Insights into the Crystal Chemistry of the Serandite–Schizolite–Pectolite Series

2021 ◽  
Author(s):  
Aaron J. Lussier ◽  
Joel D. Grice ◽  
Henrik Friis ◽  
Glenn G. Poirier
Keyword(s):  
Compositional Data ◽  
Crystal Structure Data ◽  
Species Determination ◽  
Site Distribution ◽  
Strain Behavior ◽  
Site Assignment ◽  
Ideal Mixing ◽  
Compositional Series ◽  
Structural Strain ◽  
Approach Unity

ABSTRACT The compositional series {Na} [[M1+M2](Ca2XMn2–2X)Si3O8(OH)] includes the minerals serandite (X = 0), schizolite (X = 0.5), and pectolite (X = 1). Six crystals are structurally and chemically characterized in detail (four from Ilímaussaq, Greenland; two from Mont Saint-Hilaire, Québec, Canada): one serandite, one pectolite, and four schizolite crystals. Those originating from Greenland show up to 0.05 apfu LREE3+ (La + Ce + Pr + Nd + Eu + Gd). For each, all H atoms were located, and final R1 factors were below 4.4% (<R1> = 2.35%). The results are compared with previously published crystal structure data from an additional 16 samples, originating from worldwide (mostly) igneous environments. Across the series, for all investigated samples, Ca and Mn order preferentially at the octahedral M1 and M2 sites, respectively, following the exchange M2Ca + M1Mn ↔ M1Ca + M2Mn. Site-occupancies closely adhere to a two-site distribution coefficient, calculated here to be K = 20.0(5), for ideal mixing where activity coefficients approach unity. For the above order-disorder exchange, ΔHex is calculated to be –1.77 kcal. With knowledge of K, site assignment and species determination may be accurately made solely with compositional data, where 0 ≤ ΣCa < 0.55 apfu, serandite; 0.55 ≤ ΣCa < 1.45 apfu, schizolite; and 1.45 ≤ ΣCa ≤ 2 apfu, pectolite, with the dominant-constituent rule mandating M1Ca < M1Mn (M2Ca < M2Mn), serandite; M1Ca > M1Mn (M2Ca < M2Mn), schizolite; and M1Ca > M1Mn (M2Ca > M2Mn), pectolite. Polyhedral distortion and structural strain at the M1 and M2 sites, calculated using the equations of Robinson et al. (1971) and solutions to Kirchhoff network equations, respectively, show a predictable, cooperative variation across the entire compositional series; however, prominent discontinuities in distortion and strain behavior are observed for the schizolite composition.

A Comprehensive Structural Strain Method Incorporating Strain-Hardening Effects: From LCF to Ratcheting Evaluations

2018 ◽  
Author(s):  
Xianjun Pei ◽  
Pingsha Dong ◽  
Shaopin Song ◽  
David Osage
Keyword(s):  
Low Cycle Fatigue ◽  
Numerical Algorithms ◽  
Complex Stress ◽  
Structural Effect ◽  
Complex Stress State ◽  
Material Nonlinearity ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Structural Strain ◽  
Strain Method

As a further extension to the structural strain method first introduced by Dong et al [1], this paper presents an enhanced structural strain method which incorporates material nonlinearity and for two typical weld structures, i.e. weldment with plate sections (e.g. gusset weld or cruciform weld etc.) and weldment with beam sections. (e.g. pipe structures). A modified Ramberg-Osgood is introduced to capture nonlinear stress strain behavior of the material. A set of numerical algorithms is used to deal with complex stress state induced by structural effect such as beam section and plane strain condition. The proposed structural strain method is then applied to analysis of fatigue data of weldment made from different materials including steel, aluminum and titanium. It is shown that the enhanced structural strain method provides a unified way to correlate fatigue life of weldment in both high cycle and low cycle fatigue regime. The method is also used to study ratcheting problem raised up by Bree. A modified Bree diagram is given by considering material nonlinearity.

ALCHEMI of B2-Ordered Fe50Al45Me5 alloys

1996 ◽  
Vol 54 ◽  
pp. 548-549
Author(s):  
Ian M. Anderson
Keyword(s):  
Room Temperature ◽  
Iron Aluminide ◽  
Low Density ◽  
Intermetallic Alloys ◽  
Practical Applications ◽  
Alloying Additions ◽  
Site Distribution ◽  
Good Corrosion Resistance ◽  
Room Temperature Ductility ◽  
The Matrix

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.

Environmental microscopy of capillary stress-induced strain behavior in ambient-pressure aerogels

1996 ◽  
Vol 54 ◽  
pp. 850-851
Author(s):  
Sudeep M. Rao ◽  
Joshua Samuel ◽  
Sai S. Prakash ◽  
C. Jeffrey Brinker
Keyword(s):  
Silica Aerogel ◽  
Ambient Pressure ◽  
Drying Shrinkage ◽  
Pore Filling ◽  
Silica Network ◽  
Strain Behavior ◽  
Partially Saturated ◽  
Capillary Stress ◽  
Wetting Liquid ◽  
Aerogel Films

Ambient pressure silica aerogel thin films have recently been prepared by exploiting reversible drying shrinkage caused by derivatization of the internal gel surface. Aerogels have porosities of upto 99.9% and due to the small size of the pores (few nanometers), large capillary stresses are produced in gels that are partially saturated with a wetting liquid. As a result of these capillary stresses, the flexible silica network undergoes strain which has been observed using environmental microscopy. This technique allows variation of the equilibrium vapor pressure and temperature, and a simultaneous monitoring of the deformation of the unconstrained film thickness. We have observed >600% deformation during the pore-filling and pore-emptying cycles. In this presentation, we discuss the unique stress-strain behavior of these films.Ref.: Sai S. Prakash, C. Jeffrey Brinker, Alan J. Hurd & Sudeep M. Rao, "Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage", Nature. Vol. 374, 30 March, 1995, 439-443.

Body-Site Distribution of Melanocytic Nevi among Children in Lithuania

2004 ◽  
Vol 30 (08/09) ◽  
Author(s):  
S Valiukeviciene ◽  
I Miseviciene ◽  
H Gollnick
Keyword(s):  
Body Site ◽  
Melanocytic Nevi ◽  
Site Distribution

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Fatigue Investigation of Elastomeric Structures

2010 ◽  
Vol 38 (3) ◽  
pp. 194-212 ◽  
Author(s):  
Bastian Näser ◽  
Michael Kaliske ◽  
Will V. Mars
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Material Behavior ◽  
Period Effect ◽  
Numerical Representation ◽  
Material Force ◽  
Strain Behavior ◽  
Dissipative Effects ◽  
Elastomeric Materials

Abstract Fatigue crack growth can occur in elastomeric structures whenever cyclic loading is applied. In order to design robust products, sensitivity to fatigue crack growth must be investigated and minimized. The task has two basic components: (1) to define the material behavior through measurements showing how the crack growth rate depends on conditions that drive the crack, and (2) to compute the conditions experienced by the crack. Important features relevant to the analysis of structures include time-dependent aspects of rubber’s stress-strain behavior (as recently demonstrated via the dwell period effect observed by Harbour et al.), and strain induced crystallization. For the numerical representation, classical fracture mechanical concepts are reviewed and the novel material force approach is introduced. With the material force approach at hand, even dissipative effects of elastomeric materials can be investigated. These complex properties of fatigue crack behavior are illustrated in the context of tire durability simulations as an important field of application.

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