Conventional Testing Machine Research Articles

A mcgyvering way to left bundle branch area pacing : using the treadmill test machine ECG system and modified V1 / V6 leads connected to the pacing system analyser for left bundle branch area pacing

Abstract Background Left bundle branch area pacing (LBBaP) is a novel pacing modality which provides physiological synchronisation of both the ventricles. However, its use and adoption requires the presence of a standardised electrophysiological (EP) system with 12 lead ECG to show left bundle branch area capture. Purpose The aim of the study was to assess the feasibility and outcomes of using the conventional treadmill test (TMT) machine 12 lead ECG system and modified V1 and V6 leads connected to the pacing system analyser (PSA) to demonstrate conduction system capture during left bundle branch area pacing (LBBaP). Methods LBBaP was attempted by a single operator in a mixed cohort of patients at peripheral hospitals lacking the standardised EP system. The presence of LBB area capture was tested with the aid of the 12 lead ECG system connected to the standard TMT machine (1). Conduction system capture was also assessed using modified V1 and V6 leads connected to the PSA for measurement of V6 left ventricular activation time (LVAT)(2) . The baseline clinical, procedural, pacing, electrocardiographic parameters, echocardiographic response (> 10% improvement in ejection fraction {EF}) and clinical response to LBBaP were assessed. Results LBBaP was attempted in 19 patients and was successful in 18 patients (94.7%). Patient characteristics include age 66.7 +/- 11.47 years, female 47.37%, male 52.63%, ischaemic cardiomyopathy 10.52% and non-ischaemic cardiomyopathy 5.26% .The mean baseline EF and QRS duration was 45%+/-14% and 130.18 +/-10.45 milliseconds(ms) respectively. LBBaP threshold was 0.59 +/-0.168 volts and R wave amplitude was 12+/-3.5 millimetres , which remained stable during the mean follow up of 15.9 +/-13.67 months. The mean fluoroscopic duration was 11.57 +/-2.58 minutes and procedural time was 108.78+/-29.20 minutes. LBBaP resulted in impressive narrowing of the QRS duration to 102.39 +/-10.55 ms (p<0.001) with LVAT of 68.94 +/-9.94 ms. LVEF improved in the patients with cardiomyopathy from 33.4 +/- 5.77 % to 48.2+/-12.37 % (p=0.028) .Clinical and echocardiographic response was noted in 87.5% of patients with cardiomyopathy. Conclusion The 12 lead ECG system with the standardised TMT machine in conjunction with the modified V1 and V6 leads connected to the PSA is a feasible alternative to the EP system to perform successful left bundle branch area pacing.ECG leads connected during LBBapClinical profile of patients

Design of novel test rig for prosthetic finger distal interphalangeal and phalanx strengths.

Testing is one of the most significant phases of any engineering process, the last process followed by conceptualization, designing, and fabricating. If the testing outcomes are not genealogy sensible measurables, then eventually it calls for a redesign overhaul. Existing testing equipment to analyze the load and failures are conventional digital universal testing machines with minimum jigs and fixtures. In addition, the existing fixtures cannot be adapted to the anatomy of a human finger. Consequently, the present work explores the best possible design of a jig for testing the naturally articulated movement of a human finger (prosthetic wear-on). Furthermore, the present jig design checks a wide range of parameters such as freedom of motion, a path along with curvature, load, failures, and intermittent positions of applied load, which is adaptable to existing universal testing machines available for broader applications.

Application of small punch test to estimate mechanical behaviour of SUS304 austenitic stainless steel

The small punch test with an application of a relatively small specimen has recently become a reliable material mechanics testing method. In this study, the small punch test is set up based on the conventional mechanical testing machine for SUS304 stainless steel to evaluate the mechanical properties of SUS304 steel at different displacement rates of the punch in quasi-static loading condition in the case of with and without heat treatment. Although heat treatment has an insignificant effect on the microstructure and hardness of the material, the mechanical properties of the material in the small punch test are greatly reduced after heat treatment. Both cases with and without heat treatment have a similar tendency for the rate - sensitivity of the applied force - displacement curve. A higher value of force is applied to obtain the same value of displacement at a low displacement rate in the stable plastic deformation zone. Meanwhile, the maximum value of applied force is higher at a higher displacement rate in the stage that initiation of crack might appear. In the examined range of displacement rate, a positive rate - sensitivity of displacement at the maximum force. Therefore, a correlation between equivalent fracture strain and fracture toughness of the material can be achieved.

Introducing a novel sheet test specimen for biaxial stretching under uniaxial loading

This paper introduces a novel sheet test specimen that plastically deforms under biaxial stretching when subjected to uniaxial loading in conventional testing machines. The specimen was designed using finite element simulation and consists of a two-dimensional reticular structure with interconnected arms in the form of triangles that converge at the center and are connected to full-width sheets at the specimen's ends. Accumulation of damage at the center is ensured through spherical cups that are milled at opposite sheet surfaces. Experimental strain loading paths obtained by digital image correlation confirm the capability of the novel sheet test specimen to provide biaxial stretching strain paths. This is achieved under friction-independent conditions and without requiring complicated multiaxial setups and machines, provided appropriate values of the inner and outer angles of the interconnected arms are used.

Study of effect of loading rate on mechanical properties of SS316LN and evaluation of parameters of Johnson-Cook model using parametric FE analysis and experimental data

The objective of this work is to evaluate the parameters of strain rate dependent Johnson-Cook material model using a hybrid procedure which uses finite element analysis as well as experimental data. The large strain rate tests were conducted to using split Hopkinson pressure bar test setup, whereas the quasi-static test was carried out using conventional testing machines. Johnson-Cook material model has been used to simulate the plastic deformation behavior of material under the high strain loading. This model provides the flow stress of the material as a function of equivalent plastic strain, plastic strain rate and temperature. The parameters, i.e., A, B, n, C and m of the model have been determined using a hybrid procedure as mentioned earlier. One of the important issues in split Hopkinson pressure bar testing is the variation of strain rate during the duration of loading. Due to decrease in reflected strain magnitude, the strain rate continuously decreases (as strain rate is proportional to reflected strain signal) and it is a characteristic of the above test method. However, this creates problem in evaluation of parameters of Johnson-Cook material model using conventional procedure. In this work, a modified procedure has been developed in order to take into account of this variation in strain rate as function of applied strain. The results of the method has been validated with experimental data. The parameters have been evaluated only for room temperature data and the effect of temperature shall be studied in future.

Determination of material properties from tissue samples of low strength and size

Abstract Uniaxial tensile tests are the most common method for investigating the mechanical properties of materials. However, due to the small strength and size of certain materials, larger conventional universal testing machines are sometimes not suitable for performing elongation testing, so dedicated test setups are required. Therefore, the authors developed a testing device to measure the mechanical properties of small, flexible materials, e.g. fragile specimens of the capsular bag of the eye. Also different variants for specimen holders were designed and tested. Initial tests using eggshell membranes as a model material demonstrated the functionality of the test setup at different strain rates.

Design and Evaluation of Virtual Compression Testing Machine Based on Multilayer Perceptron for Vocational-Education Virtual Laboratory

The weaknesses of Conventional Compression Testing Machines (CCTM) for student practicum are the high costs of procurement, maintenance, electricity, concrete materials, and human/equipment error factors. This research proposed of Virtual Compression Testing Machine (VCTM) based on Multilayer Perceptron that uses 2 hidden layers, 60 neurons with bagging, and other parameters of a Deep Neural Network with RMSE value of 4.738. The application of VCTM has been successfully carried out and there was no significant difference with CCTM. VCTM can be used for various types of concrete with high testing intensity. Lecturers and researchers can use VCTM to conduct research.

Mixed mode (I/III) fracture studies using a new specimen setup

In the present work, mixed mode (I/III) fracture studies have been investigated using a new specimen and an out-of-plane loading fixture that can be used with the conventional uniaxial universal testing machines. The proposed specimen is a single edge cracked circular (SECC) specimen which can be employed on both metallic and non-metallic materials under static and fatigue loads. A large number of three-dimensional finite element analyses have been performed on the proposed specimen setup to demonstrate the efficacy of the proposed setup. Experimental fracture studies have also been performed under mixed mode (I/III) loading conditions. The present experimental results are in very good agreement with the available mixed mode (I/III) fracture criteria. Experimental results indicate that the pure mode III fracture toughness is nearly 1.46 times greater than that of the mode I. This has been found due to an increase in the inelastic region around the crack tip in pure mode III and is in accordance with the published results. Detailed analyses of the fractured surfaces have also been carried out. It has been demonstrated that the fractured surfaces become more rough as the mode III component increases. Preliminary results of mixed mode (I/III) fatigue crack growth studies on Al 7075-T6 using the metallic SECC specimen have also been presented. The results of the present study confirm that the proposed specimen setup can be used to study the mixed mode fracture behavior of linear elastic materials under static and fatigue loading.

Estimating the residual resource of basic structures using a model of fatigue durability under complex loading

This paper reports the construction of a durability model of basic structures, which takes into consideration the complex stressed state under the cyclic action of the complex load. The models that take into consideration this factor are categorized on the basis of equivalent for a certain indicator of the stressed-strained state. The equivalence models based on the tangent stresses and strains have been recognized as the most effective ones. However, they hold when the ratio of the limits of fatigue under tangent and normal stresses exceeds 0.5. In addition, determining the latter requires specific testing equipment. The concept of basic bearing structures for industrial equipment has been formulated. The issue related to the multi-axis fatigue of basic structures was considered from the standpoint of combining the reliability indicators of systems. The durability model has been derived from the rule of combining resource safety indices. The load is represented as a combination of individual subprocesses of simple types of deformation with their amplitudes and asymmetries. A model of durability with multi-axis fatigue has been built, which takes into consideration the parameters of the form of the strain cycle, and the type of process (synphase, disproportionate, unchanging static stress). The possibility of obtaining parameters for the multi-axis fatigue model during tests for three-point bending under conditions of varying the multiplicity of the span has been confirmed. According to this scheme, fatigue tests of prismatic samples of the steels 09G2 and 40X were carried out. For them, the parameters of fatigue resistance were found; additionally, the ratio of the fatigue limit for tangent stresses of displacement and fatigue limits for normal bending stresses, which is equal to 0.385, was established. A test procedure has been devised to determine the initial data for the multi-axle fatigue model, which is suitable for conventional test machines and simple-shape samples. The latter advantage is important precisely for basic structures, from fragments of which it is difficult to fabricate a sample of a complex shape

An Alternative Way of Measuring Tensile Characteristics of Handsheets

In this work, the laboratory-made handsheets having different grammages were obtained at certain production conditions. The tensile characteristics of the laboratory-made handsheets were analysed by using two measuring techniques. The main method for determining tensile behaviour was performed on the universal testing machine, which is a generally accepted conventional testing machine. A rheometer device was used as a second and alternative method for measuring the tensile properties of handsheets. The given data were investigated and compared with the data of conventional tensile tester. Linear least square regression was applied to analyse the association of the data from the Instron 5564 Universal Testing Machine and Hybrid Rheometer Discovery HR-2 Machine with examined tensile characteristics depending on the various grammage range. The experiments on the handsheets having different grammage groups showed that the methods give results in reasonable agreement. These results showed that there are acceptable differences in the tensile index and elastic modulus values of the samples as a function of their basis grammages.

Development and implementation of a simultaneous fatigue crack growth test setup for polymeric hybrid laminates

Delamination is a common and highly relevant in-service failure mode of laminated structures. Cyclic mechanical loads superimposed with environmental factors, such as hot-humid air, are most critical. To evaluate the cyclic debonding resistance of polymeric hybrid laminates, fracture mechanics approaches based on double cantilever beam (DCB) specimens are well established. However, conventional fatigue test setups allow for measurement of just one specimen which is rather time consuming. The main objective of this paper was to develop and implement a novel fatigue test setup for simultaneous characterization of multiple DCB specimens. To validate the simultaneous fatigue testing system, steel/epoxy laminates of different number of steel plies and epoxy adhesive layers with or without filler were characterized using the novel fatigue test setup and a conventional electrodynamic test machine. Fatigue crack growth data was fitted by a form of the Hartman-Schijve crack growth equation. To derive a statistically significant threshold value a fitting procedure was employed. A good agreement of the crack growth kinetics data at ambient conditions was obtained confirming the high quality and reliability of the novel simultaneous fatigue test setup. Moreover, reliable data were gathered at the beginning of the displacement–controlled experiments in the instable crack propagation regime, as the displacement amplitude was reached from the first cycle onward. The novel test methodology is of special relevance for development and screening of adhesive formulations.

Determination of local constitutive behavior of AA6061–T6 friction stir welds using digital image correlation

The local constitutive behavior of aluminum alloy 6061–T6 friction stir welds was characterized by uniaxial tensile tests using digital image correlation. The global tensile stress–strain relations for friction stir weld specimens were determined using a conventional testing machine equipped with an extensometer. The digital image correlation method was simultaneously applied to measure the full-field strain distributions over a 30 mm gauge length of the friction stir weld specimens during loading. The global specimen strains over the gauge length were determined by superimposing local strains measured by digital image correlation using the “inverse rule of mixtures” for composites. The Hollomon and Ludwik constitutive models were used to describe the local flow curves for the weld zones. The global true stress–true strain curves obtained from uniaxial tensile tests were compared with those constructed by superimposing local strains measured using digital image correlation. Both the global mechanical responses were in good agreement with each other. It is shown that the global true stress–true strain curves can be constructed using the inverse rule of mixtures method from the local constitutive equations for the different weld zones determined by the uniaxial tensile tests using digital image correlation.

Material characterization of GFRP by ultrasonics

In general, material selection for an application depends on its mechanical properties such as the young’s modulus, shear modulus and bulk modulus. There is no material science without material characterization. The conventional mechanical testing involves breaking of the test piece while determining the mechanical properties, thus rendering the sample piece useless after testing. Moreover, conventional testing machines are bulky and costly. Non–destructive testing techniques were most commonly used for the detection and characterization of flaws. But in the past few decades many researchers are conducting experiments to even calculate material properties using NDT methods. In the present work an attempt has been made to use a NDT technique, namely Ultrasonic testing, to determine the mechanical properties of three Glass fiber reinforced polymer (GFRP) plates (Unidirectional, Bidirectional & cross directional).

Post-peak Stress–Strain curves of brittle hard rocks under axial-strain-controlled loading

A super stiff rock mechanics testing machine called Stiffman is introduced in this paper. This test facility uses composite loading frames and relay loading by two loading hydraulic actuators and overcomes the technical difficulties of conventional rock mechanics testing machines such as insufficient loading system stiffness, inability to use axial-strain-controlled loading in the post-peak deformation stage, limited straining amount to reach the residual deformation stage. To validate the reliability of the newly developed test machine, a benchmark study was carried out first. Then, systematic uniaxial and triaxial compression tests under axial-strain-controlled loading for three brittle hard rocks were conducted and the results are compared with those obtained using a conventional rock mechanics testing system called Rockman. The test results of Rockman show that under uniaxial compression and triaxial compression under axial-strain-controlled loading at low confining pressures, the rock specimens failed violently in the post-peak deformation stage and it was not possible to obtain complete stress–strain curves of the rocks. On the other hand, it was possible to load the rocks under axial-strain-controlled loading in a stable fashion using Stiffman and complete stress–strain curves of the rocks under uniaxial compression and triaxial compression at low confining pressures could be obtained. Stiffman-tested rock specimens showed signs of spalling but stayed mostly in one piece. Finally, peak and residual strength envelopes of the three brittle rocks are given based on the test results of Stiffman. The experiment results show that Stiffman can be used to capture complete post-peak stress–strain curves of brittle rocks reliably under axial-strain-controlled loading. It provides a new platform for studying post-peak deformation behaviors of brittle hard rocks reliably in a loading control mode that other conventional test machines cannot provide.

Effect of organic matrix alteration on strain rate dependent mechanical behaviour of cortical bone

The organic matrix phase of bone plays important role in its mechanical performance, especially in the post-yield regime. Also, the organic phase influences loading rate-dependent behaviour of bone which is relevant during the high-speed loading events. Many diseases, as well as aging, affect the matrix phase of bone which causes compromised mechanical properties. Improved understanding of alterations in the organic matrix phase on mechanical response of bone will be helpful in the mitigation of fractures associated with inferior matrix quality. In the present work, effect of alteration in organic matrix of cortical bone on its strain-rate dependent behaviour was investigated. To produce different amounts of collagen denaturation, bovine cortical bones were heated at the temperature of 180 °C and 240 °C. Further, compression testing was performed at quasi-static strain rates of 10−4 s−1 to 10−2 s−1 using a conventional testing machine whereas a modified Split Hopkinson Pressure Bar (SHPB) was used for high strain rate (∼103) testing. Thermal treatment-induced changes in the mineral and organic phases of bone were assessed using X-ray diffraction (XRD) and Fourier-transform infrared-attenuated total reflection (FTIR-ATR) techniques respectively. Compression test results show that thermal treatment of bone up to 180 °C did not affect mechanical properties significantly whereas treating at 240 °C significantly reduced elastic modulus, failure stress and failure strain. Also, thermal denaturation of collagen reduced the strain rate sensitivity of cortical bone at high strain rates. Similar to the compression test observations, nanoindentation results show a significant reduction in elastic modulus and hardness of denatured samples. Further, FTIR results revealed that with the heat treatment of bone, collagen structure undergoes conformational changes at the molecular level. The initial helix structure breakdowns into unordered/random coil structures which subsequently reduced the mechanical competence of bone. The present study provides insight into the effect of organic matrix modification on mechanical behaviour of cortical bone which could be helpful in understanding bone disorders associated with organic matrix phase and development of therapeutic interventions.

Mechanical properties of thermal aged HTPB composite solid propellant under confining pressure

With the purpose of investigating the effects of confining pressure and aging on the mechanical properties of Hydroxyl-terminated polybutadiene (HTPB) based composite solid propellant, tensile tests of thermal accelerated aged propellant samples under room temperature and different confining pressure conditions were performed through the use of a self-made confining pressure device and conventional testing machine. Afterwards, the maximum tensile stress σm and the corresponding strain εm for the propellant under different test conditions were obtained and analyzed. The results indicate that confining pressure and aging can significantly affect the mechanical properties of HTPB propellant, and the coupled effects are very complex. On the one hand, the stress σm increases as a whole when confining pressure becomes higher or thermal aging time rises. Besides, this stress is more sensitive to aging with increasing confining pressure. There are almost three regions in the stress increments σmP−σm0/σm0 and thermal aging time curves for HTPB propellant. The maximum value of the stress increment σmP−σm0/σm0 for the propellant is about 98% at 7.0 MPa and 170 d. On the other hand, the strain εm decreases with increasing thermal aging time under the whole confining pressure conditions. However, the variation of this strain with confining pressure is more complex at various thermal aging time, which is different from that of unaged solid propellant in previous researches. In addition, this strain is slightly less sensitive to aging as the confining pressure increases. Furthermore, there is also a critical confining pressure in this investigation, whose value is between 0.15 MPa and 4.0 MPa. Beyond this critical pressure, the trends of the stress σm and the corresponding strain εm all change. Moreover, there are some critical thermal aging time for the stress increment (σmP−σm0)/σm0 and strain increment (εmP−εm0)/εm0 of HTPB propellant in this investigation, which are about at 35, 50 and 170 d. Finally, based on the twin-shear strength theory, a new modified nonlinear strength criterion of thermal aged HTPB propellant under confining pressure was proposed. And the whole errors of fitted results are lower than 6%. Therefore, the proposed strength criterion can be selected as a failure criterion for the analysis the failure properties of aged HTPB propellant under different confining pressures, the structural integrity of solid propellant grain and the safety of solid rocket motor during ignition operation after long periods of storage.

A Novel Oscillation-Free Force Measurement for the Determination of Material Properties during High-Speed Tests

Abstract The determination of material properties under high-speed loading has been a challenge for many years. Structural vibrations, or system ringing, in a conventional tensile testing machine deteriorate the quality of the force measurement, which prevents the precise determination of stress-strain curves and the corresponding mechanical properties. In this work, a new sample geometry and a corresponding measurement method are presented and analyzed. This new method allowed for the determination of oscillation-free, true stress-strain curves at high strain rates. Because a new minor plastic deformation area exists in the new Generation III sample, a quasi-movable bearing condition for the sample fixation is created. The forces acting on the sample deformed the cross section and created a displacement in this minor plastic deformation area. In this way, the elastic ringing effect was reduced significantly. This new method could also be applied to the quasi-static test and strain rates ranging from 10−4 to 103/s. Moreover, the filtering or similar manipulation of the results is no longer needed. The validity of the new method was proven by testing two steels with different strain-hardening behaviors.

Effects of stress path on brittle failure of sandstone: Difference in crack growth between tri-axial compression and extension conditions

The tri-axial testing of rocks under compression is a widely popular measure for the assessment of strength of geological materials in the laboratory. In this regard, mechanical complexities of true tri-axial testing machines impel researchers to opt for simpler conventional tri-axial testing machines. To account for influential factors that affect quality of experimental data, observations derived from laboratory experiments that enable overcoming some drawbacks are presented herein. In the present study, a series of tri-axial tests on Kimachi sandstone under Conventional Tri-axial Compression (CTC), Conventional Tri-axial Extension (CTE), Reduced Tri-axial Compression (RTC), and Reduced Tri-axial Extension (RTE) conditions were carried out. The results suggested higher compressive strengths for the rock under tri-axial extension tests than the compression tests. This observation proves that the effect of intermediate confining pressure on material behavior is important and if feasible, should not be sacrificed for more economical alternatives. Generally, the loading and unloading experiments for a specific test type rendered the same results and the conventional and reduced paths in both the compression and extension tests did not affect the failure strength of the specimens. The effect of pre-existing cracks orientation with respect to the principal loading directions on crack growth was focused upon and related conclusions were subsequently drawn.

A Novel Method for High Temperature Fatigue Testing of Nickel Superalloy Turbine Blades with Additional NDT Diagnostics.

In this paper, a novel method for high temperature fatigue strength assessment of nickel superalloy turbine blades after operation at different times (303 and 473 h) was presented. The studies included destructive testing (fatigue testing at temperature 950 °C under cyclic bending load), non-destructive testing (Fluorescent Penetrant Inspection and Eddy Current method), and finite element modelling. High temperature fatigue tests were performed within load range from 5200 to 6600 N using a special self-designed blade grip attached to the conventional testing machine. The experimental results were compared with the finite element model generated from the ANSYS software. It was found that failure of turbine blades occurred in the area with the highest stress concertation, which was accurately predicted by the finite element (FE) model.

The effect of strain rate on compressive behavior and failure mechanism of CMDB propellant

The compressive mechanical behavior of composite modified double base (CMDB) propellant was investigated across a wide scope of strain rates ranging from 10−3 s−1 to 4210 s−1 at room temperature, by applying a conventional universal testing machine and a split Hopkinson tension bar (SHPB), respectively. The derived stress-strain curves at different strain rates show a strong rate dependence, indicated that yield stress, ultimate stress and strain energy density of CMDB propellant all increase with strain rate by following a power law function, while the amplification of increase are different. The deformation and damage modes of CMDB propellant has changed from a typical ductile manner (cracking along the axial direction) to a brittle manner (maximum shear failure) with increasing of strain rate. Scanning electron microscopy (SEM) was employed to explore the microscopic failure characteristics of CMDB propellant. Under quasi-static loading, the nearly parallel micro-cracks propagating along the axial direction and the debonding of RDX particle without particle crushing can be observed. While under dynamic loading, the micro-crack is 45° angle to the axial direction, and multiple cracking modes of RDX particles appeared. Finally, the correlation between strain energy density and failure mechanisms of CMDB propellant was revealed by developing four characteristic failure modes. The findings of this study is very important to evaluate the structural integrity of CMDB propellant.