Recent advances in modelling of metal machining processes

A new material constitutive law is implemented in a 2D finite element model to analyse the chip formation and shear localisation when machining titanium alloys. The numerical simulations use a commercial finite element software (FORGE 2005®) able to solve complex thermo-mechanical problems. One of the main machining characteristics of titanium alloys is to produce segmented chips for a wide range of cutting speeds and feeds. The present study assumes that the chip segmentation is only induced by adiabatic shear banding, without material failure in the primary shear zone. The new developed model takes into account the influence of strain, strain rate and temperature on the flow stress and also introduces a strain softening effect. The tool chip friction is managed by a combined Coulomb–Tresca friction law. The influence of two different strain softening levels and machining parameters on the cutting forces and chip morphology has been studied. Chip morphology, cutting and feed forces predicted by numerical simulations are compared with experimental results.

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A new material model for 2D numerical simulation of serrated chip formation when machining titanium alloy Ti–6Al–4V

In the analysis of orthogonal cutting process using finite element (FE) simulations, predictions are greatly influenced by two major factors; a) flow stress characteristics of work material at cutting regimes and b) friction characteristics mainly at the tool-chip interface. The uncertainty of work material flow stress upon FE simulations may be low when there is a constitutive model for work material that is obtained empirically from high-strain rate and temperature deformation tests. However, the difficulty arises when one needs to implement accurate friction models for cutting simulations using a particular FE formulation. In this study, an updated Lagrangian finite element formulation is used to simulate continuous chip formation process in orthogonal cutting of low carbon free-cutting steel. Experimentally measured stress distributions on the tool rake face are utilized in developing several different friction models. The effects of tool-chip interfacial friction models on the FE simulations are investigated. The comparison results depict that the friction modeling at the tool-chip interface has significant influence on the FE simulations of machining. Specifically, variable friction models that are developed from the experimentally measured normal and frictional stresses at the tool rake face resulted in most favorable predictions. Predictions presented in this work also justify that the FE simulation technique used for orthogonal cutting process can be an accurate and viable analysis as long as flow stress behavior of the work material is valid at the machining regimes and the friction characteristics at the tool-chip interface is modeled properly.

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The influence of friction models on finite element simulations of machining

This paper provides a comprehensive review of literature, mostly of the last 10–15 years, on modeling of machining of composite materials with a focus on the process of turning. The paper discusses modeling of both fiber reinforced and particle reinforced composites. Modeling studies include molecular dynamic simulations, 2-D and 3-D finite element models and the emerging field of multi-scale models. In fiber reinforced composites the focus is on glass and carbon fiber reinforced polymeric composites as well as long fiber reinforced metal matrix composites. On the other hand modeling of particulate composites is restricted to that of metal matrix composites (MMC). The paper includes recent modeling work to predict cutting forces, tool–particle interaction, cutting temperatures and machined sub-surface damage. A case study on the machining of the MMC A359 aluminum matrix composite reinforced with 20% by volume fraction silicon carbide particles is included to showcase the hierarchical multi-scale machining model.

Modeling of machining of composite materials: A review

Prediction of chip morphology and segmentation during the machining of titanium alloys

FEM simulation of orthogonal cutting: serrated chip formation

The aim of the study is to evaluate clinical applications, safety, and effectiveness of a porcine-derived acellular cross-linked dermal matrix biological mesh in chest wall reconstruction.We retrospectively analyzed a prospective multicenter database of chest wall reconstructions using a biological mesh in adult patients undergoing operation between October 2013 and December 2020. We evaluated preoperative data, type of resection and reconstruction, hospitalization, 30-day morbidity and mortality, and overall survival.A total of 105 patients (36 women [34.2%]; mean age, 57.0 ± 16.1 years; range, 18-90 years) were included, they have admitted for: primary chest wall tumor (n = 52; 49.5%), secondary chest wall tumor (n = 29; 27.6%), lung hernia (n = 12; 11.4%), trauma (n = 10; 9.6%), and infections (n = 2; 1.9%). The surgical sites were preoperatively defined as at high risk of infection in 28 patients (26.7%) or as infected in 16 (15.2%) patients. Thirty-days morbidity was 30.5% (n = 32 patients); 14 patients (13.3%) had postoperative complications directly related to chest wall surgical resection and/or reconstruction. We experienced no 30-day mortality; 1-year and 2-year mortality was 8.4% and 16.8%, respectively.Biological mesh represents a valuable option in chest wall reconstruction even when surgical sites are infected or at high-risk of infections. This mesh shows low early and late postoperative complication rates and excellent long-term stability. 

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M Lucchi

Papers

FEM simulation of orthogonal cutting: serrated chip formation

Chest wall reconstruction with implantable cross-linked porcine dermal collagen matrix: Evaluation of clinical outcomes