High Strain Low Cycle Fatigue Research Articles

Structure and fatigue behavior of electroless plated Ni-Zn-P films using pretreatments, annealing and an applied magnetic field

Electroless ternary Ni-Zn-P films are plated onto a low carbon steel substrate. The surface morphology, microstructure, hardness, fatigue life and corrosion properties of the Ni-Zn-P coatings are respectively determined using scanning electron microscopy, X-ray diffraction, nano-indentation, high-strain low-cycle fatigue and polarization tests. The substrates pretreated using the proposed roughening (15 % H2SO4, 20 min) and activation (10 % H2SO4, 1 min) produce good Ni-Zn-P film deposition. When the annealing temperature reaches 400 °C, the Ni–P-Zn films contain crystalline Ni, FeNi and a precipitation Ni3P structures phase. Applied magnetic field improves the film growth rate, mechanical properties and corrosion resistance.

Influence of Surface Roughness on the High Temperature /High Strain Low Cycle Fatigue Behavior of Nickel-Based Superalloy Rene®80

Influence of Surface Roughness on the High Temperature /High Strain Low Cycle Fatigue Behavior of Nickel-Based Superalloy Rene®80

Fatigue life prediction of HTRB630E steel bars based on modified coffin-manson model under pre-strain

High strain low cycle fatigue performance is one of the important indicators for evaluating seismic reinforcement. The earthquake is often accompanied by aftershocks. At this time, the steel bars in the structure are subjected to the low cyclic load under pre-strain. In this article, fatigue life prediction of a new type of HTRB630E (T63E) ultra-high-strength steel bars based on modified Coffin-Manson model under pre-strain is presented. Firstly, the constant amplitude strain low cycle fatigue test for T63E steel bars without and with pre-strain is carried out. The test results indicates that the application of pre-strain causes the fatigue life of T63E steel bars to decrease by 30%–50%, but different pre-strain has the same effect on the fatigue life under the same strain amplitude. Secondly, the Coffin-Manson model is used to simulate the test results using OpenSees software. Thirdly, the modified plastic strain formula is used to predict the fatigue life of T63E steel bars under pre-strain. The simulation results indicate that the modified formula can predict the fatigue life of the steel bar under pre-strain more accurately, and the error is reduced from 50% to 10%. Finally, the main factor of the low-cycle fatigue performance of T63E steel bars under strain control is the maximum stress level in the process, which provides new methods and ideas for the later development of complex strain low cycle fatigue life prediction under different paths.

Electro-less plating nickel-phosphorus of low carbon steel using various pretreatments and an external magnetic field

Electro-less plating nickel-phosphorus (EPNP) subject to various pretreatments and an external magnetic field, are prepared onto low carbon steel (LCS). The surface hardness (SH), fatigue life (FL) and corrosion behavior (CB) of Ni-P coated are respectively obtained using a nano-indenter and a high strain low cycle fatigue life (HSLCFL) and polarization test. The experimental outcome reveals that LCS substrates that are pretreated using the proposed acid mixture (25% H2SO4 + 5% HCl) roughening and activation allow good Ni-P films to be deposited. In terms of EPNP, as the P content decreases, the SH and FL increase. Specimens that a coated in a Ni–P film using an external magnetic field have better mechanical performance than those that are not produced in an external magnetic field. As the external magnetic field intensity is increased, the film thickness, SH and FL increase, the concentration of P decreases and thin grains are formed on the film surface. The specimens without using an external magnetic field that are coated with a Ni–P film exhibit better resistance to corrosion than the uncoated sample of LCS. However, the Ni–P film that is coated using an external magnetic field has higher SH, so it exhibits increased resistance to corrosion.

High-Strain Low-Cycle Fatigue Behavior of Thermomechanically Treated Rebar

Low-cycle fatigue (LCF) behavior of a thermomechanically treated Fe 500 grade rebar has been evaluated under high-strain ranges to understand its seismic performance. The total strain-controlled LCF tests have been performed at five different strain (1.0, 2.0, 3.0, 4.0 and 5.0%) ranges at ambient temperature until failure maintaining a constant true strain rate of 1 × 10−3 s−1 and a fixed strain ratio of − 1. Fatigue data have been analyzed following strain-life relationship; while, macro- and micro-features of the failed specimens have been critically examined under SEM. Evaluation of fatigue behavior has been supplemented by microstructural characterization apart from measurements of hardness and tensile property. Continued cyclic softening has been observed till failure, and the cyclic yield strength is found to be significantly lower than the monotonic one. Cross-sectional microhardness measurements of rebar before and after fatigue reveals significant reduction in hardness specifically in the rim region with tempered martensite microstructure. The strain-life relationship accurately predicts the cyclic plastic behavior of the selected rebar which also exhibits non-Masing behavior. The fatigue crack is always found to initiate from the transverse rib root and propagates along the rim region following the rib.

High Strain Low Cycle Fatigue and Anti-Seismic Behavior of HRB400 QST Reinforced Steel Bars

Based on the failure model of building structural steels under earthquake loading, High strain low cycle fatigue properties of HRB400QST (yield strength grade 400MPa, Quenched and Self Tempered) reinforced steel bars with diameters of 20mm and 16mm(unmachined) and HRB400V-N MA(microalloying)with diameters of 16mm (unmachined) were investigated. Based on the tests of total strain controlling, cycle strain response character of three kinds of steel bars and the relationship between cyclic stress and strain were researched. Hollomon and Coffin-Manson formulas were used to induce fatigue life formulas of three kinds of steel bars, and then the values of σa·Δεt were gained when Nf =100, calculated results show that the high strain low cycle fatigue properties of HRB400V-N MA rebars tested are much better than HRB400QST steel bars. Rupture surface scan reveals that surface hardened layer will reduce the cyclic toughness, and is bad for the anti-seismic performance.

A low cycle fatigue model of a short-fibre reinforced 6061 aluminium alloy metal matrix composite

A low cycle fatigue model has been developed to predict the fatigue life of both the unreinforced aluminium alloy and the short-fibre reinforced aluminium alloy metal-matrix composites based solely on crack propagation from microstructural features. In this approach a crack is assumed to initiate and grow from a microstructural feature on the first cycle. The model assumes that there is a fatigue-damaged zone ahead of the crack tip within which the actual degradation of the material takes place. The low-cycle fatigue crack growth and the condition for failure are controlled by the amount of cyclic plasticity generated within the fatigue-damaged zone ahead of the crack tip and by the ability of the short fibres to constrain this cyclic plasticity. The fatigue crack growth rate is directly correlated to the range of crack-tip opening displacement. The empirical Coffin–Manson and Basquin laws have been derived theoretically and applied to compare with total-strain controlled low-cycle fatigue life data obtained on the unreinforced 6061 aluminium alloy at 25 °C and on the aluminium alloy AA6061 matrix reinforced with Al 2O 3 Saffil short-fibres of a volume fraction of 20 vol.% and test temperatures from −100 to 150 °C. The proposed model can give predicted fatigue lives in good agreement with the experimental total-strain controlled fatigue data at both high strain low-cycle fatigue and low strain high-cycle fatigue regime. It is remarkable that the addition of high-strength Al 2O 3 fibres in the 6061 aluminium alloy matrix will not only strengthen the microstructure of the 6061 aluminium alloy, but also channel deformation at the tip of a crack into the matrix regions between the fibres and therefore constrain the plastic deformation in the matrix. The overall expected effect is therefore the reduction of the fatigue ductility.

Modelling low-cycle fatigue life of particulate-reinforced metal-matrix composites

A low-cycle fatigue life prediction model for particulate-reinforced metal-matrix composites (MMCs) is presented. The low-cycle fatigue behaviour of particulate-reinforced MMCs is treated as a localised damage development phenomenon activated by applied cyclic loading. The localised cyclic stress and strain concentration and fatigue damage evolution of microstructural elements within the fatigue damaged zone ahead of the crack tip are considered to dominate the whole low-cycle fatigue processes. In high-strain low-cycle fatigue conditions, the fatigue-damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the composite and within which the actual degradation of the composite material takes place. The fatigue crack growth rate is directly correlated to the range of the crack tip opening displacement. The empirical Coffin–Manson relationship is derived and the model naturally predicts that in strain-controlled low-cycle fatigue tests the MMCs with the higher volume fraction of reinforcement particles exhibit shorter fatigue lives than composites with a smaller volume fraction. The theoretical predictions from this model are in good agreement with the low-cycle fatigue life data of AA6061-T6 aluminium alloy reinforced with 15 and 20 vol.% alumina particles, respectively, for a temperature range between −100 and 150 °C in total-strain controlled mode.

Fatigue strength of bandsaws with hard coatings : Dugdale, D.S. and Sarwar, M. J. Mater. Processing Technol. (1 Jan. 1996) 56 (1–4), 729–732

A low-cycle fatigue life prediction model for particulate-reinforced metal-matrix composites (MMCs) is presented. The low-cycle fatigue behaviour of particulate-reinforced MMCs is treated as a localised damage development phenomenon activated by applied cyclic loading. The localised cyclic stress and strain concentration and fatigue damage evolution of microstructural elements within the fatigue damaged zone ahead of the crack tip are considered to dominate the whole low-cycle fatigue processes. In high-strain low-cycle fatigue conditions, the fatigue-damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the composite and within which the actual degradation of the composite material takes place. The fatigue crack growth rate is directly correlated to the range of the crack tip opening displacement. The empirical Coffin–Manson relationship is derived and the model naturally predicts that in strain-controlled low-cycle fatigue tests the MMCs with the higher volume fraction of reinforcement particles exhibit shorter fatigue lives than composites with a smaller volume fraction. The theoretical predictions from this model are in good agreement with the low-cycle fatigue life data of AA6061-T6 aluminium alloy reinforced with 15 and 20 vol.% alumina particles, respectively, for a temperature range between −100 and 150 °C in total-strain controlled mode.

Fatigue behaviour and life prediction of a SiC/Ti-24Al-11Nb composite under isothermal conditions: Bartolotta, P.A. Diss. Abst. Int. Feb. 1992 52 (8) 147 pp

A low-cycle fatigue life prediction model for particulate-reinforced metal-matrix composites (MMCs) is presented. The low-cycle fatigue behaviour of particulate-reinforced MMCs is treated as a localised damage development phenomenon activated by applied cyclic loading. The localised cyclic stress and strain concentration and fatigue damage evolution of microstructural elements within the fatigue damaged zone ahead of the crack tip are considered to dominate the whole low-cycle fatigue processes. In high-strain low-cycle fatigue conditions, the fatigue-damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the composite and within which the actual degradation of the composite material takes place. The fatigue crack growth rate is directly correlated to the range of the crack tip opening displacement. The empirical Coffin–Manson relationship is derived and the model naturally predicts that in strain-controlled low-cycle fatigue tests the MMCs with the higher volume fraction of reinforcement particles exhibit shorter fatigue lives than composites with a smaller volume fraction. The theoretical predictions from this model are in good agreement with the low-cycle fatigue life data of AA6061-T6 aluminium alloy reinforced with 15 and 20 vol.% alumina particles, respectively, for a temperature range between −100 and 150 °C in total-strain controlled mode.

High temperature deformation in engineering alloys control

A generalised constitutive description of deformation of engineering alloys that exhibit a dominant tertiary creep is presented that extends a previous treatment of creep deformation. The model parameters of the constitutive equations that are determined by analysis of creep curves are supplemented by the Young's modulus to provide a database from which illustrative calculations are made. Simulations of constant strain rate, stress relaxation and high strain low cycle fatigue (both strain and stress control) are made for the superalloy IN738LC; the predictions are compared with limited available experimental data.

Low-cycle fatigue crack advance and life prediction

A new concept for a fatigue process zone within which the actual degradation of the material takes place is proposed. This zone is described as the region in which the stress distribution of the HRR field approaches the maximum flow stress of the material, with the strain localization caused by a sliding-off process. In high-strain low-cycle fatigue conditions, this new concept is shown to be more realistic for the prediction of the fatigue life than that of previous work which has been based on a rough approximation. The proposed feature of the zone is experimentally supported by microhardness measurements. In particular, although this zone is formulated from continuum mechanics, it reflects microstructural factors such as precipitates and stacking-fault energy. Using the developed fatigue process zone and strain intensification in the zone near the crack tip, a modified analytical model for prediction of the continuous low-cycle fatigue life is proposed. The exponent of the Coffin-Manson law obtained from the present prediction is suggested to be 1/(3n + 1), which is different from the previously reported value of 1/(2/'n + 1), and is shown to be in good agreement with experimental results for five alloy systems.

The high strain cyclic fatigue and fracture behavior of 2090 aluminum alloy

A study has been made to understand the high strain low cycle fatigue properties and cyclic fracture behavior of aluminum alloy 2090 (A1-2.85Cu-2.04Li-0.12Zr; where the composition is in weight percent). The alloy was cycled over a range of plastic strains giving lives of less than 10 4 cycles. The specimens were cycled using tension-compression loading under total strain control. The alloy, in the peak-aged condition, exhibited a distinct discontinuity or break in the Coffin-Manson curve. The abnormal plastic strain-fatigue life behavior is attributed to possible differences in the homogeneity of deformation as a function of plastic strain amplitude, and to a change in fracture mode from ductile monotonie type to brittle crystallographic as a function of plastic strain amplitude. Cyclic deformation was found to produce softening at all strain amplitudes. The presence of shearable matrix precipitates in the peak-aged microstructure results in a local decrease in resistance to dislocation movement, leading to loss of ordering contributions to hardening and plastic strain inhomogeneity. The observed softening is due to dislocation-precipitate interactions, and is a mechanical effect. The cyclic fracture behavior of the alloy is discussed in terms of plastic strain amplitude, response stress, intrinsic microstructural features and matrix slip characteristics.

Near-threshold fatigue crack growth properties and fractographic features of various steels in 3% NaCl aqueous solution: Shimodaira, M., Matsuoka, S. and Masuda, H. J. Soc. Mater. Sci., Jpn. Sept. 1988 37, (420), 1097–1103 (in Japanese)

A low-cycle fatigue life prediction model for particulate-reinforced metal-matrix composites (MMCs) is presented. The low-cycle fatigue behaviour of particulate-reinforced MMCs is treated as a localised damage development phenomenon activated by applied cyclic loading. The localised cyclic stress and strain concentration and fatigue damage evolution of microstructural elements within the fatigue damaged zone ahead of the crack tip are considered to dominate the whole low-cycle fatigue processes. In high-strain low-cycle fatigue conditions, the fatigue-damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the composite and within which the actual degradation of the composite material takes place. The fatigue crack growth rate is directly correlated to the range of the crack tip opening displacement. The empirical Coffin–Manson relationship is derived and the model naturally predicts that in strain-controlled low-cycle fatigue tests the MMCs with the higher volume fraction of reinforcement particles exhibit shorter fatigue lives than composites with a smaller volume fraction. The theoretical predictions from this model are in good agreement with the low-cycle fatigue life data of AA6061-T6 aluminium alloy reinforced with 15 and 20 vol.% alumina particles, respectively, for a temperature range between −100 and 150 °C in total-strain controlled mode.

Damage tolerance in discontinuously reinforced metal-matrix composites: Rack, H.J. and Ratnaparkhi, P. J. Met. Nov. 1988 40, (11), 55–57

A low-cycle fatigue life prediction model for particulate-reinforced metal-matrix composites (MMCs) is presented. The low-cycle fatigue behaviour of particulate-reinforced MMCs is treated as a localised damage development phenomenon activated by applied cyclic loading. The localised cyclic stress and strain concentration and fatigue damage evolution of microstructural elements within the fatigue damaged zone ahead of the crack tip are considered to dominate the whole low-cycle fatigue processes. In high-strain low-cycle fatigue conditions, the fatigue-damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the composite and within which the actual degradation of the composite material takes place. The fatigue crack growth rate is directly correlated to the range of the crack tip opening displacement. The empirical Coffin–Manson relationship is derived and the model naturally predicts that in strain-controlled low-cycle fatigue tests the MMCs with the higher volume fraction of reinforcement particles exhibit shorter fatigue lives than composites with a smaller volume fraction. The theoretical predictions from this model are in good agreement with the low-cycle fatigue life data of AA6061-T6 aluminium alloy reinforced with 15 and 20 vol.% alumina particles, respectively, for a temperature range between −100 and 150 °C in total-strain controlled mode.