Fatigue and Fracture of Engineering Materials and Structures
8756-758X
1460-2695
Anh Quốc
Cơ quản chủ quản: WILEY , Wiley-Blackwell Publishing Ltd
Lĩnh vực:
Materials Science (miscellaneous)Mechanics of MaterialsMechanical Engineering
Các bài báo tiêu biểu
Analysis of cracked steel members reinforced by pre‐stress composite patch ABSTRACT Pre‐stress bonded composite patch is a promising technique to reinforce steel member damaged by fatigue. The effectiveness of this technique was verified by fatigue tests on notched steel plates. Results showed that the application of carbon fibre reinforced plastic (CFRP) strips and, eventually, the introduction of a compressive stress by pretension of the CFRP strips prior to bonding produced a significant increment of the remaining fatigue life. In this paper, the stress intensity factor in the notched plates is computed by a two‐dimensional finite element model in connection with the three‐layer technique in order to reduce the computational effort. Due to high stress concentration at the plate crack tip, debond is assumed at the adhesive–plate interface. The goal is to illustrate the influence of some reinforcement parameters such as the composite strip stiffness, the pre‐stress level, the adhesive layer thickness and the size of the debonded region on the effectiveness of the composite patch reinforcement.
Tập 26 Số 1 - Trang 59-66 - 2003
EFFECT OF PROCESSING ON THE HIGH TEMPERATURE LOW CYCLE FATIGUE PROPERTIES OF MODIFIED 9Cr‐1Mo FERRITIC STEEL The high temperature low cycle fatigue properties of modified 9Cr‐1Mo ferritic steel in a hot forged and a hot rolled condition have been evaluated. The hot forged material exhibited inferior fatigue properties as compared to the finer grained hot rolled material. Analysis of the data indicates that a larger grain size adversely affects the initiation stage but has little effect on the propagation stage. A steeper slope on the Coffin‐Manson plot results when the number of cycles to initiation is reduced.
Tập 7 Số 4 - Trang 299-314 - 1984
THE ENGINEERING FATIGUE PROPERTIES OF WROUGHT COPPER*<sup>†</sup> Abstract— The paper presents a comprehensive review, supplemented by original data, of the engineering fatigue behaviour of copper. Variations in manufacturing route and softening treatments are shown to have little effect on the fatigue of annealed copper but the high cycle fatigue strength is increased by cold work. The high strain fatigue behaviour is defined in terms of the plastic strain range and the cyclic stress‐strain characteristics are documented. Fatigue behaviour in bending and torsion is defined by data and related to that in tension by simple design rules. Notches are found to reduce the laboratory measured fatigue strength of copper by ∼ 30% and the effect of surface finish, surface distortion and surface residual stress is defined in the literature. Fatigue crack growth is defined in terms of stress intensity factor range ΔK by an upperbound law and, together with the conditions for non‐growth (ΔK 0 ), shown to relate to the equivalent conditions for steels via the ratio of the respective elastic moduli. The effect of environment on the fatigue of copper has received scant attention in the literature, such results as exist suggesting little if any reduction in strength to be brought about by gaseous or aqueous environments. The most dramatic change is the improvement of about an order of magnitude which results when tests in vacuum are compared with equivalent tests in air. Results of fatigue tests on copper in ammoniacal environments are conspicuously absent from the literature. As the test temperature is reduced below room temperature there is a predictable increase in high cycle fatigue strength, a reduction in fatigue strength occurring above room temperature. High strain fatigue test results presented in terms of plastic strain range appear insensitive to temperature although at very low strain rates and high temperatures a reduction in fatigue strength occurs. A linear life fraction cumulative damage creep‐fatigue law appears sometimes to be non‐conservative but much more testing is needed to evaluate fatigue damage summation laws generally for copper. Numerical data are given in support of all the aspects of the engineering fatigue behaviour reviewed in the paper.
Tập 4 Số 3 - Trang 199-234 - 1981
INTERACTION OF HIGH CYCLE FATIGUE AND CREEP IN 9%Cr‐1%Mo STEEL AT ELEVATED TEMPERATURE Abstract High‐cycle‐fatigue/creep experiments were performed on a 9%Cr‐1%Mo temperered marten‐site ferritic steel at 873 K in air. The stress ratio R=σmin /σmax ranged from‐1 (“pure” fatigue) to 1 (“pure” creep). The maximum stress σmax was kept constant at 240 MPa. The lifetime depends on the stress ratio R in a non‐monotonic way. In the stress ratio interval 0.6 < R < 1.0 both the creep strain rate and the lifetime are controlled by mean stress σmass of the stress cycle. In the stress ratio interval — 1 < R < 0.2 the lifetime is controlled by the stress amplitude na. The fatigue/creep interaction occurs in between these intervals. The fatigue/creep loading induces transformation of the tempered martensite ferritic structure into an equiaxed subgrain structure. The resulting subgrain size depends strongly on the stress ratio.
Tập 18 Số 1 - Trang 27-35 - 1995
Self‐healing materials: what can nature teach us? Abstract Natural materials such as bone and insect cuticle are capable of self‐repair, a facility that greatly increases their durability and safe working stress. Some engineering materials have also been designed to be self‐healing, although currently they cannot match the performance of natural materials as regards the efficiency and longevity of the healing process. In this paper, we review the state of the art regarding these two types of materials. We discuss the role of fracture mechanics in the development of theoretical models of self‐healing; we identify certain crucial parameters that make natural materials successful and discuss how these lessons can be applied to improve the performance of self‐healing materials for engineering applications.
Tập 40 Số 5 - Trang 655-669 - 2017
The effect of laser power density on the fatigue life of laser‐shock‐peened 7050 aluminium alloy ABSTRACT Laser shock peening (LSP) is an innovative surface treatment method that can result in significant improvement in the fatigue life of many metallic components. The process produces very little or no surface profile modification while producing a considerably deeper compressive residual stress layer than traditional shot peening operations. The work discussed here was designed to: (a) quantify the fatigue life improvement achieved by LSP in a typical high strength aircraft aluminium alloy and (b) identify any technological risks associated with its use. It is shown that when LSP conditions are optimal for the material and specimen configuration, a —three to four times increase in fatigue life over the as‐machined specimens could be achieved for a representative fighter aircraft loading spectrum when applied at a representative load level. However, if the process parameters are not optimal for the material investigated here, fatigue lives of LSP treated specimens may be reduced instead of increased due to the occurrence of internal cracking. This paper details the effect of laser power density on fatigue life of 7050‐T7451 aluminium alloy by experimental and numerical analysis.
Tập 30 Số 11 - Trang 1110-1124 - 2007
Laser peening and shot peening effects on fatigue life and surface roughness of friction stir welded 7075‐T7351 aluminum ABSTRACT The effects of laser peening, shot peening, and a combination of both on the fatigue life of Friction Stir Welds (FSW) was investigated. The fatigue samples consisted of dog bone specimens and the loading was applied in a direction perpendicular to the weld direction. Several laser peening (LP) conditions with different intensities, durations, and peening orders were tested in order to obtain the optimum peening parameters. The surface roughness resulting from various peening techniques was assessed and characterized. The results indicate a significant increase in fatigue life using LP compared to shot peening when tested on their native welded specimens.
Tập 30 Số 2 - Trang 115-130 - 2007
Fatigue crack initiation assessment of welded joints accounting for residual stress Abstract The impact of residual stresses on the fatigue crack initiation life of welded joints is evaluated by the finite element method. The residual stresses of nonload‐carrying cruciform joints, induced by welding and ultrasonic impact treatment, are modelled by initial stresses, using the linear superposition principle. An alternative approach of using modified stress‐strain curves in the highly stressed zone is also proposed to account for the residual stress effect on the local stress‐strain history. An evaluation of the fatigue crack initiation life of welded joints based on the local strain approach is carried out. The predicted results show the effect of residual stresses and agree well with published experimental results of as‐welded and ultrasonic impact treated specimens, demonstrating the applicability of both approaches. The proposed approaches may provide effective tools to evaluate the residual stress effect on the fatigue crack initiation life of welded joints.
Tập 41 Số 8 - Trang 1823-1837 - 2018
FATIGUE MICROCRACKS IN A LOW CARBON STEEL Abstract— The behaviour of a low carbon steel has been studied, in particular the initiation, growth and coalescence of fatigue microcracks on the surfaces of smooth specimens via surface replicas and photomicrographs. From the study, quantitative information on the initiation period, growth and coalescence of cracks, statistical distributions of crack length and crack depth, density of cracks, distribution pattern and characteristics of the major crack, were obtained. Knowledge of these parameters is critical for non‐destructive inspection during service life and the application of fracture mechanics to life assessment.
Tập 8 Số 2 - Trang 193-203 - 1985
CONFOCAL SCANNING LASER MICROSCOPY MEASUREMENTS OF THE GROWTH AND MORPHOLOGY OF MICROSTRUCTURALLY SHORT FATIGUE CRACKS IN A1 2024‐T351 ALLOY Abstract— A new technique for studying the growth and morphology of microstructurally short fatigue cracks is described. The technique allows short crack growth, crack depth, and crack front configuration to be measured using Confocal Scanning Laser Microscopy (CSLM). Good agreement is shown between CSLM measurements of the initial stage of crack growth (along an inclined shear plane), crack depth and aspect ratio, together with the measurements obtained using a surface layer removal technique. It is also found that non‐propagating short fatigue cracks have approximately the same aspect ratios in different specimen orientations and that the aspect ratio is independent of stress amplitude.
Tập 19 Số 9 - Trang 1153-1159 - 1996