Prediction of Defects in Multistage Cold Forging by Using Finite Element Method

2014 ◽  
Vol 622-623 ◽  
pp. 659-663 ◽  
Author(s):  
Fabio Bassan ◽  
Paolo Ferro ◽  
Franco Bonollo
Keyword(s):  
Radial Flow ◽  
Surface Defects ◽  
Plastic Instability ◽  
Cold Forging ◽  
Formation Mechanisms ◽  
Fe Model ◽  
Pipe Fitting ◽  
Tooling Design ◽  
Simulated Flow ◽  
Good Agreement

In this work, the formation mechanisms of surface defects in multistage cold forging of axisymmetrical parts have been studied through FEM simulations. As case history, the industrial production of an heating pipe fitting by cold forging has been analyzed. Based on simulated flow behaviour of material, several types of surface defects are identified and attributed to plastic instability of the work-material, inappropriate axial/radial flow ratio, excessive forming-pressure and uncorrect tooling design. The results of the FE model are finally compared with those obtained from real forging process and good agreement is observed.

Predicting the surface waviness of sheet moulding compound parts by simulating process-induced thermal stresses

2011 ◽  
Vol 31 (8-9) ◽  
Author(s):  
Walter Michaeli ◽  
Christoph Kremer
Keyword(s):  
Thermal Stresses ◽  
Surface Defects ◽  
Computation Method ◽  
Surface Waviness ◽  
Curing Reaction ◽  
Calculated Stress ◽  
Moulding Compound ◽  
Different Types ◽  
Sheet Moulding Compound ◽  
Good Agreement

Abstract This paper describes an opportunity to compute the surface waviness of compression moulded sheet moulding compound (SMC) parts by simulating residual stresses. First, different types of surface defects occurring on SMC parts are discussed. A method for calculating the surface waviness of the compression moulded part is presented, which combines the simulation of the production process and the structural computation. Modelling of the curing reaction and the development of mechanical properties are discussed and implemented. The potential of the computation method is shown for an automotive fender made of SMC. The results state that the curing reaction of SMC can be well described using the approach of Ng and Manas-Zloczower. The position of the measured waviness on the examined fender is in good agreement with the calculated stress distribution.

Simulation and Optimization of Wedge-Shaped Ultrasonic Transducers Using Finite Element Method (FEM)

2013 ◽  
Vol 281 ◽  
pp. 112-115 ◽  
Author(s):  
Dan Jin ◽  
Zhao Hui Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Effect ◽  
Ultrasonic Transducers ◽  
Fe Model ◽  
Limited Size ◽  
Simulation And Optimization ◽  
Ultrasonic Flaw ◽  
Shape And Size ◽  
Good Agreement

Wedge-shaped transducers have been widely used in industry as probes for ultrasonic flowmeters or for ultrasonic flaw detectors. But by now, few studies have focused on the influence to the performance of the wedge-shaped transducers brought by their limited size. In this paper, the effect of the shape and size of wedge-shaped substrates on the whole transducer system is discussed and the shape and size of a transducer (0.5MHz) is optimized to eliminate the influence of the boundary effect by using a 2-D Finite Element (FE) model. Lastly, wedge-shaped transducers have been manufactured for experiment which shows a good agreement with the simulation.

Capillary water absorption by a porous cylinder

2017 ◽  
Vol 42 (2) ◽  
pp. 120-124 ◽  
Author(s):  
Christopher Hall
Keyword(s):  
Radial Flow ◽  
Effective Porosity ◽  
Capillary Absorption ◽  
Porous Cylinder ◽  
Capillary Water ◽  
Cylinder Axis ◽  
Flow Through ◽  
Front Model ◽  
Sharp Front ◽  
Good Agreement

Capillary absorption (imbibition) of water by a porous cylinder is described by means of a Sharp-Front model. The cumulative absorption increases as (time)1/2 at early times, but more slowly as the wet front approaches the cylinder axis. Results are given in terms of dimensionless variables. Experimental data on plaster cylinders are in good agreement with theory. Estimates of the sorptivity and effective porosity of the material can be obtained. The model may be useful in testing drilled cores and may also be applied to radial flow through the wall of a porous tube (hence to conduits and arches).

A Coupled Multibody Finite Element Model for Investigating Effects of Surface Defects on Rolling Contact Fatigue

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zamzam Golmohammadi ◽  
Farshid Sadeghi
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Surface Defects ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Internal Stresses ◽  
Fe Model ◽  
Elastic Plastic ◽  
Pile Up

A coupled multibody elastic–plastic finite element (FE) model was developed to investigate the effects of surface defects, such as dents on rolling contact fatigue (RCF). The coupled Voronoi FE model was used to determine the contact pressure acting over the surface defect, internal stresses, damage, etc. In order to determine the shape of a dent and material pile up during the over rolling process, a rigid indenter was pressed against an elastic plastic semi-infinite domain. Continuum damage mechanics (CDM) was used to account for material degradation during RCF. Using CDM, spall initiation and propagation in a line contact was modeled and investigated. A parametric study using the model was performed to examine the effects of dent sharpness, pile up ratio, and applied load on the spall formation and fatigue life. The spall patterns were found to be consistent with experimental observations from the open literature. Moreover, the results demonstrated that the dent shape and sharpness had a significant effect on pressure and thus fatigue life. Higher dent sharpness ratios significantly reduced the fatigue life.

A Numerical Study for the Relationship between Natural Manganese Dendrites and DLA Patterns

2016 ◽  
Vol 71 (3) ◽  
pp. 225-234
Author(s):  
Tugba Ozbey ◽  
Mehmet Bayirli
Keyword(s):  
Critical Exponent ◽  
Numerical Study ◽  
Formation Mechanisms ◽  
Diffusion Limited Aggregation ◽  
Density Correlation ◽  
Diffusion Limited ◽  
Crystalline Anisotropy ◽  
The Relationship ◽  
Good Agreement ◽  
Dla Model

AbstractThe formation mechanisms and the origin of manganese dendrites on the magnesite ore have been under discussion. The growth process of the manganese dendrites is statistically studied by comparing them to aggregations obtained according to the diffusion limited aggregation (DLA) model via Monte Carlo simulations. In this case, ten manganese dendrite patterns changing from the least dense to the densest aggregations on the surface are separately selected to determine the relationship between real and simulated patterns. The sticking parameter is ranged from 0.05≤t≤1. The density–density correlation functions C(r) (their critical exponent A), fractal dimension Df, critical exponent α, and critical exponent β pertaining to the root mean square (rms) thickness have been computed for both the ten manganese dendrites and the simulated aggregations representing them. The results indicate that manganese dendrites may be determined with the general DLA model. Analyses of manganese dendrites, both scaling and simulations, suggest the growth mechanism for the macroscopic expression of crystalline anisotropy for the dendritic patterns. These results are in good agreement with the values in other literature and can be helpful in comparing natural and simulated aggregations (both dendritic and compact deposits).

scholarly journals Pelvic Construct Prediction of Trabecular and Cortical Bone Structural Architecture

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Dan T. Zaharie ◽  
Andrew T. M. Phillips
Keyword(s):  
Cortical Bone ◽  
Structural Model ◽  
Thickness Distribution ◽  
Bone Adaptation ◽  
The Body ◽  
Lower Limbs ◽  
Fe Model ◽  
Adaptation Algorithm ◽  
Modeling Framework ◽  
Good Agreement

The pelvic construct is an important part of the body as it facilitates the transfer of upper body weight to the lower limbs and protects a number of organs and vessels in the lower abdomen. In addition, the importance of the pelvis is highlighted by the high mortality rates associated with pelvic trauma. This study presents a mesoscale structural model of the pelvic construct and the joints and ligaments associated with it. Shell elements were used to model cortical bone, while truss elements were used to model trabecular bone and the ligaments and joints. The finite element (FE) model was subjected to an iterative optimization process based on a strain-driven bone adaptation algorithm. The bone model was adapted to a number of common daily living activities (walking, stair ascent, stair descent, sit-to-stand, and stand-to-sit) by applying onto it joint and muscle loads derived using a musculoskeletal modeling framework. The cortical thickness distribution and the trabecular architecture of the adapted model were compared qualitatively with computed tomography (CT) scans and models developed in previous studies, showing good agreement. The sensitivity of the model to changes in material properties of the ligaments and joint cartilage and changes in parameters related to the adaptation algorithm was assessed. Changes to the target strain had the largest effect on predicted total bone volumes. The model showed low sensitivity to changes in all other parameters. The minimum and maximum principal strains predicted by the structural model compared to a continuum CT-derived model in response to a common test loading scenario showed good agreement with correlation coefficients of 0.813 and 0.809, respectively. The developed structural model enables a number of applications such as fracture modeling, design, and additive manufacturing of frangible surrogates.

Possible formation mechanisms for surface defects observed in heteroepitaxially grown 3C-SiC

2007 ◽  
Vol 204 (7) ◽  
pp. 2216-2221 ◽  
Author(s):  
K. M. Speer ◽  
P. G. Neudeck ◽  
M. A. Crimp ◽  
C. Burda ◽  
P. Pirouz
Keyword(s):  
Surface Defects ◽  
Formation Mechanisms

Orifice Restrictor Losses in Journal Bearings

1979 ◽  
Vol 193 (1) ◽  
pp. 47-52 ◽  
Author(s):  
E. G. Pink ◽  
K. J. Stout
Keyword(s):  
Radial Flow ◽  
Load Capacity ◽  
Journal Bearings ◽  
Experimental Results ◽  
Pressure Recovery ◽  
Pressure Profiles ◽  
Compensation Factor ◽  
Good Agreement

Details of a study concerning orifice restrictor losses in externally pressurized gas lubricated journal bearings are given. The type of compensation considered is the pocketed orifice design. The analysis presented includes the effects of pressure recovery in the pocket and entrance loss effects at inlet to the bearing film. Also, by treating the flow in the bearing film local to the pocket as radial flow, the effect of dispersion is accounted for. It is shown that good agreement exists between computed and experimental results in pressure profiles and also for load capacity up to touch-down conditions. From the analysis, the effect of the inherent compensation factor, number of orifices and pocket diameter on load capacity is discussed.

Residual Stress Prediction for Non-Axisymmetric Vessel Penetration Welds

2008 ◽  
Author(s):  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Three Dimensional ◽  
Measurement Data ◽  
Fe Model ◽  
Stress Distributions ◽  
Dimensional Finite Element ◽  
Stress Prediction ◽  
Three Dimensional Finite Element ◽  
Good Agreement

Residual stress distribution in an oblique nozzle jointed to a vessel with J-groove welds was analyzed using a three-dimensional finite element method. All welding passes were considered in a 180-degree finite element (FE) model with symmetry. Temperature and stress were modeled for simultaneous bead laying. To determine residual stress distributions at the welds experimentally, a mock-up specimen was manufactured. The analytical results show good agreement with the experimental measurement data, indicating that FE modeling is valid.

An assessment of the Sachs method for measuring residual stresses in cold worked fastener holes

1998 ◽  
Vol 33 (4) ◽  
pp. 263-274 ◽  
Author(s):  
D J Smith ◽  
C G C Poussard ◽  
M J Pavier
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Cold Working ◽  
Element Model ◽  
Fe Model ◽  
Working Process ◽  
Element Analysis ◽  
Near Surface ◽  
Cold Worked ◽  
Good Agreement

Measurements of residual stresses in 6 mm thick aluminium alloy 2024 plates containing 4 per cent cold worked fastener are made using the Sachs method. The measurements are made on discs extracted from the plates. The measured tangential residual stress distribution adjacent to the hole edge are found to be affected by the disc diameter. The measured residual stresses are also in good agreement with averaged through-thickness predictions of residual stresses from an axisymmetric finite element (FE) model of the cold working process. A finite element analysis is also conducted to simulate disc extraction and then the Sachs method. The measured FE residual stresses from the Sachs simulation are found to be in good agreement with the averaged through-thickness predicted residual stresses. The Sachs simulation was not able to reproduce the detailed near-surface residual stresses found from the finite element model of the cold working process.

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