Shakedown and creep rupture assessment of a header branch pipe using the Linear Matching Method

Many power plant components are subject to combined mechanical and thermal loading conditions during their operating lifetime. It is important that potential failure mechanisms of such components are extensively investigated in order to ensure sufficient confidence in their reliability. This paper presents shakedown and creep rupture analyses of a header branch pipe subjected to cyclic thermo-mechanical loading performed using the Linear Matching Method (LMM). The detailed investigation of failure mechanisms under the combined action of the internal pressure and the cyclic thermal load due to the temperature difference between the inner and outer pipe surfaces will be the primary focus of this paper. The header branch pipe considered here is composed of a single material with properties that are dependent upon both temperature and rupture life. A novel study investigating the effect that two geometric parameters – branch diameter and separation – have upon the failure mechanisms of the header branch pipe has also been carried out. The impact that these geometric parameters have upon the limit load, shakedown and creep rupture limits is one of the principal areas that is investigated in this work. In addition to this, an understanding of the dependency of the creep rupture limit upon the defined time to creep rupture is also studied. Verification of these results is then given by full elastic-plastic analyses performed within ABAQUS

On the creep fatigue behavior of Metal Matrix Composites

The mechanical behaviour of Metal Matrix Composites (MMCs) subjected to a high temperature and cyclic load condition is difficult to understand. The significantly differing coefficients of thermal expansion between ceramic and metal give rise to micro thermal stresses. Their performance under varying load and high temperature is complex and inconsistent, where fatigue and creep damages become the main failures of MMCs. To improve current understanding of the relationship between creep fatigue interaction of MMCs, the history of thermal and mechanical loading, and the creep dwell period, a highly accurate but robust direct simulation technique on the basis of the Linear Matching Method (LMM) framework has been proposed in this paper, and been applied to model the fatigue and creep behaviour of MMCs. A homogenised FE model is considered in all analyses, which consist of continuous silicon carbide fibres embedded in a square 2024T3 aluminium alloy matrix array. Various factors that affect creep and fatigue behaviours of composites are analysed and discussed, including effects of the applied load level, dwell period and temperature on the MMC's performance. The effects of reversed plasticity on stress relaxation and creep deformation of MMC are investigated, and the behaviours of cyclically enhanced creep and elastic follow-up are presented. The applicability and accuracy of the proposed direct method has also been verified by the detailed step-by-step analysis via Abaqus

Creating Value By Object Hyperlinking Along The Consumer Buying Decision Process In The IoT Era

Within the IoT scope, a new application named ‘object hyperlinking’ has evolved. Object hyperlinking is the pervasive presence of different things or objects identified by tags, sensors, and mobile phones that can interact with each other as well as with their neighbors through unique addressing schemes for business purpose. Enabled by Automatic Identification and Data Capture (AIDC) technologies such as QR code and NFC, object hyperlinking services make it possible link any object or location to a more comprehensive and editable information. While tagging technologies have good prospects to offer more opportunities in a company’s interaction with its consumers, how this capability can be best applied and what innovative business services be created with object hyperlinking remain to be discovered. This study surveys and examines 76 projects of object hyperlinking in Taiwan and provides a framework to figure out business value and issues of object hyperlinking along the five stages of a consumer buying decision process. Based on the functionality and purpose of object hyperlinking services, this framework is conducted in dimensions of value creation, value orientation, functionality, key factor and challenges, key activities within organization, and managerial issues concerned. Some innovative business models enabled by object hyperlinking will also be introduced. The research results found that only when the information gathered by identified objects is used, analyzed, and distributed into wide business activities in term of marketing, customer service and firm level strategy planning, the effectiveness and value of object hyperlinking services can be realized at its maximum. The integration across different consumer buying decision process is also important. The more applications of object hyperlinking in different buying decisions, the more benefits will be created for customers. Managers can use the list of dimensions proposed in the framework to develop rich IoT business from enhancing service operations with object hyperlinking

Shakedown analysis for rolling and sliding contact problems

There is a range of problems where repeated rolling or sliding contact occurs. For such problems shakedown and limit analyses provides significant advantages over other forms of analysis when a global understanding of deformation behaviour is required. In this paper, a recently developed numerical method. Ponter and Engelhardt (2000) and Chen and Ponter (2001), for 3-D shakedown analyses is used to solve the rolling and sliding point contact problem previously considered by Ponter, Hearle and Johnson (1985) for a moving Herzian contact, with friction, over a half space. The method is an upper bound programming method, the Linear Matching Method, which provides a sequence of reducing upper bounds that converges to the least upper bound associated with a finite element mesh and may be implemented within a standard commercial finite element code. The solutions given in Ponter, Hearle and Johnson (1985) for circular contacts are reproduced and extended to the case when the frictional contact stresses are at an angle to the direction of travel. Solutions for the case where the contact region is elliptic are also given

The electronic specific heat in the pairing pseudogap regime

When pairing correlations in a quasi two dimensional electron system induce a pseudogap in the single particle density of states, the specific heat must also contain a sizeable pair contribution. The theoretically calculated specific heat for such a system is compared to the experimental results of Loram and his collaborators for underdoped YBa_2Cu_3O_{6+x} and La_{2-x}Sr_{x}CuO_4 samples. The size and doping dependence of the extracted pseudogap energy scale for both materials is comparable to the values obtained from a variety of other experiments.Comment: 4 pages, 5 eps figure

Finite Element Analysis of the Displacement Adjustment Scheme for Column Bases of a 10000 m3 Spherical Tank During Whole-body Heat Treatment

AbstractThe stress of spherical tank and displacement of column bases were calculated by finite element method, considering the uneven gravity loads on support columns which was caused by manufacturing and setting errors. The preliminary displacement adjustment scheme for column bases was made, according to the safety range of column bases displacement which was determined by the maximum stress restricted by allowable stress at the set heat treatment temperatures. The final scheme was made after checking the preliminary scheme. The method of making adjustment scheme of column bases for a 10000m3 spherical tank during the whole-body heat treatment may provide a reference for other large spherical tank

Heme iron from meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved

Red meat and processed meat intake is associated with a risk of colorectal cancer, a major cause of death in affluent countries. Epidemiological and experimental evidence supports the hypothesis that heme iron present in meat promotes colorectal cancer. This meta-analysis of prospective cohort studies of colon cancer reporting heme intake included 566,607 individuals and 4,734 cases of colon cancer. The summary relative risk of colon cancer was 1.18 [95%C.I.: 1.06-1.32] for subjects in the highest category of heme iron intake compared with those in the lowest category. Epidemiological data thus show a suggestive association between dietary heme and risk of colon cancer. The analysis of experimental studies in rats with chemically-induced colon cancer showed that dietary hemoglobin and red meat consistently promote aberrant crypt foci, a putative pre-cancer lesion. The mechanism is not known, but heme iron has a catalytic effect on (i) the endogenous formation of carcinogenic N-nitroso compounds and (ii) the formation of cytotoxic and genotoxic aldehydes by lipoperoxidation. A review of evidence supporting these hypotheses suggests that both pathways are involved in heme iron toxicit