Download or read book Processing Surface Integrity and Performance of Biodegradable Magnesium calcium Implants by Laser Shock Peening written by Michael Patrick Sealy and published by . This book was released on 2014 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: Every year, several million people suffer bone fractures caused by accidents or age related diseases in the U.S. alone. The annual incidence of bone fractures is expected to escalate in the coming years due increased life expectancy. The aggregate cost of treating bone fractures is estimated at a staggering $220 billion per year with an annual growth rate of 12%. Many of those fractures have to be surgically fixed by orthopedic implants to replace and act as missing biological structures. However, some patients require a secondary surgery to revise or often remove an implant which has failed. This imposes a heavy burden on the national healthcare system. Implants fail because they are designed to be permanent fixtures attached to bone; however, current implant materials made from titanium, stainless steel, or cobalt-chromium alloys cause stress shielding when left permanently in place. Stress shielding arises when metal implants carry the majority of stress because of their much higher Young's modulus than that of bone. As a consequence, bones are in a reduced stress state which allows them to become brittle and weak over time. Weakened bones are more susceptible to re-fracture and could potentially dislodge an implant causing severe harm and discomfort to a patient. There is a need for a biomaterial that is not permanent because it has the capability to degrade. This reduces stress shielding over time as well as the need for a second removal surgery. The similar mechanical properties of magnesium (Mg) to bone indicate it is an ideal implant material to minimize the damaging effects of stress shielding. Mg alloy implants have the ability to gradually dissolve and absorb into the human body after implantation. Mg alloys as a biodegradable implant material have the potential to minimize stress shielding as well as eliminate the need for secondary surgery while providing both biocompatibility and adequate mechanical properties. The critical issue that hinders the application of a Mg alloy implant is its rapid corrosion in human body fluids. Since corrosion occurs too quickly, mechanical properties cannot be maintained long enough for bone to properly heal. Therefore, how to control the biodegradation rate of Mg-based implants to make them commercially viable for orthopaedic applications is a critical technical barrier to realizing its great socioeconomic benefits. Laser shock peening (LSP) is an innovative surface treatment to impart deep compressive residual stresses and a surface topography across a broad area on an implant. The high compressive residual stress has great potential to slow corrosion rates and improve wear and fatigue performance. Also, the peened surface topography has the potential to promote bone ingrowth and attachment. The goal of this work is to develop and evaluate LSP as an enabling manufacturing process to control the corrosion and fatigue performance of a degradable magnesium-calcium (MgCa) implant by imparting a unique surface integrity. Fabricating such a unique surface integrity for various types of orthopedic implants relies on the peening process parameters such as laser power and the peening overlap. Unique surface integrities were fabricated by changing the laser power from 3 W to 8 W as well as changing the dent overlap ratio from 25%, 50%, and 75%. The effects of LSP on surface integrity, corrosion, and fatigue were investigated. The surface integrity was characterized by topography, microstructure, microhardness, and residual stress. Corrosion rate was assessed by potentiodynamic polarization in Hank's solution. Fatigue life was measured by rotating bending fatigue test in air. LSP reduced the corrosion rate for every tested condition. Also, LSP increased the fatigue life for every tested condition. LSP at high peening overlap ratios reduced the tensile pile-up region which resulted in lower corrosion rates and the highest fatigue life. Low overlap ratios caused more surface area and more pile-up regions which translated to higher corrosion rates and reduced the fatigue life. Increasing the laser power increased the surface roughness and the size of the pile-up region which caused the corrosion rate to increase. Also, surface topography and corrosion rate models have been established based on finite element analysis (FEA) and linear regression analysis, respectively. Therefore, a manufacturing process was developed that controlled the performance of a degradable MgCa implant within the ranges needed for orthopedic applications. In addition, this research has begun modeling the relationship between surface modification and clinical performance in order to be able to develop the next generation of orthopedic implants that can be tailored to degrade to meet individual patient's needs.

Download or read book High Repetition Rate Laser Shock Peening on Biodegradable Magnesium Alloys written by Hossein Kamkarrad and published by . This book was released on 2016 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, Magnesium based alloys have been identified as a potential bio-degradable material for implants. While the biggest advantage of magnesium based implants is that it eliminates the need for additional surgery for removal, magnesium corrodes within human body much faster than the cure of broken bones. Hence, reduction of corrosion rate in magnesium surface is important to successful implementation. Laser Shock Peening (LSP) as mechanical treatment has been used successfully on implant surfaces to reduce the corrosion rate. Having reviewed the literature in LSP, it can be seen that the lasers used are low repetition rate high power lasers. Owing to cost of low repetition lasers, high repetition laser shock peening (HRLSP) is introduced in this work. The general objective of this thesis dissertation is to develop HRLSP for low mechanical strength metals/alloys like Magnesium. To this end, a feasibility study of HRLSP was performed and pertinent laser parameters for successful peening of magnesium were evaluated. The finite element analysis using Abaqus Dynamic/Static was performed in both single shot mode as well as in multi shot mode. The simulation was used to predict the surface deformation on the peened area, magnitude of Compressive Residual Stress (CRS), and the propagation of CRS along the depth from the surface. The effect of laser parameters and scanning parameters on these values have been analyzed by Finite Element Analysis (FEA). Based on the results from the feasibility study, an experimental setup involving both optical as well as scanning arrangement was performed and design of experiment was done for peening. From the experiments, with two laser intensities at 0.91GW/cm2 and 2GW/cm2, peening was possible only at 2GW/cm2. The magnitude of peening was varied by changing the %overlap between subsequent spots, and the total number scans. Increasing the number of peened shots within the specimen surface area of 10 X 10 mm, increases the magnitude of CRS that was shown by Finite Element Analysis. Comparison of peened samples to unpeened samples showed significant improvements in the mechanical attributes, comparable to that seen in the literature. The hardness increased from 45 HV to 103 HV; Surface roughness (Ra) increased from 0.35 m to 3.3 m; surface wettability measured as function of contact angle reduced from 68.5° to 44.4°; and wear resistance improved from 5.5E-4 gr/s to 1.8E-4 gr/s. The results mentioned above clearly indicate the relationship between improvements in mechanical attributes to the magnitude of peening.

Download or read book Superior Surface Integrity by Hybrid Dry Cutting hydrostatic Burnishing for Controlled Biofluid Corrosion Performance of Novel Biodegradable Magnesium Calcium Implants written by Meisam Salahshoor Pirsoltan and published by . This book was released on 2012 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compared to Young's modulii (3~30 GPa) of bones, the higher modulii (100~200 GPa) of traditional permanent metallic implants cause stress shielding and result in artificial osteoporosis. To avoid the progress of this undesirable side effect, annually many second surgeries with all their social and economical consequences must be performed to remove the permanent implants after one or two years. Magnesium-Calcium (Mg-Ca) alloys are a promising alternative to tackle the aforementioned issues since they have modulus of elasticity (40 GPa) close to those of bones and they are biodegradable. However, these alloys corrode very fast and produce a large amount of dissolved Mg cations, a large volume of hydrogen, and a remarkable increase in local pH value which will cause significant imbalance in physiological reactions. To develop Mg-Ca alloys as a successful orthopedic material, corrosion rate of these alloys should be adjusted to match the healing rate of bone tissue and local absorption rate of corrosion by-products. In this context, hybrid cutting-burnishing process has been utilized to tailor surface integrity of the Mg-Ca implants in such a way which results in gaining control on the corrosion kinetics. A synergistic numerical-experimental investigation was conducted to study process mechanics in hybrid dry cutting-hydrostatic burnishing and to characterize the induced surface integrity on processed implants. A series of short-term and long-term in-vitro corrosion tests were performed to evaluate the effects of the hybrid technique on degradation kinetics and to find the likely correlations between process parameters, surface integrity characteristics, and bioperformance of the processed Mg-Ca0.8 implants. Hybrid dry cutting-hydrostatic burnishing technique was able to reduce the in-vitro degradation kinetics. The amount of this reduction was also adjustable depending on the selected process parameters and the subsequent induced surface integrity characteristics on the implants. These results suggest that it is feasible to tailor degradation kinetics of the Mg-Ca0.8 implants at the manufacturing stage so that the degradation rate matches healing rate of the bone trauma and absorption rate of the corrosion products under various physiological conditions. Magnitude of the compressive residual stresses and the depth of the compressed layer were key parameters affecting the bioperformance.

Download or read book The Effects of Laser Shock Peening on the Residual Stress and Corrosion Characteristics of Magnesium Alloy Az91d for Use as Biodegradable Implants written by James Russo and published by . This book was released on 2012 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a continuing interest in exploring magnesium and its alloys for biomedical applications due to its low density and high strength properties that are very similar to bone. However, the high corrosion rate of magnesium and its alloys while immersed in body fluid restrict the material from use as permanent implants. The ability to control the corrosion rate of a material is an important factor in the development of biodegradable implants. An emerging topic of study for controlling the corrosion rates of different material is through imparting high levels of compressive residual stress on the surface. One effective process of imparting high levels of compressive residual stress on a material is Laser Shock Peening (LSP). Laser Shock Peening is a material process in which a high-pulsed laser creates a pressure shock wave that travels through the depth of the material, leaving high levels of compressive residual stress through its depth. This thesis will present a study on the effects of compressive residual stresses imparted through laser shock peening on the corrosion characteristics of magnesium alloy AZ91D. In order to understand all aspects of this, an in-depth material characterization of the alloy is performed. Next, an LSP study is performed in which the optimal LSP parameters are determined. The experimental results are validated using Finite Element Analysis in LS-DYNA. Once LSP parameters have been optimized, corrosion tests are performed to link the relationship between compressive residual stress and corrosion rates of AZ91D.

Download or read book Fatigue and Fracture Behaviour of Additively Manufactured Mechanical Components written by Roberto Citarella and published by MDPI. This book was released on 2021-02-19 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: The advent of additive manufacturing (AM) processes applied to the fabrication of structural components creates the need for design methodologies supporting structural optimization approaches that take into account the specific characteristics of the process. While AM processes enable unprecedented geometrical design freedom, which can result in significant reductions of component weight, on the other hand they have implications in the fatigue and fracture strength due to residual stresses and microstructural features. This is linked to stress concentration effects and anisotropy that still warrant further research. This Special Issue of Applied Sciences brings together papers investigating the features of AM processes relevant to the mechanical behavior of AM structural components, particularly, but not exclusively, from the viewpoints of fatigue and fracture behavior. Although the focus of the issue is on AM problems related to fatigue and fracture, articles dealing with other manufacturing processes with related problems are also be included.

Download or read book Analyzing the Effects of High Repetition Laser Shock Peening on Corrosion Resistance of Magnesium written by Vinodh Krishna Caralapatti and published by . This book was released on 2017 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium based alloys have been considered as a promising replacement to conventional implants owing to their compliant material properties, biocompatibility and most importantly, their biodegradability. Magnesium has properties similar to human bone, which avoids stress shielding effect, a major problem experienced with conventional implants. In addition, magnesium implants eliminate the need for successive surgery due to their biodegradable nature, which is inevitable in the case of conventional implants. Despite having numerous advantages, the major challenge in implementation is its high corrosion rate. The rapid in-vivo corrosion of magnesium implants result in instability and affect bone growth. In addition, corrosion results in hydrogen gas evolution, which is considered undesirable inside human body. It is evident from the literature that there are many methods developed with an aim to control their high corrosion rate and implement them as implants. Of these, Laser Shock Peening (LSP) is considered the most suitable method owing to its ability to provide precise control over the parameters that affect corrosion performance. However due to its prohibitive cost, its implementation is limited.Recently a new method called High Repetition Laser Shock Peening (HRLSP) was developed to make peening more affordable and encourage widespread implementation. While some previous work on the effect of HRLSP on hardness, wettability and wear resistance have been studied, in this work, the effect of HRLSP on corrosion resistance and biocompatibility of magnesium is analyzed. In addition, the effect of peening process parameters such as % overlap and number of scans on corrosion rate are studied. The experiments are initiated with unpolarized techniques and the corrosion rate & pH variation results formed the basis to validate the effectiveness of HRLSP and determine the feasibility of peened samples as implants. In the subsequent phase, the corrosion rate is tested using a specially designed test bench maintaining physiological conditions. Using this study, the importance of circulation, for understanding dynamic corrosion was stressed and the difference between static and dynamic corrosion of both peened and unpeened magnesium are highlighted. Finally, the change in hardness, surface profile and wettability resulted due to peening are determined to summarize the overall effects.Throughout the experiments, peening is confined to an area of 10 x 10 mm with laser density set at 1.4 GW/cm2. Hanks solution is used as the test medium and the results of peened samples are compared against unpeened sample to understand the effects of peening and its process parameters.Under static conditions, the corrosion rate of peened samples reduced by at least 2 times compared to unpeened sample while under dynamic conditions it reduced by 6 times. The differences in results from both studies are compared to stress the influence of surrounding conditions on corrosion process. In addition, peening reduced the size of hydrogen bubbles due to refined grain layer, which is advantageous from biological aspect. The enhanced surface hardness and precise corrosion controlling ability improve the suitability of magnesium as implants.

Download or read book Magnesium Alloys as Degradable Biomaterials written by Yufeng Zheng and published by CRC Press. This book was released on 2015-10-09 with total page 601 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnesium Alloys as Degradable Biomaterials provides a comprehensive review of the biomedical applications of biodegradable magnesium and its alloys. Magnesium has seen increasing use in orthopedic and cardiovascular applications over the last decade, particularly for coronary stents and bone implants.The book discusses the basic concepts of biodeg

Download or read book Laser shock peening Performance and process simulation written by K. Ding and published by CRC Press. This book was released on 2006-01-24 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser shock peening (LSP) is a process for inducing compressive residual stresses using shock waves generated by laser pulses. It is a relatively new surface treatment for metallic materials that can greatly improve their resistance to crack initiation and propagation brought on by cyclic loading and fatigue. This book, the first of its kind, consolidates the scattered knowledge about LSP into one comprehensive volume. It describes the mechanisms of LSP and its substantial role in improving fatigue performance in terms of modification of microstructure, surface morphology, hardness, and strength. In particular, it describes numerical simulation techniques and procedures that can be adopted by engineers and research scientists to design, evaluate, and optimize LSP processes in practical applications.

Download or read book Effect of Shot Peening on Stress Corrosion Behavior of Biodegradable Magnesium WE43 written by Tejaswita Patil and published by . This book was released on 2018 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventionally used metals for orthopedic devices made of titanium, stainless steel, and Co-Cr alloys are designed to be permanently implanted. However, long-term complications arise and a secondary implant removal surgery is often necessary. A mismatch in stiffness between the bone and implant results in stress shielding that negatively affects bone density. To overcome these problems, magnesium alloys (e.g., WE34) are favored due to a lower Young’s modulus (45 GPa) and biodegradability. The critical technical barrier with magnesium alloys is their high corrosion rate in physiological (salt-based) environments. One solution is to use surface treatments, such as shot peening (SP), to induce surface residual stresses and slow the degradation rate. The corrosion rate can be customized according to patient specific parameters, such as age and bone health, or application (i.e., pelvic fracture vs. spinal fracture) through SP process parameter manipulation (e.g., peening pressure). However, the effect of residual stresses from SP on stress corrosion behavior of magnesium alloys remains inconclusive. The purpose of this study is to evaluate the effect of shot peening with different peening pressures on the stress corrosion rate of WE43 using polarization tests. The results for this study indicate that the corrosion resistance of the alloy increased as the pressure of shot peening increased and is inversely proportional to the applied external load. A relation between the surface integrity and the stress-corrosion behavior of the shot peened samples has been found.

Download or read book Conversion Coatings for Magnesium and its Alloys written by Viswanathan S. Saji and published by Springer Nature. This book was released on 2022-02-01 with total page 577 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers fundamentals and recent advancements on conversion coatings for magnesium and its alloys. The contents are presented in two sections, respectively dealing with chemical and electrochemical conversion coatings. The chemical conversion coating section is further subdivided into inorganic conversion coatings, organic conversion coatings and advanced approaches/coatings. The section on electrochemical conversion coatings spans from fundamentals to state-of-the-art progress on electrochemical anodization and plasma electrolytic oxidation of magnesium and its alloys.

Download or read book Magnesium Alloys and Their Applications written by Barry L. Mordike and published by . This book was released on 1998 with total page 764 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Degradation of Implant Materials written by Noam Eliaz and published by Springer Science & Business Media. This book was released on 2012-08-21 with total page 521 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the current understanding of the mechanical, chemical and biological processes that are responsible for the degradation of a variety of implant materials. All 18 chapters will be written by internationally renowned experts to address both fundamental and practical aspects of research into the field. Different failure mechanisms such as corrosion, fatigue, and wear will be reviewed, together with experimental techniques for monitoring them, either in vitro or in vivo. Procedures for implant retrieval and analysis will be presented. A variety of biomaterials (stainless steels, titanium and its alloys, nitinol, magnesium alloys, polyethylene, biodegradable polymers, silicone gel, hydrogels, calcium phosphates) and medical devices (orthopedic and dental implants, stents, heart valves, breast implants) will be analyzed in detail. The book will serve as a broad reference source for graduate students and researchers studying biomedicine, corrosion, surface science, and electrochemistry.

Download or read book Surface Modification to Improve Properties of Materials written by Miran Mozetič and published by MDPI. This book was released on 2019-04-16 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains selected contributions on surface modification to improve the properties of solid materials. The surface properties are tailored either by functionalization, etching, or deposition of a thin coating. Functionalization is achieved by a brief treatment with non-equilibrium gaseous plasma containing suitable radicals that interact chemically with the material surface and thus enable the formation of rather stable functional groups. Etching is performed in order to modify the surface morphology. The etching parameters are selected in such a way that a rich morphology of the surfaces is achieved spontaneously on the sub-micrometer scale, without using masks. The combination of adequate surface morphology and functionalization of materials leads to superior surface properties which are particularly beneficial for the desired response upon incubation with biological matter. Alternatively, the materials are coated with a suitable thin film that is useful in various applications from food to aerospace industries.

Download or read book Advances in Manufacturing and Industrial Engineering written by Ranganath M. Singari and published by Springer Nature. This book was released on 2021-01-13 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents selected peer reviewed papers from the International Conference on Advanced Production and Industrial Engineering (ICAPIE 2019). It covers a wide range of topics and latest research in mechanical systems engineering, materials engineering, micro-machining, renewable energy, industrial and production engineering, and additive manufacturing. Given the range of topics discussed, this book will be useful for students and researchers primarily working in mechanical and industrial engineering, and energy technologies.

Download or read book Nanomaterials and Their Biomedical Applications written by Tuhin Subhra Santra and published by Springer Nature. This book was released on 2021-04-16 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the evolution of, and novel challenges currently facing, nanomaterials science, nanoengineering, and nanotechnology, and their applications and development in the biological and biomedical fields. It details different nanoscale and nanostructured materials syntheses, processing, characterization, and applications, and considers improvements that can be made in nanostructured materials with their different biomedical applications. The book also briefly covers the state of the art of different nanomaterials design, synthesis, fabrication and their potential biomedical applications. It will be particularly useful for reading and research purposes, especially for science and engineering students, academics, and industrial researchers.

Download or read book Additive Manufacturing written by Amit Bandyopadhyay and published by CRC Press. This book was released on 2015-09-08 with total page 547 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of additive manufacturing has seen explosive growth in recent years due largely in part to renewed interest from the manufacturing sector. Conceptually, additive manufacturing, or industrial 3D printing, is a way to build parts without using any part-specific tooling or dies from the computer-aided design (CAD) file of the part. Today, mo

Download or read book Laser Surface Engineering written by Jonathan R. Lawrence and published by Elsevier. This book was released on 2014-10-02 with total page 719 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lasers can alter the surface composition and properties of materials in a highly controllable way, which makes them efficient and cost-effective tools for surface engineering. This book provides an overview of the different techniques, the laser-material interactions and the advantages and disadvantages for different applications. Part one looks at laser heat treatment, part two covers laser additive manufacturing such as laser-enhanced electroplating, and part three discusses laser micromachining, structuring and surface modification. Chemical and biological applications of laser surface engineering are explored in part four, including ways to improve the surface corrosion properties of metals. Provides an overview of thermal surface treatments using lasers, including the treatment of steels, light metal alloys, polycrystalline silicon and technical ceramics Addresses the development of new metallic materials, innovations in laser cladding and direct metal deposition, and the fabrication of tuneable micro- and nano-scale surface structures Chapters also cover laser structuring, surface modification, and the chemical and biological applications of laser surface engineering