Effect of repeated heating and cooling cycles on the degree of conversion and microhardness of four resin composites

2021 ◽  
Author(s):  
Mohamed Gebril ◽  
Marc P. Grüll ◽  
Martha Smith Brillant ◽  
Braden Sullivan ◽  
Richard B. Price
Keyword(s):  
Degree Of Conversion ◽  
Resin Composites ◽  
Repeated Heating ◽  
Heating And Cooling

POTOMAC

Alloy Digest ◽  
1975 ◽  
Vol 24 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Heat Treating ◽  
General Purpose ◽  
Low Carbon ◽  
Repeated Heating ◽  
Temperature Changes ◽  
Heating And Cooling ◽  
Temperature Performance ◽  
Heat Checking

Abstract POTOMAC is a general-purpose, low-carbon, chromium-molybdenum-tungsten hot-work steel. It has excellent resistance to shock and heat checking after repeated heating and cooling. Potomac is suitable for hot-work applications involving severe conditions of shock and sudden temperature changes. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on high temperature performance as well as forming, heat treating, and machining. Filing Code: TS-290. Producer or source: Allegheny Ludlum Corporation.

scholarly journals Formation of Incrustations during the Cocombustion of Biomass in Fluidised Bed Boilers

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Petr Buryan
Keyword(s):  
Raw Materials ◽  
Combustion Process ◽  
Power Equipment ◽  
Fluidised Bed ◽  
Boiler Furnace ◽  
Repeated Heating ◽  
Equipment Operation ◽  
Heating And Cooling ◽  
First Pass ◽  
Pass Through

In this article, we focus on causes of formation of incrustations in fluidised bed boilers that result from combustion of biomass-containing energy-producing raw materials and can significantly limit the efficiency of the respective power equipment operation. We applied laboratory procedures followed for assessment of characteristic eutectics of mixtures of coal ashes, desulphurisation components (dolomite and limestone), and woodchip ashes. Our analysis proved that combustion of these (or similar) raw materials, accompanied by repeated heating and cooling of combustion and flue gas desulphurisation products, leads to the formation of unfavourable incrustations. These incrustations can grow up to several tens of centimetres in size, thereby significantly restricting the power equipment functionality. They arise due to incrust reheating that results in the formation of eutectics, which have lower melting temperatures than that during their first pass through the combustion process. The same holds for desulphuriation components themselves. Formation of these new eutectics can be attributed both to recycling of substances produced during the first pass through the furnace as well as to mixtures formed both from recycled materials and from components initially combusted in the boiler furnace.

scholarly journals Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 337 ◽  
Author(s):  
Elham Mirkoohi ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo ◽  
You-Cheng Chang ◽  
Hung-Yu Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Kinematic Hardening ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Repeated Heating ◽  
Powder Bed ◽  
Heating And Cooling ◽  
Body Load ◽  
Point Body

Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model.

scholarly journals Influence of irradiation time on subsurface degree of conversion and microhardness of high-viscosity bulk-fill resin composites

2014 ◽  
Vol 19 (4) ◽  
pp. 831-840 ◽  
Author(s):  
Z. Tarle ◽  
T. Attin ◽  
D. Marovic ◽  
L. Andermatt ◽  
M. Ristic ◽  
...  
Keyword(s):  
Irradiation Time ◽  
High Viscosity ◽  
Degree Of Conversion ◽  
Resin Composites

A STUDY ON EVALUATION OF RESIDUAL STRESS BY MULTILAYER WELDING

2011 ◽  
Vol 25 (31) ◽  
pp. 4285-4288 ◽  
Author(s):  
SUN-CHUL HUH ◽  
JONG-SEOK LEE ◽  
GWI-NAM KIM ◽  
WON-JO PARK ◽  
JOUN-SUNG PARK ◽  
...  
Keyword(s):  
Residual Stress ◽  
High Strength ◽  
Optical Microscope ◽  
Welding Residual Stress ◽  
Surface Microstructure ◽  
Repeated Heating ◽  
Heating And Cooling ◽  
Ansys Analysis ◽  
Large Structures ◽  
Welding Technology

Today, ships and structures are becoming larger (large structures, vessels, FPSO, etc.). Thus, high-strength welding material is required. The advantages of welding over other joining methods, depending on the development of welding technology, include such things as ease of operation and the structures of simplification and the confidential excellence, etc. However, shrinkage and deformation also occur, because of the repeated heating and cooling. Welding residual stress has an adverse effect on stability, but, it was closely related fatigue strength and brittle fracture of structures. In this study, experimental and analysis were conducted, and AIS3000 used to measure residual stress, which were compare with ANSYS analysis results. Metal surface microstructure was observed at various weld spots, as well as HAZ, and base metal using the optical microscope, and component analysis and crystal plane were measured using an XRD and EPMA.

scholarly journals Monomers used in resin composites: degree of conversion, mechanical properties and water sorption/solubility

2012 ◽  
Vol 23 (5) ◽  
pp. 508-514 ◽  
Author(s):  
Vinícius E. S. Gajewski ◽  
Carmem S. Pfeifer ◽  
Nívea R. G. Fróes-Salgado ◽  
Letícia C. C. Boaro ◽  
Roberto R. Braga
Keyword(s):  
Mechanical Properties ◽  
Water Sorption ◽  
Flexural Modulus ◽  
Triethylene Glycol ◽  
Degree Of Conversion ◽  
Resin Composites ◽  
Triethylene Glycol Dimethacrylate ◽  
Three Point Bending ◽  
Rate Of Polymerization ◽  
Urethane Dimethacrylate

The organic phase of resin composites is constituted by dimethacrylate resins, the most common monomers being the bisphenol A diglycidildimethacrylate (BisGMA), its ethoxylated version (BisEMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA). This study compared the homopolymers formed from the monomers used in restorative dental composites in terms of their degree of conversion (DC) and reaction kinetics (by near infra-red spectroscopy, n=3), mechanical properties (flexural modulus and strength in three point-bending, FM and FS, respectively, n=15), water sorption and solubility (WS and SL, respectively - ISO 4049, n=5). Materials were made photopolymerizable by the addition of camphoroquinone/dimethylamine ethyl methacrylate. TEGDMA showed the highest DC, followed by BisEMA, UDMA and BisGMA, both at 10 min and at 24h (p<0.001). UDMA showed the highest rate of polymerization, followed by TEGDMA, BisEMA and BisGMA (H0=13.254, p<0.001). UDMA and TEGDMA presented similar FM, significantly higher (p<0.001) than BisEMA and BisGMA, which in turn present statistically similar values (p>0.001). For FS, UDMA presented the highest value (p<0.001), followed by TEGDMA, then by BisEMA and BisGMA, which were statistically similar (p>0.001). BisGMA showed the highest WS, and TEGDMA and BisEMA the lowest. UDMA was statistically similar to all (H0=16.074, p<0.001). TEGDMA presented the highest SL, followed by UDMA, BisGMA and BisEMA (p<0.001). The tested homopolymers presented different behaviors in terms of polymerization kinetics, flexural properties, water sorption and solubility. Therefore, the use of copolymers is justified in order to obtain high DC and mechanical properties, as well as good resistance to water degradation.

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