Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

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Graded/Gradient Porous Biomaterials

Metallic Functionally Graded Materials: A Specific Class of Advanced Composites

Functionally graded materials (FGMs) are advanced composite materials that are used to solve a number of engineering problems, as well as in the biomedical implant applications for the replacement of human tissues. These materials are used to eliminate the stress singularities that occur, as a result of the property mismatch in the constituent materials in a composite. There are different types of FGMs that are used today, depending on the type of application, for which the material is intended. In this chapter, the different types of FGMs are presented. The areas of application of this novel material are also explained.

Types of Functionally Graded Materials and Their Areas of Application

Nucleation of biomimetic apatite in synthetic body fluids: dense and porous scaffold development

This paper provides a review of papers published in the Journal of Engineering Design from 2007 to 2008 Included are the different perspectives on key challenges existing within, and state-of-the-art technologies developed as solutions to current design issues The intention of this paper is not to provide detailed coverage of all the papers published over the last two years, but rather to provide an overview of research efforts focusing upon key research streams and to illustrate trends within design research and practice

Engineering design: perspectives, challenges, and recent advances

Highly interconnected porous yttria stabilised zirconia ceramics were prepared by slurry infiltration of expanded polystyrene powder compacts, followed by sintering at 1500 C. The porous zirconia ceramics exhibited a high porosity (60%) with uniform or graded pore sizes ranging from 300 μm to 1000 μm. The compressive strength of the uniform porous ceramics decreas d with the increase of pore size, whereas the compressive strength of the graded porous cer amics was anisotropic, depending on the direction of measurement. Compressive strengths from 8 MPa to 36 MPa were obtained for the porous zirconia ceramics.

Highly Interconnected and Functionally Graded Porous Bioceramics

Fixture plays an important role in enhancing the weld quality of the sheet metal assembly process. However, the traditional experience-based fixturing scheme and the purely optimal fixturing scheme are often sensitive to location fluctuation of the designed locators. In this paper, the three quality design models of a non-linear programming model, a polynomial response surface methodology (RSM) and a neural network (NN)-enhanced RSM are presented for fixture planning of a sheet metal assembly with resistance spot weld. In the non-linear programming model, both performance and variance are considered in the formulation of objective function. The polynomial RSM is used to fit a feasible response surface by 3 k fractional factorial design and analysis of the variance; by inspecting the influence of each design variable, one can gain insight into the existence of multiple design choices and select the optimum design based on more factors. NN can be used to confidently generate additional design point...

A comparative study on quality design of fixture planning for sheet metal assembly

Tolerance directly influences the functionality of the products and the related manufacturing costs, and tolerance allocation is of great importance for improving the assembly quality. However, the information required to allocate tolerances for complex 3D assemblies is generally not available at the initial design stage. In this paper, a new quality design methodology is developed, which makes use of both original design data obtained by the response surface methodology and the extra interpolation data obtained by the Kriging method. The finite element modelling is presented for the sheet metal assembly process as no explicit relationship of the variations for key characteristic points are available. The robust tolerances can be allocated based on the quality design model. A case study with the typical assembly process of the rear compartment pan and the wheelhouse is carried out in the paper, the tolerance allocation results show that the developed quality design methodology is capable of determining the robust manufacturing tolerance before assembly, which satisfies the product requirements. This method enables a robust tolerancing scheme to be used in the sheet metal assembly process.

Quality design of tolerance allocation for sheet metal assembly with resistance spot weld

The utility model relates to a two-dimension moving two-dimension rotation parallel connection robot mechanism as well as a thus forming five-axis and more than five-axis series-parallel connection machine tool. The basic structure comprises a fixed frame, a moveable platform and five branches. Four drive branches therein of the same structure are positioned at the circumference of the platform with six or more than six degrees of freedom thus producing no restriction to the mechanism. As a result, the degrees of freedom of the parallel platform is determined by the degrees of freedom of the passive branch chain placed at the center of the mechanism. As the passive restriction brancn chain provides two-dimension moving and two-dimension rotation degree of freedom, the utility model possesses five branches and four degrees of freedom. The utility model is characterized by a simple structure, good rigid, easy control and a fine dynamic performance. Various five-axis and more than five-axis processing machine tools can be designed out based on the utility model.

Parallel robot mechanism for realizing two dimension moving and rotation

The present invention discloses one kind of planar parallel three-freedom robot mechanism and relates to industrial robot The planar parallel three-freedom robot mechanism consists of one pedestal, one motion platform and two planar link rod mechanisms connecting the pedestal and the motion platform These two link rod mechanisms, including one planar 5R mechanism and one planar 4R mechanism, are staggered in parallel, and each of the planar 5R mechanism and the planar 4R mechanism has driving rod connected to the pedestal and driven rod connected to the motion platform The three freedoms of the mechanisms in the plane are controlled by two link rod mechanisms, the motion of the platform in the plane is controlled by the 5R mechanism, and the posture of the platform is controlled by the 4R mechanism

Planar parallel three-freedom robot mechanism

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