All Test & Inspections - Test Methods

Test Methods

Brittle Lacquer

A brittle lacquer test is a preliminary test used to identify areas of concentrated stress, either compression or tension, in a structure. The brittle lacquer is a coating sprayed over a reflective undercoat. After application, the structure is loaded in order to induce strain patterns in the coating. Careful examination of the sprayed areas of the structure will indicate the location and direction of stresses present in the parent material.

The sensitivity of the coating is affected by the ambient temperature, the temperature of the structure, and the relative humidity. Therefore, the reliable use of the brittle lacquer test method is the result of thorough knowledge of the product, accurate anticipation of the conditions at test time, and extensive experience of its use on a variety of structures.

The use of brittle lacquer can confirm the presence of stress in areas identified by engineering calculations, or it may identify areas of stress that had been previously overlooked. Ultimately, the brittle lacquer test is used to locate areas where strain gages will be placed, allowing the recording of stress in the structure while under load.

For additional information about brittle lacquer supplies, please see the Stresscoat homepage at: www.stresscoat.com.

Strain Gage Testing

Strain gage testing is the real-time computerized recording of stress in the parent material of a structure while in a loaded condition. The purpose is to record the actual level of stress present, and to identify those areas that may approach or exceed the accepted strength margins of the parent material.

All Test & Inspection is equipped to record structural, mechanical, and hydraulic test data under static, steady-state, or dynamic conditions. Our proprietary strain gage data acquisition system can record up to 320 channels statically, and 27 channels dynamically.

Brittle lacquer and strain gage testing are complementary test methods in that brittle lacquer identifies general areas of stress concentration. Once these areas have been identified, strain gages applied to the structure record the actual stress levels under a variety of test conditions. These test results are independent verification that a machine has satisfied the applicable test code requirements, and can be operated safely at it’s maximum capacity without exceeding the structural limitations of the machine.