The Experts below are selected from a list of 37788 Experts worldwide ranked by ideXlab platform
Zili Wang - One of the best experts on this subject based on the ideXlab platform.
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probabilistic fatigue crack growth analysis under stationary random loading with spike loads
IEEE Access, 2018Co-Authors: Shan Jiang, Wei Zhang, Zili WangAbstract:The in-service loading condition of many engineering structures is generally composed of a stationary random loading caused by the mechanical vibration, and the spike loads due to occasional events, such as the sudden shock and accidental turbulence. In this paper, a physical-based method is proposed to evaluate the reliability of structure subjected to the stationary random fatigue loading superimposed by occasional spike loads. First, since the interaction effects of stationary random loading are approximately stable, the realistic random loading can be transferred to an equivalent constant amplitude loading. This equivalent transformation method can avoid the complicated Cycle-by-Cycle Calculation. This approach is derived from the two-parameter fatigue crack growth model, in which the driving parameters of the fatigue crack growth are the stress intensity factor of peak load and the stress intensity factor range. Second, the spike loads lead to the high nonlinearity of interaction effect, which can be accounted for by the plasticity. Therefore, the generalized Willenborg model is employed to calculate the fatigue crack propagation under the spike loading effects. Then, the extensive experimental data of aluminum alloys are used to validate the proposed method, in which the indeterminacies of material parameter and spike loads are considered. It is observed that all the testing data are contained within the prediction 90% confidence interval bounds. In addition, a Monte Carlo simulation example of fatigue life reliability assessment under stationary random loading with spike loads is performed. Two scenarios of different spike load distributions are discussed. In the first scenario, the spike loads are applied at a fixed time interval, while in the other scenario, the spike loads occur with varying time period. The results indicate that the proposed approach can appropriately evaluate the fatigue reliability of the structure under stationary random loading with spike loads.
Serina Ahlgren - One of the best experts on this subject based on the ideXlab platform.
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ethanol production in biorefineries using lignocellulosic feedstock ghg performance energy balance and implications of life Cycle Calculation methodology
Journal of Cleaner Production, 2014Co-Authors: Hanna Karlsson, Pal Borjesson, Peranders Hansson, Serina AhlgrenAbstract:Abstract Co-production of high-value biobased products in biorefineries is a promising option for optimized utilization of biomass. Lignocellulosic materials such as agricultural and forest residues have been identified as attractive alternative feedstocks because of their high availability and low resource demand. This study assessed the greenhouse gas (GHG) performance and energy balance of ethanol co-production with biogas and electricity in biorefineries using straw and forest residues. Two Calculation methods were used: Method I (ISO), which applied the international standard for life Cycle assessment, and Method II, which applied the EU Renewable Energy Directive (RED) methodology. These methods differed in allocation procedure, functional unit and system boundaries. Analysis of the importance of significant methodological choices and critical parameters showed that the results varied depending on Calculation method, with co-product handling and the inclusion of upstream impacts from residue harvesting explaining most of the differences. Important life Cycle steps were process inputs in terms of enzymes and changes in soil organic carbon content due to removal of residues. Ethanol produced from forest residues generally gave lower GHG emissions than straw-based ethanol. The GHG savings for both feedstocks were 51–84% relative to fossil fuel. Omission of upstream impacts from residue recovery in agriculture and forestry in the RED method means that it risks overlooking important environmental effects of residue reuse. Furthermore, the default allocation procedure used in the RED method (energy allocation) may need revision for biorefineries where multiple products with different characteristics are co-produced.
Shan Jiang - One of the best experts on this subject based on the ideXlab platform.
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probabilistic fatigue crack growth analysis under stationary random loading with spike loads
IEEE Access, 2018Co-Authors: Shan Jiang, Wei Zhang, Zili WangAbstract:The in-service loading condition of many engineering structures is generally composed of a stationary random loading caused by the mechanical vibration, and the spike loads due to occasional events, such as the sudden shock and accidental turbulence. In this paper, a physical-based method is proposed to evaluate the reliability of structure subjected to the stationary random fatigue loading superimposed by occasional spike loads. First, since the interaction effects of stationary random loading are approximately stable, the realistic random loading can be transferred to an equivalent constant amplitude loading. This equivalent transformation method can avoid the complicated Cycle-by-Cycle Calculation. This approach is derived from the two-parameter fatigue crack growth model, in which the driving parameters of the fatigue crack growth are the stress intensity factor of peak load and the stress intensity factor range. Second, the spike loads lead to the high nonlinearity of interaction effect, which can be accounted for by the plasticity. Therefore, the generalized Willenborg model is employed to calculate the fatigue crack propagation under the spike loading effects. Then, the extensive experimental data of aluminum alloys are used to validate the proposed method, in which the indeterminacies of material parameter and spike loads are considered. It is observed that all the testing data are contained within the prediction 90% confidence interval bounds. In addition, a Monte Carlo simulation example of fatigue life reliability assessment under stationary random loading with spike loads is performed. Two scenarios of different spike load distributions are discussed. In the first scenario, the spike loads are applied at a fixed time interval, while in the other scenario, the spike loads occur with varying time period. The results indicate that the proposed approach can appropriately evaluate the fatigue reliability of the structure under stationary random loading with spike loads.
Hanna Karlsson - One of the best experts on this subject based on the ideXlab platform.
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ethanol production in biorefineries using lignocellulosic feedstock ghg performance energy balance and implications of life Cycle Calculation methodology
Journal of Cleaner Production, 2014Co-Authors: Hanna Karlsson, Pal Borjesson, Peranders Hansson, Serina AhlgrenAbstract:Abstract Co-production of high-value biobased products in biorefineries is a promising option for optimized utilization of biomass. Lignocellulosic materials such as agricultural and forest residues have been identified as attractive alternative feedstocks because of their high availability and low resource demand. This study assessed the greenhouse gas (GHG) performance and energy balance of ethanol co-production with biogas and electricity in biorefineries using straw and forest residues. Two Calculation methods were used: Method I (ISO), which applied the international standard for life Cycle assessment, and Method II, which applied the EU Renewable Energy Directive (RED) methodology. These methods differed in allocation procedure, functional unit and system boundaries. Analysis of the importance of significant methodological choices and critical parameters showed that the results varied depending on Calculation method, with co-product handling and the inclusion of upstream impacts from residue harvesting explaining most of the differences. Important life Cycle steps were process inputs in terms of enzymes and changes in soil organic carbon content due to removal of residues. Ethanol produced from forest residues generally gave lower GHG emissions than straw-based ethanol. The GHG savings for both feedstocks were 51–84% relative to fossil fuel. Omission of upstream impacts from residue recovery in agriculture and forestry in the RED method means that it risks overlooking important environmental effects of residue reuse. Furthermore, the default allocation procedure used in the RED method (energy allocation) may need revision for biorefineries where multiple products with different characteristics are co-produced.
Vicente Bermudez - One of the best experts on this subject based on the ideXlab platform.
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sensitivity of diesel engine thermodynamic Cycle Calculation to measurement errors and estimated parameters
Applied Thermal Engineering, 2000Co-Authors: Magin Lapuerta, Octavio Armas, Vicente BermudezAbstract:The use of thermodynamic models for the Calculation of the heat release law from the experimental in-cylinder pressure signal has been a common practice as a way to study the combustion process of internal combustion engines. However, the results of this procedure depend mainly on two factors: the validity of the assumed hypothesis and the quality of the measurement of the experimental parameters (both mean and instantaneous ones) used as input data. In this work a sensitivity study of a thermodynamic diagnostic model is presented, with the objective of evaluating the influence of errors in the measuring techniques or in the estimation of parameters on the main results, such as mean gas temperature, heat release and rate of heat release. In order to eliminate the effect of the uncertainty associated with the combustion process itself, the study focused on motored engine conditions. Otherwise, the effect of the inadequacy of the assumed hypothesis was eliminated by using as input in the diagnostic thermodynamic model the results from a predictive thermodynamic model with the same hypothesis as the diagnostic one, instead of an experimental pressure signal.
