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81.
针对现场中长床身导轨调平不便之处,介绍了以一条通过首测量点的水平线作为检测,调整及评定基的调平方法。并说明了导轨直线度检测及调整量准确控制等具体措施。 相似文献
82.
为进一步拓展AlFeSi系耐磨涂层的应用领域,对建筑用6063铝合金表面AlFeSi耐磨涂层施加不同载荷,分别测试研究了在干摩擦和浸入3.5 ％NaCl腐蚀溶液下时的摩擦磨损性能.结果 表明:6063铝合金表面AlFeSi涂层表面没有发现明显涂层剥落,可以和基底形成良好结合状态.该涂层形成了微裂纹、孔洞与圆形未熔颗粒,... 相似文献
83.
《Materials and Manufacturing Processes》2012,27(5):543-549
Optimization of a sensor location for effective characterization of a hot forging process using acoustic emission (AE) signals is discussed in this paper. Acoustic emission signals generated during forging operations on an aluminium alloy were recorded using three sensors simultaneously by mounting them on the top bolster, bottom bolster, and bottom die of the press. The AE signals with maximum sensitivity could be detected with a sensor attached to the bottom die in preference to the other positions. Using AE parameters, the forging process could be differentiated into three regions, i.e., 1) yielding of the workpiece material, 2) intermediate deformation region, and 3) filling of the die. The results show that the optimum position of the AE sensor for monitoring hot forging is found to be the bottom die of the forging press. 相似文献
84.
《Materials and Manufacturing Processes》2012,27(7):690-697
In this work, an analysis of the energy vanished by friction of thin-walled tube drawing processes in conical converging dies with a fixed conical inner plug has been conducted. The method used for analysis is the upper bound method (UBM), and the plastic deformation zone has been modelled by three triangular rigid zones (TRZ). The tube inner diameter is considered constant during the process, and therefore, a state of plane strain can be assumed. In addition, the existent friction between the external surface of the tube and the die (material-die), as well as that between the inner surface of the tube and the plug (material-plug) has been modeled by Coulomb friction (μ1 and μ2, respectively). Some significant findings emerged from this study are: the establishment of explicit expressions for evaluating the non-dimensional energy vanished by friction in the die and in the plug, the ability to select the plug that enables the process to be performed with a lower requirement of energy under defined conditions, and the detection of coupled effects between the friction coefficients define above. 相似文献
85.
《International Journal of Pavement Engineering》2012,13(1):49-60
Durability of porous or permeable friction courses (PFC) is an important aspect to address when designing this type of hot mix asphalt. At present, several agencies perform the mix design of PFC primarily by determining volumetric mixture properties. This approach ensures adequate mixture functionality, but it does not guarantee mixture durability. This paper evaluates the Cantabro loss test, the Hamburg Wheel-Tracking test (HWTT) and the Overlay test (OT) to determine the one most appropriate for mix design and laboratory performance evaluations. The Cantabro loss test, performed in both dry and wet conditions, is recommended for PFC mix design to corroborate the suitability of the optimum asphalt content defined based on volumetric determinations. The HWTT and the OT are not recommended, since the variability of the test results indicated that these tests may not be suitable for PFC mixtures. 相似文献
86.
《International Journal of Pavement Engineering》2012,13(6):579-589
Functionality of concrete pavements can be restored through conventional diamond grinding (CDG) that improves ride quality and friction. Recently, an alternative diamond grinding configuration was proposed by the Institute for Safe Quiet and Durable Highway at Purdue University as part of a nationwide interest in quiet pavements. This paper discusses the field-testing of the CDG and alternative (innovative) diamond grinding as well as the pre-existing transverse tined (TT) texture at the MnROAD research facility. Acoustic properties, ride quality and friction performance of the diamond ground surfaces are compared to data obtained in the pre-existing TT surface. The initial performance of the innovative grind over a period of 3 years is also compared to that of the conventional grind and the TT surface. Test results, analysis, merits and demerits of the grinding types are also accentuated. 相似文献
87.
《International Journal of Pavement Engineering》2012,13(8):721-729
Tyre operating temperature is an important concern for both tyre manufacturers and highway agencies which is known to have a major influence on the tyre traction. Most of the past tyre–pavement interaction studies were focused on the performance of the tyre while giving limited importance to the effect of the pavement texture profile. This paper presents a methodology of coupled thermomechanical finite element (FE) model to determine the progressive temperature development in tyre cross section. The model is developed for a test tyre rolling over an FE mesh of an asphalt pavement surface, and the effect of the developed temperature on the hysteretic friction is evaluated. Such a model will enable tyre manufacturers to come up with optimised tyre design; on the other hand, road agencies can design their friction test protocol. In this study, an attempt has been made to examine the developed tyre–temperature in time at different regions of tyre. 相似文献
88.
《International Journal of Pavement Engineering》2012,13(2):168-179
This article features a field experiment conducted on existing road pavements to characterise macro- and micro-texture variations at actual road conditions and to substantiate links to friction values. Three-dimensional inspections of the wearing course surface of three asphalt mixes were performed during a short period of 9 months. Several statistical texture indicators, spectral analysis and photo-simulated images of surface height maps were employed to analyse macro/micro-texture evolution and to study the physical phenomena behind it. Fractal and non-fractal parameters, with a focus on Hurst exponent (H), were used in associating texture with friction. The results of texture evolution clearly state that changes in macro/micro-scales occur within full surface profile and not solely from the polishing phenomena of a small percentage of top surface topographies. It was demonstrated that H, as an indicator of full surface profile specification, could not be employed for road texture–friction studies at actual road conditions. 相似文献
89.
《International Journal of Pavement Engineering》2012,13(4):402-416
AbstractRutting or plastic deformation is one of most frequently observed distress types in the wheel paths of flexible road pavements. This distress may cause the pavement structure to be attributable to early failure by expediting the deterioration due to load and environmental detrimental agents. Therefore, it is ideal to simulate the rutting performance of different asphalt mixtures in laboratory-controlled conditions before exposing them to aggressive field conditions. Different rutting simulation computer-controlled equipments are available to predict the mixture performance in laboratory at nearly similar conditions to actual in-service pavements. Cooper wheel tracking equipment is one such precise equipment. Mostly, the wearing course is likely to be damaged by this distress type in flexible asphalt pavements. Therefore, in this research study, thirty representative wearing course mixtures commonly used in road pavements were tested for rutting distress using Cooper wheel tracker. Three aggregate sources, three binders from two sources, five mixture gradations and two temperature conditions were included in the testing scheme. Mixtures were evaluated based on the terminal value of rut depth. Consistent ranking of mixtures has been observed for variable combinations of aggregates, binders, temperatures and gradations. Flakiness index (FI) of aggregates, binder penetration values, per cent coarse material retained on 4.75 mm sieve and temperature values are considered as independent variables based on past researches. The significance of these independent variables on the dependent variable of rut depth has been analysed by analytical tools of general full factorial design analysis. It has been concluded that temperature has highest significance for the rut depth prediction, followed by FI of aggregates, bitumen penetration value and percentage of coarse fraction. 相似文献
90.
《International Journal of Pavement Engineering》2012,13(10):881-893
Most design methods for road pavements require the design traffic, based on the transformation of the traffic spectrum, to be calculated into a number of equivalent passages of a standard axle using the equivalent axle load factors (EALFs). In general, these factors only consider the type of axle (i.e. single, tandem or tridem), but they do not consider the type of wheel on the axles, i.e. single or dual wheel. The type of wheel has an important influence on the calculation of the design traffic. The existing design methods assume that the EALFs are valid for all pavement structures and do not consider the thickness and stiffness of the pavement layers. This paper presents the results of the development of a model for the calculation of the EALFs considering the type of axle, the type of wheel and the constitution of the pavement. The model was developed based on the tensile strain at the bottom of the asphalt layer that is responsible for bottom-up cracking in asphalt pavement, which is the most widely considered distress mode for flexible road pavements. The work developed in this study also presents the influence of the type of wheel (single and dual) on pavement performance. The results of this work allowed the conclusion that the EALFs for single wheels are approximately 10 times greater than those for a dual wheel. This work also proposes average values for the EALFs. An artificial neural network was developed to calculate the EALFs. 相似文献