摘要:

AbstractIn this paper, test conditions and microstructural factors have been investigated for newly developed nitrogen steels at load rates and test temperatures suitable for future operating conditions. Static tests have been carried out at ε∼ 10−4s‐1and dynamic tests at ε∼ 102s−1. Different test temperatures enable fracture mechanisms and fracture toughness variations to be studied. Anisotropy of some characteristics in the initial (non‐heat‐treated) state, together with heat treatment effects and structural changes under two load rates have been analysed. Fracture appearance transition temperature (FATT) values have been obtained from absorbed energy and fracture surface crystallinity values. Using yield strength and fracture toughness data, an estimate has been made of critical crack lengths for un

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractConventional experimental/knowledge records (usually tables, graphs and/or equations) are not suitable for an efficient uncertainty‐reasoning because of the poor knowledge‐acquisition methods used to develop them. A fuzzy knowledge base is a suitable framework for acquisition of vague, sparse and inconsistent knowledge. A revitalization of valuable records and re‐used literature knowledge items is a retrospective application of knowledge engineering algorithms. This is anad hocprocess and a general theoretical background does not exist. Therefore this paper presents a detailed description of a case study (49 variables, 4000 statements).A query as an element of a man‐machine dialogue is presented. Noa prioriknowledge of fuzzy mathematics is

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractUsually, there is large scatter in fatigue data and this should be evaluated quantitatively when fatigue data are applied to the design of machines and structures. Consequently it is important to clarify the physical basis of scatter in fatigue life. In this present study, rotary bending fatigue tests were performed on an annealed 0.21% carbon steel. At least sixteen smooth specimens were fatigued at each of three stress ranges and successive observations of the surface were studied for all the specimens using the plastic replica method. By examining the initiation and propagation behaviour of cracks the physical basis of scatter in fatigue life is analysed and discussed. To estimate the scatter characteristics quantitatively, the distributions of crack initiation life, propagation life, fatigue life and crack length were individually studied by assuming a Weibull distribution for each set of data.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe majority of methods for predicting the direction of propagation of mixed mode cracks have assumed that they branch to grow as mode I cracks. However, under some circumstances mode II crack growth occurs. Rolling contact fatigue cracks are one example of an industrial problem where cracks appear to grow under predominantly mode II loading without branching. This paper reviews the available models and the experimental studies in the literature on mixed mode I and II loading, and discusses the parameters that affect the mode of crack growth.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe fatigue lives, the fatigue limit stress ranges and fatigue notch factors for metallic specimens can be predicted using a modified fracture mechanics model for short cracks based on the combination of solutions for the non‐uniform strains at the surface of a metal and the development of crack closure. The resulting local stress intensity factor exceeds that indicated by linear elastic fracture mechanics at short crack lengths. The model predicts a smooth and continuous variation of the fatigue notch factor with notch size between a lower bound of unity and an upper bound equal to the theoretical notch stress concentration factor. The model is verified using experimental data for a 2024‐T351 aluminium alloy for smooth and notched specimens tested at various stress rat

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe fundamental aspect of composites is that of stress transfer from the matrix to the fibers, and a number of mechanisms derive from this basic consideration. A previous analysis, although relatively simple and elegant, has a basic flaw, in that it assumes that there is no adhesion between the fiber and the matrix at the fiber ends, leading to the sometimes erronous condition of no stress transfer through those points. In this paper a modified end condition that better describes stress transfer is investigated and applied in determining the development of fiber, matrix and interfacial shear stress distribution in the uncracked, singly cracked and multiple cracked matrix configurations, with emphasis on the effects due to constituent dimensions.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAxisymmetric notched bars with notch roots of large and small radius were tested under large strain cyclic loading. The main attention is focused on the fracture behaviour of steels having cycles to failure within the range 1‐100. Our study shows that a gradual transition from a static ductile nature to one of fatigue cleavage can be observed and characterized by the Coffin‐Manson formula in a generalized form. Both the triaxial tensile stress within the central region of specimens and static damage caused by the first increasing load have effects on the final failure event. A generalized cyclic strain range parameter δε is proposed as a measure of the numerous factors affecting behaviour. Fractographs are presented to illustrate the behaviour reported in the

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00028.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThermal fatigue experiments performed with an austenitic steel give rise to an irregular pattern of cracks on the specimen surface. The investigations are aimed at characterizing the patterns in quantitative terms and at discerning trends with increasing numbers of cycles. Statistical methods based on different models of stochastic geometry are applied to take into account the random influence in pattern formation. Descriptive statistics as well as stochastic models are used to characterize the damage level. The stochastic models, such as fibre processes and random mosaics, will finally correlate the physical damage process with the random crack pattern observed. It is shown in this paper how the statistical characteristics of the random crack patterns can be related to the statistical characteristics of the stochastic models and the way the physical nature of the damage process influences these quantities.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA path‐independent integral is introduced for calculating stress intensity factors. The derivation of the integral is based on the application of the known Bueckner's fundamental field solution for a crack in an infinite body and on the reciprocal theorem. The method was applied to two‐dimensional linear elastic mixed‐mode crack problems. The key advantage of the present path‐independent integral is that the stress intensity factor components for any irregular cracked geometry under any kind of loading can be easily obtained by a contour integral around the crack tip. The method is simple to implement and only the far field displacements and tractions along the contour must be known. The required stress analysis can be made by using any analytical or numerical method, e.g. the finite element method, without special consideration of the modelling of crack tip singularity. The application of this integral is also independent of the crack type, that is, there is no difference between an edge crack and an embedded crack, provided that the crack tip asymptotic behaviour

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY