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A reasonable coupled triggering mechanism has greater potential to produce a progressive crushing mode and improve the crashworthiness of composite absorbers. To clearly understand coupled triggering mechanisms, the crashworthiness of composite tubes triggered by double- and triple-coupled triggers is comprehensively evaluated. Five double-coupled triggers including chamfer/hole, chamfer/slit, chamfer/saw tooth, chamfer/plug, and chamfer/material degradation (C-GMD) triggers are designed. To exhibit better crashworthiness, triple-coupled triggers are designed by coupling each double-coupled trigger with a plug trigger. Based on Finite Element Methods (FEM), comparisons of the crashworthiness of tubes using double- and triple-coupled triggers are conducted. Effects of width and height of plug on failure modes are further studied. From the predicted results, coupled triggering and energy-absorbing mechanisms are extensively revealed. Double-coupled triggers further weaken triggered regions to reduce the initial peak while triple-coupled triggered tubes improve Energy-Absorption (EA). Triple-coupled C-GMD-plug trigger presents 26.62% higher EA than C-GMD trigger. Material folding and buckling mechanisms have great effects on the material accumulating process. Failure modes are highly sensitive to plug width, plug height and a combination of both. Some design proposals for C-GMD-plug trigger are recommended.

The conventional tapping tool development consists of costly investigative experiments. The development time and cost can be significantly reduced, if these test were replaced by virtual analyses, before the tool prototypes are fabricated. Compared to turning, milling and drilling, in which many valid simulative methods have been established, the tapping process has been given rather little research attention. In this paper an approach is presented, which could be used during the design phases, to predict the relative torque, so that resources, energy and cost can be saved. Based on a simulated reference model, which is in good agreement with corresponding experimental results, the problem of a long computing time could be solved by using a proper segmentation method, which offers a process simulation along the whole chamfer length. With an according mathematical model, the discontinuous torque curve could be summarized to a total load cycle.

As a common type of ceramic inserts, the round inserts with high hardness and super high wear resistance are now widely used in high efficiency machining of some key components of aviation industry and nuclear industry. Cutting forces have an important effect on the surface quality of key components and tool life of inserts in machining process. However, the lack of understanding on the complex geometry and detailed description of uncut chip thickness (UCT) restrict the cutting force prediction of round inserts. In this paper, an analytical model for cutting force prediction of round inserts based on the precise cutting geometry is presented. First, a new geometric method for the cutting edge discretization of ceramic round insert in high speed turning is proposed. Different from the previous methods, the discretization of cutting edge in this research is performed on the rake face rather than the reference plane, which makes the prediction more accurate for the reason that the projection of tool edge is ellipse on the reference plane. Second, the shear flow stress in the primary deformed area, used to estimate the cutting force coefficients, is calculated based on the unequal division shear zone model. Then, a new prediction model considering shear flow stress and chamfer length is developed in edge force coefficients forecasting and is verified by the simulation of finite elements method (FEM). Finally, a series of cutting experiments are implemented to verify the feasibility of the proposed analytical model for cutting force prediction of round inserts. It indicates that the forecast results are in good agreement with the measured cutting forces, which proves the correctness and accuracy of the model.

Carbon fiber reinforced polymer (CFRP) tubes have been widely used as energy absorption devices. Because it is inclined to deform in progressive crushing mode (PCM) with low initial peak force Fp and high specific energy absorption SEA (the energy absorption per unit mass). In many cases, cutouts are introduced into these tubes to meet engineering requirements. However, the cutouts can cause a collapse in the middle height (i.e., mid-height collapse mode), and thus the SEA of the CFRP tubes is even reduced by 56%. Therefore, in this research, a chamfer is introduced into the CFRP tubes with cutout to trigger the PCM, thereby increasing the energy absorption capacity. A series of validation experiments show that the chamfer can trigger the PCM with about 64% decrease of Fp and 52% increase of SEA. The parameter study is conducted to investigate the effect of size and position of the cutout on the energy absorption of CFRP tubes with a 45-degree chamfer. The result indicates that the chamfer can eliminate the negative effects of cutouts and improve the energy absorption capacity in most cases. Furthermore, the contrastive analysis between CFRP and metal tubes reveals the difference in energy absorption characteristics of these two types of tubes and further explains the advantages of energy absorption of the CFRP tubes with a 45-degree chamfer and a cutout.

The prediction of force in metal cutting is essential when estimating tool wear, surface quality and energy consumption. As a significant characteristic in tool design, edge geometry results in more challenges in force modeling especially under the condition of cutting with chamfered insert. In this paper, a semi-analytical model is proposed to describe the effect of chamfered edge on cutting force considering multiple material flow state. In orthogonal cutting, shear effect is calculated based on the unequal division shear-zone model and Johnson-Cook's material constitutive law. Two kinds of chip-tool contact patterns are considered to discuss the effect of tool edge, chip flows on both chamfered edge and rake face when chamfer length is close to Uncut Chip Thickness (UCT), or chip flows only on chamfered edge when chamfer length is much larger than UCT. Edge force coefficients of chamfered edge are modeled as linear functions with respect to shear stress, chamfer length and chamfer angle. The variation of edge force with respect to edge geometry is studied through Finite Element Method (FEM) simulations. The modified force prediction model is established by introducing a factor S to describe the trend of edge effect with respect to the ratio of chamfer length to UCT. Finally, a modified force prediction model is presented and the constants in the model can be calibrated through a Particle Swarm Optimization (PSO)-based algorithm. Experiments of orthogonal cutting AISI304 with different chamfered carbide inserts are performed to validate the correctness and feasibility of the proposed model. The experimental results show that this model is effective in predicting the cutting force components under the condition of different edge preparations and cutting parameters.

Chamfered inserts have shown superior edge resistance and prolonged tool life in practical machining process. However, such kind of inserts find limited application in metal cutting due to the inadequate understanding of their sophisticated influences on cutting performance. Researches on material flow mechanism and heat generation issues in the vicinity of the chamfer may contribute to the comprehensive cognition of high-performance cutting with chamfered inserts. In this paper, a novel slip-line field model has been developed for negative-rake-angle machining with chamfered insert. The slip-line field geometry concerning dead metal zone (DMZ) formation is demonstrated utilizing the slip-line approach. Moreover, an iterative methodology is developed to determine local shear flow stresses, interface frictional factors and heat sources intensity. Then, analytical modeling of temperature fields in tool and workpiece is carried out by employing classical orthogonal cutting theory and semi-boundary heat transfer principles. Finally, two main approaches including two-dimensional (2-D) finite-element (FE) simulations and orthogonal cutting trials of AISI 304 stainless steel are adopted for verification. Simulated slip-line field geometry with respect to DMZ and involved angles are extracted to compare against the predictions from the proposed slip-line solution. The simulated and measured temperature fields are compared with the predicted results from the developed thermal model. In addition, a contrastive model from previous literature is also compared with the proposed model. Encouraging agreements have been detected between those comparisons, which indicate the reasonableness and reliability of the given analytical model. The result reveals that the presented model gives much better prediction of temperature distribution upon chamfer insert over the contrastive model, especially at the DMZ-tool interface.

A new volume of solid (VOS) method is proposed for simulating metal cutting applications. The method utilizes the Eulerian finite element formulation along with a numerical scheme to calculate volume of solid fractions in empty elements or cells. The method is shown to overcome problems with existing finite element formulations and may easily track and model the unconstrained flow of the material at free boundaries. As a sample application, the method is used to study the effect of introducing a chamfer angle to the tool or using a blunt (worn) tool on some of the process variable and on the cutting forces both in the cutting and thrust directions. The results of the VOS method are compared to similar results obtained using the arbitrary Lagrangian–Eulerian approach and to experimental results that were performed for one sharp and two chamfered tools.