Torsional Forces Research Articles

Performance Assessment of Stress Concentration Reduction Methods in Mild Steel Transmission Shaft

A shaft is subjected to tensile stress, compressive stress, torsional force and bending moment due to reaction on the components. The stress distribution in a shaft can be is similar to the flow of fluid in a channel. So, it is perfectly logical to use the fluid analogy to understand the phenomenon of stress concentration. When the cross section is uniform the flow is uniform whereas if there is a sudden change in the cross section then the velocity increases to keep the flow rate constant .The same phenomenon is observed in the shaft i.e. when the cross section of the shaft is uniform throughout , the stresses are uniform where as if the cross section changes abruptly then the stress lines come closer to each other in order to keep the force same . When there are sharp changes then it results in stress concentration.The effect of stress concentration can be reduced effectively as there are numerous discontinuities which makes it impossible to eradicate it fully .This could be done by numerous some of which are removal of material , providing fillet radius and also by choosing appropriate material for manufacturing . Software like Solid works can be used for the design and analysis of the component. An object drawn with Solid works can be analysed interactively and physical information can be extracted from it.

Integrated cutting force measurement system based on MEMS sensor for monitoring milling process

In manufacturing process, the stability of cutting state is especially important for processing quality. Monitoring cutting force is a research hotspot for a long time. In this paper, an integrated cutting force measurement system based on piezoresistive MEMS sensor for measuring axial force and torque in milling process is proposed. Based on the thin-walled cylinder and the arch structure, the stress-transforming element of composite splitted structure of conical and cylindrical shell is developed to detect cutting force. The natural frequency of the proposed element has a great improvement in strain sensing sensitivity that can satisfy most cutting situations. A piezoresistive MEMS sensor designed as sensitive component and used in the cutting force measurement system. When the elastic body was sustained cutting force, the piezoresistive MEMS sensors that arranged on the element sense the deformation and output voltage signals to reveal the change of cutting force. In order to verify the basic performance of the cutting force measurement system, static calibration and modal impact tests are carried out. The results indicate that the sensor’s original sensitivity is 2.85 × 10−2 mV/N and 2.90 mV/Nm in axial and torsional directions. Dynamic cutting tests show that the cutting force measurement system can reflect the variation of cutting status very well. It is qualified to monitor the change of axial and torsional forces in practical applications. The cutting test results indicate the measurement system scarcely reduce the workpiece surface quality in machining process.

Mechanical stability study of three techniques used in the fixation of transverse and oblique metaphyseal-diaphyseal junction fractures of the distal humerus in children: a finite element analysis

BackgroundManagement of distal humerus metaphyseal-diaphyseal junction (MDJ) region fractures can be very challenging mainly because of the higher location and characteristics of the fracture lines. Loss of reduction is relatively higher in MDJ fractures treated with classical supracondylar humerus fractures (SHFs) fixation techniques.MethodsThree different fracture patterns including transverse, medial oblique and lateral oblique fractures were computationally simulated in the coronal plane in the distal MDJ region of a pediatric humerus and fixated with Kirschner Wires (K-wires), elastic stable intramedullary nails (ESIN), and lateral external fixation system (EF). Stiffness values in flexion, extension, valgus, varus, internal, and external rotations for each fixation technique were calculated.ResultsIn the transverse fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion, varus, internal, and external rotations, while 3L (3-divergent lateral K-wires) was the most stable in extension and valgus. In the medial oblique fracture model, EF had the best stiffness in flexion, extension, valgus, and varus loadings, while the best stiffness in internal and external rotations was generated by 3MC (2-medial, 1-lateral K-wires). In the lateral oblique fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion and internal and external rotations, while ESIN had the best stiffness in extension and valgus and varus loadings.ConclusionThe best stability against translational forces in lateral oblique, medial oblique, and transverse MDJ fractures would be provided by ESIN, EF, and K-wires, respectively. K-wires are however superior to both ESIN and EF in stabilizing all three fracture types against torsional forces, with both 2-crossed and 3-crossed K-wires having comparable stability. Depending on the fracture pattern, a 3-crossed configuration with either 2-divergent lateral and 1-medial K-wires or 2-medial and 1-lateral K-wires may offer the best stability.

Minimization of Torsional Parameters in Dual Asymmetrical Building through Proper Configuration of Centres

Columns are the core lateral load resisting elements in the buildings which do not have any other forms of resisting components. The sectional dimensions of the columns are often judge based upon the gravitational loading or a combined effect of gravitational and lateral loading on the structure. As per the early research on irregular buildings, they are highly vulnerable for damage when subjected to lateral forces (seismic/wind) when compared to regular shaped buildings, due to the presence of torsional forces. It has also been proved that these torsional forces are generated due to structural eccentricities of the system. The centres of stiffness and strength are predominantly dependent upon the configuration of the lateral load resisting elements. In this study, the effect of proper configuration of column’s dimensions on torsional parameters of irregular buildings is carried out. Non-linear Time History analysis on Plan irregular building with dual asymmetry is performed using scaled acceleragrams and the torsional parameters such are diaphragm’s rotation, torsional irregularity ratio, angular acceleration of the diaphragm are compared with the basic model.

Failure Analysis and Repair of a Broken Extruder Shaft

In this paper a failure analysis of a screw shaft used in a co-rotating intermeshing twin-screw extruder was carried out; furthermore a detailed description for the repair procedure of the fractured part was presented. By means of the preliminary analyses of the failed shaft which includes a visual examination, appearance of fracture face, and photographic documentation of the fractured surfaces, and by summarizing and analyzing all relevant data it was possible to determine that the combination of torsion and bending forces was the cause of the failure. The shaft fractured with evidences of fatigue failure. Repairing of the fractured shaft was mainly performed by welding technique followed by suitable heat treatments and appropriate inspection methods. After repair process is completed, the extruder was put back into service, the recorded data during the trial and regular operations were satisfactory and within the design limits. Finally, in order to avoid future accidents and to prevent such problems in similar equipment, precautionary measures and recommendations were proposed.

Failure Analysis and Repair of a Broken Extruder Shaft

In this paper a failure analysis of a screw shaft used in a co-rotating intermeshing twin-screw extruder was carried out; furthermore a detailed description for the repair procedure of the fractured part was presented. By means of the preliminary analyses of the failed shaft which includes a visual examination, appearance of fracture face, and photographic documentation of the fractured surfaces, and by summarizing and analyzing all relevant data it was possible to determine that the combination of torsion and bending forces was the cause of the failure. The shaft fractured with evidences of fatigue failure. Repairing of the fractured shaft was mainly performed by welding technique followed by suitable heat treatments and appropriate inspection methods. After repair process is completed, the extruder was put back into service, the recorded data during the trial and regular operations were satisfactory and within the design limits. Finally, in order to avoid future accidents and to prevent such problems in similar equipment, precautionary measures and recommendations were proposed.

Lowering the resonance frequency of a two-dimensional high-power piezoelectric energy harvester with reducing the stiffness of the harvester

Generating more power in lower frequencies is one of the most challenging purposes in designing cantilever beam energy harvesters. Using geometrically symmetric two-dimensional beam shapes is one of the most effective ways that has been proposed to increase the output power of harvesters. With symmetry in the geometry, torsional forces on piezoelectric elements eliminate. Consequently, the output power of the harvester increases. However, the resonance frequency of these designed harvesters is still high for some applications. In this work, we demonstrate a strategy to decrease the stiffness of a two-dimensional harvester named Elephant type, without changing in its output power. The output power and the resonance frequency of our proposed harvester are calculated using a finite element simulation. The finite element model is in a good agreement with the analytical and experimental data for the Elephant type harvester. The finite element model predicts lower resonance frequency for our model compared to Elephant type, without a major drop in the output power. Finally, we propose a dimensionless parameter to evaluate the performance of piezoelectric harvesters which have a direct relation with the output power and an inverse relation with the resonance frequency of the harvester.

Span operational aspects under offsetting the axis of the track panel

The stress-strain state of a small railway bridge with a beam design is considered in the article for the case of offsetting the track panel axis relative to the bridge axis by the value exceeding the limit determined by regulatory documents. The differential equation is considered in the analytical calculation of the behavior parameters and the state of the span under the action of the load. This equation describes the vertical vibrations of the beam and allows considering them as a combination of forced and free vibrations. In numerical modeling, the finite element method is used as the solution procedure. Determining equations of the method contain linear and angular displacements of nodes in the model as unknowns. As a result of the calculations, graphical dependences for normal and horizontal displacements, internal forces, principal and equivalent stresses at various points of the span are obtained. Values are presented that show an increase in bending and torsional forces, as well as in principal stresses when the axis of the railway track is displaced relative to the bridge axis.

Torsion Value Assessment of Human Humerus Bone

Human Bones are very important elements of human body. A bone is a rigid and brittle organ that constitutes part of the vertebral skeleton. The skeletal system is subjected to a complex System of loading exerted by the forces of gravity and the muscles attached to the bones. Such loading modes include tensile, compressive, bending, and torsional forces applied to the bones of the skeletal system. The proposed work is aimed to investigate correlation between HU, STRENGTH & BMD of humerus bone and evolution of humerus by torsion testing setup. Model of human humerus bone sample obtained from CT- scan in the form of Hounsfield Units (HU) scale and BMD obtained from Dual-Energy X-ray Absorptiometry (DEXA) scan.

The Rotating Speed Set of Wind Turbine Using the Pendulum as an Angle Blades Control

Abstract: Besides the wind speed, the angle of the blades in the wind turbine can affect the rotational speed of the wind turbine. In order for the blade to adjust the angle of the blade automatically, it needs to be equipped with a pendulum. The focus of this article is the design and testing of wind turbine rotational speed control using a pendulum. The pendulum is positioned at a certain radius to the turbine shaft (X axis) for the sensitivity of the speed sensor and at the blade edge (Y axis) to provide torsional force on the blade. Then designed a wind turbine prototype equipped with a pendulum which is based on the characteristic angular curve when it comes to changes in wind speed. The test results show that controlling the rotational speed using a pendulum at a certain position can work quite effectively even though it cannot provide a completely constant speed.

Game changers in vascular and endovascular surgery

Game changers in vascular and endovascular surgery

PHOTOTUNABLE SELECTIVE REFLECTION OF CHOLESTERIC LIQUID CRYSTALS

The dependence of the helical pitch of a cholesteric liquid crystal based on a composite photosensitive chiral dopant (cChD) on the intensity of light irradiation was studied. The transmission spectra and the selective reflection spectra of cholesteric liquid crystal cells were measured. The concentration of the cChD additive is calculated, so that the peak of selective reflection and its rearrangement occurs in the visible range of the electromagnetic radiation spectrum (380-780 nm). The possibility of photo-control by shifting the peak of the selective reflection of the cChD additive was studied, when exposed to LEDs with wavelengths of 365 nm and 450 nm, while reducing or increasing the intensity, a change in the spiral pitch was observed. Depending on the light intensity, part of the molecules of the chiral additive containing the azo group underwent isomerization, i.e. molecules in the trans-form passed to the cis-form, which led to a spectral shift of the selective reflection peak. If a small intensity of the 365 nm LED was applied, then some of the molecules were forced to transition from the trans- to the cis-form, and then, when illuminated with a 450 nm LED, from the cisto the trans-form. After reversible rearrangement, the properties of cholesteric liquid crystal changes due to interaction with light, because under the influence of light, the equilibrium ratio of the trans- and cis-isomers of the molecules of the substance changed, which macroscopically changed the torsion force of the chiral additive. Using two LEDs of 365 nm and 450 nm with different emission spectra, a reversible control of the cChD selective reflection peak in the visible range was obtained. The maximum displacement occurred at approximately 145 nm.

Seismic Reliability of Concrete Buildings considering Probabilistic Distribution of Crack

One of the effective factors in the analysis of concrete structures is consideration of the effect of cracking on the structural elements, which directly affects the calculation of the natural periods, the story displacement and other response parameters. In different codes for design of concrete structures, cracking effect is considered as a mean and constant coefficient for each element, while clearly the condition of various components will be different based on loading situation and specifications. In this paper, reliability of stiffness reduction coefficients of the beams and columns due to cracking of concrete in the ACI code is investigated under random distribution of floor live loads using Monte Carlo simulation method, By considering 1,000 modelling loops, calculating accurate crack coefficients of beams and columns and applying them in each model, the reliability of cracking coefficients has been obtained. The results show that the reliability index of these coefficients is very low. Also, other results of this modeling and applying accurate cracking coefficients show that the story displacements and the time period of first and second modes decrease about 40–55% and 20–30%, respectively, and the reaction forces of the elements, especially the axial and torsional forces increase about 20–30%.

The anatomic substrate of mitral annular contraction

BackgroundDespite the absence of contractile elements, the mitral annulus undergoes sphincter-like “contraction” resulting in an area reduction of approximately 25%. Its anatomic basis has not, however, been delineated. Since annular contraction helps draw the mitral leaflets into apposition, an appreciation of its anatomic basis could enhance our understanding of the pathogenesis of mitral regurgitation. MethodsGross dissection of >100 bovine, ovine and human hearts as well as histologic examination of 5 ovine hearts was performed to ascertain the origins, course and insertion points of the atrial and ventricular muscle bundles related to the annulus. ResultsSignificant circumferentially-oriented left atrial fibers derived from Bachman's bundle flank the annulus internally. These fibers encircle the base of the atrium and insert into the right fibrous trigone. Externally, the annulus is anatomically related to the superficial obliquely-oriented fibers of the left ventricular inlet which course from the subepicardium to the subendocardium. ConclusionsIntercalation of the annulus between the musculature of the left atrium and left ventricle subjects it to extrinsic contractile forces resulting in sphincter-like narrowing. The circumferential fibers of the left atrial base are favorably positioned such that their contraction imparts a centripetal force onto the inner aspect of the adjacent fibrous annulus which causes it to translate inward in late diastole. During systole, the superficial oblique fibers of the left ventricular inlet, impose a torsional force onto the outer aspect of the annulus causing it to translate inwards. These observations may have mechanistic implications in mitral regurgitation.

The Effect of Skewness on Rotational Response of the Curved Bridge Deck under Near-Fault Motions

Acquiring knowledge on the complex behaviors of bridges in an earthquake is of utmost importance for designing safe transportation systems. Earthquakes like Northridge 1994 showed that skewed angle in the bridge could lead to the failure of abutment and column because of the intensified demand for deck rotation around the vertical axis, especially in the near-fault zone. The present study attempted to examine how the skewed angle change affects the seismic response of curved and skewed bridges. To this end, a software model of two curved and skewed bridges verified through a field test was obtained. The results showed that the skewed angle change in far-fault zones has no significant effect on the seismic responses of these bridges, while in near-fault zones its effect is remarkable. In ramp bridges, the torsional force increases in the columns next to the abutment.

Torsional comparative biomechanical test of modified tibial-plateau-leveling osteotomy plate and locking plate in canine synthetic tíbias

ABSTRACT The objective of this study was to develop a locked tibial-plateau-leveling osteotomy (TPLO) plate and to compare this implant with the conventional bone fixation method using a locked plate to determine bone stabilization against torsion forces. Maximum force, angle at peak torque, and stiffness values were determined. Ten synthetic tibias were used, divided into 2 groups. The results in Group 1 (modified TPLO plate) and Group 2 (locked plate) were assessed using analysis of variance and the means were compared using Tukey’s test at 5% probability. There were significant differences in the angle at peak torque and stiffness. The group Modified TPLO plate had higher mean values of stiffness compared with Group locked plate. Group locked plate showed a greater angle at peak torque compared with Group modified TPLO plate. All constructs failed due to tibial fractures distal to the plate. The modified TPLO plate presented higher stiffness indexes than conventional locked plate in torsion. The locked plate presented greater elasticity than modified TPLO plate having greater angle at the peak of torque.

Energy Absorption Evaluation of CFRP-Strengthened Two-Spans Reinforced Concrete Beams under Pure Torsion

For more than a decade, externally bonded carbon fiber reinforced polymer (CFRP) composites successfully utilized in retrofitting reinforced concrete structural elements. The function of CFRP reinforcement in increasing the ductility of reinforced concrete (RC) beam is essential in such members. Flexural and shear behaviors, ductility, and confinement were the main studied properties that used the CFRP as a strengthening material. However, limited attention has been paid to investigate the energy absorption of torsion strengthening of concrete members, especially two-span concrete beams. Hence, the target of this work is to investigate the effectiveness of CFRP-strengthening technique with regard to energy absorption of two-span RC beams subjected to pure torsion. The experimental program comprises the investigation of two groups; the first group comprises eight un-strengthened beam specimens, while the second group consists of eight strengthened beam specimens tested under torsional forces. The energy absorption capacity measured from the area under the curve of torque-angle of twist for tested beams. Two parameters were studied, the influence of concrete compressive strength and the angle of a twist. Experimental results indicated that all beams wrapped with CFRP sheet display superior torsional energy absorption capacity compared to the control specimens. The energy absorption may consider as a safety index for the torsional capacity of two-span RC beams under service loadings. Therefore, it is possible to avoid structural as well as material damages by understanding the concept of energy absorption that is one of the important experimental findings presented in this study.

Standard plating vs. cortical strut and plating for periprosthetic knee fractures: a multicentre experience.

Aim Periprosthetic fracture after knee arthroplasty occurs more frequently in the supracondylar area of femur, especially after low energy trauma associated with torsional or compressive forces. Several techniques have been described for the treatment of displaced fractures. The aim of this study is the evaluation of the outcomes and bone healing of periprosthetic femoral fractures managed by standard plate fixation compared to plating with bone grafting. Methods Thirty-six periprosthetic fractures around the knee were selected. Eighteen patients underwent standard plate and screws fixation while other eighteen were treated by plating associate with a cortical strut. Knee Society Score (KSS) and Short Form 12 (SF12) with the UNION SCORE (RUS) were used for the evaluation of results. Results After a minimum follow-up of 12 months, the results showed a statistically significant difference in SF-12, KSS, and RUS in favour of plating associated to bone graft with respect to the plating alone; four cases of non-union were recorded in the group of patients treated by standard plating. Conclusions Our experience once again demonstrated that plating and bone grafting may ensure a mechanical and biological support for the healing of periprosthetic fracture of the knee more than simple plating.

Research and Field Application of the Axial-Torsional Coupled Percussion Drilling Technology

Abstract Enhancing the rate of penetration (ROP) is one of the goals pursued by the oil and gas drilling industry. It has been proved that percussion drilling is a feasible method to increase drilling efficiency. However, single percussion drilling technology (axial percussion or torsional percussion) cannot cater to the current needs. This paper proposed a new technology/tool called the axial-torsional coupled percussion drilling, which can use the advantages of the percussion drilling in a better way. Mechanical structure and working principle of this tool were first introduced in detail and the theoretical analysis of the impact force and the impact frequency were then conducted. It was found that both the axial impact force and the torsional impact force are in direct proportion to the fluid density and are in direct proportion to the square of the pump rate. Both the axial impact frequency and the torsional impact frequency are in direct proportion to the pump rate and are in direct proportion to the square root of the fluid density. Subsequently, a laboratory experiment was conducted to verify the above theoretical results. The tools were applied to the oil field in Xin Jiang province, China. Field application results indicate that the penetration rate of the test well is averagely 1.6–3.3 times as fast as that of the adjacent well.

Strength assessment of biomaterial models using selective sintering technology

The article presents an innovative method for the assessment of mechanical properties of biomaterials. 3D models were used for this purpose, obtained by selective laser sintering, designed in various spatial configuration (size of pores, orientation of pores ). The Rotational Bridge test stand was used to carry out the tests, which allowed generating of twisting deformations in the tested materials. The values of the moment of torsion forces transferred by the tested models were analyzed and compared, depending on their spatial structure.