Vision guided automatic cell injection system has become increasingly important in the past ten years. The existing cell injection systems mainly deal with large cells with size bigger than 40 micrometers. However, when dealing with small cells, the internal and external disturbances presented in the system may affect the success rate of injections significantly. In this paper, the system setup of vision guided cell injection system is presented. Feature tracking, micropipette positioning, cell membrane penetration and biological material injection processes for small cell with size around 20 micrometers are discussed. Sum of square difference (SSD) tracking algorithm based on 2 dimensional (2D)-to-2D feature correspondences is used to handle disturbances. A modified proportional position controller is adopted to control the micropipette. The importance of cell membrane penetration modeling is emphasized.

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This paper describes slide-bending formation of thin metal sheet by using an industrial robot. The formation of parts made of very thin sheets has become increasingly important following the miniaturization of industrial products, including electrical and mechanical devices. A new process called a slide-bending formation was proposed. The authors have made an automatic slide-bending formation system which consists of an industrial robot, z-axis stage, a force sensor and a CCD camera. The bending formation of metal foil with 0.03-0.04mm in thickness made by stainless steel was investigated systematically. From the results of the experiment, it was shown that the larger the reactive force, the larger the bending angle of the thin metal sheet.

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We investigated a method to measure displacement distribution in the whole view field of a video camera using digital image correlation (DIC) technique. This method intends to measure displacement field on a surface by comparing two images before and after deformation. Random pattern is painted on the object surface as gage marks. In this method, accuracy of the search method of the corresponding points on the two images influences largely on the accuracy of the measured result. We investigated a search method of corresponding points in the two images with accuracy less than one pixel. We considered methods to find position shift between two images with the accuracy less than one pixel and interpolate gray level using neighboring pixel data for moving template image. Combining these methods, we found that it is possible to make template matching with sub-pixel accuracy. We also investigated about factors influencing accuracy of this method.

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In recent years, the digital image analysis and processing techniques have been gradually developed in the deformation analysis of soil microstructure. By optical measurement method, the series images of soil microstructure under loading conditions are captured and stored in the computer. In light of the large particles and porous of "smart soil ", the depth of field of images is not enough in the soil microstructure experiment. In other words, part of the images is clear, while the other part is fuzzy. Most importantly, the analysis precision of soil microstructure depends on the quality of series images. So, the processing method, which is wavelet transformation, for improving the quality of series images is presented in this paper. In order to obtain the series images, by driving the step-motor set up the auto-tracking system of soil microstructure in the Z direction, the multi-focus images at the different step distances under same loading conditions are obtained by the CCD camera. Then, based on two-dimensional wavelet decomposition of gray scale images, the wavelet coefficients are optimized and applied to the inverse wavelet transformation. In this way, the high-quality images are obtained by fusing the multi-focus images. Furthermore, the qualities of transformed images are discussed using the evaluation functions. It should be noted that, by calculating the evaluation functions, the signal noise rate is improved and the mean square deviation decreases based on the fused images. Finally, the processing results show that the proposed method is benefit for enhancing the image clarity of the soil microstructure series images. Next, by comparing the parameters extracted from the original images and the fused image, the analysis precision has been improved obviously.

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Temporal phase analysis techniques are a series of phase extraction methods which were introduced to study the transient response of a continuously-deforming or vibrating object in recent years. In temporal phase extraction, a series of fringe or speckle patterns is recorded during the deformation or vibration of the specimen. The intensity variation on each pixel is analyzed along time axis. Fourier transform is a predominant algorithm in temporal phase analysis. However, selecting a proper filtering window is always a challenge in automatic phase extraction, as the spectrum on each pixel may be different. In this study, a new robust temporal phase analysis method is proposed based on continuous wavelet transform. The detailed procedure of one-dimensional wavelet phase extraction technique is presented, followed by a discussion on several problems involved in wavelet phase extraction. The proposed algorithm is applied with digital shearing speckle interferometry for the measurement of derivative of displacement.

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Electronic speckle pattern interferometry (ESPI) which is one of full-field measurement methods is technique for measuring out-of-plane and in-plane displacements of a diffusely scattering object. This paper describes a measurement method of the dynamic phenomena such as thermal deformation and creep deformation, etc. which is based on temporal phase analysis at the single pixel of the temporal speckle pattern image. The speckle pattern images are obtained by using ESPI system combined with a one-axis stage, which generated a temporal phase carrier. A Fast Fourier transform method is used to calculate the phase map and both magnitude and direction of deformation are obtained. As an application, deflections of a cantilever beam and out-of-plane deformation of a driving electronic package are measured using this method.

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Electronic speckle pattern interferometry and digital holography are two representative full-field coherent optical techniques used in mechanical vibration measurement. The simplest and most well-known metod is, in both techniques, the time-average method. In time-average digital holography, as in time-average speckle interferometry, the quantitative data processing is affected by several difficulties. Among them, the most important are the weak contrast of Bessel- type fringes and the speckle noise. Fundamentally, the greatest obstacle in achieving a complete amplitude field estimation comes from the two orthogonal components of time-averaged digital holograms or speckle interferograms, corrupted by multiplicative, high-frequency phase noise covering the deterministic vibration-related phase. Several earlier papers presented partial solutions to these problems, sometimes with confusing or misleading explanations; in the present contribution, the author presents in a single, unifying approach, these methods which are basically identical in speckle interferometry and digital holography. In both techniques, an important reduction of multiplicative high-frequency phase noise allows obtaining fringe-averaged patterns whose intensity noise is much lower than in classical time-average holography. The analysis allows choosing the most appropriate method leading not only to a higher fringe pattern quality, lower noise and extended measurement range, but also to a method of complete vibration-related phase estimation, which may include in some stages subpixel precision. The method is equivalent to phase unwrapping, but it only uses time-averaged fringe patterns.

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Terahertz (Thz) technology makes possible imaging of phenomena, inaccessible to visible light, but suffers from speckles, produced by coherent sources. This problem is of special importance for THz imaging, because surface roughness is closer to the object dimension as in optical imaging. Here we proposed a phase diversity Hadamard solution for speckle-free imaging with a coherent beam. First the Hadamard principle has been proven by experimental conversion of the sum of electrical THz fields (coherent) into a sum of intensities (incoherent). Then Hadamard diffusers of two different geometries have been designed, built and tested. Speckle reduction was measured using W-band (75-110 GHz) free-space measurement setups.

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We have constructed a prototype of a Dynamic ESPI system which makes it possible to analyze dynamic feature of two-dimensional strain field completely. The system consists of two orthogonal sets of in-plane sensitive ESPI systems including two PZT actuators for phase modulation of two interfering optical branches. Spatio-temporal phase analysis is done by temporal Hilbert transformation algorithm which is applied to whole speckle data set acquired by a digital camera successively without any additional data. Attainable resolution of in-plane deformation is around 20 nm. Two normal and tangential strain components are calculated by numerical differentiation of two components of in-plane deformation. Resolution of the analyzed strain is estimates around 10^<-5>-10^<-6>. Temporal resolution of the system depends on data acquiring rate of a digital camera. In the present experiment, high speed camera was used and temporal resolution was 60 frames per second.

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The displacement and strain fields of PLC bands are quantitatively measured using a technique based on high-speed digital photography and digital speckle correlation (DSC) method. The results show the nucleation process of a type B band within a few milliseconds, the propagation of a type A band during the capture process and the growth of the deformation bands. The maximum strain rate inside PLC band is over three orders of magnitude larger than the nominal strain rate. The avalanche-like deformation of a PLC band may exceed the displacement of the crosshead within very short time, thus there exists an elastic shrinkage deformation outside a PLC band during avalanche-like deformation. The propagation of type A band, which is traditionally considered to be continuous, is detected to be intermittent in time-resolved results of this paper.

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Dynamic deformation behaviors in tensile experiments of austenitic stainless steel SUS304 under strain rate of 6.7×10^<-5> s^<-1> were investigated by dynamic electronic speckle pattern interferometry (DESPI). In the method, contour maps of an in-plane component of deformation can be sequentially displayed as an animation of speckle correlation patterns. In a later process of the plastic deformation state, X-shaped localized deformation bands which ran over the specimen, were observed. Correspondingly, projection-like variation appeared on the stress-strain curve. In order to investigate the phenomena related to strain induced martensitic transformation (SIMT), changes of magnetic properties of the materials were also measured using FERRITESCOPE. A two-dimensional map of permeability coincided with a deformation contour obtained by DESPI. We concluded that the X-shaped localized deformation band running over the specimen is the front of SIMT.

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A new extensometer has been developed that detects displacements of the marking positions on a specimen by real-time digital speckle correlation. It needs neither markings nor mechanical clips to be attached on the specimen and perfectly noncontacting to automatize tensile test. Two marking positions are illuminated by separate laser beams and imaged on separate CCD's. Each of the optical systems is installed in a separate movable probe head. For small amount of speckle displacement less than a few millimeters the optical head is fixed to output speckle displacement. A resolution of 1 μm has been attained by comparison with a laser linear encoder. Larger displacement was detected from displacement of the probe head that cancels the speckle displacement signal by feedback control of the head movement. We also conducted tensile test in a temperature chamber controlled in a range between -50℃ and 200℃ by placing the probe heads outside a window of the chamber.

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This study presents a new technique to investigate the dynamic behavior of fine roots of Pinus densiflora (Japanese red pine) seedlings with very high sensitivity in the order of sub-nanometer by using a novel optical interference method called statistical interferometry. Principle of the statistical interferometry is based on the statistics of a fully developed speckle field, which is generated when a rough surface is illuminated by the laser light. The technique facilitates to obtain minute root growth measurements in very short periods, in the order of sub-seconds. Three types of pine seedlings were investigated, where two types were infected with ectomycorrhizas called, Pisolithus sp. (Ps) and Cenococcum geophilum (Cg), while the third, which was used as the control, was without any fungal infection. Further, the impact of air pollution caused by photochemical oxidant; ozone, on the growth behavior of these seedlings were distinguished. In experiments, two points on a root 3 mm apart were illuminated by laser beams and the elongation was measured continuously by analyzing speckle patterns successively taken by a CCD camera. It was found that the root growth rates of ectomycorrhiza-infected seedlings were significantly higher than that of non-infected seedlings, and Ps-infected roots showed the highest root growth rate. Moreover, the effect of ozone stress was clearly observable in non-infected seedlings, while the impact on ectomycorrhiza infected seedlings depended on the ozone concentration and the period of exposure. Our study revealed that the statistical interferometry offers high potential with a sub-nanometer sensitivity for measuring crucial dynamic parameters of biological objects in very short-periods as well as with high frequency, suggesting that exploration of new insights on dynamic behavior of living materials becomes much feasible in future studies.

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In this paper, a theoretical and analytical model of the conical projectile penetration into metallic targets under oblique impact is presented .The failure (or refraction) is assumed to be asymmetry petaling and the analysis is performed by using the energy balance and done work. The done work consist of the required work for plastic transformation W_p, the work for transferring the matter to new position Wd and the work for bending of the petals W_b. The results obtained from analytical model were compared with empirical results presented in reference [7] and their agreement is completely evident.

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The high measurement accuracy in dynamic tension testing is required for designs and numerical simulations based on the accurate modeling of stress-strain relations at various strain-rates. The non-coaxial Hopkinson bar method (NCHBM) is one of the recently proposed techniques for dynamic tension tests. In our previous study, the effects of the testing conditions were numerically examined in detail. In this study, first, the effects of the constraint condition and the dimensions of specimen were investigated by experiment. The experimental confirmation, in which the additional outputs of stress and strain were obtained through the strain gauges glued on the specimen, was also tried to check the stress-strain relation obtained by NCHBM. On the other hand, in order to verify the experimental results, some numerical models were examined through the FEM simulation, in which the whole finite-element model of the apparatus and the plate-type specimen were made in detail. Then, a few concrete approaches for the modification of the specimen fixation were examined by numerical simulation. The target material employed in this study was SUS316 stainless steel. If the experimental and calculated results were both obtained under the same condition, those were compared with each other. Finally, the results of the numerical trials were compared with each other and that without any modification.

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It is important to evaluate stress-strain relations for many kinds of aerospace materials at high-strain-rate in CAD or CAE of aircraft safety cabins to maintain a survivable environment for passengers and the crew in a crash. However, there are almost no data on mechanical properties of materials at the strain-rate 10^6 s^<-1> or more. Three or four kinds of compression testing systems are used for determining stress-strain curves of commercially pure aluminum: A1100P-H14 [JISH4000] and super duralumin: A2024P-T3 [JISH4000] in a wide strain-rate range up to 10^6 s^<-1>. On the basis of the newly modified Unsteady-Wave-Sensing-System (UWSS), which is composed of a plate impact experiment (PIE) using three in-material stress gauges and nanosecond Lagrangian analyses, various variables are determined at the sensing part of the central gauge.

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Polypropylene foams are widely used in many impact-absorbing applications (head protective helmet, packaging, passive safety application of vehicle). To improve the mechanical performance of these applications, these structures have to be modeled. This approach requires the characterisation of the foam behavior with high strain rate tests in order to identify parameters of rheological models commonly implemented in FE code. Tests were achieved on polypropylene foams under compression at high strain rate. The material behavior has been determined as a function of two parameters, density and strain rate. Samples (at several values of density 70, 80, 90 and 100 kg/m3) were impacted on a dynamic apparatus - a fly wheel-. This test consists in compressing the sample by an uniaxial compression module mounted on a metallic wheel (diameter 1 m, mass 617kg) turning at high speed. With this testing machine, the dynamic compressive behavior has been evaluated in the strain rate range of 40-400 s^<-1>.These classical tests allow to apply uniaxial compression on cellular material but these rheological tests were not sufficient to describe the foam behavior under complex state of stress. New rheological experiments have to be developed. For that, a complementary module was designed to apply hydrostatic compression at different strain rates. From these tests, stress-strain responses of polypropylene foam were defined as a function of density, strain rate and type of solicitation (uniaxial and hydrostatic compressions). Result curves show three regimes : an elastic behavior followed in a second step by a stress plateau corresponding to plastic yielding. Finally, for high strains, a rising hardening phase occurs due to foam densification.

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Cellular materials such as polymeric foams are often used for the development of composite materials as core in sandwich structures. Their use in the aircraft, naval, or automotive industries does not cease increasing by the way of their lightness and their great capacity to absorb energy. Generally used under a large range of strain rates the behavior of these materials must be identified in experiments before being integrated in finite element codes. The structural response of these foams strongly depends on their density, their cell structures, and the solid material properties. The viscoelastic nature of the solid polymer is, such as the gas trapped in the closed-cells, responsible of the sensitivity of the foam behavior. A viscoelastic Split Hopkinson Pressure Bar (SHPB) apparatus is used to perform tests at high strain rates.

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The present work is concerned with the determination of stress-strain hysteresis loops of several polymers in compression at strain rates of nearly 700/s using the standard split Hopkinson pressure bar. Four polymers or typical thermoplastics: ABS, PA-6, PA-66 and PC are tested. Cylindrical specimens of slenderness ratio (= height/diameter) of 0.5 are used in the Hopkinson bar tests, and those of slenderness ratio of 1.5 as specified in the ASTM Standards are used in the static tests. The low strain-rate stress-strain hysteresis loops in compression are measured in an Instron testing machine. The effects of strain rate on Young's modulus, 2.5% flow stress and dissipation energy (energy loss due to damping) are examined. It is demonstrated that the area within the stress-strain hysteresis loop (or dissipation energy) increases with increasing strain rate, that is, all polymers tested exhibit intrinsic dynamic viscoelasticity and a high elastic aftereffect following unloading.

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The high strain-rate compressive behavior of a unidirectional carbon/epoxy (T700/2521) composite in all three principal material directions (or fiber, in-plane transverse and thickness directions) is investigated using the stress reversal split Hopkinson pressure bar. To avoid uncertainties related to size effects, the specimens in all the tests have the same geometry, i.e., cubic specimen of nominal size 8 mm. The low and medium strain-rate compressive characteristics are measured using an Instron testing machine. It is shown that the ultimate compressive strength exhibits the positive strainrate sensitivity, while the ultimate compressive strain (or failure strain) and the absorbed energy up to failure exhibit the negative one in all three directions. The failure mechanisms of the test composite are discussed. The present study provides important data for the design of composite structures in high strain-rate applications.

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Recycled asphalt mixture is a multiphase system, which consists of sized recycled asphalt pavement (RAP), new asphalt, and/or recycling agents and new aggregates. RAP percentages may have influences on performance of total recycled asphalt mixture. The performance of an asphalt pavement is significantly affected by its resistance to permanent deformation (rutting) and its fatigue performance (crack formation and propagation). The indirect tensile test (ITT) represents an appropriate procedure for the study of crack formation (crack development) in asphalt pavements. The paper presents the results of a project aimed at investigating static and dynamic response as cracking and fatigue behaviors of recycled asphalt mixtures using the ITT. In particular ITT were performed in which the RAP percentages, loading mode and test temperature was varied. The analysis of the test results summarized below. (1) The indirect tensile strength and failure stiffness modulus show significant increase with RAP percentages in static loading test using ITT, especially in high loading speed. (2) Recycled asphalt mixture with recycling agent shows high fracture energy, which can prevent crack propagation. (3) The number of load cycles to fatigue failure expected presents a bit decrease with RAP percentages in dynamic loading test using ITT. (4) Recycling agent shows significant decrease in tensile strength and increase in fatigue life. It can be concluded that the ITT provides information of the influences of RAP and recycling agent to the recycled asphalt mixture.

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Recently, the interests in smart monitoring of various structures are increased. Especially, as the civil infrastructures such as bridges, tunnels and buildings become large-scale, it is necessary to monitor and maintain the safety state of the structures, which requires smart systems that can supply long-term monitoring during the service time of the structures. The composite and concrete hybrid structures are becoming very popular because of their long term reliability. Their structural behaviors also need to be monitored with a concept of smart structures. Korean civil engineers have been applied monitoring system to several structures, for example, Seo-Hae bridge, New Haeng-Ju Bridge and tunnels for Korean Express Railway, etc., but these applications have some problems in long term durability of sensors, high noise levels due to electro-magnetic interference and lead wire treatments due to lack of multiplexing capability. In the present study, optical fiber Bragg grating sensor smart system which is the probable means for long term assessments was tested and confirmed by laboratory tests of various structural members in Korea. Applying optical fiber sensors to structural members of real big structures, the responses of the structures were observed. In this paper, a fiber optic smart system was applied to Sungsan Bridge in Han River in Korea and the load capacity of the bridge was assessed. The real field test was performed to verify the behaviors of fiber Bragg grating (FBG) sensors attached to the containment structure in Uljin nuclear power plant in Korea as a part of structural integrity test which demonstrates that the structural response of the non-prototype primary containment structures. A fiber optic WIM (Weigh in Motion) system was also tested in the laboratory and experimented with actual high speed trucks. The system shows good capability of measuring the truck weight with ambient actual truck velocity.

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This work deals with the study of two innovative joint techniques for aluminum composites: bonding with structural adhesives and hybrid laser-arc welding. The research objective is the mechanical behaviour of the roof of a railway carriage made by aluminum foam sandwich (AFS) panels, which are bonded or welded one to the other and to the vertical rod. As well known, bonding with structural adhesive is a less expensive joining technology, that does not affect the material characteristics and results in a better distribution of stresses. So, the aim of the experimental analysis is to investigate and validate the use of this technique. Several static and fatigue test on the components were executed and the results achieved for the welded components and the bonded ones were compared. At the beginning static tensile tests were performed submitting the adhesive to shear stresses, in order to reproduce the real loading condition on the component. Then, fatigue test were done on welded components to plot fatigue curves.

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The in-plane orthotropic elastic constants of machine-made paper and paperboard were determined in a compact testing machine equipped with an optical extensometer and using a highspeed digital image sensor. Commercial copy paper, sack paper and paperboard were tested in a standard atmosphere of 23±2 ℃ and 50±2% relative humidity. A dumbbell-type specimen specified in the JIS Z 2201for sheet materials was used in the tension tests. Tensile specimens were cut in three different orientations from each type of paper and paperboard. Their thicknesses were carefully measured with a high-precision digital micrometer under a constant pressure. The in-plane elastic (Young's) moduli, shear modulus and Poisson's ratios as an orthotropic material were determined. It was shown that the in-plane elastic constants of commercial paper and paperboard roughly obey the theory of orthotropic linear elasticity.

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A pin joint of composite laminates has three failure modes: tensile, shear out and bearing and it is designed to yield the bearing failure mode since the endurance limit is high and the load-displacement curve has rather tough characteristics compared to other two modes. However, it is difficult to obtain the damage of the pin at the maximum load. Conventional manual control could not eliminate the time lag between detection of the maximum load and action to the machine by the operator. Thus, the additional damage evolution due to the stored elastic energy appears in the failed joint even if the bearing mode is rather tough and there are several hundred milliseconds between times at the maximum load and catastrophic failure. This paper shows that the damage at the maximum load is preserved by using the control code TestStarTM applied to MTS hydraulic loading machines. Previous papers on pin joints could not present the damage at the maximum point and missed the critical damage to trigger the bearing failure of a pin joint. This control method could separate clearly the critical damage and additional ones and contribute to the understanding of the failure mechanism of a CFRP pin joint.

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Numerical solutions of singular integral equations are discussed in the analysis of a planar rectangular interfacial crack in three dimensional bimaterials. The problem is formulated as a system of singular integral equations on the basis of the body force method. In the numerical analysis, unknown body force densities are approximated by the products of the fundamental density functions and power series, where the fundamental density functions are chosen to express a two-dimensional interface crack exactly. The calculation shows that the present method gives smooth variations of stress intensity factor along the crack front for various aspect ratios. The present method gives rapidly converging numerical results and highly satisfied boundary conditions throughout the crack boundary. The stress intensity factors are given with varying the material combination and aspect ratio of the crack. It is found that the stress intensity factors K_I and K_<II> are determined by bimaterials constant ε alone, independent of elastic modulus ratio and Poisson's ratio.

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In this study, an interfacial crack subjected to shear loading in three dimensional bimaterials is analyzed by singular integral equations on the basis of the body force method. In the numerical analysis, unknown body force densities are approximated by the products of the fundamental density functions and power series, where the fundamental density functions are chosen to express a two-dimensional interface crack exactly. The results show that the present method yields smooth variations of mixed mode stress intensity factor along the crack front accurately. The effect of crack shape on the stress intensity factor for 3D interface cracks is also discussed on the basis of present solution. Then, it is found that the stress intensity factors K_<II> and K_<III> are always insensitive to the varying ratio of shear modulus, and determined by Poisson's ratio alone. Distributions of stress intensity factor are indicated in tables and figures with varying aspect ratio of crack and Poisson's ratio.

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In this paper, three-point and five-point bend tests for evaluating the interlaminar shear strength (ILSS) of carbon fiber aluminum laminates (CFML) are investigated. CFML is a kind of fiber metal laminate (FML) and consists of carbon fiber reinforced polymer layers and metal layers. Aluminum alloy sheet of 0.5 mm thickness is selected as the metal. General formulae for the evaluation of ILSS of CFML from three-point and five-point bend tests are presented. Three-point and five-point bend tests and elastoplastic finite element analysis are conducted and the results of two kinds of bend tests are compared. It is found that five-point bend test gives more accurate evaluation for the ILSS of CFML than three-point bend test in the case of that the interface is not located at the neutral plane.

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In order to develop a High Speed Civil Transport, weight reduction by the use of advanced composite materials is one of the most important technical issues. However, composite laminates have very low interlaminar fracture resistance. Therefore, the interlaminar fracture toughness of composites has consequently become a critical design parameter for the aircraft structures. In this research, mode-I interlaminar fracture behavior of heat-resistant polyimide CFRP (Carbon Fiber Reinforced Plastics) was investigated by way of the double-cantilever-beam (DCB) test at high temperature up to 200℃. In the DCB tests at high temperature, fiber cross-over bridging was observed. In order to evaluate the influence of the bridging zone length on the crack growth resistance curve (R-curve), the DCB tests were conducted using specimens with different thicknesses. Fractographic observations of the fracture surface were performed in order to assess the crack growth behavior. The bridging characteristics were evaluated using a bridging law which describes the relationship between the crack closure traction resulting from the bridging fibers and the local crack opening displacement.

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We originally developed the micro-test system for evaluating the shearing strength under pull and push loadings. The evaluation of the static and cyclic shearing strength at the interface between fiber and the resin-matrix in PMC can be made at room temperature by using this test system. The sample with single boron fiber embedded in the resin was prepared. Then the shearing strength was examined at the fiber/resin interface by performing pulling out and pushing test for the fiber. The shear stress at which the first separation occurs between the fiber and resin was studied through the load-displacement response during the pull and push loadings. Moreover, the interface shear stress was discussed from FEM analysis; the shear stress reaches the maximum at the interface around the near top surface, which is the side the fiber is loaded on. It is suggested that the first separation between the fiber and resin-matrix is induced by this shear stress.

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Interfacial shear strength between epoxy and carbon fiber was analyzed utilizing the mi- crodroplet-bond specimens adhered onto single carbon fiber. The shear stress distributions along the fiber/matrix interface were calculated by finite element analyses using such models as droplet, sphere and cylindrical pull-out. (1) The interfacial shear stress analysis showed that larger stress concentration arose along the fiber/matrix interface for the microdroplet-bond specimen than for the cylindrical one. (2) Microdroplet-bond specimens showed high interfacial strength, which was caused by various effects of the geometry and size of microdroplet as well as stress concentration in the region contacting with the micro-vise tip. (3) Analysis of the octahedral shear stress in the micro-droplet specimens indicated that the average τ_<oct> over the embedded length was suitable to the evaluation of interfacial shear strength.

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Advanced Pore-Free SiC (APF-SiC) with super-high strength is developed by reaction sintering method improved newly. Authors had constructed a peculiar fracture mechanism model of this material differing from the fracture mechanism of usual ceramics. The fracture mechanism is that fracture occur at cluster crack (one of the formed some clusters). This fracture is called cluster fracture. In this study, to clarify adequacy of this model, clusters were researched in detail by using mapping analysis and observing some clusters. Crack growth behavior is researched by using AE censer. As the results, it is clarified that some clusters are formed by aggregate of un-reacted substance and the cluster fracture doesn't occur due to growth of cluster crack. In the case of 4-point bending tests is carried out at low loading rate, nonlinear behavior appeared on stress-strain curve before failure. In addition, bending strength increased with decreasing loading rate. On the basis of these results, fracture mechanism is considered as follows. Some clusters are formed by aggregate of un-reacted substance at near rupture. Cluster fracture occurs at the same time with cluster crack being one of the formed some clusters are formed. Therefore increasing strength is because to forms cluster crack stops by internal energy accumulated by loading was released since residual metallic silicones are preferentially failed.

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Our study deals with the recycling and strain rate effects on the mechanical behaviour of polymer composites. We particularly focus on high impact polypropylenes (rubber filled PP). These materials used for car bumpers and front shields are talc filled and unfilled impact modified polypropylene. Virgin specimens have been reprocessed (extruded) six times in order to evaluate the degradation due to recycling. Tensile tests have been performed for different strain rates. A comparison between experimental data obtained for both materials, virgin and recycled, have been carried out. These have permitted to quantify not only strain rate sensitivity but also the degradation of the mechanical properties after the recycling. Two approaches for the modelling of the stress-strain response are suggested in order to simulate the macroscopic behaviour: one valid for small strains and the other for large strains. Preliminary results of our simulations have been compared with the experimental data for virgin (none recycled) materials only and good agreements have been found.

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The unceasingly increasing establishment of composite materials in the manufacturing of structures intended for transport has given place to many studies in order to characterize their behaviour in a specific environment. One of the characteristics of these materials is the difficulty to visually detect the damage in the case of accidents such as dynamic collisions (tool drop, impact of flying debris...). Considering that it is difficult to avoid this kind of damage, it is necessary to appreciate the criticality of the caused defects, or in other words, to make sure that they are not detrimental to the structure during its life. This concern requires the set up of tests which consist, mainly, of impact tests in order to create the damage and loading representative of the ultimate load permitted by the structure (i.e. mostly by fatigue or quasi-static loadings). In the case of curved structures, such as laminated tubes, the main characterization test used is the CAI ("Compression After Impact") test . Therefore, the literature is quite rich concerning the set up of this kind of tests, as well as the results obtained. However, the Residual Tensile Strength After Impact (RTSAI) test is not used very often for this type of structures. The aim of the study, presented in this paper, is to determine the residual strength of pre-impacted curved panels stressed in tension. For each stage of the study, such as: i) impact testing, ii) non destructive testing and microscopic observation, iii) fracture in tension, a detailed description of the test methodology (i.e. sample preparation, device used ...) is presented. Experimental results obtained are presented and discussed in this paper.

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Dyneema (Ultra High Molecular Weight Polyethylene) based composite panels are used as armor material and give protection against fragments, bullets or other projectiles. In this paper, a new modeling approach to predict the ballistic strength of Dyneema composite is described. This approach is based on detailed modeling in combination with a decomposition of material properties. In the past, continuum approaches and discrete layered modeling have been used by other researchers to predict the response of Dyneema composite panels loaded by impact. These approaches were however not successful in predicting the ballistic strength, because fiber sliding, fiber failure and delamination of layers were not taken into account and static properties of the material were used. This often resulted in a calculated ballistic strength that was too low. In this research, these phenomena are taken into account in the proposed model together with dynamically determined material properties and it is expected that a better strength prediction should be possible. The modeling of Dyneema composite is done in ABAQUS/Standard for the quasi-static simulations and in ABAQUS/Explicit for the dynamic simulations and show more details than previously developed models.

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A new adaptive rate-dependent cohesive element is proposed in this paper. In this model, a pre-softening zone is proposed ahead of the existing softening zone. In this pre-softening zone, the initial stiffness and the interface strength are gradually decreased. The onset displacement corresponding to the onset damage is not changed in the proposed model. In addition, the critical energy release rate of the materials is kept constant. Moreover, the constitutive equation of the new cohesive model is developed to be depended on the opening velocity of the displacement jump. The traction based model includes a cohesive zone viscosity parameter (η) to vary the degree of rate dependence and to adjust the maximum traction. The new cohesive element is implemented in the explicit finite element code (LS-DYNA) as a user defined material subroutine (UMAT) designed for solid elements. The numerical simulation results of DCB in Mode-I is presented to illustrate the validity of the new model. It is shown that the proposed model brings stable simulations and can be widely used in quasi-static, dynamic and impact problems.

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Temperature influences the mechanical behaviour of polymers, but also - vice versa - deformation itself can cause a temperature change. This is a mutual effect which is well known to prevail especially in polymers at increased deformation rates. However, it is often not regarded in the analysis of material behaviour. The thermo-mechanical effect can be roughly divided in the thermo elastic effect, which is reversible, and the irreversible heat dissipation effect which is related to plastic deformation. In this paper the test setup for the thermo-mechanical analysis, consisting of a servo hydraulic testing machine and an infrared camera for the real time temperature field measurement, is presented. Tests were performed on different polymers under monotonic tensile test conditions. The various thermo-mechanical effects which can appear in polymers and the influence of the loading rate are exemplarily shown and discussed. Furthermore, a thermo-mechanic model is presented which allows the separation of the thermo elastic and the dissipative heat contributions. The test data of two different polymers are closer analysed using this model and the results are discussed. Aim of this analysis finally shall be the development of a new approach for the definition of a material damage point.

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The deformation process in polyolefinic thermoplastic elastomers (TPE) prepared by dynamic vulcanization of iPP/EPDM blends was investigated by FTIR spectroscopy and wide angle x-ray diffraction. The molecular orientation of the EPDM domains in TPE was higher than that of iPP matrix in TPE at the high uniaxial strain whereas the molecular orientation of the pure iPP at the high strain was strong. The molecular and crystallite orientation of EPDM in TPE was released whereas the orientation of iPP in TPE remained when the strain was released. The deformation of EPDM domains showed the elastic deformation and dominated the TPE deformation at the high uniaxial strain, after the fracture of iPP matrix phase occurred in the equatorial iPP region neighboring elongated rubber domains at the low strain. The elasticity of TPE was caused by the EPDM domains.

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The effect of number of methylene chain of aliphatic polycarbonate glycol (C_3-C_6) on their properties themselves and polyurethane elastomers (PUEs) incorporating them was investigated. Viscosity of the PC glycols decreased with increasing number of methylene chain. The PC glycols with even numbers of methylene chain (C_4 and C_6) were more crystallizable than for odd numbers (C_3 and C_5). The degree of microphase separation of the PC glycol-based PUEs became stronger with decreasing number of methylene chain. In the tensile testing, the PC glycol-based PUEs with even number of methylene chain exhibited larger tensile strength and smaller strain at break in comparison with those with odd number. Odd-even effect of methylene chains was clearly observed not only the properties of the original PC glycols but also those of the PUEs incorporating these PC glycols.

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We study the stretching driven director-switching in a thin film of liquid crystal elastomers having the initial director in the thickness direction (x-direction). The thin film specimen is uniaxially stretched in the z-direction normal to the initial director. The stress-strain curve has the three characteristic regions: the small strain region (I) obeying linear elasticity, the moderate strain region (II) exhibiting a quasi-plateau stress, and the large strain region (III) where the stress increases again. The Poisson's ratio μ_<yz> in the strain region (II) is considerably small (〜0.17) while those in the region (I) and (III) are nearly 0.5. These features in the strain region (II) result from the cooperative uniform rotation of director towards the stretching direction. The strain dependence of the IR dichroic ratio of the mesogen also supports this picture.

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Anisotropy of the bridge fraction of middle isoprene block chains in sheared films of sphere-forming polystyrene-b-polyisoprene-b-polystyrene triblock copolymers in different directions are examined by breaking stress under simple elongation measurements at a fast draw rate, which reflect the bridge fraction. There was no practical difference between the data obtained for the films cut in the directions parallel and perpendicular to the shear flow direction at each shear rate. The breaking stress for the samples sheared at high shear rates become slightly lower than those obtained at low sher rates. The absolute values and the difference is consistent with the previous study, in which pull out of end blocks due to the flow is examined. Thus, we conclude that when flow is applied to sphere-forming triblocks, only small portion of end blocks are pulled out to flow and there is no orientation dependent anisotropy of bridge fractions.

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PA6/PTFE blends with varying PTFE content from 3 wt.% to 15 wt.% were irradiated by ^<60>Co gamma ray with various doses (20kGy, 50kGy and 100kGy) at ambient conditions. Moisture absorption test, U-notched Charpy impact test and quasi-static tension and bending were conducted to investigate the effect of irradiation on moisture absorption and mechanical properties of the blends. It is shown that the exposure of the blend to ^<60>Co irradiation improves the tensile modulus, tensile strength and flexural modulus due to irradiation induced cross-linking in PA6 phase. However, the Charpy impact strength of the blends is much lower than the original PA6 and it decreases slightly with the irradiation dose. Moreover, the flexural modulus is found to increase to a maximum value and then decreases with further increasing the PTFE content, and the moisture absorption decreases with the increases both in PTFE content and in irradiation dose.

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Since two decades unfilled and filled high impact polypropylenes have been used increasingly in automobile applications. The current economical and environmental contexts compel the car industry to focus their research on the recycling process of these materials. Of course, this process intervenes after a life cycle of use so degradation occurred due to oxidants, pollutions, loadings, etc. The studied materials are composed of polypropylene for matrix phase, EPDM or EPR as elastomeric nodules and talc as fillers. Therefore this study deals as well with recycling process effect and pollution effects on mechanical properties of unfilled and talc-filled high impact polypropylene. The recycling process is simulated by a six times reprocessing of virgins materials and the life cycle simulation is made by an adding of pollutants as engine oil and windshield washer fluid during the first extrusion process. Interactions between these products are also studied. In order to characterize the recycling and pollution effects, tensile test for small strain domain were conducted. Evolutions of Young modulus and yield stress are quantified in order to study the degradation occurred during recycling and pollution processes. Physical explanations are also proposed to elucidate these effects. Some post mortem SEM observations are made in order to confirm experimental observations on these effects on the microstructure.

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The fracture behavior of a brittle polymer, polymethyl methacrylate (PMMA) resin, under impact tensile loading was studied using single-edge-cracked specimens. The dynamic load and displacement were measured with a Piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e., the external work U_<ex> applied to the specimen was used to determine the elastic energy E_e and non-elastic energy E_n due to viscoelastic and plastic deformation, and the fracture energy E_f for creating new fracture surface As. The energy-release rate was then estimated using G_f=E_f/A_s. The values of E_e, E_n, E_f and G_f were correlated with the fracture loads, and compared with the ones earlier determined for the static loading conditions.

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Thermoplastic resin was practically used without post cure treatment and physical aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. And the effect of physical aging has the time and temperature dependency. The effect was occurred on the materials after molded, and the effect saved on the materials as the thermal history. This history has big influence on mechanical properties, especially creep properties. Therefore, it is necessary to understand the progress of the physical aging. In this report, the creep deformation of polycarbonate (PC) was researched to grasp the effect of physical aging on creep behavior. Two types of materials were prepared. One was "molded material", and another was pre-physical aged material. It was confirmed that the effect had the time and temperature dependency, and it had been able to apply the time-pre-aging time superposition principle and time-pre-aging temperature superposition principle of physical aging on creep behavior. The estimation corresponding to temperature change of creep deformation became possible using this superposition principle. The estimation result of the creep deformation of glass fiber reinforced polycarbonate (GFRPC) with temperature change during a creep test had the tendency similar to the experimental data. Therefore, it should be able to estimate the creep behavior with arbitrary thermal history since the materials reached to the saturated state of physical aging.

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It is shown that both the tensile strength and ductility increase with an increase in strain rate for the nanocomposites, but the tensile strength increases and the ductility decreases with an increase in strain rate for nylon 6. The 2 wt% clay-reinforced nylon and 5 wt% clay-reinforced nylon have similar strengths, which are increased by about 30% compared to those of nylon 6. With an increase in loading rate, the ultimate tensile strength increases. The fatigue strength of 2 wt% clay-reinforced nylon is also increased by about 30% compared to that of nylon 6, but the fatigue strength of 5 wt% clay-reinforced nylon is slightly increased or similar to that of nylon 6. The cyclic deformation has been examined using stress-strain hysteresis loops. The small cyclic deformation in 5 wt% clay-reinforced nylon is attributed to the no increase in fatigue strength. Furthermore, time-dependent behavior and microscopic damage mechanisms are discussed.

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Polymer blends of poly(lactic acid) (PLA) with poly (ε-caprolacton) (PCL) and tri-isocyanate (LTI) were developed to improve the fracture resistance of biodegradable PLA. LTI was added to improve the miscibility between PLA and PCL. The study shows that the fracture toughness increases dramatically due to the addition of LTI. Microscopic examination also shows that size of the PCL phase decreases due to the LTI addition, leading to reduction of void formation and suppression of local stress concentration, thus the toughness improvement. The improved miscibility also contributes to the ductility enhancement, which further increases the fracture toughness.

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This paper presents an improved rail shear method of ASTM D 4255/D4255M and the design procedure of new fixture for low cyclic shear loading. This fixture is designated to determine mechanical properties of in-plane shear modulus, nonlinear shear stress-strain curves, shear strength and visco-elastoplastic behaviour of fibrous composites under cyclic shear loads. A series of experiments have been carried out using the new rig to determine shear stress-strain response of unidirectional fibre reinforced laminated specimens under various cyclic loading conditions. An FE simulation has been conducted using a commercial code ABAQUS and its user subroutine UMAT to define nonlinear material behaviour as a verification of the accuracy of the new Cyclic Rail Shear Fixture (CRSF).

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The logarithmic strain, which is sometimes called as "true strain" or "natural strain", is defined as the sum of each differential change in specimen length divided by its current length. This paper proposes a new interpretation, that is, the logarithmic strain is the difference of Eulerian displacement of the specimen measured at two separate reference points, which are fixed in space, divided by the distance between them. An Eulerian type displacement meter which gives Eulerian description of the displacement directly is also proposed and it is shown that PC mouse, which is now an indispensable input device of computers, is by itself an excellent Eulerian displacement transducer. While in computer environments, mouse moves on the fixed pad and it measures its own movement, in this study, the movement of the object is measured by the mouse fixed in space. It is analytically and experimentally shown that the logarithmic strain is obtained by dividing the difference of the readings of two Eulerian displacement meters by their separation distance.

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Recent advances in experimental mechanics for smart materials are listed in three categories of modeling, shape memory alloy, structural health monitoring and sensors.

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