Damage analysis in Fe–Cr–Ni centrifugally cast alloy tubes for reforming furnaces

Reformer furnaces tubes work under high temperature and pressure for a long time, which are very critical conditions for creep deformation and life of most common materials. Cast austenitic Fe–Cr–Ni alloys in the widely know HP grades are used for reformer tubes to allow a good service at temperatures that can be close to 1000 °C. This paper reports a study devoted to the damage analysis of reformer furnace tubes after more than 100,000 h of service. Tubes, made of a HP grade modified with Nb and Ti additions, were inspected in situ by a laser optic system to measure their internal diameter and evaluate creep deformation. With the aim of developing a criterion for deciding the substitution of components, samples of as cast material and samples, cut from the most deformed tubes put out of service, were considered to check changes of mechanical properties and metallurgical characteristics. Tensile and creep tests were carried out; moreover the metallographic observations included optical and scanning electron microscopy and energy dispersive X-ray microanalysis in order to measure locally the chemical composition.     

R-curve behaviour in weak interface-toughened SiC-C laminates by discrete element modelling

Tough ceramics can be made by introducing weak interfaces which deflect a growing crack. A simple discrete element model was employed to study crack growth in SiC-C laminate with graphite as weak interfaces. By modelling the three-point-bending test of the notched laminate, de-bonding, de-lamination and crack deflection were observed dynamically. The fracture features of the laminate as like “graceful failure” and R-curve behaviour were replicated both qualitatively and quantitatively. It has been revealed that the strength of the weak interface should be in a certain range to assure the appearance of the toughening effect. A minimum presence of the weak interface is required to increase the strength of the laminate. The employed model is explicit and simple, it can be used to reproduce the dynamic process of crack propagation in ceramic laminates and guide the design of the laminate's structure in the future.     

大底盘结构地下车库基坑挖距主楼的安全距离

针对当前工程建设中的大底盘结构先进行主楼施工,再进行裙房或地下车库基坑开挖,对主楼地基安全会产生不利影响这一问题,通过太沙基地基整体剪切破坏模型,对裙房或地下车库基坑开挖距主楼的安全距离进行了探讨,以确定最佳的安全距离,保证主楼地基安全。     

节理峰前剪切刚度软化模型及其影响因素分析

节理峰前剪切应力-位移曲线是研究节理剪切行为的重要内容。然而目前对于节理峰前剪切行为大多以线性描述,不能较好的描述非线性的特点。对于非线性的描述也仅仅是唯象描述剪切应力-位移曲线,未能反映影响模型的参数物理意义及影响因素。以峰前节理刚度软化行为为出发点,采用归一化的思想将节理剪切刚度与位移无量纲化,用双曲线函数表示出剪切刚度与位移之间的关系。提出了考虑刚度软化的峰前剪切本构关系,通过与试验结果对比验证了本构关系的合理性。影响该模型最重要的两个因素是初始剪切刚度与峰值剪切位移。以Greenwood和Williamson模型为基础在细观上探讨了初始剪切刚度的影响因素;抓住法向应力与节理粗糙度主要因素,探讨了影响峰值剪切位移的影响因素。对模型参数的研究有助于进一步阐明节理峰前剪切机理。     

台达20PM运动控制器在包装膜打孔机上的应用

台达20PM运动控制器及伺服驱动系统已被应用于食品包装膜打孔机。应用实例表明，采用基于非周期凸轮控制模式和CAMTABLE表的高速交流伺服驱动来代替快速气缸打孔是一种极佳的解决方案。该文简介了该打孔机控制系统的构成，着重分析了追剪和高速比较与捕捉功能这两个控制要素和部分应用程序。     

Critical Analysis of Fibre‐Reinforced Polymer Near‐Surface Mounted Double‐shear Pull‐out Tests

The study of the bond behaviour between fibre‐reinforced polymer (FRP) systems and concrete is an issue that nowadays attracts many researchers. The scientific community dedicated to the research of FRP reinforcement has been conducting numerous experimental programmes aiming to assess the local bond–slip law of the FRP–adhesive–concrete connection. This paper reports the relevant results obtained by the Structural Composite Research Group of Minho University in the scope of an international Round Robin Test. The suitability of the recommended test setup to derive a local bond constitutive law for modelling the bond behaviour of near‐surface mounted reinforcement systems is discussed based on a deep interpretation of the results.     

浮动式液压剪的结构特点及参数计算

本文结合作者的浮动式液压剪的设计、调试体会,分析了液压剪的结构组成,并对液压剪设计所需的一些重要参数进行确定。     

Incentives for early adoption of carbon capture technology: Further considerations from a European perspective

This note details two comments on a recent policy proposal in Comello and Reichelstein (2014) aimed at favoring the early adoption of Carbon Capture (CC) technology in the next generation of thermal-based power plants to be installed in the United States. First, we examine the implications of a worst-case scenario in which no new CC is adopted internationally beyond what is in place in 2014. Second, we show the potential, under the original proposed subsidy, for the emergence of coordination failures capable of hampering the desired early CC deployment. We propose and evaluate modified schedules of tax-credits sufficient to overcome these concerns. These additions strengthen the argument in the original article: namely, though higher incentive levels are necessary, our findings confirm that the cost of the proposed policy is not out of reach.     

Effects of molding conditions on injection molded direct joining using a metal with nano-structured surface

Injection molded direct joining (IMDJ) is one of the metal-plastic direct joining processes and is based on a combination of a special surface treatment of a metal piece and an insert molding. This study employed a chemical processing as the special surface treatment to form nano-structures on the metal piece. We investigated relationship between joining strengths and molding conditions; we focused on pressure of a mold cavity and injection speed as molding conditions in this work. To evaluate the IMDJ samples processed under various molding conditions, we carried out tensile-shear tests. Then we compared the results of the tests to discuss how much each condition variation affected the joining strength. From the discussion, we found an interesting effect of the injection speed, which is unique to the IMDJ using a metal piece with nano-structures. The findings of this study will promote a better understanding of the IMDJ.     

Loadbearing capacity of infill masonry walls considering the deformation‐based membrane effect

According to currently valid codes, it is not possible to determine the loadbearing capacity of unreinforced infill walls considering the deformation‐based membrane effect by incorporating the exact support conditions. One reason for this is the lack of a validated calculation procedure, which in addition to the equilibrium conditions also realistically represents the compatibility conditions of these systems. In the present paper, therefore, a new non‐linear analytical calculation procedure is presented. The main focus of the analysis of walls subject to area loading is the incorporation of the support conditions and thus the consideration of the deformation‐based membrane compressive force. Through generalised formulation and a standardised notation of the determination equations, different material behaviours and various support conditions can be taken into account with few parameters. On the action side, both lighter loading like wind loads and heavier loading like explosion loads can be considered. Through the implementation of the partial factor concept, it is possible to comply with the requirements of European codes and thus ensure the applicability of the analysis model.