Evaluation of an energy-based fatigue approach considering mean stress effects

In this paper, an attempt is made to extend the total strain energy approach for predicting the fatigue life subjected to mean stress under uniaxial state. The effects of means stress on the fatigue failure of a ferritic stainless steel and high pressure tube steel are studied under strain-controlled low cycle fatigue condition. Based on the fatigue results from different strain ratios, modified total strain energy density approach is proposed to account for the mean stress effects. The proposed damage parameter provides convenient means of evaluating fatigue life with mean stress effects considering the fact that the definitions used for measuring strain energies are the same as in the fully-reversed cycling (R = ?1). A good agreement is observed between experimental life and predicted life using proposed approach. Two other mean stress models (Smith-Watson-Topper model and Morrow model) are also used to evaluate the low cycle fatigue data. Based on a simple statistical estimator, the proposed approach is compared with these models and is found realistic.     

Mean stress effects in fretting fatigue life estimation method using fatigue damage gradient correction factor

In our previous study, we developed a fretting fatigue life estimation method that considers stress gradient effect [Journal of Mechanical Science and Technology 28 (2014) 2153–2159]. In this method, fatigue damage value at the cracking location is corrected with the factor that is a function of fatigue damage gradient, and the corrected value is treated as the fatigue damage value in plain fatigue for life estimation. In the present study, we examined the effect of mean stress on fatigue damage gradient correction function, because the reliability of the developed method was only verified at a stress ratio (R) of ?1 in previous studies. Fretting fatigue experiments were conducted to obtain the fatigue life data of three different fretting pad shapes with R values ranging from ?1.0 to 0.3. Finite element analyses were then conducted to evaluate the fatigue damage parameter in the cracking region. The results revealed that fretting fatigue life decreases at increased stress ratio. Furthermore, the fatigue damage gradient correction function was unaffected by the stress ratio, although it is affected by plastic deformation at the cracking location. Thus, a correction function for the occurrence of plastic deformation and another for the absence of plastic deformation are necessary. The developed method was demonstrated to predict the fretting fatigue life at various levels of stress ratio with the use of plain fatigue data.     

Simulation on the motion of crankshaft with a slant crack in crankpin

A new model for vibration analysis of a crankshaft with a slant crack in crankpin is proposed, and the influence of crack depth on the transient response of a cracked crankshaft is investigated. A slant cracked shaft element is developed by deducing the local flexibility due to a slant crack. The frequently occurred slant crack in crankpin is studied, and a new finite element model of crankshaft including the slant crack in crankpin, which combines the slant cracked shaft element and Timoshenko beam elements, is derived. The support of engine block and the switching behaviour of the crack are considered, and the non-linear equation of motion for cracked crankshaft-bearing system is set up in a rotating coordinate system. The motion of a crankshaft of a four in-line cylinder engine with and without an initial crack is simulated. The influence of the crack depth on the transient response is investigated. The numerical simulation demonstrates that the current model is valid for simulating the motion of cracked crankshaft system. The results show that a useful foundation is laid for crack detection of crankshaft.     

起重机自重应力对安全评估中应力测试实验结果的影响

应力测试是起重机安全评估中必须进行的一项检测。目前在安全评估工作中常采用应变电测法来采集起重机工作过程中的应力时程数据,由于该方法只能采集到结构由于载荷变化产生的应力,而无法采集到结构因自重产生的应力,导致应力测试无法获取结构的完整应力。利用起重机金属结构自重应力在总应力中占有的权重,分析其对应力测试实验结果的影响大小,试验结果表明在危险截面自重应力大小占总应力大小可达60%,此时不考虑自重应力进行结构安全性的判定是不全面的。可考虑利用仿真技术获取自重应力^[1,2],从而使得安全评估应力测试实验结论更加准确。     

Analysis of PCBN tool failure mechanisms in face milling of hardened steel using damage equivalent stress

The International Journal of Advanced Manufacturing Technology - An attempt was made in the present study to apply damage mechanics to investigate the polycrystalline cubic boron nitride (PCBN)...     

Evaluating the value of information sharing in a supply chain using an ARIMA model

This paper considers a two-echelon supply chain, which contains one supplier and one retailer. It studies the quantification of the bullwhip effect and the value of information-sharing between the supplier and the retailer under an autoregressive integrated moving average (ARIMA) demand of (0, 1, q). The results show that with an increasing value of q, bullwhip effects will be more obvious, no matter whether there is information sharing or not. When there exists information sharing, the value of the bullwhip effect is greater than it is without information sharing. With an increasing value of q, the gap between the values of the bullwhip effect in the two cases will be larger.     

4105柴油机曲轴扭转振动与减振器匹配研究

利用软件EXCITE-designer对柴油机4105曲轴进行数学建模,建立了基于集中质量-弹簧-阻尼的系统模型,获得了曲轴扭转振动的自由振动频率和振型,计算了曲轴的强迫振动;分析了减振器的惯性块惯量对谐次波的影响,匹配了减振器。结果表明,柴油机在2 560,2 735和3 125 r/min附近转速下发生了较大的扭转共振;随着减振器惯性块惯量ID的增大,各谐次波的临界转速逐渐减小,匹配减振器后大幅降低了曲轴的扭转振幅,表明所设计减振器有较好效果。     

Analysis of forces in an automobile ECV using in external variable displacement swash plate type compressor for air conditioning control system

To meet the demand of improved comfort for passengers, drive ability and standard in fuel economy; external variable displacement swash (wobble) plate type compressors are used in automobile air conditioning control system because of their low energy consumption and highly efficient characteristics. It controls the compressor displacement by increasing or reducing the swash plate angle. Solenoid operated electromagnetic control valve (ECV) in the compressor controls the air conditioning system by means of a pulse width modulation (PWM) input signal supplied from an external source (controller). The mechanism changes the swash plate angle by increasing or reducing the pressure of swash plate chamber using the ECV functions. The force (solenoid) for ECV operation is important as the force directly related to the movement of the internal feature i.e. mainly plunger of the ECV which is responsible for the amount of air/refrigerant flow that results the air conditioning control procedures with various pressure ports. The research paper highlights the improved theory and equation for calculating the working force (solenoid force) in ECV and experimental analysis of 3 (three) ECV samples followed by the comparison of theoretical and experimental force results.     

Damage detection of concrete piles subject to typical damage types based on stress wave measurement using embedded smart aggregates transducers

Concrete piles are the most common types of foundation structures. Pile damages, such as fractures, cracks, mud intrusion and secondary concrete pouring, are the leading causes of pile structural failure, which may directly result in casualties and economic loss. It is desirable to develop a monitoring system that can detect these pile damages. In this paper, embedded piezoceramic-based smart aggregates transducers along with the active sensing approach are developed to detect common types of pile damages, including crack, partial mud intrusion, secondary pouring, and full mud intrusion, based stress wave measurement. With the active sensing approach, one smart aggregate is used as an actuator to generate a stress wave that will propagate along the pile, and other smart aggregate(s) will measure the propagating wave. All damages, which introduce new interfaces and discontinuities, attenuate the stress wave propagation. The attenuations of the stress waves based on different pile damages were compared by the received sensor signal in time domain. A wavelet packet-based energy analysis was used to develop an energy index to assist the detection of damages. Experimental results demonstrated the feasibility that the proposed approach can detect all four types of common damages associated with concrete piles.     

The effects of using different type of inlet vents on the thermal characteristics of the automobile cabin and the human body during cooling period

A three-dimensional (3-D) transient numerical analysis was performed inside an automobile cabin during cooling period. A three-dimensional vehicle cabin including glazing surfaces was modelled by using the real dimensions of a car. A virtual manikin with real dimensions and physiological shape was added to the model of the vehicle cabin, and it was assumed that the manikin surfaces were subjected to constant temperature. The virtual manikin was divided into 17 parts in standing posture to evaluate the local heat transfer characteristics of the human body during transient cooling period. We considered three different cases that the cooling capacity of the automobile cabin was same for all cases. Three-dimensional fluid flow, temperature distribution and heat transfer characteristics inside the automobile cabin were calculated with different type of inlet vents. Comparisons of the numerical results were presented and discussed.     

Suppression of the noise-induced effects in an electrostatic micro-plate using an adaptive back-stepping sliding mode control

In this work, an adaptive backstepping sliding mode control approach is applied through the piezoelectric layer in order to control and to stabilize an electrostatic micro-plate. The mathematical model of the system by taking into account the small fluctuations in the gap considered as bounded noise is carried out. The accuracy of the proposed modal equation is proven using the method of lines. By using both approaches, the effects of noise are presented. It is found that they lead to pull-in instability as well as to random chaos. A suitable backstepping approach to improve the tracking performance is integrated to the adaptive sliding mode control in order to eliminate chattering phenomena and reinforce the robustness of the system in presence of uncertainties and external random disturbances. It is proved that all the variables of the closed-loop system are bounded and the system can follow the given reference signals as close as possible. Numerical simulations are provided to show the effectiveness of proposed controller.     

Optimum coverage of uncertainties in a supply chain with an order size constraint

Supply chain (SC) uncertainties are present in both the demand and supply sides of the chain. If these uncertainties are not countered appropriately, the customer service level (CSL) and customer satisfaction will decrease, and this, in turn, will lead to a loss of sales volume and SC profitability. Maintaining an appropriate level of safety stock as a counteracting solution to SC uncertainties can boost the CSL. In traditional decision making, the retailer determines the CSL by determining its own safety stock level. However, the CSL affects the sales volume and profitability of the upstream members. This paper investigates the joint decision making on CSL in a two-stage SC with a constraint on the retailer's order size to analyze the benefits of coordination and cooperation when determining the CSL. The results of this study show that CSL coordination can significantly increase the profitability of the SC.     

变传动比汽车转向器齿轮副的机理分析

运用啮合原理分析方法，给出了余弦函数传动比的汽车转向器齿条齿扇啮合方程，齿廓方程，导出锥形齿扇小端不根切，大端不变尖的条件和齿扇几何尺寸的计算公式。     

Effect of lubrication on the stress distribution in an extruded material

The visioplasticity method is used to find the complete strain, strain rate and stress distribution in the deformation zone, according to the deformation grid lines marked on the surface of the workpiece. From the experimental data (the values of the flow function for the extrusion), the velocity, strain rate and stress fields can be calculated by the finite-difference method from the stream function, equilibrium and plasticity equations. In this article, stress components distribution in forward extruded specimens of copper alloy are analysed using the visioplasticity method. Comparisons are made between stress distribution of the specimens extruded with three different coefficients of friction. The results are shown in the form of diagrams.     

双压力角齿轮在汽车变速箱中应用及加工分析

本文把双曲线螺旋锥齿轮的双压力角的设计思想运用于汽车变速箱中的圆柱齿轮设计 ,加大非工作齿面压力角提高轮齿的抗弯强度 ,并通过齿形系数进行定量的分析。同时 ,对双压力角齿轮加工中的剃齿和齿厚的测量进行了详细的分析 ,提出装配式剃齿刀设计方案 ,以解决双压力角剃齿和改善剃齿中凹的难点     

Tool condition classification in turning process using hidden Markov model based on texture analysis of machined surface images

Tool condition monitoring has found its importance to meet the requirement of production quality in industries. Machined surface texture is directly affected by the extent of tool wear. Hence, by analyzing the machined surface images, the information about the cutting tool condition can be obtained. This paper presents a novel technique for tool wear classification using hidden Markov model (HMM) technique applied on the features extracted from the gray level co-occurrence matrix (GLCM) of machined surface images. The tool conditions are classified into sharp, semi-dull and dull tool states. The proposed method is found to be cost effective and reliable for on-machine tool classification of cutting tool wear with an average of 95% accuracy.     

Functional and structural effects of percutaneous edge-to-edge double-orifice repair under cardiac cycle in comparison with suture repair

Percutaneous procedures for double-orifice mitral valve repair using the MitraClip device (clip) have been recently introduced as new treatment options as alternatives to medical management and open-heart surgery, especially for patients with high estimated operative risk. Similarly to the open-heart surgical technique, where suturing is used, the clip creates a double-orifice configuration that not only improves the closing function of the valve, but also significantly modifies its behaviour, particularly in the diastolic phase. While several clinical trials have been conducted, and are ongoing, in order to assess the safety and effectiveness of this technique, a deeper knowledge of the structural and functional effects on the valve, and of the cyclic loads transmitted to the clip itself, would allow a comparison with other repair techniques, and could serve as a foundation for possible further optimization of the clip design. The effects of the MitraClip device developed by Evalve Inc. were studied by means of a finite element model of the mitral valve, specifically developed to study the structural effects of the original, suture-based, edge-to-edge technique. A second model was developed in order to simulate the effects of a suture with similar extension from the leaflet edge in a direction to the annulus, in order to compare the two repair techniques. The mitral valve area and transvalvular pressure gradient predicted by the models for the clip and the suture are quite similar. Similar leaflet cyclic stresses, both in value and in location, were noted for the two mechanisms of linking the leaflets, while minor differences were found in the load transmitted to the suture and the clip, with slightly higher values for the clip. The model satisfactorily allowed functional parameters (valve area and transvalvular pressure gradient) and structural parameters (load, leaflet stress) to be determined. Overall, the structural effects of the clip and the suture are quite similar under the cyclic loading conditions imposed by the cardiac cycle.     

Experimental study of the effects of the cycle characteristics on the refrigerant-induced noise in system air-conditioner

The main sources of the refrigerant-induced noise can be classified 2 types according to its characteristics. One is due to the cyclic characteristics such as quality, velocity of the refrigerant, pressure drop and mass flow rate. The other is due to the structural characteristics such as distributed path pipe layout, distributor and expansion device. In this paper, the effects of cycle characteristics on the noise of multi-type system air-conditioner are investigated experimentally. In the indoor unit of multi-type air-conditioner, the variation of noise is examined when the in-flowing and out-flowing refrigerant to the indoor unit are 2-phase state according to its cycle control. And several factors are recommended in order to reduce the refrigerant-induced noise of the air-conditioner.     

Assessment of information technology effects on management of supply chain based on fuzzy logic in Iran tail industries

Evolutions rooted in technology in market arena, business, and demands reforms in supply chain and consequently more demands for created value by end user are among factors causing reforms on management of supply chain. Integrity of supply chain activities and utilized technologies is an essential factor to survive competitions in the market. Organizations, therefore, need to adopt policies to coordinate themselves with new arena in market and electronic commerce. Despite bad news from Iran tail industries about unplanned production, the industry is still in growing path. In addition to easy access to mineral resources and low-energy costs, which have made it quite reasonable to invest in the industry, state tariff policies for imported tail products have made new investment chances in the industry. As a result, Iran recently won a position among five leading counties in world tail industry. However, knowing about high profit margin in tail industries, many countries have stepped into the market and through producing high-quality products have intensified competition in the market. This study tries to identify and assess IT indexes in Iran tail industry’s supply chain and hopes to take a step forward to gain better market position in international market by prioritizing the indexes using fuzzy logic.     

Investigation of operational and environmental variability effects on damage detection algorithms in a woven composite plate

Variability in structural health monitoring systems can result in reduced reliability by increasing the likelihood of false-positive/-negative indications of damage. It is important to understand how sources of operational, environmental, and even computational variability influence damage indicator functions. A sensitivity model-based technique, which focuses on the physical rather than the statistical nature of variability, is described. Each source of static/dynamic variability is sequentially isolated with a variability test matrix for a woven composite plate. Computational sources of variability are investigated by comparing two different damage detection algorithms (i.e., transmissibility and embedded sensitivity). It is determined that by using a piecewise variability feedback process, certain parameters of the frequency response measurement and analysis (e.g., frequency band, input–output locations, etc.) can be chosen to reduce sensitivity of the damage indices to variability. It is also shown that the sensitivity due to changes in the sensor frequency bandwidth accounts for the largest source of static variability. Finally, by using a root mean square normalization procedure, static and dynamic sources of variability can be compared with changes in damage indicators due to actual damage. It is shown that damage detection algorithms can be improved by selecting specific frequency ranges that accentuate damage indicators while minimizing the effects of variability.