121,803 research outputs found
Knock induced erosion on Al pistons: Examination of damage morphology and its causes
No full textIn the present study, a systematic and deep examination of knocking damage on Al pistons is carried out, highlighting that only when exceeding a certain threshold knock compromises engine functionality. Controlled knocking combustions were induced during bench tests, by varying the spark advance for each cylinder. Several knock intensities and frequencies were investigated, with the aim to evaluate the possible knocking damages and to understand their influence on piston functionality. All the observed damages have been separately described and studied through failure analysis techniques, in particular optical and scanning electron microscopy and 3D digital microscopy, providing explanations of their occurrence. Among them, the erosion damage was predominantly observed and therefore fully evaluated. Preliminary attempts to relate engine parameters to knock damage were also made. This study is part of a wider project, whose aim is to increase knocking limits from the “safe calibration area” up to the limits which produce acceptable damages on pistons, in order to enhance engine efficiency
AISI 316L carbocementato a bassa temperatura (su scala industriale vs. via plasma su scala di laboratorio): studio del comportamento tribologico in condizioni di strisciamento a secco
No full textAISI 316L; Tribologia; Cementazione a bassa temperatur
Sliding Contacts for the Pharmaceutical Industry: Failure Analysis and Dry Sliding Tests for the replacement of Hard Cr on AISI 316L Steel
No full textSeveral alternatives were compared for the replacement of hard electroplated Cr coating to improve the tribological properties of the AISI 316L austenitic stainless steel for pharmaceutical packaging applications, including: low temperature carburising (LTC), thermal spray coatings (Al2O3-13TiO2, WC-17Co), substitution of the AISI 301 reference counterface with polymeric materials (PTFE, UHMWPE, PEEK). In dry sliding block on ring tests, the LTC AISI 316L cylinders lead to the lowest wear rates of the AISI301 sliders under low loads (up to 10 N). When considering the polymer vs. uncoated AISI 316L couple, PEEK and UHMWPE lead to lower friction and comparable wear rates with respect to the reference couple (AISI 301 vs. Hard Cr coated-AISI 316L) in the whole range of tested load
Microstructure and tribological properties of a co-continuous alumina/aluminum composite
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Linear Friction Welding of a 2024 Al Alloy: Microstructural, Tensile and Fatigue Properties
No full textThe possibility of using linear friction welding (LFW) to produce high quality joints on an aerospace grade aluminium alloy (AA2024) was evaluated. In this solid state joining process the bonding of two flat edged components is achieved through frictional heating, induced by their relative reciprocating motion, under an axial compressive force. The Al joints were subjected to microstructural and mechanical characterization, including hardness and tensile tests. S–N probability curves were also computed after preliminary axial fatigue tests. No post-weld heat treatment was performed. The microstructural analyses showed substantially defect-free joints, with a relevant plastic flow in the thermo-mechanically altered zone. Maximum hardness decrease in the joint zone was approximately only 5% in respect to the base material. The joint efficiency was about 90% with respect to the ultimate tensile strength, with a slight reduction in the elongation to failure. Good fatigue performances were also detected
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Laser Remelting for Enhancing Tribological Performances of a Ductile Iron
No full textAbstractWith the aim to improve the tribological behaviour of a high performance component made of a ferritic ductile cast iron (GJS400-12), a laser surface modification treatment by a solid-state laser beam is proposed. The induced microstructural modifications have been investigated in a previous experimental work by means of experimental tests in various process conditions. It was thus possible to verify that the achieved hardness profile is a function of the energy density delivered towards the surface and that the process shows a saturation phenomenon when melting occurs. Depending on the available process power and the interaction time for microstructural modification, the higher energy density determines the deeper transformation: initially related to the diffusion mechanisms in the solid matter and then due to the melting of the outer layers.In the present study, the tribological behaviour of the laser remelted ductile cast iron was compared to the base material in order to evaluate the performance enhancement. The highest achieved value of the surface hardness was selected for the tests.The tribological behaviour has been investigated by means of dry sliding tests carried out on a flat-on-cylinder tribometer (block-on-ring contact geometry). Flat sliders consisted of the untreated and laser surface treated ductile cast iron, while the rotating cylinder was a carburised UNI-EN 16MnCr5 steel. The tests allowed measuring and comparing the coefficient of friction and the volume of loss for the untreated and laser modified material. Laser surface treatment led to a significant increase in the wear resistance of the ferritic ductile cast iron, due to the enhanced surface hardness; the coefficient of friction however increased, due an increase of both the adhesive and abrasive component
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Replacement of Hard Cr on AISI 316L Steel in Sliding Contacts for the Pharmaceutical Industry: Failure Analysis and Dry Sliding Tests
No full textAustenitic stainless steels (SS) such as AISI 316L are widely used in the pharmaceutical industry in components such as pumps and distributors. However, the poor tribological behaviour of SS 316L requires the use of coatings or surface hardening techniques. Among overlay coating, also electroplated hard chromium coatings have been applied for improving the tribological behaviour of SS 316L. However, hard chromium plating is today recognized as a major source of environmental pollution and different solution for its replacement are available. In the present work, several alternatives are compared, concerning a SS 301 vs. SS 316L contact in packaging components for solid dose processing, where the surface modifications are applied to the SS316L rotating component, dry sliding against a stationary SS 301 part. In particular, the tribological performance of thermal spray coatings (Air Plasma Sprayed (APS) Al2O3-13TiO2 and High Velocity Oxy-Fuel (HVOF) WC-17Co) deposited onto SS 316L is compared with that of the same steel, thermochemically treated by Low Temperature Carburised (LTC). The main advantage of LTC is the ability to increase the hardness of the austenitic steel, owing to the formation of carbon-supersaturated austenite, without adversely affecting corrosion resistance.
In the first step of the work, failure analysis techniques, such as 3-D digital microscopy and SEM/EDS, were used for identifying the main wear mechanisms in components from the SS301/Cr-coated SS 316L contact of the packaging device. Subsequently, laboratory dry sliding tests by a flat-on-cylinder tribometer were carried out, so as to investigate and compare the tribological behaviour of alternative solutions for the replacement of hard Cr. Both Hard Cr and thermal sprayed coatings or LTC treated SS 316L were used as the rotating cylinder, whereas the stationary slider consisted of SS 301. Tests were carried out at room temperature, with applied loads ranging from 5 to 15 N, sliding speed of 0.3 m s-1 and a sliding distance of 1000 m. Among the alternatives for the replacement of hard Cr, LTC treated SS 316 L showed the better tribological behavior in terms of wear (even slightly lower than hard Cr), also leading to lower wear rates in the SS 301 counterpart
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
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