Fatigue Experimental of AS-CAST Ti-6Al-7Nb Implemented on Designed Femoral Stem for Indonesian People Through Finite Element Analysis

Rahman F.F.

Taraka H., Pardeep P., Pankaj B., Anilkumar D., Indira B., Aadarsh K.

Abstract Friction stir welding is a solid-state joining process used to weld various materials. Tool life is an important consideration when welding strong metals with the Friction stir welding technique (FSW). The current research aims to calculate tool life by mathematical derivation and simulation using ANSYS transient structural analysis. There are two tool materials and five-pin profiles to consider. The calculated tool life using mathematical formulation is within 15% of the simulation outcome. Further changes are made to the simulation to make the tool life estimate more realistic under FSW’s operation. PcBN tool has superior mechanical properties over the tungsten carbide tool, so the procedure started with the tungsten carbide tool. The conical pin profile is giving 31466 cycles of tool life, which is 70 min run time while working at 450 rpm rotational speed. As a result, for high-strength materials joining, the tool must be chosen based on tool life parameters. The addition of a 1.5 mm fillet at the pin-to-shoulder junction has improved the tool life by 1147 cycles. The PcBN tool is simulated with a conical tool with new pin profiles of conical with grooves and cylindrical fillet with grooves. The maximum tool life of 94018 cycles is obtained for the conical PcBN tool.

Joshi T., Sharma R., Mittal V.K., Gupta V., Krishan G.

In the present work, a finite element model with standard Charnley’s implant of hip joint is considered for investigation under different patient-specific dynamic activities obtained in vivo. The application of forces occurred due to human movement, which ultimately generates dynamic stress over the prosthesis. Anatomical loading constraints are more clinically relevant than ISO standards. The performance of different materials for each suitable gait pattern is analyzed using commercial finite element code. A liner isotropic material Ti-6Al-4V and PMMA material is utilized for an implant and bone cement, respectively. However, cortical and cancellous bone are treated as non-isotropic in nature. Clinically obtained dynamic forces and torque are being used for the present investigation. Additionally, Goodman, Solderberg, Gerber and ASME elliptic fatigue theories were considered to obtain the fatigue life of the implant. The most strenuous activity in terms of stress and strain are, going downstairs followed by going upstairs, walking, standing up and sitting down, which have been found in good agreement with the safety factor for every activity. Additionally, the life expectancy of the implant was a minimum of 23 years under every dynamic motion. The present work exhibits the greater relevance in terms of the life expectancy of implant for the pre-surgical analysis before implanted in vivo.

Guzmán M., Durazo E., Ortiz A., Sauceda I., Siqueiros M., González L., Jiménez D.

Choosing a suitable prosthesis to restore the functionality of the hip joint is a complex problem. The stem geometries, materials, and type of hip damage are critical factors for avoiding potential issues (aseptic loosening, fracture, and natural wear and tear). Comparing the available stems to select the best option is not straightforward because of the various loads and boundary conditions used in the tests, making the process difficult to compare the advantages and disadvantages among them. This work proposes stem assessment using a standardized base (generated from a literature review and ISO standards) to compare the stem geometries and present a new hybrid design to improve performance using the best qualities of the implants reported in the literature review. Sixteen hip prostheses were evaluated with the finite element method (FEM) using the same boundary and loading conditions through multi-objective analysis (von Mises stress and strain). Consequently, a hybrid geometry proposal was obtained by assessing specific points through the stem length (medial and lateral region) to define the cross-section (trapezoidal) and the new profile. The new hybrid implant proposal presented a stress reduction of 9.6% when compared to the reference implant P2-T (the implant with the best behavior) in the most critical activity (activity 4) using a titanium alloy. A similar stress reduction of 9.98% was obtained using ASTM F2996-13 and ISO 7206–4:2010(E) standards.

Al Zoubi N.F., Tarlochan F., Mehboob H.

Repetitive loads acting on the hip joint fluctuate according to the type of activities produced by the human body. Repetitive loading is one of the factors that leads to fatigue failure of the implanted stems. The objective of this study is to develop lightweight femoral stems with cubic porous structures that will survive under fatigue loading. Cubic porous structures with different volumetric porosities were designed and subjected to compressive loading using finite element analysis (FEA) to measure the elastic moduli, yield strength, and ultimate tensile strength. These porous structures were employed to design femoral stems containing mechanical properties under compressive loading close to the intact bone. Several arrangements of radial geometrical porous functionally graded (FG) and homogenous Ti-6Al-4V porous femoral stems were designed and grouped under three average porosities of 30%, 50%, and 70% respectively. The designed stems were simulated inside the femoral bone with physiological loads demonstrating three walking speeds of 1, 3, and 5 km/h using ABAQUS. Stresses at the layers of the functionally graded stem were measured and compared with the yield strength of the relevant porous structure to check the possibility of yielding under the subjected load. The Soderberg approach is employed to compute the safety factor (Nf > 1.0) for each design under each loading condition. Several designs were shortlisted as potential candidates for orthopedic implants.

Safitri P.N., Amelia, Asmaria T., Rahma O.N., Rahyussalim A.J., Aurellia S., Kartika I.

Total Hip Replacement (THR) requires careful planning preparation, especially in the geometry suitability between the patient's bone and the implant. If it is applied incorrectly, it will be dangerous for the patient, such as the risk of complications, dislocation, and re-surgery. This paper aims to compare the size of the patient's THR geometry as a basis for consideration in implant designs to minimize the risk of harm after implantation. This study was limited to male patients only. The computed tomography scanning data (CT-Scan data) in the lower abdomen, segmented to hip joint area belonging to the American race and an Indonesian male, were compared. The comparison indicates that the American race data has a greater dimension than Indonesian. The American hip bone geometry result is following the standard modern implant by Johnson and Johnson size. By all analysis, the fittest geometry for the Indonesian male patient needs to adjust and has a smaller size than the commercial implant. This study finally recommends the specific length of the femoral stem for the optimal THR implant with the parameter values of Femoral Head Offset, Neck Length, Neck Shaft Angle, Mediolateral Width 1, Mediolateral Width 2, Mediolateral Width 3 respectively for the right THR, namely 37.9; 31.6; 134.3; 43.1; 13.62; 12.36; while the left THR is 38.9; 31.7; 134.5; 43.1; 13.70; 12.4 in mm. Overall, the precise implant planning based on real patient conditions and anthropometry is necessary to match implants and bone anatomy.

Okazaki Y., Mori J.

We investigated the microstructures, tensile properties, fatigue strengths, and durability limits of hot-forged Ti-15Zr-4Nb (Ti-15-4) alloy artificial hip stems. These properties were compared with those of Ti-15Zr-4Nb-4Ta (Ti-15-4-4) and Ti-6Al-4V (Ti-6-4) alloy stems annealed after selective laser melting. The tensile and fatigue properties of test specimens cut from Ti-15-4 stems annealed after hot forging were excellent compared with those of the Alloclassic Zweymüller Stepless (SL) stem, which is used globally. The 0.2% proof stress (σ0.2%PS), ultimate tensile strength (σUTS), total elongation (TE) at breaking, and fatigue strength (σFS) after 107 cycles were 919 ± 10, 983 ± 9 MPa, 21 ± 1%, and 855 ± 14 MPa, respectively. The durability limit (PD) after 5 × 106 cycles of Ti-15-4 stems was excellent compared with that of the SL stem. The σUTS values of 90°- and 0°-direction-built Ti-15-4-4 rods were 1032 ± 1 and 1022 ± 2 MPa, and their TE values were 14 ± 1% and 16 ± 1%, respectively. The σFS values of annealed 90°-direction-built Ti-15-4-4 and Ti-6-4 rods were 640 ± 11 and 680 ± 37 MPa, respectively, which were close to that of the wrought Ti-15-4 rod (785 ± 17 MPa). These findings indicate that the hot forging and selective laser melting (SLM) techniques can also be applied to the manufacture of artificial hip prostheses. In particular, it was clarified that selective laser melting using Ti-15-4-4 and Ti-6-4 powders is useful for the low-cost manufacturing of custom-made artificial joint prostheses and other prosthetic implants.

García-González M., Blasón-González S., García-García I., Lamela-Rey M.J., Fernández-Canteli A., Álvarez-Arenal Á.

Mechanical complications in implant-supported fixed dental prostheses are often related to implant and prosthetic design. Although the current ISO 14801 provides a framework for the evaluation of dental implant mechanical reliability, strict adherence to it may be difficult to achieve due to the large number of test specimens which it requires as well as the fact that it does not offer any probabilistic reference for determining the endurance limit. In order to address these issues, a new software program called ProFatigue is presented as a potentially powerful tool to optimize fatigue testing of implant-supported prostheses. The present work provides a brief description of some concepts such as load, fatigue and stress-number of cycles to failure curves (S-N curves), before subsequently describing the current regulatory situation. After analyzing the two most recent versions of the ISO recommendation (from 2008 and 2016), some limitations inherent to the experimental methods which they propose are highlighted. Finally, the main advantages and instructions for the correct implementation of the ProFatigue free software are given. This software will contribute to improving the performance of fatigue testing in a more accurate and optimized way, helping researchers to gain a better understanding of the behavior of dental implants in this type of mechanical test.

Qurashi S., Pelletier M.H., Wang T., Bramich N., Chinnappa J., Walsh W.R.

Background: The aim of this study was to investigate total hip arthroplasty (THA) Morse taper pull-off strengths after impaction prior to cyclical loading compared to cyclical loading alone. The practical relevance of the experiment is to provide a perspective on what may be clinically satisfactory taper assembly given the spectrum of head tapping patterns used by surgeons, as well as compare traditional impaction performed in standard THA with alternate methods of taper engagement such as ‘ in situ assembly’ used in micro-invasive techniques. Methods: 36 taper constructs utilising a combination of cobalt-chrome alloy and ceramic-titanium alloy junctions were investigated in vitro in wet and dry conditions with cyclical loading of the constructs. Taper disengagement strengths with and without impaction were compared. Secondary investigation of the surface roughness of the heads and tapers was also assessed. Results: An impaction to a wet taper resulted in a greater pull off force compared to a dry taper with a CoCr head and taper combination. Impacting the head and dryness of the taper did not affect pull off forces of a ceramic femoral head on titanium taper. Pulling a head off a taper significantly alters the head surface roughness. Conclusion: Impaction of a taper does not provide any benefit over cyclical loading of a taper assembly alone for pull-off strength.

Babić M., Verić O., Božić Ž., Sušić A.

• The total hip prosthesis CAD model was developed by using 3D scanning. • Fatigue life to crack initiation of a loosened total hip prosthesis femoral component was assessed based on FEA. • High tensile stresses were identified in locations where fatigue cracks occur in real cases. • Introduced procedure can be implemented to other implants and components. Fatigue life of a loosened total hip prosthesis femoral component cemented into bone was investigated assuming loads specified by the standard ISO 7206-4. The total hip prosthesis CAD model was developed by implementing a 3D scanning procedure. Based on the created CAD model, the FE model was developed. A linear elastic analysis was carried out for the created FE model of the prosthesis. The analysis showed that high tensile stresses occur on the distal region of the femoral component shaft on the anterior lateral side, where fatigue cracks occur in real cases. This procedure can be implemented in other components where the geometry needs to be reconstructed by the 3D scanning.

Castillo E., Muniz-Calvente M., Fernández-Canteli A., Blasón S.

Different empirical models have been proposed in the literature to determine the fatigue strength as a function of lifetime, according to linear, parabolic, hyperbolic, exponential, and other shaped solutions. However, most of them imply a deterministic definition of the S-N field, despite the inherent scatter exhibited by the fatigue results issuing from experimental campaigns. In this work, the Bayesian theory is presented as a suitable way not only to convert deterministic into probabilistic models, but to enhance probabilistic fatigue models with the statistical distribution of the percentile curves of failure probability interpreted as their confidence bands. After a short introduction about the application of the Bayesian methodology, its advantageous implementation on an OpenSource software named OpenBUGS is presented. As a practical example, this methodology has been applied to the statistical analysis of the Maennig fatigue S-N field data using the Weibull regression model proposed by Castillo and Canteli, which allows the confidence bands of the S-N field to be determined as a function of the already available test results. Finally, a question of general interest is discussed as that concerned to the recommendable number of tests to carry out in an experimental S-N fatigue program for achieving “reliable or confident” results to be subsequently used in component design, which, generally, is not adequately and practically addressed by researchers.

Seitl S., Miarka P., Blasón S., Canteli A.F.

Delikanli Y.E., Kayacan M.C.

This study aims to design, analyze and manufacture lightweight hip implants which have sufficient fatigue performance to enable use in total hip arthroplasty (THA).The lattice structure was applied on an implant geometry, which is frequently used in THA, to provide a reduction in mass and increase flexibility. The implant surfaces were roughened using semispherical pores to improve the osseointegration. The specimens were manufactured by means of direct metal laser sintering (DMLS) and fatigue tests were performed according to ISO 7206-4:2010. Moreover, fatigue analyses of the designed implants were numerically carried out using the finite element method.The applied lattice structure on implant geometry leads to 15-17% reduction in the masses of implants compared to a solid one. It has also been determined that the lightweight implants show more flexible behavior with increasing pore diameter used on the implant surfaces while keeping the lattice structure geometry constant. The fatigue test and finite element analysis (FEA) results are in reasonable agreement. In addition, additively manufactured solid implants have exhibited similar fatigue performance with one produced by conventional methods.This paper presents design, analysis, manufacturing and fatigue test processes of lightweight hip implants. The lattice structure and the semispherical pores were applied on a reference implant geometry and they were manufactured by DMLS. The fatigue tests and FEA were performed to evaluate newly designed implant performance. All the implants successfully completed the fatigue tests without any damage.

Koizumi H., Ishii T., Okazaki T., Kaketani M., Matsumura H., Yoneyama T.

Łagoda A., Niesłony A.

Abstract The aim of the paper is to obtain the values of dental implant stress analysis. The dental implant was inserted in the part of mandible bone. Stress analysis was carried out using the Finite Elements Method and simplified models.