Applied Mechanics and Materials Vol. 897

Abstract: A railway bridge over several decades will be degraded due to localized corrosion. As a result, the load capacity of the bridge decreases, especially under the live load caused by trains. This paper examines the residual load capacity of a bridge deteriorated by localized corrosion by using the multibody dynamics approach. This approach allows an accurate description of the interaction between trains and bridges. At the same time, it allows the formation of corrosion marks on each structural member of the bridge in a numerical model precisely based on actual measured data. In order to describe accurately the remaining load of the bridge under the moving load of the train, a dynamic testing and finite element modeling of a steel bridge are conducted and compared. At the same time, the results are also compared with the simulation results of the bridge model before being corroded. In addition, the paper also tests the reliability of the numerical model for assessments of similar bridges without actual measurement results that are costly and time-consuming.

Abstract: Interlocking Concrete Block Pavement (ICBP) poses as the most suitable alternative to traditional pavement construction techniques. This is because of the increased advantages in countries wherein durability, and operational or environmental constraints limit the efficiency of the conventional process. The construction industry everywhere faces problems and significant challenges including manpower, quality of productivity, preservation of the environment, mass transportation, water management, raw materials, durability and design life of construction products, chemical resistance, etc. The increased expense on the raw materials for construction is the primary focus of the study. The study aims to search for suitable alternatives that would allow sustainable development. The study emphasizes on the rising costs of construction materials and the necessity to work towards sustainability, alternative construction techniques and materials. Indigenous production of interlocks with mineral admixtures raises the potential applicability of the interlock pavers. To enhance the strength property and keeping sustainability in point of view, fly ash is used as a mineral admixture and partially replaced with cement in various proportions like 0%, 5%, 10%, 15%, 20%, 25%, 30% and 35%. Fourty eight interlock concrete paver blocks were cast and compressive strength for all specimens was calculated and later compared. A notable rise in the strength of the interlock pavers was observed at 15% and 20% replacement levels with fly ash. The optimum level for replacement was determined as 20% of the fly ash.

Abstract: The present study investigated the air permeability of three representative sportswear brands products (OUDIKE, NIKE and an unknown brand bought from the boutique) in Hong Kong marketplace. It was found that NIKE sportswear had the highest air permeability (0.23kPa*s/m) among the samples, which indicates that it allows more air flow passing through the textile and provides good comfort property to wearer, while OUDIKE samples showed the lowest air permeability in capacity (0.08kPa*s/m). The fiber content and fabric structure may be the reason that affects the air permeability. This study would provide a comparative information about air permeability property of the mainstream sportswear brands product in Hong Kong market.

Abstract: This study evaluated the cooling properties of summer cooling towels of different brands by analyzing the moisture management behavior. It was found that all the samples could provide a cooling effect at first contact after being wetted. The samples of Cooldyxm and Ice Towel showed the highest cooling effect followed by the N-rit samples, which was regarded as “fast absorbing and quick drying fabric, whereas Perfect Fitness samples had the poorest cooling effect and was labeled as “slow absorbing and slow drying fabric”. The reason may be explained by the yarn density, fabric structure and thickness.

Abstract: This study evaluated the quick dry properties of summer men’s sportswear T-shirts of different brands (Nike, Adidas, Laishilong and Columbia) by studying the water vapor transmission behavior. The results indicate that Laishilong was the best sample in terms of water vapor transmission rate, whereas Columbia was the poorest. Moreover, samples of Nike, Adidas, Laishilong and Columbia, had similar water vapor transmission rate. This implies that they had comparatively similar performance in water vapor permeability.

Abstract: To investigate the effects of different temperatures for heat treatment of custom-made NiTi closed coil springs. NiTi closed coil springs (50.8% Ni-49.2%Ti) were manually fabricated around a 0.9mm diameter mandrel and heat treated at temperatures of 400°C, 450°C, and 500°C for 20 minutes. The outer diameter of each specimen was measured to determine the effect of heat treatment temperature on spring geometry. Tensile tests were carried out to measure the force levels at 3, 6, 9, and 12 mm of spring extension. Non-parametric statistical analyses were done to assess and compare the effects of different temperatures of heat treatment on the custom-made orthodontic closed coil springs. Heat treatment at lower temperatures produced larger outer coil diameters than at higher temperatures. Raising the temperature of heat treatment produced significant increases in force levels by 13-18 g especially between 400°C and 500°C at spring extensions of 3, 6 and 9 mm. The highest superelastic ratio of 5.44 was found in the NiTi coil springs that were heat treatment at 500°C for 20 minutes which signifies superelastic tendencies. The mechanical properties of NiTi closed coil springs are influenced by the temperature of heat treatment. The NiTi closed coil springs that were heat treated at 500°C for 20 minutes produce appropriate force levels to display a superelastic tendency for orthodontic use.

Abstract: An experimental program was directed in this study to evaluate the abrasion resistance of reactive powder concrete (RPC) under direct normal impact of water jet. Abrasion and compressive strength specimens were cast from six RPC mixtures using different single and hybrid distributions of 6 mm-length and 15 mm-length micros-steel fibers and 18 mm-length polypropylene fiber. Fixed mix proportions were used for the six RPC mixtures and with fixed total volumetric fiber content of 2.5%. In addition to the RPC mixtures, a normal concrete mixture was prepared for comparison purposes. All specimens were cured in the same conditions and tested at an age of 28 days. The test results showed that abrasion weight losses increase with time at rates that are independent of fiber type and fiber distribution. The results also showed that all RPC mixtures exhibited significantly lower abrasion losses than normal concrete. The lowest percentage abrasion weight losses were recorded for the mixture with pure 15 mm micro-steel, where after 12 testing hours, it was 0.41% of the total weight before testing. On the other hand, the mixture with pure 6 mm micro-steel fiber exhibited the highest percentage abrasion weight loss (0.98%) among the six RPC mixtures. Another conclusion is that the inclusion of polypropylene fiber to compose hybrid fiber distribution with micro-steel fiber led mostly to lower abrasion losses.

Abstract: The impact resistance of micro-steel fiber-reinforced and hybrid fiber-reinforced reactive powder concrete is investigated in this study. Six groups of specimens were prepared with 2.5% volumetric contents of different combinations of fibers. For this purpose, micro-steel fibers with 6 and 15 mm length in addition to polypropylene fibers were used. Each group includes 12 identical specimens. The impact tests were conducted using the repeated drop-weight impact test of ACI 544-2R. However, higher drop-height (700 mm) and drop-weight (10 kg) were adopted to accelerate the failure and reduce the effort required to crack the specimens. The test results showed that the use of only 15 mm micro-steel fiber led to much higher impact resistance than other micro-steel fiber combinations. The recorded number of blows for the group with SF15 was 247, while those of SF6 and combined SF6 and SF15 were 127 and 112, respectively. The replacement of 0.5% of micro-steel fiber by 0.5% of PP fiber was found to reduce the impact resistance regardless of the type or combination of the used micro-steel fiber.

Abstract: The adhesion strength of plasma-sprayed ceramic coatings was studied. Alumina powder was used for plasma spraying. A titanium oxide Nano powder with a particle size of 40-50 [nm] was used as a modifier. The optimal conditions of plasma spraying of coatings are established. The adhesion strength was used as an optimization criterion. Coating adhesion was determined by tensile adhesion testing. A mathematical model is obtained that allows one to determine the effect of spraying conditions (lens current, arc current, and the position of the solenoid relative to the nozzle) on the adhesion strength.