Adaptive Grey Wolf Optimization Technique for Stock Index Price Prediction on Recurring Neural Network Variants

In this paper, we propose a Long short-term memory (LSTM) and Adaptive Grey Wolf Optimization (GWO)--based hybrid model for predicting the stock prices of the Major Indian stock indices, i.e., Sensex. The LSTM is an advanced neural network that handles uncertain, nonlinear, and sequential data. The challenges are its weight and bias optimization. The classical backpropagation has issues of dangling on local minima or overfitting the dataset. Thus, we propose a GWO-based hybrid approach to evolve the weights and biases of the LSTM and the dense layers. We have made the GWO more robust by introducing an approach to improve the best possible solution by using the optimal ranking of the wolves. The proposed model combines the GWO with Adam Optimizer to train the LSTM. Apart from the LSTM, we have also implemented the Adaptive GWO on other variants of Recurring Neural Networks (RNN) like LSTM, Bi-Directional LSTM, Gated Recurrent Units (GRU), and Bi-Directional GRU and computed the corresponding results. The Adaptive GWO here evolves the initial weights and biases of the above-discussed neural networks. In this research, we have also compared the forecasting efficiency of our proposed work with a particle-warm optimization (PSO) based hybrid LSTM model, simple Grey-wolf Optimization (GWO), and Adaptive PSO. According to the experimental findings, the suggested model has effectively used the best initial weights, and its results are the best overall

Overview of LVDS and HVDS with Distribution Losses

The distribution system is a part of the electronic energy system by giving power to individual homes. Highly standardized LV distribution cables build a network in large towns and cities via link devices. For each (fused) distribution leaving a transformer, certain interconnections are disconnected, resulting in a branching wide radial distribution system. A more expense tapering circumferential supply chain, in which thinner connections are added as the distances from the a transformer increases, is typically utilized in less population centers. This study discussed transmission systems . for example as well as several types of promotional systems, including such high power and high power logistics operation

Severe Esophagitis and Chemical Pneumonitis as a Consequence of Dilute Benzalkonium Chloride Ingestion: A Case Report

Background: Benzalkonium chloride (BAC) has been used as an active ingredient in a wide variety of compounds such as surface disinfectants, floor cleaners, pharmaceutical products and sanitizers. Solutions containing <10% concentration of BACs typically do not cause serious injury. As the available data regarding acute BAC toxicity is limited, we report a case of dilute benzalkonium chloride ingestion resulting in bilateral chemical pneumonitis and significant gastrointestinal injury requiring mechanical ventilatory support. The Case: A 42-year-old male presented with chief complaints of nausea, vomiting and excessive amount of blood- mixed oral secretions after accidental ingestion of approximately 100ml of BAC solution (<10%). Later he developed respiratory distress with falling oxygen saturation for which he was intubated and mechanical ventilatory support was administered. Computed tomography (CT) chest was suggestive of bilateral chemical pneumonitis and upper gastrointestinal (GI) endoscopy revealed diffuse esophageal ulcerations. The patient was managed with intravenous fluids, corticosteroids, proton pump inhibitor, empiric antibiotics and total parenteral nutrition. Conclusion: The present case report emphasizes that dilute BAC compounds can cause severe respiratory and gastrointestinal injuries. Immediate and aggressive medical treatment is crucial for improving patient outcomes and reducing the complication rates

Comparison of Dentoskeletal Changes, Esthetic, and Functional Efficacy of Conventional and Novel Esthetic Twin Block Appliances among Class II Growing Patients: A Pilot Study

Objective:A twin block appliance used for correction of skeletal Class II malocclusion suffers from undesirable dental effects and bulkiness. To overcome these limitations and the need for more esthetic appearance of this appliance, an esthetic twin block was designed and used in patients. This study aimed to compare dentoskeletal changes and esthetic and functional efficacy in patients treated with conventional and newly designed esthetic twin block (CTB and ETB) appliances using cephalometric measurements and a questionnaire.Methods:A pilot study with a 2-arm parallel-randomized double-blind clinical trial was conducted on 24 patients (20 males, 4 females) in the age group of 11-13 years. Subjects were treated with CTB (group 1 [G1]: n=12; mean age=11.67±0.49 years) and ETB (group 2 [G2]: n=12; mean age=11.75±0.62 years) appliances. A modified Pancherz analysis was performed to evaluate skeletal and dental changes. The esthetic and functional efficacy was evaluated by a questionnaire using Likert scale. Wilcoxon and Mann-Whitney U tests were employed for intra and intergroup comparisons respectively (p<0.05).Results:In G1, a significant increase in lower incisor inclination was observed (p<0.05) whereas it was insignificant in G2. The changes were predominantly skeletal in G2 whereas they were both skeletal and dental in G1. ETB was found to be esthetically and functionally acceptable in all the patients while CTB patients were esthetically conscious, lacked confidence and had discomfort and difficulty in eating, chewing and speaking.Conclusion:ETB had greater skeletal effects with a reduced tendency of lower incisor proclination, was esthetically acceptable, and functionally more comfortable than the CTB

On mechanical characterization and multi-scale modeling of Lithium-ion batteries

Over the last few decades, rechargeable lithium-ion batteries have been extensively used in portable instruments due to their high energy density and low self-discharge rate. Recently, lithium-ion batteries have emerged as the most promising candidate for electric vehicles and stationary energy storage. However, the maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Lithium-ion batteries are complex systems to understand, and various processes and their interactions are responsible for the degradation over time. The mechanical integrity and stability of the electrode layers inside the battery highly influence the battery performance, which makes it a necessity to characterize the mechanical behavior of electrode active layers for mesoscopic and macroscopic level modeling. In papers 1 and 2, the macroscopic mechanical behavior of active layers in the electrodes is investigated using U-shape bending tests. The active layers are porous and a different tensile and compressive behavior is captured by performing tests on single side coated dry specimens. The experiments reveal that the active layer is stiffer in compression as compared to tension. The compressive stiffness increases with bending strain whereas the tensile stiffness is almost independent of the bending strain. A very low value of modulus of the active layer (1-5 GPa) is measured in comparison to the metal foils (70-110 GPa) and the active particles (50-200 GPa) which shows that the electrode properties are governed majorly by the binders present in the active layers.  The time-dependent and hysteresis effects are also captured by the method which circumvents the flaws of many other test methods presented in the literature.   In paper 3, we present a multiscale homogenization method that couples mechanics and electrochemistry at the particle, electrode, and battery scales. The active materials of lithium-ion battery electrodes exhibit volume change during lithium intercalation or deintercalation. A lithium concentration gradient develops inside particles, as well as inside the active layer. The developed stress due to deformations further affects solid diffusion.  We utilized models that have already been developed to couple particle and electrode layer levels. The mechanical coupling between the electrode and the battery level is achieved by homogenization of the layered battery using three-dimensional laminate theory.  By application of the model, we demonstrate that the stresses on all considered scales can be predicted from the homogenized model. It is furthermore demonstrated that the effects of external battery loadings like battery stacks, casings, and external pressure can be captured by the model. The model can also capture the effect of various electrochemical cycling rates and mechanical parameters like layer thicknesses, stiffnesses, and swelling properties. The presented multi-scale model is fast, accurate and the efficiency of the method is demonstrated by comparisons to detailed finite element computations where each layer is individually modeled.

Experimental Characterization of Electrodes and Multi-Scale Modeling of Swelling Induced Stresses in Lithium-ion Batteries

Over the last few decades, rechargeable lithium-ion batteries have been extensively used in portable instruments due to their high energy density and low self-discharge rate. Recently, lithium-ion batteries have emerged as the most promising candidate for electric vehicles and stationary energy storage. However, the maximum energy that lithium-ion batteries store decreases as they are used because of various irreversible degradation mechanisms. The mechanical properties of the electrode layers inside the battery highly influence the battery's performance. There is, however, a fundamental lack of understanding of the mechanical properties of electrodes and how they evolve during electrochemical cycling, which makes it a necessity to characterize their mechanical behavior for mesoscopic and macroscopic level modeling. Lithium-ion batteries are complex systems to understand, and various processes and their interactions make battery modeling challenging. This thesis contributes to understanding the mechanical behavior of electrodes in lithium-ion batteries and provides methods for the design and efficient modeling of battery systems.         In Paper A and Paper B, the macroscopic mechanical behavior of active layers in the electrodes is investigated using U-shape bending tests. The active layers are porous and a different tensile and compressive behavior is captured by performing tests on single side coated dry electrodes. The experiments reveal that the active layer is stiffer in compression as compared to tension. The compressive stiffness increases with bending strain whereas the tensile stiffness is almost independent of the bending strain. A very low value of modulus of the active layer (1-5 GPa) is measured in comparison to the metal foils (70-110 GPa) and the active particles (50-200 GPa) which shows that the electrode properties are governed majorly by the binders present in the active layers. The time-dependent and hysteresis effects are also captured by the method which circumvents the flaws of many other test methods presented in the literature.           Paper C focuses on characterizing the layer-level evolution of mechanical and electrochemical properties of a Ni-rich positive electrode during early-stage electrochemical cycling, along with complementary cross-section analyses to understand the relationship between macroscopic and microscopic changes. Macroscopic constitutive properties were measured using the U-shaped bending test method developed in papers A and B, which revealed that the compressive modulus was primarily influenced by the porous structure and binder properties. It decreased notably with electrolyte wetting but increased with cycling and aging. Electrochemical impedance spectra showed an increase in local resistance near the particle-electrolyte interface with early-stage aging, which was likely due to secondary particle grain separation and carbon black redistribution. Cross-section analyses reveal significant variations in particle properties between pristine and cycled samples, including particle swelling, compression of the binder phase, and increased particle contact, contributing to the rise in the elastic modulus of the porous layer during cycling.         In Paper D and Paper E, we present a multiscale homogenization method that couples mechanics and electrochemistry at the particle, electrode, and battery scales. The active materials of lithium-ion battery electrodes exhibit volume change during lithium intercalation or deintercalation. A lithium concentration gradient develops inside particles, as well as inside the active layer. The developed stress due to deformations further affects solid diffusion.  We utilized models that have already been developed to couple particle and electrode layer levels. Electric vehicle battery packs consist of numerous battery modules, each of which includes multiple battery cells composed of electrode, separator, and current collector layers. A finite element model capable of capturing stresses at the layer level would need to be very large to account for all the details. The mechanical coupling between the electrode and the battery level is achieved by homogenization of the layered battery using three-dimensional laminate theory, which greatly reduces the number of finite elements required for stress simulations in batteries. After obtaining a homogenized solution, layer-level stresses can be determined in a post-processing step. The method accurately predicts stresses on various scales and captures the effects of external battery loadings, cycling rates, and mechanical parameters. The efficiency of the method is demonstrated by comparing it to detailed finite element computations. The simulations indicate that layer-wise stresses, such as pressure, can be predicted as functions of position and time, providing insights into the inhomogeneous aging state of the battery.Under de senaste decennierna har uppladdningsbara litiumjonbatterier använts flitigt i bärbara instrument på grund av deras höga energitäthet och låga självurladdningshastighet. Just nu ses en kraftig ökning av eldrivna fordon. Den maximala energin som litiumjonbatterier kan lagra minskar dock med tiden på grund av olika irreversibla nedbrytningsmekanismer. De mekaniska egenskaperna hos elektrodskikten inuti batteriet påverkar här i hög grad batteriets prestanda. Det finns dock en bristande kunskap om elektrodernas mekaniska egenskaper och hur de utvecklas under elektrokemisk cykling. Behovet av nya experimentella och teoretiska metoder för karaktärisering på mikro- och makroskalor är stort. Litiumjonbatterier är komplexa system att förstå, och olika processer och deras interaktioner gör batterimodellering utmanande. Denna avhandling bidrar till en ökad förståelse av elektrodernas mekaniska beteende i litiumjonbatterier. Även metoder för design och effektiv modellering av batterisystem presenteras.         I de bilagda rapporterna A och B undersöks det makroskopiska mekaniska beteendet hos aktiva skikt i elektroder med hjälp av böjprovning med U-formade provstavar. De aktiva skikten är porösa och skillnader i drag- och tryckbeteende fångas upp genom att utföra tester på ensidigt belagda torra elektroder. Experimenten visar att det aktiva lagret är styvare i kompression jämfört med dragning. Kompressionstyvheten ökar med töjningsnivån medan dragstyvheten är nästan oberoende av töjning. De uppmätta E-modulerna för det aktiva skiktet (1-5 GPa ) är låga i jämförelse med metallfolierna (70-110 GPa ) och de aktiva partiklarna (50-200 GPa ) vilket visar att elektrodegenskaperna huvudsakligen styrs av bindemedlen som finns i de aktiva skikten. Tidsberoende effekter och hystereser fångas också upp av den använda mätmetoden som även kringgår de begränsningar som alternativa testmetoder uppvisar.          I rapport C karakteriseras utvecklingen av mekaniska och elektrokemiska egenskaper som funktion av antalet laddningscykler i en positiv elektrod. För att bättre förstå orsaken till förändringar av egenskaper genomfördes parallella mikroskopiundersökningar. Makroskopiska konstitutiva egenskaper uppmättes med den böjprovningsmetod som utvecklades i rapporterna A och B. Resultaten visar att kompressionsmodulen främst påverkas av den porösa strukturen och bindemedlets egenskaper. Styvheten minskade märkbart efter vätning med elektrodvätska och därpå följande torkning. Med ökande antal laddningscykler ökade styvheten åter i jämförelse med denna referensnivå. Elektrokemiska impedansspektra visade på en ökning av lokal resistans nära partikel-elektrolytgränsytorna vid tidig åldring, vilket sannolikt berodde på sekundär kornseparation i elektrodpartiklarna samt omfördelning av kolpartiklar i bindemedlet. Mikroskopianalyser visade på betydande variationer i partikelegenskaper mellan virgina och cykliska prover. Förändringar i partikelstorlek och form kunde konstateras vilka kunde korreleras till utvecklingen av kompressionsstyvhet i den porösa elektroden.          I rapporterna D och E presenteras en flerskalig homogeniseringsmetod som kopplar mekanik och elektrokemi på partikel-, elektrod- och batteriskala. De aktiva materialen i litiumjonbatteriets elektroder uppvisar volymförändringar vid laddning och urladdning. En gradient i koncentrationen av litium utvecklas såväl inuti partiklar som inom elektrodskiktet under laddning eller urladdning. Dessa gradienter leder till mekaniska spänningar som i sin tur påverkar diffusionen av litium. För modellering av diffusion och därtill hörande litiumkoncentrationer applicerades är väl etablerad modell från litteraturen. Batteripaket för elfordon består av ett stort antal batterimoduler, som var och en innehåller flera battericeller vilka i sin tur består av många elektrod-, separator- och metallskikt. En finit elementmodell som kan fånga spänningar på skiktnivåer skulle behöva vara mycket stor för att ta hänsyn till alla variationer på små skalor. I rapporterna D och E utvecklas i stället en modell för homogenisering av det skiktade batteriet med hjälp av tredimensionell laminatteori. På detta sätt kan antalet frihetsgrader och därigenom beräkningskostnad för en finit elementmodell kraftigt reduceras. Baserat på en homogeniserad lösning kan spänningar på skiktnivå bestämmas i efterhand. Metoden förutsäger spänningar på olika skalor och fångar effekterna av laddningshastighet, extern mekanisk belastning och de ingående skiktens mekaniska egenskaper. Metodens effektivitet demonstreras genom att jämföra den med detaljerade finita elementberäkningar. Simuleringarna indikerar att skiktspänningar, såsom tryck, kan förutsägas som funktioner av position och tid, vilket ger insikter om åldrande i olika deler av ett batteri.QC 230620</p

On mechanical characterization and multi-scale modeling of Lithium-ion batteries

Over the last few decades, rechargeable lithium-ion batteries have been extensively used in portable instruments due to their high energy density and low self-discharge rate. Recently, lithium-ion batteries have emerged as the most promising candidate for electric vehicles and stationary energy storage. However, the maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Lithium-ion batteries are complex systems to understand, and various processes and their interactions are responsible for the degradation over time. The mechanical integrity and stability of the electrode layers inside the battery highly influence the battery performance, which makes it a necessity to characterize the mechanical behavior of electrode active layers for mesoscopic and macroscopic level modeling. In papers 1 and 2, the macroscopic mechanical behavior of active layers in the electrodes is investigated using U-shape bending tests. The active layers are porous and a different tensile and compressive behavior is captured by performing tests on single side coated dry specimens. The experiments reveal that the active layer is stiffer in compression as compared to tension. The compressive stiffness increases with bending strain whereas the tensile stiffness is almost independent of the bending strain. A very low value of modulus of the active layer (1-5 GPa) is measured in comparison to the metal foils (70-110 GPa) and the active particles (50-200 GPa) which shows that the electrode properties are governed majorly by the binders present in the active layers.  The time-dependent and hysteresis effects are also captured by the method which circumvents the flaws of many other test methods presented in the literature.   In paper 3, we present a multiscale homogenization method that couples mechanics and electrochemistry at the particle, electrode, and battery scales. The active materials of lithium-ion battery electrodes exhibit volume change during lithium intercalation or deintercalation. A lithium concentration gradient develops inside particles, as well as inside the active layer. The developed stress due to deformations further affects solid diffusion.  We utilized models that have already been developed to couple particle and electrode layer levels. The mechanical coupling between the electrode and the battery level is achieved by homogenization of the layered battery using three-dimensional laminate theory.  By application of the model, we demonstrate that the stresses on all considered scales can be predicted from the homogenized model. It is furthermore demonstrated that the effects of external battery loadings like battery stacks, casings, and external pressure can be captured by the model. The model can also capture the effect of various electrochemical cycling rates and mechanical parameters like layer thicknesses, stiffnesses, and swelling properties. The presented multi-scale model is fast, accurate and the efficiency of the method is demonstrated by comparisons to detailed finite element computations where each layer is individually modeled.

Experimental Characterization of Electrodes and Multi-Scale Modeling of Swelling Induced Stresses in Lithium-ion Batteries

Over the last few decades, rechargeable lithium-ion batteries have been extensively used in portable instruments due to their high energy density and low self-discharge rate. Recently, lithium-ion batteries have emerged as the most promising candidate for electric vehicles and stationary energy storage. However, the maximum energy that lithium-ion batteries store decreases as they are used because of various irreversible degradation mechanisms. The mechanical properties of the electrode layers inside the battery highly influence the battery's performance. There is, however, a fundamental lack of understanding of the mechanical properties of electrodes and how they evolve during electrochemical cycling, which makes it a necessity to characterize their mechanical behavior for mesoscopic and macroscopic level modeling. Lithium-ion batteries are complex systems to understand, and various processes and their interactions make battery modeling challenging. This thesis contributes to understanding the mechanical behavior of electrodes in lithium-ion batteries and provides methods for the design and efficient modeling of battery systems.         In Paper A and Paper B, the macroscopic mechanical behavior of active layers in the electrodes is investigated using U-shape bending tests. The active layers are porous and a different tensile and compressive behavior is captured by performing tests on single side coated dry electrodes. The experiments reveal that the active layer is stiffer in compression as compared to tension. The compressive stiffness increases with bending strain whereas the tensile stiffness is almost independent of the bending strain. A very low value of modulus of the active layer (1-5 GPa) is measured in comparison to the metal foils (70-110 GPa) and the active particles (50-200 GPa) which shows that the electrode properties are governed majorly by the binders present in the active layers. The time-dependent and hysteresis effects are also captured by the method which circumvents the flaws of many other test methods presented in the literature.           Paper C focuses on characterizing the layer-level evolution of mechanical and electrochemical properties of a Ni-rich positive electrode during early-stage electrochemical cycling, along with complementary cross-section analyses to understand the relationship between macroscopic and microscopic changes. Macroscopic constitutive properties were measured using the U-shaped bending test method developed in papers A and B, which revealed that the compressive modulus was primarily influenced by the porous structure and binder properties. It decreased notably with electrolyte wetting but increased with cycling and aging. Electrochemical impedance spectra showed an increase in local resistance near the particle-electrolyte interface with early-stage aging, which was likely due to secondary particle grain separation and carbon black redistribution. Cross-section analyses reveal significant variations in particle properties between pristine and cycled samples, including particle swelling, compression of the binder phase, and increased particle contact, contributing to the rise in the elastic modulus of the porous layer during cycling.         In Paper D and Paper E, we present a multiscale homogenization method that couples mechanics and electrochemistry at the particle, electrode, and battery scales. The active materials of lithium-ion battery electrodes exhibit volume change during lithium intercalation or deintercalation. A lithium concentration gradient develops inside particles, as well as inside the active layer. The developed stress due to deformations further affects solid diffusion.  We utilized models that have already been developed to couple particle and electrode layer levels. Electric vehicle battery packs consist of numerous battery modules, each of which includes multiple battery cells composed of electrode, separator, and current collector layers. A finite element model capable of capturing stresses at the layer level would need to be very large to account for all the details. The mechanical coupling between the electrode and the battery level is achieved by homogenization of the layered battery using three-dimensional laminate theory, which greatly reduces the number of finite elements required for stress simulations in batteries. After obtaining a homogenized solution, layer-level stresses can be determined in a post-processing step. The method accurately predicts stresses on various scales and captures the effects of external battery loadings, cycling rates, and mechanical parameters. The efficiency of the method is demonstrated by comparing it to detailed finite element computations. The simulations indicate that layer-wise stresses, such as pressure, can be predicted as functions of position and time, providing insights into the inhomogeneous aging state of the battery.Under de senaste decennierna har uppladdningsbara litiumjonbatterier använts flitigt i bärbara instrument på grund av deras höga energitäthet och låga självurladdningshastighet. Just nu ses en kraftig ökning av eldrivna fordon. Den maximala energin som litiumjonbatterier kan lagra minskar dock med tiden på grund av olika irreversibla nedbrytningsmekanismer. De mekaniska egenskaperna hos elektrodskikten inuti batteriet påverkar här i hög grad batteriets prestanda. Det finns dock en bristande kunskap om elektrodernas mekaniska egenskaper och hur de utvecklas under elektrokemisk cykling. Behovet av nya experimentella och teoretiska metoder för karaktärisering på mikro- och makroskalor är stort. Litiumjonbatterier är komplexa system att förstå, och olika processer och deras interaktioner gör batterimodellering utmanande. Denna avhandling bidrar till en ökad förståelse av elektrodernas mekaniska beteende i litiumjonbatterier. Även metoder för design och effektiv modellering av batterisystem presenteras.         I de bilagda rapporterna A och B undersöks det makroskopiska mekaniska beteendet hos aktiva skikt i elektroder med hjälp av böjprovning med U-formade provstavar. De aktiva skikten är porösa och skillnader i drag- och tryckbeteende fångas upp genom att utföra tester på ensidigt belagda torra elektroder. Experimenten visar att det aktiva lagret är styvare i kompression jämfört med dragning. Kompressionstyvheten ökar med töjningsnivån medan dragstyvheten är nästan oberoende av töjning. De uppmätta E-modulerna för det aktiva skiktet (1-5 GPa ) är låga i jämförelse med metallfolierna (70-110 GPa ) och de aktiva partiklarna (50-200 GPa ) vilket visar att elektrodegenskaperna huvudsakligen styrs av bindemedlen som finns i de aktiva skikten. Tidsberoende effekter och hystereser fångas också upp av den använda mätmetoden som även kringgår de begränsningar som alternativa testmetoder uppvisar.          I rapport C karakteriseras utvecklingen av mekaniska och elektrokemiska egenskaper som funktion av antalet laddningscykler i en positiv elektrod. För att bättre förstå orsaken till förändringar av egenskaper genomfördes parallella mikroskopiundersökningar. Makroskopiska konstitutiva egenskaper uppmättes med den böjprovningsmetod som utvecklades i rapporterna A och B. Resultaten visar att kompressionsmodulen främst påverkas av den porösa strukturen och bindemedlets egenskaper. Styvheten minskade märkbart efter vätning med elektrodvätska och därpå följande torkning. Med ökande antal laddningscykler ökade styvheten åter i jämförelse med denna referensnivå. Elektrokemiska impedansspektra visade på en ökning av lokal resistans nära partikel-elektrolytgränsytorna vid tidig åldring, vilket sannolikt berodde på sekundär kornseparation i elektrodpartiklarna samt omfördelning av kolpartiklar i bindemedlet. Mikroskopianalyser visade på betydande variationer i partikelegenskaper mellan virgina och cykliska prover. Förändringar i partikelstorlek och form kunde konstateras vilka kunde korreleras till utvecklingen av kompressionsstyvhet i den porösa elektroden.          I rapporterna D och E presenteras en flerskalig homogeniseringsmetod som kopplar mekanik och elektrokemi på partikel-, elektrod- och batteriskala. De aktiva materialen i litiumjonbatteriets elektroder uppvisar volymförändringar vid laddning och urladdning. En gradient i koncentrationen av litium utvecklas såväl inuti partiklar som inom elektrodskiktet under laddning eller urladdning. Dessa gradienter leder till mekaniska spänningar som i sin tur påverkar diffusionen av litium. För modellering av diffusion och därtill hörande litiumkoncentrationer applicerades är väl etablerad modell från litteraturen. Batteripaket för elfordon består av ett stort antal batterimoduler, som var och en innehåller flera battericeller vilka i sin tur består av många elektrod-, separator- och metallskikt. En finit elementmodell som kan fånga spänningar på skiktnivåer skulle behöva vara mycket stor för att ta hänsyn till alla variationer på små skalor. I rapporterna D och E utvecklas i stället en modell för homogenisering av det skiktade batteriet med hjälp av tredimensionell laminatteori. På detta sätt kan antalet frihetsgrader och därigenom beräkningskostnad för en finit elementmodell kraftigt reduceras. Baserat på en homogeniserad lösning kan spänningar på skiktnivå bestämmas i efterhand. Metoden förutsäger spänningar på olika skalor och fångar effekterna av laddningshastighet, extern mekanisk belastning och de ingående skiktens mekaniska egenskaper. Metodens effektivitet demonstreras genom att jämföra den med detaljerade finita elementberäkningar. Simuleringarna indikerar att skiktspänningar, såsom tryck, kan förutsägas som funktioner av position och tid, vilket ger insikter om åldrande i olika deler av ett batteri.QC 230620</p

Early assessment of composite structures : Framework to analyse the potential of fibre reinforced composites in a structure subjected to multiple load case

To meet the need of lightweight chassis in the near future, a technological step of introducing anisotropic materials like Carbon Fibre Reinforced Plastics (CFRP) in structural parts of cars is a possible way ahead. Though there are commercially available tools to find suitability of Fibre Reinforced Plastics (FRPs) and their orientations, they depend on numerical optimization and complexity increases with the size of the model. Nevertheless, the user has a very limited control of intermediate steps. To understand the type of material system that can be used in different regions for a lightweight chassis, especially during the initial concept phase, a more simplified, yet reliable tool is desirable.The thesis aims to provide a framework for determining fibre orientations according to the most-ideal loading path to achieve maximum advantage from FRP-materials. This has been achieved by developing algorithms to find best-fit material orientations analytically, which uses principal stresses and their orientations in a finite element originating from multiple load cases. This thesis takes inspiration from the Durst criteria (2008) which upon implementation provides information on how individual elements must be modelled in a component subjected to multiple load cases. This analysis pre-evaluates the potential of FRP-suitable parts. Few modifications have been made to the existing formulations by the authors which have been explained in relevant sections.The study has been extended to develop additional MATLAB subroutines which finds the type of laminate design (uni-directional, bi-axial or quasi-isotropic) that is suitable for individual elements.Several test cases have been run to check the validity of the developed algorithm. Finally, the algorithm has been implemented on a Body-In-White subjected to two load cases. The thesis gives an idea of how to divide the structure into sub-components along with the local fibre directions based on the fibre orientations and an appropriate laminate design based on classical laminate theory