Reduction of springback by intelligent sampling-based LSSVR metamodel-based optimization

This paper deals with the variable blank holder force in sheet metal forming in order to reduce springback effects after forming. A structural risk minimization principle-based metamodeling technique, least square support vector regression (LSSVR) method is applied to optimization. In order to improve the efficiency, an intelligent sampling strategy proposed by Wang et al. (Mater Des 30:1468–1479, 2009a) is integrated with the LSSVR. Therefore, the proposed strategies establish an adaptive metamodeling optimization system. The optimization procedure can be carried out automatically. To valid the flexibility of this system, the presented method is used to optimize the variable blank force parameters of the models from NUMISHEET’96 and torsion rail model. Compared with other popular metamodel-based optimization methods, the test results demonstrate the potential capability for nonlinear engineering problems.     

Reduction of radioactive waste volume using selective crystallization processes

Satisfactory combination of small volume of compositions incorporating ¹³⁷Cs, ⁹⁰Sr, and ²⁴⁴Cm with the admissible heat release rate can be attained by crystallization of definite compounds from high-level solutions. The concentrate of cesium isotopes is obtained by their precipitation in the form of phosphoromolybdate and, after additional storage, in the form of CsMgPO₄·6H₂O; the concentrate of Am, Cm, Sr, Ba, and Ln can be obtained using the known but somewhat modified (increased pH of solution) OXAL process. It is appropriate to remove Am and long-lived Cm isotopes from this concentrate also after storage ensuring the decay of ⁹⁰Sr and ²⁴⁴Cm. The remaining rare-earth elements with traces of Am and Cm and stable isotopes of Sr and Ba can be disposed of, e.g., in the form of a mineral-like phosphate.     

汽车中央通道冲压回弹及其补偿研究

为了研究回弹量及回弹补偿对冲压件成形的影响,以某车型中央通道为研究对象,针对其型面复杂、模型边界高、成形曲度大的特点,采用有限元分析软件Dynaform5.7.1对其进行成形分析、回弹模拟分析和回弹补偿模拟分析.利用截面法对成形及回弹后的零件进行分析,获得边缘回弹量和角度回弹量;经两次反向修模补偿,得到优化的模具型面;利用优化后的模具型面进行模具设计,并对中央通道进行实际生产验证,结果表明,采用截面法和模具型面补偿法能够使最终生产出的零件的回弹量减小,且成形效果更好.     

型材拉弯的力学与回弹分析

回弹是弯曲成形中普遍存在的现象,是由卸载过程中内力重新分布引起的,回弹的存在直接影响弯曲件的成形精度.本文针对转台拉弯成形过程,对等边型材等曲率拉弯进行了应力-应变分析,并按照卸载预拉力与不卸载预拉力两种情况对工件回弹进行了研究与探讨,得到两组半径回弹率理论曲线.通过与试验结果对比,不卸载拉力计算的结果与试验值比较吻合.     

Recent advances in the simultaneous bioreaction and product separation processes

Recent advances in the development of processes of simultaneous bioreaction and product separation are reviewed and presented. Such processes that, in principle, may be realized by combining bioreaction with various separation methods such as adsorption, gas stripping, extraction, membrane separation, and so forth have the advantages of enabling the bioreaction to be conducted with high substrate concentration, diminishing the effect of product inhibition, reducing the energy requirement for separation and enhancing bioreaction rates. Comments concerning important future studies in this area are also offered as part of the presentation.     

铝合金矩形管拉弯成形过程的数值模拟

采用动力显式有限元程序Pam-Stamp2000对铝合金矩形管的一种拉弯成形过程进行了模拟,分析了模具最大作用力、管材截面畸变、成形件回弹的变化规律.模拟结果和文献给出的实验结果相当吻合,即模具最大作用力、管材截面畸变均随预拉力的增加而增加,而成形零件的回弹随预拉的增加而减小;相同预拉状况下,增加壁厚有利于减小截面畸变.此外,数值模拟给出了模具对管材作用力及管材夹持端轴向拉伸作用力随模具行程的变化规律,揭示了本文的拉弯实质上是一种非恒定轴向作用力(呈渐增趋势)的拉弯成形方式,这与本文的解析结果高度一致.     

Experimental and simulation studies of springback in rubber forming using aluminium sheet straight flanging process

Rubber forming is very widely used in aircraft manufacturing. Springback of rubber forming process is an important and decisive parameter in obtaining the desired geometry of the part and design of the corresponding tooling. In this research, the rubber forming of aluminium sheet was conducted. To investigate the springback, the straight flanging was employed in die design. The deformation process was studied by preparing the sheets with different thicknesses and different die radii. The influence of process parameters (time and pressure) on the rubber forming process was studied. Based on the analysis of experimental results, it was found that springback of straight angle decreased with the increase of blank thickness t, whilst increased with the increase of the die radius r. The springback can be eliminated with the bending ratio r/t < 2. The increase of forming pressure and time of rubber forming had little effect on the springback when the blank coincided with the die face. Springback of flanging in rubber forming process was smaller than that of stamping. In the jogged flanging, a better shape was formed by using the polyurethane.     

Study on springback from thermal-mechanical boundary condition imposed to V-bending and L-bending processes coupled with infrared rays local heating

This paper shows differences of thermal-mechanical boundary condition and springback between V-bending and L-bending processes. Although a recently conducted study showed that an infrared (IR) local heating method substantially reduces springback of dual-phase (DP) 980 steel sheet in V-bending, its application to L-bending, which is one of widely used forming processes in industrial applications, has not been sufficiently reported. In the L-bending experiment conducted in this work, springback does not sufficiently decrease as much as it does in the V-bending test, even though the sheet is deformed under the same temperature condition. For analysis of the difference in springback, thermo-elastic-plastic simulation for both V-bending and L-bending processes were conducted. The numerical analysis shows that the V-bending and L-banding processes have significantly different thermal and mechanical boundary conditions even though both processes go through a bending deformation. The differences in the boundary conditions have a strong effect on the thermal-mechanical behavior of the blank, so that the springback results are different between the two bending processes. Finally, it is also shown that the L-bending process requires a higher temperature condition than the V-bending process in order to sufficiently reduce springback.     

A two-pronged approach for springback variability assessment using sparse polynomial chaos expansion and multi-level simulations

In this study, we show that stochastic analysis of metal forming process requires both a high precision and low cost numerical models in order to take into account very small perturbations on inputs (physical as well as process parameters) and to allow for numerous repeated analysis in a reasonable time. To this end, an original semi-analytical model dedicated to plain strain deep drawing based on a Bending-Under-Tension numerical model (B-U-T model) is used to accurately predict the influence of small random perturbations around a nominal solution estimated with a full scale Finite Element Model (FEM). We introduce a custom sparse variant of the Polynomial Chaos Expansion (PCE) to model the propagation of uncertainties through this model at low computational cost. Next, we apply this methodology to the deep drawing process of U-shaped metal sheet considering up to 8 random variables.     

Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds

In this paper, we introduce an original shape representation approach for post-springback characterization based on the automatic generation of parameterized level set functions. The central idea is the concept of the shape manifold representing the design domain in the reduced-order shape-space. Performing Proper Orthogonal Decomposition on the shapes followed by using the Diffuse Approximation allows us to efficiently reduce the problem dimensionality and to interpolate uniquely between admissible input shapes, while also determining the smallest number of parameters needed to characterize the final formed shape. We apply this methodology to the problem of springback assessment for the deep drawing operation of metal sheets.     

Oxidation processes using ion beams

Recent work demonstrates that reactive ion beams can be used to grow compound layers on metal and semiconductor surfaces. Ion beams are characterized by easily controlled ion flux and energy, with a narrow energy spread. Also, the ion species are delivered to the sample in a low pressure environment. These advantages allow greater control and simpler analysis of compound formation processes than other techniques do. Ion beam oxidation is reviewed and compared with thermal, plasma and r.f. oxidation and with oxidation by ion implantation. The ion energy range of several electronvolts to hundreds of electronvolts is suitable for depositing the oxidizing species in the metal in an active state, and simultaneous sputtering can produce a self-limiting oxide thickness when the sputtering yield and oxidation rate are in proper balance. The process of ion beam oxidation is also discussed in light of the etching behavior of metals under combined inert gas and oxygen ion bombardment and of the related technique of reactive ion beam sputter deposition using ion bombardment of a growing film. Additional examples are drawn from the use of other reactive ion beam species, including nitrogen and hydrogen.     

Reduction of clinkerization temperature by using phosphogypsum

Valorization of phosphogypsum as mineralizer in the burning of Portland cement clinker was studied in our laboratory. X-ray fluorescence, optical microscope technique and powder X-ray diffraction were then used to characterize the synthesized clinker and its raw mixture in terms of chemical composition and clinker mineralogical composition. The effects of phosphogypsum on structural and morphological properties of clinker minerals and on the presence of alite were followed by scanning electron microscopy combined with microprobe analysis. The addition of phosphogypsum to the cement raw mixture shows that the burning temperature decreases and therefore improves the production process of clinker. The addition of 10% phosphogypsum permits a complete clinkerization at low burning temperature (1200 degrees C), instead of 1470 degrees C, which increases the cement factory efficiency by 25% and extends the service life of furnace fire brick. Structural and morphological analysis of clinker produced under the new conditions show that phosphogypsum preserve perfectly the crystalline structure of silicate phases, which leads to the improvement of physical and mechanical properties of cement.     

The kinetic behaviors of simultaneous phosphorus release and denitrification on sludge for BNR processes

Abstract

In this study, we investigated the kinetic behaviors of phosphorus release and denitrification on sludge for two biological nutrient removal (BNR) processes, i.e., suspension growth process (A₂O) and combined suspension‐biofilm growth process (TNCU) under anoxic condition. The readily biodegradable substrate and nitrate loadings, 20–180 mg HAc‐COD/g MLSS and 4–25 mg NO₃‐N/g MLSS respectively, are controlled in a batch reactor for phosphorus release and denitrification of sludge taken from A₂O and TNCU processes under various SRT (5, 10 and 15 days) operating conditions. Experimental results indicated that the occurrence of simultaneous phosphorus release and denitrification is a kinetic competition mode under anoxic condition in the presence of a readily biodegradable substrate. Moreover, the available substrate in bulk solution determined the kinetic behaviors of phosphorus release and denitrification. To prevent nitrate inhibition, the sludge is exposed to a C/N ratio higher than 6.1 for phosphorus release. The sludge's phosphorus content (as created by different SRT processes) and initial nitrate loading dominated the kinetics of phosphorus release and denitrification, respectivley. Moreover, the sludge of suspension gorwth process demonstrated a higher phosphorus release potential than the combined suspension‐biofilm growth process. However, the nitrate inhibition is significant for A₂O sludge also. Based on proposed phosphorus release rate equation, the rate constant would be reduced by denitrification about 31–67% and 20–45% for A₂O and TNCU processes, respectively.     

Dynamic processes monitoring using predictive PCA

Abstract

Principal component analysis (PCA) has been extensively used for the monitoring of industrial systems when the measurements are highly correlated or corrupted with noise. The basic assumptions for monitoring using PCA are that the considered processes are stationary and their operating regions are unchanged. In an actual plant, the operation conditions might sometimes vary with time because of its dynamic behavior or the effects of disturbance. In this paper, a new predictive monitoring method is proposed that is composed of three parts: (1) the training data is divided into several parts, and each part stands for the operating region at that stage (2) PCA is applied to the first part of the divided raw data sets, and the other parts will be projected by the same PCA model (3) time series models are built to interpret the operating centers obtained in step 2, and the operating region can be estimated for future monitoring. From these, a more reasonable monitoring region and future process deviations can be built. Based on this monitoring scheme, false alarms will be reduced. Moreover, a measure of the difference of the principal component directions between the training data set and the monitored data set is used to check whether a process fault occurs in processes. The effectiveness of this proposed method is demonstrated with simulation results.     

Investigation of SHS processes using laser hardening

Using the titanium-boron system as an example, a procedure for ultrafast hardening (10⁶–10⁷ K/sec) of the SHS reaction using pulse laser radiation is developed. The dynamic scheme of the component interaction is obtained on the basis of metallographical and micro X-ray spectrum analysis. It is shown that under conditions of high-speed heating mass transfer on the interfaces has a pronounced convective character, ensuring an increased interaction rate.Institute of Structural Macrokinetics of the Russian Academy of Sciences, Tomsk Branch. Scientific-Research Institute of Applied Mathematics and Mechanics. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 5, pp. 598–601, November, 1993.     

Ultrasonic ranging sensor using simultaneous emissions from different transducers

In recent applications based on ultrasound, several ultrasonic transducers have been geometrically and electronically associated to constitute a global sensor. There are several different methods used to process the ultrasonic signals obtained from these transducers. In this work, multimode techniques using Golay complementary sequences are proposed for processing the ultrasonic signal. The system increases scan rate, precision, and reliability. It is also capable of echo discrimination, allowing simultaneous measurements to be made and detection of the same obstacle by different transducers without cross-talk problems. The real-time implementation of the algorithm is presented on a field-programmable gate array (FPGA) device.     

Fault diagnosis of batch processes using discriminant model

A new statistical online diagnosis method for a batch process is proposed. The proposed method consists of two phases: offline model building and online diagnosis. The offline model building phase constructs an empirical model, called a discriminant model, using various past batch runs. When a fault of a new batch is detected, the online diagnosis phase is initiated. The behaviour of the new batch is referenced against the model, developed in the offline model building phase, to make a diagnostic decision. The diagnosis performance of the proposed method is tested using a dataset from a PVC batch process. It has been shown that the proposed method outperforms existing PCA-based diagnosis methods, especially at the onset of a fault.