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The development of low noise engines and vehicles, accompanied by the reduction of costs and development time, can be obtained only if the design engineer is supported by complex calculation tools in a concurrent engineering process. In this respect, the reduction of vibrations (passenger comfort) and of vehicle noise (accelerated pass by noise) are important targets to meet legislative limits. AVL has been developing simulation programs for the dynamic-acoustic optimization of engines and gear trains for many years. To simulate the structure-born and air-born noise behavior of engines under operating conditions, substantial efforts on the mathematical simulation model are necessary. The simulation tool EXCITE, described in this paper, allows the calculation of the dynamic-acoustic behavior of power units.

Torsional dampers have been attached to engine crankshafts only for the control of the crankshaft torsional vibrations. However, a torsional damper is a mass-spring system of three-dimensions, so the torsional damper could exert some influence on the three-dimensional vibrations of the crankshaft system. Since the inertia ring of the torsional damper has moments of inertia and it rotates with the crankshaft, gyroscopic vibrations of the inertia ring can also be generated. For a V-type ten-cylinder diesel engine (V- 10, ϕ119 × 150), the three-dimensional vibrations of the crankshaft system were calculated by the dynamic stiffness matrix method, taking account of the influence of the gyroscopic vibrations of the inertia ring of the torsional damper. The dynamic bending stresses were measured at the fillets of both the No.1 crank journal and the No.1 crank pin in the No.1 crank throw plane.

Coast-by tire road noise is much effected by temperature. As temperature goes up, coast-by tire road noise level becomes lower in the case of passenger car tire. Temperature gradient of coast-by tire road noise is around -0.07 dB(A)/°C using air temperature. On the other hand, the tire is under torque during a pass-by test and some amount of extra noise is radiated from the tire pavement interface. Generally speaking, the level of tire road noise during pass-by mode becomes higher than coast-by mode. How much tire road noise is increased due to the applied torque and how its extra noise is effected by air temperature are reported here. Pass-by tire road noise consists of two components. The first component is the coast-by noise and the second component is the extra noise by the torque that is obtained by the noise level calculation of pass-by minus coast-by.

IMPLEMENTATION OF A THIRD GENERATION SOUND POWER TEST FOR PRODUCTION TESTING OF EARTHMOVING EQUIPMENT. In 1988, Caterpillar, Inc. developed an automated sound power measurement system to measure construction equipment sound levels prior to their shipment from various assembly plants. This system was primarily developed to address stationary or static sound power regulations prevalent in Europe. However, this system is not capable of verifying compliance to new dynamic sound power requirements effective January, 1997. To address the more complex dynamic procedures, Caterpillar has developed a new automated test system capable of measuring static and dynamic sound power. The automation level of this system is such that tests can now be conducted in a matter of minutes by one person, thereby eliminating the lengthy 1-2 hours of set up time and the need for additional support personnel. This paper will describe the new Caterpillar System and its implementation at our worldwide facilities.

With the introduction of ISO 9001, periodic recalibration of accelerometers and other transducers has become a requirement. Many companies have elected to purchase calibration systems that might result in a savings of time and financial resources, but without a thorough understanding of the equipment and its operation, the user may receive incorrect readings and make costly errors. This paper provides a broad overview of the Back-to-Back Calibration technique, a quick and easy method for determining the sensitivity of a test accelerometer over a wide frequency range, as well as an alternative method for making the same determination.

New technologies and new materials have changed the manufacturing process of measurement microphones within the past few years. The basic construction is internationally standardized, ensuring that the acoustic performance of the new generation of microphones is unchanged relative to the old types, but with improved long term stability and electrical performance.

In highly reverberant enclosures, the identification of noise sources is a difficult and time consuming task. One effective approach is the Inverse Frequency Response Function (IFRF) method. This technique uses the inverse of an acoustic FRF matrix, that when multiplied by operating pressure response data reveals the noise source locations. Under highly reverberant conditions the deployment of a sound absorbing body is especially useful in reducing the effects of resonant modes that obscure important information in the FRFs. Without the absorption, the IFRF method becomes practically difficult to perform in these environments due to poor conditioning of the FRF matrix. This study investigates the feasibility of using Boundary Element and Finite Element Methods to establish the frequency response functions between selected panel points and microphones in the array.

This paper examines the feasibility of using the boundary element method (BEM) and the Rayleigh integral to assess the sound radiation from engine components such as oil pans. Two oil pans, one cast aluminum and the other stamped steel, are used in the study. All numerical results are compared to running engine data obtained for each of these oil pans on a Cummins engine. Measured running-engine surface velocity data are used as input to the BEM calculations. The BEM models of the oil pains are baffled in various ways to determine the feasibility of analyzing the sound radiated from the oil pan in isolation of the engine. Two baffling conditions are considered: an infinite baffle in which the edge of the oil pan are attached to an infinite, flat surface; and a closed baffle in which the edge of the oil pan is sealed with a rigid structure. It is shown that either of these methods gives satisfactory results when compared to experiment.

This paper is concerned with the prediction and experimental verification of the interior noise of cabs used on construction, highway, and farm equipment. The typical heavy equipment cab is totally enclosed and partially lined with absorbing materials but is much stiffer and more massive than automobile passenger compartments. The process to analyze a construction cab is explained in detail. Selected results are also presented to show the value of the method.

The perturbed boundary condition (PBC) model updating procedure has been developed to correct the finite element model [1]. The use of additional structural configurations adds more experimental information about the system and so better updating results can be expected. While it works well for simulated examples, practical limitations and additional requirements arise when it is used to update engineering structures. In this paper, the merits and the practical limitations of the techmques will be discussed in depth through the updating of a simulated system where the “measured” data is generated by computer and a real test structure where the experimentally measured data is noisy and distorted due to leakage. Useful suggestions and recommendations are drawn to guide the model updating of practical engineering structures.

A new method to estimate a structure's inertia properties using a prototype load cell designed to measure all loads and moments applied to a structure is presented. This prototype six-axis transducer approach employs 32 piezoelectric sensing elements which are arranged to form the load cell. These redundant measurements are used to determine the principal forces and moments from an overdetermined set of equations. Calibration of this multi-crystal load cell is performed with a fixture that utilizes a calibration mass and quasi-free-free boundary conditions. The resulting calibration matrix is a 6×32 transformation from the coupled measurements to a decoupled set of pseudo measurements consisting of the forces acting on a structure. With this transducer and its calibration matrix, a system's inertia properties can be estimated. A thorough discussion of both the calibration and inertia estimation procedure with a experimental test case is presented.

An experimental study has been carried out to investigate the effect of the level of fuel pump shaft Torsional Vibration (T.V.) on engine noise. The study was carried out on several 6 cylinder automotive DI heavy duty diesel engines. The level of fuel pump T.V. was changed by fitting torsional dampers to the fuel pump shaft. A strong correlation was found between the T.V. level at 12th order of fuel pump rotation and the overall engine noise. Reducing the 12th order of fuel pump T.V. gave significant reductions in both overall and broad-band engine noise.

Recently, for the purposes of shortening the development period, the estimation of powerplant vibration has become more important in the early design stage, and eigenvalue analysis by FEM is commonly used to solve this problem. Eigenvalue analysis cannot directly predict vibration levels that affect the durability of each component and the vibration of a car body, however it is necessary to predict powerplant vibration in order to estimate exciting force under running conditions. Another factor adding to the difficulty of prediction is the instability of exciting force and various other non-linear characteristics. This paper presents a new approach using FRF data from FE models for accurate prediction of engine vibration under running conditions. By applying this approach to an in-line four cylinder engine, the predicted vibration is reasonably comparable with experimental results.

In recent years attainment of high automotive sound quality has become a major effort in automotive vehicle refinement programs. Low frequency vibration phenomena, such as idle shake and transmission rattle, have emerged as major issues in the efforts to minimize undesirable sound qualities. Low gear rattle noise is often touted to differentiate automobile quality. Transmission rattle is caused by engine excitation and backlash in geared transaxles. Backlash yields piecewise nonlinear characteristics in gear mesh stiffness. Despite intensive research efforts in the past, it is known that numerical difficulties in handling the nonlinearity have prohibited the development of general criteria of design of transmissions to eliminate the rattle noise. This paper describes an analysis technique for investigation of the rattle dynamics in geared transmissions.

Post Consumer Recyclate (PCR) or Post Industrial Regrind (PIR) use to manufacturer thermoplastic (or thermoset) automotive parts and components, has increased over the last 20 years. Therefore, automotive designers are challenged with the question of how recycled material differs in performance from virgin? In addition, automotive OEMs are requiring increased durability of thermoplastic parts and their attachments (joints), so that warranty costs, associated with interior squeaks and rattles are minimized. From this durability need there have grown several techniques for determining an attachment's performance capabilities, they are: strip-to-drive torque ratios, screw pull-out force, and clamp load fall-off. For example, if a boss has a low strip-to-drive torque ratio (< 3) there exists the potential for assembly and/or field failures.

Since powertrain noise sources are usually “hidden” within the engine compartment, it is difficult to use NAH to identify those sources and the associated partial radiation fields that together create the exterior noise field of a motor vehicle. Integrated Nearfield Acoustical Holography (INAH) has been developed to address this concern. INAH represents a combination of NAH, reference microphone selection procedures, and coherence techniques. The procedure entails sensing the sources inside the engine compartment by using an array of reference microphones, and then calculating the associated partial radiation fields by using NAH. A key factor in the success of this procedure is the selection of a good reference microphone sub-set. A selection procedure has been developed by combining condition number and coherence analyses. The partial field determination problem has been approached by using both partial coherence and Singular Value Decomposition (SVD) procedures.

Localization and ranking of sound radiating regions on tyres under transient conditions is very difficult both because of the transient nature and because it is difficult to measure sufficiently close to the sound radiating regions. Using Near-field Acoustic Holography it is possible to measure at some distance and then extrapolate back to the surface of the tyre. With the Time Domain Acoustical Holography it is further possible to study the transient nature of the sound generation in any desired detail. As an example, the present paper compares the sound radiation under stationary and under accelerating conditions.

A simple mathematical model was developed and experimentally validated to evaluate how the materials and construction of an automobile tire affect its vibration-radiated noise performance. The mathematical model uses Statistical Energy Analysis (SEA) with modal joint acceptance formulations for wavespeed and radiation efficiency of orthotropically-stiffened and pressurized cylindrical shells. Experimental validation of the model included wavenumber decomposition to determine the dispersion characteristics of an inflated, non-rolling tire in the laboratory. The model is used to conduct a preliminary study into how the various tire constituent materials and construction parameters influence the vibration-radiated noise performance.

A laboratory technique has been developed for simulating high frequency tyre noise in a car. The technique characterises air-borne tyre noise and its transmission from the tyre and road contact patch to the occupant positions. The technique could be applied to the rapid definition of design modifications in a laboratory environment and the generation of competitive criteria for vehicle benchmarking.

Tires are one of the dominate sources of exterior vehicle noise. In this study, Nearfield Acoustical Holography (NAH) is used to investigate the sources of noise generated by tire interaction with an outdoor road surface. One tire on a two wheel trailer is examined while towed by a vehicle at 56 km/hr (35 mph) along a smooth, consistent road surface. The complex pressure is measured at discrete points along a plane parallel to the side of the tire by scanning with an array of five microphones. Because of the incoherence of noise generated at the leading and trailing edges of the contact patch, and radiation from the side wall, three reference microphones are used. NAH is used to reconstruct the pressure on planes towards and away from the tire, thereby obtaining a three dimensional image of the acoustic pressure, particle velocity, and intensity for noise generated at the contact patch leading edge and trailing edge, and by the tire sidewall vibrations.