Paineastioiden, säiliöiden ja niiden varusteiden materiaalien murtuminen alhaisissa lämpötiloissa

Kansainvälisissä vaarallisten aineiden kuljetuksesta tiellä annetuissa määräyksissä (ADR-määräykset) ja vaarallisten aineiden kuljetuksesta rautatiellä annetuissa määräyksissä (RID-määräykset) määrätään, että paineastioiden ja säiliöiden sekä niiden varusteet on suunniteltava, valmistettava, testattava ja varustettava niin, että ne kestävät kaikki tavanomaisissa kuljetus- ja käyttöolosuhteissa esiintyvät rasitukset. Tässä selvityksessä: - päivitettiin paineastioiden ja säiliöiden riskejä ja vaaratekijöitä, joihin vaikuttaa alhainen lämpötila. - selvitettiin, sisältävätkö ADR- ja RID-viitestandardit ja niissä viitatut standardit -40°C kestävyysvaatimuksen sekä mahdollistavatko standardit säiliö- ja paineastiamateriaaleja, jotka eivät kestäisi alhaisia lämpötiloja, kuten -40°C. - selvitettiin mahdollisuutta kumota osittain tai kokonaan paineastioiden, kuten kaasuastioiden, ja/tai säiliöiden -40°C vaatimus ilman, että turvallisuus heikkenee aiheuttaen riskiä, ja tarvitaanko ehtoja, joiden avulla varmistutaan ja taataan kaasuastioiden ja/tai säiliöiden kuljetusturvallisuudesta myös alhaisessa lämpötilassa, kuten -40°C. - kartoitettiin mahdollisia onnettomuuksia liittyen rakennemateriaalien heikentymiseen alhaisten lämpötilojen vuoksi. Johtopäätös on, että -40°C kestävyysvaatimusehtoja tarvitaan edelleen tiettyjen paineastioiden ja säiliöiden tapauksessa

A Review of the Proposed KIsi Offset-Secant Method for Size-Insensitive Linear-Elastic Fracture Toughness Evaluation

Recently proposed modifications to ASTM E399 would provide a new size-insensitive approach to analyzing the force-displacement test record. The proposed size-insensitive linear-elastic fracture toughness, KIsi, targets a consistent 0.5mm crack extension for all specimen sizes by using an offset secant that is a function of the specimen ligament length. The KIsi evaluation also removes the Pmax/PQ criterion and increases the allowable specimen deformation. These latter two changes allow more plasticity at the crack tip, prompting the review undertaken in this work to ensure the validity of this new interpretation of the force-displacement curve. This paper provides a brief review of the proposed KIsi methodology and summarizes a finite element study into the effects of increased crack tip plasticity on the method given the allowance for additional specimen deformation. The study has two primary points of investigation: the effect of crack tip plasticity on compliance change in the force-displacement record and the continued validity of linear-elastic fracture mechanics to describe the crack front conditions. The analytical study illustrates that linear-elastic fracture mechanics assumptions remain valid at the increased deformation limit; however, the influence of plasticity on the compliance change in the test record is problematic. A proposed revision to the validity criteria for the KIsi test method is briefly discussed

Computer modelling and simulation approach to developing wear resistant materials

VTT researchers have been pioneers in international science with their computer modelling and simulation techniques for the development of coated surfaces with superior wear resistance and low friction properties. They have introduced a novel PPSP (Performance-Properties-Structure-Processing) multi-scale concept that is based on linking wear and friction performance by micro-FEM computer models to mechanical surface properties, surface microstructure and coating processing parameters. The modelling methods have been applied on 1–5 μm thick hard coatings, such as TiN, DLC and MoS2, on steel as well as on about 200 μm thick thermally sprayed WC-CoCr coatings developed through a Process Mapping concept. The novel approach offers completely new possibilities of systematic and focused material development of wear resistant and low friction coated surfaces with the aim to control and prolong the lifetime of machine components and industrial tools

Crystal structure of aqua-(2-{[2-({2-[bis-(carboxyl-ato-κ O -meth-yl)amino-κ N ]eth-yl}(carboxyl-ato-κ O -meth-yl)amino-κ N)eth-yl](carb-oxy-meth-yl)aza-niumyl}acetato)-gallium(III) trihydrate

In the title GaIII complex compound with pentetic acid, [Ga(C14H20N3O10)(H2O)]·3H2O, the GaIII centre is bound in a slightly distorted octa­hedral coordination sphere by two amine N atoms, three carboxyl­ate O atoms and one water O atom. The complex mol­ecule exists as a zwitterion. In the crystal, the complexes are linked to each other via O—H⋯O and C—H⋯O hydrogen bonds, forming layers parallel to (001). Three uncoordinating water mol­ecules link the complex layers via O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network

Boundary Effects on Dynamic Behavior of Josephson-Junction Arrays

The boundary effects on the current-voltage characteristics in two-dimensional arrays of resistively shunted Josephson junctions are examined. In particular, we consider both the conventional boundary conditions (CBC) and the fluctuating twist boundary conditions (FTBC), and make comparison of the obtained results. It is observed that the CBC, which have been widely adopted in existing simulations, may give a problem in scaling, arising from rather large boundary effects; the FTBC in general turn out to be effective in reducing the finite-size effects, yielding results with good scaling behavior. To resolve the discrepancy between the two boundary conditions, we propose that the proper scaling in the CBC should be performed with the boundary data discarded: This is shown to give results which indeed scale well and are the same as those from the FTBC.Comment: RevTex, Final version to appear in Phys. Rev.

STUDI TENTANG FISIBILITAS DAUR ULANG AKTINIDA MINOR DALAM BWR

Studi awal tentang fisibilitas daur ulang aktinida minor (MA) tanpa melibatkan plutonium dalam reaktor air mendidih (boiling water reactor, BWR) telah dilakukan. Hasil yang diperoleh menunjukkan bahwa dengan menaikkan konsentrasi fisil MA dalam bahan bakar mixed oxide (MOX) dan/atau memperkecil fraksi hampa maka faktor multiplikasi efektif pada awal siklus akan naik juga, tetapi kenaikan ini belum cukup untuk membuat reaktor kritis. Disisi lain memperkecil void fraction akan menaikkan ayunan reaktivitas yang pada akhirnya akan menurunkan faktor keselamatan dari reaktor.

Universality and diversity of folding mechanics for three-helix bundle proteins

In this study we evaluate, at full atomic detail, the folding processes of two small helical proteins, the B domain of protein A and the Villin headpiece. Folding kinetics are studied by performing a large number of ab initio Monte Carlo folding simulations using a single transferable all-atom potential. Using these trajectories, we examine the relaxation behavior, secondary structure formation, and transition-state ensembles (TSEs) of the two proteins and compare our results with experimental data and previous computational studies. To obtain a detailed structural information on the folding dynamics viewed as an ensemble process, we perform a clustering analysis procedure based on graph theory. Moreover, rigorous pfold analysis is used to obtain representative samples of the TSEs and a good quantitative agreement between experimental and simulated Fi-values is obtained for protein A. Fi-values for Villin are also obtained and left as predictions to be tested by future experiments. Our analysis shows that two-helix hairpin is a common partially stable structural motif that gets formed prior to entering the TSE in the studied proteins. These results together with our earlier study of Engrailed Homeodomain and recent experimental studies provide a comprehensive, atomic-level picture of folding mechanics of three-helix bundle proteins.Comment: PNAS, in press, revised versio

Current--Voltage Characteristics of Two--Dimensional Vortex Glass Models

We have performed Monte Carlo simulations to determine current--voltage characteristics of two different vortex glass models in two dimensions. The results confirm the conclusions of earlier studies that there is a transition at $T=0$. In addition we find that, as $T\to 0$, the linear resistance vanishes exponentially, and the current scale, $J_{nl}$, where non-linearities appear in the $I$--$V$ characteristics varies roughly as $T^3$, quite different from the predictions of conventional flux creep theory, $J_{nl} \sim T$. The results for the two models agree quite well with each other, and also agree fairly well with recent experiments on very thin films of YBCO.Comment: 18 pages with 10 figures available upon request from R. A. Hyman at [email protected]. The only change in the new version is the deletion of an unimportant comment.IUCM94-01

A Review of the Proposed K (sub Isi) Offset-Secant Method for Size-Independent Linear-Elastic Toughness Evaluation

The proposed size-independent linear-elastic fracture toughness, K (sub Isi), for potential inclusion in ASTM E399 targets a consistent 0.5 millimeters crack extension for all specimen sizes through an offset secant that is a function of the specimen ligament length. The K (sub Isi) method also includes an increase in allowable deformation, and the removal of the P (sub max)/P (sub Q) criterion. A finite element study of the K (sub Isi) test method confirms the viability of the increased deformation limit, but has also revealed a few areas of concern. Findings: 1. The deformation limit, b (sub o) greater than or equal to 1.1 times (K (sub I) divided by delta (sub ys) squared) maintains a K-dominant crack tip field with limited plastic contribution to the fracture energy; 2. The three dimensional effects on compliance and the shape of the force versus CMOD (Crack-Mouth Opening Displacement) trace are significant compared to a plane strain assumption; 3. The non-linearity in the force versus CMOD trace at deformations higher than the current limit of 2.5 times (K (sub I) divided by delta (sub ys) squared) is sufficient to introduce error or even "false calls" regarding crack extension when using a constant offset secant line. This issue is more significant for specimens with W (width) greater than or equal to 2 inches; 4. A non-linear plasticity correction factor in the offset secant may improve the viability of the method at deformations between 2.5 times (K (sub I) divided by delta (sub ys) squared) and 1.1 times (K (sub I) divided by delta (sub ys) squared)