Screw Blade Research Articles

Evaluation of Dynamic Hip Screw Blade in Extracapsular Fracture Neck of Femur in the Elderly

Evaluation of Dynamic Hip Screw Blade in Extracapsular Fracture Neck of Femur in the Elderly

Improvement of Hole Drilling in High-Strength Polymer Laminate

When the end section of helicopter screw blades made of polymer laminate based on glass–carbon fiber and reinforced by titanium foil is drilled, peeling is noted at the entrance to the hole. Such peeling is investigated in the present work. The influence of the cutting speed and supply on the extent of the peeling is established.

Internal fixation with proximal femoral nail anti-rotation for intertrochanteric fracture involving lateral wall: a finite element analysis

Objective To study the biomechanical performance of proximal femoral nailing anti- rotation (PFNA) in the treatment of femoral intertrochanteric fracture involving the lateral wall using finite element analysis and the significance of the lateral wall. Methods A healthy senior volunteer, male, 80 years of age, was recruited for this study.The CT data of his proximal femur were used to establish a three-dimensional finite element model of proximal femur by software Mimics17.0 and Geomagic Stusio. After the intertrochanteric fracture of AO-type 31-A1.2 was simulated together with coronal displacement of the lateral wall fracture, it was assembled with PFNA into the three-dimensional finite element model. Finite element analysis was performed on the femoral head, neck, fracture ends, lateral wall, and internal components of the model to observe the stress values of various parts of the model under the same load, with different degrees of fracture reduction (no displacement, anterior displacement of 5%, 10%, 15% and 20%, posterior displacement of 5%, 10%, 15% and 20%) and with or without the lateral wall. Results The stress values for internal components at the femoral head, neck, fracture ends, main nail with anatomical reduction of fracture ends and integrity of the lateral wall were 0.40 MPa, 30.05 MPa, 74.35 MPa and 121.68 MPa, respectively. The respective stress values of the above with lateral wall fracture were 0.82 MPa, 47.32 MPa, 151.92 MPa and 266.88 MPa, increased by about 100%. With every horizontal reduction loss increased by 5% forward or backward, the stress exerting on the corresponding spots would see a 10% progressive growth, plus 20% lateral wall fracture and reduction loss. The stress of the main nail (468.43 MPa) was thrice that (121.68 MPa) of the stress posing on the complete lateral wall with the fracture ends 100% reduced. Conclusions When PFNA is used in the treatment of femoral intertrochanteric fractures involving the lateral wall, stresses on the internal components may be doubled. Loss of coronal reduction may lead to the most significant increase in stress on the bonding site between the main nail and screw blade. Key words: Hip fractures; Fracture fixation, intramedullary; Bone nails; Finite element analysis; Lateral wall

The simulations of helical blade interaction with ice

This paper presents the methodology for determination of the parameters of interaction between a rotary-screw vehicle and ice surface. The key parameter is the value of ice cutting force by means of a screw blade. The methodology allowed to obtain results, showing that the value of the cutting force depends on shape of the helical blade. Developed model of the cutting force allowed to conclude that that the width of the cut exerts the greatest influence on the cutting force, but depth and speed of the cutting have the less influence. Analysis of the study results provides the opportunity to find rational geometric parameters of the helical blade. The methodology can be applied for rotary-screw all-terrain vehicles designing.

A meta-analysis of integrated compression screw compared to single screw nails using a single lag screw or single helical blade screw for intertrochanteric hip fractures

A meta-analysis of integrated compression screw compared to single screw nails using a single lag screw or single helical blade screw for intertrochanteric hip fractures

Application of 3D printing rapid prototyping-assisted percutaneous fixation in the treatment of intertrochanteric fracture.

The aim of the present study was to investigate the application of 3D printing (3DP) rapid prototyping (RP) technique-assisted percutaneous fixation in the treatment of femoral intertrochanteric fracture (ITF) using proximal femoral nail anti-rotation (PFNA). A total of 39 patients with unstable ITF were included in the current study. Patients were divided into two groups: 19 patients were examined using computed tomography scanning and underwent PFNA with SDP-RP whereas the other 20 patients underwent conventional PFNA treatment. Anatomical data were converted from the Digital Imaging and Communications in Medicine format to the stereolithography format using M3D software. The 3DP-RP model was established using the fused deposition modeling technique and the length and diameter of the main screw blade was measured during the simulation. The postoperative femoral neck-shaft angle (NSA), surgery duration, intraoperative and postoperative blood loss, and the duration of hospital stay were recorded and compared with the corresponding values in conventional surgery. No significant differences were observed in mean PFNA size between the implants used and the preoperative planning estimates. It was demonstrated that the 3DP-RP assisted procedure resulted in more effective reduction of the NSA. Furthermore, patients undergoing 3DP-RP experienced a significant reduction in duration of surgery (P<0.01), as well as reductions in intraoperative (P=0.02) and postoperative (P=0.03) blood loss, compared with conventional surgery. At 6 months post-surgery, no cases of hip varus/vague deformities or implant failure were observed in patients that underwent either the 3DP-RP-assisted or conventional procedure. The results of the present study suggest that the 3DP-RP technique is able to create an accurate model of the ITF, which facilitates surgical planning and fracture reduction, thus improving the efficiency of PFNA surgery for ITFs.

Experimental Study of Screw Turbine Performance based on Different Angle of Inclination

Abstract Potential energy from fluid flow of small rivers or irrigations could be extracted become electricity by using screw turbine. This turbine is promising because the advantages of ultra-low head and fish friendly.Experimental performance of screw turbine for ultra-low head hydro resource is presented in this paper. The screw turbine with anoutside diameter of 142 mm and the water flowrate of 1.2 l/s with the head of 0.25 m, can produce maximum power 1.4 W with 49% efficiency at 22 o angle of inclination. This turbine has one blade screw and screw turbine experiment apparatus is made by using locally available materials. The screw turbine has shown good potential to be used for low head micro hydro-electric installations. This paper reports on a performance analysis based on the experimental data collected from different performance tests carried out on some inclination angle position of screw turbine prototype.

Measurement of Tip Apex Distance and Migration of Lag Screws and Novel Blade Screw Used for the Fixation of Intertrochanteric Fractures.

Fixation with a dynamic hip screw (DHS) is one of the most common methods for stabilizing intertrochanteric fractures, except for unstable and reverse oblique fracture types. However, failure is often observed in osteoporotic patients whereby the lag screw effectively ‘cuts out’ through the weak bone. Novel anti-migration blades have been developed to be used in combination with a lag screw (‘Blade Screw’) to improve the fixation strength in osteoporotic intertrochanteric fractures. An in-vitro biomechanical study and a retrospective clinical study were performed to evaluate lag screw migration when using the novel Blade Screw and a traditional threaded DHS. The biomechanical study showed both the Blade Screw and DHS displayed excessive migration (≥10 mm) before reaching 20,000 loading cycles in mild osteoporotic bone, but overall migration of the Blade Screw was significantly less (p ≤ 0.03). Among the patients implanted with a Blade Screw in the clinical study, there was no significant variation in screw migration at 3-months follow-up (P = 0.12). However, the patient’s implanted with a DHS did display significantly greater migration (P<0.001) than those implanted with the Blade Screw. In conclusion, the Blade Screw stabilizes the bone fragments during dynamic loading so as to provide significantly greater resistance to screw migration in patients with mild osteoporosis.

Fatigue Life Assessment of Screw Blades in Screw Sand Washing Machine under Extreme Load

The aim of this study is to estimate the fatigue life of the screw blades in the screw sand washing machine under the extreme load (i.e., the load caused by the full load condition). Firstly, the extreme load is taken into consideration in the fatigue life assessment of screw blades by means of the finite element analysis (FEA). Next, the P-S-N curve is fitted by the fully reversed rotating bending testing on standard specimens and theory deduction. Then, s are generated according to the maximum and minimum stresses of the root of screw blades under different thicknesses. Finally, the service life of screw blades is assessed based on the P-S-N curve, s, and Soderberg mean stress correction method. In particular, the effects of the surface finish factor, fatigue notch factor, and residual stress on the fatigue life of screw blades are considered. The results show that the stress concentration is at the root of screw blades; the screw blades with the thickness of 10 mm, whose service life is around 35 years, are the optimum in terms of the screw sand washing machine proposed in this study; the safety factor of screw blades should be 2, considering the influence of the fatigue load.

Comparison of clinical effect betweem reconstructing femoral calcar and proximal femoral antirotation nail for the treatment of unstable femoral intertrochanteric fracture in elderly patients

To compare the clinical effects of two methods of internal fixation in treating unstable femoral intertrochanteric fractures in elderly patients. From August 2009 to August 2014, 68 elderly patients with unstable femoral intertrochanteric fracture treated with locking proximal femur plate and auxiliary short reconstructed plate (reconstructing calcar group) and proximal femoral nail antirotation (PFNA group) with clinical course from 1 to 3 days were retrospectively analyzed. In reconstructing calcar group, there were 30 patients including 8 males and 22 females, aged from 63 to 85 years old with an average of (73.41±5.12) years old, the fractures were classified to type AO 31-A2.2 in 12 cases, A2.3 in 11 cases, A3.3 in 7 cases according to AO/ASIF classification. In PFNA group, there were 38 patients including 10 males and 28 females, aged from 65 to 90 years old with an average of (74.26±4.53) years old, the fractures were classified to type AO 31-A2.2 in 15 cases, A2.3 in 13 cases, A3.3 in 10 cases. All fracture were caused by injury, leading pain and swelling. Femoral intertrochanteric fracture was confirmed by X ray films. The data of each group were collected for statistical analysis on the following aspects: the incision length, operation time, blood loss volume, postoperative partial weight bearing standing time, clinical healing time of fracture, postoperative complications, and hip functional score of Harris. All incisions were healed at stage I. In the aspect of postoperative complications, there were 1 case of screw blade cutting and 1 case of deep venous thrombosis in PFNA group; there was 1 case of deep venous thrombosis in the reconstructing calcar group (χ²=0.000, P=1.000). Patients were followed up from 20 to 24 months with an average of 22.5 months. There were no significant in postoperative partial weight bearing standing time, postoperative complications, hip functional score of Harris between two group. There were significant in the incision length, operation time, blood loss volume, clinical healing time of fracture. In the incision length, operation time, blood loss volume, clinical healing time of fracture, the PFNA group was significantly differently less than that of the reconstructing calcar group (P<0.001). In the clinical healing time of fracture, the PFNA group was significantly differently less than that of the reconstructing calcar group (P<0.05). For the treatment of unstable femoral intertrochanteric fractures in elderly patients, reconstructing calcar and PFNA are both effective, and proximal femoral intramedullary nails may be the best choice, which can be simpler operation, smaller incision and less healing time.

Comparison of Second and Third Generation of Nails in the Treatment of Intertrochanteric Fracture: Screw versus Helical Blade

Comparison of Second and Third Generation of Nails in the Treatment of Intertrochanteric Fracture: Screw versus Helical Blade

Performance improvement of a falling-film-type heat exchanger by insertion of shafts with screw blade in a heat exchanger tube

Highly-efficient heat exchange is expected for the falling-film-type heat exchanger handled in this study by utilizing a falling liquid film, etc. The heat medium is flowed inside the heat exchanger tube. In contrast, the falling film is flowed outside the heat exchanger tube, thereby exchanging heat. In the previous study, considering the basic heat transfer characteristic of the falling-film-type heat exchanger, the design equation was developed in the limited extent. In this study, focusing on the flow condition in a heat exchanger tube of the falling-film-type heat exchanger, various shafts with screw blade were inserted in a single heat exchanger tube and it was evaluated how the pitch and height of screw and the flow rate of cooling water would give an effect on the heat exchange performance. Additionally, the heat transfer coefficient and the overall heat transfer coefficient of the falling-film-type heat exchanger were logically calculated, and then a theoretical value and an experimental value were compared and evaluated. As a result, it was clarified that the heat exchange performance of the falling-film-type heat exchanger was improved by inserting the shaft with screw blade, and theoretical and experimental values were roughly matched.

Fatigue Life Prediction of Screw Blade in Screw Sand Washing Machine under Random Load with Gauss Distribution

The purpose of this study is to present a new method for estimating the fatigue life of the screw blade in the screw sand washing machine. To ensure the accuracy of numerical simulation, the loading area and the value of load are determined by means of the theoretical analysis. To ascertain the location of the stress peak and stress range, the static analysis of the screw blade is executed via the finite element method. To reduce the research cost and ensure the feasibility of the research method, Markov chain Monte Carlo (MCMC) is employed to simulate the random load with the Gauss distribution on the screw blade. In addition, the Nondominated Sorting Genetic Algorithm (NSGA-II) is utilized to find out an optimum variation coefficient of the stress, aiming at guaranteeing the precision of the random load. The rainflow cycle extrapolation is adopted to generate the fatigue load spectrum closer to the real condition, taking account of the possibility of the extreme loads caused by overload occurrence. Subsequently, the rainflow matrix after extrapolation, the estimated P-S-N curve, Goodman stress correction method and Miner's rules are made use of assessing the service life of the screw blade. In particular, the effects of the surface roughness, residual stresses and fatigue notch factors on the fatigue life are taken into consideration. Ultimately, the non-linear surface fitting technique is used to obtain the equation concerning the fatigue life of the screw blade versus residual stresses and fatigue notch factors. The numerical results show that the stress peak is in the root of the screw blade and the service life of the screw blade declines exponentially with growing residual stresses and fatigue notch factors.

Numerical studies on the heat transfer and friction characteristics of the first wall inserted with the screw blade for water cooled ceramic breeder blanket of CFETR

The Water Cooled Ceramic Breeder (WCCB) blanket based on Pressurized Water Reactor (PWR) condition is one of the blanket candidates for Chinese Fusion Engineering Test Reactor (CFETR). The first wall (FW) which plays an important part in the blanket design must remove the high heat flux radiated from plasma and nuclear heat deposition on the structure in any operating conditions. In this paper, the characteristics of enhanced heat transfer and friction for the FW with the inserted screw blade are studied by the numerical method. After the comparison between the numerical and experimental results, the standard k–ε turbulent model is selected to do the numerical calculation. The numerical results show that the peak temperature of RAFM steel could be reduced by decreasing screw pitch or increasing screw diameter, while accompanied with ascending flow resistance. Besides, among all of the chosen calculation cases compared with the smooth channel, the maximum value of temperature reduction is 10°C under the conditions of heat flux of 0.5MW/m2 as well as screw pitch of 18mm and screw diameter of 6mm. The maximum increment ratio of the friction factor is 257% under the conditions of screw pitch of 10mm and screw diameter of 4mm. Furthermore, screw blade of 74mm pitch and 4mm diameter presents the highest overall performance evaluation criterion (PEC) value of 0.93 under Reynolds number of 270 000 conditions, and shows the best overall heat transfer enhancement performance.

Modified screw conveyor-mixers – Discrete element modeling approach

Screw conveyors are widely used in the food industry, building construction and mining companies, chemical, agricultural and processing industries, mostly for elevating and/or transporting bulk materials over short to medium distances. Despite their apparent simplicity, the improvement of the transport parameters is a very demanding task and designers usually have to rely on data obtained from empirical investigations.In this paper, fifteen horizontal single-pitch screw conveyors with modified geometry and the different lengths were investigated for premixing action, during the transport of materials. All investigations were performed experimentally and numerically, by using Discrete Element Method (DEM).The influences of screw length, observed geometry variations and different types of screw design, on the performances of the screw conveyor-mixer during material transport were explored. The auxiliary mixing action (used to improve the mixing process) was achieved during the transport of the material. The geometry of the screw conveyor is changed by adding three complementary helices oriented in the same or the opposite direction from screw blades. The particles of the material being transported tumble down from the top of the helix to the next free surface, and that segment of helix was used for additional mixing action. According to experiments and DEM analysis, the particle path length is increased, with the observed modification of screw conveyor, and the improved geometry could be determined for increasing the quality of mixing.

Rotational Efficiency of Photo-Driven Archimedes Screws for Micropumps

In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated in our previous studies. In this paper, the blade thickness and the central rod of the screw were further investigated. The experimental results indicate that the blade thickness contributes to rotational stability, but not to rotational speed, and that the central rod stabilizes the rotating screw but is not conducive to rotational speed. Finally, the effect of the numerical aperture (NA) of the optical tweezers was investigated through a demonstration. The NA is inversely proportional to the rotational speed.

Characterizing Effects of the Shape of Screw Conveyors in Gas–Solid Fluidized Beds Using Advanced Numerical Models

A numerical study of the effects of the shape of an enclosed screw conveyor on the mixing and heat transfer in a horizontal gas–solid fluidized bed was conducted using computational fluid dynamics (CFD). A two-fluid model (TFM) was employed to model the gas and solid phases as continua through mass, momentum, and energy conservations. The motion of the screw conveyor was simulated by using a rotating reference frame (RRF) such that the computational mesh was free from dynamic reconstruction. The diameters of the screw flight and shaft, the pitch, and the blade thickness were varied in the parametric study. Under the operating conditions studied, it was found that the increase in the diameter of the screw flight results in the enhancement of the solid mixing and conveyance. The increase in the diameters of the screw shaft and the screw blade thickness lead to the enhanced solid mixing but reduced conveyance. The variation in the screw pitch gives rise to rather complex behaviors in the solid mixing and conveyance. As the screw pitch is decreased, the solid mixing increases initially but then decreases before it increases eventually. The solid conveyance capability was found to first increase and then decrease. Explanations to the effects of the shape of the screw conveyor were discussed in this work.

Advances and Recent Patents about Cracking Walnut and Fetching Kernel Device

In recent years, many patents have been devoted to develop the walnut mechanical cracking and kernel fetching, kernel shell separation and walnut classification techniques that can significantly improve the walnut shell cracking rate and decrease the walnut kernel breaking rate. However, those machines adjust poorly to different sizes of walnuts, requiring size grading by human with high kernel breaking rate, low efficiency. This paper analyzes the patent on new walnut cracking, kernel fetching and shell kernel separation equipment in recent years. Based on the sphere walnut models and the advantages of variety of walnut shell machine, the walnut shearing, pressing and cracking device is designed by the author. Different sizes of walnuts are adjusted to these machines, including the conveyor belt shear extrusion flexible shell system, flexible blade hammer kernel fetching system and the air-flexible screw blade coupling walnut kernel shell roller two-way separation system, realizing the function of walnut crashing, kernel fetching and shell kernel separation, with the walnut shell cracking rate being 98%, the kernel breaking rate 2.9% and the kernel revealing rate 70%, improving the walnut shell cracking rate and reducing the kernel breaking rate. Keywords: Air-flexible screw blade, cracking the shell, flexible blade hammer, roller two-way separation, walnut, walnut classification screening.

Discrete element modelling of screw conveyor-mixers

Screw conveyors are used extensively in food, plastics, mineral processing, agriculture and processing industries for elevating and/or transporting bulk materials over short to medium distances. Despite their apparent simplicity in design, the transportation action is very complex for design and constructors have tended to rely heavily on empirical performance data. Screw conveyor performance is affected by its operating conditions (such as: the rotational speed of the screw, the inclination of the screw conveyor, and its volumetric fill level). In this paper, horizontal, several single-pitch screw conveyors with some geometry variations in screw blade was investigated for mixing action during transport, using Discrete Element Method (DEM). The influence of geometry modifications on the performance of screw conveyor was examined, different screw designs were compared, and the effects of geometrical variations on mixing performances during transport were explored. During the transport, the particle tumbles down from the top of the helix to the next free surface and that segment of the path was used for auxiliary mixing action. The particle path is dramatically increased with the addition of three complementary helices oriented in the same direction as screw blades (1458.2 mm compared to 397.6 mm in case of single flight screw conveyor) Transport route enlarges to 1764.4 mm, when installing helices oriented in the opposite direction from screw blades. By addition of straight line blade to single flight screw conveyor, the longest particle path is being reached: 2061.6 mm

Specific features of the simulation of propeller operation іn free water in the Flow Vision environment

The need of carrying out numerical experiments has been discussed when studying the operation of designed screw propellers in free water. It will allow reducing the number of model experiments, the costs and the design terms. The influence of geometrical and hydrodynamic characteristics of the screw propeller on its efficiency is discussed. The aim of the studies is to determine experimentally the time step (the integration step over the time of the equations of the convective and diffusive transfer), which would correspond to the best convergence of the calculation of the screw propeller in free water in the CFD–package Flow Vision environment. The influence of the set time step on the results of the calculation of the hydrodynamics of the three–blade screw propeller is experimentally studied. The ratio of the optimum size of the time step and various flow rates is determined. The correctly set time step allows modeling a problem in an optimum time period with the acceptable convergence of the calculation.