Investigating the relationship of hardness and flow stress in metal forming

Rudnytskyj, André; Varga, M.; Krenn, Stefan; Vorlaufer, Georg; Leimhofer, Josef; Jech, Martin; Gachot, Carsten

doi:10.1016/j.ijmecsci.2022.107571

Cited by 26 publications

(5 citation statements)

References 71 publications

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“…If it is assumed that the hardness is arising as result of the mechanical work upon the bar during manufacturing, then the residual stresses formed, in terms of their magnitude and the locations of regions of high compressive stress, are of importance. Interdependence between the levels of residual stress present and the hardness [28], and the arising impact of hardness upon the flow stress of the material [29] would suggest that relatively small variation along the radius in hardness can cause a stiffening of the material. This could prevent it from shearing as required.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Ti-6Al-4V Bar for Aerospace Fastener Pin Axial Forging

Turner,

Smith,

Zneimer

et al. 2024

Mater. Plus

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Ti-6Al-4V warm forged fasteners are a critical part of the aerospace industry, as they are used in vast quantities for mechanical joining of components for the fuselage, wing-skin and aero-engine. These components are produced in vast quantities at rapid production rates through multi-blow axial forging However the rate that they are manufactured means that manufacturers rely upon periodic part conformance testing to understand if the part is within tolerance or if any undesirable manufacturing defects such as cracks or underfilling are present. Thus, a right-first-time manufacturing approach is essential to minimize non-conformant scrap. An analysis of the Ti-6Al-4V supplied raw material for axial forging, in a variety of different bar diameter sizes and from different industrial suppliers, was conducted. This was to attempt to understand whether material property variation or operator variation was the root cause for some material behaving differently during the manufacture route. Experimental testing was performed through microstructure characterization and mechanical testing methods. The volume fraction of the β-phase was noted to be marginally higher in material with good forgeability. The hardness of the inner core of the bar appears to be a critical material property for the Ti-6Al4V bar, with an overly hard bar-core hindering forgeability of the bar. This is believed to be due to the hotter central region malleability being key for forgeability. Micro-void porosity was also noted which could lead to stress concentration locations, or crack initiation, and as such is a deleterious property for forgeability. The experienced forgeability of the Ti-6Al-4V bars have been demonstrated to be sensitive to rather small variation in measured microstructure and mechanical property. It is believed that cumulative impacts of small differences, 1% variation in α-phase volume fraction, small variations in elongation to failure, 1% variation in elastic modulus and microhardness profile variation at the center of the bar of less than 10 HV0.3, can combine to significantly impact the forgeability of Ti-6Al-4V bar.

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Section: Discussionmentioning

confidence: 99%

Characterization of Ti-6Al-4V Bar for Aerospace Fastener Pin Axial Forging

Turner,

Smith,

Zneimer

et al. 2024

Mater. Plus

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“…However, the determination of the yield stress and other mechanical parameters is crucial for determining the plastic behavior of materials. This applies in particular to computer simulations, which use constitutive models with material parameters that need to be known for each material, e.g., [17].…”

Section: Introductionmentioning

confidence: 99%

Material point simulations as a basis for determining Johnson–Cook hardening parameters via instrumented scratch tests

Leroch

Eder

Varga

et al. 2023

International Journal of Solids and Structures

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“…Poole et al [14] give a thorough review of work hardening in aluminum alloys that highlights some of the most crucial factors to consider. Hence, an enormous drawback of conventional mechanical testing (with large specimens) for parametrizing material models is their investigation of "bulk" properties, while wear processes take place on the surface and may require entirely different parameter sets [15]. Abrasion tests employ a multitude of abrasive events, such as in the dry sand/rubber wheel apparatus [16].…”

Section: Introductionmentioning

confidence: 99%