Location

La Jolla, CA

Start Date

1-1-1993 12:00 AM

Description

The numerous potential applications of metal matrix composites (MMCs) in the military and aerospace industries have resulted in the widespread study of their mechanical properties to determine optimum fabrication techniques for improved composite strength. Due to the difference in the thermal expansion coefficients of the matrix material and its reinforcement, thermally-induced residual stresses exist in the composite as a direct result of cooling from the MMC fabrication temperature. Several nondestructive techniques have been used to determine the residual stress present in various engineering materials. Radiographic techniques have been used extensively, but are somewhat limited in penetration depth and spatial resolution. However, ultrasonic techniques have proven to be a useful nondestructive means of determining bulk mechanical properties of a material. To determine the influence of internal stresses in MMCs on ultrasonic velocities, specimens of various second-phase silicon carbide content were subjected to a change in temperature. As the specimen temperature was raised, interfacial stresses between the aluminum matrix and silicon carbide reinforcement were relaxed, resulting in an overall change in the stress state of the material. Longitudinal ultrasonic waves were used to measure the acoustoelastic effect due to this change in the internal stress of the MMC. Longitudinal waves have been successfully used to determine internal stresses due to the influence of temperature on railroad rails [1] and prestrained aluminum and copper specimens [2]. The ultrasonic velocities in this investigation were measured with a computer automated time-of-flight acquisition system accurate to better than 1 part in 10,000.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

12B

Chapter

Chapter 7: Nonlinearity, Deformation and Fracture

Section

Nonlinear Effects

Pages

2099-2104

DOI

10.1007/978-1-4615-2848-7_267

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Study of Interfacial Stress in Metal Matrix Composites Using Ultrasonic Velocity Measurements

La Jolla, CA

The numerous potential applications of metal matrix composites (MMCs) in the military and aerospace industries have resulted in the widespread study of their mechanical properties to determine optimum fabrication techniques for improved composite strength. Due to the difference in the thermal expansion coefficients of the matrix material and its reinforcement, thermally-induced residual stresses exist in the composite as a direct result of cooling from the MMC fabrication temperature. Several nondestructive techniques have been used to determine the residual stress present in various engineering materials. Radiographic techniques have been used extensively, but are somewhat limited in penetration depth and spatial resolution. However, ultrasonic techniques have proven to be a useful nondestructive means of determining bulk mechanical properties of a material. To determine the influence of internal stresses in MMCs on ultrasonic velocities, specimens of various second-phase silicon carbide content were subjected to a change in temperature. As the specimen temperature was raised, interfacial stresses between the aluminum matrix and silicon carbide reinforcement were relaxed, resulting in an overall change in the stress state of the material. Longitudinal ultrasonic waves were used to measure the acoustoelastic effect due to this change in the internal stress of the MMC. Longitudinal waves have been successfully used to determine internal stresses due to the influence of temperature on railroad rails [1] and prestrained aluminum and copper specimens [2]. The ultrasonic velocities in this investigation were measured with a computer automated time-of-flight acquisition system accurate to better than 1 part in 10,000.