Titanium Alloy Discs Research Articles

Diamond-like carbon (DLC) surface treatment decreases biofilm burden by S. aureus on titanium alloy in vitro- a pilot study.

Periprosthetic joint infection is a complication of total joint arthroplasty with treatment costs over $1.6billion dollars per year in the US with high failure rates. Therefore, generation of coatings that can prevent infection is paramount. Diamond-like carbon (DLC) is an ideal coating for implants as they are wear-resistant, corrosion-resistant, inert, and have a low friction coefficient. The purpose of this study was to test the efficacy of DLC surface treatment in prevention of biofilm on titanium discs infected with Staphylococcus aureus in vitro. Titanium alloy discs (n = 4 non-coated and n = 4 DLC-coated) were infected with 5 × 105 colony-forming units (CFU) of S. aureus for 2 weeks then analysed via crystal violet and scanning electron microscopy (SEM). Crystal violet analysis yielded differences in the appearance of biofilm on implant surface where DLC-coated had a clumpier appearance but no difference in biofilm quantification. Interestingly, this clumpy appearance did lead to differences in SEM biofilm coverage where significantly less biofilm coverage was found on DLC-coated discs (81.78% vs. 54.17%, p < 0.003). DLC-coated titanium alloy implants may have preventative properties in S. aureus infection. Observing differences in biofilm coverage does warrant additional testing including CFU titration and biofilm kinetics with eventual use in an animal model of periprosthetic joint infection.

Nanoparticle ultrasonication outperforms conventional irrigation solutions in eradicating Staphylococcus aureus biofilm from titanium surfaces: an in vitro study.

Bacterial biofilms create a challenge in the treatment of prosthetic joint infection (PJI), and failure to eradicate biofilms is often implicated in the high rates of recurrence. In this study, we aimed to compare the effectiveness of a novel nanoparticle ultrasonication technology on Staphylococcus aureus biofilm eradication compared to commonly used orthopedic irrigation solutions. Twenty-four sterile, titanium alloy discs were inoculated with a standardized concentration of methicillin-resistant S. aureus and cultured for seven days to allow for biofilm formation. Discs were then treated with either ultrasonicated nanoparticle therapy or irrigation with chlorhexidine gluconate, povidone-iodine or normal saline. The remaining bacteria on each surface was subsequently plated for colony-forming units of S. aureus. Bacterial eradication was reported as a decrease in CFUs relative to the control group. Mann-Whitney U tests were used to compare between groups. Treatment with ultrasonicated nanoparticles resulted in a significant mean decrease in CFUs of 99.3% compared to controls (p < 0.0001). Irrigation with povidone-iodine also resulted in a significant 77.5% reduction in CFUs compared to controls (p < 0.0001). Comparisons between ultrasonicated nanoparticles and povidone-iodine demonstrated a significantly higher reduction in bacterial CFUs in the nanoparticle group (p < 0.0001). Ultrasonicated nanoparticle were superior to commonly used bactericidal irrigation solutions in the eradication of S. aureus from a titanium surface. Future clinical studies are warranted to evaluate this ultrsonication technology in the treatment of PJI.

In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Coculture

BackgroundCobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by coculturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a coculture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups. MethodsMurine macrophages were cultured on American Society for Testing and Materials F1537 CoCrMo and F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a coculture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy. ResultsPitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < .01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < .001), activated macrophages alone (P < .01), and nonactivated macrophages and lymphocytes (P < .05). No differences in the oxide levels were found among the Ti6Al4V groups. ConclusionsThis study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

The Effect of Titanium Anodization on the Bond Strength of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) Resin Cement.

To examine the effects of anodization and different surface modifications of titanium on bond strength to 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) resin cement. Grade 5 titanium alloy disks (n = 160) were assigned to one of five prebonding surface treatment study groups (polished; polished and anodized; polished, etched, and anodized; sandblasted; sandblasted and anodized). Disks were adhesively bonded with 10-MDP resin cement (Panavia 21; bonding area: 3.3 mm in diameter) to composite resin cylinders. In each study group, tensile bond strength tests were conducted after 24 ± 1 hours and after 6 months (180 ± 2 days) of water storage (n = 16 specimens per water storage subgroup). Debonded specimens were stereomicroscopically analyzed to determine their fracture mode. Statistics included one-way and multifactorial ANOVA and Tukey post hoc tests (α = .05). Anodization and water storage did not significantly (P ≥ .389) affect tensile bond strength. Although subgroups of polished samples had significantly (P ≤ .031) lower bond strengths (subgroup mean values: 20 to 26 MPa) than etched or sandblasted samples (subgroup mean values: 29 to 33 MPa), they nonetheless exceeded the empirical threshold of 10 MPa used as a criterion for clinical recommendation. The fracture mode of all test specimens was predominantly cohesive. Anodization of titanium surfaces can be performed without weakening the adhesion of 10-MDP-based resin cement to titanium.

Study on noise behavior of micro-textured composite coated cemented carbide surface grinding titanium alloy based on HHT analysis

In modern industrial production, noise can reflect the cutting state of the workpiece and tool to a certain extent, and the noise collection method cannot interfere with the complex processing environment. To further improve the cutting performance of coated cemented carbide micro-textured tools, this paper builds a friction and wear test platform for micro-textured cemented carbide pins with AlSiTiN-AlCrN coating and titanium alloy discs. Based on the test noise signal, the relationship between friction and wear and the noise of the workpiece was studied by the Hilbert–Huang transform (HHT). Through the change of noise in different periods, the micro-texture and coating life of cemented carbide pin under other processing parameters were analyzed. Based on the influence of the interaction between processing parameters and micro-texture diameter on the test results, the test parameters were optimized. The results show that the change of noise signal during the test presents a “V” curve with the grinding process, which mainly affects the noise through the shift of pin-disc friction form and the anti-wear effect of micro-texture. The interaction mainly affects the test results by affecting the micro-texture diameter, laser energy concentration, and the roughness of the inner wall of the pit. The optimized micro-texture geometry and preparation parameters are as follows: scanning times is 8, micro-texture diameter is 50 μm, scanning speed is 1500 mm/s, micro-texture spacing is 170 μm, and laser power is 40 W. The research content of this paper provides a reference for improving the surface properties of cemented carbide.

Piezoelectric ultrasonic debridement as new tool for biofilm removal from orthopedic implants: A study in vitro.

Pulse lavage (PL) debridement is the standard treatment used in Debridement, Antibiotics and Implant Retention (DAIR) for bacterial biofilm removal during acute and early postoperative cases of periprosthetic joint infection (PJI). The failure rate of DAIR is still high due to the inadequacy of PL in removing the biofilm. Ultrasound-based techniques are a well-established tool for PJI diagnosis due to their ability to completely eradicate the biofilm from implant surfaces. Hence, this study investigates the efficiency of a piezoelectric ultrasonic scalpel (PUS) in removing bacterial biofilm from different orthopedic implant materials in vitro and compares the results with PL. Biofilms of methicillin-resistant Staphylococcus aureus strains were grown on titanium alloy (Ti6Al4V ELI), stainless steel (AISI 316L), and ultrahigh molecular weight polyethylene (UHMWPE) disks for 24 h. The disks of each material were divided into three groups: (i) a control group (no lavage/debridement), (ii) a group treated with PL, (iii) a group treated with PUS. The disks were then sonicated for viable cell count to measure the residual biofilm content. Compared to the initial cell count (105 CFU/mLfor each material), PL showed a two-log reduction of CFU/mL(p < 0.001 for each material), while for PUS a four-log reduction was found (p < 0.001 for each material). The comparison between the two lavage/debridement displayed a two-log reduction of CFU/mL(p < 0.001 for each material) of PUS compared with PL. Its increased efficiency compared with PL promotes the use of PUS in removing bacterial biofilm from orthopedic implants, suggesting its implementation to improve the success rate of DAIR.

Antibacterial Efficacy and Surface Characteristics of Boron Nitride Coated Dental Implant: An In-Vitro Study.

This in vitro study evaluated bacterial cell proliferation and biofilm adhesion on titanium discs with and without antibacterial surface treatment to reduce the chances of peri-implant infections. Hexagonal boron nitride with 99.5% purity was converted to hexagonal boron nitride nanosheets via the liquid phase exfoliation process. The spin coating method was used for uniform coating of h-BNNSs over titanium alloy (Ti6Al4V) discs. Two groups of titanium discs were formed: Group I (n = 10) BN-coated titanium discs and Group II (n = 10) uncoated titanium discs. Two bacterial strains, Streptococcus mutans (initial colonizers) and Fusobacterium nucleatum (secondary colonizers), were used. A zone of inhibition test, microbial colony forming units assay, and crystal violet staining assay were used to evaluate bacterial cell viability. Surface characteristics and antimicrobial efficacy were examined by scanning electron microscopy with energy dispersion X-ray spectroscopy. SPSS (Statistical Package for Social Sciences) version 21.0 was used to analyze the results. The data were analyzed for probability distribution using the Kolmogorov-Smirnov test, and a non-parametric test of significance was applied. An inter-group comparison was done using the Mann-Whitney U test. A statistically significant increase was observed in the bactericidal action of BN-coated discs compared to uncoated discs against S. mutans, but no statistically significant difference was found against F. nucleatum.

199. A novel and scalable antimicrobial surface modification technology to prevent and mitigate implant related surgical site infections: an in-vivo safety and efficacy study

<h3>BACKGROUND CONTEXT</h3> Despite significant technological advancements in material science, a high level of hand-hygiene and systematic use of antiseptics and antibiotics, surgical site infections (SSI) are still to date the number one complication seen after surgery in the United States. Methicillin-resistant Staphylococcus aureus (MRSA) is the largest purveyor of health care-acquired infections (HCAI) and is responsible for significant morbidity and mortality. <h3>PURPOSE</h3> This study aimed to demonstrate the in-vivo safety and antibacterial efficacy of non-eluting titanium implants covalently bound with a novel broad-spectrum biocidal quaternary ammonium compound (DBG21) against MRSA biofilm. <h3>STUDY DESIGN/SETTING</h3> Subcutaneous MRSA infection mouse model comparing the antimicrobial efficacy of untreatedversusDBG21-treated titanium alloy discs. A separate comparative safety study was performed in the absence of infection. <h3>PATIENT SAMPLE</h3> Sixty-five 11-week-old balb/c mice. <h3>OUTCOME MEASURES</h3> Efficacy study: Number of adherent bacteria on implants (CFU) and in the surrounding tissue (CFU/g) at days 7 and 14. Safety study: systemic and subacute toxicity (clinical tolerance, blood tests and histology). <h3>METHODS</h3> Efficacy Study: TiAl6V4 discs, 6mm ø, 0.5 mm thick, were activated, dip-coated in a polymer solution, and baked to produce covalently bound DBG21-treated discs. Untreated TiAl6V4 discs were used as controls. All discs underwent subsequent sterilization by 25kGy gamma-irradiation, were implanted either untreated for control mice or DBG21-treated for treated mice, and were challenged with a high-bacterial inoculum of MRSA (ATCC43300) in a well-established subcutaneous infection mouse model (11-week-old balb/c) in the absence of antibiotics. A veterinary ethics committee validated the protocol. Sixty-five mice (33 controls, 32 treated) were included in an antibacterial efficacy study. After implantation of one disc in a posterior subcutaneous pocket and closure of the skin for each mouse, 7 log10CFU (colony forming units) of MRSA were injected through a catheter into the operating site. Mice were sacrificed after either 7 days (18 treated, 18 controls) or 14 days (15 controls, 14 treated) to determine the number of adherent bacteria (biofilm) on implants and in the peri-implant surrounding tissues. Results were expressed respectively as median log10CFU reduction on implants and median log10CFU/g reduction in tissue compared with untreated control mice. The statistical significance (p) was determined using Mann-Whitney tests. Safety Study: Ten mice implanted with either control (5 mice) or DBG-21 treated (5 mice) discs were assessed in a safety study in the absence of infection (ISO 10993-11:2017 for systemic and subacute toxicity including clinical tolerance, blood tests and local histology). <h3>RESULTS</h3> Efficacy Study: At both 7 and 14 days, DBG21-treated implants yielded a significant decrease in MRSA biofilm (respectively 3.6 median log10CFU (99.97%) reduction (p < 0.001) and 1.9 median log10CFU (98.7%) reduction (p = 0.037)) and peri-implant surrounding tissues (respectively 2.7 median log10CFU/g (99.8%) reduction (p < 0.001) and 5.6 median log10CFU/g (99.9997%) reduction (p < 0.001)). At day 7, three treated mice (16.6%) were completely sterilized on both tissue and implant. At day 14, 10 treated mice (71.4%) had sterile peri-implant tissue. Safety Study: There were no significant differences between control and treated mice in terms of clinical scores, blood tests and local histology after up to 11 days from implantation. <h3>CONCLUSIONS</h3> Preventing biofilm formation has been recognized as a key element of SSI prevention. Yet, no biofilm-resistant titanium implants are available in clinical practice to prevent and mitigate the burden of SSIs. This small animal safety and efficacy trial suggests that DBG-21 is a promising candidate for antimicrobial surface modification of titanium implants. <h3>FDA DEVICE/DRUG STATUS</h3> DBG21 antimicrobial surface modification (Not approved for this indication).

The effect of surface roughness and chitosan deposition volume on microbial growth in biofilm involving titanium surfaces for orthopaedic applications

Orthopaedic hardware infections are a significant health and economic burden and have been reported to be the cause of many revision surgeries in total hip and knee arthroplasties. Many of these infections are caused by microbial growth in biofilm on the surface of the implanted device. Chitosan surface modifications of fracture fixation implants have shown to reduce infection rates and improve clinical results in orthopaedic procedures. Additional work is needed to determine the role of the chitosan deposition volume and substrate surface roughness on biofilm growth. In this study, titanium alloy discs were prepared to have a range of six surface roughness magnitudes, as well as four different concentrations of chitosan coatings. Analysis of in vitro tests with Staphylococcus aureus (S. aureus) showed that the bacterial concentration in biofilm was significantly affected by surface roughness and chitosan concentration. Titanium surfaces with low to intermediate average roughness values (between 0.1 and 1.5 µm) and higher concentrations of chitosan best inhibited biofilm adhesion. Additional work should explore the mechanisms of chitosan's antibacterial activity.

Shear Bond Strength of Dental Cements on Titanium Alloy: Use of Different Restorative Materials

Different dental cements and restorative materials may have various impacts on the shear bond strength (SBS) to titanium alloy of dental implants, and some fluoride-containing cements may destroy the oxide layer of Ti alloys. The aim of this study was to evaluate the retention and SBS of different dental cements to titanium alloy using different restorative materials and also the corrosive effect of dental cements on titanium alloy. In this in-vitro study, a total of ninety titanium alloy discs (10×3 mm) and restorative material discs (7×3mm) consisting of Co-Cr soft metal, zirconia, and Ni-Cr were constructed. Three dental cement of 2 different compositional classes, glass ionomer (GI) and zinc phosphate (ZP), were used to cement the discs (n=10 in each paired disks). SBS was evaluated using a universal testing machine with a cross-head speed of 1mm/min. A stereomicroscope (×32) and a scanning electron microscope were used to determine the fracture pattern and titanium corrosion, respectively. Data were then analyzed statistically using one-way ANOVA and Tamhane comparison test (P&lt;0.05). The mean SBS of studied groups ranged from 0.12±0.07 to 6.2±0.97 Mpa, with the Ni-Cr and zirconia were demonstrated as the materials with the highest and lowest SBS to GI and ZP, respectively. The cements created a strong bond to the Co-Cr soft metal while the GI cement remained on restorative material disc surfaces in all samples, except in the zirconia sample. Mixed patterns were mostly seen in ZP cement groups. To conclude, applying fluoride-containing cements have no effect on titanium.

Improving hard metal implant and soft tissue integration by modulating the "inflammatory-fibrous complex" response.

Soft tissue integration is one major difficulty in the wide applications of metal materials in soft tissue-related areas. The inevitable inflammatory response and subsequent fibrous reaction toward the metal implant is one key response for metal implant-soft tissue integration. It is of great importance to modulate this inflammatory-fibrous response, which is mainly mediated by the multidirectional interaction between fibroblasts and macrophages. In this study, macrophages are induced to generate M1 and M2 macrophage immune microenvironments. Their cytokine profiles have been proven to have potentially multi-regulatory effects on fibroblasts. The multi-reparative effects of soft tissue cells (human gingival fibroblasts) cultured on metal material (titanium alloy disks) in M1 and M2 immune microenvironments are then dissected. Fibroblasts in the M1 immune microenvironment tend to aggravate the inflammatory response in a pro-inflammatory positive feedback loop, while M2 immune microenvironment enhances multiple functions of fibroblasts in soft tissue integration, including soft tissue regeneration, cell adhesion on materials, and contraction to immobilize soft tissue. Enlighted by the close interaction between macrophages and fibroblasts, we propose the concept of an “inflammatory-fibrous complex” to disclose possible methods of precisely and effectively modulating inflammatory and fibrous responses, thus advancing the development of metal soft tissue materials.

The Effect of Functionally Graded Materials on Temperature during Frictional Heating at Single Braking.

A mathematical model for evaluation of the temperature mode of the disc–pad system during single braking is proposed. The model is based on the thermal problem of friction formulated for two semi-infinite bodies, compressed with pressure increasing over time while reducing the sliding velocity from the initial value to zero at the stop. The exact solution to this problem was obtained by means of Duhamel’s theorem. Validation of the solution was performed by achieving in special cases parameters of known solution to this problem with constant pressure and velocity (under uniform sliding). The results of the numerical calculations are presented for a selected friction pair, made of functionally graded materials with titanium alloy (disc) and aluminum alloy (pad) cores coated with ceramics graded toward friction surfaces. For the established values of the parameters such as the rise time in pressure and the FGM gradients, the ability to quickly obtain spatiotemporal temperature distributions in the disc and pad was presented. The influence of the variability of these parameters on the maximum temperature of the brake system was also investigated.

Tribological behaviours of black phosphorus/MoS2 composites as water‐based lubrication additives

AbstractIn this investigation, a self‐assembly method was used to fabricate black phosphorus (BP)/MoS2 composites as water‐based lubrication additives. The tribological behaviours of the lubrication additives for GCr15 steel ball/TC4 titanium alloy disk contact under different mass ratios, loads and rotational speeds were also investigated. The experimental results showed that 0.01 wt.% BP and 0.04 wt.% MoS2 as water‐based lubrication additive have the best the synergistic lubrication effect. Compared with pure water, coefficient of friction (COF) and wear rate of the lubrication additive at the test conditions of 8 N and 150 r/min were reduced by 32.6% and 68.8%, respectively. As the loads increased, the COFs and wear rates of all the lubricants including pure water, BP as water‐based lubrication additive (BP‐WL), MoS2 as water‐based lubrication additive (MS‐WL) and BP/MoS2 composites as water‐based lubrication additive (BM‐WL) were all reduced. As the rational speeds increased from 100 to 250 r/min, all the lubricants were firstly decreased and then increased. Based on tribological tests and wear surface analysis, the lubrication mechanism of BM‐WL is proposed. The interlaminar shear and the adsorption of BP/MoS2 composites on the wear surface of the friction pairs are the key to reducing COFs sand wear rates. In addition, the tribo‐chemical reaction films consists of FeO/Fe2O3, Al2O3 and TiO2 were formed during the friction process, which can effectively protect the surface of the titanium alloy/steel contact from wear.

Influence of Sequential CAD/CAM Milling on the Fitting Accuracy of Titanium Three-Unit Fixed Dental Prostheses.

This study investigated the fitting accuracy of titanium alloy fixed dental prostheses (FDP) after sequential CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) fabrication. A three-unit FDP model connecting mandibular second premolars and molars was prepared and scanned to fabricate titanium FDPs by CAD/CAM milling. A total of six FDPs were sequentially milled in one titanium alloy disk using a new set of burs every time (n = 4). The fitting accuracy of FDPs was mesiodistally evaluated by a silicone replica technique and the measurement was triplicated at four different locations: MO (marginal opening), MG (marginal gap), AG (axial gap), and OG (occlusal gap). Data were statistically analyzed using ANOVA and Tukey’s HSD test. The fitting accuracy of PMMA (polymethyl methacrylate) FDPs milled using the worn or new bur were evaluated by the same procedure (n = 6). The mean dimensions of titanium FDP for all measuring positions, except for AG, were significantly increased from the third milling. However, no difference was noted between the first FDP and the second FDP milled with the same set of burs. Severe edge chippings were observed in all milling burs. Detrimental effects of the worn burs on the fitting accuracy were demonstrated in the CAD/CAM-milled PMMA FDP. The results recommend proper changing frequency of cutting burs to achieve the quality of fit and predictable outcomes for dental CAD/CAM prostheses.

Characterization and evaluation of a femtosecond laser-induced osseointegration and an anti-inflammatory structure generated on a titanium alloy.

Cell–material interactions during early osseointegration of the bone–implant interface are critical and involve crosstalk between osteoblasts and osteoclasts. The surface properties of titanium implants also play a critical role in cell–material interactions. In this study, femtosecond laser treatment and sandblasting were used to alter the surface morphology, roughness and wettability of a titanium alloy. Osteoblasts and osteoclasts were then cultured on the resulting titanium alloy disks. Four disk groups were tested: a polished titanium alloy (pTi) control; a hydrophilic micro-dislocation titanium alloy (sandblasted Ti (STi)); a hydrophobic nano-mastoid Ti alloy (femtosecond laser-treated Ti (FTi)); and a hydrophilic hierarchical hybrid micro-/nanostructured Ti alloy [femtosecond laser-treated and sandblasted Ti (FSTi)]. The titanium surface treated by the femtosecond laser and sandblasting showed higher biomineralization activity and lower cytotoxicity in simulated body fluid and lactate dehydrogenase assays. Compared to the control surface, the multifunctional titanium surface induced a better cellular response in terms of proliferation, differentiation, mineralization and collagen secretion. Further investigation of macrophage polarization revealed that increased anti-inflammatory factor secretion and decreased proinflammatory factor secretion occurred in the early response of macrophages. Based on the above results, the synergistic effect of the surface properties produced an excellent cellular response at the bone–implant interface, which was mainly reflected by the promotion of early ossteointegration and macrophage polarization.

The lubrication performance and viscosity behavior of castor oil under high temperature

Castor oil is an environment-friendly lubricant with good biodegradability and renewable behavior. However, castor oil as a green lubricant has a few shortcomings, such as a low viscosity index and low oxidative stability due to the presence of unsaturated bonds. The temperature affects the lubrication performance of castor oil. In the present study, the lubrication performance and viscosity behavior of castor oil lubricating the friction pair of a steel ball and a nickel–titanium (NiTi) alloy disk were systematically investigated under different temperatures. The results show that the lubrication performance of castor oil is influenced by temperature due to the fact that the viscosity of castor oil varies with the temperature. The coefficient of friction (CoF) of castor oil is as super-low as 0.076 at a temperature of 40°C, but is relatively high at other temperatures. The factors affecting the lubrication performance were investigated, and a possible antifriction mechanism is proposed in this study.

ОЦЕНКА ДЕФЕКТНОСТИ ЗАГОТОВОК ИЗ ТИТАНОВЫХ СПЛАВОВ ДЛЯ ВЕРОЯТНОСТНОГО РАСЧЕТА РИСКА РАЗРУШЕНИЯ ДИСКОВ ГАЗОТУРБИННЫХ ДВИГАТЕЛЕЙ В ЭКСПЛУАТАЦИИ

The paper observes the issues of calculation of anomalic distribution of frequencies and sizes of defects in titanium alloy billets and forgings for gas turbine engine disks, for the case of absence of statistical information of defects detected during non-destructive testing. Deficiency evaluation method is proposed, taking into account individual scanning schemes at ultrasonic testing. A mathematical apparatus is given, which makes it possible to numerically evaluate deficiency for titanium alloy billets and disks for gas turbine engine.

Effects of Ti6Al4V Surfaces Manufactured through Precision Centrifugal Casting and Modified by Calcium and Phosphorus Ion Implantation on Human Osteoblasts

(1) In order to enable a more widespread use of uncemented titanium-based endoprostheses to replace cobalt-containing cemented endoprostheses for joint replacement, it is essential to achieve optimal osseointegrative properties and develop economic fabrication processes while retaining the highest biomedical quality of titanium materials. One approach is the usage of an optimized form of Ti6Al4V-precision casting for manufacturing. Besides the chemical and physical properties, it is necessary to investigate possible biological influences in order to test whether the new manufacturing process is equivalent to conventional methods. (2) Methods: Primary human osteoblasts were seeded on discs, which were produced by a novel Ti6Al4V centrifugal-casting process in comparison with standard machined discs of the same titanium alloy. In a second step, the surfaces were modified by calcium or phosphorus ion beam implantation. In vitro, we analyzed the effects on proliferation, differentiation, and apoptotic processes. (3) Results: SEM analysis of cells seeded on the surfaces showed no obvious differences between the reference material and the cast material with or without ion implantation. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) proliferation assay also did not reveal any significant differences. Additionally, the osteogenic differentiation process tested by quantitative polymerase chain reactions (PCR), Alizarin red S assay, and C-terminal collagen type I propeptide (CICP) Elisa was not significantly modified. No signs of induced apoptosis were observed. (4) Conclusions: In this study, we could show that the newly developed process of centrifugal casting generated a material with comparable surface features to standard machined Ti6Al4V material. In terms of biological impact on primary human osteoblasts, no significant differences were recognized. Additional Ca- or P-ion implantation did not improve or impair these characteristics in the dosages applied. These findings indicate that spin casting of Ti6Al4V may represent an interesting alternative to the production of geometrically complex orthopedic implants.

Fracture resistance parameters for the compressor disk imitation model

This paper presents a calculation and experimental technique for determining stress intensity factors in an imitation model of a titanium alloy disk. We studied a low-pressure compressor disk of a gas turbine engine (GTE) D-36. During operations, there occur fatigue cracks initiated and developed in the slot fillet under the blade at the place of transition of the bottom to the lateral surface of the inter-groove projection, which lead to a separation of the disk’s part within its rim. The mixed-mode crack growth occured in the compressor disks. Based on the principles of imitation modeling, the geometry and loading condition of the imitation model of the compressor disk was developed. The fatigue test of the imitation model was carried out with a frequency of 5 Hz, at room temperature and with stress ratio Rc = 0.1, by means of a biaxial testing machine. The crack growth was monitored using an optical microscope. The criterion for failure was the condition for reaching a growing crack of the compensation hole. During the test, the positions and sizes of the crack fronts were fixed, which are the basis for the numerical calculation of the fracture resistance parameters. In the order of the numerical studies, six three-dimensional finite element models with different positions and sizes of the crack fronts are considered. The results of the numerical calculations based on the finite element method were used to determine the distributions of elastic and plastic stress intensity factors along each crack front. We demonstrated the advantages of the calculation and experimental methods for solving the problems of interpretation and prediction of the crack growth in the rotating disks of turbomachines using the methods of fracture mechanics.

Evaluation of Antibacterial and Cytotoxic Properties of a Fluorinated Diamond-Like Carbon Coating for the Development of Antibacterial Medical Implants.

Peri-implant infection is a serious complication in surgical procedures involving implants. We conducted an in vitro study to determine whether the use of a fluorinated diamond-like carbon (F-DLC) coating on a titanium alloy surface can prevent peri-implant infection. After applying the F-DLC, we evaluated its antibacterial and cytotoxic properties. The coating groups, containing controlled fluorine concentrations of 5.44%, 17.43%, 24.09%, and 30%, were examined for the presence of Staphylococcus aureus and Escherichia coli according to ISO 22196 for the measurement of antibacterial activity on plastics and other nonporous surfaces. Biological toxicity was evaluated using Chinese hamster V79 cells according to ISO 10993-5 for the biological evaluation of medical devices. In the control group, populations of S. aureus and E. coli substantially increased from 2.4 × 104 to (1.45 ± 1.11) × 106 colony-forming units (CFUs) and from 2.54 × 104 to (4.04 ± 0.44) × 106 CFUs, respectively. However, no bacteria colonies were detected in any F-DLC group with a fluorine concentration of ≥ 17.43%. In the biological toxicity study, an F-DLC coating with a fluorine concentration of 30% showed a colony formation rate of 105.8 ± 24.1%, which did not differ significantly from the colony formation rate of 107.5 ± 31.1% in the nontoxic control group. An F-DLC coating on titanium alloy discs showed excellent in vitro antibacterial activity with no biological toxicity.