scholarly journals Investigation of thermo-mechanical response of a geothermal pile through a small-scale physical modelling

2020 ◽  
Vol 205 ◽  
pp. 05016
Author(s):  
Hussein Hashemi Senejani ◽  
Omid Ghasemi-Fare ◽  
Davood Yazdani Cherati ◽  
Fardin Jafarzadeh
Keyword(s):  
Mechanical Response ◽  
Thermal Response ◽  
Physical Modelling ◽  
Elastic Response ◽  
Small Scale ◽  
Thermal Cycles ◽  
Prolonged Heating ◽  
Excessive Heat ◽  
Head Displacement ◽  
Bed Changes

Energy piles have been used around the world to harvest geothermal energy to heat and cool residential and commercial buildings. In order to design energy geo-structures, thermo-mechanical response of the geothermal pile must be carefully understood. In this paper, a small scale physical model is designed and a series of heating thermal cycles with various vertical mechanical loads are performed. The instrumented pile is installed inside a dry sand bed. Changes in pile head displacement, shaft strains and pile and sand temperatures are monitored using an LVDT, strain gauges and thermocouples, respectively. Prolonged heating cycles, which would continue until boundary temperature changes, would allow the investigation of excessive heat injection when service loads are active on the pile. The thermal response is discussed including confirmation of a temperature influence zone around the pile, the increase in soil temperature, and minimum vertical heat dispersion in the soil. The mechanical response includes plastic settlements when the vertical load passes 20% of ultimate capacity. Plastic settlements have been observed at the half of the capacity reported for the shorter thermal cycles in similar models. The decrease in the capacity indicates a reduction in elastic response of the soil during longer thermal cycles.

scholarly journals Investigation of the effects of heat loss through below-grade envelope of buildings in urban areas on thermo-mechanical behaviour of geothermal piles

2020 ◽  
Vol 205 ◽  
pp. 05010
Author(s):  
Maryam Saaly ◽  
Pooneh Maghoul ◽  
Hartmut Holländer
Keyword(s):  
Heat Loss ◽  
Mechanical Behaviour ◽  
Urban Areas ◽  
Energy Demand ◽  
Heat Dissipation ◽  
Mechanical Response ◽  
Pile Head ◽  
Thermal Cycles ◽  
Head Displacement ◽  
Heat Leakage

Harvesting geothermal energy through the use of thermo-active pile systems is an eco-friendly technique to provide HVAC energy demand of buildings. Mechanical behaviour of thermo-active piles is impacted by thermal cycles. Moreover, in urban areas, the temperature of the ground is higher than non-constructed areas due to the heat loss through the below-grade enclosure of buildings. This heat dissipation increases the thermal capacity of the soil and affects the mechanical response of the geothermal pile foundation subjected to thermo-mechanical loading. To investigate the effect of buildings heat loss on thermo-active piles, a numerical thermo-mechanical (TM) analysis was carried out on a proposed energy foundation system for an institutional building, the Stanley Pauley Engineering Building (SPEB) in the campus of the University of Manitoba, Winnipeg, Canada. The mechanical response of the geothermal piles to the thermal cycles with and without considering heat leakage through the basement of the SPEB is compared. Results showed that the cooling loads induced a maximum vertical pile head displacement of -1.18 mm. After 5 years operation of the system, the maximum vertical pile head displacement decreased to -1.05 mm for the case in which heat loss through the basement in considered in the models. In addition, the maximum axial load effective along the pile axis was 6% higher for the case that considers heat loss through the basement compared to the case without considering heat leakage through the building’s below-grade envelope.

scholarly journals Nonlinear magneto-thermo-elastic vibration of mass sensor armchair carbon nanotube resting on an elastic substrate

2020 ◽  
Vol 7 (1) ◽  
pp. 153-165
Author(s):  
Rajendran Selvamani ◽  
M. Mahaveer Sree Jayan ◽  
Rossana Dimitri ◽  
Francesco Tornabene ◽  
Farzad Ebrahimi
Keyword(s):  
Carbon Nanotube ◽  
Mechanical Response ◽  
Scale Effects ◽  
Nonlocal Elasticity Theory ◽  
Wave Dispersion ◽  
Elastic Vibration ◽  
Ultrasonic Waves ◽  
Small Scale ◽  
Dimensionless Frequency ◽  
Mass Sensors

AbstractThe present paper aims at studying the nonlinear ultrasonic waves in a magneto-thermo-elastic armchair single-walled (SW) carbon nanotube (CNT) with mass sensors resting on a polymer substrate. The analytical formulation accounts for small scale effects based on the Eringen’s nonlocal elasticity theory. The mathematical model and its differential equations are solved theoretically in terms of dimensionless frequencies while assuming a nonlinear Winkler-Pasternak-type foundation. The solution is obtained by means of ultrasonic wave dispersion relations. A parametric work is carried out to check for the effect of the nonlocal scaling parameter, together with the magneto-mechanical loadings, the foundation parameters, the attached mass, boundary conditions and geometries, on the dimensionless frequency of nanotubes. The sensitivity of the mechanical response of nanotubes investigated herein, could be of great interest for design purposes in nano-engineering systems and devices.

Mechanical Response of Different Lattice Structures Fabricated Using the CLIP Technology

2016 ◽  
Author(s):  
Anil Saigal ◽  
John R. Tumbleston ◽  
Hendric Vogel
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Response ◽  
Elastic Response ◽  
Lattice Structures ◽  
Rhombic Dodecahedron ◽  
Structured Materials ◽  
Specific Strength ◽  
Strain Behavior ◽  
End Use ◽  
Continuous Liquid Interface Production

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral, octet, vertex centroid, dode, diamond, rhombi octahedron, rhombic dodecahedron and solid lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, plastic strain hardening to a peak in strength, followed by a drop in flow stress to a plateau region and finally rapid hardening associated with contact of the deformed struts with each other as part of densification. It was found that the elastic modulus and strength of the various lattice structured materials are proportional to each other. In addition, it was found that the octahedral, octet and diamond lattice structures are amongst the most efficient based on the measured specific stiffness and specific strength.

Virtual trabecular bone models and their mechanical response

2008 ◽  
Vol 222 (8) ◽  
pp. 1185-1195 ◽  
Author(s):  
F E Donaldson ◽  
P Pankaj ◽  
A H Law ◽  
A H Simpson
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Elastic Response ◽  
Anatomical Site ◽  
Virtual Samples ◽  
Micro Level ◽  
Architectural Characteristics

The study of the mechanical behaviour of trabecular bone has extensively employed micro-level finite element (μFE) models generated from images of real bone samples. It is now recognized that the key determinants of the mechanical behaviour of bone are related to its micro-architecture. The key indices of micro-architecture, in turn, depend on factors such as age, anatomical site, sex, and degree of osteoporosis. In practice, it is difficult to acquire sufficient samples that encompass these variations. In this preliminary study, a method of generating virtual finite element (FE) samples of trabecular bone is considered. Virtual samples, calibrated to satisfy some of the key micro-architectural characteristics, are generated computationally. The apparent level elastic and post-elastic mechanical behaviour of the generated samples is examined: the elastic mechanical response of these samples is found to compare well with natural trabecular bone studies conducted by previous investigators; the post-elastic response of virtual samples shows that material non-linearities have a much greater effect in comparison with geometrical non-linearity for the bone densities considered. Similar behaviour has been reported by previous studies conducted on real trabecular bone. It is concluded that virtual modelling presents a potentially valuable tool in the study of the mechanical behaviour of trabecular bone and the role of its micro-architecture.

Double-Sided Microchannel Cooling of a Power Electronics Module Using Power Overlay

2009 ◽  
Author(s):  
Adam G. Pautsch ◽  
Arun Gowda ◽  
Ljubisa Stevanovic ◽  
Rich Beaupre
Keyword(s):  
Power Electronics ◽  
High Performance ◽  
Mechanical Response ◽  
Thermal Contact ◽  
Small Scale ◽  
Micro Channel ◽  
Performance Technology ◽  
Actual Performance ◽  
Low Performance ◽  
Microchannel Cooling

In the continuing effort to alleviate the increasing thermal loads for power electronics devices, numerous aggressive solutions have been developed, such as small-scale micro-channel heat exchangers. Although these methods can improve overall surface heat transfer to the order of 500 W cm−2, they are limited to single-sided cooling due to the typical wire-bonded electrical connections of the devices. Power overlay (POL) technology provides a stable planar structure for electrical connection, as well as attachment of an additional top-side heat exchanger. This study presents an analysis of double-sided microchannel cooling of a power electronics module. Two optimized, integral micro-channel heat sinks were attached above and below silicon power devices, with more traditional attachment on one side and a POL interface on the other. A compliant TIM was selected for low thermal resistance and good mechanical response, which allowed top-side connection to the POL surface. A theoretical model is presented that predicts the benefit of double-sided cooling based on the known performance of a single-sided heat sink and given addition thermal contact resistance for the top side. For microchannels with water, an enhancement of 26% was predicted. An experiment was also carried out to measure the actual performance benefit seen with double-sided cooling. An enhancement of over 30% was measured for a particular design. As the theory predicts, the benefit of double-sided cooling is limited for high performance designs. However, double-sided cooling could lead to high levels of thermal performance using low-performance technology.

scholarly journals Mechanical assessment of defects in welded joints: morphological classification and data augmentation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hugo Launay ◽  
François Willot ◽  
David Ryckelynck ◽  
Jacques Besson
Keyword(s):  
Welded Joints ◽  
Spherical Harmonic ◽  
Data Augmentation ◽  
Mechanical Response ◽  
Training Data ◽  
Distance Functions ◽  
Elastic Response ◽  
Reduction Techniques ◽  
Harmonic Decomposition ◽  
Spherical Harmonic Decomposition

AbstractWe develop a methodology for classifying defects based on their morphology and induced mechanical response. The proposed approach is fairly general and relies on morphological operators (Angulo and Meyer in 9th international symposium on mathematical morphology and its applications to signal and image processing, pp. 226-237, 2009) and spherical harmonic decomposition as a way to characterize the geometry of the pores, and on the Grassman distance evaluated on FFT-based computations (Willot in C. R., Méc. 343(3):232–245, 2015), for the predicted elastic response. We implement and detail our approach on a set of trapped gas pores observed in X-ray tomography of welded joints, that significantly alter the mechanical reliability of these materials (Lacourt et al. in Int. J. Numer. Methods Eng. 121(11):2581–2599, 2020). The space of morphological and mechanical responses is first partitioned into clusters using the “k-medoids” criterion and associated distance functions. Second, we use multiple-layer perceptron neural networks to associate a defect and corresponding morphological representation to its mechanical response. It is found that the method provides accurate mechanical predictions if the training data contains a sufficient number of defects representing each mechanical class. To do so, we supplement the original set of defects by data augmentation techniques. Artificially-generated pore shapes are obtained using the spherical harmonic decomposition and a singular value decomposition performed on the pores signed distance transform. We discuss possible applications of the present method, and how medoids and their associated mechanical response may be used to provide a natural basis for reduced-order models and hyper-reduction techniques, in which the mechanical effects of defects and structures are decorrelated (Ryckelynck et al. in C. R., Méc. 348(10–11):911–935, 2020).

Linear thermoelasticity

2020 ◽  
pp. 257-285
Author(s):  
Lallit Anand ◽  
Sanjay Govindjee
Keyword(s):  
Linear Theory ◽  
Mechanical Response ◽  
Thermal Response ◽  
Engineering Applications ◽  
Temperature Changes ◽  
Weakly Coupled ◽  
Linear Thermoelasticity ◽  
Basic Equations ◽  
Fully Coupled ◽  
Coupled Theory

This chapter presents a theory for the coupled thermal and mechanical response of solids under circumstances in which the deformations are small and elastic, and the temperature changes from a reference temperature are small --- a framework known as the theory of linear thermoelasticity. The basic equations of the fully-coupled linear theory of anisotropic thermoelasticity are derived. These equations are then specialized for the case of isotropic materials. Finally, as a further specialization a weakly-coupled theory in which the temperature affects the mechanical response, but the deformation does not affect the thermal response, are discussed; this is a specialization which is of importance for many engineering applications, a few of which are illustrated in the examples.

Analysis, Design, and Optimization of Thermal In-Plane Microactuator—Chevron Type

2011 ◽  
Vol 8 (3) ◽  
pp. 102-109
Author(s):  
K.B. Puneeth ◽  
K.N. Seetharamu
Keyword(s):  
Neural Network ◽  
Mechanical Response ◽  
Thermal Response ◽  
Structural Response ◽  
Design Tool ◽  
Thermal Actuator ◽  
Coupled Models ◽  
Element Analysis ◽  
Design And Optimization ◽  
Analysis Design

A predictive model of thermal actuator behavior has been developed and validated that can be used as a design tool to customize the performance of an actuator to a specific application. Modeling thermal actuator behavior requires the use of two sequentially or directly coupled models, the first to predict the temperature increase of the actuator due to the applied voltage and the second to model the mechanical response of the structure due to the increase in temperature. These models have been developed using ANSYS for both thermal response and structural response. Consolidation of FEA (finite element analysis) results has been carried out using an ANN (artificial neural network) in MATLAB. It is seen that an ANN can be successfully employed to interpolate and predict FEA results, thus avoiding necessity of running FEA code for every new case. Furtheroptimization of geometry for maximum actuation length has been carried out using a GA (genetic algorithm) in MATLAB. The results of the GA were verified against the ANN and FEA results.

Mechanical Response and Incomplete Filling in Compression Molding With Microscale Double-Punch Sets

2019 ◽  
Author(s):  
Bin Zhang ◽  
M. Dodaran ◽  
S. Shao ◽  
W. J. Meng
Keyword(s):  
Mechanical Response ◽  
Ion Beam ◽  
Compression Molding ◽  
Molding Pressure ◽  
Small Scale ◽  
Width Ratio ◽  
Significant Dependence ◽  
Incomplete Filling ◽  
Surface Patterns ◽  
Scale Surface

Abstract Forming nano-/micro-scale surface patterns on metal surfaces by direct compression molding is an important means for achieving small scale surface features with potential usage in wide ranging technological applications. Geometric fidelity of molded features and the corresponding molding response are of critical importance in determining the usefulness of the molding replication technique. In this paper, two series of microscale punches made of tool steels were fabricated using Ga+ focused ion beam (FIB). In one series, the punch consists of a single protruding rectangular strip of different width, w (dubbed the “single punch”). In the other series, the punch consists of two rectangular strips of identical dimensions separated by a spacing in between, s (dubbed the “double punch”). These so-fabricated punches were used to mold elemental single crystal Al. The mechanical response during compression molding was measured and analyzed. For the double-punch experiments, measured characteristic molding pressure exhibited a significant dependence on the spacing to punch width ratio, λ = s/w, as well as a significant dependence on s when λ was fixed. The molded features were examined and the phenomenon of incomplete filling was observed to occur at λ < 0.5.

Concept Design of Very Large Floating Structures and Laboratory-Scale Physical Modelling

2019 ◽  
Author(s):  
Lorenzo Cappietti ◽  
Irene Simonetti ◽  
Ilaria Crema
Keyword(s):  
Numerical Models ◽  
Physical Modelling ◽  
Building Blocks ◽  
Small Scale ◽  
World Population ◽  
Concept Design ◽  
Wave Loads ◽  
Experimental Database ◽  
Floating Structures ◽  
Very Large Floating Structures

Abstract The use of Very Large Floating Structures, VLFS, may represent a strategic approach in order to cope with some of the future societal challenges arising from the impressive growth of the world population. In this article, the motivations of this perspective are briefly discussed, the main issues for the development of VLFS are summarized and a concept structural design based on building-blocks technology is proposed. A small-scale physical model was manufactured and tested in the wave-current flume of the Laboratory of Maritime Engineering, LABIMA, of the Florence University, Italy. The aim of this study is the assessment of the structural feasibility and the effectiveness of the proposed VLFS concept, in terms of resistance to wave loads and control of floating behavior. The experimental measurements provide a first contribution to the necessary knowledge, about load magnitudes and floating behavior, for sizing some of the key structural components. The results appear to support the feasibility of the system in terms of usage of structural materials, technical components and building technologies, available at present, that can withstand the measured loads. Moreover, the acquired experimental database is fundamental in order to validate numerical models, in the perspective of using also such tools as complementary methodology for further improvement of the knowledge of design issues.

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