Light-weight design of vehicle roof panel for stiffness and crash analyses

Vehicle crashworthiness refers to proper designing of the vehicle structure to reduce the risk of death and injury during the vehicle accidents. In the recent years, due to the enforcement of new EU normative, the interest of all the car manufacturers in producing lightweight vehicles is progressively increased as the combustion engine optimization has already used most of the improvements they had and the residual ones are becoming more and more difficult and costly. Based on this auto industry’s interest, lightweight materials such as composite have absorbed lots of attention due to their superior characteristic of high stiffness to weight ratio. In this thesis, efforts have been made to present a broad research on the light-weight design of vehicle roof panel for stiffness and crash analyses. The first part of the analyses belongs to the vehicle chassis static and dynamic stiffness analyses via the finite element code with the specific focus on substituting the steel roof panel with the lightweight materials of aluminum and composites. The structural response of the vehicle roof panel, made of different solutions, in full frontal crash with respect to NHTSA standard has been investigated at the second step. The effects of increasing the vehicle roof panel thickness at the both steps have been tested and compared for different solutions. At the third step an innovative design solution for the vehicle roof structure has been developed and tested in rollover crash analysis. In order to perform this task, After determining the performance of tubes made of steel, composite and composite foam-filled solutions under the three points bending test and proving the efficiency of composite-foam design; the same idea is implemented on the vehicle roof panel during the roof quasi-static crush test. Besides the composite solutions, the sandwich design consists of composite face-sheets and foam core are tested in the roof crushing test based on the FMVSS 216 standard. After assessment of the sandwich roof panel in crushing test, the geometrical optimization of the foam core is implemented to determine the optimum design with respect to vehicle strength-to-weight ratio and mass reduction percentages. Besides different foam core configurations that have been tested, the final optimization have been implemented using the foam core with various densities and also the optimum face-sheets thickness has been determined. At the last chapter, challenges of vehicle composite roof panel assembly have been discussed. Results in the case of stiffness and frontal crash analyses at step one and step two proved that although the composite solutions have lower energy absorption capacity in comparison with the steel one, they have large contribution to the weight reduction of the vehicle roof panel and still stays in the acceptable range of structural performance. Using the new design of sandwich solutions in roof crushing test have proved that while theses designs have reduced the vehicle roof panel weight by 68%, they have the same structural performance as the steel solution and could be considered as interesting solutions. Evaluating the behavior of the vehicle roof structure made of different solutions with various configurations under distinct analyses of stiffness and crashworthiness will help to improve the vehicle roof structure performance

Highly Efficient Method for Solvent-Free Synthesis of Diarylmethane and Triarylmethane from Benzylic Alcohols Using P2O5/Al2O3 or P2O5/SiO2 at Room Temperature

A highly efficient procedure for the synthesis of triarylmethane and diarylmethane via benzylation of aromatic hydrocarbons from benzyl alcohols using supported P2O5 on SiO2 and/or Al2O3 under solvent-free conditions is described. Excellent yields of triarylmethane and diarylmethane were obtained using P2O5-SiO2 (50% W/W) and/or P2O5-Al2O3 (50% W/W) at room temperature. The reusability of both supported P2O5 on SiO2 and Al2O3 were examined. Both supported reagents show favorable activities in first and second runs, however, a decline in reactivity was observed in following attempts. The reaction is scalable to >0.03 mole amounts.Keywords: Diarylmethane, triarylmethane, aromatic alcohol, P2O5, silica gel, alumin

Effect of cutting parameters on cutting temperature of TiAL6V4 alloy

A Finite Element Modeling (FEM) and Simulation was Used to Investigate the Effect of Tool Rake Angle, Cutting Speed and Feed Rate on the Cutting Temperature of Tial6v4 Alloy. the Purpose of this Study was to Find Proper Cutting Parameters for Machining of Titanium Alloy where Cutting Temperature was Lowest. A FEM Based on ABAQUS Software which Involves Jonson-Cook Material Model and Coulomb’s Friction Law was Applied to Simulate an Orthogonal Cutting Process. in this Simulation Work, a Range of Tool Rake Angle from 0° to 10°, a Range of Cutting Speed from 300 m/min to 600 m/min and a Range of Feed Rate between 0.1 Rev/mm and 0.25 Rev/mm were Investigated. the Simulation Results Indicated that Increase in Rake Angle Reduces Cutting Temperature while Increasing Cutting Speed and Feed Rate Increase the Cutting Temperature

Validation and Psychometric Properties of the Anger Management Skills Test

Background: More awareness of anger in different social situations can help us to manage it efficiently. Unfortunately, the questionnaire measuring these differences hasn't been validated in Iran. The primary purpose of this study was to investigate the psychometric properties of the Persian version of the Springer anger control skills test. Method: The statistical population of this study was 200 college students consisted of 180 undergraduate, 15 M.Sc, and 5 Ph.D. students at Shiraz University. A random sampling method was used in this research. Springer anger control skills test was completed to assess the validity and reliability, Cronbach's alpha and internal validity, and exploratory factor analysis was used.  Results: Results indicated the reliability of 0.62 and a significant value (0.001).  KMO value was 0.45. Also, a significant difference was found between males and females in anger‏ management and allocated to sociality and non-family relationships (0.001). Simultaneously, there was no significant difference between females and males in other variables and subscales of anger control. Conclusion: Findings illustrate that this scale is reliable and valid and can be used in a clinical context. The difference between male and female in controlling anger in social situations can be related to Cultural influences and having more education; also, this sample only represents the population who had a higher level of education in comparison to others. Besides, they have received more educational training and necessary skills to cope with impulses and social encounters more appropriately

The effect of Short-term Plyometric Training Program on Sprint, Strength, Power and Agility Performance in non-athletic Men

Plyometric training to increase physical ability and leads to increase of muscles power. The aim of the study was to assess the effects of short term plyometric training program on sprint, strength, and power and agility performance in non-athletic men. In this research, 40 non-athletic men (year 18-23) participated. The participants were chosen randomly and they participated in four tests strength (Swedish swimming, sit-ups), power (vertical jumps, Horizontal jumps), agility (Illinois Agility Test, T Agility Test) and 30 meters speed. The participants were divided into two groups, i.e. experimental (plyometric training) and control group (did not perform PT training). They participated in the training for 5 weeks and each week 1 session and each session 90 minutes. The results of the study revealed that in experimental groups, significant increase observed in Swedish swimming, horizontal jumps test and also significant decrease observed in 30 meters speed and test in comparison with control group (p-value of the respectively 0.001, 0.02, 0.00). The differences were significant not observed of agility test in comparison with control group. Conclusion: Therefore, it seems that plyometric training have been effective on the physical preparation indices and can improve the non athletes’ performance

Finite element analysis of aluminum-Kevlar/Epoxy pressure vessel

In this present work, the composite pressure vessel type three has been investigated by finite element method (FEM). The aluminum pressure vessel reinforced with Kevlar/Epoxy (Aramid 149) was analyzed under internal pressure to predict the ultimate failure pressure of the vessel. Also the optimum winding angle which provides the highest strength for the vessel was determined by applying Tsai-Wu and Tsai-Hill failure theories. The asymmetric fiber orientation for six different winding angles was utilized to reinforce the aluminum vessel. The commercial code ABAQUS/CAE was employed to analyze the composite vessel. Results obtained from the simulation were in good consistency with the analytical and the experimental outcomes

Effect of cutting parameters on tool-chip interface temperature in an orthogonal turning process

The aim of this paper is to investigate the effect of cutting speed and uncut chip thickness on cutting performance. A Finite Element Method (FEM) based on the ABAQUS explicit software which involves Johnson-Cook material mode and Coulombs friction law was used to simulate of High Speed Machining (HSM) of AISI 1045 steel. In this simulation work, feed rate ranging from 0.05 mm/rev to 0.13 mm/rev and cutting speed ranging from 200 m/min to 600 m/min at three different cutting speeds were investigated. From the simulation results it was observed that increasing feed rate and cutting speed lead to increase temperature and stress distribution at tool/chip interface. The results obtained from this study are highly essential to predict machining induced residual stresses and thermo-mechanical deformation related properties on the machined surface

Modeling and Characterization of Lithium Iron Phosphate Battery Electrodes

A detailed understanding of lithiation/delithiation dynamics of battery active materials is crucial both for optimizing the existing technologies and for developing new materials. Among all, LiFePO4 (LFP) has been subject to intensive fundamental research due to its intriguing phase-transformation dynamics which, unexpectedly, yields an outstanding rate capability and a long cycle life for electrodes made of this insertion material. In this thesis mathematical models are used as cheap and simple tools to investigate the electrochemical performance of LFP electrodes. The thesis begins with the investigation of the solid-state transport (bulk effects) and electronic conductivity (surface effects) of LFP by means of variable solid-state diffusivity (VSSD) and resistive-reactant (RR) models, respectively. Both models are effectively validated against experimental galvanostatic discharge data over a wide range of applied currents. However, a very small solid-state diffusion coefficient (~〖10〗^(-19) "m" ^2 "s" ^(-1)) is required for both models to fit the experimental data. VSSD model features a particle-size distribution (PSD) which is estimated via model-experiment comparison. The fitted PSD, which is a geometric property and essentially invariable, requires to be different at different rates for the model to match experimental data; it is shifted towards smaller particles in order to accurately predict the electrode performance during galvanostatic discharge at higher applied currents. A contact-resistance distribution (CRD) replaces the PSD in the RR model. The fitted CRD turns out to be extremely broad spanning from ~1" to " ~〖10〗^2 "Ω" "m" ^2. Next, following recent observations of ultra fast lithiation/delithiation of LFP, a simple mesoscopic model is developed which, in contrast to the first part of this research, completely disregards solid-state diffusion limitations. Instead, the model accounts for the inherent inhomogeneity of physico-chemical properties and bi-stable nature of phase-change insertion materials such as LFP with no consideration of any geometric detail of the active material. The entire active material domain is discretized into meso-scale units featuring basic thermodynamic (non-monotonic equilibrium potential as a function of composition) and kinetic (insertion/de-insertion resistance) properties. With only these two factors incorporated, the model is able to simultaneously explain a number of unique features associated with lithium iron phosphate electrochemical performance including the quasi-static potential hysteresis, high rate capability, cycle-path dependence, mismatch in electrode polarization during GITT when compared with continuous cycling at the same current, bell-shaped current response in PITT and the most recently observed memory effect. Detailed analysis of the electrode dynamics suggests that a necessary condition for the memory effect to appear in an LFP electrode is the existence of a non-zero residual capacity at the onset of memory-release charging which may originate either from a non-zero initial SOC or from an imbalanced writing cycle. A memory effect should therefore not be observed in an electrode that has been preconditioned at extremely low currents (i.e., zero initial SOC) and has undergone an extremely slow memory-writing cycle (i.e., approaching a balanced cycle). In the next step, the mesoscopic model developed at the unit level is incorporated into porous-electrode theory and validated by comparing the simulation results with experimental data from continuous and intermittent galvanostatic discharge of a commercial LiFePO_4 electrode at various operating conditions. A bimodal lognormal resistance distribution is assumed to account for disparity of insertion dynamics among elementary units. Good agreement between the model and experimental data confirms the fidelity of the model. Investigation of three different GITT experiments suggests that the slow evolution of electrode polarization during each current pulse and the subsequent relaxation period is contributed by the inter-unit rather than intra-unit Li transport in LiFePO_4 electrodes. As such, GITT experiments once formulated for the determination of diffusion coefficient of inserted species in solid-solution systems may also be used to estimate the single-unit equilibrium potential (i.e., thermodynamic properties) as well as the dynamic properties (e.g., resistance distribution) of phase-change insertion materials. Further analysis of the GITT experiments suggest that, depending on the overall depth-of-discharge of the electrode and the incremental depth-of-discharge of each GITT pulse, the solid-solution capacity available in the Li-rich end-member may be able to accommodate Li insertion entirely without the need for active (closed-circuit) phase transformation. Instead, redistribution of Li among units during relaxation equilibrates the solid-solution composition by transforming a few Li-poor units to Li-rich ones. Despite rigorous research in the literature, this thesis presents the first attempt to quantitatively explain the above-mentioned irregularities simultaneously using a single unifying model and pinpoint the dominant contributing factors under various operating conditions. A realistic account of porous-electrode effects in the experimental validation of the mesoscopic model requires accurate estimation of the electrolyte transport properties. In addition to the modeling of phase-change electrodes, this thesis work presents a novel four-electrode-cell method to determine transport properties and the thermodynamic factor of concentrated binary electrolytes. The cell consists of two reference electrodes (i.e., potential sensors) in addition to the working and counter electrodes. The sensors measure the closed-circuit as well as open-circuit potential in response to an input current across the working and counter electrodes. The new method requires the application of only a single galvanostatic polarization pulse and appropriate concentration-cell experiments. By fitting a suitable model to the data obtained from these experiments, the three independent transport properties of a concentrated binary electrolyte, namely, ionic conductivity, diffusion coefficient and transference number as well as the thermodynamic factor can be determined. In particular, the measurement of the closed-circuit potential using this cell provides a simpler and essentially more accurate means to estimate the transference number than the conventional semi-infinite diffusion method