Nondestructive Evaluation of Materials and Structures

This SwRI-designed remote reactor vessel inspection system is employed during full-vessel, pressurized water reactor examinations. Scanner control, data acquisition, data processing, and imaging operate under fully automated computer control.

The Institute is a recognized leader in developing and applying nondestructive evaluation (NDE) technology for industry and government. Technical priorities over the past year have included extensive work in magnetostrictive technology for the petrochemical industry, technical programs to improve NDE applications for gas transmission pipelines, the development of special sensors for automotive airbag systems, and a variety of nuclear power programs in waste management and reactor vessel safety assessment.

Conventional nondestructive evaluation of piping requires direct contact of instrumentation with the pipe wall, a problem in the case of insulated pipe. SwRI scientists are developing a field-ready instrument to inspect insulated carbon steel pipes used in the chemical and petroleum industries. Using magnetostrictive sensor technology, the device detects internal or external corrosion and cracks in pipe walls without direct contact and without use of a couplant. The technique can be used to inspect more than a hundred feet of insulated pipe from a single sensor location.

The Institute has launched a multiphase joint industry program to develop an instrument for detecting defects in insulated pipes without removing the insulation. Based on magnetostrictive sensor (MsS™) technology, the instrument transmits and detects elastic waves in pipe walls without direct contact with the pipe surface and without use of a couplant. As the elastic waves (in frequencies up to a few hundred kilohertz) are transmitted along the pipe, defects cause the signals to be reflected, allowing detection of corrosion and cracks. The technique can be used to inspect the entire cross section of a pipe wall for both inside and outside diameter defects and is capable of inspecting more than 100 feet of pipe from a single sensor location. The sensor has been used successfully on a variety of piping materials up to 16 inches in diameter and with pipe temperatures of -55 to 850 degrees F.

To improve automotive airbag performance, Institute engineers have developed a device based on magnetostrictive sensor (MsS) technology. The device detects stress waves traveling through a car's structure, evaluates motion severity, and deploys the airbags, if warranted. Manufacturer testing has shown that the MsS device performs significantly better than available equipment.

A critical element in vehicle airbag safety systems is the sensor and data processing unit, which detects and processes crash signals and determines if the airbag should be deployed. For reliable operation of the airbag, the sensor and data processing unit must accurately distinguish severe crash events that do require deployment from events that do not, such as door banging, rough rides, or light collision. Although accelerometers have been used successfully to detect and respond to frontal crashes, they have not been as successful in detecting side crashes. Institute engineers developed MsS technology that senses crash-generated stress waves as they propagate through a vehicular structure. Recent testing by airbag manufacturers showed that MsS technology performed significantly better than accelerometers in side-crash airbag deployment.

A major expense associated with pipeline inspection programs is the cost to excavate pipe for repair when significant corrosion problems are indicated. Unnecessary excavations caused by inaccuracies in the inspection process add to this expense. Even more costly is the case when inspection equipment fails to detect or underestimates defects that later result in a leak or rupture. For the Gas Research Institute (GRI), SwRI recently completed a project to improve defect characterization. Teamed with university and research institute partners, SwRI performed computer modeling and laboratory experiments to determine the relationships between pipe wall stress and corrosion defect response. The results of this work are being used by two commercial inspection companies to adjust inspection operating parameters and to correct defect signals for stress effects.

The U.S. Department of Transportation (DOT) has funded a landmark program for the development of technology to detect and characterize mechanical damage in transmission pipelines. Mechanical damage caused by third parties is the leading source of pipeline incidents and the cause of a number of major pipeline failures. As part of the DOT program, SwRI will use modeling and laboratory techniques to determine the magnetic property effects of mechanical damage to pipeline steels. When damage such as a dent occurs, the magnetic properties of the deformed pipe wall change. These changes, if better quantified, can be used as indicators of damage severity. Both elastic and plastic deformations will be considered in developing sensing techniques and analysis procedures.

The Institute has developed specialized automated ultrasonic scanning systems to assess the structural integrity of aging storage tanks for the petrochemical industry. In a recent project, approximately 2,000 linear feet of weld in a 60-foot diameter spherical liquid propane tank were examined from inside the sphere. The examination was performed with SwRI-developed multibeam transducers mounted on a scanner car, which was guided along the weld by magnetically attached tracks. Scanner car movements were remotely controlled, and scan data were collected and analyzed using the SwRI-developed Enhanced Data Acquisition System (EDAS,^TM), an ultrasonic inspection system designed for the NDE of large structures.

SwRI engineers developed a specialized ultrasonic scanning system to assess the welds of a large spherical liquid propane tank. Mounted on a temporary track inside the tank, the scanning system collected examination data for more than 2,000 feet of weld. The system then transmitted the data to the Institute's Enhanced Data Acquisition SystemTM in a nearby mobile laboratory for analysis.

The Institute has delivered an eight-channel EDAS equipment set, EDAS II^TM, to Japan's Mitsubishi Heavy Industries (MHI). The system will be integrated with an MHI advanced ultrasonic testing robot to provide preservice and inservice inspections of reactor pressure vessels at nuclear power plants throughout Japan. The MHI robot will remotely position NDE sensors at the areas to be examined, sending data to the EDAS II system for on-line data acquisition and analysis. These two devices represent the latest technology for reactor vessel inspection in the world. EDAS II incorporates updated electronics and computer technology, allowing it to record full waveform data from up to eight channels simultaneously at scan speeds up to six inches per second. Institute-developed EDAS equipment sets are used in inspections of approximately 15 percent of the world's nuclear power plant reactor pressure vessels.

SwRI is working to detect high-cycle fatigue (HCF) in jet aircraft engines. HCF, caused by a large number (approximately 10⁸) of low-stress cycles over a long period of normal operation, weakens the engine disk material and can result in catastrophic failure. No NDE technique has yet demonstrated the ability to detect HCF damage in a field application prior to failure. SwRI is preparing HCF test specimens that will be used to determine if new, innovative NDE technology will produce improved results. Methods being evaluated include ultrasonic surface waves, ultrasonic multibeam transducers, positron annihilation, and eddy current techniques. If successful, this program will permit early diagnosis of HCF damage in both commercial and military aircraft engines.

1996 Annual Report SwRI Home