Engineering Commons^™

Residual Stress Effects On Fatigue Life Via The Stress Intensity Parameter, K, Jeffrey Lynn Roberts

Doctoral Dissertations

Residual stresses are known to have a significant effect on fatigue crack propagation and thus fatigue life. These effects have generally been quantified through an empirical approach, lending little help in the quantitative prediction of such effects. The weight function method has been used as a quantitative predictor, but its use neglects residual stress redistribution, treating the residual stress as a constant during crack growth. At least three different behaviors contribute to the redistribution of residual stress. First, the residual stress behind the crack tip is reduced to a negligible level as soon as the crack tip passes. Second, the …

Intelligent Fault Tolerant Control For Telerobotic System In Operational Space, Sewoong Kim

Doctoral Dissertations

Telerobotic systems combine conventional teleoperation with industrial automation techniques, such as control, vision, planning, etc, to improve work efficiency, and have been expanding their applications from hazardous and remote areas to unstructured industrial uses. Unstructured environments and uncertainties in task space require human-in-the loop control to ensure and supervise safe operation since present autonomous capabilities cannot handle the vast range of tasks and uncertainties. The inherent characteristics of telerobotic systems make operational faults more likely, and require autonomous fault detection, isolation (FDI) and recovery abilities since the nature of task space makes it difficult for human operators to detect and …

A Taxonomy Of The Adoption Of Lean Production Tools And Techniques, Bradley Mullins Greene

Doctoral Dissertations

The purpose of this study is to discover if the pattern of lean tool adoption for mature lean enterprises varies by type of value stream. The study empirically tests the effect of types of production processes, production volume, and order fulfillment strategies on lean production tool adoption in mature lean enterprises. The results of the study show that each of these factors does affect the pattern of tool adoption among mature lean enterprises.

Eleven different value stream profiles are identified in the study (ex. Discrete, Low Volume, Build-to-Order, value stream such as a commercial satellite producer). A binary logistical regression …

Preparation And Electrochemical Lithium Intercalation Performance Of Different Shaped Carbon Nanotube, Mao-Hui Chen, Zhen-Cai Huang, Guo-Tao Wu, Jin-Kua You, Zu-Geng Lin

Journal of Electrochemistry

In the present work, different shaped carbon nanotubes were produced by the general CVD and the template method at different temperature (600 ℃,700 ℃) with the reaction gas of acetylene. The morphology, structure and the electrochemical lithium intercalation performance were comparatively studied and characterized by TEM, HRTEM, SEM, XRD, Raman techniques and Charge/Discharge Test. It was found that the different preparation methods and temperatures all had an obvious effect on these properties of carbon nanotubes. In our samples, with the increase of preparation temperature, the degree of crystallinity decreased, and the reversible specific capacity increased respectively.

Mechanistic Study Of Oxidation Of Hypophosphite On Pt Electrodes By Sniftirs, Tai-Xiang Jiang, Hui-Huang Wu

Journal of Electrochemistry

The oxidation of hypophosphite on a polycrystalline platinum electrode was studied by SNIFTIRS and cyclic voltammetry, the in-situ IR spectra were analyzed as a function of Pt electrode potentials in the solution of 0.5 mol/L H 2SO 4+0.1 mol/L NaH 2PO 2. It was found that the dissociative adsorption of hypophosphite ions occurs on Pt surface, and the oxidation product is H 3PO 4, rather than H 2PO 3 - which was considered to produce on Ni electrodes, thereby a new insight into mechanism of hypophosphite oxidation on Pt in acidic media was provided.

Nano-Sized Cobalt-Based Oxides As Negative Electrode For Lithium-Ion Batteries, Feng Huang, Zheng-Yong Yuan, Yun-Hong Zhou, Ju-Tang Sun

Journal of Electrochemistry

Nanosized cobalt-based oxide (Co 3O 4, CoB 1.36 O 2.8 and CoB 0.5 Al 0.1 O 1.5 ) samples were prepared by rheological phase method and were tested as anodes in secondary lithium batteries. The cells were cycled between 0.01V and 3.00 V. The best electrochemical performance was obtained from the Li/Co 3O 4 cell, which retained 95% of its initial capacity (931 mAh/g) after 30 cycles. The doping of B, Al reduced the reversible capacity during the first discharge/charge cycle, and the quantity of reversible capacity reduced with B, A1 increasing. The modifying structures at difference charge and discharge …

Electrocatalytic Oxidation Of Formic Acid On Molybdate-Modified Platinum Electrode, Jun-Hua Du, Xue-Hui Xu, Hong Li, Hong-Yu Cheng, Wei-Shan Li

Journal of Electrochemistry

The electrochemical behavior of molybdates on a platinum electrode in H 2SO 4 solutions with different H 2SO 4 concentrations was studied by cyclic voltammetry and double chronoamperometry. Molybdates were reduced to adsorb hydrogen molybdenum bronzes on the platinum electrode in H 2SO 4 solutions during cathodically potential sweep. The hydrogen molybdenum bronzes were oxidized to different forms of hydrogen molybdenum bronzes with less hydrogen, depending on the H 2SO 4 concentration. Platinum electrode was modified by these hydrogen molybdenum bronzes. However, this modified electrode was not stable in H 2SO 4 solutions. The modified electrode was used to study …

Preparation And Performance Of Lifeo_2 Coated Nickel Oxide Cathode For Molten Carbonate Fuel Cells, Chun-Ming Wang, Fei Li, Ke-Ao Hu

Journal of Electrochemistry

A novel cathode for molten carbonate fuel cells was prepared by coating LiFeO 2 over the surface of porous NiO cathode by a simple combustion process. The analytical results of X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the LiFeO 2 coating on the surface of NiO particles consisted of nonometer-sized LiFeO 2 grains and sintered tightly with the NiO particles. The LiFeO 2 coating dramatically reduced the contacting area of NiO with the carbonate melts, thus the solubility of NiO in the carbonate melts was decreased. Meanwhile, …

Steady State Simulation Of Ysz Intermediate-Temperature Fuel Cell, Zi-Jing Lin, Ye Gu, Xiao-Hua Zhang

Journal of Electrochemistry

With a coupled 2D electrochemical and thermal modeling software, the characteristics of the steady state operation of the intermediate-temperature fuel cell with thin yttria-stabilized zirconia(YSZ) electrolyte was analyzed. The parameters of I-V equation were obtained from fitting the experiment results and the choice of grid points was determined by balancing the accuracy requirement and computational efficiency. The temperature fields at different operation circumstances such as flow designs, material choices for interconnect, were examined. The dependences of the output power and cell efficiency on the operating voltage at different temperatures were studied. Based upon the analysis of the temperature profile, it …

Effect Of Dissolved Oxygen On The Corrosion Behavior Of Coalesced Copper And Stainless Steel-206 In Acetic Solutions, Rong-Zong Hu, Xiong-Cao Zhao, Yu-Hua Weng, Chang-Jian Lin

Journal of Electrochemistry

Linear sweeping technique and dissolving oxygen sensor were used to study the effect of dissolved oxygen and relating factors on the corrosion behavior of coalesced copper and stainless steel-206 in acetic solutions. It was found: 1. The existing of dissolved oxygen is one of the important factors, which strongly influenced the corrosion behavior of coalesced copper and stainless steel-206 in acetic solution. 2. The existing of dissolved oxygen is benefitial to the preventing stainless steel-206 from corrosion in acetic solutions, but damage to the preventing coalesced copper from corrosion. 3. At the high temperature since the dissolved oxygen was escaping …

Improvement Of The Low Temperature Electrochemical Performance Of Ab_5-Type Hydrogen Storage Alloy, Hui Ye, Zhu Wu, Zhi-Lin Li, Hong Zhang

Journal of Electrochemistry

Optimizing the rare earth composition and doping with boron have been used to improve the low temperature performance of AB 5 hydrogen storage alloy.The results show that Ce-rich alloy with a proper amount of boron is suitable for Ni/MH battery with the lower-limit temperature down to 238 K under smaller current density (120 mA/g). The improvement of low temperature performance of hydrogen storage alloy is well consistent with its microstructure,thermodynamic and kinetic properties.

Review Of Mathematical Model For Proton Exchange Membrane Fuel Cell, Shan-Hai Ge, Bao-Lian Yi, Hua-Min Zhang

Journal of Electrochemistry

In the review with 49 references, the mathematical models for proton exchange membrane fuel cell (PEMFC) were summarized. The mechanistic model and empirical model were introduced. Transfer in the membrane, catalyst layer,diffusion layer and flow field of PEMFC were described. The importance of water and heat management was analyzed. The dimension, complexity and solving methods of the PEMFC model were discussed. The importance and validity to develop a model with time dimension are put forward.

Manufacture Of 1 Kw Molten Carbonate Fuel Cell Stack, Sheng Sui, Xin-Jian Zhu, Zheng-Yu Fan, Cao Guang-Yi And

Journal of Electrochemistry

A molten carbonate fuel cell stack with an active area of 240 mm×140 mm consisted of 30 cells.The gas feed system works via interior manifolds,and the stack placed in a couple of self-chest,coupled with a heater at the bottom and other fours surrounded,to keep uniformity of temperature.Under ambient pressure and 650 ℃,fed with hydrogen and air as anode and cathode gases respectively,the stack gave a current density of 150 mA/cm 2 at an average cell voltage of 0.7 V.The peak output of the stack was 1.06 kW during its performance of 300 h.

Lithium Intercalation Performance Of P-Doped Phenolic Resin Pyrolysis Carbon, Bao-Hua Li, Kai-Xi Li, Yonggen Lv, Chun-Xiang Lv, Dong Wu, Li-Cheng Ling

Journal of Electrochemistry

Phosphorus-doped phenolic resin carbon was prepared by low temperature(700 ℃)pyrolysis of thermoplastic phenolic resin containing different amounts of phosphorus pentoxide after curing. X-ray diffraction pattern and the constang-current charge-discharge properties of phenolic resin carbon were studied. The results showed that the phenolic resin carbon microstructure became out of order with increasing of content phosphorus pentoxide,otherwise,the first discharge reversible capacities increased firstly and then decreased. The first discharge reversible capacity of phenolic resin carbon containing 9wt% phosphorus pentoxide was 528 mA·h·g -1 which was higher than that of non-phosphorus doped phenolic resin carbon(230 mA·h·g -1 ) did.

Studies On The Inhibition Of Yki-05 Corrosion Inhibitor To 907a Steel In Different Immersed Environments, Hui Yu, Jian-Hua Wu, Hong-Ren Wang, Jian-Hua Qian, Guang-Zhang Chen

Journal of Electrochemistry

The inhibition of YKI-05 Corrosion inhibitor in different conditions was studied using potentiodynamic polarization technique. The resuled shown that (i) the inhibitor film layer was formed stably on the surface of 907A steel electrode when it was persistently immersed in static seawater and the inhibition efficiency reached 90% or so. The inhibition mechanism is negative catalytic effect. (ii)the inhibitior film layer was not stable when the electrode was periodically immersed in seawater and was destroyed more significantly with the increase of electrode exposing time. The film was only a covered layer on the surface of electrode and it retarded both …

Properties Of Domestic Natural Graphite Used For Li-Ion Batteries, Cui-Wei Du, Yu-Juan Zhao, Gang Zhang, Yin-Shun Wu, Qing-Guo Liu

Journal of Electrochemistry

The structure, physical characteristics and electrochemical properties of the natural graphite produced in Shandong province have been studied. The result of X-ray diffraction showed that the graphite consisted of hexagonal structure and rhombic structure (30% rhombic structure). It was fine crystal graphite. Used as a negative material of Lithium ion battery, the natural graphite showed excellent voltage and high energy capacity, but poor compatibility with electrolyte solution containing propylene carbonate (PC) for its own structure limitation.

Rectangular Bursting Energy Absorber, John D. Reid, John R. Rohde, Dean L. Sicking

Department of Mechanical and Materials Engineering: Faculty Publications

A bursting energy absorber System having an impact head, and energy absorption mechanism. The energy absorbing mechanism has a generally rectangular mandrel for rupturing cooperating thin-walled generally rectangular tubes in a controlled rupture to absorb impact forces for a colliding vehicle. A frame may be used to mount the System to a truck, trailer, guardrail, median barrier end treatment, or a crash cushion. Stress concetrators such as saw cuts or scoring may be incorporated into the absorption tubes to selectively control rupturing and energy dissipation. The mandrels may be tapered, rectangulary shaped with beveled edges to reduce frictional forces along …

In Situ Corrosion Studies On The Battleship Uss Arizona, John D. Makinson, James D. Carr, Matthew A. Russell, David L. Conlin, Larry E. Murphy

Department of Mechanical and Materials Engineering: Faculty Publications

U.S. National Park Service Submerged Resources Center archaeologists and University of Nebraska-Lincoln metallurgists are assessing hull corrosion by drilling through accumulated concretions and measuring pH and corrosion potentials. Concretion samples are being analyzed to determine the role of microbes in the corrosion process, identify chemical species, and measure electrical and physical properties. The lowest values of pH and E corr occur at the metal/concretion interface. Analysis suggests a variable corrosion rate supported by hydrogen discharge and/or oxygen reduction inside the concretion.

Electrochemical Techniques For Measuring Anti-Corrosion Behavior Of The Thin Corrosion Inhibitor Layer To The 907a Steel, Yong-Tao Zhao, Jian-Hua Wu, Fan-Cai Chen, Zhong-Ping Gao, Jia Wang, Chang-Jiu Zhao

Journal of Electrochemistry

The corrosion inhibiting behavior of 907A steel,which was covered with thin inhibitor layers in moist seawater atmosphere,was studied.The electrochemical measurements,including EIS method and the coulostatic method,were used to atmospheric corrosioed monitor(ACM)under thin inhibitor layers to determine its corrosion rate.The results shown that the application of electrochemical methods such as the coulostatic technique and EIS could readily detect the on going process of film formation. Hence, the rapid evaluation of the thin inhibitor layers for 907A steel might be possible.

Some Consideration For Lithium-Ion Cells' Safety, Guang-Xia Hu, Jing-Ying Xie

Journal of Electrochemistry

The safety is the most important problem for lithium ion cells, especially for large lithium ion cells. In this paper, some information about lithium ion cells' safety can be learned by discussing several aspects of lithium ion cells, such as, materials of lithium ion cell , manufacturing processes, using conditions and so on.

Study On Hydrogen Evolution Performance Of Nickel-Tin Electrode, Tian-Yi Chang, Bao-Hong Zhang, Wenbo Cong, Yao Luo

Journal of Electrochemistry

The cathode active material with low hydrogen evolution overvoltage was prepared by electroplating Ni_Sn alloy on the ferrous basic body.This kind of material can be applied in the diaphragm type of electrolytic tank to decrease cell voltage and save energy.On the condition according with cathode solution in the electrolytic tank(NaOH 120 g/L,NaCl 190 g/L,90 ℃, i =150 mA/cm 2),the overvoltage of hydrogen evolution was 88 mV.By the X_ray diffraction analysis,it was found that the structure of this kind of material was different from that of Ni_Sn alloy applied in traditional decoration.By using CV method to analyse the Fe electrode and …

Research Progress On Electrode Material In All-Vanadium Redox Battery, Hua Li, Shou-Wen Chang, Chuan-Wei Yan

Journal of Electrochemistry

An all_vanadium redox flow storage battery possesses many advantages over conventional storage batteries.The development statue of two types electrode materials(metal and compound type)is introduced in this article.

Initial Stages Of Copper Electrodeposition On Glassy Carbon Electrode, Ling Huang, Rui Zhang, Min Gu, Fang-Zu Yang, Shu-Kai Xu, Shao-Min Zhou

Journal of Electrochemistry

Initial stages of copper electrodeposition on glassy carbon electrode from acid sulphate solutions were studied using cyclic voltammetry and chronoamperometry.The electrolyte solution was a 0.05 mol.L -1 copper sulphate,1.4～1.8 mol.L -1 sulphuric acid containing 1 mg.L -1 2_mercaptobenzoimidazole,Results show that 2_mercaptobenzoimidazole produced an inhibition of the copper deposition,probably related to the adsorption,sulphuric acid promote copper electrodeposition.The initial deposition kinetics corresponded to a model including instantaneous nucleation and diffusion controlled growth.Addition of 2_mercaptobenzoimidazole and sulphuric acid did not change the initial nucleation of copper electrocrystallization,it increased the nucleation rate and the number density of nuclei at the surface.

Synthesis And Characterization Of Lini_(0.8-X)Al_Xco_(0.2)O_2 As Cathodes For Lithium-Ion Batteries, Jun Zhang, Zhong-Kao Jin, Qing-He Yang, Qing-Mei Song, Xiao-Hua Ma, Xiang-Fu Zong

Journal of Electrochemistry

Single_phase solid solution of LiNi 0.8- x Al x Co 0.2 O 2 (0≤ x <0.1)had been synthesized and characterized by X_ray diffraction(XRD) and scanning electron microscopy (SEM). Their electrochemical performance was examined by charge_discharge cycling.The LiNi 0.71 Al 0.09 Co 0.2 O 2 compound showed a discharge capacity of 152 mAh/g after 20 cycles that corresponds to 97.4% capacity retention. The beneficial effect of co_doping with Al and Co elements was corro_borated by slow scanning cyclic voltammograms(SSCV),electrochemical impedance spectrum(EIS)and differential scanning calorimetry(DSC) data on charged cathodes. These results show that the 2D_character of the crystal lattice was stabilized by co_doping with Al and Co, the phase transitions that occur during deintercalation or intercalation of Li_ions were significantly suppressed,and thermal stability in the charged state was also improved.

Ionic Conduction In Ba_(0.95)Ce_(0.9)Y_(0.1)O_(3-Α)Solid Oxide And Its Performance In Fuel Cell, Gui-Lin Ma, Ding-Xian Jia, Li-Gan Qiu, Hui Shi, Rong Chen

Journal of Electrochemistry

Using Ba 0.95 Ce 0.9 Y 0.1 O 3-α as a solid electrolyte and porous platinum as electrodes,hydrogen and oxygen concentration cells and hydrogen_air fuel cell were constructed,respectively.Electromotive forces(MEFs)of the gas concentration cells and I_V characteristics of the fuel cell were detdrmined in the temperature range of 600～1 000 ℃.The Ba 0.95 Ce 0.9 Y 0.1 O 3-α exhibited almost the pure protonic conduction under hydrogen gas,and a mixed conduction of oxide_ion and electron hole with oxide_ion transport number of 0.3～0.5 under oxygen gas.It exhibited a mixed conduction of proton and oxide_ion with the total ion transport number above 0.9 …

Electrochemical Properties Of Nitrate Immobilized On Gold Electrodes With 2-Aminoethanethiol Sams, Ya-Ru Song, Hong Wu, Hui-Bo Shao

Journal of Electrochemistry

Nitrate reductase (NR) and phospholipids were immobilized on gold electrodes with 2_aminoethanethio(AET) SAMs. After Au/AET/NR and Au/AET/NR/lipid were soaked in pH 7 phosphate buffers for days,a pair of pre_reversible peak appeared at around 0.202 V and 0.149 V,respsctively, irregularly grew with soaking time in blank buffer.The cathodic peak current(i pcl )of Au/AET/NR system had linear relationship with scan rate between 0.02 and 0.5 V.s -1 ,while i pcl was proportional to V 1/2 in Au/AET/NR/lipid system.The direct electron transfer of enzyme electrodes was strongly affected by pH.Compared with Au/AET,NR exhibited a higher electrochemical activity in Au/AET/lipid system.

Xrd Study On Highly Preferred Orientation Cu Electrodeposit, Min Gu, Fang-Zu Yang, Ling Huang, Shi-Bing Yao, Shao-Min Zhou

Journal of Electrochemistry

Copper electrodeposit was obtained in CuSO 4+H 2SO 4 electrolyte solution by electrodeposition and its structure was studied by XRD.The results showed that copper electoddeposits with the highly preferred orientations of (220)and (111) could be obtained at current density 4.0 A/dm 2 and 15.0 A/dm 2,respectively. The texture coefficient ( TC ) values were increased by thickness of Cu deposits. The thickness would be, to obtain Cu electrodeposit with(111) highly preferred orientation,about 7 times of that of (220) highly preferred orientation, which indicated that(220) face was easier to be remained than (111)face and that electrocrystallization of Cu at low current …

Optimum Of Catalyst Layers For Direct Methanol Fuel Cells, Jun Zhang, Lei Li, Li Xu, Yu-Xin Wan

Journal of Electrochemistry

The performances of membrane electrode assemblies (MEAs)with various Pt loading were compared.The amount of Nafion in a catalytic layer was optimized,and the effect of Nafion loading on the resistance of MEAs was investigated with ac impedance spectroscopy.For a MEA with both Pt 4 mg/cm 2 in the anode and the cathode,suitable Nafion loading was 21.4 wt% in the anode.With 21.4 wt% Nafion loading in the cathode,the Direct Methanol Fuel Cells(DMFC) showed the highest performance at high current density.While,the DMFC performances came down,as Nafion loading increasing,for ohm and concentration polarization.

Electrochemical Degradation Of Organic Wastewater By Three-Dimensional Electrode Reactor, Chun He, Tai-Cheng An, Ya Xiong, Dong Shu, Hui-Ling Hu, Xi-Hai Zhu

Journal of Electrochemistry

The electrochemical degradation of aniline was investigated using a novel electrochemical reactor, three_dimensional electrode reactor. The experimental results indicated that the reactor could efficiently remove aniline. The removal efficiency could be attributed to a combination of direct and indirect electrochemical reactions,that is,anodic oxidation and oxidation of electrogenerated H 2O 2 and hydroxyl radicals generated in electro_Fenton process. It was also observed that the removal efficiency was significantly dependent on applied voltage,Fe 2+ concentration,pH value and electrolysis time. In the experimental range they all have a positive effect on the removal efficiency except for pH value. Furthermore,hydroxyl radicals generated in electro_Fenton …

Modification Of Molybdenum Nitride Electrode For Supercapacitor(I)——The Effect Of Ammonium Vanadate On The Properties Of Molybdenum Nitride Electrode, Xue-Liang Li, Dao-Rong Luo, Hua-Lin Wang, Jian-Bo He, Yun-Guei Zhu

Journal of Electrochemistry

The effect of vanadium on the properties of the electrode of molybdenum nitride has been studied by using XRD?SEM and cyclic voltammetry.Modified molybdenum nitride was made as follow:films were coated by dipping titanium sheet in the solution containing different composition of molybdenum oxide,ammonium vanadate,ammonia,glycol and oxalic acid,and coated films are reacted with free ammonia.The results show that the specific capacitance of modified electrode was considerably increased and the operation voltage was broadened with the addition of ammonium vanadate in the dipping solution.The mechanism of these effects generated is the formation of new phase VOMoO 4 in the electrode of molybdenum …