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  • 1.
    Aoki, S.
    et al.
    Tokyo Institute of Technology, Department of Mechanical and Environmental Informatics.
    Amaya, K.
    Tokyo Institute of Technology, Department of Mechanical and Environmental Informatics.
    Noguchi, T.
    Tokyo Institute of Technology, Department of Mechanical and Environmental Informatics.
    Ståhle, P.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Identification of elastic/visco-plastic material constants under impact loading2000Inngår i: IUTAM Symposium on Field Analysis for Determination of Material Parameters - Experimental and Numerical Aspects :: proceedings of the IUTAM Symposium held in Abisko National Park, Kiruna, Sweden, July 31 - August 4, 2000 / [ed] P. Ståhle, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method for identifying the material constants of an elastic/visco-plastic meterial under tensile impact loading is proposed. In this method, the Kalman filter and the finite element method are used together with a few test data. To obtain data for high strain rates, notched specimens are employed, because arbitrarily shaped specimens are available in this method. To increase the accuracy of identification, a test under a relatively low strain rate is needed in addition to a test under a high strain rate. The optimum strain rate is determined in such a way that the largest eigen value of the covariance matrix of the estimated parameters becomes minimum. A numerical simulation in performed to demonstrate the validity and usefulness of this method

  • 2. Carlsson, J.
    et al.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Determination of force, particle velocity and related quantities in a dynamically loaded non-uniform rod from strain histories at two cross sections1990Inngår i: Experimental mechanics : 9th International conference : Papers., Lyngby: Technical University of Denmark , 1990Konferansepaper (Fagfellevurdert)
  • 3.
    Carlsson, J.
    et al.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Method for determination of in-hole dynamic force-penetration data from two-point strain measurement on a percussive drill rod1990Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 27, nr 6, s. 553-558Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the present investigation is to establish a testing method suited for determination of in-hole dynamic force-penetration data for non-uniform standard percussive drill rod-bit configurations. The method is based on a version of the method of two-point strain measurement, which permits non-uniform rods, i.e. rods with variable characteristic impedance. This version allows normal force and particle velocity to be evaluated at an arbitrary cross-section of a homogenous non-uniform elastic rod from strain measurements performed at two different cross-sections of the same rod. The main problem of this investigation is to assess whether the influence of threads can be considered insignificant. As a part of the study force-penetration relationships have been determined for the penetration of a standard Sandvik Rock Tools button bit into Swedish Bohus granite.

  • 4. Eman, Jesper
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Spatially resolved observations of strain fields at necking and fracture of anisotropic hardened steel sheet material2009Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 46, nr 13, s. 2750-2756Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work plastic strain localization, also referred to as necking, of press-hardened ultra-high strength steel is observed using digital speckle correlation. The region of the neck is studied during tensile tests of specimens specially designed to facilitate strain localization at an inner point of the material, thus avoiding edge effects on localization and fracture. By using measurements with a length scale small enough to properly resolve the neck, its growth and shape can be studied. Furthermore, the anisotropy of the material is investigated by examining specimens cut out at different angles to the rolling direction. It is seen that the local fracture strain of specimens cut out along the rolling direction is approximately twice as high as it is for specimens cut out perpendicular to the rolling direction.

  • 5. Färm, J.
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modified split-Hopkinson pressure bar for testing of high-strength ceramics1994Inngår i: Recent advances in experimental mechanics :: 10th International conference on experimental mechanics : Papers / [ed] J.F. Silva Gomes, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1994Konferansepaper (Fagfellevurdert)
  • 6.
    Hernandez, Sinuhe
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Leiro, Alejandro
    Ripoli, Manel Rodriguez
    AC²T research GmbH - Austrian Center of Competence for Tribology, Viktor-Kaplan-Straße 2 D, 2700 Wiener Neustadt.
    Vuorinen, Esa
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sundin, Karl-Gustaf
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    High temperature three-body abrasive wear of 0.25C 1.42Si steel with carbide free bainitic (CFB) and martensitic microstructures2016Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 360-361, s. 21-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, the wear behaviour of different steels has been investigated under a three body abrasive environment at room and elevated temperatures. High-silicon steel (0.25C-1.42Si) was austempered at 300 and 320 ˚C in order to obtain two carbide-free bainitic steels with different mechanical properties. The same steel subjected to two different quench and temper heat treatments was used as a reference material for mechanical and wear testing. The steels were subjected to three-body abrasive wear by means of a high temperature continuous abrasion tester (HT-CAT). The tests were done at 25, 300 and 500 °C respectively. All samples showed similar wear rates at room temperature. At 500 °C, the material austempered at 320 ˚C showed the highest toughness and the lowest wear rate. High temperature hardness and impact toughness tests showed that abrasive wear is not only influenced by hardness but also by the toughness of the material. Owing to their good strength/toughness combination CFB steels could prove to be an important material for abrasive wear applications

  • 7.
    Häggblad, Hans-Åke
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Berglund, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Formulation of a finite element model for localisation and crack initiation in components of ultra high strength steels2009Inngår i: Hot sheet metal forming of high-performance steel, CHS2: 2nd international conference, June 15-17 2009, Luleå, Sweden. Proceedings / [ed] Mats Oldenburg; Kurt Steinhoff; Braham Parkash, Auerbach: Verlag Wissenschaftliche Scripten , 2009, s. 229-237Konferansepaper (Fagfellevurdert)
  • 8. Isaksson, Erik
    et al.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Correlation of vehicle crash model parameters to car properties in low-speed collisions: a design of experiments approach2010Inngår i: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 15, nr 3, s. 241-249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the current study, a methodology for relating model parameters in a one dimensional Mass Spring Damper (MSD) model to global properties of a car, e.g. axial stiffness, bending stiffness and mass, is presented. It is shown that these three vehicle properties affect the vehicle's crash performance in low-speed collision tests used for industrial verification of bumper system performance. Based on information of the properties for a vehicle under development, parameters in the MSD model can be adjusted to give the correct boundary conditions for a finite element (FE) crash simulation with a candidate bumper design. In the FE simulations, the MSD model is then coupled to the FE mesh of candidate bumper design to find a bumper that meets the crash performance requirements of a car under development. The methodology is based on Design of Experiments (DOE) and FE simulations on a public domain model of a Ford Taurus. The knowledge gained from this study gives a valuable tool to use in design and development of bumper systems for the automotive industry.

  • 9. Jonsson, Mikael
    et al.
    Karlsson, Lennart
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental and numerical analysis of damped transient vibration of beam structures1989Inngår i: Proceedings of the International conference on noise and vibration: August 16-18, 1989 at Novetel Orchid Inn Singapore, Singapore: Nanyang Technological Institute , 1989, s. B.53-B.64Konferansepaper (Fagfellevurdert)
  • 10.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Isaksson, Erik
    Luleå University of Technology.
    Sundin, Karl-Gustaf
    Oldenburg, Mats
    Identification of lumped parameter automotive crash models for bumper system development2009Inngår i: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 14, nr 6, s. 533-541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the design and development process of bumper systems for the automotive industry, information about the future car model is limited. Normally, iterative finite element (FE) analyses of different crash loading tests are used to find an appropriate bumper system to the coming car model. Because of the lack of information, only a rough model of the car is normally utilised in the FE simulations. This leads to uncertainties in the bumper design since the dynamic response of the car is dependent on the load case and the properties of the actual bumper system. This paper presents a method for identification of lumped parameter models based on results from crash tests of a Volvo S40. The ability to predict the measured results for models with different number of degrees of freedom (DOF) is investigated. Also, a validation of the model together with an FE mesh of the bumper system is presented. The results clearly show that a linear mass spring damper model with 2 DOF can be used to predict the response from the measurements in case of symmetric loading. Further increase of the number of DOF only causes small or no improvements of the agreement between the predicted and measured crash response.

  • 11.
    Kajberg, Jörgen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    High-Temperature Split-Hopkinson Pressure Bar with a Momentum Trap for Obtaining Flow Stress Behaviour and Dynamic Recrystallisation2014Inngår i: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 50, nr 6, s. 547-554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In hot forming processes at elevated temperatures like wire rolling, microstructural changes such as repeated dynamic recrystallisation and grain growth occur. An experimental method to obtain the flow stress behaviour and to capture the recrystallised microstructure for materials subjected to large deformations, high temperatures between 900 and 1200 °C and high strain rates around 5000 s− 1 is presented. The method is based on the split-Hopkinson pressure bar arrangement complemented with an inductive heat source. Furthermore, a momentum trap is added to ensure that the specimen is loaded only once. By quenching the specimen directly after the single loading, the dynamically recrystallised microstructure is preserved. The quenching is performed within 0.1 s of loading by dropping the specimen into a water bath. By applying the momentum trap technique, the compressive loading of the specimen could be interrupted at a strain level slightly above the strain level corresponding to the peak stress, which is a good estimation for the onset of dynamic recrystallisation.

  • 12.
    Kajberg, Jörgen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Material characterisation using high-temperature Split Hopkinson pressure bar2013Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 213, nr 4, s. 522-531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to characterise the mechanical response of materials in manufacturing processes, such as wire and bar rolling involving very high strain rates, temperatures and level of straining, an experimental device is presented. The device is suitable for testing at strain rates up to approximately 4000 s−1, temperatures up to 1200 °C (≈1500 K) and strains around 0.5. It is based on the classical split Hopkinson pressure bar and is complemented with an inductive heating source for achieving requested temperatures. By keeping the specimen separated from the Hopkinson bars just until an instant before impact (50 ms) considerable cooling and temperature gradients in the specimen are avoided. Three steel grades, two stainless steels and a high-speed steel, were tested. Four different material models whose parameters were fitted to the obtained experimental data were used for mechanical characterisation: two empirically based and two physically based. Overall, one of the physically based models showed the best agreement between experimental results and the predicted flow stresses.

  • 13. Kajberg, Jörgen
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Melin, L.Gunnar
    Luleå tekniska universitet.
    Ståhle, Per
    Luleå tekniska universitet.
    High strain-rate tensile testing and viscoplastic parameter identification using microscopic high-speed photography2004Inngår i: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 20, nr 4-5, s. 561-575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combined experimental/numerical method for determination of constitutive parameters in high strain-rate material models is presented. Impact loading, using moderate projectile velocities in combination with small specimens (sub mm) facilitate tensional strain rates in the order of 104-105 s-1. Loading force is measured from one-dimensional wave propagation in a rod using strain gauges and deformation is monitored with a high-speed camera equipped with a microscope lens. A sequence of digital photographs is taken during the impact loading and the plastic deformation history of the specimen is quantified from the photographic record. Estimation of material parameters is performed through so called inverse modelling in which results from repeated FE-simulations are compared with experimental results and a best choice of constitutive parameters is extracted through an iterative optimisation procedure using the simplex method. Results are presented from a preliminary tension test of a mild steel (A533B) at a strain rate well over 104 s-1. The sensitivity of the evaluated material parameters to errors in measured quantities is studied. The method, especially the optical technique for measurement of deformation will be further developed.

  • 14. Karlsson, Lars G.
    et al.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental study of a percussive process for rock fragmentation1989Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, nr 1, s. 45-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The efficiency of a percussive process for fragmentation of rock and similar materials has been studied experimentally. The percussive system comprised a cylindrical hammer and a cylindrical bit with the same characteristic impedance. The bit was terminated with a wedge. In front of the wedge there was a heavy block of concrete. The length of the bit and the initial gap between bit and concrete were varied systematically. The force versus penetration relationship and the work of fragmentation were determined in each test using a new technique based on measurement of strains at two cross-sections of the bit. Each test was simulated individually using a previously developed one-dimensional model. The results of simulations and experimental tests were found to agree well.

  • 15. Lagerkvist, L.
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental determination of mechanical impedance through strain measurement on a conical rod1982Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 85, nr 4, s. 473-481Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An impedance gauge based on measurement of strains at two different cross-sections of a conical gauge rod is tested. The gauge rod is in contact with the object at its narrow end while its wide end is driven by a harmonic vibrator. The length of the gauge rod is 260 mm and its end diameters are 9·8 mm and 20·1 mm. For cylindrical test objects a fair agreement is generally obtained between experimental and theoretical point impedances in the frequency range 50 Hz to 5 kHz. Further improvements in accuracy are expected to be feasible

  • 16.
    Lagerkvist, L.
    et al.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mechanical impedance gauge based on measurement of strains on an impacted rod1983Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 88, nr 2, s. 225-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An impedance gauge based on measurement of strains at two cross-sections of a slender rod is studied. The gauge rod is in contact with the object at one end while it is impacted at the other end. The impedance is evaluated from the two strain signals by means of a two-channel FFT-analyzer and a desk-top computer. Gauge prototypes with cylindrical and conical geometries are tested in the frequency range 50 Hz to 5 kHz for cylindrical objects with known theoretical point impedances. Satisfactory agreement between experimental and theoretical impedances is obtained for both prototypes

  • 17. Lagerkvist, L.
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Effect of contributions from bending in evaluation of axial strain in rods with circular cross-section1983Inngår i: Journal of Strain Analysis for Engineering Design, ISSN 0309-3247, E-ISSN 2041-3130, Vol. 18, nr 1, s. 77-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contributions from bending to the evaluated axial strain in an elastic rod are commonly suppressed by forming half the sum of measured surface strains at diametrically opposite positions. A simple method is presented which gives a useful estimation of the bending suppression (the ratio of the bending strain to the absolute value of the evaluated axial strain when a rod is subject to bending only) from (i) optically measured mis-positioning and (ii) estimated differences between the gauge constants for the two strain gauges. Good agreement is obtained with results obtained from strain measurements on a rod loaded in bending

  • 18.
    Lagerkvist, Lars
    et al.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Determination of mechanical impedance through strain measurement on an impacted slender rod1982Rapport (Annet vitenskapelig)
  • 19.
    Lagerkvist, Lars
    et al.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental investigation of a mechanical impedance gauge based on measurement of strains on a conical rod1981Rapport (Annet vitenskapelig)
  • 20.
    Leiro, Alejandro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Roshan, Arash
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Vuorinen, Esa
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Fatigue of 0.55C-1.72Si Steel with Tempered Martensitic and Carbide-Free Bainitic Microstructures2014Inngår i: Acta Metallurgica Sinica (English Letters), ISSN 1006-7191, E-ISSN 2194-1289, Vol. 27, nr 1, s. 55-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-Si spring steel was heat treated in three different ways: Quenching and tempering at 460 °C to obtain a tempered martensite microstructure, and austempering at 300 and 350 °C, respectively, to obtain two different carbide-free bainitic microstructures. In the steel austempered at 350 °C, both the bainite lath thickness and retained austenite content were higher than those of the steel austempered at 300 °C. Rotating-bending fatigue tests were done in order to evaluate the effect of each heat treatment on the high-cycle fatigue behavior of the steel. When the austempering temperature was 300 °C, the endurance limit was increased by 25% despite a 5% reduction in tensile strength when compared with that of the quenched and tempered steel. The relationship between endurance limit [Rfat (50%)] and ultimate tensile strength (Rm) was higher for the austempered samples in comparison with that of the quenched and tempered material. Therefore, it is believed that the presence of retained austenite affects the relationship between endurance limit and tensile strength.

  • 21.
    Leiro, Alejandro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vuorinen, Esa
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sourmail, T.
    ASCOMETAL-CREAS.
    Samanio, V.
    ASCOMETAL-CREAS.
    Caballero, F.C.
    National Center for Metallurgical Research (CENIM-CSIC), Madrid.
    Garcia-Mateo, C.
    National Center for Metallurgical Research (CENIM-CSIC), Madrid.
    Elvira, Roberto
    Gerdau Sidenor I+D.
    Wear of nano-structured carbide-free bainitic steels under dry rolling-sliding conditions2013Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 298-299, nr 1, s. 42-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Specially designed steels with carbon contents from 0.6 to 1.0 wt.% were isothermally transformed at very low temperatures, between 220 and 270 °C, in order to obtain a nano-structured bainitic microstructure. It is shown that the wear resistance in dry rolling-sliding of these nano-structured steels is significantly superior to that ofbainitic steels transformed at higher temperatures with similar hardness values.In addition to the highly refined microstructure, the transformation under strain to martensite (TRIP effect), contributes to the plasticity of the nano-scaled steels, increasing surface hardness during testing, thus reducing the wear rate.

  • 22.
    Lundberg, Bengt
    et al.
    Luleå tekniska universitet.
    Carlsson, J.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Analysis of elastic waves in non-uniform rods from two-point strain measurement1990Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 137, nr 3, s. 483-493Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method is established which permits evaluation of the histories of normal force and particle velocity at an arbitrary cross-section E of a non-uniform linearly-elastic rod from measured strain histories at two different cross-sections, A and B. Other quantities at E, such as stress, strain, displacement, acceleration and power transmission, can be determined in terms of the evaluated normal force and particle velocity. The method is an extension of that developed by Lundberg and Henchoz for uniform rods. Theoretical results, based on one-dimensional elastic wave theory, are provided for the general case as well as for cases of piecewise constant characteritic impedance. Experimental tests with different configurations of non-uniform rods and strain gauges show that the normal force histories determined at E with the present method (from measured strains at A and B) agree well with those obtained through direct strain measurement at E.

  • 23.
    Melin, L.Gunnar
    et al.
    Luleå tekniska universitet.
    Ståhle, P.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    High strain rate tensile testing using microscopic high speed photography1998Inngår i: Experimental mechanics : advances in design, testing and analysis / [ed] I.M. Allison, Taylor and Francis Group , 1998, s. 175-179Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method is presented that combines advanced experimental and numerical techniques in the determination of constitutive parameters. The general principle is that a specimen, producing a non-homogeneous stress state, is deformed rapidly. Load and deformation is recorded during the deformation and the event is also simulated using FEM. For the numerical calculation a set of constitutive parameters is used which can be systematically adapted so that a good agreement with experimental results is achieved. Strain rates of 10 exp 4 - 10 exp 5 s exp -1 are possible because the specimen can be made small. Microscopic high-speed photography is used to record the deformation of specimens of sub millimetre size. The method allows both tensile and compressive testing.

  • 24.
    Nilsson, P.
    et al.
    Luleå tekniska universitet.
    Ståhle, P.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    On the behavior of crack surface ligaments1998Inngår i: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 184, nr 1, s. 145-153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Small ligaments connecting the fracture surfaces just behind a moving crack front are assumed to exist under certain conditions. The ligaments are rapidly torn as the crack advances. Inelastic straining of such ligaments influences the energy balance in the fracture process. The rapid tearing of a single ligament is studied both numerically and experimentally. An elastic visco-plastic material model is adopted for finite-element calculations. The results show that relatively large amounts of energy are dissipated during the tearing process. Further, the energy needed to tear a ligament increases rapidly with increasing tearing rate. The computed behavior is partly verified in a few preliminary experiments. The implications for slow stable crack tip speeds during dynamic fracture are discussed.

  • 25.
    Nilsson, P.
    et al.
    Luleå tekniska universitet.
    Ståhle, P.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    On the temperature in dynamic crack surface ligaments1996Inngår i: Mechanisms and mechanics of damage and failure: proceedings of the 11th Biennial European Conference on Fracture - ECF 11 - held in Poitiers Futuroscope, France, 3 - 6 September 1996, EMAS , 1996, Vol. Vol. 1, s. 627-632Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Small ligaments connecting the crack surfaces just behind the moving crack front are assumed to exist during fast cleavage crack growth. The production and conduction of heat during the process of tearing these ligaments are studied. The straining is computed by assuming an elastic visco-plastic material model. The produced heat during plastic work is calculated. Heat conduction is considered. The results reveal that the temperature increases several hundred centigrades for a low yield stress. For a high yield stress the temperature increases to > 1000 deg C. The appropriateness of the selected constitutive relationship is discussed in view of the result (for structural steels).

  • 26.
    Nilsson, P.
    et al.
    Luleå tekniska universitet.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Ståhle, P.
    Luleå tekniska universitet.
    On the Behavior of Crack Surface Ligaments1996Inngår i: Constitutive relation in high/very high strain rates / [ed] Kozo Kawata, Tokyo: Encyclopedia of Global Archaeology/Springer Verlag, 1996Konferansepaper (Fagfellevurdert)
  • 27.
    Oldenburg, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Wikman, Bengt
    Kajberg, Jörgen
    Åkerström, Paul
    Material characterisation using advanced experiments and inverse methods2006Inngår i: Computational mechanics: Abstracts : abstracts of the papers presented at the regular sessions of the sixth world congress on computational mechanics in conjunction with the second Asian-Pacific congress on computational mechanics, September 5-10, 2004, Beijing, China / [ed] Zhenhan Yao; Mingwu Yuan; Wanxie Zhong, Bejing: Tsinghua University Press, 2006Konferansepaper (Annet vitenskapelig)
  • 28.
    Sjöberg, Ted
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Reverse ballistic experiment resembling the conditions in turbine blade off event for containment structures2016Inngår i: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 107, s. 671-677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental technique has been developed which allows loading of heated sheet material under impact conditions with simultaneous measurement of the impact force history. The combined characteristics of impact loading at elevated temperature makes the experiment ideal for validation of models used to simulate the containment structure surrounding aircraft engines. In this paper experimental results for Alloy 718 are presented, a nickel based super alloy commonly used in hot parts of the containment structure. The experimental results are then compared to simulations in order to validate previously calibrated material parameters. The basic principle of the validation experiment is based on reverse ballistics, in which a thin circular specimen with free boundaries impacts the end of an instrumented rod. Using induction heating the specimen is heated to temperatures up to 650 °C and a gun driven by compressed air accelerates the specimens to desired velocity. In the reported work velocities are kept low enough to avoid cracking and thus the study is limited to plastic conditions, even though the technique is applicable also for fracture studies. The free boundaries of the experiment makes numerical modelling and simulation straightforward, making it valuable as a validation tool. All numerical simulations are performed using the commercial finite element code LS-Dyna and plastic behaviour of the material was modelled with the Johnson-Cook material model

  • 29.
    Sjöberg, Ted
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Calibration and validation of plastic high strain rate models for alloy 7182013Inngår i: Computational Plasticity XII / [ed] E. Oñate; D.R.J. Owen; D. Peric; B. Suárez, Barcelona, 2013, s. 469-479Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Alloy 718 (Inconel™ 718), composed mainly of nickel, iron and chromium has properties that are of interest in many high temperature applications. One such application is the containment structure in aero engines which prevents fragments from penetrating the structure in case of blade failure. Impact of blade fragments on the containment structure includes both high strain rates and high temperatures and simulation models must therefore have their base in experimental conditions including transient loading and heating. An experimental method has been developed that utilizes induction heating in a high rate tensile test machine. Strain rates up to the order of 1000 s-1 and temperatures up to 650 °C have been included in the test program. Material parameters for the Johnson-Cook and the Zerilli-Armstrong models are evaluated from experimental data using optimisation. These parameters are then used to simulate a specially designed impact experiment and a direct comparison of a calculated and measured quantity can be made in order to validate model and parameters. The result from the validation experiment showed better agreement for the Johnson-Cook model than the Zerilli-Armstrong model

  • 30.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Performance of a mechanical impedance gauge under harmonic excitation1984Rapport (Annet vitenskapelig)
  • 31.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Performance test of a mechanical impedance gauge based on strain measurement on a rod1985Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 102, nr 2, s. 259-268Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An impedance gauge based on measurement of strains at two cross sections of a slender rod has been tested on practical objects. Sensitive semiconductor strain gauges are used and the impact force necessary for excitation is therefore low. Measurements were conducted with the gauge held in contact with the test objects by hand and excited by light strokes from a hammer. With this technique impedances in the transverse direction of beams were measured in the frequency range 20 Hz to 2 kHz. Similar measurements were also conducted with a conventional impedance head for comparison. From the results of the measurements it is concluded that the performance of the impedance gauge is good under the prevailing experimental conditions.

  • 32.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tillsats för tvåaxlig utmattningsprovning: konstruktion och provning av prototyp 111981Rapport (Annet vitenskapelig)
  • 33.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Transducers for impact force and mechanical impedance based on strain measurement1984Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Transducers for impact force and mechanical point impedance are studied. In both cases the transducers are based on resistive strain measurement. Two prototypes of impact force transducers based on different concepts of mean strain measurement are developed and tested. The results are satisfactory and show that the suggested concepts are suitable. The transducer for mechanical point impedance is based on strain measurement at two points along a linearly elastic rod which acts as a wave guide for longitudinal waves. One end of the rod is in contact with the object while the other end is excited by impact. Tests are conducted on attached cylindrical rods as well as on unattached beams. The performance of the transducer is generally good. Impedances measured on the unattached beams are generally in good agreement with corresponding results obtained with a conventional impedance head.

  • 34.
    Sundin, Karl-Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Eman, Jesper
    Fracture strains at holes in high-strength steel: a comparison of techniques for hole-cutting2007Inngår i: Experimental analysis of nano and engineering materials and structures: proceedings of the 13th International Conference on Experimental Mechanics, Alexandroupolis, Greece, July 1-6, 2007 / [ed] Emmanuel E. Gdoutos, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2007Konferansepaper (Fagfellevurdert)
  • 35.
    Sundin, Karl-Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Granström, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental investigation of plastic and fracture behaviour of 22MnB5 at hot stamping conditions2013Inngår i: 4th International Conference Hot Sheet Metal Forming of High-performance Steel CHS: June 9-12, Luleå, Sweden : Proceedings / [ed] Mats Oldenburg; Braham Prakash; Kurt Steinhoff, Auerbach: Verlag Wissenschaftliche Scripten , 2013, s. 557-564Konferansepaper (Fagfellevurdert)
  • 36.
    Sundin, Karl-Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsson, Mikael
    A stiff and compact impact-force transducer based on strain measurement1985Inngår i: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 25, nr 1, s. 48-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stiff and compact transducer for both static and impact compressive forces has been developed. The principle of the transducer is based on measurement of tangential strain around the periphery of an axially loaded short and axisymmetric body. It is shown that for an appropriate choice of transducer geometry the output is nearly insensitive to the distribution of the force over the loaded surface. In an experimental investigation, a prototype of the transducer was subjected to both static and impact loads of different distributions. The results show only a few percent variation in transducer sensitivity for the load distributions used. The transducer consists essentially of a homogeneous body and is simple to make. The size and material can be chosen to fit special applications

  • 37.
    Sundin, Karl-Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsson, Mikael
    Force transducer based on measurement of mean strain in a compact body1989Inngår i: Journal of Strain Analysis for Engineering Design, ISSN 0309-3247, E-ISSN 2041-3130, Vol. 24, nr 1, s. 31-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A force transducer based on measurement of mean strain in a body has been developed. The transducer can be made stiff and compact and is therefore suitable for measurement of impact forces as well as static forces. An experimental test of a simple first prototype was performed using both static and impact loads with different distributions over the load-carrying area of the transducer. The results of the experiments show that the requirement of insensitivity to differences in load distribution is acceptably fulfilled. Improvements are expected to be possible if the transducer is made in a more accurate way.

  • 38.
    Sundin, Karl-Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Åhrström, Bert-Olof
    Method for investigation of frictional properties at impact loading1999Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 222, nr 4, s. 669-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the assessment of lubricant performance and also in various other contact applications it is of importance to know the frictional qualities of a surface. Under quasi-static conditions, normal and frictional forces are measured using force transducers but the task is more difficult when loads are transient. The experimental method presented in this paper is based on the analysis of propagating waves in a beam, due to an impact on the end surface. The impact is oblique and therefore a transverse as well as a normal force is generated. The normal force history is measured from the axial non-dispersive wave using strain gauges. Transverse force and bending moment both generate dispersive flexural waves. From the FFT of two transverse acceleration histories, the frictional force at the end of the rod is evaluated using beam theory. The relation between normal and frictional force histories displays the frictional properties at the impact. Preliminary results are presented

  • 39.
    Sundqvist, Jesper
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Ingemar
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Keskitalo, Markku
    University of Oulu, University of Oulu, Oulu Southern Institute.
    Mäntyjärvi, Kari
    University of Oulu.
    Granström, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Measuring the influence of laser welding on fatigue crack propagation in high strength steel2013Inngår i: ICALEO, 32nd International Congress on Applications of Lasers & Electro-Optics: October 6-10, 2013, Hyatt Regency Miami, Miami, FL USA, Orlando, Fl.: Laser institute of America , 2013Konferansepaper (Fagfellevurdert)
  • 40.
    Sundqvist, Jesper
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Granström, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Sundin, Karl-Gustaf
    Keskitalo, Markku
    University of Oulu, University of Oulu, Oulu Southern Institute.
    Mäntyjärvi, Kari
    University of Oulu.
    Ren, Xiaobo
    SINTEF Materials and Chemistry, Trondheim.
    Identifying residual stresses in laser welds by fatigue crack growth acceleration measurement2015Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 27, nr 4, artikkel-id 42002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During laser welding, residual stresses are thermally induced. They can have strong impact on the fatigue behavior and fatigue life. A standardized measurement method for the fatigue crack growth rate was expanded to identify residual stress along the cracking path. The second derivative of the measured crack opening and in turn the crack acceleration corresponded well with distinct acceleration maxima and minima and accordingly with tensile and compressive stress, as was basically proven by numerical simulation. The method is simple and extendable. It provides valuable information, as was demonstrated for various situations.

  • 41. Åhrström, Bert-Olof
    et al.
    Lindqvist, S.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modified split Hopkinson pressure bar method for determination of the dilatation-pressure relationship of lubricants used in elastohydrodynamic lubrication2002Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 216, nr 2, s. 63-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In theoretical calculations of film thickness, pressure distribution and friction in an elastohydrodynamically lubricated (EHL) conjunction it is necessary to model the physical/mechanical behaviour of the lubricant. It is important to know, for example, the dilatation-pressure or the density-pressure relationship. In this paper a modified split Hopkinson pressure bar system for determination of the compressibility of oil is presented. It makes it possible to test oils under conditions similar to those found in real EHL contacts: loading duration in the range of 100-300 μs and pressures of almost 2 GPa. An empirical model has been suggested for mathematical description of the dilatation-pressure relation of the specific oils. A naphthenic mineral oil and a synthetic oil, 5P4E, have been tested under adiabatic conditions and at pressures up to 1.5 and 1.9 GPa respectively. The adiabatic results have been recalculated to isothermal conditions for comparison

1 - 41 of 41
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