Ali Alhelli | Alnahrain University (original) (raw)

Papers by Ali Alhelli

— Sheet metal technologies are challenged especially by the improvement in the automotive industr... more — Sheet metal technologies are challenged especially by the improvement in the automotive industry in the last decades to fulfill the customer expectations, safety requirements and market competitions, new production technologies have been implemented [1]. In this work the sheet metal used is 1060AA 1mm thick Aluminum alloy usually used for its light weight, high corrosion resistant, easy to recyclables and high strength to weight ratio. This sheet metal is to be formed by hydroforming process which used the hydraulic pressure as a punch to force the sheet metal to take the shape of the die cavity and study the formability of this alloy under different heat treatment procedures.

Fiber reinforced composite materials are used increasingly in many military and civil application... more Fiber reinforced composite materials are used increasingly in many military and civil applications due to their excellent mechanical properties like high specific strength, specific stiffness, resistance to corrosion, increased fatigue life among others. However, one of the main concerns in the use of advanced composites is their poor translaminar properties, which become critical under situations like impact loading. Composites that are used in aerospace and land based structural components are often subjected to high velocity impact threats like broken engine parts, turbine blades, fragments from bombs, shells, mortars, …etc.
In this work, the energy absorbed due to impact of small rigid projectile on composite materials targets is studied analyticaly and experimentally. Analytically, the energy absorbed due to impact of conical nose projectiles on composite laminates is investigated. Four types of observed energies are studied. They are the strain energy due to deformation of plate (contact energy), the large deformation near the impact zone, the delamination energy and the energy losses due to friction.
The equation of motion of plates is solved for the transient contact load at high velocity with its boundary conditions. Large deformation of delaminated zone is derived assuming a deformation shape formulation to calculate the penetration depth and delamination radius. Delamination energy is calculated by solving the delamination failure criteria with equation of motion. Friction energy is calculated assuming constant friction coefficient.
The experimental work is divided into two parts. First, fabrication and testing the mechanical properties of woven laminate composite materials. Three types of fibers are used which are E-Glass, Carbon, and Kevlar fibers with different types of weave style. The matrices used are epoxy and polyester. Fabrication of matrix and composite samples is done by using successful new molding materials as the (paste for pans), and ceramic plate with x-ray films. The sets of standard tests are done to measure the needed mechanical properties. From these tests new woven factors are evaluated which are the ratios of mechanical properties for the woven composite to that for equivalent cross-ply composite. It is found that these factors were higher for Kevlar composite for the same matrix material. It was higher for fiber-reinforced epoxy than the fiber reinforced polyester. And it is increased as the yarn section increased and the end satin increased.
Second, testing the manufactured composite plates for the ballistic impact, for this reason, an Impact rig is designed and built using special type of gun made for this purpose with clamped fixation for the square target plate. The computerized counter device is designed for measuring the incident and resting velocity, and to evaluate the approximate penetration time. This rig is used to compare theoretical results with tests, and also to study the effect of hybrid arrangement on the impact.
The results show that the contact energy has a lower value for the energy absorbed, the delamination and large deformation energy are increased as the incident velocity increased until reaching the ballistic velocity limit then they remain constant. The friction energy remaining increased without affecting the ballistic limit. The absorbing energy was increased with increasing the thickness of the plates. The resistance of the carbon composites is shown to be lower than the Kevlar composite and higher than the E-Glass composite.
To improve the impact properties of the E-Glass, a layer of Kevlar is added to the composite, a 3-location of Kevlar lamina was used to reinforce the E-Glass, which at the front, back and center of the composite. Results of this work indicate that the damage is well contained within the Kevlar lamina. However, ballistic limit is higher for the composite that has the Kevlar layer in the back of the target, while it is lower for the case when the Kevlar layer is in the front location.

Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have a... more Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have always been made to make up for such a loss. The basis of this investigation is to research current prosthetic in order to design and build a more human like prosthesis. Also this investigation aims at combining these characteristics in order to achieve a more multi functional prosthesis. In undertaking such a design, the new prosthesis will be exhibit a broader range of characteristics than those displayed in current prosthetic feet. In doing so, the new prosthesis will enable a closer representation of the functions inherent of a normal human foot. The characteristics involved in normal walking include dorsiflexion, impact absorption and fatigue foot test. The characteristics displayed in the manufactured new foot tested were compared to those of SACH foot. The characteristics exhibited by prostheses which compared favorably to those of a human foot were investigated further. A new prosthetic foot is designed and manufactured from polyethylene and a comparison study with SACH foot was used to determine if there are differences in the gait pattern while wearing the NEW foot and whether these differences would be problematic. The basis of the new prosthetic design combines current prosthetic design elements, such as materials and components. The analytical part presents the results of the static and fatigue analysis by methods; numerical methods (Finite Element method FEM) and experimental methods. The new foot was designed and the number of cycle, dorsiflexion and impact were measured. The new prosthetic foot has a good characteristic when compared with the SACH foot, such as good dorsiflexion (7.8 -6.4 o), force transmitted at impact heel (9.82N-9.50N) and life of foot (2,103,445-896,213) cycles respectively.

In recent years, the elastomer forming technique has found acceptance on the shop floor and is us... more In recent years, the elastomer forming technique has found acceptance on the shop floor and is used increasingly as a pressure- transmitting medium for various metal-forming operations. This is due mainly to the introduction of a new range of materials and of new concepts in tooling, which have served to kindle industrial interest in the process.
The purpose of this paper is to study the sheet formability with compressible die (natural rubber). The forming was occurred using hemi-spherical punch and rubber die. Experimental tests were used to know the mechanical properties for rubber and sheet materials which were brass and aluminum. After that several forming processes were prepared with a 58 mm diameter steel ball as a punch to form 0.5 thickness brass and aluminum dishes with different diameters (15-40 mm). Force-stroke history was plotted through forming to find the stiffness of formed plate with rubber die and later to compare this parameter for different diameters. Wrinkling and springback were pointed for the formed dishes. It was found that the stiffness of the formed dish increases with diameter until reaching to the diameter at which wrinkling will takes place (about 33 mm for aluminum and 28mm for brass), and then the stiffness will decreases with diameter above this value. It was found that the springback ratio (ratio of final high to the stroke) was increased with diameter until wrinkling takes place, and this ratio is greater for aluminum than that for brass.
The results show that it is able to use natural rubber as a die for sheet metal forming with limitation of using small sheet thickness.

The fatigue damage is a dangerous and could be considered as the most unwanted failure in the mat... more The fatigue damage is a dangerous and could be considered as the most unwanted failure in the materials that are used to construct the engineering components. As composites take an advanced position in the industry of aircraft, marine and many other high performance components, because of their high ability and their light weight and for their strength, this forces us to find the deformation and data to give a good expectation for the composite behavior under fatigue and other types of damage.
In this study the material used is the glass fiber with a polyester resin; the experiment used a device to force the composite to be under a bending fatigue through specified deflection and then the force is measured. The results for different values of imposed deflection and different thicknesses are presented, as S-N curves and in a logarithmic way.
Fractography has been used to characterize the fatigue damage in the composite, it is shown that the fatigue damage in the composite is a complex, interactive damage process and combines between several damage mechanisms such as delamination, fiber breakage, matrix cracking and fiber matrix debounding.

The urinary bladder is probably the only visceral smooth-muscle organ that is under complete volu... more The urinary bladder is probably the only
visceral smooth-muscle organ that is under
complete voluntary control from the cerebral
cortex. Normal bladder function requires
interaction of sensory and motor components of
both the somatic and autonomic nervous system.
Recent advances in the understanding of neural
pathways and neurotransmitters have shown that
most levels of the nervous system are involved in
the regulation of voiding function. Therefore
many neuralgic diseases causes changes in the
bladder function [1].
In this paper, Number of patients selected from
Ibn-Alkiff hospital (for treatment and
rehabilitation of Spinal cord injuries), in
Baghdad, who were referred to the urology
department for complains of some urinary
symptoms, and examined by cystometry in the
urology out patient and/or inpatient department.
These cases were selected randomly who
already consult these departments and were
followed up and managed by the expert
urosurgeons. They were adults complaining of
general neuropathic bladder disorder symptoms
like frequency, urgency, dysuria, urinary
incontinence and were diagnosed as having
neuropathic bladder disease, whether:
1. Upper motor neuropathic bladder lesions.
2. Lower motor neuropathic bladder lesions.
And finally they were examined by cystometry.
The collections of data from patients were about:
1. Accommodation (compliance).
2. Bladder capacity.
3. Contractility.
4. Sensation.
5. Voluntary control.
These data with the final definition diagnosis
about the neuropathic bladder lesion were
processed to 3- layers Neural Network algorithm
that was constructed in a matlab computer
package.
Consequently after all data processing, the
neural network model was tested by its capability
of processing an already diagnosed neuropathic
bladder case and its accuracy in explaining the
real neurological bladder behavior of that selected
patient.

In the industrial forming of metal sheet or plate component by means of bending operation, a cons... more In the industrial forming of metal sheet or plate component by means of bending operation, a constant problem is the change of shape, or Springback of the formed part under the stress that are released elastically when the forming load is removed, for the close tolerance forming of such component, an accurate means of calculating the Springback is of great value, as this enables a corrective allowance to be made when designing and performing the forming operation itself. In this research, the effect of material type, sheet thickness, blankholder force, punch speed rate, rolling direction and friction conditions on springback values were studied analytically under the plane strain conditions, Springback device has been designed and manufactured experimentally with a specimen. These devices can carry out all the tests of the Springback. The results showed the effect of the parameters on the die angle, punch angle and the sidewall curvature. by using MATLAB program, a polynomial function could be estimate the relationship between all the parameters to find the value of slops and curvature with fixed dimensions: die Angle = 1.8519x3 - 2.9630x2 - 1.0926x + 13.3222, punch Angle = -2.7778x3 + 8.6111x2 - 10.4444x + 21.7667, radius of Curvature = 1.1111x3 - 1.7778x2 + 1.3444x + 5.0933, where x is the holdown force value between (200-1100 N).

the effect of curing time on the mechanical properties of particular composite. Of critical impor... more the effect of curing time on the mechanical properties of particular composite. Of critical importance was the capability to predict resin flow and compaction during cure. Such a model could be used to determine optimum cure cycles without a need for experimental trial and error.
The experimental work includes steps .The first step is mixing the polyester with the Alumina powder with particular size ranged from 25 to 36 m with different weight ratios (0, 10, 20, and 30%) and the second steps is putting it in the heater furnace at 70oC at different curing time (1, 2 and 3 hours) to known the properties acquired and the third step is tested in the tensile test for all specimens. The conclusion of this test is summarized that the curing time of the presented composite is about 2 hour with 70oC.

Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have a... more Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have always been made to make up for such a loss. The basis of this investigation is to research current prosthetic in order to design and build a more human like prosthesis. Also this investigation aims at combining these characteristics in order to achieve a more multi functional prosthesis. In undertaking such a design, the new prosthesis will be exhibit a broader range of characteristics than those displayed in current prosthetic feet. In doing so, the new prosthesis will enable a closer representation of the functions inherent of a normal human foot. The characteristics involved in normal walking include dorsiflexion, impact absorption and fatigue foot test. The characteristics displayed in the manufactured new foot tested were compared to those of SACH foot. The characteristics exhibited by prostheses which compared favorably to those of a human foot were investigated further. A new prosthetic foot is designed and manufactured from polyethylene and a comparison study with SACH foot was used to determine if there are differences in the gait pattern while wearing the NEW foot and whether these differences would be problematic. The basis of the new prosthetic design combines current prosthetic design elements, such as materials and components. The analytical part presents the results of the static and fatigue analysis by methods; numerical methods (Finite Element method FEM) and experimental methods. The new foot was designed and the number of cycle, dorsiflexion and impact were measured. The new prosthetic foot has a good characteristic when compared with the SACH foot, such as good dorsiflexion (7.8-6.4o), force transmitted at impact heel (9.82N-9.50N) and life of foot (2,103,445-896,213) cycles respectively.

The problem of critical velocity of fluid-conveying pipes resting on a Winkler foundation with el... more The problem of critical velocity of fluid-conveying pipes resting on a Winkler foundation with elastically supported of the pipe is studied in this paper. The aim of this work is deriving a new analytical model to perform a general study to investigate the dynamic behavior of a pipe under general boundary conditions by considering the supports as compliant material with linear and rotational springs, and study the effect of foundation and stiffness values on the critical velocity. This model describes both the classical (simply support, free, built, guide) and the restrained boundary condition and it is not required to derive a new critical velocity equation if the boundary conditions is changed ,also the result will be near to reality by knowing the physical parameters for the compliant material and the pipe. The cases studied in this work are flexible support of the ends pipe with or without intermediate restrain support, and pipe resting on Winkler foundation. . The general theoretical conclusions are that the supports and foundation values have significant effects on the dynamic characteristics of the pipe.

This work presents a complete solution for the Forward and Inverse Kinematics for a 5DOF robot ma... more This work presents a complete solution for the Forward and Inverse Kinematics for a 5DOF robot manipulator and use XNA game studio as a simulator. The work include mathematical modeling of the robot Kinematics which it used in a 3D virtual environment. This text show that it can be use XNA GS as an excellent tool to simulate robots behavior.

Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have a... more Loss of the lower limb can cause loss of mobility .At all places and at all times, efforts have always been made to make up for such a loss. The basis of this investigation is to research current prosthetic in order to design and build a more human like prosthesis. Also this investigation aims at combining these characteristics in order to achieve a more multi functional prosthesis. In undertaking such a design, the new prosthesis will be exhibit a broader range of characteristics than those displayed in current prosthetic feet. In doing so, the new prosthesis will enable a closer representation of the functions inherent of a normal human foot. The characteristics involved in normal walking include dorsiflexion, impact absorption and fatigue foot test. The characteristics displayed in the manufactured new foot tested were compared to those of SACH foot. The characteristics exhibited by prostheses which compared favorably to those of a human foot were investigated further. A new prosthetic foot is designed and manufactured from polyethylene and a comparison study with SACH foot was used to determine if there are differences in the gait pattern while wearing the NEW foot and whether these differences would be problematic. The basis of the new prosthetic design combines current prosthetic design elements, such as materials and components. The analytical part presents the results of the static and fatigue analysis by methods; numerical methods (Finite Element method FEM) and experimental methods. The new foot was designed and the number of cycle, dorsiflexion and impact were measured. The new prosthetic foot has a good characteristic when compared with the SACH foot, such as good dorsiflexion (7.8-6.4o), force transmitted at impact heel (9.82N-9.50N) and life of foot (2,103,445-896,213) cycles respectively.