Vorrichtung zur Prüfung von Feinblech unter Druckbeanspruchung

Jig for testing thin sheet under compression load The experimental determination of the stress strain relation of thin sheet under uniaxial compression load is difficult, because the specimen are thin‐walled. A jig for testing thin sheet under uniaxial compression load and reversed tension‐compression load as well is presented in this article. It is shown, that in the relevant cross section an uniaxial stress state is dominating, which is not effected by the devices for lateral support. This jig gives the possibility to determine material properties, which are important for the manufacturing process and for the design of thin‐walled building components and verify valid assumptions.     

Experimentelle und analytische Untersuchung des out‐of‐plane‐Verhaltens von unbewehrten Mauerwerkswänden unter Erdbebenbelastung

Experimental and analytical investigation of the seismic out‐of‐plane behavior of unreinforced masonry walls In addition to the vertical and horizontal load‐bearing in‐plane, masonry must also withstand out‐of‐plane loads that occur in earthquake scenarios. The out‐of‐plane behavior of unreinforced masonry walls depends on a variety of parameters and is very complex due to the strong non‐linearity. Current design methods in German codes and various international codes have not been explicitly developed for out‐of‐plane behavior and contain considerable conservatism. In the present work, shaking‐table experiments with heat‐insulating masonry walls have been conducted to investigate the out‐of‐plane behavior of vertical spanning unreinforced masonry walls. As shown in previous numerical investigations, important parameters are neglected in existing design and analysis models and the out‐of‐plane capacity is underestimated significantly. In the conducted experiments the results of these numerical investigations are verified. Furthermore, the development of an analytical design model to determine the force‐displacement relationship and the out‐of‐plane load‐bearing capacity considering all significant parameters is presented.     

Betriebsfestigkeit in der Fahrzeugentwicklung – von der Theorie zum Produkt

Durability Evaluation in the automotive engineering – from theory to product The procedures for durability evaluation in the automotive engineering are represented, especially the methods, load assumption, fatigue testing and the regulations for the release and quality control. By practical examples of the vehicle development from chassis, aggregate and body the procedure is described, in particular the used experimental and virtual simulation methods     

Fatigue at high number of cyclic loads: Testing methods and failure mechanism

A significant proportion of machinery and equipment is operated up to a number of cycles greater 10⁸, which is in the range of conventionally fatigue limit design. For materials with a face‐centred cubic crystal lattice and for high‐strength steels with a body‐centred cubic crystal lattice fatigue failures were observed even in the Very High Cycle Fatigue (VHCF) regime of load‐cycles greater N = 10⁷. To reduce the testing time in the VHCF regime, one possibility is to perform the tests at a higher frequency. In addition to the typical servo‐hydraulic testing machines or resonant fatigue testing machine with test frequencies up to f = 400 Hz, ultrasonic fatigue testing machines with frequencies up to f = 20 kHz were used. In different comparative investigations it was shown that the testing method has a significant influence on fatigue life and fatigue strength. In this paper the influence of the testing method and test frequency on fatigue behaviour in the VHCF regime is presented using the example of steels and aluminium alloys and different hypotheses for the decrease in fatigue strength in this area are discussed.     

Quick‐mount grips: Towards an improved standard for uniaxial tensile testing of metallic superplastic sheets

It is the steady interest in the extraordinary ductility of superplastic materials that led to the launch of several standards on characterising their tensile behaviour, all within the past decade. However, those standards do not agree on many of the issues they cover, and fail to tackle some of the important and controversial issues in superplastic materials’ testing; leaving the reader without adequate guidelines on those particular issues. In this work, a detailed review of the three main standards that describe the proper method for testing superplastic materials (JIS H7501, ASTM E2448 and BS ISO 20032) is carried out. The review focuses on the critical issues that significantly impact testing results, pointing out the points of agreement and disagreement among the three standards. And in an attempt to resolve some of those critical issues, an integrated testing methodology centred about a unique set of quick‐mounting grips that facilitates mounting and retrieving the test specimen in a very short time, is presented. The methodology promises resolving the majority of the aforementioned testing issues, and is hoped to provoke the development of a new more universally‐accepted standard method for testing superplastic materials at elevated temperatures.     

Investigation of the seismic out‐of‐plane behaviour of unreinforced masonry walls

The structural stability of unreinforced masonry (URM) walls has to be guaranteed not only under static (permanent and live) loads but also under earthquake loads. Loads transverse to the plane (out‐of‐plane) often have a decisive influence on the load‐bearing capacity. In practical applications, simplified methods from codes, guidelines and literature are often used to analyse and evaluate the out‐of‐plane capacity of load‐bearing and non‐load‐bearing URM walls. The results of these simplified methods can be significantly conservative and inaccurate since essential influencing effects are neglected. For many existing buildings, the simplified methods underestimate the capacity, which leads to cost‐intensive retrofitting and strengthening measures or complete replacement by other wall systems. In order to realistically estimate the out‐of‐plane capacity, parameters such as wall geometry, boundary conditions, vertical loads and especially dynamic effects (e.g. inertia forces) have to be taken into account. In this paper, non‐linear time history simulations are presented to investigate the influence of these effects. The numerically determined maximum acceptable earthquake acceleration is compared with results from simplified analysis models. The comparison shows that the out‐of‐plane capacity is significantly higher than the values predicted by simplified models. Finally, several initial experimental seismic tests conducted on the shaking table of the TU Kaiserslautern are presented, together with the planned extensive experimental test program on the out‐of‐plane capacity of masonry walls.     

Determining the masonry compressive strength / Bestimmung der Druckfestigkeit von Mauerwerk

Masonry is a building material primarily suited for building structures under compressive load and therefore it is mainly used for vertical load transfer. The decisive characteristic to assess the load bearing capacity of such building members is their compressive strength. It can either be derived experimentally from compression tests on wall specimens or by calculation. In this paper, firstly the current procedure in the derivation of compressive strength values based on experimental compression tests is described. Furthermore, empirical approaches and theoretical models for determining the masonry compressive strength, which have been developed in the past, are presented.     

航天设备力限振动试验复杂二自由度方法研究

在航天产品振动试验领域,力限方法采用力和加速度条件双控策略可缓解传统振动试验中的过试验,但力条件的确定困难,尤其对于设备级产品的试验存在源的界定问题。针对固定边界的设备级产品,介绍了复杂二自由度法用于获取固定边界下力条件的修正方法,对于其中关键的源和负载的质量参数给出获取方法,并应用于试验实例,为工程中力限条件的合理制定提供了参考。     

New experimental methods for investigating variable amplitude loading effects in HCF and VHCF regimes

For the investigation of variable amplitude loading effects, it is necessary to increase the test frequency of conventional testing facilities because, for the evaluation of many components, test results with more than 10⁷ cycles are also needed. However, due to the restriction of conventional testing facilities and the associated costs and required time, variable amplitude testing is almost limited to 10⁷ cycles. Service loading with more than 10⁷ cycles to failure is characterized by low amplitudes with a high number of cycles. The challenge in investigation of material fatigue in the regimes of high cycle and very high cycle fatigue is to apply this large number of cycles to failure in an acceptable time frame. For this reason, it is essential to use a machine, which is able to operate at high frequencies. In this paper, two testing machine concepts with piezo actuators are presented. In the first concept, a high performance piezo stack actuator is presented, in which the specimen and the load cell are mechanically assembled in series. This set‐up applies forces up to 10 kN and testing frequencies up to 1000 Hz. The second testing facility is a hybrid testing system, which consists of an inertial mass actuator and a servo hydraulic actuator connected in parallel. Both systems are capable of testing normal specimen dimensions and provide the possibility to work with variable amplitude loading as well as constant amplitude loading.     

Zeitstandprüfung von Polypropylen bei 120 °C

Long Term Creep Tests of Polypropylene at 120 °C The mechanism of damage in the pipe wall during the internal pressure creep test of polypropylene-pipes at a test temperature of 120° is described. The resulting consequences from the investigations relating to the test method are shown and a test station with automatic recording of the time of damage is presented. Further on solutions are explained to eliminate the security risks during the tests of big pipes. A practical performance is described. On the basis of the time-temperature-correlation of the long term behavior of polypropylene the mathematical basis to interpolate minimum requirements for quality control are presented.     

Einfluß der Belastungsfrequenz auf die Lebensdauer von Punktschweißverbindungen

The Effect of Different Test Frequencies on the Lifetime of Spot-Welded Joints In general lifetime prediction of welded joints is basing on S-N-curves where the influence of the variation of the S-N-curve is not taken into consideration. Moreover, it is not possible to specify the valid frequency range for the endurance limit of spot-welded joints. The test frequency defines the load velocity as a function of the phase relation of the strength. At the same time, the strength properties of the base material, the HAZ and the weld nugget are affected by load velocity. This means that the endurance limit of spot-welded joints is a function of the test frequency. This correlation was confirmed with tests on spot-welded deep-drawing sheets of R St 1403 (similar to AISI C 1008). In the report test results and the different fracture mechanisms are presented.     

Miniaturization of low cycle fatigue‐testing of single crystal superalloys at high temperature for uncoated and coated specimens

A newly developed miniature specimen and respective fixture for high temperature low cycle fatigue testing of nickel based single crystal superalloys is presented. Miniaturization allows the preparation of test specimens in all main crystallographic orientations of the cubic nickel crystal using laboratory sized material samples and enables excellent utilization of the costly material. The specimen geometry is optimized by means of parameter studies employing numerical calculations such that for the main crystallographic orientations the stress concentration at the fillet between gauge length and specimen head is minimized, and failure is likely to occur within the gauge length. The designed fixture allows easy specimen mounting and provides sufficient support for applying an extensometer for strain measurement. Protective metallic coatings against oxidation can be applied on the specimen by plasma spraying for studying the effect of coatings on the fatigue lifetime. The functionality of the specimen geometry and fixture design for low cycle fatigue testing is demonstrated for temperatures up to 950 °C.     

Die Abteilung Medizin‐Produkte in der MPA Darmstadt – eine Erfolgsgeschichte

The department Medical Products in the MPA Darmstadt – a success story The development (since1980) and meaning of the department Medical Products in the MPA Darmstadt are described and future prospects shown. The activities (testing, surveillance, consulting, failure analyses, calibration and standardization) are explained under consideration of the essential, not active medical devices exemplarily for the test lab (condoms, med. gloves, catheters, toothbrushes).     

Beitrag zur Untersuchung des Ermüdungsverhaltens von Koronarstents

Comments to the Investigation of Fatigue Properties of Coronary Stents Since 1986 PTCA with implantation of a stent became a more and more important invasive method of treatment for coronary heart disease. The stent implanted during PTCA has to sustain a combined load of mechanical and chemical load. The pulsating artery leads to an expansion and cyclic mechanical load on the implanted stent. To eliminate the possibility of fail in vivo stents have to be tested regarding fatigue behaviour. As result of the complex geometry and the up to now not well investigated qualities of oligocrystalline structures [1], so far fatigue properties of stents can only be carried out on the implants themselves. Additionally stent design plays a decisive role in terms of mechanical factors.     

Erprobungsmethodik für zyklisch überelastisch beanspruchte Bauteile unter Torsion – Bauschinger‐Kenngrößen für 54SiCr6

Power transmission contains several torsion‐stressed parts. Especially shafts and springs are numerous considered. Helical springs as a special type of springs are mainly stressed by torsion load. During operation the spring's load is basically elastic. In some cases, like overload or machine disaster, the load exceeds the spring's yield stress. For a single event the deformations can be calculated easily by using flow charts. However in other cases the spring will be stressed several times with alternating plastic load. Therefore the calculation will not be as easy as in the single load case. Especially the hardening and softening mechanisms have major influence on material behavior. For high strength steel this material behavior is not fully investigated right now. Present article shows a way how to investigate several important Bauschinger parameters based on plastic torsion load for the high strength steel 54SiCr6. Finally it can be shown that 54SiCr6 is influenced by the Bauschinger effect. On the other hand the needed material characteristic can be investigated by the shown methodology. Based on the identified data, analytical and numerical calculation of alternating plastic torsion load can be done.     

Ansätze zur Lastannahme für die PKW‐Betriebsfestigkeitsauslegung

As an essential part of the product development and design, the derivation of load assumptions and design requirements has to reflect the concept of the product verification process. An overview is given on the key elements of the process of defining load assumptions for passenger cars where the full set of external loads acting on a vehicle has to be considered, but also the structural response, which leads to the final load requirements on a component level. Some information is presented on the process where load assumption and strength and fatigue design requirements are derived on the basis of a number of sources including systematic measurements on new vehicles, consolidation of measurements within a load data‐base, numerical analyses and customer usage surveys. The topic of standardised load‐time histories is added by a comparison of load requirements given by CARLOS multi to those obtained from a test track.     

冷弯薄壁卷边Z形钢梁的弹性畸变屈曲荷载

该文以既有理论研究成果为基础,结合应用广义梁理论,对两端简支的冷弯薄壁卷边Z形钢梁在绕截面强轴弯矩作用下的弹性畸变屈曲荷载进行了深入细致的分析。通过对45个截面的参数分析,将原先适用于冷弯薄壁卷边槽钢梁的参数计算公式推广应用于Z形钢梁,并根据Z形钢截面的几何特性对相应参数进行了重新推导和修改。利用以上结果,最后提出了冷弯薄壁卷边Z形钢梁在绕强轴弯矩作用下的弹性畸变屈曲荷载简化计算公式。简化公式具有足够的精度、便于手算、实用性强,可供工程设计人员和各国冷弯薄壁型钢设计规范修订相应内容时参考采用。     

System analysis of Neo‐Gothic vaults / Systemanalyse neugotischer Gewölbe

From the middle of the 19th century until the beginning of World War I, many buildings were built in the Neo‐Gothic style. In this period, Gothic elements were built regarding the former needs to save material. These lightweight and thin vaults are often relatively fragile support systems. They tend to show systemic damages in the form of significant crack patterns in the vault caps and arches. In the research project Preservation of Neo‐Gothic vault structures, typical damages of Neo‐Gothic vaulted structures are analyzed with the objective to find sustainable and rehabilitative measures. In this context, since 2011, numerical and experimental studies have been carried out on a reference structure. Measured values of a 3D laser scanning, including all the imperfections of the structure, provide the basis of the geometry model, created for the finite element simulation. The system behavior was studied experimentally in the non‐critical load range with a load test for the calibration of this numerical model. In this paper, the project framework as well as the implementation and the evaluation of the load test are presented. In further papers, the transfer of the geodetic measurement data to the numerical model and the consideration of the load test results within a realistically finite element simulation will be addressed.     

Pull‐out strength of anchor pins for brickwork masonry and earth block masonry / Auszugsfestigkeit von Verpressankern für Ziegel‐ und Lehmsteinmauerwerk

In this paper results of the experimental testing performed on brick masonry and earth block masonry are presented. The paper outlines the development of the testing procedures for two different types of anchors. For this purpose, two experimental campaigns of pull‐out tests on masonry corner connections strengthened by metallic rod grouted were carried out. Experimental results proved that the implemented testing procedures are suitable to determine the most recurring failure modes of the anchor pins. Moreover, a procedure is proposed to estimate the capacity of grouted anchor pins based on experimental studies.