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Introduction
Published in Xi Frank Xu, Multiscale Theory of Composites and Random Media, 2018
In the field of mechanics of materials, there are two classical and fundamental modeling methodologies, phenomenological and micro–macro, as shown in Figure 1.1. A phenomenological model is defined as a mechanics model that describes the empirical relationships of macroscopic phenomena to each other, in a way that directly applies or is at least consistent with fundamental laws of mechanics, but has no use of microscopic information including physical mechanisms and statistics. Note that, according to this definition, a model traditionally falling into the category of so-called mechanistic models would still be a phenomenological one when no microscopic information is explicitly taken into account. A phenomenological model in mechanics of materials typically consists of the following three basic steps: Define a number of state variables and parameters (e.g. constitutive parameters),Formulate a mathematical model using the defined variables and parameters to describe an observed phenomenon, andMeasure the parameters and validate the model experimentally.
An Overview on Neural Networks in Physical Properties and Drying Technology
Published in Alex Martynenko, Andreas Bück, Intelligent Control in Drying, 2018
Fábio Bentes Freire, Flavio B. Freire, Maria do Carmo Ferreira, José Teixeira Freire
Drying rates are affected by numerous factors, including the dryer configuration, the process variables (such as air temperature and velocity), and the product’s physical-chemical characteristics. Given the complex phenomena involved, modeling based on purely phenomenological models is often unfeasible. A classical method is to fit empirical or semi-empirical equations to experimental data, based on a lumped approach that assumes isothermal conditions in the samples. The semi-empirical equations are generally simplified or modified forms of Fick’s second law, such as the Lewis and Page equations, where k is a drying constant (Akpinar, 2006; Kaya and Aydin, 2009). Empirical models may be derived by analogy to Newton’s law of cooling and originate the equations known as drying kinetic models. Some examples of well-known equations commonly used to predict drying kinetics of a variety of products are shown in Table 15.1.
Soil shear–the phenomenological model
Published in Paul G. Joseph, Dynamical Systems-Based Soil Mechanics, 2017
A phenomenological model is a model that describes observed behavior (phenomena), without trying to model the underlying physical processes that cause or drive such behavior. Often in problems that appear to be complex, the first step in modeling something is simply to model only the observed behavior. Then, with this model in hand, one can dig deeper and search for the likely physical basis of the observed behavior. This chapter describes this initial work modeling the observed behavior of a soil sample when sheared. With the phenomenological model firmly in hand, the next chapter will proceed to determine the root cause of the behavior, i.e., the physical basis of the behavior and use this to create the so-called “physical model.”1
A survey on the modelling of air springs – secondary suspension in railway vehicles
Published in Vehicle System Dynamics, 2022
I. Mendia-Garcia, N. Gil-Negrete Laborda, A. Pradera-Mallabiabarrena, M. Berg
Phenomenological or mechanical models are physically based, represented as equivalent mechanical circuits (composed of springs, dashpots, masses and other elements) and where the values of parameters are usually experimentally derived. Their easy and fast implementation makes them the most popular option in multibody simulations. The first mechanical model [62] was used in 1963, a basic model to analyse the air spring performance in the low-frequency range.
Determination of the master curves of shear modulus and phase angle for asphalt binders with consideration of relaxation spectrum
Published in International Journal of Pavement Engineering, 2022
Rheological properties such as complex shear modulus and relaxation spectrum provide important information on the mechanical behaviours of soft matters under deformation. The phenomenological approach to determine the master curves of the rheological properties is to calibrate the curves with data from mechanical tests. Despite the fact that one can also adopt the theoretical approach like Rouse model (1953) and Zimm model (1956) to develop the curves, such approach often requires micromechanical information that is not easily available. Therefore, the phenomenological approach is often adopted in engineering applications. For asphalt binder, dynamic shear rheometer (DSR) is a commonly used piece of equipment to phenomenologically determine its master curves. The obtained test data such as the magnitude of complex shear modulus and phase angle at certain temperatures and frequencies can be directly used to derive some performance-related parameters such as those used in the Performance Grading system (Anderson et al.1994). Alternatively, the data may be used to acquire rheological properties not directly measured by taking advantage of the time temperature superposition (TTS) principle (Ferry 1980). Particularly, the master curves of and can be constructed by TTS at a reference temperature over a wide range of frequency using test data obtained at different temperatures over much narrower ranges of frequencies. The master curves are useful for pavement engineers, not only in revealing other fundamental properties of asphalt binders but also in estimating the complex moduli of asphalt mixtures (e.g. Krishnan and Rajagopal 2005, Kim et al.2007, Mo et al.2008, Alavi et al.2013).
Faith and fakes – dealing with critical information in decision analysis
Published in Civil Engineering and Environmental Systems, 2019
Linda Nielsen, Sebastian Tølbøll Glavind, Jianjun Qin, Michael H. Faber
Phenomenological models are typically defined as models that represent only empirical observations of the physical world without resorting to a-priori assumptions. Data models or statistical models (e.g. regressions) are a kind of phenomenological model in that they do not attempt to form an explanation or theory of why given variables are correlated in a particular way, but rather aim to represent the relation among the variables. In phenomenological models truth is always subjective and dependent on the interpretation of the observer. In contrast, models of theories make a claim on the truthfulness of a proposition, which is derived on logical principles and require no evidence of observations in the physical world. The polarity truth-appearance is a legacy of the split between the pre-Socratic doctrine of flux of Heraklitus and Parmenides’ doctrine of denial of the existence of change. Heraklitus held that what is real is constantly changing and that no object retains all its constituent parts or qualities from one moment to the next. Parmenides developed a logical argument against the existence of change. From the premise that it is impossible to think or talk about what does not exist, he deduced that (i) there is no coming into existence or ceasing of existence, i.e. nothing can be created and nothing can be destroyed; (ii) alteration or change is therefore impossible; (iii) movement is therefore impossible; (iv) plurality is therefore impossible. Here we have in a nutshell the two opposing views of truth – the Heraklitean notion that what is true or real is constantly undergoing change, so at no given point in time is truth or reality monolithic and absolute and the Parmenidean notion of truth as an absolute and of eternal duration. These views were further developed by Aristotle and Plato respectively and have been used to distinguish scientific, phenomenological and experimentalist view of truth and reality from the theological and analytical- mathematic perspectives. In the present paper when we apply the term truth we distance ourselves from the Platonic logico-analytical interpretation. Our approach bears a connotation to the flux doctrine of Heraklitus and to Aristotle’s application of the phenomenological method. Essentially this implies the underlying assumption that the truth about a system of consideration can be established in phenomenological terms. The available knowledge about the truth of the system (what in the social sciences might be referred to as the ‘lifeworld’) is fundamentally subjective as we perceive it.