Urethane Material Research Articles

Additively Manufactured Stress-strain Dependant Frequency Reconfigurable Antenna for Pressure Sensor Applications

A novel additive-manufactured antenna for stretchable sensor application is designed, simulated and measured. The fully transparent antenna has air as a substrate and a conductive aluminium metal sheet as a patch. The layers are defined with thin Thermo Poly Urethane (TPU) material, as its flexible/stretchable property doesn't disturb the actual property of air. The air substrate is locked within the flexible TPU with a thickness of 200 microns, and the conducting patch is also dimensioned with the 3D printing method. The stretchable antenna is fabricated with 3D printing technology, considered a dielectric medium, and the conducting medium is a conducting aluminium sheet. Re-configurability is achieved with the pressure level applied over the air–substrate antenna. Hence, the minimal change in shape changes the dielectric constant, thus changing the antenna parameter and radiation pattern. The antenna achieves improved size and performance with a gain of 7.2 dB, a directivity of 7.574 dB, a radiation efficiency of 95.67 %, and a 12:509 front-to-back ratio. The fabricated antenna is tested for its resonant characteristics and radiation properties. This reconfigurable antenna can be used for various applications, including Wireless Local Area Network (WLAN) communication.

Comparison of Constraint-Induced Movement Therapy Vs Traditional Rehabilitation Therapy to Improve Upper Limb Function in Hemiplegic Acute and Subacute Stroke Patients

Background: Stroke is a generic term in use to describe the sudden interruption of blood flow to the part of brain, resulting loss of brain function. A stroke may be also known as cerebrovascular accident. Cerebrovascular accident which defines as pathology in which brain disease occurs secondary to disorders of blood supply of brain. It is essential to know about the magnitude of impact of stroke globally. Aim: To determine effectiveness of constraint induced movement therapy and comparing its efficacy to traditional rehabilitation in acute and sub-acute stroke survivors exhibiting upper limb hemiplegia Methodology: This was a randomized clinical trial study, conducted in Lahore in which eighteen stroke patients had participated. Current study includes MAL and WMFT questionnaire in it and sample size was 18. Patients were treated 4 times a week and unaffected limb was constrained for two hours in therapy session and onwards to 10 hours to motivate the use of effected limb. Readings were taken weekly and patients were reassessed by using MAL and WMFT. CIMT treatment protocol consists of 3 or 4 month of daily intensive training of the affected extremity for 2 hours in association with restriction of the non-affected extremity for 10 hours a day. Group B: Traditional rehabilitation therapy used Sling (shoulder immobilizer) made of poly urethane material. Hair brush, cup, marbles, cards, blocks, tissue paper, cones, Swiss ball, dexterity board. Results: Statistical analysis was set at p ≤ 0.05. huge and direct to vast impacts existed on WMFT (P=0.010) noteworthy and direct to extensive impacts existed When p-value is not as much as the foreordained importance level which is frequently 0.05 or 0.01, showing that the watched results would be profoundly impossible under the alternate theory. In this way, the alternate hypothesis was supported. Subsequently null hypothesis is rejected and alternate hypothesis is accepted. Conclusion: This study concluded that the patients who were treated with CIMT showed remarkable change in upper extremity functions. While patients who were treated with traditional rehabilitation therapy they exhibited less change in their functional activities than Constraint-Induced Movement Therapy. Keywords: Comparison, traditional rehabilitation therapy, Constraint-Induced Movement Therapy (CIMT) Approaches

Investigation The Effect of Clearance and Body Weight on The Contact Pressure of Metal on PCU Hip Prosthesis using Finite Element Method

A common problem with artificial hip replacements is increased wear of the material in contact. Materials that are in contact result in contact pressure caused by the patient's daily activities so that it triggers wear. This study adopts a finite element method (FEM) to predict wear of the artificial hip joint, by studying the behavior of a hip joint prosthesis that has clearance under a certain load. The aim of this study was to observe contact as a function of clearance and body weight. The modeling uses metal as femoral head and polycarbonate urethane (PCU) material as the acetabular cup. Contact modeling as a hard material in contact with a deformable material. Four variations of clearance (0.001, 0.005, 0.01, 0.016) and three variations of body weight (500N, 700N, and 1000N) were used in this study. The simulation results show that the lower the distance and weight, the lower the contact pressure.

Longevity Expectations for Polymers in Medical Devices Demand New Approaches to Evaluating Their Biostability.

Ten years after a new poly(dimethylsiloxane)urethane material was introduced as part of a long-term medical device implant, an unexpectedly high rate of in-service degradation was observed. The chemical signatures of molecular degradation in the materials were not identified during the comparatively short preclinical assessment of biostability. This outcome highlights the need to transform the assessment of biostability for new materials used in long-term implanted medical devices to protocols that rely more heavily on accelerated in vitro testing. The industry has over-relied on in vivo exposure to assess the stability of a material due to the perceived complexities associated with the accurate simulation of the biological environment. Strategically designed accelerated in vitro testing can provide important insights into the long-term biostability of materials: insights that cannot be readily gleaned through the in vivo studies that dominate current regulatory guidelines. Real-time validation of previously published accelerated data combined with clinical observations substantiates the accelerated approach and creates a compelling case for shifting the emphases in biostability assessment, especially for devices that have anticipated lifespans that exceed a decade.

Reply to Giannakos, K. Comment on: Toughness of Railroad Concrete Crossties with Holes and Web Openings. Infrastructures 2017, 2, 3

This paper responds to the discussion [1] by Dr. K. Giannakos over our technical note [2].[...]

치과용 구강 스캐너와 모델 스캐너를 이용하여 제작된 보철물의 변연적합도

The purpose of this study was to compare the marginal fit of the dental prosthesis with the oral scanner and the model scanner. The model(3-unit bridges) used urethane material on the chamfer margin. The urethane model was scanned with a oral scanner and a model scanner, and then designed with CAD software. Each test piece was made of a subtractive manufacturing and an additive manufacturing process. The marginal fit was measured using a replica technique. We analyzed the marginal opening(MO), the marginal gap(MG) of the maximum curvature area, the axial gap(AG), and the occlusal gap(OG) with a CCD camera mounted on a microscope. And then, the distance was measured using an image analysis software. In order to analyze the changes of the scanning method and the manufacturing method, two-way ANOVA was performed. For data of each parameter, a one-way ANOVA was conducted.BR Overall, the average value of the marginal fit was less than 169μm, and the average value of MO and AG was 79 μm or less. There was no difference in the mean values of MO and AG in the prosthesis milled by subtractive manufacturing with oral scanner and model scanner. MG, OG showed better fit of the prosthesis made by the oral scanner than the prosthesis manufactured by the model scanner.

3D printing of tough hydrogel composites with spatially varying materials properties

Biofabrication is the process of transforming materials into systems that reproduce biological structure and function. Previous attempts to create biomimetic systems have often used single materials shaped into limited configurations that do not mimic the heterogeneous structure and properties of many biological tissues. The identification of new bio-inspired materials alongside the development of appropriate fabrication techniques is the key to overcoming the challenge of replicating the functional gradients of these heterogeneous tissues. This paper presents a new extrusion-based gradient printing system that utilizes custom software to control the rates at which two inks are dispensed through a mixing nozzle. The printer was used to fabricate a range of composite materials containing varying blends of a tough alginate/poly(acrylamide) ionic covalent entanglement hydrogel and an acrylated urethane based UV-curable adhesive material. The hard adhesive material acted as particulate reinforcement within the matrix of composites printed with a large hydrogel volume fraction. The composite materials were characterized mechanically and their performance could be modeled with standard composite theory. The platform of a 3D printer allowed these composite materials to be fabricated directly with a smooth and continuous gradient of modulus between the soft hydrogel and harder acrylated urethane material, which may be useful in the development of bio-inspired structures such as artificial tendons.

ウレタンエラストマーを用いた小型積層ゴムの設計

In previous study, the research and development of laminated type base isolation device using urethane elastomer was carried out to upgrade a seismic safety for various structures. The fundamental characteristics was investigated from several loading test by using various experimental devices, and the design formula for the stiffness and equivalent damping coefficient is formulated as an approximate expression of mechanical characteristics until now. The mechanical characteristics based on the loading test up to 500% shear strain using experimental specimen with 100 × 100 mm cross-sectional shape. It was confirmed that urethane elastomer is not hardening up to 500% shear strain. Moreover, the experimental examination for aged deterioration in the urethane material has been continuously carried out. As the results, it was confirmed that the laminated type seismic isolation device using urethane elastomer is possible to develop as a practicable device from the stable mechanical properties as considering in design step. In this study, the small-scale laminated type base isolation device using urethane elastomer is advanced to the direction of further technical upgrading and of scale down for light-weight structure as a sever rack. The first stage, basic properties of the urethane elastomer has been investigated by loading test. The second stage, the compression creep test with laminated type base isolation device has been investigated to confirm an effect on light-weight mechanical devices.

지대치 변연 형태에 따른 수작업과 CAD/CAM으로 제작한 coping 패턴의 적합도 비교

Abstract The purpose of this study is to compare the marginal and internal fit of metal and zirconia coping whichis fabricated by manual and CAD/CAM(Computer Aided Design/Computer Aided Manufacturing). The model is prepared with Urethane material and two abutment teeth are fabricated with a knife and chamfer margin. Silicon replica technique is used to measure the marginal fit of manually fabricated and the CAD/CAM coping. Internal fittinglevel is measured with a microscope and the image is captured with a CCD camera. The distance between abutmentteeth and coping is measured with a callibrated image analyzer software; marginal opening (MO), marginal gap (MG),internal gap (IG) at maximum curvature area, axial gap (AG), and occlusal gap (OG). Two-way ANOVA test is applied to compare fabrication technique and to analysis of abutment pattern. In addition, one-way ANOVA and Scheffe's test is used to analyze each parameter of the test. The result shows that the fit is <120 µm except OG ofCAD/CAM and MO of knife margin. The CAD/CAM fabricated coping showed higher fit level at chamfer margin. However, knife margin showed better fitness compared to chamfer margin at MG. AG showed the minimum dimension with a constant result (<38 µm).

Design and Development of Three-Bladed Propeller for Micro Air Vehicles

CSIR-National Aerospace Laboratories (CSIR-NAL) is having a major program on development of Micro Air Vehicles (MAV) for civil, surveillance, and defense use. Under this program, MAV components development has been undertaken in various divisions of NAL. Propulsion system for one of the configurations of NAL MAV having fixed wing is battery-driven miniature motor and mini propellers. Efficient propulsion system plays a major role in deciding the endurance, payload, and maneuverability of MAV’s. Design of efficient propellers for these classes of vehicles is a challenging task because of their lower operating Reynolds number as well as conservative power utilization to enhance the endurance. Earlier, 2-bladed, fixed pitch, variable speed, 6-inch diameter propellers with different plan form has been carried out and reported. The present requirement is for 3-bladed, fixed pitch, variable speed mini propellers to augment thrust within the geometrical constraints as envisaged in the design of two-bladed propellers. To meet the mission requirements, design of three-bladed, fixed pitch, variable speed mini propellers were carried out using minimum induced loss method, and Eppler-193 airfoil is used in the design in view of its higher lift to drag ratios at low Reynolds numbers. This resulted in slight penalty on weight as well as power consumption and reduced noise level. Propeller CAD model is generated using SOLID WORKS and used for analysis as well as for fabrication. Performance estimation for this propeller is carried out using blade element momentum theory and ANSYS FLUENT. Fabrication of this propeller is carried out using three methods namely rapid prototype (RPT) using poly carbonate and conventional vacuum casting using poly urethane material and CFRP material with conventional casting using aluminum mold. The overall performance parameters like thrust, propulsive efficiency and motor power are evaluated for CFRP propeller and tested at uninstalled condition. Overall performance of the propellers is evaluated at MAV Aerodynamics Research Tunnel (MART), CSIR-NAL for different wind velocities and propeller rotational speeds in uninstalled conditions. This paper brings out the work carried out on design, development and testing of three-bladed miniature propeller for MAVs and its analysis using computational tools at propulsion division, CSIR-NAL.

J1010405 ウレタンエラストマーを用いた実機型免震装置の性能評価([J101-4]耐震・免震・制震 免震(2))

Base isolation system will be aggressively applied to not only architectural and civil structures but also various structures, because the effectiveness on seismic safety had been demonstrated again in the Great East Japan Earthquake. In generally, although the base isolation system is divided into laminated rubber bearing type and friction sliding bearing type. In the case of former type, shape factor, maximum or minimum outer shape and so on are restricted by the material characteristics in visco-elastic material. In this study, the research and development of laminated type base isolation device using urethane elastomer has been carried out to upgrade a seismic safety for various structures. The fundamental characteristics have been investigated from several loading test by using various experimental devices, and the design formula for the stiffness and equivalent damping coefficient is formulated as an approximate expression of mechanical characteristics until now. Moreover, the experimental examination for aged deterioration in the urethane material has been continuously carried out. As the results, it was confirmed that the laminated type seismic isolation device using urethane elastomer is possible to develop as a practicable device from the stable mechanical properties as considering in design step.

450 減衰性ウレタンゲル材料を用いた振動低減要素に関する研究

The seismic safety should be constantly considered for mechanical, architectural and civil structures in Japan because of one of severe quake-prone countries in the world. The aseismic construction, seismically isolated structure and response control structure have been applied to the several structures for upgrading of seismic safety, and then the design technique for large scale structure in the current situation is close to standard range in recent years. However, the quake-proof technique for the smaller scale structure such as a detached house, server rack and art and craft has not yet been in the development stage until now, and especially there is a problem in the damping element in the practical stage because the downsizing of damping element is often difficult to be adapted to design specification such as a performance, a cost, a mechanism and so on for comparatively small structure. In this study, the urethane material has been developed to use as a damping element in the response control device. The newly urethane gel material is compounded to become the characteristic that a spring element in the material to minimize the effect against the structural rigidity. This paper describes the efficiency of newly developed urethane gel material as a damping element is considered from several material characteristic evaluations and basic mechanical characteristic investigations.

C14 ウレタンゴム材料を用いた減振装置の基礎的研究(OS8 機械・機械構造物の耐震・免震・振動制御(2)1)

The detached house designed by old design index that was damaged at Hyogo-ken Nanbu earthquake is over 47% in total detached houses in Japan. The upgrading for seismic safety such detached houses is urgent duties because a possibility of occurrence of huge earthquake is expected in a high probability. This study tries to apply urethane material not only to seismic safety element but also to energy absorbing element for detached house as a vibration reduction material at the same time. A linearity of basic mechanical characteristics of urethane rubber is generally much stronger than viscoelastic material such as a natural rubber. Moreover, it is possible to arrange a proper mechanical characteristics that is satisfied the design demand to fit each application cases. The application of urethane material to a detached house contributes to expand the techniques for seismic safety of structures that is a social imperative duties, and also to realize ultra long life of detached house in Japan. As the result, it is confirmed that the test specimen using urethane rubber indicates high linearity in mechanical characteristics and deformation performance by loading tests in condition with the test parameters of shaking frequency and amplitude

Simulation study of effects of speed of sound and attenuation on ultrasound lateral resolution

Experiments have shown that the lateral profile of a point target measured with a clinical ultrasound scanner is wider when the target is embedded in a urethane phantom than when it is in a traditional gel phantom. The behavior has been attributed to the low speed of sound in the urethane material, with the possibility that some of the broadening is caused by increased attenuation in this material. In this paper we apply a computer simulation model to study this behavior. Lateral beam profiles modeled for targets within a medium having a speed of sound and an attenuation matching that of urethane are compared with profiles for targets in a water-based gel. Simulations yield results that agree qualitatively with published experimental results. The lateral profile broadening in urethane is caused by the 6 % mismatch between speed of sound in this material and the speed of sound assumed in the receive focusing and beam forming. Attenuation plays a lesser role than the mismatch of the speed of sound. (E-mail: jazagzeb@facstaff.wisc.edu)

A BASIC STUDY ON CHARACTERISTICS OF URETHANE MATERIAL FOR GROUT FOREPOLING APPLIED FOR TUNNELLING

トンネル先受工としてのウレタン注入式ファアポーリングに通常使用されているウレタン注入材2種類について, 実施工での施工性および地山改良効果に着目した各種室内試験を実施し, 以下の知見を得た. (1) ウレタン注入材は発泡現象が急激であるとともに, 施工性を左右する粘性やライズタイムは温度に大きく左右される. (2) 改良効果については, 強度の発現が早く, 圧縮強度のみならず引張強度や引張接着強度が大きい.

Fiber-optic catheter-tip sensor based on the photoelastic effect

A fiber-optic catheter-tip sensor for the measurement of intravascular pressure and sounds is described. Sensor functioning is based on the photo-elastic effect. A simple theoretical model is proposed to provide guidance in the choice of the material and optical parameters capable of fulfilling the required specifications for cardiovascular catheter-tip pressure transducers. The fabrication of an instrumented catheter incorporating a photo-elastic sensor made of urethane material is described. Results of in vitro experiments indicate that the proposed device may represent an attractive technique for the development of a practical microtip sensor, competitive with existing catheter-tip pressure transducers.

Global Young's modulus of urethane plastic cast of left ventricular myocardium calculated from Roentgen angiographic silhouettes

A method based on the principle of conservation of energy is proposed for the evaluation of the global Young's modulus of the left ventricular myocardium in the passive state. Left ventricular transmural pressure and chamber volume data suffice for calculation of the external work performed during diastole, while the shape and dimensions of the left ventricle (recorded as videoroentgen angiograms) provide the necessary geometric information for the approximate evaluation of the strain energies by an axisymmetric, finite-element technique. To quantitate the accuracy of the proposed method, the global Young's moduli for six urethane casts of a canine left ventricle were determined and compared with the moduli of strips of the same urethane material measured directly. Roentgen silhouettes of the casts filled with known volumes of roentgen contrast medium were recorded on videotape at various stages of inflation. The calculated global Young's modulus corresponded to within ± 15% of the 0.5 to 6.0 × 10 6 dyn/cm 2 range of values calculated directly from the stress-strain relationship of strips of the same urethane material.

Some Aspects of the Microcellular Urethane Material and Process

The use of novel intermediates for the production of integral- skin microcellular urethane rubber has been explored in detail from the standpoints of polymer physical properties and process ability. Polymer/polyols and quasi-prepolymers were combined to yield extremely reactive, yet controllable, systems which are cured at room temperature and demoldable in less than 10 minutes. The ingredients are liquid at room temperature, shelf stable, and con tain no aromatic diamines, which are relatively expensive and can cause handling and discoloration problems. These novel urethane polymers possess physical properties which were heretofore ob tainable only with the use of aromatic diamine curing agents. Formu lation and process variables were explored to provide the technol ogy necessary for the practical utilization of the raw materials by microcellular urethane rubber parts producers. By proper manipu lation of formulation and processing conditions, rubbers suitable for a wide range of applications have been developed.