Key Engineering Materials Vols. 385-387

Abstract: It is known that the properties of asphalt-aggregate adhesion show great effect on the performance of asphalt pavement, while the temperature plays an important role in determining the fundamental properties of asphalt binder between single aggregate-aggregate contacts surfaces. The temperature sensitivity is considered to be very important on understanding the failures of asphalt pavement, especially on the asphalt-aggregate adhesion. Knowledge the temperature sensitivity of asphalt-aggregate adhesion is very important in asphalt mixture design. The purpose of this paper was to quantify the effect of temperature on the adhesion and cohesion of asphalt film between aggregate and asphalt. The adhesive/cohesive failure of asphalt film between single aggregate-aggregate contacts was investigated using dynamic mechanical analyzer under dynamic tension stress test with force-control mode, then fracture surface were analysis by a Polarizing Microscope. Contrastive experiments were conducted on SBS modified asphalt under different temperatures. Experimental results indicate that the area percentage of adhesive failure was decreased with the increase of test temperature. And the adhesive failure percentage is enhancing with the increase of loading max-stress level.

Abstract: The anchoring energy of Liquid Crystals (LCs) is influenced by several parameters. Many scientists have exploited LCs anchoring in order to develop several LC based optical sensors. This paper proposes and proves a new principle of operation for corrosion sensing based on the anchoring energy of liquid crystals. For the work of this paper 5CB (4-cyano-4-n-pentylbiphenyl) nematic LCs were used to coat iron substrates forming films of about 7µm thickness. Both corroded and non-corroded iron substrates were coated and the differences in LC anchoring between the two substrates are reported. These differences were studied experimentally using the atomic force microscope (AFM) and the laser profilometer.

Abstract: Asphalt ageing induced by heat, oxidation and ultraviolet (UV) radiation was investigated using various laboratory simulation ageing methods and outdoor ageing. One normal 70 penetration asphalt and its styrene-butadiene-styrene (SBS) modified asphalt were employed to assess the changes in chemical and rheological properties by infrared spectroscopy and dynamic shear rheometer under various ageing conditions, thus the relationship among rolling thin-film oven(RTFO), pressurized ageing vessel (PAV) and UV radiation ageing was distinguished. Experimental results showed that photodegradation caused by outdoor exposure UV ageing of 50~200µm thin films for a month, was found to be the most severe, following by PAV and then RTFO with respects to rehological and chemical changes. Photodegradation effect decreased as the thickness of asphalt film increases. Dynamic shear tests indicated that polymer networks were gradually destroyed during ageing, but the aged SBS modified asphalts still displayed better rheological properties than the corresponding base asphalt. The weight percent of oxygen as carbonyl increased and of SBS as butadiene decreased after ageing based on infrared spectrums. However, chemical and rheological changes were not generally consistent, and ageing susceptibility may be ranked differently when different evaluation methods were used.

Abstract: The research work behind this paper focused a rather extensive assessment of hybrid composites made of pure aluminium sheets, alternating with GFRP and CFRP layers. Static, fatigue and low velocity impact tests were performed, combined with NDI on damaged samples, using Lockin thermography, on specimens obtained from the two hybrid laminates and from genuine GFRP and CFRP laminates, all having five layers. The static and fatigue tests were made on parallel specimens, un-notched and having a central 5 mm drilled hole, with various failure modes. The low velocity impact tests were followed by CAI tests, meant to evaluate residual mechanical performance and damage tolerance. Lockin thermography was used for prior assessment of damage.

Abstract: The major objective of this research was to evaluate the tensile and fracture properties of micro-surfacing, which as a preventive maintenance surface treatment on asphalt pavement, that formed the basis for the ISSA recommendation of an optimum micro-surfacing design incorporating crumb rubber. The research involved a full-factorial experiment with different rubber contents (0, 2 and 5%) and different polymer modified asphalt emulsion contents ranged from 10 to 13% by total weight of crushed aggregate in micro-surfacing. Fracture and indirect tension tests were performed on micro-surfacing beams and Marshall test samples, respectively, at two different test temperatures of 25 and -10°C. The variables studied were indirect tensile strength, peak center-point load carried, and load-point displacement. The results show that higher mean values of indirect tensile strength were obtained corresponding to the highest modified asphalt emulsion content (13%), irrespective of rubber contents, particularly at lower temperatures. A statistical analysis of the test results reveals that there are no significant differences among the means of most of the variables studied corresponding to different rubber contents. However, the differences are significant for different asphalt emulsion contents.

Abstract: According to three-point bending test, this paper explores the influence of low temperature on the flexural strength, the tensile strain and bending stiffness modulus of the aged Stone Mastic Asphalt (SMA-13) concrete. The asphalt mixtures are aged according to the short-term aging (at 135°C, 4 hours), and long-term aging (asphalt concrete at 85°C, 120 hours) and natural aging (3 months, 6 months and 9 months). The result shows that, with the same loading rate, the tensile strain of specimens at -30°C are smaller than those at -10°C; but when temperature is certain, the tensile strain of specimens lager than those of aged specimens. The longer the aging time lasts, the more flexural strength differences between high and low temperatures can be found. A pretty well index variation can be found between the tensile strain and temperature. The same trend also appears between the bending stiffness modulus and temperature of SMA-13 asphalt concrete.

Abstract: A translucent amido modified microemulsion was synthesized by the adding of amido silane coupling agent. Transmission electron microscope (TEM), Fourier Transform Infrared Spectra (FT-IR), Photon Correlation Spectroscopy (PCS) were used to characterize the structures and properties of amido microemulsion, respectively. IR spectroscopy confirmed that amido group was successfully introduced into the polysiloxane microemulsion. TEM images indicated that the granules agglomerated heavily when the coupling agent was in a larger content. The effects of PH values, amount of coupling agent on the size and the configuration of the amido microemulsion were investigated. The results indicated that the properties of amido microemulsion were stable when the microemulsion was under weak acid condition (pH=3-7). When the amount of coupling agent increased, the particles size of microemulsion increased and the particle size distribution became narrow.

Abstract: The high temperature deformation behavior and flow instabilities of Ni-Fe-Co base superalloy, INCONEL alloy 783 during hot working process were investigated with process maps consisting of a power dissipation of dynamic materials model (DMM) and various flow instability criteria. In order to establish the processing map of INCONEL alloy 783, hot compression tests were carried out under different temperature and strain rate conditions, with true strain up to 0.7. On the basis of the comparison between processing maps and microstructural analysis, the reliability of various flow instability criteria was estimated. Finally the useful instability criterion for predicting the forming defects was suggested through the compression test results and experimental observations of actual ring rolling process of INCONEL alloy 783.

Abstract: The effects of martensitic transformation on the coaxing behavior were studied in austenitic stainless steels. The materials used were austenitic stainless steels, type 304 and 316. Conventional fatigue tests and stress-incremental fatigue tests were performed using specimens subjected to several tensile prestrains from 5% to 60%. Under conventional tests, the fatigue strengths of both steels increased with increasing prestrain. Under stress-incremental tests, 304 steel showed a marked coaxing effect, where the failure stress significantly increased irrespective of prestrain level. On the other hand, the coaxing effect in 316 steel decreased with increasing prestrain up to 15%, where the failure stresses were nearly the same. Above this prestrain level, the coaxing effect increased with increasing prestrain. In 304 steel, the coaxing effect is primarily dominated by work hardening at low prestrains, while the effect of strain-induced martensitic transformation increases with increasing prestrain. The coaxing effect in 316 steel is dominated by both work hardening and strain aging at low prestrains, but strain-induced martensitic transformation could play a significant role at high prestrains.

Abstract: Characteristics of deformation-induced transformation (DIT) in the refractory low alloy steel 2.25Cr1Mo were experimentally studied. Effect of different controlled-rolling and controlled-cooling process on the steel microstructure and mechanical properties were investigated and the mechanism was discussed. Results show that the grain size and the ferrite volume fraction were obviously affected by the rolling and cooling processes. Proper DIT technique may significantly accelerate the transformation of austenite to ferrite in the steel and improve the steel strength.