摘要:

Abstract—A model based upon linear elastic bridging and fiber crack tip shielding is proposed for predicting fatigue crack growth in a SCS‐6/Ti‐6–4 composite. The model is characterized by the fiber/matrix debond length rather than the fiber/matrix interfacial frictional shear strength used in most current fatigue models. Finite elements combined with fracture mechanics are applied for computing the local stress intensity. The local stress intensity in the matrix is then utilized to predict crack growth in the composite via comparison to monolithic fatigue crack propagation data for a similar Ti‐6–4 matr

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—When an initially‐parallel‐sided tab of material, cut into an isotropic finite‐width sheet, is torn by pulling the outer tabs in one direction, and the center in the opposite, the cracks may follow a parallel path, diverge outwards, or converge inwards depending on the widths of the inner and outer “legs”. At the same time, the untorn portion of the material may rotate relative to the pulling axis. The phenomenon is observed in globally elastic tearing, elastoplastic tearing, and in rigid‐plastic tearing. A fracture mechanics model using minimum energy explains the tear paths and rotations. Experiments on NS4 aluminium alloy confirm the analysis. The relationship of leg widths and bend radii with standard trousers tear testing of ductile materials

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00796.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—The Modified Crack Closure Integral (MCCI) technique based on Irwin's crack closure integral concept is very effective for estimation of strain energy release rates G in individual as well as mixed‐mode configurations in linear elastic fracture mechanics problems. In a finite element approach, MCCI can be evaluated in the post‐processing stage in terms of nodal forces and displacements near the crack tip. The MCCI expressions are however, element dependent and require a systematic derivation using stress and displacement distributions in the crack tip elements.Earlier a general procedure was proposed by the present authors for the derivation of MCCI expressions for 3‐dimensional (3‐d) crack problems modelled with 8‐noded brick elements. A concept of sub‐area integration was proposed to estimate strain energy release rates at a large number of points along the crack front. In the present paper a similar procedure is adopted for the derivation of MCCI expressions for 3‐d cracks modelled with 20‐noded brick elements. Numerical results are presented for center crack tension and edge crack shear specimens in thick slabs, showing a comparison between present results and those available

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—The biaxial fatigue behaviour of two batches of a structural steel, termed isotropic and anisotropic batches, is examined. Tests were carried out using thin‐walled hollow specimens subjected to axial load and internal and external pressure. The fatigue life of the isotropic batch is found to be about two to three times greater than the fatigue life of the anisotropic material. The ratio however is found to be dependent on the degree of biaxiality. Three equivalent strain parameters were used to correlate the fatigue lives, octahedral strain, Brown‐Miller and Lohr‐Ellison parameters. The difference between the theories are compared and the relation between the shear strain orientation and failure is di

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00798.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Since heat‐treated high strength steels are often used as materials for machines and structures that operate under severe service conditions, it is important to evaluate their fatigue life. Hence the growth law of a small fatigue crack must be known in order to estimate the fatigue life of machines and structures since the life of such members is controlled mainly by the behaviour of a small crack. The growth rate of a small crack can not be predicted usually by linear elastic fracture mechanics, but can be determined uniquely by the term σnal, where σais stress amplitude,lis crack length andnis a material constant. In this paper, the small‐crack growth law of heat‐treated carbon steels and low alloy steels was studied. An effective and convenient method based on a small‐crack growth law, dl/dN=C3(σa/σa)nlis proposed, where σuis the ultimate tensile strength, for predicting the small crack propagation life of heat‐ treated steels with different tensile strength levels, together with a method for determining the fatigue life

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00799.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Five kinds of silicon nitride samples with different microstructure were prepared in order to examine the effect of sintering condition on grain size and mechanical properties. The degradation in strength of ceramics caused by grinding is investigated in detail. It is shown that the critical process zone size is closely related to the grinding process. Futhermore, the crack size caused by grinding is estimated by the process zone size failure criterion and the Newman‐Raju formula. It can be concluded that the process zone size failure criterion is useful when evaluating the sensitivity of ceramics to grind

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00800.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Experiments have been performed on specimens subjected to strain cycles similar to those experienced by sub‐surface elements of material in rolling/sliding contact. It has been observed that if the strain cycle is closed then failure takes place by low cycle fatigue and the Coffin‐Manson relationship may be used to predict the number of cycles to failure. If however, the strain cycle is open, so that the material accumulates unidirectional plastic strain (the situation known as “ratchetting”) a different type of failure, which is termed ratchetting failure may occur. It occurs when the total accumulated plastic strain reaches a critical value which is comparable with the strain to failure in a monotonic tension test. The number of cycles to failure under these circumstances may be estimated by dividing this critical strain by the ratchetting strain per cycle. It is suggested that low cycle fatigue and ratchetting are independent and competitive mechanisms so that failure occurs by whichever of them corresponds to a shorter life. The results of both uniaxial and biaxial tests reported in the literature have been re‐evaluated and these, together with new data on biaxial tests on copper, found to be consistent with this

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00801.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Large scale, structurally representative, double tension crack arrest tests have been undertaken at temperatures between −99°C and −87°C. Applied stresses and the length of the embrittled crack starter sections were varied to give different applied stress intensity factors in the tests. The results indicate that crack arrest in structures is not governed solely by a so‐called crack arrest temperature but that static linear elastic fracture mechanics can be used to describe it. The measured crack arrest toughness temperature curve of the 1.5%Ni TMCP steel investigated lies at the lower bound of publi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00802.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—A study has been made of fatigue crack formation and growth at the root of different notch profiles in a structural steel subjected to fully reversed tension‐compression loading. The scale of stage I microstructural crack growth at notches decreased with increasing notch root strain and was comparable to the size of stage I cracks in shallow hourglass profile specimens at the same strain. Stage II crack growth rates were faster within the notch plastic field than in the elastic stress field of the bulk mater

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00803.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00794.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY