Alloy Specimens Research Articles

A Walker-based mean strain correction models for low-cycle fatigue life prediction

A Walker-based mean strain correction model of low-cycle fatigue (LFC) life prediction is proposed for high loaded parts. The model is based on a function depending on the strain range and strain ratio controlled in the strain-controlled LCF test of fatigue specimens and a constant reflecting the material sensitivity to strain ratio. The independence from the stress cycle parameters which can change during the strain-controlled LCF test is an obvious advantage of the model. The model was verified using the results of strain-controlled LCF tests of smooth titanium alloy Ti-6A1-4V ELI and iron-based alloy specimens conducted at room temperature. The proposed model was compared to the Smith - Watson - Topper and Walker models that take into account the mean stress effect. The proposed model provided the best prediction accuracy for titanium alloy. For Iron-based alloys the results obtained by the Walker model and the model proposed are close to each other. A simplified model based on the analysis of model parameters tailing into account the mean strain effect for predicting fatigue life of aeroengine critical parts is developed using a limited amount of experimental data when only the results of Rε = 0 tests are known. A comparison of the predicted life with the number of cycles to failure showed satisfactory results of fatigue life prediction for Ti-6A1-4V ELI and Iron-based alloys specimens.

Rotating Bending Fatigue Behaviors of C17200 Beryllium Copper Alloy at High Temperatures.

The purpose of this paper is to investigate the fatigue properties of C17200 alloy under the condition of quenching aging heat treatment at high temperatures, and to provide a design reference for its application in a certain temperature range. For this purpose, the tensile and rotary bending fatigue (RBF) tests were carried out at different temperatures (25 °C, 150 °C, 350 °C, and 450 °C). The tensile strength was obtained, and relationships between the applied bending stress levels and the number of fatigue fracture cycles were fitted to the stress-life (S-N) curves, and the related equations were determined. The fractured surfaces were observed and analyzed by a scanning electron microscopy (SEM). The results show that the RBF fatigue performance of C17200 alloy specimens is decreased with the increase in test temperature. When the temperature is below 350 °C, the performance degradation amplitudes of mechanical properties and RBF fatigue resistance are at a low level. However, compared to the RBF fatigue strength of 1 × 107 cycles at 25 °C, it is decreased by 38.4% when the temperature reaches 450 °C. It is found that the fatigue failure type of C17200 alloy belongs to surface defect initiation. Below 350 °C, the surface roughness of the fatigue fracture is higher, which is similar to the brittle fracture, so the boundary of the fracture regions is not obvious. At 450 °C, due to the further increase in temperature, oxidation occurs on the fracture surface, and the boundary of typical fatigue zone is obvious.

Effect of moderate plastic deformation on structure and properties of the ordered Cu–56Au (at.%) alloy

The effect of plastic deformation on the structure and properties of the ordered Cu–56Au (at.%) alloy has been studied. The deformation strain has been expressed in the cross-section area reduction (CSAR) percent from 10 to 80%. The dependences of electrical resistivity and microhardness on CSAR of both ordered and disordered alloy specimens have been plotted. Mechanical tensile tests of specimens in various structural states have also been carried out. It has been shown that after plastic deformation, the microhardness of the pre-ordered Cu–56Au alloy increases significantly and becomes higher than the microhardness of the severely deformed initially disordered alloy. It has been established that the deformation up to 70% CSAR does not cause a complete destruction of the atomic order. It has been shown that moderate plastic deformation (at 10–30% CSAR) of the ordered Cu–56Au alloy leads to obtaining of a thermal stability material exhibiting an excellent balance between high strength and low electrical resistivity. Such behavior of the alloy is attributed to the occurrence of an enriched dislocation density in the deformed ordered structure in which the deformation-induced disordered phase has not begun to form yet.

Short-Time Creep Deformation of the Coarse-Grained Nickel-Base Alloy 247 and Its Implications on the High-Cycle Fatigue Behavior

Abstract Cast polycrystalline nickel-base superalloys are typically used for critical high temperature aerospace and automotive components, such as turbine blades or turbocharger wheels. These high temperature components can undergo creep damage caused by, e.g., centrifugal forces on the turbine rotor blades, as well as high-cycle fatigue (HCF) from, for instance, vibrations of the rotor blade. Therefore, both, creep resistance and fatigue strength are important mechanical properties of these materials. The study presented here addresses the introduction of creep damage and its influence on the high-cycle fatigue behavior. For this purpose, fatigue specimens of coarse-grained Alloy 247 LC CC blade root material were prestressed on a pneumatic creep test rig to achieve creep-induced microstructural damage. The isothermal 900 °C short-time creep investigations below 1000 h test duration were performed at different tensile stresses which result in different strain rates. After the creep tests, scanning electron- and optical microscopy investigations of metallographic cross section of selected specimens were performed to determine the creep-induced grain boundary damage such as pore count, pore size, and coarsening of the γ' structure. This was followed by uniaxial, stress-controlled isothermal 850 °C high cycle fatigue tests on undamaged and predamaged specimens at a frequency of 10 Hz and a load ratio of R = −1. Subsequently, fractographic and cross section investigations, which provide information on the fatigue cracking, the failure initiating defects, and the pore morphology, were performed. The results of this study show that the degree of creep induced porosity is a dominant structural parameter for the HCF behavior of the investigated nickel-base superalloy.

Mechanism of grain refinement and mechanical property enhancement of Ti-45Al-8Nb alloy by directed laser deposition

Directed laser deposition (DLD) as an important additive manufacturing process, has a good application prospect for the fabricating of complex high Nb-TiAl alloy parts in aerospace and energy industries. The mechanical properties of parts manufactured by DLD are affected by the interlamellar spacing of precipitated phases. In this paper, Ti-45Al-8Nb alloy specimens were manufactured by DLD, and the interactions between the semi-coherent interfaces, deformation twins, and dislocations were analyzed by transmission electron microscopy (TEM), it revealed the strengthening mechanism of interlamellar spacing on mechanical properties of Ti-45Al-8Nb alloy. The results indicate that the laser power is one of the important factors affecting the interlamellar spacing, and the microstructures of the specimens are composed of α2 phase, γ phase, and B2 phase. By the laser power adjusting, the interlamellar spacing λ decreases by 40.1%, the microhardness of the alloy was increased by 15.9%, and the tensile strength increased by 14.8%. Also, the relationship between the tensile strength σb and the interlamellar spacing λ satisfies the Hall-Petch relationship: σb=161.4+3204λ−1/2. The obstruction and absorption of dislocation motion by the lamellar interface and deformation twins are the main reasons for the improved mechanical properties of the alloy.

Mechanical behaviour of a novel biomimetic lattice structure for bone scaffold

In this research, a new lattice structure based on the octagonal geometry and produced by Additive Manufacturing (AM) technique was proposed. Eight octagons with the same dimensions are combined to each other forming a ring. To obtain an isotropic lattice structure, cubic symmetry was imposed; thus, the unit cell is made of three rings mutually perpendicular, one ring for each principal direction.The aim of this study is the morphological and mechanical characterization of the novel unit cell to check its suitability to the biomechanical field, along with its comparison with other lattice structures currently used as bone scaffold.Electron Beam Melting (EBM) technique was used to produce Ti6Al4V ELI alloy specimens of the novel unit cell and of the truncated octahedron (Kelvin) cell. Three different unit cell sizes were selected to investigate the effect of cell dimensions on the mechanical properties.Morphological analysis was performed through a scanning electron microscope (SEM), to compare the actual structures to the designed ones.On the whole, the new lattice structure provided adequate mechanical properties to be considered as a bone substitute; further tests will be focused on its osteointegration capability.

Effects of tetrabutylammonium dihydrogen trifluoride etchant on bond strengths of resin composites with Ti-6Al-4V and Co-Cr alloys.

This study aimed at evaluating the effects of surface treatments with tetrabutylammonium dihydrogen trifluoride (TDTF) on the bond strengths of indirect resin composites with titanium-aluminum-vanadium (Ti-6Al-4V) and cobalt-chromium (Co-Cr) alloys. Disk-shaped Ti-6Al-4V and Co-Cr alloy specimens were air-abraded with alumina, treated with an etchant (MEP) containing TDTF for 10 s (MEP10) or 30 s (MEP30), and rinsed with water. Subsequently, a primer containing 6-methacryloyloxyhexyl phosphonoacetate was applied to the surfaces, and the specimens were veneered with a light-curing indirect resin composite. Specimens without MEP were prepared as controls (no-MEP). Shear bond strengths were determined before or after 100,000 thermocycles, and the data were analyzed using the Steel-Dwass test (α = 0.05, n = 10). No significant difference was found in the bond strengths between the Ti-6Al-4V and Co-Cr alloys. In each metal alloy, the MEP10 and MEP30 specimens exhibited higher bond strengths than the no-MEP controls after 100,000 thermocycles. Scanning electron microscopy observations revealed that submicron-pits and crevices were formed on both the metal alloys upon applying the MEP etchant. Surface treatments with TDTF following air abrasion are useful for improving bonding durability while veneering resin composites on Ti-6Al-4V or Co-Cr alloy frameworks.

Fast neutron fluence estimation by measurement of 93mNb and 93Mo

The possibility for estimation of fast neutron fluence from 93mNb produced from Nb contained in structural component materials of nuclear power plants was investigated as an evaluation tool for extending plant operating lifetime. First, to establish a measurement method for 93mNb in structural component materials, chemical separations and measurements of 93mNb were carried out using specimens of fast neutron-irradiated XM-19 and X-750 alloy; these are used as structural component materials and contain Nb as a component. The 93mNb activities obtained from the measurements of both XM-19 and X-750 alloy agreed well with the calculated values of 93mNb, which were simply calculated from the evaluated fast neutron fluence. On the other hand, in the case of type 316L stainless steel, which contains Mo, Mo derived 93mNb presents a problem, so an approach was used that estimates the amount of Mo derived 93mNb based on 93Mo measurements with the third specimen, neutron-irradiated type 316L stainless steel. The difference between the measured and calculated 93mNb values was about two-fold, indicating that the estimation method for 93mNb produced from Mo needs to be improved.

Improving Tribological Behaviors of Invar 36 Alloy under Extremely Cryogenic and Dry Conditions Through Surface Micro-Texturing

Invar 36 alloy is an iron-nickel alloy with an ultra-low coefficient of thermal expansion, which is widely used in cryogenic fields of liquefied natural gas (LNG) and aerospace. However, the wear under extremely cryogenic and dry conditions is a key problem for Invar 36 alloy applied in the bearing of cryogenic submersible pump. In this work, we are mainly for improving the cryogenic tribological performance of Invar 36 alloy through laser surface texturing. Three different types of surface micro-textures were prepared on Invar 36 alloy specimens. And the effects of these micro-textures on the friction and wear properties of Invar 36 alloy were investigated. The results show that groove-channel micro-texture has the lowest coefficient of friction and wear rate under normal and -196 °C. Further research shows that this is because the channel structure of groove-channel micro-texture is more conducive to the transfer of most debris generated caused by wear, which successfully reduces the occurrence of abrasive wear. Scanning Electron Microscopy/Energy-dispersive X-ray spectroscopy was utilized to explain the cryogenic tribological performance of the micro-textures.

Скоростная чувствительность механических свойств сплава ZK60 с высокой степенью коррозионных повреждений

According to the stable opinion, hydrogen absorbed by magnesium alloys during corrosion can cause their stress corrosion cracking. One of the characteristic markers indicating the involvement of diffusible hydrogen into the fracture mechanism of metals is the negative strain rate dependence of the embrittlement degree. Recent studies show that the loss of ductility of the ZK60 alloy specimens subjected to a short-term (1.5 h) pre-exposure in a corrosive medium actually decreases with the increasing strain rate. However, after the removal of corrosion products from the surface of specimens, the strain rate dependence of the ductility loss becomes positive, which indicates the absence of hydrogen in the bulk of a metal. At a short-term exposure in a corrosive environment, the deep penetration of hydrogen into a metal could be limited due to the insufficient time for hydrogen diffusion. The paper studies the mechanical behavior of the ZK60 alloy subjected to a longer (12 h) pre-exposure in a corrosive medium followed by tensile testing in air at various strain rates. The authors consider the effect of strain rate, long-term pre-exposure in a corrosive medium, and subsequent removal of corrosion products on the strength, ductility, stages of work hardening, and localized deformation, as well as on the state of the side and fracture surfaces of specimens. The study identified that the ductility loss of specimens pre-exposed in a corrosive medium for 12 h decreases with the increasing strain rate, regardless of whether the corrosion products have been removed from their surface or not. It is shown that in this case, the negative strain rate dependence of the ductility loss is associated not with hydrogen dissolved in the bulk of a metal but with the presence of severe corrosion damage of the specimens’ surface. The authors proposed an explanation for the effect of corrosion damage on the mechanical properties and their strain rate sensitivity.

Impact of Fluoride on the Corrosion Pattern of Pure Titanium and Titanium Alloy Combined with Nickel-Chromium Alloy and Gold Alloy: An In-vitro Study

Introduction: Currently, Fluoride ions are added to commercially available tooth paste, mouth washes and cariostatic gels for their prophylactic action. However, the preventive effect may also be accompanied by the corrosive activity, through infiltration of fluoride-containing saliva in the contact between crowns and bridges or into the implant supported structure. Aim: To evaluate the corrosion action of Sodium Fluoride (NaF) on Pure Titanium (PT) and its alloy coupled with NickelChromium (Ni-Cr) alloy (NC) and Gold (Au) Alloy (GA). Materials and Methods: This in-vitro study was conducted in the Department of Prosthodontics at Central Electrochemical Research Institute, Karaikudi, Tamil Nadu, India. The duration of the study was six months, from April 2010 to September 2010. A total of 48 specimens were categorised under four groups. The four groups included for the study were pure group I (PT+GA), group II (PT+NC alloy), group III {Titanium Alloy (TA)+GA) and group IV (TA+NC alloy}. The specimens under each group were divided into half and were immersed in 100 mL of either artificial saliva or artificial saliva with 1000 Parts Per Million (ppm) fluoride. The current was passed at a scanning rate of 1800 mV/hour for 60 minutes and changes in corrosion potential were observed. The elemental release analysis test was conducted by using inductively coupled plasma-mass spectrometry to quantitatively analyse the elements (metal ions) released in the test solution from the galvanic coupling alloys. In order to evaluate the corrosion behaviour, the surfaces of the specimens were examined with an optical microscope (Eclipse LV100D, Nikon, USA). Analysis of Variance (ANOVA) was done for intergroup comparison. Statistical significance was set at 5%. Results: The mean value of corrosion of PT+GA and PT+NC was 13 μg/cm2 and 27 μg/cm2 respectively. The mean value of corrosion of TA+GA and TA+NC was 12 μg/cm2 and 24 μg/cm2 respectively, in artificial saliva without sodium fluoride. In the presence of sodium fluoride, the mean value of corrosion of PT+GA and PT+NC was 17 μg/cm2 and 60 μg/cm2 respectively, and the mean value of corrosion of TA+GA and TA+NC was 15 μg/cm2 and 41 μg/cm2 . The PT and TA specimens coupled with NC alloy specimens showed more corrosion in saliva either with or without sodium fluoride compared to GA. Conclusion: The NC alloy specimens coupled with PT and TA specimens showed severe pitting corrosion in artificial saliva containing sodium fluoride.

Experimental evaluation of bio medical titanium alloy stabilized with niobium

Niobium stabilized titanium alloy has very less cytotoxicity effect compared to commercially pure titanium alloy (Ti-6Al-4 V). Flow behavior of the metals during hot deformation depends mainly on the strain rate and temperature. Such parameter plays a major role in understanding, and enhancing the workability of metals alloys in real life applications. When bio medical metal alloys are considered where, complex shapes of bio implants are major concern for which mechanical properties are analyzed experimentally. Further allows to optimizing those parameters for hot forging process based on required geometrical modelling. Experimental analysis can make reliable and precise prediction of flow behavior in real time industrial forming process. In this experiment, tensile test on bio medical titanium alloy specimen carried out at two different elevated temperatures ranging from 300℃ and 400℃ at strain rate of 10-3. Experiment carried out shows us flow stress, relation between engineering stress vs strain and true stress vs true strain. Along with this tensile fracture behavior of titanium alloy is examined with electron microscope (SEM) over a range of magnification. Micro hardness and microstructure are observed on the specimen appear to show how dislocation density changes increases with increasing strain rate, but decreases with increasing temperature. Deliberate outcomes manifest the yield and ultimate tensile strength continuously decreased with increase in temperature, and ductility (% elongation) increased with rise in temperature.

A Study on the Fatigue Life of the Laser Additive Manufactured Metallic Material

As more and more structural parts of military aircraft are formed with additive manufacturing (AM) technology, it was very urgent to study fatigue characteristics of additive manufacturing materials and structures. In order to study the fatigue life characteristics of aluminum alloy and titanium alloy manufactured by selective laser melting (SLM), a series of specimens with various structural details were designed and tested under constant amplitude and random spectrum. The basic reliability life of each test results was statistically analyzed and the reliability safety life curve was obtained. Fractography analysis showed that there were more defects and mixed failure characteristics in aluminum alloy specimens, while the fatigue-scatter of titanium alloy counterpart was larger than that of forgings.

Study on the surface integrity of 7050 aluminum alloy with different crystal orientations during high-speed machining

This paper investigates the effect of crystal orientations and machining parameters on the surface integrity of 7050 aluminum alloy in high-speed machining. Three groups of pre-compression deformations (10%, 15%, and 20%) are performed on the aluminum alloy to fabricate specimens with different crystal orientations. A single-factor dry-cutting experiment was designed, and the surface roughness, surface morphology and defects, work hardening, and X-ray diffraction (XRD) were tested. The results show that the 15% pre-deformed 7050 aluminum alloy specimen had lower surface roughness and the best surface quality under the same cutting parameters. The surface roughness of 7050 aluminum alloy with different crystal orientations tended to first increase and then decrease with the increase of the cutting speed, and the surface roughness was positively correlated with the cutting depth and feed rate. Under different cutting parameters, the machined surfaces of 7050 aluminum alloy specimens with different crystal orientations exhibited different degrees of plowings, apophysis, sticky chips, and pits. Moreover, the degree of work hardening of the 15% pre-deformed 7050 aluminum alloy specimen was small, while that of the 20% pre-deformed specimen was more serious. XRD analysis demonstrated that the diffraction peak width of the 10% pre-deformed 7050 aluminum alloy specimen slightly increased with the increase of the cutting depth. Moreover, the (111) and (200) diffraction peak intensities of the 15% pre-deformed 7050 aluminum alloy specimen increased with the increase of the cutting speed, and there was no obvious Al2CuMg phase on the machined surface of the 20% pre-deformed specimen.

Microstructures and mechanical behavior of Ti-(38+x)Ni-12Cu (at%) (x=0∼3) alloys

In this study, various aging conditions were done on (Ni,Cu)-rich Ti-(38+x)Ni-12Cu (at %) (x=0∼3) alloy sheets to improve the superelasticity and it is found that precipitation hardening is available on some alloys at proper aging conditions, leading to the realization of perfect superelasticity with small stress hysteresis. For the solution-treated specimens, their microstructures and mechanical properties are dependent on the Ni content and solution treatment temperature. In 39 at %Ni and 40 at %Ni alloys, Ti(Ni,Cu)2 particles were embedded in the matrix of as-rolled specimens and disappeared after solution treatment at 1373 K, while they remained in the 41 at %Ni alloy. The 40 at %Ni alloy containing Ti(Ni,Cu)2 particles showed a fracture strain of 30.0 % which was large compared with the alloy without the particles (∼10.2 %). Aging treatment on the specimen solution treated at 1373 K increased micro Vickers hardness and the maximum hardness of the aged 39 at %Ni and 40 at %Ni alloys were Hv 274 and Hv 377, respectively, which was ascribed to the precipitation of the C11b-type precipitates. After optimizing aging conditions, 39 at %Ni and 40 at %Ni alloys showed perfect superelasticity, which was due to the precipitation hardening effect by the C11b-type precipitates. More importantly, the properly precipitation-hardened 40 at %Ni alloy specimen aged at 723 K for 2.5 h following the solution treatment at 1373 K for 1 h showed perfect superelasticity with a small stress hysteresis of 36 MPa associated with the B2-B19 transformation, which was ascribed to the short mean free path between the C11b-type precipitates. With raising the aging temperature to 873 K, the stress hysteresis increased up to 112 MPa, which was attributed to the increase in the mean free path between the C11b-type precipitates.

Effect of Hydrogen Exposure Temperature on Hydrogen Embrittlement in the Palladium–Copper Alloy System (Copper Content 5–25 wt.%)

The yield strength, ultimate strength, and elongation/ductility properties of a series of palladium-copper alloys were characterized as a function of the temperature at which each alloy underwent absorption and desorption of hydrogen. The alloys studied ranged in copper content from 5 weight percent copper to 25 wt.% copper. Compared to alloy specimens that had been well-annealed in a vacuum and never exposed to hydrogen, alloys with copper content up to 15 wt.% showed strengthening and loss of ductility due to hydrogen exposure. In these alloys, it was found that the degree of strengthening and loss of ductility was dependent on the hydrogen exposure temperature, though this dependence decreased as the copper content of the alloy increased. For alloys with copper contents greater than 15 wt.%, hydrogen exposure had no discernible effect on the strength and ductility properties compared to the vacuum-annealed alloys, over the entire temperature range studied.

The study on the influences of residual stresses on fatigue crack propagation in titanium alloy specimens

Fatigue crack growth is a harmful physical phenomenon in engineering materials that can be intensified by the presence of tensile residual stresses. In the present study, the effect of tensile residual stresses on the fatigue crack growth in single-edge notched bending specimens of Ti- 6Al-4V is studied. Mechanical residual stresses were created by applying a 4-point bending process. The residual stresses were evaluated utilizing the hole drilling approach under the ASTM E-837 standard. Fatigue crack propagation was measured by experimental test in specimens with and without initial residual stresses. A finite element analysis was conducted using commercial finite element software to study the plastic zone at the crack tip and fracture mechanic parameters. It was observed that the residual stress field is redistributed after each step of crack propagation. The tensile residual stress in front of the crack tip decreased from near yield strength to approximately 30% of yield strength. The tensile residual stresses near the yield strength in Ti-6Al-4V increased the fatigue crack propagation rate by approximately 50%.

Structural, Thermal and Magnetic Analysis of Two Fe-X-B (X = Nb, NiZr) Nanocrystalline Alloy.

High-energy ball milling was used to produce two Fe-X-B (X = Nb, NiZr) nanocrystalline alloys. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and vibrating sample magnetometry (VSM) were used to analyze the microstructure, thermal, and magnetic characteristics of the milled powders, the agglomerated particles (also generated during the milling process), and the compacted specimens of both alloys. The main crystallographic phase is always a bcc Fe-rich solid solution; whereas a minor Nb(B) phase is detected on powders and agglomerated particles in the Fe80Nb8B12 alloy. The crystalline size of the Fe80(NiZr)8B12 alloy is between 11 and 14 nm, whereas in the Fe80Nb8B12 alloy, it ranges between 8 and 12 nm. Microstrain and dislocation density are higher in agglomerated samples for both alloys than in milled powders. Thermal analysis detects structural relaxation and crystal growth exothermic processes with high dispersion in the temperature intervals and in the calculated apparent activation energy of the main crystallization process. Regarding magnetic behavior, the coercivity values of all powdered-agglomerated specimens were around 800 A/m. The coercivity is higher in compacted sample, but controlled annealing favors enhanced soft behavior.

Decomposing Organic Molecules on Titanium with Vacuum Ultraviolet Light for Effective and Rapid Photofunctionalization.

Ultraviolet (UV) photofunctionalization counteracts the biological aging of titanium to increase the bioactivity and osseointegration of titanium implants. However, UV photofunctionalization currently requires long treatment times of between 12 min and 48 h, precluding routine clinical use. Here, we tested the ability of a novel, xenon excimer lamp emitting 172 nm vacuum UV (VUV) to decompose organic molecules coated on titanium as a surrogate of photofunctionalization. Methylene blue as a model organic molecule was coated on grade 4 commercially pure titanium and treated with four UV light sources: (i) ultraviolet C (UVC), (ii) high-energy UVC (HUVC), (iii) proprietary UV (PUV), and (iv) VUV. After one minute of treatment, VUV decomposed 57% of methylene blue compared with 2%, 36%, and 42% for UVC, HUVC, and PUV, respectively. UV dose-dependency testing revealed maximal methylene blue decomposition with VUV within one minute. Equivalent decomposition was observed on grade 5 titanium alloy specimens, and placing titanium specimens in quartz ampoules did not compromise efficacy. Methylene blue was decomposed even on polymethyl methacrylate acrylic specimens at 20-25% lower efficiency than on titanium specimens, indicating a relatively small contribution of titanium dioxide-mediated photocatalytic decomposition to the total decomposition. Load-testing revealed that VUV maintained high efficacy of methylene blue decomposition regardless of the coating density, whereas other UV light sources showed low efficacy with thin coatings and plateauing efficacy with thicker coatings. This study provides foundational data on rapid and efficient VUV-mediated organic decomposition on titanium. In synergy with quartz ampoules used as containers, VUV has the potential to overcome current technical challenges hampering the clinical application of UV photofunctionalization.

Drilling Strategies to Improve the Geometrical and Dimensional Accuracy of Deep through Holes Made in PA6 Alloy.

This article shows how different drilling strategies may affect the geometrical and dimensional accuracy of deep through holes. The tests were conducted on a three-axis direct-drive turning center. The holes were drilled in cylindrical PA6 aluminum alloy specimens 30 mm in length and 30 mm in diameter using 6 mm Ø VHM HPC TiAlN-coated twist drill bits. The cutting fluid was supplied to the cutting zone through the spindle. The experiments involved applying three strategies to drill deep through (5D) holes. The first required the workpiece to be fixed and the tool to perform both rotary and reciprocating motions. The second assumed that the workpiece performed the primary (rotary) motion whereas the tool moved in reciprocating motion. In the third strategy, the workpiece and the tool rotated in opposite directions and the tool also performed a reciprocating motion. The straightness, roundness, cylindricity, and diameter errors were the key output parameters in the analysis of the geometrical and dimensional accuracy of holes. The Taguchi orthogonal array design of experiment (DOE) was employed to determine the effects of the input (cutting) parameters (i.e., spindle speed and feed per revolution) and the type of hole making strategy on the hole errors by means of multi-factor statistical analysis ANOVA. The use of the highest spindle speed (n = 4775 rpm), the highest feed per revolution (fn = 0.14 mm/rev) and strategy I resulted in the lowest values of the output parameters (STR = 22.7 µm, RON = 8.6 µm, CYL = 28.2 µm, and DE = 9.9 µm). Strategy I was reported to be the most effective for hole drilling in PA6 aluminum alloy because, irrespective of the values of the process parameters used, three out of four output parameters, i.e., straightness, roundness and diameter errors, reached the lowest values.