Showing papers in "Applied Mechanics and Materials in 2010"

The Research on Control of the Electronic-Mechanical CVT

Abstract: Nowadays, the variable speed function of metal belt CVT assemblied on vehicle is completely based on hydraulic system which is driven by the engine. The extra energy consumption is obvious and the reliability is low during the speed-change process of system because of low efficiency of hydraulic components such as pump and valve. In this paper, Electronic-Mechanical CVT (EMCVT) that is a new kind of metal belt CVT is proposed, which uses DC motor driving system to implement the variable speed function. The model of speed ratio control and the clamping force of cone-plates control is established and the PID algorithm of speed ratio control is presented while the transmission principle and mechanical structure of EMCVT is introduced through the study of artificial characteristic of DC motor and dynamics of the system.

Mapping residual stress profiles at the micron scale using FIB micro-hole drilling

Abstract: Measuring residual stress at the sub-micron scale imposes experimental challenges. We propose a new technique, namely the incremental micro-hole-drilling method (IµHM), for measurement of residual stress profiles as a function of depth with high spatial definition. Like its macroscale counterpart, it is applicable to either crystalline or amorphous materials, but at the sub-micron scale. Our method involves micro-hole milling using the focused ion beam of a dual beam FEGSEM/FIB microscope. The surface displacements are tracked by digital image correlation of SEM images recorded during milling. The displacement fields mapped around the whole are used to reconstruct the variation of the in-plane stress tensor as a function of depth. In this way the multi-axial state of residual stress has been characterised around drilled holes of 2 microns or so, enabling the profiling of the stress variation at the sub-micron scale to a depth of 2 microns. Here we demonstrate the efficacy of this method by measuring the stresses in a surface-severe-plastically-deformed (S2PD) Zr50Cu40Al10 bulk metallic glass (in atomic percent, at.%) sample after failure under four-point-bending-fatigue.

Towards a Planar Cruciform Specimen for Biaxial Characterisation of Polymer Matrix Composites

Abstract: This paper details work undertaken towards the development of a standard test method for the biaxial response of planar cruciform specimens manufactured from carbon fibre-reinforced plastic (CFRP) laminates and subject to tension-tension loading. Achieving true biaxial failure in a cruciform specimen without the need for the inclusion of a stress raiser, such as a hole, in the gauge- section, is a subject attracting much research globally and is by no means a trivial exercise. Coupon designs were modelled using finite element analysis (FEA) in order to predict the stress and strain distributions in the central region of the specimen. An Instron biaxial strong-floor test machine was used to test the specimens. Strain gauges were used to measure the strain in the specimen arms and to assess the degree of bending. Digital image correlation (DIC) was used to measure the full-field strain distribution in the central gauge-section of the specimen and this was compared to values measured using strain gauges. The strain readings obtained from strain gauges, DIC and FEA predictions were in good agreement and showed that the strain distribution was uniform in the central gauge-section, but that strain concentrations existed around the tapered thickness zone. These regions of strain concentration resulted in interlaminar failure and delamination of the laminate propagating into the specimen arms.

Experimental Study on Flexural Behavior of Recycled Coarse Aggregate Concrete Beam

Abstract: In order to investigate flexural behavior of simply-supported beam using recycled coarse aggregate concrete, the difference of the component normal section stress distortion performance and failure characteristic between the recycled concrete beam and the normal concrete beam is researched. The approaches of testing the flexural behavior of 6 recycled course aggregate beams with the same section size, different replacement ratio of recycled coarse aggregate (0%, 50%, 70% and 100%) and different percentage reinforcement (0.68%, 0.89% and 1.13%). Based on the experimental the following conclusions are draw. There are also 4 phases of elasticity, cracking, yield and ultimate during the stress course of recycled concrete beam component normal section stress; the average strain measured on cross-section obliges to the plane section assumption; the characteristics of stress distortion and destruction of recycled concrete beam are basically the same as those of the normal concrete beam. Under same conditions, the cracking moment and the ultimate flexural carrying capability of recycled concrete beam is almost the same as those of normal concrete beam. The deformation of recycled concrete beam is larger than concrete beam. The conclusion of the paper is that it is still feasible to calculate the ultimate bending moment, cracking moment, and the biggest crack width of recycled concrete beam according to the formula in China Concrete Structure Design Code, but the deflection formula needs to be adjusted.

Practical In Situ Applications of DIC for Large Structures

Abstract: The paper describes recent use of Digital Image Correlation (DIC) for in-situ measurements of deformation and cracking of large civil engineering structures like bridges and power plant. Recent work at NPL has demonstrated the potential of DIC as a novel NDT tool for measuring deformation and cracking in reinforced concrete structures. This has particular application where the area of interest is in a region where inspection is difficult or costly and where direct access may have safety implications. In this case accurate measurements from pairs of images can be very cost effective.

Digital Holographic Interferometry by Using Long Wave Infrared Radiation (CO2 Laser)

Abstract: We show how digital holographic interferometry in the Long Wave InfraRed spectral range (LWIR) can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO2 Laser. Experimental results showing that the method can be used to locate defects in a panel are presented and advantages and disadvantages of this approach are discussed.

Comparison of the Drop Weight Impact Performance of Sandwich Panels with Aluminium Honeycomb and Titanium Alloy Micro Lattice Cores

Abstract: This paper is a study of the drop weight impact behaviour of small sandwich panels of carbon epoxy skins with aluminium honeycomb and titanium alloy micro-lattice cores. A series of experimental tests have shown that the specific impactor penetration behaviours are similar for both cores. The reasons for this are a result of the detailed deformation and rupture behaviour of the two types of core. The deformation and rupture mechanisms of honeycomb and micro-lattice structures will be discussed in general terms, and these observations will be used to inform discussion of actual deformation and rupture in the panel tests. In this way, micro energy absorbing mechanisms will be related to panel performance, and conclusions on the way forward for improved penetration performance using other core materials and geometries will be identified.

Researches into Influence of Process Parameters on FDM Parts Precision

Abstract: In the field of RPM( rapid prototyping manufacturing), accuracy and efficiency have become the bottleneck that slows down its development, so how to improve parts precision has been one of the hot research questions. A variety of factors are analyzed which have effect on parts precision , such as extrusion temperature, envelope temperature, extrusion velocity, filling velocity, slicing orientation, slicing thickness, filament-width compensation, and delay time, and then corresponding measures to improve parts precision is presented.

The Effect of Ultrasonic Excitation in Metal Forming Tests

Abstract: The use of ultrasonic excitation of tools and dies in metal forming operations has been the subject of ongoing research for many years. However, the lack of understanding about the effects of ultrasonic vibrations on the forming process has resulted in difficulties in maximising the benefits and applications of this technology. In particular, experimental characterisations of the effects of superimposing ultrasonic oscillations have largely relied on interpretations of measurements of the mean forming load and have ignored the oscillatory forces. Previous research [1] has shown that by applying ultrasonic vibrations to the lower platen in compression tests on pure aluminium specimens, the resulting stress-strain relationship can be characterised by a temporary effective softening of the material during intervals of ultrasonic excitation. The current research investigates this effect in a series of simple forming tests using a number of different metal specimens. In this research, the forming tests are conducted using a piezoelectric force transducer to measure the oscillatory force data during ultrasonic excitation of the die. It is shown that the benefits of superimposing ultrasonic excitation of the die are highly dependent on the material being formed and that, in many cases, the maximum oscillatory force exceeds the static forming load even where the mean forming load is reduced significantly during the interval of ultrasonic excitation.

The Influence Rules of Stress about Technical Parameters on Synchronous Rolling Railway Axis with Multi-Wedge Cross-Wedge Rolling

Abstract: Multi-wedge synchronous rolling by cross-wedge rolling is one of the most advanced methods that can form rolling railway axis. Its rolling quality mainly lies on inner transversal stress and shearing stress of rolling workpiece. In this paper, based on the rotated theory of multi-wedge rolling, through using Ansys/Ls-Dyna FEM software, multi-wedge synchronous rolling railway axis by cross-wedge rolling is simulated. It has been systemically researched that technical parameters effect transversal stress and shearing stress. In the meantime, the calculating model is verified by experiment. Through this study, It is obtained that the law of technical parameters effect on rolling railway axis by multi-wedge synchronous cross-wedge rolling. These research conclusions can provide scientific basis for rolling railway axis by multi-wedge synchronous cross-wedge rolling and rolling better quality.

Some Similarity Measures of Interval-Valued Intuitionistic Fuzzy Sets and Application to Pattern Recognition

Abstract: In this paper, we present an effective method for evaluating some similarity measures of interval-valued intuitionistic fuzzy sets(IvIFSs) on the basis of Hausdorff metric. Some properties of the proposed similarity measures are discussed and the related similarity measures are also compared. Finally, one numerical example is given to demonstrate the application of the presented similarity measures of IvIFSs to pattern recognition problem.

An Improved Algorithm for Clustering Gene Expression Data Using Minimum Spanning Trees

Abstract: Genes are classified in order to understanding the categories of animals and plants, and to getting the knowledge about their connatural structures in the research of the biology. It is important to use clustering methods to recognize and classify modes of gene expression data effectively for studying the relationship between different species of genes. In this paper, an improved algorithm for clustering gene expression data based on Minimum Spanning Tree (MST) is proposed. The improved algorithm mainly uses direct clustering and recursive calculation method to shorten the running time. According to the results of the experiments, Through the use of multiple data sets, the results show that the improved algorithm than the original algorithm is greatly increased in the running time.

Research on License Plate Recognition Technology

Abstract: With the growth in number of vehicle, intelligent vehicle management has become the research hotspot, and license plate automatic recognition system is also of great concern as a important technology of intelligent traffic system. In this paper, Hough transform used to edge extraction, tilt correction algorithm and character recognition based on Haursdorff distance are discussed. At last, the license plate recognition system is designed and implemented, and then the experimental result is analyzed.

Experiment and Simulation of Electromagnetic Stiffness for Stepper Motor

Abstract: Electromagnetic stiffness is an important parameter of stepper motor. It impacts obviously on system natural frequency. In this paper, the torsional vibration mechanism of stepper motor rotor caused by electromagnetic stiffness is studied and the mathematical formula for electromagnetic stiffness is established derived from stepper motor mathematical models. We simulate and experiment on stepper motor with parameters in the paper. Simulation value and experiment value of the electromagnetic stiffness are consistence with the numerical one. So it verifies the existence of electromagnetic stiffness, which provides a basis for researching on frequency variation of motor dragging flexible load.

Automatic License Plate Recognition System

Abstract: This paper proposed an algorithm for license plate recognition system(LPRS). The vertical edge was first detected by sobel color edge detector. Then, the invalid edge was removed regarding edge density. Next, the license plate(LP) image was converted into HSV color model, and by edge density template and fuzzy color information judgement, the LP region was located. Then, color-reversing judgement and tilt correction was conducted. Afterward, characters were segmented by means of vertical projection and convolution, by which character width and position can be exactly confirmed, and character recognition was conducted based on radial basis function (RBF) neural network. With a lot of samples verified in night hours and daytime under real conditions, the experimental results show that the proposed method can achieve accuracy and effectiveness in LPRS.

Effect of Cryogenic Minimum Quantity Lubrication (CMQL) on Cutting Temperature and Tool Wear in High-Speed End Milling of Titanium Alloys

Abstract: Cryogenic minimum quantity lubrication (CMQL) is a kind of green cooling/lubrication technique, which consists of the application of a small amount of lubricant (6-100 ml/h), delivered in a refrigerated compressed gas stream to the cutting zone. This paper experimentally investigates the effect of CMQL on cutting temperature and tool wear in high-speed end milling of titanium alloys. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry milling, refrigerated air cutting, and CMQL. The refrigerated gas equipment was manufactured based on composite refrigeration method to provide the refrigerated air. The experimental results show that application of CMQL resulted in drastic reduction in cutting temperature and tool wear especially when machining titanium alloys at a high cutting speed.

Performance Comparison between an MRF Damper and an MRE Isolator Incorporated with a Building Structure

Abstract: As an important member of smart materials, magnetorheological elastomers (MREs) exhibit characteristics that their modulus can be controlled by an external magnetic field. Based on these experimental results, a viscoelastic solid model with four parameters was proposed to predict the performance of MRE. A building model, three stories high, was constructed using MATLAB SIMULINK to evaluate the performance of an MRE device in structural control. In addition, the performance of an MRF damper and an MRE device in structural control, where the resultant peak force was selected as a criterion in the evaluation process, was compared and discussed. Two controllers, passive on and passive off control strategy were used to compare the response of structure. The effectiveness of an MRE bearing in structural control was well justified.

Preparation of Plywood Using Starch Adhesives Modified with Isocyanate

Abstract: The purpose of the study was to manufacture plywood using starch adhesives modified by isocyanate, the influence factors on the bonding strength and water resistance of starch adhesive were studied by different solid content, adding additives and adding isocyanate. X-ray photoelectron spectroscopy (XPS) analysis was used to characterize the chemical structure of bonding interface. The results show that the bonding strength of starch adhesive was increased significantly when solid content increased to 50%. Bonding strength and water resistance were improved significantly by adding additives and isocyanates to starch adhesive. The analysis of XPS indicated that the chemical bonding derived from the reactions of isocyanate was the key factor to increase bonding strength and water resistance.

An Improved Artificial Bee Colony Algorithm for Job Shop Problem

Abstract: Job shop scheduling problem (JSP) plays a significant role for production management and combinatorial optimization. An improved artificial bee colony (IABC) algorithm with mutation operation is presented to solve JSP in this paper. The results for some benchmark problems reveal that IABC is effective and efficient compared to those of other approaches. IABC seems to be a powerful tool for optimizing job shop scheduling problem.

Modeling and Simulation Research of Coaxial Parallel Hybrid Loader

Abstract: After analyzing the loader duty cycle with hybrid drive theory and gaining the characteristics of loader duty cycle, an integrated started generator-ISG based coaxial parallel hybrid loader is designed. Two simulation models are built with the simulation software Cruise, one is tradition loader another is hybrid loader. The simulation result of tradition loader model compare with the test data to amend the model. To gain same accuracy, the hybrid loader model is rebuilt based on the tradition loader model. According to the “I” type duty cycle, comparing the simulation result of tradition and hybrid loader, the result shows that hybrid loader can save fuel 10.4%.

Applying Support Vector Machines to Predict Tunnel Surrounding Rock Displacement

Abstract: Displacement prediction of tunnel surrounding rock plays a significant role for safety estimation during tunnel construction. This paper presents an approach to use support vector machines (SVM) to predict tunnel surrounding rock displacement. A stepwise search is also introduced to optimize the parameters in SVM. The data of Fangtianchong tunnel is use to evaluate the proposed model. The comparison between artificial neural network (ANN) and SVM shows that SVM has a high-accuracy prediction than ANN. Results also show SVM seems to be a powerful tool for tunnel surrounding rock displacement prediction.

Biomechanics and Numerical Evaluation of Cervical Porcine Models Considering Compressive Loads Using 2-D Classic Computer Tomography CT, 3-D Scanner and 3 -D Computed Tomography

Abstract: In this paper the biomechanical behavior and numerical evaluation results of three C3-C5 porcine cervical models created with different modeling techniques are shown. The objective of this evaluation is to know the differences between the biomechanical effects on a bone graft, which replaces a damaged C4 vertebral body, a titanium alloy (Ti-6A1-4V) cervical plate, used to isolate the C4 damaged vertebra, and the influence on the compressive loads on the complete and instrumented C3-C5 cervical model. The biomechanical integrity of the healthy C3 and C5 vertebral body after the fixation of the cervical plate using titanium alloy screws is considered. Besides, 2-D Computer Tomography classic technique, 3-D Scanner Z-Corp 700 and a CT scanning Philips Brilliance system was used to create the three FEM models. In addition, 3-D Software as Pro-E Wildfire 4.0, ScanIP 3.1, UGS NX-4 and Geomagics R 10.0 was used to create specific numerical model. Main displacements and von Misses stresses between the upper and lower surfaces of the vertebral bodies and the bone graft and the influence of the titanium alloy (Ti-6A1-4V) screws on the vertebral body of C3 and C5 were evaluated. The contribution of this study is to optimize the actual surgical technique once the numerical results on the FEM model have been analyzed. In other words, the numerical disparity between classic CT techniques versus 3-D modern techniques is established.

Development of a Methodology to Assess Mechanical Impulse Effects Resulting from Lightning Attachment to Lightweight Aircraft Structures

Abstract: The effect of lightning attachment to structures and vehicles is a cause of major concern to a number of different industries, in particular the aerospace industry, where the consequences of such an event can be catastrophic In 1963, a Boeing 707 was brought down in Maryland killing 81 people on board, triggering the improvement of lightning protection standards However, commercial jets are still struck on average once every 10,000 hours of flight time and between 1963 and 1989 forty lightning related accidents were recorded within the USA alone The rapid increase in the use of composite materials in aircraft design and the consequent increase in complexity when determining the effects of a lightning strike, has led to new challenges in aircraft protection and the requirement for improved understanding and standardisation The attachment of lightning to a structure causes damage through three mechanisms Primarily a supersonic acoustic shock wave, caused by rapid heating of the arc channel during initial attachment, resulting in a large and rapid overpressure Secondly a magnetic force generated by the fields developed in the high current areas around the lightning attachment point Finally a mechanism specifically related to composite materials, where the rapid vaporisation of an expanded copper foil layer (designed to quickly transmit current across a structure, thus reducing its focus) trapped between the composite material and the protective paint layers causes an additional overpressure, which is exacerbated by additional paint layers acting to contain the explosion and direct it inwards The work described in this paper looks to develop a technique to measure these forces in order to better understand and assess their effects A novel methodology has been developed to allow the estimation of peak overpressure forces produced by the acoustic shock wave resulting from the attachment The methodology utilises Digital Image Correlation and ultra-high speed photography to acquire full-field displacement measurements of panel deflections at frame rates of up to 1,000,000 frames per second The experimental results are used in the optimisation of a finite element model, outputting the parameters of an acoustic shock that produces representative displacements, velocities and accelerations The method is currently being validated by performing a series of tests on aluminium panels subject to instrumented impact testing The next stage will be to use the technique developed to aid a program of investigation into the effects of artificial lightning strike events on aluminium and composite panels

Mechanical behavior of syntactic foams for deep sea thermally insulated pipeline.

Abstract: Ultra Deep offshore oil exploitation (down to 3000 meters depth) presents new challenges to offshore engineering and operating companies. Flow assurance and particularly the selection of insulation materials to be applied to pipe lines are of primary importance, and are the focus of much industry interest for deepwater applications. Polymeric and composite materials, particularly syntactic foams, are now widely used for this application, so the understanding of their behavior under extreme conditions is essential. These materials, applied as a thick coating (up to 10-15 cm), are subjected in service to: - high hydrostatic compression (up to 30 MPa) - severe thermal gradients (from 4°C at the outer surface to 150°C at the inner wall), and to high bending and shear stresses during installation. Damageable behavior of syntactic foam under service conditions has been observed previously [1] and may strongly affect the long term reliability of the system (loss of thermal properties).This study is a part of a larger project aiming to model the in-service behavior of these structures. For this purpose it is important to identify the constituent mechanical properties correctly [2, 3]. A series of tests has been developed to address this point, which includes: - hydrostatic compression - shear loading using a modified Arcan fixture This paper will describe the different test methods and present results obtained for different types of syntactic foams.

Multi-Threshold Image Denoising Based on Shearlet Transform

Abstract: Shearlet is a new effective signal representation tool in many image applications. A novel image denoising scheme based on Shearlet transform is proposed in this paper. The original image is first decomposed using shearlet transform, then the shrink threshold of each decomposed subband adopts the different best threshold, producing the preliminary primary denoised image after reconstruction. Experiments show that the proposed scheme can remove the pseudo-Gibbs artifacts and image noise effectively. Besides, it outperforms the existing schemes in regard of both the peak-signal-to-noise-ratio (PSNR) and the edge preservation ability.

Detection of cracking in gear teeth using acoustic emission

Abstract: The detection of damage in gear teeth is paramount to any condition monitoring or structural health monitoring (SHM) tool for aerospace power transmissions such as those used in helicopters. Current inspection techniques include vibration analysis and time-inefficient visual inspection. Acoustic Emission (AE) is a very sensitive detection tool that has been successfully used in many SHM systems. Successful application of AE for damage detection in gear teeth will enable the optimisation of gear box design (and hence weight saving) in addition to safety improvements. This paper details a small aspect of a larger project designed to demonstrate automatic detection and location of common gear tooth defects. A novel test rig was designed to allow the fatigue loading of an individual gear tooth which was monitored using AE. The gear tooth was static in order to exclude the detection of AE signals arising from rotation; this allows initial development of the methodology prior to investigating rotating gears. Digital Image Correlation was used to determine the onset of cracking for comparison with the detected AE. Preliminary results of the investigation show that the developed methodology is appropriate for developing an automated gear health monitoring system and that future work should concentrate on the development of sensors and data acquisition methods associated with obtaining signals from rotating machinery.

Finite Element Simulation and Experiment of Chip Formation during High Speed Cutting of Hardened Steel

Abstract: As an advanced manufacturing technology which has been developed rapidly in recent years, high speed machining is widely applied in many industries. The chip formation during high speed machining is a complicated material deformation and removing process. In research area of high speed machining, the prediction of chip morphology is a hot and difficult topic. A finite element method based on the software ABAOUS which involves Johnson-Cook material model and fracture criterion was used to simulate the serrated chip morphology and cutting force during high speed cutting of AISI 1045 hardened steel. The serrated chip morphology and cutting force were observed and measured by high speed cutting experiment of AISI 1045 hardened steel. The effects of rake angle on cutting force, sawtooth degree and space between sawteeth were discussed. The investigation indicates that the simulation results are consistent with the experiments and this finite element simulation method presented can be used to predict the chip morphology and cutting force accurately during high speed cutting of hardened steel.

Rheological Investigation of ZK60 Magnesium Alloy Feedstock for Metal Injection Moulding Using Palm Stearin Based Binder System

Abstract: This paper investigates the characteristic important to metal injection moulding (MIM) process via rheological behavior of MIM feedstock. A gas atomized spherical ZK60 magnesium (Mg) alloy powder and the binder of 60wt.% palm stearin (PS) + 40wt.% low density polyethylene (LDPE) were used in this investigation. Prior to mixing process, critical powder volume percentage (CPVP) was determined and subsequently four different feedstocks with powder loading of 62, 64, 66 and 68vol.% were prepared. The properties of the feedstocks were then analyzed rheologically. Here, the flow behavior index n, the flow activation energy E and the mold ability index αSTV of the Mg alloy MIM feedstocks were determined. Results show that feedstock with 64% powder loading has the best rheological properties and therefore it is considered to be the best for the injection moulding process.

Validation of Acoustic Emission (AE) Crack Detection in Aerospace Grade Steel Using Digital Image Correlation

Abstract: Acoustic Emission (AE) is a passive form of non-destructive testing that relies on the detection and analysis of stress waves released during crack propagation. AE techniques are successfully employed number of industries there remains some scepticism in aerospace engineering. The reported investigation details a single four point bend test specimen undergoing fatigue loading. This test is part of a much larger programme designed to demonstrate a technology readiness level (TRL) of five of the use of AE to detect crack initiation and growth in landing gear structures. The completed test required that crack growth had to be monitored to allow a comparison with the detected and located AE signals. The method of crack monitoring had to be non-contact so as not to produce frictional sources of AE in the crack region, preventing the use of crack mouth opening displacement gauges. Furthermore adhesives on the specimen surface had to be avoided to eliminate the possibility that the detected AE was from adhesive cracking, thus the use of strain gauges or foil crack gauges was not possible. A method using Digital Image Correlation (DIC) to monitor crack growth was investigated. The test was stopped during fatigue loading at 1000 cycle intervals and a DIC image captured at peak load. The displacement due to crack growth was observed throughout the investigation and the results compared with the detected AE signals. Results showed a clear correlation between AE and crack growth and added further evidence of TRL5 for detecting fractures in landing gears using AE.

A Review of Piezoelectric Vibration Generator for Energy Harvesting

Abstract: Piezoelectric vibration generator has the advantages of small volume and simple technology and working in various poor environments, so it will inevitably power for wireless sensor network, micro electromechanical system (MEMS) devices, and other electric devices, instead of traditional cell. First of all, the generation power principle as well as the vibration mode of piezoelectric vibration generator is presented. Then, the basic theory and its application of structural behavior and damping influence are analyzed. Finally, the problems and the challenge of piezoelectric vibration generator are discussed.