Experimental Investigation of Laser Metal Deposition of Functionally Graded Copper and Steel

Laser metal deposition is an emerging technology for producing fully dense metallic parts. This process shows a promising future for the deposition of functionally graded steel - copper alloys. Good thermal conductivity of copper and a high wear resistance of steel can be achieved in dies and cores. However, to accomplish this, there are many issues to be resolved, such as the formation of an undesirable phase, solidification cracking, porosity at the interface and difference in thermal coefficient of expansion between steel and copper. The influences of process variables, such as laser power, laser scan speed, composition, powder flow rate, on the success of the process, should be studied.Mechanical Engineerin

Experimental Investigation of Laser Metal Deposition of Functionally Graded Copper and Steel

Laser metal deposition is an emerging technology for producing fully dense metallic parts. This process shows a promising future for the deposition of functionally graded steel - copper alloys. Good thermal conductivity of copper and a high wear resistance of steel can be achieved in dies and cores. However, to accomplish this, there are many issues to be resolved, such as the formation of an undesirable phase, solidification cracking, porosity at the interface and difference in thermal coefficient of expansion between steel and copper. The influences of process variables, such as laser power, laser scan speed, composition, powder flow rate, on the success of the process, should be studied

Optimization of the laser aided manufacturing process (LAMP) using the design of experiments approach - Taguchi way

The Laser Aided Manufacturing Processes (LAMP) developed at the University of Missouri-Rolla is used to fabricate three dimensional metal and ceramic parts...This thesis describes the optimization methods used in the process to obtain a combination(s) of parameters that provide an ideal result(s), namely the part quality. --Abstract, page iv

Application of a Diagnostic Tool in Laser Aided Manufacturing Processes

Lasers play a vital role in producing parts with high dimensional accuracy, strength and quality in today\u27s rapid prototyping industry. In the process of Laser Metal Deposition, many problems are encountered where the part quality does not meet the required standards. This could be due to the nonconformity of control parameters or unnecessary interactions between the control factors. This paper discusses the implementation of Dr. Genichi Taguchiï\u27s optimization techniques using Design of Experiments (DOE) where a series of fractional factorial experiments are performed on the laser deposition process. The results from these experiments are evaluated with respect to the rate of deposition alongside the part quality and the optimized level setting of control parameters are determined efficiently. This tool can be used to detect and diagnose flaws and discrepancies in the Laser Metal Deposition process and optimize it accordingly

Laser Aided Part Repair-A Review

Laser aided part-repair is an emerging trend that has great potential for future industrial applications. Part-repair technologies are currently used in repairing military and civilian equipment. The focus of this paper is to review the current repair processes, which use the laseraided metal deposition technology. Many metal parts, which are worn by continual use, can be restored to working condition by the deposition of metal with a laser and machining. This not only extends the life of the part, but also, saves on cost. A comparison between various processes, their parameters, efficiency, cost, and etc. are also presented. The process limitations, materials, and areas that are best suited for each process are also discussed.This research was supported by the National Science Foundation Grant Number DMI-9871185, Missouri Research Board, and a grant from the Missouri Department of Economic Development through the MRTC grant.Mechanical Engineerin

The Origin of regional failure in oral cavity squamous cell carcinoma with pathologically negative neck metastases

Importance: Squamous cell carcinoma of the oral cavity (OSCC) is a common malignant tumor worldwide. OBJECTIVE To determine if regional failure in patients with OSCC and pathologically negative neck nodes (pN-) is due to an incomplete sampling procedure during surgery. Design, setting, and participants: We retrospectively reviewed the medical records of 2258 patients from 11 cancer centers worldwide who underwent neck dissection for OSCC (1990-2011) and who were pN-. Of those, 345 had clinical evidence of nodal metastases (cN+) on radiologic workup. The neck specimens were available for reanalysis in 193 patients. Survival rates were calculated using the Kaplan-Meier graphs and analyzed by multivariable analysis. Main outcomes and measures: Five-year overall survival (OS), disease-specific survival (DSS), and disease-free survival (DFS). Results: Resectioning and analysis of the neck dissection specimens in the cN+/pN-subgroup revealed false-negative results in 29 (15%) of 193 patients. The negative predictive value of the initial pathologic examination was 85%. The 5-year OS and DSS in the cN-/pN-group were 77.6% and 87.2%, respectively. The 5-year OS and DSS of the cN+/pN- group were 62.6% and 78.5%, respectively (P < .001). In multivariable analysis, cN+ classification was significantly associated with poor OS (hazard ratio [HR], 1.7; 95%CI, 1.1-3.8; P = .03) and poor DSS (HR, 1.46; 95%CI, 1.1-4.1; P = .04). A cN+ classification was associated with lower DFS (66.3%vs 76.2%; P = .05) and lower regional recurrence-free survival (68.6%vs 78.8%; P = .02) but not with local (P = .20) or distant recurrence (P = .80). Conclusions and relevance: Pathologic staging underestimates the incidence of nodal metastases in cN+ disease. After correction for pathologically missed nodal metastases, radiologic evidence of neck nodes is an independent predictor of outcome, suggesting that traditional sampling during surgery might miss metastases, and this fact might explain the origin of treatment failure in these patients.8 page(s