共查询到20条相似文献，搜索用时 46 毫秒
1.
Based on the real size and constrain of the wet clutch, the friction pair of temperature, stress fields coupling model, and the heat convection coefficient model are established. The transient thermal-structural coupling and the thermoelastic instability of the phenomenon of friction discs generated in overload tests are numerically simulated and analyzed with ANSYS/LS-DYNA. Additionally, the distribution of the hot spots in the circle direction and surface of the friction discs are revealed, the distribution of the stress and strain caused by the thermoelastic instability is analyzed and tested. The results show that hot spots and contact pressure are mutual promotion. The thermal expansion and stress concentration caused by temperature gradient lead to steel disc warp. The heat fading caused by the thermoelastic instability leads to steel disc failure. 相似文献
2.
Aiming at the cutter head thermal damage and other failure problems caused by shield cutter head mud formation in residue and clay soil,the problem of thermal-stress coupling of shield cutter head under the effect of mud in the tunnelling process is studied,and the cutter head temperature and thermal-stress distribution of coupling fields under mud effect are acquired. A shield cutter head three-dimensional finite element model is built by using software ANSYS and Solidworks. The results shows that when the mud is formed,the temperature rises sharply in a short time,which leads to a rapid increase of thermal stress to 168.2 MPa,at the same time,the maximum thermal deformation reaches 3.1 mm,then the center of cutter head is wrapped. 相似文献
3.
A Simplified Method to Calculate the Wet Bulb Globe Temperature 总被引：1，自引：0，他引：1
The wet bulb globe temperature (WBGT) is difficult to measure and calculate in field observation and numerical simulation. To solve this problem, the air dry bulb temperature, wet bulb temperature, globe temperature, relative humidity, mean air velocity, solar radiation and wet bulb globe temperature in Guangzhou, P. R. China, first were collected during the summer (July). Next, correlation and regression analyses were used to derive a simplified model for calculating WBGT. The results show that dry bulb temperature, relative humidity, solar radiation, mean air velocity and WBGT were interrelated to some extent. These four parameters with high linear correlation can be used to predict WBGT in a simplified model with high precision. The simplified WBGT model can be used in field observation and simulation research regarding urban thermal environments. 相似文献
4.
Li Xin Li He Wan Ling Xu Jiang Yin Guangzhi 《保鲜与加工》1990,(4):84-86
In this paper, the fracture process of specimen with pre-cracks is studied by using photo-elastic expe' merit.The analysis results of cracks stress field show that because the inter-effection appears between the the two cracks and the tensile fracture occured when the tensile stress concentration reaches to a certain degree, and cracks link up with each other, macroscopic failure will gradually result. Positions of cracks will have different effections to speciment's fracture. 相似文献
5.
Defects detection in the inner surface of pipes based on inverse heat conduction problem 总被引：1，自引：0，他引：1
It is a typical ill posed inverse heat conduction problem to estimate the geometry boundary of the inner surface of pipe by the temperature of outer surface. With the establishment of a two dimensional steady model for pipe with irregular inner surface, the inverse problem is transformed into a direct problem and an optimization problem. Based on the temperature at the outer surface obtained from the infrared thermography and the variation of the object function, the conjugate gradient method (CGM) is introduced into the geometry problem. With the numerical analysis of three typical defects, the effects of the measurement errors, choice of the initial value, boundary conditions and number of discrete temperature points are discussed and the proposed methodology is approved. 相似文献
6.
It has been established that a pavement slab will curl up if a temperature gradient exists across the depth of a slab. A negative temperature gradient causes the slab edge to curl up while a positive temperature gradient curls up the slab center. Temperature stress in slabs is induced by self-weight and other slab constraints. At present in P. R. China, the total stress considered in cement concrete pavement design includes the load stress plus the temperature stress, and only transverse cracking from bottom to top is considered for concrete pavement. Slab responses under axial loads and temperature gradient coupling are not included. We modeled a single slab with a frictionless interface between the slab and foundation using the finite element method. Slab deflection and stress were calculated under axial loads at different slab positions and negative or positive temperature gradient coupling. The calculated results show that the different conditions of axial loads and temperature gradient coupling will change the maximum tension and cause various types of cracks in a slab. 相似文献
7.
It is recognized that the scaling failure of nodular iron composite rolls in hot rolling is a problem of fatigue brittle fracture. The temperature field,stress,critical crack size as well as the interior quality of the rolls are presented. The theory of fracture mechanics is used to explain the cause of the scaling failure. At the same time, the way to extend the durability of the rolls is also studied. 相似文献
8.
焊接加固热作用对工形截面压弯钢构件承载性能的影响 总被引：1，自引：0，他引：1
为研究焊接加固热作用及不同初始负载对工字形压弯钢柱承载性能的影响,基于考虑热影响的热结构耦合分析方法进行了热源模型热输入改进,并考虑初始几何缺陷、初始残余应力及摩擦等,完成了不同负载下焊接加固的3个工字形压弯钢柱的模拟分析。研究了焊接位移时程、腹板应力应变重分布及荷载位移关系,通过有限元分析与相应试验结果对比验证,进而获得了试验无法获得的焊接温度场、翼缘与加固板间的焊接应力应变重分布以及翼缘边缘屈服承载力等结果,并将承载力结果与规范计算结果对比,考察了现有设计方法。结果表明,焊接顺序决定焊接变形的发展过程,焊接热输入和初始负载共同决定持载焊接的位移变化范围和焊接残余变形的大小;初始负载越大,应力应变重分布往偏心受力方向发展更多,承载力越低,而初始残余应力不影响极限承载力;采用考虑热影响的有限元方法具有一定可行性和总体安全性,规范设计方法仍有可提升空间。 相似文献
9.
Although rolling lubrication can decrease rolling forces and energy consumption, it also causes defects such as uneven flange lateral spread and web eccentricity during H-beam rolling process. To solve the problem caused by lubrication, finite element models of H-beam universal rolling were established. The different friction conditions of the contact surface between the rollers and work piece were simulated individually. The mechanism of rolling lubrication impacting on flange spread was studied, and the law of flange lateral spread was gained by analyzing the factors such as friction distribution and metal flow in different situations. Analytical results show that lubrication in rolling process can effectively decrease rolling forces and energy consumption. In the condition that technological parameters except friction are fixed, the flange lateral spread decreases in a linear way as the friction coefficient between flange and roller increases, and the flange lateral spread is more sensitive to the friction of flange's the inner side. Design of lubrication process should take full account of the sensitiveness differences of flange lateral spread to the lubrication conditions of different parts of roller surface. 相似文献
10.
The application of lock-up clutch slip control balances the fuel economy and drivability, and greatly improves the performance of hydraulic automatic transmission. The structure of the lock-up clutch and the friction material of lock-up clutch lining are discussed, a detailed research on varying characteristic due to engaging time during the lock-up clutch engagement is developed, too. By applying the slip control, lower fuel consumption is achieved. 相似文献
11.
A theoretical analysis is presented for heat transfer in micro-annular channel with an adiabatic wall and a heated wall with uniform wall temperature in slip flow regime. The energy equations with the boundary conditions of temperature jump are solved for the hydrodynamical and thermal fully developed laminar flow of the incompressible fluid in this microchannel. The influences of the Kn number, the ratio of inner diameter to outer diameter on the heat transfer characteristics are discussed respectively. The results show that the Nusselt number in microchannel decreases with the increasing of Kn number comparing with that in macrochannel. 相似文献
12.
Xin Yide Hu Yisu 《保鲜与加工》1988,(4)
The influence of temperature and stress state on delamination in the pipe-line steel has been studied by tensile tests at different temperature and stress states. It is found that the' delamination always takes place along the centerline segregation band in pipe-line steel produced by continuous casting and then controlled rolling. At room temperature, the delamination appears to be caused by micrbvoid nucleation and coalecence. And the delamination appears to be caused by the cleavage cracking along (100) plane at low temperatur.e. The best way to eliminate the delamination is to reduce the degree of centerline segregation. 相似文献
13.
In this paper, the finite element method is used to analyze the behavior of the prestressed V-shape Slab Roof structure, especially the effect of temperature change on the stress of slab. The calculated results indicate that when the temperature changes, the tensile stress at the lower extreme fibers of the flange plate near rib exceeds the tensile strength of concrete subjected to the combined action of triaxial stresses and results in the longitudinal cracks of the flange plate. The deflection analysis is based on the mechanical model of the prestressed V shape slab with the longitudinal cracks. The calculated results are in general agreement with the field observations. 相似文献
14.
CVT刚性联接发动机曲轴轴系结构的扭振分析 总被引：1，自引：0，他引：1
因非道路车辆的特殊结构和成本限制,提出四缸柴油发动机中采用CVT刚性联接曲轴轴系结构。阐述了该新型结构的特征和工作原理,建立了四缸柴油发动机离合式曲轴计算模型和CVT刚性联接曲轴计算模型。通过曲轴前端实验,证明了所建模型和模型参数确定方法的正确性。求解所有计算模型,并对结果进行对比分析。结果表明,CVT刚性联接使曲轴轴系振动波动加大,减振器耗散能增加,各阶共振峰值对应转速低减。对曲轴各拐剪切应力幅度的影响不大,但有高转速工况降低而中低转速剪切应力幅值增加的普遍趋势,CVT端的扭振振幅和剪切应力较大些。综合研究得出结论：非道路车辆低速四缸柴油发动机可以采纳CVT刚性联接曲轴轴系结构。 相似文献
15.
To accurately analyze the loss and heat of large hydro generator,the finite element models of 2D steady state electromagnetic field,moving electromagnetic field and field circuit coupling are established respectively.As an example,the losses of the rotor iron and damper winding of a 36 MW tubular hydro generator are calculated.Furthermore,the influences of 3 different electromagnetic field models on the thermal sources and temperatures are analyzed by 3D finite element calculation of the temperature field.The results are compared with the test data and indicate that the precision of the field circuit coupling model is better.The losses of each damp bar are different and the heat of the damp bar at the lee side is larger than that at the windward with the full load.The maximal temperature of the rotor is located at the damper winding,instead of the field winding.The research is valuable for improving the calculation precision of the rotor losses and temperature field and enhancing the reliability of the hydro generator design and operation. 相似文献
16.
The surface of EPS is of hydrophobic nature, which can not wet binding material. As in the freshly mixed mortar, EPS particle is not affined with cement paste and has a low bulk density, which will be apt to make EPS particle buoy, and lead to the segregation of mortar, the decrease of water retentivity and affect its workability. When pretreated, the surface of EPS can be changed into that of hydrophilic nature, and be wetted by freshly mixed silicate paste. The technology channel of EPS surface modification is that select proper high-molecular binder and coupling agent, prepare polymer silicate binding material of low water-cement ratio, and utilize the double effect of binder and coupling agent to form silicate grout of hydrophilic nature on the surface of EPS, by composite binding material wrapping the surface of EPS. A new thermal insulating mortar with good properties of thermal engineering, weather-resisting and crack-resisting can be made by modified EPS as light aggregate and cement as binder, modification with fiber and polymer. This new type of insulating mortar can be used as outer thermal insulation of outside wall, which breaks the limitation of traditional insulating mortar only as interior insulation. It has been widely used in the building energy-saving model project. 相似文献
17.
High thermal resistance resulted by fouling in heat exchanger restricts the application of sewage source heat pump (SSHP) system. The fouling forming mechanism was applied with solid-liquid fluidized bed technique for fouling prevention and removing of SSHP system. Shearing stress model of solid-liquid fluidized bed heat-exchanger is analyzed, and collision stress model is modified. Preventing and removing fouling mechanisms of solid-liquid fluidized bed technique by shearing stress and collision stress was explained. An experimental study on how to solve the fouling problem (such as fouling prevention and removing, heat transfer enhancement, etc) is discussed. The results of theory and experiment show that solid-liquid fluidized bed technique can be used not only to increase convection coefficient, but also to restrict fouling growing, it can effectively solve the fouling problem in SSHP system. 相似文献
18.
Clutch Control for Automotive Start-up Process 总被引：1，自引：0，他引：1
The conventional driveline with manual gearbox and dry clutch can be retro-fitted to manipulate automatically,so that the electo-mechanical components or the Automated Mechanical Transmission has been obtained.The clutch engagement position for automotive start-up process can be controlled by the fast-low-fast speed.How to control the clutch engagement during the slipping stage is the key to clutch control.The mostly influent factors of the clutch engagement during start-up process have been analysed thoroughly from the practical point of view.The strategy of clutch control has been proposed on the principle of lessening the start-up jerk and the friction work.It is successfully applied to Santana model,which can be proved by the road test of the vehicle on the slope. 相似文献
19.
A 33-hour field test of outdoor thermal environment was carried out in a typical teaching building cluster located in the hot and humid zone in summer. From the experiment results of local climate data, air temperature, humidity, wind velocity and wet bulb globe temperature (WBGT) at the pedestrian-level, and the typical ground surface temperature, the main characteristics of summer outdoor thermal environment of teaching building cluster in hot and humid zone are obtained. The results show that the patio, overhead and porous pavement can reduce the pedestrian air temperature and WBGT effectively at summer daytime. And the function of the following design methods to improve the outdoor thermal comfort at the summer daytime has the order like overhead>patio>porous pavement>imporous pavement>concrete road. The WBGT at all measuring points at nighttime are almost the same. The test results are further used to verify the existing mathematical models of outdoor velocity and WBGT. The results show that the relative errors are within 6%. Then, the calculation values are in good agreement with the experimental values. 相似文献
20.
This paper proposes a new method of generating a rough cut Numerical Control(NC) codes directly from industrial computerized tomography(CT) slice images for the products which work-piece did not need to be redesigned.The contour structure data of the work-piece are obtained by the threshold segmentation,edge extraction and contour tracing. The inner and outer contours are judged,and the tool radius compensation and the allowance reservation are performed by offsetting the contours according to the judgments. The authors generate the rough cut NC code cut area distinguishing and rough cut path generating in a slice by slice manner. In contour offsetting step, a new approach is proposed to judge inner and outer contours. A software system is developed to generate NC codes. An example is used to verify this approach and results show the feasibility and validity of the approach. 相似文献