Matjaz Sraml - Academia.edu (original) (raw)
Papers by Matjaz Sraml
Sustainability, 2022
Pedestrian safety is a well-known issue, such that many road safety associations emphasize measur... more Pedestrian safety is a well-known issue, such that many road safety associations emphasize measures to improve this aspect. One of the main conflict points is pedestrian crossings, where motorized and non-motorized traffic flows directly interact and where pedestrian attention and reaction are two elements that can strongly influence their safety. Nowadays, these aspects are often deviated by the use of smartphones to surf the Internet or social media. The aim of the present study is to find out (1) whether and how intersection typology affects pedestrian behavior, both in terms of attention and crossing performance, and (2) whether and how gaze and behavioral characteristics are affected by smartphone use and social media browsing. To achieve this goal, eye-tracking technology was used to obtain qualitative and quantitative information on the number of fixations, their duration, and reaction times of pedestrians. Additionally, from the eye-tracking videos, it was possible to derive...
Transactions on Transport Sciences, 2022
Pedestrian behavior and safety are emerging issues in current transportation. One way to safely s... more Pedestrian behavior and safety are emerging issues in current transportation. One way to safely study pedestrian dynamics, especially at potential conflict points such as crosswalks, is through micro-simulation. This tool provides the opportunity to repeatedly study pedestrian behavior and safety under different scenarios of interest. However, to obtain reliable results, micro-simulation models need to be calibrated and their parameters fine-tuned. One way to methodically calibrate these models is to identify the outcomes of interest, develop a predictive model for those specific outcomes, and use it as a tool to fine-tune the input parameters of the micro-simulation model. To be reliable, the results of the predictive model should be comparable to those of the micro-simulation model, and these should be validated. The aim of this research is to present a predictive model of pedestrian behavior and to evaluate this model and a conventional micro-simulation model developed using Vissim/Viswalk, given that the chosen common output is pedestrian crossing time. To achieve this goal, a multi-step procedure is followed, which is part of a more general methodological framework for calibrating the Vissim/ Viswalk micro-simulation model. This evaluation consisted in a threestep validation procedure, i.e. visual, conceptual and operational validation. Operational (statistical) validation was performed by comparing the variances of the results to understand whether the predicted sample is representative of the simulated sample. A correlation of 97% have been found between the predicted and micro-simulated crossing time values, with mean values of 6.41s and 6.32s for the simulated and predicted crossing times, respectively. Furthermore, both the predicted and simulated crossing time values fall within the ranges found in the literature for field measurements of this variable, indicating good agreement with real observed pedestrian behavior.
For the analysis of the existing and planned segments of the traffic system, a traffic modelling ... more For the analysis of the existing and planned segments of the traffic system, a traffic modelling is used, and the choice of models depends on temporal and spatial limits of a model and the context of application of modelling results. Functioning of a traffic system is under the influence of variable human behaviour. Researches show that the behaviour of a driver is, among other things, territorially and culturally conditioned. Accordingly, there is no universally applicable model, so the adjustment of modelling to local characteristics of traffic system and its users is a necessary prerequisite for the use of any traffic model. The success of modelling of urban traffic networks and its segments is interrelated with successful modelling of critical network segments. According to a number of criteria, the most critical point of every traffic system is the intersection. The simulation models are very useful tool for the analysis of existing critical network segments and prediction of t...
Sustainability, 2020
Walking is the original form of transportation, and pedestrians have always made up a significant... more Walking is the original form of transportation, and pedestrians have always made up a significant share of transportation system users. In contrast to motorized traffic, which has to move on precisely defined lanes and follow strict rules, pedestrian traffic is not heavily regulated. Moreover, pedestrians have specific characteristics—in terms of size and protection—which make them much more vulnerable than drivers. In addition, the difference in speed between pedestrians and motorized vehicles increases their vulnerability. All these characteristics, together with the large number of pedestrians on the road, lead to many safety problems that professionals have to deal with. One way to tackle them is to model pedestrian behavior using microsimulation tools. Of course, modeling also raises questions of reliability, and this is also the focus of this paper. The aim of the present research is to contribute to improving the reliability of microsimulation models for pedestrians by testin...
IOP Conference Series: Materials Science and Engineering, 2019
Nowadays, pedestrian safety is a growing problem: on the one hand pedestrian movement is increasi... more Nowadays, pedestrian safety is a growing problem: on the one hand pedestrian movement is increasing, on the other hand measures to improve walkers' safety are still scarce. During the years, various behavioural models have been proposed, which consider several parameters characterizing both the environment and the road users. Many studies define accident risk as a combination of three main factors, which are the accident occurrence probability, the vulnerability of the involved users and the economic and social damages due to the accident. The approaches spotted in literature about pedestrian safety assessment are various and they mainly deal with vehicle-pedestrian accidents. These studies have been developed in order to foresee and reduce possible losses in human lives. Also pedestrian-pedestrian encroachments can lead to dangerous consequences, but researches about them are still limited. This study aims to highlight the correspondence and/or the differences between different analysis methods applied to pedestrian field, focusing on situations where no interactions with vehicular traffic exist. This is one step of a wider research, which has been carried out on a confined space, selected because of easy replicability of its general geometrical features and of the effects on pedestrian trajectories induced by some local peculiarities of the facility. The study focuses on the evaluation of a real case, which has been monitored through the use of cameras and analysed via a dedicated tool. The achieved results have been then compared to the outputs obtained by reconstructing the same situation in a micro-simulation model. The first step-video acquisition and elaboration-allowed to observe how people behave in the examined area and how the environment influences their trajectories, while the second phase permitted to understand if a microsimulation tool can reliably reply pedestrian movement in the analysed scenario and therefore provide surrogate safety values comparable to the ones obtained from real data. In the model, a simplified but still accurate environment has been set up: homogeneous geometric features have been drawn and no obstacles have been considered. The modelled pedestrian flow is a bi-directional, 2400 ped/h flux, characterized by heterogeneity of agents: both male and female adults. In order to be able to compare the data obtained by video footages and elaborated through an ad hoc tracking tool with outputs of the microsimulation model, from the whole flow on the ramp some intersecting pedestrians have been selected in both directions of walking. This cross-study of two different techniques has allowed to inspect the effects of the environment on pedestrian dynamics and to precautionary estimate the level of safety via calculation of surrogate safety parameters.
Elektronički časopis građevinskog fakulteta Osijek, 2015
Microsimulation models are frequently used in traffic analysis. Various optimization methods are ... more Microsimulation models are frequently used in traffic analysis. Various optimization methods are used in calibration, and the one method that has shown success is neural networks. This paper shows the responses of neural networks during calibration of a microsimulation traffic model. We analyzed two calibration methods by applying neural networks and comparing their neural network learning (according to their achieved correlation and the mean error of prediction) and their generalization ability (comparison of generalization results was analyzed in two steps). The best correlation between the microsimulation results and neural network prediction was 88.3%, achieved for the traveling time prediction, on which the first calibration method is based.
Journal of Materials Processing Technology, Dec 1, 2004
Automated storage and retrieval systems (AS/RS) brought to industry the advantages of faster stor... more Automated storage and retrieval systems (AS/RS) brought to industry the advantages of faster storages and retrieval of products, efficient utilization of storage space, high reliability and better control inventory, improved safety and decrease in damages of products. Therefore AS/RS which are used in manufacturing, warehousing and distribution centers have to be designed to provide quick response for storages and retrievals of products in order to keep the system operating efficiently. Heuristics travel time models for AS/RS with equal-sized cells in height and randomized storage under single-and multi-shuttle system are presented in this paper. The main contribution of proposed model is the implementation of the "Strategy x" and determination of relationship between average travel times and throughput capacity for different types of high storage racks and velocity profiles of storage retrieval machine.
Civil-comp proceedings, May 26, 2009
Forests, Dec 13, 2019
The objective of this paper is the computational and experimental study of the fracture behavior ... more The objective of this paper is the computational and experimental study of the fracture behavior of spruce wood under quasi-static loading conditions during a three-point bending test. The experimental tests were performed on the electronic testing machine Zwick Z100 (Zwick-Roell GmbH & Co. KG, Ulm, Germany) with displacement control, according to the standard International Standard Organisation (ISO) 13061-4: 2014. The specimens were made of Norway spruce (Picea abies) wood, with dimensions of 25 mm × 25 mm in cross-section and 549 mm in length. Six tests were performed for each orientation (radial and tangential) of the wood fibres. Based on the experimental results, the computational model was created and validated by considering the mechanical responses in two different directions due to the orientation of the wood fibres. An orthotropic material model with damage evolution was selected as the computational model. The computational model was validated using the inverse procedure for the determination of the constitutive material parameters, including the damage parameters of three-point bending test specimens. A finite element method (FEM) in the framework of program package ABAQUS was used for the computational simulation, while the open code Optimax was used for the optimization procedure. Comparison between the experimental and computational force vs. the displacement response showed a very good correlation in the results for the spruce wood specimens under three-point bending tests, with Pearson s correlation coefficient of r = 0.994 for the tangential and r = 0.988 for the radial orientation. Therefore, validation of the proposed computational model was confirmed, and can be used further in numerical simulations of the fatigue behavior of wood specimens.
Journal of Vibroengineering, 2013
Nowadays one of the major topics in the brake development community is the NVH (noise, vibration ... more Nowadays one of the major topics in the brake development community is the NVH (noise, vibration and harshness) problem. Although reasonably well researched in the disc brake systems, the squeal prediction in the drum brakes is often neglected, manly due to its complexity. The newly developed methodology presented in this work gives the directions on how to develop a squeal free drum brake design using some novel approaches to closely correlate the numerical results with the experimental brake tests. The goal is to make a robust drum brake design that is stable under the different noise factors and under broad operational conditions. In order to predict if a brake system will generate the squeal noise during the operation, the finite element method was used to simulate the system. By solving the complex eigenvalues of the FEM (finite element method) matrices, the presence of unstable modes was predicted. A good correlation with the SAE J2521 noise matrix dynamometer test procedure was established.
Strojniški vestnik, 2004
V prispevku je predstavljen simulacijski model avtomatiziranega regalnega skladiscnega sistema z ... more V prispevku je predstavljen simulacijski model avtomatiziranega regalnega skladiscnega sistema z enojno pomicno in vecpomicnimi mizami. Glavni namen predstavljene raziskave je dolocitev zmogljivosti sistema z vecpomicnimi mizami, glede na sistem z enojno pomicno mizo. Slednje pomeni glavni delež in pomoc pri postopku nacrtovanja avtomatiziranega regalnega skladiscnega sistema. Povecanje pretocne zmogljivosti transportno-skladiscnih enot je mogoce z uporabo sistema z vecpomicnimi mizami, glede na sistem z enojno-pomicno mizo. V inženirski praksi se najveckrat uporablja sistem z enojno pomicno mizo, ki temelji na dvojnem delovnem krogu, medtem ko sistem z vecpomicnimi mizami temelji na stirikratnem in sestkratnem delovnem krogu. Problem se pojavi pri uporabi ustrezne upravljalne strategije, za zagotovitev pogoja o najmanjsih vožnjah regalnega dvigala. V ta namen smo uporabili posebno domiselno metodo, poimenovano "Strategija x", ki razvrsca zaporedje skladiscnih in odpremnih zahtev, z namenom po minimizaciji povprecnega casa vožnje regalnega dvigala. Za ovrednotenje domiselne metode s sistemom vecpomicnih miz smo uporabili tehniko diskretnih numericnih simulacij. Rezultati simulacijske analize so pokazali ocitno povecanje pretocnih zmogljivosti sistema z vecpomicnimi mizami v primerjavi s sistemom enojne pomicne mize.
Journal of Applied Mathematics and Mechanics, 2000
On the Numerical Analysis of the Contact Problems at Crane Mechanisms In several construction com... more On the Numerical Analysis of the Contact Problems at Crane Mechanisms In several construction components of cmne mechanisms, contact loading is very important, which msults in the need for the non-linear analysis. The numerical treatment of contact problems was performed by the finite element method (FEM). The algorithm of the sti&ess update with friction, based on the penalty function method, is included in the numerical calculation of the above mentioned contact problems. The potential contact areas are defined throughout the slide-line contact elements, which enable the handling of the sepamtion and sliding of the finite amplitude between the deformable bodies.
The successful performance of the automated storage and retrieval systems is dependent upon the a... more The successful performance of the automated storage and retrieval systems is dependent upon the appropriate design and optimization process. In the present work a comprehensive model of designing automated storage and retrieval system for the single-and multi-aisle systems is presented. Because of the required conditions that the automated storage and retrieval systems should be technically highly efficient and that it should be designed on reasonable expenses, the objective function represents minimum total cost. The objective function combines elements of layout, time-dependant part, the initial investment and the operational costs. Due to the non-linear, multi-variable and discrete shape of the objective function, the method of genetic algorithms has been used for the optimization process of decision variables. The presented model prove to be very useful and flexible tool for choosing a particular type of the single-or multi-aisle system in designing automated storage and retrieval systems. Computational analysis of the design model indicates the model suitability for addressing industry size problems.
A multi objective optimization of automated warehouses is discussed and evaluated in present pape... more A multi objective optimization of automated warehouses is discussed and evaluated in present paper. Since most of researchers in material handling community had performed optimization of decision variables with single objective function only (usually named with minimum travel time, maximum throughput capacity, minimum cost, etc.), the multi objective optimization (travel time – cost – quality) will be presented. For the optimization of decision variables in objective functions, the method with genetic algorithms is used. To find the Pareto optimal solutions, the NSGA II genetic algorithm was used. The main objective of our contribution is to determine the performance of the system according to the multi objective optimization technique. The results of the proposed model could be useful tool for the warehouse designer in the early stage of warehouse design.
The numerical model for analysing damage due to contact fatigue of mechanical elements is present... more The numerical model for analysing damage due to contact fatigue of mechanical elements is presented in this paper. Mechanical behaviour of various machine elements depends upon interacting influences of contact elements. Contact fatigue can be divided into the initiation of micro-cracks and crack propagation. The purpose of present study is to elaborate a numerical model for prediction of contact fatigue initiation, based on continuum mechanics. The influence of friction on the contact loading cycles and fatigue initiation should be examined. The results of loading cycles, required for initial fatigue damages to appear Ni and the place yi (on/under contact surface) where contact fatigue damage starts, were presented.
Fracture and Structural Integrity, 2016
A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjecte... more A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjected to biaxial in-phase loading cycles is presented in this paper. Fatigue properties of porous materials are less frequently published in the literature. This paper evaluates computational analyses, where different pore distribution and biaxial loading conditions in relation to the pore orientations is considered in each simulation. The fatigue analysis is performed by using a damage initiation and evolution law based on the inelastic strain energy. The computational results are subjected to the appropriate statistical analysis, because of different pore topology a different fatigue lives are obtained on the same loading level. Results of computational simulations show also a qualitative understanding of porosity influence on low-cycle fatigue failures of lotus-type porous material under biaxial loading conditions.
The successful performance of the automated storage and retrieval systems is dependent upon the a... more The successful performance of the automated storage and retrieval systems is dependent upon the appropriate design and optimization process. In the present work a comprehensive model of designing automated storage and retrieval system for the single- and multi-aisle systems is presented. Because of the required conditions that the automated storage and retrieval systems should be technically highly efficient and that it should be designed on reasonable expenses, the objective function represents minimum total cost. The objective function combines elements of layout, time-dependant part, the initial investment and the operational costs. Due to the non-linear, multi-variable and discrete shape of the objective function, the method of genetic algorithms has been used for the optimization process of decision variables. The presented model prove to be very useful and flexible tool for choosing a particular type of the single- or multi-aisle system in designing automated storage and retri...
Strojniški vestnik, 2006
Like with other non-traffic-lighted intersections, the capacity of roundabouts can be reduced by ... more Like with other non-traffic-lighted intersections, the capacity of roundabouts can be reduced by special traffic conditions. In such cases the pedestrian 's and/or cyclist's traffic flow, crossing one or more roundabout arms, is the size that influences the roundabout filling or emptying. The purpose of this paper is to show how the use of discrete simulation methods contributes to the decision on implementing a roundabout, or to help decide if the roundabout is going to fulfil appropriately the condition of the expected flow of pedestrians and/or cyclists. A new approach is suggested for dimensioning roundabouts, with mathematical modelling of the traffic flows using the discrete simulation method, and considering the statistically evaluated entry data for vehicles' and pedestrians' traffic flows. The simulation results are useful when determining the capacity of foreseen and suggested roundabouts, which will function in different circumstances. The presented model ...
Izvorni znanstveni rad Sažetak: Cilj ovog članka analizirati je zamornu čvrstoću ćelijaste lotusn... more Izvorni znanstveni rad Sažetak: Cilj ovog članka analizirati je zamornu čvrstoću ćelijaste lotusne strukture crvićastog lijevanog željeza kao osnovnog materijala. Broj ciklusa naprezanja potrebnih za širenje pukotine od inicijalne do kritične dužine pukotine određeno je numerički pomoću modela konačnih elemenata, u okviru Abaqus computation FEM koda. Kriterij maksimalnog vlačnog naprezanja razmatra se kad se analizira putanja pukotine unutar ćelijaste strukture. Izvršenje računalne analize pokazuju kako su koncentracije naprezanja oko individualnih ćelija veće kada vanjsko opterećenje djeluje u transverzalnom smjeru u odnosu na distribuciju ćelija. Članak je produljenje rada, prezentiranog na posljednjoj MATRIB konferenciji u 2014. godini [1]
Sustainability, 2022
Pedestrian safety is a well-known issue, such that many road safety associations emphasize measur... more Pedestrian safety is a well-known issue, such that many road safety associations emphasize measures to improve this aspect. One of the main conflict points is pedestrian crossings, where motorized and non-motorized traffic flows directly interact and where pedestrian attention and reaction are two elements that can strongly influence their safety. Nowadays, these aspects are often deviated by the use of smartphones to surf the Internet or social media. The aim of the present study is to find out (1) whether and how intersection typology affects pedestrian behavior, both in terms of attention and crossing performance, and (2) whether and how gaze and behavioral characteristics are affected by smartphone use and social media browsing. To achieve this goal, eye-tracking technology was used to obtain qualitative and quantitative information on the number of fixations, their duration, and reaction times of pedestrians. Additionally, from the eye-tracking videos, it was possible to derive...
Transactions on Transport Sciences, 2022
Pedestrian behavior and safety are emerging issues in current transportation. One way to safely s... more Pedestrian behavior and safety are emerging issues in current transportation. One way to safely study pedestrian dynamics, especially at potential conflict points such as crosswalks, is through micro-simulation. This tool provides the opportunity to repeatedly study pedestrian behavior and safety under different scenarios of interest. However, to obtain reliable results, micro-simulation models need to be calibrated and their parameters fine-tuned. One way to methodically calibrate these models is to identify the outcomes of interest, develop a predictive model for those specific outcomes, and use it as a tool to fine-tune the input parameters of the micro-simulation model. To be reliable, the results of the predictive model should be comparable to those of the micro-simulation model, and these should be validated. The aim of this research is to present a predictive model of pedestrian behavior and to evaluate this model and a conventional micro-simulation model developed using Vissim/Viswalk, given that the chosen common output is pedestrian crossing time. To achieve this goal, a multi-step procedure is followed, which is part of a more general methodological framework for calibrating the Vissim/ Viswalk micro-simulation model. This evaluation consisted in a threestep validation procedure, i.e. visual, conceptual and operational validation. Operational (statistical) validation was performed by comparing the variances of the results to understand whether the predicted sample is representative of the simulated sample. A correlation of 97% have been found between the predicted and micro-simulated crossing time values, with mean values of 6.41s and 6.32s for the simulated and predicted crossing times, respectively. Furthermore, both the predicted and simulated crossing time values fall within the ranges found in the literature for field measurements of this variable, indicating good agreement with real observed pedestrian behavior.
For the analysis of the existing and planned segments of the traffic system, a traffic modelling ... more For the analysis of the existing and planned segments of the traffic system, a traffic modelling is used, and the choice of models depends on temporal and spatial limits of a model and the context of application of modelling results. Functioning of a traffic system is under the influence of variable human behaviour. Researches show that the behaviour of a driver is, among other things, territorially and culturally conditioned. Accordingly, there is no universally applicable model, so the adjustment of modelling to local characteristics of traffic system and its users is a necessary prerequisite for the use of any traffic model. The success of modelling of urban traffic networks and its segments is interrelated with successful modelling of critical network segments. According to a number of criteria, the most critical point of every traffic system is the intersection. The simulation models are very useful tool for the analysis of existing critical network segments and prediction of t...
Sustainability, 2020
Walking is the original form of transportation, and pedestrians have always made up a significant... more Walking is the original form of transportation, and pedestrians have always made up a significant share of transportation system users. In contrast to motorized traffic, which has to move on precisely defined lanes and follow strict rules, pedestrian traffic is not heavily regulated. Moreover, pedestrians have specific characteristics—in terms of size and protection—which make them much more vulnerable than drivers. In addition, the difference in speed between pedestrians and motorized vehicles increases their vulnerability. All these characteristics, together with the large number of pedestrians on the road, lead to many safety problems that professionals have to deal with. One way to tackle them is to model pedestrian behavior using microsimulation tools. Of course, modeling also raises questions of reliability, and this is also the focus of this paper. The aim of the present research is to contribute to improving the reliability of microsimulation models for pedestrians by testin...
IOP Conference Series: Materials Science and Engineering, 2019
Nowadays, pedestrian safety is a growing problem: on the one hand pedestrian movement is increasi... more Nowadays, pedestrian safety is a growing problem: on the one hand pedestrian movement is increasing, on the other hand measures to improve walkers' safety are still scarce. During the years, various behavioural models have been proposed, which consider several parameters characterizing both the environment and the road users. Many studies define accident risk as a combination of three main factors, which are the accident occurrence probability, the vulnerability of the involved users and the economic and social damages due to the accident. The approaches spotted in literature about pedestrian safety assessment are various and they mainly deal with vehicle-pedestrian accidents. These studies have been developed in order to foresee and reduce possible losses in human lives. Also pedestrian-pedestrian encroachments can lead to dangerous consequences, but researches about them are still limited. This study aims to highlight the correspondence and/or the differences between different analysis methods applied to pedestrian field, focusing on situations where no interactions with vehicular traffic exist. This is one step of a wider research, which has been carried out on a confined space, selected because of easy replicability of its general geometrical features and of the effects on pedestrian trajectories induced by some local peculiarities of the facility. The study focuses on the evaluation of a real case, which has been monitored through the use of cameras and analysed via a dedicated tool. The achieved results have been then compared to the outputs obtained by reconstructing the same situation in a micro-simulation model. The first step-video acquisition and elaboration-allowed to observe how people behave in the examined area and how the environment influences their trajectories, while the second phase permitted to understand if a microsimulation tool can reliably reply pedestrian movement in the analysed scenario and therefore provide surrogate safety values comparable to the ones obtained from real data. In the model, a simplified but still accurate environment has been set up: homogeneous geometric features have been drawn and no obstacles have been considered. The modelled pedestrian flow is a bi-directional, 2400 ped/h flux, characterized by heterogeneity of agents: both male and female adults. In order to be able to compare the data obtained by video footages and elaborated through an ad hoc tracking tool with outputs of the microsimulation model, from the whole flow on the ramp some intersecting pedestrians have been selected in both directions of walking. This cross-study of two different techniques has allowed to inspect the effects of the environment on pedestrian dynamics and to precautionary estimate the level of safety via calculation of surrogate safety parameters.
Elektronički časopis građevinskog fakulteta Osijek, 2015
Microsimulation models are frequently used in traffic analysis. Various optimization methods are ... more Microsimulation models are frequently used in traffic analysis. Various optimization methods are used in calibration, and the one method that has shown success is neural networks. This paper shows the responses of neural networks during calibration of a microsimulation traffic model. We analyzed two calibration methods by applying neural networks and comparing their neural network learning (according to their achieved correlation and the mean error of prediction) and their generalization ability (comparison of generalization results was analyzed in two steps). The best correlation between the microsimulation results and neural network prediction was 88.3%, achieved for the traveling time prediction, on which the first calibration method is based.
Journal of Materials Processing Technology, Dec 1, 2004
Automated storage and retrieval systems (AS/RS) brought to industry the advantages of faster stor... more Automated storage and retrieval systems (AS/RS) brought to industry the advantages of faster storages and retrieval of products, efficient utilization of storage space, high reliability and better control inventory, improved safety and decrease in damages of products. Therefore AS/RS which are used in manufacturing, warehousing and distribution centers have to be designed to provide quick response for storages and retrievals of products in order to keep the system operating efficiently. Heuristics travel time models for AS/RS with equal-sized cells in height and randomized storage under single-and multi-shuttle system are presented in this paper. The main contribution of proposed model is the implementation of the "Strategy x" and determination of relationship between average travel times and throughput capacity for different types of high storage racks and velocity profiles of storage retrieval machine.
Civil-comp proceedings, May 26, 2009
Forests, Dec 13, 2019
The objective of this paper is the computational and experimental study of the fracture behavior ... more The objective of this paper is the computational and experimental study of the fracture behavior of spruce wood under quasi-static loading conditions during a three-point bending test. The experimental tests were performed on the electronic testing machine Zwick Z100 (Zwick-Roell GmbH & Co. KG, Ulm, Germany) with displacement control, according to the standard International Standard Organisation (ISO) 13061-4: 2014. The specimens were made of Norway spruce (Picea abies) wood, with dimensions of 25 mm × 25 mm in cross-section and 549 mm in length. Six tests were performed for each orientation (radial and tangential) of the wood fibres. Based on the experimental results, the computational model was created and validated by considering the mechanical responses in two different directions due to the orientation of the wood fibres. An orthotropic material model with damage evolution was selected as the computational model. The computational model was validated using the inverse procedure for the determination of the constitutive material parameters, including the damage parameters of three-point bending test specimens. A finite element method (FEM) in the framework of program package ABAQUS was used for the computational simulation, while the open code Optimax was used for the optimization procedure. Comparison between the experimental and computational force vs. the displacement response showed a very good correlation in the results for the spruce wood specimens under three-point bending tests, with Pearson s correlation coefficient of r = 0.994 for the tangential and r = 0.988 for the radial orientation. Therefore, validation of the proposed computational model was confirmed, and can be used further in numerical simulations of the fatigue behavior of wood specimens.
Journal of Vibroengineering, 2013
Nowadays one of the major topics in the brake development community is the NVH (noise, vibration ... more Nowadays one of the major topics in the brake development community is the NVH (noise, vibration and harshness) problem. Although reasonably well researched in the disc brake systems, the squeal prediction in the drum brakes is often neglected, manly due to its complexity. The newly developed methodology presented in this work gives the directions on how to develop a squeal free drum brake design using some novel approaches to closely correlate the numerical results with the experimental brake tests. The goal is to make a robust drum brake design that is stable under the different noise factors and under broad operational conditions. In order to predict if a brake system will generate the squeal noise during the operation, the finite element method was used to simulate the system. By solving the complex eigenvalues of the FEM (finite element method) matrices, the presence of unstable modes was predicted. A good correlation with the SAE J2521 noise matrix dynamometer test procedure was established.
Strojniški vestnik, 2004
V prispevku je predstavljen simulacijski model avtomatiziranega regalnega skladiscnega sistema z ... more V prispevku je predstavljen simulacijski model avtomatiziranega regalnega skladiscnega sistema z enojno pomicno in vecpomicnimi mizami. Glavni namen predstavljene raziskave je dolocitev zmogljivosti sistema z vecpomicnimi mizami, glede na sistem z enojno pomicno mizo. Slednje pomeni glavni delež in pomoc pri postopku nacrtovanja avtomatiziranega regalnega skladiscnega sistema. Povecanje pretocne zmogljivosti transportno-skladiscnih enot je mogoce z uporabo sistema z vecpomicnimi mizami, glede na sistem z enojno-pomicno mizo. V inženirski praksi se najveckrat uporablja sistem z enojno pomicno mizo, ki temelji na dvojnem delovnem krogu, medtem ko sistem z vecpomicnimi mizami temelji na stirikratnem in sestkratnem delovnem krogu. Problem se pojavi pri uporabi ustrezne upravljalne strategije, za zagotovitev pogoja o najmanjsih vožnjah regalnega dvigala. V ta namen smo uporabili posebno domiselno metodo, poimenovano "Strategija x", ki razvrsca zaporedje skladiscnih in odpremnih zahtev, z namenom po minimizaciji povprecnega casa vožnje regalnega dvigala. Za ovrednotenje domiselne metode s sistemom vecpomicnih miz smo uporabili tehniko diskretnih numericnih simulacij. Rezultati simulacijske analize so pokazali ocitno povecanje pretocnih zmogljivosti sistema z vecpomicnimi mizami v primerjavi s sistemom enojne pomicne mize.
Journal of Applied Mathematics and Mechanics, 2000
On the Numerical Analysis of the Contact Problems at Crane Mechanisms In several construction com... more On the Numerical Analysis of the Contact Problems at Crane Mechanisms In several construction components of cmne mechanisms, contact loading is very important, which msults in the need for the non-linear analysis. The numerical treatment of contact problems was performed by the finite element method (FEM). The algorithm of the sti&ess update with friction, based on the penalty function method, is included in the numerical calculation of the above mentioned contact problems. The potential contact areas are defined throughout the slide-line contact elements, which enable the handling of the sepamtion and sliding of the finite amplitude between the deformable bodies.
The successful performance of the automated storage and retrieval systems is dependent upon the a... more The successful performance of the automated storage and retrieval systems is dependent upon the appropriate design and optimization process. In the present work a comprehensive model of designing automated storage and retrieval system for the single-and multi-aisle systems is presented. Because of the required conditions that the automated storage and retrieval systems should be technically highly efficient and that it should be designed on reasonable expenses, the objective function represents minimum total cost. The objective function combines elements of layout, time-dependant part, the initial investment and the operational costs. Due to the non-linear, multi-variable and discrete shape of the objective function, the method of genetic algorithms has been used for the optimization process of decision variables. The presented model prove to be very useful and flexible tool for choosing a particular type of the single-or multi-aisle system in designing automated storage and retrieval systems. Computational analysis of the design model indicates the model suitability for addressing industry size problems.
A multi objective optimization of automated warehouses is discussed and evaluated in present pape... more A multi objective optimization of automated warehouses is discussed and evaluated in present paper. Since most of researchers in material handling community had performed optimization of decision variables with single objective function only (usually named with minimum travel time, maximum throughput capacity, minimum cost, etc.), the multi objective optimization (travel time – cost – quality) will be presented. For the optimization of decision variables in objective functions, the method with genetic algorithms is used. To find the Pareto optimal solutions, the NSGA II genetic algorithm was used. The main objective of our contribution is to determine the performance of the system according to the multi objective optimization technique. The results of the proposed model could be useful tool for the warehouse designer in the early stage of warehouse design.
The numerical model for analysing damage due to contact fatigue of mechanical elements is present... more The numerical model for analysing damage due to contact fatigue of mechanical elements is presented in this paper. Mechanical behaviour of various machine elements depends upon interacting influences of contact elements. Contact fatigue can be divided into the initiation of micro-cracks and crack propagation. The purpose of present study is to elaborate a numerical model for prediction of contact fatigue initiation, based on continuum mechanics. The influence of friction on the contact loading cycles and fatigue initiation should be examined. The results of loading cycles, required for initial fatigue damages to appear Ni and the place yi (on/under contact surface) where contact fatigue damage starts, were presented.
Fracture and Structural Integrity, 2016
A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjecte... more A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjected to biaxial in-phase loading cycles is presented in this paper. Fatigue properties of porous materials are less frequently published in the literature. This paper evaluates computational analyses, where different pore distribution and biaxial loading conditions in relation to the pore orientations is considered in each simulation. The fatigue analysis is performed by using a damage initiation and evolution law based on the inelastic strain energy. The computational results are subjected to the appropriate statistical analysis, because of different pore topology a different fatigue lives are obtained on the same loading level. Results of computational simulations show also a qualitative understanding of porosity influence on low-cycle fatigue failures of lotus-type porous material under biaxial loading conditions.
The successful performance of the automated storage and retrieval systems is dependent upon the a... more The successful performance of the automated storage and retrieval systems is dependent upon the appropriate design and optimization process. In the present work a comprehensive model of designing automated storage and retrieval system for the single- and multi-aisle systems is presented. Because of the required conditions that the automated storage and retrieval systems should be technically highly efficient and that it should be designed on reasonable expenses, the objective function represents minimum total cost. The objective function combines elements of layout, time-dependant part, the initial investment and the operational costs. Due to the non-linear, multi-variable and discrete shape of the objective function, the method of genetic algorithms has been used for the optimization process of decision variables. The presented model prove to be very useful and flexible tool for choosing a particular type of the single- or multi-aisle system in designing automated storage and retri...
Strojniški vestnik, 2006
Like with other non-traffic-lighted intersections, the capacity of roundabouts can be reduced by ... more Like with other non-traffic-lighted intersections, the capacity of roundabouts can be reduced by special traffic conditions. In such cases the pedestrian 's and/or cyclist's traffic flow, crossing one or more roundabout arms, is the size that influences the roundabout filling or emptying. The purpose of this paper is to show how the use of discrete simulation methods contributes to the decision on implementing a roundabout, or to help decide if the roundabout is going to fulfil appropriately the condition of the expected flow of pedestrians and/or cyclists. A new approach is suggested for dimensioning roundabouts, with mathematical modelling of the traffic flows using the discrete simulation method, and considering the statistically evaluated entry data for vehicles' and pedestrians' traffic flows. The simulation results are useful when determining the capacity of foreseen and suggested roundabouts, which will function in different circumstances. The presented model ...
Izvorni znanstveni rad Sažetak: Cilj ovog članka analizirati je zamornu čvrstoću ćelijaste lotusn... more Izvorni znanstveni rad Sažetak: Cilj ovog članka analizirati je zamornu čvrstoću ćelijaste lotusne strukture crvićastog lijevanog željeza kao osnovnog materijala. Broj ciklusa naprezanja potrebnih za širenje pukotine od inicijalne do kritične dužine pukotine određeno je numerički pomoću modela konačnih elemenata, u okviru Abaqus computation FEM koda. Kriterij maksimalnog vlačnog naprezanja razmatra se kad se analizira putanja pukotine unutar ćelijaste strukture. Izvršenje računalne analize pokazuju kako su koncentracije naprezanja oko individualnih ćelija veće kada vanjsko opterećenje djeluje u transverzalnom smjeru u odnosu na distribuciju ćelija. Članak je produljenje rada, prezentiranog na posljednjoj MATRIB konferenciji u 2014. godini [1]