Mechanical Testing Methods Research Articles

Study on the extension mechanism of fissures in expansive soil based on fracture mechanics test method

Study on the extension mechanism of fissures in expansive soil based on fracture mechanics test method

Explaining the spread in measurement of PDMS elastic properties: influence of test method and curing protocol.

Accuracy in the measurement of mechanical properties is essential for precision engineering and for the interrogation of composition-property relationships. Conventional methods of mechanical testing, such as uniaxial tension, compression, and nanoindentation, provide highly repeatable and reliable results for stiff materials, for which they were originally developed. However, when applied to the characterization of soft and biological materials, the same cannot be said, and the spread of reported properties of similar materials is vast. Polydimethylsiloxane (PDMS), commonly obtained from Dow as SYLGARD 184, is a ubiquitous such material, which has been integral to the rapid development of biocompatible microfluidic devices and flexible electronics in recent decades. However, reported shear moduli of this material range over 2 orders of magnitude for similar chemical compositions. Taking advantage of the increased mechanical scrutiny afforded to SYLGARD 184 in recent years, we combine both published and new experimental data obtained using 9 mechanical test methods. A statistical analysis then elucidates the significant bias induced by the test method itself, and distinguishes this bias from the influence of curing protocols on the mechanical properties. The goal of this work is thus two-fold: (i) it provides a quantitative understanding of the different factors that influence reported properties of this particular material, and (ii) it serves as a cautionary tale. As researchers in the field of mechanics strive to quantify the properties of increasingly complex soft and biological materials, converging on a standardized measurement of PDMS is a necessary first step.

An integrated push-to-pull micromechanical device: Design, fabrication, and in-situ experiment

The rapid advancement of micro-nano machining technology has led to a decrease in the dimensions of microdevices and microchips, following the principles of Moore’s law. In addition to conventional semiconductor materials like silicon, emerging nanoscale materials such as nanowires, nanotubes, and two-dimensional materials are being considered as promising alternative constituent materials. The mechanical properties of these materials have a significant impact on the performance and service life of these microdevices and microchips. However, conventional mechanical testing methods have difficulty in accurately measuring the properties of these materials at the nanoscale due to limitations in displacement control and microforce sensing. Consequently, there is an urgent need to develop a micromechanical device capable of testing nanoscale solid materials. In this study, we propose a concept based on high-resolution image sequences for the design of an integrated micromechanical device capable of synchronously measuring the force and deformation of tested specimens. The device has been fabricated using ultrafast femtosecond laser etching technology, which offers an efficient and cost-effective approach for manufacturing microstructures and is suitable for processing various materials such as metals and nonmetals. The stiffness of the device plays a crucial role in the design of the micromechanical device, and a stiffness-matching criterion is introduced to ensure appropriate design parameters. The fabricated device is employed to conduct in-situ tension experiments on SiC nanowires and multilayer molybdenum disulfide nanosheet within a scanning electronic microscope, enabling accurate measurement of their strength, modulus, and fracture strain.

Potential of Current Direct Mechanical Testing Methods in Assessing Intraoperative Samples of Aortic Aneurysm Caused by Uncontrolled Arterial Hypertension

Potential of Current Direct Mechanical Testing Methods in Assessing Intraoperative Samples of Aortic Aneurysm Caused by Uncontrolled Arterial Hypertension

Parallel-beams magnetic actuator for in-situ transmission electron microscope observation of mechanical testing

Abstract Understanding the microscopic mechanisms behind mechanical fractures is essential for enhancing material properties and increasing reliability through fatigue suppression. Conventional mechanical testing methods, such as indentation tests that press a sharp needle into a specimen or tensile tests using hydraulic pumps, are unable to capture nanoscale deformations under applied forces. As a result, the microscopic mechanisms that influence mechanical properties are often inferred indirectly, and material design largely depends on the engineer’s intuition and occasional serendipity. To overcome these challenges, in-situ observation techniques utilizing transmission electron microscopes (TEMs) have been developed to enable the observation of sample deformations at the nanoscale. However, despite their high resolution, conventional TEMs are limited by a small available space -often just a few millimeters- that restricts the application of sufficient force to fracture specimens. Traditional actuation methods, such as thermal expansion, electrostatic force, and piezoelectric actuators, fail to generate significant forces within such confined spaces. In response to these limitations, our research involved the development of a micromachine with multiple parallel beams. This device leverages the Laplace force generated by an electric current passing through the beams and the magnetic field of the TEM. We demonstrated the capability to produce significant force using the magnetic field from the microscope’s magnetic lens. The actuator developed in our study successfully generated forces exceeding 50 µN, marking a significant advancement in the in-situ observation capabilities for mechanical testing.

Equivalent stiffness analysis of flexible lithium-ion batteries with repeated unit cell: A computational approach

Flexible batteries have recently developed significant advancements in structural design, diverging substantially from traditional battery architectures. However, conventional mechanical testing methods and metrics, tailored for standard battery structures, prove inadequate when evaluating the flexibility of these innovative designs. How to assess the mechanical performance of diverse structural configurations of flexible batteries poses a considerable challenge. In this study, a general computational approach is proposed to evaluate the equivalent stiffness of flexible lithium ion batteries (FLIBs) by analyzing the force–deformation response of a repeated unit cell (RUC), thereby enabling a comprehensive comparison of different FLIB designs. Moreover, to further enhance their deformability, the interconnected supple components of FLIBs have been optimized. This research lays a critical foundation for comparing the mechanical performance and optimizing the design of flexible batteries in the future.

Planar biaxial testing of CXL strengthening effects

The stiffening effect of corneal crosslinking (CXL) treatment, a therapeutic approach for managing the progression of keratoconus, has been primarily investigated using uniaxial tensile experiments. However, this testing technique has several drawbacks and is unable to measure the mechanical response of cornea under a multiaxial loading state. In this work, we used biaxial mechanical testing method to characterize biomechanical properties of porcine cornea before and after CXL treatment. We also investigated the influence of preconditioning on measured properties and used TEM images to determine microstructural characteristics of the extracellular matrix. The conventional method of CXL treatment was used for crosslinking the porcine cornea. The biaxial experiments were done by an ElectroForce TestBench system at a stretch ratio of 1:1 and a displacement rate of 2 mm/min with and without preconditioning. The experimental measurements showed no significant difference in the mechanical properties of porcine cornea along the nasal temporal (NT) and superior inferior (SI) direction. Furthermore, the CXL therapy significantly enhanced the mechanical properties along both directions without creating anisotropic response. The samples tested with preconditioning showed significantly stiffer response than those tested without preconditioning. The TEM images showed that the CXL therapy did not increase the diameter of collagen fibers but significantly decreased their interfibrillar spacing, consistent with the mechanical property improvement of CXL treated samples.

The mechanics of tissue-engineered temporomandibular joint discs: Current status and prospects for enhancement.

The temporomandibular joint (TMJ) disc is an essential protective but vulnerable fibrocartilage. Their high mechanical strength is vital in absorbing loads, reducing friction, and protecting the condylar surface. Many diseases can lead to the destruction or degeneration of the mechanical function of the TMJ disc. Unfortunately, conservative treatment is ineffective in restoring the defective mechanical properties of the discs. Tissue engineering has been investigated as a promising alternative treatment approach to approximate the properties of native tissue. However, it is difficult for tissue-engineered discs to obtain sufficient mechanical properties. Several approaches have been proposed to improve the mechanical properties of tissue-engineered constructs. In this review, we summarized the mechanical properties of native TMJ discs and discussed the current mechanical testing methods. We then summarized the current advances in improving the mechanical properties of TMJ disc tissue-engineered constructs. Moreover, existing challenges and outbreak directions are discussed. This review assists future research in better understanding the mechanical properties of both native and tissue-engineered TMJ discs. It provides new insights into future mechanical property enhancement for TMJ disc tissue engineering.

Optimasi Desain Geometri Lereng Material Old Dump Pada Usaha Penggalian Ulang Pit X PT. Bukit Asam Tbk

In doing slope design, it is necessary to pay attention to slope geometry and soil shear strength. Determination of slope geometry design also considers the balance between height and slope and production benefits. Research was conducted to analyze slope stability through physical and mechanical properties testing, limit equilibrium, and probabilistic Monte Carlo methods. The surface area of the Overburden stripping area in the 2024 RKP design is 8,172.79 m2. The production target is 2,000,000 tons of coal with a volume of overburden material that must be stripped of 29,000,000 BCM and obtained a Stripping Ratio value of 14.5. The results of the evaluation of the overall slope of the Old Dump material with an overall slope height of 66.582 m, a slope width of 447.69 m, an overall slope of 8.32˚ and a bench width of 25 m, a bench height of 6 m with a comparison ratio of 1:3 and a single slope angle of 18.43˚. Then the redesign was carried out and obtained recommendation results of 64.799 m overall slope height, 303.33 m slope width, 13.02˚ overall slope, and 25 m bench width, bench height at elevation 131-110 of 8 m with a comparison ratio of 1:2, single slope 26.57˚ and at elevation 110-50 of 8 m with a comparison ratio of 1:1.5, single slope 33.69˚.

Innovative design addressing complex airway stenosis: Multidimensional performance assessment of a novel Y-shaped airway stent

“Y-shaped” airway stents have been widely used in the treatment of airway diseases, especially airway stenosis, due to their excellent flexibility. However, the current research on the flexibility of “Y-shaped” airway stents is still blank, limiting the possibility of improving the performance of stents in complex clinical disease. This study aimed to establish multi-dimensional evaluation of the flexibility of a novel segmented “Y-shaped” airway stent and two kinds of conventional stents. We evaluated the flexibility of the segmented stent, wholly knitted stent, and silicone stent by in vitro mechanical testing and finite element analysis methods. That is, the bending force and spring-back force of three kinds of stent were measured in left–right, anterior-posterior and longitudinal directions. The torque of the stents in torsion-recovery test of branches of stent was also executed. Finite element analysis was performed to evaluate the change of diameter. According to the detection, the bending force and spring-back force of the branch of the segmented stent during left–right and anterior-posterior compression, and the torque during torsion and recovery were lower than those of the other two stents. In finite element analysis, the diameter change of the segmented stent was minimal among the three stents. The flexibility of the segmented “Y-shaped” airway stent was better than that of the conventional “Y-shaped” airway stents, indicating that it has better adaptability and resistance to compression when implanted in the body.

Computational and Experimental Characterization of Aligned Collagen across Varied Crosslinking Degrees.

Collagen-based scaffolds have been widely used in tissue engineering. The alignment of collagen fibers and the degree of crosslinking in engineering tissue scaffolds significantly affect cell activity and scaffold stability. Changes in microarchitecture and crosslinking degree also impact the mechanical properties of collagen scaffolds. A clear understanding of the effects of collagen alignment and crosslinking degrees can help properly control these critical parameters for fabricating collagen scaffolds with desired mechanical properties. In this study, combined uniaxial mechanical testing and finite element method (FEM) were used to quantify the effects of fiber alignment and crosslinking degree on the mechanical properties of collagen threads. We have fabricated electrochemically aligned collagen (ELAC) and compared it with randomly distributed collagen at varying crosslinking degrees, which depend on genipin concentrations of 0.1% or 2% for crosslinking durations of 1, 4, and 24 h. Our results indicate that aligned collagen fibers and higher crosslinking degree contribute to a larger Young's modulus. Specifically, aligned fiber structure, compared to random collagen, significantly increases Young's modulus by 112.7% at a 25% crosslinking degree (0.1% (4 h), i.e., 0.1% genipin concentration with a crosslinking duration of 4 h). Moreover, the ELAC Young's modulus increased by 90.3% as the crosslinking degree doubled by changing the genipin concentration from 0.1% to 2% with the same 4 h crosslinking duration. Furthermore, verified computational models can predict mechanical properties based on specific crosslinking degrees and fiber alignments, which facilitate the controlled fabrication of collagen threads. This combined experimental and computational approach provides a systematic understanding of the interplay among fiber alignment, crosslinking parameters, and mechanical performance of collagen scaffolds. This work will enable the precise fabrication of collagen threads for desired tissue engineering performance, potentially advancing tissue engineering applications.

Application of image processing technology based on field programmable gate array in mechanical part inspection

Introduction: In the field of industrial manufacturing, accurate inspection of mechanical components such as gears and bearings is of Paramount importance. However, the traditional mechanical testing methods are often disturbed by human factors, which not only affects the stability of the test results, but also leads to low efficiency and large error. In order to solve these problems, this research focuses on developing a new edge detection model.Methods: A novel edge detection model based on field-programmable gate array image processing technology was used in this study. The model uses adaptive threshold multi-directional edge detection technology to identify the edge features of mechanical gears and bearings, aiming at improving the precision of detection.Results and Discussion: After performance verification, the running time of the model was controlled within 11 s, and the detection error was limited to less than 9%. Compared with the control group and the experimental group, their performance was superior. Further analysis data show that the detection accuracy of this model is as high as 0.9004, its internal resource utilization rate is 88%, and the detection rate is as high as 91%, which are better than the comparison model.Conclusion: The proposed test model not only significantly improves the efficiency and accuracy of the test, but also fully meets the requirements of the test. This new edge detection model has potential application value in industrial manufacturing field, and provides a new solution for industrial manufacturing quality inspection.

Comparison of Thermal and Mechanical Pain Testing Modalities in Sprague Dawley and Fischer 344 Rats (Rattus norvegicus).

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Design and characterization of 3D-printed hollow microneedle arrays for transdermal insulin delivery

The delivery of insulin to diabetic patients remains a challenge due to the limitations of current insulin delivery paradigms, including painful cannula insertion, potential infections, interference with activity, embarrassment, and sometimes cost. To address this problem, we designed and fabricated nine prototypes of stereolithographic 3D-printed microneedle arrays (MNAs) appropriate for the minimally invasive delivery of insulin. We characterized their transdermal penetration performance by delivering fluid at a constant rate to porcine skin through these MNAs. Moreover, we characterized the force required for these MNAs to puncture porcine skin using a mechanical testing apparatus. We developed an improved method of mechanical testing for the MNAs against porcine skin by incorporating an imitation soft tissue layer under the skin and compared the MNA results with those using a single microneedle and a hypodermic needle. In addition, we investigated the mechanical flexural strength of the MNAs by performing a flexural failure load test on them. We confirmed that the prototype MNAs are mechanically robust and do not fracture during skin penetration, setting the stage for future trials in vitro and in vivo. The final, optimized designs are freely available in stereolithography (STL) file format.

A review of helicoidal composites: From natural to bio-inspired damage tolerant materials

Helicoidal composites have been found in shrimp club, lobster claw, beetle cuticle, crab shell, scorpion pincer, and fish scale as a natural material. The helicoidal composite possesses excellent impact resistance and extraordinary damage tolerance due to its hierarchical structure and the unique helicoidal arrangement of its reinforcement fibres. Its structure and performance have been studied through various characterisation and mechanical testing methods. Based on the structure-property relationship of the natural helicoidal composite, researchers have been able to mimic the unique fibre arrangement and develop bio-inspired helicoidal composites with enhanced impact performance. Various helicoidal composites comprising of synthetic fibrous materials such as carbon fibre (CF), glass fibre (GF), and aramid fibre, and matrix materials such as thermoset and thermoplastic polymers have been developed through biomimicry. The failure mechanisms of the bio-inspired helicoidal composites have been studied and the advantages of arranging the fibre reinforcement into helicoidal architectures have been elucidated over conventional composite constructions such as quasi-isotropic (QI) and cross-ply layups. This review systematically elaborates the recent progress of the research work on both natural and bio-inspired helicoidal composites. It sheds light on the distinctive construction of the natural helicoidal composites found in different animals such as shrimps, lobsters, crabs, beetles, scorpions, and fish, and their energy absorption mechanisms. Different manufacturing methods for developing bio-inspired helicoidal composites are discussed and various reinforcements and matrix materials used in the composites are described. The processing-structure-property interrelationship of the bio-inspired helicoidal composites is summarised. This review will contribute to the advancement of the knowledge of the natural helicoidal composite and potentially help researchers to develop highly efficient bio-inspired damage tolerant helicoidal composites.

Numerical simulation of concrete strength based on microstructure and mineral composition analysis using micro-CT and XRD technology

The investigation of mechanical properties in porous materials, such as concrete, has been a significant area of interest in the fields of civil engineering and architecture. Traditional macroscopic mechanical testing methods are limited due to destructive experimental conditions, time-consuming procedures, and the inability to characterize internal structures. To overcome these limitations, researchers have utilized microscopic factors with micro-CT and simulation models. Different simulation methods demand mechanical parameters to effectively model the constituent materials; however, there exists variability in the amount and standard values of these input parameters, which leads to a decrease in the reliability of the obtained results. In order to tackle this issue, a novel approach is proposed, which integrates mineral component analysis using X-ray diffraction (XRD) and establishes coefficients to minimize the number of necessary input parameters. Simulation results demonstrate excellent agreement with experimental measurements, accurately reproducing the stages of elastic deformation, failure, and fracture in the stress-strain curve of concrete. Our findings reveal that changes in the concrete skeletal structure, microstructure, and mineral composition significantly influence compressive strength. Coarse aggregates and high-mechanical-performance minerals, in particular, have a substantial impact. Additionally, the mechanical properties show a significant linear relationship with the strength reduction coefficient of aggregates and concrete cores. In conclusion, the proposed method, combining CT scanning and XRD with FDEM, proves to be a reliable and practical approach for accurately assessing the mechanical properties of concrete. This methodology simplifies the intricate processes associated with the time-intensive parameter calibration, leading to a more efficient parameter allocation procedure. As a result, this method enhances concrete design, promotes a better understanding of parameter impacts, and enables accurate prediction of concrete behavior across diverse scenarios.

Production of low-CO2 ternary binder using red sandstone, cement, and granulated blast furnace slag: A comprehensive performance analysis

Red sandstone is rich in reserves, and using it as a mineral admixture to partially replace cement can save cement consumption and reduce carbon dioxide emissions. This study uses spectral characterization, electron microscopy image analysis, mechanical property testing and other methods to study the fluidity, compressive strength, heat of hydration, carbonation degree, microstructure and thermal damage of composite cement-based materials containing red sandstone and slag. The experiment results showed that in ternary mixed cement, the composite cement mixed with 5% slag and 10% red sandstone shows similar flow properties to cement paste. Moreover, as the mineral content (red sandstone and slag) increases, the dissolution peak of the Al phase appears earlier, and the degree of carbonation increases. Furthermore, the CO2 emissions per unit strength gradually decrease. After 28 days of curing, thermal damage experiments demonstrated that the strength of the sample increases by more than 3.6% when the mineral content is greater than 15% at 200℃. Samples were subjected to 600 °C and 900 °C, and the strength of the red sandstone sample with a content of 15% decreased significantly. Moreover, as the temperature increases to (600 °C and 900 °C), the lattice of CnS becomes more and more ordered.

Fabrication of geopolymer composites using egg-shell and fly-ash: Comparison between the strength and stability, physio-chemical and mechanical properties

Nowadays, the demand for developing new structural materials, particulate composites made from industrial waste has been preferred along with conventional fiber-reinforced composites. In this work, two new composites were fabricated by reinforcing flyash and eggshell separately in epoxy with equal volume fractions and were termed geopolymer composites. Further thermo-mechanical characterization of these fabricated geopolymer composites was carried out by conducting various mechanical, physical, chemical, and thermal testing methods. The results were compared with the outcomes of neat epoxy composites. It was demonstrated that eggshell-epoxy composites have 28.48 % and 1.5 % more tensile strength than neat epoxy and flyash-epoxy composites. The flexural strength and hardness in a similar fashion were observed as increased by 31.7 %, 7.37 %, and 29.45 %, 15.6 % over neat epoxy and flyash-epoxy composites. The composites were crystalline confirmed from the XRD analysis. In contrast to the above, the thermal conductivity and thermal stability of flyash-epoxy composites were found superior though eggshell-epoxy composite visualized higher stability at the initial stage of thermal degradation. Further, the change of thermal conductivity of these materials with a temperature change was investigated by finite element modeling in MATLAB using the PDE toolbox. It was examined that thermal conductivity increases non-linearly with the increase in temperature up to 700 °C and then follows a uniform trend on further increase.

Relaxation behavior of thin-ply high strain composites using a dynamic mechanical analyzer based column bending test

Deployable space structures made from thin-ply high-strain composite (HSC) laminates can be compactly stowed, but prolonged stowage under high curvature can alter their deployed shape due to relaxation. In this research, a dynamic mechanical analyzer-based column bending test (CBT) method, with a custom-developed fixture was used to characterize the relaxation behavior of thin-ply HSCs. Four laminate configurations were prepared from thin-ply unidirectional IM7/PMT-F7 and Astroquartz/PMT-F7 prepregs: (i) IM7/PMT-F7 [0°], (ii) Astroquartz/PMT-F7 [±45°], (iii) Flexlam [±45°/0°/±45°] and (iv) Flexlam [±45°/90°/±45°]. Surface strains of 0.5, 1.0, 1.5, and 2.0% were sequentially applied to the specimen for 100-min durations, each separated by a 1000-min recovery period. This stepped strain approach was performed at 30°C, 50°C, and 70°C. The relaxation results indicate that the fiber-dominated test configuration, UD IM7/PMT-F7 [0°] lamina, shows no measurable relaxation. However, the matrix-dominated configurations, Astroquartz/PMT-F7 [±45°] lamina and the Flexlam laminates, show measurable relaxation. The Flexlam laminates show less relaxation than the Astroquartz/PMT-F7 [±45°] lamina due to the inclusion of unidirectional IM7 carbon fiber. The result also indicates that the relaxation behavior is time and strain-dependent, not temperature-dependent.

Contact area analysis of an asphalt-concrete boundary layer with X-ray computed tomography imaging

This study focusses on the bond between asphalt and concrete. The bond is a decisive factor for the transfer of traffic loads. A lack of bond between the layers can quickly reduce the load-bearing behavior and thus lead to pavement failure. In the literature, the bond between asphalt pavements and concrete substrates is usually analyzed using mechanical test methods. With mechanical test methods, the effects of interlocking, glue adhesion and friction, which have an effect at the layer boundary, are not considered individually. Based on previous findings, the aim of this study is to carry out a precise analysis of the bonding at the layer interface between concrete and asphalt using bitumen emulsion by means of measurements with a high-resolution X-ray computer tomography (CT). To determine the effect of the surface texture of the substrate, the investigations were carried out on milled and smooth surface textures. In addition to the variation of the substrate profiles, the influence of the application quantity of the bitumen emulsions C40 B5-S and C60 BP4-S was analyzed by spraying quantities of 90 g/m² and 180 g/m² bitumen after breaking. A newly developed method was used to determine the effective degree of gluing at the layer boundary, which allowed the bonding efficiency to be determined. The results of the calculated degree of gluing for the individual variants show that the highest degree of gluing of 61.94% is achieved with the smooth texture variant and high application quantity of bitumen emulsion. The lowest degree of gluing of 17.01% was achieved with the milled texture variant without the application of bitumen emulsion. Overall, the results showed that the degree of gluing was increased for both surface textures by applying the bitumen emulsion. Compared to the smooth texture, the milled textures exhibit a lower degree of gluing for both bitumen quantities, which could be explained by the distribution of the bitumen emulsions on the substrate profiles.