Modified Test Rig Research Articles

Vibration Measurement of a Rotating Shaft using Electrostatic Sensor

Measuring Vibration parameter for rotating machinery is essential for monitoring and diagnosis system in industrial plants. This paper demonstrates another approach to vibration measurement for rotating machine using electrostatic sensor and signal processing techniques. A single electrostatic sensor is used to detect charges surrounding the moving shaft of the machine. The signal from the electrostatic sensor is processed in MATLAB using Autocorrelation, Fast-Fourier, and Root Mean Square. The implementation of this technical approach was conducted on a modified test rig using three different shafts. The three shafts represent three different vibration modes: normal, abnormal, and severe. Each shaft was experimented under low and high rotation speed to observe amplitude and frequency level. Although the results of the tests did not show a direct measure of vibration displacement, due to the complex nature of the induced charges by the surface pattern. However, the results showed an indicative level of vibration at different amplitudes for the three shafts.

Full scale experiments on splitting behaviour of concrete slabs in steel concrete composite beams with shear stud connection

This paper presents the results of 15 push-off tests to determine, with a high degree of precision, the longitudinal splitting characteristics of a concrete slab in a novel steel-concrete composite beam with headed shear stud connectors. A modified test rig was developed, instead of the standard push-off test rigs. Both monotonic and cyclic loadings were considered. The experiments allowed the exploration of several currently unknown effects of various loads on components of steel-concrete composites, such as transverse loading and low-level cyclic loading on shear stud capacity. The results allowed the splitting failure mode to be characterised in unprecedented detail. It was found that for the case of cyclic loading, when many cycles were applied, it did not lead to premature failure of the composite beam, but instead increased the capacity of the beam against longitudinal splitting. This is significant for composite members under variable loading, such as floor supporting beams in car parks. It was also shown that the transverse compression forces across the base of the studs would increase the capacity of the beam against longitudinal splitting. Also studied were the differences and limitations of EuroCode 4 and New Zealand (NZS) standards and their effects on composite beam failure characteristics. It was shown that the presence of anti-splitting reinforcement would result in a gradual loss of load carrying capacity, compared to a sudden loss when not present. Even with sufficient side cover from the stud to the edge of the concrete, following the NZS standard, longitudinal splitting in composite beams continues to be observed.

Tribological properties of brass materials and their application for cages in rolling bearings

The continuously growing demands on standard components of machine elements with respect to power density, efficiency and durability while operating can reach the borders of load bearing capacity and lead to premature failure. Especially in engineering applications with insufficiently predictable operating conditions, bearings can usually meet these requirements. Possible correctives are the use of new materials with modified properties or changes in the design. In the railway industry, particularly high impact loads on bearing cages can occur. Brass cages are primarily used here. Thus, new brass alloys are applied whose properties have been improved in terms of their mechanical and tribological behaviour. Various brass alloys have been selected on the basis of the mechanical properties and cost aspects. Using a modified test rig for precision bearings, these alloys have been studied with respect to the tribological properties, which are correlated with the results of tests with brass rolling bearing cages. This gives the possibility to choose optimised brass materials for bearing cage application under increased requirements.

Optimization of a Test Bench for Testing Compliant Elements Under Shear-Force-Free Bending Load

As a contribution to the efficient cyclic testing of textile-reinforced compliant structures, a kinematic test rig for the static and dynamic bending test of composite stripe specimens has been developed [1]. This multifunctional six-membered linkage allows a moment application free of shear force by providing a pure bending load while bending the specimen in one direction up to 90°. During cyclic testing with a frequency of 1 or 2Hz the progressive damage behaviour meaning the initiation and propagation of fibre breaks with increasing load cycles up to complete structural failure has been monitored using industrial computer tomography [2]. The test results showed considerable differences within the results and therefore led to a need for a modified test rig to reach higher frequencies. Hence, a new concept for a shear-force-free bending test bench has been developed which allows a periodic bending in both directions from 90° up to 90°. This paper intends to make contributions to the efficient cyclic testing of textile-reinforced compliant structures by optimizing this new mechanism structure to minimize the induced shear force.

Abstract 3750: Embolus Adhesion to Activated Endothelium After Embolization: A Parameter To Predict Outcomes Of Mechanical Thrombectomy In Acute Ischemic Stroke

Background: In the MERCI trial and a prior animal study (Catch device), it was reported that when the thrombus retrieval maneuver was performed, the deployed device failed to mobilize the thrombus. Increased pulling force was applied and resulted in device rupture. These experiences lead us to hypothesize that the occlusive mass interacts with the activated endothelium, and the stability of the embolus on the vessel wall is related to the outcomes of mechanical thrombectomy. The aim of this study is to establish a methodology to quantitatively characterize the embolus-vessel wall adhesion. Methods: A rabbit CCA stenosis model was developed for creation of embolic occlusion with allogeneic clot. To evaluate the morphology of the embolus analogue (EA)-endothelium interface, two occluded vessel segments were explanted at 5-hour for Martius Scarlet Blue (MSB) staining and double immunofluorescence labeling for glycoprotein (GP) IIb/IIIa and fibrin. A modified test rig with a carbon steel wire (0.6 mm in diameter) fixture was used to detach the EA from the vessel wall (n=4). The wire moved down at the test speed of 0.1mm/s. The mean force was recorded and the energy to dislodge the EA from the vessel wall was calculated by numerical integration of the force versus distance curve below. Data were presented as mean±standard error. Results: MSB results showed that, the EA conformed to the shape of the underlying tunica intima and the undulated internal elastic lamina tended to flatten out after the occlusion. Immunofluorescent staining showed that GP IIb/IIIa (red) co-localized with fibrin(green), mainly observed at the EA-endothelium interface (yellow) ( Fig 1 A). In the detachment tests, a test distance of 6.07±1.18 mm was achieved after imposing 422.9±113.1 gram-force*cm of energy ( Fig 1 B). The mean force was 73.08±8.5 gram-force. Conclusions: Presence of GP IIb/IIIa and fibrin immunoreactivity indicates the interactions between border of the EA and the luminal surface, and this finding is supported by the quantitative adhesion force acquired during the detachment test. This project is ongoing to investigate thrombus-vessel wall interactions caused by acute thrombosis. The fibrin crosslink number and the platelet volume will be characterized by using confocal laser scanning microscope, and correlated with the adhesion results.

Dual-motion fretting behavior of mandibular cortical bone against pure titanium

Dual-motion fretting tests of flat cortical bone specimens from fresh human mandible against pure titanium (TA2) ball were carried out on a modified test rig with tilt angle of 45°. The imposed maximal loads varied from 100 to 200 N. Dynamic characteristics of dual-motion fretting tests were analyzed in combination with micro-examinations via optical microscopy (OM), laser confocal scanning microscopy (LCSM) and scanning electron microscopy (SEM) together with energy dispersive X-ray spectrum (EDX). Two types of F– D curves (the trapezoid and elliptic mode) were recorded during the tests. The examination showed that the wear scars of the dual-motion fretting were asymmetric, and the tangential component of dual-motion fretting was in the mixed fretting regime. Under the lower imposed load, only some detachment of particles and scratches without cracking were observed even after 5×10 4 cycles. The main wear mechanisms of the dual-motion fretting damage were the abrasive and adhesive wear. Under higher imposed loads, the cracks initiated and propagated mainly at the high stress side of contact edges. The wear mechanisms of the dual-motion fretting of cortical bone under higher imposed loads were the combination of the adhesive wear, abrasive wear, cracking and lubrication of the human bone tissue debris. And the lubrication of the debris played an important role during the dual-motion fretting processes.

Laminar-burning velocities of hydrogen–air and hydrogen–methane–air mixtures: An experimental study

The laminar burning velocities of hydrogen–air and hydrogen–methane–air mixtures are very important in designing and predicting the progress of combustion and performance of combustion systems where hydrogen is used as fuel. In this work, laminar flame velocities of hydrogen–air and different composition of hydrogen–methane–air mixtures (from 100% hydrogen to 100% methane) have been measured at ambient temperatures for variable equivalence ratios ( ER = 0.8 – 3.2 ). A modified test rig has been developed from the former Cardiff University ‘Cloud Chamber’ for this experimental study. The rig comprises of a 250 mm length cylindrical stainless steel explosion bomb enclosed at one end with a stainless steel plug which houses an internal stirrer to allow mixing. The other end is sealed with a 120 mm diameter round quartz window. Optical access for filming flame propagation is afforded via two diametrically opposed quartz windows in both sides. Flame speeds are determined within the bomb using a high-speed Schlieren photographic technique. This method is an accurate way to determine the flame–speed and the burning velocities were then derived using a CHEMKIN computer model to provide the expansion ratio. The design of the test facility ensures the flame is laminar which results in a spherical flame which is not affected by buoyancy. The experimental study demonstrated that increasing the hydrogen percentage in the hydrogen–methane mixture brought about an increase in the resultant burning velocity and caused a widening of the flammability limits. This experiments also suggest that a hydrogen–methane mixture (i.e. 30% hydrogen+70% methane) could be a competitive alternative fuel for existing combustion plants.

Pressurized fluidized bed combustion and gasification of coal using flue gas recirculation and oxygen injection

A combined cycle incorporating pressurized fluidized bed combustion of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO2 concentration. CO2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO2 emissions. The specific aim of the project is to assess the technical feasibility of this process. For this purpose a 1.6 MWth pressurized fluidized bed combustion test rig has been modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The objectives of the project, the modified test rig and the experimental results obtained from combustion experiments with coal, recirculated flue gas and pure oxygen are described. The conversion efficiencies and the emission of harmfull components measured during these experiments are analyzed and compared with values obtained during combustion and gasification using air.

Pressurized fluidized bed gasification of coal using flue gas recirculation and oxygen injection

A combined cycle incorporating pressurized fluidized bed gasification of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO 2 concentration. CO 2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO 2 emissions. The specific aim of the project described in this paper is to to assess the technical feasibility of this process. For this purpose an existing 1.6 MW th pressurized fluidized bed combustion test rig is being modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The paper gives a description of the objectives of the project, the modified test rig and the experimental programme which is planned for the second half of 1995.