Deposition of Ti/TiC Composite Coatings on Implant Structures Using Laser Engineered Net Shaping

A new method of depositing hard and wear resistant composite coatings on metal-onmetal bearing surfaces of titanium implant structures is proposed and demonstrated. The method consists of depositing a Ti/TiC composite coating (~ 2.5 mm thick) on titanium implant bearing surfaces using Laser Engineered Net Shaping (LENS®). Defect-free composite coatings were successfully produced at various amounts of the reinforcing TiC phase with excellent interfacial characteristics using a mixture of commercially pure Ti and TiC powders. The coatings consisted of a mixture of coarser unmelted/partially melted (UMC) TiC particles and finer, discreet resolidified (RSC) TiC particles uniformly distributed in the titanium matrix. The amounts of UMC and RSC were found to increase with increasing TiC content of the original powder mixture. The coatings exhibited a high level of hardness, which increased with increasing TiC content of the original powder mixture. Fractographic studies indicated that the coatings, even at 60 vol.% TiC, do not fail in a brittle manner. Various aspects of LENS® deposition of Ti/TiC composite coatings are addressed and a preliminary understanding of structure-property-fracture correlations is presented. The current work shows that the proposed approach to deposit composite coatings using laser-based metal deposition processes is highly-effective, which can be readily utilized on a commercial basis for manufacture of high-performance implants.Mechanical Engineerin

Process Parameters Optimization for Ultrasonically Consolidated Fiber-Reinforced Metal Matrix Composites

As an emerging rapid prototyping technology, Ultrasonic Consolidation (UC) has been used to successfully fabricate metal matrix composites (MMC). The intent of this study is to identify the optimum combination of processing parameters, including oscillation amplitude, welding speed, normal force, operating temperature and fiber orientation, for manufacture of long fiber-reinforced MMCs. The experiments were designed using the Taguchi method, and an L25 orthogonal array was utilized to determine the influences of each parameter. SiC fibers of 0.1mm diameter were successfully embedded into an Al 3003 metal matrix. Two methods were employed to characterize the bonding between the fiber and matrix material: optical/electron microscopy and push-out tests monitored by an acoustic emission (AE) sensor. SEM images and data from push-out tests were analyzed and optimum combinations of parameters were achieved.Mechanical Engineerin

Multi-Material Ultrasonic Consolidation

Ultrasonic consolidation (UC) is a recently developed direct metal solid freeform fabrication process. While the process has been well-demonstrated for part fabrication in Al alloy 3003 H18, including with intricate cooling channels, some of the potential strengths of the process have not been fully exploited. One of them is its flexibility with build materials and the other is its suitability for fabrication of multi-material and functionally graded material parts with enhanced functional or mechanical properties. Capitalizing on these capabilities is critical for broadening the application range and commercial utilization of the process. In the current work, UC was used to investigate ultrasonic bonding of a broad range of engineering materials, which included stainless steels, Ni-base alloys, brass, Al alloys, and Al alloy composites. UC multimaterial part fabrication was examined using Al alloy 3003 as the bulk part material and the above mentioned materials as performance enhancement materials. Studies were focused on microstructural aspects to evaluate interface characteristics between dissimilar material layers. The results showed that most of these materials can be successfully bonded to Al alloy 3003 and vice versa using the ultrasonic consolidation process. Bond formation and interface characteristics between various material combinations are discussed based on oxide layer characteristics, material properties, and others.Mechanical Engineerin

Interface Microstructures and Bond Formation in Ultrasonic Consolidation

The quality of ultrasonically consolidated parts critically depends on the bond quality between individual metal foils. This necessitates a detailed understanding of interface microstructures and ultrasonic bonding mechanism. There is a lack of information on interface microstructures in ultrasonically consolidated parts as well as a lack of consensus on the mechanism of metal ultrasonic welding, especially on matters such as plastic deformation and recrystallization. In the current work, interface microstructures of an ultrasonically consolidated multi-material Al 3003-Ni 201 sample were analyzed in detail using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and orientation imaging microscopy. Based on the results of microstructural studies, the mechanism of metal ultrasonic welding has been discussed. The reasons for formation of defects/unbonded regions in ultrasonically consolidated parts have also been identified and discussedMechanical Engineerin

Improving Linear Weld Density in Ultrasonically Consolidated Parts

Ultrasonic consolidation is a novel additive manufacturing process with immense potential for fabrication of complex shaped three-dimensional metallic objects from metal foils. The proportion of bonded area to unbonded area along the layer interface, termed linear weld density (LWD), is perhaps the most important quality attribute of ultrasonically consolidated parts. Part mechanical properties largely depend on LWD and a high level of LWD must be ensured in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD or defect formation and devise methods to enhance bond formation during ultrasonic consolidation. The current work examines these issues and proposes strategies to ensure near 100% LWD in ultrasonically consolidated aluminum alloy 3003 parts. The work elucidates the effects of various process parameters on LWD and a qualitative understanding of the effects of process parameters on bond formation during ultrasonic consolidation is presented. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility are discussed. A preliminary understanding of defect morphologies and defect formation is presented, based on which a method (involving surface machining) for minimizing defect incidence during ultrasonic consolidation is proposed and demonstrated. Finally, trade-offs between part quality and build time are discussed.Mechanical Engineerin

Maximum Height to Width Ratio of Freestanding Structures Built Using Ultrasonic Consolidation

Ultrasonic consolidation (UC) is a process whereby metal foils can be metallurgically bonded at or near room temperature. The UC process works by inducing high-speed differential motion (~20kHz) between a newly deposited layer and a substrate (which consists of a base plate and any previously deposited layers of material). This differential motion causes plastic deformation at the interface, which breaks up surface oxides and deforms surface asperities, bringing clean metal surfaces into intimate contact, where bonding occurs. If the substrate is not stiff enough to resist deflection during ultrasonic excitation of newly deposited layers, then it deflects along with the newly deposited layer, resulting in no differential motion and lack of bonding. Geometric issues which control substrate stiffness and deflection were investigated at Utah State University by building a number of free-standing rib structures with varying dimensions and orientations. Each structure was built to a height where lack of bonding between the previously deposited layers and the newly deposited layer caused the building process to fail, a height to width ratio (H/W) of approximately 1:1. The parts were then cut, polished, and viewed under a microscope. An ANSYS model was created to investigate analytically the cause of this failure. It appears build failure is due to excessive deflection of the ribs around a 1:1 H/W, resulting in insufficient differential motion and deformation to achieve bonding. Preliminary results show, when the H/W reaches 1:1, the von Mises stress is found to be tensile along portions of the bonding interface, which eliminates the compressive frictional forces necessary for plastic deformation and formation of a metallurgical bond. These tensile stresses are shown to be concentrated at regions near the edges of the newly deposited foil layer.Mechanical Engineerin

Occupational exposure to solvents and risk of head and neck cancer in women: a population-based case–control study in France

Objective Our objective was to investigate the association between head and neck cancer and occupational exposure to chlorinated, oxygenated and petroleum solvents in women. Methods Investigation of occupational and environmental CAuses of REspiratory cancers (ICARE), a French population-based case–control study, included 296 squamous cell carcinomas of the head and neck (HNSCC) in women and 775 female controls. Lifelong occupational history was collected. Job-exposure matrices allowed to assess exposure to 5 chlorinated solvents (carbon tetrachloride; chloroform; methylene chloride; perchloroethylene; trichloroethylene), 5 petroleum solvents (benzene; special petroleum product; gasoline; white spirits and other light aromatic mixtures; diesel, fuels and kerosene) and 5 oxygenated solvents (alcohols; ketones and esters; ethylene glycol; diethyl ether; tetrahydrofuran). OR and 95% CIs, adjusted for smoking, alcohol drinking, age and geographical area, were estimated with logistic models. Results Elevated ORs were observed among women ever exposed to perchloroethylene (OR=2.97, 95% CI 1.05 to 8.45) and trichloroethylene (OR=2.15, 95% CI 1.21 to 3.81). These ORs increased with exposure duration (OR=3.75, 95% CI 0.64 to 21.9 and OR=4.44, 95% CI 1.56 to 12.6 for 10 years or more, respectively). No significantly increased risk of HNSCC was found for occupational exposure to the other chlorinated, petroleum or oxygenated solvents. Conclusions These findings suggest that exposure to perchloroethylene or trichloroethylene may increase the risk of HNSCC in women. In our study, there is no clear evidence that the other studied solvents are risk factors for HNSCC

Clinical case-study describing the use of skin-perichondrium-cartilage graft from the auricular concha to cover large defects of the nose

<p>Abstract</p> <p>Background</p> <p>The composite graft from the conchal cartilage is a graft that is often used, especially in surgery on the nose, due to its capacity to resolve problems of cover and tissue deficit, arising from the removal of neoplasms or as the result of trauma, burns or following over-aggressive rhinoplasty. We have started to use skin-perichondrium-cartilage graft from the ear to cover large areas of the nose with very satisfying results as well as we describe in the reported clinical case.</p> <p>Methods</p> <p>The operation consisted of reconstruction of the cartilaginous nasal septum, which had previously been removed, using two vestibular labial mucosa flaps to reconstruct the mucosa, and cartilage from the ear conch for the cartilaginous septum. After this, the skin edges of the fistula were turned to recreate the inner lining of the nose and form a vascular base of wide area to accept the composite graft. The case concerns a female 74-year old patient who had undergone several oncological surgery for a relapsing basal cell carcinoma on the dorsum of the nose. The operation consisted of reconstruction of the cartilaginous nasal septum using two vestibular labial mucosa flaps to reconstruct the mucosa, and cartilage from the ear conch for the cartilaginous septum.</p> <p>Results</p> <p>The perichondrial cutaneous graft has shown in this surgical case very favorable peculiarities that make it usable even in facial plastic surgery.</p> <p>Conclusions</p> <p>We believe that the positive experience that we achieved in the use of composite grafts for the reconstruction of large areas of the nose could be interesting for others surgeons.</p

Mendelian randomization study of adiposity-related traits and risk of breast, ovarian, prostate, lung and colorectal cancer

Background: Adiposity traits have been associated with risk of many cancers in observational studies, but whether these associations are causal is unclear. Mendelian randomization (MR) uses genetic predictors of risk factors as instrumental variables to eliminate reverse causation and reduce confounding bias. We performed MR analyses to assess the possible causal relationship of birthweight, childhood and adult body mass index (BMI), and waist-hip ratio (WHR) on the risks of breast, ovarian, prostate, colorectal and lung cancers. Methods: We tested the association between genetic risk scores and each trait using summary statistics from published genome-wide association studies (GWAS) and from 51 537 cancer cases and 61 600 controls in the Genetic Associations and Mechanisms in Oncology (GAME-ON) Consortium. Results: We found an inverse association between the genetic score for childhood BMI and risk of breast cancer [odds ratio (OR)=0.71 per standard deviation (s.d.) increase in childhood BMI; 95% confidence interval (CI): 0.60, 0.80; P=6.5×10-5). We also found the genetic score for adult BMI to be inversely associated with breast cancer risk (OR=0.66 per s.d. increase in BMI; 95% CI: 0.57, 0.77; P=2.5×10-7), and positively associated with ovarian cancer (OR=1.35; 95% CI: 1.05, 1.72; P=0.017), lung cancer (OR=1.27; 95% CI: 1.09, 1.49; P=2.9×10-3) and colorectal cancer (OR=1.39; 95% CI: 1.06, 1.82, P=0.016). The inverse association between genetically predicted adult BMI and breast cancer risk remained even after adjusting for directional pleiotropy via MR-Egger regression. Conclusions: Findings from this study provide additional understandings of the complex relationship between adiposity and cancer risks. Our results for breast and lung cancer are particularly interesting, given previous reports of effect heterogeneity by menopausal status and smoking status.</p

Three‐dimensional P wave velocity structure of the Northern Hikurangi margin from the NZ3D experiment: evidence for fault‐bound anisotropy

We present a high‐resolution three‐dimensional (3‐D) anisotropic P wave velocity (Vp) model in the northern Hikurangi margin offshore Gisborne, New Zealand, constructed by tomographic inversion of over 430,000 first arrivals recorded by a dense grid of ocean bottom seismometers. Since the study area covers a region where shallow slow slip events (SSEs) occur repeatedly and the subduction of a seamount is proposed, it offers an ideal location to link our understanding of structural and hydrogeologic properties at megathrust faults to slip behavior. The Vp model reveals an ~30‐km‐wide, low‐velocity accretionary wedge at the toe of the overriding plate, where previous seismic reflection studies show a series of active thrust faults branching from the plate interface. We find some locations with significant Vp azimuthal anisotropy >5% near the branching faults and the deformation front. This finding suggests that the anisotropy is not ubiquitous and homogeneous within the overriding plate, but more localized in the vicinity of active thrust faults. The fast axes of Vp within the accretionary wedge are mostly oriented to the plate convergence direction, which is interpreted as preferentially oriented cracks in a compressional stress regime associated with plate subduction. We find that the magnitudes of anisotropy are roughly equivalent to values found at oceanic spreading centers, where the extensional stress regime is dominant and the crack density is expected to be higher than subduction zones. This consideration may indicate that additional effects such as fault foliation and clay mineral alignment also contribute to upper plate anisotropy along subduction margins