Thermo-Mechanical Analysis of Elasto-Plastic Cyclic Torsion of a Tubular Element

The paper treats a tubular element which presents a cantilever beam loaded by a torque moment on the free end. The value of torque is chosen so that the stresses range in the elasto-plastic domain. The rheological properties of the material follow the elastic-linear hardening model. The tubular element is subjected to a cyclic torsion of such frequency that heat is generated in the tubular element. The quantity of the generated heat depends on the amplitude of the torque, frequency of the load and mechanical properties of the tubular element material. The paper compares the results of the temperature change at characteristic points along the tubular element obtained via numerical analysis as well as experimentally.     

可靠性和维修性——现代设计的关键因素（三）

3.提高可靠性的方法可以系统提高整个寿命周期内技术系统可靠性的方法称为可靠性改进法,它包括以下主要步骤:A.评估设备可靠性情况。B.确定可靠性目标。C.引进提高可靠性的活动。D.进行评估。E.将评估结果与目标比较,制定后续措施。F.查出问题以及主要的造成不可靠性的原因。重复执行从步骤C到F,直到实现可靠性目标。设备的寿命周期可以粗略地分为如下阶段:方案和可行性、设计和研制、生产和使用。如果增加用于提高可靠性的费用,则对设备可靠性可能的不利影响会显著下降。3.1在使用阶段可靠性的提高大多数设备的可靠性是在使用阶段前定…     

Morphology and electrical properties of conductive carbon coatings for cathode materials

Many interesting cathode materials, such as LiFePO₄, LiMnPO₄, LiFeBO₃ or the recently discovered Li₂FeSiO₄ and Li₂MnSiO₄, exhibit extremely low electronic conductivity (<10⁻⁹ S cm⁻¹). A very efficient way for improving the electronic transport in such materials is supposed to be the preparation of carbon coatings around individual active particles. Despite the increasing number of reports on preparation of various carbon coatings, neither the formation mechanism nor the detailed coating properties have been explained satisfactorily. The present paper is an attempt to find a clear correlation between the synthesis parameters, the resulting coating morphology and, finally, its electrical properties. As a substrate material for deposition of coatings, more or less monodisperse TiO₂ particles in various sizes were used. As a carbon precursor, citrate was used because it had given excellent results in our previous investigation of the LiFePO₄ system. It is shown that citrate precursor delivers pretty good conductivity (ca. 30 S cm⁻¹) after a 10 h heat treatment at 700 °C or higher. The conductivity percolation threshold can be reached already at 1.5 vol.% of carbon, while the plateau conductivity of the whole composite is about 0.1 S cm⁻¹. At that level, the carbon phase is supposed to form a well-distributed 3D electrical network within the composite.     

Laser deposition of Metco 15E, Colmony 88 and VIM CRU 20 powders on cast iron and low carbon steel

In the tooling industry, there is often the need to repair damaged or worn out components, or to apply coatings on functional surfaces of tools. When depositing a material which properties are very different from the properties of the substrate material, difficulties, such as cracks, can occur. In this paper, we investigate the deposition of three different powders (Metco 15 E, Colmony 88 and VIM CRU 20) on cast irons and low carbon steel with the laser engineered net shaping (LENS?) technology. Coatings with a maximum of four layers were deposited with different process parameters. Although most bonds itself were of good quality, some coatings had numerous cracks. Preheating of the cast iron samples with the laser beam was used to reduce the number of cracks. In the preheating process, the surface of samples was partially melted in order to dissolve graphite nodules which were often the starting point of cracks.     

可靠性和维修性——现代设计的关键因素（一）

提高利润的压力迫使管理人员不得不改进技术以降低资产管理成本,这改变了维修人员和维修操作的地位。日益复杂的技术系统、公众对产品质量的要求以及关于产品责任的新法律等也进一步推进了可靠性和维修性的发展。本文描述了可靠性和维修性在总体设计中的地位以及其对寿命周期费用和总体设备效率的影响,列举了一些实际可行的可靠性和维修性的评估方法,并给出了一些实例。最后简单地介绍了一些系统方法在斯洛文尼亚“早期设备管理”领域的基本运用和早期成果。     

Product identification in industrial batch fermentation using a variable forgetting factor

For reliable operation and the optimization of production, industrial fermentation processes require appropriate tools for monitoring the process in real time. This work presents the structure and operation of a soft sensor for the on-line monitoring of biomass and product concentration during salinomycin and bacitracin fermentation in an industrial, 80-m³ batch reactor; moreover it provides a tool for evaluation of batch production verified in industrial application. The process estimation algorithm consists of decoupled growth and product models, which ensures an unbiased convergence of the estimator and the robustness of the model. The production of secondary metabolites is described with a non-structured model upgraded with a variable forgetting factor that demonstrated a successful estimation of the non-measured parameters and states of this highly interactive and interlinked system with complex dynamics. The possibility of using various input signals in product identification yields independent soft sensors. This serves to improve the reliability of the predictions, mutual sensor control and enables the detection of irregularities in the fermentation process before the broth becomes useless.     

Optimization of cutting process by GA approach

The paper proposes a new optimization technique based on genetic algorithms (GA) for the determination of the cutting parameters in machining operations. In metal cutting processes, cutting conditions have an influence on reducing the production cost and time and deciding the quality of a final product. This paper presents a new methodology for continual improvement of cutting conditions with GA. It performs the following: the modification of recommended cutting conditions obtained from a machining data, learning of obtained cutting conditions using neural networks and the substitution of better cutting conditions for those learned previously by a proposed GA. Experimental results show that the proposed genetic algorithm-based procedure for solving the optimization problem is both effective and efficient, and can be integrated into an intelligent manufacturing system for solving complex machining optimization problems.     

Emergence of intelligence in next-generation manufacturing systems

In the paper we propose a fundamental shift from the present manufacturing concepts and problem solving approaches towards new manufacturing paradigms involving phenomena such as emergence, intelligence, non-determinism, complexity, self-organization, bottom-up organization, and coexistence with the ecosystem. In the first part of the paper we study the characteristics of the past and the present manufacturing concepts and the problems they caused. According to the analogy with the terms in cognitive psychology four types of problems occurring in complex manufacturing systems are identified. Then, appropriateness of various intelligent systems for solving of these four types of problems is analyzed. In the second part of the paper, we study two completely different problems. These two problems are (1) identification of system in metal forming industry and (2) autonomous robot system in manufacturing environment. A genetic-based approach that imitates integration of living cells into tissues, organs, and organisms is used. The paper clearly shows how the state of the stable global order (i.e., the intelligence) of the overall system gradually emerges as a result of low-level interactions between entities of which the system consists and the environment.     

Load-Dependent Transition in Sliding Wear Properties of TiCN–WC–Ni Cermets

The present investigation aims at evaluating the sliding wear behavior of TiCN–20 wt%Ni cermets, containing varying amounts of WC (5–25 wt%) against 100Cr6 steel at different loads (5, 20, and 50 N). The dominant wear mechanisms were established by using surface topography analysis (Stylus profilometry), scanning electron microscopy, and X-ray diffraction. The steady-state coefficient of friction varies over a wide range: 0.73–0.27 at different loads for the investigated cermets. The volumetric wear loss of the cermets in general increases with load, while the wear rate varies in the order of 10⁻⁷ mm³·(N·m)⁻¹. The worn surface characterization reveals that a transition in wear mechanism occurs from abrasion and mild tribo-oxidation at low loads to the formation of a dense tribo-oxide layer, containing oxides of Fe and Ti (essentially Fe₉TiO₁₅) at high loads. Efforts have been made to discuss the possible reaction pathways to explain the formation of the tribochemical layer. The addition of WC to TiCN–Ni-based cermets results in increased abrasion at low loads and severe fracture of the tribo-oxide layer at high loads.     

Wavelet analysis for gear crack identification

There are many typical damages and faults that can cause problems in relation to gear unit operation, a crack in the tooth root being probably the least desirable among them. It often results in failure of gear unit operation. Fault analyses presented in this article are based on gear units with real damages or faults, produced on the basis of real operating conditions. A test plant has been used. A possible damage can be identified by monitoring vibrations. The influences of a crack in a single-stage gear unit on produced vibrations are presented. A fatigue crack in the tooth root causes significant changes in tooth stiffness, whereas, in relation to other faults, changes of other dynamic parameters are more expressed. Different methods are used to analyse signals acquired by experiments. Signal analysis has been carried out in relation to a non-stationary signal, using the family of Time Frequency Analysis tools, such as Wavelets Analyses. Typical spectrogram and scalogram patterns resulting from reactions to faults or damages indicate the presence of damages in a very reliable way.