Key Engineering Materials Vol. 667

Abstract: In this paper, the birch flour was the raw material with its particle size less than 100μm and the polyester hot-melt adhesive was used as binder with its particle size less than 60μm. The birch flour was dried using high speed mixer with heating function. The birch flour/polyester composite were prepared using the physical mixing method. The surface of the specimen and fracture surface of specimen were analyzed through the micrographs of scanning electron microscopy. In order to study the characteristics of laser sintering, the preheating temperature of the powder bed of laser sintering machine and the processing parameters of the birch flour/polyester composite were determined using single layer sintering method and empirical method. The tensile, flexural and impact specimens were built in the two scanning laser ways of subarea scan and progressive scan. The testing results show that the mechanical properties using subarea scan method are superior to those of progressive scan method and the mechanical properties of the specimens increase as the laser scan speed decreases. The best mechanical properties of SLS specimens of brich flour/polyester composite powder were obtained with the following parameters: the laser power was 11W, layer scan speed was 1800mm/s; layer thickness was 0.1mm; laser scan spacing was 0.1mm and the average tensile, flexural and impact strength of specimens were 1.35MPa, 3.69Mpa and 0.73KJ/m2 respectively.

Abstract: Bamboo flour is a kind of a cheap reproducible natural plant powder. The polyamide hot melt adhesive (polyamide) is good bamboo adhesives. The bamboo flour/polyamide blend is prepared through mechanical mixing method. The powder bed preheating temperature of the laser sintering processing and the processing parameters of bamboo flour/polyamide blend are determined through the differential scanning calorimetry method (DSC method) and single layer sintering experiment. The mechanical testing parts are successfully fabricated by selective laser sintering using the bamboo flour/polyamide blend of 25/75 (wt/wt). In this series of experiments, the average tensile strength, flexural strength and impact strength of 5.9Mpa、11.5Mpa and 4.5KJ/m² are obtained when the laser power is 11W, scan spacing is 0.1mm, the thickness of a layer is 0.1mm and scanning speed is 2000mm/s. The tensile strength and flexural strength of the SLS specimens are improved through wax infiltrating process, while the average impact strength of the wax-infiltrated specimens decreases compared with the SLS specimens processed under the same set of parameters. Bamboo flour/polyamide composite powder is new laser sintering with good forming property and low cost.

Abstract: Elgiloy is a cobalt-based alloy with excellent physical and chemical performance, which is used widely in medical and industrial applications. In this paper, the professional finite element analysis software for metal cutting is used to establish the finite element simulation model of micro cutting this kind of cobalt-based alloy, and the effect of feed rate, which is considered as the most important processing parameter, on the cutting force of micro cutting Elgiloy is analyzed. The cutting force measurement system based on ultra-precision micro milling machine tool is established for experimental study on the cutting force of micro milling Elgiloy by using ultra-fine gain tungsten carbide micro milling tool. The cutting force is measured with different feed rate parameters and the influence of the parameters on the cutting force is analyzed. The simulation and experimental results show that the trends observed at the micro scale are the same as the trends for machining at the macro scale, which implies that the Elgiloy material behaves in a similar manner at both length scales.

Abstract: In order to study the pavement performance of the soil that improved by ionic liquid soil stabilizer, the red-brown clay was concerned as the typical soil, mixed with the ionic soil stabilizer, the ordinary Portland cement and the hydrated lime, was tested to characterize its durability. The engineering classification of the typical soil was determined and the physical parameters of the ionic soil stabilizer was obtained, according to tests of the particle size analysis, crucial water content coefficient, organic matter content, PH, conductivity, plasma emission spectra, etc. In addition, the tensile strength, durability and shrinkage property were analyzed by split tests, freezing and thawing tests, fatigue tests and shrinkage tests. As a result, the typical soil was a kind of low liquid-limit clay, denoted by CL. The ionic soil stabilizer was a water soluble, high conductivity, strongly acidic sulfonated oleoresin. The ion exchange reaction between the soil and the ionic soil stabilizer begun after treating by the ionic soil stabilizer, and then the role of soil particles became stronger. Furthermore, the void between soil particles was decreased, the structure became closer, and then the tensile strength, durability and shrinkage property were improved. As mentioned above, the research provided theoretical foundation and practical support for using the ionic soil stabilizer in China's highway construction.

Abstract: To explore the ionic liquid soil stabilizer improved soil mechanical properties, this experiment conducted liquid-plastic limit test and compaction test. On the basis of determining the optimal dosage of ionic soil stabilizer and mastering different mixture optimum moisture content and maximum dry density, the standard sample which consists of the Zhejiang red-brown clay and curing material including ionic soil stabilizer, cement and lime carried out the unconfined compressive strength test in different curing age and compaction degree. This paper analyzed the change reason of compaction and curing age about the stabilized soil. The results show that the ionic soil stabilizer has a significant effect on the compressive strength improvement of stabilized soil. Compared stabilized soil with traditional treatment soil, the compressive strength of stabilized soil has improved obviously with the increase of curing age and compaction degree. Research findings provide useful technical support and practice basis for promoting and applying ionic soil stabilizer in infrastructure construction.

Abstract: Asphalt mixtures have a highly sensitive and dependent on temperature. The typical modulus values of asphalt mixtures vary dramatically at different temperatures. Therefore, adjusting the modulus values of asphalt pavements of different testing temperatures to that of the criterion temperature condition is an important task to sustain asphalt mixtures modulus based the structural bearing capacity estimation of asphalt pavements comparable between time and space. According to the dynamic finite element numerical analysis method and the multivariate nonlinear regression analysis technique, the paper firstly established the back calculation model of asphalt mixtures modulus in term of the relationship between asphalt moduli and deflection basin parameters. Secondly, considering the correlation between the temperature at the middle of asphalt wearing course and the asphalt mixture modulus, the conversion analysis procedure of asphalt mixtures moduli of different temperatures was presented based on BELLS3 temperature adjustment coefficient method. Finally, the in-service monitoring over the existing pavements was conducted to test the validity of the procedure. The research provides a practical basis for evaluating pavement performance of asphalt wearing mixtures and a theory support for overlaying thickness design of asphalt pavements.

Abstract: This paper conducted the EN-1 ionic liquid improved soil comparison and evaluation between the stabilization soil and the stabilized aggregate materials in order to analyze its economic cost and solve the issues of road base material selection with the multiple influence factors. Firstly analytic hierarchy process (AHP) was used to establish the hierarchical structure of the decision index and the weight of each indicator in an index layer. Secondly the fuzzy relation matrix of the evaluation criteria were determined by expert evaluation method, and then a comprehensive fuzzy evaluation model can be established for the selection of road base materials. Finally, based on the comprehensive sequencing of different materials derived from fuzzy mathematical calculations, the optimal selection can be achieved. The proposed evaluation model comprehended the availability of material, construction requirements, load capacity, durability, energy consumption, environment protection and material cost etc. This research provided a theoretical basis as well as an effective and practical solution for the future development of highway construction in China.

Abstract: In the areas of South China, the asphalt pavement will appear various forms of water damages under the condition of vehicle loads and humid rainy environment. The interface of between aggregate and asphalt is the weaknesses position of the mixture internal structure, which will impose a significant influence on the service life of asphalt mixtures. However, the existing mesomechanics models of asphalt mixtures are almost based on the three-phase composite materials (asphalt mortar, aggregate, void) and have no enough consideration for the actual mechanics characteristics of the weak interface. It is no doubt that the effectiveness of the numerical simulation results will face a great challenge. The main purposes of this paper is to analyze and summary the relative basic characteristics of asphalt-aggregate interface including interface contact behavior, microstructure characterization methods, interface damage features and the macro-micro quantitative evaluation method of the interface damage The results show that the existing mechanical model ignores the asphalt-aggregate interface imperfect bonding, which make the asphalt-aggregate interface mechanical properties difficult to be perceived. Therefore, establishing a more rational micromechanical analysis model to predict asphalt macroscopic mechanical properties of asphalt mixtures will certainly be an urgent task and will provide a theoretical and scientific support for the optimization of asphalt mixture design.

Abstract: Based on the assumption of thin plate of elastic foundation and vibration theory, a method for calculating the fundamental natural frequency of cement slab is presented and the certain relationship between the fundamental natural frequency of cement slab and cement slab boundary condition is discussed. As well, according to the analysis results of fundamental natural frequencies of the typical cement pavements of China, the selected proposals of the excitation frequency of the resonant rubblization machine are presented .The research results provide a theory support to popularize resonant rubblization technology in overlaying and rebuilding engineering of the existed cement pavements in China.

Abstract: In order to study the treatment mechanism of the ionic liquid soil stabilizer, a series tests were performed for a typical soil, the red-brown clay. The basic physical parameters of typical soil were conducted by variety of tests, including particle size analysis, crucial water content coefficient, loss on ignition, organic matter content, etc. Furthermore, the treatment mechanism of the ionic soil stabilizer was analyzed, involving PH, conductivity, plasma emission spectra, scanning electron microscopy, X-ray diffraction and BET test. The results indicate: Firstly, the ionic soil stabilizer is a sulfonated oleoresin with the features of water soluble, high conductivity and strongly acidic, which exchanged with cations adsorbed on the surface of clay particles to reduce the thickness of hydrated film and the electric double layer thickness. Secondly, it reduced the mutual repulsion energy between soil particles and made the flaky particles of clay minerals contact closely. Finally, it made the particles of clay be close to each other and gradually formed larger particles. Hence, the clay became denser. Therefore, the research provided a theoretical foundation and practical basis for the wide application of the ionic soil stabilizer in China's highway construction.