Search results

1 – 10 of 34
To view the access options for this content please click here
Article
Publication date: 16 July 2019

Behnam Gomari, Farzam Farahmand and Hassan Farkhondeh

An important challenge of the osteotomy procedures, particularly in the case of large and complex corrections, is the fixation of the osteotomy site. The purpose of this…

Abstract

Purpose

An important challenge of the osteotomy procedures, particularly in the case of large and complex corrections, is the fixation of the osteotomy site. The purpose of this study is to propose a practical and cost-effect methodology for the plate adapting problem of osteotomy surgery.

Design/methodology/approach

A novel patient-specific plate contouring methodology, based on rapid prototyping (RP) and multi-point forming (MPF) techniques, was developed and evaluated. In this methodology, a female mold is fabricated by RP, based on the geometry of the osteotomy site and estimation of the plate spring back. The mold is then used to configure a MPF die, which is then used for press forming of the factory-made locking plate. The applicability of the methodology was assessed in two case studies.

Findings

The results of implementing the methodology on a femoral and a tibial locking plate indicated very good conformity with the underlying bone, in both the frontal and sagittal planes. The surgical application of the pre-operatively contoured tibial plate facilitated the plate locating and screw inserting procedures, and provided a secure fixation for bone fragments.

Practical implications

The results are promising and provide a proof of concept for the feasibility and applicability of the proposed methodology in clinical practice, as a complementary to the existing surgical preplanning and patient-specific instrument preparations.

Originality/value

The advantageous features of RP and the MPF were used to provide a solution for the plate adapting problem of osteotomy surgery.

To view the access options for this content please click here
Article
Publication date: 6 April 2010

A.R. Khoei, Sh. Keshavarz and A.R. Khaloo

The purpose of this paper is to present a shape optimization technique for powder forming processes based on the genetic algorithm approach. The genetic algorithm is…

Abstract

Purpose

The purpose of this paper is to present a shape optimization technique for powder forming processes based on the genetic algorithm approach. The genetic algorithm is employed to optimize the geometry of component based on a fixed‐length vector of design variables representing the changes in nodal coordinates. The technique is used to obtain the desired optimal compacted component by changing the boundaries of component and verifying the prescribed constraints.

Design/methodology/approach

The numerical modeling of powder compaction simulation is applied based on a large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for large powder deformations. A cap plasticity model is used in numerical simulation of nonlinear powder behavior. The influence of powder‐tool friction is simulated by the use of penalty approach in which a plasticity theory of friction is incorporated to model sliding resistance at the powder‐tool interface.

Findings

Finally, numerical examples are analyzed to demonstrate the feasibility of the proposed optimization algorithm for designing powder components in the forming process of powder compaction.

Originality/value

A shape optimization technique is presented for powder forming processes based on the genetic algorithm approach.

Details

Engineering Computations, vol. 27 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 22 August 2008

Zengxi Pan and Hui Zhang

This paper aims to present the critical issues and methodologies to improve robotic machining performance with flexile industrial robots.

Downloads
1832

Abstract

Purpose

This paper aims to present the critical issues and methodologies to improve robotic machining performance with flexile industrial robots.

Design/methodology/approach

A complete solution using active force control is introduced to address various issues during the robotic machining process.

Findings

Programming complex couture parts without a CAD model is made easy by using force control functions such as lead‐through and path‐learning. The problem of process control is treated with a novel methodology that consists of stiffness modeling, real‐time deformation compensation for quality and controlled material removal rate for process efficiency.

Originality/value

Experimental results showed that higher productivity as well as better surface quality can be achieved, indicating a promising and practical use of industrial robots for machining applications that is not available at present.

Details

Industrial Robot: An International Journal, vol. 35 no. 5
Type: Research Article
ISSN: 0143-991X

Keywords

To view the access options for this content please click here
Article
Publication date: 16 November 2010

Wu‐Lin Chen, Chin‐Yin Huang and Chi‐Wei Hung

The purpose of this paper is to find the optimal values of process parameters in injection molding when both warpage and shrinkage are minimized.

Abstract

Purpose

The purpose of this paper is to find the optimal values of process parameters in injection molding when both warpage and shrinkage are minimized.

Design/methodology/approach

In finding the optimal values, advantages of finite element software, Moldflow, and dual response surface method (dual RSM) combined with the nonlinear programming technique by Lingo are exploited. Considering the nine process parameters, injection time, injection pressure, packing pressure, packing time, cooling time, coolant temperature, mold‐open time, melting temperature and mold surface temperature, a series of mold analyses are performed to exploit the warpage and shrinkage data. In the analyses, warpage is considered the primary response, whereas shrinkage is the secondary response.

Findings

The results indicate that dual RSM combined with the nonlinear programming technique can outperform the Taguchi's optimization method. The optimal process values are also confirmed by re‐running experiments on Moldflow. Additionally, an auxiliary dual RSM model is proposed to search for a better result based on the given findings by dual RSM at the cost of running extra experiments. Based on dual RSM, a multiple objective optimization for the whole plastic product is finally suggested to integrate the dual RSM models that are developed for the individual nodes or edges.

Originality/value

This paper proposes a new method to find the optimal process for plastic injection molding.

Details

Engineering Computations, vol. 27 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 22 May 2008

Eligiusz W. Postek, Roland W. Lewis and David T. Gethin

This paper sets out to present developments of a numerical model of squeeze casting process.

Abstract

Purpose

This paper sets out to present developments of a numerical model of squeeze casting process.

Design/methodology/approach

The entire process is modelled using the finite element method. The mould filling, associated thermal and thermomechanical equations are discretized using the Galerkin method. The front in the filling analysis is followed using volume of fluid method and the advection equation is discretized using the Taylor Galerkin method. The coupling between mould filling and the thermal problem is achieved by solving the thermal equation explicitly at the end of each time step of the Navier Stokes and advection equations, which allows one to consider the actual position of the front of the filling material. The thermomechanical problem is defined as elasto‐visco‐plastic described in a Lagrangian frame and is solved in the staggered mode. A parallel version of the thermomechanical program is presented. A microstructural solidification model is applied.

Findings

During mould filling a quasi‐static Arbitrary Lagrangian Eulerian (ALE) is applied and the resulting temperatures distribution is used as the initial condition for the cooling phase. During mould filling the applied pressure can be used as a control for steering the distribution of the solidified fractions.

Practical implications

The presented model can be used in engineering practice. The industrial examples are shown.

Originality/value

The quasi‐static ALE approach was found to be applicable to model the industrial SQC processes. It was found that the staggered scheme of the solution of the thermomechanical problem could parallelize using a multifrontal parallel solver.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 1 September 2004

M. Poursina, C.A.C. António, C.F. Castro, J. Parvizian and L.C. Sousa

A numerical method for shape optimisation in forging is presented. The goal of the optimisation is to eliminate work‐piece defects that may arise during the forging process

Abstract

A numerical method for shape optimisation in forging is presented. The goal of the optimisation is to eliminate work‐piece defects that may arise during the forging process. A two‐dimensional finite element code has been developed for the simulation of the mechanical process. The material is incompressible and it follows the Norton‐Hoff law. To deal with contact constraint the velocity projection algorithm is used. The optimisation process is conducted using a genetic algorithm supported by an elitist strategy. A new genetic operator called adaptive mutation has been developed to increase the efficiency of the search. The developed scheme is used to design optimal preform shapes for several axisymmetric examples. Continuous and discrete design variables are considered. The objective function of the optimisation problem is associated with the quality of the final product. Comparing the obtained optimal results with the literature validates the proposed optimisation method.

Details

Engineering Computations, vol. 21 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 9 February 2010

Cem S. Çetinarslan and Mumin Sahin

The purpose of this paper is to determine the influence of surface roughness on materials flow of various materials using grid lines during cold forming.

Abstract

Purpose

The purpose of this paper is to determine the influence of surface roughness on materials flow of various materials using grid lines during cold forming.

Design/methodology/approach

The study is focused on the investigation of the influence of the surface roughness on the materials flow for different materials using grid lines in the upsetting. Stainless steel, SAE 1020 steel, commercially pure aluminum, commercially pure copper and CuZn40Pb2 brass are used as the test materials. Upsetting process is applied to the cylindrical specimens using the flat end dies. Strain distributions on the free surfaces of cylindrical upset specimen are measured for different upsetting reductions. Strain distributions on the free surfaces are obtained by the measurements of the dimensions of the square grid elements before and after the upsetting process. Experimental results are placed into graphical plots.

Findings

It is found that surface roughness is effectual on the strain changes on the free surfaces with the increasing deformation ratio for especially two types of steel specimens. There has been no considerable effect on aluminum, copper and brass specimens.

Research limitations/implications

It would be interesting to search the surface roughness, Rsk and other parameters describing the bearing properties of the surface of more materials. Future work could be concentrated on the cold forming of these materials.

Practical implications

Different forming technologies are nowadays widely applied in mass production of mechanical components for needs of transportation, electronics, household appliances, etc. In order to reduce costs, manufacturers are trying to minimize additional machining and therefore to implement the influence of surface roughnesses on materials flow of various materials.

Originality/value

The main value of this paper is to contribute to studies on the influence of surface roughness on materials flow of various materials.

Details

Industrial Lubrication and Tribology, vol. 62 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 29 May 2009

Rodrigo Rossi, Marcelo Krajnc Alves and Hazim Ali Al‐Qureshi

The purpose of this paper is to investigate the application of the element‐free Galerkin (EFG) method to the simulation of metal forming processes and to propose a…

Abstract

Purpose

The purpose of this paper is to investigate the application of the element‐free Galerkin (EFG) method to the simulation of metal forming processes and to propose a strategy to deal with volumetric locking problem in this context.

Design/methodology/approach

The J2 elastoplastic material model, employed in the work, assumes a multiplicative decomposition of the deformation gradient into an elastic and a plastic part and incorporates a non‐linear isotropic hardening response. The constitutive model is written in terms of the rotated Kirchhoff stress and the logarithmic strain measure. A Total Lagrangian formulation of the problem is considered in order to improve the computational performance of the proposed algorithm. The imposition of the essential boundary conditions and also of the unilateral contact with friction condition are made by the application of the Augmented Lagrangian method. Here, aspects related to the volumetric locking are investigated and an F‐bar approach is applied.

Findings

The results show that the proposed approach presents no volumetric locking phenomenon when using the mean dilation approach. Moreover, differently from finite element approximations, no hour‐glass instabilities in the deformation pattern are observed, avoiding in this way the need to devise additional stabilization procedures in the proposed procedure.

Originality/value

This paper demonstrates the implementation and validation of the mean dilation approach, in the scope of the EFG, which was successful in coping with the volumetric locking phenomena and presented no hour‐glass instabilities in the problem cases considered in this work.

Details

Engineering Computations, vol. 26 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 11 September 2009

Ubeidulla Al‐Qawabeha, Aiman Eid Al‐Rawajfeh and Ehab Al‐Shamaileh

Roller burnishing (RB) is a finishing treatment method that is used to impart certain physical and mechanical properties, such as surface roughness, improved visual…

Abstract

Purpose

Roller burnishing (RB) is a finishing treatment method that is used to impart certain physical and mechanical properties, such as surface roughness, improved visual appearance, or increased corrosion, friction, wear, and fatigue resistance. The purpose of this paper is to study, the influence of RB on corrosion resistance in A53 steel in HCl solution.

Design/methodology/approach

Microhardness (MH), microstructure, weight loss, and potentiostatic polarization are investigated at pressing forces of 40, 60, 80, 100 and 120 N.

Findings

MH increases with increasing the applied force and the percentage improvements are found to be 12, 24, 28, 35 and 65 percent for 40, 60, 80, 100 and 120 N RB pressing forces, respectively. Weight losses, in general, showed an optimum value at about 80 N. Corrosion potential and corrosion current decrease with increasing pressing force and reached a minimum at about 80 N, then begin to increase with increasing RB force.

Originality/value

The results present in this paper are important to the understanding of the effect of the surface plastic deformation methods on surface properties and corrosion resistance in steel.

Details

Anti-Corrosion Methods and Materials, vol. 56 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

To view the access options for this content please click here
Article
Publication date: 1 August 2006

Carola Esposito Corcione, Francesco Montagna, Antonio Greco, Antonio Licciulli and Alfonso Maffezzoli

In this work, the production of ceramic moulds for aluminium casting using a stereolithographic apparatus (SLA) is presented.

Downloads
1359

Abstract

Purpose

In this work, the production of ceramic moulds for aluminium casting using a stereolithographic apparatus (SLA) is presented.

Design/methodology/approach

Suspensions of silica powders in a photoreactive resin were used in a standard SLA equipment in order to build green parts. SLA, SLA‐250 (3D System, Valencia, CA) was modified in order to fabricate a ceramic green parts.

Findings

A characterization of mechanical properties of the material samples was performed. Finally, moulds for aluminium casting were obtained either using the stereolithographic part as a green mould, either by pyrolisis of the organic binder and subsequent sintering at high temperature.

Research limitations/implications

Future investigations will be devoted to optimise the process and the mechanical performances of the sintered parts, improving the rheological properties of suspensions and reducing the building time.

Originality/value

This is a novel work on the production of ceramic moulds for aluminium casting using a SLA.

Details

Rapid Prototyping Journal, vol. 12 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

1 – 10 of 34