A mathematical representation of the multiaxial Bauschinger effect by C.O. Frederick and P.J. Armstrong, originally published as an internal CEGB report in 1966, has been reproduced in the journal "Materials at High Temperatures." The report, which was never published in the open literature, discusses the Bauschinger effect, a phenomenon where the elastic limit of a material decreases after prior tensile or compressive loading. This effect is crucial for understanding the behavior of materials under cyclic loading and is modeled using constitutive equations that account for isotropic and kinematic hardening, as well as the Bauschinger effect. The report was later referenced by J.L. Chaboche in 1977, leading to its increased recognition in the field. Chaboche's work built upon the Armstrong-Frederick model, which was developed to describe the evolution of material behavior under cyclic and multiaxial loading conditions. The model incorporates a 'recall' term that influences plastic flow differently for tensile or compressive loading, depending on the accumulated plastic strain. This model has been widely adopted in finite element analysis and is now a standard in the field. The Armstrong-Frederick model has been cited over 300 times in the open literature, despite its initial lack of publication. The model's ability to predict the Bauschinger effect and its incorporation of back stress mechanisms have made it a cornerstone in the study of material behavior under cyclic loading. The report's original authors, Frederick and Armstrong, were instrumental in developing the model, which has since been recognized as a fundamental contribution to the field of materials science and engineering. The report's re-publication in the journal highlights its significance and the importance of its original contributions to the understanding of material behavior under complex loading conditions.A mathematical representation of the multiaxial Bauschinger effect by C.O. Frederick and P.J. Armstrong, originally published as an internal CEGB report in 1966, has been reproduced in the journal "Materials at High Temperatures." The report, which was never published in the open literature, discusses the Bauschinger effect, a phenomenon where the elastic limit of a material decreases after prior tensile or compressive loading. This effect is crucial for understanding the behavior of materials under cyclic loading and is modeled using constitutive equations that account for isotropic and kinematic hardening, as well as the Bauschinger effect. The report was later referenced by J.L. Chaboche in 1977, leading to its increased recognition in the field. Chaboche's work built upon the Armstrong-Frederick model, which was developed to describe the evolution of material behavior under cyclic and multiaxial loading conditions. The model incorporates a 'recall' term that influences plastic flow differently for tensile or compressive loading, depending on the accumulated plastic strain. This model has been widely adopted in finite element analysis and is now a standard in the field. The Armstrong-Frederick model has been cited over 300 times in the open literature, despite its initial lack of publication. The model's ability to predict the Bauschinger effect and its incorporation of back stress mechanisms have made it a cornerstone in the study of material behavior under cyclic loading. The report's original authors, Frederick and Armstrong, were instrumental in developing the model, which has since been recognized as a fundamental contribution to the field of materials science and engineering. The report's re-publication in the journal highlights its significance and the importance of its original contributions to the understanding of material behavior under complex loading conditions.