, and tensile strength of cylinders. Different compressive strengths of concrete and different size of aggregate were considered in this investigation. The test results show that, the re-vibration operation improves the tensile and compressive strength of concrete. The stiffness of columns increased with increasing the re-vibration duration up to1.5 times the initial vibration duration. Size of aggregate has significant effect on the improvement properties of concrete due to re-vibration. Increase the time duration of re-vibration delay the appearance of first crack.

The Influence of The Hydraulic Pumps Design Characteristics and Temperature of Mineral Oil on The Stability of Actuator

Abdul Karim Swadi Saleh; Farid Abou Hamed; Jafer Mehdi Hasan

Engineering and Technology Journal, 2014, Volume 32, Issue 10, Pages 324-337

Much research dealt with the problem in the pulsation of hydraulic pumps, studies, research and literature for vibration did not interfere with the effect of the medium which make vibrations and effect of temperature on the medium (the indirect effect on mechanical vibration). In this research a practical correlation between pulsation of pumps and temperature, pressure and vibration will be developed. To achieve this goal the hydraulic system was designed and implemented to deduce the effect of the internal design of the three main hydraulic pumps, gear pump, vane pump and piston pump, in conjunction with the high temperature of the mineral oil on the vibration generated by the piston arm and the stability of the actuator. Vibration Meter device used to indicate the vibration at the tip of the arm plunger for hydraulic piston and uploaded with a variable load (spring), as well as a computer-aided reading was recorded. It was shown that the interior design of the pumps had an effective influence on the values of acceleration and speed of vibration, even if convergence frequency pulse outside of the slot pressure pumps. This effect cannot be separated from the oil temperature which affect the increasing values of acceleration and speed of vibration recorded on the tip of the plunger arm (performance of the piston) also the pressure has an effect on the values of acceleration and speed of vibration . The temperature of the mineral oil had a strong influence on the performance of hydraulic systems, at the resonance condition.

Finding the Weight Loss Rate of Metallic Surfaces Exposed To Corrosion Presence of Vibration (Corrosion - Vibration)

Mouhmad Abdultef Ahmed

Engineering and Technology Journal, 2012, Volume 30, Issue 20, Pages 448-462

In this research the structural steel type (A36) samples were prepared by
traditional preparation operations , chemical composition of samples was analyzed
, hardness tested, then testing corrosion was achieved for two major cases, a
general corrosion case when the corrosive medium (sea water) is static for five
days period ,and the second case is the corrosion with presence of mechanical
vibration, which included two branch cases , first case; corrosion of vibrated
samples with the vibrated corrosive medium, and the second case when the
samples are fixed and corrosive medium is vibratory , a total test period is five
hours for each case ,then found weight loss and the corrosion rate of all cases of
corrosion mentioned by a traditional weight loss method , as well as study the
microstructures before and after the corrosion cases and to find an experimental
mathematical formula that illustrate the relationships between corrosion and
corrosion with presence of vibration, note that the used device to study the
mechanical vibration effect was locally designed and manufactured, according to
the modified American Standard (ASTM G32).Observed that the weight loss and
corrosion rate reached the highest value in the second case of corrosion with
presence of mechanical vibration (fixed samples and corrosive medium is
vibratory), followed by the first case of corrosion with presence of mechanical
vibration (vibrated samples with the vibrated corrosive medium), and less the value
of the corrosion rate and weight loss is the state of general corrosion (corrosion in
the static medium). It was noted that the microstructure of the structural steel
became uniformly corroded after general corrosion case (in static corrosive
medium) and corrosion regions were spread or scattered over all parts of the
sample surface on a regular basis, while the microstructure in the two cases of
corrosion with presence of mechanical vibration containing irregular corrosion
cavitations and scattered randomly on the surface, and more deeply especially the
second case (fixed samples and corrosive medium is vibratory). Illustrated from the
results and carves there was relationship between mentioned corrosion cases, it was
an experimental mathematical formula:
Acc.C.R.= Vib-C.R2 – ( Vib-C.R1 +Static C.R.)

The Effect of Thermal Loadings on the Dynamic Behavior of Cylindrical – Conical Intersection shell

Ali B. Assi; Ammar A. Al-Filfily; Muhsan J. Jweeg

Engineering and Technology Journal, 2009, Volume 27, Issue 4, Pages 831-851

This paper presented a numerical methods based on FEM were used to study
the effect of temperature on the dynamic characteristic of composite cylindrical
conical shell with different cone angle and wall thickness. The study taken into
account the effect of temperature on the material properties of the selected
material and the effect of pre stressing on the natural frequency of the shell. A
general conclusions could be obtained from the static analysis ,i.e. for higher
circumferential wave number, the effect of increasing the thickness is to produce
higher natural frequencies. The natural frequency of the system may drops by
about (12 %) as a result of the degeneration of the material properties due to
temperature elevation. The higher circumferential wave number, the more
pronounced is the influence of ply orientation on the resulting natural frequency
changing the ply orientation for 0/90/0 to 75/-75/75 may increase the natural
frequency by about (100 %). Finally the transient dynamic stresses may exceeds
the design stress by a bout (50 %).