摘要:

Abstract—Predictions of a new cumulative damage theory established by Hashin and Rotem (HR) are compared with an extensive series of test data for two‐level shear strain cycling and a double linear exponential damage rule, all given by Miller and Zachariah (MZ), demonstrating good agreement. While MZ requires determination of two parameters to assess crack development by fit to the two level test data the only testing parameter needed for HR is the fatigue lifetimeNebeyond which the fatigue limit occurs. This parameter has here been estimated on the basis of recent advances in understanding cyclic deformat

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01092.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—A reanalysis has been carried out on the results of Zachariah. An elastic‐plastic analysis based onS‐Ndata indicates that the mechanism of growth of very small cracks is similar to that expressed by linear elastic fracture mechanics, i.e. crack growth in mild steel is given bywhere Δγpis the plastic shear strain range andais the crack length.Crack initiation occurs within a single grain and crack propagation is given by the above equation for cracks which can be smaller than a few microns. The size of an initiated crack is a function of stress level varying from 0·1–1·0 μm in the high strain fatigue regime to 2·3 μm close to the fatigue limit. The period of crack initiation is negligible in the HSF regime whilst the initiation period can dominate lifetime at low

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01093.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—This paper comments on the eleven papers presented in the “Materials Behaviour” section of the Extension Seminar of I.C.M.3 and reported in Vol. 2, No. 1 of this Journal. It is hoped that this permanent recording of the opinions stated during the Conference will stimulate further discussion as to the directions future work in this field should take. For conciseness, points of detail and specific aspects not related to the “Microstructure‐Fatigue Resistance” theme have b

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01094.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—A simple model for the estimation of the total fatigue life of notched members is presented. The number of cycles to failure is estimated as the summation of the cyclic life spent in: (1) the initiation of a dominant fatigue crack at the notch root; (2) the very early growth of this crack within the notch plastic zone; (3) the subsequent fatigue crack growth in the elastic stress‐strain field of the notch; and (4) the elastic stress field of the bulk material. Theoretical and experimental results are compa

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01095.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—A statistical approach to the failure of engineering components is presented which takes account of the size distribution of defects within the structure, and growth of these defects caused by cyclic loading during service. Statistical design methods are illustrated by considering the failure of simple bars which are assumed to contain pre‐existing defects. It is argued that more efficient designs should result if safety factors are applied to failure rates rather than to design stresses (or some equivalent) since small reductions of the design stresses can lead to substantial decreases in the predicted failure rates. The statistical approach offers a controlled method of reducing conventional safety factors thus leading to more efficient designs. It also offers: (i) a rational method of assessing the safety of potentially hazardous engineering structures, e.g. pressure vessels, and (ii) a quantitative treatment of product reliability which can highlight methods of improving performance in serv

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01096.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—This work was conducted to study the significant increases in fatigue crack growth rates at low frequencies commonly observed at high temperature. Creep tests and fatigue tests at 0·01, 0·1 and 1·0 Hz were conducted at 650°C in air and in helium on samples of INCONEL alloy 718 in two different heat treatments. Creep crack growth rates were 50–100 times greater in air than in helium. Fatigue tests in helium showed little sensitivity to frequency, but tests in air showed considerable increases in crack growth rates at lower frequencies. The results indicate the air environment played a predominant role in both the creep and the fatigue tests. Oxygen diffusion into grain boundaries appeared responsible for the accelerated crack growth in air. An overaging heat treatment reduced the crack growt

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01097.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The effects of shot‐peening residual stresses on bending fatigue behaviour of welded plate and surface‐flawed plate were investigated. The results show that shot peening residual stresses may significantly increase fatigue strength as well as the threshold stress‐ intensity factor range of a surface‐flawed plate. This paper presents a simple analytical method for determining the residual stresses. The calculated values are essentially in agreement with the experimenta

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01098.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—This paper introduces an analytical procedure for predicting engineering crack formation life of high temperature turbine components. This procedure is based upon elastic‐plastic fracture mechanics rather than linear elastic fracture mechanics. State of the art, some experimental results and future developments are discus

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01099.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The high temperature low‐cycle fatigue behaviour of two turbine disc alloys was studied at 600 and 650°C, at total strain ranges, between 0·6 and 2·1%. These results showed that the life of both alloys may be predicted by a Coffin‐Manson type equation.The fracture surfaces of the specimens were examined by scanning electron mi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb01100.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY