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This study elaborates the influence of blends formulated by waste oil (WO) and styrene-butadiene rubber (SBR) on thermo-mechanical and chemical compositional characteristics of rejuvenated bitumen. The results show that both WEO (waste engine oil) and WCO (waste cooking oil) can compensate viscous component for reclaimed bitumen, and the effect of WCO is more significant. However, WO-rejuvenated bitumen has considerable drawbacks in terms of temperature susceptibility and flow resistance, but dramatic improvement after being added with SBR has been noticed. Furthermore, the rejuvenation mechanism of WO/SBR blends is revealed by using FTIR tests, which shows that the physical blending mainly determines the rejuvenation mechanism when the WO/SBR blends are used in bitumen. The combination of WO and SBR is beneficial for improving the temperature susceptibility and rutting resistance of rejuvenated bitumen.

Lignin, one of the most abundant natural polymers, has been extensively studied as liquid or solid additive in bituminous binders. Despite the fact the organosolv lignin in bitumen improves the overall resistance against oxidative aging, lignin could lead to binders of high thermal cracking sensitivity. In this study, a bio-based oil is implemented in a lignin modified bitumen to ameliorate characteristics, such as fatigue and thermal cracking resistance. Pressure aging vessel conditioning was applied to new binders formulated by different proportions of bio-oil to simulate the long-term aging. A series of rheological tests were performed. Based on the linear amplitude sweep test results, fatigue damage of lignin-bitumen could be reduced by increasing the oil content. According to relaxation test results, the addition of oil significantly decreased the ratio of residual stress and relaxation time. This study has shown preliminary conclusions on the use of bio-oil to improve the low-intermediate temperature performance of lignin-bitumen binders.

In the process of large aspheric optical surfaces fabrication, the distortion of the removal function is a big problem that affects the producing efficiency and accuracy, due to the misfit between the tool and the aspheric surface in the contact region. Consequently, this paper aims to find out the influence factors and the distortion rule of aspheric removal function in the computer-controlled optical surfacing. Firstly, based on the analysis of the sub-aperture polishing technology for the large aspheric optical surfaces, the local asphericity of aspheric surface and the viscoelasticity of polishing tool are supposed to be the main sources. After that, a method to calculate the local asphericity considering the misfit between the tool and the aspheric surface is proposed based on the least square method, and the viscoelasticity of the polishing tool is obtained through viscoelastic experiment. Subsequently, combining the results of the local asphericity of aspheric surface and the viscoelasticity of polishing tool, the prediction of the distortion rule of aspheric removal function is presented. Finally, the comparative experiment is carried out, and the removal function on different regions of the aspheric surface is obtained. The experimental result indicated that the distortion of the removal function is consistent with the theoretical result. Through this study, the distortion rule of aspheric removal function in the computer-controlled optical surfacing with pitch tool is finally mastered, which provides a theoretical guidance for the computer-controlled optical surfacing process optimization.

In order to figure out the effect of tool wear on the material removal process in bonnet polishing, an experimental study based on the comparison of removal characteristics of bonnet tools with various wear conditions is presented. Before the experiments, the tool surfaces were measured using a digital microscope, and it revealed that not only the surface contour but also the surface topography were changed by tool wear. For this reason, a preprocessing, i.e., a uniformity controlling method for the spot size, was proposed and validated to keep the spot size constant using static stress sensor. Subsequently, the comparative experiments were conducted, and it was indicated that along with the increase of the wear degree of the bonnet tool, the removal shape changed and the peak removal depth, peak removal in unit time, and removal volume reduced significantly, but the roughness of the polished surface becomes better. Based on the results and the analysis, we deduced that the probably causation for the above phenomenon is the variation of the friction between the workpiece and bonnet tool, because of the alteration of the tool surface topography brought by tool wear. Consequently, the forces in the polishing process were measured using a 3-component dynamometer, and the friction coefficient was calculated. The results showed that the variation trend of the friction coefficient is similar to that of the removal volume, i.e., the removal volume and the friction coefficient of the mild wear tool are basically the same to the new tool, but apparently larger than the severe wear tool, which demonstrates that the reduction of the friction coefficient by tool wear is one of the most important reasons for the decrease of the removal efficiency.

Aiming at the disadvantage of small diameter, low efficiency, poor accuracy and can only measure sub-aperture of traditional contact surface shape measurement method to detect grinding optics surface, this paper uses non-contact laser displacement sensor, and proposes an in-situ measurement method to measure full-aperture surface of grinding optics, it has the characteristics of high measurement efficiency, high accuracy, large measurement aperture and the ability to measure full-aperture surface. This method is in-situ measurement, so it can measure full-aperture surface of optics with arbitrary aperture and shape after rough grinding, semi-precision grinding and fine grinding. Orthogonal co-directional grating measurement path can effectively avoid the influence of machine backlash. Therefore, the optics can be directly compensated according to the results of surface measurement, so that the surface of optics can meet the requirements. After the measurement is completed, a set of orthogonal measurement data are obtained, and the invalid data are manually clipped. Linear interpolation, nearest neighbor interpolation and cubic spline interpolation are used to interpolate the clipped data, and the orthogonal data are superimposed to obtain the final shape. The validity of this method is verified by the sub-aperture surface detection method, experiments show that the optimal surface measurement results can be obtained by cubic interpolation for both planar and aspheric optics. Using this method to compensate the grinding of 530mm×530mm 2-D off-axis aspheric optics, the full-aperture surface shape accuracy PV is better than 3.5μm.

Aiming at the problem of poor uniformity and large amplitude of aspherical small-scale waviness caused by grinding aspheric surface by traditional grating parallel grinding technology, in this paper, the reasons for the poor uniformity of aspherical small-scale waviness in traditional grating parallel grinding technology are analyzed from the perspective of grinding force. Considering the influence of the uniformity of the grinding force during the grinding process on the aspherical small-scale waviness, an up-grinding grating parallel grinding method and a down-grinding grating parallel grinding method are proposed. The effects of the grinding force of the two grinding methods on the aspherical small-scale waviness uniformity are analyzed experimentally. Finally, among these three grating parallel grinding methods, the aspherical small-scale waviness obtained by the down-grinding grating parallel grinding method is the most uniform and the waviness amplitude is the smallest, the waviness amplitude is less than 2μm.

In this paper, the polishing properties of the zirconia slurry on the fused silica were studied, comparing with the effect of the ceria polishing. The polyurethane without dopant was applied as polishing pad. The experiment results show that it is easier to produce surface scratches when compared with ceria polishing owing to the high Mohs hardness of zirconia. The surface roughness(Rq) of the workpiece was less than 1nm after polishing with submicron size polishing slurry and suitable polishing pad. The R-on-1 test of 355 nm laser-induced damage threshold for fused silica show that zirconia polishing performance is 3.02% higher, however the exposed subsurface damages with HF etching were more than ceria polishing.The subsurface defect density is 0.10def/cm2 (@1μm)with ceria polishing and 1.19def/cm2 (@1μm)with zirconia polishing. Based on the fine polishing performance and abundant resources in nature, the zirconia slurry may be an alternative for fused silica polishing in prospect with the appropriate technological solution.

Magnesium alloys have a significant advantage, low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks needing to be broken through, and a lot of researches have to be carried out. This review comprehensively covers the research progress and the up-to-date summary of Mg and Mg alloys as functional materials in recent years. The six kinds of functional materials above all will be discussed.

The as-cast Mg-Y-Zr- x Nd alloys with different Nd contents were prepared, and the effects of Nd content on microstructure, mechanical properties and electromagnetic interference (EMI) shielding properties were investigated. The results show that the grain sizes are refined from 70.1 μm to 45.2 μm, discontinuous bone-shaped β phases are formed mostly in the triple junction of grain boundaries when the content of Nd increases to 2.63 wt%. The mechanical properties and EMI shielding capacity are both enhanced significantly by adding Nd element. The alloy with 2.63 wt% Nd has a good combination of mechanical properties and EMI properties. T6 heat treatment is able to further improve the EMI shielding effectiveness. The above-mentioned experiment results are attributed to the microstructural variation caused by adding different contents of Nd.

During the ultra-precision grinding process of fused silica optics, the micro-removal processes of brittle and hard fused silica material by diamond grits in different wheel wear states are inconsistent, which leads to the instability of the grinding quality of the components. First, the wear forms of diamond wheel in the process of grinding brittle and hard fused silica material were analysed. The main wear form of diamond grinding wheel was diamond abrasive wear. Then taking the cumulative removal volume of material as the evaluation parameter of wheel wear state, the evolution laws of surface roughness and sub-surface defects of components under different cumulative removal volume of material were studied. With the aggravation of grinding wheel wear, the surface roughness and depth of sub-surface defects layer decreased first, and then fluctuated and increased slowly. In the rapid wear stage, the falling diamond particles scratched deep grooves on the surface of components, and the roughness and sub-surface depth increased sharply. According to the results, it’s reliable to monitor the wheel wear state and predict the life of wheel.

A model for interactions of a single large impurity particle with the optic and pad during pad-polishing has been developed to detailedly illustrate the scratch formation process. Equations for calculating the normal load applied on the optic by the impurity particle are provided, and the friction between the optic and impurity particle has also been considered in scratch formation. Initiation and evolution of the scratches under the combined effects of the normal and friction forces are illustrated in the model. The most important factors affecting the normal load and thus scratch formation have been analyzed and verified using published experimental results. Based on the model, the implications in reduction of scratch formed on optics during pad polishing have been analyzed.

Mid-spatial frequency wavefront error of optics is characterized with the power spectrum density (PSD) specification, and is divided into two parts: PSD1 (wavelength 2.5-33 mm) and PSD2 (wavelength 0.12-2.5 mm). Rather than the PSD1 error which has been researched in the literature, the present work focuses on the PSD2 range. Potential factors affecting PSD2 error are firstly analyzed. Polishing experiments reveal that computer controlled small-tool polishing process does not worsen PSD2 error compared to the full-aperture process, while the lap has a decisive effect. The optics polished by pitch laps shows a fair PSD2 error of 0.7 nm (RMS), which is much lower than the specified 1.1 nm. The polyurethane pad commonly results in a much higher PSD2 error of more than 1.5 nm (RMS). For this problem, we adopt diamond conditioner to dress the pad and decrease pad surface roughness. The validation of restraining PSD2 error by diamond dressing has been confirmed.