Prediction of flank wear by using back propagation neural network modeling when cutting hardened H-13 steel with chamfered and honed CBN tools

Productivity and quality in the finish turning of hardened steels can be improved by utilizing predicted performance of the cutting tools. This paper combines predictive machining approach with neural network modeling of tool flank wear in order to estimate performance of chamfered and honed Cubic Boron Nitride (CBN) tools for a variety of cutting conditions. Experimental work has been performed in orthogonal cutting of hardened H-13 type tool steel using CBN tools. At the selected cutting conditions the forces have been measured using a piezoelectric dynamometer and data acquisition system. Simultaneously flank wear at the cutting edge has been monitored by using a tool makers microscope. The experimental force and wear data were utilized to train the developed simulation environment based on back propagation neural network modeling. A trained neural network system was used in predicting flank wear for various different cutting conditions. The developed prediction system was found to be capable of accurate tool wear classification for the range it had been trained.     

Dissolution Behavior of Electrodeposited Ni–W Alloys

Nickel (Ni)–Tungsten (W) alloys were electrodeposited galvanostatically (at–10 mA cm^–2) on copper substrate with 3 different W contents under the controlled hydrodynamic conditions and then the anodic dissolution behaviors of the alloys were observed by potentiodynamic polarization and electrochemical quartz crystal microbalance (EQCM) techniques. While the structure of the electrodeposited Ni–W alloy with low W content (15.90% W) was crystalline, that of the alloy with high W content (50.80% W) was nano-crystalline according to X-ray diffraction patterns. The increase in the W content of the electrodeposited Ni–W alloy resulted decrease at pH 3 and increase at pH 7 and 12.5 in the anodic currents of the alloy. The pH dependent dissolutions caused electrodeposited alloy surface to have W—enrichment at pH 3 and Ni—enrichment at pH 7 and 12.5. These observations indicated that the selective dissolution of Ni or W was the main mechanism in the anodic dissolution of the electrodeposited Ni–W alloys. The EQCM experiments conducted at pH 7 supported the presence of the selective dissolution mechanism that the anodic dissolution potential of W was 0.42 V lower than that of Ni in the electrodeposited Ni–W alloys.     

Experimental and finite element simulation based investigations on micro-milling Ti-6Al-4V titanium alloy: Effects of cBN coating on tool wear

Micro-milling process is a direct and flexible fabrication method in producing functional three dimensional micro-products. The advance of micro-milling process ultimately depends on the development of micro cutting tools since it is a tool-based process. Therefore, in this study an attempt to improve the performance of carbide micro-end mills by applying cubic boron nitride (cBN) coating was carried out. Experiments and finite element method (FEM) based simulations were used to study the effect of cBN coated tool in micro-machining of Ti-6Al-4V titanium alloy. The experiments were conducted to compare the performance of cBN coated and uncoated micro-end mills in terms of surface roughness, burr formation and tool wear. FE simulations were employed to investigate chip formation process in micro-milling to reveal the effects of cBN coated micro-end mills with increased edge radius in terms of cutting force generation, tool temperature and contact pressure, sliding velocity and hence tool wear rate. The simulation results were further utilized for estimating tool life using a sliding wear rate model and compared with experiments. This study clearly showed that the cBN coated carbide tool outperformed the uncoated carbide tool in generation of tool wear and cutting temperature.     

Micro milling of titanium alloy Ti-6Al-4V: 3-D finite element modeling for prediction of chip flow and burr formation

Cutting process of titanium alloy Ti-6Al-4V is considered difficult due to chemical affinity between tool and work material, adhesion, built-up edge and burr formation, and tool wear resulting in loss of productivity. Three dimensional (3-D) chip flow together with local field variables such as temperature, elastic/plastic strain, strain-rate and velocity in the shear zones during micro milling process can be predicted using continuum-mechanics based 3-D Finite Element (FE) modelling and simulation of elastic/viscoplastic work material deformations. This paper provides much needed process insight for chip flow, built-up edge and burr formation by using modeling work with experimental validation. Scanning electron microscopic (SEM) observation of the 3-D chip morphology and burrs demonstrate ductile fractured surfaces together with localized instability and failure behaviors. FE simulations are utilized to investigate the effects of micro milling operation i.e. up and down milling and tool edge radius on 3-D chip flow, built-up edge, and 3-D burr formation. Simulated results are compared with measurements of chip morphology, shape, and dimensions together with tool edge condition of built-up edge and chip adhesion yielding to good agreements.     

Infrared and Structural Properties of Y1?xNdxBa2Cu3O7?δ (0 ≤ x ≤ 1)

Infrared and structural properties of Y_1–x Nd _x Ba₂Cu₃O_7– (0 x 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80–100 K. It was observed that by the substitution of Nd to Y in YBa₂Cu₃O_{7 –} IR band at 573 cm^–1 that is assigned as Cu–O axial antisymmetric stretching mode shifts to 533 cm^–1 while the band at 620 cm^–1 that is due to Cu–O symmetric stretching mode in YBa₂Cu₃O_7– shifts to 588 cm^–1.     

Grouting a tunnel cave-in from the surface: a case study on Kurtkula ı irrigation tunnel, Turkey

This paper describes the treatment of tunneling problems at Kurtkula ı irrigation tunnel, particularly focusing on the Kurtkula ı tunnel which is 1255 m in length and 3.50 m in diameter, is an important of the Yumurtalık Plain Irrigation Project. The tunnel was excavated using conventional dull and blast, but during the tunneling problems occurred. Within a 70 m long section of the tunnel, cave-in occurred at two locations both along the fault zone in tunnel alignment. Slope stability problems were experienced too at inlet and outlet section of the tunnel. A sinkhole was formed at the surface as a result of the cave-in. There are an Allocthonous Cretaceous complex sequence and Miocene sandstone–claystone units, which have a faulty contact in the tunnel alignment area. The complex sequence consists of mainly weathered andesite, spilitic agglomerate, radiolarite, serpentinite and limestone blocks. The claystone to sandstone is thin-medium bedded and has medium-weak rock substance properties. The fault zone with an approximate width of 150 m and consisting of extremely weak crushed rocks crosses the tunnel alignment at mid-section. Some treatment methods were applied to remedy this collapse. Cut and cover method was applied for the first 955 m of the tunnel inlet due to the shallow overburden and very weak rock properties. However, cave-ins delayed the tunnel construction for 1 year and increased the cost by 9%.     

A sensitive seminested PCR method for the detection of Shigella in spiked environmental water samples

A rapid seminested polymerase chain reaction (PCR) method for the specific, sensitive detection of virulent Shigella spp. in spiked environmental water samples was developed. A set of primers specific for the invasion plasmid antigen gene (ipaH) of virulent Shigella spp. and enteroinvasive Escherichia coli produced a 620-bp fragment that was used as template for the seminested primer pair delineating a 401-bp fragment. By using agarose gel electrophoresis for detection of the seminested PCR-amplified products, a detection limit of 1.6 x 10(3) cfu S. flexneri was obtained with amplification reactions from crude bacterial lysates. The PCR procedure coupled with an enrichment culture incubated for 6 h detected as few as 1.6 S. flexneri organisms in pure culture. Treated sewage, ground, surface and drinking water samples collected from various sources were seeded with S. flexneri and incubated in GN broth for 6 h before detection by seminested PCR. A detection limit lower than 14 cfu/ml was achieved in some water samples. The results indicate that the described seminested PCR has the advantage of a rapid turnaround time and it fulfills the requirements of sensitivity and specificity for use in an environmental laboratory.     

Biological activities of the essential oil and methanolic extract of Micromeria fruticosa (L) Druce ssp serpyllifolia (Bieb) PH Davis plants from the eastern Anatolia region of Turkey

The in vitro antimicrobial and antioxidant activities of the essential oil and methanolic extract of Micromeria fruticosa ssp serpyllifolia as well as the composition of the essential oil were examined. The essential oil exhibited activity against 14 bacteria, three fungi and a yeast, with minimal inhibitory concentration (MIC) values ranging from 31.25 to 125 µl ml^?1, whilst the methanolic extract was inactive. Antioxidant activity was measured by two methods, namely scavenging of the free radical DPPH and inhibition of linoleic acid oxidation. The methanolic extract exhibited significant antioxidant activity in both assays, providing 50% inhibition at 70.9 ± 0.5 µg ml^?1 concentration in the DPPH assay and inhibiting linoleic acid oxidation to 59% at 2 mg ml^?1 concentration, whilst the essential oil showed activity only at higher concentrations. The gallic acid equivalent total phenolic content of the methanolic extract was found to be 55.2 ± 2.00 µg mg^?1 dry weight extract (5.5% w/w). The chemical composition of the hydrodistilled essential oil was analysed by means of GC/MS. Twenty‐nine constituents were identified, the main ones being piperitenone (50.61%) and pulegone (29.19%). Copyright © 2004 Society of Chemical Industry