Investigation of Tool Wear and Surface Finish by Analyzing Vibration Signals in Turning Assab-705 Steel

Various occurrences in machining influence the machining dynamics and thus produce vibration in the cutting tool-workpiece arrangement. In this investigation, with tri-axial accelerometer mounted on the tool-holder in turning ASSAB-705 steel, vibration signals have been captured with and without cutting. The nature of vibrations arising in the cutting tool at different cutting conditions has been investigated. It has been observed that the RMS amplitude of vibration along all three axes for the increasing cutting speed was mixed in nature; however, an increasing trend was noticed in the vibrations along the feed, V_x and radial, V_y directions. The vibration along the main cutting direction, V_z was mixed, initiated by large vibration and then decreased until a particular cutting speed was reached and finally increased steadily. The feed vibration component, V_x has a similar response to the change of the workpiece surface roughness, while the other two components, V_y and V_z have the more coherent response to the rate of flank wear progression throughout the tool life. The natural frequency of different machine parts vibration has been found to be within the band of 0 Hz – 4.2 kHz, whereas the frequencies of different occurrences in turning varied between 98 Hz and 42 kHz.     

An apparatus for in situ spectroscopy of radiation damage of polymers by bombardment with high-energy heavy ions

A new target station providing Fourier transform infrared (FT-IR) spectroscopy and residual gas analysis (RGA) for in situ observation of ion-induced changes in polymers has been installed at the GSI Helmholtz Centre for Heavy Ion Research. The installations as well as first in situ measurements at room temperature are presented here. A foil of polyimide Kapton HN(?) was irradiated with 1.1 GeV Au ions. During irradiation several in situ FT-IR spectra were recorded. Simultaneously outgassing degradation products were detected with the RGA. In the IR spectra nearly all bands decrease due to the degradation of the molecular structure. In the region from 3000 to 2700 cm(-1) vibration bands of saturated hydrocarbons not reported in literature so far became visible. The outgassing experiments show a mixture of C(2)H(4), CO, and N(2) as the main outgassing components of polyimide. The ability to combine both analytical methods and the opportunity to measure a whole fluence series within a single experiment show the efficiency of the new setup.     

Instrumented impact properties of some advanced nuclear reactor pressure vessel steels

Steels used to construct nuclear reactor pressure vessels are low-alloy ferritic steels. These steels should have good impact properties, i.e., low transition temperature and high upper shelf energy, both before and during service conditions. The most important service condition is the neutron irradiation. Extensive research and development was conducted to develop such steels. Instrumented impact testing was conducted on three advanced pressure vessel steels and, for comparison, a conventional pressure vessel steel. Both microstructures and fracture surfaces were examined using optical and scanning electron microscopic (SEM) techniques. In general, the advanced steels showed much better impact properties (lower ductile-brittle transition temperature and higher upper shelf energy) than the conventional steel. Loadtime traces showed that increase in the fracture energy was mainly due to increase in the fracture propagation energy rather than the initiation energy. Improvement in the toughness level of the advanced steels compared to that of the HSST steel was related to the difference in chemical composition, microstructure, and fracture surface morphology.     

A new approach to investigate tool condition using dummy tool holder and sensor setup

The industrial demand for automated machining systems to enhance process productivity and quality in machining aerospace components requires investigation of tool condition monitoring. The formation of chip and its removal have a remarkable effect on the state of the cutting tool during turning. This work presents a new technique using acoustic emission (AE) to monitor the tool condition by separating the chip formation frequencies from the rest of the signal which comes mostly from tool wear and plastic deformation of the work material. A dummy tool holder and sensor setup have been designed and integrated with the conventional tool holder system to capture the time-domain chip formation signals independently during turning. Several dry turning tests have been conducted at the speed ranging from 120 to 180?m/min, feed rate from 0.20 to 0.50?mm/rev, and depth of cut from 1 to 1.5?mm. The tool insert used was TiN-coated carbide while the work material was high-carbon steel. The signals from the dummy setup clearly differ from the AE signals of the conventional setup. It has been observed that time-domain signal and corresponding frequency response can predict the tool conditions. The rate of tool wear was found to decrease with chip breakage even at higher feed rate. The tool wear and plastic deformation were viewed to decrease with the increased radius of chip curvature and thinner chip thickness even at the highest cutting speed, and these have been verified by measuring tool wear. The chip formation frequency has been found to be within 97.7 to 640?kHz.     

Temperature-dependent electrical resistance of conductive polylactic acid filament for fused deposition modeling

This study characterizes the microstructure and temperature dependence of resistance of two commercially available electrically conductive polylactic acid (PLA) composites for fused deposition modeling (FDM): PLA-carbon black and PLA-graphene. No microstructural changes were observed between the filament and the printed parts; however, the resistivity of the filament was found to drop by four to six times upon FDM. Also, compared to the resistivity of individual extruded wire, the resistivity of the printed parts was found to be up to 1500 times higher for PLA-graphene and up to 300 times higher for PLA-carbon black. The raw PLA-carbon black filament and printed wire showed a positive temperature coefficient of resistance (α) value between ~?0.03 and 0.01 °C^?1, which makes them more suitable for sensor development. The raw PLA-graphene filament and printed wire did not exhibit a significant α, which makes them more suitable for printing wires. However, the parts made with multilayer FDM exhibited a negative or a negligible α up to a certain temperature prior to exhibiting a positive α; further, these α values were significantly lower than those obtained for the filaments before or after extrusion. These findings enable proper selection of commercial conductive FDM filaments for enabling quicker prototyping of electronics and sensors.     

Molecular typing of Neisseria gonorrhoeae causing repeated infections: evolution of porin during passage within a community

Thirty-three Neisseria gonorrhoeae isolates from 15 persons infected multiple times with the same serovar were compared using por gene sequencing, opa-typing, and arbitrarily primed-polymerase chain reaction. All three molecular techniques were more discriminatory than serotyping and identified differences between some isolates belonging to the same serovar. Although there were differences among Por sequences within some serovars, 10 of 15 subjects became reinfected with gonococci expressing identical Por proteins. Sequence analysis of por genes revealed evidence of horizontal genetic exchange and point mutations in potential surface-exposed regions during passage in the community.     

Effects of nicotine and stress on startle amplitude and sensory gating depend on rat strain and sex

We recently reported that 14 days of nicotine administration (12 mg/kg/day) reduced acoustic startle reflex amplitude and impaired prepulse inhibition (PPI) of startle in male and female Long-Evans rats. These findings contrasted with reports of nicotine-induced enhancement of startle and PPI in Sprague-Dawley (a different strain) male rats. The present experiment administered 0, 6, or 12 mg/kg/day nicotine via osmotic minipump for 14 days to 120 Sprague-Dawley rats (male and female) and to 120 Long-Evans rats (male and female) and examined ASR and PPI. Half of the subjects also were stressed by immobilization once each day to examine nicotine-stress interactions. Nicotine enhanced ASR and PPI responses of Sprague-Dawley rats but impaired these responses in Long-Evans rats, regardless of sex. Effects of stress were complex and depended on strain, sex, and drug dose. These findings indicate that effects of nicotine on measures of reactivity (ASR) and sensory gating (PPI) depend on genotype and that nicotine stress interactions depend on genotype, sex, and nicotine dosage.     

Myosin light chain 2a and 2v identifies the embryonic outflow tract myocardium in the developing rodent heart

BACKGROUND: Volatile general anesthetics increase agonist-mediated ion flux through the gamma-aminobutyric acid(A), glycine, and 5-hydroxytryptamine3 (5-HT3) receptors. This action reflects an anesthetic-induced increase in the apparent agonist affinity of these receptors. In contrast, volatile anesthetics block ion flux through the nicotinic acetylcholine receptor (nAcChoR). The authors tested the hypothesis that in addition to blocking ion flux through the nAcChoR, isoflurane also increases the apparent affinity of the nAcChoR for agonist. METHODS: Nicotinic acetylcholine receptors were obtained from the electroplax organ of Torpedo nobiliana. The apparent agonist affinity of the nAcChoR was determined using a new stopped-flow fluorescence assay. This assay derives the apparent agonist affinity of the nAcChoR from the apparent rates with which agonists convert nAcChoRs from the resting state to the desensitized state. RESULTS: Isoflurane significantly increased the apparent affinity (decreased the apparent dissociation constant) of acetylcholine for the nAcChoR at clinically relevant concentrations. The apparent dissociation constant decreased exponentially with the isoflurane concentration from a control value of 44+/-4 microM to 1.0+/-0.1 microM in the presence of 1.5 mM isoflurane, the highest concentration studied. CONCLUSIONS: Isoflurane increases the apparent agonist affinity of the nAcChoR; however, this effect is poorly resolved in ion flux studies because isoflurane also causes channel blockade. The lack of saturation of isoflurane's effect on the apparent agonist affinity even at relatively high isoflurane concentrations argues against a single site of anesthetic action. However, it is consistent with isoflurane interactions with several receptor sites that exhibit a range of anesthetic affinities, sites within the membrane lipid, or both.     

Phase II study of CI-958 in colorectal cancer

We report the first cytogenetic investigation of a Dupuytren's subungual exostosis. The clonal abnormalities found suggest that at least some of these heterotopic ossifications could be neoplastic in nature, instead of being a purely reactive process or exuberant growth in response to trauma.     

A flexible edge matching technique for object detection in dynamic environment

Considering the robustness, stability and reduced volume of data, researchers have focused on using edge information in various video processing applications including moving object detection, tracking and target recognition. Though the edge information is more robust compared to intensity, it also exhibits variations in different frames due to illumination change and noise. In addition to this, the amount of variation varies from edge to edge. Thus, without making use of this variability information, it is difficult to obtain an optimal performance during edge matching. However, traditional edge pixel-based methods do not keep structural information of edges and thus they are not suitable to extract and hold this variability information. To achieve this, we represent edges as segments that make use of the structural and relational information of edges to allow extraction of this variability information. During edge matching, existing algorithms do not handle the size, positional and rotational variations to deal with edges of arbitrary shapes. In this paper, we propose a knowledge-based flexible edge matching algorithm where knowledge is obtained from the statistics on the environmental dynamics, and flexibility is to deal with the arbitrary shape and the geometric variations of edges by making use of this knowledge. In this paper, we detailed the effectiveness of the proposed matching algorithm in moving object detection and also indicated its suitability in other applications like target detection and tracking.