Laser machining of different diameter holes in alumina ceramic: Thermal stress analysis

Laser machining of different diameter holes into alumina tiles is carried out. Temperature and stress fields are predicted by using the finite element code. Surface temperature and residual stress predictions are validated through the thermocouple data and X-ray diffraction measurements. Morphological changes in the cutting section are examined by incorporating optical and scanning electron microscopes. It is found that the predictions of surface temperature and the residual stress formed at the cut section agree well with the experimental findings. In general, cut sections are free from large asperities; however, local dross attachments at the kerf edge and crack network formation at the kerf surface are observed.     

DETERMINATION OF MOISTURE DIFFUSIVITY OF PINE NUT SEEDS

The mechanism of drying and the diffusion of water in fresh pine nut seeds (2.5-2.62mm diameter) were successfully interpreted and modeled by using Fick's law. The initial moisture content of fresh pine nut seed was 23-24% and drying temperatures (45-60°C) were varied, but the drying air was kept at constant velocity and humidity.

The effective diffusivity was estimated from drying rate curves and expressed by an Arhenius relation. In addition, the absorption, and desorption-isotherms for fresh pine nuts were estimated at 20°C at water activity of 0.15-1.00. The isotherms of the fresh pine nuts were estimated in experimental runs.     

Laser nitriding of tool steel: thermal stress analysis

In this paper, bees algorithm (BA) has been used for determine the optimal number of material handling equipment (MHE) used on the production centers. The unmet demands become zero at the end of the planning horizon, i.e., the part demands are totally satisfied through the horizon. The newly developed model provides network information, such as unmet demands and number of loaded and empty of MHE at any given time and centers. Consequently, the model provides a tool for helping managers with planning and decision-making in manufacturing systems. Computational tests showed that small-sized instances can be solved by the exact approach in a fair amount of central processing unit time, but it is not feasible for medium and large-sized instances. To tackle this problem, a bees algorithm is proposed to solve the model. The algorithm is a search procedure inspired by the way honeybees forage for food. The results obtained show the robust performance of the bees algorithm.     

Removal of Cd(II), Pb(II), Cu(II) and Ni(II) from water using modified pine bark

This paper describes the removal of Cd(II), Pb(II), Cu(II), and Ni(II) ions from aqueous solutions using chemically modified pine barks (Pinus nigra). In this article, effects of chemical modification methods on the adsorption capacity have been investigated. Changes of the surface properties were examined by the FTIR, SEM and zeta potential analyses. HCl, NaOH, Fenton reactive, polymerization, acetone, ethanol, chloroform, tetra ethylene glycol, diethyl ether and glycol were used for modification processes. Maximum adsorption capacities were obtained by modification with NaOH (13-20 mg/g), Fenton (12-17 mg/g) and polymerization (12-16.5 mg/g). These modification processes also decreased Chemical Oxygen Demand of water from 1820 mg/L for raw pine barks to 35 mg/L for NaOH modified barks. Adsorption capacities of adsorbents increased from 2 mg/g to 20 mg/g as a result of modification that accordingly increase adsorbent surface activity.     

CO2 laser cutting of Kevlar laminate: influence of assisting gas pressure

In the present study, laser cutting of Kevlar laminate is considered, and the effect of assisting gas pressure and laser output power on the end product quality is examined. The end product quality is judged via measurement of out-of-flatness and kerf width ratios. Experimental tests are carried out using a CO₂ laser beam with pulse repetition rate of 300 Hz. The cutting model introduced previously is accommodated to predict the kerf size for various laser output power and assisting gas pressures. The predictions are compared with the experimental results. It is found that the predictions of kerf size are in good agreement with the experimental results. The influence of assisting gas pressure is significant on the resulting cut quality, in which case, out-of-flatness and kerf width ratio improve considerably at high assisting gas pressures (500 kPa).     

The Synthesis and Characterization of s-Triazine-Cored and [Fe(III)Salen]-Capped Polymer Complexes

2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride, C₃N₃Cl₃, 1) was used as the starting material. 2-(4-Carboxyphenylamino)-4,6-dichloro-1,3,5-triazine (2) was obtained from the reaction of cyanuric chloride with 4-aminobenzoic acid in the presence of sodium bicarbonate in acetone. A mononuclear complex (4) was obtained by reacting 2 and [FeSalen]₂O (3). A series of polymeric compounds was obtained by reacting 4 with a series of diamines. The polymeric complexes were characterized by elemental analysis, AAS, FT-IR, ¹H NMR, TGA and magnetic susceptibility measurements. The complexes are low-spin, distorted octahedral Fe(III) species that are bridged by carboxylic acids. The [FeSalen]-containing compounds may have the electronic structure t_2g⁵e_g⁰. All the complexes have six coordination and are polymeric.     

Laser treatment of aluminum surface: Analysis of thermal stress field in the irradiated region

Laser surface treatment of aluminum is considered and the temperature as well as the stress fields developed in the laser irradiated region are predicted using the finite element method (FEM). The predictions are obtained for two laser pulses with different pulse lengths. In the simulations, the variable thermal properties of the substrate material are used. The experiment is conducted to treat the aluminum specimen surface with the laser beam. The laser output pulse intensity consists of repetitive pulses, which are used in the model study to examine the metallurgical changes in the irradiated region. SEM and XRD are carried out in this regard. It is found that the von-Mises stress reaches the maximum in the surface vicinity, particularly at the onset of cooling cycle starts. The von-Mises stress attains values less than the critical values for the crack formation, which is particularly true after the end of the cooling cycle. The residual stress formed in the surface region is in the order of a few MPa.     

Effects of sulphurisation on vitamins (A,C and E) and malondialdehyde in apricots

In this study, the 1.0 m H₂SO₄ solution was used as a sulphur source to sulphurise apricots. Apricot samples were immersed into 1.0 m H₂SO₄ solution at room temperature for time of 30, 60 , 120, 180 and 240 min. Amounts of vitamins (A, C and E) and malondialdehyde (MDA) were determined as function of sulphurisation time and thus, sulphur content. It was determined that the optimum immersion time for sufficient sulphur content is 120 min. It is concluded that while amounts of vitamins decrease, the level of MDA increases with increasing immersion time and thus, sulphur contents.