Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

EFFECTS OF VISCOSITY OF LIQUID FOODS ON PALATAL PRESSURE

The deglutition of non-Newtonian liquids introduced into the mouth was studied dynamically by measuring palatal pressure (P) with pressure transducers set at three locations on the palate. The value of P and the swallowing pressure (S) changed only from 100 to 200 g/cm² over the viscosity range 10⁻² to 10¹ Pa.s. The retaining time (T) and work (W), required for swallowing after the liquid entered the mouth, remained almost constant up to a critical value of 1.0 Pa.s. above which both T and W increased markedly. When the viscosity was low, all of the liquid was swallowed in one deglutition, up to 15 mL volume. Therefore, T was almost constant but S increased with the volume. When the viscosity was high, the liquid was swallowed in several smaller portions. When the volume was high, T increased and S was either constant or it decreased.     

Fe-Cr-Mn奥氏体合金的辐照体胀与诱起晶界偏析行为的研究SCIEI

本文采用电子束辐照,研究了Fe-15Cr-xMn合金以及添加W,V合金的孔洞体胀和诱起晶界偏析行为,并对包含晶界在内的辐照区进行成分分析。结果表明,在Fe-Cr-Mn系合金中孔洞体胀孕育期可以被强烈抑制,晶界偏析也减少。特别是,合金中添加W,V效果更加明显。用Mn代替Ni,通常要发生体胀和相的不稳定性,由于反Kirkendall效应导致Ni和Mn的扩散行为不同,使Fe富集在尾闾处,局部地区形成铁素体,有利于减少体胀和晶界偏析。     

展望21世纪新技术革命中的传感器

在回顾了以往产业革命中传感器的作用 ,比较工程传感器与人的感官的异同点之后 ,阐述了预计将于 2 1世纪爆发的新产业革命中传感器的使命及发展趋势     

双束强辐照对氧化物弥散强化铁素体型合金强化相稳定性影响

采用双束复合辐照装置,研究了He存在条件下,强辐照对长期时效后的ODS合金中强化相(Y2O3)的稳定性和辐照损伤特征的影响。实验结果表明:双束强辐照下,ODS合金中强化相不稳定,发生聚集长大并造成附近基体中Ti、Y浓度增高,导致空洞尺寸和空洞肿胀增加,并对这一结果从理论上进行解释。     

Iron Loss Analysis of Permanent Magnet Motors Fed by PWM Inverter

Carrier harmonic losses that consist of iron loss, eddy current loss, and ac copper loss are produced in a permanent magnet machine driven by a PWM inverter. It is already known that a higher motor inductance can lead to lower carrier harmonic losses. This paper investigates the carrier harmonic loss composition of two motors with identical dimensions but different inductances. The results of finite element analysis (FEA) showed that the eddy current loss in the iron core accounts for most of the carrier harmonic loss. It is also shown that the carrier harmonic loss of the iron core is quantifiable using theoretical calculations.     

Prototype Experiments on a 1/32‐Scale Model Via‐Wheel Power Transfer Electric Vehicle

Electric vehicles (EVs) are expected to play a leading role in the changeover from fossil fuels to clean energy. However, EVs are currently not very popular, owing to their short cruising distance and long charging time. Wireless power transfer from the infrastructure to running EVs is expected to be the solution to these problems. Electric vehicle and electrified roadway (EVER) has been proposed as a wireless power transfer system for EVs while in motion. Via‐wheel power transfer (V‐WPT) is expected to be a wireless power transfer scheme for EVER. We designed and prototyped a 1:32 scale model of a V‐WPT system that consists of an RF inverter, an electrified roadway, a rectifier, and an EV with a dc motor. The output power of the prototype RF inverter was 5.9 W and the dc–RF conversion efficiency was 36.6%. The LC matching circuits for the V‐WPT were designed with two‐port conjugate matching because S₁₁ of the V‐WPT was intrinsically –0.06 dB. After matching, the S₁₁ value was reduced to –21.5 dB. The power transmission efficiency of the V‐WPT system was 75%. The RF–dc conversion efficiency of the rectifier was 62%. The total efficiency of the EVER system was 24.2%.     

污水处理排放水对小流量河流水体生态的影响

针对日本国鬼怒河流域小流量河流,通过对河床上附着生物膜的组成、底栖生物、细菌活性分析和AGP试验,研究了污水厂二级处理排放水对小流量河流生态的影响.研究表明,当污水厂二级处理排放水占河流流量比例较大时(研究河流所占比例为35%),同样会引发河流富营养化和影响河流水体的生态.因此,从保护水环境及其生态考虑,有必要对污水进行深度处理.     

Electrical Resistivity of Titanium-Containing Glasses

Titanium-containing glasses were prepared by fusion of a base glass (BaO·B₂O₃SiO₂) and TiO₂ and/or Ti₂O₃ in Ar. Their resistivities did not vary with melting time and temperature. Interaction of Ti⁴⁺ and Ti³⁺ in the glasses was deduced by spectroscopy, but the valence states in the batch compositions were preserved in the glasses, according to the chemical analysis. Glasses containing either Ti⁴⁺ or Ti³⁺ had very high resistivities, whereas the glass prepared by melting a mixture of a Ti⁴⁺-containing and a Ti³⁺-containing glass had much lower resistivity. All results confirmed the possibility of controlling the resistivity by batch composition for these glasses.     

He对低活性Fe-Cr-Mn(W,V)合金辐照产生点缺陷行为的影响

采用超高压电镜与离子加速器相连结的复合辐照装置，研究了注He对低活性Fe-Cr-Mn(W，V)合金辐照产生的点缺陷及二次缺陷行为的影响．实验结果表明：辐照初期形成的点缺陷与He相互作用，进而影响二次缺陷(位错、位错环和空洞)的形成；He明显促进位错密度增大和空洞核心形成，并导致空洞肿胀增加．对辐照产生的点缺陷与He相互作用的机理进行了理论分析。