An Evaluation of Chip Separation Criteria for the FEM Simulation of Machining

1996 ◽  
Vol 118 (4) ◽  
pp. 545-554 ◽  
Author(s):  
J. M. Huang ◽  
J. T. Black
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Fem Simulation ◽  
Shear Plane ◽  
Machining Process ◽  
Stress And Strain ◽  
Machined Surface ◽  
Average Maximum ◽  
Chip Separation ◽  
Chip Geometry

Different chip separation criteria for the FEM simulation of machining were examined. Criterion based on distance between the tool tip and the node located immediately ahead, criterion based on maximum shear stress in the element ahead of the tool tip, criterion based on average maximum shear stress in the shear plane, and criterion based on a combination of distance and stress were investigated. Under conditions of smooth separation of chip from workpiece, simulation results showed that, during steady-state cutting, the type of chip separation criteria did not greatly affect chip geometry, nor distributions of stress and strain. The magnitude of the chip separation criteria also did not significantly affect chip geometry and distributions of stress in the chip but it did affect the chip separation process, distributions of stress in the machined surface, and distributions of effective plastic strain both in the chip and in the machined surface. During the initiation of cutting, neither the geometrical nor physical criteria simulate the machining process correctly. A combination of geometric and physical criteria was also recommended in this study.

scholarly journals Finite Element Prediction of Transchondral Stress and Strain in the Human Hip

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Corinne R. Henak ◽  
Gerard A. Ateshian ◽  
Jeffrey A. Weiss
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Tensile Strain ◽  
Maximum Shear Stress ◽  
Cartilage Damage ◽  
Constitutive Models ◽  
Hip Osteoarthritis ◽  
Principal Strain ◽  
Stress And Strain ◽  
Fiber Distribution

Cartilage fissures, surface fibrillation, and delamination represent early signs of hip osteoarthritis (OA). This damage may be caused by elevated first principal (most tensile) strain and maximum shear stress. The objectives of this study were to use a population of validated finite element (FE) models of normal human hips to evaluate the required mesh for converged predictions of cartilage tensile strain and shear stress, to assess the sensitivity to cartilage constitutive assumptions, and to determine the patterns of transchondral stress and strain that occur during activities of daily living. Five specimen-specific FE models were evaluated using three constitutive models for articular cartilage: quasilinear neo-Hookean, nonlinear Veronda Westmann, and tension-compression nonlinear ellipsoidal fiber distribution (EFD). Transchondral predictions of maximum shear stress and first principal strain were determined. Mesh convergence analysis demonstrated that five trilinear elements were adequate through the depth of the cartilage for precise predictions. The EFD model had the stiffest response with increasing strains, predicting the largest peak stresses and smallest peak strains. Conversely, the neo-Hookean model predicted the smallest peak stresses and largest peak strains. Models with neo-Hookean cartilage predicted smaller transchondral gradients of maximum shear stress than those with Veronda Westmann and EFD models. For FE models with EFD cartilage, the anterolateral region of the acetabulum had larger peak maximum shear stress and first principal strain than all other anatomical regions, consistent with observations of cartilage damage in disease. Results demonstrate that tension-compression nonlinearity of a continuous fiber distribution exhibiting strain induced anisotropy incorporates important features that have large effects on predictions of transchondral stress and strain. This population of normal hips provides baseline data for future comparisons to pathomorphologic hips. This approach can be used to evaluate these and other mechanical variables in the human hip and their potential role in the pathogenesis of osteoarthritis (OA).

Analysis of Three-Dimensional Cutting Process With Thin Shear Plane Model

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Eiji Shamoto ◽  
Masahiro Kato ◽  
Norikazu Suzuki ◽  
Rei Hino
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Minimum Energy ◽  
Three Dimensional ◽  
Shear Plane ◽  
Cutting Edge ◽  
Cutting Process ◽  
Energy Principle ◽  
Chip Flow ◽  
Minimum Energy Principle

A new and basic analytical model of three-dimensional cutting is proposed by assuming multiple thin shear planes with either the maximum shear stress or minimum energy principle. The three-dimensional cutting process with an arbitrarily shaped cutting edge in a flat rake face is formulated with simple vector equations in order to understand and quickly simulate the process. The cutting edge and workpiece profile are discretized and expressed by their position vectors. Two equations among three unknown vectors, which show the directions of shear, chip flow, and resultant cutting force, are derived from the geometric relations of velocities and forces. The last vector equation required to solve the three unknown vectors is obtained by applying either the maximum shear stress or minimum energy principle. It is confirmed that the directions and the cutting forces simulated by solving the proposed vector equations agree with experimentally measured data. Furthermore, the developed model is applied to consider the three-dimensional cutting mechanics, i.e., how the chip is formed in the three-dimensional cutting with compressive stress acting between the discrete chips, as an example.

Material Characterization for Metal-Cutting Force Modeling

1989 ◽  
Vol 111 (2) ◽  
pp. 210-219 ◽  
Author(s):  
D. A. Stephensen
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Cutting Force ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Stress And Strain ◽  
Force Model ◽  
Wide Range

Widely applicable machining simulation programs require reliable cutting force estimates, which currently can be obtained only from process-dependent machinability databases. The greatest obstacle to developing a more basic, efficient approach is a lack of understanding of material yield and frictional behavior under the unique deformation and frictional conditions of cutting. This paper describes a systematic method of specifying yield stress and friction properties needed as inputs to process-independent cutting force models. Statistically designed end turning tests are used to generate cutting force and chip thickness data for a mild steel and an aluminum alloy over a wide range of cutting conditions. Empirical models are fit for the cutting force and model-independent material parameters such as the tool-chip friction coefficient and shear stress on the shear plane. Common material yield behavior assumptions are examined in light of correlations between these parameters. Results show no physically meaningful correlation between geometric shear stress and strain measures, a weak correlation between geometric stress and strain rate measures, and a strong correlation between material properties and input variables such as cutting speed and rake angle. An upper bound model is used to fit four- and five-parameter polynomial strain-rate sensitive constitutive equations to the data. Drilling torques calculated using this model and an empirical turning force model agree reasonably well with measured values for the same material combination, indicating that end turning test results can be used to estimate mean loads in a more complicated process.

Prediction of Temperature and Stress Distribution During Micro-Cutting of Ti-6Al-4V

2007 ◽  
Author(s):  
Dong Lu ◽  
Jianfeng Li ◽  
Yiming Rong ◽  
Jie Sun ◽  
Zhongqiu Wang
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Cutting Temperature ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Machining Process ◽  
Maximum Temperature ◽  
Uncut Chip Thickness ◽  
Micro Cutting

A finite element method (FEM) for predicting the temperature and stress distribution in micro-cutting of Ti-6Al-4V is presented. The flow stress of Ti-6Al-4V is taken as a function of strain, strain rate and temperature in order to reflect realistic behavior in machining process. Diamond cutting tool is used. From simulation, cutting force, thrust force, cutting temperature and distribution of cutting temperature and stress are obtained. The effects of cutting speed and uncut chip thickness on the maximum temperature and maximum shear stress are analyzed and size effect is observed. The simulation results show that in micro-cutting of Ti-6Al-4V the maximum temperature locates on the shear plane. And the maximum shear stress locates on the stick region. The maximum temperature decreases as the uncut chip thickness decreases, and it increases with an increase in cutting speed. The maximum shear stress increases as the uncut chip thickness decreases, and it decreases with an increase in cutting speed.

Interior Stress for Axisymmetric Abrasive Indentation in the Free Abrasive Machining Process: Slicing Silicon Wafers With Modern Wiresaw

1999 ◽  
Vol 121 (3) ◽  
pp. 191-195 ◽  
Author(s):  
F. Yang ◽  
I. Kao
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Closed Form Solution ◽  
Local Maximum ◽  
Silicon Wafers ◽  
Machining Process ◽  
Von Mises Stress ◽  
Abrasive Machining ◽  
Von Mises ◽  
Free Abrasive

In wiresaw manufacturing processes, such as those in slicing silicon wafers for electronics fabrication, abrasive slurry is carried by high-speed wire (5 to 15 m/s), which exerts normal load to the surface via hydrodynamic effects and bow of taut wire. As a result, the abrasives carried by slurry are constrained to indent onto and roll over the surface of substrate. In this paper, the axisymmetric indentation problem in the free abrasive machining (FAM) is studied by modeling a rigid abrasive of different shapes pushing onto an elastic half space. Based on the harmonic property of dilatation, the closed-form solution of stress distribution inside the cutting material for three different indentation processes in common FAM process are presented: cylindrical and conical abrasives as well as uniform pressure distribution. Along the symmetrical axis, von-Mises stress is two times larger than that of local maximum shear stress for all three indentation conditions. The von-Mises stress is infinity at the contact point for sharp pointed indentation, a location of crack initiation and nucleation. For indentation by abrasive of flat surface, which also can be provided by the localized effects due to the hydrodynamic pressure acting on the surface, both the von-Mises and local maximum shear stress reach maximum underneath the contact zone.

scholarly journals Tensile and Shear Testing of Basalt Fiber Reinforced Polymer (BFRP) and Hybrid Basalt/Carbon Fiber Reinforced Polymer (HFRP) Bars

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5839
Author(s):  
Kostiantyn Protchenko ◽  
Fares Zayoud ◽  
Marek Urbański ◽  
Elżbieta Szmigiera
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Tensile Testing ◽  
Maximum Shear Stress ◽  
Fiber Reinforced Polymer ◽  
Strength Testing ◽  
Fiber Reinforced ◽  
Shear Testing ◽  
Reinforced Polymer ◽  
Average Maximum

The use of sustainable materials is a challenging issue for the construction industry; thus, Fiber Reinforced Polymers (FRP) is of interest to civil and structural engineers for their lightweight and high-strength properties. The paper describes the results of tensile and shear strength testing of Basalt FRP (BFRP) and Hybrid FRP (HFRP) bars. The combination of carbon fibers and basalt fibers leads to a more cost-efficient alternative to Carbon FRP (CFRP) and a more sustainable alternative to BFRP. The bars were subjected to both tensile and shear strength testing in order to investigate their structural behavior and find a correlation between the results. The results of the tests done on BFRP and HFRP bars showed that the mechanical properties of BFRP bars were lower than for HFRP bars. The maximum tensile strength obtained for a BFRP bar with a diameter of 10 mm was equal to approximately 1150 MPa, whereas for HFRP bars with a diameter of 8 mm, it was higher, approximately 1280 MPa. Additionally, better results were obtained for HFRP bars during shear testing; the average maximum shear stress was equal to 214 MPa, which was approximately 22% higher than the average maximum shear stress obtained for BFRP bars. However, HFRP bars exhibited the lowest shear strain of 57% that of BFRP bars. This confirms the effectiveness of using HFRP bars as a replacement for less rigid BFRP bars. It is worth mentioning that after obtaining these results, shear testing can be performed instead of tensile testing for future studies, which is less complicated and takes less time to prepare than tensile testing.

scholarly journals Studying the performance of fully encapsulated rock bolts with modified structural elements

2021 ◽  
Author(s):  
Jianhang Chen ◽  
Hongbao Zhao ◽  
Fulian He ◽  
Junwen Zhang ◽  
Kangming Tao
Keyword(s):  
Shear Stress ◽  
Load Transfer ◽  
Maximum Shear Stress ◽  
Coupling Model ◽  
Numerical Approach ◽  
Rock Bolt ◽  
Structural Elements ◽  
Rock Bolts ◽  
Two Stage ◽  
Bolt Diameter

AbstractNumerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

scholarly journals Design of plate and screw anchors in dense sand: failure mechanism, capacity and deformation

2019 ◽  
Vol 92 ◽  
pp. 16010
Author(s):  
Benjamin Cerfontaine ◽  
Jonathan Knappett ◽  
Michael Brown ◽  
Aaron Bradshaw
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Failure Mechanism ◽  
Progressive Failure ◽  
Vertical Direction ◽  
Shear Plane ◽  
Design Methods ◽  
Embedment Depth ◽  
Limiting State ◽  
Dense Sand

Plate and screw anchors provide a significant uplift capacity and have multiple applications in both onshore and offshore geotechnical engineering. Uplift design methods are mostly based on semi-empirical approaches assuming a failure mechanism, a normal and a shear stress distribution at failure and empirical factors back-calculated against experimental data. However, these design methods are shown to under- or overpredict most of the existing larger scale experimental tests. Numerical FE simulations are undertaken to provide new insight into the failure mechanism and stress distribution which should be considered in anchor design in dense sand. Results show that a conical shallow wedge whose inclination to the vertical direction is equal to the dilation angle is a good approximation of the failure mechanism in sand. This shallow mechanism has been observed in each case for relative embedment ratios (depth/diameter) ranging from 1 to 9. However, the stress distribution varies non-linearly with depth, due to the soil deformability and progressive failure. A sharp peak of normal and shear stress can be identified close to the anchor edge, before a gradual decrease with increasing distance along the shear plane. The peak stress magnitude increases almost linearly with embedment depth at larger relative embedment ratios. Although further research is necessary, these results lay the basis for the development of a new generation of design criteria for determining anchor capacity at the ultimate limiting state.

Surface Roughness and Cutting Force Components Evaluation in Hard Turning by Differently Shaped Cutting Tools

2016 ◽  
Vol 862 ◽  
pp. 26-32 ◽  
Author(s):  
Michaela Samardžiová
Keyword(s):  
Surface Roughness ◽  
Cutting Force ◽  
Hard Turning ◽  
Cutting Tool ◽  
Single Point ◽  
Machining Process ◽  
Tool Geometry ◽  
Machined Surface ◽  
Cutting Force Components ◽  
Force Components

There is a difference in machining by the cutting tool with defined geometry and undefined geometry. That is one of the reasons of implementation of hard turning into the machining process. In current manufacturing processes is hard turning many times used as a fine finish operation. It has many advantages – machining by single point cutting tool, high productivity, flexibility, ability to produce parts with complex shapes at one clamping. Very important is to solve machined surface quality. There is a possibility to use wiper geometry in hard turning process to achieve 3 – 4 times lower surface roughness values. Cutting parameters influence cutting process as well as cutting tool geometry. It is necessary to take into consideration cutting force components as well. Issue of the use of wiper geometry has been still insufficiently researched.

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