Microstructural Changes Research Articles

Research on the material removal mechanism of vibration-assisted nano-scratch on single-crystal GaN by molecular dynamics.

Single-crystal gallium nitride (GaN) is a semiconductor material known for its hardness and brittleness. This research aims to reveal the differences in the micro-mechanisms of material removal during traditional grinding and ultrasonic vibration-assisted grinding and to provide guidance for the high-efficiency, high-quality planarization processing of single-crystal GaN. To achieve this purpose, molecular dynamics (MD) simulation methods were used to establish a model (30nm × 40nm × 15nm) of single-crystal GaN being scratched by a single abrasive grain with and without ultrasonic vibration assistance. The differences in the surface morphology and subsurface damage formation mechanisms of single-crystal GaN under conditions with and without ultrasonic assistance were compared. The results indicate that, compared to traditional grinding, the periodic ultrasonic vibrations reduce the normal force and result in a more uniform distribution of stress and temperature, thereby mitigating local stress concentration and thermal accumulation effects. Ultrasonic vibration alters the motion of the abrasive grain, expanding the material removal range from 7.384 to 10.315nm, decreasing the number of residual atoms in the machining area, and lowering the chip pileup height at the leading edge of the abrasive grain from 2.063 to 1.528nm. Additionally, the micro-shear deformation induced by ultrasonic vibrations helps to suppress brittle fracturing caused by excessive local stress, thus reducing the thickness of the damaged subsurface. At a scratch depth of 2nm, the total length of dislocation lines in the ultrasonic-assisted scratch is reduced from 185.256 to 33.315 nm compared to traditional scratching. These findings offer new insights into the microscopic mechanisms of material removal in high-efficiency, high-quality grinding processes of single-crystal GaN. This study adopts LAMMPS software for MD simulations to investigate the physical behavior of GaN during the grinding process. The simulation results are then visualized and analyzed using OVITO software to elucidate microstructural changes in the material. During the simulation, the temperature of the Newtonian layer is calculated based on the statistical analysis of atomic velocities under the NVE ensemble. The grinding force applied to the GaN workpiece is determined by differentiating the atomic potential energy. Von Mises stress analysis is adopted to ascertain the stress distribution during the scratching process. Finally, the changes in the crystal structure during scratching are identified and classified using analysis of identified defect structures.

Assessment of Mechanical Behavior and Microstructure of Unsaturated Polyester Resin Composites Reinforced with Recycled Marble Waste

The quarrying and utilization of natural stones such as marble and granite are growing rapidly in developing countries. However, the processing, cutting, sizing, and shaping of these stones to render them functional generates huge quantities of waste and dust. These materials are often disposed of openly in the environment, and their potentially hazardous nature has negative repercussions on both the environment and human health. In this study, marble waste (MW) was used as a filler in the unsaturated polyester resin (UPR) matrix to enhance performance and characteristics while adding value to the waste and minimizing manufacturing costs. For this purpose, samples of UPR/MW composites were produced with 0, 5, 10, 15, and 20 wt.% of MW incorporated into the UPR. A full characterization that focused on the microstructure, thermal stability, and physical and mechanical properties was carried out. The results revealed that the use of 10 to 15% of MW improves mechanical performance, with increases from 17 to 26 kJ/m2, 14 to 17 MPa, and 794 to 1522 GPa in impact strength, tensile strength, and elastic modulus, respectively. By introducing a 20% MW filler, the composite loses its performance, particularly Shore D hardness, and becomes very brittle. Thermogravimetric analysis (TGA) indicated significant thermal stabilization, with a delay in the start decomposition temperature of 28 °C for 20 UPR/MW compared to 0 UPR/MW. Additionally, morphological and microstructural tests, namely, FT-IR, XRD, and SEM analysis, show a microstructural change, including the formation of crystalline phases, enhancing matrix-filler interactions due to the creation of Mg-O and Ca-O chemical bonds and the forming of filler agglomeration at high introduction rates that lead to defects in the microstructure. These results confirmed the mechanical results of the UPR/MW composites.

Alterations of white matter microstructure in migraine patients vary in the peri-ictal phases

Alterations in white matter (WM) microstructure are commonly found in migraine patients. Here, we employ a longitudinal study of episodic migraine without aura using diffusion MRI (dMRI) to investigate whether such WM microstructure alterations vary through the different phases of the pain cycle. Fourteen patients with episodic migraine without aura related with menstruation were scanned through four phases of their (spontaneous) migraine cycle (interictal, preictal, ictal and postictal). Fifteen healthy controls were studied in the corresponding phases of the menstrual cycle. Multi-shell dMRI data was acquired and pre-processed to obtain maps of diffusion parameters reflecting WM microstructure. After a whole-brain analysis comparing patients with controls, a region-of-interest analysis was performed to determine whether the patients’ microstructural changes varied across the migraine cycle in specific WM tracts. Compared with controls, patients showed reduced axial diffusivity (AD) in several WM tracts across the whole brain in the interictal phase, and increased fractional anisotropy (FA) in commissural fibers in the ictal phase. Interestingly, AD returned to baseline levels during peri-ictal phases in specific projection and association fibers. In contrast, FA values decreased in the ictal phase away from normal values in a few commissural and projection tracts. Widespread WM fiber tracts suffer structural variations across the migraine cycle, suggesting microstructural changes potentially associated with limbic and salience functional networks and highlighting the importance of the cycle phase in imaging studies of migraine.Significance StatementOur study reveals dynamic changes in white matter microstructure across different phases of the migraine cycle, using advanced diffusion MRI. By employing a case-control longitudinal design on patients with episodic menstrual migraine, we identified transient reductions in axial diffusivity and fractional anisotropy in specific white matter tracts, which varied with migraine phases independently of hormonal influences. This is the first study to document such phase-dependent microstructural changes, highlighting the brain's ability to adapt rapidly to pain. Our findings provide significant insights into neuroplasticity, enhancing the understanding of migraine and potentially informing broader neurological research on the brain's response to pathological states.

Research on the fatigue performance of continuous beam bridges with vibration-mixed steel fiber-reinforced concrete

To address the fatigue damage issues in continuous beam bridges under vehicle loads, a method using vibration-mixed steel fiber-reinforced concrete to improve critical vulnerable areas of the bridge is proposed, thereby enhancing the bridge’s fatigue resistance. Fatigue performance and micro electron microscopy tests were designed for vibration-mixed steel fiber-reinforced concrete, analyzing its damage conditions and microstructural changes under 0 to 2 million cyclic loads, and the key mechanical parameters of the concrete were determined. Based on this, a numerical analysis model was established to simulate the fatigue damage of continuous beam bridges under moving vehicle loads. The results show that piers made with vibration-mixed steel fiber-reinforced concrete exhibit a 56.86% reduction in compressive damage compared to conventional piers, a reduction in stiffness damage range, and a 29.35% increase in fatigue life.

Connectivity-based striatal subregion microstructural changes in sporadic amyotrophic lateral sclerosis patients: Relation to motor disability, cognitive deficits, and serum biomarkers.

To date, no previous studies have used multishell diffusion MRI to identify striatal microstructural damage invivo in amyotrophic lateral sclerosis (ALS) patients. Thus, in the present study, we aimed to comprehensively explore connectivity-based selective striatal subregion microstructural damage in sporadic ALS patients and its associations with motor disability, cognitive deficits, and serum biomarkers. In this retrospective study, 79 ALS patients and 53 healthy controls (HCs) who underwent clinical assessment, serum neurofilament light (NfL) measurement, genetic testing, and multishell diffusion MRI scanning were included. Using a probabilistic tractography approach, the striatum was segmented into six subregions based on their corticostriatal connectivity. Three neurite orientation dispersion and density imaging (NODDI) parameters, the neurite density index (NDI), orientation dispersion index (ODI), and isotropic volume fraction (ISO), of the connectivity-based striatal subregions were measured. Compared with HCs, ALS patients had a significantly lower NDI in the bilateral motor and right frontal subregions, a significantly lower ODI in the right motor and frontal subregions, and a significantly higher ISO in the bilateral motor and frontal subregions of the striatum after familywise error (p < 0.05). Moreover, striatal subregion microstructural damage was significantly correlated with motor disabilities, cognitive deficits, and serum NfL levels in ALS patients (p = 0.020-0.002). Our study provides clear evidence demonstrating that connectivity-based selective striatal subregion microstructural damage is a definite feature of sporadic ALS patients and suggesting that striatal damage may play an important role in motor disability and cognitive deficits in ALS patients.

Superior Capacitive Energy Storage Enabled by Molecularly Interpenetrating Interfaces in Layered Polymers.

Polymer dielectrics are essential for advanced electronics and electrical power systems, yet they suffer from low energy density (Ue) due to their low dielectric constant (K) and the inverse relationship between K and breakdown stength (Eb). Here a scalable approach utilizing the designed molecularly interpenetrating interfaces is presented to achieve all-organic dielectric polymers with high Ue and charge-dischage efficiency (η). Distinctive intermolecular interactions and microstructural changes, as demonstrated experimentally and theoretically, are introduced by the molecularly interpenetrating interfaces, resulting in simultaneous improvements in dielectric responses and mechanical strength while inhibiting electrical conduction - outcomes unattainable in conventional layered polymers. Consequently, exceptional improvments in both K and Eb are achieved, yielding a very high Ue of 22.89Jcm-3 with η ≥ 90%, outperforming current layered polymer dielectrics. The bilayers can be easily fabricated into large-area films with high uniformity and outstanding capacitive stability (>500 000 cycles), offering a practical route to scalable high-Ue polymer dielectrics for electrical energy storage.

Impact of nano-TiO2 on white Portland cement mortars: a combined XRD coupled rietveld, crystallographic and microstructural analysis

The present study investigated the structural, microstructural, and crystallographic changes associated with the addition of nano-TiO2 (NT) by intermixing and surface coating on freshly cast and hardened coatings on white Portland cement matrix samples at minimal dosages. Scanning electron microscopy (SEM) and VESTA were employed to analyze the microstructure morphology of the hydration products and the crystal structure parameters of the NT-modified white Portland cement mortar. Additionally, Rietveld refinement analysis was performed to quantify the crystal phases coupled with XRD using Xpert High Score Plus and Expo-2014 software. The Rietveld refinement analysis of the hardened coating surface followed by the fresh cast coating resulted in the most refined structural model compared with that of the intermixed and reference samples. The integration of NT also reduced the bond distances and polyhedral volumes, indicating denser atomic packing and enhanced interactions between the smaller NT particles and the white Portland cement matrix and enhancing the structural integrity within the matrix. Furthermore, SEM micrographs revealed a compact microstructure with enhanced CSH and reduced CH crystals in the NT-modified white cement mortar samples. The presence of hydration products and corresponding bonds were confirmed by Fourier Transform Infrared Spectroscopy.

The improvement on the properties and heavy metal solidification of phosphogypsum-steel slag cementitious material: Enhancement from Bi-directional carbonation

Despite the carbonation curing methods have been applied in many building materials, the low efficiency in solid waste utilization is still a big issue for applying this technique. Therefore, bi-direction carbonation curing was proposed and its performance, especially for the improvement in solidification/stabilization of heavy metal (Pb2+ and Cr3+), in phosphogypsum-steel slag cementitious materials (PSSC) was determined. In this study, PSSC with phosphogypsum (PG) and three kinds of steel slag (SS) with different fineness were prepared, and the bi-directional curing was achieved by mixing with Na2CO3 powder as the internal carbon source and curing under CO2 gas as the external carbon source. In addition to determining its effect on solidification efficiency, comprehensive strength, including X-ray diffraction, thermogravimetric analysis, and pore structure analysis were employed to reveal the changes in microstructure during carbonation after the addition of Na2CO3, and reveal the mechanism of PG on the hydration-carbonation of steel slag. The results showed the early-stage performance of PSSC was significantly improved and the solidification/stabilization performance for heavy metals was enhanced. The addition of Na2CO3 as an internal carbon source accelerates the time of carbonation curing, leading to higher early-stage strength of PSSC. By applying bi-directional carbonation curing, the solidification ability of PSSC with spatial structure denser for heavy metals Pb2+ and Cr3+ are improved by 80 % and 87 %, respectively, which could be attributed to the formation of nano-CaCO3 crystals.

Influence of the mechanical activation process on the corrosion of Ti2⁠AlN MAX phase obtained by hot pressing

The Ti2AlN MAX phase is known for its unique blend of metallic and ceramic properties, including high electrical and thermal conductivity and excellent oxidation and corrosion resistance. This study focuses on the influence of the mechanical activation process on the electrochemical properties of Ti2AlN in a saline environment. High-purity powders of AlN and Ti were mechanically activated or mixed and sintered to synthesize the Ti2AlN MAX phase. The electrochemical behavior was assessed through potentiodynamic curves and electrochemical impedance spectroscopy, while surface characteristics were analyzed using SEM-EDS and XPS post-exposure to a 3.5% NaCl solution. Results reveal that Ti2AlN forms protective Al2O3 and TiO2 layers, enhancing its corrosion resistance. Mechanically activated samples (MAP) displayed different corrosion behavior than non-activated samples (NMAP), with MAP showing reduced corrosion resistance. This discrepancy is attributed to differences in oxide formation and microstructural changes due to mechanical activation. This research not only elucidates the corrosion mechanisms of MAX phases in chloride-rich environments but also analyzes the effect of mechanical processing on their properties, contributing to developing Ti2AlN applications where high durability and resistance are critical.

Physical, mechanical, and microstructural changes in concretes subjected to slow and fast cooling in a fire situation simulation

Physical, mechanical, and microstructural changes in concretes subjected to slow and fast cooling in a fire situation simulation

Non-destructive AC impedance spectroscopy (ACIS) analysis to characterize the evolution of impact damage in UHPC

Ultra-high performance concrete (UHPC) widely serves as protection material owing to superior impact resistance. Rapid and effective assessment of impact damage level is crucial for ensuring structural safety. The non-destructive AC impedance responds sensitively to impact-induced microstructural changes, providing important information for understanding the damage development mechanism. Therefore, this paper intends to investigate the feasibility of AC impedance spectroscopy (ACIS) for UHPC impact damage detection. UHPC specimens with different types and volume fractions of steel fibers were prepared, subjected to multiple repetitive low-velocity hammer impacts to induce cumulative damage, and the impedance responses were simultaneously tested in the frequency range of 10 Hz-5 MHz. Additionally, the effects of steel fiber distribution characteristics and pull-out mechanism on the conductive path and impact resistance were explained through microstructural analysis and 3D reconstructed model. The results show that ACIS exhibits a strong correlation with impact damage, where the increment of the imaginary part can be used as an effective and sensitive indicator to achieve whole-process damage assessment. Compared to straight steel fibers, hooked-end and corrugated fibers greatly enhance the impact resistance of UHPC but cause a nonlinear response in impedance due to extracted deformations and orifice complexities. These findings demonstrate the potential application of ACIS for detecting impact damage in UHPC and warrant further investigation.

Effect of polyacrylate polymer on the mechanical and water retention properties of cemented soil: A multiscale investigation

Granitic residual soils (GRS) occupy substantial deposits in many regions but exhibit deficiencies restricting direct engineering applications. This study investigated polyacrylate (PA) polymer treatment to enhance the mechanical and hydrological properties of GRS. Triaxial tests evaluated the effects of PA content (0–3 %) on shear strength parameters under varied confining pressures. Soil-water retention characteristics were determined using pressure plate and filter paper methods. Microstructural analyses via scanning electron microscopy and pore attribute quantification furnished insights. Results showed PA increased peak deviator stress and cohesion in a content-sensitive manner up to an optimum 2 % dosage. A modified Duncan-Chang model accurately described the nonlinear stress-strain behavior. PA amplified water retention across the entire suction domain by elevating the air entry value attributed to microstructural changes. Morphological analyses indicated PA formed binding membranes consolidating particles with redistributed pore attributes towards stabler, load-resisting configurations. Quantitative links validated hypothesized mechanisms whereby optimized pore architectures directly translated bulk fabric cohesion and friction enhancement. Multi-scale evidence synthesized a self-consistent microscopic mechanism of PA-mediated pore network reconstitution systematically strengthening the granular framework. This study demonstrated polyacrylate modification optimizes key engineering properties of naturally deficient GRS, offering design guidance for sustainable geotechnical applications exploiting abundant residual soil resources.

Sintering of copper nanoparticles using intense pulsed light for screen-printed films on flexible substrate

Abstract Rapid growth in applications involving large area flexible electronics has led to wide adoption of the technique of sintering printed films using intense pulsed light due to its pulse mode operation and ability to reach high sintering temperatures without affecting the underlying substrate significantly. We study the sintering mechanisms of screen-printed thin films of copper nanoparticles on polyethylene terephthalate plastic substrates by varying the irradiance energy over a wide range to monitor conductivity and associated microstructure changes. We obtain optimized parameters which indicate the existence of a sharp threshold irradiance energy to kickstart sintering, and two distinct regimes beyond that. The low temperature regime has a high energy barrier while the high temperature regime has a substantially reduced energy barrier with a change of phase due to local melting.

Mechanical Characteristics and Microstructural Changes in Phosphogypsum-Cement-Lime Composite Modified Loess

Loess is widely distributed in China but suffers from inherent deficiencies limiting its direct use as a subbase material in road construction without modifications. This study investigated the utilization of Phosphogypsum (PG), an industrial waste, in a composite stabilizer containing cement, lime and slag powder for modifying loess in the subbase application. An orthogonal test design was employed to optimize the composite proportions. Laboratory tests evaluated the mechanical properties including unconfined compressive strength (UCS), splitting tensile strength, resilient modulus and water stability of modified loess over curing periods up to 90 days. Microstructural evolution was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed the composite containing 25% PG, a cement-slag ratio of 4:6 and 5% lime imparted the highest strengths. Mechanical performances increased with curing time and stabilizer content. Water stability and heavy metal immobilization were satisfactory. Microstructural results revealed microstructural densification occurred through hydration product development binding soil particles. This work demonstrated the technical and environmental viability of recycling PG through loess improvement, offering a sustainable solution for problematic soil stabilization and industrial waste utilization.

Low cycle fatigue properties and life prediction based on plastic work of back stress in a Zr-2.5Nb alloy

Pressure tubes of Zr-2.5Nb alloy in Pressurized Heavy Water Reactors experience low cycle fatigue (LCF) due to cooling water flow and power fluctuations, which could be a factor destroying their structural integrity. Therefore, it is essential to systematically investigate their LCF properties and develop accurate life prediction models. Existing research primarily focuses on single-phase Zr alloys, leaving a gap in understanding the fatigue behavior and microstructural evolution of the dual-phase Zr-2.5Nb alloy. This study addressed these gaps by conducting LCF tests on the Zr-2.5Nb alloy under strain amplitudes ranging from ± 0.50 % to ± 1.5 % at room temperature. The results indicated that the cyclic response can be divided into three stages (Ⅰ, Ⅱ, Ⅲ) based on the relative number of cycles. Cyclic softening/hardening originated from microstructural changes such as dislocation sub-structure, grain rotation, and texture evolution. A novel fatigue life prediction model was proposed based on the plastic work of back stress. For non-Masing materials, this model overcame the limitations of traditional plastic strain energy models and demonstrated higher prediction accuracy. This work contributes to a more accurate prediction of fatigue life in Zr alloys and provides new insights into their fatigue behavior and microstructure evolution under LCF conditions.

On the role of the preheat temperature in electron-beam powder bed fusion processed IN718

Process parameters optimization in additive manufacturing (AM) is usually required to unlock superior properties, and this is often facilitated by modeling. In electron beam powder bed fusion (E-PBF), the preheat temperature is an important parameter to be optimized as it significantly influences the microstructure and properties. Here we compare the effect of two preheat temperatures (1000 and 950°C, above and below δ-phase solvus temperature) on the microstructural evolution of E-PBF IN718 Ni-based superalloy. Using thermal and thermo-kinetic modeling, we predict microstructural changes and compare them with experimental findings. A decrease of only 50°C in the preheat temperature has a low impact on the solidification microstructure with a slight reduction in columnar grain width. In the solid-state, higher preheating causes intergranular δ-phase precipitation, contributing to a higher γ" precipitation potential, formation of co-precipitates, and higher hardness. The lower preheat temperature induces intergranular and intragranular δ-phase precipitation, reducing the γ" precipitation potential and hardness. The chemical composition of γ' and γ" is largely unaffected by the preheat temperature variation. These insights underscore the importance of preheat temperature optimization in microstructure design and property control during E-PBF.

Effect of ZrB2 and ZrC and mixing method on Mechanical properties and wear behaviour of Al7075 based composites for aircraft aerofoil surfaces

Developing lightweight materials with notable properties for aerospace applications is a great challenge. The impact of ZrB2 and ZrC reinforcement on the mechanical and wear behaviour of stir-cast Al7075-ZrB2-ZrC composites is investigated with a weight percentage of 2, 4, 6 and 8% ZrB2, and fixed 2% ZrC. The results showed notable improvements with a hardness of 96 HRB, tensile strength of 423MPa and compressive strength of 385MPa; hardness increased by 14%, tensile strength increased by 11% and compressive strength was enhanced by 13% when compared with pure Al7075. The wear behaviour has been analysed by pin-on-disc wear test at room temperature with loads of 10N and 20N against the sliding distance of 400m to 1200m; the wear resistance is improved by 17% and CoF is reduced by 11% compared to pure Al7075. SEM micrographs display the wear mechanism and microstructural changes happened during the wear test. Al7075-ZrB2-ZrC composites are the optimum replacement for aerofoil surfaces because of their remarkable properties.

Female rat liver after sub-acute dibutyl phthalate treatment: Histological, stereological, biochemical, and global gene expression study

Although it has been recognized that females are more susceptible to chemical-induced liver injury, the effects of dibutyl phthalate (DBP), a widely used synthetic chemical, on female liver structure and function are under-researched. Here, we sought to investigate the effects of DBP on histological, stereological, and biochemical parameters, as well as global gene expression in female rat liver. Female Wistar rats were exposed to 100, 500, and 5000 mg DBP/kg diet for 28 days, corresponding to 8.6, 41.43, and 447.33 mg DBP/kg body weight (B.W.)/day, respectively. The highest dose (447.33 mg DBP/kg B.W./day) was between the no-observed-adverse-effect level (NOAEL) and the lowest-observed-adverse-effect level for liver toxicity, whereas two lower doses (8.6 and 41.43 mg DBP/kg B.W./day) were below the NOAEL. Analysis of hematoxylin and eosin-stained sections revealed an increased volume of hepatocytes, their nuclei and cytoplasm, while the volume of sinusoids decreased in DBP-exposed groups compared to the control. Examination of Periodic acid-Schiff-stained sections showed reduced glycogen content, which was the most prominent in the highest dose group. Increased glutathione S-transferase and catalase activities, and decreased GSH content and superoxide dismutase activity were observed in DBP-exposed groups. The mRNA sequencing revealed DBP-induced dose-specific changes in various genes and biological functions in female rat liver. The highest number of deregulated genes was observed in the 500 mg DBP/kg diet group. In summary, exposure to DBP caused significant liver microstructural changes, decreased glycogen content, disturbed the redox status, and affected global gene expression in female rat liver.

Investigating the Multifaceted Changes in Physicochemical and Nutritional Attributes of Chicken-Based Nutri Cereal Mix under Cold Plasma Treatment

In this study multifaceted changes in physicochemical and nutritional properties of nutri-cereal mix (NCM) under cold plasma treatment (CPT) were investigated. In present investigation NCM was prepared and treated under CPT using a DBD-based plasma source for 5 min, 10 min, and 15 min at 9 kv. The results revealed that the water and oil absorbing capacity of cold plasma treated Nutri cereal mix (CPT-NCM) increased with increasing CPT time. The carbohydrate content in CPT-NCM decreased with increasing CPT time. From the colour analysis it was observed that the total colour difference (TCD) and whiteness index (WI) increased from 0.23 (NCM -5) to 0.97 (NCM -15), and 55.11 (NCM -5) to 56.08 (NCM -15), respectively. Additionally, the differential scanning calorimetry (DSC) analysis suggested that the thermostability of CPT-NCM is likely affected by NCM levels and changes in protein structure and conformation. The diffractograms and micrographs confirmed the crystallinity and microstructural changes in protein content, respectively. Amino acid profiling confirmed that NCM -10 comprises the higher amount of most of the analysed amino acids. Overall, the current study recommends that CPT enhances the physicochemical and nutritional properties of NCM, making it suitable for producing a variety of food products with improved quality characteristics.

Post-traumatic osteoarthritic-mediated changes in condylar shape do not covary with changes in the internal microstructure of the bone

Post-traumatic osteoarthritis (PTOA) in the temporomandibular joint (TMJ) is associated with remodeling of the subchondral bone. This remodeling changes both the external appearance of the condylar bone and the internal bony microstructure. The external geometry can be quantified using shape, a multivariate mathematical measurement that contains all of the structure's geometric information with location, scale, and rotation effects removed. There is an important gap in knowledge related to how TMJ PTOA affects the shape of the mandible and if the external shape covaries with the internal bony microstructure. To evaluate these gaps, TMJ PTOA was induced in male and female skeletally mature mice using a surgical destabilization procedure. After four weeks, tissues were collected and characterized using a high-resolution μCT scanner. Shape was calculated from surface reconstructions of the mandibular condyle, and the internal bony microstructure was characterized by the region of interest including the subchondral trabeculae. The covariance of shape with and without corrections for allometric scaling and internal bony microstructure was calculated using a Procrustes ANOVA. The data illustrate that PTOA significantly alters the shape of the condyle in a sex-independent manner. PTOA does alter some aspects of the internal bony microstructure in a sex-dependent manner. Allometric scaling was a significant factor in the variance of shape. Shape including the effects of allometric scaling significantly covaries with some internal bony microstructure variables in both sexes. Shape scaled to remove the effects of allometric scaling does not covary with internal bony microstructure in either sex. These findings indicate that PTOA progression is associated with changes in the size and shape of the condyle but variance in trabecular bone remodeling is only associated with size related shape change. Thus, the allostatic response of subchondral bone is multimodal, coordinating two independent biological processes controlling size and shape. Since subchondral bone participates in and guides the progression of PTOA, these findings have implications for identifying select and specific mechanisms contributing to the progression and pathophysiology of the PTOA in the TMJ.