Dimpling process in cold roll metal forming by finite element modelling and experimental validation

The dimpling process is a novel cold-roll forming process that involves dimpling of a rolled flat strip prior to the roll forming operation. This is a process undertaken to enhance the material properties and subsequent products’ structural performance while maintaining a minimum strip thickness. In order to understand the complex and interrelated nonlinear changes in contact, geometry and material properties that occur in the process, it is necessary to accurately simulate the process and validate through physical tests. In this paper, 3D non-linear finite element analysis was employed to simulate the dimpling process and mechanical testing of the subsequent dimpled sheets, in which the dimple geometry and material properties data were directly transferred from the dimpling process. Physical measurements, tensile and bending tests on dimpled sheet steel were conducted to evaluate the simulation results. Simulation of the dimpling process identified the amount of non-uniform plastic strain introduced and the manner in which this was distributed through the sheet. The plastic strain resulted in strain hardening which could correlate to the increase in the strength of the dimpled steel when compared to plain steel originating from the same coil material. A parametric study revealed that the amount of plastic strain depends upon on the process parameters such as friction and overlapping gap between the two forming rolls. The results derived from simulations of the tensile and bending tests were in good agreement with the experimental ones. The validation indicates that the finite element analysis was able to successfully simulate the dimpling process and mechanical properties of the subsequent dimpled steel products.     

油罐区泄漏及火灾危险危害评价

对某大型油罐区进行泄漏及火灾的危险危害评价.采用毒性物质泄漏扩散模型模拟油罐的泄漏事故,得出了泄漏介质在罐区附近的等质量浓度分布曲线;采用池火火焰与辐射强度模型,计算油罐、输油管道、汽车装油栈台等发生池火灾时的热辐射强度,并结合不同辐射强度值对人和设备的影响程度,给出了池火灾的影响范围.     

大型游艺机——过山车的安全性分析

研究基于虚拟样机技术的过山车的安全性问题,旨在解决传统设计的弊端,有效降低设计成本,提高过山车的安全性能。在ADAMS软件中建立过山车的虚拟样机模型。研究轨道圆环直径、车厢重量、制动力对过山车安全性能的影响,获得以上各参数的合理范围,使车厢连接副受力状况与加速度得到改善,制动力精确性得到提高。为探索运动类特种设备———过山车的安全保障技术提供了新途径。     

Biomass use in chemical and mechanical pulping with biomass-based energy supply

The pulp and paper industry is energy intensive and consumes large amounts of wood. Biomass is a limited resource and its efficient use is therefore important. In this study, the total amount of biomass used for pulp and for energy is estimated for the production of several woodfree (containing only chemical pulp) and mechanical (containing mechanical pulp) printing paper products, under Swedish conditions. Chemical pulp mills today are largely self-sufficient in energy while mechanical pulp mills depend on large amounts of external electricity. Technically, all energy used in pulp- and papermaking can be biomass based. Here, we assume that all energy used, including external electricity and motor fuels, is based on forest biomass. The whole cradle-to-gate chain is included in the analyses. The results indicate that the total amount of biomass required per tonne paper is slightly lower for woodfree than for mechanical paper. For the biomass use per paper area, the paper grammage is decisive. If the grammage can be lowered by increasing the proportion of mechanical pulp, this may lower the biomass use per paper area, despite the higher biomass use per unit mass in mechanical paper. In the production of woodfree paper, energy recovery from residues in the mill accounts for most of the biomass use, while external electricity production accounts for the largest part for mechanical paper. Motor fuel production accounts for 5–7% of the biomass use. The biomass contained in the final paper product is 21–42% of the total biomass use, indicating that waste paper recovery is important. The biomass use was found to be about 15–17% lower for modelled, modern mills compared with mills representative of today's average technology.     

浅谈镀锌工艺对环境的影响

从环境保护的角度出发，分析了目前应用物镀锌工艺－热镀锌与电镀锌对环境的影响。并介绍了机械镀锌这一新的利于环境控制的镀锌工艺的原理和工艺过程。     

电梯层门机械强度的探讨

层门机械强度是电梯层门的一项重要特性,层门机械强度不足时门扇受力后容易产生较大变形甚至脱落,造成人员坠落井道的伤亡事故。本文对国内外电梯标准t层门机械强度要求条文进行了解析,基于国家标准中层门机械强度的规定,通过试验方法进行测试验证,指出国家现有标准中关于层门机械强度要求的不足之处。在此基础上,提出适合于我国的提高电梯层门机械强度的措施和方法,以期提升我国在用电梯层门的安全性。     

机械加工业清洁生产的一则技改实例

一家机械加工厂采用先进的工艺和设备代替落后的工艺和设备，并且撤消了一些工序和对生产车间进行了重新布局，不仅提高了工作效率，而且减少了环境污染，促进了清洁生产，对此，从废水，废气，噪声和废渣四个方面进行了详细评述。     

“三泥”处理现状

国内石化“三泥”处理现状及其存在的问题和发展趋势。     

铝合金厚壁圆筒二次机械自紧技术的实验研究

采用铝合金厚壁圆筒进行了二次机械自紧实验研究,获得的结果充分表明,二次机械自紧技术作为降低冲头推力为目的的工艺方法,效果是明显的和有效的,可满足不同口径厚壁筒机械自紧的要求.     

浅析电子废弃物的破碎与分级

采用机械方法处理电子废弃物，分选前的破碎分级作业是实现高质量分离、富集废弃物中有用物质的保证。从破碎对物料的解离作用入手，分别阐述了不同机械分选作业对入料粒度和形状的要求，这对电子废弃物分选前的破碎分级环节有一定的指导意义。