Noha Fouda | Mansoura University (original) (raw)

Papers by Noha Fouda

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...

Trends in biomaterials & artificial organs, 2015

Shape optimization of a cemented tibia stem has been carried out in this study to solve the stres... more Shape optimization of a cemented tibia stem has been carried out in this study to solve the stress shielding at the proximal tibia as well as the stress concentration at the stem tip. It is found that the optimal shape is a short stem with small diameter at the distal stem tip increased gradually to reach a maximum value at the proximal tibia stem. This optimal shape is increased von Mises stress at the lateral and medial cancellous bone by 130% and 140%, respectively compared to initial stem shape. On the other hand the stress concentration in bone at stem tip using the optimal stem shape is reduced by 25% compared to initial shape. However, the optimal stem shape is reduced the stresses in cement at stem tip by 28% laterally and 17% medially compared to the initial stem shape. Finally, a bimaterial stem (titanium with a polymer stem tip) has been applied to the optimal shape to improve the stress concentration reduction at the stem tip. The results are approximately the same compa...

Geometry and material property optimization represent the possible methods of using prosthesis st... more Geometry and material property optimization represent the possible methods of using prosthesis stiffness for alignment with bone stiffness and increasing total hip replacement lifespan. Previous researchers have tried to substitute conventional materials for new materials such as composites in femoral prosthesis. The concept of functionally graded materials (FGMs) was taken from biological structures. Previous study was carried out by Hedia and Fouda [1] to design the coating of a cementless hip prosthesis as a vertical FGM. In this study a finite element analysis and optimization method have been carried out in order to design the coating of cementless hip stem using the horizontal FGM to diminish stress shielding at the medial proximal region of the femur, as well as reducing the interface shear stress between the coating and bone that affects the long term stability of the hip implant. The optimal design compared with HAP coating and with homogenous uncoated titanium stem. The op...

International Journal of Mechanics and Materials in Design, 2004

Ideally, a bone implant should be such that it exhibits an identical response to loading as real ... more Ideally, a bone implant should be such that it exhibits an identical response to loading as real bone and is also biocompatible with existing tissue. A stiff stem, which is usually made of titanium, shields the proximal bone from mechanical loading (stress shielding). On the other hand, decreasing the stem stiffness increases the proximal interface shear stress and the risk

Dental Materials Journal, 2014

Biomedical Materials, 2006

Metal backing has been widely used in acetabular cup design. A stiff backing for a polyethylene l... more Metal backing has been widely used in acetabular cup design. A stiff backing for a polyethylene liner was initially believed to be mechanically favourable. Yet, recent studies of the load transfer around acetabular cups have shown that a stiff backing causes two problems. It generates higher stress peaks around the acetabular rim than those caused by full polyethylene cups and reduces the stresses transferred to the dome of the acetabulum causing stress shielding. The aim of this study is to overcome these two problems by improving the design of cementless metal-backed acetabular cups using the two-dimensional functionally graded material (FGM) concept through finite-element analysis and optimization techniques. It is found that the optimal 2D FGM model must have three bioactive materials of hydroxyapatite, Bioglass and collagen. This optimal material reduces the stress shielding at the dome of the acetabulum by 40% and 37% compared with stainless steel and titanium metal backing shells, respectively. In addition, using the 2D FGM model reduces the maximum interface shear stress in the bone by 31% compared to the titanium metal backing shell.

Trends in biomaterials & artificial organs, 2015

The geometry of the prosthesis has a strong effect on the bone compared to its material, so this ... more The geometry of the prosthesis has a strong effect on the bone compared to its material, so this study investigates the optimal shape of uncemented tibial tray to relieve the stress shielding by changing the dimensions of the metal tibial tray. Results from the model show that the optimization of the uncemented tibial component indicates a trend toward using a shorter cylindrical stem with a smaller diameter and longer metal tibial tray height to house the UHMWPE polyethylene insert compared with the initial design. This new design increases the maximum von-Mises stress magnitude five times the initial model on medial cancellous bone region. The maximum von-Mises stress magnitude of the optimal shape model is very close to the natural bone with about 6.5% reduction on medial cancellous region. Also it increases the maximum von-Mises stress magnitude by 3% compared to the initial model on lateral cancellous bone region. In addition, it reduces the maximum interface shear stress magn...

Applied and Computational Mechanics, 2017

This study presents the effect of porosity on mechanical behaviors of a power distribution functi... more This study presents the effect of porosity on mechanical behaviors of a power distribution functionally graded beam. The Euler-Bernoulli beam is assumed to describe the kinematic relations and constitutive equations. Because of technical problems, particle size shapes and micro-voids are created during the fabrication which should be taken into consideration. Two porosity models are proposed. The first one describes properties in the explicit form as linear functions of the porosity parameter. The second is a modified model which presents porosity and Young’s modulus in an implicit form where the density is assumed as a function of the porosity parameter and Young’s modulus as a ratio of mass with porosity to the mass without porosity. The modified proposed model is more applicable than the first model. The finite element model is developed to solve the problem by using the MATLAB software. Numerical results are presented to show the effects of porosity on mechanical behaviors of fu...

One of the most sensitive features of sheet metal forming processes is the elastic recovery durin... more One of the most sensitive features of sheet metal forming processes is the elastic recovery during unloading, called spring back, which leads to some geometric changes in the product. In this paper spring back dependence on the mechanical properties of different materials and tools geometry has been examined numerically and experimentally in sheet metal Ubending test. The computer code MARC was used to simulate the Ubending process under plane strain condition. A Comparison between the experimental and the finite element simulation results also performed. A complete knowledge of the spring back phenomenon and its dependence on material and process variables is strongly required in order to develop effective real time process control systems.

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...

British Journal of Applied Science & Technology, 2016

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...

Materials Testing

After hip replacement surgery there will be a clear distinction between the stiffness of the meta... more After hip replacement surgery there will be a clear distinction between the stiffness of the metallic implant and the more supple femur bone which will cause stress shielding and bone resorption. In order to treat this phenomenon, the stiffness of the femoral stem implant must be reduced. The effect of using porous and non-porous implants of steel, titanium and FGM will be studied in this research. The assembly of the femur bone and the implant was modeled by means of the 3D finite element method. It will be noticeable from this analysis that for all stem materials using porous implant materials lead to an increase in stress in cortical and cancellous bone as compared to non-porous implant materials which lead to reduced stress shielding and bone resorption. Gradually increasing the porosity of a steel stem from the distal part of the stem to the proximal part increased maximum von Mises stress at the proximal medial cortical bone by 29 % when compared to the non-porous steel stem. ...

Trends in Biomaterials and Artificial Organs, Feb 2, 2015

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...

Trends in biomaterials & artificial organs, 2015

Shape optimization of a cemented tibia stem has been carried out in this study to solve the stres... more Shape optimization of a cemented tibia stem has been carried out in this study to solve the stress shielding at the proximal tibia as well as the stress concentration at the stem tip. It is found that the optimal shape is a short stem with small diameter at the distal stem tip increased gradually to reach a maximum value at the proximal tibia stem. This optimal shape is increased von Mises stress at the lateral and medial cancellous bone by 130% and 140%, respectively compared to initial stem shape. On the other hand the stress concentration in bone at stem tip using the optimal stem shape is reduced by 25% compared to initial shape. However, the optimal stem shape is reduced the stresses in cement at stem tip by 28% laterally and 17% medially compared to the initial stem shape. Finally, a bimaterial stem (titanium with a polymer stem tip) has been applied to the optimal shape to improve the stress concentration reduction at the stem tip. The results are approximately the same compa...

Geometry and material property optimization represent the possible methods of using prosthesis st... more Geometry and material property optimization represent the possible methods of using prosthesis stiffness for alignment with bone stiffness and increasing total hip replacement lifespan. Previous researchers have tried to substitute conventional materials for new materials such as composites in femoral prosthesis. The concept of functionally graded materials (FGMs) was taken from biological structures. Previous study was carried out by Hedia and Fouda [1] to design the coating of a cementless hip prosthesis as a vertical FGM. In this study a finite element analysis and optimization method have been carried out in order to design the coating of cementless hip stem using the horizontal FGM to diminish stress shielding at the medial proximal region of the femur, as well as reducing the interface shear stress between the coating and bone that affects the long term stability of the hip implant. The optimal design compared with HAP coating and with homogenous uncoated titanium stem. The op...

International Journal of Mechanics and Materials in Design, 2004

Ideally, a bone implant should be such that it exhibits an identical response to loading as real ... more Ideally, a bone implant should be such that it exhibits an identical response to loading as real bone and is also biocompatible with existing tissue. A stiff stem, which is usually made of titanium, shields the proximal bone from mechanical loading (stress shielding). On the other hand, decreasing the stem stiffness increases the proximal interface shear stress and the risk

Dental Materials Journal, 2014

Biomedical Materials, 2006

Metal backing has been widely used in acetabular cup design. A stiff backing for a polyethylene l... more Metal backing has been widely used in acetabular cup design. A stiff backing for a polyethylene liner was initially believed to be mechanically favourable. Yet, recent studies of the load transfer around acetabular cups have shown that a stiff backing causes two problems. It generates higher stress peaks around the acetabular rim than those caused by full polyethylene cups and reduces the stresses transferred to the dome of the acetabulum causing stress shielding. The aim of this study is to overcome these two problems by improving the design of cementless metal-backed acetabular cups using the two-dimensional functionally graded material (FGM) concept through finite-element analysis and optimization techniques. It is found that the optimal 2D FGM model must have three bioactive materials of hydroxyapatite, Bioglass and collagen. This optimal material reduces the stress shielding at the dome of the acetabulum by 40% and 37% compared with stainless steel and titanium metal backing shells, respectively. In addition, using the 2D FGM model reduces the maximum interface shear stress in the bone by 31% compared to the titanium metal backing shell.

Trends in biomaterials & artificial organs, 2015

The geometry of the prosthesis has a strong effect on the bone compared to its material, so this ... more The geometry of the prosthesis has a strong effect on the bone compared to its material, so this study investigates the optimal shape of uncemented tibial tray to relieve the stress shielding by changing the dimensions of the metal tibial tray. Results from the model show that the optimization of the uncemented tibial component indicates a trend toward using a shorter cylindrical stem with a smaller diameter and longer metal tibial tray height to house the UHMWPE polyethylene insert compared with the initial design. This new design increases the maximum von-Mises stress magnitude five times the initial model on medial cancellous bone region. The maximum von-Mises stress magnitude of the optimal shape model is very close to the natural bone with about 6.5% reduction on medial cancellous region. Also it increases the maximum von-Mises stress magnitude by 3% compared to the initial model on lateral cancellous bone region. In addition, it reduces the maximum interface shear stress magn...

Applied and Computational Mechanics, 2017

This study presents the effect of porosity on mechanical behaviors of a power distribution functi... more This study presents the effect of porosity on mechanical behaviors of a power distribution functionally graded beam. The Euler-Bernoulli beam is assumed to describe the kinematic relations and constitutive equations. Because of technical problems, particle size shapes and micro-voids are created during the fabrication which should be taken into consideration. Two porosity models are proposed. The first one describes properties in the explicit form as linear functions of the porosity parameter. The second is a modified model which presents porosity and Young’s modulus in an implicit form where the density is assumed as a function of the porosity parameter and Young’s modulus as a ratio of mass with porosity to the mass without porosity. The modified proposed model is more applicable than the first model. The finite element model is developed to solve the problem by using the MATLAB software. Numerical results are presented to show the effects of porosity on mechanical behaviors of fu...

One of the most sensitive features of sheet metal forming processes is the elastic recovery durin... more One of the most sensitive features of sheet metal forming processes is the elastic recovery during unloading, called spring back, which leads to some geometric changes in the product. In this paper spring back dependence on the mechanical properties of different materials and tools geometry has been examined numerically and experimentally in sheet metal Ubending test. The computer code MARC was used to simulate the Ubending process under plane strain condition. A Comparison between the experimental and the finite element simulation results also performed. A complete knowledge of the spring back phenomenon and its dependence on material and process variables is strongly required in order to develop effective real time process control systems.

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...

British Journal of Applied Science & Technology, 2016

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...

Materials Testing

After hip replacement surgery there will be a clear distinction between the stiffness of the meta... more After hip replacement surgery there will be a clear distinction between the stiffness of the metallic implant and the more supple femur bone which will cause stress shielding and bone resorption. In order to treat this phenomenon, the stiffness of the femoral stem implant must be reduced. The effect of using porous and non-porous implants of steel, titanium and FGM will be studied in this research. The assembly of the femur bone and the implant was modeled by means of the 3D finite element method. It will be noticeable from this analysis that for all stem materials using porous implant materials lead to an increase in stress in cortical and cancellous bone as compared to non-porous implant materials which lead to reduced stress shielding and bone resorption. Gradually increasing the porosity of a steel stem from the distal part of the stem to the proximal part increased maximum von Mises stress at the proximal medial cortical bone by 29 % when compared to the non-porous steel stem. ...

Trends in Biomaterials and Artificial Organs, Feb 2, 2015