Plastic deformation behavior of extruded alloy mainly composed of long-period stacking ordered phase (LPSO-phase) was examined by compression test, as a function of extrusion ratio, temperature and loading orientation. The yield stress showed a strong loading orientation dependence and the values were much higher along the extrusion direction (0°-orientation) than those along the direction inclined 45° with respect to the extrusion direction (45°-orientation), irrespective of the extrusion ratio. In the deformation along the 45°-orientation the basal slip predominantly occurred in all the specimens. In the deformation along the 0°-orientation, on the other hand, formation of deformation kink band was accompanied in addition to the basal slip, and its formation frequency was different depending on the extrusion ratio. The influence of the variation in texture as a function of extrusion ratio, and in addition the influence of kink deformation bands introduced in the alloy during the extrusion process to the plastic deformation behavior and mechanical properties are quantitatively discussed.

Yttrium addition has been known as an effective methods to improve high temperature strength of magnesium. The strengthening effect of yttrium addition is also observed in dilute solid solution range and significantly enhanced by simultaneous addition of zinc. Compressive creep strength and creep deformation mechanism of hot-rolled Mg-0.3Y-0.02Zn and Mg-0.87Y-0.02Zn (in mol%) ternary solid solution alloys were investigated in this investigation. The values of stress exponent of two alloys are almost the same in the present creep conditions (455 ~ 610 K, 50 ~ 120 MPa). High activation energy for creep around 500 K (about 190 kJ/mol) and many non-basal a-dislocations are observed in both Mg-0.3Y-0.02Zn and Mg-0.87Y-0.02Zn alloys. Therefore, main rate controlling mechanism of these Mg-Y-Zn ternary alloys is considered cross-slip controlled dislocation creep. On the other hand, the difference of their creep strength is negligible below 570 K, despite clear yttrium concentration dependence of the creep strength is observed in Mg-Y binary alloys at 550 K. Transmission electron microscopic observation revealed that the many stacking faults are observed in (0001) magnesium matrix during in crept Mg-0.87Y-0.02Zn alloy. The solution hardening by solute yttrium diminishes in Mg-0.87Y-0.02Zn, since the segregation of yttrium and zinc occurs around planar type stacking faults.

Kink deformation, which occurs in the long period stacking ordered (LPSO) structure phase of Mg-TM-RE alloys, is considered to affect the excellent mechanical properties of this alloy. Although the mechanism of kink band formation was explained by segregation and rearrangement of dislocation, it is recently attempted to express the kinking process from the viewpoint of a rotational line defect called disclination. We developed a new model of Cosserat continuum consistent with the framework of the crystal plasticity by describing the microscopic plastic rotation as a quantity of each slip system. However, a meshfree method using background integration cannot ensure balance at each node. Therefore, extrapolation from sampling points to nodes is needed for the calculation of crystal defects such as geometrically necessary (GN) dislocation density. In this study, meshfree analyses with stabilized conforming nodal integration (SCNI) based on the dislocation-based crystal plasticity Cosserat model considering disclination density is conducted and it is shown that this model can reproduce the kink formation by use of disclination quadrupole structure and array structure of GN dislocation formed in the vicinity of the kink band. Furthermore, a size effect owing to the intrinsic length scale of Cosserat model is properly expressed by imposing boundary condition on rotational degree of freedom.

Reducing the car weight is very important for the development of automobiles to, since it is one of the solutions for the environmental issues. Adoption of materials with high specific tensile strength such as Magnesium and CFRP is under investigation. Those materials have the creep characteristic under high temperature atmosphere. Therefore, the combination of the temperature and clamping force potentially causes decreases in the bolt axial tensions for the bolted joints.

The purpose of this study is to propose the precise prediction method for the reductions of the bolt axial tension in case that material of clamped parts has the creep characteristics. The experiments and elasto-plastic FEM analyses with creep characteristic are conducted on the bolted joints with two hollow disc specimens made of Magnesium alloy AZ80-F. The FEM analyses show good correspondence with experimental results by using compressive creep characteristic of AZ80-F which is under the yield point.

There are many types of slip modes and twins in hcp metals. Knowledge of their activities during plastic deformation is very important to improve their mechanical properties efficiently. According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation of polycrystalline material. Basal slip system is the main slip mode of hcp metals such as magnesium, but the independent slip number is one two. Therefore, activation of non-basal slip systems is important for hcp metals to show good ductility. In this study, to investigate activity of non-basal slips in polycrystalline hcp metals, pure magnesium and Mg – (0.5 - 1.2) at.%Y alloy rolled sheet were stretched at room temperature. Activated slip systems in each grains were evaluated from orientations of slips lines. In pure magnesium and Mg – Y alloys, slip lines of second order pyramidal (c+a) slip (SPCS), first order pyramidal (c+a) slip (FPCS) and prismatic slip (PS) were observed even at yielding in addition to basal slip lines. Activities of FPCS and prismatic slips were increased with increasing strain in Mg - Y alloy polycrystals. Our study suggested that active non-basal slip system is (c+a) pyramidal slip and enhanced ductility of magnesium - yttrium alloy would be caused from increased activity of FPCS by yttrium addition.

A single pass of equal channel angular pressing (ECAP) at 223 K was applied to six kinds of Zn bulk single crystals with different crystal orientations, and the deformation behavior was investigated, such as grain refinement and texture development. Zn bulk single crystals with several millimeters can be divided into a number of grains with several tens micron meters by a single pass of ECAP. Also, texture formed by activation of basal and second order pyramidal slips. Increasing twin boundaries by double twinning, and occurrences of recrystallization at the twin boundaries are required for grain refinement before passing through the theoretical shear plane in the ECAP die.

Kink and slip type deformation bands are frequently formed during plastic deformation in Mg-based long-period stacking ordered (LPSO) structure. In this study, kink band formation process in LPSO structure subjected to uniaxial loading was numerically investigated by means of a crystal plasticity finite element method. The numerical results exhibited that kink type deformation bands were formed during both tensile and compressive loadings whereas stress-strain behavior and morphology of band shapes were significantly different depending on loading direction. Influence of initial crystal orientation, material parameters, and boundary conditions on development of kink bands were also studied.

The non-normality effect of polycrystalline pure magnesium is numerically investigated using the crystal plasticity approach. A homogenization-based finite element method is introduced to compute the macroscopic material behaviors with a crystalline scale structure. Numerical analyses with two types of initial textures, the random and rolled textures, are conducted, and the effect of initial texture is discussed. It is shown that the intensity of the non-normality depends on the amplitude of the offset strain, while that of FCC metal is almost independent from the offset strain. Additionally, the non-normality angle of rolling textured material is lower than that of random textured material.

Deformation modes in hcp α-titanium are energetically analyzed by using first-principles calculations. For the prismatic and basal slip, the generalized stacking fault energy curves are calculated. While a quasi-stable state existed at the center of the prismatic slip path in the Al-doped case as well as pure titanium, the local minimum disappeared for the substitutional doping of Cu. For the {1012} and {1122} deformation twinnings, the twin boundary energy is evaluated. In the case of the {1122} twin boundary, the mirror glide structure is more stable than the mirror reflection structure.

In this study, the complex 3D microstructure and short crack in a Ti-6Al-4V alloy were reconstructed by employing the X-ray micro-tomography coupled with EBSD serial sectioning. Global sensitivity analysis can be used to determine the most important features affecting the crack growth behavior. Afterwards, using a surrogate model, the relationship between microstructural features and short crack growth can be further analyzed. Using the aforementioned approach in a Ti-6Al-4V, it was found that a high number of α grains in contact with a long cracked α grain in the loading direction may impose a constraint on the crack opening resulting in low crack growth rate. As the crack length increases, crack bifurcations and formation of secondary cracks in surrounding grains leads to a decrease of crack driving forces at the crack front with lower average crack growth rates.

In recent years, direct comparisons between simulations and experiments dedicated to test samples containing a small number of grains (oligocrystals) instrumented using full field measurements techniques (DIC, grid method) have proved fruitful to investigate and accurately reproduce the behavior of BCC and FCC crystals. The extension of this approach to hcp metals and CP-Ti in particular is the objective of the present work. In particular, the influence of CRSSs ratios in a grade 2 CP-Ti sheet is investigated numerically, by comparing the predictions of strain field in a 32 grains oligocrystal loaded in tension with experimental results. It is found that the set of constitutive parameters identified by the authors in a previous study [Hama et al., Int. J. Plast., 2017(91), 77] reflects the experimental behavior satisfactorily for strain fields.

In order to elucidate the plastic deformation behavior, biaxial tensile stress tests using tubular specimens for multiaxial tube expansion method are carried out under seven liner stress paths. Contours of plastic work (CPW) at different levels of plastic work are measured. The range of the reference plastic strain, ε₀^p , applied to the material is ε₀^p d 0.17 . It is observed that the shape of CPW significantly change; this material shows strong DH. From the biaxial stress tests data, the applicability of anisotropic yield functions to the accurate prediction of the plastic deformation behavior is discussed. Furthermore, DH model which is based on Yld2000-2d yield function with exponent and material parameters changing as functions of ε₀^p is determined. Using these yield function, finite element analysis of the hole expansion forming process are conducted. It is found that the yield function which represent the material anisotropy and DH predict the direction of minimum thickness. But the magnitude of plastic strain is not correctly predicted. This would be attributed to the material modeling method in which the variation of the r-values with ε₀^p is note taken into account.

The aim of present study is to fabricate a micro pillar from polycrystalline Ti plate, to perform a compression examination for a micro polycrystalline Ti pillar and to investigate its deformation behavior using Acoustic Emission (AE) technique. First, a micro polycrystalline Ti pillar, which width is several hundred from tens of micrometer, is fabricated by original technique. Then, its crystalline structure is investigated by Electron Back Scatter Diffraction (EBSD) device. Second, in-house micro compressive device is developed, and compressive test is performed for a fabricated micro pillar. In addition, AE signals are measured during compressive loading. As a result, it was seen that a lot of small twin regions occured at early deformation, then small number of large twin region occured with the progress of deformation for present micro Ti pillar.

Crystal plasticity analysis of a single α-β colony in Ti-6Al-4V alloys (Ti-64) was conducted using a geometric model converted from an image obtained by the electron back-scatter diffraction patterns (EBSD), and the relationship between the yielding of β phase and the accumulation of geometrically necessary dislocations (GNDs) was investigated. A dislocation-density-based constitutive equation was employed, and the deformation of the α-β colony was numerically simulated under the condition of uniaxial tensile loading. The results showed that GNDs were accumulated near the α-β interfaces in the conditions that β phase could and could not plastically deform. This is because the spatial gradient of slip strain forms near the α-β interfaces in both conditions. The dependency of vanadium concentration in the β phase (V_β) on the elastic compliance was taken into account in the analysis, and the dependency of V_β on the GND density was also investigated. The GND density was higher with lower V_β on the condition that the β phase did not plastically deform while the relationship could not be observed on the condition that the β phase plastically deformed.

Recently, the strain rate effects of the indentation are frequently discussed with the nano-indentation. For the nano-indentation, undesirable effects such as grain boundaries and precipitates may influence test results, which may act as obstacles to understand strain rate effect. Effects of grain boundaries can be minimized by using milli-scale indenter. Additionally, it is difficult to analyze the strain rate effect of indentation, which is distributed inside a material. Thus, it is necessary to investigate strain rate effect without considering those distributions. In this study, in order to clarify the strain rate effect, the serration behavior of Al-Zn-Mg alloy was used, since serration behavior of this alloy would change depending on the strain rate. The purpose of this study is to investigate strain rate effect of Al-Zn-Mg alloy using displacement controlled milli-indentation. In experiment, displacements rates were changed twice from 1.0×10^-1 to 1.7×10^-3 m/s and from 1.7×10^-3 to 5.0×10^-4 m/s and each displacement changes were made after holding displacement for 150 s . It was found that loads were increased after the displacement holding. Additionally, severe serrations were observed when the displacement rate was changed to lower rates. It was surmised that strain rate effect of indentation can be analyzed using effective strain rate.

Powder such as sand show different properties from both solid and liquid, and its behavior is difficult to understand due to their nonuniformity. Research about sand has been actively conducted in recent years. If the projectile penetrates into the sand at high speed, complex phenomena can't be seen at low speed, and they are very interesting. Previous studies confirmed that the packing density of sand greatly contributes to the penetration behavior of the projectiles. However, the influence by parameters other than packing density is still unknown. In the static penetration test, it is known that the shape of the particle influences the behavior of the penetrating object. Therefore, in this study, to verify the influence of sand particle shape on projectile behavior at high speed penetration, the particle shape of two types of sand, which are different in shape, was quantified. To evaluate the particle shape quantitatively, use the coefficient of form unevenness. In order to calculate the coefficient of form unevenness, the projected area of sand particles and the perimeter of the particles were measured using a digital microscope. The influence of the shape of sand particles on the behavior of the projectile at high speed penetration was investigated.

Foamed resin materials have been widely used as cushioning materials for protective equipment for sports and daily life. In order to apply to the protective equipment, flexible epoxy foams having extremely high strain rate dependency of compressive properties was fabricated by reducing the crosslink density of the resin. Compression tests in wide range of strain rate were performed to evaluate strain rate effects on compressive property of the foams. The experimental results revealed that the fabricated soft epoxy foams have excellent flexibility in low strain rate and high compressive stress in high strain rate, independent of the foam density. Furthermore, the application of the epoxy foam to protectors was examined.

In this study, with the aim of establishing a method to estimate the effect of deterioration of ground anchor on the tensile force, numerical studies of the relationship between ground anchor deterioration, the tensile force, and anchor deformation. We created a computational model that can reproduce the reduction of the withstanding ground strength with full wall thinning. The soil was modeled with SPH particles with a diameter of 30 mm. The anchor was a FEM model with shell elements, and the thickness were 3.2 mm, 1.6 mm , and 1.0 mm. The tensile force of the anchor was calculated from the resultant contact force of the FEM anchor surface and the SPH soil particles. The yield strength of the soil decreased with the reduction of the thickness of the anchor. It was suggested that this is due to an increase in plastic deformation of the anchor due to thinning.

Nano carbon materials are attracting a great deal of attention, and a new material diamond nanothreads (DNT) is discovered in 2014. We aim to develop new superior materials by braiding DNT. On the other hand, Kuimihimo is one of the traditional Japanese culture. It is a technique to make beautiful patterns by knitting threads or to make a sturdy thread. Therefore, we just think of combination the latest material with Japanese traditional technology. Using molecular dynamics methods, we analyze the braiding of three DNTs and do the tensile test for them. As a result, we finds that energy increase and oscillate when creating a braided structure. The differences in the arrangement of three DNTs affect the stress-strain relationship. Furthermore, we find in the stress-strain diagram that the breaking strain is larger with decreasing the number of rotation per unit length.

The Lamb wave propagation in a linear elastic isotropic bent plate is studied theoretically and numerically. The modal amplitudes of reflected and transmitted Lamb waves when a monochromatic Lamb wave impinges on a smooth corner zone are calculated using the modal decomposition method. As a result, it is shown that the single mode incidence of either the lowest-order symmetric (S0) or the lowest-order antisymmetric (A0) mode in the frequency range below the cutoff frequencies of the higher-order modes generates both S0 and A0 modes in the reflected and transmitted fields. Furthermore, these reflected and transmitted waves are found to satisfy the reciprocal relation. Namely, the energy ratio of the scattered A0 to the incident S0 modes coincides with that of the scattered S0 to the incident A0 modes. These findings of the theoretical analysis are validated by comparing with the results of a two-dimensional plane-strain dynamic finite element simulation.

The purpose of the present study is developing a novel protective headwear compatible with flexibility and impact absorption. In order to achieve the purpose, the soft epoxy foams, which shows extremely high strain rate dependency of compressive properties, was used as a cushioning material of headwear. To evaluate the performance of the epoxy foam as a cushioning material of headwear, the falling impact test assuming a head impact in daily life was performed, measuring HIC (Head Injury Criterion). The impact tests suggested that the proposed epoxy foams are effective as a cushioning material of a headwear.

We performed numerical analysis of high speed penetration into sand to compare with experimental result. Numerical analysis can visualize and digitize behavior of sand and a projectile. On the other hand, in the experiment, methods which can measure inside of granular material sequentially are exceedingly limited. Therefore, numerical analysis also plays an important role. The impact experiments were performed at a speed of 146509 m/s by using a powder gun. Packing density of sand was around 1.34×103 kg/m3. Impact and penetration speed of the projectile were temporally measured by coil method that is contactless. Smoothed Particle Hydrodynamics (“SPH”) was used as analytical method, because SPH is good at simulating with large deformation such as convection and ejection of sand. Equation of state (“EOS”) and constitutive equation were same as previous research. In order to simulate sand used in the experiments, input data of EOS and constitutive equation were collected and estimated from our experiments and previous research by Hagiwara, et al. Regarding penetration velocity history and penetration depth history, a numerical analysis model based on new input data was better agreement with experimental result than a numerical analysis model based on input data of previous work. Agreement with penetration speed history suggests that the numerical analysis model based on new input data can simulate forces exerted to the projectile and absorption energy of sand accurately.

Local deformation in tensile tests of polymer material is important because of necking. Beside this, it is necessary to considering temperature rise because temperature rise affects strain and stress. We carried out tensile tests of PLA/PCL composites at 2 deformation speed. We examined about strain rate of necking area dependence by using digital image correlation and temperature rise by using infrared camera.

Acoustic emission (AE) is the elastic wave phenomenon due to the energy release by fracture in materials, then AE is widely used for one of nondestructive inspection techniques. Because dislocation motion in crystalline materials also release the elastic energy, AE can be observed during plastic deformation in crystalline materials. In general, dislocations construct a stable structure to reduce their self-energies and the dislocation structure strongly determine the strength of the materials. Therefore, there is a possibility that the information of AE contains the information of dislocation structure and the strength of the materials. In order to investigate the relationship among AE caused by plastic deformation, dislocation structure, and material strength, we perform the molecular dynamics simulations of the collapse of dislocation structures under shear deformation. It is confirmed that the influence of dislocation structure on the strength observed in MD simulations well corresponds to the dislocation theory and the relationship between material strength and AE caused by plastic deformation take a positive correlation. Hence, it is found that the information of AE possibly contains the information of dislocation structures and the strength.

Up to now, it is still difficult to shoot a table tennis ball with high speeds in terms of vertical, horizontal and gyroscopic spins by a commercial table tennis robot (table tennis machine). We have designed and produced a table tennis ball shooting machine, which can shoot the ball with various shot types (loop, smash, drive, knuckle, chiquita, etc.). The produced machine has two launch and two gyro rollers, where the rotation revolutions and directions of the four rollers can be controlled independently. In the present work, we perform shooting tests of this machine to evaluate its performance and to study the ball shooting mechanism. According to the experimental results, this machine has high power to shoot the balls with assorted spin types (top, back, side and gyro spins), the maximum spin rate (over 7,800 rpm), and a wide range of speeds from 2.8 m/s (10 km/h) to 42.3 m/s (152 km/h). Moreover, the direction of the spin axis of the shot ball can be altered freely within 360 degrees by the rotary control of the two gyro rollers.

Polypropylene/Polyamide11 (PP/PA11) alloy has a unique phase structure, which is called “salami structure”, of nano order. It has been found that this material is superior to a polycarbonate alloy known as an impact resistant resin. However, the impact evaluation method is Charpy test or puncture test. Therefore, the compressive strength of PP/PA11 alloy and its strain rate dependence are unknown. In this study, the impact deformation properties of PP/PA11 alloy having salami structure are evaluated, and the possibility of application as automobile material is considered. 100%PP/PA11 alloy (PP/PA11), 100%PP (PP) and 70%-PP/PA11 alloy/30%-PP (70/30) were prepared. All three specimens showed a tendency of higher flow stress in the impact test than in the quasi-static test. When observing the change in flow stress, the initial stress of PP/PA11 is lower than that of the other two types, and the stress increases as deformation progresses. It was suggested that PP/PA11 has high impact energy absorption characteristics.

The purpose of this study is to develop a flexible football shin guard with wearability and high impact absorption. To fabricate the flexible shin guard, the crosslink density of soft epoxy resin was changed to control the relaxation modulus of soft epoxy resin Prototype shin guards were fabricated with the epoxy resin as an outer shell and epoxy foam as an inner foam to evaluate the performance as a shin guard for football. The fabricated shin guards were confirmed to be sufficiently flexible to wearing. The impact tests revealed that the proposed shin guards had high impact absorption characteristics compared with a commercially available one.

It is known that the ice is easily fractured by percussion with back of the metal spoon. However, this mechanism has not been clarified in detail. In the previous study, we carried out the percussion test of the ice specimen using flat plate, which showed that the ice fractured with low stress compared to compression test. In this study, in order to further investigate the fracture phenomenon of the ice, the percussion test was conducted in which hemispherical protrusion simulating the shape of back of the spoon was attached to the tip of the flat plate. The diameter of the hemispherical protrusion used in this study was 10 mm, 15 mm and 20 mm. It was observed that the time to fracture in hemispherical protrusion percussion became shorter than the flat plate percussion. The maximum load was approximately 18-22 N, regardless of the diameter of the hemispherical protrusion. This value is less than 1/10 in comparison with the result of the flat plate percussion test, which indicates that the fracture of the ice occurred with lower load. In addition, it was shown that the maximum load decreased with decreasing the diameter of the hemispherical protrusion.

In this study, a series of hypervelocity impact (HVI) experiments for silica glass plate targets were conducted to evaluate the nucleation and propagation mechanisms of spall-like damage on backside of the plates by impacting a small projectile with various conditions. Backside damage nucleation and propagation behavior was observed from two directions (side-backside) simultaneously by means of in-situ scattered light imaging coupled with an ultra-high-speed video camera. spall-like damage nucleated discontinuously with any front side damages at an area on back surface which had certain relation with change of target thickness. Nucleated damage propagated radially from each point. when the expanded damages connected with each other in high energy conditions, circular spall appeared on back surface. These observation results were compared with estimated stress wave propagation behavior, and it was suggested that the impact induced transversal stress wave affect to the nucleation and propagation. It was suggested that this damage process was quite different from the spallation of metal or other ceramics materials.

Stress-strain curve (SS curve) for some polymer materials are characterized by softening behavior accompanied with necking deformation and re-hardening behavior before rupture. Since non-uniform deformation of specimen is observed with the behaviors mentioned above, it is challenging to identify material input parameters for non-linear finite element method solver from experimental results. Although employing an optimization tool is effective for the identification of material parameters, it is necessary to approximate SS curve into an appropriate certain function with design variables. It is found that approximating SS curve of some polymer materials into several Bezier curves and choosing of design variables proposed here are good in identifying non-linear material properties.

This paper reports numerical results underwater shock wave generation phenomena by an explosion in a closed space for establishment of shock wave pressure profile method related to the shock wave medical and biomedical application. In this study, a metal tube made of aluminum (AL5052) or stainless steel (SUS304) was used as a closed space. A shock wave was generated in a thick-walled metal tube by detonating a micro-explosive. The process of underwater shock wave interaction with a thick-walled metal tube and the generated shock wave propagation phenomena was simulated by using hydrocode ANSYS AUTODYN. Three underwater shock waves were generated from a thick-walled metal tube. Peak over pressure of shock wave in a stainless-steel tube was higher than in an aluminum tube.

This paper proposes the principle of an expansion mechanism using the deformation of a flexible gel membrane. This mechanism is developed for simulation of deforming crystalline lens in human eyeball. The crystalline lens is soft and convex. The thickness of the crystalline lens varies according to the expansion/shrink of surrounding biological tissue. We propose the mechanism to simulate the deformation using the soft and circular gel membrane. The simulated crystalline lens is surrounded by soft and thin gel membrane. If the mechanism is compared to a sunny-side up egg, simulated crystalline lens is the yellow of the egg and gel membrane is the white of the egg. The outer edge of the membrane is fixed. When a hollow cylinder pushes the membrane, the circular boundary between simulated crystalline lens and the membrane is expanded and the radius of the lens becomes larger. The cross-sectional shape of the membrane is expected to affect its deformation characteristic. Near-future 3D printing technologies will enables the complex shapes of the gel. Better shape of the membrane will be able to be selected using the mechanics of elasticity.

Fiber reinforced polypropylene(FRPP) has advantages of low cost and light weight. However, because of its low surface energy, bonding strength of FRPP is generally very low. Surface treatment before bonding is one of the candidates to solve this problem. In this study, the adherend was subjected to plasma treatment to improve the bonding strength of FRPP. As the condition of surface treatment, preheating condition and nitrogen atmosphere condition were discussed. Lap shear test was conducted to find appropriate method for the plasma treatment of FRPP and the fracture strength of adhesively bonded joints has been investigated. Tensile rate was set to 10mm/s. Experimental results showed that the fracture strength improved by 1.3 times under preheating condition. Also, the fracture strength improved by 1.2 times under nitrogen atmosphere condition. It was found that it is possible to improve the effect of plasma treatment by changing the state of the test specimen during the surface treatment. Additionally, it was found that the rate of material failure of the bonding area increased by introduction of preheating condition and nitrogen atmospher condition.

Bonding qualities of aluminium-alloy adhesive joints are evaluated by ultrasonic spectroscopy using the transmission characteristics for a normal incidence wave. Double-through transmission measurement was carried out for perfect bond (PB) and weak bond (WB) specimens immersed in a water tank. For the WB specimen, contamination was intentionally introduced at an adhesive-adherend interface in the bonding process. The doubly transmission coefficient was obtained by spectral analysis for the measured waveform of each specimen, showing local maxima at different frequencies. To further examine the peak behavior, the transmission coefficient was calculated by the theoretical analysis based on the one-dimensional model of a tri-layer structure in fluid. Two adhesive interfaces were modeled by linear spring-type interfaces, which are characterized by interfacial stiffnesses. The theoretical result shows that the transmission coefficient has multiple local maxima at different frequencies due to the multiple reflections at the interfaces. The frequencies of several peaks decrease when the interfacial stiffness of an adhesive interface is decreased. The interfacial stiffness is estimated for each specimen by comparing the peak frequencies of the measured and theoretical transmission coefficients. As a result, the interfacial stiffness for the WB interface is estimated to be approximately 20 percent of the PB interfacial stiffness. The peak frequencies of the measured transmission coefficients are well reproduced by the theoretical results based on the estimated interfacial stiffnesses.

Concrete is the most basic structure materials and it is used for various structures. Therefore, many impact experiments have been performed so far. However, most of experiments have been performed for only normal strength concrete. In this study, shock experiments have been performed to investigate the shock response of ultra-high-strength concrete. The stress wave profiles propagating into the impacted concrete are directly measured by using PVDF stress gauges embedded in specimen. The compression-release paths under shock loading are derived from the measured stress wave profiles. The longitudinal stress profiles show the formation of precursor wave associated with the compaction of pores. Compression paths derived from wave propagation profiles indicate that the pores of this material are fully compacted by the dynamic compression stress of about 1 GPa. The derived loading-unloading paths also show large hysteresis. These results indicate that the large part of the work by shock-loading is consumed by the collapse of the pores inside concrete.

This study will develop a small machine tool that can machine general steels with high precision while having small dimensions. Miniaturization of machine tools is necessary to reduce the scale of production equipment. However, miniaturization of the machine tool causes deterioration of the structural rigidity. As a result, because the machine body easily deforms with respect to the cutting resistance, small machine tools can't process with high precision as compared with large ones. Therefore, in previous research, we manufactured the machine tool with dimensions can be installed on a desk and ensures high rigidity even in the compact structure. This machine was able to process steel materials which could not be processed by the conventional small machine tools. However, it caused the machining error caused by the low rigidity compared with the large machine tools. Therefore, this study, rather than strengthening the machine rigidity, permits such machine deformation and tries to reduce machining errors by controlling the drive system to correct machining error due to the deformation. Previously, we proposed a method to reduce machining error from the relationship between the tool position displacement and cutting resistance. Therefore, we will construct this method and confirm to reduce machining error by adapting the proposed method to the prototype machine.

Concrete and metal pieces may scatter to the surroundings during demolition work. In some cases, this scattered material flies at high speed and has a risk of injuring a person. However, the curing sheet currently used in demolition work is mainly aimed at soundproofing and dustproofing, and it is not considered to prevent penetration of scattering matter at high speed. Therefore, in this research, we tried to develop a scattering prevention sheet using high strength fiber fabric. First, the penetration resistance performance of high-strength fiber fabric was investigated by using a projectile simulating a metal piece which may possibly scatter. It was revealed that the projectile shape influences the penetration resistance property of the high strength fiber fabric. In addition, it was clarified that the order of superposition is important when using high strength fiber fabrics in layers.

The purpose of this study is clarifying the effect of deformation of adhesive layer on evaluation of fracture toughness in adhesively bonded joints and identifying crack length and energy release rate GII by finite element method. The result of numerical analysis demonstrated that crack length and energy release rate GII were identified accurately by using equation that is added the section of shear deformation to conventional compliance equation, and critical compliance that is obtained by connecting the beginning point to critical point of load displacement curve.

In order to evaluate quantitatively the relation between the dynamic flow stress and the activation distance of Aluminums at very high strain rates, high strain rate and decrement strain rate tests are performed in the strain rate range from 4000/sec to 22000/sec. The reduction ratio caused by the collision between an impact bar and a decelerator is 0.586 of the strain rate before reduction. The flow stress drop obtained by the rate reduction increases with the strain rate, and which was assumed to be a response to an instantaneous strain rate. High strain rate tests at high temperatures of 373 K and 473K are also conducted in the above strain rate range. Calculation curves predicted by thermally activated process show a good agreement with experimental results. The rate controlling mechanism of Aluminums at very high strain rates can be represented by the thermal activation process. The activation distance is determined from the activation volume which is derived from the amount of the flow stress drop obtained from the reduction tests. The activation distance decreases with increasing flow stress. The force – displacement curves of A1070 and A6061 – O are presented.

It is necessary to grasp the impact behavior of railway vehicles accurately when considering measures for reducing damage to passengers and crews of a train at the time of a collision accident from the viewpoint of vehicle body structure. Since it is difficult to carry out collision tests by using real car bodies under various collision conditions, analytical models are often used for investigating collision situation. We focused on car body structure for railway vehicles that has double skin panels made of aluminum alloy. In collision analysis, it is important to construct accurate analytical models in which the strain rate dependency of stress-strain characteristics is taken into account. Therefore, we conducted tensile tests on aluminum alloys used for car bodies at several strain rates, and we also conducted simulations in order to examine whether the test results are reproducible or not. Furthermore, we conducted a crash test by using a roof of the car body structure made of an aluminum alloy. This paper shows the results of the tensile tests and its simulation, and the outline of the results of the crash test. In all aluminum alloys, Stress-strain characteristics changed according to the strain rates. Simulations had good agreement with the results of the tensile tests until nominal stress reaches tensile strength. In the crash test, deformation occurred locally in the collision area.

Appreciations of anitiquities are generally based not only on uniqueness and qualities but also on the additional change of their original forms through time and circumstances. Even fading and spalling sometime gives special impression on anitiquities. In the present paper falling behaviours of dust on the antiquities are focused and investigated together with considering their rolling up motions. It is found that even though velocities of falling dust are estimated as well bellow as several centimeters per seconds, high strain rate deformation well over several hundred per sec may be associated in the events. Fading and spalling on the anitiquities seems to proceed steadily over several hundreds of years, but impact mechanics might be involved as elemental processes.

Automobiles are indispensable means of transportation for daily life, and ensuring the safety of occupant passengers is an important issue. Therefore, researches for improving the impact energy absorption characteristics of automobile crash boxes are actively conducted. In this research, in order to develop a shock absorbing member with higher energy absorption characteristics, the purpose is to predict the shock absorbed energy in a double circular tube filled with water inside. FEM analysis of water filled double circle tubes subjected to axial impact was carried out. In addition, a theoretical model for determining the axial average load was constructed, and the energy absorption was calculated using the theoretical equations for the empty tube and the value when 60% of the total length of the model was compressed. Theoretical estimations of the amount of energy absorption are carried out by these products and compared with the result of FEM analysis. It is found that the average axial load is accurately matched in the FEM analysis and theoretical predictions and the energy absorption can be obtained by setting the energy absorption range to the theoretical equations for the empty tube or 60% of the total length ofthe model. It enables us to estimate impact absorption energy in a double circular tube filled with water inside.

In order to give creep resistance to the PTFE gasket, a particulate-filler is compounded. Indentation test was carried out using TMA with Berkovich indenter to evaluate the viscoelastic characteristics of a PTFE based sheet gasket. The time-temperature superposition principle was applied to obtain the master curve of the creep compliance of gasket material at elevated temperature. The shift factor was arbitrarily determined. We found that the higher the blending ratio gets, the stronger the creep resistance becomes by examining the influence of this particulate-filler blending ratio on creep characteristics of gasket.

Pressure and temperature are important physical quantities for understanding high speed impact phenomena. The pressure caused by high speed impact can be measured with a PVDF gauge. But measurement method of the temperature generated by high speed impact has not been established. So, we focused on the plasma induced by the impact. By grasping the energy of the plasma induced by the impact, it is a clue to estimate the temperature change at the impact point. In the experiment, the plasma was generated by colliding a tip hemispherical projectile of A5052 with same material plate at 630 m/s. Triple probe method was used for measurement of plasma induced by impact. A measuring device was placed at 12 mm from the impact point. The electron density calculated from experimental results decreased with time. This showed that plasma was diffused. As a result of fitting to the time history of electron density using the diffusion equation, it was found that 6.7×10¹³ electrons are generated at the impact point. Assuming that all the ionized atoms are monovalent ions or trivalent ion, the energy at the impact point was estimated from the number of electrons and the ionization energy and it was 10^-4-10^-5 J. In the future, we will pay attention to atmospheric diffusion phenomena and ionization degree and confirm the validity of the obtained value.

The crash safety structure of the railway vehicles is effective as one of the safety measures against the passengers and the train crews in the event of a collision accident. However there is no standard for crash safety in Japan. In order to discuss guidelines for the crash safety design of the vehicle structure, it is important to grasp the impact deformation behavior of the railway carbody and passenger's injury degree in a collision accident. Therefore, we carried out finite element analyses of a level crossing accident with a dump-truck under various conditions (collision position, collision angle, collision speed and mass of the load on the dump-truck) and evaluated their results in terms of the mean deceleration of passenger's area (conformable to European standard), and the maximum deceleration of passenger's area and the secondary impact velocity of the passenger (North American standard). We also evaluated passenger's injury value by using crash-test dummy's FEM model. As a result of comparing these values, it was clarified that the secondary impact velocity was the most effective to evaluate passenger's safety.

The shock due to the blast causes a large acceleration on an object in very short time. In order to obtain such a blast load, it is necessary to perform an explosion experiment. However, it is not easy to perform a blast experiment. The purpose of this research is to reproduce the large acceleration of the blast by collision of the ground due to fall instead of blast experiment. First, the acceleration of the steel block acting on a blast load was measured. Next, the same steel block was dropped from a certain height, and the acceleration of collision with the ground was measured. We calculated the impulse obtained from the acceleration at collision with ground and decided the drop height so as to be equal to the impulse of the explosion. We set blocks of three types of top shapes and three types of materials on the ground. As a result, it shows a sharp steel block is suitable in order to obtain the acceleration as a substitute for blast experiments.

Hypervelocity-impact experiments have been performed on polycarbonate to investigate the impact-induced damage process progressing inside polymer material. The damage evolution and stress-wave propagation associated with hypervelocity impact have been observed by means of the two-directional (side-view and rear-view) scattered light imaging using two ultra-high-speed cameras. The obtained time-resolved images offer the information about the three-dimensional time evolutions of not only stress wave propagation and damage development but also damage texture which is not obtained in shadow graph. Under the 4.99 km/s impact of an alumina ceramics sphere, the alumina impactor is fractured at impact moment and the lump of impactor-fragments penetrates into polycarbonate with its collapsing. The stress wave generated by the impact propagates into target and reflects on the rear surface as the rarefaction wave. This wave induces spall fracture inside polycarbonate. After some development of spall fracture, a stress wave propagates from the spall plane. Compering the side-view and rear-view images, this stress-wave generation is considered to be tensile-stress-release from the free-surface plane formed by spallation.

The newly developed method of the roller burnishing process and tip burnishing process were summarized. The burnishing process is a micro-plastic forming process, which can simultaneously achieve the smooth surface and enhanced subsurface. As a newly roller burnishing process, the authors developed the inclined roller burnishing process with driven rotary tool. The sliding effect can be obtained in addition to the rolling effect by the developed roller burnishing process, and it is possible to flexibly control the sliding direction. As a newly tip burnishing process, the authors developed the tip burnishing process using rotary spherical tool. It can be expected that the flat and free curved surfaces of the dies and molds are finished without setup of the workpiece from the preliminary machining process.

In recent years, the natural disasters such as tornadoes, typhoons and volcanoes occur at a high level. As a result, there are incidents involving human life. Therefore, urgent countermeasure are necessary. In common with these natural disasters, the damage is caused by high-speed collision due to objects flying. Therefore, the knowledge of the impact engineering will be a field to be tested. However, it is impossible for the engineers alone to copel with the sudden natural disasters.In this research, we introduce the case of prevention engineering for volcanic disaster where the impact engineering and volcanology are fused, mainly focusing on volcanic disaster countermeasures.

In order to secure independent spaces in factories or large warehouse, unit rooms have been widely used. In Japan, large scale earthquakes occur frequently. Therefore, this study aims to review seismic design of the current unit room and propose seismic design assuming repeated ground motion. In addition, the unit room has various types and sizes according to the purpose of use. Although demand for large unit rooms has been increasing, seismic evaluation of a large unit room is difficult by experiment. Therefore, the second objective of this study is to evaluate vibration characteristics of the unit room by computer simulation using discrete element method.