Engineering the residual stress state of the metastable austenitic stainless steel (MASS) disc springs by incremental sheet forming (ISF)

2018 ◽  
Vol 13 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Fawad Maqbool ◽  
Ramin Hajavifard ◽  
Frank Walther ◽  
Markus Bambach
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress State ◽  
Austenitic Stainless Steel ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Residual Stress State ◽  
Metastable Austenitic Stainless Steel

scholarly journals Influence of process parameters on the residual stress state and properties in disc springs made by incremental sheet forming (ISF)

2021 ◽  
Author(s):  
Muhammad Junaid Afzal ◽  
Ramin Hajavifard ◽  
Johannes Buhl ◽  
Frank Walther ◽  
Markus Bambach
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Residual Stresses ◽  
Process Parameters ◽  
Shot Peening ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Installation Space ◽  
Residual Stress State ◽  
Compressive Residual Stresses

AbstractDisc springs are machine elements that are used when high forces need to be supplied and in limited installation space. They need to fulfil high demands on the stability of the spring characteristics, reliability and lifetime. In corrosive environments, metastable austenitic stainless steels (MASS) disc springs are often used. Tensile stresses that occur during service limit the lifetime of disc springs. Usually, their durability is enhanced by generating favorable compressive residual stresses using shot peening operations. Such operations lead to extra efforts and additional production costs. In this study, the adaptive and targeted generation of residual stresses via incremental sheet forming (ISF) is investigated as alternative to shot peening focusing on EN 1.4310 and EN 1.4401 stainless steel. Previous work has shown that ISF is capable of controlling the radial and tangential stresses in the springs. However, no analysis of the influence of the residual stress state in the rolled sheet strips and the ISF process parameters was performed. The goal of the current work is to analyze the evolution of residual stress during rolling and subsequent incremental forming of disc springs. In order to examine the role of dissipation and temperature increases in the rolling process, sheet blanks rolled at room and elevated temperature are analyzed. The characteristics of the compressive residual stresses induced by ISF are studied for different process parameters. X‑ray diffraction is used to investigate the buildup of these stresses. Using ISF, the generation of compressive residual stresses can be integrated into the forming process of disc springs, and further post-treatment may be skipped. The results show that the residual stress state in the rolled material is crucial, which requires tight control of the rolling temperature. Another result is that ISF is able to yield high compressive residual stresses and improved spring characteristics when small tool diameters and step-down values are used.

Evolution of the residual stress state in a duplex stainless steel during loading

1999 ◽  
Vol 47 (9) ◽  
pp. 2669-2684 ◽  
Author(s):  
J. Johansson ◽  
M. Odén ◽  
X.-H. Zeng
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress State ◽  
Duplex Stainless Steel ◽  
Residual Stress State

scholarly journals Targeted residual stress generation in single and two point incremental sheet forming (ISF)

2021 ◽  
Author(s):  
Fawad Maqbool ◽  
Fabian Maaß ◽  
Johannes Buhl ◽  
Marlon Hahn ◽  
Ramin Hajavifard ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Stress State ◽  
Residual Stresses ◽  
Incremental Forming ◽  
Incremental Sheet Forming ◽  
Generation Mechanism ◽  
Stress Generation ◽  
Process Variants ◽  
Residual Stress State

AbstractThe mechanical properties and the operating life of a formed component are highly dependent on the residual stress state. There is always a high magnitude of residual stresses in the components formed by incremental sheet forming (ISF) due to the localized deformation mechanism. Hence, a thorough understanding of the generation of the residual stresses by ISF is necessary. This study investigates the residual stress generation mechanism for two process variants of ISF, i.e., Single Point Incremental Forming (SPIF) and Two Point Incremental Forming (TPIF). This understanding is used to control and targetedly generate the residual stresses to improve the part performance. In this regard, the residual stress state in a truncated cone geometry manufactured using SPIF and disc springs manufactured using TPIF was experimentally analyzed. Validated numerical models for both process variants were developed to study the residual stresses in detail. The residual stress state in SPIF is such that the tool contact side develops tensile residual stresses and the non-contact side undergoes compressive residual stresses. The tool step-down variation was used to control residual stresses and improve the fatigue strength of truncated cones manufactured using SPIF. For TPIF, two different forming strategies were used to analyze the residual stress generation mechanism and the role of major process parameters. The residual stresses for TPIF are pre-dominantly compressive in both directions of forming tool motion. For both process variants of the ISF process, it is shown that the residual stresses can be beneficially utilized to improve mechanical properties of the components.

scholarly journals Engineering the residual stress state and microstructure of stainless steel with mechanical surface treatments

2010 ◽  
Vol 99 (3) ◽  
pp. 549-556 ◽  
Author(s):  
M. Turski ◽  
S. Clitheroe ◽  
A. D. Evans ◽  
C. Rodopoulos ◽  
D. J. Hughes ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress State ◽  
Surface Treatments ◽  
Residual Stress State ◽  
Mechanical Surface

A TEM microscopical investigation of the magnetic domain structure of a metastable austenitic stainless steel

1994 ◽  
Vol 52 ◽  
pp. 696-697
Author(s):  
G. Fourlaris ◽  
T. Gladman
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Cold Rolling ◽  
Solution Treatment ◽  
Magnetic Domain ◽  
High Strength ◽  
Medium Carbon Steel ◽  
Magnetic Characteristics ◽  
Metastable Austenitic Stainless Steel

Stainless steels have widespread applications due to their good corrosion resistance, but for certain types of large naval constructions, other requirements are imposed such as high strength and toughness , and modified magnetic characteristics.The magnetic characteristics of a 302 type metastable austenitic stainless steel has been assessed after various cold rolling treatments designed to increase strength by strain inducement of martensite. A grade 817M40 low alloy medium carbon steel was used as a reference material.The metastable austenitic stainless steel after solution treatment possesses a fully austenitic microstructure. However its tensile strength , in the solution treated condition , is low.Cold rolling results in the strain induced transformation to α’- martensite in austenitic matrix and enhances the tensile strength. However , α’-martensite is ferromagnetic , and its introduction to an otherwise fully paramagnetic matrix alters the magnetic response of the material. An example of the mixed martensitic-retained austenitic microstructure obtained after the cold rolling experiment is provided in the SEM micrograph of Figure 1.

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