Kylmämuovattujen putkipalkkien X-liitosten äärikestävyyden ja jäykkyyden määrittäminen sekä materiaalimallin kehittäminen

Työssä on tutkittu elementtimenetelmän avulla kylmämuovattujen nelikulmaisten putkipalkkien materiaalimallin kehittämistä ja putkipalkkien X-liitosten jäykkyyden ja äärikestävyyden määrittämistä. Työn tavoitteena on tutkia kylmämuovauksen vaikutuksia putkipalkkiprofiilin materiaaliominaisuuksiin materiaalikokeiden ja elementtianalyysien avulla sekä kehittää putkipalkille anisotrooppista materiaalimallia. Työssä määritettyjä materiaalimalleja on sovellettu X-liitosten elementtimalleihin, joiden käyttäytymistä on verrattu äärikestävyyskokeiden tuloksiin. Tutkimuksen perusteella Eurocode 3:n mitoitusohjeita voidaan turvallisesti soveltaa kylmämuovattujen putkipalkkien X-liitosten laskennassa. Työssä tehtyjen materiaalikokeiden ja elementtianalyysien perusteella materiaalin anisotrooppisuuden vaikutus liitoksen kestävyyteen on vähäistä, ja putkipalkin pituussuuntaista materiaalimallia voidaan soveltaa myös kehäsuuntaisille materiaaliominaisuuksille. Materiaalikokeiden simulointi osoittaa, että elementtimenetelmää voidaan käyttää materiaalimallin määrittämisen apuvälineenä.

Kaksoislaatuisesta rakenneputkesta hitsatun X-liitoksen kestävyys ja muodonmuutoskyky

Rautaruukki Oyj:n uusi Ruukki double grade S420MH/S355J2H -rakenneputki yhdistää putkilajien S420MH ja S355J2H ominaisuudet. Eurocode 3:n suunnitteluohjeiden mukaan Ruukki double graden käyttöön on sovellettava lujuusluokan S420 mukaista hitsien mitoitusta ja rakenneputkiliitosten staattista mitoituskestävyyttä alentavaa varmuuskerrointa, kun halutaan hyödyntää lujuusluokan S420 ominaisuudet Ruukki double gradea käytettäessä. Tässä työssä tutkittiin S420-lujuusluokkaa vastaavien suunnittelumääräysten soveltamistarvetta Ruukki double grade -rakenneputken käyttöön. Työn tavoitteena oli arvioida Ruukki double grade -rakenneputkesta hitsaamalla valmistetun X-liitoksen kestävyyden ja muodonmuutoskyvyn riittävyys, kun hitsit mitoitettiin S355-lujuusluokkaa vastaavien Eurocode 3:n suunnitteluohjeiden mukaisesti. X-liitosten kestävyyttä ja muodonmuutoskykyä tutkittiin kokeellisesti -40 C lämpötilassa suoritettujen laboratoriokokeiden avulla sekä analyyttisen laskennan ja elementtimenetelmän keinoin. Kestävyyden riittävyyttä arvioitiin vertaamalla laboratoriokokeista saatuja liitosten kestävyyksiä Eurocode 3:n ja myötöviivateorian mukaisiin kestävyyksiin. Elementtimenetelmän ja laboratoriokokeen pohjalta piirrettyjä liitoksen voima-siirtymäkuvaajia vertailtiin keskenään, kun elementtimalli analysoitiin eri materiaalimalleilla. Lisäksi verrattiin elementtimallin voima-venymäkuvaajia liitoksen venymäliuskan arvoihin. Kaikki koesarjan S355-lujuusluokan mukaisilla hitsin a-mitoilla valmistetut liitokset täyttivät kestävyydelle ja muodonmuutoskyvylle asetetut vaatimukset. Täten tämän koesarjan perusteella ei ollut tarpeellista soveltaa S420-lujuusluokan mukaista hitsien mitoitusta ja staattista mitoituskestävyyttä alentavaa varmuuslukua Ruukki double grade -rakenneputkeen. Elementtimenetelmästä ja laboratoriokokeesta saadut liitoksen voima-siirtymäkuvaajat vastasivat hyvin toisiaan. Sen sijaan elementtimallin voima-venymä-kuvaajat eivät vastanneet venymäliuskojen mittausdataa kovin hyvin.

Ultimate capacity of stainless steel rectangular hollow section X- joints at low temperatures

Growing demand for stainless steel construction materials has increased the popularity of substitutive materials for austenitic stainless steels. The lean duplex grades have taken their place in building of structures exposed to corrosive environments. Since the duplex grades are relatively new materials, the current codes and norms do not fully cover the newest duplex grades. The joints tested in this thesis were designed and studied according to Eurocode 3, even though all the materials are not yet accepted to the standards. The main objective in this thesis was to determine the differences of the used materials in behaviour under loading at low temperatures. Tests in which the deformation and strength properties of the joints were determined were done at the temperature of -46°C, which is the requirement of temperature for structures designed according to Norsok standards. Results show that replacing the austenitic grade with the lean duplex grade is acceptable.

Simulation and material calibration of ultra high strength steel (UHSS) S960 welded joint under static tensile test utilizing finite element method (FEM)

The aim of this work was to calibrate the material properties including strength and strain values for different material zones of ultra-high strength steel (UHSS) welded joints under monotonic static loading. The UHSS is heat sensitive and softens by heat due to welding, the affected zone is heat affected zone (HAZ). In this regard, cylindrical specimens were cut out from welded joints of Strenx® 960 MC and Strenx® Tube 960 MH, were examined by tensile test. The hardness values of specimens’ cross section were measured. Using correlations between hardness and strength, initial material properties were obtained. The same size specimen with different zones of material same as real specimen were created and defined in finite element method (FEM) software with commercial brand Abaqus 6.14-1. The loading and boundary conditions were defined considering tensile test values. Using initial material properties made of hardness-strength correlations (true stress-strain values) as Abaqus main input, FEM is utilized to simulate the tensile test process. By comparing FEM Abaqus results with measured results of tensile test, initial material properties will be revised and reused as software input to be fully calibrated in such a way that FEM results and tensile test results deviate minimum. Two type of different S960 were used including 960 MC plates, and structural hollow section 960 MH X-joint. The joint is welded by BöhlerTM X96 filler material. In welded joints, typically the following zones appear: Weld (WEL), Heat affected zone (HAZ) coarse grained (HCG) and fine grained (HFG), annealed zone, and base material (BaM). Results showed that: The HAZ zone is softened due to heat input while welding. For all the specimens, the softened zone’s strength is decreased and makes it a weakest zone where fracture happens while loading. Stress concentration of a notched specimen can represent the properties of notched zone. The load-displacement diagram from FEM modeling matches with the experiments by the calibrated material properties by compromising two correlations of hardness and strength.

Joint criminal enterprise

The doctrine of joint criminal enterprise is in disarray. Despite repeated judicial scrutiny at the highest level, the doctrine's scope, proper doctrinal basis and function in relation to other modes of complicity remain uncertain. This article examines the doctrine's elements and underlying principles. It argues that while joint criminal enterprise is largely used to make individuals liable for offences committed by their associates in excess of the common criminal purpose, its proper function is to police the limits of associate liability and thus to exculpate rather than inculpate. The doctrine governs not only instances of accessorial liability; it also applies where the parties involved are joint principal offenders. As this puts into question the prevalent view that joint criminal enterprise is a form of secondary participation that results in accessorial liability, the article concludes that it is best seen as a doctrine sui generis.

Accurate molecular structures of chlorothiazide and hydrochlorothiazide by joint refinement against powder neutron and X-ray diffraction data

The compounds chlorothiazide and hydrochlorothiazide (crystalline form II) have been studied in their fully hydrogenous forms by powder neutron diffraction on the GEM diffractometer. The results of joint Rietveld refinement of the structures against multi-bank neutron and single-bank X-ray powder data are reported and show that accurate and precise structural information can be obtained from polycrystalline molecular organic materials by this route.

Joint (X)over-bar and R charts with variable sample sizes and sampling intervals

Recent studies have shown that the (X) over bar chart with variable sampling intervals (VSI) and/or with variable sample sizes (VSS) detects process shifts faster than the traditional (X) over bar chart. This article extends these studies for processes that are monitored by both the (X) over bar and R charts. A Markov chain model is used to determine the properties of the joint (X) over bar and R charts with variable sample sizes and sampling intervals (VSSI). The VSSI scheme improves the joint (X) over bar and R control chart performance in terms of the speed with which shifts in the process mean and/or variance are detected.

Joint conomic design of (x)over-bar and R charts under Weibull shock models

This paper deals with the joint economic design of (x) over bar and R charts when the occurrence times of assignable causes follow Weibull distributions with increasing failure rates. The variable quality characteristic is assumed to be normally distributed and the process is subject to two independent assignable causes (such as tool wear-out, overheating, or vibration). One cause changes the process mean and the other changes the process variance. However, the occurrence of one kind of assignable cause does not preclude the occurrence of the other. A cost model is developed and a non-uniform sampling interval scheme is adopted. A two-step search procedure is employed to determine the optimum design parameters. Finally, a sensitivity analysis of the model is conducted, and the cost savings associated with the use of non-uniform sampling intervals instead of constant sampling intervals are evaluated.

Joint (X)over-bar and R charts with two-stage samplings

When joint (X) over bar and R charts are in use, samples of fixed size are regularly taken from the process, and their means and ranges are plotted on the (X) over bar and R charts, respectively. In this article, joint (X) over bar and R charts have been used for monitoring continuous production processes. The sampling is performed, in two stages. During the first stage, one item of the sample is inspected and, depending on the result, the sampling is interrupted if the process is found to be in control; otherwise, it goes on to the second stage, where the remaining sample items are inspected. The two-stage sampling procedure speeds up the detection of process disturbances. The proposed joint (X) over bar and R charts are easier to administer and are more efficient than the joint (X) over bar and R charts with variable sample size where the quality characteristic of interest can be evaluated either by attribute or variable. Copyright (C) 2004 John Wiley Sons, Ltd.

Joint X̄ and R Charts with Variable Sample Sizes and Sampling Intervals

Recent studies have shown that the X̄ chart with variable sampling intervals (VSI) and/or with variable sample sizes (VSS) detects process shifts faster than the traditional X̄ chart. This article extends these studies for processes that are monitored by both the X̄ and R charts. A Markov chain model is used to determine the properties of the joint X and R charts with variable sample sizes and sampling intervals (VSSI). The VSSI scheme improves the joint X̄ and R control chart performance in terms of the speed with which shifts in the process mean and/or variance are detected.

Joint conomic design of x̄ and R charts under Weibull shock models

This paper deals with the joint economic design of x̄ and R charts when the occurrence times of assignable causes follow Weibull distributions with increasing failure rates. The variable quality characteristic is assumed to be normally distributed and the process is subject to two independent assignable causes (such as tool wear-out, overheating, or vibration). One cause changes the process mean and the other changes the process variance. However, the occurrence of one kind of assignable cause does not preclude the occurrence of the other. A cost model is developed and a non-uniform sampling interval scheme is adopted. A two-step search procedure is employed to determine the optimum design parameters. Finally, a sensitivity analysis of the model is conducted, and the cost savings associated with the use of non-uniform sampling intervals instead of constant sampling intervals are evaluated.

Joint economic design of X̄ and R control charts for processes subject to two independent assignable causes

A model for the joint economic design of X̄ and R control charts is developed. This model assumes that the process is subject to two assignable causes. One assignable cause shifts the process mean; the other shifts the process variance. The occurrence of the assignable cause of one kind does not block the occurrence of the assignable cause of another kind. Consequently, a second process parameter can go out-of-control after the first process parameter has gone out-of-control. A numerical study of the cost surface to the model considered has revealed that it is convex, at least in the interest region.