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This paper aims to reveal the mechanism for improving ductile machinability of 3C-silicon carbide (SiC) and associated cutting mechanism in stress-assisted nanometric cutting.

Molecular dynamics simulation of nano-cutting 3C-SiC is carried out in this paper. The following two scenarios are considered: normal nanometric cutting of 3C-SiC; and stress-assisted nanometric cutting of 3C-SiC for comparison. Chip formation, phase transformation, dislocation activities and shear strain during nanometric cutting are analyzed.

Negative rake angle can produce necessary hydrostatic stress to achieve ductile removal by the extrusion in ductile regime machining. In ductile-brittle transition, deformation mechanism of 3C-SiC is combination of plastic deformation dominated by dislocation activities and localization of shear deformation. When cutting depth is greater than 10 nm, material removal is mainly achieved by shear. Stress-assisted machining can lead to better quality of machined surface. However, there is a threshold for the applied stress to fully gain advantages offered by stress-assisted machining. Stress-assisted machining further enhances plastic deformation ability through the active dislocations’ movements.

This work describes a stress-assisted machining method for improving the surface quality, which could improve 3C-SiC ductile machining ability.

Many countries have started to use post-tensioned (PT) concrete because of its sustainability and low cost. However, it is not quite popular in Sri Lanka as the required knowhow and technology are not available within the country. By introducing PT concrete to the country, unwanted costs and time overruns could be eliminated from the construction projects. This paper, therefore, aims to identify the suitability and acceptability of PT concreting for/in Sri Lanka.

An extensive literature review was first carried out to gather knowledge on PT concreting. The four case studies that followed it included eight semi-structured interviews and a document review. Ten expert interviews were conducted finally to strengthen the findings of the literature review and case studies. Cross-case analysis and NVivo 11 content analysis software were used to analyze the data gathered.

Findings reveal that PT concreting saves cost and time of construction and that it can have a control over the resources required for construction, which makes it environment-friendly. PT concreting allows thinner concrete sections, extended spans, stiffer walls that resist lateral loads and stiffer foundations that resist the effects of shrinking and swelling soils.

It is found that PT concreting is more suitable for the construction industry in Sri Lanka than traditional concreting.

The Government’s investment in infrastructure projects is considerably high, especially in bridge construction projects. Government authorities must establish an initial forecasted budget to have transparency in transactions. Early cost estimating is challenging for Quantity Surveyors due to incomplete project details at the initial stage and the unavailability of standard cost estimating techniques for bridge projects. To mitigate the difficulties in the traditional preliminary cost estimating methods, there is a requirement to develop a new initial cost estimating model which is accurate, user friendly and straightforward. The research was carried out in Sri Lanka, and this paper aims to develop the artificial neural network (ANN) model for an early cost estimate of concrete bridge systems.

The construction cost data of 30 concrete bridge projects which are in Sri Lanka constructed within the past ten years were trained and tested to develop an ANN cost model. Backpropagation technique was used to identify the number of hidden layers, iteration and momentum for optimum neural network architectures.

An ANN cost model was developed, furnishing the best result since it succeeded with around 90% validation accuracy. It created a cost estimation model for the public sector as an accurate, heuristic, flexible and efficient technique.

The research contributes to the current body of knowledge by providing the most accurate early-stage cost estimate for the concrete bridge systems in Sri Lanka. In addition, the research findings would be helpful for stakeholders and policymakers to propose policy recommendations that positively influence the prediction of the most accurate cost estimate for concrete bridge construction projects in Sri Lanka and other developing countries.

Pre‐stressing. SURFACE EFFECTS Controlled Pre‐Stressing is the impingement on a surface of relatively small spherical particles of steel, glass or ceramic. These particles on impact, yield the skin and deform the surface plastically, leaving a residual compressive stress. The magnitude of that stress varies with the material being treated and the kinetic energy on impact.

The purpose of this paper is to investigate the use of embedded Shape Memory Alloy (SMA) nitinol wire for the enhancement of vibration and damping characteristics of filament-wound fiber-reinforced plastic composite hollow shafts.

The plain Glass Fiber-Reinforced Plastic (GFRP) and plain Carbon Fiber-Reinforced Plastic (CFRP) hollow shafts were manufactured by filament winding technique. Experimental modal analysis was conducted for plain hollow shafts of C1045 steel, GFRP and CFRP by subjecting them to flexural vibrations as per ASTM standard C747, with both ends clamped (C-C) end condition to investigate their vibration and damping behavior in terms of first natural frequency, damping time and damping ratio. Nitinol wires pre-stressed at various pre-strains (2, 4 and 6 per cent) were embedded with CFRP hollow shafts following same manufacturing technique, and similar experimental modal analysis was carried out by activating nitinol wires. The first natural frequencies of all the shaft materials were also predicted theoretically and compared with experimental measurements.

Among the three materials C1045 steel, plain GFRP and plain CFRP, the vibration and damping behavior were found to be the best for plain CFRP. Hence, CFRP shafts were considered for further improvement by embedding nitinol wires at pre-stressed condition. For CFRP shafts embedded with nitinol wires, the damping time decreased; and damping ratio and first natural frequency increased with increase in percentage of pre-strain. In comparison with plain CFRP, 7 per cent increase in first natural frequency and 100 per cent increase in damping ratio were observed for nitinol embedded CFRP shafts with 6 per cent pre-strain. Theoretical predictions of the first natural frequencies agree well with the experimental results for all the shaft materials.

The effect of nitinol on vibration and damping characteristics of filament wound hollow CFRP composite shafts with different pre-strains has not been studied extensively by the previous researchers. This paper addresses the effect of embedded nitinol wires pre-stressed at three varied pre-strains, that is, 2, 4 and 6 per cent on the vibration and damping characteristics of composite hollow CFRP shafts manufactured by filament winding technique.

In the construction of this engineering feat by the North of Scotland Hydro‐Electric Board, pre‐stressed concrete was used employing the Lee McCall post‐tensioning system. The basic idea being to anchor the dam to the foundation rock by means of groups of high tensile steel rods.

This paper is devoted to the theoretical and numerical study of a new topological sensitivity concerning the insertion of a small bolt connecting two parts in a mechanical structure. First, an idealized model of bolt is proposed which relies on a non-local interaction between the two ends of the bolt (head and threads) and possibly featuring a pre-stressed state. Second, a formula for the topological sensitivity of such an idealized bolt is rigorously derived for a large class of objective functions. Third, numerical tests are performed in 2D and 3D to assess the efficiency of the bolt topological sensitivity in the case of no pre-stress. In particular, the placement of bolts (acting then as springs) is coupled to the further optimization of their location and to the shape and topology of the structure for volume minimization under compliance constraint.

The methodology relies on the adjoint method and the variational formulation of the linearized elasticity equations in order to establish the topological sensitivity.

The numerical results prove the influence of the number and locations of the bolts which strongly influence the final optimized design of the structure.

This paper is the first one to study the topology optimization of bolted systems without a fixed prescribed number of bolts.

The type 9271A measuring platform is based on a two component annular cell mounted highly pre‐stressed between the base and the cover plate. It measures axial compression forces up to 2,000kgf and tensile forces up to 500kgf as well as torques about this axis up to 1,000kgf/cm. The use of quartz gives a rigid transducer with small deflections. Approximate price is £435. Delivery: ex stock.

Admixtures are materials that are added to concrete at some stage in its production to give concrete new properties whether in fluid or plastic conditions. The admixtures used in the construction industry are broadly classified into Mineral and Chemical admixtures. In recent years, the use of mineral and chemical admixtures in producing high performance concrete has increased significantly. The chemical reaction of cement with admixtures differs from material to material. Calcium nitrite based corrosion inhibiting admixtures have gained popularity for protection of reinforced and pre‐stressed concrete structures but calcium nitrite is not commercialized indigenously in India due to manufacturing difficulties. Hence, the objective of the present investigation was to study a novel corrosion inhibiting admixture system and to compare its effectiveness with sodium nitrite.

Di‐sodium phthalate, sodium orthophosphate and sodium nitrite‐based corrosion inhibiting admixtures were selected for the present investigation. The critical quantities of corrosion inhibiting additives were determined by accelerated laboratory tests. The following types of tests were conducted to evaluate the efficiency of the corrosion inhibiting admixtures: compressive strength of 100 × 100 × 100 mm concrete cubes after 3,7,14 and 28 days of curing, linear polarization resistance measurements, electrochemical impedance spectroscopy measurements, an accelerated 12 V controlled potential test.

From the above tests, the inhibitor admixtured concrete not only improved in compressive strength but also increased its corrosion resistance properties. Of the inhibitors studied, di‐sodium phthalate showed superior corrosion resistance properties, compared to sodium nitrite.

Di‐sodium phthalate may be considered a better substitute for calcium nitrite‐based corrosion inhibiting admixtures for durable concrete structures. This fulfils the objective of the investigation.

Concrete is the most basic of building materials and yet, in the hands of the expert, is capable of providing strength, durability and even elegance far in excess of many of its manufactured competitors. The technology is by now well established but the production of concrete of a consistently good quality is by no means simple.