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Sprayed concrete provides today the combined features of high productivity, increased quality and low cost in work which concerns repairs, preservations, and general work which requires support. Cement usually mixed with fine aggregate (up to 8mm) is forced with pressure to walls with appropriate and controlled addition of water into the pump at mixture stage (wet process) or just before the exit by nozzle (dry method). Even if with enough advantages -included the increased bonding strength— this particular process and hence whole the final product (sprayed concrete) is infected by many uncontrolled factors [ 1 ]. Multivaried parameters as substrate morphology, aggregate character and also of cement type and aggregates, the non-constant flow of water and material, the unavoidable rebound of aggregates and mainly the human factor through pump and nozzle handling leads to a varied water to cement ratio (w/c) and also of bulk properties of sprayed concrete. In such a situation the final product will be hardly controlled and investigated [ 2 ]. So experimental work in this specific area is internationally limited. In present study we try to describe the influence of aggregate type, modifying the traditional composition replacing the limestone aggregates with marble particles. Marble grains are a sub product of marble extraction industry and efforts for satisfactory uses has also an environmental meaning besides the special modifications of final product.

In the context of a project of characterisation of Spain marble and its integration in the construction domain like a building support material, an analysis of the different Macael’s marbles is in progress. The final purpose is the conception of a simulation tool able to transform the material from a safe status to a ruin one. The damage description software tool is based on the Incremental Self Consistent method which permits to realise the transition between the mesoscopic and the macroscopic scales [ 1 ]. This method takes into account the void inclusions (pores), which represent one of the principal sources of the local-failure mechanisms initiation.

Diverse specialties as Geology, Chemistry, and Civil Engineering, are responsible for the selection of materials utilized to produce and prepare construction materials. The isolated knowledge between who manufactures and who constructs, leads, in general, to control its quality for its mechanical behavior without knowledge of external properties of the mineralogical components of the matrix that conforms them.

The detection of damage at early stage is of prime important to initiate timely and cost effective repair and maintenance. In a shell structures such as pipes or pressure vessels, cracks may initiate at the internal surface and propagate through the thickness. The cracks are usually semi-elliptical or semi-circular shape. These type of defects can be observed using traditional inspection techniques such as ultrasound. The aim of the current research is to devise an approach of using thermoelastic stress analysis (TSA) to detect, analyse and quantify the severity of these sub-surface cracks in terms of the stress field surrounding the crack.

Experimental Fracture Mechanics is based on the study of specimens containing “machinednatural” cracks, a term which is self-contradicting. In practice, an artificial (machined) notch of considerable thickness is opened in the specimen by using various techniques and, then, a “natural” crack extension of the notch is created through fatigue. This procedure is, in details, described by ASTM standards [ 1 ], where an artificial notch is considered as acceptable when, among other restrictions, it must have a radius of curvature of the tip equal to ∼0.25×10^−3m and the through-fatigue crack extension has a quiet uncontrolled length of (1–2)×10^−3m. Geometrically, this “natural” crack satisfies two of the requirements of a slit to be a natural crack, i.e. no loss of mass and small (but not near- zero) tip-radius. In many cases, it is not straight or forms a small angle with the notch axis. In addition, this method cannot be applied in case of notches inclined to the loading axis and special loading apparatuses are required. To facilitate and improve ASTM standard many attempts have been presented (e.g. [ 2 , 3 ]). However, an important side-effect of this method has not been discussed. It is that fatigue causes changes of unpredictable severity in the mechanical properties of the material, exactly in the tip area, where the final crack is expected to initiate. In this area material fails and around the tip of the “natural” crack plasticized zones and hardening processes are observed. Consequently, fracture criteria are based on a slippery ground.

When performing Structural Integrity assessments using Failure Assessment Diagrams, a point with coordinates K_r and L_r is representative of the component situation. The first one represents its situation against fracture and the second one against plastic collapse: (1) $$ K_r = \frac{{K_I }} {{K_{IC} }},{\text{ }}L_r = \frac{P} {{P_L }} $$ The fracture toughness value, K_IC, is obtained in tests under high constraint conditions in such a way that the obtained value is a lower bound of the material resistance to fracture. This working scheme often leads to overconservative results when the component being assessed has lower constraint conditions, as shown in Fig.1, where point A represents the component at failure. The point should lead over the Failure Assessment Line (point B) but actually it is far away from it, leading to a safety factor bigger than two (defined as OA/OB).

In recent years, most of plant owners have tried to extend the continuous run length and shorten a turnaround period in order to enhance the competitiveness. In the case of high temperature components, in which creep is a major damage mechanism, creep resistance decays depending upon the localized condition to which a component is exposed. Thus, condition assessment should be performed with a suitable interval to evaluate the remaining operability. However, conventional techniques to predict the remnant life requires long hours especially for low stressed components like superheater tubes in a boiler. Choosing the most damaged tube among numerous ones is not necessarily easy. Since the distribution of tube skin temperatures is rather erratic, a spot inspection cannot be recommended. Therefore, a non-destructive screening technique would be useful for a timely judgement. Due to carbides coarsening associated with high temperature exposure, hardness decreases continuously with operating hours. In the present work, the effectiveness of hardness measurement to find the weakest tube fabricated from 2.25Cr-1Mo steel was confirmed. The mean rupture life against hardness compensated stress, defined as / H _v, for virgin and service-exposed materials was correlated with Manson-Haferd Parameter by the following equation. $$ MHP = (\log t_r {\text{ - }}16.053)/(T{\text{ - }}380) = {\text{ - }}0.02975 - 0.01828 \times log{\text{ }}(/H_v ){\text{ - }}0.01146 \times log^2 (/H_v ), $$ where t _r is the mean rupture life, T is the temperature in K and H _ v is the hardness prior to a test.

The pseudoelastic deformation of some shape memory alloys (SMAs) such as Au-Cd, Au-Cu-Zn, Cu-Zn-Al, and Cu-Al-Ni proceeds through the reversible movement of twin boundaries (Ren and Otsuka [ 1 ]). The behavior of these materials is commonly referred to as rubber-like due to its resemblance to the behavior of soft and pseudoelastic rubber (Otsuka and Wayman [ 2 ]). A similar behavior and a shape memory effect (SME) are discovered in single-crystalline Cu nanowires with lateral dimensions between 1.76 and 3.39 nm through molecular dynamics simulations. This behavior at the nanoscale is due to reversible crystallographic lattice reorientations through the movement of twin boundaries within the FCC crystalline structure (Fig. 2), allowing Cu nanowires to exhibit recoverable strains of up to more than 50% which are well beyond the recoverable strains of 5–8% of most SMAs. The reorientation is driven by high internal stresses resulting from the surface stress and high surface-to-volume ratios of the nanowires. This phenomenon only occurs in nanowires within the size range of 1.76–3.39 nm and is not observed in bulk Cu. Furthermore, it is temperature-dependent and hence gives rise to an SME. Specifically, the critical temperature for spontaneous reorientation upon unloading increases from 100 to 900 K as the wire size increases from 1.76 to 3.39 nm, making it possible to design nanoscale components of varying sizes for operation over a wide range of temperature. Such an objective is more difficult to achieve with conventional bulk SMAs since their transition temperatures (martensite start and finish temperatures, austenite start and finish temperatures) only vary with material structures and composition, not size. Moreover, the nanowires have very short response times which are on the order of nanoseconds due to their extremely small dimensions compared with bulk SMAs.

Bulk nanocrystalline (NC) alloys are an exciting new class of materials that have only recently established their potential for real-world applications. The tensile yield strength of nanocrystalline 5083 aluminum produced by consolidation of cyromilled powders is about twice that of conventional 5083 as shown in Fig. 1. The material is extruded which accounts for the anisotropy in tensile properties and has a grain size on the order of 50 nm. The elongation to failure is lower than for conventional coarse-grained 5083, however not much different from similar high strength alloys such as 5082-H19: 370 MPa yield strength, 4% elongation [ 1 ]. In addition, these materials are thermally stable; heating tensile bars to 500C for 2 hours results in only modest loss in room temperature strength.

Recent advances in the application of micromachined structures have increased the demand for more reliable structures. Stiction, fatigue and microwear [ 1 ] are large issues in the reliability of microelectromechanical systems (MEMS), especially now that designs become more demanding. Silicon is an excellent construction material at the micro-scale, because of highly developed processing methods directly related to semiconductor electronics processing and its high strength. However, it is an inherently brittle material and reliability is the limiting factor as far as commercial and defence applications are concerned. Since the surface to volume ratio of these structures is very large, surface forces become dominant and classical models for failure modes cannot always be applied.