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Measurement and determination of the absorbed impact energy for conveyor belts of various structures under impact loading
Accepted Manuscript Measurement and Determination of the Absorbed Impact Energy for Conveyor Belts of Various Structures under Impact Loading Anna Grincova, Miriam Andrejiova, Daniela Marasova, Samer Khouri PII: DOI: Reference:
S0263-2241(18)30831-5 https://doi.org/10.1016/j.measurement.2018.09.003 MEASUR 5861
To appear in:
Measurement
Received Date: Revised Date: Accepted Date:
25 July 2017 17 August 2018 1 September 2018
Please cite this article as: A. Grincova, M. Andrejiova, D. Marasova, S. Khouri, Measurement and Determination of the Absorbed Impact Energy for Conveyor Belts of Various Structures under Impact Loading, Measurement (2018), doi: https://doi.org/10.1016/j.measurement.2018.09.003
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Measurement and Determination of the Absorbed Impact Energy for Conveyor Belts of Various Structures under Impact Loading Anna Grincovaa, Miriam Andrejiovab, Daniela Marasovac, Samer Khouric a
Faculty of Electrical Engineering and Informatics, Technical University of Kosice, Letna 9, 042 00 Kosice, Slovak Republic b Faculty of Mechanical Engineering, Technical University of Kosice, Letna 9, 042 00 Kosice, Slovak Republic c Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University of Kosice, Park Komenskeho 14, 042 00 Kosice, Slovak Republic
Abstract The effect of impact loading at the transfer point is often manifested by mechanical damage to a conveyor belt. To describe the phenomena related to the conveyor belt damage caused by the impact of the material, it is important to monitor the amount of the absorbed impact energy. Therefore, the focus of the present article is on the identification of the effect of the conveyor belt’s structure (textile or steel conveyor belt carcass), as well as the strength, the material’s drop height and the drop weight on the relative amount of impact energy absorbed by a conveyor belt. The result of the article is determining the capabilities of different conveyer belts through the monitoring and the identification of the relationship between the relative amount of the absorbed energy and the selected parameters. Keywords: rubber-textile conveyor belt, steel-cord conveyor belt, puncture resistance, absorbed energy
1. Introduction A rubber conveyor belt with a textile or steel carcass is the most vulnerable structural element in a belt conveyor. At the point of impact of the transported material onto a conveyor belt, the extreme drop heights and sharp edges of the material may result in damage to the cover layers and to conveyor belt punctures [1]. In particular, this regards stones and other bulky materials that cause substantial damage to the machine belts on the excavator which is not detected, and is then transferred downstream to the substations of the belt conveyors and the spreader, where they generate the associated maintenance costs. In a study by Borchart et al. [2] a sensor-based stone detection system was developed on the one hand, and an automatic bulk material discharge system was created on the other hand, with the aim of eliminating such damage to the conveyor belts. In addition to causing damage to the most expensive element of a belt conveyor, the transportation of materials by belt conveyors is also an energy-intensive industrial application [3,4]. The cost-efficient operation of belt conveyors, just like any other application, requires using accurate plant models with optimised algorithms. When creating such models, the energy model should indicate the amounts of materials that can be transported by the belt conveyors to optimise the costs of the energy. This was determined by Mathaba [5], who assessed the optimal scheduling of conveyor belts (CB) under the Critical Peak Pricing (CPP)
tariff, using the Model Predictive Control (MPC) and the effects of the MPC and the storage size on the load profile, as well as the resulting energy cost. Authors Ristić and Jeftenić [6] implemented the fuzzy control to improve the energy efficiency of variable speed bulk material transportation. The current energy models include models by authors [7, 8, 9]. Conveyor belt damage generally occurs as a result of a number of factors. The most important damage results from insufficient puncture resistance of the conveyor belt due to an inappropriate conveyor belt structure, a wrongly-selected support system at the impact site, the wrong chute structure, and primarily from a too high drop height which means that the conveyor belt is not able to absorb the impact energy. The effects of various factors on the likelihood of a conveyor belt puncture have been examined by several authors [10,11,12]. For example, Honus [10] analysed the occurrence of conveyor belt failures at the impact site where the materials lands. They studied how the number of conveyor carrying the idlers can affect the belt’s compressive stress at the impact site. The creation of energy models, or FEM models [13], is only possible if they are based on laboratory [14] or operational measurements [15]. In many cases, the measurement results are used as input data for the creation of models, or the results of the models are often verified with the results obtained by applying various measurement methods [16, 17, 18]. The FEM method was also used in the monitoring of conveyor belt damage and in the determination of the conditions in which damage to the cover layer of the conveyor belt occurs [13]. Bajda [14] presented the results of tests which allow defining the influence of the conveyor belt design on the belt’s wear and tear, in particular with regard to punctures. In this test, a belt’s puncture resistance was determined by using a method based on calculating the mean impact energy and the critical energy. The authors of another study, Bajda, Blazej and Jurdziak [15], described a new tool in determining a belt’s resistance to punctures. Their research was carried out with a newly-developed high resolution magnetic diagnostic device intended for the assessment of the condition of steel cord conveyor belts. In addition to monitoring the belts during their use on the conveyors, this device can be used as a new tool in belt puncture investigations. Qiao et al. [16] monitored the longitudinal tearing of conveyor belts while applying the method of Integrative Binocular Vision Detection (IBVD). The longitudinal tears on conveyor belts were also investigated by Binchao et al. [17]. In order to detect the longitudinal tears, they applied the method of Dual Band Infrared Detection (DBID) that is based on a combination of mid-infrared and long infrared vision. The dynamic deformations of the conveyor belts were tested using a specifically engineered testing machine, by the authors of the work and the results were described in their paper [18]. In this case, the authors compared the experimental approach based on the photogrammetry technique with a model created by the FEM and DEM methods. Authors Ilic and Wheeler [11] compared the results of laboratory experiments and simulation of interactions between the number of bulk solid materials and the belt sag ratios, where the outcomes led to improved methods of calculating the optimal loads on conveyor idler rolls and increasing the accuracy in predicting the energy loss due to the bulk solid flexure. Zhang [12] describe the options for improving the energy efficiency of belt conveyors that can be achieved at the level of the equipment and the operation processes. An analytical energy model was designed in compliance with the ISO 5048 standard. Off-line and an on-line parameter estimation schemes were also applied to identify the new energy model. Furthermore, a parametric energy model for energy management is proposed by Mathaba [5] for long belt conveyors. Another group of experts examined the energy losses occurring during the transportation of materials by belt conveyor systems. This was determined as a function of: the CB structure [19, 20] and the cover layer category [21], as well as the support system structure [22,23] and the belt conveyor drive [18]. The authors of the paper [20] dealt with the
foundation and the parameter identification of a rubber belt non-linear restoration model, while applying the second-order Fourier series. The results of the neural network were then tested by experiments. These results may serve as a theoretical basis for the development of an energy-saving rubber belt. Chen [19] simulated the cores of rubber belts with wire ropes, where the properties of pressure resistance in the St2000 type of conveyor belt were researched. The authors created a simulation to serve as the basis for calculating the energy dissipation of rubber conveyor belts. Qiu and Chai [22] analysed the energy losses in conveyor systems caused by the indentation of the idler into the rubber cover of the belt, and they proposed a model which will be useful for the designing and optimisation of the energy consumption in conveyor systems. In the model, in addition to the energy losses with respect to the inlet provisions, accelerations and the intake, as well as the resistance of the pulleys, scrapers and the bending resistance of the rubber belt, we have to add other factors, according to Brands [23]. This includes the resistance per metre, as mentioned below, which has a greater influence the longer the belt is, and the value of the impact load that runs parallel to the results for the double idler configuration (with a slight deviation) and that is proportional to the length of the product flight. Halepoto [24] proposed a mathematical model for an energy-efficient conveyor system with the variable speed drive (VSD). The proposed system would optimally switch a conveyor system to the on/idle/off status to minimise the energy consumption of the conveyor belt. An examination of the friction and surface energy properties of belt conveyors was dealt with by [21]. In this case, the friction at the interface of the raw material and the belt cover layer was tested using the standard inclined-plane method, and the adhesion and stickiness were evaluated by determining the surface-free energies of the belt cover layer and the wood-plastic composites (WPCs) at temperatures of 23 and 100 °C. On the basis of these measurements, the authors investigated the key aspects of selecting the belt cover material and proposed a conveyor belt configuration for a prototype post-extrusion process line. 2. Material and methods 2.1. Problem formulation The impact of transported material onto a conveyor belt often causes damage that is classified as a puncture. This kind of damage simultaneously affects the top cover layer, the carcass and the bottom cover layer of a conveyor belt. This kind of damage occurs when a conveyor belt’s capacity to absorb the impact energy of the material falling onto it is surpassed. In this article, we will examine how much energy a conveyor belt is able to absorb before such damage will occur. The amount of the absorbed energy will be expressed in relative terms, or as a percentage. The absorption of the impact energy also partially represents some damage to the internal and external structure of a conveyor belt. 2.2. Conveyor belts There are several types of belts that are currently used on conveyer systems. From a constructional point of view, the belt categorisation depends on the carcass type, the covering method, the material covering the carcass, the surface finishing, etc. The basic structural elements of a conveyor belt include the carcass (textile, steel) and the cover layers, the thickness of which is affected by the properties of the material being transported.
Fig. 1 Rubber-textile conveyor belt
Fig. 2 Steel-cord conveyor belt
The most frequently-used conveyor belts include rubber-textile (Fig. 1) and steel-cord conveyor belts (Fig. 2). A carcass of a rubber-textile conveyor belt consists of one or more textile plies while the carcass is reinforced with various types of natural or synthetic fibres. The carcass of steel-cord conveyor belt consists of steel cords in various diameters and strengths. 2.3. Testing device The experimental measurements were carried out using a testing device intended for testing the puncture resistance of conveyer belts (Fig. 3). A more detailed specification of the device is described in the paper [25].
Fig. 3 Testing device scheme (1 – skeleton, 2 – sliding of drop hammer, 3 – drop hammer, 4 – impactor, 5 – hydraulic jaws)
The testing machine comprises the PP065 electronics. It records the data obtained during the measurement (time, drop hammer height, and the stretching and impact forces). In this experiment, we were interested in the time [ms] and the height [mm]. The object’s impact heights were measured using the Banner LT3 laser sensor. The precision of the measurements of the distance from the LT3 laser sensor depended on the measured distance. The maximum measuring range of the LT3 sensor was 5m. The lowest
measuring precision, at the refresh frequency of 1 ms (Fast), was determined by the value of the (resolution/repeatability) of individual measurements, as stated in the technical specification as 5 mm (Fig. 4). The value of 5 mm can therefore be regarded as the achievable measurement precision. The accuracy of the measurements of the distance from the LT3 laser sensor was determined by the linearity error (Fig. 5), which also depended on the measured distance. The worse linearity defect was approximately 15 mm at a measured distance of 1.2 m. The reflection of the object was measured within the measuring range of 4 m, where the maximum linearity error was+/- 3 mm, which can be regarded as the achievable measurement accuracy.
Fig. 4 LT3 resolution
Fig. 5 LT3 linearity (typical)
The experiment was carried out using a roller support system, where the impact of the material was directed between the rollers (Fig. 6). The distance between the roller axes was 0.16 m. During the experiments, the weights of the falling materials were simulated in trials ranging from 50 to 90 kg, with 10 kg increments. The drop heights were chosen within heights ranging from 1 to 2.2 m, with 0.2 m increments, while the specimens of rubber-textile conveyor belts used in the experiment were of P1250 and P2500 types (with four component textile-polyamide plies) and the specimens of the steel-cord conveyor belts were of ST1250 and ST2500 types. In the above designations, “P” means a polyamide textile layer; “ST” means steel cords; and the numbers 2500 and 1250 express the conveyor belt rigidities [N.mm-1]. Every specimen was the same size: 1400 x 160 mm. The method of the specimen preparation is described in [26]. All of the specimens were stretched using the force recommended by the conveyor belt manufacturer (1/10 of the belt strength for a millimetre of the width). Measurements of the impact and of the stretching forces were then carried out for each test specimen. The testing was carried out using a pyramidal impactor (Fig. 7), which simulated the impact of a sharp-edged material.
Fig. 6 Support system
Fig. 7 Shape of the impactor used
3. Theory/calculation 3.1. Physical fundamentals The amount of impact energy caused by the impact of the material onto a conveyor belt may be expressed as the amount of kinetic energy Ek of an object with the weight m , with the velocity right before the impact v . If we neglect the impact of the environment (environmental resistance) and apply the law of the conservation of mechanical energy, then the amount of kinetic energy Ek of the object right before the impact Ek
1 mv 2 2
(1)
can be substituted by the amount of the potential energy E p E p mgh
(2)
of the object with the weight m , falling from the height h , where g 9.81 m.s-2 is the gravitational acceleration. The following applies: Ek
1 mv 2 mgh E p . 2
(3)
A conveyor belt structure and the properties of the material from which the conveyor belt is manufactured will result in a subsequent bouncing of the material off the conveyor belt. If we neglect the impact of the environment and we know the height to which the material bounces, we can use then the difference in the potential energies of the object before the impact and after the impact to identify how much energy the conveyor belt was able to absorb. This principle is represented in Fig. 8.
Fig. 8 Determination of absorbed energy By applying this method, we can determine the absolute value of the amount of the absorbed energy E absorbed
Eabsorbed Ep 1 Ep 2
(4)
Considering the number of executed measurements, it is more beneficial to identify the amount of the absorbed energy in a comprehensive manner, by using a relative expression (5) or a percentage (6)
E relat
E relat
Ep 1 Ep 2
(5)
Ep 1 Ep 1 Ep 2 Ep 1
100 %
(6)
When we apply this method, we can determine what portion (percentage) of the initial impact energy the conveyor belt is able to absorb. This portion of the initial impact energy can be further designated as the relative amount of the absorbed energy. In the relation (2) used for the calculation of the energy E p , the weight m and the gravitational acceleration g are constants. Therefore, after the modification of the relation (5) we will get
E relat
mgh 1 mgh 2 mgh 1
h 1 h2 h1
.
(7)
It is evident that if we express the relative amount of the absorbed energy using the relation (7) at a random drop height, we will always reach the theoretical maximum value 1.
3.2. Model formation The relation between the explained (dependent) variable Y and the k-explanatory (independent) variables X j , where j 1, 2, , k , can be expressed by the following mathematical model:
Y f X, β ε ,
(8)
where Y is the vector of the values of the explained variable Y , X is the matrix of the values of explanatory variables X j , where j 1, 2, , k , β is the vector of the model parameters, f X, β is the regression function, and ε is the vector of the accidental errors. In our case, we will consider the linear regression model in the following matrix form:
Y Xβ ε .
(9)
The verification of the statistical significance of the model was carried out using the F-test of the statistical significance. The statistical significance of the regression model parameters was verified by applying the test of the statistical significance of the regression parameter. The measure of strength of the relationship between the variable Y and the joint effect of the k variables is expressed by the multiple coefficient of determination R2.
4. Result The experimental tests were carried out with two types of rubber-textile conveyor belts, P1250 and P2500, and for two types of steel-cord conveyor belts, ST1250 and ST2500. The input parameters were the weight m of the falling material and the drop height h . The objectives of the experimental research were to: identify the relative amount of the absorbed energy for both conveyor belt types (P, ST) and to determine the impact of the parameters (conveyor belt strength, structure, drop weight, drop height) on the relative amount of the absorbed energy; and determine a model of the relationship between the relative amount of the absorbed energy and the selected parameters. The real data of the measured heights with the time when the drop hammer impacted the conveyor belt (with a certain weight and at a certain drop height) is shown in Fig. 9 and Fig. 10. The graphs were created for all four tested conveyor belt types. In the case of the steel-cord conveyer belt, a puncture occurred with the drop hammer of 90 kg and a drop height of 1.8 m or higher.
Fig. 9 Drop hammer’s impact curve (rubber-textile conveyor belt)
Fig. 10 Drop hammer’s impact curve (steel-cord conveyer belt) In the next part, we monitored only the first and the second impact of the drop hammer onto the conveyor belt.
4.1 Determination of the relative amount of absorbed energy and the impact of the selected parameters Fig. 11 and Fig. 12 (resp. Fig. 13 and Fig. 14) illustrate examples of the relative amount of absorbed energy after the first impact (resp. the second impact) of the drop hammer onto the conveyor belt at all the tested drop weights, where only four drop heights are used for the purpose of clarity. The relative amount of absorbed energy was determined using the relation (7).
Fig. 11 Relative amount of absorbed energy (first impact, rubber-textile conveyor belt)
Fig. 12 Relative amount of absorbed energy (first impact, steel-cord conveyor belt)
Fig. 13 Relative amount of absorbed energy (second impact, rubber-textile conveyor belt)
Fig. 14 Relative amount of absorbed energy (second impact, steel-cord conveyer belt) At each drop weight, falls from seven different drop heights were simulated. The differences between the obtained relative amounts of the absorbed energy were minimal. The mean values of the relative amounts of absorbed energy after the first and second impacts of the drop hammer onto the conveyor belt are indicated in Table 1.
Table 1 Relative amount of absorbed energy – interval within the whole range of the drop hammer heights 50 kg 60 kg 70 kg 80 kg 90 kg P2500 First impact 0.51 0.46 0.45 0.42 0.41 Second 0.49 0.45 0.43 0.41 0.39 impact P1250 First impact 0.67 0.67 0.65 0.65 0.64 Second 0.71 0.66 0.65 0.63 0.61 impact ST2500 First impact 0.78 0.75 0.75 0.74 0.74 Second 0.83 0.77 0.75 0.72 0.71 impact ST1250 First impact 0.80 0.79 0.78 0.78 0.78 Second 0.90 0.87 0.88 0.78 0.80 impact
The impact of the strength of the belt on the relative amount of absorbed impact energy was significant in the case of the rubber-textile conveyor belts (Fig. 9). At a strength of 2500 N.mm-1, the rubber-textile conveyor belt was able to absorb after the first impact of the drop hammer approximately 40-50% of the impact energy. At a strength of 1250 N.mm-1, the belt was able to absorb as much as 60-70% of the impact energy. However, the impact of the strength on the relative amount of absorbed impact energy in the case of the steel-cord conveyor belts was negligible (Fig. 10). At a strength of 2500 N.mm-1, the steel-cord conveyor belt was able to absorb approximately 70-85% of the impact energy; while at a strength of 1250 N.mm-1, the belt was able to absorb approximately 73-85% of the impact energy. These values were comparable for both belts. The results for the second impact of the drop hammer onto the conveyor belt were similar (Fig. 11, Fig.12). The impact of the conveyor belt structure on the relative amount of the absorbed impact energy is evident: the rubber-textile conveyor belts with determined properties were able to absorb a smaller relative amount of impact energy than the steel-cord conveyor belts with the same properties. On the basis of an analysis of all the resulting values, we can state that with a growing drop weight (and also with a growing drop height) the relative amount of the absorbed impact energy decreases in the majority of cases. 4.2. Creation of a model of the relationship between the relative amount of absorbed energy and the selected parameters We will consider the following conventional linear regression model
k
Y 0 j X j ,
(10)
j 1
where 0 and j for j 1, 2,, k are the model parameters, Y is the observed value of the explained variable Y , X j , j 1, 2, , k , are the k-explanatory (independent) variables, and is the accidental error. First, we monitored the impact of the weight of the falling material m and the drop height h on the relative amount of the absorbed energy during the first and the second impact of the drop hammer onto the conveyor belt. For all the examined conveyor belts, the point estimate of the regression model was as follows Y b0 b1 X 1 b2 X 2 or Erelat b0 b1h b2 m ,
(11)
where b0 , b1 and b2 are the point estimates of the model parameters, whereas Y E relat , X 1 h , and X 2 m . The point estimates of the parameters, their statistical significance, the significance of the model and the coefficient of determination are listed in Table 2 and Table 3. Table 2 Point estimate of the model parameters – first impact of the drop hammer (α=0.05) b0 P2500 value p-value P1250 value p-value ST2500 value p-value ST1250 value p-value
b1
0.611 0.011 <0.0001 0.018
b2
R2
p-value
-0.003 0.911 <0.0001
<<0.0001
0.836 -0.026 -0.002 0.924 <0.0001 <0.0001 <0.0001
<<0.0001
0.986 -0.033 -0.003 0.933 <0.0001 <0.0001 <0.0001
<<0.0001
1.022 -0.046 -0.003 0.935 <0.0001 <0.0001 <0.0001
<<0.0001
Table 3 Point estimate of the model parameters – second impact of the drop hammer (α=0.05) b0 P2500 value p-value P1250 value p-value ST2500 value
b1
b2
R2
p-value
0.571 0.014 -0.002 0.944 <0.0001 <0.0001 <0.0001
<<0.0001
0.827 -0.013 <0.0001 0.014
-0.002 0.890 <0.0001
<<0.0001
0.912
-0.003
<<0.0001
0.020
0.851
p-value ST1250 value p-value
<0.0001 0.009
<0.0001
1.112 -0.023 <0.0001 0.027
-0.003 0.884 <0.0001
<<0.0001
The regression models and the model parameters were statistically significant in all the cases (p-value<α). The regression model, expressing the relationship between the relative absorption of the potential energy and the drop hammer weight (m), the drop height (h), the conveyor belt type (rubber-textile, steel-cord), and the conveyor belt strength (S) is as follows: Erelat b0 b1h b2 m b3CB b4 S .
(12)
The CB variable is a dichotomous qualitative variable, transformed into a numerical variable with a permutation of 1 for a rubber-textile conveyor belt and with a permutation of 0 for a steel-cord conveyor belt. The S variable represents the conveyor belt strength [N.mm-1]. The point estimates of the parameters, the significance of the model and the coefficient of determination are listed in Table 4. It was found that the regression models and the model parameters were statistically significant. Table 4 Point estimate of the model parameters (α=0.05) b0 First impact value 1.121 Second impact value 1.196
b1
b2
b3
b4
R2
p-value
-0.012
-0.002
-0.216
-0.0001
0.887
<<0.0001
-0.012
-0.002
-0.237
-0.0001
0.903
<<0.0001
5. Conclusions The issues related to increasing the technical and economic levels of belt conveyor systems are associated with increasing the service life and the operational reliability of the conveyor belts, as well as improving the technology of the belt conveyor systems. This article present information regarding the absorption of the impact energy by conveyor belts, depending on their basic technical parameters – in particular, with regard to the CB strength and the carcass. The article also points out the optimal chute structures, with the optimal drop height at which a conveyor belt puncture does not occur. Drop hammers were designed to fall onto the conveyor belt specimens in the experiment, in order to simulate the impact of real materials onto the conveyor belts. The experiments simulated various situations (impacts of materials of various weights, as well as those dropped from various heights). The objective was to identify the ability of a conveyor belt to absorb the energy of the falling material without causing a belt puncture. Within the scope of our experimental research, we came to the following conclusions: The drop hammer behaviour over time is specific for a particular conveyor belt type. Steel-cord conveyor belts dampen the impact of the falling material faster than rubbertextile conveyor belts.
The impact of the strength on the relative amount of the absorbed impact energy was only observed with rubber-textile conveyor belts. Belts of this kind are able, at a strength of 2500 N.mm-1, to absorb approximately 40-50% of the impact energy after the first impact of the drop hammer, and at a strength of 1250 N.mm-1 the belts are able to absorb as much as 60-70% of the impact energy. This means that with belts of a higher strength, the internal damage is smaller than with belts of a lower strength. In the case of steel-cord conveyor belts, at a strength of 2500 N.mm-1, the belt is able to absorb approximately 70-85% of the impact energy after the first impact of the drop hammer; and at a strength of 1250 N.mm-1 the belt is able to absorb almost the same amount, i.e. 73-85% of the impact energy. Therefore, with this type of belt, the strength does not have a strong impact on the relative amount of the absorbed energy. The impact of the conveyor belt structure on the relative amount of absorbed impact energy is significant. Specifically, rubber-textile conveyor belts absorb a smaller relative amount of impact energy than steel-cord conveyor belts. In the majority of cases, with a growing drop weight (and also with a growing drop height), the relative amount of the absorbed impact energy decreases.
With regard to four various types of conveyor belts that were used in the experiment we can state the following: in the case of rubber-textile conveyor belts, the internal damage is smaller; thus, they are more resistant to serious damage, such as punctures. Therefore, it can be concluded that rubber-textile conveyor belts are more appropriate for operations with the increased occurrence of this particular kind of damage. The results of this experimental research for the purpose of determining the ability of a conveyor belt to absorb the impact energy indicate that there is the potential for further research, in terms of the utilisation of new reinforcement materials resistant to punctures, which have not yet been subjected to more detailed research. Acknowledgements This article is the result of the projects implementation KEGA 009TUKE-4/2016 Design of the specialized training concept oriented to the development of experimental skills within the frame of education in the study branch logistics and project VEGA 1/0577/17 Transfer of knowledge from laboratory experiments and mathematical models in the creation of a knowledge based system for assessing the quality environmentally friendly conveyor belts.
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Highlights Experimental measurements of impact loading of various conveyor belt structures Determination of the relative absorbed energy by a conveyor belt Relationship between the relative absorbed energy and some impact parameters
S0263-2241(18)30831-5 https://doi.org/10.1016/j.measurement.2018.09.003 MEASUR 5861
To appear in:
Measurement
Received Date: Revised Date: Accepted Date:
25 July 2017 17 August 2018 1 September 2018
Please cite this article as: A. Grincova, M. Andrejiova, D. Marasova, S. Khouri, Measurement and Determination of the Absorbed Impact Energy for Conveyor Belts of Various Structures under Impact Loading, Measurement (2018), doi: https://doi.org/10.1016/j.measurement.2018.09.003
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Measurement and Determination of the Absorbed Impact Energy for Conveyor Belts of Various Structures under Impact Loading Anna Grincovaa, Miriam Andrejiovab, Daniela Marasovac, Samer Khouric a
Faculty of Electrical Engineering and Informatics, Technical University of Kosice, Letna 9, 042 00 Kosice, Slovak Republic b Faculty of Mechanical Engineering, Technical University of Kosice, Letna 9, 042 00 Kosice, Slovak Republic c Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University of Kosice, Park Komenskeho 14, 042 00 Kosice, Slovak Republic
Abstract The effect of impact loading at the transfer point is often manifested by mechanical damage to a conveyor belt. To describe the phenomena related to the conveyor belt damage caused by the impact of the material, it is important to monitor the amount of the absorbed impact energy. Therefore, the focus of the present article is on the identification of the effect of the conveyor belt’s structure (textile or steel conveyor belt carcass), as well as the strength, the material’s drop height and the drop weight on the relative amount of impact energy absorbed by a conveyor belt. The result of the article is determining the capabilities of different conveyer belts through the monitoring and the identification of the relationship between the relative amount of the absorbed energy and the selected parameters. Keywords: rubber-textile conveyor belt, steel-cord conveyor belt, puncture resistance, absorbed energy
1. Introduction A rubber conveyor belt with a textile or steel carcass is the most vulnerable structural element in a belt conveyor. At the point of impact of the transported material onto a conveyor belt, the extreme drop heights and sharp edges of the material may result in damage to the cover layers and to conveyor belt punctures [1]. In particular, this regards stones and other bulky materials that cause substantial damage to the machine belts on the excavator which is not detected, and is then transferred downstream to the substations of the belt conveyors and the spreader, where they generate the associated maintenance costs. In a study by Borchart et al. [2] a sensor-based stone detection system was developed on the one hand, and an automatic bulk material discharge system was created on the other hand, with the aim of eliminating such damage to the conveyor belts. In addition to causing damage to the most expensive element of a belt conveyor, the transportation of materials by belt conveyors is also an energy-intensive industrial application [3,4]. The cost-efficient operation of belt conveyors, just like any other application, requires using accurate plant models with optimised algorithms. When creating such models, the energy model should indicate the amounts of materials that can be transported by the belt conveyors to optimise the costs of the energy. This was determined by Mathaba [5], who assessed the optimal scheduling of conveyor belts (CB) under the Critical Peak Pricing (CPP)
tariff, using the Model Predictive Control (MPC) and the effects of the MPC and the storage size on the load profile, as well as the resulting energy cost. Authors Ristić and Jeftenić [6] implemented the fuzzy control to improve the energy efficiency of variable speed bulk material transportation. The current energy models include models by authors [7, 8, 9]. Conveyor belt damage generally occurs as a result of a number of factors. The most important damage results from insufficient puncture resistance of the conveyor belt due to an inappropriate conveyor belt structure, a wrongly-selected support system at the impact site, the wrong chute structure, and primarily from a too high drop height which means that the conveyor belt is not able to absorb the impact energy. The effects of various factors on the likelihood of a conveyor belt puncture have been examined by several authors [10,11,12]. For example, Honus [10] analysed the occurrence of conveyor belt failures at the impact site where the materials lands. They studied how the number of conveyor carrying the idlers can affect the belt’s compressive stress at the impact site. The creation of energy models, or FEM models [13], is only possible if they are based on laboratory [14] or operational measurements [15]. In many cases, the measurement results are used as input data for the creation of models, or the results of the models are often verified with the results obtained by applying various measurement methods [16, 17, 18]. The FEM method was also used in the monitoring of conveyor belt damage and in the determination of the conditions in which damage to the cover layer of the conveyor belt occurs [13]. Bajda [14] presented the results of tests which allow defining the influence of the conveyor belt design on the belt’s wear and tear, in particular with regard to punctures. In this test, a belt’s puncture resistance was determined by using a method based on calculating the mean impact energy and the critical energy. The authors of another study, Bajda, Blazej and Jurdziak [15], described a new tool in determining a belt’s resistance to punctures. Their research was carried out with a newly-developed high resolution magnetic diagnostic device intended for the assessment of the condition of steel cord conveyor belts. In addition to monitoring the belts during their use on the conveyors, this device can be used as a new tool in belt puncture investigations. Qiao et al. [16] monitored the longitudinal tearing of conveyor belts while applying the method of Integrative Binocular Vision Detection (IBVD). The longitudinal tears on conveyor belts were also investigated by Binchao et al. [17]. In order to detect the longitudinal tears, they applied the method of Dual Band Infrared Detection (DBID) that is based on a combination of mid-infrared and long infrared vision. The dynamic deformations of the conveyor belts were tested using a specifically engineered testing machine, by the authors of the work and the results were described in their paper [18]. In this case, the authors compared the experimental approach based on the photogrammetry technique with a model created by the FEM and DEM methods. Authors Ilic and Wheeler [11] compared the results of laboratory experiments and simulation of interactions between the number of bulk solid materials and the belt sag ratios, where the outcomes led to improved methods of calculating the optimal loads on conveyor idler rolls and increasing the accuracy in predicting the energy loss due to the bulk solid flexure. Zhang [12] describe the options for improving the energy efficiency of belt conveyors that can be achieved at the level of the equipment and the operation processes. An analytical energy model was designed in compliance with the ISO 5048 standard. Off-line and an on-line parameter estimation schemes were also applied to identify the new energy model. Furthermore, a parametric energy model for energy management is proposed by Mathaba [5] for long belt conveyors. Another group of experts examined the energy losses occurring during the transportation of materials by belt conveyor systems. This was determined as a function of: the CB structure [19, 20] and the cover layer category [21], as well as the support system structure [22,23] and the belt conveyor drive [18]. The authors of the paper [20] dealt with the
foundation and the parameter identification of a rubber belt non-linear restoration model, while applying the second-order Fourier series. The results of the neural network were then tested by experiments. These results may serve as a theoretical basis for the development of an energy-saving rubber belt. Chen [19] simulated the cores of rubber belts with wire ropes, where the properties of pressure resistance in the St2000 type of conveyor belt were researched. The authors created a simulation to serve as the basis for calculating the energy dissipation of rubber conveyor belts. Qiu and Chai [22] analysed the energy losses in conveyor systems caused by the indentation of the idler into the rubber cover of the belt, and they proposed a model which will be useful for the designing and optimisation of the energy consumption in conveyor systems. In the model, in addition to the energy losses with respect to the inlet provisions, accelerations and the intake, as well as the resistance of the pulleys, scrapers and the bending resistance of the rubber belt, we have to add other factors, according to Brands [23]. This includes the resistance per metre, as mentioned below, which has a greater influence the longer the belt is, and the value of the impact load that runs parallel to the results for the double idler configuration (with a slight deviation) and that is proportional to the length of the product flight. Halepoto [24] proposed a mathematical model for an energy-efficient conveyor system with the variable speed drive (VSD). The proposed system would optimally switch a conveyor system to the on/idle/off status to minimise the energy consumption of the conveyor belt. An examination of the friction and surface energy properties of belt conveyors was dealt with by [21]. In this case, the friction at the interface of the raw material and the belt cover layer was tested using the standard inclined-plane method, and the adhesion and stickiness were evaluated by determining the surface-free energies of the belt cover layer and the wood-plastic composites (WPCs) at temperatures of 23 and 100 °C. On the basis of these measurements, the authors investigated the key aspects of selecting the belt cover material and proposed a conveyor belt configuration for a prototype post-extrusion process line. 2. Material and methods 2.1. Problem formulation The impact of transported material onto a conveyor belt often causes damage that is classified as a puncture. This kind of damage simultaneously affects the top cover layer, the carcass and the bottom cover layer of a conveyor belt. This kind of damage occurs when a conveyor belt’s capacity to absorb the impact energy of the material falling onto it is surpassed. In this article, we will examine how much energy a conveyor belt is able to absorb before such damage will occur. The amount of the absorbed energy will be expressed in relative terms, or as a percentage. The absorption of the impact energy also partially represents some damage to the internal and external structure of a conveyor belt. 2.2. Conveyor belts There are several types of belts that are currently used on conveyer systems. From a constructional point of view, the belt categorisation depends on the carcass type, the covering method, the material covering the carcass, the surface finishing, etc. The basic structural elements of a conveyor belt include the carcass (textile, steel) and the cover layers, the thickness of which is affected by the properties of the material being transported.
Fig. 1 Rubber-textile conveyor belt
Fig. 2 Steel-cord conveyor belt
The most frequently-used conveyor belts include rubber-textile (Fig. 1) and steel-cord conveyor belts (Fig. 2). A carcass of a rubber-textile conveyor belt consists of one or more textile plies while the carcass is reinforced with various types of natural or synthetic fibres. The carcass of steel-cord conveyor belt consists of steel cords in various diameters and strengths. 2.3. Testing device The experimental measurements were carried out using a testing device intended for testing the puncture resistance of conveyer belts (Fig. 3). A more detailed specification of the device is described in the paper [25].
Fig. 3 Testing device scheme (1 – skeleton, 2 – sliding of drop hammer, 3 – drop hammer, 4 – impactor, 5 – hydraulic jaws)
The testing machine comprises the PP065 electronics. It records the data obtained during the measurement (time, drop hammer height, and the stretching and impact forces). In this experiment, we were interested in the time [ms] and the height [mm]. The object’s impact heights were measured using the Banner LT3 laser sensor. The precision of the measurements of the distance from the LT3 laser sensor depended on the measured distance. The maximum measuring range of the LT3 sensor was 5m. The lowest
measuring precision, at the refresh frequency of 1 ms (Fast), was determined by the value of the (resolution/repeatability) of individual measurements, as stated in the technical specification as 5 mm (Fig. 4). The value of 5 mm can therefore be regarded as the achievable measurement precision. The accuracy of the measurements of the distance from the LT3 laser sensor was determined by the linearity error (Fig. 5), which also depended on the measured distance. The worse linearity defect was approximately 15 mm at a measured distance of 1.2 m. The reflection of the object was measured within the measuring range of 4 m, where the maximum linearity error was+/- 3 mm, which can be regarded as the achievable measurement accuracy.
Fig. 4 LT3 resolution
Fig. 5 LT3 linearity (typical)
The experiment was carried out using a roller support system, where the impact of the material was directed between the rollers (Fig. 6). The distance between the roller axes was 0.16 m. During the experiments, the weights of the falling materials were simulated in trials ranging from 50 to 90 kg, with 10 kg increments. The drop heights were chosen within heights ranging from 1 to 2.2 m, with 0.2 m increments, while the specimens of rubber-textile conveyor belts used in the experiment were of P1250 and P2500 types (with four component textile-polyamide plies) and the specimens of the steel-cord conveyor belts were of ST1250 and ST2500 types. In the above designations, “P” means a polyamide textile layer; “ST” means steel cords; and the numbers 2500 and 1250 express the conveyor belt rigidities [N.mm-1]. Every specimen was the same size: 1400 x 160 mm. The method of the specimen preparation is described in [26]. All of the specimens were stretched using the force recommended by the conveyor belt manufacturer (1/10 of the belt strength for a millimetre of the width). Measurements of the impact and of the stretching forces were then carried out for each test specimen. The testing was carried out using a pyramidal impactor (Fig. 7), which simulated the impact of a sharp-edged material.
Fig. 6 Support system
Fig. 7 Shape of the impactor used
3. Theory/calculation 3.1. Physical fundamentals The amount of impact energy caused by the impact of the material onto a conveyor belt may be expressed as the amount of kinetic energy Ek of an object with the weight m , with the velocity right before the impact v . If we neglect the impact of the environment (environmental resistance) and apply the law of the conservation of mechanical energy, then the amount of kinetic energy Ek of the object right before the impact Ek
1 mv 2 2
(1)
can be substituted by the amount of the potential energy E p E p mgh
(2)
of the object with the weight m , falling from the height h , where g 9.81 m.s-2 is the gravitational acceleration. The following applies: Ek
1 mv 2 mgh E p . 2
(3)
A conveyor belt structure and the properties of the material from which the conveyor belt is manufactured will result in a subsequent bouncing of the material off the conveyor belt. If we neglect the impact of the environment and we know the height to which the material bounces, we can use then the difference in the potential energies of the object before the impact and after the impact to identify how much energy the conveyor belt was able to absorb. This principle is represented in Fig. 8.
Fig. 8 Determination of absorbed energy By applying this method, we can determine the absolute value of the amount of the absorbed energy E absorbed
Eabsorbed Ep 1 Ep 2
(4)
Considering the number of executed measurements, it is more beneficial to identify the amount of the absorbed energy in a comprehensive manner, by using a relative expression (5) or a percentage (6)
E relat
E relat
Ep 1 Ep 2
(5)
Ep 1 Ep 1 Ep 2 Ep 1
100 %
(6)
When we apply this method, we can determine what portion (percentage) of the initial impact energy the conveyor belt is able to absorb. This portion of the initial impact energy can be further designated as the relative amount of the absorbed energy. In the relation (2) used for the calculation of the energy E p , the weight m and the gravitational acceleration g are constants. Therefore, after the modification of the relation (5) we will get
E relat
mgh 1 mgh 2 mgh 1
h 1 h2 h1
.
(7)
It is evident that if we express the relative amount of the absorbed energy using the relation (7) at a random drop height, we will always reach the theoretical maximum value 1.
3.2. Model formation The relation between the explained (dependent) variable Y and the k-explanatory (independent) variables X j , where j 1, 2, , k , can be expressed by the following mathematical model:
Y f X, β ε ,
(8)
where Y is the vector of the values of the explained variable Y , X is the matrix of the values of explanatory variables X j , where j 1, 2, , k , β is the vector of the model parameters, f X, β is the regression function, and ε is the vector of the accidental errors. In our case, we will consider the linear regression model in the following matrix form:
Y Xβ ε .
(9)
The verification of the statistical significance of the model was carried out using the F-test of the statistical significance. The statistical significance of the regression model parameters was verified by applying the test of the statistical significance of the regression parameter. The measure of strength of the relationship between the variable Y and the joint effect of the k variables is expressed by the multiple coefficient of determination R2.
4. Result The experimental tests were carried out with two types of rubber-textile conveyor belts, P1250 and P2500, and for two types of steel-cord conveyor belts, ST1250 and ST2500. The input parameters were the weight m of the falling material and the drop height h . The objectives of the experimental research were to: identify the relative amount of the absorbed energy for both conveyor belt types (P, ST) and to determine the impact of the parameters (conveyor belt strength, structure, drop weight, drop height) on the relative amount of the absorbed energy; and determine a model of the relationship between the relative amount of the absorbed energy and the selected parameters. The real data of the measured heights with the time when the drop hammer impacted the conveyor belt (with a certain weight and at a certain drop height) is shown in Fig. 9 and Fig. 10. The graphs were created for all four tested conveyor belt types. In the case of the steel-cord conveyer belt, a puncture occurred with the drop hammer of 90 kg and a drop height of 1.8 m or higher.
Fig. 9 Drop hammer’s impact curve (rubber-textile conveyor belt)
Fig. 10 Drop hammer’s impact curve (steel-cord conveyer belt) In the next part, we monitored only the first and the second impact of the drop hammer onto the conveyor belt.
4.1 Determination of the relative amount of absorbed energy and the impact of the selected parameters Fig. 11 and Fig. 12 (resp. Fig. 13 and Fig. 14) illustrate examples of the relative amount of absorbed energy after the first impact (resp. the second impact) of the drop hammer onto the conveyor belt at all the tested drop weights, where only four drop heights are used for the purpose of clarity. The relative amount of absorbed energy was determined using the relation (7).
Fig. 11 Relative amount of absorbed energy (first impact, rubber-textile conveyor belt)
Fig. 12 Relative amount of absorbed energy (first impact, steel-cord conveyor belt)
Fig. 13 Relative amount of absorbed energy (second impact, rubber-textile conveyor belt)
Fig. 14 Relative amount of absorbed energy (second impact, steel-cord conveyer belt) At each drop weight, falls from seven different drop heights were simulated. The differences between the obtained relative amounts of the absorbed energy were minimal. The mean values of the relative amounts of absorbed energy after the first and second impacts of the drop hammer onto the conveyor belt are indicated in Table 1.
Table 1 Relative amount of absorbed energy – interval within the whole range of the drop hammer heights 50 kg 60 kg 70 kg 80 kg 90 kg P2500 First impact 0.51 0.46 0.45 0.42 0.41 Second 0.49 0.45 0.43 0.41 0.39 impact P1250 First impact 0.67 0.67 0.65 0.65 0.64 Second 0.71 0.66 0.65 0.63 0.61 impact ST2500 First impact 0.78 0.75 0.75 0.74 0.74 Second 0.83 0.77 0.75 0.72 0.71 impact ST1250 First impact 0.80 0.79 0.78 0.78 0.78 Second 0.90 0.87 0.88 0.78 0.80 impact
The impact of the strength of the belt on the relative amount of absorbed impact energy was significant in the case of the rubber-textile conveyor belts (Fig. 9). At a strength of 2500 N.mm-1, the rubber-textile conveyor belt was able to absorb after the first impact of the drop hammer approximately 40-50% of the impact energy. At a strength of 1250 N.mm-1, the belt was able to absorb as much as 60-70% of the impact energy. However, the impact of the strength on the relative amount of absorbed impact energy in the case of the steel-cord conveyor belts was negligible (Fig. 10). At a strength of 2500 N.mm-1, the steel-cord conveyor belt was able to absorb approximately 70-85% of the impact energy; while at a strength of 1250 N.mm-1, the belt was able to absorb approximately 73-85% of the impact energy. These values were comparable for both belts. The results for the second impact of the drop hammer onto the conveyor belt were similar (Fig. 11, Fig.12). The impact of the conveyor belt structure on the relative amount of the absorbed impact energy is evident: the rubber-textile conveyor belts with determined properties were able to absorb a smaller relative amount of impact energy than the steel-cord conveyor belts with the same properties. On the basis of an analysis of all the resulting values, we can state that with a growing drop weight (and also with a growing drop height) the relative amount of the absorbed impact energy decreases in the majority of cases. 4.2. Creation of a model of the relationship between the relative amount of absorbed energy and the selected parameters We will consider the following conventional linear regression model
k
Y 0 j X j ,
(10)
j 1
where 0 and j for j 1, 2,, k are the model parameters, Y is the observed value of the explained variable Y , X j , j 1, 2, , k , are the k-explanatory (independent) variables, and is the accidental error. First, we monitored the impact of the weight of the falling material m and the drop height h on the relative amount of the absorbed energy during the first and the second impact of the drop hammer onto the conveyor belt. For all the examined conveyor belts, the point estimate of the regression model was as follows Y b0 b1 X 1 b2 X 2 or Erelat b0 b1h b2 m ,
(11)
where b0 , b1 and b2 are the point estimates of the model parameters, whereas Y E relat , X 1 h , and X 2 m . The point estimates of the parameters, their statistical significance, the significance of the model and the coefficient of determination are listed in Table 2 and Table 3. Table 2 Point estimate of the model parameters – first impact of the drop hammer (α=0.05) b0 P2500 value p-value P1250 value p-value ST2500 value p-value ST1250 value p-value
b1
0.611 0.011 <0.0001 0.018
b2
R2
p-value
-0.003 0.911 <0.0001
<<0.0001
0.836 -0.026 -0.002 0.924 <0.0001 <0.0001 <0.0001
<<0.0001
0.986 -0.033 -0.003 0.933 <0.0001 <0.0001 <0.0001
<<0.0001
1.022 -0.046 -0.003 0.935 <0.0001 <0.0001 <0.0001
<<0.0001
Table 3 Point estimate of the model parameters – second impact of the drop hammer (α=0.05) b0 P2500 value p-value P1250 value p-value ST2500 value
b1
b2
R2
p-value
0.571 0.014 -0.002 0.944 <0.0001 <0.0001 <0.0001
<<0.0001
0.827 -0.013 <0.0001 0.014
-0.002 0.890 <0.0001
<<0.0001
0.912
-0.003
<<0.0001
0.020
0.851
p-value ST1250 value p-value
<0.0001 0.009
<0.0001
1.112 -0.023 <0.0001 0.027
-0.003 0.884 <0.0001
<<0.0001
The regression models and the model parameters were statistically significant in all the cases (p-value<α). The regression model, expressing the relationship between the relative absorption of the potential energy and the drop hammer weight (m), the drop height (h), the conveyor belt type (rubber-textile, steel-cord), and the conveyor belt strength (S) is as follows: Erelat b0 b1h b2 m b3CB b4 S .
(12)
The CB variable is a dichotomous qualitative variable, transformed into a numerical variable with a permutation of 1 for a rubber-textile conveyor belt and with a permutation of 0 for a steel-cord conveyor belt. The S variable represents the conveyor belt strength [N.mm-1]. The point estimates of the parameters, the significance of the model and the coefficient of determination are listed in Table 4. It was found that the regression models and the model parameters were statistically significant. Table 4 Point estimate of the model parameters (α=0.05) b0 First impact value 1.121 Second impact value 1.196
b1
b2
b3
b4
R2
p-value
-0.012
-0.002
-0.216
-0.0001
0.887
<<0.0001
-0.012
-0.002
-0.237
-0.0001
0.903
<<0.0001
5. Conclusions The issues related to increasing the technical and economic levels of belt conveyor systems are associated with increasing the service life and the operational reliability of the conveyor belts, as well as improving the technology of the belt conveyor systems. This article present information regarding the absorption of the impact energy by conveyor belts, depending on their basic technical parameters – in particular, with regard to the CB strength and the carcass. The article also points out the optimal chute structures, with the optimal drop height at which a conveyor belt puncture does not occur. Drop hammers were designed to fall onto the conveyor belt specimens in the experiment, in order to simulate the impact of real materials onto the conveyor belts. The experiments simulated various situations (impacts of materials of various weights, as well as those dropped from various heights). The objective was to identify the ability of a conveyor belt to absorb the energy of the falling material without causing a belt puncture. Within the scope of our experimental research, we came to the following conclusions: The drop hammer behaviour over time is specific for a particular conveyor belt type. Steel-cord conveyor belts dampen the impact of the falling material faster than rubbertextile conveyor belts.
The impact of the strength on the relative amount of the absorbed impact energy was only observed with rubber-textile conveyor belts. Belts of this kind are able, at a strength of 2500 N.mm-1, to absorb approximately 40-50% of the impact energy after the first impact of the drop hammer, and at a strength of 1250 N.mm-1 the belts are able to absorb as much as 60-70% of the impact energy. This means that with belts of a higher strength, the internal damage is smaller than with belts of a lower strength. In the case of steel-cord conveyor belts, at a strength of 2500 N.mm-1, the belt is able to absorb approximately 70-85% of the impact energy after the first impact of the drop hammer; and at a strength of 1250 N.mm-1 the belt is able to absorb almost the same amount, i.e. 73-85% of the impact energy. Therefore, with this type of belt, the strength does not have a strong impact on the relative amount of the absorbed energy. The impact of the conveyor belt structure on the relative amount of absorbed impact energy is significant. Specifically, rubber-textile conveyor belts absorb a smaller relative amount of impact energy than steel-cord conveyor belts. In the majority of cases, with a growing drop weight (and also with a growing drop height), the relative amount of the absorbed impact energy decreases.
With regard to four various types of conveyor belts that were used in the experiment we can state the following: in the case of rubber-textile conveyor belts, the internal damage is smaller; thus, they are more resistant to serious damage, such as punctures. Therefore, it can be concluded that rubber-textile conveyor belts are more appropriate for operations with the increased occurrence of this particular kind of damage. The results of this experimental research for the purpose of determining the ability of a conveyor belt to absorb the impact energy indicate that there is the potential for further research, in terms of the utilisation of new reinforcement materials resistant to punctures, which have not yet been subjected to more detailed research. Acknowledgements This article is the result of the projects implementation KEGA 009TUKE-4/2016 Design of the specialized training concept oriented to the development of experimental skills within the frame of education in the study branch logistics and project VEGA 1/0577/17 Transfer of knowledge from laboratory experiments and mathematical models in the creation of a knowledge based system for assessing the quality environmentally friendly conveyor belts.
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Highlights Experimental measurements of impact loading of various conveyor belt structures Determination of the relative absorbed energy by a conveyor belt Relationship between the relative absorbed energy and some impact parameters