Power Transmission Shaft Research Articles

Determination of Effective Ply-level Properties of Filament Wound Composite Tubes Loaded in Compression

Abstract Flexible matrix composites are a class of fiber-reinforced polymers characterized by a low modulus of elasticity and high ultimate strain of the matrix material. Such composites are attractive for power transmission shafts, which are commonly made via processes that cause undulation (waviness) along the path of the reinforcement fibers, such as filament winding and braiding. Fiber undulations can be expected to reduce the in situ modulus and strength of the composite material in the fiber direction. The reported investigation proposes and evaluates a method for determining the effective in situ properties of the plies in filament wound tubes so that classical lamination theory (CLT) can be used to calculate effective ply-level stresses and to predict the overall modulus and strength of tubes loaded in axial compression. An experimental method is proposed to back-calculate the undulation-influenced ply properties from representative filament wound tubes using CLT together with other required ply properties determined via simpler conventional tests. This approach, along with an interactive failure criterion proposed to predict fiber microbuckling in the presence of combined compression and shear on the fibers, is able to accurately predict the axial compressive modulus and strength of a variety of tubes made with different winding angles and matrix moduli. In general, the fiber-direction compressive strength of the composites increased with increasing matrix modulus and decreased in the presence of undulation. The reduction in strength due to undulation was more apparent with increasing matrix modulus. The fiber-direction modulus of elasticity was not very sensitive to matrix modulus in undulated composites. Undulation reduced the fiber-direction modulus significantly relative to unidirectional composites, although the percent reduction could not be correlated with matrix modulus.

Effects of carburization on expected fatigue life of alloys steel shafts

The motivation of this work is to improve fatigue life of the alloys steel power transmission shafts of the palm oil screw press machines in a Malaysia palm oil company. In order to improve daily productions of the palm oil, a high extraction efficiency of the machine with bigger crushing forces are required. Consequently, the failures due to torsional fatigue would become susceptible to the shafts. The shaft materials of SAAB 709 which has nearest equivalent properties to AISI4140 were then taken for sequential treatments and examinations. Carburizing processes with different combinations of soaking temperatures of 850 °C and 900 °C and soaking times of 2 h and 4 h were carried out. Standard mechanical tests were then conducted for determining the hardness and the ultimate tensile strength of the specimens. Different soaking temperature and time would result in different carburizing depths that in turn influence the fatigue endurance limit under bending torsional loadings.

Methods for the capture of manufacture best practice in product lifecycle management

The capture of manufacturing best practice knowledge in product lifecycle management systems has significant potential to improve the quality of design decisions and minimise manufacturing problems during new product development. However, providing a reusable source of manufacturing best practice is difficult due to the complexity of the viewpoint relationships between products and the manufacturing processes and resources used to produce them. This paper discusses how best to organise manufacturing best practice knowledge, the relationships between elements of this knowledge plus their relationship to product information. The paper also explores the application of UML-2 as a system design tool which can model these relationships and hence support the reuse of system design models over time. The paper identifies a set of part family and feature libraries and, most significantly, the relationships between them, as a means of capturing best practice manufacturing knowledge and illustrates how these can be linked to manufacturing resource models and product information. Design for manufacture and machining best practice views are used in the paper to illustrate the concepts developed. An experimental knowledge based system has been developed and results generated using a power transmission shaft example.

강 봉(SM45C) 맞대기 용접부의 피로수명 평가

SM45C steel rods being used generally for power transmission shafts and machine components was selected and welded by Butt-GMAW(Gas Metal Arc Welding) method. An estimation of fatigue life was studied by constructing S-N curve. Fatigue strength of base metal zone showed higher values than one of weld zone in low cycles between <TEX>$10^4$</TEX> and <TEX>$10^6$</TEX>cycles. However, significant decrease in fatigue strength of base metal was found around <TEX>$10^6$</TEX>cycles, which were almost same as one of heat affected zone. This decrease was attributed that initial residual stress of the steel rods distributed by drawing process was diminished by continually applied load, and resulted in softening of base metal. The fatigue limit of the weld zone was highest in the boundary between deposited metal zone and heat affected zone, and followed by in the order of deposited metal zone, base metal zone, and heat affected zone. Based on these results, it is revealed that the stress for safety design of machine components using SM45C butt-welded steel rods must be selected within the region of the lowest fatigue limit of heat affected zone.

SM45C 환봉 용접재의 피로거동에 관한 실험적 연구

Abstract For this study, SM45C steel rods using generally for power transmission shafts and machine components was selected and welded by butt-GMAW method. And then it was studied about estimation of fatigue strength and the region of infinite life by Haigh diagram using Goodman's equation. Fatigue strength in weld zone presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. This result agrees with distribution of hardness in weld zone. Fatigue strength in base metal zone presents highly compared with weld zone in low cycles between 10  cycles and 10  cycles, but it presents the lowest fatigue strength on the order of heat affected zone in the vicinity of 10  cycles. It is the result that the first high compressive residual stress distributed by drawing process of the steel rods is released and the base metal is softened by alternating stresses. The region of infinite life by Haigh diagram presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. From this results, it is demanded that the stress for safety design of machine components using SM45C butt-welded steel rods must be selected in the region of the lowest infinite life of heat affected zone.

Scroll expander for power generation from a low-grade steam source

This paper addresses the development of a scroll expander for power generation from a relatively low-temperature steam source. It has a double-sided orbiting scroll member so that no thrust bearing is needed to support the base plate of the orbiting scroll. Three power transmission shafts are placed at the periphery of the orbiting scroll base plate, and these shafts can also function as antirotation devices. Power output is obtained from the main central shaft engaged with the three power transmission shafts through gear assembly. From the measurement of the mass flowrate and shaft power output for the scroll expander prototype with the scroll clearance of ɛ ≈ 64 μm, it was observed that the volumetric efficiency was ηv = 42.3–52.1 per centage and total expander efficiency was nearly constant at ηt ≈ 34 per cent over the shaft speed of 1000–1400 r/min. According to the computer simulation, the volumetric and total efficiencies could be improved to 83 and 65 per cent, respectively, by reducing the clearance by half.

Torsional Fatigue Characteristics of Aluminum–Composite Co-Cured Shafts with Axial Compressive Preload

Power transmission shafts such as driving shafts or automotive propeller shafts should transmit static and dynamic torques with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability: composite increases the fundamental bending natural frequency due to its high specific stiffness and metal such as aluminum or steel transmits the required torque. However, fabrication-induced thermal residual stresses due to the coefficient difference of thermal expansion of the composite and the metal are developed during manufacturing hybrid shafts so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this paper, the torsional fatigue characteristics of aluminum–composite co-cure joined shafts with axial compressive preload were investigated. To change the thermal residual stresses, an axial compressive preload was given to the aluminum tube by a compressive jig during the co-cure bonding operation. In order to determine the thermal residual stresses with respect to the preload and temperature difference, stress analyses were performed by simple equations from mechanics of materials and finite element method. Then the static torque capacities and fatigue strengths of the hybrid shafts from static and fatigue torsional tests were correlated with the calculated thermal residual stresses. The fatigue strength of the hybrid shaft was much improved by the axial compressive preload, exceeding that of a pure aluminum shaft. Also, the degradation of the fatigue resistance of the hybrid shaft at subzero operating temperature was overcome by the axial compressive preload.

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Fatigue failure of a hollow power transmission shaft

A micro/hairline crack was noticed on a low speed, hollow shaft of a single stage helical gearbox during service. Though this had not resulted in a catastrophic failure, the shaft was withdrawn from service because of leakage of oil. Subsequent investigation revealed that the crack had initiated by fatigue at one of the keyway edges and progressed about 3/4 of the shaft periphery in a helical manner but had not given rise to final fracture of the shaft. The fatigue crack initiation was due to stress concentration arising from a depression mark at the keyway end surface. The problem was further aggravated due to inadequate radius at the keyway edges and rough machining marks. An analysis of the failure, together with recommendations for failure prevention, is presented in this paper.

Grinding Characteristics of Carbon Fiber Epoxy Composite Hollow Shafts

Since carbon fiber epoxy composite materials have excellent structural properties due to their high specific strength, high modulus, high damping and low thermal expansion, composite hollow shafts have been widely used for power transmission shafts for motor vehicles, spindles for machine tools, and rollers for thin film processing. However, the surfaces of molded composite shafts are not always satisfactory for precise mechanical elements, which often requires turning or grinding of surfaces. The machining characteristics of composite hollow shafts are different from those of conventional metal hollow shafts because composite hollow shafts have anisotropic inhomogeneous material characteristics. In this paper, the grinding characteristics of composite hollow flexible shafts were investigated experimentally and analytically with respect to stacking sequence and stiffness of carbon fiber epoxy hollow composite shafts.

FREE BENDING VIBRATION OF A MULTI-STEP ROTOR

The free bending vibration of a rotating shaft composed of multi-step segments with each segment having a uniform circular cross-section has been analyzed using the Timoshenko beam model. Torque has been applied at each end as in a power-transmission shaft and the gyroscopic effect due to the shaft rotation has also been considered. The separation of time and spatial variables has been performed for the differential equation of motion, and then the spatial solution in a segment of uniform cross-section has been expressed in a closed form. Application of boundary conditions has induced global equations of a rotor system, from which the natural frequencies and corresponding mode shapes have been obtained. The entire procedure is straightforward, and thus the resultant mode shapes are continuous unlike the result of existing methods such as the finite element method and transfer matrix method. Effects of the rotating speed and the applied torque at both ends on the free vibration of the rotating shaft have been discussed. The natural frequencies of the forward and backward modes have been compared with the results using the finite element method. The shear force and bending moment distributions along the shaft at each mode have been derived by differentiating the mode curves.

An optical system for monitoring torsion in a power transmission shaft in realtime

An optical system has been proposed and verified experimentally for monitoring the torsion of a power transmission shaft in realtime. The system consists of a pair of lasers, mirrors and light receivers as a sensor head, and logic circuit, high-frequency oscillator, and computer as a data processing system. The smallest measurable angle of torsion can be expressed by ω/ f, where ω is the rotational frequency of the power transmission shaft and f is the frequency of the oscillator. The experimental error was found to be a few percentage points.

Manufacturing of Co-Cured Composite Aluminum Shafts with Compression during Co-Curing Operation to Reduce Residual Thermal Stresses

Shafts made of carbon fiber composite have higher fundamental bending natural frequency when the stacking angle of fiber is close to zero from the axial direction compared to that of metals such as aluminum and steel, which is an important property for power transmission shafts. However, the small stacking angle not only reduces the torque transmission capability of composite shafts but also makes the joining of composite shafts to other materials difficult. If a shaft is made of both carbon fiber composite and metal such as aluminum, the bending natural frequency as well as the torque transmission capability of the shaft can be increased: the carbon fiber composite increases the bending natural frequency and the aluminum increases the torque transmission capability. In this paper, a hybrid shaft was manufactured by co-curing carbon fiber epoxy composite to an aluminum shaft to increase the bending natural frequency and damping without reducing the torque transmission capability of the shaft. In order to reduce the residual thermal stress at the interface of the two materials, the aluminum shaft was compressed by giving a compressive preload during co-curing operation. From the fatigue test and finite element analysis of the co-cured hybrid shafts, it was found that the compression by a preload increased the torque transmission capability of the hybrid shafts.

An Optical Method for Detecting Torsion in a Power Transmission Shaft in Realtime.

An Optical Method for Detecting Torsion in a Power Transmission Shaft in Realtime.

Optimal Design of Composite Helicopter Power Transmission Shafts with Axially Varying Fiber Layup

Optimal Design of Composite Helicopter Power Transmission Shafts with Axially Varying Fiber Layup

Failures in large gas turbines due to liquid-metal embrittlement

The failures of three gas turbine components, attributed to liquid-metal embrittlement or solid-metal-induced embrittlement, are described. High temperatures inherent in the gas turbine can aggravate these phenomenon if the necessary conditions are present. Examples chosen include a power transmission shaft, flange bolts from a cooling steam line, and a turbine rotor bolt. The respective material couples involved are 17-4PH stainless steel-copper, AISI 4130-cadmium, and IN 718-cadmium. Each case includes information on the source of the aggressive material and relevant operating environment. The implications of the failures with regard to the general failure mechanism are briefly discussed.

Development of the anthropomorphic robot with carbon fiber epoxy composite materials

The material for the robot structure should have high specific stiffness (stiffness/density) to give positional accuracy and fast maneuverability to the robot. Also, the high material damping is beneficial because it can dissipate the structural vibration induced in the robot structure. This cannot be achieved through conventional materials such as steel and aluminum because these two materials have almost the same specific stiffnesses which are not high enough for the robot structure. Moreover, steel and aluminum have low material dampings. Composites which usually consist of very high specific modulus fibers and high damping matrices have both high specific stiffnesses and high material dampings. Therefore, in this work, the forearm of an anthropomorphic robot which has 6 degrees of freedom, 70 N payload and 0·1 mm positional accuracy of the end effector was designed and manufactured with high modulus carbon fiber epoxy composite because the magnitudes of the mass and moment of inertia of the forearm of an anthropomorphic robot are most important due to its farthest position from the robot base. Two power transmission shafts which deliver the power of the motors positioned at the rear of the robot forearm to the wrist and the end effector were also designed and manufactured with high modulus carbon fiber epoxy composite to reduce weight and rotational inertia. The mass reduction of the manufactured composite forearm was 15·9 kg less than the steel forearm. The natural frequencies and damping capacity of the manufactured composite arm were measured by the fast Fourier transform method and compared to those for the steel arm. From the test, it was found that both the fundamental natural frequency and damping ratio of the composite arm of the robot were much higher than those of the steel arm.

Analytical Method of Static Power Transmission for Mechanical Transmission Shaft System with Belt and/or Gear using a Two-Dimensional CAD System.

There are power transmission shaft systems consisting of many belts and gears in automatic teller machines. In these systems, parts may be modeled by two-dimensional structures and may often be drawn by two-dimensional CAD systems. This paper presents an effective transmitted-torque analytical method for the power transmission shaft systems of drive-bill carrying machines. The main results are: (1) The driving-driven relationship of a power transmission system is introduced by a combination of motor, belts, pulleys, gears and shafts. (2) Using this relationship, a tree model is composed which defines the power transmission route. (3) Transmission torque and driving torque are calculated by adding the transmission torque of the lower layer in the tree model. The processing is carried out interactively in a two-dimensional CAD system.

Optimal tubular adhesive-bonded lap joint of the carbon fiber epoxy composite shaft

The effects of adhesive thickness and adherend surface roughness on the fatigue strength of the tubular adhesive-bonded single lap joint were experimentally investigated using small fatigue test specimens (φ21 mm) whose adherends were made of S45C carbon steel. From the fatigue experiments, it was found that the optimal arithmetic surface roughness of the adherends was about 2 μm and the optimal adhesive thickness was about 0·15 mm. Also, the manufacturing method of the adhesive-bonded tubular single lap joint was discussed for the reliable and optimal joint quality. Using the optimal adhesive thickness and the optimal adherend roughness, the prototype torsional adhesive joints for the power transmission shafts (φ66 mm) of an automotive or a small helicopter were manufactured and statically tested under torque. The tests were performed on the single lap joint, the single lap joint with scarf, the double lap joint, and the double lap joint with scarf. The one part of the adherend of the joint was made of high strength carbon fiber epoxy composite material and the other part of the adherend was made of S45C carbon steel. The stresses of joints were analyzed by the finite element method. In applying the finite element method to the composite adherends, the smeared laminate properties were used. From the experiments, it was found that the double lap joint was the best among the joints in terms of torque capacity as well as manufacturing cost.

Computer-Aided Fatigue Design of Power Transmission Shafts Using Three-Dimensional Finite Shaft Element and Updated Mean Stress Diagram

A three-dimensional flexural shaft element is developed for elastic analyses of power transmission shafts and geared systems. It is used for the computer-aided fatigue design of three-dimensionally loaded power transmission shafts on many rigid or elastic bearings. Bagci’s mean stress diagram—which removes the flaw related to the load line slope of zero value in the presently used mean stress theories—is used to determine the failure value of the reduced fatigue strength of the shaft at the critical sections considered. Basic stresses are defined using maximum energy of distortion theory. An interactive computer program is prepared for fatigue design of power transmission shafts, in which some of the strength reducing factors for each notch location are determined using generalized expressions. The program initially locates the weakest section on the shaft, then it redefines the dimensions for the desired factor of safety, reliability and the fatigue life at that section. An application example is included.