Papers by A.M. Al-Mukhtar
Journal of Applied Science and Engineering, 2025
For decades, resistance spot welding (RSW) between aluminum and copper has encountered difficulti... more For decades, resistance spot welding (RSW) between aluminum and copper has encountered difficulties; however, it remains essential for modern applications. Additionally, crack propagation and the stress intensity factor (SIF) of dissimilar RSW have not been extensively investigated. The welding parameters used for Al-Al joints were as follows: welding current, time, and electrode force were set at 14,000 Amps, 0.8 seconds, and 7,000 N, respectively. Conversely, for Al-Cu joints, 14,000 Amps, 1 second, and 8,800 N were determined. The similar joints exhibited an average weld nugget size of 6 mm, whereas the dissimilar joints had a nugget size of 5.2 mm. The tensile shear force was 690 N and 780 N for dissimilar and similar joints, respectively. Accordingly, the fatigue load, as a percentage of the tensile force, was utilized at 414 N and 468 N for Al-Cu and Al-Al, respectively. Finite Element Analysis (FEA) was employed to determine the SIF. The initial crack length was determined to be 0.1 mm. The numerical solution was then compared with theoretical solutions for the opening SIF-KI, such as the equations proposed by Pook and Zhang. The FEA results showed higher values of SIF compared to those from theoretical solutions. Additionally, crack propagation was investigated for both dissimilar and similar joints at a determined failure load. Cracks tended to develop close to the heat-affected zone (HAZ) around the weld nugget diameter (d n). SIF and crack path have been verified.
Experimental and Numerical Investigation of Mechanical Properties and Stress Intensity Factor of Dissimilar Spot Weld Joints
Journal of Materials Engineering and Performance, 2024
In this work, finite element analysis (FEA) was used to simulate the resistance spot welding proc... more In this work, finite element analysis (FEA) was used to simulate the resistance spot welding process (RSW) of aluminum (Al), and copper (Cu). By determining the optimum welding parameters for similar aluminum (Al-Al) and dissimilar (Al-Cu) joints, the weld nugget diameter was determined numerically and experimentally. Hence, the tensile force has been determined and compared with the FE model. The tensile shear force was determined to be equal to 690 N and 780 N for dissimilar and similar joints, respectively. To study the fracture behavior of such joints, crack propagation and stress intensity factor (SIF) have been simulated and calculated. The fatigue load as a percentage of the tensile force was used at 414 and 468 N for Al-Cu and Al-Al, respectively. The SIF solutions have been verified by comparing FE with available solutions from literature such as Pook and Zhang. The results revealed the optimum parameters to be a welding current of 14,000 A, an electrode force of 8,800 N, and a welding time of 1 second, Crack propagation was investigated at a stress ratio R = 0.1 and initial length 0.1 mm. Cracks tended to develop close to the heat-affected zone (HAZ) around weld nugget diameter (dn). The results show that the numerical results are in good agreement with the experiment results and the available theoretical solution of SIF.
Journal of Applied Science and Engineering, 2025
Deep drawing of high-density polyethylene (HDPE) reinforced with woven carbon fibers (WCFs) demon... more Deep drawing of high-density polyethylene (HDPE) reinforced with woven carbon fibers (WCFs) demonstrates excellent resilience under stress, making it a promising material for applications demanding high strength and durability. This study investigated the influence of forming parameters, including temperature, forming depth, and punch velocity, on the deep drawability of HDPE-WCF composites. A dedicated experimental rig was designed and constructed for this purpose. Results indicate that increasing the forming temperature enhances the material’s flexibility, thereby reducing the required forming force. However, careful temperature control is crucial to prevent melting and potential degradation of material properties. The optimal forming temperature range was determined to be between 80◦C and 90◦C, significantly improving material formability. Conversely, at temperatures below 80◦C, increasing the forming depth and velocity can increase the risk of material tearing and significantly elevate the required forming force.
Procedia Structural Integrity, 2024
This review examines three primary forming techniques for composite materials: single-point incre... more This review examines three primary forming techniques for composite materials: single-point incremental forming (SPIF), vacuum forming, and compression molding. SPIF involves applying localized pressure to thermoplastic sheets, enabling the formation of complex geometrical shapes. Vacuum forming uses vacuum pressure to mold heated sheets over forms, making it well-suited for large-scale production of simpler components. Compression molding, including techniques like Sheet Molding Compound (SMC) and Injection Molding, entails compressing heated composite materials in molds under high pressure to produce strong, durable parts. The discussion of the SPIF method will cover process parameters and optimization, SPIF of hole flanges, workpiece geometry, software tools, biocompatible polymers, and heating techniques. Additionally, the review will explore different formation types in vacuum forming and compression molding. Understanding these methods is crucial for various industries utilizing composite materials, particularly with regard to their cracking behavior. These techniques offer flexibility, efficiency, and precision in producing composite components with diverse geometries and properties, addressing contemporary engineering and design challenges.
Journal of Science And Engineering Application, 2018
This work presents a short overview about the spot welding and metal weldability. This process ha... more This work presents a short overview about the spot welding and metal weldability. This process has important applications in industry. The ease of use, ability to use in field, and adjustable according to the work-piece conditions, makes spot welding one of the best processes for sheet metal fabrications. Stainless steel has a good weldability in a sheet form; however, still there is a lack of information about their spot weldabiltiy. Nevertheless, aluminium and carbon steel have been welded widely in a plate form using resistance spot welding (RSW). Galvanized steel has a fusion problem at the faying coated surfaces. The parameters of welding process have been conducted extensively. These parameters are influenced the joint strength. The main parameter is the welding current. It has a big role in the heat generation equation. Higher machine setting causes an expulsion of molten metal and reduction in strength. The microstructure and design parameters are still under investigation regarding the nugget, cracks formation and weldability. Moreover, dissimilar materials welding and the effect weld area of fatigue properties are investigated.
Procedia Structural Integrity, 2026
Cracking in teeth is often caused by defects, aging, or poorly designed fillings. Vertical openin... more Cracking in teeth is often caused by defects, aging, or poorly designed fillings. Vertical opening fractures are particularly common. Therefore, Mode-I fracture mechanics were applied in the current simulation based on the simulated stress distribution at the dentin. Using finite element analysis, the crack path and fracture behavior were simulated. An oblique bite force of 453 N, applied at a 45° angle to the longitudinal axis of the tooth structure, was used. Minimum and maximum dentin properties were investigated to assess their influence on fracture initiation and propagation. Three different load levels were applied to examine and compare the degree of crack propagation and the effect of varying loads on crack growth. Results showed that teeth with maximum anisotropic dentin required approximately 100 N more force than those with minimum properties to transition into the crack development phase. The stress intensity factor (SIF), which determines stress concentration and crack tip propagation, was calculated for the applied loads. Higher loads resulted in higher SIF values, thereby reducing fatigue life.
Fatigue & Fracture of Engineering Materials & Structures, 2025
This letter presents a focused, simulation-based investigation of the fatigue fracture behavior o... more This letter presents a focused, simulation-based investigation of the fatigue fracture behavior of human enamel and dentin, with an emphasis on stress intensity factors (SIFs) at crack tips under cyclic loading. The findings aim to contribute to a better understanding of crack propagation in biological materials using a simulator based on the Linear Elastic Fracture Mechanics (LEFM) approach.
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.
Jordan journal of mechanical and industrial engineering, May 28, 2024
Resistance spot welding (RSW) is the most commonly used method for joining sheet metals structure... more Resistance spot welding (RSW) is the most commonly used method for joining sheet metals structures in the automotive industry. The cyclic loading conditions on RSW joints can lead to fatigue failure, hence, affecting their reliability and durability. The comprehension of the fatigue strength for the RSW is very critical, especially for the dissimilar RSW joints. This study presents analyses to characterize the fatigue behavior of these joints. Therefore, the crack propagation, and fatigue life under specific loading conditions have been studied. The fatigue strength of similar aluminum Al-1050, and dissimilar copper with aluminum Cu-Al RSW joints was examined experimentally and numerically. The lap-sheet materials were spot welded using optimum welding parameters to ensure a consistent range for the produced weld nugget. In this work, the experimental test rig has been designed and established to have an axial fatigue load. The high cycle fatigue tests were performed, and the P-N curves were obtained. The work was analyzed numerically using finite element (FE) analysis, in conjunction with experimental results. Aluminum sheet joint has the highest fatigue limit as compared to dissimilar Cu-Al joints. The crack growth rate of the similar RSW joint is slower than those of dissimilar joints because it has higher stress intensity factor (SIF). The coefficients of the Paris’ constants, C and m, have been determined.
Engineering and Technology Journal, Dec 27, 2023
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, which represents 99.8, 99.66, and 99.49% for Al-Cu, Al-Al, and Cu-Cu RSW joints, respectively. At the maximum force of 650 N and maximum stress of 33.1 MPa, the electrical resistance was measured, and 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.
Maaen Journal for Medical Sciences, Aug 13, 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.
Advanced engineering forum, Aug 1, 2019
Fatigue plays a significant role in the crack growth of the fuselage skin structures. In addition... more Fatigue plays a significant role in the crack growth of the fuselage skin structures. In addition, the fuselage may suffer also from the corrosion damage, and the wear defects. The proper maintenance and scheduled test intervals can avoid the sudden skin failure. Therefore, the inspection interval has to be shortened. Nevertheless, the young machines may be also suffering from the unexpected skin rupture. The cracks are emanating from the rivets and the holes under cyclic loading. The stress concentration around the notch has an effective role under the effect of cyclic loading. The cracks propagate toward the high stressed area such as the notches or other crack locations. The propagation into a critical crack size is rather fast and causes a sudden aircraft fuselage cracking. Hence, the number of cycles to failure will be decreased dramatically. During the last decades, the fracture toughness, design, and the new alloying element have been enhanced. The previous fuselage failures show that the inspections against the cracking are recommended even after a few thousand of cycles. To prevent the crack extending, the crack arresting is recommended to use around the fuselage.
Procedia structural integrity, 2020
The fatigue failure is predominate in the aircraft fuselage. The fuselage skin consists of the sh... more The fatigue failure is predominate in the aircraft fuselage. The fuselage skin consists of the shell and stingers. Fatigue plays a significant role in the crack growth of the skin structures. The proper maintenance and scheduled test intervals may avoid sudden skin failure and crack path (CP). With exiting the cracks, the propagation rate increases dramatically. Therefore, shortening the regular inspection intervals is recommended. Nevertheless, the young machines may have also unexpected skin rupture. The cracks are emanating from the notches such as rivets and the holes under the cyclic loading. The stresses concentrated around these notches. The stress concentration provides the unique conditions for crack initiation. Therefore, the cracks tend to connect with each other. Hence, the number of cycles to failure is decreased dramatically. Although the last decades, the fracture toughness, design, and new alloying element are enhanced. According to the traditional fuselage failure, the crack inspections are recommended even after a few thousand cycles.
Advanced engineering forum, Aug 1, 2018
The shear strength of 302 austenitic stainless steel spot welds has been studied. Thewelding curr... more The shear strength of 302 austenitic stainless steel spot welds has been studied. Thewelding current in resistance spot welding process (RSW) plays a significant role. However,this item's effect is well known and extensively studied in the previous literature. This work aims toshow the heat treatment’s effect on different joints that welded at various current. The experimentalresults show that the tensile shear strength is increased with increasing the current. Annealingtreatment improves the tensile shear strength due to the reformation of the grain size and removesthe residual stresses. Grain refinement is an effective technique for improving the strength.Therefore, the tensile shear strength is increased by annealing treatment temperature up to 750 °C.However, at 850°C, the tensile shear strength is dropped down.
Procedia structural integrity, 2020
Hydrogels have been studied for replacing the degenerative nucleus pulpousus (NP) due to their bi... more Hydrogels have been studied for replacing the degenerative nucleus pulpousus (NP) due to their biocompatibilities and they resemble the viscoelastic properties of the native tissue. The mechanical behavior of these materials under unconfined compression that exhibited the non-linear behavior has not been intensively highlighted. The goal of this study is to utilize the strain energy density functions (SEDFs) to determine a suitable constitutive model that represents the nonlinear behavior of the hydrogels under unconfined compression test. In this context, hyperelastic models, such as Ogden, Neo-Hookean, Mooney-Rivlin and Yeoh models are selected to fit the experimental data for the hydrogels. The aim of using these models is also to predict the behavior of these materials out of range of the test (i.e. in tension). Therefore, FEA using ABAQUS/CAE is adopted to verify the hyperelastic models in compression and to validate the ability of the hyperelastic models of predicting the nonlinear behavior of the hydrogels in tension. The results showed that all hyperelastic models are fitted the experimental data and the predicted results by FEA agree with those of the test data. Ogden (N=1) model has well defined the nonlinear behavior of those types of material and was used in the FEA simulation.
Material design & processing communications, Aug 1, 2021
Hydrogels are viscoelastic material, soft and fragile materials that contain high water percent. ... more Hydrogels are viscoelastic material, soft and fragile materials that contain high water percent. These properties cannot sustain high axial compression loads. In this study, a foam was infused into hydrogel, agarose, to enhance the mechanical properties of the hydrogel/foam composite. Besides, it is difficult to measure the mechanical properties of the hydrogel alone specifically in tension because of the slipping in the grip during using the common tensile test. Therefore; the goal of this study is to investigate the influences of infused cellulose foam into the prepared hydrogels on the mechanical properties of the hydrogels by conducting the unconfined compression on hydrogel/foam composite and the hydrogel alone. It is also to utilize the strain energy density functions (SEDFs) to determine a suitable constitutive model that represents the nonlinear behavior of the materials. It is to predict the behavior of these materials out of range of the test (i.e., in tension) by implementing a finite elements analysis (FEA) using ABAQUS. The results showed that the strength of the hydrogel/foam composite was significantly greater than hydrogel alone. All hyperelastic models have well defined the nonlinear behavior of the experimental data. FEA results in tension are in good agreement with those predicted using hyperelastic models. K E Y W O R D S hydrogel, hyperelastic models, hydrogel/foam composite, unconfined compression 1 | INTRODUCTION Hydrogels are three-dimension cross-linked networks highly utilized as a tissue scaffold. For instance, agarose, low acylgellan gum, and alginate were used as a promising material for nucleus pulposus (NP) replacements 1 because they exhibited viscoelastic behavior, and their mechanical behavior resembles the native tissue such as the NP. 2 Because hydrogels show a nonlinear behavior under mechanical compression test, it is important to understand their mechanical behavior out of the test range by adapting the hyperelastic models such as Ogden, Neo-Hookean, Mooney-Rivlin, and Yeoh models. The models depend on the strain energy density functions (SEDFs). 3 The predication of the suitable fit of the models can be implied in the future in the biomedical applications such as NP replacement. Moreover, understanding the viscoelastic properties of the hydrogel is crucial to develop material for replacing the degenerative NP. 4 It is also vital for modeling to understand the compression behavior of natural tissue. 5 Hyperelastic models have been used in literature to characterize a natural tissue such as whale blubber, 6 or hydrogel like agar, where the compression data were modeled using the Ogden model. 7,8 Hydrogels are incompressible materials
Advances in Materials Science and Engineering, 2013
The specimens of thickness 0.8 mm carbon steel number 1.8902 in a strip form were welded. The str... more The specimens of thickness 0.8 mm carbon steel number 1.8902 in a strip form were welded. The strips of lap joints and curved peeljoints configurations have been welded. The welding parameters such as weld current and weld time have been investigated. The relation between the weld area and the joint strength properties has been presented. The obtained results were showing that the weld joint strength and the molten area (weld nugget volume) highly increase with the increasing of weld current. Therefore, the correlation between the maximum load (joint strength) and area has been given. The reliable weldability under the tensile and shearing loading was considered. Therefore, the new limits of weldability have been presented to consider these two types of loading. Moreover, the experimental results were compared with the empirical relations that consider the sheet thickness only.
Procedia structural integrity, 2018
Resistance spot welding process (RSW) is one of remarkable manufacturing processes in automotive ... more Resistance spot welding process (RSW) is one of remarkable manufacturing processes in automotive industry. There are several process parameters; quantum of weld current, weld time, and electrode force which affect the weld nugget formation and its strength. Therefore, it is necessary to optimize the process parameters of RSW. In this paper spot welded joints of similar sheets thickness have been welded. The tensile specimens have been made according to AWS standard. The optimal parameters for welding machine are evaluated by using Design Expert Program. The tensile shear tests presented three failure modes, interfacial, partial interfacial and pullout failure. These modes related to diversity metallic composition of each steel type and the variance of the sheet thickness.
Journal of Failure Analysis and Prevention, 2013
In welded joint, the residual stresses effect can be considered using the residual stress intensi... more In welded joint, the residual stresses effect can be considered using the residual stress intensity factor (Kres). In this study, Kres is calculated using the analytic weight function method (WFM) and the polynomial distribution of residual stresses (σres). The different residual stress distributions have been used analytically. It is to be emphasized that the current approach is little investigated. This is because the weight function has already been developed to calculate K for a crack that had already existed, and hence to calculate the stress distribution and stress intensity factor over the crack face. Therefore, the current approach calculates Kres with σres consideration for the crack which initiates and propagates until failure. The validity to use the proposed weight function has been shown. The results of Kres have been compared with those obtained from FEM.
Fatigue & Fracture of Engineering Materials & Structures, Jun 27, 2013
To better understand the crack closure and propagation, an analytical model is established. The r... more To better understand the crack closure and propagation, an analytical model is established. The residual stress effect on fatigue crack growth equations has been considered using the residual stress intensity factor (SIF) (Kres). The joint geometries, residual stress distributions (σres) and residual stress ratio (Rres) were considered also. Kres are calculated using the analytical weight function (WF) method and different residual stress distributions. It is to be emphasized that the current approach is little investigated. This is because the WF has already been developed to calculate SIF for an existing crack. The current approach calculates Kres for the crack that initiates and propagates until failure. Different stress distributions have been used, and Rres is defined. The validity of using the WF has been shown. SIF due to applied load (Kapp) and applied stress ratio (Rapp) have been considered. Fatigue crack growth rate was investigated in accordance with the current approach...
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Papers by A.M. Al-Mukhtar