Cyclic Thermomechanical Loading Research Articles

Integrating interfacial bonding and coordinated deformation in steel/Al bilayers via a pin-less friction stir-assisted synchronous joining-forming approach

The potentials of steel/Al alloy laminated structures for lightweighting in the automotive industry are increasingly recognized, particularly for reducing energy consumption. However, optimal formability and high-temperature stability in these hybrid structures remain a persistent challenge during the current manufacturing process. This challenge arises from the intricate control required over the Fe-Al intermetallic compounds (IMCs) layer at the dissimilar interface. In this work, steel/Al alloy bilayer laminated structures were fabricated by a thermomechanical joining-forming approach involving pin-less friction stir-assisted incremental sheet forming with synchronous bonding technology. These structures exhibit desirable shear bonding strength of 129 MPa (equivalent to 93.5 % of the shear strength of the AA5052-H32 base material). Mechanisms of local plastic flow, viscoplastic flow, and fast inter-atomic diffusion are evaluated using quasi-static elements. A phenomenological bond fraction model is proposed to describe the collapse of interfacial ellipsoidal microvoids. Cohesive numerical simulation reveals that the interfacial plastic strain is dispersedly distributed with slight cohesive damage due to stable heat-force conditions. Experimental results with confirmed models demonstrate the stability of the programmable process for mechanical-metallurgical bonding and coordinated deformation. Furthermore, a cyclic thermomechanical loading mode is proven effective in tuning interfacial diffusion and inhibiting the growth of the IMC layer. This integrated joining-forming strategy is also applicable to other challenging metallic pairs that are prone to brittle IMCs.

Cyclic Thermomechanical Loading of Epoxy Polymer: Modeling with Consideration of Stress Accumulation and Experimental Verification.

Developing a viscoelastic model for the cyclic thermomechanical loading of thermosetting polymers is the main goal of this study. The model includes memory for residual thermal stresses and can consider stress accumulation across many loading cycles. By considering stress accumulation, we can improve predictions and understand how thermosetting polymers' stress-strain state changes under cyclic thermomechanical loading. This approach was validated through experimental verification to ensure its applicability in practical engineering scenarios. The experiment showed that the thermosetting polymer can accumulate stress during cycles of heating and mechanical loading during use. The results of the modeling and experiment are compared. The results have led to corrections in the way this model is applied to thermosetting polymers like the epoxy resin in this study. The corrected results matched well with the experimental measurements of stress under cyclic thermomechanical load, with a difference of only 1 to 6%.

Possibilities of Increasing the Durability of Punches Used in the Forging Process in Closed Dies of Valve Forgings by Using Alternative Materials from Tool Steels and Sintered Carbides.

This study refers to an analysis of the durability of forging tools applied in the second operation of producing a valve forging from the chromium-nickel steel, NC3015. Due to the extreme working conditions of the tools, caused by cyclic thermo-mechanical loads, the average durability of tools made from tool steel WLV (1.2365) equals about 1500 forgings. An in-depth, complex analysis was performed on the technology, using macroscopic tests combined with a measurement of the wear/allowance on the tool working surface through 3D scanning; microstructural tests by means of light microscopy; observations of the changes taking place on the working surface with a scanning electron microscope; microhardness measurements; and multi-variant numerical simulations. It was established that the key issue is the proper selection of the process technological parameters, such as the input material and tool temperature, friction, lubrication, tribological parameters, type of tool material, or punch design, because even small changes made to them significantly affect the service life of forging punches. Therefore, to increase the durability of the forging dies, alternative materials made of W360, as well as two high speed steels, S600 and S705, were applied. However, the implemented punch materials did not bring the assumed effect of increased durability, as the highest average durability of steel W60 equaled only 1500 forgings, whereas in the case of the tool steels, this was below 900 forgings. For this reason, at the further stage, punches with sintered carbide inserts were introduced, which made it possible to significantly improve the durability up to the level of as many as 20,000 forgings, which, at the same time, points to a promising direction of further studies on the use of materials and solutions of this type.

Possibilities of Increasing the Durability of Dies Used in the Extrusion Process of Valve Forgings from Chrome-Nickel Steel by Using Alternative Materials from Hot-Work Tool Steels.

This study refers to an analysis of the dies used in the first operation of producing a valve forging from chromium-nickel steel NC3015. The analyzed process of manufacturing forgings of exhaust valves is realized in the co-extrusion technology, followed by forging in closed dies. This type of technology is difficult to master, mainly due to the increased adhesion of the charge material to the tool substrate as well as the complex conditions of the tools' operations, which are caused by the cyclic thermo-mechanical loads and also the hard tribological conditions. The average durability of tools made from tool steel WLV (1.2365), subjected to thermal treatment and nitriding, equals about 1000 forgings. In order to perform an in-depth analysis, a complex analysis of the presently realized technology was conducted in combination with multi-variant numerical simulations. The obtained results showed numerous cracks on the tools, especially in the cross-section reduction area, as well as sticking of the forging material, which, with insufficient control of the tribological conditions, can cause premature wear of the dies. In order to increase the durability of forging dies, alternative materials made of hot work tool steels were used: QRO90 Supreme, W360, and Unimax. The preliminary tests showed that the best results were obtained for QRO90, as the average durability for the tools made of this steel equaled about 1200 forgings (with an increase in both the minimal and maximal values), with reference to the 1000 forgings for the material applied so far.

Integrating State of the Art Zirconia Thermal Barriers with Ytterbium Silicate Environmental Barriers for Silicon-Based Ceramic Turbine Components

AbstractAs gas turbine firing temperatures continue to increase for the sake of improved operating efficiency, the material's transition from Ni-based superalloy components toward ceramic matrix composites (CMCs) is concurrently in progress. Due to the complex nature of the turbine operating environment (envisaged ultrahigh temperatures, presence of water vapor, etc.), coating solutions for these CMCs are still on the forefront of design optimizations. Typically, rare-earth (RE) silicate environmental barrier coatings (EBCs) have been utilized to protect the CMCs from impinging water vapor; however, they lack the thermal insulation properties to enable continued use of simple and/or easily accessible bond coat materials (i.e., silicon). Combined thermal-environmental barrier coatings (T-EBCs) are such a multifaceted surface solution. T-EBCs have been considered in the past, but to this point have not been demonstrated to be technologically robust either due to high implementation costs or complex processing. This study utilizes and combines straightforward and well-established processes—such as plasma-sprayed 7 wt.% yttria-stabilized zirconia—to demonstrate the feasibility of MultiLayered T-EBCs comprised of zirconia-based oxides and RE silicate EBCs in a single coating. The results show that despite high thermal mismatch strains, the structures cannot only be deposited, but also in certain circumstances sustain cyclic thermomechanical loading.

Analysis of the cyclic strength of technical systems in conditions of complex operation loading

The main cyclic thermomechanical loads, as well as changeable in time vibration and aerohydrodynamic loadings accompanying them affect modern energy facilities, space, air, water and ground transport. At the same time the total number of loading cycles taking into account the duration of service turns out to be within in very wide limits. It is shown that a general spectrum of loads changing in time which affect the aforementioned objects is very complicated in terms of load levels, frequency ratios and time of their action. Taking into account a large variation of service impacts in the loading levels, frequency ratio and total number of loading cycles we performed a generalized analysis of the resistance to deformation, damage and fracture of high-loaded objects of modern technics. The results obtained revealed that in conditions of combined mechanical, vibration and aero-, gidro-, acoustic loadings the limit state (by criteria of cyclic strength using the rule of linear summation of damages expressed in deformation parameters) will be attained earlier, than that obtained only with allowance of the main thermomechanical loading. To substantiate the strength and service life of the objects under consideration, traditional standard and unified mechanical isothermal tests for static and cyclic loading are carried out to determine the basic characteristics of the mechanical properties of the material, as well as special mechanical programmed tests with variable modes that simulate complex processes of operational thermomechanical, vibration and aerohydrodynamic impacts. The results of testing are taken into account in computation and experimental estimations of the strength and the fatigue life for the corresponding spectra of operational loads. A refined verification calculation of the cyclic strength and durability is becoming increasingly relevant for modern machines and units operating under conditions of increasing speeds of movement, operating pressures with increased levels of pulsations, as well as in the occurrence of accompanying mechanical oscillations, vibrations and aerohydroacoustic impacts.

Impact of Various Lining Materials on Fracture Resistance of CAD/CAM Fabricated Ceramic Onlays Subjected to Thermo-mechanical Cyclic Loading

Impact of Various Lining Materials on Fracture Resistance of CAD/CAM Fabricated Ceramic Onlays Subjected to Thermo-mechanical Cyclic Loading

Impact of Different Surface Treatments on Bond Strength of CAD/CAM Fabricated Y-TZP Ceramic Onlays Subjected to Thermo-mechanical Cyclic Loading

Impact of Different Surface Treatments on Bond Strength of CAD/CAM Fabricated Y-TZP Ceramic Onlays Subjected to Thermo-mechanical Cyclic Loading

ProCrackPlast: a finite element tool to simulate 3D fatigue crack growth under large plastic deformations

Many structural components and devices in combustion and automotive engineering undergo highly intensive cyclic thermal and mechanical loading during their operation, which leads to low cycle (LCF) or thermomechanical (TMF) fatigue crack growth. This behavior is often characterized by large scale plastic deformations and creep around the crack, so that concepts of linear-elastic fracture mechanics fail. The finite element software ProCrackPlast has been developed at TU Bergakademie Freiberg for the automated simulation of fatigue crack growth in arbitrarily loaded three-dimensional components with large scale plastic deformations, in particular under cyclic thermomechanical loading. ProCrackPlast consists of a bundle of Python routines, which manage finite element pre-processing, crack analysis, and post-processing in combination with the commercial software Abaqus . ProCrackPlast is based on a crack growth procedure which adaptively updates the crack size in finite increments. Crack growth is controlled by the cyclic crack tip opening displacement varDelta CTOD, which is considered as the appropriate fracture-mechanical parameter in case of large scale yielding. The three-dimensional varDelta CTOD concept and its effective numerical calculation by means of special crack-tip elements are introduced at first. Next, the program structure, the underlying numerical algorithms and calculation schemes of ProCrackPlast are outlined in detail, which capture the plastic deformation history along with the moving crack. In all simulations, a viscoplastic cyclic material law is used within a large strain setting. The numerical performance of this software is studied for a single edge notch tension (SENT) specimen under isothermal cyclic loading and compared to common finite element techniques for fatigue crack simulation. The capability of this software is featured in two application examples showing crack growth under mixed-mode LCF and TMF in a typical austenite cast steel, Ni-Resist. In combination with a crack growth law identified in terms of varDelta CTOD for a specific material, the tool ProCrackPlast is able to predict the crack evolution in a 3D component for a given thermomechanical loading scenario.

Crystal plasticity analysis of fatigue-creep behavior at cooling holes in single crystal Nickel based gas turbine blade components

We build a crystal plasticity finite element framework to investigate slip localisation and fatigue-creep behaviour at the cooling holes of single crystal Nickel (Ni) based components under cyclic thermomechanical loading. The total slip rate is decomposed into a thermally activated dislocation glide rate which dominates at moderate/low temperatures (T) and/or high stresses, and a climb rate which dominates at high temperatures and increases as inelastic strain accumulates. This formulation captures the monotonic and long-term creep response of Ni alloys in the wide range 20 <T < 1100 °C and indicates that room temperature plasticity during unloading increases the high temperature creep rate during loading (creep dwell), eventually increasing the total slip accumulation per cycle; the effect depends on the way the inelastic strain accumulates upon successive slip reversals. Elastic material anisotropy is shown to modify drastically the stress concentration around holes such that slip tends to localise at locations where the max principal stress, tangent to the hole surface, aligns with stiff crystallographic directions. This highlights the importance of plastic and creep anisotropy and creates new avenues for optimising hole shape to minimise slip activity. Our study brings to light key material-component relationships that concern the wider material science, high temperature and fatigue communities.

Transient coupled thermo-elasticity analysis of a temperature-dependent thick-walled cylinder under cyclic thermo-mechanical loads

AbstractSeveral studies have reported the solution of the classical coupled thermo-elasticity for thick-walled cylinders under different boundary conditions; however very limited studies have been conducted on the analysis of temperature-dependent thick-walled cylinders under cyclic nonlinear boundary conditions. Therefore, this study investigates the transient response of temperature-dependent thick-walled cylinders under cyclic nonlinear thermo-mechanical loads based on classical coupled thermo-elasticity. Also, it studies the impact of considering temperature-dependent material properties (TDMP) and temperature-independent material properties (TIMP) hypotheses on the accuracy of the results. The governing equations of the classical nonlinear coupled thermo-elasticity are numerically solved based on the finite-difference method, namely the Crank-Nicolson method. Then, an experimental setup is designed to further investigate the impact of considering TDMP and TIMP through a temperature measurement of the outer surface of a machine gun barrel under burst shooting. It has been found that considering TIMP overestimates the residual temperature and residual stress values through the cylinder thickness compared with TDMP. Moreover, based on the temperature measurement, TDMP estimates results with higher accuracy of 7% than TIMP.

Investigation on the thermo-mechanical properties of hot stamped parts by using laser-implanted tool surfaces

In the automotive industry, hot stamping has been established as a key technology for manufacturing safety-related car body components with high strength-to-weight ratio. During the forming operation, however, hot stamping tools are highly stressed by cyclic thermo-mechanical loads, which encourage the formation of severe wear and high friction at the blank-die interface. Against this background, an innovative surface engineering technology named laser implantation has been investigated for improving the formability of the parts and the efficiency of the hot stamping process. The laser implantation process is based on the generation of highly wear resistant microfeatures on tool surfaces by embedding hard ceramic particles via pulsed laser radiation. As a consequence, the contact area of the tool and thus the tribological and thermal interactions at the blank-die interface are locally influenced. In previous studies, the improved tribological performance of the modified tool surfaces has already been proven. However, the thermal interactions between tool and workpiece have not been analyzed, which in turn have a significant impact on the resulting part properties. In this regard, quenching tests have been carried out under hot stamping conditions by using conventional as well as laser-implanted tooling systems. Based on these results, Vickers hardness test and optical measurements have been performed on the quenched blanks, to qualify the mechanical properties and clarify the cause-effect relations.

Efficiency of 3D-printed composite resin restorations compared with subtractive materials: Evaluation of fatigue behavior, cost, and time of production

Statement of problemThree-dimensionally (3D)-printed composite resins have been marketed as materials for definitive restorations. However, limited information is available regarding the stability of the adhesive interface and the efficiency of 3D-printed composite resins. PurposeThe purpose of this in vitro study was to evaluate the integrity of the marginal adhesive interface before and after thermal and mechanical fatigue of an initial formulation of a 3D-printed composite resin and to evaluate the efficiency of this manufacturing method. Material and methodsFreshly extracted molars were prepared for onlays and adhesively restored with either 3D-printed composite resin (VarseoSmile Crown Plus) (Group 3D), milled composite resin (Tetric CAD) (Group MCOMP), milled PMMA (Telio CAD) (Group PMMA), and milled lithium disilicate (IPS e.max CAD) (Group EM). Marginal analysis was performed under a scanning electron microscope before and after fatigue by thermomechanical cyclic loading, and initial and terminal percentages of continuous margin (%CM) were compared. The time required for the production of each type of restoration was recorded, and the production costs were also compared. ResultsBefore aging, 3D, MCOMP, and EM presented comparable values of %CM (69.8%, 75.9%, and 63.1%, respectively) that were statistically significantly higher (P<.05) than those of PMMA (45.1%). After aging, 3D and EM had comparable results (44.7% and 43.7%, respectively), which were lower than those of the MCOMP group (68.5%) but higher than those of the PMMA group (20.5%). Regarding time efficiency, 3D printing took less time than MCOMP or PMMA if more than 8 restorations were fabricated. For the production costs, 3D printing was 5.5, 8.7, and 10.2 times less expensive than PMMA, MCOMP, and EM, respectively. The initial equipment cost was also lower for the additive manufacturing method. However, 3D printing did not always considerably reduce waste. ConclusionsIn terms of marginal adaptation, the evaluated initial formulation of a 3D-printed composite resin behaved similarly to other well-established definitive restoration materials and better than milled PMMA, both before and after fatigue. Three-dimensionally printed resins present advantages in terms of equipment and consumable costs, even for a single restoration, but also for production time when more than 8 restorations were fabricated.

Surface Properties and Wear Resistance of Injectable and Computer-Aided Design/Computer Aided Manufacturing-Milled Resin Composite Thin Occlusal Veneers.

This study was conducted to investigate the microhardness, surface roughness (Ra), and wear behavior of thin occlusal veneers (TOV) fabricated from different injectable composite materials and compare them to a Computer-Aided Design (CAD)/Computer-Aided Manufacturing (CAM) resin-based material. A 1-mm occusal veneer preparation was done in a mandibular right second molar typodont tooth. The prepared model was duplicated to fabricate 32 replicas and divided into four groups (n = 8). Standard TOV were fabricated either indirectly from Cerasmart blocks, Cerasmart, GC (CS), or directly from Beautifil Injectable X, Shofu (BF), G-ænial Universal injectable, GC (GU), or SonicFill 2, Kerr (SF) using the injection molding technique. All the specimens were subjected to both thermomechanical cyclic loading (TMC) in a chewing simulator. Wear measurement was conducted by three-dimensional (3D) scanning of the veneered models before and after TMC, and the difference in the volume of the sample was recorded as the volumetric material loss due to wear. Ra before and after TMC and Vickers microhardness (VHN) of the tested materials were measured using standardized samples (n = 8). Representative samples from each group were investigated under a stereomicroscope and a scanning electron microscope. One-way analysis of variance (ANOVA) was applied to detect the effect of material on VHN and wear. Two-way ANOVA was utilized to examine the impact of material and TMC on Ra. Multiple comparisons between the groups were conducted using Tukey's post hoc test (α = 0.05). The Pearson's correlation coefficient was used to determine the relationship between hardness and wear and between roughness and wear (α = 0.05). CS exhibited the highest mean VHN (p ≤ 0.001), followed by GU and SF which were statistically similar (p = 0.883) but significantly higher than BF (p < 0.001). After TMC, GU revealed the lowest Ra and volumetric wear (VW), followed by CS, BF, and SF (p < 0.5). A highly significant correlation existed between Ra and VW (p = 0.001, R 2 = 0.9803). The effect of TMC on the surface properties and wear resistance of the investigated TOV is material-dependent. GU injectable TOV are less influenced by TMC than CS milled TOV. In contrast, BF and SF demonstrated significant VW and Ra which might limit their clinical use as TOV.

Shakedown and limit analyses of a pressurised water reactor vessel nozzle under cyclic thermo-mechanical loadings

This paper has investigated cyclic plasticity of a reactor pressure vessel (RPV) nozzle subjected to cyclic thermo-mechanical loads thoroughly: cyclic thermal loads, cyclic bending moments, and cyclic internal pressures. By utilising an advanced direct numerical method known as the Linear Matching Method, elastic shakedown limit boundaries of the RPV nozzle are constructed to evaluate the effects of different load combinations on the cyclic plasticity behaviours. In additions, limit load boundaries of the RPV nozzle are constructed to confirm whether alternative plasticity or ratchetting response appear under the same loading combinations. Through comprehensive numerical studies, the effects of geometric parameters of the nozzle geometries on the cyclic plastic behaviour are identified and the parametric study results are formulated as semi-empirical equations to predict both limit load and elastic shakedown limit boundaries. Ultimately, this research provides reactor design engineer insight into the design of the RPV nozzle in consideration of cyclic plasticity.

Multi-Scale Modeling of the Thermo-Mechanical Behavior of Cast Iron

This work presents a multi-scale modelling framework for thermo-mechanical behaviour of Compacted Graphite Iron cast iron. A general thermo-elasto-visco-plastic model is developed to describe the matrix (pearlite) behavior under thermo-mechanical cyclic loading, for which the parameters are identified from tests on pearlitic steel. The pearlite model takes into account the temperature dependent rate-dependency and kinematic hardening. The importance of properly accounting for the graphite anisotropy is emphasised, for which a numerical procedure for estimating the local anisotropy directions from the graphite particle geometry and experimental observations is proposed. A high quality conforming finite element mesh is generated on a representative volume element using discrete voxelized microstructural data in combination with signed distance functions from the interfaces. For fully constraint thermal cyclic loading conditions with different holding times, the capabilities of the developed multi-scale model are demonstrated at both scales: the macroscale, where the simulation results are in very good agreement with the experimental data, and the microscale, providing the evolution of local fields.

Energy-based method for the assessment of the cumulative slip increment in frictional contacts subjected to cyclic loadings

The cumulative slip phenomenon is often observed as a limit state in mechanical assemblies involving interference or press-fits and subjected to cyclic thermomechanical loadings. In engineering structural applications, it may prove very difficult to annihilate completely the occurrence of this phenomenon by targeting a slip-shakedown limit state, due to design and other mechanical constraints. Consequently, the cumulated relative slip magnitude on the contact interface, after a given of applied cycles, should be anticipated to prevent any unexpected contact with other mechanical components that may result in seizure or affect the normal structural behaviour of the assembly. In this paper, a novel theoretical approach is proposed to derive the cumulative relative slip increment from the frictional dissipated energy per cycle. In particular, two independent methods – one based on the rigid body slip property and the other using the unified energy-based approach from fatigue crack growth theory – are considered here to determine the same expression of the expected quantity. The obtained formula is evaluated through various analytical examples with a special focus on bushing migration in interference-fit assemblies. It is shown, in each case, to be in perfect agreement with the incremental displacement calculation of the cumulative slip increment when the cumulative slip phenomenon occurs.

Implant-Abutment Misfit after Cyclic Loading: An In Vitro Experimental Study.

This study aimed to evaluate the influence of thermomechanical cycling (TMC) and type of abutment on the misfit and compressive strength of the implant–abutment interface. Forty 3.75-mm external hexagon implants with 25° angled abutments were divided into four groups (N = 10). Group A: overcast plus TMC; Group B: overcast without TMC; Group C: completely cast plus TMC; Group D: completely cast without TMC. Abutments were fixed to the implants with 32-Ncm torque, and groups A and C specimens were cyclically loaded at 80 N with 2 Hz for 1 million cycles. The misfit on the implant–abutment interface was evaluated by optical microscope (100×) and the compressive strength test was performed in a universal test machine. For statistical analysis, a two-way ANOVA and post hoc Tukey test were used. There was no difference in misfit presented by all the abutments in the absence of TMC (p > 0.05). When TMC was performed, the completely cast abutments showed greater misfit than overcast ones (p = 0.001). Regarding compressive strength, irrespective of TMC performed, the overcast abutments showed higher compressive strength values than completely cast abutments (p = 0.003). Moreover, disregarding the type of abutment used, the absence of TMC provided higher compressive strength values (p < 0.001). It was concluded that thermomechanical cyclic loading aggravated the misfit, especially in completely cast abutments, regardless of material or fabrication technique, and reduced the compressive strength of the two types of abutments tested.

Ratchetting and Creep Failure in Twin-Wall Turbine Blades Experiencing Severe Thermal and Centrifugal Loading

Abstract Twin-wall structures can be cooled both externally and internally, raising great potential for use in high-temperature applications. However, their increased geometric complexity imposes a range of potential failure mechanisms for consideration in design. The primary aim of this study is to identify the nature of such mechanisms by constructing Bree type interaction diagrams for idealized double-wall systems under cyclic thermomechanical loading that shows the combination of loading conditions for which cyclic plasticity (leading to fatigue failure)-creep ratchetting occur. Through an extension of the classical Bree analysis, we determine analytical boundaries between different regimes of behavior. We also quantify the effects of wall thickness ratio, temperature field, and yield and creep material properties. Local cyclic plasticity is shown to dominate over structural/global ratchetting when the yield strength reduces with temperature and/or when the temperature gradient through the hot wall thickness dominates over the temperature difference between the walls. Thus, we conclude that global ratchetting is unlikely to occur in the practical loading range of Nickel-based twin-wall turbine blades, but instead these systems suffer from local fatigue at cooling holes and excessive creep deformation. This is verified by 3D cyclic finite element (FE) simulations, demonstrating that the analytical approach provides a powerful, cost-effective strategy for providing physical insight into possible deformation mechanisms in a range of thin-walled components; highlighting the key trade-offs to be considered in design; and directing the use of computer methods toward more detailed calculations.

Cyclic t-z model for the long-term thermomechanical analysis of energy piles

Many elastoplastic and nonlinear models have simulated the long-term behavior of energy piles under cyclic thermomechanical loads. Although they considered the strain–stress hysteretic relationship at the pile–soil interface, the interface strength was assumed independent of the number of thermomechanical cycles. This simplification may cause errors in predicting the long-term responses of energy piles. Therefore, we proposed a cyclic t-z model for the long-term thermomechanical analysis of an energy pile. Here, the interface strength of the model changes with the cycle number of thermomechanical loads. In addition, the accumulation of irreversible deformation at the pile–soil interface can be modeled. Moreover, the cyclic performance of interface shear tests and the long-term behavior of an in situ energy pile were simulated. Comparisons between the measured and simulated results indicated several vital aspects of the energy pile–soil interaction, including strength degradation, strain ratcheting phenomenon of the interface, and long-term pile responses under cyclic thermomechanical loading. Furthermore, numerical simulations were used to evaluate the effects of model parameters on the long-term behavior of energy piles under thermomechanical loads.