Process Simulation Test Research Articles

Application of Elastomeric Polyurethane in Performance Improvement of Rail Ballast Subjected to Cyclic Loading

The deformation and degradation behavior of unstabilized ballast and that stabilized with elastomer and geogrid was evaluated using process simulation test (PST) apparatus at various loading frequencies (f). The results indicated that elastomer has significantly reduced the extent of both vertical and lateral deformations of ballast. For example, elastomer reduced the extent of vertical settlement (Sv) in ballast from 22.76 to 9.83 mm, and the lateral deformation (ld) from 8.14 to 1.95 mm (f=15 Hz). It was also seen that the deformation and degradation of both stabilized and unstabilized ballast increased nonlinearly with the increase in the applied loading frequency (f). Further, the beneficial effect of elastomer in restraining the lateral flow of ballast was seen over the entire depth of treated ballast, unlike the geogrid, whose efficiency was maximum at its placement location and then reduced at farther locations. Moreover, elastomer has significantly enhanced the resilient modulus (Mr) and damping ratio (D) of ballast when compared with geogrid-reinforced ballast. For example, the elastomer increased the Mr and D of ballast by 25.9% and 66.6%, respectively, in comparison with an increment of only 15.1% and 25.3% in the case of geogrids (f:15 Hz). The Mr and D of ballast were found to be influenced by the effectiveness of the ballast stabilization technique in reducing lateral displacements. Additionally, elastomer has significantly reduced the vertical stress (σv) at the ballast–subballast interface by 34%. Further, elastomer was found to be more efficient than the geogrid in reducing the dynamic amplification factor (DAF) at any loading frequency. Similarly, elastomer reduced the breakage of ballast by 71% compared with the 40% of geogrid reinforcement (f=15 Hz).

Effect of geogrid on deformation response and resilient modulus of railroad ballast under cyclic loading

Laboratory investigations were carried out using process simulation test (PST) apparatus to assess the role of geogrid on the deformation response and resilient modulus of railroad ballast at different loading frequencies (f) varying from 10 to 40 Hz. The materials used for testing involved fresh granite ballast and subballast having mean particle sizes (D50) of 42 mm and 3.5 mm, and geogrids with different aperture shapes and sizes. The results from the laboratory investigations reveal that the degradation and deformation behavior of ballast is influenced by the loading frequency (f). The use of geogrids is shown to reduce the extent of deformations in ballast (both lateral and vertical) and its degradation (Bg: ballast breakage), but the effect of geogrid diminishes with the increase in frequency (f). The assessment of the lateral strain profiles along the ballast depth indicates that the geogrid influence zone (GIZ) is dependent on both the type of geogrid used and the loading frequency (f). The GIZ is found to vary from 38 mm (0.90 D50) to 237 mm (5.64 D50), with it being the lowest at f = 40 Hz and for geogrid having relatively larger apertures. Further, the geogrids are found to significantly enhance the resilient modulus (Mr) of ballast. In addition, the Mr is established to increase with f and Bg. The inclusion of geogrids also reduced the extent of vertical stress (σv) including the dynamic amplification factor (DAF).

Discrete element modelling of railway ballast performance considering particle shape and rolling resistance

To simulate ballast performance accurately and efficiently, the input in discrete element models should be carefully selected, including the contact model and applied particle shape. To study the effects of the contact model and applied particle shape on the ballast performance (shear strength and deformation), the direct shear test (DST) model and the large-scale process simulation test (LPST) model were developed on the basis of two types of contact models, namely the rolling resistance linear (RRL) model and the linear contact (LC) model. Particle shapes are differentiated by clumps. A clump is a sphere assembly for one ballast particle. The results show that compared with the typical LC model, the RRL method is more efficient and realistic to predict shear strength results of ballast assemblies in DSTs. In addition, the RRL contact model can also provide accurate vertical and lateral ballast deformation under the cyclic loading in LPSTs.

Investigation of deformation and degradation response of geogrid-reinforced ballast based on model track tests

A series of large-scale cyclic tests was conducted using process simulation test ( PST) apparatus to capture the influence of loading frequency ( f) on the deformation and degradation behavior of ballast with and without geogrids. Fresh granite ballast and subballast having mean particle diameter ( D50) of 42 mm and 3.5 mm, respectively and five geogrids of different aperture shapes and sizes were used in this study. The tests were conducted at f ranging from 10 to 40 Hz and up to 250,000 load cycles. The test results from the laboratory investigations confirmed that the deformation and degradation behavior of ballast is highly influenced by loading frequency ( f). Moreover, the results showed that geogrid reinforcement stabilizes ballast by reducing the extent of lateral spreading ( ld) and vertical settlement ( Sv) and by minimizing particle breakage ( BBI). The inclusion of geogrids also reduces the extent of vertical settlement in subballast layer ( Svsb). In addition, the extent of volumetric ( εv) and shear strains ( εs) including void ratio ( ef) and density ( γbf) were found to be highly influenced by f. It is further seen that lateral spread and vertical settlement reduction index ( LSRI and VSRI) of all the geogrids decreases with the increase in f. Moreover, it is revealed that with the decrease in LSRI, the extent of Sv and BBI increases. A correlation is developed between the deformations ( ld and Sv) and interface efficiency factor ( α). The effectiveness of geogrid in keeping the ballast in place is evaluated in terms of a new parameter ‘geogrid efficiency factor ( Gef)’. The value of Gef for geogrids used is found to vary from 0.02 to 0.27. It is further shown that Gef under cyclic loading conditions is a function of the interface efficiency factor ( α) evaluated under direct shear conditions.

Simulation on cutting forces and cutting temperature in broaching of 300M steel

In this paper, using the method of single factor experiment, set the test parameters of 300M steel through AdvantEdge software broaching process simulation test, simulation results for the finishing, analyzed the influence of broach rake angle and relief angle, tooth lift and cutting speed on cutting force and cutting temperature in the process of broaching, observed the cutting temperature in the broaching process of regional changes, through the analysis, provides theory basis for reasonable design of the broach. The results show that the tooth lift has the greatest influence on the cutting speed, and the tooth lift and cutting speed have the greatest influence on the cutting temperature.

Pengembangan Sistem Simulasi Ujian Nasional Sekolah Menengah Atas (SMA) Online Berbasis Web

The national exam is a method of testing to education in Indonesia for determining students graduation in senior high school. The determine graduate base on the minimum value that must be obtained by students and established by the government. Students follow the simulated exam before faced the national exam for value of the capability test. The purpose in this research is develop a simulation system the national exam for senior high school students with a web-based, so it can be accessed online. In addition, the purpose in this research to build the another alternative in simulation exams except in the school. Development systems using the programming language PHP and the MySQL database. The testing system indicates that the system can function properly when doing the process simulation test and get the results right after finish working on problems such as the simulation test. Keywords: National Exam, Simulation System, Web .

Discrete element modelling of lateral displacement of a granular assembly under cyclic loading

Railway ballast is an unbound granular medium which undergoes non-uniform lateral spread when subjected to high-frequency cyclic loading. In order to simulate the lateral spread of ballast upon loading, a modified large-scale process simulation test (PST) apparatus with five independent movable plates of equal height forming one of the side walls has been built at University of Wollongong, Australia. However, the experiments alone cannot provide a comprehensive study of the lateral flow of ballast in a micro-mechanical perspective. The discrete element method (DEM) has therefore been used to complement the modified large-scale PST apparatus and to provide much needed micro-mechanical insight to the lateral flow of aggregate particles, such as the contact force distribution, particle movement and porosity change. The simulation results provided acceptable predictions of the trend of vertical and lateral displacements of two-ball clump assembly upon loading. In addition, these simulations evaluate the effect of confining pressures (10–30kPa) due to the crib and shoulder ballast, on vertical settlement and the lateral spread of ballast under high frequency cyclic load. The vertical stress decreases significantly with depth from an applied vertical stress of 460kPa at the sleeper–ballast interface to 210kPa at the base wall (ballast–subballast interface), which is in agreement with the experimental results. In addition, geogrid model using PFC3D was used in the ballast layer to examine the ability of geogrid on arrest lateral displacement of ballast and reduce settlement under cyclic loading.

Performance assessment of geogrid-reinforced railroad ballast during cyclic loading

Recently, rail practitioners have resorted to the use of geogrids as a low-cost solution to stabilise ballast. In view of this, large-scale cyclic tests have been conducted on reinforced ballast using a modified process simulation test (MPST) apparatus at a loading frequency of 20Hz, with geogrid placed at the subballast–ballast interface and within the ballast. Fresh latite basalt having a mean particle size of 35mm and geogrids with different aperture sizes was used. The experimental results indicate that the geogrid arrests the lateral spreading of ballast, reduces the extent of permanent vertical settlement and minimises the particle breakage. However, the in track performance is shown to be influenced by the shear behaviour at the ballast–geogrid interface, wherein the extent of both lateral and vertical deformation reduce with the increase in shear strength at the ballast–geogrid interface. Moreover, the geogrid also helps in minimising the extent of differential track settlement that arises due to the difference in sleeper–ballast contact stress along the track length. The efficiency of geogrid is found to be identical at vertical stresses of 230 and 460kPa. These test results highlight the role of geogrid in stabilising ballast, thus encouraging its use in railway applications.

The lateral displacement response of geogrid-reinforced ballast under cyclic loading

Ballast being an unbounded granular medium spreads laterally when subjected to high-frequency cyclic loading. To reduce lateral movement of ballast and to optimize track performance, rail tracks can be reinforced with geogrid. In this study, a novel large-scale process simulation test (PST) apparatus that can capture the lateral strain variation upon loading is described. Laboratory tests were conducted to explore the deformation and degradation response of both unreinforced and reinforced ballast under high-frequency cyclic loading. Fresh Latite basalt having an average particle size (D50) of 35 mm, and geogrids with different aperture sizes were tested. The laboratory experimental results reveal that the ballast deformation (both lateral and vertical) and the breakage during cyclic loading are influenced by the geogrid type and its placement location. Moreover, the lateral strain profiles along the ballast depth have been measured and the geogrid influence zone (GIZ), defined as the distance to which the effect of geogrid in arresting the lateral displacement of ballast exists, has been determined. The GIZ is found to vary from 160 mm (4.60D50) to 225 mm (6.45D50) depending on the location of the geogrid. In addition, the optimum geogrid position in the track has been identified to be 65 mm above the subballast. The test results also exemplify the ability of geogrid to arrest lateral displacement of ballast, reduce settlement and minimize particle degradation under high-frequency cyclic loading.

Research on the Real-Time Simulation System Design for Missile Based on RT-LAB

Abstract A semi-physical simulation system is developed based on the RT-LAB real-time simulation environment which is used to process simulation test of missile guidance controlling system. The system adopts design idea of modularization, development of all sub-system together and it integrates the Hi-fi missile aerodynamics environment, missile boron computer system, inertia measurement unit, high accurate aviation posture simulator, real missile boron port equipment, three-dimensional view and data backup system into one so that the performance of guidance controlling algorithm could be reflected comprehensively, directly and really. According to the comparison between test result of digital simulation and semi-physical system simulation, the feasibility of semi-physical simulation could be certified so that under the semi-physical simulation environment, more real and effective test could be checked for guidance controlling algorithm.

Time-independent and time-dependent deformation of small tunnels—III pre-failure behaviour

Process simulation tests have been conducted to investigate the time-dependent deformation processes near tunnels at large depth or in weak rock. The tests equipment has been described in Part I together with a presentation of the loading history adopted for the tests. In Part II typical test results have been presented to document the behaviour of small tunnels in a jointed rock mass with time-dependent strength and deformation properties. A qualitative interpretation of the observed displacement pattern has been given. In this third part the measured tunnel closure and radial strain patterns are compared with those predicted from simple material models. The time-independent behaviour is compared with predictions assuming linear elastic material properties and the time-dependent tunnel response is compared with solutions assuming linear visco-elastic material properties. It is concluded that excessive deformations can be attributed to softening processes near the tunnel wall. The practical implications of this interpretation are discussed.

Deformation properties of a sub-bituminous coal mass

Process simulation tests have been carried out to investigate the relative importance of various time-dependent processes on the deformation behaviour of tunnels in weak rock or at large depth. Back analysis of loading and unloading tests on two large coal specimens before and after excavation of a tunnel yielded values for the elastic parameters. The results show that the elastic parameters of the coal tested are relatively insensitive to pressure (between 3 and 10 megapascals), and that a typical Poisson's ratio lies between 0.3 and 0.4 for loading parallel to the bedding plane and less than 0.1 for loading perpendicular to the bedding. The bulk and Young's moduli vary widely within a relatively small area. Very few rock types exhibit such variation in deformation properties on the same scale, and this should be recognised when testing coal or designing structures in or on coal.

Time-dependent deformation of small tunnels—II. Typical test data

Abstract Process simulation tests have been conducted to investigate the time-dependent deformation processes near tunnels at large depth or in weak rock. The test equipment has been described in Part I together with a presentation of the loading history adopted for the tests. This second Part includes a detailed description of typical test results and a discussion of the time-dependent processes, such as failure propagation and associated stress redistribution, which cause the observed behaviour. Both the time-dependent and time-dependent tunnel convergence and radial strain pattern inside the rock mass are presented in plots of field stress, strain or tunnel closure with time, and strain rate or tunnel closure rate. The performance of the tunnel in the pre-failure stress range, during the transition to an unstable opening and after a yield zone has developed is evaluated. Even though a detailed interpretation of the test results will follow in subsequent publications, several important conclusions can be made with respect to time-dependent processes controlling tunnel convergence, observation of the rock mass response to local yielding, position and type of instrumentation to detect time-dependent processes and propagation of instabilities in overstressed rock.