Prediction of flange wrinkling in deep drawing process using bifurcation criterion

Surface distortions in the form of wrinkles are often observed in sheet metals during stamping and other forming operations. Because of the trend in recent years towards thinner, higher-strength sheet metals, wrinkling is increasingly becoming a more common and troublesome mode of failure in sheet metal forming. The prediction and prevention of wrinkling during a sheet forming process are important issues for the design of part geometry and processing parameters. This paper treats the phenomenon of flange wrinkling as a bifurcated solution of the equations governing the deep drawing problem when the flat position of the flange becomes unstable. Hill’s bifurcation criterion is used to predict the onset of flange wrinkling in circular and square cup drawing. In particular, the maximum cup height that can be drawn without the onset of flange wrinkling is predicted for the given set of process parameters. A parametric study of the maximum cup height is also carried out with respect to various geometric, material and process parameters. Finite element formulation, based on the updated Lagrangian approach, is employed for the analysis. The incremental logarithmic strain measure, which allows the use of a large incremental deformation, is used. The stresses are updated in a material frame. The material is assumed to be elastic–plastic, strain hardening, yielding according to an anisotropic yield criterion of Barlat et al. (2005) [23] (named as Yld2004-18p). Isotropic power law hardening is assumed. Inertia forces are neglected due to small accelerations. Modified Newton–Raphson iterative technique is used to solve the nonlinear incremental equations.     

一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

Magnetic properties of biogenic selenium nanomaterials

Environmental Science and Pollution Research - Bioreduction of selenium oxyanions to elemental selenium is ubiquitous; elucidating the properties of this biogenic elemental selenium (BioSe) is thus...     

An innovative technique for lake management with reference to aeration unit installed at lower lake, Bhopal, India

Water is key element in human life. All forms of life upon the earth depend upon water for their mere existence. Life & water may be aptly said to be two facets of the same coin. Most of the water bodies are getting polluted due to domestic waste, sewage, industrial waste and agricultural effluent. The present study is designed to ascertain the effectiveness of artificial aeration cum Ozonizer unit installed at Lower Lake, Bhopal for assessment of water quality. Various physico- chemical parameters like pH, Dissolved oxygen, Biochemical Oxygen demand, Chemical oxygen demand, nitrate, phosphate and bacteriological status were studied to assess the extent of deterioration in water quality of Lower lake and at the same time to assess the performance of the dual aeration system in improvement of water quality.     

An Effective Means of Biofiltration of Heavy Metal Contaminated Water Bodies Using Aquatic Weed Eichhornia crassipes

Various aquatic plant species are known to accumulate heavy metals through the process of bioaccumulation. World’s most troublesome aquatic weed water hyacinth (Eichhornia crassipes) has been studied for its tendency to bio-accumulate and bio-magnify the heavy metal contaminants present in water bodies. The chemical investigation of plant parts has shown that it accumulates heavy metals like lead (Pb), chromium (Cr), zinc (Zn), manganese (Mn) and copper (Cu) to a large extent. Of all the heavy metals studied Pb, Zn and Mn tend to show greater affinity towards bioaccumulation. The higher concentration of metal in the aquatic weed signifies the biomagnification that lead to filtration of metallic ions from polluted water. The concept that E. crassipes can be used as a natural aquatic treatment system in the uptake of heavy metals is explored.     

Water quality improvement through macrophytes—a review

Increasing urbanization, industrialization and over population is leading to the degradation of the environment. The main hazardous contents of the water pollution are heavy metals etc. Water bodies are the main targets for disposing the pollutants directly or indirectly. They are again at the receiving end as the storm water, residential and commercial waste is disposed into it. The prevailing purification technologies used to remove the contaminants are too costly and sometimes non-eco friendly also. Therefore, the research is oriented towards low cost and eco friendly technology for water purification, which will be beneficial for community. The present paper is a comprehensive review of approximately 38 literature sources. The paper discusses the potential of different aquatic plants (macrophytes) in purifying water and wastewater. Experimental work was developed to test the hypothesis that nutrient enrichment enhances metal tolerance of relative macrophyte.     

酸沉降作用的降低和安大略省基拉尼湖泊的化学恢复

毗邻加拿大安大略省萨德伯里市的基拉尼公园中的湖泊都表现出明显的水质变化,其中包括pH值和碱度的普遍增加,SO2- 4、碱基阳离子和金属浓度的减少.经过数十年的改善,尽管一些湖泊的pH值已经大于6,但仍有许多湖泊的湖水酸度却一直很高.过去,萨德伯里金属冶炼厂排放引起的过高的硫沉降左右了这一地区的酸化过程.然而,自从冶炼厂的硫排放被严格控制之后(排放量降低了90%),萨德伯里地区的硫排放就不再是该地区最主要的硫沉降源了.目前,基拉尼地区的SO2- 4湿沉降和湖水中SO2- 4浓度已经十分接近约200km外的安大略省多赛特地区,这就表明基拉尼地区的硫沉降现在主要来自于长距离传输,而不是当地污染源.对基拉尼湖泊的研究揭示了化学恢复过程的复杂本质.一旦湖水的酸度降低,就会引起一系列的变化,包括Ca2+浓度的减少,透明度增加和热力学状态改变.这些变化可能会潜在地影响一些生态体系.因此很明显需要对基拉尼湖泊的恢复在多胁迫因子的框架内继续进行评价.