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Summary Vibration control of structures under near‐fault earthquakes by employing a friction pendulum supplemented with thermally modulated shape memory alloy (SMA) springs as damper system is studied. Temperature modulation of the SMA spring during the earthquake effectively alters its hysteretic energy dissipation capacity and thereby the control efficiency of the isolation system. The response of a structure with the isolation system is evaluated through nonlinear dynamic time‐history analysis under a set of recorded near‐fault ground motions. Through temperature modulation that effectively yields a large SMA hysteretic energy dissipation, the hybrid friction pendulum system with SMA temperature modulation shows enormous control efficiency. A parametric study reveals that under a wide range of conditions, the thermally modulated SMA friction pendulum isolation system shows improved control efficiency over conventional friction pendulum and SMA friction pendulum isolation systems. Further, the temperature‐tuned SMA hysteresis loops substantially suppress the high frequency components of earthquake motions, thus reducing the possibility of damage to the structure.

A coupled thermo-mechanical bond-based peridynamical (TM-BB-PD) method is developed to simulate thermal cracking processes in rocks. The coupled thermo-mechanical model consists of two parts. In the first part, temperature distribution of the system is modeled based on the heat conduction equation. In the second part, the mechanical deformation caused by temperature change is calculated to investigate thermal fracture problems. The multi-rate explicit time integration scheme is proposed to overcome the multi-scale time problem in coupled thermo-mechanical systems. Two benchmark examples, i.e., steady-state heat conduction and transient heat conduction with deformation problem, are performed to illustrate the correctness and accuracy of the proposed coupled numerical method in dealing with thermo-mechanical problems. Moreover, two kinds of numerical convergence for peridynamics, i.e., m - and δ -convergences, are tested. The thermal cracking behaviors in rocks are also investigated using the proposed coupled numerical method. The present numerical results are in good agreement with the previous numerical and experimental data. Effects of PD material point distributions and nonlocal ratios on thermal cracking patterns are also studied. It can be found from the numerical results that thermal crack growth paths do not increases with changes of PD material point spacing when the nonlocal ratio is larger than 4. The present numerical results also indicate that thermal crack growth paths are slightly affected by the arrangements of PD material points. Moreover, influences of thermal expansion coefficients and inhomogeneous properties on thermal cracking patterns are investigated, and the corresponding thermal fracture mechanism is analyzed in simulations. Finally, a LdB granite specimen with a borehole in the heated experiment is taken as an application example to examine applicability and usefulness of the proposed numerical method. Numerical results are in good agreement with the previous experimental and numerical results. Meanwhile, it can be found from the numerical results that the coupled TM-BB-PD has the capacity to capture phenomena of temperature jumps across cracks, which cannot be captured in the previous numerical simulations.

Laser direct energy deposition (DED) is an advanced additive manufacturing technology, which can produce fully dense and functionally graded materials (FGMs) metal parts. Residual stress and distortion are crucial issues in DED process reducing the mechanical strength and the geometrical accuracy of the fabricated components. This work provided a combined approach involving thermo-mechanical model and experimental validation toward two FGM cases fabricated by DED process to reveal the residual stress and distortion distribution. Two fabrication approaches were used: a direct deposition of Cu on SS304L and a structure graded from iron alloy SS316L to nickel alloy In718 to pure Cu based on SS304L substrate. Thermal histories of the substrate and the residual stress on cross-section of the FGM part were measured to calibrate the 3D coupled thermo-mechanical model. The predicted temperature and stress results showed a good agreement with the experimental measurements. The distortion results of both fabricated walls showed an upwards bent trend. Because of the high-temperature gradient induced by the mismatch in the thermal expansion coefficient of different materials, very high distortion was observed at two edge regions of the second printing material of FGM part. From the residual stress standpoint, direct joining Cu on SS304L resulted in extremely high residual stress at the bi-material interface due to mismatch in the thermal expansion coefficient of different materials. By introducing SS316L and In718 buffer layers, defect-free Cu can be successfully deposited on SS304L. This model can be used to predict the stress behavior of products fabricated by DED process and to help with the optimization of design and material chosen of FGMs process.

Laser-induced thermotherapy (LITT) offers a minimally invasive approach to tumor ablation but requires accurate modeling of photon transport, heat deposition, and thermo-mechanical tissue response. Conventional bioheat and diffusion-based models oversimplify these interactions, especially in irregular, heterogeneous tumors. To overcome this, a Monte Carlo–Dual Reciprocity Boundary Element Method (MC-DRBEM) framework is developed, combining stochastic photon transport with nonlinear bioheat and thermoelastic stress analysis. The method efficiently handles complex geometries using boundary-only discretization and accounts for temperature-dependent properties. Validation against analytical and finite element benchmarks shows strong accuracy. Results highlight the significant role of tissue anisotropy and functional grading on stress distribution, with isotropic tissues showing highest stress sensitivity. Parametric studies further confirm the model’s robustness in predicting temperature gradients and safe ablation margins. Overall, MC-DRBEM provides a scalable, geometry-aware tool for patient-specific treatment planning in laser-based cancer therapy.

Heat generated during the friction stir welding (FSW) process is of complex nature and plays a vital role in influencing the quality of the fabricated joints. In this experimental research, an thermo mechanical process model was formulated to estimate the values of peak temperatures generated during the employment of FSW tools with four different pin geometries (namely cylindrical, taper cylindrical, square and triangle) for joining of AZ80A Mg alloy flat plates, to understand their significant role in influencing the size of the grains, their mechanical strength and in the quality of the joints. The peak temperature values of the formulated thermo mechanical process model are found to be consistent with that of the actual experimental results and exhibited relatively very small variation It was observed that the joints fabricated by taper cylindrical pin geometry was found to possess very fine sized grains, due to the generation of ideal peak temperature (i.e., 348 °C which is nearly 81–82% of the melting temperature of AZ80A Workpiece).

Ball screws are robust and economical linear positioning systems widely employed in high-speed and high-precision machines. Due to precision and stability requirements, the preload force is considered one of the main parameters defining the axial stiffness and the maximum axial load of the ball screw feed drives. In high-speed motions, thermal effects are also considerably relevant regarding positioning precision and dynamic stability of the machine. The temperature increase and the thermal gradient between the screw, the balls and the nuts result in geometrical variations and, consequently, variations in the preload force. This paper presents a numerical modelling strategy to predict the preload variation due to temperature increase using a thermo-mechanical 3D finite element method (FEM)-based model for double nut-ball screw drives. Two different thermo-mechanical coupling strategies are compared, and the obtained results are validated with experimental measurements for different initial preload and linear speeds. In the mechanical analysis, the nut-screw ball contact interface, the offset-based preloading and the restrictions of the ball bearings are included in the model, while the thermal analysis considers heat generation and heat diffusion. The causes of the thermal preload variation are discussed considering the ball load distribution and the axial and radial thermal displacements of the contacting points.

Thermo-mechanical finite element (FE) models predict the thermal behavior of machine tools and the associated mechanical deviations. However, one disadvantage is their high computational expense, linked to the evaluation of the large systems of differential equations. Therefore, projection-based model order reduction (MOR) methods are required in order to create efficient surrogate models. This paper presents a parametric MOR method for weakly coupled thermo-mechanical FE models of machine tools and other similar mechatronic systems. This work proposes a reduction method, Krylov Modal Subspace (KMS), and a theoretical bound of the reduction error. The developed method addresses the parametric dependency of the convective boundary conditions using the concept of system bilinearization. The reduced-order model reproduces the thermal response of the original FE model in the frequency range of interest for any value of the parameters describing the convective boundary conditions. Additionally, this paper investigates the coupling between the reduced-order thermal system and the mechanical response. A numerical example shows that the reduced-order model captures the response of the original system in the frequency range of interest.

Laser-assisted forming provides a perfect solution that overcomes the formability of low-ductility materials. In this study, laser-assisted robotic roller forming (LRRF) was applied to bend ultrahigh-strength steel sheet (a quenching and partitioning steel with a strength grade of 1180 MPa), and the effects of laser power density on the bending forces, springback, and bending radius of the final parts were investigated. The results show that LRRF is capable of reducing bending forces by 43%, and a compact profile with high precision (i.e., a springback angle smaller than 1° and a radius-to-thickness ratio of ~1.2) was finally achieved at a laser power density of 10 J/mm2. A higher forming temperature, at which a significant decrease in strength is observed, is responsible for the decrease of forming forces with a laser power density of higher than 7.5 J/mm2; another reason could be the heating-to-austenitization temperature and subsequent forming at a temperature above martensitic-transformation temperature. Forming takes place at a higher temperature with lower stresses, and unloading occurs at a relatively lower temperature with the recovery of Young’s modulus; both facilitate the reduction of springback angles. In addition, the sharp bending radius is considered to be attributed to localized deformation and large plastic strains at the heating area.

Flow organization into systems of fast-moving ice streams is a well-known feature of ice sheets. Fast motion is frequently the result of sliding at the base of the ice sheet. Here, we consider how this basal sliding is first initiated as the result of changes in bed temperature. We show that an abrupt sliding onset at the melting point, with no sliding possible below that temperature, leads to rapid drawdown of cold ice and refreezing as the result of the increased temperature gradient within the ice, and demonstrate that this result holds regardless of the mechanical model used to describe the flow of ice. Using this as a motivation, we then consider the possibility of a region of ‘subtemperate sliding’ in which sliding at reduced velocities occurs in a narrow range of temperatures just below the melting point. We confirm that this prevents the rapid drawdown of ice and refreezing of the bed, and construct a simple numerical method for computing steady-state ice sheet profiles that include a subtemperate region. The stability of such an ice sheet is analysed in a companion paper.

Friction stir welding (FSW) technology has been applied for aluminum profiles which are widely used in rail vehicles, while process and flow behavior investigations by numerical simulation technology are still insufficient as the geometric complexity of profile joint. In this study, a fully coupled thermo-mechanical model is presented for the FSW process of AA6082-T6 profile. The numerical modeling scheme is executed on the basis of rigid-viscoplastic finite element theory with adaptive re-meshing technology, which is validated firstly by experimental measured temperatures for a sheet case in literature. The temperature field and material deformation are investigated for two different rotational directions of welding tool. The material flow around the tool is visualized and elaborated using a material trajectory demonstration manner based on the point tracking method. The material flow behavior in the three-dimensional space is clearly captured, which shows that the material flow along both the horizontal and vertical directions on the advancing side is more complicated and essentially different with that on the retreating side. Especially, a “sparse material area” is found at the rear of the pin which explains the formation mechanism of void or groove defects. Furthermore, the material stir zone is also presented by the material flow characteristics and analyzed at different welding process.