The ENGIN-X beamline is mainly used to determine residual strains/stresses deep within the interior of bulk engineering components. It is mainly used by scientists and engineers for the development of modern engineering processes and structural integrity investigations. ENGIN-X diffraction and transmission mode can be a very useful tool to measure strain, phase transitions, texture and material composition in spatial resolution in historical or archaeological artifacts and modern materials. The complexity of the shapes and sizes of the samples measured on ENGIN-X varies significantly between experiments, and this required the development of better planning, simulation and control software, SScanSS. In this paper an overview of recent developments in strain scanning on ENGIN-X and a highlight of current scientific research are presented.

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Powder injection molding (PIM) is one of the most versatile methods for the manufacturing of small complex shaped components from metal, ceramic or cemented carbide powders for the use in many applications. PIM consists of mixing the powder and a polymeric binder, injecting this mixture in a mold, debinding and then sintering. Catalytic debinding of polyoxymethylene (POM) is attractive since it shows high debinding rates and low risk of cracking. This work examines the possibility of using POM with bimodal molecular mass distribution as the main component of the binding agent by studying its time-dependent properties and comparing them to monomodal POM. Furthermore, possible optimization of the binder formulation was investigated by the addition of shorter polymeric chains (wax) to bimodal POM, as to create a multimodal material. It was observed that the magnitude of the complex viscosity for the commercial bimodal material was more than 2 times lower than for the chemically identical monomodal POM within the investigated frequency range and temperature. Viscosity values were observed to drop as the content of wax was increased, without compromising the binders mechanical properties in solid state. A new formulation of bimodal POM plus 8 wt.% of added wax provided the most appropriate results from investigated combinations. This work has shown how the addition of short polymeric chains in POM influences its time-dependent properties in solid and molten state, which can be an important tool for the optimization of binders designed to be used in PIM technology.

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Fine particle peening (FPP) treatment was introduced to improve the oxidation resistance of austenitic stainless steel. After FPP treatment, oxidation tests were performed at 700 and 800 °C for 1, 4 and 12 h in an atmospheric environment. The surface microstructures of the oxidized specimens were observed using optical microscopy, scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GD-OES), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The amount of oxygen diffused into the FPP-treated specimens was significantly less than that into un-peened specimens. Iron oxides were formed in the un-peened specimens as a result of the oxidation tests. In contrast, a protective chromium oxide layer was created on the FPP-treated surface, because the fine grains and dislocations induced by FPP treatment accelerated the diffusion of chromium during the subsequent oxidation tests. These results indicate that FPP treatment is a very efficient process to improve the atmospheric oxidation resistance of austenitic stainless steel.

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High cycle fatigue (HCF) damage caused by normal traffic loading is one of the major modes of failures in steel bridges. During bridge service life, there are extreme loading situations such as typhoons, earthquakes which cause higher amplitude loading than normal traffic loading. Due to this reason, critical members could undergo overstress cycles in the plastic range. Therefore, such members are subjected to low cycle fatigue (LCF) during these situations while subjecting to HCF in serviceable condition. Bridges, which are not seriously damaged, generally continue to be functioned after these extreme loading situations and fatigue life estimation is required to ensure their safety. Therefore, this paper presents a new damage indicator based fatigue model to predict life of steel bridges due to combined effect of extreme and normal traffic loadings. It consists of a modified strain life curve and a strain based damage indicator. Both the strain life curve and the damage indicator are newly proposed in the study. Modified strain life curve consists of Coffin Manson relation in the LCF regime and a new strain life curve in the HCF regime. Damage variable is based on von Mises equivalent strain and modified by factors to consider effects of loading non proportionality and loading path in multiaxial stress state. The new damage indicator can capture the loading sequence effect. The proposed model is verified with experimental test results of combined HCF and LCF of three materials; S304L stainless steel, Haynes 188 (a Cobolt superalloy) and S45C steel obtained from the literature. The verification of experimental results confirms the validity of the proposed model.

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Civil infrastructure systems are prone to age related deterioration due to the exposure to aggressive environmental conditions and inadequate maintenance, and often causes reduction of their carrying capacities. Designing these systems for a particular service life and maintaining them in a safe condition during their entire service life have been recognized as very critical issues worldwide. There have been many damage examples of older steel bridge structures due to corrosion around the world during past few decades and they intensified the importance of attention to the careful evaluation of existing structures for the feasibility of current usage and strengthening them by retrofitting some selected corroded members to ensure the public safety. Therefore, a simple and accurate method to calculate the remaining yield and tensile strength by using a concept of representative effective thickness with correlation of initial thickness and the maximum corroded depth is proposed in this study, based on the results of many tensile coupon tests conducted on corroded specimens cut from a steel girder used for about hundred years with severe corrosion. The proposed methodology revealed more accurate and reliable estimation for the maintenance management of existing corroded steel structures.

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Rubber O-rings exposed to high-pressure hydrogen gas swell, and the volume increase induced by swelling influences tensile properties of the O-rings. Samples of nonfilled (NF), carbon black-filled (CB), and silica-filled (SC) sulfur-vulcanized acrylonitrile-butadiene rubber were exposed to hydrogen at 30 °C and pressures of up to 100 MPa, and the effect of hydrogen exposure on the volume increase, hydrogen content, and tensile properties was investigated. The residual hydrogen content, measured 35 minutes after decompression, increased with increasing hydrogen pressure in the range 0.7-100 MPa for all three samples. In contrast, the volumes of NF, CB, and SC barely changed at pressures below 10 MPa, whereas they increased at pressures above 10 MPa. This nonlinear volume increase is probably related to the free volume of the rubber structure. The volume increase of the CB and SC samples was smaller than that of the NF samples, possibly because of the superior tensile properties of CB and SC. As the volumes of the NF, CB, and SC samples increased, their tensile elastic moduli decreased as a result of a decrease in crosslink density and elongation by volume increase. Although the true fracture stress of NF was barely dependent on the volume of the specimen, those of CB and SC clearly decreased as the volume increased. The decrease in the true fracture stress of CB and SC was related to the volume increase by swelling, showing that the boundary structure between the filler and the rubber matrix was changed by the volume increase.

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The purpose of this study is to investigate the influence of peening on the rolling contact fatigue (RCF) life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings. In particular, they were most increased by the FPP. On the other hand, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the RCF tests, the RCF lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the p_max - N curves and the [A(σ_y/√3 HV)]_max - N curves, the improvement in RCF lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the RCF were equivalent under the same surface roughness and the same surface hardness. It follows from these that the surface treatment condition should be selected according to the rolling contact conditions and the failure modes of machine elements.

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Fracture phenomena in industrial structures are initiated mostly at the surface or from internal cracks due to defects already existing in the material, and generally propagate in all directions, often having irregular shapes. In structures and machinery, inclusions in the material, corrosion, and fatigue from use and other reasons cause the inevitable occurrence of defects or cracks. There are not only material metallurgical defects but also the discontinuity of parts due to fastening, configuration design, lubrication, etc., in structures and machinery. In actual overloading accidents, not only crack opening load but also shear load affects the propagation phenomena of defects or the crack tip. Therefore, fracture behavior under mixed fracture mode is caused and these behaviors are not simple. In this study, we carried out a three-point bending experiment in mixed mode including mode I, and showed that the crack growth route varies in the fracture when the shape of the initial crack changes. It is important to establish a fracture route prediction theory for different shapes of initial cracks in order to minimize possible damage or prevent accidental failure, and to prevent the crack from propagating to the most important parts of the structure. From the results, the difference among the fracture routes was examined, showing that the extent and velocity of crack propagation, the stress intensity factor, and the energy release rate varied with the degree of initial crack of the specimen.

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This study aims at showing a measurement procedure for quantitative assessment of the global and local plastic strains using electron backscatter diffraction (EBSD). In an experiment, duplicate crystal orientation measurements were made for the same area under different measurement conditions using a deformed stainless steel specimen. Then, distribution of the local misorientation was investigated. Although the global plastic strain could be quantified by using the parameter MCD, the local misorientation for assessing the local plastic strain depended on the measurement conditions. It was shown that, by applying a smoothing filter, dependency of the local misorientation on the measurement conditions could be made negligibly small. It was concluded that the smooth filtering was a practical technique for quantitative assessment of local misorientation.

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A hybrid process combining electrolytic in-process dressing (ELID) grinding with thermal oxidation (TO) was performed to improve the corrosion resistance of Co-Cr-Mo alloy. The treated surfaces were observed and analyzed using scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GD-OES) and X-ray photoelectron spectroscopy (XPS). Corrosion resistance was evaluated using potentiodynamic polarization measurements and metallic ion elution tests. The color of the treated surfaces was changed and the level of oxygen content was significantly increased by thermal oxidation treatment. In particular, specimens treated with ELID/TO hybrid processing had thicker oxide layers than those of the polished and thermal oxidation hybrid processed (P/TO) specimens. In addition, the amount of cobalt on the surface was diminished by ELID/TO hybrid processing. Specimens treated by ELID/TO hybrid processing exhibited lower amounts of cobalt ion elution among all the specimens. These results suggest that application of the ELID/TO hybrid process as a surface finishing method for metal implants can improve corrosion resistance.

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Scanning electron-induced acoustic microscope (SEAM) has been developed as a new tool for non-destructive observations of the internal microstructures of materials. It consists of the electric chopper to pulse the high current electron beam and the detector of the longitudinal acoustic waves, both being attached to the commercial scanning electron microscope (SEM). The cyclic chopping of electron beam with extremely high frequency of a few hundred kilohertz makes the thermal wave due to the cyclic temperature rise with the short period. The wavelength of thermal wave may determine the essential SEAM resolution, because it's much smaller than the thermal stress wave (that is, the acoustic wave), which has just the role of conveying the information of thermal wave disturbance due to unexpected change as defects. Our own-built SEAM gives the best performance for observing the internal defects like the micro-voids, because it susceptibly senses the local difference of thermal properties in the sample. The paper indicates that some non-destructive observations for the micro-voids with a few microns order existing in the sintered materials are exhibited in conjunction with their destructive observations using focused-ion beam (FIB) technique to make certain of those as the proof.

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The present authors proposed the smart layer composed of piezoelectric film and flexible printed circuit for the crack identification. The smart layer was used in the passive electric potential CT method, which identifies cracks from the electric potential distribution incurred due to the direct piezoelectric effect on a piezoelectric film pasted on a structure. On the contrary by applying an electric pulse actively on an electrode on the smart layer, a pulse echo can be emitted due to the inverse piezoelectric effect. Reflected waves received at several electrodes can be used for crack identification. In the present study a large number of electrodes on the smart layer were used for emitting the pulse echo and also for receiving the reflected echo. The mono probe method and the dual probe method were proposed. The multiple electrodes active pulse echo method using the smart layer was applied to the identification of through-thickness cracks. It was found that the cracks can be easily detected and a rough estimation of the crack location can be made by receiving flaw echo and bottom echo in the mono probe method. The dual probe method was found useful for detailed identification of the cracks from the time-of-flight of reflected signals for various combinations of the pulsing and receiving electrodes.

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EBSD(Electron BackScatter Diffraction) analyses were conducted for studying the quantitative microstructural metrics of creep and creep-fatigue damage for austenitic SUS304HTB boiler tube steel and ferritic Mod.9Cr piping steel. KAM(Kernel Average Misorientation) maps and GOS(Grain Orientation Spread) maps were obtained for these samples and the area averaged values KAM_ave and GOS_ave were obtained. While the increasing trends of these misorientation metrics were observed for SUS304HTB steel, the decreasing trends were observed for damaged Mod.9Cr steel with extensive recovery of subgrain structure. To establish more universal parameter representing the accumulation of damage to compensate these opposite trends, the EBSD strain parameters were introduced for converting the misorientation changes into the quantities representing accumulated permanent strains during creep and creep-fatigue damage process. As KAM values were dependent on the pixel size (inversely proportional to the observation magnification) and the permanent strain could be expressed as the shear strain which was the product of dislocation density, Burgers vector and dislocation movement distance, two KAM strain parameters M_εKAMnet and M_εδKAMave were introduced as the sum of product of the noise subtracted KAM_net and the absolute change from initial value δKAM_ave with dislocation movement distance divided by pixel size. M_εδKAMave parameter showed better relationship both with creep strain in creep tests and accumulated creep strain range in creep-fatigue tests. This parameter can be used as the strain-based damage evaluation and detector of final failure.

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Strain measurements around the eye during the blink are performed for four human subjects in order to investigate the relationship between the wrinkle formation with aging and the strains by daily motion. In addition to the strain measurement, the moisture content, the flexibility and the elasticity of the skin surface are measured for investigating the skin condition. For observing the wrinkle formed on the facial skin, the replicas of the skin surfaces are also collected. Results show that the relationship between the wrinkle and the strain distribution at the inner corner of the eye is different from that at the corner of the eye. The results indicate that different methods for the corner of the eye and the inner corner of the eye are required for avoiding the wrinkle formation.

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This paper is concerned with the development of micro actuator using magnetic materials. The micro actuator is composed of two permanent NdFeB magnets and kerosene-based magnetic fluid, Ferricolloid HC-50. The actuator is characterized by wireless operation with alternating magnetic field. The driving characteristics of micro magnetic fluid actuator were examined by using a high-speed digital video camera system. The dynamic behavior of magnetic fluid surface at higher frequencies of external alternating field was also examined. It was found that the amplitude of reciprocating actuator depends on significantly frequency and amplitude of alternating magnetic field. The effect of the volume of magnetic fluid adsorbed to the permanent magnets was also examined. The detail of surface oscillation of magnetic fluid subjected to alternating magnetic field was also revealed experimentally.

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Machine components of industrial products are often produced by press cutting. However, the mechanism of cutting (ductile fracture of metals) is not perfectly understood. In order to clarify this mechanism, cutting processes were observed by an ultrahigh-speed camera. The ultrahigh-speed camera is capable of recording maximum record rate 1,000,000 frames per second (preserved images102 frames); each frame has 80,000 pixels. Therefore, this ultrahigh-speed camera is currently the world's most advanced camera in terms of spatial and time resolutions. A detailed movie of the cutting process was recorded. The details of the cutting process include the crack length versus time, crack tip opening angle, and fracture path. The crack tip opening angles were evaluated approximately 0.1 mm behind the tip of the propagating crack. The CTOA criterion was found to be almost valid during the cutting process. Furthermore, in order to use the image correlation method, random patterns were generated by spraying paint onto the metal sections. Images of a specimen section were taken after punching the sheet metal. The distributions of displacements were evaluated by the digital image correlation method. We found smoothly cut sections and rough surfaces. A smoothly cut section is very important for industrial products. In this study, the optimal speed of punching and punch-die clearances were examined. The ductile fracture criterion determined in this study is extremely useful for fabricating machine components by press cutting because it can be used for simulations without the need for a cutting system. The data of the image correlation method can be used for an intelligent hybrid method that can provide very accurate strain and stress distributions and fracture parameters such as the T^* integral, which is the most promising fracture parameter for assessing the quality of metallic materials.

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Residual stress distributions of 35 mm thick dissimilar metal butt-weld between A533B ferritic steel and Type 304 austenitic stainless steel (304SS) with Ni alloy welds and similar metal butt-weld of 304SS were measured using neutron diffraction. Effects of differences in thermal expansion coefficients (CTEs) and material strengths on the weld residual stress distributions were discussed by comparison of the residual stress distributions between the similar and dissimilar metal butt-welds. Residual stresses in the similar metal butt-weld exhibited typical distributions found in a thick butt-weld and they were distributed symmetrically on either side of the weld line. Meanwhile, asymmetric residual stress distributions were observed near the root of the dissimilar metal butt-weld, which was caused by differences in CTEs and yield strengths among both parent materials and weld metals. Transverse residual stress distribution of the dissimilar metal butt-weld was similar trend to that of the similar metal butt-weld, since effect of difference in CTEs were negligible, while magnitude of the transverse residual stress near the root depended on the yield strengths of each metal. In contrast, the normal and longitudinal residual stresses in the dissimilar metal butt-weld distributed asymmetrically on either side of weld line due to influence of differences in CTEs.

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The effectiveness of stress-relief groove that significantly improves the fretting fatigue strength has been validated through many fatigue tests using a full-scale railway wheelset. However, the reason for this increase has not been yet fully understood. The objective of this study is to clarify the mechanism responsible for the improvement of the fretting fatigue strength by a stress-relief groove. In this study, fretting fatigue tests using a pre-cracked specimen was done based on the assumption that the fretting fatigue phenomenon can be regarded as a crack propagation problem. In the experiment, the fretting fatigue strength was improved by the stress-relief groove. The result suggested that the propagation of the pre-crack was suppressed by the stress-relief groove. An FEM analysis showed the reason for the suppression of the crack propagation. The mode I stress intensity factor of the pre-crack was reduced by the stress-relief groove. This was achieved by both relaxation of the stress around the contact edge and development of static compressive stress field by severe concentration of the contact pressure due to overhang.

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This paper deals with an inverse problem for estimating welding residual stresses in a butt-welded plate from measured data. In previous papers, a method of thermo-elastic boundary element inverse analysis was proposed to estimate the inherent strains in the butt-welded plate. It was found in the papers that the accuracy of the evaluated inherent strain in the butt-welded plate was low when the location of the measurement points was far from the welding line or the number of measurement points was small. This paper examines how the shape of the inherent strain distribution affects the accuracy of the estimated results. Trapezoidal and triangular inherent strain distributions were assumed in each analysis model of the butt-welded plate. Numerical simulations were conducted for those analysis models. In the simulations, measurement errors were included in stresses at measurement points. From all calculation results, it was found that the inherent strains in the butt-welded plate were evaluated in high accuracy from a few measured data by using Tikhonov's regularization regardless of the shape of the inherent strain distribution. The residual stresses in the whole butt-welded plate were calculated from the evaluated inherent strains. Accordingly, it became clear that the proposed boundary element inverse analysis with Tikhonov's regularization was useful in evaluating the residual stresses in the butt-welded plate.

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The structural components which are used in high temperature gas turbines have various shapes which may cause the notch effect. Moreover, the site of stress concentration might have the heterogeneous microstructural distribution. Therefore, it is necessary to clarify the creep fracture mechanism for these materials in order to predict the life of creep fracture with high degree of accuracy. In this study, the creep crack growth tests were performed using in-situ observational testing machine with microscope to observe the creep damage formation and creep crack growth behavior. The materials used are polycrystalline Ni-base superalloy IN100 and directionally solidified Ni-base superalloy CM247LC which were developed for jet engine turbine blades and gas turbine blades in electric power plants, respectively. The microstructural observation of the test specimens was also conducted using FE-SEM/EBSD. Additionally, the analyses of two-dimensional elastic-plastic creep finite element using designed methods were conducted to understand the effect of microstructural distribution on creep damage formation. The experimental and analytical results showed that it is important to determine the creep crack initiation and early crack growth to predict the life of creep fracture and it is indicated that the highly accurate prediction of creep fracture life could be realized by measuring notch opening displacement proposed as the RNOD characteristic.

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In order to develop ultrasonic method for the quantitative measurement of in-situ rock stresses, we investigate the influence of stress concentration on the body-wave velocities around a borehole. First, the acoustoelasticity theory of finite-deformation solids yields a direct and explicit quantitative borehole acoustoelasticity, which reveals that the orientations of the maximum and minimum wave-velocity shifts at the borehole surface coincide with the directions of the minimum and maximum far-field principal stresses, respectively. Second, pulse-echo measurement of wave-velocity variations at the borehole surface in the sandstone sample under the biaxial compressional loadings is performed to validate the quantitative borehole acoustoelasticity. The consistence of the experimental results with the theoretical prediction means that the ultrasonic method based on acoustoelasticity theory could be a promising noncontact and non-destructive method for the quantitative measurement of in-situ rock stresses.

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A method for extracting optimum images from a large amount of speckle images is proposed for ESPI measurement under environmental disturbance. During the measurement of static deformation under environmental disturbance, optimum images which can make interference fringes are extracted from the speckle images before the image subtraction. The extraction is performed based on the evaluation of the highest speckle contrast in time series value. The validity of the method is investigated by experiments under the environmental disturbance coming from the floor. Results indicate that the extraction method is effective and it is possible to measure static surface deformation by ESPI without a vibration isolator under environmental disturbance.

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ISO 15653 is a Crack Tip Opening Displacement (CTOD) testing standard for welds, and has issued since 2010. This new testing standard consists of two different CTOD calculations, displacement-conversion CTOD for deep-notched specimens and J-conversion CTOD for shallow-notched specimens, and ISO 15653-based CTOD changes at the boundary of crack length between deep-notched and shallow-notched specimens. In this study, changes in ISO 15653-based CTOD were investigated by using experimental and analytical data for the wide range of steel mechanical properties. J-conversion CTOD did not correspond to displacement-conversion CTOD, and there were significant mismatches in ISO 15653-based CTOD at the crack length boundary particularly for the steels of the low strain hardening exponent of the Ramberg-Osgood relation. Displacement-conversion CTOD calculation by using the modified plastic rotational factor or using the CTOD transformation equation proposed in this study is helpful in moderating the underestimated CTOD for low strain hardening exponent shallow-notched specimens.

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We studied the modification process of polystyrene (PS) samples by using plasma irradiation to achieve long lived hydrophilic surface. PS samples were treated using by electron cyclotron resonance plasma. The plasma irradiation process that we developed is consisted of two steps treatment. The first step is the pretreatment by only argon plasma irradiation, and the second step is the treatment by argon/oxygen plasma irradiation. The hydrophilicity of PS samples was evaluated by water contact angle and X-ray photoelectron spectroscopy (XPS). The water contact angle of PS samples decreased after plasma irradiation, and this result of the contact angle is indicating the obvious hydrophilic transformation of the plasma irradiated PS samples. Furthermore, this two steps process including pretreatment of argon plasma irradiation is effective to inhibit the contact angle increasing with time and keep the hydrophilicity of PS samples for long time. The pretreatment of argon plasma irradiation is considered to improve the reaction efficiency of oxygen radical at PS sample surface because the argon ion had the physical effect and increased the reactive site or surface area of PS surface. XPS analysis shows that the functional groups including oxygen are existing on PS sample surface after treated by plasma, and these groups were responsible for the change of hydrophilicity. XPS spectra of the plasma treated PS sample showed that the peak area assigned to O-C=O group was decreasing with time. The functional group as O-C=O is presumed to be the most important factor for the hydrophilicity of PS sample.

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The fracture behavior of a light-cured resin composite under impact tensile loading was studied using single-edge-cracked specimens fabricated by packing the composite between two rectangular plates of polymethyl methacrylate (PMMA). The impact 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 applied to the specimen was partitioned into three parts: the elastic energy left in the fractured specimen, the nonelastic energy due to viscoplastic deformation and the fracture energy for creating new surfaces. The energy release rate G_f was then estimated using the fracture energy in the composite and PMMA specimens. The results indicated that, although the value of G_f in both materials increased with the fracture load, they showed different increasing behaviors.

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This paper presents tensile properties of a polyimide thin film used in electronic devices. Tensile tests were performed to determine Young's modulus, proportional limit, yield stress, ultimate tensile strength and elongation of the polyimide film. Effects of strain rate and temperature on the tensile properties were discussed. There was a little effect of strain rate on Young's modulus but proportional limit, yield stress and ultimate tensile strength increased with increasing strain rate. Only elongation decreased with strain rate. Young's modulus, proportional limit, yield stress and ultimate tensile strength decreased with increasing temperature, but elongation increased. Applicability of a viscoelastic model for describing the stress-strain curves of the polyimide film was discussed.

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In this study we attempted to evaluate the degree of degradation of an unsaturated polyester resin when it was degraded by exposing it to hot water at 90°C, using the frequency of zero-group-velocity (ZGV) Lamb waves. The energy of ZGV Lamb waves does not propagate while the phase velocity remains finite. We generated ZGV Lamb waves with a Q-switched YAG laser and detected them with a focused air-coupled transducer at the same area of an irradiation point of the YAG laser in con-contact matter. A change in measured frequencies of ZGV Lamb waves decreased with increase of exposed period to hot water and are corresponding to the change in Young's modulus and thickness of the plate near the exposed surface

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A method of reducing the concentration of dynamic stress that utilizes the circumferential propagation and interference effect of a stress wave was investigated. An impact compression load was applied to a strip specimen made of polymethylmethacrylate with circular holes. These holes consist of a central hole and two additional holes on the strip whose respective diameters, d₀ and d₁, and the distance between the holes, pitch p, were varied. Dynamic elastic stresses on the minimum cross section of the holes were calculated using DYNA3D software to obtain the stress concentration factor K. The value of K at the central hole decreased as the diameter of the additional holes was increased because of the interference of the reflected wave and the circumferential propagation of the stress wave around the edges, which are considered to have reduced the amplitude of the stress at the edge of the central hole. Therefore, this reduction method involving the addition of holes is useful for the impact safety design of mechanical structures. Experiments gave similar results to those obtained by calculations.

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Metallic implant rods that are used to design spinal fixtures should have a Young's modulus that is not only sufficiently low to prevent stress shielding for the patient but also sufficiently high to suppress springback for the surgeon. Therefore, there is a need for novel titanium alloys with good biocompatibility and a changeable Young's modulus. Molybdenum is non-toxic, and Ti-Mo alloys possess good biocompatibility. In metastable β-type Ti-Mo alloys, an ω phase can be introduced by deformation at room temperature. This study investigated the effects of deformation-induced phases on the mechanical properties of a metastable β-type Ti-16Mo alloy. The experimental results indicate that the Young's modulus, tensile strength, and Vickers hardness are increased remarkably by cold rolling. The microstructural observation result by transmission electron microscopy (TEM) shows that the deformation-induced ω phase transformation occurs during cold rolling in the Ti-16Mo alloy. Therefore, the increase in Young's modulus of the alloy after cold rolling at room temperature can be attributed to a deformation-induced ω phase.

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Full-field strain measurement is implemented in order to detect the time-dependent occurrence and progress of internal damage during tensile creep loading condition for CFRP notched laminates. Employing digital image correlation method, the damage occurrence and increase with accelerated time is in-situ observed, subjected to time-temperature superposition principle, under a creep load condition. The creep load test is interrupted after 1 hour in real time, which corresponds to various accelerated time; the accelerated rate depends on test temperature. Tensile residual strength of the interrupted test specimen is then examined. While the internal damage increases with the creep loading time, the residual strength also increases with time in the range of this study.

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Engineering plastics are used widely in the field of production of motor vehicles, electromotive tools and others. Most part of plastics has a remarkable strain rate dependency on the flow stress. It is, therefore, required to make clear the strain rate dependency of plastics over a wide range of strain rates on the order from 10^-2 s^-1 to 10³ s^-1, and to make use of these properties for the simulation of the behavior of crashing parts of automobiles and of work-pieces under dynamic plastic working. In this paper, dynamic tensile properties of polyamide, polycarbonate, polypropylene, and ABS plastic were studied over the wide range of strain rate. The strain-rate dependencies of these tested plastics were made clear quantitatively. The strain rate sensitivity of the flow stress, for a group of plastics whose elastic modulus does not depend significantly on the strain rates, is expressed clearly by using the constitutive model as a special case of Tanimura-Mimura model 2009 (T-M 2009). The rate sensitivity of the flow stress, for another group of plastics whose elastic modulus depends obviously on the strain rates, is also expressed with high accuracy by using the T-M 2009.

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Electronic packaging is a series of processes toward the end of the microelectronics manufacturing, where functional semiconductors and discrete elements are electronically interconnected and mechanically assembled. Out-of-plane displacement or warpage is one of the major thermomechanical reliability concerns for board-level electronic packaging. In this study, temperature-dependent warpage distribution of electronic packaging is studied using FLCOS-based fringe projection profilometry. Phase-shifting technique effectively attains high resolution and high accuracy in analyzing phase information on a projected fringe pattern. A 50 by 50 mm size flip chip - ball grid array (FC-BGA) package was measured from 25 to 225°C at 30°C/min rate. Experimental results show that our FLCOS-based measurement system using phase-shifting technique provides powerful means of monitoring and studying warpage in electronic packaging design and manufacturing reflow processes.

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The present paper is concerned with constitutive modeling of the compressive stress-strain behavior of selected polymers at strain rates from 10^-3 to 10³/s using a modified Ramberg-Osgood equation. High strain-rate compressive stress-strain curves within a strain range of nearly 0.08 for four different commercially available extruded polymers are determined on the standard split Hopkinson pressure bar. The low and intermediate strain-rates compressive stress-strain relations are measured in an Instron testing machine. The five parameters for the modified Ramberg-Osgood equation are determined by fitting to the experimental compressive stress-strain data using a least-squares fit. It is shown that the compressive stress-strain behavior at different strain rates up to the maximum stress can successfully be predicted by the modified Ramberg-Osgood equation. The limitations of the modified Ramberg-Osgood models are discussed.

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Welding is widely used for construction of many structures. It is well known that residual stress is generated near the bead because of locally given heat. Tensile residual stress on the surface degrades fatigue strength. On the other hand, welding is used for repair of mold and die. In this case, reduction of residual stress is required because of protection from crack of welded part in mold and die. In this paper, a new method for reduction of residual stress of welded joint is proposed for repair welding of mold and die. In this method, low frequency and ultrasonic vibrations are used during welding. Thick plates are used as specimens of mold and die. Residual stresses are reduced when low frequency and ultrasonic vibrations are used during welding. Experimental results are examined by simulation method using an analytical model. One mass model considering plastic deformation is used as an analytical model. Experimental results are demonstrated by simulation method.

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This paper is focused on waveband analysis of the lateral and vertical track irregularities from the on-board acceleration measurement of in-service high-speed trains. The track irregularities play important roles to determine dynamic stability of vehicles and ride quality of passengers, so that their amplitude and wavelength should be monitored continuously and carefully. Measuring acceleration at the axle-box or bogie of the trains has been under consideration for low-cost implementation and robust to a harsh railway environment. To estimate the track irregularities, lateral and vertical vibration caused by the wheel/track interaction is measured by the axle-box and bogie mounted accelerometers of an in-service high-speed train. A Kalman filter is used to prevent unrealistic drifts in the estimation. By applying the waveband-pass and compensation filters to the estimated displacement, it is possible to estimate the track irregularities. A distance-wavelength representation is used to identify their waveband in an intuitive way. It is verified by comparing with a commercial track geometry measurement system. From their comparison, it confirms that the representation can produce a satisfactory result.

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Deformation behavior of multi-layered ceramic capacitors (MLCCs) during production press process is very important to reduce over all MLCC size and increase the capacity of the MLCC through the enlargement of the electrode area. In this study, compression tests of MLCC blocks, which were composed of stacked ceramic dielectric sheets and printed internal electrodes, were carried out, and the deformation process was clarified based on the results of cross-sectional observation. Deformation of MLCC block was modeled and predicted using the area fraction of dielectric sheets, internal electrodes, and internal space. The prediction agreed well with the experimental results and helps the optimization of MLCC design.

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Most commercial ultrasonic phased array systems implement B- and C-scan methods which use flight time and amplitude of flaw echoes. However, these methods are based on the fundamental ray-tracing theory in homogeneous media, and they are not directly applicable to heterogeneous media because of the complicated phenomenon of wave propagation. Time reversal techniques are adaptive methods that can be used in nondestructive evaluation to improve flaw detection in heterogeneous media. In this study, we propose a simulation-aided flaw imaging method based on the time reversal approach. Scattered waves from a flaw are recorded using an array transducer, and the time-reversed waves are re-emitted in the image-based FIT simulation. The re-emitted waves propagate through the heterogeneous media and focus on the flaw. The shape of the flaw can be visually estimated from the focal point of the ultrasonic wave in the simulation.

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The current paper deals with the ability of the Small Punch Test [SPT] to detect material behaviour changes. The authors investigated two experimental materials with a range of mechanical properties. The different material properties of the experimental materials were obtained by heat treatment, simulating material property changes due to service conditions. The ability of SPT to detect such changes was investigated on the basis of tensile and fracture toughness properties. In order to be able to perform such an investigation, standard tensile tests and fracture toughness tests were performed for reference. A wide range of tensile strengths, ranging from 700 to 2000 MPa, and fracture toughness values covering the brittle-to-ductile region from 90 to 350 MPa.m^0,5 were utilized for the method sensitivity assessment. The results of standard tests are compared with SPT results and their applicability is evaluated.

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When a bar is subjected to a tensile or a compressive load, the natural frequencies of the bar varies in proportion to a magnitude of the axial load. A round steel bar with fixed-end supports or with simple-end supports was subjected experimentally to a tensile or a compressive load and impacted by a steel ball. Making use of a laser beam displacement detector, a deflection of the vibrating bar after the impact was measured. Natural frequencies of the bar were obtained applying FFT analyzer to the variation of the deflection. Working stress in the bar was measured by strain gauges. Vibration equation of a bar subjected to an axial stress with fixed-end supports or with simple-end supports was analyzed to obtain a theoretical relation between an axial stress and a natural frequency. Experimental results and a theoretical relation between an axial stress and a natural frequency of a bar were compared.

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