Mechanical Test Platform Research Articles

Iron nanowire/carbon microsphere composite flexible fabric strain sensor for human motion monitoring

People pay more and more attention to sports and health, especially the goal of sports recovery and scientific sports is more and more clear. In order to avoid human injury caused by unreasonable sports, it is necessary to carry out real-time detection of human motion state. In this paper, the motion state of human body was taken as the test object, a flexible strain sensitive material combining iron nanowires and carbon microspheres was proposed, and polyester fabric was introduced as the sensor substrate to construct a sandwich structure flexible fabric strain sensor. Then a mechanical test platform was built to carry out mechanical property testing and practical application verification research. The mechanical test results show that the iron nanowires/carbon microspheres flexible fabric strain sensor has good linearity, the response time is 42 ms, and the hysteresis error is approximately 8.7 %. Finally, the flexible fabric strain sensor is fixed on the part of the human body that needs to be detected, and the electrical signal curve of the response is output by the electrochemical workstation. Through the analysis of the response curve, it can be seen that the iron nanowires/carbon microspheres flexible fabric strain sensor prepared in this paper has great potential in human movement health monitoring.

Apple mechanical damage mechanism and harvesting test platform design

Abstract Apple is easily damaged in the process of the mechanical harvesting, which reduces the fruit’s quality. It is of great significance to study the damage principle of apple in the transport process of picking platform. In this study, the apple compression test was carried out. The compression and drop process of the fruit was analyzed by the finite element analysis (FEA). The experimental platform of apple harvesting was designed, the conveying process of apple was analyzed. The results of compression finite element analysis showed that when the compression force is greater than 15.0 N, both radial compression and axial compression will be damaged. The results of drop finite element analysis showed that when the drop direction is axial, the maximum contact stress of the peel and kernel decreases with the increase of drop angle, the maximum contact stress of the pulp increases first and then decreases. When the drop direction is radial, the maximum contact stress between pulp and kernel decreases with the increase of drop angle, the maximum contact stress of the peel first decreases and then increases. The simulation results of the harvesting platform transportation showed that the damage rate of apples is less than 10 % when the sub-conveyor belt speed is 0.02 m–0.04 m/s. This study can provide theoretical guidance for the design of the harvesting test platform and the reduction of the damage of apples during transportation.

Mechanical performance evaluation and structural optimization of ceramic lined thin-walled vacuum chambers

Thin-walled vacuum chamber internally supported by ceramic spacers is a promising approach to provide sufficiently robust, ultra-high vacuum compatible and low gap vacuum devices for high energy, high current, heavy ions accelerators. The mechanical performance of the ring shaped ceramic spacers is a key factor in the structural design of these vacuum chambers. An extensive campaign was devoted to develop methodologies and equipment for evaluating the mechanical and structural properties of the ceramic spacers and to optimize the chamber design. To this aim, a force analysis on single ceramic rings was first conducted, and formulas for calculating the elastic modulus and bending strength of the ceramic rings were derived. The elastic modulus and critical position strength limits of alumina and zirconia ceramic rings were tested using a mechanical testing platform. Based on the test results of a single ceramic ring, a preliminary design and processing of ceramic lined thin-walled vacuum chamber test samples was finalized. A testing device capable to apply known water pressure values was then designed and built to test the chamber ability to withstand externally applied forces and measure the mechanical parameters of the ceramic spacers. Thanks to this, the acceptable stress limits of alumina and zirconia ceramic rings as the supporting components of the vacuum chamber were obtained. Knowing these values, through an iteration process, the whole design and properties of the ceramic lined thin-wall vacuum chamber was optimized. Finally, to reduce the impact of eddy current heat effect on ceramic strength and outgassing, a suitable cooling structure was designed and implemented.

Developing the Optimal Osteotome Hand-Sharpening Method.

Background: Rhinoplasty osteotomes can be sharpened in various ways: professional sharpening or hand sharpening using whetstones or rotary powered devices. Objective: To compare the effectiveness of sharpening osteotomes using various sharpening methods with that of professional sharpening as measured by a custom edge tester. Materials and Methods: We performed repeated serial osteotome impacts on bovine femoral cortical bone. These dull osteotomes were sharpened using preidentified sharpening techniques. Edge morphology was evaluated. Sharpness was tested using a custom mechanical testing platform. Optimized sharpness was achieved with a whetstone sharpening method wherein the osteotome is flipped after every stroke. Results: Seven distinct sharpening methods were tested for sharpness five times each to determine the optimal sharpening method versus professional sharpening (control). The two sharpening methods, 5 (5.51 ± 0.32) and 6 (5.55 ± 0.32), that used this flipping technique were significantly sharper than other methods. Methods 5 (p = 1.0) and 6 (p = 1.0) were the only methods that were not significantly different from control. Conclusion: Single stroke with successively alternating surfaces created the sharpest blades that achieved results similar to professional sharpening.

Analytical modeling and calculation of mechanical characteristics for few-piece main-auxiliary parabolic leaf spring with root diagonal segment

For the shortcomings of the analytical calculation method and the design of few-piece main-auxiliary parabolic leaf springs, based on the theory of material mechanics, through analyzing the actual structural characteristics of the few-piece main-auxiliary parabolic leaf spring with root diagonal segment, an analytical calculation model of the deformation and stress for the few piece main-auxiliary parabolic leaf spring with root diagonal segment was established. The reliability of the analytical calculation model was verified by using the leaf spring mechanical characteristics test platform. The results show that the maximum deviation between the analytical calculation values of the deformation and stress obtained by the calculation model and the test value is only 4.76% and 6.06%, respectively, which can effectively characterize the mechanical characteristics of the actual few-piece main-auxiliary parabolic leaf spring. The research can quickly and accurately realize the stiffness check, strength check, and forward design of the few-piece main-auxiliary parabolic leaf spring with root diagonal segment, which provides an effective theoretical basis and technical reference for the parabolic leaf spring design.

Experimental Study on the Optimization of Polymer-Modified Cement-Based Composite Sealing Materials and Mechanical Properties and Permeability of Cemented Coal Bodies

As a critical technical issue, gas extraction borehole sealing significantly restricts the effects of gas extraction. Polymer-modified cement-based composite (PMCC) sealing materials were developed to improve the sealing effect of gas extraction drilling. In this study, a self-built mechanical property and permeability test platform for grouting-based cemented coal bodies was used to test the viscosity, gelation time, and mechanical properties of PMCC sealing materials and the permeability of cemented coal bodies. Through the obtained relevant results, it was demonstrated that the material viscosity of PMCC sealing materials and the permeability and compressive strength of cemented bodies are under the influence of additive ratios. Moreover, the viscosity of sealing materials was found to be linearly related to the gelation time. In particular, the higher the viscosity, the shorter the gelation time. Additionally, on one hand, it was found that the viscosity of such sealing materials is positively correlated to the compressive strength of cemented coal bodies. On the other hand, it forms a negative correlation with their permeability. Based on relevant analysis outcomes, it was deemed that the sufficient hydration reaction and the interspace reticulate microstructure formed by the polymer of PMCC sealing materials allow the cemented coal body to achieve high compressive strength and low permeability.

Cluster-based acoustic emission signal processing and loading rate effects study of nanoindentation on thin film stack structures

This paper presents a high-resolution, in-situ material testing system that integrates acoustic emission (AE) testing with a nanoindentation system for crack generation and detection in thin film stack structures. This is used to find the critical contact load during wafer probing of crack-sensitive backend-of-line (BEOL) structures in semiconductor integrated circuits. Scanning electron microscopy (SEM) and load–displacement curve analysis were used to confirm the formation and propagation of cracks in the multilayer structures. In order to improve the manual classification performance and understand the physical meaning of AE signals, this paper introduces a machine learning based signal processing approach based on a k-means clustering algorithm applied on collected AE signals. To obtain the optimal number of k-means clusters, Davies–Bouldin, Dunn, and Silhouette indices were calculated, and the individual ratings were cumulated based on a voting scheme. Multiple feature extraction methods, including raw time-domain AE signals, conventional AE extracted parameters, short-term signal energy, and representation features learned by the autoencoder, were used and evaluated by manually labeled clusters and binary confusion matrices. A supervised learning technique, the k-nearest neighbors algorithm, was also utilized on different AE signal datasets using different loading rates to further investigate the damage processes during nanoindentation and the physical meaning of different AE signals. The influences of loading rates on AE signals have been investigated, and loading rate effects on the critical load were observed – higher loading rates led to higher critical loads. This integrated test system and signal processing approach provides a high-resolution mechanical testing platform for studying and enabling automatic crack detection in wafer probing.

Meso/macro-scale ultra-soft materials' mechanical property evaluation device and testbed.

Ultra-soft materials find applications in biomedical devices, sensors and actuators, robotics, and wearable electronics. The mechanical properties of soft materials are often determined using nanoindentation and atomic force microscope techniques, which provide localized properties at a small-scale length. There is a need to evaluate the meso/macro-scale properties of ultra-soft materials to develop integrated devices made of the same. Metallic probes in the existing macroscale equipment cannot be used as they can pierce through the soft materials and fail to capture the associated adhesion forces, resulting in inaccurate values. This study has developed a meso/macro-scale mechanical testing platform to characterize ultra-soft materials accurately. This probe can be adapted to any mechanical testing load frame with a small load cell to capture the adhesion forces during the approach and detachment segments of soft materials' indentation. The integrated camera with the probe enables overcoming the challenge of surface detection and capturing the pull-on and pull-off events. Indentation tests on soft materials with varying stiffness (e.g., high-fat yogurt, chicken breast, aloe Vera, toothpaste, gelatin, and a chocolate bar) were conducted using a 10mm stiff flat-end polymer probe. A variation of the Johnson-Kendall-Roberts technique was adopted to account for adhesion forces and compute stiffness. Our results suggest that the novel device and methodology can measure mechanical stiffness in the extensive range of 0.5kPa to a few MPa with high reproducibility at the macro-scale length. The validation was carried out using a commercially available nanoindenter for soft materials.

High throughput mechanical testing platform and application in metal additive manufacturing and process optimization

Agility of additive manufacturing (AM) warrants a development of an equally agile, high-throughput properties evaluation technique that can efficiently assess properties of AM specimens as functions of materials and process variables. High throughput (HTP) tensile testing rig has been developed, enabled by miniature sample design and Python based control codes for a full automation of testing and data processing. The rig is capable of testing 60 specimens per hour, much faster than conventional tensile testing. To luminate the merit of its use, an efficient process optimization workflow based on HTP testing is proposed and demonstrated on laser powder bed fusion (LPBF) built stainless steel 316 L. A total of 40 miniature specimens were built with various LPBF parameters (i.e., power and scanning speed) by design of experiment (DoE) incorporating 2 factors, 3 levels, and 4 repeats. Ultimate tensile strength (UTS) and elongation at fracture (EL) were used to study sensitivity of processing parameters. An analytical model was employed to optimize the LPBF parameters to maximize UTS or EL or both. In addition, the as-printed microstructure and post-testing fracture surfaces were examined by optical and scanning electron microscopy. Rapid assessment of properties enabled to efficiently optimize the AM processing parameters, and to establish a more robust processing-structure-property relationship, which would ensure and promotereliable application of AM components.

A novel apparatus to measure the biomechanical properties of blood vessels

PurposeThe study of vascular mechanics is important. The purpose of this paper is to present an apparatus to measure the biomechanical properties of blood vessels, which can be used for tensile test and fatigue test.Design/methodology/approachThis equipment consists of a mechanical test platform, a hardware circuit based on FPGA and control software. The torque generated by stepper motor is converted to axial force by ball screw, and the vascular specimen is stretched axially. The tension is measured by a load cell, and the displacement is recorded by a grating displacement sensor.FindingsAccording to the results of calibration experiment and stability experiment, the linearity error of the system is 0.251, the hysteresis error is 0.047, the repeatability error is 0.185, the comprehensive error is 0.315 and the standard deviation of the output is less than 0.01 N. A test of animal vascular mechanical properties was carried out, and the results are consistent with the theory.Originality/valueThis apparatus is designed to measure biomechanical properties of blood vessels, and the results of experiments indicate that it is stable and reliable. This work is valuable for studying vascular disease and testing artificial blood vessels.

Quality attributes and evaluation of pharmaceutical glass containers for parenterals.

Pharmaceutical containers for parenterals have been predominantly manufactured using glass as a packaging material of choice, especially Type-I glass, since it has been regarded as a chemically inert and an effective container closure system (CCS). Nevertheless, there have been reports and recalls related to glass quality issues, such as breakage, flakes, and particles observed in marketed products. The novelty of this research is based on the knowledge gathered from our previously conducted risk assessments and establishing a comprehensive testing platform focused on risk factors for glass container failure modes and applicability to other types of pharmaceutical containers. The evaluation of container quality attributes was performed for three model glass vials using a mechanical and chemical durability testing platform: freeze-thaw, lyophilization, compression, scratch tests; visual inspection, pH, particle size analyses, extractable, leachable and imaging studies that were conducted under normal (4 and 25 °C), and stress condition (60 °C), respectively. The performance between the glass containers tested under certain stress conditions (failure modes) were variable and differentiated. The systematic platform testing approach shows the importance of lab-based risk evaluation in assessing common failure modes of pharmaceutical containers, since the quality attributes for injectable products are complex and can impact final product quality.

On the Planarization Mechanism and Pad Aging Effects of Soft Pad Polishing: A Perspective From the Micro-Mechanical Properties of Soft Pads

The local viscoelastic properties of soft polishing pads with different usage durations are measured by a micro-scale mechanical analysis testing platform. The testing reveals stimulus-adaptive local viscoelasticity of soft pads under the activation of asperity contact. This phenomenon suggests asperity-dependent local modulus. Such an increase of local modulus induced by higher asperity provides a further enhancement effect to the planarization of surface asperity. Furthermore, the measurement outcomes suggest that the reaction of local micro-scale viscoelastic properties of the soft pad surface to the workpiece asperity will decay with usage time. The current study provides a detailed understanding of the aging effects for the soft pad and explains the performance decay during soft pad polishing from a local micro-scale interfacial perspective.

Wind tunnel testing and improved blade element momentum method for umbrella-type rotor of horizontal axis wind turbine

The umbrella-type rotor concept for horizontal axis wind turbine is proposed. The rotor allows blades to fold along the hinge which is fixed at the hub. The blade pitching and rotor coning are coupled as the hinge is inclined. This rotor is designed as a new approach to realize power control in high wind speed. The model-scale umbrella-type rotor with three blades was made and a rotor mechanical power testing platform was set up. Wind tunnel testing was conducted to supply data to estimate the rotor power performance. In the field of wind turbine aerodynamics theory, the blade element momentum model was improved for the umbrella-type rotor aerodynamics calculation. Comparison between wind tunnel testing data and simulation result has been made. Experiment result showed that umbrella-type rotor was effective in adjusting power output by folding blades. The highest power coefficient was 0.259 in current study. Nevertheless it dropped down to 0.06 when the blades were folded at 20°. In wind speed from 5 m/s to 9.54 m/s, a constant power output of 8.87 W was achieved. The calculated rotor power coefficient was found to be in good agreement with the experiment data. The highest average deviation was 11.81%.

The design and analysis of the mechanical property test platform frame for marine structures

In order to realize mechanical properties test of the emergency towing arrangements, anchor chain and other large marine components, a large-tonnage and multi-function horizontal tension test platform is put forward in this paper. The paper analyzes the disadvantages of the frame structure of the existing experimental platform and designs the composite structure of the concrete and steel. The steel has good elasticity and toughness, the concrete has good performance of high rigidity and compression resistance, so the composite structure takes the advantages of both. The sharp of the frame is like “L”, which can be used to testing different projects. The paper gives the detailed size and analysis procedure of the frame. And it finds a more reasonable structure by means of finite element to analyze and optimize. The frame structure has the advantages of low weight and cost. The platform has been installed in Zhoushan, China successfully.

Evaluation of Nitinol Stents Using a 3-Dimensional Printed Superficial Femoral Artery Model: A Preliminary Study

Mechanical tests assessing Nitinol stents used for the superficial femoral artery (SFA) are designed without taking into account their deployment environments. The objectives of this study were (1) to create normal and pathologic femoral artery models, (2) to run mechanical tests reproducing the stresses of the SFA, and (3) to study and compare Nitinol stents in those conditions. Femoral artery models with identical mechanical properties to the SFA were created using the 3-dimensional printing technology. Those models were designed with and without an asymmetric focal 50% stenosis. Three mechanical tests (bending-compression, bending-compression-torsion, and multiple bending tests) were created and 1 flexible stent was tested, of 6 and 7-mm diameter. Three samples of the stent, LifeStent (Bard(®)), were deployed and tested in the models. Stents alone were evaluated in the same conditions. The analysis focused on the comparison of rheologic curves, level of kink, and the energy deployed for each stent to kink. In the 3 tests, all stents deployed in the models presented a kink during their evaluation. When tested alone, during the compression-bending and bending-compression-torsion tests, no plicature was observed. During the multiple bending test, the energy deployed to plicature for the stent tested alone was of 1.4±0.10 and 2.84±0.1J compared with 9.7±0.6 and 8.25±0.6J when deployed in the model for the Lifestent 6×80 and 7×80mm, respectively. For all of these 3 tests, 6-mm diameter stents exhibited a level of kink and energy of kink higher than 7mm stents. The behavior of the stents changed in the stenosed model whatever diameter is taken into account. Analysis of the rheologic curves showed a decrease in the inflection of the curve related to the plication. In the bending-compression test, the presence of a stenosis lead to an early plication of the model, with less deployed kinking energy whereas in the bending, compression, and torsion test, this earliness was absent. This study permitted the creation of a mechanical test platform evaluating Nitinol stents in bending situations. It tends to confirm the mechanical deleterious effect of excessive oversizing. This study confirms the necessity to evaluate Nitinol stents in their deployment environments.

A high-throughput model of post-traumatic osteoarthritis using engineered cartilage tissue analogs

A number of in vitro models of post-traumatic osteoarthritis (PTOA) have been developed to study the effect of mechanical overload on the processes that regulate cartilage degeneration. While such frameworks are critical for the identification therapeutic targets, existing technologies are limited in their throughput capacity. Here, we validate a test platform for high-throughput mechanical injury incorporating engineered cartilage. We utilized a high-throughput mechanical testing platform to apply injurious compression to engineered cartilage and determined their strain and strain rate dependent responses to injury. Next, we validated this response by applying the same injury conditions to cartilage explants. Finally, we conducted a pilot screen of putative PTOA therapeutic compounds. Engineered cartilage response to injury was strain dependent, with a 2-fold increase in glycosaminoglycan (GAG) loss at 75% compared to 50% strain. Extensive cell death was observed adjacent to fissures, with membrane rupture corroborated by marked increases in lactate dehydrogenase (LDH) release. Testing of established PTOA therapeutics showed that pan-caspase inhibitor [Z-VAD-FMK (ZVF)] was effective at reducing cell death, while the amphiphilic polymer [Poloxamer 188 (P188)] and the free-radical scavenger [N-Acetyl-L-cysteine (NAC)] reduced GAG loss as compared to injury alone. The injury response in this engineered cartilage model replicated key features of the response of cartilage explants, validating this system for application of physiologically relevant injurious compression. This study establishes a novel tool for the discovery of mechanisms governing cartilage injury, as well as a screening platform for the identification of new molecules for the treatment of PTOA.

Sequential multimodal microscopic imaging and biaxial mechanical testing of living multicomponent tissue constructs.

Understanding relationships between mechanical stimuli and cellular responses require measurements of evolving tissue structure and mechanical properties. We developed a 3D tissue bioreactor that couples to both the stage of a custom multimodal microscopy system and a biaxial mechanical testing platform. Time dependent changes in microstructure and mechanical properties of fibroblast seeded cruciform fibrin gels were investigated while cultured under either anchored (1.0:1.0 stretch ratio) or strip biaxial (1.0:1.1) conditions. A multimodal nonlinear optical microscopy-optical coherence microscopy (NLOM-OCM) system was used to delineate noninvasively the relative spatial distributions of original fibrin, deposited collagen, and fibroblasts during month long culture. Serial in-culture mechanical testing was also performed to track the evolution of bulk mechanical properties under sterile conditions. Over the month long time course, seeded cells and deposited collagen were randomly distributed in equibiaxially anchored constructs, but exhibited preferential alignment parallel to the direction of the 10% stretch in constructs cultured under strip biaxial stretch. Surprisingly, both anchored and strip biaxial stretched constructs exhibited isotropic mechanical properties (including progressively increasing stiffness) despite developing a very different collagen microstructural organization. In summary, our biaxial bioreactor system integrating both NLOM-OCM and mechanical testing provided complementary information on microstructural organization and mechanical properties and, thus, may enable greater fundamental understanding of relationships between engineered soft tissue mechanics and mechanobiology.

Study on Mechanical Automation with Design of Mechanism Transmission System for Automobile Transmission Test Platform

In this paper, the mechanical automation system of automobile transmission test platform were designed, it has been used to test the performance of the transmission after the automobile transmission is assembled. The working condition of the analogue automobile is achieved by the mechanical automation test platform.

Study on Mechanical Automation with Design of Electric Control System of Automobile Transmission Assembly Test Platform

The input and output axis equipment is designed in the mechanical automation test platform. The input axis pull (positive pull) completes the noise test of the transmission at different gears. The output axis pull (reverse pull) test the shifting at different gears. The rotate speed adjustment of the input electromotor is done by transducer, and the rotate speed and torque design of the output electromotor is completed by the servo system. The mechanical automation electric control system of automobile transmission assembly test platform was designed. The working condition of the analogue automobile is achieved by means of the electric control systems control over the input electromotor and the output electromotors repeated power switch.

A Novel Device to Quantify the Mechanical Properties of Electrospun Nanofibers

Mechanical deformation of cell-seeded electrospun matrices plays an important role in cell signaling. However, electrospun biomaterials have inherently complex geometries due to the random deposition of fibers during the electrospinning process. This confounds attempts at quantifying strains exerted on adherent cells during electrospun matrix deformation. We have developed a novel mechanical test platform that allows deposition and tensile testing of electrospun fibers in a highly parallel arrangement to simplify mechanical analysis of the fibers alone and with adherent cells. The device is capable of optically recording fiber strain in a cell culture environment. Here we report on the mechanical and viscoelastic properties of highly parallel electrospun poly(ε-caprolactone) fibers. Force-strain data derived from this device will drive the development of cellular mechanotransduction studies as well as the customization of electrospun matrices for specific engineered tissue applications.