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Fused deposition modeling has provided a cheap and effective method for the rapid production of prototypes and functional products in many spheres of life. In this study, three-dimensional (3D) pri...

Determining the efficacy of hip protectors designed to reduce the menace of the alarming rise in hip fracture due to fall among the elderly population is particularly challenging. Hip protector evaluation has been done using different soft tissue surrogate and at different energy level to determine the effectiveness of various hip protectors. However, some hip protectors that had been ranked effective in mechanical testing systems proof otherwise when deployed for clinical trials, this may be due to lack of optimization of the testing condition, most notably in testing when the soft tissue surrogate attenuates impacts that may be unduly attributed to the effectiveness of the hip protector. In this study, the performance of a surrogate soft tissue, fabricated from polyethylene, was evaluated at different energy levels (3.68 J – 37.9 J) to ascertain the optimal position for evaluating the efficacy of a hip protector to simulate a representative condition of an actual fall to the sideways by a person. A drop-weight impact testing machine was used to evaluate the impact force response of an employed femoral geometry with and without the soft tissue at various residual impact energy. The result showed that the soft tissue might be responsible for up to about 95.17 % of peak impact force attenuation if not adequately modelled. Therefore various conditions were examined to get representative sideways impact condition where the soft tissue employed do not attenuate beyond 11 - 28 % of the peak impact force. This finding demonstrates that the impact condition is as critical as all other parameters in determining the performance of a hip protector.

There have been different types of simplified femoral geometry incorporated into test systems for testing the biomechanical effectiveness of hip protectors. However, the effect of the simplification of femoral geometry in simulated sideways impact experiment has not been reported. In this study, an actual femoral geometry was fabricated and examined along with a simplified femoral geometry in a surrogate hip arrangement to mimic the fracture-causing situation in a sideways fall. A pendulum impact testing machine was used to evaluate the impact force response of both the femoral geometries at various velocity and constant residual impact energy for both geometries. The result showed that the peak impact force varied only 9% between actual and simplified geometries after normalizing the weight for both femurs in testing without a hip protector. However, a higher distinction of the impact force responses of both femurs was observed when testing with a hip protector. This findings at this moment suggest that the femur geometry affects the performance of a testing system. Therefore, the simplified femur geometry may not accurately substitute for the actual femur geometry in comparison of the impact attenuation of a hip protector in a simulated sideways fall.

Proximal femoral fractures can be categorized into two main types: Neck and intertrochanteric fractures accounting for 53% and 43% of all proximal femoral fractures, respectively. The possibility to predict the type of fracture a specific patient is predisposed to would allow drug and exercise therapies, hip protector design, and prophylactic surgery to be better targeted for this patient rendering fracture preventing strategies more effective. This study hypothesized that the type of fracture is closely related to the patient-specific femoral structure and predictable by finite element (FE) methods. Fourteen femora were DXA scanned, CT scanned, and mechanically tested to fracture. FE-predicted fracture patterns were compared to experimentally observed fracture patterns. Measurements of strain patterns to explain neck and intertrochanteric fracture patterns were performed using a digital volume correlation (DVC) technique and compared to FE-predicted strains and experimentally observed fracture patterns. Although loaded identically, the femora exhibited different fracture types (six neck and eight intertrochanteric fractures). CT-based FE models matched the experimental observations well (86%) demonstrating that the fracture type can be predicted. DVC-measured and FE-predicted strains showed obvious consistency. Neither DXA-based BMD nor any morphologic characteristics such as neck diameter, femoral neck length, or neck shaft angle were associated with fracture type. In conclusion, patient-specific femoral structure correlates with fracture type and FE analyses were able to predict these fracture types. Also, the demonstration of FE and DVC as metrics of the strains in bones may be of substantial clinical value, informing treatment strategies and device selection and design.

Traditional rigid-body mechanisms consist of a number of components to implement their functions. Therefore they face problems such as backlash, wear, increase in part-count, weight, assembly cost and time, regular maintenance. Reducing these problems will help in increasing mechanism performance and cost reduction. Recently, there are several examples of compliant mechanisms that have been designed and widely used in various fields such as for adaptive structures, biomedical, hand-held tools, components in transportations, MEMS and robotics. However, the largest challenge was relative difficulty in analyzing and designing compliant mechanisms. Two approaches known in the literature for the systematic synthesis of compliant mechanisms are the kinematics-based approach and the structural optimisation based approach.

The main goal of this work is to investigate the performance of zirconia toughened alumina (ZTA) and ZTA reinforced with magnesium oxide (MgO) used as cutting insert in end milling of AISI 1018 steel with hardness of 27 HRC. Performances of the cutting insert were compared according to tool life and surface finish of workpiece. Insert flank wear that indicates tool life was studied carefully using Optical 3D Surface Metrology. Surface roughness values were evaluated using Surftest Sufrcom 130A. Both of the cutting inserts failed to exhibit good performance in end milling operation. However, wear condition and magnitude of the ZTA reinforced with MgO insert was slightly better than ZTA insert. Addition of MgO may increase wear resistance.

Urinary catheter has been widely used as a solution for urinary incontinence problem. But it can induce pressure stress at the human bladder neck. However, owing to the complexities in balloon geometries, material properties and interactions in bladder, analyses of the complete stress inflation of balloon are limited. This study describes some numerical simulations of the expansion phase of catheter balloon on bladder and to study the stress distribution at the balloon. In order to investigate the mechanical characteristics of inflation catheter balloon, a three-dimensional model of the complete catheter balloon were developed, which made the simulation well close to the real situation. Finite element analysis (FEA) ABAQUS 6.4-PR11 was used to simulate the balloon inflation and deflation. The hyperelastic behavior of the Mooney-Rivlin model is considered. Mechanical properties of the balloon have been taken from the literature. Simulated results showed that the stress distributed on the surface of the balloon. The maximum Von Mises stress for natural rubber from the analysis is 5.11 MPa. High stress concentrates on the center of it. In conclusion, FEM can help illustrate and quantify some mechanical characteristics of the balloon and it would be helpful for the general understanding of inflation of urinary catheter balloon.