Lattice structures possess many superior properties over solid materials and conventional structu... more Lattice structures possess many superior properties over solid materials and conventional structures. Application-oriented lattice structure designs have become a choice in many industries, such as aerospace, automotive applications, construction, biomedical applications, and footwear. However, numerical and empirical analyses are required to predict mechanical behavior under different boundary conditions. In this article, a novel surface-based structure named O-surface structure is designed and inspired by existing Triply Periodic Minimal Surface morphologies in a particular sea urchin structure. For comparison, both structures were designed with two different height configurations and investigated for mechanical performance in terms of compression, local buckling, global buckling, and post-buckling behavior. Both simulation and experimental methods were carried out to reveal these aforementioned properties of samples fabricated by multi jet fusion technology. The sea urchin struct...
2019 International Conference on Robotics and Automation in Industry (ICRAI)
Technological innovation in additive manufacturing has enabled it to reach the consumer market ve... more Technological innovation in additive manufacturing has enabled it to reach the consumer market very rapidly since the last decade. The word ‘additive manufacturing’ is now widely replaced with the word ‘3D Printing’. The 3D printing industry is evolving from desktop to Industrial 3D printers all over the world, which will fulfill the requirements in Industry 4.0. The current usage of 3D printing is in medical and dental applications, rapid prototyping, food industry, and Jewelry making. This emerging technology disrupts the $12 Trillion manufacturing sector. In 2017, there is a 21% increase in the industrial growth of Additive Manufacturing from $6.06 billion to $7.3 billion. This article explains the current global trends in 3D printing in technologically advanced countries and emphasizes the use of 3D printing in accelerating the research and development in emerging economies, in particular to Pakistan. Further, it helps to bring the success stories regarding 3D printing for startups and the challenges related to the adaptation of 3D printing technologies in Pakistan to limelight.
Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate ... more Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate complex and intricate light-weight geometries with the use of lattice structure that have potential applications including construction, aerospace and biomedical applications, where mechanical properties are the prime focus. Buckling instability in lattice structures is one of the main failure mechanisms that can lead to major failure in structural applications that are subjected to compressive loads, but it has yet to be fully explored. This study aims to investigate the effect of surface-based lattice structure topologies and structured column height on the critical buckling load of lattice structured columns. Four different triply periodic minimal surface (TPMS) lattice topologies were selected and three design configurations (unit cells in x, y, z axis), i.e., 2 × 2 × 4, 2 × 2 × 8 and 2 × 2 × 16 column, for each structure were designed followed by printing using HP MultiJet fusion. U...
Design for additive manufacturing (DfAM) enables the design and fabrication of intricate but appl... more Design for additive manufacturing (DfAM) enables the design and fabrication of intricate but application-based functionally optimized geometries by reducing the manufacturing time. It also gave unlimited design freedom to alter any specific parameter and re-generate the design with improved mechanical properties. However, designing a complex and application-specific component needs comprehensive knowledge of drawing, intended usage, high expertise, and command on designing software with ample time. Mechanical springs e.g., wave springs of uniform/complex shaped designs consume a lot of manual hard work. A new design tool is developed for constructing wave springs of different morphologies with uniform or varying design parameters or the combination of both by successfully controlling the number of waves per coil, coil diameter, geometric shape, thickness/width of the strip, the diameter of the wire, wave height, overlap between coils, etc. In this methodology, a graphical user inter...
European Journal of Applied Engineering and Scientific Research, 2020
The current global energy scenario and consumption rate is alarming greatly as the tremendous inc... more The current global energy scenario and consumption rate is alarming greatly as the tremendous increase in population causes a sharp increase in electrical energy demand. The exhaustive extraction and production of fossil energy is the main reason and contributor to many environmental issues. As these fuels will ultimately get depleted resulting into increased energy shortfall, climate change and energy insecurity. In this regards every country is putting an effort to increase energy efficiency as well as switching over to new and renewable energy technologies. Among such solar energy from the sun is free and abundant. It offers number of strategic benefits which replaces the fossil-fuel combustion for the various electrical and thermal needs by minimizing the emissions of harmful gases and air pollutants. Currently, solar energy's contribution to the total global energy supply is very low and small but the potential is enormous. Historically solar systems suffer from huge initial cost than conventional energy sources but once the solar technologies are installed, they have very low operating costs and require minimal input this provides security against conventional fuel supply disruptions and their prices. However present innovation and supports for solar manufacturing and sales prices have dropped greatly from the past few decades resulting into at energy price parity. Shockley-Queisser limit is the theoretical maximum efficiency that a single junction solar cell can exhibit. The current research in this direction is going on to find out the best substitute materials and technology to improve the performance of solar cells. The study of light spectrum and different absorption levels in semiconductor material, special coating, application of nano technology and use of organic polymers have led to greater saving and rapid production.
In this study, five different auxetic structures were designed into dog bone specimens and printe... more In this study, five different auxetic structures were designed into dog bone specimens and printed with approximated similar masses, intended as the constant parameter. These specimens were then simulated by Finite Element Analysis before being subjected to tensile testing. In the simulation, yield stress comparisons between auxetic structures and non-auxetic were analyzed. UTS (Ultimate Tensile Stress) and maximum strain from tensile test results were compared with 3D printed non-auxetic with concentric infill. The results showed agreement between simulation and testing in terms of deformations and failure spots. In the end, simulated auxetic structures showed extensions in yielding limit at a range of 5-20% compared to control. Meanwhile, four out of five tested auxetics were proved to gain increment in UTS value at a range of 25.14%-160.9% and additional maximum strain percentage by 4.1-31.49% compared to non-auxetic with 10.1 MPa and 2.48%, UTS and maximum strain Respectively.
Abstract Wave springs have better properties than helical springs in terms of load bearing capaci... more Abstract Wave springs have better properties than helical springs in terms of load bearing capacity, mass, energy absorption efficiency, and stiffness. Currently, available wave springs have waves that do not merge with each other (non-contact) with uniform shape and dimensions, manufactured by traditional manufacturing processes using customized machines in which forming, twisting, and cutting processes take place simultaneously. This study aims to design and manufacture wave springs with waves that merge with each other by additive manufacturing (AM). Variable-dimension wave springs are complex in design and can only be manufactured by AM owing to its design freedom, but they have much higher performance in load bearing, stiffness, energy absorption, and energy release compared to both uniform-dimension and uniformly shaped wave springs. To accomplish wave springs manufactured by AM, ten different wave springs were designed and manufactured with variable and uniform dimensions, using a HP MultiJet Fusion printer, by keeping the mass and height of each design constant. Compression tests were carried out for up to ten cycles to study and compare the load bearing capacity, energy absorption, stiffness, and energy loss for all designs. The results showed that the stiffness of the spring increased in the contact wave springs, which ultimately led to more energy absorption in these designs. The taper-wave spring was the best among all designs for load bearing, and it had the highest energy loss capacity, which was validated by finite element analysis of each design.
Functionally graded lattice structures have attracted much attention in engineering due to their ... more Functionally graded lattice structures have attracted much attention in engineering due to their excellent mechanical performance resulting from their optimized and application-specific properties. These structures are inspired by nature and are important for a lightweight yet efficient and optimal functionality. They have enhanced mechanical properties over the uniform density counterparts because of their graded design, making them preferable for many applications. Several studies were carried out to investigate the mechanical properties of graded density lattice structures subjected to different types of loadings mainly related to tensile, compression, and fatigue responses. In applications related to biomedical, automotive, and aerospace sectors, dynamic bending and rotational stresses are critical load components. Therefore, the study of torsional properties of functionally gradient lattice structures will contribute to a better implementation of lattice structures in several s...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The International Journal of Advanced Manufacturing Technology, 2020
The mechanical properties such as energy absorption, crushing behavior, and strength-to-weight ra... more The mechanical properties such as energy absorption, crushing behavior, and strength-to-weight ratio of graded density structures are significantly better when compared with uniform density counterparts. Graded density structures have been widely investigated due to recent developments in additive manufacturing (AM) technology, which can easily manufacture complex geometries. The study explores the significance of variable-dimension helical spring (VDS) to be used in shoe midsole to improve the stiffness, energy absorption, and energy return. Two novel shoe midsoles are designed using the variable-dimension helical springs and their performance was compared with a third shoe midsole designed using uniform-dimension helical spring (UDS). Variable-dimension shoe midsoles were designed according to the actual pressure distribution applied by the human foot on the midsole. The Multijet fusion AM process was employed for the fabrication of all shoe midsole samples. It is revealed that despite the same mass and bounding box, variable-dimension midsoles have significantly improved mechanical properties compared to uniform-dimension midsole. It is found that the VDS midsole has sixfolds higher force-bearing capacity, and has a lower permanent material setting phenomena when compared to UDS midsole. Moreover, a higher (45%) distortion was found in the UDS midsole after the loading-unloading experiment when compared to the VDS midsole (24%) distortion. A further comparison of the VDS midsole was carried out with the commercially available wave spring-based midsole. Despite about 2-fold higher weight of the wave spring-based midsole, the VDS polymer midsole has higher mechanical properties found in terms of flexibility and force-bearing capacity. Finally, it is concluded that the VDS structure of the midsole can enhance the mechanical properties such as force-bearing capacity, flexibility, and stability with a higher strength-to-weight ratio. This study also proves the feasibility of design and AM of customer-specific shoe midsole.
Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) ... more Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) processes to obtain the desired global and local mechanical properties, such as stiffness and energy absorption. Lattice structures usually fail from the sharp edges owing to the high stress concentration and residual stress. Therefore, it is crucial to analyze the failure mechanism of lattice structures to improve the mechanical properties. In this study, several lattice topologies with fillets were designed, and the effects of the fillets on the stiffness, energy absorption, energy return, and energy loss of an open-cell lattice structure were investigated at a constant relative density. A recently developed high-speed AM multi-jet fusion technology was employed to fabricate lattice samples with two different unit cell sizes. Nonlinear simulations using ANSYS software were performed to investigate the mechanical properties of the samples. Experimental compression and loading–unloading ...
The International Journal of Advanced Manufacturing Technology, 2021
Cellular biomaterials with highly controlled microstructures are auspicious materials for medical... more Cellular biomaterials with highly controlled microstructures are auspicious materials for medical orthopedics applications either as scaffold or implants due to their capability of encouraging better osseointegration and cell proliferation. This work focuses on the design and optimization of the hip implant by introducing a cellular structure into a solid implant to allow bone tissue ingrowth and reduce stress shielding. The cellular hip implant is incorporated with vintiles lattice topologies having different strut thickness and unit cell sizes to achieve the requirements of bone ingrowth and biomechanical mimic strength. All four optimized cellular hip implants with different unit cell size and porosity were manufactured via selective laser melting (SLM) using the Ti6Al4V material. To predict the mechanical property of hip cellular implant, finite element analysis (FEA) was employed and optimization methods were used for improving the mechanical performance of the hip cellular implant. To evaluate the reduction in stiffness of hip cellular implants, experimental tests were performed based on ISO 7206-4(2010) under static loading conditions. The experimental and simulation force-displacement results show that the optimized cellular hip implant has 62% lower stiffness than its solid counterpart. Moreover, the cellular hip implant was 50% lower in weight than the solid implant. Finally, the result of this study shows that the cellular implants with porosity of 56% and 58% have the potential to be used in orthopedic and prosthetic applications to improve osseointegration.
Computer Methods in Biomechanics and Biomedical Engineering, 2020
(2020): Design and application of personalized surgical guides to treat complex tibial plateau ma... more (2020): Design and application of personalized surgical guides to treat complex tibial plateau malunion, Computer Methods in Biomechanics and Biomedical Engineering,
The International Journal of Advanced Manufacturing Technology, 2020
Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate sh... more Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate shapes such as metamaterials and complex geometries easier, more efficient, faster, and optimally functional, as compared with the manufacturing of simple solid blocks. In this study, the authors conducted experimental investigations and simulations on the energy absorption, stiffness, and deflection of various variable dimension helical springs fabricated by a recently developed high-speed AM technology, namely, the multijet fusion (MJF) system. The variable dimension helical springs were designed by defining various parameters such as the pitch, diameter of the spring wire and spring coil, and total height of the spring. For comparison, the total masses, bounding boxes, and total heights of all samples were kept constant. The results show that the variable parameters (e.g., shape) significantly affect the properties of helical springs; therefore, the stiffness and deformation can be controlled by varying them for a particular application. Furthermore, in designing variable dimension helical springs, nonlinear force-displacement behaviors and stiffness, along with reductions in weight and maximum stresses, can be obtained. Finally, it was concluded that by optimally defining the above parameters, a spring with an ideal geometry can be designed, thereby realizing comfort, stability, and reliability, along with other application-specific benefits (e.g., lightweight).
The International Journal of Advanced Manufacturing Technology, 2020
The mechanical properties of lattice structure are affected by the properties of the parent mater... more The mechanical properties of lattice structure are affected by the properties of the parent material, the relative density, and the topology of the unit cell. In many applications, the goal is to have a lightweight and stiff structure. Increase in stiffness can be achieved by increasing relative density but this also increases the mass. The second method to enhance the mechanical properties is by tailoring the topology of the unit cell. This method has an advantage over the previous method as it results in an increase in stiffness without any increase in mass of the structure. Periodic lattice structures can be designed for multiple constraints such as optimization of stiffness and energy absorption. Presence of sharp corners and edges causes stress concentrations which lead to lower energy absorption efficiency. This can be rectified by adding fillets. In this paper, two methods are shown to increase the stiffness and the specific energy absorption efficiency of the lattice structures without increasing the mass or relative density. Improvement in mechanical properties can be achieved by addition of fillets at the edges and by placing beams parallel to the loading direction. These improvements were applied to two lattice structures: Kelvin and Octet truss. Multi-jet fusion additive manufacturing was used to fabricate the samples for performing uniaxial compression testing. The results show a marked improvement in stiffness and energy absorption efficiency in the structures which incorporate fillets and vertical beams in the unit cells. Stiffness of Kelvin was improved by 32% by adding fillets and 70% by adding crossbars. The energy absorption efficiency was increased by 50% in Kelvin by adding fillets. Furthermore, the post-yield behavior and failure mechanism were also changed due to the addition of these elements.
Cellular materials with very highly regulated micro-architectures are promising applicant materia... more Cellular materials with very highly regulated micro-architectures are promising applicant materials for orthopedic medical uses while requiring implants or substituting for bone due to their ability to promote increased cell proliferation and osseointegration. This study focuses on the design of an acetabular cup (AC) cellular implant which was built using a vintiles cellular structure with an internal porosity of 56–87.9% and internal pore dimensions in the range of 600–1200 μm. The AC implant was then optimized for improving mechanical performance to reduce stress shielding by adjusting the porosity to produce stiffness (elastic modulus) to match with the bone, and allowing for bone cell ingrowth. The optimized and non-optimized AC cellular implant was fabricated using the SLM additive manufacturing process. Simulation (finite element analysis, FEA) was carried out and all cellular implants are finally tested under static loading conditions. The result showed that on the finite el...
Lattice structures possess many superior properties over solid materials and conventional structu... more Lattice structures possess many superior properties over solid materials and conventional structures. Application-oriented lattice structure designs have become a choice in many industries, such as aerospace, automotive applications, construction, biomedical applications, and footwear. However, numerical and empirical analyses are required to predict mechanical behavior under different boundary conditions. In this article, a novel surface-based structure named O-surface structure is designed and inspired by existing Triply Periodic Minimal Surface morphologies in a particular sea urchin structure. For comparison, both structures were designed with two different height configurations and investigated for mechanical performance in terms of compression, local buckling, global buckling, and post-buckling behavior. Both simulation and experimental methods were carried out to reveal these aforementioned properties of samples fabricated by multi jet fusion technology. The sea urchin struct...
2019 International Conference on Robotics and Automation in Industry (ICRAI)
Technological innovation in additive manufacturing has enabled it to reach the consumer market ve... more Technological innovation in additive manufacturing has enabled it to reach the consumer market very rapidly since the last decade. The word ‘additive manufacturing’ is now widely replaced with the word ‘3D Printing’. The 3D printing industry is evolving from desktop to Industrial 3D printers all over the world, which will fulfill the requirements in Industry 4.0. The current usage of 3D printing is in medical and dental applications, rapid prototyping, food industry, and Jewelry making. This emerging technology disrupts the $12 Trillion manufacturing sector. In 2017, there is a 21% increase in the industrial growth of Additive Manufacturing from $6.06 billion to $7.3 billion. This article explains the current global trends in 3D printing in technologically advanced countries and emphasizes the use of 3D printing in accelerating the research and development in emerging economies, in particular to Pakistan. Further, it helps to bring the success stories regarding 3D printing for startups and the challenges related to the adaptation of 3D printing technologies in Pakistan to limelight.
Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate ... more Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate complex and intricate light-weight geometries with the use of lattice structure that have potential applications including construction, aerospace and biomedical applications, where mechanical properties are the prime focus. Buckling instability in lattice structures is one of the main failure mechanisms that can lead to major failure in structural applications that are subjected to compressive loads, but it has yet to be fully explored. This study aims to investigate the effect of surface-based lattice structure topologies and structured column height on the critical buckling load of lattice structured columns. Four different triply periodic minimal surface (TPMS) lattice topologies were selected and three design configurations (unit cells in x, y, z axis), i.e., 2 × 2 × 4, 2 × 2 × 8 and 2 × 2 × 16 column, for each structure were designed followed by printing using HP MultiJet fusion. U...
Design for additive manufacturing (DfAM) enables the design and fabrication of intricate but appl... more Design for additive manufacturing (DfAM) enables the design and fabrication of intricate but application-based functionally optimized geometries by reducing the manufacturing time. It also gave unlimited design freedom to alter any specific parameter and re-generate the design with improved mechanical properties. However, designing a complex and application-specific component needs comprehensive knowledge of drawing, intended usage, high expertise, and command on designing software with ample time. Mechanical springs e.g., wave springs of uniform/complex shaped designs consume a lot of manual hard work. A new design tool is developed for constructing wave springs of different morphologies with uniform or varying design parameters or the combination of both by successfully controlling the number of waves per coil, coil diameter, geometric shape, thickness/width of the strip, the diameter of the wire, wave height, overlap between coils, etc. In this methodology, a graphical user inter...
European Journal of Applied Engineering and Scientific Research, 2020
The current global energy scenario and consumption rate is alarming greatly as the tremendous inc... more The current global energy scenario and consumption rate is alarming greatly as the tremendous increase in population causes a sharp increase in electrical energy demand. The exhaustive extraction and production of fossil energy is the main reason and contributor to many environmental issues. As these fuels will ultimately get depleted resulting into increased energy shortfall, climate change and energy insecurity. In this regards every country is putting an effort to increase energy efficiency as well as switching over to new and renewable energy technologies. Among such solar energy from the sun is free and abundant. It offers number of strategic benefits which replaces the fossil-fuel combustion for the various electrical and thermal needs by minimizing the emissions of harmful gases and air pollutants. Currently, solar energy's contribution to the total global energy supply is very low and small but the potential is enormous. Historically solar systems suffer from huge initial cost than conventional energy sources but once the solar technologies are installed, they have very low operating costs and require minimal input this provides security against conventional fuel supply disruptions and their prices. However present innovation and supports for solar manufacturing and sales prices have dropped greatly from the past few decades resulting into at energy price parity. Shockley-Queisser limit is the theoretical maximum efficiency that a single junction solar cell can exhibit. The current research in this direction is going on to find out the best substitute materials and technology to improve the performance of solar cells. The study of light spectrum and different absorption levels in semiconductor material, special coating, application of nano technology and use of organic polymers have led to greater saving and rapid production.
In this study, five different auxetic structures were designed into dog bone specimens and printe... more In this study, five different auxetic structures were designed into dog bone specimens and printed with approximated similar masses, intended as the constant parameter. These specimens were then simulated by Finite Element Analysis before being subjected to tensile testing. In the simulation, yield stress comparisons between auxetic structures and non-auxetic were analyzed. UTS (Ultimate Tensile Stress) and maximum strain from tensile test results were compared with 3D printed non-auxetic with concentric infill. The results showed agreement between simulation and testing in terms of deformations and failure spots. In the end, simulated auxetic structures showed extensions in yielding limit at a range of 5-20% compared to control. Meanwhile, four out of five tested auxetics were proved to gain increment in UTS value at a range of 25.14%-160.9% and additional maximum strain percentage by 4.1-31.49% compared to non-auxetic with 10.1 MPa and 2.48%, UTS and maximum strain Respectively.
Abstract Wave springs have better properties than helical springs in terms of load bearing capaci... more Abstract Wave springs have better properties than helical springs in terms of load bearing capacity, mass, energy absorption efficiency, and stiffness. Currently, available wave springs have waves that do not merge with each other (non-contact) with uniform shape and dimensions, manufactured by traditional manufacturing processes using customized machines in which forming, twisting, and cutting processes take place simultaneously. This study aims to design and manufacture wave springs with waves that merge with each other by additive manufacturing (AM). Variable-dimension wave springs are complex in design and can only be manufactured by AM owing to its design freedom, but they have much higher performance in load bearing, stiffness, energy absorption, and energy release compared to both uniform-dimension and uniformly shaped wave springs. To accomplish wave springs manufactured by AM, ten different wave springs were designed and manufactured with variable and uniform dimensions, using a HP MultiJet Fusion printer, by keeping the mass and height of each design constant. Compression tests were carried out for up to ten cycles to study and compare the load bearing capacity, energy absorption, stiffness, and energy loss for all designs. The results showed that the stiffness of the spring increased in the contact wave springs, which ultimately led to more energy absorption in these designs. The taper-wave spring was the best among all designs for load bearing, and it had the highest energy loss capacity, which was validated by finite element analysis of each design.
Functionally graded lattice structures have attracted much attention in engineering due to their ... more Functionally graded lattice structures have attracted much attention in engineering due to their excellent mechanical performance resulting from their optimized and application-specific properties. These structures are inspired by nature and are important for a lightweight yet efficient and optimal functionality. They have enhanced mechanical properties over the uniform density counterparts because of their graded design, making them preferable for many applications. Several studies were carried out to investigate the mechanical properties of graded density lattice structures subjected to different types of loadings mainly related to tensile, compression, and fatigue responses. In applications related to biomedical, automotive, and aerospace sectors, dynamic bending and rotational stresses are critical load components. Therefore, the study of torsional properties of functionally gradient lattice structures will contribute to a better implementation of lattice structures in several s...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The International Journal of Advanced Manufacturing Technology, 2020
The mechanical properties such as energy absorption, crushing behavior, and strength-to-weight ra... more The mechanical properties such as energy absorption, crushing behavior, and strength-to-weight ratio of graded density structures are significantly better when compared with uniform density counterparts. Graded density structures have been widely investigated due to recent developments in additive manufacturing (AM) technology, which can easily manufacture complex geometries. The study explores the significance of variable-dimension helical spring (VDS) to be used in shoe midsole to improve the stiffness, energy absorption, and energy return. Two novel shoe midsoles are designed using the variable-dimension helical springs and their performance was compared with a third shoe midsole designed using uniform-dimension helical spring (UDS). Variable-dimension shoe midsoles were designed according to the actual pressure distribution applied by the human foot on the midsole. The Multijet fusion AM process was employed for the fabrication of all shoe midsole samples. It is revealed that despite the same mass and bounding box, variable-dimension midsoles have significantly improved mechanical properties compared to uniform-dimension midsole. It is found that the VDS midsole has sixfolds higher force-bearing capacity, and has a lower permanent material setting phenomena when compared to UDS midsole. Moreover, a higher (45%) distortion was found in the UDS midsole after the loading-unloading experiment when compared to the VDS midsole (24%) distortion. A further comparison of the VDS midsole was carried out with the commercially available wave spring-based midsole. Despite about 2-fold higher weight of the wave spring-based midsole, the VDS polymer midsole has higher mechanical properties found in terms of flexibility and force-bearing capacity. Finally, it is concluded that the VDS structure of the midsole can enhance the mechanical properties such as force-bearing capacity, flexibility, and stability with a higher strength-to-weight ratio. This study also proves the feasibility of design and AM of customer-specific shoe midsole.
Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) ... more Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) processes to obtain the desired global and local mechanical properties, such as stiffness and energy absorption. Lattice structures usually fail from the sharp edges owing to the high stress concentration and residual stress. Therefore, it is crucial to analyze the failure mechanism of lattice structures to improve the mechanical properties. In this study, several lattice topologies with fillets were designed, and the effects of the fillets on the stiffness, energy absorption, energy return, and energy loss of an open-cell lattice structure were investigated at a constant relative density. A recently developed high-speed AM multi-jet fusion technology was employed to fabricate lattice samples with two different unit cell sizes. Nonlinear simulations using ANSYS software were performed to investigate the mechanical properties of the samples. Experimental compression and loading–unloading ...
The International Journal of Advanced Manufacturing Technology, 2021
Cellular biomaterials with highly controlled microstructures are auspicious materials for medical... more Cellular biomaterials with highly controlled microstructures are auspicious materials for medical orthopedics applications either as scaffold or implants due to their capability of encouraging better osseointegration and cell proliferation. This work focuses on the design and optimization of the hip implant by introducing a cellular structure into a solid implant to allow bone tissue ingrowth and reduce stress shielding. The cellular hip implant is incorporated with vintiles lattice topologies having different strut thickness and unit cell sizes to achieve the requirements of bone ingrowth and biomechanical mimic strength. All four optimized cellular hip implants with different unit cell size and porosity were manufactured via selective laser melting (SLM) using the Ti6Al4V material. To predict the mechanical property of hip cellular implant, finite element analysis (FEA) was employed and optimization methods were used for improving the mechanical performance of the hip cellular implant. To evaluate the reduction in stiffness of hip cellular implants, experimental tests were performed based on ISO 7206-4(2010) under static loading conditions. The experimental and simulation force-displacement results show that the optimized cellular hip implant has 62% lower stiffness than its solid counterpart. Moreover, the cellular hip implant was 50% lower in weight than the solid implant. Finally, the result of this study shows that the cellular implants with porosity of 56% and 58% have the potential to be used in orthopedic and prosthetic applications to improve osseointegration.
Computer Methods in Biomechanics and Biomedical Engineering, 2020
(2020): Design and application of personalized surgical guides to treat complex tibial plateau ma... more (2020): Design and application of personalized surgical guides to treat complex tibial plateau malunion, Computer Methods in Biomechanics and Biomedical Engineering,
The International Journal of Advanced Manufacturing Technology, 2020
Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate sh... more Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate shapes such as metamaterials and complex geometries easier, more efficient, faster, and optimally functional, as compared with the manufacturing of simple solid blocks. In this study, the authors conducted experimental investigations and simulations on the energy absorption, stiffness, and deflection of various variable dimension helical springs fabricated by a recently developed high-speed AM technology, namely, the multijet fusion (MJF) system. The variable dimension helical springs were designed by defining various parameters such as the pitch, diameter of the spring wire and spring coil, and total height of the spring. For comparison, the total masses, bounding boxes, and total heights of all samples were kept constant. The results show that the variable parameters (e.g., shape) significantly affect the properties of helical springs; therefore, the stiffness and deformation can be controlled by varying them for a particular application. Furthermore, in designing variable dimension helical springs, nonlinear force-displacement behaviors and stiffness, along with reductions in weight and maximum stresses, can be obtained. Finally, it was concluded that by optimally defining the above parameters, a spring with an ideal geometry can be designed, thereby realizing comfort, stability, and reliability, along with other application-specific benefits (e.g., lightweight).
The International Journal of Advanced Manufacturing Technology, 2020
The mechanical properties of lattice structure are affected by the properties of the parent mater... more The mechanical properties of lattice structure are affected by the properties of the parent material, the relative density, and the topology of the unit cell. In many applications, the goal is to have a lightweight and stiff structure. Increase in stiffness can be achieved by increasing relative density but this also increases the mass. The second method to enhance the mechanical properties is by tailoring the topology of the unit cell. This method has an advantage over the previous method as it results in an increase in stiffness without any increase in mass of the structure. Periodic lattice structures can be designed for multiple constraints such as optimization of stiffness and energy absorption. Presence of sharp corners and edges causes stress concentrations which lead to lower energy absorption efficiency. This can be rectified by adding fillets. In this paper, two methods are shown to increase the stiffness and the specific energy absorption efficiency of the lattice structures without increasing the mass or relative density. Improvement in mechanical properties can be achieved by addition of fillets at the edges and by placing beams parallel to the loading direction. These improvements were applied to two lattice structures: Kelvin and Octet truss. Multi-jet fusion additive manufacturing was used to fabricate the samples for performing uniaxial compression testing. The results show a marked improvement in stiffness and energy absorption efficiency in the structures which incorporate fillets and vertical beams in the unit cells. Stiffness of Kelvin was improved by 32% by adding fillets and 70% by adding crossbars. The energy absorption efficiency was increased by 50% in Kelvin by adding fillets. Furthermore, the post-yield behavior and failure mechanism were also changed due to the addition of these elements.
Cellular materials with very highly regulated micro-architectures are promising applicant materia... more Cellular materials with very highly regulated micro-architectures are promising applicant materials for orthopedic medical uses while requiring implants or substituting for bone due to their ability to promote increased cell proliferation and osseointegration. This study focuses on the design of an acetabular cup (AC) cellular implant which was built using a vintiles cellular structure with an internal porosity of 56–87.9% and internal pore dimensions in the range of 600–1200 μm. The AC implant was then optimized for improving mechanical performance to reduce stress shielding by adjusting the porosity to produce stiffness (elastic modulus) to match with the bone, and allowing for bone cell ingrowth. The optimized and non-optimized AC cellular implant was fabricated using the SLM additive manufacturing process. Simulation (finite element analysis, FEA) was carried out and all cellular implants are finally tested under static loading conditions. The result showed that on the finite el...
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