Mitchell M. Marchi

Practical applications of holometric methods in automotive testing

The purpose of this paper is to relate several automotive industry applications of holographic interferometry, or holometry. Holographic nondestructive test methods are now routinely used in industry to study structural integrity and to assess vibrational response of components. This work is usually performed to verify that a component will not fail in service. The work cited in this paper was performed instead for the purpose of assessing the noise, vibration, and harshness implications of various hardware configurations. Four examples of such work will be presented; objectives, methods, and results will be discussed for each example.

Recent advances in brake noise and vibration engineering using laser metrology

Noise, vibration, and harshness (NVH) can be predominate brake noise described as roughness/judder, brake creep groan, and brake squeal, all of which are important issues and concerns for customer satisfaction in the automotive industry. Brake roughness and groan are low-frequency vibration and noise, while brake squeal is a high-frequency noise. These have been the challenging issues for engineers and researchers for many years due to their complex nature that involves multiple disciplines such as nonlinear dynamics, contact mechanics, and tribology or nanotribology. As in the body/chassis and power-train arena, laser metrology can be uniquely applied in brake NVH to shed light on this complex issue. Engineers can gain insight on NVH fundamental root causes and provide guidance for optimal design resolution. We provide some examples that illustrate the recent progress and novel applications of holographic interferometry, pulsed laser holographic interferometry, pulsed laser electronic speckle pattern interferometry, and laser Doppler vibrometry methodology to identify the root causes of brake concerns and verify engineering solutions.

Powertrain Engineering Using Holographic/Electronic Speckle Pattern Interferometry

Novel applications of computer aided holographic interferometry and electronic speckle pattern interferometry in automotive powertrain engineering are presented. Four applications are described: engine manifold/cylinder head interface deformation measurement, engine camcover strain analysis, throttle bore deformation measurement, and alternator modal characterization.

Phase determination of a single fringe pattern by regional Fourier transform method for transient event analysis

This paper proposes a regional Fourier transform method for determination of a phase map from a single fringe pattern. This method can be used for transient event analysis.

Current applications of hologram interferometry at Ford USA

Testing of vehicle components with holometry to improve their structural characteristics is a proven methodology. Full field, high sensitivity holometric measurement capabilities are used for the iterative improvement of prototype structures (static and dynamic). The combination of modeling methods and Computer Aided Holometry (CAH) is just beginning to impact structural design. Current examples of studies of static and dynamic behavior of vehicle components using continuous wave CAH techniques are presented.

Holographic interferometry and its application in brake vibration and noise analysis

Brake roughness and brake squeal are important issues/concems of customer satisfaction in the automotive industry. Brake roughness is a low frequency vibration while brake squeal is a high frequency noise. Some fundamental root causes of brake roughness are rotor runout, rotor surface flat spots, etc., which cause brake torque variation that in turn produces unwanted low frequency vibration. Brake squeal is a dynamic instability and nonlinear phenomenon that occurs in a frequency range of lKHz to 15KHz, which is in the range of sensitivity for the human ear. Squeal is usually caused by excitation of brake components brought on by slip-stick of the brake caliper pad material and rotor surface during brake actuation. This paper will provide an overview of examples that illustrate the application of holographic interferometry methodology to identify the root causes of brake concerns and verify engineering solutions.

Comparison of holographic interferometry to other test methods in automotive testing

Hologram interferometry is one of many testing techniques used to study and improve vehicle structures and subsystems. Other test methodologies serve to provide data on component loadings and input conditions for holometric testing or serve to correlate holometric results at discrete locations. This paper includes applications that show the benefits of holometric testing and its ability to predict the in-vehicle behavior of a wide variety of automotive components.

Hologram interferometry in automotive component vibration testing

An ever increasing variety of automotive component vibration testing is being pursued at Ford Motor Company, U.S.A. The driving force for use of hologram interferometry in these tests is the continuing need to design component structures to meet more stringent functional performance criteria. Parameters such as noise and vibration, sound quality, and reliability must be optimized for the lightest weight component possible. Continually increasing customer expectations and regulatory pressures on fuel economy and safety mandate that vehicles be built from highly optimized components. This paper includes applications of holographic interferometry for powertrain support structure tuning, body panel noise reduction, wiper system noise and vibration path analysis, and other vehicle component studies.

Holometric Testing Applications For Vehicle Component Structural Improvement

Holometric testing of vehicle components to improve their structural characteristics is now a proven methodology. The inherent advantages of a full-field, high sensitivity measurement capability are emphasized for the iterative improvement of prototype structures (static and dynamic) and the timely application to understanding structure related concerns on vehicles in production. Successful acquisition of usable and valid test results requires considerable thought and effort to create a test set-up that recreates as closely as possible the test subject boundary and loading or excitation conditions existing in-vehicle. The recent addition of advanced Computer Aided Holometry (CAH) has significantly enhanced the understanding and utilization of holometric testing by Ford engineering. Recent examples of studies that address both the static and dynamic behavior of components are presented. Continuous wave and pulsed laser holometric techniques have been applied to study the following subjects: (1) self generated brake noise, (2) engine block noise radiation, (3) steering column vibration, (4) engine structure deformation under fastener torque loads and (5) cylinder head deformation under simulated combustion chamber pressure loads.