Lightweight-structural durability design by consideration of variable amplitude loading

International audienceThis paper deals with a method to evaluate and optimize the design of railway wheels subjected to multiparameter variable fatigue loading. The fatigue loads are statistically evaluated from in-service measurements. Representative realistic loading paths are built from the knowledge of the influence of various factors (such as train speed and track curvature). Using these paths, the method combines finite element computations and the fatigue equivalence method for damage evaluation in the structure. An extension of the Dang Van fatigue criterion in the high-cycle fatigue finite life domain associated with a damage accumulation law is adopted. The probability of failure of the structure is directly obtained from the interference between a local fatigue equivalent stress and fatigue strength distributions (based on the stress-strength interference approach). The result is useful for the optimization during the design stage or the validation of the fatigue strength of structures

Section: Fatigue Damage Evaluationmentioning

confidence: 99%

Fatigue design of railway wheels: a probabilistic approach

Roux

Lorang

Maïtournam

et al. 2014

“…[1][2][3] The process is realized under in-service conditions and at different combinations of variable amplitude loading. [4][5][6][7][8][9] It follows that the fundamental principle of in-service aircraft is the knowledge that the total process of damage accumulation should be divided into two separate stages, that is, crack nucleation and propagation stages. It is worth noting that if the cracks grow for a rather long period of a lifetime, the initiated cracks can be monitored by the non-destructive tests.…”

Section: Introductionmentioning

confidence: 99%

“…The process of fatigue damage accumulation in different zones of aircraft leads to the initiation of fatigue cracks due to various reasons and their following propagation with different intensity 1–3 . The process is realized under in‐service conditions and at different combinations of variable amplitude loading 4–9 . It follows that the fundamental principle of in‐service aircraft is the knowledge that the total process of damage accumulation should be divided into two separate stages, that is, crack nucleation and propagation stages.…”

Section: Introductionmentioning

confidence: 99%

Foundation of damage tolerance principles in‐service for the RRJ‐95 aircraft structural components

Shanyavskiy

Soldatenkov²,

Toushentsov³

2021

Fatigue cracks initiated from holes in several zones and structural components of the RRJ‐95 aircraft frames were investigated. Using the method of quantitative fractography, the crack growth duration in the wing panels during full‐scale bench tests and in the brackets of the in‐service airframe was estimated by measuring the spacing of meso‐beach‐marks (MBM) and fatigue striations. The applied program of bench test consisted of blocks of variable loads that were equivalent to the wing loading in flight and reproducing schematized flight‐cycle. It was shown that the duration of fatigue crack propagation in several structural components of the RRJ‐95 aircraft frames was approximately the same as for the crack nucleation duration. The total lifetime is sufficiently long for cracks in the structural components to be detected and reliably monitored with a large operating time interval between adjacent inspections.

“…Gassner 5 recommends characterizing the fatigue strength with an eight‐step block program sequence with a Gaussian‐like distribution of load instead of using a critical damage less than 1. Later, thanks to the improvement of testing machines, characterization with random‐like sequences becomes possible and can replace block programs, as recommended by Sonsino 4 and Sonsino et al 6 These methods assume implicitly that the distributions of amplitudes in the signals used for testing and in the in‐service signals are sufficiently similar or equivalent in some sort of way. However, precise directions to build such equivalent signals are not available, which can be explained by the complexity of the phenomena at stake.…”

Section: Introductionmentioning

confidence: 99%

Thermographic approach for high cycle fatigue of seam welded steel joints under variable amplitude loadings

Pierron

Maïtournam

Raoult

2020

In the automotive field, welded joints are the weak points of the steel parts of the chassis in terms of fatigue. The fatigue strength of arc-welded parts is generally evaluated using fatigue tests under constant amplitude loadings designed according the Palmgren-Miner rule. In this paper, the relevance of this process is tested with an experimental campaign on welded specimens subjected to various variable amplitude loads. In addition, to solve the recurrent issue of lack of fatigue data, a thermographic method is investigated as an alternative for monitoring the damage rate evolution. A theoretical thermal model is proposed to estimate a local heat source from the infrared thermal measurements during constant and variable amplitude loading tests. This heat source is shown to be correlated with fatigue damage, which provides a further insight on the evolution of damage during nonconstant amplitude fatigue tests.