为解决硬岩TBM在掘进时滚刀磨损检测难的问题,以岩石断裂力学为理论基础,深入分析了TBM滚刀的破岩机理,并基于Colorado school of mincs(CSM)模型提出了一种新的滚刀磨损预测方法。通过滚刀与岩石相互作用的力学模型,利用刀盘比能预测了滚刀的磨损。结合秦岭隧道工程实例,对滚刀磨损水平进行了量化研究,预测结果与实际情况相符,从而验证了模型的有效性。 相似文献
ABSTRACTTo improve the wear resistance of disc cutters for tunnel boring machines (TBMs), this study is devoted to investigating the effects of rocks and cutter ring properties on the wear behaviors of disc cutters and the matching characteristics between the cutter ring properties and hard rocks. Cutter–rock wear tests were performed and the results show that the cutter ring properties and rock types significantly affect the cutter ring wear. The mass losses of cutter ring samples sliding against different types of hard rock are different and vary with the cutter ring properties because of the discrepancies in loads, vibrations, rock properties, and transition of the wear mechanisms. Finally, matching characteristics between the cutter ring properties and hard rocks are revealed. 相似文献
This paper deals with the influence of phase modulated synthetic jet on the aerodynamics of the hump in a closed test section Of the Eiffel-type wind tunnel. Three experimental methods of measurement techniques of this phenomenon were used: the pressure profile using the Kiel total pressure probe, the velocity profile using the CTA (constant temperature anemometry) probe and the visualization of the flow field using the hot film and the thermo camera, The experimental results with and without the influence of the synthetic jet were compared, as well the impact of the phase shift of the neighbouring synthetic jets. As a reference case, the flow around the hump without the influence of the synthetic jet was selected. The results of the measurement are presented in figures and compared. 相似文献
Fluid film bearings are widely used as support elements of rotating shaft for HDD (hard disk drive) spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipments such as mobile PCs, car navigation systems. Hence, the rotating shaft has a possibility to come in contact with the bearing and it causes wear or seizure to the bearing surface. In order to avoid the problems, it is extremely important to enhance the dynamic characteristics of the fluid film bearings for spindles. However, verification from both theory and experiment of dynamic characteristics such as spring coefficients and damping coefficients is rare and few. In this paper, the bearing vibration characteristics when the HDD spindle is oscillated are investigated theoretically and experimentally. And then the identification method ofoil film coefficients of fluid film bearing spindles is described. 相似文献
This work continues the approach of one of our topics relating to a MOM-THP (metal on metal-total hip prostheses) with self-directed movement balls. Experiments revealed a certain seizure in some strain conditions. Laboratory trials for balls/plane Hertzian contacts have been restarted in order to determine seizure behaviour depending on the roughness of the flat area. The trials have been carried out in BSF (body simulated fluid) lubrication conditions, much closer to the real operating conditions up against the initial tests with distilled water. Seizure burdens to different loadings and contact surfaces roughness influence over the seizure burden have been determined. Even though the minimum value of the wear must be the same with the minimum value of the surfaces roughness, given the experimental conditions, it came out from the trials results on wear that the lowest level of wear is acquired at a certain value of roughness, not at the lowest level of roughness. 相似文献
Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%–25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures. 相似文献
At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased. 相似文献
Laboratory tests can help in the analysis of tribological failures of elements, and improve tribo‐systems by choosing appropriate materials. In order to characterise the friction and wear behaviour of candidate materials, various different test methods have been developed in the past and are still in use. One such method is the reciprocating sliding of a ball against a disc. In the work reported here, the repeatability of friction and wear results was evaluated with ten tests under identical conditions with a steel (100Cr6) or alumina (Al2O3) ball against a steel (100Cr6) disc under unlubricated conditions at room temperature. The influence of ambient humidity on friction and wear behaviour was determined in three additional tests in dry and in moist air, respectively. The repeatability of friction coefficient in normal air was better than 5% for alumina/100Cr6 and 12% for 100Cr6/100Cr6, while the repeatability of volumetric wear was slightly better than 10% for alumina/steel, and slightly worse than 10% for steel/steel. For both couples the coefficient of friction is lowest in moist air and about 50% higher in dry air. The coefficient of wear is also least in moist air and higher by a factor of 3(5) in dry air for tests with a 100Cr6 (alumina) ball. 相似文献
As one of the most wear monitoring indicator, dimensional feature of individual particles has been studied mostly focusing on off-line analytical ferrograph. Recent development in on-line wear monitoring with wear debris images shows that merely wear debris concentration has been extracted from on-line ferrograph images. It remains a bottleneck of obtaining the dimension of on-line particles due to the low resolution, high contamination and particle’s chain pattern of an on-line image sample. In this work, statistical dimension of wear debris in on-line ferrograph images is investigated. A two-step procedure is proposed as follows. First, an on-line ferrograph image is decomposed into four component images with different frequencies. By doing this, the size of each component image is reduced by one fourth, which will increase the efficiency of subsequent processing. The low-frequency image is used for extracting the area of wear debris, and the high-frequency image is adopted for extracting contour. Second, a statistical equivalent circle dimension is constructed by equaling the overall wear debris in the image into equivalent circles referring to the extracted total area and premeter of overall wear debris. The equivalent circle dimension, reflecting the statistical dimension of larger wear debris in an on-line image, is verified by manual measurement. Consequently, two preliminary applications are carried out in gasoline engine bench tests of durability and running-in. Evidently, the equivalent circle dimension, together with the previously developed concentration index, index of particle coverage area (IPCA), show good performances in characterizing engine wear conditions. The proposed dimensional indicator provides a new statistical feature of on-line wear particles for on-line wear monitoring. The new dimensional feature conveys profound information about wear severity. 相似文献
Being one of their prominent exploitative characteristics, cutting tools durability depends on the character, intensity and the speed of wearing. Identification of tool wearing is of great significance for the purpose of avoiding sooner or later replacement of tools. The parameters of tool wearing can be measured by out-process and in-process-measuring systems. Given the extremely limiting role of the former in modern production lines, development of the latter (the indirect measuring systems) has gained prominence, The basis of indirect measuring systems comprises a set of various signals originating from the units of the system under treatment which stand in certain correlations with the wearing parameters. The paper presents mathematical models of axial force designed on the basis of experimental research in drilling tempered steel by twist drills made of high-speed steel manufactured by powder metallurgy. 相似文献
Bismaleimides are the addition type of polyimide resin. They are synthesized by reaction of diamino compounds with maleic anhydride. By varying the structure of the diamino compound it is possible to make various bismaleimides. This paper discusses improvement of the friction and wear properties of bismaleimide resin, by the addition of solid lubricant additives such as MoS2, graphite and PTFE. The bismaleimide tested has the following structure: On heating, bismaleimide cross links through its unsaturated bonds, thus producing a highly cross linked polyimide. The friction and wear measurements were done on a Plint friction and wear machine (pin on disc type), wherein polymer pins slid against a steel disc at different loads and speeds. The polymer itself had a high coefficient of friction, ranging from 0.3 to 0.6 and a higher wear rate. Solid lubricant additives helped in improving its friction and wear characteristics. The addition of graphite brought the coefficient of friction to 0.3 but wear remained high at high loads. Best results were obtained with additions to the resin of MoS2-Sb2O3 and PTFE. Composites with MoS2-Sb203 and PTFE had low coefficient of friction and low rate of wear, at low as well as at high loads. It appears that these solid lubricant additives transfer to the counterface, thereby reducing effective counterface roughness, hence reducing both friction and wear. 相似文献
Laser surface texturing (LST) followed by an ultrasonic nanocrystalline surface modification (UNSM) process was applied to graphite cast iron to improve the friction and wear behavior. The surface hardness of the UNSM-treated and UNSM + LST-treated specimens was increased significantly compared to the polished and LST-treated specimens. The friction and wear behavior of the specimens was assessed using a ball-on-disk friction tester at an applied load of 10 N and a speed of 5 cm/s in both dry and lubrication conditions. The friction coefficient of the UNSM-, LST-, and UNSM + LST-treated specimens reduced in both dry and lubrication conditions compared to the polished specimen by 64, 30, and 64% and 63, 67, and 75%, respectively. In lubrication condition, the friction coefficient of the UNSM- and LST-treated specimens was further reduced by about 30 and 25% by UNSM + LST processes. In dry condition, the UNSM + LST-treated specimen exhibited a reduction in the friction coefficient of 46% compared to the LST-treated specimen, whereas no reduction in friction coefficient was found compared to the UNSM-treated specimen. The wear resistance of the UNSM-, LST-, and the UNSM + LST-treated specimens was enhanced by 22, 11, and 37% in the dry condition, respectively, whereas minuscule wear was observed in the lubrication condition that was difficult to quantify in our experiment. UNSM and LST processes were effectively combined to improve the friction and wear behavior of graphite cast iron. 相似文献