Mechanical Analysis Techniques Research Articles

Design, Analysis, and Optimization Testing of a Novel Modular Walking Device for Pipeline Robots

This article investigates the limitations associated with traditional wheel-type pipeline walking devices, which are characterized by a single movement mode and an inability to navigate complex or irregular pipeline structures. A modular walking device (MWD) designed for pipeline robots was developed utilizing structural and mechanical analysis techniques. The reliability of the mechanical analysis was validated through single-factor dynamic testing. To analyze and optimize the factors influencing the maneuverability and obstacle-crossing capabilities of the MWD, a three-factor, three-level orthogonal testing method was utilized. The factors examined included the rotational speed of the walking wheel (RS), the pre-tightening force of the wheel brackets (PF), and the height of the annular obstacle (OH). The evaluation metrics used were the slip rate and passability. The results indicated that a parameter combination of RS at 70 rpm, PF at 30 N, and OH at 10 mm produced a slip rate of 11.6% ± 1.5%. During the obstacle traversal process, the remainder of the device maintained a safe distance from the obstacles, with only the walking wheel making contact. The verification testing also confirmed that the MWD is capable of executing three distinct modes of motion: rectilinear, rotational, and helical. The MWD designed and developed in this study can switch between multiple motion modes and successfully overcome obstacles within 15 mm, providing a new equipment for universities to enhance mechanized pipeline detection technology.

Mechanical properties assessment of composite solid propellant based on different aziridine bonding agents

Abstract The employment of the dynamic mechanical analyzer (DMA) represents a modern methodology for the monitoring of the thermo-mechanical characteristics and also the thermomechanical loads of polyurethane-based composite solid rocket propellants during combustion. A meticulous preparation of composite propellant samples based on different bonding agents was carried out to examine the influence of various bonding agents on mechanical properties. To simulate the effects of natural aging, an accelerated aging program was implemented and subjected to the propellant samples for 5-day exposure at 90°C, equivalent to 5 years of natural aging. The dynamic mechanical modern analysis technique was used to assess the viscoelastic behavior and degree of viscoelasticity of both fresh and aged propellant samples. It is concluded that M4 based on MT-X bonding agent is the most valuable formulation of CSRP with tan δ of 0.183591, also with mechanical results; implying that M4 formulation based on MT-X bonding agent has the highest degree of viscoelasticity.

Effect of crosslinker molecular weight on the characteristics of thermoelectric ionogels

Abstract The present study investigates an ionic thermoelectric gel with adjustable functionality through the manipulation of crosslinker molecular weight. The thermoelectric properties of 2-hydroxyethyl acrylate (2-HEA) ionogels, prepared using PEGDA200, PEGDA575, and PEGDA1000 as crosslinkers, were thoroughly examined. Furthermore, dynamic thermal mechanical analysis (DMA) and X-ray diffraction (XRD) techniques were employed to elucidate the underlying reasons for variations in the thermoelectric material properties resulting from changes in crosslinker molecular weight. Notably, the thermoelectric gel synthesized with PEGDA575 exhibited a remarkable thermal power output of 19.19 mV•K-1 along with a tensile capacity of 231%. Additionally, the developed ionic thermoelectric capacitor demonstrated an impressive energy density of 4.288 J•m−2, thereby showcasing its potential application in flexible low-grade heat energy recovery devices.

Effect of Gamma Irradiation on the Stability of Tanned Leather

Leather tanning involves several processes of converting putrescible hide to stable leather resistant to harsh environmental conditions. Severe conditions such as high temperatures and UV radiation, when exposed to the leather materials, cause degradation and decrease physical, chemical, and structural properties. The effect of gamma irradiation on viscoelastic properties and stability of tanned leather against thermal and photodegradation was studied using the Dynamic Mechanical Analysis (DMA) technique. The thermal stability of chrome and mimosa-tanned leather was inferred from the peak of storage modulus graphs. Gamma irradiation of samples with low doses increased the storage modulus of chrome and mimosa-tanned leathers. Doses up to 20 kGy decreased the stability of thermally aged chrome-tanned leather. However, for mimosa-tanned, there was an increase at higher doses as a result of gamma irradiation inducing additional bonds that enhance the stability of the tanned leather. Nevertheless, there is a variation in the stability of chrome-tanned leather at different doses of irradiation.

Evaluation of the viscoelastic behavior, thermal transitions, and self‐healing efficiency of microcapsules‐based composites with and without a catalyst using dynamic mechanical analysis technique

AbstractThis comprehensive study investigates the viscoelastic behavior, thermal transitions, and self‐healing efficiency of microcapsule‐based composites with and without a catalyst. The composites consist of urea‐formaldehyde/dicyclopentadiene microcapsules embedded in an epoxy matrix, with the addition of Grubbs' catalyst. Our research examines the impact of repetitive dynamic mechanical analysis (DMA) testing and the presence of Grubbs' catalyst on the composites' self‐healing efficiency and dynamic mechanical properties. Using laser microscopy, optical microscopy, Fourier‐transform infrared spectroscopy, and thermogravimetric analysis, we employ various characterization techniques to enhance our understanding of the composite behavior. The findings emphasize the importance of evaluating self‐healing efficiency through DMA, which is a reliable, expeditious, and non‐destructive method. The results show that incorporating Grubbs' catalyst significantly enhances the self‐healing performance of the composites, effectively mitigating the degradation of mechanical properties due to aging. Furthermore, the inclusion of catalyst particles improves stiffness, rigidity, and energy dissipation characteristics, facilitating the self‐healing process. However, careful consideration is necessary to balance mechanical properties and the glass transition temperature when designing self‐healing composites. This study demonstrates a promising self‐healing efficiency of approximately 73% and 44% in the second and third DMA tests, respectively, for composites containing microcapsules and Grubbs' catalyst.

Physics-motivated fractional viscoelasticity model for dynamic relaxation in amorphous solids

Dynamic mechanical relaxation is an important metric to understand the mechanical/physical properties of amorphous solids which are of viscoelastic nature. Due to the heterogenous microstructure, the relaxation behavior of amorphous solids usually shows strong deviation from the Debye relaxation. The distribution of relaxation time derived from either the stretched exponential function (KWW function) or the power law form is probably the most adopted paradigm to describe the non-Debye relaxation. They are essentially the continuous spectrums given in analytical forms. However, whether a real amorphous material conforms to such distribution law remains to be discussed. Here we test the assumption in typical metallic glasses (MGs) as representatives of the general amorphous solids. The mechanical spectrum of a Cu46Zr47Al7 MG in wide frequency domain is probed by the dynamic mechanical analysis technique. It is found that both the KWW function and the modified fractional (MF) model based on power law can well describe the experimental data. As a step forward, we combine the quasi-point defect theory with the MF model to theoretically reveal the feature of temperature-dependent structural evolution in MG. Finally, the distribution of relaxation time corresponding to the experimental data is discretized to argue the theoretically predicted microstructural heterogeneity in the MGs.

4D Printing of Polyvinyl Chloride (PVC): A Detailed Analysis of Microstructure, Programming, and Shape Memory Performance

AbstractIn this research, polyvinyl chloride (PVC) with excellent shape‐memory effects is 4D printed via fused deposition modeling (FDM) technology. An experimental procedure for successful 3D printing of lab‐made filament from PVC granules is introduced. Macro‐ and microstructural features of 3D printed PVC are investigated by means of wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) techniques. A promising shape‐memory feature of PVC is hypothesized from the presence of small close imperfect thermodynamically stable crystallites as physical crosslinks, which are further reinforced by mesomorphs and possibly molecular entanglement. A detailed analysis of shape fixity and shape recovery performance of 3D printed PVC is carried out considering three programming scenarios of cold (Tg −45 °C), warm (Tg −15 °C), and hot (Tg +15 °C) and two load holding times of 0 s, and 600 s under three‐point bending and compression modes. Extensive insightful discussions are presented, and in conclusion, shape‐memory effects are promising,ranging from 83.24% to 100%. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state‐of‐the‐art shape‐memory materials library for 4D printing, and provide pertinent results that are instrumental in the 3D printing of shape‐memory PVC‐based structures.

Integrating mechanical sensor readouts into organ-on-a-chip platforms.

Organs-on-a-chip have emerged as next-generation tissue engineered models to accurately capture realistic human tissue behaviour, thereby addressing many of the challenges associated with using animal models in research. Mechanical features of the culture environment have emerged as being critically important in designing organs-on-a-chip, as they play important roles in both stimulating realistic tissue formation and function, as well as capturing integrative elements of homeostasis, tissue function, and tissue degeneration in response to external insult and injury. Despite the demonstrated impact of incorporating mechanical cues in these models, strategies to measure these mechanical tissue features in microfluidically-compatible formats directly on-chip are relatively limited. In this review, we first describe general microfluidically-compatible Organs-on-a-chip sensing strategies, and categorize these advances based on the specific advantages of incorporating them on-chip. We then consider foundational and recent advances in mechanical analysis techniques spanning cellular to tissue length scales; and discuss their integration into Organs-on-a-chips for more effective drug screening, disease modeling, and characterization of biological dynamics.

Studies of curing cycle of carbon fiber/epoxy resins (8552� and M21�) prepregs based on thermal and rheological analyses

Thermal and rheological characterizations were performed on prepreg produced with two different commercial epoxy resins - M21� and 8552� � aiming to study and optimize the curing cycle of structural components used in aerospace industry. Characterizations were performed by differential scanning calorimetry (DSC), rheology and dynamic mechanical analysis techniques were assessed and the results were correlated and supported by Fourier Transform Infrared spectroscopy. Additionally, to heating rates suggested by the material supplier, DSC analysis allowed to evaluate further heating rates: 2, 5, 10, 15 and 20 �C/min. Materials presented the n fractional order kinetic of cure and have in its formulation the presence of thermoplastics, in addition to epoxy and amine. Results confirmed that the best heating rates for processing both materials are the lower ones, as they result in a better control of the reactions between chemical compounds involved and the physical changes that are part of curing process stages. Results have analytically confirmed the suggested proposal for curing cycle from supplier is the best choice for materials involved.

Indium-gallium-zinc oxide Schottky diodes on softening substrates for rectifying bioelectronic circuits

Incorporating electronic components onto soft materials facilitates the development of compliant electronics suited for bioelectronic applications. In this work, we present indium-gallium-zinc-oxide (IGZO) Schottky diodes fabricated on a stimuli-responsive polymer that undergoes softening (i.e. orders-of-magnitude drop in modulus) upon exposure to physiological stimuli. These diodes rectify megahertz radio-frequency (RF) signals in half-wave rectification circuits across the softening of the polymer substrate and withstand mechanical and chemical stresses such as repeated folding up to 10 000 cycles and aging in a simulated physiological medium for up to two weeks. The effects of thermal annealing and ultraviolet-ozone treatment processes are evaluated using dynamic mechanical analysis and x-ray photoelectron spectroscopy techniques, showing that these processes lead to a large improvement in the interface properties of the platinum-IGZO Schottky contact while preserving the thermomechanical properties of the softening polymer substrate. The RF rectification capabilities of these diodes in softened and deformed states are particularly interesting for the next generation of soft wireless bioelectronics.

Unique Ligand Exchange Dynamics of Metal–Organic Polyhedra for Vitrimer-like Gas Separation Membranes

Unique Ligand Exchange Dynamics of Metal–Organic Polyhedra for Vitrimer-like Gas Separation Membranes

Bio‐basedbenzoxazine from renewableL‐tyrosine: Synthesis, polymerization, and properties

AbstractDeveloping thermosets derived from renewable sources is of great importance. In this work, a fully bio‐based benzoxazine monomer, 3,6‐bis((3‐(furan‐2‐ylmethyl)‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazin‐6‐yl)methyl)piperazine‐2,5‐dione (TCDPF), is conveniently synthesized from L‐tyrosine cyclic dipeptide (TCDP), furfurylamine and paraformaldehyde. The chemical structure of TCDPF is confirmed by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy (FT‐IR) techniques. The curing behavior of TCDPF is investigated by differential scanning calorimetry and in situ FT‐IR techniques. After temperature‐programmed curing, the thermomechanical property and thermal stability of the resulting TCDPF polymer (PTCDPF) are evaluated by dynamic mechanical analysis and thermogravimetric analysis techniques, respectively. It is found that PTCDPF have excellent comprehensive performance such as high glass transition temperature (Tg = 322 °C), high thermal degradation temperature (T5% = 342 °C,T10% = 395 °C in N2atmosphere), and high char yield (CY = 51.3% at 800 °C in N2atmosphere). The results demonstrate that L‐tyrosine is a promising bio‐based raw material for preparing high performance polybenzoxazines.

Mechanical Modulation of Ovarian Cancer Tumor Nodules Under Flow.

Perfusion models are valuable tools to mimic complex features of the tumor microenvironment and to study cell behavior. In ovarian cancer, mimicking disease pathology of ascites has been achieved by seeding tumor nodules on a basement membrane and subjecting them to long-term continuous flow. In this scenario it is particularly important to study the role of mechanical stress on cancer progression. Mechanical cues are already known to be important in key cancer processes such as survival, proliferation, and migration. However, probing cell mechanical properties within microfluidic platforms has not been achievable with current technologies since samples are not easily accessible within most microfluidic channels. Here, to analyze the mechanical properties of cells within a perfusion chamber, we use Brillouin confocal microscopy, an all-optical technique that requires no contact or perturbation to the sample. Our results indicate that ovarian cancer nodules under long-term continuous flow have a significantly lower longitudinal modulus compared to nodules maintained in a static condition. We further dissect the role of distinct mechanical perturbations (e.g., shear flow, osmolality) on tumor nodule properties. In summary, the unique combination of a long-term microfluidic culture and noninvasive mechanical analysis technique provides insights on the effects of physical forces in ovarian cancer pathology.

Theoretical and Experimental Investigation of Warpage Evolution of Flip Chip Package on Packaging during Fabrication.

This study attempts to investigate the warpage behavior of a flip chip package-on-package (FCPoP) assembly during fabrication process. A process simulation framework that integrates thermal and mechanical finite element analysis (FEA), effective modeling and ANSYS element death-birth technique is introduced for effectively predicting the process-induced warpage. The mechanical FEA takes into account the viscoelastic behavior and cure shrinkage of the epoxy molding compound. In order to enhance the computational and modeling efficiency and retain the prediction accuracy at the same time, this study proposes a novel effective approach that combines the trace mapping method, rule of mixture and FEA to estimate the effective orthotropic elastic properties of the coreless substrate and core interposer. The study begins with experimental measurement of the temperature-dependent elastic and viscoelastic properties of the components in the assembly, followed by the prediction of the effective elastic properties of the orthotropic interposer and substrate. The predicted effective results are compared against the results of the ROM/analytical estimate and the FEA-based effective approach. Moreover, the warpages obtained from the proposed process simulation framework are validated by the in-line measurement data, and good agreement is presented. Finally, key factors that may influence process-induced warpage are examined via parametric analysis.

Research Techniques Made Simple: Analysis of Skin Cell and Tissue Mechanics Using Atomic Force Microscopy

Atomic force microscopy (AFM) is a powerful technique for nanoscale imaging and mechanical analysis of biological specimens. It is based on the highly sensitive detection of forces and displacement of a sharp-tipped cantilever as it scans the surface of an object. Because it requires minimal sample processing and preparation, AFM is particularly advantageous for the analysis of cells and tissues in their near-native state. Moreover, recent advances in Bio-AFM systems and the combination with light microscopy imaging have greatly enhanced the application of AFM in biological research. In the field of dermatology, the method has led to important insights into our understanding of the biomechanics of normal healthy skin and the pathogenesis of a variety of skin diseases. In this Research Techniques Made Simple article, we review the fundamental principles of AFM, how AFM can be applied to the analysis of cell and tissue mechanics, and recent applications of AFM in skin science and dermatology.

A novel semi-analytical methodology for predicting sound absorption of anechoic coatings with arbitrary rotary cavities dependent on temperature and frequency

In response to the shortcomings of existing studies on the sound-absorbing characteristics of an anechoic coating, which most ignore the frequency factor and are expensive for temperature-tunable hydroacoustic experiments, a novel semi-analytical methodology that considers both frequency and temperature is proposed in this paper. Based on the dynamic mechanical thermal analysis technique and time–temperature superposition principle, the temperature and frequency spectra of two rubber materials are tested and expanded in turn. Meanwhile, a complete acoustic prediction model is developed employing the non-uniform waveguide theory for an overburden containing arbitrary rotary cavities. Furthermore, taking a lining embedded with ramped cavities as the research structure, the theoretical model is firstly validated by an absorptive measurement conducted with the hydroacoustic impedance tube test-system, and then the acoustic influences of the material properties and geometric parameters of each sublayer, as well as the temperature factor, are investigated in-depth to reveal the multiple energy dissipation mechanisms. These results show that the present semi-analytical method can accurately and effectively predict the dynamic sound absorptions of a covering in the wide temperature-frequency range of Tg ~ Tg + 50 ℃ and 10 Hz ~ 106 Hz.

Self-healing disulfide-containing polyester-urethane networks composed of 6-armed star-shaped oligolactide and oligocaprolactone segments

The ring opening polymerization reactions of e-caprolactone and L-lactide in the presence of the initiator dipentaerythritol, generated the hydroxy-terminated 6-armed star-shaped e-caprolactone and L-lactide oligomers (H6CLO and H6LAO), respectively. The disulfide-containing polyester-urethane networks (PN-LCxy-DSz, weight ratios of H6LAO/H6CLO: x/y = 1/0, 3/1, 1/1, 1/3, and 0/1, BHEDS/(H6LAO + H6CLO) molar ratios: z = 0, 1, and 3) were produced by reacting H6LAO, H6CLO and bis(2-hydroxyethyl)disulfide (BHEDS) with hexamethylene diisocyanate (HDI). Fourier-transform infrared (FT-IR) spectroscopy and gel fraction analyses were conducted, which revealed that the urethanization reaction proceeded smoothly to generate the polymer networks. The differential scanning calorimetry (DSC) experiments with the PN-LCxy-DSz networks revealed that the oligocaprolactone (CLO) segments were crystallized, while the oligolactide (LAO) segments were not. The dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) techniques were used to reveal the high compatibility of the LAO and CLO segments in the PN-LC31-DS1 network. The compatibility of the co-networks decreased with increasing CLO fraction. The cut lines in the PN-LCxy-DS1 (xy = 10, 31, 11, and 31) films self-healed at room temperature within 24 h. The PN-LC31-DS1 film exhibited the highest healing efficiency on the tensile strength (98.5%). In contrast, the cut lines in the PN-LC10-DS0 and PN-LC01-DS0 films, devoid of disulfide bonds, did not exhibit the self-healing property.

Development of a portable instrument for non-destructive characterization of the polymers viscoelastic properties

The non-destructive quantification of the mechanical properties of solid materials is a growing research topic for many applications. It could be used for monitoring material performance during the whole lifecycle of a component, for when sampling is limited or impossible or for applications that require sample identification. In this paper a portable instrument for non-destructive viscoelastic characterization of polymers, based on instrumented indentation, is presented, its aim is to allow a real-time assessment of viscoelastic storage and loss moduli (E’ and E”) directly in-situ. The designed architecture of the device is described in details alongside the procedure adopted for testing polymers, the corresponding signal processing procedure for the identification of materials stiffness and damping parameters is also described. For the scope of this paper the aforementioned procedure was tested on two different rubber compounds. Finally, the storage and loss moduli are calculated based on the linear viscoelasticity theory and the results are compared to the ones obtained with the standard Dynamic Mechanical Analysis technique (DMA): both these approaches show the same relative ranking between the compounds and a different trend in temperature due to the reached indentation depth. To overcome this limitation of linear viscoelasticity theory, normally valid for low indentation depths, a generalized formulation is proposed that takes into account the indentation depth on the moduli estimation. The results obtained with the generalized formulation show that this approach allows to evaluate accurately the trends and rankings of viscoelastic moduli, giving reliable results.

Dynamic mechanical relaxation in Zr65Ni7Cu18Al10 metallic glass

Dynamic modulus and internal friction of Zr65Ni7Cu18Al10 metallic glass was probed by dynamic mechanical analysis (DMA) technique. The apparent activation energy of main α relaxation is 4.18 eV. Experimental results can be analyzed in the framework of the quasi-point defect (QPD) theory. Current investigations demonstrated that annealing below the glass transition temperature Tg leads to a decrease in loss factor tanδ of Zr65Ni7Cu18Al10 metallic glass. The evolution of loss factor tanδ with annealing time can be well described by the stretched Kohlrausch-Williams-Watts (KWW) exponential equation. The Kohlrausch exponent βaging is 0.43 of Zr65Ni7Cu18Al10 metallic glass annealed at 573 K.

Structural Evolution and Micromechanical Properties of Ternary Ni-Fe-Ti Alloy Solidified Under Microgravity Condition

Both the microgravity solidification mechanism and resultant micromechanical properties of ternary Ni41Fe40Ti19 alloy were investigated by means of drop tube, nanoindentation, and nano-dynamic mechanical analysis (Nano-DMA) techniques. The microstructure of the Ni41Fe40Ti19 alloy droplets consisted of γ-(Fe,Ni) dendrites and interdendritic pseudobinary eutectic phases. The average cooling rate and undercooling increased significantly as the droplet diameter decreased during free fall. Owing to the refinement of the rapidly solidified microstructure, and the Ti solute hardening of the primary γ-(Fe,Ni) dendrites, the microhardness of this alloy was remarkably increased with the decrease of droplet size. Moreover, the nanohardness of the γ-(Fe,Ni) dendrite increased as the indentation displacement decreased within the depth range of 40 to 244 nm, indicating a conspicuous indentation size effect (ISE). However, the ISE increased as the undercooling increased, because additional geometrically necessary dislocations (GNDs) were required, while intragranular dislocation motion was further hindered as the Ti content increased. The size effect factor increased linearly with the reduced droplet diameter.