Neuber Method Research Articles

On the Glinka and Neuber methods for calculating notch tip strains under cyclic load spectra

To maintain the continued airworthiness of civil and military aircraft it is essential that the fatigue behaviour of components subjected to complex multiaxial stress conditions be both understood and predicted. This topic is extremely complex and numerous criteria ranging from the purely empirical to the theoretical have been proposed. To this end it is necessary to know the localised stress–strain history. Whilst a detailed finite element analysis can be performed it is often very time consuming. Consequently, the present paper focuses on the development of a simple method which combines modern constitutive theory with either Neuber's, or Glinka's, approach to calculate the localised notch strains. Here particular attention is paid to the effects of cyclic loading, mean stress relaxation and its effect of fatigue damage.

Papkovich–Neuber solution for a mixture of two elastic solids and Kelvin problem

First, the equations of equilibrium are transformed into a more generalized form of Navier’s equations using the linearized constitutive equations for a mixture of two elastic solids which are given by Green and Steel. Second, these new Navier’s equations are solved by the Papkovich–Neuber method. Finally, the Kelvin’s problem of an infinite mixture of two elastic solids, under a single force acting in the interior of the mixture, is solved.

Closed form solution of stress and strain concentration factors of axially symmetric bodies with small scale plasticity by means of the conservative integral method

A conservative integral of axially symmetric bodies is established and applied to the determination of stress and strain concentration factors. Under the condition of small scale plasticity, a closed form solution of the above two factors can be obtained with given elastic stress concentration factors for arbitrary hardening materials. It can be verified by calculations that the results given by this method agree with the average values given by Neuber's method and other empirical formulas. The computations in this method are very time saving and can be carried out even by calculators.

Rupture strength of welded T-joints on pipes

Results are presented from experimental studies of the rupture strength of models of welded T-joints made of heat-resistant steel. Rupture strength is determined while the joint is subjected to internal pressure. The finite-elements method and a modification of the Neuber method are used as a basis for a new approach to predicting the strength of T-joints under internal pressure during steady-state creep. The calculated results agree satisfactorily with experimental findings.

ガスタービン用ロータディスク材ＦＶ５３５合金の疲労寿命推定法

A rotor disk of jet engine and/or gas turbine is subjected to the intermittent stress waves, that is, the repetition of centrifugal stress at the start and stop of machine with superimposed vibrating stress. The serrated part and bolt hole of the rotor disk are important parts needed for fatigue strength evaluation.A number of studies have been conducted on the fatigue strength under the intermittent stress wave and the fatigue strength estimation of notched specimens. The fatigue strength evaluation method under the intermittent stress proposed by authors is being used for the fatigue life prediction of piston crown of a diesel engine. However, the adaptability of the method to the rotor disk has not been verified yet. The present paper aims at the verification of the adaptability of the method for a rotor disk made of martensite stainless steel FV535.The following conclusions were obtained from this experimental study.1) The fatigue crack initiation life of a notched specimen under constant stress amplitude was well predicted by Koe's or Neuber's method.2) The fatigue life prediction method proposed by the authors may well predict the fatigue life of a smooth specimen in the region of higher stress level than the fatigue limit by using the interaction coefficient C of 0.3. However, in the region of stress near the fatigue limit, the method predicted very conservative life and the coefficient C was more than 5.

Calculation of stress and strain gradients in the concentration zone in cyclic elastoplastic deformation. 1

A method is proposed of calculating the gradients of true stresses and strains in the stress concentration zone in cyclic elastoplastic deformation of the material based on calculating the true stresses and strains in the stress concentration zone using approximate dependencies. The gradients of the true stresses, calculated using the method of equivalent energy and Neuber's method, are compared with the gradients of elastic stresses. It is shown that this also applies to other materials in which the gradients of the true stresses in cyclic elastoplastic deformation are considerably lower than the gradients of elastic stresses.

Stress and strain concentration factor evaluation using the equivalent energy concept

The energy approach to local stress and strain evaluation in a notch in materials with a power law type of hardening curve is generalized. The formulae for relative stress and strain concentration factor evaluation using the generalized equivalent energy method, the Neuber method and the Hardrath-Ohman method are derived and the results are compared for low carbon steel. Comparison with experimental data and with finite element calculations is made for a low alloy steel. The local strains evaluated according to the generalized equivalent energy method are in good agreement with experimental data.

Predicting Crack-Formation Life

This paper discusses the parameters likely to influence the crack-formation life of components. In particular, the relationship between the fatigue life of plain and notched specimens is considered, and a mathematical model for predicting the crack-formation life of components is proposed. This allows for the effects of mean stresses and strains and is dependent upon the determination of local material behaviour. The approach is original in that it makes allowances for the influence of the degree of plasticity around a notch, represented in terms of the strain gradient. The Neuber method is evoked, suitably modified to allow for strain gradient effects, and strain gradients are estimated by differentiating Neuber's rule in the immediate vicinity of the notch. Experimental studies have been conducted to determine strain distributions, strain gradients and cyclic lives, and the results compared with predicted values; correlation is good.

Stress Analysis of a Bolt-Nut Joint by the Finite Element Method and the Copper-Electroplating Method : 1st Report, Stress at the Root of a V-Grooved Rod under a Tensile Load

There are many studies on the stress at the root of a loaded bolt thread which is screwed in a nut thread, but most of them are being based on the two dimensional analysis. This paper presents a three dimensional analysis of a bolt-nut joint by the finite element method and Okubo's copper-electroplating method. In the 1st report, such two methods of analysis are applied to a V-grooved rod under a tensile load as the first step. Firstly, the numerical solution of the stress concentration factor by the finite element method is computed by an electric digital computer. Secondly, a high accurate measuring method of the stress concentration factor of the V-groove by the copper-electroplating method is presented. These two methods of analysis are applied to V-grooved rods having three kinds of root radius, and the results are compared with each other. They show good agreement, but the value by Neuber's method is smaller than those two values.

Stresses in an Orthogonal Aerotropic Plate with Hyperbolic Reentrances

The problem of determining the stresses in an orthogonal aerotropic plate have been investigated by many authors, but they are hiefly in the cases, either of a plate having straight boundaries or of an infinite plate with a circular or an elliptic hole. In the present paper the aerotropic plate is supposed to be bound by two hyperbolic edges, and solutions are sought in three cases, namely under pure tension, pure shear and pure bending. The process used is similar to the Neuber's method, and in each case the coefficient of stress concentration is obtained in a simple form.

THE TREATMENT OF OSTEOMYELITIS WITH IODOFORM BONE PLUGGING.

The usual methods employed in the treatment of osteomyelitis had given such poor results in my own and in the work of others that I was led to try the iodoform plugging recommended by Moorhof. The methods of treating osteomyelitis are practically the same up to the point of filling the cavity. The methods of filling the cavity are as follows: With iodoform gauze. This has given very poor results, usually requires numerous operations and too frequently amputation of the limb. Senn's method of filling the cavity with decalcified bone chips dusted with iodoform powder and allowing it to fill with blood clot. In this method the chips are frequently extruded and the cavity usually becomes infected. Schede's method of filling the cavity with blood clot has had some success, but the clot very frequently becomes infected and the patient is worse than before the operation. Neuber's method of tacking