Volume 59, Issue 1

The fatigue behavior of cast iron is usually investigated on machined specimens. Components of cast iron, however, have a casting skin. Therefore, the investigation of the influence of the casting skin on the lifetime is of interest. To study this influence, isothermal fatigue tests were carried out on heat resisting spheroidal graphite cast iron EN GJS SiMo 4.05 in 4-point bending setup at 400 °C. Specimens with and without casting skin were investigated comparatively. The number of cycles to failure was significantly lower for specimens with casting skin. Metallographic investigations underline the reduction of lifetime caused by casting skin.

Polypropylene has a higher melt viscosity and low surface tension that lead to harder interfacial bonding in composite production. However, it has some advantages like good impact strength, low water absorption, low density, low coefficient of friction and high insulating properties. In this study, E-glass fiber and basalt fiber were used to reinforce polypropylene. Powder with compatibilizer was impregnated to E-glass and basalt fiber and prepregs were produced. Then, these were embedded into polypropylene matrix and samples were obtained. Tensile properties and fiber volume ratios were determined. Also, T-peel test was applied to check bonding at the fiber-matrix interface. Fractured parts were observed and fracture types were investigated. It was concluded that both had similar bonding strength, but E-glass reinforced polypropylene composite had higher tensile properties than basalt fiber reinforced composite.

The corrosion behavior of commercially available and welded Haynes ® 160 ® Ni-Co-Cr-Si alloy samples was investigated by exposure to coal-gasifying integrated coal gasification combined cycle pilot plant facilities under typical conditions as 2.005 MPa and 160 to 300 °C. The morphological and microstructural analyses of the exposed samples were conducted using scanning electron microscopy and energy dispersive X-ray spectroscopy analysis on the external surface of the recovered corrosion test samples to obtain information of the corrosion scale. These analyses based on the pre- and post-exposure corrosion test samples combined with thermodynamic Ellingham-Pourbaix stability diagrams provided preliminary insight into the mechanism of the observed corrosion behavior prevailing in the piping materials that connected the particulate removal unit and the water scrubber of the integrated coal gasification combined cycle pilot plant. Uniform material wastage was observed after 46 hours of operation, and a preliminary corrosion mechanism was suggested: the observed material waste and corrosion behavior of the Haynes ® 160 ® Ni-Co-Cr-Si alloy samples cut off from the coal syngas integrated coal gasification combined cycle plant were explained by the formation of discontinuous (complex) oxide phases and subsequent chlorine-induced active oxidation under the predominantly reducing environment encountered. This contribution supplements the already published studies of Haynes ® 556 ® Fe-Ni-Cr-Co alloys and Haynes ® 230 ® nickel-based superalloys and completes the comprehensive series of such coal-gasifying integrated coal gasification combined cycle pilot plant exposure tests using the facilities affiliated with the Institute for Advanced Engineering.

Armor grade Q&T steels very similar to AISI 4340 are used for construction of combat vehicles due to its high hardness, high strength to weight ratio and excellent toughness. The influence of friction welding parameters on microstructure and mechanical properties of such armor steel friction weld joints were evaluated. The microstructural properties of the various weld joint regions were examined by optical microscopy. It was also observed that the fully deformation zone (FDZ), the partially deformation zone (PDZ) and the heat affected zone (HAZ) have a vital effect on the tensile strength of the welded joints. Nearly 83 % of the tensile strength of the parent material (PM) can be achieved in friction welded joints. This is a 17 % higher strength than with the same parent material welded by shielded metal arc welding (SMAW) and flux cored arc welding (FCAW). The respective tensile and impact properties of the welded joints were correlated with the weld metal microstructures and fracture morphologies.

Kurzfassung Seitens der Industrie besteht großes Interesse Polyethylenterephthalat (PET) als Werkstoff für Verpackungen zum Transport von Gefahrgütern einzusetzen, da aufgrund der hohen Festigkeit und Steifigkeit von PET die Wanddicken und somit die Kosten der Verpackungen reduziert werden können. Die Prüfung der Spannungsrissbeständigkeit von Polyethylenformstoffen als Werkstoffe von Verpackungen erfolgt mit Labormethoden unter Verwendung einer Standardflüssigkeit als Prüfmedium für die Spannungsrisse auslösende Wirkung auf Polyethylen (PE), wodurch Zeit und Kosten der Prüfungen reduziert werden. Ziel dieser Arbeit war es, eine Laborprüfmethode zum Vergleich der Spannungsrissbeständigkeit von PE und PET auf ihre Anwendbarkeit zu prüfen, wie z. B. den Full Notch Creep Test (FNCT). Es wurde untersucht, ob die Prüfkörper aus PE und PET mit umlaufender Kerbe in dieser durch die chemische Industrie entwickelten und von der BAM konzipierten Apparatur auf der Basis des FNCT zu messbaren Ergebnissen unter Einfluss eines Ölsäureamidethoxylates als Netzmittel bei 50 °C führen. Die Testergebnisse bestätigten die Eignung des Prüfverfahrens für die acht eingesetzten Formstoffe aus PE. Dieses Prüfverfahren konnte nicht für PET angewandt werden, da die Prüfkörper aufgrund der hohen Festigkeit und Steifigkeit des PET beim Kerbvorgang zerbrachen. Die gleiche Aussage konnte für den Nachweis der Spannungsrissbeständigkeit von Verpackungen, der in der BAM Gefahrgutregel BAM-GGR 015 beschrieben wird, getroffen werden. Die einzige Möglichkeit zum Nachweis der Spannungsrissbeständigkeit von PET besteht in der Durchführung von Stapeldruckprüfungen.

This paper deals with the prediction of high-cycle fatigue behavior for four different materials (7075-T6 alloy, Ti-6Al-4 V alloy, JIS S10C steel and 0.4 wt.-% C steel) using Chapetti's approach to estimate the fatigue crack propagation curve. In the first part of the paper, a single integral equation for studying the entire propagation process is determined using the recent results of Santus and Taylor, which consider a double regime of propagation (short and long cracks) characterized by the model of El Haddad. The second part of the paper includes a comparison of the crack propagation behavior model proposed by Navarro and de los Rios with the one mentioned in the first half of this work. The results allow us to conclude that the approach presented in this paper is a good and valid estimation of high-cycle fatigue crack propagation using a single equation to describe the entire fatigue crack regime.

The wear resistance of as-cast AZ31 magnesium alloy samples fabricated by extrusion shear (ES) with various preheating temperatures (420, 400, 370 °C) of billets was tested by using pin-on-disc experiments under dry sliding wear conditions. Wear rates and friction coefficient were measured at various sliding frequencies and normal forces. To define the wear mechanism for each tested condition, the worn surfaces were analyzed using scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Based on the test results, the wear resistance of the ES-processed samples decreases with drop of the billet temperatures. The friction coefficients and wear rates of the samples with a preheating temperature of 370 °C are lower than those with deformation temperatures of 400 °C and 420 °C. With the increase of normal loads and reciprocating frequencies, the wear mechanism changes from mild wear (adhesion, abrasion and oxidation) to severe wear (delamination, plastic deformation and melting). Therefore, the extrusion methods have significant influences on the wear behaviors of the samples, and the wear resistance of AZ31 magnesium alloy can be improved by ES process.

Welding is the most important joining technique and offers the advantage of customizable plate thicknesses. On the other hand, welding causes residual stresses and deformations influencing the load carrying capacity. Their consideration in the design requires simple and fast models. Though welding simulation has contributed to accurately access to these values nowadays, their application to large components remains still in a less practicable range. Nevertheless, many studies emphasized the need to make corrections in recently available simplified models. Especially the influence of residual stresses seems somewhat overestimated in many cases if comparing conventional structural steel S355 and high-strength steel S690. In times of computer-aided design, an improved procedure to implement weld-inducted imperfections appears overdue. This will be presented in two parts. The first part illustrates the potential influence of post-welding imperfections exemplified for weak axis buckling in comparison with the general method in accordance with Eurocode 3. Residual stresses and initial crookedness were varied systematically in order to produce a scatter band of capacities. An approach to characterize the borders of these imperfections was untertaken before that. The excessive scattering of reduction factors for the load bearing capacity demonstrates the importance of these variables. Results were finally evaluated against advanced simulation models which will be further detailed in part two of this contribution.

Burnishing is used as the final operation in machining, and brings along advantages such as increase of hardness, resistance against material fatigue and abrasion resistance on the workpiece on which it is applied. Improving the surface roughness of workpiece, improvements on the surface hardness, increase of the abrasion resistance of the material, decreasing depths on the material surface which may cause cracks, etc., directly depend on parameters such as progression, number of passes, press amount and ball diameter used in burnishing operation. For this study, an apparatus was designed which has different heads for a burnishing operation of rotary pieces. The surface of an Al 6061-T6 alloy was subjected to a respective burnishing operation and the effect of the parameters (i. e., pressure force, progression, number of passes and ball diameter) used in the burnishing operation on the surface roughness and surface hardness was determined. In addition, an artificial neural network (ANN) and an adaptive neuro-fuzzy interference system (ANFIS) model are developed for these parameters. Both models provide accurate results that are comparable to the experimental results. However, the ANFIS based model appears more accurate, compared to the ANN based model with respect to the same conditions for the surface roughness and surface hardness.

Friction stir welding (FSW) is a solid phase welding method, developed for aluminum alloys by The Welding Institute (TWI), which is applied in non-traditional welding techniques. The industrial applications of this method have been intensified in recent years. In this method, parts in various geometries can be joined in solid state. In this study, Al-Mg based 5083 aluminum alloys, which are widely used in industry, were joined by friction stir welding method and the mechanical properties of the joints were determined. The mechanical properties of joined parts were experimentally investigated using tensile, hardness and fatigue tests for 550, 700, 800 and 1400 rpm rotation speeds with 40 mm × min −1 and 80 mm × min −1 progressing speed, respectively.

In this study, the effects of machining parameters on surface roughness (Ra) and tool life (Tl) were investigated in the milling of Hastelloy C22 alloy with TiAlN-coated carbide inserts. A number of milling experiments were conducted using the L 27 (3 3 ) Taguchi orthogonal array on a CNC milling machine under different cutting conditions (dry, compressed air and wet). The cutting condition, cutting speed and feed rate were determined as the essential machining parameters. Analysis of variance (ANOVA) and signal-to-noise (S/N) ratio were employed to evaluate the effects of the machining parameters on Ra and Tl, and prediction models were created using quadratic regression analyses. The results revealed that the feed rate and cutting condition were the most influential factors on surface roughness and flank wear. The maximum tool life was achieved under wet cutting condition using a cutting speed of 30 × min −1 and a feed rate of 0.08 mm × rev −1 , while the minimum surface roughness value was obtained under wet cutting condition using a cutting speed of 50 m × min −1 and the same feed rate. Using the optimum cutting parameters for Tl (30 m × min −1 , 0.08 mm × rev −1 ), increases of 234 % and 67 % in tool life were observed under wet and compressed air cutting conditions, respectively, compared to the dry cutting condition.

This study focuses on optimizing cutting parameters based on the Taguchi method to minimize surface roughness in turning of studs manufactured from AISI 5140 steel. The Taguchi method, which is a powerful tool for designing optimized quality, is used to find the optimum surface roughness in turning operations. Rotational speed, feed rate and depth of cut were considered as control factors for the surface roughness, and L9 orthogonal array was determined for experiment trials. An orthogonal array, a signal-to-noise ratio, and an analysis of variance were employed to investigate the surface roughness characteristics of AISI 5140 steel. Minimum surface roughness was obtained at 2000 rpm rotational speed, 0.2 mm × rev −1 feed rate and 0.5 mm depth of cut. Optimal surface roughness was calculated as 1.70 μm by using optimal level of design parameters. Confirmation test showed that Taguchi method can be used precisely for optimizing the cutting parameters in turning of AISI 5140 steel. Through this study, it is possible to not only obtained the optimum surface roughness for turning operations, but also the main cutting parameters affecting the performance of turning operations. The developed model can be used in the metal machining industries in order to determine the optimum cutting parameters for minimum surface roughness.

The superhydrophilic phenomenon of titanium dioxide (TiO 2 ) has some potential applications. However, the superhydrophilicity can be obtained only using ultraviolet (UV) light irradiation and cannot be regained conveniently due to the energy band gap of TiO 2 . In this study, superhydrophilic TiO 2 film on a glass substrate was prepared by a simple sol-gel method and the sol was doped with nitrogen, fluorine and polyethylene glycol (PEG). The preparation method was discussed and the film was characterized. Results show that the anatase TiO 2 was obtained at about 500 °C, and the redshift of nitrogen-doped film was the largest, whereas the transmittance of fluorine-doped film was increased. The sizes of TiO 2 particles in the films are uniform and the films are homogeneous except PEG-doped TiO 2 . Superhydrophilicity of films doped with PEG can maintain 12 days and can be regained by the irradiation of sunlight.

In this study, PP-based composites reinforced were produced by using three injection pressures I P (50, 55, 60 MPa), three injection temperatures I T (210, 220, 230 °C), three holding pressures H P (35, 40, 45 MPa), three reinforcement rates R r (5, 10, 15 wt.-%) and three reinforcement sizes R s (44–100, 101–210, 210–300 μm) and their mechanical properties were investigated. Moreover, 0.2 % maleic anhydride was also added in order to prevent oxidation during addition of aluminum powders. The best results in terms of tensile strength were obtained from the specimen with the code C2, with the parameter values R s = 100 – 210 μm, R r = 15 wt.-%, I T = 230 °C, I P = 50 MPa and H P = 40 MPa. The best results in the tensile tests were received from the specimen with code A2, having the parameter values R s = 100–210 μm, R r = 5 wt.-%, I T = 210 °C, I P = 50 MPa and H P = 35 MPa. On the other hand, the best results in the izod tests were obtained for the specimen with the code C1 with the parameter values R s = 44–100 μm, R r = 15 wt.-%, I T = 210 °C, I P = 60 MPa and H P = 45 MPa.

Amitraz (AZ) that is used as acaricide was extracted by using clay adsorbent. The experimental data were modeled via Langmuir and Freundlich isotherms in which adsorption data fit well. The monolayer adsorption capacity was found as 28.53 mg × g −1 at a temperature of 30 °C. The effects of the phases contact time, the initial solution pH value and the initial pesticide concentration were investigated regarding the points of adsorption equilibrium and yield. The adsorption kinetics were investigated by applying pseudo-first-order, pseudo-second-order and intra-particle diffusion laws. Adsorption of AZ was found to be best fitted by the pseudo-second-order model. The intra-particle diffusion also plays an important role in adsorption phenomenon. This adsorption is a physical and spontaneous phenomenon. The pesticide removal by adsorption technique was successfully applied in industrial plants.