Ein Konzept zur Dauerfestigkeitssteigerung autofrettierter Bauteile unter Innendruck

Greuling, Steffen; Bergmann, J.; Thumser, Rayk

doi:10.1002/1521-4052(200104)32:4<342::aid-mawe342>3.0.co;2-7

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…In this research, only static considerations are taken into account in order to visualize the concept. The potential of the process is even greater for dynamic or cyclic applications as reported in [4,5,10,12,23,24]. Application example.…”

Section: Wgp Congress 2012mentioning

confidence: 99%

Full Exploitation of Lightweight Design Potentials by Generating Pronounced Compressive Residual Stress Fields with Hydraulic Autofrettage

Brünnet

Bähre

2014

AMR

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Internally pressurized components in hydraulic systems are subjected to high mechanical stresses. In case of dynamic pressure profiles this may lead to fatigue and hence a limited lifetime. This is particularly the case for fuel injection systems in combustion engines. Components of diesel injection systems in automobiles are popular examples for these demands. They have to withstand pressures of 2,200 bar and higher for at least 250,000 km. The increasing usage of high-strength materials and higher wall thicknesses will lead to a dead end as the weight and the complex manufacturing will tie up costs and resources. Autofrettage is a manufacturing process with high potential for the lightweight design of highly stressed hydraulic components. By considering the same wall thickness and applying optimal parameters, the fatigue strength may be increased by a factor of 3.5. If transferred to lightweight concepts wall thickness reductions as well as cost and resource savings by more than 45 % may be realized. However, from the manufacturing perspective the Autofrettage process poses some challenges. This paper presents results from Finite Element simulations and experiments and discusses the interaction between manufacturing processes with respect to residual stresses and deformations. The scientific findings may be used to tear down barriers in the application of Autofrettage and to optimize process chain layouts. It also serves to make a significant contribution to weight reduction in car manufacturing and other high performance hydraulic applications. Abbreviations: AF : Autofrettage; AFM : Abrasive Flow Machining; ECM : Electro-Chemical Machining; FEA : Finite Element Analysis; K-ratio : outer to inner radius ratio; L = length of the cylinder (mm); pAF : Autofrettage pressure (bar); pWP : working pressure (bar); piY : pressure to initiate yielding at the bore (bar); Ra : roughness average (μm); Rz : average maximum height of the roughness profile (μm); RPM : Revolutions Per Minute (1/min.); ri : inner radius (mm); ro : outer radius (mm); ρ : density (kg/dm3); σVM : von Mises equivalent stress (MPa); σy : yield stress (MPa); σt : tensile stress (MPa); σY : yield strength (MPa); SF : Safety Factor;

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Section: Wgp Congress 2012mentioning

confidence: 99%

Full Exploitation of Lightweight Design Potentials by Generating Pronounced Compressive Residual Stress Fields with Hydraulic Autofrettage

Brünnet

Bähre

2014

AMR

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“…Furthermore, autofrettaged components with bore intersections showed a strong improvement of fatigue life and a limitation of the fatigue crack growth. [1][2][3][4][5][6][7] But relaxation, if occurring, could reduce residual stress and would lead to higher mean stress (F-G) and hence to lower fatigue life.…”

Section: Introductionmentioning

confidence: 99%

“…Autofrettage is a single static well-controlled overloading pressure to induce residual compressive stresses at the critical inner surface for internally pressurized tubes in service. This compressive residual stress highly increases fatigue life even at bore intersections for steel [1][2][3][4][5] and aluminum 6,7 materials. In the case of more complex geometries like high-pressure valves, the optimum autofrettage pressure is more difficult to find, but still very beneficial as compressive residual stresses help even after crack initiation as closing mechanism, 8 if stress relaxation can be excluded.…”

Section: Introductionmentioning

confidence: 99%

Analysis of residual stress relaxation of aluminum alloys EN AW 6061/‐82 T6 under cyclic loading

Repplinger

Sellen²,

Kędziora

et al. 2021

Fatigue Fract Eng Mat Struct

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Stress relaxation describes the reduction of stress under static or cyclic loading at a constant strain level. Several processes induce intentionally residual stresses, for example, autofrettage of thick-walled pressurized tubes to improve their fatigue life. This well-known process induces residual compressive stresses at the critical inner surface by using a single static but controlled overloading internal pressure. Relaxation of residual stresses due to cyclic loading in service would endanger the effectiveness of autofrettage and could finally lead to unexpected fatigue failure. In this study, strain-controlled experiments up to 500,000 load cycles and amending nonlinear finite element simulations were done for the aluminum alloys EN AW 6061 T6 and EN AW 6082 T6 to study potential cyclic stress relaxation in four-point bending tests after controlled single static plasticization for residual stress generation. This analysis identifies almost stable residual stresses for both materials under different cyclic strain-controlled load levels.

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Autofrettage innendruckbelasteter Bauteile

Greuling

Seeger

Vormwald

2006

Mat.-wiss. u. Werkstofftech.

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Autofrettage is a local surface strengthening procedure to enhance the fatigue resistance of pressurized components. It is used since the beginning of the 20th century. The beneficial effect of the autofrettage is based on compressive residual stresses, which are induced by a single pressure overload applied before the service loading. This pressure overload is much higher than the subsequent service pressure.In the present contribution, a survey over the state of the art of the development of calculation concepts is given. After the presentation of some experimental results, which are the starting point for different calculation concepts, these concepts will be explained and used. In the end an outlook on finite life design and variable amplitude loading is given.

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Ein Konzept zur Dauerfestigkeitssteigerung autofrettierter Bauteile unter Innendruck

Cited by 5 publications

References 6 publications

Full Exploitation of Lightweight Design Potentials by Generating Pronounced Compressive Residual Stress Fields with Hydraulic Autofrettage

Full Exploitation of Lightweight Design Potentials by Generating Pronounced Compressive Residual Stress Fields with Hydraulic Autofrettage

Analysis of residual stress relaxation of aluminum alloys EN AW 6061/‐82 T6 under cyclic loading

Autofrettage innendruckbelasteter Bauteile

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