omar S zaroog
University of Juba, Mechanical engineering, Faculty Member
- Sohar University, Mechanical and Mechatronics Engineering, Faculty MemberUniversiti Tenaga Nasional, Mechanical engineering, Faculty Memberadd
Abstract: Fuer die Auslegung von Bauteilen ist generell die Reduktion von Eigenspannungen zu beruecksichtigen. In der diesem Beitrag zugrunde liegenden Studie wurden Proben der Aluminiumlegierung 2024 T351 mit zwei verschiedenen... more
Abstract: Fuer die Auslegung von Bauteilen ist generell die Reduktion von Eigenspannungen zu beruecksichtigen. In der diesem Beitrag zugrunde liegenden Studie wurden Proben der Aluminiumlegierung 2024 T351 mit zwei verschiedenen Intensitaeten kugelgestrahlt und nachfolgend bei zwei Belastungen Ermuedungsversuchen unterzogen. Die Ermuedungsversuche wurden in zwei Stadien unterteilt. Die Eigenspannungen und die Mikrohaerte wurden dabei zu Beginn und nach jeder zyklischen Beanspruchung fuer die ...
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Many automotive parts produced undergo surface treatment process such as sandblasting or shot peening. Coil spring is one of the parts that were exposed to this process. Warm shot peening process was found in previous research to generate... more
Many automotive parts produced undergo surface treatment process such as sandblasting or shot peening. Coil spring is one of the parts that were exposed to this process. Warm shot peening process was found in previous research to generate longer fatigue life. The objective of this project is to determine the temperature of shot peening process to achieve the highest fatigue life for coil spring. The method used in this study was by testing 5 peening temperature, measuring the residual stress introduced by each shot peening process and conducting fatigue test to confirm. The result showed that shot peening at 220â°C would increase the fatigue life of the product and prolong the product life by almost five times longer compared to normal shot peening process at room temperature.It is proven that the most effective way to improve the fatigue life of coil spring is through implementation of warm shot peening process during production.
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Natural fibre composite (NFC) displays a rapid development in the study and innovation sector due to the increasing benefits of the material compared to other types of fibre such as synthetic fibre composites, which includes low price and... more
Natural fibre composite (NFC) displays a rapid development in the study and innovation sector due to the increasing benefits of the material compared to other types of fibre such as synthetic fibre composites, which includes low price and low environmental impacts. These composites can be explored through various variables and can be tested through various factors such as fibre interfacial adhesion, fibre orientation and fibre strength. However, this thesis focuses only on the testing on the vertical (90°) and horizontal (0°) of fibre orientation as it is still not well investigated, yet. The main objective of this research is to investigate the performance of mechanical properties of kenaf fibre reinforced epoxy resins for 90° and 0° of fibre orientation and analyse the effect of changing the orientation on the material. For the fabrication of the material, manual preparation method has been used and several mechanical testing has been and alkali treatment of kenaf fibre prior fabrication process. For hardness test, the 90° of fibre orientation produced 31.6% higher of hardness strength than 0° of fibre orientation while for impact test, 90° of fibre orientation resulted 39.5% greater of impact energy than 0° of fibre orientation. 6% of kenaf fibre composition with 90° of fibre orientation generated the highest stress to breaks while 2% of kenaf fibre composition with 0° of fibre orientation has the lowest stress to fracture. By conducting the SEM tests, it can be seen clearly that 6% of kenaf fibre composition with 90° of fibre orientation has the smallest gap between the fibres and 2% of kenaf fibre composition with 0° of fibre orientation has the largest gap between fibres. Thus, the performance of mechanical of vertical (90°) of fibre orientation produced better performance in mechanical testing compared to horizontal (0°) of fibre orientation.
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Natural fibre reinforce polymer composite is gaining attention from researchers worldwide due to its potential as a replacement for synthetic fibre. Its main properties which are environmental-friendly and lightweight make is suitable to... more
Natural fibre reinforce polymer composite is gaining attention from researchers worldwide due to its potential as a replacement for synthetic fibre. Its main properties which are environmental-friendly and lightweight make is suitable to be used in many industries such as automotive industry. However, it has low mechanical properties compared to synthetic fibre composite. Hence, to improve its mechanical properties, researchers started to hybridised natural fibre which has proven that this method maximise the mechanical properties of natural fibre composite. This paper investigated the mechanical properties of hybrid pineapple/kenaf fibre reinforced polymer composite with three different fibre loading which are, 3%, 6% and 9%. The method of fabrication is solvent casting method and the matrix used is epoxy resin. The results obtained shows that, for impact strength and hardness, higher fibre loading has higher impact strength and hardness. In the other hand, for tensile test, lower fibre loading has higher tensile strength.
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Shot peening process is a cold performed function to enhance the mechanical properties which is widely used in many industries. This process introduces compressive residual stress which was proven to increase the fatigue life, geometry... more
Shot peening process is a cold performed function to enhance the mechanical properties which is widely used in many industries. This process introduces compressive residual stress which was proven to increase the fatigue life, geometry stability and corrosion resistance. However, the benefit of the residual stress is still unstable due to the relaxation during the operation. This paper will study on the trend of the relaxation of residual stress against cyclic loading as well as the change in the hardness. The material used in this study is carbon steel ASTM A516/ SA 516 Grade 70. Shot peening process with steel shots was applied to the samples to introduce compressive residual stress in the samples. Cyclic load was applied to samples after shot peening process with low load of 52Mpa (20% of Yield Strength) and high load of 208Mpa (80% of Yield Strength). The measurement of residual stress using X-Ray diffraction and hardness test was done on the samples to study the trend of the re...
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Nowadays, sandblasting is commonly use in industries. The ability of sandblasting is to remove any stain, unwanted matter and many other functions making this process generally used worldwide. The effect of sandblasting on mechanical... more
Nowadays, sandblasting is commonly use in industries. The ability of sandblasting is to remove any stain, unwanted matter and many other functions making this process generally used worldwide. The effect of sandblasting on mechanical properties of ASTM A516 grade 70 was investigated in this study. Samples of the material have been sandblasted with different size of grits and times. Surface roughness, hardness and tensile was measured before and after sandblasting. The roughness test result showed that when the time duration of sandblasting increased, the roughness of the specimen also increased. Based on hardness test result, it showed that the hardness improved when the smallest size of grits was applied. However, the hardness decreased when the size of grits and time was increased. The tensile test result pattern showed quite similar to hardness test result. The size of grits and time duration for sandblasting need to set depending on application of the sandblasting process usage ...
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The current study examines the energy absorber capacities of the aluminum alloy AA6060 material in frontal longitudinal members of the crashworthiness applications. The aluminum alloy is subject of various studies because of its lighter... more
The current study examines the energy absorber capacities of the aluminum alloy AA6060 material in frontal longitudinal members of the crashworthiness applications. The aluminum alloy is subject of various studies because of its lighter weight, which helps to decrease the fuel consumption, and to protect the environment. The simulations are based on the non-linear finite element (ABAQUC CAD 6.10). The thin walled rectangular tube, enhanced by trigger mechanism, was subjected to direct loading. Elliptical, square, and circular trigger geometries were combined with different trigger positions and reductions. The best achieved result was the energy absorption enhanced by 16.2%, and the CFE enhanced by 16%, which results contributes to the safety of the passengers. This outcome has been given by the elliptical trigger situated at the distance of 50 mm from the free end of the tube with 10% reduction.
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In common engineering practice, the shot-peened aluminum alloy 2024-T351 is often subjected to loading. After time passes, the residual stress induced by shot peening might relax leading to respective metal cracking and failure. For this... more
In common engineering practice, the shot-peened aluminum alloy 2024-T351 is often subjected to loading. After time passes, the residual stress induced by shot peening might relax leading to respective metal cracking and failure. For this study, samples were stored for two years and a comparison of the hardness and microstructure before and after two years storage was carreid out. The primary aim of this study was to determine the effect of time on hardness and microstructure of shot-peened sample, thus to calculate the residual stress relaxation depending on time parameter. The results showed that the hardness and the residual stress of the material reduced after two years. The average reduction of the hardness is 20 % and the residual stress reduction ranged at 47 %
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In nature copper is found as a pure metal. It is low in the reactivity series which make copper not tending to corrode. The resistance to corrode combined with other desirable properties, such as thermal and electrical conductivity, ease... more
In nature copper is found as a pure metal. It is low in the reactivity series which make copper not tending to corrode. The resistance to corrode combined with other desirable properties, such as thermal and electrical conductivity, ease of fabrication, and low cost, results in their wide commercial use in such environments applications. Mixing copper with other metal result in excellent copper alloy properties made copper more important. Copper alloys developed for highly specialized applications with desirable characteristics on their composition. This paper reviews the corrosion mechanisms of copper and copper alloys to provide a foundation for understanding the corrosion behavior of copper alloys which is important for the design of new copper alloys with enhanced corrosion properties. In considering copper and its alloys for such applications the cautious selection of the appropriate copper alloy, based on an understanding of the nature of the process streams, will prevent local failure of the equipment by phenomena such as dealloying or stress corrosion cracking. Some cases of copper corrosion resistance were highlighted such as atmospheric exposure, soil, water, oxidation, and hydrogen embrittlement.
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In arid regions, global warming raises indoor air temperatures and consequently energy demand. Innovative cool roofing systems has to be developed to reduce indoor air temperatures and hence building energy consumption. The current study... more
In arid regions, global warming raises indoor air temperatures and consequently energy demand. Innovative cool roofing systems has to be developed to reduce indoor air temperatures and hence building energy consumption. The current study examines the advantages of using polystyrene foam insulation with a radiation reflector as a cool roof in Omani summers, as well as the thermal barrier effect of air circulation between them. The ventilated cool room has lower indoor air and heat flux values than the normal reference roof in field tests. The heat flux through the cool roof was reduced by 14 W/m2, 23 W/m2, and 29 W/m2 when the ventilation between the PsF insulation and the radiation reflector roof was 0, 25 cm, or 50 cm, respectively. The roof’s thermal resistance increased due to the ventilation system’s dynamic air flow between the PsF insulation and the radiation reflector (enhanced convective heat flux). During hot sunny days, the experimental studies demonstrated that the ventilated PsF insulation-radiation reflector cool roof lowers the temperature of the interior by a substantial amount and decreases heat flux through the roof.
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Natural fiber had recently been used as reinforcement with polymer in a composite is increasing, due to benefits. The benefits in natural fiber is the lightweight, low cost, environmentally friendly with a good specific mechanical... more
Natural fiber had recently been used as reinforcement with polymer in a composite is increasing, due to benefits. The benefits in natural fiber is the lightweight, low cost, environmentally friendly with a good specific mechanical property. However, several factors need to take into account to affecting the mechanical properties of natural fiber reinforced polymer, such as fiber fraction, fiber condition and fiber orientation. This study presents the simulation study on the mechanical properties of different natural fiber reinforced in a diagonal orientation and to compare the mechanical properties such as tensile and bending properties of Kenaf Fiber, PALF, and Ramie reinforced polymer composites. This study of mechanical properties will be investigated using ANSYS 18.1. The composites are designed in different natural fiber with fiber orientation in direction of 45° and 135° alternately in five layers. Tensile and bending test are analyze based on ASTM standard to determine the ef...
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Surface treatment such as shot peening are often used to enhance fatigue life of components. The simulation and experimental work has been carried out under variable amplitude tests to three different shot peening treatments of 2024-T351... more
Surface treatment such as shot peening are often used to enhance fatigue life of components. The simulation and experimental work has been carried out under variable amplitude tests to three different shot peening treatments of 2024-T351 aluminum alloy. Experiments were conducted on subjected to three different shot peening intensities which on 4-6A, 6-8A and 8-10A and tested under cyclic loading. The cyclic test for tow applied stress amount, 170MPa and 280MPa, was performed for the 1, 2, 10, 1000, 10000 cycles. The maximum relaxation for load of 170MPa is 45% of the initial residual stress at 10000 cycles for intensities (4-6A, 6-8A) while the maximum relaxation for load 0f 280MPa is 53% at 10,000 cycles for the intensity of 4-6A.This result showing that the redistribution of residual stress depended on the amplitude of applied load and shot peened material. Computer simulation was carried out using finite element method (FEM) by ANSYS software to investigate the residual stresses...
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The main conception of materials fracture in homogeneous, isotropic and composite materials is discussed. Important relations related to the linear elastic fracture mechanics are presented based on the Griffith-Irwin approach. Overview of... more
The main conception of materials fracture in homogeneous, isotropic and composite materials is discussed. Important relations related to the linear elastic fracture mechanics are presented based on the Griffith-Irwin approach. Overview of composite failure modes and some facts about the fracture toughness was discussed next. Some testing methods for fracture toughness of composites are then compared, studied and analyzed. The composites materials which used in this test are ceramic composites such as Duceram, Duceram LFC, Sintagon Zx and Carrara Vincent. Three fracture toughness testing methods were involved in this experiment are the indentation strength method (IS), the single edge notched beam (SENB) and the Chevron notched beam method (CN). Finally, A revision of a new method for testing the fracture toughness was proposed. A Conclusion and recommendations for future work on fracture of structural composites was done.
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Sandbalsting is a method used for surface treatment and at the same time this process also improves the mechanical properties of the material. ASTM A516 Grade 70 is widely used in industrial sector as it provides very good mechanical... more
Sandbalsting is a method used for surface treatment and at the same time this process also improves the mechanical properties of the material. ASTM A516 Grade 70 is widely used in industrial sector as it provides very good mechanical properties in tough conditions. The main usage of this material is in moderate and low operating services. This paper focus on the effect of sandblasting process on ASTM A516 Grade 70 on improving the mechanical properties and fatigue life of this material. Samples have been blasted with sand grade SAE G-80. The focus of this paper is the result of the microhardness, tensile and fatigue test before and after the sandblasting process to study the improvement in mechanical properties as well as the fatigue life. The research was extent to the microstructure analysis using SEM to study the change in microstructure after sandblasting process and fatigue test. Result shows that the hardness increases with respect to blasting time. Result also shows 2.3% incr...
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Compressive residual stress below the surface of material could increase fatigue life as it encounters the tensile loading applied on the material during operation. Shot peening process is a common surface treatment to introduce this... more
Compressive residual stress below the surface of material could increase fatigue life as it encounters the tensile loading applied on the material during operation. Shot peening process is a common surface treatment to introduce this stress. This study will investigate on how to introduce the same amount of residual stress by simulation using FEM as introduced in experimental shot peening process. Actual shot peening process was done using a particular sets of parameters and FEM with single shot is used to simplify the simulation procedure. Result shows that using a single shot simulation could also introduce the equivalent amount of residual stress as in the experimental multi-shots shot peening process. This value could be used in further study to study the relaxation of the stress after load is being applied.
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This paper investigates the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm x 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test... more
This paper investigates the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm x 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against slab thickness and mesh reinforcement spacing. There is a good linear correlation between impact resistance of ferrocement against slab thickness and its mesh spacing. The first and ultimate crack impact resistance for 40 mm slab are 2.00 times and 1.84 times respectively against the 20 mm slab with the same mesh spacing. The first and ultimate crack impact resistance for 40 mm slab with 20 mm mesh spacing are 2.24 times and 3.70 times respectively against 50 mm mesh spacing with the same slab thickness. The mesh with higher content of reinforcement provides more contribution to the slab resistance as compare with the thickness.
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This paper investigate the effect of the thickness and fibre volume fraction (VF) on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced subjected to low impact... more
This paper investigate the effect of the thickness and fibre volume fraction (VF) on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the relationship of impact resistance SFRC against slab thickness and volume fraction. There is a good linear correlation between impact resistances of SFRC against slab thickness. However the impact resistance of SFRC against percentage of volume fraction exhibit a non-linear relationship.
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This paper investigate the performance of lightweight rice husk concrete (LWRHC) with varied bamboo reinforcement content for the concrete slab of 300mm × 300mm size reinforced with varied slab thickness subjected to low impact projectile... more
This paper investigate the performance of lightweight rice husk concrete (LWRHC) with varied bamboo reinforcement content for the concrete slab of 300mm × 300mm size reinforced with varied slab thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.65 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter and slab thickness. 5% RH content exhibit better first and ultimate crack resistance up to 1.80 times and up to 1.72 times respectively against 10% RH content.
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This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to... more
This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance SFRC for various slab thickness and fraction volume. Random fibre distribution is the more effective than the top and bottom fibre distribution in terms of absorption of impact energy, crack resistance, the ability to control crack formation and propagation against impact energy.
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This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg... more
This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)
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Compressive residual stress, induced by mechanical surface treatment, may relax during component operation life, due to thermal or mechanical mechanism. Fatigue life prediction for the components which have residual stress will be misled... more
Compressive residual stress, induced by mechanical surface treatment, may relax during component operation life, due to thermal or mechanical mechanism. Fatigue life prediction for the components which have residual stress will be misled and inaccurately predicted the phenomenon of ...
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Abstract: In this study, 2024-T351 aluminum alloy specimens were shot peened into three shot peening intensities condition to induce compressive residual stresses (RSs). Fatigue test was performed for the first and second cyclic load.... more
Abstract: In this study, 2024-T351 aluminum alloy specimens were shot peened into three shot peening intensities condition to induce compressive residual stresses (RSs). Fatigue test was performed for the first and second cyclic load. Initial RSs at initial condition and after first and second cycle of fatigue loading were measured using X-ray diffraction method. Relaxation for first cycle was found to reach over 40% of initial RS and it depended on load amplitude.
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This research Investigates the new composite materials are fabricated of two or more materials raised. The fibers material from the sources of natural recycled materials provides certain benefits above synthetic strengthening material... more
This research Investigates the new composite materials are fabricated of two or more materials raised. The fibers material from the sources of natural recycled materials provides certain benefits above synthetic strengthening material given that very less cost, equivalent strength, less density, and the slightest discarded difficulties. In the current experiments, silk and fiber-reinforced epoxy composite material is fabricated and the mechanical properties for the composite materials are assessed. New composite materials samples with the dissimilar fiber weight ratio were made utilizing the compression Molding processes with the pressure of 150 pa at a temperature of 80 °C. All samples were exposed to the mechanical test like a tensile test, impact loading, flexural hardness, and microscopy. The performing results are the maximum stress is 33.4MPa, elastic modulus for the new composite material is 1380 MPa, and hardness value is 20.64 Hv for the material resistance to scratch, SEM ...
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Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the... more
Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the relaxation of residual stress phenomenon. In this study, equations to predict residual stress relaxation of 2024 T351 aluminium alloy specimens were proposed. The equations developed from the experimental data of 2024 T351 aluminium alloy specimens that were shot peened under three different shot ...
Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the... more
Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the relaxation of residual stress phenomenon. In this study, equations to predict residual stress relaxation of 2024 T351 aluminium alloy specimens were proposed. The equations developed from the experimental data of 2024 T351 aluminium alloy specimens that were shot peened under three different shot ...
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Abstract The residual stress relaxation can be divided into two stages: The first cycle relaxation and the following cycles. In both stages, residual stress relaxed considerably from the initial state. The aim of this study is to... more
Abstract The residual stress relaxation can be divided into two stages: The first cycle relaxation and the following cycles. In both stages, residual stress relaxed considerably from the initial state. The aim of this study is to investigate the residual stress relaxation and microhardness reduction after first and second cyclic load. A 2024 T351 aluminum alloy specimens were shot peened into three shot peening intensities. The fatigue test for first and second cyclic loads of two loads 15.5 kN and 30 kN was performed. The initial residual ...
Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the... more
Abstract The initial compressive residual stresses induced or inherent in a component will not remain stable during the life of the component, it relax and redistributed. In design of the component, it is important to consider the relaxation of residual stress phenomenon. In this study, equations to predict residual stress relaxation of 2024 T351 aluminium alloy specimens were proposed. The equations developed from the experimental data of 2024 T351 aluminium alloy specimens that were shot peened under three different shot ...