Celebrating 50 years of the groundbreaking Hunt and Crossley contact force model

• This article celebrates the 50th anniversary of Hunt and Crossley force model. • A brief biography of Professor Kenneth Henderson Hunt is presented. • A brief biography of Professor Francis Rendel Erskine Crossley is presented. • The Hunt and Crossley contact force model is revisited. • The impact of Hunt and Crossley force model is presented. The Hunt and Crossley contact force model, published in 1975, marked a key transformative milestone in the field of contact mechanics. Compared with previous formulations, this pioneering model offered a more realistic and dynamic representation of the contact forces due to the incorporation of energy dissipation during collisions between solid materials. Over the past 50 years, the Hunt and Crossley contact force model has significantly influenced a wide range of disciplines, such as multibody dynamics, machines and mechanisms, robotics, biomechanics, vehicle dynamics, crashworthiness, and materials science, just to mention a few. This paper celebrates the golden jubilee of the Hunt and Crossley revolutionary approach, revisiting its theoretical foundations and tracing its historical development and impact. The Hunt and Crossley contact force model is probably the most well-known and useful approach to investigate contact-impact events in dynamical systems.