Rock drilling is a crucial process in many industries, one example being the mining industry, where it is used for exploration and blasting. In a typical rock drilling process, the rock surface is fractured by dynamic mechanical interaction with a drill bit, resulting in rock fragments detaching from the surface. These cuttings are then transported through the borehole via water or air, and the rock fragment size is important for efficient borehole flushing. In this work, a heterogeneous bonded particle model was calibrated and applied to a laboratory scale rock drilling process. The mineral grain structure was obtained from an electron microscope scan of the rock surface, and the average grain size, volume percentage and stiffness of the three most common minerals were represented in the model. The dynamic mechanical behaviour of the rock material was obtained by conducting uniaxial compression and Brazilian disc tests in a split-Hopkinson pressure bar configuration. The results were used to calibrate the model. After the heterogeneous model was shown to be able to capture the macroscopic strengths and fracture modes of the split-Hopkinson experiments, it was used to simulate the laboratory scale rock drilling experiment, where two tool indentation depths were investigated. Here, the simulation was compared to experimental results in terms of vertical load acting on the tool, machine compliance as well as rock-cutting size distributions. The results from the simulation were in good agreement with the experimental observations.

The automotive industry is currently in a paradigm shift transferring the fleet over from internal combustion vehicles to battery electric vehicles (BEV). This introduces new challenges when designing the Body-In-White (BIW) due to the sensitive and energy-dense battery that needs to be protected in a crash scenario. Press hardening steels (PHS) have emerged as an excellent choice when designing crash safety parts due to their ability to be manufactured to complex parts with ultra-high strength. It is however crucial to evaluate the crash performance of the selected materials before producing parts. Component testing is cumbersome and expensive, often geometry dependent, and it is difficult to separate the bulk material behaviour from other influences such as spot welds. Fracture toughness measured using the essential work of fracture method is a material property which has shown to be able to rationalise crash resistance of Advanced High Strength Steel (AHSS) grades and is thereby an interesting parameter in classifying steel grades for automotive applications. However, most of the published studies have been performed at quasi-static loading rates, which are vastly different from the strain rates involved in a crash. These higher strain rates may also lead to adiabatic self-heating which might influence the fracture toughness of the material. In this work, two PHS grades, high strength and very high strength, intended for automotive applications were investigated at lower and higher strain rates to determine the rate-dependence on the conventional tensile properties as well as the fracture toughness. Both PHS grades showed a small increase in conventional mechanical properties with increasing strain rate, while only the high-strength PHS grade showed a significant increase in fracture toughness with increasing loading rate. The adiabatic heating in the fracture process zone was estimated with a high-speed thermal camera showing a significant temperature increase up to 300 degrees Celsius.

The gradually more stringent environmental and safety regulations in the transport sector have made third generation Advanced High Strength Steel (3rd-gen AHSS) grades excellent alternatives to lower strength steel grades and have continuously been adopted by the automotive industry for body-in-white parts and energy absorbing safety components. Recently, essential work of fracture (EWF) has emerged as a viable material characterisation method to rationalise edge crack resistance and crashworthiness. However, much of the published data is still based on quasi-static conditions, which do not reflect the conditions during crash situations typically involving high deformation rates. This paper presents an experimental study on the deformation rate-dependence of fracture characteristics of three 3rd-gen AHSS grades. The results show that the fracture toughness, measured using the EWF method, increases significantly with the loading rate, although the differences in conventional tensile properties are modest. The increase is due to a combination of rate-dependent hardening combined with a much more ductile failure at a higher loading rate.

The usage of recycled alloys in the high pressure die casting (HPDC) applications for automobiles is gaining rapid interest. Even though the skin microstructure, which is typically induced on the casting surface during the HPDC process, is believed to improve the properties of the HPDC castings, it may not always form continuously throughout on the casting surface, and thereby can influence the mechanical properties. Thus, the current study evaluated and compared the effects of inhomogeneously formed surface skin with that of other defects on the ductility exhibited by the HPDC castings of a recycled secondary AlSi10MnMg(Fe) alloy. The formation of inhomogeneous skin in the current study was attributed to a phenomenon related to the “waves and lakes” type of defects created by the HPDC process. Such skin structure limited the ductility of the HPDC castings, irrespective of the tested strain rates in the current case, by undergoing abrupt fracture due to its poor bonding with the adjoining matrix resulting from the aforementioned inhomogeneity. Even if the investigated AlSi10MnMg(Fe) alloy contained an abundance of porosity, cold flakes and intermetallics, which are usually considered the driving factors behind the fracture of HPDC processed alloys, the effect from the inhomogeneous skin layer dominated all other factors in the current case. The order of detrimental effect on the ductility of HPDC processed AlSi10MnMg(Fe) alloy followed a sequence of inhomogeneous skin, cold flakes and pores, with the inhomogeneity in skin turning out to be the most harmful one.

The current study investigated the microstructure evolution, mechanical properties, and fracture behavior of a high pressure die cast (HPDC) novel secondary alloy. The as-cast microstructure comprised (i) Primary α-Al, (ii) α-Al15(FeMn)3Si2 intermetallics, and (iii) Al–Si eutectics. The microstructure starting from the surface through the depth of the HPDC casting consisted of (i) fine-grained skin at surface, (ii) increased Al–Si eutectics at intermediate location, and (iii) coarse α-Al dendrites at center. Accordingly, the hardness increased from skin to the intermediate section and then decreased toward the center of the casting. The formation of skin layer was highly discontinuous, which was attributed to the complicated fluid flow pattern inside the die cavity. The skin layer indicated to slightly improve the strength of the HPDC alloy; however, it restricted the ductility of the material with a large variation. Such ductility behavior resulted from a fracture mechanism triggered by the inhomogeneous skin because of its poor bonding with the adjacent matrix. Even though the secondary alloy contained casting defects and α-Al15(FeMn)3Si2 intermetallics that are known to be driving factors for the fracture in such materials, the effects from the inhomogeneous skin turned out to be predominant in the current study. 

Laser Powder Bed Fusion (LPBF) enables complex metal components for the space industry. However, as-built surface roughness affects material properties and is closely linked to design geometry. As computer-aided design tools struggle to model roughness accurately, this study explores Additive Manufacturing Design Artefacts (AMDAs) to investigate design-related roughness and its impact on fatigue performance. A space industry case study using AMDAs to replicate a 4 mm unsupported roof radius of a rocket engine component found fatigue performance reductions of 88% in horizontal builds and 65% in vertical builds compared to machined surfaces. Microstructural analysis confirmed the influence of roughness and grain structure on fatigue behaviour. Findings highlight how AMDAs provide design-specific insights and support engineers in investigating uncertainties.

In the automotive industry, structural components are often produced via press hardening, enabling rapid production and the use of ultra-high-strength steels. In this process, steels are heated to an austenitic state and are then formed and quenched in rapid succession. The initial steel that enters the press-hardening production line varies, where the microstructure is a result of previous production steps. This work was performed to investigate the possible effects of the initial microstructure on the final mechanical properties for rapidly quenched samples. Although the initial microstructure is transformed during austenitization, the steel can still be affected by its prior history. Steels with three different initial microstructures were evaluated, with only minor variations in chemical composition and thicknesses. The Lankford coefficients and the failure strains were dependent on the orientation of the samples. However, for a given orientation, there were only minor variations between the different steels with respect to anisotropy, strength, and ductility. The anisotropy could be correlated with the microstructure through the calculation of Taylor factors based on measurements using electron backscatter diffraction. The minor influence from the initial steel microstructure on the final mechanical properties indicates robustness suitable for mass production.

The lightweighting of heavy-duty vehicles (HDVs) is an effective strategy to reduce fuel consumption and lower CO2 emissions in the transport sector. The widespread application of ultra-high-strength steels (UHSSs) in HDV construction offers a viable solution, particularly for thick-walled chassis components. This study aimed to support the lightweighting of heavy vehicles by developing a methodology capturing the entire warm-forming process in the range of 430–580 °C for thick-walled UHSSs—from material characterisation, including elastoplastic and fracture properties, to downstream forming process simulations. A novel 7 mm thick UHSS grade, WARMLIGHT-980 (ultimate tensile strength (UTS) of 980 MPa), intended for warm forming was investigated at 430, 505, and 580 °C using samples of reduced thickness. The results showed that thickness reduction had minimal influence on mechanical response at elevated temperatures, enabling flexible specimen design. The thermal uniformity improved in thinner samples, enhancing testing reliability. The calibrated hardening and fracture models demonstrated strong agreement with experimental data. Validated simulations of thick-walled components confirmed the accuracy of the modelling approach. The findings support the development of reliable, temperature-dependent models for warm-forming applications and contribute to the design of lighter, more sustainable HDV components without compromising structural integrity.

The growing global demand for minerals and metals, coupled with the need for improved energy and water efficiency in resource extraction, has led to the use of numerical modeling, particularly the discrete element method (DEM), to evaluate and optimize comminution processes that account for a significant portion of the energy consumption in mineral and metal extraction. Despite advancements, a significant challenge remains in balancing the local resolution of fractures at the rock particle level, where physics-based material models using the finite element method (FEM) have excelled, with the resolution of industrial-scale total particle interactions within the machine system. This work explores the high-resolution fracture of rock particles using an established material model implemented within FEM as a valuable reference for fractures with a balanced mid-level resolution achieved through a bonded discrete element method applicable to industrial-scale systems. Brazilian tests were performed on two rock types to calibrate the models. Single particle breakage (SPB) experiments employing digital image correlation (DIC) were conducted to evaluate the performance of the models. Finally, the DEM model was demonstrated in an industrial-scale cone crusher application. The results show good agreement for the highly resolved FEM approach (requiring only two material parameters to be determined, which is particularly advantageous for generating virtual particle breakage data across various rock materials, shapes, and sizes) and reasonable agreement for the DEM fracture response, which is attributed to the much coarser mesh used that does not capture the crumbling mechanism (as revealed by the comparison between the two numerical approaches). Despite these discrepancies, the cone crusher predictions fall within the expected ranges for the system response at the machine level.