The effects of constraint and residual stress on ductile and brittle fracture

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Evaluation of Two-Parameter Approaches to Describe Crack-Tip Fields in Engineering Structures

The application of two-parameter approaches to describe crack-tip stress fields has generally focused on Ramberg-Osgood (RO

Overcoming the Strong Metal−Support Interaction State: CO Oxidation on TiO

We combine low-temperature scanning tunneling microscopy and measurements of the catalytic activity to establish a structure-reactivity correlation for the CO oxidation on Pt nanoclusters on rutile TiO2(110)-(1 x 1). Annealing of the clusters to 1100 K leads to their encapsulation by a reduced titania layer. We present a method how this catalytically passive strong metal-support interaction state can be transformed into a very active one. We believe that our method is of general interest well beyond the presented system

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt-n/TiO2(110)-(1x1)

We determined the CO oxidation rates for size-selected Pt-n (n is an element of {3,7,10}) clusters deposited onto TiO2(110). In addition, we investigated the cluster morphologies and their mean sizes before and after the reaction. While the clusters are fairly stable upon annealing in ultrahigh vacuum up to 600 K, increasing the temperature while adsorbing either one of the two reactants leads to ripening already from 430 K on. This coarsening is even more pronounced when both reactants are dosed simultaneously, i.e., running the CO oxidation reaction. Since the ripening depends on the size initially deposited, there is nevertheless a size effect; the catalytic activity decreases monotonically with increasing initial cluster size

Effect of the TiO2 Reduction State on the Catalytic CO Oxidation on Deposited Size-Selected Pt Clusters

The catalytic activity of deposited Pt-7 clusters has been studied as a function of the reduction state of the TiO2(110)-(1 x 1) support for the CO oxidation reaction. While a slightly reduced support gives rise to a high catalytic activity of the adparticles, a strongly reduced one quenches the CO oxidation. This quenching is due to thermally activated diffusion of Ti3+ interstitials from the bulk to the surface where they deplete the oxygen adsorbed onto the clusters by the formation of TiOx (x similar or equal to 2) structures. This reaction is more rapid than the CO oxidation. The present results are of general relevance to heterogeneous catalysis on on TiO2-supported metal clusters and for reactions involving oxygen as intermediate

PVP2008-61513 NUMERICAL INVESTIGATION TO EXAMINE THE EFFECT OF INTRODUCING A CRACK IN A RESIDUAL STRESS FIELD

ABSTRACT This paper presents a detailed two dimensional finiteelement study to examine the effect of introducing a crack either progressively or instantaneously into a residual stress field. A progressive crack is defined as a crack which is introduced in fixed increments of crack extension until the desired crack length is achieved. An instantaneous crack is one in which a crack of the required length is introduced instantaneously into the finiteelement mesh. Inspection is made of the crack tip fields and the crack opening displacements. A modified definition of the Jintegral, which accounts for the initial plastic strain due to residual stress, is assessed, in order to examine its ability to characterise the intensity of the near crack tip fields. The implications of the results on fracture assessment of structural components are discussed

Pistacia Atlantica Desf., a Source of Healthy Vegetable Oil

Pistacia atlantica, which belongs to the Anacardiaceae family, is an important species for rural people in arid and semi-arid areas. The fruit, rich in oil, is used in traditional medicine for the treatment of various diseases. The oil extracted from this species growing in a northern area of Algeria and its fatty acid composition were previously studied. However, the largest areas where this species is present (traditional cultivation) is located in southern Algeria. Moreover, studies on oil fatty acid composition and essential oil were always conducted separately. This study was performed in order to assess the fatty acid and volatile organic compound composition of P. atlantica vegetable oil. The seeds were collected randomly from Djelfa (300 km South of Algiers, Algeria). Oil content and fatty acid composition were determined by Soxhlet extraction. The seeds contained high concentrations of oil (32–67%). The major fatty acids were oleic (39–49%), linoleic (23.6–31%), and palmitic (21.3–26.6%) acids. The ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids (SFA) indicated that the content of unsaturated fatty acids was approximately three times higher than that of SFA. This ratio is widely used in epidemiological studies and research on cardiovascular diseases, diabetes, and metabolic syndrome. The ratios of ω-acids, i.e., ω-9/ω-6 and ω-6/ω-3, were 1.3–2 and 18.5–38.3, respectively. Crushed seeds were analyzed by headspace solid-phase microextraction (SPME) coupled with gas chromatography–mass spectrometry. More than 40 compounds were identified, mainly monoterpenes (C10H16), such as α-terpinene and terpinolene, but also sesquiterpenes (C15H24) at lower levels. The value of this species as a source of healthy oil rich in ω-3 acid and its effects on cardiovascular disease risk are discusse

Long term and performance testing of NaMg double salts for H2/CO2 separation

This work investigates the synthesis and performance of double salts for H/CO separation. A series of NaMg double salts were prepared based on xMg(NO): yNaCO: zHO and characterised. The best sorbents reached CO uptake of 17.9\ua0wt% at 0.62\ua0MPa and 375\ua0°C. The NaMg double salts preferentially sorbed CO as determined by breakthrough tests. The NaMg double salts were packed in a sorbent bed and tested for H/CO separation at the back end of a water gas shift reactor. The space velocity had the largest impact on the performance of the sorbent bed, as increasing the space velocity from 2.16\ua0×\ua010 to 9.51\ua0×\ua010\ua0s sped up the breakthrough time by 84%. Increasing the feed gas pressure from 0.3 to 0.6\ua0MPa reduced the breakthrough time by ∼45%. The NaMg double salt sorbents were exposed for over 1000\ua0h of continuous temperature including 28 cycles of sorption and desorption, and proved to be stable during changes of operating conditions such as flow rates and pressures

Long term and performance testing of NaMg double salts for H2/CO2 separation

This work investigates the synthesis and performance of double salts for H/CO separation. A series of NaMg double salts were prepared based on xMg(NO): yNaCO: zHO and characterised. The best sorbents reached CO uptake of 17.9\ua0wt% at 0.62\ua0MPa and 375\ua0°C. The NaMg double salts preferentially sorbed CO as determined by breakthrough tests. The NaMg double salts were packed in a sorbent bed and tested for H/CO separation at the back end of a water gas shift reactor. The space velocity had the largest impact on the performance of the sorbent bed, as increasing the space velocity from 2.16\ua0×\ua010 to 9.51\ua0×\ua010\ua0s sped up the breakthrough time by 84%. Increasing the feed gas pressure from 0.3 to 0.6\ua0MPa reduced the breakthrough time by ∼45%. The NaMg double salt sorbents were exposed for over 1000\ua0h of continuous temperature including 28 cycles of sorption and desorption, and proved to be stable during changes of operating conditions such as flow rates and pressures