Experimental Investigation and Analysis on Dynamic Strain of Leading Trailing Shoe Drum Brake

The research on the dynamic strain of drum brakes is of great significance in performance evaluation, structure optimization and fatigue prediction. Based on current research of strain experiments and measuring technology, a new test procedure is proposed to investigate strain and temperature information of a working drum. Wireless data acquisition system and high-temperature strain gauges are applied. The strain-time and temperature-time curves are studied on the conditions of emergency brake and continuous brake. A tribological and thermo-mechanical analysis are conducted by using software ABAQUS. Results show that the strain is uneven when the drum contacts different zones of friction plates. Seasonal variation is another feature and a set of four wave crests repeats during the rotation. Meanwhile, thermal effect is proved important to strain. The simulation results coincide well with experiments, proving that this method provides a practical way to verify the calculation. The study also lays the foundation for the following fatigue analysis and optimization design.

Value of Bootstrapping Staged Deployment of Infrastructure: Case Study in Space Infrastructure Deployment

This paper analyzes the value of staged deployment for complex infrastructure system and propose a concept of bootstrapping staged deployment. Staged deployment has been well known for its advantage of providing flexibility in an uncertain environment. In contrast, this paper demonstrates that the proposed bootstrapping staged deployment can even add values in a deterministic environment. The key idea of bootstrapping staged deployment is to have the previously deployed stages support the subsequent deployment. We develop an analytical model to demonstrate the effects of bootstrapping staged deployment with a case study in space exploration. Our analysis results show that with a well-coordinated deployment plan, staged deployment can overperform single-stage deployment even in a deterministic environment, and that there is an optimal number of stages in terms of lifecycle cost under certain conditions. Our method can find the analytical expression for the optimal number of stages and its deployment strategies. The general findings from the proposed concept and analytical method can advance our knowledge about systems staged deployment, and make operational planning of resource generation infrastructure more efficient.

Developing and Comparing Alternative Design Optimization Formulations for a Vibration Absorber Example

In some cases, the level of effort required to formulate and solve an engineering design problem as a mathematical optimization problem is significant, and the potential improved design performance may not be worth the excessive effort. In this article we address the tradeoffs associated with formulation and modeling effort. Here we define three core elements (dimensions) of design formulations: design representation, comparison metrics, and predictive model. Each formulation dimension offers opportunities for the design engineer to balance the expected quality of the solution with the level of effort and time required to reach that solution. This paper demonstrates how using guidelines can be used to help create alternative formulations for the same underlying design problem, and then how the resulting solutions can be evaluated and compared. Using a vibration absorber design example, the guidelines are enumerated, explained, and used to compose six alternative optimization formulations, featuring different objective functions, decision variables, and constraints. The six alternative optimization formulations are subsequently solved, and their scores reflecting their complexity, computational time, and solution quality are quantified and compared. The results illustrate the unavoidable tradeoffs among these three attributes. The best formulation depends on the set of tradeoffs that are best in that situation.

Comparing the Sustainability Performance of Metal-Based Additive Manufacturing Processes

While there have been many advancements in additive manufacturing (AM) technologies for metal products, there has not been a great deal of attention paid toward developing an understanding of the relative sustainability performance of various AM processes for production of aerospace components, such as wire feed and powder bed fusion processes. This research presents a method to calculate and compare quantitative metrics for evaluating metal AM process on a basis of sustainability performance. The process-level evaluation method encompasses a triple bottom line analysis for low volume part production. A representative aerospace titanium alloy (Ti-6Al-4V) component is considered for the study and the production of the part is modeled using direct energy deposition (DED) as the representative wire feed AM process and selective laser melting (SLM) as the representative powder bed AM process. The results indicate that DED has a superior sustainability performance to SLM, mainly due to the relatively slower deposition rate and higher cost of material for SLM than DED. This research provides decision makers an approach method and a demonstrated case study in comparing DED and SLM AM processes. This understanding reveals advantages between the two options and offers avenues of future investigation for these technologies for further development and larger scale use.

Modified Jacobian-Torsor Based Error Modeling and Quantitative Sensitivity Analysis for Single Axis Assembly of Machine Tool

The influence of component errors on the final error is a key aspect of error modeling of CNC machine tool. Nevertheless, the mechanism by which the errors in mechanical parts accumulate to result in the component errors and then impact the final error of CNC machine, has not been identified; the identification of this mechanism is highly relevant to precision design of CNC machine. In this study, error modeling based on the Jacobian-torsor theory is founded to determine the mechanism by which fundamental errors in mechanical parts influence the comprehensive error of single-axis assembly. Firstly, the constraints of small displacement torsors (SDTs) for typical features and the statistical solution are proposed to perfect the modified Jacobian-torsor model theoretically. Next, the modified Jacobian-torsor model is applied to the error modeling of a single-axis assembly in a three-axis machine center. Furthermore, the comprehensive errors of the single-axis assembly are evaluated by Monte Carlo simulation based on the synthesized error model. The accuracy and efficiency of the modified Jacobian-torsor model are verified through a comparison between the simulation results and the measured data from a batch of similar vertical machine centers. Based on the modified Jacobian-torsor model, the application of quantitative sensitivity analysis of single-axis assembly is investigated, along with an analysis of the analysis of key error sources to the synthetical error ranges of the single-axis assembly. This model is providing a comprehensive method for the better understanding of the key error source of the machine tool and has the potential to enable error allocation and precision improvement of the assembly and the whole machine tool in future.

A Concurrent Design Exploration Method for Realizing Networked Manufacturing Systems

Multistage manufacturing processes (MMPs) are networked manufacturing systems consisting of multiple operational stations that have characteristics of mechanical and control systems. Common challenges in the design of MMPs are the selection of sensors and tools as this not only affects the dimensional quality of the finished product, but also influences the computational complexity in representing and analyzing the problem. Imprecise or incomplete information results in uncertainty in the models used to represent the MMP and limit the use of traditional design approaches. In this paper, an exploration method for the concurrent design (CDEM) of MMPs under uncertainty is presented wherein the attributes of tools and sensors are treated as design variables, thereby allowing flexibility in a design process. The proposed method is illustrated using an example of automotive panel stamping process. Our focus in this paper is on the method rather than the results per se.

Influence of Distributed Reaction Regime on Fuel Reforming

Previous works have demonstrated that the Distributed Reaction regime impact on the reformate product distribution. Using previous works, a theory of how the Distributed Reaction regime influences the reformate product composition is provided. Distributed Reaction regime is achieved by entraining exhaust products into the premixed fuel air mixture. As some steam and carbon dioxide will form in the exhaust, it is theorized that the mixing of the entrained flow (containing heat, carbon dioxide, and steam) into the premixed fuel air mixture will promote dry and steam reforming reactions, improving conversion. As kinetic information on reforming literature is limited, the activity and time scales of these reactions were determined from existing experimental data. This was then used to determine which reactions were active under Distributed Reforming conditions.

Lifecycle Tools As a Support for the Eco-Design Innovation of Domestic Appliances

The goal of sustainable development through the product innovation is a global challenge that Academia and Industries are addressing. The regulatory pressure and the growing demand of eco-friendly products by consumers are two of its main drivers, especially in the household appliances sector. For this aim, manufactures need to change the design approach in order to extend the boundaries of the benchmark analysis of possible innovations: (i) multi-objective criteria should be taken into account such as the environmental issues, costs, technical performances, etc., and (ii) a life cycle thinking has to be adopted to consider long terms benefits or impacts. However, the literature highlights the lack of structured methods able to support the R&D activity according to these perspectives. For this aim, the present paper provides a systematic approach, which exploits lifecycle and innovation tools to effectively support designers in the development of sustainable solutions in a long term perspective. The proposed approach has been applied in real case study to increase the energy efficiency of a domestic refrigerator. In particular, the insulation module has been redesigned by comparing several alternatives in terms of environmental performances and costs over the product lifespan to effectively evaluate the consistency of the developed eco-innovations.

Conceptual Regenerative Nozzle Cooling Design for a Hydroxyl-Terminated Polybutadiene and Oxygen Hybrid Rocket Engine

Regenerative rocket nozzle cooling technology is well developed for liquid fueled rocket engines, but the technology has yet to be widely applied to hybrid rockets. Liquid engines use fuel as coolant, and while the oxidizers typically used in hybrids are not as efficient at conducting heat, the increased renewability of a rocket using regenerative cycle should still make the technology attractive. Due to the high temperatures that permeate throughout a rocket nozzle, most nozzles are predisposed to ablation, supporting the need to implement a nozzle cooling system. This paper presents a proof-of-concept regenerative cooling system for a hybrid engine which uses hydroxyl-terminated polybutadiene (HTPB) as its solid fuel and gaseous oxygen (O2) as its oxidizer, whereby a portion of gaseous oxygen is injected directly into the combustion chamber and another portion is routed up through grooves on the exterior of a copper-chromium nozzle and, afterwards, injected into the combustion chamber. Using O2 as a coolant will significantly lower the temperature of the nozzle which will prevent ablation due to the high temperatures produced by the exhaust. Additional advantages are an increase in combustion efficiency due to the heated O2 being used for combustion and an increased overall efficiency from the regenerative cycle. A computational model is presented, and several experiments are performed using computational fluid dynamics (CFD).

Implementation of an Object-Oriented Life Cycle Assessment Framework Using Functional Analysis and Systems Engineering Principles

Given that a significant percentage of a product’s impacts are defined during design and development, there is a need to effectively integrate Life Cycle Assessment (LCA) into these early phases. However, the lack of standardized practices, the lack of appropriate modeling approaches, data issues, special training requirements for designers, and uncertainties in the results make it difficult to apply LCA in these early stages. In order to address this gap, this work builds on previous research that integrated system engineering and functional analysis into LCA to develop an object-oriented framework for LCA. The framework is applied to a consumer product and the results of the approach demonstrate the potential for an easy to update and scalable LCA model that facilitates comparability. Each module in this model can be developed separately and integrated effectively into a larger model guided by functional analysis techniques. This framework holds the promise to better integrate LCA into the design and development phases.