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Solder joint failure history has generally been assumed to follow a straight line when plotted as a lognormal or 2‐parameter Weibull distribution. Test results presented here show that a deviation from straight‐line behaviour occurs at low percentage failure probabilities. This indicates that solder joint failure history is more correctly characterised as a 3‐parameter Weibull distribution with a failure‐free period of life for true wearout failures. The solder joint failure distribution characteristic is also affected by applied strain. Lower strain, in addition to increasing median life, also improves the distribution such that the number of cycles‐to‐first‐failure is increased compared with the median cycles‐to‐failure. The ratio of cycles‐to‐first‐failure/median cycles‐to‐failure and apparent Weibull slope increases as strain decreases in a predictable manner. The effects of part elevation, part size, solder joint volume and shape, conformal coating, temperature differential, and alternative board materials are also presented with test data showing the effect of variation of these parameters.

The problem is to devise a life‐test acceptance procedure of an electrical item that has a Weibull failure distribution with an increasing hazard rate. The test‐bed facility has some constraints on the number of test samples and testing time.

The life‐test plan is obtained using censoring of experiments and the properties of order statistics. In this article, the author has derived expressions for order statistics and their moments for some commonly used hazard‐rate functions; for example, constant, linearly increasing, exponentially increasing, power function, etc. and the same is used in planning the life‐test acceptance procedure.

Results and findings are discussed in full. It is postulated that further research in this direction will definitely bring some fruitful results that have immense importance in the field of reliability analysis and life‐testing experiments.

The same methodology can be adopted for devising life‐test acceptance procedure using censoring of experiments.

The purpose of this paper is to identify and quantify the key components of the overall cost of software development when warranty coverage is given by a developer. Also, the authors have studied the impact of imperfect debugging on the optimal release time, warranty policy and development cost which signifies that it is important for the developers to control the parameters that cause a sharp increase in cost.

An optimization problem is formulated to minimize software development cost by considering imperfect fault removal process, faults generation at a constant rate and an environmental factor to differentiate the operational phase from the testing phase. Another optimization problem under perfect debugging conditions, i.e. without error generation is constructed for comparison. These optimization models are solved in MATLAB, and their solutions provide insights to the degree of impact of imperfect debugging on the optimal policies with respect to software release time and warranty time.

A real-life fault data set of Radar System is used to study the impact of various cost factors via sensitivity analysis on release and warranty policy. If firms tend to provide warranty for a longer period of time, then they may have to bear losses due to increased debugging cost with more number of failures occurring during the warrantied time but if the warranty is not provided for sufficient time it may not act as sufficient hedge during field failures.

Every firm is fighting to remain in the competition and expand market share by offering the latest technology-based products, using innovative marketing strategies. Warranty is one such strategic tool to promote the product among masses and develop a sense of quality in the user’s mind. In this paper, the failures encountered during development and after software release are considered to model the failure process.

To obtain an optimal simple time‐step stress accelerated life test for the case involving pre‐specified censoring time. Such a test saves time and expenses over tests at normal conditions.

Most of the available literature on step‐stress accelerated life testing deals with the exponential and weibull distribution. The log‐logistic life distribution has been found appropriate for high reliability components.

The method developed has been illustrated using the data simulated from cumulative exposure log‐logistic step‐stress model with censoring time specified.

The model suggested is appropriate in the field of high reliability components such as insulation system.

The purpose of this paper is to investigate how to reduce the time and cost required to conduct reliability testing. With increasing competition in the electronics industry and reduction in product life cycles, it is essential to diminish the time required for new product development and thus time to market.

This study conducts empirical sample test for wireless card and analyzes the fatigue life through finite element modeling (FEM). Simulation results are compared to the data collected from a temperature cycling test under conditions of −40°C to 150°C and −40°C to 100°C.

Assuming that the results of product lifetime from empirical sample test and software simulation exhibit a linear relationship, a “scale factor” should exist for any given product structure, process condition and materials composition scenario. The scale factors were found to be approximately 0.1 in both temperature cycling scenarios. Also, the effectiveness of various adhesive dispensing patterns on solder joint reliability is evaluated through software simulation. The L shape adhesive dispensing was proven to effectively enhance the fatigue life of chip scale package solder joints roughly 100‐fold.

The scale factor is used to convert the results from software simulation to empirical sample test for a given set of processing environments and materials. This helps to reduce the time and cost required to conduct reliability testing.

An Outline of Project Development, Detail, Pre‐Flight Prototype, Resonance, Static, and Full‐Scale Fatigue Testing. THE designer of an aircraft is allowed a considerable amount of latitude with regard to the method adopted to prove compliance with the strength requirements. It is necessary at the commencement to decide on a design philosophy balancing theoretical structural analysis and previous experience with laboratory strength testing in order to achieve an efficient airframe with the required standard of strength. Agreement must be reached with the Air Registration Board on the extent to which each factor will be used. The research and development costs on a new project are high, and the necessary work must be carefully considered in the light of useful information gained. Basing design on calculation and experience with an absolute minimum of testing is the economical method with regard to initial expenditure but this approach can lead to a heavy structure. An intermediate path using a single airframe for static and fatigue work allows for a comprehensive series of tests, but here the time scale of the important high static loadings required to demonstrate the safety factor is retarded to a degree where aircraft will be in service before this work is completed. Safety, and secondly retrospective modification action have to be considered and it may be that the engineer will in this case think it prudent to err on the heavy side when deciding on the sizes of the main scantlings. Efficiency is then sacrificed but with certain designs the cost of two airframes for test cannot be justified especially so if the design is a carry‐over of previous experience on similar types of structure.

This paper aims to characterise the hardness, tensile properties, corrosion behaviour and fatigue properties (in air and in a 3.5 per cent NaCl solution) of aluminium 6061-T651 in the as-received and as-welded conditions.

Aluminium 6061-T651 plate material, prepared with double-V or square butt joint preparations was welded using semi-mechanised or mechanised pulsed gas metal arc welding. Magnesium-alloyed ER5356 or ER5183 filler material or silicon-alloyed ER4043 filler wire was used. The material was characterised in the as-supplied and as-welded conditions, and fatigue tests were performed in air and in a 3.5 per cent NaCl solution. The fatigue results were compared to the reference fatigue design curves for aluminium published in Eurocode 9 – Part 1-3.

Significant softening, attributed to the partial dissolution and coarsening of precipitates, grain growth and recrystallisation during welding, was observed in the heat-affected zone (HAZ) of the 6061-T651 welds. During tensile testing, failure occurred in the HAZ of all 6061 welds tested. Welding reduced the room temperature fatigue life of all specimens evaluated. In 6061 welds, failure occurred preferentially in the softened HAZ of the welds. The presence of a corrosive environment (a 3.5 per cent NaCl solution in this investigation) during fatigue testing reduced the fatigue properties of all the samples tested. Corrosion pits formed preferentially at second phase particles and reduced the overall fatigue life by accelerating fatigue crack initiation.

The fatigue properties of welded aluminium structures under dynamic loading conditions have been studied extensively. Welding is known to create tensile residual stresses, to promote grain growth, recrystallisation and softening in the HAZ, and to introduce weld defects that act as stress concentrations and preferential fatigue crack initiation sites. Several fatigue studies of aluminium welds emphasised the role of precipitates, second phase particles and inclusions in initiating fatigue cracks. When simultaneously subjected to a corrosive environment and dynamic loading, the fatigue properties are often adversely affected and even alloys with good corrosion resistance may fail prematurely under conditions promoting fatigue failure. The corrosion-fatigue performance of aluminium welds has not been systematically examined to date.

Three main subjects are presented in this paper: (i) A description of tests made for the purpose of determining design data; (ii) a discussion of the problems arising in the establishment of the approval procedures necessary to ensure safety and reliability; and (iii) a discussion of proposals for cyclic reliability tests. In the first section, tests to provide design data for glazing materials are described with particular emphasis placed on glasses. Types of specimen and apparatus for obtaining data at room temperature are mentioned and illustrations given of apparatus and specimens used in long term elevated temperature tests. In the second section, the overall level of reliability of complete components is discussed both in terms of structural safety and satisfactory service. While the current requirements have proved satisfactory for the past generation of aircraft, proposals are now put forward for patterns of testing that are more closely linked to the various design conditions now in use with both high‐speed and low‐speed aircraft, in order to place equal importance on the effects of temperature. In the third section, proposals are put forward for cyclic testing to overcome what appears to be an increasingly unsatisfactory record of reliability. The purpose of the tests is not to establish a safe life for any particular design but to reveal design deficiencies occurring from repeated applications of flight and thermal loadings.

THE Trident has been designed with the objective of achieving freedom from fatigue cracks on the primary structure, during the operational life of the aircraft. Additionally, in areas where the fail safe concept can be applied, the design aim has been to provide multiple load paths and/or crack stoppers so that, in the event of any one member failing, the remaining structure can sustain at least limit loads for a longer period than the interval specified between major inspections of the structure. In the places where it is not possible to apply the fail safe concept, that is on flap and slat tracks, tailplane hinge fitting, engine mountings and landing gear, a substantial margin of safe life is provided.

Acceptance sampling plans are designed to decide about acceptance or rejection of a lot of products on the basis of sample drawn from it. Accelerating the life test helps in obtaining information about the lifetimes of high reliability products quickly. The purpose of this paper is to formulate an optimum time censored acceptance sampling plan based on ramp-stress accelerated life test (ALT) for items having log-logistic life distribution. The log-logistic life distribution has been found appropriate for highly reliable components such as power system components and insulating materials.

The inverse power relationship has been used to model stress-life relationship. It is meant for analyzing data for which the accelerated stress is nonthermal in nature, and frequently used as an accelerating stress for products such as capacitors, transformers, and insulators. The method of maximum likelihood is used for estimating design parameters. The optimal test plan is obtained by minimizing variance of test-statistic that decides on acceptability or rejectibility of lot. The optimal test plan finds optimal sample size, stress rates, sample proportion allocated to each stress and lot acceptability constant such that producer’s risk and consumer’s risk is satisfied.

Asymptotic variance plays a pivotal role in determining the sample size required for a sampling plan for deciding the acceptance/rejection of a lot. The sample size is minimized by optimally designing a ramp-stress ALT so that the asymptotic variance is minimized.

The model suggested is of use to quality control and reliability engineers dealing with highly reliable items.