A dedicated strain gage has been developed to measure the stress intensity factor of cracks. Conventional strain gages dedicated to stress intensity factor analysis have been made by combining multiple elements into a single gage. Therefore, it took time and effort to analyze the stress intensity factor. Therefore, in this research, we have developed a dedicated strain gage that can analyze the stress intensity factor more easily than before with only one gage of one element. The developed strain gage analysis formula uses the strain component εθ formula at the crack tip. We focused on the gage angle θ that brings the second term of the crack analysis strain component εθ close to 0. By setting the second term to 0, the stress intensity factor of the first term can be analyzed accurately in consideration of the second term. The developed gage has a donut shape with radii r1 and r2 and a width of 1 mm with the crack tip as the origin, and the gage grid angle has an angle from 0 ° to 52 °. A tensile test piece with a crack opening mode load was manufactured and a tensile experiment was conducted. The experimental value of the stress intensity factor was obtained within an error of ±10% from the theoretical value.
Lead bronze had been widely used as the bearing materials. However, the utilization of that material is limited, because the lead and the lead compound are noxious to the human body. Therefore, though the lead free bronze (LFB) alloys using the rare metals are developed, the problem on resources has been pointed out. On the other hand, the powder of LFB including the sulfide (Cu5FeS4) of Cu-Fe-S series was developed, and it was reported that the materials sintered the powder show the higher sliding characteristics than those of lead bronze. Therefore, the bimetal materials sintered after spraying that powder on the substrates have achieved high functionality. However, it is desired to establish the method for quantitatively evaluating the progress of the breakage conditions and for acquiring the design information on the realization of the requested mechanical properties. By comparing the breakage types occurred in the tensile test with the characteristics of the AE events emitted by those types, the parameters for evaluating those types were proposed and those effectiveness were reported in the previous study. On the other hand, the establishment of the life judgment method is desired as the main causes of many breakage accidents are fatigue phenomenon. However, the accident analyses are difficult because the traces of the breakage are not clear as for the fatigue breakage of the sintered materials. In this study, the Ib-value derived from the amplitude distribution of the AE events detected in the fatigue test was applied for the life judgement, and that effectiveness was examined.
A wire rope is one of the main components of cranes and elevators. The wires of the rope gradually break with long-term use, and the rope eventually leads to fracture. Rope fracture might cause a serious accident, so it is important to clarify the mechanism of rope damage in order to prevent such accidents. In recent years, IWRC ropes, which have become a mainstream crane rope, are found to have wire breakage inside the rope. Therefore, it is difficult to properly identify the damage of a rope by visual observation, and a method to obtain the wire breakage state in the rope cross section including the inner wires is required. This study proposes a method for estimating the position of wires in the rope cross-section based on geometrical formulation. A damaged rope including wire breakage was produced by S-bending fatigue test, and the locations of wire breakages were estimated by this method. As a result of evaluating the positional relationship between the wire breakage position and the S-bending fatigue test sheave, it was clarified that the relationship between the area prone to wire breakage and the wire position relative to the rope or the test sheave was different for each type of wire. Furthermore, by comparing the wire breakage positions obtained from the cross-sectional images taken by X-ray CT, it was confirmed that the developed method can predict the wire breakage positions with sufficient accuracy to evaluate the damage status of ropes. This study makes it possible to evaluate the relationship between the fatigue test conditions and each wire in the rope cross-section, which is expected to further analyze the damage mechanism of wire ropes.
High Reynolds number turbulent boundary layer measurement is performed in the RTRI ’s low-noise wind tunnel in Maibara Japan. The momentum thickness Reynolds number Rθ is up to approximately 8×104. Mean velocity statistics are compared with those of large wind tunnel facilities in Melbourne, Sweden, New Hampshire, Netherland, France and UK. The ratio of momentum thickness θ，displacement thickness δ* and Rotta-Clauser thickness Δ against the boundary layer thickness δ99 does not show the similar trend but depends on the facility. Mena velocity profile is approximated by the log-law relations; U+ = 1/κ ∙ ln(y+) + B + Π/κ ∙ W(y/δc) and (U0 − U)/uτ = − 1/κ ∙ ln(y/Δ) + B1 , where W is wake function, U0 is free stream velocity, uτ is friction velocity, and δc is Coles’ boundary layer thickness. Parameters κ，B, B1, and Π distribute in wide range, but they relate with one another and the simple relation between κ and B is presented. Also the relation between κB1 and Π is confirmed. When the effect of virtual origin is corrected, the Reynolds number Rx′ ≡ U0x′/ν , where x′ = x + x0, x is the distance from the leading edge and x0 is virtual origin, indicates the same trend against Rθ independent of facilities. Also, the skin friction coefficients agree with one another as a function of Reynolds number based on displacement thickness.
In this study, the effective thermal conductivity of glass wool was measured under different temperature and packing ratio conditions using a high-precision guarded hot plate (GHP) apparatus, which adopted a Peltier module. From the measurement results, it was confirmed that the effective thermal conductivity was linearly proportional to the cubic of absolute temperature. Varying the packing ratio, the influence amount of the radiative heat transfer on the effective thermal conductivity varied from 44 to 66% for different packing ratio. The influence of the radiative heat transfer on the effective thermal conductivity decreases with increasing of the packing ratio. From the variation of the effective thermal conductivity against cubic of the temperature, the Rosseland mean extinction coefficient were evaluated and the equivalent thermal conductivity by the radiation was estimated. The equivalent thermal conductivity by the radiation decreases as increasing of packing ratio of the glass wool and this result could be explained by the increment of the Rossleand mean extinction coefficient. From the comparison between the theoretical and experimental results of the equivalent thermal conductivity by radiation, a correction value that depends on the packing ratio is required. Furthermore, we compared the experimental values and the calculated values by Kunii's formula for the thermal conductivity of the glass wool with different packing ratio and it was confirmed that the quantitative evaluation of the equivalent thermal conductivity by the radiation is important for estimating the total effective thermal conductivity of the glass wool.
In nuclear power plants, measures against radioactive noble gases are required. Until now, special activated carbon that easily adsorbs noble gases has been used in some nuclear facilities. However, activated carbon has a small adsorption capacity and is greatly affected by other gases and environmental humidity. Therefore, it is necessary to develop a new adsorbent with high adsorption performance. At emergency response stations, it is also necessary to take measures using air cylinders. It was confirmed that the newly developed silver zeolite XeA has more than 10 times adsorption efficiency of activated carbon for noble gas adsorption. In this paper, we will report on the basic noble gas adsorption performance of XeA and compare the adsorption performance between XeA and activated carbon. In addition, some applications of the noble gas adsorbent XeA are recommend, for example, (1) applied to noble gas countermeasures at emergency response stations, (2) applied to activated carbon noble gas hold-up systems, and (3) applied to emergency gas treatment systems (SGTS). Since silver zeolite XeA has excellent noble gas retention performance, it is possible to reduce the size and simplification of equipment by using it instead of the existing activated carbon. Furthermore, since XeA is nonflammable, it can be expected to improve safety.
Vortex structures behind two highly heated cylinders of equal diameter in tandem arrangements have been investigated experimentally. The experiments were performed under the following conditions: cylinders diameter, D = 4 mm; mean flow velocity of air, U∞ = 1.0 m/s; Reynolds number, Re = 250; cylinders spacing ratio, S/D = 1.0~10.0; and cylinder heat flux, q = 0~72.6 kW/m2. Two distinct flow structures are formed in the region of the cylinder clearance which depends on the S/D and the cylinder surface temperature, Tw. One is a quasi-stationary twin vortex at the small S/D condition (S/D<3.0~5.0) and the other is a shedding Karman vortex for large S/D condition (S/D>3.0~5.0). Behind the downstream cylinder, the Karman vortex street is formed in all conditions. The critical S/D changing to the Karman vortex increases with increasing the temperature of the upstream cylinder. The Strouhal number St under the twin vortex forming is in the range of 0.150 to 0.155 regardless of the S/D and heating conditions, while the St of the Karman vortex formed behind the downstream cylinder is decreased significantly as the S/D increases. For the large S/D, the Karman vortex is formed behind both of the cylinders then the upstream St agreed with the downstream St. St of the Karman vortex coincides with St in the single-cylinder condition taken into account of the cylinder heating conditions. For the small S/D and the upstream cylinder in a highly heated condition, the twin vortex structure behind the upstream cylinder plays a key role in the downstream shedding Karman vortex structure.
We propose control method of Eye-And-Hand robot arm by visual space based visual servoing which directly generates command values from visual space coordinate by using jacobian of between velocity of feature points on visual space coordinate and velocity of robot arm on 3D coordinate. Visual space based visual servoing can suppress unexpected movement in space because it is control method which minimizes deviation on visual space coordinate which deeply relates to spatial recognition of human beings and is derived from image coordinate of stereo camera, camera angles and camera focal length. On the other hand, image based visual servoing which is conventional method of visual servoing sometimes causes unexpected movement in space because it is control method which minimizes deviation on image coordinate by using jacobian of between velocity of feature points on image coordinate and velocity of robot arm on 3D coordinate. And we show that visual space based visual servoing suppresses unexpected movement in space by comparing it with image based visual servoing by simulations. First simulation shows that difference of hand trajectory between visual space based visual servoing and image based visual servoing is little. Second simulation shows that the difference becomes larger because image based visual servoing causes unexpected movement by making deviation of posture between first hand posture and target posture larger than first simulation.
This study investigates a wall-climbing machine to reduce the friction between a seal and a wall surface. The climbing machine uses the adhesion mechanism of negative pressure generated by the blower impeller. A side wall created by flexible bellows, which are connected to the seal from the top outer wall of the climbing machine to maintain negative pressure, can reduce the force with which the seal pushes against the wall. However, in order to prevent the seal from sliding off owing to gravity, it is necessary to press the seal against the wall with springs. Therefore, this seal pressing force causes energy loss because of friction between the seal and the wall when moving the machine. To further reduce the friction, a sealing mechanism using the negative pressure in the machine is developed, and the effect of the mechanism is investigated experimentally in this report. The ratio of the dynamic friction force of the seal with the friction-reducing mechanism to that of the wheel was less than 10%. It was confirmed that the climbing machine using a small power motor can climb a vertical wall made of plywood independently with the battery installed. The conditions of the adhesion limit in the experiment were consistent with theoretical one obtained.
In this study, we proposed a new rotational multi-stable vibration energy harvesting system to harvest vibration energy using elastic spring and piezoelectric element. Theoretical studies such as the equation of dynamic motion of the proposed rotational multi-stable vibration model, the distribution characteristics of elastic potential energy, and the prediction of the periodic excitation frequency by the natural vibration mode measurement experiment will be conducted. Using the developed rotational multi-stable vibration energy harvesting experimental device, we investigated the amplitude increase effect due to the new stochastic resonance phenomenon that occurs in the proposed rotary multi-stable vibration system, and evaluated the performance of the multi-stable vibration energy harvesting.
For the past several years, large scale earthquakes happened. A lot of industrial facilities were damaged. For example, a lot of power plants were stopped in The 2011 off the Pacific coast of Tohoku Earthquake or The Southern Hyogo prefecture earthquake in 1995. These earthquakes had larger acceleration level than the seismic design level. Therefore, the earthquake proof measures are required. In this study, earthquake proof effect of the beam with initial torsion is focused. The design guidelines for application to the thin-walled beam with initial torsion structure is proposed. The thin-walled beam with initial torsion is modelled by FEM and calculated. The static and dynamic loading characteristics of the actual beams are compared with the analytical results to verify the validity of the analysis. The comparison result of analysis and experiment shows that the FEM analysis of the beam element is valid up to 0.23 aspect ratio. The analysis was used to clarify the static characteristics, for example, stiffness or displacement, and dynamic characteristics, for instance, frequency or vibration mode, under the conditions of the aspect ratio and total torsion angle of the beam. By the time history analysis, it was shown that the vibration response changed by the initial torsion, and that it was possible to reduce the acceleration response. In order to evaluate the response reduction effect, the acceleration response for the condition of the aspect ratio and total torsion angle of the beam was analyzed. And the response reduction map is proposed. Using this map, it is possible to estimate the advantage of the initial torsion effect for the response reduction effect in a simple manner.
Ducts are widely used in an industry field. For example, air conditioning ducts, exhaust ducts, smoke elimination ducts and silencers have been used in various ducts. In general, the ducts have a flow and the vortices generated in the duct sometimes cause a resonance phenomenon and a self-sustained tone. Once the resonance occurs, the high level sound is generated and the suppression of this sound is strongly and quickly required. It is necessary to know the natural acoustic frequency of the duct for examination of the cause. The natural acoustic frequency of the straight duct with uniform cross section can be easily obtained but that of varying cross section can’t be obtained immediately. Of cause the natural acoustic frequency of the duct with an arbitrary cross section can be obtained by using the transfer matrix method, FEM and BEM. In our previous studies, many interesting findings of the natural acoustic frequency of ducts with varying cross section were obtained but the understandings of the findings have not been adequate. Then in this paper, in frequency range where plane waves hold, the mode order independent of the ratio of two cross sectional areas is discussed and the table which makes obtaining of the natural acoustic frequency easily is presented. Furthermore, we will show how to understand the relation between the ratio of the cross sectional areas and the natural acoustic frequency for an arbitrary length ratio.
The purpose of this paper is to clarify the damping mechanism of the wheel that we have developed. In high-speed railway vehicles, noise associated with speed increase is a problem. We have developed a new wheel that can damp the rolling noise radiated from the wheel. This noise damped wheel has a special device attached to the inner circumference of the rim, which consists of steel sandwiched with vibration absorbing rubber. The noise damping effect was confirmed by the wheel rolling test, but the mechanism was unclear. Therefore, we elucidated the vibration damping mechanism using FEM. Using frequency response analysis, the equivalent radiated power (ERP) was calculated based on the response speed and element area when a load was repeatedly applied at a specified frequency. By calculating the modal ERP for a specific frequency, the natural vibration of the wheel, which contributes significantly to that frequency, was clarified. From this result, it became clear that the developed wheel disperses the natural vibration modes. It was also found that the vibration is reduced by damping of the rubber that acts on the dispersed natural vibration. Based on these findings, we concluded that increasing the Young's modulus of the rubber would improve the damping performance.
In Japanese railway networks, the gauge corner cracking (GCC) occurs to the head hardened rail of the high rail in curved sections of R600 to R800m. In case of the GCC propagates deeply, it will be a possibility of causes rail broken. Therefore, the appearance of GCC is considered a serious problem from the viewpoint of safety transportation. Since GCC appears mixed with head checks, it is very difficult to find GCC in the early stages. Furthermore, GCC appears in the cluster conditions, it is very difficult to remove all cracks of GCC. Hence, it is very important to control the initiation of GCC. However, the countermeasure method for GCC initiation has not been developed. The aim of this study is to examine the reduction method for GCC initiation due to the relief of the contact pressure between wheel/rail. Therefore, the wear development of rail was focused, the influence of the worn profiles of rail on wheel/rail contact condition was examined. In the beginning of this study, rolling contact fatigue (RCF) test were conducted by use of the twin disc test equipment. Secondly, wear analysis of rail with multibody dynamics which was modeled the locations of GCC appearance was conducted. Finally, the effect of the worn profiles of rail on wheel/rail contact and the suppression of RCF initiation was examined by the wheel/rail contact analysis. In summary, the worn profiles of rail were confirmed the suppression effect for RCF by reducing the contact pressure between wheel/rail.
At Tokyo Metropolitan Vocational Skills Development Center, job trainings are provided for job seekers to attain basic skills for employment. We carried out 20 years manufacturing competition for improvement of the skill and interest to manufacturing. The competition was divided into four branches and the teaching material of the machine course is a Stirling engine. At the machine course of the Itabashi school, we worked on the production of Stirling engine to acquire the digital manufacturing technology. The digital manufacturing technology is a design technology by the 3D CAD, programing for the NC machine and operation of the NC machine. We reported the class situation, the production of Stirling engine for five years from 2007 to 2012. And we verified the class effect by the acquisition degree investigation and the questionnaire survey from students. As a result, those class training succeeded considerably in their job search. It was made clear those class training had the good effects for the students to acquire the skill of digital production technology. And we researched company about the introduction situation of the digital production technology and completion students about the situation after the employment passing for a certain period of time about 10 years.