Effect Of Cyclic Deformation Research Articles

The effect of cyclic deformation on the mechanical, elastic and acoustic characteristics of austenitic stainless steel

The effect of elastoplastic cyclic straining on the elastic and acoustic characteristics of austenitic stainless steel AISI 321 is investigated. A change of the elastic characteristics of austenitic stainless steel associated primarily with martensitic transformations that affect the accumulated energy density is found. The influence of the amplitude of strain cycle on development of the elastic anisotropy is analyzed. The possibility of determining the stress amplitude of the fatigue loading cycle by an acoustic method involving measuring the elastic characteristic of the material has been demonstrated. The relationship between changes of elastic characteristics and damage is suggested; it can be used for evaluation of fatigue life by the acoustic method.

Effects of cyclic deformation on a barrier thin film for flexible organic optoelectronic devices

Effects of cyclic bending on the encapsulation properties of a barrier thin film are investigated. Water vapor transmission rate (WVTR) of the given barrier film is measured after variously cyclic bending conditions using a calcium corrosion test technique. Experimental results show that microcracks in the barrier thin film are found after applying a certain number of bending cycles. They are responsible for an increase in WVTR. Given a bending radius, a greater number of bending cycles leads to a larger amount of damage, and consequently a greater extent of moisture ingress. A smaller bending radius produces a greater amount of damage than a larger one, in a short period of loading time (≤104 cycles). However, after 105 cycles of cyclic bending, the amount of damage reaches a saturated level regardless of bending radius, as all the WVTR values become comparable. A simplified 3D finite element analysis (FEA) model is established in microscale to analyze the moisture diffusion mechanism. Numerical results show that, with the presence of cracking and delamination, the WVTR value increases significantly. Good agreement between the simulation and experimental measurements on WVTR confirms that the failure mechanism involves cracking and delamination under cyclic bending. The 3D FEA modeling developed could offer a method to predict the change of WVTR in correlation with cracking and delamination in the barrier thin film.

Electrical conductivity and dynamic mechanical properties of silicon rubber-based conducting composites: effect of cyclic deformation, pressure and temperature

The effects of cyclic deformations such as bending and compressive flexing, temperature and pressure on electrical and dynamic mechanical properties of conductive polydimethylsiloxane (PDMS) composites have been investigated. Conductive elastomeric composites were prepared by incorporating various carbon blacks in insulating PDMS matrix. Electrical conductivity was measured against varying concentration of different carbon blacks to assess the percolation threshold of the composites. AC and DC conductivity was found to increase with an increase in some bending flex cycles. However, with compressive flexing, DC conductivity initially dropped but later started increasing with an increase in flex cycles. The variations in electrical conductivity and dynamic mechanical modulus due to bend flexing are found to be similar, i.e. both characteristics show an increase in magnitude with an increase in some flex cycles. DC resistivity was found to increase with heating–cooling cycles, and this change in resistivity did not follow the same path leading to electrical set and hysteresis. © 2017 Society of Chemical Industry

Osteosynthesis of partial rib osteotomy in a miniature pig model using human standard-sized magnesium plate/screw systems: Effect of cyclic deformation on implant integrity and bone healing

Magnesium alloys are candidates for resorbable material in bone fixation. However, the degradation and performance of osteosynthesis plate/screw systems in vivo, under cyclic deformation, is unknown. We evaluated the outcomes of human standard-sized magnesium plate/screw systems with or without plasma-electrolytic surface modifications in a miniature pig rib model. Of a total of 14 minipigs, six were implanted with coated magnesium WE43 six-hole plates/screws, six received magnesium uncoated plates/screws, and two received titanium osteosynthesis systems.The performance of the plate/screw fixation system on partially osteotomized 7th ribs was compared with that on intact 9th ribs. Radiological examinations were performed in vivo at 1, 4 and 8 weeks and after euthanasia at 12 and 24 weeks. After euthanasia the bone blocks were analyzed by computed tomography (CT), microfocus computed tomography (micro-CT), histology and histomorphometry. Follow-up post-surgery showed no trouble with wound healing. In vivo radiological examinations showed higher amounts of gas formation above the uncoated magnesium plates fixed on the partially osteotomized and intact ribs. CT scans showed no broken plates or implant displacement. The micro-CT examination demonstrated better surrounding bone properties around the coated than the uncoated magnesium implants 12 weeks after surgery. No negative influence of magnesium degradation on bone healing was observed with histological examinations. Plastic deformation during surgery and cyclic deformation did not affect the integrity of the used magnesium plates. This study showed promising results for the further development of coated magnesium plate/screw systems for bone fixation.

Effects of cyclic deformation on conductive characteristics of indium tin oxide thin film on polyethylene terephthalate substrate

Abstract Effects of cyclic deformation and annealing treatment on conductive durability of indium tin oxide (ITO) thin film deposited on polyethylene terephthalate (PET) substrate are investigated. In-situ electrical and mechanical tests of ITO/PET sheet under various combinations of cyclic and static loadings are conducted at room temperature. Experimental results show that the number of cycles to failure is significantly decreased with an increase in displacement amplitude, given a specific extent of electrical resistance change of ITO/PET sheet. A static holding period of 1000 s in various loading modes plays a role in influencing the failure of ITO/PET sheet. Cyclic bending combined with a static tensile holding generally generates more damages and a smaller number of cycles to failure than does that combined with a compressive holding, neutral holding, or no holding. Under a small fatigue loading, the conductive durability of ITO/PET sheet is increased with an increase in annealing temperature. However, there is little effect of annealing temperature on ITO/PET fatigue life under a larger displacement amplitude of fatigue loading. Using a surface-based cohesive modeling technique, a simplified three-dimensional finite element analysis micromodel subjected to tensile and compressive loadings is numerically analyzed to clarify the failure mechanism of interfacial and buckling-like delamination which governs the change in electrical conductivity of ITO/PET sheet. Modeling results indicate that buckle height of the ITO/PET micromodel subjected to tensile loading is significantly greater than that of compressive loading, providing more evidence of the aforementioned effect of loading mode.

Cyclic Stress-Strain Response of Superelastic Polycrystalline Cu-12wt%Al-0.5wt%Be Alloy

The effect of cyclic deformation on the stability of superelasticity was investigated for the Cu-12wt%Al-0.5wy%Be alloy. The loading and unloading cyclic tensile tests were performed at room temperature and at 57oC with the maximum constant strain of 4%. The effect of holding the applied strain for a period of time on the superelastic properties was also investigated. It was confirmed that the total volume fraction of the retained martensite changes with time after unloading cycle, leading to the reduction of the residual strain. Additionally, the residual strain increases as the loading cycle of the applied strain is kept constant for a period of time.

SHAPE MEMORY EFFECT AND CYCLIC DEFORMATION BEHAVIOR OF Ti–Nb–N ALLOYS

The effect of 1 at.% N addition on the shape memory effect of Ti – Nb alloys was investigated. The shape memory effect and superelasticity were observed in Ti –(18–20) Nb –1.0 N and Ti –(21–25) Nb –1.0 N alloys, respectively. The Ti –23 Nb –1.0 N alloy exhibits the best superelastic properties with almost perfect recovery and small stress hysteresis among N added ternary alloys. The effect of cyclic deformation on the stability of superelasticity was investigated for the Ti –23 Nb –1.0 N alloy by loading and unloading cyclic tensile tests up to 500 cycles with a constant maximum applied strain of 2.5%. It was confirmed that the stability of superelasticity was improved by the addition of N due to the increase of the critical stress for slip.

Cyclic deformation behavior of a Ti–26 at.% Nb alloy

The effect of cyclic deformation on superelasticity was investigated in a Ti–26 at.% Nb alloy. Loading and unloading tensile tests with a constant maximum applied strain of 2.5% were carried out until the 500th cycle. The critical stress for inducing the martensitic transformation and superelastic strain decreased, while the accumulated residual strain increased with increasing number of cycles. The increase in the residual strain during cyclic deformation was due mainly to α′′ martensite phase stabilization. Both the residual strain and the residual α′′ martensite phase increased with increasing number of cycles. The stability of superelasticity was improved, i.e. the residual strain decreased and the superelastic strain increased, by intermediate-temperature annealing and/or aging. The specimen annealed at 873 K for 0.6 ks followed by aging at 573 K for 3.6 ks exhibited the most stabilized superelasticity, owing to the combination effect of work hardening and fine ω-phase precipitation.

709 Ti-Nb系合金の超弾性特性に及ぼす繰返し変形の影響(OS5-(1) インプラントおよび生体材料,オーガナイズドセッション)

The effect of cyclic deformation on superelastic behavior was investigated in Ti-26Nb and Ti-23Nb-1.0N (at.%) alloys. Cyclic loading-unloading tensile tests with a constant maximum applied strain of 2.5% were carried out until the 500th cycle. With increasing number of cycles, the critical stress for inducing the martensitic transformation decreased and the residual strain increased. In the Ti-26Nb alloy, it was confirmed that the increase of the residual strain during the cyclic deformation was due primarily to the increase in the residual martensites. More stable cyclic deformation behavior was confirmed in the Ti-23Nb-1.0N alloy compared with the Ti-26Nb alloy owing to the higher critical stress for slip.

A neutron-diffraction study of the low-cycle fatigue behavior of HASTELLOY ® C-22HS TM alloy

The HASTELLOY ® C-22HS TM alloy is a face-centered cubic (fcc), nickel-based, corrosion-resistant superalloy. In the present study, the low-cycle-fatigue behaviors of the alloy were examined by in situ neutron diffraction at room temperature. The fatigue parameters included a total strain range of Δ ε = 2% and a strain ratio of R = −1 ( R = ε min/ ε max, where ε min and ε max are the applied minimum and maximum strains, respectively). The effect of cyclic deformation on the lattice strains was studied as a function of cyclic straining. The cyclic hardening and softening behaviors during fatigue is discussed in light of the relationship between the peak widths and lattice strains.

The effect of cyclic deformation and solute binding on solute transport in cartilage

Diffusive transport must play an important role in transporting nutrients into cartilage due to its avascular nature. Recent theoretical studies generally support the idea that cyclic loading enhances large molecule transport through advection. However, to date, reactive transport, i.e. the effects of solute binding, has not yet been taken into consideration in cyclically deformed cartilage. In the present study, we develop a reactive transport model to describe the potential role of binding of solute within cyclically deformed cartilage. Our results show that binding does have a significant effect on transport, particularly for the low IGF-I concentrations typical of synovial fluid. A dynamic loading regime of high strain magnitudes (up to 10%) in combination with high frequencies (e.g. 1 Hz) was seen to produce the most dramatic results with enhanced total uptake ratio as high as 25% averaged over the first 5 h of cyclic loading.

Thermally and stress-induced martensitic transformation in Co–Ni–Al ferromagnetic shape memory alloy single crystals

In the present study, the shape memory characteristics of Co 38Ni 33Al 29 (numbers indicate at.%) alloy single crystals are investigated. Transformation behavior under constant stress levels, two-way shape memory behavior, the effect of cyclic deformation and pseudoelasticity as a function of strain and temperature were studied. The single crystals demonstrate large two-way shape memory strain, a near perfect pseudoelastic behavior with up to 4% pseudoelastic strain, low pseudoelastic stress hysteresis, a large pseudoelastic temperature window and high resistance for dislocation slip.

Effects of cyclic deformation on subgrain evolution and creep in 9–12% Cr-steels

Power plant components from modern 9–12% CrMoV-steels having fine precipitate stabilized subgrain structure undergo cyclic deformation as well as creep during service. The present work studies changes in subgrain structure due to cyclic straining and their effects on the creep behaviour in 12CrMoWVNbN10-1-1 steel. It was found that the cyclic plastic straining causes significant coarsening of the subgrain structure. Presence of hold periods during deformation significantly increases the extent of coarsening. Evolution of subgrain structure during cyclic deformation has been treated by extending the phenomenological law known from creep. Subgrain coarsening induced by cyclic deformation leads to significant increase in the resistance against creep.

A Cyclic Microbend Study on LIGA Ni Microelectromechanical Systems Thin Films

This paper presents the results of recent studies of cyclic microbend experiments and their consequences for plasticity length-scale phenomena in LIGA Ni microelectromechanical systems (MEMS) thin films. The strain–life fatigue behavior of LIGA Ni thin films is studied by performing fully reversed cyclic microbend experiments that provide insights into cyclic stress/strain evolution and cyclic failure phenomena. The effects of cyclic deformation on the plasticity length-scale parameters are also considered within the context of strain gradient plasticity theories. The implications of the results are then discussed for the analysis of plasticity and cyclic deformation in MEMS structures and other microscale systems.

Ferromagnetic properties of cyclically deformed Fe3Ge and Ni3Ge

The magnetisation behaviour of cyclically deformed and non-deformed Fe3Ge and Ni3Ge is examined at sufficiently low temperatures below the Curie point. Despite these two intermetallics having the same L12 structure, they are found to show quite different behaviour in their ferromagnetic properties; the spontaneous magnetisation (M S) remains unaffected in the former whereas it decreases notably in the latter after cyclic deformation. The origin of the difference is investigated and attributed to the difference in operative shear planes. These are mainly on {001} planes without the introduction of notable amounts of anti-phase boundary (APB) tubes in Fe3Ge and mainly on {111} planes with the introduction of a high density of APB tubes composed of {111} APBs in Ni3Ge. The effects of cyclic deformation on the high-field susceptibility χ and the coercive force (H C) are also discussed by taking into account the dislocation distributions introduced by the {001} and {111} slips.

Effect of cyclic deformation on Barkhausen noise in a mild steel

The rms value of the Barkhausen noise and residual stresses were followed as a function of loading cycles in alternating bending fatigue of mild steel specimens. The measurements were carried out in several directions so that the changes in the angular anisotropy of the Barkhausen noise and reorientation of the macroscopic easy axis of magnetisation could be detected. In the loading direction the Barkhausen noise amplitude decreased due to build-up of compressive residual stresses. This was followed by either an increase or a decrease in the Barkhausen noise amplitude depending on the direction of the initial magnetic easy axis with respect to the loading direction. After the commencement of macroscopic plastic deformation the angular anisotropy of Barkhausen noise augmented substantially. In the transverse direction to the loading axis Barkhausen noise decreased in the beginning of loading, reached thereafter a minimum followed by an increase in Barkhausen noise. When cycling under larger strain amplitudes the loading direction and the direction transverse to the loading axis exhibited least changes as a function of loading cycles compared to other directions. The results indicated that following Barkhausen noise only in one direction, usually in the loading direction, as a function of loading cycles, may lead to misevaluation of the fatigue damage development. Monitoring of several directions gives much more reliable results and therefore it is highly recommended.

The effect of cyclic deformation in a 13% Cr ferritic steel on structure and Barkhausen noise level

It has been demonstrated that there is a relation between changes in the microstructure of the chromium ferritic steel and the Barkhausen noise (BN) intensity resulting from cyclic deformation. The non-linear dependence of the BN on the number of cycles has been shown. The dislocations formed in the course of cyclic deformations have been identified as prefect screw ones of Burgers vector b= a/2 1 1 ̄ 1 . It was found that both the cell size and dislocation structure and redistribution of vacancies considerably affect the BN intensity. Dislocation structures and redistribution of vacancies have been correlated with the course of the BN intensity, which enables non-destructive assessment of the condition of the chromium ferritic steel microstructure subjected to cyclic deformation. Persistent slip bands were identified after a large number of cycles, close to the crack initiation. They are of the highest density near the crack tip. Their structure is similar to that of deformation bands in a heavily deformed material.

Interfaces and fatigue damage in a metastable beta titanium matrix composite

The results of a systematic study of the effects of interfacial microstructure on fatigue damage in a metastable β Ti15V3Cr3Al3Sn/SiC (SCS-9) composite are presented. Interfacial microstructure is controlled by heat treatment in the β phase field of the matrix, which promotes coarsening of the fiber-matrix interface without significant changes in the metastable β matrix microstructure (grain size). The effects of interfacial microstructure on debone and friction strengths are also discussed using results from fiber push-out tests. Fatigue damage initiation and propagation mechanisms are elucidated via optical/scanning electron microscopy and acoustic emission analysis of specimens that were deformed to failure in incremental cyclic loading steps. The effects of cyclic deformation on matrix hardness and composite modulus are also examined prior to the presentation of a fracture mechanics (micromechanics) approach for the prediction of fatigue life, and the effects of crack-tip shielding via bridging mechanisms. The paper highlights the potential for the development of accurate life prediction methodologies that are based on experimental observations of damage in titanium matrix composites. It also illustrates the need for multidisciplinary mechanics and materials approaches in the study of composite behavior.

The effect of cyclic deformation on the elastic constants in a nickel superalloy

In order to determine residual stresses in engineering components from neutron-diffraction strain measurements it is necessary to use the appropriate elastic constants (Plane Specific Elastic Constants—PSEC's). These constants can be obtained by calibration measurements or by calculations using for example the Kröner model. This paper presents results that show the effect of cyclic plasticity on the PSEC's in a nickel-base superalloy from measurements made in TEST BEAM at ISIS at the Rutherford Appleton Laboratory, UK. A tensile sample was loaded in situ in the neutron beam. Elastic constants were obtained for the virgin material, then after one cycle of loading to 2% strain and finally after 5 cycles of loading to 5% strain. Stress-strain curves have been plotted for each crystallographic reflection investigated and elastic moduli calculated after each load cycle. The elastic constants obtained after cyclic plasticity are compared with the values obtained in the virgin material. It was found that the (311) reflection was unaffected by the cyclic loading and plastic deformation.

Non-destructive evaluation of metallic electrodes under corrosion fatigue conditions by holographic interferometry

A study on the effect of cyclic deformation on the corrosion behaviour of polarised metallic electrodes in aqueous solution was conducted. The study aimed to determine the initial behavior of a nickel (Ni) electrode in 1 m H 2SO 4 and molybdenum (Mo) electrode in 0.75 m KCl solutions under a condition known as corrosion fatigue (CF) by using methods of real time holographic interferometry. As a result, a relationship between the deformation, obtained by holographic interferometry, and corrosion current density, produced by typical electrochemical methods, are established.