Titanium Alloy Plates Research Articles

Ultraviolet photofunctionalization of nanostructured titanium surfaces enhances thrombogenicity and platelet response.

The purpose of this study was to evaluate blood and platelet response to nanostructured TiO2 coatings and to investigate the effect of Ultraviolet (UV) light treatment on blood clotting ability, platelet activation and protein adhesion. Ti-6Al-4V titanium alloy plates (n = 138) were divided into three groups; a sol-gel derived MetAliveTM coating (MA); hydrothermal coating (HT); and a non-coated group (NC). Sixty nine titanium substrates were further treated with UV light for 1 h. The thrombogenicity of the titanium substrates was assessed using fresh human blood with a whole blood kinetic clotting time method. The platelet adhesion test was conducted to evaluate the morphology and adhesion behavior of the platelets on the titanium substrates. Human diluted plasma and bovine fibronectin were used to evaluate protein adsorption. Total clotting time for the UV treated HT, MA and NC titanium substrates was almost 40 min compared to 60 min for non-UV substrates, the total clotting time for the UV treated groups were significantly lower than that of the non UV NC group (p < 0.05). UV light treatment had significantly enhanced coagulation rates. The HT and MA substrates presented more platelet aggregation, spreading and pseudopod formation in comparison with the NC substrates. UV treatment did not affect the platelet activation and protein adsorption. This in vitro study concluded that nanostructured titanium dioxide implant surfaces obtained by sol-gel and hydrothermal coating methods increased coagulation rates and enhanced platelet response when compared with non-coated surfaces. UV light treatment clearly improved thrombogenicity of all examined Ti-6Al-4V surfaces.

Prediction of Fatigue Crack Growth in Gas Turbine Engine Blades Using Acoustic Emission.

Fatigue failure is the main type of failure that occurs in gas turbine engine blades and an online monitoring method for detecting fatigue cracks in blades is urgently needed. Therefore, in this present study, we propose the use of acoustic emission (AE) monitoring for the online identification of the blade status. Experiments on fatigue crack propagation based on the AE monitoring of gas turbine engine blades and TC11 titanium alloy plates were conducted. The relationship between the cumulative AE hits and the fatigue crack length was established, before a method of using the AE parameters to determine the crack propagation stage was proposed. A method for predicting the degree of crack propagation and residual fatigue life based on the AE energy was obtained. The results provide a new method for the online monitoring of cracks in the gas turbine engine blade.

Calculation Method of Curvature Radius and Bending Deformation of Titanium Alloy under Multiple Laser Shocks

TC4 titanium alloy plate was processed under multiple laser shocks and bending deformation was studied. A method was proposed to determine the curvature radius of bending deformation of metal plate under multiple laser shocks based on the theoretical model of curvature radius of bending deformation and the eigenstrain field was calculated by a modified finite element analysis method. Effect of shock wave peak pressure and the number of impacts on the curvature radius was studied. Results show that bending deformation increases rapidly at the beginning and then it stops growing. Bending deformation increases rapidly with the increase of the number of impacts and it cannot increase after three impacts.

Residual Stress Distribution and the Concept of Total Fatigue Stress in Laser and Mechanically Formed Commercially Pure Grade 2 Titanium Alloy Plates

This paper discusses the investigation of residual stresses developed as a result of mechanical and laser forming processes in commercially pure grade 2 titanium alloy plates as well as the concept of total fatigue stress (TFS). The intention of the study was to bend the plates using the respective processes to a final radius of 120 mm using both processes. The hole drilling method was used to measure residual strains in all the plates. High stress gradients were witnessed in the current research and possible cases analyzed and investigated. The effects of processing speeds and powers used also played a significant role in the residual stress distribution in all the formed plates. A change in laser power resulted in changes to residual stress distribution in the plates evaluated. This study also dwells into how the loads that are not normally incorporated in fatigue testing influence fatigue life of commercially pure grade 2 titanium alloy plates. Also, the parent material was used to benchmark the performance of the two forming processes in terms of stresses developed. Residual stresses developed from the two forming processes and those obtained from the parent material were used. The residual stress values were then added to the mean stress and the alternating stress from the fatigue machine to develop the concept of TFS. This exercise indicated the effect of these stresses on the fatigue life of the parent material, laser and mechanically formed plate samples. A strong link between these stresses was obtained and formulae explaining the relationship were formulated. A comparison between theory and practical application shown by test results is found to be satisfactory in explaining concerns that may arise. The laser forming process is more influential in the development of residual stress, compared to the mechanical forming process. With each parameter change in laser forming, there is a change in residual stress arrangement. Under the influence of laser forming, the stress is more tensile in nature making the laser formed plate specimens more susceptible to early fatigue failure. The laser and mechanical forming processes involve bending of the plate samples and most of these samples experienced a two-dimensional defect, which is a dislocation. The dislocation is the defect responsible for the phenomenon of slip by which most metals deform plastically. Also, the high temperatures experienced in laser forming were one of the major driving factors in bending.

The influence of the concept of “line energy” on the mechanical properties of laser formed commercially pure grade 2 titanium alloy plates

The study has found that the use of higher line energies compromises fatigue properties of commercially pure grade 2 titanium alloy plates as there is no surface temperature control and therefore precise thermo-mechanical control is needed for the enhancement of the process. Line Energy is defined as the ratio of laser power to scanning velocity and is an important factor to consider during the laser forming process. Other factors which play a significant role in the overall laser forming process are also included in this paper and these are beam interaction time, heat flux and the thermal gradient. The concept of line energy which is responsible for the bending behavior of materials in laser forming is analyzed and some principles of engineering thermodynamics form part of the analysis. The effect of line energy on the mechanical properties is also affected by material properties such as thermal conductivity and the material’s melting temperature. The study also discovered that the depth of laser beam penetration and the effects thereof depend on the line energy generated.

Biocompatibility of Bespoke 3D-Printed Titanium Alloy Plates for Treating Acetabular Fractures.

Treatment of acetabular fractures is challenging, not only because of its complicated anatomy but also because of the lack of fitting plates. Personalized titanium alloy plates can be fabricated by selective laser melting (SLM) but the biocompatibility of these three-dimensional printing (3D-printed) plates remains unknown. Plates were manufactured by SLM and their cytocompatibility was assessed by observing the metabolism of L929 fibroblasts incubated with culture medium extracts using a CCK-8 assay and their morphology by light microscopy. Allergenicity was tested using a guinea pig maximization test. In addition, acute systemic toxicity of the 3D-printed plates was determined by injecting extracts from the implants into the tail veins of mice. Finally, the histocompatibility of the plates was investigated by implanting them into the dorsal muscles of rabbits. The in vitro results suggested that cytocompatibility of the 3D-printed plates was similar to that of conventional plates. The in vivo data also demonstrated histocompatibility that was comparable between the two manufacturing techniques. In conclusion, both in vivo and in vitro experiments suggested favorable biocompatibility of 3D-printed titanium alloy plates, indicating that it is a promising option for treatment of acetabular fractures.

Deformation characteristics of Ti-6Al-4V plate in mandrel-free hot spinning

A mandrel-free hot spinning process was developed as a near-net-shape forming technique for a titanium alloy plate. To investigate the deformation characteristics in a mandrel-free hot spinning, a Ti-6Al-4V alloy conical product was formed from a plate which has small penetration holes. Dimensions and positions of holes in the formed products were measured. It was found that the wall thickness of formed products roughly followed the sine law. However, the result of deformation characteristics of penetration holes showed that the deformation did not follow the ideal shear deformation. It is found that shear and bending as well as torsional deformation occurs during a mandrel-free hot-spinning.

The technology of forming Ti-Nb layers on the surface of titanium alloy plates using a high-voltage electron beam output into a protective argon medium

The structure and properties of layers obtained by electron-beam melting of titanium-niobium powder mixtures in a protective argon medium are studied in the work. The method allows cladding traces 16.5 … 17.5 mm wide with a maximum thickness of 3.5 … 4.5 mm. The concentration of niobium in the formed surface layers is 6.6 and 13.8%. The cladded material has a predominantly lamellar structure. The production of layers in the protective medium of argon makes it possible to increase the microhardness level, as well as the corrosion resistance of titanium in boiling solutions of nitric and sulfuric acid.

Study on stress-wave propagation and residual stress distribution of Ti-17 titanium alloy by laser shock peening

Laser shock peening has advantages of less restriction, better reinforcement, stronger controllability, and so on, which could greatly improve the fatigue properties of the material compared with traditional processes. In this paper, dual phase titanium alloy Ti-17 has been studied, and numerical simulation has been taken to analyze the stress-wave propagation rules in Ti-17 titanium alloy plates with different thicknesses. In addition, the distribution of residual stress which is obtained by experiments is used to verify the accuracy of the above rules. Furthermore, the variation rules of fatigue characteristics of plates with different thicknesses under the same laser shock peening parameters are analyzed. The results show that due to the reflection of the stress-wave, the final residual stress and fracture toughness of the specimen decrease, resulting in an increase of the crack propagation rate and crack length. Since thinner specimens have a higher frequency of stress-wave reflection, they show greater effects.

Fatigue and crack-growth behavior in a titanium alloy under constant-amplitude and spectrum loading

A titanium alloy (Ti-6Al-4V STOA) plate material was provided by the University of Dayton Research Institute from a previous U.S. Air Force high-cycle fatigue study. Fatigue-crack-growth tests on compact, C(T), specimens have been previously performed at Mississippi State University on the same material over a wide range in rates from threshold to near fracture for several load ratios (R = Pmin/Pmax). These tests used the compression pre-cracking method to generate fatigue-crack-growth-rate data in the near-threshold regime. Current load-reduction procedures were found to give elevated thresholds compared to compression pre-cracking methods. A crack-closure model was then used to determine crack-front constraint and a plasticity-corrected effective stress-intensity-factor-range relation over a wide range in rates and load ratios. Some engineering estimates were made for extremely slow rates (small-crack behavior), below the commonly defined threshold rate. Newly-developed single-edge-notch-bend, SEN(B), fatigue specimens were machined from titanium alloy plates. These specimens were fatigue tested at two constant-amplitude load ratios (R = 0.1 and 0.5) and a modified Cold-Turbistan engine spectrum. All of the tests were conducted under laboratory air and room temperature conditions. Calculated fatigue lives from FASTRAN, a fatigue-life-prediction code, using small-crack theory with an equivalent-initial-flaw-size (semi-circular surface flaw) of 9-μm in radius at the center of the semi-circular edge notch fit the constant-amplitude test data fairly well, but under predicted the spectrum loading results by about a factor of 2–3. The reasons for the large under prediction were discussed. Life predictions made with linear-cumulative damage (LCD) calculations agreed fairly well with the spectrum tests.

Biomechanical comparison of three different plate configurations for comminuted clavicle midshaft fracture fixation

The aim of this study was to compare the fixation rigidity of anterior, anterosuperior, and superior plates in the treatment of comminuted midshaft clavicle fractures. Six-hole titanium alloy plates were produced according to anatomic features of fourth-generation artificial clavicle models for anterior (group I; n = 14), anterosuperior (group II; n = 14), and superior (group III; n = 14) fixation. After plate fixation, 5-mm segments were resected from the middle third of each clavicle to create comminuted fracture models. Half the models from each group were tested under rotational forces; the other half were tested under 3-point bending forces. Failure modes, stiffness values, and failure loads were recorded. All models fractured at the level of the distalmost screw during the failure torque, whereas several failure modes were observed in 3-point bending tests. The mean stiffness values of groups I to III were 636 ± 78, 767 ± 72, and 745 ± 214 N ∙ mm/deg (P = .171), respectively, for the torsional tests and 38 ± 5, 20 ± 3, and 13 ± 2 N/mm, respectively, for the bending tests (P < .001 for group I vs. groups II and III; P = .015 for group II vs. group III). The mean failure torque values of groups I to III were 8248 ± 2325, 12,638 ± 1749, and 10,643 ± 1838 N ∙ mm (P = .02 for group I vs. II), respectively, and the mean failure loads were 409 ± 81, 360 ± 122, and 271 ± 87 N, respectively (P = .108). In the surgical treatment of comminuted midshaft clavicle fractures, the fixation strength of anterosuperior plating was greater than that of anterior plating under rotational forces and similar to that of superior plating.

Quasi-Static and Dynamic Properties of Ti-4Al-3V-0.6Fe-0.2O Titanium Alloy Plates

This paper aimed to study the quasi-static and dynamic properties of the titanium alloy with nominal composition Ti-4Al-3V-0.6Fe-0.2O. The ingots Ti-4Al-3V-0.6Fe-0.2O alloy were forged into slabs of 32 mm thickness by one heat above Tβ-transus temperature and one heat below Tβ-transus temperature, and then rolled into plates of 8 mm thickness by one heat below Tβ-transus temperature. The quasi-static tensile properties were tested by MTSTM testing system at strain rate of 10-3 s-1. The dynamic compression properties were tested by Split Hopkinson Pressure Bar system at strain rate of 3000±200 s-1. The results show that the quasi-static properties of the Ti-4Al-3V-0.6Fe-0.2O plate are comparable to ATI 425TM alloy plate and commercial Ti-6Al-4V plate. The average dynamic flow stress of Ti-4Al-3V-0.6Fe-0.2O plate is comparable to ATI 425TM alloy plate, over 100MPa higher than that of Ti-6Al-4V plate. The maximum strain during homogeneous dynamic plastic deformation of Ti-4Al-3V-0.6Fe-0.2O plate is approximately 15 ∼ 20% higher than that of ATI 425TM alloy plate, and is approximately 80% of that of Ti-6Al-4V plate.

Friction spot welding between porous TC4 titanium alloy and ultra high molecular weight polyethylene

Due to the advantages of light-weight, excellent integrated physical/chemical properties and design flexibility, metal/polymer hybrid structures have been increasingly used in automotive, aerospace and biomedical industries, which calls for effective method for joining metal and polymer. In this study, biomedical 3D-printed porous TC4 titanium alloy plate and ultra high molecular weight polyethylene (UHMWPE) plate were successfully joined by friction spot welding (FSpW) technology. The unique welding temperature (Tw) - z-axis force (Fz) evolution at the TC4 plate/UHMWPE plate interface were characterized. During dwell stage, Tw and Fz were identified to be coupled. An arch-shaped embedded zone (EZ) which characterized by the embedment of UHMWPE into porous TC4 formed under non-uniformly distributed Tw at the interface, which provided the most effective bonding mechanism. The porous structure of TC4 plate is critical for the mechanical interfacial bonding formation. As a result, TC4/UHMWPE joints of high lap shear strength can be obtained by forming large EZ. Failure occurred at either TC4 or UHMWPE base plates rather than the TC4 plate/UHMWPE plate interface.

Robotic Nd:YAG Fiber Laser Welding of Ti-6Al-4V Alloy

In the present study, Ti6Al4V titanium alloy plates were joined using a robotic fiber laser welding method. The laser welding process was carried out at two different welding speeds. Effects of different heat input conditions on the microstructure and mechanical properties of robotic fiber laser welded joints were investigated. Some grain coarsening was observed in the microstructure of weld metal in samples joined using high heat input, compared to those using low heat input, and volume rates of primary α structures increased in the weld metal. The microstructure of weld metal in samples joined using low heat input was made of basket-weave or acicular α' grains and primary β grains in grain boundaries. Tensile and yield strength of samples joined using low heat input were higher than for those joined using high heat input, but their ductility was lower.

Spallation affected fracture pattern of a titanium alloy plate subjected to linear shaped charge jet penetration

In this paper, the commercial finite element code LS-DYNA is employed to simulate the process of a certain kind of a linear shaped charge jet penetrating into a TC4 (Ti–6Al–4V) titanium alloy plate of moderate thickness. The fracture profiles agree well with experimental observations, which confirms the validity of the code and the Johnson–Cook material model applied to describe the TC4 plate. The fracture pattern of the plate is drawn based on this comparison.

Lamb wave mode and frequency selection for assessment of creep damage in titanium alloy plates

Lamb wave mode and frequency selection for assessment of creep damage in titanium alloy plates

Nonlinear harmonic response characteristics and experimental investigation of cantilever hard-coating plate

The nonlinear harmonic response of a cantilever hard-coating plate which is made of a layer of anisotropic hard-coating material and isotropic metal substrate is investigated based on the theory of high-order shear deformation of plate. Firstly, based on the theories of von Karman and Reddy’s three-order shear deformation, the nonlinear dynamic equations of hard-coating plate are built by Hamilton variation principle. Secondly, to obtain nonlinear governing equation of hard-coating plate under transverse load, these equations are discretized in Galerkin method. The system averaged equations with 1:3 internal resonances are obtained by the method of multiple scales, and the multi-periodic responses behavior of cantilever hard-coating plate under transverse loading could be presented. Finally, the vibration response experiment of hard-coating plate is conducted, and the multi-periodic responses are also present for the hard-coating plate with three-to-one internal resonance. Besides, through the vibration response experiment of uncoated titanium alloy plate, the damping characteristic of hard coating is further analyzed.

Response of aramid honeycomb sandwich panels subjected to intense impulse loading by Mylar flyer

The deformation/failure modes and impact resistance of composite sandwich panels with titanium alloy plates and aramid honeycomb cores subjected to intense impulse loading were investigated experimentally using electric gun technique. A velocity measuring instrument, known as the velocity interferometer system for any reflector (VISAR), measured the velocity history at the mid-point of the back plates. Typical deformation/failure modes were analyzed and classified systematically, and then a comparison of structural deformation resistance between sandwich panels and plates of equivalent mass was studied. It was found that both the deformation/failure modes and the dynamic response of the plates were sensitive to the impact velocity. The impact resistance of sandwich panels could be improved by core crushing and deformation of the front plate. Finally, effects of impact velocity and boundary conditions on the dynamic response of sandwich panels were identified. It was worth noting that the fully clamped boundary reduced the damage extent of the front plate, but increased the local plastic deformation of the back plate.

Measurement capabilities for ball bearing wear assessment

Wear measurement for research, control and minimization is mostly accomplished traditionally through gravimetric methods. An experimental study is developed to evaluate the alternative dimensional metrology capabilities. Standardized wear ball-on-flat tests are conducted for a set of steel balls against titanium alloy plates. Dimensional results are obtained through contact metrology of the parts and their surfaces, as well as contactless optical microscopy. Both volumetric and surface roughness metrology are analyzed. Results discussion shows the capability of dimensional metrology for wear assessment and the uncertainty behavior associated with the different methodologies. The complex wear process seems to be independent from conventional surface roughness measurement, but the experimental trials in areal methods suggest some parameters candidates for further research in relation with the coefficient of friction.

Two-sided laser shock processing

The principles of two-sided laser shock processing (LSP) are considered. The differences between two-sided and one-sided laser shock processing are noted. For the example of a thin VT-6 titanium-alloy plate, finite-element modeling is used to investigate the residual stress field when using two-sided LSP. The distribution of surface microhardness is analyzed.