Mechanical Tests Research Articles

Multi-stage evolution characteristics and particle size effect of sandstone granules subjected to cyclic loads

Broken granules of different sizes and poor bearing capacities produced by repeated mining of coal seams contribute to natural disasters, such as rock strata movement. In this study, mechanical tests were performed on broken sandstone granules to explore their compaction and recrushing characteristics under repeated mining. The change characteristics of the relevant mechanical parameters of sandstone granules with different particle sizes and changes in energy density were examined, and compaction and recrushing mechanisms of sandstone granules under cyclic loading were identified. The results show that an increase in the initial particle size of sandstone granules has a significant effect on the increase in the strain under load. The cumulative dissipation energy corresponding to final crushing was greater for granules with larger initial sizes. The particle size of sandstone was found to be proportional to the fractal dimension after compaction and crushing. The probability of granular particles with larger initial particle sizes being broken into smaller particles is greater, resulting in the porosity attenuating most rapidly during the stress loading process of granular particles under repeated mining. Therefore, the degree of sample breakage was relatively severe. Particles were rearranged after compaction and crushing. Repeated mining results in dynamic evolution of the pore compaction, deformation, and fractur of the rock mass, as well as stable recombination. The study results provide important theoretical support for understanding of the movement mechanism of rock strata in the goaf under repeated mining.

Assessing the Effect of Minimally Invasive Lipid Extraction on Parchment Integrity by Artificial Ageing and Integrated Analytical Techniques.

To assess the short and long-term effect of a newly developed minimally invasive lipid extraction method on parchment, sacrificial pieces of parchments were subjected to artificial ageing and investigated using various analytical methods. Lipids were extracted using our novel vacuum-aided extraction method and characterised by high-temperature gas chromatography (HTGC-FID). Lipids were identified as arising from degraded animal fats. The physical, molecular, and mechanical properties of the parchment samples before/after lipid extraction, and before/after ageing were assessed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and pure shear single notch fracture testing. SEM imaging allowed for an assessment of potential structural changes of the collagen fibres while FTIR was used to investigate the possible molecular changes indicated by changes in amide I and II bands. Mechanical tests were used to record the changes in brittleness and stiffness occurring in the materials through lipid extraction and ageing. The multimodal investigation did not highlight measurable changes in the structural, molecular, and mechanical properties of the lipid-extracted parchment, thus indicating the suitability for the minimally invasive lipid extraction method to be applied to historical parchments.

Modifiers for the preparation of starch composites under mechanochemical activation: An extended set of criteria

Modification of starch with synthetic polymers under mechanochemical activation is a convenient way to regulate the operational properties of composite materials. The widespread use of this approach is limited by the lack of data on the influence of synthetic polymer nature on the properties of starch and the absence of clear criteria for modifiers selection in the form of aqueous dispersions. To eliminate existing problems, the work proposes to use five integral criteria − polarity, hydrophilicity, and flexibility of synthetic modifiers, as well as particle size and ζ-potential of their aqueous dispersions. To achieve this goal, we studied the dielectric constant, contact angles, IR spectra, and dynamic mechanical properties of four acrylic copolymers and an aliphatic polyurethane. Using the mechanochemical activation, blends and composite films based on corn starch and synthetic modifiers (80:20) were manufactured. Methods of rotational viscometry, X-ray diffraction analysis, DMA, mechanical tests, and moisture permeability allowed us to reveal the influence of the modifier integral parameters on the rheological characteristics of the molding blends and the impact of joint mechanical activation on them, as well as on the crystal structure of the composites, their storage modulus, strength, and transport characteristics.

Performance and Hydration Mechanism of Fly Ash Coal-Based Solid Waste Backfill Material Affected by Multiple Factors

Masses of coal-based solid waste like fly ash are emitted during coal combustion, with low utilization rate. Preparing fly ash into backfill material can not only improve waste utilization efficiency, but also repair the cracks in mining areas. In this research, the performance and hydration mechanism of fly ash coal-based solid waste backfill material were investigated through slurry performance experiment, mechanical strength test and microstructure analysis. Besides, the grouting effect of the backfill material was verified by grouting experiment. The research demonstrated that the increase of fly ash to cement ratio (from 0.5 to 1.5) improved the fluidity, viscosity and bleeding rate of the slurry, but prolonged the setting time. The adjustability of backfill material was good, and the compressive strength of specimen reached its highest value of 27.1 Mpa through changing multiple factors. The grouting effect of fine-grained macadam was better than that of coarse-grained macadam. The compressive strength and Young's modulus of the backfill material specimens containing 0.5-1cm macadam were 12.2% and 17.4% higher, respectively, than those with 1-2cm macadam. The primary hydration product of backfill material was gel, which structural elements were Si, Al and Ca. As the curing age increased, the distribution of the three elements became denser, and more gel was formed, corresponding to the changes in the compressive strength of the backfill material. The research offers material source and selection basis for backfilling cracks in mining areas and enhances utilization efficiency of coal-based solid waste.

Influence of Transportation Exhaust and Acid Rain on the Strength of Concrete Bridges and Possible Solutions to Reduce Harmful Effects

The quality control and safety assessment of existing bridge decks as a result of integrated field tests are presented in this work as a systematic technique. The aim of this research is to determine an effective approach for directly protecting concrete bridges exposed to transportation exhaust and acid rain. Mechanical property, permeability, chloride effect and abrasion resistance tests at days 28, 91, 180, 360 and 540 of the concrete specimen were used to evaluate the concrete strength. The results demonstrated the efficacy of the nanomortar, insulating paints and epoxy resin in improving concrete characteristics. In terms of water permeability, the specimen with 0% epoxy resin performed poorly compared with the control. Fuzrthermore, compared with the other combinations, the mixture with epoxy resin presented the lowest water permeability, followed by the mixtures with insulating paints and nanomortars. The specimen with epoxy resin obtained the lowest water penetration (0 mm). The specimen with insulating paint obtained the lowest water penetration (216 mm) at 91 days (with effect). This ratio can be explained by the reduction in permeability of 68.37% with respect to the control. The specimen with nanomortar obtained the lowest water penetration (14.5 mm) at 91 days, with effect.

Study on road performance of asphalt mixture based on surface modification of coal gangue

In order to solve the problem of coal gangue environmental pollution and the shortage of aggregate resources in road engineering, this paper studies the feasibility of using waste coal gangue as coarse aggregate of asphalt mixture. Through the physical and mechanical properties test, the difference between coal gangue and natural aggregate was compared and analyzed. The surface modification and strengthening treatment of coal gangue aggregate was carried out by using methyl sodium silicate solution, and the best modification scheme was determined. The influence of different content and surface modification on the road performance of coal gangue asphalt mixture was studied by laboratory test. With the help of scanning electron microscope test, the change characteristics of the microstructure of coal gangue asphalt mixture before and after surface modification were explored. The results show that although the indexes of coal gangue are inferior to those of natural aggregate, it can be used to prepare asphalt mixture within the scope of specification requirements. The modification effect of sodium methyl silicate solution with modification time of 6h is the best, which can significantly improve the water absorption, density and crushing value of coal gangue. When the content of coal gangue is controlled within 30%, the performance of asphalt mixture meets the requirements of the specification, and the amount of coal gangue in asphalt mixture can be increased after surface modification. After surface modification, the surface pores and cracks of coal gangue asphalt mixture are reduced, and the surface micro-damage under high temperature immersion and freeze-thaw cycle conditions is improved.

Digital Economy, Government Efficiency, and Regional Administrative Monopolies: Evidence from China

In this study, we utilized Chinese panel data covering 30 provincial-level administrative regions from 2000 to 2022 to examine the effects of digital economic development on regional administrative monopolies. The findings demonstrate the following. (1) The digital economy significantly curbs regional administrative monopolies, a conclusion supported by several robustness tests, including those addressing endogeneity. (2) The suppressive effect of the digital economy on regional administrative monopolies is pronounced in the eastern region but less evident in the central and western regions, suggesting regional imbalances. (3) Further analysis using threshold effects indicates the existence of a dual threshold for the influence of the digital economy on regional administrative monopolies. (4) Mechanism tests reveal that government efficiency partially mediates the digital economy's impact on restraining regional administrative monopolies.

Fabrication of Novel Polyurethane matrix-based Functional Composites with Enhanced Mechanical Performance

Thermoplastic polyurethane (TPU) has gained significant interest in several fields, including automobile steering wheels, and the electronics sector due to their easier processability, abrasive resistance, and self-lubricating performances. However, their strong inherent flammability and significant smoke and heat production during burning limit their industrial applications. Therefore, its applicability can be enhanced with the addition of high-strength reinforcement and making them antibacterial and flame-retardant. This research is designed to examine the influence of zirconium phosphate (ZrP) and zinc oxide (ZnO) nanoparticles on the novel polyurethane/glass fiber reinforced composites for flame retardant and antibacterial applications with improved mechanical performance. Three different types of novel polyurethane (PU1, PU2, PU3) matrices were prepared using different recipes, and 7% ZrP and 5% ZnO nanoparticles were added to the polyurethane matrices separately, and their corresponding composite samples were fabricated using glass reinforcement. Mechanical i.e., Charpy impact, hardness and tensile, and functional i.e., flame retardancy (FR) and antibacterial tests were performed to compare their performance. Mechanical testing results showed that PU3-based composite samples showed the highest values of impact force, hardness, and tensile strength in both ZrP and ZnO nanoparticle-based composite samples. Furthermore, 7% ZrP-PU3 composite exhibited the best performance of flame retardancy due to the presence of hexamethylene diisocyanates (HDI) content. Likewise, the 5% ZnO-PU3-based composite exhibited the highest antibacterial activity along with enhanced mechanical performance.

Effect of theoretical volume fraction (TVF) of reinforcements on Al5083/SiC and Al5083/ZrB2 surface composites produced by friction stir processing

This study focuses on the effects of theoretical volume fraction (TVF) on the microstructure and mechanical properties of silicon carbide (SiC) and zirconium diboride (ZrB2) ceramic reinforced Al5083 surface composites (SC). Al5083-H111 was used as the base material (BM), SiC and ZrB2 were used as reinforcement materials, and TVFs were determined as 5, 10, 15, and 20% for SCs produced by the friction stirring process (FSP). Macrostructure, microstructure, X-ray diffraction (XRD) analysis and mechanical properties such as microhardness, tensile strength (UTS), and wear behaviour were characterised. When the TVF and AVF values of SiC and ZrB2 particles were compared, it was found that the AVFs were lower than the TVFs. Significant decreases in the changes in the SZ areas of SiC and ZrB2 particle SCs were detected depending on the reinforcement size. In the time-dependent axial load graphs of SiC and ZrB2 reinforced samples, load values ranging from 7800 to 8200 N were obtained and it was determined that these values were sufficient for friction heat, hydrostatic pressure, and plasticization in FSP. As a result of mechanical characterisation processes, the microhardness values and wear rates of ZrB2 reinforced SCs in the stir zone (SZ) were higher than SiC reinforced SCs. When the reinforcement particles were compared, it was observed that ZrB2 reinforced SCs exhibited higher microhardness and wear resistance than SiC reinforced SCs. As a result of all tests and investigations, it was determined that the ideal TVFs were 15% for SiC reinforced SCs and 5% for ZrB2 reinforced SCs. The microhardness value of ZrB2 reinforced SC with 20% TVF was 119.6 HV, while the UTS and volume loss values of ZrB2 reinforced SC with 5% TVF were found to be the highest values with 305.86 MPa and 1.83 mm3, respectively. Compared to BM, these values showed significant improvements in mechanical test results, especially in wear behavior. The results obtained showed an improvement of 55% in microhardness, 3.3% in UTS values, and 309% in wear behavior.

Wellbore Stability Analysis Based on the Combination of Geomechanical and Petrophysical Studies

Determining the physical and mechanical properties of rocks is crucial for planning drilling operations. Ignoring geomechanical studies and tools has led to millions of dollars in additional costs related to drilling, meshwork optimization, production optimization, casing collapse, and other issues. These costs can be managed with a thorough geomechanical study. Additionally, some costs may not be apparent in the short term but will become significant over the life of the field. Long-term reservoir management is essential to control these costs. Issues such as reservoir compression, rock cover fractures, and gas storage, if neglected in the short term, can lead to substantial and irreparable damage to the reservoir over time. The "geomechanical model" is fundamental to geomechanical studies, particularly regarding wellbore stability. Given the importance of reservoir geomechanics and petrophysics, this research investigates wellbore stability analysis by combining geomechanical and petrophysical studies through the construction of a one-dimensional geomechanical model of the well. First, the dynamic geomechanical coefficients of the rock for the studied depth range were calculated from wells and petrophysical charts. Then, the static geomechanical coefficients of the rock were estimated based on laboratory-developed relationships. Subsequently, rock mechanics test results were used to estimate rock resistance parameters. The pore pressure was estimated using the compressibility and Eaton methods for the studied range from Well No. 5. Comparing the results of these two methods with RFT test data indicated that the compressibility method is more accurate than Eaton’s method. By estimating the in situ and induced stresses in the well's studied area, the lower and upper limits of the safe mud weight were calculated using the Mohr-Coulomb and Hooke-Brown criteria. Comparison of the results showed that the Mohr-Coulomb criterion is more accurate and, moreover, more conservative than the Hooke-Brown method.

A study on influence of sintering temperature, diameter and volume fraction of metal hollow spheres on the mechanical properties of metal hollow spheres composites

The structural parameters (the sintering temperature, diameter, and volume fraction of the hollow spheres) have a considerable influence on the mechanical properties of metal hollow sphere composites (MHSCs). Hence, the influence laws of the structural parameters on the mechanical properties of MHSCs possess certain research significance. To obtain these laws, MHSCs with different structural parameters were fabricated using a pressure casting method. Subsequently, the density of the MHSCs was determined through the direct measurement method. Meanwhile, X-ray diffraction and scanning electron microscopy were employed to conduct in-depth analyses of the phase composition and microstructure of the MHSCs. Additionally, the compression performance of the MHSCs was measured with the assistance of a universal mechanical testing machine. The analysis of the microstructure and phase composition results revealed that MHSCs consisted of γ-Fe, Al, Si, Fe₂Al₇Si, Fe₂Al₄Si, and Al₈Si₆Mg₃Fe phases, with the transition layer composed of the Fe₂Al₇Si phase. The results of the compression performance indicated that the compression performance of MHSCs increased with the rise of the sintering temperature and decreased with the increase of the volume fraction. However, as the diameter of MHS increased, the yield strength of MHSCs declined while the deformation strength of MHSCs increased. When the diameter of the MHSs was 2.55mm and the volume fraction was 40%, the compression performance of the MHSCs reached its optimum. At that point, the yield strength was 113.65±3.37 Mpa, and the average deformation strength was 81.26±5.45 Mpa.

Automated experimental platform and mechanics testing of rock breaking using different lasers

Automated experimental platform and mechanics testing of rock breaking using different lasers

Promotion or Inhibition? Understanding the Impact of Public Environmental Concerns on Energy Transition in China

It is the theme of today to achieve the “dual carbon target” and promote sustainable development through energy transition (ET). Considering the importance of public environmental concern (PEC) in social operation, this study examines the impact of PEC on ET using panel data of Chinese cities spanning from 2011 to 2019 and a fixed-effects model. A proxy variable for PEC is constructed using the Baidu search index of 25 specific environmental keywords. The results of our study suggest that PEC can facilitate ET and that the effects are heterogeneous, i.e., PEC is more likely to promote ET in central and western China. Investigations of the mechanism test show that PEC mainly facilitates ET by promoting industry structure upgrade and green technology innovation. Furthermore, the results indicated that government environmental concerns (GECs) have a moderating effect on the PEC–ET nexus. The threshold analysis reveals that PEC can have a positive effect only in areas where GEC is relatively low, indicating that PEC can have a positive impact on ET when GEC is absent and acts as a complement to formal environmental regulation. These results provide important insights into strategies for advancing sustainable development and promoting ET in the aspect of government regulation, particularly focusing on synergies between the government, industry, corporate, and the public.

Reconstructing 3D histological structures using machine learning (artificial intelligence) algorithms.

Histomorphometry is currently the gold standard for bone microarchitectural examinations. This relies on two-dimensional (2D) sections to deduce the spatial properties of structures. Micromorphometric parameters are calculated from these sections based on the assumption of aplate-like 3D microarchitecture, resulting in the loss of 3D structure due to the destructive nature of classical histological processing. To overcome the limitation of histomorphometry and reconstruct the 3D architecture of bone core biopsy samples from 2D histological sections, bone core biopsy samples were decalcified and embedded in paraffin. Subsequently, 5 µm thick serial sections were stained with hematoxylin and eosin and scanned using a3DHISTECH PANNORAMIC 1000 Digital Slide Scanner (3DHISTECH, Budapest, Hungary). Amodified U‑Net architecture was trained to categorize tissues on the sections. LoFTR feature matching combined with affine transformations was employed to create the histologic reconstruction. Micromorphometric parameters were calculated using Bruker's CTAn software (v. 1.18.8.0, Bruker, Kontich, Belgium) for both histological and microCT datasets. Our method achieved an overall accuracy of 95.26% (95% confidence interval (CI): [94.15%, 96.37%]) with an F‑score of 0.9320 (95% CI: [0.9211, 0.9429]) averaged across all classes. Correlation coefficients between micromorphometric parameters measured on microCT imaging and histological reconstruction showed astrong linear relationship, with Spearman's ρ‑values of 0.777, 0.717, 0.705, 0.666, and 0.687 for bone volume/tissue volume (BV/TV), bone surface/TV, trabecular pattern factor, trabecular thickness, and trabecular separation, respectively. Bland-Altman and mountain plots indicated good agreement between the methods for BV/TV measurements. This method enables examination of tissue microarchitecture in 3D with an even higher resolution than microcomputed tomography (microCT), without losing information on cellularity. However, the limitation of this procedure is its destructive nature, which precludes subsequent mechanical testing of the sample or any further secondary measurements. Furthermore, the number of histological sections that can be created from asingle sample is limited.

Design, Evaluation, and Implementation of a Novel Magnetic Resonance Imaging-Compatible Physiologic Loading Simulator for Ex-Vivo Joints.

Quantitative magnetic resonance imaging (qMRI), in combination with mechanical testing, offers potential to investigate how loading (e.g., from daily physical exercise) is related to joint and tissue function. However, current testing devices compatible with magnetic resonance imaging (MRI) are often limited to uniaxial compression, often applying low loads, or loading individual tissues (instead of multiple), while more complex simulators do not facilitate MRI. Hence, in this work, we designed, built and tested (N = 1) an MRI-compatible multi-axial load-control system, which enables scanning cadaveric joints (healthy or pathologic) loaded to physiologically relevant levels. Testing involved estimating and validating physiologic loading conditions before implementing them experimentally on cadaver knees to simulate and image gait loading (stance and swing). The resulting design consisted of a portable loading device featuring pneumatic actuators to reach a combined loading scenario, including axial compression (≤2.5 kN), shear (≤1 kN), bending (≤30 N·m) and muscle tension. Initial laboratory testing was carried out; specifically, the device was instrumented with force and pressure sensors to evaluate loading and contact response repeatability in one cadaver knee specimen. This loading system was able to simulate healthy or pathologic gait with reasonable repeatability (e.g., 1.23-2.91% coefficient of variation for axial compression), comparable to current state-of-the-art simulators, leading to generally consistent contact responses. Contact measurements demonstrated a tibiofemoral to patellofemoral load transfer with knee flexion and large contact pressures concentrated over small sites between the femoral cartilage and menisci, agreeing with experimental studies and numerical simulations in the literature.

Sustainable Smart Packaging from Protein Nanofibrils.

Smart packaging technologies are revolutionizing the food industry by extending shelf life and enhancing quality monitoring through environmental responsiveness. Here, a novel smart packaging concept is presented, based on amyloid fibrils (AM) and red radish anthocyanins (RRA), to effectively monitor food spoilage by color change. A protein nanofibrils biofilm is developed from whey protein, which is functionalized with RRA to endow the resulting films with advanced monitoring capabilities. A comprehensive characterization, including pH responsiveness, water vapor permeability, thermal and mechanical testing, and colorimetric responses, demonstrates the superiority of AM/RRA films compared to control films based on whey monomer building blocks. The findings indicate that the AM/RRA films can effectively monitor, for example, shrimp freshness, showing visible changes within one day at room temperature and significant alterations in color after two days. Furthermore, these films exhibit high antibacterial and antioxidant activities, reinforcing their suitability for efficient food packaging. By integrating bio-based materials from whey and natural anthocyanins, this research presents a biodegradable, sustainable, and cost-effective smart packaging solution, contributing to eco-friendly innovations in food preservation.

Improving the antibacterial properties of polyethylene food packaging films with Ajwain essential oil adsorbed on chitosan particles.

The aim of this research is to develop a composite antibacterial film for food packaging using low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyethylene-graft-maleic anhydride (PE-g-MA), and incorporating chitosan (CS) particles onto which ajwan essential oil (AEO) is adsorbed. The films were characterized using various techniques, including Fourier-transform infrared spectroscopy (FTIR), Gas chromatography/mass spectroscopy (GC-MS), X-ray diffraction (XRD), tensile testing, oxygen transmission rate (OTR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and antibacterial assays. FTIR results confirmed the presence of CS and/or AEO in the films. Mechanical testing indicated a decrease in tensile strength and an increase in elongation at break with the addition of AEO, while CS reduced elongation. In the sample containing only 7.5% chitosan (PE-7.5-0), the oxygen permeability was reduced to 910cm2/m2·day·bar due to the presence of CS. However, the inclusion of AEO in the sample (PE-0-10) increased the oxygen permeability to 2200cm2/m2·day·bar, which is higher than that of the control sample (PE-0-0) with an oxygen permeability of 1680cm2/m2·day·bar. The antibacterial activity results demonstrated a synergistic inhibitory effect of CS and AEO. Data from GC-MS and inhibition zone (IZ) tests indicated that while chitosan alone does not exhibit significant antibacterial activity due to its incorporation in the bulk of the film, its combination with AEO enhances antibacterial efficacy. This enhancement occurs as the oil is adsorbed and protected from evaporation during the film formation process. Overall, the findings from this research suggest that the composite film PE-7.5-10, which possesses suitable mechanical properties and significant antibacterial activity, could be an effective candidate for food packaging applications.

The influence of plastic flow localization on the surface morphology of aluminum alloy specimens subjected to complex loading

This study investigates the effects of complex (nonproportional) loading on plastic deformation in aluminum alloys (Al-6% Mg), with a focus on understanding surface morphology changes driven by the Portevin–Le Chatelier effect. Mechanical tests on the deformation of thin-walled tubular specimens were carried out on an Instron 8850 two-axis servohydraulic testing system. Quantitative analysis of the lateral surface of the specimens roughness was carried out based on data obtained using a NewView 5010 interferometer-profilometer. Localized plasticity zones in a wide spectrum of spatial scales were determined using the Hurst exponent as a roughness characteristic. The results of measuring changes in the surface geometry of specimens under various programs of complex (disproportionate) loading are presented. A compact representation of data on the specimens surface relief in the form of amplitude-frequency characteristics was obtained using wavelet analysis. The results obtained can be used to assess the surface roughness of products, especially at the final stages of their manufacturing process by plastic deformation.

Fracture characteristics of human cortical bone influenced by the duration of in vitro glycation

Abstract Advanced glycation end products (AGEs) accumulate in various tissues, including bone, due to aging and conditions like diabetes mellitus. To investigate the effects of AGEs on bone material quality and biomechanical properties, an in vitro study utilized human tibia, sectioned into 90 beams, and randomly assigned to three mechanical test groups. Each test group included ribose (c=0.6 M) treatment at 7-, 14-, and 21-day, alongside control groups (n=5 per group). Fluorescent AGE (fAGE) and carboxymethyl-lysine (CML) levels were assessed through fluorometric analysis and mass spectrometry, while bone matrix composition was characterized using Fourier-transform infrared and Raman spectroscopy. Mechanical properties were determined through nanoindentation and three-point bending tests on non-notched and notched specimens. The results showed significant increases in fAGEs levels at 7-, 14-, and 21-day compared to controls (119%, 311%, 404%; p=0.008, p<0.0001, p<0.0001; respectively), CML levels also rose substantially compared to controls (383%, 503%, 647%, p<0.0001, p<0.0001, p<0.0001; respectively). Analysis of bone matrix composition showed greater sugars/Amide I ratio at 21-day glycation compared to controls, 7-day, and 14-day (p=0.001, 0.011, 0.006; respectively); and higher carbonate-to-phosphate ratios in the ribose treatment group compared to controls (p<0.05) in the interstitial bone area. Mechanical testing of notched specimens exhibited a higher yield force, pre-yield toughness, and growth toughness at 14-day glycation compared to controls and to both 7-day and 21-day glycation (p<0.05). Nanoindentation showed that the hardness was lower at 7-day glycation compared to the controls and 21-day glycation (p<0.05). In conclusion, the study found altered mechanical properties at 7 and 14 days of glycation, which then returned to control levels at 21 days, indicating a dynamic relationship between glycation duration and mechanical characteristics that deserves further exploration.

Long-duration type 1 diabetes is associated with deficient cortical bone mechanical behavior and altered matrix composition in human femoral bone.

Type 1 diabetes (T1D) is associated with an increased risk of hip fracture beyond what can be explained by reduced bone mineral density, possibly due to changes in bone material from accumulation of advanced glycation end products (AGEs) and altered matrix composition, though data from human cortical bone in T1D are limited. The objective of this study was to evaluate cortical bone material behavior in T1D by examining specimens from cadaveric femora from older adults with long-duration T1D (≥50years; n= 20) and age- and sex-matched non-diabetic controls (n= 14). Cortical bone was assessed by mechanical testing (4-point bending, cyclic reference point indentation, impact microindentation), AGE quantification (total fluorescent AGEs, pentosidine, carboxymethyl-lysine (CML)), and matrix composition via Raman spectroscopy. Cortical bone from older adults with T1D had diminished post-yield toughness to fracture (-30%, P=.036), elevated levels of AGEs (pentosidine, +17%, P=.039), lower mineral crystallinity (-1.4%, P=.010), greater proline hydroxylation (+1.9%, P=.009), and reduced glycosaminoglycan (GAG) content (-1.3%, P<.03) compared to non-diabetics. In multiple regression models to predict cortical bone toughness, cortical tissue mineral density (Ct.TMD), CML, and Raman spectroscopic measures of enzymatic collagen crosslinks and GAG content remained highly significant predictors of toughness, while diabetic status was no longer significant (adjusted R2> 0.60, P<.001). Thus, impairment of cortical bone to absorb energy following long-duration T1D is well explained by AGE accumulation and modifications to the bone matrix. These results provide novel insight into the pathogenesis of skeletal fragility in individuals with T1D.