The influence of various types of small defects on the fatigue limit of precipitation-hardened 17-4PH stainless steel

In compression coil springs subjected to cyclic load, fatigue cracks can sometimes initiate and propagate from scratch‐like small defects produced during the manufacturing process and degrade the fatigue strength. In this study, torsional and rotating bending fatigue tests were conducted to examine the fatigue behavior of a high‐strength spring steel (JIS G 3561, SWOSC‐V) in the presence of small scratches. The sensitivity of the HCF and VHCF strength to small scratches was evaluated based on the area parameter model.

Section: Resultsmentioning

confidence: 91%

“…11 The absence of frequency effect is also reported for 17-4PH stainless steel. 29,33,34 The frequency effect for other materials is reviewed and discussed by Stanzl-Tschegg. 35 In this study, the fatigue limit is defined as the maximum stress amplitude that endured the load cycles of N = 10 7 cycles.…”

Section: Resultsmentioning

confidence: 99%

Fatigue strength of spring steel with small scratches

Nishimura

Yanase

Ikeda

et al. 2018

“…Moreover, the applicability of existing models is unclear for various microstructural morphologies, defect size ranges, and strength levels . For example, Schönbauer et al reported that the

\sqrt{area}

parameter model was applicable only up to a defect size of 80 μm in a precipitation‐hardened stainless steel, although it was reported to be applicable up to 1000 μm in carbon steels and other non‐ferrous metals . Therefore, for a material whose fatigue strength is strongly dependent on microstructural features, heat treatment procedures, and alloying elements (as is the case with Alloy 718), elucidation of the effect of these factors on the small crack behaviours and the applicability of existing models is crucial.…”

Section: Introductionmentioning

confidence: 99%

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Kevinsanny

Okazaki

Takakuwa

et al. 2019

Tension‐compression fatigue tests were performed on two types of Ni‐based superalloy 718 with different microstructures in which small artificial defects of various sizes and shapes were introduced. The susceptibility of the fatigue strength to the defects varied significantly with the microstructure morphology, ie, a smaller grain size made the alloy more susceptible to defects. The fatigue limit as a small‐crack threshold was successfully predicted using the area parameter model. The evaluation of the fatigue limit was classified into the following three stages depending on the defect size: (a) harmless defect regime, (b) small‐crack regime, and (c) large‐crack regime. Such a classification enabled comprehensive evaluation of the fatigue limit in a wide range of defect size, considering (a) defect size over a range of small crack to large crack and (b) characteristics of matrix represented by grain size and hardness.

“…The largest defect size estimation results are summarized in Table 3. In particular, Murakami et al 28 first proposed to consider the whole area of the samples analyzed (or the volume of the component in case of 3D data), but this hypothesis has been overtaken by Schönbauer et al 29 In fact, it is more reasonable to consider only the most stressed area of the samples, where most of the fatigue cracks can initiate. A 0 is the area of the metallographic investigation (500 mm 2 ), and A is the area of prediction.…”

Section: Shrinkage Porosity Consists In Interdendritic Cavitiesmentioning

confidence: 99%

A356‐T6 wheels: Influence of casting defects on fatigue design

Tebaldini

Petrogalli

Donzella

et al. 2018

Rotating bending fatigue tests were executed on A356‐T6 wheels. The tests were performed both on components containing only the casting defects and on wheels in which artificial holes were machined. Results show the detrimental effect of sub‐superficial porosities on fatigue endurance. A predictive model was proposed. It resulted in a useful tool for the designer because knowing the applied stress, it is possible to estimate the number of cycles for crack nucleation considering the size of the defect, whereas knowing the endurance target requested it is possible to find the maximum defect size acceptable considering the applied stress.