Application of the hottest virtual product develop

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Application of virtual product development technology in vehicle driveline acoustics

I. preface

today, the development of vehicle driveline has various objectives and requirements, such as high performance, low emission, high comfort and high quality. In addition, in order to give passengers more space, the space requirements of the product are very small, and the development time should be short and the cost should be low; In particular, the noise and vibration characteristics of vehicles have become one of the most important factors for users to judge the quality of vehicles. This is not only reflected in high-end luxury vehicles, but also in some mid-range vehicles. For the noise and vibration characteristics of vehicles, the total noise level should be kept at a low level, and the quality of noise is also the most concerned problem

for the whole vehicle, to achieve the artistic NVH (noise, vibration, harness) characteristics, the crucial problem is to pay attention to the noise and vibration problems in the conceptual stage of engine development. For those specific indicators related to vehicle NVH performance, such as engine natural frequency, vibration amplitude and noise radiation, they need to be defined at the initial stage of product development. One of the main characteristics of graphene is its excellent heat dissipation performance, which tracks the changes of these basic parameters over time in the whole development process

it is not an optimal product development method to optimize existing products by finding problems and making improvements in the process of use. In order to obtain the best vehicle acoustic performance, we need to use virtual product development (VPD) technology at the initial stage of the concept of product development. Because in the early stage of product development, through reasonable efforts, it is relatively easy to modify the design without any cost; However, modifying the design in the later stage of product development will not only waste time, but also increase the development cost. Figure 1 reflects the role of CAE (Computer Aided Engineering) in each stage of product development and the change of product development cost with development time. It can be seen that in the later stage of product development, the role of CAE gradually decreases, and the higher the cost of modifying the product

II. Engine noise and vibration simulation

in the whole development process of engine NVH characteristics, the method commonly used by major automobile companies in the world is to use virtual development technology. A fully parameterized simulation model is needed in all stages of engine development. Therefore, it depends on the current design status to provide this model, and the models produced by different simulation tools and models with different complexity can be put into virtual development tools

in the conceptual stage of engine development, the determination of commonly used parameters such as piston stroke, cylinder diameter and cylinder spacing is based on a fairly simple simulation model. With the development of design, more design parameters can be determined, so the complexity of the simulation model will increase. Until a complete and flexible engine model is established and installed into the transmission system, the NVH characteristics of the whole transmission system can be simulated and predicted. At each stage of the design, the ongoing design must be able to continuously analyze the possible weak links. Once individual optimized single parts are installed into the system, unexpected noise problems may be caused. Noise calculation is also carried out in the whole powertrain. This method can ensure that the possible noise problems between parts can be found and eliminated in the early stage of product development. In the past, the virtual technology of NVH applied to product development and optimization was mainly concentrated in a single component or subsystem. At present, due to advanced simulation methods and high-speed computer computing power, a complete simulation model of the power train can predict the detailed acoustic performance of the developed final product

at present, major automobile companies all over the world use a variety of methods to simulate the acoustic performance of power train. In order to make the simulation results more accurate, the combined structure simulation MBS (multi body simulation), finite element method FEM (finite element method) and boundary element method BEM (boundary element method) are usually mixed together for calculation. Figure 2 shows a complete calculation process

the calculation of exciting mechanical mechanism usually uses composite structure to simulate MBS. Based on measurement or calculation, we can get the internal pressure of the cylinder block, the dynamic effect, the reverse force on the interface between the crank connecting rod mechanism and the cylinder block, and so on. By embedding the flexible structure into the MBS model, the dynamic structure influence of components can be considered. In this way, the dynamic effects of crankshaft bending and torsion and engine mount vibration can be calculated. Figure 3 shows an example of MBS Adams with a built-in four cylinder engine model, which includes a crank connecting rod mechanism and a valve train

after the MBS calculation of the composite structure simulation, the next step is to carry out the finite element calculation of the reaction force, that is, the reverse force borne by the finite element model. In general, the advantage of finite element calculation in time domain is that the whole velocity scanning area can be completed in one calculation. Moreover, through standard software, all analyses can be verified on the test bench at the same time, and sound can be produced. This kind of calculation is often carried out on a complete power train, but sometimes it is also carried out on a single structure. Therefore, various sound design and optimization can be tested according to frequency characteristics, total noise level and sound quality. In this example, the number and position of the power train fulcrum are optimized according to the minimum structural load-bearing noise transmitted to the vehicle body. Based on the optimization results, the air noise radiation can be further simulated and calculated. It can calculate the air radiated noise with various complexity, from a simple method based on the noise radiation efficiency determined by experiments to a complex calculation using the boundary element method

III. correction of simulation process

the calculation method described above has been successfully applied in many engine projects of some large European automobile manufacturers, and the performance of the software has been continuously modified in view of the problems in the application process. Next, the industrialization and range utilization results of the computer simulation of the tested vehicle are compared with the corresponding bench test results

with regard to vehicle interior noise, especially the structural bearing noise in the low-frequency range is very important. The structural bearing noise of the power train is transmitted through the bearings, and then radiated in the form of air noise in the vehicle interior. Therefore, in order to predict the NVH characteristics of the vehicle powertrain, the part of the structural load-bearing noise of the powertrain transmitted to the vehicle body must be accurately simulated. Figure 4 shows the comparison of the two results of the acceleration supported by the engine under the conditions of simulation calculation and actual measurement. The measuring points of the two groups of acceleration curves are on the transmission support, close to the transmission. It can be seen from the figure that the calculated simulation results are particularly consistent with the bench test measurement results. The vibration order of the natural vibration is particularly consistent with the ignition sequence of the engine. In two cases, the resonance point of the excitation sequence appears at 400Hz, 600Hz and 800Hz

IV. vehicle interior noise simulation

in addition to the airborne noise and structural load-bearing noise of the power train, the noise transmission characteristics of the vehicle body also play a vital role in the vehicle interior noise caused by the engine. This means that the interior noise of the vehicle caused by the engine cannot be calculated only from the noise characteristics of the power train. For engine development, its contribution to vehicle interior noise has certain development goals. Europe has developed a method to simulate vehicle interior noise, which combines the simulation of radiated noise with an annual production capacity of 85000 tons of tepov products and the vins (vehicle interior noise simulation) method of test vehicle interior noise simulation to obtain the final ideal result

v. analysis of test transmission path

simulation of vehicle interior noise vins is a test analysis tool used to produce the synthesis result of vehicle interior noise. It is a measure to combine the transmission characteristics of the vehicle body determined by the test with the structural load of the power train and the air radiation noise to synthesize the vehicle interior noise. For each noise transmission channel of the vehicle body, the transfer function is determined by the test. Through the adjustable phase superposition of all noises obtained from the bench test, and using the body noise transfer function, the interior noise caused by the engine can be synthesized completely. Under normal circumstances, the interior noise can be decomposed into structural bearing noise and airborne noise. In many vehicles, vehicle structure borne noise affects the interior noise mainly in the low-frequency region, while airborne noise dominates in the high-frequency region. In many published literatures, this method has been modified, and the consistency between the test results of vehicle interior noise and the synthetic results is particularly high

combine the vehicle interior noise simulation vins with the structural load-bearing and airborne noise simulation, and apply it to the virtual vehicle interior noise simulation (v-vins) in which the price has not changed much all over the country, so that the evaluation of vehicle interior noise can be realized before the initial model is released. Figure 5 shows the comparison between this new method and the simulation results of standard vehicle interior noise based on the measured results of bench test. This is two groups of curves of engine interior noise under full load. These two groups of curves compare the noise quality. The engine ignition sequence represents the sound perception and noise levels with resonance frequencies of 300Hz, 480HZ and 700Hz, as described above. The noise characteristics of the interior noise distribution results obtained by full simulation calculation are relatively unified, which means that the simulation results and the actual measurement results can identify the same noise peak, so the same noise optimization measures can be obtained

therefore, the vehicle interior noise caused by the engine can be calculated and optimized at the engine model development stage, so the development time can be saved; Moreover, for the internal noise of the vehicle, the engine can be designed and optimized at the conceptual stage of the vehicle. This method can ensure that the target engine focuses on the excellent interior noise characteristics from the beginning of the development process, making the development process more convenient and easy

VI. conclusion

for NVH simulation of vehicle power train, virtual product development (VPD) technology has reached a relatively high level. Modern simulation tools can allow us to design goal oriented NVH simulation calculation, as well as the design of vehicle interior noise. Due to the application of a series of VPD in the process of product development, it is possible to save a physical model. Of course, this requires the development of a large number of CAE (Computer Aided Engineering) resources in the early stage of vehicle powertrain development. (end)

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