Master of Science / Department of Industrial & Manufacturing Systems Engineering / John English / This research builds upon previous efforts to explore the use of Statistical Process Control (SPC) in lieu of cycle counting. Specifically a three pronged effort is developed. First, in the work of Huschka (2009) and Miller (2008), a mixture distribution is proposed to model the complexities of multiple Stock Keeping Units (SKU) within an operating department. We have gained access to data set from a large retailer and have analyzed the data in an effort to validate the core models. Secondly, we develop a recursive relationship that enables large samples of SKUs to be evaluated with appropriately with the SPC approach. Finally, we present a comprehensive set of type I and type II error rates for the SPC approach to inventory accuracy monitoring.

Predicting fatigue failure is a critical design element for many engineering components and structures subject to complex service conditions. In high-temperature and corrosive environments, many materials exhibit rate dependent phenomena that can significantly alter safe service life predictions. Existing cycle processing techniques such as Peak Counting, Simple Range, and the Rain Flow method are able to resolve complex service histories into sets of simple cycles, but these methods are unable to handle time-related parameters such as engage rate and cycle sequence. To address this, a cycle processor was written in FORTRAN 95 later termed the Multi-Algorithm Cycle Counter (MACC). This code was utilized as a platform to develop, test, and study various methods of extracting and interpreting rate parameters extracted from cycles defined by existing counting algorithms.

Although a component satisfies all operating static requirements, failures can still occur due to vibration induced fatigue. Vibration induced fatigue is a frequent phenomenon, in cases where the natural frequencies of the structures are excited by the loading. Hence, the methods which consider all dynamic characteristic of the structure should be used to obtain accurate fatigue life predictions. These methods in frequency domain are called vibration fatigue methods which give accurate, reliable and fast results. In this thesis, a numerical code is developed in order to predict fatigue life of structures and it is used for a bracket that is installed on an air platform. However, for verification of the numerical code, a cantilever beam is used as a case study at the beginning. First, finite element model of the cantilever beam is constructed and experimental analyses are performed to verify the finite element model. Then fatigue life is calculated using the numerical code and it is verified comparing the results obtained by both commercial software and performed fatigue tests. For predicting fatigue life of the bracket, flight test is performed in order to obtain acceleration loading. Finite element modeling of bracket and verification of it by experimental analyses are performed and finally, accelerated fatigue life of the bracket is obtained by the developed numerical code, commercial software and fatigue test. It is concluded that the results obtained from the fatigue analyses and fatigue test are considerably close enough to justify that the analysis is significantly accurate.

The actual service loading histories of most engineering components are characterized by variable amplitudes and are sometimes rather complicated. The goal of this study was to estimate the fatigue life of nickel-chromium-molybdenum 30CrNiMo8HH steel alloy under axial and pure torsion variable amplitude loading (VAL) conditions. The investigation was directed at two primary factors that are believed to have an influence on fatigue life under such loading conditions: load sequence and mean stress. The experimental work for this research included two-step loading, non-zero mean strain loading, and VAL tests, the results of which were added to previously determined fully reversed strain-controlled fatigue data. The effect of load sequence on fatigue life was examined through the application of the commonly used linear damage accumulation rule along with the Manson and Marco–Starkey damage accumulation methods, the latter of which takes load sequence into account. Based on the two-step experimental results, both the Manson and Marco–Starkey methods were modified in order to eliminate the empirically determined constants normally required for these two methods. The effect of mean stress on fatigue life was investigated with the use of three life prediction models: Smith–Watson–Topper (SWT), Fatemi–Socie (FS), and Jahed–Varvani (JV). The cycles from the VAL histories were counted using a rainflow counting procedure that maintains the applied strain sequence, and a novel method was developed for the estimation of the total energy density required for the JV model. For two-step loading and for all three fatigue models employed, the modified damage accumulation methods provided superior fatigue life predictions. However, regardless of the damage accumulation method applied, the most satisfactory fatigue life correlation for VAL was obtained using the energy-based JV model.

In this thesis, fatigue life of a cantilever aluminum plate with a side notch under certain loading conditions is analyzed. Results of experimental stress analysis of the cantilever aluminum plate by using a uniaxial strain gage are presented. The strain gage is glued on a critical point at the specimen where stress concentration exists. Strain measurement is performed on the base-excited cantilever beam under random vibration test in order to examine the life profile simulation. The fatigue analysis of the test specimen is carried out in both time and frequency domains. Rainflow cycle counting in time domain is examined by taking the time history of load as an input. Number of cycles is determined from the time history. In frequency domain analysis, power spectral density function estimates of normal stress are obtained from the acquired strain data sampled at 1000 Hz. The moments of the power spectral density estimates are used to find the probability density function estimate from Dirlik&rsquo / s empirical expression. After the total number of cycles in both time and frequency domain approaches are found, Palmgren-Miner rule, cumulative damage theory, is used to estimate the fatigue life. Results of fatigue life estimation study in both domains are comparatively evaluated. Frequency domain approach is found to provide a marginally safer prediction tool in this study.

The actual service loading histories of most engineering components are characterized by variable amplitudes and are sometimes rather complicated. The goal of this study was to estimate the fatigue life of nickel-chromium-molybdenum 30CrNiMo8HH steel alloy under axial and pure torsion variable amplitude loading (VAL) conditions. The investigation was directed at two primary factors that are believed to have an influence on fatigue life under such loading conditions: load sequence and mean stress. The experimental work for this research included two-step loading, non-zero mean strain loading, and VAL tests, the results of which were added to previously determined fully reversed strain-controlled fatigue data. The effect of load sequence on fatigue life was examined through the application of the commonly used linear damage accumulation rule along with the Manson and Marco–Starkey damage accumulation methods, the latter of which takes load sequence into account. Based on the two-step experimental results, both the Manson and Marco–Starkey methods were modified in order to eliminate the empirically determined constants normally required for these two methods. The effect of mean stress on fatigue life was investigated with the use of three life prediction models: Smith–Watson–Topper (SWT), Fatemi–Socie (FS), and Jahed–Varvani (JV). The cycles from the VAL histories were counted using a rainflow counting procedure that maintains the applied strain sequence, and a novel method was developed for the estimation of the total energy density required for the JV model. For two-step loading and for all three fatigue models employed, the modified damage accumulation methods provided superior fatigue life predictions. However, regardless of the damage accumulation method applied, the most satisfactory fatigue life correlation for VAL was obtained using the energy-based JV model.

Durability is the most important factor in the design of heat-exchangers to meet the specifications of the customers. To predict the durability, endurance tests are carried out. In this thesis, one of the endurance tests, thermal cycling is performed for three different internal coolant flows until failure which is known as Wöhler test. A tool is developed in MATLAB that could import data from all kinds of endurance tests and visualizes time histories of every channel of the test (test parameters such as temperature, pressure, flow). An algorithm is developed for Level Crossing counting method which works based on the Markov cycle counting method. This produces Level crossing curves (LCC) for all the channels of the test which says how well a test has been performed and the total number of cycles of the test. It was observed that the LCCs obtained from the tool gives accurate results when compared with those obtained from LMS software whose approach of producing LCCs is Rainflow cycle counting method. Strain measurements are performed for the same flowrates as that of the Wöhler tests. The results from strain measurements and Wöhler tests are used in the determination of Basquin’s coefficient of the Wöhler curve. It was observed that the optimal value of Basquin’s coefficient is 3.4.

Sammanfattning Kurs: Examensarbete i Logistik för Civilekonomprogrammet, 30 hp, 4FE19E.  Författare: Jakob Bergman och Jim Andersson. Examinator: Peter Berling Handledare: Peter Berling  Medbedömare: Hana Hulthén Titel: Saldoavvikelser i producerande företag, en fallstudie på Getinge Disinfection AB. Bakgrund: En välfungerande lagerhållning är en väsentlig grundsten för ett företags framgångar. I takt med att lagerhållningen blivit mer automatiserad och effektiviserad ställs högre krav på att informationen om lagersaldon stämmer överens med verkligheten. Saldoavvikelser är ett utbrett problem som kan påverka många olika delar av en verksamhet, såsom felaktiga underlag för inköp, den dagliga driften och företagets servicegrad. Fallföretaget Getinge Disinfection AB upplever främst att saldoavvikelser på företaget får effekt på den dagliga driften, något som denna studie ämnar undersöka. Syfte: Studien syftar till att identifiera konsekvenser och orsaker till saldoavvikelser på Getinge Disinfection AB samt ge förbättringsförslag som kan reducera saldoavvikelser på företaget. Metod: Denna studie har en kvalitativ forskningsstrategi. Vidare är studiens forskningsdesign en fallstudie då den endast undersöker ett fall ingående och detaljerat. Resultat: Studien fann att saldoavvikelser kan uppstå i alla steg i den studerade processen, med varierande primära orsaker i de olika stegen i processen. Bland de konsekvenser som funnits är de främsta icke-värdeskapande aktiviteter, opålitliga underlag för inköpsbeslut, OOS och ökade ledtider. Majoriteten av orsakerna grundar sig i den mänskliga faktorn, det vill säga att anställda inte följer rutiner eller gör misstag i processen. Dessa misstag kan ske i olika aktiviteter i processen och det finns olika primärorsaker beroende på var i processen misstaget sker. Vidare har författarna tagit fram förbättringsförslag för att effektivisera Getinge Disinfection ABs produktionsprocess. De mest lämpliga förbättringsförslagen är att skapa förståelse om saldoavvikelser bland de anställda, införa Cycle counting, digitalisera olika aktiviteter och utvärdera det nuvarande artikelsortimentet. Nyckelord: Saldosäkerhet, Saldoavvikelser, Producerande företag, Medicinteknik, Life Science, Assemble to Order, ATO, Cycle Counting, RFID, Streckkoder. / Abstract  Course: Degree project in Logistics, the Business Administration and Economics Programme, 30 credits, 4FE19E.    Authors: Jakob Bergman and Jim Andersson. Examiner: Peter Berling.  Tutor: Peter Berling. Co-judger: Hana Hulthén Title: Inventory record inaccuracies in manufacturing companies, a case study on Getinge Disinfection AB. Background: Effective inventory management is of considerable importance for most successful businesses. Without it, companies would be hard-pressed to meet the demands of consumers that place a high value on fast deliveries and product availability. As a result, businesses have turned to increased automation of their inventory management. This automation relies heavily on information such as inventory records being accurate and up to date. Inventory record inaccuracies result in purchases or decisions being made on incorrect assumptions of the companies’ actual inventory status, which has a negative effect on many aspects of the business. However, most studies on this subject focus on inventory record inaccuracies in a retailing context, whereas this study focuses on a large manufacturing company (Getinge Disinfection AB) using an Assemble to Order model. Purpose: The purpose of this study is to identify the different causes and consequences of inventory record inaccuracies (IRI) at Getinge Disinfection AB. Furthermore, the study aims to offer proposals on how to improve inventory record accuracy at Getinge Disinfection AB.    Methodology: This paper adopts a qualitative research strategy with a case-study approach.  Findings: The study concluded that inventory record inaccuracies can arise in all areas of the studied process, with different primary reasons for different stages of the process. Most of the causes of IRI can be attributed to the human factor, such as incorrect identification of the items, unregistered movements of goods, and transaction errors. The consequences of (IRI) were mainly the resulting non-value adding activities, purchasing decisions being made based on unreliable inventory data, stockouts and longer lead times. The study also gives suggestions on how Getinge could reduce these inventory record inaccuracies. Improvement measures such as Cycle counting, bar coding of the items and locations and increased staff training are discussed. Keywords: Inventory Record Accuracy, Inventory Record Inaccuracy, Manufacturing, Health Care, Life Science, Assemble to Order, ATO, Cycle Counting, RFID, Bar coding.

<p>In today‟s manufacturing environment, different parts manufactured in-house and bought from suppliers are often assembled together into a finished product. Competition has made it very important for companies to deliver a customized product on a promised date. However, when inventory items are missing at the time of production, lead times for products become uncertain and this makes it difficult to fulfill a customer order on the promised date. It is thus important to explore the causes of missing items at the time of production in order to solve such a problem. This Master of Science thesis carried out through a case study at Fläkt Woods in collaboration with Jönköping University is about the problem of not finding specific inventory items in the locations specified by the computer system. It is delimited to inventory items which are physically within the company premises or which according to the computer system are within the premises of the company. The questions at issue have been what the causes of the problem of missing items within the company are and how to effectively reduce the problem. The thesis has been carried out over an entire academic semester as a full-time work in the company. The sources of the problem have been found to be the result of the work procedure, the underlying software used during work (the in-house developed ERP system), stealing from orders, ineffective barcode scans, re-sequencing at the component manufacturing department (called pre-manufacturing in the company) due to the need to fulfill multiple objectives, set-up times at the component manufacturing department and human errors among others. The suggestions given include: modification of the work procedure and the underlying software used at work, increasing effective scanning and using some checks at critical points in the material flow. Areas for further research are given to further reduce the impact of the problem on the production system.</p>

In today‟s manufacturing environment, different parts manufactured in-house and bought from suppliers are often assembled together into a finished product. Competition has made it very important for companies to deliver a customized product on a promised date. However, when inventory items are missing at the time of production, lead times for products become uncertain and this makes it difficult to fulfill a customer order on the promised date. It is thus important to explore the causes of missing items at the time of production in order to solve such a problem. This Master of Science thesis carried out through a case study at Fläkt Woods in collaboration with Jönköping University is about the problem of not finding specific inventory items in the locations specified by the computer system. It is delimited to inventory items which are physically within the company premises or which according to the computer system are within the premises of the company. The questions at issue have been what the causes of the problem of missing items within the company are and how to effectively reduce the problem. The thesis has been carried out over an entire academic semester as a full-time work in the company. The sources of the problem have been found to be the result of the work procedure, the underlying software used during work (the in-house developed ERP system), stealing from orders, ineffective barcode scans, re-sequencing at the component manufacturing department (called pre-manufacturing in the company) due to the need to fulfill multiple objectives, set-up times at the component manufacturing department and human errors among others. The suggestions given include: modification of the work procedure and the underlying software used at work, increasing effective scanning and using some checks at critical points in the material flow. Areas for further research are given to further reduce the impact of the problem on the production system.