scholarly journals Case Study and Failure Analysis of a total hip Stem Fracture

2015 ◽  
Vol 15 (2) ◽  
pp. 5-13 ◽  
Author(s):  
Ż. A. Mierzejewska
Keyword(s):  
Grain Size ◽  
Stress Concentration ◽  
Joint Infection ◽  
High Stress ◽  
Hardness Test ◽  
Normative Values ◽  
Clear Correlation ◽  
Element Analysis ◽  
Total Hip ◽  
Average Grain Size

AbstractA 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

Fatigue Failure Analysis Using the Theory of Critical Distance

2011 ◽  
Vol 462-463 ◽  
pp. 663-667 ◽  
Author(s):  
Ruslizam Daud ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Al Emran Ismail
Keyword(s):  
Stress Concentration ◽  
Fatigue Failure ◽  
Notch Root ◽  
High Stress ◽  
Critical Distance ◽  
Future Research ◽  
Element Analysis ◽  
Linear Elastic ◽  
The Finite Element Analysis ◽  
Elastic Fracture

This paper explores the initial potential of theory of critical distance (TCD) which offers essential fatigue failure prediction in engineering components. The intention is to find the most appropriate TCD approach for a case of multiple stress concentration features in future research. The TCD is based on critical distance from notch root and represents the extension of linear elastic fracture mechanics (LEFM) principles. The approach is allowing possibilities for fatigue limit prediction based on localized stress concentration, which are characterized by high stress gradients. Using the finite element analysis (FEA) results and some data from literature, TCD applications is illustrated by a case study on engineering components in different geometrical notch radius. Further applications of TCD to various kinds of engineering problems are discussed.

scholarly journals Finite Element Analysis of Dynamic Recrystallization of Casting Slabs during Hot-Core Heavy Reduction Rolling Process

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 181
Author(s):  
Haijun Li ◽  
Tianxiang Li ◽  
Meina Gong ◽  
Zhaodong Wang ◽  
Guodong Wang
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Volume Fraction ◽  
Rolling Process ◽  
Reduction Ratio ◽  
Secondary Development ◽  
Innovative Technology ◽  
Element Analysis ◽  
The Core ◽  
Average Grain Size

Hot-core heavy reduction rolling (HHR2) is an innovative technology, where a two-high rolling mill is installed after the solidification end of a strand, which can significantly eliminate the core defects of the slab. The mill exhibits a heavy reduction ratio, which promotes the dynamic recrystallization (DRX) of the slab. This study aims to optimize the parameters of the HHR2 process considering the effect of DRX on microstructure homogeneity. The secondary development of commercial software DEFORM-3D is conducted to calculate the deformation and DRX behavior of HHR2 for different reduction ratios. The parameters of DRX volume fraction and DRX grain size are compared, and finer DRX grains are obtained when the greater reduction ratios are conducted in HHR2. Then, corresponding to the deformation conditions in the HHR2, the thermal–mechanical simulations are conducted on the Gleeble3800 to obtain the average grain sizes before and after this process. When the reduction amount increases from 20 mm to 50 mm, the difference of average grain size between the core and the surface reduces by 52%. In other words, appropriately enhancing the reduction ratio is helpful to reduce the average austenite grain and promote the microstructure uniformity of the slab. These results provide some valuable information on the design of deformation parameters for HHR2.

Microstructure Prediction by Finite Element Analysis during Hot Rolling of Magnesium Alloy Sheets

2015 ◽  
Vol 661 ◽  
pp. 105-112
Author(s):  
Yeong Maw Hwang ◽  
Tso Lun Yeh
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Optimal Conditions ◽  
Compression Tests ◽  
Element Analysis ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Microstructure Prediction ◽  
Alloy Microstructure ◽  
The Relationship

Material’s plastic deformation by hot forming processes can be used to make the materials generate dynamic recrystallization (DRX) and fine grains and accordingly products with more excellent mechanical properties, such as higher strength and larger elongation can be obtained. In this study, compression tests and water quenching are conducted to obtain the flow stress of the materials and the grain size after DRX. Through the regression analysis, prediction equations for the magnesium alloy microstructure were established. Simulations with different rolling parameters are conducted to find out the relationship between the DRX fractions or grain sizes of the rolled products and the rolling parameters. The simulation results show that rolling temperature of 400°C and thickness reduction of 50% are the optimal conditions. An average grain size of 0.204μm-0.206μm in the microstructure is obtained and the strength and formability of ZK60 magnesium alloys can be improved.

scholarly journals Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

2020 ◽  
Author(s):  
Shuang G Yan ◽  
Yan Chevalier ◽  
Fanxiao Liu ◽  
Xingyi Hua ◽  
Anna Schreiner ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Total Hip Arthroplasty ◽  
Hip Arthroplasty ◽  
Load Transfer ◽  
High Stress ◽  
Short Stem ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Total Hip

Abstract Background: Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a metaphyseal anchoring short and standard stem in native biomechanical femora. Methods: The subject specific finite element models of biomechanical femora, one native and two with implanted metaphyseal anchoring SHA (Metha, B.Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution. Results: Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally. Conclusions: Both, short and standard THA, cause unloading of the proximal femur. However, the metaphyseal anchoring SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load pattern implicate a reduced stress shielding proximally for metaphyseal anchoring SHA stems and might be able to translate in a better bone preservation.

scholarly journals Short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

2020 ◽  
Author(s):  
Shuang G Yan ◽  
Yan Chevalier ◽  
Fanxiao Liu ◽  
Xingyi Hua ◽  
Anna Schreiner ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Total Hip Arthroplasty ◽  
Hip Arthroplasty ◽  
Load Transfer ◽  
High Stress ◽  
Short Stem ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Total Hip

Abstract Background: Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a cementless short and standard stem in native biomechanical femora.Methods: The subject specific finite element models of biomechanical femora, one native and two with implanted SHA (Metha, B.Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution.Results: Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally.Conclusions: Both, short and standard THA, cause unloading of the proximal femur. However, SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load pattern implicate a reduced stress shielding proximally for SHA and might be able to translate in a better bone preservation.

Finite Element Analysis on Stress Concentration of Well Casing With Corrosion Pits

2010 ◽  
Author(s):  
Jing Zhang ◽  
Jianchun Fan ◽  
Laibin Zhang ◽  
Dong Wen ◽  
Yumei Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Spherical Cavity ◽  
High Stress ◽  
Orifice Diameter ◽  
Element Analysis ◽  
Corrosion Pits

Corrosion-induced pits will disturb the original stress distribution of casing and appear local high stress area. Through 3-D finite element analysis on casing with spherical and cylindrical corrosion cavity, the stress concentration degree and the influences of cavity shape, size and orifice diameter on stress concentration factor are determined and analyzed. The results show that the depth and shape of corrosion cavities are major factors impacting the stress concentration factor. For the casing with corrosion pits, the smaller orifice diameter, the more obvious influence of hemisphere effect on stress concentration factor. With the transition from shallow-spherical cavity to exact hemispherical cavity or from exact hemispherical cavity to deep-spherical cavity or from exact hemispherical cavity to cylindrical cavity, the changes of stress concentration factor show different characteristics.

Development of Design Curve for Sweepolet Subjected to Acoustic Induced Vibration

2016 ◽  
Author(s):  
Yuqing Liu ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Ismat Eljaouhari ◽  
Ajay Prakash
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Fatigue Failure ◽  
High Stress ◽  
Peak Stress ◽  
Acoustic Energy ◽  
Piping System ◽  
Element Analysis ◽  
Design Curve ◽  
High Stress Concentration

High acoustic energy has the potential to cause severe Acoustic Induced Vibration (AIV) that leads to fatigue failure at high stress concentration regions such as fittings in a piping system. Sweepolet fittings have been extensively used as mitigation to counteract the risk of fatigue failure caused by AIV. The advantages of a sweepolet are its integrally reinforced contoured body and low stress concentration. However, there are inconsistencies in published standards and regarding the design limits for sweepolet subjected to AIV. In this paper, Finite Element Analysis is conducted to simulate high frequency pipe shell wall vibration caused by acoustic energy inside the pipe. Peak stress and the associated minimum fatigue life are calculated for sweepolet and sockolet under the same acoustic excitation. By comparing the stress level to that of a sockolet whose design limit to AIV had been published, the design curve and fatigue life equation for sweepolet are developed.

Effect of TiB2 Content on Microstructure and Hardness of In Situ TiB2 Reinforced High Zinc Content Al-Zn-Mg-Cu-Zr Composite Materials

2017 ◽  
Vol 894 ◽  
pp. 34-37 ◽  
Author(s):  
He Li ◽  
Li Hua Chai ◽  
Zi Yong Chen ◽  
Hai Jing Wang ◽  
Tou Nan Jin
Keyword(s):  
Grain Size ◽  
Zinc Content ◽  
Hardness Test ◽  
Matrix Alloy ◽  
Pure Zinc ◽  
Average Grain Size ◽  
Master Alloys ◽  
High Zinc ◽  
The Matrix

TiB2p/Al-10Zn-1.7Mg-1.0Cu-0.12Zr composite was prepared by synthesis of in-situ Al-TiB2 master alloy, high purity aluminum, pure zinc, pure magnesium, Al-50 wt% Cu and Al-4 wt% Zr master alloys. The mass fraction of TiB2 particles was varied from 0% to 9.14%. SEM and TEM were applied to evaluate the microstructure and phase component. HB hardness test were carried out on hardness value of the matrix alloy and the composite. The results showed that TiB2 particles uniformly distributed in the composite and well combined with the matrix alloy. The average grain size of the composites decreased from 110.35μm to 52.07μm when the TiB2 particles is 4.47%, and the grain size changed slightly when TiB2 content increased further. The hardness value of the composites which raised from 189HB to 206HB is superior to that of the matrix alloy. As the content of TiB2 particles increased, HB hardness value also increased.

Finite Element Analysis on Microstructure Evolution of Hot Ring Rolling Process

2008 ◽  
Vol 575-578 ◽  
pp. 1455-1460 ◽  
Author(s):  
Zhi Chao Sun ◽  
He Yang ◽  
Xin Zhe Ou
Keyword(s):  
Grain Size ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Small Deformation ◽  
Local Area ◽  
Rolling Process ◽  
Ring Rolling ◽  
Rigid Plastic ◽  
Element Analysis ◽  
Average Grain Size

Hot ring rolling (HRR) is a 3D unsteady-state and coupled thermo-mechanical process, the metal undergoes complicated unequal deformation and microstructure evolution. In this paper a 3D rigid-plastic and coupled thermo-mechanical FEM model for hot ring rolling was developed based on DEFORM3D platform, taking dynamic recrystallization (DRX) volume fraction, DRX grain size, recystallization volume fraction and average grain size as objects, the mechanism of material microstructure evolution and distributions in HRR process are thoroughly studied. The results show that: with the HRR progressing, the DRX volume fraction, volume fraction, DRX grain size and average grain size have the similar distributing characteristic, and the distribution zones expand from a small local area into the whole ring strip, then diffuse to the mid-layer of ring with small deformation, their distributions become more uniform. Meanwhile with increase of deformation, the values of the DRX volume fraction and recrystallization volume fraction augment, i.e. the degree of recystallization increases. The DRX grain size also augments due to local high temperature, while the average grain size decreases. In general during HRR process the distributions of DRX volume fraction, recrystallization volume fraction, DRX grain size, and average grain size are ununiform due to unequal deforming in HRR process.

Validation of a Conventional Finite Element Model for Simulation of a Micropunching Process

2014 ◽  
Author(s):  
Amrit Sagar ◽  
Christopher R. Nehme ◽  
Anil Saigal ◽  
Thomas P. James
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
Bulk Material ◽  
Foil Thickness ◽  
Homogeneous Material ◽  
Element Analysis ◽  
Hardening Material ◽  
Material Inhomogeneity ◽  
Finite Element Software ◽  
Average Grain Size

Finite element analysis (FEA) of metal microforming processes may require Crystal Plasticity Finite Element (CPFE) formulations to incorporate material inhomogeneity as feature size approaches grain size. Presently, it is unknown if the micropunching process, where holes are formed by shearing thin metal foils with a thickness on the same scale as grain size, can be accurately simulated by using the material’s bulk material properties or if CPFE is required. In the current research, validity of conventional FEA in simulating micropunching is investigated as CPFE formulations have yet to be integrated with most commercially available programs. Using DEFORM finite element software, strain hardening and strain rate hardening material models were employed to approximate flow stress when punching 200 μm diameter holes in 25 μm thick annealed copper foil. For validation of peak punching force, micro holes were fabricated with a nominal diameter of 200 μm for die clearances ranging from 7.6% to 48% of material thickness. The average grain size of the foil was determined to be approximately 47 μm. Therefore, micropunching was predominantly through a single grain across foil thickness and less than a grain in the direction of radial die clearance. Results indicate that the homogeneous material model in DEFORM is capable of predicting the maximum punching forces with reasonable accuracy, concluding that a CPFE model is not necessary for this category of micropunching. Regardless of die clearance, the maximum punching force was approximately 3 N.

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