@article{wang_lowrie_ngaile_fang_2019, title={High injection pressure diesel sprays from a piezoelectric fuel injector}, volume={152}, ISSN={["1359-4311"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062213294&partnerID=MN8TOARS}, DOI={10.1016/j.applthermaleng.2019.02.095}, abstractNote={Increasing injection pressure can increase combustion efficiency in direct injection (DI) diesel engines attributing to enhanced atomization. In this paper, a high pressure experimental setup was built to generate ultra-high fuel pressure. An intensification unit was used to magnify the pressure by about 10 times. Preliminary testing of the high pressure system produced a peak pressure of about 8700 bar. Due to the pressure limitation of the commercially available diesel fuel system, the maximum pressure tested in a practical piezoelectric fuel injector was 2500 bar. A high-speed imaging technique was used to visualize the fuel injection events and spray images were taken by a high speed camera for quantitative analysis. A Schlieren technique was used to visualize the shock waves generated during spray penetration. The near nozzle early stage spray development was also studied using a long distance microscope and an intensified charge coupled device (ICCD) camera. Results show that the spray penetration velocity increases with the increase of the injection pressure, while a higher injection pressure leads to a later opening of the piezoelectric injector. The spray angle first has a large value, then remains relatively steady throughout the injection process. Schlieren results clearly demonstrate detached shock waves during the spray penetration. The near nozzle results show that during the very early stage the spray penetration is quite linear for different injection pressures and the spray angle also appears to be very large at the beginning, which is consistent with the high-speed imaging results. Both high-speed imaging and near nozzle results were compared with published empirical equations. The high-speed imaging result shows a good match with the linear stage of empirical equation, while near nozzle result shows lower penetration velocity, indicating that there exists a very short “acceleration stage” for spray development at the starting moment of fuel injection.}, journal={APPLIED THERMAL ENGINEERING}, author={Wang, Libing and Lowrie, James and Ngaile, Gracious and Fang, Tiegang}, year={2019}, month={Apr}, pages={807–824} }
 @article{lowrie_pang_ngaile_2017, title={Weight reduction of heavy-duty truck components through hollow geometry and intensive quenching}, volume={28}, ISSN={["1526-6125"]}, DOI={10.1016/j.jmapro.2017.04.021}, abstractNote={Increasing environmental awareness has put pressure on heavy duty truck manufacturers to improve the fuel economy and reduce the emissions of their vehicles. Light weighting efforts are a useful tool in meeting these goals. As a demonstration of how light weighting practices can be applied to the power trains of heavy duty vehicles, this paper focuses on reducing the weight of the rear axle shaft. Two methods are focused on, i) hollow shaft geometry and ii) intensive quenching, as possible avenues to shed mass from the shaft. Load mapping is used to establish a finite element model which can be used to evaluate the light weight designs and techniques proposed in the paper. It is discovered that weight savings of around 26% can be achieved by changing the traditionally solid axle shaft into a hollow shaft. The intensive quenching process is shown to be superior to the oil quenching process in regards to both residual stresses and strength, allowing for material removal accounting for 3% of the shaft weight. Additionally, the compressive residual stresses created on the surface of the part during the intensive quenching process may also serve to slow crack initiation and increase fatigue life. Further optimization of the intensive quenching process may provide additional weight reduction opportunities.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Lowrie, James and Pang, Hao and Ngaile, Gracious}, year={2017}, month={Aug}, pages={523–530} }
 @article{lowrie_ngaile_2016, title={Analytical Modeling of Hydrodynamic Lubrication in a Multiple-Reduction Drawing Die}, volume={5}, ISSN={["2351-9789"]}, DOI={10.1016/j.promfg.2016.08.058}, abstractNote={The hydrodynamic lubrication regime is reported to exist in numerous metal forming applications, such as wire drawing and hydrostatic extrusion, but it has not been achievable in the drawing of large diameter rods due to the relatively low drawing speeds common for larger parts. By creating a stable fluid film between the workpiece and the die during the drawing process friction and die wear could be significantly reduced, leading to energy savings, increased achievable reductions, and increased die life. An analytical model of the hydrodynamic drawing process is proposed which considers the geometry of the workpiece and die, as well as, the material properties (including work hardening effects), and (temperature dependent) fluid properties to determine the fluid film thickness over the reduction die. This model is then used to analyze several case studies, including a proposed multiple reduction die with high pressure lubricant supplied to the space between the dies. It is shown that a stable fluid film can be established for low drawing speeds through the combination of a multiple reduction die and elevated lubricant pressure in the inlet of the dies.}, journal={44TH NORTH AMERICAN MANUFACTURING RESEARCH CONFERENCE, NAMRC 44}, author={Lowrie, James and Ngaile, Gracious}, year={2016}, pages={707–723} }
 @article{lowrie_ngaile_2016, title={New punch design for the elimination of punch ejection load through manipulation of the elastic strain field in the punch nose}, volume={22}, ISSN={["1526-6125"]}, DOI={10.1016/j.jmapro.2016.01.008}, abstractNote={The extreme tribological conditions present during both the forward stroke and the punch ejection stroke of a backward cup extrusion process can adversely affect the quality of the extruded part and diminish the life of the punches. A novel punch design based on the segmentation of the extrusion punch into a main body and a nose cone insert is proposed to reduce or eliminate the pressure between the punch and work piece during the punch removal stroke. This is facilitated by manipulating the elastic strain field at the punch nose. With the aid of the finite element analysis, a parametric study on the segmented elastic punch assembly was carried out to establish optimal conditions and punch design guidelines. Experiments were carried out to determine the effectiveness of the segmented elastic punch. A significant reduction in the punch ejection load was observed along with a reduction in material pickup on the punch and galling on the surface of the part. The elastic deflection of the punch also allowed the researchers to discover that a significant amount of damage could occur during the punch ejection stroke.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Lowrie, James and Ngaile, Gracious}, year={2016}, month={Apr}, pages={49–59} }
 @inproceedings{lowrie_ngaile_2015, title={Novel extrusion punch design for improved lubrication and punch ejection}, DOI={10.1115/msec2015-9496}, abstractNote={The extreme surface expansion and pressures observed during the backward extrusion process can have adverse effects on the surface of the workpiece and the life of the punches used in the process. After the forming process is complete, the ejection of the punch can further damage the part surface and reduce tool life because the pressures on the land of the punch remain quite high. The research presented in this investigation aims to reduce or eliminate the galling and surface damage for the backward extrusion process by creating a new class of punch which can create the opportunity for lubrication transport to the area underneath the punch and lessen the damaging conditions during punch ejection. The proposed tooling divides the traditional punch into two pieces, a hollow punch body and an insert with micro channels for lubrication transport. The tooling was developed and used in a series of tests to determine the benefits of the new punch. Preliminary data shows that the extrusion loads for proposed punch are similar to the conventional punch, but the surface finish is significantly enhanced using the modified punch design and the galling is minimized. Furthermore, there is a marked reduction in the ejection load required to remove the punch from the part after forming.}, booktitle={Proceedings of the ASME 10th International Manufacturing Science and Engineering Conference, 2015, vol 1}, author={Lowrie, J. and Ngaile, G.}, year={2015} }
 @article{ngaile_lohr_lowrie_modlin_2014, title={Development of chemically produced hydrogen energy-based impact bonding process for dissimilar metals}, volume={16}, ISSN={["2212-4616"]}, DOI={10.1016/j.jmapro.2014.07.005}, abstractNote={There has been a growing demand in the fabrication of dissimilar metal parts for application in the automotive, aerospace, defense, chemical and nuclear industries. Welding of dissimilar materials can be accomplished via impact welding, which can minimize the formation of a continuous inter-metallic phase, while chemically bonding dissimilar metals. This paper discusses an innovative technique for bonding dissimilar metals by chemically produced hydrogen energy by reacting aluminum powder and water. Experiments were carried out to study impact bond characteristics using copper and stainless steel cylindrical billets. The influence of nosed flyer billet angle and billet mass on bonding characteristics were studied. The test results have demonstrated that the nosed flyer billet angle has significant influence on wavy bond patterns at the interface. Among the three flyer billet nose angles of 9°, 12° and 15°, the billets with a flyer angle of 15° resulted in a complete wave morphological pattern along the whole sample cross-section. This study shows the potential of developing a cost effective system/machinery where discrete metal parts can be bonded at near net shape.}, number={4}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Ngaile, Gracious and Lohr, Peter and Lowrie, James and Modlin, Rhyne}, year={2014}, month={Oct}, pages={518–526} }
 @inproceedings{lowrie_ngaile_2014, title={Enhancement of tribological performance via innovative tooling design for extrusion processes}, DOI={10.1115/msec2014-4170}, abstractNote={Due to the expense and negative environmental impact of commonly used conversion coating type lubricants a new method for reducing the friction in the extrusion process is desired. This paper investigates the possibility of modifying the die set to better the tribological conditions and reduce friction in the extrusion process. A novel design of extrusion tooling is proposed, in which the die set is segmented into three separate pieces, a punch, a wall die, and a bottom die. Additionally, the wall die is given the freedom to move along the axis of the punch and a high pressure lubricant is supplied to the interface between the wall and bottom dies. Preliminary tests of the segmented tooling show that, if the tribological conditions are severe enough, the forming load will decrease in comparison to a conventional extrusion system.}, booktitle={Proceedings of the ASME 9th International Manufacturing Science and Engineering Conference, 2014, vol 2}, author={Lowrie, J. B. and Ngaile, G.}, year={2014} }