Ultrasonic non-destructive on-line estimation of the tensile stiffness of a running paper web

A new method for measuring the elastic properties of paper on-line in a paper machine by using ultrasound has been developed. The unique feature of the method is that a continuous stochastic ultrasonic signal is used for measurements, which is generated by means of a dry friction between a running paper web and a rigidly fixed friction head. The signals from the web are picked up by an array of air-coupled ultrasonic receivers, which have no mechanical contact with the paper web. The ultrasound velocity in the web is obtained by means of the correlation processing. By using advanced digital signal processing, the tensile stiffness index (TSI) of the running web is determined. From the sensor we get the TSI values both in the machine direction and the cross-machine direction.The on-line ultrasonic sensors have been installed on two different paper machines for more than two years. This paper describes the background of the method, as well as some experiences and applications from two mill installations.     

Effects of the amount of fillers and of the crosslink density on the mechanical behavior of carbon‐black filled styrene butadiene rubbers

Several carbon‐black filled styrene‐butadiene rubbers are subjected to monotonic uniaxial tension tests in order to investigate the effects of the amount of fillers and of the crosslink density on their mechanical properties. The Young modulus, the volume changes associated with material damage and the stretch to failure are extracted and discussed. Results compare well to the literature results when exist and quantitative analysis are proposed when possible. Results show that filled rubbers are not incompressible when submitted to uniaxial tension tests and their volume changes are strongly dependent of the amount of fillers but are unaffected by the crosslink density. The latter shows strong impact on the filled rubbers stretch to failure but more interestingly this impact is comparable to what is encountered in unfilled rubbers. The stretch to failure is improved by the addition of fillers with an optimum for material filled around 30 phr. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Verhalten von Mauerwerksbauten unter Erdbebeneinwirkung: Auswertung der Schäden des Albstadt‐Erdbebens vom 3. September 1978

Numerische Untersuchungen zum Verhalten von Mauerwerksbauten unter Erdbebeneinwirkung führen oft zu pessimistischen Schadensprognosen, welche im Gegensatz zu den Beobachtungen stehen. Um diesen Widerspruch aufzulösen, werden erfahrungsbasierte Verletzbarkeitsfunktionen für typische Mauerwerksgebäude auf der Grundlage der durch das Erdbeben vom 3. September 1978 bei Albstadt (mit einer Lokalmagnitude M_L von 5,7 und Epizentralintensität I₀ = VII—VIII) verursachten Schäden entwickelt. Anhand des Bauwerksbestandes von 1978 erfolgt die Einordnung der beobachteten Schäden in Schadensgrade auf Basis der European Macroseismic Scale EMS‐98 [1]. Die für den Bauwerksbestand repräsentativen Bauweisen werden herausgearbeitet; für die vorherrschenden Gebäude aus unbewehrtem Mauerwerk ist eine weitere Unterscheidung nach Baualter, Geschosszahl und phänomenologischen Gesichtspunkten möglich. Vulnerability of masonry structures under seismic action: Damage analysis of the September 3, 1978 Albstadt earthquake. Numerical studies of the earthquake behavior of masonry buildings in Central Europe based on national building codes acc. to the Eurocode 8 lead to pessimistic damage prognoses, which are in contradiction to the observed behavior. In order to eliminate this discrepancy realistic experience‐based vulnerability and displacement functions for typical masonry constructions are developed. Because of the rather limited number of earthquake damage observations, the Magnitude M_L 5.7 Albstadt earthquake from September 3, 1978 (intensity VII—VIII) in South Germany also based on its excellent documentation is reconstructed with the building stock existing at that time. The prevailing building types and for these the characteristic damage cases are investigated in close cooperation with the local authorities. The presented unreinforced masonry structures are divided by year of construction, number of storeys and phenomenological aspects.     

Reconfigurable handling system

The demand for more versatile assembly and handling systems to facilitate customized production is gaining in importance, especially with regard to the constantly-increasing cost pressure, to expansion of the range of product versions and the shortening of innovation cycles. As a cost-effective approach for frequently changing assembly tasks, a novel manipulation concept has been developed by combining given robot technologies. This new handling system has a modular and adaptable layout, which consists of several mobile arms to manipulate the object in six-dimensional Cartesian space. After grasping, when the arms are attached to the object, the mechanical architecture is similar to parallel manipulators or cooperating robots. As the mounting and gripping points of the arms can easily be changed, the manipulator can be reconfigured so as to match the user’s preferences and needs. In addition to the kinematic adaption the regarding task, the hardware and new functions can be reconfigured as well. Contact elements, measurement and assembly devices as well as testing modules can easily be in integrated in the concept. A modular automatic control concept combined with a self-optimizing planning tool helps the user to find the optimal configuration and realize it in an economic way.     

New wood-polymer composites containing ethyl α-hydroxymethyl acrylate polymers

Ethyl α-hydroxymethyl acrylate (EHMA) was synthesized and evaluated as a candidate for wood impregnation and in-situ polymerization. Southern Pine softwood was impregnated under a variety of conditions with EHMA alone and with various comonomers plus free radical initiator. Following thermal polymerization, the wood-polymer composites were tested for increased dimensional stability (water soaking swell resistance) and mechanical properties over untreated wood. The greatest increase in dimensional stability was attained using EHMA alone, while the maximum compression modulus was achieved by impregnating with 1:1 EHMA-styrene and styrene alone. The composites were further characterized by ¹³C CP/MAS solid state NMR and scanning electron microscopy.     

Low‐loss TCP/IP header compression for wireless networks

Wireless is becoming a popular way to connect mobile computers to the Internet and other networks. The bandwidth of wireless links will probably always be limited due to properties of the physical medium and regulatory limits on the use of frequencies for radio communication. Therefore, it is necessary for network protocols to utilize the available bandwidth efficiently. Headers of IP packets are growing and the bandwidth required for transmitting headers is increasing. With the coming of IPv6 the address size increases from 4 to 16 bytes and the basic IP header increases from 20 to 40 bytes. Moreover, most mobility schemes tunnel packets addressed to mobile hosts by adding an extra IP header or extra routing information, typically increasing the size of TCP/IPv4 headers to 60 bytes and TCP/IPv6 headers to 100 bytes. In this paper, we provide new header compression schemes for UDP/IP and TCP/IP protocols. We show how to reduce the size of UDP/IP headers by an order of magnitude, down to four to five bytes. Our method works over simplex links, lossy links, multi‐access links, and supports multicast communication. We also show how to generalize the most commonly used method for header compression for TCP/IPv4, developed by Jacobson, to IPv6 and multiple IP headers. The resulting scheme unfortunately reduces TCP throughput over lossy links due to unfavorable interaction with TCP's congestion control mechanisms. However, by adding two simple mechanisms the potential gain from header compression can be realized over lossy wireless networks as well as point‐to‐point modem links. This revised version was published online in June 2006 with corrections to the Cover Date.     

Detection and Localization of Delaminations in Thin Carbon Fiber Reinforced Composites with the Ultrasonic Polar Scan

In this paper, the hybrid compliance-stiffness matrix method for simulating wave propagation in (delaminated) multilayered media with viscoelastic anisotropy has been confronted with high-quality amplitude and phase experiments on delaminated composites, obtained using the ultrasonic polar scan setup (UPS) in transmission by considering harmonic as well as pulsed ultrasound. Results are presented for multiple thin carbon/epoxy laminates with an artificial edge delamination induced by a foil insert, showing a good agreement between experimental recording and numerical modeling. The obtained results further reveal the feasibility of the harmonic UPS to detect and even locate the depth-position of multiple delaminations in fiber reinforced composites. Considering that the harmonic UPS method does not rely on the detection of different echoes like the classical C-scan, but rather expounds the conditions for efficient stimulation of guided waves in the solid, the method is found to be highly suited for inspecting thin composite materials for the presence of delaminations.