bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Particle Impact Erosion within Electric Submersible Pump Based on Fluent
Authors: Mei Si Jie , Wang Zun Ce , Chen Si , Lu Feng Xia , He Jin Gang
Published: March 2014

In the same well water flooding process, solid particles contained in the fluid often result in the impeller submersible electric pump to erosion wear. We use Fluent software to establish the model of flow field,and use numerical simulation method to analyze the erosion wear. We use the erosion theory to calculate the erosion wear rate,and verify the correctness by the contrast between the results of numerical simulation and actual value.
The Summary Research on the Noise of High-Speed Traction Elevators
Authors: Wang Xiao Wei , Yu Yan Jie , Zhang Rui Jun , Wang Sheng Chun , Tian Yan
Published: March 2014

With the increasing of speed of elevator, noise has been becomming an important factor of the ride comfort. Mechanical noise and aerodynamic noise are the main types of elevator noise. The research of mechanical noise are mainly focused on vibration characteristics of the structure and the friction which is on elevator cars, counterweight and guide rails as well as wire ropes. The research of aerodynamic noise are mainly included three aspects: the influences of aerodynamic noise resulted in the shape of elevator cars, the research of noise reduction technology on different noise bands and the research of elevator system dynamics model’s optimal design. Based on the analysis of high-speed elevator noise research, we investigate the existing problems and trends on high-speed traction elevator noise.
Development of Multifunctional Nanomaterials in Phototherapy
Authors: Huang Y.N. , Liu F.R. , Zhu Z.
Published: March 2014

Phototherapy as a promising therapy has attracted great attention due to its significant effect on tumor cells with low damage of normal tissue simultaneously, the crucial technology of which is preparation of multifunctional photo-thermal nanomaterials. In this paper , the current research status of the main nanomaterials were reviewed including gold-based nanomaterials and carbon-based nanomaterials for their preparation methods, properties, absorption of near-infrared light and disadvantages. Moreover, the problems and challenges to be solved in this field were also analyzed.
Movement Simulation of NC Lathe Machine Based on EON Studio
Authors: Khlil Alhadi , Li Guo Qin , Luo Lu Feng , Song Xi Ping
Published: March 2014

The NC lathe machine has many moving parts all with a special functions. To operate the machine you should understand the names and their movements. The Movement Simulation of NC Lathe Machine is developed by virtual reality development platform of Eon Studio. A 3D model of NC Lathe machine is built through 3D realistic modeling tools of Solidworks software, and transformed into Eon Studio. Collision object node is used to avoid the overlapping between objects during simulation.
Research and Control for Inertia of Automobile Steering Test System
Authors: Lu Xiang , Luo Yan Jie , Mai Yun Fei
Published: March 2014

This paper is focused on the study of pressure shocks caused by inertia of automobile steering gear. The system transfer function mathematical model was established. In order to meet the system technical specification, a feed-forward compensator was designed to eliminate the interference force; a fuzzy PID controller was devised to accelerate responding speed, eliminating oscillation and improve the dynamic performance. The simulation results indicate that the negative effect of inertia can be well overcome and passive loading system works steadily and satisfies technical requirements.
Development of Piezo Driven Motion Amplified Stage
Authors: Kim Jung Hyun
Published: March 2014

This paper presents a novel piezo driven motion stage employing multiple motion levers allowing for an amplification ratio that exceeds 60x enabled by a newly contrived cross hinge structure. Measurements of the motion stage were made using an optical microscope. The motion stage was incorporated into a visually served close loop motion control scheme and experimental results prove that the feedback system is capable of 20nm nanostepping.
Experimental Investigation and Numerical Simulation for High Temperature Air Source Heat Pump with New Mixed-Refrigerant
Authors: Yang Jun , Ding Guo Zhong , Zhang Xiao Yan , Shu Shui Ming , Tan Jun Yi
Published: March 2014

Studies on air source heat pump (ASHP) transfer to high temperature, the performance of air source heat pump greatly depends on the ambient temperature. Aimed at the prototype aeroplane of high temperature air source heat pump, New mixed-refrigerant M-R was adopted, and a simulation was made under a standard conditions with Aspen Plus software. And the results was validated by the experiments. The results showed that a well trend between theory and experiments. In addition, experimental investigation of high temperature air source heat pump were carried out at different conditions. The COP was 1.15, the discharge temperature of compressor was 108.6°Cwhen the outlet water temperature was 85.1°C. The heating capacity is superior. This achieved a leading level at home and abroad.
Simulation Study on the Combined Harvester with Four Tracked Feet Passing through Ditch Based on RecurDyn
Authors: Hu Zhi Dong , Du Shuo Ran , Yang Jia Bao
Published: March 2014

Combine harvester is the most widely used modern forest machinery; tracked and wheeled logging machine is the common stumper. But each type of logging machine has its shortcomings and therefore it is need to develop a combination of tracked and wheeled logging machine. This logging mechanism takes the form of tracked feet while preserving the flexibility of wheeled logging machine, and also it has the obstacle-crossing ability of tracked harvester. The most important indicator of the performance of this new logging machine is its trafficability in soft and uneven road. This thesis uses multi-body dynamic simulation analysis software RecurDyn to build up the 3D model of such four feet tracked logging machine, and analyzes its dynamical process when meeting ditch. Eventually the logging mechanism performance is got. The conclusions provide foundation for design of combined harvester with four tracked feet.
A Simple Optical Coupling Method for Water-Jet Guided Laser Machining System
Authors: Li Meng , Zhang Wen Wu , Zhang Xi Ping , Zhang Tian Run
Published: March 2014

In this paper a simple optical coupling method for water-jet guided laser machining system is introduced and its characteristics are studied. By the introduced method the output spot pattern behind the water-jet was observed instead of the laser focus. In order to acquire the pattern a piece of glass was used to block the water-jet but let the laser through, and a light screen was placed behind the glass in a certain distance to display the pattern image. Since the image scale could be adjusted by changing the distance between the glass and the light screen, the CCD magnifying system was no longer needed. It is found that the pattern varied while the coupling condition changed. Only in small chance the pattern was a tiny spot but more commonly it was in a ring-like shape which could be easily recognized. So such ring-like patterns could be signals for optical coupling guidance. Furthermore a series of study to analyze the correlation between the pattern shape and coupling parameters was carried out by simulation with the help of Zemax.
Machining Evaluation of High-Speed Milling for Thin-Wall Machining of Al7075-T651
Authors: Koo Joon Young , Kim Pyeong Ho , Cho Moon Ho , Kim Hyuk , Oh Jeong Kyu , Kim Jeong Suk
Published: March 2014

This paper presents finite element method (FEM) and experimental analysis on high-speed milling for thin-wall machining of Al7075-T651. Changes in cutting forces, temperature, and chip morphology according to cutting conditions are analyzed using FEM. Results of machining experiments are analyzed in terms of cutting forces and surface integrity such as surface roughness and surface condition. Variables of cutting conditions are feed per tooth, spindle speed, and axial depth of cut. Cutting conditions to improve surface integrity were investigated by analysis on cutting forces and surface roughness, and machined surface condition.
Effect of Changing the Position of Tool Point on the Moving Platform on the Kinematics of a 3RRR Planar Parallel Manipulator
Authors: Abo-Shanab Roshdy Foaad
Published: March 2014

This paper discusses the effect of changing the location of the tool point, on the mobile platform, on the kinematics of a planar parallel manipulator. It is shown that changing the position of the end-effector greatly changes the shape and the area of the reachable workspace. Global conditioning index and the structural length index are used as global indices to find the optimum location of the end-effector on the mobile platform of a parallel manipulator. The results show that the performance criteria are varying in opposite directions, the dexterity is decreasing when the workspace area is increasing. Hence, the problem of optimal design becomes a problem of determination an acceptable compromise between the two requirements.
The results of the present work show that the position of the end-effector on the mobile platform should be considered while optimizing the performance of a parallel manipulator.
Development of Post Processor for Dual-Spindle Turning Center
Authors: Cai An Jiang , Ma Fang Rong , Ding Ming Wei , Guo Shi Hong
Published: March 2014

This paper takes dual-spindle turning center as the research object, researching on the key technology of the efficient processing and integration application, the special post processor for dual-spindle turning center was developed based on the IMSPOST, the technical problems of dual-spindle structural system and post processing algorithm for varies of processing modes were solved, the NC processing programs were generated effectively and correctly. Production application showed that: the development of post processor for dual-spindle turning center improves the automation level and quality of NC programming effectively, brings the processing capability of dual-spindle turning center full play, and provides technical support for the manufacturing of complex mechanical products.
Synthesis of Planar Four-Bar for Generating Path with Prescribed Arc
Authors: Chung Wen Yeuan
Published: March 2014

This paper demonstrates the synthesis of planar four-bar for path generation. The feature is that the path includes an arc segment. The users can prescribe coordinates of arc center, a precision point on the arc, and the corresponding pole. The four-bar is synthesized mainly with the aid of the Bobillier theorem. The tasks that the paths or coupler curves pass through at most two additional precision points are also considered. Several nonlinear equations thus have to be derived and combined to find the coordinates of the pivots in synthesizing the four-bar.
The Modified Quadruple-Tanks Process: A Flexible Mathematical Model with an Adjustable Simulink Block
Authors: Numsomran A. , Chaoraingern J. , Trisuwannawat T.
Published: March 2014

This paper presents the modified quadruple-tanks process, a flexible laboratory process with an adjustable Simulink block, which is multivariable system consisting of four interconnected water tanks included with lower interacting valve. The new general form of modified quadruple-tanks mathematic model and Simulink block is developed for the advantage of control system analysis and design which can make practical use for many styles of multivariable process by adjusting the value of connected valve resistance, inlet and outlet valve ratio. In this paper described clearly about physical properties of modified quadruple-tanks process, mathematical modeling, transformation of modified quadruple-tanks process, analysis of right half-plane zeros characteristic and controller design for multivariable system. By the several models of transformed modified quadruple-tanks, they can be used to teach students in the skills of multivariable control system analysis and design, understanding control limitation due to interactions, model uncertainties, non-minimum phase behavior, and unpredictable time variations, design decentralized controllers, Implementing decouples to reduce the effect of interactions, and understanding their limitations.
A Study on Conventional versus Independent Suspension System of an Automobile
Authors: Balaraju A. , Venkatachalam R.
Published: March 2014

the suspension system of an automobile helps to support the car body, engine and passengers, and at the same time absorbs shocks received from the ground while vehicle moves on rough roads. There are two types of suspension systems which are being used in the automobiles, namely, conventional suspension system and independent suspension system. in this paper it is aimed at studying the dynamic behaviour of the two types of suspension systems, using full car model.
The Influence on the Hardness and Form of U75V from the Different Cooling Rates
Authors: Wang Peng Fei , Wei Ran , Liu Zhi Min , Chen Lin , Li Ge
Published: March 2014

This paper analyzes the TTT and CCT curves of U75V as a research basis, detailed anatomical U75V chemical properties and grain structure, through thermal simulation machine, heating 820 °C, respectively, and 920 °C, respectively, the sample detection U75V 2 °C / s, 4 °C / s, 6 °C / s, 10 °C / s, 15 °C / s, 20 °C / s speeds cooled Rockwell hardness, and observing samples taken U75V phase diagram. Through data analysis and image contrast, pearlite lamellar microstructure observation, analysis hardness and lamellar spacing, summed pairs of different cooling rates U75V organizations and hardness.
Quantitative Mixing Analysis of Laminar Flow in Circle Grid Perforated Plate with 50% Porosity Static Mixer
Authors: Zamadi Mat Loddin Mohd , Khalid Amir , Manshoor Bukhari
Published: March 2014

The applications of the static mixers are widely applied in many industries to obtain the desired type of mixing. In this context, to perform the mixing process should have two different fluids that also have different properties which will combines it in a single equipment to make an another fluid. The main objective of this research study is to propose a new approach of fractal concept (circle grid perforated plate) for internal rapid mixing by determining the coefficient of variation (COV). This study was implemented by fully numerical simulations. The simulations of mixing fluid were carried out with the help of commercial computational fluid dynamic (CFD) package ANSYS CFX 14.0 software. The simulation was done primarily in cylindrical pipe with insertions of circle grid perforated plate with porosity of 50%. Three levels of laminar flow have been chosen to result in Reynolds numbers (Re) equal to 100, 200 and 400. The effectiveness of circle grid perforated plate static mixer has been evaluated by comparing the homogeneity level of mixing fluids to the Kenics static mixer that readily available in industries applications. Based on the research findings, the COV value for circle grid perforated plate with 50% porosity at Re 100 was 0.0744 which is out of the range while Reynolds number at 200 and 400 were 0.0483 and 0.0247 respectively which are in the range in term of reasonable target of mixing homogeneity. The values of COV between 0.01 and 0.05 are the reasonable target for many applications. In term of manufacturing cost and energy loss due to static mixer, definitely this new approach of 50% porosity circle grid perforated plate is better design compared to the Kenics static mixer because of lower number of inserts and simpler design of static mixer to produce.
Design and Kinematics of a Cable-Driven Humanoid Ankle Joint
Authors: Chen Lu Min , Zhu Zhi Zhong , Lin Qi , Wang Xin Jie
Published: March 2014

A 2DOF ankle joint mechanism with cross rotation axis was designed to imitate the human ankle joint structure. The kinematic model of the ankle joint mechanism was established by D-H method. The synergistic influences of the angle of ankle joint and subtalar joint on the foot motion of inversion/eversion, adduction/abduction, dorsiflexion/plantar flexion were analyzed by kinematics simulation. The simulation results show that the designed ankle joint has similar motion range and function to that of human ankle. This study provides a theoretical basis for the development of high performance ankle joint for humanoid robots.
Symmetrical Pneumatic Muscle Actuated Gripper System with Two Mobile Jaws
Authors: Negrea Doina , Deaconescu Tudor , Deaconescu Andrea
Published: March 2014

The paper argues the possibility of utilising artificial muscles actuated with compressed air in the construction of industrial gripper systems. Their utilisation as motors comes as a response to the increasingly sophisticated requirements these have to satisfy, related to the developed force, structural rigidity, compliance and dexterity. The paper presents a variant of symmetrical gripper system with two mobile jaws actuated by a pneumatic muscle. The main requirements for this gripper are defined, the structure of the mechanism is presented and the transmission functions of forces and velocities are determined. Eventually the paper discusses the construction of the system and its functional limitations.
Parameters Analysis of Bracing Structure with Friction Energy Dissipation System
Authors: Zhou Wei , Xu Xiao , Hao Wen Xiu
Published: March 2014

Friction energy dissipating bracing is the kind of efficient system in reducing seismic of buildings. The main parameters are bracing stiffness and yielding displacement of friction energy dissipating devices in this system, which are important to the design of reducing seismic systems. Five-story steel frame building model with friction energy dissipating bracing in each floor is established, whose dynamic response of structure is studied when the value of main parameters is changed. The results show that the displacement of structure are decreased obviously and the acceleration of structure is first decreased and then increased when the bracing stiffness and yield displacement of friction energy dissipating devices are increased. In addition, the rational range of parameters is suggested for the design of friction energy dissipation systems.
Study on a Quantitative Risk Assessment Method of Primary Equipments Based on Power Grid Safety Analysis
Authors: Deng Kun Ling , Li Dan Dan , Wang Ying , Cheng Xiao Lei , Li Ming , Fan Xin Qiao
Published: March 2014

A quantitative risk assessment method of primary equipments based on power grid safety analysis is presented in this paper, and the risk assessment model of power grid primary equipments is established. On the basis of the calculated losses caused by various faults of N-1 and N-2 under the normal operation mode and the equipment maintenance mode, whether an equipment needs to be maintained is determined by comparing the size of the possible losses in two operation modes of a power grid. Then, the purpose of guiding the condition based maintenance of the power grid primary equipments is achieved. Finally, the presented risk assessment model of power grid primary equipments is applied to a certain practical power system.
Study on the Different Dynamic Models and its Simplified Standards of the PWR Neutron
Authors: Wu Ping , Yu Qiang , Chen Hao , Yi Jun , Pu Guang Quan
Published: March 2014

According to the world average generation levels, the nuclear power generation is the third-largest energy generation form following the thermal and hydroelectric ones. Among all the operating nuclear generation, the type of the PWR has occupied more than 50%. The paper constructed three most commonly used dynamic PWR neutron models, which are six-groups delayed, single-group delayed and linearized neutron model, and made a detail analysis of those different models. An investigation of the different errors among the models under different perturbations is taken by simulation and a standard for the simplification of the models had been proposed, which can provide a reference for the selection of the future PWR neutron dynamic model.
Modeling and Practice of Wind/PV/Pumped-Storage Hybrid System
Authors: Yi Peng Fei , Zhang Jian , Zhang Zhao Yuan
Published: March 2014

This paper built a hybrid power system, including wind power, PV power and hydro power generation. It is presented mathematical model for the optional design of hybrid power system. The object of the model are to minimize the initial investment cost, power supply reliability and power complementation. The constraint condition are included system working, installed capacity and load balance, So the capacity matching model is established. A stand-alone photovoltaic of pasturing area is calculated by using the model. The result shows that the optional design model have an important sense, which improved power supply reliability, complementary characteristics of hybrid power and reduce the total cost of the system.
Component Characteristics of Coal-Based Jet Fuel and Petroleum-Based Jet Fuel
Authors: Lin Yang , Zhou Ting Ya , Wang Xin , Yang Xiao Yi
Published: March 2014

There are mainly four pathways to get liquid fuels from the coal including the direct liquefaction process, the Fischer-Tropsch process, coal-tar refining, and pyrolysis process. The characteristics of these four processed have been described. As the first two pathways are considered to be promising, the characteristics of these two types of coal-based jet fuels are discussed and the component characteristics of coal-based synthesis fuels are investigated, respectively. The component characteristics of coal-based jet fuels are compared with the traditional petroleum-based jet fuels. There are large differences between the properties of the coal-based jet fuel via direct and indirect liquefaction pathways. Comparing with the conventional petroleum-based jet fuel, the coal-based jet fuel via direct liquefaction pathway has the higher aromatics content, while the fuel via indirect pathway (F-T process) has more paraffin and nearly no naphthenes or aromatics. In additional, the carbon numbers of the coal-based synthesis jet fuels are compared with the conventional petroleum-based jet fuel.
Status of Unconventional Oil and Gas Resources and its Environment Risk Factors in China
Authors: Cai Bo , Ding Yun Hong , Lu Yong Jun , Shen Hua , Yang Zhen Zhou
Published: March 2014

The development of resources has achieved revolution from unconventional resources to conventional resources in North America. China's tight oil and gas reservoirs are widely distributed and the exploration potential is tremendous. The abundant unconventional natural gas resources, if exploited reasonably and efficiently, will provide stable energy supply for the sustainable development of Chinese economy. In this paper, a few key techniques including drilling and hydraulic fracturing for the development of unconventional oil and gas resources were introduced. The factors of unconventional oil and gas were put forward,the costs of drilling and well completion and environmental concerns for the development of tight oil and gas in China included ground water contamination, risks to air quality, migration of gases were also introduced which has raised combined with the analysis of future prospects and future technology development. We also offer some technology which has the merits of low cost, efficient for the development of unconventional tight reservoir in horizontal wells. Good conditions have been found in Sichuan, Tarim and Ordos basins for both development and exploitation, finally we can come to a conclusion that the tight oil and gas should be realistic replacement resources of conventional oil and gas.
Reliability Evaluation of Generation and Transmission Systems Considering the Effects of Wind Farm
Authors: Liu Bo , Wu Hao
Published: March 2014

Because wind energy fluctuates randomly, the output power of wind turbine generators is uncertain. The reliability of power systems including wind generation is analyzed in this paper. In this paper, the reliability model of wind generators and the model of transmission network are combined by considering the sequential and autocorrelation of wind speed, the output power function and the forced outage of wind units. Then a reliability evaluation model of generation and transmission system, in which the system security constraints are satisfied, is built and the objective function is LSC. Taking IEEE-RTS96 system as an example, the reliability index which can reflect the effects of wind farms is calculated. The result provides the scientific reference for connecting wind farms to power systems.
The Research Progress on Biomass Fuel Reburning
Authors: Yang Dong , Lu Xiao
Published: March 2014

Biomass is the great potential and renewable energy, and technologies of its use have become an important topic today. As a way to use biomass fuel, biomass reburning significantly reduce NOx in boilers, and has good application prospects. This article describes the application , background and technical overview of biomass reburning, and focuses on biomass reburning research progress in order to work for the follow-up study providing a valuable reference.
Potential Analysis of Architectural Application of Solar Energy Resource in Panzhihua
Authors: Li Shun Mei , Mei Jun , Yao Yong
Published: March 2014

Basing on the meteorological data of Panzhihua, such as monthly solar radiation, sunshine duration, sunshine percentage, sunny days, and transmission coefficient, etc, we analyzed the distribution and application potential of solar energy resource . The result is as follows:(1) there are obvious seasonal characteristic for solar energy resource;(2) the solar water heater can meet the requirements of the standard domestic hot water the whole year;(3)it’s necessary to pay attention to usage and control for the sunshade and the day-lighting technology, where the east and west window should be avoided in the architectural design, and the south window with movable level external shading should be set up; (4)the photovoltaic system in the building which can reduce converted units exhaust emissions of 14.20 kg/ WP, produce the environmental benefits of about 1.72￥/ WP, and bring good environmental benefits.
Integrated AHP-BPNN Model for Wind Farm Investment Evaluation
Authors: Zhang Xiang Feng , Liu Tian Yu , Jiao Bin
Published: March 2014

The construction of wind farms grows quickly in China. It is necessary for stakeholders to estimate investment costs and to make good decisions about a wind power project by making a budget for the investment. This paper proposed an evaluation method by integrating the analytic hierarchy process (AHP) with back-propagation neural network (BPNN) to evaluate wind farm investment. In the AHP-BPNN model, the AHP method is used to determine the factors of wind farm investment. The factors with high importance are reserved while those with low importance are eliminated, which can decrease the number of inputs of the BPNN. The experiment results show that the integrated model is feasible and effective.
Wind Energy Resource Assessment at Tindouf Region, Extreme Southwest of Algeria
Authors: Boudia Sidi Mohammed , Benmansour Abdelhalim , Tabet Hellal Mohamed Abdellatif
Published: March 2014

In this paper, with the help of two-parameter Weibull distribution, the monthly, seasonal and annual assessment of wind energy potentiality was made using the wind speed data collected in the last decade, from 2001 to 2010 for the meteorological station of Tindouf region. The vertical extrapolation of Weibull parameters and mean wind speed at a height of 50m and the analysis of temporal energy efficiency using a wind turbine of 600kW rated power from Fuhrländer manufacturer was made. The results show that Tindouf situated in extreme Algerian southwest, in the natural region of the Sahara, on the border with Morocco (west), the non-autonomous territory of Western Sahara (south-west) and Mauritania (south), is one of windiest region in the country, swept by local winds with a good annual mean wind speed =5.67m/s and an annual mean wind power density equal to 200W/m2 at 10m, while the highest monthly wind energy produced may be reached in May, the seasonal in Spring and the annual gross electric energy produced is equal to 1.85GWh/year.
The Design and Implementation of PV Inverter for Grid-Connected System Base on SVPWM
Authors: Zhang Ling , Li Ming Yong , Zhang Hang Hang
Published: March 2014

A PV inverter Grid-Connected system based on SVPWM is designed here, which is consisted of DC/DC circuit, TMS320F2812 , optical isolating circuit and driver circuit, three-phase inverter bridge, Grid signal acquisition circuit. Besides,program of the system is built with CCS3.3. SVPWM, MPPT, Grid-Connected, control comes true with the help of C language. Improved variable step size perturbation and observation method is applied in MPPT, which saves time of searching maximum power point and avoids oscillation generated. The experimental results show that the system can not only meet the design requirements, the Grid-Connect effect is also ideal.
Study of Heat Losses from Cylindrical Cavity Receiver of Solar Concentrator
Authors: Barahate Sanjay D. , Dongarwar P.R. , Shewale Vinod C.
Published: March 2014

In this paper heat losses from cavity receiver of solar concentrators are presented. Convective and radiative losses for specified cavity receiver are estimated by MATLAB programming and effect of the various parameters is studied. Radiation losses are analyzed for operating temperature in range of 127°C to 527 °C and aspect ratio of 0.5 to 2.5. Convective losses are investigated for operating temperature in range of 127°C to 527 °C, inclination angle from 0 to 90o, aspect ratio of 0.5 to 2.5 and wind effect for 0 to 10 m/s. Radiation losses and convective losses increases as operating temperature of cavity receiver increases. The convective losses are more for sidewise facing cavity (0o inclination) and less for downward facing cavity (90o inclination). As aspect ratio and wind velocity increases, convective loss increases.
Effect of Load Spectra and Stress Magnitude on Crack Growth Behavior Variability from Typical Manufacturing Defects
Authors: Gallagher Joseph P. , Molent Lorrie
Published: March 2014

DSTO conducted a comprehensive series of fatigue coupon tests as part of the fatigue life substantiation of the RAAF F/A-18 Hornet. The study employed five spectra which were applied to flat aluminium alloy 7050-T7451 coupons to determine the effects of manufacturing discontinuities and stress magnitude on the fatigue nucleation and crack growth behavior. Crack growth behavior was established using optical microscopy and scanning electron fractography, measuring crack sizes greater than approximately 0.05 mm. This paper reports the fraction of life to failure as well as the probability of occurrence of a crack with a defined size.
Fatigue Crack Growth and Coalescence Algorithm Starting from Multiple Surface Cracks
Authors: Pang John Hock Lye , Chew You Xiang
Published: March 2014

Fatigue crack growth and propagation analysis in welded joints have to deal with the complexity of modeling multiple weld toe surface cracks originating from weld toes. Fitness-For-Service (FFS) assessments for weld toe surface cracks employ a fracture mechanics and Paris Law approach to predict the fatigue crack propagation life of a semi-elliptical surface crack (SESC) to failure. A fatigue crack growth algorithm for assessing multiple surface crack growth, coalescence and propagation life was initially validated with previuously report crack growth data for a fillet shoulder specimen. Next a parametric study for single, double, and triple SESCs located along the weld toe line of a fillet weld was investigated with three starting crack depth sizes (0.1mm, 0.5mm, 1.0mm) coupled with three different crack aspect ratios (a/c = 1.0, a/c = 0.5 and 0.25) giving a total of 27 cases studied.
Integrating Fatigue Crack Growth into Reliability Analysis and Computational Materials Design
Authors: McClung R. Craig , Enright Michael P. , Moody Jonathan P. , Lee Yi Der , McFarland John
Published: March 2014

Recently a new methodology was developed for automated fatigue crack growth (FCG) life analysis of components based on finite element stress models, weight function stress intensity factor solutions, and algorithms to define idealized fracture geometry models. This paper describes how the new methodology is being used to integrate FCG analysis into highly automated design assessments of component life and reliability. In one application, the FCG model automation is supporting automated calculation of fracture risk due to inherent material anomalies that can occur anywhere in the volume of the component. Automated schemes were developed to divide the component into a computationally optimum number of sub-volumes with similar life and risk values to determine total component reliability accurately and efficiently. In another application, the FCG model automation is supporting integration of FCG life calculations with manufacturing process simulation to perform integrated computational materials engineering. Calculation of full-field, location-specific residual stresses or microstructure is being linked directly with automated life analysis to determine the impact of manufacturing parameters on component reliability.
Localized Fatigue Failure Analysis of Aluminium Crewboats due to Propeller Pulse Loads: A Case Study
Authors: Leacy Trevor M. , Ojeda Roberto
Published: March 2014

Marine grade alloys are extensively being used in high speed vessels such as patrol crafts, ferries and crew boats, where a reduction of the structural weight is critical to achieve higher speeds [1]. The use of aluminium has forced marine industry engineers to develop methods to design against fatigue failure. This has largely been addressed by the development of design standards, analysis techniques and the improvement of quality control and construction methods [2]. Nevertheless, even with these advancements there is a continued need for the development and improvement of aluminium analysis methods and guidelines [3].
Bayesian Updating of Aircraft Risk Assessments Using Results of Inspection
Authors: Torregosa Ribelito F. , Hu Wei Ping
Published: March 2014

This paper illustrates a technique that may be used to evaluate the risk of structural failure of each aircraft in a fleet when a crack has been detected in a particular member aircraft, or the risk of failure for that member has become too high. When a crack is detected, the calculated risk of failure for other aircraft in the fleet will increase significantly, and the aircraft operators need to decide which aircraft should be temporarily grounded for unscheduled inspection and which ones be allowed to fly. The proposed method applies the Bayesian inference to update the risk assessment by updating the equivalent initial flaw size distribution, which is one of the key inputs for risk analysis. To illustrate the method, a hypothetical fleet aircraft is considered and the single flight probability of failure of each aircraft in the fleet is revised after the occurrence of a failure in one fleet aircraft.
Structural Integrity – Yesterday – Today – Tomorrow
Authors: Guillaume Michel , Uebersax Andreas , Mandanis Georges , Huber Cyril
Published: March 2014

Early airplanes were designed using purely static conditions and mainly tested only with simple wing tests. But despite the significant advances in design, manufacturing and testing capabilities, structural failures may still occur. Thus new concepts are required to ensure safe operations over the lifetime of an airframe. In 1952 Juerg Branger developed a concept for a fatigue simulator at the Federal Swiss Aircraft Factory (F+W). The Pilatus P3 trainer became the first airplane to be tested in Emmen, Switzerland to demonstrate the safety of the airframe over a lifetime of 2500 FH. This first test demonstrated the importance of full scale fatigue tests to ensure the structural integrity of the airframe. Due to the intense usage of the fighters deployed by the Swiss Air Force, further full scale fatigue tests were undertaken on the Venom, the Mirage III, and the F/A-18. As the complexity of the materials used in modern aircraft design increases, more and more analysis is being taken over by highly sophisticated software and test procedures. Structural integrity is still an important means to ensure safe operations in aviation for all types of airplanes.
Fatigue Crack Growth in Ultrafine-Grained Copper Obtained by ECAP
Authors: Arzaghi Mandana , Sarrazin-Baudoux Christine , Petit Jean
Published: March 2014

The propagation of long fatigue cracks in ultra fine-grained (UFG) copper obtained by equal channel angular pressing (ECAP) is investigated in the mid ΔK range and in the near threshold regime. The crack growth rates in UFG copper are substantially faster than in coarse-grained (CG) copper. A huge influence of environment is observed, with growth rates faster of more than two orders of magnitude in air compared to vacuum. The crack growth mechanisms are discussed on the basis of microfractographic observations and the deformation texture.
Fatigue Behavior and Life Prediction of an Equiaxed Crystal Nickel-Base Superalloy under Different Dwell Times and Strain Ratios
Authors: Yu Hui Chen , Dong Cheng Li , Li Ying
Published: March 2014

Strain-controlled low cycle fatigue (LCF) and creep-fatigue interaction (CFI) tests of an equiaxed crystal nicke-base superalloy were conducted at 850oC in order to investigate the effects of different dwell times and strain ratios on the fatigue behavior and life distribution. The cyclic damage accumulation (CDA) method and modified CDA method were employed to predict the fatigue life for the superalloy under complex loading condition, respectively. CDA method is employed to predict the fatigue life for the superalloy and the predicted fatigue life is within the scatter band of±6X. The fatigue life predicted by the modified CDA method agrees very well with the experimental fatigue life and the predicted fatigue life is well within the scatter band of±3X, which means that the modified CDA method is able to consider the influences of dwell time and strain ratio on the fatigue life for the superalloy.
Fatigue of Ultra-Fine Grained α-Brass
Authors: Nakai Yoshikazu , Imanaka Takuto , Shiozawa Daiki
Published: March 2014

Combined methods to obtain ultra-fine grain (UFG) α-brass samples are proposed. Severe plastic deformation followed by recrystallization was conducted, where multiple rolling and equal channel angular pressing (ECAP) were employed. Recrystallization was accomplished by heat-treatment after the severe plastic deformation, and the grain size after the severe plastic deformation was decreased. By multiple rolling, plates with thickness of 0.1 mm and grain size of 1.0 μm were obtained. By ECAP process, square bar with cross-section of 6 mm × 6 mm and minimum grain size of 4.1 μm was obtained. The 0.2 % proof strength, ultimate tensile strength, and fatigue limit were increased with the value of inverse square root of grain size (Hall-Petch relationship). Then, the 0.2 % proof strength of UFG brass was tenfold, the ultimate tensile strength and the fatigue limit were two fold increases from the conventional α-brass. Because of the high strength, the scatter of fatigue strength of UFG brass was large, which reflects the sensitivity to defects in material.
Cyclic Deformation of a Modern TiAl Alloy at High Temperatures
Authors: Kruml Tomáš , Chlupová Alice , Obrtlík Karel
Published: March 2014

Ternary TiAl alloy with 8 at.% Nb and lamellar microstructure is subjected to low cycle fatigue tests at temperatures ranging from room temperature to 800 °C. The aim of the study is to find limit conditions when the microstructure is still stable and to study mechanisms of microstructural degradation when this limit is exceeded. Up to 750 °C, no cyclic softening or hardening is observed and cyclic stress-strain curve follows the tensile curve. Cyclic softening is characteristic for 800 °C. The TEM observation did not reveal any substantial changes in the microstructure due to the cycling up to 700°C. The lamellar structure is altered by cyclic straining at 750 °C and, to a higher extent, at 800°C. In specimens cycled to fracture at 800 °C, the domains without lamellar structure cover about 10% of volume and are almost dislocation free. The destruction of lamellar microstructure is the reason for the marked cyclic softening at 800 °C.
On Constitutive Models for Ratcheting of a High Strength Rail Steel
Authors: Pun Chung Lun , Kan Qian Hua , Mutton Peter J. , Kang Guo Zheng , Yan Wen Yi
Published: March 2014

The ratcheting behaviour of a hypereutectoid high strength rail steel with carbon content of 0.85% was experimentally studied under both uniaxial and bi-axial cyclic loadings recently by the authors. To numerically simulate the multiaxial ratcheting behaviour of the rail steel, the Abaqus built-in Lemaitre-Chaboche model was applied first in current study. Following Abaqus documentation, the material data for the Lemaitre-Chaboche model were calibrated from the uniaxial loading test results. Comparing with experimental data, the Lemaitre-Chaboche model with the calibrated data provides overpredictions for the ratcheting responses of the rail steel under both uniaxial and bi-axial loadings. After that, a modified cyclic plasticity model with a coupling multiaxial parameter in the isotropic and kinematic hardening rules was applied for the material. The material data for this modified model were calibrated from both uniaxial and bi-axial loading tests. Comparison between the simulated results and the experimental data show that this modified cyclic plasticity model has the capacity to simulate both uniaxial and multiaxial ratcheting behaviour of the hypereutectoid rail steel with an acceptable accuracy.
On the Evaluation of the Stress State in Rail Head for Assessing Fatigue Resistance
Authors: Pun Chung Lun , Kan Qian Hua , Mutton Peter J. , Kang Guo Zheng , Yan Wen Yi
Published: March 2014

To search for a single parameter to evaluate the stress state in rail head during wheel/rail rolling contact situations, the stress-based and the strain based phenomenological approaches for multiaxial fatigue analysis can be considered as the candidates. Following the stress-based approach, the maximum von Mises stress range can be applied as a single parameter to evaluate the stress state in the rail head. However, the von Mises stress range only relies on the stress field in the rail head for the fatigue analysis, which is not sufficient for assessing the fatigue resistance of the rail steel. The Smith-Watson-Topper (SWT) method, the strain-based phenomenological approach for multiaxial fatigue analysis which considers stress, elastic strain and plastic strain components, is then adopted to study rolling contact fatigue in the rail head. Combining with the three-dimensional finite element modelling of a steady-state wheel/rail rolling contact, the numerical procedure to calculate the SWT parameter in the rail head is presented. The capability of the SWT method to predict the initiation of fatigue cracks in the rail head is confirmed in a case study. Consequently, the maximum SWT parameter is proposed as a single parameter to effectively evaluate the stress state in the rail head.
Rail Bogie Structural Assurance
Authors: Stewart Ross , Hayes Peter , Trezise Stuart , Houston Michael , Jackson Adrian , Cooper Timothy
Published: March 2014

Two types of cast steel rail bogies have been affected by cracking and defects. The cast steel design was from a period when bogie loads were lower than the endurance limit. However, the bogies as manufactured included a large number of casting defects and 60 years of operations has resulted in many repairs being applied. Thus like all ageing structure, the original basis for safe operations may be invalid. Structural assurance instructions were developed based on the following work. A condition data survey was undertaken to obtain configurations and defects within the fleet. This was used to assist in identifying critical areas, types and shapes of defects. Two bogies were instrumented to obtain operational loads that were compared to modern standards to provide both a spectrum for future operations and loads for Finite Element Analysis (FEA), Fatigue and Damage Tolerance Assessment (DTA). Finite Element Models (FEM) were developed to provide internal bogie loads and stresses for use in the fatigue and DTA and identify additional critical locations not identified in the condition data survey. DTA were undertaken to determine maximum flaw sizes and to verify the safe period of operation; given the loads, usage and stress data of the previous tasks. Based on the work undertaken, instructions for continued management documenting acceptable flaw criteria, life limits, and ongoing inspections were provided.
Calculation of Critical Crack Size of Repair Welded Rail
Authors: Jun Hyun Kyu , Seo Jung Won
Published: March 2014

Repair of damaged rail surface by overlay welding is the common rail maintenance method. But the discontinuity in material between base and weld brings initiation of cracks and they causes a rail fracture. Unfortunately, such cracks are hard to detect on site because the weld boundary prevents the echo signals penetration by reflection. So estimation of the critical crack size (CCS) has been a critical issue in railroad industry to prevent a rail from sudden fracture.
In this study, we calculated the critical size of crack which was initiated and propagated underneath of the overlay welded rail by applying linear elastic fracture mechanics. For this purpose, we measured the maximum load carrying capacities of cracked UIC60 by inverted 3 point bend tests and checked the feasibility of the finite element (FE) analysis procedure. We could find the correlation in crack size between the test and 3D FE analysis results and applied the proposed 3D FE analysis model to calculate the CCS of a rail. We calculated the stress intensity factors on cracked rail by increasing the size of crack until the rail broke. The CCS was calculated as around 30.0 mm under the normal railway service operating condition.
Probabilistic Damage Tolerance Analysis for General Aviation
Authors: Millwater Harry , Ocampo Juan D. , Castaldo Anthony
Published: March 2014

The General Aviation (GA) fleet includes about 150,000 airplanes that were certificated with no fatigue evaluation requirements. The average age of these airplanes is about 40 years, and many are high-time. To mitigate the aging effects on the GA fleet, a probabilistic damage tolerance analysis (PDTA) program has been developed. A PDTA approach also provides a mechanism whereby inspection and maintenance operations can be included into the simulation, thus providing engineers the opportunity to assess the benefits of maintenance actions. This paper describes the probabilistic methodology to be utilized in a computer software program (SMART|DT) that performs risk assessment of small airplanes employing NASGRO® or a user selected code as the crack growth engine. The methodology can assess a range of random variables, calculate the extreme value distribution (EVD) of maximum stress per flight from a general aviation (GA) spectrum, and generate a surrogate model for accurate and fast calculations of crack grow. The main objective is to develop a comprehensive probabilistic methodology such that engineers can conduct a risk assessment of GA structural issues in support of policy decisions.