Fourier basis for the engineering assessment of cracks in residual stress fields

A theoretical basis is presented for determining the significance of a residual stress distribution of arbitrary shape on the crack tip stress intensity factor for a centre-cracked plate as a function of crack length. The Fourier series based approach enables one to increasingly add more spatial definition to the stress field and thereby determine the level of detailed knowledge of the residual stress required to make a reliable assessment of structural integrity. The approach is applied to examples of measured symmetric distributions of residual stresses in welded plates and used to determine the significance of residual stress lengthscales in fracture mechanics analysis

pyCM: An open-source computational framework for residual stress analysis employing the Contour Method

The contour method for assessing residual stress is a widely accessible method in terms of the equipment required and experimental protocol. However, its application is hampered by the absence of a common computational framework to reconstruct the residual stress field and visualise the final result. In order to help regularise the analysis an open-source reconstruction package is presented: the Python Contour Method (pyCM). This package comprises a graphical user interface framework for the purposes for analysing and resolving stresses from experimental contour method data. The code requires no proprietary software and is expandable and fully transparent, enabling users to evaluate it and extend it to develop best practice. The framework is presented and compared against results stemming from a widely published edge-welded beam dataset produced as part of the EC 5th Framework ENPOWER project to highlight applicability

The Influence of Porosity on Fatigue Crack Initiation in Additively Manufactured Titanium Components

Without post-manufacture HIPing the fatigue life of electron beam melting (EBM) additively manufactured parts is currently dominated by the presence of porosity, exhibiting large amounts of scatter. Here we have shown that the size and location of these defects is crucial in determining the fatigue life of EBM Ti-6Al-4V samples. X-ray computed tomography has been used to characterise all the pores in fatigue samples prior to testing and to follow the initiation and growth of fatigue cracks. This shows that the initiation stage comprises a large fraction of life (>70 %). In these samples the initiating defect was often some way from being the largest (merely within the top 35 % of large defects). Using various ranking strategies including a range of parameters, we found that when the proximity to the surface and the pore aspect ratio were included the actual initiating defect was within the top 3 % of defects ranked most harmful. This lays the basis for considering how the deposition parameters can be optimised to ensure that the distribution of pores is tailored to the distribution of applied stresses in additively manufactured parts to maximise the fatigue life for a given loading cycle

Do the developments in telecommunication leads to the Solow paradox on economic growth in Turkey?

Telecommunications infrastructure is critical not only for domestic growth, but also for combining credit with international commodity and financial markets, such as the smooth flow of foreign investment, facilitating the positive value of net exports, and increasing the added value in the economy's GDP. In this study, fixed telephone lines in the period since the Republic of Turkey, is to investigate whether mobile phone and affect the economic growth of the telecommunications sector showing growth in internet connection. In our study, the penetration rate represents the development of telecommunications industry. Penetration rate is defined as the number of fixed line and mobile phone subscribers per 100 people. In order to measure the penetration rate in Turkey, we have used the ratio of the total number of fixed line, mobile subscribers and internet users to the population, taking into account the dates when mobile communication and the internet started. Economic growth is represented as the rate of change to Gross Domestic Product. The data used in this study cover an annual period 1935-2017. After investigating the stationarity of the series of variables, a causal relationship between the Toda-Yamamoto causality test and the penetration rate and GDP change rate series was examined. The findings of the analysis, the development of telecommunications in Turkey revealed that does not affect economic growth. According to this result, the Solow paradox is valid in the period examined in Turkey.peer-reviewe

Prediction of residual stresses in girth welded pipes using an artificial neural network approach

Management of operating nuclear power plants greatly relies on structural integrity assessments for safety critical pressure vessels and piping components. In the present work, residual stress profiles of girth welded austenitic stainless steel pipes are characterised using an artificial neural network approach. The network has been trained using residual stress data acquired from experimental measurements found in literature. The neural network predictions are validated using experimental measurements undertaken using neutron diffraction and the contour method. The approach can be used to predict through-wall distribution of residual stresses over a wide range of pipe geometries and welding parameters thereby finding potential applications in structural integrity assessment of austenitic stainless steel girth welds

Tracking capsule activation and crack healing in a microcapsule-based self-healing polymer

Structural polymeric materials incorporating a microencapsulated liquid healing agent demonstrate the ability to autonomously heal cracks. Understanding how an advancing crack interacts with the microcapsules is critical to optimizing performance through tailoring the size, distribution and density of these capsules. For the first time, time-lapse synchrotron X-ray phase contrast computed tomography (CT) has been used to observe in three-dimensions (3D) the dynamic process of crack growth, microcapsule rupture and progressive release of solvent into a crack as it propagates and widens, providing unique insights into the activation and repair process. In this epoxy self-healing material, 150 µm diameter microcapsules within 400 µm of the crack plane are found to rupture and contribute to the healing process, their discharge quantified as a function of crack propagation and distance from the crack plane. Significantly, continued release of solvent takes place to repair the crack as it grows and progressively widens

Development of a risk assessment tool to assess the significance of septic tanks around freshwater SSSIs. Phase 1 – Understanding better the retention of phosphorus in the drainage fields

The findings contained within this report have allowed Natural England to refine and implement a risk assessment methodology for septic tanks, which was developed through a previous project with CEH (NECR170)

Study of overload effects in bainitic steel by synchrotron X-ray diffraction

This work presents an in-situ characterisation of crack-tip strain fields following an overload bymeans of synchrotron X-ray diffraction. The study is made on very fine grained bainitic steel, thus allowing avery high resolution so that small changes occurring around the crack-tip were captured along the crack plane atthe mid-thickness of the specimen. We have followed the crack as it grew through the overload location. Oncethe crack-tip has progressed past the overload event there is strong evidence that the crack faces contact in theregion of the overload event (though not in the immediate vicinity of the current locations of the crack tip) atKmin even when the crack has travelled 1mm beyond the overload location. It was also found that at Kmax thepeak tensile strain ahead of the crack-tip decreases soon after the overload is applied and then graduallyrecovers as the crack grows past the compressive region created by the overload