Thermal stresses due to internal friction of the tube of a pneumatic tire clutch

A method is examined of determining the design thermal stresses due to friction of the material during operation of a pneumatic tire clutch. An example is given of the calculation of the thermal stresses in the tube of a PM 300 X 100 clutch.     

Spray formed bearing steel insensitive to distortion

To minimize the distortion of bearing steel components during manufacturing processes, 100Cr6 steel (SAE 52100) has been produced by spray forming as an alternative approach to conventional continuous casting process. Material characteristics and distortion behaviour of the spray formed 100Cr6 steel were investigated in comparison with continuous cast material. The investigation showed that the spray formed 100Cr6 steel exhibited lower distortion potential than the conventional material due to much better metallurgical homogeneity.     

Induction of optical vortex in the crystals subjected to bending stresses

We describe a method for generation of optical vortices that relies on bending of transparent parallelepiped-shaped samples fabricated from either glass or crystalline solid materials. It is shown that the induced singularity of optical indicatrix rotation leads in general to appearance of a mixed screw-edge dislocation of the phase front of outgoing optical beam. At the same time, some specified geometrical parameters of the sample can ensure generation of a purely screw dislocation of the phase front and, as a result, a singly charged canonical optical vortex.     

Spray formed bearing steel insensitive to distortion Part I Material characterization

To minimize the distortion of bearing steel components during manufacturing processes, 100Cr6 steel (SAE 52100) has been produced by spray forming as an alternative approach to conventional continuous casting process. Material characteristics and distortion behavior of the spray formed 100Cr6 steel were investigated in comparison with continuous cast material. The investigation showed that the spray formed 100Cr6 steel exhibited less distortion potential than the conventional material due to much better metallurgical homogeneity.     

Rapid change of stresses in thickness direction in long orthotropic tube under internal pressure and axial load

Exact solution for long orthotropic tube under internal pressure and axial load suggests the existence of very dangerous combinations of elastic properties. We demonstrate that such elastic properties can be thermodynamically stable. Close to a dangerous combination, stress components change very rapidly in radial direction, resulting in huge peak stresses exceeding the membrane theory predictions by several orders of magnitude, even for relatively thin-walled tubes. Another manifestation of this effect is extreme sensitivity of peak stresses to variations in elastic properties. Away from the critical condition the anomaly in stress distribution disappears and this can be the key point in the design of related structures. The rapid change of stresses in thickness direction is attributed to the auxetic property (negative Poisson’s ratio) of highly anisotropic material of the tube. As an example, we consider the filament wound tube with closed ends under internal pressure and demonstrate that, for highly anisotropic fiber-reinforced plastic, winding with angle close to 45° is potentially dangerous.     

Water absorption of glass/epoxy laminates under bending stresses

The water absorption characteristics of unidirectional glass/epoxy laminates have been studied during hygrothermal ageing at 95% relative humidity and temperatures up to 80°C for periods of up to 900 days. Initial water absorption behaviour approximately followed Fick's Laws, but deviations occurred at higher temperatures (∼ 80°C). No classical equilibrium absorption plateau was obtained at any temperature and irregular changes in specimen weight were observed after prolonged exposure at 80°C. These changes are explained in part by postulating a degradation process, involving interaction between water and the curing agent. Four-point bending stresses were applied to some specimens during hygrothermal exposure. These stresses were insufficient to have much effect on the diffusivity, but surface damage was induced between the two loading noses on the compressive face. Failure occurred after prolonged exposure to high stresses at 45°C. Pre-stressing does not affect water uptake, but post-loading already soaked laminates lowers the the flexural modulus.     

Competitive giga-fatigue life analysis owing to surface defect and internal inclusion for FV520B-I

Research of material giga-cycle fatigue shows that fatigue failure is caused by a comprehensive effect of the competition between surface defect and internal inclusion, and the competition is more significant with high strength steal FV520B-I. A clear understanding of fatigue failure mechanism can improve the accuracy of the fatigue life prediction for FV520B-I. There is currently no available fatigue-life model that describes the competition mechanism of giga cycle behavior for FV520B-I. In this paper, ultrasonic fatigue experiment is presented, which revealed the existence of the competition during the giga-cycle process. The giga-fatigue life prediction models for FV520B-I are established with the consideration of surface defect and internal inclusion. Based on fracture mechanics, the surface roughness is correlated to surface defect. The competition analysis is carried out on the basics of fatigue strength to obtain the critical defect value. The critical defect value is the direct criterion in practical engineering and the primary factor of final failure is determined by comparing the actual defect with the critical value. Then the competitive giga-fatigue model for FV520B-I is established and the actual fatigue life is calculated by substituting the actual defect value into the corresponding fatigue life model.     

An automatic design optimization procedure to minimize fillet bending stresses in involute spur gears

This paper presents the development of an automatic design algorithm for gears. The criterion on which the design performance is assessed is the maximum tensile stress induced in the gear tooth fillet under service conditions. Starting from an initial set of design parameters the stresses in the gear tooth fillet are calculated. The maximum value of the stress is then expressed as a function of the design variables. By minimizing this function, the objective function, subject to both equality and inequality constraints a new set of design parameters, is produced. Iterative application of the analysis and minimization stages forms a sequence of non-linear optimization problems which converges to yield the optimal design. Finite element techniques employed to calculate accurately the stresses in the gear tooth are again used to compute the design derivatives. This process is very economical, owing to its efficient reuse of the factorized stiffness matrix. The algorithm is illustrated by its application to a spur gear tooth of involute profile. Both linear and non-linear forms of the objective function are used and a comparison made between the solutions obtained.     

A design optimization procedure to minimize fillet bending stresses in an epicyclic gear system

This paper presents the development of a design algorithm for epicyclic gear systems. The criterion on which the design performance is assessed is the maximum tensile stress induced in the fillets of the sun, planet and annulus gears. From an initial set of prescribed real and integer design parameters the finite element method is used to determine the maximum tensile fillet stresses in each gear. An objective function is formulated to represent the total stress in the system by combining the maximum fillet stresses in each component. A sequential procedure is then used to minimize the objective function subject to equality, inequality and integer function constraints. The finite element method is used to evaluate the stresses in the gear teeth and iterative application of the analysis and optimization stages converges to produce a design vector such that the maximum stress produced in all components of the system is minimized. Since the effectiveness of each design is assessed using the finite element method, the factorized stiffness matrix is reused to calculate the design derivatives. This makes the processes very efficient in its use of computer resources.     

Determining the residual stresses in plastically deformed tubes subjected to combined bending and torsion

Moscow. Translated from Problemy Prochnosti, No. 10, pp. 86–92, October, 1988.     

铜管弯管工艺参数计算方法

制冷系统铜管弯管制备过程存在反复试弯带来的材料、人工浪费和弯管作业效率低下等问题,为保证在弯管前的下料制备中获得准确的下料尺寸和起弯点,通过理论计算和试验验证的方法对弯曲角度、铜管直径、壁厚、中轴线弯曲半径等变量对铜管弯曲拉伸变形量的影响进行研究,确定下料尺寸、起弯点位置、拉伸变形量等弯管工艺参数理论计算模型,实际作业效率提高30%～40%,材料利用率提高10%。     

Somigliana dislocations and internal stresses; with application to second phase hardening

A general integral theory for an important class of internal stress problems in anisotropic elastic media has been obtained. The basic problem that was solved was that of the stress field which arises when a certain region within the interior of a crystal undergoes a change in shape while constrained by the bulk of the crystal. The problem assumes that the shape change, whatever its physical origin, can be represented by a polynomial of arbitrary degree in the three spatial variables. When the transformed region is ellipsoidal in shape the following useful theorem has been indicated: If, in the absence of the matrix, the shape change were given by a polynomial of degree N in the spatial variables, then the state of internal strain, within the region, caused by the constraint of the matrix is given by a polynomial of degree N?1. This fact enables us to recast this above internal strain problem to include those cases where the ellipsoidal region is different elastically than the matrix. The theory is applied to a model of dispersion hardening.