scholarly journals Length scales and statistical characteristics of outer bank roughness for large elongate meander bends: The influence of bank material properties, floodplain vegetation and flow inundation

2017 ◽  
Vol 42 (13) ◽  
pp. 2024-2037 ◽  
Author(s):  
Kory Konsoer ◽  
Bruce Rhoads ◽  
James Best ◽  
Eddy Langendoen ◽  
Mick Ursic ◽  
...  
Keyword(s):  
Material Properties ◽  
Statistical Characteristics ◽  
Floodplain Vegetation ◽  
Length Scales ◽  
Outer Bank ◽  
Meander Bends

Effect of Moisture and Graded-Layer Mechanical Properties on Deformation and Interfacial Adhesion

2003 ◽  
Vol 778 ◽  
Author(s):  
Lorraine C. Wang ◽  
Reinhold H. Dauskardt
Keyword(s):  
Mechanical Properties ◽  
Layer Thickness ◽  
Material Properties ◽  
Interface Fracture ◽  
Material Structure ◽  
Second Phase ◽  
Length Scales ◽  
Adhesion Properties ◽  
Micron Size ◽  
Thermal And Electrical Properties

AbstractControlling material properties over nanometer length scales is crucial for current and emerging high-density microelectronic device packages. Miniaturization of devices is increasingly limited by the ability to “connect” to the device, and the required packaging structures must be fabricated where layer thickness and feature sizes approach micron size scales while achieving the required mechanical, thermal and electrical properties. Second phase additions such as sub-micron sized particles are often added to locally adjust the material properties of constituent layers in the complex package structure. This results in significant variation of mechanical properties over sub-micron length scales. Such manipulation of material structure and its effects on mechanical and interfacial fracture behavior are addressed using experimental and modeling studies. Underfill layers consisting of an epoxy matrix with dispersed silica beads are shown to exhibit variations of elastic and flow properties in excess of three-fold across the layer thickness. Mechanical properties are not only affected by the distribution of second-phase fillers, but also by the adhesion properties of the filler/matrix interface. Interfaces are susceptible to stress corrosion cracking associated with moisture which can lead to progressive debond growth at loads much lower than that required to exceed the critical interface fracture energies. Subcritical debonding is affected by temperature, humidity, and the bond chemistry of the interface. The effects of these variations are considered on the adhesive and subcritical debonding behavior of interfaces between model epoxy underfills and SiNx chip passivation. Implications for other constrained complex layered structures are considered.

A Simulation Method of Establishing Fatigue Life Distribution

1976 ◽  
Vol 98 (1) ◽  
pp. 183-188 ◽  
Author(s):  
H. A. Elmaraghy ◽  
J. N. Siddall
Keyword(s):  
Fatigue Life ◽  
Material Properties ◽  
Digital Simulation ◽  
Simulation Method ◽  
Fatigue Tests ◽  
Design Tool ◽  
Statistical Characteristics ◽  
Life Distribution ◽  
Parametric Studies ◽  
Life Distributions

This paper presents a Monte Carlo simulation method for fatigue failure, by which the randomness of two material properties as well as that of the applied load can be incorporated into a stochastic model using an appropriate failure criterion to predict the statistical characteristics of fatigue life under constant and random amplitude cyclic loading conditions. In this technique, both the endurance limit Se and the fatigue strength coefficient Sf′ are treated as stochastic variables. The combined effect of the randomness of Se, Sf′, and the applied stress on the statistical characteristics of fatigue lives is predicted analytically using digital simulation of fatique tests. The life distributions and their statistical characteristics are found to be in good agreement with those obtained from analyzing the experimental results, indicating that the proposed technique and the underlying assumptions and hypotheses are adequate. The suggested method is believed to be an effective, fast, and easy-to-use design tool which is suitable for use on electronic computers. It is ideal for parametric studies compared with the costly and time-consuming laboratory fatigue tests. Minimum experimental data are needed as a basis for the analysis. New results are presented which show the effect of the randomness of the loads and material properties on the randomness of fatigue life distribution.

scholarly journals Modal Analysis of Beam Structures with Random Field Models at Multiple Scales

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Dan Feng
Keyword(s):  
Random Field ◽  
Modal Analysis ◽  
Material Properties ◽  
Multiple Scales ◽  
Heterogeneous Material ◽  
Modal Parameters ◽  
Fe Method ◽  
Length Scales ◽  
Beam Structures ◽  
Random Field Theory

Structure material properties are heterogeneous in nature and would be characterized with different statistics at different length scales due to the spatially averaging effects. This work develops a framework for the modal analysis of beam structures with random field models at multiple scales. In this framework, the random field theory is adopted to model heterogeneous material properties, and the cross-correlations between material properties are explicitly considered. The modal parameters of a structure are then evaluated using the finite element (FE) method with the simulated heterogeneous material properties taken as input. With the aid of Monte Carlo simulation, the modal parameters are analyzed in a probabilistic manner. In addition, to accommodate the necessity of different mesh sizes in FE models, an approach of evaluating random field parameters and generating random field material properties at different length scales is developed. The performance of the proposed framework is demonstrated through the modal analysis of a simply supported beam, where the formulation of the multiscale random field approach is validated and the effects of heterogeneous material properties on modal parameters are analyzed. Parametric studies on the random field parameters, including the coefficient of variation and the scale of fluctuation, are also conducted to further investigate the relations between the random field parameters at different scales.

scholarly journals A new perspective on new materials

2018 ◽  
Vol 49 (4) ◽  
pp. 23-26
Author(s):  
Johannes Jobst ◽  
Sense Jan van der Molen
Keyword(s):  
Material Properties ◽  
Small Length ◽  
New Materials ◽  
Length Scales ◽  
New Perspective

We live in an age of nanomaterials in which new materials are discovered almost every day. Moreover, we are starting to engineer material properties at the nanoscale. Hence, we need new tools to investigate different materials routinely and on small length scales.

scholarly journals Evolutionary optimization of material properties of a tropical seed

2011 ◽  
Vol 9 (66) ◽  
pp. 34-42 ◽  
Author(s):  
Peter W. Lucas ◽  
John T. Gaskins ◽  
Timothy K. Lowrey ◽  
Mark E. Harrison ◽  
Helen C. Morrogh-Bernard ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Material Properties ◽  
Turgor Pressure ◽  
Selection Pressures ◽  
Damage Mechanisms ◽  
Length Scales ◽  
Damage Resistance ◽  
Heterogeneous Microstructure ◽  
Upper Limit

Here, we show how the mechanical properties of a thick-shelled tropical seed are adapted to permit them to germinate while preventing their predation. The seed has evolved a complex heterogeneous microstructure resulting in hardness, stiffness and fracture toughness values that place the structure at the intersection of these competing selective constraints. Analyses of different damage mechanisms inflicted by beetles, squirrels and orangutans illustrate that cellular shapes and orientations ensure damage resistance to predation forces imposed across a broad range of length scales. This resistance is shown to be around the upper limit that allows cracking the shell via internal turgor pressure (i.e. germination). Thus, the seed appears to strike an exquisitely delicate adaptive balance between multiple selection pressures.

scholarly journals Uncertainty in Resistance Models for Steel Members

2014 ◽  
Vol 14 (2) ◽  
pp. 26-37 ◽  
Author(s):  
Vitali Nadolski ◽  
Miroslav Sykora
Keyword(s):  
Material Properties ◽  
Model Uncertainty ◽  
Steel Structures ◽  
General Concept ◽  
Statistical Characteristics ◽  
Model Uncertainties ◽  
Practical Applications ◽  
Applied Model ◽  
Steel Members

Abstract Resistance of steel structures is primarily dependent on material properties, geometry and uncertainties related to an applied model. While materials and geometry can be relatively well described, the uncertainties in resistance models are not yet well understood. In many cases significant efforts are spent to improve resistance models and reduce uncertainty associated with outcomes of the model. However, these achievements are then inadequately reflected in the values of partial factors. That is why the present paper clarifies a model uncertainty and its quantification. Initially a general concept of the model uncertainty is proposed. Influences affecting results obtained by tests and models and influences of actual structural conditions are overviewed. Statistical characteristics of the uncertainties in resistance of steel members are then provided. Simple engineering formulas, mostly based on the EN 1993-1-1 models, are taken into account. To facilitate practical applications, the partial factors for the model uncertainties are derived using a semiprobabilistic approach.

Inverse Multi-Scale Robust Design of Composite Structures Using Design Capability Indices

2020 ◽  
Author(s):  
Soban Babu Beemaraj ◽  
Rizwan Khan Pathan ◽  
Amit G. Salvi ◽  
Gehendra Sharma ◽  
Farrokh Mistree ◽  
...  
Keyword(s):  
Composite Materials ◽  
Material Properties ◽  
Composite Structures ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Robust Performance ◽  
Length Scales ◽  
Macro Scale ◽  
Capability Indices ◽  
Micro Structures

Abstract Composite materials are heterogeneous materials, and are hierarchical in nature consisting of multiple length scales. In the design of structures with composite materials, the micro-structure of the materials have a direct bearing on the final behavior of the structure. The deviations in the bulk material properties are caused due to uncertainties associated with the micro-structures and its propagation through different length scales. Uncertainties in the design parameters (geometry and materials properties etc.) at macro-scale also contribute to variations in the final behavior. Currently, these uncertainties are included as a large factor of safety in deterministic design, which may result in over design of the product. The robust performance of the structure can be achieved by considering these uncertainties explicitly in the design process. In this paper, a method for designing a robust composite structure subjected to different loading conditions is illustrated. Structural models are run to compute robust material properties and geometries for different load scenarios that yield most robust materials and micro-structures. Most robust combination of material and geometries is selected that results in most robust performance under all loading scenarios. These materials are designed using multiscale models in which micro-structural uncertainties are accounted. The uncertainties in the material properties and geometrical parameters at different length scales are explicitly modelled as ranges in the set of input parameters. Final performance variations are calculated using design capability index. Consolidated single material parameters and dimensions are selected using efficiency metrics. Design capability indices are formed as goals and constraints in compromise decision support problem. Robust micro-structures are designed inductively rather than deductively.

Multiple particle tracking microrheology measured using bi-disperse probe diameters

Soft Matter ◽  
2018 ◽  
Vol 14 (28) ◽  
pp. 5811-5820 ◽  
Author(s):  
Matthew D. Wehrman ◽  
Seth Lindberg ◽  
Kelly M. Schultz
Keyword(s):  
Particle Tracking ◽  
Material Properties ◽  
Length Scales ◽  
Multiple Length Scales ◽  
Particle Tracking Microrheology ◽  
Multiple Particle Tracking ◽  
Different Diameters ◽  
Multiple Particle ◽  
Probe Particles

Multiple particle tracking microrheology using probe particles with different diameters to simultaneous characterize material properties at multiple length scales.

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