Engine Mount Characteristics Identification of Large Outboard Motor Using Experimental Modal Analysis

<div class="section abstract"><div class="htmlview paragraph">Engine mount is one of the temperature sensitive components in the vehicle under-hood. Due to increasing requirements for improved fuel economy, the under-hood thermal management has become very challenging in recent years. In order to study the effects of material thermal degradation on engine mount performance and durability; it is required to estimate the temperature of engine mount rubber during various driving conditions. The effect of temperature on physical properties of natural rubber can then be evaluated and the life of engine mount can be estimated.</div><div class="htmlview paragraph">In this paper, a bench test is conducted where the engine mount is exposed to a step change in the environment around it, and the temperature of the rubber section is recorded at several points till a steady state temperature is reached. A time response curve is generated, from which a time constant is determined. Based on the time constant, an engine mount thermal model is built using a series of first order system response curves. The developed model is compared against measured temperatures from actual vehicle test data. Modeling approach and results discussed in this paper provide guidance for predicting temperature distribution inside the engine mount rubber material under various driving conditions for future vehicle programs to improve the component robustness and durability.</div></div>

<div class="htmlview paragraph">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

<div class="section abstract"><div class="htmlview paragraph">Producing 3D models of cooling water passages of outboard motors, and calculating distribution of electric potential on the water passage surfaces using BEM, we have developed the new method for simulation of electric potential distribution. The outboard motor is a propulsion system attached to the transom of the boat with steering function. As the water around the boat is drawn in for cooling of the engine, the engine parts are susceptible to severe corrosion. As a means to help prevent corrosion, a part referred to as the anode metal, which has a lower natural potential, is provided. Such a method is called the sacrifice protection because the anode metal corrodes before the engine parts due to the difference of electric potential. Since anti-corrosion currents occur preferentially to areas close to the anode metal, the anode metal is required to be located at the most effective place for corrosion protection. However, there are certain restrictions in the layout of anode metal from the engine configuration and parts layout. In addition to it, the identification of potential distribution requires measurements from the actual outboard motor. That was why it was challenging to realize a design having an ideal potential distribution. To deal with the issue, we conducted simulation of secondary current distribution in order to help predict potential distribution at the design stage. Taking actual measurements of polarization curves of outboard motor parts in the environment that matched the actual water passages and where the flow velocity existed, the measured data was uploaded as the simulation parameter. The calculated data of the potential distribution simulation are very close to the actual measurement. With the potential distribution simulation method established, it is now possible to lay out necessary number of anode metals at appropriate locations for corrosion prevention.</div></div>

<div class="htmlview paragraph">It was desired to optimize an existing design concept of an active engine mount technology intended for engines with controlled cylinder deactivation. Specifically, this case study addresses how this active Noise & Vibration countermeasure was optimized using techniques derived from Taguchi Robust Engineering and DFSS strategies.</div> <div class="htmlview paragraph">This paper will focus primarily on how the appropriate robust design strategy was applied including the selection of the response function, a properly sized orthogonal array for the design control factors, and a sufficient noise strategy.</div> <div class="htmlview paragraph">A discussion of the design control factors, noise factors, Design of Experiment (DOE), and post-experiment standardized signal-to-noise ratio optimization analysis of the non-linear response function will be presented.</div> <div class="htmlview paragraph">Design control parameters included passive attributes of hydraulic engine mounts, as well as active/electronic components. Noise strategy was defined using three variables; heat and load cycling aging, ambient temperature, and static preload.</div> <div class="htmlview paragraph">In addition, passive performance of the active mount was analyzed using non-dynamic response functions and checked against best practice performance requirements.</div> <div class="htmlview paragraph">Results obtained from the study have documented the process to optimize a design for variation using dynamic response function for the active behavior of the mount, and nominal-the-best Type I from Taguchi Methods for passive behavior. The optimized design is planned to be prototyped and verified by experiment.</div> <div class="htmlview paragraph">The paper documents the application of the latest thinking in the field of Robust Engineering and DFSS strategies. The methods, techniques, and process are equally applicable to other elastomer based anti-vibration devices.</div>

<div class="htmlview paragraph">Recent interest in applications of adaptive engine mounts to improve ride quality and passenger comfort has introduced new research areas in the field of vehicle dynamics and control. Introduction of vehicles with smaller engines and lighter and more flexible frames, for the purpose of improving fuel economy, has led to increased frame vibration levels. Frame vibration at engine idle speeds is caused by engine firing and imbalance forces which are transmitted primarily through the engine mounts. Consequently, effort has been focused on improving engine mount technology to achieve better vibration isolation.</div> <div class="htmlview paragraph">Introduction of adaptive engine mounts into the dynamics of a flexible engine-frame system requires an integrated study from both vibration and control points of view. This paper presents the results of an on-going research on applications of adaptive hydraulic mounts, manufactured by Cooper Industrial Products, on a Ford Ranger Light Truck. Several issues have been studied which form the fundamentals for optimal implementation of adaptive engine mounts. These include: system modeling, controller design, required sensors, and design of new actuators. The focus of this paper is on the controller design for hydraulic engine mounts. In particular, the issue of open-loop control versus closed-loop control will be discussed and performance of these control schemes once implemented on the actual vehicle will be compared.</div>

<div class="htmlview paragraph"><b>VIBRATION formerly was classed as such without much thought as to the determination of its sources, Mr. Taub states, and then came isolation of the various causes. The first two vibrations to be segregated and vigorously attacked were the secondary inertias of reciprocating units and torsional vibration. The development of the six-cylinder engine was among the earliest attempts to eliminate secondaries, and it was also the earliest producer of torsional vibration.</b></div> <div class="htmlview paragraph"><b>Dynamics, combustion roughness, torsional roughness and structural weakness, are a few of the contributing causes of engine roughness. Consideration must be given to all these factors if an engine is to be considered inherently smooth, and each is analyzed.</b></div> <div class="htmlview paragraph"><b>Engine mountings should have low resistance to rotation about the longitudinal principal axis and to rotation about the vertical axis through the center of gravity, together with minimum shift of affective principal axis and vertical axis. The kind of material used in engine mountings should be determined after considering the overall characteristics of the mounting and the durability of those characteristics.</b></div>

<div class="htmlview paragraph">Traditionally, vibration analysis in operating conditions (on the road or on a bench) had to be combined with experimental modal analysis in controlled laboratory conditions in order to understand the modal behaviour of the structure. This requires additional measurements, costs and time. However, in many applications, the real operating conditions may differ significantly from those applied during the modal test and hence the vibration modes from the modal test might not be representative for the active modes in operation conditions. The need for a capability of doing a modal analysis on data from operating conditions is obvious.</div> <div class="htmlview paragraph">Over the last years, several modal parameter estimation techniques have been proposed and studied for modal parameter extraction from output-only data. Each method needs to make a number of assumptions and has some limitations. In this paper, the capabilities and limitations of the Least Squares Complex Exponential and two subspace techniques, referred to as the Balanced Realization (BR) and the Canonical Variate Analysis, are evaluated for its applicability to industrial cases.</div>

<div class="htmlview paragraph">This paper presents an analytical modeling and performance analysis of the hydraulic engine mount by using bond graph method, which is becoming more common in the industry for engine vibration and noise control. It is well known that the hydraulic engine mount can provide excellent frequency and amplitude response characteristics compared to the conventional elastic rubber type one. Numerous study has been attempted up to now to explain the complex dynamic performance characteristics of this mount through a variety of analytical methods but it is not yet fully understood. In the present study, the bond graph design model, having an analytical simplicity and clarity, have been developed to analyze and predict the design performance of a “sandwich type” hydraulic engine mount with a spiral inertia track and free decoupler specifically designed for an in-line gasoline engine in order to control and reduce the high amplitude low frequency engine vibration and noise in the frequency range 1 - 50 Hz in particular. To investigate the reliability of the present developed methodology the dynamic response spectra results from the bond model such as the dynamic stiffness and the loss angle are validated with the experimental data over 1-50 Hz and 1-100 Hz frequency range. The bond graph method developed in the study had shown excellent agreements with the experimentals over the cases investigated. The present study results has shown that the bond method has an excellent applicability for the analysis and prediction of hydro engine mount performance if the dynamic system can be properly modeled.</div>

<div class="section abstract"><div class="htmlview paragraph">“The purpose of this study is to explore the structural behavior of motorcycle frames that are fabricated from metals such as steel and aluminum, and that are welded together to generate beams. The components of the wheel, handlebar, and saddle are assembled together to form the chassis of the bicycle. For the purpose of determining modal characteristics such natural frequencies and mode shapes, two different analytical approaches, namely finite element analysis (FEA) and experimental modal analysis (EMA), were utilized. The framework of the chassis was design in 3D using CAD software to carry out the FEA, and after specifying the meshing type and material parameters, normal mode analysis was carried out. To contrast modal characteristics with FEA results, EMA utilized impact hammer testing with a roving accelerometer approach. The study discovered differences between the two methods, which were effectively minimized to less than 10% by carrying out a model, update technique to increase the FEA model's precision. According to the results, model updating can help reduce differences between EMA and FEA and increase the accuracy of FEA models that are impacted by modeling difficulties and predictions of material characteristics.</div></div>

<div class="section abstract"><div class="htmlview paragraph">During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.</div><div class="htmlview paragraph">A new vibration isolation technology using passive and active vibration isolation system named Active Torque Rod(ATR) was studied for application to a new vehicle to realize quietness targets with a smaller, lighter, and less expensive engine mount system. The basic concept of the active torque rod is to set it’s resonance below 200 Hz so as not to degrade the acceleration noise due to down-sizing by utilizing the passive vibration-isolation region. However, the engine primary order (2<sup>nd</sup> order) booming noise degrades due the torque rod resonance below 200 Hz. Therefore, the resonance amplitude is suppressed by utilizing an inertia mass actuator in the torque rod and inputting an out-of-phase control force corresponding to the engine 2nd order input.</div><div class="htmlview paragraph">Technical details of ATR has been previously presented by R. Yamauchi, et al. [<span class="xref">4</span>]. Therefore this paper focuses on the benefits of applying an ATR to a premium C-segment SUV under development with a new inline 4-cylinder turbocharged engine. In order to achieve the acceleration noise targets, an active upper torque rod was applied to counter the large roll reaction force input. Acceleration noise levels were reduced by about 4 dB in the 250-800 Hz range when compared to conventional (passive) torque rod system. Both acceleration noise and booming noise achieved class leading levels. The proposed mounting system is approximately 8 kg lighter than the existing active control engine mount system.</div></div>

<div class="htmlview paragraph">In recent years, high performance engines and the reduction in engine room due to aerodynamic styling has caused increases in engine room temperature. Because of this increasing temperature, the conventional natural rubber engine mount is now at the marginal point on its performance and durability. Several heat resistant materials have been considered for engine mount applications because of this reason. Polychloroprene rubber could be a strong candidate for engine mount application due to its balance of heat resistance, dynamic properties, and fatigue life. This paper will discuss the development of the technology, property characteristics and part performance simulations on the HYUNDAI BUSH TYPE COMPLEX ENGINE MOUNT (for 2.0L DOHC ENGINE). This type of mount requires higher creep resistance and fatigue life than those of other designs, such as block or simple shear type mounts. Early evaluations of polychloroprene mounts have shown some deficiencies in creep resistance. Therefore to adress this concern, the design and formulation development to overcome the initial lack of creep resistance of polychloroprene are shown. Also, the effect of heat aging on dynamic characteristics and performance are investigated. All the test results are compared with those of natural rubber mounts. The results will show the possibility of the first application of polychloroprene rubber on this type engine mount giving improved fatigue life even after heat aging with balanced dynamic properties.</div>

<div class="section abstract"><div class="htmlview paragraph">Vibration testing is an essential component of automotive product development, ensuring that components such as engines, transmissions, and electronic systems perform reliably under various operating conditions. The adoption of electronics in the automotive industry, particularly during the 1950s and 1960s, marked a shift in vibration testing approaches, moving from primarily low-frequency tests to methods that could address high-frequency vibrations as well. This evolution highlights the need for effective vibration fixture designs that can simulate real-world conditions, enabling manufacturers to detect potential weaknesses before products are integrated into vehicles. A key aspect of vibration testing is the identification of resonant frequencies within components. The coupled mass-spring-damper system, for example, can exhibit multiple resonances characterized by a Bode Diagram, where the Q factor technique is utilized to assess damping levels. Accurate vibration analysis can be achieved through various methodologies, including modal analysis and frequency response calculations, which help engineers understand how components will behave under different stimulus.</div><div class="htmlview paragraph">Furthermore, the use of advanced analytical tools, such as Finite Element Analysis (FEA) has become increasingly important in the automotive industry. These modern approaches allow for more precise and efficient vibration analysis, providing deeper insights into potential issues and enhancing overall product reliability.</div><div class="htmlview paragraph">By adhering to industry standards such as International Organization for Standardization standard i.e. (ISO) 16750-3, Society of Automotive Engineers standard i.e. (SAE) J1455, and Military standard (MIL-STD)-810G, manufacturers can ensure their products meet rigorous safety and durability requirements, ultimately leading to reduced warranty claims and increased customer satisfaction.</div><div class="htmlview paragraph">Utilizing FEA allows for virtual prototyping, which reduces the reliance on physical prototypes traditionally used to test and refine designs. This approach not only shortens the design-to-production cycle but also allows for comprehensive testing and optimization, ultimately resulting in a more efficient development process and lower costs associated with prototype creation.</div><div class="htmlview paragraph">The design process for vibration fixtures involves a cyclical approach where simulations guide modifications. By continuously analysing and adjusting designs based on performance data, engineers can refine fixtures to meet specific criteria such as cost efficiency, structural performance, and overall functionality. This iterative nature of design helps in exploring multiple configurations and ensuring that the final product achieves all desired performance targets within the constraints of the given package space.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The study of vibrations in the structures of vehicles are very important to ensure its quality and integrity; thus, the study of the dynamic behavior of a motorcycle chassis is highly significant for their improvement. For that study, the modal analysis allows us to obtain the dynamic properties of the structure, such as its inertia and stiffness. Likewise, the damping is also an important parameter, which could be obtained by the frequency response function (FRF) of an impact load. In a motorcycle the engine, producing a broad frequency range, is the main source of excitation. A harmonic analysis with a shaker producing a frequency sweep allows one to better understand the vibratory transfer function between the engine and all the parts of the motorcycle. The experimental modal analysis (EMA) was used to characterize the dynamic behavior of the chassis. For that, a software was developed to use in a commercial board for the acquisition and processing of the accelerometer’s signals to obtain the FRFs and the eigenvectors. In parallel a numerical model was adjusted and used to compute the transfer function of vibration between engine and chassis and to test the modifications proposed for the reduction of the vibration’s transmissibility. The methodology adopted in this study managed to reduce the displacement in the motorcycle by 88% at 60 Hz, 13% at 100 Hz, and 47% at 117 Hz.</div></div>

This study carried out an experimental and numerical modal analysis of the Turkish traditional instrument 'Bendir' by an acoustical excitation source. In experimental modal analysis, Bendir was excited acoustically for specified frequencies and elastic deformations of different areas of Bendir due to the excitation were observed with a laser vibrometer. Using the Fourier series handled gained data, modal analysis was done. The first six natural frequencies obtained experimentally and numerically were compared. In addition, other hits in Bendir, symbolizing three fundamental voices such as 'dum', 'te', 'ke' were used to excite the instrument. As a result, time dependent deformation & velocity data were determined and different responses of Bendir were compared.

<div class="htmlview paragraph">A vehicle drifts due to several reasons from its intended straight path even in the case of no steering input. The multibody dynamic analysis of vehicle drift during accelerating and braking are performed. This paper focuses on modeling and evaluating effects of suspension parameters, differential friction, engine mounting and C.G. location of the vehicle under multibody dynamic simulation environment.</div> <div class="htmlview paragraph">Asymmetry of geometry and compliance between left and right side is considered cause of drift. The sensitivities of the suspension parameters are presented for each driving condition. In case of acceleration, the interaction of differential friction and driveshaft stiffness and their influence on drift are also studied. For braking condition, suspension parameters such as initial toe variation of rear coupled torsion beam axle type suspension and kingpin inclination deviation of front suspension are studied including the braking force difference.</div> <div class="htmlview paragraph">The significant factors of drift are ordered and compared for straight line accelerating, driving and braking condition. Using a co-simulation model, it is shown that significant parameters for accelerating condition are driveshaft angle and its stiffness difference between left and right side. It is shown that the location of center of gravity altered by passenger seating position has a great influence on drifting under braking condition.</div>