A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

Abstract

A new application of Fe-Mn-Si based shape memory alloys (SMAs) was developed under the form of truncated cone-shaped module, for self-adaptive axial preload control in angular contact bearings. The modules were processed by high-speed high-pressure torsion (HS-HPT), from circular crowns cut from axially drilled ingots of Fe-28Mn-6Si-9Cr (mass%) SMA. The specimens were mechanically tested in the hot rolled state, prior to HS-HPT processing, demonstrating free-recovery shape memory effect (SME) and high values for ultimate tensile stress and strain as well as low cycle fatigue life. The HS-HPT modules were subjected to static loading–unloading compression, without/with lubrication at specimen-tool interface, both individually and in different coupling modes. Dry compression cycles revealed reproducible stress plateaus both during loading and unloading stages, being associated with hardness gradient, along cone generator, caused by HS-HPT processing. Constrained recovery tests, performed using compressed modules, emphasized the continuous generation of stress during heating, by one way SME, at a rate of ∼9.3 kPa/%. Dynamic compression tests demonstrated the capability of modules to develop closed stress–strain loops after 50 000 cycles, without visible signs of fatigue. HS-HPT caused the fragmentation of crystalline grains, while compression cycles enabled the formation of ε hexagonal close-packed stress-induced martensite (ε), which is characterized by a high density of stacking faults. Using an experimental setup, specifically designed and manufactured for this purpose, both feasibility and functionality tests were performed using HS-HPT modules. The feasibility tests proved the existence of a general tendency of both axial force and friction torque to increase in time, favoured by the increase of initial preloading force and the augmentation of rotation speed. Functionality tests, performed on two pairs of HS-HPT modules fastened in base-to-base coupling mode, demonstrated the capacity of modules to accommodate high preloads while maintaining both axial force and friction torque at constant values in time. These preliminary results suggest that, for the time being, the modules can operate only as single use applications, more effective during the running-in period. This bevahior recommends HS-HPT modules as a new application of Fe-Mn-Si SMAs, with the potential to be used for the development of new temperature-responsive compression displacement systems.

Structural Change in Ni-Fe-Ga Magnetic Shape Memory Alloys after Severe Plastic Deformation

“…The compressive force applied concomitant with torsion effort produces the refinement by grains shearing. Also the HSHPT processing technique combines a very efficient grain refining with the capability of keeping shape memory properties due to dynamic recrystallization as our research shows on other metallic alloys [12,13,14]. The technology leads to heat generation by intense friction between the anvils and the sample.…”

“…The as-cast Ni 57 Fe 18 Ga 25 , Ni 50 Fe 22 Ga 25 Co 3 , Ni 52 Fe 20 Co 2 Ga 26 , and Ni 52 Fe 20 Co 3 Ga 23 Al 2 in at% ingots (about 10 mm × 7 mm × 5 mm) were processed via HSHPT. We used a variation of the classical HPT technique whereby alloys were simultaneously subjected to compressive and torsion strain, described in detail in [12,13,14]. More specifically, in this process friction is introduced between the anvils and the sample by high speed rotation of the superior anvil.…”

“…For superior mechanical properties, including high strength and hardness together with increased fatigue resistance, originally coarse-grained alloys can be substantially refined down to nanometric structures [11]. Over the last two decades severe plastic deformation (SPD) has proven to be the most appropriate method to produce bulk ultrafine–grained and nanocrystalline materials [12,13]. Microstructural refinement by recourse of SPD is crucial for acquiring optimal mechanical properties in bulk Ni-Fe-Ga ferromagnetic SMA.…”

Selbstvorspannende ultrahochfeste Betonelemente

“…Die zyklische Belastung von Beton, der mit Ni‐TI‐Formgedächtnisfasern und Stahlfasern bewehrt wurde, wurde in untersucht. Intelligente selbsteinstellende Lager aus eisenbasierter Formgedächtnislegierung (Fe‐28Mn‐6Si‐5Cr (mass %)) wurden in untersucht.…”

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

“…The most prominent practical applications of Fe-Mn-Si-based SMAs include lock rings for bicycle frame pipes (Otsuka, 1991), pipe coupling rings (Druker et al, 2014), fishplates for crane rail fastening (Maruyama et al, 2008), concrete pre-straining rods (Sawaguchi et al, 2006) and embedded stripes for concrete beam curvature control (Shahverdi et al, 2016). More recently, truncated cone modules, produced by high speed -high pressure torsion, were proposed for self-adjustable axial preloading of angular contact bearings (Paleu et al, 2018).…”