Current challenges in modelling vibrational fatigue and fracture of structures: a review

2021

Materials

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The robustness and stability of the system depend on structural integrity. This stability is, however, compromised by aging, wear and tear, overloads, and environmental factors. A study of vibration and fatigue cracking for structural health monitoring is one of the core research areas in recent times. In this paper, the structural dynamics and fatigue crack propagation behavior when subjected to thermal and mechanical loads were studied. It investigates the modal parameters of uncracked and various cracked specimens under uniform and non-uniform temperature conditions. The analytical model was validated by experimental and numerical approaches. The analysis was evaluated by considering different heating rates to attain the required temperatures. The heating rates were controlled by a proportional-integral-derivative (PID) temperature controller. It showed that a slow heating rate required an ample amount of time but more accurate results than quick heating. This suggested that the heating rate can cause variation in the structural response, especially at elevated temperatures. A small variation in modal parameters was also observed when the applied uniform temperatures were changed to non-uniform temperatures. This study substantiates the fatigue crack propagation behavior of pre-seeded cracks. The results show that propagated cracking depends on applied temperatures and associated mass. The appearance of double crack fronts and multiple cracks were observed. The appearance of multiple cracks seems to be due to the selection of the pre-seeded crack shape. Hence, the real cracks and pre-seeded cracks are distinct and need careful consideration in fatigue crack propagation analysis.

Section: Introductionmentioning

confidence: 93%

“…Researchers considered that early detection is the solution to prevent catastrophic damage. Modal analysis is one of the common techniques used to study structure health monitoring [1][2][3]. This paper aims to study the modal and crack propagation behavior of a beam subjected to thermal and mechanical loads.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Structural Dynamics and Crack Propagation Behavior under Uniform and Non-Uniform Temperature Conditions

Kamei

2021

Materials

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“…However, only tensile stress was responsible for the propagation of the crack. Therefore, the stress amplitude σ i (l c ) was used to show the stress range per cycle instead of the difference among the peak and trough as shown in Equation (12). After that, the bending moment 𝑀 (𝑙 ) at the crack location in i th cycle can be calculated by Equation (10):…”

Section: Calculation Of Sif Range and Fcg Ratementioning

confidence: 99%

“…These structures can experience fatigue failure due to dynamic loads in a complex thermo-mechanical environment [10][11][12]. Compared with other materials [13][14][15][16][17], the crack propagation during fatigue is highly complicated for FDM polymeric structures because of the significant differences in its microstructure due to various printing parameters.…”

Section: Introductionmentioning

confidence: 99%

Modelling and Investigation of Crack Growth for 3D-Printed Acrylonitrile Butadiene Styrene (ABS) with Various Printing Parameters and Ambient Temperatures

Alshammari

2021

Polymers

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Three-dimensional (3D) printing is one of the significant industrial manufacturing methods in the modern era. Many materials are used for 3D printing; however, as the most used material in fused deposition modelling (FDM) technology, acrylonitrile butadiene styrene (ABS) offers good mechanical properties. It is perfect for making structures for industrial applications in complex environments. Three-dimensional printing parameters, including building orientation, layers thickness, and nozzle size, critically affect the crack growth in FDM structures under complex loads. Therefore, this paper used the dynamic bending vibration test to investigate their influence on fatigue crack growth (FCG) rate under dynamic loads and the Paris power law constant C and m. The paper proposed an analytical solution to determine the stress intensity factor (SIF) at the crack tip based on the measurement of structural dynamic response. The experimental results show that the lower ambient temperature, as well as increased nozzle size and layer thickness, provide a lower FCG rate. The printing orientation, which is the same as loading, also slows the crack growth. The linear regression between these parameters and Paris Law’s coefficient also proves the same conclusion.

“…Vibration-based inspection of mechanical structures for structural health monitoring is widely studied [1][2][3]. However, many engineering practical applications such as automotive, aircraft, power plants, etc.…”

Section: Introductionmentioning

confidence: 99%

Characterising Modal Behaviour of a Cantilever Beam at Different Heating Rates for Isothermal Conditions

Kamei

2021

Applied Sciences

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The effect of temperature on structural response is a concern in engineering applications. The literature has highlighted that applied temperature loads change the system vibration behaviour. However, there is limited information available about temperature impacting the dynamic response. This paper investigated the heating rates effects on modal parameters for both with crack and without crack conditions in a cantilever beam. A beam subjected to three heating rates was considered: 2, 5, and 8 °C/min. The first one was assumed as a slow heating rate while the others were assumed as moderate and high, respectively. This controlled rate of heating was achieved by using a proportional-integral-derivative (PID) temperature controller. The results showed that heating at different rates has little impact on modal parameters. While this effect is minimal at lower temperatures and more evident at higher temperatures. The results of temperature ramped at 2, 5, and 8 °C/min were compared with the numerical and analytical results only for all the isothermal conditions. It was observed that the beam natural frequency and its modal amplitude decrease with the increase in temperatures and crack depths. Therefore, it is concluded that the rate of heating can make a slight impact on the dynamics response of any mechanical system.