Foreign objects impact damage characteristics of aluminum/composite hybrid drive shaft

In this work, the low velocity impact damage characteristics of aluminum/composite hybrid drive shaft were investigated. The hybrid drive shaft was manufactured by stacking carbon epoxy composite prepregs and insulating layer for galvanic corrosion on the inner surface of an aluminum tube, and co-curing them in an autoclave under recommended cure cycle. After impacting the co-cured hybrid drive shafts using a drop-weight impact tester, the damage and delamination of the composite layers were observed with an ultrasonic C-scan, from which the damage modes of aluminum/composite hybrid shaft were found with respect to the stacking sequence of composite materials, the thickness of the aluminum tube and the impact energy. Finally, optimal stacking sequence of the composite material and optimal thickness of the aluminum tube for the drive shaft for low velocity impact were suggested.     

Uncertainty analysis and optimization of automotive driveline torsional vibration with a driveline and rear axle coupled model

The driveline torsional vibration issue is one of the most significant Noise, Vibration and Harshness (NVH) problems, especially in rear-wheel drive vehicles with manual transmission. In this article, a new driveline and rear axle coupled torsional vibration model (DRCTVM) is developed that considers the relationship between the driveline and the rear axle. The experiments show that the DRCTVM can provide much better results than the traditional model. In addition, for the first time, uncertainty theory is introduced to the analysis and optimization of driveline torsional vibration based on the DRCTVM. A truncated normal distribution is used to describe the uncertainty of DRCTVM, which considers both the probability distribution and the bounds of uncertain variables. Furthermore, robustness of the driveline torsional vibration was analysed using the Monte Carlo (MC) process and optimized using the Multi-Island Genetic Algorithm. The optimization results show that the proposed model and method are effective and improve the robustness of driveline torsional vibration performance.     

Study on Forced Torsional Vibration of CFRP Drive-Line System with Internal Damping

The use of CFRP transmission shaft has positive effect on the weight and flexural vibration reduction of drive-line system. However, the application of CFRP transmission shaft will greatly reduce the torsional stiffness of the drive-line, and may cause strong transient torsional vibration. Which will seriously affect the performance of CFRP drive-line. In this study, the forced torsional vibration of the CFRP drive-line system is carried out using the lumped parameter model. In addition, the effect of rotary inertia, internal damping, coupling due to the composite laminate, and excitation torque are incorporated in the modified transfer matrix model (TMM). Then, the modified TMM is used to predict the torsional frequency and forced torsional vibration of a CFRP drive-line with three-segment drive shafts. The results of modified TMM shown that the rotational speed difference of the CFRP transmission shaft segment is much larger than metal transmission shaft segment under excitation torque. And compared the results from finite element simulation, modified TMM and torsional vibration experiment respectively, and it has shown that the modified TMM can accurately predict forced torsional vibration behaviors of the CFRP drive-line system.     

Effect of torsional strain-rate and lay-up sequences on the performance of hybrid composite shafts

In this study, the torsional behavior of hybrid composite shafts was examined by a combined experimental and numerical approach. Glass and carbon fiber reinforced hybrid shafts with three lay-up sequences were manufactured using filament winding technique. All three shafts had same amount of glass and carbon fiber. Angular velocities of 0.1°/min and 5°/min were used as torsion test speeds. The effect of torsional strain-rate and lay-up sequences on the response of hybrid shafts was studied. Torque–twisting angle changes were recorded. Test results revealed that changing angular velocities did not affect the torsional behavior of composite shafts significantly. However, three different lay-up sequences resulted in remarkably different torsional behavior.Torsional behavior of composite shafts was simulated using Finite Element (FE) software, Abaqus. The elastic orthotropic composite model was used for simulations. FE models were validated using experimental test results. Numerically and experimentally obtained results exhibited quite similar torsional behavior.     

Effect of stacking sequence on the torsional stiffness of the composite drive shaft

Torsional stiffness is an important parameter judging the performance of composite drive shaft. In this paper, a new mechanical analytical solution of torsional stiffness for the composite drive shaft with balance laminate is derived based on classical lamination theory and mechanical analysis. Finite element analysis (FEA) has been used to calculate the torsional stiffness of carbon fiber-reinforced plastic (CFRP) drive shaft. A torsion test platform has also been constructed to measure the torsional stiffness of CFRP drive shaft specimens. Results of the mechanical analytical solution, FEA, and experiments show that the composite tube with the location of ±45° layers near to the outer surface is larger than the ones with the location of ±45° layers near to the inner surface. The effect of stacking sequence on torsional stiffness is larger in the thick-walled than that in the thin-walled composite drive shaft. The mechanical analytical solution can complement classical lamination theory which cannot reflect the effect of stacking sequence in calculating the torsional stiffness.     

Torsion response of a cracked stainless steel shaft

Pump shafts used for power generation are susceptible to fatigue cracking while often in near-continuous operation. Technology based on torsional vibration is under development for condition-based assessment of shaft health. The focus of this paper is on the relationship between a crack, which propagated due to bending loads, and the torsional stiffness of the shaft. An analytical method to determine the compliance associated with a crack has been implemented for a semi-elliptical surface crack. A 3-D finite element model of a shaft section with a crack has also been used to predict the effect of a crack on stiffness. Fatigue cracks were seeded in shafts on a three-point bend apparatus. A benchtop test rig was constructed to evaluate the torsional natural frequencies of a cracked shaft system. Quasistatic torsional stiffness tests indicated that crack closure has an effect on the results. A torsional finite element model of the benchtop test rig indicates that the first torsional natural frequency is reduced by the propagation of a crack. The reduction in torsional stiffness of the shaft inferred from the natural frequency results is in reasonable agreement with the quasistatic results and the model predictions.     

后驱车动力传动系扭振分析

研究后驱车辆动力传动系扭转振动分析方法,根据实际工程问题,建立合适的仿真模型,计算传动系扭振模态频率,并与测试结果进行对比,验证该方法和仿真模型的正确性;在此基础上,分析了动系各部件对扭振模态的灵敏度,以便项目前期根据目标对扭振模态进行控制。本研究提供了一套有效的传动系扭振的分析方法,并取得良好的工程应用效果。     

汽车传动系扭振引起的车内轰鸣声控制方法

某前置后驱微型客车存在低转速车内轰鸣声的问题,研究表明该轰鸣声由传动系扭振引起。首先对传动系扭振影响车内噪声的机理进行分析,在此基础上建立传动系扭振当量系统模型并进行自由振动计算。同时建立对象车型发动机仿真模型,从而获取发动机激振力矩,完成受迫振动计算。然后开展传动系扭振测试,并将自由振动及受迫振动计算结果与试验数据进行对比,验证了模型的有效性。然后利用此模型研究对象车型传动系扭振特性,从减小经后桥及后悬架向车身传递的扭振激励的角度出发,提出了一系列控制主减速器处扭振幅值的方案。试验结果表明所提方案对改善低转速车内轰鸣声效果明显。上述工作对解决同类问题具有一定意义。     

碳纤维复合材料传动轴承扭性能优化设计

利用数值模拟分析的方法研究了铺层角度、厚度、顺序以及对称性对碳纤维复合材料传动轴抗扭性能的影响规律。研究发现结构抗扭截面系数在单向铺层方向为接近0°、45°及接近90°时较高,且随着铺层厚度增加而增大;扭转刚度则在40°～70°较好。在接近0°和接近90°铺层间铺设45°铺层能提高零件抗扭性能;与反对称铺层方案相比对称铺层方案更有利于零件承受扭矩。将优化铺层方案应用在某型号风机传动轴的设计中,试验证明能够满足使用要求并达到节约原材料的目的。     

旋转复合材料薄壁轴的不平衡非线性弯曲振动

研究几何非线性复合材料薄壁轴在偏心激励作用下的非线性振动特性。在轴的应变位移关系中引入Von Kármán几何非线性,基于Hamilton原理和变分渐进法(VAM)导出复合材料传动轴的拉-弯-扭耦合非线性振动偏微分方程组。为了着重研究轴的横向弯曲非线性振动特性,在上述模型中忽略轴向变形和扭转变形,得到轴的横向弯曲非线性振动偏微分方程,其中考虑了黏滞外阻和内阻的影响。采用Galerkin法,将偏微分方程转离散化为常微分方程,在此基础上利用四阶Runge-Kutta法对常微分方程组进行数值模拟,获得位移时间响应图、相平面图和功率谱图,研究了外阻、内组、偏心距和转速对非线性振动响应的影响,发现旋转复合材料薄壁轴存在混沌运动。     

Manufacture of one-piece automotive drive shafts with aluminum and composite materials

The natural bending frequency of a torque transmission shaft can be increased without reducing the torque transmission capability if the shaft is made using both carbon fiber composite and aluminum: the former increases the natural bending frequency and the latter sustains the applied torque. The high natural bending frequency of a shaft makes it possible to manufacture the drive shaft of passenger cars in one piece.

In this work, a hybrid one-piece drive shaft composed of carbon fiberepoxy composite and aluminum tube was manufactured by co-curing the carbon fiber on the aluminum tube.

The fabricational thermal residual stresses due to the coefficient difference of thermal expansions of aluminum and carbon fiber composite were eliminated by applying a compressive preload to the aluminum tube before the co-curing operation.

From the dynamic tests, it was found that the first natural bending frequency and the minimum static torque transmission capability of the hybrid shaft were 9000 rpm and 3550 Nm, respectively, and the shaft did not fail until 10⁷ cycles under a dynamic load of ± 500 Nm.     

Effect of the smart cure cycle on the performance of the co-cured aluminum/composite hybrid shaft

In this work, a smart curing method for the co-cured aluminum/composite hybrid shaft which can reduce the thermal residual stresses generated during co-curing bonding operation between the composite layer and the aluminum tube was applied. In order to reduce the thermal residual stresses generated during co-cure bonding stages due to the difference of coefficients of thermal expansions (CTE) of the composite and the aluminum tube, a smart cure cycle composed of cooling and reheating cycles was applied. The heating and cooling operations were realized using a pan type heater and water cooling system. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a DSC (differential scanning calorimetry) and rheometer to obtain an optimal time to apply the cooling operation. Curvature experiment of the co-cure bonded steel/composite strip was performed to investigate the effect of cure cycle on generation of the thermal residual stress. Also, the thermal residual stresses of the aluminum/composite hybrid shaft were measured using strain gauges with respect to cure cycles.

Finally, torsional fatigue test and vibration test of the aluminum/composite hybrid shaft were performed, and it has been found that this method might be used effectively in manufacturing of the co-cured aluminum/composite hybrid propeller shaft to improve the dynamic torque characteristics.     

考虑齿隙影响的牵引车拖载起步时传动系扭振瞬态响应分析

牵引车传动系为小阻尼多自由度非线性系统。系统各部件之间存在相互激励作用，使传动系呈现复杂动态特性。例如传动齿轮间隙引起传动系的冲击现象，车辆行驶中发动机节气门快速变化和离合器的突然结合引起的喘振和啸振现象。由此可见，传动系扭转振动对车辆的振动和噪声有着重要的影响，本采用Maflab／Simulink仿真分析软件，通过建立牵引车传动系扭转振动非线性模型，分析牵引车拖载起步时传动系瞬态扭转振动。从仿真结果中找到牵引车存在喘振和啸振现象。并进一步对影响传动系扭转振动性能的主要部件进行了参数化分析。本采用的建模仿真分析方法，对同类工程车辆的传动系性能的研究与设计也有一定参考价值。     

Analytical study of stress distributions due to semi-elliptic notches in shafts under torsion loading

Closed form solutions for the stress fields created by a semi-elliptic circumferential notch in an axisymmetric shaft under torsional loading are developed. The boundary value problem has been formulated by an approach using complex potential functions and the natural elliptic coordinate system. The solutions obtained for the shear stresses have a wide range of applicability, both in terms of the size and shape of the notches and the diameter of the shafts.     

Pitting corrosion of triggering initial fractures of palm oil screw press machine shafts

Investigation was carried out following the frequent occurrences of shaft failures in a number of palm oil screw press machines in a Malaysia palm oil mill company. Visual inspection, chemical analysis on the shaft material, fatigue analyses by utilizing traditional method and microscopic examinations were performed to support the investigation. Overview on pitting corrosion problems is presented. Common locations of the failure are at around bottom edges of keyway and shoulder fillets of the shafts. The findings indicate that pitting corrosion is identified as the main root causes of the premature shaft failures. In turn, poor surface condition would significantly reduce the fatigue endurance limit of the shafts under torsional loading.     

扭振信号拓扑网络的轧机动态扭矩测量

为解决实际测试中轧机传动系统关键点处动态扭矩不易同时测量的难题,提出一种扭振信号拓扑网络的轧机动态扭矩测量方法。通过把扭振计算的力矩和转角位移看作系统的输入输出信号,依据拓扑思想,建立信号之间的扭振信号拓扑网络模型。把有限实测点的测试数据代入扭振信号拓扑网络模型,可获得传动系统中其它关键点处的扭振参数值。轧机实际现场扭矩测试和数据分析处理结果验证了理论推导的正确性。这为轧机现场监测中不易同时布置传感器且非同轴的关键测点的振动参量获取提供了有效方法。通过编制程序可以实现轧机扭振在线监测和故障分析,从而保证轧机正常平稳运行。     

轧机转速波动测量的扭振监测实验研究

通过弹性转轴和电机轴的转速波动研究轧机扭振的动特性。用动力学理论推导,得到转轴瞬时转速波动的非平稳描述。通过合理抽象轧机主传动系统为二质量自由度转动惯量系统,得到弹性接轴模型的转轴瞬时转速的辨识方法。在扭振实验平台模拟轧制过程的实验验证了瞬时转速波动的表达式;扭振抑制实验表明了转速波动监测扭振的意义及其应用可行性。这项研究也为重型复杂机械传动系统实时在线扭振监测提供了一种实用的实现途径。     

轧机主传动系统扭振盲测点测量模型的研究

为解决轧机主传动系统实际测试中不可测点处物理参数测取的难题,构造了一类连续轴段质量扭振分析模型,并推导出轴段上盲测点处的扭振参数计算公式。通过把实测点的测试数据代入盲测点计算公式,可计算盲测点的振动参数。轧机实际现场扭矩测试和数据分析处理结果验证了理论推导的正确性。这为轧机现场监测中一些不易布置传感器关键点处的物理量测取提供了理论依据和技术支持,通过编制程序可以实现轧机在线系统监测和故障分析,从而确保轧机正常平稳运行。     

An experimental investigation on dynamic analysis of high speed carbon–epoxy shaft in aerostatic conical journal bearings

Advanced composite materials are being increasingly used in aerospace and aircraft industry where high stiffness and strength to weight ratios are important. Most of the components usually designed are static components and often non-load bearing components. But focus by designers is now shifted to critically loaded structural components such as discs, blades, etc. In early stages composite shafts were operated in the sub critical region, therefore the research was directed towards the problem associated with their sub critical operation. However, the recent trend in design of high performance rotating machinery is towards higher operating speeds leading inevitably to supercritical operation of such shafts that gives rise to issues of vibration, stability and stress. As composite material like carbon–epoxy exhibits excellent properties for structures owing to high specific modulus, high damping and low thermal expansions and therefore composite shaft made of carbon–epoxy has been made for the high speed CNC grinding machines and the centrifuges. For the analysis purpose the one step composite shaft made of carbon–fibers in epoxy matrix has been manufactured with 16 layers having stacking angles [0°/90°/45°/−45°]_2s using filament winding process. The experimental set up has been designed to investigate static and dynamic analysis and performance characteristics of the carbon–epoxy shaft in aerostatic conical journal bearing at high speeds in the range of 10,000–65,000 rpm. The vibration spectrum analysis has been observed and studied for the same. Comparison of amplitude of vibration decides the maximum operational speed of the shaft with low vibration in aerostatic conical bearings.     

Torsion fatigue failure of bus drive shafts

The mystery surrounding high failure rates in the drive shafts of a large municipal transit agency's fleet of 40 newly acquired articulated buses is investigated. The drive shafts were fabricated from a low-carbon (0.45%) steel such as AISI 5046. An examination of the drive shafts on all 40 buses is conducted, and 6 different drive shaft designs are identified among the fleet, but all of the failures, 14 in all, are limited to just one of the identified designs. Microscopic examination of the fracture surface of one of the failed drive shafts under a scanning electron microscope is conducted to determine the failure mode. Evidence of high-cycle fatigue is found, and a finite-element analysis is conducted to compare the maximum stress of the design exhibiting failures with the most common of the other designs that exhibits no failures. A fatigue life prediction is performed to determine just how much longer the expected fatigue life of the surviving design is compared to the design that suffered the early failures.