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.
Manufacturing technology in the photomask process is critical for building devices of today's specifications. However, when building masks for equipment suppliers, it is necessary to provide capability at least two years in advance of current requirements. Of particular interest are masks used to characterize and benchmark inspection tools. This paper demonstrates and compares the mask processing capabilities of 50keV e-beam writing platforms in the effort to build a new inspection test mask pattern. Both standard and OPC patterns will be examined to understand the impact of each to the mask manufacturer. In addition to 50keV e- beam platforms, complementary high-end process and metrology tools will be utilized and reported.
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.
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.
Shape and vibration measurements of structures are required in many automotive product
development and manufacturing processes. Optical measurement methods are attractive because they do
not require contact with the structure and offer high precision and accuracy. Nevertheless optical
techniques also suffer from a number of limitations which prohibit wide application. Typically the
object is viewed and illuminated from two different points making objects situated in confined areas
difficult to measure. In addition, most optical techniques are not easily scaleable in measurement
range. Finally, most shape measurement techniques cannot measure vibration without a change in
configuration.
This paper presents a single electronic speckle interferometry (ESPI) method to measure both
surface shape and vibration. A two-wavelength approach is used to measure shape and a stepped strobed
phase technique is employed to measure vibration amplitude and phase. The technique requires only one
line of sight to the object and can be scaled to measure surface roughness as well as large surface
contours. The technique features the ability to coincidentally measure shape and dynamic behavior for
structural design, modification, and optimization. The theory of the technique along with results of an
experiment are presented.
This paper presents a simple method to design a recursive filter for processing ESPI fringe pattern to obtain a quality results according to the frequency of the fringe. This method of speckle noise reduction has the advantages of both less computation time and improved results.
This paper employs the iteration algorithm proposed in reference to process shearography fringe patterns. The algorithm processes speckled fringe pattern several times until the quality of the processed fringe pattern is acceptable. Examples and description of the algorithm are presented.
This paper presents a method for measuring time dependent displacement using a dual speckle pattern acquisition and single camera TV holographic system. Two speckle patterns with 90 degree phase difference are acquired simultaneously. As the displacement changes with respect to time, a series of dual speckle patterns can be digitized into a computer image processing system. A Fourier transformation is used to remove the DC terms of the speckle patterns. A phase unwrapping algorithm is employed to calculate the phase distribution related to the time dependent displacement. The theoretical concept together with experimental simulation are presented.
This paper presents a method for measuring the complex mode of a vibrating structure using two separate dual reference stepped strobe phase (0, 90 degrees) holograms and a new spatial phase shifting technique during reconstruction. Spatial phase shifting is accomplished by scanning a pencil of a laser conjugate reconstruction beam in four equal steps across the hologram; four shifted phase real images are obtained for each of the two holograms and each set of four images is processed to get the unwrapped phase distribution. The vibration amplitude and phase are then obtained using these two phase distributions. The new spatial phase shifting technique greatly simplifies data acquisition and optical readout since only a single reconstruction beam is used to reconstruct both wavefronts for each hologram. The theory and experimental results are presented.
This paper presents a method for obtaining the shape of an object using digital shearography. The technique makes use of two types of phase shifting. One provides a nonuniform phase shift which is related to the shape of the object. The other is independent of the shape of the object and utilizes uniform phase shifting. Theory together with experimental verification are demonstrated.
This paper presents several practical techniques for processing and analyzing speckled fringe patterns. Speckle averaging by known phase shifts or random phase changes is used to acquire quality fringe patterns. Speckle location rearranging is employed to tolerate rigid body motion and speckle rearranging in phase gives enhanced speckle fringe patterns. A simple recursive filter is designed to further suppress speckle noise and an iteration algorithm applied to reconstruct quality fringe patterns. A digital Fourier transformation is utilized to process and analyze carrier like fringe patterns. A computer generated carrier combined with a reconstruction technique is developed to eliminate speckle noise. Combined use of the techniques optimize the results. The techniques and applications are described.
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