In the paper three kinds of framework of strain gradient plasticity recently developed and their applications are reviewed: strain gradient plasticity for CS solid-the couple stress-theory, strain gradient plasticity for SG solid, and mechanism-based strain gradient (MSG) plasticity. The applications are mainly focussed on the fracture problems. One way of accounting for material compressibility is suggested. The review is confined to the deformation theory version, though the flow theory version can be parallelly constructed.
In xNa2O·(40-x)B2O3·60SiO2 (mol%) (x=5, 10, 15, 20, 25, 30) glasses with 0.25mol% Eu2O3 as additive, the local structure around Eu3+ was explored by employing the phonon sideband spectra of Eu3+ associated with the 5D2 ←7F0 transition. It was found that the types and fraction of the structural units around Eu3+ varied with glass composition. Moreover, the B-O vibrational mode of BO3 unit exists around Eu3+ when x≤15, which is not present in the same composition glasses free of Eu3+. A greatest asymmetry in the surrounding of Eu3+ occurs at x=10, inconsistent with a maximum of some physical properties found in sodium borosilicate glasses at a Na: B ratio of about unity. In addition, various structural units possess different coordination preference to Eu3+. The highest theoretical microscopic optical basicity on the oxygen atoms in these units was advocated as a criterion of the coordination preference, which successfully elucidated a series of coordination preference phenomena occurring in silicate, borate and borosilicate glasses.
Two sodium borosilicate glasses containing Er3+ were isothermally heat treated for phase separation, followed by the formation of the droplet and interconnected textures, respectively. The effects of heat treatment condition and the phase separated texture on photoluminescence (PL) intensity of 4S3/2→4I15/2 transition of Er3+ were studied. It was found that the PL intensity increased with phase separation developing in both glasses. Moreover, the maximum PL intensities obtained by the phase separation in both glasses are 8.5 and 4.1 times as high as those in the respective untreated samples, the droplet texture being superior to the interconnected one. The mechanism of augmentation of the PL intensity was discussed in terms of the derived expression of the PL intensity. It was supposed that the induced interface after phase separation, causing notable increase in the radiative decay rate from the 4S3/2 to 4I15/2 levels, was responsible for the significant enhancement in the PL intensity.
In a global expansion of environmental pollutions, trihalomethanes in water and aromatic toxic substances in air are both increasing. In this study, therefore, an effort has been made to develop carbonized woody materials to remove specifically these polluting materials and explore a potential of developing more functionalized new woody carbonized materials. It was found by elemental analysis that carbonized woody material prepared under hydrogen gas flow was more reduced, compared with that under nitrogen gas flow, particularly over 550°C. Both carbonized woody materials were decreased in vapor adsorption of water with increasing the temperature, whereas adsorption of chloroform and benzene was instead improved and over 550°C, carbonized woody materials under hydrogen gas flow was superior to that under nitrogen gas flow in their adsorption. Carbonized woody materials with these characteristics were found to adsorb chloroform in water and benzene in atmosphere effectively. These lines of evidence would support a concept that hydrogenative reduction of woody materials would be effective to enhance its adsorptivity against chloroform in water and benzene in atmosphere.
Aluminum sludge is production waste from aluminum industry. The purpose of this paper is to investigate the effective utilization of this industrial waste as road base stabilization material. As ferrum lime stabilized soil has been used as road base material for a long time, mixing aluminum sludge with ferrum lime to form a new stabilizer may be beneficial to improve pavement performance as well as utilization of the waste. In order to assess engineering properties of the new stabilizer for its application to road construction, a series of laboratory tests such as unconfined compressive and bending tests had been carried out. Based on test results, both compressive strength and flexural strength of the stabilized soil can be promoted by addition of aluminum sludge, and in particular, the fracture surface energy γs, a parameter which indicates the resistance of a material to cracking, can be improved significantly compared with ferrum-lime or hydrated lime stabilized soils. It can be inferred that the durability of pavement is improved when stabilized with ferrum lime-aluminum.
In semiconductor devices, the stresses in the silicon substrate sometimes produces dislocations during high-temperature fabricating processes. Although most of the dislocations are generated at stress singularity fields, dislocation generation has been discussed without paying attention to stress-singularity matters. This paper shows that dislocation generation can be predicted considering stress singularity problem. In the experiments discussed, silicon substrates with stressed thin film bands, at whose edges the stress singularity fields were formed, were used as specimens. The strength of the singularities was controlled by changing the bandwidth. Data concerning whether or not dislocations appeared was compared with the values of the singularity parameter. This comparison was performed for two structures of thin films and at three temperatures, and the results show that the singularity parameter can be used to predict the generation of dislocations.
This paper describes the microstructural study of a chemical vapor deposited diamond-like carbon (DLC) thin film, ranging the thickness from 1μm to 1.36μm. The effect of deposition condition on the microstructure of the DLC film was analyzed by Raman spectroscopy. Increasing the bias voltage and the discharge current shifted the peak shift of G band toward high frequency and enlarged I(D)/I(G) ratio. Lower density films were obtained by lowering bias voltage at discharge current of 5A, but conversely higher density films by lowering bias voltage at 10A and 20A. The hardness and Young's modulus were directly proportional to density of the film. Molecular dynamics analyses gave a linear relationship between the bonding ratio, density and Young's modulus of the film. These analytical results qualitatively agreed with the experimental results. The thermal conductivity of the DLC films was discussed based on the molecular dynamics results.
Superelasticity is very applicable property of shape memory alloys, and for its wide implementation engineering practice it is important to have an efficient method which would enable designers to consider the material properties with sufficient precision in their calculations. From the application point of view a new model is proposed in the paper. The general characteristic of the model is that modelling is based on the experimentally obtained stress-strain diagrams what is important for direct implementation of the material properties in design. With the model various tension and pure bending loading conditions were simulated numerically and the results are compared with the corresponding results obtained experimentally.
A study was conducted on the effects of cooling conditions on flexural properties of aramid fiber knitted fabric (AFKF) and glass fiber knitted fabric (GFKF) reinforced thermoplastic polypropylene composites. To study these effects, composite laminates were fabricated under a molding pressure of 3MPa for 20min, then consolidated from the melt at different cooling conditions: rapid cooling i.e., quasi-quenching and gradual cooling. Flexural tests were carried out on specimens in two directions: wale and course. Evaluation on thermal properties and morphology was studied using a differential scanning calorimetry (DSC). Flexural properties were little sensitive to the cooling rates; however, gradually cooled specimens showed higher level of crystallinity than rapidly cooled specimens. Furthermore, flexural strengths displayed higher in the wale than in the course directions. SEM micrographs of fracture surfaces revealed poor adhesion between the fiber and polypropylene matrix.
Aramid fiber reinforced plastics (ArFRP) is being applied in severe service conditions, such as aeronautical or space environments. Therefore, it is necessary to elucidate their strength in various environments. In the present study, static tensile and fatigue tests of dry and wet specimens of ArFRP were carried out at room temperature and at cryogenic temperature, 77K. Two types of aramid fibers, du Pont's Kevlar49® and Teijin's Technora® were used for the reinforcement. The fractured specimens were inspected under a Scanning Electron Microscope (SEM) after the tests and the fracture mechanisms were analyzed. The tensile strength of individual aramid fibers was also measured at the same temperatures. The effects of cryogenic temperature and water absorption on the strength of ArFRP and aramid fibers were made clear.
In this work, an estimation of residual stress by using the IF method was presented for assumed nonuniform distributions of residual stress. By applying the present procedure to the case of ground silicon nitride, it was revealed that compressive residual stresses estimated for non-uniform stress distributions were almost twice as large as those for the uniform stress distribution. A larger residual stress was estimated in the material ground using a rougher wheel. Comparing results by X-ray stress measurements, it was suggested that the residual stress was reasonably estimated by the present procedure.