Measurement and Analysis of Vibration Levels in Rail Transport in Central Europe

Transcription

1 Measurement and Analysis of Vibration Levels in Rail Transport in Central Europe Péter Böröcz 1 and S. Paul Singh 2 1 Associate Professor, Széchenyi István University, Győr, Hungary 2 Professor Emeritus, Michigan State University, East Lansing 48824, USA of Corresponding Author: Péter Böröcz (boroczp@sze.hu) Abstract In the last decade, with a continued change in world economic conditions and global trade, transportation of goods has continued to increase. The opening of new and existing markets requires that products and packages move through various regions of the world using available logistical equipment and networks at a faster pace. It also requires that damage be kept at a minimum while providing maximum safety to individuals. This can be achieved by properly designing packages to transportation levels that occur in the supply chain. The purpose of this research is to both measure and analyze the vibration physical forces that occur during rail transport. Rail shipments are widely used across the world and they are an integral part of the intermodal transfer of ISO containers from ships and trucks to rail. The aim of this paper is to provide vibration levels measured for rail shipments on a major railway line in Central-Europe that has not been previously published. The vibration levels that were measured in this study were compared to ASTM, MIL STD and DEF STAN standards and ISTA procedures in the form of PSD spectrums. A composite PSD spectrum is provided which can be used to simulate the measured rail vibration levels in Central Europe. Results are also compared to rail travel in other international shipments for North America and Asia. KEYWORDS: vibration, power spectral density (PSD), spectrum, rail, Europe INTRODUCTION Rail transport is a prominent method of transportation of goods for almost two centuries across the world. It is also widely used for the distribution of goods in Central Europe. From 1990s the connection between countries in Central Europe has been vastly improved to create a smoother transition of goods and services. Rail also provides a smoother transition between ships and a truck with the use of inter-modal transport containers and provides connectivity between various geographic regions across continents and oceans facilitating trade. With the change in political structure in the eastern part of Central Europe, making its borders more accessible to trade, it has become a distribution logistics hub due to its geographical location. Six vital European transport corridors pass through area, providing unparalleled access to all parts of Europe, from the north to south and from the west to east. As a result of intensive construction works in recent years along the main European transport corridors, lot of new major motorways, main roads, rail track, faster and safer transportation across all of Europe is now viable. Previous studies have also measured and analyzed the vibration levels and developed power spectral density (PSD) for rail shipments and developed test methods based on

2 this data in testing of containers and package systems [1-4]. These studies represent data averaged over several varied trip lengths and railcars. There is a study (SRETS) that has measured transportation vibration in Western Europe, including a segment of 400km railway too [5], but the rail data was not used to the final results, because they were not statistical secured due to the low quantity of vibration data. In addition some previous studies have measured both rail transport and intermodal transport i.e. in North America, India and Thailand [6-10]. These studies above determined that the vertical vibration intensities were higher than the lateral and longitudinal levels for both truck and rail transportation. There is a study that presents the method of simulating vibration levels on railway for railcar components [11]. In addition the role of protective packaging methods that can prevent damage and enhance safety were also discussed. Some measured and analyzed data was also compared to different vibration test methods recommended by ASTM, ISTA or military standards. However, the authors could not find any published research that measures the vibration levels for rail transportation in Central Europe. Therefore this study and paper are presenting the new measured and analyzed data that can help packaging engineers gain a better understanding about this distribution environment and design appropriate protective packaging. This research attempts to measure and analyze the vibration levels and intensity on railcar shipments on the major rail lines in Central Europe using data recorders to record vibration events and present them in the form of PSD spectrums. The data from this study was also compared to vibration test profiles recommended in popular and commonly used package testing such as the ASTM D4169 [12] (American Society of Testing and Materials), ISTA 3H [13] (International Safe Transit Association), MIL-STD-810G [14] (United States Military Standards) and DEF STAN [15] (United Kingdom Defense Standard). Data and results from this study can be used to compare packaging vibration test methods used by packaging engineers and develop vibration test methods for shipping products in Central Europe by rail. In addition the data is analyzed by orientation and levels presented in lateral, longitudinal and vertical orientations. RAIL TRANSPORTATION IN CENTRAL EUROPE There is a significant amount of cargo and goods that are shipped by rail in Europe. In addition the European continent is well connected with comprehensive rail networks. These networks play an important role in the long-distance freight traffic in Europe. The rail networks in Central Europe were previously only well developed in regions that had democratic governments and those in communist regimes often had infrastructure problems before the 1990 s. This was prevalent mostly on the eastern side of Central Europe which is now undergoing modifications and improvements. This is also the reason why one of the goals of the European Parliament is to develop and maintain rail corridors in this region to facilitate a single and unified economy. In Central Europe the rail lines only use the standard gauge (1435mm wide track). In addition, the electrification system to operate the rail engines use 15kV and 16.7Hz AC power in Austria, Germany and Switzerland while a 25kV and 50Hz AC system

3 is used in Hungary, Czech Republic and Slovakia. Poland and Slovenia use a 3kV DC power system to operate. The total railway line length in EU-27, in 2012, was approximately 216,200 km [17] compared to approximately 204,700 km [16] in the United States. The total rail freight transport in the EU was estimated to be close to 407 billion [15] tonkilometers (tkm) in This is about 20% of the US freight transportation estimated to be around 2,650 billion [16] ton-km in USA in 2011, on Class 1 rail. Rail shipments accounted for 18% of total freight that was transported in 2012 in Europe [16]. Table 1 shows the distribution of rail lines and geographic area covering various countries of Central Europe. Table 1. Railway transport, rail lines lengths and area in Central European countries in 2012 [17,18] Country Railway transport Rail lines Area (million tkm) (route-km) (km2) Austria Czech Republic Germany Hungary Poland Slovakia Slovenia Switzerland Total According to Table 1, there was more than 50% of the total rail turnover in EU-27, and almost half of the EU rail lines lie in Central Europe. The countries in Central Europe and corresponding regions can be seen in Figure 1. It also shows the specific routes and cities covered in this study. The countries covered in this study include Hungary, Slovakia, Czech Republic, Austria and Germany. Figure 1. The railway network in Central Europe and the routes measured

4 The line hierarchy for rail in Central Europe is similar to that in other regions of the world. It consists of main-lines, side-lines (branch lines) and industrial sidings. There is a guideline being used by the European Community for the development of the Trans-European transport network in order to promote the smooth operation of internal markets while strengthening economic and social cohesion. This Trans- European transport networks (TEN-T) developed continuously from 1996 based on the 1692/96/EC decision of the European Parliament, has a specific and separate section that applies to rail networks. The Trans-European rail network is made up of high-speed and conventional rail networks. The guideline [19], in 2013, defined nine core transport network corridors such as Baltic Adriatic, North Sea Baltic, Mediterranean, Orient East-Med, Scandinavian Mediterranean, Rhine Alpine, Atlantic, North Sea Mediterranean, Rhine Danube. Five of these nine corridors pass through Central Europe. A significant part of the rail freight transport travels on rail mainlines in these corridors. The quality of these main rail lines is practically similar. MEASURED ROUTES AND VEHICLES The rail measurements were conducted along rail routes shown in Figure 1. The measured rail routes included mainline, sideline and industrial line in the following countries: Hungary, Austria, Germany, Slovakia, Czech Republic and Poland. More than 80% of the routes studied were along major rail lines, thereby covering a large portion of the Trans-European transport corridors. The details of these routes are shown in Table 2. The rail measurements for this study were conducted in March Table 2. The details of rail shipment routes Route Category Distance (km) Route 1: Győr (H) Wien (A) Regensburg (GE) - Ingolstadt (GE) and return Industrial line Mainline (Trans-European) Sideline 2x 2 2x 545 2x 76 Route 2: Győr (H) Rusovce (SK) Lanzhot (CZ) Bad Schandau (GE) Wolfsburg (GE) and return Route 3: Győr (H) Kuty (SK) Lichkov (CZ) Poznan (PL) and return Total Industrial line Mainline (Trans-European) Sideline Industrial line Mainline (Trans-European) Sideline 2x 1 2x 927 2x 2 2x 3 2x 696 2x The railcars were 4-axle Habiins 274 (on Routes 1 and 2) and Habiis 284 (on Route 3) with sliding sidewalls, shown in Figure 2, with a capacity of 180m 3 and 186m 3 respectively, and with maximum payload capacity of 50,000 kg. The speed at which the trains traveled was in the range of km/h, and km/h on the sidelines. Although these wagons can go up to 120 km/h, these types of trains have to

5 be under the speed limit of 110 km/h in Austria and Germany, because they only have one brake post. In all cases the shipments weighed approximately 45,400 49,900kg on the outbound shipments and 42,500 46,700kg on the return trip. The shipments consisted of products in racks or stands, and on the return trip the racks or stands were returned in a collapsible state. Figure 2. Railcars measured in the study INSTRUMENTATION AND ANALYSING METHOD The vibration events for transportation were measured in all three axes (vertical, lateral and longitudinal). Lansmont (SAVER) 3X90 (Shock and Vibration Environment Recorder, Lansmont Corp., CA, USA) data recorder was used to collect the data. The settings of the recorder used for this study are shown below: Wakeup interval: every 1 minutes Trigger threshold level: 2.0 G Recording Time: s Sample/sec: 500 Hz Sample size: 1024 Frequency resolution for PSD: 0.48 Hz Anti-aliasing filter frequency 250 Hz The SAVER was mounted directly to the floor located to the center of the storage area. This is approximately where the doorframe opening is. In the case of vibration analysis power density (PD) levels were determined as function of frequency. These were based on the recorded vibration acceleration levels from all of the trips together. This way the PD levels cover and combine the vibration with various speeds, route conditions and loads for Routes 1, 2 and 3 together. The reason for combining the various trips into one power spectral density (PSD) plot is that the measured railcars (Habiins 274 and Habiis 284) practically have the same vehicle body and structure. The power density within a narrow band of frequencies of a given spectrum was determined by Grms values based on the number of samples for a given bandwidth. The Grms is the root mean square value of the acceleration in G s in the given

6 bandwidth of frequency, based on the number of (N) samples analyzed in that window. The vibration environment is described by power spectral density (PSD) spectrums that show a graphic plot of the power density levels versus frequency. In this study, the spectrums are presented from 0.5 to 200 Hz. The vibration data was filtered to remove all undesirable events such as any noise or non-vibration featured movements from the analysis. This way data below 0.01 G rms was filtered out. The power density spectrums were then created using the remaining measured data in which a spectrum for the top 5 and 20 percent of the highest measured data are shown and then followed by a lower spectrum representing the remaining 80 percent of all recorded data. Therefore spectrums are presented for the top 5 and top 20 percent of saved events and bottom 80 percent of remaining events [6][7]. In addition a spectrum representing the average for all (100%) events measured is also presented. Power Density Spectrums in all three axes (lateral, longitudinal and vertical) are presented in this paper and each PSD is reported with a Kurtosis (K) and Skewness (S) along recorded acceleration time histories, where the acceleration values are adjusted by their positive or negative direction. The reason for reporting these values is that the random vibration testing system controller mostly generates the signal from normal distribution, so field measured Kurtosis can be used as the input parameter to control the variability of the random signal at rail pre-shipment vibration testing, or to compare the results to other studies. Additional statistical analysis was performed on the recorded absolute peak acceleration values for the total trips, in order to determine cumulative distribution functions (CDF) for all three axes separately, and then they were fitted in the Weibull two-parameter distribution model. In this case, there was no particular reason for choosing Weibull distribution, simply this distribution model was determined to be the best fitting to the data. The Weilbull distribution is widely used in reliability engineering, due to its relative simplicity. Its CDF has two parameters, presented in equation (1), as follows: α > 0 is the scale parameter, β > 0 is the shape parameter. F(x α, β) = x βα β t β 1 e (t/α )β dt =1 e (x/α )β (1) 0 DATA AND RESULTS Table 3 shows the result of measured peak acceleration values and Figure 3 shows the CDFs for the measured accelerations values in all axes. The CDF s shows the percentage of the events that are below a certain level of the measured peak acceleration value. It can be seen that the acceleration values in longitudinal direction were generally lower than those of the vertical or lateral. These phenomena could be partly attributed to the lateral oscillation of the railway vehicles [20]. The highest acceleration values in this study were in the vertical axis. Table 4 contains the statistical parameters of these distributions that use recorded acceleration data and based on best fit regression analysis. The R-square values indicate confidence level (1 representing 100%) of each fit for the three axes monitored. Table 3. Summary of acceleration data measured Acceleration data Longitudinal Lateral Vertical Maximum acceleration (g, peak)

7 Acceleration at 99% Occurrence (g, peak) Acceleration at 95% Occurrence (g, peak) Acceleration at 90% Occurrence (g, peak) Figure 3. CDFs of acceleration events in all three axes (g, peak) Table 4. Statistical parameters of distributions based on best fit regression analysis Predicted Mean Actual Mean Variance Estimate α Estimate β R-square RMSE Vertical Long Lateral Figures 4-6 show the PSD plots developed for this study. Figure 4 shows the PD levels for rail vibrations in vertical axis. This figure also shows the PSD plots in different levels of severity based on the amount of data analyzed to reflect the top 5%, top 20%, bottom 80% as well as the entire 100% of recorded and saved data by the SAVER recorder. Based on the spectrums shown in Figure 4, it is clear that the highest vertical vibration intensity levels were between frequencies of 1 to 5Hz. These results are similar to those published in other international studies [5-10] in Australia, India, Thailand or US. The results showed that the measured PD levels for vertical vibration were generally low after 8Hz. An important observation is that that the measured and analyzed levels of power spectral density around 20Hz were 10 times lower than in other previous rail studies, except the results of Roulliard et al. from Melbourne to Perth [4]. It could be caused by the nearly constant speed on mainlines and the relative good quality of these rail networks. Rail lines in Europe are generally known to be better in Europe as compared to North America or India and permit higher traveling speeds. The same is true for high-speed rail in China and Japan that is used for passenger travel.

8 Figure 4. Rail vertical vibration levels with PSD plots on measured routes It should be noted at the point that similarly to trucks, the speed of the railcar, railcar suspension stiffness and damping, load capacity, truck conditions, as well as the location of the recorder or its setting-up parameter (trigger levels) can also affect the final PD levels. In addition to this, the vibration environment is further complicated by the dynamics interaction of couplers between railcars during traveling. Therefore, according to the results, several other studies can only cautiously be compared to each other. The PSD plots for lateral and longitudinal vibration levels are also shown in Figure 5 and 6. Similarly to previous studies that provided the PSD spectra in the lateral or longitudinal modes, the lateral PSD spectra were higher than those in the longitudinal modes [6-7]. However, both in the lateral and longitudinal axis, the PSD spectra in this study were lower than what was observed in India [6] or in Thailand [7]. Figure 5. Rail longitudinal vibration levels with PSD plots on measured routes

9 Figure 6. Rail lateral vibration levels with PSD plots on the measured routes Overall G rms and Kurtosis values for each PSD plots are shown in Table 5. Kurtosis is a way to measure whether the observed data are heavy-tailed or light-tailed compared to a normal distribution [21]. This definition is used with the following meaning: when the standard normal distribution has a kurtosis of zero, then a positive kurtosis indicates a "heavy-tailed" distribution, while a negative kurtosis indicates a "light tailed" distribution, compared to a normal distribution. All of the measured vibration levels in this study indicated positive kurtosis, so the acceleration values (adjusted with their positive or negative direction) in the function of time did not follow the normal distribution. Former studies have proven and presented the non- Gaussian nature of measured data for vehicle random vibration [22] [23] [24]. All these previous observations were conducted on over-the road vehicles. However, the statistical results of this study show the non-gaussian nature of acceleration levels during railcar transport, with over 95% confidence level. Figure 7 shows the distribution for railcar vibration records along with the kurtosis values. This is also presented in Table 5. Table 5. Overall G rms and Kurtosis values for railcars on measured routes Events Vertical Lateral Longitudinal Kurtosis G rms Kurtosis G rms Kurtosis G rms Top 5% Top 20% % Bottom 80%

10 Figure 7. Distribution for vibration records with kurtosis in all three axes. (a) Longitudinal, (b) Lateral, (c) Vertical Table 6 and Figure 8 show the recommended composite PSD spectrum that is developed using the average PD levels for each frequency from the various trips using the 100% of measured events at each frequency breakpoint. The recommended spectrum was smoothed between the highest breakpoints of all measured data at 9 breakpoints. These 9 breakpoints ensured that the recommended spectrum could cover the measured intensity between Hz. Of course, the other PSD spectra concerning the events of the Top 5 %, Top 20% and Bottom 80% can also be used as test spectra as more or less severe testing protocols or as split level vibration test intensities [25] [26]. Figure 8 also shows ASTM D4169 Assurance Level I-III, ISTA 3H, MIL-STD 810G and DEF-STAN rail spectra for comparison purposes, and those PSD spectra from other studies where composite or recommended spectra were presented like in India and Thailand. As shown in Figure 7, the PSD of vertical vibration significantly differs from those included in ASTM, MIL-STD or DEF-STAN, but shows similarity with the ISTA 3H and field data from Thailand. The recommended spectrum also shows that the levels of vibration testing are higher in the lower frequency than those used and recommended by ASTM D4169, which is one of the popular test methods used for simulating rail vibration. In comparison to the ISTA 3H the recommended PSD spectrum approaches 77% of the ISTA overall G rms in the bandwidth of Hz, and 63% in 1-100Hz.

11 Table 6. Breakpoints and frequencies for recommended test spectrum Rail Frequency (Hz) PD level G 2 /Hz , , , , ,00003 Figure 8. PSD spectra for vertical rail vibration test Table 7 shows numerical data of overall G rms of the spectra presented in Figure 8 for the three different frequency bandwidths (1-10Hz, Hz and 1-100Hz) respectively. The reasons of splitting these bands is due to the fact that these are commonly used to develop the PSD spectra. This is in exception to the DEF STAN 00-35, and the 1-10Hz lower frequency range which show a significant difference to the rest of the spectrum band-with between Hz presented in ISTA 3H and previous studies. It can be easily seen that the G rms of recommended PSD in the range of 1-10Hz is approximately equal to the field measured and exceeds the recommended spectra reported in India and Thailand. Furthermore over 10Hz the recommended spectrum slightly exceeds the field measured data due to the smoothing as well as the less intense segment between 15-30Hz.

12 Table 7. Overall G rms in different frequency bandwidths 1 10Hz Hz 1 100Hz ISTA 3H ASTM Level II DEF STAN * * MIL-STD 810G India (SP Sing et al.) Thailand (Chonchenchob et al) Vertical PSD of 100% events Recommended spectrum * The lower limit of DEF STAN is 5Hz It has to be recognized by the readers of this paper that the intensity of the test standards applies time-compression, which artificially amplifies the vibration magnitude. This way the overall G rms values of different test spectra cannot be compared directly. The recommended spectrum from data in this study can also be used as time-compressed vibration testing for packaging systems for vibration levels in the vertical axis. These breakpoints and PD levels are informative and recommended for simulating the rail transport vibration on major railway lines in Central-Europe. Furthermore, it is necessary to mention that using of time compression at test levels does not sometimes expose the test items to extreme levels of vibration or transients like rail weld joints, severe track misalignment or longitudinal impact between adjacent decoupled railcars which can be happened during real transportation [27]. Therefore averaged vibration data alone may not replicate damage that is produced by transients. The recommended test schedule is also not representative of railcars equipped with high-speed magnetic levitation or airride suspension systems. CONCLUSION The study shows that the levels of rail vibration that were measured in rail shipments on major railway lines in Central Europe show higher levels in the vertical orientation than lateral and longitudinal orientations between 1-10 Hz. The levels above 10 Hz for vertical vibration are lower in the Central Europe rail transport as compared to North America and India. This is attributed to better rail track. The acceleration levels of random rail-car vibration during transport show the existence of a non-gaussian vibration. The recommended rail test method for measured rail lines in Central Europe has higher levels in the lower frequencies when compared to rail vibration test methods recommended by ASTM, but shows similarity to ISTA recommendations. The overall G rms in the frequency bandwidth of 1-100Hz was 66% compared to recommended ISTA test methods.

13 REFERENCES [1] Singh SP, Singh J, Joneson E. Measurement and Analysis of Global Truck, Rail and Parcel Shipments. 15 th International IAPRI World Conference on Packaging, International Association of Packaging Research Institutes, Tokyo, Japan, [2] Singh SP, Burgess G, Rojuckarin P. Test Protocol for Simulating Truck and Rail Vibration and Rail Impacts in Shipments of Automotive Engine Racks. Packaging Technology and Science 1995, 8(1), pp , DOI: /pts [3] Association of American Railroads. Study of the Shock and Vibration Environment in Boxcars. Damage Prevention Research Report No. DP 7-92, November [4] Rouillard V, Richmond R. A novel approach to analysing and simulating railcar shock and vibrations. Packaging Technology and Science 2007; 20(1), pp DOI: /pts.739 [5] Braunmiller U. Source Reduction by European Testing Schedules (SRETS) Final Report. Fraunhofer ICT: Pfinztal, Germany. 1999, 0European%20Testing%20Schedules.pdf [accessed 20 Febr 2016] [6] Singh SP, Sandhu APS, Singh J, Joneson E. Measurement and analysis of truck and rail shipping environment in India. Packaging Technology and Science 2007; 20(6): DOI: /pts.764 [7] Chonhenchob V, Singh SP, Singh J, Sittipod S, Swasdee D, Pratheepthinthong S. Measurement and analysis of truck and rail vibration level in Thailand. Packaging Technology and Science 2010; 23(2), pp DOI: /pts.881. [8] Singh SP, Saha K, Singh J, Sandhu APS. Measurement and analysis of vibration and temperature levels in global intermodal container shipments on truck, rail and ship. Packaging Technology and Science 2012; 25(3): pp DOI: /pts.968. [9] Singh SP, Antle J, Singh J, Topper E, Grewal G. Load Securement and Packaging Methods to Reduce Risk of Damage and Personal Injury for Cargo Freight in Truck, Container and Intermodal Shipments. Journal of Applied Packaging Research 2014, 6(1), DOI: /japr [10] Lamoreaux, GH, Trujillo AA, Magnuson DF. Truck and rail shock and vibration environments during normal transport. Sandia National Laboratories Transportation Technical Center, Albuquerque, NM (USA), [11] Wolfsteiner P, Werner B. Fatigue assessment of vibrating rail vehicle bogie components under non-gaussian random excitations using power spectral densities.

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15 [25] Young D, Gordon R, Cook B. Quantifying the Vibration Environment of a Small Parcel System. Proceedings of TransPack 97. IoPP: Herndon, VA, 1998, [26] Singh J, Singh PS, Joneson E. Measurement and analysis of US truck vibration for leaf spring and air ride suspensions, and development of tests to simulate these conditions. Packaging Technology and Science 2006; 19(6): pp , DOI: /pts.732. [27] Shires D. On the time compression (test acceleration) of broadband random vibration tests. Packaging Technology and Science 2011; 24(2), pp DOI: /pts.915