机械零件的接触应力计算毕业课程设计外文文献翻译、中英文翻译

1 英文文献翻译1.1英文文献原文题目Calculation of contact stress of mechanical parts.Abstract The hing-pairs mechanism of delivering power, e.g .friction wheel、protrusive wheel、gear、chain wheel、rolling bearing and rolling spiral ect.There are all the problem of contacting strength, contacting stress is also be involved naturally.Over-all discussions will proceed to the calculation of contacting stress here.Keywords contacting stress hertz-formulaTwo curved surface of the elastomer under the effect of pressure, the mutual contact, the contact stress can be generated transfer power of high vice institutions tend to appear in the job is alternating stress, contact stress by alternating the machine parts under certain conditions will appear the phenomenon of fatigue pitting, pitting spread to a certain degree, the parts cant use, that is to say the failure, the failure form of such as fatigue pitting damage, in ISO standard is based on the Hertz stress formula.In this paper, the Hertz stress formulae of several common surfaces and the calculation methods of contact stress for common mechanical parts are discussed in this paper, which is convenient for the design and strength checking of such parts.1 Stress concentration phenomena and conceptsThe damage caused by material under alternating stress is called fatigue failure.Usually, the deformation of the material is much less than the strength limit under its static load.In addition, the local increase of stress due to the change of section size is known as stress concentration.For components made of brittle materials, the stress concentration will remain until the maximum local stress reaches the limit.Therefore, stress concentration should be considered when designing brittle materials.For the components made of plastic materials, the stress concentration has little effect on the strength under static load.Therefore, when studying the static strength problem of the plastic material components, the effect of stress concentration is usually not considered.The stress on the cross section is distributed evenly in the region where the axial tension and compression are confined, and only in the area with a little distance and no drastic change in the cross section size.However, in actual engineering components, some parts often have incisions, grooves, oil holes, threads, etc., resulting in sudden changes in the sectional dimensions of these parts.Such as open hole and lath with incision, when its under axial tensile, within the local area near the round hole and incision, dramatic increase the value of stress, and where to leave the area is a bit far, tend to be more uniform stress reduced quickly.At this time, the stress on the cross section is no longer uniformly distributed, which has been proved by theory and experiment.Under static load, the sensitivity of various materials to stress concentration is different.When the maximum stress in the vicinity of the hole reaches the yield limit, the material first yields and the stress is no longer increased.Such as external forces continue to increase, increasing the stress is on the cross section has not yet to material yield, is a section on other points of stress increases to yield limit, the stress on the cross section gradually tends to the average, as shown in figure 2-32.Therefore, the effects of stress concentration can be neglected under static load with the parts made of plastic materials.In the case of uniform brittle material, the material does not yield, and when the maximum stress value of the hole reaches the strength limit of the material, it first breaks.Therefore, the stress concentration will greatly reduce the strength of the components, and the damage is serious.In this way, the effect of stress concentration on the bearing capacity of materials should be considered even under static load.For groups, however, heterogeneous brittle material, such as cast iron, its internal organization inhomogeneity and defects, and is often a major factor in the production of stress concentration, and the cross section shape change caused by stress concentration can be minor, it for component bearing capacity does not necessarily cause obvious problems.1.1 Some methods of avoiding stress concentration in reality.1.1.1 In packaging design, stress concentration is avoided and used.There is a significant increase of stress in the parts or components in the shape and size.If the transmission shaft shoulder Angle, key groove, oil hole and tight fit, the stress concentration after the stress.The peak stress of these sites decreased significantly from the concentration point to the adjacent area, which showed a high stress gradient.The early failure of parts often occurs in the area of stress concentration, so it is of great significance to understand and master the problem of stress concentration and to rationally design and reduce mechanical parts.In elastic mechanics, the phenomenon of stress in a solid local area increases significantly.It is often found in sharp corners, holes, gaps, grooves, and rigid constraints and their neighborhood.Stress concentration can cause brittle material fracture;To cause fatigue cracks in an object.In the stress concentration area, the maximum stress (peak stress) is related to the geometrical shape and loading method of the object.The stress value of local heighten decreases rapidly with the increase of the distance between the peak point.Because the peak stress often exceeds the yield limit and causes the redistribution of stress, the actual peak stress is often lower than the theoretical peak stress calculated by elastic mechanics.The parameter that reflects the increase of local stress is called the stress concentration factor k, which is the ratio between peak stress and stress concentration without considering stress concentration, which is greater than 1 and has no relation to the load size.In the case of one-way tension of the infinite plate, k = 3 on the edge of the circular hole;In the case of bending, the ratio between the radius of the different circular holes and the thickness of the plate is equal to 1.8 3.0;In the case of torsion, k = 1.6 4.0.In 1898 German g. kirsch first obtained the results of stress concentration near the circular hole.In 1910 Russias G.V. kolosov obtained a formula for the stress concentration near the elliptical hole.In the late 1920 s, the Soviet unions N.I. moose hurley mikheil saakashvili and others introduce the complex function elastic mechanics, using conformal mapping to a irregular piecewise smooth curve transformation to the unit circle, stress expression of complex function and its boundary conditions is derived, and then get a batch of exact solution of stress concentration.Various experimental methods have been developed rapidly, such as electrical measurement, photoelastic method, speckle interferometry, moire method and other experimental methods (see experimental stress analysis), which can measure the stress concentration of objects.In recent years, the rapid development of computer and finite element method and boundary element method has opened a new way to find the numerical solution of stress concentration.In order to avoid the damage caused by stress concentration, it can be used to eliminate the sharp Angle, improve the shape of the component, strengthen the hole edge and improve the surface finish of the material.In addition, the surface of the material can be sprayed, rolled and oxidized to improve the fatigue strength of the material surface.Using ANSYS to simulate the two-point symmetric loading of reinforced concrete beams, how can the concentrated load be arranged to avoid the premature failure of concrete?Add a pad at the loading point.It seems worth trying to apply the equivalent line load, but the line load distribution should not be too large!Role replacement, according to the equivalent load curve prestressed end axial force according to the actual pressure end plate anchorage size divide a surface, the surface pressure shaft, can solve the problem of excessive concentration.Design of the curtain wall ETFE membrane structure curtain wall of Beijing Olympic Games stadium (4) design of key nodes to avoid stress concentration;Abstract: to explore the weighted combination forecast method in the application of stress concentration problem, with holes pull board, for example, the data of the sample point, GM (1, 1) model is set up respectively, trend curve prediction model and the optimal weighted combination forecast model, and the error of each model and comparison. The results show that the combination forecast model fitting and forecast precision is higher than a single model. Therefore, using the optimal weighted combination forecast model to derive the maximum stress, stress, high is a kind of practical engineering testing data processing of the new method. The boundary element method in hatch corner corner stress concentration problem, the application of grey system model and its application in the stress concentration problem in the Angle of the engineering structure, gap, grooves, holes are stress concentration happens nearby, where near the hole stress increased local called hole edge stress concentration.In the water conservancy project, the stress local increase near the dam heel and the inside of the dam is a typical example of stress concentration.1.2.2 In practical engineering, the rounded corners avoid stress concentration.When making all kinds of pulling tools, the corners should be rounded at the corners, which is not for the sake of aesthetics. This is to avoid stress concentration.Stress concentration refers to the phenomenon that internal stress increases significantly in local area due to the abrupt change of geometrical shape and dimension.Stress concentration can cause fracture of components.The size of the rounded corners should be determined according to the size of the tool, too big influence tool effect, too small tool easily break damage.For the commonly used smaller drawing tools, the rounded radius is better than 2-3 mm, and the larger is about 5 mm.Tools for special shapes are determined based on actual conditions.But you have to have a rounded corner.2 The contact stress of any two surfaces.2.1 Coordinate systemFIG. 1 shows a part of a surface body, which is in contact with another surface body at E point, which is called the initial contact point.Take surface in E normal to the z axis, including z axis can have an unlimited number of cutting plane, each cutting surface with a plane intersection, the intersecting line is a plane curve, each plane curve has a radius of curvature in E.The curvature radius of the plane curve on the different cutting plane is generally not equal to the curvature radius of E.The radius of curvature has a maximum and minimum radius of curvature, called the principal curvature radius, R and R respectively, said the two radius of curvature in the direction of the, mathematics can be proved to be perpendicular.The plane of the plane curve AEB is yz plane, which gives us the position of x and y.Any contact surface can be used to determine the coordinate system.Due to the z axis is normal direction, so when two surface E contacts, z axis is overlap each other, between x1 and x2 , the angles between y1 and y2 in (figure 2).2.2 Contact stressTwo surface contact and compaction, pressure P along the z axis, near the initial contact point, the deformation of the material in the local by the contact point to form a small oval plane, elliptical semi-major axis on the x axis, a short half shaft on the y axis b (figure 3).The unit pressure size of each point on the elliptic contact surface is related to the deformation of the material. The deformation on the z-axis is large, and the maximum unit pressure will be generated along the z-axis.The other units of pressure P is P. Figure 1.Coordinates of the surface body Figure 2.Coordinate relation and contact ellipse.Figure 3. thecontactpressurel The equation forl specific pressurel total pressuredF In geometric terms is equal to the volume of the ellipsoid, soThe maximum unit pressure on the contact surface P 0 is called contact stressH （1）The size of a and b is related to the material and geometry of the contact surface.3 The contact stress of two spheres.When the two spheres of radius R 1 and R 2 are in contact with each other, under the action of pressure P, a circular contact area with a radius of a is equal to a=b(figure 4), which is obtained by the Hertz formula.In the formula :E 1 and E 2 are the elastic modulus of two spherical materials;The poisson of two sphere materials is one and two.The radius of the integrated curvature is R.If the materials of the two spheres are steel, E1 =E2=E, and1=2=0 .3, （2）If it is contact between two spheres (figure 5), the integrated curvature radius is.The contact stress can be calculated by substituting equation (2).If the sphere is in contact with the plane, R 2 is equal to infinity, then R =R1 is substituted into equation (2). Figure 4. Two balls in vitro contact Figure 5. Two balls on vitro contact4 The contact stress of two cylinders parallel to the axisparallel to the axis of two cylinders contact deformation before both along a straight line contact, pressing force P, the elastic contact point and contact wires into the rectangular surface width is 2 b (figure 6), unit according to the law of elliptic cylinder pressure distribution on the surface of the contact.The maximum pressure on the X-axis with the largest deformation is indicated by P 0. The pressure of the remaining points on the contact surface is distributed according to the semi-elliptic rule, as shown in fig.7. The volume of the semi-elliptical cylinder is equal to the total pressure P, so.Figure 6.Contact of two cylindersMaximum unit pressure (3)It is known by the Hertz formulaFigure7. The pressure distribution of two cylinders that are parallel to the axisPlug in type（3），soIf two cylinders are steel, E1 = E2 = E, u1 = u 2 = 0.3, P/L = q, 1 / R = 1/ R2 + 1 / R1, the contact stressIf the contact in the body of two beads (figure 8) is calculated by substituting 1/R=1/R1-1/R2 into equation (4), if the cylinder is in contact with the plane, R2= infinity, and R=R1 is substituted into equation (4). Figure8. Two cylinders in contact.5 Calculation of contact stress of mechanical parts.5.1 Friction wheel driveThe main form of the failure of the metal friction wheel drive is the fatigue point erosion of the rolling surface surface, and the contact stress on the contact surface of the rolling body is usually measured by the contact fatigue strength design.For the transmission of disc and friction wheel (figure 9), the pressure of the rolling body is substituted into the Hertz stress formula.Figure9. The disk is in contact with the friction wheel.Where :T is the torque on the friction wheel;F is the friction coefficient;B is the contact length;S is the friction margin, and the power transmission is between 1.25 and 1.5, which is not greater than 3 in the instrument transmission.5.2 Gear driveA pair of gears contact outside the node, which is equivalent to two cylinders with a radius of 1 and 2, which is also used in equation (4) to find the contact stress.By substituting formula (4), the contact stress formula of the gear surface can be obtained, and the design calculation formula of the contact strength of gear transmission is derivedFigure 10. The contact stress of a pair of gears at the node.5.3 Cam mechanismThe roller and CAM working face of CAM mechanism also have contact stress, which can be checked by formula (4).In the formula, q=P/ L, P is the normal pressure of the contact between the CAM and the push rod in the school nucleus, and the normal pressure of the normal roller push rod disc CAM mechanism is shown in figure 11.Where :Q is the load on the push rod;Alpha is the pressure Angle;F is the friction coefficient between the guide slot and the push rod;La is the length of the guide slot for the roller center on the push rod.5.4 Roller clutch (figure 12)When the clutch enters the joint state, the roller is wedged between the star wheel and the sleeve, and the sleeve will rotate with the star wheel. Figure 11. Force condition of CAM Figure 12. A schematic diagram of a roller-type directional clutch.The coordinates of the working face of the star wheel are the forces acting on the roller , the force on the clutch shaft, and the force on the roller, if the transmission moment is Mk,The contact of the roller and the star wheel is the contact of the cylinder and the plane, so the integrated curvature radius R=R1=d/2 unit length of the load q =Q/L, The contact stress formula between roller and star wheel can be obtained by substituting formula (4).Where: L is roller length;D is roller diameter.5.5 Contact stress between rolling body and raceway of rolling bearing.The contact between the roller bearing and the inner ring is equivalent to the outer contact of the two cylinders (figure 13) , The load q= P/L in the unit length is substituted into equation (4), and the contact stress of the roller with the maximum force and the contact of the inner ring can be obtained.In the formula :P is the force exerted by the most stressed roller;L is the roller working length.6 Epilog(1) based on the analysis of the high secondary contact stress between surfaces, the Hertz formula was furth