Effects of mean stress and stress concentration on fatigue behavior of short fiber reinforced polymer composites

Effects of temperature and mean stress on fatigue behaviour of talc‐filled polypropylene (PP‐T) and short glass fibre reinforced polypropylene (PP‐G), polyamide‐66 (PA66), and a blend of polyphenylene ether and polystyrene (PPE/PS) were investigated. Load‐controlled fatigue tests were conducted under positive stress ratios (R = 0.1 and 0.3) and at several temperatures (T = 23, 85 and 120 °C). Larson–Miller parameter was used and a shift factor of Arrhenius type was developed to correlate fatigue data at various temperatures. Effect of mean stress on fatigue life was significant for some of the studied materials; however, for the PPE/PS blend no effect of mean stress was observed. Modified Goodman and Walker mean stress equations were evaluated for their ability to correlate mean stress data. A general fatigue life prediction model was also used to account for the effects of mean stress, temperature, anisotropy and frequency.

Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 84%

\frac{S_{a}}{S_{N f}} + \frac{S_{m}}{S_{u}} = 1

where S m is the mean stress, S u is the ultimate tensile strength and S Nf is the equivalent fatigue strength at cycle N f for fully reversed condition.…”

Section: Mean Stress Effect and Modellingmentioning

confidence: 99%

See 1 more Smart Citation

Fatigue behaviour and modelling of talc‐filled and short glass fibre reinforced thermoplastics, including temperature and mean stress effects

Eftekhari

Fatemi

2016

“…The emphasis of their review was on fatigue crack initiation behaviour of synthetic SFRPCs, mainly processed with injection moulding and mostly used in automotive applications. Mortazavian and Fatemi have also considered several of these effects including temperature, water absorption, anisotropy, mean stress, stress concentration and cyclic frequency, on fatigue behaviour of two commonly used short glass fibre composites in recent publications …”

Section: Isothermal Fatigue Behaviourmentioning

confidence: 99%

Tensile, creep and fatigue behaviours of short fibre reinforced polymer composites at elevated temperatures: a literature survey

Eftekhari

Fatemi

2015

Self Cite

Polymer composites are suitable alternatives to metals in some applications as they are cost effective, lightweight and corrosion resistant. Short fibre reinforced polymer composites (SFRPCs) are typically subjected to complex loadings in applications, including static, cyclic, thermal and their combinations. These applications may also involve harsh environmental conditions such as elevated temperature and moisture which can dramatically affect mechanical properties. In this paper, a broad survey of the literature on mechanical behaviour of SFRPCs at elevated temperatures is presented. The mechanical behaviours included consist of tensile, creep, isothermal fatigue, thermo‐mechanical fatigue and creep–fatigue interaction. Environmental effects such as moisture and ageing at elevated temperatures are also included. The studies reviewed include experimental works, modelling works and failure mechanisms studies. A critical assessment of the information from the literature presented for each type of behaviour is also provided.

“…Stress amplitudes and mean stresses are then calculated for each node of the flex member (Figure B) by converting the averaged stress tensors to uniaxial normal stresses using the critical plane approach. Equivalent stress for each node is then calculated using a mean stress sensitivity parameter in the form:

σ_{eq} = σ_{a} + α \cdot σ_{m}; 0 \leq α \leq 1,

…”

Section: Calculation Of the Flex Member Fatigue Lifementioning

confidence: 99%

The influence of piston shape on air‐spring fatigue life

Oman

Nagode

2017

This paper presents how the piston shape of an air‐spring can influence both its load‐deflection characteristic and the fatigue life. Two piston shapes are considered in this study for which load‐deflection characteristics and fatigue lives are compared. A method for the estimation of air‐spring fatigue life is upgraded by adding the influence of the mean stress level and afterwards used together with finite element analysis to predict the fatigue life and, ultimately, the timing and global location of failure within the air‐spring. These predictions are then compared with measured results and show good agreement thus proving the validity of the method used here for calculating fatigue life. Both experimental and predicted results show that the highest fatigue life can be expected if a noncylindrical, back tapered piston is used. This is only the case if the air‐spring is mounted at its optimal design height as the study also shows that moving away from optimal design height does have a detrimental effect on the fatigue life of back tapered air‐springs. This is due to the appearance of higher stress amplitudes in the flex member during operation. Such stress amplitudes and consequently fatigue damage can be reduced by avoiding sharp transitions in the piston design that cause additional bending of the flex member in a direction opposite to the deflection in the flex member fold.