A new long-term indentation relaxation method to measure creep properties at the micro-scale with application to fused silica and PMMA

Increased efficiency and emission reduction in modern power plants lead to the use of new advanced materials with enhanced creep strength, with the objective to increase the steam parameters of power plants. With over ten years on market and wide experience related to its use, ASTM Grade 92 is becoming one of the most required materials when high service temperatures are reached (max. 610°C). Its composition, with 9%Cr and 1.5%W, gives rise to martensitic microstructures which offer very high creep strength and long term stability. The improved weldability and creep-strength between 500 and 580°C of the low alloy ASTM Grade 23, as well as a cost advantage over higher Cr materials in this temperature range, make it one of the possible candidates to meet the stringent requirements of modern power plants. Air Liquide Welding (ALW) has optimized and distributes a complete product family for the welding of Grades 23 and 92. TenarisDalmine (TD) focused on the development of Grade 23 tubes and pipes and is working on the development of Grade 92. A deep characterization work of the microstructural evolution and long term creep performances of these high temperature resistant materials was thus undertaken by ALW and TD, in collaboration with the Centro Sviluppo Materiali (CSM). The joint characterization program consisted in the assessment of welded joints creep properties. Welded joints were produced using the gas tungsten (GTAW), shielded metal (SMAW) and submerged arc welding (SAW) processes. Mechanical and creep properties of weldments were measured both in the as welded and post weld heat treated conditions and proper WPS’s were designed in a manner such that industrial production needs were satisfied. Short term creep resistance of cross weld specimens was measured to be within the base material acceptance criteria. Long term base material and cross weld creep performance evaluation are now in progress.

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Short Term Relaxation of Stuffing Box Packings

Volume 2: Computer Applications/Technology and Bolted Joints ◽

10.1115/pvp2007-26094 ◽

2007 ◽

Cited By ~ 1

Author(s):

Mohammed Diany ◽

Abdel-Hakim Bouzid

Keyword(s):

Contact Pressure ◽

Threshold Value ◽

Element Model ◽

Packing Material ◽

Ansys Software ◽

Short Term ◽

Creep Properties ◽

Contact Pressures ◽

Key Parameter

The long term tightness performance of stuffing box packings, used in valves, is conditioned by the capacity of its material to maintain a contact pressure to a predetermined minimal threshold value. Due to creep, this contact pressure decrease with time depending on the creep properties and the stiffness of the housing. Assessing relaxation is a key parameter in determining the tightness performance of the stuffing box packing over time. Using Ansys software, an axisymmetric 2D finite element model is developed to assess the contact pressures between the packing material and the stem and the housing and its variation with time. The assessment of the packing relaxation is a major obstacle to the good leakage performance of the Stuffing Box Packing.

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A coral-on-a-chip microfluidic platform enabling live-imaging microscopy of reef-building corals

Nature Communications ◽

10.1038/ncomms10860 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 40

Author(s):

Orr H. Shapiro ◽

Esti Kramarsky-Winter ◽

Assaf R. Gavish ◽

Roman Stocker ◽

Assaf Vardi

Keyword(s):

Live Imaging ◽

Live Coral ◽

Powerful Method ◽

Microfluidic Platform ◽

Experimental Platform ◽

Micro Scale ◽

Algal Symbionts ◽

Spatio Temporal

Abstract Coral reefs, and the unique ecosystems they support, are facing severe threats by human activities and climate change. Our understanding of these threats is hampered by the lack of robust approaches for studying the micro-scale interactions between corals and their environment. Here we present an experimental platform, coral-on-a-chip, combining micropropagation and microfluidics to allow direct microscopic study of live coral polyps. The small and transparent coral micropropagates are ideally suited for live-imaging microscopy, while the microfluidic platform facilitates long-term visualization under controlled environmental conditions. We demonstrate the usefulness of this approach by imaging coral micropropagates at previously unattainable spatio-temporal resolutions, providing new insights into several micro-scale processes including coral calcification, coral–pathogen interaction and the loss of algal symbionts (coral bleaching). Coral-on-a-chip thus provides a powerful method for studying coral physiology in vivo at the micro-scale, opening new vistas in coral biology.

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Microstructure and Creep Properties of AISI 316LN Steels with Niobium Additions

Materials Science Forum ◽

10.4028/www.scientific.net/msf.482.275 ◽

2005 ◽

Vol 482 ◽

pp. 275-278 ◽

Cited By ~ 4

Author(s):

Vlastimil Vodárek ◽

Gabriela Rožnovská ◽

Jaromír Sobotka

Keyword(s):

S Phase ◽

Creep Life ◽

Creep Ductility ◽

Niobium Content ◽

Creep Properties ◽

Size Refinement ◽

Tertiary Stage ◽

Type Aisi ◽

Term Creep

The long-term creep rupture tests have been carried out on three casts of a type AISI 316LN steel at 600 and 650°C. Two of the casts investigated contained additions of 0.1 and 0.3 wt.% of niobium. The growing niobium content strongly reduced the minimum creep rate and prolonged the time to the onset of the tertiary stage of creep and also shortened this stage. The enhanced creep resistance of niobium containing steels is not accompanied by the longer creep life that might have been expected. At both temperatures of creep exposure the niobium-bearing casts displayed an inferior creep ductility. Microstructural investigations revealed that niobium provoked significant grain size refinement and the formation of Z-phase. Particles of this phase were considerably dimensionally stable. Furthermore, niobium accelerated the formation and coarsening of s-phase, h-Laves and M6(C,N). The coarse intergranular particles facilitated the formation of cavities which resulted in intergranular failure mode.

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