Aggregate fracture in unbound granular materials (UGMs) can influence performance of both unbound and bitumen-bound layers. This study introduces a new method to characterize aggregate fracture in UGMs through a combined experimental and analytical approach that accounts for gradation variability and incrementally applied loading. Confined monotonic uniaxial compression tests were conducted at various load magnitudes, and discrete element method simulations of the experiments, were used to estimate UGM load-displacement response without aggregate fracture. The differences between the experimental and simulated load–displacement responses at specific load levels were correlated with the measured amount of aggregate fracture for UGMs of different gradations and aggregate types. The proposed parameter shows a unique relationship with experimentally measured aggregate breakage and can thus be used to evaluate the evolution of aggregate fracture in UGMs under applied loading.

Mechanical degradation of the positive electrode in lithium-ion batteries is one of the leading causes of charge capacity degradation over charge cycling. This study utilises a discrete element method modelling framework to investigate the mechanical degradation of the positive electrode constituents, the active particles and the conductive binder domain. The mechanical degradation is modelled as the fracture of the layer's two constituents, and simulations are performed to represent calendering, charge cycling, and tensile testing. The modelling results indicate that active particle fracture reduces the load-bearing capacity of the layer in compression. In contrast, the conductive binder domain fracture presents a dominant influence on the mechanical integrity of the full active layer. Charge cycling induces significant mechanical degradation during the first charge cycle, driven by the volumetric expansion of the active particles, for the conductive binder domain. Further charge cycling resulted in minimal additional degradation. Under tensile loading, the conductive binder domain governs the mechanical response as fracture limits the maximum tensile stress. The study concludes that the mechanical properties of the conductive binder domain are critical to the electrode's overall mechanical performance. The discrete element method framework captures multiscale interactions and degradation mechanisms that are challenging to observe experimentally, providing new insight into optimising electrode design for improved mechanical stability.

Stamping and shot peening of chassis components such as wheels and cross beams introduce residual stresses that affect the fatigue life. The tensile residual stresses from stamping are often found in the most critical areas for fatigue. These areas are commonly subject to bending stress states while smooth material fatigue data for steel sheets more commonly is obtained by uniaxial testing. Both the sensitivity to residual stresses and change in load condition are material dependent posing a challenge in fatigue life estimation of formed and shot-peened specimens. This paper aims to provide a convenient tool for high cycle fatigue life estimations in these conditions solely dependent on uniaxial tensile properties without parameter fitting. The underlying causes for the material dependency is discussed and reflected in the methodology. Uniaxial fatigue testing and fatigue testing of formed specimens with and without subsequent shot peening are performed for validation.

Shear-cutting processes are arguably among the most preferred technologies for performing material removal operations in the manufacturing of chassis components due to the combination of high production rate and cost-efficiency. Nevertheless, they may severely jeopardize the fatigue response of high strength metals, compromising the current trend of using this class of materials for weight reduction of automotive chassis parts. Thus, the generation of reliable data featuring the influence of these operations on the material fatigue behavior is essential to further support this lightweighting tendency. Commonly employed for this aim, traditional fatigue tests are usually time-consuming and rather expensive. In this context, numerical simulations arise as a viable alternative, providing not only material-related information but also assisting engineers in the design of new components. In this work, an isotropic damage-based high cycle fatigue model is employed to estimate the fatigue life of trimmed and punched specimens of two complex phase steels. The residual stresses obtained from each process simulation and the roughness measured on the cut surface are included in the model to account for the influence of these operations on the material fatigue strength. Furthermore, standard uniaxial tensile properties and S–N data resulting from fatigue tests on as-polished specimens are the only material information required. A good agreement is found between the numerical fatigue life predictions and the experimental measurements, remaining below an error factor of three for all the estimated cases. In addition to coupon specimens, the model is also readily extensible to component-level applications, enabling the fatigue assessment of metallic engineering structures featuring shear-cut surfaces.

Fracture of rock particles is important in many applications like mining, mineral comminution, unbound granular materials (UGMs) for railway and road structures. The latter application is the main interest presently, as fracture of rock particles in UGMs affects the UGMs performance and may compromise structural integrity of a pavement, potentially leading to premature road failures. Therefore, it is important to assess their resistance to aggregate fracture accurately. In this study, a new statistical fracture model for particle fracture, based on the results of single particle crushing tests, is introduced to investigate aggregate fracture. The proposed model is tested for UGMs composed of three different aggregate types: brick, granite and a volcanic material and its results are compared with other widely used fracture force models. The performance of the models is also investigated by simulating uniaxial monotonic compression tests on UGMs with different aggregate size distributions using the Discrete Element Method (DEM) and comparing the results with experiments. Fracture at two different load levels for three different particle size distributions are investigated for each material. One particle size distribution at one load level is used to identify the contact law parameters for each material, and single particle breakage test are used to identify the fracture force model parameters. The DEM models with a new fracture force model agrees well with the macro-mechanical behaviour observed in experiments and exhibits the highest degree of correlation to fracture results obtained from experiments.

Adequate aggregate resistance to crushing and abrasion is crucial for good performance of unbound road layers, in particular when incorporating marginal aggregates in road construction. In this study, aggregate crushing in unbound granular materials (UGMs) is investigated experimentally with uniaxial compression tests, and numerically with discrete element method (DEM). A DEM model of UGMs subjected to uniaxial monotonic compression is implemented in a commercial DEM software, incorporating granular mechanics-based particle-contact and breakage laws. Based on comparison with the experimental findings, it is shown that the implemented model captures the UGMs behavior well including aggregate breakage characteristics. The model is used furthermore to evaluate aggregate crushing in UGMs subjected to cyclic loading representative for unbound road layers of low-volume roads. The feasibility of using the developed DEM approach for evaluating the implications of using marginal UGMs in unbound road layers and for optimizing structural design of those layers is discussed.

Mitigating the loss of charge capacity is one of the main challenges in developing lithium-ion batteries. Mechanical degradation is one of the causes of charge capacity loss, and insight into these processes is necessary for battery development. This study uses a discrete element method (DEM) framework to model the mechanical properties of a positive electrode active layer. In particular, how the active layer properties are affected by the volumetric change and material degradation of the active material linked to charge cycling. The results show a stiffening of the active layer following charge cycling, stemming from the volumetric expansion of the active particles. These results agree with trends seen in experimental measurements.

Sheet metal punching is an important process in manufacturing of heavy-duty vehicle chassis components. The cut edges have a detrimental effect on high cycle fatigue life in uniaxial- and in-plane-bending but the reduction is less pronounced in out-of-plane bending. This paper aims to explain the reduced process sensitivity in out-of-plane bending fatigue, to quantify the high cycle fatigue life reduction at different load ratios, and to propose a methodology for fatigue life estimation. This could enhance the possibilities to identify critical load cases of chassis components, to judge whether fatigue life improving post-processes are necessary, and to locate critical initiation sites for fatigue. Fatigue testing of punched and polished specimens was conducted, and the punching process and four-point bending were simulated using FEM. The results were used to estimate crack initiation site, fatigue life reduction, and for validating the predictions. Fatigue life reduction is found to increase with increased load ratio, but to a smaller extent than expected. A contributing factor the reduced tensile residual stresses due to plasticity during the first load cycle. The reduced process sensitivity as compared to uniaxial fatigue could be explained by the separate locations of crack initiation and high tensile residual stresses in the cut edge. Specimen orientation seems to have a minor influence on the fatigue life. Only improving the outer surfaces, and not the central parts of the cut edge, could increase the high cycle fatigue life for pulsating and reversed loading.

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.