Key Engineering Materials Vol. 904

Abstract: The present study evaluated the engineering properties and microstructure of an alternative binder composed of calcium carbide residue and silica fume. The cementitious mechanisms of this alternative binder based on the pozzolanic reaction in raw materials. The ratio of calcium carbide residue and silica fume was decided based on the chemical composition of raw materials and their chemical reaction. The calcium carbide residue-silica fume mortar was prepared and tested for its compressive strength at several curing periods, with results then compared to conventional mortar made with ordinary Portland cement. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the microstructure of hardened mortars. The test results suggest that the compressive strength of calcium carbide residue-silica fume mortar continuously developed throughout the curing period. The relative compressive strength of calcium carbide residue-silica fume mortar reached 72.78% of the ordinary Portland cement mortar strength at 28 days curing age.

Abstract: Adding 0, 20, and 50 wt% natural-rubber latex compound into the plaster ceiling matrix affected to increase the physical-mechanical-thermal performance properties of plaster ceiling composites. Adding 50 wt% natural rubber latex compound into plaster composites can increase the superior adhesion of the nail-tensile resistance equal to 57.54 N and decrease thermal conductivity equal to 0.0634 W/m.K. In addition, adding natural rubber latex compounds into plaster composites can reduce water solubility, brittleness, impact, and cost of energy consumption due to the exterior temperature. Adequate thermal insulation for roofing, ceiling, and wall systems also reduces radiative losses that chill occupants in cold weather, and reduce interior surface temperatures in the summer, thereby optimizing the comfort of building occupants. The mechanical and thermal properties of plaster composites were investigated by using a Universal Testing Machine (UTM) and heat flow meter, respectively, measured according to TIS 1211-50, TIS 219-2522, and ASTM C518.

Abstract: Ongoing studies show that an effective demand for using natural fibers as a substitution of an artificial fiber in fiber-reinforced composites formation has increased their applicability in an industrial area worldwide. The hydrophobic nature of natural fiber makes week adhesion among the cellulose fiber and matrix components; these problems are usually encountered in fiber-reinforced composites production. To overcome such a limitation of a cellulose fiber, specific physical and chemical treatment strategies were advised by researchers around the world for surface modification of natural cellulose fibers. One of the most basic and efficient surface modification approaches adopted today by the researchers was alkali treatment, widely used in natural fiber composites formation. This technique effectively improved the Mechanical property of natural cellulose fiber, such as tensile strength and flexural properties, while the impact strength result was reduced.

Abstract: The self-consolidating concrete (SCC) become the material of choice by concrete industry due to its superior properties. However, these properties need to be verified under hot weather conditions. The paper investigates the behavior of SCC under hot weather. Six SCC mixtures were prepared under high temperatures. The SCC mixtures incorporated polycarboxylate admixture at different dosages and prolonged mixed for up to 2 hours at 30 °C and 40 °C. The cement paste was replaced with 20% of fly ash (FA). The fresh properties were investigated using slump flow, T₅₀, and VSI tests. The compressive strength was measured at 3, 7, and 28 days. The durability of SCC mixtures was evaluated by conducting rapid chloride penetration and water absorption tests.

Abstract: The work deals with the detection of presence of RAP (reclaimed asphalt pavement) in asphalt mixtures. Information about the presence of RAP in an asphalt layer can be technically advantageous, for example, when planning further recycling of the layer. The method described in the paper can also be used to verify the success of a treatment of an aged binder in RAP, which is dosed in the production of new asphalt mixtures. The asphalt binder was obtained by a method of successive extraction from asphalt mixtures with different RAP content. Basic empirical tests of the asphalt binder (needle penetration and softening point) were chosen to detect the presence of RAP. The complex shear modulus G* was further determined on the extracted binders using a dynamic shear rheometer (DSR).

Abstract: The efforts embedded in this paper have been devoted to designing, preparing, and testing warm mix asphalt (WMA) mixtures and comparing their behavior against traditional hot mix asphalt mixtures. For WMA preparation, the Sasobit wax additive has been added to a 40/50 asphalt binder with a concentration of 3%. An experimental evaluation has been performed by conducting the Marshall together with volumetric properties, indirect tensile strength, and wheel tracking tests to acquire the tensile strength ratio (TSR), retained stability index (RSI), and rut depth. It was found that the gained benefit of reduction in mixing and compaction temperatures was reversely associated with a noticeable decline in Marshall properties and moisture susceptibility indices designated by TSR, and RSI, and even the rut resistance was adversely affected. Modification of WMA mixtures by 3% of Styrene-Butadiene-Styrene (SBS) polymer coupled with replacement of virgin ingredient by 50% of recycled asphalt concrete granted a 20% and 15% growth in Marshall stability and tensile strength, respectively. Moreover, both TSR and IRS indices have risen to 87% and 90%, respectively associated with a 39% increase in rutting resistance ability.

Abstract: The object of research is geometric models of the process of incremental forming of parts from sheet material. The subject of research is a graphical model for finding the optimal values of the parameters of the forming process based on multidimensional descriptive geometry. The author of the article discusses the main optimizing factors and process parameters. Particular attention was paid to the problems of constructing geometric models for determining the optimizing factors for incremental forming. The research method is a way of constructing a graphical optimization model of the process using the projection drawing of Radishchev for multidimensional space. Mathematical modeling was also applied to check the correctness of the obtained optimal parameters.

Abstract: This study dealt with the rotary draw bending method most used for tube bending and investigates how applied bending such as normal bending, using mandrels or pressing with booster have an effect on machining accuracy, focusing on dimensional defects due to springback and flat deformation to the transverse plane. The study used particle swarm optimization (PSO) algorithms to investigate the optimal machining conditions for improving the accuracy of dimension and shape of a bent part. The following findings were obtained: The springback during applied machining using a mandrel, or using a mandrel and booster together, is almost the same as during normal processing; The flattening near the center of the bend in applied processing using a mandrel, or a mandrel and booster together, decreases more than with normal processing at mandrel protrusion L ≥ 4 mm, and the maximum can be suppressed to approximately 0.15%; When the sum of the springback and the flattening is taken as the objective function and the minimum value is obtained, the optimal solution is around L = 7 mm.

Abstract: The dilution ratio of the Ni coating prepared by the laser cladding under the assistance of the follow-up feeding pulsed current was optimized by combining back propagation (BP) neural network and genetic algorithm. The model was trained according to the results of the 6-factor 3-level orthogonal experiments. A BP genetic neural network forecast model between cladding parameters (laser power, scanning speed, powder feeding rate, pulsed current, pulse frequency and pulse width) and dilution ratio of coating was constructed. On this basis, technological parameters under the target dilution ratio of the coating were optimized by a genetic algorithm. Results demonstrated that the predicted results of the model are very close to the experimental results in term of dilution ratio of the coating, with a relative error no higher than 2.63%. This demonstrates that the model is reliable and effective. The optimal technological parameters are gained when the dilution ratio of the coating is 17.5%, including laser power=1926.3 W, laser scanning speed =·s^-1, powder feeding rate= ·min^-1, average pulsed current =, pulse frequency=445.6 Hz, pulse width= 108.4 μs.

Abstract: Hard coatings applied by the Physical Vapor Deposition method often provide very good mechanical properties, especially when applied to metal parts that are mentioned to withstand certain level of wear. In this study, TiN coating combined with deep rolling were applied to the investigated steel samples, prepared by powder metallurgy and subjected to contact-fatigue stress. Computational analysis of stress states in samples by the finite element method helped to reveal the behavior and formation of fatigue failures when loading samples. The results, processed in the form of fatigue curves, probabilistic Weibull curves using metallography and electron microscopy, showed a positive effect of the used coatings and their combination with other surface treatments on the contact-fatigue strength of the examined samples. Microscopic study also showed the different mechanisms of crack formation and of crack propagation rate due to contact loading of material with a laser hardened surface, which has an obvious impact on material lifetime.