Steel conveying rollers used in a heating furnance must have been changed very frequently. High temperate of the furnace induces the wear on the roller's surface coating in a short period. This paper deals with a new roller structure for a ceramics sleeve connected with two steel shafts by shrink fitting utilizing the high temperature resistance and high corrosion resistance of the ceramics. However, it is necessary to reduce the stress due to the large thermal expansion difference between the ceramics and steel, and the stress concentration appearing at the connected portion. In this study, therefore, the finite element method is applied to analyze three types of models by changing geometries. It is found that short tapered shafts may be most suitable because the contact stress is always smaller than the allowable stress.

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Repair composites has high stiffness and flexible workability. Therefore, they have been used as efficient repair material for surface damages including cracks and erosions. Catalog parameters such as stiffness, water resistance, chemical resistance, and delamination strength. However, catalog delamination strength for lining-application has not been well clarified. In this study, we examined tensile test using particle-reinforced composite material bonded on tensile test pieces. Delamination strength was evaluated by nominal strain and effect of material and surface condition of tensile specimen.

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In the field of tool making, brazing is sometimes used to join cemented carbide. Recently, the size of tools is becoming smaller and smaller. For example, polycrystalline diamond punch with a cross section of 2 by 2 mm are required. So a high and stable strength in such brazing joints is required. The authors examined the strength of brazing joints between cemented carbides with Ag-based filler metals containing indium. We determined that the optimum thickness of the filler metal is 20 to 30μm to ensure the brazing joints.

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The bolts and nuts are widely used in various fields as an important joining machine element. It is known that failures usually happen at the root of the first bolt thread where the maximum stress concentration occurs. In this paper, a special nut whose pitch is slightly larger than the one of the bolt is studied by applying the finite element method. Then it is found that these special bolt and nut reduce the stress concentration at the first root of the bolt thread effectively because the contact condition different from the normal bolt and nut. The reduction of the stress concentration is also confirmed under dynamic bolt axial forces. The experiments results show that the fatigue strength can be improved under slightly different pitches in accordance with the FEM analysis.

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This paper deals with the analysis of the thermal stress intensity factor for interfacial crack beneath a coating-layer subjected to uniform change of temperature by using the finite element method. In the present method, the stress values at the crack tip calculated by FEM are used under the same mesh pattern and the stress intensity factors are evaluated from the ratio of stress values at the crack-tip-node between a given and a reference problems. This method is based on the fact that the singular stress field near the interface crack tip is controlled by the stress values at the crack tip calculated by FEM. In this calculation, for the center interface crack in the finite rectangular bonded plate, it is found that the dimensionless stress intensity factors for various material combinations are the same when the Dundurs' parameter is the constant. The dimensionless factors of interface crack beneath the coating layer are analyzed for any material combinations and the effect of material combinations and the crack size on the dimensionless stress intensity factors are considered.

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The use of thin-film technology has rapidly expanded. Multilayer structures composed of thin film with specific properties are used in many fields, for example liquid crystal displays and solar cells. In a multi-layer structure, the interface between films has the lowest strength, thus the interface strength between film and adhesive is important for designing products and improving interface strength. Peeling test is used widely as a method to measure the interface strength. In that test, stick-slip phenomenon sometimes occurs in particular conditions, and it is difficult to evaluate the interface strength if that happens. Therefore the research about stick-slip behavior in peeling test is important to establish the method measuring the interface strength appropriately. This paper focuses on the relation between adherend stiffness and stick-slip phenomenon, and clarifies the effect of adherend stiffness on stick-slip phenomenon.

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In this study the debonding strength of an adhesively bonded joint is investigated in terms of the intensities of the singular stress fields. Here, two types of models are used to evaluate the tensile adhesive strength σ_y; one is the perfectly-bonded strip model, and the other is partially-debonded model assuming different debonded lengths. Then, the previous experimental data are examined, which are obtained for S35C JIS medium carbon steel plates bonded with epoxy resin. From the comparison between the results, it is found that the critical values of the stress intensity factors are almost constant. In other words, the adhesive strength can be estimated from the intensities of singular stress usually with less than 20% error for both the perfectly- and partially-debonded models.

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In this paper, the debonding fracture criteria are examined in terms of the intensity of the singular stress appearing at the corner of single lap joints. In order to explain the previous experimental results, two types of models are considered to simulate the tensile forces. One is a tensile load with simply supported ends; the other is point forces applied at the center of both ends. It is found that the debonding condition for carbon steel bonded with epoxy resin is expressed by the constant value of the stress intensity for lap joint under tensile load with simply supported ends. On the other hand, the debonding condition for aluminum alloy bonded with epoxy resin is expressed by the constant value of the stress intensity for lap joint under point forces applied at the center of both ends.

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Recently, plastic materials have been widely used in automotive industries due to its good chemical and electrical properties with low density. However, plastics easily get damage at elevated temperature. On the other hand, FSW (Friction stir welding) and FSSW (Friction stir spot welding) have been used for welding of aluminum alloys. These processes are well known as low heat input processes. In addition, new surface modification technique called FSP (Friction stir processing) has been also developed. It is possible to refine grain size and remove casting defects with applying FSP. Additionally, FSP has been also applied to fabricating composite material. However, friction stir welding and friction stir processing are not commonly applied to plastics. The aim of this study is to apply friction stirring process to plastic materials. In this paper, in order to improve strength of FSSWed PVC joint, effect of a composite material fabricated at joining part was studied. The joining strength and fracture behavior were investigated in experimentally as well as analytically. Result of cross sectional observation of the joint indicated that the present process was applicable to fabricate a composite material during FSSW at the joining part. The stir zone size increased due to applying the present process. It is considered that using reinforcement induced larger strain and enlarged the stir zone size. Tensile shear failure load of the joint with composite material at the joining part was higher than that of the joint without composite material at the joining part. According to the result of FEM analysis, value of K_<θmax> decreased with increase in the stir zone size. Fabricating the composite material during FSSW can increase the stir zone size and stiffness of the joining part, and results in increase tensile shear failure load of the joint.

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The following conclusions are obtained in this report. (1) The stress decreasing rate in the S-N diagram for the elastic bonding butt joint is smaller than that for the epoxy resin joint. (2) The effect of adhesive area on fatigue strength cannot be seen.(3) Stress concentration are observed at the interface edge area with increasing thickness of adhesive layer in tensile loading but no stress concentration in torsion.(4)The mean value of principal stress distribution at the interface edge area is found to be the most dominant factor of adhesive strength for the elastic bonding joint.

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We conducted crack propagation experiments on freestanding copper films with thicknesses ranging from about 60 to 800 nm deposited by electron beam evaporation to clarify the size effect on fracture toughness in the nano-scale. It was found that the fracture toughness K_C shows a clear size effect where thinner films have smaller fracture toughness. The fracture surface suggested that the crack underwent large plastic deformation accompanied by many multiple slips in the thicker 500-nm and 800-nm films whereas it propagated with highly localized plastic deformation and flat brittle fracture occurred in some region in the thinner 100-nm film. In situ TEM observation of the crack propagation in a 100-nm thick film revealed that the crack propagated via the processes of nucleation and coalescence of voids ahead of the crack tip, and the flat fracture was brought about by the void nucleation along grain boundaries or by highly localized slip deformation. The size effect in fracture toughness in the nano-scale is closely related to the transition in fracture mechanism.

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Fatigue crack propagation properties of about 500 nm-thick freestanding copper (Cu) films have been investigated. Fatigue crack propagation rate da/dN-stress intensity factor range ΔK relationship clearly depended on stress ratio R in entire ΔK region. On the other hand, da/dN-maximum stress intensity factor K_<max> relationship was independent of R in high K_<max> (K_<max> &ge; 4.5 MPa・m^<1/2>) region and was dependent on R in low K_<max> (K_<max> &le; 4.5 MPa・m^<1/2>) region. In order to clarify the effects of stress ratio on fatigue crack propagation mechanisms, fracture surfaces and fatigue damage around crack tip were clearly examined by a field emission scanning electron microscope (FE-SEM). In high K_<max> region, microstructure-insensitive or chisel-point fracture was observed in the fracture surface, and slip deformation and necking were observed at the crack tip of both R=0.1 and 0.8. At R=0.1 in low K_<max> region, microstructure-sensitive fracture was observed in the fracture surface, and intrusion/extrusion-like damage was observed ahead of the crack tip. At R=0.8 in low K_<max> region, chisel-point fracture was partly observed in the fracture surface and the fatigue crack propagated in a similar mechanism to the fatigue crack propagation in high K_<max> region.

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High-cycle fatigue experiment is carried out for a nano-components specimen, which is composed of silicon (Si) substrate, copper (Cu) nano-film, and silicon nitride (SiN) layer, using resonant oscillation. The specimen has a cantilever-shape. A gold (Au) weight is attached to the cantilever end in order to reduce the resonant frequency. Resonant oscillation is applied to the specimen by means of a piezoelectric actuator. In the experiment, no change appears in the specimen at low displacement range. However, the displacement range suddenly drops at 1.1×10^5 cycles of Δδ_2=16 nm (Δδ_2: deformation range at the base of specimen). After the decrease, fine slip bands with a width of 5 nm is observed in the Cu film. The critical resolved shear stress for the slip bands formation is approximately evaluated to be 400 MPa.

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In order to investigate the high-cycle fatigue behavior of submicron Au single crystal, resonant fatigue is conducted for a specimen with a submicron-scale test section. The displacement range at the end of weight, Δδ_1, is measured by means of in-situ SEM observation. Δδ_1 monotonically increases with increasing ΔV_<in>/2 (ΔV_<in>/2: input voltage amplitude). However, Δδ_1 decreases at 2.7×10^5 cycles of ΔV_<in>/2=2.25 V, and crystallographic slip bands and extrusions and intrusions with a width of 15 nm are formed on the surface of the test section. The critical stress for the slip bands formation is evaluated to be higher than 200 MPa by the FEM analysis. Although the morphology of the slip bands are similar to persistent slip bands in bulk, the size and the formation stress are extremely different from those of bulk.

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Tensile deformation property of the SUS316L stainless steel containing nanostructured twins was investigated at various temperatures. By the equal channel angular pressing (ECAP) at 43K, the nanostructured twins with average thickness of 50nm could be generated in the SUS316L steel. In the present study, the SUS316L steels processed by the ECAP for one pass and three passes were prepared. The tensile tests on the ECAPed SUS316L steels shaped to strip specimens were conducted at temperatures ranging from 77K to 673K. Ultimate tensile strength of the 3-pass, 1-pass and as-prepared specimens at 673K were 976MPa, 839MPa and 435MPa, while those at room temperature were 1200,900, and, 560 MPa. As well as the as-prepared specimen, the tensile strength of the 1-pass specimen was almost unchanged even at 673K. This thermal stability can be attributed to high-density twin boundaries which certainly have stable interface atomic arrangement. At tensile deformation tests below room temperature, the tensile strength increased with decreasing temperature for all the specimens. It should be noted that ductility of the 1-pass specimen was significantly improved, compared with the ductility at room temperature. The enhanced strength and ductility at the low temperature should be associated with strain-induced martensitic transformation.

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The purpose of the present study is to show possibility of a new scheme which can clarify fracture process by means of microstructure observation near fracture surface. In the present study, strip specimens of Cu-10%Zn alloy were fractured under monotonic tensile deformation, fatigue, and corrosive conditions. Microstructure near fracture surface was investigated by electron channeling contrast imaging (ECCI) technique and by electron backscatter diffraction (EBSD) analysis. For the specimen fractured under tensile deformation, the microstructure imaged by the ECCI technique consisted of blurred patches, which would be caused by heavily distorted grains. In the ECC image of the fatigued specimen, dislocation wall structure - which was self-organized by cyclic plastic deformation - was observed. No specific structure was detected for the stress-corrosion cracking. Through the EBSD analysis, distortion of a grain near fracture surface was investigated quantitatively. For the tensile deformation test, the maximum deviation angle from average grain orientation was amounted to about 10°, while those for the fatigue and the stress-corrosion cracking were less than 2°. It is hence suggest that fracture mode could be identified by the ECCI and EBSD analyses of the microstructures developed near fracture surface.

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Vickers hardness of Ni-Cu alloy films which have composition gradient along thickness direction was investigated. The composition-gradient Ni-Cu films were fabricated on copper substrate by the special electrodeposition technique where electrode potential changed continuously. The films were composed of alternate stack of layers having positive and negative gradients. Total thickness of all the films was 1.2μm. The gradient films differed in both composition gradient dc_<Ni>/dx and amplitude of Ni concentration Δc_<Ni>. The dc_<Ni>/dx and Δc_<Ni> values varied from 5×10^<-6> to 2×10^<-2>nm^<-1> and 0.006 to 0.6, respectively. The composition-gradient Ni-Cu films having high gradient or high Ni concentration amplitude showed higher Vickers hardness than the Ni-Cu multilayered film with defined Ni/Cu interfaces: the maximum hardness of the composition-gradient Ni-Cu films was amounted up to Hv250 while that of the multilayered film was Hv140. The hardness of the composition-gradient Ni-Cu films revealed good correlation with the gradient dc_<Ni>/dx, compared with the Ni concentration amplitude Δc_<Ni>. From this result, the high strength of the composition-gradient Ni-Cu films could be explained not by internal stress induced by lattice mismatch, but by high-density misfit dislocations caused by the composition gradient.

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Metastable SUS304 steels were cyclically deformed in tension/compression in aqueous 3%NaCl solution in order to clarify the influence of deformation-induced-martensite (DIM) on the corrosion fatigue life in a pitting-forming environment. The number of cycles to failure, N_f increased with decreasing plastic strain amplitude, dε_<p1>. However, under dε_<p1> of 0.3%, the N_f increased in higher rate in terms of dε_<p1>. DIM was not detected after the fatigue test at dε_<p1> smaller than 0.3% while the volume fraction of DIM increased with increasing dε_<p1> at higher than 0.3%. Pitting was observed after the fatigue tests at dε_<p1> larger than 0.4% and increased with increasing DIM, suggesting that the formation of pitting was caused by DIM. Thus, the formation of DIM facilitates pitting and reduces corrosion fatigue life.

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Crack tip dislocations in silicon single crystal were observed by high-voltage electron microscopy (HVEM). The crack tip area was selectively thinned by using an ion milling machine. Dislocation structures around the crack tip were elucidated from a tilt series of dislocation images, suggesting a dislocation growing process near the crack tip. Slip planes and Burgers vector of those dislocations were characterized in detail. In the present paper, self driven dislocation source multiplication process will be presented.

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The measurement of stress/strain components in Si wafer on microscale area has been developed. In this study, micro-Raman spectroscopy with a device for controlling the polarization direction of irradiation and scattering lights was proposed in order to decompose a single triply degenerate Raman peak in Si. From polarization analysis of backscattered Raman spectrum for (001), (110) and (111) Si wafers, three independent Raman peaks could be decomposed for only (111) Si wafers by determining the polarization direction corresponding to crystallographic orientation of specimen. Measurement of Raman shift change in (001) Si wafers under uniaxial and equi-biaxial stress condition was measured. In both conditions, the relationships between Raman shift change and applied strain were linear function, and phonon deformation potentials were determined from these relationships. The obtained values were good agreement with the values reported in other papers. Therefore, three independent Raman peaks were able to be evaluated by polarized micro-Raman spectroscopy.

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A novel evaluation method of the crystallinity of grains and grain boundaries was proposed by analyzing the quality of Kikuchi lines obtained from the conventional EBSD analysis. This method can evaluate the porous and brittle grain boundaries by IQ (Image Quality) and CI (Confidence Index) . Both IQ and CI values are the parameters which are calculated from the observed result of the Kikuchi pattern obtained from the area where electron beams penetrate during EBSD analysis. The position of the grain boundaries is determined by this CI value, and the crystallinity of the film around the grain boundaries is evaluated by the IQ value quantitatively.

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Electroplated copper thin films have started to be applied to thin film interconnections and TSV (Through Silicon Via) in semiconductor devices because of its low electric resistivity. However, both mechanical and electronic properties of electroplated copper films vary drastically depending on the electroplating conditions and thermal history. That is because the micro texture of the film is largely changed as a function of the electroplating conditions and the annealing temperature. In this study, the change of the crystallographic quality of the polycrystalline copper thin-film was observed by using an EBSD (Electron Back Scatter Diffraction) method. This EBSD analysis clearly showed that the degradation of the crystallinity of the electroplated copper thin film after the annealing was caused by stress-induced migration around the grain boundaries with low crystallinity.

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The carbon nanostructures consisting of two graphene sheets connected with carbon nanotubes as pillars are called pillared-graphene nanostructures, which are expected to be applicable to electronic devices. In this paper, the mechanical properties of pillared-graphene under shear or torsional loads are investigated via molecular-dynamic simulation. Their deformation characteristics under such loads are examined.

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Depositing graphene on substrates is one of the promising methods of fabricating graphene for commercial use. Graphene fabricated by this method is well suited to the conventional thin film technology. In this paper, the configurations of single- and multi-layered graphene on SiC substrate are investigated via molecular dynamics. How the surface anisotropy affects their configurations is examined. Furthermore, simulations of peeling graphene from substrates are performed. The forces necessary to peeling are estimated.

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We investigated the possible origin of ferromagnetism due to a vacancy on a nonmagnetic ferroelectric PbTiO_3 surface by performing first-principles calculations within density-function theory. The results demonstrated that an oxygen vacancy intrinsically induced ferromagnetism, which is remarkably enhanced and stabilized on the TiO_2-terminated surface favorably rather than inside PbTiO_3. Detailed electronic structure analysis revealed that the ferromagnetism originated from the spin-polarized d_<x2-y2> and d_<zx> states of the two Ti atoms nearest to the oxygen vacancy on the surface. The results presented here provide fundamental insights into the design of multiferroics in conventional ferroelectrics.

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Lattice defects in a ferroelectric material strongly affect its physical properties. However, there are fewer studies on plane and line defects, which are important lattice defects. In the present study, LiNbO_3 bicrystals with low-angle tilt grain boundaries were successfully fabricated by diffusion bonding. Here, LiNbO_3 is a widely used ferroelectric material with pyroelectric, piezoelectric, electro-optic and photoelastic properties, and a high Curie point. The resultant boundary was then investigated using conventional TEM and high-resolution TEM, and it was found that a boundary dislocation dissociated into two or three partial dislocations with a narrow separation distance. A crystallographic consideration with the TEM observations suggests the Burgers vectors of the partial dislocations and structures of stacking fault.

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When the bolt is tightened, the rotational force working on the nut is transferred to the flank within the engagement length and transformed to the longitudinal bolt force. It has been recognized, however, it has not been defined as a calculation formula so far. Somebody says it is equivalent to four threads, the other says fifty percent of the nominal bolt size. The modern bolt tightening method measures the bolt elongation during bolt tightening by means of ultrasonic equipment and controls the longitudinal bolt force. The elongation of bolt is calculated based on the bolt length including the engagement length of bolt and nut. Therefore, accurate estimation of the engagement length leads to achieve the correct bolt longitudinal force. Focusing on the unified coarse thread exceeding one inch in nominal size in eight threads series, how to estimate the correct engagement length of bolt and nut during tightening based on the tensile experiment data of 1 1/4-8un will be described.

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When bolted joints are subjected to cyclic loading conditions, fatigue strength of the bolts is critical for integrity of the joints. In the present study, two types of fatigue tests were applied for M8 bolts made of alloy steel, SNB7, used for flange joints of pipes in petro-chemical plants up to 400℃. The bolts were fixed with double nuts at the both ends and applied cyclic loadings at various stress ratios at 5Hz by a hydraulic fatigue testing machine. In the other fatigue test, the bolts were cut with a length having resonance frequency of 20Hz, and tested by an ultrasonic fatigue testing machine, which is suitable for evaluating very high cycle regime. Stress analyses for the bolt specimens were performed by finite element method (FEM) in order to obtain the stress concentration by the screw and to adjust the nominal stress values for the two types of the fatigue tests. Wide range of fatigue life of the bolts were determined by those tests and the effect of stress ratio on the fatigue strength were investigated.

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The effect of the plain washer's thickness on the contact stress distributions and the plastic displacements (permanent set) at the bearing surfaces are analyzed using elasto-plastic FEM analyses in case of the initial bolt clamping state. It is found that the contact stress and the plastic deformation decrease as the thickness of washer increases. It is shown that the plastic displacements at the bearing surfaces in case of hexagon bolts with flanges are smaller than in case of hexagon head bolts. Also even if the average contact stress is the same at the bearing surface, the plastic displacements are smaller in case of smaller bolt holes of clamped parts.

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A lot of pressure boundary bolted flange joints have been used in connecting a lot of piping, equipment, and facilities in some industries such as the refineries, the chemical plants, the nuclear plants and so on. Under utilization of many bolted flange joints, a lot of times and powers are needed when torque methods are applied for bolt loosening. This bolt loosening work by torque methods is expected not only to improve the efficiency of work, but also to pursue a safer work. In this paper, the effect of washers on the loosening bolts is examined. As the result of the investigation, it was recognized that the use of through-hardened steel washers will improve a loosening work by providing a smooth and low friction bearing surfaces for the nuts. The results of investigation using several type of washers in the laboratory and in the actual flange are reported.

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The leakage accidents may occur by the pipe bending in case of an earthquake. In this study, leakage properties of the connection with the sheet gasket or the spiral wound gasket when the connection is bended are investigated by experiments and FEM calculations. Moreover, the advance of the gasket for pipe bending is also considered.

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A method which takes into account the effects of external bending moment for the load factor based load calculation of pipe flange connections for the sealing performance design is proposed. Previously authors proposed the simplified load calculation method by using the load factor of the pipe flange connection subjected to internal pressure. The present method is the extension of the previous method to handle the external bending moment loading on it. The flange rigidity apparently increases under the external bending moment loading due to the contribution of the torsional rigidity of the flange ring as Koves pointed out. The apparent increase of flange rigidity proposed by Koves has been incorporated into the equivalent axial force representing the applied bending moment by multiplying the flange rigidity increase factor and it is used to the load factor based load calculation to evaluate the changes in the bolt load and the gasket load of the pipe flange connection subjected to the external bending moment. By using the factored equivalent axial force, the equations of the load factor based load calculation can be easily extended to handle the external bending moment.

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Pipe flange connections have been widely used in mechanical structures such as power, chemical plants and so on. Sometimes leakage accidents occur from the connections. In assembling the pipe flange connections, the bolt preloads are scattered and then the connections are subjected to external bending moment due to earthquakes as well as internal pressure. In the present paper, the changes in the axial bolt forces are measured in assembling. The bolts are tightened with torque wrench. Using the history of the axial bolt force changes and FEM calculation the gasket stress distribution is estimated. The amount of leakage of the connection was measured. It is found that the effect of the scatter of bolt preload is substantial on the sealing performance of the connections. And it is found that the effect of the scatter of bolt preload and the effect of bending moment can be added. The changes in axial bolt forces obtained from experimental result are in a fairly good agreement with FEM result.

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Bolted flange connections with ring joint gaskets have been used to seal the inner fluid under higher internal pressure and higher temperature conditions where soft gaskets such as compressed sheet gaskets cannot be applied. Bolted flange connections are frequently tightened using torque wrench, and it is known that the values of bolt preloads are scattered. The effect of the scatter on the sealing performance for bolted flange connections with compressed sheet gasket or semi-metal gasket has been examined. However, no research on the characteristics for the bolted flange connections with ring joint gasket has been carried out. It is necessary to know the effect of the scattered bolt preloads on the sealing performance and mechanical behavior of the connection with ring joint gasket. In addition, it is important to know an optimum method for determining the bolt preloads taking account of the scatter in bolt preloads. In this paper, leakage tests for bolted flange connections with octagonal ring joint gaskets were conducted for cases where the bolt preloads are uniform and scattered. The sealing performance of these connections with ring joint gaskets was measured and evaluated. In addition, the leak rate was estimated using the contact gasket stress distributions of the connections when the bolt preloads were uniform and scattered using 3-D FEM. Finally, the measured leak rate for the connection using helium gas was compared with the estimated results. The estimated results are in fairly good agreement with the measured values. It is found that the sealing performance of the connections tightened with the uniform bolt methods is better than that with scattered bolt preloads.

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Metal gaskets have been used in bolted flanged connections under high pressure and high temperature conditions. However, it is difficult to estimate an amount of leakage from the metal contact interfaces in the connections where internal pressure. Recently, it has been noticed that a tiny leakage occurs from the gasket interfaces in bolted flanged connections. Thus, it is necessary to study on the sealing characteristics of the metal to metal contact gasket in the connections under internal pressure and high temperature. In the present paper, the amount of gas leakage from the metal contact gaskets is measured at room temperature. The gaskets used are aluminum, copper and Cr-Mo steel flat gaskets. According to JIS B 2490, the sealing characteristics are measured taking account the surface roughness of the metal gaskets. that is, the gaskets are compressed using a material testing machine while the leakage is measured. The relationship between the stress and the amount of leakage is obtained. In addition, the amount of leakage is measured for bolted flanged connections with metal gaskets. The flange nominal diameter used is 2". The relationship between the gasket stress and the leak rate is examined. Furthermore, the contact gasket stress distributions in the connection are analyzed using 3-D FEM analysis. Using the obtained gasket stress distribution, the characteristic of bolted flanged connections with metal gasket is estimated. The estimated result is compared with the measured results. Discussion is made on the leakage mechanism of metal gaskets.

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In the depreciation evaluations for pressure equipment, it is important for engineers to evaluate the reduction in the sealing performance in bolted flange joints. In this study the effects of nut thinning due to corrosion on the sealing performance in 3 inch and 20 inch bolted flange joints under internal pressure The stress distributions in the bolted joints, in particular, in bolts are examined from both FEM calculations and measurements. The following results are obtained. 1) when the height of the nut was kept the 2/3 height of the original dimensions according to the JPI standard , the sealing performance of the joints with the thinned nuts is the same as that with the original height nuts under internal pressure. 2) when the height of the nut was reduced to 1/3 height of the original dimensions according to the JPI standard , the sealing performance of the joints could no longer be assured. Thus, it can be concluded that the reduction of the nuts should be checked.

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The gasket stress distribution in fixing flange was examined using 3D finite element method (FEM). The gasket stress was increased to the radial direction under the influence of flange rotation. The flexible graphite sheet gasket (FGSG) reduced its thickness much more than compressed sheet gasket (CSG) when compressed between flange joints. Flange rotation of FGSG was less than that of CSG. Surface observation of the gaskets revealed that the FGSG replicated the surface roughness of the flange joints. The sealing performance was tested by using Helium gas leak detector. Under the uniform axial bolt force conditions, FGSG had better sealing performance than CSG. The sealing performance was investigated under the tightening and loosening process when the axial bolt force was ununiform. The Leak level in the loosening process was less than that in tightening process for CSG, while for FGSG this behavior was not observed.

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Bolted connections with gasket such as box-shaped flange connections have been widely used in mechanical structures, such as nuclear and chemical industry, and so on. They are usually used under internal pressure. The high sealing performance of flange connection is required to avoid the unexpected leakage accident. The two methods, which are Diagonal and Clock-wised, are used in the bolts tightening procedure for the pipe flange connection. The effects of the difference between Diagonal and Clock-wised method on the sealing performance of pipe flange connection have been examined. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM) of each bolting procedure, taking into account a hysteresis in the stress-displacement curve of a gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test, a method for estimating an amount of leakage is examined. The leakage tests were also conducted to measure an amount of gas leakage using an actual box-shape flange connection with the gasket. In addition, the effect of bolt spacing is examined on the sealing performances of box-shape flange connections under internal pressure. The effects of the above factors are discussed on the sealing performance in designing box-shape flange connections.

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With the recent increase of a safety and environmental concern, the tightness of gasketed flange connections becomes an important issue. In order to estimate the tightness of gasketed flange connections, test methods to examine the sealing behavior of gaskets have been established in North America, Europe and Japan. When the leak rates are measured, stabilizing time of leak rate is needed to obtain reliable leak rates. It is thought that when a flange connection is pressurized, the leak rate begins to increase and finally reaches a constant value if the stabilizing time is long enough. In this paper, the transient sealing behavior was measured using a gasketed flanged connection. Leak rates were measured using a helium spectrometry and a pressure decay method. Both the results were compared and the mechanism of leak through gasket and the stabilizing time to obtain leak rate with enough accuracy were discussed.

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In multi-bolt system, the scatter in axial bolt force is largely dependent on the method of tightening operation and elastic interaction due to the successive tightening of bolts. For tightening bolt operation, mainly two operations can be cited. It is JIS B 2251 and ASME PCC-1. In JIS B 2251, the range of application of gaskets is exclusive to Compressed Fiber Sheet Gasket and Spiral Wound Gasket. Because elastic modulus of Expanded PTFE Gasket is low value, there is a possibility of uneven gasket stress. Therefore Expanded PTFE Gasket is not applicable to JIS B 2251. In this study, focus is placed on elastic modulus of gasket. The present paper describes consideration of appropriate tightening round and scope application of JIS flange joint assembly guidelines by tightening test and three-dimensional finite element analysis in accordance with JIS B 2251. If elastic modulus of gasket is over 0.06, JIS B 2251 is effective procedure for flange joint assembly. Because average bolt force preload ratio to the target is more 85 percent on round three, appropriate the number of tightening round is three rounds.

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Asbestos-related regulations have virtually eliminated asbestos from gasket products and the industry is now transitioning to mastering safer and more efficient uses of non-asbestos gaskets. To ensure safety in the long-term use of non-asbestos gaskets, control methods for using non-asbestos gaskets safely and techniques to evaluate and estimate the long-term performance of gasket connections must be developed, compensating for actual data. In this report, we make predictions on long-term variations in the contact pressure of gasket connections according to stress relaxation tests for flange connections. Particularly, we discuss the advantages of retightening period and temperature.

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Nanoindentation test was carried out using TMA with Berkovich indenter to evaluate the viscoelastic characteristics of a gasket containing PTFE. The time-temperature superposition principle using W.L.F equation was applied to obtain the master curve of the creep compliance of gasket material at elevated temperature. The elastic-viscoelastic correspondence principle was also applied to estimate the gasket creep strain in the flanges from the master curve of the creep compliance. Gasket creep strain rate can be estimated at an elevated temperature for a long term of 10^5 hours. Estimation of the gasket creep strain rate in the flanges at 140℃ shows a good agreement with the experiment data obtained by the HPIS Z105 test procedure.

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This paper shows that the thermo-oxidative decomposition rate at elevated temperature measured by isothermal thermogravimetry (TG) is useful for evaluation of heat resistance of exfoliated graphite which is widely used as the material for gasket since asbestos has been banned. The decomposition onset temperature t_d obtained from TG operated in usual manner in which the sample is heated at a constant speed. t_d is the temperature that drastic decomposition is occurred so that it is inappropriate for estimation of heat resistance for prolonged use. TG instrument is also able to obtain v_d from measuring the decrease in weight at isothermal heating. The relationship between v_d and temperature is useful for estimating temperature effect for decomposition of graphite. Arrhenius plot provides the temperature effects on v_d. This kinetic approach is effective for estimating heat resistance of graphite gaskets.

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Cerebrospinal fluid hypovolemia onsets by the cerebrospinal fluid leak which might be induced by the impact loading at traffic accidents, sports and so on. However, the detail mechanism has not been clarified. We guess that the leaking starts at a dura mater around spinal nerve root and investigated the impact strength of the nerve root part. Spontaneously, it could be important to investigate the basic tensile properties, especially strain rate dependency of them, of dura mater to clear the leaking mechanism. In the present study, to investigate the mechanical properties of dura mater, tensile tests were performed using bovine dura mater of the cervical spine. The test pieces were taken from the dura mater along the spinal axial direction, then the tensile tests were carried out at strain rate ε^.e= 0.01, 0.1, 1.0, 10, and 100 s^<-1>. Stiffness of dura mater was calculated by applying the stress-strain responses to Ogden model. Tensile strength tended to increase with increase in strain rate. Especially, this tendency was remarkable at higher strain rate level. On the other hand, the stiffness tended to be smaller with increase in strain rate.

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Cauda equina nerves start at the spinal cord end of which shape is conical, and go down in the spinal canal. Cauda equina syndrome, which is one of a degenerative disease, occurs around spinal cord cone because of a herniated disc or vertebral fracture. However, the pathogenic mechanism is unknown still now. In order to elucidate this mechanism, FEM simulation technique is required. In this research, we performed tensile tests to the cauda equina nerve to obtain the basic material properties which is needed in FEM simulation. The samples were taken from fresh pig spine, the tensile loading was applied to samples at a strain rate ε^.= 0.01 - 10 [s^<-1>]. In each specimen, in the earlier loading process stresses gradually increase as other kinds of biological soft tissues. And, stresses rapidly decrease just after a peak. Tensile strength is relatively smaller in higher strain rate. The maximum value of tensile strength was 0.78〜4MPa in this study.

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We evaluated stress distributions of a human common carotid artery (CCA) by finite element modeling of various combinations of wall layers. In the experiment, we separated intima, media, and adventitia from ring-shaped vascular walls and carried out uniaxial stretching tests on each of them. The experimental stress-strain relationship for each hyperelastic layer was later used to determine the material constants with an assumption of uniaxial loading condition. At last these material constants were used in the finite element analysis of the vessel. Models with various combinations of vascular layers including their stress-free configurations were compared by evaluating the stress distribution of a CCA under a constant axial stretch of 1.1 and a blood pressure of 16 kPa. By considering the stress-free state of the intimal layer, the maximum principal stress reduced significantly in the intima. This result indicates that the stress-free state of the intimal layer should be used for geometrical modeling if it bends backward by releasing the residual stress.

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Bone is often regarded as a composite material consisting of mineral particles, organic matrix and water phases in microscopic scale. The mechanical properties of bone at macroscopic scale depend on the structural organization and properties of constituents in the microscopic scale. Raman spectroscopy is known to be useful tool for the analysis of material at ultra-structural level. In this study, bovine cortical bone specimens were analyzed by Raman spectroscopy to examine the mechanical response of constituents in the microscopic level by using the Raman microscopy in combination with micro-tensile loading device. As the results, the structural information of both mineral and organic phases of bone tissue could be detected by Raman spectroscopy. The Raman shift of mineral crystal to lower wave numbers was observed with increase of tensile strain. Therefore it was confirmed that this method is sufficiently useful to evaluate the stress state related to microscopic response of constituents in bone tissue.

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To the best of our knowledge, there have been few reports on test methods for the viscoelastic properties of soft objects using an air jet instead of plungers for loading and unloading. We propose a method of evaluating their viscoelastic properties, such as soft processed foods and industrial products, using an air jet with newly developed test equipment. In this method, loading and unloading can be performed using an air jet in a very short time, loading time can be arbitrarily set, and the shape of the dents formed on the surface of soft objects can be instantaneously measured using light from a semiconductor laser. In this study, using the developed equipment, we measured the shape of the dents formed on soft samples, measured the depth of the dents for various loading times, types of soft sample, and pressures, and evaluated the viscoelastic properties of the soft samples with respect to elastic compliance and equivalent dent depth.

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In this study, we developed a cell stretching micro device for in situ observation of cellular response to stretch loading. In studies that using conventional observation apparatus only investigate the cellular response which slowly arise (ex. in minutes, hours, days) aster stretch loading. Our device is fabricated by applying the MEMS technique. We demonstrated the performance of the device. Rigid displacement of the cell body during stretching loading was well suppressed. We conducted a real-time in situ observation of single osteoblastic cell and evaluated the cellular response to stretch l.

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To discuss an effect of stress ratio on very high cycle fatigue properties of the extruded magnesium alloys, axial loading fatigue tests have been performed under three conditions of stress ratio, R, of 0, -1 and -1.5 in laboratory air at room temperature using hourglass shaped specimen of three kind of alloys. Specimens tested under R=-1 and -1.5 showed a step-wise S-N curve on which two knees appear while under the test of R=0 clear fatigue limit existed on the S-N diagram. From the detail observation of fracture surface, It is suggested that fatigue crack initiation mechanism changed from the twin-induced failure mode at high stress amplitude level to the slip-induced one at low stress amplitude level. This transition was occurred by the relation between the minimum stress during a cycle and the compressive yield stress at which deformation twin occurred. The deformation twin is formed during fatigue process when the minimum stress exceeds the yield stress in compression that is smaller than that in tension.

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