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•Characterization of 3D residual stress state of additively manufactured Ti-6Al-4V.•Energy dispersive diffraction validates additive manufacturing thermomechanical ...code.•Thermomechanical code predicts complex residual stress state in printed Ti-6Al-4V.
The production of metallic parts via laser-powder bed fusion (L-PBF) additive manufacturing is rapidly growing. To use components produced via L-PBF in safety-critical applications, a high degree of confidence is required in their quality. This qualification can be supported by means of a validated thermomechanical model capable of predicting the final residual stress state and subsequent performance. In this work, we use high-energy X-ray diffraction to determine a three-dimensional residual strain and stress state in a Ti-6Al-4V L-PBF component. The experimental results are used to provide validation of simulations, showing strong quantitative agreement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Here, we introduce molecular dynamics simulations of shock and release in micron-scale tantalum crystals that exhibit postbreakout temperatures far exceeding those expected under the standard ...assumption of isentropic release. We illustrate via an energy-budget analysis that this is due to plastic-work heating from material strength that largely counters thermoelastic cooling. The simulations are corroborated by experiments where the release temperatures of laser-shocked tantalum foils are deduced from their thermal strains via in situ x-ray diffraction and are found to be close to those behind the shock.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
We present molecular dynamics simulations of shock and release in micron-scale tantalum crystals that exhibit postbreakout temperatures far exceeding those expected under the standard assumption of ...isentropic release. We show via an energy-budget analysis that this is due to plastic-work heating from material strength that largely counters thermoelastic cooling. The simulations are corroborated by experiments where the release temperatures of laser-shocked tantalum foils are deduced from their thermal strains via in situ x-ray diffraction and are found to be close to those behind the shock.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Sudan has a great diversity of tree species and wood resources which are mainly used in furniture and tradition houses. However, the structural properties of these woods are not structurally ...classified which hinder use them by structural designers. Therefore, this paper aims to structurally classify some Sudanese timber species. Namely Sahab (Anogeissus leiocarpus), Heglieg (Balanites aegyptiaca), and Humeid (Seclerocarya birrea). Both physical properties and mechanical are tested using 540 test specimens from the three species and their characteristic strength was determined in accordance with BS EN 384 (2004). Based on the results, Sahab is structurally characterized as D27 hardwood, Heglieg is characterized as D45 hardwood, and Humeid is characterized as C14 softwood as per BS EN 338:2004 strength classes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The ongoing COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed an extraordinary threat to global public health, wealth, and well-being. As the carriers ...of human life and production, infrastructures need to be upgraded to mitigate and prevent the spread of viral diseases. Developing multifunctional/smart civil engineering materials to fight viruses is a promising approach to achieving this goal. In this Perspective, a basic introduction on viruses and their structure is provided. Then, the current design principles of antiviral materials and structures are examined. Subsequently, the possibility of developing active/passive antiviral civil engineering materials (including cementitious composites, ceramics, polymers, and coatings) is proposed and envisioned. Finally, future research needs and potential challenges to develop antiviral civil engineering materials are put forward. The proposed strategies to develop multifunctional/smart antiviral civil engineering materials will aid in the construction of smart infrastructures to prevent the spread of viruses, thus improving human life and health as well as the sustainability of human society.
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IJS, KILJ, NUK, PNG, UL, UM
A one-port coaxial/cylindrical transition line is considered for the broadband complex permittivity measurement of civil engineering materials. Cylindrical samples of heterogeneous material with ...large aggregate dimensions (up to 25 mm) can be measured over a frequency range from 50 MHz to 1.6 GHz. The choice of this line technology results in the simplification of the sample machining and enhancement in the high frequency limit, in comparison to the classical coaxial line technology. From a mode-matching technique, the relation between the material complex permittivity and the reflection coefficient at the coaxial/cylindrical transition is obtained including axisymmetric higher order modes excited at the transition. Once the line is calibrated using a specific calibration kit, complex permittivities are retrieved from an iterative optimization procedure. Preliminary results obtained for a set of bituminous concrete samples with different porosities and natures of rock aggregates are shown.
For the limitation of single-component superplasticizer, condensate-type and copolymer-type combined superplasticizers were prepared. The adsorption of compound superplasticizers on cement paste was ...tested by Total Organic Carbon (TOC) measurement. Influences of superplasticizers on early hydration process of cement and Organo-mineral phase formation were studied by X-Ray Diffraction Analysis (XRD), Scanning Electron Microscope analysis (SEM) and so on. The results show that owing to the electrostatic repulsion and steric effect cooperative mechanism, condensate-type and copolymer-type combined superplasticizers reduce the superplasticizers adsorption in cement minerals and its hydration products surface, delay the process of hydration of C3A, form Organic-Layered double hydroxides (LDH), increase the early chemical shrinkage and promote the growth of cement early hydration and Ettringite
Study on the compressive strength, shrinkage and effect of aluminum insertion materials on the hydration products of Autoclaved Aerated Concrete (AAC). The types and properties of hydration products ...are studied by X-Ray Diffraction Analysis (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscope analysis (SEM) and so on. The results showed that the strength and the shrinkage resistance capability of the product could be improved effectively. Al3+successfully doped into C-S-H gel and tobermorite crystals, then replaced si4+of tobermorite and formed the system of C-A-S-H. Tobermorite in aluminum insertion aerated concrete is smaller and more compact. All hydration products interlace to form a whole, then the structure turns denser. Low porosity, high crystal gel volume ratio and high hydration degree are the key of the high strength aluminum insertion aerated concrete. Aluminum insertion materials improve the performance of the products.
A moment tensor inversion (MTI) code originally developed to compute source mechanisms from mining-induced seismicity data is now being used in the laboratory in a civil engineering research ...environment. Quantitative seismology methods designed for geological environments are being tested with the aim of developing techniques to assess and monitor fracture processes in structural concrete members such as bridge girders. In this paper, we highlight aspects of the MTI_Toolbox programme that make it applicable to performing inversions on acoustic emission (AE) data recorded by networks of uniaxial sensors. The influence of the configuration of a seismic network on the conditioning of the least-squares system and subsequent moment tensor results for a real, 3-D network are compared to a hypothetical 2-D version of the same network. This comparative analysis is undertaken for different cases: for networks consisting entirely of triaxial or uniaxial sensors; for both P and S-waves, and for P-waves only. The aim is to guide the optimal design of sensor configurations where only uniaxial sensors can be installed. Finally, the findings of recent laboratory experiments where the MTI_Toolbox has been applied to a concrete beam test are presented and discussed.
•We present a novel application of a moment tensor inversion code (MTI_Toolbox).•The MTI_Toolbox was designed for mining-induced seismicity for uniaxial measurements.•We explore and explain the novel hybrid MTI option available in the MTI_Toolbox in detail.•We propose to use the so-called condition number as a measure of accuracy for a result.•We apply and evaluate the MTI_Toolbox to a concrete beam fracture experiment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Offers quantity surveyors, engineers, building surveyors and contractors clear guidance on how to recognise and avoid measurement risk. The book recognises the interrelationship of measurement with ...complex contractual issues; emphasises the role of measurement in the entirety of the contracting process; and helps to widen the accessibility of measurement beyond the province of the professional quantity surveyor. For the busy practitioner, the book includes: Detailed coverage of NRM1 and NRM2, CESMM4, Manual of Contract Documents for Highway Works and POM(I) Comparison of NRM2 with SMM7 Detailed analysis of changes from CESMM3 to CESMM4 Coverage of the measurement implications of major main and sub-contract conditions (JCT, NEC3, Infrastructure Conditions and FIDIC) Definitions of 5D BIM and exploration of BIM measurement protocols Considerations of the measurement risk implications of both formal and informal tender documentation and common methods of procurement An identification of pre- and post-contract measurement risk issues Coverage of measurement risk in claims and final accounts Detailed worked examples and explanations of computer-based measurement using a variety of industry-standard software packages.
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