Tensile Apparatus Research Articles

A multi-mode stretching apparatus for in situ synchrotron x-ray scattering of polymer materials.

A compact and versatile tensile apparatus for polymer materials is designed and fabricated. Three distinct stretching modes are developed: constant speed, cyclic, and sinusoidal, with adjustable speeds ranging from 0.001 to 120 mm/s. To capture the true strain of the central region, a high-speed camera has been integrated into the apparatus. The temperature of the sample chamber is controlled by flowing air, enabling a homogeneous temperature in the range of RT ∼200 °C. The apparatus is particularly suitable for a synchrotron beamline. The structural evolution of natural rubber during sinusoidal stretching is investigated by in situ wide-angle x-ray scattering. Scattering patterns, force, clamp position, and sample images are saved simultaneously during stretching. Notably, the results reveal a sinusoidal variation in the crystallinity of crosslinked natural rubber when a sinusoidal strain was applied to the sample. The integration of advanced measurement techniques and controlled experimental conditions ensures the acquisition of reliable and accurate data, providing valuable insights into the structural evolution of materials under dynamic deformation conditions.

Intelligent carbon-based TRC as self-strain sensor

Abstract: This study investigates the monitoring capabilities of a carbon yarn embedded in a cementitious matrix as an intelligent strain sensor by means of a gauge factor (GF). In the proposed configuration, the yarn simultaneously functions as the structural system and as the sensory platform, yielding efficient and intelligent concrete elements. The concept of the smart self-sensory system is based on monitoring changes in the electrical properties of the carbon yarn, namely: resistance, inductance, or impedance, and correlating them to the structural health. These capabilities were investigated in carbon yarns that were inserted within textile-reinforced concrete (TRC) structural elements, in which the correlation yielded important information in the macro-structural level. The integrative measurements were used to estimate the structural state associated with cracking and straining along the element. Yet, to fully understand the structural-electrical mechanism and to further enhance the development of the smart carbon-based sensor, it is essential to explore the electrical-micro-structural mechanism at the component level. Therefore, the study offers to explore the correlation between straining and cracking at the component level by means of GF. Separately investigating strained or cracked zones at the yarn’s level will provide vital information on the monitoring capabilities of the carbon yarn. To answer these goals, the study will perform an experimental investigation of carbon-based TRC elements subjected to a designated pull-out test based on a uniaxial tensile setup. The proposed setup aims to correlate between changes in the electrical properties characterizing the carbon yarn and the micro-structural mechanism associated with the degradation of the structural health associated with the propagation of the crack. The outcomes of this study aim to enhance the understanding of the structural-electrical correlation, which paves the way for the development of intelligent strain sensors for TRC structures.

Micro-tensile rheology of fibrous gels quantifies strain-dependent anisotropy

Semiflexible fiber gels such as collagen and fibrin have unique nonlinear mechanical properties that play an important role in tissue morphogenesis, wound healing, and cancer metastasis. Optical tweezers microrheology has greatly contributed to the understanding of the mechanics of fibrous gels at the microscale, including its heterogeneity and anisotropy. However, the explicit relationship between micromechanical properties and gel deformation has been largely overlooked. We introduce a unique gel-stretching apparatus and employ it to study the relationship between microscale strain and stiffening in fibrin and collagen gels, focusing on the development of anisotropy in the gel. We find that gels stretched by as much as 15 % stiffen significantly both in parallel and perpendicular to the stretching axis, and that the parallel axis is 2–3 times stiffer than the transverse axis. We also measure the stiffening and anisotropy along bands of aligned fibers created by aggregates of cancer cells, and find similar effects as in gels stretched with the tensile apparatus. Our results illustrate that the extracellular microenvironment is highly sensitive to deformation, with implications for tissue homeostasis and pathology. Statement of significanceThe inherent fibrous architecture of the extracellular matrix (ECM) gives rise to unique strain-stiffening mechanics. The micromechanics of fibrous networks has been studied extensively, but the deformations involved in its stiffening at the microscale were not quantified. Here we introduce an apparatus that enables measuring the deformations in the gel as it is being stretched while simultaneously using optical tweezers to measure its microscale anisotropic stiffness. We reveal that fibrin and collagen both stiffen dramatically already at ∼10 % deformation, accompanied by the emergence of significant, yet moderate anisotropy. We measure similar stiffening and anisotropy in the matrix remodeled by the tensile apparatus to those found between cancer cell aggregates. Our results emphasize that small strains are enough to introduce substantial stiffening and anisotropy. These have been shown to result in directional cell migration and enhanced force propagation, and possibly control processes like morphogenesis and cancer metastasis.

Biaxial Extension of Cruciform Specimens: Embedding Equilibrium Into Design and Constitutive Characterization

BackgroundMain desired features of biaxial tests are: uniformity of stresses and strains; high strain levels in gauge areas; reliable constitutive parameters identification. Despite cruciform specimen suitability to modern tensile devices, standard testing techniques are still debated because of difficulties in matching these demands.ObjectiveThis work aims at providing rational performance objectives and efficient cruciform specimens shapes in view of constitutive characterization.MethodsObjective performance is evaluated along particular lines lying on principal directions in equibiaxial tensile tests. A rich specimen profile geometry is purposely optimized via finite elements analysis by varying cost function and material compressibility. Experimental tests, monitored via digital image correlation, are carried out for validation.ResultsNew shapes are designed and tested in a biaxial tensile apparatus and show to perform better than existing ones. Elastic parameter identification is efficiently performed by only exploiting full field strain measurements along statically significant lines.ConclusionsSmall gauge areas and small fillet radii cruciform specimens approach the ideal deformation behaviour. For the constitutive parameters identification in planar tensile experiments, it suffices to monitor strains along the gauge lines.

Mechanical Properties and Reinforcement of Paper Sheets Composited with Carboxymethyl Cellulose.

The mechanical properties for paper sheets composited with glucose (Glc), methyl cellulose (MC), and carboxymethyl cellulose (CMC) were investigated. The paper composites were prepared by immersing paper sheets in aqueous solutions of these materials and drying at 100 °C for 30 min. The stress-strain curves for these paper composites were measured by a uniaxial tensile apparatus with a stretching speed of 2 mm/min. The breaking stress and strain for untreated paper were 24 MPa and 0.016, respectively. The paper composites demonstrated stress-strain curves similar to the untreated paper; however, the breaking point largely differed for these composites. The breaking strain and breaking stress for the Glc composite slightly decreased and those for the MC composite gradually increased with the concentration of materials composited. Significant increases in the mechanical properties were observed for the CMC composite. The breaking stress, breaking strain, and breaking energy for the 3 wt.% CMC composite were 2.0-, 3.9-, and 8.0-fold higher than those for untreated paper, respectively. SEM photographs indicated that the CMC penetrated into the inner part of the paper. These results strongly suggest that the mechanical improvement for CMC composites can be understood as an enhancement of the bond strength between the paper fibrils by CMC, which acts as a bonding agent. It was also revealed that the breaking strain, breaking stress, and breaking energy for the CMC composites were at maximum at the first cycle and decreased gradually as the immersion cycles increased.

INVESTIGASI AREA SERRATED YIELDING PADA PADUAN 800H

Detailed information about the mechanical properties of components in the power plant was crucial in process design. One essential piece of information was the characteristics of the material at various temperatures in a tension load. In this study, the tensile test was applied to the Alloy 800H with various temperatures ranging from 24oC to 900oC at a constant deformation rate of 10-4/s. Alloy 800H was a promising candidate for components in power plants due to its high corrosion resistance in a high-temperature environment. A test was conducted by following the ASTM E8 and ASTM E21. The tensile apparatus was equipped with a furnace, and a thermocouple was attached to the specimen surface of the cylindrical during the test. The data was recorded by the data acquisition connected to the PC. This preliminary study aimed to determine the serrated yielding area that occurred based on several data from tensile test results.

Microstructural and texture evolution investigation of laser melting deposited TA15 alloy at 500°C using in-situ EBSD tensile test

The deformation behavior in polycrystalline Laser melting deposited (LMD) TA15 alloy was investigated at a temperature of 500°C using advanced in-situ Secondary electron microscopy (SEM) tensile setup coupled with Electron backscatter diffraction (EBSD). The grains morphology, crystal orientation, preferred pole texture, activated slip traces, grain boundaries evolution, and strain-induced misorientation were systematically analyzed during tensile straining. It was determined that the diverse α-grains (crystal orientation and morphology) revealed inhomogeneous deformation under tensile loading. The overall strain was allocated by grain rotation and substructure formation. The preferred oriented (0001) pole texture maximum was increased during initial strain level. In contrast, at higher strain, the texture intensity was decreased due to the formation and relocation of the newly formed substructures. The fraction of low angle grain boundaries (LAGBs 2–10°) was increased continually with increasing strain. Strain-induced dislocations within larger grains formed new LAGBs, and the increasing fraction of LAGBs was validated by Kernel average misorientation (KAM) map. The prismatic slip mode was identified as the primary active slip system at the initial deformation stage. The fraction of basal and pyramidal <a> slips increased as the strain increased, describing the opposite trend to prismatic slip. The grains rotation and strain accumulation at the grain boundaries accommodated the plastic deformation, ultimately causing boundary sliding.

Understanding the role of bond point strain in the mechanical response of nonwoven polypropylene materials

A method was developed to study micromechanics of a bond point in nonwoven polypropylene materials. The micromechanical behavior of the thermal bonded nonwovens was studied using the digital image correlation (DIC) technique to understand the bond points deformation during mechanical stretching. An electrospray technique was used as a fast and reliable method to create the speckle pattern on the nonwovens. Various parameters of the electrospraying and their influence on the pattern accuracy and repeatability was studied and the best pattern in terms of dot size and distribution was determined from experimentation. Plasma treatment also proved to be essential to enhance the uniform distribution and adherence of the particles on the surface. Unloaded DIC experiments were carried out and proved the accuracy of technique with errors of lower than 0.5% strain. An automated high-resolution tensile apparatus was built and loaded DIC experiments were carried out using the device. The fabric was tested in Machine Direction (MD) direction and Cross Direction (CD) directions, both showing good correlation with low errors. Average strain values in bond points were plotted against total strain in fabric and the results showed noticeable amounts of strains developed in the bond points, contradictory to most of the FEM models which consider no deformation in the bond points. Results also indicated that in MD direction deformation, bond points can experience more than 30% of the overall strain presented in the fabric.

Shape Memory Polyurethane as a Drilling Fluid Lost Circulation Material

AbstractDrilling fluid loss is a major problem with serious economic and environmental consequences. The use of traditional lost circulation materials (LCMs) to seal wide fractures increases the risk of bit nozzle plugging. In this work, smart LCMs based on shape memory polyurethane (SMPU) are proposed for the first time. SMPU can be programmed to recover at temperatures suited to a given well. As such, SMPU smoothly passes through the bit nozzles, while effectively seal wide fractures once activated. The SMPU is prepared by two step pre‐polymerization and characterized by Fourier transform infrared spectra, X‐ray diffraction, and differential scanning calorimeter. The SMPU is programmed by changing and fixing the original shape to a temporary shape through a thermo‐mechanical process. The shape memory behavior of SMPU is analyzed by tensile apparatus. Compatibility of SMPU with WBMs is determined from mud rheology and filtration tests. Fracture sealing efficiency and shape recovery of SMPU are evaluated by a modified particle permeability apparatus fitted with a model fracture. The results confirm high sealing and shape recovery attributes of SMPU. The plug formed at 114 kg m–3 SMPU and 80 °C experiences a sealing pressure of 100 bar with 71.5 cm3 cumulative fluid loss.

Optimization of Nanoclay/Polyacrylonitrile Scaffold Using Response Surface Method for Bone Differentiation of Human Mesenchymal Stem Cells.

Response surface methodology (RSM) based on the D-optimal algorithm was employed here for the electrospinning of nanoclay/polyacrylonitrile (PAN) composite scaffold by the aim of obtaining the lower fiber diameter and better mechanical properties for bone regeneration. The input parameters included the electrospinning voltage, flow rate and the ratio of nanoclay/PAN and the obtained values for the optimum point were 17 kV for the applied voltage, 0.41 ml/hr for flow rate, and 19.06% for the nanoclay/PAN ratio. The composite scaffold was fabricated in accordance with these optimum values and then studied by scanning electron microscopy and tensile apparatus. The fiber diameter and Young's modulus of the prepared scaffold were respectively 145 ± 12 nm and 267 ± 8.7 MPa that the values were between predicted by RSM. Moreover, the biocompatibility and osteogenic differentiation of the composite scaffold were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphatase assays. The bare scaffold and tissue culture polystyrene were used as control groups. The results approved stronger bioactivity and bone regeneration with the composite scaffold as a presence of clay nanoparticles.

Inferring material parameters from imprecise experiments on soft materials by virtual fields method

Inferring material parameters of soft materials, especially soft tissues from experiments, has always been a challenge because of the inaccuracy of specimen geometry, difficulty in proper gripping and difficulty in obtaining reliable displacement data. If one is able to obtain full field data with Digital Image Correlation or other similar techniques, we show that in spite of poor quality experimental data, it is still possible to get the material parameters using Virtual Fields Method with carefully chosen virtual fields. We demonstrate the approach by two cases. The first is Ecoflex (silicone rubber) under biaxial deformations at controlled loading rates, and the second is rat skin samples with imperfect shape under biaxial deformations at controlled loading rates. In both cases, rather than trying to obtain homogeneous deformation conditions, we use a technique based on the Virtual Fields Method to extract the material properties from the deformation of the specimen collected by Digital Image Correlation (DIC) and the force load measured by the load sensor. In order to apply loads in two principal directions simultaneously, a custom biaxial set-up was built and mounted into a uniaxial Instron tensile set-up. We show here that in spite of significant inhomogeneity in the deformation, errors, and missing data in the measured displacement field, we are still able to recover the material properties of the soft solid by suitable choices of virtual fields.

On the mechanical behaviour of industrial PVC pipes under pressure loading: experimental and numerical studies

The purpose of this work is to assess the circumferential mechanical characteristics and the mechanical strength of industrial PVC pipes, especially under pressure loading. The investigation and the prediction of the resistance to deformation or failure of PVC pipes under internal pressure are essential to develop their potential application. To this end, two approaches are retained in this paper. The first one consists of developing an experimental apparatus devoted to study the mechanical properties of PVC pipes at laboratory scale. A split disk tensile (SDT) apparatus was developed according to the tensile test machine available in our laboratory. Such developed apparatus permits to characterize successfully more than one pipe diameter. The second approach consists of building a successful finite element (FE) model which will be able to predict the mechanical response of the pipes when submitted to pressure loading in radial direction. The obtained experimental and numerical results were firstly evaluated and then, their correlation was discussed. The robustness and efficiency of the FE model is assessed on the basis of the experimental/numerical correlation analysis. From the main results, the established model is shown to well predict the mechanical properties of polymeric pipes when will be exposed to mechanical loadings and other factors.

Passive load-deformation properties of human temporal muscle

The passive load-deformation properties of the human temporal muscle applicable to computer simulations of the human head or the comparison of the temporal muscle to other graft materials are unexplored to date and it is unclear, if these properties depend on age, sex, post-mortem interval or body side. Eighty-eight fresh temporal muscle samples from 69 human cadavers (age range 4 months – 94 years) were investigated in a quasi-static tensile setup. For comparative reasons, 20 age-matched human temporal muscle fascia and scalp samples were tested in the same manner as the temporal muscle. Human temporal muscle showed an elastic modulus of 1.58 ± 0.64 MPa, an ultimate tensile strength of 0.26 ± 0.11 MPa and a strain at maximum force of 26.21 ± 12.48%. These parameters were independent of sex (p > 0.88), side (p > 0.92) and post-mortem interval (p > 0.09). All passive load-deformation parameters of the human temporal muscle differed from temporal muscle fascia and scalp except for the strain at maximum force of the temporal muscle and scalp. Significantly different load-deformation properties of the human temporal muscle from temporal muscle fascia and scalp indicate the need for a separate simulation of these soft tissue layers in computational head models to reflect lifelike conditions. Contrary to other tissues such as scalp or temporal muscle fascia the biomechanical temporal muscle properties in head models may not require adjustments for sex, side and age based on the here-presented findings.

Finite Element Simulation Study of Ultrasonic Vibration-Assisted Tensile High-Volume Fraction SiCp/Al Composite.

Silicon carbide particle-reinforced aluminum matrix composite (SiCp/Al) has been widely used in the military and aerospace industry due to its special performance; however, there remain many problems in the processing. The present paper introduces an ultrasonic vibration tensile apparatus and a composite tensile specimen and performs Abaqus finite element simulation on high-volume SiCp/Al. The results show that the stress-strain curve increases linearly during conventional tensile strength; the intermittent vibration tensile strength is similar to the full course vibration tensile strength: The magnitude of the stress reduction increases as the amplitude of the ultrasound increases and the vibration frequency increases. The tensile rate is inversely proportional to the magnitude of the stress reduction, and in the ultrasonic parameters, the amplitude has the greatest influence on the magnitude of the stress reduction, followed by the tensile rate; additionally, the frequency has the least influence on the magnitude of the stress reduction. The experimental results show that the simulation results are consistent with the experimental results.

A miniaturized biaxial tensile apparatus based on torsional loading design

A miniaturized biaxial tensile apparatus is presented. Based on a torsional loading design, the total dimensions and weight of the apparatus have been reduced, while the output force has been increased. Owing to the use of four independent stepping motors, the apparatus can realize arbitrary displacement ratios during the loading processes. The apparatus is designed to be applied with a laser scanning confocal microscope realizing in situ mechanical tests. Through a proof-of-principle experiment with an optimized cruciform shaped specimen, the developed biaxial tensile apparatus is proved to be suitable for in situ tests of biaxial stress analysis.

Combined photogrammetry and mechanical testing of fired clay brick

A novel experimental tensile apparatus and testing methodology, developed in order to define necessary material parameters for mathematical formulation of a constitutive model of fired clay brick is presented in this paper. In order to account for irregularities in sample geometry, a photogrammetry workflow for digital 3D reconstruction of samples was conducted, and non-dimensional coefficients accounting for geometric irregularities of test specimen was introduced. Mechanical tests were carried out on a series of fired clay brick specimens, sampled from brick blocks. Statistically analysed experimental data, corrected with the aforementioned coefficients, yielded modulus of elasticity, Poisson’s coefficient, and extreme tensile stress/strain relationships that, were used in the proposed numerical constitutive model.

Characteristics of Epoxy Resin Polymer Mortar with Different Filler Materials

A binding material forms the core of any construction material as it physically, chemically and mechanically holds the mix together. From lime to cement, the binding materials used conventionally has changed and evolved. Cement is a mineral binding material which reacts with water and has to be cured over a 28-day period to attain its characteristic strength in addition to holding the mix together as a homogenous substance. An organic binding material is one in which an organic substance like resins, bitumen, etc., make a transition from a plastic state to hardened state by a physical or chemical process. In this investigation, cement is completely replaced by epoxy resin as an organic binder and specimen were cast with combinations of epoxy and different filler materials. The filler materials used are Fly Ash, Fumed Silica, GGBS, Quartz, Copper Slag and Silica Fume. The specimen were tested for compressive strength, tensile strength, Flexural Strength and Chemical Resistance. The flexural test was conducted on prisms with and without fibre subjected to three-point and four-point cyclic loading. Compressive Strength was done on cubes 40X40X40 mm on 1,3,5 and 7th days of casting. Dog-bone shaped specimens were subjected to tensile stress by a specially prepared tensile setup. The chemical resistance of the specimen was also tested by immersing it in 5% diluted solutions of Sulphuric acid, Nitric Acid and Hydrochloric acid. The main objective of this project is to analyse each mix design and deduce its suitable field of application based on its various characteristics exhibited by each mix combination.

Prediction of mechanical behavior of composites under high strain rate tensile loading

Non-standardization of specimen size and shape, complexities involved in specimen fabrication and its mounting on split Hopkinson pressure bar (SHPB) make it difficult to achieve reliable high strain rate mechanical properties under tensile loading experimentally. A formulation based on variable rate power law is proposed to predict the tensile strength at higher strain rates based on the experimentally obtained values at comparatively lower strain rates. Experiments were conducted on typical plain weave composite along warp direction, unidirectional composite along and across fiber direction made of E-glass/epoxy and epoxy resin along in-plane direction in the strain rate range up to 470/s using a tensile SHPB apparatus. Predictions of high strain rate tensile behavior of all the four materials have been made up to strain rate of 2000/s. A comparison between analytical predictions and available experimental data is also made and a good match is observed.

In Situ Scanning Electron Microscope (SEM) Observations of Damage and Crack Growth of Shale.

To better understand the formation and evolution of hierarchical crack networks in shales, observations of microscopic damage, and crack growth were conducted using an in situ tensile apparatus inside a scanning electron microscope. An arched specimen with an artificial notch incised into the curved edge was shown to afford effective observation of the damage and crack growth process that occurs during the brittle fracturing of shale. Because this arched specimen design can induce a squeezing effect, reducing the tensile stress concentration at the crack tip, and preventing the brittle shale from unstable fracturing to some extent. Both induced and natural pores and cracks were observed at different scales around the main crack path or on fractured surfaces. Observations indicate that the crack initiation zone develops around the crack tip where tensile stresses are concentrated and micro/nanoscale cracks nucleate. Crack advancement generally occurs by the continuous generation and coalescence of damage zones having intermittent en echelon microscopic cracks located ahead of the crack tips. Mineral anisotropy and pressure build-up around crack tips causes crack kinking, deflection, and branching. Crack growth is often accompanied by the cessation or closure of former branch cracks due to elastic recovery and induced compressive stress. The branching and interactions of cracks form a three-dimensional hierarchical network that includes induced branch cracks having similar paths, as well as natural structures such as nanopores, bedding planes, and microscopic cracks.

Deformation behavior of isotactic polypropylene with oriented α- and β-crystals

In this work, the oriented α- and β-crystals were simultaneously fabricated in the iPP parts with a β-nucleating agent by means of the oscillation shear injection molding (OSIM) technique. The β-nucleated iPP parts demonstrated an interesting deformation behavior, traced by in situ synchrotron X-ray diffraction equipped with a uniaxial tensile apparatus. In the small strain region (6.7%) from the yield point to the strain hardening point, dramatic changes in terms of the crystal orientation and phase transition took place. In this region, the content and orientation degree of oriented α-crystals kept continuously increasing. On the contrary, the content of oriented β-crystals was successively decreasing until they almost disappeared, along with their fluctuant orientation. The formation of oriented α-crystals was initially at the sacrifice of oriented β-crystals, and subsequently the unoriented crystal and amorphous phase. Our work provides a theoretic foundation for the application of iPP parts with oriented α- and β-crystals under loading.