Analysis of the Deformation Characteristics of Loess Based on Thermal–Mechanical Coupling under an Energy Internet

2021 ◽  
Author(s):  
Zengle Li ◽  
Bin Zhi ◽  
Enlong Liu
Keyword(s):  
Mechanical Properties ◽  
Temperature Change ◽  
Clean Energy ◽  
Model Parameters ◽  
Stress Strain ◽  
Energy Internet ◽  
Influence Of Temperature ◽  
Medium Model ◽  
Strain Relationship ◽  
Natural Loess

In response to the major challenges faced by China’s transition to green low-carbon energy under the dual-carbon goal, the use of energy Internet cross-boundary thinking will help to develop research on the integration of renewable clean energy and buildings. Energy piles are a new building-energy-saving technology that uses geothermal energy in the shallow soil of the Earth’s surface as a source of cold (heat) to achieve heating in winter and cooling in summer. It is a complex thermomechanical working process that changes the temperature of the rock and soil around the pile, and the temperature change significantly influences the mechanical properties of natural loess. Although the soil temperature can be easily and quickly obtained by using sensors connected to the Internet of Things, the mechanical properties of natural loess will change greatly under the influence of temperature. To explore the influence of temperature on the stress–strain relationship of structural loess, the undrained triaxial consolidation tests were carried out under different temperatures (5, 20, 50 and 70∘C) and different confining pressures (50, 100, 200 and 400[Formula: see text]kPa), and a binary-medium model was introduced to simulate the stress–strain relationship. By introducing the damage rate under temperature change conditions, a binary-medium model of structural loess under variable temperature conditions was established, and the calculation method of the model parameters was proposed. Finally, the calculated results were compared with the test results. The calculation results showed that the established model has good applicability.

scholarly journals Damage constitutive model of stratified cemented backfill based on coupling macroscopic and mesoscopic deformations

2020 ◽  
Vol 194 ◽  
pp. 05024
Author(s):  
Yanan Tang ◽  
Weidong Song ◽  
Jianxin Fu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Compressive Load ◽  
Strain Curve ◽  
Strength Distribution ◽  
Stress Strain ◽  
Strain Relationship ◽  
Damage Constitutive Model ◽  
Stratified Structure ◽  
Relationship Of

The mechanical properties and stress-strain relationship of cemented backfills with different stratified structure have a direct effect on the mining-filling cycle and the mining of adjacent pillars. To obtain the stress-strain evolution curves, the uniaxial compressive strength tests were performed on backfills with stratified numbers of 0, 1, 2 and 3. The deformation of stratified backfill under the compressive load is regarded as a compound of closed deformation of the macroscopic stratified structure and elastic deformation of material. The damage constitutive model of cemented backfills with different stratified structure are established by considering the influence of compacted section. Comparative analysis reveals that the calculated curve based on the established sectional damage constitutive model conforms well to the trial curve. The maximum closed strain of the structural plane has a more significant effect on the mechanical properties of backfill. In the Weibull distribution, with the increase of the parameter m, the peak strength of backfill gradually increases and then reaches to a certain value, and the stress-strain curve gradually becomes steeper, which shows that m is a reflection of the concentration level of micro-unit strength distribution in the backfill..

scholarly journals Prediction of Mechanical Properties of Local Concrete in Compression Using Artificial Neural Networks

2020 ◽  
Vol 27 (1) ◽  
pp. 105-121
Author(s):  
Baylasan Mohamad ◽  
Soleman Alamoudi ◽  
Abd alrahman Issa
Keyword(s):  
Mechanical Properties ◽  
Neural Networks ◽  
Compressive Strength ◽  
Artificial Neural Networks ◽  
Actual Behavior ◽  
Stress Strain ◽  
Strain Relationship ◽  
Artificial Neural ◽  
Local Materials ◽  
Ready Mix Concrete

Mechanical properties of concrete are highly dependent on the local materials used in its preparation. experiments on ready mix concrete in our region illustrate the actual behavior of concrete produced by local materials. Six standard cylinders (D=150mm, H=300mm) were casted of most ready mix concrete in central area in Syria (13 of them) covering a wide range of compressive strength . Tests were carried out using a testing machine which gives the applied force values and the corresponding displacement simultaneously until failure. The mean curves representing the (stress-strain) relationship of concrete in compression are drawn, from which the mechanical properties of each mixture were derived, such modulus of elasticity compressive strength ,  and the corresponding strain . Artificial neural networks were trained on experimental test results (using MATLAB). The laws of concrete behaviour were well assimilated by Artificial neural networks, which is possible to be used as an alternative method of available models of stress-strain relationship, by predicting the curve directly for various concrete mixtures prepared using local materials with different mixing ratios, or a complementary method through the adoption of an appropriate mathematical model and then predict its parameters ( ، ، ). ANNs proved their ability to predict mechanical properties of concrete better than linear regression equations, which promises a more accurate and comprehensive prediction.

A Revised Anand Constitutive Model for Lead Free Solder That Includes Aging Effects

2013 ◽  
Author(s):  
Mohammad Motalab ◽  
Munshi Basit ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Constitutive Equations ◽  
Mechanical Tests ◽  
The Other ◽  
Lead Free ◽  
Model Parameters ◽  
Aging Effects ◽  
Stress Strain ◽  
Profile Matching

Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model) and failure models (e.g. energy dissipation per cycle model) that do not evolve with material aging. Thus, there will be significant errors in the calculations with lead free SAC alloys that illustrate dramatic aging phenomena. In this study, we have developed a revised set of Anand viscoplastic stress-strain relations for solder that include material parameters that evolve with the thermal history of the solder material. The effects of aging on the nine Anand model parameters have been examined by performing stress-strain tests on SAC305 samples that were aged for various durations (0–6 months) at temperature of 100 C. The stress-strain data were measured at three strain rates (.001, .0001, and .00001 1/sec) and five temperatures (25, 50, 75, 100, and 125 C). The mechanical tests have been performed using both water quenched (WQ) and reflowed (RF) samples (two unique specimen microstructures). In the case of the water quenched samples, there is rapid microstructural transitioning during the brief time that occurs between placing molten solder into the glass tubes and immersing the tubes in water bath. On the other hand, the reflowed samples are first cooled by water quenching, and then sent through a reflow oven to re-melt the solder in the tubes and subject them to a desired temperature profile matching that used in PCB assembly. As expected, the observed mechanical properties of water quenched samples were better (higher in magnitude) than the corresponding mechanical properties of the reflowed samples. Although the differences in elastic modulus between the water quenched and reflowed samples are small, significant differences are present for the yield and ultimate tensile stresses (for each aging condition). For both the water quenched and reflowed specimens, significant degradation of the mechanical properties has been observed with aging. Using the measured stress-strain and creep data, mathematical expressions have been developed for the evolution of the Anand model parameter with aging time. Our results show that 2 of the 9 constants remain essentially constant during aging, while the other 7 show large changes (30–70%) with up to 6 months of aging. The revised Anand constitutive equations for solder with aging effects have also been incorporated into commercial finite element codes (ANSYS and ABAQUS).

scholarly journals The Application of Improved Duncan-Chang Model in Unloading Soil

2014 ◽  
Vol 8 (1) ◽  
pp. 410-415 ◽  
Author(s):  
Yi He ◽  
Xuejun Chen
Keyword(s):  
Triaxial Test ◽  
Stress Path ◽  
Model Parameters ◽  
Silty Clay ◽  
True Triaxial Test ◽  
Stress Strain ◽  
Foundation Pit ◽  
Foundation Soil ◽  
Strain Relationship ◽  
Chang Model

On the basis of the representative samples of silty clay found in Wuhan, China, the lateral unloading of soil’s stress path produced by excavating foundation pit engineering, was simulated by triaxial experiment. A series of consolidated- drained true triaxial test and normal triaxial test were conducted. According to the results of tests, the parameter of the Duncan-Chang Model was determined. A modulus formula was used for the foundation soil in the lateral unloading stress path tests to replace the modulus formula of Duncan-Chang Model based on the σ3 =const . Moreover, the Duncan- Chang hyperbola nonlinear elastic constitutive model was used to simulate the plane strain test. A method to improve the ability of Duncan-Chang model in order to take into account the effects of the intermediate principal stress on the strength and deformation was presented as well as all the model parameters were also determined. The adaptability of the model for unloading the stress path was verified by comparing the theoretical stress-strain relationship and empirical stress-strain relationship.

scholarly journals Mechanical Properties and Constitutive Model Applied to the High-Speed Impact of Aluminum Foam That Considers Its Meso-Structural Parameters

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6206
Author(s):  
Qian Guo ◽  
Wenbin Li ◽  
Wenjin Yao ◽  
Xiaoming Wang ◽  
Changqiang Huang
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Strain Rate ◽  
High Speed ◽  
Aluminum Foam ◽  
Structural Parameters ◽  
Stress Strain ◽  
Different Temperatures ◽  
Strain Relationship ◽  
Relationship Of

In this work, quasistatic mechanical compression experiments were used to study the stress–strain relationship of aluminum foam, and the mechanism of the compressive deformation of aluminum foam under quasistatic compression conditions is discussed based on the experimental observations. Since the interactions among cells of the aluminum foam and differences in compressive strength among cells substantially impacted the mechanical properties of the material, the cellular structural parameters, namely the cell size and cell wall thickness, were defined. Along with the mechanism of deformation of a single cell, the influence of structural parameters on the micro failure mechanism and the stress–strain relationship of the aluminum foam material was analyzed. In combination with the factors influencing the mechanical properties of the aluminum foam, a mechanical constitutive model of aluminum foam suitable for multi-density and multi-impact environments that considers cellular structure density was established to predict the complete stress–strain relationship of aluminum foam under a high strain rate. The coupling function of strain rate and temperature in the original model was verified and the parameters were determined by the compression experiments under different strain rates and different temperatures.

Mechanical Behavior Simulation of PMMA for Nano Imprint Lithography Using Molecular Dynamics

2007 ◽  
Vol 345-346 ◽  
pp. 979-982 ◽  
Author(s):  
Jung Yup Kim ◽  
Jae Hyun Kim ◽  
Byung Ik Choi
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Strain ◽  
Process Condition ◽  
Imprint Lithography ◽  
Stress Strain ◽  
Behavior Simulation ◽  
Strain Relationship ◽  
Relationship Of ◽  
Nano Imprint

NIL(Nano Imprint Lithography) is one of the most promising lithography techniques. There are many variants of NIL, and two major techniques of them are thermal NIL and UV NIL. Here, we focus ourselves on the thermal NIL. During the thermal NIL, the polymeric patterns experience large mechanical strain and high temperature, and this often leads to malformation of polymeric patterns. So it is needed to improve the pattern fidelity and contrast, and these are believed to be closely related to the process condition and mechanical properties. In thermal NIL, PMMA is widely used and chosen as target polymer. Generally, mechanical properties in nano scale are really hard to acquire. In this study, we estimate the mechanical properties of PMMA by molecular dynamic simulation. These properties will be used as input of continuum simulation. We will estimate stress-strain relationship of PMMA. This stress-strain relationship depends on strain rate and temperature. So we will study about strain rate and temperature effect.

scholarly journals Quantitative Representation of Mechanical Behavior of the Surface Hardening Layer in Shot-Peened Nickel-Based Superalloy

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1437
Author(s):  
Wu Zeng ◽  
Junjie Yang
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Surface Hardening ◽  
Indentation Test ◽  
Tensile Tests ◽  
Model Parameters ◽  
Instrumented Indentation ◽  
Stress Strain ◽  
Nickel Based Superalloy

Surface hardening treatment can usually introduce severe grain distortion with a large gradient in the surface layer. It results in mechanical properties being difficult to accurately determine through macroscopic tests due to the non-uniformity of the shot-peened material. In this study, the mechanical behavior of uniformly pre-deformed nickel-based superalloy IN718 was investigated with monotonic tensile tests and instrumented indentation tests. For the shot-peened material, the hardness distribution of the surface hardening layer after shot peening was identified through the instrumented indentation method. According to the stress–strain results of pre-deformed materials, Ramberg–Osgood model parameters could be presented with plastic deformation. Assuming the power-law relationship between hardness and plastic deformation, the plastic deformation distribution along the depth of the surface hardening layer was clarified. Based on the results, a method to identify the stress–strain relationships of hardened material at different depths was established. Finally, the finite-element simulations of the instrumented indentation test considered residual stress and strain hardening were built to verify the method presented herein. The results show that the solution to evaluate the mechanical properties of hardening layer materials in the microscopic zone is feasible, which can provide the foundation for the failure analysis of shot-peened materials.

Viscoplastic Constitutive Model for Lead-Free Solder Including Effects of Silver Content, Solidification Profile, and Severe Aging

2015 ◽  
Author(s):  
Munshi Basit ◽  
Mohammad Motalab ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Silver Content ◽  
Material Behavior ◽  
Lead Free ◽  
Model Parameters ◽  
Strain Rates ◽  
Lead Free Solder ◽  
Stress Strain ◽  
Free Solder

In the electronic packaging industry, it is important to be able to make accurate predictions of board level solder joint reliability during thermal cycling exposures. The Anand viscoplastic constitutive model is often used to represent the material behavior of the solder in finite element simulations. This model is defined using nine material parameters, and the reliability prediction results are often highly sensitive to the Anand parameters. In this work, an investigation on the Anand constitutive model and its application to SAC solders of various Ag contents (i.e. SACN05, with N = 1, 2, 3, 4) has been performed. For each alloy, both water quenched (WQ) and reflowed (RF) solidification profiles were utilized to establish two unique specimen microstructures, and the same reflow profile was used for all four of the SAC alloys so that the results could be compared and the effects of Ag content could be studied systematically. In addition, we have performed tensile testing on reflowed specimens subjected to 6 months of aging at 100 C. After this level of aging, any further changes in the mechanical response and properties will be rather small. Thus, the results for these tests can be regarded as approaching the highest level of mechanical behavior degradation possible for a “severely aged” lead free solder material. The nine Anand parameters were determined for each unique solder alloy and microstructure from a set of stress strain tests performed at several strain rates and temperatures. Testing conditions included strain rates of 0.001, 0.0001, and 0.00001 (sec−1), and temperatures of 25, 50, 75, 100, and 125 C. As expected, the mechanical properties (modulus and strength) increase with the percentage of Ag content, and these changes strongly affect the Anand parameters. The sensitivity of the mechanical properties and Anand parameters to silver content is higher at lower silver percentages (1–2%). Also, the observed mechanical properties of water quenched samples were better (higher in magnitude) than the corresponding mechanical properties of the reflowed samples. Although the differences in elastic modulus between the water quenched and reflowed samples are relatively small, significant differences are present for the yield and ultimate tensile stresses of all four SAC alloys. The changes in the Anand model parameters after severe aging (6 months at 100 °C) were significant. The measured experimental results have been used to illustrate the range of values possible for Anand parameters for the SACN05 alloys. The upper extreme was the water quenched limit, where the materials have extremely fine microstructures and high mechanical properties. The lower extreme was the severely aged limit, where the materials have extremely coarsened microstructures and highly degraded mechanical properties. While further degradations are certainly possible with even further aging, the limiting values found for a severely aged SAC alloy can be used by designers as a conservative set of constitutive parameters representing the lower end of the material properties for that alloy. After deriving the Anand parameters for each alloy and microstructure, the stress-strain curves have been calculated for various conditions, and excellent agreement was found between the predicted results and experimental stress-strain curves.

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