bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pitting Corrosion Induced Fatigue Fracture on a Gas Turbine Compressor Blade
Authors: Neidel Andreas , Riesenbeck Susanne 
Published: December 2013

Abstract
According to VDI Guideline 3822-3 “this type of corrosion is … caused by the formation of anodic regions of slight local expansion on the electrolyte-wetted surface. The presence of protective layers (passive layers) is a prerequisite for the occurrence of pitting corrosion.”
Both requirements are met on gas turbine compressor blades if water condensates on the turbine blades when the machine is at standstill and/or if the compressor temperature remains low enough in a running machine to allow aqueous media to persist, i.e. for the condensation not yet to have evaporated. This is the case with the front row of blades, generally up to stage 6.
Passive layers are present on the gas turbine compressor blades, since these parts are generally manufactured from martensitic 12–16% chrome steel, as also the case for steam turbine blades and discussed in detail in other case studies in the book. The failed compressor stator blade in this case study is made of X15Cr13, material no. 1.4024.
Pitting corrosion on the front row compressor blades was not uncommon before the introduction of high temperature corrosion protection coatings containing aluminium pigments on these blades. After the introduction of protective coatings, this corrosion mechanism was absent on the coated blades. The coating systems contain aluminium spherules which, given the correct coating method, are in contact with each other to form a continuous electrically conducting layer between the surface of the blade and the protective coating, creating a sacrificial anode resulting in the less noble aluminium – as compared to steel – preferentially corroding to protect the blade material.
The damaged part discussed in this case study originates from an older model gas turbine commissioned in 1955 already, having accumulated almost 163000 hours of operation when the damage was diagnosed. Depending on the type of operation, this represents a period of operation of 15 to 25 years. Such compressor blades were not coated back then.
The Preparation of Magnesium Specimens for EBSD Using Ion Polishing
Authors: Ullrich Ch. , Schwarz F. , Franke A. , Marr T. , Rafaja D. , Krüger L. , Freudenberger J. 
Published: December 2013

Abstract
EDSD measurements were made for various thermally treated or deformed states of the magnesium alloy AZ31, which were produced from twin-roll cast strips. The article shows that a preparation route via the ion polishing method produces the best condition of the sample surface for the examinations and, in particular, yields very good results even in case of samples which are deformed or those the chemical composition of which is inhomogeneous.
Investigation of Vapor Phase Deposited Columnar Plasma Spray Coatings
Authors: Hospach A. , Kappertz M. , Mauer G. , Vaßen R. 
Published: December 2013

Abstract
The relatively new PS-PVD method (Plasma Spray – Physical Vapor Deposition) allows for an almost complete evaporation of the spray powder by means of a high energy input and a low ambient pressure. On the substrate to be coated, the spraying material condenses to columnar, feather-like structured layers as are known from the EB-PVD process (Electron Beam – Physical Vapor Deposition). These layer structures are of interest in applications in which high strain tolerances are required, such as for thermal barrier coatings in gas turbines where cyclic heating and cooling of the coatings takes place. Courtesy of the high growth rate, PS-PVD can represent a more cost-effective alternative to EB-PVD.
The main difference compared to EB-PVD coatings is the higher porosity of the PS-PVD coatings. However, this higher porosity leads to difficulties during the preparation when coatings are characterized.
This publication describes how YSZ-coatings (Yttrium-stabilized zirconia) produced by means of PS-PVD are characterized with regard to specific surface area, density, pore distribution, hardness, and sintering activity and compared with EB-PVD coatings.
Orientation and Phase Analysis of Nanoscale Grains Using Transmission Electron Microscopy
Authors: Seyring M. , Song X. , Rettenmayr M. 
Published: December 2013

Abstract
The nanostructuring of materials is a process which enables their properties to be drastically changed as compared to their coarse crystalline condition. For example, peculiar features were achieved, e.g. extremely high yield and ultimate strengths. The structure of such nanoscale materials has not been characterized yet in detail as compared to materials of a coarser crystalline structure because an appropriate analytical technique did not exist. Nano beam diffraction (NBD) by transmission electron microscopy (TEM) makes possible a local resolution up to 1 nm and, thus, a diffraction analysis of individual nanograins. A recently developed method based on NBD allows determining crystallographic orientation relationships and analyzing the phases of individual nanograins. This article below sets forth the analytical possibilities of this method by way of a complete evidence of twin and small-angle grain boundaries in nanocrystalline copper and a phase identification of precipitates in an AlMg5Si2 alloy.
TEM Sample Preparation of a Hard Metal by Semiautomatic Wedge Polishing
Authors: Neumayer S. M. , Fisslthaler E. , Feistritzer S. , Grogger W. 
Published: December 2013

Abstract
Sintered hard metals like tungsten carbide compounds are a challenge for TEM sample preparation due to the diverging properties of the individual components. Especially when both very thin as well as large areas are required, for example for nanoanalysis investigations, conventional preparation techniques like ion milling and FIB preparation are often incapable of delivering samples of necessary quality. In this study, the preparation of a hard metal consisting of a tungsten carbide/cobalt compound via a technique called “Wedge Polishing” is described, along with the results of concomitant TEM investigations. The impact of the preparation procedure on the crystallographic structure of the material is discussed, and a post-treatment process to dispose of these artefacts is presented.
Stress Corrosion Cracking (SCC) in Copper Piping for Domestic/HVAC Heating and Cooling Systems
Authors: Hineman M. A. , Schmidt F. E. 
Published: December 2013

Abstract
Copper piping systems for HVAC (Heating Ventilation Air Conditioning) are used to transport heating and cooling water in high rise buildings. Commercial and residential plumbing has a design life that must be specified with respect to the water quality parameters associated with the geographic location. Stress corrosion cracking has been identified as one of the failure mechanism normally occurring in the infancy of the life of the systems that is highly associated with contamination. A metallurgical analysis of the characteristics of typical cold worked tubing, used in copper piping, with insulation, contamination and crack morphology are presented.
Preparation and Microstructural Characterisation of Metal Injection Moulded Powder Metallurgical Components (MIM) in the Green and Sintered Conditions
Authors: Maier J. , Knoblauch V. , Bernthaler T. 
Published: December 2013

Summary
The aim of this work was to develop a reproducible method of preparation for green and brown bodies which, after injection moulding and sintering, would permit an entire MIM component to be microscopically examined for internal inhomogeneities such as porosity and segregation. The particular challenge was to prepare the fragile MIM microstructure prior to the sintering process free of artefacts.
Three different methods of preparation (variations in the polishing substrates and suspensions used) were compared. To evaluate the quality of the resulting preparation, the microscopically determined volume fraction of metal particles was chosen. This was determined after set preparation times using quantitative microstructural analysis (QMA/QGA) and evaluated during the various stages and times of the preparation process. The feedstock composition which had a defined volume fraction of 68 % was used as the reference value. The preparation of the brown sintered body proved to be the most successful. The volume fraction determined microscopically measured 67 %. The duroplastic infiltration mounting resin penetrates into the open pore structure effectively stabilising and fixing the powder particles. In contrast the preparation of the green body proved to be much more difficult as the breaking out of the metal powder particles from the comparatively soft thermo-plastic binder was not able to be prevented completely. The volume fraction measured microscopically was 62 % which is about 6 % less than the actual value.
The chemical removal of the binder from the surface of the green body significantly improved the overall result of the preparation as it was then possible to effectively fix the powder particles by subsequent infiltration with the duroplastic mounting resin, as in the case of the brown body. In addition to the qualitative appraisal of the microstructural specimens, quantitative microstructural analysis proved to be a valuable instrument for systematically and objectively evaluating the results of the preparation and for developing the preparation processes. Using the methods of preparation developed it is now possible to carry out qualitative examinations on almost artefact free microstructural specimens prior to the lengthy and costly thermal processing.
Identification of Precipitates in an IN792 Gas Turbine Blade after Service Exposure
Authors: Dahl K. V. , Hald J. 
Published: December 2013

Abstract
Plate-like precipitates were found in an exposed IN792 gas turbine blade after service exposure for 40,000–60,000 service hours at a temperature of 680–760 °C. The blade was heavily oxidised and therefore removed. During subsequent metallurgical investigations extensive precipitation was found in the metallic region beneath the outer oxide layer.
Further investigations were undertaken in order to understand the failure mechanism, especially the precipitate type and formation mechanism. Cross sections prepared from the turbine blade were studied using LOM and SEM. Composition profiles across the interface between bulk material and oxide layer revealed significant depletion of chromium below the oxide.
Thermodynamic equilibrium calculations were used as a practical tool supporting the investigations.
Chemical mapping using energy filtered TEM and selected area diffraction were used to prove that the precipitates were carbides and not an intermetallic phase like σ. The extensive oxidation resulted in dissolution of carbides near the outer surface, while reactive elements, e. g. chromium, released from this process would then diffuse outwards towards the oxide, carbon diffused inwards resulting in extensive re-precipitation of carbides.
Numerical Simulation of Extrusion Coating
Authors: Devisme S. , Haudin J.-M. , Agassant J.-F. , Rauline D. , Chopinez F. 
Published: December 2013

Abstract
In packaging industry, many structures are produced by extrusion coating. In this process, a polymer film is extruded through a slit die, then stretched in air, coated on a substrate (paper, aluminium or steel foil) between a chill roll and a flexible pressure roll, and finally cooled on successive chill rolls. Due to their non-polar character, polypropylenes are not suitable for extrusion coating on metallic surfaces. Adhesive properties can be improved by grafting on the polymer chain a polar group like maleic anhydride which may react with the aluminium surface.
Our purpose was to develop a general model in order to predict the temperature field in the thickness of the multilayered structure along the stretching, laminating and cooling steps, and especially near the polymer/metal interface. This model includes crystallization kinetics and accounts carefully for the heat transfer coefficient with the successive rolls and surrounding air. Its predictions have been successfully compared to experimental temperature measurements along the coating line for various processing conditions (velocity, roll temperature, etc). Moreover, thermal history has a real impact on structure and morphology in the film. All these aspects are revealed by microscopic observations of thin microtomed sections of the film and X-ray diffraction experiments. Finally, adhesion properties of the laminate have been tested for the same process conditions. A good correlation has been established between adhesion properties and the thermal history experienced by the grafted polypropylene near the interface with aluminium before crystallization.
New Multicomponent Compatibilization System for Polyolefin/Polystyrene Blends
Authors: Starý Z. , Kruliš Z. , Hromádková J. , Šlouf M. , Kotek J. , Fortelný I. 
Published: December 2013

Abstract
An efficient compatibilization system based on a combination of styrene-butadiene block copolymer (SBS) with ethene-propene random copolymer (EPM) has been developed for polyolefin/polystyrene blends. Model blends of polypropylene and polystyrene have been taken for compatibilization studies. Concentration of combined compatibilizer in all studied blends was 5 or 10 wt. %. The ratio of EPM/SBS in the compatibilizers was varied from 4/1 to 1/4. Tensile impact strength was used as the main criterion of compatibilization efficiency. Besides mechanical properties, basic morphological investigation of the prepared blends was carried out. The compatibilization efficiency of the EPM/SBS system in PS/PP blends depends on the type of blend matrix. Generally, the use of EPM/SBS leads to better or comparable mechanical properties of final polystyrene/polypropylene blends compared with those using common SBS compatibilizers.
Asymmetric Surface Roughness Formationon Moving Non-isothermal Liquid Coatings
Authors: Yamamura M. , Uchinomiya T. , Mawatari Y. , Kage H. 
Published: December 2013

Abstract
We present a lubrication model of thermo-capillary flows in moving volatile liquid film coatings. The forced air impingement from a slit nozzle onto the moving coating imposes an axi-symmetric surface temperature distribution, and thus the local surface-tension gradients on the liquid surface. Despite the symmetric temperature profile, local thickness variations became asymmetric and exhibited a particular ridge in downstream and a depression in upstream. The competing feature between the surface-tension-driven and the pressure-driven flows gives a characteristic growth and decay in the surface roughness as the temperature profile travels in the opposite direction to the moving coating. The model prediction showed that the surface roughness was first enhanced and then suppressed with increasing the impinging air velocity, suggesting some directions for achieving more uniform coatings at higher speeds.
Investigation of the Heat Affected Zone of Hot-gas Welded PP Joints
Authors: Marczis B. , Czigány T. 
Published: December 2013

Abstract
A large series of experiments was performed using an automated hot-gas welding apparatus to investigate the effect of welding parameters (welding temperature, welding gas flow rate, welding speed, welding force) on the structure of the heat affected zone (HAZ) in polypropylene sheets. Based on optical micrographic studies the HAZ can be divided into three well distinguishable parts: the cool, plastic and flow zone of the raw material. A strong correlation was found among the width of the HAZ and the macroscopic size of the welded seam and its strength. It was demonstrated that (under the given boundary conditions) the strength of the welded joint can be estimated from the external geometrical size of the welded seam well.
Rheology and Processing of Molten Poly(methyl methacrylate) Resins
Authors: Stamboulides C. , Hatzikiriakos S. G. 
Published: December 2013

Abstract
The rheological and processing behavior in capillary extrusion of several poly(methyl methacrylate) (PMMA) resins was studied. The rheological characterization included: (i) frequency sweep experiments at various temperatures and application of the time-temperature superposition to obtain the master curves from which the activation energy of flow was found to be independent of molecular weight, (ii) extensional measurements using the Sentmanat Extensional Rheometer (SER) where it was found that poly(methyl methacrylate) resins exhibit strain hardening effects only at high strain rates. The capillary extrusion experiments were performed for three poly(methyl methacrylate) resins using additives in order to identify suitable processing aids for PMMA resins. First it was found that poly(methyl methacrylate) polymers exhibit spiral/helical type of distortions at a critical shear stress value of about 0.35 ± 0.03 MPa, independent of temperature and molecular weight. “Traditional” processing aids used mainly in the extrusion of polyolefins and some other commercial polymers were found ineffective in eliminating instabilities in the case of poly(methyl methacrylate) processing. On the other hand, mixing of poly(methyl methacrylate) with a proprietary blend of synthetic resins and fatty glycerides with modified organic fatty acids, MoldWiz INT-35UDH, was able to reduce the extrusion pressure and postpone the onset of gross melt fracture to higher shear rates. Finally and most importantly, the addition of different polyethylenes (LLDPE, LDPE and HDPE) resulted into a significant pressure reduction along with significant postponement of gross melt fracture to higher shear rates.
Moisture Sorption and Transport in Polylactide
Authors: Cairncross R. A. , Ramaswamy S. , O'Connor R. 
Published: December 2013

AbstractManagement of moisture penetration and hydrolytic degradation of polylactide (PLA) is extremely important during manufacturing, shipping, storage, and end-use of PLA products. Crystallinity in PLA was measured with Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). Moisture sorption isotherms in PLA films were measured with Quartz Crystal Microbalance (QCM) and Dynamic Vapor Sorption (DVS) experiments with samples of varying crystallinity. A surprising result is that crystalline and amorphous PLA films exhibit nearly identical sorption isotherms, within the accuracy of the experiments. The effect of hydrophobicity of PLA end groups on degradation was evaluated by synthesizing PLA with hydrophobic and hydrophilic end groups.
A Novel High Flow Rate Pin for Water-assisted Injection Molding of Plastic Parts with a More Uniform Residual Wall Thickness Distribution
Authors: Liu S.-J. , Wu Y.-C. 
Published: December 2013

Abstract
Three types of water pins are currently used in the water-assisted injection molding technologies to mold plastic parts, including orifice, ring and piercing type pins. Nevertheless, the former two types of pins have the disadvantages of a low flow rate and high pressure drop, while the drawbacks for the latter type are that timing the piercing pin into the cavity is a challenge and the cost of a mold is high. This report describes the development a novel high flow rate water pin for water-assisted injection molding of plastic parts. The pin, which consists of a sintered porous surface outlet, has been tested on parts with two different geometries: a plate with a channel across the center and a float-shaped tube part. The experimental results suggests that the proposed water injection pin can mold parts of a large size with a more uniform residual wall thickness distribution.
Rheological and Theoretical Estimation of the Spinnability of Polyolefines
Authors: Vogel R. , Brünig H. , Beyreuther R. , Tändler B. , Voigt D. 
Published: December 2013

Abstract
Melt spinning is a polymer processing technique that makes great demands on the extensibility of the polymer melt in the distance between die exit and solidification point [1]. The polymer material is exposed to a rapidly growing deformation rate over a large range of deformation within a short time of about 100 milliseconds. Simultaneously an extreme cooling occurs with cooling rates of about 1000 K/s. For this reason only a few polymer materials are usable for this kind of polymer processing with sufficient take-up speeds. Most polymers show a fiber break in the molten state either by brittle cohesive rupture or ductile failure when approaching critical conditions of deformation. The rheological behaviour of a polymer melt at the critical conditions of deformation in the fiber forming process can not be predicted by means of usual rheological material functions. This paper reports the attempt to find out material functions, which describe the critical deformation states of the melt spinning process. The established material functions are compared with the results of spinning experiments to estimate their practicality.
Bulk and Dispersed Phase Polymerization of Urethane in Twin Screw Extruders
Authors: Cassagnau P. , Nietsch T. , Michel A. 
Published: December 2013

Abstract
The bulk and dispersed phase polymerizations of urethane were investigated in a co-rotating twin screw extruder. The residence time has predominant influence on the bulk polymerization in twin screw extruders. Furthermore, the polyurethane polydispersity decreases going down the screws, as the result of the extent of the reaction and mixing in the extruder. As expected, the polyurethane polydispersity at the die exit of the extruder is close to the theoretical value (Ip = 2). In the case of urethane polymerization in molten polyethylene matrix, the residence time distributions showed that the two monomers (isocyanate and alcohols) have different behaviors in the extruder in presence of PE due to the solubility of isocyanate and non-solubility of alcohols in PE. Furthermore, this solubility phenomenon PE induces an imbalance stoichiometry which limits the degree of polymerization (molecular weight) and a broadening of the molecular weight distribution during the blending process in extruder. Slip phenomenon was also observed at the die because of the presence of polyurethane, with low molecular weights, at the sample surfaces. An in-situ pre-polymerizing step of isocyanate/alcohols tends to eliminate this phenomenon. Then, the aim of the present work was to study the formation of a polyethylene/polyurethane blend polymer via in situ polymerization of diols and diisocyanate monomers dispersed in a twin screw extruder.
Injection Velocity Control Using A Self-tuning Adaptive Controller
Authors: Yang Y. , Gao F. 
Published: December 2013

Abstract
The injection velocity dynamics are found to be both time-varying and non-linear and therefore difficult to control using a conventional fixed parameter controller. In this work, an adaptive injection velocity control system with some special features such as anti-estimation windup, adaptive feed-forward, profile shifting and cycle-to-cycle adaptation is designed, implemented, and experimentally tested. The developed system is demonstrated to have excellent control performance with very good robustness for a wide range of operating conditions.