Structural Dynamics and Acoustics

Southwest Research Institute provides research, development, analysis, and testing services to ensure the functionality, structural integrity, and environmental compatibility of systems and components subject to adverse dynamic operating environments, such as those in the transportation, aerospace, and electronics industries.

As an independent, nonprofit research and development organization, SwRI neither manufactures nor endorses industrial products and keeps all investigations impartial. Client confidentiality is also protected. With 13 technical divisions and extensive laboratory facilities, analytical capabilities, and additional staff expertise in materials, chemistry, electronics, and other support fields, SwRI staff members use a multidisciplinary approach to solve problems for clients worldwide.

SwRI's technical expertise in structural dynamics and acoustics encompasses:

• Product Development
• Simulations
• Acoustic Engineering
• System Testing

Product Development

Based on service requirements, SwRI engineers design and fabricate a specialized mechanical device to measure lift and drag forces on tubes in steam generators.

The SwRI staff improves existing products or designs and prototypes new products, systems, and components. The multidisciplinary nature of the Institute also allows for appropriate in-house testing and analysis.

SwRI product development capabilities include:

• Design and analysis of systems to meet special operating requirements
• Fabrication of prototypical systems
• Field validation of product performance
• Product improvement through application of concurrent engineering principles to enhance resistance to environmental degradation
• Form, fit, and function duplication of assemblies and components
• Identification of critical processes
• Automated design optimization for performance criteria
• Preparation of technical drawings, specifications, and quality requirements

In a U.S. Air Force program, SwRI engineers redesigned and assembled a device to perform reliability and durability testing for bearings and aircraft accessories. Simulating operating speed and load conditions, the instrument tests components such as alternators, bearings, couplings, gear boxes, and hydraulic pumps. Inset shows bearings used with power takeoff shafts.

Simulations

SwRI laboratory simulation of propeller wake impingement on wing surfaces (inset) allowed development of procedures to detect the level of in-flight structure-borne noise transmission with direct application to the prop fan test assessment aircraft.

Simulating environments to pinpoint and solve operational problems can save time and money. Environmental conditions that are impossible to otherwise recreate, such as earthquakes, can also be simulated to determine their effects on systems and components.

SwRI's range of services includes:

• Simulation of in-service vibration loading
• Unique instrumentation development for nonstandard experimental applications
• Data acquisition and advanced signal-processing techniques
• Seismic simulations using SwRI- or client-defined earthquake inputs
• Simulation of natural environments
• System dynamic response characterization
  • Test plan development
  • Instrumentation development and installation
  • Failure mode identification 
• Vibroacoustic system simulation services
  • Model design and development
  • Laboratory experimentation
  • Test procedures development
  • Full-scale application 
• Analytical modeling and simulations of vehicle platforms, civil structures, machines, and process equipment response to shock and vibration during operation, accident, and natural catastrophes
• Validation of analysis scenarios from model data

Acoustic Engineering

SwRI performed vibroacoustic testing on these aircraft to develop component transmission models for potential cabin noise control measure developments. Rotor mass imbalance of the engine and propeller can be major sources of structure-borne noise in vehicle cabins.

SwRI has more than 30 years experience in solving noise, vibration, and harshness problems for industry and government.

Services include:

System vibroacoustic modeling

• Experimental characterization
  • Structural impedance measurements
  • Component coupling predictions 
• Analytical modeling
  • Structural dynamic finite element modeling
  • Boundary element acoustic radiation prediction

System noise source identification

• In-service noise ranking and path identification
  • Sound power-level measurement
  • Acoustic intensity -- noise source ranking
  • Acoustic imaging
  • Structure-borne noise identification

Noise control measure development

• Noise barriers and absorbing materials
• Vibration isolation and panel-damping treatments
• Absorptive materials
• Active noise and vibration control

System Testing

Engineers expose products to environmental vibration and shock to verify designs and prove product durability and reliability. SwRI also performs qualification testing to ensure products meet appropriate government and industry standards. MIL-810, Bellcore, and IEEE-344 are only a few of the standards for which tests are provided.

Replacement of well-logging vehicle instrumentation is costly and time consuming. Engineers measure the in-service vibration environment and apply vibration control measures to ensure functionality of critical instrumentation.

Electronics equipment undergoes dynamic testing in the high-frequency range while shaken in a horizontal axis on an SwRI uniaxial electromagnetic shaker system.

SwRI capabilities in vibration and shock testing include:

Vibration

• Assessment of component or system structural integrity as affected by dynamic loading
• Design and construction of custom experimental apparatus
• Custom data acquisition and data processing using SwRI-developed systems or LabView®
• Multiaxial or uniaxial dynamic loading
• Durability and reliability testing
• Development of vibration test specifications for new products

Shock

• Specialized fixture design
  • Uniform input into test item
  • Allowances for excitation in any transverse direction 
• Free-fall shock simulation
  • Various classical waveforms
  • Adjustment of peak acceleration and dwell time
  • Repeatability 
• Response measurements
  • Input, supports, and board-level measurements
  • Development of elevated response spectra 
• New system design
  • Structural integrity
  • Support for isolation of shock environment
  • Critical item placement 
• Development of shock test specifications

This brochure was published in August 1997. For more information about structural dynamics, contact Timothy A. Fey, Assistant Director, Mechanical Engineering Division, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-3253, Fax (210) 522-4506. For more information about acoustics, contact Mike Ladika, Business Development, Phone (210) 522-2122, Fax (210) 522-3496. To learn more about SwRI's environmental testing, visit nebs.swri.org.

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