Papers by Keyword: Ratcheting

Abstract: Wear of materials in rail/wheel industry is closely related to the cyclic creep. This contribution presents main results of experimental testing on R7T wheel steel. The cyclic creep is investigated under non-proportional loading conditions simulating a line rolling contact case. McDowell extrapolation was successfully applied to the calculation of twist. Cyclic material model MAKOC and MAKOC with memory surface were used for cyclic creep prediction. The plasticity model is based on AbdelKarim-Ohno kinematic hardening and Calloch isotropic hardening rules. Second material model was extended with Jiang-Sehitoglu memory surface, which is introduced in stress space. Material models were successfully used for predicting accumulation of shear strain.

Abstract: 4043 aluminum alloy was printed by cold metal transfer (CMT) additive manufacturing (AM) technology. The microstructure and mechanical properties were analyzed. The effect of ratcheting behavior was analyzed by the tensile test after ratcheting. The results indicate that the dendrite structure of 4043 aluminum alloy has obvious directivity. The binary eutectic structure of α (Al) + Si is mainly distributed at the grain boundaries and the interior of grain is mainly α (Al). The increase of stress amplitude and mean stress leads to ratcheting strain, which can cause plastic damage of AM aluminum alloy. This is related to holes aggregation and dislocation slip caused by ratcheting behavior. Compared to the aluminum alloy of un-ratcheted test, the tensile and yield strength increased and the elongation decreased, but the change of tensile and yield strength are not obvious between the s specimens of different ratcheting.

Abstract: This paper proposes a cyclic plasticity model to describe the closure of a cyclic stress-strain hysteresis loop based on the Y-U model. In this model, the backstress moves in a cyclic memory surface following a newly proposed kinematic hardening law. For this model just the same Y-U parameters can be used, and no additional material parameters are needed. By using a supplementary rule, this model is also able to describe ratcheting.

Abstract: In this work our goal is to better understand the origin of the cyclic accumulation of the inelastic strain (often called ratcheting) observed in 304L SS subjected to uniaxial cyclic stress control at room temperature. Recent works performed in the frame of small strain assumption attribute this phenomenon essentially to creep [1]. However, outside this frame, it seems that creep is not the only contributor in this phenomenon [2]. New experiments are performed here in order to investigate the role played by creep, cyclic softening, fatigue damage and ratcheting in this observation.

Abstract: Recently, Halt (Highly accelerated limit test) is widely employed for evaluation of reliability of electronic products. Halt condition is quite severe. The tested products are subjected to mechanical impacts, thermal shock, and vibration at same time. However, there has not been a reasonable and accurate evaluation method for Halt yet. To construct an accurate evaluation method of Halt, basic deformation mechanism of parts of the electronic products should be clarified from both experimental and theoretical points of view. In this paper, focusing on solder joints of circuit boards of electronic products, ratchetting deformation, especially, biaxial ratchetting deformation of solder joints is revealed from both experimentally and theoretically. The authors have already conducted biaxial ratchetting test combining axial and torsional cyclic loading using a tubular specimen of Type 304 stainless steel. However, as for solders, it is difficult to make tubular specimen. Since size of the solder joints is micron, a small size joint specimen of copper tube and solder is employed in this paper. First, to confirm the quality of the joint specimen such as boundary between copper and solder, both the tensile and cyclic loading tests are conducted at several temperatures using Sn-3Ag-0.5Cu. The basic characteristic of tensile and fatigue failure is obtained from these tests. After the confirmation of the accuracy of the joint specimen, biaxial ratchetting tests are conducted superposing the tensile load on cyclic torsion. The biaxial ratchetting tests are conducted using a biaxial loading testing machine developed for the joint specimens of solder and copper.

Abstract: Ratcheting deformation is studied on elbow pipe made of Z2CND18.12N by FEM software. The simulation is conducted by ANSYS. Chen-Jiao-Kim (CJK) kinematic hardening model is added in ANSYS for the study. The elbow pipe is subjected to internal pressure and reversed in-plane bending. Internal pressure can be constant or cyclic. Many different loading paths are used in the study. Ratcheting deformations of under different ways are studied. The result shows that ratcheting deformation occurs mainly in the circumferential direction. Ratcheting deformation at the crown and intrados of elbow pipe is more notable because of higher stress. Tensile or compressed load can influence the position of dangerous point. It is found that ratcheting deformations under different paths with same peak load are different.

Abstract: Uniaxial ratcheting behaviors of Z2CN18.10 austenitic stainless steel under both tensile pre-strain (TP) and compressive pre-strain (CP) were experimentally studied at room temperature. The experimental results show that: TP restrains ratcheting strain accumulation of subsequent cycling with positive mean stress; lower level of CP is found to accelerate ratcheting strain accumulation while higher level of CP retards the accumulation. Based on the Ohno-Wang II kinematic hardening rule, rate-independent model, viscoplastic model, isotropic hardening model and a modified model were constructed to describe the ratcheting behaviors under various pre-strain conditions. All the four models gave fairly good prediction on ratcheting strains for various TP. The isotropic hardening model and modified model predicted acceptable ratcheting strain though still showed slight tendency of over prediction.

Abstract: Macroscopic cyclic tension-unloading experiments are conducted to investigate the cyclic deformation behaviors of CB filled vulcanized hydrogenated nitrile butadiene rubber at room temperature. In the load-controlled cyclic tension-unloading tests, remarkable ratchetting occurs, and the effects of the level and rate of cyclic loading on the ratchetting are also investigated. The ratcheting strain increases with the increasing mean stress and stress amplitude, and more obvious ratchetting is observed in the cyclic test with load-hold or at lower loading rate. In the displacement-controlled cyclic tension-unloading tests, the responding peak stress of the H-NBR decreases continuously, but the residual strain increases with the increasing number of cycles. Furthermore, the zero-stress hold at the end of cyclic test demonstrates that the residual strain will be recovered partially, which implies that the residual strain of the H-NBR after cyclic test consists of the reversible and irreversible parts.

Abstract: This work deals with the study of ratcheting for extruded 2017A aluminum alloy subjected to different loading conditions: unsymmetrical one-dimensional stress control as well as multi-dimensional combinations of stress-stress or stress-strain control. All tests have been conducted within the small strain assumption conditions at room temperature. The results point out the absence of ratcheting under unsymmetrical torsional stress control which enlarge the result given in (Taleb, L., 2013, Int. J. Plast., 43 (2013), 1-19) in which the absence of ratcheting under unsymmetrical tension-compression is demonstrated for the same material. However, under constant axial stress and cyclic shear strain, ratcheting is clearly observed. The results may be explained mainly by the evolution of the isotropic cyclic hardening exhibited by the material.

Abstract: The study presented in this paper uses a multi-mechanism model (MM) in order to simulate the cyclic behavior of an anisotropic aluminum alloy 2017A subjected to complex loading. Two sets of parameters were used. The first set is proposed in [1]; it is identified considering cyclic tests performed under strain control following proportional and non-proportional paths. The second set of parameters has been identified recently on a larger database [2]. In this work, we propose to evaluate the capability of the according to the set of parameters under consideration. Note that the identification process in both cases was performed using strain controlled experiments while the evaluation of the model uses stress controlled experiments.