scholarly journals Relationship between microstructure and deformation of porous Ni-based cermets under redox cycling

2021 ◽  
Vol 3 (10) ◽  
Author(s):  
Kazuhisa Sato ◽  
Satoshi Watanabe ◽  
Yihui Huang ◽  
Taihei Miyasaka ◽  
Toshiaki Matsui ◽  
...  
Keyword(s):  
Mechanical Damage ◽  
Dimensional Change ◽  
Electrical Performance ◽  
Microstructural Changes ◽  
Dimensional Changes ◽  
Redox Cycles ◽  
Ni Content ◽  
Change Behavior ◽  
Deformation Properties ◽  
Component Material

AbstractThis paper discusses the relationship between the elongation and compression behavior and microstructural changes under redox cycles of porous Ni(O)–YSZ cermets for solid oxide fuel cells (SOFC). Mechanical damage in SOFC and SOEC is one of the most important degradation factors governing the electrical performance of cells. Therefore, it is necessary to know the mechanical properties of each component material, such as elastic and deformation properties, in the operating environment. Particularly, of the Ni(O)–YSZ cermets which currently makes up 90% of the volume of the cell, with present mainstream anode supported SOFC and SOEC. Therefore, understanding the properties of the Ni(O)–YSZ cermets plays an important role in ensuring the performance of the entire SOFC and SOEC. In this study, the microstructural changes of Ni(O)–YSZ cermet by reduction, re-oxidation and re-reduction were observed in detail using microstructural observations and systematically compared with the dimensional change behavior. For the dimensional change behavior, a simple model considering the initial porosity and Ni content is proposed, which successfully predicts the dimensional change due to re-oxidation. Furthermore, Ni(O)–YSZ cermets with high Ni content show large initial dimensional changes, but the dimensional reversibility improves with increase of the number of redox cycles.

Dimensional Precision in Sinter-Hardening PM Steels

2007 ◽  
Vol 534-536 ◽  
pp. 665-668 ◽  
Author(s):  
Bruce Lindsley ◽  
Thomas Murphy
Keyword(s):  
Retained Austenite ◽  
Critical Parameter ◽  
Dimensional Change ◽  
Large Impact ◽  
Thermal Treatments ◽  
Microstructural Changes ◽  
Dimensional Changes ◽  
Dimensional Precision ◽  
Large Expansion ◽  
Shape Processing

Dimensional precision is a critical parameter in net shape processing of ferrous PM components. Beyond the dimensional changes associated with pressing and sintering of typical low alloy PM steels, sinter-hardening alloys undergo a transformation from austenite to martensite. The formation of martensite results in a large expansion during cooling, as martensite is the lowest density phase in steels. Tempering hardened steels results in shrinkage, as the martensite converts to a ferrite and carbide microstructure of higher density. Both of these transformations have a large impact on the dimensional change. In addition, martensitic regions with high Cu and C contents may contain large amounts of retained austenite. As austenite is the highest density phase, retained austenite results in less growth of the compact. The presence of martensite and retained austenite, in addition to the tempering step, all play a role in the final dimensions of a component. This paper reviews two sinter-hardening grades and investigates the dimensional and microstructural changes of those grades through different post-sintering thermal treatments.

A Simple Numerical Method for Determining the Sensitivity of Bending Deflections of Stepped Shafts to Dimensional Changes

1985 ◽  
Vol 107 (1) ◽  
pp. 141-146
Author(s):  
G. Umasankar ◽  
C. R. Mischke
Keyword(s):  
Dimensional Change ◽  
Element Model ◽  
Neutral Axis ◽  
Computationally Efficient ◽  
Simple Method ◽  
Dimensional Changes ◽  
Stepped Shaft ◽  
Dimension Change ◽  
Deflection Analysis ◽  
Uniform Diameter

A simple method of computing the effect of a dimensional change at a particular element of a stepped shaft on two bearings, on bending deflections, and on slopes of the neutral axis at any of the nodes of interest is presented. The changes in deflection and slope of the neutral axis are derived as incremental quantities and as functions of the dimension change and the prior deflections and slopes of the neutral axis of the shaft. For shaft synthesis, the implications are that one can begin with a uniform diameter bar subjected to the loading and make a complete deflection analysis with superposed closed-form relations. Then the geometry can be modified element by element and the deflectional changes easily updated. This is computationally efficient. Further, deflections and deflection changes computed using the proposed method are identical to those obtained using a finite beam element model of the shaft.

Dynamic moisture sorption and dimensional stability of furfurylated wood with low lignin content

Holzforschung ◽  
2019 ◽  
Vol 74 (1) ◽  
pp. 68-76
Author(s):  
Tiantian Yang ◽  
Erni Ma ◽  
Jinzhen Cao
Keyword(s):  
Relative Humidity ◽  
Dimensional Stability ◽  
Furfuryl Alcohol ◽  
Lignin Content ◽  
Moisture Sorption ◽  
Dimensional Change ◽  
Poplar Wood ◽  
Sorption Coefficient ◽  
Dimensional Changes ◽  
Sinusoidal Shape

AbstractDegradation of lignin occurs naturally in wood due to the influence of microorganisms or photic radiation. To improve the properties of wood with low lignin content, furfuryl alcohol (FA) at the concentration of 25% was used to modify poplar wood (Populus euramericana Cv.) after partial delignification. Moisture sorption and dimensional stability of the samples were investigated under dynamic conditions where the relative humidity (RH) was changed sinusoidally between 45% and 75% at 25°C. Both the moisture content (MC) and the tangential dimensional change varied with a sinusoidal shape similar to the RH. Hygroscopicity and hygroexpansion increased after delignification, while furfurylation led to an inverse impact by reducing MC, dimensional changes, amplitudes of MC and dimensional changes, moisture sorption coefficient (MSC), and humidity expansion coefficient (HEC). After delignification and further furfurylation, the MC and the dimensional changes were reduced by about 20%, and the maximum drop in amplitudes of MC and dimensional changes was about 30%, while the MSC and the HEC decreased by over 15%. In addition, the furfurylated wood with low lignin content exhibited lower sorption hysteresis and swelling hysteresis.

Changes in the dimensions of the venae cavae

1959 ◽  
Vol 196 (4) ◽  
pp. 741-744 ◽  
Author(s):  
Hiroshi Irisawa ◽  
Alexander P. Greer ◽  
Robert F. Rushmer
Keyword(s):  
Venous Pressure ◽  
Dimensional Change ◽  
Venous Flow ◽  
Dimensional Changes ◽  
Cyclic Patterns ◽  
Venae Cavae ◽  
Surgical Conditions ◽  
Two Phases ◽  
Pressure Changes ◽  
Clockwise Hysteresis

In 11 dogs a variable resistance gauge, a bonded strain gauge, or mutual inductance coils were installed on the venae cavae under aseptic surgical conditions so that dimensional changes in unexposed veins could be measured directly. The cyclic patterns of dimensional change resembled inverted images of venous flow records obtained by others. Since some changes in the venous dimensions apparently were not related to pressure, active contraction of the walls may have been responsible. Studies involving infusion and hemorrhage confirmed the existence of two phases in the pressure-diameter relationship correlated with the level of venous pressure. The pattern of diameter and venous pressure changes during transfusion and withdrawal of blood tended to be a clockwise hysteresis loop.

Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron

2018 ◽  
Author(s):  
Naoya Tada ◽  
Takeshi Uemori
Keyword(s):  
Cast Iron ◽  
Tensile Test ◽  
Internal Combustion Engines ◽  
Gray Cast Iron ◽  
Early Stage ◽  
Dimensional Change ◽  
Tensile Tests ◽  
High Ratio ◽  
Gray Cast ◽  
Dimensional Changes

Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high ratio of performance to cost. On the other hand, the weak graphite flakes present in gray cast iron act as stress concentrators and negatively affect the strength of this material. It is therefore important to know the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, a tensile test of gray cast iron was carried out using a plate specimen in a scanning electron microscope, and the microscopic deformation was observed on the surface of specimen. Particularly, the change in the size of graphite flakes during the tensile test was examined, and the observed trend was discussed. We found from the experimental results that the dimensional changes in the graphite flakes varied in the observed area, and that the final fracture occurred in an area where a relatively large dimensional change was observed. This suggests that the fracture location or the critical parts of gray cast iron, can be predictable from the dimensional changes of the graphite flakes at an early stage of deformation.

Dimensional Changes by Heat Treatment of Helical Gear

2013 ◽  
Vol 535-536 ◽  
pp. 271-274
Author(s):  
Jeongsuk Lim ◽  
Sunghoon Kang ◽  
Young Seon Lee
Keyword(s):  
Heat Treatment ◽  
Elastic Deformation ◽  
Gear Tooth ◽  
Three Dimensional ◽  
Dimensional Change ◽  
Helical Gear ◽  
Tooth Profile ◽  
Dimensional Changes ◽  
Gear Teeth ◽  
Experimental Works

The dimensional change of tooth profile by heat treatment of helical gear was investigated by experimental and numerical approaches. Especially, the three-dimensional elasto-plastic finite element (FE) simulation was adopted to analyze the elastic deformation during load, unloading, ejecting of workpiece. Quenching simulation was also carried out to investigate the change of tooth profile on the forged gear. In experiments, the amount of elastic deformation of the forged gear was quantitatively determined by comparing the tooth profiles on the forged gear and die. The dimensional change of the forged gear tooth after quenching was also evaluated from the comparision of the cold forged and quenched gear teeth. From experimental works, it was found that the amounts of dimensional changes after forging and quenching of helical gear are 10 and 10 μm, respectively.

scholarly journals Anodization Parameters Influencing the Growth of Titania Nanotubes and Their Photoelectrochemical Response

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Ying-Chin Lim ◽  
Zulkarnain Zainal ◽  
Wee-Tee Tan ◽  
Mohd Zobir Hussein
Keyword(s):  
Dimensional Change ◽  
Bath Temperature ◽  
Tube Length ◽  
Complexing Agent ◽  
Dimensional Changes ◽  
Photoelectrochemical Response ◽  
Voltage Ramp ◽  
Wide Range ◽  
Electrode Cell ◽  
Nanotube Growth

TiO2nanotubes (TNTs) were fabricated by electrochemical oxidation of Ti foil in a standard two-electrode cell-containing NH4F. The effects of bath temperature, voltage ramp prior to constant voltage held during anodization and present of complexing agent on the crystalline phase, nanotube growth, and dimensional change of TNT were investigated using XRD and FESEM. The results show that tube length decreases with bath temperature attributed to faster chemical dissolution rate at high temperature. However, nanotubes growth rate was enhanced by ~260% with the addition of EDTA as the complexing agent. Meanwhile, the nanotubes diameter was found to be proportionally dependent on bath temperature but independent of the voltage ramp and addition of EDTA. Photoelectrochemical response under illumination was enhanced by using the calcined TNT and is strongly affected by its dimensional changes. Thus, desired properties of TNT can be obtained by tuning the electrochemical condition for a wide-range application.

Recent Developments of Magnetic SMA

2008 ◽  
Vol 59 ◽  
pp. 1-10 ◽  
Author(s):  
Outi Söderberg ◽  
Ilkka Aaltio ◽  
Yan Ling Ge ◽  
Xu Wen Liu ◽  
Simo Pekka Hannula
Keyword(s):  
Magnetic Field ◽  
Phase Transformation ◽  
Shape Memory ◽  
Dimensional Change ◽  
Magnetic Shape Memory ◽  
Dimensional Changes ◽  
Different Types ◽  
Recent Developments ◽  
Giant Magnetocaloric Effect ◽  
The Magnetic Field

In the shape memory alloys (SMAs) the thermal triggering induces reversible dimensional change by the phase transformation – these materials may also be ferrior ferromagnetic, however, here only the ferromagnetic SMAs are discussed. In certain SMAs the austenitemartensite phase transformation is influenced by the magnetic field as either austenite or martensite is promoted by the field and this is exploited for the dimensional changes. However, in the magnetic shape memory (MSM) alloys no phase transformation occurs as the remarkable dimensional changes take place by the twin variant changes in the martensitic phase activated by the external magnetic field at constant temperature. In addition to the phase transformation or magnetic shape memory effect, the applied magnetic field may also result in the conventional magnetostriction (MS), enhance the superelasticity (magneticfieldassisted superelasticity MFAS) or induce the giant magnetocaloric effect (GMCE). Certain alloys such as NiMnGa may even be multifunctional showing more than one of these effects. The present paper gives an overview of the different types of the magnetically activated SMA alloys, their properties as well as their potentials for applications in the frameworks of the recent studies.

scholarly journals Extended-pour and conventional alginates: effect of storage time on dimensional accuracy and maintenance of details

2021 ◽  
Vol 26 (3) ◽  
Author(s):  
Sandro Basso BITENCOURT ◽  
Isabela Araguê CATANOZE ◽  
Emily Vivianne Freitas da SILVA ◽  
Karina Helga Leal TURCIO ◽  
Daniela Micheline dos SANTOS ◽  
...  
Keyword(s):  
Dimensional Stability ◽  
High Stability ◽  
Digital Camera ◽  
Dimensional Accuracy ◽  
Dimensional Change ◽  
Clinical Results ◽  
Dimensional Changes ◽  
Plastic Bags ◽  
Significant Difference ◽  
Student’S T

ABSTRACT Objective: This study aimed to evaluate the dimensional stability and maintenance of details of conventional and high stability alginates up to 5-day storage. Methods: Two types of alginates were selected (n=10) for this study, conventional (Hydrogum) and high stability alginates (Hydrogum 5), which were produced with the aid of a cylindrical metal block and a ring-shaped metal mold (Specifications 18, 19, and 25, ANSI/ADA). Ten images were obtained from the molds for the dimensional stability test, which were taken immediately after their production and at each different storage periods (15 min, 24 h, 48 h, 72 h, 96 h, and 120 h) by a digital camera. The specimens were kept hermetically sealed in plastic bags (23°C) and then used to obtain 140 (n=70) dental stone models, used in the detail reproduction test, in which the angular accuracy of three grooves (20 µm, 50 µm, and 75 µm) was observed at each period. The details reproduction accuracy was classified using a predetermined score classification. Measurements of dimensional changes were made in the Corel DRAW X6 program. The data were submitted to the Student’s t-test (α?#8197;= 0.05). Results: A statistically significant difference concerning the size of the matrix was observed after 24h for both alginates, and a statistically significant negative linear dimensional change (contraction) was verified after 24 h of storage (1.52% for the high stability alginate, and 1.32% for the conventional alginate). The high stability alginate kept the full details for 72 hours, while the conventional alginate, for 24 h. Both alginates reproduced the 75 µm groove at all storage periods. Conclusion: Impressions made with both alginates presented satisfactory clinical results when the alginates were immediately poured.

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