Stress intensity factor solutions for estimation of fatigue lives of laser welds in lap-shear specimens

Fatigue behavior of laser welds in lap-shear specimens of high strength low alloy (HSLA) steel is investigated based on experimental observations and two fatigue life estimation models. Fatigue experiments of laser welded lap-shear specimens are first reviewed. Analytical stress intensity factor solutions for laser welded lap-shear specimens based on the beam bending theory are derived and compared with the analytical solutions for two semi-infinite solids with connection. Finite element analyses of laser welded lap-shear specimens with different weld widths were also conducted to obtain the stress intensity factor solutions. Approximate closed-form stress intensity factor solutions based on the results of the finite element analyses in combination with the analytical solutions based on the beam bending theory and Westergaard stress function for a full range of the normalized weld widths are developed for future engineering applications. Next, finite element analyses for laser welded lap-shear specimens with three weld widths were conducted to obtain the local stress intensity factor solutions for kinked cracks as functions of the kink length. The computational results indicate that the kinked cracks are under dominant mode I loading conditions and the normalized local stress intensity factor solutions can be used in combination with the global stress intensity factor solutions to estimate fatigue lives of laser welds with the weld width as small as the sheet thickness. The global stress intensity factor solutions and the local stress intensity factor solutions for vanishing and finite kinked cracks are then adopted in a fatigue crack growth model to estimate the fatigue lives of the laser welds. Also, a structural stress model based on the beam bending theory is adopted to estimate the fatigue lives of the welds. The fatigue life estimations based on the kinked fatigue crack growth model agree well with the experimental results whereas the fatigue life estimations based on the structural stress model agree with the experimental results under larger load ranges but are higher than the experimental results under smaller load ranges.     

A novel nanofluid manufacturing process using a cylindrical flow cooling method in an induction heating system

The main purpose of this study is to develop a cylindrical flow cooling method in an induction heating system that is capable of producing the nanofluid. The system consists of a high frequency induction heating system, vacuum system, temperature control system, and a cylindrical curtain collector. The raw material Zn is evaporated by the high frequency induction heating system. The gas phase Zn is condensed and collected by a water cylindrical curtain collector. During the process, the gas phase Zn is oxidized. The ZnO nanoparticles were collected and suspended in de-ionized water. Through transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and particle size analyzer (PSA), a set of applicable parameters size can be obtained. Results show that the lower the collecting liquid temperature and the shorter the collecting distance, the smaller the nanoparticle size obtained. An aspect of UV/V is absorbency, the produced ZnO nanofluid absorbed UV when the wavelength is 360 nm to 380 nm.     

Fabrication of diamond nanopowder using microwave plasma torch technique

This article presents a manufacturing process for diamond nanopowder by using a microwave plasma torch technique in a laboratory at near atmospheric pressure. The unique technique utilized in the arrangement is the hybrid plasma torch which was patented in 1997 by Dr. Cheng-Ming Wu in Taiwan. It has the advantage of working at near atmospheric pressure and does not require an extreme vacuum system, which is a necessary condition for fabrication of a large amount of nanoparticles. The applied constituents of gas mixtures for synthesizing diamond nanopowder in the process are CH₄ with AR and CH₄ with N₂, where AR and N₂ serve as catalysts. In processing the reaction chamber, it is first pumped to varied pressures from 40–300 Torr to induce plasma; then, the input reactive gas CH₄ is fixed at a constant flow rate of 0.6 l/min and mixed up with varied input flow rate of the catalysts Ar and N₂ from 0.6–1.2 l/min. The particle size of synthesized diamond nanopowder is within about 25--50 nm diameter, which mainly depends on flow rate of CH₄:AR and CH₄:N₂.     

A study on the effects of temperature and volume fraction on thermal conductivity of copper oxide nanofluid

By using copper oxide nanofluid fabricated by the self-made Submerged Arc Nanofluid Synthesis System (SANSS), this paper measures the thermal conductivity under different volume fractions and different temperatures by thermal properties analyzer, and analyzes the correlation among the thermal conductivity, volume fraction, and temperature of nanofluid. The CuO nanoparticles used in the experiment are needle-like, with a mean particle size of about 30 nm. They can be stably suspended in deionized water for a long time. The experimental results show that under the condition that the temperature is 40 degrees C, when the volume fraction of nanofluid increases from 0.2% to 0.8%, the thermal conductivity increment of the prepared nanofluid towards deionized water can be increased from 14.7% to 38.2%. Under the condition that the volume fraction is 0.8%, as the temperature of nanofluid rises from 5 degrees C to 40 degrees C, the thermal conductivity increment of the prepared nanofluid towards deionized water increases from 5.9% to 38.2%. Besides, the effects of temperature change are greater than the effects of volume fraction on the thermal conductivity of nanofluid. Therefore, when the self-made copper oxide nanofluid is applied to the heat exchange device under medium and high temperature, an optimal radiation effect can be acquired.     

Adaptive Fuzzy Strong Tracking Extended Kalman Filtering for GPS Navigation

The well-known extended Kalman filter (EKF) has been widely applied to the Global Positioning System (GPS) navigation processing. The adaptive algorithm has been one of the approaches to prevent the divergence problem of the EKF when precise knowledge on the system models are not available. One of the adaptive methods is called the strong tracking Kalman filter (STKF), which is essentially a nonlinear smoother algorithm that employs suboptimal multiple fading factors, in which the softening factors are involved. Traditional approach for selecting the softening factors heavily relies on personal experience or computer simulation. In order to resolve this shortcoming, a novel scheme called the adaptive fuzzy strong tracking Kalman filter (AFSTKF) is carried out. In the AFSTKF, the fuzzy logic reasoning system based on the Takagi-Sugeno (T-S) model is incorporated into the STKF. By monitoring the degree of divergence (DOD) parameters based on the innovation information, the fuzzy logic adaptive system (FLAS) is designed for dynamically adjusting the softening factor according to the change in vehicle dynamics. GPS navigation processing using the AFSTKF will be simulated to validate the effectiveness of the proposed strategy. The performance of the proposed scheme will be assessed and compared with those of conventional EKF and STKF     

电泳沉积法制备多层膜染料敏化太阳能电池

将纳米TiO2颗粒以电泳沉积法披覆于导电玻璃上,同时整合光电极、反电极、电解质及染料制备出染料敏化太阳能电池.首先将TiO2纳米颗粒与异丙醇所混合的电泳悬浮液通过电泳技术沉积出适当厚度的多层膜结构;精确控制制程中的电流、电压与沉积时间而获得单层厚度为3.3μm的TiO2薄膜.此多层膜通过低温烧结增加其致密性及染料披覆效果.最后将此多层薄膜作为工作电极,封装成染料敏化太阳能电池,经由I-V曲线检测结果显示,所制染料敏化太阳能电池的光电转换效率为5.29%,且这种染料敏化太阳能电池的制造成本十分低廉.     

Plane-stress crack-tip fields for power-law hardening orthotropic materials

Plane stress mode I near-tip fields in orthotropic materials are examined. Plastic orthotropy is described by Hill's quadratic yield function and the strain hardening behavior is given by an appropriate generalization of a uniaxial tensile power-law stress-strain relation. Pronounced changes in the pattern of the angular variations of crack-tip fields have been observed with the degree of plastic orthotropy and the amount of strain hardening. Possible shapes and sizes of plastic zones (as inferred from effective stress contours) are presented for high- and low-hardening materials and a wide range of plastic orthotropy. The shape of the plastic zone for a particular case of plastic orthotropy agreed remarkably well with the zone of intense straining induced by an appropriately orientated crack within a graphite/epoxy laminate.

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Résumé On examine les champs de contraintes planes selon un mode I au voisinage de l'extrémité d'une fissure dans des matériaux orthotropes. L'orthotrope plastique est décrite par la fonction quadratique de plastification de Hill, et le comportement à l'écrouissage est donné par une généralisation adéquate d'une relation tensioncilatation de forme parabolique, sous traction mono-axiale. On a observé des modifications profondes dans l'aspect des variations angulaires des champs d'extrémité de fissure, selon le degré d'orthotropie plastique et infensité de l'écrouissage. Pour des matériaux très sujets ou peu sujets à l'écrouissage, et pour une large gamme d'orthotropies plastiques, on présente les formes et dimensions possibles des zones plastiques, telles qu'elles se deduisent des contours effectifs de contraintes. La forme de la zone plastique correspondant au cas particulier d'une orthotropie plastique s'accorde remarquablement bien à la zone de dilatation importante créée par une fissure d'orientation appropriée, dans une plaque de graphite-epoxy.

     

Agent-Based Control Framework for Mass Customization Manufacturing With UHF RFID Technology

Radio frequency identification (RFID) technology adoption in business environments has seen strong growth in recent years. Adopting an appropriate RFID-based information system has become increasingly important for enterprises making complex and highly customized products. However, most firms still use conventional barcode and run-card systems to manage their manufacturing processes. These systems often require human intervention during the production process. As a result, traditional systems are not able to fulfill the growing demand for managing dynamic process flows and are not able to obtain real-time work-in-process (WIP) views in mass customization manufacturing. This paper proposes an agent-based distributed production control framework with UHF RFID technology to help firms adapt to such a dynamic and agile manufacturing environment. This paper reports the design and development of the framework and the application of UHF RFID technology in manufacturing and logistic control applications. The framework's RFID event processing agent model is implemented in a smart end-point (SEP) device. A SEP can manage RFID readers, wirelessly communicate with shop-floor machines, make local decisions, and coordinate with other SEPs. A case study of a bicycle manufacturing company demonstrates how the proposed framework could improve a firm's mass customization operations. Results of experiments show the decentralized multiagent coordination scheme among SEPs outperformed the current practice of the firm in terms of reducing work-in-process and parts inventory.