An experimental method to determine the minimum uncut chip thickness (Hmin) in orthogonal cutting

Chip formation has been studied for more than a century using, initially, process description followed by experimental procedures and mathematical models. At first, cutting edges were modelled as perfectly sharp, but real cutting tools contain small radius. Some of them are as low as few micrometers. Micro-machining operations often need uncut chip thickness (h) lower than edge radius. In such conditions a minimum value (hmin) may be found, under which material may not be properly removed. There is an extensive range of values for hmin in literature, as a percentage only of the edge radius (re). The criterion for establishing hmin also extensively varies as well as the cutting conditions used. The present work proposes an innovative method to study hmin with realistic values of cutting and feed speed (vc and vf) in orthogonal cutting. Using the proposed method several edges were tested and two of them, one sharp (re = 6 μm) and one blunt (re = 120 μm), are here presented in 3 different conditions. Values of hmin were detected for each of the cutting conditions. They were found to depend on the cutting conditions, on the maximum hmax established and on the way it grows during the interaction between edge radius and workpiece material. It was also suspected that BUE can be formed in front of the tool, depending on the way the uncut chip thickness increases during the interaction. The method also proved to be capable of detecting hmin and several other associations with the main parameters affecting that minimum value10194207FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão temmachinin

The impact of the cutting parameters and tool condition on surface integrity when milling Inconel 625

During machining, the workpiece material tends to undergo mechanical and thermal transformations. Machining Inconel 625 is a challenging task since this material has low thermal conductivity, rapidly work hardening, and maintains its strength even at high temperatures. This superalloy is used extensively by the aerospace and oil and gas industries due to both its corrosion and heat resistance. All these characteristics influence tool life, cutting forces, and the integrity of the machined surface, which, in turn, significantly impacts the fatigue life of the components. It is therefore important to understand the surface integrity induced during milling. Although many reports have been published about tool wear and surface integrity studies for Inconel alloys, especially on the effect of the tool condition on the surface and subsurface which address residual stress, corrosion, and deformed layers have not been investigated so far. This study highlights the importance of assessing the surface integrity of Inconel 625 clad workpieces milled with both fresh and worn tools at different cutting speeds and feed rates. The results show that the best conditions for maintaining surface integrity among the conditions tested are vc = 55 m/min and fz = 0.10 mm/tooth. The workpiece milled with a fresh tool presented better corrosion resistance, whereas the worn tool produced more compressive stress, indicating that such conditions would improve the fatigue life of the part

Evaluating the use of a new type of impact damper for internal turning tool bar in deep holes

In internal turning operation of long holes, the tool is not rigid, since it must be out from the lathe turret in a length longer than the machined hole length. This problem is even more serious in the internal turning of hardened steels, where the requirements for surface quality are more restrict, due to the fact that this is a finishing operation, which aims to replace grinding. Therefore, some procedures have to be taken in order to minimize vibration and, consequently, to make the attainment of a good workpiece surface quality possible. One of these procedures is the use of a damped tool. In this work, we tried a simple and different kind of impact damped tool bar, using spheres placed in a cavity manufactured in the tool bar. The performance of this impact damper with three different sizes of spheres was compared to the performance of a solid steel bar, in terms of workpiece surface roughness, tool vibration, and tool life. The main conclusion of this work is that the use of the kind of impact damper tested in this work makes possible the increase of the tool overhang (tool length outside the machine turret) without damaging surface roughness and tool life and, consequently, it also makes possible the turning of longer holes than when a solid bar is used10113751390sem informaçãosem informaçã

Perfil antropométrico de mulheres adultas da área urbana e rural no município de Barcelos, AM Anthropometric profile of women from the urban and rural areas in Barcelos municipality. (Amazonas, Brazil)

De um total de 203 mulheres adultas entrevistadas, foram avaliadas 175 (entre 16 a 73 anos), por meio de medidas antropométricas: peso, altura, prega cutânea tricipital (PCT), circunferência braquial (CB), circunferência muscular (CMB) e Índice de Massa Corpórea (IMC). Das mulheres analisadas, 84,0% (n=147) residiam na zona urbana e 16,0% (n=28) na zona rural. Verificou-se que o peso médio das mulheres não nutrizes residentes na área urbana foi de 54,1 kg; altura de 149,0 cm e o IMC de 24,4 kg/m², enquanto que a PCT, CB e a CMB forneceram valores médios de 19,2 mm, 27,5 cm e 21,5 cm, respectivamente. Na área rural, as mulheres apresentaram um peso médio de 50,4 kg, altura de 148,6 cm, IMC de 23,0 kg/cm² e a PCT, CB e a CMB foram 13,8 mm, 26,4 cm e 22,1 cm, respectivamente. Houve diferença estatisticamente significativa apenas nos valores médios da PCT entre as mulheres procedentes da área urbana e rural (p<0,05). Nas mulheres da área urbana, a ocorrência de baixo peso foi de 6,5%, 28,2% de sobrepeso e 11,3% de obesidade. Nas mulheres da área rural, a prevalência de baixo peso e obesidade foi de 4% e de sobrepeso de 16%. A maioria da população estudada situou-se no limite máximo de normalidade do IMC, e os índices representantes das reservas adiposas (PCT) foram maiores nas mulheres residentes na área urbana.<br>From a total of 203 adult women interviewed, 175 subjects aged 16 to 73 years were evaluated for the anthropometrics variables: weight, height, triceps skinfold thickness, mid-upper arm circumference, arm muscle circumference and body mass index (BMI). Of these women, 84,0% (147) were living in the urban area and 16,0% (28) in the rural area. Observing the mean values for non-lactating women in the urban area were: weight 54,1 kg, height 149,0 cm, BMI 24,4 kg/m², triceps skinfold thickness 19,2 mm, arm circumference 27,5 cm, arm muscle circumference 21,5 cm. For women in the rural area the values were: weight 50,4 kg, height 148,6 cm, BMI 23,0 kg/cm², triceps skinfold thickness 13,8 mm, arm circumference 26,4 cm, arm muscle circumference 22,1 cm. There was a significant difference in the average triceps skinfold thickness values between women in the rural area and women in the urban area (p<0,05). In the urban area women a 6,5% prevalence of low weight was found, a 28,2% prevalence of overweight and a 11,3% prevalence of obesity. In the rural area women low weight and obesity were found in 4%, and overweight in 16%. In this study, most women were at the upper limit of normality for BMI, with the indices of fat reserves being highest in the women of the urban area