Ultrasonic measurement of residual stress in steels using critically refracted longitudinal waves (Lcr) /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1988.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | The problem of measuring residual stress in steel welded plates by applying the acoustoelasticity of the critically refracted longitudinal waves (L[CR] waves) was approached. Residual stresses are self-equilibrating and exist in a material that is deformed in a non-homogeneous manner, and in cases such as welded plates the longitudinal residual stress can be as high as the yielding point of the weld metal. When high residual stress is present in a structure, the working stress is added to the residual stress producing an unknown and usually damaging stress field. Highly stressed areas in a material that are located in a corrosive environment are prone to stress corrosion cracking. This situation is often found near welds that have not been properly stress relieved. In the present study two welded plates were investigated, one hot rolled and one cold rolled. The plates were 19 mm thick and 762 mm x 508 mm in width (0.75 in x 30 in x 20 in). It is known from other studies that the longitudinal residual stress (i.e. the stress parallel to the weld bead in the plates) has the largest residual stress gradient after welding, and the L[CR] waves acoustoelastic behavior is largest when a uniaxial stress is applied parallel to its propagation direction. Thus, the L[CR] waves technique was used and found to be capable of measuring stress changes after welding and after stress relieving of the welded plates. The L[CR] waves characteristics makes them potentially useful in the measurement of residual stress at different depths below the surface of a plate by varying the frequency of the excited waves. Two differential probes of 1 MHz and 2.25 MHz transducers were used to measure longitudinal residual stress and effectively measured stress changes at different depths in the plates. The hole drilling technique (HDT) is a semidestructive surface stress technique that was used to verify the results from the ultrasonic technique. The HDT showed about same stress level but with an opposite orientation at the weld which was caused by the grinding process used to flatten the weld bead. The HDT verified the stress relief process by showing a decrease in stress after the stress relief. The (110) texture also was investigated by using a neutron diffraction technique. The technique yields an average of the orientation distribution of the (110) planes since it is a through the thickness transmission technique... |
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| Item Description: | Typescript (photocopy). The letters "cr" in (Lcr)--at the end of title are capital subscript letters. Vita. "Major subject: Mechanical Engineering." |
| Physical Description: | xiii, 97 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |