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Hans Dück, CLAAS Selbstfahrende Erntemaschinen GmbH
The presentation is about…
the big question: “How to choose measurement sensors and their positions to determine the load data required for the dimensioning of our products?”
A semi-automated process will be presented to define a measurement concept and strain gauge positions to determine the required load data out of measured strains
Knowing the loads that occur in field condition is essential to properly dimension any product. Obtaining this data for the use in a simulation or a test bench, however, is not an easy task.
Therefore, at CLAAS, a process was developed to determine the most relevant loads a given structure experiences during its use which can then be used in the development process for a fatigue analysis or a test bench.
This is not a straightforward task, and the approach can vary based on the subject. Nonetheless, there are some process steps to define and check a possible measurement concept. In iterative steps of defining and checking sensor definitions a feasible measurement concept can be developed.
Apart from the general methodology, two practical examples (Pictures above) how we measure loads in field conditions and their specifics towards the process will be shown.
Dr. Gernot Jedinger-Pauschenwein, AVL List GmbH
Accurate load case definition plays a pivotal role in the virtual development of tractors. To effectively predict dynamic behavior and perform strength and mechanical fatigue analysis, it is essential to establish a reasonable correspondence between simulation conditions and realworld field conditions. Forces in the wheel hubs could be investigated with measurement rims. However, this procedure is expensive, and the determined forces refer to only one special tractor parameter set. This means, even a change of a ballast mass makes the measured forces unusable for further simulations. Therefore, developers seek input parameters that are independent of the specific tractor configuration, whereby the field path profile emerges as a promising solution.
The method presented here allows the identification of the road profile traversed by a tractor based on measuring accelerations. The objective is to obtain a profile that, when simulated, produces accelerations in the tractor as close as possible to those generated by the original profile. Starting with a complex nonlinear tractor model in ADAMS, a simplified model with a reduced number of degrees of freedom is derived.
The simplified model is linearized to a linear time-invariant (LTI) system, whereby the wheel hub forces are the input variables. Under certain conditions, especially in view of number and positions of the acceleration sensors, the LTI system can be inverted, resulting in forces as outputs, and the measurement signals are used as inputs. Knowing forces, state vector, tire stiffness and damping, a differential equation is applied to deduce the actual field path profile under consideration of the tire geometry.
The original accelerations refer to a complex model, whereas the identification is carried out with a simplified LTI model. As a result, the identified profile deviates from the original one. Therefore, a virtual iteration process in time domain was developed so that the identified profile converges to the original one. Finally, three examples will be presented. The first one is the field path detection of the Merry-Go-Round test (MGR). Based on accelerations measured close to the wheel hub centers, the obstacle shape can be identified. The accelerations achieved with the iterated path profile correspond sufficiently accurately with those ones referring to the original profile.
A further test track is the ISO 5008 rougher road. In this case, too, the accelerations owing to the iterated path profile match with those caused by the original one.
The last example is the four-poster test rig, which consists of four hydraulic actuators, each positioned under a wheel of the vehicle. Objective is to achieve the same vertical accelerations as measured in the field. The presented algorithm provides the input signals for the actuators, and the target of reproducing the original acceleration on the test rig is met very well.
A cost-effective and sufficiently accurate method has been established for field path detection based on virtual iteration in time domain. Therefore, field path detection is a good basis to define accurate load cases for finite element analysis.
In vehicle development process, chassis rig test is carried out to assess durability of chassis structural parts and bushings. Digital Twin (DT) is a multi-body dynamics (MBD ) simulation tool which is virtual model of chassis rig test set up. It is used to facilitate iteration process of drive signals and investigate fatigue failures of suspension components. Simulation model is built from full vehicle MBD model with boundary conditions and actuators corresponding to physical chassis rig.
The project work involved close collaboration between Magna rig test engineers and Zeekr Tech EU simulation engineers focused on shared insight into chassis system loading and test improvements. Simulation results are subsequently used in analysis of failures of chassis components. Presentation shows some examples of digital twin application from chassis rig tests performed during 2022-2024.
Koji Baydoun-Hidding, Jungheinrich Moosburg AG & Co. KG
In recent years, the acoustic performance of industrial trucks has become a major development goal with view to improve health and safety of the truck drivers as well as people working or living in the surrounding. In an electric forklift truck, the powertrain and the hydraulic pump are two of the main noise sources transmitting structure-borne noise into the truck chassis. Acoustic simulations are often employed to assess the sound propagation in the truck chassis and the noise level inside the driver’s cabin. In an early phase of the development, the passive structural components such as the truck chassis and the cabin are typically designed independently from the source components. Here, one faces the challenge to define a representative set of excitation forces, which allows to assess the effect of design changes in the truck structure with respect the noise sources.
In this paper, we address this issue and employ a component-based transfer path analysis to characterize the structure-borne noise transmission at the interface between an electric powertrain and the chassis structure of a forklift truck. Following an in-situ approach, the blocked forces at the interface are derived based on operational drive measurements and the corresponding transfer functions. These experimentally determined blocked forces are then applied as excitation in a structure finite element simulation of the forklift truck. Lastly, the sound field inside the cabin and the pressure level at the driver’s ear are determined using an acoustic finite element simulation and the results are compared with microphone measurements. The presented approach enables a simulation-based assessment of the effect of design changes in the passive truck structure while taking the inherent excitation of source components into account.
Dr. Stefan Reichl. Wacker Neuson Linz GmbH
In construction machinery the focus on driver’s comfort in the context of cabin noise and human vibrations has been increased significantly in the last years. Therefore, Wacker Neuson started to put noticeable effort in NVH development on numerical simulation side as well as on physical measurements.
In this contribution current methods in NVH development are shown on the example of a wheel loader platform. Powertrain and drivetrain consist of a Diesel engine, an axial piston pump (drive pump), a gear pump (working pump) and an axial piston motor. A new cabin is developed and used for a whole platform from 4t up to 8t.
In the first step structural stiffness properties are analyzed and optimized. Engine isolation is simulated and suitable engine mounts are defined. In the next task dynamic stiffness optimizations are done on chassis and cabin frame. Target values are specified together with consulting partners and suppliers. The big advantage of this method is that such simulations can be done in an early project phase and that it is fully independent from excitation data.
In the next step the driver’s comfort is investigated in the cabin and therefore structural and fluid interactions are considered. Cabin cavity modes are simulated to avoid resonances of the air volume in a critical frequency range. Then vibrational and acoustic transfer functions are simulated for a better physical understanding of the influences in sound pressure at driver’s ears.
For the exterior noise the cooling fan is the most critical component and therefore aero-acoustic investigations are done on a fan test rig, which has been developed in-house at Wacker Neuson. This analysis is based on purely physical measurements, because no simulation software or hardware is available at Wacker Neuson for such a complex task. To reduce the effects of background noises in an interior surrounding of the protype area sound intensity measurements are used.
A side topic which should also not be neglected is the vibrational behavior of attachment parts like exterior mirrors or light brackets. These components are always inside the field of the driver’s view and contribute to the sense of comfort, too. Eigenfrequency simulations are shown in combination with validation measurements.
After the implementation of all recommended optimizations final NVH measurements are done on the prototype machine. Beside the typical measurements for the fulfillment of ISO standards customer-relevant operating conditions are analyzed in more detail. The focus is on dynamic driving cycles as well as stationary operating cycles with active working hydraulics. A root-cause analysis and an optimization of hydraulically induced cabin noise will be presented. Finally the validation of cabin mount decoupling and structural stiffness influence of the chassis is done to check accuracy and trends of previous numerical simulations.
An outlook of development methods will be given and future NVH trends should be part of an open discussion with the community at the conference.
In an increasingly competitive automobile industry, accurate simulations and predictions play a central role in optimizing costs and lead time.
While static-based fatigue simulation has proven sufficient in numerous applications for durability estimation, it falls short when it comes to accurately predicting damages for vehicles with lower natural frequencies within the range of road load excitation frequencies. Light commercial vehicles often fall into this category. To address this challenge, dynamic-based fatigue simulation techniques have emerged as an essential tool. By considering the dynamic behavior of the vehicle, these simulations provide a more accurate prediction of damages caused by road load excitation.
This presentation will showcase a comprehensive study conducted on the Renault Master, a prime example of a light commercial vehicle.
Viktor Jakab, Knorr-Bremse Fékrendszerek Kft.
The truck industry plays a significant role in the automotive market, and its products are a catalysator for the development of transportation and establishing international connections across borders and even continents. Knorr-Bremse is a leader in supplying a wide range of highquality parts for truck manufacturers, who want to build strong, durable and capable vehicles for various applications for their customers. Fast and effective product development is a key in successful business operation, and it requires the application of state-of-the-art solutions that are highly reliant on modern calculation methods, such as virtual testing i.e., simulations.
Vibration is one key aspect that needs to be considered during product development, because structural durability is vital for any part being installed on any truck or work-equipment. The effects of long-term vibrational impacts can be evaluated with tests, but these are often costly, they can last for a long time and require at least a real-life prototype of the product, which means they can only be carried out at a later stage of the development process. However, if any issue arises with the design, it’s always best to make it visible as soon as possible, and correct it right away. The use of simulations can eliminate most of the above-mentioned drawbacks of real-life testing, because it’s cheaper, faster and can be carried out already in the early conceptional phase of the design.
Here at Knorr-Bremse we have been using simulations for decades now as a support of the “conventional” product development. In this presentation we will introduce a workflow for structural durability testing using multiple simulation software (incl. MAGNA products such as FEMFAT Spectral) on the example of a piston compressor, where the crankcase and the mounting flange are the main subjects of the evaluation.
The process is based on a structural analysis carried out in ANSYS Mechanical, where numerous loads need to be considered e.g., bearing forces and cylinder pressure (coming from the rotational movement of the inner mechanism of the compressor), that are calculated using a separate GT-Suite model specifically developed for this application. The effect of thermal changes in the environment can be taken into consideration as well. The structural calculation is followed by a modal analysis, to evaluate the eigenfrequencies of the whole assembly in the given frequency range (that is impacted by the range of the PSD excitation profile used later). The final step in ANSYS is a Harmonic Response calculation that gives us the transmission characteristics of the parts. These results are all used as inputs for a FEMFAT Spectral calculation, where a given PSD profile (coming from a standard or measurement data) is defined and the different parts are evaluated with consideration of multiple factors (such as surface roughness or temperature field amongst others). Usually there are multi-directional excitation profiles, and their effects need to be considered simultaneously as well.
In my presentation I’ll talk about the possibilities and challenges of applying a sinusoidal excitation (coming from the internal operation of the compressor) on top of the random excitation coming from the environment of the parts as well. Our method has proved itself over the years to be capable of eliminating failures caused by long-term fatigue damage. This will be shown by an example on how such simulations can provide evidence in case of an issue during any stage of the product lifecycle.
Christian Neubacher, Magna Powertrain Engineering Center Steyr
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Dipl.-Ing. Markus Breitfuss, Magna Powertrain Engineering Center Steyr
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Location will be announced soon
Marius Franck, FEV Europe
Electric machines are increasingly being used as the primary drive technology due to the electrification of vehicles. The design of these machines is subject to high-quality requirements regarding acoustic behavior. Parasitic force excitations during electromagnetic energy conversion lead to vibration excitation and tonal sound radiation, which can be perceived as disturbing. To improve acoustic behavior, numerical calculations and optimizations are already carried out during the design phase. Precise damping models are necessary to evaluate vibration phenomena. However, these models can only be parameterized on a prototype through experimental modal analyses and are only valid for the investigated geometry.
To enable transferability and prediction, a damping modeling approach is chosen that considers the effective damping phenomena separately. An energy-based and linearized damping model for electric machines is developed to enable an initial prediction of acoustic behavior in the design process.
This includes considering internal damping phenomena such as material and joint damping, as well as external damping phenomena such as radiation damping in surrounding fluids.
Analytical and numerical homogenization methods are investigated for modeling the stiffness and material damping of laminated cores and winding systems. Experimental modal analyses are conducted on individual components, assemblies, and a mounted electric machine to validate the proposed models. Methods for model-based planning of experimental modal analyses are further developed to reduce uncertainties in damping determination and model correlation.
For the model validation of the mounted machine, measurements are carried out using a robot-assisted 3D scanning laser Doppler vibrometer. This measurement method enables a non-intrusive analysis of the vibration behavior up to approximately 12 kHz. Different methods for exciting the structure with a shaker or automated modal hammer are investigated. It is shown that the proposed linear damping models underestimate the measured damping, but the qualitative trend can be well represented. Material and joint damping are particularly significant.
Finally, the methods for damping modeling are integrated into a system model for a preliminary calculation of the operational vibration behavior. The results of this calculation are compared with measurements on an acoustic test bench.
Dr. Siegfried Silber, Linz Center of Mechatronics, GmbH
Multiphysics is becoming increasingly important in the optimization of electric vehicle (EV) motors. As motor speeds continue to increase, rotor strength considerations become more critical. The increased speed requires a deeper analysis of the rotor mechanics, where material properties, thermal effects and dynamic stresses interact in a complex way. In this context, it is particularly important to consider the nonlinear material behavior (nonlinear stress-strain curve) and to allow a small amount of plastic deformation during optimization. Allowing controlled plastic deformation can lead to designs that make better use of the capabilities of the material without compromising reliability. The accuracy of the models must be high enough to ensure that valid rotor designs are not later deemed unacceptable during detailed calculations, while avoiding excessive design margins that would negatively affect performance or cost-effectiveness.
Another critical aspect is the NVH (Noise, Vibration, and Harshness) behavior of the motor, which must also be improved as part of the optimization process. NVH optimization aims to reduce noise emissions and vibrations, which directly affects user comfort and the perceived quality of the electric vehicle. This can be achieved by evaluating different orders and harmonics in the force excitation spectrum. Specific vibration modes that contribute significantly to the noise are targeted during optimization, allowing for noise reduction. By shaping the rotor contour, specific harmonics can be influenced and reduced.
In addition, it is important to account for manufacturing tolerances, such as static or dynamic eccentricities, during the optimization process to ensure robust motor performance. Manufacturing imperfections, such as rotor and stator misalignment, can cause significant deviations in motor behavior if not properly accounted for. Incorporating these tolerances into simulations helps develop a robust design that maintains consistent performance despite real-world variations.
In summary, optimizing EV motors requires a comprehensive approach that integrates multi-physics interactions, rotor strength, NVH behavior, and manufacturing tolerances. By addressing these factors together, the performance, efficiency, and compactness of EV motors can be significantly improved, supporting the advancement of EV technology and promoting its widespread adoption in the automotive industry.
Anton Plank, Magna Powertrain Engineering Center Steyr
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There is for sure a high demand for nonlinear structural dynamics in implicit Finite Element Analysis (FEA). Although such methods are available, there are severe obstacles to use them daily. One is their extreme and not predictable computation time, which makes it often impossible to get results in time. Another point is the restriction of the methods to the time domain, which is in many cases in contrary to the usual design rules based on frequency domain results.
With the Harmonic Balance Method (HBM), there is a solution for at least an important sub-class of analysis cases, which resolves the two mentioned obstacles. As a starting point, we define HBM as a frequency response analysis with nonlinear elements like springs, dampers, or control elements. This allows to solve e.g. contact problems or mounting problems with nonlinear force-deflection curves. In fact, the HBM is a method in frequency domain, but an alternating use of frequency domain and time domain is necessary to cope with the nonlinearities. The primary results are in frequency domain. On this basis, for all calculated frequencies, a solution in time domain is also available.
The paper will use a simplified radiator as industrial example to demonstrate the HBM. To prove the validity of the HBM procedure, a comparison with a linear frequency response analysis is performed, which shows same results. Then, rubber bushes and contact are added to the model as nonlinearities. Sufficient damping is applied to avoid multiple solutions for any frequency in the observed frequency range. Then, stress results are presented. Finally, the computation times are analysed to demonstrate the feasibility of the described process for practical applications in research and industry.
All simulations are performed with the commercial FEA software PERMAS, which contains the HBM among a lot of other analysis methods in structural dynamics.
Mathilde Laporte, Deutsches Zentrum für Luft- und Raumfahrt
The German Aerospace Center (DLR) develops pioneering rail vehicle concepts that enable improvements in terms of energy and resource efficiency, as well as wear and comfort. To make rail transport more attractive and sustainable, it is important to improve passenger comfort, but also to reduce resource consumption and CO2 emissions. However, these requirements are contradictory, since increasing comfort results in a mass increase. The increase in mass can be explained by adding accessories or improving existing components inside the train, such as increasing the size of the seatsfor instance. To meet these requirements, a lightweight design must be used for the car body.
In order to respect our challenges, suitable design methods and verification concepts are needed that fully exploit the lightweight potential of the materials used. So far, static equivalent loads are generally used in the design of rail vehicles in accordance with the fatigue strength verification defined in the standards, as for example EN 12663-1. However, this procedure assumes metallic materials, and it is not suitable for adequately considering the dynamic loads that actually occur during operation. This can lead to unnecessary oversizing of the vehicles, which runs counter to the goal of lightweight construction. We developed then a methodology in which design and strength verification are carried out using dynamic loads from flexible multi-body simulation and fatigue strength calculation. This can pave the way for the application of lightweight construction concepts for railway vehicle car bodies.
Our method consists first to create a finite element (FE) model that includes geometry, materials, initial conditions and interface nodes to the multi-body simulation (MBS) model. This model is prepared for integration as a flexible body in the MBS model by model reduction and exported. The model reduction method according to Craig-Bampton is a mathematical method for drastically reducing the numerical complexity of the FE model, assuming small deformations and a limited frequency range, so that the computational effort for the simulation is reduced accordingly.
In the next step, the reduced car body model is imported into the MBS model of the center car. This model is used to simulate various scenarios relevant for the damage calculation of the car body. The flexible modeling not only has the advantage of more realistic loads, but also makes it possible to calculate car body stresses directly in the MBS simulation. This data is finally imported into the fatigue software FEMFAT to estimate damage accumulation and the service life of the structure. In addition, aerodynamic loads from CFD simulations are considered for the fatigue analysis. For the last step of our method, the welds are defined directly in the fatigue analysis software and a structural durability analysis is done. This last simulation allows us to detect the first damaged location on the structure and finally adapt it for the required life time. The simulations described above were carried out using the FEMFAT MAX module. This makes it possible to import a *.max file that contains multiaxial loads and is generated from the results of the MBS simulation.
In a first step, our simulation-based design process is made only for metallic structures. In a second time, the same with composites will be analyzed and compared to metal structures.
Location will be announced soon