Effect of presetting and deep rolling on creep of torsion spring bars

Močilnik, Vinko (author), Gubeljak, Nenad (author), Predan, Jožef (author)

This study investigates the creep behavior of torsion spring bars by combining experimental testing and numerical modeling. Experimental investigations were performed on torsional specimens subjected to different presetting levels and deep rolling surface treatments, showing different effects on stress relaxation at a constant torsion angle. Finite element method (FEM) simulations incorporating elasto-visco-plastic material behavior successfully reproduced the time-dependent deformation observed experimentally. Material parameters for the FEM model were derived from experimental data. The findings show that a two-stage presetting process combined with intermediate deep rolling results in higher residual compressive stresses in the surface layers compared to a single-stage presetting process. Although this method aims to mitigate creep under constant loading conditions, its effectiveness is limited. A reduction in creep strains is only observed up to a presetting level of approximately 4.3 %; above this threshold, creep strains increase significantly and loading capacity decreases.

• Language: English
• Keywords: creep, torsion bar, FEM analyzis, presetting, deep rolling, torque, twist angle
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 8 str.
• Numbering: Vol. 71, no. 9/10
• PID: 20.500.12556/RUL-177374
• UDC: 539.414:519.6
• ISSN on article: 2536-3948
• DOI: 10.5545/sv-jme.2025.1407
• COBISS.SI-ID: 259515651
• Publication date in RUL: 22.12.2025

Record is a part of a journal

• Title: Strojniški vestnik
• Shortened title: Stroj. vestn.
• Publisher: Fakulteta za strojništvo
• ISSN: 2536-3948
• COBISS.SI-ID: 294943232

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian

Abstract

Prispevek obravnava obnašanje lezenja torzijskih vzmetnih palic s kombinacijo eksperimentalnega testiranja in numeričnega modeliranja. Eksperimentalne raziskave so bile izvedene na torzijskih vzorcih, ki so bili podvrženi različnim stopnjam prednapenjanja in različnim površinskim obdelavam z globokim valjanjem, pri čemer so se pokazali različni učinki na sproščanje napetosti pri konstantnem kotu zasuka. Simulacije z metodo končnih elementov (MKE), ki vključujejo elasto-visko-plastično obnašanje materiala, so uspešno reproducirale časovno odvisno deformacijo, ki smo izmerili tudi med eksperimentom. Materialni parametri za model MKE so bili izpeljani iz eksperimentalnih podatkov. Ugotovitve kažejo, da dvostopenjski postopek prednastavitve v kombinaciji z vmesnim globokim valjanjem povzroči višje preostale tlačne napetosti v površinskih plasteh v primerjavi z enostopenjskim postopkom prednastavitve. Čeprav je cilj te metode ublažiti lezenje pri konstantnih pogojih obremenitve, ugotavljamo, da je njena učinkovitost omejena. Zmanjšanje deformacij lezenja je opaziti le do stopnje prednastavitve približno 4,3 %; nad tem pragom se deformacije lezenja znatno povečajo in vzmet zgublja na nosilnosti.

• Keywords: lezenje, torzijska palica, metoda končnih elementov (MKE), prednapenjanje, globoko valjanje, torzijski moment, kot vzvoja

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0137
• Name: Numerična in eksperimentalna analiza nelinearnih mehanskih sistemov