Modelling and Simulation of Rate-Dependent Stress-Strain Behaviour of Granular Materials in Shear

A constitutive modelling of the elasto-viscoplastic stress-strain behaviour of geomaterials in shear that has been developed within a non-linear three-component model framework is validated by simulating a comprehensive series of drained triaxial compression (TC) and direct shear (DS) tests on a wide variety of granular materials. Illustrative simulations of rate-dependent stress-strain behaviour of geomaterial under typical laboratory test conditions were performed to analyse the structure of the model. The versatility of the proposed model and its applicability to a wide variety of shear loading histories is examined and demonstrated by these simulations. The following results are shown. Commonly with different basic viscosity types, Isotach, TESRA and P&N, the viscous stress component has a positive component that increases with an increase in the irreversible strain rate, which makes feasible stable and realistic simulations of rate-dependent stress-strain behaviour, including creep deformation, based on the proposed model. With different unbound granular material types having similar relative densities, the creep strain in TC tests and creep shear displacement in DS tests that develop by sustained loading at a given shear stress level for a given period tends to decrease with an increase in the particle roundness. This trend of behaviours is explained by a decrease in the viscosity type parameter, θ, associated with an increase in the particle roundness based on the simulations of these tests.     

Hydrothermal synthesis of giant single crystals of MFI type zeolite: Modified bulk material dissolution method

In the present study, we aimed at the development of an easy and reproducible synthesis method of giant MFI zeolite crystals. We used a new synthesis method, modified bulk material dissolution (M-BMD) method, in which a piece of quartz glass tube was inserted as a silica source in a small PTFE sleeve together with ZSM-5 powder as seed crystals. We adopted a higher HF concentration (25 mmol/25 ml) of the synthesis solution than that usually used. By using this method, only a few crystal nuclei were formed separately from each other on the surface of the quartz glass tube in the PTFE sleeve and giant zeolite crystals were reproducibly synthesized on it. Giant single crystals of MFI as large as 5.0 mm were successfully synthesized at 453 K for 90 days by using the M-BMD method.     

模具润滑温压成形法制作的高密度铁基烧结体的磁性与组织

烧结铁是一种好的软磁材料,但其磁通密度比铸造材料的低。低的磁通密度是由于密度低所引起的。本研究开发了一种温压与硬脂酸锂模壁润滑技术(WC-DWL)。使用该技术,得到了密度非常高的成形体。纯铁粉在1176MPa的压力下成形,经1523K烧结后的性能如下:密度=7.76Mg/m3,μm=5300,B160=1.16T,B240=1.28T,B400=1.40T,B2k=1.60T,bHc=110A/m。一些烧结铁表现出各向异性的变化与组织,这导致异常晶粒长大到长度为数毫米。这种异常长大在试样成形密度较高时更为明显。     

Scattering of elastic waves by a diamond shaped inclusion with cracks

This paper studies the scattering of in-plane compressional and shear waves by a diamond shaped inclusion with cracks using the boundary element method. The special case that the shape of the diamond becomes square is also considered. Numerical calculations are carried out for the limited cases of diamond shaped hole and rigid inclusions, and the effects of frequency and inclusion shape on the scattering cross section and dynamic stress intensity factor are shown in graphical form. The results where the elastic properties of the inclusion are the same as those of the matrix are also discussed.     

A patient transfer apparatus between bed and stretcher.

This paper presents a patient transfer apparatus between bed and stretcher. This apparatus makes it possible for the nurse to move weak, injured, or paralyzed patient from bed to stretcher, or vice versa, alone. Moreover, the suffering, stress, and uneasy feeling of the patient can be alleviated. This paper describes the specification, mechanical design, control system, and motion control of the apparatus. A special devised mechanism is developed, and a new servo system is used in this control system. The control principle and algorithm of the new servo system are proposed, and the motion-control method and safety function of the apparatus are described. The experimental results and evaluation indicated the effectiveness of this system.     

Improvement of Processability of PCL and PBS Blend by Irradiation and its Biodegradability

Poly(ε‐caprolactone) (PCL) was blended with poly(butylene succinate) (PBS), (PCL/PBS = 30/70) to improve the heat stability of PCL. The processability of the blended samples (PHB02) was improved due to enhancing of melt strength by γ‐rays irradiation in the dose range between 10 and 50 kGy. High speed production of a thin film and production of foam have been achieved by this process. The soil degradation test showed that PHB02 film buried in the soil was almost degraded (97%) after two months and completely degraded after two and a half months. On the contrary, the sample on the surface degraded to only 3.5% after four months. From these findings it was confirmed that microorganisms contribute to degradation in the soil. In the case of PHB02 foam samples, 65% degradation was achieved after four months. The PHB02 sample used as garbage bags was well degraded (almost 50%) after a two months burial test. The enzymatic degradation test showed that after treatment for 24 h, the weight loss of PHB02 irradiated with 30 kGy and unirradiated samples were 80% and 90%, respectively. Enzymatic degradation for PHB02 films led to the suggestion that the biodegradation process proceeds from the surface to the inside of the sample by erosion.     

Surface modification processing of synthetic rubbers by ultraviolet irradiation and sputter ion etching treatment

The mechanism by which surface modification of two kinds of synthetic rubbers (ethylene-propylene and chloroprene) was brought about by ultraviolet (UV) irradiation and sputter ion etching treatments was studied from a physicochemical point of view. The most remarkable effect of this irradiation treatment was the rapid increase in adhesion properties and the simultaneous decrease in self-stickiness. This nonsticking effect was particularly important for the rapid production of articles from thin rubber sheets. The surface modification mechanism was studied by use of SEM, ESCA, FTIR, and related interfacial analytical procedures. It was shown that surface roughening with a quite thin layer of surface oxidation (∼0.5 μm in depth) is a key factor for the development of nonsticking properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1625–1633, 1997     

Fatigue Behavior of PZT-Based Nanocomposites with Fine Platinum Particles

Nanocomposites of lead zirconate titanate (Pb(Zr _x ,Ti_{1− x} )O₃, PZT) with secondary-phase dispersoids of metallic platinum were fabricated. Fatigue (crack-growth) behavior of the unpoled PZT/platinum nanocomposite that contained precracks produced by a Vickers diamond indenter under electrical cyclic loading was investigated. The crack growth was monitored via optical microscopy and was dependent on the number of cycles to which the sample was subjected. The growth of the indentation crack was significantly reduced in the PZT/platinum nanocomposite.     

Evaluation of polybutene electrofusion joint performance

This paper describes methods of evaluating polybutene electrofusion joints and results of mechanical strength measurements for an electrofusion joint. Suitable fusion conditions were determined qualitatively through measurement of fusion interface temperatures and observation of the fusion zone. A method of determining standard fusion conditions, based on the relation between heating time and tensile strength, is also indicated. Differences in thermal properties between polybutene and polyethylene resins are discussed. It was found that polybutene required less supplied power per unit fusion area for suitable fusion. It was also confirmed that an electrofusion joint required a cold zone.