High pressure coolant is expected to dramatically improve the machinability of difficult-to-machine materials and develop new strategic approaches to high speed machining. This paper reviews high speed machining technology with high pressure coolant with regard to chip breakage, reduction of tool wear and drilling technology without pecking cycles. The film boiling of coolant near the tool tip due to high tool temperature is discussed based on the results of cutting experiments of stainless steel.
Pulp injection molding （hereafter PIM） is a new molding technique which carries out injection molding using recyclable molding compounds consisting of pulp and starch to obtain three-dimensional configurations. The clarification of the rheological characteristics of PIM compounds which are extremely affected by water content is an important task. However, it is difficult to measure them using existing rheometers for plastic melts. For this reason, in this study, the authors developed an equipment for evaluating the viscosity characteristics. Mounted on injection molding machines, this equipment is capable of measurements in high pressures without changing the water content. Viscosity was successfully measured for the first time at various temperatures, water content ratios and material compositions, and the measured data were also compared.
Among the various additive manufacturing technologies, laser sintering / melting can provide higher fineness of built parts and wider range of material choice. Previously, the authors reported introduction of this technology to fabrication of tissue engineering scaffold. In the report, high porosity, which is required by a cell culture reason, was successfully obtained by making it from mixture of grains of sodium chloride and powder of the scaffold material and leaching the filler afterward. On the other hand, high thermal conductivity of the filler led to low process resolution. In this paper, use of poly-glycolic acid as the filler material is introduced. The resolution is successfully improved with the porosity maintained above 90%. Fabricated tissue engineering scaffolds are tested in cell culture.
The accumulation of the tramp elements is a growing problem in the repeated recycling process. Thus, the effective separation technology of the tramp elements from aluminium alloy scrap is very important in the aluminium recycling and refining processes. In this study, the tramp elements of aluminium alloy scrap were separated by using the backward extrusion process in the semisolid condition. According to the results of optical microscopic images, Rockwell hardness testing and Electron Probe Micro-analyzer （EPMA） analysis, it was found that the tramp elements were accumulated on the grain boundaries of the extruded part and the purified aluminium was enriched in the unextruded part.
The forming processes at warm condition of carbon-fiber-reinforced plastics （CFRPs） sheets for mass production have been investigated. The bendability and stretchability can be evaluated by a stretch-bending test and a stretching test, respectively. A stretch-bending test is a bending test in which a tensile load is placed on a sheet. In the stretching test, a method of fixing the specimen is a kind of important condition for CFRP. We have proposed suitable forming tests and evaluated the formability of CFRP sheets compared to the metal sheets.
In this research, a remote AE measurement method with an optical fiber sensor was proposed to detect AE waves in composite materials under ultimate environments, and the effectiveness of the method was evaluated. As a result, this method was confirmed to have a broadband sensitivity. Moreover, based on the mode conversion of AE waves, the remote sensor was found to obtain the AE waves with the same waveform as that at the adhesion point of the optical fiber. Then, the relation between the dominated modes in AE waves and the damage types was clarified for a CFRP laminate. The result indicated that damage types under a bending load were able to be identified from the AE modes.
This paper deals with a new production system model, proposed and developed by the authors, for manufacture of products at lower cost and higher quality by introduction of small production machines. In such a system, only the assembled products are totally inspected directly for their functions and quality , while the quality of individual parts that compose the final products are assured, not by measuring themselves but by monitoring the their production parameters, based on theory that if only the production machine works normally, the part or final product produced with it must be of required quality. There are two critical factors that dominate such production system function, which are process or quality evaluation and effective process monitoring. To determine whether the machine works normally or not, we applied MT （Mahalanobis-Taguchi）system. This production system needs a single molding and measurement of the production process with low noise. To meet these requirements, the authors have developed a small injection molding machine and a small press machine. Each machine has a precise force sensor embedded in its mold for measuring the machine motion during the machining process. The small mold has a size of 80mm x 130mm x 80mm. It allows low noise measurements of the processes, and one-to-one correspondence of the product data and process data. Using the small production machines, we carried out experiments to produce micro parts. The experiments showed that the new production system could determine the quality of the products from the measurement data of the machine motion. The result indicates it is possible to increase the quality of the products and to decrease the cost of the quality management.
This study experimentally investigated effects of manufacturing conditions on metal-polymer direct joining. The direct joining was processed by a special insert molding using a surface treated metal piece. The metal piece had a nano-structures on a surface that were created by a chemical etching. In this particular work, we focused on the effects of cavity pressure during molding and of an annealing time length. We evaluated the joining samples that were processed under various conditions by tensile shear tests. From results of the tests, we can see that both cavity pressure and annealing time length had positive correlations with joining strength. Some samples were broken at base materials （polymer parts） by the tests, which indicates that the joining was significantly strong.
While the South Hyogo Prefecture Earthquake in 1995 is known as a severe earthquake having killed more than six thousand people, damage to non-structural components in large enclosures was significant. We investigated 35 large enclosures just after the earthquake and after 14 years. Its purpose was to figure out not only the situations of damage but also how they had been recovered or improved because, in many cases, they are used as shelters during disasters. In this report, we discuss the results showing three examples of each large enclosure.
Ceiling collapse has often occurred in the world. Cable nets are one of the most effective solutions for ceiling collapse as prevention. At first we examined the mechanical characteristics of cable nets by membrane theory and numerical analysis, and proposed the simplified formula to be safe. Furthermore, we conducted the drop tests to measure the axial load and the sag of the cable nets. Here we report the test results.
On the 11th of March 2011, the Off the Pacific Coast of Tohoku Earthquake （MW=9） has hit Japan and caused severe liquefaction damage over entire stretch of reclaimed lands along the coast of Tokyo Bay. The aim of this study is to investigate the relationship between liquefaction potential and liquefaction-induced road subsidence occurred in Urayasu city in the 2011 the Off the Pacific Coast of Tohoku Earthquake, and then to develop a new hazard map reflecting this relationship, which provides expected liquefaction-induced road subsidence in the scenario earthquake. This map would be useful not only for damage estimates by the liquefaction, but also for determination of the best routes for emergency vehicles for local governments.
In recent years, ‘Gel-Push’ （GP） sampling has become popular as one of the high quality soil sampling techniques. The GP is able to collect high quality samples by using a lubricant gel that reduces the friction between the tube wall and soil sample. However, an applicability for liquefiable sandy soils has not been examined yet. In this study, the quality of sandy samples collected by GP sampler and conventional triple-tube （TB） sampler were evaluated. The samples were collected in Mihama ward, Chiba City, Japan, where severe liquefaction occurred during the 2011 Off the Pacific Coast of Tohoku Earthquake. Based on the comparisons of void ratio and shear wave velocity between field and laboratory, it was demonstrated that the quality of the GP sample is slightly better than the TB sample. However, there was no significant difference in the value of liquefaction resistance between GP and TB.
In the period between 2010 and 2011, a series of Christchurch earthquake hit Christchurch City, New Zealand. The occurrences of severe liquefaction were repeatedly observed during the earthquakes. In addition, liquefaction-induced lateral deformation ranging from centimeters to several meters was observed. In this paper, a series of large strain undrained cyclic torsional shear tests were conducted on Christchurch boiled sand to evaluate its liquefaction resistance and large liquefaction-induced deformation characteristics. The boiled sand sample was retrieved at the liquefaction site along the Avon River after the earthquakes in February 2011 and in June 2011. It is found that the liquefaction characteristics of Christchurch sand at the normal strain level is similar to Toyoura sand, while higher liquefaction resistance for Christchurch sand was observed at the large strain level.
This study investigates the effects of cyclic loading history on shear wave velocity and liquefaction resistance of Toyoura sand. Cylindrical specimens with relative density of 50% were subjected to isotropic consolidation up to 100 kPa, followed by 100, 1000, 2000 and 3000 drained cyclic loadings under triaxial condition with constant vertical strain amplitude of 0.1%. In order to investigate variation of shear wave velocity and liquefaction resistance of the sand specimen caused by the different number of cyclic loading histories, first, a series of dynamic measurement by trigger and accelerometer methods were conducted. It was found that the shear wave velocity of the specimen increases with increase in the number of drained cyclic loading history. Second, undrained cyclic triaxial tests were conducted on the above-mentioned specimens. The liquefaction resistance increases with a large number of cyclic loading history, and there is good correlation between shear wave velocity and liquefaction resistance. Third, in order to obtain a lower limit of shear wave velocity and liquefaction resistance, another series of experiments were performed on a specimen which has several liquefaction histories. The result shows that the smallest values of the shear wave velocity and liquefaction resistance of the specimen were measured at the second stage of liquefaction test.
This paper examines, through a series of laboratory tests, the effect of the flyash improver, FAI, on liquefaction susceptible backfilling soils for underground pipes and excavatability of the improved soils. Unconfined compression tests show that the unconfined compressive strength of soil increases with both increasing FAI additive ratio and curing time. Undrained cyclic triaxial tests are conducted for specimens with different additive ratio of FAI. It is found that the FAI additive ratio of about 2% is optimum in the light of both liquefaction resistance and excavatability. This paper also suggests that small strain shear moduli can serve as a good index of the in-situ improver’s effect.
For the last two decades, geosynthetic-reinforced soil retaining walls （GRS RWs） have been constructed for important facilities such as railways and highways. In order to achieve greater seismic performance, a new-type of geocell with three dimensional structures, having straight longitudinal members with transversal members has been developed. In this paper, in order to investigate the seismic stability of the new-type of geocell reinforced retaining, a series of pullout test and shaking table model tests was carried out by using the new-type geocell and geogrids as a tensile-reinforcement in the sandy and gravelly backfills. Furthermore, an unreinforced retaining wall （T-shape） model was also tested for comparison. It was found that new-type geocell reinforced soil retaining wall model exhibited higher seismic performance than both geogrid reinforced soil retaining wall model and unreinforced retaining wall model.
This report summarizes geotechnical and structural damage features caused by the earthquake, which were observed during a field investigation. The survey was conducted in Kathmandu, Trishuli, Melamchi, Baluwa （epicentral area） and Pokhara from 1 to 6 May 2015. A significant damage to the historical architectures in the Durbar Square of Downtown Kathmandu was observed, while the damage to masonry structures in the surrounding area was limited. In mountainous areas including epicentral area, non-engineered masonry structures were severely damaged, and traces of medium to large scale landslides and rock falls were frequently observed. Dam embankment in Trishuli suffered from cracking at the reservoir side along its entire length. Such damages to the structures and slopes are posing risks of secondary disasters to the local residents.
In the present study, the cyclic plasticity constitutive equation is formulated, considering both damage and yield point phenomena. The tangential stress-strain matrix considering elasto-plastic damage is derived as a computational algorithm. More accurate stress-strain curves have been obtained in the analysis of material testing.The computational accuracy in less time-consuming locally-coupled analysis has been increased in the analysis of a machine part.
There is an increasing need to automate handwork by skilled workers in industry. However, that handwork is usually difficult to express clearly in words. Furthermore, human’s motion contains time and spatial perturbations, and this makes the automation even more difficult. In this report, spline functions are applied first to motion-capture data of brush strokes of Japanese calligraphy, and a mathematical model of human’s technique is established. In the mathematical model, the isomorphism mapping method is introduced to deal with the time perturbations, and Min-Max norm is applied to deal with the spatial perturbations.