Fatigue damage analysis based on energy parameters in reinforced polyamide

This article proposes an analysis method for the identification of the damage caused in a reinforced polyamide fatigue process through the evolution of the generated energy per cycle. Monotonous fatigue tests have been carried out at different stress levels using Polyamide 6 reinforced with short fibre glass tensile specimens. The loss of mechanical properties is measured using a damage parameter, defined as the variation in energy per cycle with respect to the initial conditions. Three clearly differentiated zones can be distinguished in the evolution of damage as a function of the energy per cycle. The first zone is one of deaccelerated rapid growth; in the second, the damage grows linearly, so that the damage growth speed can be determined as a function of the potential of variation of the stress applied; and finally, the third is a zone of accelerated growth of the damage until fracture.     

Analysis of the energy and damage evolution rule for sandstone based on the particle flow method

We use the particle flow code PFC3D to simulate the triaxial compression of sandstone under various radial stresses and loading strain rates to determine the triaxial stress-strain curves, crack propagation path, and contact forces to investigate the failure process of sandstone. We analyze the energy and damage evolution during triaxial compression. The results indicate that the tension and shear-induced cracks increase with the increase of radial stress under the same loading strain rate. Both normal and tangential contact forces exhibit strong anisotropy and increase with radial stress and strain rate. The normal contact force has an approximately symmetrical distribution with respect to the horizontal plane, whereas the tangential contact force has an approximately symmetrical distribution with respect to the axis. For the characteristics of the energy evolution, the boundary energy density, strain energy density, and dissipated energy density all increase linearly with the radial stress, and the boundary energy density increases at the fastest rate, followed by the strain energy density and dissipated energy density. In the post-peak stage the primary energy consumption is the dissipated energy. After that, in the remaining stage the strain energy decreases gradually. By analyzing the evolution of the damage variables in the prepeak area we observed that the damage variable followed an exponential relationship with the axial strain. When the loading strain rate is constant, the damage variable corresponding to the same strain value decreases with increase of radial stress. The results indicate that the increase in radial stress delays the damage acceleration. In contrast, the effect of the loading strain rate on the damage variable is small. The findings reveal the internal structural evolution of rocks during deformation and failure.

     

Degradation science: Mesoscopic evolution and temporal analytics of photovoltaic energy materials

Based on recent advances in nanoscience, data science and the availability of massive real-world datastreams, the mesoscopic evolution of mesoscopic energy materials can now be more fully studied. The temporal evolution is vastly complex in time and length scales and is fundamentally challenging to scientific understanding of degradation mechanisms and pathways responsible for energy materials evolution over lifetime. We propose a paradigm shift towards mesoscopic evolution modeling, based on physical and statistical models, that would integrate laboratory studies and real-world massive datastreams into a stress/mechanism/response framework with predictive capabilities. These epidemiological studies encompass the variability in properties that affect performance of material ensembles. Mesoscopic evolution modeling is shown to encompass the heterogeneity of these materials and systems, and enables the discrimination of the fast dynamics of their functional use and the slow and/or rare events of their degradation. We delineate paths forward for degradation science.     

The energy demand estimation for Turkey using differential evolution algorithm

The energy demand estimation commands great importance for both developing and developed countries in terms of the economy and country resources. In this study, the differential evolution algorithm (DE) was used to forecast the long-term energy demand in Turkey. In addition to being employed for solving regular optimization problems, DE is also a global, meta-heuristic algorithm that enables fast, reliable and operative stochastic searches based on population. Considering the correlation between the increase in certain economic indicators in Turkey and the increase of energy consumption, two equations were used—one applying the linear form and the other the quadratic form. Turkey’s long-term energy demand from 2012 to 2031 was estimated through the DE method in three different scenarios and in terms of the gross domestic product, import, export and population. To prove the success of the DE method in addressing the energy demand problem, the DE method was compared to other methods found in the literature. Results showed that the proposed DE method was more successful than the other methods. Furthermore, the future projections of energy demand obtained using the proposed method were compared to the indicators of energy demand estimated and observed by the Ministry of Energy and Natural Resources.     

On the role of kinetic energy during unstable propagation in a heterogeneous peeling test

We study the dynamic debonding of a one-dimensional inextensible film, subject to a monotonic loading and under the hypothesis that the toughness of the glue can take only two values. We first consider the case of a single defect of small length in the glue where the toughness is lower than in the remaining part. The dynamic solution is obtained in a closed form and we prove that it does not converge to the expected quasi-static one when the loading speed tends to zero. The gap is due to a kinetic energy which appears when the debonding propagates across the defect at a velocity which is of the same order as the sound velocity. The kinetic energy becomes negligible again only when the debonding has reached a critical distance beyond the defect. The case of many defects is then considered and solved using an exact numerical solution of the wave equation and the Griffith law of propagation. The numerical results highlight the effects of the time evolution of the kinetic energy which induce alternate phases of rapid and slow debonding, these oscillations depending essentially on the volume fraction of the highest toughness.     

Wavelet energy spectrum for time‐frequency localization of earthquake energy

The authors recently developed a method for time‐frequency signal analysis of earthquake records using Mexican hat wavelets. Ground motions in earthquakes are postulated as a sequence of simple penny‐shaped ruptures at different locations along a fault line and occurring at different times. In this article, a wavelet energy spectrum is proposed for time‐frequency localization of the earthquake input energy. The ground acceleration generated by a simple penny‐shaped rupture is used as the basis to form the mother wavelet. The symmetric Mexican hat wavelet is chosen as the mother wavelet. The spectrum is presented pictorially in a two‐dimensional, time‐frequency domain. The proposed wavelet energy spectrum can be used to observe the evolution of the frequency contents of earthquake energy over time and distance of the site from the epicenter in a more accurate manner than the traditional time series (accelerogram) or frequency domain (Fourier amplitude spectrum) representation. It can be viewed as a microscope for looking into the time‐frequency characteristics of earthquake acceleration records. The wavelet energy spectrum provides frequency evolution information to be used in the structural design process. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 133–140, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10038     

Kinetic energy and collapse of granular materials

This paper attempts to elucidate the mechanism of failure in rate-independent granular materials using the discrete element method. For this purpose, the dynamic response of dense and loose specimens has been simulated over drained and undrained loading paths. Then, this paper revisits the relation between the occurrence of an outburst in kinetic energy with the second-order works evolution. It is shown that the prediction of the evolution of the specimen’s kinetic energy over time, according to the second-order work approach, is satisfactorily verified by the discrete numerical simulations. In particular, the conflict between external and internal second-order works is shown to play a basic role during the failure process.     

Modeling the relaxed cohesive energy of metallic nanoclusters

A model is developed to calculate the cohesive energy of metallic nanoclusters with relaxed structure. It is found that the relaxed cohesive energy is higher than that of the un-relaxed one due to relaxation process decreasing the total energy. The relaxed nanoclusters in present model are more close to real ones, and the efficiency of the model is confirmed by molecular dynamics results on Cu nanoclusters.     

Hydrogen energy

The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.     

平板断面颤振过程中的能量输入特性研究

通过风洞试验研究了流线型较好的平板断面的颤振性能,基于流固松耦合的计算策略,应用CFD数值方法, 模拟了平板的颤振过程,并用相位平均的方法研究了颤振临界状态下模型尾部旋涡的演化规律, 分析表明模型尾部风嘴处呈直线排列的涡街的规律性摆动主导了结构振动直到模型振动发散。利用分块分析的思路研究颤振过程中气流能量在模型表面不同区域的输入特性,以及模型尾部旋涡的演化过程对模型表面气动力分布和能量输入特性的影响。分块分析的结果表明振动的模型通过迎风端风嘴从气流中吸收大量的能量, 且在一个完整的振动周期内气流输入到振动系统的能量不断增加,造成平板的颤振多为结构稳定性的突然丧失。     

Snow avalanche energy estimation from seismic signal analysis

A method to determine the dissipated seismic energy into the ground by a down going avalanche is presented. Evaluation of the seismic energy is useful for avalanche size classification, model validation, and for characterization and better understanding of the avalanche evolution as it propagates downhill along the changing slope. The method was applied to two different type avalanches that were released artificially on 2004/02/28 and 2005/04/15 at Ryggfonn (Norway) avalanche experimental site, operated by the Norwegian Geotechnical Institute (NGI). The analysed seismic data were recorded by the University of Barcelona seismic instruments consisting of two three-component wide-range seismometers located respectively, in the middle and on the side of the avalanche path. The energy determination requires a priori seismic characterization of the site and the knowledge of the avalanche front speed. In this paper a seismic characterization (surface wave phase velocity and amplitude attenuation factor) of the Ryggfonn site is presented. This characterization will serve for subsequent studies. We attribute the main source of seismic signals for the studied events to basal friction and ploughing occurring at the avalanche front and related to the changing slope in the propagation path, which causes high seismic energy dissipation. A comparative study of the evolution of the dissipated seismic energy with the energy generated by a simple sliding block model of constant mass was performed. The observed differences highlight the importance of ploughing and basal friction and the specific characteristics of the avalanches, such as their length and type. The difference between the calculated total dissipated seismic energy for the two similar size avalanches reflects their different flow type. As expected, the dry/mixed event dissipates a smaller amount of energy (∼ 1.2 MJ) than the dry/dense event (∼ 2.8 MJ).     

基于应变能耗散的复合材料层合板面内缺口强度分析CDM模型

基于伴随能量释放的渐进损伤演化思想,建立了复合材料层合板面内失效分析的连续介质损伤力学（CDM）分析模型,该模型包含损伤表征、损伤起始判定和损伤演化法则3个方面。基于CDM模型,通过引入损伤状态变量表征损伤,建立了平面应力状态下的材料损伤本构模型。采用损伤参量 f_E改写Hashin准则,以判定损伤的起始。损伤演化由特征长度内的应变能释放密度控制,建立了损伤状态变量关于等效应变的渐进损伤演化法则。模型中还同时考虑了面内剪切非线性和网格敏感性,并进行了对比分析。对含缺口的[90/0/±45]_3s和[（±θ）₄]_s 2类典型复合材料层合板的面内拉伸失效进行了分析,结果表明,本文中的模型能有效预测复合材料层合板的面内拉伸强度。     

Overcoming internal barriers to industrial energy efficiency through energy audit: a case study of a large manufacturing company in the home appliances industry

Energy efficiency plays a key role in reducing global energy consumption, especially in the industrial sector, with an indirect positive impact on the competitiveness of industrial firms. Although a cultural shift toward recognizing the strategic importance of energy efficient and environmental friendly solutions is diffusing among industrial companies, also pushed by the evolution of local and international regulatory frameworks, strong barriers hampering the adoption of energy efficiency measures (EEMs) still exist. These barriers, and in particular those linked to behavioral issues, may be overcome by the use of a well-designed energy audit methodology. However, how energy audit can help overcome behavioral barriers to industrial energy efficiency remains an under-researched topic in literature. This paper presents and discusses a novel methodology for energy audit developed and implemented by a large manufacturing company. The methodology is built around four phases, and it pays special emphasis to the initial step of the audit, where the strongest resistance to the implementation of EEMs is typically found due to a lack of awareness and commitment which hampers the identification of needs and opportunities associated with the adoption of EEMs. The proposed methodology has been able to overcome in practice the typical behavioral barriers that affect the implementation of EEMs in the manufacturing sector and has strong applicability in other firms and industries.     

LSE investigation of the thermal effect on band gap energy and thermodynamic parameters of BInGaAs/GaAs Single Quantum Well

In this paper, we report on the experimental and theoretical study of BInGaAs/GaAs Single Quantum Well elaborated by Metal Organic Chemical Vapor Deposition (MOCVD). We carried out the photoluminescence (PL) peak energy temperature-dependence over a temperature range of 10–300 K. It shows the S-shaped behavior as a result of a competition process between localized and delocalized states. We simulate the peak evolution by the empirical model and modified models. The first one is limited at high PL temperature. For the second one, a correction due to the thermal redistribution based on the Localized State Ensemble model (LSE). The new fit gives a good agreement between theoretical and experimental data in the entire temperature range. Furthermore, we have investigated an approximate analytical expressions and interpretation for the entropy and enthalpy of formation of electron-hole pairs in quaternary BInGaAs/GaAs SQW.     

A study on rate-type constitutive equations and the existence of a free energy function

Summary Demanding that rate-type constitutive equations in solid mechanics has to be in accord with the thermodynamical requirement of the existence of a free energy function, the restrictions to be imposed on stress evolution equations in terms of theLie (Oldroyd) as well as theZaremba-Jaumann objective rate of theCauchy stress tensor are discussed. Explicit forms of generalized constitutive equations are given according to which the tangent modulus relating the objective rate of the stress tensor to the strain velocity tensor is no more constant but assumed to depend on the stress state itself. The use of theKirchhoff stress tensor is handled as well. It is shown that theZaremba-Jaumann derivative necessarily reduces to theLie one. As an application the case of simple shear is discussed where a monotonously increasing stress-strain relation is obtained. The paper closes with remarks concerning elasto-plasticity.     

Energy policy shifts towards sustainable energy future for Malaysia

As a developing country, Malaysia’s prosperity and welfare depends heavily on having access to reliable and secure supplies of energy. As a result, the country’s future energy requirements have become a policy priority in recent years. Energy is essential for human life, and a secure and accessible supply of energy becomes important for the modern societies. Fossil fuels such as coal, oil, and natural gas are currently the world’s primary energy sources and continue to provide energy source to the world. These energy sources have depleted in reserves in recent years and they can also cause irreparably damage to the environment such as global warming and climate change. These environmental concerns can be addressed, to some extent, through more sustainable solutions such as the use of renewable energy resources. In Malaysia, the economic and environmental impacts of fossil fuels use have become hard to ignore. The government has introduced and implemented policy measures to address concerns surrounding the use of fossil fuels and to promote energy efficiency and renewable energy use. In this paper, we review the historical evolution of Malaysian energy policies and initiatives designed to secure diverse energy sources and avoid over-reliance on fossil fuels. In recent years, Malaysia has been catching up with global call to shift to renewable energy use and is now putting a focus on renewable energy in its future energy mix. The paper also discusses challenges and concerns over the future of sustainable energy of the country.     

Superconducting magnetic energy storage

After a brief review of the reasons for and forms of secondary energy storage and of the elements and history of inductive or magnetic storage, we discuss the four distinct areas in which superconducting magnetic energy storage can be applied. Differences in energy transfer times place different requirements on the storage coil, on the switch or transfer element, and on the energy losses in the superconductor. We report on designs and experiments in one of these areas with 2 to 300 kJ units, and on the analysis and plans for an installation that is to provide 250 MJ of plasma compression energy for the theta-pinch controlled thermonuclear fusion test reactor. We point out those elements of inductive storage that need further development before a theta-pinch fusion reactor can become economically competitive. Finally, we compare the size and costs of the energy storage components of these systems with similar and with larger inductive storage systems that are to interact reversibly with electric utility networks.     

Studying energy evolution in the discharge chamber of a multichamber lightning protection system

We present experimental data on the distribution of energy deposition along the discharge chamber of a multichamber lightning protection system at the initial stage of a discharge process modeling a lightning current pulse with 10 kA amplitude. The multichamber system comprised serially connected gas-discharge chambers. The breakdown between electrodes situated on the bottom of a channel in each chamber induces the formation of a shock wave. Subsequent energy evolution during the development of discharge proceeds in the entire volume bounded by the shock wave.     

A quantum stochastic equation describing evolution of the transverse energy of a channeled particle

A stochastic equation describing evolution of the nth quantum energy level of a relativistic electron (positron) moving in planar channels of a crystal is derived using the condition of conservation of the transverse motion energy comprising a sum of the energies of interaction with atomic electrons and crystal lattice nuclei.     

Energy distribution in the squeezing of particles in concentrated suspension

In the present work, the squeeze flow geometry is used to investigate the properties of concentrated suspensions. The suspensions consist on hard glass spherical particles dispersed in a viscoplastic fluid. With such a material, following the solid volume fraction, the material rheological behaviour ranges from purely viscoplastic fluid to granular media. During the squeezing action, the material structure evolves with energy variation due to particle displacement and interaction. The goal of our study is to identify the effect of energy evolution on the flow properties of suspensions and detect granular contact evolution. The proposed study consists on an energy approach based on the analysis of the global squeeze force and sample height with time. The squeeze force is decomposed in a combination of an average force component and a fluctuating one. This local fluctuating component is investigated from Fourier analysis as a function of solid volume fraction and compression velocity. Results show the evolution of the energy distribution during compression and allow the flow regime modification to be evaluated.