## 6 Systematic Literature Review
### Comparative Evaluation of Abaqus and Ansys  
Abaqus(r) has been widely used to simulate the mechanical behavior of FFF-processed PLA, particularly through implementations that support advanced thermo-mechanical modeling. [PERSON] et al. (2017) [(83)] explored recent functionalities in Abaqus(r), based on the sequentially coupled thermo-mechanical approach developed by [PERSON] (2017) [(84)], incorporating UMAT subroutines to define material behavior. In a separate study, [(57)] performed detailed mesoscopic and macroscopic simulations of the FFF process using Abaqus(r). [PERSON] et al. (2015) [(85)] modeled the additive manufacturing of a full-scale vehicle with Abaqus(r) and GENOA, where GENOA automatically generated a structured mesh based on G-code tool paths. Abaqus(r) has proven effective in modeling the tensile, compressive, and flexural testing of PLA specimens using Finite Element Analysis [(82; 86; 87; 88; 89; 90; 91; 82)]. Across the reviewed studies, the integration of subroutine codes--often based on G-code--has contributed to robust mechanical representations of PLA parts [(85; 89)]. Ansys(r) has also demonstrated significant capability in simulating the FFF process. [PERSON] and [PERSON] (2006) [(93)] developed a model incorporating heat and mass transfer, mechanical loading, and phase change using element activation within Ansys(r), enabling the simulation of residual stresses and part distortion. They assumed complete contact between deposited layers and the substrate, simplifying the representation of bead interfaces. In a follow-up study, [PERSON] and [PERSON] (2008) [(94)] examined how variations in printing parameters influence distortion through sequentially coupled thermo-mechanical simulations. Expanding on this approach, [PERSON] et al. [(95)] presented a non-isothermal viscoelastic fluid dynamics model using Ansys Fluent(r) to analyze the effects of transient and constant feeding forces, phase transitions, and the viscoelastic behavior of semi-crystalline polymers. These simulations addressed flow behavior, heat transfer, and structural responses using finite volume methods. In addition to thermo-mechanical analysis, Ansys(r) has supported the modeling of PLA's rheological properties [(96; 97; 98; 99; 100)] via the Fluent(r) module and mechanical characterization using its Solid module [(96; 97; 98; 99; 101; 102; 103)]. These studies explored material behavior under various loading and processing conditions, including melt flow, fracture growth, shear stress, and the optimization of extrusion parameters. The comparative analysis of Abaqus(r) and Ansys(r) also involves practical criteria such as potentiality, usability, scalability, and accessibility (Table 2). Ansys(r) offers specific modules for additive manufacturing, such as Additive Print and Additive Suite, which streamline simulation setup for metallic and polymeric materials. Its integration with Fluent(r) provides comprehensive support for CFD and thermo-mechanical problems. Abaqus(r), on the other hand, offers extensive flexibility through subroutines such as UMAT and VUMAT, and is frequently chosen for tasks requiring customized material definitions and process control. In terms of file compatibility, both platforms support a wide range of import and export formats. Ansys(r) accepts formats such as.igs,.step,.stl,.txt,.csv,.inp,.xml,.dat, and Fluent-specific formats (.cas,.dat). Abaqus(r) supports.sim,.prt,.mdl,.cdb,.eaf,.cfx,.CATPart,.CATProduct,.igs,.nas,.bulk,.x_t,.stp,.step, and.wrl, among others. Abaqus(r) also demonstrates better integration with SolidWorks and CATIA, which are common in industry environments. Programming environments differ as well. Abaqus(r)primarily uses Python for scripting and automation and Fortran for user-defined subroutines (e.g., UMAT, VUMAT, USDFLD). Ansys(r) relies on APDL for parametric modeling and provides Python support through its Workbench environment and ACT extension. Although APDL is powerful, users generally report greater accessibility with Abaqus(r)'s Python-based scripting.