A Type-Safe Model of Adaptive Object Groups

Services are autonomous, self-describing, technology-neutral software units that can be described, published, discovered, and composed into software applications at runtime. Designing software services and composing services in order to form applications or composite services requires abstractions beyond those found in typical object-oriented programming languages. This paper explores service-oriented abstractions such as service adaptation, discovery, and querying in an object-oriented setting. We develop a formal model of adaptive object-oriented groups which offer services to their environment. These groups fit directly into the object-oriented paradigm in the sense that they can be dynamically created, they have an identity, and they can receive method calls. In contrast to objects, groups are not used for structuring code. A group exports its services through interfaces and relies on objects to implement these services. Objects may join or leave different groups. Groups may dynamically export new interfaces, they support service discovery, and they can be queried at runtime for the interfaces they support. We define an operational semantics and a static type system for this model of adaptive object groups, and show that well-typed programs do not cause method-not-understood errors at runtime.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432

Fuzzy variable linear programming with fuzzy technical coefficients

Fuzzy linear programming is an application of fuzzy set theory in linear decision making problems and most of these problems are related to linear programming with fuzzy variables. In this paper an approximate but convenient method for solving these problems with fuzzy non-negative technical coefficient and without using the ranking functions, is proposed. With the help of numerical examples, the method is illustrated

Thermomechanical behaviour of semi-crystalline polymers: experiments, modelling and simulation

This work presents experimental investigations on two semi-crystalline materials: a rubbermodified polypropylene (PP) and a cross-linked low density polyethylene (XLPE). Uniaxial tension and compression tests were performed at different temperatures and strain rates using a novel experimental set-up that involves optical measurements of the deformation. A thermomechanical constitutive model was developed, implemented and used to describe the mechanical behavior of the XLPE material. The thesis is organized as follows: A synopsis presents the background, motivation, objectives and scope along with a summary of the work, while the three journal articles in Parts 1 to 3 describe the scientific contributions in detail. Part 1 presents the experimental set-up established to conduct tests at low temperatures. The experimental set-up consists of a transparent polycarbonate (PC) temperature chamber which, in contrast to conventional temperature chambers, allows the use of several digital cameras to monitor the test specimen during experiments. Consequently, local strain measurements could be performed by using for example digital image correlation (DIC). To facilitate instrumentation with an infrared thermal camera, a slit was added in the front window of the PC temperature chamber to obtain a free line-of-sight between the test specimen and the infrared camera. Utilizing this experimental set-up, a semi-crystalline XLPE under quasi-static tensile loading was successfully analysed using DIC at four different temperatures, T = 25 ◦C, T = 0 ◦C, T = −15 ◦C and T = −30◦C. At the lower temperatures, the conventional spray-paint speckle became brittle and cracked during deformation. An alternative method was developed using white grease with a black powder added for contrast. It was shown that neither the PC chamber nor replacing the conventional spray-paint speckle pattern with grease and black powder influenced the stress-strain curves as determined by DIC. Part 2 presents uniaxial tension and compression experiments performed on both materials: the semi-crystalline rubber-modified polypropylene (PP) and the semi-crystalline cross-linked low density polyethylene (XLPE). The experimental set-up presented in Part 1 was used to perform uniaxial tension and compression tests at four different temperatures (T = 25 ◦C, T = 0 ◦C, T = −15 ◦C and T = −30 ◦C) and three initial nominal strain rates ( ˙ e = 0.01 s−1, ˙ e = 0.1 s−1 and˙ e = 1.0 s−1). DIC was used to obtain local stress-strain data from the tension experiments, while a combination of point tracking and edge tracing was used in the compression experiments. A scanning electron microscopy (SEM) study was performed to give a qualitative understanding of the substantial volumetric strain observed in the PP material and the small volumetric strains in the XLPE material. The mechanical behaviour of both materials was shown to be dependent on temperature and strain rate. More specifically, Young’s modulus increased for decreasing temperatures in both materials and for increasing strain rate in the XLPE material. The Ree-Eyring flow theory was used to successfully capture the temperature and strain rate dependent yield stress in both materials. In terms of volume change, the XLPE material was found to be nearly incompressible at room temperature, while it became slightly compressible at the lower temperatures. For the PP material the observed volumetric strains were substantial, ranging from approximately 0.5 to 0.9. Part 3 presents the proposed thermoelastic-thermoviscoplastic constitutive model consisting of two parts: an intermolecular part described by an elastic Hencky spring coupled with two Ree-Eyring dashpots augmented with kinematic hardening from an inelastic Hencky spring, and an orientational part capturing entropic strain hardening due to alignment of the polymer chains using an eight chain spring. The objective of the study is to describe the effect of temperature and strain rate on the mechanical behaviour of the XLPE material investigated in Parts 1 and 2. The constitutive model was implemented in the commercial finite element (FE) program Abaqus/Standard as a UMAT subroutine. A numerical method was used to establish the consistent tangent operator together with a sub-stepping scheme to ensure convergence. The FE model yields accurate predictions of the stress-strain behaviour of the material, along with the volumetric strains, self-heating, strain rate and force vs. global displacement

Mål- og resultatstyring i arbeids- og velferdsetaten

Oppgaven tematiserer mål- og resultatstyring i Arbeids- og velferdsetaten. Den første hypotesen er at mål- og resultatstyring fører til frikobling mellom organisatoriske mål og organisatorisk praksis. Den andre hypotesen er: fører utformingen av målekortet til målforskyvninger i henhold til målet om å få flere i arbeid? Den tredje hypotesen er: etableringstidspunktet for organisasjonen gjorde valget av mål- og resultatstyring naturlig, og det var liten kulturell motstand mot implementeringen. Oppgaven finner at det er en indikasjon på frikopling mellom hovedmål og organisasjonspraksis. Hypotesen om målekortets utforming diskuteres, der det er indikasjoner på at det kan skape målforskyvninger. Den tredje hypotesen kan diskuteres. Det er en indikasjon på at det forekommer stiavhengighet og at det er var en lav grad av kulturell motstand under implementeringen av mål- og resultatstyring. Funnene er for usikre til at det kan konkluderes

Influence of strain rate and temperature on the mechanical behaviour of rubber-modified polypropylene and cross-linked polyethylene

acceptedVersio

Effects of Heat Treatment on the Ballistic Properties of AA6070 Aluminium Plates

The thesis includes a summary of important theory in the fields of impact engineering and plasticity theory, and a literature study is carried out on aluminium designations, alloying and heat treatment. The true stress-strain curves of aluminium alloy AA6070 in O-, T4-, T6-, and T7-configurations are identified by tensile tests where the behavior is continuously measured to fracture. The aluminium was delivered as 20 mm rolled plates; microstructural images and strain ratios are reported. Material constants are found by direct calibration and inverse modeling. Ballistic tests are done in a laboratory using 7.62 mm APM2 bullets, 20 mm blunt projectiles and 20 mm ogival projectiles (CRH = 3). From these tests the ballistic limit curves and the ballistic limit velocities are found for all temper/projectile combinations. In the material tests it was shown that the O-temper is the most ductile temper and consequently almost no fragmentation takes place in the ballistic tests for this temper. The T6-temper proved to be brittle, and fragmentation was commonly seen in the ballistic tests. The degree of fragmentation is found to be of vital importance for the ballistic performance. The Cockcroft-Latham fracture criterion is implemented by using the plastic work to fracture. Numerical analyses are performed with the IMPETUS Afea Solver and LS-DYNA, with 3D-models and 2D axisymmetric models, respectively. Ballistic limit curves and the ballistic limit velocities are calculated on the basis of the numerical results and then compared to the experimental values. Limited sensitivity studies are conducted on mesh size, heat-expansion dependency, strain-rate dependency, etc. Overall the results from 2D axisymmetric models are found to be consistent with previous studies, and the 3D-analyses carried out with the IMPETUS Afea Solver gave some good results. The IMPETUS Afea Solver proved to be a user-friendly finite element program with some powerful features. In addition to the numerical studies, a thorough derivation of the Cylindrical Cavity Expansion Theory (CCET) is given. Results from CCET are good for 7.62 mm APM2 bullets. A case-study where the ballistic performance is determined without conducting any experiments is also conducted. The results are promising, but less conservative than the original simulations, due to the inability to calibrate a fracture criterion. Some suggestions for further work within the field of impact engineering and the application of the finite element method are provided at the end of the thesis, followed by an appendix that includes graphical representations and photographs of the multiple material tests and program-codes written for use in the thesis

Cylindrical cavity expansion approximations using different constitutive models for the target material

In this article, we investigate the results obtained using different constitutive models for the solution of the cylindrical cavity expansion problem under plane strain conditions. The cylindrical cavity expansion solutions are employed with the cylindrical cavity expansion approximation to obtain ballistic limit and residual velocities for ductile metals perforated by rigid projectiles. Many of the previously developed cylindrical cavity expansion approximations use simplified constitutive models. However, in the present work, we first extend the cylindrical cavity expansion theory with the Voce strain hardening rule, before we utilize three different strain hardening constitutive models in cylindrical cavity expansion calculations to predict ballistic limit and residual velocities of aluminum and steel target plates struck by rigid projectiles. The results show that when strain hardening is accurately represented by the constitutive models until necking in a uniaxial tension test, all cylindrical cavity expansion models predict ballistic limit velocities that are close to the experimental data