علي صادق ياسر العذاري

Fatigue failure is the most reason for materials failure due to stresses under the strength limits of materials. The fatigue properties of composite materials can be improved by using high properties reinforcements such as carbon, Kevlar, and glass fibers. Several procedures can be used to increase the stiffness, strength, fatigue strength, and fatigue life composite materials. These procedures such as applying pre-stress to the fibers during curing porcess , and/or adding Nanoparticles like Multi-wall Carbon Nanotubes (MWCNTs) to the resin of the composite. This research studied experimentally the effect of adding MWCNTs that had high mechanical properties with different percentage ratios (0.5, 1 and 2wt.%) to the epoxy and composite(epoxy +carbon fiber with volume fraction of 30%). The pre-stress of (2.5, 5, 7.5, and 10MPa) applying to the carbon fibers during the curing process of hand layout of composite to produce residual stresses inside the resin of composite that may gave extra stiffness to the fibers. The fatigue test results of fully reversed bending stress with (R= -1) showed maximum increasing ratio in fatigue life for the epoxy reached 350% when adding 1wt.% MWCNTs, while the improvement ratio for hybrid composite reaches 2850% when adding 1wt.%MWCNTs with fiber pre-stressing value of 10MPa. The adding MWCNTs to the resine with ratio of 2wt% will decrease the fatigue life of the composite due to the agglomerate of Nanomaterials inside the resin that make it been as weakness points and cant transfer the load between MWCNTs , and that reduces the positive effect of adding MWCNTs. Keywords: Composite, Carbon Fiber, MWCNTs, Fiber Pre-Stressing, Fatigue Life

Fiber pre-stress composites are used nowadays in many applications that need extra strength without adding more reinforcements. Nano graphene platelets are selected to be added to the composite as it has high tensile properties. This work studied the effect of adding Nano graphene platelets with different weight ratios of 0.5%,1%, and 2% to the resin during the curing process in the presence of fiber pre-stressing of 1MP and 2MPa. The results show improvement in most properties of composites like tensile strength, modulus of elasticity, flexure strength, and modulus of flexure with the ratio of (43-57%),(35-55%),(100-134%), (60-90%) respectively. A numerical model was built to simulate tensile and flexure tests using ANSYS software. The divergence between the experimental and numerical results did not exceed 5%. Adding Nano graphene with a weight ratio of more than 2% will have a negative effect on the properties as the Nano graphene will agglomerate and lose most of its high properties

Nanotechnology is one of the great techniques that helping to considerably improve many technologies and industry sectors such as information technology, homeland security, medicine, transportation, energy, food safety, and environmental science. Low carbon steel is widely used in many applications because it is cheap and it has high workability. However, low surface hardness and impact toughness are its main disadvantages. In this work, the nanocoating of tungsten carbide (WC) has been added to the low carbon steel surface with a thickness of 30, 40, and 50μm by using the thermal spray process with the HVOF technique. The present work aims to investigate the coating layer influence on the hardness and impact toughness. The results showed a significant improvement in the hardness, reaching 94.7%, while the impact toughness improved by 36% for a sample coated with a 50μm comparing with uncoated samples. The improvement in the hardness and impact toughness is due to the good adhesion of nano coat with the steel surface and the high hardness of tungsten Carbide as well as the good toughness of tungsten. The thickness of the coating layer is detected by using the scanning electron microscope images for each spray time. The results show that the coating with a layer of a thickness of more than 50μm will cause flaking and removing the coating layers

This work investigated reasons and factors that cause the failure due to mechanical wear (Erosion) for the inside surface of elbows and pipes used in cement transportation which manufactures from low carbon steel and finds out a method for reducing this failure. The technique of Nano‑coating layers is used to coat the surface of samples with layers of nanoparticles of tungsten carbides of different thicknesses of (30, 40, and 50 μm). The test was done for these samples by placing them inside the elbow under the same operating conditions, pin on disc test. The results of the test under the same operation condition showed a decrease in erosion rate by 71% for the sample coated with 50 μm of layer, while the results of the pin on disc test showed a decrease in erosion rate by 97% for the thickness of 50 μm as this test is done under ideal testing conditions. The decrease in wear rate for elbow and pipes will increase their life work two times at least and that reduces the cost of maintenance by about 75%. The numerical simulation was also implemented to simulate the erosion profile inside the elbow, and the agreement with experimental results was 90%

The grinding media play an important role in cement industry, and these balls suffered from severe wear during the grinding process of clinker inside horizontal mill. The aim of this research is to decrease the wear rate of the grinding balls manufacturing from cast iron alloy by using Nano coating layers of tungsten carbides (WC). The samples of white cast iron prepared according to standards specifications for wear test (pin on disc) and micro hardness test. High-velocity oxy-fuel system used to coat the samples with layers of thicknesses (50, 70, and 80μm) with Nano particles of tungsten carbides depending on the coating time. The results showed the best coat thickness was 70μm that gave best improvement mechanical wear resistance reach to 79%, due to its properties and good adhesion with the base material. The increasing in microhardness H.V reach to 14.7% for samples coated with 70μm layer thickness. The coating layer thickness of 80μm will subjected to flaking and failure due to low adhesion between the metal surface and thick coating layers.

This work studied the effect of welding joint location on the critical load value, buckling strength, and maximum deflection for slender long columns of mild steel. Numerical models are used also to simulate the buckling of welded columns with two types of ends fixity (Pin-fixed and Fixed-Fixed) and compare the results with experimental results. Results show that the location of the welding joint at the middle point of the column gave the lower value of the critical load, buckling strength, and maximum deflection of the column. While the location of the welding joint at the first quarter of column length will give the best critical load, buckling strength, and minimum deflection of the column. The maximum divergences between the experimental and numerical results reach 9% for pin-fixed ends type and 11% for pin-pin fixed ends.

The increasing of composite materials applications in different engineering fields makes it necessary to improving the properties of these materials. One of these methods to improve some of mechanical properties is the fiber pre-stressing during curing process. This paper studies the effect of applying the pre-stress on the glass fiber inside composite material during the curing process of epoxy matrix. The range of pre-stressing levels that applied on the fibers during curing process were (0,2,4,6,8,10,15, and 20 MPa).The results bending test show that the increasing in bending strength will be linear with pre-stress value, and the bending strength will increasing about ( 67%), shearing strength increase about (42%) at pre-stress of (20 MPa) while the increasing in bending stiffness will reach to about (31%). Numerical method used with finite element and package of (ANSYS V.14.) software to get the effect of fiber pre-stressing on the bending strength numerically, the divergent between the experimental and numerical results not exceed (10%).

The application of nanotechnology in the welding process has great importance in developing the mechanical properties of welding joints. The aim of this paper was to investigated the effect of addition titanium dioxide nanoparticles(TiO2) to welding joints by using cold spary technique and study the possibility of improving the impact toughness of the welding joint and increase its operation life. Three weight fraction are used of TiO2 (0.75%, 1.5%, and 2%).The results showed there are improvements in the Impact toughness of welded joints with an increase of TiO2 concentrations. The average Impact toughness for the welded sample without TiO2 was (162.4 J), while the average Impact toughness for the welded sample with (1.5) % TiO2 NPs. was (231.2 J) at increasing ratio of (42.36 %) due to the good toughness properties of TiO2 that increase the toughness of welding zone. The Microstructure image by SEM showed that the addition of TiO2 decreases the grain size in the welding zone and makes it more homo-geneous, which gives it more toughness. The EDS analysis shows that increase TiO2 NPs leads to increase the amount of Ti and decrease the amount of Mn, and Si.

Continuous development in transportation sector makes the development of tires a necessity as manufacturers strive to meet increasingly high requirements. This work aims to study the effect of using a pre-tensioning technique to improve the tensile properties of bead ply in rubber tire to enhance performance and increase working life. Pre-tension levels ranging between 0 and 1,250 MPa were applied on single reinforcing wires at room temperature prior to the vulcanization process. The results show that the tensile strength and maximum tensile strain of bead specimens were increased by 86.66% and 14.7%, respectively, as the pre-tension level increased from 0 to 1,250 MPa. The stress strain curves for the specimens showed a large increase in strength with little increase in strain. The modulus of elasticity (Young's modulus) of bead specimens increased by 85.92 % as the pre-tension level increased from 0 to 1,250 MPa.

The one of main problem in cement industry is the continouse abrasion in lining plates of cement mill as a result of impact, abrasive and erosion by steel balls grinding media inside cement mill. The hardness property is the one of important characteristic in this field. In this paper the microhardness of lining plate which made from high chromium white cast iron (HCWCI) studied and improved by using coating with nano materials like tungestin carbid particles (WC). The coating process used High velocity oxyfuel (HVOF) technique to coat the samples of HCWCI with different thicknesses layers at different time of coating. The results show that the microhardness increases with increasing of coating thickness. The maximum microhardness was (743.7 HV) with improvement of 34% compared wit un-coated samples.

The Lining of horizontal clinker mill were made from high chromium white cast iron (HCWCI), that subjected to mechanical wear inside mill due to sever operation conditions, and that causes extra cost for maintenance. This paper deals with the improvement of the mechanical wear resistance for this lining by coat the surface of lining with nano particles of tungsten carbide. The thermal coating technique used as process for coating by high velocity oxeye fuel (HVOF) machine which assembled for this purpose. The wear tests were done for uncoated and coated samples by pin on disk test according to standard (ASTM G99-05). Also, the morphology of samplessurface was test by SEM and EDX. The coating process done for three value of coating layers (200, 400 and 700) µm. The results show that the weight loss at wear test will decreased when increase the thickens of nano particles of (WC) as coating material till reach to thickness (700 µm) . The results show the improvement in wear resistance may reach to (88%) for samples coated with layer thickness of (700 μm).

The continuous development in transportation sector makes the development of the tire a necessity to suit the modern requirements of transportation sector. This work aims to study the effect of using pre-tension technique to improve the flexural and adhesion properties of bead ply in rubber tire that enhances its perpormance and increase its working life. Pre-tension levels ranging between (0 - 1250 MPa) were applied on each single reinforcing wire at room temperature before vulcanization process. The results showed that the increasing in maximum bending strength, bending stiffness, and maximum shear strength was (26 %) due to pre-tension. The single fiber pull-out test results revealed that the debond shear strength was increased by (27% ) pre-tension on steel wires .

The fiber pre-tension is one of techniques that used to improve the properties of fibrous composite plate. In this paper, we study the fiber pre-tension effect on dynamic behavior for composite plate. The natural frequency and mode shapes studied for pre-tensioned fiber composite plate. The pre-stressing ranges(2¬¬-¬¬¬¬20MPa) applied on the fibers during curing process at room temperature. Dynamic model achieved using finite element to get the natural frequencies and modes shape and compare the results with analytical solution by used iteration of JACOBI method that solved by using FORTRAN language. The results show that the Fiber pre-tension will increasing the natural frequency (ωn) of cantilever composite plate by (53%) and the modes shape show that the models will deform in three directions (Z , θx , and θy ) for most modes. Key words: Composite Plate , Fiber Pre-tension, Natural frequency, Modes shape

The fatigue failure is the reason of most mechanical failure for engineering materials. This work tried using the nano-coating technique to coat the steel bars and study the effect of this coating layers on fatigue life of steel. The Zinc Oxide (ZnO) used as it cheap and available in most labs of nanotechnology. The coating process done at different time of coating to get different thickness of coating layers. The result of fatigue tests for coated samples show increased in fatigue life for samples that coated for long time (thick layer of nano coat)

The fatigue failure is the reason of (90%) of mechanical failures. This work tries improving the fatigue strength and increasing the fatigue life for steel bars that used in concrete reinforcing. Tensile test were done to find the mechanical properties of steel bar. The heating over critical temperature (AC3) and cooling by different cooling rates were done for steel bars, and tested this samples by tensile and fatigue tests. The tensile test results show increasing in yield and tensile strength for sample that cooled by oil (medium cooling rate).The fatigue test results show increasing in the fatigue life for samples that cooled by oil.

In this paper, the non-linear analyses of beam deflection were used to calculate the modulus of elasticity of stainless steel (grade 410) beams that exposed to heating and then cooling with different rate. Several specimens of alloy steel were heated to temperature above critical temperature AC3 at iron-carbon diagram (about 920Co) and then cooling with different cooling rate by using various cooling media. The cooling rates were (0.11, 1.2, 17, 77 and 150oC/Sec).

يهدف البحث الى دراسة تأثير معلات التبريد بعد تسخين عينات انبعاج من الفولاذ المارتنسايتي المقاوم للصدأ على مقاومة الانبعاج له

The welding process is one of the oldest joining processes between the materials, this paper try to find the effect of welding joint location in the steel on the fatigue strength of steel. The welding process done by electrical arc welding to joining steel samples at different locations at (X/L= 0.25, X/L= 0.5, and X/L= 0.75), where (X) the location of welding zone centre and sample subjected to fully reversed bending stress, then comparing the fatigue test results with un-welded sample. The experimental results show that the welding

استخدام صور المجهر الالكتروني الماسح في دراسة تأثير ضربة ليزر على قطعة سن بشري وتحديد العناصر الداخلة في تركيبه والحصول على صور مجهرية له باستخدام المجهر الالكرتوني الماسح

يهدف البحث الى دراسة تأثير عمليات تسليط الاجهاد المسبق على الياف الزجاج المكونة للمواد المتراكبة مع اساس من الايبوكسي على مقاومة الشد للمواد المتراكبة المتكونة حيث تم تحسين مقاومة الشد بتسليط اجهاد شد مسبق بنسب عالية

Chopped fiber reinforced epoxy composites are considered advanced solutions in many industrial applications, including ship building industry, due to their excellent mechanical, chemical, and weight properties. With the development of technology, it has become possible to enhance these materials with nanoparticles such as tungsten carbide (WC) and titanium dioxide (TiO₂) to improve their mechanical performance especially impact strength. The aim of this study is to investigate the effect of two types of additives nanoparticles, WC and TiO2, with chopped glass and carbon fiber reinforced epoxy composites on the impact strength and their potential use in journal bearings in ships as an alternative to metallic composites. Many samples were prepared utilizing different percentages of chopped glass and carbon fibers in addition of different ratios of tungsten carbide and titanium dioxide nanoparticles. Impact test was performed and the results showed that the addition of 1.5 % tungsten carbide with 4 % glass and 4 % carbon fibers achieved the highest improvement in impact resistance; about 446.6 % compared to pure epoxy sample. Also, the highest improvement in impact resistance by the addition of 1.5 % titanium dioxide is found to be about 420 % compared to pure epoxy.

Tribology is the science of studying friction, wear, and lubrication. Composite materials consist of two or more constituents (phases): the discontinuous phase represents the reinforcement and the continuous phase represents the matrix. Journal bearing is manufactured from various composite materials. This article reviews the literature on improving the tribological properties of journal bearings made of composite materials (polymer matrix composite materials and metal matrix composite materials) by dividing the previous studies into six primary sections depending on the kinds of composite materials. An efficient method was utilized to solve the problems of composite journal bearings in water lubrication such as wear resistance, reduced friction, and increased service life of journal bearings in various applications especially in ships. The impact of composite materials, whichwere added through thermoplastic such as polytetrafluoroethylene (PTFE), polyether- ether-ketone, POM, and PA66, thermoset such as epoxy, polyester, and phenolic reinforced with fibers, and thermoplastic with thermoset (PTFE/epoxy composite) to reduce wear rate and coefficient of friction, and also the addition of nanomaterials to composite journal bearing to enhance the tribological properties in various applications were examined. The last section used metal matrix composite reinforced to other metal or alloy to give the attractive mechanical properties used to improve wear resistance and friction coefficient of journal bearing. The novelty of this article lies in the comprehensive analysis of various composite materials and their effect on the tribological properties of journal bearings, providing future insights into bearing design and optimization to improve performance.

The current focus in armor development is on the creation of lightweight, thin, and cost-effective solutions. This study explores innovative techniques by incorporating nanomaterials into composite plates, combined with fiber pre-stressing methods during the polymer matrix curing process. Woven Kevlar fibers experienced a pre-stress of 2 MPa in two dimensions while being cured with an epoxy resin containing varying ratios of Nanographene (0.5, 1, and 2 wt.%). Results demonstrated that the optimal combination for enhanced mechanical properties, particularly impact strength, occurred with a 2 wt.% nanographene ratio and 2 MPa fiber pre-stressing. However, exceeding a 2 wt.% nanographene ratio led to nanoparticle agglomeration within the resin, negating their positive effects. The proposed armor model successfully passed ballistic testing and comprises four layers of composite plates, each layer consisting of epoxy resin with 2 wt.% nanographene, Kevlar fibers pre-stressed at 2 MPa, and a 3mm thickness. These layers are interspersed with additional 1mm layers of Kevlar fiber. This innovative approach offers a promising advancement in armor design, achieving a balance between low density, reduced thickness, and cost-effectiveness.

The Failure due to fatigue is responsible of more than 85% materials failure, which occurs under ultimate strength. The fatigues properties of polymers can be improved by utilize reinforcement materials (fibers, particles, etc) to form composite materials with good properties. The improving in fatigue properties for composite can be done by subjecting the reinforcement fibers to preload and make them under prestressing that give extra stiffness to material. The Nanoparticles can be added to the resin to enhance the mechanical properties. In this research, the tensile prestress of (2.5, 5, 7.5, and 10MPa) was applied on fibers to make material under compression after curing. Nanoparticles of Multi Wall Carbon Nanotubes (MWCNTs) added to epoxy resin and composite (epoxy +carbon fiber) with various weight ratios (0.5, 1 and 2wt.%) . The fatigue test results showed the fatigue life for the epoxy enhanced by 350% at 1wt.% of MWCNTs, while it reach to 2850% for composite at 1wt.%MWCNTs and 10MPa of fibers prestressing . The amount of 2wt% MWCNTs will reduce the fatigue life for epoxy and composite due to agglomeration phenomena of MWCNTs inside the matrix and been as weakness zone inside the resin that may decrease the fatigue properties.