This challenge has driven more advanced test methodologies and measurement techniques that allow to unravel unknown material properties at high rates of strain and complex stress states. The desire to conceive new engineering materials, to design optimal architectures of engineering systems, and to improve structural integrity, however, is hindered by a lack of data at a broad range of strain rates that could otherwise contribute to either more precisely identifying the existing plasticity models and assess their predicative capabilities, or developing new models. Such extreme mechanical environments are also experienced in a wide range of engineering applications featuring rapid rebalancing of energy and momentum, such as impact penetration, metal forming and cutting, drilling and blasting, etc. During impact loading of aircraft turbine engines, from small-scaled rapid interactions like blade tip rubbing to major events such as bird ingestion or blade containment, the bulk of underlying materials experiences complex stress states and severe plastic deformation at rates of strain that significantly exceed those in normal operations. The understanding of the physical phenomena governing the response of materials and structures in extreme impact environments is of paramount importance particularly in transportation and defence sectors. The presented apparatus, testing and analysis methods allow for the direct population of the dynamic failure stress envelopes of engineering materials and for the accurate evaluation of existing and novel constitutive models. The analysis indicates that the developed TTHB is capable of characterising the dynamic behaviour of materials under tension, torsion, as well as under a wide range of complex stress states. ![]() Different wave rise time were obtained via the controlled release of the clamp using fracture pins of various materials. The experimental results demonstrate that the synchronisation of the longitudinal and torsional waves was achieved within 15 microseconds. Thin-walled tube specimens made of two metallic materials were utilised to examine the capability of the developed TTHB system by comparing the experimental measurements with those obtained from conventional split Hopkinson tension and torsion bars. A parametric study of the material and geometry of the clamp was implemented via numerical simulations to optimise critical aspects of the wave generation. MethodsĪn energy store and release mechanism was employed to generate both the longitudinal and shear waves via the rapid release of a bespoke clamp assembly. The objective of the current study is the development of a novel combined tension–torsion split Hopkinson bar (TTHB) conceived to generate a combination of tensile and torsional stress waves in a single loading case, and to measure material data representative of real case impact scenarios. ![]() ![]() Advanced testing methodologies and measurement techniques to identify complex deformation and failure at high strain rates have drawn increasing attention in recent years.
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