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Current techniques for orthognathic surgery after Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO) rely on intermediate and final occlusal splints for proper positioning of the dental arches without any control in positioning the condyle and ramus segments. Setting the 2 condyles in centric relation in the glenoid fossae at fixation is paramount for condylar function and the accuracy and stability of postoperative occlusion. Usually the 2 ramus segments are manually positioned and fixated in the final position according to the surgeon's experience. This report describes a novel technique to position the condyle and ramus segments in centric relation using skeletal guides designed by computer-assisted designed and computer-assisted manufactured (CAD-CAM) technology. The skeletal guides have a double-U shape designed to be tooth borne on the distal segment and bone borne on the proximal segment. The guides fit on the last molar crown and the anterior border of the ramus; using these reference points will position the mandibular arch and 2 ramus segments in ideal centric occlusion and centric relation. The condyle position in the sagittal, horizontal, and transverse planes was analyzed by computed tomography and differences in measurements were calculated. This technique confirms precise control of the condylar segment in centric relation with stable centric occlusion using CAD-CAM guides during BSSO.

Rapid in situ synthesis of bulk nanostructured titanium boride (TiB) ceramic, at the lowest possible processing temperature, is demonstrated. Using electric-field-activated-sintering (EFAS), nanoscale TiB whiskers were formed and densified uniformly throughout the volume, from a mixture of micron-sized Ti, TiB 2 and FeMo powders, at 1100 °C in 30 min and at a relatively low pressure. Microstructure and X-ray diffraction (XRD) analysis, revealing the formation of TiB whiskers in this rapid processing condition, are presented. The formation of a transitional quaternary liquid phase, facilitated by localized joule heating at particle contacts, are hypothesized as contributors to rapid and low-temperature synthesis.

A phenomenological constitutive equation for the stress–life (S–N) fatigue behavior of metal single crystals is presented and is validated on the basis of physical definition of fatigue endurance limit. The constitutive equation is developed here on the basis of probabilistic arguments for fatigue fracture in cyclic loading. The physical endurance limit for fatigue is taken as the stress amplitude corresponding to the critical resolved shear stress for dislocation slip initiation in ductile single crystals. It is shown that the constitutive equation is surprisingly compact and very flexible to accurately describe a wide range of S–N behaviors, as found in fatigue of nickel-based superalloy single crystals as well as in Fe and Zn single crystals. The S–N constitutive equation is also expanded by the superposition of the mean stress effect and the cyclic effect in fatigue. A remarkable outcome of this is a master S–N fatigue equation that yields S–N curves for any mean stress, on the basis of the S–N parameters for fully reversed fatigue behavior. The application of the presented equations to characterize the S–N behavior of polycrystalline materials is quite promising.

In fatigue crack growth experiments of miniature specimens of Ti-6Al-4V alloy, it is shown that the stress intensity factor range (∆K) cannot uniquely correlate the crack growth rates based on the standard stress intensity factor solution, but can only on the basis of the solution for uniformly displaced ends. It also is shown that, remarkably, a similar and strong correlation exists between the change in the net section strain energy amplitude and the rate of fatigue crack growth. The proposed approach is direct and simpler and it throws a new light on the nature of driving force for fatigue crack growth in structural materials.

This work demonstrates that a continuum-based characterization of mechanical fatigue fracture of polymers, in the absence of thermal effects, is possible on the basis of macroscopic crack growth mechanism. The macroscopic mechanism is that the fractional remaining fatigue life of a given polymer specimen is uniquely related to the fractional size of the remaining uncracked section, which includes the intact craze length, anytime during fatigue. A crack growth functional is proposed and is the used to represent the cyclic fatigue crack advance due to the increasing net-section stress amplitude in fatigue. A crack growth equation, which is consistent with Frost, Dugdale and Weibull's observations of macroscopic crack growth mechanics, is proposed as a base equation. A compact constitutive equation for the stress-life (S N) fatigue behavior of polymers is then derived. The constitutive equation accurately describes the mechanical S N fatigue behavior of a large number of polymers under test conditions in which the thermal effects were absent. The effect of temperature is rationalized on the basis of beta relaxation, glass transition and the variation of strength with temperature, depending on the polymer. The constitutive equation is then expanded to create a master equation to include the mean-stress effects, which allowed the prediction of stress-life behavior and endurance limit for any mean stress solely from the S N behavior of fully reversed fatigue data. It is demonstrated that the present the S N constitutive equations can quantitatively and accurately describe the polymer fatigue phenomenon.

Tensile properties of Ti-6Al-4V titanium alloy, sintered by a new process (sintering, phase transformation, and dehydrogenation of titanium hydride compacts, termed HSPT process), were investigated to determine how the sintering pores influence the tensile strength and ductility. It was found that the ductility in the sintered alloy is severely affected by the size of the largest pore, referred here as extreme-sized pore, even when the average volume fraction of porosity is nearly constant between a large number of samples. It is shown that the rapid decrease in ductility, with an increase in the extreme pore size, is caused by strain localization around the extreme-sized pore and early crack initiation. This crack initiation leads to fracture of the plane containing the pore thereby limiting the extent of uniform plastic strain that can be attained before fracture. Interestingly, the strength properties are, however, found to be independent of the size of the extreme-sized pore. The results are explained on the basis of stress concentration and strain localization around the extreme-sized pores. The work also reveals that if the extreme-sized pores are eliminated, PM Ti-6Al-4V alloy with high strength (~1100 MPa) and good ductility (~12 pct), which is easily comparable to a wrought Ti-6Al-4V alloy, can be achieved even at oxygen levels up to 0.4 wt pct.

A comprehensive assessment of fatigue performance of powder metallurgy (PM) Ti-6Al-4V alloy, manufactured using various powder-based processing approaches to-date, is performed in this work. The focus is on PM processes that use either blended element (BE) or pre-alloyed (PA) powder as feedstock. Porosity and the microstructure condition have been found to be the two most dominant material variables that control the fatigue strength. The evaluation reveals that the fatigue performance of PM Ti-6Al-4V, in the as-sintered state, is far lower than that in the wrought condition. This is largely caused by residual porosity, even if it is present in small amounts, or, by the coarse lamellar colony microstructure. The fatigue strength is significantly improved by the closure of pores, and it approaches the levels of wrought Ti-6Al-4V alloys, after hot-isostatic-pressing (HIPing). Further thermo-mechanical and heat treatments lead to additional increases in fatigue strength–in one case, a high fatigue strength level, exceeding that of the mill-annealed condition, was achieved. The work identifies the powder, process and microstructure improvements that are necessary for achieving high fatigue strength in powder metallurgical Ti-6Al-4V alloys in order for them to effectively compete with wrought forms. The present findings, gathered from the traditional titanium powder metallurgy, are also directly applicable to additively manufactured titanium, because of the similarities in pores, defects, and microstructures between the two manufacturing processes.

The high temperature phase fields of a multicomponent titanium alloy system have been determined by the CALPHAD approach to assist in rapid processing of a titanium metal matrix composite by electric-field-assisted reaction sintering. The phase field calculations revealed the existence of a wide composition range (in terms of B, Fe, Mo and Al content) for the flexible synthesis of various β-Ti-TiB composites. After processing, the uniform dispersion of in-situ formed titanium boride (TiB) whiskers, in the ductile beta titanium (β-Ti) matrix, has resulted in a composite with a flexural strength of 1622 MPa and a fracture toughness of 23 MPa m , which are much greater than the levels achieved before in this class of materials.

Fracture mechanics analysis of a generalized compact tension specimen, on the basis of the mechanics of deformation of the net-section, is shown to provide a simple and a broadly useful expression for stress intensity factor calculations. A single analytical expression is found to be sufficient for the characterization of crack behavior in compact tension, extended compact tension and wedge splitting test specimens without any restriction on the specimen length (or height) and width. The analysis is enabled by the concept of the change in net-section energy, which is determined by summing the changes in strain energies of the net-section of the generalized specimen for tension and bending deformation modes, which result from the introduction of the crack. This is equivalent in concept to the increase in strain energy upon the introduction of the crack, as in the Griffith’s fracture theory. The square-root of the change in net-section strain energy parameter multiplied by the elastic modulus provides an expression that is equivalent to the conventional stress intensity factor expression. The application of the net-section based expression to the standard compact tension, the extended compact tension and the wedge-splitting test specimens shows very good agreements with the crack behaviors as expressed by the stress intensity factor expressions for the respective geometries. The proposed method enables easy analytical determination of stress intensity factors for any asymmetrically-loaded mode-I crack problem.

In this paper, we evaluate a nature inspired algorithm namely Social Spider Optimization (SSO) for data clustering that performs local and global searches in a balanced way. We compare CPU elapsed time of the proposed algorithm SSO with K-means and Particle Swarm Optimization (PSO). Though the convergence speed of K-Means clustering is very high when compared with other clustering algorithms, it has the weakness of getting stuck in the local optima in the solution space. Though SSO solves this problem to an extent, it has to be combined with K-means in order to speed up the convergence. Hence, we combine SSO with K-means that produces good results in local searches. We compare CPU elapsed time of proposed hybrid algorithm SSO + K-means (SSOKC) with K-means + Bat algorithm (KBat), K-means + Firefly algorithm (KFA) and K-means + Flower pollination algorithm (KPA). The study is carried out on real life datasets taken from UCI machine learning repository.

PURPOSE The purpose of this study was to create three-dimensional composite models of quad zygomatic implant-supported maxillary prostheses with a variety of alveolar bone defects around implant sites, and to investigate the stress distribution in the surrounding bone using the finite element analysis (FEA) method. MATERIALS AND METHODS Three-dimensional models of titanium zygomatic implants, maxillary prostheses, and human skulls were created and assembled using Mimics based on microcomputed tomography and cone beam computed tomography images. A variety of additional bone defects were created at the locations of four zygomatic implants to simulate multiple clinical scenarios. The volume meshes were created and exported into FEA software. Material properties were assigned respectively for all the structures, and von Mises stress data were collected and plotted in the postprocessing module. RESULTS The maximum stress in the surrounding bone was located in the crestal bone around zygomatic implants. The maximum stress in the prostheses was located at the angled area of the implant-abutment connection. The model with anterior defects had a higher peak stress value than the model with posterior defects. All the models with additional bone defects had higher maximum stress values than the control model without additional bone loss. CONCLUSION Additional alveolar bone loss has a negative influence on the stress concentration in the surrounding bone of quad zygomatic implant-supported prostheses. More care should be taken if these additional bone defects are at the sites of anterior zygomatic implants.

Since the last decade, researchers have been concentrating on high quality clustering methods for the effective analysis of the growing data. Algorithms inspired by nature have become part of a widely used class of computing methods, because of their ability to adjust to variety of conditions. These nature inspired algorithms have been frequently used for solving complex, real-world optimization problems. In recent years, they have emerged as powerful optimization techniques. These algorithms inspired by the cooperative behavior of social animals have the ability to provide better solutions for clustering problems. Social Spider Optimization (SSO) is a population based stochastic optimization algorithm. It has been used to solve many complicated optimization problems. It simulates the behavior of social spiders. In this paper, a new and more effective implementation of SSO (ESSOSC) for solving text document clustering problem is specified by using single cluster implementation for each spider.

Introduction: Lyme disease is associated with multiple inflammatory and neurological symptoms such as arthralgia, arthritis, Bell’s palsy, severe headaches, encephalitis, and temporomandibular joint (TMJ) syndrome. Rare in occurrence, Lyme Disease induced TMJ arthritis is often missed or lower on the differential. Hereby, new onset TMJ arthritis, likely associated with acute Lyme Disease, is reported. Case Description: 16 years-old male was evaluated for a 6-week history of left temporomandibular joint pain and dislocation, …

In this paper, the feasibility of producing Ti-6Al-4V with a range of wrought-like microstructures and mechanical properties via a novel powder metallurgy (PM) process with simple heat treatments is investigated. The wrought-like PM Ti-6Al-4V is obtained by sintering blended elemental (BE) powder in a hydrogen atmosphere, followed by conventional Ti-6Al-4V heat treating profiles. This is achieved without resorting to energy-intensive thermomechanical processing (TMP) that is compulsory for producing high performance titanium alloys via wrought processing or traditional powder metallurgy.

A unique relationship between the normalized remaining section size and the normalized remaining fatigue life has been discovered to exist during fatigue crack growth in a wide spectrum of materials. A crack growth functional that relates the two variables, and which is in excellent agreement with experimental data, is proposed. This functional suggests that all fatigue cracks propagate uniquely to sever the material cross-section and is promising as a new physical basis for characterizing fatigue crack growth mechanisms in materials.

The hydrogen sintering and phase transformation (HSPT) process is a novel powder metallurgy method for producing Ti alloys, particularly the Ti-6Al-4V alloy, with ultra-fine microstructure in the as-sintered state. The ultra-fine microstructure is obtained as a direct result of the use of H2 gas during sintering. The refinement of the microstructure during HSPT is similar to that of thermal hydrogen processing (THP) of bulk Ti alloys. For both THP and HSPT of Ti-6Al-4V alloy, the mechanisms of the grain refinement depend on the phase equilibria and phase transformations in the presence of hydrogen, which are surprisingly still not well established to date and are still subjected to research and debate. In recent work by the present authors, a pseudo-binary phase diagram of (Ti-6Al-4V)-H has been determined by using in situ synchrotron XRD and TGA/DSC techniques. Aided by this phase diagram, the current paper focuses on the series of phase transformations during sintering and cooling of Ti-6Al-4V in a hydrogen atmosphere and the mechanisms for the formation of the ultra-fine microstructures obtained. Using experimental techniques, including in situ synchrotron XRD, SEM, EBSD, and TEM, the microstructural refinement was found to be the result of (1) the precipitation of ultra-fine α/α2 within coarse β grains during an isothermal hold at intermediate temperatures, and (2) the eutectoid transformation of β → α + δ at approximately 473 K (200 °C).

Transient Joule heating of graphene or nanowires, supported by substrates, is an important and complex heat transfer problem to be solved in the context of nanoscale electronic devices. We formulate here an analytical model that allows the examination of the effects of input power, heat transfer through substrate and the end contacts on the transient temperature evolution. An exact analytical solution is obtained here by the superposition of the Joule heating, the substrate heat transfer and the temperatures at the ends of contacts, within the Fourier formalism, through Laplace transformations. The transient solution explicitly relates temperature profile to the input power, size and the thermal properties of the element, and the heat transfer properties of the substrate. The transient solution naturally reduces to steady state solution. The solutions can be useful for the thermal design of devices made of graphene or nanowires or electrically heated filaments. Experimental steady-state temperature distribution data, obtained by 2D phonon band spectroscopy, are used to confirm the accuracy of the solution. It is found that the time to achieve steady-state temperatures in graphene is of the order of nanoseconds and is a strong function of substrate heat transfer. Further, the maximum temperature and the gradient in steady state profile temperature profile are greatly affected by heat transfer to the substrate.

Hydrogen has been investigated for decades as a temporary alloying element to refine the microstructure of Ti–6Al–4V, and is now being used in a novel powder metallurgy method known as “hydrogen sintering and phase transformation”. Pseudo-binary phase diagrams of (Ti–6Al–4V)–xH have been studied and developed, but are not well established due to methodological limitations. In this paper, in situ studies of phase transformations during hydrogenation and dehydrogenation of (Ti–6Al–4V)–xH alloys were conducted using high-energy synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The eutectoid phase transformation of β ↔ α + δ was observed in the (Ti–6Al–4V)–xH alloy via in situ synchrotron XRD at 211 °C with a hydrogen concentration of 37.5 at.% (measured using TGA–DSC). The relationships of hydrogen composition to partial pressure and temperature were investigated in the temperature range 450–900 °C. Based on these results, a partial pseudo-binary phase diagram of (Ti–6Al–4V)–xH is proposed for hydrogen compositions up to 60 at.% in the temperature range 100–900 °C. Using the data collected in real time under controlled parameters of temperature, composition and hydrogen partial pressure, this work characterizes relevant phase transformations and microstructural evolution for practical titanium–hydrogen technologies of Ti–6Al–4V.

Physically-based analytical models that provide insights into the diffusion and/or interface charge transfer effects in bulk (lithiating/delithiating) electrodes are needed to truly assess the performance/limitations of electrode materials for Li-ion batteries. In this context, an analytical modeling framework is constructed here to predict the electrochemical charge–discharge characteristics during lithiation and delithiation of solid amorphous Si (a-Si) thin film electrodes. The framework includes analytical expressions that satisfy Fick's second law for Li transport and the requisite flux boundary conditions of lithiation and delithiation steps. The expressions are derived here by the method of separation of variables. They enable the determination of transient Li concentration profiles in the thin film electrode as a function of state of charge/discharge. The time-dependent electrode surface concentrations (at the electrode–electrolyte interface) obtained from these profiles were used to determine the activation overpotentials and thus, the non-equilibrium cell potentials, as a function of state of charge/discharge using Butler–Volmer kinetics. The simulated charge/discharge characteristics agreed well with the experimental data of a-Si thin film electrodes obtained at different C-rates. The model offers insights into how the charge-discharge behavior is controlled by diffusion limitation within electrode and/or the activation overpotentials at the interface. The analytical framework is also shown to predict successfully the hysteretic behavior of lithiation/delithiation voltage curves.

The axillary reverse mapping (ARM) technique has been described as an attempt to map and preserve the upper extremity lymphatic drainage during axillary lymph node dissection (ALND) and/or SLNB. This technique is based on the hypothesis that the lymphatic pathway from the upper extremity is not involved by metastasis from primary breast cancer. The ARM node/s however, has been found, in various studies, to be involved with metastatic foci in patients with extensive axillary lymph node metastases. Therefore, the oncological safety of this procedure has not yet been determined. In this pilot study, we assessed the ARM node intraoperatively for various parameters and compared it to final HPR, to try and determine the oncologic safety of preserving the ARM node. Seventy-two breast cancer patients were screened for this prospective pilot study which was planned to recruit 20 patients. The study was initiated on May 2014, 20 patients were recruited till July 2015. Eligibility criterion was as follows: patients requiring primary axillary lymph node dissection based on a clinically positive axilla. Forty-five patients were ineligible because they had either received neoadjuvant chemotherapy or underwent previous axillary surgery or axillary radiation (exclusion criteria). Seven patients refused to give consent. ARM node identification rate was 75%. The most common location of the ARM node was lateral to the latissimus dorsi pedicle (42.10%), none of them being malignant. None of the oval or firm nodes were malignant. Tumor deposits were identified in 13%. Fine-needle aspiration cytology (FNAC) had 100% specificity, 94.4% negative predictive value, 100% positive predictive value, and 50% sensitivity. ARM is feasible using blue dye alone, with an acceptable identification rate. Location, consistency, and intraoperative FNAC of the ARM node, put together, may be reliable parameters to predict involvement of the ARM node with metastasis.

The growing demand for eye care services and a lack of training opportunities for ophthalmic healthcare professionals have prompted the launch of new educational programmes in Singapore. This article outlines the development of ophthalmic nursing in Singapore and provides an introduction to the Singapore National Eye Centre (SNEC). The new Ophthalmic Academic Clinical Programme at the SNEC focuses on developing a comprehensive framework of research and training capabilities to ensure effectiveness in promoting clinical competence and performance. It is hoped that the pilot project to form a Dedicated Education Unit will act as an innovative model of transforming clinical nursing education into an environment of support. This will enable nurses to continue to provide high-quality care to ophthalmic patients. SNEC aims to provide continuing education, in partnership with other educational institutions, for nurses across the continuum of care as they navigate the rapidly changing ophthalmic nursing environment. This education and training has introduced a diversity of career paths, which provide nurses and allied healthcare professionals with innovative opportunities to advance their opthalmic nursing practice.

Solid state boriding of titanium is a very effective and inexpensive way to create surface layers that can impart high hardness and wear resistance. In this work, the growth kinetics of hard titanium boride layers created by the solid-state boron (B) diffusion through titanium (Ti) surface at various temperatures has been determined. The hard boride layers comprised of a monolithic titanium diboride (TiB2) layer at the top and a titanium boride (TiB) sub-layer that mostly consisted of TiB whiskers with high aspect-ratio growing normal to the surface. The structure and the crystallography of the layers were also confirmed by X-ray diffraction. Experimental results show that the growth rates of the TiB2 as well as the composite (TiB2þTiB) coating layers follow the parabolic kinetics. It is shown that the thickness development as a function of time can be predicted reasonably accurately, using the error function solutions for the two simultaneously growing boride layers developed in our previous work. The maximum degree of growth as dictated by the diffusivity of B in the boride phases was achieved using a solid state B powder pack in an ambient furnace atmosphere. & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Atopic dermatitis of sensitive areas such as the face, particularly in children, is a difficult disease to treat as the standard therapeutic, topical steroids, is contraindicated for this application in children. Hydrocortisone (HC) can be used in these instances because it has been shown to be safe, but is often ineffective as it is a relatively weak steroid, especially at over-the-counter concentrations. To enhance the local topical activity of HC, the terminal inactive metabolite of prednisolone, Δ(1)-cortienic acid (Δ(1)-CA), is added to HC, as Δ(1)-CA preferentially binds transcortin, liberating more HC to elicit its therapeutic effect. Skin blanching studies, which are used to evaluate the potency of topical steroids, were employed to assess the ability of Δ(1)-CA to enhance the activity of HC. The results demonstrate that Δ(1)-CA, when applied in combination with HC, does indeed potentiate the vasoconstriction effect of topically applied HC, while having no effect alone. Thus, addition of the inert prednisolone metabolite Δ(1)-CA can increase the therapeutic effect of over-the-counter concentrations of HC when applied topically.

Recently, as clustering problem can be mapped to optimization problem, evolutionary optimization techniques have been used by researchers to improve accuracy and efficiency. Evolutionary techniques are stochastic general purpose methods for solving optimization problems. Swarm Intelligence is one such technique that deals with aggregative behavior of swarms and their complex interactions without any supervision. But, because of its robustness, Swarm intelligence paradigm seems to be even more attractive. We proposed a swarm intelligence algorithm called social spider optimization for text document clustering. This algorithm uses cooperative intelligent behavior of social spiders. Depending on its gender, each spider tends to reproduce a specialized behavior. It also helpsin reducing premature convergence and local minima problems considerably in text document clustering. It is compared with K-means clustering technique and found to give better results.

TRI has constructed and commissioned a process demonstration unit (PDU) at Durham, NC. This integrated gasification and gas to liquids biorefinery plant is designed to process 4 dry tons per day of biomass, generate, clean up, compress and condition syngas, and catalytically convert it to Fischer-Tropsch (F-T) liquids. The gasification system uses TRI's proprietary indirectly heated gasification technology. The synthesis reactor is designed by Emerging Fuels Technology (EFT) and utilizes their proprietary cobalt catalyst to produce fuels and waxes. The PDU gasifier has been in operation for 7500 h, the primary gas cleanup for 3100 h, and the overall system with F-T has operated in the integrated mode for 2800 h, all on woody biomass. F-T liquids have been produced for a total of 4000 h with 2800 h on biosyngas and 1100 h on bottled syngas. The trials have demonstrated clean syngas production with stable H2 to CO molar ratio (∼1.9), 60+% CO conversion in the first stage of F-T and the generation of high quality, sulfur-free, 100% renewable fuels, i.e., pure white wax and water clear, medium fraction hydrocarbon liquids. Operation of the F-T in the second stage mode has also demonstrated up to 65% CO conversion. System configuration details are provided and test results on performance, products, and emissions are presented. © 2011 American Institute of Chemical Engineers Environ Prog, 2012

An approach to synthesize bulk nanostructured titanium boride (TiB) ceramic material having a whisker-like microstructure with a very attractive combination of mechanical properties is presented. The material is made of a three-dimensional network of high aspect ratio TiB whiskers that are created in situ during reaction sintering of micron-sized component powders at pressures of 15–20 MPa and at relatively low temperatures (

Accelerated kinetics of titanium boride (TiB) layer growth on titanium surfaces during solid-state diffusion of boron at temperatures very close to the α → β phase transition temperature (β-transus) has been demonstrated. On the basis of the fact that hcp metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of interstitial/substitutional atoms, thereby accelerating the growth kinetics of the hard boride layer. It is shown in this work that a much deeper growth of TiB into the Ti substrate and an increased coating thickness (∼75 μm) indeed occurs at temperatures very close to the transition temperature, compared with that at temperatures away from the transition. Hardening of the surface layers was also achieved to a significant depth (∼100 μm), with the maximum surface hardness reaching ∼20 GPa (HK), which are desirable for improved surface performance. A diffusion model based on error function solutions to Fick’s second law was developed to quantitatively illustrate the combined effects of normal B diffusion in the TiB phase and anomalous B diffusion in the Ti phase in accelerating TiB layer growth. It has been found that this model adequately explains the accelerated boride layer growth kinetics near the phase transition temperature. The results of the study generally suggest that diffusion near the phase transition temperature can be used as a means of achieving greater diffusion depth of penetration of hard coatings in phase transforming metals.

Competing failure modes in S – N fatigue, involving surface- and internally-initiated cracks often lead to large variations in fatigue lives, especially in high-strength materials including steels, titanium and nickel alloys. Typically, there exists a shorter-life-distribution that is usually associated with surface-crack-initiated failures. The longer-life-distribution generally occurs due to internal-crack-initiated failures. There can be a complete separation of the two failure distributions in terms of fatigue life or they can dominate at high and low stress ranges with a discontinuity (step) in fatigue life in the mid-stress-range, depending on the material. It is shown that complex shapes of S – N curves, including the very-high-cycle-fatigue segments can exist due to competing failure modes. To support this, some examples of competing fatigue failures in steels, titanium alloys and nickel-base superalloys are reviewed. Some of the metallurgical, mechanical and environmental conditions that would trigger this type of behavior in structural materials are illustrated. Using Monte Carlo simulations of surface- and internal-defect-induced fatigue failures, the effects of number of fatigue tests on the S – N behavior under the competing modes scenario, are also illustrated.

Alumite treatment is one of surface treatments for aluminum alloy and it provides an oxide layer (Al2O3) on the surface by anodizing. The oxide layer is called “alumite” in Japanese industry. This method has been widely used for aluminum alloy because the alumite possesses characteristics such as high hardness, wear resistance, and electrical resistance. In order to examine the effect of alumite layer on the fatigue behavior, fatigue tests were carried out on aluminum alloy specimens with two different alumite treatments by means of a dual-spindle rotating bending fatigue testing machine. Tests were also conducted on untreated specimens for comparison. Fracture surfaces of all the failed specimens were examined in a scanning electronic microscope (SEM). Fatigue fracture mechanisms are discussed in the light of fractography and fracture mechanics. As results of fatigue tests, significant deteriorations of the fatigue strength for alumite-treated specimens having each thickness of the alumite layer were observed in comparison with the results for untreated specimen in the short life regime. However, in long-life regime of >107, the fatigue strength of alumite-treated specimen having 3 μm alumite layer becomes a little higher than the results for untreated specimen.

Effects of grain orientation on fatigue crack nucleation in Waspaloy were investigated. Fatigue testing was carried out at 85–99% of the yield stress of the material, at R = 0.1 using electropolished specimens extracted from the web of a forged aircraft engine compressor disk. Multiple nucleations of cracks of the order of a few grain diameters in size, and the propagation of the dominant crack were documented for a total of fourteen cracks. Orientation Imaging Microscopy (OIM) was used to investigate individual orientations of grains in 10 of the cracks’ nucleation and adjacent areas. Cracks appeared to nucleate in groups of similarly-oriented grains, due to the closeness of Schmid factors between the grains in these groups. This neighborhood effect was seen in nine of the 10 cracks investigated.

The crystallographic texture and formability of aluminium alloy 5086 annealed at 160, 200, 250 and 300°C have been studied. Experimentally determined forming limit diagrams (FLDs) for the above said Al 5086 sheets, their crystallographic textures and their orientation distribution function plots made by X-ray diffraction were analysed. The present study shows a comparison between these FLDs of Al 5086 sheets and the corresponding result of crystallographic texture analysis. The FLDs and crystallographic textures were then correlated with normal anisotropy of the sheet metal. It was found that aluminium alloy 5086 annealed at 300°C possessed good formability, preferred texture and high normal anisotropy value.