The thermal effects of stitch welding the coolant conduits of a water-cooled flat plate solar collector to its absorber plate have been studied. A physical model of the heat transfer process from the plate to the fluid flowing inside the tube has been presented. The heat transfer coefficient based on the difference between bond temperature and fluid bulk mean temperature is an important factor in determining the collector efficiency factor F'. The upper and lower limits of the actual value of F' have been predicted by considering two extreme boundary conditions to which the fluid is subjected. For a thick and conductive tube wall, F' does not depend on spot size and spot spacing, and tends to an upper limit of 0.883. For a thin and non-conductive tube wall, the boundary condition comprises of a series of step changes in both the axial and circumferential directions of the heat flux. In this case, the heat transfer coefficient and hence F' approach their lower limits which are determined by the welding spot configuration. It was also found that F' increases with the following parameters: the spot angle; the percentage of tube length being welded; and the number of spots among which the welding is being distributed. Furthermore, the temperature distribution inside the fluid has also been computed for this case. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

This thesis was prepared as a result of the growing interest in and the increasing importance of electric welding as applied to many types of manufactured products. Although the art of electric welding is comparatively new, great steps have been taken in its adaptation to industry. As yet the process is underdeveloped, and no information is available whereby one may know with certainty the behavior to expect from a welded joint. The composition of the metal to be welded, the composition of the welding rod, and the method used in welding are but a few of the factors which determine the ultimate strength and behavior of an electrically welded specimen. Far from claiming the credit for a comprehensive report on electric welding, the authors of this thesis admit that it of necessity is limited in its treatment of the subject. Both steel and wrought iron specimens were tested, the steel specimens ranging from 0.2 to 0.5 per cent carbon content. At first the investigation embraced lap-welded and butt-welded joints, but because of the fact that properly made lap-welds never break in the weld, and hence give no indication as to the strength of the weld, this type was abandoned, and all V-type butt-welds were used. All of the welds, with a few exceptions which will be mentioned later, were tested in tension, their tensile strength being used as an indication of their ultimate strength. The Tinius Olsen strain gage was used in obtaining the elongations of the specimens. In the tables which follow, the values in the deformation column will be expressed in Tinius Olsen units, each unit being 0.0003333 of an inch. If the value in the deformation column were 2.3 and this value were desired in inches, the conversion factor 0.0003333 should be multiplied by 2.3, giving 0.00076659 inches as a result. The welding was done with a Lincoln Stable Arc Welder. During the welding operations the voltage was kept at 60 and the amperage was about 150. / M.S.

The primary objectives of this thesis investigation were: 1. To establish the maxima and minima values, within limits of the welding machine parameters: current and time, for 28 gauge, 24 gauge, 20 gauge, 18 gauge, and 16 gauge of SAE CR 1010 steel. 2. To implement and calibrate the instrumentation necessary to determine accurate values, within limits, of the variables under investigation. Also, to devise suitable controls for those fixed variables not investigated. 3. To correlate values of welding current and time with resulting tensile-shear strengths of the lapped welding joints. 4. To establish the combination of welding current and weld time which gives a maximum value of tensile strength for the metal gauges under investigation. A brief review of the more important literature on resistance spot welding variables was presented. The calibration process of determining voltage, resistance, and current was described. The mathematical prediction models (relationship between weld strength and weld time) were established for each heat control setting for different thicknesses under investigation, based on non-linear regression techniques. From the prediction models and the use of Calculus, the maximum tensile-shear strengths and corresponding maximum weld cycles were computed. The minimum weld strengths and weld cycles were determined by the welding conditions that just produced a weld of measurable strength. / Master of Science

The primary objectives this investigation are: 1. To present a discussion of known submerged arc welding variables and their general affect on weld bead appearance 2. To design an experiment to investigate the affect on weld joint strength and hardness distribution across the weldment by using (1) Four different welding currents (450, 500, 550, and 650 amps). (2) Three different steels (M 1020, SAE 1045 and SAE 1095) and (3) Two different electrodes (Hobart type C-10 and C-20) as variables in the experiment. 3. To establish the welding technique and procedure to control welding variables. 4. To collect unavailable data about the submerged arc process by experimentation and statistically interpret this data. After the preliminary investigation, the author statistically designed the testing procedure for the randomized test specimens for hardness of weld zone and hear-affected zone and applied statistical technique to determine significant effects on weld quality due to the variables. The conclusions are given in chapter I. / Master of Science

The results of this investigation are based on the statistical and visual analyses of the data collected during this experiment / Master of Science

This thesis is an investigation of the effect of welding heat on the properties of hardened concrete. In precast concrete structures, where the bearing plates are embedded in the concrete, the welding heat on these plates, generated by the electric arc, penetrates into the concrete. It has been known for many years that high temperatures will lower the modulus of elasticity and the ultimate strength. This thesis is concerned with the “critical” temperatures at which losses begin and the arc energy required to develop this temperature at a reasonable depth into the concrete. In the investigation, the “critical” temperature, using limestone aggregate concrete that might be typical for precast construction, was found to be between 900°F and 1,000°F. The investigation, to determine the arc energy required to develop this temperature, was halted when under severe heating, where the arc burned through both plates, the maximum temperature at a point one half inch from the bearing plate was 710°F. Although cracking was severe in the immediate vicinity of the plate, the moduli of elasticity were lowered only slightly and the welding heat was not high enough to affect the ultimate strength. / Master of Science

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / This thesis details the conceptual design of a fixture-based, reconfigurable, automated spot welding system aimed at manufacturing various sub-assemblies of circuit breakers. The welding operations are currently done using manual welding equipment, making this stage of the assembly process highly labour intensive. A range of product models and variants are assembled in quantities requiring frequent change-overs. Low-cost automation within a developing country’s manufacturing industry, more specifically within the Republic of South Africa, is the target context. The chosen design restriction, of incorporating a part fixturing design approach, distinguishes this research from F. S. D. Dymond’s work, who addressed the same problem while restricted to a fixtureless assembly approach. A conceptual layout design was developed to address part feeding, manipulation, transportation, fixturing and welding requirements, for an entire breaker model range. A simulation model for three possible layouts of the selected conceptual design provided a means to investigate each layout’s ability to tolerate and balance variation in production requirements, and to establish objective comparative performance data. This showed that the optimal configuration consists of four single loop layout systems. The thesis concludes that the final concept possesses the flexibility to produce the primary product range. Reconfiguration for production beyond this range is assisted by the modular nature of the layout. Ultimately, a reconfigurable design should focus on a properly selected base of core product ranges, providing an expandable and reusable system. The system can be supported by manual assembly stations which handle highly variant, incompatible product ranges.

No description available.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Gordon Bruce Hunter. / M.S.

One-, two- and three-dimensional transient heat transfer finite element models are developed to simulate the resistance welding process of pre-consolidated unidirectional AS4 carbon fibre reinforced Poly-ether-ether-ketone (APC-2/AS4) laminates with a metal mesh heating element, in a lap-shear configuration. The finite element models are used to investigate the effect of process and material parameters on the thermal behaviour of the coupon size welds, yielding to a better understanding of the process. The 1-D model determines: (a) the importance of including the latent heat of PEEK, and (b) the through-thickness temperature gradient away from the edges, for different tooling plate materials. The 2-D model simulates the cross-section of the process, considering the convective and irradiative heat losses from the areas of the heating element exposed to air. The 3-D model includes the heat conduction along the length of the laminates, to fully depict the thermal behaviour of the welds. Finally, the models are compared with experimental data.