Influence Of Cyclic Deformation Research Articles

Using Poisson’s ratio and acoustic anisotropy parameter to assess damage and accumulated plastic strain during fatigue loading of austenitic steel

The work investigated the effect of fatigue failure on the elastic characteristics of metastable austenitic steel AISI 321: Poisson’s ratio and acoustic anisotropy parameter. The elastic characteristics were calculated using ultrasonic measurements of the propagation time of longitudinal and shear elastic waves. The volume fraction of strain-induced martensite was determined by the eddy current method. Theoretical studies have shown that the main factors influencing Poisson’s ratio are the accumulation of microdamages and changes in phase composition. The change in the acoustic anisotropy parameter is associated with the influence of cyclic deformation on the crystallographic texture of the material matrix and the formation of oriented crystals of strain-induced martensite. Based on the analysis of experimental results, expressions were obtained for calculating damage and relative accumulated plastic deformation based on acoustic measurement data, which are widely used in engineering practice to determine the fatigue life of structural materials.

Cyclic strain has antifibrotic effects on the human cardiac fibroblast transcriptome in a human cardiac fibrosis-on-a-chip platform

In cardiac fibrosis, in response to stress or injury, cardiac fibroblasts deposit excessive amounts of collagens which contribute to the development of heart failure. The biochemical stimuli in this process have been extensively studied, but the influence of cyclic deformation on the fibrogenic behavior of cardiac fibroblasts in the ever-beating heart is not fully understood. In fact, most investigated mechanotransduction pathways in cardiac fibroblasts seem to ultimately have profibrotic effects, which leaves an important question in cardiac fibrosis research unanswered: how do cardiac fibroblasts stay quiescent in the ever-beating human heart? In this study, we developed a human cardiac fibrosis-on-a-chip platform and utilized it to investigate if and how cyclic strain affects fibrogenic signaling. The pneumatically actuated platform can expose engineered tissues to controlled strain magnitudes of 0–25% – which covers the entire physiological and pathological strain range in the human heart – and to biochemical stimuli and enables high-throughput screening of multiple samples. Microtissues of human fetal cardiac fibroblasts (hfCF) embedded in gelatin methacryloyl (GelMA) were 3D-cultured on this platform and exposed to strain conditions which mimic the healthy human heart. The results provide evidence of an antifibrotic effect of the applied strain conditions on cardiac fibroblast behavior, emphasizing the influence of biomechanical stimuli on the fibrogenic process and giving a detailed overview of the mechanosensitive pathways and genes involved, which can be used in the development of novel therapies against cardiac fibrosis.

The Influence of Cyclic Deformation on Elastic and Acoustic Properties of Chromium-Nickel Steels

The Influence of Cyclic Deformation on Elastic and Acoustic Properties of Chromium-Nickel Steels

The influence of cyclic deformation on the strength and elongation at break of carded and combed wool yarns

There are various factors that influence yarn strength. Yarn breaking is due to fiber breakages and fiber’s slippages. In reality, a part of the fibers slip while the other part breaks. In this study, we have shown that fatigue yarn, resulting in a fundamental way impact on the number of breaks on the weaving machine, and sometimes on the physical properties of fabrics. Given the importance of the issue and the very limited directed research number in this direction, a tests series were carried out with the aim to highlight the changes to the physical characteristics of the yarn resulting from mechanical treatment comparable to that which they are subjected on the weaving machine. In the first part of our investigation, the residual deformation, tensile strength, and elongation at break of combed and carded threads were measured. In the second part, the influence of the extensions number, their amplitudes, and frequencies were analyzed. In order to examine the influence of these parameters, carded and combed yarns, with different characteristics were prepared. Therefore, based on the separate treatment results of three test series, it appears that: the warp yarns subjected to repeated extensions undergo the phenomenon of fatigue. Yarns fatigue reduces their elasticity and resistance and it is the cause for break yarn during weaving. The fatigue of wool yarns is very low compared to other textile materials.

Influence of Cyclic Deformation on Shape Memory Characteristics of Ti-Ni-Cu Alloys Fabricated by Pulse-Current Pressure Sintering Method

Ti-Ni-Cu shape memory alloy by elemental powders was fabricated by using a pulse-current pressure sintering method, and it was subjected to solid-solution heat treatment after sintering to homogenize the microstructure of the alloy. The influence of the thermo-mechanical cyclic deformation on the shape memory and thermo-mechanical characteristics of Ti-Ni-Cu alloy was investigated. The thermo-mechanical cyclic deformation improved the deformation behavior of the sintered alloy and made the thermo-mechanical behavior of the alloy stable caused by the introduction of dislocations. As a result, the recovery stress of the alloy after the cyclic deformation fairly increased. The transformation temperatures of the alloy after the cyclic deformation became lower than those of the alloy before the cyclic deformation. Therefore, the superelastic-like behavior of the alloy after the cyclic deformation appeared in an isothermal tensile test at lower holding temperature.

パルス通電加圧焼結法によるTi-Ni-Cu合金の形状記憶特性に及ぼす繰返し変形の影響(OS7-1 形状記憶合金の作製とその変形特性,OS7 形状記憶合金の特性と応用化技術)

This paper aims to find out the influence of cyclic deformation on the shape memory characteristics of Ti-Ni-Cu alloy fabricated by pulse-current pressure sintering method. The properties examined here were the microstructure, the thermo-mechanical characteristics and the cyclic deformation characteristics of the alloy after the cyclic deformation. The alloy after the cyclic deformation showed a superelastic-like behavior. It was found that the. cyclic deformation slightly deteriorates the temperature-response of the alloy, but it relatively makes the thermo-mechanical behaviors of the alloy stable.

Influence of cyclic deformation on surface microstructure and hardness of ion-implanted nickel: Morrison, D.J., Jones, J.W., Alexander, D.E. and Was, G.S. Metall. Trans. A July 1991 22A, (7), 1633–1646

The anomalous anisotropy and tension (t)/compression (c)-asymmetry of the critical resolved shear stress τo of the L12-long-range ordered intermetallic γ′NIM are analysed in the light of a published (Miner RV, Gabb TP, Gayda J, Hember, KJ. Met Trans A 1986; 17A: 507) analytical expression τohkℓ,t/c,To⩽T⩽Tpeak. Particles of γ′NIM strengthen the commercial nickel-base superalloy NIMONIC 105. hkℓ characterises the orientation of the specimen, and To≈300 K and Tpeak≈ 1000 K mark the temperature (T) range in which τo is anomalous. Except for γ′NIM-single crystals with the [011]-orientation, the formula describes the anisotropy and (t/c)-asymmetry of the critical resolved shear stress satisfactorily.

Influence of cyclic deformation on surface microstructure and hardness of ion-implanted nickel

The effects of cyclic deformation on near-surface dislocation structure and hardness of ion-implanted nickel were characterized and correlated with the evolution of fatigue damage. Polycrystalline nickel fatigue specimens were implanted at 220 °C with 350 keV and 3 MeV nickel ions to a fluence of 1 × 1016 ions/cm2 or at 220 °C and 500 °C with 350 keV aluminum ions to a fluence of 5 × 1017 ions/cm2. Both the self-implantations and aluminum implantations approximately doubled the hardness of the near-surface region. During cyclic deformation, the near-surface regions of self-implanted specimens cyclically softened and formed clear channels through which subsurface persistent slip bands (PSBs) penetrated the implanted region. The near-surface regions of aluminum-implanted specimens maintained a high hardness during cyclic deformation and effectively suppressed the evolution of fatigue damage and extended fatigue life. The results of the study indicate that the cyclic stability of implantation-induced surface hardening is a key factor in the ability of an ion implantation treatment to suppress the evolution of fatigue damage.