Abstract: The inventive fatigue-testing apparatus features a compact orbital mechan which rotates a bending force around a non-rotating test section and a stationary test bed. In addition to applying a bending force, some inventive embodiments apply an axial force and a torsional force, thereby accomplishing full-scale evaluation of test sections under three-dimensional loading; the inventive practice for applying bending, torsional and axial loads compares favorably with conventional practice in terms of reliability and cost. The inventive orbital mechanism increases the reliability of the entire inventive test apparatus by reducing the number of moving parts, component wear, maintenance and complexity. The invention also provides maximum access to the test section for instrumentation, inspection, maintenance and modification. The inventive benefits will permit evaluations of larger test sections and will afford extended evaluations to more accurately determine fatigue limitations of complex joints.