A.M. Al-Mukhtar | Al-Hussain University College (original) (raw)

Papers by A.M. Al-Mukhtar

Mining of Mineral Deposits, 2024

This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, fo... more This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, focusing on the complex mechanisms within hot reservoirs. Non-commercial finite element (FE) software is used to visualize and present the results. Methods. The study involved the use of FE method with Visual Finite Element Analysis (VisualFEA) software to analyze the coupled phenomena of fluid flow and heat transfer in a rock sample. Special attention was given to incorporating material structure and geotechnical analysis in the software, as well as the treatment of cracked elements. In addition, the validation was done by comparing the current numerical solution using VisualFEA with the numerical solution using ANSYS Software. Findings. The study findings highlight the capabilities of VisualFEA software to accurately represent fluid flow, stress, and heat transfer in borehole-containing rocks. The results include insights into flow direction within the borehole, temperature distribution, and the validation of the software performance against expected system behavior. The study demonstrates the effectiveness of VisualFEA in handling complex loading and its ability to visualize multiple flow directions within a 2D model. The results are presented in the form of contours and curves. Originality. This study contributes to the field demonstrating the application of VisualFEA software in analyzing fluid flow and heat transfer in rocks with boreholes. The focus on incorporating material structure, geotechnical analysis, and treatment of cracked elements adds originality to the study, providing a comprehensive understanding of the coupled phenomena in hot reservoirs. Practical implications. The practical significance of this study is in the validation and benchmarking of VisualFEA software for studying fluid flow and heat transfer in geotechnical application. The findings can be utilized by geotechnical engineers and researchers to better understand the behavior of borehole-containing rocks under specific pressure and thermal loading conditions. The insights gained from this study can be used in decision-making processes related to resource mining, reservoir engineering, and geothermal energy use.

Case Studies in Thermal Engineering, 2024

The free convection of a non-Newtonian fluid in an equilateral triangular cavity containing a tri... more The free convection of a non-Newtonian fluid in an equilateral triangular cavity containing a triangle obstruction in various positions is investigated numerically in this paper. The research is carried out using the finite element method. The sloped side walls are adiabatic, while the bottom is kept heated. At the obstacle, three positions are examined. The effects of different power law indexes on free convection have been investigated. The temperature field, fluid flow, and heat transfer are all highly influenced by the obstacle's location, Rayleigh number, and power law index. The resulting outcomes are confirmed using existing results in the literature and verified using a grid sensitivity analysis. A comparison of the current results to those found in the literature demonstrates the study's dependability and trustworthiness. Nomenclature B cold obstacle location ε ij strain rate = 1/2(∂ u i / ∂ x j + ∂ u j / ∂ x i

Engineering and Technology Journal, 2024

Resistance spot welding (RSW) is widely used in the automotive industry, particularly for copper-... more Resistance spot welding (RSW) is widely used in the automotive industry, particularly for copper-aluminum alloys in electric cars. RSW joint conductivity is crucial for electric vehicles. Welded parts may fracture due to tension, altering conductivity. The study examines resistance spot post-weld joint metallurgy and deformation-induced conductivity changes. The electric resistance of similar and dissimilar RSW joints was examined during tensile tests. Metallurgical tests for RSW joints revealed an increase in grain size from the base metal (BM) to the heat-affected zone (HAZ) and finally the fusion zone (FZ). Satisfactory shear tension strength results were obtained for dissimilar joints (Al-Cu) at 690 N and similar joints (Al-Al) at 780 N, exceeding the minimum limit of 643 N. However, weld strength in similar joints (Cu-Cu) only achieved 933 N, less than the required strength of 1528 N. Furthermore, the relationship between deformation rate (i.e., applied stress) and electrical resistance has been shown. It was found that resistivity increases with increasing deformation stress, resulting in decreased electrical conductivity with a high percentage, representing 99.8, 99.66, and 99.49% for Al-Cu, Al-Al, and Cu-Cu RSW joints, respectively. The electrical resistance was measured at the maximum force of 650 N and maximum stress of 33.1 MPa. The results show (15.7 Ώ, 5.9 Ώ, and 1.99 Ώ) and the electrical conductivities (0.063 IS, 0.169 IS, and 0.502 IS) for the joints (Al-Cu), (Al-Al), and (Cu-Cu), respectively

Diagnostyka, 2024

Recently, dissimilar metals have found applications in the process of resistance spot welding (RS... more Recently, dissimilar metals have found applications in the process of resistance spot welding (RSW), particularly within the electric vehicle industry. Notably, copper and aluminum have gained significant importance in these sectors due to their advantageous characteristics for the industry requirements. The mechanical behavior of these materials is essential to maintaining structural integrity. The study aims to estimate the mechanical behavior of dissimilar RSW joints and optimize welding parameters for Cu-Al joints. Hence, understanding the joining processes in the electric vehicle industry to design reliable components. Combining different types of materials, such as T2-grade commercially pure copper sheets and aluminum AA1050 with the same thickness of 1 mm has been welded. The determination of optimal welding conditions takes into account material thicknesses and types. Through tensile-shear testing, welding parameters that yield maximal joint strength were identified. Using Minitab 19 software, the Taguchi method helped achieve optimized welding parameters. The hardness, fracture characteristics, and weld strength have been investigated. Hardness measurements were conducted across the nugget thickness and surface, offering insights into potential failure modes. The welding process involves the transition to a liquid state for the aluminum components, resulting in the formation of intermetallic compounds. Consequently, crack initiation was observed within the aluminum segments, leading to a plug-out fracture mechanism. In contrast, copper exhibits superior strength and hardness compared to aluminum, where increased hardness correlates with heightened strength. The discrepancy in hardness, especially the lower values observed on the aluminum side, caused fractures to appear within the heat affected zone (HAZ). Subsequently, this fracture propagated until pull-out failure was realized. The study revealed that dissimilar joining of Cu and Al resulted in an ultimate tensile stress of 26 MPa, while similar joining of copper showcased a strength of 98 MPa. Additionally, the symmetric join in aluminum exhibited a strength of 93 MPa. The maximum tensile shear force is equal to 512 N at a maximum welding current of 14000 A. The pull-out failure mode occurs in the Cu-Al RSW joint. The maximum hardness was noted in the fusion zone (FZ). Relevant literature sources have supported and confirmed these outcomes.

Journal of Failure Analysis and Prevention, 2016

The focus of this research was on determining the cracking behavior when parameter such as the bi... more The focus of this research was on determining the cracking behavior when parameter such as the biaxiality ratio was varied. The crack propagation under mixed-mode loading was simulated by means of finite element method. The stress intensity factors have been calculated by the linear elastic fracture mechanics approach using fracture analysis code-2D (Franc2D). The crack growth under opening mode-I was considered because the crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. The numerical integration of Paris’ equation was carried out. The effect of normal and transverse applied load (σ x, and σ y, respectively) on crack propagation was presented. It was found that the fatigue crack growth was faster at a smaller biaxial stress ratio (λ), i.e., higher σ y on the horizontal crack plan. Moreover, fatigue strength values decrease as λ decreases. The results confirm the use of fracture mechanics approach in biaxial fracture.

Journal of Applied Science and Engineering, 2023

In the automotive industry, resistant spot welding is now frequently utilized to join similar or ... more In the automotive industry, resistant spot welding is now frequently utilized to join similar or dissimilar materials. Among these metals are copper and aluminum alloys. Electrical conductivity plays a significant role in the electromotive industry and its performance. Welded parts in electric cars are subjected to axial deformation and are often fractured due to tensile force. Hence, the conductivity may change due to the deformation. In this work, the changes in electrical conductivity due to the deformation will be studied. Therefore, electric resistance has been investigated in similar and dissimilar weld joints during the tensile tests. The relationship between weld deformation and conductivity has been presented. In general, similar weld joints will show high tensile shear strength. Therefore, dissimilar welds (Al-Cu) are showing less strength as compared with similar Cu-Cu and Al-Al joints. The results have been verified with the American Welding Society Standards. The electrical conductivity decreases with increasing deformation. Hence, similar weld joints conduct higher currents even after deformation.

Procedia Structural Integrity, 2020

Materials’ cracking is a first step of the fracture. Enamel and dentin like other materials suffe... more Materials’ cracking is a first step of the fracture. Enamel and dentin like other materials suffering from the cracks. During life or even through the denture treatments, the damage can be started. In this work, the crack path and fracture behavior of the teeth have been monitored. It was shown that the linear elastic fracture mechanics approach (LEFM) could evaluate the fracture toughness in teeth. The vertical crack is a traditional path of the fracture. The crack due to the cyclic loading like chewing will be propagated. The understanding of failure in teeth like another solid body, aims to decrease the failure risk. In addition, gives an insight for repairing treatments. Hence, early observations of the cracks will protect the teeth. Due to the brittleness of enamel and a little toughness of dentin, the dentin-enamel margins resist the crack propagation due to their fracture toughness and the cohesive properties. The crack path in teeth was simulated using the finite element software (FE).

The velocity of flow, permeability, and pressure distribution have been considered in this work. ... more The velocity of flow, permeability, and pressure distribution have been considered in this work. The transient simulation of a porous rock block has been carried out. Specific storage and Darcy's constants have been used as input parameters to investigate the material's behavior. Physically, the Darcy's constant and the storability are used to indicate the permeability in this simulation. Hence, the transient porous analysis was selected in this model using LISA FE software. This model describes the simulation of the fluid movement (velocity potential) using the injection of the fluid in a central hole of a block. In addition, the production well hole was simulated. Dramatically, the injection of fluid will produce the fracture surface. Hence, the flow behavior of a fractured surface was investigated in porous rock. Then the nature of the cracking surface and direction can be estimated using the flow map.

Ma’aen Journal for Medical Sciences (MAJMS), 2023

This work aims to explain the behavior of cracks in bones because the bone repairing mechanism is... more This work aims to explain the behavior of cracks in bones because the bone repairing mechanism is still somehow unknown. In this matter, different issues exist, such as the biological parameters (e.g., osteoblasts and osteoclasts), and the physical parameters (e.g., microcracks and defects). Traditionally, the bones respond to any load or defect within their microstructures. The defects and microcracks are increasing in the aged bone. Therefore, the damage increases unless the remodeling is completed. Remolded bones have increased fracture toughness. Hence, it is a basic mechanism for repair based on Wolff's law. The smaller crack lengths (e.g., less than 1 mm) are subjected faster to the repair process due to their intrinsic conditions like remodeling, plasticity, and bridging. The extension of the crack around the osteon and fiber bridging will increase the bone's toughness. In this work, the schematic conclusions have been presented.

Journal of Applied Science and Engineering, 2023

The investigation of the effects of rotary cylinders on the transfer of heat in a semicircular ca... more The investigation of the effects of rotary cylinders on the transfer of heat in a semicircular cavity occupied with air is presented in this paper. A constant and 2D laminar flow was assumed. Moreover, a Boussinesq approximation is applied to calculate density variations with temperature. Using a flexpde software program to solve the governing equations of energy, momentum, and continuity. The studied parameters are the rotational speed (Ω = 0 − 2000), the angle of inclination (γ = 0 − 90 •), Rayleigh number (10 4-10 7), and Prandtl number (0.7). The findings indicate that the average Nusselt number decreases with the increase in inclination angle, as the greatest value of the Nusselt number was found for an angle of inclination close to 0 •. Furthermore, for the range of inclination angles between 0 • − 45 • , the average Nusselt number increases gradually with increasing angular velocity values. The results have been benchmarked and a good agreement has been obtained. The objective of this study is to scrutinize the effect of the angle of inclination, and the rotational position of the cylinder on heat transfer. The largest and lowest values of the average Nusselt number take place at a location 0.1 and 0.2 of the cylinder center.

Advanced Engineering Forum, 2023

The effect of fracturing on the permeability and fluid flow of various Iraqi oil reservoirs has b... more The effect of fracturing on the permeability and fluid flow of various Iraqi oil reservoirs has been studied. Rumaila, Majnoon, and Zubair fields were investigated in this study. These reservoirs have different flow properties. The Element based Finite Volume Method (EbFVM) corresponding to the Dual Porosity Dual Permeability Model (DPDP) was used. The fractured reservoir in the Iraqi fields was studied for its single-phase fluid flow behavior. To represent the pressure distributions, ANSYS-CFX program was used. By making an internal hole, comparisons between the fractured and non-fractured cores have been presented. In this paper, the pressure for permeable cores of Rumaila field has been determined, since it requires a lower pressure. Therefore, experimental and numerical simulation can be verified. Hence, the proposed model for permeable cores will be used for impermeable cores. The required pressure for the impermeable cores of Majnoon and Zubair fields has been numerically determined due to the difficulties of the measuring of such high pressure using an experimental test. Therefore, the motivation of this study is to predict the pressure that the fluid-permeability device has to be considered to measure the permeability in impermeable environments. The results show that the expected pressure to make a flow into the core belonging to the Majnoon field reaches 1.724×10 7 Pa (2500 psi), while the expected pressure for the fluid to flow into the core belonging to the Zubair field reaches 1.379×10 8 Pa (20000 psi). Experimentally, the latter value is inapplicable.

Materials Science Forum, 2022

This work presents a comparative study of the mechanical properties of resistance spot welded joi... more This work presents a comparative study of the mechanical properties of resistance spot welded joints (RSW). RSW is widely used in sheet joining. Hence, the mechanical properties and their strength are presented. The main parameter is the welding current that has a big role on the heat generation and joint strength. The strength improvement due to the current increasing is regular and more effective than the weld time and the electrode pressure. Stainless steel has good weldability in sheet form. Galvanized steel, aluminum and carbon steel have been widely spotwelded. Moreover, dissimilar materials are also spot weldable where the two sheets of different metals can be joined. For the same sheet thickness at 1 mm, it was shown the shear strength of mild steel 3.8 KN, while for aluminum 1.4 KN this mean the shear strength of mild steel higher than aluminum. For the same metals, the increasing of the thickness will increase the strength. This is due to the weld area increasing. All the values were taken at the pull-out fracture condition. Hence, the suitable weld area at the welding condition was assumed. Fatigue strength for some metals has been presented. Fatigue strength of MS1300 is higher than those of steel DQSK, and steel DP800 at the for 1.6 mm thickness and stress ratio, R= 0.1. Because of the thickness, it has a minor effect on the fatigue properties of spot welded joints.

Material Design & Processing Communications, Nov 19, 2020

Early observations of cracks protect the teeth. The crack in teeth initiates due to the flaws, de... more Early observations of cracks protect the teeth. The crack in teeth initiates due to the flaws, defect, or inappropriate fillings design. The brittleness allows the crack to extend from any notches over the enamel due to the lower plasticity. Therefore, in this issue, linear elastic fracture mechanics (LEFM) assumptions will be used instead of the elastic–plastic fracture mechanics (EPFM). Traditionally, the vertical crack in the teeth is predominated. The load distributions over the crown and the cyclic loading will propagate the crack. There are limited works trying to simulate the crack in the teeth. In this work, the crack path (CP) and the fracture behavior of the tooth have been simulated. It was shown that LEFM is sufficient for such simulation.

The International Conference on Shape Memory and Superelastic Technologies , 2014

The fatigue crack growth under mixed-mode loading was simulated using finite element method (FEM)... more The fatigue crack growth under mixed-mode loading was simulated using finite element method (FEM). The stress intensity factors (SIFs) have been calculated by the linear elastic fracture mechanics approach (LEFM) using fracture analysis code-2D (Franc2D). Due to the symmetrical stress distribution around the crack tip in biaxial stressed specimen, the crack growth under opening mode-I was considered. The crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. Therefore, KI was used only in the numerical integration of the fatigue life equation. It was found that the fatigue crack growth was faster at a smaller λ, i.e., higher σy on the horizontal crack plan. Moreover, fatigue strength (FAT) values decrease as λ increasing. Finally, it was shown that FAT under λ can be predicted using the SIF and the concept of LEFM.

CP 2009, 2009

ABSTRACT. The determination of fatigue strength of welded joint across the board has big draw to ... more ABSTRACT. The determination of fatigue strength of welded joint across the board has big draw to evaluate fatigue life of welded joints. In spite of considerable fatigue design data which exist for welded joints in the recommendations, the studies for the effect of crack growth parameters C, m and initial crack length determinations of welded structures are still not clear and have not been discussed enough. Therefore, this paper aims to present procedures to find the FAT for welded geometries and determine initial crack depth. The new recommended limits of FAT for new geometries not listed yet in recommendations can be calculated according to backward calculations. Initial crack and crack growth parameter are determined.

Arabian Journal of Geosciences, 2021

This paper presents an experimental and numerical study to investigate the hydrodynamics behavior... more This paper presents an experimental and numerical study to investigate the hydrodynamics behavior of the fractured and nonfractured cores. The comparison between the simulated and experiments result is also presented. In this work, the Element Based Finite Volume Method (EbFVM) was used according to the Dual Porosity Dual Permeability Model (DPDP). The behavior of single-phase fluid flow in actual cores was studied for a fractured reservoir in Iraqi fields from Rumaila/Mishrif formation at different depths. ANSYS-CFX, a finite element based simulator was used to represent the pressure and velocity distributions. Therefore, the comparison between a fractured core and a nonfractured core was performed. The representation of fluid flow behavior in a fractured reservoir was presented. It is found that the presence of cracks increase the percentage of improvement in the productivity index to reach about (6.59% and 10.46%) for Rumaila core 14 and Rumaila core 15, respectively.

5th Scientific Conference of Baghdad University, 2003

Stainless steel has excellent mechanical properties and excessive corrosion resistance permits to... more Stainless steel has excellent mechanical properties and excessive corrosion resistance permits to use in the jet engine manufacture. Austenitic stainless steel specimens of type AISI 321 in a strip form were welded in a lap-joint form under various welding parameters (weld current and time) to show the effect of heat treatment (annealing and stress relieving) on the mechanical properties. It was shown that the welding variable and heat treatment has effects on the weld nugget properties. A metallurgical examination was made for weld area. This resulted in determination of the phenomena of high temperature crack growth due to holding time temperature of 750 ˚C. The delta-ferrite content increases with the heat input as confirmed by the magnetic scope examination. Finally, the most common defects that could experimentally appear in spot welding were found and detected. The authors believe that these phenomena are found for the first time and they did not publish any thing like it in literature.

Journal of Failure Analysis and Prevention, 2016

The focus of this research was on determining the cracking behavior when parameter such as the bi... more The focus of this research was on determining the cracking behavior when parameter such as the biaxiality ratio was varied. The crack propagation under mixed-mode loading was simulated by means of finite element method. The stress intensity factors have been calculated by the linear elastic fracture mechanics approach using fracture analysis code-2D (Franc2D). The crack growth under opening mode-I was considered because the crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. The numerical integration of Paris’ equation was carried out. The effect of normal and transverse applied load (σ x, and σ y, respectively) on crack propagation was presented. It was found that the fatigue crack growth was faster at a smaller biaxial stress ratio (λ), i.e., higher σ y on the horizontal crack plan. Moreover, fatigue strength values decrease as λ decreases. The results confirm the use of fracture mechanics approach in biaxial fracture.

Technische Universität Bergakademie Freiberg, 2010

Fracture Mechanics process of Welded Joint is a very vast research area and has many possibiliti... more Fracture Mechanics process of Welded Joint is a very vast research area and has
many possibilities for solution and prediction. Although the fatigue strength (FAT) and
stress intensity factor (SIF) solutions are reported in several handbooks and
recommendations, these values are available only for a small number of specimens,
components, loading and welding geometries. The available solutions are not always
adequate for particular engineering applications. Moreover, the reliable solutions of SIF
are still difficult to find in spite of several SIF handbooks have been published
regarding the nominal applied SIF. The effect of residual stresses is still the most
challenge in fatigue life estimation. The reason is that the stress distributions and SIF
modified by the residual stresses have to be estimated. The stress distribution is
governed by many parameters such as the materials type, joint geometry and welding
processes.
In this work, the linear elastic fracture mechanics (LEFM), which used crack tip SIFs
for cases involving the effect of weld geometry, is used to calculate the crack growth
life for some different notch cases.
The variety of crack configurations and the complexity of stress fields occurring in
engineering components require more versatile tools for calculating SIFs than available in handbook’s solutions that were obtained for a range of specific geometries and load combinations.
Therefore, the finite element method (FEM) has been used to calculate SIFs of
cracks subjected to stress fields. LEFM is encoded in the FEM software, FRANC,
which stands for fracture analysis code.
The SIFs due to residual stress are calculated in this work using the weight function
method.
The fatigue strength (FAT) of load-carrying and non-load carrying welded joints
with lack of penetration (LOP) and toe crack, respectively, are determined using the
LEFM. In some studied cases, the geometry, material properties and loading conditions
of the joints are identical to those of specimens for which experimental results of fatigue life and SIF were available in literature so that the FEM model could be validated.
For a given welded material and set of test conditions, the crack growth behavior is
described by the relationship between cyclic crack growth rate, da/dN, and range of the stress intensity factor (
K) , i.e., by Paris’ law. Numerical integration of the Paris’
equation is carried out by a FORTRAN computer routine. The obtained results can be
used for calculating FAT values. The computed SIFs along with the Paris’ law are used
to predict the crack propagation. The typical crack lengths for each joint geometry are
determined using the built language program by backward calculations.
To incorporate the effect of residual stresses, the fatigue crack growth equations
which are sensitive to stress ratio R are recommended to be used. The Forman, Newman and de Konig (FNK) solution is considered to be the most suitable one for the present purpose.
In spite of the recent considerable progress in fracture mechanics theories and
applications, there seems to be no, at least to the author’s knowledge, systematic study of the effect of welding geometries and residual stresses upon fatigue crack propagation based completely on an analytical approach where the SIF due to external applied load (Kapp) is calculated using FEM. In contrast, the SIF due to residual stresses (Kres) is calculated using the analytical weight function method and residual stress distribution.
To assess the influence of the residual stresses on the failure of a weldment, their
distribution must be known.
Although residual stresses in welded structures and components have long been
known to have an effect on the components fatigue performance, access to reliable,
spatially accurate residual stress field data are limited. This work constitutes a
systematic research program regarding the concept for the safety analysis of welded
components with fracture mechanics methods, to clarify the effect of welding residual
stresses upon fatigue crack propagation.

The determination of fatigue strength of welded joint across the board hasbig draw to evaluate fa... more The determination of fatigue strength of welded joint across the board hasbig draw to evaluate fatigue life of welded joints. In spite of considerable fatigue designdata which exist for welded joints in the recommendations, the studies for the effect ofcrack growth parameters C, m and initial crack length determinations of weldedstructures are still not clear and have not been discussed enough. Therefore, this paperaims to present procedures to find the FAT for welded geometries and determine initialcrack depth. The new recommended limits of FAT for new geometries not listed yet inrecommendations can be calculated according to backward calculations. Initial crackand crack growth parameter are determined

Mining of Mineral Deposits, 2024

This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, fo... more This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, focusing on the complex mechanisms within hot reservoirs. Non-commercial finite element (FE) software is used to visualize and present the results. Methods. The study involved the use of FE method with Visual Finite Element Analysis (VisualFEA) software to analyze the coupled phenomena of fluid flow and heat transfer in a rock sample. Special attention was given to incorporating material structure and geotechnical analysis in the software, as well as the treatment of cracked elements. In addition, the validation was done by comparing the current numerical solution using VisualFEA with the numerical solution using ANSYS Software. Findings. The study findings highlight the capabilities of VisualFEA software to accurately represent fluid flow, stress, and heat transfer in borehole-containing rocks. The results include insights into flow direction within the borehole, temperature distribution, and the validation of the software performance against expected system behavior. The study demonstrates the effectiveness of VisualFEA in handling complex loading and its ability to visualize multiple flow directions within a 2D model. The results are presented in the form of contours and curves. Originality. This study contributes to the field demonstrating the application of VisualFEA software in analyzing fluid flow and heat transfer in rocks with boreholes. The focus on incorporating material structure, geotechnical analysis, and treatment of cracked elements adds originality to the study, providing a comprehensive understanding of the coupled phenomena in hot reservoirs. Practical implications. The practical significance of this study is in the validation and benchmarking of VisualFEA software for studying fluid flow and heat transfer in geotechnical application. The findings can be utilized by geotechnical engineers and researchers to better understand the behavior of borehole-containing rocks under specific pressure and thermal loading conditions. The insights gained from this study can be used in decision-making processes related to resource mining, reservoir engineering, and geothermal energy use.

Case Studies in Thermal Engineering, 2024

The free convection of a non-Newtonian fluid in an equilateral triangular cavity containing a tri... more The free convection of a non-Newtonian fluid in an equilateral triangular cavity containing a triangle obstruction in various positions is investigated numerically in this paper. The research is carried out using the finite element method. The sloped side walls are adiabatic, while the bottom is kept heated. At the obstacle, three positions are examined. The effects of different power law indexes on free convection have been investigated. The temperature field, fluid flow, and heat transfer are all highly influenced by the obstacle's location, Rayleigh number, and power law index. The resulting outcomes are confirmed using existing results in the literature and verified using a grid sensitivity analysis. A comparison of the current results to those found in the literature demonstrates the study's dependability and trustworthiness. Nomenclature B cold obstacle location ε ij strain rate = 1/2(∂ u i / ∂ x j + ∂ u j / ∂ x i

Engineering and Technology Journal, 2024

Resistance spot welding (RSW) is widely used in the automotive industry, particularly for copper-... more Resistance spot welding (RSW) is widely used in the automotive industry, particularly for copper-aluminum alloys in electric cars. RSW joint conductivity is crucial for electric vehicles. Welded parts may fracture due to tension, altering conductivity. The study examines resistance spot post-weld joint metallurgy and deformation-induced conductivity changes. The electric resistance of similar and dissimilar RSW joints was examined during tensile tests. Metallurgical tests for RSW joints revealed an increase in grain size from the base metal (BM) to the heat-affected zone (HAZ) and finally the fusion zone (FZ). Satisfactory shear tension strength results were obtained for dissimilar joints (Al-Cu) at 690 N and similar joints (Al-Al) at 780 N, exceeding the minimum limit of 643 N. However, weld strength in similar joints (Cu-Cu) only achieved 933 N, less than the required strength of 1528 N. Furthermore, the relationship between deformation rate (i.e., applied stress) and electrical resistance has been shown. It was found that resistivity increases with increasing deformation stress, resulting in decreased electrical conductivity with a high percentage, representing 99.8, 99.66, and 99.49% for Al-Cu, Al-Al, and Cu-Cu RSW joints, respectively. The electrical resistance was measured at the maximum force of 650 N and maximum stress of 33.1 MPa. The results show (15.7 Ώ, 5.9 Ώ, and 1.99 Ώ) and the electrical conductivities (0.063 IS, 0.169 IS, and 0.502 IS) for the joints (Al-Cu), (Al-Al), and (Cu-Cu), respectively

Diagnostyka, 2024

Recently, dissimilar metals have found applications in the process of resistance spot welding (RS... more Recently, dissimilar metals have found applications in the process of resistance spot welding (RSW), particularly within the electric vehicle industry. Notably, copper and aluminum have gained significant importance in these sectors due to their advantageous characteristics for the industry requirements. The mechanical behavior of these materials is essential to maintaining structural integrity. The study aims to estimate the mechanical behavior of dissimilar RSW joints and optimize welding parameters for Cu-Al joints. Hence, understanding the joining processes in the electric vehicle industry to design reliable components. Combining different types of materials, such as T2-grade commercially pure copper sheets and aluminum AA1050 with the same thickness of 1 mm has been welded. The determination of optimal welding conditions takes into account material thicknesses and types. Through tensile-shear testing, welding parameters that yield maximal joint strength were identified. Using Minitab 19 software, the Taguchi method helped achieve optimized welding parameters. The hardness, fracture characteristics, and weld strength have been investigated. Hardness measurements were conducted across the nugget thickness and surface, offering insights into potential failure modes. The welding process involves the transition to a liquid state for the aluminum components, resulting in the formation of intermetallic compounds. Consequently, crack initiation was observed within the aluminum segments, leading to a plug-out fracture mechanism. In contrast, copper exhibits superior strength and hardness compared to aluminum, where increased hardness correlates with heightened strength. The discrepancy in hardness, especially the lower values observed on the aluminum side, caused fractures to appear within the heat affected zone (HAZ). Subsequently, this fracture propagated until pull-out failure was realized. The study revealed that dissimilar joining of Cu and Al resulted in an ultimate tensile stress of 26 MPa, while similar joining of copper showcased a strength of 98 MPa. Additionally, the symmetric join in aluminum exhibited a strength of 93 MPa. The maximum tensile shear force is equal to 512 N at a maximum welding current of 14000 A. The pull-out failure mode occurs in the Cu-Al RSW joint. The maximum hardness was noted in the fusion zone (FZ). Relevant literature sources have supported and confirmed these outcomes.

Journal of Failure Analysis and Prevention, 2016

The focus of this research was on determining the cracking behavior when parameter such as the bi... more The focus of this research was on determining the cracking behavior when parameter such as the biaxiality ratio was varied. The crack propagation under mixed-mode loading was simulated by means of finite element method. The stress intensity factors have been calculated by the linear elastic fracture mechanics approach using fracture analysis code-2D (Franc2D). The crack growth under opening mode-I was considered because the crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. The numerical integration of Paris’ equation was carried out. The effect of normal and transverse applied load (σ x, and σ y, respectively) on crack propagation was presented. It was found that the fatigue crack growth was faster at a smaller biaxial stress ratio (λ), i.e., higher σ y on the horizontal crack plan. Moreover, fatigue strength values decrease as λ decreases. The results confirm the use of fracture mechanics approach in biaxial fracture.

Journal of Applied Science and Engineering, 2023

In the automotive industry, resistant spot welding is now frequently utilized to join similar or ... more In the automotive industry, resistant spot welding is now frequently utilized to join similar or dissimilar materials. Among these metals are copper and aluminum alloys. Electrical conductivity plays a significant role in the electromotive industry and its performance. Welded parts in electric cars are subjected to axial deformation and are often fractured due to tensile force. Hence, the conductivity may change due to the deformation. In this work, the changes in electrical conductivity due to the deformation will be studied. Therefore, electric resistance has been investigated in similar and dissimilar weld joints during the tensile tests. The relationship between weld deformation and conductivity has been presented. In general, similar weld joints will show high tensile shear strength. Therefore, dissimilar welds (Al-Cu) are showing less strength as compared with similar Cu-Cu and Al-Al joints. The results have been verified with the American Welding Society Standards. The electrical conductivity decreases with increasing deformation. Hence, similar weld joints conduct higher currents even after deformation.

Procedia Structural Integrity, 2020

Materials’ cracking is a first step of the fracture. Enamel and dentin like other materials suffe... more Materials’ cracking is a first step of the fracture. Enamel and dentin like other materials suffering from the cracks. During life or even through the denture treatments, the damage can be started. In this work, the crack path and fracture behavior of the teeth have been monitored. It was shown that the linear elastic fracture mechanics approach (LEFM) could evaluate the fracture toughness in teeth. The vertical crack is a traditional path of the fracture. The crack due to the cyclic loading like chewing will be propagated. The understanding of failure in teeth like another solid body, aims to decrease the failure risk. In addition, gives an insight for repairing treatments. Hence, early observations of the cracks will protect the teeth. Due to the brittleness of enamel and a little toughness of dentin, the dentin-enamel margins resist the crack propagation due to their fracture toughness and the cohesive properties. The crack path in teeth was simulated using the finite element software (FE).

The velocity of flow, permeability, and pressure distribution have been considered in this work. ... more The velocity of flow, permeability, and pressure distribution have been considered in this work. The transient simulation of a porous rock block has been carried out. Specific storage and Darcy's constants have been used as input parameters to investigate the material's behavior. Physically, the Darcy's constant and the storability are used to indicate the permeability in this simulation. Hence, the transient porous analysis was selected in this model using LISA FE software. This model describes the simulation of the fluid movement (velocity potential) using the injection of the fluid in a central hole of a block. In addition, the production well hole was simulated. Dramatically, the injection of fluid will produce the fracture surface. Hence, the flow behavior of a fractured surface was investigated in porous rock. Then the nature of the cracking surface and direction can be estimated using the flow map.

Ma’aen Journal for Medical Sciences (MAJMS), 2023

This work aims to explain the behavior of cracks in bones because the bone repairing mechanism is... more This work aims to explain the behavior of cracks in bones because the bone repairing mechanism is still somehow unknown. In this matter, different issues exist, such as the biological parameters (e.g., osteoblasts and osteoclasts), and the physical parameters (e.g., microcracks and defects). Traditionally, the bones respond to any load or defect within their microstructures. The defects and microcracks are increasing in the aged bone. Therefore, the damage increases unless the remodeling is completed. Remolded bones have increased fracture toughness. Hence, it is a basic mechanism for repair based on Wolff's law. The smaller crack lengths (e.g., less than 1 mm) are subjected faster to the repair process due to their intrinsic conditions like remodeling, plasticity, and bridging. The extension of the crack around the osteon and fiber bridging will increase the bone's toughness. In this work, the schematic conclusions have been presented.

Journal of Applied Science and Engineering, 2023

The investigation of the effects of rotary cylinders on the transfer of heat in a semicircular ca... more The investigation of the effects of rotary cylinders on the transfer of heat in a semicircular cavity occupied with air is presented in this paper. A constant and 2D laminar flow was assumed. Moreover, a Boussinesq approximation is applied to calculate density variations with temperature. Using a flexpde software program to solve the governing equations of energy, momentum, and continuity. The studied parameters are the rotational speed (Ω = 0 − 2000), the angle of inclination (γ = 0 − 90 •), Rayleigh number (10 4-10 7), and Prandtl number (0.7). The findings indicate that the average Nusselt number decreases with the increase in inclination angle, as the greatest value of the Nusselt number was found for an angle of inclination close to 0 •. Furthermore, for the range of inclination angles between 0 • − 45 • , the average Nusselt number increases gradually with increasing angular velocity values. The results have been benchmarked and a good agreement has been obtained. The objective of this study is to scrutinize the effect of the angle of inclination, and the rotational position of the cylinder on heat transfer. The largest and lowest values of the average Nusselt number take place at a location 0.1 and 0.2 of the cylinder center.

Advanced Engineering Forum, 2023

The effect of fracturing on the permeability and fluid flow of various Iraqi oil reservoirs has b... more The effect of fracturing on the permeability and fluid flow of various Iraqi oil reservoirs has been studied. Rumaila, Majnoon, and Zubair fields were investigated in this study. These reservoirs have different flow properties. The Element based Finite Volume Method (EbFVM) corresponding to the Dual Porosity Dual Permeability Model (DPDP) was used. The fractured reservoir in the Iraqi fields was studied for its single-phase fluid flow behavior. To represent the pressure distributions, ANSYS-CFX program was used. By making an internal hole, comparisons between the fractured and non-fractured cores have been presented. In this paper, the pressure for permeable cores of Rumaila field has been determined, since it requires a lower pressure. Therefore, experimental and numerical simulation can be verified. Hence, the proposed model for permeable cores will be used for impermeable cores. The required pressure for the impermeable cores of Majnoon and Zubair fields has been numerically determined due to the difficulties of the measuring of such high pressure using an experimental test. Therefore, the motivation of this study is to predict the pressure that the fluid-permeability device has to be considered to measure the permeability in impermeable environments. The results show that the expected pressure to make a flow into the core belonging to the Majnoon field reaches 1.724×10 7 Pa (2500 psi), while the expected pressure for the fluid to flow into the core belonging to the Zubair field reaches 1.379×10 8 Pa (20000 psi). Experimentally, the latter value is inapplicable.

Materials Science Forum, 2022

This work presents a comparative study of the mechanical properties of resistance spot welded joi... more This work presents a comparative study of the mechanical properties of resistance spot welded joints (RSW). RSW is widely used in sheet joining. Hence, the mechanical properties and their strength are presented. The main parameter is the welding current that has a big role on the heat generation and joint strength. The strength improvement due to the current increasing is regular and more effective than the weld time and the electrode pressure. Stainless steel has good weldability in sheet form. Galvanized steel, aluminum and carbon steel have been widely spotwelded. Moreover, dissimilar materials are also spot weldable where the two sheets of different metals can be joined. For the same sheet thickness at 1 mm, it was shown the shear strength of mild steel 3.8 KN, while for aluminum 1.4 KN this mean the shear strength of mild steel higher than aluminum. For the same metals, the increasing of the thickness will increase the strength. This is due to the weld area increasing. All the values were taken at the pull-out fracture condition. Hence, the suitable weld area at the welding condition was assumed. Fatigue strength for some metals has been presented. Fatigue strength of MS1300 is higher than those of steel DQSK, and steel DP800 at the for 1.6 mm thickness and stress ratio, R= 0.1. Because of the thickness, it has a minor effect on the fatigue properties of spot welded joints.

Material Design & Processing Communications, Nov 19, 2020

Early observations of cracks protect the teeth. The crack in teeth initiates due to the flaws, de... more Early observations of cracks protect the teeth. The crack in teeth initiates due to the flaws, defect, or inappropriate fillings design. The brittleness allows the crack to extend from any notches over the enamel due to the lower plasticity. Therefore, in this issue, linear elastic fracture mechanics (LEFM) assumptions will be used instead of the elastic–plastic fracture mechanics (EPFM). Traditionally, the vertical crack in the teeth is predominated. The load distributions over the crown and the cyclic loading will propagate the crack. There are limited works trying to simulate the crack in the teeth. In this work, the crack path (CP) and the fracture behavior of the tooth have been simulated. It was shown that LEFM is sufficient for such simulation.

The International Conference on Shape Memory and Superelastic Technologies , 2014

The fatigue crack growth under mixed-mode loading was simulated using finite element method (FEM)... more The fatigue crack growth under mixed-mode loading was simulated using finite element method (FEM). The stress intensity factors (SIFs) have been calculated by the linear elastic fracture mechanics approach (LEFM) using fracture analysis code-2D (Franc2D). Due to the symmetrical stress distribution around the crack tip in biaxial stressed specimen, the crack growth under opening mode-I was considered. The crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. Therefore, KI was used only in the numerical integration of the fatigue life equation. It was found that the fatigue crack growth was faster at a smaller λ, i.e., higher σy on the horizontal crack plan. Moreover, fatigue strength (FAT) values decrease as λ increasing. Finally, it was shown that FAT under λ can be predicted using the SIF and the concept of LEFM.

CP 2009, 2009

ABSTRACT. The determination of fatigue strength of welded joint across the board has big draw to ... more ABSTRACT. The determination of fatigue strength of welded joint across the board has big draw to evaluate fatigue life of welded joints. In spite of considerable fatigue design data which exist for welded joints in the recommendations, the studies for the effect of crack growth parameters C, m and initial crack length determinations of welded structures are still not clear and have not been discussed enough. Therefore, this paper aims to present procedures to find the FAT for welded geometries and determine initial crack depth. The new recommended limits of FAT for new geometries not listed yet in recommendations can be calculated according to backward calculations. Initial crack and crack growth parameter are determined.

Arabian Journal of Geosciences, 2021

This paper presents an experimental and numerical study to investigate the hydrodynamics behavior... more This paper presents an experimental and numerical study to investigate the hydrodynamics behavior of the fractured and nonfractured cores. The comparison between the simulated and experiments result is also presented. In this work, the Element Based Finite Volume Method (EbFVM) was used according to the Dual Porosity Dual Permeability Model (DPDP). The behavior of single-phase fluid flow in actual cores was studied for a fractured reservoir in Iraqi fields from Rumaila/Mishrif formation at different depths. ANSYS-CFX, a finite element based simulator was used to represent the pressure and velocity distributions. Therefore, the comparison between a fractured core and a nonfractured core was performed. The representation of fluid flow behavior in a fractured reservoir was presented. It is found that the presence of cracks increase the percentage of improvement in the productivity index to reach about (6.59% and 10.46%) for Rumaila core 14 and Rumaila core 15, respectively.

5th Scientific Conference of Baghdad University, 2003

Stainless steel has excellent mechanical properties and excessive corrosion resistance permits to... more Stainless steel has excellent mechanical properties and excessive corrosion resistance permits to use in the jet engine manufacture. Austenitic stainless steel specimens of type AISI 321 in a strip form were welded in a lap-joint form under various welding parameters (weld current and time) to show the effect of heat treatment (annealing and stress relieving) on the mechanical properties. It was shown that the welding variable and heat treatment has effects on the weld nugget properties. A metallurgical examination was made for weld area. This resulted in determination of the phenomena of high temperature crack growth due to holding time temperature of 750 ˚C. The delta-ferrite content increases with the heat input as confirmed by the magnetic scope examination. Finally, the most common defects that could experimentally appear in spot welding were found and detected. The authors believe that these phenomena are found for the first time and they did not publish any thing like it in literature.

Journal of Failure Analysis and Prevention, 2016

The focus of this research was on determining the cracking behavior when parameter such as the bi... more The focus of this research was on determining the cracking behavior when parameter such as the biaxiality ratio was varied. The crack propagation under mixed-mode loading was simulated by means of finite element method. The stress intensity factors have been calculated by the linear elastic fracture mechanics approach using fracture analysis code-2D (Franc2D). The crack growth under opening mode-I was considered because the crack growth occurs mainly along the direction where the mode-I stress component becomes the maximum. The numerical integration of Paris’ equation was carried out. The effect of normal and transverse applied load (σ x, and σ y, respectively) on crack propagation was presented. It was found that the fatigue crack growth was faster at a smaller biaxial stress ratio (λ), i.e., higher σ y on the horizontal crack plan. Moreover, fatigue strength values decrease as λ decreases. The results confirm the use of fracture mechanics approach in biaxial fracture.

Technische Universität Bergakademie Freiberg, 2010

Fracture Mechanics process of Welded Joint is a very vast research area and has many possibiliti... more Fracture Mechanics process of Welded Joint is a very vast research area and has
many possibilities for solution and prediction. Although the fatigue strength (FAT) and
stress intensity factor (SIF) solutions are reported in several handbooks and
recommendations, these values are available only for a small number of specimens,
components, loading and welding geometries. The available solutions are not always
adequate for particular engineering applications. Moreover, the reliable solutions of SIF
are still difficult to find in spite of several SIF handbooks have been published
regarding the nominal applied SIF. The effect of residual stresses is still the most
challenge in fatigue life estimation. The reason is that the stress distributions and SIF
modified by the residual stresses have to be estimated. The stress distribution is
governed by many parameters such as the materials type, joint geometry and welding
processes.
In this work, the linear elastic fracture mechanics (LEFM), which used crack tip SIFs
for cases involving the effect of weld geometry, is used to calculate the crack growth
life for some different notch cases.
The variety of crack configurations and the complexity of stress fields occurring in
engineering components require more versatile tools for calculating SIFs than available in handbook’s solutions that were obtained for a range of specific geometries and load combinations.
Therefore, the finite element method (FEM) has been used to calculate SIFs of
cracks subjected to stress fields. LEFM is encoded in the FEM software, FRANC,
which stands for fracture analysis code.
The SIFs due to residual stress are calculated in this work using the weight function
method.
The fatigue strength (FAT) of load-carrying and non-load carrying welded joints
with lack of penetration (LOP) and toe crack, respectively, are determined using the
LEFM. In some studied cases, the geometry, material properties and loading conditions
of the joints are identical to those of specimens for which experimental results of fatigue life and SIF were available in literature so that the FEM model could be validated.
For a given welded material and set of test conditions, the crack growth behavior is
described by the relationship between cyclic crack growth rate, da/dN, and range of the stress intensity factor (
K) , i.e., by Paris’ law. Numerical integration of the Paris’
equation is carried out by a FORTRAN computer routine. The obtained results can be
used for calculating FAT values. The computed SIFs along with the Paris’ law are used
to predict the crack propagation. The typical crack lengths for each joint geometry are
determined using the built language program by backward calculations.
To incorporate the effect of residual stresses, the fatigue crack growth equations
which are sensitive to stress ratio R are recommended to be used. The Forman, Newman and de Konig (FNK) solution is considered to be the most suitable one for the present purpose.
In spite of the recent considerable progress in fracture mechanics theories and
applications, there seems to be no, at least to the author’s knowledge, systematic study of the effect of welding geometries and residual stresses upon fatigue crack propagation based completely on an analytical approach where the SIF due to external applied load (Kapp) is calculated using FEM. In contrast, the SIF due to residual stresses (Kres) is calculated using the analytical weight function method and residual stress distribution.
To assess the influence of the residual stresses on the failure of a weldment, their
distribution must be known.
Although residual stresses in welded structures and components have long been
known to have an effect on the components fatigue performance, access to reliable,
spatially accurate residual stress field data are limited. This work constitutes a
systematic research program regarding the concept for the safety analysis of welded
components with fracture mechanics methods, to clarify the effect of welding residual
stresses upon fatigue crack propagation.

The determination of fatigue strength of welded joint across the board hasbig draw to evaluate fa... more The determination of fatigue strength of welded joint across the board hasbig draw to evaluate fatigue life of welded joints. In spite of considerable fatigue designdata which exist for welded joints in the recommendations, the studies for the effect ofcrack growth parameters C, m and initial crack length determinations of weldedstructures are still not clear and have not been discussed enough. Therefore, this paperaims to present procedures to find the FAT for welded geometries and determine initialcrack depth. The new recommended limits of FAT for new geometries not listed yet inrecommendations can be calculated according to backward calculations. Initial crackand crack growth parameter are determined