Durability Tester Research Articles

Comparison of measured values from single pellet durability tester and standard tumbler tester

Comparison of measured values from single pellet durability tester and standard tumbler tester

Bioactive surface coating for preventing mechanical heart valve thrombosis

BackgroundProsthetic heart valves are the only treatment for most patients with severe valvular heart disease. Mechanical valves, made of metallic components, are the most long-lasting type of replacement valves. However, they are prone to thrombosis and require permanent anticoagulation and monitoring, which leads to higher risk of bleeding and impacts the patient’s quality of life. ObjectivesTo develop a bioactive coating for mechanical valves with the aim to prevent thrombosis and improve patient outcomes. MethodsWe used a catechol-based approach to produce a drug-releasing multilayer coating adherent to mechanical valves. The hemodynamic performance of coated Open Pivot valves was verified in a heart model tester, and coating durability in the long term was assessed in a durability tester producing accelerated cardiac cycles. Coating antithrombotic activity was evaluated in vitro with human plasma or whole blood under static and flow conditions and in vivo after surgical valve implantation in a pig’s thoracic aorta. ResultsWe developed an antithrombotic coating consisting of ticagrelor- and minocycline-releasing cross-linked nanogels covalently linked to polyethylene glycol. We demonstrated the hydrodynamic performance, durability, and hemocompatibility of coated valves. The coating did not increase the contact phase activation of coagulation, and it prevented plasma protein adsorption, platelet adhesion, and thrombus formation. Implantation of coated valves in nonanticoagulated pigs for 1 month efficiently reduced valve thrombosis compared with noncoated valves. ConclusionOur coating efficiently inhibited mechanical valve thrombosis, which might solve the issues of anticoagulant use in patients and the number of revision surgeries due to valve thrombosis despite anticoagulation.

Effect of Co/P micro-alloying on stress relaxation behaviour of Cu-15Ni-8Sn alloy

To improve the stress relaxation resistance of the Cu-5Ni-S8n alloy, the effects of Co or P addition on its stress relaxation resistance were investigated by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction), X-ray diffraction, and high-temperature creep durability tester. The results revealed that the relaxation rate increased dramatically as the temperature rose. The thermal stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition; After 100 h of stress relaxation tests at 200°C or 250°C, the residual stress value of the Cu-15Ni-8Sn alloy increased by 23 MPa or 22 MPa with Co addition, which was associated with the consumption of vacancies by Co atoms and the pinning effect of Co atoms on dislocation. However, at 250°C, the stress relaxation resistance of the Cu-15Ni-8Sn-0.2P alloy was lower than that of the Cu-15Ni-8Sn alloy. This difference was due to the inclusion of P, which promoted the recrystallization reaction. Article highlights Recrystallization and the decrease of dislocation density are the major reasons for the stress relaxation of the samples. The stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition. The addition of the P element is not conducive to the improvement of thermal stress relaxation resistance.

Potential of Dimensional Measurements of Individual Pellets for Evaluating Feed Pellet Quality

HighlightsPellet length but not width increased significantly with increasing inclusion of a pellet binder in a pelleted feedMachine vision capably and rapidly measures pellet lengthThe narrow range in pellet length measurements prevents its use as an effective discriminator of pellet qualityPellet durability index from aggressive pellet durability testing is the better discriminator of feed pellet qualityAbstract. Pellet durability index (PDI) detailed in ASAE Standard S269.4 (ASAE Standards, 2007) has been the widely accepted measure for pellet quality in the U.S. and, by extension, the measure for evaluating the effect of ingredients and pelleting process variables on the quality of pelleted feed products. The PDI is calculated as the mass percentage of intact pellets remaining after tumbling a 500 g sample in a tumbling can durability tester for 10 min. In the case where pellet quality is good, oftentimes the resulting PDI for different experimental treatments are very close in magnitude. In these situations, it is desirable to have another measurement that would allow for finer discrimination among treatments. It was hypothesized that the average linear dimensions of animal feed pellets in a unit mass sample would vary as a function of formulation and pelleting process variables for a consistent knife setting in the pellet mill. This hypothesis was tested in a study involving effectiveness testing of varying inclusion levels of a potential pellet binder in a typical corn-soy swine diet pelleted by both conventional and cold pelleting processes. Pellet lengths and diameters measured by a machine vision implemented in ImageJ matched to measurements taken manually and varied with treatments. Pellet length varied with treatments but could not be a good discriminator of pellet durability between pelleted products because of the narrow range in measurement numbers (8.53 to 11.15 mm by machine vision). With the wider range in numerical values of the PDIs obtained through aggressive durability testing (23.0% to 81.0% in a tumble can with steel hexagonal screw nuts versus 91.0% to 97.5% in a tumble can without hexagonal nuts), PDI from aggressive testing is the better discriminator of quality among pelleted products because of its greater resolution. Keywords: Animal feed, Durability, Linear dimensions, Machine vision, Pellet, Pellet binder, Pelleting, Quality.

TAVI-Mimic for testing of heart valve leaflet materials in physiological loading situations

Abstract The loading situation of the aortic valve is complex, complicating the identification of innovative approaches for heart valve leaflet materials, e.g. for transcatheter aortic valve implantation (TAVI). Materials engineering experiments allow for screening of materials but especially for durability testing, the consideration of physiological loads is vital/critical for the suitability-assessment of innovative leaflet materials. For this reason, a framework structure for the testing of leaflet materials in physiological loading (TAVI-Mimic) was developed. The exemplary use case for the TAVI-Mimic was a test for calcification propensity of pericardium during durability testing. The TAVI-Mimic was designed as a fourparted frame, based on previous work of our group. The leaflet material can be attached between inner and outer shells without sewing. In a second step, the TAVI-Mimic was optimized regarding radial load-deformation in comparison to a commercial TAVI by means of finite element analysis (FEA) and hydrodynamic characterization in a pulse duplicator system. Mechanical properties dependent on water uptake of different materials for 3D-printing of the TAVI-Mimic were investigated. After optimization, TAVI-Mimics were equipped with glutaraldehyde-fixated pericardial tissue and prototypes were calcified by using a heart valve durability tester and a metastable calcification-liquid, developed in earlier studies. The development of the TAVI-Mimic using FEA and experiments was successful, leading to a radial load dependent deformation of 0.6 mm which correlates with commercial TAVI. Two methacrylic photopolymers were identified for 3D-printing of the TAVI-Mimic and prototypes attached with pericardial tissue were manufactured. Pericardium TAVI-Mimics were calcified in vitro for one week and an average calciumphosphate precipitate of 0.34- 0.54 mg/cm² was measured. The optimization of the TAVR-Mimic led to an improved load-dependent behaviour compared to a commercial prosthesis while testing. The calcification method, combining the TAVI-Mimic, the metastable calcification solution and the durability tester enabled a successfully calcification of pericardial tissue, approaching the in vivo situation.

Preview the Products on Display at Display Week 2021

Preview the Products on Display at Display Week 2021

In Vitro Calcification of Bioprosthetic Heart Valves: Investigation of Test Fluids

Calcification is a major reason for the failure of bioprosthetic heart valves. Therefore, several attempts towards an accelerated in vitro model were undertaken in order to provide a cost- and time-saving method for the analysis of calcification processes. Due to the problem of superficial or spontaneous precipitation, which occurred in the fluids applied, we focused our study on the development of a near-physiological calcification fluid. The desired fluid should not precipitate spontaneously and should neither promote nor inhibit calcification. Eleven different fluid compositions were tested without contact to potentially calcifying materials. Crucial factors regarding the fluid properties were the ionic product, the ionic strength, and the degree of supersaturation concerning dicalciumphosphate-dihydrate, octacalciumphosphate, and hydroxyapatite. The fluids were kept in polyethylene bottles and exposed to a slight vibration within a durability tester at 37°C. The precipitation propensity was monitored optically and colorimetrically. A structural analysis of the deposits was carried out by x-ray powder diffraction and IR-spectroscopy, which showed the development of the crystal phases that are relevant in vivo. Only two of the fluids did not precipitate. Resulting from the computations of the effective fluid contents, the saturation degree concerning dicalciumphosphate-dihydrate seems to be the key factor for spontaneous precipitation.

Development of an accelerated durability tester for a transcatheter aortic valve using calcified aortic valve model

Development of an accelerated durability tester for a transcatheter aortic valve using calcified aortic valve model

Development of an accelerated durability tester for a transcatheter aortic valve

Development of an accelerated durability tester for a transcatheter aortic valve

Comparative Study on Wear Characteristics between Flow Mode and Shear Mode Magnetorheological Dampers

ABSTRACTThis comparative study experimentally examines the wear characteristics of magnetorheological (MR) dampers operated in flow mode and shear mode. First, electromagnetic coil structures are designed for two different MR dampers to maximize the field-dependent damping force. Two MR dampers are also designed to have the same volume of MR fluid for reasonable comparison. After identifying the field-dependent damping force at the initial state, the two dampers are operated up to 60,000 cycles using a reciprocating-type wear durability tester. The field-dependent damping forces are then evaluated before and after operation. The wear properties of the MR fluid are investigated using scanning electron microscope (SEM) images that show the changes in the MR fluid particles' size and shape. The surface roughness of the MR damper's piston areas are also measured. In addition, the effects of the permeability of the piston sleeve materials on the wear properties are investigated by selecting three different sleeve materials that have different permeability values: 0.2% carbon steel (S20C), 0.45% carbon steel (S45C), and tool die casting steel (STD-11). The surface roughness of each case is tested and the atomic spectrum is investigated after long operation using energy-dispersive X-ray spectroscopy (EDS) inside the piston. The experimental results obtained from this work indicate that the motion of the operating mode significantly affects the wear characteristics of the MR fluid itself as well as the magnetic effective areas of the MR dampers.

Investigation of the Durability of a Diaphragm for a Total Artificial Heart.

One of the most critical components regarding the durability of the ReinHeart total artificial heart (TAH) is its biocompatible diaphragm, which separates the drive unit from the ventricles. Hence, a durability tester was designed to investigate its required 5-year lifetime. The aim of this study was to prove the validity of accelerated testing of the polyurethane diaphragm. The durability tester allows simultaneous testing of 12 diaphragms and mimics physiological conditions. To accelerate the time of testing, it operates with an increased speed at a frequency of 8 Hz. To prove the correctness of this acceleration, a servo-hydraulic testing machine was used to study the effect of different frequencies and their corresponding loads. Thereby the viscoelastic behavior of the polyurethane was investigated. Additionally, high-speed video measurements were performed. The force against frequency and the high-speed video measurements showed constant behavior. In the range of 1-10 Hz, the maximum resulting forces varied by 3%, and the diaphragm movement was identical. Frequencies below 10 Hz allow a valid statement of the diaphragm's mechanical durability. Viscoelasticity of the polyurethane in the considered frequency-range is negligible. The accelerated durability test is applicable to polyurethane diaphragms, and the results are applicable to TAH use. The reliability of the diaphragm for a lifetime of 5 years was found to be 80% with a confidence of 62%.

Abstract 17991: Angulation Range of Coronary Artery During the Cardiac Cycles is a Key Factor Inducing Stent Fracture; Demonstration by an in vitro Accelerated Durability Test

Introduction: Stent fracture (SF) is recognized as one of the unsolved issues inducing restenosis or thrombosis. Hinge motion has been identified as a predictor of SF. The aim of this study is to elucidate SF probability of current drug eluting stents (DESs) against angulation ranges during the cardiac cycles, utilizing an in vitro accelerated durability tester. Methods: A cyclic-bend accelerated durability tester we have developed was used. Stents were deployed in elastic bend-artery replicas those mechanical stiffness was adjusted to that of referenced human coronary artery (stiffness parameter β=30±2). Three-link L605 CoCr stent (Xience Prime, Abbott Vascular), 2-link MP35N CoCr stent (Resolute Integrity, Medtronic), and 2-link PtCr stent (Promus Element, Boston Scientific) were chosen as test subjects. Influences of magnitude of angulation ranges on incidences of SF were investigated under the following bend conditions from 130 to 100 degrees (angular difference during the cycle (AD): 30 degrees), from 130 to 90 degrees (AD: 40 degrees), and from 130 to 80 degrees (AD: 50 degrees), respectively. Under each bend condition, three samples for each stent were tested for 1.0х10 8 cycles at 20Hz, those duration is equivalent to 2.5 years in vivo. Results: Under the AD of 30 degrees, multiple and single strut fracture were observed for each one of three L605 CoCr and MP35N CoCr stents, whereas no fracture was observed for PtCr stents. Under the severer ADs of 40 degrees and 50 degrees, all the three L605 CoCr and MP35N CoCr stents were multiply fractured, whereas PtCr stents had one single-strut-fracture and two multiple-strut-fractures among each three stents under the above conditions. These data indicated that PtCr stent platform has higher resistance to SF among wide ranges of cyclic-bend angulations. The total numbers of stent strut fractures of L605 CoCr, MP35N CoCr, and PtCr stents were 3, 1, 0 in the AD of 30 degrees, 20, 8, 1 in the AD of 40 degrees, and 18, 13, 4 in the AD of 50 degrees. Links were frequent sites of SF for CoCr stents, whereas crowns were those for PtCr stents. Conclusions: This study elucidated differences in fracture resistance against cyclic angulation ranges during the cardiac cycles and the critical angulation ramges for current three DESs.

해석과 실험을 이용한 고장력 강판으로 된 자동차 시트 프레임의 구조적 연구

시트 프레임의 연구 개발이 활발하게 진행됨에 따라 본 연구에서는 고장력강판으로 제작된 시트 프레임의 전변형량을 실험과 해석을 통하여 고찰하였다. SPFC 980 t=2mm 고장력강판으로 된 시트 프레임을 반복피로 내구 시험기를 이용하여 전변형량 실험을 한 후, 동일한 조건으로 시뮬레이션하여 전변형량을 해석하였다. 실험과 해석 결과 값을 비교 분석한 후 그 값을 토대로 SPFC 780 t=2mm와 SPFC 780 t=1.5mm으로 된 시트 프레임 모델들의 구조적 안전성을 유한 요소 해석으로서 조사하였고 본 연구 결과를 통하여 어떤 모델이 상용화하는데 더 적합한지를 알 수 있었다. As research development of seat frame is being studied actively, the total deformation of seat frame made of high tension steel plate(HTSP) is examined in this study. The seat frame made of SPFC 980 t=2mm with HTSP is tested to obtain total deformation through repeated fatigue durability tester and total deformation is analyzed by simulation under the same condition as experiment. After analyzing by comparing the results of experiment and analysis, structural stabilities of seat frame models with SPFC 780 t=2mm and SPFC 780 t=1.5mm are investigated by FEM analysis on the basis of these results. And it is considered that which model is more suitable at commercial use can be found through this study result.

2D32 屈曲負荷型加速耐久試験装置による屈曲角度変化量が冠動脈ステントの破損耐久性に及ぼす影響の検討(OS9-5:臨床バイオメカニクスと医療デバイス(5))

2D32 屈曲負荷型加速耐久試験装置による屈曲角度変化量が冠動脈ステントの破損耐久性に及ぼす影響の検討(OS9-5:臨床バイオメカニクスと医療デバイス(5))

고장력 강판으로 된 자동차 시트 리크라이너 하우징에 대한 구조 해석

자동차 시트 리크라이너는 시트 등받이의 각도를 조절하는 기능을 가지며, 시트의 안전성과 밀접한 영향이 있다. 따라서 리크라이너를 구성하는 각 부품들은 매우 중요하며, 이러한 부품들을 각종 동적 하중들로부터 보호할 수 있는 리크라이너 하우징 역시 중요하다고 할 수 있다. 본 연구에서는 고장력강판(SPFC 980)으로 제작된 t=3mm 리크라이너 하우징을 실제 차량 시트에 적용한다. 또한 내구 실험기를 통하여 변형량을 조사하였으며, 실험과 동일한 조건하에서 시뮬레이션 해석을 수행하여 변형량과 등가응력을 분석하였다. 실험값과 해석값을 토대로 하여 1mm 및 2mm 두께의 리크라이너들을 모델링 한 후 구조해석을 통하여 변형량 및 등가응력을 알아보았다. Automotive seat recliner has the function to control the angle at the back of chair and has the relation close to the safety of seat. Therefore each of parts constituting the recliner is important and the recliner housing to protect these parts from various dynamic loads is also important. In this study, the recliner housing with t=3mm which is made of high tension steel plate(SPFC 980) is applied to actual automotive seat. The deformation is investigated through the durability tester. Deformation and equivalent stress are also analyzed by simulation analysis under the same condition with experiment. After recliners with thicknesses of 1mm and 2mm are modeled by bases of experimental and analysis values, deformation and equivalent stress are investigated through structural analysis.

Failure behavior of rubber O-ring under cyclic exposure to high-pressure hydrogen gas

This paper presents the effects of hydrogen pressure, ambient temperature and pressure cycle pattern on fracture behavior of O-rings moulded from a peroxide-crosslinked EPDM rubber with white reinforcing filler under cyclic exposure to high-pressure hydrogen gas. By using a developed durability tester which enables the O-rings to expose cyclically high-pressure hydrogen gas, pressure cycle tests were performed at hydrogen pressures ranging from 10 to 70MPa and ambient temperatures ranging from 30 to 100°C under two pressure cycle patterns (test frequencies). The cyclic hydrogen exposure caused cracks in the O-rings, and their crack damage became more serious with an increase in the hydrogen pressure and the ambient temperature. The serious crack damage under high temperature is believed to be due to degradation of mechanical properties with increasing ambient temperature. At a hydrogen pressure of 10MPa, cracks (blisters) caused by bubbles formed from supersaturated hydrogen molecules after decompression were observed. At a hydrogen pressure of 35MPa or more, a large volume increase of the O-rings was observed by swelling; then, its volume increase induced extrusion fracture of the O-rings in addition to blister fracture. The crack damage also became more serious with a decrease in test frequency. The effect of the test frequency on the crack damage of the O-rings is presumed to be attributed to time-dependent crack growth behavior of the EPDM rubber.

Accelerated in vitro durability testing of nonvascular Nitinol stents based on the electrical potential sensing method

In this paper, we report an evaluation of the performance of a new stent durability tester based on the electrical potential sensing method through accelerated in vitro testing of six different nonvascular Nitinol stents simulating physiological conditions. The stents were subjected to a pulsatile loading of 33 Hz for a total of 62,726,400 cycles, at constant temperature and pressure of 35±0.5 °C and 120±4 mmHg, respectively. The electrical potential of each stent was measured in real-time and monitored for any changes in readings. After conducting test-to-fracture tests, the stents were visually checked, and by scanning electron microscopy. A sudden electrical potential drop in the readings suggests a fracture has occurred, and the only two instances of fracture in our present results were correctly determined by our present device, with the fractures confirmed visually after the test. The excellent performance of our new method shows good potential for a highly reliable and applicable in vitro durability testing for different kinds and sizes of metallic stents.

8F44 右冠動脈屈曲モデルを用いた加速耐久試験装置による新生内膜がSUS316L製ステントの破損耐久性に及ぼす影響の検討(GS02 循環系のバイオメカニクス(モデリング,シミュレーション)2)

8F44 右冠動脈屈曲モデルを用いた加速耐久試験装置による新生内膜がSUS316L製ステントの破損耐久性に及ぼす影響の検討(GS02 循環系のバイオメカニクス(モデリング,シミュレーション)2)

Research and Implementation of Monitoring System for Injection Pump Durability Tester

Taking the background of the durability test for high-pressure common rail injection pump which is made in the Bosch firm, we have designed the monitoring system of injection pump durability tester based on fieldbus control system (FCS) [1,2]. Firstly, the paper total analyses the injection pump durability test. Then it mainly introduces the hardware of the monitoring system and puts forward configuration of the test. Finally we completed the software of the monitoring system based on the platform of Lab Windows/CVI. It improves the working efficiency greatly of the tester.

Evaluation on High-Pressure Hydrogen Decompression Failure of Rubber O-ring Using Design of Experiments

The rubber O-rings used in high-pressure hydrogen environment sometimes suffer from the decrease in durability due to decompression failure. A high-pressure durability tester, which enables rubber O-rings to expose repeatedly high-pressure hydrogen gas at arbitrary test conditions, was employed, and then sensitive factors for the durability of the O-rings were evaluated by using a L18 orthogonal array. Of lower-limit pressure, upper-limit pressure, material, temperature, O-ring filling ratio, holding time at lower limit, holding time at upper limit, and decompression time, it was clarified that the material, temperature, O-ring filling ratio, and decompression time were sensitive factors.