Vergleich von Gasfedervarianten mit variabler Kennlinie für einen Freikolbenmotor

In this paper two different gas spring designs for a free-piston application are introduced. On the basis of thermodynamic calculations the spring characteristics of a mass-variable and a volume-variable gas spring are analyzed for different operating points. A comparison of the spring performances indicates that the spring characteristics of the two designs only match at one operation point. Therefore, a calculation method minimizing the difference between the two spring characteristics over the entire operating range of a free piston engine is introduced. The theoretical examination is confirmed by measurements on a gas spring test stand.     

Elastic deformation of a hypoid gearbox

High load carrying capacity in the gear mesh can be achieved when the contact load is well distributed. Designing an adequate tooth flank geometry requires a thorough calculation approach. This is particularly important for automotive hypoid gearboxes with aluminum housing. In this paper, the deformation analysis of housing, bearings and shafts for a hypoid gearbox is validated by measurements at a static test rig. The challenge of compensating friction effects to get high-quality measurement results is successfully met by the presented approach.There are several computer programs to calculate the elastic deformation behavior of the system shaft-bearing-housing. Most of the calculation programs use analytical approaches. The advantage of these programs, in comparison to a full FEM approach, is an efficient parameterization of gears and a very short calculation time, while delivering high precision results. The deformation behavior of housings can be considered in different ways. The deformation behavior of a bearing seat can be modelled by its stiffnesses. For housings with lower stiffnesses (for example aluminum housings), crossover influences become more and more important. The deformation behavior of a housing can be taken into account by a stiffness matrix. The stiffness matrix of a housing can be determined by using the finite elements method. Therefore, the complex elastic deformation behavior of housings can be considered in analytical calculation approaches. Within the scope of a research project, investigations have been made to validate the calculated elastic deformations of the shaft-bearing-housing system. For this purpose, deformation measurements of a test gearbox were taken by using a 3D coordinate measuring machine. The test gearbox is static and consists of a hypoid gearbox for automotive applications. The input torque is provided by a lever mechanism. The elastic deformation of the test gear box has been measured and compared to calculation results. Therefore, different approaches of modelling the elastic deformation behavior of the housing can be validated and compared to each other.     

Tests on Loosening of Aviation Threaded Fasteners with Different Washer Configurations

This paper presents results from an experimental investigation on loosening of aviation threaded fasteners with internal teeth lock washers and plain washers. The tests are performed on a transverse test machine which provides dynamic shear. Five different configurations are tested: (1) only lock washer, (2) lock washer on plain washer, (3) no washers, (4) only plain washer, and (5) lock washer on hardened plain washer. The resistance to loosening of these configurations is assessed by comparing loss of preload versus cycles of dynamic shear loading. Internal teeth washers used alone under a plain nut without additional plain washer are found to provide the worst case with respect to loosening resistance. Use of a plain washer under the lock washer provides significant improvement in resistance to loosening. In addition to providing protection to clamped part surfaces and better load distribution in a joint, the data presented reveals the use of plain washers under a plain nut can provide improved resistance to loosening. Relative hardness of the components, e.g., plain washer compared to lock washer, influence the performance.     

Prüfstand mit piezoelektrischen Schwingungserzeugern zur Ermittlung der dynamischen Steifigkeit von Elastomerbauteilen

To determine the dynamic behavior of elastomer components a corresponding test bench for the frequency range 500 Hz to 2000 Hz was developed [1]. This was carried out in a joint project, funded in the ZIM initiative of the BMWi, by the partners m + p international, ContiTech, and the Institute of Dynamics and Vibrations Research. In this paper the essential requirements for the test bench and especially the vibration generators are worked out with regard to the measurement task. Then various actuation principles are discussed. Due to the combination of large forces needed and required compactness a piezoelectric actuator principle was selected. Accordingly, two different actuator concepts were designed and will be presented in the contribution at hand. A special feature here is the innovative preload concept, which is used for the realization of one presented concept. Here, the piezoelectric elements are wrapped with thin steel wire, causing a low stiffness and mass. This process in addition is characterized by good reproducibility and cost-effectiveness. Another focus of this paper is on the power electronics and the control. In order to ensure the necessary system behavior for the measurement task, these two components must meet high demands. Finally, the entire structure of the test bench as well as the results of exemplary measurements are described and presented.     

Effect of stamping deformation on microstructure and properties evolution of an Al–Mg–Si–Cu alloy for automotive panels

The effect of 5 % tensile deformation, which simulates the stamping process of Al–Mg–Si–Cu automotive outer panels, on the microstructural evolution during age strengthening, has been investigated. In addition, its benefit on key mechanical properties including hardness, yield strength, ductility, and corrosion resistance has been linked to the microstructural features. It was found that the aging precipitation sequence, SSSS → clusters and G.P. zones → β″ → β′ + Q′ → Q, was not influenced by the dislocations introduced through the stamping deformation prior to aging. On the other hand, stamping deformation could promote the formation of precipitates and refine the precipitates because of the enhanced heterogeneous nucleation and the accelerated precipitation kinetics, leading to superior strength of the alloy at the early stage. Meanwhile, the larger amount of Cu incorporated into nanoprecipitates leads to better intergranular corrosion resistance of the stamped alloy compared with the unstamped one. Due to the reduction in free Si amount at grain boundaries, the formation of fine subgrain structures and the increase of dislocation accumulation, the ductility of the stamped alloy was increased.     

Development of an anti-loosening fastener and comparing its performance with different other threaded fasteners

Threaded fasteners are widely used for temporary joining of different components that require occasional disassembling. However, threaded fasteners may have the problem of loosening under vibrating conditions, which may lead to decreasing clamping force and, thereby, a system failure. In the present experimental investigation, anti-loosening ability of various fastening elements, such as conventional nut, nylock nut, flat washer, spring washer, inside and outside serrated washer, is tested with a conventional M16 high-tension steel bolt. A hybrid double nut is used to clamp the plates in which a conventional nut is used to tighten first, and one nylock nut is then placed at the outer side for further tightening. An adhesive-bonded nut is also tested, where an adhesive is placed between bolt and nut threads. All these fasteners are tested in terms of their loosening characteristics. Accelerated vibrating conditions are used for the test on an indigenously made test rig. A split bolt with taper pin is introduced for the first time to reduce loosening of fasteners. The split bolt with taper pin shows considerably good anti-loosening property compared with other threaded fasteners tested in this work.     

Ist eine Über-Carnot-Maschine möglich?

A hyper-Carnot engine, i.e. a heat engine with a conversion coefficient exceeding the Carnot value, is forbidden by the second law. However, this law is not proven and, by principle, cannot be proven. It is an axiom. It is only based on all earlier unsuccessful attempts to circumvent it. In this paper, concept and calculation of a hyper-Carnot engine are presented the individual components of which all operate in agreement with all known physical laws. The crucial point is generating high phase space density synchrotron radiation by low phase space density thermal electron radiation.     

Sintering Characteristics of a Powder Injection Molded Ceria-Stabilized Zirconia–Mullite Composite

Powder injection molding (PIM) technology has the potential for economically manufacturing several complex-shaped zirconia–mullite components in mass production. The sintering behavior of a zirconia–mullite composite fabricated by injection molding was analyzed in this paper. The focus of this study is to assess the dependence on properties and microstructure on PIM processing conditions. The sintered density of the samples displayed a strong dependence on sintering temperature. The hardness of the samples followed a similar trend as sintered density. A maximum fracture toughness of 4.1 ± 0.3 MPa · m^1/2 and strength around 450 ± 60 MPa was observed for samples sintered at 1500°C for 4 h. The properties from this study are significantly higher than the values reported in majority of the prior studies where other technologies like uniaxial and cold isostatic pressing were used to fabricate zirconia–mullite composites. The above results support the suitability of PIM as a manufacturing process for complex-shaped zirconia–mullite components with good mechanical properties.     

Water hammer and condensation hammer scenarios in power plants using new measurement system

This contribution presents experimental results of the investigation of water hammer and cavitational hammer at the pipeline test facility at Fraunhofer UMSICHT in the context of the EURATOM project WAHALoads. The main objective of this running project is the prediction of the strain on equipment and support structures caused by water and condensation hammer. Thus, some typical scenarios of power plants are conducted. For this purpose the test facility at Fraunhofer UMSICHT (PPP) was modified in order to simulate a piping system and associated supports that are typical for a power plant. For a better understanding of thermohydraulic processes, new wire mesh sensors with thermocouples for the measurement of condensation heat transfer and other innovative transient measurement techniques were implemented into PPP additionally.     

Effiziente Finite-Elemente-Lösung der Energiegleichung zur thermischen Berechnung tribologischer Kontakte

The reduction of the fuel consumption and pollutant emissions, as well as the increase in service life and reliability with decreasing size and higher loads, are regarded as a conflict of aims in today’s engine development. In order to solve this problem time and cost effectively, the numerical calculation of conformal tribological contacts in the industrial practice is currently carried out using EHD/MBS programs. In such programs the fluid is isothermal with a constant viscosity. The thermal deformation of the solid structures can only be considered as a fixed predetermined contour. A more accurate design of highly loaded tribological systems requires taking the thermal effects and their interactions occurring in the mixed friction area into account in a TEHD/MBS simulation. The implementation in the program FIRST using the FEM is presented in this work. In this context, the focus is especially on an economical solution with high computing time efficiency. A validation of the TEHD algorithm was carried out on the basis of measured temperatures, which were determined on a connecting rod test rig with a steadily and also transient loaded connecting rod bearing.     

Stochastic modelling and simulation of production lines: a computer-based approach towards model validation

This study employs a simulation-based design methodology to investigate the performance of two models of manufacturing systems. In the first model, the dynamic behaviour of a single parallel-machine stage with unreliable work stations is modelled as a Markov process. A similar analytical method for evaluating the performance of a buffered production line is presented in the second model. A simple approach towards coding and simulating the models is presented, and numerical examples based on these simulation models indicate that the approach is viable.     

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.     

Nachgiebiger Elektrodenträger für Cochlea-Implantate mit fluidischer Aktuierung

The cochlear implant, consisting of a compliant electrode carrier (ET) and embedded electrodes with contact wires, is an auditory neuroprosthesis, which is surgically inserted into the inner ear (cochlea) in order to create an auditory impression in the hearing-impaired patients. For simplification of the insertion, a fluidically actuated electrode carrier with a changeable curvature is presented. The deformation of the ET is specifically manipulated by applying pressure to its interior and also by a non-stretchable thin fibre or stripe embedded in its wall. An analytical examination of scaling properties allows to use scaled structures for models and measurements. In order to determine the geometry of the ET, a model-based synthesis – FE method combined with analytical modelling – is carried out. The synthesis resulted in a conical shape of the ET with a cylindrical cavity closed at one end and a fiber running parallel to the cavity. Experimental studies on a measuring geometry show a maximum deviation of 0,6 bar at a maximum internal pressure of 6 bar. The investigations show that the proposed synthesis method is suitable for the development of surgical instruments with adjustable curvature.     

Interfacial fracture toughness of APS bond coat/substrate under high temperature

Thermal barrier coating (TBC) is an essential requirement of a modern gas turbine engine. The TBC failure is the delamination and spallation. The failure mechanism is interfacial expansion mismatch and oxidation of bond coat (BC). The oxidation damage under high temperature results in the reduction of interfacial adhesion. The interfacial fracture toughness is an important property to analyze the TBC failure. Using the simple tensile test, pushout test method and three-point or four-point-bending test and so on, the interfacial fracture toughness of ceramic top coat/BC has been researched in the past. However, the fracture toughness of the BC/substrate due to the Al depletion was very few studied. In this study, a NiCrAlY bond coat by air plasma spray (APS) was deposited. The substrate is directionally solidified superalloy (DZ40M). The Young’s modulus of bond coat was obtained by the nanoindentation and average Young’s modulus of bond coat is 66.9 GPa. Isothermal oxidation was performed at 1,050^?C for 100 h. Using the HXZ-1000 micro-hardness equipment and fracture mechanics approach, the five different times was chosen to test the hardness and the crack length, and then the fracture toughness was obtained. While the oxidation exposure time increased at 1,050^?C, the hardness of the substrate close to the bond coat decreased with the increase of the bond coat in hardness. Meanwhile, the interfacial fracture toughness of the bond coat–substrate decreased because of the Al depletion.     

复合材料螺旋弹簧刚度及其影响因素分析

该研究制备了一种与中空圆截面簧丝轴线成±45°铺层的新型复合材料圆柱螺旋压缩弹簧,并对该弹簧进行准静态压缩试验。将纤维复合材料平板的剪切模量等效替代各向同性材料弹簧刚度表达式中的剪切模量,从而理论导出该类复合材料弹簧的刚度表达式。针对该表达式分析影响弹簧刚度的各种因素及其影响程度。结果表明:弹簧的刚度系数随着纤维弹性模量、纤维体积分数、簧丝外直径的增加而急剧增加,随它们的下降而显著下降;基体弹性模量与复合材料泊松比对弹簧刚度的影响十分微小;簧丝内直径在一定范围内变化时对弹簧刚度的影响几乎可以不计,但却能显著降低弹簧质量,超出该范围后,弹簧刚度随内直径增加而急剧下降;刚度系数随弹簧有效圈数和弹簧圈平均直径的增加而剧烈下降,随着它们的下降而急剧增加。     

Efficient CFD Simulation Model for a Planetary Gearbox

Planetary gears are used to transmit power at high gear ratios in limited space. Typical applications are drive trains in the automotive industry, e.?g. in cars, trucks and buses. The oil distribution in planetary gearboxes is difficult to predict. There is only basic knowledge about lubrication designs with effective oil distribution and high efficiency. Advanced methods are very helpful in improving the design of planetary gearboxes in respect of their lubrication.In recent years, CFD (computational fluid dynamics) has become a valuable tool for simulating the oil distribution in gearboxes. By comparison with experimental and empirical methods, CFD provides oil distribution simulation results and can be applied to arbitrary geometries. However, CFD simulations tend to require comparatively high computing time and capacities. Therefore, efficient CFD simulation models are required, especially for complex gearbox topologies.Within the framework of this study, a finite volume CFD model of a dip-lubricated planetary test gearbox has been developed. It includes the modelling of all gear meshes and bearings and has a very high level of detail. The element number was reduced as far as reasonable possible, resulting in little computing time with regard to the modeling depth. Moreover, the computational effort was further reduced by considering the bearings to be static. Through use of the developed simulation model, the influence of different parameters was investigated. This work will help to improve the lubrication design of planetary gearboxes.     

Application of analytical network process for analysis of product design characteristics of lean remanufacturing system: a case study

The modern manufacturing systems are adopting with lean practices to ensure value addition and waste elimination. Also, product recovery options are found to be vital. Appropriate product design characteristics are identified, and their prioritization is framed as decision-making problem with multiple criteria. Analytical network process is used as solution methodology. The objective of the study is to formulate multi-criteria decision making problem for assessment of lean remanufacturing product design characteristics. The priority order of lean remanufacturing operations is obtained. The study is exemplified with a case conducted with reference to remanufacture of an automotive component. The priority order of criteria is Disassembly > Cleaning > Inspection > Remanufacturing > Reassembly. The inferences desired from the study would facilitate cleaner manufacturing practices. Sensitivity analysis is conducted and practical validity of the method has been tested with an industrial case study.     

Strain controlled fatigue testing of the metastable β-titanium alloy Ti-6.8Mo-4.5Fe-1.5Al (Timetal LCB)

The present work covers the mechanical behaviour of Timetal LCB under fatigue loading and utilizes transmission electron microscopy (TEM) to study the associated microstructural evolution. Fatigue specimens were taken out of LCB wire made for automotive suspension spring manufacturing in a solution treated as well as an additionally aged state. Uniaxial fatigue tests were carried out in total strain control with R = 0.1. Solution treated specimens tested at 3% and 4% maximum total strain showed a saturating force response, which differed from all other total strain controlled tests, and a distinct fracture behaviour. In addition, an increase of the dynamic Young's modulus is observed under these test conditions and in this material state. These findings are interpreted as a deformation induced precipitation of nanosize α- or ω-phase.In the aged state, the α-phase carries the major part of deformation work, noticeable by distinct α-substructures in fatigued specimen states.     

Potenzial von freien Flankenmodifikationen für Beveloidverzahnungen

In recent years the beveloid gear, also known as conical involute gear, is shifting more and more into the spotlight. The beveloid gear has been an important part of marine transmissions for years and is nowadays used to transmit the torque of the output shaft of the gearbox onto the front axle in a four wheel drive vehicle. The small need of design space and the reduced amount of design parts necessary in comparison to conventional transfer gearboxes, distinguish the beveloid gear. The conjugate flank of beveloid gears promises the best operational behavior. However because of its geometry the conjugate flank cannot be manufactured with standard manufacturing processes. Standard modification such as crowning offer a possibility to enhance the operational behavior of involute beveloid gears but cannot reach the whole potential given by conjugated beveloid gears. Therefore, the objective of the following report is to investigate the potential of free flank modifications of beveloid gears regarding the operational behavior. After a brief overview on existing geometry optimization methods for beveloid gears, the method for free flank modifications by means of a weighted objective function is defined and applied to an example gear. The results of the investigation show that free flank modifications offer a high level of improvement of the operational behavior. The comparison with a non-modified gear, a gear with standard modifications and a gear with free flank modifications for three different load steps proves that free flank modifications offer a higher durability and lower noise excitation.