Effect of cutting tools and working conditions on the machinability of TI-6AL-4V using vegetable oil-based cutting fluids

The cutting of titanium alloys is usually associated with low productivity, poor surface quality, short tool life and high machining costs. This is due to the excessive generation of heat in the cutting zone and difficulties in heat dissipation due to the relatively low heat conductivity of this metal. Cooling applications in machining processes are crucial, since many operations cannot be performed efficiently without cooling. Improving machinability, increasing productivity, and enhancing surface integrity and part accuracy are the main advantages of the use of cutting fluids (CFs). Conventional cutting fluids such as mineral oil-based, synthetic and semi-synthetic fluids are the most common types used in the machining industry. Although these cutting fluids can be beneficial, they pose a great threat to human health and to ecosystems. Vegetable oils (VOs) are being investigated as a potential source of environmentally favourable lubricants, due to a combination of biodegradability, good lubrication properties, low toxicity, high flash points, low volatility, high viscosity indices and thermal stability. The fatty acids of vegetable oils are known to provide thick, strong, and durable lubricant films. These strong lubricating films give the vegetable oil base stock a greater capability to absorb pressure and a high load carrying capacity. This paper details the main experimental results from an investigation of the impact of various vegetable oil-based cutting fluids, cutting tool materials and working conditions when turning Ti-6Al-4V. A full factorial experimental design was employed involving 24 trials to evaluate the influence of process variables on average surface roughness (Ra), tool wear and chip formation. In general, values of Ra varied between 0.5 µm and 1.56 µm and the Vasco1000 cutting fluid exhibited a level of performance comparable to other fluids in terms of surface roughness, while the uncoated coarse grain WC carbide tool achieved lower flank wear at all cutting speeds. On the other hand, all tools tips were subject to uniform flank wear during the cutting trials. Additionally, formed chip thickness (tc) ranged between 0.1 mm and 0.14 mm with a noticeable decrease in chip size when higher cutting speeds were used

Development and Evaluation of a Novel Supply System to Reduce Cutting Fluid Consumption and Improve Machining Performance

Reducing cutting fluid consumption remains a goal of the machining industry. Despite their reported advantages such as heat dissipation, friction reduction, extended tool life, and improved surface quality, cutting fluids pose several health and environmental concerns throughout their lifecycle, in particular when conventional mineral oil-based, semi-synthetic or synthetic fluids are used. Manufacturers are encouraged to reduce the use of harmful conventional fluids. However, the usage of cutting fluid is still an unavoidable industrial practice, especially when machining titanium alloys, due to the generation of large quantities of heat. High cutting temperature is one of the main reasons for rapid tool wear and hence the poor machinability of titanium alloys. Vegetable oil (VO)-based fluids have been suggested as favourable alternatives to the conventional fluids due to their superior tribological properties and high biodegradability. Several cutting fluid supply systems have been developed to reduce cutting fluid use, such as minimum quality lubricant (MQL) and cryogenic cooling or to control the temperature in the cutting zone, for example flood, and high pressure cooling (HPC) systems, to improve productivity and increase the overall performance of machining processes. Even though process improvements are achieved by these systems, inaccuracies in estimating cutting fluid flow rates, high fluid consumption and low penetrability, as well as high set-up costs, are their technical and economic drawbacks. For these reasons, the need for an innovative supply system to deliver fluids in machining processes has become crucial. In this PhD project, a novel controlled cutting fluid impinging supply system known as ‘CUT-LIST’ is developed to deliver an accurate quantity of cutting fluid into machining zones through precisely-oriented coherent nozzles. The design of CUT-LIST is supported by numerous fluid dynamic and metal cutting theories along with extensive experimentation. The performance of the new system is evaluated against a conventional flood system during the step shoulder milling of Ti-6Al-4V using a water-miscible vegetable oil-based cutting fluid. The effect of cutting conditions on the key measures of the process are investigated, including cutting force, workpiece temperature, tool flank wear, burr formation and average surface roughness (Ra). The effect of CUT-LIST on the micro-hardness and microstructure of the machined surface as well as chip formation are also evaluated. The study shows that the new system provides a dramatic decrease in cutting fluid consumption of up to 42% with noticeable reductions in cutting force, tool flank wear and burr height of 16.41%, 46.77% and 60% respectively. Relatively smaller surface roughness (Ra) values are also found with the use of the CUT-LIST supply system. In terms of the effect of the new system parameters on key process measures, feed rate has a major effect on cutting force, burr formation and surface roughness, with the highest percentage contribution ratios (PCRs) of 47.46%, 38.69% and 39.10% respectively. Meanwhile, the cutting speed has a major effect on workpiece temperature and flank wear, with the highest PCRs of 46.5% and 59.23% respectively. Nozzle position at a 15˚ angle in the feed direction and 45˚or 60˚ against feed direction helped in minimising workpiece temperature. An impinging distance of 55 or 75 mm is also necessary to control burr formation, workpiece temperature, and Ra. Metallurgical observation shows that both systems achieved acceptable micro-hardness values for aerospace components (386.3 to 419 HV100). However, a slight reduction in micro-hardness of ~5.5% was recorded with the use of CUT-LIST. The hardness is lower at distances < 50 μm below the machined surface as a result of thermal softening, while it becomes higher at distances <100 μm from the surface due to cyclic internal work hardening. The micro-hardness then gradually decreases until it reaches the base material’s nominal hardness. Both systems also produce a thin, plastically deformed layer below the machined surface under all conditions investigated. Despite the noticeable reduction in cutting fluid consumption achieved by CUT-LIST, no significant disparity is found in the microstructural subsurface damage caused by the two systems. Microstructural alteration is strongly affected by cutting speed and fluid flow rate. At higher cutting speeds, the conventional system shows visible surface defects such as smearing, surface cavities and erosion in workpiece material. With both systems, desirable discontinued serrated chips are generated. However, the increase in fluid flow rate significantly influences chip morphology, while the average distance between chip segments is more pronounced and evident with the increase in cutting speed. Severe crack propagation (up to a depth of 200 μm) is observed in the chip end free surface, with the use of the conventional system. In addition, CUT-LIST shows decreases of up to 12.5 % in saw-tooth height (hmax) and increased segment width up to 13.63 % at higher speeds, while the transition from aperiodic to periodic serrated chip formation is closely controlled by cutting speed and feed rate. Chip segmentation frequency and shear angle are also found to be sensitive to cutting speed, whilst CUT-LIST provides a larger shear angle compared to the conventional system. Based on the results achieved by CUT-LIST, it is apparent that the new system possesses various advantages over the conventional system. Hence, CUT-LIST can be considered as a feasible, efficient, and ecologically beneficial solution, offering less fluid consumption in machining processes

A gênese da sociedade do espetáculo: Teatro em Paris, Berlim, Londres e Viena.

A gênese da sociedade do espetáculo: Teatro em Paris, Berlim, Londres e Viena

Clouds over IMD? Perspectives for inherited metabolic diseases in adults from a retrospective cohort study in two Swiss adult metabolic clinics.

Inherited metabolic diseases (IMD) are complex medical conditions. Thanks to improvements in diagnosis and treatment, a growing number of pediatric IMD patients reach adulthood. Thus, clinical care of adults with IMD has emerged as a new and challenging reality. This purpose of this study of adults with IMD in an adult metabolic clinic at two academic hospitals (Lausanne and Geneva) was to help inform decisions on the future organization of health care for this group of patients. All adult patients with a biochemical and/or genetic diagnosis of IMD followed at the clinics were included in the study. Electronic patient records were reviewed for clinical features, diagnostic studies, treatment and long-term outcome. Data of undiagnosed patients referred for suspected IMD were analyzed separately. 126 patients were included in the study. The most prevalent group of diseases was small molecules disorders with 82 (65%) patients, followed by energy defects disorders with 29 (23%) patients and complex molecules disorders with 15 (12%) patients. Overall, 64% of patients were diagnosed before, and 36% after the age 16 years. Among the 126 cases, 51% suffered from medical complications. 79% of the patients were receiving a specific treatment for their disease. Among the 138 undiagnosed patients referred for suspicion of IMD, investigations lead to a genetic diagnosis in 24 (17%) patients. 19 had confirmation of an IMD, 5 were found to have another genetic condition. This retrospective study reveals significant features of adult IMD cohort. The disorders are heterogeneous, and there is no one-size-fits-all approach - treatment must be tailored to fit each specific disorder in each individual patient. Even patients who are followed at the dedicated clinic are not protected from metabolic decompensations and/or chronic organ-specific complications. While it is commonly assumed that patients with IMD are more stable once they become adults, our data show that the diseases continue to exact a lifelong toll. A coordinated monitoring of target organs by a multidisciplinary team is needed. To ensure that the success in diagnosis and treatment of individuals with IMD is sustained, there is a clear requirement for adequately staffed adult IMD clinics

Influence of Skin Commensals on Therapeutic Outcomes of Surgically Debrided Diabetic Foot Infections-A Large Retrospective Comparative Study

In diabetic foot infections (DFI), the clinical virulence of skin commensals are generally presumed to be low. In this single-center study, we divided the wound isolates into two groups: skin commensals (coagulase-negative staphylococci, micrococci, corynebacteria, cutibacteria) and pathogenic pathogens, and followed the patients for ≥ 6 months. In this retrospective study among 1018 DFI episodes (392 [39%] with osteomyelitis), we identified skin commensals as the sole culture isolates (without accompanying pathogenic pathogens) in 54 cases (5%). After treatment (antibiotic therapy [median of 20 days], hyperbaric oxygen in 98 cases [10%]), 251 episodes (25%) were clinical failures. Group comparisons between those growing only skin commensals and controls found no difference in clinical failure (17% vs. 24 %, p = 0.23) or microbiological recurrence (11% vs. 17 %, p = 0.23). The skin commensals were mostly treated with non-beta-lactam oral antibiotics. In multivariate logistic regression analysis, the isolation of only skin commensals was not associated with failure (odds ratio 0.4, 95% confidence interval 0.1-3.8). Clinicians might wish to consider these isolates as potential pathogens when selecting a targeted antibiotic regimen, which may also be based on oral non-beta-lactam antibiotic agents effective against the corresponding skin pathogens

The Influence of Skin Commensals on the Therapeutic Outcomes of Surgically-Debrided Diabetic Foot Infections

In diabetic foot infections (DFI), the clinically virulence of skin commensals are generally presumed to be of low virulence. In this single-center study, we divided the wound isolates into two groups: skin commensals (coagulase-negative staphylococci, micrococci, corynebacteria, cutibacteria); and, pyogenic pathogens, and followed the patients for ≥ 6 months. In 1,018 DFI episodes (392 [39%] with osteomyelitis), we identified skin commensals as the sole culture isolates (without accompanying pyogenic pathogens) in 54 cases (5%). After treatment (antibiotic therapy [median of 20 days], hyperbaric oxygen in 98 cases [10%]), 251 episodes (25%) were clinical failures. Group comparisons between those growing only skin commensals and controls found no difference in clinical failure (17% vs 24 %, p=0.23) or microbiological recurrence (11% vs 17 %, p=0.23). The skin commensals were mostly treated with non-beta-lactam oral antibiotics. In multivariate logistic regression analysis, isolation of only skin commensals was not associated with failure (odds ratio 0.4, 95% confidence interval 0.1-3.8). Clinicians might wish to consider these isolates as potential pathogens when selecting a targeted antibiotic regimen, which may equally base on oral non-beta-lactam antibiotic agents susceptible to the corresponding skin pathogens

Overweight and obesity in adult patients with phenylketonuria: a systematic review.

Excess weight is a rising concern in patients with phenylketonuria (PKU). It is commonly observed in children and adolescents with PKU; but data on adults are inconsistent. This review aims to summarize available data on excess weight in adult PKU individuals. We conducted a systematic search of literature in English, from inception to October 2021, on PubMed and Embase to identify articles on overweight and obesity in adult PKU patients. Prevalence of overweight and obesity, body mass index (BMI) and gender differences were the outcomes of interest. Of 260 articles identified, only 8 fulfilled quality criteria for inclusion after screening of titles, abstracts and full texts. The mean BMI of adult PKU patients in these studies ranged from 26 ± 5.4 to 30.3 ± 1.8 kg/m &lt;sup&gt;2&lt;/sup&gt; . When compared to matched controls, adult PKU patients had higher BMI and higher prevalence of obesity. However, results were inconsistent when PKU adults were compared to the general population. The prevalence of obesity in the included studies varied widely between 4.5% up to 72% in individual studies. Obesity was 2-3 times more frequent in female PKU patients. Excess weight is frequent in adult PKU patients, especially in females, even if the difference with the general population is debatable. The heterogeneity of the studies makes it difficult to interpret the results and the factors that contribute to obesity. Content of the diet, psychological status, diet-associated disordered eating, patient's social environment and lifestyle are listed as potentials contributors to excess weight in PKU adult population. Further studies are needed to better elucidate this question. In the meantime, weight control and healthy eating habits should be considered in the management and follow-up of these patients

Parsonage-Turner Syndrome rather than Zoster Neuritis?

We report the case of an 86-year-old man with acute left shoulder pain, followed by left limb monoparesis and a herpetic rash on the left upper limb and thoracic region. This situation presented a diagnostic challenge because of the simultaneity of symptoms attributable to Parsonage-Turner syndrome and herpes zoster neuropathy. A detailed clinical history, physical examination and electroneuromyography were essential to distinguish the neurological structures involved and to ascertain the diagnosis

Current knowledge of morbidities and direct costs related to diabetic foot disorders: a literature review

Diabetes is a chronic disease associated with numerous complications including diabetic foot disorders, which are associated with significant morbidity and mortality as well as high costs. The costs associated with diabetic foot disorders comprise those linked to care (direct) and loss of productivity and poor quality of life (indirect). Due to the constant increase in diabetes prevalence, it is expected that diabetic foot disorder will require more resources, both in terms of caregivers and economically. We reviewed findings on management, morbidity, mortality, and costs related to diabetic foot disorder

Investigation of Cutting Tools and Working Conditions Effects when Cutting Ti-6al-4V using Vegetable Oil-Based Cutting Fluids

Power consumed in metal cutting is typically converted into heat near the cutting tool edge. Cutting fluids are then provided to a cutting zone in order to improve the tribological characteristics of machining processes and to dissipate the generated heat. The use of conventional cutting fluids however has lately been questioned due to the adverse impact on the environment and human health. Therefore, trends are directed to various alternatives such as vegetable oils (VOs). VOs offer a combination of good biodegradability and high lubricity, eco-friendly and compatibility with additives, low toxicity and volatility, high flash points and high viscosity indices. This paper details preliminary experimental results when turning Ti-6Al-4 V. The impact of VO-based cutting fluids, cutting tool materials and working conditions were investigated. Two sets of experimental plans were designed comprising 25 and 27 tests with analysis of variance (ANOVA) employed to evaluate the effect of process variables on Ra and tool flank wear. In general, surface roughness Ra ranged between 0.56 μm and 1.81 μm and statistical analysis showed that the main contributing factor for Ra is feed rate having a high Percentage Contribution Ratio (PCR) of 94.4%. Noticeable increase in tool tip flank wear was recorded when higher cutting speeds were used