Fatigue failure is a complex phenomenon. Therefore, development of a fatigue damage model that considers all associated complexities resulting from the application of different cyclic loading types, geometries, materials, and environmental conditions is a challenging task. Nevertheless, fatigue damage models such as critical plane-based models are popular because of their capability to estimate life mostly within ±2 and ±3 factors of life for smooth specimens. In this study, a method is proposed for assessing the fatigue life estimation capability of different critical plane-based models. In this method, a subroutine was developed and used to search for best estimated life regardless of critical plane assumption. Therefore, different fatigue damage models were evaluated at all possible planes to search for the best life. Smith-Watson-Topper (normal strain-based), Fatemi-Socie (shear strain-based), and Jahed-Varvani (total strain energy density-based) models are compared by using the proposed assessment method. The assessment is done on smooth specimen level by using the experimental multiaxial fatigue data of 3 alloys, namely, AZ31B and AZ61A extruded magnesium alloys and S460N structural steel alloy. Using the proposed assessment method, it was found that the examined models may not be able to reproduce the experimental lives even if they were evaluated at all physical planes. KEYWORDS critical plane approach, damage assessment method, fatigue damage model, fatigue life estimation, multiaxial fatigue Nomenclature: b, axial fatigue strength exponent; b s , torsional fatigue strength exponent; c, axial fatigue ductility exponent; c s , torsional fatigue ductility exponent; k, Fatemi-Socie constant; B, axial energy-based fatigue strength exponent; B s , torsional energy-based fatigue strength exponent; C, axial energy-based fatigue toughness exponent; C s , torsional energy-based fatigue toughness exponent; E, tensile modulus of elasticity; E ′ e , axial energy-based fatigue strength coefficient; E ′ f , axial energy-based fatigue toughness coefficient; G, shear modulus; N A , fatigue life under purely axial loading; N f , number of cycles to failure; N T , fatigue life under purely torsion loading; W ′ e , torsional energy-based fatigue strength coefficient; W ′ f , torsional energy-based fatigue toughness coefficient; ΔE, total strain energy density; ΔE A , axial strain energy density; ΔE T , torsional strain energy density; Δε 1 , principal normal strain range; Δγ max , maximum shear strain range; ε ′ f , axial fatigue ductility coefficient; γ ′ f , torsional fatigue ductility coefficient; v, Poisson ratio; σ ′ f , axial fatigue strength coefficient; σ n , max , maximum normal stress at critical plane; σ uc , ultimate compressive strength; σ ut , ultimate tensile strength; σ yc , compressive yield strength; σ yt , tensile yield strength; τ ′ f , torsional fatigue strength coefficient

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Friction stir welding (FSW) and friction stir spot welding (FSSW) techniques are becoming widely popular joining techniques because of their increasing potential applications in automotive, aerospace, and other structural industries. These techniques have not only successfully joined similar and dissimilar metal and polymer parts but have also successfully developed polymer-metallic hybrid joints. This study classifies the literature available on the FSW and FSSW of thermoplastic polymers and polymer composites on the basis of joining materials (similar or dissimilar), joint configurations, tooling conditions, medium conditions, and study types. It provides a state-of-the-art and detailed review of the experimental studies available on the FSW and FSSW between similar thermoplastics. The mechanical properties of FSW (butt- and lap-joint configurations) and FSSW weld joints depend on various factors. These factors include the welding process parameters (tool rotational speed, tool traverse speed, tool tilt angle, etc.), base material, tool geometry (pin and shoulder size, pin profile, etc.) and tool material, and medium conditions (submerged, non-submerged, heat-assisted tooling, cooling-assisted tooling). Because of the dependence on many factors, it is difficult to optimize the welding conditions to obtain a high-quality weld joint with superior mechanical properties. The general guidelines are established by reviewing the available literature. These guidelines, if followed, will help to achieve high-quality weld joints with least defects and superior mechanical properties. Apart from parametric-based studies, the statistical-based studies (e.g., analysis of variance (ANOVA)-based studies) are covered, which helps with the determination of the influential parameters that affect the FSW and FSSW weld joint strength. Also, the optimal ranges of the most influential process parameters for different thermoplastic materials are established. The current work on the development of general guidelines and determination of influential parameters and their operating ranges from published literature can help with designing smart future experimental studies for obtaining the global optimum welding conditions. The gaps in the available literature and recommendations for future studies are also discussed.

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Microplastic contamination was found in fish and chicken bought on the market, in food stores and in chain supermarkets in the Middle East with the contamination ranging from 0.03 ± 0.04 to 1.19 ± 0.72 particles per gram of meat in chicken and from 0.014 ± 0.024 to 2.6 ± 2.8 particles per gram in fish. Only one fish was found to be free of microplastic. The source of the microplastic was established to be the polythene-based plastic cutting board the food was cut on. More microplastic contamination was found in food cut from the bone than in cut fillets when the fillets themselves were prepared on surfaces other than plastic. Washing the fish and chicken before food preparation decreased but did not completely remove the microplastic contamination. The fate of the microplastic in grilled fish was studied. The mechanical properties of typical plastic cutting boards commercially used in the markets were investigated in the form of tensile, hardness, and wear tests. Overall, the plastic cutting boards showed similar wear rates.

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