Measurement and Analysis of Vibration Levels for Truck Transport in Spain as a Function of Payload, Suspension and Speed

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1 PACKAGING TECHNOLOGY AND SCIENCE Packag. Technol. Sci. 2008; 21: Published online 19 November 2007 in Wiley InterScience ( Measurement and Analysis of Vibration Levels for Truck Transport in Spain as a Function of Payload, Suspension and Speed By Manuel-Alfredo Garcia-Romeu-Martinez, 1 * S. Paul Singh 2 and Vicente-Agustin Cloquell-Ballester 3 1 ITENE (Packaging, Transport and Logistics Research Institute), Valencia, Spain 2 School of Packaging, Michigan State University, East Lansing, MI, USA 3 Valencia University of Technology, Valencia, Spain The vibration levels that occur during transportation in vehicles are complex and play a significant role in the level of damage experienced by products when shipped. In the past decade, technology has allowed packaging engineers to measure and analyse the vibration levels in commercial shipments. Recent studies have measured vibration in shipping environments on a global basis to allow packaging designers to develop packaging to meet worldwide distribution challenges. The purpose of this study was to measure and develop simulation methods for truck transport in Spain. The study quantifies vibration characteristics in trucks as a function of speed, payload and suspension type. The shipments were instrumented with vibration data recorders to measure the vibration levels and a global position system to measure the truck speed. The recorders were mounted at the rear and front location of the trailer. Two different trucks, one with leaf spring suspension and the other with air ride suspension were studied using two different load conditions. The road surface was asphalt. The data is presented in the form of power spectral density that can be used to program electrohydraulic vibration tables using ASTM, ISTA and ISO vibration test methods. Results showed that the air ride vibration levels were lower than that of leaf spring suspension trailers. Overall, the vibration intensity was lower for both types of truck as compared with the levels measured in North America, China, India and Southeast Asia. Copyright 2007 John Wiley & Sons, Ltd. Received 18 January 2007; Revised 1 September 2007; Accepted 14 September 2007 KEY WORDS: packaging vibration; truck transport; suspensions; air ride; Spain INTRODUCTION Today truck transport is the most common way used to distribute products inside Spain, accounting for almost 90% of all tonnes-kilometres of manufactured goods. The required protective packaging systems have therefore been increased in order to reduce damage. It is important for packaging engineers to provide packaging for protection and at the same time reduce packaging based on environmental concerns. These contradictory and opposing factors, along with a need to deliver products to consumers, have increased the demand for the just-right or optimum; packaging so that both * Correspondence to: M.A. Garcia-Romeu-Martinez, ITENE (Packaging, Transport and Logistics Research Institute), Pol. Industrial D Obradors C/Soguers 2, 46110, Godella-Valencia (Spain). mgarciaromeu@itene.com Copyright 2007 John Wiley & Sons, Ltd.

2 Packaging Technology under-packaging and over-packaging are avoided. In order to develop optimum packaging it is important that packaging engineers know the expected physical and climatic hazards that packages will experience during shipping and handling. This information allows them to engineer the right amount of protective packaging needed. To help designers reduce cost, either by avoiding wasting packaging materials for over-packaging or avoiding damage from under-packaging, pre-shipment test methods are used to simulate the actual measured levels. During transportation, vibration is a continuously occurring phenomenon. In a lot of cases, failure is due to resonance, where there is maximum magnification resulting from the product being vibrated at its natural frequency. Continuous vibration motion can produce for instance, a mechanical failure, a fatigue failure, cosmetic damage, undesirable settling of contents, breaking up between solid/liquid suspensions, static charge buildup, bottle-closure cap back-off and leaking fluids and powdered products. Previous studies have been done in several geographic regions including North America, 1 5 China, 6,7 India 6,8 and Southeast Asia 6,9,10 to measure and quantify logistical channels used to deliver packaged goods. Studies from North America show that air ride suspensions have better performance and lower vibration levels than leaf spring trailers. 1,3 The leaf spring vibration levels are at least 50% higher than air ride vibration levels. 2 The lateral and longitudinal levels are extremely low compared with the vertical vibration levels. 4 The highest vibration levels in the leaf spring suspension occurred at 4 Hz in the vertical direction for truck shipments. 5 It is known that vibration levels depend on various parameters such as vehicle suspension, pressure and condition of the tires, who is driving and how fast, road roughness and potholes, load conditions of the vehicle, experimental set-up, and analysis procedure. Because of this, to compare the vibration levels obtained from various countries in different studies is not always appropriate. Nevertheless, it is an interesting aspect that the measured vertical vibration levels obtained by studies from China 7 and Thailand 9 show levels similar to those obtained in studies from North America. 1 5 Moreover, the measured vertical vibration levels are M.-A. GARCIA-ROMEU-MARTINEZ ET AL. significantly more severe in India than in North America. Furthermore, in a study from India, 8 vibration data shows excessive lateral and longitudinal movement. Another study from Thailand 10 shows that the laterite road conditions produce the most severe vibration, followed by concrete and asphalt roads. This study measured and analysed vibration levels that occur in truck transport in Spain and compared the results with those from other geographic regions. In addition, the results can be used to develop a vibration test method as a function of truck suspension, payload and truck speed. This study measured the truck transport levels on asphalt road surfaces because in Spain, 95% of covered road surface is asphalt and bituminous. EXPERIMENTAL DESIGN AND SET-UP In order to measure and quantify the vibration levels in truck transportation in Spain as a function of the truck suspension, payload and truck speed, the following equipment and instrumentation was used: 1. Vehicles: Truck semi-trailer, double-axle truck with air ride suspension and three-axle semi-trailer with air ride suspension [truck Renault Magnum 480 and semi-trailer Guillém G100 with 30 tonnes ( kg) payload capacity]. Figure 1 shows the air ride suspension trailer. Truck semi-trailer, double-axle truck with air ride suspension and three-axle semi-trailer with leaf spring suspension [truck Mercedes and semi-trailer Prim Ball with 30 tonnes ( kg) payload capacity]. Figure 2 shows the leaf spring suspension trailer. 2. Measurement equipment: Three vibration acceleration data recorders: Lansmont Corporation, (Ryan Ranch Research Park, 17 Mandeville Court, Monterey CA, 93940, USA) model two Saver 9 30 and one Saver 3 90 GPS + GSM data recorder: model TecnoGPS, AVL Inc. (Laipac Tech Europe SL, Pla de Salt no 14, Gerona, Spain) Copyright 2007 John Wiley & Sons, Ltd. 440 Packag. Technol. Sci. 2008; 21:

3 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN Packaging Technology Figure 1. Air ride suspension trailer. Figure 2. Leaf spring suspension trailer. Computer: Toshiba Inc. (Toshiba America Inc, 1251 Avenue of the Americas Suite, 4110 New York, NY USA), model Satellite L The acceleration data recorders were mounted at the rear and at the front of the trailer. They were both mounted in the centre of the wheel-span, between the two sidewalls of the trailer. The GPS + GSM data recorder was installed in both truck vehicles. The GPS + GSM aerial was mounted on the top of the truck vehicles in order to avoid interferences from the semi-trailer walls. Figure 3 shows exactly the installation of the data recorders and GPS + GSM aerial. Prior to shipment, the data recorders were configured with the following settings: 1. Signal-triggered data: Record time for each signal-triggered event: s Sampling rate: 1000 samples per second Signal pre-trigger: 20% Trigger level: 0.5 G Data retention mode: Max overwrite Memory allocation: 1225 events Full scale: 50 G Filter: 500 Hz 2. Time-triggered data: Record time for each signal-triggered event: seconds Sampling rate: 1000 samples per second Time-triggered sampling: 1 min Data retention mode: Max overwrite Memory allocation: 1225 events Full scale: 50 G Filter: 500 Hz 3. Speed measurement data: Time-triggered sampling: 1 min Time historic data recorder upload FTP sampling: 60 min Store data: Date (dd:mm:yyyy), time (HH: mm:ss), latitude, longitude, speed (km/h) Copyright 2007 John Wiley & Sons, Ltd. 441 Packag. Technol. Sci. 2008; 21:

4 Packaging Technology M.-A. GARCIA-ROMEU-MARTINEZ ET AL. Figure 3. Installation of data recorders and GPS + GSM aerial. Clock synchronized with acceleration data recorders. It is important to clarify the meaning of the recording parameters as the data recorders in general have different approaches and terminologies: Record time is the time period during which waveform data is taken for each triggered event. Signal pre-trigger is the amount of time that will be recorded prior to the instant that the trigger conditions are met, expressed as a percentage of the total record time. Time-triggered sampling in the Time-triggered data partition sets the time between the timetriggered events. Data retention mode determines how newly acquired events will be handled if the memory partition is full. Max overwrite, when Full replaces the smallest event already in the partition with the just-taken event; final data in the partition will contain the larger events, regardless of when they occurred. Memory allocation establishes the percent of total instrument memory allocated to each partition, and also the number of events (with the given set-up) that can be recorded. Full scale sets the maximum measurement range for the acquisition channel. Filter frequency sets the frequency of the lowpass filter to be applied to the acquisition channel. To prevent aliasing (the potential of a sampled data system to generate false information if the sampling rate is not significantly higher than the highest frequencies present in the measured signal), the filters should be set to 50% of the sampling rate or lower. Example: for a sampling rate of 1000 samples/s, the filter frequency should be set to 500 Hz or less, as this is the upper limit on the basis of the Nyquist Shannon criteria for Fourier analysis. In order to avoid aliasing problems in the power spectra results of this study, the data was filtered to 400 Hz after acquisition. Trigger level sets the acceleration value for the acquisition channel. If the acquisition channel meets its trigger criterion, a trigger state is generated and a signal-triggered data is stored. Also, it is important to make clear the significance of the signal- and time-triggered data. The data recorders obtain a number N S of signaltriggered events and a number N T of timertriggered events. Depending on which value of trigger level is configured, N S can be less, equal or Copyright 2007 John Wiley & Sons, Ltd. 442 Packag. Technol. Sci. 2008; 21:

5 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN Packaging Technology more than the N T value. As a result, the time-triggered events are usually vibration signals, but the signal-triggered events can be vibration signals or shocks. Because it is not statistically correct to introduce a bias in the distribution of the root mean square acceleration [RMS(G)], only those signal-triggered events that have an RMS(G) greater than the time-triggered events and which were not registered within a timer event should be included in the analysis. Four shipments were measured, two with each type of vehicle in order to measure four test configurations (two different payloads with two diferents suspension vehiches): 1. Shipment 1: Date: 11 July 2006 Departure: Moncada (Valencia) Arrival: Palau de Plegamans (Barcelona) Distance: 365 km Truck semi-trailer with leaf spring suspension Payload: 3000 kg 2. Shipment 2: Date: 12 July 2006 Departure: Sentmenat (Barcelona) Arrival: Moncada (Valencia) Distance: 365 km Truck semi-trailer with leaf spring suspension Payload: 0 kg 3. Shipment 3: Date: 13 July 2006 Departure: Yuncos (Toledo) Arrival: Aspe (Alicante) Distance: 387 km Truck semi-trailer with air ride suspension Payload: kg 4. Shipment 4: Date: 14 July 2006 Departure: Alcoy (Alicante) Arrival: Yuncos (Toledo) Distance: 387 km Truck semi-trailer with air ride suspension Payload: 3300 kg It must be noted that the measurements were done on actual shipments. Leaf spring suspensions and vehicles are used for almost all types of rugged and common products that do not require extra protection. Air ride suspension vehicles are used for products that are extremely sensitive and usually are lightweight. DATA AND RESULTS The data obtained from the recorders were analysed to determine the power density (PD) levels of vibration associated with a given frequency. A power spectral density (PSD) represents the plot of different PD levels plotted versus frequency. 11 The levels of acceleration amplitudes occur in a random manner over a range of frequencies when data is collected in a real truck shipment. This vibration acceleration data for the events acquired by the environmental data recorders were analysed as a function of frequency to calculate the average distribution of PD levels for selected events over a range of frequencies up to 400 Hz, i.e the PSD. As shown in Equations 1 and 2, the PSDs were obtained by subjecting each vibration acceleration record to the fast Fourier transform (FFT) and calculating their folded magnitude spectra G f,i. The FFT frequency resolution f = s f (FFTsize) 1 was Hz. The magnitude spectra were converted to the power spectra and then normalized to the PSD by dividing the power spectra by f to produce the PSD in G 2 /Hz. The average PSD plots shown in Figures 4 7, and Figures 8 11 are linear averages of PSDs for selected events. n n 1 1 Average( PSD) = PSD = G n i n = 1 2 f i= 1 f = 0, f, 2 f,..., FFT size f 2 G f, i f f, i f, 2 i FFT f { ait, 1, ait, 2,..., ait, FFT size } f = 2 FFT size (1) f FFT size,,,..., f =012 2 (2) i= 123,,,..., n where G f,i is the acceleration magnitude spectrum in g associated with a given frequency of the spectrum f and a selected event i, n is the number of selected events, FFTsize is the number of instants sampled for a given event, f = (sampling frequency) (FFTsize) 1 is the spectral frequency resolution and a i,t is the vibration acceleration data recorded in g for each selected event i at the time t. Copyright 2007 John Wiley & Sons, Ltd. 443 Packag. Technol. Sci. 2008; 21:

6 Packaging Technology M.-A. GARCIA-ROMEU-MARTINEZ ET AL. Figure 4. PSD of empty air ride trailer for each speed interval. Figure 5. PSD of loaded ( kg) air ride trailer for each speed interval. Copyright 2007 John Wiley & Sons, Ltd. 444 Packag. Technol. Sci. 2008; 21:

7 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN Packaging Technology Figure 6. PSD of empty leaf spring trailer for each speed interval. Figure 7. PSD of loaded (3000 kg) leaf spring trailer for each speed interval. Copyright 2007 John Wiley & Sons, Ltd. 445 Packag. Technol. Sci. 2008; 21:

8 Packaging Technology M.-A. GARCIA-ROMEU-MARTINEZ ET AL. Figure 8. PSD of empty air ride trailer for the highest and lowest events of the CDF. Figure 9. PSD of loaded ( kg) air ride trailer for the highest and lowest events of the CDF. Copyright 2007 John Wiley & Sons, Ltd. 446 Packag. Technol. Sci. 2008; 21:

9 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN Packaging Technology Figure 10. PSD of empty leaf spring trailer for the highest and lowest events of the CDF. Figure 11. PSD of loaded (3000 kg) leaf spring trailer for the highest and lowest events of the CDF. Copyright 2007 John Wiley & Sons, Ltd. 447 Packag. Technol. Sci. 2008; 21:

10 Packaging Technology M.-A. GARCIA-ROMEU-MARTINEZ ET AL. Figure 12. CDF of the RMS(G) for each speed interval. Figure 13. RMS(G) versus the type of suspension and the load. Figure 14. Peak(G) versus the type of suspension and the load. Copyright 2007 John Wiley & Sons, Ltd. 448 Packag. Technol. Sci. 2008; 21:

11 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN Packaging Technology Figure 15. Crest factor versus the type of suspension and the load. The spectra analysed with the described method can be used to compare levels of vibration and frequencies among varying geographical regions and logistical equipment. The raw data for a given shipment was separated based on truck speed. Data intercepts for stationary vehicle input were ignored so that they do not reduce actual vibration levels during motion. The data set analysed for each event included the RMS(G), the peak acceleration [Peak(G)], time, latitude, longitude and speed (km/h). The data were divided in three speed groups: 0 40 km/h, km/h and speeds greater than 70 km/h. The data for each speed group was then used to determine the cumulative distribution function (CDF) of the RMS(G) and fitted in a modified Weibull four-parameter distribution model (Figure 12). This function represents the percentage of the events that are below a certain level of RMS(G). The mean, median and standard deviation of the RMS(G) was obtained for each distribution. The PSD level shown in Figures 4 7 represents 100% of the CDF. This means that the PSD for each speed interval represents all events in that group. In addition, the PSD for the 25% of the highest events of the CDF and the remaining 75% of all events were used to create additional spectra to be used for test simulation methods (Figures 8 11). Comparing the mean and standard deviation of the RMS(G), Peak(G) and crest factor versus the type of suspension and the load, it showed that the unloaded leaf spring suspension revealed greater values than the loaded air ride suspension (Figures 13 15). Based on the data analysed, and comparing the mean and median values of the RMS(G) versus truck speed, it showed that the vibration level [RMS(G)] increased with vehicle speed (Figure 12). Similar results were obtained when the Peak(G) was compared with the speed (Figure 16). The crest factor decreased with an increase in speed due to the shorter response time of the suspension at higher vehicle speeds (Figure 17). Comparing the shape of the PSD for each speed, it was observed that the general shape was similar. It is therefore possible to develop a scaleable PSD as a function of trailer speed for the vehicle type, load, road surface and range of truck speeds tested in this study. The summarized results from this study are presented in the form of various PSDs for the range of load conditions and type of trailer used. These are shown in Figures The data show that the levels of RMS(G) of the air ride suspension of the truck are significantly lower than the levels of RMS(G) of the leaf spring suspension. The average RMS(G) for a 100% of the data recorded for a loaded air ride suspension trailer was G, and for an empty air ride trailer was G. Similarly, the RMS(G) for a loaded leaf spring trailer was G, and that for an empty leaf spring trailer was G. CONCLUSIONS 1. The data shows that the levels of RMS(G) of the air ride suspension of the truck are significantly lower than the levels of RMS(G) of the leaf spring suspension. The average RMS(G) for a 100% of the data recorder for the loaded air ride was G, for the unloaded air ride Copyright 2007 John Wiley & Sons, Ltd. 449 Packag. Technol. Sci. 2008; 21:

12 Packaging Technology M.-A. GARCIA-ROMEU-MARTINEZ ET AL. Figure 16. CDF of the Peak(G) for each speed interval. Figure 17. CDF of the crest factor for each speed interval. Copyright 2007 John Wiley & Sons, Ltd. 450 Packag. Technol. Sci. 2008; 21:

13 VIBRATION LEVELS FOR TRUCK TRANSPORT IN SPAIN was G, for the loaded leaf spring was G and for the unloaded leaf spring was G. 2. The predominant suspension frequency for air ride trailers was measured to be between Hz, and for the leaf spring to lie between 4 5 Hz. Package designers should avoid designing package systems whose natural frequencies lie between these ranges to avoid conditions of resonance during transportation. Moreover, it is interesting to notice a significantly high level of RMS(G) close to 100 Hz with the leaf spring suspension. 3. The measured levels for truck transport in Spain are lower than those measured in the USA in recent years on road surfaces that are both concrete and asphalt The measured levels in this study are also significantly lower than those used by existing ASTM, ISTA and ISO test methods for vibration testing during truck transportation. 5. It is proposed to use representative test spectra, as described in Figures 4 11, that represent actual vehicle and load conditions measured in this study for simulating truck transport in Spain. The test time can vary between 30 min to 6 h based on trip distance and the recommendations of vibration test methods such as the ASTM D ACKNOWLEDGEMENTS We are grateful to the managers of Salvaplast (Salvador Sebastia) and Romavesan (Atanasio Sanchez Olaeta and Antonio Ocaña Caballero), to their truck drivers and to Ajelandro Marquez Montero. We would also like to acknowledge professors Michael Sek and Vincent Rouillard, from Victoria University, Australia, for their specific comments during the development of the study. The equipment used in this study was provided by the ITENE (Packaging, Transport and Logistics Research Institute, Spain), and we thank Javier Zabaleta Meri, general manager, for allowing us access to this. Packaging Technology REFERENCES 1. Singh SP, Marcondes J. Vibration levels in commercial truck shipments as a function of suspension and payload. J Test. Eval. 1992; 20(6): Pierce C, Singh SP, Burgess G. A comparison of leaf spring to air cushion trailer suspensions in the transportation environment. Int. J. Packag. Technol. Sci. 1992; 5(1): Singh SP, Joneson E, Singh J. Measurement and analysis of US truck vibration for leaf spring and air ride suspensions, and development of tests to simulate these conditions. Int. J. Packag. Technol. Sci. 2006; 19(6): Singh SP, Antle J, Burgess G. Comparison between lateral, longitudinal and vertical vibration levels in commercial truck shipments. Int. J. Packag. Technol. Sci. 1992; 5(2): Singh SP, Burgess G, Rojnuckarin P. Test protocol for simulating truck and rail vibration and rail impacts in shipments of automotive engine racks. Int. J. Packag. Technol. Sci. 1995; 8(1): Singh SP, Sandhu A, Singh J, Joneson E. Measurement and analysis of global truck, rail and parcel shipments. Proceedings of 15th IAPRI World Conference on Packaging. The Society of Packaging Science and Technology, Japan, 2006; Yuan S, Dejian Z, Xiangying Z et al. Data acquisition for distribution environment in the region of south-central of China. Proceedings of 15th IAPRI World Conference on Packaging. The Society of Packaging Science and Technology, Japan, 2006; Singh SP, Sandhu APS, Singh J, Joneson E. Measurement and analysis of truck and rail shipping environment in India.; Packaging Technology Chonhenchob V, Sittipod S, Pratheepthinthong S, Rachtanapun P, Singh SP. Measurement and analysis of distribution environment in Thailand: the case of produce distribution. Proceedings of 15th IAPRI World Conference on Packaging. The Society of Packaging Science and Technology, Japan, 2006; Jarimopas B, Singh SP, Saengni W. Measurement and analysis of truck transport vibration levels and damage to packaged tangerines during transit. Int. J. Packag. Technol. Sci. 2005; 18(4): Randall RB. Frequency Analysis. Bruel & Kjaer: Naerum (Denmark), Annual Book of ASTM Standards. Vol American Society of Testing and Materials: West Conshohocken, PA, Copyright 2007 John Wiley & Sons, Ltd. 451 Packag. Technol. Sci. 2008; 21: