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Ż. A. Mierzejewska

Abstract

Manufacturing is crucial to creation of wealth and provision of quality of life. Manufacturing covers numerous aspects from systems design and organization, technology and logistics, operational planning and control. The study of manufacturing technology is usually classified into conventional and non-conventional processes. As it is well known, the term "rapid prototyping" refers to a number of different but related technologies that can be used for building very complex physical models and prototype parts directly from 3D CAD model. Among these technologies are selective laser sintering (SLS) and direct metal laser sintering (DMLS). RP technologies can use wide range of materials which gives possibility for their application in different fields. RP has primary been developed for manufacturing industry in order to speed up the development of new products (prototypes, concept models, form, fit, and function testing, tooling patterns, final products - direct parts). Sintering is a term in the field of powder metallurgy and describes a process which takes place under a certain pressure and temperature over a period of time. During sintering particles of a powder material are bound together in a mold to a solid part. In selective laser sintering the crucial elements pressure and time are obsolete and the powder particles are only heated for a short period of time. SLS uses the fact that every physical system tends to achieve a condition of minimum energy. In the case of powder the partially melted particles aim to minimize their in comparison to a solid block of material enormous surface area through fusing their outer skins. Like all generative manufacturing processes laser sintering gains the geometrical information out of a 3D CAD model. This model is subdivided into slices or layers of a certain layer thickness. Following this is a revolving process which consists of three basic process steps: recoating, exposure, and lowering of the build platform until the part is finished completely.

Open access

Ż. A. Mierzejewska

Abstract

A total hip replacement is a procedure that requires removal of the affected joint lesions and replacing it with artificial elements. Nevertheless, like any invasive surgery, it is associated with the risk of complications, including joint infection, fracture of the bone during and after surgery, scarring and limitation of motion of the hip, and loosening of the prosthesis. In this work we present and describe the results of its investigations. In order to determine the mechanism of failure, a broken stem components were analyzed by means of macroscopic and microscopic observations and hardness measurements. The hardness, microstructure and chemical composition of the broken part of the hip stem were analyzed. Microscopic examination revealed numerous defects in material. Among them are pores and emptiness, located on the outskirts of the tested samples and a plurality of micro-cracking, debonding and delamination of the material due to the overloading of a fatigue character. There were no changes caused by intergranular corrosion or pitting, which may indicate for an even distribution of the major alloying components such as chromium and nickel. Observations of the material by using scanning electron microscopy (SEM), clearly proved that the destruction was caused by material fatigue. The investigation showed that the crack had originated due to a high stress concentration on the lateral corner section of the stem. Large surface of the fatigue crack zone area indicated for small stresses and small crack propagation velocities. There was a clear correlation between the grain size of the steel hardness. The results of hardness test revealed a significant increase hardness of stem in relation to the normative values. In addition, the measured average grain size is less than the standard accepted. Using Solid Works simulation and FEM a model of the stem was created and analyzed in terms of strength and rated the distribution of the generated stress. The finite-element analysis confirmed that there is the highest stress concentration in the middle of the stem

Open access

Ż. A. Mierzejewska and W. Markowicz

Abstract

Rapid prototyping technology (RP), based on designing and computer aided manufacturing, is widely used in traditional branches of industry. Due to its ability to accurately and precisely manufacture designed elements of various dimensions and complicated geometry, this technology is more and more frequently applied in the field of biomedical engineering. Selective laser sintering (SLS) is a universal RP technique, utilizing a laser beam to sinter powdered materials and create three-dimensional objects. Data for producing parts for tissue replacement come from medical imaging capabilities and digital presentation of test results. This paper presents the following: general classification of RP methods, the concept and methodology of performing laser sintering, sintering mechanisms, and the application of elements manufactured using this technology in biomedical engineering, particularly for the production of scaffolds used in tissue cultures, skeletal and dental prostheses in dental implantation, manufacturing of custom-made implants that are individually adjusted to the patient, and for production of training models on which a team of surgeons can train a surgical technique.