Papers by Keyword: Strain

Abstract: This article describes the applications and benefits of a recently developed smart building material namely Engineered cementitious composite (ECC), also known as flexible or bendable concrete. Conventional concretes have a strain capacity of only 0.1 percent and are highly brittle and rigid. This lack of bendability is a major cause of failure under strain and has been a pushing factor in the development of an elegant material which is capable to exhibit an enhanced flexibility. An ECC has a strain capacity of more than 3 percent and thus acts more like a ductile metal rather than like a brittle glass. The aim of this paper is to highlight a probable success of ECC in terms of industrial and commercial use in Pakistan. With the introduction of flexible concrete in building technology, it is likely to have safer and more durable construction. The material is expected to display reduced detrimental impacts on the natural environment. A bendable concrete is composed of all the ingredients of a traditional concrete minus coarse aggregates or crushed stones and is reinforced with micromechanically designed polymer fibers. The mechanism of action of the micro-polymeric fibers in concrete has also been emphasized. The principles of mix designs of the mortar incorporating fibers to make an ECC have also been explained. It has also been mentioned in detail as how this technology can be used to enhance the flexibility of some modern concrete types like flowing concrete, self-compacting concrete, and lightweight concrete. ECC is a green construction material. The possible benefits like environment friendliness, cost effectiveness, and durability have been also been elucidated in the paper.

Abstract: Copper thin films are potentially used in optical and laser applications due to their intrinsic reflective indexes in visible and infrared region of the spectrum. The reflective properties of the thin films are mainly driven by their thickness, structure, and residual strain induced during the processing stages. Copper thin films of various thicknesses were deposited on glass slides using a thermal evaporation unit. The deposited substrates were thermally treated, in inert environment for 30 minutes, for various temperatures. Further, the substrates were characterized using various techniques. Structural studies of the thin films were carried out using XRD on the as deposited and heat treated films to study the phases, the crystallographic preferred orientation, residual strain and crystallite size. The polycrystalline Cu phase was revealed and no oxide phases were identified. The films were preferentially oriented along (111). The crystallite size increases while the residual strain decreases as the film thickness increases. The crystallite sizes were very small as compared to the film thickness. The optical properties of these coatings were investigated by double beam spectrophotometer. It was found that reflectance of these coatings strongly depends upon the film thickness and post deposition heat treatment. The optimum deposition procedure was established to obtain the enhanced reflecting power.

Abstract: This paper presents a comparative bibliographic study of different materials with elevated biomechanical biocompatibility regarding the stent-blood vessel interaction. Only the materials used in coronary stents’ manufacturing are considered: stainless-steel (316L), Cobalt-Chromium alloys (CoCrMo, CoNiCrMo), Nickel-Titanium alloys (Nitinol), Tantalum. The main characteristics that result from the stress-strain curve of each material are presented, as well as the biocompatibility and durability. The stainless-steel has good mechanical properties, excellent biocompatibility and low price. Cobalt-Chromium alloys have excellent mechanical properties, excellent biocompatibility, acceptable shape memory properties, but high density and low flexibility. The Nitinol represents the best choice, with excellent mechanical properties, excellent biocompatibility, good corrosion resistance, high flexibility (super-elastic behavior), low density, but high price. Tantalum alloys present the best biocompatibility and high flexibility, but the mechanical properties are relative modest.

Abstract: This article established 3D FE model of dual-radius arc finishing groove and tangent expansion angle finishing groove using ANSYS / LS-DYNA software for Wuhan Iron and Steel plant Ф16 hot continuous bar, and analyzed metal flow pattern, stress and strain distribution of two types finishing grooves. The results show that surface stress and strain distribution of dual-radius arc finishing groove have better uniform than them of tangent expansion angle finishing groove, and dual-radius arc finishing groove ensures the stability of the rolled piece in finishing groove, improve the dimensional accuracy and surface quality of rolled finishing product.

Abstract: This paper presents the analysis of energy absorbed that produced from an instrumented charpy impact in order to evaluate the toughness of materials. Alloy rims made from aluminium 6061-T6 are easily damage, fracture and can even destroy after impact loading compared to the steel rim. For this reason, an idea was initiated to determine the strain signal pattern and strain energy for evaluting the toughness of materials. Strain gauges were experimentally connected to the data acquisition system and it was then attached to the charpy striker for the impact signal collection. Specimens of aluminium alloy of 6061-T6 and carbon steel 1050 were used and its were designed according to the ASTM E23 standard. In this work, the signal was converted from the time domain to the frequency domain using the power spectrum density (PSD) method and the area under its graph was then used to calculate strain energy. The comparison between absorbed energy and strain energy was performed based on different materials and thicknesses. It was found the effect of the strain signal pattern with different materials and thicknesses to be influnced the strain energy.

Abstract: During large-strain plastic deformation, subgrain structures typically develop within the grains. At large enough equivalent strains above, say 0.5, recrystallization occurs via abnormal coarsening of the subgrain structure or abnormal (sub-) grain growth (AsGG). The fraction of subgrains that develop into new, recrystallized grains has been quantified as a function of texture spread (Grain Reference Orientation Deviation) using Monte Carlo simulation. When this fraction is combined with the known monotonic increase in mean misorientation with strain, the recrystallized grain size can be predicted as a function of von Mises strain. The prediction is in good agreement with experimental results drawn from the literature.

Abstract: Equal channel angular extrusion (ECAE) is a severe plastic deformation (SPD) method for obtaining bulk nanostructured materials. The ECAE die consists of two equal channels that intersect at an angle, usually between 90。and 135。. In the present study, the plastic deformation behavior of copper during the ECAE process with 120o die was investigated. To analyze the deformation behavior and the related strain distributions in the specimen, the commercial FE code ABAQUS has been used. The properties of the materials are strongly dependent on the shear plastic deformation behavior during equal channel angular extrusion (ECAE), which is controlled mainly by die geometry, material properties, and the friction between billet and the die. The ECAE process for these conditions was explained using the two different friction conditions of 0.15 and 0.08 to all sliding surfaces. The effective strain by the theoretical equation is in good agreement with the FEM results.

Abstract: This paper presents the outcomes from a laboratory based research study undertaken to evaluate the fundamental properties of permeable concrete, including compressive strength, global and local strain, elastic modulus (stiffness), porosity and permeability. Six permeable concrete mixtures were made with constant water - cement ratio of 0.34, using different aggregate sizes and sand percentages. The compressive strength range was 15-35 MPa, while the permeability varied between 1.5 to 5.5mm/s and the porosity varied between 25 to 35 %. Two testing methods were used to measure the strain and modulus of elasticity (MOE) of the permeable concrete namely, platen-to-platen method and strain gauge method. Considerable difference was found between the MOEs obtained by the two methods. The MOE determined using the platen-to-platen method consistently were lower in value, which has been attributed to the softness of the capping components, the interface between the specimens and the platen and overall machine compliance. The pore characteristics and their distribution were seen to have an influence on the material responses such as material stiffness and strain. A comparison drawn between the axial strain obtained by the strain gauge measurement and that deduced from the platen-to-platen measurement was undertaken to evaluate the strain homogeneity along with possible detection of the localization phenomena.

Abstract: The most important characteristics for service safety of complex metal structures are those describing crack initiation and growth caused by static or dynamic, variable loading. Crack initiation and growth is subject of numerous investigations by different methods. The paper shows the possibility of applying infrared thermography to the problems of fracture mechanics. The main aim of testing was to qualitative relate the temperature changes of the spacemen measured by infrared thermography with the evaluation of fatigue cracks in steel specimen. Based on the distribution of temperature on the surface of the sample, during the action of force, the spread of plastic zones and crack tip are determined. The increase of temperature produced by the plastic deformation at the crack tip has been measured by infrared camera Thermal CAM SC640, FLIR Systems. SE(B) specimens were tested in three-point bending (TPB), following the procedures of ASTM E1820, on electrical mechanical testing machine with crack tip opening displacement (CTOD) control, at room temperature. Numerical simulation of stress distribution on the same model under same condition is presented, too. The results showed that thermography is a method suitable for monitoring and prediction of crack initiation and growth, as well as critical stress in elastic and elastic-plastic deformations. Fatigue crack growth behaviour of cracked TPB specimen made of S355 J2 G3 steel using Paris relation is considered.

Abstract: According to the factual demand of produce, some corporation wants to enlarge the capacity of the idle from 65t to 75t. This paper aims at the changing ladle which the capacity is 75t. It makes research to the iron ladle's promotion process and stress analysis. This paper uses ANSYS-Workbench software to make the finite element analysis of the iron ladle and extracts the largest stress, strain and the location. Then this paper analyses whether the changing ladle can be fit for the intensity demand or not so that it could provide the important theory gist to the corporation