<div>Due to reduced pain, shortened hospital stay and recovery, minimally invasive surgery (MIS) is becoming more and more popular in healthcare systems. MIS requires some devices for the motion and force transformation from outside to the inside of the body of a patient, and the strangled cables play a significant role in developing the instrumentations to serve for such purposes. However, current design and selection of a strangled cable is mostly intuitive that depend greatly on designers’ experiences and availability of experimental data, which leads to non-optimized designs and longer design cycles. In this thesis, both of analytical modelling and numerical simulation are proposed to build the relation of applied torque and deflection of part, so that a strangled cable with a given configuration can be characterized in term of its load-deflection relation. The defined relation has its great significance and application potential in the design optimization and precise controls of medical devices for MISs.Besides the various patterns of strangled cables, a Helical hollow strand (HHS®) tube is a special type of strangled cables with single- or multiple- layer configurations., In each layer, each of the helical wires touches its two neighboring helical wires, and it has a coreless hollow at the center. Its primary application is to carry a torsional load in a twisting mode. As an extreme, there is a possibility that all helical wires touch each other, and this forms a statically indeterminate contact obstacle in design analysis. Numerical simulation would predict that contacts occur simultaneously at all possible contacting points under the circumference that the strand is fixed at one end against rotation. In addition, the friction at contacts will affect the torsional deformation; therefore, these contacts must be taken into consideration in the development of analytical and numerical simulation models.This thesis reports the results of the investigation on the characteristics of Helical hollow strand tube (HHS®), more specifically, the relation of torsional deflection and the applied torque over a tube in the clockwise (CW) direction. The numerical simulation approach to predict the torsional deflection of HHS with various design parameters and configurations is emphasized. </div><div><br></div>

A nonlinear finite element analysis was performed for an existing road bridge in order to see if that could show a higher load bearing capacity, as an alternative to repairing or replacing. The regular linear analysis had shown that the bridge could not take any traffic load due to the effects from large and uneven support settlements. It is a five-span reinforced concrete bridge with a continuous slab on supports made out of rows of columns. The width-to-span ratio was around 1 and the supports were angled up to about 30°, giving rise to a complex three-dimensional behaviour, which was seen and studied in the nonlinear results. Since the bending moment was the limiting factor, the nonlinear analysis focused on that. The direct result was that the load bearing capacity was 730 kN for the traffic vehicle boogie load, B, in the ultimate limit state. This was however only for the load case tested, and several more disadvantageous vehicle positions may exist. Other aspects also became limiting, as the maximum allowed vertical deflection in the serviceability limit state was reached at 457 kN. The most restraining though, was the shear capacity from the linear analysis; 78 kN, since it was not possible to simulate that type of failure with the shell elements used in the nonlinear finite element analysis. The main aim of the thesis was nonetheless reached, since the nonlinear analysis was able to show a significant increase in load bearing capacity.  A comparison was made with the settlements for the nonlinear case, to see how much influence they had on the load bearing capacity for traffic load. This was performed for both the bridge and a simple two-span beam. Both showed that there was no effect on the load bearing capacity in the ultimate limit. One thing to note was that the full settlements were applied, and with no relaxation due to creep.  Another aim of the thesis was to make comments on the practical usability of the nonlinear finite element method in load bearing capacity assessments. A linear analysis was performed before the nonlinear in order to be able to determine the load case to be used in the latter. This worked well, as the strengths of the two methods could then be utilized. Convergence problems were however encountered for the nonlinear when using the regular static solver. Due to this, the dynamic explicit calculation scheme was used instead, treating the case as quasi-static. This managed to produce enough usable results. It was concluded that the nonlinear finite element method is useable for assessment calculations, but that its strengths and weaknesses must be known in order to make it an efficient method.

As the plastic and packaging industry is looking to increase the longevity of plastic products as well as recycling used material, there is a need to understand how material properties respond and change during long periods of mechanical loading. Physical tensile experiments on thin plant-based High-Density Polyethylene (HDPE) are conducted with the intent of capturing relaxation behavior from a short-term (1-3 hours) and long-term (29-56 days) perspective. Experimental tests aiming to capture short-term relaxation behavior prior to necking at various loads are made on a MTS Qtest100 tensile-machine in the laboratory at BTH. Long-term experiments are conducted on a custom-built tensile machine stationed in the author’s apartment.   Data gathered from the experiments are swiftly converted into true stress and strain based on the derived mathematical expressions in preparation for computer simulations, i.e. modeling the behavior using two expressions and the Finite Element Method (FEM) in the general purpose FE-software AbaqusTM R2020. The loading curve, i.e. uniform deformation, prior to geometrical necking, was modeled using the Ramberg-Osgood expression and captured the mechanical non-linear behavior accurately. Two expressions are initially used to capture the stress decay, referred to as relaxation behavior: the first one is Guiu and Pratt and the second one is a data-generated Four Parameter Logistics (4PL) expression. A comparison between the two expressions, show that the 4PL expression captures the entire short-term behavior of the experiments. The 4PL expression could also predict the long-term behavior without further calibration. The Guiu and Pratt expression could not predict the behavior as accurately as the 4PL expression.   Using the converted physical data to calibrate a Parallel Rheological Framework (PRF) model in the MCalibration software proved to be time consuming. A combination of the Ramberg Osgood and 4PL expression is used to re-create the converted physical experiment data which reduces both noise and size of the datasets dramatically. The calibration time was significantly reduced because the datasets were much smaller. With a material model calibrated using the re-created data, simulations could be conducted in Abaqus, creating a virtual twin of the physical experiments. Results from the physical experiments are compared to the results of the virtual simulations proving that the PRF model can capture the relaxation behavior shown in the short-term experiments. The model also works for long-term relaxation behavior and only a slight increase in stress relaxation compared to the physical experiments was observed. / I dagens plast och paketeringsindustri finns ett behov att öka produkters livstid samt att använda återvunnet material. Med detta finns då behovet av att bättre förstå hur plasternas egenskaper förändras under långa lastperioder. Fysiska tester kommer därav genomföras med tunna testbitar gjorda av organiskt HDPE med målet att fånga spännings relaxationen från både ett kort (1-3 timmar) till ett långt (29-56 dagar) tidsperspektiv. Experimentella tester som fångar det korta tidsperspektivet görs med olika lastfall före “necking” och genomförs på en MTS Qtest100 dragprovsmaskin på labbet på campus BTH. Tester som fångar det långa tidsperspertivet görs på en dragprovsmaskin som är tillverkad för detta syftet och är stationerad i författarens lägenhet.  Datan som är tagen från experimenten är först konverterade till sann spänning och töjning för att sedan modeleras utav två matematiska uttryck och en model i Finita Element Metod programmet AbaqusTM R2020. Det matematiska uttrycket Ramberg-Osgood användes för att modellera pålastningskurvan före “necking” och gorde detta tillfredställande. Två uttryck jämfördes för att modellera relaxationskurvan, ena var Guiu and Pratt uttrycket och det andra var en data-genererad Fyra Parameter Logistik (4PL) uttryck. Jämförelsen visade att 4PL uttrycket fångade hela kurvaturen ur det korta tidsperspektivet. Det visade sig även att 4PL uttrycket kunde prediktera det långa tidsperspektivet utan att göra några extra kailbreringarna från de korta tidsperspektivets kalibrering. Guiu and Pratts uttryck hade problem i bade de korta och långa tidsperspektivet.  Med den omvandlade datan från de fyska testerna börjades kalibreringen av en “Parallel Rheological Model” (PRF)  materialmodel i programmet MCalibration. Detta visade sig kräva mycket tid då datafilerna från de fysiska testera var mycket stora och hade även en del brus. Med detta gjordes valet att använda Ramberg Osgood uttrycket samt det data-genererade 4PL uttrycket för att skapa matematiskt beräknade testdata för att minska mängden datapunkter samt ta bort bruset. Med de nya datafilerna blev kalibreringstiden av materialmodellen mycket mindre och det kunde användas för att skapa en “virtual twin” av dragprovsanordningen. Resultatet från simuleringarna av den virtuella dragprovsbiten visar på att modellen fångar den korta tidsaspeketen väldigt bra. För det långa tisperspektivet fungerade modellen men med lite större stress relaxation jämfört med de fysiska experimenten.

Laser welding is an advanced joining technique with the capability to form deep, narrow, and precise welds. Numerical models are used to simulate the process in attempts of predicting distortions and stresses in the material. This is done to reduce physical testing, optimize processes and enable integrated product- and process development. The Virtual Manufacturing Process research group at University of Skövde wishes to increase their knowledge on modeling options of thermomechanical simulations to grant local industries these benefits. A numerical model for the laser welding process was developed in ABAQUS. This was done by examining the macrograph structure of a simple weld and applied to a stainless-steel T-joint welding application. The macrograph data was used to calibrate a mathematical heat source model. User subroutine DFLUX was used to enable movement of the heat source and element activation was used to simulate the fusion of the two parts. A T-joint welding experiment was carried out to measure deflection and the result was compared to numerical simulations. Different combinations of heat source models, coupling type and element activation was compared in relation to predicting the deflection. Computational time and modeling complexity for the techniques was also considered.The results showed that a 3D Gaussian heat source model will imitate the keyhole weld achieved superior to the compared 2D model. The 3D model provides greater flexibility since it enables combinations of any geometrical bodies. It was shown that element activation has a significant contribution on part stiffness and thus resulting distortions. To implement element activation a fully coupled analysis is required. The deflection of the fully coupled 3D simulation with element activation showed a 9% deviance in deflection compared with experiments.

No description available.

No description available.

A nonlinear finite element analysis was performed for an existing road bridge in order to see if that could show a higher load bearing capacity, as an alternative to repairing or replacing. The regular linear analysis had shown that the bridge could not take any traffic load due to the effects from large and uneven support settlements. It is a five-span reinforced concrete bridge with a continuous slab on supports made out of rows of columns. The width-to-span ratio was around 1 and the supports were angled up to about 30°, giving rise to a complex three-dimensional behaviour, which was seen and studied in the nonlinear results. Since the bending moment was the limiting factor, the nonlinear analysis focused on that. The direct result was that the load bearing capacity was 730 kN for the traffic vehicle boogie load, B, in the ultimate limit state. This was however only for the load case tested, and several more disadvantageous vehicle positions may exist. Other aspects also became limiting, as the maximum allowed vertical deflection in the serviceability limit state was reached at 457 kN. The most restraining though, was the shear capacity from the linear analysis; 78 kN, since it was not possible to simulate that type of failure with the shell elements used in the nonlinear finite element analysis. The main aim of the thesis was nonetheless reached, since the nonlinear analysis was able to show a significant increase in load bearing capacity. A comparison was made with the settlements for the nonlinear case, to see how much influence they had on the load bearing capacity for traffic load. This was performed for both the bridge and a simple two-span beam. Both showed that there was no effect on the load bearing capacity in the ultimate limit. One thing to note was that the full settlements were applied, and with no relaxation due to creep. Another aim of the thesis was to make comments on the practical usability of the nonlinear finite element method in load bearing capacity assessments. A linear analysis was performed before the nonlinear in order to be able to determine the load case to be used in the latter. This worked well, as the strengths of the two methods could then be utilized. Convergence problems were however encountered for the nonlinear when using the regular static solver. Due to this, the dynamic explicit calculation scheme was used instead, treating the case as quasi-static. This managed to produce enough usable results. It was concluded that the nonlinear finite element method is useable for assessment calculations, but that its strengths and weaknesses must be known in order to make it an efficient method.

No description available.

Ribbed plates comprising cross-laminated timber slab, CLT, with glulam beams allow for increased span length compared to pure CLT slabs. At the moment the Eurocodes do not provide any recommendations to design a CLT plate or a ribbed plate. There are handbooks for designing ribbed plates. But are their methods the best suited? Should one use Eurocode’s gamma-method, Timoshenko, shear analogy method or maybe an FE-model? This is difficult to answer, but nevertheless important questions for a structural engineer today. This master thesis investigates some of the different design methods used today in a numerical study. The study compares analytical methods and FE-models by investigating different parameters, like span lengths 6 m, 12 m, and 18 m, or uniform load and point load. Furthermore, this thesis provides guidance and help to apply design methods for ribbed plates. The outcome of the study shows a tendency for the gamma-method and the extended gamma-method giving the lowest deflections and normal stresses in many situations. Thus, there could be a risk of underestimating these properties by using the gamma-method. On the other hand there were consistent results with the gamma-methods compared to Timoshenko- and shear analogy-method which showed more deviations from the extended gamma-method as reference. The Timoshenko-method showed anomalies with thicker CLT. In addition, an Abaqus model with 3D elements and RFEM models with 2D and 1D elements were applied. The Abaqus models gave in general higher deflections and consistent results. Concluding from this thesis the Abaqus model together with the extended gamma-method would complement each other most efficiently in the design process of ribbed plates.

Civil engineering projects involve great investments and great impacts. For that reason,engineers have a commitment with an efficient and optimal use of resources. Researchers inuniversities claim that a lot could be achieved by applying structural optimization into realprojects, even though this approach has not gained the same popularity in the industry over thelast decades.The purpose of the present thesis is to explore the possibilities offered by structural optimizationand to verify its applicability in realistic and complex structural engineering problems. Amongthe questions regarding design optimization, it was emphasized feasibility, efficiency and userfriendliness. The chosen structural system was a bridge cantilever deck. The analysis was limitedto the transversal design of the structure and the goal of the optimization was to reduce investmentcosts. In order to guarantee efficiency of the simulations, a "longitudinal length convergence"analysis was performed. It consisted of determining the minimum required longitudinal length(perpendicular to the cantilever length) that ensured reasonable accuracy. The purpose of thisanalysis was to reduce the computational time during the optimization process. In order toautomate the analysis, MATLAB was used in connection to Abaqus (to perform the FE Analysis).There were three different sets of results presented: the length convergence, application toreal projects and parametric study. In the first application, it was shown that the requiredlongitudinal length (lx) proportionally decreased as the cantilever length (lc) increased. It wasalso observed the presence of the edge beam implied in consistently larger longitudinal lengthsfor the same accuracy tolerance. With respect to the second application, two projects wereconsidered and the structural optimization presented alternatives with significant investment costreduction in a reasonable time. Furthermore, it was observed that a design solution without theedge beam reduced the costs even more. Finally, the parametric study confirmed that the costreduction obtained by eliminating the edge beam was not restricted to only certain cantileverlengths. Furthermore, it was possible to obtain the pattern of thickness variation as function ofthe cantilever length.The results of this research suggest that structural optimization could be an alternative totraditional design methods used today in consulting offices and its possibilities transcend puredesign achievements.