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Papers by ibrahim eldesouky

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Cellular structures are a favorite selection for the design of lightweight components and energy ... more Cellular structures are a favorite selection for the design of lightweight components and energy absorption applications due to several advantages such as their customizable stiffness and strength. In this investigation, functionally graded (FG) triply periodic minimal surfaces, Schoen-IWP (SIWP), and Schwarz primitive (SPrim) cellular structures were fabricated by masked stereolithography (MSLA) technique using ABS-like gray resin. The sample morphology, deformation behavior, mechanical characteristics, and energy absorption of graded and uniform structures were studied using experimental compression tests. The FG sample structures exhibited layer-by-layer collapse delaying shear failure. On the other hand, uniform samples showed complete diagonal shear failure. The total energy absorption to the densification point was 0.52 MJ/m3 and 0.58 MJ/m3 for graded and uniform SIWP, respectively. Additionally, the absorbed energy of the graded SPrim structure was 0.59 MJ/m3 while the unifor...

Progress in Additive Manufacturing

Progress in Additive Manufacturing

Journal of Biomedical Physics and Engineering, 2022

Background: Porous materials are recommended for orthopedic applications as they eliminate issues... more Background: Porous materials are recommended for orthopedic applications as they eliminate issues of interfacial instability with tissues and reduce mechanical mismatch of the young's modulus. Objective: The current research provides a finite element analysis (FEA) to investigate porous gyroid Ti6Al4V structure compared to a solid stem model for human tibial-knee implantation of total knee replacement (TKR). Material and Methods: In this study, the implant proximal portion was designed as porous gyroid Ti6Al4V structure with 500 µm pore size. CATIA V5R18 was used for modeling both gyroid and full solid models. Structural analysis was carried out using ANSYS R18.1 to evaluate the implant performance. Results: After gyroid implantation, the maximum von-Mises stress obtained under the tibial tray was increased to 10.081 MPa. Also, the maximum shear stress at the stem/bone interface was reduced to 0.7347 MPa. The stress concentration at the stem tip and the bone strain energy were also improved. The minimum factor of safety is 4.6 for the gyroid porous implant. A proof of concept model was additively manufactured successfully with pore size 577.7733 ±34.762 µm. Conclusion: The results indicated enhanced clinical performance of the porous tibial-knee implant compared to the solid titanium implant via increasing the maximum von-Mises bone stresses and decreasing the maximum shear stress at the bone/ implant interface.

Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the qual... more Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the quality of life of thousands of patients all over the globe. Nevertheless, the expected service life of such surgery remains unsuitable for patients under 50 years old. This is mainly related to stress shielding and the potential adverse tissue reaction to some of the elements of the market-dominant implant materials. In this research, functionally graded (FG) implant designs of several titanium alloys layered with hydroxyapatite (HA) are proposed to provide lower implant stiffness compared to a solid stem to approach the requirements of human bone. Moreover, TNZT (Ti35Nb7Zr5Ta), and TMZF (Ti12Mo6Zr2Fe) second-generation titanium alloys are studied as a replacement for the famous Ti6Al4V alloy to avoid the adverse tissue reactions related to aluminum and vanadium elements. The different FG models are numerically tested using a 3D finite element simulation after virtual implantation in a femu...

Solid State Phenomena

The current research presents a novel porous tibia implant design based on porous structure. The ... more The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve i...

Biomedical instrumentation & technology

Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adve... more Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adverse tissue reaction to certain elements of the implant material. In this regard, a porous implant provides lower stiffness and vacancies for bone ingrowth, making it more suitable for the human bone compared with a solid stem. Moreover, second-generation titanium biomedical alloys, such as TNZT (Ti35Nb7Zr5Ta) and TMZF (Ti12Mo6Zr2Fe), have been introduced to prevent the adverse tissue reactions related to aluminum and vanadium elements of the popular Ti6Al4V alloy. In the current work, an analysis was performed based on uniaxial compression testing of cubic Ti6Al4V structures of different porosities to predict the governing equations that relate the relative density of the structure to the mechanical properties of the structure according to the Gibson-Ashby model. A numerical study was conducted to evaluate the change in stress distribution obtained by incorporating the new titanium alloy...

Journal of medical engineering & technology, 2017

In total hip arthroplasty (THA), the femoral stem can be fixed with or without bone cement. Cemen... more In total hip arthroplasty (THA), the femoral stem can be fixed with or without bone cement. Cementless stem fixation is recommended for young and active patients as it eliminates the risk of loss of fixation at the bone-cement and cement-implant interfaces. Cementless fixation, however, suffers from a relatively high early revision rate. In the current research, a novel low-stiffness hip stem was designed, fabricated and tested. The stem design provided the option to inject biodegradable bone cement that could enhance initial stem stability. The stem was made of Ti6Al4V alloy. The proximal portion of the stem was porous, with cubic cells. The stem was fabricated using electron beam melting (EBM) technology and tested in compression and bending. Finite-element analysis was used to evaluate stem performance under a dynamic load representing a stair descending cycle and compare it to the performance of a solid stem with similar geometry. The von Mises stresses and maximum principal str...

Additive Manufacturing

Abstract Ti6Al4V porous scaffolds of two unit cell geometries (reentrant and cubic) were investig... more Abstract Ti6Al4V porous scaffolds of two unit cell geometries (reentrant and cubic) were investigated as candidates for load-bearing biomedical applications. Samples were fabricated using an Arcam A2 electron beam melting (EBM) machine and evaluated for geometric deviation from the original CAD design using a digital optical microscope. The mass and bounding volume of each sample were also measured to calculate the resulting relative density. The scaffolds were loaded in compression in the build direction to determine the relative modulus of elasticity and ultimate compressive load. Experimental results were used to calculate the Gibson and Ashby relation parameters for the studied unit cell geometries. The results suggest that samples with the cubic unit cell geometries, with struts oriented at an angle of 45° to the loading direction, exhibited higher stiffness than samples with the reentrant unit cell geometry at equivalent relative densities. A cubic scaffold is verified to withstand high compressive loads (more than 71 kN) while having an approximate pore size in the range of 0.6 mm. These characteristics demonstrate its suitability for load bearing biomedical implants.

Research and development of hip stem implants started centuries ago. However, there is still no y... more Research and development of hip stem implants started centuries ago. However, there is still no yet an optimum design that fulfills all the requirements of the patient. New manufacturing technologies have opened up new possibilities for complicated theoretical designs to become tangible reality. Current trends in the development of hip stems focus on applying porous structures to improve osseointegration and reduce stem stiffness in order to approach the stiffness of the natural human bone. In this field, modern additive manufacturing machines offer unique flexibility in manufacturing parts combining variable density mesh structures with solid and porous metal in a single manufacturing process. Furthermore, additive manufacturing machines became powerful competitors in the economical mass production of hip implants. This is due to their ability to manufacture several parts with different geometries in a single setup and with minimum material consumption. This paper reviews the appli...

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Cellular structures are a favorite selection for the design of lightweight components and energy ... more Cellular structures are a favorite selection for the design of lightweight components and energy absorption applications due to several advantages such as their customizable stiffness and strength. In this investigation, functionally graded (FG) triply periodic minimal surfaces, Schoen-IWP (SIWP), and Schwarz primitive (SPrim) cellular structures were fabricated by masked stereolithography (MSLA) technique using ABS-like gray resin. The sample morphology, deformation behavior, mechanical characteristics, and energy absorption of graded and uniform structures were studied using experimental compression tests. The FG sample structures exhibited layer-by-layer collapse delaying shear failure. On the other hand, uniform samples showed complete diagonal shear failure. The total energy absorption to the densification point was 0.52 MJ/m3 and 0.58 MJ/m3 for graded and uniform SIWP, respectively. Additionally, the absorbed energy of the graded SPrim structure was 0.59 MJ/m3 while the unifor...

Progress in Additive Manufacturing

Progress in Additive Manufacturing

Journal of Biomedical Physics and Engineering, 2022

Background: Porous materials are recommended for orthopedic applications as they eliminate issues... more Background: Porous materials are recommended for orthopedic applications as they eliminate issues of interfacial instability with tissues and reduce mechanical mismatch of the young's modulus. Objective: The current research provides a finite element analysis (FEA) to investigate porous gyroid Ti6Al4V structure compared to a solid stem model for human tibial-knee implantation of total knee replacement (TKR). Material and Methods: In this study, the implant proximal portion was designed as porous gyroid Ti6Al4V structure with 500 µm pore size. CATIA V5R18 was used for modeling both gyroid and full solid models. Structural analysis was carried out using ANSYS R18.1 to evaluate the implant performance. Results: After gyroid implantation, the maximum von-Mises stress obtained under the tibial tray was increased to 10.081 MPa. Also, the maximum shear stress at the stem/bone interface was reduced to 0.7347 MPa. The stress concentration at the stem tip and the bone strain energy were also improved. The minimum factor of safety is 4.6 for the gyroid porous implant. A proof of concept model was additively manufactured successfully with pore size 577.7733 ±34.762 µm. Conclusion: The results indicated enhanced clinical performance of the porous tibial-knee implant compared to the solid titanium implant via increasing the maximum von-Mises bone stresses and decreasing the maximum shear stress at the bone/ implant interface.

Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the qual... more Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the quality of life of thousands of patients all over the globe. Nevertheless, the expected service life of such surgery remains unsuitable for patients under 50 years old. This is mainly related to stress shielding and the potential adverse tissue reaction to some of the elements of the market-dominant implant materials. In this research, functionally graded (FG) implant designs of several titanium alloys layered with hydroxyapatite (HA) are proposed to provide lower implant stiffness compared to a solid stem to approach the requirements of human bone. Moreover, TNZT (Ti35Nb7Zr5Ta), and TMZF (Ti12Mo6Zr2Fe) second-generation titanium alloys are studied as a replacement for the famous Ti6Al4V alloy to avoid the adverse tissue reactions related to aluminum and vanadium elements. The different FG models are numerically tested using a 3D finite element simulation after virtual implantation in a femu...

Solid State Phenomena

The current research presents a novel porous tibia implant design based on porous structure. The ... more The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve i...

Biomedical instrumentation & technology

Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adve... more Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adverse tissue reaction to certain elements of the implant material. In this regard, a porous implant provides lower stiffness and vacancies for bone ingrowth, making it more suitable for the human bone compared with a solid stem. Moreover, second-generation titanium biomedical alloys, such as TNZT (Ti35Nb7Zr5Ta) and TMZF (Ti12Mo6Zr2Fe), have been introduced to prevent the adverse tissue reactions related to aluminum and vanadium elements of the popular Ti6Al4V alloy. In the current work, an analysis was performed based on uniaxial compression testing of cubic Ti6Al4V structures of different porosities to predict the governing equations that relate the relative density of the structure to the mechanical properties of the structure according to the Gibson-Ashby model. A numerical study was conducted to evaluate the change in stress distribution obtained by incorporating the new titanium alloy...

Journal of medical engineering & technology, 2017

In total hip arthroplasty (THA), the femoral stem can be fixed with or without bone cement. Cemen... more In total hip arthroplasty (THA), the femoral stem can be fixed with or without bone cement. Cementless stem fixation is recommended for young and active patients as it eliminates the risk of loss of fixation at the bone-cement and cement-implant interfaces. Cementless fixation, however, suffers from a relatively high early revision rate. In the current research, a novel low-stiffness hip stem was designed, fabricated and tested. The stem design provided the option to inject biodegradable bone cement that could enhance initial stem stability. The stem was made of Ti6Al4V alloy. The proximal portion of the stem was porous, with cubic cells. The stem was fabricated using electron beam melting (EBM) technology and tested in compression and bending. Finite-element analysis was used to evaluate stem performance under a dynamic load representing a stair descending cycle and compare it to the performance of a solid stem with similar geometry. The von Mises stresses and maximum principal str...

Additive Manufacturing

Abstract Ti6Al4V porous scaffolds of two unit cell geometries (reentrant and cubic) were investig... more Abstract Ti6Al4V porous scaffolds of two unit cell geometries (reentrant and cubic) were investigated as candidates for load-bearing biomedical applications. Samples were fabricated using an Arcam A2 electron beam melting (EBM) machine and evaluated for geometric deviation from the original CAD design using a digital optical microscope. The mass and bounding volume of each sample were also measured to calculate the resulting relative density. The scaffolds were loaded in compression in the build direction to determine the relative modulus of elasticity and ultimate compressive load. Experimental results were used to calculate the Gibson and Ashby relation parameters for the studied unit cell geometries. The results suggest that samples with the cubic unit cell geometries, with struts oriented at an angle of 45° to the loading direction, exhibited higher stiffness than samples with the reentrant unit cell geometry at equivalent relative densities. A cubic scaffold is verified to withstand high compressive loads (more than 71 kN) while having an approximate pore size in the range of 0.6 mm. These characteristics demonstrate its suitability for load bearing biomedical implants.

Research and development of hip stem implants started centuries ago. However, there is still no y... more Research and development of hip stem implants started centuries ago. However, there is still no yet an optimum design that fulfills all the requirements of the patient. New manufacturing technologies have opened up new possibilities for complicated theoretical designs to become tangible reality. Current trends in the development of hip stems focus on applying porous structures to improve osseointegration and reduce stem stiffness in order to approach the stiffness of the natural human bone. In this field, modern additive manufacturing machines offer unique flexibility in manufacturing parts combining variable density mesh structures with solid and porous metal in a single manufacturing process. Furthermore, additive manufacturing machines became powerful competitors in the economical mass production of hip implants. This is due to their ability to manufacture several parts with different geometries in a single setup and with minimum material consumption. This paper reviews the appli...