Uniaxial Tensile Testing Machine Research Articles

Development of gallic acid-loaded ethylcellulose fibers as a potential wound dressing material

In this study, novel fibers were designed based on ethylcellulose (EC), loaded with different concentrations of gallic acid (GA) using the electrospinning technique, in order to investigate the potential of these materials as wound dressings. The chemical structure and morphology, along with the antimicrobial and biocompatibility tests of the EC_GA fibers were investigated. To observe the chemical interactions between the components, fourier transform infrared spectroscopy (FTIR) was used. The morphological analyzes were performed using scanning electron microscope (SEM). The uniaxial tensile test machine was used to obtain mechanical performance of the fibers. MTT assay was applied to get the biocompatibility properties of the fibers and antimicrobial test was applied to obtain the antimicrobial activity of the fibers. Based on the obtained results, the highest viability value of 67.4 % was obtained for 10%EC_100GA on the third day of incubation, demonstrating that with the addition of a higher concentration of GA, the cell viability increases. The antimicrobial tests, evaluated against Staphylococcus (S.) aureus, Escherichia (E.) coli, Pseudomonas (Ps.) aeruginosa and Candida (C.) albicans, showed a >90 % microbial reduction capacity correlated with a logarithmic reduction ranging from 0.63 to 1, for 10%EC_100 GA. In vitro release tests of GA from the fibers showed that GA was totally released from 10%EC_100 GA fibers after 2880 min, demonstrating a controlled release profile. These findings demonstrated that EC_GA fibers may be suitable for application in biomedical fields such as wound dressing materials. However, further studies should be performed to increase the biocompatibility properties of the fibers.

Experimental study and hybrid optimization of material extrusion process parameters for enhancement of fracture resistance of biodegradable nanocomposites

Among the additive manufacturing processes, the material extrusion (ME) is the most popular and affordable technique in production of a wide range of products, from prototypes to the final products, for different industrial sectors. The most popular raw material in this process is the biodegradable polylactic acid (PLA) polymer that offers ease of production in relatively low price and wide applications in synthesis of medical proteases. However, the mechanical strength of fabricated samples and their resistance against the fracture loadings, which are critical for components synthesized for medical applications, are strongly dependent on the ME process parameters and the composition of the base material. Therefore, this study is aimed to address both the strengthening mechanisms of inorganic CaCO3 nanoadditives in the PLA matrix and the influence of ME process parameters on the fracture resistance of fabricated samples. To this aim, the PLA/CaCO3 nanocomposite filaments have been produced by mix-blending/extrusion technique and were employed to fabricate tensile and fracture test samples in ME process under different sets of parameters, including printing speed, layer thickness, filling ratio and printing pattern, determined by Taguchi L27 orthogonal array. The fracture experiments were conducted on a uniaxial tensile test machine using a specially designed fixture that makes the application of mixed-mode loading on fracture samples possible. The results of fracture toughness of specimens were employed as input data to model the response of fabricated samples and to determine the ME parameter levels and nanoparticle concentrations for maximum fracture resistance of fabricated samples based on a hybrid algorithm of artificial neural network and ant colony optimization (ANN/ACO). Differential scanning calorimetry was used to characterize the thermal features (i.e. glass transition, crystallization and melting temperatures) as well as the degree of crystallization of ME samples. Scanning electron microscopy of fracture surfaces were employed to study the influence of ME parameters and CaCO3 nanoadditives on the characteristics of fracture of 3D printed specimens under various modes of loading. Overall, the results showed that the effects of ME parameters on the fracture behavior of 3D printed samples are highly interconnected and, in the case of a semicrystalline polymer, are highly dependent on the physical characteristics of the fabrication process, including the heat transfer and crystallization rate of the matrix.

Microstructure evolution and tensile property of deformed Al–Mg–Sc alloy: comparison of ECAP and FSP

In this paper, the effects of two severe plastic deformation (SPD) methods, ECAP and FSP, on the microstructure evolution and tensile strength of an Al–6Mg–0.4Mn–0.25Sc–0.1Zr (wt.%) alloy are comparatively studied. The microstructure was characterized by SEM, EBSD, T-EBSD, TEM and HRTEM, and the tensile strength of the material was tested by uniaxial tensile testing machine. The results show that ECAP has a stronger grain refining effect than FSP. ECAP can refine the average grain size of Al–Mg-Sc alloys to about 1 μm, while the grain size of the FSP samples is mostly 2–3 μm. In addition, the effects of the two SPD methods on the second phase particles in the Al–Mg–Sc alloy are also different, but both methods will change the distribution and morphology of Al3(Sc, Zr) particles, which is due to the different deformation mechanisms of ECAP and FSP. The yield strength of the ECAP sample is higher than that of the FSP sample, but the elongation after fracture is slightly less than that of the FSP sample.

Plantaris tendon is valuable graft for the medial patellofemoral ligament reconstruction: A biomechanical study

BackgroundMedial patellofemoral ligament (MPFL) reconstruction is a standard treatment option for selected patients with patellar instability. Although frequently performed, the optimal graft source for the procedure has not yet been established. This study aimed to determine whether a two-strand plantaris tendon construct possesses the biomechanical properties needed to act as an MPFL reconstruction graft. MethodsThirty paired plantaris and gracilis tendons were harvested from 15 cadavers, mean age at death of 42.7 years. All specimens were frozen and maintained at −20 °C until biomechanical testing. Prior to mechanical testing, specimens were thawed at room temperature. The two-strand plantaris tendon and two-strand gracilis tendon constructs were created and secured in a uniaxial tensile testing machine in a triangular-shaped mode. Biomechanical properties for tensile testing to failure were determined using validated method. Results obtained were compared with the previously published data on native MPFL biomechanical properties. ResultsThe mean maximal force was 220.3 ± 108.1 N and 448.1 ± 117 N for the two-strand plantaris tendon construct and two-strand gracilis tendon construct, respectively. Significant differences were observed between all biomechanical properties of two-strand plantaris tendon and two-strand gracilis tendon constructs. The mean maximal force of a two-strand plantaris tendon construct and a two-strand gracilis tendon construct were greater than the mean maximal force of the native MPFL reported in all previous studies. ConclusionsThis study suggests that, due to its biomechanical properties, the two-strand plantaris tendon graft is suitable as a graft for MPFL reconstruction.

Assessment of the Tribological Properties of the Steel/Polymer/Steel Sandwich Material LITECOR

The article presents the results of tribological investigations into the steel/polymer/steel sandwich material LITECOR® developed by ThyssenKrupp Steel Europe for applications in the automotive industry. Friction tests were carried out by means of a strip drawing test with the use of a special tribotester mounted on a uniaxial tensile test machine. The influence of sheet deformation on the value of the coefficient of friction (COF) was considered. For this purpose, the samples were subjected to a pre-deformation of 4%, 8% and 12%. Friction tests were carried out with different force values and under different friction conditions, i.e., in dry friction conditions and lubrication of the sheet surface with L-AN 46 machine oil. The highest values of COF were observed for as-received sheets. In contrast, apart from the friction process under the conditions of the lowest force analysed, the lowest value of the COF was observed for pre-strained sheets with a deformation of 12%. The lubrication efficiency of the pre-strained strip specimens with ε = 4% was between 10.5% and 16.3%, with a trend of increasing lubrication efficiency with increasing force. For pre-strained sheets with deformation ε = 12%, there was a trend of decreasing effectiveness from 14.9% to 9.03% with an increase in force.

Static and Dynamic Properties of Al-Mg Alloys Subjected to Hydrostatic Extrusion.

The aim of this study is to determine the influence of the amount of magnesium in Al-Mg alloys and strain rate on the grain refinement and mechanical properties of the material as determined in a dynamic tensile test. Hydrostatic extrusion was used to process the material. This method is not commonly used to impose severe plastic deformation of Al-Mg alloys. The article presents the results of static and dynamic strength tests on aluminium alloys subjected to plastic deformation in the hydrostatic extrusion process. Technically pure aluminium Al99.5 and three aluminium alloys with different magnesium content, Al-1Mg, Al-3Mg and Al-7.5Mg, were used in the tests. The samples were subjected to static tests using the uniaxial tensile test machine and dynamic tests using a rotary hammer. Compared to pure aluminium, increasing the magnesium content in Al-based alloys strengthened them in hydrostatic extrusion (logarithmic strain ε = 0.86) and caused an increase in the static ultimate tensile stress Rm, relative strain εr and the value of the yield stress. For strengthened aluminium alloys, an increase in the strain rate from 750 to 1750 s−1 caused an increase in the dynamic ultimate tensile stress from 1.2 to 1.9 times in relation to the static ultimate tensile stress. The increase in magnesium content results in the formation of a larger strengthening phase, influences a different state of stress during dynamic loading and leads to a change in the orientation of the fracture surface. It was also found that an increase in magnesium content is associated with an increased number of voids, which is also directly proportional to the strain rate in the dynamic rotary hammer test.

Tribological behaviour of Ti-6Al-4V titanium alloy sheets measured by a strip drawing test

This article presents the results of friction testing of Ti-6Al-4V titanium alloy 0.5 mm thickness sheets. The strip drawing test is the basic test for assessing the frictional properties of sheets intended for the sheet forming process. The device was mounted on a typical uniaxial tensile testing machine. The tests were carried out under dry friction and lubrication conditions with the use of a wide spectrum of oil types: gear oil 75W-85, engine oil 10W-40, machine oil L-AN 46 and hydraulic oil L-HL 46. Moreover, the use of biodegradable vegetable lubrication is also examined, i.e., rape-seed and palm oils, with the addition of boric acid with a concentration of 5% w/w. Experimental studies have shown that 10W-40 engine oil was the most effective in reducing the coefficient of friction in the pressure range of 10.7 MPa-16.3 MPa (typical pressure range for the deep drawing process).

Effect of Lubricant Type on the Friction Behaviours and Surface Topography in Metal Forming of Ti-6Al-4V Titanium Alloy Sheets

The aim of the research described in this paper is to analyse the synergistic effect of types of synthetic oil and their density on the value of the coefficient of friction (COF) of Ti-6Al-4V titanium alloy sheets. Lubrication performance of commercial synthetic oils (machine, gear, engine and hydraulic) was tested in a strip draw friction test. The friction tests consisted of pulling a strip specimen between two cylindrical fixed countersamples. The countersamples were placed in the simulator base mounted on a uniaxial tensile test machine. Due to the complex synergistic effect of different strip drawing test parameters on the COF, artificial neural networks were used to find this relationship. In the case of both dry and lubricated conditions, a clear trend was found of a reduction of the coefficient of friction with nominal pressure. Engine oil 10W-40 was found to be the least favourable lubricant in reducing the coefficient of friction of Grade 5 titanium sheets. The two main tribological mechanisms, i.e., galling and ploughing, played the most important role in the friction process on the test sheets. In the range of nominal pressures considered, and with the synthetic oils tested, the most favourable lubrication conditions can be obtained by using a type of oil with a low viscosity index and a high kinematic viscosity.

The Measurement of Acoustoelastic Constant to evaluate Stress by UsingUltrasonic Waves

This experimental study aims to investigate the capability of the ultrasonic method by using critically refracted longitudinal (LCR) wave for measuring welding stress in elastic limits.Ultrasonic technique is based on the linear relation between the ultrasonic wave velocity and the stress, known as the acoustoelastic effect.To determine acoustoelasticconstants, different amounts of stress were applied to the specimens by using uniaxial tensiletesting machine. The outcome of the study showed a linear relation between time-of-flight (TOF) measured and the tensile stress in the samplesand providedthe acoustoelasticconstants of Q345. This paper also analyzed the measurement influence factors including the thickness of couplant, temperature and residual stress.

The microstructural and mechanical characterization of the β-type Ti-11.1Mo-10.8Nb alloy for biomedical applications

Ti-Mo alloys are promising biocompatible materials with lower elastic modulus than the extensively used Ti-6Al-4V alloy. However, research work done on these alloys indicate that their elastic modulus is still higher than that of the bone, even after the execution of numerous heat treatment procedures. Therefore, this study was aimed at adding Nb (non-toxic β stabilizer) to Ti-Mo system followed by the characterization of its microstructural and mechanical properties in the as-cast condition. This study will provide systematic preliminary information towards the design and development of novel biomedical components. The microstructure and phase analysis were carried out using optical microscope, SEM, and XRD. Mechanical tests were conducted using the uniaxial tensile test machine and Vickers microhardness tester. The as-cast Ti-11.1Mo-10.8Nb alloy consisted primarily of β phase and a possible small volume fraction of ω phase. The Vickers micro-hardness, elastic modulus, bending strength were measured as 311.62 HV0.5, 56.9 GPa 1671.4 MPa, respectively. The Ti-11.1Mo-10.8Nb alloy also exhibited ductile fracture behaviour during bend testing. The Ti-11.1Mo-10.8Nb design is a promising alloy for biomedical applications.

Highly conductive carbon nanotubes and flexible cellulose nanofibers composite membranes with semi-interpenetrating networks structure

Highly conductive multi-walled carbon nanotubes (MWCNTs) and flexible cellulose nanofibers (CNF) membranes with semi-interpenetrating networks structure were fabricated using the typical paper-making method, which was simple and cost-effective. The Scanning electron microscope (SEM), Fourier-transform infrared (FT-IR), and thermal gravimetric analysis (TGA) were used to estimate the morphology, chemical structure, and thermal stability of the membranes. The mechanical, optical, and electrical properties of the membranes were characterized with a uniaxial tensile testing machine, ultraviolet visible spectroscope, and digital multimeter, respectively. The results indicated that the membranes containing 10 wt% of MWCNTs showed a high conductivity value of 37.6 S/m, and the sheet resistances of the membranes were stable at different bending states. Furthermore, we demonstrated the electrical features of membrane-based capacitive pressure sensors based on CNF/MWCNTs. The proposed method for fabricating CNF/MWCNTs membranes can simplify the production process and have great practical potential in various electronics applications such as touch screens.

Experimental and Numerical Investigations of Thin-Walled Stringer-Stiffened Panels Welded with RFSSW Technology under Uniaxial Compression.

Many aircraft structures are thin walled and stringer-stiffened, and therefore, prone to a loss of stability. This paper deals with accurate and validated stability analysis of the model of aircraft skin under compressive loading. Both experimental and numerical analyzes are conducted. Two different methods of joining panel elements are considered. In the first case, the panel is fabricated using rivets. In the second variant, the refill friction stir spot welding technique is used. Both types of panels are loaded in axial compression in a uniaxial tensile testing machine. The geometrically and physically nonlinear finite element analyzes of the panels were carried out in ABAQUS/Standard. The Digital Image Correlation measurement system ARAMIS has been utilized to monitor the buckling behavior and failure mode in the skin-stringer interface of the stiffened panels. The results of experiments and the digital image correlation system are presented and compared to the numerical simulations.

Determination of acoustoelastic/acoustoplastic constants to measure stress in elastic/plastic limits by using LCR wave

This experimental study aims to investigate the ability of the ultrasonic method (UM) by using critically refracted longitudinal (LCR) wave for measuring stress in both elastic and plastic limits. In so doing, nine tensile test specimens are used. In order to send and receive the LCR wave into the specimens, the investigation led to design two different types of ultrasonic fixtures (constant fixture and variable fixture). The constant fixture, used to evaluate and compare the results of variable fixture. Three initial distances (0, 30, 50 mm) employed for variable fixture to detect the accurate results and compare with the constant fixture. To determine acoustoelastic and acoustoplastic constants different amounts of stress are applied to the specimens using uniaxial tensile testing machine. Measurement of longitudinal applied stress by UM is done by using 2 MHz probes based on Acoustoelasticity. The results of the study indicated that there is a significant relation between stress and time of flight wave in both elastic and plastic limits. For the first time, this study shows that entering the plastic limit takes tremendous sensitivity. By using variable fixture (without initial distance) enable the process to evaluate stress in the plastic limit accurately. The outcome of the study provides three acoustoplastic and three acoustoelastic constants. All of these constants, by increasing the initial distance between two parts of the variable fixture will reduce. In other words, the comparison between different initial distance tests indicates that increasing initial distance caused to less accuracy of measuring stress.

Papillary Muscle Related Biomechanical Properties of Mitral Valve Chordae Tendineae

. Introduction Mitral valve is a complex structure including the annulus, the anterior leaflet, the posterior leaflet, the papillary muscles (PM), and the chordae tendineae connecting the leaflets and PM. The mechanical properties of the chordae play an important role in the normal functioning of the mitral valve: the chordae assists in maintaining the opening and closing configuration of the valve during cardiac cycle. Failure of certain chordae may lead to failure of the mitral valve and in severe cases, will lead to heart disease and mortality. In some cases, the ruptured chord need to be corrected by repair or replacement. Therefore, there has been high interest in the analysis of the function, mechanical properties and shape features of the mitral apparatus to improve the surgical effect. Chordae can be distinguished by leaflet location insertion as primary and secondary chordae. These finger-like chords connect the mitral valve to either anterolateral papillary muscle (APM) or posteromedial papillary muscle (PPM). The PPM has a higher risk to necrose and rupture in myocardial ischemia and infarction in clinic, but it is underlying mechanism is still unknown. Previous studies have shown importance in maintaining the asymmetric structure and realistic material property of the mitral valve for physiological load condition, but simplified the chord as symmetric structure, which is not true. In this study, the porcine heart chords were classified and measured according to the attached PMs. The uniaxial tensile test was utilized to analyze the biomechanical properties of the papillary muscle related chordae and histology observation was carried out for microstructure analysis. This study aims to analyze the anatomical and mechanical property differences in chords based on PMs which may help to understand the mitral valve function and to optimize the design of the artificial implantation or repair. Methods and materials Studies have shown that porcine valve was identified as an appropriate model for further investigation of the mitral valve system when considering the rarity of human valve. A total of 16 fresh porcine hearts were collected, infused in 4°C PBS buffer and infiltrated in physiological saline during the experiment, 9 of which were used for tensile testing, 6 for histological section staining, and 1 for TEM scanning. Based on insert position to PM (APM or PPM) and leaflets (primary on free edge and secondary on belly), the chord were divided into the APM primary chord, APM secondary chord, and PPM primary chord, and PPM secondary chord. The chords were separated from the valve, and the chordae diameter and length were measured via microscope, Markers were added at the target area of ​​the chord for strain measurement. The sample was then fixed on an Instron1000 uniaxial tensile test machine with sandpaper. Before the experiment, the specimens were preload from 0N to2N until the displacement curves were substantially coincident, and then tensile test. The sensor is used to record the stress change, and the CCD camera synchronously collects the displacement footage of the markers on target area until the chord sample is broken or slipped from tensile test machine. The MATLAB code was used to perform imaging processing and to obtain the stress-strain curve. Histological samples were fixed in 4 % glutaraldehyde in PO4 buffer (pH 7.4) for 5 hours, dehydrated with graduated concentrations of ethanol and embedded in paraffin. Radial sections were cut to 5 µm thick, masson stained and photos were then taken with microscope (ZEISS Stemi 2000-C) and camera (ZEISS AxioCam ICc5). The cross-sectional area ratio of collagen fibers and the amount of micro-vessel were observed. The microstructure sample were processed for transmission electron microscopy (TEM) observation. They were trimmed and fixed with 2.5 % glutaraldehyde, post-fixed with 1 % Osmium Tetroxide for 1 hour, 1 % uranyl acetate in Maleate buffer for 1 hour, and dehydrated with ethanol and propylene oxide, and then embedded in Epon. The difference in the configuration of collagen fibers was observed by TEM scanning. Result and conclusion There was no significant difference in the number of chord on each PM, and the PPM chord was longer. The Green strain-Cauchy stress curve showed that the Tangent Modulus (TM) of the PPM secondary chord was larger than that of the APM secondary chord. The number of blood vessels on APM primary chord was more than that of PPM primary chord, there was no significant difference in the area ratio of collagen fiber on chord of each PM. In our research, the Ogden nonlinear strain energy function was used to fit the experimental stress-strain data and to obtain material parameters. It provides a theoretical basis for the subsequent dynamic simulation using finite element method.

The role of smoking on the mechanical properties of the human lung.

The mechanical functions of the lungs are concerned with ventilating the alveoli and aiding venous return to the heart. The mechanical properties of the lung allow this to be fulfilled with a very small expenditure of energy. Smoking via chronic obstructive pulmonary disease (COPD) can affect this mechanical function through the alteration of the mechanical properties of the lung tissue. So far, no study has been conducted to experimentally compare the in vitro mechanical properties of the human lung tissue among the healthy nonsmokers and unhealthy smokers. Therefore, there is a paucity of knowledge on how the macro-mechanical properties of the lung tissue as a consequence of at least 7years of smoking can alter. This study was, hence, aimed at performing a comparative study to compare the linear elastic and nonlinear hyperelastic mechanical properties of the healthy nonsmokers and unhealthy smokers' lung using uniaxial tensile testing under two different loading directions, i.e., the axial and transversal. To do that, the COppm (Carbon Monoxide part per million) and %COHb (blood Carboxyhemoglobin) of 18cadaveric individuals, including 9nonsmokers and 9smokers were measured. The COppm and %COHb were found to be 26 ± 1.58 (Mean ± SD) and 4 ± 1.16 for the smokers and 4.79 ± 0.25 and 1.27 ± 0.16 for the nonsmokers, respectively. The lung tissues were excised from the cadavers and mounted on the uniaxial tensile test machine under the loading rate of 5mm/min. The stress-strain data of the tissues revealed the axial elastic modulus of 58 ± 4.21 and 142 ± 8.84kPa for the nonsmokers and smokers' lungs, respectively. Similarly, the transversal elastic modulus of 53 ± 7.16 and 127 ± 11.15kPa were found for the nonsmokers and smokers' lungs, respectively. The results revealed a significant difference between the axial and transversal mechanical properties of the nonsmokers and smokers' lung tissues (p< 0.05, post hoc Scheffe method). The hyperelastic material coefficients of the lung tissues were also calculated and reported. These findings have implications not only for understanding the role of smoking on the mechanical properties of the lung tissue but also to give rise to novel therapeutic strategies for the management of the disease and prevention of smoking addiction.

Rupture limit evaluation of human cerebral aneurysms wall: Experimental study

Background and purposeRupture risk of intracranial aneurysms is a major issue for public healthcare. A way to obtain an individual rupture risk assessment is a main objective of many research teams in the world. For many years, we have investigated the relationship between the mechanical properties of aneurysm wall tissues and the rupture risk. In this work, we try to go further and investigate rupture limit values. MethodsFollowing surgical clipping, a specific conservation protocol was applied to aneurysmal tissues in order to preserve their mechanical properties. Thirty-nine intracranial aneurysms (27 females, 12 males) were tested using a uniaxial tensile test machine under physiological conditions, temperature, and saline isotonic solution. These represented 24 unruptured and 15 ruptured aneurysms. Stress/strain curves were then obtained for each sample, and a fitting algorithm was applied following a Yeoh hyperelastic model with 2 parameters. Moreover, uniaxial tensile tests were conducted until rupture of samples to obtain values of stress and strain rupture limit. ResultsThe significant parameter a C2 of the hyperelastic Yeoh model, allowed us to classify samples’ rigidity following the terminology we adopted in previous papers (Costalat et al., 2011; Sanchez et al., 2013): Soft, Stiff and Intermediate. Moreover, strain/stress rupture limit values were gathered and analyzed thanks to the tissue rigidity, the status of the aneurysm (initially ruptured or unruptured) and the gender of the patient. ConclusionStrain rupture limit was found quite stable around 20% and seems not to be correlated with the status of the aneurysm (initially ruptured or unruptured), neither with the gender of the patient. However, stretch and stress rupture limit seems not to be independent on the rigidity.The study confirms that ruptured aneurysms mainly present a soft tissue and unruptured aneurysms present a stiff material.

Synthesis and Evaluation of Fracture Behaviour of Cu-Al-Be-Mn Quaternary Shape Memory Alloy

Cu-based quaternary SMA’s are less expensive, easy to prepare and exhibits excellent shape memory effect. In this paper, Cu-Al-Be-Mn quaternary alloys taken in the range of 11-14 wt% of Al, 0.2-0.4 wt % of Mn, 0.47 wt% of Be and rest is copper were synthesized through ingot melting method in the inert atmosphere and also conducted bend test to demonstrate the shape memory property after step quenching process at room temperature. Beryllium kept constant and manganese concentration in the alloy was varied to evaluate the fracture toughness of each alloy specimens by taking stress intensity factor (KIC) into account. In the current study modified single edge cracked plate tension specimen was prepared by using wire EDM. Fracture toughness of shape memory alloys is determined by testing the alloy specimens on uniaxial tensile testing machine, which are initially tested under low fatigue tensile loading to create a pre crack and then subjected to a uniaxial tensile loading until fracture. After fracture maximum load was noted down and stress intensity factor (KIC) can be evaluated for all the alloy samples. The fractured surface of the specimens was studied under scanning electron microscope (SEM) and examined the effect of composition and notch configuration on the fracture behaviour of SMA. An experimental result shows that the alloys exhibits good fracture toughness with KIC values up to 41 MPa m ^ 0.5 and stress intensity factor (KIC) increases with the increase in wt % of manganese

Studying the Effect of Different Environmental Conditions on the Tensile Strength of RGO Reinforced Adhesively Bonded Butt Joints

Nanoscale reinforcements are increasingly being used to improve mechanical, electrical and thermal behavior of polymers. In this study, the effects of reduced graphene oxide (RGO) epoxy filler on the tensile strength of adhesively bonded butt joints were investigated in a variety of environments. Firstly, dry butt joints with different RGO contents were tested using a uni-axial tensile test machine and it was observed that the joints reinforced with 0.5 wt.% RGO showed 22% higher strength than the joints without RGO reinforcements. Secondly, the effects of moisture, salt environment, and dry heat condition were investigated on the strength of the butt joints with different RGO contents. Results show that RGO particles significantly improve the strength values of the joints exposed to moist and dry heat conditions, but have less effect in salt environments.

Effect of Annealing Process on Microstructure and Mechanical Property of 1100 MPa Grade TRIP Steel

To develop super-high strength TRIP steel for automobile application with good combination of strength and plasticity, an ultra-high-strength TRIP steel 0. 2%C-2. 0% Si-1. 8% Mn was investigated at different intercritical annealing temperatures and bainitic isothermal temperatures. Microstructures were observed by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and X-ray diffraction, and mechanical properties were tested under a uniaxial tensile testing machine. It shows that the best comprehensive mechanical properties were obtained for the experimental steel particularly annealed at 820 °C and austempered at 410 °C. Yield strength of the tested steel mainly depends on ferrite, while the high strength of the tested steel is related to martensite which forms through blocky austenite transformation during cooling and subsequent tensile test attributed to the TRIP effect. Hence, it could be concluded that the grain size of the retained austenite and carbon content in retained austenite are the main reasons for high elongation of the tested steel.

A tensile machine with a novel optical load cell for soft biological tissues application

The uniaxial tensile testing machine is the most common device used to measure the mechanical properties of industrial and biological materials. The need for a low-cost uniaxial tension testing device for small research centers has always been the subject of research. To address this need, a novel uniaxial tensile testing machine was designed and fabricated to measure the mechanical properties of soft biological tissues. The device is equipped with a new low-cost load cell which works based on the linear displacement/force relationship of beams. The deflection of the beam load cell is measured optically by a digital microscope with an accuracy of 1 µm. The stiffness of the designed load cell was experimentally and theoretically determined at 100 N mm−1. The stiffness of the load cell can be easily adjusted according to the tissue’s strength. The force-time behaviour of soft tissue specimens was obtained by an in-house image processing program. To demonstrate the efficiency of the fabricated device, the mechanical properties of amnion tissue was measured and compared with available data. The obtained results indicate a strong agreement with that of previous studies.