It is very important to know the residual stress states in a single crystal since the residual stresses affects the mechanical properties or functionality of some devices such as semiconductors or micromachines. X-ray diffraction technique is non destructive and detached method to know the residual stresses of crystalline materials in various atmospheres. Using a position sensitive proportional counter (PSPC) as an X-ray detector, it is very easy to obtain the reasonable diffraction profile of single crystal. In the case of using PSPC, crystal oscillation is required to obtain a perfect diffraction profile. In this paper, we explained the stress measurement technique for single crystal by using PSPC and the principle for stress measurement of single crystal with unknown stress-free lattice parameter.

View full abstract

The phase stress of the WC and Co phases in a WC-Co cemented carbide was determined by x-ray diffraction. The diffraction lines of WC (121) and Co (311) planes were measurcd with CoKα radiation. The surface of a specimen was sandblasted and polished with abrasive papers. The peak position of the diffraction line of the WC (121) plane which locates at a high diffraction angle of 164.17 deg was precisely determined by the Gaussian curve method. Various stresses were applied to the specimen to determine the stress constant K of the two phases. To determine the stress of the Co phase induced by an applied load, the stress constant was calculated theoretically from the elastic constants of a single crystal by using Kroner's model. The stress in the WC phase was determined from the stress in the Co phase using the equation of the equilibrium for microstresses. An extremely high compressive residual stress of 2 GPa was measured in the WC phase.

View full abstract

In present study, firstly, several basic deformation behaviors of Polycarbonate (PC) were experimentally investigated. Nextly, experiments and analysises based on the over stress theory were conducted on deformation behavior at unloading process. Results obtained from the experiments and the analysises were as follows; (1) Deformation behaviors of the material were very complicated under unloading. Also, it was found from the infrared radiation thermometry method that there was no effect of generation of heat on deformation behavior. (2) Analytical results based on the over stress theory showed agreement with experimental results for deformation behavior under tensile loading. On the other hand, analytical results showed good agreement with experimental results in the case of unloading after tensile loading and full relaxation. But, analytical results did not show agreement with experimental results in the case of unloading after tensile loading.

View full abstract

Liquid plugs are generated in a partially filled horizontal circular pipe during the period from normal gravity to microgravity. If the liquid plugs are solidified, the structure of the pipe will be like a bamboo having low weight and high strength. The structure however is uniquly determined provided that the size of the pipe and the physical properties and the volume of the liquid are given. In this study the possibility of changing the structure was investigated by varying the wettability of the inner wall of the pipe. The wettability of the inner wall was locally varied by coating repellent on the wall. It was possible to make liquid plugs of different structures by this method.

View full abstract

Square specimens of laminated glass having different glass layer and polymer layer thicknesses were prepared and tested under impact loading. Impact absorbed energy was measured using an instrumented drop weight testing system. The measured energy was then divided into two parts, namely, energy I and energy II. The energy I is related to the initial fracture of glass layers, and the energy II is associated with the subsequent crack propagation in glass layers, plastic deformation and shear fracture of polymer layer. The energy III is defined as the total absorbed energy, i. e., the sum of the energy I and II. Effects of glass layer and film thickness on these energies were examined. The energy absorbed by each of the three mechanisms, glass fracture, plastic deformation and shear fracture of polymer film, was estimated independently by conducting a unique impact testing method designed for each mechanism. For each configuration of laminated glass, an analytical value of impact absorbed energy was derived from these energy values, and compared with the three energies I, II and III. Good correspondence was then obtained, and thus, impact fracture behavior of laminated glass was qualitatively characterized.

View full abstract

A small single bubble was generated with a single-hole nozzle facing upward in a water bath contained in a rotating cylindrical vessel. The bubble size falls in the surface tension force dominant regime. The vertical, radial, and tangential migration velocities of the bubble were measured with two CCD cameras and a high-speed video camera. The tangential velocity component of water flow was measured with particle image velocimetry (PIV). A helical motion of the bubble was observed under every experimental condition. The direction of the helical motion was the same as that of the tangential velocity component. This helical motion is associated with large initial shape deformation of the bubble near the nozzle exit and subsequent regular shedding of vortices behind it. The period and amplitude of the helical motion were obtained by analyzing the trajectory of the bubble. These quantities were nondimensionalized by the volume equivalent bubble diameter and the terminal bubble velocity in the vertical direction and correlated as functions of the Eotvos number. Empirical equations were proposed for the period and amplitude.

View full abstract

The impact strength was evaluated for a butt adhesive shaft joint of Al alloy and PMMA materials. The materials were bonded together by cold-setting epoxy, commercial base adhesive. An impact tension test was carried out using a drop-weight testing machine. The fracture initiation time in the adhesive interface was determined from the measured strain gage signal. In order to establish the method of strength evaluation, the impact tensilestrengths of the adhesive joints were evaluated by the stress singularity field parameter and the average fracture stress. Fracture toughness in the dynamic stress field was determined from the stress distribution in the vicinity of the edge of the adhesive interface calculated by the finite element method at the fracture initiation time. The static fracture toughness was also determined by a similar method using the same type of specimen used in the dynamic test. It was found that the dynamic strengths exhibited considerably larger values than the static strengths. Furthermore, the dynamic strengths were evaluated for the butt adhesive shaft joints of Al and Al alloys, and also PMMA and PMMA materials. In order to confirm the reliability of the measurement, the location of fracture and the stress distribution in the vicinity of the adhesive interface were investigated in detail.

View full abstract