Effects of Surface Integrity on In-Vitro Corrosion of Biodegradable Magnesium-Calcium Orthopedic Implants

2011 ◽  
Author(s):  
M. Salahshoor ◽  
Y. B. Guo
Keyword(s):  
Surface Integrity ◽  
Human Body ◽  
Rolling Force ◽  
Cutting Speed ◽  
Orthopedic Implants ◽  
Critical Issue ◽  
Dry Cutting ◽  
Modify Surface ◽  
Biodegradable Magnesium

Biodegradable magnesium-calcium (MgCa) alloys are capable of gradually dissolving and becoming absorbed in the human body after implantation. The critical issue that hinders the application of MgCa implants is their fast corrosion rate in human body fluids. A promising approach to tackle this issue is to tailor surface integrity of orthopedic implants for tuning the corrosion kinetic. The synergistic dry cutting and burnishing is used in this study to modify surface integrity of MgCa0.8 (wt%) implants for controlled corrosion performance. The effects of cutting speed and rolling force, as key parameters in the synergistic dry cutting-finish burnishing, on the electrochemical responses of the processed surfaces are investigated in the simulated body fluid (SBF). Potentiodynamic polarization curves are measured, and morphology and elemental composition of corroded surfaces are studied utilizing scan electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively.

Surface Integrity of Magnesum-Calcium Orthopedic Biomaterial Procesed by Dry High-Speed Face Milling

2010 ◽  
Author(s):  
M. Salahshoor ◽  
Y. B. Guo
Keyword(s):  
Surface Integrity ◽  
Human Body ◽  
High Speed ◽  
Mechanical Load ◽  
Cutting Speed ◽  
Polycrystalline Diamond ◽  
Orthopedic Implants ◽  
Face Milling ◽  
Depth Of Cut ◽  
Machining Parameter

Biodegradable magnesium-calcium (Mg-Ca) implants have the ability to gradually dissolve and absorb into the human body after implantation. The critical issue that hinders the application of Mg-Ca implants is its poor corrosion resistance to human body fluids. A promising approach to tackle this issue is tailoring the surface integrity characteristics of the orthopedic implants to get an appropriate corrosion kinetic. High speed face milling of biodegradable Mg-Ca alloy is used in this study as a possible way to achieve that goal. Polycrystalline diamond inserts are used to avoid material adhesion and likely fire hazards. All the cutting tests are performed without using coolant to keep the manufacturing process ecological. High cutting speed of 40 m/s and 200 μm depth of cut are applied in a broad range of feed values to cover finish and rough cutting regimes. The effect of feed as a key machining parameter which defines the amount and duration of thermo-mechanical load and ultimately provides higher chances for surface integrity changes are investigated.

Characterization and Modification of Surface Topography by Sequential Laser Peening Biodegradable Magnesium-Calcium Alloy

2010 ◽  
Author(s):  
M. P. Sealy ◽  
Andrew Guo ◽  
Y. B. Guo
Keyword(s):  
Surface Topography ◽  
Human Body ◽  
Stress Shielding ◽  
Treatment Method ◽  
Critical Issue ◽  
Biodegradable Implants ◽  
Superior Surface ◽  
Shock Peening ◽  
Biodegradable Magnesium

The development of biodegradable implants has had a beneficial effect on in-vivo treatment of patients with various bone ailments. Currently, biodegradable implants are mainly made of polymers, such as PLA or PMMA. However, these polymer based implants usually have unsatisfactory mechanical strength and are prone to considerable amounts of wear [1]. An alternative to polymers is a biodegradable magnesium-calcium (Mg-Ca) alloy which has the ability to gradually dissolve and absorb into the human body after implantation. The similar properties of Mg to bone indicate it is an ideal implant material to minimize the damaging effects of stress shielding. The critical issue that hinders the application of Mg implants is poor corrosion resistance to human body fluids. Sequential laser shock peening (LSP) of a biodegradable Mg-Ca alloy was initiated to create a superior surface integrity for improving implant performance. LSP is an innovative surface treatment method to impart deep compressive residual stresses across a broad area of an implant. The high compressive residual stress has great potential to slow corrosion rates and improve wear and fatigue performance. Also, LSP produces a unique surface topography. Structural surface modifications are an effective way to alter the implant/tissue interface in order to improve biocompatibility.

Investigations on the Effect of CNC Dry Hard Turning Process Parameters on Surface Integrity: A Multi-performance Characteristics Optimization

2014 ◽  
Vol 14 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Suha K. Shihab ◽  
Zahid A. Khan ◽  
Aas Mohammad ◽  
Arshad Noor Siddiquee
Keyword(s):  
Surface Roughness ◽  
Surface Integrity ◽  
Feed Rate ◽  
Hard Turning ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Influential Factor ◽  
Depth Of Cut ◽  
Micro Hardness ◽  
Dry Cutting

AbstractThe cutting parameters such as the cutting speed, the feed rate, the depth of cut, etc. are expected to affect the two constituents of surface integrity (SI), i.e., surface roughness and micro-hardness. An attempt has been made in this paper to investigate the effect of the CNC hard turning parameters on the surface roughness average (Ra) and the micro-hardness (μh) of AISI 52100 hard steel under dry cutting conditions. Nine experimental runs based on an orthogonal array of the Taguchi method were performed and grey relational analysis method was subsequently applied to determine an optimal cutting parameter setting. The feed rate was found to be the most influential factor for both the Ra and the μh. Further, the results of the analysis of variance (ANOVA) revealed that the cutting speed is the most significant controlled factor for affecting the SI in the turning operation according to the weighted sum grade of the surface roughness average and micro-hardness.

The Effects of Cutting Conditions on Surface Integrity in Machining Waspaloy

2014 ◽  
Vol 611-612 ◽  
pp. 1243-1249
Author(s):  
Domenico Umbrello
Keyword(s):  
Tool Wear ◽  
Surface Integrity ◽  
Cutting Speed ◽  
Production Costs ◽  
Cutting Conditions ◽  
Dry Cutting ◽  
Important Indicator ◽  
Coated Tools ◽  
Coated Tool ◽  
Environmentally Safe

Machining of advanced aerospace materials have grown in the recent years although the difficult-to-machine characteristics of alloys like titanium or nickel based alloys cause higher cutting forces, rapid tool wear, and more heat generation. Therefore, machining with the use of cooling lubricants is usually carried out. To reduce the production costs and to make the processes environmentally safe, the goal is to move toward dry cutting by eliminating cutting fluids. This objective can be achieved by using coated tool, by increasing cutting speed and by improving the product performance in term of surface integrity and product quality. The paper addresses the effects of cutting speed and feed on the surface integrity during dry machining of Waspaloy using coated tools. In particular, the influence of the cutting conditions on mechanical power consumption, the tool wear and some important indicator of the surface integrity (surface roughness, affected layer, microhardness, grain size and microstructural alteration) were investigated. Results show that cutting conditions have a significant effect on the parameters related to the surface integrity of the product affecting its overall performance.

scholarly journals Keutuhan Permukaan Bahan Keluli Perkakas Setelah Pengisaran Hujung Menggunakan Perkakas Karbida Bersalut

2012 ◽  
Author(s):  
Che Hassan Che Haron ◽  
Andanastuti Muchtar ◽  
Nik Faizu Nik Kundor
Keyword(s):  
Tool Steel ◽  
Surface Integrity ◽  
End Milling ◽  
Cutting Speed ◽  
Milling Process ◽  
Cutting Condition ◽  
Dry Cutting ◽  
Machined Surface ◽  
Aisi D2 ◽  
Coated Carbide

Projek ini dijalankan bertujuan untuk mengkaji kesan proses pengisaran terhadap keutuhan permukaan keluli perkakas D2. Dalam kajian ini, keluli perkakas kerja sejuk AISI D2 yang telah dikeraskan kepada 62 HRC dimesin menggunakan sisip karbida bersalut CVD boleh indeks yang dipegang oleh perkakas pengisaran hujung berdiameter 20 mm. Siri–siri ujian dijalankan dalam keadaan kering. Penilaian ke atas permukaan yang dimesin melibatkan kekasaran permukaan dan analisis mikrostruktur. Keputusan kajian menunjukkan bahawa tiada hubungan yang jelas di antara variasi kelajuan pemotongan dan suapan terhadap kekasaran permukaan. Umumnya, permukaan yang dihasilkan adalah sangat licin dengan nilai Ra berada dalam julat 0.10 μm – 0.43 μm dan analisis permukaan pada sampel–sampel ujikaji juga mendapati hampir tiada perubahan dapat dikesan pada mikrostruktur bahagian bawah permukaan yang dimesin. Walau bagaimanapun, pada kelajuan pemotongan tertinggi (160 m/min) dan suapan yang tinggi (0.02 mm/sisip), terdapat kesan termampat dan terherot pada mikrostruktur pada kedalaman yang sangat cetek iaitu lebih kurang 2.2 μm dari permukaan termesin. Kata kunci: Keutuhan permukaan, keluli perkakas terkeras, pengisaran hujung, mikrostruktur, perkakas karbida bersalut The effect of milling process on the surface integrity of newly machined surface of D2 tool steel is presented. The hardened AISI D2 (62 HRC) was machined under dry cutting conditions using a 20 mm diameter end–milling tool with indexable CVD coated carbide insert. Analyses revealed that the variation in cutting speeded and feed did not significantly affect the surface roughness of the machined surface. Generally, the surfaces produced are very smooth with Ra values in the range of 0.1 – 0.43 μm, and studies showed almost no microstructure alteration on the machined surfaces. However, at the highest cutting condition, i.e. a cutting speed of 160 m/min, and feed of 0.02 mm/tooth, some compression and distortion effects were detected on the microstructure at the very shallow depth of approximately 2.2 μm from the machined surface. Key words: Surface integrity, hardened tool steel, end-milling, microstructure, coated carbide tool

scholarly journals Effect of Calcination Time on Bovine-Derived Hydroxyapatite as Bone Implant Material: An In Vitro Study

2020 ◽  
Vol 8 (5) ◽  
Author(s):  
Jojorlamsihar Manalu ◽  
, Francisca Tjhay ◽  
Theodora Kristoforus
Keyword(s):  
Human Body ◽  
Cost Effective ◽  
Orthopedic Implants ◽  
Holding Time ◽  
Bovine Bone ◽  
Calcination Time ◽  
Bone Implant ◽  
X Ray ◽  
Implant Material

Bone fracture incidence has been increasing, according to recent studies. For a fracture to heal, orthopedic implants are usually employed. One of the bioceramics used is hydroxyapatite (HAp), which has a similar chemical structure with bone mineral and is biocompatible, bioactive as well as non-toxic to the human body. Current methods of HAp synthesis are mostly still toxic to the human body and expensive. Hydroxyapatite originated from natural resources can provide more favorable materials. The purpose of this study is to characterize HAp extracted from bovine bone calcination at 850°C for various holding times as bone implant material. The toxicity of the bovine-derived HAp is also assessed. Prepared bovine bones were subjected to calcination at 850°C over various holding times. The characterization was carried out with thermogravimetric analysis (TGA) instrument followed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier-Transform Infrared Spectroscopy (FT- IR). The toxicity of the bovine HAp was assessed using MTT (3-[4, 5-dimethyl-thiazol-2-yl-]-2, 5-diphenyltetrazolium bromide) assay. Each of the parameters was compared between the HAp extracted from bovine and the commercial HAp. Analysis of the phase, purity, and crystallinity showed that the bovine-derived HAp was similar to the standard HAp. Crystal agglomeration was observed at increased calcination time. The optimal holding time of 5 hours was demonstrated through the closest Ca/P ratio (1.679) to the stoichiometric HAp (Ca/P ratio = 1.67) in EDX analysis. The toxicity test using the MTT assay showed that the viabilities of CPAE cells treated with bovine HAp were well above 60% (non-toxic threshold). In conclusion, hydroxyapatite produced from bovine bone calcination at 850°C with 5 hours of holding time has the characteristics which are similar to the commercial HAp. This natural HAp has proven to be non-toxic and also cost-effective.  

Effects of cutting fluid with different pressures and jetting paths on machined surface integrity in cutting compacted graphite iron: An experimental study

2019 ◽  
Vol 233 (13) ◽  
pp. 2410-2418 ◽  
Author(s):  
Limin Feng ◽  
Guosheng Su ◽  
Jin Du ◽  
Jingjie Zhang ◽  
Baolin Wang
Keyword(s):  
Surface Integrity ◽  
Fluid Pressure ◽  
Cutting Speed ◽  
Cutting Fluid ◽  
Compacted Graphite Iron ◽  
Dry Cutting ◽  
Machined Surface ◽  
Compacted Graphite ◽  
Flank Face ◽  
Machined Surface Integrity

Compacted graphite iron is one of the existing structural materials for automobile engines that is difficult to machine using the conventional machining method. This article focuses on the effects of cutting fluid with different pressures and jetting paths on machined surface integrity in the machining of compacted graphite iron. The machined surface integrity is compared between dry cutting and 6 MPa wet cutting at cutting speeds of 100–500 m/min and the influences of the cutting fluid jetting paths (pouring, 2–6 MPa) along the tool flank face and rake face on the machined surface integrity are evaluated. Microstructure, roughness, work hardening, and residual stresses of the machined surface are also analyzed. The results suggest that cutting fluid can reduce surface defects and improve the machined surface finish. Of note, the roughness reduction effect decreases with an increase in fluid pressure; the roughness Ra of 6 MPa wet cutting with the cutting fluid jetting along the flank face is 0.2–1.56 µm lower than that seen with dry cutting in the cutting speed range of 100–500 m/min. The degree of hardening in 6 MPa wet cutting is 11%–19% lower than in dry cutting, and cutting fluid enhances the formation of residual compressive stress in the machined surface which reaches its maximum at 3 MPa.

Effects of Process Parameters on Surface Roughness and MRR in the hard turning of EN 36 steel

2018 ◽  
pp. 102-110
Author(s):  
Amritpal Singh ◽  
Rakesh Kumar
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Material Removal ◽  
Hard Turning ◽  
Control Parameter ◽  
Removal Rate ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Cutting Condition ◽  
Dry Cutting

In the present study, Experimental investigation of the effects of various cutting parameters on the response parameters in the hard turning of EN36 steel under the dry cutting condition is done. The input control parameters selected for the present work was the cutting speed, feed and depth of cut. The objective of the present work is to minimize the surface roughness to obtain better surface finish and maximization of material removal rate for better productivity. The design of experiments was done with the help of Taguchi L9 orthogonal array. Analysis of variance (ANOVA) was used to find out the significance of the input parameters on the response parameters. Percentage contribution for each control parameter was calculated using ANOVA with 95 % confidence value. From results, it was observed that feed is the most significant factor for surface roughness and the depth of cut is the most significant control parameter for Material removal rate.

scholarly journals YAP1 overexpression contributes to the development of enzalutamide resistance by induction of cancer stemness and lipid metabolism in prostate cancer

Oncogene ◽  
2021 ◽  
Author(s):  
Hsiu-Chi Lee ◽  
Chien-Hui Ou ◽  
Yun-Chen Huang ◽  
Pei-Chi Hou ◽  
Chad J. Creighton ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Lipid Metabolism ◽  
Critical Issue ◽  
Castration Resistant Prostate Cancer ◽  
Cancer Stemness ◽  
New Treatment ◽  
Underlying Mechanisms ◽  
Transcriptional Complex

AbstractMetastatic castration-resistant prostate cancer (mCRPC) is a malignant and lethal disease caused by relapse after androgen-deprivation (ADT) therapy. Since enzalutamide is innovated and approved by US FDA as a new treatment option for mCRPC patients, drug resistance for enzalutamide is a critical issue during clinical usage. Although several underlying mechanisms causing enzalutamide resistance were previously identified, most of them revealed that drug resistant cells are still highly addicted to androgen and AR functions. Due to the numerous physical functions of AR in men, innovated AR-independent therapy might alleviate enzalutamide resistance and prevent production of adverse side effects. Here, we have identified that yes-associated protein 1 (YAP1) is overexpressed in enzalutamide-resistant (EnzaR) cells. Furthermore, enzalutamide-induced YAP1 expression is mediated through the function of chicken ovalbumin upstream promoter transcription factor 2 (COUP-TFII) at the transcriptional and the post-transcriptional levels. Functional analyses reveal that YAP1 positively regulates numerous genes related to cancer stemness and lipid metabolism and interacts with COUP-TFII to form a transcriptional complex. More importantly, YAP1 inhibitor attenuates the growth and cancer stemness of EnzaR cells in vitro and in vivo. Finally, YAP1, COUP-TFII, and miR-21 are detected in the extracellular vesicles (EVs) isolated from EnzaR cells and sera of patients. In addition, treatment with EnzaR-EVs induces the abilities of cancer stemness, lipid metabolism and enzalutamide resistance in its parental cells. Taken together, these results suggest that YAP1 might be a crucial factor involved in the development of enzalutamide resistance and can be an alternative therapeutic target in prostate cancer.

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