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  • 1.
    Beccu, E.
    et al.
    AB Sandvik Rock Rools.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Efficiency of percussive drilling of rock with dissipative joints1990Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 9, nr 3, s. 277-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nonlinear dissipative spring mass (NDSM) model for a percussive drill rod joint of the coupling sleeve (CS) type has been implemented into a Modula-2 program with the aid of which percussive drilling of rock is simulated. Transmission and dissipation of energy are first studied when a rectangular stress wave, generated through the impact by a uniform hammer, is transmitted through a single joint. The efficiency of energy transmission increases from 81 to 94% and the relative energy dissipation decreases from 8 to 1 or 2% when the length of the hammer varies from relatively short to relatively long. The effect of the joint preload is weak in the range from medium to relatively high preload. The efficiency of the percussive drilling process decreases with the number of joints but depends little on the joint preload. For soft rock, the efficiency increases with hammer length, whereas for medium and hard rock the dependence of efficiency on hammer length is not monotonic. This is because soft rock requires a long incident wave for efficient conversion of energy to work at the bit, whereas the reverse is true for hard rock. It is also found that the efficiency of the percussive drilling process may be considerably underestimated if the effects of each joint on the length and shape of the transmitted wave and of multiple reflections within the drill string are neglected

  • 2. Beccu, R.
    et al.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Transmission and dissipation of stress wave energy at a percussive drill rod joint1987Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 6, nr 3, s. 157-173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transmission and dissipation of stress wave energy at a percussive drill rod joint is determined for three joint types, three joint preload levels, three hammer lengths ( incident wave lengths) and a range of impact velocities ( incident wave amplitudes). The energies of the incident, reflected and transmitted waves are evaluated from measured strains, and then the dissipated energy is determined as the deficit of energy in the two latter waves compared with the first. The accuracy needed is obtained by introducing a compensation factor and determining its value from the requirement of momentum conservation. The experimental results for threaded standard joints are compared with experimental results for threadless dummy joints, made in one piece, and also with theoretical results. The latter are based on one model which represents the joint as a well on a one- dimensional elastic rod (characteristics impedance or CI model) and on another model which represents the joint as a rigid mass between one-dimensional elastic rods (rigid mass or RM model). For the joints 70-100% of the incident wave energy is transmitted and 0-20% is dissipated. The corresponding figures for the dummies are 90-100% and (±)1%, repectively. The latter figure indicates the inaccuracy in the measurement and evaluation procedures. The two models agree fairly well with the dummies. Under certain conditions they also give reasonably accurate predictions for the energy transmitted through a joint. As they sometimes give quite inaccurate results for energy transmission and furthermore fail to predict energy dissipation they need be refined.

  • 3.
    Börvik, Tore
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Clausen, Arild H.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Eriksson, Magnus
    Berstad, Torodd
    SINTEF Materials and Chemistry.
    Langseth, Magnus
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Experimental and numerical study on the perforation of AA6005-T6 panels2005Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 32, nr 1-4, s. 35-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Extruded aluminium panels find their use in many different structures such as offshore platforms, bridge decks, train and ship components and lightweight protection systems. Impacts or other types of high-speed loading conditions are thus a relevant issue for several of these applications. There are, however, not many investigations published on the perforation of extruded aluminium panels covering experiments in combination with numerical analyses. This paper presents an experimental and numerical study on the perforation of AA6005-T6 aluminium panels impacted by ogival-nosed steel projectiles. The chosen panel has three triangular-shaped cells with a total depth of 130 mm. The wall thickness is 6 mm in the front and rear side plate, and 3 mm in the slanting webs. A rather comprehensive material test programme has been carried out in order to determine the material's response to dynamic loading. The experimental results were used to calibrate slightly modified versions of the Johnson-Cook constitutive relation and fracture criterion. 3D numerical simulations of the perforation process were then performed on a high-performance computer using the MPP version of the explicit finite element code LS-DYNA. In the simulations, the typical dimension of the elements was less than 1 mm. The numerical model is able to capture the main trends in the experiments in an adequate manner, and excellent agreement between numerical and experimental results is obtained.

  • 4.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Msahiro
    Nagoya Institute of Technology, Gokisocho, Showa-ku, Aichi.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Fracture probability modelling of impact-loaded iron ore pellets2017Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 102, s. 180-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blast furnace iron ore pellets are sintered, centimetre-sized ore spheres with a high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. In transporting pellets from pelletizing plants to customers, iron ore pellets are exposed to different static and dynamic loading situations, resulting in strength degradation and, in some cases, fragmentation. This can lead to a reduced gas flow in the blast furnace, which causes reduced quality in steel production. Reliable numerical simulations that can predict the ability of the pellets to endure their handling are important tools for optimizing the design of equipment for iron ore handling. This paper describes the experimental and numerical work performed to investigate the impact fracture behaviour of iron ore pellets at different strain rates. A number of split Hopkinson pressure bar tests with different striker velocities are carried out and analysed to investigate the strain rate dependency of the fracture strength of iron ore pellets. Fracture data for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. A stress based, strain-rate dependent fracture model that takes triaxiality into account is suggested. The fracture model is used and validated with impact tests of iron ore pellets. In the validation experiment, iron ore pellets are fired against a steel plate, and the percentage of fractured pellets at different impact velocities are measured. Finite element simulations of the experiment are carried out and the probability of pellets fracturing during impact are calculated and compared with the experimental results. The agreement between the experiments and numerical simulations shows the validity of the model.

  • 5.
    Lundberg, Bengt
    et al.
    Luleå tekniska universitet.
    Beccu, Rainer
    Luleå tekniska universitet.
    Nilsson, A.
    Luleå tekniska universitet.
    Nonlinear dissipative spring mass model for a percussive drill rod joint of the coupling sleeve type1989Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 8, nr 4, s. 303-313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A nonlinear dissipative spring mass (NDSM) model for a percussive drill rod joint of the coupling sleeve (CS) type is established. Such a joint consists of a cylindrical coupling sleeve with internal thread which connects two drill rods with external threads at their ends. The model disregards wave motion in the coupling sleeve but accounts for axial mobility of the sleeve relative to the rods. This mobility is due to local deformation and slip of the threads. The model is characterized by the mass of the sleeve and by three parameters which represent the coupling between the sleeve and the drill rods through the threads. A static and a dynamic test have been developed for determining the coupling parameters. The model is validated by simulating previous impact tests with a commercial CS joint.

  • 6.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Slip and energy dissipation in cylindrical friction joints loaded by impact-induced waves1987Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 6, nr 1, s. 35-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cylindrical friction (CYLF) joints subjected to impact-induced wave (IIW) loading are studied theoretically and experimentally. The system considered consists of a long, straight, cylindrical and linearly elastic rod which is impacted axially at one end by a cylindrical and linearly elastic hammer. A body is attached at the other end by means of a CYLF joint. The conditions are such that the wave propagation is 1-D in the hammer and the rod and can be neglected in the attached body which is therefore treated as rigid. The agreement between numerical and analytical solutions is good. There is also fair agreement between theoretical and experimental results.

  • 7.
    Nordlund, Erling
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Lundberg, B.
    Luleå tekniska universitet.
    Slip and energy dissipation in conical friction joints loaded by impact-induced waves1986Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 4, nr 2, s. 127-144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conical friction (CF) joints subjected to impact-induced wave (IIW) loading are studied theoretically and experimentally. The system considered consists of a long, straight, cylindrical and linearly elastic rod which is impacted axially at one end, and which has a body attached by means of a CF joint at the opposite end. The conditions are such that the wave propagation is 1-D in the rod and can be neglected in the attached body, which is therefore treated as rigid. Slip and energy dissipation in the CF joint due to a single IIW load are determined as functions of four dimensionless parameters which represent the duration of the incident wave, the mass of the attached body, the behaviour of the CF joint and the initial slip due to a compressive preload. The conditions under which detachment occurs are also found. Results for repeated noninteracting IIW loads are derived from those obtained for a single IIW load. The theoretical results exhibit phenomena which may sometimes have a spectacular appearance. For example, four consecutive and identical IIW loads may have the effect of fastening, loosening, fastening again and, finally, detaching the CF joint. There is a fair agreement between theoretical and experimental results.

  • 8.
    Odd-Geir, Lademo
    et al.
    SINTEF.
    Berstad, Torodd
    SINTEF.
    Eriksson, Magnus
    SINTEF Materials and Chemistry; Structural Impact Laboratory (SIMLab), Department of Structural Engineering, Norwegian University of Science and Technology.
    Tryland, Tore
    Hydro Aluminium Structures.
    Furu, Trond
    Hydro Aluminium R&D.
    Langseth, Magnus
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Hopperstad, Odd Sture
    Norwegian University of Science and Technology (NTNU), Trondheim.
    A model for process-based crash simulation2008Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 35, nr 5, s. 376-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Manufacturing of a bumper system from aluminium extrusions often involves series of forming operations performed in the soft W-temper condition, and then artificially age-hardening of the components to the material's peak hardness T6 condition. It is probable that proper finite element (FE) modelling of the crash performance of the resulting systems must rely upon a geometry obtained from an FE model following the process route, i.e., including simulation of all major forming operations. The forming operations also result in an inhomogeneous evolution of some internal variables (among others the effective plastic strain) within the shaped components. Results from tensile tests reveal that plastic straining in W-temper leads to a significant change of the T6 work-hardening curves. In addition, the tests show that the plastic pre-deformation causes a reduction of the elongation of the T6 specimens. In the present work, these process effects have been included in a user-defined elastoplastic constitutive model in LS-DYNA incorporating a state-of-the-art anisotropic yield criterion, the associated flow rule and a non-linear isotropic work hardening rule as well as some ductile fracture criteria. A first demonstration and assessment of the modelling methodology is shown by ‘through-process analysis' of two uniaxial tensile test series. The industrial use and relevance of the modelling technique is subsequently demonstrated by a case study on an industrial bumper beam system.

  • 9.
    Tilert, Dan
    et al.
    Industrial Metrology and Optics, School of Industrial Engineering and Management, KTH.
    Svedbjörk, Göran
    Carl Bro AB, Eskilstuna.
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nilsson, Bruno
    Industrial Metrology and Optics, School of Industrial Engineering and Management, KTH.
    Temun, Attila
    Industrial Metrology and Optics, School of Industrial Engineering and Management, KTH.
    Mattsson, Lars
    Industrial Metrology and Optics, School of Industrial Engineering and Management, KTH.
    Measurement of explosively induced movement and spalling of granite model blocks2007Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 34, nr 12, s. 1936-1952Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Charges of high explosives have been buried (countersunk) in granite blocks and detonated. This article describes the measurement and evaluation of the shock wave propagating through the granite blocks. It also demonstrates how the shock wave data can be used to improve computer simulations of granite's behaviour. The overall goal has been to investigate how granite withstands penetrating weapons, that first penetrate the ground and then detonates within the created cavity. Several variables have been investigated. It is shown that water content of the granite can increase the shock wave amplitude with up to a factor 2, and a crack in the granite often attenuates the shock wave amplitude with a factor 4 or more. Also, the granite block thickness needed to prevent internal crack formation has been investigated.

  • 10.
    Zakrisson, Björn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Wikman, Bengt
    Numerical simulations of blast loads and structural deformation from near-field explosions in air2011Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 38, nr 7, s. 597-612Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Numerical simulations of air blast loading in the near-field acting on deformable steel plates have been performed and compared to experiments. Two types of air blast setups have been used, cylindrical explosive placed either in free air or in a steel pot. A numerical finite element convergence study of the discretisation sensitivity for the gas dynamics has been performed, with use of mapping results from 2D to 3D in an Eulerian reference frame. The result from the convergence study served as a foundation for development of the simulation models. Considering both air blast setups, the numerical results under predicted the measured plate deformations with 9.4–11.1%. Regarding the impulse transfer, the corresponding under prediction was only 1.0–1.6%. An influence of the friction can be shown, both in experiments and the simulations, although other uncertainties are involved as well. A simplified blast model based on empirical blast loading data representing spherical and hemispherical explosive shapes has been tested as an alternative to the Eulerian model. The result for the simplified blast model deviates largely compared to the experiments and the Eulerian model. The CPU time for the simplified blast model is however considerably shorter, and may still be useful in time consuming concept studies. All together, reasonable numerical results using reasonable model sizes can be achieved from near-field explosions in air.

  • 11.
    Ödéen, Sven
    et al.
    Luleå tekniska universitet.
    Lundberg, Bengt
    Luleå tekniska universitet.
    Prediction of impact force by impulse response method1991Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 11, nr 2, s. 149-158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method has been established which permits prediction of impact force history from the velocity response of each impacting body to an impulsive force applied to its impact face, and the impact velocity. The bodies may consist of one or several linearly elastic or viscoelastic materials. However, the method is limited to cases of impact without significant effects of friction and slip, with constant contact area and with small deformations. It has been applied to four cases of axial impact of a truncated cone or a compound cylinder on a long cylindrical rod. The truncated cone was made of Nylon-6, the compound cylinder of Nylon-6 and aluminum, and the long cylindrical rod of steel. For the truncated cone and the compound cylinder, measured as well as theoretically predicted impulse responses were used, while for the long cylindrical rod only a theoretically predicted impulse response was employed. In all cases good agreement was obtained between the impact force histories predicted, using the impulse response method, and those measured with the aid of strain gauges on the long cylindrical rod. Because of three-dimensional effects the best agreement was obtained for the predictions based on measured impulse responses for the truncated cone and the compound cylinder

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