Tsuneo Hirai

Plastic metal flow under frictional boundary in forward extrusion die and stress distribution of the die

Abstract Cracks which progress across the vertical and horizontal plane section of forging dies appear to be caused by stress concentration. This paper reports an investigation into the relationship between the working pressure and the induced stresses distribution of the die during the process. In this paper, a simulation method is presented as a solution to the metal forming problem involving the plastic flow pattern of the metal and working pressure distribution along the tool surface. This method makes use of the Galerkin finite element formulation in conjunction with a special calculation procedure of stress boundary over metal deformation regions by axisymmetric analysis. Also, under the hypothesis of a fluid lubricant layer, the frictional condition between the deformed metal and tool surface is taken into consideration for the analysis. This simulation method is applied to some steady states of plastic deformation in axisymmetric forward extrusion die, and operating the working pressure distributions over the die surface obtained by above method, the stress distributions of the die are calculated by the usual axisymmetric finite element method. Then, the assumption of uniform working pressure usually used for a simplified calculation of the die design is confirmed by comparison with the stress distributions of the die above obtained.

The effect of tooling geometry on a new continuous fabrication system for SMC using roll forming

In an effort to further decrease the power requirement caused by the spherical stress tensor in SMC compression moulding, further developments in roll forming have been pursued. A continuous cross section such as a channel beam is produced by longitudinal rolling in progressive stages. As the product has a shear centre away from the centroid when the component is used as a structural part, the forming process must avoid the development of stress concentrations resulting from unsuitable orientation of reinforcements.

Design concept for one-piece panel vehicular components in SMC compression molding

Products molded from fiber reinforced material are subject to several problems during the manufacturing process such as sink marks, warpage and short shots. In an earlier work, the authors used finite element analysis to analyze the in-mold flow behavior of sheet molding compound (SMC) during the compression molding process. The analytical results were then verified through experimentation. This report first proposes an explanation for the mechanism generating sink marks in a ribbed product having a simple shape. Based on that understanding of the mechanism, a method for minimizing sink marks has been devised and confirmed through experimentation to be effective. The results of the present work are now being used to establish a molding concept for a one-piece outer panel.

Rheology of Carbon Fibre Composite Prepreg Materials

Carbon fibre composite prepreg materials are essentially heterogeneous structures and moulding them results in unstable deformation. The flow state during a press forming process can be analysed by representing the material flow as being unsteady.

The Elastic Modulus of Cancellous Bone: Dependence on Trabecular Orientation

We have developed a method of quantitative analysis of trabecular orientation on the cancellous bone by a Fourier analysis of the soft X-ray image. The relationship between the trabecular orientation and tensile modulus E was investigated on the cancellous bone specimens removed from the fresh bovine tibia. The proportion of trabeculae in a group at an angle θ to the loading direction, f(θ), and the volume fraction of the trabeculae, Vf, were obtained by applying the soft X-ray image of the test specimen. The equivalent volume fraction in the loading axis, Vfeq, was determined from a netting analysis, that is, Vfeq = Σ cos4θ f(θ)Vf. A linear regression was performed, giving the equation, E = -119+15234 Vfeq (MPa) ( r=0.96, P<0.01 ).

Roll forming of SMC and TMC, considering the resin-fibre interface

Abstract The principal purpose of this study is to develop a design procedure for a new roll forming process. With SMC, the advantages are reduced forming force and power consumption caused by a spherical stress tensor during compression moulding. Basic information on the deformation behaviour is obtained from a T-shaped profile using carrier type roll forming. As the SMC is a laminate with heterogeneous properties, consideration must be given to the macroscopic and microscopic interfaces caused by resin-rich surfaces and different stiffnesses of fibre and resin. The effect of feed rate on the flow pattern is also an important problem for the fabrication of different shape products. The fabrication behaviour is investigated with relation to the interfaces in the sequent process to target areas for future development.

Stress Analysis of the Proximal Tibia After Total Knee Arthroplasty with the Finite Element Method

Two-dimensional finite element analysis, considering heterogeneous and anisotropic properties of cancellous bone, was applied to the analysis of stress distribution in the natural proximal tibia before and after total knee arthroplasty. The detailed material properties of the proximal tibia were estimated by image analysis of soft X-rays. In the natural proximal tibia under bi-condylar uniform loads, which is regarded as ideal, the stress concentration was located in the middle portion between the condyles when the model was based on homogeniety and isotropy of cancellous bone. On the other hand, stress concentration was not found in analysis assuming heterogeniety and anisotropy. The stress distribution in the proximal tibia with the model of heterogeneity and anisotropy of cancellous bone was shown to be close to the actual clinical outcome. The finite element analysis employed in the present study may be beneficial in the evaluation of tibial component prosthetic designs.

Optimum Structure of Knee Prosthesis Using Laminate Composites Considering the Stress Dispersion at Prosthesis/Bone Interface

Composite materials are useful as replacement materials for human bone, signifying complicated mechanical characteristics because of many degrees of freedom of design. In the previous work, the authors indicated a numerical approach to force transmission from artificial knee joint (prosthesis) to cancellous bone by finite element analysis and verified the usefulness of composite materials for knee prosthesis. This paper describes a design procedure of replacement materials for the prosthesis based on the theoretical model of cancellous bone structure. Optimum ply construction and configuration of laminate composites for the prosthesis are analysed by considering stress dispersion at the prosthesis/bone interface.

Optimization of the Design of a Filament Wound Composite Ring for Use in a Shock Absorbing System

This paper is concerned with the design of filament wound rings applied to shock absorbing vehicular components operating in the initial period of an accident without increasing subsequent impact responses during the process. The impact force could be reduced without appreciably affecting the energy absorption by putting shallow notches on the inside of the ring by carrying out sequent cracking caused by debonding dependent on the stress concentration at the notch corner. The purpose of this investigation is to study the effects of varying the notch position and to determine the optimum geometry.

Design Concept of Projection Forming in Profile Ring Rolling

This paper describes developments aimed at improving quality and productivity in profile ring rolling. Rings of T-shaped cross-section with Internal or external projections are investigated When plain rectangular-section blanks are used, problems often arise in achieving a full profile« To overcome the problem it is necessary to investigate flow behaviour in the roll gap.