Investigation of sequential cryogenic hard turning and ball burnishing processes

This paper presents a sequential machining process which incorporates CBN hard turning with cryogenic pre-cooling of the workpiece (CHT) and ball burnishing (BB). The main goal of this study was to select machining conditions enhancing the quality of parts machined by hard turning including the surface roughness Ra of about 0,2 μm, good bearing properties and reducing the white layer. Changes of surface roughness, surface texture, microstructure alterations and micro-hardness distribution are discusses

Investigation of the machining process of spheroidal cast iron using cubic boron nitride (CBN) tools

This paper presents the experimental results of the turning of spheroidal iron (EN-GJS-500-7 grade) using L-CBN tools. The cutting process can be classified as a High Performance Cutting (HPC) due to a relatively high material removal rate of about 190 cm3/min. The investigations performed include fundamental process quantities and machined surface characteristics, i.e. componential cutting forces, specific cutting energy, average and maximum values of cutting temperature as well as temperature distribution in the cutting zone, tool wear progress visualized by appropriate wear curves and 2D/3D surface roughness parameters

Investigation of the machining process of spheroidal cast iron using cubic boron nitride (CBN) tools

This paper presents the experimental results of the turning of spheroidal iron (EN-GJS-500-7 grade) using L-CBN tools. The cutting process can be classified as a High Performance Cutting (HPC) due to a relatively high material removal rate of about 190 cm3/min. The investigations performed include fundamental process quantities and machined surface characteristics, i.e. componential cutting forces, specific cutting energy, average and maximum values of cutting temperature as well as temperature distribution in the cutting zone, tool wear progress visualized by appropriate wear curves and 2D/3D surface roughness parameters

Genetic variation in FADS genes is associated with maternal long-chain PUFA status but not with cognitive development of infants in a high fish-eating observational study

AbstractLong-chain n-6 and n-3 PUFA (LC-PUFA), arachidonic acid (AA) (20:4n-6) and DHA (22:6n-3), are critical for optimal brain development. These fatty acids can be consumed directly from the diet, or synthesized endogenously from precursor PUFA by Δ-5 (encoded by FADS1) and Δ-6 desaturases (encoded by FADS2). The aim of this study was to determine the potential importance of maternal genetic variability in FADS1 and FADS2 genes to maternal LC-PUFA status and infant neurodevelopment in populations with high fish intakes. The Nutrition Cohorts 1 (NC1) and 2 (NC2) are longitudinal observational mother-child cohorts in the Republic of Seychelles. Maternal serum LC-PUFA was measured at 28 weeks gestation and genotyping for rs174537 (FADS1), rs174561 (FADS1), rs3834458 (FADS1-FADS2) and rs174575 (FADS2) was performed in both cohorts. The children completed the Bayley Scales of Infant Development II (BSID-II) at 30 months in NC1 and at 20 months in NC2. Complete data were available for 221 and 1310 mothers from NC1 and NC2 respectively. With increasing number of rs3834458 minor alleles, maternal concentrations of AA were significantly decreased (NC1 p=0.004; NC2 p<0.001) and precursor:product ratios for linoleic acid (LA) (18:2n-6)-to-AA (NC1 p<0.001; NC2 p<0.001) and α-linolenic acid (ALA) (18:3n-3)-to-DHA were increased (NC2 p=0.028). There were no significant associations between maternal FADS genotype and BSID-II scores in either cohort. A trend for improved PDI was found among infants born to mothers with the minor rs3834458 allele.In these high fish-eating cohorts, genetic variability in FADS genes was associated with maternal AA status measured in serum and a subtle association of the FADS genotype was found with neurodevelopment

Estimating the cutting force when skiving with a radius cutter

The paper considers the method of determining the components of the cutting force under cutting completed with a radius cutter. The authors provide the design of the experimental study. The authors provide the data on the cutting force change in the process of turning with a radius cutter according to the cutting edge inclination, cutting depth and supply obtained experimentally and calculated analytically. The paper also provides the results of experimental work approximation and theoretical error checking related to experimental data

The history of degenerate (bipartite) extremal graph problems

This paper is a survey on Extremal Graph Theory, primarily focusing on the case when one of the excluded graphs is bipartite. On one hand we give an introduction to this field and also describe many important results, methods, problems, and constructions.Comment: 97 pages, 11 figures, many problems. This is the preliminary version of our survey presented in Erdos 100. In this version 2 only a citation was complete

Effect of cooling methods on dimensional accuracy and surface finish of a turned titanium part

In metal cutting, the choice of cooling method influences the deformation mechanism, which is related to the dimensional accuracy and surface finish of the parts. The deformation mechanism of titanium alloys under machining conditions is known to be very different from that of commonly used industrial materials. Therefore, the effect of cooling methods on dimensional accuracy and surface finish in machining titanium is of particular interest. This paper investigates experimentally and analytically the influence of cooling method and cutting parameters on two major dimensional accuracy characteristics of a turned titanium part—diameter error and circularity, and surface finish. Data were analyzed via three methods: traditional analysis, Pareto ANOVA, and Taguchi method. The findings indicate that the cooling method has significant effect on circularity error (contribution ratio 76.75 %), moderate effect on diameter error (contribution ratio 25.00 %), and negligible effect on surface finish (contribution ratio 0.16 %)