Fatigue Performance of Natural and Synthetic Rattan Strips Subjected to Cyclic Tensile Loading

Tensile fatigue performances of selected natural rattan strips (NRSs) and synthetic rattan strips (SRSs) were evaluated by subjecting them to zero-to-maximum constant amplitude cyclic tensile loading. Experimental results indicated that a fatigue life of 25,000 cycles began at the stress level of 50% of rattan material ultimate tensile strength (UTS) value for NRSs evaluated. Rattan core strips’ fatigue life of 100,000 cycles started at the stress level of 30% of its UTS value. Rattan bast strips could start a fatigue life of 100,000 cycles at a stress level below 30% of material UTS value. SRSs didn’t reach the fatigue life of 25,000 cycles until the applied stress level reduced to 40% of material UTS value and reached the fatigue life of 100,000 cycles at the stress level of 40% of material UTS value. It was found that NRSs’ S-N curves (applied nominal stress versus log number of cycles to failure) could be approximated by S=σou(1−H×log10⋅Nf). The constant H values in the equation were 0.10 and 0.08 for bast and core materials, respectively.

Ultrasonic Surface Rolling Process: Properties, Characterization, and Applications

Ultrasonic surface rolling process (USRP) is a novel surface severe plastic deformation (SPD) method that integrates ultrasonic impact peening (UIP) and deep rolling (DR) to enhance the surface integrity and surface mechanical properties of engineering materials. USRP can induce gradient nanostructured surface (GNS) layers on the substrate, providing superior mechanical properties, thus preventing premature material failure. Herein, a comprehensive overview of current-state-of-the art USRP is provided. More specifically, the effect of the USRP on a broad range of materials exclusively used for aerospace, automotive, nuclear, and chemical industries is explained. Furthermore, the effect of USRP on different mechanical properties, such as hardness, tensile, fatigue, wear resistance, residual stress, corrosion resistance, and surface roughness are summarized. In addition, the effect of USRP on grain refinement and the formation of gradient microstructure is discussed. Finally, this study elucidates the application and recent advances of the USRP process.

Post-impact mechanical characterization of HMPE yarns

The present work evaluates the mechanical behaviour of High Modulus Polyethylene (HMPE) yarns after being impacted by sudden axial loads. The influence of loading conditions on the structural integrity of yarns is assessed by tensile, fatigue, and creep tests before and after the impact events. The impact loads were inferred by drop-weight adopting a 300mm height and weights corresponding to 4, 5, and 6% of Yarn Breaking Load (YBL). At 5% YBL, most specimens fail after the impact, and at 6% YBL, all specimens fail. The application of 4% YBL tests results in enhanced creep and fatigue resistances and a decrease in the tensile resistance. Finally, a Scanning Electron Microscopy (SEM) analysis showed that the yarn filaments tend to straighten after the impact, while a decrease in their diameter is noticed due to the longitudinal deformation.

Small specimen techniques for estimation of tensile, fatigue, fracture and crack propagation material model parameters

Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of material. These methods are particularly useful when there is limited source material to facilitate a sufficient number of standard specimen tests, if any at all. Such situations include the development of new materials or when performing routine maintenance/inspection studies of in-service components, requiring that material conditions are updated with service exposure. The potentially more challenging loading conditions and complex stress states experienced by small specimens, in comparison with standard specimen geometries, has led to a tendency for these methods to be used in ranking studies rather than for fundamental material parameter determination. Classifying a specimen as ‘small’ can be subjective, and in the present work the focus is to review testing methods that utilise specimens with characteristic dimensions of less than 50 mm. By doing this, observations made here will be relevant to industrial service monitoring problems, wherein small samples of material are extracted and tested from operational components in such a way that structural integrity is not compromised. Whilst recently the majority of small specimen test techniques development have focused on the determination of creep behaviour/properties as well as sub-size tensile testing, attention is given here to small specimen testing methods for determining specific tensile, fatigue, fracture and crack growth properties. These areas are currently underrepresented in published reviews. The suitability of specimens and methods is discussed here, along with associated advantages and disadvantages.

Acoustic Emission of Metallic Specimen with Surface Defect During Fatigue Crack Growth

Acoustic emission is defined as the phenomena whereby transient elastic waves are generated by the rapid release of localized sources within a material. During fatigue crack growth, the formation of new crack surfaces is associated with a sudden release of energy, which constitutes acoustic sources for acoustic emission. This paper investigates the acoustic emission signature arising from fatigue test of a metallic specimen under tensile fatigue test. In this experimental study, dog-bone aluminium alloy specimen with a surface defect was fatigued to failure. It is found that the acoustic emission characteristics are different during the propagation of surface crack, because the source is changing. The results provide a useful guide in identifying source origin based on the characteristics of the acoustic emission waveform.

Properties of Surface Engineered Metallic Parts Prepared by Additive Manufacturing

The potential of the Additive Manufacturing technologies is impeded by the surface finish obtained on the as-manufactured material. Therefore, the influence of various surface treatments, commonly applied to space hardware, on the mechanical properties of three selected metallic alloys (SS316L, AlSi10Mg, Ti6Al4V) prepared by using Selective Laser Melting (SLM) and Electron Beam Melting (EBM) additive manufacturing processes have been investigated. Within this study, SLM using EOS M400 and EOS M280 equipment and in addition EBM using an ARCAM Q20 machine have been applied for sample manufacturing. A half-automated shot-peening process followed by a chemical and/or electrochemical polishing or Hirtisation® process has been applied in order to obtain lower surface roughness compared to their as-received states. Special emphasize has been taken on their tensile, fatigue, and fracture toughness properties. In addition, their stress corrosion cracking (SCC) behaviour including microstructural analysis using HR-SEM have been investigated.