Two-dimensional and axisymmetric unit cell models in the analysis of composite materials

Unit cell models have been widely used for investigating fracture mechanisms and mechanical properties of composite materials assuming periodically arrangement of inclusions in matrix. It is desirable to clarify the geometrical parameters controlling the mechanical properties of composites because they usually contain randomly distributed particulate. To begin with a tractable problem this paper focuses on the effective Young’s modulus E of heterogeneous materials. Then, the effect of shape and arrangement of inclusions on E is considered by the application of FEM through examining three types of unit cell models assuming 2D and 3D arrays of inclusions. It is found that the projected area fraction and volume fraction of inclusions are two major parameters controlling effective elastic modulus of inclusions.     

Study of crack propagation behavior during low cycle fatigue in spheroidal graphite cast iron based on observation of surface and fracture sections

In this paper, in order to clarify the effect of crack coalescence for crack growth rate, low cycle fatigue tests were carried out using two kinds of spheroidal graphite cast iron (SGI). Crack propagation behavior from crack initiation to fracture was investigated by observing the surface of specimens and their fracture section. The main results obtained are as follows: (1) The variation range in the crack growth curves in SGI is larger than that in its matrix material. This tendency is caused by the occurrence of crack coalescence and the difference in crack initiation length. (2) In most of the cases where the crack growth rate accelerated, there was microshrinkage on the neighboring surface. (3) Crack coalescence is not the main factor in accelerating crack growth rate.     

Measurement of droplet size distribution in core region of high-speed spray by micro-probe L2F

In order to investigate the distribution of droplet sizes in the core region of diesel fuel spray, instantaneous measurement of droplet sizes was conducted by an advanced laser 2-focus velocimeter （L2F）. The micro-scale probe of the L2F is made up of two foci and the distance between them is 36 lain. The tested nozzle had a 0.2 mm diameter single-hole. The measurements of injection pressure, needle lift, and crank angle were synchronized with the measurement by the L2F at the position 10 mm downstream from the nozzle exit. It is clearly shown that the droplet near the spray axis is larger than that in the off-axis region under the needle full lift condition and that the spatial distribution of droplet sizes varies temporally. It is found that the probability density distribution of droplet sizes in the spray core region can be fitted m the Nukiyama-Tanasawa distribution in most injection periods.     

Significance of the small crack growth law and its practical application

The effects of microstructure and specimen size on the fatigue crack growth rate of an annealed 0.42 C steel were investigated under uniaxial fatigue loading in air. Although a dramatic fluctuation of crack growth rate was found in the propagation process of microstructurally small cracks, the mean value of crack growth rate can be evaluated by a simple mechanical parameter, σ _a ⁿ l (l, crack length; n, constant), under high stress levels where small-scale yielding conditions are exceeded. This parameter is also effective for cracks larger than 1 to 2 mm under high stress levels, as long as the finite boundary effect of a specimen on the driving force of crack propagation is considered. The crack growth rate of the alloy was described as a function of stress amplitude and crack length in terms of two mechanical parameters, σ _a ⁿ l and ΔK. The applicable conditions of the two parameters were discussed and manifested.     

Flexible electrophoretic display driven by solution‐processed organic thin‐film transistors

Abstract— An organic thin‐film‐transistor (OTFT) backplane has been fabricated by using a solution‐processed organic semiconductor (OSC) and organic insulators. The OSC, a peri‐xanthenoxanthene derivative, provides a mobility of 0.5 cm²/V‐sec. These organic materials enhance the mechanical flexibility of the backplane. The developed backplane successfully drives a 13.3‐in. flexible UXGA electrophoretic display that can operate when bent at a radius of 5 mm.     

具有皮肤屏障功能的MPC聚合物

Lipidure的第一个效能是使人的细胞和组织柔软。根据保护人体皮肤的效能介绍了MPC聚合物,该聚合物是Lipidure的主要成分。介绍了用Lipidure改性的纺织品。MPC聚合物不仅具有降低毒性作用和抗刺激效能,而且用Lipidure改性的纺织品提高了皮肤的屏障性能。     

Effect of silane coupling on the joint characteristics of friction lap joined Al alloy/CFRP

Dissimilar materials joining of an A5052 plate and a carbon fibre reinforced thermoplastic (CFRTP), which consisted of polyamide 6 (PA6) with 20 wt% carbon fibre addition, was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the CFRTP plate as a bottom. The joint characteristics were evaluated to investigate effects of the surface treatment by the silane coupling treatment for A5052 and the joining speed on the joining properties. The joint strength was increased by inducing the silane coupling treatment for the A5052 plate surface. The tensile shear fracture load of the silane coupling treated FLJ joint increased by increasing the joining speed up to 6.67 mm/s and then decreased. The maximum tensile shear fracture load of 5.0 kN was obtained at the joining speed of 6.67 mm/s, and the fracture occurred at the CFRTP base plate with the joint efficiency of 97%. The shear strength of the joint interface of the joint formed at the joining speed of 1.67 mm/s, which fractured at the joining interface by the tensile shear test, was estimated to be about 19 MPa. The covalent bondings between the A5052 plate and the silane coupling layer, and the silane coupling layer and the CFRTP plate were indicated by inducing the silane coupling treatment.     

Fabrication and Analysis of Three-Layer All-Silicon Interference Optical Filter with Sub-Wavelength Structure toward High Performance Terahertz Optics

We propose an all-silicon multi-layer interference filter composed solely of silicon with sub-wavelength structure (SWS) in order to realize high performance optical filters operating in the THz frequency region with robustness against cryogenic thermal cycling and mechanical damage. We demonstrate fabrication of a three-layer prototype using well-established common micro-electro-mechanical systems (MEMS) technologies as a first step toward developing practical filters. The measured transmittance of the three-layer filter agrees well with the theoretical transmittances calculated by a simple thin-film calculation with effective refractive indices as well as a rigorous coupled-wave analysis simulation. We experimentally show that SWS layers can work as homogeneous thin-film interference layers with effective refractive indices even if there are multiple SWS layers in a filter.