Dynamic Elastic Recovery Research Articles

Influence of structural arrangements on static and dynamic properties of additively manufactured polyester elastomer lattice metamaterials

In the current study, we present novel carbon organic framework-inspired lattice metamaterials (CFLM) with thermoplastic polyester elastomer (TPEE) to analyze the structural effects. The CFLMs (S1, S2, S3, and SS) from TPEE were successfully produced by material extrusion (MEX) via fused-filament fabrication and had never been reported previously. In the beginning stage, static compression tests were utilized to evaluate mechanical properties, densification strain, and energy absorption, which were validated using the finite element method (FEM). According to static compression results, S2 had the largest energy absorption, followed by the SS structure. In the second stage based on the static test, dynamic sinusoidal compression was performed to calculate the dynamic elastic recovery (DER), hysteresis work absorption, and Tan δ. The results showed that the proposed lattice metamaterials showed different the hysteresis energy absorption, DER, and viscoelasticity nature from Tan δ. To apply static and dynamic compression results to shoe midsoles, they were subjected to a dynamic drop weight impact test. Based on static and dynamic compression testing, including the results of dynamic drop weight impact tests, S1 was the most suitable for the toe part of the shoe midsole, whereas SS was the best for the heel part of the shoe midsole. From the overall results of all characterizations, it was concluded that the structural effect of CFLMs successfully provided different mechanical properties in the static and dynamic tests from the signal TPEE material.

Assessment of the Influence of Fabric’s Dynamic Elastic Recovery Behavior on the Ease of Body Movement

Assessment of the Influence of Fabric’s Dynamic Elastic Recovery Behavior on the Ease of Body Movement

Slow dynamic elastic recovery in unconsolidated metal structures.

Slow dynamic nonlinearity is widely observed in brittle materials with complex heterogeneous or cracked microstructures. It is seen in rocks, concrete, and cracked glass blocks. Unconsolidated structures show the behavior as well: aggregates of glass beads under pressure and a single glass bead confined between two glass plates. A defining feature is the loss of stiffness after a mechanical conditioning, followed by a logarithmic-in-time recovery. Materials observed to exhibit slow dynamics are sufficiently different in microstructure, chemical composition, and scale (ranging from the laboratory to the seismological) to suggest some kind of universality. There lacks a full theoretical understanding of the universality in general and the log(time) recovery in particular. One suspicion has been that the phenomenon is associated with glassy grain boundaries and microcracking. Seminal studies were focused on sandstones and other natural rocks, but in recent years other experimental venues have been introduced with which to inform theory. Here, we present measurements on some simple metallic systems: an unconsolidated aggregate of aluminum beads under a confining pressure, an aluminum bead confined between two aluminum plates, and a steel bead confined between steel plates. Ultrasonic waves are used as probes of the systems, and changes are assessed with coda wave interferometry. Three different methods of low-frequency conditioning are applied; all reveal slow dynamic nonlinearities. Results imply that glassy microstructures and cracking do not play essential roles, as they would appear to be absent in our systems.

Wicking behavior and dynamic elastic recovery properties of multifunction elastic warp-knitted fabrics

The purpose of this study was to evaluate the moisture transport and dynamic elastic recovery (DER) properties of the multifunction elastic warp-knitted fabric that may be used in electromagnetic shielding personal protective clothing (PPC) to protective wearers from electromagnetic radiation and other occupational hazards. The wicking behaviors of the produced elastic warp-knitted fabrics in terms of vertical wicking, horizontal wicking, transfer wicking, and siphon wicking abilities were discussed. The obtained results showed that increasing the amount of crisscross-section polyester yarns had a significant influence on the wicking behavior of the produced elastic warp-knitted fabrics. Moreover, the stretch and recovery properties of the produced elastic warp-knitted fabric caused by bodily movement were also assessed in terms of DER values at different extension levels of the fabric. The results indicated that increasing the extension level would affect the residual energy in the fabric and increase the stress values to the skin. These results provide a better understanding of the characteristics of these elastic knitted fabrics prior to use for tight-fit PPC.

Dynamics of Elastic Knitted Fabrics for Sports Wear

The garment stretch and recovery characteristics due to body movements can be indirectly assessed by the dynamic elastic recovery (DER) value of the fabrics at different extension levels. In order to study DER of elastic fabrics, a comparative analysis was made between spandex-plated cotton fabric and spandex core cotton spun (SCCS) fabric. It was found that the spandex-plated cotton fabric has higher DER value than that of SCCS fabric. The results of this study show that this phenomenon is due to the residual energy of the elastane unraveled from these fabrics. The stress values of these fabrics have no significant effect at 95% confidence level. It is concluded that the spandex-plated cotton fabric is suitable than SCCS fabric, for the tight fit garments meant for the sports like Javelin, shot-put, and athletics.

Atomic Force Microscope Investigation on Static Nanomechanical Properties Versus Dynamic Nanotribological Evaluation of Metal–ZrN and ZrN Thin Films

The present study offers for the first time a correlation between static nanomechanical properties (nanohardness (H), elastic modulus (E), H/E and H3/E2 ratio) and dynamic properties (resulting from nanoscratch measurements) for Metal–ZrN thin films (Inconel–ZrN, Cr–ZrN and Nb–ZrN) as well as monolayer polycrystalline ZrN thin films. Metal–ZrN thin films have a great industrial potential, as they can combine high hardness with good elasticity and toughness making them effective for wear resistant application. Nanomechanical and nanotribological properties of Metal–ZrN and ZrN thin films deposited by DC unbalanced magnetron sputtering were investigated using an atomic force microscope interfaced with a Hysitron Triboscope. The elastic recovery of thin films under a normal load applied during nanoindentation was evaluated and correlated with elastic recovery of thin films under dynamic loading during nanoscratch measurements in order to asses which film compositions provide superior wear resistance. It is demonstrated that dynamic elastic recovery measurements correlated well with those derived from static nanoindentation tests. The nanoscratch test combines both normal and tangential loading, therefore, it is expected to be an even better predictor of wear-resistance. The AFM nanoindentation and nanoscratch measurements show superior nanomechanical and nanotribological properties for Metal–ZrN thin films when compared to polycrystalline ZrN thin films.

Structure and Elasticity of Fine Elastomeric Yarns

In this study, spandexes of three degrees of fineness are used as the core material with cotton fibers as the sheath to spin fine elastomeric yarns. We observe the cross sections of the core yarns and the migration of the spandex inside the core yarn concluding that producing a finer elastomeric yarn with a uniform structure is feasible. The results show that choosing the optimum spinning conditions gives a better cover effect to fine elastomeric yarn. In terms of elasticity, a 10 tex elastomeric yarn produced with a 2.2 tex/2f spandex core at a draw ratio of 4.0 and with a twist factor of 40 exhibits the best dynamic elastic recovery percentage.

Structure and Performance of Elastic Core-Spun Yarn

In this experiment, we use a 44.4 dtex/4f spandex filament as the core and cotton fibers as the sheath to spin 19.7 tex elastic core-spun yarn. In order to improve yarn performance, we examine the yams cross-sectional structure and investigate the effect of draw ratio and feed-in angle of the spandex on the yarns' structure and performance. The results show that a higher feed-in angle provides a better cover effect and a draw ratio of 3.5 yields better dynamic elastic recovery.

Dose effect on mechanical properties of high-energy nitrogen implanted 316L stainless steel

In this work, we investigated the influence of nitrogen dose on mechanical properties of 316L stainless steel. Implantation energy was fixed at 1 MeV and the fluence was varied between 5×10 16 at cm −2 and 10 18 at cm −2. The current density and the sample temperature during treatment were kept at constant values, 1.5 μA cm −2 and T imp=−30 °C, respectively. Nano-indentation tests show improved mechanical properties. Maximum hardness values linearly increased with increasing implantation dose, from 5.25 to 7.5 GPa. However, hardness profiles indicate that these values are highly affected by the unimplanted substrate just beneath the implanted layer. Nano-scratch tests confirm the previous results, showing an increase of dynamic elastic recovery ( R d) and a significant decrease of the dynamic friction coefficient (μ d) from 0.55 to 0.35. These improvements of mechanical properties are correlated with the surface modifications: results of micro-structural analysis through grazing incidence X-ray diffraction (GIXRD) show iron-nitride formation (ε-Fe 2N and ε-Fe 3N) and high level of residual stresses. The variation of the glancing angle indicates that the residual stress is non-homogeneously distributed through the depth.