This work addresses the problem of tyre tread pattern design for optimum wet grip performance. A mathematical model of tyre behaviour on wet roads has been developed. This utilizes the finite element method in the representation of tread pattern geometry. The performance of a particular tread pattern is found in terms of the fluid pressures and film thicknesses existing within the contact patch, under wet conditions. Many modern tread patterns are based on 'blocks', and a computer model has been developed specifically to assist the tyre designer in the design of these blocks for improved wet grip. Numerical results are presented both for complete contact patches and for individual tread blocks. To allow the use of the computer models by the tyre designer, with no specialist knowledge of the finite element method, special purpose mesh generation and plotting programs have been developed. Experiments have been undertaken whereby the fluid pressures and film thicknesses existing in the tyre contact patch have been measured under high speed conditions in the wet. These measure- ments were made on an indoor testing machine, and the techniques developed can be used in the routine evaluation of tyre wet grip performance. Some results of experiments performed on plain and simple patterned tyres are presented. The main purpose of this work was the development of the mathematical models which can be used for future research into, and design of, tyres for improved wet grip. However, some conclusions are made as to possible features which could be utilized in future tyre designs.

The friction of tyres on roads has been of practical importance for many years with nearly 80% of terrestrial traffic making use of rubber tyres. Tyres provide the grip required for vehicle acceleration, braking and cornering. In order for a tyre to grip on a snow covered surface friction mechanisms such as “ploughing”, (where sharp tread block edges dig into and break bonds between the snow grains) and fluid film lubrication must be considered. These are not present when a tyre interacts with tarmac. In addition metamorphism of the snow over time can result in variations of the structure and mechanical properties, this can occur rapidly especially when dealing with temperatures close to snows melting point. When full car-scale outdoor testing is carried out the snow conditions cannot be controlled and vary daily. This means the snow properties must be measured every day so that any observed variations in friction can be attributed to the tyres rather than the snow. At present the simple measurements being carried out on the snow tracks have not proved sufficient to pick up on the variations in the snow. This leads to inconsistent results: one tyre behaves differently on two different days, even though the snow was measured to be the same. This has resulted in the need for further study of the way snow variations influence the grip of winter tyres. The primary aim of this study is to identify which snow properties contribute to the friction of tyres on snow and be able to estimate the friction from measurements of snow properties. This work is the first comprehensive study to combine: multiple snow properties, microstructure characterisation, measurement of friction behaviour and different snow (both artificial and natural). In order to study the way snow affects the grip of winter tyres, methods of manufacturing artificial snow with consistent mechanical properties and microstructure are used. A method of blending ice chips (a solid state fracturing process) and compressing the resulting snow to form a test track was developed during a previous PhD carried out in our group. An alternate snow microstructure was created by using an established process of creating snow by vapour deposition. The process was simplified and downscaled, the resulting snow consisted of large dendritic grains, very different to the blended ice chips. Both snows were pressed in identical manners to create snow testing tracks. In addition, natural snow collected from the field was tested to compare with the artificial snow. In order to investigate how the variations in the snow affected the friction of tyres extensive testing was carried out in a cold room using a linear tribometer, using procedures established in previous studies. Two analytical rubber samples were used to investigate the friction, a rounded edge sample and a siped sample. Testing was carried out at -10°C at speeds of 0.01m/s, 0.1m/s and 1m/s. A significant part of this PhD involved the development of new methods and equipment which have not been used to study snow in this way before. In order to characterise mechanical properties, shear testing, compression testing and cohesion testing were carried out. To investigate snow microstructure, surface profilometry, microscopy and X-ray microtomography were used. Correlating the changes observed in snow characteristics with the changes recorded in the coefficient of friction has allowed the development of an empirical equation. This can be used to predict the coefficient of friction of a given snow based on three relatively simple snow measurements: a compression test to calculate the effective modulus, a roughness measurement to calculate the peak count density and a snow penetration test. For the first time this study allows us to use the empirical equation to estimate the relative contributions of the ploughing and surface friction mechanisms to the total friction. This allows the comparison of full car-scale test data as it is now possible to account for variations in the snow test tracks.

yes / Background: Falls sustained when descending stairs are the leading cause of accidental death in older adults. Highly visible edge highlighters/friction strips (often set back from the tread edge) are sometimes used to improve stair safety, but there is no evidence for the usefulness of either. Objective: To determine whether an edge highlighter and its location relative to the tread edge affect foot placement/clearance and accidental foot contacts when descending stairs. Method: Sixteen older adults (mean ± 1 SD age; 71 ± 7 years) with normal vision (experiment 1) and eight young adults (mean ± 1 SD age; 24 ± 4 years) with visual impairment due to simulated age-related cataract (experiment 2) completed step descent trials during which a high contrast edge highlighter was either not present, placed flush with the tread edge, or set back from the edge by 10 mm or 30 mm. Foot placement/ clearance and the number of accidental foot contacts were compared across conditions. Results: In experiment 1, a highlighter set back by 30 mm led to a reduction in final foot placement (p b 0.001) and foot clearance (p b 0.001) compared to a highlighter placed flush with the tread edge, and the percentage of foot clearances that were less than 5 mm increased from 2% (abutting) to 17% (away30). In experiment 2, a highlighter placed flushwith the tread edge led to a decrease in within-subject variability in final foot placement (p = 0.004) and horizontal foot clearance (p = 0.022), a decrease in descent duration (p = 0.009), and a decrease in the number of low clearances (b5 mm, from 8% to 0%) and the number of accidental foot contacts (15% to 3%) when compared to a tread edge with no highlighter present. Conclusions: Changes to foot clearance parameters as a result of highlighter presence and position suggest that stairswith high-contrast edge highlighters positioned flushwith the tread edgewill improve safety on stairs, particularly for those with age-related visual impairment.

The tire-terrain interaction is complex and tremendously important; it impacts the performance and safety of the vehicle and its occupants. Icy roads further enhance these complexities and adversely affect the handling of the vehicle. The analysis of the tire-ice contact focusing on individual aspects of tire construction and operation is imperative for tire industry's future. This study investigates the effects of the tread rubber compound on the drawbar pull performance of tires in contact with an ice layer near its melting point. A set of sixteen tires of eight different rubber compounds were considered. The tires were identical in design and tread patterns but have different tread rubber compounds. To study the effect of the tread rubber compound, all operational parameters were kept constant during the testing conducted on the Terramechanics Rig at the Terramechanics, Multibody, and Vehicle Systems laboratory. The tests led to conclusive evidence of the effect of the tread rubber compound on the drawbar performance (found to be most prominent in the linear region of the drawbar-slip curve) and on the resistive forces of free-rolling tires. Modeling of the tire-ice contact for estimation of temperature rise and water film height was performed using ATIIM 2.0. The performance of this in-house model was compared against three classical tire-ice friction models. A parametrization of the Magic Formula tire model was performed using experimental data and a Genetic Algorithm. The dependence of individual factors of the Magic Formula on the ambient temperature, tire age, and tread rubber compounds was investigated. / Master of Science / The interaction between the tire and icy road conditions in the context of the safety of the occupants of the vehicle is a demanding test of the skills of the driver. The expected maneuvers of a vehicle in response to the actions of the driver become heavily unpredictable depending on a variety of factors like the thickness of the ice, its temperature, ambient temperature, the conditions of the vehicle and the tire, etc. To overcome the issues that could arise, the development of winter tires got a boost, especially with siping and rubber compounding technology. This research focuses on the effects on the tire performance on ice due to the variation in the tread rubber compounds. The experimental accomplishment of the same was performed using the Terramechanics rig at the Terramechanics, Multibody, and Vehicle Systems (TMVS) laboratory. It was found that the effect of the rubber compound is most pronounced in the region where most vehicles operate under normal circumstances. An attempt was made to simulate the temperature rise in the contact patch and the water film that exists due to the localized melting of ice caused by frictional heating. Three classical friction models were used to compare the predictions against ATIIM 2.0, an in-house developed model. Using an optimization technique namely the Genetic Algorithm, efforts were made to understand the effects of the tread rubber compound, the ambient temperature, and the aging of the tire on the parameters of the Magic Formula model, an empirical model describing the performance of the tire.

The in-plane phenomena of interaction between the tyre structural response and contact force generation are investigated in this work. The challenges of the physical tyre simulation are identified, primarily associated with the computational load imposed by the need to capture the space distributed mechanisms that prescribe the above interaction. The method of modal expansion and reduction is proposed for the moderation of this load. The theoretical framework for the transformation of a tyre modal representation into a transient contact and shear force generation model is developed. Various modelling approaches are examined with regards to their modal prediction characteristics. Linear and non linear structural features as well as the physical properties that define the broad range modal behaviour are identified. A discretised form of the ring model is derived and combined with a foundation of viscoelastic tread elements for simulating the transient contact behaviour of the tyre. The resulting pattern of the modes' excitation justifies the validity of the modal reduction method and reveals the relative importance of various mechanisms and physical properties in tyre contact behaviour. The interaction between the friction controlled shear slip of the tread, the belt compliance and the sidewall buckling is found to be reflected on the two-dimensional contact pressure distribution patterns. A method able to simulate the dynamic transient rolling and slipping operating conditions is developed, although the small displacement assumption of the modal approach is dropped. The method, which is based on the combined modal-time and space-time domain solutions, is applied on the study of the physical mechanism of the launch process. The examination of the model under steady state kinematic conditions reveals the saturation of the traction force for profound levels of slip, which highlights the contribution of the structural mechanisms on the macroscopically observed shear force performance of the tyre. The variation of the modes' level of excitation, as induced by the operating conditions, is proposed for the capture of the physical properties effect on tyre behaviour and performance.

No description available.

Mitt eksamensarbeid på Carl Malmsten Furniture Studies tar for seg en problemstilling om hvorvidt dagens profil på trappetrinnet er optimal, ut fra krav om at trappen skal være sikker, komfortabel og lite anstrengende å gå i. Det omhandler kun trapper i tre for innendørs bruk, og faktorer som produksjonsvennlighet og økonomiske aspekter er ikke tatt hensyn til. Interessen for temaet ble skapt under min praksisperiode hos snekkerverkstedet ”Studio Furniture Maui”, hvor man hadde spesialisert seg på å bygge trapper. Etter å ha søkt etter erfaringer om emnet hos bransjen og på internett, gikk det klart frem at dette var et lite utforsket tema. Jeg definerte tre punkter som jeg mente var viktige for et bedre trinn. Det skulle være sikkert, komfortabelt og lite anstrengende å gå på. I samarbeid med Kjell Ohlsson, professor i ergonometri på Linköpings universitet, arbeidet jeg frem fire alternativer som jeg ville teste i tillegg til det vanlige trappetrinnet. Disse profilene ble så testet av en testgruppe på 40 personer. Utfallet av denne testen viste at majoriteten av testpersonene foretrakk en av de alternative profilene fremfor det vanlige trappetrinnet. Basert på resultatet av testen har jeg i denne rapporten konkludert med at dagens profil på trappetrinnet ikke er optimal, og at temaet burde studeres nærmere. / ´My final work for the Bachelor Degree at Carl Malmsten Furniture Studies discusses whether today’s shape of the tread in a staircase is optimal. There are some limitations to this project. Only indoor stairs made from wood will be discussed. Production and financial aspects will not be part of this study. My interest for this subject was created during my internship at the workshop “Studio Furniture Maui”. They had specialised in building staircases. After searching for information from the industry and online, it became clear to me that this was an unexplored subject. I defined three qualities that I meant was important for a better tread. It needed to be safe, comfortable, and less exhausting to walk on. Working together with Kjell Ohlsson, a professor in ergonomics on Linköpings University, I made four alternative treads in addition to a normal one. 40 people tested these treads. The result from the test showed that the majority of the people preferred one of the alternative profiles to the normal one. Based on the result from the test, this report concludes that the tread we are used to is not optimal, and that more research should be done on the subject.

This final thesis describes the currently available processes for testing security threads in banknote papers. The currency market has generally two types of security threads, embedded and window threads.  It is generally important to optimize the adhesive used. This requires a test method with good precision and low operator independence. By achieving and using good test methods the process of evaluating a new products pros and cons can be done with higher precision. The thread adhesion properties are of great importance when developing new adhesion systems. The main reason for testing the threads adhesion is to verify that the thread cannot be removed in an intact form from the banknote but also for product development processes.  The current test methods were developed by introducing new parameters and sample preparations specifications. The data evaluation system was also upgraded.  The measurement of thread adhesion vs. position in CD and vs. time showed expected results. A new and more reliable test method was implemented and evaluated and was together with the improved current method able to detect same properties independently.

Antalet bilar har ökat stadigt genom åren och i mars 2019 befann sig nästan 4,9 miljoner personbilar i aktiv användning i Sverige. Något som inte får lika mycket uppmärksamhet som koldioxidutsläpp från trafiken och slitage av vägar är slitaget av bildäck. Regeringen har därmed tillsatt ett uppdrag där mängden mikroplastutsläpp ska kvantifieras, sprida kunskap om problemet och utveckla åtgärder mot utsläppen. En av myndigheterna som fått detta uppdrag är Statens väg- och transportforskningsinstitut (VTI), med vilka detta arbete genomfördes. Arbetet går ut på att försöka kvantifiera utsläppen av mikroplastutsläpp från personbilar samt undersöka vilka typer av slitage som är vanligast förekommande. Rapporten består av två delar, en litteraturstudie som ska ge en klar bild av nuläget, typer av däck, vad mikroplaster är samt varför slitage uppstår. Under den andra delen genomfördes mätningar på kasserade däck, där mönsterdjupsprofiler, vikt, mönsterdjup, DOT märkning, modell, märke, typ av däck och dimensioner antecknades. Med hjälp av profilerna och originaldata som tillhandahölls av olika däcktillverkare kunde de vanligaste slitagen bestämmas och den bortslitna vikten och volymen kunde uppskattas. De vanligaste typerna av slitage är centrum-, jämnt- och sidoslitage, vilket beror på för högt lufttryck i däcken, samt fel hjulinställningar. Den totala årliga mängden utsläpp av mikroplaster från personbilar uppskattades ligga mellan 8 300 och 16 700 ton. / The number of cars has been on a steady increase in Sweden and in mars 2019 there were almost 4,9 million cars in active use. Nowadays most of the attention is focused on pollution through carbon dioxide and the wear of roads. However, a problem that often goes unrecognized is the tear of car tyres and the release of microplastics into the environment. In order to quantify the amount of microplastics released into the environment, the Swedish government has instructed The Swedish National Road and Transport Research Institute (VTI) to carry through with this. The aim of this report is to, with the help of VTI, try to quantify the amount of microplastics released from private car traffic and examine the main types of tyre wear. This report consists of two parts, one study of what microplastics is and how tyre wear arises. The second part consists of measuring, where used tyres have had their weight and tread measured. The profile of the tear, DOT number, production date, model, dimensions and type of tyre is additional data that was collected. Through the use of data provided by the tyre companies and the collected data, the total loss of weight and volume together with a yearly weight and volume loss could be calculated. Through analysis of the tyre profiles and their tread depths the most occurring type of wear patterns was determined, which were central, even and side wear. The estimated yearly amount of microplastics released in Sweden was between 8 300 and 16 700 tonnes.

The objective of this project was to design, construct and test a wall climbing vehicle which uses a novel vacuum tread system for both adhesion and locomotion. The design and manufacturing of this proof of concept vehicle is detailed with particular emphasis on the design decisions that proved most impactful to the performance of both the vehicle and the tread system. Adhesion performance was characterized by a series of tests that validate the concept, but also identify improvements and design recommendations for future embodiments of the adhesion/locomotion system.