bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple Fractures of Used In-Service Disc Springs in a Stationary Gas Turbine Engine
Authors: Neidel A. , Cagliyan E. 
Published: December 2013

Abstract
Multiple cracking was observed in disc springs made from an austenitic stainless steel and used in large stationary gas turbine engines. It was determined that they failed in service by bending overload. The metallurgical cause of the cracking was found to be grain boundary embrittlement by secondary chromium carbide precipitates. They formed upon heat treatment during manufacture of the components. It was recommended to either alter heat treatment parameters to avoid embrittlement, or to select a different spring steel that does not require heat treatment.
Embrittlement of Fuel Gas Piping Made of Wrought Nickel-Based Superalloy Due to Inadequate Heat Treatment
Authors: Neidel A. , Gädicke T. 
Published: December 2013

Abstract
Cold-drawn and cold-bent seamless Alloy 617 pipes were received by a gas turbine engine manufacturer for final assembly. They exhibited multiple cracking on the surface. The extrados of bending zones were most affected by this condition. It was determined that the metallurgical root cause of the problem was inadequate heat treatment by the supplier of the semi-finished product. The cracking upon cold bending the seamless pipes was caused by embrittlement of the pipes’ surface due to nitridation and a further drop in formability as a result of grin boundary embrittlement by secondary carbide precipitates.
The Preparation of Metallic Joinings to Optimise their Topography
Authors: Herbst S. , Jablonik L. , Gerstein G. , Nürnberger F. , Bach F.-W. 
Published: December 2013

Abstract
Modern light structures increasingly require different alloys or metals to be joined with one another in the form of composite materials [1]. As a result of their different melting temperatures or of the formation of brittle inter-metallic phases, many combinations of metals cannot be produced using thermal methods. One alternative, however, is the use of solid state welding such as explosive or magnetic impulse welding [2; 3]. The examination and analysis of the bonding interfaces is therefore of central importance in the evaluation of the quality of the bond produced. Scanning electron microscopy together with electron probe micro­analysis of the characteristic X-rays emitted using EDX and WDX techniques can reveal information regarding the distribution of the metals present within the bonding interface [4], the presence of inter-metallic phases [5] and of areas of inadequate bonding. For an accurate evaluation of the characteristic X-rays produced, however, the surface of the specimen must be guaranteed to be both flat and smooth in order to prevent the effects of shadowing and deflection of the primary beam which might otherwise cause erroneous results in the elements present and their distribution [6]. A specimen surface which is not perfectly flat also makes it difficult to focus the electron beam.
The simultaneous flat and smooth preparation of metallic composites which have very different strength and hardness properties is very difficult due to the different rates of removal of material during grinding and polishing [7; 8]. In view of this, the following methods of preparation used to produce flat and smooth specimen surfaces on two types of metallic joinings are presented.
Mapping the Local Structure of Nanowires
Authors: Persson J. M. , Wagner J. B. 
Published: December 2013

Abstract
The crystallographic and compositional structure of heterostructured semiconductor nanowires has been studied by means of transmission electron microscopy. The native geometry of the studied InP-GaAs nanowires (80–100 nm in diameter) is in general too thick for reliable high-resolution TEM imaging. Nano Beam Electron Diffraction (NBED) is shown to be a powerful technique to reveal strain near the interface of compositional change in heterostructured semiconductor nanowires. Furthermore, the relative orientation of the nanowires is studied by means of NBED revealing the nanowires to be very flexible. NBED proves to be a good alternative to convergent beam electron diffraction and electron backscatter diffraction in terms of crystal orientation determination and mapping.
Effect of Distributor Geometry on Crimp Contraction of PET Side-by-side Bicomponent Fibers
Authors: Oh T. H. 
Published: December 2013

Abstract
The effect of distributor geometry on crimp contraction in the melt spinning and drawing of polyethylene terephthalate (PET) side-by-side bicomponent fibers was studied. Three different distributors located on top of the spinneret were designed to change curvature ratio of a side-by-side cross-section of bicomponent fibers. Regular and modified PET were selected to make latent crimp yarns. Spinning and drawing conditions were changed to choose the effective variables heat set temperature and draw ratio. Crimp contraction increased with increasing draw ratio and decreasing heat set temperature. Die geometry had a significant effect on crimp contraction by changing the curvature ratio of the cross-section. Under the same spinning and drawing conditions, the crimp contraction with higher curvature ratio was larger.
Modeling and Practice of Ethanol-devolatilization of Silica-silane Rubber Compoundsin an Internal Mixer
Authors: Dierkes W. , Noordermeer J. W. M. 
Published: December 2013

Abstract
During mixing of a rubber compound containing silica and silane, the mixer is not only used for the dispersion of the filler and other ingredients, but also for a chemical reaction. These two functionalities of the mixer result in opposite processing requirements: A good dispersion is reached by high shearing forces, increasing the compound temperature. The silanization is not dependent on high shearing forces; it is positively influenced by high temperatures, but with an increasing risk of scorch. Another drawback is the equilibrium between the ethanol concentration in the vapor phase in the void space of the mixing chamber and in the rubber phase, which is limiting the reaction rate of the silanization. Devolatilization of the compound is a crucial factor for the efficiency of the silanization reaction.
In this article a model for devolatilization of a rubber compound in an internal mixer is developed, including a chemical reaction replenishing the volatile component during the devolatilization process. The model is based on the penetration theory, with the main contribution to the devolatilization being convective mass transfer. The main influencing factors, theoretically deducted and practically verified, are temperature, mixer volume, fill factor, rotor speed, reaction time and partial pressure of the volatile component in the void volume of the mixer.
Paste Extrusion of Polytetrafluoroethylene: Temperature, Blending and Processing Aid Effects
Authors: Ochoa I. , Hatzikiriakos S. G. , Mitsoulis E. 
Published: December 2013

Abstract
Blends of different PTFE fine powder resins have been prepared and extruded in an attempt of improving the PTFE paste extrusion process and/or the extrudates. The extrusion pressure and the mechanical properties of the extrudates were found to fall between those exhibited by the pure components. While this is an expectable behavior, it offers opportunities for controlling the degree of fibrillation needed in the final products by mixing highly fibrillated with low fibrillated PTFE resins. Boron nitride and organically modified montmorillonite clays (solid lubricants) are also tested as additives to the lubricants used in the PTFE paste extrusion in order to identify enhanced processing aids. It was found that the addition of boron nitride and clays increase the extrusion pressure but at the same time improve the mechanical properties of the final extrudates in most cases. This again offers possibilities for controlling the final mechanical properties by controlling the degree of fibrillation, i. e., by adding a small amount of solid lubricants to adjust pressure, fibrillation, and thus the final mechanical properties. Finally, it is shown that fibrillation depends on temperature. Moreover, the mechanical properties of extrudates increase as the temperature goes through its two transition temperatures of 19 °C and 30 °C that render PTFE particles more deformable and prone to fibrillation.
A Process Classification Number for the Solidification of Crystallizing Materials
Authors: Janeschitz-Kriegl H. , Eder G. , Ratajski E. 
Published: December 2013

Abstract
A critical number, which one may call a process classification number, has been introduced more than twenty years ago [1, 2, 3]. It has been called the Janeschitz-Kriegl number Jk [4]. It gives the ratio of two times governing the solidification process of a crystallizing material: one for the thermal equilibration and the other for the crystallization process itself. With one class of materials (mainly metals) the thermal equilibration time is usually the longest time, dependent of course on the sample thickness. With another class (glass forming minerals) always the crystallization time is the longest time. So, one obtains (as extreme cases) purely heat diffusion controlled and purely crystallization kinetics controlled processes. Only polymers (and probably also other crystallizing soft condensed matters) show an intermediate behavior, as can be characterized by the announced number.
So far, however, this number could not be made operational because of a lack of crystallization kinetics data. This shortcoming could now be cleared away. It turns out that between the values of Jk for HDPE and for i-PS a gap exists of more than six decades. In their behavior all other known industrial polymers lie between these limiting cases. In this way the transition from heat diffusion controlled to crystallization kinetics controlled processes is clearly marked. For the now relevant interaction between cooling and crystallization a new mathematics was required [2]. It enables also the description of the development of structures, which are of particular interest for the quality of the product.
Welding of Plastics: Fundamentals and New Developments
Authors: Grewell D. , Benatar A. 
Published: December 2013

Abstract
This paper provides a general introduction to welding fundamentals (section 2) followed by sections on a few selected welding processes that have had significant developments or improvements over the last few years. The processes that are discussed are friction welding (section 3), hot plate welding (section 4), ultrasonic welding (section 5), laser/IR welding (section 6), RF welding (section 7) and hot gas/extrusion welding (section 8).
Preparation and Characterization of HMW PA 6 via Anionic Polymerization of ∊-Caprolactam by Using a Mixture of Di- and Tri-functional Chain Initiators
Authors: Barmi M. M. S. , Assempour H. , Nazockdast H. 
Published: December 2013

Abstract
In the present work, an attempt was made to synthesis polyamide 6 through anionic polymerization of e-Caprolactam by using a mixture of Diphenylmethan 4, 4-di and tri-isocyanate as a chain initiator and sodium caprolactamate as a catalyst. Polymerization was carried out in a laboratory internal mixer (Brabender). The rotor speed, reaction temperature and reaction time were among the processing variables studied. The prepared samples were characterized by Thermogravimetry Analysis (TGA), Differential Scanning Calorimeter (DSC) and FT-IR spectroscopy. The flow behavior and melt viscoelastic properties of the samples were studied by using a Rheometric Mechanical Spectrometer (RMS). The polymerization reaction was found to be very fast and was completed within 6 minutes. This was detected by following the mixing torque which reached to a steady state after passing through a maximum. The pronounced decrease in the torque was found to be determine by the thermomechanical degradation as a predominating mechanism. The polyamide 6 prepared in this work showed greater melt elasticity, much higher molecular weight and slightly narrower molecular weight distribution in comparison with the commercial grades of polyamide 6. The crystallinity of the samples was also higher than that of the commercial polyamide 6. These results were explained in terms of contribution of fraction of the molecules possessing single long chain branch formed as a result of three functional nature of the chain initiator. Increasing the rotor speed was found to have strong influence on lowering molecular weight as well as narrowing the molecular weight distribution through increasing the extent of thermomechanical degradation. Increasing the initial set temperature in the studied range had no appreciable effect on polymerization rate and degree of conversion. It was demonstrated that the results of melt viscoelastic measurements performed on the samples collected at different polymerization times can provide valuable information to follow the polymerization reaction.
Method for the Optimisation of Screw Elements for Tightly Intermeshing, Co-rotating Twin Screw Extruders
Authors: Potente H. , Thümen A. 
Published: December 2013

Abstract
Demanding mixing tasks are usually solved through the use of tightly intermeshing, co-rotating twin screw extruders. Since both the barrel and the screw are of a modular design, the extruder can be optimised for a given task. In the framework of this investigation, the screw-element geometry for tightly intermeshing co-rotating twin screw extruders is optimised in order to achieve specific aims. The threaded elements have been optimised for different materials and operating conditions.
The investigation set out to achieve a screw-element geometry that would generate the maximum pressure gradient while, at the same time, ensuring that the temperature increase and the power consumption were kept to a minimum. The pressure profile, the temperature progression and the power consumption have been calculated on the basis of one-dimensional models of the type used in the SIGMA process simulation software. The geometrical data of the individual elements was varied with the aid of non-linear algorithms, and the quality of an individual geometry was assessed on the basis of quality functions. Subsequent to the theoretical optimisation, experimental analyses were performed for purposes of verifying the optimisation method used.
Structure Development in Melt Spinning and Cold Drawing of Poly(ethylene-co-octene) Copolymer
Authors: Shan H. , White J. L. 
Published: December 2013

Abstract
An experimental study of melt spinning and cold drawing of polyethylene and its Dow Chemical INSITEØ catalyst octene copolymers was carried out. The structure and morphology of both melt spun and cold drawing fibers were investigated using wide angle x-ray diffraction (WAXD), small angle x-ray scattering (SAXS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and birefringence. Up to 5.9 mol.% octene, the fibers exhibit only the Bunn orthorhombic crystal structure. Fibers with 9.7 mol.% and 13.3 mol.% octene, whose DSC crystallinity is 0.23 and below, have an additional reflection at about 0.45nm. The Hermans-Stein orientation factors for the melt spun fibers were determined and correlated with spinline stress. Cold drawn polyethylene fibers exhibited additional reflection at 0.45, 0.38 and 0.35nm which may be associated with the Tanaka-Seto et al. monoclinic unit cell. The copolymers contained a decreased monoclinic level which disappears at about 5.9 mol.%. However, a broad reflection at 0.45nm, reappears at 9.7 mol.% octene. This reflection is also present at the 13.3 mol.% level. It is surmised that a pseudohexagonal or mesomorphic structure is developing. The Hermans-Stein orientation factors were determined for the drawn fibers as a function of cold draw ratio. Drawing results in high crystalline orientation and fibrillation for polyethylene fibers. For copolymers, with higher octene content, the fibrillation decreases.
Experimental Investigation of the Cooling Flow in the Film Blowing Process
Authors: Peters F. , Ruppel C. 
Published: December 2013

Abstract
The film blowing process relies on external air cooling of the extruded polymer hose. The air is supplied by a ring nozzle surrounding the die. We investigate the flow as it emanates from a commercial nozzle by a laser light sheet method which reveals the instantaneous rather than the mean flow structure. Flow separation in the nozzle is diagnosed as well as a high degree of disturbances affecting the thermal boundary layer. To improve the flow a modified nozzle is investigated in the same way, which shows how separation is avoided and how the regular structure of a wall jet is attained. The limits of this approach are highlighted. The optical measurements are amended by pressure measurements inside and outside the nozzle. They show what the flow disturbances mean in terms of normal forces on the film.
Mechanical Properties of Rubber-toughened Post-industrial Glass-fiber-reinforced PA66
Authors: Alsewailem F. D. , Gupta R. K. 
Published: December 2013

Abstract
When compounding engineering thermoplastics with glass fibers for reinforcement purposes, a tremendous amount of polymer-containing waste is generated. However, the polymer of interest is usually commingled with the polymer used to purge the extruder. Reclaiming valuable polymer from this waste is hindered by the incompatibility with the purging material since this leads to a blend system that has poor mechanical properties and low economic value. For this reason, this potentially valuable post-industrial polymer-waste is normally land filled. The current research is directed at the characterization and reuse of a post-industrial PA66 filled with glass fibers; this was separated from LDPE purge material and its impact resistance was modified through rubber toughening. Styrene-Ethylene-Butylene-Styrene and Ethylene-Propylene elastomers grafted with maleic anhydride (SEBS-g-MA and EP-g-MA respectively) were used as the toughening agents in this study due to their compatibility with PA. Izod impact strength, tensile strength and modulus, flexural strength, and elongation at break were used to characterize mechanical properties of the rubber-toughened recycled glass-filled PA66. The morphology of the fracture surfaces of the composites was examined by Scanning Electron Microscopy (SEM). It was found that both impact strength and elongation at break increase with increasing rubber content while flexural strength and tensile strength suffer upon incorporating rubber; however, by adding moderate amounts of rubber to the recycled glass-fiber-reinforced PA66 a balance between stiffness and toughness of the material could be obtained. For example, the addition of 10 wt.% of SEBS-g-MA to the recycled PA66 with 23.62 wt.% glass fiber loading resulted in a 27% and 151% increase in tensile strength and impact strength respectively of the blends when compared with neat PA66. This suggests that compounding both glass fibers and elastomers with PA66 is a useful strategy to recycle PA66, especially for reuse in under-the-hood automotive applications.
Effect of Compatibilizer Distribution on Thermal and Rheological Properties of Gelatinized Starch/Biodegradable Polyesters Blends
Authors: Xie F. , Yu L. , Liu H. , Dean K. 
Published: December 2013

Abstract
Thermal and rheological properties of various blends of gelatinized starch and biodegradable polyester, polycaprolactone (PCL) or poly(butylene succinate adipate) (PBSA), were studied by DSC, TGA and rheometry. Methylenediphenyl diisocyanate (MDI) was used as a compatibilizer and was distributed in different phases through controlled processing. The addition of MDI showed a stronger effect on thermal and rheological properties when it was mainly distributed in the polyester phase prior to blending. Starch was shown to increase the shear viscosity of both types of polyesters. The two blends, starch/PCL and starch/PBSA, showed a similar pattern of a power law dependence of viscosity on shear rate. MDI was shown to enhance the effect of starch on the melting and decomposition temperatures, especially when distributed in the polyester phase.
Study of the Compatibilizer Effect on Blends Prepared from Waste Poly(ethylene-terephthalate) and High Density Polyethylene
Authors: Kratofil L. , Hrnjak-Murgić Z. , Jelencć J. , Andricć B. , Kovacć T. , Merzel V. 
Published: December 2013

Abstract
In this work mechanical recycling of waste poly(ethylene-terephthalate) (PET) in the presence of high density polyethylene (HDPE) was studied. The fraction of HDPE in PET/HDPE blends was 3, 5, 6 and 10 wt.%. Isocyanate HI compatibilizer was first synthesized and then added to the blends at a fraction of 5 wt.%. Ethylene-propylene-diene masterbatch (EPDM-M) was prepared by mixing and added in fraction of 15, 30 and 50 wt.%. All PET/HDPE blends studied were characterized by scanning electron microscopy SEM, differential scanning calorimetry DSC and melt flow rate (MFR). Blends prepared with isocyanate HI compatibilizer were also studied by FTIR spectroscopy. Appearance of new vibrations in the FTIR spectra confirms that during the blending reactions between isocyanate HI compatibilizer and blend components appear. Results show that used compatibilizers significantly improved compatibility of polymers in studied blends. From the results it is obvious that immiscibility of PET and HDPE can be overcome.
Melting Temperature Characteristics for Polyethylenes from Crystal Size Distribution
Authors: Feng L. , Kamal M. R. 
Published: December 2013

Abstract
Semi-crystalline polymers exhibit broad and multiple peaks in their melting traces. Thus, the melting temperature characteristics of polymers should consider both melting peak positions and melting temperature polydispersity. In this work, the effective melting temperature and temperature polydispersity are defined and calculated from DSC traces, using the crystal size number distribution and the melting temperature equation. Three methods are proposed for calculating melting temperature characteristics. These methods are based on: (i) average crystal size, (ii) the crystal stem number distribution function, and (iii) the monomer structural unit distribution function. They were employed to analyze the isothermal and non-isothermal experimental results for polyethylene polymers, especially linear low-density polyethylene copolymers. The first method, based on the value of average crystal size, gives the most reasonable results, taking into consideration agreement with experimental observations and structural data.