金属磁记忆检测技术及其再制造应用(英文版)

Part Ⅰ Introduction to the Metal Magnetic Memory (MMM) Technique 　　Chapter 1 Nondestructive Testing for Remanufacturing 　　1.1 Motivations 　　Global environmental pollution and resource scarcity have become increasingly serious at present. In addition， many pieces of mechanical equipment have been scrapped from various industries， including the automobile， shipping， aerospace and petroleum industries. Taking China as an example， official statistical data from the China Construction Machinery Association in 2014 indicated that product ownership of engineering machinery reached as high as 7 million， 80% of which exceeded warranty. Moreover， the number of registered and scrapped automobiles reached 33.52 million and 8.58 million， respectively， in 2017， as shown in Fig. 1.1 based on the Chinese automobile market investigation report. It can be predicted that the quantity of automobile scrappage will exceed 18 million in the next few years. In addition， there are still 7.28 million engineering machinery， 8 million high-end machine tools， and 1.2 thousand shield tunneling machines in service at present. All of these machinery will be scrapped or upgraded after reaching lifetime limitations， which has great potential for remanufacturing. 　　Therefore， maximizing the usefulness of waste products has been the key to improving the resource utilization level under this new background. Compared with the products of the traditional manufacturing industry， remanufactured products can reduce costs by 50%， save more than 60% in energy consumption and 70% in materials and reduce emissions by 80%. Taking the first remanufacturing shield tunneling machine in China as an example， the remanufacturing process can save over 20 million yuan， 200 tons of steel， and 260 tons of standard coal while cutting down 700 tons of carbon dioxide. 　　Consequently， remanufacturing exhibits an affinity to the concepts of sustainable production and sustainable society and has been attracting increasing attention worldwide [1]. For example， the USA has the largest industry scale， exceeding 75 billion dollars [2]. Europe enforces recycling and remanufacturing laws for waste automotive parts， and the European Commission lists remanufacturing as the research plan in “Horizon 2020”. Among them， the remanufacturing industry in the UK can create 5 billion pounds of gross national product. The British Lister Petter company can remanufacture 3 thousand disused engines every year. In addition， at least 90% of parts in German automobiles can be reused. In East Asia， Japan exports one-third of its remanufactured products and earns high profits from such practices [3]， and China has exerted immense efforts in recent years to promote the sustainable and healthy development of the remanufacturing industry based on the “Made in China 2025” plan. 　　Fig. 1.1 Number variation of automobiles in China: a registered automobiles and b scrapped automobiles 　　Remanufacturing， which is an emerging green technology， is defined as a series of processes that allow end-of-life products and parts to be recommercialized as new products with the same quality， functionality and warranty [4]. The main remanufacturing process consists of disassembling， cleaning， inspecting， repairing and reassembling， as shown in Fig. 1.2. Remanufacturing cores disassembled from used products should be inspected before repair. Cores that satisfy remanufacturability requirements will be restored to their original specifications via a series of repair techniques， including laser cladding， plasma spraying， plasma transferred arc welding and electroplating deposition. During the repair process， a cladding coating is prepared by these surface engineering technologies on the damaged surfaces of the cores so that their performance can be improved and the remanufactured parts can remain in service [5]. Therefore， quality control and evaluation of the remanufacturing process is essential because they are directly related to determining whether the reliability of remanufactured parts can meet the standard for new parts. From the perspective of remanufacturing engineering， inspection plays a key role in assessing the damage degree and repair quality of the cores to ensure that the remanufacturing process proceeds smoothly. 　　Fig. 1.2 Typical remanufacturing process 　　1.2 Conventional Nondestructive Testing Techniques 　　A nondestructive testing (NDT) technique， which can detect flaws from the interior or surface of a component based on the variations in heat， sound， light， electricity or magnetism attributed to unusual structures and defects， is essential. Compared with traditional destructive testing techniques， NDT has the following advantages: (1) the performance of objects cannot be affected; (2) all the objects can be tested comprehensively rather than sampled in part; and (3) the whole process of manufacturing， service and remanufacturing can be monitored. Therefore，